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%.