Search Results (5,197)

Powder coating, as a promising coating material, has attracted widespread attention due to its convenient construction and being a green option, promoting environmental protection. However, the existence of defects such as insufficient leveling and poor mechanical properties of the coating during the coating process limits the further expansion of its application fields. Therefore, for this article, powder coatings with high leveling performance were prepared by composite modification of nylon 12 (PA-12) resin with polyacrylates and ethylene-α-olefin copolymers (POE). The introduction of modified polyacrylates reduces the surface tension of nylon chains, enhancing melt flowability during curing and making the coating surface smooth. Furthermore, by introducing POE, the flexibility of the powder coating was improved, and its fracture elongation increased from 59% for pure PA-12 to a maximum of 234%. This study provides an effective method for the modification of nylon powder coatings and offers new insights into their use in high-performance coating applications. Full article

In the river environments of Xinjiang characterized by high sediment content and high flow velocities, hydraulic concrete is highly susceptible to damage from the impact and abrasion of bed load. Consequently, this imposes more stringent requirements on its mechanical properties and abrasion resistance. The incorporation of crumb rubber, a recyclable material, into concrete presents a dual benefit: it enables resource recycling while simultaneously offering a novel pathway for the development of concrete technology. This study takes rubber powder concrete as the research object. With the same water-to-binder ratio, rubber powder was incorporated at three volume fractions: 0%, 5%, and 10% of the cementitious material. The drop weight impact test and underwater steel ball method are adopted to evaluate its impact resistance and anti-scouring-abrasion performance, respectively. By testing the compressive strength, impact toughness, wear rate, anti-scouring-abrasion strength and three-dimensional morphological characteristics, the influence of rubber powder content on the mechanical properties and anti-scouring-abrasion performance of concrete is systematically analyzed. The research results show that the addition of rubber powder reduces the compressive strength of concrete, but significantly improves its impact resistance and anti-scouring-abrasion performance. Among all test groups, the concrete with 10% rubber powder content has the most significant decrease in compressive strength, with a decrease of about 37% compared with the 5% content group, while the 5% content group has a decrease of about 27% compared with the control group. However, its impact toughness at 3d, 7d and 15d is increased by about 84.7%, 88.4% and 84.4%, respectively, compared with the control group, showing the largest improvement range. At the same time, the wear rate of this group is reduced by about 42.5%, and the anti-scouring-abrasion strength is increased by about 61%. Combined with the three-dimensional morphology analysis, it can be seen that the specimens in this group exhibit the optimal anti-scouring-abrasion performance. In terms of microstructure, the porosity of rubber powder concrete increases, the generation of C-S-H gel decreases and its continuity is damaged, leading to a significant decrease in compressive strength. The reduction in the generation of delayed ettringite enhances the toughness and anti-scouring-abrasion performance. In general, the increase in rubber powder content will lead to a decrease in the compressive strength of concrete, but within a certain range, it can significantly improve its impact resistance and anti-scouring-abrasion performance. Crumb rubber effectively enhances the impact and abrasion resistance of hydraulic concrete, demonstrating strong application potential in high-flow, sediment-laden river environments. Full article

This study investigated Coffee arabica husk (CAH) as a reinforcing filler to create sustainable biocomposites from agro-industrial waste. The research explored the relationship between processing, structure, and properties using two matrices: polylactic acid (LA) and a bio-based epoxy resin (BER). We found that CAH incorporation increased the elastic modulus in all composites, with the stiffening effect being more significant in BER-based systems. However, filler inclusion dramatically reduced composite toughness. Our analysis showed that melt processing significantly reduced the CAH aspect ratio, with BER causing a more pronounced reduction than LA. Conversely, LA showed a greater tendency to fill the porous voids of the CAH particles. This work demonstrates the crucial interaction of filler, matrix, and processing on a composite’s final performance. These materials have shown promises for sustainable packaging and other technical applications. Full article

Microwave (MW) sintering offers a promising alternative to conventional heating in powder metallurgy, providing faster processing, lower energy consumption, and improved microstructural control. In the diamond tool industry—where cost-efficiency and competitiveness are critical—MW–hybrid sintering shows strong potential for producing segments designed for cutting and polishing natural stone and construction materials. This study investigates the effects of sintering temperature, dwell time, and green density on the densification and mechanical properties of metal matrix composite (MMC) segments containing diamond particles. MW sintering reduced the optimum sintering temperature by 90–170 °C when compared to conventional free sintering. Under optimal conditions (57% green density, 820 °C, 5 min dwell), segments achieved ~95% densification and mechanical properties comparable to hot-pressed (HP) samples. Although MW–hybrid sintered matrices exhibited slightly lower Young’s modulus (~15%) and Vickers hardness (~20%), their flexural strength and fracture toughness remained comparable to HP counterparts. Overall, MW hybrid sintering provides a cost-effective, energy-efficient, and scalable route for fabricating high-performance diamond tool segments, supporting both economic viability and sustainable, competitive manufacturing. Full article

This study investigates how poly (vinyl alcohol) (PVA) influences melamine–urea–formaldehyde (MUF) resin, particularly regarding tensile properties, bonding strength, water resistance, curing temperature, chemical structure, and microscopic morphology. By altering the PVA content, we observed changes in the tensile strength and elongation of MUF resin. The tensile strength peaked at a 2% PVA addition. PVA significantly enhanced the dry, cold water, and boiling water bonding strengths of MUF resin, with the most notable effect at a 10% addition. A low PVA addition (2%) notably improved the water resistance of glued wood. Differential scanning calorimetry revealed that PVA increased the curing temperature of MUF resin, though excessive PVA led to a decrease. Nuclear magnetic resonance analysis showed changes in chemical bonds after PVA modification, indicating increased polymerization. X-ray diffraction and scanning electron microscopy analyses further confirmed the effects of PVA on the crystal structure and microscopic morphology of MUF resin, with modified resins exhibiting higher toughness fracture characteristics. These findings suggest that PVA can effectively enhance the overall performance of MUF resin, making it more suitable for applications of glued wood. Full article

By alternately depositing hydrogen-free amorphous carbon (a-C) and hydrogenated amorphous carbon (a-C:H) nanolayers on HSLA-100 steel through arc-ion plating, multilayer diamond-like carbon (DLC) architectures were engineered, with the modulation period adjusted from 1 to 10 cycles. SEM and Raman spectroscopy served as the analytical tools for characterizing the microstructure. For assessing key functional behaviors, nanoindentation was used to test mechanical properties, dry-sliding tribometry and in-situ tribocorrosion tests targeted tribological and tribocorrosion performance, and polarization tests focused on corrosion resistance. Introducing C₂H₂ increased the sp³ fraction and hardness relative to pure a-C. The ten-period film (S5) yielded the highest H/E (0.0767) and H³/E² (0.171), reflecting the best hardness–toughness synergy. All coatings lowered the dry friction coefficient to 0.08–0.10 and cut wear by more than 1 order of magnitude versus the substrate; the ten-period film (S5) showed the minimum dry wear rate (1.39 × 10⁻⁷ mm³·N⁻¹·m⁻¹) and tribocorrosion wear rate (4.53 × 10⁻⁷ mm³·N⁻¹·m⁻¹) in 3.5 wt% NaCl. The superior performance is due to interlayer interfaces that dissipate stresses, arrest crack propagation, and block electrolyte ingress through defects. These findings indicate that the rational stacking of a-C/a-C:H significantly improves the tribological and tribocorrosion resistance of HSLA-100, providing a reliable protective approach for components used in marine services. Full article

To elucidate the influence of the extrusion-based 3D printing of concrete on the tensile performance of polyethylene fibre-based engineered cementitious composites (PE-ECC), quantitative analyses of reinforcing filament alignment and pore morphology were carried out using backscattered electron (BSE) imaging and X-ray computed tomography (X-CT). A micromechanics analytical model based on microstructural characteristics was further employed to predict the tensile response of additively manufactured PE-ECC. Due to the extrusion process, fibres in 3D-printed PE-ECC were predominantly oriented along the printing path, resulting in a smaller average inclination angle compared with the randomly distributed fibres in cast specimens. Internal pores exhibited elongated flattened ellipsoidal shapes, with more pronounced anisotropy in axial lengths across the three principal directions. Taking the major semi-axis of the equivalent ellipsoidal voids as a representative pore parameter, the analytical model accurately reproduced the cracking strength, stress-strain evolution, and crack pattern of the printed PE-ECC. This extrusion process enhanced multiple cracking capacity and strain-hardening performance by improving fibre orientation, strengthening interfacial bonding, and altering matrix fracture toughness. The integration of micromechanical modelling with experimentally measured microstructural parameters effectively revealed the intrinsic mechanisms underlying the enhanced tensile behaviour of 3D-printed PE-ECC and provides theoretical support for the optimized design of fibre-reinforced cementitious composites in 3D printing. Full article

Surface coatings have proven highly effective in addressing the critical challenges of friction, wear, and corrosion on steel substrates, which are responsible for over 80% of mechanical failures in industrial applications. Recent research highlights that advanced coatings—such as ceramic carbides/nitrides, high-entropy alloys, and metal-matrix composites—significantly enhance hardness, wear resistance, and environmental durability through mechanisms including protective oxide film formation, solid lubrication, and microstructural refinement. Moreover, these coatings exhibit robust performance under combined tribological-corrosive (tribocorrosion) conditions, where synergistic interactions often accelerate material degradation. Key developments include multilayer and composite architectures that balance hardness with toughness, self-lubricating coatings capable of in situ lubricant release, and active or self-healing systems for sustained corrosion inhibition. Despite these advances, challenges remain in predicting coating lifetime under multifield service conditions and optimizing interfacial adhesion to prevent delamination. Future efforts should prioritize multifunctional coating designs, improved tribocorrosion models, and the integration of sustainable materials and AI-driven process optimization. This review consolidates these insights to support the development of next-generation coatings for extending the service life of steel components across demanding sectors such as marine, aerospace, and energy systems. Full article

The field of dental restorations continues to demand durable prosthetic materials with a focus on esthetic appeal. This systematic review and meta-analysis compared the mechanical properties and bonding performance of computer-aided design (CAD)/computer-aided manufacturing (CAM)-milled and three-dimensionally (3D) printed zirconia fixed dental prostheses. A systematic search of major databases identified 15 eligible recent in vitro studies. Random-effects meta-analyses (based on standard mean deviation) and heterogeneity (I²) and sensitivity analyses were performed. The meta-analysis showed no significant differences between the groups in flexural strength, hardness, density, bond strength, and fracture toughness. However, heterogeneity remained high, reflecting possible differences in the build orientation, additive manufacturing technique, and sintering protocols. A qualitative analysis of the literature also revealed that milled zirconia was generally associated with greater consistency in strength, hardness, and accuracy. Three-dimensionally printed zirconia, while more variable due to porosity and processing factors, frequently reached clinically acceptable values, with certain orientations achieving flexural and bonding strengths equal to or surpassing those of milled zirconia. Both fabrication methods benefited from surface treatments, and artificial aging confirmed stability within functional ranges. Overall, CAD/CAM-milled zirconia remains the benchmark for predictability; however, advances in additive manufacturing suggest a growing potential for 3D-printed zirconia in complex restorations. Full article

As a support material for mine roadways, shotcrete (SC) exhibits performance limitations in extreme deep-mining environments characterized by high stress and water seepage. Polyoxymethylene (POM) fiber, with its properties of high strength, high modulus, and corrosion resistance, holds potential for application in surrounding rock support of deep roadways. To investigate the effect of POM fiber on the flexural performance of shotcrete, four-point bending tests were conducted on fiber-reinforced concrete specimens with different fiber lengths and dosages. Combined with ABAQUS numerical simulation, damage simulation analysis was performed on each group of specimens, and the stress propagation state of the fibers was tracked. The results show that the flexural strength of polyoxymethylene fiber shotcrete (PFS) increases with the increase in fiber length and dosage, and the influence of fiber dosage is more significant. POM fiber can effectively inhibit the crack development of shotcrete, enhancing its crack resistance and residual strength. The load-deflection curves indicate that PFS exhibits excellent fracture toughness, with the P9L42 group showing the highest flexural strength improvement, reaching an increase of 94%. The numerical simulation results are in good agreement with the experimental conditions, accurately reflecting the damage state and load-deflection response of each group of concrete specimens. Based on the above research, POM fiber is more conducive to meeting the stability requirements of roadway surrounding rock support, providing a scientific basis for the application of PFS in mine roadway surrounding rock support. Full article

Replacing natural aggregates in cement-stabilized macadam (CSM) with waste rubber particles reduces mineral resource consumption, manages solid waste, and enhances the long-term performance of cementitious materials, addressing environmental challenges. An optimized gradation of rubber particles was proposed based on different combinations of particle sizes. Five rubber particle combinations with different gradations were incorporated into CSM to create a rubberized cement-stabilized macadam (RCSM). The strength of RCSM was verified through compressive and flexural tensile tests. The toughness of RCSM was evaluated using the flexural ultimate failure strain and flexural tensile resilient modulus. Crack resistance was evaluated through freeze–thaw, fatigue, and shrinkage tests. The results indicate that the compressive and flexural strengths of RCSM with 1.18–4.75 mm rubber particles are closest to those of CSM. The ultimate strain of CSM increased by up to 1.83 times with optimized rubber gradation, while its modulus decreased by more than half. Furthermore, RCSM with 1.18–4.75 mm rubber particles exhibited the best performance in fatigue life under high stress ratio, frost resistance, and shrinkage behavior. Comprehensive test results showed that rubber particles ranging from 1.18 to 2.36 mm were most effective in improving the road performance of RCSM. Full article

This study examines the flexural behavior of reinforced concrete (RC) beams that utilize steel, glass fiber-reinforced polymer (GFRP), and hybrid steel–GFRP longitudinal bars. It considers variations in stirrup material (steel or GFRP) and stirrup spacing (100 mm or 200 mm). Nine beam specimens were subjected to three-point bending tests until failure. Their performance was assessed based on ultimate load, deflection, stiffness, ductility, energy absorption, and failure mode. The experimental program aimed to isolate the effects of transverse reinforcement detailing and to elucidate the role of stirrup characteristics in governing the transition between flexure and shear-controlled behavior. The findings indicated that both the type of reinforcement and the configuration of stirrups significantly influenced structural performance. Steel-reinforced beams demonstrated stable and ductile flexural behavior, whereas GFRP-reinforced beams supported loads up to 18% higher but experienced abrupt failure in brittle shear with restricted ductility. Hybrid beams effectively integrated the benefits of both materials: The HS100 specimen, which featured closely spaced steel stirrups, achieved the highest ultimate load (162.5 kN), maximum deflection (19.7 mm), and greatest energy absorption (2450 kN·mm). In contrast, beams utilizing GFRP stirrups exhibited early diagonal cracking and abrupt failure, even with closely spaced stirrups. The study indicates that hybrid steel–GFRP reinforcement can enhance the strength, ductility, and toughness of reinforced concrete beams, contingent upon the application of sufficient steel confinement. The findings provide practical recommendations for enhancing hybrid RC design by positioning steel in tension and utilizing steel stirrups for confinement, while effectively employing GFRP in compression zones or in corrosive environments. Full article

In this study, the J-integral method was used to evaluate the fracture toughness (J_Q) of the isolation layer at the top of SA508-III-309L/308L-316L dissimilar metal welded joints (DMWJs) of a pressure vessel. Tests were carried out at varying temperatures, from room temperature to 320 °C, to study the mechanism underlying temperature effects on unstable crack propagation. The results show that failure occurs in the middle position of the weld isolation layer of the welded joint at all test temperatures. The J_Q of the inner diameter of the joint decreases with increased temperature, with a maximum decrease of 31.8%. The analysis shows that the lath ferrite structure in the isolation layer provides a favorable path for crack propagation. The increase in temperature enlarges the difference in thermal expansion between SA508-III steel and the isolation layer, making it easier for second-phase particles in the isolation layer to induce crack initiation and propagation, thus reducing the J_Q of the steel. In addition, at high temperatures, the dislocation density of the isolation layer, the deformation resistance of the material, and the difference in the yield ratio of the joint weld all decrease, which is not conducive to the redistribution of the stress field at the tip of the fatigue crack, leading to further reduction in the J_Q. Full article

High-strength concrete (HSC) is widely used in coastal regions, but its durability and structural safety is threatened by chloride ingress in marine environments. This study investigates the effects of different curing methods, normal, steam, and high-temperature autoclave on the chloride resistance of HSC using the electric flux test. A critical chloride concentration of 4.5% was identified, and accelerated deterioration tests were conducted to evaluate mechanical properties development (compressive strength, elastic modulus, toughness, specific toughness) under the various curing conditions. Additionally, the development of hydration products and microstructural characteristics were analyzed to elucidate the mechanisms underlying the observed differences. The results indicate that steam and autoclave curing enhance cement hydration and the initial mechanical properties of HSC but also increase permeability and susceptibility to chloride ion penetration compared to normal curing. Chloride penetration was found to be most severe at moderate chloride concentrations (~4.5%), while higher concentrations resulted in reduced ion migration. Although intensive curing under elevated temperature and pressure improves early strength and stiffness, it accelerates mechanical degradation under chloride exposure, highlighting a trade-off between short-term performance and long-term durability. Full article

A series of TiB₂-Ni multilayer films with different Ni layer thicknesses was prepared by magnetron sputtering technology. The effect of Ni layer thickness on the microstructure and mechanical properties of the multilayer films was investigated, and the deformation and fracture mechanisms underlying the observed behavior were analyzed in detail. The results show that all multilayer films exhibit a well-defined layered architecture with sharp interfacial boundaries. Specifically, the Ni layers grow as columnar grains with an average diameter of approximately 10 nm, while the TiB₂ layers form a very fine acicular nanocolumnar structure. With the increase in Ni layer thickness, the hardness of the multilayer films shows a decreasing trend, gradually decreasing from 27.3 GPa at a 4 nm Ni thickness to 19.3 GPa at 50 nm. In contrast, the fracture toughness increases gradually from 1.54 MPa·m^1/2 to 2.73 MPa·m^1/2. This enhancement in toughness is primarily attributed to a transition in the deformation and fracture mechanism. With the increase in Ni layer thickness, the crack propagation mode in the multilayer films gradually changes from the integral propagation penetrating the film layers to the crack deflection propagation within the layers. This transformation is the result of the combined effect of the stress state of each layer and the crack energy dissipation. Full article