TAN Li , DONG Yingchao , SUN Li

(Jingdezhen Ceramic Institute, Jingdezhen Jiangxi 333001, China)

Abstract: Low-cost mullite ceramics were synthesized by reaction-sintering with natural bauxite and industrial waste fly ash as starting materials. The results indicate that secondary mullite was produced at 1200~1300℃ by the solid state reaction of cristobalite and corundum, followed by the dissolution of corundum into transitory glassy phase at higher temperatures (≥1300℃). The formation of secondary mullite and its growth resulted in a volume expansion, which was higher than the

shrinkage induced by liquid-phase sintering. The samples sintered at 1600℃ had average thermal expansion coefficient of

5.40×10^-6℃^-1 and average bending strength of 186.19 MPa. The sintered mullite exhibited two corrosion stages in hot strong acidic and alkaline solutions: fast stage (0~5h) and low-rate stage (5~20h), which respectively corresponded to the surface corrosion and bulk corrosion processes of the samples.

Key words: fly ash; bauxite; mullite; sintering; corrosion