Materials

16 pages, 4468 KiB

Open AccessArticle

Enhancing Fatigue Lifetime of Secondary AlZn10Si8Mg Alloys Through Shot Peening: Influence of Iron Content and Surface Defects

by Denisa Straková, Zuzana Šurdová, Eva Tillová, Lenka Kuchariková, Martin Mikolajčík, Denisa Závodská and Mario Guagliano

Materials 2025, 18(16), 3901; https://doi.org/10.3390/ma18163901 - 20 Aug 2025

Abstract

The rising demand for aluminium and environmental concerns highlight the need for a circular economy using recycled alloys. This study examines the effect of shot peening on the high-cycle fatigue life of secondary AlZn10Si8Mg alloys with different iron contents: Alloy A (0.14 wt.% [...] Read more.

The rising demand for aluminium and environmental concerns highlight the need for a circular economy using recycled alloys. This study examines the effect of shot peening on the high-cycle fatigue life of secondary AlZn10Si8Mg alloys with different iron contents: Alloy A (0.14 wt.% Fe) and Alloy B (0.56 wt.% Fe). Although both alloys showed similar tensile properties, Alloy B had higher porosity and finer β-Al₅FeSi intermetallics. Shot peening was applied at 100% and 1000% coverage to evaluate changes in surface roughness, porosity, residual stresses, and fatigue performance. The treatment significantly reduced surface-connected porosity via plastic deformation, enhancing fatigue life despite increased roughness. Fatigue tests showed a 21% increase in fatigue limit for Alloy A and a 6% gain for Alloy B at higher coverage. Fractographic analysis revealed that 95% of fatigue cracks initiated at surface pores. Residual stress measurements confirmed compressive stresses were limited to the near-surface layer, with minimal influence on subsurface crack propagation. Overall, shot peening proves to be an effective method for improving fatigue resistance in recycled aluminium alloys, even in alloys with elevated iron content, reinforcing their potential for structural applications under cyclic loading. Full article

(This article belongs to the Special Issue Fatigue, Damage and Fracture of Alloys)

► Show Figures

Graphical abstract

11 pages, 1720 KiB

Open AccessArticle

Chemical Ordering in Liquid and Supercooled Ge₂Sb₂Te₅ Phase-Change Materials

by Tae Hoon Lee

Materials 2025, 18(16), 3900; https://doi.org/10.3390/ma18163900 - 20 Aug 2025

Abstract

The origin of chemical ordering in liquid and supercooled liquid Ge₂Sb₂Te₅ (GST) was investigated using ab initio molecular dynamics (AIMD) simulations. Bond dynamics were analyzed via continuous (

τ_{con}

) and intermittent (

τ_{i n t}

[...] Read more.

The origin of chemical ordering in liquid and supercooled liquid Ge₂Sb₂Te₅ (GST) was investigated using ab initio molecular dynamics (AIMD) simulations. Bond dynamics were analyzed via continuous (

τ_{con}

) and intermittent (

τ_{i n t}

) lifetimes. The intermittent lifetime (

τ_{i n t}

) reveals that chemically ordered Ge-Te and Sb-Te bonds are the most stable, although

τ_{con}

exhibits a stability anomaly. The faster increase of

τ_{i n t}

for these bonds upon cooling explains the overall chemical ordering. A novel ordering mechanism was identified through the analysis of bond separation dynamics. Te-Te ‘wrong’ bonds exhibit a unique dynamic instability, breaking and separating much faster than any other bond type, which actively drives the system towards chemical order. A correlation between lifetime and bond strength, as calculated by the Integrated Crystal Orbital Hamilton Population (ICOHP), supports these dynamic findings. Chemical ordering shows a positive correlation with medium-range structural order, evidenced by the instability of 4-fold rings containing wrong bonds. This study provides a detailed dynamic origin for ordering in liquid GST, highlighting the role of Te-Te bond relaxation. Full article

► Show Figures

Figure 1

17 pages, 6566 KiB

Open AccessArticle

Microstructural and Mechanical Property Variations in 316L Stainless Steel Fabricated by Laser Powder Bed Fusion Under High-Density Processing Conditions

by Shun Zhang, Xudong Wu, Zhong Wang, Meiling Jiang, Guoliang Huang, Xiaoqiang Peng, Chen Yang, Junyan Zhu and Ke Huang

Materials 2025, 18(16), 3899; https://doi.org/10.3390/ma18163899 - 20 Aug 2025

Abstract

It has become a trend to precisely control the additive manufacturing process parameters within the high-density process window to obtain high-performance metal parts. However, there are few reports on this topic currently, leaving this research without sufficient references. This study took 316L austenitic [...] Read more.

It has become a trend to precisely control the additive manufacturing process parameters within the high-density process window to obtain high-performance metal parts. However, there are few reports on this topic currently, leaving this research without sufficient references. This study took 316L austenitic stainless steel as a case study. In total, 36 groups of specimens were manufactured by Laser powder bed melting (LPBF), and then, two highly dense specimens were selected to study the variation in their microstructure and properties. The densities of the selected specimens, S1 (VED = 81 J/mm³) and S2 (VED = 156.3 J/mm³), are 99.68% and 99.99%, respectively. The results indicated that, compared with the S1 specimen, the S2 specimen significantly decreased in terms of yield strength (YS), ultimate tensile strength (UTS), and elongation (EL), which are 7.28%, 6.34%, and 19.15%, respectively. The differences in mechanical properties were primarily attributed to differences in their microstructures. Further, compared with the S1 specimen, the fitted ellipse aspect ratio and average grain size of the S2 specimen increased by 79.88% and 53.45%, respectively, and the kernel average misorientation (KAM) value and geometric necessary dislocation (GND) density increased by 36.00% and 58.43%, respectively. Furthermore, the S1 specimen exhibited a strong texture in the <101>//Z direction, whereas no obvious texture was observed in the S2 specimen. Obviously, the reason why precise regulation within the dense parameter range can achieve better performance is that the microstructure and mechanical properties of the specimens prepared within the dense range are different. More importantly, this study provides a feasible framework for optimizing alloys with broad and dense parameter ranges, demonstrating the potential to achieve high-performance components through precise parameter control. Furthermore, the results reveal that even within a wide range of high-density forming parameters, significant variations in microstructure and mechanical properties can arise depending on the selected parameter combinations. These findings underscore the critical importance of meticulous process parameter optimization and microstructural regulation in tailoring material properties. Full article

(This article belongs to the Special Issue New Advances in High-Temperature Structural Materials)

► Show Figures

Figure 1

14 pages, 4377 KiB

Open AccessArticle

Compressive Mechanical Properties of Lattice Structures with Varied Structural Parameters Prepared by Stereolithography

by Jianhua Sun, Hai Gu, Jie Zhang, Guoqing Dai, Bin Li, Zhonggang Sun and Zulei Liang

Materials 2025, 18(16), 3898; https://doi.org/10.3390/ma18163898 - 20 Aug 2025

Abstract

The use of additive manufacturing technology for the lightweight design of complex lattice structures is becoming increasingly popular, but research on lattice structure design and strength evaluation still relies on the visual comparison of stress distributions and lacks quantitative assessment data. Given this [...] Read more.

The use of additive manufacturing technology for the lightweight design of complex lattice structures is becoming increasingly popular, but research on lattice structure design and strength evaluation still relies on the visual comparison of stress distributions and lacks quantitative assessment data. Given this perspective, this study explored the effects of structural parameters (relative density, cell size, and sample size) on the compressive strength of diamond lattice structures prepared by Stereolithography (SLA) and revealed the underlying mechanisms through stress distribution simulations and the calculation of characteristic stress distribution parameters (structural efficiency and stress concentration coefficient). The results showed that a greater relative density can increase structural efficiency, but it hardly affects the stress concentration coefficient, and smaller cell sizes and larger sample sizes increase the stress concentration coefficient without affecting the structural efficiency. Lattice structures with a greater relative density, higher structural efficiency, and a larger stress concentration coefficient exhibit higher compressive strength according to the lattice strength formula, which indicates that lattice strength is determined by the product of structural efficiency, stress concentration coefficient, relative density, and material strength. The relevant conclusions could guide the analysis of lattice stress distribution and the design of lattice structures. Full article

(This article belongs to the Section Mechanics of Materials)

► Show Figures

Figure 1

16 pages, 10820 KiB

Open AccessArticle

Synergistic Enhancement of Li-O₂ Battery Capacity and Cycle Life Using Carbon Nanochain/Multiwall Carbon Nanotube Composites

by Michael D. Womble, Cynthia Adebayo, Silas Cascio and Michael J. Wagner

Materials 2025, 18(16), 3897; https://doi.org/10.3390/ma18163897 - 20 Aug 2025

Abstract

Multiwalled carbon nanotube (MWCNT) Li-O₂ cathodes can achieve high gravimetric capacity. However, the macropores of these cathodes require a relatively large mass of electrolyte to fill, resulting in lower true gravimetric and volumetric capacities. Here we report a simple method to incorporate [...] Read more.

Multiwalled carbon nanotube (MWCNT) Li-O₂ cathodes can achieve high gravimetric capacity. However, the macropores of these cathodes require a relatively large mass of electrolyte to fill, resulting in lower true gravimetric and volumetric capacities. Here we report a simple method to incorporate a mesoporous material, carbon nanochains (CNCs), into the macropores of MWCNTs, resulting in composite cathodes that fully utilize their pore structure to store Li₂O₂ product. The composite cathodes exhibit additional mesopores with an average diameter of ~100 nm. This results in dramatic increases in true gravimetric (21% to 870 mAh/g) and volumetric (>200% to 5664 mAh/cm³) capacities. The composite cathodes demonstrate improved electrochemical reversibility, increasing the cycle life by more than 50%. Full article

(This article belongs to the Special Issue Nanostructured Materials for Environmental Friendly and Related Energy Applications)

► Show Figures

Figure 1

10 pages, 2642 KiB

Open AccessArticle

Welding Technology and Heat Treatment Butt-Welded Joints of Thin-Walled Inconel 718 Alloy Tubes

by Patryk Warchoł and Lechosław Tuz

Materials 2025, 18(16), 3896; https://doi.org/10.3390/ma18163896 - 20 Aug 2025

Abstract

The subject of this research was the development of technology for welding and the heat treatment of butt-welded joints of thin-walled Inconel 718 alloy tubes, a process based on orbital TIG welding without a filler metal. The developed technology allows favorable conditions to [...] Read more.

The subject of this research was the development of technology for welding and the heat treatment of butt-welded joints of thin-walled Inconel 718 alloy tubes, a process based on orbital TIG welding without a filler metal. The developed technology allows favorable conditions to obtain the appropriate hardness and mechanical properties in the weld area required by AMS 5589. In the tests, the microstructure and mechanical properties were evaluated. Compliance with the requirements was evaluated on the basis of metallographic and mechanical properties tests. The results obtained indicate that the weakest area of the joint is the base material of the thin-walled tube. The welded joints reveal elongation above 10% and tensile strength above 1400 MPa despite the dendritic structure of the weld. In the area of the welded joint, the occurrence of precipitates of the γ’ phase and mainly niobium carbide was revealed. Full article

(This article belongs to the Section Metals and Alloys)

► Show Figures

Figure 1

20 pages, 7133 KiB

Open AccessArticle

Reconstruction and Microstructure Characterization of Tailings Materials with Varying Particle Sizes

by Zhenkai Pan, Mingnan Xu, Tingting Liu, Junhong Huang, Xinping Li and Chao Zhang

Materials 2025, 18(16), 3895; https://doi.org/10.3390/ma18163895 - 20 Aug 2025

Abstract

With the continuous increase in mining activities, effective tailings management has become a critical concern in geotechnical and environmental engineering. This study systematically investigates the microstructural characteristics and 3D reconstruction behavior of copper tailings with different particle sizes using X-ray computed tomography (micro-CT), [...] Read more.

With the continuous increase in mining activities, effective tailings management has become a critical concern in geotechnical and environmental engineering. This study systematically investigates the microstructural characteristics and 3D reconstruction behavior of copper tailings with different particle sizes using X-ray computed tomography (micro-CT), digital image processing, and 3D modeling techniques. Two particle size groups (fine: 0.075–0.15 mm; coarse: 0.15–0.3 mm) were analyzed to quantify differences in particle morphology, pore structure, and orientation anisotropy. Binary images and reconstructed models revealed that coarse particles tend to have more irregular and angular shapes, while fine particles exhibit more complex pore networks with higher fractal dimensions. The apparent porosity derived from CT data was consistently lower than laboratory measurements, likely due to internal agglomeration effects. Orientation analysis indicated that particle alignment and anisotropy vary systematically with section angle relative to the principal stress direction. These findings offer new insights into the particle-scale mechanisms affecting the packing, porosity, and anisotropy of tailings, providing a scientific basis for enhancing the structural evaluation and sustainable management of tailings storage facilities. Full article

(This article belongs to the Section Construction and Building Materials)

► Show Figures

Figure 1

23 pages, 4447 KiB

Open AccessArticle

Study on the Filler Composition Optimization and Performance Evaluation of Cold-Patch Asphalt Mixture

by Congwei Bi, Xueqi Wang, Jikai Fu, Hongxu Zhao, Mulian Zheng and Jinghan Xu

Materials 2025, 18(16), 3894; https://doi.org/10.3390/ma18163894 - 20 Aug 2025

Abstract

Filler dramatically affects the rheology of cold-patched asphalt (CPA) slurry, as well as the related mechanical properties; its physical and chemical properties will also affect the road performance of cold-patch asphalt mixture (CPAM). In order to optimize the filler composition ratio for CPAM, [...] Read more.

Filler dramatically affects the rheology of cold-patched asphalt (CPA) slurry, as well as the related mechanical properties; its physical and chemical properties will also affect the road performance of cold-patch asphalt mixture (CPAM). In order to optimize the filler composition ratio for CPAM, this study uses an orthogonal test to determine the optimal ratio of bentonite to cement, partially substituting mineral powder. Additionally, a performance verification test suitable for CPAM is designed and performed. The results indicate that the total filler dosage is 4.3%, the proportion of mineral powder replacement is 50%, and the ratio of bentonite to cement is 0.2:1; the forming strength, residual stability, and freeze–thaw splitting strength of CPAM are improved by 7.37%, 20.95%, and 17.13%, respectively, and the water stability is significantly enhanced. Scanning electron microscope images show that the cement and bentonite are dispersed as fillers in CPA, and a hydration reaction occurs, which reveals the mechanism of the optimized cold-patched filler ratio related to performance enhancement. Full article

(This article belongs to the Special Issue Rapid Inspection, Evaluation, and Repair Materials on Transportation Infrastructures)

► Show Figures

Figure 1

18 pages, 1216 KiB

Open AccessArticle

Predictive Modeling and Experimental Optimization of the Electrodeposition–Sintering Process for Functional Ceramic Coatings

by Jesús M. Rodríguez-Rego, Antonio Macías-García, Laura Mendoza-Cerezo, Juan Pablo Carrasco-Amador and Antonio Díaz-Parralejo

Materials 2025, 18(16), 3893; https://doi.org/10.3390/ma18163893 - 20 Aug 2025

Abstract

This study focuses on optimizing a sol–gel based electrodeposition–sintering process for producing yttria-stabilized zirconia (YSZ) ceramic coatings on stainless steel substrates. Four key process variables—precursor concentration, current density, sintering time, and temperature—were evaluated in terms of two response variables: R (electrodeposition yield) and [...] Read more.

This study focuses on optimizing a sol–gel based electrodeposition–sintering process for producing yttria-stabilized zirconia (YSZ) ceramic coatings on stainless steel substrates. Four key process variables—precursor concentration, current density, sintering time, and temperature—were evaluated in terms of two response variables: R (electrodeposition yield) and S (sintering yield). A fractional factorial design was used to reduce the number of experiments while enabling robust statistical modeling. Multiple linear regression analysis revealed that precursor concentration and current density were the most influential factors for both R and S, whereas sintering time and temperature had a lesser effect. Under central conditions (42.9 g·L⁻¹, 1.5 A·cm², 500 °C, 20 min), coatings exhibited yields of ~3.9 mg·cm² and superior morphological uniformity. Higher current density (3 A·cm²) increased R to 6.9 mg·cm² but induced porosity and cracking. Compared to conventional sol–gel derived coatings, the proposed methodology enables a more controlled microstructure with a trade-off between mass deposition and structural integrity. This predictive, statistically validated approach facilitates the optimization of electrodeposition parameters to obtain defect-minimized ceramic coatings, particularly suited for protective and thermal barrier applications in demanding environments. Full article

(This article belongs to the Section Advanced Materials Characterization)

► Show Figures

Graphical abstract

27 pages, 33038 KiB

Open AccessArticle

Assessment of Durability and Degradation Resistance of Geopolymer Composites in Water Environments

by Kacper Oliwa, Barbara Kozub, Katarzyna Łoś, Piotr Łoś and Kinga Korniejenko

Materials 2025, 18(16), 3892; https://doi.org/10.3390/ma18163892 - 20 Aug 2025

Abstract

This article presents experimental studies on the characterization of geopolymer composites intended for applications in aquatic environments, with particular emphasis on underwater infrastructure. The motivation for conducting the research was the growing need to develop durable and ecological building materials that will be [...] Read more.

This article presents experimental studies on the characterization of geopolymer composites intended for applications in aquatic environments, with particular emphasis on underwater infrastructure. The motivation for conducting the research was the growing need to develop durable and ecological building materials that will be resistant to long-term exposure to moisture and aggressive chemical agents, typical for the underwater environment, where traditional cement concretes undergo gradual degradation due to long-term water impact, including hydrotechnical and underwater infrastructure. Geopolymer binders were produced based on metakaolin activated by alkaline solutions containing sodium hydroxide. Several series of mixtures with additives such as blast furnace slag, amphibolite and carbon fibers were developed to evaluate the effect of these components on mechanical strength, water absorption and chemical durability. The conducted studies showed that slag additions improved mechanical properties, for the best composition it across 50 MPa. In contrast, the addition of amphibolite had an unfavorable effect, which probably results from introducing inhomogeneity into the material structure. The presence of carbon fibers promoted matrix cohesion, but their uneven distribution could lead to local strength differences. Water absorption tests have shown that geopolymers reach full water saturation within 24 to 48 h, which indicates rapid establishment of capillary equilibrium and limited further water penetration. The conclusions from the work indicate that geopolymer composites with a moderate amount of blast furnace slag and subjected to appropriate curing conditions. High strength, water and chemical resistance make them suitable for, among others, the construction of marine foundations, protection and structural shields of submerged applications. Full article

(This article belongs to the Special Issue Sustainable Eco-Friendly Advanced Geopolymers: Leveraging Recycled, Bio-Based, and Industrial Waste Constituents)

► Show Figures

Figure 1

36 pages, 9447 KiB

Open AccessReview

Research Progress on Ultrahigh-Temperature Ceramics Modified C/C Composites

by Ruize Gao, Shuibin Wang, Tianci Zhou, Tianxing Jiang, Li Lu, Qingbo Wen, Shasha Tao and Xiang Xiong

Materials 2025, 18(16), 3891; https://doi.org/10.3390/ma18163891 - 20 Aug 2025

Abstract

C/C composites have excellent high-temperature mechanical properties and are one of the most promising high-temperature structural materials. However, poor oxidation and ablation resistance of the C/C composites in high-temperature oxygen-containing environments seriously hinder their practical applications. Ultrahigh-temperature ceramics (UHTCs)-modified C/C composites (C/C-UHTCs) are [...] Read more.

C/C composites have excellent high-temperature mechanical properties and are one of the most promising high-temperature structural materials. However, poor oxidation and ablation resistance of the C/C composites in high-temperature oxygen-containing environments seriously hinder their practical applications. Ultrahigh-temperature ceramics (UHTCs)-modified C/C composites (C/C-UHTCs) are considered to be the most effective way to improve the oxidation and ablation resistance of C/C composites, demonstrating significant application prospects in aerospace and related fields. This article reviews recent research progress on C/C-UHTCs composites, including application prospects, performance testing methods, preparation techniques, phase composition, structural design principles, microstructural characteristics, as well as oxidation/ablation mechanisms. Addressing current challenges in C/C-UHTCs composites and future research directions are also proposed. Full article

(This article belongs to the Special Issue Processing, Characterization and Applications of Ceramic Matrix Composites)

► Show Figures

Figure 1

14 pages, 1476 KiB

Open AccessArticle

Magnetic Field-Driven Transport Properties of an Oxygen-Deficient Rectangular YBa₂Cu₃O_7-δ Superconducting Structure

by Artūras Jukna

Materials 2025, 18(16), 3890; https://doi.org/10.3390/ma18163890 - 20 Aug 2025

Abstract

The transport properties of biased type II superconductors are strongly influenced by external magnetic fields, which play a crucial role in optimizing the stability and performance of low-noise superconducting electronic devices. A major challenge is the stochastic behavior of Abrikosov vortices, which emerge [...] Read more.

The transport properties of biased type II superconductors are strongly influenced by external magnetic fields, which play a crucial role in optimizing the stability and performance of low-noise superconducting electronic devices. A major challenge is the stochastic behavior of Abrikosov vortices, which emerge in the mixed state and lead to energy dissipation through their nucleation, motion, and annihilation. Uncontrolled vortex dynamics can introduce electronic noise in low-power systems and trigger thermal breakdown in high-power applications. This study examines the effect of a perpendicular external magnetic field on vortex pinning in biased YBa₂Cu₃O_7-δ devices containing laser-written, rectangular-shaped, partially deoxygenated regions (δ ≈ 0.2). The results show that increasing the magnetic field amplitude induces an asymmetry in the concentration of vortices and antivortices, shifting the annihilation line toward a region of lower flux density and altering the flux pinning characteristics. Oxygen-deficient segments aligned parallel to the current flow act as barriers to vortex motion, enhancing the net pinning force by preventing vortex–antivortex pairs from reaching their annihilation zone. The current–voltage characteristics reveal periodic voltage steps corresponding to the onset and suppression of thermally activated flux flow and flux creep. These features indicate magnetic field–tunable transport behavior within a narrow range of temperatures from 0.94·T_c to 0.98·T_c, where T_c is the critical temperature of the superconductor. These findings offer new insights into the design of vortex-motion-controlled superconducting electronics that utilize engineered pinning structures. Full article

(This article belongs to the Section Materials Physics)

► Show Figures

Figure 1

12 pages, 355 KiB

Open AccessArticle

Functional Coating Effects of Silver Diamine Fluoride (SDF) on Artificial Caries Lesions: A Microhardness-Based Evaluation

by Mohammed H. Alshamrani, Reem A. Alajlan, Waad E. Alsaadi, Amjad M. Alabdulmohsen, Munira Abuthnain, Carlos Fernando Mourão and Adam Lowenstein

Materials 2025, 18(16), 3889; https://doi.org/10.3390/ma18163889 - 20 Aug 2025

Abstract

Background: Dental caries is a prevalent dental problem affecting primary and permanent teeth. Early demineralization of enamel lesions can be reversed through remineralization. Many studies have focused on caries prevention and disease progression arrest using silver diamine fluoride (SDF). No in vitro [...] Read more.

Background: Dental caries is a prevalent dental problem affecting primary and permanent teeth. Early demineralization of enamel lesions can be reversed through remineralization. Many studies have focused on caries prevention and disease progression arrest using silver diamine fluoride (SDF). No in vitro studies have compared the remineralization effects of different 38% SDF solutions on artificially demineralized enamel lesions. This study aimed to compare the remineralization potential of three commercial 38% silver diamine fluoride formulations on artificial enamel lesions in primary teeth using a pH cycling model. The hypothesis was as follows: different commercial SDF formulations would exhibit varying remineralization effects, as measured by surface microhardness, due to potential differences in their compositions. Materials and Methods: In this study, 75 primary molars were randomized into five groups (N = 15): I: baseline, II: SDF Riva Star Aqua^® 38%, III: Riva Star^® 38%, IV: SDF Advantage Arrest^® 38%, and V: control. Artificial caries were created by submerging teeth in 10 mL of demineralization solution (pH 4.5) for three days in a light-resistant container, ensuring distinct visual changes in the enamel as per the International Caries Detection and Assessment System (ICDAS level 2). After pH cycling, all samples underwent a standardized Vickers microhardness test (VMHT) with a 50 g load for 15 s. Data were analyzed using one-way ANOVA and Tukey’s post hoc test, with a significance level set at p ≤ 0.05. Results: The one-way ANOVA test indicated a significant difference in microhardness among the groups (SDF Riva Star Aqua, SDF Riva Star, and SDF Advantage Arrest), with an F-value of 167.73 and p < 0.001. The post hoc Scheffé test showed that SDF Riva Star Aqua and SDF Riva Star were not significantly different (p = 0.388). However, SDF Advantage Arrest had a significantly higher mean microhardness compared to both groups (p < 0.001). Overall, these results show that SDF Advantage Arrest leads to greater microhardness than SDF Riva Star Aqua or SDF Riva Star. Conclusions: SDF Advantage Arrest showed superior performance among the SDF-treated groups, significantly increasing microhardness compared to SDF Riva Star Aqua and SDF Riva Star. This suggests that SDF Advantage Arrest offers enhanced remineralization and structural strengthening, making it the most effective option for managing demineralized primary teeth. Future research should investigate the long-term performance and mechanisms of these treatments to optimize clinical protocols for preserving primary tooth integrity. Full article

(This article belongs to the Section Biomaterials)

► Show Figures

Figure 1

25 pages, 10485 KiB

Open AccessArticle

Investigation of Stress Distribution and Fatigue Performance in Restored Teeth Using Different Thicknesses of Adhesive Materials and Different Restorative Materials: 3D Finite Element Analysis (FEM)

by Reza Mohammadi, Sinem Alkurt Kaplan, Abdulkadir Harmankaya and Hakan Yasin Gönder

Materials 2025, 18(16), 3888; https://doi.org/10.3390/ma18163888 - 20 Aug 2025

Abstract

Background: This study aimed to compare the stress distribution and fracture resistance of dental tissues and restorative materials with varying adhesive layer thicknesses and different restorative materials. Methods: A caries-free mandibular first molar (tooth #36) was scanned using CBCT. The scanned files were [...] Read more.

Background: This study aimed to compare the stress distribution and fracture resistance of dental tissues and restorative materials with varying adhesive layer thicknesses and different restorative materials. Methods: A caries-free mandibular first molar (tooth #36) was scanned using CBCT. The scanned files were processed in Mimics 12 software for segmentation of enamel, dentin, and pulp tissues and then exported to STP format. Cavity preparations (DO, MO, MOD, and O) were designed in SolidWorks 2023. Bulk-fill composite, conventional composite, and hybrid composite were used for restorations with adhesive layers of 10, 15, and 20 μm thick. Stress distribution and fracture resistance were analyzed using 3D finite element analysis. Results: The highest stress values in enamel, dentin, and adhesive material were observed in models restored with bulk-fill composite, while the highest stress values within the restoration were found in models restored with hybrid composite. As the adhesive layer thickness decreased, stress accumulation within the restorative material increased. Enamel fractures occurred first in models with bulk-fill composite. Among restorative materials, fractures initiated first in models restored with hybrid composite, while the latest fracture onset was observed in models with bulk-fill composite. Conclusions: Restorative materials with low Young’s modulus cause excessive stress accumulation in enamel and dentin, leading to early fracture of these tissues. In contrast, materials with a high Young’s modulus transfer more stress to the restoration, causing premature fracture of the restorative material. Full article

(This article belongs to the Special Issue Biomaterials for Restorative Dentistry)

► Show Figures

Figure 1

20 pages, 4966 KiB

Open AccessArticle

New Glass-Ceramics in the System Ca₂SiO₄-Ca₃(PO₄)₂—Phase Composition, Microstructure, and Effect on the Cell Viability

by Irena Mihailova, Petya Dimitrova, Georgi Avdeev, Radostina Ivanova, Hristo Georgiev, Milena Nedkova-Shtipska, Ralitsa Teodosieva and Lachezar Radev

Materials 2025, 18(16), 3887; https://doi.org/10.3390/ma18163887 - 19 Aug 2025

Abstract

The CaO-SiO₂-P₂O₅ system is one of the main systems studied aiming for the synthesis of new bioactive materials for bone regeneration. The interest in materials containing calcium-phosphate-silicate phases is determined by their biocompatibility, biodegradability, bioactivity, and osseointegration. The [...] Read more.

The CaO-SiO₂-P₂O₅ system is one of the main systems studied aiming for the synthesis of new bioactive materials for bone regeneration. The interest in materials containing calcium-phosphate-silicate phases is determined by their biocompatibility, biodegradability, bioactivity, and osseointegration. The object of the present study is the synthesis by the sol-gel method of biocompatible glass-ceramics in the Ca₂SiO₄-Ca₃(PO₄)₂ subsystem with the composition 6Ca₂SiO₄·Ca₃(PO₄)₂ = Ca₁₅(PO₄)₂(SiO₄)₆. The phase-structural evolution of the samples was monitored using X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and surface area analysis. A powder (20–30 µm) glass-ceramic material containing fine crystalline aggregates of dicalcium silicate and plates of silicon-substituted hydroxyapatite was obtained after heat treatment at 700 °C. After heat treatment at 1200 °C, Ca₁₅(PO₄)₂(SiO₄)₆, silicocarnotite Ca₅(PO₄)₂(SiO₄), and pseudowollastonite CaSiO₃ were identified by XRD, and the particle size varied between 20 and 70 µm. The compact glass-ceramic obtained at 1400 °C contained Ca₂SiO₄-Ca₃(PO₄)₂ solid solutions with an α-Ca₂SiO₄ structure as a main crystalline phase. SEM showed the specific morphology of the crystalline phases and illustrated the trend of increasing particle size depending on the synthesis temperature. Effects of the glass-ceramic materials on cell viability of HL-60-derived osteoclast-like cells and on the expression of apoptotic and osteoclast-driven marker suggested that all materials at low concentrations, above 1 µg mL⁻¹, are biocompatible, and S-1400 might have a potential application as a scaffold material for bone regeneration. Full article

(This article belongs to the Section Electronic Materials)

► Show Figures

Figure 1

23 pages, 2479 KiB

Open AccessReview

Role of Structural Changes at Vitrification and Glass–Liquid Transition

by Michael I. Ojovan and Dmitri V. Louzguine-Luzgin

Materials 2025, 18(16), 3886; https://doi.org/10.3390/ma18163886 - 19 Aug 2025

Abstract

Structural rearrangements at calorimetric glass transition are behind drastic changes of material characteristics, causing differences between glasses and melts. Structural description of materials includes both species (atoms, molecules) and connecting bonds, which are directly affected by changing conditions such as the increase of [...] Read more.

Structural rearrangements at calorimetric glass transition are behind drastic changes of material characteristics, causing differences between glasses and melts. Structural description of materials includes both species (atoms, molecules) and connecting bonds, which are directly affected by changing conditions such as the increase of temperature. At and above the glass transition a macroscopic percolation cluster made up of configurons (broken bonds) is formed, an account of which enables unambiguous structural differentiation of glasses from melts. Connection of transition caused by configuron percolation is also discussed in relation to the Noether theorem, Anderson localisation, and melting criteria of condensed matter. Full article

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

► Show Figures

Figure 1

20 pages, 10135 KiB

Open AccessArticle

Precipitation Behavior and Properties Evolution of Cu-1.16Ni-0.36Cr Alloy During Heat Treatment

by Shaolin Li, Shuaibin Li, Wenming Sun, Qiangsong Wang and Kexing Song

Materials 2025, 18(16), 3885; https://doi.org/10.3390/ma18163885 - 19 Aug 2025

Abstract

In this paper, Cu-1.16Ni-0.36Cr alloy was obtained by adding Ni-Cr intermediate alloy, and the effects of aging parameters on its microstructural evolution and mechanical properties were studied. The results show that after secondary aging (solid solution + one time cold rolling at 87.5% [...] Read more.

In this paper, Cu-1.16Ni-0.36Cr alloy was obtained by adding Ni-Cr intermediate alloy, and the effects of aging parameters on its microstructural evolution and mechanical properties were studied. The results show that after secondary aging (solid solution + one time cold rolling at 87.5% + annealing at 300 °C for 2 h + secondary aging at 450 °C for 2 h), dispersed BCC structure Cr precipitates are obtained in the alloy, which shows good comprehensive properties (strength of 512.0 MPa, elongation of 17.2%, and electrical conductivity of 45.5%). The change in aging parameters significantly affects the existing form of Cr precipitates. When the aging temperature increases from 400 °C to 450 °C, the precipitated phase begins to have a stable boundary, which shows that the precipitated phase with BCC structure Cr precipitates (~10 nm in range). When the aging temperature further increases to 500 °C, the size of Cr precipitated phase begins to grow, from 5.0 nm to 16.7 nm. The strengthening mechanism of the alloy with different aging time at 450 °C is calculated, and the relationship among aging parameters, microstructure characteristics, strengthening mechanism and mechanical properties is established. It is concluded that precipitation strengthening and dislocation strengthening are the main strengthening mechanisms of the alloy. Full article

(This article belongs to the Section Metals and Alloys)

► Show Figures

Figure 1

25 pages, 10982 KiB

Open AccessArticle

Homogenization Method for Modeling and Analysis of the Honeycomb Structure—Simulation Study and Validation

by Łukasz Michalski, Tomasz Kubiak and Luigi De Mercato

Materials 2025, 18(16), 3884; https://doi.org/10.3390/ma18163884 - 19 Aug 2025

Abstract

This study presents a comprehensive approach to modeling honeycomb structures using the homogenization method, utilizing a Representative Volume Element (RVE) to derive equivalent orthotropic mechanical properties of the honeycomb structure. Three finite element models (two-dimensional and three-dimensional) were examined, considering the decreasing complexity [...] Read more.

This study presents a comprehensive approach to modeling honeycomb structures using the homogenization method, utilizing a Representative Volume Element (RVE) to derive equivalent orthotropic mechanical properties of the honeycomb structure. Three finite element models (two-dimensional and three-dimensional) were examined, considering the decreasing complexity and computational effort associated with each modeling approach. The outcomes of the analysis for each modeling approach were reported, with attention to boundary condition application and numerical singularities. Validation through four-point bending tests and an analytical approach confirmed the model’s ability to replicate the mechanical behavior of the panel. The obtained results have shown perfect agreement between the results of the numerical test employing the proposed model and the experimental test results of real structures. It was found that the proposed simplified numerical model allows for a reduction in the calculation time of c.a. 54%. Additionally, some disadvantages of using procedures included in commercial software such as a black box have been shown. Full article

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

► Show Figures

Figure 1

23 pages, 3133 KiB

Open AccessReview

Recent Advances in the Characterization of Subsurface Damage in Optical Materials

by Liwei Ou, Hongtu He, Fang Wang, Laixi Sun and Jiaxin Yu

Materials 2025, 18(16), 3883; https://doi.org/10.3390/ma18163883 - 19 Aug 2025

Abstract

Subsurface damage (SSD) in optical materials is easily induced during ultra-precision processes and plays a critical role in the surface performance and lifetime of optical materials. Without proper characterization of SSD in optical materials, it is difficult to fully understand its properties across [...] Read more.

Subsurface damage (SSD) in optical materials is easily induced during ultra-precision processes and plays a critical role in the surface performance and lifetime of optical materials. Without proper characterization of SSD in optical materials, it is difficult to fully understand its properties across various manufacturing processes and thus find effective ways to eliminate it. Despite the rapid development of SSD characterization, many unique features, principles, and applications of SSD characterization in optical materials are not known to this community. This review systematically reviewed the recent literature on characterization methods of SSD in optical materials in both destructive and non-destructive ways. The major drawbacks and limitations of all the characterization methods are presented in this paper, and future trends in the characterization of SSD in optical materials are also proposed. Full article

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

► Show Figures

Figure 1

Journal Description

Materials

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI