Electromechanical: behavior

Takeuchia I, Asakaa K, Kiyoharaa K et al (2009) Electromechanical behavior of fully plastic actuators based on bucky gel containing various internal ionic liquids. Electrochim Acta 54 1762-1768... 

Equations (2.24)-(2.30) provide a fundamental guideline to predict the direction of bending depending upon the operational voltage in connection with the surface reactions involved. The CV results reflect the associated surface reactions and the related electromechanical behavior of IPMCs. 

Describe the thermal and electromechanical behavior of piezoelectric and ferroelectric compounds. 

Figure 4. Effect of epitaxial (or deposition) strains on the average extrinsic ferroelectric behavior of a polycrystalline thin-film [83], Left inset summarizes the predicted out-of-plane hysteretic response, while the right inset embodies the predicted out-of-plane extrinsic electromechanical behavior. Note that while the electromechanical response for large fields corresponds to the equilibrium (intrinsic) behavior, a great potential for reaching electromechanical enhancements up to one order of magnitude greater than the ones currently available are possible by harnessing the time-dependent switching behavior.

The forth direction, analytical modeling for understanding the behaviors of these materials, has been popular approach. Testing and characterization have been conducted for developing the models. Such attempts have been done especially for ionic polymer metal composites (IPMCs)[58, 70, 72, 120]. Nemab Nasser and his co-workers carried out extensive experimental studies on both Nafion- and Flemion-based IPMCs consisting of a thin perfluorinated ionomer in various cation forms, seeking to imderstand the fundamental properties of these composites, to explore the mechanism of their actuation, and finally, to optimize their performance for various potential applications[121]. They also performed a systematic experimental evaluation of the mechanical response of both metal-plated and bare Nafion and Flemion in various cation forms and various water saturation levels. They attempted to identify potential micromechanisms responsible for the observed electromechanical behavior of these materials, model them, and compare the model results with experimental data[122]. A computational micromechanics model has been developed to model the initial fast electromechanical response in these ionomeric materials[123]. A number... 

As reported, ferroelectrets are thin polymer films with open or closed cavities, such as a foamed material although they differ from those due to the trapped electrical charges on the inner void surfaces. These characteristics allow the material to exhibit high J33 piezoelectric coefficients. In this section we describe the most accepted model, which explains this electromechanical behavior. 

The effective use of dielectric elastomers (DE) in actual transducers requires the definition of rehable design tools which correctly predict their electromechanical behavior. In this chapter, we present two different approaches for modeling DE. The first approach is focussed on describing the electroelastic behavior of DEs in the framework of finite-strain electromechanics. The second approach,... 

Ismail, M.N., Turky, G.M., and Nada, A.M.A. (2000) Electromechanical behavior of natural rubber-lignocellulosic material composites, Polym. Phst, Tech-nol. Eng., 39, 249-263. 

As can be seen from aU of the examples given above, the study of the physical properties of nanotubes in general and their electromechanical behavior in particular requires... 

Takeuchi I, Asaka K, Kiyohara K, Sugino T, Mukai K, Randriamahazaka H (2010) Electrochemical impedance spectroscopy and electromechaniced behavior of bucky-gel actuators containing ionic liquids. J Phys Chem C 114(34) 14627-14634. doi 10.1021/jpl018185... 

Polarization which can be induced in nonconducting materials by means of an externally appHed electric field is one of the most important parameters in the theory of insulators, which are called dielectrics when their polarizabiUty is under consideration (1). Experimental investigations have shown that these materials can be divided into linear and nonlinear dielectrics in accordance with their behavior in a realizable range of the electric field. The electric polarization PI of linear dielectrics depends linearly on the electric field E, whereas that of nonlinear dielectrics is a nonlinear function of the electric field (2). The polarization values which can be measured in linear (normal) dielectrics upon appHcation of experimentally attainable electric fields are usually small. However, a certain group of nonlinear dielectrics exhibit polarization values which are several orders of magnitude larger than those observed in normal dielectrics (3). Consequentiy, a number of useful physical properties related to the polarization of the materials, such as elastic, thermal, optical, electromechanical, etc, are observed in these groups of nonlinear dielectrics (4). 

Uncoupled solutions for current and electric field give simple and explicit descriptions of the response of piezoelectric solids to shock compression, but the neglect of the influence of the electric field on mechanical behavior (i.e., the electromechanical coupling effects) is a troublesome inconsistency. A first step toward an improved solution is a weak-coupling approximation in which it is recognized that the effects of coupling may be relatively small in certain materials and it is assumed that electromechanical effects can be treated as a perturbation on the uncoupled solution. 

From the mechanical viewpoint, ferroelectrics exhibit unsteady, evolving waves at low stresses. Waves typical of well defined mechanical yielding are not observed. Such behavior is sensitive to the electrical boundary conditions, indicating that electromechanical coupling has a strong influence. Without representative mechanical behavior, it is not possible to quantitatively define the stress and volume compression states exciting a particular electrical response. 

The semiconducting properties of the compounds of the SbSI type (see Table XXVIII) were predicted by Mooser and Pearson in 1958 228). They were first confirmed for SbSI, for which photoconductivity was found in 1960 243). The breakthrough was the observation of fer-roelectricity in this material 117) and other SbSI type compounds 244 see Table XXIX), in addition to phase transitions 184), nonlinear optical behavior 156), piezoelectric behavior 44), and electromechanical 183) and other properties. These photoconductors exhibit abnormally large temperature-coefficients for their band gaps they are strongly piezoelectric. Some are ferroelectric (see Table XXIX). They have anomalous electrooptic and optomechanical properties, namely, elongation or contraction under illumination. As already mentioned, these fields cannot be treated in any detail in this review for those interested in ferroelectricity, review articles 224, 352) are mentioned. The heat capacity of SbSI has been measured from - 180 to -l- 40°C and, from these data, the excess entropy of the ferro-paraelectric transition... 

Lee, R.C., Frank, E.H., Grodzinsky, A.J. and Roylance, D.K. (1981) Oscillatory com-pressional behavior of articular cartilage and its associated electromechanical properties. ASME Journal of Biomechanical Engineering 103, 280-292... 

The dynamic behavior of the film s shear displacement vs position across the film thickness hf can be predicted from a continuum electromechanical model described by Reed et al. [10]. Several distinct regimes of dynamic behavior can be identified [40], determined by the acoustic phase shift, , across the film. 

As a consequence, the joins for (Pbi. (Bajc)Ti03 at low temperature and for Pb(Zri cTy03 at room temperature are interrupted by a morphotropic phase boundary (MPB), which separates tetragonal and rhombohedral phases (Fig. 14). The structural state of the oxides in the vicinity of the MPB is a subject of active inquiry, because many of the physical properties of PBZT ferroelectrics are maximized at the MPB. These include the dielectric constant, the piezoelectric constant, and the electromechanical coupling coefficients (Jaffe 1971, Thomann and Wersing 1982, Heywang and Thomann 1984). For industrial purposes, this behavior is exploited by annealing PBZT ferroelectrics with compositions near the MPB close to the Curie temperature in an... 

Only three standard components - an anchor, a beam, and a beam with an electrode - are needed to represent the electromechanical switch s behavior on the circuit level. The beam models simulate the 3D nonlinear mechanical behavior, based upon a complete set of parameters describing the dimensions and material... 

Functional electrochemically controlled supramolecular machines based on CyD units now being actively studied and already presenting motor-like behavior on the molecular level, following new routes in the bottom-up approach, should soon enter the world of useful micro- and mesoscale electromechanical devices. This subject is discussed in Chapter 16. 

Koh et al. [6] have rigorously modeled the electromechanics of this interaction for the simplified case of uniform biaxial stretching of an incompressible polymer film including many important effects such as the nonlinear stiffness behavior of the polymer film and the variation in breakdown field with the state of strain. With regard to the latter effect, Pelrine et al. [5] showed the dramatic effect of prestrain on the performance of dielectric elastomers (specifically silicones and acrylics) as actuators. We would expect the same breakdown enhancement effects to be involved with regard to power generation. There are many additional effects that may be important, such as electrical and mechanical loss mechanisms, interaction with the environment or circuits, frequency, and temperature-dependent effects on material parameters. The analysis by Koh provides the state equations... 

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