Fabrication and characterization of YSZ/Ni-YSZ bi-layered composites using thermoplastic coextrusion

The thermoplastic coextrusion process was used to fabricate YSZ/Ni-YSZ bi-layered composites. In this method, an initial feedrod was prepared by assembling YSZ and NiO-YSZ thermoplastic compounds to produce a monolithic body with a cross-section of 24 mm × 24 mm and then coextruded through various orifices having dimensions of 24 × 2, 1 and 0.6 mm at 120 °C. This simple process produced thin plates with a remarkable reduction in thickness, while preserving the YSZ:NiO-YSZ thickness ratio of 1:39. After binder removal, the samples were co-fired at 1350 °C for 3 h in air, followed by reduction at temperatures ranging from 700 to 900 °C for 5 h in an Ar-5% H₂ atmosphere. Using this method, it was possible to fabricate a YSZ/Ni-YSZ bi-layered composite without any noticeable defects, in which a 11-μm thick dense YSZ layer was coated onto a 400-μm thick Ni-YSZ cermet. Furthermore, the fabricated samples showed reasonable electrical conductivities, thus rendering them suitable for use as the basic components of planar solid oxide fuel cells (SOFCs).