Materials

13 pages, 4511 KB

Open AccessEditor’s ChoiceArticle

Crystallographic Engineering of CrN Buffer Layers for GaN Thin Film Epitaxy

by Kyu-Yeon Shim, Seongho Kang, Min-Joo Ahn, Yukyeong Cha, Eojin-Gyere Ham, Dohoon Kim and Dongjin Byun

Materials 2025, 18(8), 1817; https://doi.org/10.3390/ma18081817 - 16 Apr 2025

Viewed by 591

Abstract

Gallium nitride (GaN) is commonly used in various semiconductor systems owing to its high mobility and thermal stability; however, the production of GaN thin films using the currently employed methods requires improvement. To facilitate the growth of high-quality GaN epitaxial thin films, this [...] Read more.

Gallium nitride (GaN) is commonly used in various semiconductor systems owing to its high mobility and thermal stability; however, the production of GaN thin films using the currently employed methods requires improvement. To facilitate the growth of high-quality GaN epitaxial thin films, this study explored the crystallographic structures, properties, and influences of chromium nitride (CrN) buffer layers sputtered under various conditions. The crystallographic orientation of CrN played a crucial role in determining the GaN film quality. For example, even when the crystallinity of the CrN (111) plane was relatively low, a single-phase CrN (111) buffer layer could provide a more favorable template for GaN epitaxy compared to cases where both the CrN (111) and Cr₂N (110) phases coexisted. The significance of a low-temperature (LT) GaN nucleation layer deposited onto the CrN buffer layers was assessed using atomic force microscopy and contact angle measurements. The X-ray phi scan results confirmed the six-fold symmetry of the grown GaN, further emphasizing the contribution of an LT-GaN nucleation layer. These findings offer insights into the underlying mechanisms governing GaN thin film growth and provide guidance for the optimization of the buffer layer conditions to achieve high-quality GaN epitaxial films. Full article

(This article belongs to the Section Thin Films and Interfaces)

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47 pages, 4349 KB

Open AccessEditor’s ChoiceReview

Metal Nanocomposites as Biosensors for Biological Fluids Analysis

by Dan Chicea and Alexandra Nicolae-Maranciuc

Materials 2025, 18(8), 1809; https://doi.org/10.3390/ma18081809 - 15 Apr 2025

Cited by 1 | Viewed by 854

Abstract

Metal nanocomposites are rapidly emerging as a powerful platform for biosensing applications, particularly in the analysis of biological fluids. This review paper examines the recent advancements in the development and application of metal nanocomposites as biosensors for detecting various analytes in complex biological [...] Read more.

Metal nanocomposites are rapidly emerging as a powerful platform for biosensing applications, particularly in the analysis of biological fluids. This review paper examines the recent advancements in the development and application of metal nanocomposites as biosensors for detecting various analytes in complex biological matrices such as blood, serum, urine, and saliva. We discuss the unique physicochemical properties of metal nanocomposites, including their high surface area, enhanced conductivity, and tunable optical and electrochemical characteristics, which contribute to their superior sensing capabilities. The review will cover various fabrication techniques, focusing on their impact on the sensitivity, selectivity, and stability of the resulting biosensors. Furthermore, we will analyze the diverse applications of these biosensors in the detection of disease biomarkers, environmental toxins, and therapeutic drugs within biological fluids. Finally, we will address the current challenges and future perspectives of this field, highlighting the potential for improved diagnostic tools and personalized medicine through the continued development of advanced metal nanocomposite-based biosensors. Full article

(This article belongs to the Special Issue Progress and Challenges of Advanced Metallic Materials and Composites)

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15 pages, 3554 KB

Open AccessEditor’s ChoiceArticle

Study of ZrO₂ Gate Dielectric with Thin SiO₂ Interfacial Layer in 4H-SiC Trench MOS Capacitors

by Qimin Huang, Yunduo Guo, Anfeng Wang, Zhaopeng Bai, Lin Gu, Zhenyu Wang, Chengxi Ding, Yi Shen, Hongping Ma and Qingchun Zhang

Materials 2025, 18(8), 1741; https://doi.org/10.3390/ma18081741 - 10 Apr 2025

Viewed by 809

Abstract

The transition of SiC MOSFET structure from planar to trench-based architectures requires the optimization of gate dielectric layers to improve device performance. This study utilizes a range of characterization techniques to explore the interfacial properties of ZrO₂ and SiO₂/ZrO₂ [...] Read more.

The transition of SiC MOSFET structure from planar to trench-based architectures requires the optimization of gate dielectric layers to improve device performance. This study utilizes a range of characterization techniques to explore the interfacial properties of ZrO₂ and SiO₂/ZrO₂ gate dielectric films, grown via atomic layer deposition (ALD) in SiC epitaxial trench structures to assess their performance and suitability for device applications. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements showed the deposition of smooth film morphologies with roughness below 1 nm for both ZrO₂ and SiO₂/ZrO₂ gate dielectrics, while SE measurements revealed comparable physical thicknesses of 40.73 nm for ZrO₂ and 41.55 nm for SiO₂/ZrO₂. X-ray photoelectron spectroscopy (XPS) shows that in SiO₂/ZrO₂ thin films, the binding energies of Zr 3d_5/2 and Zr 3d_3/2 peaks shift upward compared to pure ZrO₂. Electrical characterization showed an enhancement of E_BR (3.76 to 5.78 MV·cm⁻¹) and a decrease of I_{ON_EBR} (1.94 to 2.09 × 10⁻³ A·cm⁻²) for the SiO₂/ZrO₂ stacks. Conduction mechanism analysis identified suppressed Schottky emission in the stacked film. This indicates that the incorporation of a thin SiO₂ layer effectively mitigates the small bandgap offset, enhances the breakdown electric field, reduces leakage current, and improves device performance. Full article

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

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14 pages, 8353 KB

Open AccessEditor’s ChoiceArticle

Design and Characterization of an Equibiaxial Multi-Electrode Dielectric Elastomer Actuator

by Simon Holzer, Bhawnath Tiwari, Stefania Konstantinidi, Yoan Civet and Yves Perriard

Materials 2025, 18(8), 1693; https://doi.org/10.3390/ma18081693 - 8 Apr 2025

Viewed by 506

Abstract

With the ongoing journey of automation advancements and a trend towards miniaturization, the choice of actuator plays a crucial role. Over recent years, soft actuators have demonstrated their usefulness in various applications, especially where light weight and high strain are required. Dielectric elastomer [...] Read more.

With the ongoing journey of automation advancements and a trend towards miniaturization, the choice of actuator plays a crucial role. Over recent years, soft actuators have demonstrated their usefulness in various applications, especially where light weight and high strain are required. Dielectric elastomer actuators (DEAs) are a class of soft actuators that provide high-strain actuation possibilities in applications like biomedicine, logistics, or consumer electronics. A variety of work featuring DEAs for actuation has been carried out in recent years, but a single work detailing the design conception, fabrication, modeling and experimental validation is lacking, especially in the context of achieving high strains with the integration of multiple electrodes and their interaction. This work discusses these issues with an equibiaxial DEA, enabling optimized equibiaxial strain patterns due to full use of the available actuation area. The developed DEA can achieve an equibiaxial strain of 12.75% for actuation at 60 V μm⁻¹ over an active area of 7 cm² which is an improvement of 1.3 times compared to traditional dot actuators. These properties position the device as a promising alternative for various applications like cell cultures or microassembly and provide an advantage of optimized use of passive regions within the actuator. Full article

(This article belongs to the Special Issue Electroactive Polymers: Fundamentals and Applications)

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31 pages, 5436 KB

Open AccessEditor’s ChoiceArticle

Study of the Relationship Between the Structures and Biological Activity of Herbicides Derived from Phenoxyacetic Acid

by Grzegorz Świderski, Natalia Kowalczyk, Gabriela Tyniecka, Monika Kalinowska, Renata Łyszczek, Aleksandra Bocian, Ewa Ciszkowicz, Leszek Siergiejczyk, Małgorzata Pawłowska and Jacek Czerwiński

Materials 2025, 18(7), 1680; https://doi.org/10.3390/ma18071680 - 7 Apr 2025

Cited by 1 | Viewed by 1405

Abstract

Chloroderivatives of phenoxyacetic acid are a group of compounds commonly used as plant protection products. Differences in the molecular structure of these compounds are related to varying substitution and the number of chlorine atoms in the aromatic ring. Different molecular structures may affect [...] Read more.

Chloroderivatives of phenoxyacetic acid are a group of compounds commonly used as plant protection products. Differences in the molecular structure of these compounds are related to varying substitution and the number of chlorine atoms in the aromatic ring. Different molecular structures may affect the activity of these compounds, their physicochemical properties, as well as their toxicity and biological effects. A group of 6 chemical compounds derived from phenoxyacetic acid was tested. The molecular structure was analysed using spectroscopic methods (FTIR, FTRaman, UV-VIS, ¹HNMR, ¹³CNMR) and quantum chemical computational methods (DFT). The reactivity of the tested compounds was determined using DFT calculations and experimentally in reaction with a hydroxyl radical. The electronic charge distribution of NBO, CHelpG and ESP was analysed and aromaticity indices were calculated for theoretically modeled structures and structures examined by X-ray diffraction (data obtained from the CSD database). Phenoxyacetic acid derivatives were tested for antimicrobial activity on soil bacterial strains. Cytotoxicity tests were performed on normal human skin fibroblasts (BJ CRL-2522) and the human prostate cancer cell line (DU-145 HTB-81). The purpose of this study was to investigate the relationship between the molecular structure of phenoxyacetic acid derivatives and their reactivity and biological activity. Full article

(This article belongs to the Special Issue From Molecular to Supramolecular Materials)

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30 pages, 4998 KB

Open AccessEditor’s ChoiceArticle

A Material Study of Persian-Period Silver Coins and Hacksilber from Samaria

by Dana Ashkenazi, Maayan Cohen, Haim Gitler, Mati Johananoff and Oren Tal

Materials 2025, 18(7), 1678; https://doi.org/10.3390/ma18071678 - 7 Apr 2025

Viewed by 852

Abstract

An assembly of fourth-century BCE Samarian silver coins and late-fifth-century BCE Samarian cut silver sheets, Sidonian and Philistian coins from a hacksilber hoard allegedly found in the region of Samaria belonging to the David and Jemima Jeselsohn collection, were characterized by metallurgical analyses. [...] Read more.

An assembly of fourth-century BCE Samarian silver coins and late-fifth-century BCE Samarian cut silver sheets, Sidonian and Philistian coins from a hacksilber hoard allegedly found in the region of Samaria belonging to the David and Jemima Jeselsohn collection, were characterized by metallurgical analyses. The aims of the research were to identify the items’ composition and manufacturing processes. We affirmed that the Samarian coins were made of silver–copper alloy produced by a controlled process. The microstructural and elemental analyses revealed that the sheets were produced from various materials, including pure silver, silver–copper, and silver–copper–gold alloys, whereas the Sidonian and Philistian coins were made of silver–copper alloy. Continuity in style and production techniques was observed. This information provides a better understanding of the material culture and technological skills in the Persian-period province of Samaria. Full article

(This article belongs to the Section Metals and Alloys)

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19 pages, 5369 KB

Open AccessEditor’s ChoiceArticle

Interactions of Terahertz Photons with Phonons of Two-Dimensional van der Waals MoS₂/WSe₂/MoS₂ Heterostructures and Thermal Responses

by Jingwen Huang, Ningsheng Xu, Yumao Wu, Xue Ran, Yue Fang, Hongjia Zhu, Weiliang Wang, Huanjun Chen and Shaozhi Deng

Materials 2025, 18(7), 1665; https://doi.org/10.3390/ma18071665 - 4 Apr 2025

Viewed by 1044

Abstract

The interaction between terahertz (THz) photons and phonons of materials is crucial for the development of THz photonics. In this work, typical two-dimensional (2D) van der Waals (vdW) transition metal chalcogenide (TMD) layers and heterostructures are used in THz time-domain spectroscopy (TDS) measurements, [...] Read more.

The interaction between terahertz (THz) photons and phonons of materials is crucial for the development of THz photonics. In this work, typical two-dimensional (2D) van der Waals (vdW) transition metal chalcogenide (TMD) layers and heterostructures are used in THz time-domain spectroscopy (TDS) measurements, low-wavenumber Raman spectroscopy measurements, calculation of 2D materials’ phonon spectra, and theoretical analysis of thermal responses. The TDS results reveal strong absorption of THz photons in the frequency range of 2.5–10 THz. The low-wavenumber Raman spectra show the phonon vibration characteristics and are used to establish phonon energy bands. We also set up a computational simulation model for thermal responses. The temperature increases and distributions in the individual layers and their heterostructures are calculated, showing that THz photon absorption results in significant increases in temperature and differences in the heterostructures. These give rise to interesting photothermal effects, including the Seebeck effect, resulting in voltages across the heterostructures. These findings provide valuable guidance for the potential optoelectronic application of the 2D vdW heterostructures. Full article

(This article belongs to the Special Issue Terahertz Vibrational Spectroscopy in Advanced Materials)

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21 pages, 3015 KB

Open AccessEditor’s ChoiceArticle

Monitoring Antioxidant Consumption and Build-Up in Polypropylene During Open-Loop and Closed-Loop Mechanical Recycling

by Niek Knoben, Max Vanhouttem, Aike Wypkema and Nithya Subramanian

Materials 2025, 18(7), 1640; https://doi.org/10.3390/ma18071640 - 3 Apr 2025

Viewed by 2024

Abstract

Polypropylene (PP), a widely used recyclable plastic in packaging and engineering applications, is prone to thermo-oxidative degradation during reprocessing and molding at high temperatures. Antioxidants (AOs) are essential for stabilizing PP in both its virgin and recycled states. The quantity of AO added [...] Read more.

Polypropylene (PP), a widely used recyclable plastic in packaging and engineering applications, is prone to thermo-oxidative degradation during reprocessing and molding at high temperatures. Antioxidants (AOs) are essential for stabilizing PP in both its virgin and recycled states. The quantity of AO added is critical: insufficient amounts can lead to poor stabilization, while excessive amounts can cause safety concerns due to build-up. This study presents a modified approach to measure the Oxidation Induction Temperature (OIT) using Differential Scanning Calorimetry (DSC), particularly for recycled PP from waste that contains unpredictable contaminations. This modified approach ensures the safety of the calorimetry cell by limiting the oxidation reaction and preventing the release of volatile compounds during measurements. By performing DSC measurements in inert environments, we obtain the OIT, which can be correlated to residual intact AO levels. This approach to monitoring AO levels is demonstrated in both open- and closed-loop recycling of rigid PP. Although the presence of contamination is known to catalyze thermo-oxidative degradation in PP, our results indicate that recycled PP from open-loop collection still contains sufficient residual AO that allows it to withstand limited thermal reprocessing. However, this tendency of AO retention leads to significant build-up during closed-loop recycling when AOs are added to each cycle, where the PP grade remains fairly homogeneous and the dispersity (Đ) does not significantly increase over multiple recycling loops. Full article

(This article belongs to the Special Issue Recycling and Degradation of Polymeric Materials: Exploring Different Perspectives in Plastic Waste Management)

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17 pages, 3636 KB

Open AccessEditor’s ChoiceArticle

DFT Investigation of a Direct Z-Scheme Photocatalyst for Overall Water Splitting: Janus Ga₂SSe/Bi₂O₃ Van Der Waals Heterojunction

by Fan Yang, Pascal Boulet and Marie-Christine Record

Materials 2025, 18(7), 1648; https://doi.org/10.3390/ma18071648 - 3 Apr 2025

Cited by 1 | Viewed by 861

Abstract

Constructing van der Waals heterojunctions with excellent properties has attracted considerable attention in the field of photocatalytic water splitting. In this study, four patterns, coined A, B, C, and D of Janus Ga₂SSe/Bi₂O₃ van der Waals (vdW) heterojunctions [...] Read more.

Constructing van der Waals heterojunctions with excellent properties has attracted considerable attention in the field of photocatalytic water splitting. In this study, four patterns, coined A, B, C, and D of Janus Ga₂SSe/Bi₂O₃ van der Waals (vdW) heterojunctions with different stacking modes, were investigated using first-principles calculations. Their stability, electronic structure, and optical properties were analyzed in detail. Among these, patterns A and C heterojunctions demonstrate stable behavior and operate as direct Z-scheme photocatalysts, exhibiting band gaps of 1.83 eV and 1.62 eV. In addition, the suitable band edge positions make them effective for photocatalytic water decomposition. The built-in electric field across the heterojunction interface effectively inhibits electron-hole recombination, thereby improving the photocatalytic efficiency. The optical absorption coefficients show that patterns A and C heterojunctions exhibit higher light absorption intensity than Ga₂SSe and Bi₂O₃ monolayers, spanning from the ultraviolet to visible range. Their corrected solar-to-hydrogen (STH) efficiencies are 13.60% and 12.08%, respectively. The application of hydrostatic pressure and biaxial tensile strain demonstrate distinct effects on photocatalytic performance: hydrostatic pressure preferentially enhances the hydrogen evolution reaction (HER), while biaxial tensile strain primarily improves the oxygen evolution reaction (OER). Furthermore, the heterojunctions exhibited enhanced optical absorption across the UV-visible spectrum with increasing hydrostatic pressure. Notably, a 1% tensile strain results in an improvement in visible light absorption efficiency. These results demonstrate that Ga₂SSe/Bi₂O₃ heterojunctions hold great promise as direct Z-scheme photocatalysts for overall water splitting. Full article

(This article belongs to the Special Issue Hierarchically Structured Materials for Photocatalysis, Electrocatalysis and Photoelectrocatalysis)

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15 pages, 6248 KB

Open AccessEditor’s ChoiceArticle

Precursor-Derived Mo₂C/SiC Composites with a Two-Dimensional Sheet Structure for Electromagnetic Wave Absorption

by Yang Li, Wen Yang, Jipeng Zhang, Yongzhao Hou, Guangwu Wen, Guodong Xin, Meixian Jiang and Yongqiang Ma

Materials 2025, 18(7), 1573; https://doi.org/10.3390/ma18071573 - 31 Mar 2025

Viewed by 486

Abstract

Precursor-derived silicon carbide (SiC) ceramics have been widely used as absorbing materials, but the residual carbon sink produced by ceramicization limits their application under high-temperature and oxygen-containing conditions, such as the nozzle or jet vane of high-speed aircraft. In this paper, a novel [...] Read more.

Precursor-derived silicon carbide (SiC) ceramics have been widely used as absorbing materials, but the residual carbon sink produced by ceramicization limits their application under high-temperature and oxygen-containing conditions, such as the nozzle or jet vane of high-speed aircraft. In this paper, a novel molybdenum carbide/silicon carbide (Mo₂C/SiC) microwave-absorbing ceramic with a two-dimensional sheet structure was obtained through the pyrolysis of polycarbosilane-coated molybdenum sulfide (PCS@MoS₂). The results indicate that addition of an appropriate amount of MoS₂ can react with the free carbon generated during the pyrolysis of PCS, thereby reducing the material’s carbon content and forming Mo₂C. Concurrently, the layered structural characteristics of MoS₂ are utilized to create a two-dimensional composite structure within the material, which enhances the material’s absorption vastly. The as-prepared Mo₂C/SiC ceramics sintered at 1300 °C exhibit a minimum reflection loss (RL_min) of −46.49 dB at 8.96 GHz with a thickness of 2.6 mm. Additionally, the effective absorption bandwidth (EAB) of Mo₂C/SiC spans the entire X-band (8–12 GHz) due to the combined effect of multiple loss mechanisms. Full article

(This article belongs to the Section Advanced and Functional Ceramics and Glasses)

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52 pages, 16956 KB

Open AccessEditor’s ChoiceReview

Advances in 2D Group IV Monochalcogenides: Synthesis, Properties, and Applications

by Angel-Theodor Buruiana, Claudia Mihai, Victor Kuncser and Alin Velea

Materials 2025, 18(7), 1530; https://doi.org/10.3390/ma18071530 - 28 Mar 2025

Cited by 1 | Viewed by 1305

Abstract

The field of newly developed two-dimensional (2D) materials with low symmetry and structural in-plane anisotropic properties has grown rapidly in recent years. The phosphorene analog of group IV monochalcogenides is a prominent subset of this group that has attracted a lot of attention [...] Read more.

The field of newly developed two-dimensional (2D) materials with low symmetry and structural in-plane anisotropic properties has grown rapidly in recent years. The phosphorene analog of group IV monochalcogenides is a prominent subset of this group that has attracted a lot of attention because of its unique in-plane anisotropic electronic and optical properties, crystalline symmetries, abundance in the earth’s crust, and environmental friendliness. This article presents a review of the latest research advancements concerning 2D group IV monochalcogenides. It begins with an exploration of the crystal structures of these materials, alongside their optical and electronic properties. The review continues by discussing the various techniques employed for the synthesis of layered group IV monochalcogenides, including both bottom-up methods such as vapor-phase deposition and top-down techniques like mechanical and/or liquid-phase exfoliation. In the final part, the article emphasizes the application of 2D group IV monochalcogenides, particularly in the fields of photocatalysis, photodetectors, nonlinear optics, sensors, batteries, and photovoltaic cells. Full article

(This article belongs to the Section Optical and Photonic Materials)

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10 pages, 3175 KB

Open AccessEditor’s ChoiceArticle

Electric Field-Defined Superlattices in Bilayer Graphene: Formation of Topological Bands in Two Dimensions

by Włodzimierz Jaskólski

Materials 2025, 18(7), 1521; https://doi.org/10.3390/ma18071521 - 28 Mar 2025

Viewed by 595

Abstract

An electric field applied to the Bernal-stacked bilayer graphene opens an energy gap; its reversal in some regions creates domain walls and leads to the appearance of one-dimensional chiral gapless states localized at the walls. Here, we investigate the energy structure of bilayer [...] Read more.

An electric field applied to the Bernal-stacked bilayer graphene opens an energy gap; its reversal in some regions creates domain walls and leads to the appearance of one-dimensional chiral gapless states localized at the walls. Here, we investigate the energy structure of bilayer graphene with superlattice potential defined by an external electric field. The calculations are performed within an atomistic π-electron tight-binding approximation. We study one-dimensional and two-dimensional superlattices formed by arrays of electric-field walls in the zigzag and armchair directions and investigate different field polarizations. Chiral gapless states discretize due to the superlattice potential and transform into minibands in the energy gap. As the main result, we show that the minibands can cross at the Fermi level for some field polarizations. This leads to a new kind of two-dimensional gapless states of topological character that form Dirac-like cones at the crossing points. This also has application potential: changing the field polarization can close the energy gap and change the character of the superlattice from semiconducting to metallic. Full article

(This article belongs to the Special Issue Quantum Transport in Novel 2D Materials and Structures)

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28 pages, 4096 KB

Open AccessEditor’s ChoiceArticle

Spontaneous and Piezo Polarization Versus Polar Surfaces: Fundamentals and Ab Initio Calculations

by Pawel Strak, Pawel Kempisty, Konrad Sakowski, Jacek Piechota, Izabella Grzegory, Eva Monroy, Agata Kaminska and Stanislaw Krukowski

Materials 2025, 18(7), 1489; https://doi.org/10.3390/ma18071489 - 26 Mar 2025

Cited by 1 | Viewed by 610

Abstract

In this study, the fundamental properties of spontaneous and piezo polarization and surface polarity were defined. It was demonstrated that the Landau definition of polarization as a dipole density could be used in infinite systems. Differences between bulk polarization and surface polarity were [...] Read more.

In this study, the fundamental properties of spontaneous and piezo polarization and surface polarity were defined. It was demonstrated that the Landau definition of polarization as a dipole density could be used in infinite systems. Differences between bulk polarization and surface polarity were distinguished, thus creating a clear identification of both components. This identification is in agreement with numerous experimental data—red shift presence and absence for wurtzite and zinc blende multiquantum wells (MQWs), respectively. A local model of spontaneous polarization was created and used to calculate spontaneous polarization as electric dipole density. The proposed local model correctly predicted the c-axis spontaneous polarization values of nitride wurtzite semiconductors. In addition, the model’s results are in accordance with a polarization equal to zero for the zinc blende lattice. The spontaneous polarization values obtained for all wurtzite III nitrides are in basic agreement with earlier calculations using the Berry phase. Ab initio calculations of wurtzite nitride superlattices in Heyd–Scuseria–Ernzerhof (HSE) approximation were performed to derive polarization-induced fields in coherently strained lattices, showing good agreement with the polarization values. Strained superlattice data were used to determine the piezoelectric parameters of wurtzite nitrides, obtaining values that are in basic agreement with earlier data. Zinc blende superlattices were also modeled using ab initio HSE calculations, showing results that are in agreement with the absence of polarization in all nitrides in zinc blende symmetry. Full article

(This article belongs to the Special Issue Advances in Density Functional Theory (DFT) Studies of Solids (Second Volume))

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12 pages, 4236 KB

Open AccessEditor’s ChoiceArticle

Capacitance and Dielectric Properties of Spin-Coated Silk Fibroin Thin Films for Bioelectronic Capacitors

by Jongyun Choi, Seung Hun Lee, Taehun Kim, Kyungtaek Min and Sung-Nam Lee

Materials 2025, 18(7), 1408; https://doi.org/10.3390/ma18071408 - 22 Mar 2025

Viewed by 742

Abstract

Silk fibroin, a biocompatible and flexible biopolymer derived from Bombyx mori silkworms, has shown promise in bioelectronics, due to its adjustable dielectric properties. This study investigates the influence of spin coating parameters on the optical, electrical, and dielectric properties of thin silk fibroin [...] Read more.

Silk fibroin, a biocompatible and flexible biopolymer derived from Bombyx mori silkworms, has shown promise in bioelectronics, due to its adjustable dielectric properties. This study investigates the influence of spin coating parameters on the optical, electrical, and dielectric properties of thin silk fibroin films. Silk fibroin solutions were spin coated onto indium tin oxide (ITO)/glass substrates at speeds ranging from 1000 to 7000 revolutions per minute (RPM), resulting in films with thicknesses that varied from 264.8 nm to 81.9 nm. Atomic force microscopy analysis revealed that the surface roughness remained consistent at approximately 1.5 nm across all the spin coating speeds, while the film thickness decreased with the increasing spin speed. Ultraviolet (UV)–visible spectroscopy showed that the transmittance at 550 nm increased from 81.2% at 1000 RPM to 93.8% at 7000 RPM, and the optical bandgap widened from 3.82 eV at 1000 RPM to 3.92 eV at 7000 RPM, which was attributed to reduced molecular packing and quantum confinement effects. Electrical characterization showed that thinner films (a spin speed of 5000–7000 RPM) exhibited a 15-fold increase in the leakage current, rising from 2.99 pA at 1000 RPM to 44.9 pA at 7000 RPM, and a decrease in resistance from 334 GΩ at 1000 RPM to 22.2 GΩ at 7000 RPM. The capacitance–voltage measurements indicated a 4-fold increase in voltage-dependent capacitance for thinner films, with capacitance values increasing from 36 pF at 1000 RPM to 176 pF at 7000 RPM. Dielectric loss analysis revealed that thinner films experienced higher energy dissipation at low frequencies (tan δ of 0.041 at 0.01 MHz for 7000 RPM), but lower losses at high frequencies (tan δ of 0.123 at 1 MHz for 7000 RPM). These findings emphasize the importance of film thickness control in optimizing the performance of silk fibroin-based bioelectronic devices. Full article

(This article belongs to the Special Issue Advanced and Smart Materials in Photoelectric Applications)

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17 pages, 7854 KB

Open AccessEditor’s ChoiceArticle

Understanding Polysiloxane Polymer to Amorphous SiOC Conversion During Pyrolysis Through ReaxFF Simulation

by Kathy Lu and Harrison Chaney

Materials 2025, 18(7), 1412; https://doi.org/10.3390/ma18071412 - 22 Mar 2025

Viewed by 604

Abstract

A significant challenge during the polymer-to-ceramic pyrolysis conversion is to understand the polymer-to-ceramic atomic evolution and correlate the composition changes with the precursor molecular structures, pyrolysis conditions, and resulting ceramic characteristics. In this study, a Reactive Force Field (ReaxFF) simulation approach has been [...] Read more.

A significant challenge during the polymer-to-ceramic pyrolysis conversion is to understand the polymer-to-ceramic atomic evolution and correlate the composition changes with the precursor molecular structures, pyrolysis conditions, and resulting ceramic characteristics. In this study, a Reactive Force Field (ReaxFF) simulation approach has been used to simulate silicon oxycarbide (SiOC) ceramic formation from four different polysiloxane precursors. For the first time, we show atomically that pyrolysis time and temperature proportionally impact the new Si-O rich and C rich cluster sizes as well as the composition separation of Si-O from C. Polymer side groups have a more complex effect on the Si-O and C cluster separation and growth, with ethyl group leading to the most Si-O cluster separation and phenyl group leading to the most C cluster separation. We also demonstrate never-before correlations of gas release with polymer molecular structures and functional groups. CH₄, C₂H₆, C₂H₄, and H₂ are preferentially released from the pyrolyzing systems. The sequence is determined by the polymer molecular structures. This work is the first to atomically illustrate the innate correlations between the polymer precursors and pyrolyzed ceramics. Full article

(This article belongs to the Special Issue Structural, Thermal, Electrical, and Electrochemical Properties of Novel Ceramics)

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11 pages, 3461 KB

Open AccessEditor’s ChoiceArticle

Effects of Multi-Fluorinated Liquid Crystals with High Refractive Index on the Electro-Optical Properties of Polymer-Dispersed Liquid Crystals

by Yunxiao Ren and Wei Hu

Materials 2025, 18(7), 1406; https://doi.org/10.3390/ma18071406 - 21 Mar 2025

Viewed by 575

Abstract

Polymer-dispersed liquid crystals (PDLCs) are composite materials, in which LCs are dispersed in the form of microdroplets in a polymer matrix. As a composite material, its electro-optical properties are affected by many factors such as molecular structure, composition, and the microstructure of the [...] Read more.

Polymer-dispersed liquid crystals (PDLCs) are composite materials, in which LCs are dispersed in the form of microdroplets in a polymer matrix. As a composite material, its electro-optical properties are affected by many factors such as molecular structure, composition, and the microstructure of the LCs and polymers. In this work, PDLC films were prepared based on the thiol-ene click reaction, and effects of refractive indexes of polymers and LCs on their electro-optical properties were studied. The refractive indexes of the polymer matrix are adjusted by controlling the content of sulfur element, and those of the LCs are adjusted by adding multi-fluorinated LCs with high refractive index. By regulating the refractive indexes of the polymer matrix and LCs, the maximum transmittance of the film is raised and the viewing angle of the film is also extended. This work could afford some ideas for the directional regulation of the viewing angles and the electro-optical properties of the PDLC film. Full article

(This article belongs to the Special Issue Advanced and Smart Materials in Photoelectric Applications)

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18 pages, 74287 KB

Open AccessEditor’s ChoiceArticle

Graining and Texturing of Metal Surfaces by Picosecond Laser Treatment

by Carmelo Corsaro, Fortunato Neri, Paolo Maria Ossi, Domenico Bonanno, Priscilla Pelleriti and Enza Fazio

Materials 2025, 18(7), 1398; https://doi.org/10.3390/ma18071398 - 21 Mar 2025

Viewed by 825

Abstract

Different approaches have been proposed to control the tribological behavior of materials under different conformal and non-conformal contact conditions with influenced surface texturing. The ever-increasing demand to improve material friction, erosion wear, and adhesion bond strength of coatings is a major concern for [...] Read more.

Different approaches have been proposed to control the tribological behavior of materials under different conformal and non-conformal contact conditions with influenced surface texturing. The ever-increasing demand to improve material friction, erosion wear, and adhesion bond strength of coatings is a major concern for the contact interface of surfaces. Laser texturing is considered a promising approach to tuning materials’ tribological properties. The latter are strongly influenced by the texture density and shape imprinted on the engineered materials and vary in dry or lubricating conditions. In this work, the physicochemical properties of picosecond laser-textured surfaces of metallic materials have been systematically analyzed. Specifically, the wettability character of laser-textured materials was correlated with their morphological/compositional features. Full article

(This article belongs to the Section Materials Physics)

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17 pages, 3853 KB

Open AccessEditor’s ChoiceArticle

Analysis of the Structural, Chemical, and Mechanical Characteristics of Polyurethane Foam Infused with Waste from Thermal Processing

by Anna Magiera, Monika Kuźnia and Wojciech Jerzak

Materials 2025, 18(6), 1327; https://doi.org/10.3390/ma18061327 - 17 Mar 2025

Cited by 1 | Viewed by 469

Abstract

The continuous generation of agricultural, industrial, and urban waste necessitates effective waste management strategies. One promising approach is incorporating these residues as fillers in polymer composites. This study investigated the influence of coal processing-derived fillers, specifically microspheres and fluidized-bed combustion fly ash, on [...] Read more.

The continuous generation of agricultural, industrial, and urban waste necessitates effective waste management strategies. One promising approach is incorporating these residues as fillers in polymer composites. This study investigated the influence of coal processing-derived fillers, specifically microspheres and fluidized-bed combustion fly ash, on the structure and properties of composite rigid polyurethane foam. Polyurethane foams were produced through manual mixing and casting, with composite foams containing a combination of 5% microspheres and 5–15% fly ash by weight. The analysis of the samples investigated their structural, thermal, and mechanical properties. The samples consistently displayed predominantly pentagonal, regularly shaped cells. Infrared spectroscopy revealed no observable chemical bonding between the matrix and filler materials. Mechanical analysis was performed to evaluate the materials’ characteristics, revealing significant variations in compressive strength and Young’s modulus values. The results indicate that the addition of fillers did not impact the cellular and chemical composition of the polyurethane matrix. Furthermore, the composite material specimens were subjected to accelerated aging in a laboratory dryer and outdoor exposure in order to assess their thermal stability. This analysis revealed notable alterations in both the cellular composition and mechanical properties of the composite foam materials. Full article

(This article belongs to the Special Issue Research on Thermal Stability and Degradation of Polymers and Their Potential Use in a Circular Economy Development)

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15 pages, 5604 KB

Open AccessEditor’s ChoiceArticle

Dynamic Response and Energy Absorption of Lattice Sandwich Composite Structures Under Underwater Explosive Load

by Xiaolong Zhang, Shengjie Sun, Xiao Kang, Zhixin Huang and Ying Li

Materials 2025, 18(6), 1317; https://doi.org/10.3390/ma18061317 - 17 Mar 2025

Cited by 1 | Viewed by 634

Abstract

This study investigates the underwater explosion resistance of aluminum alloy octet-truss lattice sandwich structures using shock tube experiments and LS-DYNA simulations. A systematic analysis reveals key mechanisms influencing protective performance. The sandwich configuration mitigates back plate displacement through quadrilateral inward deformation, exhibiting phased [...] Read more.

This study investigates the underwater explosion resistance of aluminum alloy octet-truss lattice sandwich structures using shock tube experiments and LS-DYNA simulations. A systematic analysis reveals key mechanisms influencing protective performance. The sandwich configuration mitigates back plate displacement through quadrilateral inward deformation, exhibiting phased deformation responses between face plates and back plates mediated by lattice interactions. Increasing the lattice relative density from 0.1 to 0.3 reduces maximum back plate displacement by 22.2%. While increasing the target plate thickness to 1.5 mm reduces displacement by 47.6%, it also decreases energy absorption efficiency by 20% due to limited plastic deformation. Fluid–structure interaction simulations correlate well with 3D-DIC deformation measurements. The experimental results demonstrate the exceptional impact energy absorption capacity of the octet-truss lattice and highlight the importance of stiffness-matching strategies for enhanced energy dissipation. These findings provide valuable insights for optimizing the design of underwater protection structures. Full article

(This article belongs to the Special Issue Mechanical Properties and Structural Reliability of Advanced Materials)

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17 pages, 3101 KB

Open AccessEditor’s ChoiceArticle

Removal of Per- and Polyfluoroalkyl Substances Using Commercially Available Sorbents

by Zhiming Zhang, Sevda Joudiazar, Anshuman Satpathy, Eustace Fernando, Roxana Rahmati, Junchul Kim, Giacomo de Falco, Rupali Datta and Dibyendu Sarkar

Materials 2025, 18(6), 1299; https://doi.org/10.3390/ma18061299 - 15 Mar 2025

Cited by 2 | Viewed by 2578

Abstract

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants of growing environmental and human health concern, widely detected across various environmental compartments. Effective remediation strategies are essential to mitigate their widespread impacts. This study compared the performance of two types of commercially available [...] Read more.

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants of growing environmental and human health concern, widely detected across various environmental compartments. Effective remediation strategies are essential to mitigate their widespread impacts. This study compared the performance of two types of commercially available sorbent materials, granular activated carbon (GAC, Filtrasorb-400) and organoclays (OC-200, and modified organoclays Fluoro-sorb-100 and Fluoro-sorb-200) for the removal of three representative PFAS compounds: perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorooctane sulfonic acid (PFOS) from water. Both organoclays and modified organoclays outperformed GAC, likely due to electrostatic interactions between the anionic PFAS compounds and the cationic functional groups of the modified organoclays. A pseudo-second-order kinetic model best described the rapid sorption kinetics of PFOA, PFNA, and PFOS. For PFOA, OC-200 demonstrated the highest adsorption capacities (q_max = 47.17 µg/g). For PFNA and PFOS, Fluoro-sorb-100 was the most effective sorbent, with q_max values at 99.01 µg/g and 65.79 µg/g, respectively. Desorption studies indicated that the sorption of the three PFAS compounds on these commercially available sorbents was largely irreversible. This study highlights the effectiveness and sorption capacities of different types of commercial sorbents for PFAS removal and offers valuable insights into the selection of reactive media for PFAS removal from water under environmentally relevant conditions. Full article

(This article belongs to the Special Issue Advanced Nanoporous and Mesoporous Materials)

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12 pages, 1759 KB

Open AccessEditor’s ChoiceArticle

One-Pot Synthesis of Pd@Pt Core-Shell Icosahedron for Efficient Oxygen Reduction

by Zisheng Tang, Dafu Zhao, Xiaoqian Wang, Yanhui Jiao, Manrui Liu, Chengqi Liu, Qi Zhang, Shujing Ren and Yong Liu

Materials 2025, 18(6), 1279; https://doi.org/10.3390/ma18061279 - 13 Mar 2025

Viewed by 1096

Abstract

Enhancing the limited utilization and overall yield of Pt-based catalysts is essential for advancing proton exchange membrane fuel cell technology. Herein, we report a facile one-pot method that utilizes TEG as both a solvent and a reductant to efficiently synthesize a Pd@Pt core-shell [...] Read more.

Enhancing the limited utilization and overall yield of Pt-based catalysts is essential for advancing proton exchange membrane fuel cell technology. Herein, we report a facile one-pot method that utilizes TEG as both a solvent and a reductant to efficiently synthesize a Pd@Pt core-shell icosahedron. By controlling the surface energy between Pd and Pt precursors, we achieved the formation of Pd@Pt core-shell icosahedra, resulting in a fourfold reduction in reaction time and an eightfold increase in yield. Moreover, the core-shell structures exhibited a significant enhancement in electrocatalytic activity, stability, and Pt utilization efficiency. In comparison to commercial Pt/C, the Pd@Pt core-shell icosahedron exhibited efficient mass activity (MA, 1.54 A mg⁻¹_Pt) and specific activity (SA, 2.24 mA cm⁻²_Pt) at 0.9 V (vs. RHE), while demonstrating excellent stability with minimal loss of activity even after 10,000 potential cycles. The Pd@Pt icosahedra configuration integrates the advantages of multiply twinned nanostructures, leading to rich electrochemical active surface sites and fast charge transport, thereby improving its catalytic performance and long-term stability during electrocatalytic reactions. Full article

(This article belongs to the Special Issue Photoelectric and Catalytic Properties of Nanomaterials and Low-Dimensional Structures)

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13 pages, 3445 KB

Open AccessEditor’s ChoiceArticle

Evaluating the Role of Unit Cell Multiplicity in the Acoustic Response of Phononic Crystals Using Laser-Plasma Sound Sources

by Emmanouil Kaniolakis Kaloudis, Konstantinos Kaleris, Nikos Aravantinos-Zafiris, Michael Sigalas, Dionysios T. G. Katerelos, Vasilis Dimitriou, Makis Bakarezos, Michael Tatarakis and Nektarios A. Papadogiannis

Materials 2025, 18(6), 1251; https://doi.org/10.3390/ma18061251 - 12 Mar 2025

Viewed by 774

Abstract

Acoustic metamaterials and phononic crystals are progressively consolidating as an important technology that is expected to significantly impact the science and industry of acoustics in the coming years. In this work, the impact of unit cell multiplicity on the spectral features of the [...] Read more.

Acoustic metamaterials and phononic crystals are progressively consolidating as an important technology that is expected to significantly impact the science and industry of acoustics in the coming years. In this work, the impact of unit cell multiplicity on the spectral features of the acoustic response of phononic crystals is systematically studied using the recently demonstrated laser-plasma sound source characterization method. Specifically, by exploiting the advantages of this method, the impact of the number of repeated unit cells on the depth of the phononic band gaps and the passband spectral features across the entire audible range is demonstrated. These experimental findings are supported by specially developed computational simulations accounting for the precise structural characteristics of the studied phononic crystals and are analysed to provide a phenomenological understanding of the underlying physical mechanism. It is shown that by increasing the unit cell multiplicity, the bandgaps deepen and the number of resonant peaks in the crystal transmission zones increases. The resonant mode shapes are computationally investigated and interpreted in terms of spherical harmonics. This study highlights the tunability and design flexibility of acoustic components using phononic crystals, opening new paths towards applications in the fields of sound control and noise insulation. Full article

(This article belongs to the Special Issue Advances in Modelling and Simulation of Materials in Applied Sciences)

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22 pages, 12982 KB

Open AccessEditor’s ChoiceArticle

Effect of Hydrothermal Coatings of Magnesium AZ31 Alloy on Osteogenic Differentiation of hMSCs: From Gene to Protein Analysis

by Viviana Costa, Lavinia Raimondi, Simone Dario Scilabra, Margot Lo Pinto, Daniele Bellavia, Angela De Luca, Pasquale Guglielmi, Angela Cusanno, Luca Cattini, Lia Pulsatelli, Matteo Pavarini, Roberto Chiesa and Gianluca Giavaresi

Materials 2025, 18(6), 1254; https://doi.org/10.3390/ma18061254 - 12 Mar 2025

Cited by 2 | Viewed by 734

Abstract

An Mg-based alloy device manufactured via a superplastic forming process (Mg-AZ31+SPF) and coated using a hydrothermal method (Mg AZ31+SPF+HT) was investigated as a method to increase mechanical and osteointegration capability. The cell viability and osteointegrative properties of alloy-derived Mg AZ31+SPF and Mg AZ31+SPF+HT [...] Read more.

An Mg-based alloy device manufactured via a superplastic forming process (Mg-AZ31+SPF) and coated using a hydrothermal method (Mg AZ31+SPF+HT) was investigated as a method to increase mechanical and osteointegration capability. The cell viability and osteointegrative properties of alloy-derived Mg AZ31+SPF and Mg AZ31+SPF+HT extracts were investigated regarding their effect on human mesenchymal stem cells (hMSCs) (maintained in basal (BM) and osteogenic medium (OM)) after 7 and 14 days of treatment. The viability was analyzed through metabolic activity and double-strand DNA quantification, while the osteoinductive effects were evaluated through qRT-PCR, osteoimage, and BioPlex investigations. Finally, a preliminary liquid mass spectrometry analysis was conducted on the secretome of hMSCs. Biocompatibility analysis revealed no toxic effect on cells’ viability or proliferation during the experimental period. A modulation effect was observed on the osteoblast pre-commitment genes of hMSCs treated with Mg-AZ31+SPF+HT in OM, which was supported by mineralization nodule analysis. A preliminary mass spectrometry investigation highlighted the modulation of protein clusters involved in extracellular exosomes, Hippo, and the lipid metabolism process. In conclusion, our results revealed that the Mg AZ31+SPF+HT extracts can modulate the canonical and non-canonical osteogenic process in vitro, suggesting their possible application in bone tissue engineering. Full article

(This article belongs to the Special Issue Nanocomposite High Performance Alloys)

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10 pages, 2639 KB

Open AccessEditor’s ChoiceCommunication

A High-Performance All-Carbon Diamond Pixel Solar-Blind Detector with In Situ Converted Graphene Electrodes

by Mingxin Jiang, Zhenglin Jia, Mengting Qiu, Xingqiao Chen, Jiayi Cai, Mingyang Yang, Yi Shen, Chaoping Liu, Kuan W. A. Chee, Nan Jiang, Kazuhito Nishimura, Qingning Li, Qilong Yuan and He Li

Materials 2025, 18(6), 1222; https://doi.org/10.3390/ma18061222 - 10 Mar 2025

Viewed by 859

Abstract

Solar-blind ultraviolet detectors, known for their low background noise and high sensitivity, have garnered significant attention in various applications such as space communications, ozone layer monitoring, guidance applications, and flame detection. Pixel photodetectors, as the cornerstone of imaging technology in this field, have [...] Read more.

Solar-blind ultraviolet detectors, known for their low background noise and high sensitivity, have garnered significant attention in various applications such as space communications, ozone layer monitoring, guidance applications, and flame detection. Pixel photodetectors, as the cornerstone of imaging technology in this field, have become a focal point of research in recent years. In this work, a solar-blind photodetector with a 6 × 6 planar pixel array was fabricated on single-crystal diamond substrate, utilizing in situ conversed graphene electrodes. The graphene electrodes achieved exceptional Ohmic contact with the diamond surface, boasting a remarkably low specific contact resistance of 6.73 × 10⁻⁵ Ω·cm². The diamond pixel detector exhibited high performance consistency with an ultra-low dark current ranging from 10⁻¹¹ to 10⁻¹² A and a photocurrent of 10⁻⁸~10⁻⁹ A under 222 nm illumination with a bias of 10 V. This work not only demonstrates the feasibility of fabricating all-carbon solar-blind photodetectors on diamond but also highlights their potential for achieving high spatial resolution in solar-blind image detection. Full article

(This article belongs to the Section Electronic Materials)

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27 pages, 9696 KB

Open AccessEditor’s ChoiceArticle

Investigations on the Deflection of Carbon-Reinforced Concrete Hollow-Core Slabs

by David Sandmann, Michael Frenzel, Steffen Marx and Manfred Curbach

Materials 2025, 18(6), 1212; https://doi.org/10.3390/ma18061212 - 8 Mar 2025

Viewed by 1078

Abstract

The article presents the experimental and computational investigations on carbon-reinforced concrete (CRC) slabs with hollow-core cross-sections. Designed for use in building construction, they combine the benefits of lightweight construction, resource efficiency, and precise prefabrication. Three geometrically identical elements were manufactured and tested until [...] Read more.

The article presents the experimental and computational investigations on carbon-reinforced concrete (CRC) slabs with hollow-core cross-sections. Designed for use in building construction, they combine the benefits of lightweight construction, resource efficiency, and precise prefabrication. Three geometrically identical elements were manufactured and tested until failure in four-point bending tests. The slabs demonstrated a high load capacity of around 50 kNm, together with high ductility due to a deformation of more than 80 mm before failure. The load-deflection curves recorded could be reproduced very well with the analytical-physical calculation model created for both the non-cracked and cracked slab states. The strengths and stiffnesses of the materials used for input were derived from small-scale, accompanying material tests. As a result, the calculation model was ultimately used to design the carbon-reinforced ceilings of the CRC technology demonstration house CUBE, which was finished in 2022 in Dresden, East Germany. Full article

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

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24 pages, 5022 KB

Open AccessEditor’s ChoiceReview

Review of Layered Double Hydroxide (LDH) Nanosheets in Corrosion Mitigation: Recent Developments, Challenges, and Prospects

by Jintao Cao, Yangmin Wu and Wenjie Zhao

Materials 2025, 18(6), 1190; https://doi.org/10.3390/ma18061190 - 7 Mar 2025

Cited by 1 | Viewed by 1448

Abstract

Layered double hydroxides (LDHs) are a typical class of two-dimensional nanomaterials that present numerous possibilities in both scientific and practical applications. LDHs, with a layered structure and unique interlayer ion-exchange properties, can be utilized to prepare various functional coatings, showing great potential in [...] Read more.

Layered double hydroxides (LDHs) are a typical class of two-dimensional nanomaterials that present numerous possibilities in both scientific and practical applications. LDHs, with a layered structure and unique interlayer ion-exchange properties, can be utilized to prepare various functional coatings, showing great potential in the field of marine corrosion protection. In this review, the preparation approaches and properties of LDHs are first briefly introduced. Subsequently, various protection types based on LDH-based composite coatings for marine corrosion protection are highlighted, including physical barriers, self-healing, chloride trapping effects, and hydrophobic effects, respectively. Furthermore, critical factors influencing the anti-corrosion performance of composite coatings are discussed in detail. Finally, remaining challenges and future prospects for LDH-modified composite coatings in corrosion protection are proposed. This review provides a distinctive perspective on fabricating LDH-enhanced corrosion-resistant materials, contributing toward the development of multifunctional, intelligent anti-corrosion coatings for diverse applications. Full article

(This article belongs to the Special Issue Research on Friction, Wear and Corrosion Properties of Materials)

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12 pages, 3089 KB

Open AccessEditor’s ChoiceArticle

Changes in Mechanical Properties of Medium Manganese Steel After Forming, Press Hardening, and Heat Treatment

by Radek Leták, Ludmila Kučerová, Hana Jirková, Štěpán Jeníček and Filip Votava

Materials 2025, 18(6), 1196; https://doi.org/10.3390/ma18061196 - 7 Mar 2025

Viewed by 1046

Abstract

Solutions and new processes are continually being developed to produce components demonstrating high strength and elongation. This paper focuses on medium manganese steel with a composition of 0.2% carbon, 3% manganese, and 2.15% aluminium (by weight percent). The mechanical properties of the steel [...] Read more.

Solutions and new processes are continually being developed to produce components demonstrating high strength and elongation. This paper focuses on medium manganese steel with a composition of 0.2% carbon, 3% manganese, and 2.15% aluminium (by weight percent). The mechanical properties of the steel and the effect of aluminium and manganese on the microstructure are investigated. The steel sheets are shaped into omega profiles using a press tool, followed by the intercritical annealing of the samples to enhance their ductility. Before the experiment, the anticipated values were a tensile strength (UTS) of approximately 1100 MPa and elongation within 30–35%. A key objective was to achieve a microstructure that incorporates residual austenite. The experimental parameters were carefully derived from an extensive exploration to identify potential weaknesses in the experiment. The main parameters selected were the intercritical annealing (IA) temperature and IA dwell time. The results revealed that the highest recorded UTS was 1262 ± 6 MPa, while the maximum elongation achieved was 16 ± 1%. Full article

(This article belongs to the Special Issue Advanced Forming Technologies, Mechanical Performance and Structural Properties of Metallic Materials and Alloys)

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13 pages, 1891 KB

Open AccessEditor’s ChoiceArticle

Microstructure-Based Magneto-Mechanical Modeling of Magnetorheological Elastomer Composites: A Comparable Analysis of Dipole and Maxwell Methods

by Shengwei Feng and Lizhi Sun

Materials 2025, 18(5), 1187; https://doi.org/10.3390/ma18051187 - 6 Mar 2025

Cited by 1 | Viewed by 822

Abstract

Magnetorheological elastomers (MREs) are smart composite materials with tunable mechanical properties by ferromagnetic particle interactions. This study applied the microstructure-based dipole and Maxwell methods to evaluate the magneto-mechanical coupling and magnetostrictive responses of MREs, focusing on various particle distributions. The finite element modeling [...] Read more.

Magnetorheological elastomers (MREs) are smart composite materials with tunable mechanical properties by ferromagnetic particle interactions. This study applied the microstructure-based dipole and Maxwell methods to evaluate the magneto-mechanical coupling and magnetostrictive responses of MREs, focusing on various particle distributions. The finite element modeling of representative volume elements with fixed volume fractions revealed that the straight chain microstructure exhibits the most significant magnetostrictive effect due to its low initial shear stiffness and significant magnetic force contributions. For particle separations exceeding three radii, the dipole and Maxwell methods yield consistent results for vertically or horizontally aligned particles. For particle separations greater than three radii, the dipole and Maxwell methods produce consistent results for vertically and horizontally aligned particles. However, discrepancies emerge for angled configurations and complex microstructures, with the largest deviation observed in the hexagonal particle distribution, where the two methods differ by approximately 27%. These findings highlight the importance of selecting appropriate modeling methods for optimizing MRE performance. Since anisotropic MREs with straight-chain alignments are the most widely used, our results confirm that the dipole method offers an efficient alternative to the Maxwell method for simulating these structures. Full article

(This article belongs to the Special Issue Smart Soft Materials: From Design to Applications)

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14 pages, 5580 KB

Open AccessEditor’s ChoiceArticle

Burst Ultrafast Laser Welding of Quartz Glass

by Xianshi Jia, Yinzhi Fu, Kai Li, Chengaonan Wang, Zhou Li, Cong Wang and Ji’an Duan

Materials 2025, 18(5), 1169; https://doi.org/10.3390/ma18051169 - 6 Mar 2025

Cited by 4 | Viewed by 1231

Abstract

Ultrafast laser welding of transparent materials has been widely used in sensors, microfluidics, optics, etc. However, the existing ultrafast laser welding depths are limited by the short laser Rayleigh length, which makes it difficult to realize the joining of transparent materials in the [...] Read more.

Ultrafast laser welding of transparent materials has been widely used in sensors, microfluidics, optics, etc. However, the existing ultrafast laser welding depths are limited by the short laser Rayleigh length, which makes it difficult to realize the joining of transparent materials in the millimeter depth range and becomes a new challenge. Based on temporal shaping, we realized Burst mode ultrafast laser output with different sub-pulse numbers and explored the effect of different Burst modes on the welding performance using high-speed shadow in situ imaging. The experimental results show that the Burst mode femtosecond laser (twelve sub-pulses with a total energy of 28.9 μJ) of 238 fs, 1035 nm and 1000 kHz can form a molten structure with a maximum depth of 5 mm inside the quartz, and the welding strength can be higher than 18.18 MPa. In this context, we analyzed the transient process of forming teardrop molten structures inside transparent materials using high-speed shadow in situ imaging detection and systematically analyzed the fracture behavior of the samples. In addition, we further reveal the Burst femtosecond laser welding mechanism of transparent materials comprehensively by exploring the difference in welding performance under the effect of Burst modes with different sub-pulse numbers. This paper is the first to realize molten structures in the range of up to 5 mm, which is expected to provide a new welding method for curved surfaces and large-size transparent materials, helping to improve the packaging strength of photoelectric devices and the window strength of aerospace materials. Full article

(This article belongs to the Special Issue Advancements in Ultrasonic Testing for Metallurgical Materials)

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30 pages, 4653 KB

Open AccessEditor’s ChoiceReview

Nanoarchitectonics of Sustainable Food Packaging: Materials, Methods, and Environmental Factors

by Tangyu Yang and Andre G. Skirtach

Materials 2025, 18(5), 1167; https://doi.org/10.3390/ma18051167 - 6 Mar 2025

Cited by 3 | Viewed by 1952

Abstract

Nanoarchitectonics influences the properties of objects at micro- and even macro-scales, aiming to develop better structures for protection of product. Although its applications were analyzed in different areas, nanoarchitectonics of food packaging—the focus of this review—has not been discussed, to the best of [...] Read more.

Nanoarchitectonics influences the properties of objects at micro- and even macro-scales, aiming to develop better structures for protection of product. Although its applications were analyzed in different areas, nanoarchitectonics of food packaging—the focus of this review—has not been discussed, to the best of our knowledge. The (A) structural and (B) functional hierarchy of food packaging is discussed here for the enhancement of protection, extending shelf-life, and preserving the nutritional quality of diverse products including meat, fish, dairy, fruits, vegetables, gelled items, and beverages. Interestingly, the structure and design of packaging for these diverse products often possess similar principles and methods including active packaging, gas permeation control, sensor incorporation, UV/pulsed light processing, and thermal/plasma treatment. Here, nanoarchitechtonics serves as the unifying component, enabling protection against oxidation, light, microbial contamination, temperature, and mechanical actions. Finally, materials are an essential consideration in food packaging, particularly beyond commonly used polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC) plastics, with emphasis on biodegradable (polybutylene succinate (PBS), polyvinyl alcohol (PVA), polycaprolactone (PCL), and polybutylene adipate co-terephthalate (PBAT)) as well as green even edible (bio)-materials: polysaccharides (starch, cellulose, pectin, gum, zein, alginate, agar, galactan, ulvan, galactomannan, laccase, chitin, chitosan, hyaluronic acid, etc.). Nanoarchitechnotics design of these materials eventually determines the level of food protection as well as the sustainability of the processes. Marketing, safety, sustainability, and ethics are also discussed in the context of industrial viability and consumer satisfaction. Full article

(This article belongs to the Special Issue Nanoarchitectonics in Materials Science, Second Edition)

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18 pages, 7417 KB

Open AccessEditor’s ChoiceArticle

An Efficient Optimization Method for Large-Solution Space Electromagnetic Automatic Design

by Lingyan He, Fengling Peng and Xing Chen

Materials 2025, 18(5), 1159; https://doi.org/10.3390/ma18051159 - 5 Mar 2025

Viewed by 816

Abstract

In the field of electromagnetic design, it is sometimes necessary to search for the optimal design solution (i.e., the optimal solution) within a large solution space to complete the optimization. However, traditional optimization methods are not only slow in searching for the solution [...] Read more.

In the field of electromagnetic design, it is sometimes necessary to search for the optimal design solution (i.e., the optimal solution) within a large solution space to complete the optimization. However, traditional optimization methods are not only slow in searching for the solution space but are also prone to becoming trapped in local optima, leading to optimization failure. This paper proposes a dual-population genetic algorithm to quickly find the optimal solution for electromagnetic optimization problems in large solution spaces. The method involves two populations: the first population uses the powerful dynamic decision-making ability of reinforcement learning to adjust the crossover probability, making the optimization process more stable and enhancing the global optimization capability of the algorithm. The second population accelerates the convergence speed of the algorithm by employing a “leader dominance” mechanism, allowing the population to quickly approach the optimal solution. The two populations are integrated through an immigration operator, improving optimization efficiency. The effectiveness of the proposed method is demonstrated through the optimization design of an electromagnetic metasurface material. Furthermore, the method designed in this paper is not limited to the electromagnetic field and has practical value in other engineering optimization areas, such as vehicle routing optimization, energy system optimization, and fluid dynamics optimization, etc. Full article

(This article belongs to the Special Issue Metamaterials and Metasurfaces: From Materials to Applications)

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20 pages, 5378 KB

Open AccessEditor’s ChoiceArticle

Comparative Analysis of Sandwich Composites with Balsa, Rohacell^®, and Nomex^® Cores for Aerospace Applications

by Joanna Pach, Roman Wróblewski and Bartłomiej Muszyński

Materials 2025, 18(5), 1126; https://doi.org/10.3390/ma18051126 - 2 Mar 2025

Cited by 1 | Viewed by 1754

Abstract

Interlayered composites with three types of cores were fabricated and tested. Quasi-static penetration tests (QSPTs), bending tests, and impact tests were conducted on the fabricated composites with carbon fiber epoxy laminate facings. Penetration test procedures were carried out until the composite was perforated [...] Read more.

Interlayered composites with three types of cores were fabricated and tested. Quasi-static penetration tests (QSPTs), bending tests, and impact tests were conducted on the fabricated composites with carbon fiber epoxy laminate facings. Penetration test procedures were carried out until the composite was perforated and completely punctured. A 9 mm diameter rounded-tip punch was used; the diameter of the support hole was 45 mm. To determine the mechanical properties in the bending tests, three-point bending was carried out at a speed of 2 mm/min. Impact tests were also carried out using a Charpy impact test and a hammer with an energy of 2 J. Our findings indicate that the core material plays a crucial role in determining a composite’s mechanical behavior. Balsa cores offer the best properties in the QSPT test and bending strength and stiffness (57 MPa and 7.4 GPa, respectively), while Rohacell^® cores provide excellent impact resistance (12 kJ/m²). Nomex^® cores demonstrate high bending stiffness (5.3 GPa) but perform worse than Balsa. The choice of core material is application-dependent; Balsa cores are optimal for bending and point loads, and Rohacell^® cores are optimal for impact-dominated scenarios. Full article

(This article belongs to the Section Advanced Composites)

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16 pages, 6479 KB

Open AccessEditor’s ChoiceArticle

Vat Photopolymerization of CeO₂-Incorporated Hydrogel Scaffolds with Antimicrobial Efficacy

by Nelly Aimelyne Mpuhwe, Gyu-Nam Kim and Young-Hag Koh

Materials 2025, 18(5), 1125; https://doi.org/10.3390/ma18051125 - 2 Mar 2025

Cited by 1 | Viewed by 1206

Abstract

We herein demonstrate the utility of gelatin methacryloyl (GelMA)/poly(ethylene glycol) diacrylate (PEGDA)–cerium oxide (CeO₂) hydrogel inks for manufacturing hydrogel scaffolds with antimicrobial efficacy by vat photopolymerization. For uniform blending with GelMA/PEGDA hydrogels, CeO₂ nanoparticles with a round shape were synthesized [...] Read more.

We herein demonstrate the utility of gelatin methacryloyl (GelMA)/poly(ethylene glycol) diacrylate (PEGDA)–cerium oxide (CeO₂) hydrogel inks for manufacturing hydrogel scaffolds with antimicrobial efficacy by vat photopolymerization. For uniform blending with GelMA/PEGDA hydrogels, CeO₂ nanoparticles with a round shape were synthesized by the precipitation method coupled with calculation at 600 °C. In addition, they had highly crystalline phases and the desired chemical structures (oxidation states of Ce³⁺ and Ce⁴⁺) required for outstanding antimicrobial efficacy. A range of GelMA/PEGDA-CeO₂ hydrogel scaffolds with different CeO₂ contents (0% w/v, 0.1% w/v, 0.5% w/v, 1% w/v, and 5% w/v with respect to distilled water content) were manufactured. The photopolymerization behavior, mechanical properties, and biological properties (swelling and biodegradation behaviors) of hydrogel scaffolds were characterized to optimize the CeO₂ content. GelMA/PEGDA-CeO₂ hydrogel scaffolds produced with the highest CeO₂ content (5% w/v) showed reasonable mechanical properties (compressive strength = 0.56 ± 0.09 MPa and compressive modulus = 0.19 ± 0.03 MPa), a high swelling ratio (1063.3 ± 10.9%), and the desired biodegradation rate (remaining weight after 28 days = 39.6 ± 2.3%). Furthermore, they showed outstanding antimicrobial efficacy (the number of colony-forming units = 76 ± 44.6 (×10³)). In addition, macroporous GelMA/PEGDA-CeO₂ hydrogel scaffolds with tightly controlled porous structures could be manufactured by vat photopolymerization. Full article

(This article belongs to the Section Biomaterials)

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23 pages, 4538 KB

Open AccessEditor’s ChoiceReview

Recent Progress in Pyro-Phototronic Effect-Based Photodetectors: A Path Toward Next-Generation Optoelectronics

by Vishwa Bhatt and Min-Jae Choi

Materials 2025, 18(5), 976; https://doi.org/10.3390/ma18050976 - 21 Feb 2025

Viewed by 1074

Abstract

Since photodetectors are widely used in a variety of applications, such as imaging, optical communication, security and safety, motion detection, environmental sensing, and more, they are a crucial part of many technologies. The performance of photodetectors has significantly improved due to the advanced [...] Read more.

Since photodetectors are widely used in a variety of applications, such as imaging, optical communication, security and safety, motion detection, environmental sensing, and more, they are a crucial part of many technologies. The performance of photodetectors has significantly improved due to the advanced development of third-generation semiconducting materials caused by the novel pyro-phototronic effect. This effect; induced by localized heating under pulsed incident light, enhances the generation, separation, and collection of charge carriers within photodetectors. The combined pyroelectric and photoelectric effects resulting from this process are collectively termed the pyro-phototronic effect. It is crucial to understand how the pyro-phototronic effect affects the optoelectronic processes that take place during photodetection. This review addresses the latest advancements in photodetector performance by presenting the pyro-phototronic effect for a range of semiconductors. We provide a comprehensive summary of the pyro-phototronic effect in different semiconducting materials and outline recent developments in photodetectors. Full article

(This article belongs to the Special Issue Advances in Nanophotonic Materials, Devices, and Applications)

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25 pages, 11591 KB

Open AccessEditor’s ChoiceArticle

Production of Nd and Nd–Fe Alloys from NdCl₃ by Calciothermic Reduction

by Joo-Won Yu, Yeon-Jun Chung and Jei-Pil Wang

Materials 2025, 18(5), 971; https://doi.org/10.3390/ma18050971 - 21 Feb 2025

Viewed by 750

Abstract

This study presents a metallothermic reduction mechanism for fabricating Nd and Nd–Fe alloys at 850–1050 °C using anhydrous NdCl₃ and Ca, which have relatively low melting points. Our method decreased the process temperature while improving the recovery rate of Nd using the [...] Read more.

This study presents a metallothermic reduction mechanism for fabricating Nd and Nd–Fe alloys at 850–1050 °C using anhydrous NdCl₃ and Ca, which have relatively low melting points. Our method decreased the process temperature while improving the recovery rate of Nd using the thermodynamic parameters of the CaCl₂–KCl–NaCl and Nd–Fe liquid solutions. To reduce the activity of the product (CaCl₂), the optimal composition of the CaCl₂–KCl–NaCl molten salt was

X_{{C a C l}_{2}} = 0.4 (X_{K C l} : X_{N a C l} = 6 : 4)

. The molten metal bath (Nd or Nd–Fe) that formed at the bottom of the reaction zone during Nd and Nd–Fe alloy production absorbed metal particles generated in the molten salt during the reaction, thereby facilitating ingot formation. In Nd produced at 1050 °C using 1.2× the stoichiometric amount (by mass) of Ca, the Nd recovery rate was 97.0%. Moreover, in the Nd–Fe alloys produced at 1050 °C targeting eutectic compositions, the Nd recovery rate was 96.3%. Increased Fe contents in the Nd–Fe liquid solution reduced the Nd recovery rates, and the Nd–Fe alloy (Nd recovery rate: 89.8%) was produced at 850 °C, suggesting the possibility of increasing the energy efficiency of the Nd production process. The Nd–Fe alloy produced through this proposed process could be used as a raw material in the NdFeB strip casting process. Full article

(This article belongs to the Section Materials Chemistry)

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16 pages, 5953 KB

Open AccessEditor’s ChoiceArticle

Memory Devices with HfO₂ Charge-Trapping and TiO₂ Channel Layers: Fabrication via Remote and Direct Plasma Atomic Layer Deposition and Comparative Performance Evaluation

by Inkook Hwang, Jiwon Kim, Joungho Lee, Yeonwoong Jung and Changbun Yoon

Materials 2025, 18(5), 948; https://doi.org/10.3390/ma18050948 - 21 Feb 2025

Cited by 2 | Viewed by 1057

Abstract

With the improvement of integration levels to several nanometers or less, semiconductor leakage current has become an important issue, and oxide-based semiconductors, which have replaced Si-based channel layer semiconductors, have attracted attention. Herein, we fabricated capacitors with a metal–insulator–semiconductor–metal structure using HfO₂ [...] Read more.

With the improvement of integration levels to several nanometers or less, semiconductor leakage current has become an important issue, and oxide-based semiconductors, which have replaced Si-based channel layer semiconductors, have attracted attention. Herein, we fabricated capacitors with a metal–insulator–semiconductor–metal structure using HfO₂ thin films deposited at 240 °C and TiO₂ thin films deposited at 300 °C via remote plasma (RP) and direct plasma (DP) atomic layer deposition and analyzed the effects of the charge-trapping and semiconducting properties of these films. Charge-trapping memory (CTM) devices with HfO₂ (charge-trapping layer) and TiO₂ (semiconductor) films were fabricated and characterized in terms of their memory properties. Al₂O₃ thin films were used as blocking and tunneling layers to prevent the leakage of charges stored in the charge-trapping layer. For the TiO₂ layer, the heat-treatment temperature was optimized to obtain an anatase phase with optimal semiconductor properties. The memory characteristics of the RP HfO₂–TiO₂ CTM devices were superior to those of the DP HfO₂–TiO₂ CTM devices. This result was ascribed to the decrease in the extent of damage and contamination observed when the plasma was spaced apart from the deposited HfO₂ and TiO₂ layers (i.e., in the case of RP deposition) and the reduction in the concentration of oxygen vacancies at the interface and in the films. Full article

(This article belongs to the Special Issue Metal Oxide Semiconductors: Synthesis, Structure, and Applications)

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15 pages, 8198 KB

Open AccessEditor’s ChoiceArticle

Differential Effects of Adding Graphene Nanoplatelets on the Mechanical Properties and Crystalline Behavior of Polypropylene Composites Reinforced with Carbon Fiber or Glass Fiber

by Hiroki Satoh, Ayumu Morita and Yoshihiko Arao

Materials 2025, 18(5), 926; https://doi.org/10.3390/ma18050926 - 20 Feb 2025

Cited by 2 | Viewed by 825

Abstract

Short fiber-reinforced thermoplastic composites (SFRTPs) have excellent recyclability and processability, but their mechanical properties are weak compared to continuous fiber products. Various studies have reported that the addition of GNPs improves the mechanical properties of SFRTPs, but it is unclear what effect different [...] Read more.

Short fiber-reinforced thermoplastic composites (SFRTPs) have excellent recyclability and processability, but their mechanical properties are weak compared to continuous fiber products. Various studies have reported that the addition of GNPs improves the mechanical properties of SFRTPs, but it is unclear what effect different types of reinforcing fibers have on a hybrid composite system. In this study, the effect of adding a small amount (1 wt%) of graphene nanoplatelets (GNPs) to fiber-reinforced polypropylene composites on their mechanical properties was investigated from a crystallinity perspective. GNPs were mixed with polypropylene (PP)/carbon fiber (CF) or PP/glass fiber (GF) using a melt blending process, and composites were molded by injection molding. The results of mechanical property characterization showed no significant effect when GNPs were added to PP/CF, but when GNPs were added to PP/GF, this increased the composite’s tensile strength and Young’s modulus by approximately 20% and 10%, respectively. The interfacial shear strength (IFSS) predicted using the modified Kelly–Tyson equation did not change much before and after the addition of GNPs to PP/CF. On the other hand, the IFSS increased from 10.8 MPa to 19.2 MPa with the addition of GNPs to PP/GF. The increase in IFSS led to an increase in the tensile strength of PP/GF with the incorporation of GNPs. Differential scanning calorimetry (DSC) indicated that GNPs accelerated the crystallization rate, and the X-ray diffraction (XRD) results confirmed that GNPs acted as a crystal nucleating agent. However, CF was also shown to be a nucleating agent, limiting the effect of GNP addition. In other words, it can be said that the addition of GNPs to PP/GF is more effective than their addition to PP/CF due to the differential crystallization effects of each fiber. Full article

(This article belongs to the Special Issue Advanced Resin Composites: From Synthesis to Application)

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19 pages, 10708 KB

Open AccessEditor’s ChoiceArticle

Evaluation of the Influence of Primary and Secondary Crystal Orientations and Selected Structural Characteristics on Creep Resistance in Single-Crystal Nickel-Based Turbine Blades

by Kamil Gancarczyk, Robert Albrecht, Paweł Sułkowicz, Mirosław Szala and Mariusz Walczak

Materials 2025, 18(5), 919; https://doi.org/10.3390/ma18050919 - 20 Feb 2025

Cited by 3 | Viewed by 887

Abstract

This study evaluates the perfection of the crystal structure of single-crystal turbine blade castings made from the CMSX-4 nickel superalloy. The analysis included primary and secondary crystal orientation measurements using the Ω-scan method and the novel OD-EFG X-ray diffractometer. The selected microstructural parameters [...] Read more.

This study evaluates the perfection of the crystal structure of single-crystal turbine blade castings made from the CMSX-4 nickel superalloy. The analysis included primary and secondary crystal orientation measurements using the Ω-scan method and the novel OD-EFG X-ray diffractometer. The selected microstructural parameters of the single crystals were also analyzed, including the assessment of stereological parameters and the degree of porosity. A creep test was performed according to standard procedures and under conditions simulating real operational environments. The model single-crystal turbine blades were manufactured using the Bridgman–Stockbarger method, with variable withdrawal rates of 1 and 3 mm/min. Heat treatment of the single-crystal castings involved solution treatment followed by double aging. The evaluation of structural perfection was carried out in three states: as-cast, after solution heat treatment, and after double aging. The crystallographic orientation of the blades was determined on both the airfoil and the root part. The study determined how crystallographic orientation and microstructural parameters influence the creep resistance of the castings. It was found that in the as-cast condition, the greatest influence on high creep strength has a small deviation of the primary and constant value of secondary crystal orientation along the height of the blade casting. After heat treatment, the highest creep resistance was obtained for the blade manufactured at a withdrawal rate at 1 mm/min. Full article

(This article belongs to the Section Metals and Alloys)

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18 pages, 7002 KB

Open AccessEditor’s ChoiceArticle

Influence of Pre-Strain on the Course of Energy Dissipation and Durability in Low-Cycle Fatigue

by Stanisław Mroziński, Michał Piotrowski, Władysław Egner and Halina Egner

Materials 2025, 18(4), 893; https://doi.org/10.3390/ma18040893 - 18 Feb 2025

Viewed by 531

Abstract

The work undertaken in this paper is the comparative analysis of the accumulation of plastic strain energy in the as-received and pre-deformed (overloaded) material states, performed on the example of S420M steel. For this reason, the low-cycle fatigue tests on S420M steel specimens [...] Read more.

The work undertaken in this paper is the comparative analysis of the accumulation of plastic strain energy in the as-received and pre-deformed (overloaded) material states, performed on the example of S420M steel. For this reason, the low-cycle fatigue tests on S420M steel specimens were conducted under controlled deformation conditions, and both as-received (undeformed) and pre-deformed specimens were used in the tests. The results of the low-cycle tests were analyzed in terms of dissipated energy. This study found that pre-straining of S420M steel specimens causes a reduction in the energy of the hysteresis loop at all strain amplitude levels. This results in a slight increase in the fatigue life of pre-strained specimens compared to as-received specimens. Based on the analysis, it was also found that despite the different lifetimes obtained at the same strain amplitude levels, the fatigue characteristics in terms of energy of the as-received and pre-strained samples are statistically the same. Experimental verification of the analytical models used to describe hysteresis loops confirmed their suitability for describing fatigue behavior for specimens made of steel in both the as-received and pre-strained state. Full article

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

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51 pages, 17258 KB

Open AccessEditor’s ChoiceReview

A Review of Simulation Tools Utilization for the Process of Laser Powder Bed Fusion

by Ľuboš Kaščák, Ján Varga, Jana Bidulská, Róbert Bidulský and Tibor Kvačkaj

Materials 2025, 18(4), 895; https://doi.org/10.3390/ma18040895 - 18 Feb 2025

Cited by 2 | Viewed by 1671

Abstract

This review describes the process of metal additive manufacturing and focuses on the possibility of correlated input parameters that are important for this process. The correlation of individual parameters in the metal additive manufacturing process is considered using simulation tools that allow the [...] Read more.

This review describes the process of metal additive manufacturing and focuses on the possibility of correlated input parameters that are important for this process. The correlation of individual parameters in the metal additive manufacturing process is considered using simulation tools that allow the prediction of various defects, thus making the real production process more efficient, especially in terms of time and costs. Special attention is paid to multiple applications using these simulation tools as an initial analysis to determine the material’s behavior when defining various input factors, including the results obtained. Based on this, further procedures were implemented, including real production parts. This review also points out the range of possible variations that simulation tools have, which helps to effectively predict material defects and determine the volume of consumed material, supports construction risk, and other information necessary to obtain a quality part in the production process. From the overview of the application of simulation tools in this process, it was found that the correlation between theoretical knowledge and the definition of individual process parameters and other variables are related and are of fundamental importance for achieving the final part with the required properties. In terms of some specific findings, it can be noted that simulation tools identify adverse phenomena occurring in the production processes and allow manufacturers to test the validity of the proposed conceptual and model solutions without making actual changes in the production system, and they have the measurable impact on the design and production of quality parts. Full article

(This article belongs to the Special Issue Plastic Deformation and Mechanical Behavior of Metallic Materials)

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20 pages, 6306 KB

Open AccessEditor’s ChoiceArticle

Nanostructured Chromium PVD Thin Films Fabricated Through Copper–Chromium Selective Dissolution

by Stefano Mauro Martinuzzi, Stefano Caporali, Rosa Taurino, Lapo Gabellini, Enrico Berretti, Eric Schmeer and Nicola Calisi

Materials 2025, 18(4), 894; https://doi.org/10.3390/ma18040894 - 18 Feb 2025

Viewed by 644

Abstract

This study investigates the fabrication of nanostructured chromium thin films via selective dissolution of PVD-deposited Cu–Cr thin films. The effects of the deposition parameters on the structural, chemical, and morphological properties of the films are systematically analyzed. Starting from a thin film composed [...] Read more.

This study investigates the fabrication of nanostructured chromium thin films via selective dissolution of PVD-deposited Cu–Cr thin films. The effects of the deposition parameters on the structural, chemical, and morphological properties of the films are systematically analyzed. Starting from a thin film composed of 50 wt.% chromium and 50 wt.% copper, deposited onto a substrate pre-heated to 300 °C, we demonstrate that the following dealloying process carried out in a diluted nitric acid solution yields nanostructured chromium films with high porosity, large surface area, enhanced wettability and neglectable copper content. These findings underline the critical influence of the deposition temperature and alloy composition on achieving optimal film properties. Full article

(This article belongs to the Special Issue Advancements in Thin Film Deposition Technologies)

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13 pages, 3773 KB

Open AccessEditor’s ChoiceArticle

Transition-Metal-Doped Nickel–Cobalt Layered Double Hydroxide Catalysts for an Efficient Oxygen Evolution Reaction

by Zhihan Li, Wenjing Yi, Qingqing Pang, Meng Zhang and Zhongyi Liu

Materials 2025, 18(4), 877; https://doi.org/10.3390/ma18040877 - 17 Feb 2025

Viewed by 1642

Abstract

Hydrogen plays a vital role in the global shift toward cleaner energy solutions, with water electrolysis standing out as one of the most promising techniques for generating hydrogen. Despite its potential, the oxygen evolution reaction (OER) involved in this process faces significant challenges, [...] Read more.

Hydrogen plays a vital role in the global shift toward cleaner energy solutions, with water electrolysis standing out as one of the most promising techniques for generating hydrogen. Despite its potential, the oxygen evolution reaction (OER) involved in this process faces significant challenges, including high overpotentials and slow reaction rates, which underscore the need for advanced electrocatalytic materials to enhance efficiency. Noble metal catalysts are effective but expensive, so transition-metal-based electrocatalysts like nickel–cobalt layered double hydroxides (NiCo LDHs) have become promising alternatives. In this research, a series of NiCo LDH catalysts doped with Fe, Mn, Cu, and Zn were effectively produced using a one-step hydrothermal technique. Among the catalysts, the Fe-doped NiCo LDH exhibited OER activity, achieving a lower overpotential (289 mV) at a current density of 50 mA/cm², which was far better than the 450 mV of the undoped NiCo LDH. The Mn-, Cu-, and Zn-NiCo LDHs also exhibited lower overpotentials of 414 mV, 403 mV, and 357 mV, respectively, at this current density. The Fe-doped NiCo LDH had a 3D layered nanoflower structure, increasing the surface area for reactant adsorption. The electrochemically active surface area (ECSA), as indicated by the double-layer capacitance (C_dl), was larger in the doped samples. The C_dl value of the Fe-doped NiCo LDH was 3.72 mF/cm², significantly surpassing the 0.82 mF/cm² of the undoped NiCo LDH. These changes improved charge transfer and optimized reaction kinetics, enhancing the overall OER performance. This study offers significant contributions to the development of efficient electrocatalysts for the OER, advancing the understanding of key design principles for enhanced catalytic performance. Full article

(This article belongs to the Special Issue Research on Electrocatalytic Materials for Hydrogen Evolution and Oxygen Evolution)

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11 pages, 1999 KB

Open AccessEditor’s ChoiceArticle

Giant Seebeck Effect in a PEDOT Material Coated on a Felt Fiber

by Hideki Arimatsu, Yuki Osada, Ryo Takagi and Takuya Fujima

Materials 2025, 18(4), 838; https://doi.org/10.3390/ma18040838 - 14 Feb 2025

Viewed by 792

Abstract

Poly(3,4-ethylenedioxythiophene) (PEDOT) has been extensively investigated not only as a conductive polymer but also as a promising thermoelectric material. Numerous efforts have been undertaken to enhance the thermoelectric performance, particularly because improving the Seebeck coefficient is crucial for practical applications. In this study, [...] Read more.

Poly(3,4-ethylenedioxythiophene) (PEDOT) has been extensively investigated not only as a conductive polymer but also as a promising thermoelectric material. Numerous efforts have been undertaken to enhance the thermoelectric performance, particularly because improving the Seebeck coefficient is crucial for practical applications. In this study, we explored the thermoelectric property modification of PEDOT using a low-molecular carrier dopant and a fibrous substrate. PEDOT was coated on a felt texture with p-toluenesulfonic acid (PTSA) as the carrier dopant. The thermoelectric properties, including the Seebeck coefficient and electric conductivity, were measured. Raman spectroscopy was used to characterize the molecular strain of the PEDOT. The PEDOT sample coated on a felt texture with PTSA exhibited a wide range of Seebeck coefficients (−2100 to 3100 μV K⁻¹). An estimation suggested the power factor reached 2400 µW m⁻¹ K⁻² for the p-type and 1100 µW m⁻¹ K⁻² for the n-type at the maxima. Raman spectroscopy showed a strong correlation between the strain in the C_β-C_β bond of the PEDOT molecule and its Seebeck coefficient. Full article

(This article belongs to the Special Issue Advanced Thin Film Materials for Energy Conversion and Storage Applications)

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14 pages, 7452 KB

Open AccessEditor’s ChoiceArticle

Light-Intensity-Dependent Control of Collagen Hydrogel Properties via Riboflavin Phosphate-Mediated Photocrosslinking

by Seungyeop Yoo, Won-Gun Koh and Hyun Jong Lee

Materials 2025, 18(4), 828; https://doi.org/10.3390/ma18040828 - 14 Feb 2025

Cited by 2 | Viewed by 1190

Abstract

While photocrosslinked collagen hydrogels show promise in tissue engineering, conventional approaches for property control often require complex chemical modifications or concentration changes that alter their biochemical composition. Here, we present the first systematic investigation of light-intensity-dependent control in riboflavin phosphate (RFP)-mediated photocrosslinking as [...] Read more.

While photocrosslinked collagen hydrogels show promise in tissue engineering, conventional approaches for property control often require complex chemical modifications or concentration changes that alter their biochemical composition. Here, we present the first systematic investigation of light-intensity-dependent control in riboflavin phosphate (RFP)-mediated photocrosslinking as a novel, single-parameter approach to modulate hydrogel properties while preserving native biochemical environments. We systematically investigated the effects of varying light intensities (100 K, 50 K, and 10 K lux) during hydrogel fabrication through comprehensive structural, mechanical, and biological characterization. Scanning electron microscopy revealed unprecedented control over network architecture, where higher light intensities produced more uniform and compact networks, while swelling ratio analysis showed significant differences between 100 K lux (246 ± 2-fold) and 10 K lux (265 ± 4-fold) conditions. Most significantly, we discovered that intermediate intensity (50 K lux) uniquely optimized mechanical performance in physiological conditions, achieving storage modulus of about 220 Pa after 24 h swelling, compared to about 160 and 109 Pa for 100 K and 10 K lux conditions, respectively. Remarkably, cellular studies using NIH/3T3 fibroblasts demonstrated that lower light intensity (10 K lux) enhanced cell proliferation by 2.8-fold compared to 100 K lux conditions after 7 days of culture, with superior cell network formation in both 2D and 3D environments. This groundbreaking approach establishes light intensity as a powerful single parameter for precise control of both mechanical and biological properties, offering a transformative tool for tailoring collagen-based biomaterials in tissue engineering applications. Full article

(This article belongs to the Special Issue Advances in Bio-Polymer and Polymer Composites)

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23 pages, 10651 KB

Open AccessEditor’s ChoiceArticle

Dynamic Behavior of Submerged Cylindrical Shells Under Combined Underwater Explosion, Bubble Pulsation, and Hydrostatic Pressure

by Ruyi Fan, Gaojian Lin, Hang Zhang, Longfei Zhang and Weifu Sun

Materials 2025, 18(4), 818; https://doi.org/10.3390/ma18040818 - 13 Feb 2025

Cited by 3 | Viewed by 1106

Abstract

Understanding the dynamic response of cylindrical shells subjected to underwater explosion is crucial for designing safe underwater vehicles, especially in deep-water environments where the shell structures are prestressed by hydrostatic pressure. The complex combination of external loading crossing different temporal scales—from underwater explosive [...] Read more.

Understanding the dynamic response of cylindrical shells subjected to underwater explosion is crucial for designing safe underwater vehicles, especially in deep-water environments where the shell structures are prestressed by hydrostatic pressure. The complex combination of external loading crossing different temporal scales—from underwater explosive shock waves to bubble pulsation and hydrostatic pressure—results in a synergic damaging effect on the target structures. In this work, the dynamic responses and buckling failure mechanisms of deeply immersed (≥1300 m) cylindrical shells subjected to underwater explosion were investigated through a numerical approach using the finite element method. A convenient and reliable routine for imposing hydrostatic pressure in the Coupled Eulerian–Lagrangian model was developed and validated. Three-dimensional models, composed of spherical charges and shell targets under deep-water conditions, were established to reveal the influences of key factors, including explosion depth and explosion distance, on the failure modes. The results show that the numerical models presented in this work are capable of simulating the complex synergic effect of hydrostatic pressure, the bubble pulsation process, and shock waves on the failure mechanisms of deeply immersed cylindrical shells. This work could provide valuable guidance for the design of safer deep-water marine structures. Full article

(This article belongs to the Special Issue Theoretical and Computational Modeling of Material Surfaces and Interfaces)

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15 pages, 8628 KB

Open AccessEditor’s ChoiceArticle

Improving Biodegradable Mg-Zn(-Ca) Alloys by Surface Treatment via Plasma Electrolytic Oxidation

by Jakub Vertaľ, Daniel Kajánek, Jiří Kubásek and Peter Minárik

Materials 2025, 18(4), 747; https://doi.org/10.3390/ma18040747 - 8 Feb 2025

Cited by 2 | Viewed by 830

Abstract

This study investigated the influence of plasma electrolytic oxidation (PEO) preparation time on the degradation resistance of Mg-1Zn (Z1) and Mg-1Zn-0.4Ca (ZX10) alloys, with comparisons to pure Mg and commercial Mg-4Y-3RE-0.4Zr (WE43). PEO layers were formed with varying preparation times (5, 10, and [...] Read more.

This study investigated the influence of plasma electrolytic oxidation (PEO) preparation time on the degradation resistance of Mg-1Zn (Z1) and Mg-1Zn-0.4Ca (ZX10) alloys, with comparisons to pure Mg and commercial Mg-4Y-3RE-0.4Zr (WE43). PEO layers were formed with varying preparation times (5, 10, and 15 min) and analyzed for microstructure, morphology, and corrosion resistance. The results indicated that PEO layers with a 10 min preparation time had the most homogeneous structure and optimal corrosion resistance. Prolonged PEO preparation times increased pore density, crack formation, and layer thickness while also promoting layer degradation during extended immersion in 0.9% NaCl corrosive media. The dissolution of phosphates from PEO layers contributes to the formation of a protective corrosion layer, enhancing long-term resistance. These findings demonstrate that low-alloyed, biocompatible Mg-Zn(-Ca) alloys can achieve corrosion resistance comparable to high-performance WE43 alloys through appropriate surface treatment. Full article

(This article belongs to the Special Issue Corrosion Behavior and Mechanical Properties of Metallic Materials)

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19 pages, 14510 KB

Open AccessEditor’s ChoiceArticle

The Influence of Roughness on the Protective Layer Formation Induced by Marine Microorganisms on 5083 Aluminum Alloy

by Julien Jaume, Marie-Line Délia and Régine Basséguy

Materials 2025, 18(3), 708; https://doi.org/10.3390/ma18030708 - 6 Feb 2025

Cited by 1 | Viewed by 812

Abstract

This study investigates the formation of a protective layer on a 5083 aluminum alloy surface induced by microorganisms from salt marsh. The influence of the initial surface roughness was examined to identify optimal conditions for maximum coverage and thickness of the protective layer. [...] Read more.

This study investigates the formation of a protective layer on a 5083 aluminum alloy surface induced by microorganisms from salt marsh. The influence of the initial surface roughness was examined to identify optimal conditions for maximum coverage and thickness of the protective layer. As two opposing effects are suspected, where high surface roughness enhances bacterial adhesion but reduces the resistance to abiotic corrosion, various degrees of roughness were tested. Using electrochemical experiments (OCP measurement, 1/Rp determination, and pitting sensitivity), SEM/TEM observation and EDX characterization, a compromise was found on the initial roughness to obtain a thick protective layer through good bacterial adhesion while minimizing abiotic corrosion. The optimal roughness, achieved through 240-grit grinding, facilitates a uniform distribution of microorganisms and the development of a dense, evenly thick protective layer that significantly enhances the alloy’s resistance to pitting corrosion. The passivity domain doubled when comparing the electrochemical behavior of electrodes immersed in the presence of microbial activity to those immersed without it. Full article

(This article belongs to the Special Issue Corrosion Mechanism and Protection Technology of Metallic Materials)

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14 pages, 4269 KB

Open AccessEditor’s ChoiceArticle

Insights into HKUST-1 Metal-Organic Framework’s Morphology and Physicochemical Properties Induced by Changing the Copper(II) Salt Precursors

by Joanna Klęba, Kun Zheng, Dorota Duraczyńska, Mateusz Marzec, Monika Fedyna and Jakub Mokrzycki

Materials 2025, 18(3), 676; https://doi.org/10.3390/ma18030676 - 3 Feb 2025

Viewed by 3064

Abstract

The HKUST-1 metal-organic framework was synthesized using four different copper(II) salt precursors, namely copper nitrate, copper sulphate, copper acetate, and copper chloride, via the solvothermal method with no mixing. Syntheses were conducted without using the N,N-dimethylformamide to allow for a greener synthesis of [...] Read more.

The HKUST-1 metal-organic framework was synthesized using four different copper(II) salt precursors, namely copper nitrate, copper sulphate, copper acetate, and copper chloride, via the solvothermal method with no mixing. Syntheses were conducted without using the N,N-dimethylformamide to allow for a greener synthesis of MOFs. The selected physicochemical properties of the obtained metal-organic frameworks were determined. The yield of the obtained products changed in the order acetate>nitrate>sulfate, while no product was obtained in the synthesis with copper(II) chloride. The obtained materials were characterized by means of XRD, nitrogen adsorption–desorption at −196 °C, FTIR, XPS, TGA, SEM, and DLS. The morphology of crystallites and their physicochemical properties were significantly affected when different copper(II) salt precursors were used. The comparison of the obtained results with already published works allows for the correlation of the synthesis parameters like synthesis temperature, time, mixing, and copper(II) salt precursor used on selected properties of the final product. Full article

(This article belongs to the Special Issue Advanced Nanoporous and Mesoporous Materials)

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17 pages, 1743 KB

Open AccessEditor’s ChoiceArticle

Fabrication and Characterization of Electrospun DegraPol^® Tubes Releasing TIMP-1 Protein to Modulate Tendon Healing

by Julia Rieber, Roger Khalid Niederhauser, Pietro Giovanoli and Johanna Buschmann

Materials 2025, 18(3), 665; https://doi.org/10.3390/ma18030665 - 3 Feb 2025

Cited by 3 | Viewed by 1141

Abstract

Background: Tendon rupture repair can result from fibrotic scar formation through imbalanced ECM deposition during remodeling. The tissue inhibitors of matrix metalloprotease (TIMPs) not only decrease ECM degradation, regulated by matrix metalloproteases (MMPs), but also restrict TGF-β1 activation and thus diminish fibrosis. Methods: [...] Read more.

Background: Tendon rupture repair can result from fibrotic scar formation through imbalanced ECM deposition during remodeling. The tissue inhibitors of matrix metalloprotease (TIMPs) not only decrease ECM degradation, regulated by matrix metalloproteases (MMPs), but also restrict TGF-β1 activation and thus diminish fibrosis. Methods: Rabbit tenocytes (rbTenocytes) and rabbit adipose-derived stem cells (rbASCs) were cultivated under different TIMP-1 concentrations. Proliferation and gene expression were assessed. TIMP-1 was incorporated into emulsion electrospun DegraPol^® (DP) tubes that were characterized by SEM for fiber thickness, pore size, and wall thickness. Static and dynamic water contact angles, FTIR spectra, and TIMP-1 release kinetics were determined. Results: While the proliferation of rbTenocytes and rbACS was not affected by TIMP-1 supplementation in vitro, the gene expression of Col1A1 was increased in rbTenocytes, the gene expression of ki67 was increased in both cell types, the gene expression of tenomodulin was increased in both cell types at 100 ng/mL TIMP-1, and alkaline phosphatase expression ALP rose significantly in rbASCs. Electrospun TIMP-1/DP fibers had a ~5 μm diameter, a ~10 μm pore size, and a mesh thickness of ~200 μm. TIMP-1/DP meshes were more hydrophilic than pure DP meshes. TIMP-1 was released from the meshes with a sustained release of up to 7 days. Conclusions: TIMP-1/DP tubes may be used to modulate the fibrotic tissue reaction when applied around conventionally sutured tendon ruptures. Full article

(This article belongs to the Special Issue Physico-Chemical Modification of Materials for Biomedical Application)

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15 pages, 8890 KB

Open AccessEditor’s ChoiceArticle

Application of Magnetic-Assisted Polishing Using Metal-Bonded Grinding Wheels for Machining Silicon Nitride Ball Bearings

by Su-Yeon Han, Seung-Min Lee, Ha-Neul Kim, Jae-Woong Ko and Tae-Soo Kwak

Materials 2025, 18(3), 677; https://doi.org/10.3390/ma18030677 - 3 Feb 2025

Viewed by 1003

Abstract

Silicon nitride (Si₃N₄) is used for high-speed rotating bearings in machine tools, aircraft, and turbo pumps due to its excellent material properties such as high-temperature strength, hardness, and fracture toughness. Grinding with fixed abrasives enables high shape accuracy and [...] Read more.

Silicon nitride (Si₃N₄) is used for high-speed rotating bearings in machine tools, aircraft, and turbo pumps due to its excellent material properties such as high-temperature strength, hardness, and fracture toughness. Grinding with fixed abrasives enables high shape accuracy and high efficiency in machining brittle materials. However, it is difficult to completely remove surface damage, which limits its use in products requiring a nano surface. These defects also result in reduced reliability and shortened lifespan. Magnetic-assisted polishing (MAP) is a technology that can achieve a fine surface by using a mixture of iron powder and abrasives, but it requires a lot of time due to the low material removal rate (MRR). Therefore, this study developed a hybrid processing technology using a metal-bonded grinding wheel and a slurry with hard abrasives for the high precision of silicon nitride ceramic ball bearings. Experiments were conducted in order to compare and analyze the surface roughness and material removal rate. Through MAP, using a grinding wheel with low grit (#325), high-efficiency machining performance was confirmed with a maximum material removal rate of 1.193 mg/min. In MAP, using a grinding wheel with high grit (#2000), a nano-level surface roughness of 6.5 nm Ra was achieved. Full article

(This article belongs to the Special Issue Functionalized Ceramics and Their Composites: Preparation, Properties and Applications)

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