Microstructure and Creep Behavior of a Si_3N_4-SiC Micronanocomposite

摘要

The microstructure and its influence on the creep behaviour of carbon derived Si_3N_4-SiC microanocomposite tested in bending at temperatures from 1200° to 1400℃ 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 Si_3N_4 grains.