Synthesis of polymeric titanium and zirconium precursors and preparation of carbide fibres and films

Polymeric precursors for carbothermal reactions were prepared from the chel ate derivatives of titanium and zirconium alkoxides L2M(OR)(2) (L is an ace tylacetonato or ethyl acetoacetato group) in alcohols by reaction with orga nic compounds having two or more reactive OH groups, such as ethylene glyco l, saccharose, tartaric acid or dihydroxybenzenes. These organic groups act as bridging ligands in transesterification and condensation polymerization yielding either spinnable viscous solutions or elastic gels. The rheologic al properties of the concentrated solutions allowed for the preparation of polymer fibres and films. At temperatures up to 1600 degrees C, bulk precur sors as well as fibres and films were thermally converted into carbide powd ers, films or coatings. The structural transformations of the polymeric mat erials into the carbides were investigated using thermogravimetric-differen tia I thermal ana lyses (TGA-DTA), X-ray diffraction (XRD), scanning electr on microscopy (SEM), Fourier transform infra-red (FTIR) analysis and Raman spectroscopy. (C) 1998 Kluwer Academic Publishers.