Polymeric precursors for carbothermal reactions were prepared from niobium
alkoxide, tantalum alkoxide and molybdenum ethylene glycolate, respectively
, by simultaneous reaction with a chelating reagent (acetylacetone) and org
anic compounds having two or more reactive OH groups, such as ethylene glyc
ol, saccharose, tartaric acid or dihydroxybenzenes. The precursors exist in
common polar and non-polar solvents mostly as linear polymers. The viscous
solutions show rheological properties that allow for the preparation of po
lymer fibres and films. At temperatures up to 1500 degrees C, bulk precurso
rs as well as fibres and films were thermally converted into carbide powder
s, fibres and coatings. The structural transformations of the polymeric mat
eria Is into carbides were investigated using simultaneous thermogravimetri
c-differential thermal ana lyses (TGA-DTA), X-ray diffraction (XRD) and sca
nning electron microscopy (SEM). (C) 1998 Kluwer Academic Publishers.