ION-EXCHANGE AND HOT CORROSION OF CERAMIC COMPOSITES MATRICES - A VIBRATIONAL AND MICROSTRUCTURAL STUDY

The association of two brittle ceramics can give a new material (a ceramic matrix composite) exhibiting non-brittle (dissipative) fracture. Such materials can be used in aircraft engines. Turbine parts are subject to both sulphuric acid and sodium molten salts corrosion due to the sulphate traces in engine fuels and to the NaCl air content. The ion exchange and the conducting properties of glass, glass-ceramic or ceramic matrices used in composites are thus important criteria but this point has not received much attention to date. We have performed a study of acidic and sodium corrosion of two (earth)-alkali aluminosilicate matrices (LAS: Li2OAl2O32-6SiO2 in the amorphous, beta-eucryptite and beta-spodumene forms, celsian, BAS:BaOAl2O32SiO2 in the hexagonal and monoclinic forms) and of their corresponding SiC reinforced composites. Ion exchange and microstructure damages have been analysed by chemical analysis X-ray diffraction, TGA, IR absorption, scanning electron microscopy and Raman scattering.