A new strategy for dense Al2O3 ceramics by spherical powders prepared via thermal plasma

It still attracts numerous research to fabricate high-performance Al2O3 ceramics with low cost by a simple and feasible process for industrial applications. In this paper, spherical Al2O3 powders with a high purity prepared via radio frequence induction thermal plasma in large scale are used to sinter dense ceramics by an easy method of pressure-less sintering under air atmosphere. The results reveal that Al2O3 ceramic with a high relative density of 98.7% is obtained at 1600 degrees C using the ball milled powders. Importantly, the sample exhibits excellent elastic modulus of 400.2 Gpa as well as high hardness of 22.9 Gpa. Besides the outstanding features of uniform sphere, well dispersity and dense structure, Al2O3 powders after ball milling possess better sintering activity, which is responsible for the relatively low sintering temperature and good mechanical properties. Subsequent analyses of sintering kinetics and crystal structure demonstrate that milled powders show decreased sintering activation energy because of introduced amorphous phase and dislocation during milling process. Therefore, our strategy provides an insight in developing high-performance Al2O3 ceramics by a low-cost and feasible method and creates more possibilities for the large-scale industrial application of products