Materials

19 pages, 3591 KB

Open AccessEditor’s ChoiceArticle

Comparison of the Effectiveness of Paper Strengthening with Gelatin, Klucel G, and Tylose Solutions in Combination with Deacidification Using Magnesium Hydroxide Nanoparticles

by Renata Wojech, Aleksandra Kwiatkowska, Grzegorz Cofta and Adam Wójciak

Materials 2026, 19(1), 126; https://doi.org/10.3390/ma19010126 - 30 Dec 2025

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Abstract

The manuscript concerns modern methods of preserving historical papers and presents research focusing on the effectiveness of paper strengthening with gelatin, Klucel G, and Tylose solutions in combination with deacidification using magnesium hydroxide nanoparticles. The aim of these procedures is to extend the [...] Read more.

The manuscript concerns modern methods of preserving historical papers and presents research focusing on the effectiveness of paper strengthening with gelatin, Klucel G, and Tylose solutions in combination with deacidification using magnesium hydroxide nanoparticles. The aim of these procedures is to extend the durability of historical records on papers, which are an important part of humanity’s cultural heritage. Gelatin and Klucel G dissolved in propyl alcohol were used simultaneously with the dispersion of Mg(OH)₂ nanoparticles, and Tylose dissolved in water was applied after deacidification in a separate step. The experiments were conducted on Whatman model papers, artificially acidified or covered with iron gall ink. The evaluation of the effectiveness was based on tests of breaking length, changes in the DP_visc of cellulose, and pH of the aqueous extracts. Additional information was provided by microscopic examinations (SEM-EDX-SE) and measurements of the optical properties of the tested papers before and after the application of strengthening agents. All the strengthening agents tested increased paper strength—Tylose to the greatest extent, followed by Gelatin, and Klucel G to the least extent. Model papers covered with Klucel G showed good dimensional stability. Gelatin-covered papers showed the greatest changes in optical properties. Full article

(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)

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13 pages, 5136 KB

Open AccessEditor’s ChoiceArticle

Precipitation of β-Mn in the Form of Widmanstätten Side-Plates in the Ferrite Matrix of an Fe–28.6 Mn–10.9 Al Alloy Steel

by Rosemary Chemeli Korir and Wei-Chun Cheng

Materials 2026, 19(1), 133; https://doi.org/10.3390/ma19010133 - 30 Dec 2025

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Abstract

The microstructural evolution and phase stability in Fe–Mn–Al alloys play a decisive role in determining their mechanical performance and potential applications. This study investigates the precipitation behavior and crystallography of the β-Mn phase in an Fe–28.6 Mn–10.9 Al (wt.%) alloy subjected to annealing [...] Read more.

The microstructural evolution and phase stability in Fe–Mn–Al alloys play a decisive role in determining their mechanical performance and potential applications. This study investigates the precipitation behavior and crystallography of the β-Mn phase in an Fe–28.6 Mn–10.9 Al (wt.%) alloy subjected to annealing at 1100 °C, followed by water quenching and subsequent isothermal holding at temperatures between 500 °C and 900 °C for 20 h. Microstructural analysis using X-ray diffraction, optical and electron microscopy revealed a single body-centered cubic (BCC) ferritic matrix above 850 °C and the formation of β-Mn precipitates with Widmanstätten side-plate morphology at lower temperatures. The β-Mn phase was thermally stable between ~500 °C and 850 °C, with the volume fraction increasing with temperature and reaching a maximum near 650 °C. The β-Mn precipitates coarsened progressively with increasing temperature and were found to be richer in Mn than the surrounding Fe-rich BCC matrix. Crystallographic analysis established an orientation relationship (OR) of (

02 \bar{1}

)_β // (100)_α and [

\bar{1} 12

]_β // [012]α, where // denotes nearly parallel alignment, signifying a semi-coherent interface between the two structures. These findings clarify β-Mn precipitation, its interfacial relationship with ferrite, and its thermal stability in high-Mn Fe–Mn–Al alloys, offering guidance for microstructural design in next-generation lightweight steels. Full article

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

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24 pages, 6273 KB

Open AccessEditor’s ChoiceArticle

Influence of Post-Processing on S-Phase Formation During Plasma Nitriding of Additively Manufactured Inconel 939

by Piotr Maj, Joanna Radziejewska, Ryszard Diduszko, Michał Marczak, Rafał Nowicki, Podolak-Lejtas Anna, Tomasz Borowski and Ryszard Sitek

Materials 2026, 19(1), 130; https://doi.org/10.3390/ma19010130 - 30 Dec 2025

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Abstract

Active screen plasma nitriding (ASPN) of additively manufactured nickel-based superalloys represents an understudied surface enhancement pathway. This study presents the first systematic investigation of ASPN applied to additively manufactured Inconel 939 (IN 939), evaluating four distinct post-processing routes combining heat treatment atmospheres (argon [...] Read more.

Active screen plasma nitriding (ASPN) of additively manufactured nickel-based superalloys represents an understudied surface enhancement pathway. This study presents the first systematic investigation of ASPN applied to additively manufactured Inconel 939 (IN 939), evaluating four distinct post-processing routes combining heat treatment atmospheres (argon versus air cooling), vibratory finishing, and lapping under identical nitriding parameters (450 °C, 8 h, 25% N₂ + 75% H₂, 3 hPa). Contrasting nitriding behaviours emerged as a function of the post-processing route: the air-cooled thermal treatment (HT-air-vibr-lap) promotes formation of a thick Al/Cr-rich oxide layer (10–15 µm) that substantially inhibits nitrogen diffusion, resulting in thin and discontinuous nitrided layers. Conversely, the inert atmosphere route (HT-Ar-vibr-lap) circumvents oxide formation, enabling continuous S-phase (expanded austenite, γN) layer development of a 6.4 ± 0.3 µm thickness with exceptional surface hardness (~1200 HV, representing 3–4× enhancement relative to base material). X-ray diffraction confirmed S-phase formation with refined lattice parameter (3.609 Å) and secondary nitride phases (CrN-type and NbN/TaN-type precipitates). The post-processing sequence—particularly heat treatment atmosphere and mechanical finishing methodology—emerged as a critical controlling parameter for S-phase formation efficiency and mechanical properties of nitrided layers in additively manufactured nickel-based superalloys. This work addresses a knowledge gap distinct from the existing literature on conventional Inconel systems, establishing that controlled surface modification through post-processing can achieve the required properties. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition))

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19 pages, 5445 KB

Open AccessEditor’s ChoiceArticle

Analysis of Surface Topography, Dimensional and Geometric Deviations, and Biocidal Properties of 3D Prints Made of Thermoplastic-Based Composites

by Urszula Kmiecik-Sołtysiak, Paweł Szczygieł, Dagmara Michta and Katarzyna Gałczyńska

Materials 2026, 19(1), 129; https://doi.org/10.3390/ma19010129 - 30 Dec 2025

Cited by 1 | Viewed by 685

Abstract

This study evaluated the properties of two commercial filaments intended for medical and sterile applications: PLACTIVE (Copper 3D, Santiago, Chile) and CPE ANTIBAC (Fiberlogy, Brzezie, Poland). The aim of the research was to compare the dimensional accuracy, repeatability of the fused deposition modeling [...] Read more.

This study evaluated the properties of two commercial filaments intended for medical and sterile applications: PLACTIVE (Copper 3D, Santiago, Chile) and CPE ANTIBAC (Fiberlogy, Brzezie, Poland). The aim of the research was to compare the dimensional accuracy, repeatability of the fused deposition modeling (FDM) 3D printing process, and the antibacterial properties of the samples using standardized procedures. Four types of samples were manufactured: geometrically differentiated specimens for metrological measurements (S1); cylinders with a diameter of 15 mm and a height of 40 mm for assessing process repeatability (S2); rectangular specimens measuring 40 × 40 × 2 mm for surface topography analysis (S3); and rectangular samples measuring 20 × 20 × 2 mm for biocidal property evaluation (S4). The results demonstrated that PLACTIVE samples exhibited higher dimensional conformity with nominal values and lower variability of diameters than CPE ANTIBAC samples, which may be associated with greater process stability. For both materials, the PSm parameter was correlated with layer height only in the 90° printing orientation. Surface topography analysis showed that increasing the layer height from 0.08 mm to 0.20 mm led to a significant rise in Rsm, Ra, and Sa values, indicating deterioration in the reproduction of micro-irregularities and increased spatial differentiation of the surface. For PLACTIVE samples, a tendency toward more convex structures with positive Rsk values and moderate kurtosis (Rku) was observed, suggesting uniform plasticization and stable interlayer bonding, particularly at the 0° orientation. In contrast, CPE ANTIBAC samples (especially those printed at 90°) were characterized by higher Ra and Sa values and negative skewness (Rsk), indicating valley-dominated, sharper surface morphology resulting from different rheological behavior and faster solidification of the material. PLACTIVE samples did not exhibit antibacterial properties against Escherichia coli (E. coli), while for Staphylococcus aureus (S. aureus), the activity was independent of printing direction and layer height. The CPE ANTIBAC material showed antibacterial effects against both tested strains in approximately 50% of the samples. The findings provide insights into the relationships between material type, printing orientation, and process parameters in shaping the dimensional and biocidal properties of FDM filaments. Full article

(This article belongs to the Special Issue Preparation, Properties and Applications of Biocomposites)

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27 pages, 5090 KB

Open AccessEditor’s ChoiceReview

Advanced High-Strength Medium-Manganese Steels as an Alternative to Conventional Forging Steels: A Review

by Aleksandra Kozłowska and Anna Wojtacha

Materials 2026, 19(1), 109; https://doi.org/10.3390/ma19010109 - 28 Dec 2025

Cited by 1 | Viewed by 1007

Abstract

This review highlights conventional forging steels and advanced medium-Mn steels containing retained austenite (RA), emphasizing their potential for industrial forging applications. Modern steels intended for forgings are required to combine strength, ductility, toughness and fatigue resistance with good hardenability and machinability at minimal [...] Read more.

This review highlights conventional forging steels and advanced medium-Mn steels containing retained austenite (RA), emphasizing their potential for industrial forging applications. Modern steels intended for forgings are required to combine strength, ductility, toughness and fatigue resistance with good hardenability and machinability at minimal cost. Medium-Mn multiphase steels fulfill these requirements by the strain-induced martensitic transformation (SIMT) of fine, lath-type RA, which can create a strength–ductility balance. Ferritic–austenitic steels provide high ductility with moderate strength, martensitic–austenitic steels show very high strength at the expense of ductility, and bainitic–austenitic steels achieve intermediate properties. Impact toughness and fatigue resistance are strongly influenced by the morphology of RA. The lath-type RA enhances energy absorption and delays crack initiation, while blocky RA may promote intergranular fracture. Low carbon (0.2–0.3 wt.%) combined with elevated manganese (3–7 wt.%) contents provides superior hardenability and machinability, enabling cost-effective air-hardening of components with various cross-sections. Advanced medium-Mn steels provide a superior mechanical performance and economically attractive solution for modern forgings, exceeding the limitations of conventional steel grades. Full article

(This article belongs to the Special Issue Advanced High-Strength Steels: Processing and Characterization)

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20 pages, 6603 KB

Open AccessEditor’s ChoiceArticle

Effect of Cryogenic Treatment on Low-Density Magnesium Multicomponent Alloys with Exceptional Ductility

by Yu Fang, Michael Johanes and Manoj Gupta

Materials 2026, 19(1), 100; https://doi.org/10.3390/ma19010100 - 27 Dec 2025

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Abstract

There is growing emphasis on lightweight and energy-efficient metallic materials, with multicomponent alloying (MCA) being one strategy to achieve this. This was combined with the inherently lightweight magnesium (Mg) as the base metal. Two Mg-based MCAs, namely Mg-71MCA and Mg-80MCA (Mg-10Li-9Al-6Zn-4Si and Mg-10Li-6Al-2Zn-2Si, [...] Read more.

There is growing emphasis on lightweight and energy-efficient metallic materials, with multicomponent alloying (MCA) being one strategy to achieve this. This was combined with the inherently lightweight magnesium (Mg) as the base metal. Two Mg-based MCAs, namely Mg-71MCA and Mg-80MCA (Mg-10Li-9Al-6Zn-4Si and Mg-10Li-6Al-2Zn-2Si, respectively, wt.%), with density in the range of 1.55–1.632 g/cc akin to plastics were synthesized via the Disintegrated Melt Deposition method in this work. The effects of cryogenic treatment (CT) at –20 °C, 80 °C, and –196 °C (LN) on the physical, microstructural, thermal, and mechanical properties were systematically evaluated. CT resulted in densification, significant grain refinement (up to a 27.9% reduction in grain diameter after LN treatment), alterations in crystallographic texture, and notable changes to secondary phases—namely, an increased precipitate area fraction. These led to enhanced mechanical performance such as damping capacity, microhardness, and compressive response (most apparent for Mg-71MCA with 12.1%, 6.7%, and 1.6% increase in yield strength, ultimate compressive strength, and energy absorbed, respectively, after RF20 treatment), coupled with exceptional ductility (>80% strain without fracture), which is superior to pure Mg and commercial Mg alloys. Overall, this work showcases the potential of MCAs compared to existing conventional lightweight materials, as well as the property-enhancing/tailoring effects brought upon by different CT temperatures. This highlights the multi-faceted nature of material designs where compositional control and judicious processing parameter selection need to be both leveraged to optimize final properties, and serves as a baseline for further lightweight MCA development to meet future needs. Full article

(This article belongs to the Special Issue Advances in Al/Mg/Cu Alloys and Their Composites: Welding, Additive Manufacturing, Heterogeneous Microstructures, and Mechanical Properties)

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13 pages, 3595 KB

Open AccessEditor’s ChoiceArticle

Study on the Application of Machine Learning of Melt Pool Geometries in Silicon Steel Fabricated by Powder Bed Fusion

by Ho Sung Jang, Sujeong Kim, Jong Bae Jeon, Donghwi Kim, Yoon Suk Choi and Sunmi Shin

Materials 2026, 19(1), 68; https://doi.org/10.3390/ma19010068 - 24 Dec 2025

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Abstract

In this study, regression-based machine learning models were developed to predict the melt pool width and depth formed during the Laser Powder Bed Fusion (LPBF) process for Fe-3.4Si and Fe-6Si alloys. Based on experimentally obtained melt pool width and depth data, a total [...] Read more.

In this study, regression-based machine learning models were developed to predict the melt pool width and depth formed during the Laser Powder Bed Fusion (LPBF) process for Fe-3.4Si and Fe-6Si alloys. Based on experimentally obtained melt pool width and depth data, a total of 11 regression models were trained and evaluated, and hyperparameters were optimized via Bayesian optimization. Key process parameters were identified through data preprocessing and feature engineering, and SHAP analysis confirmed that the input energy had the strongest influence on both melt pool width and depth. The comparison of prediction performance revealed that the support vector regressor with a linear kernel (SVR_lin) exhibited the best performance for predicting melt pool width, while the multilayer perceptron (MLP) model achieved the best results for predicting melt pool depth. Based on these trained models, a power–velocity (P-V) process map was constructed, incorporating boundary conditions such as the overlap ratio and the melt pool morphology. The optimal input energy range was derived as 0.45 to 0.60 J/mm, ensuring stable melt pool formation. Specimens manufactured under the derived conditions were analyzed using 3D X-ray CT, revealing porosity levels ranging from 0.29% to 2.89%. In particular, the lowest porosity was observed under conduction mode conditions when the melt pool depth was approximately 1.0 to 1.5 times the layer thickness. Conversely, porosity tended to increase in the transition mode and lack of fusion regions, consistent with the model predictions. Therefore, this study demonstrated that a machine learning-based regression model can reliably predict melt pool characteristics in the LPBF process of Fe-Si alloys, contributing to the development of process maps and optimization strategies. Full article

(This article belongs to the Special Issue Intelligent Processing Technology of Materials)

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11 pages, 4932 KB

Open AccessEditor’s ChoiceArticle

Enhanced Electron–Phonon Coupling of Superconductivity in Indium-Doped Topological Crystalline Insulator SnTe

by Kwan-Young Lee, Gareoung Kim, Jae Hyun Yun, Jin Hee Kim and Jong-Soo Rhyee

Materials 2026, 19(1), 73; https://doi.org/10.3390/ma19010073 - 24 Dec 2025

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Abstract

Indium-doped SnTe (Sn_1−xIn_xTe) provides a model platform for exploring the emergence of superconductivity within a topological crystalline insulator. Here, we present a systematic investigation of the structural, transport, and thermodynamic properties of high-quality single crystals with 0.0 ≤ x [...] Read more.

Indium-doped SnTe (Sn_1−xIn_xTe) provides a model platform for exploring the emergence of superconductivity within a topological crystalline insulator. Here, we present a systematic investigation of the structural, transport, and thermodynamic properties of high-quality single crystals with 0.0 ≤ x ≤ 0.5. All compositions up to x = 0.4 form a single-phase cubic structure, enabling a controlled study of the superconducting state. Electrical resistivity and specific heat measurements reveal a bulk, fully gapped s-wave superconducting phase whose transition temperature increases monotonically with In concentration, reaching Tc ≈ 4.7 K at x = 0.5. Analysis of the electronic specific heat and McMillan formalism shows that the electron–phonon coupling constant λ_el_-_ph systematically increases with doping, while the Debye temperature systematically decreases, resulting in the lattice softening. This behavior, together with the observed evolution of the normal-state resistivity exponent from Fermi-liquid (n ≈ 2.04) toward non-Fermi-liquid values (n ≈ 1.72), demonstrates a clear crossover from weak to strong interaction with increasing In content. These results establish Sn_1−xIn_xTe as a tunable superconducting system in which coupling strength can be continuously controlled, offering a promising platform for future studies on the interplay between phonon-mediated superconductivity and crystalline topological band structure. Full article

(This article belongs to the Special Issue Advances in Superconductor Materials: Preparation and Characterization)

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14 pages, 3045 KB

Open AccessEditor’s ChoiceArticle

Effectiveness of Ozone Treatment, Ultrasonic Treatment, and Ultraviolet Irradiation in Removing Candida albicans Adhered to Acrylic Resins Fabricated by Different Manufacturing Methods

by Chihiro Kaneko, Tomofumi Sawada, Taichi Ishikawa, Toshitaka Miura, Takuya Kobayashi and Shinji Takemoto

Materials 2026, 19(1), 53; https://doi.org/10.3390/ma19010053 - 23 Dec 2025

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Abstract

Acrylic resins are commonly used for denture bases due to ease of molding but are prone to water absorption and microbial contamination. This study aimed to evaluate the effects of ozonated water immersion (OZ), ultrasonic cleaning (US), and ultraviolet (UV) irradiation on the [...] Read more.

Acrylic resins are commonly used for denture bases due to ease of molding but are prone to water absorption and microbial contamination. This study aimed to evaluate the effects of ozonated water immersion (OZ), ultrasonic cleaning (US), and ultraviolet (UV) irradiation on the removal of Candida albicans from acrylic resins produced by heat curing and additive manufacturing. The resin specimens were then subjected to treatment with OZ, US, UV irradiation, and commercial denture cleansers. Following treatment, the number of viable C. albicans cells was quantified and statistically analyzed (α = 0.05), morphology was observed under a scanning electron microscope (SEM) and fluorescence imaging. OZ, US, and UV irradiation significantly reduced the viable C. albicans count. Notably, the combination of the three treatments achieved a reduction exceeding 99.9% of viable cells. Although SEM revealed that C. albicans remained on the specimens, fluorescence imaging demonstrated a progressive decrease in viable cells and an increase in dead cells with each treatment, with the greatest effect observed when the three treatments were combined. The difference of removal behaviors of C. albicans among fabrication methods was not observed, comparable to denture cleaners. The combined application of all three treatments was the most effective strategy for microbial removal. Full article

(This article belongs to the Special Issue Advances and Applications of 3D Printing and Additive Manufacturing)

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14 pages, 1892 KB

Open AccessEditor’s ChoiceArticle

In Situ Dose Measurements in Brachytherapy Using Scintillation Detectors Based on the Al₂O₃:C, Al₂O₃:C,Mg, and GAGG:Ce Crystals

by Sandra Witkiewicz-Lukaszek, Janusz Winiecki, Bogna Sobiech, Mark Akselrod and Yuriy Zorenko

Materials 2026, 19(1), 45; https://doi.org/10.3390/ma19010045 - 22 Dec 2025

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Abstract

Currently, the use of scintillation crystals connected via optical fiber to a luminescence spectrometer (so-called fiber-optic dosimeters) offers a promising approach for real-time dosimetric measurements during brachytherapy treatments with γ-ray sources. This study aims to evaluate the applicability of fiber-optic dosimeters for in [...] Read more.

Currently, the use of scintillation crystals connected via optical fiber to a luminescence spectrometer (so-called fiber-optic dosimeters) offers a promising approach for real-time dosimetric measurements during brachytherapy treatments with γ-ray sources. This study aims to evaluate the applicability of fiber-optic dosimeters for in situ dose measurements during brachytherapy procedures, using Al₂O₃:C and Al₂O₃:C,Mg crystals, which have near-tissue density and effective atomic number (ρ = 3.99 g/cm³, Z_eff = 10.8), as well as heavy GAGG:Ce scintillation crystals (ρ = 6.63 g/cm³, Z_eff = 54.4). Radiation dose delivery was assessed through measurements of the resulting radioluminescence of the aforementioned scintillation crystals, connected via long optical fibers and recorded with highly sensitive, compact luminescence spectrometers. Measurements were performed in a dedicated phantom under clinical conditions at the Oncology Center in Bydgoszcz, Poland. The dosimeters were evaluated for in situ dose monitoring within the 0.5–8 Gy range during brachytherapy procedures using a ¹⁹²Ir (392 keV) source. The results showed a clear linear relationship between the delivered radiation dose and the scintillation output measured by the fiber-optic detector. The Gd₃Al_2.5Ga_2.5O₁₂:Ce crystal detector exhibited excellent linearity, while the Al₂O₃:C and Al₂O₃:C,Mg crystal detectors also showed a nearly linear dose–response relationship. Full article

(This article belongs to the Special Issue Advanced Scintillator and Detector Materials for Radiation Physics and Nuclear Medicine)

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33 pages, 2704 KB

Open AccessEditor’s ChoiceReview

Why Does Mucoadhesion Matter? Mucoadhesive Drug Delivery Systems with Antifungal Activity in the Local Treatment of Oral Cavity Candidiasis

by Katarzyna Olechno, Julia Higuchi and Katarzyna Winnicka

Materials 2026, 19(1), 33; https://doi.org/10.3390/ma19010033 - 21 Dec 2025

Cited by 1 | Viewed by 1203

Abstract

Disorders in the oral cavity caused by pathogenic fungi pose a significant clinical challenge, particularly in immunocompromised patients, as well as those undergoing oncological therapy or antibiotic treatment. A practical therapeutic approach involves the topical application of mucoadhesive drug dosage forms. However, only [...] Read more.

Disorders in the oral cavity caused by pathogenic fungi pose a significant clinical challenge, particularly in immunocompromised patients, as well as those undergoing oncological therapy or antibiotic treatment. A practical therapeutic approach involves the topical application of mucoadhesive drug dosage forms. However, only a limited number of such preparations are available on the pharmaceutical market. Mucoadhesive systems are especially advantageous, as they ensure prolonged retention and adequate concentrations of the active substances at the site of infection. Localized drug delivery enhances therapeutic efficacy compared to systemic administration, enabling lower drug doses, and consequently reducing the risk of side effects. Moreover, many fungal conditions require long-term treatment, which may be optimized by the use of mucoadhesive systems, improving patient compliance. Considering the issue of limited adhesion of conventional drug dosage forms and the moist environment in the oral cavity, providing optimal mucoadhesive properties is a key aspect. This article presents a comprehensive overview of the significance of treating oral candidiasis using mucoadhesive drug dosage forms, the mechanisms and advantages of mucoadhesion (including relevant polymers), and, most importantly, recent scientific reports on the development and quality assessment of mucoadhesive drug delivery systems for the management of oral fungal diseases. Full article

(This article belongs to the Section Biomaterials)

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20 pages, 6044 KB

Open AccessEditor’s ChoiceArticle

Photocatalytic Decomposition of Carmoisine and Crystal Violet by Ho-Doped TiO₂ Sol-Gel Powders

by Nina Kaneva, Stefani Petrova and Albena Bachvarova-Nedelcheva

Materials 2026, 19(1), 17; https://doi.org/10.3390/ma19010017 - 20 Dec 2025

Cited by 1 | Viewed by 843

Abstract

This study explores the sol–gel synthesis, structural characterization, and photocatalytic performance of Ho³⁺-doped TiO₂ nanopowders at two dopant levels (0.5 and 2 mol%). Transparent, homogeneous gels were prepared using titanium (IV) butoxide and holmium (III) nitrate pentahydrate in ethanol, followed [...] Read more.

This study explores the sol–gel synthesis, structural characterization, and photocatalytic performance of Ho³⁺-doped TiO₂ nanopowders at two dopant levels (0.5 and 2 mol%). Transparent, homogeneous gels were prepared using titanium (IV) butoxide and holmium (III) nitrate pentahydrate in ethanol, followed by drying and optional annealing at 500 °C. X-ray diffraction confirmed anatase TiO₂ as the dominant crystalline phase, with Ho incorporation suppressing crystal growth and yielding smaller crystallite sizes than undoped TiO₂. FT-IR and UV-Vis spectroscopy verified complete hydrolysis–condensation during gel formation, while diffuse reflectance spectra revealed a red-shifted absorption edge, indicating reduced band gaps. SEM analysis showed nanoscale particles with agglomeration, which intensified after annealing. Photocatalytic activity was tested under UV irradiation using Crystal Violet (anionic dye) and Carmoisine (cationic dye). Annealed Ho-doped powders exhibited markedly higher degradation rates, with the 2 mol% sample achieving the greatest efficiency, particularly against Crystal Violet. These findings demonstrate that Ho³⁺ doping enhances TiO₂’s UV-driven photocatalytic activity by tailoring its structural and optical properties. Full article

(This article belongs to the Special Issue Photocatalysis for a Green Future: Breaking Barriers in Energy, Environment, and Healthcare)

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16 pages, 9578 KB

Open AccessEditor’s ChoiceArticle

Effect of Molybdenum on Microstructural Evolution and High Cycle Fatigue Properties of Ti-xMo-2Fe Alloys

by HyoWoon Hwang and Dong-Geun Lee

Materials 2026, 19(1), 10; https://doi.org/10.3390/ma19010010 - 19 Dec 2025

Cited by 1 | Viewed by 606

Abstract

Ti-xMo-2Fe alloys with high specific strength were designed by adding Mo and Fe as β-stabilizing elements. The influence of cold swaging on the martensitic transformations in Ti-xMo-2Fe (x = 3.4, 5, 9.2 wt.%) alloys was investigated. In these alloys, appropriate chemical compositions promote [...] Read more.

Ti-xMo-2Fe alloys with high specific strength were designed by adding Mo and Fe as β-stabilizing elements. The influence of cold swaging on the martensitic transformations in Ti-xMo-2Fe (x = 3.4, 5, 9.2 wt.%) alloys was investigated. In these alloys, appropriate chemical compositions promote a stress-induced phase transformation from the β phase to orthorhombic α″ martensite, which improves elongation while maintaining high strength. As the Mo content increases from 3.4 to 5 wt.%, the amount of β-stabilizing elements increases and the β stability is enhanced, thereby altering the phase transformation mechanism. In the Ti-9.2Mo-2Fe alloy, both α″ martensite and a very hard ω phase were identified by X-ray diffraction and transmission electron microscopy. The hard and brittle ω phase causes premature brittle fracture prior to macroscopic yielding. Among the investigated alloys, the Ti-5Mo-2Fe alloy exhibits the best overall combination of high tensile strength, elongation to failure, and high fatigue strength. Full article

(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Third Edition))

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30 pages, 13137 KB

Open AccessEditor’s ChoiceArticle

Effect of Ni Addition on the Solidification of Liquid Al and Solid Cu Diffusion Couples

by Vigneshwar Hari, Stuart D. McDonald, Xin Fu Tan and Kazuhiro Nogita

Materials 2025, 18(24), 5689; https://doi.org/10.3390/ma18245689 - 18 Dec 2025

Cited by 1 | Viewed by 790

Abstract

Al-Ni alloys have a unique set of properties including high conductivity, high fluidity, good thermal stability, and reasonable strength. These properties are also needed for effective braze fillers, a novel application for Al-Ni alloys. A Cu substrate was reacted with pure liquid Al, [...] Read more.

Al-Ni alloys have a unique set of properties including high conductivity, high fluidity, good thermal stability, and reasonable strength. These properties are also needed for effective braze fillers, a novel application for Al-Ni alloys. A Cu substrate was reacted with pure liquid Al, and the resulting microstructure upon solidification was observed and analysed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). This diffusion couple was compared with the diffusion couple between liquid eutectic Al-3at.%Ni and a Cu substrate. Several phases unique to the solidified liquid in the Al-Ni/Cu diffusion couple were observed, such as Al₇Cu₄Ni (τ), Al₃(Cu, Ni)₂, and Al₃Ni. These microstructures were compared with a mathematical model based on Fick’s second law, as well as calculation of phase diagram (CALPHAD) modelling. The approximate calculated concentration profile of Cu in the liquid phase was validated against the microstructural observations and proved effective to explain the observed microstructural features. Liquid Al-3at.%Ni was found to limit the growth of the brittle Al₂Cu (θ) phase during solidification by limiting Cu solubility in the liquid phase, which would be beneficial for use in dissimilar joints between Al and Cu. Full article

(This article belongs to the Section Metals and Alloys)

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14 pages, 11633 KB

Open AccessEditor’s ChoiceArticle

Molybdenum Nitride and Oxide Layers Grown on Mo Foil for Supercapacitors

by Dong Hyun Lim and Young-Il Kim

Materials 2025, 18(24), 5649; https://doi.org/10.3390/ma18245649 - 16 Dec 2025

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Abstract

In this study, thin molybdenum nitride (MoN_x) layers were directly synthesized on molybdenum foil via thermal treatment under an NH₃ atmosphere, and their phase evolution, structural characteristics, and electrochemical performance were investigated. The thickness and morphology of the MoN_x [...] Read more.

In this study, thin molybdenum nitride (MoN_x) layers were directly synthesized on molybdenum foil via thermal treatment under an NH₃ atmosphere, and their phase evolution, structural characteristics, and electrochemical performance were investigated. The thickness and morphology of the MoN_x layers were controlled by varying ammonolysis time and temperature, while subsequent annealing in N₂ converted the nitride layer into MoO₂. Meanwhile, oxidation in air yielded crystalline MoO₃ layers. X-ray diffraction and X-ray photoelectron spectroscopy confirmed progressive oxidation of molybdenum, with Mo 3d binding energies increasing in the sequence of Mo < MoN_x < MoO₂ < MoO₃, consistent with their nominal oxidation states. Electrochemical characterization revealed that both MoN_x/Mo and MoO₂/Mo electrodes exhibit notable pseudocapacitive behavior in 0.5 M H₂SO₄ electrolyte, with areal specific capacitances reaching up to 520 mF cm⁻² at 10 mV s⁻¹. Increasing layer thickness led to enhanced capacitance, likely due to an increase in the electrochemically accessible surface area and the extension of ion diffusion pathways. MoO₂-coated samples showed stronger faradaic contribution and superior rate capability compared to MoN_x counterparts, along with a gradual shift from predominantly electric double-layer capacitance toward hybrid pseudocapacitive charge storage mechanisms. Full article

(This article belongs to the Special Issue Sustainable Functional Materials for Energy and Environmental Applications)

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16 pages, 1905 KB

Open AccessEditor’s ChoiceArticle

Modifying Polylactide with Powdered Cork Filler

by Mariusz Fabijański, Jacek Garbarski and Zbigniew Szymaniak

Materials 2025, 18(24), 5606; https://doi.org/10.3390/ma18245606 - 13 Dec 2025

Cited by 1 | Viewed by 582

Abstract

The paper presents the results of experimental testing of a PLA-based composite, modified with powdered cork and a compatibilizer. The purpose of applying these additives was to evaluate their influence upon the physical, structural and functional properties of the obtained material. Specimens with [...] Read more.

The paper presents the results of experimental testing of a PLA-based composite, modified with powdered cork and a compatibilizer. The purpose of applying these additives was to evaluate their influence upon the physical, structural and functional properties of the obtained material. Specimens with various cork and compatibilizer contents were analyzed to evaluate the synergic interaction between the polymer base and the filler. The tests of the mechanical properties, water absorption and FTIR analysis were carried out. The results confirmed that the cork filler improved the PLA-based composite both in terms of the utility and ecological aspects. Despite a certain mechanical deterioration, the properties remain fully acceptable for packaging applications. Also, the improvement of hardness at higher cork content was observed, which points to effective phase interaction and a good adherence of the components. The FTIR spectroscopy confirmed chemical stability of the base and the lack of unwanted degradation reactions. The obtained composite is an innovative, biodegradable polymer material that utilizes natural waste in a way which is both economic and environmentally friendly. The obtained results point to a high application potential of this kind of composite, mainly in the packaging industry and in the field of ecological utility materials. Full article

(This article belongs to the Section Polymeric Materials)

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20 pages, 4134 KB

Open AccessEditor’s ChoiceArticle

Effect of Hyaluronic Acid Content on Functional Properties, Antioxidant Activity, and In Vitro Digestion of Food-Grade Furcellaran Hydrogels and Emulgels

by Anna Stępień, Lesław Juszczak, Aneta Koronowicz, Aleksandra Such, Grzegorz Kowalski, Beata Synkiewicz-Musialska, Piotr Zachariasz and Ewelina Jamróz

Materials 2025, 18(24), 5581; https://doi.org/10.3390/ma18245581 - 12 Dec 2025

Viewed by 593

Abstract

Gel biocomposites, with their wide range of properties, are increasingly popular in many industries, while hyaluronic acid (HA), due to its unique water-binding mechanisms, has a high application potential in these types of materials. Furcellaran-based composite hydrogels and emulsion gels with different HA [...] Read more.

Gel biocomposites, with their wide range of properties, are increasingly popular in many industries, while hyaluronic acid (HA), due to its unique water-binding mechanisms, has a high application potential in these types of materials. Furcellaran-based composite hydrogels and emulsion gels with different HA additions were produced and the effect of HA concentration on physical, color, textural, mechanical, rheological, and antioxidant properties was evaluated. A polysaccharide network was observed, which—according to Fourier transform infrared spectroscopy(FTIR) and X-ray diffraction (XRD) data—is stabilized by hydrogen bonding. Emulsion gels revealed denser structures. Small deformation tests confirmed elastic–solid type of all investigated gels. The opposite effect of HA on the swelling behavior of hydro- and emulgels was observed. Increasing hyaluronic acid content resulted in elasticity enhancement and hardness reduction. Antioxidant potential of composites significantly increased with HA concentration. The obtained materials have potential applications as plat-based delivery systems for hydrophilic and lipophilic bioactive components. Full article

(This article belongs to the Special Issue Functional Hydrogels: Design, Properties and Applications (Second Edition))

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18 pages, 10014 KB

Open AccessEditor’s ChoiceArticle

Directional Coupling of Surface Plasmon Polaritons at Exceptional Points in the Visible Spectrum

by Amer Abdulghani, Salah Abdo, Khalil As’ham, Ambali Alade Odebowale, Andrey E. Miroshnichenko and Haroldo T. Hattori

Materials 2025, 18(24), 5595; https://doi.org/10.3390/ma18245595 - 12 Dec 2025

Viewed by 680

Abstract

Robust control over the coupling and propagation of surface plasmon polaritons (SPPs) is essential for advancing various plasmonic applications. Traditional planar structures, commonly used to design SPP directional couplers, face limitations such as low extinction ratios and design complexities. These issues frequently hinder [...] Read more.

Robust control over the coupling and propagation of surface plasmon polaritons (SPPs) is essential for advancing various plasmonic applications. Traditional planar structures, commonly used to design SPP directional couplers, face limitations such as low extinction ratios and design complexities. These issues frequently hinder the dense integration and miniaturisation of photonic systems. Recently, exceptional points (EPs)—unique degeneracies within the parameter space of non-Hermitian systems—have garnered significant attention for enabling a range of counterintuitive phenomena in non-conservative photonic systems, including the non-trivial control of light propagation. In this work, we develop a rigorous temporal coupled-mode theory (TCMT) description of a non-Hermitian metagrating composed of alternating silicon–germanium nanostrips and use it to explore the unidirectional excitation of SPPs at EPs in the visible spectrum. Within this framework, EPs, typically associated with the coalescence of eigenvalues and eigenstates, are leveraged to manipulate light propagation in nonconservative photonic systems, facilitating the refined control of SPPs. By spatially modulating the permittivity profile at a dielectric–metal interface, we induce a passive parity–time (

PT

)-symmetry, which allows for refined tuning of the SPPs’ directional propagation by optimising the structure to operate at EPs. At these EPs, a unidirectional excitation of SPPs with a directional intensity extinction ratio as high as 40 dB between the left and right excited SPP modes can be reached, with potential applications in integrated optical circuits, visible communication technologies, and optical routing, where robust and flexible control of light at the nanoscale is crucial. Full article

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

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17 pages, 16918 KB

Open AccessEditor’s ChoiceArticle

Key Factors Influencing the Mechanical Properties of Binodal Decomposed Metallic Glass Composites

by Yongwei Wang, Guangping Zheng and Mo Li

Materials 2025, 18(24), 5593; https://doi.org/10.3390/ma18245593 - 12 Dec 2025

Viewed by 550

Abstract

Structural heterogeneity plays a crucial role in enhancing the mechanical properties of metallic glasses (MGs) by impeding the propagation of shear bands (SBs). Metallic glass matrix composites (MGCs) consisting of reinforcements are of great interest as they enhance the mechanical performance of brittle [...] Read more.

Structural heterogeneity plays a crucial role in enhancing the mechanical properties of metallic glasses (MGs) by impeding the propagation of shear bands (SBs). Metallic glass matrix composites (MGCs) consisting of reinforcements are of great interest as they enhance the mechanical performance of brittle MGs. However, managing the dispersity of hetero-phases within the glassy matrix presents technical challenges due to surface tension and thermal property incompatibility. Binodal phase separation is an effective approach for fabricating MGCs with uniformly dispersed glassy droplets or particles. The species of matrix and characteristics of particle reinforcements significantly influence mechanical properties. This study theoretically examines how the fraction, size, and variety of particle reinforcements influence performance using finite element models based on free volume theory. The synergistic mechanisms for performance tuning involve stress fields generated by particle reinforcements that modify the nucleation and propagation of SBs in the matrix. Additionally, the size effect of particles depends on their interaction with SBs. This comprehensive understanding could substantially enhance the design and optimization for MGCs. Full article

(This article belongs to the Special Issue Next-Generation Alloys: Nanostructured Metals, Complex Steels, and Multi-Component Systems)

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27 pages, 8431 KB

Open AccessEditor’s ChoiceArticle

A Comparison Between the Growth of Naturally Occurring Three-Dimensional Cracks in Scalmalloy^® and Pre-Corroded 7085-T7452 and Its Implications for Additively Manufactured Limited-Life Replacement Parts

by Daren Peng, Shareen S. L. Chan, Ben Main, Andrew S. M. Ang, Nam Phan, Michael R. Brindza and Rhys Jones

Materials 2025, 18(24), 5586; https://doi.org/10.3390/ma18245586 - 12 Dec 2025

Viewed by 780

Abstract

This paper is the first to reveal that the conventionally built aluminium alloy (AA) 7085-T7452 has mechanical properties, viz: a yield stress, ultimate strength, and an elongation to failure, that are similar to that of laser powder bed fusion (LPBF) built Scalmalloy^® [...] Read more.

This paper is the first to reveal that the conventionally built aluminium alloy (AA) 7085-T7452 has mechanical properties, viz: a yield stress, ultimate strength, and an elongation to failure, that are similar to that of laser powder bed fusion (LPBF) built Scalmalloy^®. Following this observation, the growth of cracks that nucleated from corrosion pits in AA7085-T7452 specimens that had been exposed to a 5 wt% NaCl salt fog environment at 35 °C according to ASTM B117-19 standard for fourteen days is then studied. The specimen geometries were chosen to be identical to those associated with a similar study on Boeing Space, Intelligence, and Weapon Systems (BSI&WS) LPBF built Scalmalloy^®. This level of prior exposure led to pits in AA7085-T7452 that were approximately 0.5 mm deep with a surface width/diameter of up to approximately 1.5 mm. These pit sizes are broadly consistent with those leading to fatigue crack growth (FCG) in AA 7050-T7451 structural parts on the RAAF F/A-18 Classic Hornet fleet operating in a highly corrosive environment. Fatigue tests on these AA7085-T7452 specimens, under the same spectrum as used in the BSI&WS LPBF Scalmalloy^® study, reveals that AA7085-T7452 and Scalmalloy^® have similar crack growth histories. This, in turn, leads to the discovery that the growth of naturally occurring three-dimensional (3D) cracks in AA 7085-T7452 could be predicted using the crack growth equation developed for BSI&WS LPBF Scalmalloy^®, albeit with allowance made for their different fracture toughness’s. These findings suggest that Scalmalloy^® may be suitable for printing parts for both current and future attritable aircraft. Full article

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

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13 pages, 4637 KB

Open AccessEditor’s ChoiceArticle

Rapid Stress Relief of Ti-6Al-4V Titanium Alloy by Electropulsing Treatment

by Aprilia Aprilia, Jin Lee Tan, Zixuan Ling, Vincent Gill, Paul Williams, Martyn A. Jones and Wei Zhou

Materials 2025, 18(24), 5555; https://doi.org/10.3390/ma18245555 - 11 Dec 2025

Viewed by 1079

Abstract

This study investigates the effectiveness and underlying mechanisms of electropulsing treatment (EPT) for rapid stress relief of Ti-6Al-4V titanium alloy. Stress relief is an essential step in manufacturing processes to ensure long component lifespan. Residual stress accumulation within a component is often undesirable, [...] Read more.

This study investigates the effectiveness and underlying mechanisms of electropulsing treatment (EPT) for rapid stress relief of Ti-6Al-4V titanium alloy. Stress relief is an essential step in manufacturing processes to ensure long component lifespan. Residual stress accumulation within a component is often undesirable, as it may lead to premature failures. Currently, the stress relief of titanium alloys is typically carried out using an annealing heat-treatment process in a vacuum furnace. However, this method is time-consuming, usually requiring several hours. In this paper, an alternative fast stress relief method by EPT was investigated. A controllable pulsing treatment using alternating high density pulsing current with short pulse width was carried out. Results showed that EPT is effective in relieving residual stress in Ti-6Al-4V alloy. Up to 90% of the surface residual stresses induced by shot peening were successfully relieved by EPT with a treatment duration of only 114 ms. Reductions of low-angle grain boundaries (2–10°), local misorientation, and deformed grains were observed, while no significant grain growth or phase transformation was found. The stress-relief mechanism of EPT is attributed to the combined effects of dislocation movement driven by electron wind force (EWF), dislocation creep at elevated temperatures, and dislocation glide due to local yielding of residual stress under high-temperature conditions. The temperature rise during EPT was identified as a significant factor enabling stress relaxation. Full article

(This article belongs to the Special Issue Microstructure, Mechanical and Corrosion Properties of Metals, Alloys, and Composite Materials)

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26 pages, 18739 KB

Open AccessEditor’s ChoiceArticle

ZnO Thin Films as Promising Corrosion Protection on Mg-Based Alloys

by Aneta Kania, Magdalena M. Szindler, Marek Szindler, Zbigniew Brytan, Monika Kciuk, Wojciech Pakieła, Łukasz Reimann and Paweł M. Nuckowski

Materials 2025, 18(24), 5568; https://doi.org/10.3390/ma18245568 - 11 Dec 2025

Viewed by 561

Abstract

The present study examined the microstructure and corrosion characteristics of MgCa4Zn1Gd1 and MgCa2Zn1Gd3 alloys that were coated with ZnO thin films, which were deposited by atomic layer deposition (ALD). Coatings of different thicknesses (42.5, 95.4 and 133.7 nm for 500, 1000, and 1500 [...] Read more.

The present study examined the microstructure and corrosion characteristics of MgCa4Zn1Gd1 and MgCa2Zn1Gd3 alloys that were coated with ZnO thin films, which were deposited by atomic layer deposition (ALD). Coatings of different thicknesses (42.5, 95.4 and 133.7 nm for 500, 1000, and 1500 cycles, respectively) were characterized using X-ray diffraction (XRD), Raman spectroscopy, SEM/EDS, AFM (atomic force microscope), and FTIR (Fourier transform infrared spectroscopy). XRD and Raman analyses were conducted to verify the formation of crystalline zinc oxide (ZnO) with a homogeneous granular morphology. Surface roughness decreased with increasing coating thickness, reaching the lowest values for the 1500-cycle ZnO layer on MgCa2Zn1Gd3 (R_a = 7.65 nm, R_s = 9.8 nm). Potentiodynamic and immersion tests in Ringer solution at 37 °C revealed improved corrosion resistance for thicker coatings, with the lowest hydrogen evolution (20.89 mL·cm⁻²) observed for MgCa2Zn1Gd3 coated after 1500 cycles. Analysis of corrosion products by FTIR identified Mg(OH)₂ and MgCO₃ as dominant and then MgO and ZnO. Phase analysis also indicated the presence of ZnO coating after 100 h of immersion. The ZnO film deposited after 1500 ALD cycles on MgCa2Zn1Gd3 provides the most effective corrosion protection and is a promising solution for biodegradable magnesium implants. Full article

(This article belongs to the Special Issue Corrosion and Corrosion Protection of Metals/Alloys)

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11 pages, 2236 KB

Open AccessEditor’s ChoiceArticle

Microwave-Induced Hydrogen Plasma as a New Synthesis Process for High-Entropy Carbides

by Muhammad Shiraz Ahmad, Kallol Chakrabarty and Shane A. Catledge

Materials 2025, 18(24), 5520; https://doi.org/10.3390/ma18245520 - 9 Dec 2025

Viewed by 717

Abstract

Microwave-Induced Hydrogen Plasma (MIHP) is introduced as a novel synthesis route for producing high-entropy carbides (HECs), offering an alternative to conventional mechanical alloying and/or sintering techniques. In this study, a representative HEC composition,

{MoNbTaVWC}_{5}

, was successfully synthesized using MIHP processing at [...] Read more.

Microwave-Induced Hydrogen Plasma (MIHP) is introduced as a novel synthesis route for producing high-entropy carbides (HECs), offering an alternative to conventional mechanical alloying and/or sintering techniques. In this study, a representative HEC composition,

{MoNbTaVWC}_{5}

, was successfully synthesized using MIHP processing at 200 Torr. The process employs microwave energy to generate hydrogen plasma to facilitate carbothermal reduction of metal oxide precursors. The plasma environment generates abundant reactive atomic hydrogen species, which enhance reaction spontaneity and promote efficient HEC formation. X-ray diffraction confirmed the formation of a single-phase rocksalt-type face-centered cubic structure. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy confirmed uniform elemental distribution within the synthesized microstructure. Nanoindentation measurements yielded hardness and elastic modulus values consistent with literature reports for similar compositions. X-ray photoelectron spectroscopy confirmed the chemical state of carbon to be primarily bonded with metals as carbides, with only minor oxygen present as metal-oxides. Raman spectroscopy performed over the 750–1900

{cm}^{- 1}

range yielded a featureless spectrum with no detectable D or G bands often observed for sp²-hybridized disordered carbon, graphite, or graphene materials. These results validate the structural and chemical purity of the synthesized HECs. This work aims to demonstrate the feasibility and reproducibility of MIHP as a synthesis method for HECs. Full article

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

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19 pages, 4311 KB

Open AccessEditor’s ChoiceArticle

Effect of Initial Relative Density on Liquid-Phase Sintering Behaviors of Al Powder Using Al–Cu Eutectic Alloy Aid: In Situ Observations Using Tomography and Microscopy

by Ryotaro Kusunoki, Erika Matsumoto, Takeshi Higaki, Asuka Suzuki, Makoto Kobashi, Yukiko Ozaki, Masato Hoshino and Masayuki Uesugi

Materials 2025, 18(24), 5499; https://doi.org/10.3390/ma18245499 - 7 Dec 2025

Viewed by 929

Abstract

Aluminum (Al) powder with low sinterability is difficult to use in binder jetting (BJT) additive manufacturing, which involves sintering a metal powder after forming a green body. A liquid-phase sintering process for Al powder using Al–Cu eutectic alloy powder as a sintering aid [...] Read more.

Aluminum (Al) powder with low sinterability is difficult to use in binder jetting (BJT) additive manufacturing, which involves sintering a metal powder after forming a green body. A liquid-phase sintering process for Al powder using Al–Cu eutectic alloy powder as a sintering aid has recently been developed. In this study, to clarify the applicability of liquid-phase sintering to BJT additive manufacturing, the effect of the initial relative density of green bodies (ρ_rel,0 = 50–90%) on the final relative density was investigated. The final relative density was not significantly affected by ρ_rel,0 and achieved 96–97% after sintering at 630 °C for 1800 s. However, pores are likely to remain in the sintered body with a high ρ_rel,0 of 90%. In situ observations using synchrotron radiation X-ray computed tomography revealed that large pores were formed at the early sintering stage of the green body with ρ_rel,0 of 90% and partially retained after sintering. By contrast, the green body with ρ_rel,0 of 50% exhibited a significant rearrangement at the early sintering stage, promoting the densification. This study provides a deep understanding of liquid-phase sintering of Al powder, which is considered a suitable post-processing method for BJT additive manufacturing. Full article

(This article belongs to the Special Issue New Insight of Powder Metallurgy: Microstructure, Durability and Mechanical Properties—2nd Edition)

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13 pages, 2845 KB

Open AccessEditor’s ChoiceArticle

Comprehensive Characterization of a Reference Ferroelectric Nematic Liquid Crystal Material

by Ayusha Paul, Milon Paul, Manisha Badu, Arjun Ghimire, Netra Prasad Dhakal, Samuel Sprunt, Antal Jákli and James T. Gleeson

Materials 2025, 18(24), 5496; https://doi.org/10.3390/ma18245496 - 6 Dec 2025

Cited by 2 | Viewed by 2335

Abstract

Among the recently developed ferroelectric nematic liquid crystals, FNLC-919, synthesized by Merck Electronics KGaA, stands out for its stable, room-temperature, ferroelectric nematic (N_F) phase. This renders it a promising candidate for both fundamental research and device-level applications. In this study, we [...] Read more.

Among the recently developed ferroelectric nematic liquid crystals, FNLC-919, synthesized by Merck Electronics KGaA, stands out for its stable, room-temperature, ferroelectric nematic (N_F) phase. This renders it a promising candidate for both fundamental research and device-level applications. In this study, we present a comprehensive experimental investigation of FNLC-919, focusing on its structural, optical, dielectric, and elastic properties in the paraelectric nematic (N) and the intermediate antiferroelectric phase (dubbed N_X) that occur in a temperature range between the N and N_F phases. Key material parameters such as ferroelectric polarization, viscosity, and nanostructure are characterized as functions of temperature in all mesophases, while the orientational elastic constants are determined only in the N and N_X phases. Our findings are compared with prior results concerning the benchmark compound DIO that also exhibits the phase sequence N-N_X-N_F and reveals a smectic-like mass density wave coinciding with antiferroelectric ordering in the N_X phase. Full article

(This article belongs to the Section Soft Matter)

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12 pages, 2304 KB

Open AccessEditor’s ChoiceArticle

Analysis of Superjunction MOSFET (CoolMOS^TM) Concept Limitations—Part II: Simulations

by Zbigniew Lisik and Jacek Podgórski

Materials 2025, 18(23), 5468; https://doi.org/10.3390/ma18235468 - 4 Dec 2025

Cited by 1 | Viewed by 686

Abstract

The CoolMOS^TM (Infineon Technologies AG, Munich, Germany) has been regarded as a device that alleviates high-voltage limitations of unipolar power devices. However, although the theoretical considerations seem to confirm this possibility, this expectation has not been fulfilled to date. It appears that [...] Read more.

The CoolMOS^TM (Infineon Technologies AG, Munich, Germany) has been regarded as a device that alleviates high-voltage limitations of unipolar power devices. However, although the theoretical considerations seem to confirm this possibility, this expectation has not been fulfilled to date. It appears that there are some limitations in the CoolMOS^TM concept, and the paper deals with their identification. Part I concentrated on the theory of high-voltage superjunction and its implementation into a power VDMOS transistor, which resulted in the CoolMOS^TM structure. This part is aimed at the physical and technological limitations that have been identified, taking advantage of numerical investigations of CoolMOS^TM structures developed on the basis of a typical VDMOS one. Full article

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

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16 pages, 2120 KB

Open AccessEditor’s ChoiceArticle

Analysis of Superjunction MOSFET (CoolMOS™) Concept Limitations—Part I: Theory

by Zbigniew Lisik and Jacek Podgórski

Materials 2025, 18(23), 5451; https://doi.org/10.3390/ma18235451 - 3 Dec 2025

Cited by 1 | Viewed by 807

Abstract

The CoolMOS™ (Infineon Technologies AG, Munich, Germany) has been considered a device that alleviates high-voltage limitations of unipolar power devices, but although the theoretical considerations seem to confirm such a possibility, this expectation has not been fulfilled until now. This paper identifies limitations [...] Read more.

The CoolMOS™ (Infineon Technologies AG, Munich, Germany) has been considered a device that alleviates high-voltage limitations of unipolar power devices, but although the theoretical considerations seem to confirm such a possibility, this expectation has not been fulfilled until now. This paper identifies limitations of the CoolMOS™ concept. The analysis was carried out in two steps. The first step aimed at the theory of high-voltage superjunction and its implementation into a power VDMOS transistor, which resulted in the modified construction called CoolMOS™. The investigations have shown that the superjunction effect is not an inherent feature of high voltage junctions formed as a characteristic meander-like p-n junction. Such a junction starts to work in SuperJunction Mode (SJM) just when the electric field strength reaches the magnitude of the threshold electric field E_th. Also, other theoretical constraints concerning the SJ diode and CoolMOS™ design have been presented. The second step aimed at the physical and technological limitations that have been identified, taking advantage of numerical investigations for CoolMOS™ structures developed on the basis of a typical VDMOS one. Full article

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

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46 pages, 10017 KB

Open AccessEditor’s ChoiceReview

The 3D Printing of Flexible Materials: Technologies, Materials, and Challenges

by Suyun Li, Zengqin Shi, Yixuan Wang, Wenqing Wang and Rujie He

Materials 2025, 18(23), 5428; https://doi.org/10.3390/ma18235428 - 2 Dec 2025

Cited by 5 | Viewed by 2881

Abstract

Due to their unique functional properties, such as deformability, bendability, stretchability, and even biocompatibility, sensing, or actuation, flexible materials have become an indispensable and crucial component in electronic systems such as wearable electronic devices and soft robots. Facing the complex demands of various [...] Read more.

Due to their unique functional properties, such as deformability, bendability, stretchability, and even biocompatibility, sensing, or actuation, flexible materials have become an indispensable and crucial component in electronic systems such as wearable electronic devices and soft robots. Facing the complex demands of various application scenarios, 3D printing technology can be utilized to customize the preparation of various flexible materials into desired shapes. However, compared to rigid materials, flexible materials still face printing issues such as pore defects and weak interlayer bonding during the 3D printing process. Therefore, this paper focuses on analyzing the key bottleneck issues and technical challenges currently existing in flexible material 3D printing technology, and provides an overview of the progress in preparing flexible materials using 3D printing technologies, such as Material Extrusion and Vat Polymerization. Finally, it looks forward to the technical challenges and future development of 3D printing with flexible materials. Full article

(This article belongs to the Special Issue Advances and Applications of 3D Printing and Additive Manufacturing)

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23 pages, 13321 KB

Open AccessEditor’s ChoiceArticle

The Influence of REE Steel Modification on the Microstructure and Mechanical Characteristics Using Fractographic Analyses

by Robert Pała and Piotr Furmańczyk

Materials 2025, 18(23), 5408; https://doi.org/10.3390/ma18235408 - 30 Nov 2025

Viewed by 501

Abstract

Improving the operational parameters of machinery necessitates the use of materials with higher mechanical characteristics. Strength characteristics, particularly fracture toughness, are strongly linked to the material’s microstructure. This article presents the results of a study examining the effect of microstructure on the mechanical [...] Read more.

Improving the operational parameters of machinery necessitates the use of materials with higher mechanical characteristics. Strength characteristics, particularly fracture toughness, are strongly linked to the material’s microstructure. This article presents the results of a study examining the effect of microstructure on the mechanical properties and fracture toughness of G17CrMo5-5 cast steel in its basic and rare-earth modified variants. The addition of rare-earth elements (REEs) to the melt resulted in a reduction and homogenization in grain size, as well as a reduction in the size and shape of non-metallic inclusions. For modified cast steel, there were no grains with a chord size above 120 μm and inclusions with a diameter above 5.5 μm. Changes in the microstructure of modified cast steel resulted in a slight increase in strength properties. It significantly increased the fracture toughness: for unmodified cast steel at a temperature of −20 °C, the fracture toughness increased from 94 kN/m to 416 kN/m for modified cast steel. Fracture fractographic analysis using non-contact microroughness measurement techniques or measuring the width of the stretch zone allowed for the calculation of fracture toughness without the need for a conventional test. Fracture toughness calculated based on fractographic analysis can be determined for brittle fracture and brittle fracture preceded by plastic growth. Numerical simulations of the loading of specimens tested for fracture toughness allowed us to determine the effect of the REE steel modification on the stress field distribution ahead of the crack front. The modification resulted in a change in the opening stress distribution and the location of its maximum at each temperature. The use of REE modification is an effective approach for homogenizing the microstructure and increasing the fracture toughness of cast steel, especially when the material operates at temperatures in the interval of the fracture mechanism change. Full article

(This article belongs to the Section Metals and Alloys)

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21 pages, 6318 KB

Open AccessEditor’s ChoiceArticle

Study on Antibacterial Powder Coatings Based on Halloysite/Biopolymer Compounds

by Katarzyna Krawczyk, Barbara Pilch-Pitera, Michał Kędzierski, Małgorzata Zubielewicz, Izabela Kunce, Ewa Langer, Sebastian Jurczyk, Grażyna Kamińska-Bach, Ewa Ciszkowicz, Marta Przybysz-Romatowska, Damian Wojda, Leszek Komorowski and Michael Hilt

Materials 2025, 18(23), 5402; https://doi.org/10.3390/ma18235402 - 30 Nov 2025

Viewed by 781

Abstract

This study presents an eco-friendly approach to antibacterial polyester powder coatings by incorporating hybrid additives composed of biopolymers immobilized on halloysite nanotubes. Polylysine (PLY) and quaternized chitosan (CH-Q) were used as natural antimicrobial agents, while halloysite (HAL) acted as a carrier to improve [...] Read more.

This study presents an eco-friendly approach to antibacterial polyester powder coatings by incorporating hybrid additives composed of biopolymers immobilized on halloysite nanotubes. Polylysine (PLY) and quaternized chitosan (CH-Q) were used as natural antimicrobial agents, while halloysite (HAL) acted as a carrier to improve dispersion and reduce leaching. HAL/PLY and HAL/CH-Q hybrids were incorporated into polyester coatings and evaluated for morphology, mechanical properties, water resistance, and antibacterial performance (ISO 22196). The HAL/PLY coating demonstrated a strong bactericidal effect, reducing Escherichia coli and Staphylococcus aureus by 99.9989% and 99.9993%, respectively. HAL/CH-Q showed moderate activity against E. coli (50.2323%) but high activity against S. aureus (98.6500%). Immobilization of biopolymers on the halloysite surface improved dispersion and barrier properties while enabling a silver-free antibacterial effect. The results demonstrate a sustainable strategy for multifunctional powder coatings based on naturally derived antimicrobial components. Full article

(This article belongs to the Special Issue Recent Advances and Emerging Challenges in Functional Coatings (2nd Edition))

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30 pages, 3715 KB

Open AccessEditor’s ChoiceReview

Graphene and Related Materials: Properties and Applications in Dentistry

by Teissir Ben Ammar, Tatiana Roman, Housseinou Ba, Vincent Ball and Naji Kharouf

Materials 2025, 18(23), 5365; https://doi.org/10.3390/ma18235365 - 28 Nov 2025

Cited by 1 | Viewed by 1257

Abstract

This review summarizes recent advances in biomolecule-mediated exfoliation of graphene and related materials, and discusses their emerging applications in dental medicine. Natural biomolecules, including polyphenols, proteins and polysaccharides, are evaluated as exfoliating agents, emphasizing their influence on the structural and biological properties of [...] Read more.

This review summarizes recent advances in biomolecule-mediated exfoliation of graphene and related materials, and discusses their emerging applications in dental medicine. Natural biomolecules, including polyphenols, proteins and polysaccharides, are evaluated as exfoliating agents, emphasizing their influence on the structural and biological properties of graphene and related materials. Particular attention is given to how the synthesis methodologies affects physicochemical properties of the resulting materials and, in turn, biological and mechanical properties. The practical relevance of these materials in dentistry is demonstrated through their applications as functional fillers in dental cements, luting agents, endodontic sealers, and restorative composites, as well as advanced protective coatings for dental substrates and devices. Mechanistic insights into how exfoliation-driven structural modifications dictate material performance in specific dental applications are provided. Collectively, the findings highlight that biomolecule-mediated approaches represent a sustainable, scalable, and versatile strategy for engineering graphene-based materials that simultaneously meet functional requirements and biocompatibility standards essential for successful dental applications. Full article

(This article belongs to the Special Issue Advanced Materials for Oral Application (3rd Edition))

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13 pages, 7494 KB

Open AccessEditor’s ChoiceCommunication

Halide-Assisted Synthesis of V-WSe₂

by Yanhui Jiao, Xiaoqian Wang, Zisheng Tang, Manrui Liu, Chengqi Liu, Qi Zhang and Yong Liu

Materials 2025, 18(23), 5360; https://doi.org/10.3390/ma18235360 - 28 Nov 2025

Viewed by 604

Abstract

Over the past few years, two-dimensional transition metal dichalcogenides (TMDCs) have garnered substantial attention in the field of two-dimensional materials research, owing to their exceptional physicochemical properties. Notably, V-WSe₂ distinguishes itself by reducing the Schottky barrier at the interface between the material [...] Read more.

Over the past few years, two-dimensional transition metal dichalcogenides (TMDCs) have garnered substantial attention in the field of two-dimensional materials research, owing to their exceptional physicochemical properties. Notably, V-WSe₂ distinguishes itself by reducing the Schottky barrier at the interface between the material and metal electrodes, thus exhibiting remarkable potential for applications in optoelectronic devices. Our work explores the synthesis of monolayer V-WSe₂ through halide-assisted atmospheric-pressure chemical vapor deposition (APCVD), with an emphasis on the effects of various halide types on the growth mechanism. In addition, we investigate the impact of vanadium (V) content on the performance of WSe₂. Comprehensive optical and structural characterizations of the synthesized material were systematically performed. The findings indicate that incorporating halide salts effectively reduces the volatilization temperature of tungsten trioxide (WO₃), thereby markedly enhancing reaction controllability and material crystallinity. Among the tested halide salts, KCl, NaCl, and KI, KI demonstrated the capability to achieve the lowest growth temperature. Varying the V content in the V-WSe₂ structure significantly influences the optical properties, with higher vanadium concentrations reducing the material’s optical bandgap and Raman frequency. This study highlights the critical role of halides and vanadium content in the material growth process, providing valuable insights for the controlled synthesis of two-dimensional TMDC materials and how varying vanadium concentrations also affect the material’s performance. Full article

(This article belongs to the Special Issue Advanced 2D Materials and Heterostructures for Photodetector Devices with Multiple Applications)

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12 pages, 2917 KB

Open AccessEditor’s ChoiceArticle

Eco-Friendly Fabrication of 2D a-SnO_x Thin-Film Transistors Derived from Deep Eutectic Solvents

by Christophe Avis and Jin Jang

Materials 2025, 18(23), 5349; https://doi.org/10.3390/ma18235349 - 27 Nov 2025

Viewed by 822

Abstract

We have fabricated amorphous tin oxide (a-SnO_x) thin-film transistors (TFTs) with Al₂O₃ gate insulator from deep eutectic solvents (DESs). DESs were formed using the chloride derivates of each precursor (SnCl₂, or AlCl₃) mixed with [...] Read more.

We have fabricated amorphous tin oxide (a-SnO_x) thin-film transistors (TFTs) with Al₂O₃ gate insulator from deep eutectic solvents (DESs). DESs were formed using the chloride derivates of each precursor (SnCl₂, or AlCl₃) mixed with urea. The DESs were then used as precursors for the semiconductor and dielectric. Our target was to form extremely thin semiconductor film, and a sufficient high capacitance insulator. We characterized the physical and chemical properties of the DES-derived thin films by X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). We could evaluate that the highest content of metal–oxygen bonds was from the DES condition SnCl₂–urea = 1:3. At a low 300 °C budget temperature, we could fabricate a 3.2 nm thick a-SnO_x layer and 30 nm thick Al₂O₃, from which the TFT demonstrated a mobility of 80 ± 17 cm²/Vs, threshold voltage of −0.29 ± 0.06 V, and subthreshold swing of 88 ± 11 mV/dec. The proposed process is adequate with the back-end of the line (BEOL) process, but it is also eco-friendly because of the use of DESs. Full article

(This article belongs to the Special Issue Eco-Sustainable Designing of Metal Oxide Thin Films with High Properties Using Advanced Micro- and Nanofabrication Technologies)

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21 pages, 16004 KB

Open AccessEditor’s ChoiceArticle

Mechanical Homogenisation of TPMS Architectures: A Comparison Between Finite Element and Mechanics of Structure Genome Approaches

by Sara Mouman, Yao Koutsawa, Lucas Binsfeld, Levent Kirkayak, Jieun Yang and Gaetano Giunta

Materials 2025, 18(23), 5357; https://doi.org/10.3390/ma18235357 - 27 Nov 2025

Cited by 1 | Viewed by 1062

Abstract

This work presents a comparative study on the mechanical homogenisation of Triply Periodic Minimal Surface (TPMS) lattice structures in the linear elastic regime, which have attracted significant interest for their unique ability to combine lightweight design with tailored properties. The study investigates the [...] Read more.

This work presents a comparative study on the mechanical homogenisation of Triply Periodic Minimal Surface (TPMS) lattice structures in the linear elastic regime, which have attracted significant interest for their unique ability to combine lightweight design with tailored properties. The study investigates the effective mechanical behaviour of Representative Unit Cells (RUCs) generated using the open-source Python tool Microgen. Two homogenisation strategies are considered: (i) Finite Element (FE)-based homogenisation carried out in Abaqus, and (ii) the Mechanics of Structure Genome (MSG), a unified theory for multi-scale constitutive modelling, implemented in an in-house software tool. The comparison encompasses multiple TPMS topologies, including well-studied cases used for validation, namely gyroid and diamond, as well as less-explored ones, such as PMY and F-Rhombic Dodecahedron, to provide new insights. RUCs are analysed across relative densities ranging from 10 to 50%. Equivalent linear elastic properties (Young’s moduli, shear moduli, and Poisson’s ratios) are derived and compared to assess the consistency, accuracy, and computational efficiency of the two approaches. The results show that both methods yield effective properties with less than 1% difference between them, and less than 5% deviation from experimental data reported in the literature for the effective Young’s modulus. Furthermore, the anisotropy of each TPMS topology across the range of relative densities is examined through the directional distribution of Young’s moduli. The outcomes are expected to clarify the strengths and limitations of FE versus MSG in capturing the effective behaviour of architected cellular solids, thus supporting the selection of homogenisation strategies for the design of lattice-based lightweight structures. Full article

(This article belongs to the Section Materials Simulation and Design)

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14 pages, 2298 KB

Open AccessEditor’s ChoiceArticle

Seawater and Sunlight as Critical Ageing Factors Affecting the Mechanical Performance of Knitted Swimwear Fabrics

by Gabriela Vanja, Vesna Marija Potočić Matković and Ivana Salopek Čubrić

Materials 2025, 18(23), 5346; https://doi.org/10.3390/ma18235346 - 27 Nov 2025

Viewed by 2604

Abstract

This study investigates the effects of seawater and sunlight ageing on the structural and mechanical properties of knitted fabrics designed for swimwear. Nine fabrics with varying polyamide, polyester, and elastane ratios in yarn were subjected to 200 h seawater exposure, with and without [...] Read more.

This study investigates the effects of seawater and sunlight ageing on the structural and mechanical properties of knitted fabrics designed for swimwear. Nine fabrics with varying polyamide, polyester, and elastane ratios in yarn were subjected to 200 h seawater exposure, with and without sunlight, followed by washing and drying cycles to simulate real training and use conditions. The evaluated properties included mass per unit area, thickness, horizontal and vertical density, bursting strength, breaking force, and breaking elongation. Results showed a slight increase in mass and thickness after ageing, reflecting fabric shrinkage in the course direction. Breaking force decreased on average after ageing, with statistically significant reductions in the wale direction under combined seawater and sunlight exposure, whereas shrinkage occasionally produced apparent strengthening effects. Breaking elongation increased in the wale direction and decreased in the course direction, though without statistical significance. Correlation analysis revealed that ageing alters the dependence of mechanical properties on fabric mass per unit area and thickness, with seawater enhancing strength in the wale direction, while sunlight shifted the effects toward the strength in the course direction. These findings demonstrate that seawater and sunlight are critical ageing factors that affect swimwear performance, emphasising the need for their inclusion in durability assessments. Full article

(This article belongs to the Special Issue Research on Fatigue and Fracture Behavior of Polymers and Composites)

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14 pages, 1567 KB

Open AccessEditor’s ChoiceArticle

Osteogenic Potential of Various Premixed Hydraulic Calcium Silicate-Based Sealers on Human Bone Marrow Stem Cells

by Na-Hyun You, Donghee Lee, Yemi Kim, Sieun Nam and Sin-Young Kim

Materials 2025, 18(23), 5326; https://doi.org/10.3390/ma18235326 - 26 Nov 2025

Viewed by 672

Abstract

This study aims to compare the osteogenic potential of premixed hydraulic calcium silicate-based sealers (HCSSs) with an epoxy resin-based sealer in human bone marrow-derived stem cells (hBMSCs). Three HCSSs (White Endoseal MTA, One-Fil, EndoSequence BC Sealer) were compared with AH Plus Jet, an [...] Read more.

This study aims to compare the osteogenic potential of premixed hydraulic calcium silicate-based sealers (HCSSs) with an epoxy resin-based sealer in human bone marrow-derived stem cells (hBMSCs). Three HCSSs (White Endoseal MTA, One-Fil, EndoSequence BC Sealer) were compared with AH Plus Jet, an epoxy resin-based sealer. Disk-shaped specimens were prepared using sterilized Teflon tubes and immersed in osteogenic medium to create eluates. hBMSCs were cultured in each eluate, and osteogenic potential was assessed by alkaline phosphatase (ALP) activity (n = 6), Alizarin Red-S (ARS) staining (n = 6), quantitative real-time polymerase chain reaction (qPCR) (n = 3), and Western blot analysis. Statistical analyses were conducted using SPSS (version 24.0), with significance set at p < 0.05. All experimental groups exhibited higher ALP activity than the control on day 4. ARS staining of HCSSs differed significantly from AH Plus Jet on day 14 (p < 0.05), while White Endoseal MTA exhibited the highest intensity. qPCR revealed that EndoSequence BC Sealer induced the highest SMAD1 expression on day 4, while One-Fil and EndoSequence BC Sealer significantly upregulated RUNX2 expression compared with AH Plus Jet (p < 0.05). Western blotting confirmed that EndoSequence BC Sealer induced the highest RUNX2 protein expression. Collectively, premixed HCSSs promoted superior mineralization and RUNX2 expression compared to conventional resin-based sealer in hBMSCs. Full article

(This article belongs to the Special Issue Development and Research of New Dental Materials)

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15 pages, 6796 KB

Open AccessEditor’s ChoiceArticle

Surface Fluorination of Magnesium Powder: Enhancing High-Temperature Oxidation Resistance

by Yu Wang, Jae-Ho Kim and Susumu Yonezawa

Materials 2025, 18(23), 5307; https://doi.org/10.3390/ma18235307 - 25 Nov 2025

Cited by 1 | Viewed by 707

Abstract

This study investigates the high-temperature oxidation mechanism of pure magnesium powder and the effect of surface fluorination on its oxidation resistance. The results showed that at high temperatures, pure Mg powder reacted with H₂O and CO₂ in air to form [...] Read more.

This study investigates the high-temperature oxidation mechanism of pure magnesium powder and the effect of surface fluorination on its oxidation resistance. The results showed that at high temperatures, pure Mg powder reacted with H₂O and CO₂ in air to form Mg(OH)₂ and MgCO₃, which decomposed at approximately 350 °C. Above 450 °C, the oxide film ruptured and catastrophic oxidation occurred. Surface fluorination with F₂ gas generated a dense, uniform MgF₂ protective film on the magnesium surface, significantly improving the ignition point and high-temperature oxidation resistance of Mg. Increasing the fluorination temperature increased the thickness and stability of the MgF₂ layer, thereby further enhancing oxidation resistance. In particular, samples fluorinated at 200 °C showed oxidation growth limited to approximately 3%, even after heating at 500 °C for 8 h in air. Adjusting the surface fluorination conditions can create a protective MgF₂ film to address high-temperature oxidation issues in magnesium powder metallurgy applications. Full article

(This article belongs to the Special Issue Surface Modification and Coating for Functional Materials)

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14 pages, 4599 KB

Open AccessEditor’s ChoiceArticle

Improvement of a Switchable Wide-Incident-Angle Perfect Absorber Incorporating Sb₂S₃

by Yaolan Tian, Guoxu Zhang, Yan Li, Mei Shen, Yufeng Xiong, Ting Li, Yunzheng Wang, Xian Zhao and Changbao Ma

Materials 2025, 18(23), 5305; https://doi.org/10.3390/ma18235305 - 25 Nov 2025

Viewed by 676

Abstract

Active metasurfaces, whose optical properties can be tuned by an external stimulus such as electric or laser pulses, have attracted great research interest recently. The phase change material (PCM), antimony sulfide (Sb₂S₃), has been reported to modulate resonance wavelengths [...] Read more.

Active metasurfaces, whose optical properties can be tuned by an external stimulus such as electric or laser pulses, have attracted great research interest recently. The phase change material (PCM), antimony sulfide (Sb₂S₃), has been reported to modulate resonance wavelengths from the visible to the infrared. Here, we present a purely numerical study of an active and nonvolatile narrow-band perfect absorber in the infrared region based on a nanostructured metal–insulator–metal (MIM) metasurface incorporating Sb₂S₃. The proposed absorber exhibits a high quality factor and achieves near-unity absorption at resonance wavelengths. In addition, the absorption spectrum can be dynamically modulated by the phase transition of Sb₂S₃, with a modulation range approaching 1 μm. Moreover, the designed absorber shows insensitivity to the angle of incidence. This study offers a feasible strategy for developing Sb₂S₃-integrated metasurface perfect absorbers with potential applications in selective thermal emitters and bolometers. Full article

(This article belongs to the Special Issue Advances in Phase Change Materials: Characterization, Design and Applications—Second Edition)

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19 pages, 3695 KB

Open AccessEditor’s ChoiceArticle

Comparative Study of Different Additive Manufacturing Methods for H13 Tool Steel

by Paweł Widomski, Marcin Kaszuba, Daniel Dobras, Dominik Terefinko and Michał Kołodziński

Materials 2025, 18(23), 5299; https://doi.org/10.3390/ma18235299 - 24 Nov 2025

Cited by 3 | Viewed by 1633

Abstract

Additive manufacturing (AM) of hot-work tool steels such as H13 offers unique opportunities for producing complex, conformally cooled tools with reduced production time and material waste. In this study, five metal AM technologies—Fused Deposition Modeling and Sintering (FDMS, Desktop Metal Studio System and [...] Read more.

Additive manufacturing (AM) of hot-work tool steels such as H13 offers unique opportunities for producing complex, conformally cooled tools with reduced production time and material waste. In this study, five metal AM technologies—Fused Deposition Modeling and Sintering (FDMS, Desktop Metal Studio System and Zetamix), Binder Jetting (BJ), Laser Powder Bed Fusion (LPBF), and Directed Energy Deposition (DED)—were compared in terms of microstructure, porosity, and post-processing heat treatment response. The as-printed microstructures revealed distinct differences among the technologies: FDMS and BJ exhibited high porosity (6–9%), whereas LPBF and DED achieved near-full densification (<0.1%). Samples with sufficiently low porosity (BJ, LPBF, DED) were subjected to tempering and quenching treatments to evaluate hardness evolution and microstructural transformations. The satisfactory post-treatment hardness was observed in both tempered and quenched and tempered BJ samples, associated with secondary carbide precipitation, while LPBF and DED samples retained stable martensitic structures with hardness around 600 HV0.5. Microstructural analyses confirmed the dependence of phase morphology and carbide distribution on the thermal history intrinsic to each AM process. The study demonstrates that while FDMS and BJ are more accessible and cost-effective for low-density prototypes, LPBF and DED offer superior density and mechanical integrity suitable for functional tooling applications. Full article

(This article belongs to the Special Issue Microstructure, Mechanical Properties and Additive Manufacturing of Steels)

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19 pages, 1050 KB

Open AccessEditor’s ChoiceArticle

Nature of the Dielectric Anomaly in Na_0.5Bi_0.5TiO₃–Based Ferrolectrics

by Eriks Birks, Marija Dunce, Šarūnas Svirskas, Algimantas Kežionis, Juras Banys and Andrei Kholkin

Materials 2025, 18(23), 5289; https://doi.org/10.3390/ma18235289 - 24 Nov 2025

Cited by 1 | Viewed by 778

Abstract

The temperature–frequency dependence of dielectric permittivity in Na_0.5Bi_0.5TiO₃ (NBT) -based compositions displays a diffused, frequency-independent maximum along with a frequency-dependent shoulder below this maximum. This behavior deviates from that of both classical ferroelectrics and conventional relaxor ferroelectrics, and [...] Read more.

The temperature–frequency dependence of dielectric permittivity in Na_0.5Bi_0.5TiO₃ (NBT) -based compositions displays a diffused, frequency-independent maximum along with a frequency-dependent shoulder below this maximum. This behavior deviates from that of both classical ferroelectrics and conventional relaxor ferroelectrics, and its interpretation is further complicated by challenges in linking it to known structural phase transitions. This study proposes a new interpretation of the dielectric behavior of NBT-based materials through a comparative analysis of temperature–frequency permittivity data in both unpoled and poled NBT samples and 0.95Na_0.5Bi_0.5TiO₃–0.05CaTiO₃ solid solution over a broad frequency range (10 Hz–100 MHz). Results reveal that the steep permittivity change between the maximum and shoulder—accompanied by pronounced thermal hysteresis—can be attributed to a phase transition between two non-ferroelectric phases. When this contribution is excluded, the dielectric response aligns with classical relaxor ferroelectric behavior. To reconcile this with other known properties of NBT, the “breathing” model is employed, offering a unified framework for understanding its relaxor-like characteristics. Full article

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

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17 pages, 3872 KB

Open AccessEditor’s ChoiceArticle

Computational Analysis of Thermal Performance of Heat Sinks with Foam Structures

by Welteji Iticha and Tomasz Stręk

Materials 2025, 18(23), 5280; https://doi.org/10.3390/ma18235280 - 22 Nov 2025

Cited by 1 | Viewed by 1104

Abstract

Ensuring efficient heat transfer to maintain optimal system performance is crucial in modern electronics owing to the rise of artificial intelligence. In the last few decades, scholars have explored various strategies for enhancing electronic device thermal management, focusing on the effects of fin [...] Read more.

Ensuring efficient heat transfer to maintain optimal system performance is crucial in modern electronics owing to the rise of artificial intelligence. In the last few decades, scholars have explored various strategies for enhancing electronic device thermal management, focusing on the effects of fin shape, dimension, and spacing on heat transfer efficiency. Recent advancements in additive manufacturing have enabled fabrication of complex geometries, such as triply periodic minimal surfaces (TPMSs), which represent promising alternatives to conventional designs. This study presents a comparative analysis of the thermal performance and fluid flow characteristics of two foam TPMS-based (gyroid and primitive) heat sinks with wavy fins made using aluminum foam. COMSOL Multiphysics version 5.1, employed along with the implemented finite element method, was used to simulate convective heat transfer, pressure drop, the Nusselt number, and thermal performance at different fluid velocities along the length of a channel. The foam structure was heated by a copper plate, and the Nusselt number was evaluated over porosity levels from 0.1 to 0.9. A porosity between 0.5 and 0.7 offers the best balance of cooling performance and pumping power. Foam TPMS heat sinks, particularly those with a gyroid structure, provide enhanced thermal dissipation owing to their high surface area-to-volume ratio and interconnected geometry. Our findings confirm that TPMS heat sinks have promising potential for use as alternatives to conventional wavy designs for advanced thermal management applications. Full article

(This article belongs to the Special Issue Modelling of Deformation Characteristics of Materials or Structures)

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17 pages, 6823 KB

Open AccessEditor’s ChoiceArticle

Analysis of a Two-Stage Magnetic Precession Gear Exploiting 3D Finite Element Method

by Lukasz Macyszyn, Cezary Jedryczka and Michal Mysinski

Materials 2025, 18(23), 5277; https://doi.org/10.3390/ma18235277 - 22 Nov 2025

Viewed by 603

Abstract

The paper presents the results of numerical simulations carried out to investigate the influence of selected geometric parameter–precession angle and dimensions of the magnetic circuit of a two-stage magnetic precession gear on the magnetic torques acting on its active components. The operating principle [...] Read more.

The paper presents the results of numerical simulations carried out to investigate the influence of selected geometric parameter–precession angle and dimensions of the magnetic circuit of a two-stage magnetic precession gear on the magnetic torques acting on its active components. The operating principle of the proposed gear and the developed numerical model based on the 3D finite element method (FEM) are discussed. The study focuses on the effects of air gap length, magnet dimensions, pole pitch coverage and precession angle. The results confirm a strong correlation between these parameters and the transmitted torque, providing valuable guidelines for the optimal design of high-torque, compact and efficient magnetic precession gears. Full article

(This article belongs to the Section Materials Simulation and Design)

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24 pages, 4241 KB

Open AccessEditor’s ChoiceArticle

Assessment of a Clothing Ensemble with an Active Heating Function Based on Thermal Manikin Tests

by Agnieszka Greszta, Magdalena Młynarczyk, Anna Dąbrowska, Sylwia Krzemińska, Monika Jangas, Łukasz Starzak, Paweł Marciniak and Bartosz Małachowski

Materials 2025, 18(23), 5258; https://doi.org/10.3390/ma18235258 - 21 Nov 2025

Viewed by 983

Abstract

Heated clothing is an alternative to passive thermally insulating clothing used so far, made of thick, multi-layered fabric compounds. In this work, a personalized two-layer heated clothing ensemble for mountain rescuers was developed. It consisted of an electrically heated inner suit and an [...] Read more.

Heated clothing is an alternative to passive thermally insulating clothing used so far, made of thick, multi-layered fabric compounds. In this work, a personalized two-layer heated clothing ensemble for mountain rescuers was developed. It consisted of an electrically heated inner suit and an outer suit made of waterproof laminate. Total thermal insulation and local thermal insulations were determined using a thermal manikin. The heating system’s performance was assessed by comparing these results with those obtained with the heating turned off in the same ensemble, as well as with a down jacket added. It was confirmed that a thick thermally insulating layer (down jacket) can be eliminated through the application of electric heating. Heating improved the resultant effective thermal insulation of the clothing ensemble by 52% at a total power of 28.4 W. This exceeded the value obtained with the additional down jacket and no heating by 4%. Full article

(This article belongs to the Special Issue Design, Optimization, and Mechanical Applications of Smart Materials and Structures)

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25 pages, 5741 KB

Open AccessEditor’s ChoiceArticle

Stabilizing the Localized Surface Plasmon Resonance (LSPR) of Citrate-Synthesized Metal Nanoparticles in Organic Solvents

by Jacob P. Magdon, Matthew J. Jasienski, Madison R. Waltz, Gabrielle A. Grzymski, Calvin Chen, Arion M. Solomon, Minh Dang Nguyen, Jong Moon Lee, John C. Deàk, T. Randall Lee and Riddhiman Medhi

Materials 2025, 18(22), 5246; https://doi.org/10.3390/ma18225246 - 20 Nov 2025

Viewed by 1346

Abstract

Gold–silver nanoshells (GS-NSs) are hollow spherical nanoparticles with an alloyed Ag-Au shell. GS-NSs exhibit a tunable localized surface plasmon resonance (LSPR) in the visible to near-IR wavelengths as a function of composition and shell thickness and offer greater stability across pH ranges compared [...] Read more.

Gold–silver nanoshells (GS-NSs) are hollow spherical nanoparticles with an alloyed Ag-Au shell. GS-NSs exhibit a tunable localized surface plasmon resonance (LSPR) in the visible to near-IR wavelengths as a function of composition and shell thickness and offer greater stability across pH ranges compared to other metal nanoparticles. These properties make GS-NSs promising materials for diagnostics, photothermal therapy, and photocatalysis. However, current research has explored GS-NSs only in aqueous systems, since they immediately aggregate in other solvents, limiting their utility. This paper provides an in-depth study of the choice and effect of non-thiol ligands on the stability and phase-transfer of GS-NSs from aqueous to non-aqueous solvents, such as ethylene glycol, tetrahydrofuran, dichloromethane, and toluene. Ligand exchange for functionalization of GS-NSs was performed with Triton X-100 (TX100), sodium stearate (NaSt), polyvinylpyrrolidone (PVP), and hydroxypropyl cellulose (HPC), prior to phase-transfer. The nanoparticles were phase-transferred to the non-aqueous solvents, and the stability of the colloids in the various solvents before and after functionalization was recorded with UV–visible spectroscopy, dynamic light scattering (DLS), zeta potential (ζ), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The study was also extended to include silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) to evaluate broad-range applicability. Among the ligands studied, HPC functionalization demonstrated the widest range of phase-transfer stability across 21 days for all three particle systems studied. UV–vis spectroscopy demonstrated sustained LSPR integrity after HPC functionalization in EG, THF, and DCM. SEM, TEM, and hydrodynamic size measurements by DLS further confirmed no aggregation in EG, THF, and DCM but suggested possible twinning or clustering in the solution. Overall, this work successfully identified non-toxic alternatives to expand the LSPR stability of citrate-synthesized metal nanoparticles in organic solvents. Full article

(This article belongs to the Special Issue Nanowires and Nanoparticles: Synthesis, Characterization and Applications)

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39 pages, 2270 KB

Open AccessEditor’s ChoiceReview

Laser Technologies of Welding, Surfacing and Regeneration of Metals with HCP Structure (Mg, Ti, Zr): State of the Art, Challenges and Prospects

by Adam Zwoliński, Sylwester Samborski and Jakub Rzeczkowski

Materials 2025, 18(22), 5237; https://doi.org/10.3390/ma18225237 - 19 Nov 2025

Cited by 2 | Viewed by 1275

Abstract

Metals with a hexagonal close-packed (HCP) structure such as magnesium, titanium and zirconium constitute key structural materials in the aerospace, automotive, biomedical and nuclear energy industries. Their welding and regeneration by conventional methods is hindered due to the limited number of slip systems, [...] Read more.

Metals with a hexagonal close-packed (HCP) structure such as magnesium, titanium and zirconium constitute key structural materials in the aerospace, automotive, biomedical and nuclear energy industries. Their welding and regeneration by conventional methods is hindered due to the limited number of slip systems, high reactivity and susceptibility to the formation of defects. Laser technologies offer precise energy control, minimization of the heat-affected zone and the possibility of producing joints and coatings of high quality. This article constitutes a comprehensive review of the state of knowledge concerning laser welding, cladding and regeneration of HCP metals. The physical mechanisms of laser beam interactions are discussed including the dynamics of the keyhole channel, Marangoni flows and the formation of gas defects. The characteristics of the microstructure of joints are presented including the formation of α′ martensite in titanium, phase segregation in magnesium and hydride formation in zirconium. Particular attention is devoted to residual stresses, techniques of cladding protective coatings for nuclear energy with Accident Tolerant Fuel (ATF) and advanced numerical modeling using artificial intelligence. The perspectives for the development of technology are indicated including the concept of the digital twin and intelligent real-time process control systems. Full article

(This article belongs to the Special Issue Microstructural and Mechanical Properties of Metal Alloys)

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16 pages, 3415 KB

Open AccessEditor’s ChoiceArticle

Poly(glycerol)-Functionalized Gadolinium Tungstate Nanoflakes Loaded with Chlorin e6: Photodynamic Efficacy and Radiosensitization Potential for Multimodal Cancer Therapy

by Heon Gyu Kang and Lukas R. H. Gerken

Materials 2025, 18(22), 5198; https://doi.org/10.3390/ma18225198 - 16 Nov 2025

Viewed by 794

Abstract

Gadolinium (Gd)-based nanomaterials have attracted a considerable amount of attention in cancer treatment research due to their applicability in radiotherapy. However, the clinical translation of Gd-based nanomaterials is limited by their high density and poor dispersibility in aqueous media, thereby necessitating surface functionalization [...] Read more.

Gadolinium (Gd)-based nanomaterials have attracted a considerable amount of attention in cancer treatment research due to their applicability in radiotherapy. However, the clinical translation of Gd-based nanomaterials is limited by their high density and poor dispersibility in aqueous media, thereby necessitating surface functionalization with biocompatible polymers. In this study, gadolinium tungstate (Gd₂(WO₄)₃) nanoflakes (GW Nfs) were functionalized with poly(glycerol) (PG) to enhance their dispersibility and stability in aqueous media. Due to their high-Z elemental composition, the GW Nfs generated reactive oxygen species (ROS) under X-ray irradiation, with improved dispersibility induced by PG functionalization further enhancing ROS productivity compared to GW Nfs. Furthermore, PG-GW loaded with the photosensitizer chlorin e6 (Ce6) demonstrated strong photocytotoxicity at Ce6 concentrations as low as 0.2 μg mL⁻¹ under light irradiation. Taken together, these results demonstrate that PG-GW/Ce6 is a promising nanomaterial for photodynamic therapy while also offering prospects for bimodal photon cancer therapy with X-rays. Full article

(This article belongs to the Special Issue Advanced Nanostructured Materials in Biomedical Applications: Synthesis and Characterization)

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21 pages, 2496 KB

Open AccessEditor’s ChoiceArticle

Nuclear Magnetic Resonance Dynamics of LiTFSI–Pyrazole Eutectic Solvents

by Emilia Pelegano-Titmuss, Muhammad Zulqarnain Arif, Giselle de Araujo Lima e Souza, Phillip Stallworth, Yong Zhang, Adam Imel, Thomas Zawodzinski and Steven Greenbaum

Materials 2025, 18(22), 5184; https://doi.org/10.3390/ma18225184 - 14 Nov 2025

Cited by 4 | Viewed by 1218

Abstract

Deep Eutectic Solvents (DESs) have emerged as promising candidates to replace conventional organic solvents in various technological applications due to their low vapor pressure, non-flammability, and ease of preparation at low costs. In particular, Type IV DESs, which are composed of metal salts [...] Read more.

Deep Eutectic Solvents (DESs) have emerged as promising candidates to replace conventional organic solvents in various technological applications due to their low vapor pressure, non-flammability, and ease of preparation at low costs. In particular, Type IV DESs, which are composed of metal salts and hydrogen bond donors, are possible replacements for lithium-ion battery electrolytes. In this study, we investigate the molecular dynamics of solvents of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and pyrazole (PYR) at varying LiTFSI:PYR molar ratios (1:2, 1:3, 1:4, 1:5) using Nuclear Magnetic Resonance Dispersion (NMRD) and Pulsed Field Gradient (PFG) Nuclear Magnetic Resonance (NMR). PFG NMR reveals composition-dependent diffusion trends, while NMRD provides molecular-level insights into the longitudinal relaxation rate (R₁ = 1/T₁). Notably, the LiTFSI:PYR (1:2) sample shows distinct behavior across both techniques, exhibiting enhanced relaxation rates and lower self-diffusion for ¹H compared to the other nuclei (¹⁹F and ⁷Li), suggestive of stronger and more efficient Li⁺–pyrazole interactions, as confirmed by the modeling of the relaxation profiles. Our study advances understanding of ion dynamics in azole-based eutectic solvents, supporting their potential use in safer battery electrolytes. Full article

(This article belongs to the Special Issue Ionic Liquid-Based Materials: Fundamentals and Applications)

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22 pages, 3634 KB

Open AccessEditor’s ChoiceArticle

Spinning and Tactile Hand/Wear Comfort Characteristics of PET/Co-PET Hollow Fabrics Made of Inorganic Particles Embedded Sheath/3-Core Bicomponent Yarns

by Jiman Kang and Hyunah Kim

Materials 2025, 18(22), 5188; https://doi.org/10.3390/ma18225188 - 14 Nov 2025

Viewed by 858

Abstract

This paper reports the spinning and wear comfort properties of polyethylene terephthalate (PET)/copolymer-PET (Co-PET) hollow yarns and their fabrics, as well as the effect of the wt.% of inorganic particles embedded in the core of the bicomponent yarns. The results are discussed in [...] Read more.

This paper reports the spinning and wear comfort properties of polyethylene terephthalate (PET)/copolymer-PET (Co-PET) hollow yarns and their fabrics, as well as the effect of the wt.% of inorganic particles embedded in the core of the bicomponent yarns. The results are discussed in terms of the types and amounts of inorganic particles (titanium dioxide (TiO₂) and calcium carbonate (CaCO₃)) embedded in the sheath of the bi-component yarns (Kolon semi-dull (KSD), Kolon full-dull (KFD), and Kolon calcium carbonate (KCC) PET/Co-PET yarns). The three sheath/3-core bicomponent yarns developed in this study exhibited good spinnability and weavability with relatively strong tenacity and breaking strain. Their optimal spinning conditions were determined. The KCC PET/Co-PET fabric showed the greatest hollowness ratio, followed by the KFD PET/Co-PET and KSD PET/Co-PET fabrics. This might be attributed to the higher wt.% (2.5 wt.%) of CaCO₃ particles embedded in the sheath of the KCC PET/Co-PET yarns and to the larger particle size (0.8 μm) of CaCO₃. Regarding the wear comfort, the moisture management system (MMT) test indicated that the KFD PET/Co-PET fabric is suitable for market applications because of its good moisture absorption and rapid drying. The KFD PET/Co-PET fabric is useful for winter clothing applications because of its relatively high heat retention rate and lack of durability issues with washing. An examination of the wearing performance for fitness with a tactile hand feel showed that KFD and KCC/Co-PET fabrics imparted a softer tactile hand feel than the KSD PET/Co-PET fabric. On the other hand, the KCC PET/Co-PET fabric was assumed to have some issues with wearing durability. Full article

(This article belongs to the Section Smart Materials)

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13 pages, 2489 KB

Open AccessEditor’s ChoiceArticle

UV-Engineered Oxygen Vacancies in MoO_X Interlayers Enable 24.15% Efficiency for Crystalline Silicon Solar Cells

by Linfeng Yang, Wanyu Lu, Jingjie Li, Shaopeng Chen, Tinghao Liu, Dayong Yuan, Yin Wang, Ji Zhu, Hui Yan, Yongzhe Zhang and Qian Kang

Materials 2025, 18(22), 5167; https://doi.org/10.3390/ma18225167 - 13 Nov 2025

Viewed by 897

Abstract

Molybdenum oxide (MoO_X) has been widely utilized as a hole transport layer (HTL) in crystalline silicon (c-Si) solar cells, owing to characteristics such as a wide bandgap and high work function. However, the relatively low conductivity of MoO_X [...] Read more.

Molybdenum oxide (MoO_X) has been widely utilized as a hole transport layer (HTL) in crystalline silicon (c-Si) solar cells, owing to characteristics such as a wide bandgap and high work function. However, the relatively low conductivity of MoO_X films and their poor contact performance at the MoO_X-based hole-selective contact severely degrade device performance, particularly because they limit the fill factor (FF). Oxygen vacancies are of paramount importance in governing the conductivity of MoO_X films. In this work, MoO_X films were modified through ultraviolet irradiation (UV-MoO_X), resulting in MoO_X films with tunable oxygen vacancies. Compared to untreated MoO_X films, UV-MoO_X films contain a higher density of oxygen vacancies, leading to an enhancement in conductivity (2.124 × 10⁻³ S/m). In addition, the UV-MoO_X rear contact exhibits excellent contact performance, with a contact resistance of 20.61 mΩ·cm², which is significantly lower than that of the untreated device. Consequently, the application of UV-MoO_X enables outstanding hole selectivity. The power conversion efficiency (PCE) of the solar cell with an n-Si/i-a-Si:H/UV-MoO_X/Ag rear contact reaches 24.15%, with an excellent FF of 84.82%. Full article

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

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18 pages, 10871 KB

Open AccessEditor’s ChoiceArticle

The Effect of In Situ Heat Treatment on the Microstructure and Mechanical Properties of H13 Tool Steel Specimens Produced by Laser-Engineered Net Shaping (LENS^®)

by Michalina Rothen-Chaja, Izabela Kunce, Agata Radziwonko, Tomasz Płociński, Julita Dworecka-Wójcik and Marek Polański

Materials 2025, 18(22), 5164; https://doi.org/10.3390/ma18225164 - 13 Nov 2025

Cited by 1 | Viewed by 1149

Abstract

Samples of H13 tool steel were produced using the LENS^® laser additive manufacturing technique. Three variants of samples were produced such that during and 2 h after deposition, both the substrate and sample temperatures were maintained at 80, 180, and 350 °C. [...] Read more.

Samples of H13 tool steel were produced using the LENS^® laser additive manufacturing technique. Three variants of samples were produced such that during and 2 h after deposition, both the substrate and sample temperatures were maintained at 80, 180, and 350 °C. After the samples were produced, the effect of the substrate temperature on their metallurgical quality, microstructure, and mechanical properties was determined. No segregation of alloying elements was observed. The test results indicate that, depending on the temperature used, the structure of the H13 alloy is martensitic or martensitic-bainitic with a slight residual austenite content of up to 2.1%. Owing to structural changes, the obtained alloy is characterized by lower impact strength compared with conventionally produced alloys and high brittleness, particularly when using an annealing temperature of 350 °C. Isothermal annealing above the martensite start temperature results in extreme brittleness due to a partial structural transformation of martensite into bainite and probable carbide precipitation processes at the nanoscale. Full article

(This article belongs to the Special Issue The Application of Materials in Modern Manufacturing Processes: Design, Performance and Applied Research)

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