Aluminum oxide and chromium oxide coatings on ceramic fibers via MOCVD

The overall strength and toughness of ceramic matrix composites is very much affected by the interfacial properties that govern the bonding between the reinforcing fibers and the matrix. The ability to control this interaction is very important. One method involves coating the ceramic fibers with an appropriate material. There is a definite advantage in using lower-temperature processes to produce the coatings: fibers subjected to high-temperature coating processes are more prone to degradation due to microstructure and crystallization changes. Matrix and fiber materials could also react at high temperatures to form a strong bond at the interface making the composite brittle. Metal-organic precursors were used to produce aluminum oxide and chromium oxide coatings on SiC and Al2O3-SiO2 based ceramic fibers. These metal oxides were deposited on the reinforcing fibers by the pyrolysis in air of their respective metal acetylacetonates at temperatures of 500 degreesC or less. The coated ceramic fibers showed some reduction in tensile strength but still had considerable strength for use in composites.