Synthesis of the Composite Ultrafine Particles of Ni-TiC by "Reactive Plasma-metal" Reaction

The composite ultrafine particle (UFP) of Ni and TiC was synthesized by arc melting, vaporization and deposition of Ni--Ti--C alloys in an atmosphere of H--Ar mixed gas ("reactive plasma-metal" reaction) at 0.1 MPa pressure. The crystal structure, the chemical composition, the morphology and sintering characteristics of obtained UFP were determined by X-ray diffractometry, energy dispersion analysis for X-ray, transmission electron microscopy and dilatometry, respectively. The UFP obtained from Ni--Ti--C parent alloys containing 60-90 mol% TiC was composed of three phases of Ni, TiC (NaCl type) and Ni sub 3 Ti. The TiC concentration of the UFP remarkably deviated negatively from TiC concentration of the parent alloys. The composite UFP consisting of Ni and TiC, whose morphology was dumbbell-like, dice-like or ball-like particles, was found in the obtained UFP. It is considered that those composite particles are formed during the solidification process of a molten Ni--Ti--C particle condensed in the gas-phase. Dilatometric measurements under hydrogen atmosphere show that the composite UFP has different sintering characteristics from mixed powders of Ni UFP and TiC UFP.