A sol-gel route to nanocrystalline TiN coated cubic boron nitride particles

Abstract

For the purpose of increasing microstructural homogeneity and enhancing the reinforcement-matrix interfacial area, cubic Boron Nitride, cBN particles were coated by nanocrystalline TiN by a sol-gel route that required neither the need for pH adjustment nor the use of surfactants or additives. Uniform shells of amorphous titania having thicknesses in the nanometers scale were formed on the surface of the cBN particles by hydrolysis and condensation reactions of titanium (IV) isopropoxide. The amorphous coated cBN powder was nitrided to crystalline TiN coated cBN by treating in NH(3) gas at 900 degrees C. After nitridation the amorphous layer was completely converted to nanocrystalline TiN particles that uniformly covered the surface of cBN. Changes in the TiO(x) coated layer thickness and the size of the TiN particles were investigated as a function of alkoxide content. TiO(2) nanoparticles were synthesized using the same reaction conditions, but without the presence of cBN. These nanoparticles were calcined in air at different temperatures (250-700 degrees C) and then nitrided at 900 degrees C. The nitridation behavior of TiO(2) nanoparticles was studied as a function of calcination temperature. (C) 2011 Elsevier B.V. All rights reserved.