Viscosity, magnetic field effects

An MR hydrogel of a crosslinked PVA network and Fe304 particles dispersed at random was also synthesized [59]. The viscosity of the gel in a magnetic field increased with time. It has been suggested that the dispersed Fe304 particles aggregate and form a cluster. The effect of the volume fraction of the particles on the viscosity has also been discussed. The authors have pointed out that when the volume fraction is about 15%, the ratio of the viscosities with and... 

The use of an electric field is not the only effective way to influence the LC polymer structure, magnetic fields displays a closely similar effect167 168). It is interesting as a method allowing to orient LC polymers, as well as from the viewpoint of determining some parameters, such as the order parameter, values of magnetic susceptibility, rotational viscosity and others. Some relationships established for LC polymer 1 (Table 15), its blends with low-molecular liquid crystals and partially deuterated polyacrylate (polymer 4, Table 15) specially synthesized for NMR studies can be summarized as follows ... 

In equations 5-8, the variables and symbols are defined as follows p0 is reference mass density, v is dimensional velocity field vector, p is dimensional pressure field vector, x is Newtonian viscosity of the melt, g is acceleration due to gravity, T is dimensional temperature, tT is the reference temperature, c is dimensional concentration, c0 is far-field level of concentration, e, is a unit vector in the direction of the z axis, Fb is a dimensional applied body force field, V is the gradient operator, v(x, t) is the velocity vector field, p(x, t) is the pressure field, jl is the fluid viscosity, am is the thermal diffiisivity of the melt, and D is the solute diffiisivity in the melt. The vector Fb is a body force imposed on the melt in addition to gravity. The body force caused by an imposed magnetic field B(x, t) is the Lorentz force, Fb = ac(v X v X B). The effect of this field on convection and segregation is discussed in a later section. 

Most spectroscopic techniques (e.g. infrared and Raman spectroscopy) provide a snapshot view of the structure of a liquid because the timescale of the techniques is of the order of lattice vibration. However, NMR can probe much lower frequency motions, motions which are important in the glass transition and the viscosity of a silicate liquid. In addition, the timescale of the NMR experiment may be varied (by changing the magnetic field, or the type of experiment, T or T fJ, or observing quadrupolar effects) from a few hertz to several hundred megahertz. 

A small effect of a magnetic field on the viscosity of mercury was found by Destriau and Massieu i2 there seems to be no effect of a magnetic field in the case of non-polar liquids, but there is a small increase with polar liquids, depending on the shape of the molecule. 

If the director is held in a fixed orientation by a magnetic field strong enough to resist the orienting effects of flow, then shear-rate-independent viscosities can be measured in a simple shearing flow. The three simplest of these, called the Miesowicz viscosities, are obtained in each of the three director orientations shown in Fig. 10-8. These viscosities can be related in a simple way to the or,- s, namely,... 

It is quite obvious that the attempt at separating the viscosity effect and the damping effect just explained is to be considered only as a provisional step in the investigation of this domain. So too much weight should not be attached to the results which may on a closer examination prove more or less false. It is contemplated to make the influence of the magnetic field on a turbulent flow the subject of a subsequent investigation. 

N,N-diaethyithiocarbaaates. Solvent viscosity has been found to Influence the effect exerted by a magnetic field on radical yields during the photoreduction of xanthene dyes. ... 

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