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Analyzing the Mechanical Performance of Solid Oxide Fuel Cells at Interfacial Anode/Electrolyte Regions Using Sub-Micron Resolution 3D X-Ray Computed Tomography

Friday, 28 July 2017: 11:40
Atlantic Ballroom 3 (The Diplomat Beach Resort)
T. M. M. Heenan, J. B. Robinson, X. Lu, J. J. Bailey, D. J. L. Brett, and P. R. Shearing (University College London)
The use of composite Ni-YSZ cermets is now commonplace, the addition of electrolyte ceramic to the electrode is observed to cause non-linear strain when outside of isothermal environments [1], thought to be maximised at the material interfaces [2, 3].

X-ray tomography has proven to be a powerful tool in the characterisation of electrochemical devices, particularly, when inspecting the structural alterations caused by degradation mechanisms [4]. Additionally, in combination with techniques such as digital volume correlation (DVC), strain and material displacement can be mapped in three dimensions with trajectory information [5], improving understanding of material migration under operationally relevant conditions.

This work presents the microstructural developments at interfacial regions within a solid oxide half-cell exposed to varying degrees of thermal shock, similar to that which would be expected in operational conditions. The microstructure is analysed with use of lab-based X-ray tomography achieving statistically relevant data with sub-micron resolutions while preserving macroscopic mechanical influence via large sample volumes, ca. 5 x107 μm3. By imaging the same volume sequentially using the authors were able to correlate the structural dynamics within the volume using computational DVC analysis.

Figure 1 presents the change in electrolyte angle of an anode supported solid oxide-half cell through increased thermal shock. Various degrees of thermal ramp-rate are examined via X-ray tomography slices and phase percolation network lengths. Decreased connectivity in the electrochemical activity maps within the anode is observed with the increasing electrolyte bowing, resulting in a reduction in the percolated triple phase boundary (TPB) reaction site density. The results here present enhance insight into the real-world mechanical influence of expansion gradients between neighbouring layers during operational thermal cycling.

  1. Robinson, J.B., et al., 2015. Journal of Power Sources, 288, pp.473-481.
  2. Clague, R., et al., 2011. Journal of Power Sources, 196(21), pp. 9018-9021.
  3. Celik, S., et al., 2014. International Journal of Hydrogen Energy, 39(33), pp.19119-19131.
  4. Shearing, P.R., et al., 2012. Solid State Ionics, 216, pp.69-72.
  5. Finegan, D.P., et al., 2015. Advanced Science.


Figure 1

Electrolyte bowing observed in an anode supported Ni-YSZ/YSZ solid oxide half-cell captured using X-ray computed tomography: a) profiles for the four thermal cycles at successively increasing ramp rates of 3, 10, 20 and 30 ᴼC/min, with accompanying single tomograph slices from the b) pre and ci) post-cycling tomograms, cii) magnified electrolyte bowing from the post-cycling tomogram, and d) Ni percolation mapping where white and red paths represent segments longer and shorter than 10 μm respectively.