Ambient-dried silica aerogel doped with TiO2 powder for thermal insulation

Two step-derived SiO2 sol doped with TiO2 powder dissolved in ethanol was prepared. After aging and washing of wet gel, surface modification with TMCS (trimethylchlorosilane) was followed to prevent additional condensation reaction during drying. Ambient-dried SiO2-TiO2 gel was heat-treated at various temperatures. The effects of the heat-treated temperature on the chemical bonding state of SiO2-TiO2 gel were investigated by means of FTIR and XRD analyses. After heat-treatment at 350 degreesC, crack-free SiO2-TiO2 gel was synthesized with density of 0.14 g/cm(3), porosity of 94%, and specific surface area of 613 m(2)/g. Ambient-dried SiO2-TiO2 gel heat-treated at 350 degreesC exhibited thermal conductivities of 0.0136 W/m.K and 0.0284 W/m.K at room temperature and 400 degreesC, respectively. (C) 2000 Kluwer Academic Publishers.