Room Temperature Synthesis of Crystalline Molybdenum and Tungsten Carbides, Mo2C and W2C, via Chemical Reduction Methods

The species MOC13TBF3, MOC14THF2 and WC14 have been reduced in THF solution with LiBEt3H to give black, homogeneous solutions. The black product could be separated from the other reaction by-products to give either a colloidal black solution or an agglomerated black precipitate. TEM of the dried colloidal solutions showed the presence of monodispersed 1-2nm sized particles which gave a broad electron diffraction rings corresponding to a d-spacing of - 2.4 Anstrom Energy dispersive spectroscopy showed only the presence of Mo or W depending on which starting material was used. The black precipitates were shown to be agglomerates of the 1-2nm crystallites. X-ray powder diffraction data also showed a broad peak centered at 2.4 Anstrom for Mo2C and 2.3 Anstrom for W2C. On heating the peaks sharpened and a number of other lower intensity peaks emerged that were consistent with the presence of crystalline M2C M Mo, 500 deg C or W, 450 deg C rather than the expected metal products. The identity Of M2C was confirmed by elemental analysis and by TGA oxidation experiments.