Characterization of abrasion powder worn from alumina balls by wet milling and its phase transformation during heating

Abrasion test of high and low purity alumina balls is conducted in different types of mills under wet condition. The abrasion powder produced by abrasion of high purity alumina balls gave extremely large value of specific surface area over 30 m(2)/g. The powder includes alpha-Al(OH)(3) of gibbsite type, while alpha-Al(OH)(3) is not included in an abrasion powder worn from the low purity alumina one. A considerable amount of amorphous aluminum hydroxide is contained in both abrasion powders. The amount of aluminum hydroxide in the powder increased as the milling becomes moderate and as the balls' size is small. The aluminum hydroxide in the abrasion powder is transformed into a single phase of alpha-alumina without forming kappa- and theta-alumina phases at a relatively low temperature of about 900 degrees C. This is completely different from the phase transformation of an ordinary powder of alpha-Al(OH)(3). The formation of alpha-alumina from abrasion powder at such low temperature is attributed to a seed-effect of fine alpha-alumina powder mixed uniformly in the abrasion powder. An abrasion powder worn in alcohol also enables us to sinter at comparatively low temperature.