Evacuated, Load-Bearing Powder Insulation for High Temperature Applications

Abstract

This report deals with the development of an evacuated, load-bearing powder insulation with a thermal conductivity of less than 10 mW/m K at temperatures between 300 and 400/sup 0/C. The solution of the problem is approached in three steps: selection of an appropriate opacifier, allowance for higher residual gas pressure because of long term stability reasons, and preparation of load-bearing insulation plates from a mixture of fumed Silica with opacifiers and glass fibers. The low total thermal conductivity of the pressed plates is achieved mainly from a reduction of the solid conduction contribution using compacted powders of high porosity while maintaining high integral extinction coefficients.