A model for the diffusion of organic additives during thermolysis of a ceramic body

Abstract The removal or organic additives which are used to assemble ceramic particles into pre-determined shapes, by diffusion during thermolysis, is modelled taking into account the simultaneous creation of surface porosity and distributed porosity in the ceramic body. A flat-plate geometry is considered and the model is used to predict the relationship between the critical heating rate Zc, which is the fastest heating rate that allows thermolysis to proceed without creating defects in the ceramic, the plate thickness 2r0, a factor X which determines the volume fraction of distributed porosity in the ceramic and the volume fraction (Vc) of ceramic in the plate. The effect of shrinkage on Zc due to the movement of ceramic particles during thermolysis is also considered. It is shown that Zc is dominated by r0. In comparison, the effect of V, and X on Zc is negligible. The increase in V c due to shrinkage had very little effect on Z. A major achievement of the present work is the development of maps which ...