Interface compatibility in ceramic-matrix composites

Critical issues of interface modifications in ceramicmatrix composites have been investigated. Minimal interaction between the fiber and the matrix is essential to achieving good toughness in ceramic-fiber-reinforced SiCO composites. Introduction of a thin barrier coating on the fiber surface has been utilized to minimize such interaction. The flexural strength of a SiCO composite containing CVD carbon-coated Nicalon fibers was found to be five times higher than that of the composite containing uncoated Nicalon fibers. Chemical reactions between the barrier coating and the matrix and those between the coating and the fiber must be avoided in such a three-phase material. A methodology for selecting candidate fiber coating materials by the use of chemical compatibility calculations is presented.