Dielectric permittivity minerals

The stability of an emulsion depends not only on the surfactant type, but also on die nature of the organic phase. To characterize die oil phase, the concept of a necessary (required) HLB number is used. This number is taken to be equal to die HLB number of die surfactant which ensures the best possible emulsification of the oil. Tables of necessary HLB numbers for various oils were published in Ref 258. For example, with respect to oil-in-water emulsions, the necessary HLB number is 17 for oleic acid, 15 for toluene, 14 for xylene and cetyl alcohol, 10.5 to 12 for mineral oils, 7.5 to 8 for vegetable oils, 5 to 7 for vaseline, and 4 for paraffin. In Refs 263 and 264 the necessary HLB numbers for various oils are compared with the relative dielectric permittivity of the oil e. In the series of saturated hydrocarbons, a weak inverse dependence between the necessary HLB number and e was observed (264) e.g., e =... 

Completely dense or dry rocks occur infrequently in the near surface crust. These rocks have—except for ores or graphite-containing rocks— very high resistivities (mostly >10 nm). The dielectric permittivity is usually relatively low and in the range of the dominant rock-forming minerals (3-5) accessory minerals (for example ores and graphite) can produce higher values. 

Most rock-forming minerals have a permittivity in the order of =3—10 higher values show, for example, sulphides and some oxides. The dielectric permittivity of water is about 80. This results in a strong correlation between permittivity and the water content of a rock. Table 8.9 shows some more data for the permittivity of fluids. 

Josh et al. (2012a,b) investigated shale properties in the laboratory. Figure 8.35 shows the real dielectric permittivity of mineral powder of quartz, kaolinite, illite, and smectite (equilibrated in laboratory atmosphere with 23 °C and 55 5% relative humidity) as a function of frequency. 

Liquid insulators are required for circuit breakers, transformers, and some cable applications. Natural hydrocarbon mineral oils are commonly-used, as well as chlorinated aromatic liquids (desirable because of nonflammability). For high-temperature situations, silicone fluids may be used. Permittivities range between 2 and 7. Insulating liquids function both as electrical insulators and heat-transfer media. See also Dielectric Theory. 

To increase the crystallization rate and to alter the product phase, an alkaline mineralizer is sometimes added to the solvothermal reaction. Some researchers believe that, compared with the hydrothermal process, solvothermal synthesis allows the product to be free from foreign ions because the organic solution, having a low relative permittivity, is free from ionic species. When precursor gels are prepared from alkoxide, one can prepare products free of foreign ions. However, when the precursor gel is prepared by precipitation from salt solutions, or when alkali/acid mineralizer or ionic surfactant is added to the solvothermal crystallization system, the above statement is a myth. In fact, ions are easily adsorbed or occluded in the product particles because of the low dielectric constant of the organic solvent. 

Genz et al. (163) found that the conductive and dielectric properties of suspensions of carbon black in mineral oil was highly dependent on shear. When a shear force was applied to the suspensions, flocculated aggregates were tom apart and a reduction in the permittivity levels was observed. When the shear stopped, the permittivity rose to previous levels. Thus, the reversibility of the shear-induced floe disintegration could be followed by means of dielectric spectroscopy. 

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