High speed centrifugal compaction and low temperature sintering of submicron alumina powder

A slip has been prepared from an alumina powder with the average particle size of 0.22 μm and the purity of 99.99%. Compacts have been formed from the slip in the high speed centrifugal compaction process by a 8 to approximately 12 kG centrifugal force, and sintered in air at 1200 to approximately 1250 °C for 2 hr. The SEM observations on polished and thermally etched sections of the sintered compacts showed fine grain structures with no void. The sintering at 1220 °C has given a 3-point bending strength of 1160 MPa (Weibull modulus: 20.5), an average particle size of 0.64 μm, a relative density of 99.3%, and a Vickers hardness of 2100. An alumina having high levels of the purity and same characteristics as Hipped materials was obtained in the centrifugal process by only sintering a non-doped green compact in air. One of the reason for obtaining such an excellent property of sintered alumina may be due to complete removal of bubbles during compaction by the high centrifugal force.