Color manipulation of silica aerogel by copper incorporation during sol-gel process

Abstract

Copper (Cu)-incorporated silica aerogel was synthesized by a sol-gel process with two-step drying process for colormodification. The microstructure of the silica aerogel was not affected significantly by the Cu concentration and an amorphousstructure was maintained without any crystalline impurity phases. The textural properties of the silica aerogels investigatedby using N2 adsorption-desorption isotherms exhibited the typical features of mesoporous materials. The pore size and porositywere not changed significantly even with the incorporation of Cu up to 1.5 M, which indicates negligible variation of thermalinsulating properties. However, the color of the aerogel changed from white and light greenish to dark greenish with increasingCu content. The color change of the silica aerogel was due to the modification of the electron energy band structure of silicaby the Cu atomic levels. Therefore, the color of the silica aerogel powders could be manipulated by incorporating Cu withoutdegrading the thermal insulating properties.