Pressureless Sintering of Ceramic Composites

This project examined the pressureless sintering and densification behavior of model ceramic composites. The effect of inclusion aspect ratio on densification was studied using SiC whiskers and fibers in an Al2O3 matrix. Composites had maximum sintered density when made from fibers with aspect ratios around ten. This peak in the density is a result of the density of short aspect composites being inhibited by inclusion size considerations while long aspect composites are prevented from densifying by percolation related effects. How inhomogeneous inclusion distribution affects densification was studied using SiCP/Al2O3 composites. Three different types of inhomogeneity known as concentration, amplitude, and size were investigated. The sintered density was maximized at moderate levels of inclusion inhomogeneity. We also found that various salts were effective coagulating agents for slip casting Al2O3/ZrO2 composites. The drying of composites found that percolation limits the green density of particulate composites. The fracture toughness of Mn-Zn ferrites was increased from 0.9 MPa(square root)m to 2.8 MPa(square root)m by addition of 25 vol % partially stabilized ZrO2. Transient liquid phase sintering of composites is not an effective densification method. Ceramic composites, Sintering, Densification, Inclusion distribution, Inclusion aspect ratio, Drying, Toughening, Ferrites, Slip coagulation