Research on impurity removal of industrial silicon powder through introduce of nano-porous structure

Based on industrial silicon powders, porous silicon powders were prepared with methods of chemical etching, one-step metal-assisted chemical etching(1-MACE), and two-step metal-assisted chemical etching (2-MACE). The effects of species and concentrations of oxidants on the morphologies and structures of porous industrial silicon as well as the removal rate of metal impurities Fe and Al were investigated. Metal nanoparticles assisted etching methods are better at controlling the growth rate and morphologies of the porous channel. With proper species and concentrations of oxidants, porous industrial silicon powders with controllable channel diameter in range of 50 -300 nm and depth within about 60 μm can be effectively obtained by MACE methods. Nano-channels can improve the removal efficiencies of Fe and Al impurities from industrial silicon, which particularly reached 99.8 % and 94.7 % under optimum experimental conditions with 2-MACE method.