Papers by Author: Jin Yu Qiu

Abstract: The sintering behavior of AlN powders with different particle sizes and specific surface areas was investigated in the present work. 4.5-8.0mass% of the as-synthesized sintering aid from the Li2O-Y2O3-CaO system was added to these AlN powders, and they were then fired at 1400-1650oC for 6h. At the initial stage of sintering the fine AlN powder, it was recognized that sintering of primary particles occurred in agglomerations. With an increase of firing temperature, particles were rearranged and grains grew rapidly at the final stage. On contrary, in sintering of samples using the coarse AlN powder, the densification increased with raising sintering temperatures slowly, and the sintering temperature higher than 1650oC was required to obtain densified specimens.

Abstract: Fine AlN powder doped with Y2O3 and CaO as sintering additives was ground by a ball mill, a planetary ball mill and a super-fine grinding mill in order to obtain fine homogenous powder for low-temperature sintering. The size reduction and the sinterability of ground powders at 1500oC for 6 h were investigated. The size and shape of the agglomeration showed no significant change after the ball mill and planetary mill processes, resulting in poor densification. On the contrary, AlN particles with size of 50~100 nm was pulverized and dispersed by a super-fine grinding mill with very small ZrO2 beads as a mill media. The microstructures of the specimen exhibited equiaxed and homogenous grains with size of 0.3~0.4 μm. Pores in the specimens were eliminated. The thermal conductivity was 70W/mK, which is better than that of Al2O3 ceramics (~20W/mK).