Materials

16 pages, 4606 KB

Open AccessArticle

AlOOH-Coated Glass Fiber-Reinforced Composites for Pipeline Rehabilitation: Enhancement of Interfacial Adhesion and Durability

by Mengfei Du, Xilai Yan, Chuandong Wu and Ke Wang

Materials 2025, 18(21), 4887; https://doi.org/10.3390/ma18214887 (registering DOI) - 24 Oct 2025

Abstract

Glass fiber (GF) reinforced unsaturated polyester resin (UP) composites are used in cured-in-place pipe (CIPP) rehabilitation technology of drainage systems due to their low cost and excellent force chemical properties. However, the weak interfacial compatibility between GF and the polymer matrix limits the [...] Read more.

Glass fiber (GF) reinforced unsaturated polyester resin (UP) composites are used in cured-in-place pipe (CIPP) rehabilitation technology of drainage systems due to their low cost and excellent force chemical properties. However, the weak interfacial compatibility between GF and the polymer matrix limits the stress transfer efficiency. Herein, a strategy of a polyhydric boehmite (AlOOH) layer coated on GF (GF-AlOOH) was developed for improving the mechanical properties of UP composites, and the enhancement effects of the coating process were analyzed. The AlOOH-modified GFs significantly improved the flexural and tensile strengths of the modified composites by 41.21% and 21.05%, respectively. Moreover, the enhancement mechanism was explored by analyzing the surface chemical structure of GF-AlOOHs. The nano-AlOOH was grafted on the GF surface by O=Al–OH. Meanwhile, the increase in the mechanical properties of UP/GF-AlOOH was mainly attributed to the combined effect of mechanical interlocking interaction, covalent bonding and hydrogen bonding, which improved the interfacial adhesion between GF and UP. In summary, this work provides effective guidance for achieving high-quality interfaces in GF composites and offers important insights into designing durable and cost-effective materials for CIPP rehabilitation and broader infrastructure applications. Full article

(This article belongs to the Special Issue Advanced Polymers and Composites for Multifunctional Applications)

► Show Figures

Figure 1

13 pages, 8008 KB

Open AccessArticle

Geopolymer Materials for Additive Manufacturing: Chemical Stability, Leaching Behavior, and Radiological Safety

by Bahar Gharehpapagh, Meike Denker, Szymon Gadek, Richard Gruhn, Thomas Grab, Kinga Korniejenko and Henning Zeidler

Materials 2025, 18(21), 4886; https://doi.org/10.3390/ma18214886 (registering DOI) - 24 Oct 2025

Abstract

Geopolymers are inorganic aluminosilicate binders formed by alkali activation of reactive powders, offering a sustainable, low-carbon alternative to Portland cement. Their rapid setting and chemical durability make them well-suited for additive manufacturing (AM) in demanding environments, including underwater construction, where chemical stability is [...] Read more.

Geopolymers are inorganic aluminosilicate binders formed by alkali activation of reactive powders, offering a sustainable, low-carbon alternative to Portland cement. Their rapid setting and chemical durability make them well-suited for additive manufacturing (AM) in demanding environments, including underwater construction, where chemical stability is essential for both structural integrity and environmental safety. This study evaluates two metakaolin-based formulations designed for underwater extrusion, differing in activator chemistry and rheology control. Standardized leaching tests revealed alkaline but stable leachates with strong immobilization of most ions; major anions and total dissolved solids remained within regulatory thresholds. Limited exceedances were observed—soluble organic carbon in the NaOH-activated mix and arsenic/selenium in the waterglass–sand system—highlighting specific areas for mix improvement rather than fundamental limitations of the material. Complementary radioactivity screening confirmed activity concentration indices well below the regulatory limit, with measured radionuclide activities falling comfortably within exemption ranges. Together, the leaching and radioactivity results demonstrate that both formulations provide robust matrix integrity and environmental compatibility, while highlighting clear opportunities for mix design improvements to further minimize ecological risks. Full article

(This article belongs to the Special Issue Geopolymers and Fiber-Reinforced Concrete Composites (Second Edition))

13 pages, 1934 KB

Open AccessArticle

Ligand-Mediated, Temperature-Tuned Synthesis of CsPbBr₃ Nanosheets for Ordered Superlattice Assembly

by Zahir Abdalla, Chengqi Liu, Shefiu Kareem, Xiaoqian Wang, Zisheng Tang and Yong Liu

Materials 2025, 18(21), 4885; https://doi.org/10.3390/ma18214885 (registering DOI) - 24 Oct 2025

Abstract

Two-dimensional (2D) colloidal CsPbBr₃ nanosheets (NSs) possess size-dependent optoelectronic properties; however, conventional hot-injection methods often lack precise growth control and well-ordered superlattice self-assembly. Herein, we introduce a modified ligand-assisted hot-injection strategy that promotes direct precursor–ligand interactions prior to solvent mixing, thereby enabling [...] Read more.

Two-dimensional (2D) colloidal CsPbBr₃ nanosheets (NSs) possess size-dependent optoelectronic properties; however, conventional hot-injection methods often lack precise growth control and well-ordered superlattice self-assembly. Herein, we introduce a modified ligand-assisted hot-injection strategy that promotes direct precursor–ligand interactions prior to solvent mixing, thereby enabling highly controlled nanosheet superlattice growth. By adjusting the reaction temperature from 130 to 150 °C, we obtained rectangular nanosheets with monodisperse, well-defined thicknesses of 3.35 ± 0.05 nm and 4.05 ± 0.09 nm at 130 and 140 °C, respectively, both below the 7 nm exciton Bohr diameter, consistent with strong quantum confinement. The resulting superlattices exhibited sharp, tunable photoluminescence peaks at 462, 464, and 513 nm, with time-resolved PL revealing a clear size–lifetime correlation, where smaller lateral superlattices at 130 °C showed a short decay time of 8.65 ns, intermediate growth at 140 °C yielded 15.42 ns, and larger lateral superlattices at 150 °C reached 35.49 ns. Importantly, the modified synthesis facilitated the formation of ordered superlattices that preserved their intrinsic emission properties, underscoring their structural stability and scalability. These findings establish a direct link between ligand-mediated synthesis, reaction temperature, nanosheet dimensions, and optical performance, offering a pathway to high-quality perovskite NS superlattices for advanced optoelectronic applications such as light-emitting diodes and sensors. Full article

(This article belongs to the Special Issue Advanced Materials in Photoelectrics and Photonics)

► Show Figures

Figure 1

24 pages, 2388 KB

Open AccessArticle

Enhancing the Chloride Adsorption and Durability of Sulfate-Resistant Cement-Based Materials by Controlling the Calcination Temperature of CaFeAl-LDO

by Lei Yang, Xin Zhao, Shaonan Cai, Minqi Hua, Jijiang Liu, Hui Liu, Junyi Wu, Liming Pang and Xinyu Gui

Materials 2025, 18(21), 4884; https://doi.org/10.3390/ma18214884 (registering DOI) - 24 Oct 2025

Abstract

Chloride-ion (Cl⁻)-induced corrosion of steel bars is a major threat to the durability of marine concrete structures. To address this, a type of calcined CaFeAl-layered double oxide (LDO-CFA) with different calcination temperatures was used to enhanced the Cl⁻ adsorption, compressive [...] Read more.

Chloride-ion (Cl⁻)-induced corrosion of steel bars is a major threat to the durability of marine concrete structures. To address this, a type of calcined CaFeAl-layered double oxide (LDO-CFA) with different calcination temperatures was used to enhanced the Cl⁻ adsorption, compressive strength, and corrosion resistance of sulphate-resistant Portland cement (SRPC)-based materials. Experimental results demonstrated that LDO-CFA exhibited high Cl⁻ adsorption capacity in both CPSs and cement-based materials. Specifically, LDO-750-CFA reached 1.98 mmol/g in CPSs—60.1% higher than LDHs-CFA—and followed the Langmuir model, indicating monolayer adsorption. It also reduced the free Cl⁻ content of SRPC paste to 0.255–0.293% after 28 days, confirming its sustained adsorption over extended curing. Furthermore, LDO-CFA positively influenced the compressive strength at all curing ages. At an optimal dosage of 0.8 wt.%, LDO-750-CFA paste significantly improved the compressive strength, increasing it by 22.1% at 7 days and 15.6% at 28 days compared to the control. Electrochemical analysis confirmed the superior corrosion resistance of the LDO-750-CFA system. The property enhancement originated from LDO-750-CFA’s synergistic effects, which included pore refinement, increased tortuosity, Cl⁻ adsorption by structural memory, a PVP-induced passive film, and PVP-improved dispersion. Overall, this work provides a framework for developing LDO-750-CFA-based composites, paving the way for more durable marine concrete. Full article

(This article belongs to the Special Issue Advanced Experimental Technology, Theory and Numerical Methods in Geomaterials and Concrete Materials)

33 pages, 10526 KB

Open AccessFeature PaperArticle

Electrodeposition of Amorphous Cobalt–Phosphorus Coating

by Noam Eliaz, Gal Weisman, Amit Kohn, George Levi, Brian A. Rosen, Alexey Moshkovich and Lev S. Rapoport

Materials 2025, 18(21), 4883; https://doi.org/10.3390/ma18214883 (registering DOI) - 24 Oct 2025

Abstract

Amorphous cobalt-phosphorous (CoP) coatings are a candidate to replace hard chromium and other traditional coatings. Here, electrodeposition of both amorphous and crystalline CoP coatings was performed at room temperature and in an air environment. The bath composition and deposition conditions were optimized to [...] Read more.

Amorphous cobalt-phosphorous (CoP) coatings are a candidate to replace hard chromium and other traditional coatings. Here, electrodeposition of both amorphous and crystalline CoP coatings was performed at room temperature and in an air environment. The bath composition and deposition conditions were optimized to offer a low cost, low maintenance, and safe process. The effects of various deposition variables such as solution composition, pH, duration, and mixing parameters were studied, and the reproducibility of the process was demonstrated. Selected coatings were then thoroughly characterized by a variety of techniques. The best amorphous/nanocrystalline coating contained ca. 6.4 wt.% P after 1.2 h of deposition, and 7.2 wt.% P after 4 h of deposition. The best crystalline coating contained ca. 2.7 wt.% P after 1.2 h of deposition and between 2.3 and 5.5 wt.% P after 4 h of deposition. The amorphous coating had excellent mechanical properties: a high hardness (7.8 ± 0.7 GPa), high Young’s modulus (153 ± 9 GPa), and surprisingly low coefficient of dry friction (between 0.11 ± 0.02 and 0.17 ± 0.01). The coating could not be scraped from the substrate using a diamond scalpel blade. In a standard adhesion test, the sample failed neither cohesively within the coating nor adhesively between the coating and the substrate. In the as-deposited conditions, the structure was uniform, nanocrystalline, or had nanocrystals embedded in an amorphous matrix. The crystallization temperature of the amorphous alloy was 284 °C, and the phase transformation occurred only between 300 and 400 °C. The coatings developed and comprehensively characterized herein may be considered for aerospace, magnetic storage, fuel cells, water splitting, and other applications. Full article

(This article belongs to the Special Issue Metal Coatings for Wear and Corrosion Applications (Second Edition))

14 pages, 1341 KB

Open AccessArticle

Branched Hyaluronic Acid for Reduced Viscosity and Enhanced Moisturization

by Hyun Ji Lee, In Young Lee, Yongseok Choi, Yun-chan Lee and Kuen Yong Lee

Materials 2025, 18(21), 4882; https://doi.org/10.3390/ma18214882 (registering DOI) - 24 Oct 2025

Abstract

Despite its remarkable moisturizing properties, the inherently high viscosity of high-molecular-weight hyaluronic acid (HA) restricts its practical application in skincare products, cosmetic formulations, and skin-contact medical devices. To overcome this limitation, we propose the incorporation of branched structures into HA to create a [...] Read more.

Despite its remarkable moisturizing properties, the inherently high viscosity of high-molecular-weight hyaluronic acid (HA) restricts its practical application in skincare products, cosmetic formulations, and skin-contact medical devices. To overcome this limitation, we propose the incorporation of branched structures into HA to create a branched HA hybrid (bHH) by chemically coupling low-molecular-weight HA (200 kDa) with high-molecular-weight HA (700–2500 kDa). The introduction of branched structures into the HA backbone alters the viscosity of high-molecular-weight HA while preserving its moisturizing potential. Branching reduces the solution viscosity of linear HA, particularly at higher polymer concentrations. In this study, the moisturizing efficacies of branched and linear HAs were extensively evaluated. Branched HA demonstrated equivalent or superior moisturizing effectiveness compared with linear HA and even significantly enhanced the water-binding capacity over simple mixtures of linear HAs. These findings suggest that introducing branched structures can effectively reduce the solution viscosity of linear HA without compromising its moisturizing properties, thereby improving the usability and hydration performance of skincare products and skin-contact devices. Full article

(This article belongs to the Special Issue Towards Functional Biohybrid Materials and Devices for Sensing and Biomedical Applications)

24 pages, 7283 KB

Open AccessArticle

Electrochemical Machining of Highly Strain-Hardenable High-Entropy FeMnCrCoSi Alloy: Role of Passivation and Selective Dissolution

by Kavindan Balakrishnan, Kundan Kumar, Indrajit Charit and Krishnan S Raja

Materials 2025, 18(21), 4881; https://doi.org/10.3390/ma18214881 (registering DOI) - 24 Oct 2025

Abstract

Fe₄₂Mn₂₈Cr₁₅Co₁₀Si₅ is a highly strain-hardenable high-entropy alloy (HEA) that is challenging to machine with traditional metal cutting tools. The electrochemical behavior of this HEA was examined in nitrate- and chloride-based electrolytes to understand the [...] Read more.

Fe₄₂Mn₂₈Cr₁₅Co₁₀Si₅ is a highly strain-hardenable high-entropy alloy (HEA) that is challenging to machine with traditional metal cutting tools. The electrochemical behavior of this HEA was examined in nitrate- and chloride-based electrolytes to understand the electrochemical machining (ECM) process. Potentiodynamic and potentiostatic tests were conducted on this alloy in 1 M and 2.35 M NaNO₃ solutions, with and without additions of 0.01 M nitric acid and 0.01 M citric acid. A 20% NaCl solution was also tested as an electrolyte. Nitrate solutions caused passivation of the HEA, while no passivation was observed in chloride solutions. Surface analysis with X-ray photoelectron spectrometry (XPS) indicated that adding citric acid helped reduce surface passivation. The Faradaic efficiency of ECM increased with higher applied voltage. The chloride solution showed higher Faradaic efficiency than nitrate-based solutions. Specifically, the Faradaic efficiency of 20% NaCl at 10 V is 57.4%, compared to 21.9% for 20% NaNO₃ + 0.01 M citric acid at 10 V. Electrochemical parameters, including anodic and cathodic exchange current densities, Tafel slopes, and corrosion current densities, were calculated from the experimental data. The corrosion current densities in the 20% nitrate solutions ranged from 2.35 to 3.2 × 10⁻⁵ A/cm², while the 20% chloride solution had a lower corrosion rate at 1.45 × 10⁻⁵ A/cm². These electrochemical parameters can help predict the dissolution behavior of the HEA in nitrate and chloride solutions and aid in optimizing the ECM process. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

► Show Figures

Graphical abstract

15 pages, 934 KB

Open AccessArticle

Computational Modelling of a Prestressed Tensegrity Core in a Sandwich Panel

by Jan Pełczyński and Kamila Martyniuk-Sienkiewicz

Materials 2025, 18(21), 4880; https://doi.org/10.3390/ma18214880 (registering DOI) - 24 Oct 2025

Abstract

Tensegrity structures, by definition composed of compressed members suspended in a network of tensile cables, are characterised by a high strength-to-weight ratio and the ability to undergo reversible deformations. Their application as cores of sandwich panels represents an innovative approach to lightweight design, [...] Read more.

Tensegrity structures, by definition composed of compressed members suspended in a network of tensile cables, are characterised by a high strength-to-weight ratio and the ability to undergo reversible deformations. Their application as cores of sandwich panels represents an innovative approach to lightweight design, enabling the regulation of mechanical properties while reducing material consumption. This study presents a finite element modelling procedure that combines analytical determination of prestress using singular value decomposition with implementation in the ABAQUS™ 2019 software. Geometry generation and prestress definitions were automated with Python 3 scripts, while algebraic analysis of individual modules was performed in Wolfram Mathematica. Two models were investigated: M1, composed of four identical modules, and M2, composed of four modules arranged in two mirrored pairs. Model M1 exhibited a linear elastic response with a constant global stiffness of 13.9 kN/mm, stable regardless of the prestress level. Model M2 showed nonlinear hardening behaviour with variable stiffness ranging from 0.135 to 1.1 kN/mm and required prestress to ensure static stability. Eigenvalue analysis confirmed the full stability of M1 and the increase in stability of M2 upon the introduction of prestress. The proposed method enables precise control of prestress distribution, which is crucial for the stability and stiffness of tensegrity structures. The M2 configuration, due to its sensitivity to prestress and variable stiffness, is particularly promising as an adaptive sandwich panel core in morphing structures, adaptive building systems, and deployable constructions. Full article

(This article belongs to the Special Issue Selected Papers from the 26th International Conference on Computer Methods in Mechanics (CMM2025))

18 pages, 12714 KB

Open AccessArticle

Femtosecond Laser Ablation of Copper-Hydroxyphosphate-Modified CFRP

by Denys Baklan, Oleksiy Myronyuk, Anna Bilousova, Paulius Šlevas, Justinas Minkevičius, Orestas Ulčinas, Sergej Orlov and Egidijus Vanagas

Materials 2025, 18(21), 4879; https://doi.org/10.3390/ma18214879 (registering DOI) - 24 Oct 2025

Abstract

Carbon-fiber-reinforced plastic (CFRP) machining by ultrashort-pulse lasers promises high precision but is limited due to the heterogeneous epoxy–carbon fiber structure, which creates heat-affected zones and variable kerf quality. This work investigates synthesized copper hydroxyphosphate as a laser-absorbing additive to improve femtosecond (1030 nm) [...] Read more.

Carbon-fiber-reinforced plastic (CFRP) machining by ultrashort-pulse lasers promises high precision but is limited due to the heterogeneous epoxy–carbon fiber structure, which creates heat-affected zones and variable kerf quality. This work investigates synthesized copper hydroxyphosphate as a laser-absorbing additive to improve femtosecond (1030 nm) laser ablation of CFRP. Copper hydroxyphosphate particles were synthesized hydrothermally and incorporated into an epoxy matrix to produce single-ply CFRP laminates. Square patterns (0.5 × 0.5 mm) were ablated with a pulse energy of 0.5–16 μJ. Then, ablated volumes were profiled and materials characterized by SEM and EDS. In neat epoxy the copper additive reduced optimum ablation efficiency and decreased penetration depth, while producing smoother, less porous surfaces. In contrast, CFRP with copper hydroxyphosphate showed increased efficiency and higher penetration depth. SEM and EDS analyses indicate more uniform matrix removal and retention of resin residues on fibers. These results suggest that copper hydroxyphosphate acts as a local energy absorber that trades volumetric removal for improved surface quality in epoxy and enhances uniformity and process stability in CFRP femtosecond laser machining. Full article

(This article belongs to the Section Advanced Composites)

26 pages, 8632 KB

Open AccessArticle

Experimental Study on the Fatigue Degradation of Prestressed Concrete Slabs for Composite Bridges

by Wenjun Li, Rujin Ma, Yuqing Liu and Chen Liang

Materials 2025, 18(21), 4878; https://doi.org/10.3390/ma18214878 (registering DOI) - 24 Oct 2025

Abstract

Concrete slabs in composite bridges are inevitably subjected to heavy vehicular loads during their service life. To evaluate the fatigue performance of the prestressed concrete slabs in composite bridges, two full-scaled models of prestressed concrete slabs were first designed and tested, with the [...] Read more.

Concrete slabs in composite bridges are inevitably subjected to heavy vehicular loads during their service life. To evaluate the fatigue performance of the prestressed concrete slabs in composite bridges, two full-scaled models of prestressed concrete slabs were first designed and tested, with the load amplitude was selected as the variable. To simulate the damage caused by the initial passage of heavy vehicles, this was simplified into the form of a static cyclic load. The mechanical deformation state and crack distribution of the slab were analyzed. Further, a finite-element model was established, and a parametric analysis based on the variation in loading form, such as monotonic displacement loading, static cyclic loading followed by monotonic displacement loading, and cyclic displacement loading, was conducted to discuss the performance-enhancement mechanism of prestressed concrete slabs. Finally, in consideration of the influence of static cyclic damage on the fatigue performance of prestressed concrete slabs, evaluation parameters were proposed to account for static cyclic damage by considering the effects of stresses in concrete, tensile rebar, prestressed tendons, and external loading. A comprehensive fatigue performance evaluation method for prestressed concrete slabs, which neglects the tensile hardening behavior of cracked concrete in the tension zone, was established and verified by test results. The results indicate that the damage caused by static cyclic loading has a significant influence on the fatigue performance of the slab. Applying prestress can significantly mitigate the influence of initial damage on the mechanical and deformation behavior of the slab, which benefits from the prestress compensating for the cracking stress at the bottom of the slab. The proposed fatigue performance-evaluation method for prestressed concrete slabs, which considers static cyclic damage, can predict fatigue deformation behavior with an error of less than 10%, while reasonably determining the fatigue life and failure modes of prestressed concrete slabs. The parametric analysis reveals that when the prestress value exceeds 9 MPa, the failure mode of the prestressed concrete slab transfers from rebar fracture to concrete failure. Full article

(This article belongs to the Section Construction and Building Materials)

► Show Figures

Figure 1

12 pages, 2548 KB

Open AccessArticle

Highly Graphitized Straw-Derived Carbon via Molten Salt Electrolysis for Potassium-Ion Batteries

by Yao Chang, Xinrui Wang, Yi Lu, Shijie Li, Zhenghao Pu, Wei-Li Song and Dongbai Sun

Materials 2025, 18(21), 4877; https://doi.org/10.3390/ma18214877 (registering DOI) - 24 Oct 2025

Abstract

The conversion of straw biomass into highly graphitized carbon materials is achieved through an efficient molten salt electrolysis process at moderate temperatures (900–950 °C). Increasing the electrolysis temperature significantly enhances the degree of graphitization, structural ordering, and heteroatom removal efficiency, as evidenced by [...] Read more.

The conversion of straw biomass into highly graphitized carbon materials is achieved through an efficient molten salt electrolysis process at moderate temperatures (900–950 °C). Increasing the electrolysis temperature significantly enhances the degree of graphitization, structural ordering, and heteroatom removal efficiency, as evidenced by multiscale characterization and electrochemical simulations. The resulting graphitic material exhibits a highly ordered layered structure with improved crystallinity and a larger specific surface area. When used as a potassium-ion battery anode, this biomass-derived carbon delivers a reversible capacity of 232.9 mA·h·g⁻¹ after 100 cycles and retains 230.8 mA·h·g⁻¹ after 500 cycles, owing to its well-developed graphite framework, which accommodates volume changes and facilitates rapid ion diffusion. This study presents a sustainable and scalable strategy for transforming low-cost agricultural waste into high-performance energy storage materials and provides valuable insights into the electrochemical graphitization process. Full article

(This article belongs to the Section Carbon Materials)

15 pages, 3438 KB

Open AccessArticle

Changes in the Tribological and Mechanical Properties of Nimonic 90 Superalloy After Irradiation with Swift Xenon Ions

by Piotr Budzyński, Mariusz Kamiński, Zbigniew Surowiec and Marek Wiertel

Materials 2025, 18(21), 4876; https://doi.org/10.3390/ma18214876 (registering DOI) - 24 Oct 2025

Abstract

The article presents the results of research on the effect of 160 MeV xenon ions irradiation on the mechanical and tribological properties of the Nimonic 90 superalloy. The alloy samples were irradiated with xenon ion fluences ranging from 1 × 10¹⁴ to [...] Read more.

The article presents the results of research on the effect of 160 MeV xenon ions irradiation on the mechanical and tribological properties of the Nimonic 90 superalloy. The alloy samples were irradiated with xenon ion fluences ranging from 1 × 10¹⁴ to 5 × 10¹⁴ Xe²⁴⁺/cm² at a temperature of 60 °C. The investigations revealed significant changes in the crystal structure of the material, including the formation of new phases and partial amorphisation of the surface layer, particularly pronounced at the highest irradiation fluence. Measurements of microhardness, coefficient of friction, and wear revealed a deterioration in the mechanical and tribological properties of the samples irradiated with fluences of 1.0 and 2.5 × 10¹⁴ Xe²⁴⁺ ions/cm², attributed to the formation of radiation-induced defects. Increased friction and wear were observed at depths greater than the predicted range of xenon ions, indicating the occurrence of a long-range effect. After irradiation with a 5.0 × 10¹⁴ Xe²⁴⁺ ions/cm² fluence, a radiation annealing effect was observed, leading to a partial reduction in the earlier damage and resulting in improved microhardness and reduced wear. To our knowledge, this is the first observation of a radiation annealing effect under these specific irradiation and test conditions. The findings suggest limitations in the application of the Nimonic 90 superalloy in environments exposed to intense ionizing radiation, such as nuclear reactors. Full article

(This article belongs to the Special Issue Computational and Experimental Modeling of Interfaces and Joints in Advanced Materials)

► Show Figures

Figure 1

18 pages, 6792 KB

Open AccessArticle

Microstructure, Mechanical and Tribological Properties of Cold Sprayed Fe-Based Metallic Glass Coatings

by Anna Góral, Anna Trelka-Druzic, Wojciech Żórawski, Łukasz Maj, Martin Vicen, Otakar Bokůvka, Paweł Petrzak and Grzegorz Garzeł

Materials 2025, 18(21), 4875; https://doi.org/10.3390/ma18214875 (registering DOI) - 24 Oct 2025

Abstract

Iron-based metallic glasses are gaining increased interest due to their good glass-forming ability, high compressive strength, high corrosion resistance, catalytic properties, excellent soft magnetic properties, and relatively low cost. Cold spraying was successfully used to produce amorphous coatings from commercially available powder without [...] Read more.

Iron-based metallic glasses are gaining increased interest due to their good glass-forming ability, high compressive strength, high corrosion resistance, catalytic properties, excellent soft magnetic properties, and relatively low cost. Cold spraying was successfully used to produce amorphous coatings from commercially available powder without any crystallization due to its high cooling rate and short processing time, minimizing thermal influences. Thick and dense amorphous coatings were obtained. The effect of a substrate on the microstructure, phase composition, microhardness, flexural strength, and wear behaviour of the coatings was investigated. The cold sprayed coatings revealed an almost complete amorphous structure and negligible porosity. The coating deposited on the steel substrate showed higher microhardness, better resistance to loose abrasive wear, and a slightly lower wear index tested in the coating and Si₃N₄ ball tribological association than that cold sprayed on an Al alloy. The force required to destroy the durability of the coating–steel substrate system estimated during three-point bending tests was also much higher. Both coatings were characterized by a comparable friction coefficient. Full article

(This article belongs to the Special Issue Microstructural and Mechanical Properties of Metal Alloys)

► Show Figures

Figure 1

27 pages, 15115 KB

Open AccessArticle

Macro-Meso Characteristics and Damage Mechanism of Cement-Stabilized Macadam Under Freeze–Thaw Cycles and Scouring

by Hongfu Liu, Sirui Zhou, Ao Kuang, Dongzhao Jin, Xinghai Peng and Songtao Lv

Materials 2025, 18(21), 4874; https://doi.org/10.3390/ma18214874 (registering DOI) - 24 Oct 2025

Abstract

This study quantifies the effects of freeze–thaw (FT) cycling and dynamic water scouring, and establishes links between mesoscale pore evolution and macroscale strength degradation in cement-stabilized macadam (CSM) bases. The objective is to provide quantitative indicators for durability design and non-destructive evaluation of [...] Read more.

This study quantifies the effects of freeze–thaw (FT) cycling and dynamic water scouring, and establishes links between mesoscale pore evolution and macroscale strength degradation in cement-stabilized macadam (CSM) bases. The objective is to provide quantitative indicators for durability design and non-destructive evaluation of CSM bases. First, laboratory tests were conducted to simulate alpine service conditions: CSM cylindrical specimens (Ø150 × 150 mm) with 4.5% cement content, cured for 28 days, were exposed to 0, 5, or 20 FT cycles (−18 °C for 16 h ↔ +25 °C for 8 h), followed by dynamic water scouring (0.5 MPa, 10 Hz) for 15, 30, or 60 min. Second, the resulting damage was tracked at two scales. Acoustic emission (AE) sensors monitored internal damage during subsequent splitting tests, while industrial computed tomography (CT) was used to scan selected specimens and quantify porosity, pore number, and average pore diameter. Third, gray relational analysis correlated pore structure parameters with strength loss. The results indicate that under 30 min of scouring, increasing FT cycles from 0 to 20 increased mass loss from 0.33% to 1.27% and reduced splitting strength by 28.8%. AE cumulative ringing count and energy decreased by 97.9% and 98.4%, respectively, indicating severe internal degradation. CT scans revealed porosity and pore count increased monotonically with FT cycles, while average pore diameter decreased (dominated by microcrack formation). Frost-heave pressure and cyclic suction enlarged edge pores and interconnected internal voids, accelerating erosion of cement paste. FT cycles compromise the cement–aggregate interfacial bond, thereby predisposing the matrix to accelerated deterioration under dynamic scouring; the ensuing evolution of pore structure emerges as the pivotal mechanism governing strength degradation. Average pore diameter exhibited the strongest correlation with splitting strength (r = 0.763), and its change was the primary driver of strength loss (r = 0.774). These findings facilitate optimizing cement dosage, validating non-destructive evaluation models for in-service base courses, and erosion durability of road base materials in permafrost regions. Full article

(This article belongs to the Special Issue Green and Sustainable Infrastructure Construction Materials (3rd Edition))

► Show Figures

Figure 1

32 pages, 6947 KB

Open AccessArticle

Duct Metamaterial Muffler with Composite Acoustic Porous Media: Acoustic Optimization via Periodic Arrangement, Particle Swarm Optimization and Experimental Validation

by Ziyi Liu, An Wang, Chi Cai, Xiao Wang, Qiyuan Fan, Bin Huang, Chengwen Liu and Yizhe Huang

Materials 2025, 18(21), 4873; https://doi.org/10.3390/ma18214873 (registering DOI) - 24 Oct 2025

Abstract

This study proposes a composite acoustic porous duct metamaterial muffler composed of a perforated tortuous channel and an externally wrapped porous layer, integrating both structural resonance and material damping effects. Theoretical models for the perforated plate, tortuous channel, and porous material were established, [...] Read more.

This study proposes a composite acoustic porous duct metamaterial muffler composed of a perforated tortuous channel and an externally wrapped porous layer, integrating both structural resonance and material damping effects. Theoretical models for the perforated plate, tortuous channel, and porous material were established, and analytical formulas for the total acoustic impedance and transmission loss of the composite structure were derived. Finite element simulations verified the accuracy of the models. A systematic parametric study was then performed on the effects of porous material type, thickness, and width on acoustic performance, showing that polyester fiber achieves the best results at a thickness of 30 mm and a width of 5 mm. Further analysis of periodic distribution modes revealed that axial periodic arrangement significantly enhances the peak noise attenuation, radial periodic arrangement broadens the effective bandwidth, and multi-frequency parallel configurations further expand the operating range. Considering practical duct conditions, a single-layer multi-cell array was constructed, and its modal excitation mechanism was clarified. By employing the Particle Swarm Optimization (PSO) algorithm for multi-parameter optimization, the average transmission loss was improved from 26.493 dB to 29.686 dB, corresponding to an increase of approximately 12.05%. Finally, physical samples were fabricated via 3D printing, and four-sensor impedance tube experiments confirmed good agreement among theoretical, numerical, and experimental results. The composite structure exhibited an average experimental transmission loss of 24.599 dB, outperforming the configuration without porous material. Overall, this work highlights substantial scientific and practical advances in sound energy dissipation mechanisms, structural optimization design, and engineering applicability, providing an effective approach for broadband and high-efficiency duct noise reduction. Full article

(This article belongs to the Section Materials Physics)

► Show Figures

Figure 1

20 pages, 5441 KB

Open AccessArticle

Study on the γ/γ′ Eutectic Inhomogeneity of a Novel 3rd Generation Nickel-Based Single-Crystal Superalloy Casting

by Xiaoshan Liu, Anping Long, Haijie Zhang, Dexin Ma, Min Song, Menghuai Wu and Jianzheng Guo

Materials 2025, 18(21), 4872; https://doi.org/10.3390/ma18214872 (registering DOI) - 24 Oct 2025

Abstract

In the manufacture of single-crystal blades for aero-engines, the problem of eutectic aggregation on the upper surface of the blades has long been restricting the casting performance improvement. To investigate this phenomenon, this paper employs a simplified blade-like shape casting and focuses a [...] Read more.

In the manufacture of single-crystal blades for aero-engines, the problem of eutectic aggregation on the upper surface of the blades has long been restricting the casting performance improvement. To investigate this phenomenon, this paper employs a simplified blade-like shape casting and focuses a 3rd generation nickel-based single-crystal superalloy as the research material. A systematic analysis is conducted to elucidate the distribution of γ/γ’ eutectic during solidification. Experimental results show distinct spatial variations in γ/γ’ eutectic distribution. Pronounced eutectic aggregation is observed on the upper surface of the blade but with sparse eutectic dispersion‌ on the lower regions of the casting. Relatively uniform eutectic distribution‌ dominates the mid-section of the specimen. To unravel the underlying mechanisms, this paper utilized a ‌multiphase volume-averaged solidification model‌, developed in prior work, to numerically simulate the γ/γ’ eutectic evolution during directional solidification. This computational framework enabled a comprehensive ‌quantitative analysis‌ of spatial and temporal variations in the eutectic volume fraction along the solidification direction. The integration of experimental and modeling approaches provides critical insights into the interplay between thermal gradients, alloy composition, and microstructural heterogeneity. Full article

(This article belongs to the Special Issue Microstructure and Defect Simulation during Solidification of Alloys)

► Show Figures

Figure 1

22 pages, 8997 KB

Open AccessArticle

Thermomechanical Processing of Medium-Carbon Boron-Bearing Microalloyed-Steel Forgings Targeting Normalized-like Structure and Properties

by Piotr Skubisz, Piotr Micek and Stanisław Flaga

Materials 2025, 18(21), 4871; https://doi.org/10.3390/ma18214871 (registering DOI) - 24 Oct 2025

Abstract

The paper presents designing thermomechanical processing routes for medium-carbon boron-bearing microalloyed steel and investigates their effect on microstructure–property characteristics obtained through controlled cooling directly from hot forging temperature. Direct cooling was carried out in situ within the industrial process of hot forging, replacing [...] Read more.

The paper presents designing thermomechanical processing routes for medium-carbon boron-bearing microalloyed steel and investigates their effect on microstructure–property characteristics obtained through controlled cooling directly from hot forging temperature. Direct cooling was carried out in situ within the industrial process of hot forging, replacing conventional heat treatment with slow and accelerated air cooling, realized with a fully automated fan-cooling laboratory conveyor which accommodates the desired cooling strategy. Comparative analysis of conventionally normalized and direct-cooled microstructure and mechanical properties obtained under varied thermo-mechanical conditions is presented to investigate the potential of medium-carbon microalloyed steel with boron addition for producing tailored properties comparable to those of the normalized condition. The obtained microstructure composed of grain-boundary ferrite and pearlite which resulted in tensile properties as good as Re ≈ 610 MPa, Rm ≈ 910 MPa, and elongation A5 ≥ 12%. Although the achieved microstructure–property parameters differ from those achieved through conventional normalizing (Rm ≤ 780 MPa, Re ≤ 460 MPa, and A ≥ 14%), they are considerable in terms of selected machinability aspects. The observed effect of the imposed treatment strategies on interlamellar spacing and morphology of ferrite showed possibilities regarding the control of mechanical properties and application of direct cooling as a beneficial alternative to conventional normalizing, where energy consumption is the main concern in manufacturing high-duty parts made of boron-bearing microalloyed steel 35MnTiB4. Full article

(This article belongs to the Section Metals and Alloys)

► Show Figures

Figure 1

20 pages, 1774 KB

Open AccessReview

Natural and Modified Zeolites as Adsorbents for Nitrogen and Phosphorus Control in Eutrophic Freshwater Bodies: A Comprehensive Review on Freshwater Applications of the Last 10 Years

by Irene Biliani and Ierotheos Zacharias

Materials 2025, 18(21), 4870; https://doi.org/10.3390/ma18214870 (registering DOI) - 24 Oct 2025

Abstract

Eutrophication of freshwater bodies is primarily caused by excessive nitrogen and phosphorus, resulting in significant environmental challenges, including harmful algal blooms and hypoxia. This review examines the potential for natural and modified zeolites to act as adsorbents and regulate nutrient concentrations in eutrophic [...] Read more.

Eutrophication of freshwater bodies is primarily caused by excessive nitrogen and phosphorus, resulting in significant environmental challenges, including harmful algal blooms and hypoxia. This review examines the potential for natural and modified zeolites to act as adsorbents and regulate nutrient concentrations in eutrophic freshwater ecosystems, excluding applications for wastewater or industrial water effluents. Natural zeolites are effective adsorbents of ammonium, whereas modified zeolites (with aluminum, iron, calcium, and many others) have been noted to have enhanced phosphate adsorption and a higher overall nutrient removal efficiency. The application of modified zeolites for controlling eutrophication in freshwater bodies has proven to have high efficiency in adsorbing nitrogen and phosphorus, resulting in reduced nutrient release from sediments and improved water quality in shallow lakes and reservoirs. This review describes the adsorption mechanisms and modification methods, with an appreciation for the multifunctional role of zeolites in nutrient immobilization and capping sediments. Finally, it presents the potential to use zeolite-based materials in eutrophic freshwater restoration through sustainable circular economy approaches. Zeolite materials present ample environmental applications for cost-effective and targeted mitigation approaches to freshwater eutrophication. Full article

(This article belongs to the Special Issue Recent Advances in the Environmental Remediation Using Zeolites and Other Adsorbent Materials (2nd Edition))

► Show Figures

Graphical abstract

19 pages, 3298 KB

Open AccessArticle

An Enhancement in the Magnetocaloric Effect in a Composite Powder Based on Lanthanum Manganites

by Fidel Ivan Reyes Patricio, Cristhian Antonio Taboada Moreno, Ana María Bolarín Miró, Claudia Alicia Cortés Escobedo, María Isabel Reyes Valderrama and Félix Sánchez De Jesús

Materials 2025, 18(21), 4869; https://doi.org/10.3390/ma18214869 (registering DOI) - 24 Oct 2025

Abstract

This study presents a dual-phase lanthanum manganite ceramic composite based on a mixture of equal weight ratios of La_0.7Ca_0.2Sr_0.1MnO₃ and La_0.7Ca_0.25Sr_0.05MnO₃ designed to enhance the magnetocaloric effect (MCE) of [...] Read more.

This study presents a dual-phase lanthanum manganite ceramic composite based on a mixture of equal weight ratios of La_0.7Ca_0.2Sr_0.1MnO₃ and La_0.7Ca_0.25Sr_0.05MnO₃ designed to enhance the magnetocaloric effect (MCE) of individual compounds, under a low magnetic field (≤18 kOe). X-ray diffraction (XRD) analysis revealed the coexistence of two orthorhombic manganite phases corresponding to the individual compounds, with no secondary phases detected. Temperature-dependent magnetization measurements in the composite evidenced two Curie temperatures at 286.8 K and 307.6 K, reflecting the effect of Ca²⁺ and Sr²⁺ concentrations. Arrott plots and β parameters confirmed that the phase transition is of second order. Although the maximum magnetic entropy change (ΔS_M) of the composite is slightly lower than that of the individual manganite phases, its relative cooling power (RCP) reaches 188.82 J·kg⁻¹, with an extended operational temperature window (OTW) of approximately 85 K, spanning from around 243 K to 328 K. This broad OTW enables efficient operation over a wider temperature range compared to similar materials, such as the individual La_0.7Ca_0.2Sr_0.1MnO₃ and La_0.7Ca_0.25Sr_0.05MnO₃ compounds, which exhibit an RCP of 55.24 and 65.12 J·kg⁻¹, respectively, under a comparable magnetic field (~18 kOe). The improved magnetocaloric performance is attributed to interfacial exchange coupling and strain-mediated effects that broaden the ΔS_M response and generate a non-additive RCP. These results demonstrate that interphase coupling and microstructural tuning effectively broaden the operating temperature range for magnetic refrigeration under moderate fields, making this composite a strong candidate for practical cooling applications. Full article

(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))

► Show Figures

Figure 1

14 pages, 2395 KB

Open AccessArticle

Strength Characteristics of Historical Mortars—Experimental Study Using the Double Punch Method

by Piotr Matysek and Michał Witkowski

Materials 2025, 18(21), 4868; https://doi.org/10.3390/ma18214868 (registering DOI) - 24 Oct 2025

Abstract

Identification of the strength characteristics of mortars in brick or stone masonry is crucial in the structural analysis of heritage buildings and selecting materials for their repairs and reconstruction. Non-destructive, minimally destructive, and minor-destructive tests have been developed to establish the strength of [...] Read more.

Identification of the strength characteristics of mortars in brick or stone masonry is crucial in the structural analysis of heritage buildings and selecting materials for their repairs and reconstruction. Non-destructive, minimally destructive, and minor-destructive tests have been developed to establish the strength of mortar in existing masonry. This paper presents strength tests on mortar samples extracted from bed joints of heritage buildings erected in the historic center of Cracow during the 19th and 20th centuries. The mortar samples were tested using the double-punch method, a minor-destructive technique especially useful for heritage structures where cutting out large masonry specimens is not possible due to conservation reasons. The impact of sample thickness and type of capping materials on the test results were analyzed in detail. Practical recommendations are also proposed for the procedure of the double-punch method in relation to historical mortars. Full article

(This article belongs to the Special Issue Advanced Materials & Methods for Heritage & Archaeology (Second Edition))

► Show Figures

Figure 1

15 pages, 10923 KB

Open AccessArticle

Effect of Electropolishing on the Microstructure and Tribological Properties of Electrolyte-Plasma Borided Layers on 30KhGSA Steel

by Laila Sulyubayeva, Nurbol Berdimuratov, Daryn Baizhan, Temirlan Alimbekuly and Balym Alibekova

Materials 2025, 18(21), 4867; https://doi.org/10.3390/ma18214867 (registering DOI) - 24 Oct 2025

Abstract

The study investigates the effect of plasma-electrolytic polishing on the structure and wear resistance of 30KhGSA steel after plasma-electrolytic boriding. Plasma-electrolytic boriding was carried out in a boron-containing electrolyte at a temperature of 900 °C, which ensured the formation of a hardened modified [...] Read more.

The study investigates the effect of plasma-electrolytic polishing on the structure and wear resistance of 30KhGSA steel after plasma-electrolytic boriding. Plasma-electrolytic boriding was carried out in a boron-containing electrolyte at a temperature of 900 °C, which ensured the formation of a hardened modified layer consisting of a surface oxide layer, a subsequent zone composed of boride phases FeB and Fe₂B, as well as a transitional martensitic zone. To remove brittle oxide phases and reduce surface roughness, plasma-electrolytic polishing in an alkaline solution was applied, which made it possible to form a smoother and more stable surface. The results showed that plasma-electrolytic boriding increases the microhardness up to 1500–1600 HV_0.1, which is 5–6 times higher compared to untreated steel, and reduces the friction coefficient and wear rate. However, the borided layers exhibit brittleness and surface roughness. Subsequent plasma-electrolytic polishing made it possible to reduce surface roughness by nearly an order of magnitude, decrease the friction coefficient by more than 30%, and almost halve the wear rate. The obtained results confirm the high potential of this combined technology for strengthening structural steel components operating under high loads and severe wear conditions. Full article

(This article belongs to the Section Metals and Alloys)

► Show Figures

Figure 1

22 pages, 4208 KB

Open AccessArticle

Parametric Design and Experiment on Compression Performance of Hierarchical Origami Honeycomb Structures

by Xiaohui Lu, Yong Yang and Xiang Peng

Materials 2025, 18(21), 4866; https://doi.org/10.3390/ma18214866 (registering DOI) - 24 Oct 2025

Abstract

This study focuses on the energy absorption characteristics of hierarchical origami honeycomb structures. By combining experimental and numerical simulation methods, it deeply explores their mechanical properties and energy absorption potential. This research emphasizes analyzing the influence of geometric parameters (including wall thickness, folding [...] Read more.

This study focuses on the energy absorption characteristics of hierarchical origami honeycomb structures. By combining experimental and numerical simulation methods, it deeply explores their mechanical properties and energy absorption potential. This research emphasizes analyzing the influence of geometric parameters (including wall thickness, folding angle, multi-layer structure design, etc.) on bearing capacity, stiffness, and energy absorption efficiency and reveals the advantages of hierarchical design in regulating gradient stiffness. The results show that the energy absorption capacity and performance of the material can be significantly improved through the reasonable optimization of geometric parameters. This research provides important theoretical support for the design of high-efficiency energy-absorbing materials and innovative solutions for energy absorption problems in related engineering applications. Full article

(This article belongs to the Section Mechanics of Materials)

► Show Figures

Figure 1

19 pages, 7223 KB

Open AccessArticle

Analysis of Failure Cause in Steel Wire-Reinforced Thermoplastic Composite Pipes for Sour Gas Field Water Transportation

by Zhiming Yu, Shaomu Wen, Jie Wang, Jianwei Lin, Chuan Xie and Dezhi Zeng

Materials 2025, 18(21), 4865; https://doi.org/10.3390/ma18214865 - 24 Oct 2025

Abstract

Steel-reinforced thermoplastic pipe is widely used for water transportation in sour gas fields. However, under the combined effects of corrosive media, internal high pressure, and long-term environmental aging, premature failures such as leakage and bursting often occur. To clarify the failure causes and [...] Read more.

Steel-reinforced thermoplastic pipe is widely used for water transportation in sour gas fields. However, under the combined effects of corrosive media, internal high pressure, and long-term environmental aging, premature failures such as leakage and bursting often occur. To clarify the failure causes and primary contributing factors of the composite pipes, this study conducted a comprehensive analysis through microscopic morphology examination of different typical failure cases, differential scanning calorimetry, Fourier transform infrared spectroscopy, and mechanical property testing. The main failure mechanisms were investigated, and targeted protective measures are proposed. Key findings reveal that the typical failure modes are ductile cracking, aging-induced brittle cracking, and aging creep cracking. These failures follow a mechanism of degradation of the inner and outer polyethylene protective layers, penetration of the medium and corrosion of the steel wires, reduction in pressure-bearing capacity, and eventual structural damage or leakage propagation through the pipe wall. Notably, oxidation induction time values dropped as low as 1.4–17 min—far below the standard requirement of >20 min—indicating severe antioxidant depletion and material aging. The main controlling factors are poor material quality, external stress or mechanical damage, and long-term aging. The polyethylene used for the inner and outer protective layers is critical to the overall pipe performance; therefore, emphasis should be placed on evaluating its anti-aging properties and on protecting the pipe body during installation to ensure the long-term safety and stable operation of the pipeline system. Full article

(This article belongs to the Special Issue High-Performance Applications of Advanced Materials: Material Properties, Behaviour Modeling, Optimal Design and Advanced Processes)

► Show Figures

Figure 1

25 pages, 4924 KB

Open AccessReview

Recent Progress in Low-Power-Consumption Metal Oxide Semiconductor Gas Sensors

by Yu Zhang, Renbo Li, Ruqi Guo, Mingzhi Jiao, Gang Wang and Zhikai Zhao

Materials 2025, 18(21), 4864; https://doi.org/10.3390/ma18214864 - 24 Oct 2025

Abstract

Metal oxide semiconductor (MOS) gas sensors offer several advantages, including low cost, high accuracy, and ease of miniaturization. Thus, they are excellent candidates for environmental monitoring and food spoilage detection applications, particularly in the safe Internet of Things field or for portable instruments. [...] Read more.

Metal oxide semiconductor (MOS) gas sensors offer several advantages, including low cost, high accuracy, and ease of miniaturization. Thus, they are excellent candidates for environmental monitoring and food spoilage detection applications, particularly in the safe Internet of Things field or for portable instruments. Typically, there are two general routes for realizing low-power-consumption MOS gas sensors: room-temperature MOS gas sensors or MEMS MOS gas sensors. The review focuses on the detection of four typical gases, namely methane, hydrogen, carbon monoxide, and nitrogen dioxide, systematically summarizing and analyzing the most recent results of low-power-consumption MOS gas sensors. The 2D materials, MOS composites, and 3D structured composites exhibit excellent room-temperature gas detection capabilities. The mechanism of the room-temperature gas sensors is also discussed in detail. Another route is MEMS MOS gas sensors. First, the progress of the micro-hotplate research is introduced. Then, several of the latest reported MEMS MOS gas sensors are shown and compared. The gas sensing mechanism of these MEMS MOS gas sensors is also given. The paper will provide a valuable guide for researchers in the MOS gas sensor field, particularly for those working towards low-power-consumption MOS gas sensors. Full article

(This article belongs to the Special Issue Advanced Applications of Electrochemical Materials for Sensors and Catalysts)

► Show Figures

Figure 1

17 pages, 5789 KB

Open AccessArticle

Method to Predict Salt Expansion Deformation in Cement-Stabilized Macadam Under Sulfate Attack Based on Pore Evolution

by Xiangyu Li, Xuesong Mao, Pei He and Qian Wu

Materials 2025, 18(21), 4863; https://doi.org/10.3390/ma18214863 - 23 Oct 2025

Abstract

Cement-stabilized macadam often shows salt expansion deformation under the action of a sulfate attack, and its pore structure determines its ability to accommodate this deformation. In this paper, the influence of the pore structure of cement-stabilized macadam on its macroscopic deformation is analyzed [...] Read more.

Cement-stabilized macadam often shows salt expansion deformation under the action of a sulfate attack, and its pore structure determines its ability to accommodate this deformation. In this paper, the influence of the pore structure of cement-stabilized macadam on its macroscopic deformation is analyzed using a single-grain salt expansion deformation test, scanning electron microscopy (SEM), and computerized tomography (CT) scanning. The results show that ettringite and sodium sulfate decahydrate crystals are key factors in salt expansion deformation. In addition, we find that when the sulfate content increases from 0% to 5%, the porosity of the mixture decreases by 1.5%, the proportion of primary pores increases by 12.1%, and the linear expansion rate increases by 0.05%. Finally, a salt expansion deformation prediction model for cement-stabilized macadam is proposed, which takes the porosity of the mixture, the proportion of graded pores, and the deformation influence factor as parameters, and the error is found to be less than 10%. Full article

(This article belongs to the Section Construction and Building Materials)

► Show Figures

Figure 1

24 pages, 6158 KB

Open AccessArticle

Multiscale Simulation of Crack Propagation in Impact-Welded Al₄Cu₉ Alloy Based on Cohesive Zone Model

by Rongqing Luo, Dingjun Xiao, Guangzhao Pei, Haixia Yan, Sen Han, Jiajie Jiang and Miaomiao Zhang

Materials 2025, 18(21), 4862; https://doi.org/10.3390/ma18214862 - 23 Oct 2025

Abstract

The fracture behavior of the Al₄Cu₉ intermetallic compound at the interface of impact-welded Cu/Al joints remains insufficiently explored through integrated multiscale modeling and experimental validation. In this study, molecular dynamic (MD) simulations, finite element (FE) analysis implemented in ABAQUS (version [...] Read more.

The fracture behavior of the Al₄Cu₉ intermetallic compound at the interface of impact-welded Cu/Al joints remains insufficiently explored through integrated multiscale modeling and experimental validation. In this study, molecular dynamic (MD) simulations, finite element (FE) analysis implemented in ABAQUS (version 2020) and a cohesive zone model (CZM) were combined with optical microscopy (OM) and scanning electron microscopy (SEM) observations of the interface and crack initiation zones in impact-welded Cu/Al specimens to investigate crack propagation mechanisms under different defect configurations. The experimental specimens consisted of 1060 aluminum (Al) and oxygen-free high-conductivity (OFHC) copper, fabricated via impact welding and subsequently annealed at 250 °C for 100 h. The interfacial morphology and crack initiation features obtained from OM and SEM provided direct validation for the traction–separation (T-S) parameters extracted from MD and mapped into the FE model. The results indicate that composite defects (blunt crack + void) cause a significantly greater reduction in fracture energy and stress intensity factor than single defects and that defect effects outweigh temperature effects within the range of 200–500 K. The experimentally observed crack initiation locations were in strong agreement with simulation predictions. This integrated simulation–experiment approach not only elucidates the multiscale fracture mechanisms of the Al₄Cu₉ interface but also provides a physically validated basis for the reliability assessment and optimization of aerospace Cu/Al welded structures. Full article

(This article belongs to the Special Issue Advances in Microstructure and Properties of Welded–Brazed Joints)

► Show Figures

Figure 1

23 pages, 3246 KB

Open AccessArticle

Characterization of Asphalt Binder Properties Modified with One-Time Use Masks: Zero Shear Viscosity, Fatigue Life, and Low-Temperature Performance

by Alaaeldin A. A. Abdelmagid, Guanghui Jin, Guocan Chen, Nauman Ijaz, Baotao Huang, Yiming Li and Aboubaker I. B. Idriss

Materials 2025, 18(21), 4861; https://doi.org/10.3390/ma18214861 - 23 Oct 2025

Abstract

The widespread adoption of one-time use masks (OUM) has resulted in a substantial new stream of polymer waste, posing a formidable challenge to circular economy and waste management initiatives. Concurrently, the pavement industry continuously seeks innovative modifiers to enhance the durability and service [...] Read more.

The widespread adoption of one-time use masks (OUM) has resulted in a substantial new stream of polymer waste, posing a formidable challenge to circular economy and waste management initiatives. Concurrently, the pavement industry continuously seeks innovative modifiers to enhance the durability and service life of asphalt binders. This study presents a novel approach to waste valorization by systematically investigating the potential of shredded OUM as a polymer modifier for asphalt. The research evaluates the impact of various OUM concentrations (up to 10% by weight) on the binder’s chemical, rheological, and performance characteristics. Fourier-transform infrared spectroscopy (FTIR) indicated that the modification is a physical blending process, with the OUM fibers forming a stable reinforcing network within the asphalt matrix, a finding supported by excellent high-temperature storage stability. Rheological assessments revealed a remarkable enhancement in high-temperature performance, with the Zero-Shear Viscosity (ZSV) increasing by nearly 700% (from approximately 450 Pa·s to about 3500 Pa·s) at 10% OUM content, signifying superior rutting resistance. Furthermore, fatigue life, evaluated via the Linear Amplitude Sweep (LAS) test, improved by up to 168% at a 2.5% strain level. However, these benefits were accompanied by a detrimental effect on low-temperature properties, where creep stiffness at −12 °C increased by over 50% and the m-value dropped below the critical 0.30 threshold, indicating a heightened risk of thermal cracking. The study concludes that OUM is a highly effective modifier for improving high-temperature and fatigue performance, with up to 10% content being viable. This research establishes a promising circular economy pathway, transforming a problematic waste stream into a valuable resource for constructing more resilient and sustainable pavement infrastructure. Full article

(This article belongs to the Section Construction and Building Materials)

► Show Figures

Figure 1

17 pages, 1493 KB

Open AccessArticle

Advanced Epoxy Resin/Boron Nitride Composites for High-Performance Electrotechnical Applications and Geological Instrumentation

by Alina Ruxandra Caramitu, Iustina Popescu, Mihai Grigoroscuta, Andrei Kuncser, Paul Constantin Ganea, Andrei Galatanu, Magdalena Galatanu, Gheorghe Aldica, Petre Badica, Mihail Burdusel and Adriana Mariana Borș

Materials 2025, 18(21), 4860; https://doi.org/10.3390/ma18214860 - 23 Oct 2025

Abstract

Composites were obtained by using a commercial bicomponent epoxy resin (containing Al₂O₃ and SiO₂) and cubic BN (cBN) (0–50 wt.%). Two preparation methods were used: (a) the cBN powder was first mixed with the resin base and further [...] Read more.

Composites were obtained by using a commercial bicomponent epoxy resin (containing Al₂O₃ and SiO₂) and cubic BN (cBN) (0–50 wt.%). Two preparation methods were used: (a) the cBN powder was first mixed with the resin base and further with the hardener, and (b) the cBN powder was first mixed with hardener and afterwards with the resin base. Both methods show a similar enhancement trend in the thermal conductivity from 0.77 W/mK in the resin without additive to 1 and 1.5 W/mK in the ones filled with 30 and 50 wt.% cBN, respectively. A reasonable decrease in bending strength from 74 for 0 wt.% cBN to 70 or 64 MPa for 30 wt.% cBN added by method (a) or (b), respectively, occurs. The bending strain at breakage decreased from 5.58% to 2.65 or 3.78%. High sensitivity vs. processing was also found for electrical properties measured for frequencies of 1–10⁷ Hz. An increasing amount of cBN decreased the room temperature conductivity, dielectric constant, and dielectric loss tangent and modified the shape of the curves vs. frequency. However, in samples with 30 wt.% or more of cBN, a partial recovery to a high insulating state was observed. Full article

(This article belongs to the Special Issue Piezoelectric, Ferroelectric, and Dielectric Materials: Properties and Related Applications)

25 pages, 2224 KB

Open AccessArticle

Laboratory Quantification of Gaseous Emission from Alternative Fuel Combustion: Implications for Cement Industry Decarbonization

by Ofelia Rivera Sasso, Elias Ramirez Espinoza, Caleb Carreño Gallardo, Jose Ernesto Ledezma Sillas, Alberto Diaz Diaz, Omar Farid Ojeda Farias, Carolina Prieto Gomez and Jose Martin Herrera Ramirez

Materials 2025, 18(21), 4859; https://doi.org/10.3390/ma18214859 - 23 Oct 2025

Abstract

The cement industry accounts for approximately 7% of global CO₂ emissions, with fuel combustion contributing 40% of sectoral emissions. Alternative fuels from industrial and municipal waste offer emission reduction opportunities while addressing waste management challenges. This study quantifies real-time gaseous emissions (CO [...] Read more.

The cement industry accounts for approximately 7% of global CO₂ emissions, with fuel combustion contributing 40% of sectoral emissions. Alternative fuels from industrial and municipal waste offer emission reduction opportunities while addressing waste management challenges. This study quantifies real-time gaseous emissions (CO₂, CO, NO_x, and SO₂) from seven alternative fuels—sawdust (SD), pecan nutshell (PNS), wind blade waste (WBW), industrial hose waste (IHW), tire-derived fuel (TDF), plastic waste (PW), and automotive shredder residue (ASR)—during calcination at 850 °C. Bituminous coal served as the reference fuel. Gas concentrations were continuously monitored using the testo 350 portable gas analyzer. Emission factors were calculated on a mass basis (kg/kg fuel) and energy basis (kg/GJ) for standardized comparisons. Alternative fuels consistently produced lower CO₂ emission factors than coal, with biomass-derived fuels (SD and PNS) showing reductions of 45% and 38%, respectively. Most alternative fuels generated lower CO and NO_x emissions per unit energy due to their higher volatile matter content, promoting complete combustion. TDF was an exception, exhibiting 2.8 times higher CO emissions. SO₂ emissions were negligible except in the case of TDF (0.14% sulfur content). The measured emission factors were 15–30% lower than theoretical IPCC values, confirming the environmental viability of alternative fuels as coal substitutes in cement production. Full article

(This article belongs to the Special Issue Eco-Friendly Materials for Sustainable Buildings)

► Show Figures

Graphical abstract

22 pages, 9476 KB

Open AccessArticle

Application of Kolmogorov–Sinai Metric Entropy to Determine the Exploitation Parameters of Epoxy–Glass Composites with Carbonisate

by Agata Wieczorska and Grzegorz Hajdukiewicz

Materials 2025, 18(21), 4858; https://doi.org/10.3390/ma18214858 - 23 Oct 2025

Abstract

This study investigates how the addition of a carbon-based filler obtained through the pyrolysis of medium-density fibreboard (MDF) waste affects the mechanical behaviour of epoxy–glass laminates. Two laminate series with different matrix-to-reinforcement ratios (60/40 and 65/35) were fabricated and modified with carbonised particles [...] Read more.

This study investigates how the addition of a carbon-based filler obtained through the pyrolysis of medium-density fibreboard (MDF) waste affects the mechanical behaviour of epoxy–glass laminates. Two laminate series with different matrix-to-reinforcement ratios (60/40 and 65/35) were fabricated and modified with carbonised particles of up to 500 μm in size, introduced at 5% and 7.5%. The strength of the samples made of the materials mentioned above was assessed in a static three-point bending test by analysing the values of stresses (

σ_{f M}

) and strains (

ε_{f M}

). For an in-depth analysis of the dynamics of the destruction process, the recorded deformation data were subjected to Kolmogorov–Sinai metric entropy (

E_{K - S}

). The test results showed that the addition of carbonisate in series A (60/40) increased the flexural strength by 32.56% for the sample with 5% addition and by 27.08% for the sample with 7.5% addition, compared to the reference material. In series B (65/35), characterised by a higher resin content, the opposite effect was observed—a decrease in strength of 9.89% (for 5% carbonisate) and 15.53% (for 7.5% carbonisate). The use of

E_{K - S}

calculations in combination with phase portrait reconstruction to analyse the results obtained allowed for the precise determination of the limit values of stresses and strains (

σ_{f M K_S}

and

ε_{f M K_S}

) at which irreversible structural changes occur in the material, initiating the destruction process. This method proved to be an effective tool for identifying early signs of composite degradation, which is crucial for assessing its long-term strength and designing safe structures. Full article

(This article belongs to the Section Advanced Composites)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Materials, Volume 18, Issue 21 (November-1 2025) – 70 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI