Microstructure and Creep Behavior of a Si3N4-SiC Micronanocomposite

The microstructure and its influence on the creep behaviour of carbon derived Si3N4-SiC micro/nanocomposite tested in bending at temperatures from 1200 degrees to 1400 degrees C in air has been studied. No phase and microstructure change after creep test implied that material is stable at tested temperature range. After creep test only partial crystallization of glassy intergranular phase has been observed. Creep parameters n close to 1, apparent activation energy around 350 kJ/mol together with TEM observation indicated that the main creep mechanisms is solution precipitation controlled by interface reaction in combination with grain boundary sliding caused by the amorphous intergranular phases present in microstructure. However, the grain boundary sliding is hindered by local SiC particles interlocking neighboring Si3N4 grains.