Synthesis And Characterization Of Molybdenum Carbide And Nitride

Molybdenum carbide and nitride are promising materials as ceramics and catalytic materials because of their high melting point, superconductivities and catalytic properties. Based on the survey of published papers and the applications of these two materials, we explored the synthetic methods for these two materials using solid state reactions. The morphologies, phases and properties of the as-prepared samples were characterized employing various methods. We also discussed the formation mechanism of the final products on account of the experimental results. The main results are summarized as follows:1. Preparation of sphere-like superconductingα-M02C nanoparticles via a solid state reaction.Sphere-likeα-M02C (orthorhombic) nanoparticles were synthesized through the reaction of sodium molybdate, anhydrous ethanol and sodium azide at 450℃for 10 h in a sealed autoclave. X-ray powder diffraction results indicated that the final product was Mo2C. Transmission electron microscopy (TEM) shows that the morphology of the as-prepared nanopaticles are mainly solid spheres with a few branches. The temperature dependence of magnetization of the final product showed that its superconducting critical temperature (Tc) was 9.5 K, which confirms the final product was orthorhombicα-M02C. The experimental parameters such as reaction temperature and reactants were studied to investigate the reaction mechanism. It was found that sodium azide and reaction temperature played key roles in the formation of sphere-like nanoparticles.2. Synthesis of Mo2N micro-scaled polyhedra at a relatively low temperature.Mo2N (cubic and tetragonal) micro-scaled polyhedra were synthesized through the reaction of ammonium molybdate, magnesium powder and sodium azide at 550℃for 12 h in a sealed autoclave. X-ray powder diffraction results indicated that the final product was mixture ofβ-Mo2N andγ-Mo2N. Scanning electron microscopy (SEM) shows that the morphology of the as-prepared micropaticles are mainly cubes, hexagonal pieces and pyritohedrons. The experimental parameters such as reaction temperature and reactants were studied to investigate the reaction mechanism. It was found that sodium azide and reaction temperature played key roles in the formation of micro-scaled polyhedra.