Thermal Shock Behavior of Si3N4/BN Fibrous Monolithic Ceramics

To develop materials suitable for aerospace applications, silicon nitride/boron nitride (Si3N4/BN) fibrous monolithic ceramics with varying BN contents were prepared. Employing analytical techniques such as XRD and SEM, coupled with mechanical testing equipment, the influence of BN concentration on the thermal shock resistance of Si3N4/BN fibrous monolithic ceramics was assessed. When the thermal shock differential is less than 800degree celsius, its residual flexural strength gradually decreases as the thermal shock differential increases. Conversely, when the differential exceeds 1000 degree celsius, the residual flexural strength of the material increases. The residual strength of all samples reached its peak after undergoing a thermal shock assessment at a 1500degree celsius differential. When the BN mass fraction is 5 wt.%, the residual strength after a thermal shock at a temperature difference of 1500degree celsius is 387 +/- 19 MPa, which is 124% higher than the original strength of the sample that did not undergo thermal shock (25degree celsius, 311 +/- 18 MPa). The oxide layer formed on the thermal shock surface played a role in bridging defects introduced during material surface processing.