Journal of Materials Science最新文献

Aerogels attract a lot of attention due to their high porosity, high specific surface area, low density, and low thermal conductivity. However, high cost, complex manufacturing process, and poor mechanical properties hinder their application in the industrial sector. Herein, we examined the effect of strengthening silica-based aerogels with short jute (Corchorus olitorius) fibers. Gels containing a commercial silica sol, water, polyvinyl alcohol (PVA), polyethylene glycol (PEG) and jute fibers were prepared, then freeze-dried for 36 h to yield SiO₂/PVA/PEG-Jute aerogels with different jute fiber contents. The aerogel prepared with a fiber content of 3 wt.% possessed excellent thermal insulation properties (thermal conductivity of 0.05355 W/m K), a linear elongation of 80%, and a compressive strength of 1.1 MPa (8 times higher than the aerogel prepared without jute fibers). The addition of low-cost jute fibers thus maintains the desirable thermal insulation properties of SiO₂-based aerogels whilst significantly improving their mechanical properties (aerogel flexibility, compression performance and shrinkage resistance) for different end uses.

The goal of this article was to analyze the microstructural, texture development, deformation mode, and mechanical properties of a Mg–8.7Gd–4.18Y–0.42Zr (wt%) magnesium alloy that underwent conventional extrusion in conjunction with equal channel angular pressing (EX-ECAP) deformation. The findings indicate that as-extruded alloy reveals a significant basal texture, while the ECAPed GW94K alloy demonstrates basal poles that are inclined ~ 45° from the extrusion direction. After 4p-ECAP process at 370 °C via the Bc path, the microstructure of the alloy exhibits a high level of uniformity, with a fine grain area fraction of 92.7% and an average grain size of 3 μm. The GW94K alloy experiences a significant increase in elongation when the ECAP pass is increased, although the ultimate tensile strength (UTS) decreases remarkably. In particular, the sample subjected to ECAP demonstrates a room-temperature tensile elongation of 36.8% in the extrusion direction. This phenomenon can be ascribed primarily to the evolution of the texture during repeated ECAP processes, leading to the activation of multiple deformation modes in ECAP deformation process of the GW94K alloy. Furthermore, the results suggest that the presence of multiple slip systems, characterized by their high Schmid factor and IGMA analyses, significantly influences the uniform elongation.

Anodization technology allows for the rapid and controlled preparation of specified regular nanostructures on the surface of metal. During anodization, the metal ions migrating outward and the oxygen ions provided by the electrolyte form oxides at the metal/electrolyte interface, and the migration rate of different kinds of metal ions is different, which leads to the complex mechanism of the anodization of alloys. This work focused on the mechanism of the anodization of alloys, and studied the effects of hydroxide ions in electrolyte and applied voltage on the reactivity of different components of brass. It was obtained that low voltage favors the migration of Zn and high KOH concentration favors the dissolution of the anodic products of Cu, so that an alloy with Zn content of 16.05% was obtained when a voltage of 40 V was applied, and when a voltage of 60 V was applied, the alloy with Cu content of 13.34% was obtained in 0.4 M KOH solution.

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The oxidation of bond coat (BC) and interdiffusion between BC layer and superalloys were two mechanisms that contribute to the degradation of thermal barrier coating system (TBCs). The oxidation and interdiffusion of TBCs on single-crystal superalloys were comparatively studied in this work at 950 °C, 1050 °C and 1100 °C over a duration of 1500 h. The results indicated that the thickness of the thermally grown oxide (TGO) progressively increased with the oxidation time and temperature, following a parabolic law. The discontinuous TGO gradually developed into a double-layer structure: the upper layer was a mixed oxide layer, while the lower layer predominantly comprises an Al₂O₃ layer. Moreover, an interdiffusion zone (IDZ) is formed at the interface between the BC layer and the substrate, with its thickness increasing in response to both temperature and oxidation time. The Cr-rich phases appeared in the IDZ, where Al initially diffused from the BC layer to the substrate, followed by a reverse diffusion process. Simultaneously, Ni and refractory elements diffused from the substrate into IDZ, resulting in the precipitation of the topologically close-packed (TCP) phases and the formation of a secondary reaction zone (SRZ). It has further been shown that Cr-rich phases further diffused into SRZ. Higher oxidation temperatures accelerated the growth of the SRZ and facilitated the transformation of the TCP phases from a blocky to a needle-like morphology. Ultimately, the continuous growth of IDZ and SRZ led to the evolution of the substrate from a monocrystalline to a polycrystalline structure. This study provides valuable data on the microstructural evolution of TBCs and the assessment of their service life.

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Zinc-air batteries (ZABs) have received considerable interest because of the growing demand for high-energy–density and safe energy storage systems. Efficient and economical catalysts for the cathodic oxygen reduction reaction (ORR) in ZABs play a crucial role in reducing expenses and facilitating industrialization. In this study, an efficient alkaline ORR electrocatalyst derived from ZIF-67 is synthesized by a simple one-pot method followed by high-temperature calcination. The optimized catalyst, CoCu-NPC-1000, demonstrates outstanding electrocatalytic performance in ORR, with a half-wave potential (E_1/2) of 0.849 V and an onset potential (E_onset) of 0.988 V. Notably, CoCu-NPC-1000 also shows excellent methanol tolerance, stability, and durability under alkaline conditions. These superior catalytic properties are attributed to the synergistic effect of Co-N_x and Cu-N_x dual active sites, along with the increased average pore diameter facilitated by the pore-forming agent Zn(NO₃)₂·6H₂O. The CoCu-NPC-1000-based zinc-air battery outperforms the power density of Pt/C, achieving 107.1 mW cm^⁻2 at a current density of 124.3 mA cm^⁻2, compared to 84.79 mW cm^⁻2 at 143 mA cm^⁻2 for Pt/C. Additionally, its specific capacity reaches 851 mAh ({g}_{Zn}^{-1}), exceeding that of Pt/C (688 mAh ({g}_{Zn}^{-1})). This study not only confirms the effectiveness of Zn(NO₃)₂·6H₂O as a pore-forming agent but also offers valuable insights into synthesizing bimetallic organic framework-derived electrocatalysts for ZABs.

The composite α-Ni(OH)₂@CNT of multi-walled carbon nanotubes (CNT) and sheet-like α-Ni(OH)₂ was prepared by a one-step hydrothermal method. The structures and electrochemical properties of α-Ni(OH)₂@CNT and α-Ni(OH)₂ have been studied in detail. Since hydroxylated CNT was used in this study, CNT provides the dual role of dispersion and conductivity for α-Ni(OH)₂@CNT. The structural characterization shows that the thickness of α-Ni(OH)₂@CNT nanosheets is significantly lower than that of α-Ni(OH)₂, and the specific surface area and pore volume are significantly higher than that of α-Ni(OH)₂, which provides more active sites for the composites. The electrochemical test results show that the specific capacitance and rate performance of α-Ni(OH)₂@CNT are much higher than that of α-Ni(OH)₂. The asymmetric supercapacitor (ASC) assembled with α-Ni(OH)₂@CNT and activated carbon (AC) can provide an energy density of 42.8 Wh kg⁻¹ at a power density of 800 W kg⁻¹, and the specific capacity can be maintained by 80% after 20,000 cycles, showing good application value. The theoretical calculation results further confirm that CNT increases the conductivity of α-Ni(OH)₂@CNT. This work provides a low cost and effective modification method for the practical application of α-Ni(OH)₂.

As an excellent solid lubricant in vacuum and inert gas environment, molybdenum disulfide (MoS₂) is easy to be oxidized in high temperature, which leads to serious deterioration or even failure of lubricating performance. The introduction of doped phase or composite can improve the high temperature lubricating performance of MoS₂-based lubricating coating to some extent. In this work, the effect of nano-particles zinc oxide (ZnO) and layered graphene oxide (GO) on the high temperature (400, 450 and 500 °C) tribological properties of MoS₂-based composite lubricating coatings were studied. It was found that the tribological performance of MoS₂-ZnO composite coating were the best for almost all test conditions, and the average friction coefficient and wear rate were about 0.25 ~ 0.27 and 4 ~ 6 × 10⁻⁵ mm³/Nm, respectively. The promising tribological performance of MoS₂-ZnO composite coating was attributed to the ZnO that mitigated the oxidation of MoS₂, and the formation of ZnS. It is the formed ZnS, nano-ZnO and a small amount of MoS₂ that provided synergistic lubrication. However, the introduction of layered GO deteriorated the tribological properties of the MoS₂-based composite coating, due to the high-temperature decomposition of GO and the formation of hard abrasive particles. The results can provide reference for the design and preparation of MoS₂-based composite lubricating coating.

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This study investigates the effect of aging temperature on the physical properties of Fe–40.32Ni–5.51Cr–2.63Ti–0.47Al–0.55Mn–0.40Si–0.016C (wt.%) alloy using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, a physical-property measurement system, and a dilatometer, among others. After a solution treatment, the microstructure of the experimental alloy was composed of the γ phase. The aging process involved the precipitation of the γ’ and η phases to regulate the Elinvar effect. No martensite or ferrite phases were observed in either the solid-solution or aged samples using X-ray diffraction and transmission electron microscopy. The Elinvar effect for traditional Fe–Ni–Cr ferromagnetic Elinvar alloys is related to spontaneous magnetisation, resulting in spontaneous volume magnetostriction. The inflection temperature of the elastic modulus exceeded the Curie temperature. The larger the precipitation amount, the weaker the ΔE effect, and the larger the Young’s modulus value. For a holding time of 2 h, the amount of precipitation was maximised at an aging temperature of 650 °C, while Young’s modulus and its temperature coefficient achieved maxima of 190 GPa and 9.0 × 10⁻⁵ °C⁻¹, respectively. In addition, the lattice constant at room temperature indirectly reflects the amount of precipitation. Young’s modulus, the temperature coefficient of Young’s modulus, the Curie temperature, and the linear-expansion coefficient obeyed an approximately parabolic law as functions of the lattice constant or its reciprocal. Moreover, Young’s modulus and its temperature coefficient can be estimated using the Curie temperature and linear-expansion coefficient, respectively.

The current study explores a new approach to investigate the CO₂ detection capabilities of cobalt-doped zinc oxide (Co-ZnO) combined with molybdenum sulfide (MoS₂) hybrid nanomaterials Co-ZnO/MoS₂ (CZM). The hydrothermally synthesized CZM composites provide unique structural and compositional properties, with 25 nm as their longest dimension (length), and specific lattice structure. CZM-based electrodes are developed by preparing the nanomaterial-dispersed ink, and potentiometric studies explore the optimal sensing performance. We found significant enhancements in sensitivity, reaction time, and reduction efficiency by systematically changing the electrolyte concentration in the electrode cell. Bode and Nyquist plots explain the influence of electrolyte concentration and the nanomaterial synergy in CO₂ sensing and conversion with the 0.1 N electrolyte with the maximum efficiency. By offering important insights into how the electrolyte content affects the performance of Co-ZnO/MoS₂ nanocomposite sensors, this study advances the field of CO₂ sensing technology. Further, the nanomaterials extend their applicability in environmental monitoring, evaluating indoor air quality, and industrial processes.

Carbon particles (CP) with functional groups are one of the promising modifiers for polymer matrices to create pervaporation mixed matrix membranes (MMM) with tailored properties. In this context, a detailed study of the effect of polymer modification with various CP is required. Thus, in this study, highly efficient MMM based on chitosan (CS) for enhanced pervaporation dehydration of isopropanol were developed by modification with graphene oxide, fullerenol, carboxyfullerene, single- and multi-walled (MWCNT) nanotubes. The effect of CP introducing into the CS matrix was investigated, where the CS/MWCNT composite demonstrated optimal transport properties as a dense membrane material. To increase efficiency, an optimal cross-linking agent for improvement of the membrane stability in an aqueous media was selected, and supported membranes from CS/MWCNT composite were developed. The structural changes during modifications were investigated by spectroscopic (FTIR and NMR) and microscopic (SEM and AFM) methods. Physicochemical properties of MMM were studied by thermogravimetric analysis, measurements of contact angles and swelling degree. The optimal cross-linked supported membrane with a thin dense layer from CS/MWCNT (5%) composite had in 2–4 times increased permeation flux and higher water content in the permeate (99.9–98.5 wt.%) compared to the pristine dense CS membrane in pervaporation dehydration of isopropanol (12–50 wt.% water). This membrane also demonstrated high stability in separation till 90 wt.% water in the feed with the following transport parameters of 1 kg/(m²h) and 97.5 wt.% water in the permeate.

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