The Search for Baby Nanotubes (SFBN) September 30, 11 am, Berry Aud. See 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 DeBoer LeTourneau University Longview, TX NASA Johnson Space Center Thermal Branch Structures and Mechanics Division Engineering Directorate Summer, 2004

Some carbon allotropes graphite diamond C 60 nanotube

Ref: Brad Files

Making Tubes: Laser Ablation target tube one method of making carbon nanotubes

SEM of Nanotube Bundles

TEM carbon nanotube ropes smalley.rice.edu

Experimental method For LIF studies of: C 2 and Ni

Nickel and C 2 Laser Induced Fluorescence (LIF) Lifetimes Ni atom: milliseconds C 2 : 100 microseconds DeBoer et al. J. Appl. Phys. A., 89, 5760 (2001)

Co Laser Induced Luminescence (LIL) Lifetimes: Co atom milliseconds Carbon seconds Geohegan et al. Appl. Phys. Letts., Vol. 76 (3) p 182 (2000)

Cast of characters 1. Ni and Co atoms  2. hot and cold C 2  3. nondescript C n  4. carbon nanotubes  star has not yet appeared on the production stage

What is under?

What is under? 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 design How do we measure target surface temperature? 1.collect emission with fiber optic 2.disperse with spectrometer 3.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 1 Gr 532 nm Laser 2 IR 1064 nm ICCD DDG

Quick, approximate, relative comparison Analysis Method 1 Temperatures obtained by relative ratio to 1473 at a given wavelength

Analysis Method 1 Temperature as a function of time and image. Quick, approximate, relative comparison

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 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…

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 (2003) use spectroscopy to detect tubes in situ…

Last Summer’s Design 1. Populate excited state with tunable dye laser 2. Collect emission with fiber optic 3.Disperse emission with NIR spectrometer fiber optic target ablation lasers (533 and 1064 nm) 1 inch tube 3/4 inch tube translatable stage dye laser (tunable) NIR spectrometer nanotube emission Spectrometer did not work as advertised

Spectrometer ICCD lens aperature windowFiber optic Graphite target White Light Source Ablation lasers Green Red Translatable support rod This Summer’s Design 1. White light introduced 2. Collect transmitted light with fiber optic 3.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 See broad band absorption that covers a long period of time

Absorption seems to reach a steady state, after a few hundred microseconds

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

Summer Conclusions The y and x tubes significantly improve the diagnostic environment, but –Challenges to reproducibility remain due to 1.Pitting of target 2.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 Arepalli Pasha Nikolaev Carl Scott Leonard Yowell NASA-ASEE Faculty Fellow Program (NFFP)