• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
17 Nov08 Jorge Frade
 

17 Nov08 Jorge Frade

on

  • 685 views

 

Statistics

Views

Total Views
685
Views on SlideShare
684
Embed Views
1

Actions

Likes
0
Downloads
6
Comments
0

1 Embed 1

http://www.slideshare.net 1

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    17 Nov08 Jorge Frade 17 Nov08 Jorge Frade Presentation Transcript

    • Guidelines for materials selection and optimization in electrochemical conversion of fuels J.R.Frade University of Aveiro, Portugal Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008
    • Fuel cells Clean; High  Hydrocarbons Partial oxidation or Reforming e.g. CH 4 +1/2O 2  CO+2H 2 Electricity Chemicals Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008 Purification H 2
      • Effects of fuel/air atmospheres on cell materials
      • Redox behaviour
      • Stability limits under reducing conditions
      • Structural changes
      • Effects on transport properties, etc.
      • Effects on carbon deposition
      • Effects of contaminants (S-tolerance) etc.?
      • Thermochemical or thermomechanical failure
      • Interactions between cell materials
      • Processing
      • Operation
      • Maintenance, thermal cycling, etc.
      Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008
    • Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008 Reducing cnditions imposed by H 2 2H 2 + O 2  2H 2 O; Po 2 = (pH 2 O/pH 2 ) 2 exp(-  G/RT)
    • Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008 Reducing cnditions imposed by CH 4 , ...
    • Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008 Guidelines for redox tolerance of metallic electrocatalysts in H 2 atmospheres
    • Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008 Stability limits of SOFC cathode materials and catalysts under reducing conditions 2LaMnO 3  La 2 O 3 + 2MnO + 1/2O 2 2LaCoO 3  La 2 CoO 4 + CoO + 1/2O 2 ...
    • Structural changes and property degradation under reducing conditions LSMCT2 = (La 0.55 Sr 0.45 ) 0.95 Mn 0.5 Cr 0.3 Ti 0.2 O 3-δ ; LSMCT4 = (La 0.35 Sr 0.65 ) 0.95 Mn 0.5 Cr 0.1 Ti 0.4 O 3-δ ... Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008
    • Stability range estimated from sudden changes in conductivity and Seebeck coefficient. Stability limits Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008
    • Typical dependence of ionic and electronic conductivity of CGO20 solid electrolytes Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008
    • Predictions of methane conversion of ionic transport number and open cell voltage of a CGO-based cell Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008
    • Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008 Predictions of carbon deposition
      • Strategies to minimize the risks of carbon deposition:
      • Steam reforming
      • Substitution of metallic catalysts by alternative catalysts
    • Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008 Better S-tolerance Poorer S-tolerance Is thermodynamics useful to predict Sulphur tolerance?
      • Thermal expansion mismatch
      • in a thin La 10 Si 5 AlO 26+x electrolyte layer on a thick LSMCT substrate, with firing at 1250ºC
      •  L/L o =  T
      •  E/(1-  )
      • Typical for ceramics: E >100 GPa and  ≈ 0.3.
      • For  ≈ 2x10 -6 K -1 , and  T ≈ 1000ºC
      •  ≈  0.002;  ≈ - 300 MPa (delamination!)
      Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008
    • Thermal expansion mismatch and ionic conductivity at 800ºC, in air Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008 Composition       I ;S/cm T, K E a (kJ/mol) La 2 Ni 0.8 Cu 0.2 O 4+  13.3 0.11* - - LSFC 12.9 0.01 1073-1223 206 LSM 11.7 1.3  10 -5 - - LSFC - 50 wt% CGO 12.6 0.04 1023-1223 82 LSM - 50 wt% CGO   11.7 0.03   1023-1223   104   La 10 Si 5 AlO 26.5   9.1 0.08   973-1223     56    
    •  
    • Chemical expansion under air/5%H 2 Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008  L/L o;  E/(1-  ) for  =0.005  200MPa (risks of fracture!)
    • EDS spectra showing cation diffusion accross the CGO buffer layer in apatite/CGO/ LSMCT4 and LSGM/CGO/LSMCT4 arrangements Interdiffusion between cell materials Economia de H 2 : Un desafio para Portugal, Vimeiro, Nov.17, 2008