Which alternative to the pyrocarbon interphase in ceramic matrix composites?

This paper deals with research carried out in our laboratory on alternative materials to pyrocarbon (PyC) for interphases in ceramic matrix composites. Two concepts of interphase were investigated. The first one consisted in porous oxide coatings deposited by the sol-gel process. The oxide films are made of meso-, macro- and microporous sub-layers with a chemical composition of 90%Al2O3-10%SiO2. The second concept consisted in (PyC/TiC)(n) nanoscale multilayered coatings. The pressure-pulsed reactive chemical vapour deposition (P-RCVD) method allowed the pyrocarbon intercalated between two adjacent TiC sub-layers to be consumed. The interfacial mechanical properties were assessed by using tensile tests carried out on SiC/SiC microcomposites with unload-reload cycles. Transmission electron microscopy observations permitted interphase structures to be correlated with their processing conditions and the mechanical behaviours.