FACTORS CONTROLLING THE SINTERING OF CERAMIC PARTICULATE COMPOSITES .1. CONVENTIONAL PROCESSING

The effect of processing and material parameters on the sintering and coarsening of model composites consisting of a fine-grained ZnO matrix and coarse, rigid, inert particulate inclusions Of ZrO2 was investigated. The green composites were formed by two methods: (i) mixing the matrix and inclusion powders in a ball-mill followed by die-pressing and (ii) slip casting. For both forming methods, the inclusions caused a significant reduction in the density and the grain size of the composite matrix but had almost no effect on the grain size vs density relationship. The effects of inclusion volume fraction and sintering temperature were somewhat independent of the forming method. However, for the slip-cast composites, the effect of inclusion size was less severe and the packing of the matrix phase immediately surrounding the inclusion showed some improvement. The sintering kinetics and microstructural observations indicated that two main factors controlled the sintering of these composites: (i) interactions between the randomly distributed inclusion particles that created a constraint on the matrix and (ii) the packing of the matrix, especially in regions immediately surrounding the inclusion particles.