The Bidispersed Model System and Binary System for Ferrofluids

Ferrofluids, dispersions of magnetic nanoparticles, are typical dipolar fluids whose behaviors can be modified using an external magnetic field. Such magnetically controlled effects result from interactions between the magnetic particles, which are enhanced by an applied magnetic field. Since the system of particles always possesses a size distribution, real ferrofluids represent a polydispersed system. A theoretical model of a bidispersed system, which contains only particles of two sizes, large and small, is presented. Experimentally, some binary ferrofluids based on two types of nanoparticles, with different magnetization or containing a mixture of micron-sized particles doped in ferrofluids are investigated. These magnetic colloidal systems have two dispersion phases in which at least one is magnetic nanoparticles and can exhibit novel behavior. This may result in novel physical properties and new potential applications. A model of a bidispersed system based on aggregated and non-aggregated particles, in which some non-aggregated particles could transform into aggregated particles with increasing magnetic field while total particles’ number is constant, may help to advance general theories of ferrofluids.