Development of interfaces in oxide matrix composites

A number of oxides are evaluated as candidates for use as "interphases" in CMCs. Compounds studied are of the MXO4 type, i.e. phosphates, vanadates & niobates, where M is a rare earth or yttrium ion. These are assessed in terms of their thermal and chemical stability and evidence of de-bonding in conjunction with selected oxides considered as potential fibre/matrix combinations, after heat treatment at 1400 degrees C, the target temperature for application of oxide CMCs in gas-turbines. Methods of deposition of these compounds onto commercially available woven oxide fibres are compared and an optimised procedure for the in-situ deposition of NdPO4 onto 3M's Nextel 720 satin weave has been developed based on the use of an immiscible liquid bi-layer and aqueous solution precursors. The fabrication of shaped components from oxide CMCs using infiltrated fabric pre-forms is also described. In addition, interphases have been successfully deposited on oxide substrates using RF-magnetron sputtering, yielding fine grained, uniform coatings.