Densification mechanism, microstructure and mechanical properties of ZrC ceramics prepared by high-pressure spark plasma sintering

The traditional way of densifying high-melting-point ceramics at high temperatures with long soaking time leads to severe grain coarsening, which degrades the mechanical properties of ceramics. Here, highly dense (similar to 98%) zirconium carbide (ZrC) ceramics with limited grain growth were obtained by spark plasma sintering (SPS) at relatively low temperatures, 1900 celcius, with a high pressure up to 200 MPa in a reliable carbon-fiber-reinforced carbon composite (C-f/C) mold. Subgrains and high-density dislocations formed in the high-pressure sintered ceramics. The hardness and fracture toughness of the prepared highly dense ZrC ceramics reached 20.53 GPa and 2.70 MPa center dot m(1/2), respectively. The densification mechanism was mainly plastic deformation under high pressure. In addition, ZrC ceramics sintered at high pressure possessed a high dislocation density of 7.30 x 10(12) m(-2), which was suggested to contribute to the high hardness.

Automated summary

Highly dense zirconium carbide (ZrC) ceramics were obtained by spark plasma sintering (SPS) at low temperatures (1900°C) and high pressure (up to 200 MPa) using a carbon-fiber-reinforced carbon composite (C-f/C) mold. The ceramics showed limited grain growth and the formation of subgrains and high-density dislocations. The resulting ZrC ceramics exhibited high hardness and fracture toughness. The densification mechanism was mainly attributed to plastic deformation under high pressure, with the high dislocation density contributing to the high hardness.