The Oxidation of Materials for Interconnects in Solid Oxide Fuel Cells
Fuel cells convert energy that is stored in a fuel to electricity and heat, and they do so with a high efficiency. As long as fuel and an oxidant gas are supplied, fuel cells can continuously produce electricity. This study focuses on materials for interconnects in solid oxide fuel cells. The interconnect is used to connect the anodes and cathodes of adjacent cells and to keep the fuel and oxidant gases separate. In this research work, ferritic stainless steels (Crofer, New Crofer, JS-3, E-brite, 26 Cr Ferritic, AL453, Modified AL453, ZMG232), an austenitic stainless steel (type 304 stainless steel), and nickel were cyclically oxidized in one hour cycles at 700oC, 800oC, and 900oC. The atmospheres studied were simulated cathode gas (dry air), simulated moist cathode gas (air + 0.1 atm H2O), and simulated anode gas (Ar/H2/H2O). Weight change versus time measurements and metallographic examination of the exposed alloys were used to attempt to determine the alloys most appropriate for use as interconnects. During the cyclic oxidation experiments, the sigma phase had formed in the 26 Cr Ferritic specimens at 700oC in all of the studied environments. Specimens of 26 Cr Ferritic and E-brite were cyclically oxidized in dry air at 700oC in 50 hour increments for 500 hours to determine when the sigma phase first appeared and the extent to which it formed. The conductivity was determined for some of the alloys that had been exposed at 900oC. Not all of the alloys were tested because for the results to be accurate, a continuous oxide layer is needed, for example, no spalling could have occurred. Experiments were also performed to measure the stresses in the oxide layer of two samples of Crofer. Both samples were cyclically oxidized at 900oC for 100 hours, but one was exposed in dry air and the other was exposed in air + 0.1 atm H2O.
Advisor:Dr. Gerald H. Meier; Dr. Frederick S. Pettit; Dr. John P. Leonard; Dr. John A. Barnard
School:University of Pittsburgh
School Location:USA - Pennsylvania
Source Type:Master's Thesis
Keywords:materials science and engineering
Date of Publication:10/13/2005