Journal of Materials Science最新文献

This study investigated the hot rolling of titanium-steel clad plates, produced via roll bonding, at four temperatures: 850, 900, 950, and 1000 °C. The aim was to produce thin-gauge titanium-steel clad plates with a total thickness of 2 mm. Interfacial compounds were analyzed using scanning electron microscopy (SEM), backscattered electron imaging (BSE), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). The mechanical properties of the interface were evaluated through microhardness, tensile shear, and tensile tests. The results showed that both the thickness of the intermetallic compound (IMC) layer and the depth of elemental diffusion increased with rolling temperature in the 850–1000 °C range. Bonding strength peaked at 218 MPa at 900 °C but decreased significantly at higher temperatures, dropping to 162 MPa at 1000 °C. The clad plate hot-rolled at 900 °C exhibited the highest tensile strength of 543 MPa. At temperatures above 950 °C, the formation of brittle compounds led to a predominantly brittle fracture mechanism on the titanium side.

This study presents a streamlined combustion technique for the rapid synthesis of carbon quantum dots (CQDs) using various organic solvents, including cyclohexane, toluene, xylene, n-heptanol, and hexane, as carbon precursors. The synthesized CQDs were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD), confirming their nanoscale size, functional groups, and crystalline properties. The CQDs were incorporated into polyurethane at concentrations of 0.1–0.5 wt%, significantly enhancing the polymer’s elasticity, as demonstrated by tensile testing. Among the tested solvents, CQDs synthesized from toluene exhibited superior uniformity and mechanical properties when integrated into polyurethane. These findings highlight the potential of CQDs as effective additives for improving material performance in various industrial applications.

The mechanical properties of composite materials are strongly related to the fiber–matrix interface properties. This study focuses on the click chemistry modification of short flax fibers using the Cu(I)-catalyzed Huisgen cycloaddition type, to strengthen the fiber–fiber interface for composite applications. The flax fibers are functionalized in three steps: a mechanical fibrillation pre-treatment of the fibers surface, followed by a chemical cleaning treatment to eliminate pectin, lignin, hemicelluloses and waxes, allowing exposure of the hydroxyl groups in flax fibers in view of the final treatment of click chemistry. The chosen strategy allows the adaptation of propargylation and tosylation reactions to flax fibers in aqueous media. FTIR and EDX analysis of fibers treated at intermediate stages confirmed the presence of various surface functions of modified fibers with a very high degree of substitution. The properties obtained are strongly improved for reinforcements containing covalent fiber–fiber contacts. Tensile, tearing and bursting tests performed on dry mat reinforcements showed increases in the tensile index, elongation at break, tensile stiffness, burst and tear indexes of 519%, 355%, 201%, 304% and 421%, respectively. Resin transfer molding (RTM) was used to fabricate epoxy composites made of click chemistry-treated short fiber flax mats at a fiber volume content (V_f) of 40%. Tensile tests results showed the positive effect of the click chemistry treatment, with increases in the tensile modulus, strength and strain at break of 41.5%, 64.3% and 30.8%, respectively. Marked improvements in strength and Young's modulus were obtained for composites made of pre-compacted and cross-linked flax-mat preforms.

Carbon–carbon composites are a material commonly used in high heat flux heat environments, such as space missions for terrestrial re-entry. Phenolic resins have been used as carbon matrix precursors due to high char yields of 50 – 55%. In this work, molecular dynamics models of a phenolic resin matrix were polymerized and pyrolyzed in the presence of a carbon fiber (CF) surface using experimentally validated protocols to quantify the nanostructural and chemical evolution of the resin matrix as a function of distances from the resin/fiber interface. After pyrolysis, the predicted char yield was 64.2 ± 0.6%, indicating the presence of the CF surface aids in mass retention relative to a model of a pyrolyzed neat phenolic resin. Ring alignment analyses of the evolving pyrolyzed structures showed signs of templating as rings aligned with the CF surface. Filtering out non-aligned rings revealed bands of charred resin matrix equidistant from one another with similar spacing as that of graphene layers in graphite. The methodology presented helps reveal nanolength scale mechanisms of pyrolysis at resin/fiber interfaces and quantifies microstructural changes difficult to observe in situ, which is important to tailor processing parameters and optimize carbon composite manufacturing.

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In the pursuit to enlarge the applicative potential of a series of polyimides containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-functionalized triazine with no processability in free-standing films, the straightforward blending method with a hexafluoroisopropylidene (6F)-based film-forming polyimide was approached to exploit the valuable characteristics of these polymers toward advanced materials. Thus, the synergistic effect of 6F and DOPO-functionalized triazine pendant moiety along ether and/or isopropylidene units enabled the development of partially miscible free-standing blend films with particle-like morphology. Both the amount of DOPO-based PI loading in the blend and variation of the diimide bridging structure proved to be the main parameters that shaped their chain mobility, morphology, thermal, mechanical, dielectric, as well as gas transport properties. The blend films displayed high thermal stability, with glass transition above 222 °C and initial decomposition temperatures beyond 404 °C, along with good mechanical properties, comparable to those of the film-forming polyimide. High chemical resistance to concentrated HCl vapors and 10% KOH solution was experienced by these blends. The gas separation performances showed that higher amount of 6F units mediate the permeability/selectivity trade-off, leading to the maintenance of permeability along with the increase of selectivity for some gases. These features suggest that blending can be a sustainable alternative to prepare valuable materials from polymers with limited processability, especially in demanding applications where thermal, mechanical and chemical resistance are crucial. Thus, the gas separation properties of the blends improved with the incorporation of a higher amount of 6F groups, which imparted loose chain packing and high free volume. For these membranes, an increased permeability was achieved with a minimum loss of selectivity.

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Carbon nanotubes (CNTs) have emerged as a highly regarded material in this century, garnering significant attention across various fields. As the demand for high-quality CNTs synthesized at low cost and on a larger scale continues to grow, researchers face numerous challenges. Although the development of floating catalyst chemical vapor deposition (FCCVD) synthesis processes has enabled the continuous generation of CNTs, achieving low-cost, large-scale synthesis of high-quality CNTs remains a significant hurdle. Among the primary challenges are the optimization of synthesis equipment and the characterization of CNTs. This review begins by examining the advancements in FCCVD synthesis of CNTs and the underlying growth mechanisms. It then discusses the role of FCCVD in the carbon nanotube growth process, with a focus on its operational parameters. Then, based on the performance differences of carbon nanotubes, the applications of FCCVD-grown CNTs in different fields are introduced. Finally, this paper anticipates the prospects of synthesizing high-quality CNTs through FCCVD and offers reasonable suggestions for future research directions.

Dye-sensitized solar cells (DSSCs) are an efficient and abundant source of available energy. As the photoanode material for DSSCs, TiO₂ has long been proven to be an ideal semiconductor material for such cells due to its excellent photovoltaic properties. However, DSSCs have not been put into mass production because of the difficulty in meeting the requirement of constant output in terms of photoelectric conversion efficiency. To address such problems, scholars have tried to solve them by reducing the bandgap of photoanode materials, reducing electron–hole complexes, and finding new dyes with suitable energy levels. Therefore, this paper focuses on reviewing the development and application of TiO₂-based photoanodes and novel dyes by scholars in the last decade from both theoretical and experimental aspects. On the theoretical side, the performance prediction of TiO₂-based photoanodes doped with different impurity elements and the calculation of the molecular structure of novel dyes are summarized by first-principles calculation methods. On the experimental side, the positive improvements of TiO₂-based DSSCs doped with metals, non-metals, and oxides are summarized, and the application of novel dyes in TiO₂-based DSSCs is also presented. In addition, different improvement methods are objectively evaluated and summarized.

The phases formed by alkaline precipitation of Ni(OH)₂ at different temperatures and different levels of carbonate and nitrate anions have been characterized by X-ray diffraction, elemental analysis, FTIR spectroscopy, TG-MS, N₂ physisorption and cyclic voltammetry. The dehydration-deanionization of α- to β-Ni(OH)₂ passes through an interstratified intermediate IS-Ni(OH)₂, which can be stabilized at 80 °C in the presence of carbonates. IS-Ni(OH)₂ materials have been prepared with CO₃²⁻/Ni²⁺ ratio ranging from 0.05 to 0.16, resulting in different ratios of interstratified α and β phase layers. IS-Ni(OH)₂, thermally stable up to 200 °C, presents a peculiar ink-bottle mesoporosity and surface area higher than 100 m² g⁻¹. The material is promising for electrocatalytic applications on the basis of the textural properties and a reproducible reduction potential of 0.37 V versus SCE. The easily reversible reducibility of Ni²⁺ is also shown by the TG-MS of the thermal dehydroxylation-deanionization to NiO, evidencing transient Ni³⁺ species formed by reaction with NO_x emitted from the decomposition of nitrates.

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The microstructure and deformation behavior are important factors in determining dynamic response for high-entropy alloy (HEA) under extreme conditions. In this work, an as-cast equiatomic CoCrFeNiMn HEA was investigated through compression test conduct at 750 °C, 850 °C, 950 °C and 1050 °C subjected to various strain rates (from 0.01 s⁻¹ to 10 s⁻¹). Microstructural characteristics and deformation behavior of CoCrFeNiMn HEA during hot compression of true strain of 0.5 at 950 °C were studied. The calculated strain rate sensitivity, active volume and activation energy for hot compression were 0.1083, 45.1 b³ and 264.92 kJ/mol, respectively. The combined effects of dislocations, twins, recovery, deformation, and recrystallization attributes to lower values during high-temperature compression. In addition, the flow stress curves were developed an Arrhenius constitutive model from 750 °C to 1050 °C. The new developed Arrhenius-type model exhibited better fit between the experimental and predicted stress. Through the analysis of microstructure evolution, deformation behavior and the constitutive model under extreme situation provide critical insights for the development of new manufacturing techniques into CoCrFeNiMn HEA.

The idea of creating an epoxy-based gradient composition with hardeners of varying activities was proposed to control the exothermic effect during the curing process. Both resin and hardeners in powder form were selected to create a composition appropriate for the production of large-scale products. By modeling the thermal balance in Thermal Simulations software (Netzsch) based on data obtained from Thermokinetics 3 (Netzsch), a comparative analysis of temperature fields in thick-walled polymer samples of non-gradient and gradient compositions was carried out. A single-stage constant heating rate mode was developed to create a controlled gradient of the resin conversion from the inner layers of the part to the outer layers. The polymerization front is created by a certain ratio of hardeners with different reactivities in the layers of the matrix. The use of this method can lead to a reduction in the curing time, the prevention of overheating and a decrease in the residual stresses in the composite part.

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