Microstructure Evolution in Metal-Ceramic Systems Under Reducing and Oxidizing Conditions

Reference Presenter Authors
12-032 Ivar Reimanis Reimanis, I.(Colorado School of Mines); Microstructure evolution in mixed metal oxides under reducing and oxidizing environments can be complex and irreversible, yet is important to understand for applications such as catalysis, solid oxide fuel cells, and solar thermal water splitting. Example materials include nickel in barium zirconate (BZY) and nickel in yttria stabilized zirconia (YSZ). The state of nickel in these materials depends on the redox condition, but also the BZY or YSZ particle size: nickel may exist as ions in solution in the bulk, as excess ions at surfaces or grain boundaries, as an oxide, or in the metallic superparamagnetic or ferromagnetic state. When the system is cycled between reducing and oxidizing conditions, the corresponding changes in the state of the nickel depend on the kinetic mechanisms. Therefore, the end state after cycling depends on the kinetic conditions and the starting microstructure. Results are shown for nickel-doped BZY and YSZ. The fundamental understanding of transitions between these different forms of nickel ultimately enables the design of optimum microstructures.
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