Nanostructure and bimodal structure of Si3N4 ceramics developed by spark plasma sintering method

Abstract The densification of high energy ball milled Si3N4 nanopowders through spark plasma sintering was investigated. Nanoceramics of Si3N4, with fine microstructure, comprising of grains with a diameter of ∼70 nm, were produced after sintering at 1600°C for 5 min in N2 atmosphere with a fast heating rate of 300 K min−1. The size and the aspect ratio of Si3N4 grains increased with decreasing heating rate and increasing holding time and temperature. Post-annealing of sintered ceramics at 1850°C for 3 h favoured development of a self-reinforced bimodal microstructure containing large elongated grains.

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