A Study on the Heat Effect and Kinetics During Magnesiothermic Reduction of Porous SiO2

Magnesiothermic reduction reaction (MRR) is an effective method to synthesis Si nanoparticles. In this paper, the heat effect and MRR kinetics were investigated by real-time temperature monitoring and analyzing the DSC curve of the MRR. It was found that the MRR onset temperature is about 465 °C, and the system temperature rose sharply at 535 °C. After the disappearance of the magnesium phase, the system temperature remained consistent with the set value. The exothermic peak lags and the spike decreases when adding NaCl into the system. The MRR was chemical reaction control, corresponding with the apparent activation energy was 193.456 kJ·mol-1 (without NaCl) and 191.434 kJ·mol-1 (with NaCl) in the temperature interval 465 °C −700 °C, respectively. NaCl affects the reaction mechanism by lowering the temperature of the system. Our work successfully prepared the spherical Si nanoparticles, which average grain size increased from 25 nm to 40 nm with the extended reaction duration. The conversion rate of porous SiO2 precursor was as high as 92%.

Pomegranate-type Si/C anode with SiC taped, well-dispersed tiny Si particles for lithium-ion batteries

Severe volume expansion and inherently poor lithium ion transmission are two major problems of silicon anodes. To address these issues, we proposed a pomegranate-type Si/C composite anode with highly dispersed tiny silicon particles as the core assisted by small amount of SiC. Skillfully exploiting the high heat from magnesiothermic reduction, SiC can assist the good dispersion of silicon and provide good interface compatibility and chemical stability. The silicon anchored to the carbon shell provides multipoint contact mode, that together with the carbon shell frame, significantly promoting the transfer of dual charge. Besides, the pomegranate-type microcluster structure also improves the tap density of the electrode, reduces the direct contact area between active material and electrolyte, and enhances the electrochemical performance.

New insights into pathways and kinetic of magnesiothermic reduction of titanium tetrachloride in titanium metallurgy

There is still no consensus on the reaction pathways and kinetic modeling of magnesiothermic reduction of titanium tetrachloride, and the theoretical innovations are required for further research of titanium metallurgy. We determined efficient reaction pathways via chemical reaction stoichiometry methodology, and proposed an innovative kinetic modeling approach of magnesiothermic reduction of titanium tetrachloride. We explained the reaction pathways by the steps of the phase change near the gas-liquid interfaces, the homogeneous reaction in the gas phase, the heterogeneous reduction near the gas-liquid interfaces, and the like dissolves like in the liquid phase. Net chemical reaction rate of titanium sponge decreased with decreasing of titanium tetrachloride feeding rata and with increasing of gauge pressure. The excellent fitness of the reaction rate constants, f(Δp) and k(Tin), show that the proposed kinetic equation accuately describes the reaction mechanism, and is reasonable and acceptable for magnesiothermic reduction of titanium tetrachloride in titanium metallurgy.