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In this paper, several new powder packing methods are proposed, and the COMSOL software is used to simulate the temperature distribution under different conditions. The influence of powder packing on the growth of SiC single crystal by physical vapor transport (PVT) is studied. The results show that the heat flux of the top region of the powder is increased by trapezoid graphite and graphite ring, the radial temperature gradient of the powder is reduced, which contributes to the improve the powder utilization rate. By covering the surface of the powder with a layer of porous graphite filter, the recrystallization on the surface of the powder is inhibited, the defects of carbon inclusion and thermal stress in the SiC crystal are reduced, and the growth quality and growth rate of the SiC crystal are obviously improved. The simulation results were verified by experiment, and the results agrees well with experiment. [ABSTRACT FROM AUTHOR]

Co3O4 has been considered a promising anode material because of its high theoretical capacity (890 mAh/g) and remarkable energy density. Unfortunately, it suffers from low initial coulombic efficiency, rapid capacity fading, poor electronic conductivity, large volume changes, and aggregation during the lithium ion intercalation/deintercalation process. In this work, a series of Fe2+-doped Co3O4 nanostructured materials Co3(1-x)Fe3xO4 (x = 0, 0.01, 0.02 and 0.03) were produced by a simple chemical co-precipitation method. The Fe doping led to a slight increase of the lattice parameter, which is beneficial to the rapid diffusion of Li+ ion during the lithiation/delithiation process. Meanwhile, the Fe-doped Co3O4 sample exhibited an excellent rate capability of 886.47 mAh/g at 500 mA/g, and outstanding cyclic stability (1156.91 mAh/g for 50 cycles, with the capacity retention rate of 83.53% at the current density of 100 mA/g), demonstrating improved electrochemical performance, compared with that of pure Co3O4. The good electrochemical performance profited from the formation of oxygen vacancies by Fe doping, which provided more space for Li+ diffusion and improved the electronic conductivity of the anode material. This work provides a simple way to improve the comprehensive electrochemical performance of the transitional metal oxide Co3O4 anode electrodes for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

NiCrAl/20%WC/MoS2 composite coatings with different MoS2 additions were prepared on the surface of 45 steel by laser cladding technology. The effects of MoS2 content on the microstructure, hardness and antifriction and wear resistance of the cladding layer were mainly studied. The results show that the content of lubricating phase has a certain influence on the hardness, anti-friction and wear resistance. With the increase of MoS2 content, the microstructure is gradually refined; the hardness gradually increases; the friction coefficient first decreases and then increases, and when the MoS2 content is 5%, the friction coefficient is at least 0.55; the wear volume first decreases and then increases, and the MoS2 addition amount is 5% When the wear volume is the smallest, the wear resistance is increased by 79% compared with the 45 steel substrate. Comprehensive analysis shows that the optimum addition amount of MoS2 is 5%. [ABSTRACT FROM AUTHOR]

Alloy composition design at the atomic scale is one of the key strategies for Ni-based single crystal superalloys (Ni-SCSs). In this article, the site preference of co-alloying elements Re-M (M: Cr, Mo, W or Re) in Ni3Al system and the strengthening effects of co-alloying elements on the shear deformation resistance of Ni3Al system are investigated using the first-principles method. It is found that the atom pairs of co-alloying elements prefer Al–Al site and the site preference of alloying elements is not affected by paired atoms. And co-alloying atom pairs occupying Ni–Ni site have a strong mutual interaction, which can be responsible for the formation of Re clusters and segregation of alloying elements. The ideal shear strength (ISS) of the quaternary Ni3Al system enhanced greatly by co-alloying elements is at least higher 11.9% than that of any Ni3Al system doped with single alloying elements, which indicates there are common effect among the co-alloying elements. The result of electronic structures shows that the strong interaction between the alloy atoms and their common the first nearest neighbors (FNN) Ni atoms is the common strengthening mechanism. The present article provides valuable guidelines for improving the mechanical strength of Ni-SCSs via alloy composition design. [ABSTRACT FROM AUTHOR]

Flexible supercapacitors (SCs) have attracted much attention from researchers on account of their excellent safety, high power density, fast charging/discharging speed and long cycle life. Conventional hydrogel electrolytes will freeze when the operating temperature drops below zero degree, limiting the practical applications of SCs. Here, we proposed a strategy to prepare a highly conductive organohydrogel electrolyte (OHE) with excellent anti-freezing property and moisture retention by soaking poly(2-acrylamido-2-methypropane sulfonic acid)/poly (acrylamide) (PAMPS/PAAm) hydrogel into phosphoric acid/glycerol (PA/Gly) co-solvent. The OHE possessed favorable flexibility and excellent electrical conductivity of 9 and1.98 S/m at room temperature and −40 °C, respectively. Meanwhile, the prepared SCs obtained high specific capacitance, superior capacitance retention rate of 75.65% and excellent mechanical flexibility at −40 °C, compared with those at room temperature. Moreover, this work would provide a novel and promising approach for the development of flexible wearable electronic devices with low-temperature stability. • A novel phosphoric acid/glycerol co-solvent was proposed for outstanding anti-freezing organohydrogel electrolyte. • High capacity retention rate under long-cycle at −40 °C. • The SC retains excellent flexibility at −40 °C. • A simple and effective strategy is provided for energy storage devices with low-temperature stability. [ABSTRACT FROM AUTHOR]