Processing and properties of ZrB2–SiC composites obtained by aqueous tape casting and hot pressing

ZrB2–SiC composites with different SiC content were prepared through aqueous tape casting and hot pressing. The influences of dispersant, SiC content and binder content on the rheological properties of slurries were investigated and the conditions for preparing stable ZrB2–SiC suspensions were optimized. After tape casting and drying, the green ZrB2–SiC tapes showed good flexibility, lubricious surface and homogeneous microstructure. The ZrB2 ceramics could be densified to 97.2% after hot-pressing, while the ZrB2 containing 20 and 30 vol% SiC ceramics were nearly fully densified (>99%). The sintered ZrB2–20 vol% SiC ceramic had improved mechanical properties compared with ZrB2 ceramic. Further increase in SiC content resulted in lower flexural strength and fracture toughness. SEM and TEM showed a fine microstructure with a clear grain boundary. The fracture mode changed from intragranular type for ZrB2 to both intragranular and intergranular type for ZrB2–SiC composites.