Influence of Grain Size Distribution on Hardness and Fracture Toughness of Si3N4/SiC Nanocomposites
Si3N4/SiC nanocomposite material with yttria as sintering additive was prepared by hot pressing method. SiC nanoinclusions were produced by in situ reaction between SiO2 and C during the sintering process. The homogenous microstructure of hot pressed samples contained fine Si3N4 grains with average diameter of 200 nm. The post-sintering treatment at 1750°C for 26 and 70 hours significantly changed the microstructure of Si3N4/SiC composites. The difference between the average grain size of hot pressed sample and sample treated for 70 hours is approx. 300 %. In sake of this fact the mechanical properties (KIC, HV1) were not changed significantly. The largest differences between the mechanical properties of hot pressed and annealed samples were only 8 %.
M. Hnatko et al., "Influence of Grain Size Distribution on Hardness and Fracture Toughness of Si3N4/SiC Nanocomposites ", Advances in Science and Technology, Vol. 45, pp. 1680-1683, 2006