Thermal shrinkage inhibition mechanism of fumed silica based thermal insulating composite

Fumed silica based thermal insulating composite is a novel nanoporous material with excellent thermal insulating performance. However, shrinkage at higher temperatures (>800 degrees C) is a great challenge in application. In this work, fumed silica based thermal insulating composite was prepared by a dry molding method and fumed alumina was introduced to improve high-temperature thermal stability of the composite. The result shows volume shrinkage can decrease from 18.49% to 2.61% at 1000 degrees C When 20 wt% fumed alumina is added as an inhibitor. Thermal shrinkage inhibition mechanism was investigated by molecular dynamics simulation. The models of fumed silica and fumed alumina super cells Were built and mean square displacement (MSD) was calculated. The result indicates MSD of fumed silica is 0.198 angstrom(2) at 1000 degrees C while that of fumed alumina is only 0.0151 angstrom(2). In addition, thermal insulating property was comprehensively studied and the effect of fumed alumina on thermal conductivity was analyzed. The result shows this composite has excellent thermal insulating performance with thermal conductivity of 0.052 W/m.K at 800 degrees C and the introduction of fumed alumina has almost no effect on thermal insulating property. This work can provide theoretical guidelines for the choice of shrinkage inhibitor. (C) 2016 Elsevier Ltd. All rights reserved.