Preparation of Alumina and Alumina-Ceria Microspheres using an Internal Gelation Process and their Characterization

Preparation of alumina and aluminium-cerium oxide microspheres was carried out by internal gelation process. The gelation behaviour of an acid deficient aluminium nitrate solution (NO3-/Al3+ = 2.5) with hexamethylenetetramine and urea was investigated to develop a gelation field diagram. However, cerous nitrate solution formed two phase mixture, thus its gelation field diagram could not be prepared. Further, using limited composition range, smooth, crack free Al2O3 and (Al Ce) mixed oxide microspheres were prepared. The size distribution analysis of these spheres implied that the size of spheres could be controlled by changing the molarity of aluminium. XRD pattern of opaque hard spheres confirmed the presence of theta-alumina phase while that of (Al Ce) mixed oxide spheres depicted that cerium oxide containing alumina could also be obtained. FTIR spectra of the spheres illustrated the stretching mode of tetrahedral and octahedral Al-O coordination and bending mode of cerium in (Al Ce) mixed oxide spheres. Specific surface area and pore volume studies implied that specific surface area increased with an increase in aluminium concentration and opaque hard spheres showed a larger pore volume. EDX analysis of (Al Ce) mixed oxide spheres portrayed that Al:Ce ratio was substantially lower than the experimental value.