Dielectric constant, effect chemical composition

Greater deviations which are occasionally observed between two reference electrodes in a medium are mostly due to stray electric fields or colloid chemical dielectric polarization effects of solid constituents of the medium (e.g., sand [3]) (see Section 3.3.1). Major changes in composition (e.g., in soils) do not lead to noticeable differences of diffusion potentials with reference electrodes in concentrated salt solutions. On the other hand, with simple metal electrodes which are sometimes used as probes for potential controlled rectifiers, certain changes are to be expected through the medium. In these cases the concern is not with reference electrodes, in principle, but metals that have a rest potential which is as constant as possible in the medium concerned. This is usually more constant the more active the metal is, which is the case, for example, for zinc but not stainless steel. 

TABLE 1. Effect Of Chemical Composition On The Dielectric Constant E and Tan 6 Of Xe3SiO(MeRSiO)xSiMe3(a)... 

The first area of ferroelectric ceramic application was that of capacitor engineering, where the dielectric effect is exploited. Most ceramic capacitors are, in reality, high-dielectric-constant ferroelectric compositions in which the ferroelectric properties (hysteresis loop) are suppressed with suitable chemical dopants while retaining a high dielectric constant over a broad temperature range. Historically, the first composition used for such capacitors was BaTi03 and its modifications, but today lead-containing relaxors and other compositions are also included. 

Effect of fiber treatment Chemical modification of fibers decreased the dielectric constant of OPF-sisal fiber-NR hybrid composites [59]. This was due to the decrease in orientation polarization of the composites upon treatment. Chemical treatment results in reduction of hydrophilicity of the fibers leading to lowering of orientation polarization and subsequently dielectric constant. Alkali treatment yielded higher dielectric constant comparing to silane treatment. However, higher concentration of alkali... 

However, after chemical treatment of C. indica fibers, dielectric constant values of finally fabricated biocomposites have been found to be lowered, which could be due to the decrease in orientation polarization of polymer composites containing surface-modified fiber. We have reported earlier that benzoylation reduces the moisture absorption behavior of fibers because of blockage of —OH groups on cel-lulosic fiber backbone. Thus resultant decrease in hydrophUicity of the polymer composites leads to lowering of orientation polarization and ultimately dielectric constant value [22]. It has also been observed that mercerization is one of the most effective methods in the reduction of dielectric constant values of the obtained biocomposites. 

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