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Progress Report on Sequential-Fab Plasma-Sprayed SOFC Components

Progress Report on Sequential-Fab Plasma-Sprayed SOFC Components Rob S. Hui , H. Zhang, X. Ma, J. Roth, J. Broadhead, D. Xiao, and D. Reisner US Nanocorp  , Inc. Fuel cells 2003 The Third Annual BCC Conference Stamford, CT. Motivation Brief Review of Previous Work Progress Report

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Progress Report on Sequential-Fab Plasma-Sprayed SOFC Components

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  1. Progress Report on Sequential-Fab Plasma-Sprayed SOFC Components Rob S. Hui, H. Zhang, X. Ma, J. Roth, J. Broadhead, D. Xiao, and D. Reisner US Nanocorp, Inc. Fuel cells 2003 The Third Annual BCC Conference Stamford, CT

  2. Motivation Brief Review of Previous Work Progress Report Summary Outline 2/23

  3. 2002 Deloitte & Touche Technology Fast 500 Award 2002 D&T Connecticut Technology Fast 50 Award US Nanocorp • Thermal Sprayed Electrodes / Electrolytes for Batteries and Fuel Cells • Fuzzy Logic Modeling Methods to Manage Batteries and Fuel Cells 3/23

  4. Solid Oxide Fuel Cells (SOFCs) Features: • Higher efficiency • More flexible fuels • All solid components Applications: Power plant Residential Transportation Military 4/23

  5. Fuel Ni-YSZ YSZ Load LSM Air Research Motivation • High temperature SOFCs (~ 1000oC) • Materials constraints • High stress of differential thermal expansion • Long term stability poor • Precludes nanomaterials • High cost of operation • Low temperature SOFCs (< 850oC) • Alternative materials • Appropriate cell design • Manufacturing routes 5/23

  6. USN’s Enabling SOFC Technology • Nanostructured electrode materials • Enable low Temperature Operation • High activity (high interfacial surface area) • Expect Improved cell performance • Plasma Spray • Integrated fabrication of membrane-type SOFC • New materials with high performance • Sr1-1.5xYxTiO3 (“SYT”) replaces Ni/YSZ • MIEC has more reaction sites than Ni-cermet • LSGM has four-time higher ionic conductivity than YSZ 6/23

  7. USN’s SOFC Strategy • Reduce cell operating temperature •  Thin film LSGM electrolyte (high conductivity) •  Nanostructured electrodes (many grain boundaries -> large interface) •  SYT anode material is a MIEC working at 600 – 800 oC • Increase fuel cell operating efficiency •  SYT could directly catalyze hydrocarbon fuel •  SYT has more reaction sites than Ni-cermet • Drive down fuel cell manufacturing cost using APS •  Inexpensive, Universal (Metco 9MB) •  Sequential fabrication of cell components •  Possibility of elimination of reforming unit 7/23

  8. Brief (on the order of 1 ms) particle residence time Rapid heating Steep gradients in HVOF and plasma flow fields Plasma Processing 8/23

  9. Nanomaterial Feedstock Substrate Thermal Spray Gun Nanocoated Component Advantages of Plasma Spray  Graded porosity & composition  Excellent interfacial contact  Large area and free geometry  Unlimited substrates (@RT)  No high temperature sintering  Rapid and sequential fabrication  Nanostructured materials  Accurately controlledThickness  Potential low cost (automation)  Robotic continuous operation 9/23

  10. 5 - 20 nm particles 5 - 20 nm particles loosely agglomerated non-agglomerated 5 - 20 nm particles m 20 m 30 mm hollow shell agglomerates reconstituted sprayable form Feedstock Reconstitution 10/23

  11. 10 m 100m Microstructure of Feedstock 11/23

  12. Anode electrode Electrolyte Cathode electrode USN’s Planar SOFC Systems Free standing plasma sprayed SOFC single cells 12/23

  13. LDC40 + Ni LDC40 LSGM SWPC tube USN’s Tubular SOFC Systems Anode: Nano LDC40 + Ni Interlayer: LDC40 Electrolyte: La0.8Sr0.2Ga0.8Mg0.2O3 Cathode: SWPC proprietary tube 13/23

  14. SYT LSGM LSM 50 mm Requirements for Sprayed Components • Porous electrodes • Dense electrolyte • Right chemical phase and • composition • Compatible electrochemical • properties 14/23

  15. LSGM 30 mm LSM LSGM SEM Images of LSGM LSGM feedstock As-sprayed LSGM on LSM 15/23

  16. Open-Circuit Voltage 16/23

  17. As-sprayed LSGM X-ray diffraction spectra Ac Impedance measurement 17/23

  18. Heat-treatment of Sprayed LSGM Change of ac Impedance spectra Chang of XRD pattern 18/23

  19. Sintered & Sprayed LSGM Sintered vs Sprayed LSGM Pressed / Sintered LSGM 19/23

  20. Atomizing Nozzle Tungsten Cathode + Gas - + Gas Plasma Tungsten Anode Pump YSZ Liquid Feed Stock Work piece Solution Feedstock Plasma Spray 20/23

  21. Advantages of SPS Electrode  Forms 3-D porous structure, leading to high fuel gas permeability for anode  Forms nanostructured anode, increases surface area of fuel – solid interaction • Enables thin layer coating formation • Higher thermal shock resistance 21/23

  22. Summary • Nanostructured SOFC was proposed based on the materials selection and fabrication technique • Planar SOFCs have been successful fabricated by plasma spray technique with dense electrolyte and porous electrodes • Thick film LSGM has been sprayed and characterized. Sprayed layer has same electrochemical properties with sintered one • Improvement of electrode structure and characterization of fuel cell performance are needed in the future 22/23

  23. Acknowledgement • This work was supported by the Department of Energy: • with Dr. Keqin Huang at Siemens Westinghouse Power Corp. under DOE Prime Contract No. DE-FC26-99FT40709 • under a DOE SBIR Grant No. DE-FG 02-01ER83340. 23/23

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