Materials

17 pages, 1618 KB

Open AccessArticle

Mechanism and Modeling of Moisture-Dependent Dielectric Properties of Cement-Based Composites for Enhanced Ground Penetrating Radar Applications

by Tao Wang, Bei Zhang, Yanlong Gao, Xiao Wang and Di Wang

Materials 2026, 19(8), 1528; https://doi.org/10.3390/ma19081528 (registering DOI) - 10 Apr 2026

Abstract

The dielectric properties of cement-based composites (CBC) are highly sensitive to environmental humidity, which seriously restricts the quantitative interpretation accuracy of ground-penetrating radar (GPR) in the non-destructive testing of cement concrete pavement. In view of the lack of targeted prediction models due to [...] Read more.

The dielectric properties of cement-based composites (CBC) are highly sensitive to environmental humidity, which seriously restricts the quantitative interpretation accuracy of ground-penetrating radar (GPR) in the non-destructive testing of cement concrete pavement. In view of the lack of targeted prediction models due to the unclear mechanism of humidity influence in existing research, the core innovations of this study are: (1) the synergistic mechanism of water vapor dipole polarization and adsorbed water multi-layer polarization is clarified, revealing the intrinsic reason for the accelerated growth of permittivity in the high humidity range; (2) the constructed four-component dielectric model of “cement mortar–aggregate–water vapor–adsorbed water” achieves high-precision prediction within the range of 50~100% RH (R² > 0.94, relative error < 5%), and shows good predictive ability within the test scope of this study; (3) a GPR humidity correction protocol based on the model is proposed, which can effectively improve the accuracy of nondestructive testing of cement concrete structures. In this study, CBC samples with water–cement ratios of 0.4~0.6 were prepared using P.O 32.5/P.O 42.5 cement and limestone aggregate. Under the conditions of 20 ± 0.5 °C, relative humidity (RH) of 50~100%, and 2 GHz (common GPR frequency), the permittivity was measured using an Agilent P5001A network analyzer to verify the model. The results show that the permittivity increases monotonically with humidity, and the growth rate in the high humidity range (70~100%) is 2.2 times that of the low humidity range (50~70%); The higher the water–cement ratio, the shorter the age, and the lower the cement strength grade, the stronger the humidity sensitivity of CBC dielectric properties. This model provides a reliable humidity correction tool for GPR detection, and significantly improves the accuracy of nondestructive evaluation of cement concrete structures. Full article

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

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24 pages, 10141 KB

Open AccessReview

Recent Advances in the Fabrication of High-Performance Polypropylene Micro-Nano Composites via Supercritical Foaming

by Xin Pan, Gang Wang, Faqi Zhan, Yuehong Zheng, Mengyao Dong, Peiqing La, Kun Li, Xiaoli Zhang and Jingbo Chen

Materials 2026, 19(8), 1527; https://doi.org/10.3390/ma19081527 (registering DOI) - 10 Apr 2026

Abstract

Against the backdrop of the global trends toward lightweighting, multi-functionalization, and greening of materials, polypropylene (PP) has been extensively applied owing to its advantages of low density and low cost. However, its inferior foaming performance fails to meet high-end application requirements, which is [...] Read more.

Against the backdrop of the global trends toward lightweighting, multi-functionalization, and greening of materials, polypropylene (PP) has been extensively applied owing to its advantages of low density and low cost. However, its inferior foaming performance fails to meet high-end application requirements, which is primarily attributed to its low melt strength and restricted crystallization behavior. In this paper, the five-dimensional selection mechanism and classification of components for PP micro/nanocomposites fabricated via supercritical foaming are systematically summarized. The regulatory effects of micro/nano additives on the crystallization, rheological properties, and foaming behavior of PP are quantitatively analyzed. The parameter optimization windows of three foaming processes, namely batch foaming, extrusion foaming, and injection foaming, are integrated (e.g., a foaming temperature of 150–170 °C and a saturation pressure of 8–20 MPa). Additionally, the application progress of PP micro/nanocomposite foams in fields such as automotive lightweighting (with a weight reduction rate of 64.29%) and building thermal insulation (with a thermal conductivity as low as 29 mW/(m·K)) is outlined. The core novel insight of this work lies in clarifying the unified mechanism of crystal refinement induced by reinforcing agents with different geometric morphologies, which is dominated by the synergy between heterogeneous nucleation and steric hindrance. This finding provides theoretical and technical guidelines for the industrial-scale preparation of high-performance PP foams. Full article

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13 pages, 6391 KB

Open AccessArticle

Microstructure Evolution and Mechanical Properties of Al_0.5Cr_0.9FeNi_2.5V_0.2 High-Entropy Alloy Fabricated by Binder Jetting 3D Printing and Vacuum Sintering

by Dezhi Zhu, Jinchuan Peng, Yongchi Wu, Xiaohui Qin, Xiaodong Wang, Qi Yang, Xi Huang, Guanghui Xu and Erlei Li

Materials 2026, 19(8), 1526; https://doi.org/10.3390/ma19081526 (registering DOI) - 10 Apr 2026

Abstract

Binder Jetting 3D Printing (BJ3DP) offers an effective pathway for the rapid fabrication of complex high-entropy alloy (HEA) components. In this study, the macroscopic characteristics, microstructural evolution and mechanical properties of Al_0.5Cr_0.9FeNi_2.5V_0.2 HEA green parts prepared [...] Read more.

Binder Jetting 3D Printing (BJ3DP) offers an effective pathway for the rapid fabrication of complex high-entropy alloy (HEA) components. In this study, the macroscopic characteristics, microstructural evolution and mechanical properties of Al_0.5Cr_0.9FeNi_2.5V_0.2 HEA green parts prepared via BJ3DP were investigated under various sintering conditions. Results showed that the relative density of the sintered parts increased significantly with temperature, transitioning from a low density (<90%) at 1300–1330 °C to near-fully dense (~98%) at 1340–1350 °C. Consequently, the mechanical properties were remarkably improved. The yield strength (σ_0.2) increased from 300 MPa to 710 MPa (a 136% increase), and the ultimate tensile strength (σ_b) rose from 310 MPa to 780 MPa (a 148% increase) as sintering temperature rose from 1300 °C to 1350 °C. Microstructural analysis revealed that at lower sintering temperatures, the alloy exhibited high porosity and a non-coherent structure composed of an FCC matrix and Cr-rich BCC phase, with Al/Ni intermetallic compounds distributed around pores. Conversely, at the final sintering stage, pore closure was achieved, and a coherent structure consisting of an FCC matrix and scale-like L1₂ precipitates was formed. Optimal mechanical properties (tensile strength ≥ 700 MPa) were achieved when sintering at 1340 °C, primarily attributed to densification and precipitation strengthening. Full article

(This article belongs to the Special Issue High-Entropy Alloys and Composite Materials: Preparation, Processing, and Performance)

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14 pages, 2318 KB

Open AccessArticle

A Flexible Wearable Data Glove Based on Hybrid Fiber-Optic Sensing for Hand Motion Monitoring

by Jing Li, Xiangting Hou, Ke Du, Huiying Piao and Cheng Li

Materials 2026, 19(8), 1525; https://doi.org/10.3390/ma19081525 - 10 Apr 2026

Abstract

Wearable data gloves often suffer from electromagnetic interference, insufficient substrate stability, and limited capability for multi-degree-of-freedom motion measurement. To address these limitations, a flexible glove incorporating a hybrid POF-FBG sensing scheme was designed and fabricated. Plastic optical fibers (POFs) were side-polished and patterned [...] Read more.

Wearable data gloves often suffer from electromagnetic interference, insufficient substrate stability, and limited capability for multi-degree-of-freedom motion measurement. To address these limitations, a flexible glove incorporating a hybrid POF-FBG sensing scheme was designed and fabricated. Plastic optical fibers (POFs) were side-polished and patterned with long-period gratings to improve sensitivity to wrist flexion-extension and abduction-adduction. Then fiber Bragg gratings (FBGs) were embedded in a polydimethylsiloxane substrate and encapsulated using thermoplastic polyurethane fixtures to reduce the influence of skin stretching and improve measurement accuracy of finger-joint angle. Moreover, a thermoplastic polyurethane skeleton with an adaptive sliding-rail structure was 3D printed to maintain the stability of the sensor placement at the joints. Experimental results demonstrated the mean absolute errors of 4.06°, 1.38° and 1.70° for wrist flexion-extension, abduction-adduction and finger-joint bending, respectively, along with excellent gesture classification using a support vector machine algorithm, which indicates great potential in virtual reality interaction and hand rehabilitation applications. Full article

(This article belongs to the Special Issue Advances in Optical Fiber Materials and Their Applications)

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23 pages, 7015 KB

Open AccessArticle

Monitoring Hydrogen-Induced Cracking in Tensile Wires of Flexible Pipes by Acoustic Emission Technique

by Kaíque do Rosário Oliveira, Sergio Luis Gonzalez Assias, Merlin Cristina Elaine Bandeira, Davi Ferreira de Oliveira, Hector Guillermo Kotik and Cesar Giron Camerini

Materials 2026, 19(8), 1524; https://doi.org/10.3390/ma19081524 (registering DOI) - 10 Apr 2026

Abstract

This study explored the continuous monitoring of hydrogen-induced cracking (HIC) in high-strength steel tension wires used in metal-based flexible pipes, exposed to a H₂S-saturated aqueous environment, using acoustic emission (AE) techniques. Armor wire samples were subjected to sour conditions under controlled [...] Read more.

This study explored the continuous monitoring of hydrogen-induced cracking (HIC) in high-strength steel tension wires used in metal-based flexible pipes, exposed to a H₂S-saturated aqueous environment, using acoustic emission (AE) techniques. Armor wire samples were subjected to sour conditions under controlled environments for 24 and 96 h. To reinforce and validate the AE findings, a comprehensive characterization was performed, including X-ray microtomography, optical microscopy, and scanning electron microscopy. The experimental results demonstrated that AE techniques effectively monitored the evolution of HIC damage in the armor wire samples, enabling the identification of distinct damage stages and cracking phenomena. These findings confirm that AE can serve as a valuable complementary tool during HIC testing, optimizing test duration and providing insights into the kinetics of the cracking process. Full article

(This article belongs to the Section Metals and Alloys)

14 pages, 820 KB

Open AccessArticle

Effect of Simulated Toothbrushing on Surface Roughness, Color Stability, and Gloss of Two Single-Shade Composite Resins

by Zeynep Hale Keles, Vasfiye Isik and Soner Sismanoglu

Materials 2026, 19(8), 1523; https://doi.org/10.3390/ma19081523 - 10 Apr 2026

Abstract

This in vitro study evaluated and compared the surface roughness, color stability, and gloss of two single-shade composite resins after simulated toothbrushing, and investigated the correlations among these parameters. Twenty disk-shaped specimens (n = 10 per group) were prepared from two single-shade [...] Read more.

This in vitro study evaluated and compared the surface roughness, color stability, and gloss of two single-shade composite resins after simulated toothbrushing, and investigated the correlations among these parameters. Twenty disk-shaped specimens (n = 10 per group) were prepared from two single-shade composite resins (Material A and Group B) and subjected to simulated toothbrushing up to 15,000 cycles. Surface roughness (Ra) was measured at baseline and after 5000, 10,000, and 15,000 cycles. Color parameters (CIE Lab*) and gloss (60°) were measured at baseline and after 15,000 cycles. Color change was calculated using the CIEDE2000 formula (ΔE₀₀). Data were analyzed using two-way mixed ANOVA, t-tests, and Pearson correlation analysis (α = 0.05). Both materials showed progressive increases in surface roughness. Material B exhibited significantly higher Ra values than Material A from 10,000 cycles onward (p < 0.01). After 15,000 cycles, Material B demonstrated significantly greater color change (ΔE₀₀: 2.21 ± 0.18 vs. 1.48 ± 0.13; p < 0.001), exceeding the acceptability threshold (ΔE₀₀ = 1.8), while Material A remained clinically acceptable. Material B also showed greater gloss reduction (60% vs. 35%; p < 0.001). Strong correlations were found between surface roughness and both gloss change (r = −0.919) and color change (r = 0.826). Material A demonstrated greater resistance to surface degradation and better preservation of optical properties compared to Material B. Surface roughness was identified as the common underlying factor driving both color instability and gloss reduction in single-shade composites. Clinical Significance: Not all single-shade composites perform equally under mechanical aging. Clinicians should consider the filler technology and long-term surface stability when selecting single-shade composite resins for clinical use. Full article

(This article belongs to the Section Advanced Composites)

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13 pages, 3809 KB

Open AccessArticle

Novel Ti6Al4V Surface Treatment for Subperiosteal Dental Implants (Part II): Matrix Deposition and Osteogenic Markers

by Valentina Schiavoni, Lucia Memé, Giovanni Tossetta, Daniela Marzioni, Fabrizio Bambini, Andrea Frontini, Chiara Santoni, Paolo Moretti, Arianna Vignini, Roberto Campagna and Eleonora Salvolini

Materials 2026, 19(8), 1522; https://doi.org/10.3390/ma19081522 - 10 Apr 2026

Abstract

In a previous study, we demonstrated that a novel surface treatment applied to laser-melted Ti6Al4V substrates supports osteoblast-like cell adhesion, proliferation, and the activation of early osteogenic pathways. Building on these preliminary findings, the present work aimed to further investigate the ability of [...] Read more.

In a previous study, we demonstrated that a novel surface treatment applied to laser-melted Ti6Al4V substrates supports osteoblast-like cell adhesion, proliferation, and the activation of early osteogenic pathways. Building on these preliminary findings, the present work aimed to further investigate the ability of the same surface to promote extracellular matrix (ECM) deposition, organization, and osteogenic maturation, which are critical events for the establishment of a stable bone–implant interface in subperiosteal dental implants. Human osteoblast-like MG-63 cells were cultured on Ti6Al4V discs subjected to different surface treatments, including a proprietary surface modification (ATcs) specifically designed for subperiosteal applications. ECM formation and maturation were evaluated through scanning electron microscopy coupled with energy-dispersive spectroscopy, immunofluorescence, and semiquantitative analyses of osteogenic markers type I collagen (COL1A1), secreted protein acidic and rich in cysteine (SPARC), and dentin matrix protein 1 (DMP1) through Western blotting. The results showed that, while all tested surfaces supported cell adhesion, the ATcs surface promoted a distinct osteogenic profile characterized by enhanced DMP1 expression, organized collagen deposition, and the formation of calcium–phosphate–rich mineralized structures. Compared to surfaces that primarily stimulated cell proliferation or early matrix production, ATcs appeared to favour progression toward late-stage osteogenic maturation and matrix mineralization. Taken together, these findings extend our previous observations and indicate that this novel surface treatment not only supports osteoblast viability and early differentiation but also promotes extracellular matrix maturation, a key prerequisite for effective osseointegration. Although further in vivo studies are required, the present data provide additional biological rationale for the use of ATcs-treated Ti6Al4V surfaces in next-generation custom-made subperiosteal implant designs. Full article

(This article belongs to the Special Issue Advanced Dental Materials: From Design to Application, Third Edition)

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16 pages, 2274 KB

Open AccessArticle

Effect of Hydrogen Charging Current Density on Hydrogen Trapping Behavior in Cu6.01Ni2.7Mn Steel

by Wenxue Wang, Jing Guo, Jian Zhang and Lili Li

Materials 2026, 19(8), 1521; https://doi.org/10.3390/ma19081521 - 10 Apr 2026

Abstract

Copper-containing steel is widely used in ship plates and other marine engineering fields due to its excellent mechanical properties and good weldability. However, in hydrogen-containing media environments, ship plate steel is prone to hydrogen embrittlement during service. Existing research primarily focuses on steel [...] Read more.

Copper-containing steel is widely used in ship plates and other marine engineering fields due to its excellent mechanical properties and good weldability. However, in hydrogen-containing media environments, ship plate steel is prone to hydrogen embrittlement during service. Existing research primarily focuses on steel grades with copper content below 3 wt.%, while the diffusion and trapping behavior of hydrogen in ultra-high-copper steel with copper content exceeding 3 wt.% remains unclear. Therefore, this study designed an ultra-high-copper-content steel with a copper content of 6.01% and investigated the diffusion behavior of hydrogen in the test steel under different hydrogen charging current densities through microstructure characterization, slow strain rate tensile testing, electrochemical hydrogen permeation, and internal friction tests. The results indicate that with an increase in hydrogen charging current density, accompanied by a slight degradation in mechanical properties, the irreversible hydrogen trap density increases by 50.7%. A large number of microstructures, such as phase boundaries, grain boundaries, and dislocations, have formed inside the material, which have reversible trapping effects on hydrogen, effectively suppressing the migration of hydrogen in the crystal structure and reducing the embrittlement phenomenon caused by hydrogen. This study expands the application potential of copper-containing steel in the field of ocean engineering, providing an important reference for the future development of high-strength, hydrogen embrittlement-resistant copper steel with ultra-high copper content. Full article

(This article belongs to the Section Corrosion)

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Graphical abstract

11 pages, 3120 KB

Open AccessCommunication

(FeNiMnMgCuCo)₃O₄ High-Entropy Cathode for Zinc-Ion Batteries

by Ningning Dong, Huanhuan Cui, Yuncheng Cai and Renzhi Jiang

Materials 2026, 19(8), 1520; https://doi.org/10.3390/ma19081520 - 10 Apr 2026

Abstract

As a result of the high safety, low cost, and environmental benignity, aqueous zinc-ion batteries are regarded as one of the most promising candidates for next-generation large-scale energy storage systems. However, their further development is constrained by performance bottlenecks in existing cathode materials, [...] Read more.

As a result of the high safety, low cost, and environmental benignity, aqueous zinc-ion batteries are regarded as one of the most promising candidates for next-generation large-scale energy storage systems. However, their further development is constrained by performance bottlenecks in existing cathode materials, including capacity, cycle life, and reaction kinetics. In this study, a high-entropy design strategy is employed to synthesize the metal oxide (FeNiMnMgCuCo)₃O₄ with a cubic spinel structure, and its electrochemical performance as a cathode for zinc-ion batteries is systematically evaluated. The prepared (FeNiMnMgCuCo)₃O₄ high-entropy cathode exhibits high reversible capacity (341.3 mA h g⁻¹ at 0.1 A g⁻¹) and remarkable long-term cycling stability (76.1% retention after 1000 cycles at 3 A g⁻¹). This work not only demonstrates a high-entropy cathode material with practical potential but also provides new research insights for optimizing zinc-ion storage performance through composition design and entropy regulation. Full article

(This article belongs to the Special Issue Advanced Electrode Materials for Batteries: Design and Performance)

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14 pages, 1699 KB

Open AccessArticle

Influence of Beverage Immersion and Repolishing on the Color Stability of CAD/CAM Restorative Materials: An In Vitro Study

by Umut Dağdeviren, Mine Betül Üçtaşlı and İrem Köklü Dağdeviren

Materials 2026, 19(8), 1519; https://doi.org/10.3390/ma19081519 - 10 Apr 2026

Abstract

Long-term aesthetic success in dentistry largely depends on the color stability of restorative materials. This study investigated the color changes (ΔE₀₀) of resin nanoceramic and lithium disilicate ceramic restorative materials used in computer-aided design and computer-aided manufacturing (CAD/CAM) systems following beverage [...] Read more.

Long-term aesthetic success in dentistry largely depends on the color stability of restorative materials. This study investigated the color changes (ΔE₀₀) of resin nanoceramic and lithium disilicate ceramic restorative materials used in computer-aided design and computer-aided manufacturing (CAD/CAM) systems following beverage immersion and after repolishing. One hundred specimens were prepared from lithium disilicate (Initial LiSi Block) and resin nanoceramic (Cerasmart), and polished. The specimens were divided into ten groups according to material and beverage type (n = 10) and immersed in distilled water, cola, tea, coffee, and turnip juice at 37 °C for 3 months. Color values were recorded at baseline, 1 week, 1 month, and 3 months, and after repolishing. ∆E₀₀ values were calculated using the CIEDE2000 color difference formula. Data were analyzed using three-way repeated measures ANOVA and post hoc Tukey and Bonferroni tests (α = 0.05). Material type, beverage type, and immersion time significantly affected color stability (p < 0.05). The highest ∆E₀₀ observed in the resin nanoceramic–tea group at 3 months (ΔE₀₀ = 11.39 ± 1.76). Lithium disilicate demonstrated better color stability. After repolishing, all ΔE₀₀ values were below the clinically acceptable limit (ΔE₀₀ ≤ 1.8). Repolishing may help maintain the long-term aesthetic success of dental restorations in the oral environment. Full article

(This article belongs to the Special Issue Recent Research in Restorative Dental Materials (2nd Edition))

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6 pages, 192 KB

Open AccessEditorial

Corrosion and Formation of Surface Films on Metals and Alloys

by Johannes Herman Potgieter, David J. Whitefield and Michael O. Bodunrin

Materials 2026, 19(8), 1518; https://doi.org/10.3390/ma19081518 - 10 Apr 2026

Abstract

Corrosion is a multibillion-dollar material degradation issue that affects process industries, transport infrastructure, as well as construction and building activities all over the world [...] Full article

(This article belongs to the Special Issue Corrosion and Formation of Surface Films on Metals and Alloys)

27 pages, 8224 KB

Open AccessArticle

Structure and Properties of Foam Concrete and Fiber-Reinforced Foam Concrete Produced Using a Complex Nanomodifier Based on Industrial Waste

by Diana M. Shakhalieva, Evgenii M. Shcherban’, Sergey A. Stel’makh, Levon R. Mailyan, Andrei Chernil’nik, Natalya Shcherban’, Alexandr Evtushenko and Alexey N. Beskopylny

Materials 2026, 19(8), 1517; https://doi.org/10.3390/ma19081517 - 10 Apr 2026

Abstract

Foam concrete and fiber-reinforced foam concrete are promising building materials for sustainable and energy-efficient construction. Improving the environmental performance of cellular composites through the use of industrial waste and additives based on them is highly relevant. This study intends to create a novel [...] Read more.

Foam concrete and fiber-reinforced foam concrete are promising building materials for sustainable and energy-efficient construction. Improving the environmental performance of cellular composites through the use of industrial waste and additives based on them is highly relevant. This study intends to create a novel complex nanomodifying additive (CNA) from industrial waste and nanomaterials, alongside new eco-friendly foam concrete (FC) and fiber-reinforced foam concrete (FFC) mixes incorporating CNA and polypropylene fiber (PF). Experimental studies yielded the optimal CNA formulation and described a method for its preparation. The test results indicate that FC’s properties are enhanced by CNA. The properties were best in the FC that was modified with 10% CNA. The FC control composition was surpassed by a 25.5% increase in compressive strength and a 23.1% increase in flexural strength, with a 9.5% reduction in thermal conductivity. Dispersed PF reinforcement also positively impacts the properties of FFCs with CNA, and the combined modification of 10% CNA and 1.2% PF provides maximum increases in compressive and flexural strength, amounting to 43.1% and 102.2%, respectively, and a 16.9% reduction in thermal conductivity. A microstructural analysis of the cellular composites confirms the feasibility of the tested formulation solutions. The FFCs, when modified by CNA and PF, display a homogeneous cellular structure, and the interpore zones contain multiple clusters of calcium silicate hydrate. Using CNA in the production of FC and FFCs will reduce cement consumption and improve their environmental friendliness. Full article

(This article belongs to the Special Issue Multi-Scale Study on Strength and Structural Stability of Low-Carbon Construction Materials)

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27 pages, 3650 KB

Open AccessArticle

Effect of the Physical and Chemical Characteristics of Polycarboxylate Ether Superplasticizers on the Spreading of Calcined Clays with Different Metakaolinite Contents Suspended in Synthetic Cement Pore Solution

by Suylan Matias Cruz, Ítalo Ribeiro Gonçalves Lima, Maria José Souza Serafim, Jorge Iván Tobón and João Henrique Silva Rêgo

Materials 2026, 19(8), 1516; https://doi.org/10.3390/ma19081516 - 10 Apr 2026

Abstract

This study investigates the influence of the physical and chemical characteristics of three polycarboxylate ether (PCE) superplasticizers—differing in main-chain length, side-chain density, and dispersing-to-stabilizing polymer ratio (75:25, 50:50, and 25:75)—on the dispersion of calcined clays with varying metakaolinite contents (30.04–74.91 wt%) in synthetic [...] Read more.

This study investigates the influence of the physical and chemical characteristics of three polycarboxylate ether (PCE) superplasticizers—differing in main-chain length, side-chain density, and dispersing-to-stabilizing polymer ratio (75:25, 50:50, and 25:75)—on the dispersion of calcined clays with varying metakaolinite contents (30.04–74.91 wt%) in synthetic cement pore solution (SCPS). Clays were characterized by XRF, XRD, TGA, FTIR, BET, Blaine fineness, and particle size distribution; PCEs were characterized by FTIR, ¹H NMR, GPC, and zeta potential. Dispersion was assessed via mini-slump tests for water demand, PCE dosage to achieve 260 ± 5 mm spread, and slump retention over 120 min, quantified by a normalized spread retention index (SR₁₂₀). Results revealed that clays with a higher metakaolinite content (58.45–74.91 wt%) and Blaine fineness (up to 13.116 m²/g) required two times higher PCE dosages and exhibited greater water demand due to enhanced surface reactivity and Ca²⁺/carboxylate affinity. Slump retention depended on PCE–clay compatibility: at a low metakaolinite content (30.04 wt%), all PCEs yielded SR₁₂₀ ≈ 1; at higher contents, dispersing-rich PCEs (e.g., 75:25 ratio) sustained superior retention (SR₁₂₀ > 1 in intermediate cases), while stabilizing-rich variants showed rapid loss. Zeta potential values remained close to zero due to the high ionic strength of the SCPS, indicating that electrostatic interactions play only a secondary role in the dispersion process, while steric effects govern the performance of the investigated PCEs. Overall, optimal PCE selection requires matching polymer architecture to clay reactivity for effective dispersion and fluidity retention in sustainable calcined clay systems. Full article

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

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15 pages, 4726 KB

Open AccessArticle

Multi-Level In Situ Surface Modification of Electrospun Tetragonal BaTiO₃ Nanofibers for High-Performance Flexible Piezoelectric Energy Harvesters

by Zijin Meng, Quanyao Zhu, Qingqing Zhang and Huajun Sun

Materials 2026, 19(8), 1515; https://doi.org/10.3390/ma19081515 - 9 Apr 2026

Abstract

The practical application of inorganic ferroelectric fillers in flexible piezoelectric composites is critically constrained by low polarization efficiency and severe interfacial incompatibility with polymer matrices. Herein, we report a multi-level in situ surface modification strategy that simultaneously addresses both limitations. High-purity one-dimensional tetragonal [...] Read more.

The practical application of inorganic ferroelectric fillers in flexible piezoelectric composites is critically constrained by low polarization efficiency and severe interfacial incompatibility with polymer matrices. Herein, we report a multi-level in situ surface modification strategy that simultaneously addresses both limitations. High-purity one-dimensional tetragonal barium titanate nanofibers (BTO NFs) are first synthesized via sol–gel electrospinning combined with a two-step gradient annealing process, which precisely controls phase evolution and preserves structural continuity. To overcome the detrimental acid-induced degradation of BTO NFs during functionalization, a polydopamine (PDA) buffer layer is first conformally coated, followed by the liquid-phase deposition of a conductive polypyrrole (PPy) shell, forming a robust core–shell PPy@PBT NFs architecture. Incorporating only 4 wt% of these multifunctional fillers into a poly(vinylidene fluoride) (PVDF) matrix yields a dramatic enhancement in electromechanical performance. The resulting flexible piezoelectric energy harvesters achieve a piezoelectric coefficient (d₃₃) of 28.7 pC/N, an output voltage of 13 V, and an output current of 0.7 μA, representing substantial improvements over unmodified filler systems. This synergistic enhancement originates from the PDA-mediated interfacial stress transfer and the PPy-induced Maxwell–Wagner polarization intensification, establishing a robust and generalizable paradigm for high-performance flexible piezoelectric composites in self-powered wearable electronics. Full article

(This article belongs to the Topic Advanced Composite Materials)

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22 pages, 5546 KB

Open AccessArticle

Evaluation of Moisture Damage in Asphalt Mixtures Under Dynamic Water Pressure Using 3D Laser Scanning

by Wentao Wang, Hua Rong, Yinghao Miao and Linbing Wang

Materials 2026, 19(8), 1514; https://doi.org/10.3390/ma19081514 - 9 Apr 2026

Abstract

Under continuous erosion of dynamic water pressure generated by vehicle–water–pavement coupling interaction, asphalt mixture will gradually deteriorate and severe moisture damage finally emerges. The fine aggregate mixture (FAM) component is notably eroded and stripped, while the aggregate component even cracks sometimes. Sufficient attention [...] Read more.

Under continuous erosion of dynamic water pressure generated by vehicle–water–pavement coupling interaction, asphalt mixture will gradually deteriorate and severe moisture damage finally emerges. The fine aggregate mixture (FAM) component is notably eroded and stripped, while the aggregate component even cracks sometimes. Sufficient attention has not been paid to these critical phenomena. This study employed the 3D laser scanning technique to detect changes in surface roughness of the asphalt mixture before and after it was eroded by dynamic water pressure. The degree of erosion of the asphalt mixture, FAM component, and aggregate component were thereby evaluated. The influences of experimental parameters such as water temperature and pore water pressure magnitude, as well as variable parameters including lithology and asphalt type, were also taken into account. By integrating the detection of physical and mechanical properties evolution of aggregates, the mechanism of moisture damage was comprehensively illustrated from the perspectives of both components of FAM and aggregate. The findings revealed that the 3D laser scanning technique could clearly detect and quantitatively assess the morphological changes on the asphalt mixture surface after been eroded in dynamic water pressure. Both types of asphalt mixtures exhibited varying degrees of erosion and wear, and obvious increases in surface unevenness were observed in each case. Variations in either temperature or pore water pressure magnitude showed limited influence on moisture damage in basalt-based asphalt mixture. In contrast, moisture damage sustained by limestone-based asphalt mixture was notably sensitive to temperature changes but remained largely insensitive to fluctuations in pore water pressure magnitude. The increase in surface roughness of asphalt mixture was primarily attributed to the scouring action of dynamic water pressure, which removed the FAM component surrounding coarse aggregate particles. Degradation in coarse aggregate particles would lead to the deterioration of the entire asphalt mixture. The compatibility between the stripping rate of FAM component and the deterioration rate of coarse aggregate governed the macroscopic manifestation of overall moisture damage in the asphalt mixture. Full article

(This article belongs to the Special Issue Sustainability in Asphalt, Concrete and Pavement Materials: Design, Performance, and Characterization)

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20 pages, 6493 KB

Open AccessArticle

Tribocorrosion Behavior of Mg Alloys on Sliding Friction in Hank’s Balanced Salt Solution

by Eri Miura, Chihiro Shiraishi and Sachiko Hiromoto

Materials 2026, 19(8), 1513; https://doi.org/10.3390/ma19081513 - 9 Apr 2026

Abstract

The tribocorrosion behavior of AZ31 and WE43 was investigated during sliding wear tests in Hank’s balanced salt solution (HBSS) and pure water. While wear volume increased monotonically with load in air and water, HBSS exhibited a distinct non-monotonic trend; the maximum material loss [...] Read more.

The tribocorrosion behavior of AZ31 and WE43 was investigated during sliding wear tests in Hank’s balanced salt solution (HBSS) and pure water. While wear volume increased monotonically with load in air and water, HBSS exhibited a distinct non-monotonic trend; the maximum material loss occurred at the minimum load (0.98 N) and decreased at 2.94 N before rising again. This indicates that at low loads, degradation is primarily driven by accelerated chemical dissolution (tribocorrosion) rather than by purely mechanical abrasion. The magnitude of wear followed the order [HBSS] > [air] > [water] in the low-load range (0.98–1.96 N), whereas it shifted to [air] > [HBSS] > [water] in the high-load range (2.94–5.88 N). A comparison of the wear rate of the alloys shows that the wear rate in HBSS differs from that in water, depending on the hardness of the substrate, similar to conditions in air. Notably, the specific wear rate decreased as test duration increased under low loads, further suggesting that corrosion-induced volume loss significantly outweighs mechanical wear in this regime. The static corrosion test revealed that volume loss during tribocorrosion was higher than that under static corrosion conditions. While the deposition of corrosion products affected net volume loss, chemical dissolution remained the primary driver of the observed wear trends at low loads. Electrochemical data from anodic polarization curves confirmed that the specimen tested under a 0.98 N load exhibited lower corrosion resistance. Mechanistically, it was suggested that Cl⁻ ions contributed to the overall increase in wear, while NaHCO₃ specifically contributed to the increase in wear in the low-load range. Full article

(This article belongs to the Special Issue Surface Modifications and Coatings for Metallic Materials)

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13 pages, 4901 KB

Open AccessArticle

Cold Sintering Technology as a Friendly and Sustainable Way of Producing Ceramic Materials from Recycled Waste

by Gyorgy Thalmaier, Nicoleta Cobîrzan, Traian Florin Marinca and Mircea Nasui

Materials 2026, 19(8), 1512; https://doi.org/10.3390/ma19081512 - 9 Apr 2026

Abstract

This paper presents a new ceramic building material produced by the cold sintering process (CSP), as a greener and cleaner technology compared to conventional ones. The ceramic composites were made from recycled clay bricks (RCBs), a byproduct resulting from construction and demolition and [...] Read more.

This paper presents a new ceramic building material produced by the cold sintering process (CSP), as a greener and cleaner technology compared to conventional ones. The ceramic composites were made from recycled clay bricks (RCBs), a byproduct resulting from construction and demolition and waterglass (WG) as a liquid solvent, pressed at 400 MPa and sintered at a temperature of 150–200 °C. After the samples were produced, their structure and physical and mechanical properties were investigated. The internal morphology of samples shows a homogeneous structure with a low porosity (up to 3%). The compressive strength of ceramic building material produced by the CSP was up to 211 MPa, considerably higher than the reference sample whose value was 45 Mpa. This high strength is due to the internal structure of the ceramic composed of a tough amorphous phase that acts like a binder holding together the powder particles and closing most of the porosity inside the material. Full article

(This article belongs to the Section Metals and Alloys)

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24 pages, 2360 KB

Open AccessReview

Research Progress on the Influence of Surface Treatment Techniques on Fatigue Properties of Titanium Alloys

by Baicheng Liu, Hongliang Zhang, Xugang Wang, Yubao Li, Shenghan Li, Xue Cui, Yurii Luhovskyi and Zhisheng Nong

Materials 2026, 19(8), 1511; https://doi.org/10.3390/ma19081511 - 9 Apr 2026

Abstract

Titanium alloys exhibit exceptional strength-to-density ratios, high hardness, and outstanding resistance to elevated temperatures, making them indispensable structural materials in aerospace engineering, marine construction, and biomedical applications. In aerospace systems specifically, fatigue failure represents the predominant failure mode for titanium alloy components. This [...] Read more.

Titanium alloys exhibit exceptional strength-to-density ratios, high hardness, and outstanding resistance to elevated temperatures, making them indispensable structural materials in aerospace engineering, marine construction, and biomedical applications. In aerospace systems specifically, fatigue failure represents the predominant failure mode for titanium alloy components. This review systematically examines prevalent surface treatment techniques for titanium alloys—including shot peening, ultrasonic rolling treatment, hot isostatic pressing (HIP), physical vapor deposition (PVD), micro-arc oxidation (MAO), and thermal spray processes—and critically evaluates their respective effects on fatigue performance. The underlying mechanisms of each technique are concisely outlined, with emphasis on stress state evolution, near-surface microstructural refinement, and interfacial integrity. Building upon the characteristic surface-dominated fatigue fracture behavior of titanium alloys, this work focuses on how coating composition, architecture (e.g., graded, multilayer, or nanocomposite designs), and interfacial bonding strength govern fatigue resistance. A unified analysis is presented on the distinct yet complementary roles of substrate deformation strengthening (e.g., residual compression, grain refinement) and coating-mediated protection (e.g., barrier function, crack deflection, stress redistribution) during fatigue crack initiation and propagation. Key determinants of fatigue performance, including residual stress distribution, coating/substrate adhesion, thermal mismatch, and environmental degradation susceptibility, are rigorously assessed. Finally, emerging research frontiers are identified, including intelligent process–structure–property mapping, in situ monitoring of fatigue damage at coated interfaces, and design of multifunctional gradient coatings that synergistically enhance strength, wear resistance, and fatigue endurance of titanium alloy components. Full article

(This article belongs to the Special Issue Advanced High-Performance Metals and Alloys: Microstructural Evolution, Mechanical Properties, and Strengthening Mechanisms)

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10 pages, 3125 KB

Open AccessCommunication

Numerical and Experimental Study on the Molten Pool Behavior and Magnetic Properties of Nano-Crystalline Alloy Ribbon Prepared by PlanarFlow Casting

by Lijun Li, Hongxin Ji, Jianliang Sun, Deren Li, Baisong Li and Jintao Yao

Materials 2026, 19(8), 1510; https://doi.org/10.3390/ma19081510 - 9 Apr 2026

Abstract

A 2D multiphase-flow coupling simulation model for preparing nanocrystalline ribbons using planar-flow casting (PFC) with a cooling roller was established. The influence of roller speed on molten pool characteristics, cooling-roller heat transfer, and ribbon thickness was analyzed. The effect of ribbon thickness on [...] Read more.

A 2D multiphase-flow coupling simulation model for preparing nanocrystalline ribbons using planar-flow casting (PFC) with a cooling roller was established. The influence of roller speed on molten pool characteristics, cooling-roller heat transfer, and ribbon thickness was analyzed. The effect of ribbon thickness on the total loss and permeability of the magnetic cores was investigated. The results indicate that the molten pool size decreased as the roller speed increased. At t = 5 ms, the maximum heat-transfer coefficient of the roller surface increased from 2.09 × 10⁶ W·m⁻²·K⁻¹ at 15 m/s to 2.6 × 10⁶ W·m⁻²·K⁻¹ at 24 m/s. The ribbon thickness decreased from 39.96 μm to 20.02 μm (a 49.9% reduction) as the roller speed increased from 18 m/s to 30 m/s. The total loss of the nanocrystalline magnetic cores increased with ribbon thickness, whereas their permeability increased as ribbon thickness decreased. At 100 kHz, the nanocrystalline magnetic core made of 10–12 μm ribbons exhibited a high permeability of 59,507. Full article

(This article belongs to the Section Metals and Alloys)

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