Materials

30 pages, 7877 KB

Open AccessArticle

Shear Performance Degradation of Fiber-Reinforced Recycled Aggregate Concrete Beams Under Salt Freeze–Thaw Cycles

by Shefeng Guo, Jin Wu, Jingmiao Zhao, Zhehong Zeng, Xiangyu Wang, Yiyuan Wang, Haoxiang Luan, Yulin Wang and Dongxia Hu

Materials 2025, 18(20), 4817; https://doi.org/10.3390/ma18204817 - 21 Oct 2025

Viewed by 373

Abstract

In saline soil and alpine regions of northwest China, fiber-reinforced recycled aggregate concrete (FR-RAC) beams are subjected to coupled degradation from a chloride–sulfate composite salt attack and freeze–thaw cycling. Existing studies predominantly focus on natural aggregate concrete in freshwater environments or single-salt solutions, [...] Read more.

In saline soil and alpine regions of northwest China, fiber-reinforced recycled aggregate concrete (FR-RAC) beams are subjected to coupled degradation from a chloride–sulfate composite salt attack and freeze–thaw cycling. Existing studies predominantly focus on natural aggregate concrete in freshwater environments or single-salt solutions, with limited documentation on the shear performance of FR-RAC beams after freeze–thaw exposure in chloride–sulfate composite salt solutions. To investigate the durability degradation patterns of FR-RAC beams in Xinjiang’s saline soil regions, two exposure environments (pure water and 5% NaCl + 2.0% Na₂SO₄ composite salt solution) were established. Shear performance tests were conducted on nine groups of FR-RAC beams after 0–175 freeze–thaw cycles, with measurements focusing on failure modes, cracking loads, and ultimate shear capacities. The results revealed that under composite salt freeze–thaw conditions: after 100 cycles, the cracking load and shear capacity of tested beams decreased by 39.8% and 22.2%, respectively, compared to unfrozen specimens representing reductions 29.6% and 82.0% greater than those in freshwater environments; at 175 cycles, cumulative damage intensified, with total reductions reaching 56.8% (cracking load) and 36.1% (shear capacity). A shear capacity degradation prediction model for FR-RAC beams under composite salt freeze–thaw coupling was developed, accounting for concrete strength attenuation and interfacial bond degradation. Model validation demonstrated excellent agreement between predicted and experimental values, confirming its robust applicability. Full article

(This article belongs to the Special Issue Sustainable Cement Materials: Preparation, Experimental Analysis and Engineering Applications)

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11 pages, 2006 KB

Open AccessArticle

Synthesis of Poly(Lactic Acid-co-Arginine) and Construction of Its Ternary Phase Diagram for Nonsolvent Induced Phase Separation

by Yinying Zhu, Hongxia Yan, Bei Wang, Zihan Shangguan and Junyan Yao

Materials 2025, 18(20), 4816; https://doi.org/10.3390/ma18204816 - 21 Oct 2025

Viewed by 289

Abstract

L-arginine, a basic amino acid, exhibits high biocompatibility, reactivity, and absorbability. It was selected as the co-polymer modification monomer for L-lactic acid with the objective of enhancing the hydrophilicity of poly(lactic acid) (PLA), neutralizing the acidity of PLA degradation products, and regulating the [...] Read more.

L-arginine, a basic amino acid, exhibits high biocompatibility, reactivity, and absorbability. It was selected as the co-polymer modification monomer for L-lactic acid with the objective of enhancing the hydrophilicity of poly(lactic acid) (PLA), neutralizing the acidity of PLA degradation products, and regulating the degradation cycle. The copolymer poly(lactic acid-co-arginine) (PLAA) was synthesized by direct melting polycondensation of L-arginine and L-lactic acid, and the structures and properties of PLAA were characterized. The results indicated the presence of –NH₂, –NH–, and NH= in the molecular chain of the copolymer PLAA. Furthermore, the PLAA was identified as an amorphous copolymer. The “PLAA/CHCl₃/C₆H₁₄” ternary phase diagram was constituted by nonsolvent-induced phase separation (NIPS) by selecting chloroform (CHCl₃) as a good solvent and n-hexane (C₆H₁₄) as a nonsolvent. The phase diagram displays three distinguishable regions: the homogeneous zone, the metastable zone, and the phase separation zone. These regions are identified by the binodal and spinodal curves. The ternary phase diagram establishes a theoretical foundation for the preparation and processing of PLAA nanoparticles, composite materials, and porous fibers or membranes. Full article

(This article belongs to the Special Issue Advances in Functional Polymer Materials: Design, Synthesis, and Performance)

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10 pages, 2217 KB

Open AccessArticle

Enhancing Mechanical Properties of Q&P Steel Through Tailoring Film-like Retained Austenite Morphology via Heating Rate Optimization

by Shengwei Wang, Mingyue Yang, Mengxiao Chen, Yuhe Huang, Shuize Wang and Xinping Mao

Materials 2025, 18(20), 4815; https://doi.org/10.3390/ma18204815 - 21 Oct 2025

Viewed by 296

Abstract

In this study, by regulating the heating rate, we have optimized the morphology of retained austenite in a quenching and partitioning (Q&P) steel with initial microstructure consisting of lath martensite. By optimizing the heating rate to 1 °C/s during the heating stage from [...] Read more.

In this study, by regulating the heating rate, we have optimized the morphology of retained austenite in a quenching and partitioning (Q&P) steel with initial microstructure consisting of lath martensite. By optimizing the heating rate to 1 °C/s during the heating stage from 700 °C to 830 °C, the formation of blocky austenite and the coarsening of film-like austenite during the two-phase region annealing process were prohibited. Ultimately, this resulted in the production of Q&P steel containing a significant volume fraction (19.0%) of fine film-like retained austenite. This fine and film-like retained austenite exhibits higher stability than blocky austenite, exhibiting an active transformation-induced plasticity (TRIP) effect over a broad strain range. This results in excellent mechanical properties characterized by a high product of tensile strength and elongation (34.1 GPa·%). Full article

(This article belongs to the Special Issue Advances in Thermomechanical Processing and Additive Manufacturing of Engineering Alloys)

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19 pages, 4138 KB

Open AccessArticle

Study on Mechanical Strength and Resistance to Freeze–Thaw Cycles and Chloride Ions of Fly Ash Mortar Mixed with Limestone Powder Cured Under Low Temperature

by Qingfeng Chen, Weizhun Jin, Jingjing Li, Min Huang, Pengfei Fang and Yuru Zhao

Materials 2025, 18(20), 4814; https://doi.org/10.3390/ma18204814 - 21 Oct 2025

Viewed by 336

Abstract

Fly ash (FA) and limestone powder (LS) are both environmentally friendly substitutes for cement. The mechanical strength and durability of hydraulic concrete with FA and LS cured under low temperature deserve attention. In this study, the mechanical strength and durability properties of cement [...] Read more.

Fly ash (FA) and limestone powder (LS) are both environmentally friendly substitutes for cement. The mechanical strength and durability of hydraulic concrete with FA and LS cured under low temperature deserve attention. In this study, the mechanical strength and durability properties of cement mortar based on FA and LS cured under a low temperature of 5 °C were investigated. The compressive strength and resistance to freeze–thaw cycles and chloride ions of mortar with FA and LS were evaluated. The results reveal that adding 5% LS can increase the compressive strength of mortar containing 30% FA by 14.31% at 3 d and 1.63% at 180 d. The addition of 5% LS can result in a 0.58% reduction in the mass loss rate and an increase of 2.98% in RDM compared to the mortar with 30% FA after 100 freeze–thaw cycles. Meanwhile, the addition of 5% LS results in a 5.68% reduction in the chloride diffusion coefficient compared to the mortar with 30% FA. However, for the mortar containing 60% FA, any proportion of LS cannot increase the compressive strength of FA mortar from 3 d to 180 d and will decrease the resistance to freeze–thaw cycles and chloride ions. For the mortar containing 30% FA, the addition of 5% LS can promote the hydration product of C-S-H and obtain the minimum total amount of large capillary pores and air pores. Adding 10% LS can result in the mortar with 30% FA obtaining the lowest unit CO₂ emission, and adding 5% LS can result in the mortar with 60% FA obtaining the lowest unit CO₂ emission. Full article

(This article belongs to the Special Issue The Development of Sustainable Concrete with Solid Waste and By-Products)

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18 pages, 5360 KB

Open AccessArticle

Anti-Icing and Frost Property of Superhydrophobic Micro-Nano Structures with Embossed Micro-Array Channels

by Han Luo, Xiaoliang Wang, Qiwei Li, Honglei Liu, Lei Chen, Debin Shan, Bin Guo and Jie Xu

Materials 2025, 18(20), 4813; https://doi.org/10.3390/ma18204813 - 21 Oct 2025

Viewed by 452

Abstract

Icing on aircraft surfaces during operation poses a threat to flight safety. As a passive anti-icing technology, hydrophobic microstructure can achieve long-term anti-icing. In this work, a composite process combining hot-embossing of PVD-coated punches with a low surface energy fluoride-modification scheme is proposed [...] Read more.

Icing on aircraft surfaces during operation poses a threat to flight safety. As a passive anti-icing technology, hydrophobic microstructure can achieve long-term anti-icing. In this work, a composite process combining hot-embossing of PVD-coated punches with a low surface energy fluoride-modification scheme is proposed to generate nanoscale cluster structures on hundreds of microns array channels to construct a superhydrophobic micro-nano composite structure. The droplet freezing and frosting behavior of the hydrophobic microstructures was analyzed, and it was found that the anti-icing and anti-frost properties of the microstructure surface improved with an increase in the microstructure period size (T). Compared with the original surface, the freezing time of the microstructure at T = 500 μm was delayed by 214.3% (7 s → 22 s), and the frost layer coverage time was delayed by 75.7% (70 s → 123 s). The maximum water contact angle of the superhydrophobic micro-nano composite structure was 153.3°, and the droplet freezing time was delayed to 95 s, which is a 1166.67% difference, indicating that the multi-stage micro-nano composite structure can significantly improve surface anti-icing performance. The main reason for this result is that the bottom of the microstructure can store air pockets, preventing droplet wetting and heat exchange. Full article

(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)

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11 pages, 7115 KB

Open AccessArticle

Analysis of the Fiber Residues Unearthed from the Dabuzi Han Tomb in Xi’an, Shaanxi

by Zhenzhen Ma, Yingpei Zhu, Jing Shao, Xianting Hou, Menghe Cui, Bei Zhang, Jianxi Li and Qixing Xia

Materials 2025, 18(20), 4812; https://doi.org/10.3390/ma18204812 - 21 Oct 2025

Viewed by 430

Abstract

In 2021, archeologists found that a bronze mirror was wrapped with a yellow-green fiber sheet in the Western Han tomb M68 in the Dabuzi Cemetery in Xi’an, China. To ascertain the composition and function, a scanning electronic microscopy–energy dispersive spectrometer (SEM-EDS), Fourier transform [...] Read more.

In 2021, archeologists found that a bronze mirror was wrapped with a yellow-green fiber sheet in the Western Han tomb M68 in the Dabuzi Cemetery in Xi’an, China. To ascertain the composition and function, a scanning electronic microscopy–energy dispersive spectrometer (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), and pyrolysis gas chromatography–mass spectrometry (Py-GC/MS) were combined for the morphology and components’ analysis. The results showed that the surface of the yellow-green fiber sheet was very rough without curtain patterns, and the fiber was disorderly intertwined. The paper was quite thick with various thicknesses (the average thickness was 0.58 mm) and the average diameter of the fiber was 20.71 μm. There were obvious transverse joint stripes on the fiber cell with longitudinal stripes characteristic of ramie or hemp. The main ingredients were cellulose, semi-cellulose, and lignin. Based on the above comprehensive joint experiments, the yellow-green fiber sheet in M68 was presumably ancient hemp paper made with the fixed-mold method. Moreover, it was speculated to be a package material since no characters were found. This paper is of great significance for studying the Chinese fixed-mold paper-making technique and for understanding the origins and developmental trajectory of ancient paper-making technology. Full article

(This article belongs to the Special Issue Advanced Materials in Cultural Heritage Conservation)

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33 pages, 5634 KB

Open AccessArticle

Electrical Curing of Metakaolin- and GBFS-Based Geopolymers: A Sustainable Technology Aligned with the European Green Deal

by Yusuf Gokcegoz, Mucteba Uysal, Orhan Canpolat, Oktay Arikan, Hasan Dilbas and Beyza Aygun

Materials 2025, 18(20), 4811; https://doi.org/10.3390/ma18204811 - 21 Oct 2025

Viewed by 280

Abstract

On-site curing of metakaolin (MK)- and granulated blast furnace slag (GBFS)-based geopolymer mortars remains a major bottleneck compared to thermal treatment for early strength development, and electrical curing is proposed here as a highly scalable and energy-efficient alternative technology. Geopolymer mortars with 0–100% [...] Read more.

On-site curing of metakaolin (MK)- and granulated blast furnace slag (GBFS)-based geopolymer mortars remains a major bottleneck compared to thermal treatment for early strength development, and electrical curing is proposed here as a highly scalable and energy-efficient alternative technology. Geopolymer mortars with 0–100% MK/GBFS binder ratios were activated using sodium silicate (SS) and sodium hydroxide (SH) solutions of the following molarities: 6, 8, 10, 12, and 14 M. Steel fiber (SF), carbon fiber (CF), waste erosion wire (EW), and carbon black (CB) microfiller were incorporated to enhance the electro-conductive efficiency of the geopolymer matrix. Specimens were subjected to electrical curing under 10 V and 20 V AC and were compared with benchmarking under ambient conditions of 23 °C and thermal conditions of 70 °C. The findings established that the incorporation of fibers substantially boosted the level of conductivity and mechanical performance, with 28-day compressive strengths of up to 88.30 MPa (0.50% EW, 20 V) and flexural strengths of up to 22.24 MPa (0.50% CF, 7 days), exceeding the results of conventional curing in various instances. Microstructural studies based on well-bonded geopolymer gels with fibers indicated uniform geopolymerization through electrical curing without deleterious fiber–matrix interactions. A multi-criteria decision support approach (the HD method) based on 273 parameters established 0.50% CF, 0.75% SF, 0.75% EW, and 1.00% CB as the group-wise optima and chose 0.75% EW as the single-best performing combination. The findings confirm that electrical curing is a low-carbon, cost-effective, and field-adjustable curing technology with the potential to achieve target strength ratings, in line with the European Green Deal’s climate-neutral building material goals. Full article

(This article belongs to the Special Issue Geopolymers and Alkali-Activated Materials: Preparation and Properties)

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14 pages, 5290 KB

Open AccessArticle

Numerical Investigation on Effect of Chamfering on Mechanical Behaviors in Continuous Network Composite

by Tao Li, Tianzi Wang, Jianchao Li, Cheng Liu, Bowen Gong, Wenting Ouyang, Likun Wang, Sainan Ma, Zhong Zheng, Bo Yuan, Huan Wang and Xiang Gao

Materials 2025, 18(20), 4810; https://doi.org/10.3390/ma18204810 - 21 Oct 2025

Viewed by 341

Abstract

The network architecture has demonstrated considerable potential for enhancing the strength–ductility synergy in metal matrix composites (MMCs). Intuitively, the intersections of network layers are expected to induce a stress concentration, leading to premature brittle fractures. Introducing chamfers to round the network cells may [...] Read more.

The network architecture has demonstrated considerable potential for enhancing the strength–ductility synergy in metal matrix composites (MMCs). Intuitively, the intersections of network layers are expected to induce a stress concentration, leading to premature brittle fractures. Introducing chamfers to round the network cells may mitigate the local stress concentration and thereby improve elongation. Here, a numerical simulation framework was developed to investigate the effect of chamfering on the mechanical behavior of a three-dimensional (3D) continuous SiC_3D/Al composite with a network architecture. A Voronoi tessellation algorithm was employed to generate the continuous network structural SiC phase. By inducing ductile and brittle damage criterions in the matrix and reinforcement elements, respectively, the mechanical behavior can be predicted via the finite element method (FEM). The predicted mechanical properties reveal an unexpected trend: chamfering results in a simultaneous reduction in both strength (from 367 MPa to 312 MPa) and elongation (from 4.1% to 2.0%). With chamfering, the enlarged intersection of the network layer bears a lower load, whereas the narrower network plates exhibit higher stress concentrations. As a result, the overall load-bearing capacity of the SiC_3D reinforcement decreases monotonically with an increasing chamfer size f. Furthermore, the non-uniform stress distribution promotes the premature fracture of the SiC_3D, which reduces elongation. Additionally, the crack deflection behavior is suppressed in the chamfered models, leading to decreasing energy dissipation. This unanticipated outcome highlights an important architectural design principle: maintaining uniform geometric dimensions is critical for achieving optimal composite performance. Full article

(This article belongs to the Section Metals and Alloys)

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40 pages, 3997 KB

Open AccessReview

Advances in Polymer Nanocomposites for Drilling Fluids: A Review

by Shahbaz Wakeel, Ammara Aslam and Jianhua Zhang

Materials 2025, 18(20), 4809; https://doi.org/10.3390/ma18204809 - 21 Oct 2025

Viewed by 270

Abstract

Hydrocarbon exploration and extraction increasingly rely on drilling fluids that guarantee operating safety and efficiency, particularly in ultra-deep, high-temperature, and unconventional reservoirs. Traditional drilling fluids, especially for water-based muds (WBMs), have several problems, including excessive fluid loss, severe swelling in shale and instability [...] Read more.

Hydrocarbon exploration and extraction increasingly rely on drilling fluids that guarantee operating safety and efficiency, particularly in ultra-deep, high-temperature, and unconventional reservoirs. Traditional drilling fluids, especially for water-based muds (WBMs), have several problems, including excessive fluid loss, severe swelling in shale and instability in high-pressure/high-temperature (HPHT) conditions. Polymer nanocomposites (PNCs) are new types of drilling fluid additives that combine the vast surface area and reactivity of nanoparticles (NPs) with the structural flexibility and stability of polymers. This combination enhances rheology, reduces filtrate loss, and, most importantly, creates hydrophobic and pore-blocking barriers that prevent shale from swelling. This review highlights important improvements in drilling fluids with PNCs regarding exceptional rheological properties, low fluid loss, and improved suppression of the shale swelling. The particular focus was placed on the specific mechanisms and role that PNCs play in enhancing shale stability, as well as their responsibilities in improving rheology, heat resistance, and salt tolerance. Current advancements, persistent hurdles, and prospective prospects are rigorously evaluated to emphasize the scientific and industrial trajectories for the development of next-generation, high-performance drilling fluids. Moreover, the current challenges and future opportunities of PNCs in drilling fluids are discussed to motivate future contributions and explore new possibilities. Full article

(This article belongs to the Special Issue Fabrication, Characteristics and Applications of Multifunctional Polymer Nanocomposites)

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7 pages, 194 KB

Open AccessEditorial

Alloy Strengthening Mechanisms, Microstructure Control, and Performance Optimization

by Hongling Zhou and Keqin Feng

Materials 2025, 18(20), 4808; https://doi.org/10.3390/ma18204808 - 21 Oct 2025

Viewed by 336

Abstract

Alloys and metal matrix composites (MMCs) are fundamental enablers of technological progress across critical engineering sectors, including aviation, aerospace, marine, automotive, and advanced electronics [...] Full article

(This article belongs to the Special Issue Alloy Strengthening Mechanisms, Microstructure Control, and Performance Optimization)

18 pages, 3234 KB

Open AccessArticle

Electrical Energy Storage from Low-Grade Heat Using Reduced Graphene Oxide–Carbon Nanotube Composite Materials

by Zhe Yang, Yijia Xu, Shuocheng Sun, Yujia Zhang, Xiaolu Li, Yan Zhao, Xusheng Hao, Caige Xue, Dening Guo, Jia Li and Jiale Wang

Materials 2025, 18(20), 4807; https://doi.org/10.3390/ma18204807 - 21 Oct 2025

Viewed by 341

Abstract

The conversion of low-grade heat into storable electrical energy using nanoporous carbon materials represents an efficient energy harvesting strategy. In this study, a reduced graphene oxide (RGO) and carbon nanotube (CNT) composite with a rich microporous structure was synthesized. A symmetrical thermoelectric cell [...] Read more.

The conversion of low-grade heat into storable electrical energy using nanoporous carbon materials represents an efficient energy harvesting strategy. In this study, a reduced graphene oxide (RGO) and carbon nanotube (CNT) composite with a rich microporous structure was synthesized. A symmetrical thermoelectric cell was constructed to harvest thermal energy. The application of a temperature difference (ΔT) generated a stable equilibrium voltage (U_s), which scaled linearly with ΔT. The resulting thermoelectric coefficient (U_s/ΔT) increased markedly with the carbon nanotube (CNT) content, underscoring the effectiveness of CNT incorporation for improving thermoelectric properties. It also shows a non-monotonic dependence on KCl concentration, first increasing and then decreasing, with a maximum value of 4.17 mV/°C achieved in 0.1 M KCl using the RGO-5%CNTs electrode. When connected to an external load, the discharge voltage and current decay rapidly before stabilizing within seconds. Circuit analysis reveals that the incorporation of CNTs reduces internal resistance and increases the equivalent capacitance. Although instantaneous discharge power declines quickly, the addition of CNTs elevates its initial value and slows the decay rate. Both the average output power and thermoelectric conversion efficiency improve with increasing ΔT and are further enhanced at higher CNT content. Overall, the RGO-CNT composite demonstrates significantly superior thermoelectric performance compared to pure RGO. Full article

(This article belongs to the Section Carbon Materials)

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22 pages, 8185 KB

Open AccessArticle

A Non-Contact Phosphor Thermometry Technique for Determining the Optical Absorptivity of Materials

by Thomas M. F. Hutchinson, Matthew Davies, Callum Fisk, Hazem Zied, Jon R. Willmott and Matthew J. Hobbs

Materials 2025, 18(20), 4806; https://doi.org/10.3390/ma18204806 - 21 Oct 2025

Viewed by 358

Abstract

This work presents a bespoke, non-contact, and low-cost Phosphor Thermometry (PT) technique for the measurement of material absorptivity. The approach circumvents the challenges associated with traditional and intrusive calorimetric techniques, which require secure contact with the sample substrate. A thermographic phosphor (TP), Manganese-activated [...] Read more.

This work presents a bespoke, non-contact, and low-cost Phosphor Thermometry (PT) technique for the measurement of material absorptivity. The approach circumvents the challenges associated with traditional and intrusive calorimetric techniques, which require secure contact with the sample substrate. A thermographic phosphor (TP), Manganese-activated Magnesium Fluorogermanate (MFG), was used as a two-colour thermometer utilising the peak intensity ratio technique, enabling an empirical temperature measurement of a given Material Under Test (MUT). The system was calibrated to temperature across a dynamic range of

20

°C to

140

°C and subsequently assessed in terms of noise and relative sensitivity. A mathematical model describing the thermal behaviour of the samples was subsequently developed and used to infer the absorptivity value of the MUTs. Two paints, Black 3.0^® and Avian-B500^®, with known but contrasting absorptivities, were analysed, resulting in measured absorptivity values of

0.9385

and

0.0651

within a range of

0.0081

and

0.0127

for the two paints, respectively. Subsequent mixtures of both paints, with inherent unknown absorptivities, provided resolvable and incremental steps between the two extremities. Further measurements at specific narrow-band wavelengths of

600

nm and

1550

nm of Black 3.0^® were performed, yielding median absorptivity values of

0.9598

and

0.9172

within a range of

0.0168

and

0.0396

, respectively, therefore demonstrating the technique for the measurement of material absorptivity at discrete wavelengths. The potential of a non-contact calorimetric PT technique could provide a scalable, non-intrusive, and low-cost solution for measuring the wavelength-dependent absorptivity values of materials that are used across engineering and research fields. Full article

(This article belongs to the Special Issue Advances in Luminescent Materials: Characterization and Device Applications)

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10 pages, 2149 KB

Open AccessArticle

Effect of MgO Additive on Properties of Corundum–Mullite Duplex Ceramic Synthesized from High-Alumina Fly Ash

by Suwei Dai, Xiaowen Wu and Bingcheng Luo

Materials 2025, 18(20), 4805; https://doi.org/10.3390/ma18204805 - 21 Oct 2025

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Abstract

Corundum–mullite duplex ceramics were fabricated via a solid-state reaction technique using high-alumina fly ash and α-alumina powders. The effects of magnesium oxide on bulk density, apparent porosity, compressive strength, and microstructure of the duplex ceramics were investigated by scanning electronic microscopy, mechanical testing, [...] Read more.

Corundum–mullite duplex ceramics were fabricated via a solid-state reaction technique using high-alumina fly ash and α-alumina powders. The effects of magnesium oxide on bulk density, apparent porosity, compressive strength, and microstructure of the duplex ceramics were investigated by scanning electronic microscopy, mechanical testing, and X-ray diffraction, respectively. Results showed that the prepared ceramics were mainly dominated by mullite and corundum phases, and the mullite was in the form of columns and crosses to form a net-like structure. The bulk density and the compressive strength increased with the increase in MgO addition, while the porosity decreased contrariwise. Optimal performance among tested compositions was observed at 12 wt% MgO addition, yielding a bulk density of 3.012 g·cm⁻³, a porosity of 8.12%, and a compressive strength of 263 MPa, demonstrating the potential of this composite for high-performance ceramic applications. Full article

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

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14 pages, 573 KB

Open AccessArticle

Physical and Functional Properties of Toothpaste Tablets

by Agata Blicharz-Kania, Justyna Kot and Dariusz Andrejko

Materials 2025, 18(20), 4804; https://doi.org/10.3390/ma18204804 - 21 Oct 2025

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Abstract

Products such as toothpaste tablets align with the concept of sustainable cosmetic production. The aim of this study was to evaluate the physical and functional properties of toothpaste tablets with different formulations—with and without fluoride, surfactants, and dried herbs. The following parameters were [...] Read more.

Products such as toothpaste tablets align with the concept of sustainable cosmetic production. The aim of this study was to evaluate the physical and functional properties of toothpaste tablets with different formulations—with and without fluoride, surfactants, and dried herbs. The following parameters were determined: friability (using a shaking method), compressive strength (using a tensile testing machine), colour parameters (spectrophotometrically), pH, and foaming capacity. The study results showed that tablet durability is closely dependent on the formulation. Tablets made with commonly used ingredients (control sample) had the highest breaking force (55.24 N). Tablets without fluoride had the lowest friability (1.46%). Optical tests showed that different formulations affected tablet brightness and colour saturation. The largest changes were observed for samples containing dried herbs—ΔE > 5. The tablets with clove added had improved foam quality, which is important from a functional perspective. The disintegration time of the tablets was significantly shorter for the modified formulation samples. The study results indicate that the developed tablets, especially the control and fluoride-free samples, are sufficiently hard and durable. The tablets with added herbal ingredients, on the other hand, exhibit good foaming and dissolving properties and are waterless products without preservatives. Full article

(This article belongs to the Special Issue Advances in Materials Science and Engineering—in Celebration of 55th Anniversary of the Faculty of Technical Sciences, Warmia and Mazury University in Olsztyn, Poland)

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15 pages, 2914 KB

Open AccessArticle

Ternary Synergistic Electrolyte Enabling Stable Li-Ion Battery Operation Across −40 °C to 60 °C

by Yali Zhao, Yutao Liu, Jingju Liu, Daofa Ying, Xuanlin Gong, Linjin Xie, Xiaohan Guo, Caiyun Yao, Baohui Chen and Chuanping Wu

Materials 2025, 18(20), 4803; https://doi.org/10.3390/ma18204803 - 21 Oct 2025

Viewed by 352

Abstract

The operational failure of lithium-ion batteries under extreme temperatures (−40~60 °C) stems primarily from electrolyte limitations. While prior efforts improved either low-temperature or high-temperature performance independently, holistic electrolyte design with practical validation remains elusive. Herein, we develop an all-climate electrolyte (ACE) through synergistic [...] Read more.

The operational failure of lithium-ion batteries under extreme temperatures (−40~60 °C) stems primarily from electrolyte limitations. While prior efforts improved either low-temperature or high-temperature performance independently, holistic electrolyte design with practical validation remains elusive. Herein, we develop an all-climate electrolyte (ACE) through synergistic coordination of solvent, Li salt, and additive, achieving low viscosity (<10 mPa·s at −40 °C) and high ionic conductivity (7.0 mS cm⁻¹ at −40 °C). Raman and NMR spectra reveal MA and EC co-occupying Li⁺ solvation sheath while EMC acts as a diluent, enabling rapid ion transport. Consequently, LiFePO₄ (LFP)|graphite (Gr) cell delivers unprecedented cyclability: zero capacity decay over 500 cycles at 0 °C, stable operation across −40~60 °C, and 94.1% retention after 100 cycles at 45 °C in Ah-level pouch cells. XPS and SEM analysis demonstrate lithium difluorophosphate (LiDFP) and lithium bis(fluorosulfonyl)imide (LiFSI) collaboratively remodel SEI/CEI interphases, enriching them with LiF, Li₃PO₄, and Li₂SO₄. This inorganic-dominant architecture enhances interfacial Li⁺ kinetics and all-climate stability compared to the baseline electrolyte. Our tripartite electrolyte strategy provides a material-agnostic solution for all-climate energy storage. Full article

(This article belongs to the Section Electronic Materials)

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17 pages, 7728 KB

Open AccessArticle

The Influence of Wide-Directional Asymmetric Spraying on Machining Deformation of Aluminum Alloy Plates

by Yang Li, Zhongkun Lin, Yanan Li, Xiwu Li, Kai Zhu, Mingyang Yu, Ying Li and Hongwei Yan

Materials 2025, 18(20), 4802; https://doi.org/10.3390/ma18204802 - 21 Oct 2025

Viewed by 280

Abstract

This study investigates the machining deformation of thick aluminum alloy plates, specifically in aerospace frame components, focusing on the influence of asymmetric residual stress states and machining strategies. Aluminum alloys are commonly used for large structural components due to their strength, formability, and [...] Read more.

This study investigates the machining deformation of thick aluminum alloy plates, specifically in aerospace frame components, focusing on the influence of asymmetric residual stress states and machining strategies. Aluminum alloys are commonly used for large structural components due to their strength, formability, and corrosion resistance. However, machining these components often leads to deformation caused by residual stress release, cutting forces, and thermal effects. Using finite element simulations and experimental validation, the study analyzes how asymmetric residual stresses, induced by spray quenching, affect deformation patterns during machining. It is found that lower initial stress asymmetry results in less deformation, while machining sequences that optimize stress release significantly reduce the final distortion. Among the strategies tested, the diagonal milling sequence yielded the smallest deformation, achieving a reduction of up to 4%. The study concludes that both the initial residual stress state and the machining strategy are critical in controlling deformation, offering insights for improving machining processes in aerospace manufacturing to enhance precision and reliability. Full article

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

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21 pages, 3058 KB

Open AccessArticle

Dynamic Identification Method for Highway Subgrade Soil Compaction Based on Embedded Attitude Sensors

by Zhizhou Su, Hao Li, Jiaye Hu, Bin Wu, Fengteng Liu, Peixin Tian and Xukai Ding

Materials 2025, 18(20), 4801; https://doi.org/10.3390/ma18204801 - 21 Oct 2025

Viewed by 260

Abstract

Compaction quality is a critical factor in ensuring the long-term performance of subgrade structures; however, traditional testing methods are limited by their destructive nature and delayed feedback. To address these shortcomings, this study proposes a dynamic identification method for subgrade compaction based on [...] Read more.

Compaction quality is a critical factor in ensuring the long-term performance of subgrade structures; however, traditional testing methods are limited by their destructive nature and delayed feedback. To address these shortcomings, this study proposes a dynamic identification method for subgrade compaction based on embedded attitude sensors. A customized sensor unit integrated with an inertial measurement module was embedded in soil samples to record triaxial acceleration and attitude angles during the compaction process. Signal processing techniques, including an improved wavelet-based denoising strategy, were employed to separate long-term compaction trends from transient impact disturbances. Attitude features such as cumulative angular change, angular velocity, root mean square values, and a comprehensive inclination index were extracted as predictive variables. Ridge regression, random forest, and XGBoost models were constructed to establish the mapping relationship between attitude features and compaction degree. Experimental results on clay, loam, and sand samples indicate that the yaw angle is most sensitive to vertical settlement, while pitch and roll angles provide complementary information on lateral and rotational behaviors. Comparative analysis of filtering methods shows that the transient masking interpolation (TMI) approach outperforms the traditional asymmetric wavelet thresholding (AWT) method in effectively preserving baseline trends. Among the regression models, XGBoost demonstrated the best predictive performance, achieving an R² exceeding 0.995 at high compaction levels. The proposed method has been experimentally demonstrated as a laboratory-scale proof of concept, showing strong potential for future real-time field application, offering a novel technological pathway for intelligent quality control in road construction. Full article

(This article belongs to the Special Issue AI-Based Material Design, Performance Evaluation and Construction Quality Control of Asphalt Pavement)

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35 pages, 4897 KB

Open AccessArticle

Machine-Learning-Based Probabilistic Model and Design-Oriented Formula of Shear Strength Capacity of UHPC Beams

by Kun Yang, Jiaqi Xu and Xiangyong Ni

Materials 2025, 18(20), 4800; https://doi.org/10.3390/ma18204800 - 21 Oct 2025

Viewed by 340

Abstract

Designing UHPC beams for shear is challenging because many factors—geometry, concrete strength, fibers, and stirrups—act together. In this study, we compile a large, curated database of laboratory tests and develop machine learning models to predict shear capacity. The best models provide accurate point [...] Read more.

Designing UHPC beams for shear is challenging because many factors—geometry, concrete strength, fibers, and stirrups—act together. In this study, we compile a large, curated database of laboratory tests and develop machine learning models to predict shear capacity. The best models provide accurate point predictions and, importantly, a 95% prediction band that tells how much uncertainty to expect; in tests, about 95% of results fall inside this band. For day-to-day design, we also offer a short, design-oriented formula with explicit coefficients and variables that can be used in a spreadsheet. Together, these tools let engineers screen options quickly, check designs with an uncertainty margin, and choose a conservative value when needed. The approach is transparent, easy to implement, and aligned with common code variables, so it can support preliminary sizing, verification, and assessment of UHPC members. Full article

(This article belongs to the Special Issue Modeling and Numerical Simulations in Materials Mechanics)

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20 pages, 4199 KB

Open AccessArticle

Study on the Thermal and Rheological Properties of Nano-TiO₂-Modified Double Phase Change Asphalt

by Xingming Liu, Xiaojun Cheng, Shanshan Wang, Sishuang Wei, Meng Guo, Shanglin Song and Fukui Zhang

Materials 2025, 18(20), 4799; https://doi.org/10.3390/ma18204799 - 21 Oct 2025

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Abstract

In this paper, paraffin-44H (PW-44H) and paraffin-5 (PW-5) were respectively selected as the high/low-temperature phase change core material, and expanded vermiculite (EVM) was selected as the phase change carrier matrix. A high-temperature composite phase change material (CPCM), 44H/EVM, and a low-temperature CPCM, 5/EVM, [...] Read more.

In this paper, paraffin-44H (PW-44H) and paraffin-5 (PW-5) were respectively selected as the high/low-temperature phase change core material, and expanded vermiculite (EVM) was selected as the phase change carrier matrix. A high-temperature composite phase change material (CPCM), 44H/EVM, and a low-temperature CPCM, 5/EVM, were prepared by combining melt blending with vacuum adsorption. Nano-TiO₂ was incorporated as a thermal conductor into the CPCMs to enhance the heat transfer efficiency between the CPCM and asphalt. The heat storage performance, chemical stability, microstructure, and thermal stability of the two CPCMs were studied. The results show that when the dosage of nano-TiO₂ is 2%, the critical temperature range and heat storage performance of the CPCMs reach the optimum. Among them, the enthalpy value of the phase transition of the high-temperature PCM 44H-nTiO₂/EVM is 150.8 J/g, and the phase transition occurs over a temperature range of 37.3 °C to 45.9 °C. The enthalpy value of the phase transition of the low-temperature PCM 5-nTiO₂/EVM is 106.6 J/g, and the phase transition range is −7.9–0.4 °C. Moreover, the incorporation of nano-TiO₂ increased the thermal conductivity of the high- and low-temperature CPCMs by 47.2% and 51.6%, respectively. Finally, the high- and low-temperature CPCMs were compounded in a 1:1 ratio and mixed into asphalt to obtain a composite double PCM asphalt. The heat storage performance of the original sample asphalt and the double phase change asphalt was investigated by DSC, DSR, and an environmental chamber. The results show that when the dosage of PCM is 20%, compared with the original asphalt, the high-temperature extreme value and the low-temperature extreme value of the double phase change asphalt are reduced by 3.4 °C and 2.1 °C, respectively. The heating rate and cooling rate decreased by 8.5% and 5.6%, respectively, and the rheological properties can meet the requirements of the specifications. It can be seen that the addition of double PCMs can effectively slow down the heating/cooling rate of asphalt, thereby improving the temperature sensitivity of asphalt. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials (5th Edition))

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15 pages, 7062 KB

Open AccessArticle

Analysis of the Causes of Damage to the Steel Drive Shaft Used in a Paint Mixer

by Wojciech Skotnicki and Dariusz Jędrzejczyk

Materials 2025, 18(20), 4798; https://doi.org/10.3390/ma18204798 - 21 Oct 2025

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Abstract

This article presents an analysis of the causes of damage to the shaft used in a paint mixer (made of 1.0501 steel, with diameter ø = 90 mm and length l = 3451 mm). The observed damage occurred in both the shaft before [...] Read more.

This article presents an analysis of the causes of damage to the shaft used in a paint mixer (made of 1.0501 steel, with diameter ø = 90 mm and length l = 3451 mm). The observed damage occurred in both the shaft before regeneration and the part regenerated by surfacing. The initial analysis consisted of both macroscopic and microscopic observations of the shaft cross sections. Additionally, hardness measurements were made using the Vickers method (HV0.1). The results of microstructure observations were used as the basis for further finite element analysis (FEA). The FEA simulations made it possible to identify the places most susceptible to damage and assess the stress distribution during the shaft’s application. Based the FEA results, in order to improve the durability of the analyzed structural element, changes in the shaft geometry and the use of different chemical steel compositions are proposed. Full article

(This article belongs to the Section Metals and Alloys)

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17 pages, 2988 KB

Open AccessArticle

Effect of Ba:Ti Molar Ratio and Sintering Temperature on the Structural and Electrical Properties of BaTiO₃-Type Solid Solutions, Synthesized by the Hydrothermal Method

by José Agustin Palmas Léon, Leandro Ramajo, Rodrigo Parra, Miguel Pérez Labra, Francisco Raúl Barrientos Hernández, Alejandro Cruz Ramírez, Vanessa Acosta Sanchez, Aislinn Michelle Teja Ruiz and Sayra Ordoñez Hernández

Materials 2025, 18(20), 4797; https://doi.org/10.3390/ma18204797 - 21 Oct 2025

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Abstract

The results of the effect of the three Ba:Ti molar ratios (MR) (1:1, 2:1, 4:1) and four sintering temperatures (1250, 1275, 1300, 1325 °C) on the structural and electrical properties of BaTiO₃ (BT)-type ceramics synthesized by the hydrothermal method are shown. The [...] Read more.

The results of the effect of the three Ba:Ti molar ratios (MR) (1:1, 2:1, 4:1) and four sintering temperatures (1250, 1275, 1300, 1325 °C) on the structural and electrical properties of BaTiO₃ (BT)-type ceramics synthesized by the hydrothermal method are shown. The BT phase formed was analyzed by x-ray diffraction (XRD), Raman spectroscopy (RS), dielectric and ferroelectric measurements and high-resolution scanning electron microscopy (HRSEM). For the samples synthesized using a Ba:Ti MR of 4:1 and at all sintering temperatures analyzed, XRD results confirmed the presence of the tetragonal ferroelectric phase, BT. In the same way, these results corroborated the results obtained by the RS technique. Dielectric properties measured at 100 kHz and 1 MHz over a temperature range of 30 °C–200 °C indicated a relative permittivity value of 4280 at 1 MHz and 4200 at 100 KHz at a Curie temperature of 110 °C in both cases for the sample synthesized at with a Ba:Ti MR ratio of 4:1 and sintered at 1300 °C. Ferroelectric measurements for the samples showed a best remnant polarization (Pr) of 3.5 µC/cm² for the sample synthesized with a Ba:Ti MR ratio of 4:1 and sintered at 1325 °C. The HRSEM results showed grains composed of Ba, Ti, and O homogeneously distributed in the BT structure, and a trend of increasing average grain size with increasing sintering temperature was observed. Full article

(This article belongs to the Special Issue Advanced Dielectric, Piezoelectric and Ferroelectric Properties of Materials)

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16 pages, 4743 KB

Open AccessArticle

Coarse Aggregate Induced Fiber Dispersion and Its Role in UHPC Mechanics Across Flexural and Compressive Loading

by Chen Shen, Yue Zhang, Jianlin Li, Haonan Zeng, Changhui Yang and Linwen Yu

Materials 2025, 18(20), 4796; https://doi.org/10.3390/ma18204796 - 21 Oct 2025

Viewed by 316

Abstract

Ultra-high-performance concrete (UHPC) exhibits exceptional mechanical properties and durability but faces challenges such as high heat of hydration and limited stiffness. Incorporation of coarse aggregates offers a potential solution; however, it alters the dispersion of steel fibers, thereby affecting the mechanical performance of [...] Read more.

Ultra-high-performance concrete (UHPC) exhibits exceptional mechanical properties and durability but faces challenges such as high heat of hydration and limited stiffness. Incorporation of coarse aggregates offers a potential solution; however, it alters the dispersion of steel fibers, thereby affecting the mechanical performance of UHPC under different loading conditions. This study systematically investigates the influence of coarse aggregates on UHPC performance under different loading conditions, including four-point bending, uniaxial compression, and triaxial compression tests. The spatial distribution of steel fibers was quantitatively analyzed via image analysis to elucidate changes induced by CA incorporation. Results reveal that with 20 vol% coarse aggregate (10 mm), UHPC’s flexural strength is essentially unchanged (≈23 MPa), whereas flexural toughness decreases by about one-third. This toughness loss is linked to a slight increase in the fiber orientation angle (from 48.77° to 48.90°) and reduced continuity, which together weaken crack-bridging. Moreover, both flexural strength and toughness are governed primarily by the local steel-fiber content within the tensile zone. Under triaxial compression, confinement dominates: as confining pressure rises from 0 to 30 MPa, compressive strength increases by approximately 32.6%, 52.6%, and 71.3%. Due to crack-suppression by confinement overlapping with fiber bridging, the contribution of fibers to strength gains decreases with increasing confinement, and the competing and complementary interaction between coarse aggregate and steel fibers correspondingly weakens. These findings clarify the coupled effects of coarse aggregate and fibers in UHPC-CA, guide mix-design optimization for improved mechanical performance, and support broader practical adoption. Full article

(This article belongs to the Special Issue Performance and Durability of Reinforced Concrete Structures)

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29 pages, 24797 KB

Open AccessArticle

Experimental Verification of Calcite Formation Potential by Ureolytic and Non-Ureolytic Bacterial Strains in Geopolymer Mortar

by Bashar Al Hayo, Orhan Canpolat, Nihal Doğruöz Güngör, Mücteba Uysal, Nahdhoit Ahamada Rachid and Issam Ali

Materials 2025, 18(20), 4795; https://doi.org/10.3390/ma18204795 - 21 Oct 2025

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Abstract

This study aimed to examine the calcite precipitation potential of non-ureolytic bacterial strains of two species, Viridibacillus arenosi (A₆) and Bacillus zhangzhouensis (D₂₅), as compared to the known ureolytic bacterial strain, Sporosarcina pasteurii (SP), within geopolymer mortar. Tests were [...] Read more.

This study aimed to examine the calcite precipitation potential of non-ureolytic bacterial strains of two species, Viridibacillus arenosi (A₆) and Bacillus zhangzhouensis (D₂₅), as compared to the known ureolytic bacterial strain, Sporosarcina pasteurii (SP), within geopolymer mortar. Tests were carried out after 56 days of injection treatment to confirm the precipitation process, incorporating healing efficiency measured by ImageJ software, recovery of UPV, water permeability, capillary water absorption, and microstructural and mineralogical analysis SEM/EDS and XRD. The non-ureolytic isolates D₂₅ and A₆ showed the highest healing efficiencies, at 96.9% and 91.9%, respectively, followed by the ureolytic bacteria SP at 77.8%. A₆ exhibited the most substantial reduction in permeability at 97.3%, indicating extensive crack healing, followed by D₂₅ at 92.9% and SP at 82.1%. Furthermore, SEM and EDS analyses confirmed the formation of calcite crystals and calcium depositions in the bacteria-treated samples. Complementary evidence was provided by XRD, which revealed distinct calcium carbonate peaks in the treated specimens, peaks that were entirely absent in the control samples, thus strongly confirming the role of bacterial activity in the precipitation process. The results confirm that non-ureolytic bacteria can efficiently boost calcite precipitation in geopolymer mortars, offering superior healing performance and a more sustainable alternative to ureolytic strains. Full article

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

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16 pages, 7276 KB

Open AccessArticle

Influence of Hydrogen-Based Direct Reduction Shaft Furnace Interior Structure on Shaft Furnace Performance

by Qingbin Xue, Haotian Liao, Jianliang Zhang and Kejiang Li

Materials 2025, 18(20), 4794; https://doi.org/10.3390/ma18204794 - 20 Oct 2025

Viewed by 429

Abstract

Hydrogen-based direct reduction of iron ore is a promising route to reduce CO₂ emissions in steelmaking, where uniform particle flow inside shaft furnaces is essential for efficient operation. In this study, a full-scale three-dimensional Discrete Element Method (DEM) model of a shaft [...] Read more.

Hydrogen-based direct reduction of iron ore is a promising route to reduce CO₂ emissions in steelmaking, where uniform particle flow inside shaft furnaces is essential for efficient operation. In this study, a full-scale three-dimensional Discrete Element Method (DEM) model of a shaft furnace was developed to investigate the effects of a diverter device on granular flow. By systematically varying the radial width and top/bottom diameters of the diverter, particle descent velocity, residence time, compressive force distribution, and collision energy dissipation were analyzed. The results demonstrate that introducing a diverter effectively suppresses funnel flow, prolongs residence time, and improves radial flow uniformity. Among the tested configurations, the smaller central diameter diverter showed the most favorable performance, achieving a faster and more uniform descent, reduced compressive force concentration, and lower collision energy dissipation. These findings highlight the critical role of diverter design in regulating particle dynamics and provide theoretical guidance for optimizing shaft furnace structures to enhance the efficiency of hydrogen-based direct reduction processes. Full article

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15 pages, 1228 KB

Open AccessArticle

Molecular Biocompatibility Assessment of PETG Aligners After Processing by Laser or Milling

by Katia Barbaro, Ginevra Ciurli, Ettore Candida, Francesca Silvestrini-Biavati, Valentina Lanteri, Paola Ghisellini, Cristina Rando, Roberto Eggenhöffner and Alessandro Ugolini

Materials 2025, 18(20), 4793; https://doi.org/10.3390/ma18204793 - 20 Oct 2025

Viewed by 341

Abstract

Polyethylene terephthalate glycol-modified (PETG) is a transparent, stable copolymer commonly used in biomedical devices such as surgical guides, clear aligners, and anatomical models. Its biocompatibility must be assessed not only for cytotoxicity, but also for subtle molecular and immunological responses, especially when in [...] Read more.

Polyethylene terephthalate glycol-modified (PETG) is a transparent, stable copolymer commonly used in biomedical devices such as surgical guides, clear aligners, and anatomical models. Its biocompatibility must be assessed not only for cytotoxicity, but also for subtle molecular and immunological responses, especially when in contact with mucosal or hormone-sensitive tissues. This study evaluated the biological safety of PETG processed via CNC milling and CO₂ laser cutting, two methods that preserve bulk chemistry but may alter surface properties. PETG diskettes were analyzed by FT-IR, ¹H-NMR, and GC–MS to confirm chemical integrity and absence of degradation products. Biocompatibility was tested using MCF-7 epithelial cells and THP-1 monocytes. Cell viability remained above 90% over seven days. Inflammatory (COX-2, TNFα, IL-8, IL-1α, IL-4, IL-10, IFNγ) and hormone-related (ERα, ERβ) gene expression was analyzed by qRT-PCR. Gene profiling revealed only modest, non-significant changes: COX-2 was upregulated 1.8-fold after laser processing, and ERα increased 1.6-fold following milling—both below thresholds considered biologically active. These findings indicate that mechanical surface treatments induce minimal bioactivity, with no meaningful immune or hormonal stimulation. PETG remains functionally inert under the tested conditions, supporting its continued safe use in intraoral and hormone-sensitive biomedical applications. Full article

(This article belongs to the Special Issue Materials and Techniques in Dentistry, Oral Surgery and Orthodontics (Second Edition))

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32 pages, 7096 KB

Open AccessArticle

Uncertainty Quantification of the Mechanical Properties of 2D Hexagonal Cellular Solid by Analytical and Finite Element Method Approach

by Safdar Iqbal and Marcin Kamiński

Materials 2025, 18(20), 4792; https://doi.org/10.3390/ma18204792 - 20 Oct 2025

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Abstract

The mechanical properties of cellular materials are critical to their performance and must be accurately determined through both analytical and numerical methods. These approaches are essential not only for understanding material behavior but also for evaluating the effects of parametric variations within the [...] Read more.

The mechanical properties of cellular materials are critical to their performance and must be accurately determined through both analytical and numerical methods. These approaches are essential not only for understanding material behavior but also for evaluating the effects of parametric variations within the unit cell structure. This study focuses on the in-plane comparison of analytical and numerical evaluations of key mechanical properties, including Young’s modulus, yield strength, and Poisson’s ratio of a 2D hexagonal unit cell subjected to systematic geometric and material variations. Analytically, the mechanical properties were derived based on the geometric configuration of the hexagonal unit cell. Numerically, the finite element method (FEM) simulations employed three different meshing methods: quadrilateral, quad-dominated, and triangular elements, to ensure precision and consistency in the results. The elastic response (Young’s modulus) was examined through a parametric sweep involving segmental length variations (4.41 to 4.71 mm) and material modulus (66.5 to 71.5 GPa), revealing percentage differences between analytical and numerical results ranging from −8.28% to 10.87% and −10.58% to 11.95%, respectively. Similarly, yield strength was evaluated with respect to variations in segmental length (4.41 to 4.71 mm) and wall thickness (1.08 to 1.11 mm), showing discrepancies between −2.86% to −5.53% for segmental length and 7.76% to 10.57% for thickness. For Poisson’s ratio, variations in the same parameters led to differences ranging from −7.05% to −12.48% and −9.11% to −12.64%, respectively. Additionally, uncertainty was assessed through relative entropy measures—Bhattacharyya, Kullback–Leibler, Hellinger, and Jeffreys—to evaluate the sensitivity of homogenized properties to input variability. These entropy measures quantify the probabilistic distance between core material distributions and their effective counterparts, reinforcing the importance of precise modeling in the design and optimization of cellular structures. Full article

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

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29 pages, 3900 KB

Open AccessArticle

Study on the Fatigue Bending Strength of Cylindrical Components Manufactured by External WAAM

by Van-Minh Nguyen, Pham Son Minh, Dang Thu Thi Phan and Huynh Do Song Toan

Materials 2025, 18(20), 4791; https://doi.org/10.3390/ma18204791 - 20 Oct 2025

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Abstract

This study investigates the fatigue bending strength, measured as the Mean of Fatigue Cycles (N), of cylindrical components produced by external wire arc additive manufacturing (WAAM) through a Taguchi L25 orthogonal array and linear regression analysis. Five welding parameters—welding current (Ampe), offset distance [...] Read more.

This study investigates the fatigue bending strength, measured as the Mean of Fatigue Cycles (N), of cylindrical components produced by external wire arc additive manufacturing (WAAM) through a Taguchi L25 orthogonal array and linear regression analysis. Five welding parameters—welding current (Ampe), offset distance (mm), step length (mm), welding speed (mm/min), and specimen gauge diameter (mm)—were evaluated to maximize N using signal-to-noise (S/N) ratios. Nominal bending stresses (σ) ranged from 45 to 54 MPa, ANOVA on raw replicate data (25 runs, 3 replicates) confirmed specimen gauge diameter = 17 mm and weld current = 125 A as dominant, with F = 171.62 (p < 0.001, eta² = 0.62 [95% confidence intervals (CI) 0.55–0.68]) for specimen gauge diameter and F = 6.13 (p < 0.001, eta² = 0.13 [95% CI 0.08–0.18]) for weld current, accounting for ~75% of the variance. Optimal settings (offset distance = 3.0 mm, step length = 1000 mm, welding speed = 550 mm/min, specimen gauge diameter = 17 mm) achieved S/N = 111.35 dB, predicting N ≈ 350,000–380,000 cycles, a 22–33% improvement. Interactions between specimen gauge diameter and speed, and between weld current and offset distance, suggested enhanced strength at speed = 400–450 mm/min for specimen gauge diameter = 17 mm. Basquin’s law (b ≈ 0.72, R² = 0.992) confirmed weld current as key. The linear regression model (adjusted R² = 0.9506) had coefficients for specimen gauge diameter (+70,120 cycles/mm, p < 0.001) and weld current (+1088 cycles/Ampe, p = 0.02), but lower test R² = 0.7212 via cross-validation (60/20/20 split) indicates overfitting due to small dataset size (25 runs), suggesting larger datasets or nonlinear models (e.g., polynomial regression, RSM). Confirmation runs (N = 317,082, 95% CI [287,000–347,000]) validated the results within ~13% error. WAAM reaches 80–90% of traditional manufacturing (TM) fatigue performance, with a 10–20% gap due to the microstructure; recommendations include post-treatments and safety factors (~1.2). Full article

(This article belongs to the Special Issue Additive Manufacturing and Forming Technologies of Alloy: Mechanical Properties and Microstructure Evaluation)

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20 pages, 1357 KB

Open AccessReview

Materials Prepared via Pickering Emulsions Stabilized by Graphene Oxide: Overview and Prospects

by Manman Liu, Wenle Zhu and Huili Wang

Materials 2025, 18(20), 4790; https://doi.org/10.3390/ma18204790 - 20 Oct 2025

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Abstract

Pickering emulsions, employing solid or colloidal particles rather than surfactants to stabilize the oil-water interface, have attracted considerable attention owing to their enhanced stability and the potential for designing functional materials. In particular, Graphene Oxide (GO) has emerged as an effective stabilizer for [...] Read more.

Pickering emulsions, employing solid or colloidal particles rather than surfactants to stabilize the oil-water interface, have attracted considerable attention owing to their enhanced stability and the potential for designing functional materials. In particular, Graphene Oxide (GO) has emerged as an effective stabilizer for such emulsions, owing to its unique physicochemical properties. This review systematically outlines the stabilization mechanisms of GO-based Pickering emulsions, providing fundamental insights that support further development in the field. We comprehensively examine recent advances in the preparation and characterization of GO-stabilized emulsions and highlight their broad applications, including the synthesis of advanced materials and uses across various industrial sectors. Finally, we discuss current challenges and suggest promising directions for future research on GO-stabilized Pickering emulsions. Full article

(This article belongs to the Section Advanced Materials Characterization)

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9 pages, 3385 KB

Open AccessArticle

Synthesis of Silver–Calcium Phosphate Visible Light Responsive Photocatalytic Materials and Their Antibacterial Properties

by Hiroaki Onoda and Chihiro Izaki

Materials 2025, 18(20), 4789; https://doi.org/10.3390/ma18204789 - 20 Oct 2025

Viewed by 329

Abstract

Photocatalytic materials use light energy to decompose harmful substances, antifouling, and deodorize. However, photocatalytic materials currently in practical use utilize ultraviolet light, and considering the ratio of ultraviolet light in sunlight and indoor specifications, there is a need for photocatalysts that can act [...] Read more.

Photocatalytic materials use light energy to decompose harmful substances, antifouling, and deodorize. However, photocatalytic materials currently in practical use utilize ultraviolet light, and considering the ratio of ultraviolet light in sunlight and indoor specifications, there is a need for photocatalysts that can act with visible light. Silver phosphate is a photocatalytic material that works with visible light, but the silver ions make it expensive and difficult to put to practical use. This material is also expected to have antibacterial properties derived from silver ions. In this study, we prepared silver–calcium phosphate with a reduced amount of silver. The composition, photocatalytic activity, and antibacterial properties of the obtained samples were evaluated to examine the potential of the novel material. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Photocatalytic Application)

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15 pages, 4510 KB

Open AccessArticle

Experimental Optimization Study on Pumping Pipeline Transportation Performance of Pure Gangue Slurry Filling Material

by Yingbo Wang, Xiaoming Tang, Feng Ju, Meng Xiao, Tengfei Wang, Dong Wang, Lidong Yin, Lu Si and Mengxin Xu

Materials 2025, 18(20), 4788; https://doi.org/10.3390/ma18204788 - 20 Oct 2025

Viewed by 297

Abstract

Gangue slurry pumping backfill offers a cost-effective and environmentally sound solution for coal mine solid waste disposal. Addressing the poor pumpability of pure gangue slurry, this study applied the Talbot gradation theory to a non-cemented gangue system by designing various particle size gradations [...] Read more.

Gangue slurry pumping backfill offers a cost-effective and environmentally sound solution for coal mine solid waste disposal. Addressing the poor pumpability of pure gangue slurry, this study applied the Talbot gradation theory to a non-cemented gangue system by designing various particle size gradations and water-solid ratios (W/S). Through tests on rheological properties, slump, spread, and bleeding rate, the optimal proportion for pumpability of pure gangue slurry (PGS) within the scope of this study was determined. Tests were conducted on rheology, slump, spread flow, and bleeding rate to determine the optimal mix proportion for pumpability. The results show that: The slurry in this study demonstrates a strong correlation with the characteristics of a Bingham fluid. Its yield stress increases significantly as the W/S decreases. At a gradation index (n) of 0.4, particle packing is densest, resulting in the lowest yield stress. Slump and spread flow decrease with a lower W/S. They initially increase and then decrease as the gradation index increases, with optimal fluidity observed at n = 0.4. Bleeding rate increases with a higher gradation index but decreases with a lower W/S. Comprehensive optimization determined the optimal mix proportion as gradation index n = 0.4 and W/S of 0.18. At this ratio: Yield stress = 144.25 Pa, Slump = 255 mm, Spread flow = 60.1 cm, Bleeding rate = 2.21%. This meets the pumping requirements (Slump > 180 mm, Bleeding rate < 3%). The research results provide important experimental value for the practical pipeline transportation of PGS and the reduction in pumping friction resistance. Full article

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

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