Physics, Instrumentation and Sensing

Optical diagnostics of nanotubes synthesis

Laser-vaporization reactor of nanotubes synthesis
(DMSC/DMPH-ONERA Palaiseau).

In situ gas phase analysis during the formation of nanotubes has been undertaken together with the Annick Loiseau’s team from Microstrutures Research Laboratory (LEM/ONERA-CNRS).

The aim is to improve the synthesis process of single-wall nanotubes (SWNTs) of different types (carbon, BN, BCN) which requires a deeper understanding of the nanotubes growth mechanism. A dedicated laser-vaporization reactor using a continuous CO₂ laser has been developed in 1998 at ONERA Palaiseau by DMSC and DMPH teams. The SWNTs of carbon were successfully produced in 1999 and those of BN in 2001.

The task of our team (DOP, Optical Diagnostics and Plasma) was to investigate in situ the vaporization plume where nanotubes are growing by a complete set of laser techniques (Raman scattering, LIF-Laser Induced Fluorescence, LII - Laser Induced Incandescence). The first optical diagnostics were achieved in 2001 [1]. The gas temperature gradient above the carbon/catalysts and BN targets has been measured by coherent anti-Stokes Raman scattering.

The measured temperature gradient has served to validate the fluid dynamics simulations of the laser-vaporization reactor by means of the MSD code from ONERA (DEFA). LIF spectroscopy has been applied to probe the atomic and molecular species formed in the vaporization plume. In the case of carbon/catalysts plume, Ni, Co, Fe, Y atoms and C₂, C₃ molecules have been diagnosed. Our German colleagues from DLR-Stuttgart have applied the LII technique to image the condensed soot particles and to measure the sizes distribution [2]. These laser optical diagnoses associated to the temperature gradient have evidenced the phase transformations vapor-liquid-solid of the chemical species during the synthesis of carbon SWNTs. Also, by comparing the LIF measurements of Ni, Co with the chemical kinetics calculations by our American colleague C.D. Scott from JSC/NASA center at Houston, the evaporation and condensation routes of Ni and Co were found different [3].

In 2003, we have begun the in situ study of BN nanotubes synthesis. The on-going laser spectroscopic investigations will provide us with the nature and the status (vapor, liquid, solid) of the synthesized species (boron, oxides, nanotubes, BN particles...). In the meantime, ex situ UV-photoluminescence experiments of the BN nanotubes will be carried out in the laboratory [4]. By crossing over the ex situ and in situ optical diagnostics, we expect to determine the optical signature of a BN nanotube.

References

• [1] N. Dorval, A. Foutel-Richard, M. Cau, A. Loiseau, B. Attal-Trétout, JL. Cochon, D. Pigache, P. Bouchardy, V. Krüger and K.P. Geigle, In situ optical analysis of the gas phase during the formation of carbon nanotubes, Journal of Nanoscience and Nanotechnology 4, 450-462 (2004).
• [2] M. Cau, N Dorval, B. Attal-Trétout, J.L. Cochon, D. Pigache, A. Loiseau, V. Krüger, M. Tsurikov, Formation of carbon nanotubes: In situ optical analysis using LII and LIF, Phys. Review B, à paraître 2006.
• [3] M. Cau, N. Dorval, B. Cao, B. Attal-Trétout, J.L. Cochon, A. Loiseau, S.Farhat, and C.D. Scott, Spatial evolutions of Co and Ni atoms during single-walled carbon nanotubes formation : measurements and modeling, Journal of Nanoscience and Nanotechnology, a paraître 2006.
• [4] J.S. Lauret, R.Arenal de la Concha, A.Loiseau, M.Cau, B. Attal-Tretout, E. Rosencher and L. Goux-Capes, Optical transitions in single wall boron nitride nanotubes, Phys. Rev. Letters 94, 037405 (2005).

Laser-vaporization reactor of nanotubes synthesis
(DMSC/DMPH-ONERA Palaiseau).

Zone of synthesis diagnosed in situ by laser techniques.

Comparison between LIF measurements and kinetics calculations of Ni and Co atoms in the laser-vaporization reactor [3].

Last Update: 15 January 2007 - © ONERA 2009 - Terms of use