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
2/23
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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
3/23
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Solid Oxide Fuel Cells
(SOFCs)
Features:
• Higher efficiency
• More flexible fuels
• All solid components
Applications:
Power plant
Residential
Transportation
Military
4/23
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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
9/23
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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
10/23
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Microstructure of Feedstock
100mm
Feedstock number
14
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
14/23
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SEM Images of LSGM
LSGM
LSGM
(b)
100mm
LSGM feedstock
LSM
30 mm
As-sprayed LSGM on LSM
15/23
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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
16/23
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As-sprayed LSGM
4500
o
4000
Intensity (arb. unit)
3500
2.0
1.5
-ZI
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
17/23
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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
18/23
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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
19/23
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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
21/23
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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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