Abstract
A commercial fine-powdered alpha-alumina was ground and mechanically activated in air by a centrifugal ball-mill. The activated powders were compacted at 18-200 MPa and fired at 1150-1450°C in air. The fired density increased by ca. 15% due to grinding for 1 h although the linear shrinkage of the fired compact remained almost unchanged. The compressive crushing strength increased up to ca. 300% and decreased with prolonged grinding time. The densification of the fired compact was enhanced either by grinding the starting powder or by raising the firing temperature. The mean pore size Rso decreased by grinding, while it increased with increasing temperature. The results of scanning electron microscopy and porosimetry on the fired compacts suggested that the porosity and mean pore size of the fired materials can be controlled by preliminary grinding of the starting powders.
