Carbon Nanotube Formation:

C2 Swan Band EmissionsFor Various Ablation Laser Combinations

Carmen RangeLeTourneau University

Longview, TX

NASA Johnson Space CenterThermal Branch

Structures and Mechanics DivisionEngineering Directorate

Increase Production of Carbon Nanotubes

Understand the chemical mechanism

modify current methods or design new methods

Laser Ablation

target

tube

Previous Work

Laser Sample

Optics

Detector

Based on Laser Induced Fluorescence

C2 LIF

Previous ResultsC2 LIF

473.0 473.1 473.2 473.3 473.4 473.5 473.6 473.7 473.8

Wavelength (nm)

Previous ResultsNi LIF

225.0 225.2 225.4 225.6 225.8 226.0

wavelength (nm)

Experimental Setup

Ablation LasersGraphiteTarget

Various combinations involving 3 ablation lasers

Emission Collected by a Fiber Optic

Monochromator disperses emmision onto an ICCD

' = 0

1

2

' = 0

1

2

3

4

20023 cm-1

0 cm-1

C2 Energy Levels

d3g

a3u

X1u+

Vibrational BandsVibrational Bands

Vibrational Bands

Δv = 0Δv = 0

Baseline Variations

Baseline VariationsBaseline Variations

File Lasers Modified Fit Unmodified Fit00jan21e IR Gr Gr 9600 K 9600 K

00jan6e Gr Gr IR 9600 K 9600 K

99dec20e IR Gr IR 8800 K 8800 K

99dec22f IR IR Gr 8600 K 8800 K

00jan21h IR Gr Gr 8000 K 8300 K

00jan6h Gr Gr IR 7600 K 8100 K

99dec22h IR IR Gr 7900 K 8000 K

00jan6g Gr Gr IR 7800 K 8000 K

00jan21g IR Gr Gr 7800 K 7900 K

99dec22i IR IR GR 7800 K 7900 K

99dec20g IR Gr IR 7700 K 7800 K

99dec20h IR Gr IR 7600 K 7700 K

Baseline Variations

Trends in TemperatureTrends in Temperature

Trends in Temperature

Temperature FitsTemperature Fits

Temperature FitsTemperature Fits

File Lasers Delay Slit Width Ratio of Δv = 1 & 0

Ratio of Δv = 1 & -1

00jan21e IR Gr Gr 1500 100 9600 K 6500 K

00jan6e Gr Gr IR 1500 100 9600 K 6300 K

99dec20e IR Gr IR 1500 100 8800 K 6000 K

99dec22f IR IR Gr 1500 100 8800 K 5900 K

00jan21h IR Gr Gr 5000 500 8300 K 5900 K

00jan6h Gr Gr IR 5000 500 8100 K 5900 K

00jan6g Gr Gr IR 5000 100 8000 K 6200 K

99dec22h IR IR Gr 5000 100 8000 K 6400 K

00jan21g IR Gr Gr 5000 100 7900 K 6200 K

99dec22i IR IR Gr 5000 500 7900 K 5800 K

99dec20g IR Gr IR 5000 100 7800 K 6000 K

99dec20h IR Gr IR 5000 500 7700 K 5800 K

Temperature Fits

Conclusions

• Different ablation laser combinations result in different C2 emmission spectra.

• Shorter wavelength lasers result in spectra with greater intensity and warmer temperatures.

• Fitting is complicated by a broad underlying contribution of uncertain origin.

• Spectra does not appear to fit well to a single temperature.

Future Work

• Further analysis of the 3 laser spectra.

• Analysis of data from Parametric Studies.

• Computational modeling for:– nanotube behavior and properties

– molecular intermediates

Acknowledgement

Carl ScottSivaram ArepalliWilliam HolmesPasha Nikolaev

Brad Files

SFF NASA-ASEE