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

Abstract

ZrO 2–phenolic resin and SiO 2–ZrO 2–phenolic resin hybrid fibres have been prepared by sol–gel processing using zirconium tetrakis(2,4-pentanedionate) (ZTP), tetraethoxysilane (TEOS), and novolac-type phenolic resins as raw materials. ZTP and the phenolic resins dissolved in a mixture of ethanol and 2,4-pentanedione have undergone a sol–gel reaction to give ZrO 2–phenolic resin hybrid fibres when H 2O and H 2SO 4 have been added to the solutions at a H 2O/Zr molar ratio of 0.45 and H 2SO 4/Zr molar ratio of 0.66. On the basis of the molar ratios and the H 2O/Si and H 2SO 4/Si molar ratios of solutions, which were demonstrated to be optimal for preparing SiO 2–phenolic resin hybrid fibres from TEOS and the phenolic resins, amounts of H 2O and H 2SO 4 to be added to TEOS-ZTP-phenolic resin–H 2O–H 2SO 4–ethanol–2,4–pentanedione solutions with numerous Si-to-Zr atomic ratios have been estimated. The solutions containing the estimated amounts of H 2O and H 2SO 4 have been found to give SiO 2–ZrO 2–phenolic resin hybrid fibres with Si-to-Zr ratios which correspond to those of the solutions, meaning that the hybrid fibres with a variety of Si-to-Zr atomic ratios can be prepared by this estimation method. The hybrid fibres have been convertible into ZrC or Si–Zr–C fibres upon firing at 1500°C for 4 h in an Ar flow.