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

Cubic boron nitride (cBN) particles coated with 20 wt% nanocrystalline TiN were prepared by coating the surface of cBN particles with TiO₂, followed by nitridation with NH₃ gas at 900 °C. Coating of TiO₂ 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 TiO₂ phase through calcination in air at 400 °C. The crystallized TiO₂ layer was 50 nm in thickness, and the size of TiO₂ particles comprising the layer was nearly 10 nm. The TiO₂ on cBN surfaces was completely converted into nanocrystalline TiN of uniform particles 20 nm in size on cBN particles by nitridation under flowing NH₃ gas.