Preparation of nano-sized TiN coated alpha-Si3N4 particles

alpha -Si3N4 particles coated with 10 and 25 vol% nano-sized TiN were prepa red by coating the surface of the Si3N4 particles with TiO2, followed by ni tridation. Coating by TiO2 was accomplished by dispersing alpha -Si3N4 powd ers (0.16 and 1.6 g l(-1)) in a solution of TiCl4, urea and aqueous HCl, an d heating at 105 degreesC for 130 and 190 min. The success of the coating p rocedure was confirmed by TEM observation with electron diffraction and EDX analysis. Zeta potential measurements suggest that the TiO2 coating on the surface of Si3N4 particles occurs at a pH between 3.7 and 4.3 by the attra ctive force of opposite charges. When the TiO2 on the surface of the Si3N4 is nitrided with NH3 gas at 1000 degreesC, it is completely changed to TiN of uniform particle size (20 nm).