Cracking during freeze drying in dense freeze cast ceramics: role of drying rate

Cracks can form during the freeze-drying of freeze cast ceramic suspensions while attempting to produce dense ceramics. The contain alumina particles dispersed in cyclohexane. rate drying is controlled by pressure and temperature (slow at atmospheric −15°C fast under vacuum slowly increases from −80°C room temperature). X-Ray micro-computed tomography was used characterize internal crack formation. were found occur rather than freezing. Both slow produced cracks, although two different morphologies observed. Mechanistic models are proposed for formation both types cracks. freezing influence Slow tended reduce cracks because slower a more heterogeneous distribution porous regions, which tends allow stress be relieved opening up existing pores forming homogeneous frozen bodies.