Journal of Materials Science最新文献

SiC_f/SiC composites were fabricated by a novel two-stage precursor infiltration and pyrolysis (PIP) process. The two types of SiC fibers (C3-BN and C3-BN-1800) were used as reinforcements. The C3-BN was the third-generation SiC fibers coated with an in-situ boron nitride (BN) layer, C3-BN-1800 was obtained by a 1 min continuous pyrolysis of C3-BN at 1800 °C. In stage I, the SiC_f/SiC composites (CMC-Is) achieved initial densification by low-temperature PIP process, while the matrix consisted of low crystallinity SiC and amorphous SiOxCy. At 1600 °C-1 h, the crystallization of SiC matrix and decomposition of SiOxCy led to a significant reduction in the strength of the CMC-Is (30% strength retention). Through several cycles of high-temperature PIP process (stage II), the SiC_f/SiC composites (CMC-IIs) had higher density than CMC-Is, and the matrix had high crystallinity SiC and significantly decreased oxygen content. Thus the CMC-IIs have better thermal resistance and the strength retention is near 50% at 1600 °C-10 h.

Creep failure is an important failure mode of Ti alloys serving in the aviation field. Therefore, in order to improve the high temperature creep property of Ti alloys. The high temperature tensile creep tests of Ti60 alloy rolled sheet before and after solution-aging treatment were carried out at 700 °C and different stress conditions. The creep stress exponent was obtained, the microstructure was observed, and the evolution behavior of the texture was analyzed. The results show that the creep life of the sample after solution-aging treatment was significantly improved. Taking 700 °C–150 MPa as an example, the creep life was increased from 200 to 8918 min. The creep stress exponent of the sample after solution-aging treatment is 6.74. This shows that at 700 °C, the mechanism of dislocation climbing is dominant, and dislocation slip is secondary. It has a strong {10-12}<10-11> texture after solution-aging treatment. The {10-12}<10-11> texture belongs to twin texture. There are a large number of ∑33c twin boundary in the samples after high temperature solution-aging treatment. The existence of ∑33c twin boundary is helpful to improve the high temperature creep property.

Impactful uses of nanomaterials are essential for addressing global energy and environmental issues, primarily via photocatalytic sustainable water splitting, which provides a sustainable pathway for the creation of hydrogen, and dye degradation, which breaks down hazardous dye wastewater pollutants. The scalable characteristics of nanomaterials, particularly their precise bandgap energy, increased surface area, and effective charge separation capability, have made them significant contributors. The present review examines four different kinds of nanocomposites that have shown enormous potential in water splitting and dye degradation: those based on zinc, iron, titanium, and cerium. Zinc oxide's photocatalytic activity shifted from the ultraviolet to the visible spectrum when dopants were added or when it was mixed with other oxides, such as copper. When combined with substances like graphene, iron oxide—which is well-known for producing hydroxyl radicals—becomes very efficient at water splitting and dye degradation. Despite being limited by UV light, titanium dioxide performs better when paired with reduced graphene oxide or silver particles, which boosts its effectiveness in both processes when exposed to visible light. Lastly, cerium oxide's distinct redox characteristics enable it to create efficient heterojunctions with substances like ZnO and TiO₂, improving charge transfer and lowering recombination. Moreover, this review provides attention to their dual use and guides how to optimize photocatalytic efficiency for environmental remediation and sustainable energy generation.

Mechanical degradation of carbon fiber-reinforced polymer composites (CFRP) under marine environment has become an increasing important concern due to its significance to reliable service. This paper aims to establish models to investigate the mechanical degradation of CFRP under marine environment, in which the evolution of component materials properties, initiation and growth of internal microcracks and delamination damage were considered. A representative volume element with randomly generated fibers was established to calculate the mechanical properties before and after environment aging. The microcracks induced by environment aging were described by a defect hypothesis, and a two-dimensional tensile model was developed to determine the numbers and size of the defects. Then the moisture absorption behavior and hygrothermal residual stress were investigated by three- and two-dimensional models. Finally, the evolution of interlayers properties was revealed by a specimen-sized interlaminar shear model according to the traction–separation cohesive law. The results show that the cracks inside the material can lead to nonlinear changes of mechanical properties. Moisture distribution in composite laminate is not affected by the ply orientation, while the hygrothermal stress is closely related to the layup sequence and significant stress concentration can be observed in the fiber–matrix interface. The evolution of interlaminar shear performance can be well explained by the degradation factors of interlaminar strength and fracture energy.

Graphical abstract

The effects of pre-twinning on deformation of a textured Mg–3Al–1Zn (AZ31) magnesium alloy are investigated with real-time, in situ synchrotron-based, multiscale diagnostics. Samples are pre-compressed along the rolling direction (RD, perpendicular to the c-axis) to introduce ({10bar{1}2}) twins, and then subjected to uniaxial tension along RD or the normal direction (ND, parallel to the c-axis). Bulk stress–strain curves (macroscale), strain fields (mesoscale) and X-ray diffraction patterns (microscale) are obtained simultaneously. The yield strength is enhanced by pre-twinning. For tension along RD, plastic deformation is primarily driven by detwinning, followed by prismatic slip. Conversely, for tension along the ND, plastic deformation is initially dominated by basal slip and subsequently by twinning. Additionally, stress relaxation occurs within the matrix upon twinning, and within the pre-compression-induced twins upon detwinning.

High-nickel layered oxide LiNi_xCo_yMn_zO₂ (where x + y + z = 1 and x ≥ 0.6) has emerged as a primary focus in research on power battery cathode materials, owing to its high energy density and cost-effectiveness. However, high-nickel cathodes are prone to Li/Ni mixing during synthesis, which can potentially affect the discharge specific capacity, rate, and cycling stability of the battery. In high-nickel cathode materials, the degree of Li/Ni mixing is significantly influenced by the sintering temperature. In this study, we comprehensively investigated sintering temperature to achieve high capacity and cycling stability in LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode materials. We identified the optimal sintering temperature and investigated the mechanism behind performance degradation caused by over-sintering. This study concludes that the NCM811 cathode material synthesized at 760 °C exhibits minimal Li/Ni mixing and demonstrates superior electrochemical performance, with a capacity retention of 89.0% after 100 cycles at 1.0 C and a low polarization voltage of 0.045 V. A series of chemical and structural characterizations reveal a correlation between over-sintering, Li/Ni mixing and capacity decay. Specifically, the over-sintering temperature during synthesis of the NCM811 cathode material exhibits a linear positive correlation with Li/Ni mixing, leading to structural degradation that impedes lithium-ion diffusion pathways. Increased surface reactivity contributes to the formation of unstable cathode–electrolyte interfaces, while elevated interfacial reaction by-products deplete active material, resulting in higher capacity loss. Additionally, the pronounced, steeper two-phase irreversible H2 → H3 phase transition triggered by over-sintering accelerates the layered structure degradation, leading to the rapid decay of capacity.

Carbon fiber-reinforced composites (CFRCs) as the load-bearing structural component are widely used in the military and industrial fields. However, CFRCs undergo the severe oxidation in high-temperature oxygen environments, seriously affecting their service safety. In current work, SiO₂ and TiO₂ coatings are selected to synthesize on the CFRCs surface for improving their anti-oxidation by a liquid-phase deposition technique. The deposition technique is simple, controllable, and reproducible. The formation process, microscopic morphologies, chemical bonding, and molecular structure of SiO₂ and TiO₂ on the CFRCs surface are systematically investigated. A series of characterizations, namely X-ray diffractometry, Raman spectrum, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, demonstrate that SiO₂ and TiO₂ coatings are successfully synthesized on the surface of CFRCs, respectively. The scanning electron microscopy and elemental distribution show that CFRCs are evenly loaded with SiO₂ or TiO₂ particles on the surface. TiO₂ particles grow faster and the synthesized particles are finer with the particle diameter of 200 ~ 300 nm in comparison with 400 ~ 500 nm of SiO₂ particles, under the same synthesis conditions. In addition, an isothermal oxidation test is conducted for the CFRCs modified by SiO₂ or TiO₂ at 1273 K for 30 min. The weight loss rate of modified composites is lower than 62.12% of bare sample. Among them, the composites modified by SiO₂ or TiO₂ at 70 °C for 3 h possess the lowest weight loss rate of 34.24 and 37.32%, respectively, indicating that the modification of SiO₂ and TiO₂ all can improve the oxidation resistance of CFRCs.

Graphical abstract

Mixing chemical pigments of basic colors to create a broad spectrum of hues is fundamental to the modern ink and coating industries. Colloidal-assembled photonic crystals offer a promising, sustainable alternative for color applications. However, due to the distinct mechanisms by which they produce color, achieving the same flexibility and consistency as pigments in commercial production has been a significant challenge. Combining colloidal particles of different sizes presents a potential solution, but the underlying mechanisms and applicability across various colloidal systems remain largely unexplored. In this study, we explore the color mixing effects of particles of different sizes in a low-viscosity matrix. Our findings show that, while the reflection colors of mixed particles depend on their average size, the brightness is influenced by both effective polydispersity and the composition of the mixtures. For particle mixtures with the same average size and polydispersity, the brightness of reflection colors varies significantly based on the number of components and their relative proportions. Remarkably, a mixture of two distinct particle sizes can achieve 3–4 times higher reflectance than a mixture of five distinct sizes, even with the same size polydispersity. Our results demonstrate how a wide range of colors can be produced using particles of several basic sizes and how their brightness and saturation can be controlled by adjusting the composition. These insights provide new strategies for color mixing in photonic crystals and may facilitate their industrial application.

MnO₂ has been proven to be highly reactive to HCHO, but the form of powder limits its application. The problems of easy agglomeration and difficult recovery of MnO₂ powder can be solved by loading it onto fibrous materials, and improved its catalytic efficiency. However, the loading amount and stability are the challenges encountered in application. In this study, MnO₂ nanosheets were in-situ grown on lignin fiber (LFs) pads by a simple impregnation method, and the morphology and chemical structure of the synthesized MnO₂-LFs composites were characterized. The results show that the fibers prepared by centrifugal spinning have a smaller diameter than traditional fibers, allowing for more MnO₂ loading. Due to the presence of abundant functional groups on the LFs surface, strong Mn–O and hydrogen bond interactions promote robust MnO₂ anchoring, achieving uniform distribution of MnO₂ on the LFs surface. Subsequently, δ-MnO₂ formed on the LFs surface after 72 h of impregnation in KMnO₄ solution exhibited the best HCHO degradation performance. After 2 h of reaction, the HCHO removal rate was as high as 80.14%, and it had good stability and reusability. Therefore, LFs are expected to be used as carrier materials for MnO₂ in the purification of indoor air HCHO.

Carbon-based composite conductive material, possessing advantages such as facile processing, cost-effectiveness, and ultralightness, represents a burgeoning electrothermal material. However, developing water-based inks using carbon-based materials that satisfy the requisites of human health safety, low-voltage operability, and durability in the realm of flexible wearable heaters remains an arduous challenge. Here, stable water-based conductive inks, with graphene nanosheets (GNs) and ultrafine carbon powder (UC) as conductive fillers, are prepared by a simple ball milling method. The conductive inks exhibited rheological properties suitable for screen printing, with a print resolution of up to 0.4 mm and an adhesion level of grade 1. When graphene nanosheets accounted for 15% of the total conductive filler content, the printed patterns displayed a “sandwich” type conductive network structure formed by both plane contact and point contact between conductive fillers at the microscale, resulting in a sheet resistance as low as 14.16 Ω sq⁻¹, which was 54.99% lower than that of pure ultrafine carbon-printed patterns. The electrothermal film prepared from these printed patterns demonstrated rapid response within 50 s under low-voltage drive ranging from 4 to 16 V and achieved an adjustable temperature range of 30–90 °C. Also, it maintained stable performance under cyclic heating–cooling and bending conditions for up to 1000 cycles. Wearable heating sleeves with excellent heat uniformity were fabricated to validate their tremendous potential in flexible wearable device applications.