Mechanism of low thermal conductivity of xonotlite-silica aerogel nanoporous super insulation material

In an effort to incorporate the low thermal conductivity of the silica aerogel and the superior structure strength of the xonotlite, a composite material of these two was produced. It was synthesized under vacuum condition and dried by supercritical drying technique. The thermal conductivity of the new material, which is at 298 K with the gas pressure ranging from 1.01 x 10(5) to 1 x 10(-2) Pa, was measured using the transient hot-strip method. The mechanism of the low thermal conductivity was studied. The results indicate that the low thermal conductivity mainly results from the significant decrease of gaseous thermal conductivity of the new material due to the restriction of the motion of gas molecules in its fine structures. The formation of the fine structures is because the new material takes the pore structure of the silica aerogel which consists of mainly nanometer-sized pores. (C) 2008 University of Science and Technology Beijing. All rights reserved.