Enhanced mechanical properties, thermal shock resistance and oxidation resistance of Si2BC3N ceramics with Zr-Al addition

Highly densified Si2BC3N ceramics were prepared through SPS sintering the Zirconium (Zr) and aluminum (Al) incorporated amorphous Si2BC3N powder obtained from mechanical alloying. The phase compositions, microstructures, mechanical properties, and thermal shock resistance, as well as the oxidation resistance were investigated. The results show that the nano ZrO2 and Al2O3 could enhance the solid diffusion and therefore induce the development of larger turbostratic BN(C) plates and SiC particles. The addition of only 1 mol% composite additive could enhance the properties of composites significantly. Therefore, the flexural strengths and fracture toughness can reach up to 590.2 MPa and 4.93 MPa m(1/2), respectively. Furthermore, the additive containing composites have much better crack initiation and propagation resistance. The residual strength of 1 mol% additive containing ceramics after thermal shock has improved by 69.8% comparing with the pristine Si2BC3N composites. Meanwhile, the oxidation resistances of Zr-Al incorporated Si2BC3N ceramics are obviously improved attributing to improved relative density and the formation of much stable SiO2-ZrSiO4 layer.