Berlin 2005 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 5: SYMPOSIUM: Dynamics of multi-component fluids POSTER
CPP 5.6: Poster
Freitag, 4. März 2005, 17:15–19:00, Poster TU D
Liquid to solid transition of inverse ferrofluids — •Ruben Saldivar-Guerrero1,2, Reinhard Richter1, Ingo Rehberg1, Nuri Aksel3, Lutz Heymann3, and Oliverio S. Rodriguez-Fernandez2 — 1Experimentalphysik V, Universität Bayreuth, D-95440 Bayreuth, Germany — 2Centro de Investigacion en Quimica aplicada, 25100 Saltillo, Mexico — 3Technische Mechanik und Strömungsmechanik, Universität Bayreuth, D-95440 Bayreuth, Germany
By disperging microsized polystyrene particles in ferrofluid an ideal magneto-rheological model fluid can be created. Because polystyrene particles are available, which are practically monodisperse (σ=0.04), this hybrid fluid allows to controll 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 suszeptibility of the displaced fluid. Due to the dipolar interactions of the holes chain formation sets in and the inverse fluid undergoes a transition from liquid to solid like behaviour. 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 (Z. Wang , and Ch. Hol, Phys. Rev. E 2003).