Densification of Ceramic Matrix Composite Preforms by Si2N2O Formed by Reaction of Si with SiO2 under High Nitrogen Pressure. Part 2: Materials Properties

Ceramic matrix composites (CMCs) have been prepared and optimized as already described in part I of this paper. The fibrous preform made Hi-Nicalon S fibers was densified by a composed Si2N2O inside the CMC reacting mixture Si SiO2 under high nitrogen pressure. This describes oxidation resistance mechanical properties CMC. submitted to wet oxygen at 1400 °C for 170 h exhibited an gradient from surface almost center sample. In outer sample, Si2N2O, Si3N4 SiC were oxidized into silica cristobalite-crystallized form. microstructure looks similar original one while large pores are observed fiber/matrix interphase is consumed oxidation. elastic modulus hardness measured room temperature nano-indentation are, respectively, 100 8 GPa. tensile tests ranges 150 160 GPa ultimate yield strength 320 390 MPa, which corresponds strain about 0.6%. identified acoustic emission 40 MPa.