Preparation and characterization of foamed microporous mullite ceramics based on kyanite

A new approach has been developed for preparing microporous mullite ceramics based on kyanite obtained by foaming with aluminate cement as the gel-former. By using this method, foams in slurries are effectively stabilized, microporous mullite ceramics with high open porosity (53–77.3%), high compressive strength (5.5–50.5 MPa), small mean pore size (2.5–9.1 μm) and low thermal conductivity (0.37–0.45 W/mK at 1100 °C) are prepared. Effects of foaming agent addition on the microstructures and properties of samples are investigated. With increasing foaming agent addition, the number and size of pores increase firstly and then tend to be constant. The pore structure looks like a bird׳s nest, in which there are a lot of needle-like mullites, which results in the effective pore size smaller.