Analytical Electron Microscopy Investigation of Coated 3M Nextel 720™ Fibers

Abstract

An oxidation resistant interfacial layer between the fiber and the matrix is important for prolonged use of ceramic-matrix composites (CMC). The interface layer has to be chemically compatible and stable in high temperature oxidizing environments. At present various oxide based interface layers in CMC are being considered. One candidate is porous interfaces. Zircon has good thermomechanical stability with SiC and mullite, and resists pore coarsening, so it is of interest as a porous interface materials.Ethanolic zirconia and silica precursors, complexed with polyelectrolytes to form fugitive carbon for porosity were doped with vanadium. These were used to continuously coat the 3M Nextel 720™ alumina-mullite fibers. These fibers were heat-treated in-line in argon at 1000-1300°C, with the aim of finding heat-treatment conditions that would convert the zirconia, silica, and polyelectrolyte into a fine mechanical mixture of zircon and carbon.