查看更多>>摘要：? 2022 Elsevier B.V.Nitride and metallic ?lms multi-element (TiVCrTaW)Nx high-entropy alloy were deposited on silicon wafers by pulse DC magnetron sputtering. The microstructure and mechanical properties of the films prepared with different nitrogen gas flow ratios were studied. The results show that the concentration of nitrogen approached the stoichiometric composition at nitrogen gas ratio RN ≥ 33.3 %. The alloy ?lm deposited with pure argon atmosphere exhibited a BCC structure and a very smooth surface, while an FCC with (111) or (200) preferred orientation and granular surface morphologies was observed in those ?lms prepared with introduction of nitrogen gas. The (TiVCrTaW)Nx films exhibited enhanced hardness upon the addition of nitrogen probably due to the solid-solution strengthening effect and grain refinement. The nitride ?lm achieved the highest hardness and Young's modulus of 38 GPa and 340 GPa, respectively. The results show that the deposition atmosphere plays a vital rule in the structure and the properties of the (TiVCrTaW)Nx high-entropy films.
查看更多>>摘要：? 2022 Elsevier B.V.In order to improve the preparation process and practical process of magnetic refrigerant, a method of accelerating phase formation by cold compression plastic deformation at room temperature is proposed. To determine the significance of this method, the grain structure, phase composition and magneto-thermal effects of LaFe13.1Co0.7Si1.4 alloy were systematically studied. The results show that with the increase of compression ratio, the number of grains per unit volume increases and the grain size tends to be uniform. Compared with the uncompressed sample, the proportion of magnetothermal phase in the pre-compressed samples increases after annealing under the same conditions. When the deformation is 40%, the ratio of 1:13 phase in pre-deformed sample after 1 day annealing is 72 vol%, which is significantly better than that of the undeformed sample. After annealing for 3 days, the Curie temperature (TC) of 40% pre-deformed LaFe13.1Co0.7Si1.4 samples is 330 K, and the magnetic entropy changes to ? 4.70 J/kg K and ? 5.42 J/kg K under 2 T and 3 T magnetic fields, respectively. The appropriate Curie temperature and value of ?SM make it an attractive potential candidate for magnetic refrigeration application at room or even high temperature.
查看更多>>摘要：? 2022 Elsevier B.V.The effect of 0.2 wt% Sc addition on the high temperature strength and microstructure evolution of Al-11.5 wt%Si-4.0 wt%Cu alloy in different states (as-cast, T6 and LTHE (long-time-heat-exposure at 300 °C for 100 h)) was studied in detail. Tensile test at RT (room temperature) and at 300 °C was used to examine the variation of strength. OM (optical microscope), SEM and TEM/HRTEM were used to characterize the microstructure. It is found that the value of σ0.2 (the yield strength) at 300 °C of the alloy with Sc-micro-alloying can be increased significantly, especially in T6 and LTHE states. During the ageing treatment, Sc-micro-alloying greatly increases the number densities of θ′′ and θ′ dispersoid particles, thus σ0.2 at 300 °C of the samples in T6 state can be increased from 86 MPa to 116 MPa. By Elements-Mapping, it is found that Sc and Si co-exist inside θ′ precipitates. This co-existence improves the thermo-stability of θ′ phase and hence suppresses the coarsening behavior of θ′ particles and phase transformation from θ′ to θ during the LTHE treatment. Therefore, the value of σ0.2 at 300 °C of the alloy with Sc-micro-alloying in LTHE state still keep at a very high level of 99 MPa, with an increment of 36 MPa compared with the base alloy.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, bismuth sulfide/tin (IV) sulfide (Bi2S3/SnS2) heterostructure nanocomposites were fabricated to obtain high-performance thermoelectric composite materials. The Bi2S3/SnS2 composites were prepared via solution mixing using a two-step hydrothermal reactor. First, flower-like-shaped Bi2S3 was prepared, after which the as-synthesized Bi2S3 was decorated with SnS2 nanocomposites. The formation of a unique Bi2S3/SnS2 heterostructure was achieved through a thioacetamide-induced surfactant-assisted reaction process. The thermoelectric power factor of the Bi2S3/SnS2 composites was optimized by controlling their Bi:Sn ratios, and changes in the thermoelectric properties of the composites were investigated by examining the change in their carrier transport properties. The composite achieved a maximum thermoelectric power factor of ~99.7 μW/m·K2 at a Bi:Sn ratio of 1:0.2, which is ~5.1 times larger than that of pristine Bi2S3. This increase in the power factor was ascribed to the fact that the enhanced electrical conductivity outweighs the reduction effect of the Seebeck coefficient. The hetero-structured Bi2S3/SnS2 composite is a promising strategy for realizing high-performance sulfur-based thermoelectric composite materials.
查看更多>>摘要：? 2022 Elsevier B.V.Precipitation and severe plastic deformation have been proven to be effective methods for separately enhancing the properties of copper alloys. This work studied microstructure evolution and properties of a CuCrZrSc alloy undergoing aging treatment and equal channel angular pressed (ECAP). After 12 passes of combined thermomechanical treatment, the high-angle grain boundary spacing of the alloy was reduced to 300 nm, and many low-angle grain boundaries appeared. When the ECAP deformation reached 8 passes, stacking faults occurred in the grains due to severe shear deformation. After 12 passes, lamellar twins were detected in the sample. The pre-aging treatment before ECAP can refine the microstructure of CuCrZrSc alloy and significantly improve the mechanical properties and electrical conductivities of the alloy. After 12 passes of deformation and aged at 400 °C for 15 min, the studied CuCrZrSc alloy had a UTS of 664 MPa, elongation of 17.5%, and electrical conductivity of 80.1% IACS. Electron back-scattered diffraction and transmission Kikuchi diffraction techniques were employed to analyze the microstructure evolution of samples with different ECAP passes.
查看更多>>摘要：? 2022 Elsevier B.V.Recently, particle-reinforced FeCrAl alloys as one of the most promising candidates for accident tolerant fuel (ATF) materials in nuclear systems have attracted widespread attention. In this study, ZrC-reinforced FeCrAl alloys with different Zr concentrations were proposed and irradiated by 6 MeV Au3+ ions to 215 displacements per atom (dpa) at 350 ℃. The pristine alloys have three typical particles of coherent Al-O-riched dispersoids, Cr-carbides, and ZrC in the matrix. After ion irradiation, the density of nanoparticles decreases significantly while the average size increases. The changes of the dispersoids in ion-irradiated FeCrAl alloys are considered to be the competition results between the diffusion-dominated growth and the radiation-induced dissolution of the Al-O-riced dispersoids. It was found that the dispersoids exhibited unequal response in the alloys with different Zr concentrations under radiation. The radiation-induced destruction or dissolution of the dispersoids is significantly suppressed by Zr addition, which could be due to that Zr could lower the interfacial energy of dispersoids by transforming Al-O dispersoids to Al-Zr-O dispersoids, therefore improving their stability under radiation condition. These insights provide experimental basis for designing highly radiation tolerant particle-reinforced FeCrAl alloys, and contribute to the ongoing development for the particle-dispersoid-strengthened alloys for the nuclear applications.
查看更多>>摘要：? 2022 Elsevier B.V.Tremendous efforts are devoted to the rational design of self-supported hierarchical architectures that are capable of delivering ultrahigh areal capacitance, and that are essential for miniaturized energy storage devices. Herein we propose a one-step-solvothermal approach for the hierarchical advancement in the morphology of the Ni3S2 on Ni foam from one-dimensional (1D) nanowires to a three-dimensional lettuce-like architecture with an internal nanowire network and corals at the edges. As the formation of this unique 3D lettuce-like architecture has resulted from the integration of 2D sheets with internal 1D nanowires, the combined features make it possible to realize ultra-high capacitance. This 3D architecture Ni3S2 electrode efficiently offers ultrahigh areal capacitance of 14.64 F cm?2, five times higher than that of nanowire arrays of 2.82 F cm?2 at the higher current density of 10 mA cm?2. A high value of 5.90 F cm?2 achieved, even at a larger current density of 50 mA cm?2, and retention of about 93% of the original capacitance over 7500 charge–discharge cycles when the applied current density is 150 mA cm?2, makes it a potential electrode material for large-scale energy storage devices with confined areas, like micro-supercapacitors. In addition, an as-fabricated asymmetric supercapacitor (ASC) exhibits areal capacitance of 597 mF cm?2, an energy density of 0.21 mWh cm?2, and a power density of 4.44 mW cm?2 at 10 mA cm?2, with high rate capability and capacitance retention of 79.5% over 10,000 cycles.
查看更多>>摘要：? 2022 Elsevier B.V.Efficient N, S-doped carbon decoration on Na3V2(PO4)3 (NSC@NVP) cathode is, for the first time, successfully prepared using L-cysteine as a single source for heteroatoms-doped carbon in sodium-ion batteries (SIBs). The effect of L-cysteine-derived N, S-doped carbon surface decoration on the electrochemical performance of NSC@NVP is investigated. The findings suggest that the NSC@NVP composite electrode with 5 wt% of L-cysteine (5-NSC@NVP) offers a high specific discharge capacity of 115.8 mAh g?1, which is 98.4% of the theoretical capacity (117.6 mAh g?1) of Na3V2(PO4)3. The 5-NSC@NVP composite electrode with the optimal amount of N, S-doped carbon leads to superior discharge capacity, cycling stability, and rate capability when compared to pristine NVP. The N, S-doped carbon matrix with active sites and defective nature can upgrade the electron and ion conductivities simultaneously while suppressing the agglomeration of NVP particles during cycling, resulting in the enhancement of electrochemical performances with NSC@NVP composites as a cathode material for SIBs.
查看更多>>摘要：? 2022 Elsevier B.V.As a viable alternative to lithium-ion batteries (LIBs), sodium ion batteries (SIBs) have attracted much more attentions. Herein, anthracite-based reduced graphene oxide/antimony (ARGO/SbX) composites have been successfully prepared as high performance anodes for SIBs. The anode composites have been synthesized by in situ reduction of Sb3+ provided by SbCl3 into Sb particles anchored onto the ARGO surface with the aid of NaBH4 and followed by annealing at 550 ℃ for 2 h. As designed, ARGO/SbX based SIBs can display high specific capacity, superior rate capability (527 mAh g?1 at 0.03 A g?1, 117 mAh g?1 at 10 A g?1), and good cycling stability (77 % of the initial capacity after 1000 cycles at 1 A g?1). The present research provides one low cost and high performance coal-based carbon anodes, which are supposed to accelerate the development of SIBs toward future large-scale applications.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, hetero-epitaxy of ε-Ga2O3 thin films are grown on c-plane sapphire by metal-organic chemical vapor deposition (MOCVD). Different oxygen precursors of deionized water (H2O) or high-purity nitrous oxide (N2O) gas are used and their impacts on crystal structure, optical absorption, cathodoluminescence, and photoelectric properties have been intensively studied. X-ray diffraction (XRD) analysis has shown that the ε-Ga2O3 epilayers are highly (001) oriented and the VI/III ratio is a critical growth parameter for the phase purity of Ga2O3. Cathodoluminescence (CL) measurements reveal that the luminescence peaks appear in the violet–blue–green region. A general increase of luminescence intensity is evidenced for samples grown using H2O as oxygen sources, which is explained by higher radiation recombination. Deep-ultraviolet (DUV) photodetectors with metal-semiconductor-metal (MSM) structure have been fabricated based on the ε-Ga2O3 thin films. The comparison of the device performances shows that faster response speed and higher responsivity are obtained for the device based on the ε-Ga2O3 grown by H2O as precursors, which indicates the potential of high quality ε-Ga2O3 to be applied in DUV photodetectors.
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