title: Colloidal Stability and Magnetic Field-Induced Ordering of Magnetorheological Fluids Studied with a Quartz Crystal Microbalance.
abstract: This work proposes the use of quartz crystal microbalances (QCMs) as a method to analyze and characterize magnetorheological (MR) fluids. QCM devices are sensitive to changes in mass, surface interactions, and viscoelastic properties of the medium contacting its surface. These features make the QCM suitable to study MR fluids and their response to variable environmental conditions. MR fluids change their structure and viscoelastic properties under the action of an external magnetic field, this change being determined by the particle volume fraction, the magnetic field strength, and the presence of thixotropic agents among other factors. In this work, the measurement of the resonance parameters (resonance frequency and dissipation factor) of a QCM are used to analyze the behavior of MR fluids in static conditions (that is, in the absence of external mechanical stresses). The influence of sedimentation under gravity and the application of magnetic fields on the shifts of resonance frequency and dissipation factor were measured and discussed in the frame of the coupled resonance produced by particles touching the QCM surface. Furthermore, the MR-fluid/QCM system has a great potential for the study of high-frequency contact mechanics because the translational and rotational stiffness of the link between the surface and the particles can be tuned by the magnetic field.
authors.affiliation: Institute of Physical and Information Technologies, CSIC, C/Serrano, 144, Madrid 28006, Spain. dr.jaimerl@gmail.com.
authors.forename: Jaime
authors.initials: J
authors.lastname: Rodriguez-López
authors.affiliation: Institute of Physical and Information Technologies, CSIC, C/Serrano, 144, Madrid 28006, Spain. pedro.castro@csic.es.
authors.forename: Pedro
authors.initials: P
authors.lastname: Castro
authors.affiliation: Department of Applied Physics, Faculty of Sciences, University of Granada, c/Fuentenueva s/n, Granada 18071, Spain. jvicente@ugr.es.
authors.forename: Juan
authors.initials: J
authors.lastname: de Vicente
authors.affiliation: Institute of Physical Chemistry, Clausthal University of Technology, Arnold-Sommerfeld-Str. 4, Clausthal Zellerfeld D-38678, Germany. johannsmann@pc.tu-clausthal.de.
authors.forename: Diethelm
authors.initials: D
authors.lastname: Johannsmann
authors.affiliation: Institute of Physical and Information Technologies, CSIC, C/Serrano, 144, Madrid 28006, Spain. luis.elvira@csic.es.
authors.forename: Luis
authors.initials: L
authors.lastname: Elvira
authors.affiliation: Department of Applied Physics, Faculty of Sciences, University of Granada, c/Fuentenueva s/n, Granada 18071, Spain. jrmorillasmedina@correo.ugr.es.
authors.forename: Jose R
authors.initials: JR
authors.lastname: Morillas
authors.affiliation: Institute of Physical and Information Technologies, CSIC, C/Serrano, 144, Madrid 28006, Spain. francisco.montero@csic.es.
authors.forename: Francisco
authors.initials: F
authors.lastname: Montero de Espinosa
keywords: QCM; TSM resonator; magnetic field intensity; magnetorheological fluid; micron-sized magnetic particles; positive resonant frequency shift; sedimentation