SECA CTP Meeting, 10/25/05 (1) R.K. Brow, [email protected] University of Missouri-Rolla
Sealing Materials forSealing Materials forSolid Oxide Fuel CellsSolid Oxide Fuel Cells
Richard K. Brow
Materials Science & Engineering DepartmentUniversity of Missouri-Rolla
Rolla, MO 65409
SECA Core Technology ProgramPeer Review Meeting
Lakewood, COOctober 25-26, 2005
SECA CTP Meeting, 10/25/05 (2) R.K. Brow, [email protected] University of Missouri-Rolla
AcknowledgementsAcknowledgementsThis research was performed primarily by• Dr. Signo Reis and Mr. Teng Zhang (UMR)
Thanks also go to• Xiao Dong Zhou, Harlan Anderson, Clarissa Vierrether
(UMR)• Raj Singh (U. Cincinnati)• Ron Loehman (Sandia National Labs),• Matt Chou (PNNL)• Matt Seabaugh (NexTech)
The financial support of the Department of Energy (SECA project NT42221/Travis Schultz program manager) is gratefully acknowledged.
SECA CTP Meeting, 10/25/05 (3) R.K. Brow, [email protected] University of Missouri-Rolla
OutlineOutline
Goal: Develop stable, resilient sealing materials for SOFCs
• Reviewing the problem; initial glass development research
• Progress over the past six months– Glasses with greater CTE’s– Developing composite materials
• Summarizing our program
SECA CTP Meeting, 10/25/05 (4) R.K. Brow, [email protected] University of Missouri-Rolla
The sealing problem is a challengeThe sealing problem is a challenge
1. Challenging compositional design problem
• Uncommon combination of properties
• Investigate uncommon families of glasses
2. Glass-ceramics are a likely option
• Crystallization studies- seal processing and long-term material stability
3. Interfacial chemistry• Glass-metal reactions• Material stability/volatility
• Thermochemical stability
SECA CTP Meeting, 10/25/05 (5) R.K. Brow, [email protected] University of Missouri-Rolla
200 400 600 8000.0
0.2
0.4
0.6
0.8
1.0
CTERT-600=8.4x10-6/ 0C
CTERT-600=11.4x10-6/ 0CG36
G27
LG38
"As made glasses"
% L
inea
r Cha
nge
Temperature ( 0C )
ZnO/(SrO+CaO)=0.00ZnO/(SrO+CaO)=0.35ZnO/(SrO+CaO)=1.00
Glass forming system under study:•Alkaline earth/zinc pyrosilicates
•35-50 SiO2•30-50 RO (R=Mg, Ca, Sr, Zn; no Ba)•0-10 B2O3, Al2O3, TiO2, etc.
Design targets include:•10<CTE<13 ppm/ºC•800ºC<Tseal< 900ºC•Thermochemical and thermomechanicalstability
Sealing glass propertiesSealing glass propertiesdepend on compositiondepend on composition
SECA CTP Meeting, 10/25/05 (6) R.K. Brow, [email protected] University of Missouri-Rolla
200 400 600 8000.0
0.2
0.4
0.6
0.8
1.0
1.2
CTERT-600=10.0x10-6/ 0CG27
CTERT-600=5.5x10-6/ 0CLG38
CTERT-600=12.4x10-6/ 0CG36
"As sealed glasses"
% L
inea
r Cha
nge
Temperature ( 0C )
ZnO/(SrO+CaO)=0.00ZnO/(SrO+CaO)=0.35ZnO/(SrO+CaO)=1.00
Sealing glass propertiesSealing glass propertiesdepend on compositiondepend on composition
Glass forming system under study:•Alkaline earth/zinc pyrosilicates
•35-50 SiO2•30-50 RO (R=Mg, Ca, Sr, Zn; no Ba)•0-10 B2O3, Al2O3, TiO2, etc.
Design targets include:•10<CTE<13 ppm/ºC•800ºC<Tseal< 900ºC•Thermochemical and thermomechanicalstability
SECA CTP Meeting, 10/25/05 (7) R.K. Brow, [email protected] University of Missouri-Rolla
Thermal properties of sealing glasses are Thermal properties of sealing glasses are controlled by the controlled by the ZnOZnO/RO ratio/RO ratio
20 40 60 80 100
(2) - CaSrAl2Si2O7
(1) - Ca2ZnSi2O7
(2)(2)(1)
(1,2)
(1,2)
(1,2)
2θ ( degree)
As-sealed G27
As-sealed G36, 750C for 10 days
As-sealed LG38
ZnO/(SrO+CaO)=0.00CTE=12.4 ppm/ºC
ZnO/(SrO+CaO)=0.35CTE=10.0 ppm/ºC
ZnO/(SrO+CaO)=1.00CTE=5.5 ppm/ºC
SECA CTP Meeting, 10/25/05 (8) R.K. Brow, [email protected] University of Missouri-Rolla
Representative crystalline phasesRepresentative crystalline phasesin the UMR glassin the UMR glass--ceramicsceramics
• Pyrosilicates– CaSrAl2SiO7, Ca2ZnSi2O7
• Orthosilicates– Sr2SiO4, Zn2SiO4
• Composition is most important parameter for final phase distribution.
20 40 60 80
0
500
1000
1500
2000
2500
CP
S
As-sealed(850°C/4 hrs)
CaSrAl2SiO7Ca2ZnSi2O7
20 40 60 80
0
400
800
120028 days/750°C
Crofer APU22/G#27750ºC/100 hrs
SECA CTP Meeting, 10/25/05 (9) R.K. Brow, [email protected] University of Missouri-Rolla
Glass#27 possesses a good CTEGlass#27 possesses a good CTE--match with YSZ match with YSZ
200 400 600 800 1000-0.04
0.00
0.04
0.08
0.12
As sealed
3 days/750oC
7 days/750oC
14 days/750oC
28 days/750oC
ΔCTE
(gla
ss-Y
SZ)
Temperature(oC)
Glass #27
Expansion of residual glass
CTE match below 650ºC
SECA CTP Meeting, 10/25/05 (10) R.K. Brow, [email protected] University of Missouri-Rolla
Greater Greater CTECTE’’ss are neededare neededfor some SOFC designsfor some SOFC designs
• Compositional modifications include– Replacing ZnO with CaO and SrO– Reducing Al2O3 content– Modifying relative SiO2 and B2O3 contents
• About fifteen new compositions prepared this past reporting period
SECA CTP Meeting, 10/25/05 (11) R.K. Brow, [email protected] University of Missouri-Rolla
Glass #36 may be more appropriateGlass #36 may be more appropriatefor some SOFC designsfor some SOFC designs
200 400 600 800 10000.0
0.2
0.4
0.6
0.8
1.0
1.2
750
% L
inea
r Cha
nge
Temperature ( 0C )
αRT-800=119x10-7/ 0C
αRT-800=100x10-7/ 0C
E-briteCroferYSZ (Y-Stabilized Zirconia)G#36, 850oC for 2hrs
SECA CTP Meeting, 10/25/05 (12) R.K. Brow, [email protected] University of Missouri-Rolla
0 10 20 30 40 50 60 70 80
20
40
60
80
100
Res
idua
l gla
ss (%
)
days
Held at 750ºC/airHeld at 800ºC/air
Crystallization Kinetics of Glass#36/DTA AnalysesCrystallization Kinetics of Glass#36/DTA Analyses
SECA CTP Meeting, 10/25/05 (13) R.K. Brow, [email protected] University of Missouri-Rolla
The CTE of glass#36 changes at 800The CTE of glass#36 changes at 800ººCC
100 200 300 400 500 600 700 800 9004
5
6
7
8
9
10
11
12
13
14
15
16
As sealed (890oC2h)
800oC 1 week
CTE
(10
-6 /
o C)
Temperature ( 0C )
‘as sealed’- 890ºC/2hrs
After one week at 800ºC
12.3 ppm/ºC11.4 ppm/ºC
Long term (1000 hrs) are underway
SECA CTP Meeting, 10/25/05 (14) R.K. Brow, [email protected] University of Missouri-Rolla
CaCa--silicate phases form on crystallizationsilicate phases form on crystallization
‘as sealed’, 890ºC(1)- CaSiO3(2)- CaSrSiO4
800ºC, one week (1)- CaSiO3(2)- CaSrSiO4
SECA CTP Meeting, 10/25/05 (15) R.K. Brow, [email protected] University of Missouri-Rolla
Crofer-Glass(UMR-36) sealAnnealed at 800ºC, tested at RT
Raj Singh- U. Cincinnati
0
200
400
600
800
1000
1200
1400
0 100 200 300 400 500 600
Time (Minutes)
Pres
sure
(Tor
r)
As MadeAfter annealing 50 hoursAfter annealing 100 hoursAfter annealing 500 hours
Leaker/500 hrs
Initial Hermeticity TestsInitial Hermeticity Tests-- Mixed ResultsMixed Results
SECA CTP Meeting, 10/25/05 (16) R.K. Brow, [email protected] University of Missouri-Rolla
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
0.05
0.055
0.06
500 600 700 800 900 1000 1100Temperature (C)
delta
Tem
p.
2-5 um30-50 um
We use DTA to characterizeWe use DTA to characterizeprocessing effects on propertiesprocessing effects on properties
Finer particles crystallize more readily
SECA CTP Meeting, 10/25/05 (17) R.K. Brow, [email protected] University of Missouri-Rolla
-12
-11.8
-11.6
-11.4
-11.2
-11
-10.8
-10.6
-10.4
0.78 0.79 0.8 0.81 0.82 0.83
1000/T (K-1)
ln(β
/T2 )
Kissinger analysis: DTA heating rates
We use DTA to characterizeWe use DTA to characterizeprocessing effects on propertiesprocessing effects on properties
FineParticles,
355 kJ/mole
CoarseParticles,
346 kJ/mole
SECA CTP Meeting, 10/25/05 (18) R.K. Brow, [email protected] University of Missouri-Rolla
0
0.2
0.4
0.6
0.8
1
1.2
100 300 500 700 900
Temperature (C)
% L
inea
r Cha
nge 'as sealed', 10.3 ppm/C
2 weeks at 750C, 11.1 ppm/C
4 weeks at 750C, 11.5 ppm/C
Glass#51 has promisingGlass#51 has promisingdilatometricdilatometric characteristicscharacteristics
SECA CTP Meeting, 10/25/05 (19) R.K. Brow, [email protected] University of Missouri-Rolla
10 20 30 40 50 60 70 80 900
200
400
600
800
(2) - SrSiO3
2 2
2
2
2
2
22
2 22
2
2
21
1 1
1
11 1 1
(1) - Sr2Al2SiO7
Cou
nts
Cou
nts
2θ (degree)
As-sealed G#51, 750oC 2 weeks
0
200
400
600
800
(2) - SrSiO3
1
1
1
1
11
(1) - Sr2Al2SiO7As-sealed G#51
As sealed G#51
Two weeks at 750ºC
SrSr--silicate phases form on crystallizationsilicate phases form on crystallization
(1) – Sr2Al2SiO7(2) - SrSiO3
(1) – Sr2Al2SiO7(2) - SrSiO3
SECA CTP Meeting, 10/25/05 (20) R.K. Brow, [email protected] University of Missouri-Rolla
0 2 4 6 8 10 12 14 1610-5
10-4
10-3
G#36
G#52G#51
G#27
ΔWei
ghta
t 800
ºC (g
/cm
2 )(w
et fo
rmin
g ga
s)
days
Glass stability in wet forming gas (800Glass stability in wet forming gas (800ººC)C)
More stable materials have•Less residual glass•Lower B2O3-contents
SECA CTP Meeting, 10/25/05 (21) R.K. Brow, [email protected] University of Missouri-Rolla
GlassGlass--metal adhesion strength measured metal adhesion strength measured by pinby pin--pull testpull test
Romulus adhesion testing machine- Quad Group Inc.
~300μm glass coatings on interconnect substrates; ‘as sealed’and after heat treatments
G#27/430 SS
G51/430SS- ‘as sealed’ 20.9±6.9 MPa
G51/430SS- 750ºC/700hrs 20.7±10.2 MPa
G52/430SS- ‘as sealed’ 19.8±3.8 MPa
G52/430SS- 750ºC/700hrs 18.9±2.6 MPa
SECA CTP Meeting, 10/25/05 (22) R.K. Brow, [email protected] University of Missouri-Rolla
Sealing materials can be Sealing materials can be modified by adding fillersmodified by adding fillers
• Tailor CTE• Control crystallization• Affect interfacial reactions• Relieve thermal stresses
– Controlled cracking in glass matrix; healing by viscous flow of residual glass• Design CTE and elastic mismatches
SECA CTP Meeting, 10/25/05 (23) R.K. Brow, [email protected] University of Missouri-Rolla
Composite OverviewComposite OverviewMaterial CTE
(ppm/ºC)Elastic Modulus (GPa)
Notes
G36 12.1 80
Ni 13.3 207
Mo 5.1 324
316SS 17 193
Ti-Ni 34-83 Phase transition
WC 5.2 669
SiC 4.3 483
ZrO2 7.0→10.5 138-210 Phase transition
Quartz 7.0→13.3 Phase transition
SECA CTP Meeting, 10/25/05 (24) R.K. Brow, [email protected] University of Missouri-Rolla
0
0.2
0.4
0.6
0.8
1
1.2
100 300 500 700 900 1100
Temperature (C)
% L
inea
r Cha
nge
G36, 864C 1h90%G36/10%Ni90%G36/10%SiC90%G36/10%SS
DilatometricDilatometric characteristics depend on fillercharacteristics depend on filler
SECA CTP Meeting, 10/25/05 (25) R.K. Brow, [email protected] University of Missouri-Rolla
0.015
0.02
0.025
0.03
0.035
0.04
0.045
0.05
0.055
0.06
0.065
500 600 700 800 900 1000 1100
Temperature (C)
delta
Tem
p.
G36/10%SiCG36(53um)
Composite crystallization behaviorComposite crystallization behaviorwill be characterized by DTAwill be characterized by DTA
SECA CTP Meeting, 10/25/05 (26) R.K. Brow, [email protected] University of Missouri-Rolla
Experiments UnderwayExperiments Underway
• Composite processing– Dense seals using tape-casting techniques
• Composite properties– Tailoring CTE– Induced cracking?
• Composite reactivity– Filler/matrix compatibility’– SOFC interfaces
SECA CTP Meeting, 10/25/05 (27) R.K. Brow, [email protected] University of Missouri-Rolla
SOFC Seal SummarySOFC Seal Summary• SOFC seals offer an interesting materials challenge• RO- polysilicate compositions have promising
combinations of properties– Polysilicate glass-ceramics can be designed with
thermal and chemical properties desired for some SOFC seal designs.
– Thermo-chemical and thermo-mechanical stabilities are critical for long-term applications.
• Composite seals based on RO-polysilicate glasses– Reduce stresses due to thermal cycling?
Thank you for your attention!Thank you for your attention!