Silicon and Boron Containing Components by CVD and CVI for High Temperature Ceramic Composites

摘要

The potential large applications of ceramic composites require the preservation of their thermomechanical properties for long duration, in oxidative environments, under high temperature fatigue conditions and/or thermal cycling. This implies that the fibers and matrix properties, cracks deviation and load transfer at the fiber-matrix interface must be maintained. Different possibilities to progress in that way, that is to reduce the oxidation penetration in the parts or to improve the oxidation resistance at the fiber-matrix interface are examined. They include the use of protective external coatings, the development of new matrices or more oxidation resistant interphases. All components of the composite are examined successively. It appears that they are often composed of silicon and boron compounds, but more complex ternary or quaternary systems which include these two elements as compositional gradient materials or multilayered materials are developing. All these systems lead to some limitations of particular deposition or infiltration processes from the gas phase that are pointed out in view to some examples on the CVD and ICVI of ternary solids and multilayered materials, and on a comparison between CVD and ICVI processes for interphase elaboration. For each component of the composite, examples showing the improvement of the final properties are given. Finally we point out the domains where further research on deposition from the gas phase are needed.