On the change of a Ni3Al phase in a Ni-12 wt. %Al MCFC anode during partial oxidation and reduction stages of sintering

It is examined what changes the Ni3Al phase, one of the two equilibrium phases in a Ni-12 wt.%Al anode, will go through during partial oxidation and reduction stages of sintering. The purpose of this study is to get basic data with which we can predict the final phase composition and eventually the creep behavior of the anode after sintering. A new phase of Ni-Al solid solution has been formed during sintering due to outward migration of Al, and coexists with the pre-existing Ni3Al phase. The amount of the solution phase increases with time, rapidly at an early stage but with an ever-decreasing rate as time passes. It also increases with temperature, but in this case exponentially. After the stage of partial oxidation or reduction, the specimen shows the morphology of a network structure with small particles scattered on its surface. The particle consists of a mixture of NiO-Al2O3 solid solution and NiAl2O4 phases after partial oxidation, but of a single Al2O3 phase after reduction. (C) 2004 Elsevier Ltd. All rights reserved.