3D net-like Co3O4@NiO nanostructures for high performance supercapacitors.

Co3O4@NiO composite electrode materials were successfully synthesized by a two-step hydrothermal method followed by annealing treatment. Due to their three-dimensional network structure, these composite materials exhibited a large specific surface area, enhancing their electrochemical performance. Consequently, the Co3O4@NiO electrode demonstrated a specific capacitance of 1306 F g-1 at a current density of 1 A g-1, an excellent specific capacitance retention rate of 95.5% after 3000 cycles even at 8 A g-1 and a coulombic efficiency approaching 100%. These outstanding properties make the Co3O4@NiO composite materials promising electrode materials for high performance supercapacitors.

Ultralow-Power RRAM with a High Switching Ratio Based on the Large van der Waals Interstice Radius of TMDs.

Low power and high switching ratio are the development direction of the next generation of resistive random access memory (RRAM). Previous techniques could not increase the switching ratio while reducing the SET power. Here, we report a method to fabricate low-power and high-switching-ratio RRAM by adjusting the interstice radius (rg) between the van der Waals (vdW) layers of transitional-metal dichalcogenides (TMDs), which simultaneously increases the switching ratio and reduces the SET power. The SET voltage, SET power, switching ratio and endurance of the device are strongly correlated with rg. When the ratio of rg to the radius of the metal ions that form the conductive filaments (rg/rAg+) is near 1, the SET voltage and SET power vertically decrease while the switching ratio vertically rises with increasing rg/rAg+. For the fabricated Ag/[SnS2/poly(methyl methacrylate)]/Cu RRAM with an rg/rAg+ of 1.04, the SET voltage, SET power and switching ratio are 0.14 V, 10-10 W and 106, respectively. After 104 switching cycles and a 104 s retention time, the switching ratio of the device can still be stable above 106. Bending has no influence on the performance of the device when the bending radius is not <2 mm.

The effect of phosphorus on solidification behaviour of undercooled Al-70 wt.%Si alloys.

Effect of refining element phosphorus (P) on the morphology of the primary silicon in the Al-70 wt.%Si alloy was investigated via the electromagnetic levitation (EML) technique. The morphology and microstructure were analyzed by using high-speed video (HSV) and scanning electron microscopy (SEM). It was found that the morphology of primary silicon transformed from dendrites with several branches to blocky shape, and then to equiaxed grains in Al-70 wt.%Si and Al-70 wt.%Si-1.0 wt.%P alloys with increasing of undercooling. The nucleation number and nucleation rate increased exponentially with the increase of undercooling for both alloys. Finally, the growth velocity of primary silicon was discussed in combination with classical theory.

Predicting the Thermodynamic Ideal Glass Transition Temperature in Glass-Forming Liquids.

The Kauzmann temperature TK is a lower limit of glass transition temperature, and is known as the ideal thermodynamic glass transition temperature. A supercooled liquid will condense into glass before TK. Studying the ideal glass transition temperature is beneficial to understanding the essence of glass transition in glass-forming liquids. The Kauzmann temperature TK values are predicted in 38 kinds of glass-forming liquids. In order to acquire the accurate predicted TK by using a new deduced equation, we obtained the best fitting parameters of the deduced equation with the high coefficient of determination (R2 = 0.966). In addition, the coefficients of two reported relations are replaced by the best fitting parameters to obtain the accurate predicted TK, which makes the R2 values increase from 0.685 and 0.861 to 0.970 and 0.969, respectively. Three relations with the best fitting parameters are applied to obtain the accurate predicted TK values.

The recalescence rate of cooling curve for undercooled solidification.

Recalescence rate (R) in cooling curve is well known that affected by undercooling in solidification, but the accurate relationship of them is not clear yet. In this paper, based on the undercooled solidification of Fe-B alloy, the factor affected on recalescence process was investigated. The relationship R = VΔT/D was first found, where V is the growth velocity, ΔT the recalescence degree (approximate the undercooling), D the focus region diameter dependent on the distance of the pyrometer. With this result the solidification interface growth velocity can be predicted from recalescence of cooling curve, vice versa. In addition, an approximate relation between growth velocity and the size of the critical nucleus was shown.

Relation between superheated temperature and cooling rate for deep supercooled niobium melt.

Research into the conditions for forming uniform melt-free crystal sites and the effect of the melt state on solidification behaviors is theoretically significant and has valuable applications. However, there are no quantitative data on these aspects due to rigorous experimental requirements. In this study, the variation of the melt structure at different superheating temperatures and the cooling rate during the deep solidification of cold niobium melt was investigated by a large-scale molecular dynamics simulation method. The solid/liquid coexistence method, the radial distribution function, an energy-temperature analysis, the average energy, an atomic cluster analysis, and a visualization analysis were adopted to analyze the variations in microstructure transitions. The temperature vs. undercooling plots of Nb melt at different superheating temperatures suggested that the metal melt structure should be classified into three regions (regions 1 and 2, each with different melt structures that vary with temperature, and region 3, whose melt structure does not change with temperature); the critical cooling rate of the crystal-amorphous transition was 1.0 × 1012.5 K s-1 and the solidification undercooling increased with increasing superheating temperature until maximal undercooling was obtained. Simultaneously, it was found that the maximal undercooling occurred at ∼0.432T m (T m is the melting point) and the maximal superheating occurred at ∼1.216T m.

The Influence of Annealing on the Structural and Soft Magnetic Properties of (Fe0.4Co0.6)79Nb3B18 Nanocrystalline Alloys.

The soft magnetic properties of Fe-based nanocrystalline alloys are determined by their grain size. In the present article, the (Fe0.4Co0.6)79Nb3B18 nanocrystalline alloys have been successfully prepared by isothermal annealing. The variation of soft magnetic properties as a function of annealing temperature and incubation time is investigated in detail. Two distinct crystallization behaviors were found for the (Fe0.4Co0.6)79Nb3B18 alloys. The initial nanocrystallization products comprise a mixture of α-Fe(Co), Fe2B, and Fe23B6-type crystalline metastable phases, and the final crystallization products are composed of α-Fe(Co), Fe2B, and Fe3B crystalline phases. The grain size decreases first and then increases with the increasing annealing temperature in the range of 764⁻1151 K, and a fine grain size with mean grain size of 12.7 nm can be achieved for alloys annealed at 880 K. As the annealing temperature increases from 764 K to 1151 K, the saturation magnetization increases first and then decreases without a significant increase of the coercivity. The alloys annealed at 880 K exhibit the optimized soft magnetic properties with high Ms of 145 emu g-1 and low Hc of 0.04 Oe.

Morphology Dependent Photocatalytic Properties of ZnO Nanostructures Prepared by a Carbon-Sphere Template Method.

Organic contaminants are a typical byproduct of industrial wastewater, and nanostructured ZnO photocatalysts have been investigated as an environmentally benign process to remove the contaminants through a degradation process. The degradation efficiency under UV irradiation can be markedly enhanced when using a catalyst with a nanostructure. The larger specific area of a nanostructure has been found to significantly enhance degradation efficiency. The complex synthesis process, expensive material costs, and generation of environmental contaminants during the synthesis process currently hinder practical application of photocatalysts. This research provides a template for a photocatalyst that is non-toxic, producing mesoporous ZnO hollow spheres and nanorods through an environmentally friendly carbon-sphere template utilizing a hydrothermal process. This research demonstrates that controlling the precursor concentration (zinc acetate) allows for the manipulation of the morphology and specific area of the ZnO nanostructures. A zinc acetate concentration of 0.171 mol/L produced uniform ZnO mesoporous hollow spheres with diameters of approximately 180 nm. Increasing the zinc acetate concentration resulted in an increase in the number of nanorods present. In contrast to nanorods, mesoporous ZnO hollow spheres have a higher specific area and higher concentration of pores in the 2-50 nm range, which result in better photocatalytic activity. This research reports the complete degradation of rhodium boride (RhB) within 50 min by means of mesoporous ZnO hollow spheres and nanorods with a degradation rate of 0.0978 min-1.

Facile Synthesis and High Photocatalytic Degradation Performance of ZnO-SnO2 Hollow Spheres.

ZnO-SnO2 hollow spheres were successfully synthesized through a hydrothermal method-combined carbon sphere template. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). The average diameter of hollow spheres is about 150 nm. The photocatalytic activity of the as-prepared samples was investigated by photodegrading Rhodamine B. The results indicated that the photocatalytic activities of ZnO-SnO2 hollow spheres are higher than ZnO hollow spheres. The degradation efficiency of the hollow spheres could reach 99.85% within 40 min, while the ZnO hollow spheres need 50 min.