Dynamic Wetting of Ni-Al Alloy Under MCFC Conditions

Abstract

Ni-Al alloy is one of the most commonly used anode materials in the molten carbonate fuel cell (MCFC). Wettability of the Ni-Al influences the active reaction area inside the porous anode and is therefore an important parameter in determining the performance of the cell. Moreover, the amount of carbonate in the electrode changes over the lifetime of a cell, and so does the extent of wetting. Therefore, the dynamic wetting of dense as well as porous substrates of Ni-Al alloy by molten carbonate was investigated. The effect of Al content on the dynamic wetting was investigated under both pure CO2 and reducing (80%H2+20%CO2 humidified at 45 °C) atmospheres. The contact angle on dense Ni-Al alloy decreased with increase of Al content under both atmospheres. It was higher under pure CO2 atmosphere than under reducing atmosphere. The effects of porosity and of degree-of-filling (the amount of carbonate in relation to the empty pore volume available) on the time-dependent behavior of the contact angle were investigated, and the rate of absorption of molten carbonate into the substrate was measured. The absorption rate was significantly slowed down only when the molten carbonate added exceeded the volume of empty pores inside the substrate.