SINTERING BEHAVIOR OF ALUMINA-MODIFIED SILICA AEROGELS

A main problem for the applicability of silica aerogels as thermal ins ulation materials at temperatures above 600 degrees C is viscous sinte ring, which may lead to a significant density increase with time. Modi fication of silica aerogels via integration of alumina yields aerogels with increased stability against sintering. The onset of sintering of alumina silica aerogels occurs at about 900 degrees C compared with a bout 600 degrees C for pure silica aerogels. The sintering process was investigated as a function of alumina content, density and particle s ize. Alumina-modified silica aerogels were studied by dilatometry, vis cosimetry and thermogravimetry during non-isothermal and isothermal he at treatment.