Preparation and characterisation of α-Al2O3 powder from γ-Al2O3 powder using mechanical milling technique

In this presented work, alpha-Al2O3 is prepared from gamma-Al2O3 by mechanical milling technique. Also the results obtained in studying the phase transformation of gamma-Al2O3 into alpha-Al2O3 during intense mechanical activation by high-energy ball milling are presented. The powder samples were characterised by the commonly used bulk techniques of scanning electron microscope (SEM), differential thermal analysis (DTA), thermal gravimetric analysis (TGA) and X-ray diffraction (XRD) analyses. The results indicated that the pure gamma-Al2O3 phase showed great stability and did not transform to any other phase even after a long milling time. On the other hand, gamma-Al2O3, which contained a small amount of the a-alumina phase, showed a gradual phase transformation from gamma-Al2O3 to alpha-Al2O3 on milling. The phase transformation mechanism during milling appears to be nucleation and growth type and promoted by the alpha-Al2O3 seed.