Catalysts in SOFC Use of Raney Nickel in Infiltration at Anode Advisors: Professors Trumble and Slamovich

How SOFC Works Cathode Reaction: ½ O 2 + 2e - O 2 - ion Anode Reactions: H 2 2H+ + 2e - 2H + + O 2 - ion H 2 0 Reaction Products: (H20, CO2, H2, CO, etc.) and Heat

Catalysts at the Anode Background research done with Pt, but too expensive Background research done with Pt, but too expensive Current catalyst is Nickel Current catalyst is Nickel Compare $8000 per ton of Ni vs. $8000 per pound of Pt Compare $8000 per ton of Ni vs. $8000 per pound of Pt Suggesting Raney Nickel infiltration as an alternative to current process 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 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? ZrO 2 NiO Ry-Ni Ni ZrO 2 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 Approach Casting the Aluminum Nickel alloy Casting the Aluminum Nickel alloy Characterization Characterization Sintering the YSZ preform Sintering the YSZ preform The infiltration experiment The infiltration experiment Analysis Analysis Leaching Leaching

Making the Alloy Mixed 48 wt% Nickel with 52% Aluminum to make approximately a 1:1 ratio alloy of Al 3 Ni and Al 3 Ni 2 Mixed 48 wt% Nickel with 52% Aluminum to make approximately a 1:1 ratio alloy of Al 3 Ni and Al 3 Ni 2 Melted Aluminum first at 660˚C Melted Aluminum first at 660˚C Added Nickel which created an exothermic reaction that grew ‘white hot’ Added Nickel which created an exothermic reaction that grew ‘white hot’ Cast melt in steel mold Cast melt in steel mold

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

(Al)+Al3Ni (eutectic) porosity Al 3 NiAl 3 Ni 2 Alloy Characterization

X-Ray Diffraction ~50% Al 3 Ni, 50%Al 3 Ni 2

Making the Preform Started with Zirconia granules of approximately µm Started with Zirconia granules of approximately µm Sintered at 1400˚C for 4 hours with ramps of 300˚C per hour Sintered at 1400˚C for 4 hours with ramps of 300˚C per hour Shrinkage occurred due to high temperature Shrinkage occurred due to high temperature Concerns with intragranular porosity Concerns with intragranular porosity 200 µm

Infiltration Set up Alumina Beads YSZ Preform Cast Alloy Crucible Tungsten Shields Cooling Apparatus Heating Element

Infiltration Process Ramped the furnace at approximately 50˚C per minute to 1350˚C under vacuum 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 Held the sample at 1350˚ for 5 minutes then applied 1 atmosphere pressure of 5% Hydrogen/Argon gas Kept under pressure upon cooling Kept under pressure upon cooling Cooled at a high rate to minimize oxidation reaction Cooled at a high rate to minimize oxidation reaction

Infiltration Results It worked!! It worked!! It did not infiltrate the YSZ disk fully It did not infiltrate the YSZ disk fully Redox reaction prevention appears to have worked well Redox reaction prevention appears to have worked well Unanalyzed metallic impurities more plentiful in infiltrated disk Unanalyzed metallic impurities more plentiful in infiltrated disk Melted Ni/Al alloyCrucible 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) 5 Seconds 25 Seconds 45 Seconds 5 Seconds 25 Seconds 45 Seconds Used 10% NaOH solution at 50˚C when leaching

Leaching (infiltrated Ysz) 5 Seconds 25 Seconds 45 Seconds Used 10% NaOH solution at 50˚C when leaching

Overall analysis Infiltration on a macro and micro scale Infiltration on a macro and micro scale Surface corrosion of granules shows how infiltration occurred Surface corrosion of granules shows how infiltration occurred Impurities found in metal ceramic matrix Impurities found in metal ceramic matrix Further Research is expected Further Research is expected Visibly equal metal/ceramic matrix Visibly equal metal/ceramic matrix High porosity High porosity

Future work More analysis of the infiltration product More analysis of the infiltration product Use SEM images to determine what occurred during infiltration Use SEM images to determine what occurred during infiltration Use chemical analysis and XRD to analyze impurities and infiltration products Use chemical analysis and XRD to analyze impurities and infiltration products Infiltrate preform with Ni/Al alloys of different compositions and process data Infiltrate preform with Ni/Al alloys of different compositions and process data Use Raney Nickel in co-sintering processes Use Raney Nickel in co-sintering processes Use SEM to determine structure’s porosity Use SEM to determine structure’s porosity Test different compositions of Ni/Al alloy at different temperatures Test different compositions of Ni/Al alloy at different temperatures

Acknowledgements Professor Trumble and Professor Slamovich Professor Trumble and Professor Slamovich Patti Metcalf Patti Metcalf Brad Allison Brad Allison Dave Roberts Dave Roberts Jeffrey Redding Jeffrey Redding NSF Grant (DMR ) NSF Grant (DMR )

Questions? Thank you.