Synthesis and Characterization of α-Al2O3 Nanocrystallines from γ-Alumina Micron Powder by Using High Energy Mechanical Milling Method

In this research, the results obtained from studying the phase transition of γ-alumina (γ-A 2O3) to α-Alumina (α-Al2O3) during intense mechanical activation in high-energy ball milling are presented. The powder samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), differential thermal and thermogravimetric analyses (TG-DTA). With respect to the results achieved from above analyses, depending on experimental conditions, the γ→α- alumina transition through δ- and θ-phases, can be initiated. Also it was detected that the pure γ- alumina phase showed great stability and no transformation to any other phase after a long milling time (30 hours). On the other hand, γ-alumina, which contained a small amount of the α Alumina phase, showed a gradual phase transition from γ-alumina to α-alumina in milling. The phase transition mechanism during milling is nucleation and growth which is promoted by the α alumina seed.