Conductivity disperse

Various theoretical attempts have been made to provide a quantitative interpretation of the dispersion region (Funke, 1986 Funke and Hoppe, 1990). While the situation is still not fully resolved, it is now clear that such a dispersion, which has been observed in a wide range of crystalline as well as glassy ionic conductors, is associated with ion-ion relaxation effects. The conductivity dispersion, ff(co), is usually linear in a plot of log a vs log CO, which means that it can be represented by a power law expression ... 

We earlier defined the hopping rate parameter, cOp. It corresponds approximately to the frequency at which the conductivity dispersion commences, arrowed in Fig. 2.8. 

Typical OAN Numbers from DBPA, BET Specific Surface Area, Relative Conductivity, Dispersibility, and Purity of Various Conductive Carbon Blacks from Different Manufacturing Processes... 

Carbon Black Type BET SSA (m2 g-1) Carbon) Conductivity Dispersibility Purity... 

For a heterogeneous solid where one solid phase is dispersed in a second solid phase, or one solid phase contains pores, we introduce an effective thermal conductivity to describe steady-state conduction. The geometry of the dispersed solid or pores affect the thermal conductivity. If we have a material made of spheres with thermal conductivity dispersed in a continuous solid phase with thermal conductivity ks, then the effective thermal conductivity ke is... 

Fiq. 33. High frequency conductance dispersion of potassium chloride... 

Applications. Considering that many properties of filled materials depend on the quality of dispersion, the reasons for conducting dispersion tests are self explanatory. 

Many unsubstituted polymeric organic semiconductors are not easily dissolved in solvents. After mechanical processing, doping with acids, and/or processing with surfactants many of these materials can be formed into conductive dispersions and applied from solution to substrates. 

The result of impedance spectroscopy for NC specimen (18hr passage of C Hj gas) measured at room temperature 20°C is shown in a Cole-Cole plot in Figure 12.34. The measured conductivity dispersion also shows an initial increase of conductivity with increasing CNP concentration. The bulk conductivity estimated from data is 4 x 10 S/cm, which is 25 times higher than that of pure background material. 

Figure 8. Comparison of equations predicting the reduced conductivity dispersions of spheres of unequal sizes with data. Bruggemann Eq. (10), Meredith/Tobias Distribution Model Eq. (11). Also included are Maxwell Eq. (6) and Prager Eq. (8) for comparison.

Suppose the emulsion consists of a noncontinuous phase and a conducting disperse phases in the form of identical small spherical drops of radius R carrying a constant charge q. The drops move between two parallel flat mesh electrodes. On a large distance from the electrodes, drops move perpendicularly to the mesh plane. Assume that drops acquire the charge as a result of collisions with electrodes. Then, according to [98],... 

A major new development in a related area is the work of DeSimone et al. [26,31,50,51,75,76], who conducted dispersion polymerizations in supercritical CO2. In the early stages of the dispersion-polymerization reaction, the solutions are homogenous microemulsions containing surface-active polymers with C02-philic moieties. The monomer is soluble in the continuous phase. As the polymer grows, its solubility rapidly diminishes to form precipitated polymer particles that are stabilized by the surface-active polymer. This approach has been expanded to several different polymer systems [50]. 

Conductive Dispersion 1000 Series Conductive Dispersion 3000 Series conductivity agent, acrylic-based systems ESP conductive coatings Conductive Dispersion 1000 Series Conductive Dispersion 3000 Series conductivity agent, coalings EFKA -6780 EFKA -6782 ElekVoslat 80/ 54 Elekiroslal 100/50 conductivity agent, electrostatic spray... 

Figure 13 shows the noise conductivity dispersion curve of a collagen solution (methanol+ 5% water, 10 mol/literHCl) prepared following the procedure proposed by Herbage. A sigmoidal conductivity curve is obtained when the solvent noise is substracted from the total measured noise conductivity. 

FIGURE 16. Noise conductivity dispersion spectrum of collagen solution. Collagen concentration (2g/liter in methanol-I-5 % water, 10 mol/liter HCl) O, at 25 °C , at 40°C. 

Besides, it is difncult to take into account such factors as dipole-dipole interactions, macromolecule-solvent interactions, and the local field. Thus, the interpretation of the noise conductivity dispersion amplitude seems difficult as far as the classical absorption dielectric relaxation is concerned. 

Table 5.3 Typical DBP absorption, specific BET surface area, relative conductivity, dispersibility and purity of various conductive carbon blacks from different manufacturing processes...

With increasing temperature, T, the conductivity values increase and the onset of conductivity dispersion shifts to higher frequency. The latter effect can be detected in the PEM spectra of Fig. 4b and it is well known to also exist in other ionconducting materials. In Fig. 5, the common definition a v ) = Ic c is used for the onset frequency, v, which characterizes the transition from the dc into the dispersive regime. In both PEC materials, the onset points are on a straight line, but their slope differs. For x = 0.40, the slope is smaller than one, for x = 0.60 it exceeds one. This is one of the marked differences between the spectra of PEC that are rich in PDADMAC and those that are rich in NaPSS. The implications of this difference will be further discussed in Sect. 5.2 in the context of scaling principles. 

Constitution Surface structure Conductivity Dispersion rheology... 

S/m (see Figure 19). The ER effect of the polyaniline particle of different conductivity dispersed into silicone oil was studied and the largest ER effect was found to occur in the suspension of polyanilinc particle of conductivity 10 S/m [621. Besides the influence on the ER effect, the particle conductivity also determines the current density of the whole suspension and the response time of the ER fluid. The current density of the oxidized polyacrylonitrile(OP)/silicone oil suspensions obtained at 2.5 kV/mm as a function of particle conductivity is shown in Figure 20 [61]. The current density almost linearly increases with the conductivity of particle. The response time was found to be inversely proportional to the particle conductivity both experimentally [63] and theoretically [64]. The response time can be determined from the relationship between the shear stress and the frequency of applied electric field. Such an example is shown in Figure 21, in which the shear stress of two aluminosilicate/silicone oil suspensions is plotted vs. frequency, fhe suspension with particle of conductivity 6.0 x 10 S/m displays a response time 0.6 ms, much shorter than that of the suspension of the particle conductivity 8.4 xlO S/m, 0.22s (42]. 

Carbon-ceramic composite electrodes (CCEs) and the closely related metal-sihcate electrodes are comprised of carbon or metal dispersion in sol-gel derived silicates or Or-mocers. In this construction the silicate serves as a porous binder for the conductive dispersion. The conductive component is added as powders, nanoparticles, or nanotubes whose particle size ranges between sub-millimeter and a few nanometers. The initial intention was to provide improved conductivity by the interconnected conductive powder, but soon, other favorable attributes of the metal-sihcate hybrids were discovered, including improved catalytic reactivity, biological compatibility, and control of the thickness of the wetted section of the electrodes in aqueous electrolyte. Since the metal silicate and graphite silicate call for different preparation protocols they are addressed separately. 

Percolation occurs at lower concentrations for smaller filler particles, fillers that tend to agglomerate, and highly anisotropic fillers. At a given filler concentration, one can achieve higher conductivity with a low conductivity filler that has percolated compared to a high conductivity filler that has not percolated [15]. Whereas one is usually striving for optimal dispersion, in the case of conductivity, dispersion means separation of particles and therefore an absence of percolation. 

Lutz R, Aserin A, Wachtel EJ, Ben Shoshan E, Danino D, Garti N. 2007. A study of emulsified microemulsion by SAXS, cryo-TEM, SD-NMR and electrical conductivity. / Dispersion Sci Technol 28(8) forthcoming. 

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