Densification of additive-free polycrystalline β-SiC by spark-plasma sintering

Additive-free β-SiC nanopowders were densified by spark-plasma sintering in the temperature range 1650-2200 °C, holding time 1-30 min, and pressure 50-150 MPa. The starting nanopowder was further refined and mechanically activated by ball milling in order to promote densification. In a detailed parametric study, temperature, holding time, and/or pressure were varied to investigate their effect on the densification and grain growth during sintering. High densifications were obtained for temperatures greater than 1800 °C. Full densification (98.0 ± 0.6%) was reached at a sintering temperature of 2100 °C. Depending on the sintering conditions, nanostructured materials can be produced with grain sizes between 90 and 100 nm, and microstructured materials with grain sizes between 0.22 and 2.39 μm. Pressure has a major effect on the grain size, it being necessary to use a pressure of 150 MPa to obtain nanostructured materials.