For inorganic aerogels, silicon aerogel is the most aerogel studied at present. In sol-gel process, three dimensional network structure silicon aerogel was obtained by hydrolysis and condensation of silicon source material. Its reaction principle is
Si(OR)4 +4H2O → Si(OH)4 +4HOR (hydrolysis)
nSi(OH)4 → (SiO2)n +2nH2O ( polycondensation )[7]