Formation, growth and deposition of particles represent a critical part of several important industrial processes, such as production of carbon black, optical fibers, micro-electronic components, and metal and ceramic powders. Laser diagnostic techniques are utilized to develop a fundamental understanding of these processes.
Formation of carbonaceous soot particles has been studied in laminar, coannular, hydrocarbon diffusion flames. Laser extinction/scattering, laser scattering dissymmetry, and velocimetry measurements have been used to determine particle volume fraction, size, number density and velocity. From this set of data, particle formation and growth rates have been determined for different fuels and at different temperatures. Similar techniques have been used to study silica particle formation in an opposed jet diffusion flame, where silicon is introduced in the form of silane (SiH4) into the fuel stream (H2/Ar); the oxidant is an O2/Ar mixture. The advantage of this geometry is that, along the stagnation point streamline, the flow may be considered one-dimensional. This should allow the extension of the results of this study to practical CVD or MCVD processes for optical fibers. Laser diagnostic techniques are also being used to investigate metal powder atomization processes, and the effect of operating conditions on particle size distribution.