Synthesis and Characterization of Nanophase Metal, M and Metal Carbide, M2C Particles of The Group 6 Elements, Cr, Mo and W.

Abstract

AbstractReduction of MCln, n = 3 for M = Cr, Mo, n = 4 for W with LiBEt3H in THF results in formation of nanometer-sized crystalline metal carbide, M2C particles whereas the same reduction reaction in toluene results in formation of the corresponding metal particles. As an example of this methodology, the reduction of MoC13(THF)3 and WC14 in THF by Li/C10H8 is described in detail. Reduction of MoC13(THF)3 in THF by Li/C10H8 resulted in formation of a black suspension from which black powder can be isolated. Electron diffraction and X-ray powder diffraction data showed the black powder is amorphous. Energy dispersive spectroscopy confirmed the presence of molybdenum, and no chlorine was detected. Ex-situ variable temperature X-ray powder diffraction experiments showed the presence of fec Mo2C which upon further heating underwent a phase transformation to hexagonal Mo2C. Crystalline molybdenum was also observed after heating to 750°C for 3 hours. Reduction of WC14 in THF by Li/C10H8 results in formation of a black powder which on heating underwent phase transitions from amorphous to fcc W2C to hexagonal W2C as determined by X-ray powder diffraction.