Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) feedstock development and optimization for thermoplastic forming of thin planar and tubular oxygen separation membranes

This paper presents the processing steps for producing thin planar and tubular oxygen separation membranes by thermoplastic forming of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) with polystyrene (PS) and stearic acid (SA) as binder. The influence of powder content on the shape stability of thin membranes (tubular and planar structures) during the thermoplastic processing route was investigated. The effect of powder content on mixing torque and the rheological behavior were investigated. The effect of the powder content could be analytically described using the model proposed by Frankel and Acrivos. The deformation of free standing green bodies was investigated using disks. The result showed that increasing the powder content is remarkably effective to minimize the deformation of the membrane during the thermal debinding step. By using a high powder content (60 vol%) and a multicomponent binder system composed of PS, SA and paraffin wax (PW), it was possible to achieve disks and thin wall tubular structures without deformation after sintering. Using capillary rheometer an unexpected decrease in the total extrusion pressure was measured for the feedstock containing PW. The change in apparent activation energy between 800–1000 °C was not related to the membrane properties.