Materials

16 pages, 4759 KB

Open AccessArticle

A Rapid Consolidation Route for Recycled NdFeB Powders and the Role of Particle Shape in Grain Growth

by Fabian Burkhardt, Alba Berja, Laura Grau, Matija Kreča, Lindrit Krasniqi, Benjamin Podmiljšak, Kristina Žužek, Carlo Burkhardt, Spomenka Kobe, Adrián Quesada and Tomaž Tomše

Materials 2025, 18(21), 5029; https://doi.org/10.3390/ma18215029 - 4 Nov 2025

Abstract

The recycling of NdFeB magnets is essential to reduce reliance on critical rare earth elements and mitigate the environmental burden of virgin magnet production. Hydrogen Processing of Magnetic Scrap (HPMS) offers an efficient method to extract magnet powders from end-of-life (EOL) products, yet [...] Read more.

The recycling of NdFeB magnets is essential to reduce reliance on critical rare earth elements and mitigate the environmental burden of virgin magnet production. Hydrogen Processing of Magnetic Scrap (HPMS) offers an efficient method to extract magnet powders from end-of-life (EOL) products, yet oxidation and microstructural degradation during powder preparation limit the magnetic performance of recycled magnets. In this work, rapid Radiation-Assisted Sintering (RAS) was systematically evaluated for the first time as a consolidation route for HPMS-derived powders. Magnets prepared via RAS exhibited performance comparable to those obtained by conventional sintering. When oxygen uptake during milling was prevented, the addition of 1 wt.% NdH₃ to the already oxygen-burdened recycled powder improved the intrinsic coercivity and squareness of the demagnetization curve. The best-performing samples achieved B_r = 1.18 T, (BH)_max = 263 kJ/m³, and H_ci = 742 kA/m at 100 °C, surpassing the properties of the original EOL magnets. Furthermore, the study revealed that, when the HPMS powder fragments preferentially break along grain boundaries, the resulting near-equilibrium powder particles exhibit limited growth, thereby restraining grain coarsening. These findings highlight the strong potential of RAS for more energy-efficient magnet-to-magnet recycling and provide new insight into optimizing HPMS powder processing to achieve enhanced magnetic performance. Full article

(This article belongs to the Special Issue Advances in Magnetic Materials and Applications)

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30 pages, 1506 KB

Open AccessReview

Recent Developments in Cellulose/Chitosan Biopolymer Composites for Winery Wastewater Treatment and Reuse: A Review

by Fisokuhle Innocentia Kumalo, Innocent Mugudamani, Ernestine Atangana and Thandi Patricia Gumede

Materials 2025, 18(21), 5028; https://doi.org/10.3390/ma18215028 - 4 Nov 2025

Abstract

Winery wastewater, characterized by high organic load, fluctuating pH, and seasonal variability, presents a major environmental challenge for sustainable water management in viticulture regions. Recent advances in bio-based polymer composites, particularly those incorporating cellulose and chitosan matrices blended with synthetic polymers such as [...] Read more.

Winery wastewater, characterized by high organic load, fluctuating pH, and seasonal variability, presents a major environmental challenge for sustainable water management in viticulture regions. Recent advances in bio-based polymer composites, particularly those incorporating cellulose and chitosan matrices blended with synthetic polymers such as polyacrylamide (PAM), polyvinyl alcohol (PVA), and polyethylene glycol (PEG), provide promising possibilities for effective wastewater treatment and water reuse in irrigation. This review critically explores the synthesis, structural properties, and functional performance of cellulose/chitosan-based composites, with a particular emphasis on their adsorption, flocculation, and biodegradability in the context of winery effluent treatment. Evidence from recent laboratory- and pilot-scale studies highlights the significance of pH-responsive functional groups, electrostatic interactions, and hydrogen bonding in controlling pollutant capture and regeneration efficiency. While notable removal efficiencies of these composites have been demonstrated to exceed 85–95% for COD, 80–98% for turbidity, and >90% for heavy metals, challenges remain in terms of regeneration, long-term field applicability, and scale-up. Overall, biopolymer composites represent a promising pathway toward sustainable wastewater treatment and irrigation reuse in winery operations. Full article

(This article belongs to the Special Issue Functional/Structural Polymers and Composites Produced by the Addition of Plant Biomass or Waste Materials Using Various Production Technologies)

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19 pages, 32582 KB

Open AccessArticle

Study on the Characteristics of Cement-Based Magnetoelectric Composites Using COMSOL

by Weixuan Huang, Cuijuan Pang, Jianyu Xu, Kangyang Liang, Cunying Fan, Zeyu Lu and Chuncheng Lu

Materials 2025, 18(21), 5027; https://doi.org/10.3390/ma18215027 - 4 Nov 2025

Abstract

A multiphysics-coupled 2–2 cement-based magnetoelectric composite model is established in COMSOL 6.2. This model is used to not only systematically investigate the magnetoelectric-coupling behavior, but also quantify the effects of the magnetic field, frequency, and layer-thickness ratio on the material’s magnetoelectric properties. The [...] Read more.

A multiphysics-coupled 2–2 cement-based magnetoelectric composite model is established in COMSOL 6.2. This model is used to not only systematically investigate the magnetoelectric-coupling behavior, but also quantify the effects of the magnetic field, frequency, and layer-thickness ratio on the material’s magnetoelectric properties. The results demonstrate that the model effectively reproduces the internal stress–strain distribution and voltage evolution. Specifically, the magnetostrictive and piezoelectric layers exhibit mechanical responses with pronounced non-uniformity, which is attributed to boundary effects. The bias magnetic field plays a crucial regulatory role: the output voltage increases linearly from 0 to 2000 Oe and then saturates at higher fields. Under an alternating magnetic field, the composite exhibits pronounced resonance characteristics, whose frequency is jointly governed by structural dimensions and the bias field. The dynamic response was further analyzed using the magnetic flux density modulus, displacement profiles at selected locations, and voltage evolution across the piezoelectric layer. Notably, the thickness of each functional phase exerts a pronounced and distinct influence on the composite’s magnetoelectric coupling, with markedly different trends between phases. Optimization results show that a thin piezoelectric layer combined with a thick magnetostrictive layer yields the highest magnetoelectric performance. Additionally, the longitudinal and transverse magnetoelectric coefficients exhibit markedly different coupling mechanisms—this is owing to the misalignment between the magnetic-field and electric-polarization directions, and this difference further reveals the intrinsic anisotropy of the magnetoelectric response. Overall, this study provides a crucial theoretical foundation for the design and optimization of high-performance cement-based magnetoelectric composites. Full article

(This article belongs to the Special Issue Modeling and Mechanical Analysis of Materials and Structures in Civil Engineering)

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17 pages, 4913 KB

Open AccessArticle

Investigation of Fatigue Load Spectrum Enhancement via Equivalent Plastic Zone

by Lindong Chai, Penghui Wang, Yifu Wang, Yihai He and Wei Zhang

Materials 2025, 18(21), 5026; https://doi.org/10.3390/ma18215026 - 4 Nov 2025

Abstract

Load spectrum enhancement is a pivotal accelerated fatigue testing methodology employed to substantially reduce test duration and associated costs. This technique operates by strategically elevating load amplitudes while ensuring the preservation of the original failure mechanism. In this study, a novel fatigue life [...] Read more.

Load spectrum enhancement is a pivotal accelerated fatigue testing methodology employed to substantially reduce test duration and associated costs. This technique operates by strategically elevating load amplitudes while ensuring the preservation of the original failure mechanism. In this study, a novel fatigue life prediction model for variable amplitude loading is developed by integrating the theories of Equivalent Initial Flaw Size (EIFS) and the Equivalent Plastic Zone (EPZ). This integrated approach explicitly accounts for both the small crack effect and load interaction effects, which are critical yet often oversimplified aspects of fatigue damage accumulation. The model is subsequently applied to quantitatively establish the relationship between the Load Enhancement Factor (LEF) and the test time or compression ratio. Finally, fatigue tests on typical 2A14 aluminum alloy structures under variable amplitude loading are conducted to validate the proposed model. The results demonstrate a significant life reduction with increasing LEF, achieving a remarkable test time reduction of over 50% at an LEF of 1.2. All experimental data fall within a scatter band of three, relative to the model prediction. Additionally, the predicted mean compression ratio exhibits approximate agreement with the experimental data, with errors within an acceptable range. This work provides a physically grounded and practically validated framework for implementing efficient and reliable load spectrum enhancement. Full article

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

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17 pages, 2265 KB

Open AccessArticle

Self-Supported Polyhedral-like Co₃S₄ Nanostructures Enabling Efficient High Current Hydrogen Evolution Reaction

by Abu Talha Aqueel Ahmed, Sangeun Cho, Abu Saad Ansari, Yongcheol Jo and Atanu Jana

Materials 2025, 18(21), 5025; https://doi.org/10.3390/ma18215025 - 4 Nov 2025

Abstract

The advancement of overall water-splitting technologies relies on the development of earth-abundant electrocatalysts that efficiently produce H₂ as a chemical fuel while offering high catalytic efficiency, structural robustness, and low-cost synthesis. Therefore, we aim to develop a cost-effective and durable non-noble electrocatalyst [...] Read more.

The advancement of overall water-splitting technologies relies on the development of earth-abundant electrocatalysts that efficiently produce H₂ as a chemical fuel while offering high catalytic efficiency, structural robustness, and low-cost synthesis. Therefore, we aim to develop a cost-effective and durable non-noble electrocatalyst for overall water splitting. A straightforward hydrothermal approach was employed to fabricate freestanding polyhedral Co₃O₄ on a microporous Ni foam scaffold, followed by anion-exchange transformation in the presence of Na₂S solution to yield its conductive sulfide analog. The engineered Co₃S₄ electrode delivers remarkable HER activity in 1.0 M KOH, requiring a low overpotential (<100 mV) to drive 10 mA cm⁻², far outperforming its pristine oxide counterpart and even closely benchmarking with a commercial Pt/C catalyst. This exceptional performance is governed by the synergistic effects of enhanced electrical conductivity, abundant catalytic sites, and accelerated charge-transfer kinetics introduced through sulfur substitution. Furthermore, the optimized Co₃S₄ electrodes enable a bifunctional overall water-splitting device that achieves a cell voltage of >1.76 V at 100 mA cm⁻² and maintains prolonged operational stability for over 100 hrs. of continuous operation. Post-stability analyses confirm insignificant phase preservation during testing, ensuring sustained activity throughout the electrolysis process. This study highlights the potential of anion-exchanged Co₃S₄ as a cost-effective and durable catalyst for high-performance HER and full-cell water-splitting applications. Full article

(This article belongs to the Special Issue Recent Advances in Electrocatalysts for Electrochemical Energy Conversion Reactions)

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22 pages, 10097 KB

Open AccessArticle

Long-Term Water Stability Analysis of Graphene-Composite-Modified Permeable Asphalt Mixture

by Suzhan Ji, Yu Li, Xu Wu, Ke Liang, Xiaojian Cao, Xiaoguang Yuan and Qiangru Shen

Materials 2025, 18(21), 5024; https://doi.org/10.3390/ma18215024 - 4 Nov 2025

Abstract

To investigate the long-term water stability of graphene-modified permeable asphalt mixtures, in this study, we analysed the effects of single factors and multi-factor coupling. The single-factor water stability was investigated through the free thawing splitting test, standard Cantabro test, and immersion Cantabro test; [...] Read more.

To investigate the long-term water stability of graphene-modified permeable asphalt mixtures, in this study, we analysed the effects of single factors and multi-factor coupling. The single-factor water stability was investigated through the free thawing splitting test, standard Cantabro test, and immersion Cantabro test; the experimental indicators were the freeze–thaw cracking ratio (TSR), mass loss rate, and immersion mass loss rate, respectively. The multi-factor water stability was studied through immersion operation tests of mixtures with different degrees of ageing. The dispersion of graphene was examined through Raman mapping, the formation of three-dimensional network structures of graphene and SBS was evaluated via the dynamic shear rheometer test (DSR), and the elemental distribution was quantitatively analysed using energy-dispersive spectroscopy (EDS) and an image pixel algorithm (RGB). The results indicate that an unaged graphene-composite- and SBS-modified permeable asphalt mixture with an optimal graphene content of 0.05% demonstrated a 4.5% improvement in the TSR, alongside reductions in the mass loss rate and water immersion mass loss rate of 25.64% and 23.52%, respectively. Even after prolonged thermal oxygen ageing, its TSR, mass loss rate, and water immersion mass loss rate improved by 5.1%, 23.04%, and 20.70%, respectively. Multi-factor coupling tests confirmed that the water stability met requirements under severe conditions, with better performance at high temperatures. Graphene was uniformly dispersed in the modified asphalt. The appearance of a plateau region at low frequencies in graphene-composite- and SBS-modified asphalt verified the formation of a three-dimensional network structure, and the oxygen content was positively correlated with deepening thermal oxidative ageing. Full article

(This article belongs to the Special Issue Advanced Road Materials and Pavement: Design, Characterization, Structural and Mechanical Performance)

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17 pages, 6966 KB

Open AccessArticle

Effect of Gd Content on the Microstructure and Mechanical Properties of Hot Extruded Mg-xGd-4Y-1Sm-0.5Zr Alloys

by Lipeng Yan, Xinglin Zhu, Ranfeng Qiu, Nannan Wang and Xiaoke Zhang

Materials 2025, 18(21), 5023; https://doi.org/10.3390/ma18215023 - 4 Nov 2025

Abstract

In this paper, the microstructure, mechanical properties, and strengthening mechanisms of hot-extruded Mg-xGd-4Y-1Sm-0.5Zr (x = 4, 7, 10, wt.%) alloys were studied. The results show that the hot extruded alloys exhibit bimodal grain structures, and with Gd content increasing, the [...] Read more.

In this paper, the microstructure, mechanical properties, and strengthening mechanisms of hot-extruded Mg-xGd-4Y-1Sm-0.5Zr (x = 4, 7, 10, wt.%) alloys were studied. The results show that the hot extruded alloys exhibit bimodal grain structures, and with Gd content increasing, the fraction of non-dynamic recrystallized grains gradually decreases, with 46.3%, 38.6%, and 9.3%. After aging for 200 °C × 96 h, all three hot-extruded alloys reach peak-aged hardness, and as Gd content increases, the area number density of the β′ phase increases with Gd increasing, being 7.1 × 10¹⁵/m², 9.9 × 10¹⁵/m², and 16.5 × 10¹⁵/m², respectively. And the yield strength (YS) increases from 287 MPa to 345 MPa, the ultimate tensile strength (UTS) increases from 365 MPa to 418 MPa, and elongation (EL) decreases from 8.5% to 4.2%. The tensile failure mechanism is quasi-cleavage fracture. With Gd content increasing, the dimples and tear ridges on fracture surfaces gradually decrease while cleavage facets increase. The peak-aged GWS741 alloy demonstrates optimal comprehensive mechanical properties, with YS, UTS, and EL reaching 332 MPa, 409 MPa, and 7.8%, respectively. During in situ tensile testing, coarse un-DRXed grains undergo prismatic (

{10 \bar{1} 0} ⟨ 11 \bar{2} 0 ⟩

) slip, while DRXed grains experience basal (

\{0001\} ⟨ 11 \bar{2} 0 ⟩

) slip and twinning deformation. Even at 6.6% strain, no microcracks are observed, indicating excellent plasticity. During the tensile failure process, the main crack propagates along tortuous paths, showing crack deflection characteristics, where it either penetrates through elongated deformed grains or bypasses un-DRXed grains. Full article

(This article belongs to the Section Carbon Materials)

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14 pages, 1360 KB

Open AccessArticle

A Super-Sensitive Voltammetric Procedure for the Determination of Pb(II) Ions in Natural Waters Using an Environmentally Friendly Microelectrode

by Malgorzata Grabarczyk and Wieslawa Cwikla-Bundyra

Materials 2025, 18(21), 5022; https://doi.org/10.3390/ma18215022 - 4 Nov 2025

Abstract

A versatile voltammetric procedure for quantitative determination of Pb(II) directly in environmental water samples has been proposed. Differential pulse technique in the variant of anodic stripping voltammetry was applied to study Pb(II) at a solid bismuth microelectrode (SBiµE). The proposed procedure was tested [...] Read more.

A versatile voltammetric procedure for quantitative determination of Pb(II) directly in environmental water samples has been proposed. Differential pulse technique in the variant of anodic stripping voltammetry was applied to study Pb(II) at a solid bismuth microelectrode (SBiµE). The proposed procedure was tested using model solutions containing 0.1 mol L⁻¹ acetate buffer (pH = 3.4) and 5 × 10⁻⁹ mol L⁻¹ Pb(II). Under optimized measurement conditions, i.e., activation potential and time −2.5 V and 30 s, respectively, and accumulation potential and time −1.4 V and 30 s, respectively, a linearity range of 1 × 10⁻¹⁰–3 × 10⁻⁸ mol L⁻¹, a detection limit of 3.4 × 10⁻¹¹ mol L⁻¹ and a relative standard deviation of 3.1% were obtained. The applicability of the developed procedure was confirmed by direct analysis of environmental waters, such as water from the Bystrzyca River and water from the Baltic Sea. Full article

(This article belongs to the Special Issue New Insight into Design and Properties of Nanomaterials (Third Edition))

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20 pages, 5641 KB

Open AccessArticle

Comparative Analysis of Cyclic Properties and Fractography of AA2519 Aluminum Alloy Samples with Different Fatigue Lives

by Robert Sołtysiak, Maciej Kotyk and Joanna Małecka

Materials 2025, 18(21), 5021; https://doi.org/10.3390/ma18215021 - 4 Nov 2025

Abstract

The article presents an analysis of the outcomes for AA2519 aluminum alloy exposed to variable loads. The variable loads were implemented with a strain control program consisting of incremental steps and increasing/decreasing multiple steps. Tests were conducted at higher and lower strain ranges [...] Read more.

The article presents an analysis of the outcomes for AA2519 aluminum alloy exposed to variable loads. The variable loads were implemented with a strain control program consisting of incremental steps and increasing/decreasing multiple steps. Tests were conducted at higher and lower strain ranges and yielded lower (LFL test) and higher (HFL test) fatigue life, respectively. The values of plastic strain, cyclic modulus, cyclic yield strength, and fractography were analyzed. Based on the analysis of the test results, a criterion was established for the division of the tested fatigue properties into two parts for which the strength coefficient and strain hardening exponent were determined. An analytical description of the cyclic stress–strain curve for the entire range of results obtained from the LFL and HFL tests was proposed. Compared to other available models describing material properties, good compliance was obtained with the experimental results for both the LFL and HFL tests. Full article

(This article belongs to the Section Metals and Alloys)

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11 pages, 2603 KB

Open AccessArticle

Effect of Different Sand Types and Fractions on Ballistic Resistance of High-Performance Steel Fibre-Reinforced Concrete

by Michal Mára, Jindřich Fornůsek, Tomáš Hrabě and Radoslav Sovják

Materials 2025, 18(21), 5020; https://doi.org/10.3390/ma18215020 - 4 Nov 2025

Abstract

High-Performance Fibre-Reinforced Concrete (HPFRC) is an advanced composite material known for its exceptional energy absorption and dissipation capabilities. To improve its ballistic resistance, HPFRC samples were prepared using 1.5% steel fibre content and varying levels of silica. Ballistic trials employed standard 7.62 × [...] Read more.

High-Performance Fibre-Reinforced Concrete (HPFRC) is an advanced composite material known for its exceptional energy absorption and dissipation capabilities. To improve its ballistic resistance, HPFRC samples were prepared using 1.5% steel fibre content and varying levels of silica. Ballistic trials employed standard 7.62 × 39 cartridges, each comprising a full metal casing around a mild steel core. Resulting damage and failure mechanisms were mapped using a 3D photogrammetry system. Six different concrete mixtures were tested, each incorporating aggregate fractions of 0/2 mm along with three types of micro sand, the largest of which measured up to 1.2 mm in grain size. The results suggested that increasing the proportion of 0/2 mm silica sand was relatively minor. Full article

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

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14 pages, 2083 KB

Open AccessArticle

Synthesis of Phosphorus-Modified Magnetic Chitosan and Its Application for Cr(VI) Removal from Aqueous Solution

by Hong Wang, Yiran Luo, Qing Hu, Anyuan Cao, Longzhen Ding and Shengbin Xu

Materials 2025, 18(21), 5019; https://doi.org/10.3390/ma18215019 - 4 Nov 2025

Abstract

Traditional Fe-based materials are limited for Cr(VI) remediation due to low reactivity, oxidation, and aggregation. Although chitosan coatings improve stability, they hinder efficient liquid-solid separation. To overcome this, a novel phosphorus-modified magnetic chitosan adsorbent (PCC/Fe₃O₄) was synthesized using Fe [...] Read more.

Traditional Fe-based materials are limited for Cr(VI) remediation due to low reactivity, oxidation, and aggregation. Although chitosan coatings improve stability, they hinder efficient liquid-solid separation. To overcome this, a novel phosphorus-modified magnetic chitosan adsorbent (PCC/Fe₃O₄) was synthesized using Fe₃O₄ as the core and tetrakis hydroxymethyl phosphonium sulfate (THPS) as a cross-linking agent. The composite exhibited a high surface area (20.67 m²/g) and superparamagnetism, enabling easy magnetic recovery. PCC/Fe₃O₄ demonstrated superior Cr(VI) removal capabilities compared to unmodified chitosan and raw Fe₃O₄, achieving a saturated adsorption capacity of 23.6 mg/g under the selected conditions (pH 6, initial Cr(VI) concentration of 1 mg/L), which were chosen to balance adsorption efficiency, adsorbent stability, and environmental relevance. The main removal mechanism includes electrostatic attraction, redox reaction, and ligand exchange. PCC/Fe₃O₄ maintained 86% efficiency after 5 d aging and >90% efficiency after five cycles, demonstrating excellent stability and reusability and strong potential for practical environmental remediation. Full article

(This article belongs to the Section Porous Materials)

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15 pages, 7033 KB

Open AccessArticle

Evaluation of Colonization by Candida albicans and Biofilm Formation on 3D-Printed Denture Base Resins

by Pedro Guilherme Lemos Corrêa, Sarah Ribeiro Cruz-Araújo, Carolina Alves Freiria de Oliveira, Raiane Rodrigues da Silva, Viviane de Cássia Oliveira, Valéria Oliveira Pagnano, Claudia Helena Silva-Lovato, Rodrigo Galo, Arunas Stirke, Wanessa C. M. A. Melo and Ana Paula Macedo

Materials 2025, 18(21), 5018; https://doi.org/10.3390/ma18215018 - 4 Nov 2025

Abstract

Beyond mechanical performance and aesthetics, the susceptibility of 3D-printed resins to microbial colonization and biofilm formation represent an important factor influencing dentures’ longevity. Therefore, this study evaluated Candida albicans colonization and mature biofilm formation on three different 3D-printed denture base resins (Bio Denture—BD; [...] Read more.

Beyond mechanical performance and aesthetics, the susceptibility of 3D-printed resins to microbial colonization and biofilm formation represent an important factor influencing dentures’ longevity. Therefore, this study evaluated Candida albicans colonization and mature biofilm formation on three different 3D-printed denture base resins (Bio Denture—BD; Denture Base Cosmos—CD; Smart Print Bio Denture—SP) and compared them to heat-curing resin (HC). Before the microbiological evaluation, the surface roughness (Sa) was assessed. Biofilm viability was determined through colony-forming units per milliliter (CFU/mL) and biofilm morphology was qualitatively examined using a scanning electron microscope (SEM). The composition of the extracellular polymeric substance (EPS) was investigated by measuring the amounts of carbohydrates (µg/mL), proteins (ng/mL), and extracellular DNA (eDNA) (fluorescence unit). One-way ANOVA was performed for eDNA and Sa and Kruskal–Wallis for the other properties (α = 0.05). Higher surface roughness mean values (standard deviation) (p < 0.05) were observed in CD [0.111 (0.013)] compared to HC [0.084 (0.018) and BD [0.078 (0.015)]. For wettability, BD [63.2 (5.2)] and SP [65.2 (3.1)] resins showed a greater wettability (p < 0.05) than HC resin [73.0 (3.5)], while SP showed lower (p < 0.01) protein levels (425 ng/mL) compared to HC (568.6 ng/mL) and BD (554.8 ng/mL) in the EPS. Despite these differences, the 3D-printed denture base resins exhibited microbial load (CFU/mL), EPS composition (carbohydrates and eDNA), and morphological features of C. albicans biofilm comparable to those of conventional heat-cured PMMA. These findings suggest that, despite resin-specific variations, 3D-printed denture base materials exhibit a similar susceptibility to C. albicans colonization and biofilm formation as conventional denture bases, thereby directing future research towards developing new 3D-printed resins with enhanced antimicrobial properties to improve clinical outcomes. Full article

(This article belongs to the Special Issue Advances and Challenges in Polymer-Based 3D Bioprinting for Biomedical Applications)

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19 pages, 8767 KB

Open AccessArticle

Discovery of Room-Temperature Topological Insulators in Functionalized Group VA-VA Binary Monolayers: A First-Principles Investigation

by Clement Ding and Xuan Luo

Materials 2025, 18(21), 5017; https://doi.org/10.3390/ma18215017 - 4 Nov 2025

Abstract

Topological insulators and semimetals are necessary to realize quantum computing and spintronics. We use first-principles calculations to investigate the atomic structure, electronic band structure, and Z₂ invariants of four sets of pure and functionalized buckled hexagonal monolayers that are promising candidates for [...] Read more.

Topological insulators and semimetals are necessary to realize quantum computing and spintronics. We use first-principles calculations to investigate the atomic structure, electronic band structure, and Z₂ invariants of four sets of pure and functionalized buckled hexagonal monolayers that are promising candidates for topological nature: BiAs, AsP, SbAs, BiSb, and functionalized monolayers BiAsX₂, AsPX₂, SbAsX₂, and BiSbX₂ (X = H, O, S). Our results show that BiAsO₂, BiAsS₂, AsPO₂, SbAsO₂, SbAsS₂, BiSbH₂, BiSbO₂, and BiSbS₂ are topological insulators with small SOC-induced band gaps ranging from 0.05 to 0.37 eV. Further, we propose AsPS₂ to be a topological semiconductor. Topological insulators stand on the boundary of induction and conductance and are crucial in realizing quantum computers. The room-temperature topological insulators predicted here will have promising impacts in quantum computing, nanoelectronics, and spintronics. Full article

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17 pages, 4459 KB

Open AccessArticle

Microstructure (EBSD-KAM)-Informed Selection of Single-Powder Soft Magnetics for Molded Inductors

by Chang-Ting Yang, Yu-Fang Huang, Chun-Wei Tien, Kun-Yang Wu, Hung-Shang Huang and Hsing-I Hsiang

Materials 2025, 18(21), 5016; https://doi.org/10.3390/ma18215016 - 4 Nov 2025

Abstract

This study systematically benchmarks the performance of four single soft magnetic powders—water-atomized Fe–Si–Cr (FeSiCr), silica-coated reduced iron powder (RIP), silica-coated carbonyl iron powder (CIP), and phosphate-coated CIP (CIP-P)—to establish quantitative relationships between powder attributes, deformation substructure, and high-frequency loss for molded power inductors [...] Read more.

This study systematically benchmarks the performance of four single soft magnetic powders—water-atomized Fe–Si–Cr (FeSiCr), silica-coated reduced iron powder (RIP), silica-coated carbonyl iron powder (CIP), and phosphate-coated CIP (CIP-P)—to establish quantitative relationships between powder attributes, deformation substructure, and high-frequency loss for molded power inductors (100 kHz–1 MHz). We prepared toroidal compacts at 200 MPa and characterized them by initial permeability (μ_i), core-loss (P_cv(f)), partitioning (P_cv(f) = K_hf + K_ef², K_h,

K_{e}

: hysteresis and eddy-current loss coefficients), and EBSD (electron backscatter diffraction)-derived microstrain metrics (Kernel Average Misorientation, KAM; low-/high-angle grain-boundary fractions). Corrosion robustness was assessed using a 5 wt% NaCl, 35 °C, 24 h salt-spray protocol. Our findings reveal that FeSiCr achieves the highest μ_i across the frequency band, despite its lowest compaction density. This is attributed to its coarse particle size (D₅₀ ≈ 18 µm) and the resulting lower intragranular pinning. The loss spectra are dominated by hysteresis over this frequency range, with FeSiCr exhibiting the largest K_h, while the fine, silica-insulated Fe powders (RIP/CIP) most effectively suppress K_e. EBSD analysis shows that the high coercivity and hysteresis loss in CIP (and, to a lesser extent, RIP) are correlated with dense, deformation-induced subgrain networks, as evidenced by higher mean KAM and a lower low-angle grain boundary fraction. In contrast, FeSiCr exhibits the lowest KAM, with strain confined primarily to particle contact regions. Corrosion testing ranked durability as FeSiCr ≳ CIP ≈ RIP ≫ CIP-P, which is consistent with the Cr-rich passivation of FeSiCr and the superior barrier properties of the SiO₂ shells compared to low-dose phosphate. At 15 A, inductance retention ranks CIP (67.9%) > RIP (55.7%) > CIP-P (48.8%) > FeSiCr (33.2%), tracking a rise in effective anisotropy and—for FeSiCr—lower M_s that precipitate earlier roll-off. Collectively, these results provide a microstructure-informed selection map for single-powder formulations. We demonstrate that particle size and shell chemistry are the primary factors governing eddy currents (K_e), while the KAM-indexed substructure dictates hysteresis loss (K_h) and DC-bias superposition characteristics. This framework enables rational trade-offs between magnetic permeability, core loss, and environmental durability. Full article

(This article belongs to the Section Electronic Materials)

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16 pages, 13233 KB

Open AccessArticle

Robotized Fabrication Strategy for Large-Scale 3D Conformal Electronics

by Jiaying Ge, Hao Wu, Hongyang Wang and Dong Ye

Materials 2025, 18(21), 5015; https://doi.org/10.3390/ma18215015 - 4 Nov 2025

Abstract

Conformal electronics are distinguished by their unique characteristics, such as the integration of structure and function and their conformability with complex geometries. These features unlock a broad spectrum of applications, including structural health monitoring and the creation of metasurfaces. However, the current landscape [...] Read more.

Conformal electronics are distinguished by their unique characteristics, such as the integration of structure and function and their conformability with complex geometries. These features unlock a broad spectrum of applications, including structural health monitoring and the creation of metasurfaces. However, the current landscape of large-scale curved electronic fabrication is characterized by a significant gap in specialized equipment and standardized strategies. In this context, we introduce a pioneering strategy that leverages robotized electrohydrodynamic (EHD) printing for the conformal fabrication of large-scale curved electronics on 3D surfaces. This comprehensive multi-robot EHD conformal printing strategy integrates several critical components, including plasma surface treatment, EHD conformal printing, and near-infrared (NIR) sintering processes. These are supported by enabling technologies such as 3D surface reconstruction and precise hybrid positioning. Notably, our strategy achieves 5 µm printing resolution via EHD lithography and 35 µm repeatable positioning accuracy. After plasma treatment, conductive patterns on FR4 substrates reach 5B-level adhesion strength. NIR sintering enables high-efficiency sintering within only 125 s. Seamless integration of these processes into multi-robot collaborative equipment enables the fabrication of large-area conformal electronics, such as 400 mm × 1000 mm unmanned aerial vehicle wings and 650 mm × 350 mm satellite shells, and supports multi-layer systems including wires, LED arrays, antennas, and sensors. This strategy possesses substantial potential to transcend the limitations inherent in traditional fabrication methods, paving the way for new frontiers in conformal electronics across a variety of applications, including smart wings and satellite surfaces. Full article

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

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33 pages, 5824 KB

Open AccessReview

Recent Advances in Photo-Responsive Microencapsulated Phase-Change Materials

by Chaofeng Yang and Binyang Du

Materials 2025, 18(21), 5014; https://doi.org/10.3390/ma18215014 - 3 Nov 2025

Abstract

Photo-responsive microencapsulated phase-change materials (MEPCMs) are attracting growing interest for their significant potential in solar energy applications and advanced intelligent thermal management systems, owing to their exceptional capacity for thermal energy storage, efficiency for photothermal conversion, and capability for multifunctional integration. This review [...] Read more.

Photo-responsive microencapsulated phase-change materials (MEPCMs) are attracting growing interest for their significant potential in solar energy applications and advanced intelligent thermal management systems, owing to their exceptional capacity for thermal energy storage, efficiency for photothermal conversion, and capability for multifunctional integration. This review provides a systematic summary of the advancements in photo-responsive MEPCMs containing photothermal, photocatalytic, and luminescent materials in the past five years, highlighting their potential in energy conversion, pollutant degradation, and intelligent sensing applications. Moreover, perspectives for future research are provided to enhance the practical application of photo-responsive MEPCMs. Full article

(This article belongs to the Section Smart Materials)

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15 pages, 1986 KB

Open AccessArticle

Design and Optimization of a Hybrid Railcar Structure with Multilayer Composite Panels

by Alessio Cascino, Enrico Meli and Andrea Rindi

Materials 2025, 18(21), 5013; https://doi.org/10.3390/ma18215013 - 3 Nov 2025

Abstract

Within contemporary railway engineering, manufacturers of rolling stock are increasingly focused on developing vehicles that combine reduced weight with enhanced reliability. This objective is largely motivated by the need to decrease energy demand and limit environmental impact, encouraging the integration of innovative materials [...] Read more.

Within contemporary railway engineering, manufacturers of rolling stock are increasingly focused on developing vehicles that combine reduced weight with enhanced reliability. This objective is largely motivated by the need to decrease energy demand and limit environmental impact, encouraging the integration of innovative materials and cut-ting-edge design strategies. The growing use of multilayer composite materials in the railway sector stems from their unique combination of high strength and low weight, making them particularly suitable for structural applications. This study investigates the structural performance and optimization of a hybrid car body system composed of an aluminum frame integrated with multilayer composite panels. A fully automated computational framework has been developed to generate and assess all possible stacking sequence permutations of the laminate plies, coupled with a high-fidelity finite element model of the car body. The methodology enables the evaluation of failure indices, including Maximum Stress, Tsai–Wu, and Interlaminar criteria, across a wide design space. A comprehensive assessment of both mechanical and dynamic performance has been carried out according to relevant railway standards, supporting the robustness and reliability of the proposed optimization framework. The results confirm the capability of the methodology to efficiently identify and compare multiple laminate configurations while maintaining compliance with structural and modal requirements. The optimized configurations demonstrated maximum Tsai–Wu values below 0.9, first-mode frequency variations below 0.5% and potential mass reductions of 25–45% on the selected components. This approach provides a powerful and versatile tool for the rapid optimization of lightweight hybrid structures in railway applications. Full article

(This article belongs to the Special Issue Advanced Composite Materials: Forming, Processing, Assembly and Maintenance)

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23 pages, 6818 KB

Open AccessArticle

Enhanced Osseointegration, Osteogenic Differentiation and Adherence Behaviour of Healthy Human Osteoblasts on a Roughened Titanium Surface by Vitamin K2 and Vitamin D3

by Katharina Tscheu, Ann Kathrin Bergmann, Christoph V. Suschek and Uwe Maus

Materials 2025, 18(21), 5012; https://doi.org/10.3390/ma18215012 - 3 Nov 2025

Abstract

The number of endoprosthetic implants is constantly increasing. Successful osseointegration of the inserted material into the bone is essential for a prosthesis to remain in the bone as long as possible. In the clinical setting, a roughened titanium surface of implants is used [...] Read more.

The number of endoprosthetic implants is constantly increasing. Successful osseointegration of the inserted material into the bone is essential for a prosthesis to remain in the bone as long as possible. In the clinical setting, a roughened titanium surface of implants is used as standard to enable the best possible osseointegration. Vitamin K2 and vitamin D3 play a decisive role in dynamic bone metabolism and therefore also influence osseointegration. For the first time, we carried out in vitro investigations with clinically relevant cells, primary healthy human osteoblasts (hOBs). We qualitatively compared the adhesion behaviour of hOBs on a plastic surface, a smooth, regular titanium surface structure and a roughened, irregular titanium surface structure by scanning electron microscopy and fluorescence microscopy. The osteogenic behaviour and the osteogenic differentiation capacity were quantitatively investigated by analysing the activity of alkaline phosphatase and the alizarin red S assay under the influence of vitamin K2, vitamin D3 and the combination of both vitamins. It was shown that more adhesion points formed between the cells and the titanium on the rough surface structure. In addition, a solid cell network developed more quickly on this side, with cell runners forming in three-dimensional space, which means the interactions between the cells across different cell layers. On the other hand, a structured cell network also appeared on the regular smooth surface structure, which means that the network seems to be formed and built up along a defined structure. The addition of vitamins further increased the osteogenic differentiation capacity on the rough titanium surface structure. In particular, the isolated addition of vitamin K2 showed an improved osteogenic differentiation in the long-term observation, whereas the combined addition of both vitamins promoted the initial osteogenic differentiation. Vitamin K2, therefore, plays a greater role in osseointegration than previously assumed. This opens up new possibilities for the use of vitamin K2 during and after the surgical insertion of an implant. The use of vitamin K2 should be reconsidered for clinical applications in implant care and further investigated clinically. Full article

(This article belongs to the Section Biomaterials)

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16 pages, 4293 KB

Open AccessArticle

Manufacturing and Application of Low-Cost Potting Adhesive with High Thermal Conductivity

by Junxiang Wang, Shiwei Zhang, Caiman Yan, Hongming Li, Shubin Yin and Yong Tang

Materials 2025, 18(21), 5011; https://doi.org/10.3390/ma18215011 - 3 Nov 2025

Abstract

The air-cored linear synchronous motor (ACLSM), characterized by high precision and stability, is widely applied in high-precision manufacturing. However, due to the absence of an iron core, the windings must be fixed with low thermal conductivity epoxy-based potting adhesive, leading to poor heat [...] Read more.

The air-cored linear synchronous motor (ACLSM), characterized by high precision and stability, is widely applied in high-precision manufacturing. However, due to the absence of an iron core, the windings must be fixed with low thermal conductivity epoxy-based potting adhesive, leading to poor heat dissipation and significant temperature rise, which risks the motor’s lifespan and accuracy. To improve heat dissipation in ACLSM, this research proposes a multi-scale filler-based strategy to enhance the thermal conductivity of the adhesive. A series of comprehensive characterizations and thermal tests demonstrates the effectiveness of this approach. The results demonstrate that the BN-AlN sample exhibits superior thermal conductivity of 1.182 W/m·K at 25 wt% filler loading, a 48.7% enhancement over commercially adhesive 381-4DZ, with only a 38% increase in cost. Meanwhile, it possesses superior electrical insulation properties and appropriate hardness, making it highly suitable for the potting of ACLSM windings. The winding encapsulating with the modified adhesive achieves a maximum temperature reduction of 8.82 °C, while improving temperature uniformity by 29.8%, confirming its exceptional thermal management capability. Full article

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

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