Synthesis and characterization of nano-Si from RH. Preserving the
nanostructure of the SiO2 species in the RHs during the whole
recovery process, especially at steps involving elevated temperature,
is key to producing high quality nano-Si. In the step of converting
RHs to nano-SiO2, simply burning RHs in air will produce
bulk SiO2, and it is necessary to first perform HCl leaching7 and then
only heat at moderate temperatures to avoid the fusion of the SiO2
product (Fig. 2a–c) while removing the organic matter. Thermogravimetric
analysis (TGA) of both raw and leached RHs (Fig. 2d)
shows a typical three-stage mass loss in simulated air