Sol-gel synthesis and characterisation of alumina-strontium hexaluminate composites

Boehmite sol was prepared by hot water hydrolysis of aluminium iso-propoxide using nitric acid as the catalyst. Strontium nitrate to yield 0 to 20 vol% calcia was added to the boehmite sol. The boehmite with additives was calcined at 500 degrees C for 3 h. The calcined powder was milled at 230 rpm for 6h and particle size was measured using laser particle size analyser. The powder samples were calcined at 1600 degrees C for 3 hand the formation of strontium hexa-aluminate was determined using phase diagram, transmission electron microscope, energy dispersive spectra and X-ray diffraction spectra. The powder samples were sintered at 1600 degrees C for 6 h and the formation of hexaluminate (plate-like) grains was confirmed using scanning electron microscopy and optical microscopy.