title: Microstructure evolution in magnetorheological suspensions governed by Mason number.
abstract: The spatiotemporal evolution of field-induced structures in very dilute polarizable colloidal suspensions subject to rotating magnetic fields has been experimentally studied using video microscopy. We found that there is a crossover Mason number (ratio of viscous to magnetic forces) above which the rotation of the field prevents the particle aggregation to form chains. Therefore, at these high Mason numbers, more isotropic clusters and isolated particles appear. The same behavior was also found in recent scattering dichroism experiments developed in more concentrated suspensions, which seems to indicate that the dynamics does not depend on the volume fraction. Scattering dichroism experiments have been used to study the role played by the volume fraction in suspensions with low concentration. As expected, we found that the crossover Mason number does not depend on the volume fraction. Brownian particle dynamics simulations are also reported, showing good agreement with the experiments.
authors.affiliation: Department of Chemical Engineering, Stanford University, Stanford, California 94305-5025, USA.
authors.forename: Sonia
authors.initials: S
authors.lastname: Melle
authors.forename: Oscar G
authors.initials: OG
authors.lastname: Calderón
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Rubio
authors.forename: Gerald G
authors.initials: GG
authors.lastname: Fuller
mesh_terms: D016880:Anisotropy; D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D004574:Electromagnetic Fields; D052203:Ferrosoferric Oxide; D017276:Friction; D007501:Iron / Q000737:chemistry* / Q000528:radiation effects*; D007700:Kinetics; D008280:Magnetics; D018715:Microscopy, Video / Q000379:methods; D008863:Microspheres; D008956:Models, Chemical; D009038:Motion; D010087:Oxides / Q000737:chemistry* / Q000528:radiation effects*; D012212:Rheology / Q000379:methods*; D012399:Rotation; D013535:Suspensions / Q000737:chemistry* / Q000528:radiation effects*; D014783:Viscosity
chemical_list: D010087:Oxides; D013535:Suspensions; D007501:Iron; D052203:Ferrosoferric Oxide