Gelcasting of complex-shaped ZrB2–SiC ultra high temperature ceramic components

Complex-shaped ZrB 2 –SiC ultra high temperature ceramic components were successfully fabricated by gelcasting technique and pressureless sintering. When 0.4   wt% poly(acrylic acid) (PAA) was used as dispersant and the pH value was 10, an aqueous ZrB 2 –SiC–B 4 C–C slurry with a high solid loading up to 50   vol% but low viscosity (3.1   Pa   s at 60   s −1 ) was prepared. For gelcasting process, the suitable monomers content (AM and MBAM) and the mass ratio of monomers (AM/MBAM) were selected as 3   wt% and 15:1, respectively. After pressureless sintering at 2100   °C for 2   h, ZrB 2 –SiC ceramics (using B 4 C and C as sintering additives) finally achieved about 98% density. Investigation of the mechanical properties revealed a flexural strength of 405±27   MPa and a fracture toughness of 4.3±0.3   MPa   m 1/2 . Complex-shaped ZrB 2 –SiC ceramic components with homogeneous microstructure were also successfully produced. This study confirms that gelcasting is a reliable process for the fabricating of complex-shaped ultra high temperature ceramic components with satisfied properties.