Mechanochemical syntheses of titanium carbide, diboride and nitride

TiC and TiB2 powders were mechanochemically synthesized from powder mixtures of elemental Ti-C (atomic ratio 1 : 1) and Ti-B (1 : 2) in 34 h 45 min and 15 h 10 min, respectively, in a planetary ball mill using tungsten carbide balls. TiN powder was also mechanically synthesized from titanium powder for 60 h in a high-energy horizontal rotary ball mill (steel balls) equipped with a nitrogen gas how system. The as-milled mixed powders have been characterized as a function of the milling time by means of X-ray diffraction, scanning electron microscopy and X-ray fluorescence spectroscopy. The reaction processes for TiC and TiB2 formation were initiated by mechanically induced solid-state diffusion in the induction period when carbon or boron atoms diffused into titanium, and a small amount of TiC or TiB2 was formed by solid-state diffusion until a mechanically induced self-propagating reaction occurred. The reaction process for TiN formation proceeded via the surface reaction of titanium particles with molecular nitrogen and the mechanically induced solid-state diffusion of nitrogen atoms into titanium. The lattice parameters obtained for TiC, TiB2 and TiN agree with previously reported measurements.