Microstructure Control of Silicon Nitride Ceramics Fabricated from #alpha#-Powder Containing Fine #beta#-Nuclei

摘要

The effect of a p-nuclei addition on themicrostructural development and mechanicalproperties of Si_3N_4 ceramics was investigated by theuse of #beta#-nuclei having various sizes, p-nucleiin the amounts of 0, 2.5, 5, 7.5 and 15wtpercent wereadded #alpha#-Si_3N_4 powder. The microstructure ofsintered materials was quantitatively analyzed usingan image analyzer. The fine-grained microstructurewas developed by adding finer #beta#-nuclei, whereasthe bimodal microstructure was developed by addinglarger #beta#-nuclei. A decrease in the mean diameterwas observed by reducing the sizes of #beta#-nucleiand/or increasing their amount. The aspect ratios werenearly constant regardless of #beta#-nuclei addedeven in small quantites, whereas a decrease in theaspect ratio was observed by a further addition. Theseresults show that the microstructural development wascontrolled by the number as well as the size of the#beta#-nuclei. The fracture strength was improved byadding a small amount of fine #beta#-nuclei.