Preparation of foamed ceramics by sol-gel reaction

Abstract

In order to prepare porous ceramics without generating a large amount of CO₂ be decomposition of organic materials contained in the raw material as pore-former, highly porous silica ceramics was prepared by mechanical foaming of silica sol. Since gelation time of silica sol was controllable to desired range by adjusting its pH, temperature and concentration of surfactant, the silica sol foamed mechanically before gelation kept its foam-like-structure after foaming. The porosity of the foamed silica calcined at 600°C was over 90%, and bending strength and young's modulus of the foamed silica heated at 1000°C were 2.4MPa and 0.9GPa, respectively. The permeability, which is important for application to filters, was 5.3 X 10^-11m².