H. Preiss et al., PREPARATION OF MOLYBDENUM AND TUNGSTEN CARBIDES FROM SOLUTION DERIVEDPRECURSORS, Journal of Materials Science, 33(3), 1998, pp. 713-722
Synthesis principles have been developed for the preparation of soluti
on derived precursors that can be selectively converted to desired ref
ractory materials, as powders, fibres or thick films. The precursors a
re prepared from aqueous or ethylene glycol solutions containing a pyr
olysable organic compound (carbonaceous gel or saccharose) and a solub
le molybdenum or tungsten compound (peroxo acid or ethylene glycolate)
. The concentrated solutions exhibit rheological properties that allow
fibre drawing and production of thick films. The sequence of the high
temperature reactions - pyrolysis, reduction, carburization - was inv
estigated by thermal gravimetric analysis (TGA), X-ray analysis and ni
trogen adsorption. Because of the high homogeneity of the reactants, c
arbon and transition metal suboxides in the pyrolysed precursors, the
observed carburization temperatures (800-1200 degrees C) are lower tha
n those used industrially. Most of the intermediate and final products
- carbon/oxide composites, Mo(C,O), Mo2C, W2C, and WC - are materials
of a high Brunauer-Emmett-Teller (BET) surface area (50-200m(2) g(-1)
). (C) 1998 Chapman & Hall.