Materials

22 pages, 3454 KB

Open AccessArticle

Wide-Temperature-Range Large-Deformation Tensile Behavior and Constitutive Modeling of Polytetrafluoroethylene

by Lushan Li, Le Chang, Jianping Zhao, Xiaowei Wang, Jizhong Yan, Zechen Yang and Shengping Wu

Materials 2026, 19(18), 3827; https://doi.org/10.3390/ma19183827 - 8 Sep 2026

Abstract

This study investigates the tensile behavior of polytetrafluoroethylene (PTFE) tube material across a wide range of temperatures, displacement rates, and sampling directions. Temperature has a dominant effect: flow stress decreases and ductility increase markedly as temperature rises, while displacement rate and sampling direction [...] Read more.

This study investigates the tensile behavior of polytetrafluoroethylene (PTFE) tube material across a wide range of temperatures, displacement rates, and sampling directions. Temperature has a dominant effect: flow stress decreases and ductility increase markedly as temperature rises, while displacement rate and sampling direction show only minor effects. A temperature-coupled three-part superposition quasi-static stress (TPS) model is developed, using Arrhenius-type relationships to describe how the model parameters evolve with temperature. This model outperforms the Johnson–Cook, Ogden, and Zhu–Wang–Tang (ZWT) models across the full strain range and the entire tested temperature range. Molecular dynamics simulations further show that rising temperature increases free volume and chain-segment mobility while reducing chain orientation, providing a molecular-scale explanation for the observed thermal softening. Full article

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

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23 pages, 22424 KB

Open AccessArticle

Fe24Ni15Cr3Al-Based AFA Steels in Oxygen-Controlled Liquid Pb at 500 °C, 600 °C, and 700 °C

by Renate Fetzer, Annette Heinzel, Alfons Weisenburger and Georg Müller

Materials 2026, 19(18), 3826; https://doi.org/10.3390/ma19183826 - 8 Sep 2026

Abstract

Heavy liquid metals such as liquid lead (Pb) are attractive heat transfer media for advanced energy applications, despite their corrosive nature. In the search for heat-resistant austenitic materials that are corrosion resistant to liquid Pb at high temperature, three new Fe24Ni15Cr3Al-based alumina-forming austenitic [...] Read more.

Heavy liquid metals such as liquid lead (Pb) are attractive heat transfer media for advanced energy applications, despite their corrosive nature. In the search for heat-resistant austenitic materials that are corrosion resistant to liquid Pb at high temperature, three new Fe24Ni15Cr3Al-based alumina-forming austenitic (AFA) steels with slightly varying compositions have been developed. The present study investigates the corrosion behavior of these AFA materials using static exposure tests to molten Pb containing 1 × 10⁻⁷ wt.% dissolved oxygen. The corrosion tests are performed at 500 °C, 600 °C, and 700 °C for 1000 h, 2000 h, and 5000 h each. In addition to the variation in material, temperature, and exposure time, two different surface finishes are also used for the tests. Examination of the specimens after exposure shows the formation of oxide scales for temperatures up to 600 °C on all three AFA materials, with minor material-specific variations. Furthermore, the scale characteristics depend on the surface finish. Coarse ground surfaces exhibit thin Al-rich protective oxide scales, while fine ground surfaces show the formation of thick multilayer oxide scales susceptible to Ni dissolution and Pb penetration. Pb exposure at 700 °C leads to a severe corrosion attack of all three Fe24Ni15Cr3Al-based AFA steels. Full article

(This article belongs to the Special Issue Structural Materials for Harsh Environments)

27 pages, 1061 KB

Open AccessReview

Insights on the Generation of Polymeric Drug Carriers via Supercritical Fluid-Assisted Technologies

by Alessandra Zanotti and Stefano Cardea

Materials 2026, 19(18), 3825; https://doi.org/10.3390/ma19183825 - 8 Sep 2026

Abstract

Polymeric drug carriers have emerged as versatile platforms for improving therapeutic efficacy, drug stability and controlled and sustained release of active pharmaceutical ingredients. Conventional manufacturing techniques often rely on high processing temperatures, utilization of organic solvents and consequent purification procedures that may compromise [...] Read more.

Polymeric drug carriers have emerged as versatile platforms for improving therapeutic efficacy, drug stability and controlled and sustained release of active pharmaceutical ingredients. Conventional manufacturing techniques often rely on high processing temperatures, utilization of organic solvents and consequent purification procedures that may compromise morphology, encapsulation efficiency and carrier biocompatibility. Supercritical fluid technologies overcome the limitations of conventional methods and emerge as environmentally friendly, sustainable and flexible alternatives to produce advanced polymeric drug carriers. This review provides insights into the most widespread supercritical fluid technologies, encompassing the most recent advancements (2022–2026) made in the field of porous materials, micro- and nanoparticles and microcapsules. Emphasis was placed on carrier characteristics, features and applicative translation; this review aims at evidencing advantages, current limitations and future perspectives of supercritical fluid technologies, aiming at encouraging technological and industrial advancement of next-generation advanced polymeric drug carriers. Full article

(This article belongs to the Special Issue Design and Development of Polymer-Based Drug Carriers for Biomedical Applications, Second Edition)

37 pages, 1777 KB

Open AccessReview

Modification and Recycling Complexity of the Bitumen Modified with SBS Polymer—A Review

by Joanna Szołtysik, Wojciech Sorociak, Sławomir Kwiecień and Jarosław Rybak

Materials 2026, 19(18), 3824; https://doi.org/10.3390/ma19183824 - 8 Sep 2026

Abstract

This paper presents a comprehensive review of bituminous binder modification using Styrene–Butadiene–Styrene (SBS) copolymer. Bitumen is one of the most widely used binder types in road engineering, and its modification has been extensively studied to enhance performance characteristics. The review outlines the historical [...] Read more.

This paper presents a comprehensive review of bituminous binder modification using Styrene–Butadiene–Styrene (SBS) copolymer. Bitumen is one of the most widely used binder types in road engineering, and its modification has been extensively studied to enhance performance characteristics. The review outlines the historical development of bitumen modification, discusses binder structural models, and examines the influence of SBS on binder properties. The review focuses on ageing process of Polymer-Modified Bitumen (PMB) and Highly Modified Bitumen (HiMA). The complexity of binder’s origin, polymer structure, ageing factors and the presence of cross-linking agents or other compounds creates significant challenges in predicting binder performance after technological and exploitation ageing. This uncertainty directly affects the assessment of long-term durability and recycling potential. Therefore, it is relevant to incorporate a broader range of ageing factors into standardized laboratory testing procedures to develop effective rejuvenation strategies for SBS-modified PMBs. Full article

(This article belongs to the Special Issue Development of Sustainable Asphalt Materials)

29 pages, 6598 KB

Open AccessArticle

Interfacial Bond Behavior and Load-Transfer Characteristics of CFRP-Strengthened Traditional Masonry with Glutinous Rice Mortar

by Xiao Liu, Yilun Li, Chaoyang Liu, Haiwei Yao and Liangyin Huang

Materials 2026, 19(18), 3823; https://doi.org/10.3390/ma19183823 - 8 Sep 2026

Abstract

Traditional brick masonry buildings in China are commonly constructed using fired clay grey bricks bonded with glutinous rice mortar, forming a unique historical masonry system with significant cultural value. During long-term service, these structures are vulnerable to environmental deterioration, material aging, and seismic [...] Read more.

Traditional brick masonry buildings in China are commonly constructed using fired clay grey bricks bonded with glutinous rice mortar, forming a unique historical masonry system with significant cultural value. During long-term service, these structures are vulnerable to environmental deterioration, material aging, and seismic actions, resulting in cracking, deformation, and degradation of structural integrity and load-carrying capacity. Carbon fiber-reinforced polymer (CFRP) sheets have been increasingly applied for strengthening masonry structures due to their high strength-to-weight ratio, corrosion resistance, and convenient installation. However, most existing studies on Fiber-reinforced polymer (FRP)–masonry interfaces have focused on conventional masonry systems, while the interfacial bond behavior and load-transfer characteristics between CFRP sheets and traditional grey brick masonry bonded with glutinous rice mortar remain insufficiently investigated. This study investigates the interfacial bond behavior of CFRP-strengthened traditional grey brick masonry through combined experimental testing and numerical analysis. First, uniaxial compression tests were conducted to determine the mechanical properties of glutinous rice mortar and fired clay grey bricks. Subsequently, double-shear tests considering different CFRP bond widths, bond lengths, and interface integrity conditions were performed to characterize the failure modes, force–displacement responses, and interfacial load-carrying behavior. The effects of interface geometric and integrity conditions were considered to evaluate the load-transfer characteristics of the strengthened interface. Based on the experimental results, a finite element model considering interface behavior was established and verified through comparison with the experimental results, which was subsequently employed to investigate the influence of bond width on interfacial stress transfer behavior beyond the experimental conditions. The results show that interfacial debonding accompanied by near-surface masonry damage dominates the failure process of CFRP–glutinous rice mortar masonry interfaces. Increasing the CFRP bond width enhances the interfacial load-carrying capacity and initial stiffness, while the ultimate capacity exhibits an approximately linear relationship with bond width within the investigated range. Numerical analyses further demonstrate that increasing bond width expands the effective load-transfer region, redistributes interfacial stresses, and delays stiffness degradation. These findings improve the understanding of interfacial bond behavior and load-transfer characteristics in CFRP-strengthened traditional masonry systems and provide references for the design and performance evaluation of strengthening applications in historic masonry structures. Full article

(This article belongs to the Special Issue Masonry and Concrete Members Strengthened with Fibre-Reinforced Composite Materials: Research Advances (2nd Edition))

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43 pages, 45739 KB

Open AccessArticle

Durability of Flax Fiber Reinforced Polymer Sheets Under Hygrothermal Conditions: Tensile and Shear Performance

by Yangyang Xia, Pengyu Li, Lingli Shen, Jifang Niu and Huiguo Zhao

Materials 2026, 19(18), 3822; https://doi.org/10.3390/ma19183822 - 8 Sep 2026

Abstract

Fiber reinforced polymers (FRPs) have gained widespread application in civil engineering due to their light weight, high strength, and excellent corrosion resistance. Among various fibers, natural fibers have recently attracted increasing attention because of their renewability, low cost, and reduced environmental impact. However, [...] Read more.

Fiber reinforced polymers (FRPs) have gained widespread application in civil engineering due to their light weight, high strength, and excellent corrosion resistance. Among various fibers, natural fibers have recently attracted increasing attention because of their renewability, low cost, and reduced environmental impact. However, natural fiber reinforced polymer composites (NFRPs) suffer from high moisture absorption and inferior mechanical properties, which are further deteriorated under hygrothermal environments, severely limiting their service conditions. This study focuses on flax fiber reinforced polymer composites (FFRPs) and, through systematic experimental testing, investigates their durability under hygrothermal conditions. Hygrothermal aging was conducted at 90% relative humidity and 40 °C for up to 30 days. Water uptake, mechanical properties, and thermomechanical behavior were evaluated for composites fabricated by two molding processes (autoclave and hand-laying) with varying ply numbers (10, 20, 30, 40, and 50 layers). The optimal ply number for mechanical performance was identified, and the influence of the different resin systems and fiber forms between the two processes on the cross-process comparison, as well as the rationale for the 30-layer laminate and the effect of laminate thickness, were clarified. Microstructural changes were examined via scanning electron microscopy. This work provides systematic experimental evidence and data for assessing the long-term durability of FFRP composites in humid and warm environments, offering valuable guidance for their practical application in civil infrastructure. Full article

(This article belongs to the Special Issue Advanced Fiber Composite Materials: Preparation, Properties and Applications)

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22 pages, 4972 KB

Open AccessArticle

Study on the Mix Design of Mastic Flow for Filling Based on Deviation Coefficient Method

by Yuekai Yao, Min Mi, Kuanghuai Wu, Changkang Lao and Yuqi Zheng

Materials 2026, 19(18), 3821; https://doi.org/10.3390/ma19183821 - 8 Sep 2026

Abstract

To quantitatively evaluate the skeleton design of the MaFF method, this study addresses five dimensions: gradation control, test method, quantitative model, correction conversion, and design method. First, the deviation coefficient method is proposed based on the Talbot method. Unlike conventional design restricted to [...] Read more.

To quantitatively evaluate the skeleton design of the MaFF method, this study addresses five dimensions: gradation control, test method, quantitative model, correction conversion, and design method. First, the deviation coefficient method is proposed based on the Talbot method. Unlike conventional design restricted to n = 0.3–0.7, this method takes the maximum density curve at n = 0.45 as the reference and enables flexible adjustment of

V_{a g}

by controlling the 4.75 mm sieve passing rate. This provides a theoretical basis for discontinuous gradation design. Second, the wet mixing test is developed to overcome aggregate segregation and inadequate lubrication inherent in the dry tamping method, offering a new detection approach that better reflects the actual skeleton structure in the mixture. The optimum parameters were determined as 2% asphalt content, layered loading, one-sided tamping and 75 blows. Using 11 gradations, the wet mixing tests show that

V_{a g}

increases from 24.13% to 38.29% as λ increases from 0 to 1.0, with a strong linear correlation (R² = 0.996). CT scanning validation indicates that the wet method results are 83–86% of those from 3D reconstruction, yielding a recommended reduction coefficient of 0.84. These findings systematically refine the MaFF method into a complete skeleton design framework. For the specific material system investigated (diabase aggregate, ultra-high-viscosity asphalt, maximum nominal particle size of 13.2 mm), this study provides a preliminary technical reference for FMA mix design. However, broader validation across diverse materials and field conditions is required before generalization. Full article

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

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15 pages, 23921 KB

Open AccessArticle

Annealing-Controlled Recrystallization, Grain Growth, and Tensile Properties of Cold-Rolled L-605 Cobalt-Based Alloy

by Choi Seong-Woo and Chenglin Li

Materials 2026, 19(18), 3820; https://doi.org/10.3390/ma19183820 - 8 Sep 2026

Abstract

This work investigated the effects of annealing temperature and holding time on recrystallization, grain growth, and tensile properties of cold-rolled biomedical Co–20Cr–15W–10Ni (L-605) alloy. The alloy was solution-treated at 1200 °C for 30 min, cold-rolled to 40% area reduction, and annealed at 800–950 [...] Read more.

This work investigated the effects of annealing temperature and holding time on recrystallization, grain growth, and tensile properties of cold-rolled biomedical Co–20Cr–15W–10Ni (L-605) alloy. The alloy was solution-treated at 1200 °C for 30 min, cold-rolled to 40% area reduction, and annealed at 800–950 °C for 15 min, 1000 °C for 5–60 min, or 1200 °C for 5–60 min. Annealing at 800–900 °C produced partially recrystallized microstructures; 950 °C yielded nearly full recrystallization with an average grain size of ~3.4 μm. At 1000 °C, the fully recrystallized microstructure retained ~5 μm fine grains even after 60 min, likely due to grain boundary migration inhibition by fine secondary-phase particles, whose composition and pinning effect remain unclarified. At 1200 °C, grains grew significantly to ~90 μm, attributed to higher grain boundary mobility and reduced particle pinning at elevated temperature. As annealing temperature rose from 800 °C to 950 °C, yield strength decreased from 1245 MPa to 800 MPa, and elongation increased from 12.6% to 45.9%. At 1200 °C, yield strength fell to 442–455 MPa and elongation reached 73.5–80.8%. The results confirm that the alloy’s strength–ductility performance is directly determined by microstructure evolution from retained cold rolling deformation substructures to fine recrystallized grains, and further to coarse recrystallized grains at higher temperatures. Full article

(This article belongs to the Section Metals and Alloys)

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19 pages, 21281 KB

Open AccessArticle

High-Temperature Performance of Metakaolin-Based Geopolymer Recycled Mortar with Pumice Powder

by Xudong Zhu, Feifei Jiang, Changwei Chen, Hui Liu, Pinghua Zhu, Yang Li and Tianyu Ma

Materials 2026, 19(18), 3819; https://doi.org/10.3390/ma19183819 - 8 Sep 2026

Abstract

This study investigates metakaolin-based geopolymer recycled mortar (GRM) in which recycled fine aggregate (RFA) was volumetrically replaced by pumice powder (PP) at 0% and 60–100%. Ambient compressive and tensile bond strengths were measured, followed by exposure to 600–800 °C for 1–3 h. The [...] Read more.

This study investigates metakaolin-based geopolymer recycled mortar (GRM) in which recycled fine aggregate (RFA) was volumetrically replaced by pumice powder (PP) at 0% and 60–100%. Ambient compressive and tensile bond strengths were measured, followed by exposure to 600–800 °C for 1–3 h. The evaluation encompassed mass loss ratio, residual mechanical properties, temperature sensitivity, micro-phase evolution, and strength-normalized carbon intensity. Results demonstrated that PP replacement produced a non-monotonic response, governed by the trade-off between improved particle packing and the depletion of the rigid granular skeleton. Among the PP-containing mixtures, PP₇₀ (70% replacement) showed a comparatively favorable mechanical response, with an ambient compressive strength of 31.7 MPa and a mean residual compressive strength of 18.8 MPa (59.3% of its initial value) after exposure to 800 °C for 3 h. Notably, tensile bond strength exhibited greater temperature sensitivity than compressive strength, with deterioration accelerating significantly above 700 °C. SEM and XRD analyses elucidated this macroscopic divergence via a two-stage damage mechanism: while dehydration and matrix contraction dominated at 600 °C, prolonged exposure at 800 °C induced structural rearrangement, with the dominant damage becoming increasingly concentrated at the RFA–matrix interface. Although substituting RFA with processed PP inherently increased the absolute embodied carbon, PP₇₀ exhibited the lowest strength-normalized carbon intensity among the modified mixtures after exposure to 800 °C for 3 h. These findings indicate that, among the investigated high-volume PP mixtures, PP₇₀ provided a comparatively favorable compromise between thermal-mechanical performance and environmental cost. Full article

(This article belongs to the Special Issue Advanced Experimental Technology, Theory and Numerical Methods in Concrete Materials)

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12 pages, 1334 KB

Open AccessArticle

Volatile Organic Compound Emissions and Human Odor Perception of Dental 3D-Printing Photopolymer Resins

by Wiktoria Kapusta, Mateusz Walerzak, Andrzej Sołtyk, Małgorzata Ponto-Wolska, Artur Winiarski, Leopold Wagner and Łukasz Zadrożny

Materials 2026, 19(18), 3818; https://doi.org/10.3390/ma19183818 - 8 Sep 2026

Abstract

The increasing use of photopolymer resins in dental three-dimensional (3D) printing has raised concerns regarding occupational exposure to volatile organic compounds (VOCs). This study aimed to characterize and compare formaldehyde (HCHO) and total volatile organic compound (TVOC) emission profiles of five commercially available [...] Read more.

The increasing use of photopolymer resins in dental three-dimensional (3D) printing has raised concerns regarding occupational exposure to volatile organic compounds (VOCs). This study aimed to characterize and compare formaldehyde (HCHO) and total volatile organic compound (TVOC) emission profiles of five commercially available dental 3D-printing resins and to explore their relationship with subjective odor perception. Subjective odor perception was assessed during routine educational laboratory activities using a numerical rating scale (0–10). Time-resolved HCHO and TVOC measurements were subsequently performed under standardized chamber conditions using a portable air-quality monitor, with three consecutive 10 min measurement cycles conducted for each resin using the same standardized 200 mL sample. Two participants reporting upper respiratory tract infection symptoms were excluded, resulting in a final sensory sample of 50 participants. Perceived odor intensity differed significantly among the tested resins (Friedman test, χ²(4) = 55.54, p < 0.001; Kendall’s W = 0.278). A positive resin-level association was observed between mean odor intensity and TVOC concentration at the 10 min endpoint of the first post-agitation measurement cycle (Spearman’s ρ = 0.70); however, this relationship was not statistically significant in the exact two-sided permutation analysis (p = 0.233) and was considered exploratory. HCHO–odor correlation analysis was not performed because HCHO concentrations for three of the five resins exceeded the upper measurement range of the instrument. Notably, a plant-based resin exhibited relatively high odor intensity despite comparatively low TVOC emissions, suggesting that total emission magnitude alone may not fully explain odor perception. The tested dental photopolymer resins exhibited distinct material-dependent emission and odor-perception characteristics. Odor perception should therefore be considered complementary to, rather than a substitute for, instrumental emission characterization. Integrating sensory assessment with instrumental emission measurements may support a more comprehensive evaluation of dental photopolymer resins and inform future occupational-safety studies. Full article

(This article belongs to the Special Issue Materials for Dentistry: Experiments and Practice)

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15 pages, 2420 KB

Open AccessArticle

Thermal Stress and Temperature Analysis of Integrated Protection-Thermal Control Multilayer Films Under Laser Irradiation in Alternating High and Low Temperatures

by Chao Zhou, Rui Zhu, Shengzhu Cao, Jun Yang and Binhua Gui

Materials 2026, 19(18), 3817; https://doi.org/10.3390/ma19183817 - 8 Sep 2026

Abstract

With the rapid advancement of space-based laser weapon technologies, on-orbit safety of spacecraft such as satellites is confronted with severe laser threats. To meet the demands for film system optimization and reliability improvement of thin films integrating space laser protection and thermal control [...] Read more.

With the rapid advancement of space-based laser weapon technologies, on-orbit safety of spacecraft such as satellites is confronted with severe laser threats. To meet the demands for film system optimization and reliability improvement of thin films integrating space laser protection and thermal control functions, this study takes the Graphene/Ag/Al₂O₃/SiO₂/ITO multilayer thin film structure as the research object. Combined with the space alternating high-low temperature environment and the action of ultra-high-density transient directional heat flux, systematic simulation research on the evolution laws of temperature and stress fields inside the multilayer thin films under laser irradiation in alternating space high-low temperature environments is carried out via COMSOL Multiphysics, and the influencing mechanisms of ambient temperature and laser operating parameters on thermal stress and temperature distribution are revealed. The simulation results demonstrate that the thin film structure reaches thermal equilibrium within several seconds under a given transient directional heat flux. As laser power rises, the peak temperature of each layer increases nonlinearly and the time required to reach thermal equilibrium shortens. The laser heat flux density acts as the dominant factor governing the temperature and thermal stress distribution. Under alternating space high-low temperature conditions, the thermal stress of the thin film varies approximately linearly with temperature while the overall stress magnitude remains low, and thermal stress is mainly concentrated in the Al₂O₃ layers. Laser loading exerts a remarkable impact on film thermal stress: the amplitude of thermal stress in all film layers rises synchronously with increasing laser power, and interlayer temperature gradients as well as stress concentration are further intensified. The stress growth of Ag and Al₂O₃ layers is the most significant, which can be attributed to the synergistic effect of interlayer thermal expansion coefficient mismatch and temperature gradients. The alternating high-low temperature and laser irradiation experiments indicate that the maximum temperature and maximum stress borne by the muti-layer film under alternating temperatures ranging from −150 °C to 150 °C and laser irradiation of 200 W/cm² will not lead to macroscopic failure behaviors and degradation of thermal control performance. Full article

(This article belongs to the Special Issue Advanced Laser and Optical Methods for Material Analysis, Surface Engineering, and Performance Enhancement)

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27 pages, 5264 KB

Open AccessReview

Clear Aligners as a Prescribed Source of Unmeasured Intra-Oral Micro- and Nanoplastic Exposure: Release Mechanisms, Human Evidence, Salivary Biomonitoring and the EU Regulatory Context

by Marcin Mikulewicz and Katarzyna Chojnacka

Materials 2026, 19(18), 3816; https://doi.org/10.3390/ma19183816 - 8 Sep 2026

Abstract

Clear orthodontic aligners are removable polymer devices worn about 22 h a day for 12 to 24 months, increasingly by children. A growing in vitro literature shows that thermoformed and 3D-printed aligners shed micro- and nanoplastics and co-release elemental or organic constituents under [...] Read more.

Clear orthodontic aligners are removable polymer devices worn about 22 h a day for 12 to 24 months, increasingly by children. A growing in vitro literature shows that thermoformed and 3D-printed aligners shed micro- and nanoplastics and co-release elemental or organic constituents under oral, gastric and mechanical conditions, yet aligner-derived particle burden and systemic dose in wearers have not been measured. This review sets aligner-derived release against the wider human micro- and nanoplastic record and evaluates saliva as a biomonitoring matrix. Directly printed devices release more and larger microplastics under mechanical stress, whereas thermoformed materials show acid-related degradation, with Sb/Sn release and nanometre-scale particles reported in a single, not yet replicated in vitro study. Particles below 5 microns, especially below 1 micron, are plausible translocation candidates, but translocation of aligner-derived particles has not been demonstrated. In vitro work reports macrophage and oxidative responses, whereas detections in blood, placenta and atheroma are not source-specific and remain associative. The EU amalgam phase-out does not regulate aligners but highlights a substitution question, because device and chemicals law addresses intentionally added microplastics, not wear-generated secondary particles. ICP-MS for antimony and tin, with Raman, micro-FTIR and electron microscopy, forms a plausible analytical toolbox. We propose harmonised release testing and validated salivary biomonitoring, prioritising children, to characterise source-proximal exposure before use expands. Full article

(This article belongs to the Special Issue Advances in Bioactive Materials and Bulk-Fill Composite Resin in Dental Restoration)

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21 pages, 5436 KB

Open AccessArticle

Study on Contact Characteristics of Aeronautical Floating Splines Considering Maneuvering Deformation

by Yongqiang Xu, Hao Chen, Dapeng Zhang, Guangyao Hu, Hongjun Li and Kerui Xiong

Materials 2026, 19(18), 3815; https://doi.org/10.3390/ma19183815 - 8 Sep 2026

Abstract

Floating involute splines are widely used in aviation power transmission systems for torque transmission. In this study, a finite element model considering the dynamic deformation of a floating involute spline shaft was established to analyze the influence of shaft deformation on the misalignment [...] Read more.

Floating involute splines are widely used in aviation power transmission systems for torque transmission. In this study, a finite element model considering the dynamic deformation of a floating involute spline shaft was established to analyze the influence of shaft deformation on the misalignment state of the spline pair under various typical dynamic overload conditions. Furthermore, a contact simulation model of the floating spline pair with an actual tooth profile was developed to investigate the effect of deformation-induced misalignment on the contact pressure distribution over the tooth surface. In addition, the contact fatigue strength of the spline pair under dynamic loading conditions, including limit loads and ultimate loads, was evaluated. The results indicate that axial overload can induce axial displacement of the mating surfaces of the floating spline, thereby reducing the effective axial contact length. Radial overload and gyroscopic moments can lead to parallel misalignment and angular misalignment of the spline, respectively. Under combined overload conditions, angular misalignment is dominant under limit loads, whereas parallel misalignment becomes more pronounced under ultimate loads. Moreover, significant stress concentration and non-uniform load distribution are observed in the contact stress field under both limit and ultimate loading conditions. A quantitative analysis method for floating spline misalignment under the superposition of multiple maneuvering loads has been established. Full article

(This article belongs to the Special Issue Mechanics of Sustainable Engineering Materials: Performance, Degradation and Applications)

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20 pages, 5970 KB

Open AccessArticle

Wet-Grinding Reactivation and Frost Resistance of Waste Sludge from a Concrete Mixing Plant: A Case Study of Large-Scale Mine Construction in the Xinjie Taigemiao Mining Area

by Lin Wang, Tao Han, Mou Lv, Tingting Luo, Maolin Liu, Bing Xue, Junwei Zhang and Yongsheng Ji

Materials 2026, 19(18), 3814; https://doi.org/10.3390/ma19183814 - 8 Sep 2026

Abstract

The consumption of concrete is enormous during coal mine construction in the Xinjie Taigemiao mining area. During the concrete production process, the cleaning of concrete tank trucks and mixer equipment generates a large amount of waste sludge separated from fresh concrete. How to [...] Read more.

The consumption of concrete is enormous during coal mine construction in the Xinjie Taigemiao mining area. During the concrete production process, the cleaning of concrete tank trucks and mixer equipment generates a large amount of waste sludge separated from fresh concrete. How to successfully recycle waste sludge has become a key issue that urgently needs to be solved in mine construction. In this work, a method is proposed for reactivating waste sludge into cementitious materials by wet grinding to peel off hydration products from the surface of cement particles, and the influence of aging time and wet-grinding time on the mechanical properties and frost resistance of reactivated waste sludge paste are investigated; furthermore, through testing methods such as hydration heat analysis, XRD, and SEM, the hydration and hardening mechanisms of waste sludge treated by wet grinding are analyzed. The results show that wet grinding can break the adhesion between agglomerated waste particles and peel off the hydration products from the surface of the waste particles to obtain fresh cement particles, thereby restoring the cement’s hydration activity and bonding properties. The cementitious properties of reactivated waste sludge first increase and then decrease with the increase in aging time, and they first increase and then tend to stabilize with the increase in wet-grinding time; the frost resistance of the reactivated waste sludge is improved. The optimal aging time and optimal wet-grinding time for reactivated waste sludge are 14–18 h and 10 min, respectively. Full article

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

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16 pages, 3043 KB

Open AccessArticle

Static and Dynamic Performance of Steel-Fiber-Reinforced Polymer-Modified Concrete: Strength, Toughness and Crack Resistance

by Zhixiang Wang, Zhijian Yi, Ya Li, Jiaming Zhang, Kang Su and Jie Liu

Materials 2026, 19(18), 3813; https://doi.org/10.3390/ma19183813 - 8 Sep 2026

Abstract

Conventional concrete pavement materials remain limited in flexural strength, deformability, post-cracking load-carrying capacity, and impact resistance. To address these deficiencies, this study investigates the effects of polymer modification and ultrashort ultrafine steel fiber reinforcement on the static and dynamic mechanical responses and crack [...] Read more.

Conventional concrete pavement materials remain limited in flexural strength, deformability, post-cracking load-carrying capacity, and impact resistance. To address these deficiencies, this study investigates the effects of polymer modification and ultrashort ultrafine steel fiber reinforcement on the static and dynamic mechanical responses and crack evolution of concrete. The results show that polymer modification enhances deformability, while steel fiber incorporation further increases flexural strength and ultimate flexural strain and improves post-cracking load-carrying capacity. Under repeated impact loading, the nominal impact energy input required for initial cracking and final failure increased; in particular, polymer-modified concrete containing 5% steel fibers showed increases of 938.76% in ultimate flexural strain and 8682.63% in the number of impacts to failure relative to ordinary concrete. The matrix and interfacial morphologies observed by scanning electron microscopy (SEM) were consistent with the macroscopic mechanical responses, supporting the interpretation that polymer modification improves matrix and interfacial integrity, while steel fibers contribute to post-cracking load transfer through crack bridging. Overall, the material exhibited high deformability and damage tolerance, indicating its potential for specialized pavement applications. Full article

(This article belongs to the Special Issue Advanced Road Materials and Pavement: Design, Characterization, Structural and Mechanical Performance)

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13 pages, 292085 KB

Open AccessArticle

Tailoring the Microstructure of Ti-6Al-4V Alloy Fabricated by Hybrid Additive Manufacturing via Rolling Strategies

by Jixin Yang, Zhiqin Yang, Xu Gu, Ying Bao and Huaping Tang

Materials 2026, 19(18), 3812; https://doi.org/10.3390/ma19183812 - 8 Sep 2026

Abstract

In situ rolling-assisted laser directed energy deposition (IR-LDED) was employed to fabricate Ti-6Al-4V titanium alloy samples, focusing on the microstructural characteristics under various rolling strategies. The results indicate that the microstructure was primarily governed by the interplay between temperature-dependent deformation and recrystallization processes. [...] Read more.

In situ rolling-assisted laser directed energy deposition (IR-LDED) was employed to fabricate Ti-6Al-4V titanium alloy samples, focusing on the microstructural characteristics under various rolling strategies. The results indicate that the microstructure was primarily governed by the interplay between temperature-dependent deformation and recrystallization processes. In situ rolling at elevated temperature, combined with complex thermal cycling, promoted recrystallization within the deposited material, leading to significant grain refinement. After remelting and high-temperature rolling, the average grain size in the middle region of the sample was refined to 21 μm, accompanied by high kernel average misorientation (KAM_avg) value of 1.92. Increasing the number of rolling passes at lower temperatures further reduced the grain size and decreased the KAM_avg. Following in situ rolling, the deposited material underwent remelting, and additional rolling at elevated temperatures increased both deformation and KAM_avg. The rearrangement of dislocations, formation of subgrain boundaries, and enhanced solute diffusion collectively facilitated the globularization of lamellar α phases, ultimately forming a microstructure composed of globular α, lamellar α/β, and dot-like β phases. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Microstructure and Mechanical Properties—Second Edition)

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15 pages, 6074 KB

Open AccessArticle

Composite Al₂O₃-Ce:LuAG Phosphor Ceramics with High Luminous Efficacy and Thermal Conductivity for High-Brightness Laser Lighting

by Haiming Li, Ziqiu Cheng, Zhenzhen Zhou, Chen Hu, Junhao Ye, Dong Huang, Yanbin Wang, Tingsong Li, Heng Liu, Shisheng Lin, Denis Yu. Kosyanov, Daqin Chen, Duyou Lu and Jiang Li

Materials 2026, 19(18), 3811; https://doi.org/10.3390/ma19183811 - 8 Sep 2026

Abstract

Despite the success of using Al₂O₃ as a secondary phase in Ce:LuAG phosphor ceramics (PCs), there is still room for improvement in the compositional design of biphasic PCs, as well as in their luminescent and thermal performance. In this study, [...] Read more.

Despite the success of using Al₂O₃ as a secondary phase in Ce:LuAG phosphor ceramics (PCs), there is still room for improvement in the compositional design of biphasic PCs, as well as in their luminescent and thermal performance. In this study, nanopowders with 40 wt.% Al₂O₃-0.4at.% Ce:LuAG stoichiometry were synthesized via a co-precipitation approach. Subsequently, a series of compositionally uniform PCs was successfully fabricated by adjusting the vacuum sintering temperature and dwelling time. The grain size distributions of the Al₂O₃ and LuAG phases, as well as the evolution of porosity and pore size, were systematically analyzed and correlated with the sintering conditions. The addition of Al₂O₃ has been demonstrated to enhance the thermal properties of ceramics. The thermal conductivity of the “1750 °C × 10 h” sample was 15.6 W·m⁻¹·K⁻¹ at room temperature. Concurrently, it exhibited excellent thermal quenching behavior, retaining 96% of its luminescence intensity upon heating to 450 K. Its fluorescence lifetime was determined to be 21.06 ns. Under 450 nm laser excitation, the optimized PC attained a luminous efficacy of 286 lm·W⁻¹ at 1 W·mm⁻². In addition, the luminous flux increased continuously with laser power from 1 to 20 W·mm⁻² without any sign of saturation, reaching a maximum of 2500 lm. The findings indicate that biphasic 40 wt.% Al₂O₃-0.4at.% Ce:LuAG PCs have potential as high-flux, green-color converters for next-generation high-power laser lighting. Furthermore, a laser illumination prototype device incorporating 40 wt.% Al₂O₃-0.4at.% Ce:LuAG ceramic samples and a 10 W blue laser was constructed. This device emits white light with an illumination range exceeding 500 m, thereby demonstrating its potential applications in laser-driven lighting. Full article

(This article belongs to the Special Issue Advances in Novel Luminescent Materials)

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19 pages, 34526 KB

Open AccessArticle

Limiting PcV and Tribological Performance of Mechanical Seals with Hard–Hard and Soft–Hard Tribopairs Under Water Lubrication

by Xiaoming Ren, Hui Song, He Li, Yuanren Zhou, Muqing Li, Shihao Yang, Chenxi Liu, Yunxiang Lu, Xin Li, Nan Jiang and Kazuhito Nishimura

Materials 2026, 19(18), 3810; https://doi.org/10.3390/ma19183810 - 8 Sep 2026

Abstract

Water-lubricated seal interfaces are particularly vulnerable to fluid-film instability, which accelerates interfacial friction and wear and compromises the reliability and service life of underwater equipment. Here, a novel graphite-microcrystalline diamond (Graphite-MCD) soft–hard seal-face tribopair was proposed and systematically benchmarked against SiC-SiC and Graphite-SiC [...] Read more.

Water-lubricated seal interfaces are particularly vulnerable to fluid-film instability, which accelerates interfacial friction and wear and compromises the reliability and service life of underwater equipment. Here, a novel graphite-microcrystalline diamond (Graphite-MCD) soft–hard seal-face tribopair was proposed and systematically benchmarked against SiC-SiC and Graphite-SiC tribopairs under high-pressure water lubrication. Their sealing capacity, friction and wear behavior, and interfacial evolution were evaluated. The polished Graphite-MCD pair achieved the highest limiting PcV (90.73 MPa·m·s⁻¹) and the lowest wear rate, markedly outperforming the SiC-SiC and Graphite-SiC pairs. Multiscale interfacial characterization showed that the SiC-SiC pair failed primarily through adhesive instability after breakdown of the water film. Although the Graphite-SiC pair reduced interfacial shear resistance, sliding generated a continuous triboreaction layer accompanied by third-body wear. In contrast, the Graphite-MCD pair preserved interfacial structural integrity and suppressed the formation of an unstable continuous reaction layer and abundant abrasive debris. This behavior enabled a synergistic combination of a low-shear lubricating interface and a stiff load-bearing counterface. These results demonstrate that improving the limiting PcV of mechanical seals cannot be achieved by reducing the friction coefficient alone; rather, it requires simultaneous control of lubricity and interfacial stability. The findings provide a mechanistic basis for designing soft–hard tribopairs for high-pressure, water-lubricated mechanical seals. Full article

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27 pages, 25756 KB

Open AccessArticle

Study on the Residual Static and Dynamic Mechanical Properties of Rubber Concrete After Elevated Temperature

by Huidong Cao, Hao Niu, Xiufeng Wu, Jinli Wang, Qiao Zhang, Jianfeng Zhao and Yang Yu

Materials 2026, 19(17), 3809; https://doi.org/10.3390/ma19173809 - 7 Sep 2026

Abstract

To address the resource utilization of waste tires and the fire-safety concerns in engineering applications of rubber concrete (RC), this study systematically investigates the residual static and dynamic mechanical properties of RC after exposure to elevated temperatures and subsequent cooling to room temperature. [...] Read more.

To address the resource utilization of waste tires and the fire-safety concerns in engineering applications of rubber concrete (RC), this study systematically investigates the residual static and dynamic mechanical properties of RC after exposure to elevated temperatures and subsequent cooling to room temperature. Specimens are prepared by replacing fine aggregate with rubber particles at equal volume replacement ratios of 0%, 5%, 15%, and 30%. After undergoing gradient heating to target temperatures ranging from 20 °C to 300 °C, the specimens are naturally cooled to room temperature prior to testing. Subsequently, static compressive and splitting tensile tests, along with dynamic impact tests using a Split Hopkinson Pressure Bar (SHPB), are performed. These experiments are supplemented by scanning electron microscopy (SEM) to elucidate the microscale mechanisms. The results show that the residual static strength decreases monotonically with increasing rubber content and temperature. For the 30% rubber content mixture, the compressive strength decreased by approximately 40.6% from ambient temperature to 300 °C, and its strength is 64.6% lower than that of NC at 300 °C. Dynamic strength exhibits a pronounced strain-rate effect, with the strain-rate sensitivity of DIF being enhanced by higher rubber content. Energy dissipation increases substantially with strain rate; rubberized mixtures generally exhibit higher energy dissipation than NC at lower strain rates, though this effect becomes less evident at higher strain rates. These findings provide a theoretical foundation for the application of RC in complex thermo-mechanical loading scenarios, particularly in evaluating its post-fire residual load-bearing capacity. Full article

(This article belongs to the Section Mechanics of Materials)

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