Inorganic-organic hybrid route to synthesis of ZrC and Si-Zr-C fibres

ZrO2-phenolic resin and SiO2-ZrO2-phenolic resin hybrid fibres have been pr epared by sol-gel processing using zirconium tetrakis(2,4-pentanedionate) ( ZTP), tetraethoxysilane (TEOS), and novolac-type phenolic resins as raw mat erials. ZTP and the phenolic resins dissolved in a mixture of ethanol and 2 ,4-pentanedione have undergone a sol-gel reaction to give ZrO2-phenolic res in hybrid fibres when H2O and H2SO4 have been added to the solutions at a H 2O/Zr molar ratio of 0.45 and H2SO4/Zr molar ratio of 0.66. On the basis of the molar ratios and the H2O/Si and H2SO4/Si molar ratios of solutions, wh ich were demonstrated to be optimal for preparing SiO2-phenolic resin hybri d fibres from TEOS and the phenolic resins, amounts of H2O and H2SO4 to be added to TEOS-ZTP-phenolic resin-H2O-H2SO4-ethanol-2,4-pentanedione solutio ns with numerous Si-to-Zr atomic ratios have been estimated. The solutions containing the estimated amounts of H2O and H2SO4 have been found to give S iO2-ZrO2-phenolic resin hybrid fibres with Si-to-Zr ratios which correspond to those of the solutions, meaning that the hybrid fibres with a variety o f Si-to-Zr atomic ratios can be prepared by this estimation method. The hyb rid fires have been convertible into ZrC or Si-Zr-C fibres upon firing at 1 500 degrees C for 4 h in an Ar flow. (C) 1999 Elsevier Science Ltd and Tech na S.r.l. All rights reserved.