Materials

15 pages, 13311 KB

Open AccessArticle

Experimental Determination of Isothermal Sections in the Ni–Al–Cr–Ru Quaternary System: Implications for Ni-Based Superalloys and High-Entropy Alloys

by Jianping Huang, Dupei Ma, Zhi Li, Yan Liu, Ruihua Wang, Huayu Xiao and Qiang Zhang

Materials 2026, 19(8), 1669; https://doi.org/10.3390/ma19081669 (registering DOI) - 21 Apr 2026

Abstract

The phase equilibria of the Ni–Al–Cr–Ru quaternary system were systematically investigated using the equilibrated alloy method combined with scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). This study focuses on three key isothermal sections within the system: 55 at.% Al [...] Read more.

The phase equilibria of the Ni–Al–Cr–Ru quaternary system were systematically investigated using the equilibrated alloy method combined with scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). This study focuses on three key isothermal sections within the system: 55 at.% Al at 1423 K, 55 at.% Ni at 1173 K, and 60 at.% Ni at 1423 K. In the 55 at.% Al section at 1423 K, a four-phase equilibrium region comprising Bcc(Cr), β-(Ni,Ru)Al, Al₈Cr₅, and Al₂Ru, along with three three-phase regions, was identified. Complete mutual solubility between the NiAl and AlRu phases was achieved with approximately 10 at.% Cr. In the 55 at.% Ni section at 1173 K, two four-phase and seven three-phase equilibrium regions were observed. The addition of Cr was found to promote the emergence of the Fcc(Ni) + β-(Ni,Ru)Al + Ni₃Al three-phase region and the Fcc(Ni) + β-(Ni,Ru)Al two-phase region. Critically, Cr addition enabled complete solubility between the β₁ (NiAl) and β₂ (AlRu) phases even at 1173 K. For the 60 at.% Ni section at 1423 K, while no four-phase equilibrium was found, two three-phase regions—(Ni,Ru)Al + Hcp(Ru) + Fcc(Ni) and (Ni,Ru)Al + Ni₃Al + Fcc(Ni)—were confirmed. Notably, the (Ni,Ru)Al + Fcc(Ni) two-phase region exhibited a wide compositional range. This work provides essential experimental phase diagram data and insights for the design of Ni–Al–Cr–Ru-X high-entropy alloys and next-generation Ni-based superalloys. Full article

(This article belongs to the Special Issue Design, Preparation, and Microstructural Characterization of High Entropy Materials)

► Show Figures

Figure 1

19 pages, 6661 KB

Open AccessArticle

Synergistic Effects of Fiber Inclination, Geometry, and Thermal Treatment on Fe-SMA Fiber Pull-Out Resistance in High-Performance Concrete

by Jan Białasik, Wojciech Podraza, Dominika Samulczyk and Alireza Tabrizikahou

Materials 2026, 19(8), 1668; https://doi.org/10.3390/ma19081668 (registering DOI) - 21 Apr 2026

Abstract

Iron-based shape memory alloy (Fe-SMA) fibers can enhance cementitious composites through both crack bridging and thermally activated recovery stresses. Since fiber pull-out governs load transfer at the micro scale, understanding the combined effects of fiber geometry, inclination, and thermal treatment is essential. This [...] Read more.

Iron-based shape memory alloy (Fe-SMA) fibers can enhance cementitious composites through both crack bridging and thermally activated recovery stresses. Since fiber pull-out governs load transfer at the micro scale, understanding the combined effects of fiber geometry, inclination, and thermal treatment is essential. This study experimentally investigated the pull-out behavior of hooked-end Fe-SMA fibers embedded in high-performance concrete (HPC). A total of 54 ASTM C307-type briquette specimens were tested using single-hook (3D) and double-hook (4D) fibers at inclination angles of 60°, 75°, and 90° under ambient, 100 °C, and 200 °C conditions. Additional flexural, compressive, and direct tensile tests were conducted on plain HPC exposed to the same thermal regime. At ambient temperature, 4D fibers showed 50–70% higher peak pull-out forces than 3D fibers. Heating to 100 °C further increased pull-out resistance by about 6–17%, and the 4D-60-100 configuration achieved the highest performance. In contrast, exposure to 200 °C reduced pull-out resistance by about 5–12% below ambient values. Overall, a 60° inclination generally provided a better response, while 90° produced the lowest. The results confirm that moderate thermal activation combined with double-hook geometry is the most effective strategy for maximizing Fe-SMA fiber–matrix load transfer in HPC. Full article

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

► Show Figures

Figure 1

24 pages, 5026 KB

Open AccessArticle

Influence of Sintering and Heat Treatment on the Microstructure, Mechanical Properties, and Tribological Performance of AlTiN-Coated PM M42 High-Speed Steel

by Zijun Qi, Yi Chen, Ji Li, Yongde Huang, Qian Wang, Qi Wei, Xiaofeng Yang and Qiang Liu

Materials 2026, 19(8), 1667; https://doi.org/10.3390/ma19081667 (registering DOI) - 21 Apr 2026

Abstract

Preparing a highly wear-resistant AlTiN coating on a powder metallurgy (PM) M42 high-speed steel substrate is a key strategy to enhance tool performance and meet the demands of efficient machining. This study adopted a process route comprising substrate preparation, heat treatment regulation, and [...] Read more.

Preparing a highly wear-resistant AlTiN coating on a powder metallurgy (PM) M42 high-speed steel substrate is a key strategy to enhance tool performance and meet the demands of efficient machining. This study adopted a process route comprising substrate preparation, heat treatment regulation, and arc-PVD deposition of AlTiN coatings to systematically investigate the influence of sintering temperature (1130, 1160, and 1190 °C) and austenitizing time (1150 °C for 0, 15, 60, and 120 min) on the microstructure and mechanical properties of the substrate, as well as on the tribological performance of the AlTiN coatings. The results indicate that elevating the sintering temperature promotes densification of the matrix, with Vickers hardness increasing from 366 HV to 462 HV and bending strength (σ) increasing from 1064 MPa to 1310 MPa. The predominant carbide phases identified are MC, M₂C, and M₆C. During austenitizing, microstructural changes consistent with a progressive transformation from M₂C to MC and M₆C carbides were indicated by SEM and XRD analyses. Precipitation strengthening was most evident after 60 min, with hardness reaching 868 HV. In contrast, bending strength (σ) exhibited a progressive decline with increasing austenitizing time, decreasing from 1310 MPa to 1015 MPa after 120 min, illustrating a clear trade-off between hardness and toughness. The wear behavior of the coating is governed synergistically by substrate hardness, bending strength (σ), coating–substrate interfacial adhesion strength (L_C), and carbide phase transformation. Elevated substrate hardness enhances anti-wear performance; bending strength influences crack propagation and spallation tendency; and L_C determines the efficiency of interfacial load transfer. The carbide phase evolution appears to modulate the coating’s wear behavior by regulating both the microstructure and mechanical properties of the substrate. Among the six sample conditions evaluated, the A3 sample (sintered at 1190 °C and austenitized for 120 min) exhibited the lowest wear rate (2.38 × 10⁻⁶ mm³·N⁻¹·m⁻¹), demonstrating superior wear resistance. These findings provide a reference for process optimization and rational design of M42/AlTiN composite coating systems. Full article

(This article belongs to the Special Issue Advance in Metallurgical Process Engineering)

► Show Figures

Figure 1

23 pages, 8567 KB

Open AccessArticle

Processing of High-Quality WC-Inconel 625 Coating via DED

by Jingjing Wang, Nellian Alagu Subramaniam, Eddie Zhi En Tan and John Hock Lye Pang

Materials 2026, 19(8), 1666; https://doi.org/10.3390/ma19081666 (registering DOI) - 21 Apr 2026

Abstract

This study examines the effects of laser power (P), scanning speed (SS), and energy density (ED) on the microstructure and hardness of WC-reinforced Inconel 625 metallic matrix composite (MMC) coatings fabricated via a powder-based directed energy deposition (DED) process developed by Makino Asia [...] Read more.

This study examines the effects of laser power (P), scanning speed (SS), and energy density (ED) on the microstructure and hardness of WC-reinforced Inconel 625 metallic matrix composite (MMC) coatings fabricated via a powder-based directed energy deposition (DED) process developed by Makino Asia Pte Ltd. Coating layers were evaluated for surface roughness (Sa), layer height (LH), porosity (Pr), dilution height (DH), dilution ratio (DR), and WC retention (WC%). Trends in the data reveal how process parameters influence deposition quality and microstructural evolution: higher P or lower SS increased melt pool depth, promoted WC dissolution, and coarsened microstructure, whereas lower P or higher SS preserved WC particles and minimized substrate dilution. Hardness variations in the Inconel 625 matrix were associated with dendrite size, solid-solution strengthening, dislocation density, and secondary carbide formation. These findings provide quantitative guidance for selecting DED parameters to produce crack-free WC-Inconel 625 MMC coatings with controlled microstructure and tailored mechanical properties. Full article

(This article belongs to the Section Advanced Composites)

► Show Figures

Graphical abstract

35 pages, 54902 KB

Open AccessReview

Flow-Line Evolution, Defect Formation, and Structure–Property Relationships in Aluminum Alloy Forging: A Review

by HaiTao Wang, GuoZheng Quan, Chenghai Pan, Xugang Dong and Jie Zhou

Materials 2026, 19(8), 1665; https://doi.org/10.3390/ma19081665 (registering DOI) - 21 Apr 2026

Abstract

Flow lines in aluminum alloy forgings are not merely post-deformation metallographic features; they are integrated indicators of material transport, microstructural evolution, defect susceptibility, and service performance. This review critically examines the mechanisms controlling flow-line evolution, with emphasis on constitutive flow behavior, dynamic recovery [...] Read more.

Flow lines in aluminum alloy forgings are not merely post-deformation metallographic features; they are integrated indicators of material transport, microstructural evolution, defect susceptibility, and service performance. This review critically examines the mechanisms controlling flow-line evolution, with emphasis on constitutive flow behavior, dynamic recovery and recrystallization, second-phase redistribution, friction, thermal gradients, and die/preform design. It then evaluates how abnormal flow paths promote key defects, including folding/laps, flow-through discontinuities, vortex-like instability, and exposed flow lines, and distinguishes well-established mechanisms from topics that still rely on indirect evidence. Particular attention is given to the effects of flow-line morphology on anisotropy, notch sensitivity, corrosion-assisted damage, and fatigue life in forged aluminum alloys. Current control strategies, including preform optimization, FE-based backward tracing, multiphysics defect indices, frictional heat management, and isothermal forging, are also assessed. The available literature shows that stable contour-following flow lines are essential for the simultaneous control of defect formation, microstructural homogeneity, and durability, while major research needs remain in in situ validation, quantitative defect criteria, and digitally closed-loop process control. This review is therefore framed as a critical narrative synthesis rather than a formal systematic review; emphasis is placed on forging-centered studies that directly relate flow-path evolution to defect formation, anisotropy, fatigue, and process optimization, while evidence transferred from adjacent processes is treated as mechanistic support rather than equivalent proof. Full article

(This article belongs to the Section Metals and Alloys)

► Show Figures

Figure 1

27 pages, 22883 KB

Open AccessReview

Janus Nanoparticles in Doxorubicin Delivery: A New Frontier in Targeted Cancer Treatment

by Valeria Flores, Moniellen Pires Monteiro, Tanya Plaza and Jacobo Hernandez-Montelongo

Materials 2026, 19(8), 1664; https://doi.org/10.3390/ma19081664 (registering DOI) - 21 Apr 2026

Abstract

Cancer remains a primary global health challenge, accounting for millions of new cases and significant mortality annually. Although doxorubicin (DOX) is a fundamental anthracycline used for various malignancies, its therapeutic index is severely limited by poor selectivity, systemic toxicity, and dose-dependent cardiotoxicity. To [...] Read more.

Cancer remains a primary global health challenge, accounting for millions of new cases and significant mortality annually. Although doxorubicin (DOX) is a fundamental anthracycline used for various malignancies, its therapeutic index is severely limited by poor selectivity, systemic toxicity, and dose-dependent cardiotoxicity. To address these issues, Janus nanoparticles (JNPs) have emerged as a promising bifunctional platform characterized by a structural asymmetry that allows for the independent functionalization of each hemisphere. This review examines primary fabrication routes—such as masking, microfluidics, self-assembly, and phase separation—and their specific applications in DOX delivery. The anisotropic architecture of JNPs enables a “separate rooms” concept, allowing for the co-delivery of incompatible drugs while facilitating multi-stimuli-responsive release mechanisms triggered by pH, enzymes, or NIR light. Furthermore, JNPs have demonstrated enhanced tumor accumulation and reduced systemic toxicity compared to conventional isotropic carriers. Recent developments even highlight the use of autonomous nanomotors to improve therapeutic delivery while minimizing premature leakage. However, clinical translation is currently hindered by manufacturing complexity, high equipment costs, scalability issues, and a lack of standardized reporting in the literature. Ultimately, JNPs represent a sophisticated frontier in precision oncology, though robust manufacturing processes and characterization protocols are required for future medical adoption. Full article

(This article belongs to the Section Biomaterials)

► Show Figures

Graphical abstract

22 pages, 1916 KB

Open AccessArticle

Assessing the Coefficients of Porosity-to-Binder Index Formulations for Stabilized Clay Through Automated Calibration Methods

by Jair De Jesús Arrieta Baldovino, Oscar E. Coronado-Hernández and Yamid E. Nuñez de la Rosa

Materials 2026, 19(8), 1663; https://doi.org/10.3390/ma19081663 (registering DOI) - 21 Apr 2026

Abstract

Since 2007, the porosity–to–cement relationship has been widely used as a unified parameter to predict mechanical strength, durability, expansion, and stiffness of stabilized soils. In this formulation, the volumetric binder content is adjusted by an internal exponent x, typically ranging between 0 and [...] Read more.

Since 2007, the porosity–to–cement relationship has been widely used as a unified parameter to predict mechanical strength, durability, expansion, and stiffness of stabilized soils. In this formulation, the volumetric binder content is adjusted by an internal exponent x, typically ranging between 0 and 1, to balance the relative contributions of porosity and cementation. Traditionally, the parameters of this relationship have been obtained using manual regression procedures. This study proposes an automated calibration methodology for the porosity–binder index, where the parameters A, B, and x are determined through an iterative optimization framework based on minimization of the sum of absolute errors (SAE) combined with a Monte Carlo search algorithm. The methodology is applied to a cement-stabilized clay blended with ground glass (GG), recycled gypsum (GY), and limestone residues (CLW). The predictive capability of the calibrated model is evaluated using unconfined compressive strength (q_u) and initial shear stiffness (Go) datasets. Two calibration strategies are considered: Calibration Process No. 1, based on CLW mixtures and q_u values only, and Calibration Process No. 2, incorporating all mixtures (CLW, GG, and GY) and both q_u and Go responses. The results indicate that Calibration Process No. 2 provides a more robust and physically consistent parameter set, yielding coefficients of determination of 0.9318 and 0.9412 for q_u and Go, respectively. The proposed algorithm-driven calibration framework improves predictive capability and provides a systematic approach for determining the parameters of the porosity–binder relationship. Full article

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

23 pages, 3169 KB

Open AccessArticle

Phase-Field Damage Modeling of Electromechanical Fracture in MEMS Piezoelectric Films

by Xuanyi Chen, Yuhan Zhang, Yu Xue, Yangjie Shi and Jiaxing Cheng

Materials 2026, 19(8), 1662; https://doi.org/10.3390/ma19081662 (registering DOI) - 21 Apr 2026

Abstract

Piezoelectric thin films have been widely used in micro-electromechanical systems (MEMSs), such as sensors, actuators, and resonant devices. Electromechanically driven fractures can severely degrade device performance and reliability. In this work, a phase-field damage model is developed for MEMS piezoelectric thin films under [...] Read more.

Piezoelectric thin films have been widely used in micro-electromechanical systems (MEMSs), such as sensors, actuators, and resonant devices. Electromechanically driven fractures can severely degrade device performance and reliability. In this work, a phase-field damage model is developed for MEMS piezoelectric thin films under coupled electromechanical loading, incorporating pre-existing defects via an equivalent local fracture toughness. Microcracks and micro-voids arising from manufacturing defects are integrated into the model through an effective local fracture toughness, enabling a unified description of their roles in crack initiation and propagation. The proposed model is implemented in ABAQUS by means of a user-defined element (UEL) subroutine and solved using a staggered scheme. Numerical results show that the level of pre-existing defects, the applied electric potential, and the polarization direction all exert significant effects on fracture behavior. As the defect parameter D_c increases from 0 to 0.10, the reaction force decreases from 87.8 N to 86.3 N, indicating reduced fracture resistance due to manufacturing-induced defects. In addition, the reaction force changes from 90.3 N at −500 V to 86.3 N at +500 V, while it decreases from 102.9 N to 87.1 N as the polarization angle β increases from 0° to 90°. These results demonstrate that pre-existing defects and electromechanical loading jointly govern crack evolution in MEMS piezoelectric thin films. The present study provides a useful numerical tool for fracture analysis, reliability assessment, and structural design of MEMS piezoelectric devices containing manufacturing defects. Full article

(This article belongs to the Section Electronic Materials)

17 pages, 2057 KB

Open AccessArticle

Experimental Investigation into the Connection Performance of Reinforcement Sleeves Utilizing MPC Grouting Materials

by Hao Shu and Lu Chen

Materials 2026, 19(8), 1661; https://doi.org/10.3390/ma19081661 (registering DOI) - 21 Apr 2026

Abstract

With the vigorous promotion of the modernization of China’s construction industry, the proportion of prefabricated buildings in new construction projects has increased steadily. Grouted sleeve connection is a mainstream joining method for prefabricated components, and the performance of grouting materials is crucial to [...] Read more.

With the vigorous promotion of the modernization of China’s construction industry, the proportion of prefabricated buildings in new construction projects has increased steadily. Grouted sleeve connection is a mainstream joining method for prefabricated components, and the performance of grouting materials is crucial to connection reliability. In this study, a modified polyurethane composite (MPC) was developed as a novel sleeve grouting material, and seven grouted splice specimens with different steel bar strength grades and anchorage lengths were fabricated for uniaxial tensile tests. The mechanical properties of MPC and the connection performance of specimens were systematically investigated, and the effects of steel bar strength grade and anchorage length on ultimate load, average bond strength, and strain characteristics were quantitatively analyzed. The results show that MPC has excellent fluidity, and its mechanical strengths meet the specified requirements. Increasing steel bar strength grade and anchorage length significantly improves ultimate load: at a 6d anchorage length, the ultimate load of the S600 series (HRB600E) is 44.85% higher than that of the S400 series (HRB400E); extending the S400 series’ anchorage length from 4d to 8d increases ultimate load by 50.61%. Average bond strength decreases with increasing anchorage length (S400-MPC-8d is 24.70% lower than S400-MPC-4d) but increases with higher steel bar strength grade (S600-MPC-6d is 32.37% higher than S400-MPC-6d). The sleeve remains elastic during the test, ensuring safety. Prediction formulas for average bond strength under slip failure were established, with good agreement between predicted and experimental results. For both HRB400E and HTRB600E steel bars, considering safety and installation errors, a critical anchorage length of 8d is recommended for engineering design. Full article

(This article belongs to the Special Issue Reinforced Concrete: Mechanical Properties and Materials Design)

► Show Figures

Figure 1

62 pages, 4910 KB

Open AccessReview

Recent Progress in Nanophotonics for Green Energy, Medicine, Healthcare, and Optical Computing Applications

by Osama M. Halawa, Esraa Ahmed, Malk M. Abdelrazek, Yasser M. Nagy and Omar A. M. Abdelraouf

Materials 2026, 19(8), 1660; https://doi.org/10.3390/ma19081660 (registering DOI) - 21 Apr 2026

Abstract

Nanophotonics, an interdisciplinary field merging nanotechnology and photonics, has enabled transformative advancements across diverse sectors, including green energy, biomedicine, and optical computing. This review comprehensively examines recent progress in nanophotonic principles and applications, highlighting key innovations in material design, device engineering, and system [...] Read more.

Nanophotonics, an interdisciplinary field merging nanotechnology and photonics, has enabled transformative advancements across diverse sectors, including green energy, biomedicine, and optical computing. This review comprehensively examines recent progress in nanophotonic principles and applications, highlighting key innovations in material design, device engineering, and system integration. In renewable energy, nanophotonics allows the use of light-trapping nanostructures and spectral control in perovskite solar cells, concentrating solar power systems, and thermophotovoltaics. This has significantly enhanced solar conversion efficiencies, approaching theoretical limits. In biosensing, nanophotonic platforms achieve unprecedented sensitivity in detecting biomolecules, pathogens, and pollutants, enabling real-time diagnostics and environmental monitoring. Medical applications leverage tailored light–matter interactions for precision photothermal therapy, image-guided surgery, and early disease detection. Furthermore, nanophotonics underpins next-generation optical neural networks and neuromorphic computing, offering ultrafast, energy-efficient alternatives to von Neumann architectures. Despite rapid growth, challenges in scalability, fabrication costs, and material stability persist. Future advancements will rely on novel materials, AI-driven design optimization, and multidisciplinary approaches to enable scalable, low-cost deployment. This review summarizes recent progress and highlights future trends, including novel material systems, multidisciplinary approaches, and enhanced computational capabilities, paving the way for transformative applications in this rapidly evolving field. Full article

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

19 pages, 1894 KB

Open AccessArticle

Electro-Oxidation and Electro-Fenton Degradation of PFASs Using a Grid-Shaped Ti₄O₇ Magnéli-Phase Anode: Effect of Concentration and Evidence of Defluorination

by Sinda Daghfous, Elissa Makhoul, Eddy Petit, Geoffroy Lesage, Mikhael Bechelany, Nizar Bellakhal and Marc Cretin

Materials 2026, 19(8), 1659; https://doi.org/10.3390/ma19081659 (registering DOI) - 21 Apr 2026

Abstract

The persistence of per- and polyfluoroalkyl substances (PFASs) in aquatic environments requires efficient and sustainable treatment technologies. In this study, the electrochemical degradation of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) was investigated using a grid-shaped Ti₄O₇ Magnéli-phase anode under [...] Read more.

The persistence of per- and polyfluoroalkyl substances (PFASs) in aquatic environments requires efficient and sustainable treatment technologies. In this study, the electrochemical degradation of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) was investigated using a grid-shaped Ti₄O₇ Magnéli-phase anode under electro-oxidation (EO) and electro-oxidation coupled with electro-Fenton (EO-EF) conditions. Structural characterization confirmed the predominance of Ti₄O₇ in the electrode material. At an initial concentration of 2 ppm, PFOS was rapidly and almost completely removed under both EO and EO-EF, whereas PFOA exhibited slower degradation kinetics, identifying it as the kinetically limiting compound. Coupling EO with electro-Fenton mainly enhanced the degradation kinetics, particularly for PFOA, while final removal efficiencies remained comparable. The influence of initial concentration was further examined, showing that lowering the PFOA concentration to 0.2 ppm, representative of environmentally relevant levels, enabled nearly complete removal within 300 min. Fluoride ion monitoring under optimized EO-EF conditions confirmed partial defluorination, demonstrating that PFOA removal is accompanied by C-F bond cleavage. These findings highlight the respective roles of EO and EO-EF processes and support the potential of Ti₄O₇-based anodes for energy-competitive PFAS remediation. Full article

(This article belongs to the Special Issue The Circular Economy and the Sustainable Development of Materials in Progressive Environmental Engineering)

► Show Figures

Graphical abstract

22 pages, 6246 KB

Open AccessArticle

Evaporative Cooling of Concrete Pavers Incorporating Recycled, Bio-Based and Lightweight Materials: Influence of Capillary Absorption and Density

by Amro Yaghi, Farjallah Alassaad, Stephane Ginestet and Gilles Escadeillas

Materials 2026, 19(8), 1658; https://doi.org/10.3390/ma19081658 (registering DOI) - 21 Apr 2026

Abstract

The urban heat island effect is strongly linked to the use of dense mineral pavements with high thermal inertia and lacking passive heat dissipation mechanisms. This article evaluates the potential of evaporatively cooled concrete pavers, based on capillary action and evaporation by incorporating [...] Read more.

The urban heat island effect is strongly linked to the use of dense mineral pavements with high thermal inertia and lacking passive heat dissipation mechanisms. This article evaluates the potential of evaporatively cooled concrete pavers, based on capillary action and evaporation by incorporating recycled, bio-based, and lightweight materials to develop functional porosity. Ten paver formulations were developed using natural or recycled sand, hemp fibers and shives, and lightweight aggregates. Compressive strength, density, capillary absorption, and thermal behavior were characterized. Tests were conducted outdoors in full sunlight over 48 h in comparison with reference urban materials. The results show that capillary action alone is insufficient to induce effective cooling. The raw recycled sand formulation exhibits high capillary absorption but reaches maximum temperatures of 43–44 °C, which may be due to its low interconnected porosity that limits evaporation. Conversely, formulations incorporating bio-based materials or lightweight aggregates showed a more favorable balance between water availability, reduced density, and surface cooling performance. Hemp-based pavers reach maximum temperatures of 38–40 °C, while those incorporating expanded clay range between 37 and 39 °C, representing a reduction of 7 to 13 °C compared to bitumen and maintaining mechanical strengths suitable for pedestrian use. The results suggest that effective evaporative cooling is associated with sufficient capillary absorption, efficient water transfer toward the surface, and moderate density limiting heat storage. This study demonstrates that high capillary absorption alone does not ensure effective evaporative cooling. By systematically comparing recycled, bio-based and lightweight aggregates, the results reveal that evaporative cooling efficiency probably depends on the functional connectivity of the pore network and on a moderate material density limiting heat storage. Full article

(This article belongs to the Special Issue Mechanical Performance and Durability of Concrete and Composite Construction Materials)

► Show Figures

Figure 1

12 pages, 1829 KB

Open AccessArticle

Multifunctional ZnO Nanomaterials with Broad-Spectrum Defect-State Absorption for Enhancing the Photocatalytic Degradation of Organic Dyes

by Ai Zhou, Hongyun Li and Jie Fang

Materials 2026, 19(8), 1657; https://doi.org/10.3390/ma19081657 (registering DOI) - 21 Apr 2026

Abstract

Zinc oxide (ZnO) nanomaterials have attracted widespread attention from researchers due to their morphology-dependent properties, eco-friendly characteristics, and potential as a sustainable photocatalyst with a broad range of applications. Therefore, in this study, three different ZnO nanostructures—nanosheets (NSs), nanoflowers (NFs), and nanorods (NBs)—were [...] Read more.

Zinc oxide (ZnO) nanomaterials have attracted widespread attention from researchers due to their morphology-dependent properties, eco-friendly characteristics, and potential as a sustainable photocatalyst with a broad range of applications. Therefore, in this study, three different ZnO nanostructures—nanosheets (NSs), nanoflowers (NFs), and nanorods (NBs)—were synthesized via a controlled precipitation method. Among these, NFs exhibited the highest photocatalytic efficiency. The obtained samples exhibited broad optical absorption edges extending into the visible region (corresponding to apparent energies of 1.81–2.09 eV), which is attributed to the sub-bandgap states induced by oxygen vacancies rather than intrinsic bandgap narrowing—far lower than the bandgap of bulk ZnO (3.37 eV). Their photocatalytic performance was evaluated by the degradation of Methyl Blue (MB), Methyl Orange (MO), and Rhodamine B (RhB) under UV or sunlight. Notably, the NFs achieved rapid degradation of MB and RhB within 90 min under UV irradiation without the addition of any H₂O₂, demonstrating their effectiveness and cost-effectiveness for practical applications. Although H₂O₂ inhibited the degradation of MB and RhB, it promoted the decomposition of MO. Furthermore, the ZnO NFs exhibited excellent recyclability in five consecutive degradation cycles. The self-synthesized ZnO nanomaterials in this study, with their broad-spectrum absorption, high stability, and eco-friendly properties, demonstrate their potential as an efficient and low-cost photocatalyst for large-scale wastewater treatment. Full article

(This article belongs to the Special Issue Multifunctional Heterogeneous Catalytic Materials for Industrial, Environmental and Biomedical Breakthroughs)

► Show Figures

Figure 1

13 pages, 2119 KB

Open AccessArticle

Influence of Thermal Treatment and Particle Size on the Physicochemical Properties and Filler Performance of Oyster Shell-Derived CaCO₃ in Mortar

by Jessica de Dios-Suárez, Brayan Leonardo Pérez-Escobar, Germán Pérez-Hernández, Francisco Iván Lizama-Tzec, Laura Lorena Díaz-Flores, Salatiel Pérez-Montejo, Juan Pablo de Dios-Jiménez and Rafael Torres-Ricárdez

Materials 2026, 19(8), 1656; https://doi.org/10.3390/ma19081656 (registering DOI) - 21 Apr 2026

Abstract

The cement industry contributes approximately 7–8% of global CO₂ emissions, motivating the development of sustainable supplementary materials. This study evaluates the partial replacement (10 wt.%) of Portland cement with calcium carbonate (CaCO₃) derived from oyster shells, both untreated and thermally [...] Read more.

The cement industry contributes approximately 7–8% of global CO₂ emissions, motivating the development of sustainable supplementary materials. This study evaluates the partial replacement (10 wt.%) of Portland cement with calcium carbonate (CaCO₃) derived from oyster shells, both untreated and thermally treated at 600 °C, in non-structural mortar blocks. Structural and physicochemical characterization was performed using XRD, SEM, EDS, BET, and TGA to assess phase composition, morphology, and surface properties. Thermal treatment modified the textural characteristics of CaCO₃, reducing the crystallite size and increasing the specific surface area (from 5.8 to 25.6 m²/g), without phase transformation. Compressive strength results, relative to a reference mortar (13.6 MPa), showed comparable performance, with variations generally within ±10%, although slightly larger deviations were observed for specific particle sizes. Finer calcined particles yielded the highest strength (15.0 MPa), reinforcing the combined influence of particle size and thermal treatment. These results suggest that CaCO₃ acts primarily through a filler effect, improving particle packing and matrix interaction. Both untreated and heat-treated CaCO₃ satisfied strength requirements for non-structural applications, supporting the valorization of oyster shell waste as a sustainable material in cement-based systems. Full article

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

► Show Figures

Figure 1

21 pages, 12237 KB

Open AccessArticle

Swing-Arc Narrow-Gap Submerged Arc-Welding Process Assisted by Pre-Embedding Cold Wires

by Shubin Liu, Yupeng Cao, Hong Li, Jie Zhu, Changxin Zhou, Zhengyu Zhu and Jiayou Wang

Materials 2026, 19(8), 1655; https://doi.org/10.3390/ma19081655 (registering DOI) - 21 Apr 2026

Abstract

To solve the problems of poor weld formation, difficult slag removal, and inferior joint microstructure and hardness in conventional narrow-gap submerged arc welding (NG-SAW), a swing arc NG-SAW process assisted by pre-embedding cold wires was proposed. Synergistically optimizing the welding energy parameters and [...] Read more.

To solve the problems of poor weld formation, difficult slag removal, and inferior joint microstructure and hardness in conventional narrow-gap submerged arc welding (NG-SAW), a swing arc NG-SAW process assisted by pre-embedding cold wires was proposed. Synergistically optimizing the welding energy parameters and additional cold wires ensured sound weld formation and enhanced slag detachability, while the efficiency of multilayer welding was improved by reducing the number of weld layers by 33.3%. The slag adhesion mechanism is clarified as follows: a high welding heat input facilitates elemental diffusion at the weld–slag interface, leading to the formation of a continuous and thick interlayer composed of (Fe,Mn)O and MgO-Al₂O₃-CaO phases. This interlayer strengthens the chemical bonding between slag and weld, thereby impeding slag removal. Microstructure evolution analysis of the multilayer welded joint revealed that the variable-angle design increases the groove volume and, combined with the heat-absorbing effect of the additional wires, accelerates molten pool cooling, thereby refining grains in both the weld metal zone and reheat-affected zone. Meanwhile, the tempering exerted by the heat-affected zone (HAZ) of the subsequent weld layer on the previous layer is attenuated. This promotes the gradual transformation of hard-brittle lath martensite in the coarse-grained heat-affected zone (CGHAZ) of the bottom layer into tougher tempered martensite/bainite in the CGHAZ of the upper layers. As a result, the hardness uniformity within the HAZ, the critical weak region of the joint, was enhanced by 54%, enabling synchronous improvement in microstructural homogeneity, hardness distribution, and overall welding efficiency. Full article

► Show Figures

Figure 1

22 pages, 5365 KB

Open AccessArticle

Design, Performance and Mechanisms of Asphalt Modified with Polyurethane and Hydroxylated Crumb Rubber

by Jun Xie, Junpeng Lin, Shaopeng Wu, Quantao Liu, Chao Li, Shibo Zhang, Huan Wang, Fusong Wang and Zoujun Wan

Materials 2026, 19(8), 1654; https://doi.org/10.3390/ma19081654 (registering DOI) - 21 Apr 2026

Abstract

Under long-term heavy load and complex service environments, polyurethane-modified asphalt (PUMA) struggles to simultaneously satisfy the requirements of rutting and cracking resistance of asphalt pavements, as cyclic stress loading reduces the elastic recovery and low-temperature toughness of polyurethane (PU). To address this issue, [...] Read more.

Under long-term heavy load and complex service environments, polyurethane-modified asphalt (PUMA) struggles to simultaneously satisfy the requirements of rutting and cracking resistance of asphalt pavements, as cyclic stress loading reduces the elastic recovery and low-temperature toughness of polyurethane (PU). To address this issue, this study employed hydroxylated crumb rubber (HCR), which is obtained by activating the surface of crumb rubber (CR) and can chemically crosslink with PU in asphalt to form a crosslinked network structure. The aim was to enhance the rutting and cracking resistance of PUMA by utilizing the elasticity and low-temperature toughness of CR. An orthogonal design was employed to systematically design a modified asphalt formulation with PU and HCR (PU/HCRMA) by controlling the isocyanate index and the contents of PU and HCR. The basic properties, rheological properties, and viscoelastic properties of PU/HCRMA were systematically investigated. The results demonstrate that the rutting and cracking resistance of PU/HCRMA are substantially enhanced, with an improvement of 28.91% in the rutting factor at 64 °C compared to PUMA and a reduction of 49.93 MPa in the stiffness modulus at −24 °C. Simultaneously, incorporating HCR in PUMA enhances its viscosity and flow resistance while reducing temperature susceptibility. Furthermore, by providing load-bearing sites, HCR endows PU/HCRMA with exceptional elastic recovery and deformation resistance. Results from FTIR and FM confirm the reaction between isocyanate groups in the PU prepolymer and the hydroxyl groups on the surface of HCR and the formation of HCR-PU crosslinked networks. Finally, PU/HCRMA asphalt mixtures demonstrate significant improvements in both rutting and cracking resistance. This research outcome provides a new direction for the development of high-performance road asphalt materials. Full article

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

► Show Figures

Figure 1

24 pages, 3339 KB

Open AccessArticle

Molybdenum/Niobium Disilicide Multilayers Fabricated by Tape Casting: Microstructure, Mechanical Properties and Oxidation Behaviour

by Dreidy Mercedes Vásquez, Elisa Padovano, Claudio Badini, Sara Biamino, Luca Lavagna and Matteo Pavese

Materials 2026, 19(8), 1653; https://doi.org/10.3390/ma19081653 (registering DOI) - 21 Apr 2026

Abstract

MoSi₂-based intermetallics are interesting materials for high-temperature applications, due to their moderate density, high melting point and significant oxidation resistance. In this paper, MoSi₂-based materials in the form of multi-layered structures were fabricated by tape casting and pressureless sintering. [...] Read more.

MoSi₂-based intermetallics are interesting materials for high-temperature applications, due to their moderate density, high melting point and significant oxidation resistance. In this paper, MoSi₂-based materials in the form of multi-layered structures were fabricated by tape casting and pressureless sintering. Composites containing up to 20 wt.% of NbSi₂ were produced, with the aim of obtaining biphasic structures with low pest oxidation at low temperature. The prepared samples were characterised with regard to phase composition, microstructure, mechanical properties and oxidation resistance. It was shown that the addition of a limited amount of NbSi₂ prevents the pest oxidation phenomenon characteristic of pure MoSi₂. Silica inclusions responsible for lowering the material toughness, were observed to disappear in the sintered silicides, thanks to the presence, during the binder burn-out, of a reducing atmosphere and to the carbonaceous residua. The phase and composition analysis also revealed the formation of small amounts of secondary phases like silicon carbide. Full article

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

► Show Figures

Figure 1

25 pages, 5693 KB

Open AccessArticle

Tribological and Corrosion Properties of Coatings of Ultradisperse TiB₂-TiAl Electrodes with Nanosized Additives Deposited on Ti-Gr2 by Non-Contact Electrospark Deposition

by Georgi Kostadinov, Antonio Nikolov, Yavor Sofronov, Todor Penyashki, Valentin Mishev, Boriana Tzaneva, Rayna Dimitrova, Krum Petrov, Radoslav Miltchev and Todor Gavrilov

Materials 2026, 19(8), 1652; https://doi.org/10.3390/ma19081652 (registering DOI) - 21 Apr 2026

Abstract

In this work, the tribological and corrosion behavior of commercially pure titanium—Ti-Gr2 with coatings obtained by mechanized contactless local electrospark deposition (LESD) with low pulse energy and a rotating electrode of TiB₂-TiAl reinforced with ZrO₂ and NbC nanoparticles was investigated. [...] Read more.

In this work, the tribological and corrosion behavior of commercially pure titanium—Ti-Gr2 with coatings obtained by mechanized contactless local electrospark deposition (LESD) with low pulse energy and a rotating electrode of TiB₂-TiAl reinforced with ZrO₂ and NbC nanoparticles was investigated. The current research is driven by the need for improved corrosion and abrasion resistance of titanium surfaces in automotive components, shipbuilding, aerospace, petrochemical and many other industrial and domestic areas. This work is a continuation of our previous study, in which the dependences of the relief, roughness, thickness, microhardness, composition and structure of the coatings obtained with this electrode on the electrical parameters of the LESD mode were studied and analyzed. In this work, the influence of the pulse parameters of the LESD process (respectively, roughness, thickness, composition and structure of the coatings) on the tribological and corrosion characteristics of the coatings has been investigated and the possibility of simultaneous protection of titanium surfaces from wear and corrosion has been demonstrated. Coatings containing nanocrystalline and amorphous-like structures have been formed, with synthesized new compounds and phases, and with increased hardness up to 13 GPa, low roughness Ra = 1.5–3 μm, thickness 8–20 μm and minimal structural defects. By comparing the potentiodynamic polarization curves, polarization resistance, electrochemical impedance and tribological characteristics of the coated surfaces, it has been established that their corrosion resistance increases by more than 1–2 orders of magnitude and their wear resistance during friction increases by 4–5 times compared to those of the substrate. Appropriate values of the electrical parameters of the LESD mode are presented, which allow obtaining uniform coatings with reduced roughness and structural defects, with predictable thickness, roughness and hardness, and with maximized corrosion and abrasive wear resistance to allow for uniform coatings with reduced roughness and structural defects, with predictable thickness, roughness and hardness, and with maximized corrosion and abrasive wear resistance. Full article

(This article belongs to the Special Issue Advances in Metal Coatings for Wear and Corrosion Applications (Second Edition))

► Show Figures

Graphical abstract

18 pages, 1642 KB

Open AccessArticle

Relationship Between Xonotlite Crystallite Size and Strength Degradation of Silica-Enriched Oil Well Cement Under 240 °C Curing Conditions

by Guodong Cheng, Lei Chen, Qian Tao, Haoguang Wei, Fuzhu Xie, Jixiang Wang and Jun Lu

Materials 2026, 19(8), 1651; https://doi.org/10.3390/ma19081651 - 20 Apr 2026

Abstract

The strength degradation of silica-enriched oil well cement under high-temperature curing conditions poses a challenge to wellbore integrity. Using the single-peak Scherrer equation, this study evaluated xonotlite crystallite size evolution in cements cured at different setting temperatures. Low-temperature setting (80 °C) maintained stable [...] Read more.

The strength degradation of silica-enriched oil well cement under high-temperature curing conditions poses a challenge to wellbore integrity. Using the single-peak Scherrer equation, this study evaluated xonotlite crystallite size evolution in cements cured at different setting temperatures. Low-temperature setting (80 °C) maintained stable crystallite size (≈35–36 nm), accompanied by strength gain and pore refinement. High-temperature setting (240 °C) induced crystallite coarsening (up to 40 nm), concurrent with strength degradation and pore coarsening. Similar crystallite sizes led to divergent mechanical performance depending on crystal morphology, highlighting the need for combined size-morphology assessment. These findings identify xonotlite crystallite coarsening as a key indicator of high-temperature cement retrogression. Full article

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

► Show Figures

Figure 1

Journal Description

Materials

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI