Silicon nitride nanoceramics densified by dynamic grain sliding

The densification behaviors of two silicon nitride nanopowder mixtures based respectively on α-Si₃N₄and β-Si₃N₄as the major phase constituent were studied by spark plasma sintering. Sintering conditions were established where a low viscous liquid not in equilibrium with the main crystalline constituent(s) stimulated the grain sliding yet did not activate the reprecipitation mechanism that unavoidably yields grain growth. By this way of dynamic grain sliding full densification of silicon nitride nanoceramics was achieved with no noticeable involvement of α- to β-Si₃N₄phase transformation and grain growth. This processing principle opens the way toward flexible and precise tailoring of the microstructures and properties of Si₃N₄ceramics. The obtained silicon nitride nanoceramics showed improved wear resistance, particularly under higher Hertzian stresses.