Authors: M. Lattuada, L. Ehrl, M. Soos, M. Morbidelli
Affilation: ETH Zürich, Switzerland
Pages: 758 - 761
Keywords: clusters, light scattering, monte-carlo, T-matrix, aggregation
The use of light scattering or laser diffraction techniques to characterize dense clusters such as those generated in shear induced coagulations is highly desirable. However, a major obstacle in the effective utilization of this technique is the lack of realistic structural models for dense clusters of spheres which allow one to extract reliable information from scattering data. In addition, the commonly used Rayleigh-Debye-Gans (RDG) theory fails in the case of dense structures and particles with a size comparable to that of the wavelength of the incident light source. We present a procedure to overcome these limitations. By making use of a tunable fractal dimension Monte-Carlo algorithm, we generate dense clusters with a desired fractal dimension (df). In order to analyze clusters with a df larger than 2.5, we introduce a new algorithm which is capable of densifying clusters and reach df equal to 3. The cluster structure is than characterized by means of its pair-correlation function, which is used to compute their scattering properties through a mean-field version of the T-Matrix theory. The mean field T-matrix theory results compensate for the RDG theory limitations and are used in the analysis of shear-induced coagulation experiments of polymer colloids.