Monoclinic Zirconia Microfiltration Membranes: Preparation and Characterization

Microfiltration zirconia membranes were prepared by slip casting from two pure zirconia powders derived from different processing techniques. Powders had almost the same mean particle size but were different in surface area, particle size distribution and morphology. Rheology of zirconia slips was studied in order to prepare a well-dispersed slip suitable for slip casting. The powders showed different dispersibility in the preparation of slips by colloidal processing. The effect of sintering temperature and holding time on porosity, pore size distribution, phase composition, microhardness and microstructure of unsupported membranes are studied and discussed in relation to the membrane processing and properties of powders resulting from different processing routes. Pore size distribution of membranes reflected the differences in morphology of particles and the state of agglomeration in the green samples.Isothermal sintering at 1100°C resulted in some tetragonal phase retained at room temperature in the monoclinic structure. Cracking occurred in membranes sintered above 1150°C due to the volume change in phase transformation. Densification behavior, removal of porosity and the hardness property showed differences that are attributed to the differences in powder processing and characteristics of powders. Crackfree membranes can be prepared by sintering at 1100°C from both powders.