Densification maps for spark plasma sintering of nanocrystalline MgO ceramics: Particle coarsening and grain growth effects

Recently densification maps for spark plasma sintering (SPS) of nanocrystalline MgO were constructed using a HIP model and constant particle size during the process. Here, the effects of particle coarsening during the early stage and grain growth during the later stage of densification were integrated into the model. Densification diagrams were calculated between 500 °C and 900 °C, pressures range 30–500 MPa and initial particle size 10–40 nm. Plastic yield and diffusion process dominated during the densification in SPS. The power law creep exhibited negligible densification rates. Threshold pressure exists for full densification of nanocrystalline compact with minimal grain growth. Particle coarsening and grain growth resulted in densification patterns that follow the experimental SPS results. The calculated densities were lower than the experimental results and fall short in describing the experimental densification rates of nanocrystalline MgO. Therefore additional densification mechanisms with faster kinetics should be incorporated.