The Search for Baby Nanotubes (SFBN)September 30, 11 am, Berry Aud.

See www.letu.edu/chemphys and the fall seminar link for a complete listing of all seminars.

Target Surface Temperature and

In situ Detection of Carbon Nanotubes

During Production in a Laser Produced Plume

Gary DeBoerLeTourneau University

Longview, TX

NASA Johnson Space CenterThermal Branch

Structures and Mechanics DivisionEngineering Directorate

Summer, 2004

Some carbon allotropes

graphite

diamond

C60

nanotube

Tensile Strength Comparison of Engineering Materials, GPa

1.5

3.4

4.7

50

0 10 20 30 40 50 60

Stainless Steel

Aramid (Kevlar)

Carbon Fiber

CarbonNanotubes

Ref: Brad Files

Making Tubes: Laser Ablation

target

tube

one method of making carbon nanotubes

SEM of Nanotube Bundleshttp://mmptdpublic.jsc.nasa.gov/jscnano/Photo%20Gallery.htm

TEM carbon nanotube ropes

smalley.rice.edu

Experimental method

For LIF studies of:

C2 and Ni

Nickel and C2

Laser Induced Fluorescence (LIF)Lifetimes Ni atom: millisecondsC2: 100 microseconds

DeBoer et al.J. Appl. Phys. A., 89, 5760 (2001)

0 500 1000 1500 2000

1mm From Target2mm From Target3mm From Target (x10)

Pump-Probe Delay ( s)

473.0 473.1 473.2 473.3 473.4 473.5 473.6 473.7 473.8

Wavelength (nm)

Co

Laser Induced Luminescence (LIL)

Lifetimes:Co atom millisecondsCarbon seconds

Geohegan et al.Appl. Phys. Letts., Vol. 76 (3) p 182 (2000)

Cast of characters1. Ni and Co atoms2. hot and cold C2 3. nondescript Cn 4. carbon nanotubes

star has not yet appeared on the production stage

What is under?

What is under?

What is under?

What is under? Saturn Rocket Park!

Saturn Rocket Park

Saturn Rocket Park

Designs and goals to uncover the nanotube picture

1. Surface temperature measurement• incorporate into modeling projects

• correlate measured surface temperatures to other measured values

2. Detect nanotubes during their formation by absorption

• chemical mechanisms

• plume dynamics

• feasibility of use as production control feedback

Y-Tube designHow do we measure target surface

temperature?1. collect emission with fiber optic2. disperse with spectrometer3. record with a CCD

fiber optic focusing lens

target

ablation lasers

black body emission

1 inch tube

translatable stage

Surface Temperature

Optical setup for surface temperature experiment using y-tube

Laser 1Gr

532 nm

Laser 2IR

1064 nm

ICCD

DDG

650 700 750 800 850 900 950 1000

3456789

wavelength (nm)

0

5000

10000

15000

20000

300 400 500 600 700 800 900 1000

Black Body Radiation

1473 K

2000 K

2500 K

wavelength (nm)

Quick, approximate,

relative comparison

Analysis Method 1

Temperatures obtained by relative ratio to 1473 at a given wavelength

1400

1600

1800

2000

2200

2400

2600

2800

3000

0 500 1000 1500 2000 2500 3000

Surface Temperature vs Position

surface temperature at zerosurface temperature at 1 mm insurface temperature 2 mm inSurface Temperature at 3 mm inSurface Temperature at 4 mm in

delay w/r to lasers (ns)

Analysis Method 1

Temperature as a function of time and

image.

Quick, approximate,

relative comparison

0

50000

100000

150000

200000

400 500 600 700 800 900 1000

Surface Temperature Analysis(Zero position at 0 ns delay)

6 corrected by response factor3000400050005500

wavelength (nm)

0

200

400

600

800

1000

1200

1400

400 500 600 700 800 900 1000

Surface Temperature Analysis(Zero position background radiation)

13 background corrected by response factor

1473

wavelength (nm)

Analysis Method 2

Temperatures obtained by fitting response corrected

spectra to black body curves.

Slower, more tedious process.

Produces a higher temperature than

ratio method.

Surface Temperature Experiments

1. standard production method.2. ablation lasers operated singly.3. ablation lasers operated in reverse order.4. ablation lasers operated with time delays of 0, 50, and

500 nanoseconds..5. varying argon flow rates, 100 (standard), 300, and 500.6. helium as a buffer gas, rather than argon.7. oven temperatures of 1200 (standard), and 1000,

degrees Celsius.8. position of emission collection, from edge of target to

center of target.

Optical setup for surface temperature using y-tube

after experiment

Detection of nanotubes in situ?

Must understand the physical nature of the tubes…

9,0

5

45,4

Indexing of nanotubes

n,0 zigzag n, n-1 armchair

Electronic Properties of Nanotubes

Energy is a function of:

diameter and chirality

(n-m)/3 = remainder of

1 or 2 semiconductor

0 metallic

different tubes different energy spacing

Laser Tubes

Sergei Lebedkin

Universitat Karlsruhe, Karlsruhe Germany

J. Phys. Chem. B. Vol. 107 p. 1949-1956 (2003)

use spectroscopy to detect tubes in situ…

Last Summer’s Design

1. Populate excited state with tunable dye laser2. Collect emission with fiber optic3. Disperse emission with NIR spectrometer

fiber optic

targetablation lasers (533 and 1064 nm)

1 inch tube

3/4 inch tube

translatable stage

dye laser (tunable)

NIRspectrometer

nanotube emission

Spectrometer did not work as advertised

Spectrom

eter

ICCD

lens

aperature

window Fiber optic

Graphite target

White Light Source

Ablation lasers

Green

Red

Translatable support rod

This Summer’s Design1. White light introduced2. Collect transmitted light with fiber optic3. Disperse transmitted light with a spectrometer onto an ICCD to

determine absorbed wavelengths.

Stainless steel

Success: in principle

Optical Setup for Absorption Experiment using X-tube

Absorption Results

0 500 1000 1500 2000 2500 3000 3500

7-20-04 Relative Transmission at 2 cm from Target vs Time

delay (microseconds)

See broad band absorption that covers a long period of time

600 650 700 750 800

Nanotube absorbance experiments 7-20-042 cm from target

32 lasers off lamp on33 2 cm 100 micros34 2 cm 200 micros35 2 cm 400 micros36 2 cm 600 micros37 2 cm 800 micros38 2 cm 1000 micros39 2 cm 1500 micros40 2 cm 2000 micros41 2 cm 2500 micros42 2 cm 3000 micros43 lasers off lamp on

wavelength (nm)

100000

120000

140000

160000

180000

200000

220000

240000

260000

600 650 700 750 800

Nanotube absorbance experiments 7-22-042 cm from target

15 laser off

16 -20

17 -10

18 0

19 10

20 20

21 30

wavelength (nm)

-50 0 50 100 150 200

160000

180000

200000

220000

240000

260000

delay (microseconds)

100% Transmission

0 5000 10000 15000delay (microseconds)

100% Transmission

Absorption seems to reach a

steady state, after a few

hundred microseconds

Is this difference real, reproducible? Don’t know.

0

200000

400000

600000

800000

1000000

600 650 700 750 800

Nanotube absorbance experiments 7-22-04 and 7-23-04Normal and Blank Targets5 mm from target surface

normal target

blank

Difference

wavelength (nm)

Summer Conclusions

• The y and x tubes significantly improve the diagnostic environment, but

– Challenges to reproducibility remain due to1. Pitting of target2. Obstruction of optical components by deposits

• Collected data from surface temperature measurements.

• Collected data from absorption measurements.• Data need additional analysis• I had a great time

Summer Follow-ups

• More analysis of surface temperature data.– obtain temperatures from curve fits.

– relate results to existing models.

• More analysis of absorption data.– Compare differences with blank

– Correct for response and look for spectral features

• Propose improvements to current absorption approach to avoid pitting and depositions.

What other actors should we look for in situ?• metal clusters.• bucky balls (may be spectroscopic methods).• open vs closed tubes.• tubes detected based on length.

Spectroscopy applications• nanotube characterization (chirality, diameter).• quantitative dispersion measurements.• nanotube selective chemistry.• sorting (destroying) of tubes based on chirality and diameter.

Longer Term Follow-Ons

Acknowledgements

William Holmes Sivaram ArepalliPasha Nikolaev

Carl ScottLeonard Yowell

NASA-ASEE Faculty Fellow Program (NFFP)