Materials doi: 10.3390/ma19224835

Authors: Siyu Liu Zengzhen Qian Ziang Li Jiayidaer Shanbayi

To improve the tensile capacity and reduce the post-peak brittleness of stabilized aeolian sand, a binder comprising steel slag, ground granulated blast-furnace slag, phosphorus slag, and calcium carbide residue was combined with basalt fibers. Axial splitting tests using a four-factor, five-level orthogonal design and three-dimensional discrete element simulations investigated tensile behavior and reinforcement mechanisms. Basalt fibers increased tensile strength by 6.58–131.82%, slowed post-peak strength degradation, and improved specimen integrity after failure. Factor influence decreased in the order of binder content, water content, fiber content, and fiber length. All four factors exhibited statistically significant main effects on tensile strength at the 0.05 level, with binder content having the greatest influence. The optimum combination within the investigated ranges was 3% water content, 18.05% binder content, 1.5% fiber content, and 12 mm fiber length, yielding a mean tensile strength of 0.195 MPa after 28 d of curing in verification tests. Simulations reproduced the experimental mechanical responses, with tensile cracks dominating both models. Through load sharing and crack bridging, fibers maintained tensile load-transfer paths near cracks and restricted relative particle displacement, delaying crack coalescence and overall failure. These findings clarify the mesoscopic reinforcement mechanisms and support aeolian sand improvement and industrial solid waste utilization.

Materials doi: 10.3390/ma19224834

Authors: Gangwei Mei Wanhua Li Jianguo Du Linmei Lyu Yongsheng He Chao Shen Xueli Lv

Comparative full-scale blast data for buried reinforced-concrete (RC) boxes in crushable coral sand remain scarce. Four lateral-detonation tests used the same instrumented box: three in loess (0.6, 1.0 and 2.0 kg TNT) and one in coral sand (1.0 kg). Apparent front velocities were 193–272 m/s for the retained loess pairs and 82–95 m/s in coral sand; an unresolved T3 timing outlier is reported separately. Loess peak free-field pressure followed P = 0.50·Z − 3.08 (P in MPa; Z inserted numerically in m·kg−1/3). For T1/T3 at Z ≈ 0.95, the peak-pressure and duration ratios were 1.045 and 1.35, whereas the impulse ratio was 1.055–1.094 rather than the theoretical 1.49; classical impulse similarity is therefore unsupported. At Z = 1.0, coral sand reduced the free-field peak by 54%, while facing-wall pressures of 1.30–1.34 MPa gave an apparent directional Kr ≈ 4. Facing-centre acceleration decreased from 258 to 26 g and velocity increased from 89 to 846 mm/s. A compaction–reflection interpretation using wall-synchronous values and a directional reference identifies Id ≈ 4.42 × 105 kg/(m2·s); Md ≈ 0.108 GPa additionally assumes ρd = 1800 kg/m3. This is single-test parameter identification, not independent validation. Because the box was reused and no quantitative crack or residual-deformation survey was available, the results demonstrate contrasting load/response signatures and motivate preliminary mechanisms, not general design coefficients or an observed failure-mode transition.

Materials doi: 10.3390/ma19224833

Authors: Yingchao Wang Jiading Jiang Mingyue Wan Ke Wu Changxin Qi Yasuo Liu Shaowu Yin Gang Wang

The recovery of high-temperature industrial waste heat and the valorization of coal-derived solid wastes are important for sustainable thermal energy systems. In this study, modified coal gasification slag (MCGS) and fly ash (MFA) were used as a porous skeleton to stabilize Al-12Si alloy, and composite phase change materials were fabricated by cold pressing and sintering. The effects of skeleton composition and alkali modification on microstructure, thermal storage, mechanical properties, leakage resistance, and cycling stability were investigated. Alkali treatment roughened the particle surfaces and generated additional pores and capillary channels, enhancing alloy infiltration and interfacial mechanical interlocking. MCF-3, prepared at an initial MCGS: MFA: Al-12Si: binder mass ratio of 25:25:40:10, exhibited a thermal conductivity of 2.51 W m−1 K−1, a compressive strength of 56.17 MPa, and a latent heat of 103.68 J g−1. No detectable interfacial reaction products were observed, indicating good chemical compatibility. After 100 melting–solidification cycles between 400 and 800 °C, the latent heat remained 96.34 J g−1, corresponding to 92.9% retention, while the leakage rate was only 0.65%. These results demonstrate that the MCGS–MFA skeleton provides effective molten-alloy confinement and mechanical support, offering a viable route for developing solid-waste-derived high-temperature thermal storage materials.

Materials doi: 10.3390/ma19224832

Authors: Angelika Skorupa Małgorzata Worwąg Mariusz Kowalczyk Paulina Szuniewicz

Growing demand for water resources and the need to reduce wastewater discharge are driving the development of integrated treatment technologies, particularly in the coffee processing sector, where wastewater has a high organic pollutant load and contains compounds that are difficult to biodegrade. The research aimed to evaluate the effectiveness of an integrated, multi-stage treatment system for synthetic wastewater containing coffee bean extract as a model contaminant. The system included biological treatment, activated carbon sorption, membrane filtration, and two-stage disinfection using ozonation and UV-C radiation. The effectiveness of removing selected pollution indicators, interactions between successive processes, and the impact of operating parameters on system efficiency were evaluated. The best results were obtained for variant D8, involving alternating aeration and mixing phases and an HRT of 8 days. Turbidity removal reached 97.0%, TOC removal 90.2%, and ammonium nitrogen removal 58.8%, with a final pH of 7.05 and complete elimination of microorganisms. The use of 30 min ozonation and 15 min UV-C irradiation ensured effective disinfection. The results indicate the potential of the developed system for industrial wastewater treatment and water recovery; however, further research using actual coffee industry wastewater is necessary, including refinement of process parameters and assessment of energy, economic, and environmental efficiency.

Materials doi: 10.3390/ma19224830

Authors: Yimeng Qin Haimei Li Hongyan Wang Liangbin Chen Xiumin Li Ran Wei

Medium- and high-entropy alloys (M/HEAs) are multi-principal-element metallic materials that overcome the performance limits of conventional single-principal alloys through four core effects: high entropy, severe lattice distortion, sluggish diffusion, and cocktail effect. They deliver exceptional mechanical properties from cryogenic to elevated temperature, superior corrosion resistance, and tunable electrocatalytic activity, making them promising for extreme-environment equipment, marine engineering, and clean energy conversion. This review covers: (1) key fabrication methods, including arc/induction melting, powder metallurgy, and nanoscale/thin-film processing; (2) multi-scale characterization of microstructure, mechanical behavior, corrosion response, and electrocatalysis; (3) mechanisms governing temperature-dependent mechanical performance; (4) synergistic passivation underlying corrosion resistance in aggressive media; (5) hydrogen/oxygen evolution reaction (HER/OER) electrocatalytic advantages, structure–activity relationships, and performance tuning strategies; (6) real-world applications in structural components, anti-corrosion systems, and energy devices; and (7) persistent challenges: imprecise synthesis control, unclear atomic-scale mechanisms, and trade-offs among multiple properties. Through cross-comparison of the reported data, three conclusions emerge: first, melt-based routes dominate bulk production, whereas powder metallurgy and severe-plastic-deformation routes are competitive for micro/nano-scale components and additive manufacturing remains limited by an immature process window; second, the strength–ductility and toughness trade-off across cryogenic-to-elevated temperatures is governed mainly by stacking-fault energy, transformation/twinning-induced plasticity, and precipitate stability; and third, the corrosion resistance and electrocatalytic activity of M/HEAs are tightly linked to passive-film chemistry and the configuration of active sites, rather than to configurational entropy alone. This review concluded with future priorities: artificial intelligence-driven composition design and low-cost, scalable manufacturing.

Materials doi: 10.3390/ma19224831

Authors: Ali Mardani Yahya Kaya Tuğçe Kaya Daniel Hatungimana

Geopolymer concrete produced from fly ash and ground granulated blast furnace slag (GGBFS) has been proposed as a lower-carbon alternative to Portland cement concrete, and blending the two precursors allows for curing at ambient temperature. However, the combined influence of the precursor proportion and activator formulation on the durability of such concretes is not well documented, because mechanical and durability properties have mostly been studied separately. The objective of this study was therefore to evaluate, within a single experimental programme, how the fly ash-to-slag proportion and three combined activator formulations affect the fresh, mechanical and durability properties of ambient-cured hybrid geopolymer concrete. This study examines the influence of the fly ash-to-slag proportion and of three combined activator formulations (nominal Si/Al of 2.0, 2.5 and 3.0, each paired with an SS/SH ratio of 1.5, 2.0 and 2.5, respectively) on the fresh-state, mechanical, and durability characteristics of ambient-cured hybrid geopolymer concrete. Twelve mixture compositions were systematically designed at a constant binder content (500 kg/m3) and NaOH concentration (10 M); the alkaline solution-to-binder ratio varied from 0.33 to 0.39 with the activator formulation. Because Si/Al and SS/SH were varied together, their individual effects could not be separated. Progressive augmentation of the GGBFS proportion from 20% to 50% increased strength and improved the measured durability indicators, while reducing slump and setting time. The best-performing mixture in most tests (M11: 50% GGBFS, nominal Si/Al = 2.5, SS/SH = 2.0) attained a 28-day compressive strength of 60.3 MPa, water absorption of 3.8%, ultrasonic pulse velocity of 4.79 km/s and the lowest freeze–thaw strength loss (4.8%); the highest formulation (M12) was marginally better in the 90-day sulfate test (1.9% versus 2.0% strength loss). Conversely, the highest activator formulation (Si/Al = 3.0, SS/SH = 2.5) slightly reduced strength and increased shrinkage and freeze–thaw strength loss relative to the intermediate one; a viscosity-related limitation of ion mobility is a possible but unverified explanation. These outcomes show that precursor blending and activator formulation strongly affect the laboratory performance of ambient-cured fly ash–GGBFS geopolymer concrete; structural suitability, field durability and environmental benefit were not assessed.

Materials doi: 10.3390/ma19224828

Authors: Jozef Mikita Petr Baron Jozef Maščenik Dušan Manduľák Ján Manduľák

This paper presents a numerical analysis of the filling and packing processes, cooling behavior, shrinkage, and warpage in a large-scale injection-molded component produced from polypropylene filled with 40% talc. Simulations were conducted using Autodesk Moldflow Insight 2021 to evaluate process behavior and identify potential dimensional quality issues during injection molding. The simulation model encompassed the filling, packing, and cooling phases, as well as the resulting warpage of the molded part. The Moldflow report listed a fill time of 3.18 s and a filling pressure requirement of approximately 62 MPa under the selected processing conditions. The predicted volumetric shrinkage ranged from 0.20% to 12.65%, and local areas with an elevated risk of sink marks, air traps, and weld lines were identified. The cooling analysis showed localized regions of elevated cycle-averaged temperature on the mold side of the part–mold interface as well as regions with longer predicted times until the specified polymer ejection temperature was reached. The maximum predicted warpage reached 2.60 mm. Dimensional measurements showed that all evaluated dimensions were within the prescribed tolerances in the measured production batch, although preliminary process-capability indices varied among the monitored characteristics, with several values below the specified acceptance criterion of Cpk > 1.67, including values below 1.0. Optical 3D scanning provided complementary experimental information on the geometric deviations of the manufactured parts; a quantitative validation of the Moldflow warpage predictions was not possible with the available data. The numerical analysis employed a substitute Moldflow database material model because a complete material model for the actual production grade was unavailable. Therefore, the quantitative transfer of the predicted shrinkage and warpage values to the production material has not been established. The simulation results provide preliminary spatial guidance for assessing the mold configuration, whereas quantitative shrinkage and warpage predictions require reassessment using a material model based on experimentally determined data for the actual production grade.

Materials doi: 10.3390/ma19224829

Authors: Lintao Cao Jiawei Yan

Traditional height-limiting warning barriers address the issues of susceptibility to damage and difficulty in operation and maintenance. This paper proposes a rubber-tube-suspended height-restriction frame. Based on the LSDYNA explicit dynamics platform, a finite element model for an over-height vehicle height-restriction frame was developed to simulate collisions between over-height vehicles and the rubber-tube height-restriction frame. The model systematically analyzes the collision response patterns under full-width frontal collisions and lateral collisions with offsets of 1/2 and 1/4. The results indicate that a frontal collision consists of two concentrated contact phases: an initial high-intensity impact followed by a secondary low-intensity impact. During these phases, the maximum contact reaction force reaches 148.3 kN, providing effective tactile feedback for the driver without damaging the vehicle’s roof steel structure. The secondary impact occurs during the phase where the vehicle and the rubber tube move in the same direction, at which point the peak contact force drops to 35 kN. This energy dissipation is attributed to the combined effect of reduced relative velocity at the contact interface and the unloading of tangential slip. Energy analysis shows that impact kinetic energy is dissipated gradually through a hierarchical process: it is first converted into strain energy, and subsequently into frictional energy, rotational kinetic energy, and gravitational potential energy. Among these dissipation pathways, frictional energy at the vehicle-tube interface (approximately 3.0 × 106 N × mm) dominates in the early stage, whereas frictional energy at the tube–beam interface (approximately 3.8 × 106 N × mm) becomes the primary dissipation mechanism during the long-period oscillation stage. The maximum von Mises equivalent stress in the rubber component is 1.678 MPa, providing sufficient safety margin. Offset collisions can reduce peak contact forces by 32.6–46.5%, although local stresses increase slightly. However, under all test conditions, the maximum von Mises stress in the rubber component remains below the material’s tensile strength, thereby ensuring a sufficient safety margin. This suspended rubber-tube-type high-speed limit warning barrier provides effective contact warning under a variety of impact conditions while minimizing damage to both the vehicle and the barrier itself. The research findings provide a quantitative basis for the design of passive high-speed limit warning facilities.

Materials doi: 10.3390/ma19224827

Authors: Dongqiao Shao Cong Liu Li Tian Kunjie Wang Kai Cui Han Dong Qifeng Li

Wetting–drying cycles threaten the integrity of earthen heritage and its repair materials. This study examined the effects of initial water content and drying temperature on crack evolution in earthen-site soil amended with a laboratory-developed water-soluble polymer (designated LST). Untreated and LST-amended specimens underwent ten cycles at initial water contents of 11%, 16%, and 21% and drying temperatures of 25 and 35 °C. Image analysis quantified crack geometry, network topology, and cumulative cracking, complemented by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In the analyzed images, LST reduced the mean final crack area ratio by 31.7–70.1% and crack length density by 35.7–69.5%. Cumulative cracking exposure, estimated from six observation points, was 40.0–71.3% lower with LST. Local connectivity varied with the test conditions. Higher initial water contents generally intensified intermediate- and late-stage cracking, whereas higher temperatures increased crack area and equivalent width without a corresponding increase in length density. Among the three initial water contents tested, relative suppression was strongest at 16% and weakened during later cycles at 21%. After the first drying stage, SEM showed particle clusters and fine particles in interparticle gaps in multiple fields of the amended soil. The XPS spectra differed in the C 1s and Ca 2p regions, and XRD detected no identifiable new crystalline phase. Local particle contacts may help restrict crack extension, although particle displacement and polymer transport during rewetting were not measured. This study can inform the performance evaluation of new materials for the consolidation of earthen heritage sites.

Materials doi: 10.3390/ma19224826

Authors: Yonghui Wang Fengxiang Wang Renzhan Zhou Chuang Cai Rongji Zhou Yuanchao Ou Dejian Wang Congcong Wu

Lightweight ultra-high-performance concrete (LUHPC) can reduce structural self-weight, but porous aggregates may compromise strength and transport resistance. This study evaluates shale ceramsite as both a lightweight aggregate and an internal-curing reservoir. Four mixtures were compared: quartz-sand UHPC (UH), dry-ceramsite LUHPC (LUC), dry ceramsite with additional free water (LUC-ad), and pre-wetted ceramsite (LUC-pr). At 7 days, LUC-pr maintained an internal relative humidity (IRH) of 87%, versus 74% for LUC. At 28 days, LUC-pr achieved compressive and flexural strengths of 128.1 and 22.0 MPa, 4.1% and 7.8% above UH. Its autogenous and dry shrinkage were reduced by 51.2% and 32.0%, respectively. Its cumulative mercury intrusion volume and electrical charge passed were 0.048 cm3/g and 917.3 C. Compared with LUC, LUC-pr increased compressive and flexural strengths by 23.1% and 31.0%, reduced cumulative intrusion volume by 34.2%, and reduced charge passed by 30.3%. Conversely, additional free water increased dry shrinkage and charge passed. Overall, storing water in pre-wetted ceramsite provided a better balance among moisture regulation, strength, dimensional stability, and transport resistance than simply increasing free-water content.

Materials doi: 10.3390/ma19224825

Authors: Long Ma Shen Zuo Jin Li Henggen Zhang Junwei Bi

Moisture-sensitive expansive tuff spoil is difficult to utilize directly in cement-stabilized pavement bases because of its susceptibility to water-induced deformation and associated mechanical and volumetric instability. This study developed an organic–inorganic stabilization system based on sodium silicate nonahydrate (Na2SiO3·9H2O) and cationic polyacrylamide (CPAM) and established a staged screening–validation framework combining swelling, mechanical, shrinkage, microstructural, and field evaluations. Within the tested range, the formulation containing 5.0% Na2SiO3·9H2O and 0.5% CPAM reduced the free swelling rate from 5.0% to 0.517%, corresponding to an 89.7% reduction. At 28 d, the mean unconfined compressive strength (UCS), splitting tensile strength (STS), and compressive resilient modulus were 15.61%, 27.0%, and 7.9% higher, respectively, than those of the cement-stabilized control. After Holm adjustment, STS showed statistically significant improvements at all tested curing ages, whereas UCS differed significantly only at 14 d, and compressive resilient modulus showed no statistically significant differences. The 90-d cumulative drying shrinkage strain (CDSS) decreased by 37.8%, while the thermal shrinkage coefficient (TSC) remained lower than that of the control over the tested temperature range. XRD and SEM–EDS analyses indicated that the dominant crystalline phases remained essentially unchanged, while qualitative SEM observations revealed a more compact interparticle morphology and fewer visible macropores in the modified material. These observations suggest possible contributions from improved interparticle bonding and interfacial regulation to the overall performance improvement. A 267-m full-scale expressway test section constructed using double-layer continuous paving achieved upper- and lower-layer compaction degrees of 98.6% and 98.4%, respectively, an average 7-d field UCS of 5.16 MPa, and a surface-evenness acceptance rate above 96%. These results support the feasibility of utilizing moisture-sensitive tuff spoil in cement-stabilized pavement bases under the tested laboratory and field conditions, providing evidence of its constructability and satisfactory early-age performance.

Materials doi: 10.3390/ma19224824

Authors: Xiaochen Zhang Jun Yao Shang Wang Qiang Wu Shuai Su Baorui Du

This study adopted laser melting forging (LMF) technology to repair surface cracks on X80 high-strength steel pipes. LMF technology combines laser cladding (LC) with in situ laser shock peening (LSP), achieving strengthening and material forming simultaneously. This study innovatively utilized a galvanometer to adjust the size of laser shock spots and the high-frequency scanning path, achieving high-efficiency strengthening along the specific isothermal zone around the molten pool. By adjusting technological parameters, a high-density microstructure can be achieved. When the edge of the molten pool is impacted, microdefects (such as pores) can be noticeably reduced, and the grain size can also be significantly refined. This is mainly attributed to the fact that the high-frequency forging induces flow in the molten pool, promoting the escape of bubbles and causing the breakup of dendritic crystals. Compared with LC repair layers, the microhardness of the LMF repair layer increased by 10%, and its residual compressive stress increased by 62.6%. These improvements enhanced the resistance to crack propagation, and the average fatigue life was extended by more than 100% under a stress of 700 MPa ultimately. Meanwhile, fracture morphologies indicate that LMF significantly reduced fatigue sources such as microdefects. A finer-grained microstructure increases resistance to crack propagation. The research provides a systematic explanation of the mechanism and technical support for the application of LMF technology in remanufacturing engineering.

Materials doi: 10.3390/ma19224823

Authors: Ali Mardani Hatice Gizem Şahin Mohammad Hematibahar Viroon Kamchoom Raja Rizwan Hussain

The structural application of 3D-printed concrete remains limited by the difficulty of integrating reinforcement with layer-wise fabrication without interrupting automation or restricting geometric freedom. This study critically examines existing reinforcement strategies for 3D-printed concrete (3DPC), focusing on their mechanical contributions, fabrication compatibility, and practical limitations. Based on the identified research gaps, the 3D-Printing Hybrid Concrete Technique (3DPHT) is discussed as a potential future framework combining 3D-Printing Concrete (3DPC) with 3D-Printed Reinforced Concrete (3DPRC). The concept is based on coordinating printable cementitious materials with digitally fabricated reinforcement, including truss, honeycomb, re-entrant, chiral, and rotating geometries. Particular attention is given to auxetic structures because their negative Poisson’s ratio enables geometry-dependent confinement, stress redistribution, crack control, deformation capacity, and energy dissipation. The reviewed studies show that the effectiveness of 3DPRC depends on the combined influence of reinforcement material, topology, orientation, bond, and printing parameters rather than on reinforcement strength alone. Polymeric systems offer high geometric flexibility, while continuous-fiber thermoplastics and metallic systems provide higher stiffness and tensile capacity. Existing findings also indicate that architected reinforcement can improve flexural, compressive, interlayer, and post-cracking behavior under specific configurations. However, a critical comparison of existing approaches reveals persistent challenges related to reinforcement continuity, reinforcement placement, geometric compatibility, and process automation. These limitations provide the rationale for exploring more integrated reinforcement strategies. Within 3DPHT, reinforcement is treated as part of the digital fabrication strategy rather than as a separate construction stage. However, large-scale implementation remains constrained by fabrication accuracy, reinforcement–matrix bond, polymer durability, fire resistance, cyclic and seismic behavior, production rate, and cost. Overall, 3DPHT provides a basis for moving from printing concrete geometry toward digitally fabricated reinforced cementitious systems.

Materials doi: 10.3390/ma19224821

Authors: Ziyi Li Zhen Dai

Enhancing the flexural strength of Portland cement pervious concrete (PCPC) is considerably more difficult than improving its compressive strength, and this parameter critically limits the application of PCPC to highway pavements. This study investigated how various admixtures modify the flexural strength of PCPC under a fixed aggregate gradation, with the analysis grounded in the properties of the corresponding cement mortars and in the apparent density of the PCPC itself. The mechanical behaviour of cement pastes at five water-to-cement (W/C) ratios and of cement mortars incorporating single or multiple admixtures was characterized first; the flexural and compressive strengths of sixteen PCPC mixtures were then related to their connected porosity and apparent density. The results show that (1) regulating the cement hydration process raised the flexural strength of the cement paste by up to 43.7% while reducing its compressive strength by less than 2%; (2) a trade-off between flexural and compressive strength exists for both the cement mortars and the PCPC; (3) under the fixed gradation, the apparent density—used here as an indirect indicator of the compaction state—governed the flexural-strength enhancement, and the highest flexural strength of 4.05 MPa was achieved by the combined admixture RA (Reinforcing Agent) + SF (Silica fume) + BF (Basalt fibres), corresponding to a 12.5% improvement over the control mixture (3.60 MPa); and (4) the modification effect was most pronounced when the apparent density remained below 2.28 g/cm3, with an optimum apparent-density band of approximately 2.28–2.35 g/cm3 identified for maximizing the flexural strength. Collectively, these findings establish a quantitative basis—including a novel threshold apparent density of ≈2.28 g/cm3—for selecting admixtures and controlling compaction to maximize the flexural strength of pervious concrete pavements.

Materials doi: 10.3390/ma19224822

Authors: Yingying Ma Rui Liu Bingxuan Li

Laser radiation near 3 μm overlaps with a strong water absorption band and is useful for medicine, materials processing, and mid-infrared frequency conversion. This review examines continuous-wave (CW) and Q-switched Er3+- and Ho3+-doped solid-state lasers in this wavelength region, with emphasis on the relationships between ion spectroscopy, host thermal properties, and laser performance. The advantages and limitations of different gain media and doping systems are compared in terms of lower-level depletion, energy transfer, pump absorption, and heat removal. Er3+ systems can use upconversion to deplete the lower laser level and recycle energy, whereas Ho3+ systems commonly employ Pr3+ codoping to reduce self-termination. Progress in CW and Q-switched operation is reviewed for individual host materials, and the roles of pumping geometry, gain-medium structure, and Q-switching method are discussed. The reported results highlight the need to assess CW power and efficiency together with pulse energy, duration, and repetition rate under their respective operating conditions. Future improvements require coordinated optimization of energy-level dynamics and pump utilization, host selection and thermal management, and pulse-generation devices. Long-term stability, damage resistance, wavelength control, and compact integration are also important for practical near-3-μm sources.

Materials doi: 10.3390/ma19224820

Authors: Wiktor Wciślik Wioletta Raczkiewicz

The aim of this paper was to assess the effect of ground-penetrating radar (GPR) wave polarization on the detection of reinforcement corrosion in concrete structures and to analyze the feasibility of improving the sound/corroded separation by fusion of selected signal parameters. The amplitude and propagation time of the surface wave and the wave reflected from the reinforcement were studied in two orthogonal polarizations: parallel (L) and perpendicular (T) to the rebar axis. The obtained results showed that, regardless of polarization, all time parameters increased with corrosion progression. Corrosion-related amplitude changes were different: a decrease was observed in the L polarization, while an increase was observed in the T polarization. Statistical analysis indicated that time parameters were the most effective in detecting corrosion, while surface wave amplitude was the least sensitive indicator of degradation. Furthermore, it was shown that data fusion in a single polarization led to only a moderate improvement in the separation ability of GPR parameters. This work demonstrates for the first time that fusion of parameters (especially time) from two orthogonal GPR polarizations significantly improves the separation ability of sound and corroded samples, indicating the complementary nature of data from both polarization configurations.

Materials doi: 10.3390/ma19224819

Authors: Temirlan Alimbekuly Laila Sulyubayeva Daryn Baizhan Gulsym Bektasova Balym Alibekova Elzhan Birzhan

This study investigates the effect of amorphous silicon dioxide (SiO2) derived from rice husk on the structure and properties of micro-arc oxidation (MAO) coatings formed on commercially pure Grade 2 titanium. The coatings were produced in a phosphate electrolyte with SiO2 concentrations of 0, 5, and 10 g/L. The effects of SiO2 content on the microstructure, porosity, tribological characteristics, and corrosion resistance of the coatings were investigated. The results showed that the addition of SiO2 reduced the porosity from 7.07 ± 0.5% for the coating without additives to 6.27 ± 0.4% and 6.10 ± 0.43% at concentrations of 5 and 10 g/L, respectively. The coating formed at an SiO2 concentration of 10 g/L exhibited a stable coefficient of friction and a 27% reduction in wear rate compared with the coating produced without SiO2 addition. X-ray diffraction analysis revealed that anatase TiO2 was the predominant crystalline oxide phase. Increasing the SiO2 concentration was accompanied by a decrease in the average coating thickness from 34.39 ± 3.56 to 29.16 ± 4.06 μm. Electrochemical tests in a 3.5 wt.% NaCl solution showed that the coating containing 10 g/L SiO2 exhibited the lowest corrosion current density (1.9 × 10−9 A/cm2) and the highest polarization resistance (2.71 × 106 Ω·cm2). These findings demonstrate the potential of rice husk-derived amorphous silicon dioxide for modifying MAO coatings on titanium to improve their functional properties.

Materials doi: 10.3390/ma19224818

Authors: Sonia Garrido-García Virginia Santamarina-Campos Laura Osete-Cortina Laura Fuster-López

Previous studies have shown that CO2 snow blasting can remove loose particulate deposits from paper, but its performance on more strongly retained graphic marks remains unclear. This study evaluated charcoal and HB-grade graphite pencil marks (H and B denote hardness and blackness, respectively) on cotton paper and assessed treatment effects on cotton, kraft and coated papers. Specimens were treated at nominal pressures of 1 and 3 bar. Digital microscopy, CIELAB colourimetry, gloss, surface pH, wettability, attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy and field-emission scanning electron microscopy (FE-SEM) were used to characterise cleaning response and substrate condition. At 1 bar, charcoal was substantially reduced, whereas HB graphite persisted despite partial attenuation. At 1 bar, the cotton-paper specimen showed a low colour difference and no appreciable morphological difference in the examined FE-SEM field relative to the untreated specimen. In contrast, kraft and coated papers showed morphological, optical or wetting changes at the same pressure. At 3 bar, FE-SEM observations indicated surface alterations in the examined fields of all three substrates, suggesting lower compatibility with the tested paper specimens. The observations indicate that CO2 snow blasting may reduce loosely retained carbon-based deposits on suitable paper surfaces, whereas more strongly entrapped graphite marks resist removal. Treatment parameters should therefore be selected according to both deposit retention and substrate structure.

Materials doi: 10.3390/ma19224817

Authors: Pawel Pawlus Slawomir Wos Wieslaw Żelasko Rafal Reizer

Abrasive wear is responsible for a substantial part of wear-related failures. Dry sand/rubber wheel tests are typically applied to analyze the abrasive wear resistances of materials. Volumetric wear, preferable to mass loss, is typically determined indirectly using the gravimetric method. It is not possible to obtain information on the amount of wear in various places of wear scar with this technique. There are other deficiencies in the gravimetric method of wear measurement. The profilometric technique based on the measurement of the areal (3D) topography of a surface allows us to directly measure the volume of a wear scar, including information on wear amount at several places of a wear track. The procedure to determine the wear volume on the basis of the measurement of the 3D surface texture is described. To shorten the time for 3D surface topography measurement, volumetric loss can be precisely evaluated based on the measurement of several profiles along the sliding direction. The proposed number of profiles was six—the relative errors were less than 5%.

Materials doi: 10.3390/ma19224816

Authors: Todor Gavrilov Todor T. Todorov Mihail Zagorski Yavor Sofronov

The machining of technical ceramics remains challenging due to the need to achieve high dimensional accuracy, good surface quality, and acceptable tool life when processing hard and brittle materials. This study investigates the influence of cutting parameters on the machining time, dimensional accuracy, surface roughness, and tool wear during ultrasonic-assisted milling of aluminum oxide (Al2O3) ceramics. A planned experiment comprising nine experimental trials is performed using a DMG Ultrasonic Linear 20 machine and a specialized diamond cutting tool with a diameter of 1.2 mm. The investigated parameters included cutting speed, feed rate, and depth of cut, varied within the ranges of 65–85 m/min, 30–50 mm/min, and 0.03–0.05 mm, respectively. A narrow channel with nominal dimensions of 1.5 mm in width, 11.5 mm in length, and 1.5 mm in depth is machined in each specimen. Dimensional measurements, surface roughness evaluation, and tool wear monitoring are performed to assess process performance. All nine specimens met the specified dimensional tolerances. The measured arithmetic mean surface roughness (Ra) ranged from 0.183 to 0.298 µm, while tool length wear remained between 0.001 and 0.003 mm. The shortest machining time is 16 min and 15 s, achieved with a cutting speed of 85 m/min, a feed rate of 50 mm/min, and a depth of cut of 0.05 mm. Compared with the initial machining conditions, this combination reduced machining time by approximately 62% while maintaining dimensional compliance and a low surface roughness. The results provide a comparative experimental reference for the investigated machining configuration, although the absence of replicate trials limits the assessment of process variability and repeatability.

Materials doi: 10.3390/ma19224815

Authors: Aleksander Iwaniak Andrzej Posmyk Łukasz Bąk

The paper presents the influence of the presence of glycerol on the structure and selected properties of anodic oxide coatings produced on aluminum tapes. These tapes are used to produce windings of electromagnets, transformers and direct drive motors of electric vehicles and timing systems of combustion engines. Replacing copper windings with aluminum strips reduces the weight of the coils by almost half. Replacing pressboard insulation with an anodic oxide coating allows the application temperatures of such coils to be increased (from 105 °C to several hundred). The unit breakdown voltage of anodic oxide coatings produced in sulfuric acid electrolyte (32–52 V/µm) used as insulation is similar to that of the insulation used so far (30–100 V/µm). The addition of 15% glycerol to an electrolyte containing 15% H2SO4 allows the production of coatings of the same thickness with half the energy consumption. Due to its higher viscosity than water, glycerol settles on the walls of the produced oxide cells, reducing their secondary dissolution by the electrolyte.

Materials doi: 10.3390/ma19224814

Authors: Tadeusz Chyży Czesław Miedziałowski Krzysztof Robert Czech Marcin Orłowski Dai Wang Hai Zhang Jacek Karpiesiuk

Cable post-tensioned concrete roof girders constructed in Poland from the 1950s to the 1970s remain in service despite concerns regarding the long-term durability of their prestressing cables. This study investigated the feasibility of using deflection monitoring supported by numerical modeling as an indirect diagnostic method for assessing the technical condition of cable post-tensioned concrete girders. A finite element model of a 24 m span KBOS-24 cable post-tensioned concrete girder assembled from precast segments was developed and verified against in situ tachymetric measurements performed on existing girders in operating industrial facilities. Numerical simulations were conducted to evaluate the effects of complete loss of prestressing force in individual cables and thermal actions on girder deflection. Complete loss of prestressing force in one cable increased the deflection by approximately 2.5–4.0 mm. Temperature differences between the top and bottom chords produced deflections of comparable magnitude, reaching approximately 4.5 mm under the observed service conditions. The results indicate that long-term monitoring of girder deflections can provide valuable information on changes in prestressing cable condition, provided that thermal effects are simultaneously monitored and accounted for when interpreting the measurements.

Materials doi: 10.3390/ma19224813

Authors: Hanjing Ma Baohua Tian Yu Ma Man Gao Guannan Han Zhetao Zhang Yuan He

Textile sensors offer a route to physiological monitoring through clothing, with practical performance determined by material properties, sensing interfaces, and stability during movement, perspiration, and repeated use. This review examines conductive fibers, polymer composites, soft ionic materials, and textile architectures for electrophysiological, respiratory, movement, temperature, and sweat monitoring. It compares application-specific material and integration strategies and examines how artificial intelligence supports composition selection, inverse design, and signal interpretation. An application-oriented framework links these choices to measurement quality, service life, repair, and recovery. Recurring trade-offs involve sensitivity and stability, conformal contact and solvent retention, and durable bonding and component separation. Data-driven methods support candidate screening and signal analysis, with their performance established through experimental validation. Heterogeneous protocols and evaluation settings limit direct comparison and translation to long-term garment use. Future priorities include durable interfaces, designs facilitating maintenance and recovery, validation across users and manufacturing batches, combined wear-and-care testing, and assessment of recovered materials in subsequent devices. These efforts would strengthen evaluation of monitoring reliability and environmental benefits over the intended service life.

Materials doi: 10.3390/ma19224812

Authors: Leigang Han Mingzhi Yao Junxia Wu Zheng Lin Rong Li Xiangrong Chen

To address blurred boundaries, pronounced texture variations, and strong background interference in images of weld seams produced by local dry underwater MIG welding after cooling, this study proposes an improved YOLO11 weld seam detection model, termed YOLO-UWI. First, a high-resolution P2 detection branch is introduced into the neck to preserve weld-seam edges and local spatial details. Second, C3k2-Strip modules are incorporated at the P3 and P4 stages of the backbone to enhance extraction of elongated morphology, continuous texture, and directional features. Finally, an Efficient Channel Attention (ECA) mechanism is added to the P2 detection branch to adaptively recalibrate channel weights, emphasize weld-related features, and suppress background interference. Ablation and comparative experiments are conducted using the original YOLO11 as the baseline. The improved model achieves Precision, Recall, and mAP@0.5 values of 82.2%, 64.1%, and 74.3%, respectively, improving by 0.6, 6.5, and 4.0 percentage points over the original YOLO11. Compared with YOLOv8, YOLOv10, YOLO12, and YOLO26, YOLO-UWI also achieves higher overall detection accuracy. The results demonstrate that the proposed model effectively improves detection accuracy and localization for weld seams produced by local dry underwater MIG welding and provides a reliable technical solution for weld-quality inspection.

Materials doi: 10.3390/ma19224811

Authors: Qiuhui Wang Yifei Hou Yifan Ma Jinling Chen Ziyuan Niu Gaowen Sun Yazhou Wang Binbin Zhang

This review examines the valorization of municipal solid waste incineration bottom ash (MSWI-BA) in alkali-activated slag (AAS) systems, focusing on the fine fraction (BAF) as a partial precursor and its high-temperature performance. The roles of activator type, silicate modulus, alkali equivalent, and precursor composition in governing thermal resistance are analyzed. Molecular dynamics simulations of C-A-S-H degradation are also discussed. Key knowledge gaps and future research directions are identified. The analysis identifies key factors governing the thermal resistance of BAF-incorporated systems, including activator type (with K-based systems often showing advantages), silicate modulus, alkali content and precursor type. Furthermore, the role of molecular dynamics (MD) simulations in elucidating the degradation mechanisms of the main binding gel, calcium aluminosilicate hydrate (C-A-S-H) at elevated temperatures is discussed. The synthesis of current knowledge indicates that while the proposed utilization pathway provides a promising route for waste recycling and developing lower-carbon construction materials, further research is needed to fully understand the long-term performance and address challenges related to the variable composition of MSWI-BA.

Materials doi: 10.3390/ma19224810

Authors: Przemysław Mania Miłosz Stasiak Franciszek Choja Magdalena Broda

Wood is a hygroscopic material, and water uptake causes dimensional changes associated with swelling. When swelling is restrained, internal stresses and swelling pressure develop, which may contribute to cracking, deformation and damage to wood elements. Knowledge of swelling pressure is therefore important for assessing the dimensional stability and appropriate application of exotic wood, particularly under variable humidity conditions. Unfortunately, comparative data for swelling pressure of tropical hardwoods and plantation-grown paulownia remain limited. Therefore, this study examined the magnitude, anisotropy, and time-dependent development of swelling pressure in sapele, khaya, framiré, tauari, abura, mansonia, and paulownia wood submerged in water while the wood was restrained from swelling. Six replicates of each wood species in each direction were examined. Maximum tangential and radial pressures were measured and related to wood density and compressive modulus of elasticity (MOE). Swelling pressure was measured from oven-dry starting conditions until the maximum swelling pressure was reached, as indicated by stabilisation or a decrease in the measured force. Maximum swelling pressure ranged from 1.81 to 7.00 MPa tangentially and from 1.17 to 8.85 MPa radially. Sapele exhibited the highest pressures in both directions (7.00 and 8.85 MPa), whereas paulownia showed the lowest (1.81 and 1.17 MPa). Pressure development differed among species: paulownia, abura, and mansonia reached comparatively low maxima rapidly, while sapele and khaya developed higher pressures more slowly. Tauari combined rapid initial development with a high maximum pressure. Following their maxima, pressures declined slightly. Swelling pressure increased significantly with wood density in both tangential (R2 = 0.68) and radial (R2 = 0.62) directions. Its relationship with MOE was significant tangentially (R2 = 0.61), but not radially. Substantial differences among species of similar density demonstrate that density and stiffness alone cannot reliably predict swelling pressure. The results indicate that swelling pressure is governed by a combination of species-specific characteristics, anatomical direction, and time-dependent behaviour, with wood density and compressive stiffness providing only partial explanations for the observed variability. These wood features need to be considered while designing moisture-exposed, dimensionally constrained wood products. Further research focusing on the detailed characterisation of wood anatomy and moisture transport properties is necessary to clarify the mechanisms responsible for differences in swelling pressure between species and anatomical directions, and to improve prediction under restrained moisture-induced swelling conditions.

Materials doi: 10.3390/ma19224809

Authors: Kristijan Šket Mirko Ficko Timi Karner Rok Belšak Janez Gotlih

Wire arc additive manufacturing (WAAM) bead geometry is commonly represented using global descriptors, even though local bead dimensions can vary substantially along the deposition path. This study presents a spatially explicit framework for extracting and predicting longitudinal bead geometry from three-dimensional laser-scanned point clouds. Fifty single bead deposits were produced over a full factorial parameter range of 65–155 A welding current and 20–40 cm/min travel speed. A dedicated point cloud workflow was used to isolate individual beads, establish local substrate references, extract transverse profiles, and calculate bead width, robust height, and cross-sectional area at multiple longitudinal positions. Machine learning models were utilized to model welding current, travel speed, and normalized longitudinal geometric position as predictors. Linear ridge regression, quadratic ridge regression, and Gaussian process regression were evaluated using repeated nested grouped cross-validation, with complete beads retained as independent validation units. The selected framework achieved mean held-out bead R2 values of 0.981 for width, 0.965 for robust height, and 0.985 for cross-sectional area. Pipeline-level holdout evaluation showed that prediction at entirely unseen torch travel speed levels was more difficult than prediction of unseen beads within the sampled process domain, particularly for width and robust height at the domain boundaries. The results demonstrate that WAAM bead geometry can be represented and predicted as a longitudinally varying quantity rather than a single global value, providing a basis for more spatially resolved process planning, geometric simulation, and future adaptive control.

Materials doi: 10.3390/ma19224808

Authors: Dosmurat Aitkulov Anar Mukhametzhanova Akmaral Rakhym Aliya Margulanovna Alimzhanova

Efficient vanadium recovery from carbonaceous siliceous ores is challenging because of the complex mineral occurrence of vanadium and the high chemical resistance of the quartz-rich matrix. In this study, a two-stage processing scheme comprising atmospheric decarbonization–neutralization followed by oxidative autoclave leaching was developed for vanadium-bearing quartzite from the Balasausqandiq deposit (Kyzylorda Region, Kazakhstan). Under the optimized autoclave conditions (140 °C, 120 min, 150 kg t−1 H2SO4, 5 kg t−1 HNO3, 3 atm O2, and a solid-to-liquid ratio of 1:1), 88.4% of vanadium was extracted. XRD and SEM–EDS analyses revealed preferential dissolution of reactive V- and Fe-bearing minor phases, while the quartz-rich matrix remained largely preserved, producing a residue containing 72.5 wt.% SiO2 and <0.01 wt.% carbon. Among the shrinking-core models tested, the product-layer diffusion model provided the closest fit to the available kinetic data (R2 = 0.9787–0.9865). A three-temperature Arrhenius analysis over 120–140 °C yielded a preliminary apparent activation energy of 54.55 kJ mol−1. Thermodynamic calculations supported the oxidative pathway, showing that V(IV) oxidation by O2 is favorable at 140 °C (ΔrG° = −75.1 kJ mol−1). The combined results indicate selective acid–oxidative dissolution of accessible vanadium-bearing phases followed by increasingly restricted extraction from resistant mineral domains within the silica-rich residual matrix. The proposed process integrates efficient vanadium recovery with the generation of a silica-rich residue with potential for use as a secondary metallurgical feedstock, subject to further evaluation.

Materials doi: 10.3390/ma19224807

Authors: Hao Wang Biliang Zhang Haidong Zhang Jiejun Yuan Yongmei Wang Leiying Han Xiaoyan Liu

Surface voids and formwork corrosion affect the appearance and maintenance of fair-faced concrete. This study evaluated an integrated waterborne release agent containing a rapeseed-oil oil-in-water emulsion, a poly (N-isopropylacrylamide-co-acrylic acid) [P(NIPAM-co-AA)] modifier, and triethanolamine borate. Emulsifier blends were screened by 24 h phase stability, followed by a 16-run, five-factor, four-level emulsification screen. The selected formulation was S80:OP-10 = 9:1 at 6 wt% total emulsion, processed at 60 °C for 70 min. On steel formwork vibrated for 120 s, three technical repeats gave a lower surface-void area fraction for the integrated formulation than for a commercial product (0.90 ± 0.10% versus 2.20 ± 0.18%; 59.1% relative reduction). The void-area share for equivalent diameters ≤1 mm increased from 73.8 ± 2.5% to 88.2 ± 2.0%. In a controlled-humidity cast-iron rust-spot test, 2.5% triethanolamine borate gave a longer time to first rust than diethanolamine borate (1920 ± 95 versus 1440 ± 80 min). A field comparison showed lower surface-void fractions on the treated pier (0.037 ± 0.008%) than on the untreated reference (0.242 ± 0.035%). These results identify a candidate formulation for surface finishing and cast-iron corrosion screening and support subsequent independent-batch, release-force, and steel-formwork validation.

Materials doi: 10.3390/ma19224806

Authors: Nawal A. Alshehri

Porous functionally graded material (FGM) sandwich beams combine ceramic heat resistance with metal toughness, but their through-thickness grading and porosity make their response in thermal environments sensitive to modelling assumptions. This paper examines the nonlinear transient response of porous FGM sandwich beams with elastically restrained ends under suddenly applied loads in thermal environments. A refined higher-order shear deformation theory (HSDT) is used with temperature-dependent properties, even and uneven porosity distributions, and symmetric and asymmetric material layouts. In asymmetric layouts, bending–extension coupling and the thermal moment produce end moments that conventional one-term strong-form Galerkin approximations omit. A multi-term weak-form Galerkin approach is developed that retains these moments for arbitrary support locations, and it is validated against exact linear solutions and an independent nonlinear finite element model. The results show that the material layout through the thickness, rather than porosity or gradation alone, determines whether strong-form approximations are adequate. For asymmetric beams, neglecting thermal bending overestimates the peak deflection at elevated temperatures, and the deviation grows when the supports act at the neutral surface. Parametric studies clarify the effects of porosity, volume fraction index, face-sheet thickness, temperature, end restraint, foundation stiffness and initial imperfection.

Materials doi: 10.3390/ma19224805

Authors: Bo Xu Jie Li Wentao Yang Zhiju Chen

The bridge condition index (BCI) is a widely used indicator for highway bridge maintenance and rehabilitation decisions. However, BCI records are collected at irregular inspection intervals, and bridges differ substantially in type, geometry, age, and load-carrying history. Imposing an equally spaced representation through interpolation can introduce artificial observations and distort the timing information that is central to deterioration modeling. This study presents Bridge-CDE, a physics-informed neural controlled differential equation (CDE) with bridge-specific covariates for irregularly sampled BCI prediction. Construction year, span, bridge length, width, standard and measured frequencies, technical condition, and load grade are encoded as a covariate vector. A bounded exponential baseline provides a physics-informed continuous path, and the CDE integrates along the path derivative from the latest inspection to the target age. A residual readout anchored to the recent BCI and a linear deterioration trend stabilizes learning on short inspection sequences. Experiments use 3308 BCI observations from 735 bridges in the Henan Province of China, grouped by bridge for model evaluation. Bridge-CDE achieves an MAE of 1.066, RMSE of 1.643, R2 of 0.955, and MAPE of 1.213%. It is competitive with the strong tabular baselines and records the lowest MAE, RMSE, and MAPE, whereas random forest has a marginally higher reported R2 (0.957). Permutation-based sensitivity analysis shows that bridge type, deck condition, measured frequency, and construction year are among the most influential external inputs.

Materials doi: 10.3390/ma19224804

Authors: Roberto Simonelli Antonio D’Angelo Luigi Vertuccio Luigi Mollo Davide Nonis Sara Fasana Marco Zerbinatti Michelina Catauro

The stone industry generates a large amount of sawing sludge (SS). Geopolymers (GPs) offer a circular pathway by incorporating SS into their aluminosilicate networks, helping to mitigate the environmental impact on the construction industry. This preliminary study addresses the feasibility of using four types of SS (SS1–SS4) in metakaolin-based GP formulation, evaluating the effect of two granulometries (75 µm < x < 125 µm and 125 µm < x < 300 µm) on GP properties. Geopolymerization is confirmed through Fourier-transform infrared (FT-IR) spectroscopy, while integrity and boiling water tests confirm that all samples maintained their integrity under the selected preliminary experimental conditions. Microstructural and mineralogical characteristics, investigated by scanning electron microscopy (SEM) and wide-angle X-ray diffraction (WAXD), respectively, reveal heterogeneous microstructures characterized by the presence of unreacted crystalline particles. Thermal behavior, examined through thermogravimetric analysis (TGA) and derivative thermogravimetry (DTG), reveals total mass losses of approximately 15–18% up to 1000 °C, with an additional loss in the 500–800 °C range associated with carbonate decomposition, which is particularly evident in SS2, GP2/1, and GP2/2. Mechanical properties, through compressive strength tests, reveal higher values for GP2/1 (24.1 ± 0.4 MPa) and GP4/2 (24.7 ± 1.7 MPa) than for the GP0 control (22.5 ± 0.2 MPa). These preliminary findings support further investigations concerning the use of sawing sludges as fillers in sustainable alkali-activated materials.

Materials doi: 10.3390/ma19224803

Authors: Sergey A. Shumeyko Ilya V. Baimler Mark O. Paskhin Vasiliy S. Novikov Alexander V. Simakin Oleg V. Uvarov Sergey V. Gudkov Denis V. Yanykin

This study aims to develop a method for the heterovalent doping of hydroxyapatite (HA) with europium (III) ions using laser fragmentation of a micropowder in a liquid medium. The samples examined after laser fragmentation of the hydroxyapatite micropowder in liquid exhibited ultrathin nanosheets (with an approximate thickness of 2–5 nm) while retaining the hydroxyapatite crystal structure; furthermore, when the process is carried out in a europium nitrate solution, it leads to the preferential incorporation of europium (III) ions into Ca(I) sites. The phase homogeneity and structural evolution of the fragmentation-derived samples were investigated by Raman and FTIR spectroscopy. Raman spectroscopy revealed that laser treatment of the HA micropowder for 30 min in the presence of 2 mol% europium nitrate (sample Eu2%-HA) modifies the crystal lattice symmetry. Conversely, the FTIR Weiner-Shemesh crystallinity index increased reflecting ordering within the basal planes. The incorporation of Eu3+ ions was confirmed by fluorescence spectroscopy supporting the predominant stabilization of europium at the Ca(I) site. Dynamic light scattering, atomic force microscopy, and transmission electron microscopy combined with energy-dispersive X-ray spectroscopy mapping were used to investigate particle morphology and assess elemental homogeneity and dopant distribution.

Materials doi: 10.3390/ma19224802

Authors: Marek Wieruszewski Miłosz Jan Gendaszyk Adam Mikołaj Janiak Edmund Smolarek Maciej Sydor

Black poplar (Populus nigra L.) is a fast-growing hardwood whose use in furniture and joinery is limited by its low density and strength. This study combined bending tests with a laminated-beam analysis to quantify and generalize the effect of symmetric oak (Quercus robur L.) and ash (Fraxinus excelsior L.) veneer facings on poplar cores. 45 specimens (15 per group) were tested in three-point bending. Facing increased the density from 432 kg/m3 to 504 kg/m3 (oak) and 494 kg/m3 (ash) and the bending strength (MOR, 12% moisture content) from 63.5 MPa to 86.8 MPa (+37%) and 77.1 MPa (+21%) (Welch’s ANOVA, p < 0.001). A dimensionless transformed-section framework was developed in which strength gain equals the product of stiffness amplification, determined by the face fraction and the face-to-core modulus ratio, and the face-to-core ratio of failure strains. Inverse analysis yielded in situ face strengths of 97 MPa (oak) and 91 MPa (ash) and failure-strain ratios of 1.06 and 0.81, which explains why the stiffer ash facings produced the smaller strength gain. The framework predicts face-governed failure, in agreement with the observations, and shear stresses below the shear strength of poplar. For components of fixed depth, the mass-specific strength is maximized at face fractions of 0.15–0.25, where faced poplar outperforms both unfaced poplar and solid oak or ash; the tested oak-faced elements were close to this optimum. Closed-form conditions and design charts generalize these results to other face–core combinations.

Materials doi: 10.3390/ma19224801

Authors: Ming Zhao Ailian Zhang Linchun Zhang Lin Chi Xiaojian Gao

The setting of gypsum-based materials is governed by β-hemihydrate (β-HH) rehydration, yet a per-unit rate measurement is still lacking industrially. DFT places the four low-index faces of β-HH between 0.52 and 0.94 J m−2; the most stable, (010), is treated as the candidate rate-determining face. HPO42− binds to (010) 0.48 eV more strongly than water, whereas F− preferentially adsorbs on (001). Time-resolved XRD across four temperatures reveals two distinct kinetic stages; no single-exponent law is adequate, and the transition coincides with the end of the exothermic peak. Acoustic emission captures the same transition, with growth before and microcracking after, crossing at 34.1 ± 1.7 min. Acoustic energy tracks heat release almost linearly. A Bayesian observer built on this relation reproduced the Rietveld-derived degree of hydration on 48 specimens (R2 = 0.993; mean absolute percentage error 4.3%) and timed the stabilisation node at 96.8 ± 4.2 min against 95.4 ± 3.1 min by diffraction. On a board line (five days, 320 boards; before-and-after, not a controlled trial), the schedule driven by this measurement was associated with a lower strength coefficient of variation (4.6% vs. 8.4%) and lower curing energy (15.2 vs. 21.5 kWh m−2); restricting to inlet-temperature-matched days attenuated these to −38% and −22%.

Materials doi: 10.3390/ma19224800

Authors: Karol Durczak

Semitransparent thin-film photovoltaics can combine electricity generation, daylight transmission, and solar energy rejection, while passive radiative cooling introduces an additional requirement for atmospheric window emission. However, simultaneous functionality cannot be established by combining properties measured in separate devices. This study introduces spectral admissibility of multifunctional architectures (SAMA), an evidence-constrained method combining metric compatibility, non-compensatory admissibility, non-dominance screening, deterministic critical margins, and the identification of spectral-function gaps. Three directly comparable semitransparent organic photovoltaic states were assessed using average visible transmittance (AVT), power conversion efficiency (PCE), and total solar energy rejection (T-SER). The ABPF architecture achieved AVT of 49.62%, PCE of 12.19%, and T-SER of 77.49%, dominating the 11 nm Ag reference. The 40 nm TeO2 architecture remained non-dominated owing to its higher AVT of 50.86%. The critical symmetric perturbation for the ABPF–Ag PCE ordering was 0.175 percentage points. Independent transparent radiative cooling materials demonstrated high atmospheric window emissivity, but this property remains unverified for the photovoltaic states. SAMA distinguishes demonstrated performance, threshold-dependent admissibility, and unresolved integration potential, providing an upstream materials selection procedure for multifunctional glazing.

Materials doi: 10.3390/ma19224799

Authors: Fagen Li Yan Han Ying Zhen Anqing Fu Zhengfang Zhang Yuguang Cao

Failure analysis was conducted on a girth weld that cracked during pressure testing of a mechanically lined pipeline. A deep-hole flaw was found in the seal-weld region near the weld toe. Lack of fusion and small cracks were observed at the triple junction of the backing pipe, CRA liner, and seal weld, while martensitic microstructure and cold cracks were present in the filler and cover passes. The leakage crack consisted of multiple individual cracks: some initiated in the filler and cover passes and propagated toward the inner and outer surfaces, while others initiated at the triple junction and extended in both directions. The failure was attributed to improper welding procedures and non-compliant operations, which resulted in deep-hole flaws, lack of fusion, microcracks, and martensitic microstructure within the weld joint. The combined action of internal pressure and welding residual stresses promoted crack propagation and coalescence. The martensitic regions in the filler and cover passes likely provided preferential paths for crack propagation.

Materials doi: 10.3390/ma19224798

Authors: Jingjing Wang Jian Yang

Melt convection strongly influences solidification microstructure, yet its three-dimensional interaction with evolving dendritic morphology remains insufficiently quantified. Here, a three-dimensional lattice Boltzmann–cellular automata (LBM–CA) model is developed to simulate the solidification microstructure of Fe–C alloys under forced convection. The LBM resolves melt flow, and the CA model employs a decentered-octahedron capture rule to track the solid–liquid interface. The capture rule is written for a general orientation; the present calculations use only (α,β,γ)=(0,0,0). The finite volume method solves heat and solute transport. Comparison with the Lipton–Glicksman–Kurz (LGK) solution shows that the simulated tip velocity in a quiescent melt approaches the analytical steady value. Under forced convection, the calculation is used to examine the directional difference in tip velocity, rather than as a validation against the same LGK value. The simulations reveal strong two-way coupling: forced convection thins the upstream solutal and thermal boundary layers while thickening them downstream, whereas the growing dendrite arms progressively obstruct and redistribute the surrounding flow. Increasing the inlet velocity makes this asymmetry more pronounced. At 0.0015 m/s, the upstream arm is longer than in the quiescent melt, the transverse arm is slightly longer, and the downstream arm is shorter. For the three inlet velocities examined, the downstream reduction is larger in magnitude than the upstream increase. These arm-length changes are numerical results for the present forced-convection calculations and are not compared with experimental measurements.

Materials doi: 10.3390/ma19224797

Authors: Duong Thi Bach Nguyen Hai Thanh Pham Thanh Tien Bui Hien Thi Thu Dang Thuy Thu Dang

Developing and expanding infrastructure along Vietnam’s central coast—a key driver of the marine economy—requires a type of concrete that is both highly durable in seawater environments and compatible with the marine ecosystem. To address this need, this study evaluates C60-grade concrete incorporating sulfate-resistant cement, 5% silica fume, and an L-arginine additive (designated as C60 HPEAC) in terms of its mechanical properties, chloride resistance, and capacity to support marine organisms. L-arginine (A) was added at 1–7% by mass of cement. The designation C60-iA (where i = 1–7) refers to a C60 HPC sample containing i % A. Laboratory tests included compressive and flexural strength, chloride penetration, SEM, XRD and A leaching, while field exposure at Da Nang and Nha Trang bays for 1–12 months was used to assess biological colonization via chlorophyll-a. Compressive and flexural strengths were determined in accordance with ASTM C39 and ASTM C78, respectively. The chloride penetrability of the concrete was evaluated in accordance with the TCVN 9337:2012 test method. Although the 28-day compressive strength of the A mixtures decreased by 1.78–18.8% relative to the control, all mixtures still satisfied the C60 grade, while chloride penetration resistance improved by 6.4–48.78%. Flexural strength decreased by 1.1–21.8% but remained within the insurance compliance with concrete grade specifications. Microstructural analyses revealed that higher A dosages (5–7%) significantly reduced the quantity and peak intensity of portlandite, which is attributed to the suppression of its crystallization and the enhancement of pozzolanic reactions. The moderate amount of CH is finely distributed within the A-containing specimens—sufficient to maintain a pH level that protects the steel—without aggregating into coarse, weakening crystals. Chlorophyll-a on specimen surfaces was two to four times higher than that of the control at A contents of 3–7%, indicating enhanced biological colonization. Leaching experiments were conducted on concrete specimens immersed in seawater representative of the coastal environment of Central Vietnam for periods of 30, 90, 150, and 180 days under laboratory conditions. The release rate of additive A decreased progressively from 90 to 180 days, and higher additive contents resulted in higher release rates. Among the tested mixtures, C60-7A exhibited the highest release rate, reaching 0.104 × 10−3 g/cm2/day after 180 days of immersion. Based on the leaching rate measured at 180 days, the average leaching-service life of the specimens investigated in this study was estimated to be approximately 10 years. The predictive models developed in this study indicate that the release process is sufficiently slow and sustained over time. Consequently, C60 environmentally active high-performance concrete (HPEAC) appears to be a promising material for marine infrastructure requiring both high durability and ecological compatibility in the coastal regions of Central Vietnam. Nevertheless, further validation through long-term field exposure studies is still required.

Materials doi: 10.3390/ma19224793

Authors: Łukasz Antolik Leszek Chałko Mirosław Rucki

Non-destructive in situ assessment of the emerging defects in the rail material structure is a critical issue due to the demanding safety requirements. The speed and accuracy of inspection are crucial for maintaining the traffic uninterrupted and safe. In this paper, a patented ultrasonic measuring head is demonstrated to be able to perform defect identification at moving speeds up to 120 km/h. In the laboratory experiments, the “defects” were prefabricated in the rotating test wheel in the form of orifices, as follows: Ø6 mm radial orifice and flat bottom axial orifices of diameters Ø6 mm, Ø8 mm, Ø10 mm, and Ø12 mm. The rotational speed of the test wheel, 800 rpm, corresponded with the relative movement between the sensor and the rail at ca. 130 km/h. Statistical analysis confirmed the accuracy of material defect identification with a random error of ±2.0 %FSH (full screen height) for static amplitude. Finally, the uncertainty of measurement for the amplitude drop was ±1.5 dB, which can be considered a very high accuracy for the ultrasonic material defect inspection.

Materials doi: 10.3390/ma19224796

Authors: Vladan Nedelkovski Milan Radovanović Srećko Stopić Dragana Medić Sonja Stanković Aleksandar Cvetković Bernd Friedrich

A porous zinc oxide/copper oxide nanomaterial was synthesized by ultrasonic spray pyrolysis at 400 °C from an aqueous 90:10 Zn:Cu cation feed, using a 1.7 MHz atomizer and argon without added hydrogen. X-ray diffraction confirms dominant wurtzite ZnO; weaker features are compatible with candidate Cu2O and CuO contributions, but the copper-containing phases are not unambiguously resolved. Reliable phase fractions and the Zn:Cu ratio in the collected powder are not established. Reflection-mode Scherrer estimates give a mean ZnO coherent-domain size of 17.1 nm after correction with an instrumental FWHM of 0.08° obtained from a silicon standard. Previously processed transmission-mode fits give apparent sizes of 22.0–27.1 nm, with the FWHM-based Halder–Wagner representation showing the strongest linearity (R2 = 0.9460). The model comparison remains exploratory because individual transmission widths are not tabulated and the W–H fits have weak linearity. The 500 and 600 °C profiles retain the principal ZnO reflections and support a qualitative temperature comparison. SEM reveals porous, agglomerated, partially hollow secondary structures, and EDS confirms Zn, O, and Cu without establishing a quantitative Zn:Cu ratio. A proposed droplet-to-particle mechanism describes possible routes to local phase contact. Surface copper speciation, nanoscale contact, and an electronic heterojunction remain unverified.

Materials doi: 10.3390/ma19224795

Authors: Karol Durczak Agnieszka Sujak Michał Juszczyk Michał Pyzalski

Cementitious materials in infrastructure undergo coupled chemical, mineralogical, transport and mechanical deterioration, yet development still largely follows a forward trial-and-test paradigm. This study formulates the problem as constrained robust inverse materials design over experimentally bounded design spaces. Published data on biological degradation, ye’elimite–aluminate–calcium (YAC) binders, modified CA2 and calcium aluminoferrites were reorganized without imputing missing observations. Mechanism–material relations were made explicit through an evidence-constrained compatibility matrix, while mechanical and processing requirements defined feasible regions evaluated by minimum-intervention, Pareto and robustness analyses. Fluorine-modified CA2 combined a synthesis temperature of 1200 °C with 67.76% hydration at 28 days and was the only non-dominated measured state in that subspace. Its guaranteed two-objective robust-dominance radius was ±4.0%; in 100,000 Monte Carlo realizations, it remained Pareto-efficient in 100% of cases for perturbation levels up to ±10%. In the mechanical subspace, YAC Variant II reached 32.1 MPa after one day and 60.2 MPa after 90 days, while CEM I 52.5R retained the highest mature strength; both were non-dominated. Calcium-aluminoferrite data demonstrated a reachable composition–processing phase field. The framework organizes degradation knowledge and phase controllability into candidate-selection decisions and suggests a basis for incorporating phase-, microstructure- and nanoscale descriptors when matched experimental data are available.

Materials doi: 10.3390/ma19224794

Authors: Cecylia Wardak Klaudia Morawska Malgorzata Grabarczyk Oguz Özbek

Potentiometric sensors constitute one of the most important groups of electrochemical sensors. Among them, ion-selective electrodes hold a prominent place. Potentiometry with fluoride ion-selective electrodes remains among the most common analytical methods for fluoride determination due to its high selectivity, cost-effectiveness, capability for in situ analysis, and wide-ranging environmental and biomedical applications. This paper provides a critical review of the development of fluoride ion-selective electrodes over the past decade, with particular emphasis on their design and analytical properties. It discusses the most important design approaches, highlighting their advantages, limitations, and challenges associated with miniaturisation or even leaching of the membrane. The properties of active membrane components responsible for fluoride-ion detection are discussed, along with the key analytical performance parameters that determine the selectivity, sensitivity, and reliability of fluoride determination. In the final section, the main areas of application for fluoride electrodes are characterised, with particular emphasis on their role in the analysis of environmental samples and biological materials.

Materials doi: 10.3390/ma19224792

Authors: Toreniyaz Shomenov Ainabat Mukan Yerzhan Ashim Bauyrzhan Myrzakhmetov Diana Otegen Saule Zholdayakova Yanwei Wang

TiFe-based alloys offer reversible hydrogen storage, but adsorption strength alone does not determine surface activation. Spin-polarized density functional theory was used to examine Sc, V, Cr, Mn, Co, and Ni substitution in the third atomic plane of Ti- and Fe-terminated TiFe(111) slabs. Adsorption and hydrogen-free electronic-structure calculations used PBE without a dispersion correction; separately prepared dissociation profiles used ordinary PBE nudged elastic band (NEB) calculations. The substituted Ti-face configurations retain molecular hydrogen at −0.023 to −0.161 eV. On the Fe face, Mn yields two separate H atoms at −1.838 eV per incident H2, Cr and Sc elongate the molecule (0.863 and 0.831 Å), and Co, Ni, and V change it by less than 0.03 Å; several Fe-face energies include a change in the slab’s magnetic state. Only the Ti/Cr band met the force criterion, under additional lateral hydrogen constraints; the other eleven bands remained unconverged. Their sampled heights therefore do not establish a quantitative dissociation-barrier ranking. Metal-projected spectra and Bader charges provide electronic context without establishing a hydrogen-orbital mechanism. The results distinguish configuration-specific binding, molecular distortion, and exploratory pathway information; they do not identify a universal optimum additive for practical hydrogen uptake or release.

Materials doi: 10.3390/ma19224788

Authors: Maciej Suliga Mateusz Wasilewski Konrad Jaroszewski Jacek Michalczyk Marek Hawryluk

In the manufacturing process of high-precision thin-walled tubes with diameters of less than 3 mm, the deformation conditions at the contact area between the die, the tube and the floating plug are the decisive factor in the stability of the drawing process. These conditions depend, amongst other things, on the rheological properties of the lubricants, temperature and friction conditions. Industrial drawing trials of ultra-thin beryllium bronze tubes have demonstrated a correlation between the physico-chemical properties of the lubricants and the susceptibility of the tubes to breakage, as well as the efficiency of the drawing process. The maximum drawing speed that guarantees stable process conditions depends on the dynamic viscosity coefficient, the thermal stability of the lubricant, the drawing force, the temperature and the amount of lubricant on the tube surface. As the tube drawing speed increases, the temperature at the material/tool interface rises. This leads to a gradual decrease in the viscosity of the lubricants, a reduction in the thickness of the lubricant film, and an increase in friction, drawing force and the strength properties of the tubes. Once the critical speed is exceeded, the tube breaks in the drawing die. The results indicate that the maximum stable drawing speed is not governed by a single lubricant property, but by the combined effects of dynamic viscosity, its temperature sensitivity, and thermal stability; both an excessively viscous oil and a very low-viscosity emulsion limited process stability. The highest drawing efficiency under industrial conditions was achieved with mineral oils (v = 15 m/min). The use of polymer-based lubricants in drawing enables the drawing process to be carried out at a speed of v = 1 m/min, and these can be used for drawing under laboratory conditions. In contrast, when drawing tubes using potassium soap-based emulsions, unstable drawing conditions occur, leading to very rapid tube breakage.

Materials doi: 10.3390/ma19224791

Authors: Selahattin Guzelkucuk

The incorporation of industrial byproducts into concrete is crucial for utilizing waste materials, reducing clinker use, and increasing the durability of cement-based materials. This study investigates the high-temperature exposure performance of cement mortars containing Class C and F fly ash from a multiscale perspective. Fly ash was used as a partial cement substitute at percentages of 5%, 10%, 15%, and 20%, and the prepared mortars were subjected to temperatures of 400, 600, and 800 °C. Flexural and compressive strengths, microstructural properties, X-ray microcomputed tomography (micro-CT) data, concrete petrography, and thermogravimetric analysis (TGA) characteristics were systematically examined to evaluate changes in mechanical performance, pore structure, microstructure, and thermal stability. The results indicated that the highest compressive strength values in mixtures subjected to 800 °C were obtained at a 10% replacement rate. Compared to the 5.64 MPa compressive strength of the reference mortar, this value was found to be 12.96 MPa in mortars containing 10% Class F fly ash and 11.86 MPa in mortars containing 10% Class C fly ash. Micro-CT and microstructural observations supported the finding that fly ash substitution reduced porosity and limited cracking, while thermogravimetric results supported the relationship between thermal stability and sustained mechanical performance. This study aims to contribute to the development of high-temperature-resistant cementitious materials by recycling fly ash, an industrial waste product.

Materials doi: 10.3390/ma19224790

Authors: Andrzej Jurecki Wojciech Grześkowiak Beata Klimek Marek Wieruszewski

Assessing historic timber requires separating service history from material variability, surface condition and sampling limitations. This study characterizes Scots pine recovered during renovation of the historic half-timbered residential building at farm no. 5 in Swołowo, Poland, dated to 1869, and compares it with contemporary pine and previously published oak results from the same building. Twenty-four historic-pine tests and four contemporary-reference tests were analysed by mass loss calorimetry at 35 and 50 kW/m2. The study extends earlier work by examining, within one historic-pine dataset, how area-normalized peak and total heat release relate to heat release normalized by initial specimen mass, while placing the results in a shared building-provenance context with published oak data. Mean ignition times of historic series ranged from 31.4 to 65.6 s at 35 kW/m2 and from 12.0 to 19.0 s at 50 kW/m2, versus 48.0 and 12.5 s for the references. Mean peak heat-release rates (pHRRs) were 8.4–32.1% higher in historic pine, whereas heat release per initial specimen mass (Q0) was 7.5–22.5% lower; these opposite directions show that peak intensity and mass-normalized heat contribution are not interchangeable. Area-normalized total heat release (THR) varied in direction. Published historic oak showed consistently lower THR, while its pHRR response depended on surface condition. The material was obtained from a historic building, rather than from a controlled ageing experiment; all historic pine tests came from one structural member, and the reference groups were small and heterogeneous. Two mass-signal discrepancies and incomplete specimen-level anatomical and density data further limit inference. Accordingly, the results do not establish an ageing effect or a fire-reaction classification. Fire-performance assessment of historic timber should consider ignition time, peak heat release and mass-normalized heat release separately, without attributing observed differences to age alone.

Materials doi: 10.3390/ma19224789

Authors: Sisi Zhu Ruizhou Zhou Kaiming Zhou Dezhen Ye Yvhao Qiu Jikai Zhou

Dams, their spillways, and water conveyance structures are constantly exposed to high-velocity water flow, making them susceptible to cavitation and erosion that can compromise structural durability and operational safety. This study conducted ultrasonic and hydraulic cavitation tests on repair and joint-filling materials, evaluating their cavitation resistance based on indicators such as loss in mass, cavitation rate, cavitation resistance strength, macroscopic and microscopic morphological evolution, pitting rate, and damaged area. The results showed that, under ultrasonic cavitation testing, epoxy-based materials primarily exhibited pitting and localized spalling, polyurea materials primarily exhibited crack damage, and silicone materials developed localized cavitation pits. Among the materials that showed no significant mass loss in the ultrasonic cavitation test, epoxy mortar A had a cumulative cavitation area that was significantly larger than that of the other materials, at 43.2 mm2, while epoxy mastic A and epoxy mastic B had similar cumulative cavitation areas of approximately 5.7 mm2. In the hydraulic cavitation tests, all three repair materials exhibited a certain degree of cavitation resistance, but differences were observed in mass loss and failure modes. Damage to the repair materials frequently occurred at surface defects, edges, and weak interfaces of the test specimens, primarily manifesting as material fracture and spalling. Among them, epoxy mastic B exhibited the best cavitation resistance, with a mass loss reduced by 68.9% and 29.4% compared to epoxy mastic A and polyurea A, respectively. No significant surface damage was observed in the joint-filling materials; polyurethane A exhibited excellent cavitation resistance, with a 45% reduction in mass loss compared to silicone A. In summary, the repair and joint-filling materials examined in this study can all provide a certain degree of cavitation resistance while accommodating structural joint deformation and may serve as a reference for the repair of flow surfaces in hydraulic structures.

Materials doi: 10.3390/ma19224787

Authors: Chawakorn Rewtragulpaibul Saravut Jaritngam Tanawan Wannawong Peerawat Puengpapat

This study investigated the potential use of asphalt concrete produced with locally sourced limestone and granite aggregates as an impervious core material in rockfill dams. An independent laboratory program evaluated 16 mixture conditions comprising two aggregate types, asphalt cement contents of 6% and 7%, and nominal target air-void contents of 1–4%. Marshall, hydraulic-conductivity, and consolidated-undrained triaxial tests were conducted to characterize the mixtures. The reported hydraulic conductivity ranged from 2.9549 × 10−10 to 3.8887 × 10−5 cm/s, while effective cohesion and friction angle ranged from 165.7 to 540.3 kPa and 34.07° to 55.61°, respectively. Four core-property datasets corresponding to a 2% target air-void content were evaluated using two-dimensional GeoStudio analyses under steady-state and rapid-drawdown conditions. Steady-state seepage discharge ranged from 1.967 × 10−9 to 6.7191 × 10−6 m3/s, with downstream global factors of safety of 2.209–2.215. The upstream global factor of safety at Day 7 of rapid drawdown was 2.041 for all four datasets. The granite mixture containing 7% asphalt cement and a target air-void content of 2% (Granite AC7% AV2%) was subsequently selected as a representative, rather than optimal, core-property dataset for a separate steady-state geometry comparison. Relative to the conventional clay-core baseline, a 0.50-m-thick asphalt concrete core with shell slopes of 1 V:1.5 H and 1 V:1.4 H reduced the calculated embankment volume per unit dam length by 21.11% and 24.83%, respectively, with corresponding global factors of safety of 1.655 and 1.557. A supplementary rapid-drawdown assessment of the steepest alternative yielded an upstream global factor of safety of 1.473 at Day 6, the lowest among the reported daily results. The findings provide comparative laboratory data and case-specific numerical results for preliminary assessment of asphalt concrete dam cores. Hydraulic acceptance and field-scale suitability are not established, and further experimental verification and numerical sensitivity assessments remain necessary before application.

Materials doi: 10.3390/ma19224786

Authors: Weiwu Dai Kaize Xie Weigang Zhao Jiaao Han Tingfeng Li Jia Zhao

To characterize curing heat release and temperature evolution during interface damage repair in China Railway Track System (CRTS) II slab ballastless track, the curing kinetics and thermal properties of repair slurry for interface damage (RSID) were investigated. Non-isothermal differential scanning calorimetry (DSC) was conducted at four heating rates, and the apparent activation energy was determined using the Kissinger, Ozawa, and Starink methods. An n-order curing kinetic model and a two-parameter (m, n) autocatalytic curing kinetic model were established and compared. The specific heat capacity and thermal conductivity were determined using laser flash analysis (LFA), and corresponding temperature-dependent constitutive models were established. These material properties were incorporated into a three-dimensional transient heat transfer finite element model considering curing heat release, which was validated through curing temperature-rise experiments. The results show that the curing exothermic peak shifts toward higher temperatures with increasing heating rate. The average apparent activation energy obtained from the three methods is 55.21 kJ/mol. The two-parameter autocatalytic model provides better agreement with the experimental curing-rate curves than the n-order model, with R2 values exceeding 0.960. The specific heat capacity increases approximately linearly with temperature, whereas the thermal conductivity exhibits an exponential growth trend. The simulated and measured temperature histories agree closely, with an R2 value of 0.979, a peak temperature difference of 0.2 °C, and a difference of 3 s in the time to reach the peak. The simulated temperature field shows greater heat accumulation in the interior, with higher temperatures internally and lower temperatures near the boundaries. These findings provide material parameters and a thermal analysis basis for optimizing interface damage grouting repair processes in ballastless track and support subsequent analyses of thermal deformation and the development of measures to control secondary damage during repair.

Materials doi: 10.3390/ma19224784

Authors: Karol Szlązak

Microcomputed tomography (microCT) enables non-destructive 3D imaging, but conventional segmentation cannot resolve objects smaller than a voxel. This study presents a microCT-based method that maps degradation-induced sub-voxel porosity by converting voxel-specific X-ray attenuation changes between registered pre- and post-degradation datasets into porosity estimates. The method also accounts for other degradation-induced physical and chemical changes that affect X-ray attenuation; however, their contributions cannot be directly separated from the estimated change in porosity. The method was demonstrated on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), Poly(lactic-co-glycolic acid) (PLGA) and tricalcium phosphate (TCP) scaffolds. Specimens were scanned before and after degradation using identical acquisition and reconstruction settings, and datasets were 3D-registered. The estimated effective sub-voxel porosity increase was 8.33 ± 0.63%, versus a gravimetric mass loss of 7.89 ± 0.82%. SEM showed a pore area fraction of 7.64 ± 0.23% and a mean equivalent pore diameter of 1.79 ± 1.15 μm, below the 5.5 μm voxel size. Maps revealed spatially heterogeneous degradation-related changes. The consistency between the microCT-derived estimate and the complementary evidence from gravimetry and SEM provides indirect validation of the interpretation of the measured X-ray attenuation changes in terms of effective sub-voxel porosity.

Materials doi: 10.3390/ma19224783

Authors: Xubin Huang Zhe Miao Guangshan Shi Yongzhi Liu Shengting Wang Shuangchao Lei Xiangyang Li Jiansheng Wang

Driven by China’s carbon peaking and carbon neutrality goals, pumped-storage hydropower projects have developed rapidly, while power stations in Northwest China face challenges posed by extreme temperature conditions. Unlike previous studies on asphalt mixtures under conventional freeze–thaw conditions, this study employs multiscale characterization methods to investigate the deterioration behavior of dense-graded hydraulic asphalt concrete under extreme temperature cycling. SBS-modified asphalt concrete specimens were vacuum-saturated and subjected to 0, 5, 10, 15, and 20 accelerated freeze–thaw cycles over a temperature range from −45 to + 60 °C. Uniaxial compression tests, relative mass change measurements, MIP, CT with three-dimensional pore reconstruction, and SEM were employed. The results show that compressive strength gradually decreased with increasing freeze–thaw cycles, while mercury-accessible pore volume, relative mass change, and interfacial defects progressively increased. After 20 cycles, compressive strength decreased by 9.29%, while the mercury-accessible volume of large capillary pores increased by 19.05%. SEM observations of the selected fields revealed more pronounced pores and cracks near the aggregate–asphalt mastic interface. These findings suggest that the aggregate–asphalt mastic interface is one of the relatively vulnerable regions under extreme cyclic exposure, although changes in the asphalt binder itself may also contribute to material deterioration. This study provides experimental evidence for understanding the deterioration behavior of hydraulic asphalt concrete under extreme temperature conditions.

Materials doi: 10.3390/ma19224785

Authors: Liu Long Wangcheng Fan Fan Xiao Xiaopeng Lv

Existing lifetime evaluation methods for IGBT modules can hardly account for either the increase in thermal load or the stress accumulation caused by solder-layer fatigue, which often leads to an overestimation of module lifetime. To address this issue, this paper proposes a lifetime evaluation method that considers the dynamic cumulative updating of the inelastic energy dissipation density of the solder layer. Firstly, based on the Clech algorithm, the variation of inelastic energy dissipation density under adjustments to mechanical parameters and increases in thermal load is analyzed, and the positive feedback of solder-layer fatigue on the accumulation of inelastic energy dissipation density is derived analytically. On this basis, the thermal resistance is adopted as a characterization parameter of the aging state of the IGBT module. A scaling factor describing the influence of the aging state on the thermal–mechanical parameters is defined to iterate the inelastic energy dissipation density, and a dynamic accumulation update strategy for inelastic energy dissipation density under solder-layer fatigue is thereby proposed. Then, the update strategy is introduced into the lifetime evaluation process to compensate for the influence of thermal resistance degradation on the thermal–mechanical parameters, thus improving the accuracy of IGBT module lifetime evaluation. Finally, the correctness and effectiveness of the proposed method are verified by comparison with commonly used lifetime evaluation methods.

Materials doi: 10.3390/ma19224781

Authors: Anna Różańska Wojciech Koryciński Klaudiusz Kalinowski Izabela Burawska Piotr Borysiuk

The evolving awareness related to environmental protection can be observed in all aspects of life. While making efforts to limit the use of synthetic coatings, it is necessary to find sustainable alternatives for wood surface preservation. By comparing the properties of natural substances, it is possible to determine if and to what extent they can be used as alternatives. The aim of this study was to compare the effects of tung, coconut, palm and linseed oils, as well as a commercial formulated oil-based finish, on colour change, gloss, scratch resistance, abrasion resistance and surface hardness of oak wood. Untreated wood served as a control group. The measured properties included colour parameters in the CIE Lab* space, gloss at 60° angle, scratch resistance, mass loss in the Taber abrasion test, as well as Brinell hardness. All the systems under study caused a visible darkening of the surface (ΔE*ab = 11.83–17.33). The most significant change in colour took place after the application of palm oil, while coconut oil was the only one that increased gloss. The formulated oil-based finish provided the best overall mechanical effect: the smallest increase in mass loss during abrasion, and hardness improved by 11% compared with untreated wood. The results suggest that finishing properties depend on the complete system, its curing degree and method of application, and not only the plant-based origin of the oil.

Materials doi: 10.3390/ma19224782

Authors: Zhiliang Wang Jinwen Tao Jialun Gou Libing Du Jingjing Peng

In the middle and late stages of oilfield development, increased water cut and pipeline shear promote stable W/O emulsions, raising viscosity, gathering and transportation friction, and energy consumption; traditional “heating + light oil blending” is energy-intensive and limited by light-oil resources, making chemical emulsification inhibition and drag reduction important. This study used field heavy oil produced fluid to develop suitable anti-emulsification agents. Physicochemical tests per industry standards analyzed component composition, carbon number distribution, density–temperature characteristics, and viscosity–temperature rheology to reveal the material basis for easy emulsification and thickening. Using water separation percentage and rate, oil–water interfacial morphology, produced water quality, and interfacial tension as indicators, bottle tests screened single agents from 11 structural types; temperature and dosage effects were investigated, and a three-factor three-level orthogonal experiment quantified factor weights. The heavy oil was enriched in asphaltenes, had an imbalanced resin-to-asphaltene ratio, and contained relatively high-carbon-number hydrocarbons. Multi-branched polyether agents performed significantly better than linear polyether and inorganic salt agents. Temperature was dominant, followed by agent type; dosage was weakest. These results clarify the heavy oil’s properties and single-agent action patterns and provide data and a theoretical basis for formulation optimization and process parameter determination for emulsification-inhibiting and drag-reducing gathering and transportation.

Materials doi: 10.3390/ma19224780

Authors: Yaxu Zhang Tao Tong Shuzhi Wang Meng Wu Xiao Ma Jianxi Li

The murals from Tomb No. 1 at Wulanquangou, Qinghai, China (633–842 CE), provide insights into mural materials and painting techniques during the Tibetan Empire. In this study, OM, SEM–EDS, XRD, μ-RS, FTIR, Py–GC/MS, ELISA, and LPSA were employed to characterize the mural materials and painting techniques. The murals comprise a multilayer structure consisting of brick and squared timber (Cupressus spp.) supports, an earthen ground layer, a lime ground layer, and a pigment layer. The lime ground is dominated by calcite, whereas the earthen ground consists mainly of fine-grained silty soil reinforced with highland barley fibers. Hematite, carbon black, and indigo were identified in the pigment layer, while animal glue was identified as the binding medium. The identification of indigo provides the first evidence of its use in a Tubo-period mural on the Qinghai–Tibet Plateau. Similarities in mural structure and painting techniques between Wulanquangou Tomb No. 1 and high-status Tang tomb murals in Shaanxi and Gansu suggest possible technological exchanges between the Tibetan Empire and Tang China.

Materials doi: 10.3390/ma19224779

Authors: Danbin Jia Yanming Zhang Xinyue Song Pan Sun Songyuan Ai Mujun Long Dengfu Chen

SUS303 austenitic stainless steel has excellent machinability owing to its relatively high sulfur content, but MnS inclusions also promote localized corrosion. In this study, electropulsing was applied at three characteristic stages, namely the high-temperature molten stage, the initial precipitation stage of MnS, and the subsequent solidification stage, to investigate its effect on the pitting corrosion behavior of SUS303 stainless steel. Samples treated at current densities of 0–127.39 A·cm−2 were evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy, and corrosion microscopy. Within each treatment group, increasing current density generally shifted the pitting potential (Epit) to more positive values, increased the fitted charge-transfer resistance (Rct), and reduced the characteristic pit size. In the 1450 °C group, Epit increased from 0.284 to 0.410 VSCE, while Rct increased from 296.4 to 440.5 kΩ·cm2. Similar within-group trends were observed for the other treatment endpoints. SEM observations showed refinement of coarse Type I MnS under electropulsing. Representative corrosion morphology indicated localized dissolution associated with coarse sulfide inclusions. The electrochemical and microstructural trends suggest that refinement of Type I MnS may contribute to improved pitting resistance.

Materials doi: 10.3390/ma19224777

Authors: Szymon Tofil Shuyang Lin Qunli Zhang Leonardo Orazi António B. Pereira Liang Wang Piotr Kurp Ruibin Chen Jianhua Yao

This exploratory study examined whether visible native cell texture alone verified chemical cleanliness in selected fields on fragments from one field-aged crystalline-silicon photovoltaic module with polyolefin elastomer (POE)-rich encapsulant. After preparatory laminate opening, eight single-pass femtosecond near-infrared (fs-NIR) raster programs were applied. Optical profilometry described 77 local regions within 24 fields. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS) examined corresponding local fields, spatially separate from the profilometry measurements. A visibly textured pre-fs-NIR reference field yielded 9.23 wt.% C in the original normalized EDS output. Selected treated fields showed irregular morphology and regional carbon signals. Visible texture therefore did not verify chemical cleanliness in the examined fields. Overall, the screening did not establish a reproducible, chemically verified cleaning outcome. Spatially unmatched observations and purposive sampling prevent the quantification of residue removal or ranking of the programs; EDS does not uniquely identify carbon as POE. Further work requires measurements at the same locations before and after irradiation, independent specimens, and a predefined chemical cleaning criterion.

Materials doi: 10.3390/ma19224778

Authors: Zhao Xu Haowen Zheng Changze Xu Rui Zhao Qingtian Su Yang Jiang Hai Yan

This study investigates the structural role of permanent flat steel bottom formwork in steel–concrete composite bridge decks from construction to long-term service through global numerical analysis and full-scale testing. A three-dimensional finite element model of a 3 × 40 m continuous composite girder bridge of the Beijing-Taipei (Jingtai) Expressway expansion project compared girders with and without the formwork during girder erection, concrete casting, secondary dead loading, and vehicle loading; a full-scale two-span specimen was tested under staged static loading, 2 million load cycles, and a failure test. The 8 mm formwork substantially reduced upper girder stresses: maximum top-flange compressive and tensile stresses fell by approximately 35% and 38% during erection and by 40% and 39% during casting, with deflection under dead and vehicle loads reduced by up to 3.9%. Increasing plate thickness from 6 to 8 mm clearly improved the response, while 10 mm gave limited further benefit. During repeated loading, cracks propagated, and stiffness degraded, but no visible steel–concrete interfacial slip was observed. After 2 million cycles, tensile strains in the midspan bottom plate and intermediate-support top reinforcement increased by approximately 13.4% and 21%, while initial flexural stiffness and ultimate flexural resistance decreased by approximately 10% and 9.7%, with residual resistance well above service-load demand. It serves as both construction formwork and a permanent structural component, informing design, plate-thickness selection, and durability assessment.

Materials doi: 10.3390/ma19224774

Authors: Vanesa Alejandra Muñoz Frida Dimarco María del Rosario Torres Deluigi Eduardo Gutiérrez Liliana Fernández Juan Manuel Pérez Iglesias César Américo Almeida Mariano Acosta María Carolina Talio

A solid-surface fluorescence method was developed for the determination of mebendazole (MBZ) in natural waters using a Triton X-114-assisted silver-containing nanosystem (Ag–TX-114) immobilized on filter paper. The nanosystem exhibited an excitation maximum at approximately 305 nm and an emission maximum at 376 nm. Increasing MBZ concentration produced a progressive decrease in fluorescence intensity. Under the selected conditions, 100 µL of 1.0 × 10−3 mol L−1 acetate buffer at pH 3.5 was used, and the filter-paper support was impregnated with the Ag–TX-114 suspension for 60 s. The method showed a linear response from 0.28 to 115 ng L−1, with detection and quantification limits of 0.08 and 0.28 ng L−1, respectively. Repeatability at 50 ng L−1 was 0.21% RSD (n = 7), and recoveries in natural-water samples ranged from 89.5 to 113.8%. Apparent MBZ concentrations measured in ten samples ranged from 6.12 to 50.12 ng L−1. The UV–Vis spectrum of MBZ showed an absorption band centered near 311 nm, indicating that a primary inner-filter effect may contribute to the observed fluorescence attenuation. The proposed method combines low sample and reagent consumption with direct solid-surface measurement and achieved an updated AGREE score of 0.65.

Materials doi: 10.3390/ma19224776

Authors: Xiangyu Li Lin Wang Andong Li Yunkun Chen Yewei Zhang Yujun Zhao Xiaotong Jin Kangkang Yuan

Mesoporous alumina fibers (MAFs) combine strong fluoride affinity with a readily recoverable fibrous form, but calcination-induced shrinkage and pore collapse can reduce the surface area available for adsorption. MAF and nine variants doped with alkali metals (Li, Na, and K), alkaline earth metals (Mg, Sr, and Ba), or rare earth metals (Y, La, and Ce) were prepared by CTAB-assisted electrospinning to evaluate how dopant selection affected post-calcination pore structure, BET surface area, and fluoride removal. Li, Na, and K doping mainly increased the pore volume and average pore diameter, whereas Mg, Sr, Ba, Y, La, and Ce doping increased the BET surface area and reduced the average pore diameter relative to MAF. Across the ten samples, fluoride removal efficiency was strongly and positively correlated with BET surface area (R2 = 0.9149, p < 0.001). MAF-Y exhibited the highest BET surface area (237.89 m2·g−1) and fluoride removal efficiency (68.00%). Its Langmuir-estimated maximum adsorption capacity was 51.49 mg·g−1 at 50 °C and pH 7. Overall, dopant selection effectively regulated the post-calcination pore structure of MAF. Y doping most effectively preserved the mesoporous structure, thereby increasing BET surface area and fluoride removal.

Materials doi: 10.3390/ma19224773

Authors: Juan A. Lazzús L. Palma-Chilla J. C. Flores

A non-Hermitian LC quadrilayer metamaterial formed by alternating right-handed (RH) and left-handed (LH) circuit layers is investigated. The layers are connected through identical nearest-neighbor imaginary couplings, providing a minimal multilayer extension of the RH/LH bilayer. The quadrilayer connectivity generates two non-Hermitian spectral scales related by the golden ratio, giving rise to two exceptional families and up to four exceptional contours in the two-dimensional reciprocal space. The RH/LH circuit duality organizes the exceptional solutions into reciprocal pairs, while the golden-ratio structure determines the relative scale of the critical couplings. Increasing the coupling consequently changes the number of physically accessible exceptional contours from four to three and finally two. In the four-contour regime, the nested exceptional structure separates reciprocal-space regions containing zero, two, and four complex eigenfrequencies. These results show that the connectivity of an LC multilayer can generate multiple exceptional boundaries and golden-ratio spectral scaling using a single microscopic non-Hermitian coupling.

Materials doi: 10.3390/ma19224775

Authors: Zhenglong Li Liang Yu Gaofeng Fu

A multiscale framework combining finite element analysis (FEM), molecular dynamics (MD) simulations, and pin–on–disc experiments was developed to optimize the Fe content of SiC3D/Cu–Fe interpenetrating phase composites (IPCs) and to reveal the load–bearing and wear mechanisms underlying their tribological performance. Because the wear resistance of IPCs is governed by the load–bearing capacity of the reinforcing skeleton through the Archard wear relation, the optimal matrix composition was predicted by compressive MD/FEM simulations rather than by directly simulating the multi–physics friction process. FEM showed that the three–dimensionally continuous SiC3D skeleton carries the dominant share of the normal load and transfers it to the matrix through the interface. MD screening over Fe contents of 5–20 at.% identified 5 at.% Fe as optimal, where the face–centered cubic phase fraction reaches its maximum and the compressive strength peaks; the Cu-5%Fe matrix was therefore selected for pressureless infiltration of a Cu film–sprayed SiC3D skeleton. The as–fabricated IPCs exhibited spontaneous oxygen segregation to the SiC/Cu interface, forming Si–O–Cu bridging bonds that strengthen interfacial bonding. Pin–on–disc tests under loads of 20–100 N showed a stable friction coefficient (0.45–0.54) and a low wear rate (0.93–3.01 × 10−12 m3·N−1·m−1) over the whole load range. The FEM–predicted wear depth deviated from the measured value by approximately 7.7%, and the friction tests confirmed the MD–predicted optimum, establishing a self–consistent simulation–to–experiment framework from macroscopic load bearing to atomic–scale matrix strengthening.

Materials doi: 10.3390/ma19224772

Authors: Xiaoli Cui Jie Liu Chao Lu Man Feng Di Tie

Improving the strength of Al conductive alloys while maintaining high electrical conductivity (EC) remains a long-standing challenge, as conventional strengthening strategies usually degrade electrical performance. Although multi-element microalloying has been explored for Al-Si alloys in the prior literature, most existing studies fail to achieve the simultaneous refinement of eutectic Si and controlled precipitation of multi-scale nanoprecipitates, often leading to a strength–conductivity trade-off. In this work, a novel Al-4Si-1.1Mg-0.13Zr-0.06Cu-0.15Sc conductive alloy was designed, integrating trace Mg/Zr/Cu/Sc microalloying with hot extrusion and tailored heat treatment. The results reveal that the individual addition of these alloying elements greatly raises alloy hardness but inevitably reduces EC. The combined hot extrusion and heat treatment solves this dilemma: eutectic Si particles are refined to ~200 nm with a uniform distribution, while nano-sized Mg2Si (~15 nm) and Al4Zr(Sc)3Si5 (~50 nm) precipitates are formed. The synergistic strengthening of these multi-scale precipitates enables prominent mechanical enhancement without sacrificing electrical conductivity, which distinguishes this work from many previous Al-Si alloy reports. After the optimized two-step heat treatment (500 °C/4 h + 200 °C/48 h), the alloy achieves excellent comprehensive performance: yield strength of 164.0 MPa, ultimate tensile strength of 364.0 MPa, hardness of 106.0 HV, elongation of 9.0%, and EC of 50.8% IACS. This work provides a feasible microstructure engineering strategy for designing high-performance conductive aluminum alloys by precise multi-component composition control.

Materials doi: 10.3390/ma19224771

Authors: Yi Song

The mechanical properties of DLC films are strongly process dependent, yet the ionization fraction of the carbon plasma, a key parameter, remains difficult to control independently in experiments. Here, classical molecular dynamics simulations with a dual-energy incident flux of 70 eV ions and 5 eV neutrals were used to investigate how the ionization fraction governs the growth of hydrogen-free DLC films over the full 0 to 100% range. Because the energy of each species is fixed and only their ratio is varied, the ionization fraction is isolated as a single variable, which a mono-energetic beam cannot provide. At 0% ionization, adsorption-dominated growth yields a sp2-rich structure with a tensile stress of +6.08 GPa. From 0% to 50%, the dominant growth mode shifts from adsorption to subplantation, and the density and the compressive stress rise concurrently while the sp3-C fraction remains essentially constant, the stress peaking at −18 GPa at 50%. Beyond 50%, further ionization produces only a marginal increase in the density and the sp3-C fraction, together with a slight relaxation of the compressive stress that is attributed to the thermal relaxation of the network under continuous ion bombardment. At full ionization, subplantation dominates and the film reaches a density of 3.09 g/cm3 and an sp3-C fraction of 33.6%, with a residual compressive stress of −16.5 GPa. The saturation observed above 50% indicates that a further increase in the ionization fraction brings little structural gain, and the results provide a quantitative relationship from which the deposition conditions can be selected according to the desired sp3-C content and the tolerable stress level.

Materials doi: 10.3390/ma19224770

Authors: Yiqing Dai Jiwang Jiang

Road networks are among the most capital-intensive and long-lived assets in modern societies, yet they are increasingly subjected to a combination of heavier and more frequent traffic loads, extreme thermal and moisture events, and pressure to reduce embodied and operational carbon [...]

Materials doi: 10.3390/ma19224769

Authors: Gregory Bennett Mark Beatty Bobby Simetich

This in vitro pilot study evaluated airbrush and brush application of a denture glaze (Palaseal) on the flexural, surface, and optical properties of a 3D-printed denture base resin (Apex Base) using a DLP printer (Sprintray Pro 2), compared with polished and unpolished controls, before and after thermocycling (1000 cycles). Water sorption and solubility were measured at baseline, with ISO 20795-1:2013 values used as reference benchmarks. Flexural, surface, and optical outcomes were measured (n = 10 per group; n = 5 for sorption and solubility). Polished specimens showed the largest decline in flexural strength after thermocycling (67.3 to 49.3 MPa). Spray-glazed specimens showed no significant decline but had the lowest baseline values. Strength was below the 65 MPa reference value in 21 of 40 specimens at baseline and 31 of 40 after thermocycling, and modulus was below the 2000 MPa reference value in 79 of 80. Sorption and solubility were above the reference values in all groups, but specimen dimensions deviated from the standard, so these comparisons are descriptive. Glazing produced a measurable color difference from the unmodified resin. Airbrush and brush protocols did not differ significantly on any outcome. Findings apply to the glaze curing conditions tested.

Materials doi: 10.3390/ma19224768

Authors: Xiaoying Guo Rui Zhang Zheng Gao Yi Wang Feng Yu Ruoyu Wang Yuanhui Su Yu Huan Pengkun Hou Tao Wei Kunfeng Chen

Cement-based structural capacitors (CSCs) combining load-bearing and energy-storage functions are promising for next-generation green buildings. However, the practical application of CSCs remains hindered by the trade-off between mechanical and electrochemical performance, together with challenges related to material complexity and scalability. To address these challenges, we propose a red mud-enabled ion–electron dual-conduction bulk-electrode concept by incorporating 25 wt% Bayer-process bauxite residue (red mud, RM) into the cement matrix, thereby forming a composite with efficient coupled ionic/electronic conduction while retaining robust mechanical performance. The resulting composite serves as an integrated electrode/electrolyte in CSCs, expanding the energy storage region from the conventional 2D planar interface to the 3D bulk electrode, increasing the areal capacitance from 0.588 mF cm−2 (pure cement) to 53.4 mF cm−2. This configuration also retains a compressive strength of 45.2 MPa, demonstrating a favorable balance between mechanical and electrochemical performance. Four building-component-scale RMCSCs (20 × 10 × 6 cm3) connected in series can power a 1 W, 3 V industrial light bulb for more than 20 min on a single charge. A building wall (100 × 90 × 10 cm3) assembled from these units can power more than ten industrial light bulbs.

Materials doi: 10.3390/ma19224765

Authors: Hongru Lyu Lin Zhu Jie Huo Anhao Li Qingxian Ma

The post-forging heat treatment process played a crucial role in the final microstructure and mechanical properties of 9Cr3W3Co martensitic heat-resistant steel. In this study, comparative experiments were systematically conducted to investigate the influence and underlying mechanisms of deformation, austenitizing temperature, and two-stage tempering processes on the microstructural evolution and hardness of 9Cr3W3Co steel. Microstructural characterization and property evaluation were performed using scanning electron microscopy (SEM), X-ray diffraction (XRD) with Rietveld refinement, energy-dispersive X-ray spectroscopy (EDS, including elemental line scans and maps), Vickers and Rockwell hardness tests. The results indicated that quenching at 1100 °C prevented the formation of harmful δ-ferrite, completely dissolved the initial M23C6 carbides and effectively inhibited the growth of martensite blocks, achieving the highest quenching hardness (47.1 HRC). The experimental XRD patterns of all five heat-treatment conditions confirmed that the final hardness was dictated not only by the total carbide content but also by the degree of carbide refinement and matrix recovery. The dispersed precipitation of M23C6, M7C3 and NbC-type MX was significantly facilitated during the second-stage tempering at 570 °C + 700 °C, enhancing the secondary hardening effect. This process effectively suppressed excessive recovery of martensite blocks and the over-coarsening of carbides, maintaining excellent microstructural stability and mechanical properties (29.0 HRC). The optimized deformation and post-forging heat treatment process achieved an ideal microstructure, providing an important theoretical foundation and practical guidance for the engineering application of 9Cr3W3Co in ultra-supercritical units.

Materials doi: 10.3390/ma19224766

Authors: Tongkun Zhao Kaiqing Dai Jun Li Kezu Wang Jian Gao Suhui Zhang Jinhua Wu Jinpeng Xie Cheng Yang Yingying Yu

Porcelain bushings are critical insulation components of high-voltage equipment, and their in-service failure, often an explosive rupture initiated at pre-existing micro-defects, remains a safety concern. Existing studies treat defect initiation and defect-to-performance mapping separately, rarely on the same material. Here, a high-alumina porcelain is characterized microstructurally and compositionally, simulated by a coupled electro-thermo-mechanical phase-field model, and measured on two parallel response channels. One normal sample, three artificial-defect samples (iron-doped, sawdust-doped, and unsieved), and samples with four thermal-shock levels (0–15 cycles) were prepared. The artificial defects leave the mean flexural strength close to that of the normal sample but broaden its distribution, with the Weibull modulus falling from 5.8 to 2.3–3.7 and the strength at 10% failure probability from 90 to 43–72 MPa. The thermal-shock levels raise the electrical conductivity from 9.0 × 10−12 to 3.1 × 10−8 S/m and lower the thermal conductivity from 4.09 to 3.56 W/(m·K). The simulation places the transition from arrested damage to through-section fracture at a defect depth of 0.03–0.04 mm for the present load state and length scale. The two transport signals move in opposite directions and are read jointly on a qualitative performance plane, which gives a directional outlook for state assessment.

Materials doi: 10.3390/ma19224767

Authors: Krzysztof Labisz Jarosław Konieczny Wojciech Kamiński Wojciech Pakieła Janusz Ćwiek Ş. Hakan Atapek Mateusz Winter

The combustion engine elements of automobiles are often built from aluminium alloy pistons that slide against cylinders made of cast iron with oil lubrication. For reducing friction and preventing scuffing between pistons and the cylinder, the pistons are sometimes coated. Another possibility is to create a specially treated surface layer, using ceramic particles and laser technology. Using a laser beam makes it possible to locally melt the surface of a piston and incorporate ceramic particles into the molten material. Since ceramic particles are significantly harder than aluminium alloys, this laser-based technology enhances a piston’s resistance to abrasive wear. Furthermore, a laser can be used to create microscopic indentations on the piston surface. This increased roughness helps retain an oil film, which improves lubrication and reduces the risk of dry friction and engine seizure. For this reason, in this work the influence of fibre laser processing parameters on the microstructure and mechanical properties of the aluminium–silicon alloy, especially the crystallographic structure changes, were studied. For alloying, iron powder was used with a size of approximately 60 µm. For investigation of the crystallographic structure, electron diffraction was used on the transmission electron microscope. The hardness measurement was performed using microhardness Vickers at a load of 150 mN and 15 s loading time. Compressive strength, plateau stress, and energy absorption were calculated using a universal testing machine. The highest value of hardness of 192.78 Hv was found when the stress relieving process is set with the following parameters: heating (500 °C); holding time (120 min); and stabilisation temperature (450 °C). Higher heating temperatures and longer holding times have been shown to lead to grain growth, which adversely affects the hardness of the material. Conversely, improvements in the material’s mechanical properties during fibre laser processing were achieved by shortening the holding time and increasing the stabilization temperature. In summary, the results indicate that the heat treatment parameters, such as heating temperature, holding time, and stabilisation temperature, have a significant impact on the mechanical properties of the resulting samples.

Materials doi: 10.3390/ma19224764

Authors: M.R. Nurul Fazita Krishnan Jayaraman Debes Bhattacharyya M.K. Mohamad Haafiz Chaturbhuj K. Saurabh M. Hazwan Hussin Abdul Khalil H.P.S.

Figures 11–19 from the original publication [...]

Materials doi: 10.3390/ma19214763

Authors: Jakub Matuszak Krzysztof Ciecieląg

Burrs formed during the machining of fibre-reinforced polymer composites reduce safety and product quality and are usually inspected off-process. This study assessed whether as-milled edge segments with burrs can be distinguished from burr-free chamfered segments on the basis of the force signal recorded during edge brushing, as a first step towards in-process burr detection, and how brush fibre stiffness affects the edge condition. On one edge of glass (GFRP) and carbon (CFRP) fabric-reinforced specimens, positioned at 45° to the tool axis, chamfered segments 0.1–0.4 mm deep, representing a burr-free edge, alternated with as-milled segments with burrs. The edges were brushed with four ceramic-fibre brushes of increasing stiffness (S1–S4) at constant parameters, and the force signal was analysed using recurrence plots (RP) and recurrence quantification analysis (RQA). Chamfers 0.1 mm deep did not produce unambiguous changes in the recurrence structure. For the stiff brushes (S3, S4), chamfers 0.2–0.4 mm deep produced local RP densifications consistent with their location. In the RQA, for chamfers ≥ 0.2 mm, DET (determinism) and L (average diagonal line length) mostly rose above and LAM(laminarity) and TT (trapping time) fell below the burred-edge reference levels. The chamfer width produced by brushing increased with fibre stiffness, from 588 to 1040 µm (GFRP) and from 389 to 1005 µm (CFRP). Under the tested conditions, the force signal distinguished the two edge conditions; its use for detecting burrs themselves requires further validation on edges with quantified burrs.

Materials doi: 10.3390/ma19214762

Authors: Jiangchuan Liu Xiaoxu Wang Yupeng He Bolin Wang Guoquan Yang Zhihui Chen Yinlin Shen

Strengthening the interfacial interaction of heterojunction photoanodes is an important route to efficient photoelectrochemical (PEC) water splitting. Herein, a SnS2/CdIn2S4 heterojunction photoanode is fabricated by a two-step solvothermal method, in which tartaric acid (TA) acts as an interfacial bridge to regulate the growth of SnS2 on trapezoid-like CdIn2S4. The optimized photoanode delivers a photocurrent density of 5.93 mA cm−2 at 1.23 V vs. RHE, approximately 6.9 times that of pristine CdIn2S4 (0.86 mA cm−2), with a maximum applied bias photon-to-current efficiency (ABPE) of 2.81%. Electrochemical impedance spectroscopy shows a reduced charge-transfer resistance, and time-resolved photoluminescence reveals a prolonged carrier lifetime. Density functional theory calculations indicate the proposed interfacial charge-transfer mechanism: the work-function difference between SnS2 (6.12 eV) and CdIn2S4 (3.95 eV) drives interfacial electron transfer from CdIn2S4 to SnS2, the charge density difference reveals electron accumulation on the SnS2 side and depletion on the CdIn2S4 side, with the interfacial charge transfer increasing from 0.33 to 0.39 e− after TA bridging, and the projected density of states (PDOS) evidences a strong electronic interaction across the junction. This organic-molecule-assisted interfacial bridging offers a facile route for designing the interfaces of sulfide photoanodes.

Materials doi: 10.3390/ma19214761

Authors: Rumeysa Bayram Büyükokuroğlu Gülsüm Sayın Özel

This study evaluated cellular responses to extracts of CAD/CAM-milled PMMA, 3D-printed methacrylate-based resin, and conventionally heat-polymerized PMMA after denture cleanser exposure. Specimens (MTT, n = 240; BrdU, n = 36) were assigned to Corega, chlorhexidine, Listerine, or distilled water. Following accelerated cumulative exposure (1825 min; not simulating clinical use), extracts were applied to human gingival fibroblasts. Cellular metabolic activity was assessed by MTT absorbance, DNA synthesis-associated proliferative activity by quantitative BrdU immunofluorescence, and morphology and F-actin organization qualitatively. Material and cleansing solution significantly affected MTT absorbance (both p < 0.001), with a significant interaction (p = 0.008). CAD/CAM-milled and 3D-printed materials exhibited higher MTT absorbance than conventional PMMA (p < 0.001 and p = 0.003, respectively), without a significant difference between them (p = 0.071). Distilled water yielded higher MTT absorbance than all cleansers (all p < 0.001). BrdU labeling showed a significant cleansing solution effect (p < 0.001) but no significant material effect or interaction. In this preliminary screening study, cleansing solution affected both metabolic and DNA synthesis-associated responses, whereas material differences were significant only for MTT absorbance. Mechanisms were not investigated; the milled material (TEMPO-CAD) is not primarily a denture base material, so findings should not be generalized.

Materials doi: 10.3390/ma19214760

Authors: Marcin Chybiński Łukasz Polus Robert Studziński

Sustainable timber–timber composite floors can facilitate CO2 reduction. The structural behaviour of composite floors strongly depends on the load-carrying capacity and stiffness of shear connections. For this reason, this investigation characterises the behaviour of timber–timber composite screwed connections. Push-out tests were conducted on twelve samples, each consisting of a glued-laminated timber beam, laminated veneer lumber panels, and screws. The effects of screw type and penetration depth on connection load–slip behaviour were analysed in terms of load-carrying capacity, slip modulus, and failure mode. The laminated veneer lumber panels in the numerical models were connected with the glued-laminated timber beams using discrete connections, the behaviour of which was described using the three-linear load–slip models. The push-out FE simulations were used to verify and calibrate the experimentally derived tri-linear spring characteristics intended for subsequent numerical analyses of timber–timber composite structural members. The numerical model was therefore focused on reproducing the global connection response rather than the detailed local mechanics of individual fasteners.

Materials doi: 10.3390/ma19214759

Authors: Xiaolong Zhu He Huang Shuhua Yang Cong Liu Chen Guo Chiheng Dong Xianping Zhang Dongliang Wang Yanwei Ma

Superconducting wires and tapes are key enabling materials for high-field magnets, nuclear fusion, superconducting power systems and medical imaging. In practical conductors fabricated by the powder-in-tube (PIT) method, the precursor powder is not merely a starting material; it establishes the chemical, microstructural and processing conditions that govern phase formation, texture, density, connectivity and ultimately the critical current density. The challenge is therefore to develop precursor powders that deliver high superconducting performance while remaining compatible with stable, cost-effective and scalable wire and tape manufacturing. This review examines the preparation of precursor powders for practical BSCCO, MgB2 and 122-type iron-based superconductors. We first clarify the functions and evaluation criteria of precursor powders, and then compare the principal synthesis routes and powder-modification strategies used for these conductor systems. Particular attention is given to the links between composition, impurity phases, particle characteristics, reactivity, heat-treatment windows and the resulting conductor properties. We further discuss how non-uniformity and process sensitivity of powders can hinder batch consistency and obstruct scale-up. Overall, the evidence shows that progress must go beyond particle-size refinement or reactivity enhancement alone. A more useful target is an engineering-oriented powder system with precise composition, controllable phase composition, designable particle structure, a matched heat-treatment window and robust production yield. Such powder design, coupled with conductor process optimization, provides a practical path toward higher-performance and more reliable superconducting wires and tapes.

Materials doi: 10.3390/ma19214758

Authors: Lingfeng Niu Junjie Zhang Mingyang Song Hanlin Shen Ming Yang Bo Liu

The high-speed growth of high-temperature industries has resulted in an increase in the generation of waste refractories (WRs) whose resource consumption is a significant concern towards low-carbon targets and the circular economy. This review thoroughly analyzes the mechanisms of physical failure, such as thermal shock and mechanical stress, and chemical failure, including oxidation, erosion, and permeation. Such processes cause compositional complexity and structural degradation, which are the main barriers to recycling. The review discusses the classification-based recycling approaches, including closed-loop recycling, which reprocesses waste into shaped or unshaped refractories through particle-size optimization and binder modification, and open-loop recycling, which converts waste into metallurgical or chemical feedstocks, construction materials, and functional ceramics or thermal storage media. Combining failure mechanisms with regeneration pathways, this review proposes innovative strategies for high-value recycling, offering systematic direction to the green transformation and sustainable use of resources in high-temperature industries.

Materials doi: 10.3390/ma19214757

Authors: Jianhang Chen Yang Yang Cunwen Wang Chaohong Shi Krzysztof Skrzypkowski Krzysztof Zagórski

With mining depth increasing, rock burst disasters are likely to occur and induce impact loading on the cable-bolt reinforcement. Based on this fact, this paper conducted a literature review on the mechanical response and failure mechanisms of cable-bolt reinforcement under impact loading. Two different experimental testing methods were summarised, including the horizontal high-speed impact-loading test and vertical drop-hammer impact-loading test. The advantages and disadvantages of these two experimental test methods were summarised. Compared with the horizontal high-speed impact-loading test, when the vertical drop-hammer impact-loading test was used, the impact energy can be adjusted conveniently. Additionally, the maximum impact velocity can be increased to several times. The influence of different parameters on the mechanical response of the cable-bolt reinforcement was reviewed, including the cable-bolt structure, impact energy and pretension force. Considering that the impact energy may be applied on the cable-bolt reinforcement along the transverse direction, the shear load-bearing behaviour of the cable-bolt reinforcement was also reviewed. Following this, when the impact loading occurred, the cable-bolt reinforcement failure modes were summarised, including the cable-bolt rupture, cable-bolt slippage and locking-nut slippage. This research is beneficial for researchers to better understand the mechanical response and failure mechanisms of the cable-bolt reinforcement subjected to impact loading.

Materials doi: 10.3390/ma19214756

Authors: Xinfu Deng Zicheng Qin Tian Qiu Yuqing Jian Yixiao Yang

The macro stage of the tea-coffee nanoscale detection device adopts an inchworm piezoelectric structure. However, this structure has the phenomenon of inconsistent action, affecting the motion accuracy. To study this phenomenon, the causes of actuation errors were first analyzed, including material dispersion, hysteresis asymmetry, and contact timing differences. Based on this, a three-level voltage adjustment method was then proposed. This method sequentially performs three steps of correction: actuation capability balance, shear hysteresis compensation, and lateral consistency alignment. It systematically improves the consistency of the inchworm piezoelectric structure’s action. Experimental results show that the three-level voltage adjustment method increases the single-step displacement consistency of the actuator by approximately 28.72%, and also significantly improves the stability of the overall movement.

Materials doi: 10.3390/ma19214755

Authors: Angelos T. Zamanis Sotiris P. Evgenidis Thodoris D. Karapantsios Margaritis Kostoglou

Foam generated during wine-must fermentation can reduce the vessel space available for processing liquid. Its practical impact depends on the amount of foam, its persistence, and its position relative to the initial liquid level. This study quantified these features in five must batches: Sauvignon Blanc, Vidiano, Xinomavro rosé, Syrah rosé, and a 50:50 Syrah/Cabernet Sauvignon co-vinification. Two types of experiments used transparent open-topped 1 L vessels. The first tested four initial liquid volumes (500, 600, 700, and 800 mL), with three independently fermented vessels per batch–volume combination (60 vessels), at approximately 12 °C for white musts and 14 °C for rosé musts. The second followed three vessels per batch containing 700 mL at a common temperature of 12.0 ± 0.3 °C, with 12 sampling times from day 0 (D0) to day 16 (D16). Photographic measurements estimated apparent foam volume and recorded the underlying bulk-liquid level. Peak foam volume increased by 11.51–14.16 mL per additional 100 mL of must; peak foam-to-initial-liquid ratios were 11.75–13.29% across batch means. Foam reached sampled maxima on days 10–11 and remained visible at D16. Area under the foam-volume curve ranged from 798.60 ± 1.89 to 954.85 ± 8.89 mL·day. At 800 mL initial fill, peak apparent foam corresponded to 46.83–53.17% of the initial 200 mL headspace. Paired data at 700 mL showed that the lower foam boundary moved downward during foam development and partly recovered as foam declined; total foam-layer burden is therefore distinct from net protrusion above the initial liquid level. These batch- and vessel-specific results support preliminary assessment of fermentation foam and freeboard, but do not establish general varietal rankings or industrial safe-fill limits.

Materials doi: 10.3390/ma19214752

Authors: Žiga Žnidarič Branko Nečemer Srečko Glodež

Laser Powder Bed Fusion (LPBF) enables the manufacturing of complex Ti6Al4V components, but the resulting mechanical and fatigue responses are condition-dependent. This critical narrative review examines how alloy grade and interstitial chemistry, powder history, processing, microstructure, residual stress, defect population, surface condition and post-processing affect quasi-static behaviour and low-, high- and very-high-cycle fatigue behaviour. Reported properties are compared with the associated material and test data, including surface condition, build orientation, stress ratio, loading mode, stress definition and run-out criterion. The review distinguishes finite-life fatigue strength from a demonstrated fatigue limit and separates stress-life data from strain-life and crack-growth parameters. The resulting condition-specific synthesis is intended to support engineering comparison and numerical modelling without treating LPBF Ti6Al4V as a single universal material dataset.

Materials doi: 10.3390/ma19214754

Authors: Kamila Mizera Kamila Sałasińska

The fire performance of hybrid epoxy composites depends on both the flame-retardant system and the reinforcement architecture. This study investigates the effects of different combinations of synthetic and natural fabrics and functional fillers on the fire behavior, thermal degradation, smoke production, and combustion products of epoxy composites containing 10 wt.% expandable graphite (EG) and 10 wt.% ammonium polyphosphate (APP). A glass-fiber-reinforced composite was used as the reference. The materials were characterized by cone calorimetry, smoke density measurements, horizontal burning tests, thermogravimetric analysis (TG/DTG), differential scanning calorimetry (DSC), simultaneous thermal analysis coupled with Fourier-transform infrared spectroscopy (STA/FT-IR), and combustion-effluent analysis using a Purser furnace coupled with a Gasmet DX4000 gas analyzer. Significant differences in fire performance were observed among the formulations. VACMGBHF exhibited the longest time to ignition (206 s), the lowest peak heat release rate (79 kW·m−2), and the lowest maximum mass-loss rate during the principal thermo-oxidative degradation stage (2.03%·min−1). It also retained 38.8% of its initial mass at 900 °C, the highest value among the hybrid composites. In contrast, ACGBF showed the lowest average heat release rate (8 kW·m−2), maximum average rate of heat emission (20 kW·m−2), and total heat release (4 MJ·m−2). Smoke production also depended on composite composition. The lowest maximum specific optical density was recorded for the glass-fabric reference (42), whereas ACGBF exhibited the lowest total smoke release (123 m2·m−2). Visual examination revealed differences in the continuity and morphology of the post-combustion residues, with several hybrid formulations forming expanded, cohesive carbonaceous–mineral layers. TG/DTG, DSC, and STA/FT-IR analyses further demonstrated formulation-dependent degradation behavior and evolved-gas profiles. All composites achieved the HB classification in the horizontal burning test. The findings demonstrate that reinforcement architecture and filler composition influence heat release, smoke generation, and thermal stability in different ways, highlighting the need to evaluate these parameters together when designing flame-retardant epoxy composites.

Materials doi: 10.3390/ma19214753

Authors: Arman Umirzakov Yedil Otunchi Alimzhan Serikbekov Ainagul Kemelbekova Aigul Shongalova Ekaterina Bondar Elena Dmitriyeva

Lithium-ion battery (LIB) recycling is usually compared across pyrometallurgical, hydrometallurgical and direct routes as if the optimal route were independent of the cathode being recycled. This review argues that cathode chemistry is the governing variable. Following the chain from cathode chemistry and degradation mechanism through pretreatment, recycling route and recovered product to electrochemical validation, we compare LiNixMnyCozO2 (NMC, 111 to 811) and LiFePO4 (LFP), with LiCoO2 and LiNi0.8Co0.15Al0.05O2 as references. LFP degradation is dominated by Li loss and Fe/Li anti-site defects in an intact olivine framework, which makes direct regeneration mechanistically well founded. Ni-rich NMC suffers microcracking, surface reconstruction and proton sensitivity, so its regeneration increasingly becomes upcycling into a different product, whereas hydrometallurgical resynthesis currently has the strongest industrial validation. Reported recovery efficiencies above 95% rarely demonstrate battery-grade products, and published energy estimates for the same route and chemistry differ by a factor of up to about 1.5 because of inconsistent system boundaries. We propose a cathode-to-cathode circularity framework and a minimum reporting set that link material recovery to validation in new cells.

Materials doi: 10.3390/ma19214751

Authors: Vasilis Nikitakos Athanasios D. Porfyris Triantafyllia Alevizaki Eleni Rakanta Beatriz Yecora Angelica Perez Rudolf Pfaendner Constantine D. Papaspyrides Konstantinos G. Beltsios

Poly(vinyl butyral) (PVB) is widely used as an interlayer in laminated safety glass in automotive and construction applications. The increasing quantities of PVB arising from end-of-life laminated glass represent a waste stream with significant potential for recycling. This study investigates the durability of high-quality retrieved PVB (re-PVB) separated from laminated glass wastes and evaluates the effect of restabilization against UV aging. Neat unplasticized PVB (u-PVB) and re-PVB were subjected to artificial UV weathering (ISO 4892-3) for up to 1500 h and then characterized in terms of chemical structure, yellowness, melt flow behavior and molecular weight. The results showed that u-PVB exhibited pronounced photooxidative degradation, while re-PVB remained comparatively stable. UV–Vis spectroscopy revealed the presence of residual UV absorbers in re-PVB, indicating that the components of the initial stabilization system might remain functional after the end of its life. Unexpectedly, the restabilization of re-PVB with phenolic antioxidants (AOs) reduced its photooxidative stability, despite their established effectiveness against thermo-mechanical degradation in melt reprocessing. A possible antagonistic effect was suggested between the newly introduced AOs and the residual stabilization system. These findings highlight that re-PVB is a valuable waste, and restabilization should be carefully considered when designing its second service life.

Materials doi: 10.3390/ma19214750

Authors: Yichao Wang Chunrong Qin Rui Luo Sihua Zeng

Multifunctional hydrogels integrating fluorescence sensing and adsorption have application potential in water treatment, but often face the problem of overlap between crosslinking sites and functional sites. To address this, a “functional differentiation of groups” strategy is proposed in this study. Using carboxymethyl chitosan (CMCS) as the precursor, aminated carbon dots (CD-NH2) were synthesized by a hydrothermal method, and CMCS was used as the gel backbone. Using oxidized sodium alginate (OSA) as an aldehyde crosslinker, a fluorescent composite hydrogel (CD–gel) was prepared within 10 min via a room-temperature aqueous Schiff base reaction. In this network, –NH2 participates in Schiff base crosslinking, while –COOH is retained to provide adsorption sites; CD-NH2 are covalently anchored in the network, endowing the gel with fluorescence responsiveness. FTIR and XPS results support the formation of the Schiff base crosslinked network and the retention of carboxyl groups. SEM and N2 adsorption–desorption measurements show that the gel has a honeycomb-like meso–macroporous structure and is negatively charged over a broad pH range. The gel exhibits a fluorescence quenching response to Cr(VI) with a linear range of 0–80 μM (R2 = 0.990), a detection limit of 0.226 μM, rapid response, and anti-interference ability. Meanwhile, the gel exhibits rapid and efficient adsorption toward the cationic dye neutral red (NR), and the adsorption process follows the pseudo-second-order kinetic equation and the Langmuir isotherm equation, with a maximum theoretical adsorption capacity of 739.13 mg g−1. This study provides a group-engineering idea for the design of multifunctional hydrogels.

Materials doi: 10.3390/ma19214749

Authors: Jiale Tang Zhuohan Wang Yuanlang Hou Hanxiao Lu Jiemin Zhang Xiangshun Geng Tian-Ling Ren

As semiconductor devices continue to scale down, conventional lithography technologies face increasingly severe challenges in resolution, stochastic defect control, and manufacturing cost. Block copolymer (BCP) directed self-assembly (DSA), which offers molecular-scale control over pattern formation and compatibility with existing lithographic processes, has emerged as a promising complementary nanopatterning technology for advanced semiconductor manufacturing. This review summarizes the microphase-separation mechanisms of DSA, major guiding strategies including graphoepitaxy and chemoepitaxy, and pattern-transfer techniques such as dry and wet etching and sequential infiltration synthesis (SIS). In terms of device applications, particular emphasis is placed on recent progress in DSA for Fin Field-Effect Transistor (FinFET) fin patterning, silicon nanostructures, high-density contact holes, memory devices, two-dimensional semiconductors, and Complementary Metal–Oxide–Semiconductor (CMOS) optoelectronic devices. Key challenges, including defect control, process-window optimization, pattern transfer, and wafer-scale manufacturing, are further discussed, together with future directions involving the integration of DSA with extreme ultraviolet (EUV) lithography, advanced etching, and data-driven process optimization. This review aims to outline the technological evolution of DSA from nanoscale self-assembly toward integration into advanced semiconductor manufacturing and to provide a reference for high-resolution patterning at advanced technology nodes.

Materials doi: 10.3390/ma19214747

Authors: Arkadiusz Madetko Platon Kapranos Krzysztof Sołek

The analysis of rheological properties provides information that allows the potential for the practical application of metal alloys to be determined and to effectively design their shaping with the use of advanced engineering modelling. The paper presents an analysis of the basic rheological properties of selected copper alloys, CuSn10 and CuAl10Fe3Mn2, in the liquid and semi-solid states. The analysis was based on viscosity measurements and rheological modelling. The measurements were carried out using a high-temperature rheometer with the Searle method. The research described in this article was undertaken to provide data for assessing the potential of using thixoforming technologies to shape copper matrix alloys; research data in this field are insufficient and information in the literature is also limited. The analysis carried out includes the complex characterisation of viscosity in terms of the influence of temperature, strain rate and time. The results were enriched with rheological models that can be used in simulation studies.

Materials doi: 10.3390/ma19214748

Authors: Marin Hodalj Ines Despotović Antonio Zandona Maja Katalinić Maja Ivanić Jozefina Katić Željka Petrović

This study investigates the influence of two collagen coating formation approaches, self-assembly and electrochemical formation by cyclic voltammetry, on the surface properties and electrochemical behavior of titanium (Ti). Collagen-modified Ti surfaces were characterized before and after 7 days of immersion in Fusayama artificial saliva using attenuated total reflectance Fourier-transform infrared spectroscopy, field emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, X-ray diffraction, and electrochemical impedance spectroscopy. Self-assembly produced a continuous collagen layer, whereas cyclic voltammetry generated a fibrillar coating. During immersion, calcium phosphate (CaP) deposits formed on both collagen-modified surfaces, but with distinctly different spatial organization. The self-assembled coating underwent reorganization, whereas the electrochemically formed coating retained its fibrillar framework closely associated with the CaP deposits. This organic–inorganic architecture was accompanied by enhanced electrochemical barrier properties after 7 days compared with the self-assembled coating. Density functional theory calculations further showed that one-electron oxidation of an adsorbed collagen-model tripeptide induces pronounced structural rearrangement, providing molecular-level insight into the redox response of collagen-derived species at the TiO2 interface. In addition, prolonged exposure of Ti surfaces to cell culture media resulted in negligible Ti release, while the resulting conditioned media did not reduce the metabolic viability of HGF-1 or MG-63 cells under the investigated conditions, supporting favorable indirect in vitro cytocompatibility.

Materials doi: 10.3390/ma19214746

Authors: Willian Queiroz Francisco Briones Carola Martínez William Haupt

This study evaluates oscillating fiber laser welding as an alternative to gas metal arc welding with an active shielding gas (GMAW/MAG) for manufacturing 4.25 mm thick SAE 1010 agricultural wheel rims. A systematic product development approach guided technology selection. The comparison included process energy, weld geometry, microstructure, grain size, Vickers microhardness, guided-bend testing, and industrial forming. Estimated GMAW/MAG heat input was 0.64 kJ/mm, whereas nominal incident laser energy was 0.019 kJ/mm; these quantities do not represent equivalent measurements of absorbed heat. Measurements from one transverse cross-section per welding condition showed a smaller weld-face width (5.70 vs. 12.97 mm), lower convexity (0.56 versus 3.93 mm), and a narrower heat-affected zone (0.85 versus 2.10 mm) for laser welding compared with GMAW/MAG. Less grain coarsening was observed in the laser-welded heat-affected zone. Mean fusion-zone hardness was 158.6 ± 18.9 HV1 for laser welding and 190.4 ± 11.0 HV1 for GMAW/MAG. Both conditions passed the guided-bend tests. All ten laser-welded specimens completed industrial forming, whereas two of ten GMAW/MAG specimens fractured during cone opening. The examined laser-welded cross-section exhibited a narrower weld profile than the examined GMAW/MAG cross-section. The laser-welding manufacturing route also eliminated the post-weld grinding operation under the investigated conditions.

Materials doi: 10.3390/ma19214745

Authors: Limu Cui Yan Li Mingshun Yang Qilong Yuan Long Li

A parametric finite element (FE) framework incorporating a finite-thickness equivalent bonding layer is developed for cold roll-beating of explosively bonded Fe/Al layered composites. The equivalent layer thickness is identified from interfacial characterization and the through-thickness microhardness gradient, while its quasi-static and strain-rate-dependent response is determined from nanoindentation, compression, split Hopkinson pressure bar tests, and inverse FE identification. The resulting properties are assigned to a three-layer FE model comprising the steel clad, equivalent bonding layer, and aluminum substrate. Experimental validation gives mean absolute relative errors of 8.35% and 6.20% for forming-force prediction in the spindle-speed and feed-speed series, respectively, and a mean profile normalized root-mean-square error (NRMSE) of 3.27% across six validation conditions. These errors are consistently lower than those of the simplified bilayer model. With increasing spindle speed, the peak forming force first increases slightly and then decreases, while the tooth root deepens and material pile-up increases. Increasing feed speed from 100 to 225 mm/min raises the predicted peak forming force from 13.62 to 14.98 kN but produces a shallower profile. These different trends indicate that peak force reflects local deformation resistance, whereas the final profile is governed mainly by plastic deformation accumulated over successive engagements.

Materials doi: 10.3390/ma19214742

Authors: Mohammed Abdulkedir Alfeki Andrzej Katunin

Active infrared thermography operates without contact, covers the full field from a single side, and can operate at a limited temperature rise, which makes it well suited to the inspection of polymer–matrix composites. However, its diagnostic performance is governed less by the detector hardware than by the mechanism through which heat is generated at, or transported to, damage. This review compares optically and mechanically excited thermography from that standpoint. The underlying material physics is summarized first: diffusive transport and the loss of contrast with damage depth for externally heated configurations, coupled thermoviscoelastic dissipation for internally heated ones, and the glass-transition constraint that limits admissible excitation power in polymers. Pulsed, lock-in, step-heating, pulsed-phase, and frequency-modulated modalities are then reviewed with the depth inversion relations they support. Mechanical excitation is treated in three branches: friction dominated ultrasonic thermography, local defect resonance as an excitation strategy, and self-heating based vibrothermography (SHVT) as a viscoelastic heat-generation mechanism. The reported detection capability of SHVT is then analyzed. Two limits emerge: one set by the size of the damage, the other by its position through the thickness. Finding damage and measuring its size also prove to be different capabilities with different limits. Signal processing is reviewed in three groups, namely classical sequence-based transforms, procedures for background suppression and quantitative characterization, and machine learning-based methods. Open issues in quantification, benchmarking, and data availability are noted, along with the limited use of machine learning-based vibrothermography processing.

Materials doi: 10.3390/ma19214744

Authors: Sangho Park Jungmin Kim Sewook Lee Dongwook Shin

Porous poly(4-vinylpyridine) (P4VP) coatings were fabricated by electrostatic slurry spray deposition (ESSD) using solution and ethanol–water composite-slurry precursors. Thirty-four solvents were screened to examine the relationship between precursor formulation, spray behavior, and deposited morphology. Gradual nonsolvent addition generated a particulate composite slurry, with a principal volume-weighted dynamic light scattering (DLS) peak at 13.78 nm for the 7.4 wt.% formulation. Under the investigated conditions, this slurry produced a more spatially uniform porous coating than the solution precursor and was successfully deposited onto a three-dimensional fibrous filter scaffold. During a preliminary 30 m3 chamber assessment of the air-purifier system equipped with the coated filter, formaldehyde (HCHO) concentration decreased from 0.846 to 0.702 ppm in 1 h, corresponding to an apparent concentration-decay-based air-cleaning rate (Qapp) of approximately 5.69 m3 h−1. This preliminary observation describes the performance of the assembled air-purifier system; the principal contribution of the study is the formulation and morphological control of porous P4VP coatings through composite-slurry ESSD.

Materials doi: 10.3390/ma19214743

Authors: Zbigniew A. Łagodowski Łukasz Stępień Grzegorz Komarzyniec

This study develops an operator-based method for constructing scenario-based boiling curves for a carbon nanotube buckypaper (BP) layer on copper in liquid nitrogen, using a reference Cu–LN2 characteristic. The reference curve is constructed using established cryogenic pool-boiling correlations, complemented by appropriate connections between the boiling regimes. The proposed operator transforms the reference characteristic to represent potential changes in boiling behavior associated with the BP layer. Two scenarios, moderately optimistic and optimistic, are considered for three surface orientations: 0°, 90°, and 180°. The resulting complete and continuous boiling curves can be used as boundary conditions in thermal and electrothermal models. The transformation parameters are scenario-based and require experimental calibration for the BP–Cu–LN2 system.

Materials doi: 10.3390/ma19214740

Authors: Habib Loubani Madumita Sadagopan Agnes Nagy

This study evaluates finely milled float glass powder (GP) as a supplementary cementitious material (SCM) through a mechanistic–empirical framework based on strength and reactivity assessment. A mechanistic approach was developed to quantify the SCM efficiency of glass powder. Compared with conventional standardized testing procedures, the proposed method enables rapid mechanical performance evaluation with minimal testing. The mechanistic model is evaluated on cementitious systems with GP inclusion and consists of the following stages: (1) Best replacement percentage, as determined by the strength activity index (SAI), evaluated on mortar specimens for 20, 25 and 30% replacements. The highest SAI of 85% is observed for 20% replacement. (2) k-value determination by Abram’s law, wherein compressive strength is used as a reference and GP-based concrete (20% replacement) at 0.42, 0.46, 0.5 and 0.61 water–binder ratios are investigated. This results in an average k-value of 0.5. (3) SAI-based k-value (kSAI), which derives the compressive strength of glass at different water–binder ratios from reference concrete strengths by multiplying by the SAI value 85% and determining the k-value (kSAI) from the resulting compressive strength values using Abram’s law, resulting in 0.43. (4) Equivalent performance of concrete for frost resistance exposure classes (XF1, XF3); according to the SIS-CEN/TR 16639 Dutch method, wherein, if the SCM concrete shows comparable strength to the reference concrete, testing for exposure classes XF1 and XF3 is not required. GP-based concrete with a k-value of 0.5 surpasses the compressive strength reference values of 45 MPa and 43 MPa, respectively. (5) Recycled aggregate-incorporated concrete with a k-value of 0.5 has also been evaluated for equivalent performance, surpassing that of crushed aggregate reference concrete by 7%, which also makes it frost-resistant for exposure classes XF1 and XF3. This approach has the potential to serve as a practical screening tool for the preliminary evaluation of SCMs, thereby accelerating the development and implementation of sustainable cementitious materials.

Materials doi: 10.3390/ma19214741

Authors: Pitcha Sawaiprakhon Supansa Paipae Jidapa Ouantavorn Thanantorn Tong-Uthai Juthathip Khanthawisooth Chawisa Sae-Iah Nichapach Suraged Juthamas Sripitak Supak Tontisirin

The shaping of zeolite powder is an essential process for enhancing zeolite utilization. It facilitates easier handling, improves fluid flow distribution, minimizes pressure drop during operation, and enhances mass transfer. Adding a bentonite binder is necessary for zeolite particle cohesion to create strong bonds between the zeolite crystals. The resulting quartz, anorthoclase, and metabentonite phases can enhance the mechanical stability of the zeolite extrudates. In addition, the bentonite binder modifies the pore size distribution of the extrudates by generating mesopores in the 7.5–24 nm range. In contrast, adding more bentonite (26.7:100 bentonite-to-zeolite weight ratio) can reduce the specific surface area and pore volume by 35.9% and 32%, respectively. NaX zeolite extrudates are effective dehumidifying adsorbents for moisture control in confined spaces. Incorporating a bentonite binder into the extrudate creates a highly suitable hierarchical structure (mesopore-to-micropore ratio). This structure facilitates the diffusion of water vapor into the active sites within the extrudate core, thereby enhancing adsorption performance. The linear driving force (LDF) model combined with the Freundlich equation is empirically fitted to the adsorption kinetics of the zeolite extrudates. The extrudates remain stable for at least four cycles of post-regeneration with no loss in efficiency. These results demonstrate that the prepared NaX extrudates are suitable for this application and can be effectively utilized in large-scale applications.

Materials doi: 10.3390/ma19214739

Authors: Minju Jeong Igor Plokhikh Ekaterina Pomjakushina Jongtae Ahn Soonbeom Seo

NdSbTe is a magnetic topological semimetal in which nontrivial electronic states coexist with antiferromagnetic order, while variation in the Sb/Te composition substantially modifies its electronic and magnetic properties. Here, we investigate the temperature- and magnetic field-dependent electrical transport properties of NdSb0.5Te1.5. The electrical resistivity exhibits nonmetallic behavior below approximately 100 K and develops a pronounced high-resistivity state below 4 K, reaching more than three orders of magnitude above its room temperature value. Multiple characteristic anomalies emerge within the high-resistivity state and are systematically suppressed by magnetic fields. The characteristic temperatures and critical fields consistently define multiple transport regimes in the H-T phase diagram. Remarkably, a relatively weak magnetic field of approximately 0.5 T induces an abrupt and hysteretic transition between high and low resistivity states. These results demonstrate an exceptionally large field-tunable resistive response closely coupled to the magnetic state in NdSb0.5Te1.5.

Materials doi: 10.3390/ma19214738

Authors: Marcin Knapiński Teresa Bajor Grzegorz Boczkal Małgorzata Perek-Nowak

This paper presents the effect of spark plasma sintering (SPS) parameters and hot plastic deformation on the microstructural evolution of the Ti-10V-2Fe-3Al titanium alloy. The study examines the effects of sintering temperature (1200 °C and 1300 °C) and sintering time (10 min and 15 min), as well as plastic deformation parameters, on microstructural transformations. It was demonstrated that the short duration of high-temperature exposure during SPS sintering favours the preservation of local differences in chemical composition, leading to the formation of regions with varying vanadium and other alloying element contents, as well as varying microhardness. Hot deformation tests at 680 °C revealed a stress peak, followed by softening, indicating that structural reorganisation occurs during deformation. It was also found that the intensity of plastic deformation and the sintering temperature influence the homogenization of the material’s chemical composition throughout its volume, the grain refinement of the β phase, and the change in the morphology of the α phase. The use of a two-stage hot plastic deformation process enabled the formation of a fine-grained, banded α + β two-phase structure in a sintered part produced at 1300 °C. The results indicate that the appropriate selection of sintering parameters and subsequent stages of plastic deformation are key tools for shaping the microstructure of the Ti-10V-2Fe-3Al alloy, thereby enabling control over its chemical and structural heterogeneity.

Materials doi: 10.3390/ma19214737

Authors: Kun Ding Xuetao Wang Xiaokun Miao

In this study, a new pressure stabilization (PS) system composed of a gas-stable vessel (SV), a PID control system, and a reaction vessel (RV) was used to investigate the dynamic characteristics of methane separation from low-concentration coalbed methane and to compare its performance with that of a pressure variation (PV) system. A bio-surfactant sulfonated lignin system was constructed using sodium lignosulfonate (SL) or calcium lignosulfonate (CL) solution, which reduced gas–liquid interfacial tension and enhanced methane dissolution and mass transfer. In addition, cyclopentane (CP) was introduced to the solution as a thermodynamic accelerator to reduce the hydration reaction conditions and improve its methane storage capacity. The experiments were carried out at 275.15 K and 3.0 MPa; the mass concentration of the lignin was 500 ppm and the volume ratio of CP to deionized water was 1:10. The results showed that the PS + SL + CP system achieved the highest CH4 recovery (66.5%) and gas uptake (0.1142 mol), whereas the PV + SL + CP system exhibited a shorter t90 (156.7 min) and a higher CH4 concentration (69.5%) in the hydrate phase. In contrast, the shortest induction time (10.3 min) was observed for the PS + CL + CP system.

Materials doi: 10.3390/ma19214736

Authors: Jingjing Yan Qing Zhao Huiling He Zhiqiang Mu Haoyu Song Yiming Chen Xiaobing Hu Jincheng Wang

Active learning (AL) promises accelerated multi-objective materials discovery, yet acquisition-function choice is often made without matching dataset, budget, and target metric. We retrospectively compared EI-random, EI-cent, EI-maxmin, and EI-prod on Al alloy, steel, and Cu alloy datasets across 100 randomized cold-start trials, using hypervolume, true Pareto-sample discovery, inverted generational distance, balanced-performance score, and iterations to 95% target. EI-prod is best overall on Al dataset; EI-maxmin improves Pareto-front recovery and convergence on steel and Cu datasets; EI-cent gives limited, inconsistent gains. No strategy dominates all datasets or budgets. These results provide a metric-aware, outcome-specific selection guide: use EI-prod for early balanced candidates, and EI-maxmin for broader Pareto-front exploration. They also warn that similar balanced performance does not ensure equivalent front reconstruction and that dataset-specific rankings should inform, not dictate, AL design in materials screening. This reframes acquisition selection as a decision-making, not universal-ranking, problem.