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Physical Mechanisms of Carbon Formation in Flames.
PURDUE UNIV LAFAYETTE IND PROJECT SQUID HEADQUARTERS
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The size, size distribution, number concentration, and number charged of carbon particles down to about 15 A diameter in a flat acetylene-oxygen flame at 20 mm Hg were measured using a molecular beam sampling system combined with electrical deflection of the beam and electron microscope analysis of beam deposits. Coagulation of carbon particles occurs at all positions sampled in the flame. This process and surface growth form particle clusters that gradually change from roughly spherical at early and intermediate stages of growth to chainlike in the flame tail. The particle size distribution changes from Gaussian in the early stages of carbon formation to lognormal in the later stages. Particle number concentration and the rate of nucleation and coagulation each exhibit a maximum soon after the onset of carbon formation, but the rate of surface growth is maximum initially. The number fraction of charged particles is 10 to 40. Author
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