1997 Volume 105 Issue 1217 Pages 57-61
Effect of dry and wet ball milling of ammonium aluminum carbonate hydroxide (AACH) on the transformation to α-alumina during heating was investigated. The dry grinding causes distortion of the AACH crystals, resulting in considerable reduction in the transformation temperature to α-alumina. This may be due to the easy nucleation of α-alumina during heating. In the heating the AACH ground under wet condition, significant reduction in the transformation temperature was recognized when high purity alumina balls were employed, while no noticeable change in the temperature was observed in case of zirconia balls. This is attributed to seed and dispersion effects of fine α-alumina powder worn from the alumina balls during grinding. α-alumina single phase appears in the AACH heated below 1000°C after grinding with the alumina balls under wet condition. The α-alumina powder formed from the ground and calcined AACH has a relatively large specific surface area and can be sintered at a lower temperature than that for the unground AACH.
