Mechanochemical syntheses of titanium carbide, diboride and nitride

TiC and TiB2 powders were mechanochemically synthesized from powder mixture s of elemental Ti-C (atomic ratio 1 : 1) and Ti-B (1 : 2) in 34 h 45 min an d 15 h 10 min, respectively, in a planetary ball mill using tungsten carbid e balls. TiN powder was also mechanically synthesized from titanium powder for 60 h in a high-energy horizontal rotary ball mill (steel balls) equippe d with a nitrogen gas how system. The as-milled mixed powders have been cha racterized as a function of the milling time by means of X-ray diffraction, scanning electron microscopy and X-ray fluorescence spectroscopy. The reac tion processes for TiC and TiB2 formation were initiated by mechanically in duced solid-state diffusion in the induction period when carbon or boron at oms diffused into titanium, and a small amount of TiC or TiB2 was formed by solid-state diffusion until a mechanically induced self-propagating reacti on occurred. The reaction process for TiN formation proceeded via the surfa ce reaction of titanium particles with molecular nitrogen and the mechanica lly induced solid-state diffusion of nitrogen atoms into titanium. The latt ice parameters obtained for TiC, TiB2 and TiN agree with previously reporte d measurements.