Influence of additives on pore size distributions of silica aergels

Silica aerobe is prepared using rice husk ash as silicon source. Several additives are added into the sol under suitable conditions, through the steps of sol-gel, solvent exchange and supercritical carbon dioxide drying. The added amount 15%~20% of glycerol and ethylene glycol have strongly influence on the pore size distributions (PSD). During this process, silica aero gel with smaller pores, more uniform, higher specific surface area and smaller average pore size is produced. High molecular weight polyethylene glycols can shorten the gelatin time and the PSD is relatively uniform. Form amide and diethyl form amide have the most significant effect on the samples with 20~40 nm PSD and high specific surface area above 750 m²/g. Polyvinylpyrrolidone can accelerate polymerization rate and the aerogel has more small pores and dense network structure.