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Carbon Nanotube Formation Detection of Ni atom and C 2 Gary DeBoer LeTourneau University

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?.

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Carbon Nanotube Formation Detection of Ni atom and C 2 Gary DeBoer LeTourneau University

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  1. Carbon Nanotube Formation Detection of Ni atom and C2 Gary DeBoer LeTourneau University Longview, TX NASA Johnson Space Center Thermal Branch Structures and Mechanics Division Engineering Directorate Summer, 2000 by Laser Induced Fluorescence

  2. What areCarbon Nanotubes?

  3. SEM of Nanotube Bundles

  4. Why should we care? Strong light-weight materials Thermal and electrical properties Gas (hydrogen) storage

  5. 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-walled Sigma-Aldrich Package Sizes US $ 100MG 395.90 500MG 1624.00 Product Comments: CarboLex SE- grade, 12-15 angstrom

  6. Increase Production modify current methods or design new methods Understand the chemical mechanism (particularly the role of the catalyst)

  7. Nanotube Formation Theories • Atomic scooter • Metal clusters (nm diameters) • Melt (mm sized particles or droplets)

  8. Laser Induced Fluorescence (LIF) Detector Optics Laser Sample

  9. Nanotube diagnostics

  10. Laser Ablation target tube

  11. Plume Emission Spectrum

  12. Physical Principles for C2 LIF Upper electronic state Fluorescence at 513 nm Long wavelength filter Detector Detector Absorbance at 473 nm Intermediate state Lower electronic state

  13. C2 LIF

  14. C2 Rotational Spectra

  15. Rotational Temperature

  16. ICCD LeCroy or Digital Scope Energy meter Boxcar Averager Laser 3 Dye Pump 355 nm DDG Laser 4 Dye tunable Laser 2 IR 1064 nm

  17. C2 Experiment and Synthetic

  18. C2 Rot Temperature and Intensity

  19. C2 Rot Temperature and Position

  20. Summary of C2 LIF results • Lifetimes of more than 50 ms • 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

  21. Physical Principles for Ni LIF Upper electronic state non radiative decay intermediate state filter detector Fluorescence at 301 nm Absorbance 224-226 nm Lower electronic state

  22. Nickel Transitions in LIF

  23. ICCD LeCroy or Digital Scope Energy meter Laser 1 Gr 532 nm Boxcar Averager DDG 2 Laser 3 Dye Pump 355 nm DDG 1 60 Hz - 10 Hz Laser 4 Dye tunable Laser 2 IR 1064 nm

  24. Nickel LIF Spectra

  25. Ni Experiment and Synthetic

  26. hot A a. 0 b b. 204 c. 879 a b c c hot cold B 0 10 20 30 40 50 cold 225.2 225.4 225.6 225.8 226.0 Wavelength (nm) 0 500 1000 1500 2000 Pump-Probe Delay (ms) Nickel Temperature

  27. Nickel Propagation

  28. 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

  29. Co resultsLaser Induced Luminescence(LIL)Lifetimes:Co atom millisecondsCarbon secondsGeohegan et al.Appl. Phys. Letts., 2000, 76 (3) p 182

  30. 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. 853Song, 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

  31. Summary of Results • ablation produces small molecules and atoms (lifetimes) • C2 - hot emission 50 ms C2 - cooler LIF/LIL 100 ms • Ni and Co LIF/LIL 3 ms • Cn LIL 3 s • C2 propagation 50 m/s • Ni propagation 10 m/s

  32. 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

  33. 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

  34. AcknowledgementsSivaram ArepalliWilliam HolmesPasha NikolaevCarl ScottBrad FilesSFF NASA-ASEE

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