The physical properties of heterogeneous materials, polymer/carbon black composites, depend closely on the arrangement of the particles in the matrix which is called the mesostructure. In order to study it, we have used an extension of the AFM microscope that takes advantage of the local electrical properties of the materials for characterizing the electrical connections among particles. The comparative study of three series of samples processed with different mixing conditions allowed us to show that percolation models do not represent adequately the actual mesostructure. Besides, appropriate numerical analysis of the images allowed us to deduce distinct information on the mesostructure at short and long scales. In a last part, we have initiated the construction of new mathematical models for the mesostructure based on transmission electronic micrographs of the materials.
