Micro-structure and Properties of Machinable AIN-BN Ceramic Nano-composites

The AlN/h-BN nanocomposite powders were prepared through the reaction of A1N powder, H3BO3, and CO(NH2)2 in nitrogen atmosphere at 850 ℃. TEM observation shows that the average particle diameter of BN is about 20~30nm. The A1N/BN ceramic composites were synthesized by hot-pressing. SEM/TEM observation shows that the BN particles are thin pin-shaped with 100~400nm pin-length and 30~50nm pin-width. The hardness of the composites decreases obviously and the machinable property increases when the BN content is more than 20wt%.