1 / 23

Rajalekshmi Chockalingam, Vasantha R.W. Amarakoon, and Herbert Giesche

Center for Advanced Ceramic Technology. Alumina / Cerium Oxide Nano-Composite Electrolyte for Solid Oxide Fuel Cell Applications. Rajalekshmi Chockalingam, Vasantha R.W. Amarakoon, and Herbert Giesche New York State College of Ceramics at Alfred University, Alfred, NY, USA.

rafe
Download Presentation

Rajalekshmi Chockalingam, Vasantha R.W. Amarakoon, and Herbert Giesche

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Center for Advanced Ceramic Technology Alumina / Cerium Oxide Nano-Composite Electrolyte for Solid Oxide Fuel Cell Applications Rajalekshmi Chockalingam, Vasantha R.W. Amarakoon, and Herbert Giesche New York State College of Ceramics at Alfred University, Alfred, NY, USA NYSCC Alfred University

  2. Center for Advanced Ceramic Technology But first: “Where on earth is Alfred ?” NYSCC Alfred University

  3. http://en.wikipedia.org/wiki/Image:Fcell_diagram_sofc.gif Center for Advanced Ceramic Technology Cathode: La1−xSrxMnO3-δ Electrolyte: 8 mol% Y2O3 stabilized ZrO2 Anode: Ni + YSZ Operated at close to 1000°C. NYSCC Alfred University

  4. S.M. Haile, “Fuel cell materials and components,” Acta materialia, 51, 5981-6000 (2003) Center for Advanced Ceramic Technology Alternative Electrolyte Materials For Example: Gadolinium doped Ceria Ce0.8Gd0.2O1.9 Leading to lower operation temp. However !!! under reducing conditions: Ce+IV→ Ce+III electronic conduction. Idea !!! Electron Trapping Interfaces. NYSCC Alfred University

  5. Center for Advanced Ceramic Technology “Electron Trapping” NYSCC Alfred University

  6. Center for Advanced Ceramic Technology So, how do we make such a microstructure? Coated Nano-particles. Densify/sinter and retain microstructure. (microwave sintering; fast & uniform) NYSCC Alfred University

  7. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Center for Advanced Ceramic Technology Heterocoagulation Use two suspensions of particles with opposite charge. Zeta-potential (pH) Surfactant adsorption Porous coating; weak adhesion forces; requires large difference in particle size + NYSCC Alfred University

  8. Center for Advanced Ceramic Technology Heteronucleation Precipitate coating material onto seed particles. Essentially “any” precipitation reaction can be used. As long as it is a “controlled” (slow) precipitation Dense and uniform coating Alfred University

  9. Example Center for Advanced Ceramic Technology Silica-Yttria: Schematic Examples of Microstructures NYSCC Alfred University

  10. Center for Advanced Ceramic Technology Heteronucleation Example Silica spheres coated with yttria. NYSCC Alfred University

  11. Center for Advanced Ceramic Technology Heteronucleation Example cont. Excess silica cores remain after phase transformation and sintering. Visualized by etching with HF. NYSCC Alfred University

  12. Center for Advanced Ceramic Technology Schematic of the “new” nano-composite electrolyte. Alumina core (seed) Cobalt and Manganese surface layer; acceptor states at the interface Gadolinium doped Ceria (50 to 100 nm)oxygen-ion-conductor; ‘continuous phase’ Microwave sintering to retainthe proposed microstructure Alfred University

  13. Al(OC4H9)3 H2O (75°C) Hydrolysis under vigorous stirring for 30 min Peptization with HNO3 & Aging at 95°C for 5 days Co (NO3)2 6H2O + H2O Mn (NO3)2 6H2O + H2O Al2O3 SOL NH4OH + H2O Stirr at 90°C for 4 hrs & Age 24 hrs Mn, Co coated Al2O3 Sol Center for Advanced Ceramic Technology Synthesis of Mn, Co doped Al2O3 Sol NYSCC Alfred University

  14. Mn, Co coated Al2O3 Sol Ce(NO3)3.6H2O +H2O Gd(NO3)3 6H 2O +H2O Vigorous stirring at 93°C for 6 hours NH4OH + H2O Aging at RT for 24 hours Gd0.2Ce0.8O1.9coated on Mn, Co coated Al2O3 Sol Dry and heat Treatment Forming and sintering Center for Advanced Ceramic Technology Coating of Gd doped CeO2 onAl2O3 Sol NYSCC Alfred University

  15. Center for Advanced Ceramic Technology Microwave Sintering Set up A B Figure (A) 2.45 GHz MW Furnace and Figure (B) Sample set up with alumina insulation box and Thermocouple. NYSCC Alfred University

  16. Center for Advanced Ceramic Technology Sintering: Temperature Profile NYSCC Alfred University

  17. Center for Advanced Ceramic Technology XRDResults for Gd0.2Ce0.8O1.9 -0.34%Mn-0.34%Co-Al2O3 ♥ matches Gd0.2Ce0.8O1.9 NYSCC Alfred University

  18. Center for Advanced Ceramic Technology SEM Micrographs:Al2O3-0.34%Mn,Co-Gd0.2Ce0.8O1.9 500nm 500nm CONV-1350C-5hr MW1250C-40min NYSCC Alfred University

  19. Center for Advanced Ceramic Technology Microwave sintering Conventional sintering NYSCC Alfred University

  20. Center for Advanced Ceramic Technology Impedance Spectroscopy in Air (‘Ionic Conductivity’) NYSCC Alfred University

  21. Center for Advanced Ceramic Technology Electrical Conductivity as a Function of Oxygen Partial Pressure NYSCC Alfred University

  22. Center for Advanced Ceramic Technology Electrical Conductivity as a Function of Oxygen Partial Pressure NYSCC Alfred University

  23. What’s next? • Better control of coating - thickness and uniformity. • Test of other material combinations. • Measure oxygen conductivity ‘directly’ (transference number). • Test in a ‘real’ device !!! Center for Advanced Ceramic Technology Conclusions • Coated powders lead to unique microstructure. • Microwave sintering is substantially faster. • Submicron grain size can be retained • Increased hardness. • Electron trapping states at the alumina-ceria interface reduce electronic conductivity. • Al2O3 inclusions have no major effect on ionic-conductivity. NYSCC Alfred University

More Related