Synthesis of Ultrafine Intermetallic Particles by the Vapor-Phase Coreduction of Metal Chlorides with Hydrogen

摘要

Fine particles of nickel aluminides and Ni_4Nowere synthesized by reducing mixtures of, respectively, AlCl_3 +NiCl_2 and NiCl_2 + MoCl_2 vapors with hydrogen. Thoughthermodynamically favorable, the coreduction of NiCl_2 andAlCl_3 by H_2 to form Ni_3Al did not readily happenexperimentally. The addition of a small amount of aluminumvapor was needed to initiate the coreduction reaction. The productparticles as observed by TEM were very fine but usuallyagglomerated. The electron diffraction pattern of particlesidentified NiAl and NiAl_3 along with Ni_3Al and metallic Ni.The content of Ni_3Al was maximized at 52 mol precnet at 1050deg C under the partial pressures of H_2, AlCl_3, and NiCl_2 at57, 1.4, and 0.5 kPa, respectively. When a mixture of NiCl_2 +MoCl_5 was reduced by hydrogen, Ni_4Mo particles with someNi or Mo particles were obtained, the maximum content ofNi_4Mo obtained being 93 mol precnet. The particle size was inthe range of 100to 200 nm. An Ni_4Mo coating of 700 nmthickness on an Ni substrate was also prepared.