Functional gradient alumina ceramic materials—Heat treatment of bodies prepared by slip casting method

The work deals with the study of heat treatment of functional gradient alumina ceramics with controlled microstructure. The bodies with different porosity layers were prepared by slip casting into a porous block. The sol–gel transition of AlO(OH) was used to stabilize the pore-generating agents with a particle size of 150–190 μm and the preparation of a reproducible aqueous suspensions of α-Al2O3 for the slip casting of bodies with defined porosity. From the technological point of view, the preparation of functional gradient alumina ceramics requires the development of a defect-free interface between compounded layers conditioned by an appropriate combination of the compounded layers with different porosity and different irreversible dilatation changes. The linear model of dilatation changes did not result in the preparation of a defect-free composite ceramics. The non-linear model developed has aided to describe the admissible difference of dilatational changes Δαirr, between individual compounded layers of green bodies during the firing process. The deformation as a result of non-uniform body formation was related to the total body thickness and did not occur for the composite bodies with thickness larger than 5 × 10−3 m. The value of admission difference of irreversible dilatation changes was used to predict the optimal preparation conditions of defect-free composite alumina ceramics with compounded layers possessing controlled porosity.