THE MORPHOLOGY OF MACROSCOPIC SOOT

The morphology of soot collected from a laminar acetylene/air diffusio n flame was studied. Collection methods included both thermophoretic a nd impaction sampling from both the luminous and nonluminous portions of the flow. The soot was viewed with both electron and optical micros copy. Cluster sizes ranged over four orders of magnitude from 50 nm to 400 mu m to include some clusters visible to the naked eye. A new met hod of micrograph analysis, necessary when the clusters were large, wa s developed to account for the unresolved primary particles. Over this entire size range, the same fractal morphology was found with a fract al dimension of D=1.8 and, within a rather large uncertainty, the same prefactor k(0)=1.7. Thus, the fractal morphology of soot remains cons tant from clusters of about 10 primary particles per aggregate to macr oscopic clusters of over 10(8) primary particles.