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One-Pot Synthesis of Fast-Chargeable Fe₃O₄@rGO Anode for Lithium-Ion Batteries
Reset-Voltage Controlled Resistance-State and Applications of Forming-Free Fe-Doped SrTiO₃ Thin-Film Memristor
Adsorption of Atomic Hydrogen on Hydrogen Boride Sheets Studied by Photoelectron Spectroscopy
Cutting-Edge Hydrogel Technologies in Tissue Engineering and Biosensing: An Updated Review
Ge-Doped BN Nanoclusters Functionalized with Amino Acids for Bisphenol Binding

Journal Description

Materials

Materials is an international peer-reviewed, open access journal on materials science and engineering published semimonthly online by MDPI. The Portuguese Materials Society (SPM), Spanish Materials Society (SOCIEMAT), Manufacturing Engineering Society (MES) and Chinese Society of Micro-Nano Technology (CSMNT) are affiliated with Materials and their members receive discounts on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), PubMed, PMC, Ei Compendex, CaPlus / SciFinder, Inspec, Astrophysics Data System, and other databases.
Journal Rank: JCR - Q1 (Metallurgy and Metallurgical Engineering) / CiteScore - Q2 (Condensed Matter Physics)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 13.9 days after submission; acceptance to publication is undertaken in 2.7 days (median values for papers published in this journal in the second half of 2024).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Testimonials: See what our editors and authors say about Materials.
Companion journals for Materials include: Electronic Materials and Construction Materials.

Impact Factor: 3.1 (2023); 5-Year Impact Factor: 3.4 (2023)

Imprint Information Journal Flyer Open Access ISSN: 1996-1944

Latest Articles

17 pages, 3390 KiB

Open AccessArticle

Nano-Fibrillated Bacterial Cellulose Nanofiber Surface Modification with EDTA for the Effective Removal of Heavy Metal Ions in Aqueous Solutions

by Sayaka Fujita, Ryosui Sasa, Nanami Kinoshita, Ryota Kishimoto and Hiroyuki Kono

Materials 2025, 18(2), 374; https://doi.org/10.3390/ma18020374 (registering DOI) - 15 Jan 2025

Nano-fibrillated bacterial cellulose (NFBC) has very long fibers (>17 μm) with diameters of approximately 20 nm. Hence, they have a very high aspect ratio and surface area. The high specific surface area of NFBC can potentially be utilized as an adsorbent. However, NFBC [...] Read more.

Nano-fibrillated bacterial cellulose (NFBC) has very long fibers (>17 μm) with diameters of approximately 20 nm. Hence, they have a very high aspect ratio and surface area. The high specific surface area of NFBC can potentially be utilized as an adsorbent. However, NFBC has no functional groups that can bind metal ions, limiting its potential applications. In this study, the hydroxyl groups on the surface of NFBC were chemically modified with EDTA monoanhydride to convert NFBC into a metal adsorbent. The fiber morphology and crystal structures of the modified NFBC were almost identical to those of the unmodified NFBC, suggesting that the surface hydroxyl groups of NFBC were well-conjugated with the EDTA groups. Surface-modified NFBC preferentially adsorbed transition metals in aqueous solutions, such as Cu(II), Hg(II), Pb(II), and Cd(II), but hardly adsorbed Mg(II) and Cr(VI). The adsorption of heavy metal ions can be explained by the pseudo-second-order kinetics of the chemisorption process and the Langmuir isotherm model. Furthermore, the EDTA-modified NFBC is a renewable and recyclable adsorbent. The results of this study indicate that surface-modified NFBC can be utilized as a biosorbent for heavy metal removal in chemical, food, pharmaceutical, and other industrial fields. Full article

(This article belongs to the Special Issue Functional Cellulosic Materials)

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20 pages, 5568 KiB

Open AccessArticle

Computational Model of the Effective Thermal Conductivity of a Bundle of Round Steel Bars

by Rafał Wyczółkowski and Marek Gała

Materials 2025, 18(2), 373; https://doi.org/10.3390/ma18020373 (registering DOI) - 15 Jan 2025

During the heat treatment of round steel bars, a heated charge in the form of a cylindrically formed bundle is placed in a furnace. This type of charge is a porous granular medium in which a complex heat flow occurs during heating. The [...] Read more.

During the heat treatment of round steel bars, a heated charge in the form of a cylindrically formed bundle is placed in a furnace. This type of charge is a porous granular medium in which a complex heat flow occurs during heating. The following heat transfer mechanisms occur simultaneously in this medium: conduction in bars, conduction within the gas, thermal radiation between the surfaces of the bars, and contact conduction across the joints between the adjacent bars. This complex heat transfer can be quantified in terms of effective thermal conductivity. This article presents the original model of the effective thermal conductivity of a bundle of round steel bars. This model is based on the thermo-electric analogy. Each heat transfer mechanism is assigned an appropriate thermal resistance. As a result of the calculations, the impact of the following parameters on the intensity of heat transfer in the bundle was examined: temperature, the thermal conductivity of the bars, the thermal conductivity of the gas, diameter, and emissivity of the bar, and bundle porosity. Calculations were performed for a temperature range of 25–800 °C, covering a wide spectrum of variables, including bar diameters, bundle porosity, and type of gas. The knowledge obtained thanks to the calculations performed will facilitate the optimization of heat treatment processes for the considered charge. The greatest scientific value of the presented research is the demonstration that, thanks to the developed computational model, it is possible to analyze a very complex heat transfer phenomenon using relatively simple mathematical relationships. Full article

(This article belongs to the Section Porous Materials)

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17 pages, 2665 KiB

Open AccessArticle

When a Small Amount of Comonomer Is Enough: Tailoring the Critical Solution Temperature of LCST-Type Thermoresponsive Random Copolymers by PEG Methyl Ether Methacrylate with 1100 g/mol Molecular Weight

by György Kasza, Bence Sármezey, Dóra Fecske, Klára Verebélyi and Béla Iván

Materials 2025, 18(2), 372; https://doi.org/10.3390/ma18020372 (registering DOI) - 15 Jan 2025

Tuning the critical solution temperature (CST) of thermoresponsive polymers is essential to exploit their immense potential in various applications. In the present study, the effect of PEG-methyl ether methacrylate with a higher molecular weight of 1100 g/mol (mPEGMA₁₁₀₀) as a comonomer [...] Read more.

Tuning the critical solution temperature (CST) of thermoresponsive polymers is essential to exploit their immense potential in various applications. In the present study, the effect of PEG-methyl ether methacrylate with a higher molecular weight of 1100 g/mol (mPEGMA₁₁₀₀) as a comonomer was investigated for its suitability for the CST adjustment of LCST-type polymers. Accordingly, a library of mPEGMA₁₁₀₀-based copolymers was established with varying compositions (X_mPEGMA1100) using four main comonomers, namely di(ethylene glycol) ethyl ether acrylate, N-isopropyl acrylamide and methacrylamide, and mPEGMA₃₀₀, with different CST values (cloud points, T_CP, and clearing points, T_CL, by turbidimetry). It was found that less than 20 mol% of the mPEGMA₁₁₀₀ in the copolymers is practically sufficient for tuning the CST in the entire measurable temperature range, i.e., up to 100 °C, regardless of the CST of the homopolymer of the main comonomer (CST₀). Moreover, a predictive asymptotic model was developed based on the measured CST values, which strikingly revealed that the CSTs of mPEGMA₁₁₀₀-containing copolymers depend only on the two main parameters of these copolymers, X_mPEGMA1100 and the CST of the homopolymer of the main comonomer (CST₀), that is, CST = f(CST₀, X_mPEGMA1100). The revealed two-parameter relationship defines a surface in 3D plotting, and it is applicable to determine the CST of copolymers in advance for a given composition or to define the suitable composition for a required CST value. These unprecedented results on the dependence of CSTs on two major well-defined parameters enable to design a variety of novel macromolecular structures with tailored thermoresponsive properties. Full article

(This article belongs to the Special Issue Applied Stimuli-Responsive Polymer Based Materials)

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23 pages, 15619 KiB

Open AccessArticle

Methodology for Surface Reconstruction and Prediction Based on the Electrical Discharge Machining Removal Mechanism of C_f-UHTC Materials

by Sirui Gong, Yizhou Hu, Leheng Zhang, Zhenlong Wang and Yukui Wang

Materials 2025, 18(2), 371; https://doi.org/10.3390/ma18020371 (registering DOI) - 15 Jan 2025

C_f-UHTC is an ideal aerospace material because of its exceptional properties, but its machinability is facing great challenges. Electrical discharge machining (EDM) offers a potential solution, but its removal mechanism remains unclear, lacking reliable prediction tools to guide the actual production. [...] Read more.

C_f-UHTC is an ideal aerospace material because of its exceptional properties, but its machinability is facing great challenges. Electrical discharge machining (EDM) offers a potential solution, but its removal mechanism remains unclear, lacking reliable prediction tools to guide the actual production. This paper deeply explores the EDM removal mechanism of C_f-ZrB₂-SiC through single-pulse experiments, high-speed camera observations, and thermal–fluid coupling simulations, revealing key processes like heat transfer, phase transformation, molten pool dynamics, crater formation, and reinforcing phase effects. And the prediction of single-pulse removal with different parameters is also realized. Based on experimental and simulation results, a random continuous discharge model is developed, which deeply studies the dynamic erosion process, reconstructs EDM surfaces, and accurately predicts surface roughness. Furthermore, the thickness of the recast layer can be predicted based on the equivalent temperature method. Undoubtedly, this model provides an ideal approach for efficient production. Full article

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10 pages, 94867 KiB

Open AccessArticle

The Influence of Initial Surface Roughness on the Current-Carrying Friction Process of Elastic Pairs

by Zhenghai Yang, Wenbo Li, Xiaomeng Zheng, Mengfeng Zhao and Yongzhen Zhang

Materials 2025, 18(2), 370; https://doi.org/10.3390/ma18020370 (registering DOI) - 15 Jan 2025

To investigate the effect of the initial surface roughness on the performance at the initial stage of the current-carrying friction of an elastic friction pair, experiments were conducted using a self-made current-carrying friction and wear tester. The results indicate that under the experimental [...] Read more.

To investigate the effect of the initial surface roughness on the performance at the initial stage of the current-carrying friction of an elastic friction pair, experiments were conducted using a self-made current-carrying friction and wear tester. The results indicate that under the experimental conditions, the lifespan of the friction pair decreases as the surface roughness and load decrease. When the surface roughness is Ra 0.2 μm and the load is 0.025 N, the lifespan is the longest, reaching 320 cycles, with an average contact resistance of 0.045 Ω and a standard deviation of 0.009 Ω. During the normal service period of the friction pair, the main wear mechanism is furrowing. As adhesion and tearing occur, the electrical contact performance begins to degrade. The impact of arc erosion on the wear surface is far greater than that of mechanical wear. This provides a reference for the design and manufacture of current-carrying friction pairs represented by connectors. Full article

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17 pages, 14897 KiB

Open AccessArticle

T700 Carbon Fiber/Epoxy Resin Composite Material Hygrothermal Aging Model

by Jinjie Lu, Chuanxiang Zheng, Liang Wang, Yuchen Dai, Zhenyu Wang and Zhaobo Song

Materials 2025, 18(2), 369; https://doi.org/10.3390/ma18020369 (registering DOI) - 15 Jan 2025

The hygrothermal aging model, based on Fick’s second law of diffusion, characterizes the degradation of engineering constants in T700 carbon fiber/epoxy resin composites. It focuses on changes in the tensile modulus, shear modulus, and transverse Poisson’s ratio due to moisture absorption and temperature [...] Read more.

The hygrothermal aging model, based on Fick’s second law of diffusion, characterizes the degradation of engineering constants in T700 carbon fiber/epoxy resin composites. It focuses on changes in the tensile modulus, shear modulus, and transverse Poisson’s ratio due to moisture absorption and temperature variations. The model validates through mass change observations before and after seawater immersion, along with surface morphology assessments and tensile experiments. The results reveal that the saturated moisture absorption rate for single-layer laminates in seawater immersion is 0.35%. Short-term seawater immersion at room temperature (≤60 days) does not induce cracks or defects (≥10 μm) on the composite’s surface. The composite’s modulus decreases as moisture absorption increases, with the longitudinal tensile modulus dropping by an order of 10⁻⁵%, while the other engineering constants decrease by an order of 10⁻³%. The modulus also decreases with rising temperature; the closer the temperature is to the matrix’s glass transition, the faster the modulus declines, with the longitudinal tensile modulus decreasing by 0.84%, and the other engineering constants decreasing by 100%. This research provides valuable insights for the engineering applications of composite materials in marine environments. Full article

(This article belongs to the Special Issue Advances in Thermal and Mechanical Properties of Polymeric Materials (2nd Edition))

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28 pages, 12034 KiB

Open AccessArticle

Numerical Study to Analyze the Influence of Process Parameters on Temperature and Stress Field in Powder Bed Fusion of Ti-6Al-4V

by Helia Mohammadkamal and Fabrizia Caiazzo

Materials 2025, 18(2), 368; https://doi.org/10.3390/ma18020368 (registering DOI) - 15 Jan 2025

This paper presents a comprehensive numerical investigation to simulate heat transfer and residual stress formation of Ti-6Al-4V alloy during the Laser Powder Bed Fusion process, using a finite element model (FEM). The FEM was developed with a focus on the effects of key [...] Read more.

This paper presents a comprehensive numerical investigation to simulate heat transfer and residual stress formation of Ti-6Al-4V alloy during the Laser Powder Bed Fusion process, using a finite element model (FEM). The FEM was developed with a focus on the effects of key process parameters, including laser scanning velocity, laser power, hatch space, and scanning pattern in single-layer scanning. The model was validated against experimental data, demonstrating good agreement in terms of temperature profiles and melt pool dimensions. The study elucidates the significant impact of process parameters on thermal gradients, melt pool characteristics, and residual stress distribution. An increase in laser velocity, from 600 mm/s to 1500 mm/s, resulted in a smaller melt pool area and faster cooling rate. Similarly, the magnitude of residual stress initially decreased and subsequently increased with increasing laser velocity. Higher laser power led to an increase in melt pool size, maximum temperature, and thermal residual stress. Hatch spacing also exhibited an inverse relationship with thermal gradient and residual stress, as maximum residual stress decreased by about 30% by increasing the hatch space from 25 µm to 75 µm. The laser scanning pattern also influenced the thermal gradient and residual stress distribution after the cooling stage. Full article

(This article belongs to the Special Issue Advanced Computational Methods in Manufacturing Processes)

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14 pages, 10628 KiB

Open AccessArticle

AlN/FeNi Microwave-Attenuating Ceramics with High-Efficiency Thermal Conductivity and Microwave Absorption

by Yuanwei Lin, Hetuo Chen, Longfei Wang, Liqiong An, Xianpeng Qin and Guohong Zhou

Materials 2025, 18(2), 367; https://doi.org/10.3390/ma18020367 (registering DOI) - 15 Jan 2025

The integration, miniaturization, and high frequency of microwave vacuum electronics put forward higher requirements for heat-conducting and wave-absorbing integrated materials. However, these materials must balance the dispersion and isolation of wave-absorbing components to optimize absorption while maintaining the continuity of thermal conductivity pathways [...] Read more.

The integration, miniaturization, and high frequency of microwave vacuum electronics put forward higher requirements for heat-conducting and wave-absorbing integrated materials. However, these materials must balance the dispersion and isolation of wave-absorbing components to optimize absorption while maintaining the continuity of thermal conductivity pathways with low defect rates and minimal interfaces. This presents a significant challenge in achieving both high thermal conductivity and efficient wave absorption simultaneously. Here, AlN/FeNi microwave-attenuating ceramics were synthesized via non–pressure sintering in a nitrogen atmosphere. The influence of FeNi content (0–20 wt%) on the density, phase composition, microstructure, microwave-absorption properties and thermal conductivity of the composites was investigated. AlN/FeNi composites consist primarily of an AlN phase with FeNi_0.0578, Fe, AlYO₃, and Al₅Y₃O₁₂ as secondary phases, and the microstructure is uniform and dense. As the FeNi content rises from 0 to 20 wt%, the density of the composites sintered at 1800 °C × 2 h increases from 3.3 to 3.7 g/cm³. Their X-band (2–18 GHz) dielectric constant goes up from 6.5 to 8.5, the dielectric loss factor rises from 0.1 to 0.9, and thermal conductivity diminishes from 130 to 123 W/m·K. Upon reaching an FeNi content of 20 wt%, the composite achieves a minimum reflection loss of −39.1 dB at 9.5 GHz, with over 90% absorption across an effective absorption bandwidth covering 2.5 GHz. It exhibits excellent impedance matching, electromagnetic wave-attenuation properties, a relative density of 98.6%, and a thermal conductivity of 123 W m⁻¹ K⁻¹. The prepared AlN/FeNi composites, with integrated outstanding microwave-absorption capabilities and thermal conductivity, holds great promise for applications in 5G communications, aerospace, and artificial intelligence. Full article

(This article belongs to the Special Issue Preparation and Characterization of Functional Composite Materials)

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11 pages, 5302 KiB

Open AccessCommunication

The Microstructures, Mechanical Properties, and Energetic Characteristics of a Novel Dual-Phase Ti₄₀Zr₄₀W₁₀Mo₁₀ High-Entropy Alloy

by Yuxian Cao, Ruming Geng, Cheng Yang, Shun Han, Simin Lei, Yong Li and Chunxu Wang

Materials 2025, 18(2), 366; https://doi.org/10.3390/ma18020366 (registering DOI) - 15 Jan 2025

High-energy structural materials (ESMs) integrate a high energy density with rapid energy release, offering promising applications in advanced technologies. In this study, a novel dual-phase Ti₄₀Zr₄₀W₁₀Mo₁₀ high-entropy alloy (HEA) was synthesized and evaluated as a potential [...] Read more.

High-energy structural materials (ESMs) integrate a high energy density with rapid energy release, offering promising applications in advanced technologies. In this study, a novel dual-phase Ti₄₀Zr₄₀W₁₀Mo₁₀ high-entropy alloy (HEA) was synthesized and evaluated as a potential ESM. The alloy exhibited a body-centered cubic (BCC) matrix with Mo-W-rich BCC precipitates of varying sizes, which increased proportionally with the W content. The compressive mechanical properties were assessed across a range of strain rates, revealing that the W10 HEA sustained a compressive strength of 2300 MPa at a strain rate of 3000 s⁻¹. This exceptional performance is attributed to the uniform distribution of circular Mo-W-rich BCC precipitates. Conversely, in the W13 HEA, the aggregated and large Mo-W-rich precipitates deteriorated its dynamic properties. Furthermore, deflagration behavior was observed during dynamic deformation of W10, highlighting its potential as a high-performance ESM. Full article

(This article belongs to the Special Issue Future Trends in High-Entropy Alloys (2nd Edition))

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18 pages, 5567 KiB

Open AccessArticle

Effects of Pre-Deformation in Corrosion Fatigue Crack Growth of Al-Mg-Zn Alloy

by Hui Jiang, Junjun Jin, Yu Fang, Guoqing Gou, Wei Lu, Zhiyi Zhang, Hongmei Zhou, Hairong Sun, Jikui Feng, Jia Chen and Zhenghong Fu

Materials 2025, 18(2), 365; https://doi.org/10.3390/ma18020365 (registering DOI) - 15 Jan 2025

This study investigated the effect of pre-deformation on the corrosion fatigue crack propagation (CFCG) of Al-Mg-Zn alloy in a corrosive environment. Tensile tests at different pre-deformation levels and molecular dynamics simulations analyzed changes in dislocation density. Corrosion fatigue experiments were conducted in a [...] Read more.

This study investigated the effect of pre-deformation on the corrosion fatigue crack propagation (CFCG) of Al-Mg-Zn alloy in a corrosive environment. Tensile tests at different pre-deformation levels and molecular dynamics simulations analyzed changes in dislocation density. Corrosion fatigue experiments were conducted in a 3.5% NaCl solution at room temperature, and crack propagation morphology was characterized using electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that tensile strength increased by 2.63% and 10.00% for 5% and 10% pre-deformation, respectively. The crack propagation threshold values were L₂ (6.36 MPa·m^1/2) > L₀ (6.05 MPa·m^1/2) > L₁ (5.13 MPa·m^1/2), attributed to increased dislocation density and material strength. At 5% pre-deformation, dislocation pile-ups created stress concentrations that facilitated crack propagation. In contrast, the non-uniform dislocation distribution at 10% pre-deformation enhanced both material strength and resistance to crack growth. Full article

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

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32 pages, 3460 KiB

Open AccessArticle

Improving Electrical Conductivity of Commercially Pure Aluminium: The Synergistic Effect of AlB8 Master Alloy and Heat Treatment

by Yusuf Zeybek, Cemile Kayış and Ege Anıl Diler

Materials 2025, 18(2), 364; https://doi.org/10.3390/ma18020364 (registering DOI) - 15 Jan 2025

This study aims to enhance the electrical conductivity of commercially pure aluminium by minimizing impurities and grain boundaries in its microstructure, ultimately improving the efficiency of electric motors constructed from rotors with squirrel cages made from this material. For this purpose, an aluminium–boron [...] Read more.

This study aims to enhance the electrical conductivity of commercially pure aluminium by minimizing impurities and grain boundaries in its microstructure, ultimately improving the efficiency of electric motors constructed from rotors with squirrel cages made from this material. For this purpose, an aluminium–boron (AlB8) master alloy was added to aluminium with a purity of 99.7%, followed by the application of a grain-coarsening heat treatment to the rotors. To obtain commercially pure aluminium with boron additions of 0.05% and 0.1% by weight, specific amounts of the AlB8 master alloy were added into aluminium with a purity of 99.7%. Using these materials, squirrel cage components of rotors were produced via the high-pressure die-casting method. Subsequently, a grain-coarsening heat treatment of the rotors was performed at temperatures of 450 °C, 500 °C, and 550 °C, with holding times of 2, 6, and 10 h. The Box–Behnken design, which is based on statistical experimental design and response surface methodology, was employed to investigate the effects of adding boron and varying the heat treatment temperature and holding time on the electrical conductivity of commercially pure aluminium. The results showed that the synergistic effect of adding boron at 0.05 wt.% and applying the grain-coarsening heat treatment at a temperature of 550 °C for a holding time of 10 h significantly enhanced the electrical conductivity of commercially pure aluminium, increasing it from 60.62% IACS to 63.1% IACS. Correspondingly, the efficiency of the electric motor increased from 90.35% to 91.53%. These findings suggest that this hybrid method not only enhances the electrical conductivity of commercially pure aluminium but also has strong potential to improve its other properties, such as thermal conductivity. This will lead to products composed of components manufactured from the materials exhibiting better performance characteristics, such as increased efficiency and extended service life. Consequently, this innovative method will contribute economically and environmentally by facilitating the manufacture of high-performance products. Full article

(This article belongs to the Special Issue Physical Metallurgy of Metals and Alloys (3rd Edition))

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29 pages, 9768 KiB

Open AccessArticle

Modeling, Design, and Laboratory Testing of a Passive Friction Seismic Metamaterial Base Isolator (PFSMBI)

by Shayan Khosravi and Mohsen Amjadian

Materials 2025, 18(2), 363; https://doi.org/10.3390/ma18020363 (registering DOI) - 15 Jan 2025

This paper focuses on the theoretical and analytical modeling of a novel seismic isolator termed the Passive Friction Mechanical Metamaterial Seismic Isolator (PFSMBI) system, which is designed for seismic hazard mitigation in multi-story buildings. The PFSMBI system consists of a lattice structure composed [...] Read more.

This paper focuses on the theoretical and analytical modeling of a novel seismic isolator termed the Passive Friction Mechanical Metamaterial Seismic Isolator (PFSMBI) system, which is designed for seismic hazard mitigation in multi-story buildings. The PFSMBI system consists of a lattice structure composed of a series of identical small cells interconnected by layers made of viscoelastic materials. The main function of the lattice is to shift the fundamental natural frequency of the building away from the dominant frequency of earthquake excitations by creating low-frequency bandgaps (FBGs) below 20 Hz. In this configuration, each unit cell contains an inner resonator that slides over a friction surface while it is tuned to vibrate at the fundamental natural frequency of the building. This resonance enhances the energy dissipation capacity of the PFSMBI system. After deriving the governing equations for four selected lattice configurations (i.e., Cases 1–4), a parametric study is performed to optimize the PFSMBI system for a wide range of harmonic ground motion frequencies. In this study, we examine how key parameters, such as the mass ratios of the cells and resonators, tuning frequency ratios, the number of cells, and the coefficient of friction, affect the system’s performance. The PFSMBI system is then incorporated into the dynamic model of a six-story base-isolated building to evaluate its effectiveness in reducing the floor acceleration and inter-story drift under actual earthquake ground motion records. This dynamic model is used to investigate the effect of stick–slip motion (SSM) on the energy dissipation performance of a PFSMBI system by employing the LuGre friction model. The numerical results show that the optimized PFSMBI system, through its lattice structure and frictional resonators, effectively reduces floor acceleration and inter-story drift by leveraging FBGs and frictional energy dissipation, particularly when SSM effects are properly accounted for. Finally, a small-scale prototype of the PFSMBI system with two cells is developed to verify the effect of SSM. This experimental validation highlights that neglecting SSM can lead to an overestimation of the energy dissipation performance of PFSMBI systems. Full article

(This article belongs to the Special Issue Recent Advances on Smart Materials and Devices for Vibration Control of Structures)

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41 pages, 3809 KiB

Open AccessArticle

Large Deflection Analysis of Bimodular Functionally Graded Truncated Thin Conical Shells Under Mechanical and Thermal Loads

by Xiao-Ting He, Ming-Wei Luo, He-Hao Feng and Jun-Yi Sun

Materials 2025, 18(2), 362; https://doi.org/10.3390/ma18020362 - 14 Jan 2025

The purpose of this study is to analyze the large deflection problem of bimodular functionally graded truncated thin conical shells under the transverse mechanical load and non-uniform thermal load, in which two different boundary constraints of the truncated shell with two ends simply [...] Read more.

The purpose of this study is to analyze the large deflection problem of bimodular functionally graded truncated thin conical shells under the transverse mechanical load and non-uniform thermal load, in which two different boundary constraints of the truncated shell with two ends simply supported and fully fixed are considered. It is assumed that the temperature distribution along the thickness direction satisfies the Fourier law of heat transfer, and the material properties change exponentially along the thickness direction while different properties in tension and compression are considered. The geometric equation of the conical shell is established based on the equivalent method of curvature correction of von-Kármán deformation theory, and the analytical solution of the problem is obtained by Ritz method. Numerical simulation of bimodular functionally graded conical shells under the thermal and mechanical loads is carried out by Abaqus, and the numerical solution agrees with the theoretical solution. The results show that the introduction of bimodular functionally graded material will affect the maximum displacement and this effect has different rules under the mechanical load and thermal load. In addition, factors such as the cone apex angle and the truncated distance have a great influence on the maximum displacement and its location of the conical shell. Full article

(This article belongs to the Special Issue Mechanics of Thin-Walled Structures and Other Lightweight Constructions)

26 pages, 12527 KiB

Open AccessArticle

Study on Synergistically Improving Corrosion Resistance of Microarc Oxidation Coating on Magnesium Alloy by Loading of Sodium Tungstate and Silane Treatment

by Ziyi Wang, Lingyun An, Chenggong Chang, Leichao Meng, Donghao Lei, Jianhong Peng and Zhanying Wang

Materials 2025, 18(2), 361; https://doi.org/10.3390/ma18020361 - 14 Jan 2025

Sodium tungstate (Na₂WO₄) was filled into the micropores and onto the surface of a magnesium alloy microarc oxidation (MAO) coating by means of vacuum impregnation. Subsequently, the coating was sealed through silane treatment to synergistically boost its corrosion resistance. [...] Read more.

Sodium tungstate (Na₂WO₄) was filled into the micropores and onto the surface of a magnesium alloy microarc oxidation (MAO) coating by means of vacuum impregnation. Subsequently, the coating was sealed through silane treatment to synergistically boost its corrosion resistance. The phase composition of the coating was inspected using XRD. FTIR was utilized to analyze the functional groups in the coating. XPS was employed to study the chemical composition and valence state of the coating. The surface and cross-sectional morphology of the coating, along with its elemental composition and distribution, were investigated by SEM and EDS. Meanwhile, the thickness of the coating was analyzed using Image J software. Electrochemical impedance spectroscopy (EIS) was employed to determine the corrosion resistance of the coating. The results show that compared with an MAO coating, M-0.125W composite coating (only filled with sodium tungstate on the surface of the MAO coating), and M-SG composite coating (only receiving silanization treatment applied to the surface of the MAO coating), the corrosion resistance of the M-nW-SG composite coating (loaded with sodium tungstate on the surface of the MAO coating and then treated with silane) is significantly improved. This is mainly attributed to the fact that sodium tungstate can be combined with Mg²⁺ to form insoluble magnesium tungstate protective film, which blocks corrosion media. At the same time, silanization treatment further seals the MAO coating and increases the compactness of the coating. In addition, with the increase in the impregnation concentration of sodium tungstate, the content of sodium tungstate in the M-nW-SG composite coating improves, and the sealing effect of silanization treatment is better. When the impregnation concentration of sodium tungstate is 0.1 mol/L or above, the MAO coating with sodium tungstate can be completely sealed. When the impregnation concentration of sodium tungstate is 0.125 mol/L, M-0.125W-SG composite coating has the best corrosion resistance, and its impedance modulus value can be maintained at 8.06 × 10⁶ Ω·cm² after soaking in 3.5 wt.% NaCl solution for 144 h, which is about three orders of magnitude higher than those of MAO coating and M-0.125W and M-SG composite coatings. Full article

(This article belongs to the Special Issue Corrosion Resistance Enhancement of the Materials Surface—Second Edition)

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14 pages, 1707 KiB

Open AccessArticle

Synthesis of Nanocrystal-Embedded Bulk Metallic Glass Composites by a Combination of Mechanical Alloying and Vacuum Hot Pressing

by Pee-Yew Lee, Pei-Jung Chang, Chin-Yi Chen and Chung-Kwei Lin

Materials 2025, 18(2), 360; https://doi.org/10.3390/ma18020360 - 14 Jan 2025

Bulk metallic glasses (i.e., BMGs) have attracted a lot of research and development interest due to their unique properties. Embedding BMG composites with nanocrystals can further extend their applications. In this study, Ta-nanocrystal-embedded metallic glass powder was prepared via the mechanical alloying of [...] Read more.

Bulk metallic glasses (i.e., BMGs) have attracted a lot of research and development interest due to their unique properties. Embedding BMG composites with nanocrystals can further extend their applications. In this study, Ta-nanocrystal-embedded metallic glass powder was prepared via the mechanical alloying of (Cu₆₀Zr₃₀Ti₁₀)₉₁Ta₉ composition for 5 h using starting elemental powders. The structural evolution during the mechanical alloying process was examined using X-ray diffraction, scanning electron microscopy, synchrotron extended X-ray absorption fine structure, transmission electron microscopy, and differential scanning calorimetry. The 5 h as-milled powder was then consolidated into a bulk sample using vacuum hot pressing with an applied pressure of 0.72, 0.96, and 1.20 GPa. The effects of the applied pressure during vacuum hot pressing on the structure of the obtained BMG were investigated. The experimental results show that Ta-nanocrystal-embedded metallic glass composite powder was prepared successfully after 5 h of mechanical alloying. The 5 h as-milled composite powder exhibited a large supercooled region of 43 K between the glass transition temperature of 743 K and the crystallization temperature of 786 K. Using vacuum hot pressing at 753 K for 30 mins with an applied pressure, dense nanocrystal-embedded BMG composites were synthesized. The relative density and the crystallization temperature of the BMG composites increased with increasing applied pressure. The nanocrystal-embedded BMG composites prepared at 753 K for 30 mins with an applied pressure of 1.20 GPa exhibited a relative density of 98.3% and a crystallization temperature of 786 K. These nanocrystals were Ta, Cu₅₁Zr₁₄, and other possible Cu–Zr–Ti alloys (e.g., Cu₁₀Zr₇) that were randomly dispersed within the glassy matrix. Full article

(This article belongs to the Special Issue Metallic Glasses and Amorphous Alloys: Recent Advances and Future Prospects)

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15 pages, 2575 KiB

Open AccessArticle

Crystal Structure and Magnetic Properties of the Novel Compound ErMn₅Ge₃

by Nidong Yang, Yunxiang Yang, Hui Luo, Shuohai Fang, Tianhua Ju, Shengyuan Lei and Wei He

Materials 2025, 18(2), 359; https://doi.org/10.3390/ma18020359 - 14 Jan 2025

The RE-M-Ge systems (RE: rare earths, M: transition group elements) contain a large number of compounds with special magnetic properties. A novel compound ErMn₅Ge₃ was found during the investigation on the phase diagram of the Er-Mn-Ge ternary system, and its [...] Read more.

The RE-M-Ge systems (RE: rare earths, M: transition group elements) contain a large number of compounds with special magnetic properties. A novel compound ErMn₅Ge₃ was found during the investigation on the phase diagram of the Er-Mn-Ge ternary system, and its crystal structure and magnetic properties were investigated. Powder X-ray diffraction results show that ErMn₅Ge₃ crystallizes in an orthorhombic YNi₅Si₃-type structure with the space group Pnma (No. 62) and the lattice parameters of a = 13.0524(6) Å, b = 3.8853(7) Å, and c = 11.4027(4) Å. The magnetization curves and isothermal magnetization curves from 100 to 300 K were measured for ErMn₅Ge₃. Magnetic tests showed that the compound was weakly magnetic and had a Curie temperature of 304 K. It is believed that its magnetic properties are determined by Mn atoms, which are surrounded by a complex environment, leading to uncertainty in the direction of the magnetic moment and hence poor magnetic ordering. This uncertainty simultaneously leads to a significant separation of the ZFC and FZ curves. First-principles calculations confirm that the magnetic properties of ErMn₅Ge₃ are mainly provided by the Mn atoms, and its magnetic moment is calculated to be about 4.5 μ_B. A possible magnetic structure model with simultaneous Mn-Mn ferromagnetic/antiferromagnetic coupling is constructed based on the Mn atom spacing, which can well explain the magnetic performance of ErMn₅Ge₃. Full article

(This article belongs to the Section Materials Physics)

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8 pages, 2121 KiB

Open AccessArticle

Large Improvements in the Thermoelectric Properties of SnSe by Fast Cooling

by Andrew Golabek, Nikhil K. Barua, Ehsan Niknam, Luke T. Menezes and Holger Kleinke

Materials 2025, 18(2), 358; https://doi.org/10.3390/ma18020358 - 14 Jan 2025

As reported during the last five years, SnSe is one of the leading thermoelectric (TE) materials with a very low lattice thermal conductivity. However, its elements are not as heavy as those of classical thermoelectric materials like PbTe or Bi₂Te₃ [...] Read more.

As reported during the last five years, SnSe is one of the leading thermoelectric (TE) materials with a very low lattice thermal conductivity. However, its elements are not as heavy as those of classical thermoelectric materials like PbTe or Bi₂Te₃. Its outstanding TE properties were revealed after repeated purification steps to minimize the amount of oxygen contamination, followed by spark plasma sintering. Recently, we showed that hot-pressing—once optimized—can yield comparable or even better TE performance using the examples of Na- and Cu- as well as Na- and Ag-co-doped SnSe. However, long-term stability remains a challenge during cycling between low and high temperatures. Here, we investigated whether the cooling procedure has a significant impact on the thermoelectric properties of SnSe. We compared cooling of the melt with a 1:1 ratio of Sn:Se from 1273 K down to room temperature in air with quenching in water. As typical for undoped SnSe, both materials were extrinsic p-type semiconductors due to Sn defects. The air-quenched sample exhibited higher thermal conductivity, lower electrical conductivity, and higher Seebeck coefficient, all consistent with a smaller number of defects and thus a smaller number of charge carriers due to the slower cooling procedure. This resulted in a comparatively low peak figure-of-merit value zT of 0.61 at 823 K for the air-quenched sample, compared to the substantially higher peak zT of 1.58 at 813 K for the water-quenched sample. Full article

(This article belongs to the Special Issue Advancements in Thermoelectric Materials for Energy Conversion)

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18 pages, 8651 KiB

Open AccessArticle

Interlaminar Fracture Toughness Analysis for Reliability Improvement of Wind Turbine Blade Spar Elements Based on Pultruded Carbon Fiber-Reinforced Polymer Plate Manufacturing Method

by Hakgeun Kim, Yunjung Jang, Sejin Lee, Chanwoong Choi and Kiweon Kang

Materials 2025, 18(2), 357; https://doi.org/10.3390/ma18020357 - 14 Jan 2025

The key structural components of a wind turbine blade, such as the skin, spar cap, and shear web, are fabricated from fiber-reinforced composite materials. The spar, predominantly manufactured via resin infusion—a process of resin injection and curing in carbon fibers—is prone to initial [...] Read more.

The key structural components of a wind turbine blade, such as the skin, spar cap, and shear web, are fabricated from fiber-reinforced composite materials. The spar, predominantly manufactured via resin infusion—a process of resin injection and curing in carbon fibers—is prone to initial defects, such as pores, wrinkles, and delamination. This study suggests employing the pultrusion technique for spar production to consistently obtain a uniform cross-section and augment the reliability of both the manufacturing process and the design. In this context, this study introduces carbon fiber-reinforced polymer (CFRP/CFRP) and glass fiber-reinforced polymer (GFRP/CFRP) test specimens, which mimic the bonding structure of the spar cap, utilizing pultruded CFRP in accordance with ASTM standards to analyze the delamination traits of the spar. Delamination tests—covering Mode I (double cantilever beam), Mode II (end-notched flexure), and mixed mode (mixed-mode bending)—were performed to gauge displacement, load, and crack growth length. Through this crack growth mechanism, the interlaminar fracture toughness derived was examined, and the stiffness and strength changes compared to CFRP based on the existing prepreg manufacturing method were analyzed. In addition, the interlaminar fracture toughness for GFRP, which is a material in contact with the spar structure, was analyzed, and through this, it was confirmed that the crack behavior has less deviation compared to a single CFRP material depending on the stiffness difference between the materials when joining dissimilar materials. This means that the higher the elasticity of the high-stiffness material, the higher the initial crack resistance, but the crack growth behavior shows non-uniform characteristics thereafter. This comparison provides information for predicting interlaminar delamination damage within the interior and bonding area of the spar and skin and provides insight for securing the reliability of the design life. Full article

(This article belongs to the Section Advanced Composites)

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13 pages, 5479 KiB

Open AccessArticle

Self-Foaming Expanded Ceramsites Prepared from Electrolytic Manganese Residue, Red Mud and Waste Soil

by Zhuowen Yang, Xuesong Lu, Jie Wang and Hongbo Tan

Materials 2025, 18(2), 356; https://doi.org/10.3390/ma18020356 - 14 Jan 2025

In this study, in order to solve the problems of resource utilization of electrolytic manganese residue and the destruction of natural resources by the over-exploitation of raw materials of traditional ceramics, electrolytic manganese residue (EMR), red mud (RM), and waste soil (WS) were [...] Read more.

In this study, in order to solve the problems of resource utilization of electrolytic manganese residue and the destruction of natural resources by the over-exploitation of raw materials of traditional ceramics, electrolytic manganese residue (EMR), red mud (RM), and waste soil (WS) were used to prepare self-foaming expanded ceramsite (SEC), and different firing temperatures and four groups with different mixing ratios of these three raw materials were considered. Water absorption, porosity, heavy metal ion leaching, and compressive strength in the cylinder of SEC were evaluated. The chemical composition and microscopic morphology of SEC were investigated by XRD and SEM. The mechanism behind the reaction among EMR, RM, and WS and self-foaming was discussed. The results showed that both the temperature and mixing ratio significantly influenced the basic performance of SEC. With the temperature lower than 1200 °C, sphere appearance could be maintained in all of these four groups; however, the density, porosity, and compressive strength in the cylinder seemed unacceptable. When the temperature rose up to 1220 °C, sphere appearance could be only found in the group whose mixing ratio of EMR, RM, and WS was 2:2.5:0.5. Under this condition, the excellent performance of SEC was observed, with a porosity of 46.7%, bulk density of 0.61 g/cm³, and 3 d compressive strength in a cylinder of 26.82 MPa. The mechanism behind the reaction among EMR, RM, and WS could be described: when the temperature is up to 1180 °C, an obvious chemical reaction took place, followed by the liquid phase being produced and the gas released by the decomposition of Fe₂O₃ in RM and gypsum in EMR. When the temperature is up to 1200 °C, the viscosity of the liquid phase and the rate of gas generation achieved the balance, and the liquid phase encapsulated the gas and anorthite (CaAl₂Si₂O₈) began to grow slowly. As time passed, self-foaming expanded ceramsite was prepared. The results of this study are of great significance in the field of artificial lightweight aggregate and industrial solid waste resource utilization. Full article

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12 pages, 6478 KiB

Open AccessArticle

Influence of Different Solvents on the Mechanical Properties of Electrospun Scaffolds

by Dovydas Cicėnas and Andžela Šešok

Materials 2025, 18(2), 355; https://doi.org/10.3390/ma18020355 - 14 Jan 2025

This article investigates the influence of different solvents on the mechanical properties of biocompatible and biodegradable polycaprolactone (PCL) scaffolds. During the research, using electrospinning technology, 27 samples of polycaprolactone nanofibers exposed to different solvents were produced. A tensile test was performed on the [...] Read more.

This article investigates the influence of different solvents on the mechanical properties of biocompatible and biodegradable polycaprolactone (PCL) scaffolds. During the research, using electrospinning technology, 27 samples of polycaprolactone nanofibers exposed to different solvents were produced. A tensile test was performed on the produced nanofiber samples, and the nanofiber mechanical properties, yield strength, elastic modulus, and elastic elongation were calculated, and load–displacement and stress–strain dependence diagrams were compared from the obtained results. The strongest nanofiber was singled out, and its mechanical properties were compared with those of biological tissues and its application in tissue engineering. The structure was determined using a scanning electron microscope, and the structures of nanofibers exposed to different solvents were compared. After calculating the influence of different solvents on the mechanical properties of the nanofibers, the strongest structure was identified, PCL and chloroform, which has an elastic modulus of 9.86 MPa and a yield strength of 1.11 ± 0.32 MPa. The type of solvent used in the production of the solution affects the homogeneity of the fibre and the shape of the filaments. In solvents with lower viscosity, the fibre filaments are more homogeneous and more evenly distributed. Full article

(This article belongs to the Special Issue Modeling and Mechanical Behavior of Advanced Biomaterials)

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