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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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10 pages, 1102 KB  
Article
Dirac Point in the Charge Compensated Single-Crystal Ru3Sn7
by Xiaoyu Ji, Xuebo Zhou, Shilin Zhu, Fengcai Ma, Gang Li and Wei Wu
Materials 2025, 18(17), 4044; https://doi.org/10.3390/ma18174044 - 29 Aug 2025
Viewed by 496
Abstract
Ru3Sn7 crystallizes in the cubic Ir3Ge7-type structure (space group Im3m), a class of intermetallic compounds. Previous studies focused primarily on its crystal structure, band calculations, and basic transport properties. Here, we report a systematic investigation [...] Read more.
Ru3Sn7 crystallizes in the cubic Ir3Ge7-type structure (space group Im3m), a class of intermetallic compounds. Previous studies focused primarily on its crystal structure, band calculations, and basic transport properties. Here, we report a systematic investigation of high-quality single crystals via electrical resistivity, Hall effect, specific heat, and thermal transport measurements. The T3X7 intermetallic family—with its diverse electronic ground states—provides an ideal platform for exploring such topology–property relationships. Ru3Sn7 exhibits metallic behavior, with consistent Hall effect and Seebeck coefficient data indicating a compensated electron-hole two-band system. Temperature-dependent modulation of electronic states near the Fermi surface alters charge carrier transport, which may imply the presence of a Lifshitz transition in Ru3Sn7. More importantly, magnetic quantum oscillations are observed for the first time, confirming the presence of two Dirac points in its band structure. Full article
(This article belongs to the Special Issue Advances in Superconductor Materials: Preparation and Characterization)
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16 pages, 2488 KB  
Article
Effect of Waste Micro-Particles on Metalworking Fluid Efficiency and Biodegradation During the Cutting Process
by Stepanka Dvorackova, Martin Bilek, Josef Skrivanek, Dora Kroisová, Anita Białkowska and Mohamed Bakar
Materials 2025, 18(17), 3988; https://doi.org/10.3390/ma18173988 - 26 Aug 2025
Viewed by 875
Abstract
This study investigates contaminants in metalworking fluids (MWFs) from an industrial band saw, focusing on microparticle classification and microbial quantification linked to fluid degradation. Most particles were under 50 µm, primarily aluminum and iron oxides from tool wear; oxygen- and sulfur-containing particles suggested [...] Read more.
This study investigates contaminants in metalworking fluids (MWFs) from an industrial band saw, focusing on microparticle classification and microbial quantification linked to fluid degradation. Most particles were under 50 µm, primarily aluminum and iron oxides from tool wear; oxygen- and sulfur-containing particles suggested corrosion. Microbiological analysis showed high contamination, with culturable microorganisms exceeding 1000 CFU/mL. A pathogenic strain associated with biodeterioration was identified, underscoring the need for microbial control. Filtration and ozonation have been used as decontamination methods to improve the purity and biological stability of the process fluid. Filtration enabled selective removal of metallic microparticles. Among six nanofiber filters, the Berry filter achieved the highest efficiency (70.8%) for particles ≥ 7.3 µm, while other filters were faster but less efficient. Ozonation proved highly effective for microbiological decontamination, reducing viable microorganisms by over 95%, improving visual clarity, and lowering pH from 9 to 8 while remaining within operational limits. Unlike filtration, ozonation significantly reduced microbial load. The combination of both methods is proposed as a sustainable strategy for maintaining process fluid quality under industrial conditions. These findings support integrated decontamination approaches to extend fluid life, reduce fresh MWF consumption and waste, and enhance workplace hygiene and safety in machining operations. Full article
(This article belongs to the Section Smart Materials)
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13 pages, 733 KB  
Article
Stabilization of Charge Density Waves in Atomic Chains on Xenes
by Tomasz Kwapiński, Marcin Kurzyna and Mariusz Krawiec
Materials 2025, 18(16), 3843; https://doi.org/10.3390/ma18163843 - 15 Aug 2025
Viewed by 509
Abstract
We investigate the electronic properties of atomic chains placed on group-14 two-dimensional materials, Xenes, by analyzing the local electronic properties. Our results show that the hybridization between the chain and the substrate leads to significant modifications in the local density of states at [...] Read more.
We investigate the electronic properties of atomic chains placed on group-14 two-dimensional materials, Xenes, by analyzing the local electronic properties. Our results show that the hybridization between the chain and the substrate leads to significant modifications in the local density of states at each chain site, including peak splitting, broadening, and asymmetry. These effects are particularly pronounced for plumbene. Owing to the substrate’s V-shaped-like density of states, the chains exhibit strong localization effects and significant intensity variations in the electronic energy spectrum. In addition the present analysis reveals the emergence of charge density waves in atomic chains, for which the appearance and stability conditions are identified and provided. The charge density waves are more pronounced and stabilized by a specific electronic spectrum of Xenes, allowing them to penetrate deeper into the chain interior. Our findings contribute to the broader understanding of the interaction between one-dimensional chains and two-dimensional Xene materials, which have significant implications for developing advanced hybrid nanostructures and next generation electronic devices. Full article
(This article belongs to the Special Issue Quantum Transport in Novel 2D Materials and Structures)
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27 pages, 6022 KB  
Review
Hydrogen Cryomagnetic a Common Solution for Metallic and Oxide Superconductors
by Bartlomiej Andrzej Glowacki
Materials 2025, 18(15), 3665; https://doi.org/10.3390/ma18153665 - 4 Aug 2025
Viewed by 495
Abstract
This article examines the physical properties, performance metrics, and cooling requirements of a range of superconducting materials, with a particular focus on their compatibility with hydrogen-based cryogenic systems. It analyses recent developments and challenges in this field, and considers how hydrogen cryomagnetic could [...] Read more.
This article examines the physical properties, performance metrics, and cooling requirements of a range of superconducting materials, with a particular focus on their compatibility with hydrogen-based cryogenic systems. It analyses recent developments and challenges in this field, and considers how hydrogen cryomagnetic could transform superconducting technologies, making them economically viable and environmentally sustainable for a variety of critical applications. The discussion aims to provide insights into the intersection of metallic and ceramic superconductors with the hydrogen economy and to chart a path towards scalable and impactful solutions in the energy sector. Full article
(This article belongs to the Special Issue Advanced Superconducting Materials and Technology)
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21 pages, 4377 KB  
Article
Superelasticity in Shape Memory Alloys—Experimental and Numerical Investigations of the Clamping Effect
by Jakub Bryła and Adam Martowicz
Materials 2025, 18(14), 3333; https://doi.org/10.3390/ma18143333 - 15 Jul 2025
Viewed by 727
Abstract
Loading and clamping schemes significantly influence the behavior of shape memory alloys, specifically, the course of their solid-state transformations. This paper presents experimental and numerical findings regarding the nonlinear response of samples of the above-mentioned type of smart materials observed during tensile tests. [...] Read more.
Loading and clamping schemes significantly influence the behavior of shape memory alloys, specifically, the course of their solid-state transformations. This paper presents experimental and numerical findings regarding the nonlinear response of samples of the above-mentioned type of smart materials observed during tensile tests. Hysteretic properties were studied to elucidate the superelastic behavior of the tested and modeled samples. The conducted tensile tests considered two configurations of grips, i.e., the standard one, where the jaws transversely clamp a specimen, and the customized bollard grip solution, which the authors developed to reduce local stress concentration in a specimen. The characteristic impact of the boundary conditions on the solid phase transformation in shape memory alloys, present due to the specific clamping scheme, was studied using a thermal camera and extensometer. Martensitic transformation and the plateau region in the nonlinear stress–strain characteristics were observed. The results of the numerical simulation converged to the experimental outcomes. This study explains the complex nature of the phase changes in shape memory alloys under specific boundary conditions induced by a given clamping scheme. In particular, variation in the martensitic transformation course is identified as resulting from the stress distribution observed in the specimen’s clamping area. Full article
(This article belongs to the Special Issue Technology and Applications of Shape Memory Materials)
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25 pages, 7687 KB  
Article
A Piezoelectric-Actuated Variable Stiffness Miniature Rotary Joint
by Yifan Lu, Yifei Yang, Xiangyu Ma, Ce Chen, Tong Qin, Honghao Yue and Siqi Ma
Materials 2025, 18(14), 3289; https://doi.org/10.3390/ma18143289 - 11 Jul 2025
Viewed by 754
Abstract
With the acceleration of industrialization, deformable mechanisms that can adapt to complex environments have gained widespread applications. Joints serve as carriers for transmitting forces and motions between components, and their stiffness significantly influences the static and dynamic characteristics of deformable mechanisms. A variable [...] Read more.
With the acceleration of industrialization, deformable mechanisms that can adapt to complex environments have gained widespread applications. Joints serve as carriers for transmitting forces and motions between components, and their stiffness significantly influences the static and dynamic characteristics of deformable mechanisms. A variable stiffness joint is crucial for ensuring the safety and reliability of the system, as well as for enhancing environmental adaptability. However, existing variable stiffness joints fail to meet the requirements for miniaturization, lightweight construction, and fast response. This paper proposes a piezoelectric-actuated variable stiffness miniature rotary joint featuring a compact structure, monitorable loading state, and rapid response. Given that the piezoelectric stack expands and contracts when energized, this paper proposes a transmission principle for stiffness adjustment by varying the pressure and friction between active and passive components. This joint utilizes a flexible hinge mechanism for displacement amplification and incorporates a torque sensor based on strain monitoring. A static model is developed based on piezoelectric equations and displacement amplification characteristics, and simulations confirm the feasibility of the stiffness adjustment scheme. The mechanical characteristics of various flexible hinge structures are analyzed, and the effects of piezoelectric actuation capability and external load on stiffness adjustment are examined. The experimental results demonstrate that the joint can adjust stiffness, and the sensor is calibrated using the least squares algorithm to monitor the stress state of the joint in real time. Full article
(This article belongs to the Special Issue Advanced Design and Synthesis in Piezoelectric Smart Materials)
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11 pages, 11723 KB  
Article
Spectrally Resolved Dynamics of Delayed Luminescence in Dense Scattering Media
by Mahshid Zoghi, Ernesto Jimenez-Villar and Aristide Dogariu
Materials 2025, 18(13), 3194; https://doi.org/10.3390/ma18133194 - 6 Jul 2025
Viewed by 655
Abstract
Highly scattering media have garnered significant interest in recent years, ranging from potential applications in solar cells, photocatalysis, and other novel photonic devices to research on fundamental topics such as topological photonics, enhanced light–matter coupling and light confinement. Here, we report measurements of [...] Read more.
Highly scattering media have garnered significant interest in recent years, ranging from potential applications in solar cells, photocatalysis, and other novel photonic devices to research on fundamental topics such as topological photonics, enhanced light–matter coupling and light confinement. Here, we report measurements of spectrally and time-resolved delayed luminescence (DL) in highly scattering rutile TiO2 films. The complex emission kinetics manifests in the non-exponential decay of photon density and the temporal evolution of the spectral composition. We found that while the energy levels of TiO2 nanoparticles broadly set the spectral regions of excitation and emission, our results demonstrate that the DL intensity and duration are strongly influenced by the inherent multiple elastic and inelastic processes determined by the mesoscale inhomogeneous structure of random media. We show that the lifetime of DL increases up to 6 s for the largest redshift detected, which is associated with multiple reabsorption processes. We outline a simple model for spectrally resolved DL emission from dense scattering media that can guide the design and characterization of composite materials with specific spectral and temporal properties. Full article
(This article belongs to the Section Smart Materials)
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13 pages, 3410 KB  
Article
Monitoring of Layered Thermoplastic Composites Using Shape Memory Alloys as Integrated Sensors for Multifunctional Lightweight Structures
by Michael Schwarz, Marius Weiler, Saravanan Palaniyappan, Steven Quirin, Maik Trautmann, Guntram Wagner and Hans-Georg Herrmann
Materials 2025, 18(13), 3193; https://doi.org/10.3390/ma18133193 - 6 Jul 2025
Viewed by 608
Abstract
Since lightweight design and construction safety is a crucial element in different sectors of industry, the use of SMA wires in composites could improve the monitoring and adjustment of mechanical properties starting from the product development process through to field use. This work [...] Read more.
Since lightweight design and construction safety is a crucial element in different sectors of industry, the use of SMA wires in composites could improve the monitoring and adjustment of mechanical properties starting from the product development process through to field use. This work shows how embedded SMA wires can lead to a better understanding of applied forces to a composite structure made of GFRP laminates. To achieve this, different methods will be addressed. Besides mechanical testing of the GFRP-samples with embedded SMA wires, NDT-methods like active thermography, high-frequency ultrasonic testing, and computer tomography are used to detect the SMA wires, whereby thermography and computer tomography are best suited. In this study, the location and the amount of the applied force on GFRP composites with embedded SMA wires could be characterized with relative resistance changes. It is shown that SMA wires with a diameter of 250 µm are preferred to wires with a diameter of 100 µm due to production process and better performance under load (4N force plateau for 100 µm in contrast to 25N force plateau for 250 µm wires). Furthermore, Young’s modulus of the GFRP composites with embedded SMA wires was measured and is similar for various samples with 30.8 GPa on average. Full article
(This article belongs to the Special Issue Technology and Applications of Shape Memory Materials)
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15 pages, 2580 KB  
Article
Dual-Particle Synergy in Bio-Based Linseed Oil Pickering Emulsions: Optimising ZnO–Silica Networks for Greener Mineral Sunscreens
by Marina Barquero, Luis A. Trujillo-Cayado and Jenifer Santos
Materials 2025, 18(13), 3030; https://doi.org/10.3390/ma18133030 - 26 Jun 2025
Viewed by 720
Abstract
The development of mineral, biodegradable sunscreens that can offer both high photoprotection and long-term colloidal stability, while limiting synthetic additives, presents a significant challenge. A linseed oil nanoemulsion co-stabilised by ZnO nanoparticles and the eco-friendly surfactant Appyclean 6552 was formulated, and the effect [...] Read more.
The development of mineral, biodegradable sunscreens that can offer both high photoprotection and long-term colloidal stability, while limiting synthetic additives, presents a significant challenge. A linseed oil nanoemulsion co-stabilised by ZnO nanoparticles and the eco-friendly surfactant Appyclean 6552 was formulated, and the effect of incorporating fumed silica/alumina (Aerosil COK 84) was evaluated. A central composite response surface design was used to ascertain the oil/ZnO ratio that maximised the in vitro sun protection factor at sub-300 nm droplet size. The incorporation of Aerosil at concentrations ranging from 0 to 2 wt.% resulted in a transformation of the dispersion from a nearly Newtonian state to a weak-gel behaviour. This alteration was accompanied by a reduction in the Turbiscan Stability Index. Microscopic analysis has revealed a hierarchical particle architecture, in which ZnO forms Pickering shells around each droplet, while Aerosil aggregates bridge neighboring interfaces, creating a percolated silica scaffold that immobilises droplets and amplifies multiple UV scattering. The findings demonstrate that coupling interfacial Pickering armour with a continuous silica network yields a greener, physically robust mineral sunscreen and offers a transferable strategy for stabilising plant-oil emulsions containing inorganic actives. Full article
(This article belongs to the Section Materials Chemistry)
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17 pages, 10861 KB  
Article
Corrosion Behaviors of Ni80A Alloy Valve in Marine Engine Within Ammonia-Rich Environment
by Ying-ying Liu, Guo-zheng Quan, Yan-ze Yu, Wen-jing Ran and Wei Xiong
Materials 2025, 18(13), 3006; https://doi.org/10.3390/ma18133006 - 25 Jun 2025
Viewed by 760
Abstract
Ammonia fuel is regarded as a promising zero-carbon alternative to diesel in next-generation marine engines. However, the high-temperature ammonia-rich environment poses significant corrosion challenges to hot-end components such as valves. This study investigates the corrosion behavior of Ni80A alloy marine valves under the [...] Read more.
Ammonia fuel is regarded as a promising zero-carbon alternative to diesel in next-generation marine engines. However, the high-temperature ammonia-rich environment poses significant corrosion challenges to hot-end components such as valves. This study investigates the corrosion behavior of Ni80A alloy marine valves under the coupled effects of a high temperature and ammonia atmosphere. Using computational fluid dynamics (CFD), the service temperature of the valve and the ammonia concentration distribution inside the engine cylinder were identified. High-temperature corrosion experiments were conducted with a custom-designed setup. Results show that corrosion kinetics accelerated markedly with temperature: the initial corrosion rate at 800 °C was four times that at 500 °C, and the maximum corrosion layer thickness reached 37 μm—double that at lower temperatures. Microstructural analysis revealed a transition from a dense, defect-free corrosion layer at 500 °C to a non-uniform layer with coarse CrN particles and aggregated nitrides at 800 °C. Notably, surface hardness increased at both temperatures, peaking at 590 HV at 500 °C, while matrix hardness at 800 °C declined due to γ′ phase coarsening and grain growth. This work provides detailed insight into the temperature-dependent ammonia corrosion mechanisms of marine Ni-based alloy valves, offering essential data for material design and durability assessment in ammonia-fueled marine engines. Full article
(This article belongs to the Special Issue Advances in Corrosion and Protection of Metallic Materials)
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17 pages, 4709 KB  
Article
Preparation of Particle-Reinforced Resin Using Highly Functional ZnO Particle Filler Driven by Supramolecular Interactions
by Haruka Nakagawa and Kohei Iritani
Materials 2025, 18(13), 2986; https://doi.org/10.3390/ma18132986 - 24 Jun 2025
Viewed by 640
Abstract
The surface modification of zinc oxide nanoparticles (ZnONPs) with organic compounds has been shown to improve their dispersibility. In this study, to develop a highly functional material, ZnONP modified with 6-amino-1-hexanol bearing both amino and hydroxyl functional groups was synthesized. Scanning electron microscopy–energy [...] Read more.
The surface modification of zinc oxide nanoparticles (ZnONPs) with organic compounds has been shown to improve their dispersibility. In this study, to develop a highly functional material, ZnONP modified with 6-amino-1-hexanol bearing both amino and hydroxyl functional groups was synthesized. Scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) analyses confirmed that functionalized ZnONP was successfully obtained by a hydrothermal synthetic method. The mechanical properties of composite films of polylactic acid (PLA) reinforced with the functionalized ZnONP were then evaluated. The composite containing functionalized ZnONP exhibited a higher maximum stress than that containing unmodified ZnONP. These ZnONP/polymer composites therefore show promise as novel high-performance materials. Full article
(This article belongs to the Special Issue Fabrication, Characteristics and Applications of Multifunctional Polymer Nanocomposites)
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22 pages, 3675 KB  
Article
Study and Evaluation of Equivalent Conductivities of [SiO(OH)3]− and [SiO2(OH)2]2− in NaOH-Na2SiO3-H2O Solutions at 277.85 K to 308.45 K
by Kai Yang, Guang Ye and Geert De Schutter
Materials 2025, 18(13), 2996; https://doi.org/10.3390/ma18132996 - 24 Jun 2025
Viewed by 613
Abstract
The equivalent conductivities of two aqueous silicate species, SiOOH3− and SiO2OH22−, are fundamental to understanding many physico-chemical phenomena of silicate materials in electrolyte solutions. These phenomena include diffusion, adsorption, and phase transformations. But [...] Read more.
The equivalent conductivities of two aqueous silicate species, SiOOH3− and SiO2OH22−, are fundamental to understanding many physico-chemical phenomena of silicate materials in electrolyte solutions. These phenomena include diffusion, adsorption, and phase transformations. But significant inconsistencies have been presented in published equivalent conductivities of the two silicate aqueous ions. Also, little work has so far been undertaken to discuss how aspects, such as temperature and solution composition, may influence electrolytic conductivity of silicate aqueous solutions. This work presents the equivalent conductivities of the two silicate species, measured with electrochemical impedance spectroscopy (EIS) from 277.85 K to 308.45 K. A conductivity model for mixed electrolytes of high alkaline was first established. This model was then verified with the electrolyte conductivities of NaOH-H2O solutions and NaOH-Na2CO3-H2O solutions. Next, the equivalent conductivities of SiOOH3− and SiO2OH22−, were calculated by solving the overdetermined equation groups for different temperatures, based on electrolyte conductivities of NaOH-Na2SiO3-H2O solutions. The accuracy of both calculations and measurements are examined in depth from various viewpoints. This work presents essential inputs for quantitatively understanding multiple physico-chemical properties of silicate materials in electrolyte solutions. Full article
(This article belongs to the Section Materials Chemistry)
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20 pages, 8742 KB  
Article
Directional Effect of Plasticity Ball Burnishing on Surface Finish, Microstructure, Residual Stress and Hardness of Laser Direct Energy Deposited Stellite 21 Alloy
by Mohammad Uddin, Joel Rech, Colin Hall and Thomas Schlaefer
Materials 2025, 18(13), 2971; https://doi.org/10.3390/ma18132971 - 23 Jun 2025
Cited by 2 | Viewed by 641
Abstract
This paper investigates the effect of plasticity ball burnishing on characteristics of surface integrity, residual stress and hardness of laser direct energy deposited (DEDed) Stellite 21 alloys, with a focus on the burnishing directional effect on surface and microstructural deformation. The results demonstrated [...] Read more.
This paper investigates the effect of plasticity ball burnishing on characteristics of surface integrity, residual stress and hardness of laser direct energy deposited (DEDed) Stellite 21 alloys, with a focus on the burnishing directional effect on surface and microstructural deformation. The results demonstrated that the burnishing improved surface finish, reducing Sa and Sz by 24% and 47%, respectively. The burnishing flattened and modified the cellular/columnar grains at a depth of 50 µm, with the most notable changes observed on the cross-sectional plane normal to the burnishing direction. Compared to the ground surface, the burnishing introduced higher and deeper compressive stresses along normal to the burnishing/grinding direction (−1341 MPa and 61 µm) as compared to that along the burnishing direction (−449 MPa and 56 µm). Likewise, the burnishing increased the full width at half maximum (FWHM) in the same fashion by broadening XRD peaks along normal to the burnishing direction. Due to higher grain modification and dislocation density, the burnishing has improved microhardness at a depth of 320 µm by 26% along normal to the burnishing direction. These findings demonstrate that the plasticity ball burnishing has a directional effect on plastic deformation and can be considered a plausible technique for tailored surface integrity, residual stress and hardness, which potentially improve the service performance of DEDed Stellite 21 alloy components. Full article
(This article belongs to the Special Issue Advances in Surface Engineering Technologies and Their Impact on Surface Integrity and Functional Performance of Additively Manufactured Parts)
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35 pages, 450 KB  
Review
An Overview of Biopolymer-Based Graphene Nanocomposites for Biotechnological Applications
by Roya Binaymotlagh, Laura Chronopoulou and Cleofe Palocci
Materials 2025, 18(13), 2978; https://doi.org/10.3390/ma18132978 - 23 Jun 2025
Cited by 5 | Viewed by 963
Abstract
Bio-nanocomposites represent an advanced class of materials that combine the unique properties of nanomaterials with biopolymers, enhancing mechanical, electrical and thermal properties while ensuring biodegradability, biocompatibility and sustainability. These materials are gaining increasing attention, particularly in biomedical applications, due to their ability to [...] Read more.
Bio-nanocomposites represent an advanced class of materials that combine the unique properties of nanomaterials with biopolymers, enhancing mechanical, electrical and thermal properties while ensuring biodegradability, biocompatibility and sustainability. These materials are gaining increasing attention, particularly in biomedical applications, due to their ability to interact with biological systems in ways that conventional materials cannot. Graphene and graphene oxide (GO), two of the most well-known nanocarbon-based materials, have garnered substantial interest in bio-nanocomposite research because of their extraordinary properties such as high surface area, excellent electrical conductivity, mechanical strength and biocompatibility. The integration of graphene-based nanomaterials within biopolymers, such as polysaccharides and proteins, forms a new class of bio-nanocomposites that can be tailored for a wide range of biological applications. This review explores the synthesis methods, properties and biotechnological applications of graphene-based bio-nanocomposites, with a particular focus on polysaccharide-based and protein-based composites. Emphasis is placed on the biotechnological potential of these materials, including drug delivery, tissue engineering, wound healing, antimicrobial activities and industrial food applications. Additionally, biodegradable polymers such as polylactic acid, hyaluronic acid and polyethylene glycol, which play a crucial role in biotechnological applications, will be discussed. Full article
(This article belongs to the Special Issue Emerging Trends and Innovations in Engineered Nanomaterials)
23 pages, 16208 KB  
Article
Low-Velocity Impact Response of Novel TPMS and Stochastic Lattice Cores of Sandwich Structures
by Alexandru Vasile, Dan Mihai Constantinescu, Iulian Constantin Coropețchi, Ștefan Sorohan and Andrei Ioan Indreș
Materials 2025, 18(12), 2889; https://doi.org/10.3390/ma18122889 - 18 Jun 2025
Viewed by 594
Abstract
This study explores the mechanical performance of triply periodic minimal surface (TPMS) and stochastic lattice structures subjected to low-velocity impact. Two structurally promising geometries—one TPMS-based and one stochastic—were tested and compared with the well-established gyroid. Specimens were fabricated using stereolithography (SLA) and subjected [...] Read more.
This study explores the mechanical performance of triply periodic minimal surface (TPMS) and stochastic lattice structures subjected to low-velocity impact. Two structurally promising geometries—one TPMS-based and one stochastic—were tested and compared with the well-established gyroid. Specimens were fabricated using stereolithography (SLA) and subjected to impact energies of 30 J and 40 J to assess the structural response and energy absorption capabilities. Experimental results show that the proposed TPMS structure exhibits higher impact forces compared with the gyroid, which are associated with significant impactor displacement and deep indentation. These samples demonstrated extensive damage, with cracking propagating through the entire core at higher energies, highlighting their susceptibility to structural failure despite their high initial strength. On the contrary, the stochastic structures allowed localized deformation in the impacted region, thus successfully avoiding catastrophic failure. The impact force efficiency was higher for both gyroid and stochastic geometries, with values ranging between 0.6 and 0.7, indicating effective energy absorption with reduced internal stress gradients. Furthermore, the evaluation of damping performance showed that most structures displayed high damping, as minimal energy was transferred back to the impactor. This work highlights the feasibility and functional versatility of TPMS and stochastic geometries for use in impact mitigation, vibration control, and related engineering applications. Full article
(This article belongs to the Special Issue Dynamic Behavior of Laminated and Sandwich Composite Materials)
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14 pages, 2266 KB  
Article
Solid-State Transformation (Stotal = 0, 1, and 2) in a Ni2+ Chelate with Two tert-Butyl 5-(p-Biphenylyl)-2-pyridyl Nitroxides
by Masataka Mitsui and Takayuki Ishida
Materials 2025, 18(12), 2793; https://doi.org/10.3390/ma18122793 - 13 Jun 2025
Viewed by 1327
Abstract
A novel S = 1/2 paramagnetic chelating ligand tert-butyl 5-(p-biphenylyl)-2-pyridyl nitroxide (bppyNO) and its S = 1 nickel(II) ion complex [Ni(bppyNO)2Br2] were synthesized. X-ray crystallography revealed a 2p–3d–2p heterospin triad, with half of the molecule being [...] Read more.
A novel S = 1/2 paramagnetic chelating ligand tert-butyl 5-(p-biphenylyl)-2-pyridyl nitroxide (bppyNO) and its S = 1 nickel(II) ion complex [Ni(bppyNO)2Br2] were synthesized. X-ray crystallography revealed a 2p–3d–2p heterospin triad, with half of the molecule being crystallographically independent. A relatively planar chelate geometry with the torsion angle ϕ(Ni-O-N-C2py) = −10.6(5)° at 300 K becomes significantly out-of-plane distorted with ϕ = −46.9(8) and 26.1(11)° at 90 K accompanied by disorder at the oxygen site. The torsion angle changes, Δϕ = 36° and 37°, are among the largest reported for related compounds. Magnetic measurements indicate gradual and incomplete spin transition-like behavior around 143(2) K. A three-state model involving an intermediate-spin (Stotal = 1) state is proposed to explain non-zero χmT plateau in a low-temperature region. Density functional theory calculations using the determined structures support the proposed mechanism. Furthermore, geometry optimizations assuming Stotal = 0, 1, and 2 are in good agreement with the present model. Full article
(This article belongs to the Special Issue From Molecular to Supramolecular Materials)
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38 pages, 6561 KB  
Review
Emerging Trends in Thermo-Optic and Electro-Optic Materials for Tunable Photonic Devices
by Muhammad A. Butt
Materials 2025, 18(12), 2782; https://doi.org/10.3390/ma18122782 - 13 Jun 2025
Cited by 5 | Viewed by 3184
Abstract
Tunable photonic devices are increasingly pivotal in modern optical systems, enabling the dynamic control over light propagation, modulation, and filtering. This review systematically explores two prominent classes of materials, thermo-optic and electro-optic, for their roles in such tunable devices. Thermo-optic materials utilize refractive [...] Read more.
Tunable photonic devices are increasingly pivotal in modern optical systems, enabling the dynamic control over light propagation, modulation, and filtering. This review systematically explores two prominent classes of materials, thermo-optic and electro-optic, for their roles in such tunable devices. Thermo-optic materials utilize refractive index changes induced by temperature variations, offering simple implementation and broad material compatibility, although often at the cost of slower response times. In contrast, electro-optic materials, particularly those exhibiting the Pockels and Kerr effects, enable rapid and precise refractive index modulation under electric fields, making them suitable for high-speed applications. The paper discusses the underlying physical mechanisms, material properties, and typical figures of merit for each category, alongside recent advancements in organic, polymeric, and inorganic systems. Furthermore, integrated photonic platforms and emerging hybrid material systems are highlighted for their potential to enhance performance and scalability. By evaluating the tradeoffs in speed, power consumption, and integration complexity, this review identifies key trends and future directions for deploying thermo-optic and electro-optic materials in the next generation tunable photonic devices. Full article
(This article belongs to the Section Optical and Photonic Materials)
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23 pages, 4562 KB  
Review
Biomimetic Superhydrophobic Surfaces: From Nature to Application
by Yingke Wang, Jiashun Li, Haoran Song, Fenxiang Wang, Xuan Su, Donghe Zhang and Jie Xu
Materials 2025, 18(12), 2772; https://doi.org/10.3390/ma18122772 - 12 Jun 2025
Cited by 4 | Viewed by 1719
Abstract
Research on bionic superhydrophobic surfaces draws inspiration from the microstructures and wetting mechanisms of natural organisms such as lotus leaves, water striders, and butterfly wings, offering innovative approaches for developing artificial functional surfaces. By synergistically combining micro/nano hierarchical structures with low surface energy [...] Read more.
Research on bionic superhydrophobic surfaces draws inspiration from the microstructures and wetting mechanisms of natural organisms such as lotus leaves, water striders, and butterfly wings, offering innovative approaches for developing artificial functional surfaces. By synergistically combining micro/nano hierarchical structures with low surface energy chemical modifications, researchers have devised various fabrication strategies—including laser etching, sol-gel processes, electrochemical deposition, and molecular self-assembly—to achieve superhydrophobic surfaces characterized by contact angles exceeding 150° and sliding angles below 5°. These technologies have found widespread applications in self-cleaning architectural coatings, efficient oil–water separation membranes, anti-icing materials for aviation, and anti-biofouling medical devices. This article begins by examining natural organisms exhibiting superhydrophobic properties, elucidating the principles underlying their surface structures and the wetting states of droplets on solid surfaces. Subsequently, it categorizes and highlights key fabrication methods and application domains of superhydrophobic surfaces, providing an in-depth and comprehensive discussion. Full article
(This article belongs to the Special Issue Superhydrophobic Coating Materials: Preparation, Strategy and Application)
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16 pages, 18981 KB  
Article
Dual-Broadband Topological Photonic Crystal Edge State Based on Liquid Crystal Tunability
by Jinying Zhang, Bingnan Wang, Jiacheng Wang, Xinye Wang and Yexiaotong Zhang
Materials 2025, 18(12), 2778; https://doi.org/10.3390/ma18122778 - 12 Jun 2025
Viewed by 686
Abstract
The rapid advancements in optical communication and sensing technologies have significantly increased the demand for advanced tunable spectral systems. This study presents a dual-band terahertz transmission and manipulation approach by leveraging the topologically protected properties of valley-topological photonic crystal edge states. The designed [...] Read more.
The rapid advancements in optical communication and sensing technologies have significantly increased the demand for advanced tunable spectral systems. This study presents a dual-band terahertz transmission and manipulation approach by leveraging the topologically protected properties of valley-topological photonic crystal edge states. The designed structure facilitates the excitation of the K valley within the range of 0.851–0.934 THz and the K′ valley from 1.604 to 1.686 THz, while also demonstrating anomalous refraction and birefringence. The calculated emission angles, derived through momentum matching, enable transitions between single-wave and dual-wave emissions and allow for precise angle control. The introduction of the liquid crystal material NJU-LDn-4 enables continuous tuning of the dual-band spectral range under a varying electric field, broadening the operating frequency bands to the ranges of 0.757–0.996 THz and 1.426–1.798 THz, respectively. These findings suggest promising applications in tunable filter design, optical communication, photonic computing, optical sensing, and high-resolution imaging, particularly in novel optical devices requiring precise control over spectral characteristics and light propagation. Full article
(This article belongs to the Special Issue Terahertz Materials and Technologies in Materials Science)
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16 pages, 3519 KB  
Article
Flexible Moisture–Electric Generator Based on Vertically Graded GO–rGO/Ag Films
by Shujun Wang, Geng Li, Jiayue Wen, Jiayun Feng, He Zhang and Yanhong Tian
Materials 2025, 18(12), 2766; https://doi.org/10.3390/ma18122766 - 12 Jun 2025
Viewed by 1496
Abstract
Moisture–electricity generators (MEGs) hold great promise for green energy conversion. However, existing devices focus on the need for complex gradient distribution treatments and the improvement in output voltage, overlooking the important role of the graphene oxide (GO) oxidation degree and the response time [...] Read more.
Moisture–electricity generators (MEGs) hold great promise for green energy conversion. However, existing devices focus on the need for complex gradient distribution treatments and the improvement in output voltage, overlooking the important role of the graphene oxide (GO) oxidation degree and the response time and recovery time in practical application. In this work, we develop printed MEGs by synthesizing reduced graphene oxide/silver nanoparticle (rGO/Ag) composites and controlling the GO oxidation degree. The rGO/Ag layer serves as a functional component that enhances cycling stability and shortens the recovery time. Additionally, compared to conventional rigid-structure devices, these flexible MEGs can be produced by inkjet printing and drop-casting techniques. A 1 cm2 MEG can generate a voltage of up to 60 mV within 2.4 s. Notably, higher output voltages can be easily achieved by connecting multiple MEG units in series, with 10 units producing 200 mV even under low relative humidity (RH). This work presents a low-cost, highly flexible, lightweight, and scalable power generator, paving the way for broader applications of GO and further advancement of MEG technology in wearable electronics, respiratory monitoring, and Internet of Things applications. Full article
(This article belongs to the Section Materials Chemistry)
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24 pages, 1374 KB  
Article
Identification of Material Constants for Composite Materials Using a Sensitivity-Based Multi-Level Optimization Method
by Ching Wen Liu and Tai Yan Kam
Materials 2025, 18(12), 2737; https://doi.org/10.3390/ma18122737 - 11 Jun 2025
Viewed by 556
Abstract
Composite materials have been widely used to fabricate highly reliable composite structures. Since the material constants of the composite structures are important parameters for the reliability assessment of the structures, it is thus desired to have an efficient and effective technique to determine [...] Read more.
Composite materials have been widely used to fabricate highly reliable composite structures. Since the material constants of the composite structures are important parameters for the reliability assessment of the structures, it is thus desired to have an efficient and effective technique to determine the actual material constants of the constituent materials. In this paper, a novel sensitivity-based multi-level optimization method, which is composed of several level-wise optimization stages, is presented to identify the actual material constants of structures using measured natural frequencies. In the proposed method, the natural frequency sensitivity information for a structure is used to establish the objective functions and conduct the selection of appropriate design variables at different optimization levels. In each level-wise optimization, the number of design variables is properly reduced to simplify the optimization so that the solution can be attained easily and efficiently. The solutions of the level-wise optimization problems produce the expected values and coefficients of variation for the estimates of the material constants. An acceptance criterion established on the basis of the coefficient of variation has been used to assist the identification of the actual material constants. The accuracy verification and applications of the proposed method have been demonstrated by means of several numerical and experimental examples on the identification of material constants for composite plates with different lamination arrangements. Full article
(This article belongs to the Special Issue Experimental Testing, Manufacturing and Numerical Modelling of Composite and Sandwich Structures (Second Edition))
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18 pages, 7993 KB  
Article
The Influence of Cr2N Addition and Ni/Mn Ratio Variation on Mechanical and Corrosion Properties of HIP-Sintered 316L Stainless Steel
by Minsu Lee, Hohyeong Kim, Seok-Won Son and Jinho Ahn
Materials 2025, 18(12), 2722; https://doi.org/10.3390/ma18122722 - 10 Jun 2025
Cited by 1 | Viewed by 785
Abstract
316L stainless steel is widely employed in various industrial sectors, including shipbuilding, offshore plants, high-temperature/high-pressure (HTHP) piping systems, and hydrogen infrastructure, due to its excellent mechanical stability, superior corrosion resistance, and robust resistance to hydrogen embrittlement. This study presents 316L stainless steel alloys [...] Read more.
316L stainless steel is widely employed in various industrial sectors, including shipbuilding, offshore plants, high-temperature/high-pressure (HTHP) piping systems, and hydrogen infrastructure, due to its excellent mechanical stability, superior corrosion resistance, and robust resistance to hydrogen embrittlement. This study presents 316L stainless steel alloys fabricated via hot isostatic pressing (HIP), conducted at 1300 °C and 100 MPa for 2 h, incorporating Cr2N powder and an optimized Ni/Mn ratio based on the nickel equivalent (Ni_eq). During HIP, Cr2N decomposition yielded a uniformly refined, dense austenitic microstructure, with enhanced corrosion resistance and mechanical performance. Corrosion resistance was evaluated by potentiodynamic polarization in 3.5 wt.% NaCl after 1 h of OCP stabilization, using a scan range of −0.25 V to +1.5 V (Ag/AgCl) at 1 mV/s. Optimization of the Ni/Mn ratio effectively improved the pitting corrosion resistance and mechanical strength. It is cost-effective to partially substitute Ni with Mn. Of the various alloys, C13Ni-N exhibited significantly enhanced hardness (~30% increase from 158.3 to 206.2 HV) attributable to nitrogen-induced solid solution strengthening. E11Ni-HM exhibited the highest pitting corrosion resistance given the superior PREN value (31.36). In summary, the incorporation of Cr2N and adjustment of the Ni/Mn ratio effectively improved the performance of 316L stainless steel alloys. Notably, alloy E11Ni-HM demonstrated a low corrosion current density of 0.131 μA/cm2, indicating superior corrosion resistance. These findings offer valuable insights for developing cost-efficient, mechanically robust corrosion-resistant materials for hydrogen-related applications. Further research will evaluate alloy resistance to hydrogen embrittlement and investigate long-term material stability. Full article
(This article belongs to the Special Issue Innovative Approaches to Enhancing Corrosion Resistance in Stainless Steel and Other Corrosion-Resistant Alloys)
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19 pages, 1500 KB  
Article
Green Design and Life Cycle Assessment of Novel Thiophene-Based Surfactants to Balance Their Synthesis Performance and Environmental Impact
by Catalina Stoica, Alina Roxana Banciu, Hisham Idriss, Justin Z. Lian, Anca-Maria Patrascu, Stefano Cucurachi, Sébastien Richeter, Sébastien Clément and Mihai Nita-Lazar
Materials 2025, 18(12), 2701; https://doi.org/10.3390/ma18122701 - 8 Jun 2025
Viewed by 1358
Abstract
Continuous human population growth, industrialization, and technical progress have increased the demand for a new design and synthesis of chemical compounds. Developing eco-friendly chemical compounds has been a priority for fostering a sustainable and healthy environment, which is directly linked to human well-being. [...] Read more.
Continuous human population growth, industrialization, and technical progress have increased the demand for a new design and synthesis of chemical compounds. Developing eco-friendly chemical compounds has been a priority for fostering a sustainable and healthy environment, which is directly linked to human well-being. In this context, green chemistry and circular economy principles have been applied to generate valuable new chemicals, such as surfactants, with high market value. Surfactants play a crucial role in various products for both domestic and industrial applications, leading to their large-scale production a diverse array of chemical structures. However, the advantages of their use must be balanced against their negative environmental impact as pollutants. Thus, there is an increasing demand for the development of new eco-friendly surfactants. Additionally, life cycle assessment (LCA) studies of new surfactants are essential for evaluating their environmental impact, enhancing energy efficiency and facilitating the transition toward sustainable energy resources. In this work, we present the chemical synthesis of oligomeric and polymeric thiophene-based surfactants with potential applications in biosensors, organic transistors, and various other fields. The newly synthesized oligomeric and polymeric thiophene-based surfactants demonstrated medium-to-high biodegradation potential and showed no significant ecotoxicological effects on bacterial communities. However, the LCA of their synthesis revealed a negative impact on the environment and human health, particularly concerning polymeric thiophene-based surfactants. The LCA identified specific chemical steps that could be optimized to develop a new generation of eco-friendly surfactants. Full article
(This article belongs to the Special Issue Advanced Nanomaterials for Biological, Medical and Environmental Applications (3rd Edition))
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40 pages, 4806 KB  
Review
On the Origin of Thermally Enhanced Upconversion Luminescence in Lanthanide-Doped Nanosized Fluoride Phosphors
by Shirun Yan
Materials 2025, 18(12), 2700; https://doi.org/10.3390/ma18122700 - 8 Jun 2025
Viewed by 1130
Abstract
Thermally enhanced upconversion luminescence (UCL), also known as negative thermal quenching of UCL, denotes a continuous increase in the UCL emission intensity of a particular phosphor with a rising temperature. In recent years, the thermal enhancement of UCL has attracted extensive research attention, [...] Read more.
Thermally enhanced upconversion luminescence (UCL), also known as negative thermal quenching of UCL, denotes a continuous increase in the UCL emission intensity of a particular phosphor with a rising temperature. In recent years, the thermal enhancement of UCL has attracted extensive research attention, with numerous reports detailing this effect in phosphors characterized by varying particle sizes, architectures, and compositions. Several hypotheses have been formulated to explain the underlying mechanisms driving this thermal enhancement. This paper rigorously examines thermally enhanced UCL in fluoride nanoparticles by addressing two key questions: (1) Is the thermal enhancement of UCL an intrinsic feature of these nanoparticles? (2) Can the proposed mechanisms explaining this enhancement be unequivocally supported by the existing literature? Upon analyzing a compilation of experimental observations alongside the concurrent phenomena occurred during spectral measurements, it is postulated that thermally enhanced UCL intensity is likely a consequence of multiple extrinsic factors operating simultaneously at elevated temperatures, rather than being an intrinsic property of nanoparticles. These factors include moisture desorption, laser-induced local heating, and lattice thermal expansion. The size-dependent properties of nanoparticles, such as surface-to-volume ratio, thermal expansion coefficient, and quantum yield, are the fundamental reasons for the size-dependent thermal enhancement factor of UCL. Temperature-dependent emission spectral intensity is not a dependable indicator for assessing the thermal quenching properties of phosphors. This is because it is influenced not only by the phosphor’s quantum yield, but also by various extrinsic factors at high temperatures. The nonlinear nature of UCL further magnifies the impact of these extrinsic factors. Full article
(This article belongs to the Special Issue Advances in Optical and Photonic Materials)
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13 pages, 3459 KB  
Article
Incremental Forming of Natural Fiber-Reinforced Polypropylene Composites: Considerations on Formability Limits and Energy Consumption
by Antonio Formisano, Dario De Fazio, Giuseppe Irace and Massimo Durante
Materials 2025, 18(12), 2688; https://doi.org/10.3390/ma18122688 - 7 Jun 2025
Viewed by 806
Abstract
Incremental sheet forming originated as an excellent alternative to conventional forming techniques for incrementally deforming flat metal sheets into complex three-dimensional profiles. Recently, its use has been extended to polymers and composites. Among these, the use of natural fiber-reinforced composites is increasing considerably [...] Read more.
Incremental sheet forming originated as an excellent alternative to conventional forming techniques for incrementally deforming flat metal sheets into complex three-dimensional profiles. Recently, its use has been extended to polymers and composites. Among these, the use of natural fiber-reinforced composites is increasing considerably compared to synthetic fiber-reinforced composites, due to the availability and unique properties of natural fibers in polymer applications. One of the dominant thermoplastics used as a matrix is polypropylene. This experimental study focuses on the incremental forming of natural fiber-reinforced polypropylene composites. Cones and spherical caps were manufactured from composite laminates of polypropylene reinforced with hemp and flax long-fiber fabrics. The formability limits, observed through failures and defects, as well as the forming forces, power, and energy consumption, were investigated to examine the feasibility of incremental forming applied to these composite materials; based on the results obtained, it is possible to say that the process can manufacture components with not very high wall angles but under low load conditions and allowing to limit the energy impact. Full article
(This article belongs to the Special Issue Manufacturing and Recycling of Natural Fiber-Reinforced Composites)
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19 pages, 3564 KB  
Article
Differential lncRNA Expression in Undifferentiated and Differentiated LUHMES Cells Following Co-Exposure to Silver Nanoparticles and Nanoplastic
by Kamil Brzóska, Malwina Czerwińska and Marcin Kruszewski
Materials 2025, 18(12), 2690; https://doi.org/10.3390/ma18122690 - 7 Jun 2025
Viewed by 703
Abstract
Human exposure to micro- and nanoplastic (MNP) has become an increasing concern due to its accumulation in the environment and human body. In the human organism, MNP accumulates in various tissues, including the central nervous system, where it is associated which neurotoxic effects. [...] Read more.
Human exposure to micro- and nanoplastic (MNP) has become an increasing concern due to its accumulation in the environment and human body. In the human organism, MNP accumulates in various tissues, including the central nervous system, where it is associated which neurotoxic effects. Beyond its inherent toxicity, MNP also acts as a carrier for various chemical contaminants, including metals. Consequently, recent studies emphasize the importance of the evaluation of co-exposure scenarios involving MNP and other types of nanoparticles. In this study, we investigated effects of co-exposure to 20 nm silver nanoparticles (AgNPs) and 20 nm polystyrene nanoparticles (PSNPs) on cell viability and the expression of inflammation-related long non-coding RNAs (lncRNAs) in undifferentiated and differentiated Lund human mesencephalic (LUHMES) cells. While PSNPs alone did not significantly affect cell viability or lncRNA expression, AgNPs markedly reduced viability and deregulated lncRNA expression in both cell types. Notably, in differentiated cells, co-exposure to AgNPs and high concentrations of PSNPs led to a significantly greater reduction in viability compared to AgNPs alone, suggesting a synergistic effect. At the molecular level, both synergistic and antagonistic interactions between AgNPs and PSNPs were observed in the regulation of lncRNA expression, depending on the cell differentiation status. These findings highlight the complex biological interactions between AgNPs and PSNPs and emphasize the importance of considering nanoparticle co-exposures in toxicological evaluations, as combined exposures may significantly affect cellular and molecular responses. Full article
(This article belongs to the Special Issue New Insight into Design and Properties of Nanomaterials (Third Edition))
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24 pages, 7912 KB  
Article
Corrosion Performance and Post-Corrosion Evolution of Tensile Behaviors in Rebar Reinforced Ultra-High Performance Concrete
by Yuchen Zhang, Sumei Zhang, Xianzhi Luo and Chaofan Wang
Materials 2025, 18(11), 2661; https://doi.org/10.3390/ma18112661 - 5 Jun 2025
Viewed by 741
Abstract
The application of rebar reinforced ultra-high-performance concrete (R-UHPC) has been increasingly adopted in engineering structures due to its exceptional mechanical performance and durability characteristics. Nevertheless, when subjected to combined saline and stray current conditions, R-UHPC remains vulnerable to severe corrosion degradation. This investigation [...] Read more.
The application of rebar reinforced ultra-high-performance concrete (R-UHPC) has been increasingly adopted in engineering structures due to its exceptional mechanical performance and durability characteristics. Nevertheless, when subjected to combined saline and stray current conditions, R-UHPC remains vulnerable to severe corrosion degradation. This investigation examined the corrosion performance and tensile behavior evolution of R-UHPC containing 2.0 vol% copper-coated steel fiber content and HRB400 steel rebar with a reinforcement ratio of 3.1%. The accelerated corrosion process was induced through an impressed current method, followed by direct tensile tests at varying exposure periods. The findings revealed that the embedding of rebar in UHPC led to the formation of fiber-to-rebar (F-R) conductive pathways, generating radial cracks besides laminar cracks. The bonding between rebar and UHPC degraded as corrosion progressed, leading to the loss of characteristic multiple-cracking behavior of R-UHPC in tension. Meanwhile, R-UHPC load-bearing capacity, transitioning from gradual to accelerated deterioration phases with prolonged corrosion, aligns with steel fibers temporally. During the initial 4 days of corrosion, the specimens displayed surface-level corrosion features with negligible steel fiber loss, showing less than 4.0% reduction in ultimate bearing capacity. At 8 days of corrosion, the steel fiber decreased by 22.6%, accompanied by an 18.3% reduction in bearing capacity. By 16 days of corrosion, the steel fiber loss reached 41.5%, with a corresponding bearing capacity reduction of 29.1%. During the corrosion process, corrosion cracks and load-bearing degradation in R-UHPC could be indicated by the ultrasonic damage factor. Full article
(This article belongs to the Special Issue Corrosion of Materials: Evaluation, Testing, Protection, and Failure Analysis, Second Edition)
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24 pages, 5160 KB  
Review
Chiral Perovskite Single Crystals: Toward Promising Design and Application
by Lin Wang, Jie Ren and Hanying Li
Materials 2025, 18(11), 2635; https://doi.org/10.3390/ma18112635 - 4 Jun 2025
Viewed by 1553
Abstract
Organic–inorganic hybrid halide perovskites have emerged as promising optoelectronic materials owing to their exceptional optoelectronic properties and versatile crystal structures. The introduction of chiral organic ligands into perovskite frameworks, breaking the inversion symmetry of the structure, has attracted significant attention toward chiral perovskites. [...] Read more.
Organic–inorganic hybrid halide perovskites have emerged as promising optoelectronic materials owing to their exceptional optoelectronic properties and versatile crystal structures. The introduction of chiral organic ligands into perovskite frameworks, breaking the inversion symmetry of the structure, has attracted significant attention toward chiral perovskites. Herein, the recent advances in various synthesis strategies for chiral perovskite single crystals (SCs) are systematically demonstrated. Then, we elucidate an in-depth understanding of the chirality transfer mechanisms from chiral organic ligands to perovskite inorganic frameworks. Furthermore, representative examples of chiral perovskite SC-based applications are comprehensively discussed, including circularly polarized light (CPL) photodetection, nonlinear optical (NLO) responses, and other emerging chirality-dependent applications. In the end, an outlook for future challenges and research opportunities is provided, highlighting the transformative potential of chiral perovskites in next-generation optoelectronic devices. Full article
(This article belongs to the Special Issue Halide Perovskite Crystal Materials and Optoelectronic Devices)
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28 pages, 3203 KB  
Article
From Pollutant Removal to Renewable Energy: MoS2-Enhanced P25-Graphene Photocatalysts for Malathion Degradation and H2 Evolution
by Cristian Martínez-Perales, Abniel Machín, Pedro J. Berríos-Rolón, Paola Sampayo, Enrique Nieves, Loraine Soto-Vázquez, Edgard Resto, Carmen Morant, José Ducongé, María C. Cotto and Francisco Márquez
Materials 2025, 18(11), 2602; https://doi.org/10.3390/ma18112602 - 3 Jun 2025
Viewed by 2335
Abstract
The widespread presence of pesticides—especially malathion—in aquatic environments presents a major obstacle to conventional remediation strategies, while the ongoing global energy crisis underscores the urgency of developing renewable energy sources such as hydrogen. In this context, photocatalytic water splitting emerges as a promising [...] Read more.
The widespread presence of pesticides—especially malathion—in aquatic environments presents a major obstacle to conventional remediation strategies, while the ongoing global energy crisis underscores the urgency of developing renewable energy sources such as hydrogen. In this context, photocatalytic water splitting emerges as a promising approach, though its practical application remains limited by poor charge carrier dynamics and insufficient visible-light utilization. Herein, we report the design and evaluation of a series of TiO2-based ternary nanocomposites comprising commercial P25 TiO2, reduced graphene oxide (rGO), and molybdenum disulfide (MoS2), with MoS2 loadings ranging from 1% to 10% by weight. The photocatalysts were fabricated via a two-step method: hydrothermal integration of rGO into P25 followed by solution-phase self-assembly of exfoliated MoS2 nanosheets. The composites were systematically characterized using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. Photocatalytic activity was assessed through two key applications: the degradation of malathion (20 mg/L) under simulated solar irradiation and hydrogen evolution from water in the presence of sacrificial agents. Quantification was performed using UV-Vis spectroscopy, gas chromatography–mass spectrometry (GC-MS), and thermal conductivity detection (GC-TCD). Results showed that the integration of rGO significantly enhanced surface area and charge mobility, while MoS2 served as an effective co-catalyst, promoting interfacial charge separation and acting as an active site for hydrogen evolution. Nearly complete malathion degradation (~100%) was achieved within two hours, and hydrogen production reached up to 6000 µmol g−1 h−1 under optimal MoS2 loading. Notably, photocatalytic performance declined with higher MoS2 content due to recombination effects. Overall, this work demonstrates the synergistic enhancement provided by rGO and MoS2 in a stable P25-based system and underscores the viability of such ternary nanocomposites for addressing both environmental remediation and sustainable energy conversion challenges. Full article
(This article belongs to the Special Issue Catalysis: Where We Are and Where We Go)
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15 pages, 4214 KB  
Article
Synthesis of Porous Polymers by Nucleophilic Substitution Reaction of Polyamines and Monochlorotriazinyl-β-Cyclodextrin and Application to Dye Adsorption
by Naofumi Naga, Risa Hiura and Tamaki Nakano
Materials 2025, 18(11), 2588; https://doi.org/10.3390/ma18112588 - 1 Jun 2025
Viewed by 768
Abstract
Network polymers with β-cyclodextrin moieties were prepared by nucleophilic substitution reactions between polyamines, linear polyethyleneimine (LPEI), polyallylamine (PAA), (ε-poly-L-lysine) (EPL), and monochlorotriazinyl-β-cyclodextrin (MCTCD) in methanol/water mixed solvent or water. The reactions under conditions of high material concentration (30 wt%) and a feed ratio [...] Read more.
Network polymers with β-cyclodextrin moieties were prepared by nucleophilic substitution reactions between polyamines, linear polyethyleneimine (LPEI), polyallylamine (PAA), (ε-poly-L-lysine) (EPL), and monochlorotriazinyl-β-cyclodextrin (MCTCD) in methanol/water mixed solvent or water. The reactions under conditions of high material concentration (30 wt%) and a feed ratio of [MCT]/[NH] = 0.5 (mol/mol) successfully yield porous polymers via reaction-induced phase separation. The molecular structure of the polyamines and reaction conditions strongly affected the morphology of the resulting porous polymers. The porous polymers were composed of connected particles, gathered (slightly connected) particles, and/or disordered bulky structures, with sizes of 10−9 m–10−8 m. An increase in the molecular weight of LPEI and PAA and the feed molar ratio of [MCT]/[NH] tended to decrease the particle size. Young’s moduli of the LPEI-MCTCD and PAA-MCTCD porous polymers increased with an increase in bulk density, which was derived from small particle sizes. The wide particle size distribution and disordered structure caused collapse by the compression under 50 N of pressure. An LPEI-MCTCD adsorbed methyl orange, methylene blue, and phenolphthalein through ionic interactions, π–π interaction, and/or β-cyclodextrin inclusion. Full article
(This article belongs to the Special Issue An Overview of Highly Porous Adsorbent Materials: Synthesis, Properties and Applications)
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32 pages, 7994 KB  
Review
Recent Advancements in Smart Hydrogel-Based Materials in Cartilage Tissue Engineering
by Jakob Naranđa, Matej Bračič, Uroš Maver and Teodor Trojner
Materials 2025, 18(11), 2576; https://doi.org/10.3390/ma18112576 - 31 May 2025
Cited by 3 | Viewed by 4186
Abstract
Cartilage tissue engineering (CTE) is an advancing field focused on developing biomimetic scaffolds to overcome cartilage’s inherently limited self-repair capacity. Smart hydrogels (SHs) have gained prominence among the various scaffold materials due to their ability to modulate cellular behavior through tunable mechanical and [...] Read more.
Cartilage tissue engineering (CTE) is an advancing field focused on developing biomimetic scaffolds to overcome cartilage’s inherently limited self-repair capacity. Smart hydrogels (SHs) have gained prominence among the various scaffold materials due to their ability to modulate cellular behavior through tunable mechanical and biochemical properties. These hydrogels respond dynamically to external stimuli, offering precise control over biological processes and facilitating targeted tissue regeneration. Recent advances in fabrication technologies have enabled the design of SHs with sophisticated architecture, improved mechanical strength, and enhanced biointegration. Key features such as injectability, controlled biodegradability, and stimulus-dependent release of biomolecules make them particularly suitable for regenerative applications. The incorporation of nanoparticles further improves mechanical performance and delivery capability. In addition, shape memory and self-healing properties contribute to the scaffolds’ resilience and adaptability in dynamic physiological environments. An emerging innovation in this area is integrating artificial intelligence (AI) and omics-based approaches that enable high-resolution profiling of cellular responses to engineered hydrogels. These data-driven tools support the rational design and optimization of hydrogel systems and allow the development of more effective and personalized scaffolds. The convergence of smart hydrogel technologies with omics insights represents a transformative step in regenerative medicine and offers promising strategies for restoring cartilage function. Full article
(This article belongs to the Section Biomaterials)
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16 pages, 4519 KB  
Article
A High-Gain and Dual-Band Compact Metasurface Antenna for Wi-Fi/WLAN Applications
by Yunhao Zhou and Yilin Zheng
Materials 2025, 18(11), 2538; https://doi.org/10.3390/ma18112538 - 28 May 2025
Viewed by 1095
Abstract
With the rapid development of Wi-Fi 6/6E and dual-band wireless systems, there is an increasing demand for compact antennas with balanced high-gain performance across both 2.4 GHz and 5 GHz bands. However, most existing dual-band metasurface antennas face challenges in uneven gain distribution [...] Read more.
With the rapid development of Wi-Fi 6/6E and dual-band wireless systems, there is an increasing demand for compact antennas with balanced high-gain performance across both 2.4 GHz and 5 GHz bands. However, most existing dual-band metasurface antennas face challenges in uneven gain distribution between lower/higher-frequency bands and structural miniaturization. This paper proposes a high-gain dual-band metasurface antenna based on an artificial magnetic conductor (AMC) array, which has a significant advantage in miniaturization and improving antenna performance. Two types of dual-band AMC structures are applied to design the metasurface antenna. The optimal antenna with dual-slot AMC array operates in the 2.42–2.48 GHz and 5.16–5.53 GHz frequency bands, with a 25% size reduction compared to the reference dual-band U-slot antenna. Meanwhile, high gains of 7.65 dBi and 8 dBi are achieved at 2.4 GHz and 5 GHz frequency bands, respectively. Experimental results verify stable radiation gains across the operation bands, where the total efficiency remains above 90%, agreeing well with the simulation results. This research provides an effective strategy for high-gain and dual-band metasurface antennas, offering a promising solution for integrated modern wireless systems such as Wi-Fi 6, Bluetooth, and MIMO technology. Full article
(This article belongs to the Special Issue Metamaterials and Metasurfaces: From Materials to Applications)
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19 pages, 20645 KB  
Article
Tensile Deformation and Transverse Strain Behavior of Carbon Black-UHMWPE Composites
by Peder C. Solberg and Douglas W. Van Citters
Materials 2025, 18(11), 2542; https://doi.org/10.3390/ma18112542 - 28 May 2025
Viewed by 538
Abstract
Electrically conductive composites of ultra-high molecular weight polyethylene (UHMWPE) may be of interest as strain sensors for event detection in high-strain scenarios, with potential applications in ballistics or orthopedics. In this study, geometric deformations of electrically conductive composites of UHMWPE were quantified for [...] Read more.
Electrically conductive composites of ultra-high molecular weight polyethylene (UHMWPE) may be of interest as strain sensors for event detection in high-strain scenarios, with potential applications in ballistics or orthopedics. In this study, geometric deformations of electrically conductive composites of UHMWPE were quantified for large plastic strains via physical measurements. These measurements were compared to neat (non-composite) control materials, and to geometrical behaviors predicted under volume conservation assumptions. This study found that material geometry remained close to that predicted by volume conservation at low-to-moderate plastic strains, with differences exceeding 5% only above 100% nominal strain. Materials with higher filler loading experienced a greater increase in measured volume than neat controls, particularly at higher strains. The results suggest that this difference could be due in part to volumetric opening in the composite materials with high filler loading. Finally, necking behavior was observed and quantified in this study, presenting another effect that should be taken into account for future work characterizing the electrical behavior of these materials under large plastic deformations. The results of this study thus lay the foundation for further characterization of these electrically-conductive composites, and to determine their intrinsic electrical properties as a function of strain in particular. Full article
(This article belongs to the Section Carbon Materials)
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10 pages, 5002 KB  
Communication
Computational Investigation of an All-sp3 Hybridized Superstable Carbon Allotrope with Large Band Gap
by Xiaoshi Ju, Kun Bu, Chunxiao Zhang and Yuping Sun
Materials 2025, 18(11), 2533; https://doi.org/10.3390/ma18112533 - 28 May 2025
Cited by 1 | Viewed by 715
Abstract
Carbon is one of nature’s basic elements, hosting a tremendous number of allotropes benefiting from its capacity to generate sp, sp2, and sp3 hybridized carbon–carbon bonds. The exploration of novel carbon architectures has remained a pivotal [...] Read more.
Carbon is one of nature’s basic elements, hosting a tremendous number of allotropes benefiting from its capacity to generate sp, sp2, and sp3 hybridized carbon–carbon bonds. The exploration of novel carbon architectures has remained a pivotal focus in the fields of condensed matter physics and materials science for an extended period. In this paper, we, by using first-principles calculation, carry on a detailed investigation an an all-sp3 hybridized carbon structure in a 20-atom tetragonal unit cell with P43212 symmetry (D48, space group No. 96), and call it T20 carbon. The equilibrium energy of T20 carbon is −8.881 eV/atom, only 0.137 eV/atom higher than that of diamond, indicating that T20 is a superstable carbon structure. T20 is also a superhard carbon structure with a large Vicker’s hardness about 83.5 GPa. The dynamical stability of T20 was verified by means of phonon band spectrum calculations. Meanwhile, its thermal stability up to 1000 K was verified via ab initio molecular dynamics simulations. T20 is an indirect band-gap insulator with approximately 5.80 eV of a band gap. This value is obviously greater than the value in the diamond (5.36 eV). Moreover, the simulated X-ray diffraction pattern of T20 displays a remarkable match with the experimental data found in the milled fullerene soot, evidencing that T20 may be a potential modification discovered in this experimental work. Our work has given a systematical understanding on an all-sp3 hybridized superstable and superhard carbon allotrope with large band gap and provided a very competitive explanation for previous experimental data, which will also provide guidance for upcoming studies in theory and experiment. Full article
(This article belongs to the Section Materials Chemistry)
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16 pages, 9841 KB  
Article
Photochromic Sensors for Paper Marking
by Elżbieta Sąsiadek-Andrzejczak, Malwina Jaszczak-Kuligowska, Mariusz Dudek, Adam K. Puszkarz and Marek Kozicki
Materials 2025, 18(11), 2501; https://doi.org/10.3390/ma18112501 - 26 May 2025
Viewed by 679
Abstract
This study presents UV radiation sensors for use as paper marking. The sensors turn pink under exposure to UVA radiation and the color change is reversible. Additionally, a UV radiation retarder was applied to the sensor to delay the reaction and weaken the [...] Read more.
This study presents UV radiation sensors for use as paper marking. The sensors turn pink under exposure to UVA radiation and the color change is reversible. Additionally, a UV radiation retarder was applied to the sensor to delay the reaction and weaken the change in sensor color. The color changes of the sensors were analyzed depending on the absorbed dose of UVA radiation using reflectance spectrophotometry. Furthermore, the chemical analysis and surface morphology of the samples were performed using Raman Spectroscopy and Scanning Electron Microscopy, respectively. In addition, the structure of the sensors on the paper surface was assessed using X-ray Micro-Computed Tomography. Finally, possible potential applications for these types of sensors were presented, including marking, securing, and protecting against the counterfeiting of documents, paper packaging, and other paper products, and creating decorative elements, as well as measuring the 2D/3D dose distribution of UV radiation on paper products. Full article
(This article belongs to the Special Issue Synthesis and Characterization of Materials for Sensors)
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21 pages, 3651 KB  
Article
Graphene Oxide-Anchored Cu–Co Catalysts for Efficient Electrochemical Nitrate Reduction
by Haosheng Lan, Yi Zhang, Le Ding, Xin Li, Zhanhong Zhao, Yansen Qu, Yingjie Xia and Xinghua Chang
Materials 2025, 18(11), 2495; https://doi.org/10.3390/ma18112495 - 26 May 2025
Viewed by 879
Abstract
Electrocatalytic nitrate reduction to ammonia (ENRA) presents a promising strategy for simultaneous environmental remediation and sustainable ammonia synthesis. In this work, a Cu–Co bimetallic catalyst supported on functionalized reduced graphene oxide (RGO) was systematically designed to achieve efficient and selective ammonia production. Surface [...] Read more.
Electrocatalytic nitrate reduction to ammonia (ENRA) presents a promising strategy for simultaneous environmental remediation and sustainable ammonia synthesis. In this work, a Cu–Co bimetallic catalyst supported on functionalized reduced graphene oxide (RGO) was systematically designed to achieve efficient and selective ammonia production. Surface oxygen functional groups on graphene oxide (GO) were optimized through alkaline hydrothermal treatments, enhancing the anchoring capacity for metal active sites. Characterization indicated the successful formation of uniform Cu–Co bimetallic heterointerfaces comprising metallic and oxide phases, which significantly improved catalyst stability and performance. Among the studied compositions, Cu6Co4/RGO exhibited superior catalytic activity, achieving a remarkable ammonia selectivity of 99.86% and a Faradaic efficiency of 96.54% at −0.6 V (vs. RHE). Long-term electrocatalysis demonstrated excellent durability, with over 90% Faradaic efficiency maintained for ammonia production after 20 h of operation. In situ FTIR analysis revealed that introducing Co effectively promoted water dissociation, facilitating hydrogen generation (*H) and accelerating the transformation of nitrate intermediates. This work offers valuable mechanistic insights and paves the way for the design of highly efficient bimetallic electrocatalysts for nitrate reduction and ammonia electrosynthesis. Full article
(This article belongs to the Special Issue Eco-Nanotechnology in Materials)
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27 pages, 16069 KB  
Article
Effect of Laser Surface Texturing and Fabrication Methods on Tribological Properties of Ti6Al4V/HAp Biocomposites
by Julia Sadlik, Edyta Kosińska, Agnieszka Tomala, Magdalena Bańkosz, Marko Polajnar, Rahul Kumar, Mitjan Kalin, Gaia Kravanja, Luka Hribar, Irina Hussainova, Marek Nykiel, Agnieszka Sobczak-Kupiec and Josef Jampilek
Materials 2025, 18(11), 2468; https://doi.org/10.3390/ma18112468 - 24 May 2025
Viewed by 1024
Abstract
Bone diseases lead to an increasing demand for implants to treat long bone defects and for load-bearing applications. Osteoporosis care and accidental injuries are major contributors to this rising need. Our research aims to demonstrate innovative material systems and methods for preparing implants [...] Read more.
Bone diseases lead to an increasing demand for implants to treat long bone defects and for load-bearing applications. Osteoporosis care and accidental injuries are major contributors to this rising need. Our research aims to demonstrate innovative material systems and methods for preparing implants that can be used in regenerative medicine. We hypothesize that by combining titanium alloys (Ti6Al4V) with hydroxyapatite (Hap), we can enhance biocompatibility and tribo-mechanical performance, which are critical for the longevity of Ti-based surgical implants. Additionally, we investigate the application of laser surface treatments to expose the underlying porosity, thereby enhancing cell transport and promoting cell growth. In this study, we investigate the effects of two fabrication techniques—Spark Plasma Sintering (SPS) and powder metallurgy (PM)—on the properties of laser-textured Ti64/Hap biocomposites. Our findings demonstrate that the selected processing route significantly influences the microstructure, tribological performance, and surface properties of these materials. An X-ray diffraction (XRD) analysis corroborates our results from incubation studies in simulated body fluids, highlighting the impact of phase transformations during sintering on the chemical properties of Ti-Hap composites. Additionally, while laser surface texturing was found to slightly increase the friction coefficient, it markedly enhanced the wear resistance, particularly for the PM and SPS Ti + 5%Hap composites. Full article
(This article belongs to the Special Issue Advances in Surface Engineering Technologies and Their Impact on Surface Integrity and Functional Performance of Additively Manufactured Parts)
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16 pages, 11068 KB  
Article
Effect of Interlayers on Microstructure and Corrosion Resistance of 304/45 Stainless Steel Cladding Plate
by Yongtong Chen and Yi Ding
Materials 2025, 18(11), 2473; https://doi.org/10.3390/ma18112473 - 24 May 2025
Viewed by 853
Abstract
During the high-temperature preparation of stainless steel cladding plate, carbon atoms from carbon steel diffused into stainless steel. When temperatures were within 450–850 °C, carbides precipitated at grain boundaries, which initiated intergranular sensitization and thereby reduced the corrosion resistance of stainless steel. This [...] Read more.
During the high-temperature preparation of stainless steel cladding plate, carbon atoms from carbon steel diffused into stainless steel. When temperatures were within 450–850 °C, carbides precipitated at grain boundaries, which initiated intergranular sensitization and thereby reduced the corrosion resistance of stainless steel. This study designed NiP and NiCuP interlayer alloys to effectively block carbon diffusion in stainless steel cladding plates. The effect of adding interlayers on the microstructure of stainless steel cladding plate was studied by using optical microscopy and scanning electron microscopy. Electrochemical tests were subsequently conducted to evaluate the impact of interlayer incorporation on the corrosion resistance of stainless steel cladding. The results demonstrated that 304/45 specimens exhibited severe carbon diffusion, resulting in the poorest corrosion resistance. The addition of interlayers improved the corrosion resistance of stainless steel cladding to varying degrees. Among these, the 304/NiCuP/45 specimen showed the best performance. It had an intergranular corrosion susceptibility of only 0.25% and pitting potential as high as 0.336 V, which indicated its superior corrosion resistance. The passive film of stainless steel cladding exhibited n-type semiconductor characteristics. And 304/NiCuP/45 specimen demonstrated the lowest carrier density of 3.02 × 1018 cm−3, which indicated the formation of the densest passive film. Full article
(This article belongs to the Special Issue Recent Advances in Stainless Steel: Characterization, Properties and Applications)
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15 pages, 3774 KB  
Article
A View on the Synthesis and Characterization of Porous Microspheres Containing Pyrrolidone Units
by Małgorzata Maciejewska
Materials 2025, 18(11), 2432; https://doi.org/10.3390/ma18112432 - 22 May 2025
Cited by 2 | Viewed by 677
Abstract
Porous materials are used in many important applications, such as separation technologies, catalysis, and chromatography. They may be obtained from various monomers via diverse polymerization techniques and a wide range of synthesis parameters. The study is devoted to the synthesis and characterization of [...] Read more.
Porous materials are used in many important applications, such as separation technologies, catalysis, and chromatography. They may be obtained from various monomers via diverse polymerization techniques and a wide range of synthesis parameters. The study is devoted to the synthesis and characterization of crosslinked porous polymeric spheres containing pyrrolidone subunits. To achieve this goal, two methods were applied: direct synthesis from N-vinyl-2-pyrrolidone (NVP) with ethylene glycol dimethacrylate (EGDMA) and via a modification reaction of porous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) with pyrrolidone (P). The polymerization was carried out with the use of different molar ratios of the monomers. In order to obtain highly porous materials, pore-forming diluents (toluene, dodecane, and dodecan-1-ol) were used. The synthesized copolymers were characterized using size distribution analysis, ATR-FTIR spectroscopy, scanning electron microscopy, thermogravimetry, and inverse gas chromatography. Determined by the nitrogen adsorption/desorption method, the specific surface area was in the range of 55–468 m2/g. The good thermal properties of the poly(VP-co-EGDMA) copolymers allowed them to be applied as the stationary phase in gas chromatography. Full article
(This article belongs to the Special Issue Porous Materials and Advanced Manufacturing Technologies (2nd Edition))
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24 pages, 4823 KB  
Article
Bioactive Glass and Melittin Thin Films Deposited by MAPLE for Titanium Implant Functionalization
by Mihaela Dinu, Bogdan Bita, Anca Constantina Parau, Carmen Ristoscu and Irina Negut
Materials 2025, 18(10), 2410; https://doi.org/10.3390/ma18102410 - 21 May 2025
Viewed by 824
Abstract
The development of bioactive coatings for metallic implants is essential to enhance osseointegration and improve implant longevity. In this study, composite thin films based on bioactive glass and melittin were synthesized using the matrix-assisted pulsed laser evaporation technique and deposited onto titanium substrates. [...] Read more.
The development of bioactive coatings for metallic implants is essential to enhance osseointegration and improve implant longevity. In this study, composite thin films based on bioactive glass and melittin were synthesized using the matrix-assisted pulsed laser evaporation technique and deposited onto titanium substrates. The coatings were characterized using physicochemical analysis methods, including scanning electron microscopy, atomic force microscopy, contact angle measurements, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy. Simulated body fluid immersion tests were also conducted to assess bioactivity over time. Scanning electron microscopy and atomic force microscopy revealed dense, irregular surface textures with nanoscale features and an average roughness of ~120 nm, favorable for cell adhesion. Contact angle measurements showed a significant shift from hydrophobic (~95° for bare titanium) to moderately hydrophilic (~62° for the bioglass and melittin coating) surfaces, indicating improved biocompatibility. Electrochemical impedance spectroscopy demonstrated enhanced corrosion resistance in simulated body fluid, with the coating exhibiting a ~45% decrease in impedance magnitude after 12 h of immersion, compared to only 4% for bare titanium. Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy analyses confirmed the progressive formation of a carbonated apatite layer after 7 days of simulated body fluid exposure, suggesting high bioactivity and osteoconductive potential. The combined effects of bioactive glass and melittin in the thin film structure offer promising applications in orthopedic and dental implants, enhancing both biological performance and structural integrity. Full article
(This article belongs to the Special Issue Multi-Scale Bionic Materials: Interfacial Design, Effective Fabrication and Functional Application)
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22 pages, 2217 KB  
Review
Biodegradability of Bioplastics in Managed and Unmanaged Environments: A Comprehensive Review
by Giovanni Gadaleta, Johana Carolina Andrade-Chapal, Sara López-Ibáñez, María Mozo-Toledo and Ángela Navarro-Calderón
Materials 2025, 18(10), 2382; https://doi.org/10.3390/ma18102382 - 20 May 2025
Cited by 3 | Viewed by 2250
Abstract
The production and utilization of conventional plastics have raised concerns regarding plastic waste management and environmental safety. In response, the emergence of biodegradable bioplastics presents a possible solution for sustainability. On the other hand, the efficacy of biodegradation is strictly dependent on both [...] Read more.
The production and utilization of conventional plastics have raised concerns regarding plastic waste management and environmental safety. In response, the emergence of biodegradable bioplastics presents a possible solution for sustainability. On the other hand, the efficacy of biodegradation is strictly dependent on both the bioplastic type and the conditions in which the biodegradation occurs. This review offers a comprehensive overview of the biodegradation behavior of several bioplastics under a managed (industrialized or controlled) environment, such as industrial composting and anaerobic digestion (at either mesophilic or thermophilic temperature), as well as under less studied unmanaged (natural or open) environments, including soil, seawater, and freshwater. Although the biodegradation trend of some bioplastics is well known, further investigation should be pursued for others in order to clearly have the knowledge and the ability to choose the most viable bioplastic for a specific application and future end-of-life. 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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14 pages, 8387 KB  
Article
Liquid-State Interfacial Reactions of Lead-Free Solders with FeCoNiCr and FeCoNiMn Medium-Entropy Alloys at 250 °C
by Chao-Hong Wang and Yue-Han Li
Materials 2025, 18(10), 2379; https://doi.org/10.3390/ma18102379 - 20 May 2025
Viewed by 682
Abstract
This study investigates the interfacial reactions of FeCoNiCr and FeCoNiMn medium-entropy alloys (MEAs) with Sn and Sn-3Ag-0.5Cu (SAC305) solders at 250 °C. The evolution of interfacial microstructures is analyzed over various aging periods. For comparison, the FeCoNiCrMn high-entropy alloy (HEA) is also examined. [...] Read more.
This study investigates the interfacial reactions of FeCoNiCr and FeCoNiMn medium-entropy alloys (MEAs) with Sn and Sn-3Ag-0.5Cu (SAC305) solders at 250 °C. The evolution of interfacial microstructures is analyzed over various aging periods. For comparison, the FeCoNiCrMn high-entropy alloy (HEA) is also examined. In the Sn/FeCoNiCr system, a faceted (Fe,Cr,Co)Sn2 layer initially forms at the interface. Upon aging, the significant spalling of large (Fe,Cr,Co)Sn2 particulates into the solder matrix occurs. Additionally, an extremely large, plate-like (Co,Ni)Sn4 phase forms at a later stage. In contrast, the Sn/FeCoNiMn reaction produces a finer-grained (Fe,Co,Mn)Sn2 phase dispersed in the solder, accompanied by the formation of the large (Co,Ni)Sn4 phase. This observation suggests that Mn promotes the formation of finer intermetallic compounds (IMCs), while Cr facilitates the spalling of larger IMC particulates. The Sn/FeCoNiCrMn system exhibits stable interfacial behavior, with the (Fe,Cr,Co)Sn2 layer showing no significant changes over time. The interfacial behavior and microstructure are primarily governed by the dissolution of the constituent elements and composition ratio of the HEAs, as well as their interactions with Sn. Similar trends are observed in the SAC305 solder reactions, where a larger amount of fine (Fe,Co,Cu)Sn2 particles spall from the interface. This behavior is likely attributed to Cu doping, which enhances nucleation and stabilizes the IMC phases, promoting the formation of finer particles. The wettability of SAC305 solder on MEA/HEA substrates was further evaluated by contact angle measurements. These findings suggest that the presence of Mn in the substrate enhances the wettability of the solder. Full article
(This article belongs to the Section Thin Films and Interfaces)
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49 pages, 7310 KB  
Review
Progress of MXene-Based Materials in the Field of Rechargeable Batteries
by Jianfei Gao, Jing Li, Qian Wang and Cheng Zou
Materials 2025, 18(10), 2386; https://doi.org/10.3390/ma18102386 - 20 May 2025
Cited by 1 | Viewed by 1558
Abstract
With the rapid development of electrical energy storage technologies, traditional battery systems are limited in practical applications by insufficient energy density and short cycle life. This review provides a comprehensive and critical summary of MXene or MXene-based composites as electrode materials for high-performance [...] Read more.
With the rapid development of electrical energy storage technologies, traditional battery systems are limited in practical applications by insufficient energy density and short cycle life. This review provides a comprehensive and critical summary of MXene or MXene-based composites as electrode materials for high-performance energy storage devices. By integrating the synthesis techniques of MXenes that have been studied, this paper systematically illustrates the physicochemical properties, synthesis strategies, and mechanisms of MXenes, and analyzes the bottlenecks in their large-scale preparation. Meanwhile, it collates the latest research achievements of MXenes in the field of metal–ion batteries in recent years, focusing on integrating their latest progress in lithium–ion, sodium–ion, lithium–sulfur, and multivalent ion (Zn2+, Mg2+, Al3+) batteries, and reveals their action mechanisms in different electrode material cases. Combining DFT analysis of the effects of surface functional groups on adsorption energy with experimental studies clarifies the structure–activity relationships of MXene-based composites. However, the development of energy storage electrode materials using MXenes and their hybrid compounds remains in its infancy. Future development directions for MXene-based batteries should focus on understanding and regulating surface chemistry, investigating specific energy storage mechanisms in electrodes, and exploring and developing electrode materials related to bimetallic MXenes. Full article
(This article belongs to the Special Issue Advanced Thin Films and 2D Materials: Mechanism, Fabrication, Characterization and Application (2nd Edition))
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12 pages, 2805 KB  
Article
Laser-Directed Energy-Deposited Ti-6Al-4V: The Anisotropy of Its Microstructure, Mechanical Properties, and Fracture Behavior
by Huan Wang, Chen-Wei Liu, Tianyu Wu and Hua-Xin Peng
Materials 2025, 18(10), 2360; https://doi.org/10.3390/ma18102360 - 19 May 2025
Cited by 3 | Viewed by 1200
Abstract
Ti-6Al-4V (Ti64) is widely used in the additive manufacturing (AM) industry for its superior mechanical properties; however, severe anisotropy is inevitable. In this work, a Ti64 sample fabricated using laser-directed energy deposition is used for fundamental investigations into the anisotropy of its microstructure, [...] Read more.
Ti-6Al-4V (Ti64) is widely used in the additive manufacturing (AM) industry for its superior mechanical properties; however, severe anisotropy is inevitable. In this work, a Ti64 sample fabricated using laser-directed energy deposition is used for fundamental investigations into the anisotropy of its microstructure, mechanical properties, and fracture behaviors. The microstructure of martensite α and prior β-Ti grains are characterized in both the XOY and XOZ planes. The tensile/compressive properties and microhardness along the building direction (BD) and scanning direction (SD) are tested, and it is found that the sample along the SD has better comprehensive mechanical properties. Due to grain boundary α (GB-α), different fracture behaviors and crack propagation paths are found along the BD and SD. When tensile force is parallel to the growth orientation of GB-α, a much higher density of microcracks caused by fractured GB-α is found to contribute to a prolonged elongation and the weakening of strength. While stretching along the SD, the cracks would propagate along the GB-α easily and straightly, which might lead to lower elongation. Full article
(This article belongs to the Section Metals and Alloys)
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16 pages, 8824 KB  
Article
Role of Surface Morphology Evolution in the Tribological Behavior of Superalloy Under High-Temperature Fretting
by Xuan He, Zidan Wang, Ying Yan, Kailun Zheng and Qian Bai
Materials 2025, 18(10), 2350; https://doi.org/10.3390/ma18102350 - 18 May 2025
Viewed by 802
Abstract
High-temperature fretting wear typically occurs on mechanical contact surfaces in high-temperature environments, with displacement amplitudes generally in the micrometer range (≤300 μm), such as the turbine disks and blades in aerospace engines, and the piston rings in automotive engines. The study performed tangential [...] Read more.
High-temperature fretting wear typically occurs on mechanical contact surfaces in high-temperature environments, with displacement amplitudes generally in the micrometer range (≤300 μm), such as the turbine disks and blades in aerospace engines, and the piston rings in automotive engines. The study performed tangential fretting wear tests between superalloy specimens and Si3N4 balls under 700 °C to investigate the influence of ground and milled surface morphologies on the high-temperature fretting wear behavior. The experimental results show distinct wear mechanisms for the two surface types: ground specimens exhibit adhesive and oxidative wear, while milled specimens experience fatigue and abrasive wear. Both wear modes intensify with increasing load and fretting frequency. A comprehensive surface morphology characterization method, combining fractal dimension (FD) and surface roughness, is proposed. The study reveals that the roughness parameters Sa and Ra are strongly correlated with the Coefficient of Friction, while FD is strongly correlated with the wear volume. This study provides a novel approach to characterizing the evolution of surface morphology during high-temperature fretting wear. Full article
(This article belongs to the Section Metals and Alloys)
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26 pages, 12237 KB  
Article
Optimizing the Manufacturing Process Control of Si-Based Soft Magnetic Composites
by Seongsu Kang and Seonbong Lee
Materials 2025, 18(10), 2321; https://doi.org/10.3390/ma18102321 - 16 May 2025
Cited by 2 | Viewed by 835
Abstract
This study attempts to enhance the formability and electromagnetic properties of Fe-Si-based soft magnetic composites via process parameter optimization. Two silicon compositions (5.0 and 6.5 wt.%) were examined to determine their influence on density, internal stress, microstructure stability, and magnetic properties using a [...] Read more.
This study attempts to enhance the formability and electromagnetic properties of Fe-Si-based soft magnetic composites via process parameter optimization. Two silicon compositions (5.0 and 6.5 wt.%) were examined to determine their influence on density, internal stress, microstructure stability, and magnetic properties using a factorial design comprising 96 different condition combinations. A Pearson correlation analysis revealed a negative relationship between Si content and formability, while magnetic permeability increased with higher Si content. The 5.0 wt.% Si samples exhibited superior density (7.42 g/cm3 vs. 7.28 g/cm3), uniform microstructure, and coating stability. Conversely, the 6.5 wt.% Si samples achieved better permeability (126 at 10 kHz) than 5.0 wt.% Si samples but exhibited higher internal stress, uneven compaction, and thicker insulation layers (~400 nm vs. <10 nm). Scanning electron microscopy and transmission electron microscopy analyses identified necking and damage to the insulation layer. X-ray diffraction verified the stability of the Fe1.6Si0.4 phase after the forming and annealing processes. Secondary molding temperature exhibited the most significant impact on densification, and annealing generally degraded the quality factor (Q-factor). The highest Q-factor value (7.18 at 10 kHz), indicating lower core loss, was observed in the 5.0 wt.% Si samples without annealing. Full article
(This article belongs to the Section Materials Simulation and Design)
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25 pages, 33768 KB  
Article
Influence of Rust Layer on Corrosion-Critical Humidity in Outdoor Environments Based on Corrosion Sensors
by Qing Li, Xinyu Wang, Zibo Pei, Kui Xiao, Xiaojia Yang and Xuequn Cheng
Materials 2025, 18(10), 2299; https://doi.org/10.3390/ma18102299 - 15 May 2025
Cited by 1 | Viewed by 1311
Abstract
In this study, the Fe/Cu-based two-electrode corrosion monitoring technique was employed to monitor the long-term atmospheric corrosion of carbon steel at five different outdoor sites within the China National Environmental Corrosion Platform. Based on the fitted monitoring data, the variation trend of corrosion-critical [...] Read more.
In this study, the Fe/Cu-based two-electrode corrosion monitoring technique was employed to monitor the long-term atmospheric corrosion of carbon steel at five different outdoor sites within the China National Environmental Corrosion Platform. Based on the fitted monitoring data, the variation trend of corrosion-critical humidity as a function of exposure time at different monitoring locations was obtained. The cross-sectional rust layer of corrosion coupons from different experimental periods at each location was characterized using scanning electron microscopy and Raman spectroscopy to identify variations in the thickness and phase composition of the carbon steel rust layer. The influence of rust layer thickness and phase structure on the critical humidity of carbon steel in atmospheric environments was investigated. Finally, the corrosion resistance of weathering steel in Tianjin, China, was validated using corrosion monitoring techniques, and the corrosion mechanism of weathering steel was elucidated by analyzing the influence of the acquired rust layer phase structure on the critical humidity of carbon steel in atmospheric environments. Full article
(This article belongs to the Section Corrosion)
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22 pages, 15244 KB  
Article
Corrosion Behavior of Shot Peened Ti6Al4V Alloy Fabricated by Conventional and Additive Manufacturing
by Mariusz Walczak, Wojciech Okuniewski, Wojciech J. Nowak, Dariusz Chocyk and Kamil Pasierbiewicz
Materials 2025, 18(10), 2274; https://doi.org/10.3390/ma18102274 - 14 May 2025
Cited by 2 | Viewed by 1077
Abstract
Ti6Al4V titanium alloy is one of the most studied for its properties after additive manufacturing. Due to its widely use in medical applications, its properties are investigated in various aspects of surface layer property improvement and later compared to conventionally manufactured Ti-6Al-4V. In [...] Read more.
Ti6Al4V titanium alloy is one of the most studied for its properties after additive manufacturing. Due to its widely use in medical applications, its properties are investigated in various aspects of surface layer property improvement and later compared to conventionally manufactured Ti-6Al-4V. In this study, the corrosion behavior in a 0.9% NaCl solution of shot peened Ti-6Al-4V prepared using direct metal laser sintering (DMLS) was examined using corrosion electrochemical testing and compared with conventionally forged titanium alloy. Shot peening was performed on previously polished samples and subsequently treated with the CrNi steel shots. Two sets of peening pressure were selected: 0.3 and 0.4 MPa. X-ray diffraction analysis (XRD), X-ray micro-computed tomography (Micro-CT), scanning electron microscope (SEM) tests with roughness and hardness measurements were used to characterize the samples. The conventional samples were characterized by an α + β structure, while the additive samples had an α’ + β martensitic structure. The obtained results indicate that the corrosion resistance of the conventionally forged Ti-6Al-4V alloy was higher than DMLSed Ti-6Al-4V alloy. The lowest corrosion rates were noted for untreated surfaces of CM/ref and DMLS/ref samples and reached 0.041 and 0.070 µA/cm2, respectively. Moreover, the development of the surface has an influence on corrosion behavior. Therefore, increasing pressure results in inferior corrosion resistance. However, better performance for shot peened samples was reported in the low frequency range. This is due to the refinement of the grain acquired after the peening process. All the results obtained, related to the corrosion behavior, were satisfactory enough that the all samples can be characterized as materials suitable for implant applications. Full article
(This article belongs to the Special Issue Study on Electrochemical Behavior and Corrosion of Materials)
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16 pages, 2251 KB  
Article
Thermo-Oxidative Aging Effects on Hyperelastic Behavior of EPDM Rubber: A Constitutive Modeling Approach
by Zhaonan Xie, Xicheng Huang, Kai Zhang, Shunping Yan, Junhong Chen, Ren He, Jiaxing Li and Weizhou Zhong
Materials 2025, 18(10), 2236; https://doi.org/10.3390/ma18102236 - 12 May 2025
Cited by 2 | Viewed by 1163
Abstract
The effect of thermo-oxidative aging on the hyperelastic behavior of ethylene propylene diene monomer (EPDM) rubber was investigated by a combined experimental and theoretical modeling approach. Firstly, the uniaxial tensile test of aged and unaged EPDM rubber was carried out. The test results [...] Read more.
The effect of thermo-oxidative aging on the hyperelastic behavior of ethylene propylene diene monomer (EPDM) rubber was investigated by a combined experimental and theoretical modeling approach. Firstly, the uniaxial tensile test of aged and unaged EPDM rubber was carried out. The test results show that the unaged EPDM rubber had the nonlinear large deformation characteristic of a “S” shape. The stiffness of the EPDM rubber was found to increase with the aging time and aging temperature. Then, in order to quantitatively characterize the hyperelastic behavior of unaged EPDM rubber, the fitting performances of the Mooney–Rivlin, Arruda–Boyce, and Ogden models were compared based on a uniaxial tensile stress–strain curve. The results show that the Ogden model provided a more accurate representation of the hyperelastic behavior of unaged EPDM rubber. Subsequently, the Dakin dynamic equation was adopted to associate the parameters of the Ogden model with the aging time, and the Arrhenius relationship was utilized to introduce the aging temperature into the rate term of the Dakin dynamic equation, thereby establishing an improved Ogden constitutive model. This improved model expanded the Ogden model’s ability to explain aging time and aging temperature. Finally, the improved model prediction results and the test results were compared, and they indicate that the proposed improved Ogden constitutive model can accurately describe the hyperelastic behavior of aged and unaged EPDM rubber. Full article
(This article belongs to the Section Polymeric Materials)
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13 pages, 2728 KB  
Article
Machine Learning-Assisted Discovery of Empirical Rule for Martensite Transition Temperature of Shape Memory Alloys
by Hao-Xuan Liu, Hai-Le Yan, Nan Jia, Bo Yang, Zongbin Li, Xiang Zhao and Liang Zuo
Materials 2025, 18(10), 2226; https://doi.org/10.3390/ma18102226 - 12 May 2025
Viewed by 990
Abstract
Shape memory alloys (SMAs) derive their unique functional properties from martensitic transformations, with the martensitic transformation temperature (TM) serving as a key design parameter. However, existing empirical rules, such as the valence electron concentration (VEC) and lattice volume (V) criteria, [...] Read more.
Shape memory alloys (SMAs) derive their unique functional properties from martensitic transformations, with the martensitic transformation temperature (TM) serving as a key design parameter. However, existing empirical rules, such as the valence electron concentration (VEC) and lattice volume (V) criteria, are typically restricted to specific alloy families and lack general applicability. In this work, we used a data-driven methodology to find a generalizable empirical formula for TM in SMAs by combining high-throughput first-principles calculations, feature engineering, and symbol regression techniques. Key factors influencing TM were first identified and a predictive machine learning model was subsequently trained based on these features. Furthermore, an empirical formula of TM = 82(ρ¯·MP¯)−700 was derived, where ρ¯ and MP¯ represent the weight-average value of density and melting point, respectively. The empirical formula exhibits strong generalizability across a wide range of SMAs, such as NiMn-based, NiTi-based, TiPt-based, and AuCd-based SMAs, etc., offering practical guidance for the compositional design and optimization of shape memory alloys. Full article
(This article belongs to the Special Issue Magnetic Shape Memory Alloys: Fundamentals and Applications)
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