Structural Ceramics Based on Nanosized Si<sub>3</sub>N<sub>4</sub> Powders

Abstract

Ceramics based on nanosized plasma chemistry Si3N4 powder compositions s (30-100 nm) is processed by activated pressureless sintering, hot pressing and hot isostatic pressing. Microstructure characterization of the obtained materials by means o light and scanning microscopy revealed no correlation between microstructure and the bulk consolidation method . Average grain size in all cases was 200-500 nm. Comparative characterization of the physical and mechanical behavior of the analyzed samples showed the following results: relative density - over 99 %, flexural strength – over 700 MPa, Vickers hardness - 16-17GPa, fracture toughness – 6.5-7.4 MPa·m1/2. The activated pressureless sintered samples demonstrated physical and mechanical behavior comparable to the samples consolidated by other methods. Activated pressureless sintering of nanosized plasma chemistry Si3N4 powders led to considerable economic advantages in processing Si3N4 spherical rotation bodies for hybrid roller bearings and cutting tools. Silicon nitride (Si3N4)-based structural ceramics is widely studied and used for over half a century due to its unique properties: low density, combined with high strength and wear-resistance, high decomposition temperature, high oxidation resistance, low friction coefficient and high resistance to chemical corrosion[1].