Abstract: Nanometer mullite was prepared through Sol-Gel-SCFD and middle temperature calcination by using aluminium-isopropoxde
and tetraethyl orthosilicate as starting materials, the alumina-silica binary aerogel and calcined nanosized materials were investigated by
using thermogravimetry-differential scanning calorimeter (TG-DSC), transmission electron microscope (TEM), X-Ray diffractometer (XRD) and specific surface
area and porosimetry. TG-DSC indicated the removal of most of the volatiles, i.e. 15.98% up to about 700℃, and in the DSC curve, the existence of two
exothermic peaks at about 445 and 1015℃ may be due to the crystallization of Si-O-Al-O in diphasic gels and mullitization, and a small
endothermic peak at about 805℃ indicated the decomposition of structural water molecules. The beginning temperature of mullitization of the
Al₂O₃-SiO₂ at about 1015℃ in gel was confirmed by TG-DSC, XRD and TEM, XRD results which also showed the formation of mullite at the
range 1100-120℃. TEM and surface area and porosimetry results showed that the nanosized mullite calcinated at 1100 and 1200℃
exhibited the sizes of 30nm and 50nm, specific surface area 138.91m²/g and 95.81m²/g respectively.

Key words: nanosized mullite, sol-gel, supercritical fluid drying