Transcript Slide 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
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Outline
•
•
•
•
Motivation
Brief Review of Previous Work
Progress Report
Summary
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US Nanocorp
•
Thermal Sprayed Electrodes / Electrolytes for
Batteries and Fuel Cells
•
Fuzzy Logic Modeling Methods to Manage
Batteries and Fuel Cells
2002 Deloitte
& Touche
Technology
Fast 500
Award
2002 D&T
Connecticut
Technology
Fast 50
Award
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Solid Oxide Fuel Cells
(SOFCs)
Features:
• Higher efficiency
• More flexible fuels
• All solid components
Applications:
Power plant
Residential
Transportation
Military
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Research Motivation
High temperature SOFCs (~ 1000oC)
Fuel
YSZ
LSM
Air
Load
Ni-YSZ
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
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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
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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
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Plasma Processing
• Brief (on the order of 1 ms) particle
residence time
• Rapid heating
• Steep gradients in HVOF and plasma flow
fields
8/23
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Advantages of Plasma Spray
Nanomaterial Feedstock
Substrate
Thermal Spray Gun
Nanocoated Component
Rapid and sequential fabrication
Nanostructured materials
Accurately controlled Thickness
Potential low cost (automation)
Robotic continuous operation
Graded porosity & composition
Excellent interfacial contact
Large area and free geometry
Unlimited substrates (@RT)
No high temperature sintering
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Feedstock Reconstitution
5 - 20 nm
particles
5 - 20 nm
particles
loosely agglomerated
non-agglomerated
5 - 20 nm
particles
20 m m
30 mm
hollow shell agglomerates
reconstituted sprayable form
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Microstructure of Feedstock
100mm
14
Feedstock number
12
10
10 mm
8
6
4
2
0
9
12 18 27 36 40 45 49 53 58 62 78
Feedstock size (um)
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USN’s Planar SOFC Systems
Anode electrode
Electrolyte
Cathode electrode
Free standing plasma sprayed SOFC single cells
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12/23
USN’s Tubular SOFC Systems
LDC40 + Ni
LDC40
LSGM
SWPC tube
Anode:
Interlayer:
Electrolyte:
Cathode:
Nano LDC40 + Ni
LDC40
La0.8Sr0.2Ga0.8Mg0.2O3
SWPC proprietary tube
13/23
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Requirements for Sprayed Components
Porous electrodes
SYT
Dense electrolyte
Right chemical phase and
composition
Compatible electrochemical
properties
LSGM
LSM
50 mm
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SEM Images of LSGM
LSGM
LSGM
(b)
100mm
LSGM feedstock
LSM
30 mm
As-sprayed LSGM on LSM
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Open-Circuit Voltage
1.2
1.2
1
1
o
0.8
0.8
Voltage V
Voltage /V
3 C/min
0.6
700oC
0.6
0.4
0.4
0.2
0.2
0
0
250
350
450
550
650
750
Temperature /oC
0
10
20
30
40
50
60
Time hour
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As-sprayed LSGM
4500
o
4000
3500
2.0
1.5
-ZI
Intensity (arb. unit)
LSGM feedstock
2.5
650 C
o
700 C
o
750 C
o
800 C
1.0
0.5
3000
0.0
0.0
0.5
1.0
1.5
2.0
2.5
ZR
-ZI
2500
2000
LSGM as sprayed
1500
1000
500
0
20
30
40
50
60
70
0
80
500
1000
1500
2000
3000
3500
4000
ZR
2
X-ray diffraction spectra
2500
Ac Impedance measurement
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Heat-treatment of Sprayed LSGM
12
o
900 C
o
10
-ZI
8
Intensity (arb. unit)
650 C
o
700 C
o
750 C
o
800 C
6
4
o
800 C
o
700 C
o
2
500 C
0
0
2
4
6
8
10
12
ZR
Change of ac Impedance spectra
30
40
50
60
70
80
2
Chang of XRD pattern
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Sintered & Sprayed LSGM
1.5
o
4
650 C
o
700 C
o
750 C
o
800 C
1.0
-ZI
-ZI
3
pressed
sprayed
2
0.5
1
0.0
0
0
1
2
3
0.0
4
1.0
1.5
ZR
ZR
Pressed / Sintered LSGM
0.5
Sintered vs Sprayed LSGM
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Solution Feedstock Plasma Spray
Atomizing
Nozzle
Tungsten
Cathode
+
-
Gas
+
Gas
Plasma
Tungsten
Anode
Pump
YSZ Liquid
Feed Stock
Work piece
20/23
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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
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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
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Acknowledgement
This work was supported by the Department of
Energy:
(1)with Dr. Keqin Huang at Siemens
Westinghouse Power Corp. under DOE
Prime Contract No. DE-FC26-99FT40709
(2)under a DOE SBIR Grant No. DE-FG 0201ER83340.
23/23
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