Internal oxidation with significant contribution of oxygen diffusion through the oxide phase

Konrad, Christian; Fuhrmann, Lars; Völkl, Rainer; Glatzel, Uwe

doi:10.1016/j.corsci.2012.06.003

Cited by 19 publications

(9 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Obviously, in this model experiment, it took about 10 s for the interface to be in equilibrium with the fuel gas. 46 It should be noted here that reoxidation kinetics influence pore formation and depend, in general, on sample geometry. 46,47 In the model system, reoxidation occurs rather slow, because of a rather long O 2− ion diffusion pathway through the 500 μm thick YSZ single crystal and impeded fuel gas access of the dense Ni thin film.…”

Section: Resultsmentioning

confidence: 94%

“…46 It should be noted here that reoxidation kinetics influence pore formation and depend, in general, on sample geometry. 46,47 In the model system, reoxidation occurs rather slow, because of a rather long O 2− ion diffusion pathway through the 500 μm thick YSZ single crystal and impeded fuel gas access of the dense Ni thin film. The Y and Zr solubility in the Ni-Zr-Y alloy decreases at first; then, Zr is reoxidized on the temporarily existing Y 2 O 3 precipitates, changing their composition into (Y x Zr 1−x ) 2 O 3 and, to a larger extent, on the Y-rich YSZ phase (Y m Zr 1−m )O 2 .…”

Section: Resultsmentioning

confidence: 94%

See 1 more Smart Citation

High-Resolution Studies on Nanoscaled Ni/YSZ Anodes

et al. 2017

View full text Add to dashboard Cite

The performance of Ni/YSZ anodes has been shown to substantially benefit by a reverse current treatment of a solid oxide fuel cell. Within seconds, a solid state reaction builds a nanoscaled layer at the anode/electrolyte interface, thereby increasing the triple-phase boundary density considerably. The reaction mechanism is thoroughly studied using a Ni thin film/YSZ single crystal/Ni/YSZ counter electrode as a model system. The microstructure was analyzed by scanning transmission electron microscopy (STEM) and the chemical composition by atom probe tomography (APT). With these insights, supported by thermodynamic calculations, we propose the following reaction model: The reverse current treatment reduces YSZ congruently with Ni, temporarily forming a Ni-Zr-Y alloy, and Y 2 O 3 precipitates. Afterward, at open circuit voltage conditions, Ni-Zr-Y is reoxidized instantaneously until thermodynamic equilibrium is reached. High-resolution STEM/APT studies disclose a newly formed nanoscaled layer consisting of (i) interconnected Ni with inclusions of 10 nm (Y x Zr 1−x ) 2 O 3 precipitates, (ii) a continuous (Y,Zr)-oxide with varying Y:Zr ratio, (iii) unaffected YSZ, and (iv) pores. The results obtained suggest that formation of the nanoscaled layer results from a diffusion-controlled mechanism, with Ni being the fastest species, but also involving Y or Zr, since alterations of the Y:Zr ratio are detected.

show abstract

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 94%

High-Resolution Studies on Nanoscaled Ni/YSZ Anodes

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Purities of the elements were 99.9% for Ni, 99.9% for Y, 99.8% for Zr and 99.99% for Pt. The ratio of Zr/Y with 7/1 in at.% is adopted from [32] in order to achieve high internal oxidation rates. In table 1 the nominal composition of the alloys is compared to the results of chemical analysis with X-ray fluorescence spectroscopy (µ-XRF, EDAX) in the as cast state.…”

Section: Alloysmentioning

confidence: 99%

“…For oxidation tests the metallic rods were sliced to discs with a thickness of 1 mm. The samples were ground with SiC paper (grit: 500, 1200 and 2000) and cleaned in ethanol before conducting isothermal oxidation experiments at 1000°C in a specially designed furnace [32].…”

Section: Internal Oxidationmentioning

confidence: 99%

See 1 more Smart Citation

Tailored platinum-nickel nanostructures on zirconia developed by metal casting, internal oxidation and dealloying

et al. 2016

Self Cite

View full text Add to dashboard Cite

Noble-metal nanostructures are crucial, highly active materials in applications such as fuel cells, sensors, electrodes and catalysts. The present work shows a new and efficient method for the in-situ synthesis of platinum-nickel nanostructures on porous zirconia. Ni-Zr-Y metallic alloys with defined Zr/Y-ratios and small amounts of platinum are internally oxidized. An interpenetrating network of yttria-stabilized zirconia (YSZ) in pure nickel is formed. Dealloying of the nickel matrix generates a multimodal porous ceramic support structure with platinum-nickel nanostructures on the surface of the zirconia-ceramic with a broad spectrum for tailored functionality, for example in after-treatment of exhaust gases.

show abstract