DEPENDENCE OF CALCINATION CONDITIONS OF BOEHMITE ON THE ALUMINA PARTICULATE CHARACTERISTICS AND SINTERABILITY

Monohydroxy aluminium oxide, boehmite (AlOOH), has been prepared by hydrolysis of aluminium nitrate under controlled conditions of pH, concentration and temperature. The boehmite passes through stages consisting of different transition aluminas on calcination until the stable alumina is formed at around 1393 K. The different transition aluminas have been characterized by surface area analysis and X-ray diffraction (XRD). The sintering studies on compacted discs from the calcined aluminas carried out at 1873 K show the maximum density of above 98% theoretical density for boehmite calcined at 1273 K containing mixed phases of gamma, delta, theta and alpha-aluminas. The study of the particle characteristics, compaction and sintered densities shows that it is possible to obtain high-density alumina with fine-grained microstructure starting from a powder with transition aluminas rather than pure alpha-alumina.