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6H-SiC powder mixed with Si3N4, Al2O3, Y2O3, and AlN was sintered in a spark plasma sintering (SPS) equipment. The 6H→3CSiC transformation was concerned. Research results indicated the polytype transformation completed in less than 30 s by imposing a 14 458 W (6.2 V, 2332 A) transitory DC current at 1700°C upon cooling down from 2000°C. The fast transformation kinetic and the significant 3C-SiC grain growth accompanying the phase transformation were suspected to be correlated with the pulsed SPS direct current.

The TaC0.7 composition was spark plasma sintered (SPS) at 1600°–1900°C using TaC and Ta as the starting powders. Densification process, phase evolution, microstructure development, and the mechanical properties of the composites were investigated. The results indicated that the TaC0.7 composition could be SPS to >95% of theoretical density in 5 min at 1600°C or above. The phase formation was associated with carbon diffusion from the starting particles TaC to Ta to form Ta2C and Ta6C5 as intermediate phases, and subsequently the equilibrium phases of TaCy and ζ-Ta4C3−x. The presence of lamellar ζ-Ta4C3−x regions enhanced the flexure strength (up to 972 MPa) and fracture toughness (up to 13.8 MPa·m1/2).