Enhanced mechanical strength of SiC reticulated porous ceramics via addition of in-situ chopped carbon fibers

Due to the poor strength of silicon carbide reticulated porous ceramics prepared by polymer sponge replica method, vacuum infiltration using a low viscosity infiltration slurry is performed to fill the flaws created during pyrolysis of the polymer sponge to improve the compressive strength. However, the flexural strength and thermal shock resistance of the porous silicon carbide ceramic are not significantly improved through this method. This paper investigates the improvement in thermal shock resistance and flexural strength of porous silicon carbide ceramics through the addition of different lengths and amounts of carbon fibers to the infiltration slurry. With the addition of 3 mm long carbon fibers at a concentration of 0.5 wt% to the infiltration slurry, the flexural strength of the porous silicon carbide ceramic was improved by 142%. Moreover, the thermal shock resistance of the SiC specimens was effectively enhanced through the addition of carbon fibers, as evidenced by a 74.4% increase in the residual strength ratio of the specimens. Due to the low thermal expansion coefficient of the carbon fibers, compressive residual stresses were generated in coating layers of SiC RPCs after sintering, which was inhibited the propagation of cracks in the coating layers. Thus, adding carbon fibers to the infiltration slurry can open more possibilities for application of SiC reticulated porous ceramics.