Preparation of Aligned Porous Ni-GDC Nano Composite by Freeze-Casting Process

This study reports preparation of Nickel-Gadolinium doped Ceria (Ni-GDC) composite via controlled unidirectional freeze casting of aqueous-based GDC slurry completed with nickel infiltration into the porous GDC samples. Gadolinium doped ceria powder was prepared by gel-combustion synthesis method. The oxide powder was confirmed by X-ray diffraction to be the fluorite-structured of Ce0.8Gd0.2O1.9 solid solution. The synthesized powder was used with dolapix as a dispersant, Ammonia solution as an agent pH, poly vinyl alcohol (PVA) as a binder and water as a solvent to prepare stable GDC slurries. Freeze casting process was done in different solid loadings of GDC at 35, 45 and 55 wt. %, and two different cooling rates of 1 and 3 ̊C/min to obtain desirable pore structure. After removing the frozen ice at -58 ̊C, the green samples were sintered for 2 h in air at 1300 °C. The pore structure and final microstructure were studied by scanning electron microscopy. The porosity of the sintered samples was in range of 60-70% , and depended on solid content and freeze casting rate. Finally, nickel solution was infiltrated into the hierarchically porous GDC samples, after reduction at 800 ̊C, Ni-GDC composite was attained.