MEASUREMENT OF PARTICULATE SIZE BY INSITU LASER-OPTICAL METHODS - CRITICAL-EVALUATION APPLIED TO FUEL-PYROLYZED CARBON

Measurement of the light scattered from carbon particulates obtained from acetylene pyrolysis has been made using a continuous wave (cw) visible laser. Measured quantities include the angular dissymmetry of the scattered light intensity, the dependence of the scattered intensity on incident light polarization, the light extinction at two different wavelengths, and the scattered intensity: extinction ratio. The results are evaluated for their usefulness in determining particulate mean size, size distribution, and number density. It is found that mean size and number density may be obtained, but not the size-distribution shape if the refractive index is poorly known and/or measurements are made outside the forward scattering cone. In addition, it is determined that extinction measurements yield incorrect size results when applied to media that are spatially inhomogeneous. The influence on the sizing results of refractive index uncertainty, different size-distribution functions, and the use of spherical-body scattering theory are discussed in detail. © 1979.