Materials

28 pages, 3203 KiB

Open AccessEditor’s ChoiceArticle

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 1006

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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32 pages, 7994 KiB

Open AccessEditor’s ChoiceReview

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

Viewed by 1905

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, 9841 KiB

Open AccessEditor’s ChoiceArticle

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 383

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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16 pages, 11068 KiB

Open AccessEditor’s ChoiceArticle

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 513

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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12 pages, 2805 KiB

Open AccessEditor’s ChoiceArticle

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 1 | Viewed by 530

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 KiB

Open AccessEditor’s ChoiceArticle

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 492

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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14 pages, 2100 KiB

Open AccessEditor’s ChoiceArticle

Improved Bone Regeneration Using Biodegradable Polybutylene Succinate Artificial Scaffold with BMP-2 Protein in a Rabbit Model

by Giulio Edoardo Vigni, Mariano Licciardi, Lorenzo D’itri, Francesca Terracina, Sergio Scirè, Giuseppe Arrabito, Bruno Pignataro, Lawrence Camarda, Giovanni Cassata, Roberto Puleio, Lucio Di Silvestre and Luca Cicero

Materials 2025, 18(10), 2234; https://doi.org/10.3390/ma18102234 - 12 May 2025

Viewed by 456

Abstract

Extensive bone loss represents a great challenge for orthopedic and reconstructive surgery. On an in vivo rabbit model, the healing of two bone defects on a long bone, tibia, was studied. A polybutylene succinate (PBS) microfibrillar scaffold was implemented with BMP-2 protein and [...] Read more.

Extensive bone loss represents a great challenge for orthopedic and reconstructive surgery. On an in vivo rabbit model, the healing of two bone defects on a long bone, tibia, was studied. A polybutylene succinate (PBS) microfibrillar scaffold was implemented with BMP-2 protein and hydroxyapatite (HA) as potential osteogenic factors. The present study was carried out on 6 male New Zealand white (4–6 months old) rabbits in vivo model. One bone defect was created in each subject on the tibia. The controls were left to heal spontaneously while the study samples were treated with the polybutylene succinate (PBS) microfibrillar scaffolds doped with BMP-2 and HA. Histological and immunohistochemical analyses were performed after euthanasia at 3 and 6 months. The bone defect treated with the BMP-2 PBS scaffold shows, from 3 months, a significantly increased presence of activated osteoblasts with mineralized bone tissue deposition. This study confirms the great potential of PBS scaffolds in the clinical treatment of bone defects. Full article

(This article belongs to the Special Issue Advanced Materials for Bone Regeneration and Treatment)

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15 pages, 3410 KiB

Open AccessEditor’s ChoiceArticle

CeO₂-Modified Ni₂P/Fe₂P as Efficient Bifunctional Electrocatalyst for Water Splitting

by Xinyang Wu, Dandan Wang, Yongpeng Ren, Haiwen Zhang, Shengyu Yin, Ming Yan, Yaru Li and Shizhong Wei

Materials 2025, 18(10), 2221; https://doi.org/10.3390/ma18102221 - 11 May 2025

Viewed by 598

Abstract

Developing efficient bifunctional electrocatalysts with excellent stability at high current densities for overall water splitting is a challenging yet essential objective. However, transition metal phosphides encounter issues such as poor dispersibility, low specific surface area, and limited electronic conductivity, which hinder the achievement [...] Read more.

Developing efficient bifunctional electrocatalysts with excellent stability at high current densities for overall water splitting is a challenging yet essential objective. However, transition metal phosphides encounter issues such as poor dispersibility, low specific surface area, and limited electronic conductivity, which hinder the achievement of satisfactory performance. Therefore, this study presents the highly efficient bifunctional electrocatalyst of CeO₂-modified NiFe phosphide on nickel foam (CeO₂/Ni₂P/Fe₂P/NF). Ni₂P/Fe₂P coupled with CeO₂ was deposited on nickel foam through hydrothermal synthesis and sequential calcination processes. The electrocatalytic performance of the catalyst was evaluated in an alkaline solution, and it exhibited an HER overpotential of 87 mV at the current density of 10 mA cm⁻² and an OER overpotential of 228 mV at the current density of 150 mA cm⁻². Furthermore, the catalyst demonstrated good stability, with a retention rate of 91.2% for the HER and 97.3% for the OER after 160 h of stability tests. The excellent electrochemical performance can be attributed to the following factors: (1) The interface between Ni₂P/Fe₂P and CeO₂ facilitates electron transfer and reactant adsorption, thereby improving catalytic activity. (2) The three-dimensional porous structure of nickel foam provides an ideal substrate for the uniform distribution of Ni₂P, Fe₂P, and CeO₂ nanoparticles, while its high conductivity facilitates electron transport. (3) The incorporation of larger Ce³⁺ ions in place of smaller Fe³⁺ ions leads to lattice distortion and an increase in defects within the NiFe-layered double hydroxide structure, significantly enhancing its catalytic performance. This research finding offers an effective strategy for the design and synthesis of low-cost, high-potential catalysts for water electrolysis. Full article

(This article belongs to the Section Catalytic Materials)

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24 pages, 2746 KiB

Open AccessEditor’s ChoiceReview

Molecularly Imprinted Titanium Dioxide: Synthesis Strategies and Applications in Photocatalytic Degradation of Antibiotics from Marine Wastewater: A Review

by Xue Han, Yu Jin, Luyang Zhao, Yuying Zhang, Binqiao Ren, Xiaoxiao Song and Rui Liu

Materials 2025, 18(9), 2161; https://doi.org/10.3390/ma18092161 - 7 May 2025

Viewed by 557

Abstract

Antibiotic residues in the marine environment pose a serious threat to ecosystems and human health, and there is an urgent need to develop efficient and selective pollution control technologies. Molecular imprinting technology (MIT) provides a new idea for antibiotic pollution control with its [...] Read more.

Antibiotic residues in the marine environment pose a serious threat to ecosystems and human health, and there is an urgent need to develop efficient and selective pollution control technologies. Molecular imprinting technology (MIT) provides a new idea for antibiotic pollution control with its specific recognition and targeted removal ability. However, traditional titanium dioxide (TiO₂) photocatalysts have limited degradation efficiency and lack of selectivity for low concentrations of antibiotics. This paper reviews the preparation strategy and modification means of molecularly imprinted TiO₂ (MI-TiO₂) and its composites and systematically explores its application mechanism and performance advantages in marine antibiotic wastewater treatment. It was shown that MI-TiO₂ significantly enhanced the selective degradation efficiency of antibiotics such as tetracyclines and sulfonamides through the enrichment of target pollutants by specifically imprinted cavities, combined with the efficient generation of photocatalytic reactive oxygen species (ROS). In addition, emerging technologies such as magnetic/electric field-assisted catalysis and photothermal synergistic effect further optimized the recoverability and stability of the catalysts. This paper provides theoretical support for the practical application of MI-TiO₂ in complex marine pollution systems and looks forward to its future development in the field of environmental remediation. Full article

(This article belongs to the Section Catalytic Materials)

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35 pages, 5269 KiB

Open AccessEditor’s ChoiceArticle

The Quantum Transport of Dirac Fermions in Selected Graphene Nanosystems Away from the Charge Neutrality Point

by Adam Rycerz

Materials 2025, 18(9), 2036; https://doi.org/10.3390/ma18092036 - 29 Apr 2025

Viewed by 581

Abstract

The peculiar electronic properties of graphene, including the universal dc conductivity and the pseudodiffusive shot noise, are usually found in a small vicinity close to the charge neutrality point, away from which the electron’s effective mass raises, and nanostructures in graphene start to [...] Read more.

The peculiar electronic properties of graphene, including the universal dc conductivity and the pseudodiffusive shot noise, are usually found in a small vicinity close to the charge neutrality point, away from which the electron’s effective mass raises, and nanostructures in graphene start to behave similarly to familiar Sharvin contacts in semiconducting heterostructures. Recently, it was pointed out that as long as abrupt potential steps separate the sample area from the leads, some graphene-specific features can be identified relatively far from the charge neutrality point. These features include greater conductance reduction and shot noise enhancement compared to the standard Sharvin values. The purpose of this paper is twofold: First, we extend the previous analysis based on the effective Dirac equation, and derive the formulas that allow the calculation of the arbitrary charge transfer cumulant for doped graphene. Second, the results of the analytic considerations are compared with numerical simulations of quantum transport on the honeycomb lattice for selected nanosystems for which considerations starting from the Dirac equation cannot be directly adapted. For a wedge-shaped constriction with zigzag edges, the transport characteristics can be tuned from graphene-specific (sub-Sharvin) values to standard Sharvin values by varying the electrostatic potential profile in the narrowest section. A similar scenario is followed by the half-Corbino disk. In contrast, a circular quantum dot with two narrow openings showing a mixed behavior appears: the conductance is close to the Sharvin value, while the Fano factor approaches the value characterizing the symmetric chaotic cavity. Carving a hole in the quantum dot to eliminate direct trajectories between the openings reduces the conductance to sub-Sharvin value, but the Fano factor is unaffected. Our results suggest that experimental attempts to verify the predictions for the sub-Sharvin transport regime should focus on systems with relatively wide openings, where the scattering at the sample edges is insignificant next to the scattering at the sample–lead interfaces. Full article

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

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14 pages, 6228 KiB

Open AccessEditor’s ChoiceArticle

Microstructure and Mechanical Property of 6082 Aluminum Alloy via Sc and Zr Addition Combined with Squeeze Casting

by Yushi Qi, Fangming Wei, Yu Wang, Yu Jin, Xusheng Chang and Gang Chen

Materials 2025, 18(9), 1988; https://doi.org/10.3390/ma18091988 - 27 Apr 2025

Cited by 1 | Viewed by 623

Abstract

To enhance the mechanical properties of 6082 aluminum alloy, a novel Sc- and Zr-microalloyed 6082 alloy was fabricated through squeeze casting technology. Microalloying with Sc and Zr substantially refined the microstructure of alloy, achieving an average grain size of 136.36 μm—a 31.7% reduction [...] Read more.

To enhance the mechanical properties of 6082 aluminum alloy, a novel Sc- and Zr-microalloyed 6082 alloy was fabricated through squeeze casting technology. Microalloying with Sc and Zr substantially refined the microstructure of alloy, achieving an average grain size of 136.36 μm—a 31.7% reduction compared to the baseline 6082 alloy. Furthermore, the addition of Sc and Zr effectively refined the coarse AlFeMnSi intermetallic phases, mitigating their inherent brittleness. The Sc/Zr-modified alloy exhibited delayed age-hardening kinetics, requiring 100% longer aging time to reach peak hardness due to Sc/Zr-induced retardation of β’’-phase precipitation. The optimized alloy demonstrated better mechanical properties, showing 10.4%, 8.0%, and 71.8% enhancements in yield strength, ultimate tensile strength, and elongation, respectively, over the non-microalloyed counterpart. The squeeze-cast Sc/Zr-modified alloy valve body showed yield strength exceeding 300 MPa and elongation above 10% across various sections, which verifies the effectiveness of this integrated microalloying and forming approach. Full article

(This article belongs to the Special Issue Review and Feature Papers in "Metals and Alloys" Section (2nd Edition))

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47 pages, 4349 KiB

Open AccessEditor’s ChoiceReview

Metal Nanocomposites as Biosensors for Biological Fluids Analysis

by Dan Chicea and Alexandra Nicolae-Maranciuc

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

Viewed by 618

Abstract

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

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

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

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15 pages, 3554 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 622

Abstract

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

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

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

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14 pages, 8353 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 406

Abstract

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

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

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

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30 pages, 4998 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 642

Abstract

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

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

(This article belongs to the Section Metals and Alloys)

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19 pages, 5369 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 775

Abstract

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

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

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

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17 pages, 3636 KiB

Open AccessEditor’s ChoiceArticle

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

by Fan Yang, Pascal Boulet and Marie-Christine Record

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

Viewed by 663

Abstract

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

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

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

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15 pages, 6248 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 398

Abstract

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

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

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

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10 pages, 3175 KiB

Open AccessEditor’s ChoiceArticle

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

by Włodzimierz Jaskólski

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

Viewed by 501

Abstract

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

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

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

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28 pages, 4096 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Cited by 1 | Viewed by 484

Abstract

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

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

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

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17 pages, 7854 KiB

Open AccessEditor’s ChoiceArticle

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

by Kathy Lu and Harrison Chaney

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

Viewed by 463

Abstract

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

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

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

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18 pages, 74287 KiB

Open AccessEditor’s ChoiceArticle

Graining and Texturing of Metal Surfaces by Picosecond Laser Treatment

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

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

Viewed by 668

Abstract

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

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

(This article belongs to the Section Materials Physics)

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17 pages, 3853 KiB

Open AccessEditor’s ChoiceArticle

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

by Anna Magiera, Monika Kuźnia and Wojciech Jerzak

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

Cited by 1 | Viewed by 373

Abstract

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

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

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

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17 pages, 3101 KiB

Open AccessEditor’s ChoiceArticle

Removal of Per- and Polyfluoroalkyl Substances Using Commercially Available Sorbents

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

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

Viewed by 2109

Abstract

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

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

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

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12 pages, 1759 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 905

Abstract

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

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

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

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13 pages, 3445 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 685

Abstract

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

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

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

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22 pages, 12982 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Cited by 1 | Viewed by 649

Abstract

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

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

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

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10 pages, 2639 KiB

Open AccessEditor’s ChoiceCommunication

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

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

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

Viewed by 735

Abstract

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

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

(This article belongs to the Section Electronic Materials)

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27 pages, 9696 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 983

Abstract

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

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

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

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12 pages, 3089 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 876

Abstract

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

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

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

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13 pages, 1891 KiB

Open AccessEditor’s ChoiceArticle

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

by Shengwei Feng and Lizhi Sun

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

Cited by 1 | Viewed by 753

Abstract

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

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

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

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30 pages, 4653 KiB

Open AccessEditor’s ChoiceReview

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

by Tangyu Yang and Andre G. Skirtach

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

Cited by 3 | Viewed by 1656

Abstract

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

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

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

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14 pages, 5580 KiB

Open AccessEditor’s ChoiceArticle

Burst Ultrafast Laser Welding of Quartz Glass

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

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

Cited by 2 | Viewed by 1026

Abstract

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

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

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

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18 pages, 7417 KiB

Open AccessEditor’s ChoiceArticle

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

by Lingyan He, Fengling Peng and Xing Chen

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

Viewed by 702

Abstract

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

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

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

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16 pages, 6479 KiB

Open AccessEditor’s ChoiceArticle

Vat Photopolymerization of CeO₂-Incorporated Hydrogel Scaffolds with Antimicrobial Efficacy

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

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

Viewed by 1047

Abstract

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

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

(This article belongs to the Section Biomaterials)

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20 pages, 5378 KiB

Open AccessEditor’s ChoiceArticle

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

by Joanna Pach, Roman Wróblewski and Bartłomiej Muszyński

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

Cited by 1 | Viewed by 1500

Abstract

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

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

(This article belongs to the Section Advanced Composites)

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16 pages, 5953 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Cited by 1 | Viewed by 808

Abstract

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

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

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

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15 pages, 8198 KiB

Open AccessEditor’s ChoiceArticle

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

by Hiroki Satoh, Ayumu Morita and Yoshihiko Arao

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

Cited by 2 | Viewed by 653

Abstract

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

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

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

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19 pages, 10708 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Cited by 2 | Viewed by 698

Abstract

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

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

(This article belongs to the Section Metals and Alloys)

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51 pages, 17258 KiB

Open AccessEditor’s ChoiceReview

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

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

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

Cited by 2 | Viewed by 1211

Abstract

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

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

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

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13 pages, 3773 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 1354

Abstract

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

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

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

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14 pages, 7452 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Cited by 1 | Viewed by 937

Abstract

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

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

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

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11 pages, 1999 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 648

Abstract

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

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

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

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23 pages, 10651 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Cited by 1 | Viewed by 882

Abstract

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

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

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

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15 pages, 8628 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Cited by 2 | Viewed by 722

Abstract

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

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

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

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14 pages, 4269 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 2301

Abstract

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

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

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

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17 pages, 1743 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Cited by 3 | Viewed by 1016

Abstract

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

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

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

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15 pages, 8890 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Viewed by 910

Abstract

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

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

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

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19 pages, 9311 KiB

Open AccessEditor’s ChoiceArticle

B-H Curve Estimation and Air Gap Optimization for High-Performance Split Core

by Minjoong Kim, Myungseo Lee, Sijeong Lee, Jaeyun Lee and Jihwan Song

Materials 2025, 18(3), 644; https://doi.org/10.3390/ma18030644 - 31 Jan 2025

Viewed by 1215

Abstract

The current transformer (CT)-based energy harvesting method has gained considerable attention for low-power devices. Accurate estimation of the B-H curve is essential to develop a high-performance CT, as it closely relates to the electromagnetic behavior of CT material. However, the existing estimation methods [...] Read more.

The current transformer (CT)-based energy harvesting method has gained considerable attention for low-power devices. Accurate estimation of the B-H curve is essential to develop a high-performance CT, as it closely relates to the electromagnetic behavior of CT material. However, the existing estimation methods for the B-H curve face several drawbacks, which include process complexity and a high cost. This study presented an intuitive method to estimate the B-H curve based on the experimentally obtained resistance-voltage data. The performance of the CT core is obtained based on the estimated B-H curve, which exhibited an error of only 2.6% when compared to the experimental results for the most accurate case. Additionally, we analyzed split-core performance deterioration caused by the presence of an air gap. The air gap formation of the split core was closely related to the surface roughness, which significantly influenced core performance. The air gap range that minimizes the reduction in performance is predicted and validated through simulations and experiments. This research highlights a straightforward approach to obtaining the B-H curve of magnetic CT core material. We believe that this study provides the design guidelines needed to develop a high-performance CT core, including considerations for core geometry and the recommended air gap range. Full article

(This article belongs to the Special Issue Functional Soft Magnetic Materials and Electromagnetic Shielding Technology)

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19 pages, 12564 KiB

Open AccessEditor’s ChoiceArticle

Compressive Properties of Composite Sandwich Structure with Fractal Tree-Inspired Lattice Core

by Jian Han, Xin Ma, Rui Yang and Shiyong Sun

Materials 2025, 18(3), 606; https://doi.org/10.3390/ma18030606 - 29 Jan 2025

Viewed by 1074

Abstract

A novel sandwich structure of a fractal tree-like lattice (SSFL) is proposed. The geometry characteristics were constructed based on the fractal tree-like patterns found in many biological structures, such as giant water lilies and dragon blood trees. The compressive performance of the proposed [...] Read more.

A novel sandwich structure of a fractal tree-like lattice (SSFL) is proposed. The geometry characteristics were constructed based on the fractal tree-like patterns found in many biological structures, such as giant water lilies and dragon blood trees. The compressive performance of the proposed structures with different fractal orders was experimentally and numerically investigated. The experimental samples were made by 3D printing technology. Axial compression tests were conducted to study the compressive performance and failure mode of the SSFLs. The results indicated that the new structure was good at multiple bearing and energy absorption. The finite element method (FEM) was performed to investigate the influence of geometry parameters on the compression behaviors of the SSFLs. The findings of this study provide an effective guide for using the fractal method to design lattice structures with a high bearing capacity. Full article

(This article belongs to the Special Issue Advances in Porous Lightweight Materials and Lattice Structures)

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