I n s i t u measurement of the fractal dimensionality of ultrafine aerosol particles

Abstract

The fractal dimension d f of gas phase agglomerated particles is measured i n s i t u for the first time. This is done by comparing aerodynamic radii R 0 and R c1 before and after tempering. By tempering, agglomerates are collapsed into close‐packed clusters of d f =3. It is shown that the equation M∼R d f 0, where M is the agglomerate mass, holds almost down to R 0=R c1 =R m (monomer radius), making d f a very useful quantity for aerosol characterization. The measurement yields d f ≂2.18 for Ag agglomerates with R m ≂7.5 nm. d f is predicted to be material dependent.