Preparation and characterization of mullite foam ceramics with porous struts from white clay and industrial alumina

Abstract

In this study, four mullite foam ceramics with porous struts and low thermal conductivities, were prepared by direct-foaming method from white clay and industrial alumina with the addition of sodium carboxymethyl cellulose (CMC) as foam stabilising agent. The effect of the CMC addition on the phase composition, pore characteristics, and strength was analysed through XRD, SEM and EDS, etc. The great part of struts for the foam ceramics was the needle-like mullite, the rest was the minor corundum and quartz. The addition of CMC decreased the apparent porosity of foam ceramics and pore area fractions of their struts, while the phase composition was nearly unaffected. Furthermore, the compressive strengths and the thermal conductivities of the foams ceramics increased. The optimized product contained 0.15 wt% CMC, which combined a high porosity of 81.3%, shown a low thermal conductivity of 0.095 W/(mK) (at 350 °C) and a minor positive reheating linear change.