Sintering behavior and mechanical properties of -SiC ceramics under oscillatory pressure

Sintering behavior and mechanical properties of beta-SiC ceramics under oscillatory pressure are investigated in this study. Compared with conventional hot pressing (HP), samples sintered under oscillatory pressure show higher densification rate and density, and thus lowering sintering temperature. Grain size of samples sintered via hot oscillatory pressing (HOP) is smaller than that of samples sintered via conventional HP. Both samples sintered via HOP (HOP-1850) and HP (HP-1850) at 1850 degrees C contain large number of defects (nano-spaced stacking faults (nSFs), nanotwins, and dislocations). However, sample HOP-1850 possesses more nSFs and high-order nanotwins in grain interior. In addition, dislocation density in the interior of grains containing nSFs and nanotwins for sample HOP-1850 is nearly twice that of sample HP-1850. Compared with sample HP-1850, sample HOP-1850 shows higher hardness (25.03 +/- 0.63 GPa) and toughness (5.08 +/- 0.02 MPa center dot m(1/2)). The highest flexural strength of sintered samples under oscillatory pressure is 813 +/- 44 MPa, which is 30 % higher than that of hot-pressed sintered sample under the same temperature.