Date of Completion

3-14-2014

Embargo Period

3-14-2014

Keywords

high temperature materials, Chromium evaporation, SOFC, metal corrosion, coating, interconnect, BOP, AFA

Major Advisor

Dr. Prabhakar Singh

Associate Advisor

Dr. Frederick S. Pettit

Associate Advisor

Dr. Harris L. Marcus

Field of Study

Materials Science and Engineering

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Recent developments of planar intermediate temperature solid oxide fuel cells (IT-SOFCs) make metallic alloys attractive candidates as interconnects as well as balance of plant (BoP) materials at operating temperatures below 900 oC. The resistance of alloys against oxidation and corrosion is one of the critical criteria for selecting candidate alloys for SOFC applications. The oxidation and corrosion resistance of the alloys service at high temperature depends on the formation of a protective oxide scale (chromia. silica, alumina). Among these, chromia forming alloys are often used in SOFCs. At higher temperature, the evaporation of chromium containing species from chromia in humid air limits the applications of chromia forming alloys. SOFCs are susceptible to chromium evaporation (known as chromium poisoning) as it can lead to severe degradation of SOFC performance.

In this study, the transpiration method was used to measure the chromium evaporation rates from chromium evaporation of chromia and alumina forming nickel and iron base alloys. The effects of the temperature and water vapor content on the chromium evaporation rates were also investigated. The measured chromium evaporation rates were used to predict the degradation rates of the SOFCs under those conditions.

The oxidation behavior of candidate alloys in air with different water vapor contents was studied. The effects of the temperature and water vapor content on physicochemical characteristics of the oxide scales formed on the surface of metallic components were also examined.

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