Hongxi Zhu

Nitrogen-doped graphene guided formation of monodisperse microspheres of LiFePO4 nanoplates as the positive electrode material of lithium-ion batteries

Three-dimensional porous composite microspheres of LiFePO4 and nitrogen-doped graphene have been synthesized by a solvothermal process coupled with subsequent calcination. The morphology and microstructure of the composites were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The electrochemical properties were evaluated by constant current charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The unique porous structure of the microspheres was constructed by the assembly of nitrogen-doped graphene and LiFePO4 nanoplates and can remarkably enlarge the electrode/electrolyte interface area, facilitate the electron transfer process, shorten the ionic diffusion path and accelerate the ionic transport throughout the electrode. In electrochemical measurements of the specific charge capacity, rate capability and cycling stability, the obtained porous composite microsphere materials offer remarkably promising results for applications in high-performance lithium-ion power batteries.

Novel preparation of a porous composite insulating scaffold from forsterite and sodium carbonate media

Abstract Porous composite insulating scaffolds were prepared from mixtures of forsterite, salt (Na2CO3), and phenolic resin by sintering at 900 to 1 100 °C for 10 h, and the sintering behaviour and mechanical properties were examined. The results show that the changes in temperature did not significantly affect the phases present in the samples. However, changing the Na2CO3 content of a sample will change its phase composition. When the Na2CO3 content was 40 wt.% and sintering undertaken at 1 000 °C, the apparent porosity of the sample was 57 %, and its strength was 3.1 MPa. The large number of pores in the samples had diameters of approximately one micron, while the mesopores had diameters concentrated over the interval of 3 to 5 nm.

Synthesis and oxidation behavior of Al4SiC4 – Al – Si composites

Abstract Al4SiC4 – Al – Si composites were synthesized using a mixture of calcined bauxite, silicon carbide and carbon black as the starting materials. Al4SiC4 began to form at >1 600 °C and Al and Si were identified at 1 800 °C. Al and Si formed only when silicon carbide was in excess of the amount of SiC necessary to form Al4SiC4. The synthesized powders consisted of irregular plate-like crystals and the surfaces were molten-like. The oxidation characteristics of Al4SiC4 – Al – Si composites as antioxidants were better than the oxidation characteristics of pure Al4SiC4, since their action took place mainly at 400 – 700 °C (Al – Si) and above 850 °C (Al4SiC4).

Slag corrosion resistance of Al4SiC4

Abstract Powdered mixtures of Al2O3/SiO2/C/Al were heated together to synthesize Al4SiC4 and the corrosion resistance of the Al4SiC4 product was subsequently investigated. The results show that the addition of aluminium accelerates the synthesis of Al4SiC4. The slag corrosion resistance of the Al4SiC4 product is excellent (as determined using the static-crucible method). At high temperatures, the surface of the Al4SiC4 initially reacts with oxygen to form Al2O3 and SiO2. The Al2O3 formed dissolves in molten slag, and further reacts with MgO to form MgAl2O4. The above reaction processes can form a protective layer on the surface of the ternary carbide, which inhibits further corrosion of the Al4SiC4 material.

Synthesis and reaction process of β-Si3N4 by means of carbothermal nitridation of serpentine

Abstract The reaction process of carbothermal nitridation synthesis of β-Si3N4 from serpentine is investigated in this paper. Samples with different molar ratios of carbon black to serpentine were calcined under nitrogen atmosphere at 1300 °C, 1400 °C and 1500 °C for 3 hrs. The phase composition and microstructure of the synthesized powders were determined using X-ray diffraction and scanning electron microscopy. The reaction process was analyzed by means of differential thermal analysis. The results show that the main reaction was that forsterite from serpentine reacted with carbon black to form SiO, Mg vapor and CO, then SiO and N2 generated β-Si3N4. Fine β-Si3N4 powders were produced under nitrogen atmosphere at 1500 °C when the carbon black/serpentine molar ratio was 6.0. The synthesized β-Si3N4 powders had uniform grain size and high β-Si3N4 content.

Synthesis, electrochemical and photoluminescence properties of titanium nitride nanoparticles

Titanium nitride nanoparticles were efficiently synthesized by molten-salt method in MgCl2–NaCl media at a low temperature of 700xa0°C for 1xa0h, using titanium dioxide and Mg as raw materials in a N2 atmosphere. The investigations of nanostructure analysis indicate that the as-prepared titanium nitride is a pure phase, and has excellent crystallinity and high Brunauer–Emmett–Teller surface area. Electrochemical tests show that the titanium nitride nanoparticles exhibit a specific capacitance of 26.4xa0F/g at 0.25xa0A/g discharge current density and a low internal resistance (Rs) of 2.0xa0Ω. The photoluminescence spectrum shows four prominent and high intense peaks centered at 279, 420, 561 and 838xa0nm, suggesting the good optical property of the titanium nitride nanoparticles.

Effects of Fine Composite Powders Addition on Properties of Corundum-Spinel Refractory Castables

The enhanced properties of refractory castables are usually designed by the addition of multifunctional mineralizers and fine powders to satisfy the requirements of steelmaking industry. In this work, the effects of fine composite powders addition on properties of corundum-spinel refractory castables were investigated. Phase composition, microstructure, physical and mechanical properties of corundum-spinel refractory castables with different contents of fine composite powders were characterized. The results showed that the smaller spinel in the fine composite powders improved the sintering activity of the spinel particles, which had an influence on the morphology and the distribution of CA6 for the limited space. As the consequence of this, the cracks caused by in situ CA6 generation decreased and the firm link between particles was gained, finally the strength of castables containing fine composite powders improved.