Water-based binder system for SOFC porous steel substrates

Porous stainless steel alloys are candidates for the support structure of thin-film solid oxide fuel cells (SOFCs) operating at intermediate temperatures (873–1073 K). A difficulty is maintaining substrates at sufficient porosity during co-firing of the SOFC membranes. This problem depends significantly on the nature of the binder that is used to assist in initial processing. A water-based acrylic polymer suspension and polyethylene glycol (PEG) system was developed to obtain an appropriate mixture of acrylic/PEG/410L alloy suitable for co-firing with the electrode and electrolyte layers. The shrinkage and final density of samples decreased gradually with increasing acrylic or PEG content. Increasing the ratio of (acrylic + PEG)/metal alloy from 21 to 27 wt.% and decreasing the ratio of acrylic/(acrylic + PEG) from 19 to 10% decreased final alloy density drastically, from 77 to 50% for 410L powder with a particle size between 24 and 45 μm after firing at 1573 K for 4 h. The amount of acrylic binder had a stronger effect on shrinkage than PEG. As expected, smaller alloy particles increased the final density of the porous alloy substrate.