Suspensions Of Anisotropic Particles Research Articles

Field induced reorientation in suspensions of anisotropic particles

The field induced reorientation of microellipsoids in suspension depends on particle parameters, e.g. intrinsic dielectric anisotropy, shape and size, as well as on the concentration of the particles. We study this process and the resulting orientational order parameter of suspensions in fields of arbitrary strength. The approach presented here provides an explicit link between particle properties and their orientation distribution, taking into account the electrostatic interaction at moderate concentrations. It reproduces published experimental observations in the steady state and should be useful for studying reorientation phenomena and electro-optical properties in these systems.

Electro-optical properties of suspensions of anisotropic particles

Liquid suspensions of microellipsoids exhibit a variety of nonlinear optical and electro-optical phenomena based on the reorientation of the particles by an applied electric field. The magnitude of these effects is determined by the concentration of the particles, their intrinsic dielectric anisotropy and their shape. An extension of the Maxwell Garnett approximation for suspensions of anisotropic particles provides an explicit link between the particle properties, their orientation distribution and the effective properties of the suspensions. It reproduces experimental observations and should be useful for studying electro-optical properties as well as reorientation phenomena in these systems.

Local field effects on reorientation in suspensions of anisotropic particles.

The field-induced reorientation of microellipsoids in suspension depends on particle parameters, e.g., intrinsic dielectric anisotropy, shape, and size, as well as on the concentration of the particles. We study this process and the resulting orientational order parameter of the suspension in fields of arbitrary strength. The mean-field approach presented here provides an explicit link between the particle properties and their orientation distribution, taking into account the electrostatic interaction among the particles at moderate concentrations. It reproduces published experimental observations in the steady state and should be useful for studying reorientation phenomena as well as electro-optical properties in these systems.

Dielectric response and electro-optical effects in suspensions of anisotropic particles.

The dielectric properties of suspensions of microellipsoids may be controlled by reorientation of the particles in an applied electric field. We study this process and the resulting electro-optical effects for fields of arbitrary strength. The magnitude of these effects is determined by the concentration of the particles, their intrinsic dielectric anisotropy and their shape. The approach presented here provides an explicit link between the particle properties, their orientation distribution and the field-induced birefringence and electro-optical phase shift of the suspensions, taking into account the electrostatic interaction among the particles at moderate concentrations. It reproduces well published experimental observations and should therefore be useful for studying electro-optical properties as well as reorientation phenomena in these systems.

Chaos in polarization relaxation of a low-conducting suspension of anisotropic particles

Abstract Chaos phenomena in the polarization relaxation of a suspension of anisotropic particles in a low-conducting fluid are studied. It is shown that due to the subcritical Hopf bifurcation at intermediate values of the electric field strength, chaotic oscillations of the polarization takes place. At higher values of the electric field strength, the chaotic behaviour disappears and a limit cycle arises. In this region intermittency of the third kind is observed.

Multimodal particle size measurement using truncated pulsed electro-optic birefringence

A pulsed electric field induces transient birefringence in a suspension of anisotropic particles. The rate of decay of the birefringence depends strongly on the particle size via the rotary diffusion coefficient, D, of the particles. A more analytical method has been developed in which values of D, obtained from the initial slope of the post-field decay for a range of applied pulses of the same low electric field strength, but for continuously decreasing pulse durations Theta , are analysed to yield size distributions for the dispersed particles. By adopting a least-squares fitting and smoothing procedure, this electro-optical method is shown to handle arbitrarily multimodal distributions. The method is appraised via regenerated theoretical data for a mixture of submicrometre spheres and for experimental data on suspensions of lozenges of polytetrafluoroethylene and iron oxide spheroids. The method is suitable for submicrometre-sized particles.