Effect of an electric field on the deformation of incompressible rubbers: Bifurcation phenomena

Well above their glass transition temperatures, polymers behave like rubber materials. In the rubbery state, the elastic modulus is low enough to allow large deformations. Rubbery materials also deform under the application of an electric field. Rubbers can be referred as electromechanically active elastomers (EMAE) or lightweight materials that convert electrical into mechanical energy and vice versa [H. Xu, Z.-Y. Cheng, D. Olson, T. Mai, Q.M. Zang, G. Kavarnos, Ferroelectric and electromechanical properties of poly(vinylidene-fluoride-trifluoroethylene-chlrotrifluoroethylene) terpolymer, Appl. Phys. Lett. 78 (2001) 2360–2362]. Possible applications include biomedical prostheses, actuators, energy harvesters and robots [R.E. Pelrine, R.D. Kornbluh, J.P. Joseph, Electrostriction of polymer dielectrics with compliant electrodes as a means of actuation, Sens. Actuators, A 64 (1998) 77–85; G. Kofod, W. Wirges, Energy minimization for self-organized structure formation and actuation, Appl. Phys. Lett., 90 (2007) 81916–81918; J.S. Plante, S. Dubowsky, Large-scale failure modes of dielectric elastomer actuators, Int. J. Solids Struct. 43 (2006) 7727–7751].However, although the engineering applications of EMAE are quite recent, the theoretical foundations of continua under simultaneous electrical and mechanical force fields date back the 1960s. In this paper we present the basis of the nonlinear electroelasticity according to the formulation by Dorfmann and Ogden [A. Dorfmann, R.W. Ogden, Nonlinear Electroelastic Deformations, J. Elasticity 82 (2006) 99–127; A. Dorfmann, R.W. Ogden, Nonlinear electroelasticity, Acta Mechanica 174 (2005) 167–183] and discuss the influence of an electrical field on the bifurcation phenomena appearing in some cases of electromechanical deformation in rubber materials.     

Effect of an electric field on crystallization

The effect of an electric field on crystallization of dielectrics is examined. It is shown by the techniques of thermodynamics that an electric field has a substantial effect on the parameters of crystallization, the number of centers, the critical dimensions, and the work and rate of nucleus formation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 29–32, April, 1977.     

Effect of an electric field on friction of silicone rubber against steel in the motor base oil's environment

The paper presents the experimental results of research on the effect of an external DC electric field on the coefficient of friction of silicone rubber (elastomer) during its rubbing against a steel surface in the „pin–on–disc” experimental set-up. In the tests there were used silicone rubber samples, the pure PAG and PAO synthetic base oils and their blends with an antiwear (ZDDP) additive. The coefficient of friction μ was determined under conditions with and without an external DC electric field. A DC electric field was generated between a silicone rubber sample and a rotating steel disc (a friction pair). A sample holder was electrically isolated from other metal parts of a tribometer and was connected to one of the poles of a DC power supply, while the other pole was connected by means of the carbon brushes to a rotating steel disc. The experimental results show that the external DC electric field established between the rotating steel disc and a silicone rubber sample causes the coefficient of friction to decrease. It was also found that the coefficient of friction μ depends on the steel disc's angular velocity n, the contact pressure p, and the type of base oil and its blends with the additive used.     

Instability of incompressible cylinder rubber tubes under radial electric fields

The possibility of instability of cylindrical tubes of elastomers is analyzed taking into account Mooney-Rivlin (M. Mooney, J. Appl. Phys. 11, 582 (1940)) and Ogden (R.W. Ogden, Proc. R. Soc. London, Ser. A 326, 565 (1972)) models. In some aspects this paper is the elasto-electric counterpart of a previous paper by Bustamante, Dorfmann and Ogden (R. Bustamante, A. Dorfmann, R.W. Ogden, J. Engn. Math. 59, 139 (2007)). However in the present case the appearance of instability is checked. The results indicate that models more complex than the Mooney-Rivlin model are necessary to predict instability zones showing minimum critical points.     

Effect of an electric field on surface combustion

The effect of an electric field on the surface combustion of both lean and rich stirred gas mixtures was studied. The voltage–current characteristics of a current flow through gas were constructed. It was found that the confinement of surface combustion and a decrease in the temperature of a wire screen over the matrix are possible in the presence of an electric field. A change in the matrix polarity from negative to positive leads to an increase in electrical current in the circuit by an order of magnitude. Upon the arrangement of an impenetrable screen over the matrix, the matrix temperature can increase or decrease with the negative or positive polarity of the matrix, respectively.     

Effect of an electric field on brucite dehydroxylation

The dehydroxylation of brucite has been investigated in electric fields up to 400 kV/m at T=623 K. It is revealed that this reaction in the presence and absence of the field is a diffusion-controlled process, and its rate is governed by the diffusion rate of “slow” protons (the O^2? states) in the Mg(OH)₂ crystal structure. A decrease in the activation energy for diffusion of these protons in an electric field can be explained by both the additional energy acquired by the proton upon its migration through a distance of about 10³ A and a certain decrease in the potential barrier. It is shown that the found decrease in height of this barrier can be caused by the ionic polarization of the brucite lattice in an electric field whose effect on the barrier depends on the net dipole moment responsible for the generation of dipoles in the structural region of radius ～200 Å.     

Behavior of an electron plasma in a thin metallic slab placed in a variable electric field

The response of an electron plasma in a thin metallic slab to a variable electric field applied normally to the slab surface is studied in the framework of the kinetic theory. The radiation power absorbed by a unit surface area is calculated under the assumption that the electric field frequency is small compared with the plasma frequency and that electron scattering by the metal surface is of a purely diffuse character.     

Effect of an electric field on ferroelastic phase transitions

The effect of an external electric field on the proper ferroelastic phase transitions described in a two-dimensional representation of the D _4h class is analyzed theoretically. The electric field induces a Lifshitz invariant. It is shown that this invariant does not lead to the formation of an incommensurate phase. The phase diagram for commensurate transitions occurring under the action of an electric field changes significantly. The second-order phase transition from the initial phase is split by an electric field of specific orientation into a sequence of two second-order phase transitions with close temperatures.     

Effect of an external electric field on two-dimensional nucleation

Summary Two-dimensional nuclei of different possible shapes are considered in the presence of an external electric field which is applied either perpendicular or parallel to the nucleation surface. The additional driving force needed for the formation of a nucleus due to the electric field is found and used in the nucleation theory. The results show that the electric field can either stimulate or inhibit the nucleation process depending on the ratio of the dielectric constants and the orientation of the applied electric field with respect to the nucleation surface. The dependence of the two-dimensional nucleation rate on the intensity of electric field is also determined.

---

Riassunto Si considerano nuclei bidimensionali di differenti forme possibili in presenza di un campo elettrico esterno che è applicato sia perpendicolare che parallelo alla superficie di nucleazione. Si trova e si usa nella teoria di nucleazione l’ulteriore forza guida necesaria per la formazione di un nucleo a causa del campo elettrico. I risultati mostrano che il campo elettrico può sia stimolare che inibire il processo di nucleazione che dipende dal rapporto delle costanti dielettriche e dell’orientamento del campo elettrico applicato rispetto alla superficie di nucleazione. Si determina anche la dipendenza del valore di nucleazione bindimensionale dall’intensità del campo elettrico.

---

Резюме Рассматриваются двумерные ядра различных возможиых форм в присутствии внешнего электрического поля, которое либо перпендикулярно, либо параллельно поверхности вародышеобразования. Определяется и используется в теории зародяшеобразования дополнительная движущая сила, необходимая для образования ядра, всл⪟дствие действия электрического поля. Полученные результатя показяают, что электрическое поле может либо стимулировать, либо тормозить процесс зародышеобразования в зависимости от отношения диэлектричеких постоянных и от ориентации приложенного электричеслог поля отнонительно поверхности зародышеодразования. Такзе определяется зависимость скорости образвания двумерных ядер от интенсивности электрического поля.

     

Effect of an electric field on the limits of liquid stability

When electric fields are applied to metastable liquids, the energy barrier for nucleation of the vapor phase will increase. Reported observations of field-induced nucleation should not be used to infer stability limits of bulk liquids.     

Effect of an electric field on the electrocaloric response of ferroelectrics

The electrocaloric effect of the model ferroelectric BaTiO_3 was investigated using phenomenological theory. The results indicate that the applied electric field strength is a key factor for the induced electrocaloric response and there are two distinguishing electrocaloric responses. When a moderate electric field is applied, the electrocaloric temperature variation is small but the electrocaloric strength is high. In contrast, the electrocaloric temperature variation is large but electrocaloric strength is low when a very high electric field is applied. These results are consistent with the experimental observations on BaTiO_3 based bulk and thin film ferroelectric materials.     

Effect of an external electric field on liquid crystalline polymers

The effect of an external electric field on the order parameter and on the isotropic-anisotropic phase transition temperature for semi-flexible liquid crystalline polymers is studied by a mean-field approximation. For the polymers whose electric dipole moments are parallel to the chain backbone, the critical transition temperature T_c is extensively changed by gDT ∼ ∥E∥², where E is the external electric field.     

Effect of an electric field on the surface tension of a liquid at low temperatures

An external electric field changes the dispersion law of waves on the surface of a liquid. Besides the usual capillary term (∝k ³, k is the wave number) and gravitational term (∝k), a term quadratic in the wave vector appears in the expression for the square of the frequency in a homogeneous field. These excitations are associated with the variation of the coefficient of surface tension of the liquid at low temperatures. In the case of a large field tangent to the surface, the correction is proportional to T ^8/3, unlike the T ^7/3 correction in the absence of a field. Zh. éksp. Teor. Fiz. 111, 1369–1372 (April 1997)     

Effect of an electric field on the fracture of ferroelectric ceramic materials

This paper reports on the experimental results of measuring the time elapsed between the loading and the fracture of ferroelectric ceramic specimens under the action of a static electric field and mechanical stresses that differ in magnitude. The dependence of the durability of the specimens on the applied stress is determined for electric fields in the range from 0 to 5 MV/m. It is shown that, in the time range 1–10³ s, the durability of the ferroelectric ceramic material substantially increases in weak electric fields (the hardening effect) and significantly decreases in strong electric fields. The results obtained can be explained in terms of the fact that the load and the electric field affect the same defects (fracture nuclei) in the ferroelectric ceramics.     

Effect of an electric field on dewetting transition of nitrogen-water system

We investigate the influence of an external electric field on the dewetting behavior of nitrogen-water systems between two hydrophobic plates using molecular dynamics simulations. It is found that the critical distance of dewetting increases obviously with the electric field strength, indicating that the effective range of hydrophobic attraction is extended. The mechanism behind this interesting phenomenon is related to the rearrangement of hydrogen bond networks between water molecules induced by the external electric field. Changes in the hydrogen bond networks and in the dipole orientation of the water molecules result in the redistribution of the neutral nitrogen molecules, especially in the region close to the hydrophobic plates. Our findings may be helpful for understanding the effects of the electric field on the long-range hydrophobic interactions.     

Effect of an electric field on photoluminescence of cadmium selenide nanocrystals

We have demonstrated a difference in the nature of the effect of a strong external electric field (>10⁵ V/cm) on the photoluminescence of cadmium selenide nanoparticles of different shapes. We have determined a correlation between the magnitude of the external electric field and the average photoluminescence decay time for two types of nanoparticles: "quantum dots" and nanorods. We discuss the mechanism for the effect of an electric field on the photoluminescence of both types of nanoparticles.     

Effect of an electric field on the characteristics of magnetoelectric interaction in a ferromagnet-ferroelectric composite structure

The characteristics of the magnetoelectric interaction in a planar nickel-lead-zirconate-titanate structure have been studied in a dc electric field applied to the ferroelectric layer. A hysteretic field dependence of the efficiency and frequency of the resonant magnetoelectric interaction has been revealed, and the vanishing of the interaction efficiency in the range of polarization switching fields due to changes in the permittivity, the piezoelectric modulus, and the dielectric loss of the ferroelectric has been observed. It has been shown that the electric field leads to a significant change in the rigidity of the ferroelectric layer.