Previous Issue
Volume 18, September-1
 
 
materials-logo

Journal Browser

Journal Browser

Materials, Volume 18, Issue 18 (September-2 2025) – 45 articles

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Select all
Export citation of selected articles as:
19 pages, 3814 KB  
Article
An Experimental and Numerical Investigation on Enhancing the Ballistic Resistance of 316L Stainless Steel Plates Against Blunt Projectiles by Covering with 2024-T351 Aluminum Alloy Thin Plates
by Xinke Xiao, Qianqian Ma, Yifan Kong, Hao Lian, Jue Han and Yubo Gao
Materials 2025, 18(18), 4264; https://doi.org/10.3390/ma18184264 (registering DOI) - 11 Sep 2025
Abstract
To improve the ballistic resistance of hydrogen storage tank-grade 316L austenitic stainless steel (ASS) plates that are prone to shear plugging failure under blunt projectile impact, this study proposes a non-bonded bilayer protective configuration: covering the 316L ASS substrate with a thin front [...] Read more.
To improve the ballistic resistance of hydrogen storage tank-grade 316L austenitic stainless steel (ASS) plates that are prone to shear plugging failure under blunt projectile impact, this study proposes a non-bonded bilayer protective configuration: covering the 316L ASS substrate with a thin front layer of 2024-T351 aluminum alloy (AA) plate. Ballistic impact tests were performed on monolithic 5 mm thick 316L ASS plates and bilayer targets composed of a 2.05 mm thick 2024-T351 AA plate and a 5 mm thick 316L ASS substrate (total thickness: 7.05 mm), using a single-stage light gas gun combined with high-speed photography. Parallel explicit dynamics models were established using ABAQUS/Explicit, incorporating a modified Johnson–Cook constitutive model and a Lode-dependent Modified Mohr–Coulomb (MMC) fracture criterion, thereby enabling rigorous mutual validation between experimental results and numerical simulations. Results demonstrate that the addition of a mere 2.05 mm thick aluminum alloy front layer significantly enhances the ballistic limit velocity (BLV) of the 5 mm thick 316L stainless steel target plate, increasing it from 167.5 m/s to 250.7 m/s. The enhancement mechanism is closely related to the transition in the failure mode from localized shear plugging to a combination of bulging, dishing, and plugging. This shift substantially improves the structure’s overall plastic deformation capacity and energy dissipation efficiency. This research provides an effective solution and establishes a reliable experimental–numerical benchmark for the lightweight, impact-resistant design of hydrogen storage tanks. Full article
(This article belongs to the Special Issue Mechanical Behavior of Advanced Engineering Materials (2nd Edition))
Show Figures

Figure 1

22 pages, 10736 KB  
Article
Optimization of Internal Chip Evacuation Cutting Tool System for Deep Bottle Holes Based on Chip Morphology Control
by Yazhou Feng, Zixiang Xu, Wanzhong Li, Kaining Shi, Yang Zhang and Weiye Yang
Materials 2025, 18(18), 4263; https://doi.org/10.3390/ma18184263 - 11 Sep 2025
Abstract
Complex deep hole parts are crucial for major equipment to achieve structural innovation and technological leapfrogging. With the continuous advancement of requirements for weight reduction, efficiency enhancement, and performance modification, the application of deep bottle hole parts has become increasingly widespread. Their structures [...] Read more.
Complex deep hole parts are crucial for major equipment to achieve structural innovation and technological leapfrogging. With the continuous advancement of requirements for weight reduction, efficiency enhancement, and performance modification, the application of deep bottle hole parts has become increasingly widespread. Their structures are mainly characterized by complex interior profiles, variable diameters, large depth-to-diameter ratios, etc. However, the traditional vibration-damping tool boring process is prone to problems such as poor hole straightness and low cutting efficiency due to poor tool rigidity and difficult chip evacuation. For this reason, this research focuses on an internal chip evacuation tool system for deep bottle holes based on cutting morphology control. First, based on the structural characteristics of deep bottle hole components, a specialized tooling system with three guide pad supports and internal chip evacuation channels was designed. Subsequently, the tool’s chip evacuation channel was optimized using fluid simulation results from the tooling system, and the coupled relationship between chip morphology and chip evacuation efficiency was analyzed. Finally, a segmented and layered boring process scheme was proposed based on the component’s structural features. Through deep bottle hole-boring experiments, the surface roughness of the hole interior reached 0.9 µm, and eccentricity was reduced by 54.39%, confirming that the scheme effectively forms chip morphology into spiral curled chips and validating the feasibility and effectiveness of the tooling system. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
18 pages, 5472 KB  
Article
Transparent Wood Fiber-Reinforced Epoxy-Resin Electromagnetic-Shielding Materials with Superior Mechanical Strength and Thermal Insulation Performance
by Jingshu Gao, Zhen Wu, Ling Zhu, Yue Gao, Liping Cai, Zunling Zhu and Yaoli Zhang
Materials 2025, 18(18), 4262; https://doi.org/10.3390/ma18184262 - 11 Sep 2025
Abstract
The development of electromagnetic-shielding materials that not only meet the requirements of electromagnetic shielding but also possess transparency and additional functionalities is a new trend in the field. In this study, delignified wood fibers were used as the base material, which were impregnated [...] Read more.
The development of electromagnetic-shielding materials that not only meet the requirements of electromagnetic shielding but also possess transparency and additional functionalities is a new trend in the field. In this study, delignified wood fibers were used as the base material, which were impregnated in epoxy resin and then reinforced with three types of electromagnetic-shielding fillers: chopped carbon fibers, silicon carbide particles, and nano-silica. The experimental results showed that the resulting wood fiber-reinforced epoxy-resin electromagnetic-shielding transparent material not only exhibited excellent mechanical strength and thermal insulation properties but also achieved high haze and effective electromagnetic-shielding efficiency (greater than 90%) while maintaining a transmittance of approximately 50%. Based on the orthogonal experimental results, the optimal performance of the wood fiber-reinforced epoxy-resin electromagnetic-shielding transparent material was obtained when chopped carbon fibers were used as the electromagnetic-shielding filler component, with an electromagnetic-shielding filler mass fraction of 0.3 wt% and a wood fiber mass fraction of 5.0 wt%. Full article
(This article belongs to the Section Materials Physics)
Show Figures

Figure 1

16 pages, 2160 KB  
Article
Utilization of Hazel (Corylus avellana L.) Wood Particles in the Production of Three-Layer Particleboards for Furniture and Interior Applications
by Paulina Rukat and Grzegorz Kowaluk
Materials 2025, 18(18), 4261; https://doi.org/10.3390/ma18184261 - 11 Sep 2025
Abstract
Hazel wood (Corylus avellana L.) is widespread in Europe but remains underutilized in industry. This study evaluated its potential as a raw material for three-layer particleboards for furniture and interior use. Boards were produced with barked and debarked hazel particles at substitution [...] Read more.
Hazel wood (Corylus avellana L.) is widespread in Europe but remains underutilized in industry. This study evaluated its potential as a raw material for three-layer particleboards for furniture and interior use. Boards were produced with barked and debarked hazel particles at substitution levels of 0–100% with industrial pine. All variants fulfilled EN 312 P2 requirements. Hazel particles increased the bulk density (211 for debarked vs. 160 kg m−3 for pine wood), affecting handling. The modulus of rupture remained stable (11.5–12.7 N mm−2), while the modulus of elasticity declined with the hazel content but stayed above 1600 N mm−2. Internal bond strength improved markedly, reaching 1.63–1.66 N mm−2 at full substitution, and screw withdrawal resistance rose to ~200 N mm−1. However, dimensional stability worsened at 100% hazel, with higher thickness swelling and water absorption, especially for debarked material. Boards from fully debarked hazel also showed reduced core density to below 80% of the nominal density, potentially influencing bonding. The findings indicate that up to 50% hazel substitution is feasible without performance loss, while full replacement requires optimization of pressing and adhesives. Hazel wood thus represents a promising, sustainable alternative to conventional species, supporting more diversified raw material use in particleboard production. Full article
10 pages, 1916 KB  
Article
Valorization of Glass Fiber Waste (VCAS) as a Precursor in Alkali-Activated Systems Cured at Room Temperature–Influence of SiO2/Na2O Molar Ratio
by Mauro Mitsuuchi Tashima, Lourdes Soriano, Ester Gimenez-Carbo, José Monzó, María Victoria Borrachero and Jordi Payá
Materials 2025, 18(18), 4260; https://doi.org/10.3390/ma18184260 - 11 Sep 2025
Abstract
Alkali-activated materials are a promising alternative for reducing CO2 emissions and raw materials consumption due to their capacity to reuse waste materials. In this study, glass fiber-derived waste (vitreous calcium aluminosilicate, VCAS) is used as a precursor in alkali-activated systems for long [...] Read more.
Alkali-activated materials are a promising alternative for reducing CO2 emissions and raw materials consumption due to their capacity to reuse waste materials. In this study, glass fiber-derived waste (vitreous calcium aluminosilicate, VCAS) is used as a precursor in alkali-activated systems for long curing age at room temperature. Here, the influence of SiO2/Na2O molar ratio on the mechanical, mineralogical, and microstructural properties is assessed. The XRD pattern, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) studies demonstrated the evolution of microstructure even after 28 curing days yielding a dense-compact microstructure, and according to the compressive strength results in mortars, about 100 MPa in compression was achieved after 360 curing days for 0.48 and 0.55 SiO2/Na2O molar ratio, confirming the stability of this system at room temperature. Full article
31 pages, 838 KB  
Review
Endodontic Sealers and Innovations to Enhance Their Properties: A Current Review
by Anna Błaszczyk-Pośpiech, Natalia Struzik, Maria Szymonowicz, Przemysław Sareło, Maria Wiśniewska-Wrona, Kamila Wiśniewska, Maciej Dobrzyński and Magdalena Wawrzyńska
Materials 2025, 18(18), 4259; https://doi.org/10.3390/ma18184259 - 11 Sep 2025
Abstract
Endodontic sealers are crucial for achieving an effective root canal obturation, preventing reinfection and promoting long-term treatment success. This review categorizes sealers by chemical composition, including traditional types such as zinc oxide-eugenol, glass ionomer, silicone, methacrylate and epoxy resins, calcium hydroxide, and the [...] Read more.
Endodontic sealers are crucial for achieving an effective root canal obturation, preventing reinfection and promoting long-term treatment success. This review categorizes sealers by chemical composition, including traditional types such as zinc oxide-eugenol, glass ionomer, silicone, methacrylate and epoxy resins, calcium hydroxide, and the latest bioceramic formulations. Each type is evaluated for its physicochemical properties, biocompatibility, sealing ability, antimicrobial activity, and clinical limitations. A significant focus is placed on recent research into modifications of these materials with antimicrobial agents, aimed at improving antibacterial properties, bioactivity, and sealing performance. Among these, chitosan emerges as the most promising additive due to its broad antimicrobial spectrum, low cytotoxicity, and enhancement of sealing capacity. While bioceramic sealers represent a notable advancement due to their bioactivity and favorable interaction with moist environments, concerns regarding potential neurotoxicity and retreatability remain. The article presents recent advancements in the enhancement of endodontic sealers through the incorporation of organic and inorganic additives. It further delineates key research priorities, particularly the integration of bioactive materials, nanotechnology, and naturally derived compounds, with an emphasis on their potential applications in pediatric endodontics. Overall, while contemporary sealers offer a wide range of benefits, continued innovation is needed to optimize their biological safety, mechanical performance, and clinical usability. Full article
Show Figures

Figure 1

24 pages, 4924 KB  
Article
Performance and Durability of Chalcedonite Reactive Powder Concrete
by Joanna Julia Sokołowska, Piotr Woyciechowski and Szymon Żerek
Materials 2025, 18(18), 4258; https://doi.org/10.3390/ma18184258 - 11 Sep 2025
Abstract
The objective of this study was to evaluate the technical properties and assess the durability of a novel high-performance concrete with aggregates composed entirely of reactive powders derived from chalcedonite—a mineral previously not utilized in HPC technology. Since there is insufficient information on [...] Read more.
The objective of this study was to evaluate the technical properties and assess the durability of a novel high-performance concrete with aggregates composed entirely of reactive powders derived from chalcedonite—a mineral previously not utilized in HPC technology. Since there is insufficient information on chalcedonite-based concretes in the scientific literature, the presented research aims to address these knowledge gaps. The characterization of the chalcedonite powder involved the determination of specific gravity, particle size distribution, specific surface area, and particle morphology through microscopic analysis. The hardened chalcedonite-based and reference quartz-based high-performance concretes were subjected to a comprehensive suite of tests to determine their physical properties (bulk density, water absorption, and capillary absorption) and mechanical properties (flexural and compressive strength). Durability was further assessed based on compressive strength criteria, including frost resistance and carbonation resistance. To simulate long-term performance and better evaluate the durability of the high-performance concretes, specimens were tested following standard water curing and after additional maturation processes, including thermal treatment, which in the extreme case resulted in a seven-day compressive strength of 176.9 MPa, a value higher by 56.7 MPa (corresponding to an increase of 47.1%) compared to the strength of the identical concrete not subjected to thermal treatment. To explore the potential for architectural applications, particularly in outdoor environments, capillary absorption testing was of particular importance, as it provided insight into the material’s resistance to eventual pigment leaching from the mineral matrix. Full article
(This article belongs to the Special Issue Characterization and Optimization of Cement-Based Materials)
Show Figures

Figure 1

16 pages, 2421 KB  
Article
High-Performance Mortar with Epoxy-Coated Lightweight Aggregates for Marine Structures
by Jin-Su Kim, Ho-Yeon Lee and Jang-Ho Jay Kim
Materials 2025, 18(18), 4257; https://doi.org/10.3390/ma18184257 - 11 Sep 2025
Abstract
Due to the global growth of the construction industry, the use of concrete has increased rapidly. Consequently, the depletion of natural aggregates, which are essential components of concrete, has emerged as a critical issue. Simultaneously, the construction of marine structures has recently increased [...] Read more.
Due to the global growth of the construction industry, the use of concrete has increased rapidly. Consequently, the depletion of natural aggregates, which are essential components of concrete, has emerged as a critical issue. Simultaneously, the construction of marine structures has recently increased due to population growth and climate change. This trend highlights the growing demand for durable and sustainable construction materials in aggressive environments. To address the depletion of natural aggregates, extensive research has focused on artificial lightweight aggregates produced from industrial waste. However, the high porosity and low compressive strength of artificial lightweight aggregates have limited their effectiveness in ensuring the performance of sustainable marine structures. In this study, a high-performance mortar (HPM) incorporating artificial lightweight fine aggregates (ALWFAs) was developed to address the depletion of natural aggregates and to serve as a protective layer material in marine environments. To enhance the physical properties of ALWFAs, the aggregates were coated with epoxy-TiO2 coatings applied to both their internal voids and external surfaces. The effectiveness of this enhancement was assessed by comparing the performance of mortars prepared with uncoated and coated ALWFAs. The HPM was evaluated for its porosity, compressive strength, split tensile strength, and chloride diffusion coefficient. The results showed that increases in the ALWFA replacement ratio led to a general reduction in performance. However, a comparison between uncoated and coated ALWFAs revealed that the coated aggregates led to improvements of up to 4.13%, 49.3%, 28.6%, and 52.0% in porosity, compressive strength, split tensile strength, and chloride diffusion coefficient, respectively. The study results are discussed in detail in the paper. Full article
(This article belongs to the Special Issue Advances in Sustainable Construction Materials, Third Edition)
Show Figures

Figure 1

13 pages, 1581 KB  
Article
Micro-Tensile Bond Strength of a Mesoporous Bioactive Glass-Containing Universal Adhesive: An In Vitro Study on the Effects of Artificial Aging
by Jiyoung Kwon, Soyoung Park, Gil-Joo Ryu and Duck-Su Kim
Materials 2025, 18(18), 4256; https://doi.org/10.3390/ma18184256 - 11 Sep 2025
Abstract
Background: We evaluated the immediate and artificially aged micro-tensile bond strengths (μTBS) of Hi-Bond Universal, a universal adhesive containing mesoporous bioactive glass (MBG). Methods: Human dentin specimens were bonded using the following four application modes: Hi-Bond Universal in etch-and-rinse mode, Hi-Bond Universal in [...] Read more.
Background: We evaluated the immediate and artificially aged micro-tensile bond strengths (μTBS) of Hi-Bond Universal, a universal adhesive containing mesoporous bioactive glass (MBG). Methods: Human dentin specimens were bonded using the following four application modes: Hi-Bond Universal in etch-and-rinse mode, Hi-Bond Universal in self-etch mode, Single Bond 2 in etch-and-rinse mode, and G-ænial Bond in self-etch mode. Specimens were tested either immediately or after artificial aging (thermocycling or water storage). μTBS values were analyzed statistically, and the resin–dentin interfaces were examined using FE-SEM (Field-emission scanning electron microscopy). Results: Results showed that both aging and adhesive mode significantly affected the μTBS (p < 0.0001). Immediately after bonding, etch-and-rinse modes produced significantly higher μTBS than the self-etch modes (p < 0.0001). Artificial aging reduced bond strength by approximately 30–50%; however, the μTBS of Hi-Bond Universal decreased less than that of Single Bond 2 after water storage. FE-SEM analysis also revealed detachment of the hybrid layer in most adhesives following aging; however, Hi-Bond Universal in the etch-and-rinse mode maintained a relatively intact adhesive layer after water storage. Conclusion: Etch-and-rinse application of MBG-containing adhesive may enhance the long-term durability of adhesive restorations. Full article
(This article belongs to the Special Issue The Application of Bioactive Glasses to Dental Restorative Materials)
Show Figures

Figure 1

24 pages, 9894 KB  
Article
Effects of Multiple Welding Thermal Cycles on Stress Corrosion of L360N Steel in a Simulated Shale Gas Gathering Environment Containing Sulfate-Reducing Bacteria
by Jie Xiao, Shouxi Wang, Yong Xu, Kexi Liao, Guiyang Wu, Jing Yan, Yongbo Wang, Lincai Peng and Puzhi Li
Materials 2025, 18(18), 4255; https://doi.org/10.3390/ma18184255 - 11 Sep 2025
Abstract
The combined effect of sulfate-reducing bacteria (SRB) and a microstructure on the stress corrosion behavior of heat-affected zones (HAZs) in pipeline steel for shale gas field applications was investigated. The results show that when the peak heating temperature reached 1020 °C, a coarse [...] Read more.
The combined effect of sulfate-reducing bacteria (SRB) and a microstructure on the stress corrosion behavior of heat-affected zones (HAZs) in pipeline steel for shale gas field applications was investigated. The results show that when the peak heating temperature reached 1020 °C, a coarse microstructure formed during multiple thermal cycles (MTCs), and Widmanstätten structures appeared in the HAZ. In the simulated environment, SRB intensified localized pitting corrosion of both the base metal and the HAZ. The welding HAZ was softened by the MTCs, and significant microcrack growth was observed in the presence of SRB. Among all subzones, the coarse-grained HAZ (CGHAZ) was the most susceptible to stress corrosion cracking (SCC) under shale gas service conditions. Cracks initiated at the metal surface and propagated vertically into the material. SRB activity further increased the SCC sensitivity of the CGHAZ. Full article
(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, 3rd Edition)
Show Figures

Figure 1

18 pages, 8688 KB  
Article
Evaluation of the Impact of Hydrogen Peroxide on ANFO-Based Materials’ Morphology
by Andrzej Biessikirski, Michał Dworzak, Magdalena Ziąbka, Krzysztof Polak, Mateusz Pytlik, Bogna Daria Napruszewska and Łukasz Kuterasiński
Materials 2025, 18(18), 4254; https://doi.org/10.3390/ma18184254 - 11 Sep 2025
Abstract
The decomposition of high-energy materials often releases large volumes of toxic fumes, contributing to environmental pollution. To reduce these emissions, eco-friendly formulations are being developed by modifying chemical composition or adding functional additives that enhance combustion and reduce toxic byproducts. Hydrogen peroxide (H [...] Read more.
The decomposition of high-energy materials often releases large volumes of toxic fumes, contributing to environmental pollution. To reduce these emissions, eco-friendly formulations are being developed by modifying chemical composition or adding functional additives that enhance combustion and reduce toxic byproducts. Hydrogen peroxide (H2O2), acting as both an oxidizer and potential fuel, shows promise in lowering NOx emissions. However, its impact on formulation stability must be assessed. This study examines the morphological and thermal behavior of an ammonium nitrate, fuel oil, and hydrogen peroxide (ANFOHP) formulation using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermal analysis based on thermogravimetry (TG) connected with differential scanning calorimetry (DSC) techniques. SEM showed that the fuel oil–hydrogen peroxide (FOHP) blend formed a thin film on ammonium nitrate prills without structural damage. XRD patterns indicated an intact crystalline structure. Moreover, FT-IR analysis performed both for fresh and 24-h stored samples evidenced no structural changes. In turn, TG/DSC revealed altered thermal behavior, with a new endothermic peak near 80 °C corresponding to the simultaneous evaporation of water and hydrogen peroxide from the ANFO surface, and reduced intensity of the main ANFO decomposition peak, indicating a shift in the thermal behavior induced by the FOHP blend. Full article
Show Figures

Figure 1

24 pages, 5990 KB  
Article
Photoelectrocatalytic Degradation of Rhodamine B in the Presence of TiO2-BiVO4
by Anli Sun, Chao Kong, Jie Wang, Beihai Zhou, Huilun Chen, Rongfang Yuan and Zhiming Bai
Materials 2025, 18(18), 4253; https://doi.org/10.3390/ma18184253 - 11 Sep 2025
Abstract
The discharge of printing and dyeing wastewater has become a key concern in global water pollution control due to its high pollutant concentration, dark color, refractory biodegradability and toxic characteristics. Photoelectrocatalytic (PEC) technology has gained widespread attention as it can effectively treat refractory [...] Read more.
The discharge of printing and dyeing wastewater has become a key concern in global water pollution control due to its high pollutant concentration, dark color, refractory biodegradability and toxic characteristics. Photoelectrocatalytic (PEC) technology has gained widespread attention as it can effectively treat refractory organic pollutants. In this study, titanium dioxide (TiO2)–bismuth vanadate (BiVO4) composite materials were synthesized through the sol–gel/solvothermal hybrid method, and layered heterojunction structures were fabricated via sol–gel precursor preparation followed by spin-coating deposition. The PEC degradation efficiency of rhodamine B (RhB) was systematically evaluated under varying operational conditions in the presence of TiO2-BiVO4. The four-layer BiVO4/four-layer TiO2 material showed the optimal catalytic activity among the tested structures, achieving an 80.3% removal of RhB under an applied bias of 4 V and illumination intensity of 14,000 lx. Through the equilibrium adjustment of the Fermi levels, the type Ⅱ heterostructure was formed. Moreover, superoxide radical (O2) was identified as the predominant reactive oxygen species driving the degradation mechanism. Mechanistic analysis revealed that RhB degradation was accomplished through deethylation, benzene ring cleavage, and subsequent ring-opening mineralization. This study prepared an efficient PEC material, which provides a theoretical basis for the PEC treatment of printing and dyeing wastewater. Full article
Show Figures

Figure 1

12 pages, 2802 KB  
Article
Photocatalytic Degradation of Rhodamine B Using 1D CuO/TiO2 Nanofibers Synthesized via the Electrospinning Method
by Shouzhen Duan, Wanjun Zhang, Xiaoyan Wang, Youqing Zhao, Hui Nan and Guijun Yang
Materials 2025, 18(18), 4252; https://doi.org/10.3390/ma18184252 - 11 Sep 2025
Abstract
This research was designed to improve the separation efficiency of photogenerated carriers in TiO2 through the construction of a PN heterojunction. The motivation behind this was to tackle the problems of the narrow light response range and the high electron-hole recombination rate [...] Read more.
This research was designed to improve the separation efficiency of photogenerated carriers in TiO2 through the construction of a PN heterojunction. The motivation behind this was to tackle the problems of the narrow light response range and the high electron-hole recombination rate of TiO2. By simple one-step implementing electrospinning and calcination procedures, CuO/TiO2 PN heterojunction nanofibers were successfully synthesized. XRD and SEM analyses confirm that the heterojunction is a nanofiber structure composed of TiO2 and CuO, with the TiO2 containing anatase and rutile phases. The PL reveals that the fluorescence intensity of the heterojunction is lower compared to that of pure TiO2, and this implies a remarkable enhancement in the carrier separation efficiency. Under xenon light irradiation, for the optimized sample, the degradation rate of RhB exceeds 80%. This degradation rate is 68% higher than that of pure TiO2. The improvement in photocatalytic performance can be ascribed to the efficient charge separation driven by the built-in electric field within the PN junction and the extended light absorption range. The photoelectrochemical test further verified that the photocurrent density of the heterojunction system was 52.42% higher than that of the single TiO2, providing a new strategy for designing efficient photocatalytic systems. Full article
(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)
Show Figures

Figure 1

17 pages, 6951 KB  
Article
Tribological Properties of DLC Coatings in Model-Based and Real-Life Tests
by Katarzyna Piotrowska, Monika Madej and Krystian Milewski
Materials 2025, 18(18), 4251; https://doi.org/10.3390/ma18184251 - 11 Sep 2025
Abstract
Machinery for internal transport in open-pit mines experiences excessive wear. Belt conveyors used for transporting aggregates are a type of equipment in which bearings are especially prone to failure. Considering the significant financial impact of equipment downtime, ensuring the high reliability of machinery [...] Read more.
Machinery for internal transport in open-pit mines experiences excessive wear. Belt conveyors used for transporting aggregates are a type of equipment in which bearings are especially prone to failure. Considering the significant financial impact of equipment downtime, ensuring the high reliability of machinery in this sector is paramount. Consequently, the design of tribological interfaces should prioritize maximizing their reliability and minimizing the frequency of malfunctions. This article presents a comparative analysis of 100Cr6 steel and a-C:H type diamond-like carbon (DLC) coatings applied using chemical vapor deposition (PACVD) on bearing components in belt conveyors. Model-based tribological tests were conducted on these materials in both laboratory and real-life settings, evaluating friction and wear under dry friction and under Renolit UNI 3 grease-lubricated conditions, the latter being the operational lubricant for these bearings. Full article
Show Figures

Figure 1

22 pages, 9976 KB  
Article
Effect of CaO in Alkali-Activated Fly Ash Mortar Under Different Curing Temperatures
by David Murillo-Silo, Enrique Fernández-Ledesma, José Ramón Jiménez, José María Fernández-Rodríguez and David Suescum-Morales
Materials 2025, 18(18), 4250; https://doi.org/10.3390/ma18184250 - 10 Sep 2025
Abstract
This work investigates the influence of CaO as a partial substitute for fly ash in alkali-activated fly ash mortars (AAFM), aiming to reduce reliance on conventional thermal curing. Mortars containing 0%, 2%, and 4% CaO were prepared and subjected to two curing regimes: [...] Read more.
This work investigates the influence of CaO as a partial substitute for fly ash in alkali-activated fly ash mortars (AAFM), aiming to reduce reliance on conventional thermal curing. Mortars containing 0%, 2%, and 4% CaO were prepared and subjected to two curing regimes: thermal curing at 70 °C for 24 h and ambient curing at 21 °C for 24 h. The materials were thoroughly characterised by XRD, XRF, TGA/DTA, SEM, and particle size distribution, while compressive and flexural strength, density, and porosity were evaluated at 7, 14, and 28 days. The results demonstrated that CaO addition improved mechanical performance in both curing environments, particularly at a 4% substitution level, where compressive strength increased by up to 13.8% under thermal curing conditions. These improvements were associated with the formation of C-S-H and C-A-S-H gels, especially margarite, which contributed to accelerated setting and earlier demoulding. Nonetheless, while CaO incorporation improved mechanical performance and allowed earlier demoulding, it could not fully replicate the effects of heat curing at the studied percentages. Ambient-cured mortars exhibited higher porosity and less compact microstructures than thermally cured samples, which displayed denser, layered morphologies. The study confirms that CaO can act as a partial substitute or reducer for conventional curing, but is not sufficient to enable in situ applications without heat treatment. Future research should explore higher CaO contents in combination with set retarders, intermediate curing regimes, or alternative strategies to balance mechanical performance with energy efficiency. Full article
(This article belongs to the Section Construction and Building Materials)
Show Figures

Figure 1

41 pages, 5816 KB  
Review
A Review of Hybrid Manufacturing: Integrating Subtractive and Additive Manufacturing
by Bruno Freitas, Vipin Richhariya, Mariana Silva, António Vaz, Sérgio F. Lopes and Óscar Carvalho
Materials 2025, 18(18), 4249; https://doi.org/10.3390/ma18184249 - 10 Sep 2025
Abstract
It is challenging to manufacture complex and intricate shapes and geometries with desired surface characteristics using a single manufacturing process. Parts often need to undergo post-processing and must be transported from one machine into another between steps. This makes the whole process cumbersome, [...] Read more.
It is challenging to manufacture complex and intricate shapes and geometries with desired surface characteristics using a single manufacturing process. Parts often need to undergo post-processing and must be transported from one machine into another between steps. This makes the whole process cumbersome, time-consuming, and inaccurate. These shortcomings play a major role during the manufacturing of micro and nano products. Hybrid manufacturing (HM) has emerged as a favorable solution for these issues. It is a flexible process that combines two or more manufacturing processes, such as additive manufacturing (AM) and subtractive manufacturing (SM), into a single setup. HM works synergistically to produce complex, composite, and customized components. It makes the process more time efficient and accurate and can prevent unnecessary transportation of parts. There are still challenges ahead regarding implementing and integrating sensors that allow the machine to detect defects and repair or customize parts according to needs. Even though modern hybrid machines forecast an exciting future in the manufacturing world, they still lack features such as real-time adaptive manufacturing based on sensors and artificial intelligence (AI). Earlier reviews do not profoundly elaborate on the types of laser HM machines available. Laser technology resolutely handles additive and subtractive manufacturing and is capable of producing groundbreaking parts using a wide scope of materials. This review focuses on HM and presents a compendious overview of the types of hybrid machines and setups used in the scientific community and industry. The study is unique in the sense that it covers different HM setups based on machine axes, materials, and processing parameters. We hope this study proves helpful to process, plan, and impart productivity to HM processes for the betterment of material utilization and efficiency. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
Show Figures

Graphical abstract

24 pages, 2018 KB  
Article
Wave Propagation Analysis in the Homogenized Second-Gradient Medium: A Direct and Inverse Approach
by Fadheelah Al Fayadh, Hassan Lakiss and Hilal Reda
Materials 2025, 18(18), 4248; https://doi.org/10.3390/ma18184248 - 10 Sep 2025
Abstract
In this work, we develop a method for homogenizing effective second-order gradient continuum models for 2D periodic composite materials. A constitutive law is formulated using a variational approach combined with the Hill macro-homogeneity condition for strain energy. Incorporating strain gradient effects enhances the [...] Read more.
In this work, we develop a method for homogenizing effective second-order gradient continuum models for 2D periodic composite materials. A constitutive law is formulated using a variational approach combined with the Hill macro-homogeneity condition for strain energy. Incorporating strain gradient effects enhances the constitutive law by linking the hyperstress tensor to the second-order gradient of displacement, capturing elastic size and microstructure effects beyond classical Cauchy elasticity. The effective strain gradient moduli are calculated for composites exhibiting strong internal length effects, validating the proposed approach by computing the strain energy at different scales. Additionally, we develop an inverse homogenization method to compute local mechanical properties (properties of the constituents) given known global properties (effective properties), showing good agreement with the literature data. This framework is extended to study wave propagation by analyzing longitudinal and shear waves in 2D composite materials. The effects of inclusion shape and volume percentage on wave propagation are examined, revealing that elliptic inclusions lead to a slight increase in both modes of propagation. Finally, we investigate the impact of property contrast between the inclusion and matrix, demonstrating its influence on wave dispersion. Full article
Show Figures

Figure 1

33 pages, 2623 KB  
Review
Biodegradable Plastics as Sustainable Alternatives: Advances, Basics, Challenges, and Directions for the Future
by Eunbin Hwang, Yung-Hun Yang, Jiho Choi, See-Hyoung Park, Kyungmoon Park and Jongbok Lee
Materials 2025, 18(18), 4247; https://doi.org/10.3390/ma18184247 - 10 Sep 2025
Abstract
This review explores the current state and future potential of bioplastics as sustainable alternatives to conventional fossil-based polymers. It provides a detailed examination of the classification, molecular structures, and synthetic routes of major bioplastics, including polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), [...] Read more.
This review explores the current state and future potential of bioplastics as sustainable alternatives to conventional fossil-based polymers. It provides a detailed examination of the classification, molecular structures, and synthetic routes of major bioplastics, including polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene adipate-co-terephthalate (PBAT), and polyhydroxyalkanoates (PHAs). Special emphasis is placed on the unique properties and degradation behaviors of each material across various environmental conditions, such as industrial composting, soil, and marine ecosystems. The manuscript further discusses advanced strategies in polymer design, such as copolymerization, reactive blending, and incorporation of nano- or micro-scale additives, to enhance flexibility, thermal resistance, barrier properties, and mechanical integrity. In addition to technical advancements, the review critically addresses key limitations impeding large-scale commercialization, including high production costs, limited availability of bio-based monomers, and inadequate end-of-life treatment infrastructure. Finally, future research directions are proposed to advance the development of fully bio-based, functionally tunable, and circular bioplastics that meet the performance demands of modern applications while reducing environmental impact. Full article
Show Figures

Figure 1

23 pages, 12524 KB  
Article
Development of Xanthan Gum-Modified Coal-Fly-Ash-Based Cementitious Firefighting Materials with Improved High-Temperature Resistance for Coal Mines
by Guolan Dou, Peng Chen, Menghan Wang, Jingyu Wang, Xiaoxing Zhong and Shuangming Wei
Materials 2025, 18(18), 4246; https://doi.org/10.3390/ma18184246 - 10 Sep 2025
Abstract
In this study, xanthan gum (XG)-modified coal-fly-ash-based cementitious materials were synthesized to realize the resource utilization of coal fly ash and to develop a low-carbon emission cementitious sealing material that can substitute cement-based sealing material to prevent coal fires. The optimal formulation for [...] Read more.
In this study, xanthan gum (XG)-modified coal-fly-ash-based cementitious materials were synthesized to realize the resource utilization of coal fly ash and to develop a low-carbon emission cementitious sealing material that can substitute cement-based sealing material to prevent coal fires. The optimal formulation for coal-fly-ash-based mining cementitious sealing material was developed using response surface methodology based on Box–Behnken Design. The optimized formulation was obtained with a coal fly ash-to-precursor ratio of 0.65, alkali-activator modulus of 1.4, and alkali-activator dosage of 7.5%. Under the optimal conditions, the initial and final setting time were 26 min and 31 min, respectively, fluidity was 245 mm, and the 7-day compressive strength approached 36.60 MPa, but there were still thermal shrinkage and cracking phenomena after heating. XG was then introduced to improve the thermal shrinkage and cracking of coal-fly-ash-based cementitious materials. Incorporating 1 wt.‰ XG was found to decrease the fluidity while maintaining the setting time and increasing the 1-day and 7-day compressive strength by 15.44% and 1.97%, respectively. The results demonstrated that the gels generated by XG cross-linking and coordinating with Al3+/Ca2+ were interspersed in the original C(N)-A-S-H gel network, which not only made the 1 wt.‰ XG modified coal-fly-ash-based cementitious material show minor expansion at ambient temperatures, but also improved the residual compressive strength, thermal shrinkage resistance and cracking resistance in comparison to unmodified cementitious material. However, due to the viscosity of XG and the coordination of Al3+ and non-terminal carboxyl groups in XG breaking the gel network, XG incorporation should not exceed 1 wt.‰ as the compressive strength and fluidity are decreased. Full article
(This article belongs to the Section Construction and Building Materials)
Show Figures

Graphical abstract

19 pages, 2866 KB  
Article
Recycling Foundry Sands in Concrete: A Comparative Study on the Use of Green Sand and Chemically Bonded Sand as Partial Replacements for Natural Sand
by Pietro Di Maida, Corrado Sciancalepore, Enrico Radi, Luca Lanzoni and Daniel Milanese
Materials 2025, 18(18), 4245; https://doi.org/10.3390/ma18184245 - 10 Sep 2025
Abstract
Currently, many foundries successfully reuse sand multiple times within their production cycle. However, when the sand can no longer be reused, it is disposed of, resulting in environmental damage and high disposal costs for the company. The present research aims to explore the [...] Read more.
Currently, many foundries successfully reuse sand multiple times within their production cycle. However, when the sand can no longer be reused, it is disposed of, resulting in environmental damage and high disposal costs for the company. The present research aims to explore the potential reuse of foundry sands as fine aggregate in concrete. Since this by-product is classified as non-hazardous waste, it can offer interesting opportunities for the recycling of a material that is currently one of the most widely used in the construction industry. This paper studies the potential reuse of green sand (GS) and chemically bonded sand (CBS) as a partial replacement for natural sand (NS) in concrete. Concrete specimens made with 10%, 20%, and 30% of foundry sand were tested, and a comparative analysis was carried out with the standard mixture in terms of chemical–physical properties, workability, and mechanical properties. The results showed a reduction in the performance of concrete specimens prepared with foundry sands. The lowest reductions in the strength, which were always below 10%, were observed for a 10% inclusion rate of both GS and CBS, with slightly better performance for CBS. Performance reductions tend to increase with higher replacement rates. However, these performance reductions turn out to be acceptable for concrete used in non-structural applications. Full article
Show Figures

Figure 1

20 pages, 4679 KB  
Article
Matrices of Different Natures for Bone Tissue Engineering—A Comparative Analysis
by D. Ya. Aleinik, A. E. Bokov, D. D. Linkova, E. A. Levicheva, E. A. Farafontova, R. S. Kovylin, V. V. Yudin, D. V. Khramova, L. A. Cherdantseva, S. A. Chesnokov, I. A. Kirilova and M. N. Egorikhina
Materials 2025, 18(18), 4244; https://doi.org/10.3390/ma18184244 - 10 Sep 2025
Abstract
Recent decades have been characterized by increasing numbers of bone tissue injuries and diseases resulting in the formation of bone defects. The number of such bone defects has also grown due to active surgical approaches implemented after surgical interventions for oncological, infectious, and [...] Read more.
Recent decades have been characterized by increasing numbers of bone tissue injuries and diseases resulting in the formation of bone defects. The number of such bone defects has also grown due to active surgical approaches implemented after surgical interventions for oncological, infectious, and dystrophic bone lesions. To repair such bone defects requires the use of bone tissue substitutes. Nowadays, constructs based on matrices of various compositions and structures, supplemented with the addition of biologically active components (including growth factors and cells), are the most promising approaches used in bone tissue engineering. The properties of the matrices are of the utmost importance in construct formation. This work presents the results of a comprehensive study of matrices of various natures intended for the formation of complex constructs for bone tissue engineering. Using a set of methods for studying the physical, mechanical, and biological characteristics, the total and associated porosity of the studied matrices, the structure, the mechanical parameters, and the level of cytotoxicity and cytocompatibility were determined. It was shown that all the studied materials were not cytotoxic (cytotoxicity rank of all matrices = 0–1). All matrices were porous, but samples of materials of biological origin had large pores ranging in size from 100 to 1000 μm, and pores of the hybrid polymer were sized from 0.1 to 100 μm. Total and open porosity ranged from 89% and 79% for the allogeneic matrix up to 67% and 48% for the hybrid polymer, respectively, while the σ values (compressive stress at break) of samples of all studied materials were close to each other. When human test culture MSCs interact with samples of these materials, it was shown that the cells adhere to the surface and structure of all materials and retain typical morphology, while also demonstrating the ability to proliferate and migrate along the surface and into the matrix structure, i.e., all materials are cytocompatible. Based on the data obtained, it can be assumed that all the studied matrices can be used for model biomedical studies and as a basis for constructs for bone tissue engineering. An adequate choice of research method at the earliest stages of the development of each material will ensure the most effective approaches for further work and subsequent use of this product. Full article
(This article belongs to the Section Biomaterials)
Show Figures

Figure 1

15 pages, 3993 KB  
Article
Influence of Moisture Invasion on the Deterioration of Epoxy Resin Performance, and Modification and Enhancement Methods
by Sixiao Xin, Jingyi Hou, Liang Zou, Zhiyun Han, Zhen Li and Hanwen Ren
Materials 2025, 18(18), 4243; https://doi.org/10.3390/ma18184243 - 10 Sep 2025
Abstract
In high-humidity environments, the epoxy resin solid insulation materials of high-frequency transformers are prone to aging, resulting in varying degrees of deterioration in the material’s dielectric properties and other aspects. To enhance the adaptability of epoxy resin in high humidity environments, this paper, [...] Read more.
In high-humidity environments, the epoxy resin solid insulation materials of high-frequency transformers are prone to aging, resulting in varying degrees of deterioration in the material’s dielectric properties and other aspects. To enhance the adaptability of epoxy resin in high humidity environments, this paper, based on the molecular dynamics simulation method, establishes epoxy resin-based nanocomposites with doped nanofillers: a pure epoxy resin model and three epoxy resin models, respectively, doped with carbon nanotubes, graphene(GR), and SiO2. Based on the above models, using LAMMPS-17Apr2024, the thermal diffusion coefficients (thermal conductivity and specific heat capacity), glass transition temperatures, and dielectric constants under different moisture contents are calculated. The results show that the various properties of the epoxy resin nanocomposites doped with nanofillers have been improved to varying degrees. Among them, the GR/epoxy resin composite model shows the most significant improvements in thermal conductivity, thermal diffusivity, and glass transition temperature, and the SiO2/epoxy resin composite model has the best dielectric properties. Considering the high-temperature operation conditions and heat dissipation requirements of the high-frequency transformer, the GR-enhanced epoxy resin becomes the optimal filler choice. Full article
Show Figures

Graphical abstract

15 pages, 1489 KB  
Article
Dissolution Kinetics in Plasma-Enhanced Nitric Acid Solvolysis of CFRCs
by Dimitrios Marinis, Ergina Farsari and Eleftherios Amanatides
Materials 2025, 18(18), 4242; https://doi.org/10.3390/ma18184242 - 10 Sep 2025
Abstract
The dissolution kinetics in conventional nitric acid and plasma-enhanced nitric acid solvolysis of composites were investigated. Unidirectional carbon fiber epoxy laminates originating from the scar of wind turbine blades were used for the study. The carbon fiber retrieval rate was experimentally determined as [...] Read more.
The dissolution kinetics in conventional nitric acid and plasma-enhanced nitric acid solvolysis of composites were investigated. Unidirectional carbon fiber epoxy laminates originating from the scar of wind turbine blades were used for the study. The carbon fiber retrieval rate was experimentally determined as a function of dissolution time and composite mass. A kinetic model, which included disintegration of the polymer matrix and the mass transport of polymer fragments to the liquid phase, was implemented to investigate the main parameters that affect the dissolution rate. The plasma enhancement and the increase of the composite mass favor the carbon fiber retrieval rate, while process time slows down the matrix dissolution rate. The composite surface in contact with the liquid, solid-to-liquid volume ratio, solubility of the polymer matrix, and disintegration and mass transport rate coefficients have a significant effect on the dissolution rate, and the rate-limiting factors were revealed and analyzed. Full article
(This article belongs to the Special Issue Carbon Fiber Reinforced Polymers (3rd Edition))
Show Figures

Figure 1

18 pages, 7158 KB  
Article
Fe-Cr-Mo-B-Si-C Metamorphic Alloy Coating with Excellent Wear Resistance Fabricated via High-Velocity Oxygen Fuel Thermal Spray Process
by Yu-Jin Hwang, Yong-Hoon Cho, Gi-Su Ham, Choongnyun Paul Kim and Kee-Ahn Lee
Materials 2025, 18(18), 4241; https://doi.org/10.3390/ma18184241 - 10 Sep 2025
Abstract
A cost-effective Fe-Cr-Mo-B-Si-C metamorphic alloy (HXA5) was newly designed and fabricated as coating material using the high-velocity oxygen fuel (HVOF) thermal spray process, and its microstructure and dry wear resistance were investigated in comparison with a conventional HVOF WC-12Co coating. The HXA5 coating [...] Read more.
A cost-effective Fe-Cr-Mo-B-Si-C metamorphic alloy (HXA5) was newly designed and fabricated as coating material using the high-velocity oxygen fuel (HVOF) thermal spray process, and its microstructure and dry wear resistance were investigated in comparison with a conventional HVOF WC-12Co coating. The HXA5 coating material consisted of a splat area and un-melted powder area. The splat area contained metallic glass, (Cr,Fe)2B, Cr2B, and minor Fe-based BCC phases, and the un-melted powder area was composed of Fe-based BCC, (Cr,Fe)2B, and Cr2B phases. Room-temperature wear tests revealed that HVOF HXA5 coating material exhibited wear resistance comparable to HVOF WC-12Co coating over ~8.4 km sliding and even superior performance at high-stress wear conditions. This superior wear behavior of HXA5 coating material was attributed to the minimal hardness difference between the metallic glass and boride, the plasticity of the metallic glass, and the formation of a lubricating tribofilm. The wear mechanisms and the influence of alloying elements on glass-forming ability were also discussed. Full article
Show Figures

Figure 1

23 pages, 6426 KB  
Article
Analysis of Filtration Coefficient of Selected Recycled Materials on the Example of Concrete Aggregate and Rubber Waste
by Katarzyna Gabryś, Karolina Damska, Raimondas Šadzevičius, Dainius Ramukevičius, Wojciech Sas, Bruno Camargo, Algirdas Radzevičius and Midona Dapkienė
Materials 2025, 18(18), 4240; https://doi.org/10.3390/ma18184240 - 10 Sep 2025
Abstract
The permeability of recycled materials such as recycled concrete aggregate (RCA) and rubber tire waste (RTW) significantly affects their suitability in geotechnical applications. RCA is typically more porous than natural aggregates, while RTW can either increase or decrease permeability depending on its content [...] Read more.
The permeability of recycled materials such as recycled concrete aggregate (RCA) and rubber tire waste (RTW) significantly affects their suitability in geotechnical applications. RCA is typically more porous than natural aggregates, while RTW can either increase or decrease permeability depending on its content and form. This study investigates the hydraulic conductivity of fine RCA (fRCA), fRCA–RTW mixtures, and compressed shredded tire waste (RTWS) using variable-gradient tests under various consolidation pressures. Permeability is closely related to material quality, depending on intended use: low permeability suits barrier or fill layers, while high permeability benefits drainage applications. Both behaviors were achieved in this study—fRCA showed low permeability (10−6 to 10−7 m/s), while RTW addition significantly increased water flow, with filtration coefficients exceeding 1 × 10−3 m/s. The permeability of fRCA–RTW mixtures increased with rubber content, though greater heterogeneity was observed. The results demonstrate that recycled materials can be tailored for specific hydraulic functions, supporting their use in sustainable construction. Full article
Show Figures

Graphical abstract

33 pages, 7923 KB  
Article
Comparative Evaluation of Different Biomass Ashes as Supplementary Cementitious Materials: Reactivity, Hydration Impact and Environmental Considerations
by Steffen Overmann, Isabell Allwicher, David Montag, Anya Vollpracht and Thomas Matschei
Materials 2025, 18(18), 4239; https://doi.org/10.3390/ma18184239 - 9 Sep 2025
Abstract
Biomass ashes are considered to be sustainable alternatives for fly ashes from hard coal combustion for the use as supplementary cementitious material (SCM). However, their diverse composition and properties are impeding their standardized use. This study aims to gain a better understanding of [...] Read more.
Biomass ashes are considered to be sustainable alternatives for fly ashes from hard coal combustion for the use as supplementary cementitious material (SCM). However, their diverse composition and properties are impeding their standardized use. This study aims to gain a better understanding of how composition affects performance. It investigates three wood ashes (one bottom ash, two fly ashes), one spelt husk ash and a mineral residue from sewage sludge ash after wet-chemical phosphorus recovery for their suitability as SCM. After characterization of the materials including the determination of environmentally relevant parameters, the reactivity was tested using the R3 test and mortar compressive strength with different substitution levels. The effect on hydration was studied in blends with Portland cement using isothermal calorimetry and X-ray diffractometry (XRD). The composition of the ashes differed significantly, also between the wood ashes. The wood ashes showed no significant reactivity (cumulative R3 heat lower than 125 J/g SCM after 7 days), while the spelt husk ash and the sewage sludge ash residue showed distinct reactivity with a cumulative R3 heat of 249 and 181 J/g SCM after 7 days, respectively. Following an initial period of unaffected hydration, the wood fly ashes were found to impede clinker reactivity. In contrast, the other materials exhibited no significant influence on the hydration process, aside from the consumption of portlandite by the reactive ones. The wood fly ashes also impaired strength development in blended mortar formulations (e.g., relative compressive strengths with a cement substitution level of 20 wt% after 28 days were <0.6), whereas the reactive spelt husk ash and the mineral residue were associated with a measurable contribution to strength gain (e.g., relative compressive strengths with a cement substitution level of 20 wt% after 28 days were >0.85). The wood bottom ash was the only material investigated which perfectly sustained mortar workability and rather acts like a nearly inert addition. The results show both the potential and the limitations of using different types of ash, which cannot be generalized due to the wide variation in raw materials and combustion conditions. Full article
(This article belongs to the Section Construction and Building Materials)
Show Figures

Figure 1

25 pages, 2572 KB  
Article
Calcium-Rich Fly Ash as a Sustainable Supplementary Cementitious Material for Enhanced Sulfate Resistance and Durability of Cementitious Composites: Experimental and Microstructural Perspectives
by Nikolaos Chousidis and George Batis
Materials 2025, 18(18), 4238; https://doi.org/10.3390/ma18184238 - 9 Sep 2025
Abstract
This study explores the potential of calcium-rich fly ash from the Ptolemais region in Greece as a partial cement replacement for improving sulfate resistance in cementitious composites. An integrated experimental program, combining mechanical testing, electrochemical corrosion monitoring and microstructural characterization, was designed to [...] Read more.
This study explores the potential of calcium-rich fly ash from the Ptolemais region in Greece as a partial cement replacement for improving sulfate resistance in cementitious composites. An integrated experimental program, combining mechanical testing, electrochemical corrosion monitoring and microstructural characterization, was designed to capture the progression of material properties over time and their impact on performance. The experimental results proved that, at early ages, incorporation of fly ash led to reductions in compressive, tensile and bond strengths, attributed to delayed pozzolanic reactivity. However, over prolonged curing, secondary reactions consumed portlandite and generated additional calcium silicate hydrate, refining the pore network and reducing permeability. These microstructural improvements were associated with enhanced mechanical performance, improved durability indices and markedly lower reinforcement corrosion rates. Bond tests further revealed a shift from brittle to a more ductile response, offering advantages for repair applications. These findings establish calcium-rich Ptolemais fly ash as a as a sustainable and promising supplementary cementitious material that substantially enhances the long-term durability and sulfate resistance of cementitious systems. Full article
(This article belongs to the Special Issue Advances in Repair Materials for Sustainable Building)
Show Figures

Figure 1

23 pages, 6297 KB  
Article
Laser-Driven Surface Alloying of Ti6Al4V: Coupled Microstructural Evolution, Phase Behavior, and Mechanical Performance
by Hana Beyene Mamo, Klaudiusz Gołombek, Gilmar Ferreira Batalha and Marcin Adamiak
Materials 2025, 18(18), 4237; https://doi.org/10.3390/ma18184237 - 9 Sep 2025
Abstract
This study investigates the microstructural and mechanical evolution of Ti6Al4V alloy surfaces modified through laser surface alloying (LSA) with antimicrobial elements silver (Ag) and copper (Cu) to enhance surface performance for biomedical applications. The as-received Ti6Al4V exhibited a typical equiaxed α-β [...] Read more.
This study investigates the microstructural and mechanical evolution of Ti6Al4V alloy surfaces modified through laser surface alloying (LSA) with antimicrobial elements silver (Ag) and copper (Cu) to enhance surface performance for biomedical applications. The as-received Ti6Al4V exhibited a typical equiaxed α-β microstructure with baseline hardness. Following LSA treatment using a 1000 W pulsed laser, distinct transformations were observed in the melt zone (MZ) and heat-affected zone (HAZ), influenced by the specific alloying element. Ag incorporation led to the development of ultrafine acicular martensitic structures and a higher fraction of high-angle grain boundaries, resulting in moderate hardness improvement. In contrast, Cu alloying promoted the formation of Ti2Cu intermetallic phases, dendritic morphologies, and pronounced solute segregation, leading to a more significant increase in hardness. Electron Backscatter Diffraction(EBSD) and Energy Dispersive Spectroscopy (EDS) analyses revealed grain refinement, texture evolution, and elemental redistribution across the modified regions, while X-ray Diffraction XRD confirmed the presence of new phases. The comparative analysis highlights that although both Ag and Cu improve microstructural complexity and hardness, Cu-modified zones exhibited higher hardness values than Ag-modified zones, suggesting a stronger surface strengthening effect under the tested conditions. These findings contribute valuable insights into the structure–property relationships of LSA-modified Ti alloys, supporting their potential for durable and antimicrobial biomedical implants. Full article
(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, 3rd Edition)
Show Figures

Figure 1

15 pages, 6299 KB  
Communication
Durability Testing of a Polymer Worm Gear Used in a Vehicle Steering System
by Jakub Franiasz and Tomasz Machniewicz
Materials 2025, 18(18), 4236; https://doi.org/10.3390/ma18184236 - 9 Sep 2025
Abstract
Polymer worm gears are increasingly utilized in electric power steering (EPS) systems due to their favorable manufacturing features and performance. Ensuring consistent mechanical properties under various operating conditions is critical for steering reliability throughout a vehicle’s lifespan. This study investigates the durability of [...] Read more.
Polymer worm gears are increasingly utilized in electric power steering (EPS) systems due to their favorable manufacturing features and performance. Ensuring consistent mechanical properties under various operating conditions is critical for steering reliability throughout a vehicle’s lifespan. This study investigates the durability of injection-molded polyamide 66 worm gears within a Pinion-EPS configuration, where torque from the assist motor is transmitted through a worm–worm gear set to the rack and ultimately to the vehicle wheels. Given the complexity of steering maneuvers and the absence of mechanical integrity in steer-by-wire systems, durability testing becomes essential to understand if the considered worm gear for a certain steering system application provides safety and the needed performance within a specified product service life. This paper compares multiple testing methodologies. Traditional approaches, such as maximum torque and rotational speed, prove insufficient for comprehensive durability assessment, especially considering the thermal sensitivity of polymer materials. The findings highlight the limitations of conventional testing methods and emphasize the need for application-specific testing methods that reflect real-world boundary conditions. This research contributes to the development of more accurate and reliable evaluation techniques for polymer gear components in modern EPS systems, with implications for both conventional and autonomous vehicle platforms. Full article
(This article belongs to the Section Polymeric Materials)
Show Figures

Figure 1

6 pages, 181 KB  
Editorial
Advances in the Experimentation and Numerical Modeling of Material Joining Processes (Second Edition)
by Raul D. S. G. Campilho
Materials 2025, 18(18), 4235; https://doi.org/10.3390/ma18184235 - 9 Sep 2025
Abstract
Material joining processes are fundamental in modern structural engineering, by combining components into functional assemblies that meet the performance, safety, and economic requirements of the industry [...] Full article
Previous Issue
Back to TopTop