Materials最新文献

Laser cladding technology is a widely applied surface modification technique; but its inherent process characteristics render it susceptible to cracking. The addition of rare earth oxides has proven to be an effective approach for curbing crack formation and enhancing the comprehensive performance of the coating. This review summarizes the mechanisms by which rare earth additives improve the coating microstructure, molten bath behavior, and interfacial bonding strength, including adjusting surface tension, purifying the molten bath, and forming interatomic chemical bonding. The addition of rare earth oxides significantly improves the forming quality of materials, which contributes to a finer and more uniform microstructure and directly enhances material hardness and resistance to plastic deformation, thereby altering wear behavior and improving wear resistance. The increased hardness provides better support for the surface oxide film, while the improved microstructure mitigates galvanic corrosion and intergranular corrosion susceptibility, leading to enhanced corrosion resistance. In addition, the article incorporates relevant quantitative analysis to provide a reference basis for the type selection, content optimization, and particle size selection of rare earth additives. This article provides a coherent framework for understanding how the addition of rare earths transfers its effects from the process to the performance. However, the industrial application of rare earth oxide laser cladding faces key bottlenecks such as additive deactivation under extreme conditions, threshold effects, nano-agglomeration, and cost constraints.

This study investigated the effect of the partial replacement of silica with carbon fillers, namely carbon black (CB), graphene, and carbon nanotubes (CNTs), on the curing behaviour, thermo-mechanical properties, ageing resistance, and degradation of styrene-butadiene rubber (SBR) vulcanizates. The aim was to determine whether small amounts of carbon fillers could improve the durability-related properties of silica-filled SBR compounds. Graphene and CNTs reduced the maximum curing torque compared with the CB-filled compound while maintaining satisfactory curing characteristics. Thermal conductivity increased with temperature for all materials and reached 0.126 W·m^-1·K^-1 for the graphene-filled vulcanizate at 40 °C, compared with 0.109 and 0.107 W·m^-1·K^-1 for the CNT- and CB-filled compounds, respectively. Dynamic ageing tests revealed significant differences in self-heating behaviour. After 10,000 De Mattia cycles, the graphene-filled compound exhibited the lowest temperature increase (1.5 °C), whereas the CB5/Sil15 formulation showed the highest value (4.5 °C). GC-IMS analysis confirmed the formation of volatile degradation products during cyclic ageing, while increasing carbon filler content reduced the intensity of the characteristic VOC signals. Analysis of the crosslink structure indicated that CNT-containing compounds exhibited the highest resistance to ageing-induced structural changes, whereas graphene promoted an increase in the proportion of monosulfidic and carbon-carbon crosslinks. Overall, the results demonstrate that partial replacement of silica with carbon nanofillers improves the thermo-mechanical stability of SBR vulcanizates. Graphene provided the greatest enhancement in thermal conductivity and the lowest heat build-up, while CNTs showed the highest resistance to structural changes during dynamic ageing.

This study evaluated the potential use of waste mineral wool recovered from heating pipe insulation as a functional additive in cement concrete. The research aimed to determine the effect of this fibrous recycled material on the mechanical, physical, durability, thermal, and microstructural properties of concrete. One reference mix and three modified mixes were prepared, incorporating waste mineral wool at 12%, 16%, and 20% by cement mass. All mixes were prepared using CEM I 32.5R cement, 0/2 mm basalt aggregate, 2/8 mm granite aggregate, and a superplasticizer. After 28 days of sample curing, compressive strength, splitting tensile strength, density, water absorption, frost resistance, and thermal parameters were determined. Microstructural observations were also performed on concrete fracture surfaces. The results showed that the addition of mineral wool reduced the compressive strength from 84.9 MPa for the reference concrete to 63.8-53.3 MPa for the modified concretes. At the same time, moderate dosing improved the splitting tensile strength, reaching a maximum of 3.93 MPa with a 16% addition. The most favorable thermal effect was achieved with a 12% addition, for which the thermal conductivity coefficient decreased from 1.3461 to 1.1988 W/(m·K). The results indicate that waste mineral wool can be used in concretes with limited structural function; however, its dosage requires optimization due to increased water absorption and decreased compressive strength.

This study investigates the strength development, crack evolution and toughening mechanism of basalt fiber-reinforced desert sand high-strength concrete. An L9(3³) orthogonal design was first used to optimize the reference mixture, after which basalt fibers with volume fractions of 0, 0.3%, 0.4% and 0.5% were incorporated. Mechanical testing, digital image correlation, SEM, XRD, TG and FTIR were combined to clarify the relationship among fiber dosage, crack propagation and microstructural reinforcement mechanisms. The optimized matrix mixture was obtained with a water-to-binder ratio of 0.32, a desert sand replacement ratio of 40% and a fly ash content of 20%. The incorporation of basalt fiber had little influence on the 28 d compressive strength, whereas the splitting tensile strength was markedly improved. The highest splitting tensile strength was observed in the 0.4% fiber group, reaching 5.46 MPa, which was 12.81% higher than that of the reference mixture. DIC results showed that basalt fiber reduced strain localization and limited crack opening. The 0.5% group had the lowest COD, while the 0.4% group showed a better balance among tensile strength, strain redistribution and crack-opening control. SEM observations showed fiber bridging and fiber-matrix interaction near the fracture region. Meanwhile, XRD, TG-DTG and FTIR showed no obvious changes in the main phases or functional groups, indicating that the improvement was mainly related to the physical crack-control effect of basalt fibers rather than chemical modification of the matrix. Overall, 0.4% basalt fiber was identified as the preferred dosage for the present system.

This study investigates the direct tensile mechanical behavior of cement mortar plates reinforced with a galvanized steel mesh and randomly incorporated alkali-resistant glass fibers. An experimental program was executed using direct tensile tests on thin mortar specimens containing fiber volumetric fractions of 0%, 4%, 6%, 8%, and 10% relative to the cement volume. To rigorously characterize the mechanical response, the study quantified the apparent initial stiffness, 0.2% offset stress, ultimate tensile strength, and post-offset energy absorption capacity. Results indicate that increasing alkali-resistant glass-fiber content systematically modified the global tensile response of the composite system. At 10% glass-fiber content, the mean crosshead-derived apparent initial tensile stiffness was 10.43 times that of the reference group without glass fibers. The characteristic stress determined using the adopted 0.2% offset criterion and the ultimate tensile strength increased by 154.5% and 74.1%, respectively, while the apparent post-offset energy absorption increased by 68.4%. Because strain was derived from crosshead displacement, the apparent stiffness and energy-absorption parameters represent the global specimen-grip-machine response rather than intrinsic material properties. The experimental results exhibited acceptable repeatability, although the apparent tensile stiffness showed greater variability than the strength-related parameters. These findings support the continued development of the investigated composite configuration for thin cementitious elements requiring improved tensile response and damage tolerance.

The conventional fabrication of concrete block moulds is characterised by persistent challenges related to standardisation, protracted redesign processes, and an absence of structural validation, all of which undermine regulatory compliance. This study proposes a standardised parametric modelling process aimed at ensuring compliance with the technical criteria of the INEN-3066 and ASTM C90 standards. An integrative methodology combining QFD/VOC matrices with CAD-CAE tools was used to parameterise three commercial mould configurations (10, 15, and 20 cm) in SolidWorks 2023. A finite element analysis (FEA) was subsequently conducted in ANSYS 2025 R1 under iterative overloads of up to 10,000 N, complemented by a rheological analysis in SolidWorks Plastics. The results show that the "male" (punch) components exhibit consistently high stiffness, maintaining fatigue safety factors above 1.61 across all three configurations. In contrast, the "female" (die) components are the more vulnerable link in the assembly: the fatigue safety factor of the 10 cm die drops below the required threshold of 1.0 at 4000 N, compared with 6175.6 N and 9254 N for the 15 and 20 cm configurations, respectively. The rheological analysis further confirmed the feasibility of an ultrafast injection cycle, with cavity filling times below 0.11 s and injection pressures ranging from 6.105 to 12.9 MPa across all formats. It is posited that, in accordance with the parametric model, a reinforced-wall geometry should be adopted for the 10 cm die, characterised by an augmentation of wall thickness by 15% and enlarged fillet radii. This is projected to elevate its fatigue-critical load beyond 4500 N without necessitating any alteration in the external block dimensions. These findings indicate that parametric CAD-CAE-CFD digitalisation can anticipate structural failures before manufacturing, offering a computational pathway toward regulatory compliance that should be confirmed through physical prototype testing.

The purpose of this paper is to determine the influence of the stearic acid and methyl esters on the properties of protective coatings applied to reinforced concrete objects. The evaluation of protective effectiveness included compositional analysis (XRD, XRF), surface properties (contact angle, surface energy, UV resistance), soiling resistance, roughness, and surface morphology (SEM). The scanning microscopy SEM images showed a relatively uniform distribution of resin on the concrete surface. The lateral dimensions of the epoxy-rich surface domains ranged from 8 μm to 40 μm. All analysed samples exhibited a very similar chemical composition, in which SiO₂ was the dominant component. In situ tests were conducted on an operating reinforced-concrete cooling tower. Among the investigated coating systems, ER1 + SA exhibited the highest observed mean apparent static water contact angle (CA) of 131°. A strong inverse empirical relationship was observed between the apparent contact angle and average surface roughness. UV ageing caused small numerical decreases in contact angle for most systems. After one year of operation, the ER2 epoxy coating modified with methyl esters was the best-preserved of the analysed variants.

Copper selenide compounds, owing to their excellent electrical transport properties and low thermal conductivity, are promising thermoelectric materials, but their poor mechanical flexibility limits practical applications in flexible devices. Herein, a simple all-electrochemical strategy was developed to fabricate polypyrrole (PPy)/Cu_2-xSe composite thermoelectric films through sequential electropolymerization of pyrrole and electrodeposition of Cu_2-xSe. By optimizing the deposition potential of Cu_2-xSe and pyrrole polymerization time, the thermoelectric performance of the composite films was significantly enhanced. The optimized PPy/Cu_2-xSe composite film achieved a maximum power factor of 174.05 ± 9.87 μW m^-1 K^-2, nearly 300 times higher than that of pristine PPy, while maintaining a low thermal conductivity of 0.30 W m^-1 K^-1. The composite film also exhibited excellent flexibility, retaining 94.77% of its initial power factor after 1000 bending cycles. A flexible thermoelectric device assembled from the composite films delivered a maximum output power of 240.5 nW at ΔT = 50 K. This work provides an effective strategy for developing Cu_2-xSe-based flexible thermoelectric composites.

Fan-Out Panel-Level Packaging (FO-PLP) enables high area utilization and manufacturing efficiency, but process-induced warpage caused by the coefficient of thermal expansion (CTE) mismatch and polymer shrinkage remains a major challenge. This study presents a classifier-gated hybrid machine-learning framework for the rapid and accurate FO-PLP warpage prediction using a database generated from a validated three-dimensional finite element process model. A Random Forest classifier first estimates the probability of each global warpage mode, while cluster analysis reduces the spatial training dataset. Two mode-specific artificial neural networks are then combined through probability-weighted fusion to predict the full warpage field and enable warpage prediction for previously unseen geometry layouts. The framework was evaluated on 16 independent finite element designs spanning both warpage modes. Compared with an equivalent single-network model, the proposed approach consistently achieved lower mean and maximum prediction errors across all designs, with the greatest improvements at the panel edges and corners where the prediction is most challenging. In addition, the clustering strategy reduced the training-set size and computational cost. These results demonstrate that integrating warpage-mode classification with mode-specific learning improves both the prediction accuracy and training efficiency, providing a practical tool for the fast warpage assessment of new FO-PLP layout designs.

Fine-aggregate source can alter both the load-bearing response and surface scaling of mortar under freezing and thawing, but these responses are often reduced to a single durability ranking. This study compared coal gangue sand mortar (CGM), river sand mortar (RSM), desert sand mortar (DSM), and standard sand mortar (StSM) after 0, 25, and 50 freeze-thaw cycles (FTCs). Compressive strength and mass loss were measured using three replicate specimens per quantitative condition, while post-compression fragments were examined by scanning electron microscopy (SEM). The primary integrative analysis was a parameter-free two-dimensional damage-trajectory map that retained absolute compressive strength and mass loss as separate measured axes; a weighted coupled index was retained only as an auxiliary sensitivity check. Before cycling, the compressive strengths of StSM, RSM, DSM, and CGM were 68.13±0.48, 53.90±0.39, 19.47±0.33, and 6.49±0.07 MPa, respectively. After 50 FTCs, StSM retained the highest absolute strength (33.61±0.39 MPa) and the lowest mass loss (0.21±0.02%), whereas DSM retained 9.91±0.19 MPa and exhibited the highest mass loss (17.46±0.05%). The StSM trajectory moved primarily toward lower strength with negligible surface-material loss, while DSM moved toward both low residual strength and severe scaling. RSM showed substantial strength reduction followed by later-stage surface loss. CGM followed an atypical trajectory in which measured strength increased to 11.13±0.13 MPa while mass loss reached 9.67±0.04%; because age-matched non-frozen controls were unavailable, this apparent gain cannot be separated from continued hydration and specimen-age effects. The SEM images suggested pores, interfacial discontinuities, cracking, and matrix loosening, although some defects may have been induced or widened by compression. The trajectory representation exposed distinct deterioration modes without arbitrary weighting, whereas the calculated ordering of CGM and RSM in the auxiliary index changed with weighting and normalization choices. The results support reporting absolute residual strength and surface loss jointly when screening alternative fine aggregates for cold-region mortar.