A novel strategy for synthesizing porous ZrB2-SiC ceramics via boro/carbothermal reaction process templated pore-forming approach

In this work, pure ZrB2-SiC composite powders were obtained using ZrO2, SiO2, B4C and carbon black as raw materials via a boro/carbothermal reduction (BCTR) reaction process at 1500 degrees C for 2 h in vacuum condition. Based on this finding, porous ZrB2-SiC ceramics were in-situ synthesized via a novel and facile boro/carbothermal reaction process templated pore-forming (BCTR-TPF) method. The phase composition, linear shrinkage, and pore size distribution were also methodically studied. Results show that the porous ZrB2-SiC ceramics with controllable porosity of 67-78%, compressive strength of 0.2-9.8 MPa and thermal conductivity of 1.9-7.0 W.m(-1)K(-1) can be fabricated by varying of ZrO2 and B4C particle sizes. The formation of ZrB2 grains was controlled via solid-solid and solid-liquid-solid growth mechanisms, the growth process of SiC grains was mainly regulated by solid-solid, vapor-vapor and vapor-solid growth mechanisms during the overall synthesis process. Finally, the pore-forming mechanism of porous samples prepared via the BCTR-TPF method was gases combined with template pore-forming mechanism, i.e., B4C and carbon black acted as pore-forming templates, and gaseous products generated in the BCTR reaction were also applied as gas pore-forming agent.