Study of thermal stability of fumed silica based thermal insulating composites at high temperatures

This work investigated thermal stability of fumed silica based thermal insulating composites prepared by dry molding technology. The results showed that the composites could keep excellent thermal stability at the temperatures below 800 degrees C. However, when the samples were used at higher temperatures (>800 degrees C), the volume shrinkage increased sharply, which directly led to a serious deformation and then affected thermal insulating properties in applications. The utilization of fumed alumina could significantly improve thermal stability of the composites. When 5 wt.% fumed alumina was added, the volume shrinkage decreased from 10.49% to 3.47% at 1000 degrees C. The desirable results would be achieved by adjusting the amount of fumed alumina according to practical using temperature. In addition, field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) were employed to characterize the microstructure and phase transformations of the composites treated at different temperatures. (C) 2011 Elsevier Ltd. All rights reserved.