Influence of AlF_3 and ZnF_2 on the phase transformation of gamma to alpha alumina

摘要

This paper focused on the effect of AlF_3 and ZnF_2 additives on the phase transformation of gamma to alpha alumina. AlF_3 and ZnF_2 were found to be effective accelerating agents on the gamma to alpha phase transformation. A single phase of Alpha alumina, with an average particle size of 22 nm, can be obtained at 920 deg. C with AlF_3 additive. ZnF_2 can reduce the Gamma to alpha transformation temperature to 900 deg. C, the average size of the particles is about 40 nm and the morphology Of some particles is platelike with an aspect ratio of 2-4. The reduction of the transformation temperature was mainly Attributed to the formation of intermediate compound of AlOF, which was considered to accelerate the mass transportation From transition alumina to alpha alumina. Moreover, mechanical milling and introducing alumina seeds uniformly worn from The milling mediums are also beneficial for reducing the transformation temperatures.