TiO 2 additives for in situ formation of toughened silicon nitride-based composites

Abstract

This paper is focussed on the reinforcing phases developing in a Si 3N 4-based composite microstructure when sintering a powder mixture of 74 wt.% Si 3N 4, 20 wt.% TiO 2, and 6 wt.% Y 2O 3. Micron- and submicron-sized as well as Al 2O 3 and Al 2O 3+SiO 2-coated submicron-sized TiO 2 powders were used to prepare these in situ composites consisting of Si 2N 2O, α-Si 3N 4, β-Si 3N 4, and TiN. The impulse excitation technique was used to evaluate the intergranular glass phase, which affects crack growth and high-temperature deformation. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to investigate the reinforcing phases. The influence of the TiO 2-additive powder characteristics on the microstructure and properties of the ceramics is reported.