Drying of ceramic layers with a graded pore structure

Thin self-supporting ceramic TiO2-layers with a graded pore structure were prepared by using centrifugal deposition of powders and sols with different particle size distributions from mixed, diluted suspensions. During the ev aporation drying step the layers have a strong tendency to warping and crac k-formation because of the resulting difference in the capillary pressure i n the upper and the bottom side pores. Four drying methods were investigate d concerning their suitability for diminishing or eliminating capillary for ces and for the production of planar, crack-free dried specimens. The dryin g techniques used in the experiments are briefly introduced. It should be e mphasized that the most successful drying method for the layers mentioned a bove is a combination of microwave drying and subsequent critical point dry ing.