Electrostrictive effect

Piezoelectrics. AH ceramics display a slight change ia dimension, or strain, under the appHcation of an electric field. When the iaduced strain is proportional to the square of the field iatensity, it is known as the electrostrictive effect, and is expressed by ... 

Jenner investigated the kinetic pressure effect on some specific Michael and Henry reactions and found that the observed activation volumes of the Michael reaction between nitromethane and methyl vinyl ketone are largely dependent on the magnitude of the electrostriction effect, which is highest in the lanthanide-catalyzed reaction and lowest in the base-catalyzed version. In the latter case, the reverse reaction is insensitive to pressure.52 Recently, Kobayashi and co-workers reported a highly efficient Lewis-acid-catalyzed asymmetric Michael addition in water.53 A variety of unsaturated carbonyl derivatives gave selective Michael additions with a-nitrocycloalkanones in water, at room temperature without any added catalyst or in a very dilute aqueous solution of potassium carbonate (Eq. 10.24).54... 

Rate constants and activation parameters (AH, AS, and AV ) for base hydrolysis of [Pg.80]

As will be shown in the theory, the electrostriction effect plays an important role in the piezoelectric effect of polymer films. Moreover, a knowledge of the complex electrostriction constant as a function of frequency reveals a new aspect of the relaxational behavior of polymers. In this review a new method for measuring complex electrostriction constant with varying frequency will be presented with some results for poly(vinylidene fluoride). 

Fig. 7. Sketch of the apparatus for measuring inverse piezoelectric effect in polymer films. B vibrating cantilever beam, E electromagnetic exciter, P electromagnetic pick-up, S specimen film, M weight, C oscillator, Vt, V2 and V3 voltmeters, Sw switch, V d.c. bias source for measuring electrostriction effect. Drawn after Kawai (1) (1969) by permission of the Japan Society of Applied Physics...

A) When an alternating voltage (frequency = to) is applied to the film, the film is strained with frequencies to and 2 to. The former is the inverse piezoelectric effect and the latter the electrostriction effect. By measuring the strain amplitude of the 2to component, we can obtain the electrostriction constant (Oshiki and Fukada, 1971). 

Greaves and Lamb (1971) observed sound emission from polyethylene film due to the electrostriction effect. 

Electrostriction Effect of Polymers Exhibiting Dielectric Relaxation... 

The electrostriction effect, beside its effect on the piezoelectricity, gives a new insight onto relaxations in polymers when the electrostriction constant is obtained over a wide frequency range. It provides us with a knowledge of the strain dependence of relaxation time. 

Electrostriction effect of polymers. 20 th Polymer Symposium, Japan (Nov. 1971) Tokyo. 

Negative values ofN —N0, the electrolyte effect on the association numbers of water, are called the structure-breaker effect. One can speak of negative hydration31. The estimation of the hydration numbers by spectroscopic or solubility methods gives only an approximation of the sum effect. The spectra of the H-bond bands show in second approximation distinct differences between the ion effects on the H-bonds7 ). — The partial molar volume Vx of water in electrolyte solutions is negative in all solutions but the series of -values corresponds to the Hofmeister ion series too. The negative V1 volume indicates an electrostriction effect around the ions. 

In conclusion the contribution to the dielectric response given by the third order susceptibility has different sources with opposite signs. Molecular simulations on ions in solution show that both dielectric saturation and electrostriction effects are presumably present and that for ions with a high charge density electric saturation predominates. This suggestion is in agreement with the general consensus that dielectric saturation is the first element to consider in the description of nonlinearities. 

We also quote the proposal, made by Luo and Tucker [19], of a model using a dielectric function with dependence of the dielectric constant on the electric field acting on the given position, used for supercritical liquids, in which the solvent density is particularly sensitive to the local value of external electric fields. Emphasis is given in this model to electrostriction effects. 

All materials undergo a small change in dimensions when subjected to an electric field. If the resultant strain is proportional to the square of the field it is known as the electrostrictive effect. Some materials show the reverse effect - the development of electric polarization when they are strained through an applied stress. These are said to be piezoelectric (pronounced pie-ease-oh ). To a first approximation the polarization is proportional to the stress and the effect is said to be direct . Piezoelectric materials also show a converse effect, i.e. the development of a strain x directly proportional to an applied field. 

In the general case, electrostriction is not isotropic even in isotropic dielectrics a field-induced anisotropy of electrostriction appears and is perceptible also in measurements of the static" and optical" Kerr effects. This anisotropy of electrostriction is particularly apparent if the field acting on the dielectric is strong, such as the intense electromagnetic field of a light wave, in which case the time-dynamics of the electrostrictive effect have to be studied s arately." ... 

An interesting finding of the authors on this system and, earlier, on Ag" in water" is that the volume of the water does not change upon adding the metal ion. The contraction of the liquid around the cation can be ascribed to electrostriction effects. 

As it was shown in section VI, as a rule the JT crystals are characterized by combination of big magnetostriction and electrostriction effects. However Mitsek and... 

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