Channeled Ni-YSZ Cermets Produced from NiO-YSZ Eutectics by Laser Melting

Abstract

NiO-YSZ was produced by directional solidification of eutectics (DSE) using laser melting. This technique produces highly structured material consisting of NiO and YSZ lamellae with variable interlamellar spacing depending on growth conditions. The microstrocture is homogeneous and the material mechanically stable during thennochemical reduction. Complete reduction of the NiO produces a porous cermet alternating lamellae of Ni and YSZ. The coefficient of thermal expansion of the cermet is that of the YSZ skeleton. Reaction kinetics at different temperatures during the reduction process was studied by gravimetric methods and SEM experiments, showing that the reduction process seems to be controlled by the O 2- diffusion through the YSZ phase. TEM experiments reveal that the low-energy interfaces formed during the eutectic growth are maintained after reduction. These interfaces are expected to prevent particle coarsening and give a long-term stability to the anode during operation at high temperatures. Resistivity values and pore distribution present no degradation after 300 hr at 900°C under H 2 /N 2 atmosphere. This stability is an improvement for its use as a functional layer in solid-oxide fuel cell (SOFC) anodes.