TEM Studies of Silicon Nitride-Silicon Carbide Nanocomposites

Abstract Si3N4/SiC nanocomposites have been shown to exhibit excellent strength and fracture toughness compared to monolithic Si3N4 materials. Recently, the microstructure and chemistry of Si3N4-based nanocomposites fabricated by hot-pressing amorphous Si-C-N precursor powders has been investigated. In the present work, our studies on the microstructure of Si3N4/SiC nanocomposites made by hot-pressing the mixture of Si3N4 and SiC commercial powders are reported. Si3N4/SiC nanocomposites were prepared by hot-pressing at 1750 °C for 1 hour at 40 Mpa in a nitrogen atmosphere, with sintering aids of 5.5 wt% Y2O3 and 3 wt% Al2O3. The details of the processing procedure have been reported elsewhere. Two different materials were investigated in this work: specimen A consisting of 5 vol% β-SiC; and specimen B consisting of 5 vol% α-SiC. TEM specimens were prepared by conventional procedures. The microstructure and chemical composition were studied in the University of Michigan Electron Microbeam Analysis Laboratory on a JEOL 2000FX.