SINTERING OF DIPHASIC MULLITE GEL

A monolithic colloidal gel of mullite composition, prepared from SiO2 and boehmite sols, was sintered under isothermal conditions. The sinte ring process was studied by dilatometry, thermogravimetric analysis, b ulk density measurements and discontinuous shrinkage measurements. The silica component of stoichiometric colloidal mullite gel prevented cr ystallization of alpha-Al2O3 in the system. The initial rapid part of the sintering is controlled by the alumina phase and it is not a visco us sintering process in the sense of Scherer's viscous sintering model . The final part of sintering, above approximately, 80% of the theoret ical density, is controlled by the silica component of the gel and agr ees very well with the Scherer model.