COMPARISON OF AGGREGATION OF RODLIKE AND SPHERICAL-PARTICLES - A FRACTAL ANALYSIS

Different structure-analyzing methods were applied to experimental and computer generated two-dimensional clusters. The real structures form ed at water-air interfaces from polydisperse, cylindrical-shape carbon (thickness: 35 mu m; average length: 140 mu m) and close to monodispe rse, spherical-shape glass (75 mu m diam) microparticles. The clusters were characterized by the fractal dimension (D-f) and the surface cov erage (q) values in the case of individual clusters. For a series of d ifferent sized aggregates, the fractal dimension (D-f) was also evalua ted from the In q versus In R-g functions where R-g is the radius of g yration. The fractal dimensions for individual clusters determined by box counting, sand box, and by correlation function methods, were comp ared with each other and with those obtained for the series of cluster s. Using the above methods, the aggregation of cylindrical carbon and spherical glass particles was studied from a structural point of view. The surface of glass beads was rendered hydrophobic chemically. Chang ing the extent of silylation, lower and higher hydrophobic samples wer e obtained (Theta/water/=68 degrees and 89 degrees, respectively). Con forming the earlier results, the In q versus In R-g functions revealed a crossover during the growth in every investigated case, which was a n indication of cluster reorganization after the primary growth. At th e first (quasi-non-equilibrium) stage of aggregation, the fractal dime nsions obtained for the carbon particles (D-f=1.44+/-0.07), for the lo wer (D-f=1.53+/-0.05), and for the higher hydrophobic (D-f=1.43+/-0.05 ) glass particles, indicated the universality of the growth. (C) 1997 American Institute of Physics.