Method for producing ceramic coatings on fibers

Abstract

Electrophoretic deposition (EPD) can be advantageously employed to uniformly coat or impregnate an array or preform of fibers with a ceramic material. As a result, more efficient methods for making composite materials of superior quality are provided. The method of this invention comprises the steps of: (a) providing an array of reinforcing fibers which array has electrically conducting characteristics; (b) disposing the array in a liquid ceramic polymer sol in juxtaposition to a surface of a first electrode, the sol including molecules having an electrical charge; (c) providing a second electrode in contact with the sol and spaced from the first electrode; (d) creating an electric field in the polymeric sol by applying voltage to the electrodes so that the molecules migrate toward the surface of the first electrode where the migrating molecules aggregate against the fiber array, thereby producing a polymer-coated fiber array; (e) removing the polymer-coated fiber array from the sol; and (f) heat treating the polymer-coated fiber array to convert the polymer sol to a ceramic material, thereby providing a ceramic coating on the fiber array. The ceramic-coated fiber array can be used to fabricate a fiber-reinforced composite material by the additional steps of: (g) combining the ceramic-coated array with a second ceramic matrix powder to provide a composite pre-form structure; and (h) consolidating the composite pre-form structure by subjecting same to heat under conditions which consolidate the ceramic-coated fiber with the second ceramic matrix powder and thereby form a dense fiber-reinforced composite material.