catalysts in sofc use of raney nickel in infiltration at anode advisors: professors trumble and...
Post on 20-Dec-2015
224 views
TRANSCRIPT
Catalysts in SOFCCatalysts in SOFCUse of Raney Nickel in Infiltration at Use of Raney Nickel in Infiltration at
AnodeAnode
Advisors: Professors Trumble and Slamovich
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
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
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
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
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
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
Infiltration Set upInfiltration Set up
Alumina Beads
YSZ Preform
Cast Alloy
Crucible
Tungsten Shields
Cooling Apparatus
Cooling Apparatus
Heating Element
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
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
Infiltration AnalysisInfiltration Analysis•Infiltration occurred in individual granules
•Chemical reaction occurred on the surface
•High porosity even before leaching
•Mostly due to metal shrinkage
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
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
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
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
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)