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Catalysts in SOFC

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Catalysts in SOFC. Use of Raney Nickel in Infiltration at Anode. Advisors: Professors Trumble and Slamovich. How SOFC Works. Anode Reactions : H 2 2H+ + 2e - 2H + + O 2 - ion H 2 0. Cathode Reaction : ½ O 2 + 2e - O 2 - ion. Reaction Products : - PowerPoint PPT Presentation
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Catalysts in SOFC Catalysts in SOFC Use of Raney Nickel in Use of Raney Nickel in Infiltration at Anode Infiltration at Anode Advisors: Professors Trumble and Slamovich
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Page 1: Catalysts in SOFC

Catalysts in SOFCCatalysts in SOFCUse of Raney Nickel in Infiltration at Use of Raney Nickel in Infiltration at

AnodeAnode

Advisors: Professors Trumble and Slamovich

Page 2: Catalysts in SOFC

How SOFC WorksHow SOFC Works

Cathode Reaction:

½ O2 + 2e O2 ion

Anode Reactions:

H2 2H+ + 2e

2H+ + O2 ion H20

Reaction Products:

(H20, CO2, H2, CO, etc.) and Heat

Page 3: Catalysts in SOFC

Catalysts at the AnodeCatalysts at the Anode

Background research done with Pt, but Background research done with Pt, but too expensive too expensive

Current catalyst is Nickel Current catalyst is Nickel Compare $8000 per ton of Ni vs. $8000 Compare $8000 per ton of Ni vs. $8000

per pound of Ptper pound of Pt Suggesting Raney Nickel infiltration as Suggesting Raney Nickel infiltration as

an alternative to current processan alternative to current process Raney Nickel is a form of nickel that Raney Nickel is a form of nickel that

can be spread in very fine dispersion, can be spread in very fine dispersion, which makes it a more effective which makes it a more effective catalystcatalyst

Page 4: Catalysts in SOFC

Why Raney Nickel?Why Raney Nickel?

ZrO2

NiO

NiO

Ry-Ni

Ni

ZrO2

Leached in caustic solution

Heated to 1400˚C in a reducing atmosphere

Cosintering and reduction (Current)

Infiltration with Ry-Ni and leaching (Suggested)

Ni/Al alloy

Page 5: Catalysts in SOFC

Experimental ApproachExperimental Approach

Casting the Aluminum Nickel alloyCasting the Aluminum Nickel alloy CharacterizationCharacterization

Sintering the YSZ preformSintering the YSZ preform The infiltration experimentThe infiltration experiment

AnalysisAnalysis LeachingLeaching

Page 6: Catalysts in SOFC

Making the AlloyMaking the Alloy

Mixed 48 wt% Nickel Mixed 48 wt% Nickel with 52% Aluminum to with 52% Aluminum to make approximately a make approximately a 1:1 ratio alloy of Al1:1 ratio alloy of Al33Ni Ni and Aland Al33NiNi22

Melted Aluminum first Melted Aluminum first at 660˚Cat 660˚C

Added Nickel which Added Nickel which created an exothermic created an exothermic reaction that grew reaction that grew ‘white hot’‘white hot’

Cast melt in steel moldCast melt in steel mold

Page 7: Catalysts in SOFC

Phase DiagramPhase Diagram

Courtesy of M.F. Singleton, J.L. Murray, and P. Nash, 1990

Page 8: Catalysts in SOFC

(Al)+Al3Ni (eutectic)

porosity

Al3Ni Al3Ni2

Alloy CharacterizationAlloy Characterization

Page 9: Catalysts in SOFC

X-Ray DiffractionX-Ray Diffraction~50% Al3Ni, 50%Al3Ni2

Page 10: Catalysts in SOFC

Making the PreformMaking the Preform

Started with Zirconia Started with Zirconia granules of granules of approximately 25-50 approximately 25-50 µmµm

Sintered at 1400˚C for Sintered at 1400˚C for 4 hours with ramps of 4 hours with ramps of 300˚C per hour300˚C per hour

Shrinkage occurred due Shrinkage occurred due to high temperatureto high temperature

Concerns with Concerns with intragranular porosityintragranular porosity

200 µm

Page 11: Catalysts in SOFC

Infiltration Set upInfiltration Set up

Alumina Beads

YSZ Preform

Cast Alloy

Crucible

Tungsten Shields

Cooling Apparatus

Cooling Apparatus

Heating Element

Page 12: Catalysts in SOFC

Infiltration ProcessInfiltration Process Ramped the furnace at approximately Ramped the furnace at approximately

50˚C per minute to 1350˚C under 50˚C per minute to 1350˚C under vacuumvacuum

Held the sample at 1350˚ for 5 minutes Held the sample at 1350˚ for 5 minutes then applied 1 atmosphere pressure of then applied 1 atmosphere pressure of 5% Hydrogen/Argon gas5% Hydrogen/Argon gas

Kept under pressure upon coolingKept under pressure upon cooling Cooled at a high rate to minimize Cooled at a high rate to minimize

oxidation reactionoxidation reaction

Page 13: Catalysts in SOFC

Infiltration ResultsInfiltration Results It worked!!It worked!! It did not infiltrate It did not infiltrate

the YSZ disk fullythe YSZ disk fully Redox reaction Redox reaction

prevention appears prevention appears to have worked wellto have worked well

Unanalyzed Unanalyzed metallic impurities metallic impurities more plentiful in more plentiful in infiltrated diskinfiltrated disk

Melted Ni/Al alloyCrucible

Alumina Beads

Infiltrated Zirconia

Page 14: Catalysts in SOFC

Infiltration AnalysisInfiltration Analysis•Infiltration occurred in individual granules

•Chemical reaction occurred on the surface

•High porosity even before leaching

•Mostly due to metal shrinkage

Page 15: Catalysts in SOFC

Sem ImagesSem Images

SEM Photograph at 500x

Page 16: Catalysts in SOFC

Leaching (metal)Leaching (metal)

5 Seconds 25 Seconds 45 Seconds

5 Seconds 25 Seconds 45 Seconds

Used 10% NaOH solution at 50˚C when leaching

Page 17: Catalysts in SOFC

Leaching (infiltrated Ysz)Leaching (infiltrated Ysz)

5 Seconds

5 Seconds 25 Seconds

25 Seconds

45 Seconds

45 Seconds

Used 10% NaOH solution at 50˚C when leaching

Page 18: Catalysts in SOFC

Overall analysisOverall analysis

Infiltration on a macro and micro scaleInfiltration on a macro and micro scale Surface corrosion of granules shows how Surface corrosion of granules shows how

infiltration occurredinfiltration occurred Impurities found in metal ceramic matrixImpurities found in metal ceramic matrix Further Research is expectedFurther Research is expected

Visibly equal metal/ceramic matrixVisibly equal metal/ceramic matrix High porosityHigh porosity

Page 19: Catalysts in SOFC

Future workFuture work More analysis of the infiltration productMore analysis of the infiltration product

Use SEM images to determine what occurred Use SEM images to determine what occurred during infiltrationduring infiltration

Use chemical analysis and XRD to analyze Use chemical analysis and XRD to analyze impurities and infiltration productsimpurities and infiltration products

Infiltrate preform with Ni/Al alloys of Infiltrate preform with Ni/Al alloys of different compositions and process datadifferent compositions and process data

Use Raney Nickel in co-sintering processesUse Raney Nickel in co-sintering processes Use SEM to determine structure’s porosityUse SEM to determine structure’s porosity Test different compositions of Ni/Al alloy at Test different compositions of Ni/Al alloy at

different temperaturesdifferent temperatures

Page 20: Catalysts in SOFC

AcknowledgementsAcknowledgements

Professor Trumble and Professor Professor Trumble and Professor SlamovichSlamovich

Patti MetcalfPatti Metcalf Brad AllisonBrad Allison Dave RobertsDave Roberts Jeffrey ReddingJeffrey Redding NSF Grant (DMR-9912195)NSF Grant (DMR-9912195)

Page 21: Catalysts in SOFC

Questions?Questions?Thank you.Thank you.


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