8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Wed 711:10-14:00P5.91Investigation of the structure factor of polydisperseferrocolloidsEkaterina Krutikova 1 and Dmitriy Anokhin 11 Ural State University, Lenin Av. 51, 620000, Ekaterinburg, Russian FederationThe study of structure properties of ferrocolloids (magnetic fluids, ferrofluids) by the constructionof the structure factor of dispersion is presented in the given work. Small-angle scatteringexperiment allows to measure the intensity of the scattering, which make it possible to obtainthe structure factor. Theoretical structure factor is the Fourier transform of the pair correlationfunction of the ferroparticle system, which means probability density of the mutual position oftwo randomly chosen ferroparticles, which magnetic moments are averaged over all orientations.Thus, for correct processing of experimental data, it is necessary to develop the theoretical modelthat would make the transition from the structure factor in Fourier’s space to the pair correlationfunction and back. In fact, magnetic fluids are polydisperse, so the model is built in bidisperseapproximation. The ferrofluid is modeled as a system of bidisperse dipolar hard spheres. Allparticles were formally divided into two types - ”large” and ”small”. For this system, the paircorrelation function is a function of the typical interparticle distances: ”small” - ”small”, ”large”- ”large” and ”small” - ”large”, and depends on the ferroparticle volume concentration and thedipolar coupling constant. The comparison of the developed theoretical model with the results ofsmall-angle scattering experiment on polydisperse magnetic fluids showed good agreement in thesphere of the model working. The influence of dipole-dipole interaction on the structure factor ofthe ferroparticle system was analyzed. It turned out that the hard sphere interaction is primarilyresponsible for the formation of the first effective coordination sphere in the system, while thedipole-dipole attraction manifests itself at the greater distances. The work was supported by theGrant of President RF No. MK-2221. 2011. 2.91