Abstract

In this study, a high energy ball milling process was employed in order to improve the densification of direct nitrided AlN powder. The densification behavior and the sintered microstructure of the milled AlN powder were investigated. Mixture of AlN powder doped with 5 wt.% Y_2O_3 as a sintering additive was pulverized and dispersed up to 50 min in a bead mill with very small ZrO_2 beads. Ultrafine AlN powder with a particle size of 600 nm and a specific surface area of 9.54 m2/g was prepared after milling for 50 min. The milled powders were pressureless-sintered at 1700°C-1800°C for 4 h under N_2 atmosphere. This powder showed excellent sinterability leading to full densification after sintering at 1700°C for 4 h. However, the sintered microstructure revealed that the fraction of yitttium aluminate increased with milling time and sintering temperature and the newly-secondary phase of ZrN was observed due to the reaction of AlN with the ZrO_2 impurity.

• Keywords: AlN;Direct nitridation;A high energy ball milling;Liquid phase sintering;