High‐Strength Porous SiC Ceramics From Truncated Pyramid‐Shaped β ‐SiC Powder via Rapid Hot‐Pressing

ABSTRACT Porous silicon carbide (SiC) ceramic is considered a promising material for many engineering applications due to its excellent chemical stability, corrosion resistance, high‐temperature stability, etc. However, preparing porous SiC ceramic without sintering aids still faces many challenges. Here, we have prepared high‐strength porous SiC ceramics without sintering aids by a one‐step rapid hot‐pressing technique using a special β‐SiC powder with truncated pyramid‐shaped structures. The formation mechanism, phase composition, and microstructure of this special powder were systematically discussed. The trends and influencing factors of the phase composition, microstructure, density, thermal conductivity, compressive strength, and flexural strength of the porous ceramics were also investigated in detail. The sample prepared at 1800°C exhibited the porosity, compressive strength, flexural strength, and thermal conductivity of 33.62%, 191.6 MPa, 71.4 MPa, and 44.96 W/(m·K), respectively. An interesting phenomenon was found that higher compressive strength and flexural strength could be achieved at a relatively lower sintering temperature due to the high‐activity and special‐structured raw material. This provided a new idea and inspiration to prepare high‐strength porous ceramics with high‐activity raw materials to obtain a weakly bonded microstructure at a lower temperature. Because this might cause a very tiny pseudo‐elastoplastic deformation before fracture.