Optimization of the purification procedure for single-walled

carbon nanotubes

By: Steven WehmeyerSupervisor: Dr. Ajay Malshe

Summer REU

Mechanical Engineering Department Colleagues in MMRL Financial Support from ONR Dr. Malshe, Dr. Demytro, Dr. Benamara,

Ranjith John.

Acknowledgements

Electronics◦ Transistors

Cell phones Computers

Biomedical◦ Cancer treatment

Ballistic◦ Body armor

Applications

Amazing properties◦ Thermal conductivity 6600 W/m-K

2-3 times higher than diamond◦ Elastic Modulus 1-5 TPa

3-4 times higher than diamond Steel ~ .2 TPa

◦ Electrical conductivity 10^4 S/cm Gold 4.5x10^5 S/cm

Need to be pure to take full advantage of properties

Importance of Carbon Nanotubes

High Pressure catalytic decomposition of carbon monoxide (HIPCO)

Arc discharge Laser ablation CVD

Synthesis

Synthesis (HIPCO)

Raw material◦ High Pressure catalytic decomposition of carbon monoxide

(HIPCO) from Unidym◦ Elicarb from Swan Chemical Inc.

Oxidize Heat

Acid reflux Hydrochloric Acid (HCl)

Purified SWNT Characterize

◦ Transmission Electron Microscope◦ Thermogravimetric Analysis◦ Raman Spectroscopy

Time= 3-4 days

General purification

Combine oxidation and acid reflux3

◦ H2O2 for oxidizing and HCl for acid reflux Different concentrations Fenton’s reagent

Combine with carbon nanotubes and heat mixture (90-110°C) for eight hours to accelerate processes

Vacuum Filtration Heat to remove moisture Characterize

◦ TEM, TGA, Raman Spectroscopy Time= 1 day

Method of Purification Used

Design of ExperimentHIPCO Run

OrderA:Reaction

TempB:Concentratio

n

TGA Respons

e

Raman Spectroscopy

Response  1 90 6M      2 80 1M      3 110 3M      4 100 3M      5 110 6M      6 80 6M      7 80 3M      8 90 3M      9 90 1M      10 100 1M      11 110 1M      12 100 6M    

Results

Vacuum FiltrationIron Dissolution

Characterization - TEM

P7 P8

TGA◦ Analysis will occur Tuesday through Friday at

UALR◦ Looking for % wt purity. Burns sample and iron is

left. Percent purity can then be obtained. Raman Spectroscopy

◦ Light scattering Technique. Uses laser to excite phonons and shift their energy level. These Raman shifts can be used to determine information about the carbon nanotubes. Looking for diameter and length of nanotubes.

Characterization

Carbon nanotubes were purified as indicated by iron dissolution◦ Percent pure not known yet◦ TEM images have shown that no big impurities

exist in samples Process works

◦ Further work may be needed to optimize further Further results and conclusions will be

known after analyzing samples at UALR

Conclusions

1. Benamara, Mourad. TEM images.2. Unalan, Husnu Emrah.  “Single walled carbon nanotube

thin films: Properties and applications”  Diss. Rutgers The State University of New Jersey, New Brunswick, 2006. Dissertations & Theses: Full Text. ProQuest. 28 May. 2009

3. Wang, Yuhuang, Hongwei Shan, Robert H. Hauge, Matteo Pasquali, and Richard E. Smalley, “A highly selective, one-pot purification method for single-walled carbon nanotubes” The Journal of Physical Chemistry B 111.6 (24 January 2007): 1249-1252

References