Preparation of HfCxN1-x Nanoparticles Derived from a Multifunction Precursor with Hf-O and Hf-N Bonds.

HfCxN1-x nanoparticles were synthesized using the urea-glass route, employing hafnium chloride, urea, and methanol as raw materials. The synthesis process, polymer-to-ceramic conversion, microstructure, and phase evolution of HfCxN1-x/C nanoparticles were thoroughly investigated across a wide range of molar ratios between the nitrogen source and the hafnium source. Upon annealing at 1600 °C, all precursors demonstrated remarkable translatability to HfCxN1-x ceramics. Under high nitrogen source ratios, the precursor exhibited complete transformation into HfCxN1-x nanoparticles at 1200 °C, with no observed presence of oxidation phases. In comparison to HfO2, the carbothermal reaction of HfN with C significantly reduced the preparation temperature required for HfC. By increasing the urea content in the precursor, the carbon content of the pyrolyzed products increased, leading to a substantial decrease in the electrical conductivity of HfCxN1-x/C nanoparticle powders. Notably, as the urea content in the precursor increased, a significant decrease in average electrical conductivity values was observed for the R4-1600, R8-1600, R12-1600, and R16-1600 nanoparticles measured at a pressure of 18 MPa, yielding values of 225.5, 59.1, 44.8, and 46.0 S·cm-1, respectively.

MOFs-Derived Flower-Like Hierarchically Porous Zn-Mn-Se/C Composite for Extraordinary Rate Performance and Durable Anode of Sodium-Ion and Potassium-Ion Batteries.

The slow kinetics and poor structural stability prevent transition metal selenides from being widely used in sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). Herein, the "flower-like" porous carbon anchored by Zn-Mn binary selenides (ZMS@FC) composites are fabricated by selenizing the modified hierarchically metal-organic frameworks. The 2D conductive hierarchically flakes' abundant pore structure and multiple active sites shorten the ion diffusion length and promote conductivity, while the synergistic effect of the binary metals and intrinsic large pseudocapacitive contribution effectively improve capacity and rate performance. ZMS@FC composites exhibit impressive rate capability of 294.4 mA h g-1 at 10 A g-1 and excellent cyclic stability with 369.6 mA h g-1 specific capacity retention at 2 A g-1 after 1000 cycling in SIBs. It is noted that 156.9 mA h g-1 can be retained at 5 A g-1 and 227.0 mA h g-1 is remained after 500 cycles at 2 A g-1 in PIBs. The ex situ X-ray diffraction patterns and transmission electron microscopy pictures are used to confirm the conversion reaction processes of the Zn-Mn-Se. Designing high-performance energy storage materials may benefit greatly from the universal synthesis technology of bimetallic sulfide anodes for enhanced SIBs and PIBs.

Effect of carbon nanotexture on the synthesis, initial growth mechanism and photoluminescence properties of SiC nanowires.

Although the spontaneous vapor-solid growth of SiC nanowires is a well-established phenomenon, the exact mechanism by which nanowires grow on substrates is still poorly understood. Here, we studied the initial growth of SiC nanowires on carbon sources with different nanotextures via a catalyst-free vapor reaction between a polyacrylonitrile-based carbon fiber and a silicon powder. The results revealed that the SiC nanowires were preferentially formed on the carbon fiber with a higher degree of graphitization. Detailed analyses suggested that the growth behavior of the underlying SiC film formed on the carbon fibers, which is strongly affected by the microstructures of the carbon fibers, plays an important role in the formation of nanowires. In addition, the photoluminescence spectrum of SiC nanowires showed strong ultraviolet-visible emission peaks at an excitation wavelength of 250 nm, which may provide potential applications in the field of optoelectronic devices.

Synthesis and Electrochemical Performance of ZnSe Electrospinning Nanofibers as an Anode Material for Lithium Ion and Sodium Ion Batteries.

ZnSe nitrogen-doped carbon composite nanofibers (ZnSe@N-CNFs) were derived as anode materials from selenization of electrospinning nanofibers. Electron microscopy shows that ZnSe nanoparticles are distributed in electrospinning nanofibers after selenization. Electrochemistry tests were carried out and the results show the one-dimensional carbon composite nanofibers reveal a great structural stability and electrochemistry performance by the enhanced synergistic effect with ZnSe. Even at a current density of 2 A g-1, the as-prepared electrodes can still reach up to 701.7 mA h g-1 after 600 cycles in lithium-ion batteries and 368.9 mA h g-1 after 200 cycles in sodium-ion batteries, respectively. ZnSe@N-CNFs with long cycle life and high capacity at high current density implies its promising future for the next generation application of energy storage.

[Preparation and properties of medical calcium phosphate cement].

The preparation of tetracalcium phosphate (Ca4(PO4)2O, TTCP)was studied. Then calcium phosphate cement (CPC) was prepared. The setting time, pH value, compressive strength, X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis of CPC were studied. The results show that TTCP containing small amount of CaO can be successfully attained heated at 1 500 degrees C for 6 h in vacuum condition. The initial setting time and final setting time of CPC is 4 min and 15 min, respectively. Its compressive strength is 20 MPa after 1-day immersion and 35 MPa after 7-day immersion. The pH value of the solution changes between 6.4 and 8.9. These properties can satisfy the clinical requirements of CPC. The final product of CPC is flake-like or needle-like hydroxyapatite (Ca5(P04)3OH, HA). The continuous network structure of HA appears in the microstructure, this leads to increase the strength of the material. This CPC can be used as bone substitute material.