Mechanical Properties and Oxidation Behaviors of Self-Healing SiCf/SiC-SiBCN Composites Exposed to H2O/O-2/Na2SO4 Environments

The oxidation behaviors and their influence on the mechanical properties of self-healing SiCf/SiC-SiBCN composites were investigated in H2O/O-2 and H2O/O-2/Na2SO(4) environments at 1200-1350 ? for 100 h. As the temperatures increase from 1200 to 1350 ?, the oxidation rate constants increase from 0.45 x 10(-7) to 1.58 x 10(-7) mg(2)/(mm(4) h) in H2O/O-2, and from 1.02 x 10(-7) to 3.42 x 10(-7) mg(2)/(mm(4) h) in H2O/O-2/Na2SO4. The involvement of Na2SO4 leads to the formation of a loose lamellar oxide layer, the breakage of the SiBCN/CVI-SiC interface and the decrease in the oxide viscosity, thus accelerating the oxidation of the composites. The composites show the maximum retention rate of strength (102%, 535.71 MPa) after oxidation in H2O/O-2 at 1200 ? due to the good self-healing capacity of the produced glass, while the minimum (82%, 430.56 MPa) in H2O/O-2/Na2SO4 at 1350 ? caused by the severe microstructural corrosion derived from Na2SO4.

Automated summary

The oxidation behaviors of self-healing SiCf/SiC-SiBCN composites were studied in H2O/O-2 and H2O/O-2/Na2SO4 environments. The involvement of Na2SO4 led to the formation of a loose lamellar oxide layer and accelerated the oxidation of the composites. The composites showed different retention rates of strength depending on the environment, with the maximum retention rate in H2O/O-2 at 1200 ? and the minimum in H2O/O-2/Na2SO4 at 1350 ?.