Preparation and microstructure of in-situ gel modified expanded vermiculite

Expanded vermiculite is an important thermal insulation material with a layered micro-porous structure. In this paper, modified expanded vermiculite was obtained using an in-situ gel method. Under experimental conditions of n(epoxy propane):n(A1(NO3)3): n(ethanol)=5.5:1:30, the alumina aerogel was distributed evenly in the structural gaps of the expanded vermiculite. The framework of the in-situ alumina aerogel is composed of sphere-like Al2O3 particles with a diameter of 40 nm and the pore size distribution is uniform with an average size of 45 nm. The modified vermiculite maintains a good multi-porous network structure, without any distinct signs of conglobation or collapse of the porous structure after being calcined at 900 °C and 1000 °C for 4 h. The modified expanded vermiculite show lower thermal conduction than the non-modified expanded vermiculites at all temperatures tested.