Application of laser-induced incandescence to the detection of carbon nanotubes and carbon nanofibers.
Laser-induced incandescence applied to a heterogeneous, multielement reacting flow is characterized by temporally resolved emission spectra, time-resolved emission at selected detection wavelengths, and fluence dependence. Two-pulse laser measurements are used to further probe the effects of laser-induced changes on the optical signal. Laser fluences above 0.6 J/cm2 at 1064 nm initiate laser-induced vaporization, yielding a lower incandescence intensity, as found through fluence-dependence measurements. Spectrally derived temperatures show that values of excitation laser fluence greater than this value lead to superheated plasmas with temperatures well above the vaporization point of carbon. The temporal evolution of the emission signal at these fluences is consistent with plasma dissipation processes, not incandescence from solidlike structures. Two-pulse laser experiments reveal that other material changes are produced at fluences below the apparent vaporization threshold, leading to nanostructures with different optical and thermal properties.
Vander Wal
Randy L
RL
National Center for Microgravity Research on Fluids and Combustion, NASA Glenn Research Center, Cleveland, Ohio 44135-3191, USA. randy@rvander.grc.nasa.gov
Berger
Gordon M
GM
Ticich
Thomas M
TM
Patel
Premal D
PD