Flash Spark Plasma Sintering (FSPS) of α and β SiC

A novel processing methodology that allows combined preheating and Flash-SPS (FSPS) of silicon carbide-based materials has been developed. Beta-SiC (+10 wt% B4C) powders were densified (? 20 mm) up to 96% of their theoretical density in 17 s under an applied pressure of 16 MPa (5 kN). The flash event was attributed to the sharp positive temperature dependence of the electrical conductivity (thermal runaway) of SiC, and a sudden increase in electric power absorption (Joule heating) of the samples after a sufficient preheating temperature (>600 degrees C) was reached. The microstructural evolution was analyzed by examining materials densified by FSPS in the range of 82%-96% theoretical densities. FEM modeling results suggest that the FSPS heating rate was of the order of 8800 degrees C/min. A comparative analysis was done between FSPS and reference samples (sintered using conventional SPS in the temperature range of 1800 degrees C-2300 degrees C). This allowed for a better understanding of the temperatures generated during FSPS, and in turn the sintering mechanisms. We also demonstrated the scalability of the FSPS process by consolidating a large -SiC disk (? 60 mm) in about 60 s inside a hybrid SPS furnace equipped with an induction heater, which allowed us to achieve sufficient preheating (1600 degrees C) of the material to achieve FSPS.