carbon nanotube formation detection of ni atom and c 2 gary deboer letourneau university
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Carbon Nanotube Formation Detection of Ni atom and C 2 Gary DeBoer LeTourneau University Longview, TX NASA Johnson Space Center Thermal Branch Structures and Mechanics Division Engineering Directorate Summer, 2000. by Laser Induced Fluorescence. What are Carbon Nanotubes?. - PowerPoint PPT PresentationTRANSCRIPT
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Carbon Nanotube FormationDetection of Ni atom and C2
Gary DeBoerLeTourneau University
Longview, TX
NASA Johnson Space CenterThermal Branch
Structures and Mechanics DivisionEngineering Directorate
Summer, 2000
byLaser Induced Fluorescence
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What areCarbon Nanotubes?
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SEM of Nanotube Bundles
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Why should we care?
Strong light-weight materials
Thermal and electrical properties
Gas (hydrogen) storage
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What’s the Problem?
Nanotubes from Tubes@Rice Price = $1000/gram Minimum order = 250 milligrams Please order in 1/4-gram increments only.
Carbon nanotubes, single-walledSigma-Aldrich Package Sizes US $ 100MG 395.90 500MG 1624.00Product Comments: CarboLex SE- grade, 12-15 angstrom
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Increase Production
Understand the chemical mechanism
(particularly the role of the catalyst)
modify current methods or design new methods
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Nanotube Formation Theories• Atomic scooter
• Metal clusters (nm diameters)
• Melt (m sized particles or droplets)
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Laser Induced Fluorescence (LIF)
Laser Sample
Optics
Detector
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Nanotube diagnostics
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Laser Ablation
target
tube
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Plume Emission Spectrum
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Physical Principles for C2 LIF
Upper electronic state
Intermediate state
DetectorL
ong wavelength filter
Detector
Fluorescence at 513 nm
Absorbance at 473 nm
Lower electronic state
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C2 LIF
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C2 Rotational Spectra
470.0 470.5 471.0 471.5 472.0 472.5 473.0 473.5 474.0
wavelength (nm)
P Branch
Q Branch
R Branch
All Branches
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Rotational Temperature
473.0 473.1 473.2 473.3 473.4 473.5 473.6 473.7 473.8
700600500400300
Wavelength (nm)
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DDG
Boxcar Averager
Laser 2IR
1064 nm
Laser 3Dye Pump
355 nm
Laser 4Dye
tunable
Energy meter
ICCD
LeCroy or Digital Scope
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C2 Experiment and Synthetic
473.0 473.1 473.2 473.3 473.4 473.5 473.6 473.7 473.8
Wavelength (nm)
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C2 Rot Temperature and Intensity
340
350
360
370
380
390
400
410
0 10 20 30 40 50
Pump-Probe Delay ( sec)
Open = Rotational TemperatureFilled = Bandhead Intensity
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C2 Rot Temperature and Position
100
200
300
400
500
600
700
800
0 1 2 3 4 5
Imaging Distance from Target (mm)
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Summary of C2 LIF results
• Lifetimes of more than 50 s
• Rotational temperatures 300-700 K
• Rotational temperature is proportional to intensity
• Signal can be seen up to 5 mm from the target surface
• Signal propagates at 50 m/s
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Physical Principles for Ni LIF
filter detector
Absorbance 224-226 nm
non radiative decay
Fluorescence at 301 nm
intermediate state
Lower electronic state
Upper electronic state
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Nickel Transitions in LIF
224.
452
3F2 ________________________ (45419)3F3 ________________________ (45281)3D1 ________________________ (45122)
3G3 ________________________ (44565)3D2 ________________________ (44475)?? ________________________ (44336)5D3 ________________________ (44206)
1D2 _________________________ (36601)
1F3 _________________________ (35639)
3D1 _________________________ (34409)
3D2 _________________________ (33611)3D3 _________________________ (33501)3F3 _________________________ (33112)
1D2 _________________________ (3410
3D1 _________________________ (1713)
3D2 _____________________________________________________________ (879.8)
3D3 _____________________________________________________________ (204.8)3F4 _________________________________________________________________ (0)
Las
er I
nd
uce
d E
xcit
atio
n (
nm
air
)
301.200________________(36601) mair
Collected
Em
ission
225.
149
225.
357
nm22
5.48
0
226.
143
225.
815
225.
956
300.249
303.793________________(36601) mair
305.764
310.156________________(36601) m
air
310.188________________(36601) m
air
313.410________________(36601) m
air
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Laser 1Gr
532 nm
DDG 1
DDG 2
Boxcar Averager
60 Hz - 10 Hz
Laser 2IR
1064 nm
Laser 3Dye Pump
355 nm
Laser 4Dye
tunable
Energy meter
ICCD
LeCroy or Digital Scope
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Nickel LIF Spectra
225.0 225.2 225.4 225.6 225.8 226.0
wavelength (nm)
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Ni Experiment and Synthetic
225.0 225.2 225.4 225.6 225.8 226.0
wavelength (nm)
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Nickel Temperature
225.2 225.4 225.6 225.8 226.0
Wavelength (nm)
A
B
a. 0 b. 204c. 879
c
b
b
c
a
0 10 20 30 40 50
0 500 1000 1500 2000
Pump-Probe Delay (s)
hot
cold
hot
cold
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Nickel Propagation
0 500 1000 1500 2000
1mm From Target2mm From Target3mm From Target (x10)
Pump-Probe Delay ( s)
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Summary of Ni LIF Results• Lifetime of several milliseconds with a hot
target, 20 microseconds with a room temperature target
• Electronic temperatures from 200 - 1500 K
• Electronic temperature is proportional to signal intensity
• Signal can be seen up to 3 mm from the target
• Signal propagates at about 10 m/s
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Co resultsLaser Induced Luminescence(LIL)
Lifetimes:Co atom millisecondsCarbon seconds
Geohegan et al.Appl. Phys. Letts., 2000, 76 (3) p 182
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Other Observations
• Hot emission and cooler LIF is not unique. Brinkman, Appl. Phys. B, 1996 64 p. 689 Pobst, IEPC, 1995 95 (28) p. 203 Raiche, Appl. Opt. 1993 32 p. 4629
• Ablation: small molecules and atoms. Becker, Nanostructured Materials, 1998 10 (5) p. 853 Song, Applied Surface Science, 1998 127-129 p 111 Aguilera, Applied Surface Science, 1998 127-129 p. 309 Dillon, Advances in Laser Ablation of Materials (USA), 1998 p. 403-408
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Summary of Results• ablation produces small molecules and atoms
(lifetimes)
• C2 - hot emission 50 s C2 - cooler LIF/LIL 100 s
• Ni and Co LIF/LIL 3 ms
• Cn LIL 3 s
• C2 propagation 50 m/s
• Ni propagation 10 m/s
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Conclusions
• Inconsistent with the melt theory
• Consistent with atomic catalyst theory
• Could be consistent with small metal cluster theory
• Need to know when and where nanotubes are formed
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Future Work
• Analysis of three laser ablation experiments
• Analysis of DC arc spectra
• Further parametric studies
• C2 LIF using two ablation lasers
• Computational modeling for– nanotube formation mechanisms– nanotube interactions with other materials
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Acknowledgements
Sivaram ArepalliWilliam HolmesPasha Nikolaev
Carl ScottBrad Files
SFF NASA-ASEE