查看更多>>摘要：? 2022 Elsevier B.V.The atomic structure, soft magnetic property and bending ductility of Fe-P-C-B-Si amorphous alloys via the change of Si content were investigated. The minor and appropriate Si addition can increase the Curie temperature and saturated magnetization (Ms) effectively. Compared with the 0 at% Si, the Ms of Fe85P10C2B2Si1 and Fe85P9C2B2Si2 can be enhanced up to 1.58 T and 1.61 T, respectively, which is related to the increase of the total magnetic moments analyzed via ab initio molecular dynamics (AIMD) simulation. Furthermore, the Ms of the annealed amorphous alloys can be continued to increase and the highest Ms of the Fe85P9C2B2Si2 amorphous alloys can reach up to 1.76 T and the lowest coercivity (Hc) can be reduced to 5.15 A/m after the ribbons were annealed at 627 K. These phenomena are related to the release of inner stress and the formation of α-Fe clusters in amorphous alloys caused by annealing. All ribbons remain good bending ductility annealed at optimal temperature (627 K) determined by Ms and Hc. The combination of high Ms, low Hc, good bending ductility after annealing as well as low production cost and high manufacturability makes the Fe-P-C-B-Si amorphous alloys with high Fe content promising as complement and even replacement of the Si-Fe alloys in magnetic and electric devices.
查看更多>>摘要：? 2022 Elsevier B.V.In a simplified heterojunction crystalline silicon (c-Si) solar cell, a molybdenum oxide/silver/molybdenum oxide (MoOx/Ag/MoOx) stack has been investigated as an alternative to the well-known p-type amorphous silicon hydrogenated (a-Si: H) layer or a single layer of MoOx. The optical characteristics of the MoOx/Ag/MoOx multilayer were studied and found to have acceptable features for embedding on the solar cell's front side. Using a straightforward fabrication technique, thermal evaporation, a device structure composed of Al/Ag/MoOx/Ag/MoOx/n-Si/MoOx/Mg/Al has been fabricated. Impedance spectroscopy measurements were performed and Nyquist plots revealed single semicircles in the frequency range (102 Hz - 106 Hz) and at different temperatures, indicating the formation of a junction between MoOx/Ag/MoOx and n-Si substrate and the establishment of good Ohmic contacts for the front/rear electrodes. Moreover, capacitance-voltage characteristics were used to determine the temperature dependency of the built-in potential, doping concentration, and depletion width. The temperature-dependent current-voltage plots for the cell suggested that the predominant carrier transport mechanisms in the forward bias regime are trap-assisted tunneling at V> 0.35 V and e-h pair recombination at 0.35–0.75 V. For the reverse bias regime, carriers transport is dominated by the current generation in the space-charge region. Additionally, the photovoltaic performance of the solar cell was measured under illumination.
查看更多>>摘要：? 2022 Elsevier B.V.Herein, a unique dodecahedron composite material of Zn-Co bimetallic zeolitic imidazolate frameworks (ZIFs) and carbon nanotubes (CNTs) is synthesized by a simple room temperature static precipitation-annealing process. As an anode material for lithium-ion batteries (LIBs), the designed nanomaterials exhibits excellent lithium storage performance and cycle performance. It demonstrates a high discharge specific capacity of 720.9 mAh g-1 at 100 mA g-1. Besides, a high reversible capacity of 608.7 mAh g-1 at a current density of 500 mA g-1 after 300 cycles. The significant improvement in the electrochemical performance of Zn/Co-ZIFs/CNTs nanocomposite can be attributed to the strong synergy between Zn/Co-ZIFs and CNTs.
查看更多>>摘要：? 2022The microstructural features and promising properties exhibited by Al0.7CoCrFeNi have led to extensive studies on the alloy. The current work discusses the microstructural evolution, thermal stability and mechanical behavior of the alloy. CALPHAD studies predicated the alloy to be near eutectic with pro-eutectic BCC and eutectic FCC and BCC/B2. However, experimental studies displayed the FCC phase to evolve from a high-temperature B2. Interfacial energy, chemical inhomogeneity and cooling rate were attributed to play a key role in the microstructural evolution and phase stability. Heat treatment resulted in the dissolution of BCC and the formation of Al-Ni-rich B2 phase. During solidification and heat treatment, Widmanst?tten FCC formed and coarsened via superledge mechanism. Further, thermal exposure resulted in lamellar instability and localized globularization of the B2 phase. The heat-treated alloy displayed excellent resistance to thermal softening when compared to the cast alloy. Further, the thermally exposed alloy exhibited a superior work hardening rate.
查看更多>>摘要：? 2022 Elsevier B.V.In this investigation, FeCrCoNi high entropy alloys doped with 0.5 at%, 1 at%, 2 at% C and 0.48 at% N, respectively, were prepared by arc melting followed by homogenization for 1 hr at 1100 °C. The deformed microstructure and compressive strength of these alloys were characterized and compared. The ingots with 0.48 at% N and 0.5 at% C retained the typical single-phase, face-centered cubic structure. In samples with 1 at% C and 2 at% C, M23C6 precipitates were found. Comparing with FeCrCoNi alloy, the yield stress of N doped FeCrCoNi was increased from 132 MPa to 202 MPa while that of 0.5 at% C doped was only increased to 152 MPa. For 1 at% C and 2 at% C alloys, the yield stresses were increased to 195 MPa and 327 MPa respectively. In the early deformation stage, the N doped alloy showed pure planar slip while that of 0.5 at% C doped and undoped FeCrCoNi showed both planar slip and wavy slip. At higher strain (50% compression strain), twinning and wavy slip prevailed in samples with 0.5 at% C and undoped alloy, while that of N doped alloy showed both wavy slip and planar slip. Wavy slip prevailed in all deformation stage and twinning was found at later deformation stage in 2 at% C doped alloys.
查看更多>>摘要：? 2022 Elsevier B.V.Lithium-sulfur batteries (LSBs) are next-generation energy storage devices owing to their high specific capacities and energy densities; however, critical problems remain unsolved, such as insulating sulfur as an active material and the dissolution of Li polysulfides into the liquid electrolyte during cycling, leading to low sulfur utilization, low rate performance, and rapidly decreasing capacity. Herein, we describe the synthesis of a nanocomposite structure comprising mesoporous tungsten carbide (meso-WC) and reduced graphene oxide (rGO) (meso-WC/rGO) and its application to an functional separator in LSBs. The resulting Li-S cell exhibits improved rate cycling performance: ~950 mAh g-1 at 1 C after 100 cycles. Moreover, even at a high sulfur loading of 3.0 mg cm-2, the Li-S cell with the meso-WC/rGO maintains enhanced performance, with a capacity of ~737 mAh·g-1 and a retention of 83% after 300 cycles. The Li-polysulfide shuttle effect was observed using H-type cells and adsorption tests. The enhanced performance results from suppression of the shuttle effect caused by the excellent adsorption of Li polysulfides, effective reuse of active materials, and promotion of the conversion reaction.
查看更多>>摘要：? 2022 Elsevier B.V.Graphite anode has been commercially applied to lithium-ion batteries (LIBs); however, its low theoretical specific capacity (372 mAh g?1) cannot meet the ever-increasing energy storage requirements with high energy/power densities. Therefore, exploring novel carbon anode with high capacity, high-rate properties, easy accessibility, and environmental benignity is urgent and indispensable. Herein, three-dimensional interconnected porous carbon nanoflakes (3DPCNs) are successfully constructed by a chemical blowing strategy followed by a washing process. The resulting 3DPCN has numerous ions/electrons fast transfer pathways, expanded interlayer spacing, high specific surface area (189.5 m2 g?1). All of which are more favorable for improving reaction kinetics and maintaining structural integrity. Based on this, the optimized 3DPCN electrode delivers an excellent electrochemical performance, including high capacity (802.6 mAh g?1 at 500 mA g?1), rate capability (581 mAh g?1 at a high current density of 2000 mA g?1), and long-cycle stability. The synthesis strategy presented in this work is expected to promote the development of carbon anodes for high-performance LIBs.
查看更多>>摘要：? 2022 The Author(s)Our current work aims to enhance the thermoelectric properties of p-type copper selenide (Cu2Se), a low toxic, earth-abundant intermediate material for thermoelectric applications by a low-cost, simple and fast microwave-assisted metallurgy route. Hot pressed copper selenide pellets were treated at various temperatures in the range of 250 oC to 425 oC in a microwave furnace. We analyze the variation of several characteristics of the samples, such as electrical, thermal, structural, microscopic, dielectric, and mechanical properties, when the samples are exposed to different annealing conditions. Broadband dielectric spectroscopy (BDS) analysis facilitated the comprehensive study of variation of AC electrical characteristics of the samples such as AC conductivity, dielectric permittivity storage, dielectric loss, and AC capacitance, with temperature and frequency. The results indicate exceptional electrical, thermal, and mechanical properties for samples annealed at 375 oC with high room temperature electrical conductivity of 538.3 S/cm and ultra-low thermal conductivity of 0.59 W/mK. The crystallinity improved as the annealing temperature increased, as did the formation of oxides over 400 oC. The samples have a high strength with maximum nanohardnesss and compression strength of 3.75 GPa and 326.75 MPa, respectively that has been a significant improvement over the existing studies on copper selenides.
查看更多>>摘要：? 2022 Elsevier B.V.The severe deterioration of the interface is a crucial factor to restrict the performance improvement of composites. In order to understand the effect of interfacial structure on the mechanical properties and failure modes of the composites, the carbon fiber reinforced aluminum matrix (Cf/Al) composites were fabricated by pressure infiltration process at different fabrication temperatures and Ni coating modification. The micro-indentation test is used to determine the mechanical properties of the matrix between fiber bundles to infer the content of the Al4C3. The results indicate that compared with Al alloy, the hardness and modulus of the matrix between the carbon fiber bundles can be significantly increased by 38.5% and 36.5%, while the matrix between Ni-coated fiber bundles remains unchanged. This is due to the Ni coating preventing the carbon fiber against reaction with liquid aluminum during processing the composite, which reduces the generation of brittle carbides. In addition, it was revealed for the first time that the oblique/axial brittle fracture modes of the fibers occurred simultaneously due to severe interfacial reaction, and the brittle failure mechanism was clarified. The presence of Ni coating on the carbon fiber significantly improves the bending strength and interlaminar shear strength (ILSS) of the composite by approximately 81% and 86%, respectively. The Ni coating optimizes the interfacial bonding, so that the interface can absorb more fracture energy under loads. This work can provide a pratical route to prepare and applicate the high-quality continuous fiber reinforced Al matrix composites.
查看更多>>摘要：? 2022 Elsevier B.V.This paper details the design process of a ternary NiTiHf shape memory alloy (SMA) with an austenite finish temperature (Af) beyond 400 °C. Specifically, available experimental data on the ternary NiTiHf SMA system was utilized to construct a database, which was employed to train and test a machine learning (ML) algorithm to predict the ideal NiTiHf SMA composition to exhibit an Af beyond 400 °C and a relatively smaller hysteresis. For this purpose, a multi-layer feedforward neural network (MLFFNN) model was proposed, trained, and tested. Consequently, the Ni49.7Ti26.6Hf23.7 and Ni50Ti27Hf23 alloys predicted by this ML algorithm were selected for validation experiments to assess the accuracy of the ML model's predictions. As a result, the Ni49.7Ti26.6Hf23.7 alloy with an Af temperature of 403.5 °C and remarkable cyclic stability was established as a new NiTiHf SMA composition, which can be utilized in applications demanding reversible austenite-to-martensite phase transformation beyond 400 °C.
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