Effect of the cold forming processes on the sintering of alumina nano-powders

This work focused in the study of the effect of the conforming process on the transformation of the alumina during the conventional sintering of spherical γ-alumina powders with a 35 nm of the average particle. We made compacts by three different method; slip casting, axial and isostatic compaction. Then sintering was carried out at 1500 °C with an isothermal plateau of 1 hour in a vertical dilatometer. Samples were evaluated by SEM and XRD in order to observe the final microstructures, the final grain size was assessed by image analysis. Results show that sintering was activated earlier for the compacts produced by compaction either axial or isostatic, however maximal densification was observed for the slip casting. The smaller final grain size was obtained when isostatic compaction is used. In the other hand the evolution into the α-alumina was promoted by the slip casting.