Wettability and interfacial reactions in the systems Ni/YSZ and Ni/Ti-TiO2/YSZ

In order to minimise the interfacial energy between metal and ceramic in the SOFC Ni/YSZ cermet anode, the wetting properties and interfacial reactions for the systems Ni/YSZ and Ni/Ti-TiO2/YSZ were studied in the temperature range 1250-1500 degrees C. In purified Ar-4 vol.% H-2 atmosphere no reaction takes place between the metallic and the ceramic phase and measurements of the contact angle between molten metals and ceramic at 1500 degrees C showed no wettability, theta > 90 degrees. The lowest contact angle, compared to that corresponding to the Ni/YSZ system (117 degrees), was achieved for the system Ni/YSZ (TiO2), (103 degrees). At 1500 degrees C and in the presence of carbon in the furnace atmosphere, an interaction was observed to occur at the metal-ceramic interface, caused by the carbon dissolved in the metallic melt. The extent of such an interaction depends on time and carbon potential in the gas phase and influences the wetting properties of the systems, leading to better wetting conditions as the interaction extent increases. Copyright (C) 1996 Acta Metallurgica Inc.