Use of Raney Nickel in Infiltration at Anode
Catalysts in SOFC
Advisors: Professors Trumble and Slamovich
How SOFC Works
Anode Reactions:
H2
Cathode Reaction:
2H+ + 2e-
2H+ + O2- ion
H20
Reaction Products:
(H20, CO2, H2, CO, etc.)
and Heat
½ O2 + 2eion
O2-
Catalysts at the Anode
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Background research done with Pt, but too
expensive
Current catalyst is Nickel
Compare $8000 per ton of Ni vs. $8000 per
pound of Pt
Suggesting Raney Nickel infiltration as an
alternative to current process
Raney Nickel is a form of nickel that can be
spread in very fine dispersion, which makes it
a more effective catalyst
Why Raney Nickel?
Cosintering and reduction (Current)
NiO
NiO
Ni
Heated to 1400˚C in a
reducing atmosphere
ZrO2
ZrO2
Ry-Ni
Ni/Al alloy
Leached in caustic
solution
Infiltration with Ry-Ni and leaching (Suggested)
Experimental Approach
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Casting the Aluminum Nickel alloy
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Characterization
Sintering the YSZ preform
 The infiltration experiment
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Analysis
 Leaching
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Making the Alloy
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Mixed 48 wt% Nickel with
52% Aluminum to make
approximately a 1:1 ratio
alloy of Al3Ni and Al3Ni2
Melted Aluminum first at
660˚C
Added Nickel which created
an exothermic reaction that
grew ‘white hot’
Cast melt in steel mold
Phase Diagram
Courtesy of M.F. Singleton, J.L. Murray, and P. Nash, 1990
Alloy Characterization
(Al)+Al3Ni
(eutectic)
Al3Ni
porosity
Al3Ni2
X-Ray Diffraction
~50% Al3Ni, 50%Al3Ni2
Making the Preform
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Started with Zirconia
granules of approximately
25-50 µm
Sintered at 1400˚C for 4
hours with ramps of 300˚C
per hour
Shrinkage occurred due to
high temperature
Concerns with intragranular
porosity
200 µm
Infiltration Set up
Cooling Apparatus
Cast Alloy
Crucible
Alumina Beads
Tungsten Shields
YSZ Preform
Cooling Apparatus
Heating Element
Infiltration Process
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Ramped the furnace at approximately 50˚C
per minute to 1350˚C under vacuum
Held the sample at 1350˚ for 5 minutes then
applied 1 atmosphere pressure of 5%
Hydrogen/Argon gas
Kept under pressure upon cooling
Cooled at a high rate to minimize oxidation
reaction
Infiltration Results
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It worked!!
It did not infiltrate the
YSZ disk fully
Redox reaction
prevention appears to
have worked well
Unanalyzed metallic
impurities more
plentiful in infiltrated
disk
Crucible
Melted Ni/Al alloy
Alumina Beads
Infiltrated Zirconia
Infiltration Analysis
•Infiltration occurred in individual granules
•Chemical reaction occurred on the surface
•High porosity even before leaching
•Mostly due to metal shrinkage
Sem Images
SEM Photograph at 500x
Leaching (metal)
255 Seconds
45
Seconds
255 Seconds
45
Seconds
Used 10% NaOH solution at 50˚C when leaching
Leaching (infiltrated Ysz)
255 Seconds
45
Seconds
255 Seconds
45
Seconds
Used 10% NaOH solution at 50˚C when leaching
Overall analysis
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Infiltration on a macro and micro scale
Surface corrosion of granules shows how
infiltration occurred
Impurities found in metal ceramic matrix
Further Research is expected
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Visibly equal metal/ceramic matrix
High porosity
Future work
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More analysis of the infiltration product
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Use SEM images to determine what occurred during
infiltration
Use chemical analysis and XRD to analyze impurities and
infiltration products
Infiltrate preform with Ni/Al alloys of different
compositions and process data
Use Raney Nickel in co-sintering processes
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Use SEM to determine structure’s porosity
Test different compositions of Ni/Al alloy at different
temperatures
Acknowledgements
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Professor Trumble and Professor Slamovich
Patti Metcalf
Brad Allison
Dave Roberts
Jeffrey Redding
NSF Grant (DMR-9912195)
Questions?
Thank you.