Journal
APPLIED PHYSICS LETTERS
Volume 108, Issue 8, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.4942459
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Funding
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-98CH10886, DE-SC0012704]
- Center for Functional Nanomaterials, U.S. DOE Office of Science Facility, at Brookhaven National Laboratory [DE-SC0012704]
- National Science Foundation [DMR-0907639, DMR-1506925]
- Direct For Mathematical & Physical Scien [1506055] Funding Source: National Science Foundation
- Division Of Materials Research [1506055] Funding Source: National Science Foundation
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The coarsening of Ni in Ni-yttria-stabilized zirconia (YSZ) anodes is a potential cause of long term solid oxide fuel cells (SOFC) performance degradation. The specifics of the Ni-YSZ structure-including Ni/YSZ ratio, porosity, and particle size distributions-are normally selected to minimize anode polarization resistance, but they also impact long-term stability. A better understanding of how these factors influence long-term stability is important for designing more durable anodes. The effect of structural details, e.g., Ni-YSZ ratio, on Ni coarsening has not been quantified. Furthermore, prior measurements have been done by comparing evolved structures with control samples, such that sample-to-sample variations introduce errors. Here, we report a four dimensional (three spatial dimensions and time) study of Ni coarsening in Ni-YSZ anode functional layers with different Ni/YSZ ratios, using synchrotron x-ray nano-tomography. The continuous structural evolution was observed and analyzed at sub-100 nm resolution. It is shown quantitatively that increasing the Ni/YSZ ratio increases the Ni coarsening rate. This is due to both increased pore volume and a decrease in the YSZ volume fraction, such that there is more free volume and a less obtrusive YSZ network, both of which allow greater Ni coarsening. The results are shown to be in good agreement with a power-law coarsening model. The finding is critical for informing the design of SOFC electrode microstructures that limit coarsening and performance degradation. (C) 2016 AIP Publishing LLC.
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