Reduction behaviour of rice husk ash for preparation of high purity silicon

The reduction of rice husk ash (RHA) silica for the preparation of high purity silicon was studied using magnesium as the reducing agent. Composite magnesium-RHA pellets with magnesium content varying 0-25 wt-% in excess of stoichiometry requirement were made and heated in the temperature range of 600-900 degrees C under flowing argon. It was found through differential thermal analysis and temperature profile recording that the reaction of RHA silica with magnesium was triggered at similar to 575 degrees C. Quantitative X-ray diffraction analyses of the reduction products showed that both initial magnesium content of the pellets and the reduction dwell temperature had a significant influence on the yield of silicon. In this study, a charge with 5 wt-% magnesium in excess of the stoichiometric amount at a reduction temperature of 900 degrees C gave a maximum silicon yield.