In-situ optical analysis of the gas phase during the formation of carbon nanotubes.

A reactor has been developed at ONERA to investigate the gas phase during carbon nanotube formation by laser-induced fluorescence (LIF), Laser-induced incandescence (LII), coherent anti-Stokes Raman Scattering (CARS), and emission spectroscopy. Continuous vaporization is achieved with a continuous wave CO2 laser. Optimized conditions are used for single-walled nanotube growth, that is, a graphite target doped with 2 atom % Ni and 2 atom % Co, helium as buffer gas at a flow rate of 50 ml/s, and a pressure of 300 hPa.

Simultaneous temperature and sensitive two-species concentration measurements by single-shot CARS.

Simultaneous spatially and temporally resolved measurements of N(2) and O(2) mole fractions and of temperature are performed using coherent anti-Stokes Raman scattering (CARS). The CARS setup is used with the crossed-beam arrangement (BOXCARS) and nonresonant-background suppression. The technique employs two Stokes lasers, broadband and narrowband, in combination with a frequency-doubled Nd:YAG laser.

Spatial averaging and multiplex coherent anti-Stokes Raman scattering temperature-measurement error.

We discuss the effect of spatial averaging within the probe volume on multiplex coherent anti-Stokes Raman scattering temperature measurements. A numerical simulation and an experimental verification on a small laminar flame burner were performed. Appreciable measurement errors can be made in reactive laminar or turbulent media with large gradients.