Preparation of anode/electrolyte ceramic composites by coextrusion of pastes

Anode/electrolyte two-layer ceramic composites for tubular solid oxide fuel cells were prepared through coextrusion of multiple pastes containing a water-based binder (an aqueous solution of hydroxypropyl methylcellulose). The multibillet extrusion (MBE) technique was found to be effective in achieving the anode/electrolyte composite pipes. Furthermore, it is possible to reduce the wall thickness of both anode and electrolyte layers by raising the extrusion ratio of each layer. The extrusion pressure and binder content required to obtain sound extrudates decreased with an increase in the fraction of nickel oxide in an anode layer. It is feasible to decrease the difference in the sintering shrinkage between the anode and electrolyte layers by incorporating calcined coarse yttria-stabilized zirconia (YSZ) powder in the electrolyte layer. The incorporation of coarse YSZ powder in an anode is effective in forming a continuous NiO network within the YSZ matrix.