Liquid to Solid Transition of Inverse Ferrofluids

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Saldivar-Guerrero, Ruben ; Richter, Reinhard ; Rehberg, Ingo ; Aksel, Nuri ; Heymann, Lutz ; Rodriguez-Fernández, Oliverio S.:
Liquid to Solid Transition of Inverse Ferrofluids.
In: Gailitis, Agris (ed.): Proceedings of the Joint 15th Riga and 6th PAMIR International Conference on Fundamental and Applied MHD : vol. 1. - Rigas Jurmala , 2005 . - p. 365

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Abstract in another language

By dispersing microsized polystyrene particles in ferrofluid an ideal magneto-rheological model fluid can be created. Because polystyrene particles are available, which are practically monodisperse (sigma=0.048), this inverse fluid allows to control particle size and polydispersity, in advantage to the common ferro- and magneto-rheological fluids, which are only polydisperse. The nonmagnetic polystyrene particles create a hole in the ferrofluid, which appear to posses a magnetic moment corresponding to the amount and susceptibility of the displaced fluid. Due to the dipolar interactions of the holes, chain formation sets in and the hybrid fluid undergoes a transition from liquid to solid like behavior.
We investigate this transition by recording the storage modulus G' and the loss modulus G'' versus the magnetic field for different volume fraction, particle size, and particle size distribution. Our results show that for a monodisperse fluid the liquid-to-solid transition is more pronounced than for a polydisperse one – a related effect has recently been found in MD simulations for standard ferrofluids.