PREPARATION OF MACRO-POROUS SIC-AL2O3 COMPOSITES WITH POLYSILANES AND POLYCARBOSILANES

Spongelike polycarbosilanes with 50% open porosity were prepared by pyrolysis of a mixture of polysilanes and polycarbosilanes at 650 degrees C in argon. Porous SiC-Al2O3 composites were prepared by oxidation of the pyrolyzed preforms at 600 degrees C in air and subsequent infiltration with an aqueous Al2O3 slurry. Sintering was performed at 1600 degrees C in 1.5 MPa argon. The precursors were analyzed by infrared-spectroscopy and by thermal decomposition. The SiC-Al2O3 composites were investigated by light microscopy, scanning electron microscopy, energy dispersive X-ray analysis and electron scanning microanalysis.