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Materials, Volume 18, Issue 15 (August-1 2025) – 297 articles

Cover Story (view full-size image): The use of small-molecule active materials in AORFBs is significantly limited by the issue of stability and crossover. To address these challenges, we designed a polymer cathode material, P-T-S, with high water solubility, which features a polyvinylimidazole backbone functionalized with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and sulfonate groups. P-T-S exhibits a solubility of 34 Ah L−1 in water and 31 Ah L−1 in 1.0 M NaCl aqueous solution (NaClaq). When paired with methyl viologen to assemble a pH-neutral AORFB with a theoretical capacity of 15 Ah L−1, the system exhibits a material utilization rate of 92.0%, an average capacity retention rate of 99.74% per cycle (99.74% per hour), and an average Coulombic efficiency of 98.69% over 300 consecutive cycles at 30 mA cm−2. This work provides a new design strategy for polymer materials for high-performance AORFBs. View this paper
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21 pages, 2909 KiB  
Article
Novel Fractional Approach to Concrete Creep Modeling for Bridge Engineering Applications
by Krzysztof Nowak, Artur Zbiciak, Piotr Woyciechowski, Damian Cichocki and Radosław Oleszek
Materials 2025, 18(15), 3720; https://doi.org/10.3390/ma18153720 - 7 Aug 2025
Viewed by 401
Abstract
The article presents research on concrete creep in bridge structures, focusing on the influence of concrete mix composition and the use of advanced rheological models with fractional-order derivatives. Laboratory tests were performed on nine mixes varying in blast furnace slag content (0%, 25%, [...] Read more.
The article presents research on concrete creep in bridge structures, focusing on the influence of concrete mix composition and the use of advanced rheological models with fractional-order derivatives. Laboratory tests were performed on nine mixes varying in blast furnace slag content (0%, 25%, and 75% of cement mass) and air-entrainment. The results were used to calibrate fractal rheological models—Kelvin–Voigt and Huet–Sayegh—where the viscous element was replaced with a fractal element. These models showed high agreement with experimental data and improved the accuracy of creep prediction. Comparison with Eurocode 2 revealed discrepancies up to 64%, especially for slag-free concretes used in prestressed bridge structures. The findings highlight the important role of mineral additives in reducing creep strains and the need to consider individual mix characteristics in design calculations. In the context of modern bridge construction technologies, such as balanced cantilever or incremental launching, reliable modeling of early-age creep is particularly important. The proposed modeling approach may enhance the precision of long-term structural behavior analyses and contribute to improved safety and durability of concrete infrastructure. Full article
(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior (Third Edition))
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13 pages, 8245 KiB  
Article
Numerical Simulation and Experimental Study of Millisecond Percussion Drilling in Titanium Alloy
by Liang Wang, Long Xu, Changjian Wu, Yefei Rong and Kaibo Xia
Materials 2025, 18(15), 3719; https://doi.org/10.3390/ma18153719 - 7 Aug 2025
Viewed by 272
Abstract
This study addresses the challenge of drilling film-cooling holes in the turbine blades of aircraft engines. Titanium alloy TC4 was selected as the experimental material. The laser-drilling process was simulated with ANSYS to determine optimal parameters, which were subsequently applied in machining trials. [...] Read more.
This study addresses the challenge of drilling film-cooling holes in the turbine blades of aircraft engines. Titanium alloy TC4 was selected as the experimental material. The laser-drilling process was simulated with ANSYS to determine optimal parameters, which were subsequently applied in machining trials. An impact-drilling method was then used to evaluate how pulse width, pulse energy, and pulse count affect micro-hole entrance and exit diameters, taper, and roundness. Simulations revealed that pulse energy and pulse count predominantly govern entrance and exit diameters, whereas pulse count and pulse width exert a stronger influence on taper. Experiments confirmed that entrance and exit diameters increased as pulse energy rose from 2.0 J to 2.8 J; taper increased as pulse width widened from 0.6 ms to 1.4 ms; and entrance diameter, exit diameter, and taper all grew as pulse count rose from 40 to 60. Pulse width and pulse count also significantly affected hole roundness. Full article
(This article belongs to the Special Issue Heat Treatment and Additive Manufacturing of Alloys: Processing, Properties and Simulations)
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49 pages, 2481 KiB  
Review
A Comprehensive Review of Numerical and Machine Learning Approaches for Predicting Concrete Properties: From Fresh to Long-Term
by Nilam Adsul, Yongho Choi and Su-Tae Kang
Materials 2025, 18(15), 3718; https://doi.org/10.3390/ma18153718 - 7 Aug 2025
Viewed by 494
Abstract
The growing demand for innovation and the use of diverse materials in cementitious composites necessitate predictive models that account for material variability. Numerical, code-based, and machine learning (ML) models have been developed to predict various concrete properties. However, their accuracy is significantly influenced [...] Read more.
The growing demand for innovation and the use of diverse materials in cementitious composites necessitate predictive models that account for material variability. Numerical, code-based, and machine learning (ML) models have been developed to predict various concrete properties. However, their accuracy is significantly influenced by factors such as mix design, composition, intrinsic properties, and external conditions. Developing robust models that integrate these variables is essential for improving predictive accuracy and optimizing material performance. This paper presents a comprehensive review of numerical, code-based, and ML modelling techniques for predicting both fresh and long-term concrete properties. Since both numerical and ML models rely on experimental data—either to determine coefficients in numerical approaches or to train ML models—data gathering, preprocessing, and handling are crucial for model performance. Previous studies indicated that data variability significantly impacts accuracy, emphasizing the importance of effective preprocessing. While larger datasets generally improve reliability, some models achieve high accuracy even with very limited data. This review not only demonstrates the superior performance of ML models over traditional numerical approaches but also highlights the relative effectiveness of different ML algorithms based on reported accuracy metrics. ML-based approaches, including both ensemble and non-ensemble models, have exhibited strong predictive capabilities across a wide range of concrete property categories. In contrast, traditional numerical models often yield lower accuracy, although modified versions that incorporate additional parameters have shown improved performance. Furthermore, the integration of optimization algorithms and interpretability tools enhances both predictive reliability and model transparency—critical aspects that are often overlooked. Full article
(This article belongs to the Special Issue Concretes and Cement-Based Composites: Additives/Admixtures, Hydration Process and Durability Research (3rd Edition))
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14 pages, 3029 KiB  
Article
In Vitro Bioactivity and Cytotoxicity Assessment of Two Root Canal Sealers
by Yicheng Ye, Sepanta Hosseinpour, Juan Wen and Ove A. Peters
Materials 2025, 18(15), 3717; https://doi.org/10.3390/ma18153717 - 7 Aug 2025
Viewed by 394
Abstract
The development of bioactive materials in endodontics has advanced tissue regeneration by enhancing the biological responses of periradicular tissues. Recently, calcium silicate-based sealers have gained attention for their superior biological properties, including biocompatibility, osteoconductivity, and cementogenic potential. This study aimed to evaluate the [...] Read more.
The development of bioactive materials in endodontics has advanced tissue regeneration by enhancing the biological responses of periradicular tissues. Recently, calcium silicate-based sealers have gained attention for their superior biological properties, including biocompatibility, osteoconductivity, and cementogenic potential. This study aimed to evaluate the cytotoxicity, biocompatibility, and bioactivity of EndoSequence BC Sealer (ES BC) and AH Plus Bioceramic Sealer (AHP BC) using human periodontal ligament stromal cells (hPDLSCs). Biocompatibility was assessed using MTT, Live/Dead, and wound healing assays. ES BC and AHP BC demonstrated significantly higher cell viability and proliferation compared to AH Plus used as a control. Gene expression analysis via real-time quantitative PCR demonstrated that ES BC, especially in set form, significantly upregulated osteogenic markers—alkaline phosphatase (2.49 ± 0.10, p < 0.01), runt-related transcription factor 2 (2.33 ± 0.13), and collagen type I alpha 1 chain (2.85 ± 0.40, p < 0.001)—more than cementogenic markers (cementum protein 1, cementum attachment protein, and cementum protein 23). This differential response may reflect the fibroblast-dominant nature of hPDLSCs, which contain limited cementoblast-like cells. This study supports the superior biocompatibility and regenerative capacity of ES BC and AHP BC compared to AH Plus. While in vitro models provide foundational insights, advanced ex vivo approaches are crucial for translating findings to clinical practice. Full article
(This article belongs to the Special Issue Functional Biomaterial Solutions for Translational Tissue Engineering and Regenerative Medicine)
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16 pages, 3763 KiB  
Article
Performance Study on Preparation of Mine Backfill Materials Using Industrial Solid Waste in Combination with Construction Waste
by Yang Cai, Qiumei Liu, Fufei Wu, Shuangkuai Dong, Qiuyue Zhang, Jing Wang, Pengfei Luo and Xin Yang
Materials 2025, 18(15), 3716; https://doi.org/10.3390/ma18153716 - 7 Aug 2025
Viewed by 308
Abstract
The resource utilization of construction waste and industrial solid waste is a crucial aspect in promoting global urbanization and sustainable development. This study focuses on the preparation of mine backfill materials using construction waste in combination with various industrial solid wastes—ground granulated blast [...] Read more.
The resource utilization of construction waste and industrial solid waste is a crucial aspect in promoting global urbanization and sustainable development. This study focuses on the preparation of mine backfill materials using construction waste in combination with various industrial solid wastes—ground granulated blast furnace slag (GGBFS), fly ash (FA), silica fume (SF), phosphorus slag (PS), fly ash–phosphorus slag–phosphogypsum composite (FA-PS-PG), and fly ash–phosphorus slag–β-phosphogypsum composite (FA-PS-βPG)—under different substitution rates (50%, 55%, 60%) as control parameters. A total of 19 mix proportions were investigated, evaluating their slump, dry density, compressive strength, uniaxial compressive stress–strain relationship, micromorphology, and phase composition. The results indicate that, compared to backfill materials prepared with pure cement, the incorporation of industrial solid wastes improves the fluidity of the backfill materials. At 56 days, the constitutive model parameter a increased to varying degrees, while parameter b decreased, indicating enhanced ductility. The compressive strength was consistently higher with PS at all substitution rates. The FA-PS-PG mixture with a 50% substitution rate achieved the highest 56-day compressive strength of 8.02 MPa. These findings can facilitate the application of construction waste and industrial solid waste in mine backfilling projects, delivering economic, environmental, and resource-related benefits. Full article
(This article belongs to the Section Construction and Building Materials)
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16 pages, 738 KiB  
Article
Modeling, Simulation, and Techno-Economic Assessment of a Spent Li-Ion Battery Recycling Plant
by Árpád Imre-Lucaci, Florica Imre-Lucaci and Szabolcs Fogarasi
Materials 2025, 18(15), 3715; https://doi.org/10.3390/ma18153715 - 7 Aug 2025
Viewed by 378
Abstract
The literature clearly indicates that both academia and industry are strongly committed to developing comprehensive processes for spent Li-ion battery (LIB) recycling. In this regard, the current study presents an original contribution by providing a quantitative assessment of a large-scale recycling plant designed [...] Read more.
The literature clearly indicates that both academia and industry are strongly committed to developing comprehensive processes for spent Li-ion battery (LIB) recycling. In this regard, the current study presents an original contribution by providing a quantitative assessment of a large-scale recycling plant designed for the treatment of completely spent LIBs. In addition to a concept of the basic process, this assessment also considers a case study of a thermal integration and CO2 capture subsystem. Process flow modeling software was used to evaluate the contribution of all process steps and equipment to overall energy consumption and to mass balance the data required for the technical assessment of the large-scale recycling plant. To underline the advantages and identify the optimal novel process concept, several key performance indicators were determined, such as recovery efficiency, specific energy/material consumption, and specific CO2 emissions. In addition, the economic potential of the recycling plants was evaluated for the defined case studies based on capital and O&M costs. The results indicate that, even with CO2 capture applied, the thermally integrated process with the combustion of hydrogen produced in the recycling plant remains the most promising large-scale configuration for spent LIB recycling. Full article
(This article belongs to the Special Issue Recycling and Electrode Materials of Lithium Batteries)
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15 pages, 7312 KiB  
Article
Influence of Strain Rate on the Strain-Induced Martensite Transformation in Austenitic Steel AISI 321 and Barkhausen Noise Emission
by Mária Čilliková, Nikolaj Ganev, Ján Moravec, Anna Mičietová, Miroslav Neslušan and Peter Minárik
Materials 2025, 18(15), 3714; https://doi.org/10.3390/ma18153714 - 7 Aug 2025
Viewed by 251
Abstract
This study investigates the evolution of strain-induced martensite (SIM) and its effect on magnetic Barkhausen noise (MBN) in AISI 321 austenitic stainless steel subjected to uniaxial tensile testing. Using X-ray diffraction and the Barkhausen noise technique, the formation and distribution of SIM were [...] Read more.
This study investigates the evolution of strain-induced martensite (SIM) and its effect on magnetic Barkhausen noise (MBN) in AISI 321 austenitic stainless steel subjected to uniaxial tensile testing. Using X-ray diffraction and the Barkhausen noise technique, the formation and distribution of SIM were analysed as functions of plastic strain and strain rate. The results show that MBN is primarily governed by plastic deformation and strain rate rather than residual stress. The martensite fraction increases from 10% at low strains to 42.5% at high strains; however, accelerated strain rates significantly reduce martensite formation to approximately 25%. The increase in martensite density enhances the magnetic exchange interactions among neighbouring islands, resulting in stronger and more numerous MBN pulses. The anisotropy of MBN is also influenced by the initial crystallographic texture of the austenite. These findings highlight the strong correlation between MBN and SIM evolution, establishing MBN as a sensitive, non-destructive tool for assessing martensitic transformation and optimising deformation parameters in austenitic steels. Full article
(This article belongs to the Special Issue Advances in the Nondestructive Testing of Construction and Building Materials)
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17 pages, 1428 KiB  
Article
The Influence of Bitumen Nature and Production Conditions on the Mechanical and Chemical Properties of Asphalt Mixtures Containing Reclaimed Asphalt Pavement
by Emiliano Prosperi, Edoardo Bocci and Giovanni Marchegiani
Materials 2025, 18(15), 3713; https://doi.org/10.3390/ma18153713 - 7 Aug 2025
Viewed by 310
Abstract
Several variables influence the performance of hot asphalt mixtures including reclaimed asphalt pavement (RAP). Among these, the virgin bitumen’s origin, the mix production temperature and the time the mix is kept at a high temperature between mixing and compaction play a fundamental role [...] Read more.
Several variables influence the performance of hot asphalt mixtures including reclaimed asphalt pavement (RAP). Among these, the virgin bitumen’s origin, the mix production temperature and the time the mix is kept at a high temperature between mixing and compaction play a fundamental role but are often neglected. This study aimed to quantify the negative effects associated with the improper choice of these variables. Therefore, their influence on the mechanical (indirect tensile stiffness modulus and strength, Cracking Tolerance Index) and chemical (Fourier Transform Infra-Red spectroscopy) characteristics of asphalt mixtures containing 50% RA were investigated. In particular, two rejuvenators, two types of virgin bitumen (visbreaker and straight-run), two production temperatures (140 °C and 170 °C) and three conditioning times in the oven (30 min, 90 min and 180 min) were analyzed. The results showed interesting findings that allow us to recommend selecting the virgin bitumen type carefully and to avoid excessively stressing the binder during the production of the mix. Full article
(This article belongs to the Special Issue The Future of Road Pavement Materials: Towards the Improvement of Performances and Sustainability)
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18 pages, 971 KiB  
Article
Optimization of Activated Rubber Asphalt Production Parameters Based on Rheological Properties and Multi-Index Evaluation
by Jing Zhao, Xiangqing Zhao, Bo Li, Yongning Wang, Huan Zhao and Kai Kang
Materials 2025, 18(15), 3712; https://doi.org/10.3390/ma18153712 - 7 Aug 2025
Viewed by 250
Abstract
This study presents a method to more reasonably control the quality performance of activated rubber asphalt by microwave activation. Different activated rubber asphalt preparation process parameters (reaction temperature, stirring rate, and reaction time) were selected to explore the influence of different process parameters [...] Read more.
This study presents a method to more reasonably control the quality performance of activated rubber asphalt by microwave activation. Different activated rubber asphalt preparation process parameters (reaction temperature, stirring rate, and reaction time) were selected to explore the influence of different process parameters on the macroscopic properties of rubber asphalt, and a multi-indicator evaluation model was set up using the theoretical method of the RSR model to determine the optimal production process parameters. The results showed that reaction temperature had the strongest influence (gray correlation > 0.85) among production parameters, followed by stirring rate and reaction time. The optimal parameters identified were a reaction temperature of 220 °C, a stirring rate of 1000 rpm, and a reaction time of 120 min, under which the viscosity–temperature sensitivity decreased by approximately 18%, and the rutting factor (G*/sinδ) increased by over 20%, indicating significant improvements in rheological stability and high-temperature performance. The integrated evaluation approach provided reliable and practical guidance for producing high-performance activated rubber asphalt. Full article
(This article belongs to the Special Issue Development of Sustainable Asphalt Materials)
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18 pages, 3045 KiB  
Article
Biodegradable NR Latex Films with Lignocellulosic and Collagen Hydrolysate Fillers
by Magdalena Kmiotek, Mirosława Prochoń and Elżbieta Sąsiadek-Andrzejczak
Materials 2025, 18(15), 3711; https://doi.org/10.3390/ma18153711 - 7 Aug 2025
Viewed by 316
Abstract
The objective of this study was to investigate the influence of the lignocellulose filler originating in wood and non-wood raw materials, alone or together with collagen hydrolysate, on the properties and biodegradation ability of natural rubber latex. The different hydrophobicity of the polymer [...] Read more.
The objective of this study was to investigate the influence of the lignocellulose filler originating in wood and non-wood raw materials, alone or together with collagen hydrolysate, on the properties and biodegradation ability of natural rubber latex. The different hydrophobicity of the polymer matrix and natural filler makes it difficult to obtain a homogenous structure of the composite. However, the easy biodegradation of the natural filler is a sufficient reason to seek a compromise between its useful properties and the environmental safety of the material. The composites were filled with lignocellulose filler: pine, spruce, and birch wood flour or willow, raspberry, and mallow non-wood flour. Collagen hydrolysate was used as a substitute for lignocellulosic filler, together or alone. The mechanical properties of the composites, their hardness, and equilibrium swelling were studied. In order to determine the morphology and interactions between filler and latex, scanning electron microscopy together with infrared spectroscopy were engaged. The results revealed that after the incorporation of 4 phr of the filler, the increase in mechanical strength was observed even despite the lack of compatibility between the filler and polymer matrix. The lignocellulose filler is a promising agent because its biodegradability contributes to the overall environmental safety of the polymer material. Full article
(This article belongs to the Section Polymeric Materials)
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17 pages, 3093 KiB  
Article
Determination of Quantum Yield in Scattering Media Using Monte Carlo Photoluminescence Cascade Simulation and Integrating Sphere Measurements
by Philip Gelbing, Joachim Jelken, Florian Foschum and Alwin Kienle
Materials 2025, 18(15), 3710; https://doi.org/10.3390/ma18153710 - 7 Aug 2025
Viewed by 304
Abstract
Accurate determination of the quantum yield (Φf) in scattering media is essential for numerous scientific and industrial applications, but it remains challenging due to re-absorption and scattering-induced biases. In this study, we present a GPU-accelerated Monte Carlo simulation framework that [...] Read more.
Accurate determination of the quantum yield (Φf) in scattering media is essential for numerous scientific and industrial applications, but it remains challenging due to re-absorption and scattering-induced biases. In this study, we present a GPU-accelerated Monte Carlo simulation framework that solves the full fluorescence radiative transfer equation (FRTE), incorporating spectrally dependent absorption, scattering, and fluorescence cascade processes. The model accounts for re-emission shifts, energy scaling due to the Stokes shift and implements a digital optical twin of the experimental setup, including the precise description of the applied integrating sphere. Using Rhodamine 6G in both ethanol and PDMS matrices, we demonstrate the accuracy of the method by comparing simulated reflectance and transmission spectra with independent experimental measurements. Φf and emission distributions are optimized using a Levenberg–Marquardt algorithm. The obtained quantum yields agree well with literature values for Rhodamine 6G. This approach eliminates the need for empirical correction factors, enabling the reliable determination of actual, undistorted emission spectra and the Φf in complex scattering media. Full article
(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))
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13 pages, 4117 KiB  
Article
Spin-Polarized DFT+U Study of Surface-Functionalized Cr3C2 MXenes: Tunable Electronic and Magnetic Behavior for Spintronics
by Zixiang Tong, Yange Suo, Shaozheng Zhang and Jianhui Yang
Materials 2025, 18(15), 3709; https://doi.org/10.3390/ma18153709 - 7 Aug 2025
Viewed by 287
Abstract
Surface functionalization is key for tuning the electronic and magnetic properties essential in spintronics, yet its impact on chromium-based MXenes (Cr3C2T2) is not fully understood. Using spin-polarized DFT+U, this study investigates how O, F, and [...] Read more.
Surface functionalization is key for tuning the electronic and magnetic properties essential in spintronics, yet its impact on chromium-based MXenes (Cr3C2T2) is not fully understood. Using spin-polarized DFT+U, this study investigates how O, F, and OH groups modify the magnetic state, electronic structure, and Curie temperature. Functionalization dramatically changes magnetism: O termination gives ferromagnetism, while F and OH yield ferrimagnetism. Our results show surface functionalization effectively adjusts the Curie temperature, critical for spintronic materials. The electronic character is highly functional group dependent: pristine Cr3C2 is half-metallic, Cr3C2O2 metallic, and Cr3C2F2/Cr3C2(OH)2 semiconducting with narrow gaps. Structures with dynamic stability are analyzed through phonon spectroscopy. These findings provide fundamental insights into controlling MXene properties via surface functionalization, guiding the design of next-generation spintronic materials. Full article
(This article belongs to the Section Electronic Materials)
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21 pages, 2803 KiB  
Article
A New Concrete Freeze–Thaw Damage Model Based on Hydraulic Pressure Mechanism and Its Application
by Lantian Xu, Yuchi Wang, Yuanzhan Wang and Tianqi Cheng
Materials 2025, 18(15), 3708; https://doi.org/10.3390/ma18153708 - 7 Aug 2025
Viewed by 396
Abstract
Freeze–thaw damage is one of the most important factors affecting the durability of concrete in cold regions, and how to quantitatively characterize the effect of freeze–thaw cycles on the degree of damage of concrete is a widely concerning issue among researchers. Based on [...] Read more.
Freeze–thaw damage is one of the most important factors affecting the durability of concrete in cold regions, and how to quantitatively characterize the effect of freeze–thaw cycles on the degree of damage of concrete is a widely concerning issue among researchers. Based on the hydraulic pressure theory, a new concrete freeze–thaw damage model was proposed by assuming the defect development mode of concrete during freeze–thaw cycles. The model shows that the total amount of defects due to freeze–thaw damage is related to the initial defects and the defect development capacity within the concrete. Based on the new freeze–thaw damage model, an equation for the loss of relative dynamic elastic modulus of concrete during freeze–thaw cycles was established using the relative dynamic elastic modulus of concrete as the defect indicator. In order to validate the damage model using relative dynamic elastic modulus as the defect index, freeze–thaw cycle tests of four kinds of concrete with different air content were carried out, and the rationality of the model was verified by the relative dynamic elastic modulus of concrete measured under different freeze–thaw cycling periods. On this basis, a freeze–thaw damage model of concrete was established considering the effect of air content in concrete. In addition, the model proposed in this paper was supplemented and validated by experimental data from other researchers. The results show that the prediction model proposed in this study is not only easy to apply and has clear physical meaning but also has high accuracy and general applicability, which provides support for predicting the degree of freeze–thaw damage of concrete structures in cold regions. Full article
(This article belongs to the Special Issue Carbon Capture, Utilization and Storage Technologies of Cement-Based Materials)
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12 pages, 5474 KiB  
Article
Flexible Sensor with Material–Microstructure Synergistic Optimization for Wearable Physiological Monitoring
by Yaojia Mou, Cong Wang, Xiaohu Jiang, Jingxiang Wang, Changchao Zhang, Linpeng Liu and Ji’an Duan
Materials 2025, 18(15), 3707; https://doi.org/10.3390/ma18153707 - 7 Aug 2025
Viewed by 574
Abstract
Flexible sensors have emerged as essential components in next-generation technologies such as wearable electronics, smart healthcare, soft robotics, and human–machine interfaces, owing to their outstanding mechanical flexibility and multifunctional sensing capabilities. Despite significant advancements, challenges such as the trade-off between sensitivity and detection [...] Read more.
Flexible sensors have emerged as essential components in next-generation technologies such as wearable electronics, smart healthcare, soft robotics, and human–machine interfaces, owing to their outstanding mechanical flexibility and multifunctional sensing capabilities. Despite significant advancements, challenges such as the trade-off between sensitivity and detection range, and poor signal stability under cyclic deformation remain unresolved. To overcome the aforementioned limitations, this work introduces a high-performance soft sensor featuring a dual-layered electrode system, comprising silver nanoparticles (AgNPs) and a composite of multi-walled carbon nanotubes (MWCNTs) with carbon black (CB), coupled with a laser-engraved crack-gradient microstructure. This structural strategy facilitates progressive crack formation under applied strain, thereby achieving enhanced sensitivity (1.56 kPa−1), broad operational bandwidth (50–600 Hz), fine frequency resolution (0.5 Hz), and a rapid signal response. The synergistic structure also improves signal repeatability, durability, and noise immunity. The sensor demonstrates strong applicability in health monitoring, motion tracking, and intelligent interfaces, offering a promising pathway for reliable, multifunctional sensing in wearable health monitoring, motion tracking, and soft robotic systems. Full article
(This article belongs to the Special Issue Advanced Materials for Flexible Sensing Applications and Electronics)
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18 pages, 2161 KiB  
Article
Performance Degradation Behavior and Service Life Prediction of Hydraulic Asphalt Concrete Under Long-Term Water Immersion
by Xinhe Cai, Feng Li, Kangping Li, Zhiyuan Ning and Jing Dong
Materials 2025, 18(15), 3706; https://doi.org/10.3390/ma18153706 - 7 Aug 2025
Viewed by 354
Abstract
Hydraulic asphalt concrete (HAC) is susceptible to performance deterioration under long-term water immersion. This study conducted compressive, tensile, and bending tests on HAC under various immersion times (0–96 h), established a multidimensional performance evaluation method, and developed a service-life prediction model for long-term [...] Read more.
Hydraulic asphalt concrete (HAC) is susceptible to performance deterioration under long-term water immersion. This study conducted compressive, tensile, and bending tests on HAC under various immersion times (0–96 h), established a multidimensional performance evaluation method, and developed a service-life prediction model for long-term water immersion. The average relative error between test values and predicted values was less than 5%, validating the model’s effectiveness and applicability. Results indicate that the rate of mechanical property degradation exhibits stage-dependent characteristics with immersion time, and the water damage resistance of alkaline aggregate is significantly superior to that of acidic aggregate. The predictive model shows that after 192 h of immersion, the retention rate of key mechanical properties for the alkaline aggregate reaches 92.71%, while that for acidic aggregate was only 73.85%. This study establishes a predictive model that provides a theoretical basis for assessing the lifespan of HAC under long-term immersion conditions. Full article
(This article belongs to the Special Issue Advances in Material Characterization and Pavement Modeling)
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16 pages, 7807 KiB  
Article
Rapid-Optimized Process Parameters of 1080 Carbon Steel Additively Manufactured via Laser Powder Bed Fusion on High-Throughput Mechanical Property Testing
by Jianyu Feng, Meiling Jiang, Guoliang Huang, Xudong Wu and Ke Huang
Materials 2025, 18(15), 3705; https://doi.org/10.3390/ma18153705 - 6 Aug 2025
Viewed by 327
Abstract
To ensure the sustainability of alloy-based strategies, both compositional design and processing routes must be simplified. Metal additive manufacturing (AM), with its exceptionally rapid, non-equilibrium solidification, offers a unique platform to produce tailored microstructures in simple alloys that deliver superior mechanical properties. In [...] Read more.
To ensure the sustainability of alloy-based strategies, both compositional design and processing routes must be simplified. Metal additive manufacturing (AM), with its exceptionally rapid, non-equilibrium solidification, offers a unique platform to produce tailored microstructures in simple alloys that deliver superior mechanical properties. In this study, we employ laser powder bed fusion (LPBF) to fabricate 1080 plain carbon steel, a binary alloy comprising only iron and carbon. Deviating from conventional process optimization focusing primarily on density, we optimize LPBF parameters for mechanical performance. We systematically varied key parameters (laser power and scan speed) to produce batches of tensile specimens, which were then evaluated on a high-throughput mechanical testing platform (HTP). Using response surface methodology (RSM), we developed predictive models correlating these parameters with yield strength (YS) and elongation. The RSM models identified optimal and suboptimal parameter sets. Specimens printed under the predicted optimal conditions achieved YS of 1543.5 MPa and elongation of 7.58%, closely matching RSM predictions (1595.3 MPa and 8.32%) with deviations of −3.25% and −8.89% for YS and elongation, respectively, thus validating model accuracy. Comprehensive microstructural characterization, including metallographic analysis and fracture surface examination, revealed the microstructural origins of performance differences and the underlying strengthening mechanisms. This methodology enables rapid evaluation and optimization of LPBF parameters for 1080 carbon steel and can be generalized as an efficient framework for robust LPBF process development. Full article
(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties)
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15 pages, 1920 KiB  
Article
Optimization of the Froth Flotation Process for the Enrichment of Cu and Co Concentrate from Low-Grade Copper Sulfide Ore
by Michal Marcin, Martin Sisol, Martina Laubertová, Jakub Kurty and Ema Gánovská
Materials 2025, 18(15), 3704; https://doi.org/10.3390/ma18153704 - 6 Aug 2025
Viewed by 380
Abstract
The increasing demand for critical raw materials such as copper and cobalt highlights the need for efficient beneficiation of low-grade ores. This study investigates a copper–cobalt sulfide ore (0.99% Cu, 0.028% Co) using froth flotation to produce high-grade concentrates. Various types of surfactants [...] Read more.
The increasing demand for critical raw materials such as copper and cobalt highlights the need for efficient beneficiation of low-grade ores. This study investigates a copper–cobalt sulfide ore (0.99% Cu, 0.028% Co) using froth flotation to produce high-grade concentrates. Various types of surfactants are applied in different ways, each serving an essential function such as acting as collectors, frothers, froth stabilizers, depressants, activators, pH modifiers, and more. A series of flotation tests employing different collectors (SIPX, PBX, AERO, DF 507B) and process conditions was conducted to optimize recovery and selectivity. Methyl isobutyl carbinol (MIBC) was consistently used as the foaming agent, and 700 g/L was used as the slurry density at 25 °C. Dosages of 30 and 100 g/t1 were used in all tests. Notably, adjusting the pH to ~4 using HCl significantly improved cobalt concentrate separation. The optimized flotation conditions yielded concentrates with over 15% Cu and metal recoveries exceeding 80%. Mineralogical characterization confirmed the selective enrichment of target metals in the concentrate. The results demonstrate the potential of this beneficiation approach to contribute to the European Union’s supply of critical raw materials. Full article
(This article belongs to the Special Issue Advances in Process Metallurgy and Metal Recycling)
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20 pages, 5638 KiB  
Article
Influence of Heat Treatment on Precipitate and Microstructure of 38CrMoAl Steel
by Guofang Xu, Shiheng Liang, Bo Chen, Jiangtao Chen, Yabing Zhang, Xiaotan Zuo, Zihan Li, Bo Song and Wei Liu
Materials 2025, 18(15), 3703; https://doi.org/10.3390/ma18153703 - 6 Aug 2025
Viewed by 354
Abstract
To address the central cracking problem in continuous casting slabs of 38CrMoAl steel, high-temperature tensile tests were performed using a Gleeble-3800 thermal simulator to characterize the hot ductility of the steel within the temperature range of 600–1200 °C. The phase transformation behavior was [...] Read more.
To address the central cracking problem in continuous casting slabs of 38CrMoAl steel, high-temperature tensile tests were performed using a Gleeble-3800 thermal simulator to characterize the hot ductility of the steel within the temperature range of 600–1200 °C. The phase transformation behavior was computationally analyzed via the Thermo-Calc software, while the microstructure, fracture morphology, and precipitate characteristics were systematically investigated using a metallographic microscope (MM), a field-emission scanning electron microscope (FE-SEM), and transmission electron microscopy (TEM). Additionally, the effects of different holding times and cooling rates on the microstructure and precipitates of 38CrMoAl steel were also studied. The results show that the third brittle temperature region of 38CrMoAl steel is 645–1009 °C, and the fracture mechanisms can be classified into three types: (I) in the α single-phase region, the thickness of intergranular proeutectoid ferrite increases with rising temperature, leading to reduced hot ductility; (II) in the γ single-phase region, the average size of precipitates increases while the number density decreases with increasing temperature, thereby improving hot ductility; and (III) in the α + γ two-phase region, the precipitation of proeutectoid ferrite promotes crack propagation and the dense distribution of precipitates at grain boundaries causes stress concentration, further deteriorating hot ductility. Heat treatment experiments indicate that the microstructures of the specimen transformed under water cooling, air cooling, and furnace cooling conditions as follows: martensite + proeutectoid ferrite → bainite + ferrite → ferrite. The average size of precipitates first decreased, then increased, and finally decreased again with increasing holding time, while the number density exhibited the opposite trend. Therefore, when the holding time was the same, reducing the cooling rate could increase the average size of the precipitates and decrease their number density, thereby improving the hot ductility of 38CrMoAl steel. Full article
(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, 3rd Edition)
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12 pages, 2376 KiB  
Article
Investigating Helium-Induced Thermal Conductivity Degradation in Fusion-Relevant Copper: A Molecular Dynamics Approach
by Xu Yu, Hanlong Wang and Hai Huang
Materials 2025, 18(15), 3702; https://doi.org/10.3390/ma18153702 - 6 Aug 2025
Viewed by 299
Abstract
Copper alloys are critical heat sink materials for fusion reactor divertors due to their high thermal conductivity (TC) and strength, yet their performance under extreme particle bombardment and heat fluxes in future tokamaks requires enhancement. While neutron-induced transmutation helium affects the properties of [...] Read more.
Copper alloys are critical heat sink materials for fusion reactor divertors due to their high thermal conductivity (TC) and strength, yet their performance under extreme particle bombardment and heat fluxes in future tokamaks requires enhancement. While neutron-induced transmutation helium affects the properties of copper, the atomistic mechanisms linking helium bubble size to thermal transport remain unclear. This study employs non-equilibrium molecular dynamics (NEMD) simulations to isolate the effect of bubble diameter (10, 20, 30, 40 Å) on TC in copper, maintaining a constant He-to-vacancy ratio of 2.5. Results demonstrate that larger bubbles significantly impair TC. This reduction correlates with increased Kapitza thermal resistance and pronounced lattice distortion from outward helium diffusion, intensifying phonon scattering. Phonon density of states (PDOS) analysis reveals diminished low-frequency peaks and an elevated high-frequency peak for bubbles >30 Å, confirming phonon confinement and localized vibrational modes. The PDOS overlap factor decreases with bubble size, directly linking microstructural evolution to thermal resistance. These findings elucidate the size-dependent mechanisms of helium bubble impacts on thermal transport in copper divertor materials. Full article
(This article belongs to the Special Issue Advances in Computation and Modeling of Materials Mechanics)
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13 pages, 5981 KiB  
Article
High-Temperature Oxidation Resistance of Fe-Free AlCoCrNiNb0.2 and AlCoCr0.5NiNb0.2 High-Entropy Alloys
by Olga Samoilova, Svetlana Pratskova, Nataliya Shaburova, Ahmad Ostovari Moghaddam and Evgeny Trofimov
Materials 2025, 18(15), 3701; https://doi.org/10.3390/ma18153701 - 6 Aug 2025
Viewed by 347
Abstract
The microstructure, phase composition, and high-temperature oxidation resistance of Fe-free AlCoCrNiNb0.2 and AlCoCr0.5NiNb0.2 high-entropy alloys (HEAs) were investigated. In the as-cast HEAs, niobium was found to mainly release as a Laves phase in the interdendritic region, and its solubility [...] Read more.
The microstructure, phase composition, and high-temperature oxidation resistance of Fe-free AlCoCrNiNb0.2 and AlCoCr0.5NiNb0.2 high-entropy alloys (HEAs) were investigated. In the as-cast HEAs, niobium was found to mainly release as a Laves phase in the interdendritic region, and its solubility in the dendrites of the BCC solid solution was about 2 at.%. Both samples exhibited parabolic behavior during 100 h oxidation at 1000 °C and 1100 °C. The AlCoCrNiNb0.2 alloy demonstrated higher resistance to high-temperature oxidation compared to AlCoCr0.5NiNb0.2. The specific weight changes after 100 h of isothermal holding at 1000 °C and 1100 °C were 0.65 mg/cm2 and 1.31 mg/cm2, respectively, which are superior compared to the Fe-containing HEAs. Cr was revealed to play an important role in the oxidation behavior of the HEAs, decreasing the parabolic oxidation rate constant and increasing the activation energy of the oxidation process in the alloys. Full article
(This article belongs to the Special Issue Advanced Science and Technology of High Entropy Materials)
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25 pages, 6471 KiB  
Article
Rheological Evaluation of Ultra-High-Performance Concrete as a Rehabilitation Alternative for Pavement Overlays
by Hermes Vacca, Yezid A. Alvarado, Daniel M. Ruiz and Andres M. Nuñez
Materials 2025, 18(15), 3700; https://doi.org/10.3390/ma18153700 - 6 Aug 2025
Viewed by 327
Abstract
This study evaluates the rheological behavior and mechanical performance of Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) mixes with varying superplasticizer dosages, aiming to optimize their use in pavement rehabilitation overlays on sloped surfaces. A reference self-compacting UHPFRC mix was modified by reducing the superplasticizer-to-binder ratio [...] Read more.
This study evaluates the rheological behavior and mechanical performance of Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) mixes with varying superplasticizer dosages, aiming to optimize their use in pavement rehabilitation overlays on sloped surfaces. A reference self-compacting UHPFRC mix was modified by reducing the superplasticizer-to-binder ratio in incremental steps, and the resulting mixes were assessed through rheometry, mini-Slump, and Abrams cone tests. Key rheological parameters—static and dynamic yield stress, plastic viscosity, and thixotropy—were determined using the modified Bingham model. The results showed that reducing superplasticizer content increased yield stress and viscosity, enhancing thixotropic behavior while maintaining ultra-high compressive (≥130 MPa) and flexural strength (≥20 MPa) at 28 days. A predictive model was validated to estimate the critical yield stress needed for overlays on slopes. Among the evaluated formulations, the SP-2 mix met the stability and performance criteria and was successfully tested in a prototype overlay, demonstrating its viability for field application. This research confirms the potential of rheology-tailored UHPFRC as a high-performance solution for durable and stable pavement overlays in demanding geometric conditions. Full article
(This article belongs to the Special Issue Advances in Material Characterization and Pavement Modeling)
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16 pages, 4746 KiB  
Article
Experimental Study on Millisecond Laser Percussion Drilling of Heat-Resistant Steel
by Liang Wang, Changjian Wu, Yefei Rong, Long Xu and Kaibo Xia
Materials 2025, 18(15), 3699; https://doi.org/10.3390/ma18153699 - 6 Aug 2025
Viewed by 315
Abstract
Millisecond lasers, with their high processing efficiency and large power, are widely used in manufacturing fields such as aerospace. This study aims to investigate the effects of different processing parameters on the micro-hole processing of 316 heat-resistant steel using millisecond lasers. Through the [...] Read more.
Millisecond lasers, with their high processing efficiency and large power, are widely used in manufacturing fields such as aerospace. This study aims to investigate the effects of different processing parameters on the micro-hole processing of 316 heat-resistant steel using millisecond lasers. Through the control variable method, the study examines the impact of pulse energy, pulse count, and pulse width on the quality of micro-holes, including the entrance diameter, exit diameter, and taper. Furthermore, combined with orthogonal experiments and COMSOL Multiphysics 6.2 simulations, the study explores the influence of pulse width on the formation of blind holes. The experimental results show that when the pulse energy is 2.2 J, the taper is minimal (2.2°), while the taper reaches its peak (2.4°) at 2.4 J pulse energy. As the pulse count increases to 55–60 pulses, the exit diameter stabilizes, and the taper decreases to 1.8°. Blind holes begin to form when the pulse width exceeds 1.2 ms. When the pulse width is 1.2 ms, pulse energy is 2.4 J, and pulse count is 50, the entrance diameter of the blind hole reaches its maximum, indicating that longer pulse widths result in more significant energy reflection and thermal accumulation effects. COMSOL simulations reveal that high-energy pulses cause intense melt ejection, while longer pulse widths exacerbate thermal accumulation at the micro-hole entrance, leading to blind hole formation. This study provides important process references for laser processing of through-holes and blind holes in heat-resistant steel. Full article
(This article belongs to the Special Issue Heat Treatment and Additive Manufacturing of Alloys: Processing, Properties and Simulations)
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15 pages, 8425 KiB  
Article
The Biocorrosion of a Rare Earth Magnesium Alloy in Artificial Seawater Containing Chlorella vulgaris
by Xinran Yao, Qi Fu, Guang-Ling Song and Kai Wang
Materials 2025, 18(15), 3698; https://doi.org/10.3390/ma18153698 - 6 Aug 2025
Viewed by 227
Abstract
In the medical field, magnesium (Mg) alloys have been widely used due to their excellent antibacterial properties and biodegradability. However, in the marine environment, the antibacterial effect may be greatly attenuated, and consequently, microorganisms in the ocean are likely to adhere to the [...] Read more.
In the medical field, magnesium (Mg) alloys have been widely used due to their excellent antibacterial properties and biodegradability. However, in the marine environment, the antibacterial effect may be greatly attenuated, and consequently, microorganisms in the ocean are likely to adhere to the surface of Mg alloys, resulting in biocorrosion damage, which is really troublesome in the maritime industry and can even be disastrous to the navy. Currently, there is a lack of research on the biocorrosion of Mg alloys that may find important applications in marine engineering. In this paper, the biocorrosion mechanism of the Mg alloy Mg-3Nd-2Gd-Zn-Zr caused by Chlorella vulgaris (C. vulgaris), a typical marine microalga, was studied. The results showed that the biomineralization process in the artificial seawater containing a low concentration of C. vulgaris cells was accelerated compared with that in the abiotic artificial seawater, leading to the deposition of CaCO3 on the surface to inhibit the localized corrosion of the Mg alloy, whereas a high concentration of C. vulgaris cells produced a high content of organic acids at some sites through photosynthesis to significantly accelerate the surface film rupture at some sites and severe localized corrosion there, but meanwhile, it resulted in the formation of a more protective biomineralized film in the other areas to greatly alleviate the corrosion. The contradictory biocorrosion behaviors on the Mg-3Nd-2Gd-Zn-Zr alloy induced by C. vulgaris were finally explained by a mechanism proposed in the paper. Full article
(This article belongs to the Section Corrosion)
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16 pages, 5284 KiB  
Article
Hydration, Soundness, and Strength of Low Carbon LC3 Mortar Using Waste Brick Powder as a Source of Calcined Clay
by Saugat Humagain, Gaurab Shrestha, Mini K. Madhavan and Prabir Kumar Sarker
Materials 2025, 18(15), 3697; https://doi.org/10.3390/ma18153697 - 6 Aug 2025
Viewed by 410
Abstract
The construction industry is responsible for 39% of global CO2 emissions related to energy use, with cement responsible for 5–8% of it. Limestone calcined clay cement (LC3), a ternary blended binder system, offers a low-carbon alternative by partially substituting clinker [...] Read more.
The construction industry is responsible for 39% of global CO2 emissions related to energy use, with cement responsible for 5–8% of it. Limestone calcined clay cement (LC3), a ternary blended binder system, offers a low-carbon alternative by partially substituting clinker with calcined clay and limestone. This study investigated the use of waste clay brick powder (WBP), a waste material, as a source of calcined clay in LC3 formulations, addressing both environmental concerns and SCM scarcity. Two LC3 mixtures containing 15% limestone, 5% gypsum, and either 15% or 30% WBP, corresponding to clinker contents of 65% (LC3-65) or 50% (LC3-50), were evaluated against general purpose (GP) cement mortar. Tests included setting time, flowability, soundness, compressive and flexural strengths, drying shrinkage, isothermal calorimetry, and scanning electron microscopy (SEM). Isothermal calorimetry showed peak heat flow reductions of 26% and 49% for LC3-65 and LC3-50, respectively, indicating a slower reactivity of LC3. The initial and final setting times of the LC3 mixtures were 10–30 min and 30–60 min longer, respectively, due to the slower hydration kinetics caused by the reduced clinker content. Flowability increased in LC3-50, which is attributed to the lower clinker content and higher water availability. At 7 days, LC3-65 retained 98% of the control’s compressive strength, while LC3-50 showed a 47% reduction. At 28 days, the compressive strengths of mixtures LC3-65 and LC3-50 were 7% and 46% lower than the control, with flexural strength reductions being 8% and 40%, respectively. The porosity calculated from the SEM images was found to be 7%, 11%, and 15% in the control, LC3-65, and LC3-50, respectively. Thus, the reduction in strength is attributed to the slower reaction rate and increased porosity associated with the reduced clinker content in LC3 mixtures. However, the results indicate that the performance of LC3-65 was close to that of the control mix, supporting the viability of WBP as a low-carbon partial replacement of clinker in LC3. Full article
(This article belongs to the Special Issue Towards Sustainable Low-Carbon Concrete—Second Edition)
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12 pages, 1530 KiB  
Article
Effect of Aggregate Type on Asphalt–Aggregate Adhesion and Its Quantitative Characterization
by Liuxiao Chen, Junlin Li, Hao Xiang, Jun Zhang, Enlin Feng and Lin Kong
Materials 2025, 18(15), 3696; https://doi.org/10.3390/ma18153696 - 6 Aug 2025
Viewed by 332
Abstract
To study the effect of aggregate type on the adhesion between asphalt and aggregate, limestone, basalt, diabase, and 70# asphalt with SBS asphalt were selected. The mineral phase composition of the aggregates was analyzed by X-ray diffraction. The surface energy theory was used [...] Read more.
To study the effect of aggregate type on the adhesion between asphalt and aggregate, limestone, basalt, diabase, and 70# asphalt with SBS asphalt were selected. The mineral phase composition of the aggregates was analyzed by X-ray diffraction. The surface energy theory was used to calculate the adhesion work and the work of flaking. The modified water boiling method combined with image processing technology was used to quantitatively characterize the flaking behavior of the asphalt. The results show that the aggregate type is closely related to the asphalt–aggregate adhesion. The mineral compositions of different types of aggregates vary significantly, with limestone, being a strongly alkaline aggregate predominantly comprising CaCO3, exhibiting better adhesion with asphalt. The contact angle test and modified boiling method also yielded the same results, and the adhesion relationship with asphalt was limestone > basalt > diabase. Image processing technology effectively characterizes the spalling situation of asphalt and conducts quantitative analysis. Full article
(This article belongs to the Section Construction and Building Materials)
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17 pages, 3157 KiB  
Article
Research on Online Traceability Methods for the Causes of Longitudinal Surface Crack in Continuous Casting Slab
by Junqiang Cong, Qiancheng Lv, Zihao Fan, Haitao Ling and Fei He
Materials 2025, 18(15), 3695; https://doi.org/10.3390/ma18153695 - 6 Aug 2025
Viewed by 287
Abstract
In the casting and rolling production process, surface longitudinal cracks are a typical casting defect. Tracing the causes of longitudinal cracks online and controlling the key parameters leading to their formation in a timely manner can enhance the stability of casting and rolling [...] Read more.
In the casting and rolling production process, surface longitudinal cracks are a typical casting defect. Tracing the causes of longitudinal cracks online and controlling the key parameters leading to their formation in a timely manner can enhance the stability of casting and rolling production. To this end, the influencing factors of longitudinal cracks were analyzed, a data integration storage platform was constructed, and a tracing model was established using empirical rule analysis, statistical analysis, and intelligent analysis methods. During the initial production phase of a casting machine, longitudinal cracks occurred frequently. The tracing results using the LightGBM-SHAP method showed that the relative influence of the narrow left wide inner heat flow ratio of the mold was significant, followed by the heat flow difference on the wide symmetrical face of the mold and the superheat of the molten steel, with weights of 0.135, 0.066, and 0.048, respectively. Based on the tracing results, we implemented online emergency measures. By controlling the cooling intensity of the mold, we effectively reduced the recurrence rate of longitudinal cracks. Root cause analysis revealed that the total hardness of the mold-cooling water exceeded the standard, reaching 24 mg/L, which caused scaling on the mold copper plates and uneven cooling, leading to the frequent occurrence of longitudinal cracks. After strictly controlling the water quality, the issue of longitudinal cracks was brought under control. The online application of the tracing method for the causes of longitudinal cracks has effectively improved efficiency in resolving longitudinal crack problems. Full article
(This article belongs to the Special Issue Advanced Sheet/Bulk Metal Forming)
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18 pages, 4127 KiB  
Article
Sustainable Use of Volcanic Ash in Mortars as a Replacement for Cement or Sand: Shrinkage and Physical and Mechanical Properties
by Luisa María Gil-Martín, Miguel José Oliveira, Manuel Alejandro Fernández-Ruiz, Fernando G. Branco and Enrique Hernández-Montes
Materials 2025, 18(15), 3694; https://doi.org/10.3390/ma18153694 - 6 Aug 2025
Viewed by 318
Abstract
The eruption of the Cumbre Vieja volcano on 19 September 2021 resulted in the deposition of over 20 million cubic meters of tephra, posing significant environmental and logistical challenges in the affected areas. This study aimed to explore the valorization of volcanic ash [...] Read more.
The eruption of the Cumbre Vieja volcano on 19 September 2021 resulted in the deposition of over 20 million cubic meters of tephra, posing significant environmental and logistical challenges in the affected areas. This study aimed to explore the valorization of volcanic ash (VA) by evaluating its potential use in producing sustainable mortar by incorporating it as a replacement for cement or sand. Various experimental mixtures were prepared with different proportions of VA which substituted either cement or sand, and these mixes were characterized through a mechanical and microstructural campaign. Additionally, shrinkage was evaluated for the mixtures which showed good mechanical results. The results suggest that partially replacing cement with up to 15% ground VA as well as substituting sand with up to 25% VA are promising strategies for the production of sustainable mortar mixes. This research contributes to the understanding of the influence of VA in cementitious matrices and offers a novel approach for integrating locally available geomaterials into infrastructure design in volcanic active regions. Full article
(This article belongs to the Section Construction and Building Materials)
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16 pages, 7134 KiB  
Article
The Impact of an Object’s Surface Material and Preparatory Actions on the Accuracy of Optical Coordinate Measurement
by Danuta Owczarek, Ksenia Ostrowska, Jerzy Sładek, Adam Gąska, Wiktor Harmatys, Krzysztof Tomczyk, Danijela Ignjatović and Marek Sieja
Materials 2025, 18(15), 3693; https://doi.org/10.3390/ma18153693 - 6 Aug 2025
Viewed by 371
Abstract
Optical coordinate measurement is a universal technique that aligns with the rapid development of industrial technologies and new materials. Nevertheless, can this technique be consistently effective when applied to the precise measurement of all types of materials? As shown in this article, an [...] Read more.
Optical coordinate measurement is a universal technique that aligns with the rapid development of industrial technologies and new materials. Nevertheless, can this technique be consistently effective when applied to the precise measurement of all types of materials? As shown in this article, an analysis of optical measurement systems reveals that some materials cause difficulties during the scanning process. This article details the matting process, resulting, as demonstrated, in lower measurement uncertainty values compared to the pre-matting state, and identifies materials for which applying a matting spray significantly improves the measurement quality. The authors propose a classification of materials into easy-to-scan and hard-to-scan groups, along with specific procedures to improve measurements, especially for the latter. Tests were conducted in an accredited Laboratory of Coordinate Metrology using an articulated arm with a laser probe. Measured objects included spheres made of ceramic, tungsten carbide (including a matte finish), aluminum oxide, titanium nitride-coated steel, and photopolymer resin, with reference diameters established by a high-precision Leitz PMM 12106 coordinate measuring machine. Diameters were determined from point clouds obtained via optical measurements using the best-fit method, both before and after matting. Color measurements using a spectrocolorimeter supplemented this study to assess the effect of matting on surface color. The results revealed correlations between the material type and measurement accuracy. Full article
(This article belongs to the Section Optical and Photonic Materials)
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21 pages, 1779 KiB  
Article
Effect of Using Rotational and Static Kilns on the Properties of Eco-Friendly Lightweight Aggregates Made with Pumice Scraps and Spent Coffee Grounds
by Fabiana Altimari, Fernanda Andreola, Isabella Lancellotti, Carlos Javier Cobo-Ceacero, Teresa Cotes-Palomino, Carmen Martínez-García, Ana Belen López-García and Luisa Barbieri
Materials 2025, 18(15), 3692; https://doi.org/10.3390/ma18153692 - 6 Aug 2025
Viewed by 318
Abstract
In this work, lightweight aggregates (LWAs) were prepared from an Italian red clay, pumice scraps, and spent coffee grounds. Chemical and physical characterization was first performed on the raw materials and then on the finished products. By studying the thermal behavior of the [...] Read more.
In this work, lightweight aggregates (LWAs) were prepared from an Italian red clay, pumice scraps, and spent coffee grounds. Chemical and physical characterization was first performed on the raw materials and then on the finished products. By studying the thermal behavior of the materials, the correct firing temperature was evaluated. The obtained aggregates were fired in two different modes: in a rotary kiln and in a static kiln; the influence of the firing processes on the finished products was assessed. This study can be useful for industrially scaling up this process. Firing in a rotary kiln reduced the average diameter of the aggregates (negative expansion index), resulting in a higher compressive strength and dry particle density compared to an aggregate containing only clay. The pH and electrical conductivity values address their use in agronomy without causing problems to crops, while the higher compressive strength, density, and porosity values could allow their use in construction. Full article
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10 pages, 1346 KiB  
Article
Scintillation Properties of CsPbBr3 Quantum Dot Film-Enhanced Ga:ZnO Wafer and Its Applications
by Shiyi He, Silong Zhang, Liang Chen, Yang Li, Fangbao Wang, Nan Zhang, Naizhe Zhao and Xiaoping Ouyang
Materials 2025, 18(15), 3691; https://doi.org/10.3390/ma18153691 - 6 Aug 2025
Viewed by 266
Abstract
In high energy density physics, the demand for precise detection of nanosecond-level fast physical processes is high. Ga:ZnO (GZO), GaN, and other fast scintillators are widely used in pulsed signal detection. However, many of them, especially wide-bandgap materials, still face issues of low [...] Read more.
In high energy density physics, the demand for precise detection of nanosecond-level fast physical processes is high. Ga:ZnO (GZO), GaN, and other fast scintillators are widely used in pulsed signal detection. However, many of them, especially wide-bandgap materials, still face issues of low luminous intensity and significant self-absorption. Therefore, an enhanced method was proposed to tune the wavelength of materials via coating perovskite quantum dot (QD) films. Three-layer samples based on GZO were primarily investigated and characterized. Radioluminescence (RL) spectra from each face of the samples, as well as their decay times, were obtained. Lower temperatures further enhanced the luminous intensity of the samples. Its overall luminous intensity increased by 2.7 times at 60 K compared to room temperature. The changes in the RL processes caused by perovskite QD and low temperatures were discussed using the light tuning and transporting model. In addition, an experiment under a pico-second electron beam was conducted to verify their pulse response and decay time. Accordingly, the samples were successfully applied in beam state monitoring of nanosecond pulsed proton beams, which indicates that GZO wafer coating with perovskite QD films has broad application prospects in pulsed radiation detection. Full article
(This article belongs to the Section Quantum Materials)
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