A three-dimensional mullite-whisker network ceramic with ultra-light weight and high-strength prepared by the foam-gelcasting method

Abstract

A three-dimensional mullite-whiskers network ceramic with ultra-light weight and high-strength was obtained by the foaming gel-casting method with active mulllite powders and NH4F. Ultrafine active mullite powder was used as the raw material and SDS (sodium dodecyl sulfate) as a pore-forming agent. The effects of sintering temperature on the microstructure, flexural strength and thermal conductivity of the porous ceramics were systematically investigated. The mullite-whisker network porous ceramic has a fibrous-framework structure composed of interweaving mullite-whiskers. Because the pore-walls are composed of interlacing whiskers and the pores are filled with whiskers, the porous ceramics exhibited good mechanical properties and low thermal conductivity. The flexural strength of the obtained mullite-whisker porous ceramic sintered at 1500°C was up to 1.45 Mpa, while the porosity was as high as 89%. In addition, the thermal conductivity of the porous ceramic at room temperature was as low as 0.045 W/m⋅K.