Structural and Electrical Properties of Composites Based on Ni and NiAl Alloys for SOFC Application

Abstract

Ni and NiAl alloys were utilized as the components of the composites on the base of Zr_0.81Y_0.19O_2-δ and Al₂O₃ ceramic powders. The synthesis of composites was performed directly from the mechanical mixtures of metal and ceramic powders by the air plasma spraying method. The samples were made in the shape of porous tubes 20 cm long by 1 cm in diameter. Phase content and their weight ratio were evaluated by the XRD method after spraying and heat treatment at 1350 °C in different atmospheres. It was found that in the deposited samples, Ni stays mainly in a metal state with a small amount of NiO which at the stage of Ar treatment completely transforms into metal Ni. Do** by Al in a small amount (5%) leads to an appearance of spinel which, after decomposition and reduction in hydrogen, favours more uniform Ni distribution in the ceramic matrix and prevents a coarsening of Ni particles. This leads to the cermet having increased conductivity and better thermal properties. The total conductivity of Ni₉₅Al₅-Al₂O₃ cermet in hydrogen was 1374 S/cm at 600 °C with the mean value of the coefficient of thermal expansion equal to 10.5 × 10⁻⁶ K⁻¹ in the range of 25–900°С which makes it a prospect for usage as a supported anode for solid oxide fuel cell production.