Ali Sedaghat - Department of Ceramic, Material and Energy Research Center, karaj, Iran.
E. Taheri-Nassaj - Department of Materials Engineering, Tarbiat Modares University, Tehran, Iran.
G. Soraru - Department of Materials Engineering and Industrial Technology, University of Trento, Trento, Italy.
R. Ceccatob - Department of Materials Engineering and Industrial Technology, University of Trento, Trento, Italy.
T. Ebadzadeh - Department of Ceramic, Material and Energy Research Center, karaj, Iran.

Homogeneous distribution of mullite in the matrix of alumina can be obtained through sol-gel method. In this work, nanopowder of alumina-mullite composite was synthesized with high homogeneity and high purity. So aluminum chloride hexahydrate and tetraethyl orthosilicate were used instead of alumina or mullite nanopowder. Studying the simultaneouse thermal analysis (STA) of mullite precursor reveals two endothermic peaks at ۱۴۵ and ۲۴۰°C due to dehydration and removal of the molecular water and the chloride component. An exothermic peak is also detected at ۸۵۵°C. According to the XRD patterns of alumina-۱۵vol.% mullite precursors calcined at different temperatures, crystallization of transitional alumina phases (γ, κ) occurs approximately at ۸۰۰°C. Then these phases transform to α alumina approximately at ۱۰۰۰°C. XRD patterns of alumina-۱۵%vol. mullite which were calcined at different temperatures show peaks of mullite relating to ۱۰۰۰°C. The specific surface area of this nanopowder calcined at ۹۰۰°C was calculated to be ۱۲۰.۹±۰.۵ m۲/g. The nanopowder was observed by TEM.

Sol–gel processes, Nanocomposites, Al۲O۳