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Novel Functional Graded Thermal Barrier Coatings in Coal-fired Power Plant Turbines
Jing Zhang Department of Mechanical Engineering
Indiana University-Purdue University Indianapolis
Grant No.: DOE DE-FE0008868Program Manager: Richard Dunst
2015 NETL Crossingcutting Research Review Meeting, Pittsburgh, PA, April 27-30, 2015
2
Acknowledgement
• Subcontract: James Knapp (Praxair Surface Technologies)• Collaborators: Li Li, Don Lemen (Praxair Surface
Technologies)• Yeon-Gil Jung (Changwon National University)• Yang Ren, Jiangang Sun (Argonne National Laboratory)• Changdong Wei (OSU), Bin Hu (Dartmouth)• Ph.D. graduate students: Xingye Guo, Yi Zhang
3
Outline• Introduction• Coating fabrications• Single ceramic layer (SCL) architecture• Double ceramic layer (DCL) architecture• Characterization of physical and mechanical properties• Microstructure and composition• Porosity and hardness• Bond strength test• Erosion test
• Characterization of thermal properties• Thermal conductivity and specific heat measurements• Jet engine thermal shock tests• Thermal gradient mechanical fatigue tests
• Summary and future work
4
Limitation of yttria stabilized zirconia
• Zirconia partially stabilized with 7 wt% yttria (7YSZ) is the current state-of-the-art thermal barrier coating material.
• However, at temperatures higher than 1200 oC, YSZ layers are prone to sintering, which increases thermal conductivity and makes them less effective.
• The sintered and densified coatings can also reduce thermal stress and strain tolerance, which can reduce the coating’s durability significantly.
5
Motivation and objective
• To further increase the operating temperature of turbine engines, alternative TBC materials with lower thermal conductivity, higher operating temperatures and better sintering resistance are required.
• The objective of the project is to develop a novel lanthanum zirconate based multi-layer thermal barrier coating system.
• The ultimate goal is to develop a manufacturing process to produce pyrochlore oxide based coating with improved high-temperature properties.
6
Pyrochlore - A2B2O7
Pyrochlore-type rare earth zirconium oxides (Re2Zr2O7,Re = rare earth) are promising candidates for thermal barrier coatings, high-permittivity dielectrics, potential solid electrolytes in high-temperature fuel cells, and immobilization hosts of actinides in nuclear waste.
Pyrochlore crystal structure: A2B2O7. A and B are metals incorporated into the structure in various combinations. (credit: NETL)
7
Why La2Zr2O7?
• Higher temperature phase stability. No phase transformation
• Lower sintering rate at elevated temperature
• Lower thermal conductivity• Lower CTE
Phase diagram of La2O3–ZrO2
Compared with YSZ, La2Zr2O7 has
8
La2Zr2O7 vs. YSZ
Materials property 8YSZ La2Zr2O7Melting Point (oC) 2680 2300Maximum Operating Temperature (oC) 1200 >1300Thermal Conductivity (W/m-K) (@ 800oC )
2.12 1.6
Coefficient of Thermal Expansion (x10-6/K) (@1000 oC)
11.0 8.9-9.1
Density (g/cm3) 6.07 6.00Specific heat (J/g-K) (@1000 oC) 0.64 0.54
9
Layered coating architecture
• The coefficient of thermal expansion of La2Zr2O7(10x10-6 /oC) is lower than those of both substrate and bondcoat (about 15x10-6/oC @ 1000 oC). As a result, the thermal cycling properties may be a concern
• The layered topcoat architecture is believed to be a feasible solution to improve thermal strain tolerance
• In this work, we develop a multi-layer, functionally graded, pyrochlore oxide based TBC system
10
La2Zr2O7 spray powder morphology Powder surface morphology
•Spherical shape with a rough surface•Good flowability and high density•Particle size between 30 ~ 100 m
+ 125 um - 125 um
Powder cross-section
•Porous interior
11
TEM image of La2Zr2O7
500 nm
credit: Bin Hu @ Dartmouth
12
La2Zr2O7 powder XRD analysisPhilips, NL/X''Pert PRO MPD, Eindhoven, NetherlandsK1 wavelength: 1.5405600 Ǻ
XRD data show that the powder composition is La2Zr2O7
20 30 40 50 60 70 80
Cou
nts
(a.u
.)
2 Theta (deg.)
(2 2 2)
(4 0 0)
(3 3 1)(5 1 1)
(4 4 0) (6 2 2)
(4 4 4)(8 0 0)
(6 6 2)(8 4 0)
13
Synchrotron XRD
In situ Synchrotron XRD shows no compositional change at high temperatures
Wavelength 0.108 Å
2 (o)
Cou
nt (a
.u.)
credit: Yang Ren @ ANL
14
Coating fabrication using APS• La2Zr2O7 coatings were deposited using air plasma spray (APS)
technique by a Praxair patented plasma spray torch.• Haynes 188 superalloy was used as the substrate.
• The bond coat is Ni-based intermetallic LN-65 using APS, with a thickness of 228 μm
• Controlled spray parameters: • Powder feed ratio• Torch current• Torch gas (Argon), Carrier gas (Argon), Shield gas (Argon), Secondary
gas (Hydrogen)• Standoff distance• Sample rig surface rotation speed (RPM and surface speed)
LN-65 Ni Cr Al Y O(w%) 67.3 21.12 9.94 1.02 0.19
Haynes 188 Co Ni Cr W Si C La Fe Mn(w%) 39 22 22 14 0.35 0.10 0.03 3 1.25
15
Outline• Introduction• Coating fabrications• Single ceramic layer (SCL) architecture – dense coating• Double ceramic layer (DCL) architecture• Characterization of physical and mechanical properties• Microstructure• Hardness and Young’s modulus• Bond strength test• Erosion test
• Characterization of thermal properties• Thermal properties• Jet engine thermal shock tests• Thermal gradient mechanical fatigue tests
• Summary and future work
16
Cross sectional view of dense coating 1 2 3
4 5 6
Processing parameters (powder feed rate, surface speed, current, stand off ) were varied to control the porosity.
17
200 400 600 800 1000 1200 1400 1600 1800 2000 22000
20
40
60
80
100
120
140
160
180
200
220
240
260
280
300
■ : 5279-13 line #1 ● : 5279-14 line #2▲ : 5279-15 line #3▼ : 5279-17 line #5◀ : 5279-18 line #6
Youn
g’s
mod
ulus
(GP
a)
Displacement (nm)
Nanoindentation Young’s modulus vs. displacement
18
0
20
40
60
80
100
120
140
160
180
200
159.50 ± 5.73156.00 ± 10.03
133.02 ± 9.52
121.76 ± 6.81116.26 ± 5.85
5279-13 line #1 5279-14 line #2 5279-15 line #3 5279-17 line #5 5279-18 line #6
Youn
g’s
mod
ulus
(GP
a)Nanoindentation Young’s modulus
Specimen species
19
0
1
2
3
4
5
6
7
8
9
10
11
12
Har
dnes
s (G
Pa)
5279-13 line #1 5279-14 line #2 5279-15 line #3 5279-17 line #5 5279-18 line #6
10.2 ± 0.5 8.8 ± 2.1
7.87 ± 0.7
7.3 ± 0.67.0 ± 0.6
Nanoindentation hardness
Specimen species
5279-15 line #310μm 10μm
20
0
1
2
3
4
5
6
H
ardn
ess
(GP
a)
5279-13 line #1 5279-14 line #2 5279-15 line #3 5279-17 line #5 5279-18 line #6
5.41 ± 0.33 5.51 ± 0.255.32 ± 0.28
4.85 ± 0.29 4.82 ± 0.24
Specimen species
Vicker’s indentation hardness
5279-15 line #310μm 10μm
21
Rockwell’s indentation hardness
0102030405060708090
5279-13-#1 5279-14-#2 5279-15-#3 5279-16-#4 5279-17-#5 5279-18-#6
Rockwell hardnessPorosity (%)
• Low density coatings with porosity between 7~10 % were achieved. • Porosity and hardness can be tuned via changing processing conditions• Powder feed rate or current porosity hardness
[Hardness = 1.99×(100-porosity) -100]
22
Outline• Introduction• Coating fabrications• Single ceramic layer (SCL) architecture – porous coating• Double ceramic layer (DCL) architecture• Characterization of physical and mechanical properties• Microstructure and composition• Porosity and hardness• Bond strength test• Erosion test
• Characterization of thermal properties• Thermal properties• Jet engine thermal shock tests• Thermal gradient mechanical fatigue tests
• Summary and future work
23
Cross sections of SCL La2Zr2O7 coatings
#1 #2 #3 #4 #5
24
Vickers hardness indentation
#1 #2 #3 #4 #5
10 µm 10 µm 10 µm
10 µm
10 µm
10 µm 10 µm 10 µm 10 µm 10 µm
10 µm
10 µm
10 µm10 µm10 µm
25
Nanoindentation
5 µm
5 µm 5 µm
5 µm
5 µm5 µm
#3 #4 #5
5 µm
5 µm
5 µm
26
0
1
2
3
4
5
6
H
ardn
ess
(GP
a)
4.22 ± 0.14 4.22 ± 0.20 3.97 ± 0.44 4.09 ± 0.30 3.90 ± 0.45
Samples#1 #2 #3 #4 #5
Vickers indentation hardness
27
0 500 1000 1500 2000 25000
20
40
60
80
100
120
140
160
180
200
220
240
0 500 1000 1500 2000 25000
20
40
60
80
100
120
140
160
180
200
220
240
0 500 1000 1500 2000 25000
20
40
60
80
100
120
140
160
180
200
220
240
0 500 1000 1500 2000 25000
20
40
60
80
100
120
140
160
180
200
220
240
0 500 1000 1500 2000 25000
20
40
60
80
100
120
140
160
180
200
220
240
Yo
ung’
s m
odul
us(G
Pa)
Displacement (nm)
■ : #1■ : #2■ : #3■ : #4■ : #5
Nano indentation Young’s modulus vs. displacement
28
0
20
40
60
80
100
120
140
Youn
g’s
mod
ulus
(Gpa
)
#1 #2 #3 #4 #5
89.04 ± 8.83
104.28 ± 9.45
100.83 ± 4.08101.11 ± 10.72
91.77 ± 14.55
Samples
Nanoindentation Young’s modulus
29
0
1
2
3
4
5
6
7
8
9
H
ardn
ess
(GP
a)
5.24 ± 1.14
6.09 ± 1.06
5.41 ± 0.13
5.41 ± 0.82 4.88 ± 1.44
Samples#1 #2 #3 #4 #5
Nanoindentation hardness
30
Porosity of low density SCL coating
Line # Density (g/cm3) Porosity (%)
7 5.3182 11.36
8 5.2587 12.36
9 5.2584 12.36
10 5.2917 11.81
11 5.2614 12.31
12 5.0089 16.52
Low density coatings with porosity between 11~17% were achieved.
31
Outline• Introduction• Coating fabrications• Single ceramic layer (SCL) architecture• Double ceramic layer (DCL) architecture• Characterization of physical and mechanical properties• Microstructure and composition• Porosity and hardness• Bond strength test• Erosion test
• Characterization of thermal properties• Thermal properties• Jet engine thermal shock tests• Thermal gradient mechanical fatigue tests
• Summary and future work
32
Double ceramic layer (DCL) architectures
Bond coat (NiCrAlY)
Porous La2Zr2O7 top
coat
Substrate (Haynes‐188)
432μm
228 μm 1
27 μ
m
Bond coat (NiCrAlY)
Porous La2Zr2O7 coat
Substrate Haynes‐188
Porous 8YSZ coat
305 μm
228 μm
#6
Bond coat (NiCrAlY)
Porous 8YSZ top coat
Substrate (Haynes‐188)
432μm
228
μm
#7 #8
127 μm
Bond coat (NiCrAlY)
Porous La2Zr2O7 coat
Substrate Haynes‐188
Dense 8YSZ coat
305 μm
228 μm
#9
33
Interfaces of DCL coatings
#6 La2Zr2O7 and bond coat interface
#8 La2Zr2O7 and porous 8YSZ interface #9 La2Zr2O7 and dense 8YSZ interface
#7 porous 8YSZ and bond coat interface
34
Energy-dispersive X-ray spectroscopy
34
Applied heat treatments on sample #8
Heat treatment1080 4h
Ar atmosphere
LD La2Zr2O7, 12 mils
LD 8YSZ, 5 mils
35
Vickers hardness of DCL
0
1
2
3
4
5
6
7
8
9
Sample 9Sample 8Sample 6
La2Zr2O7 layer
Dense 8YSZ layerPorous 8YSZ layer
Har
dnes
s (G
Pa)
Sample 7
3.58±1.013.96±0.6
4.86±1.66
3.21±0.77
7.05±1.01
4.32±0.6
36
Bond strength testEpoxy (FM 1000 adhesive film) to glue coating buttons to a mating cap. Tensile test according to ASTM-C-633.
8YSZLa2Zr2O70
2
4
6
8
10
12
14
16
0
2
4
6
8
10
12
14
16
Sample 7 Porous 8YSZ
Strength
10.48±1.66 MPa
13.59±1.97 MPa
5.31±0.33 kN
Stre
ngth
(MP
a)
Lo
ad (k
N)
Load
6.88±0.99 kN
Sample 6, SCL La2Zr2O7
37
Residual stress distribution in coating
-3.2 -2.8 -2.4 -2.0 -1.6 -1.2 -0.8 -0.4 0.0 0.4-200
-150
-100
-50
0
50
100
150
Res
idua
l stre
ss (G
Pa)
Distance (mm)
Townsend et al
Zhang et al
Bond coat
Substrate
La2Zr2O7
1
( )n
k ki k i
k s s
E tT TE t
1
ni i
si s s
E t TE t
11
22
ns i i
i ii s s
t E t h tE t
21
6n i ii s s
E t TKE t
where α is the coefficient of thermal expansion (CTE), k is the ceramic coating layers range from 1 to n, ti is the thickness of ith layer.
s s sE K z i i iE K z
X.C. Zhang, Thin Solid Films, 488 (2005) 274-282.
where
38
Erosion test
#9, La2Zr2O7 +Dense 8YSZ#7, Porous 8YSZ. #8, La2Zr2O7 +Porous 8YSZ#6, Single layer La2Zr2O7
• 600±0.2g alumina sands with a diameter of 50 μm
• Spray rate 6 g/s; duration 100 s; spray angle 20o
39
0
200
400
600
800
1000
Sample 9Sample 8Sample 7Sample 6
Crit
ical
vel
ocity
(m/s
)
La2Zr2O7
Porous 8YSZ
Dense 8YSZ
Erosion rate & critical erosion velocity
3/4 3
13/4 1/2 3/2105IC
critE KV
H R
Critical erosion velocity is used toexpress the critical condition to initiatecracks [2]:
0
400
800
1200
1600
2000
2400
1562.0±25.8
1858.8±12.8
Sample 9Sample 8Sample 7
Ero
sion
rate
(μg/
g)
Sample 6
831.3±20.7
1914.6±7.3
Erosion rate describes the erosionresistance of TBC sample [1]:
[1] D. Park, Int J Adv Manuf Technol, 23 (2004) 444-450. [2] R.G. Wellman, Wear, 256 (2004) 889-899.
E: Young’s modulusH: hardnessKIC :fracture toughnessρ: density of erodent particleR: particle radius
40
Relationship between Vcrit and erosion rate
800 1000 1200 1400 1600 1800 20000.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
0.016
1/
Crit
ical
vel
ocity
(s/m
)
Erosion rate (g/g)
● Sample 1 ▲ Sample 2■ Sample 3◆ Sample 4
6789
41
Outline• Introduction• Coating fabrications• Single ceramic layer (SCL) architecture• Double ceramic layer (DCL) architecture• Characterization of physical and mechanical properties• Microstructure and composition• Porosity and hardness• Bond strength test• Erosion test
• Characterization of thermal properties• Thermal properties• Jet engine thermal shock tests• Thermal gradient mechanical fatigue tests
• Summary and future work
42
Thermal conductivity
Thermal conductivity is determined from thermal diffusivity Dth, specific heat capacity Cp, and measured density ρ:
Thermal diffusivity is measured using laser flash diffusivity system (TA instrument DLF1200). Specific heat is measured by analytical method (TA instrument DLF1200)
k = Dth·Cp·ρ
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 200 400 600 800 1000
Spe
cific
hea
t (kJ
/kg/
o C)
Temperature (oC)
-
0.2
0.4
0.6
0.8
1.0
1.2
0 200 400 600 800 1000
Ther
mal
con
duct
ivity
(W/m
/o C)
Temperature (oC)
Sample #6 porous La2Zr2O7
Porous 8 wt% YSZ sample
43
Thermal conductivity and heat capacity map
TBC is 90.55% dense (=5.478g/cc), with a nominal thickness of 600mIndentation marks are from previous study
credit: Jiangan Sun @ ANL
44
TBC: Material: La2Zr2O7Thickness: ~600m (this is used in calculation)Density: 90.55% dense, dense density=6 g/cc, so density = 5.478 g/ccSpecific heat: c = 0.54 J/g-K @1000C
Substrate (following are room temperature properties obtained from matweb):Material: Haynes 188Density: = 8.98 g/ccThermal conductivity: k = 10.4 W/m-K,Specific heat: c = 0.403 J/g-K, (therefore, c = 3.62 J/cm3-K)Thickness used in calculation: L = 4 mm (may have a small effect to results)
Sample information
Test conditionFlash thermal imaging test with one flash lampImaging speed: 994 Hz; imaging duration: 3 seconds
Thermal conductivity and heat capacity map
45
Measured TBC thermal properties
Predicted average TBC properties (within red rectangular area): k = 0.55 W/m-K, c = 2.16 J/cm3-K
Thermal conductivity k image Heat capacity c image
0 1 W/m-K 0 2.5 J/cm3-K
These results were based on a TBC thickness of 600 m TBC specific heat @RT: c = 0.393 J/g-K; predicted TBC density is: =c/c=2.16/0.393=5.5 g/cc
credit: Jiangan Sun @ ANL
46
3
4
5
6
7
8
9
10
11
12
0 200 400 600 800 1000 1200 1400
Coe
ffici
ent o
f the
rmal
exp
ansi
on (×
10-6
/K)
Temperature (oC)
This work
LZ CTE expriment ( Lehmann )
8YSZ CTE expriment ( Hayashi )
LZ CTE Experiment ( Zhang )
LZ CTE Experiment ( Kutty )
LZ CTE Experiment ( Xu )
H. Lehmann, D. Pitzer, G. Pracht, R. Vassen, D. Stöver, Journal of the American Ceramic Society, 86 (2003) 1338-1344.H. Hayashi, T. Saitou, N. Maruyama, H. Inaba, K. Kawamura, M. Mori, Solid State Ionics, 176 (2005) 613-619.J. Zhang, J. Yu, X. Cheng, S. Hou, Journal of Alloys and Compounds, 525 (2012) 78-81.K.V.G. Kutty, S. Rajagopalan, C.K. Mathews, U.V. Varadaraju, Materials Research Bulletin, 29 (1994) 759-766C. Xu, C. Wang, C. Chan, K. Ho, Physical Review B, 43 (1991) 5024-5027.
CTE is measured using a BAEHR dilatometer from 25 to 1400 oC.
Coefficient of thermal expansion (CTE)
47
Jet engine thermal shock tests (JETS)• Jet engine thermal shock (JETS) tests are
conducted to investigate the thermal cycling performance.
• TBC samples are heated to 2250 oF (1232.2 oC) at the center for 20 s, and then cooled by compressed N2 cooling for 20 s, and then ambient cooling for 40 s.
• Temperatures are measured by thermal couple and pyrometer.
48
Jet engine thermal shock test (JETS) results
#6, Single layer La2Zr2O7 #7, Porous 8YSZ
#8, Porous 8YSZ+ La2Zr2O7 #9, Dense 8YSZ+ La2Zr2O7
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 10 20 30 40 50
Tem
prea
ture
diff
eren
ce (F
)
Cycles
#6-A
#6-B
#6-C
#7-A
#7-B
#7-C
49
Thermal gradient mechanical fatigue (TGMF)
0 10 20 30 400
200
400
600
800
1000
Time (minute)
Tem
pera
ture
(�)
0
50
100
150
200
Ten
sile
load
(MP
a)
Sample
Sample jig
TorchThermalcouple
Load sensor
Sample Test cycleSCL porous 8YSZ 1200
DCL porous 8YSZ + La2Zr2O7 220
DCL dense 8YSZ + La2Zr2O7 50
At 850 oC
Sample Test cycleDCL porous 8YSZ + La2Zr2O7 38
DCL dense 8YSZ + La2Zr2O7 49
At 1100 oC
50
La2Zr2O7 thermal conductivity calculation1x1x20 super cell
Replicate 20 conventional cells along the heat flow direction to form a super cell
(K)
The calculated thermal conductivity is 1.2 W/m/K at the temperature of 1000 oC, which is reasonably in agreement with the experimentally measured thermal conductivity ~1.5 W/m/K [1].
[1] R. Vassen, X. Cao, F. Tietz, J. Am. Ceram. Soc., 83 (2000) 2023–2028.
51
Imaged based FEM calculation of thermal conductivity of La2Zr2O7 TBC
k=0.723 W/m/K
k=0.538 W/m/K
k=0.550 W/m/K
Thermal conductivity of fully dense LZ k=1.5 W/m/K
SEM image Binary image FEM model
52
0 200 400 600 800 10000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Ther
mal
con
duct
ivity
(W/m
/o C)
Temperature (oC)
Experiment Calculation
Imaged based FEM calculation of thermal conductivity of La2Zr2O7 coating
Calculated thermal conductivity 0.60±0.08 W/m-K, in good agreement with experimental data.
53
Summary• La2Zr2O7 powder, coating microstructure and chemistry
characterizations show that La2Zr2O7 is stable at high temperatures, which makes it suitable for TBC applications.
• Mechanical properties (hardness, bond strength) are similar to 8YSZ.
• Thermal conductivity of La2Zr2O7 is lower than 8YSZ of similar porosity.
• Thermal properties using ab initio and image-based finite element model calculations are in good agreement with experiments.
• Thermal cycling behavior of La2Zr2O7 needs to be improved.
Future work
54
Composite coatings with buffer layers
Bond coat (NiCrAlY)
La2Zr2O7 (50 vol%) +
8YSZ (50 vol%)coat
Substrate
430μm
1
60 μ
m
Bond coat (NiCrAlY)
La2Zr2O7 (50 vol%) +
8YSZ (50 vol%)coat
Substrate
Porous YSZ coat
370μm
1
120 μm
Bond coat (NiCrAlY[1])
La2Zr2O7 (75 vol%) +
8YSZ (25 vol%)coat
Substrate
310μm
2
LZ (25)+YSZ (75)
Porous YSZ coat
60 μm
Composite top coats:thermal conductivity + matching CTEs
Introducing buffer layer:Increasing strain compliance + Decreasing CTEs mismatch
2nd buffer layer:Further decrease CTEs mismatch
Bond coat (NiCrAlY)
La2Zr2O7 (25 vol%) +
8YSZ (75 vol%)coat
Substrate
430μm
2
55
Publications and presentations1. Jing Zhang, Yeon-Gil Jung, Li Li, co-organize “Advanced Coating Materials for Energy and
Environmental Applications” symposium in Materials Science & Technology 2015 (MS&T15), October 4-8, 2015, Columbus, OH
2. Jing Zhang, Yeon-Gil Jung (eds.), 1st International Joint Mini-Symposium on Advanced Coatings, Materials Today: Proceedings, 2014
3. Yeon-Gil Jung, Zhe Lu, Ungyu Paik, and Jing Zhang, Lifetime Performance of Thermal Barrier Coatings in Thermally Graded Mechanical Fatigue Environments, The 11th International Conference of Pacific Rim Ceramic Societies(PacRim-11), Jeju, Korea, August 30 - September 4, 2015
4. Yeon-Gil Jung, Zhe Lu, Qi-Zheng Cui, Sang-Won Myoung, and Jing Zhang, Thermal Durability and Fracture Behavior of Thermal Barrier Coatings in Thermally Graded Mechanical Fatigue Environments, the International Symposium on Green Manufacturing and Applications 2015 (ISGMA 2015), Qingdao, China, June 23 - June 27, 2015
5. Xingye Guo, Jing Zhang, Zhe Lu, Yeon-Gil Jung, Theoretical prediction of thermal and mechanical properties of lanthanum zirconate nanocrystal, the 1st International Conference & Exhibition for Nanopia, Changwon Exhibition Convention Center, Gyeongsangnam-do Province, Miryang City, Korea, November 13-14, 2014
6. Sang-Won Myoung, Zhe Lu, Qizheng Cui, Je-Hyun Lee, Yeon-Gil Jung, Jing Zhang, Thermomechanical properties of thermal barrier coatings with microstructure design in cyclic thermal exposure, the 1st International Conference & Exhibition for Nanopia, Changwon Exhibition Convention Center, Gyeongsangnam-do Province, Miryang City, Korea, November 13-14, 2014
7. Zhang, J., X. Guo, Y.-G. Jung, L. Li, and J. Knapp, Microstructural Non-uniformity and Mechanical Property of Air Plasma-sprayed Dense Lanthanum Zirconate Thermal Barrier Coating. Materials Today: Proceedings, 2014. 1(1): p. 11-16.
8. Guo, X. and J. Zhang, First Principles Study of Thermodynamic Properties of Lanthanum Zirconate. Materials Today: Proceedings, 2014. 1(1): p. 25-34.