Preparation of Nanocrystalline TiN Coated Cubic Boron Nitride Powders by a Sol-Gel Process

摘要

Cubic boron nitride (cBN) particles coated with 20 wt% nanocrystalline TiN were prepared by coating the surface of cBN particles with TiO_2, followed by nitridation with NH_3 gas at 900℃. Coating of TiO_2 on cBN powders was accomplished by a sol-gel process from a solution of titanium (IV) isopropoxide and anhydrous ethanol. An amorphous TiO_x layer of 50 nm thickness was homogenously formed on the surface of the cBN particles by the sol-gel process. The amorphous layer was then crystallized to an anatase TiO_2 phase through calcination in air at 400℃. The crystallized TiO_2 layer was 50 nm in thickness, and the size of TiO_2 particles comprising the layer was nearly 10 nm. The TiO_2 on cBN surfaces was completely converted into nanocrystalline TiN of uniform particles 20 nm in size on cBN particles by nitridation under flowing NH_3 gas.