Electrostatic and hydrodynamics effects in a sedimented magnetorheological suspension.
We present experimental results on the equilibrium microstructure of a sedimented magnetorheological suspension, namely, an aqueous suspension of micron-sized superparamagnetic particles. We develop a study of the electrical interactions on the suspension by processing video-microscopy images of the sedimented particles. We calculate the pair distribution function, g(r), which yields the electrostatic pair potential u(r), showing an anomalous attractive interaction for distances on the order of twice the particle diameter, with characteristic parameters whose values show a dependence with the two-dimensional concentration of particles. The repulsive body of the potential is adjusted to a DLVO expression in order to calculate the Debye screening length and the effective surface charge density. Influence of confinement and variations on the Boltzmann sedimentation profile because of the electrostatic interactions appear to be essential for the interpretation of experimental results.
Depto. Física de Materiales, UNED, Senda del Rey 9, 28040 Madrid, Spain. pdominguez@fisfun.uned.es
P
P
Domínguez-García
J M
JM
Pastor
Sonia
S
Melle
Miguel A
MA
Rubio