Wall slip phenomena in concentrated ionic liquid-based magnetorheological fluids
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Rheol Acta (2012) 51:793–803
SponsorshipFinancial support by Ministerio de Ciencia e Innovación (Spain) under project FIS2009-07321 and by Junta de Andalucía (Spain) under projects P08-FQM-3993 and P09-FQM-4787 is gratefully acknowledged. AG-R and MTLL acknowledge financial support by Secretaría de Estado de Universidades e Investigación (MEC, Spain) through its FPU program and by Universidad de Granada (Spain), respectively.
Ionic liquids (IL)have beenrecentlyproposed as carrier for magnetorheological (MR) fluids. Their specialproperties,such as low vapor pressure and high thermal stability, makeIL aperfect dispersing mediato increase the broad range of technological applications that magnetorheological fluids already have. It has been just reported that using ILas carrier in MF fluids an improvement inthe colloidal stability and suspension redispersibity is obtained.In this work the magnetorheological behavior of highly concentrated suspensions in IL is studied. Two kinds of suspensions were analyzed:using an ionic liquidof low conductivityandaclassicalmineral oilas carriers. In both casessilica-coatediron microparticles were used as solid phase, being the solid volume concentrationof50 %vol. A complete magnetorheologicalanalysis focused on the wall slip phenomenonwas performed. Viscositmetry and oscillatory experiment were carried out. In order to study wall slip effects, all experiments were performedwith a plate-plate system, using both smooth and rough measuring surfaces. An interestingeffect of wall slip phenomenon was observed when experimentswere performed using smooth surfaces.The novelty of this paper is based on two factors, the use of IL as carrier to prepare MR fluids andthe analysis of wallslip phenomena.