Preparation of nanoporous alumina superinsulator with ultra-low thermal conductivity and improved heat resistance up to 1200 °C

Nanoporous alumina superinsulator (NanoASI) with ultra-low thermal conductivity and excellent thermal stability has been prepared by a low-cost and simple dry pressing method. The thermal conductivity of the NanoASI is as low as 0.11 W/m K at 1200 °C and the linear shrinkage is less than 2% after heating at 1200 °C for 1 h. These values are superior to that of previous reported nanoporous insulation materials. Thermal conductivities of this material in the temperature range of 25-1200 °C and pressure range of 10-105 Pa were firstly measured by the transient hot-plane method. The mechanism that improves the heat resistance of the NanoASI is discussed and found that the stabilization of the alumina nanoparticles contributes significantly to the thermal stability of the NanoASI.