Characterization of nanocrystalline tantalum nitride formed by solid-gas reaction during mechanical alloying

Tantalum nitride formed by solid-gas reaction of tantalum with molecular nitrogen driven by mechanical alloying has been examined by X-ray diffraction and transmission electron microscopy. The experimental results reveal that Ta2N with nanometric structure with grain size of 5-20 nm is produced by milling tantalum powders in nitrogen atmosphere. Trace Ta3N5 is also detected by electron diffraction pattern. The formation of tantalum nitrides is believed to be associated with the chemisorption of nitrogen onto clean metal surfaces created by milling. The defects generated by mechanical alloying may have also an effect on solid-gas reaction. (C) 1998 Elsevier Science S.A.