Ceramics-Silikáty 51 (3) 142-146 (2007)

LENGTH CHANGES OF SLIP CASTING ALUMINA-ZIRCONIA CERAMICS

I. Zedníková , J. Andertová , J. Havrda

The main topic of this study is the preparation of functionally graded zirconia-alumina ceramics. The ceramics were prepared by utilizing a slip casting method into a porous mold. From the technological point of view, the preparation of functional layered alumina and zirconia ceramics requires the development of a defect-free interface between the compound layers. The important factor in the preparation of these ceramics is the study of length changes between each individual layers. The first part of this work focuses on the preparation of mono-layer bodies with variable zirconia-alumina composition. The optimal deflocculant content was proposed based on colloidal and rheological properties of the Al₂O₃–ZrO₂ systems. Dilatometric behavior was studied on green samples during firing. The results indicated a critical temperature interval having the biggest differences of linear expansion coefficient, i.e. 20-400°C. Based on measurements conducted in this temperature range, it was observed that increasing volume of deflocculant causes the coefficient of linear expansion and the temperature of shrinkage to rise. In the next part two characteristics were studied on zirconia samples - whether the difference in dilatation changes is caused by firing of deflocculant or by porosity of bodies. It was observed that dilatation changes are caused by the porosity and distribution of pores within the dried samples at the low temperature range. The content of deflocculant influences the size of linear changes.

Keywords: FGC, Al₂O₃, ZrO₂, Slip casting, Shrinkage