Pressure dielectric constant

Flammability information Flash point Fire point Flammable limits (LEL, UEL) Ignition temperature Spontaneous heating Toxic thermal degradation products Vapour pressure Dielectric constant Electrical resistivity Electrical group Explosion properties of dust in a fire... 

Vapour pressure Dielectric constant Electrical resistivity Electrical group... 

A series of works by Matsuda et al. composed perhaps the first systematic study to explore the physical foundation for such a mixing effect. Using PC/DME as a model system, they investigated the dependence of vapor pressure, dielectric constant, and viscosity on solvent composition, and they correlated these variations with ion conductions. It was found that the dielectric constant varied with solvent composition by following an almost linear relation, with slight positive deviations, while viscosity always showed a pronounced negative deviation from what a linear relation would predict (Figure 6b). For such binary solvent systems, approximate quantifications... 

Temperature, Heat capacity. Pressure, Dielectric constant. Density, Boiling point. Viscosity, Concentration, Refractive index. Enthalpy, Entropy, Gibbs free energy. Molar enthalpy. Chemical potential. Molality, Volume, Mass, Specific heat. No. of moles. Free energy per mole. 

Dipole moment Cohesive pressure Dielectric constant Refractive index Melting point and boiling point Donor numbers Acceptor numbers E, a, and 7t ... 

Bulk physical properties Cohesive pressure Dielectric constant... 

Water as a solvent has several anomalous features (e.g. anomalous density, the only nontoxic and liquid hydride of the nonmetals, melting point varying with pressure, dielectric constant) and with its two- or even three-dimensional structure has still not been fully researched. 

Flere u. j(r,T,P) is the short-range potential for ions, and e is the dielectric constant of the solvent. The solvent averaged potentials are thus actually free energies that are fimctions of temperature and pressure. The... 

For gases the values of the dielectric constant can be adjusted to somewhat different conditions of temperature and pressure by means of the equation... 

A variety of experimental techniques have been employed to research the material of this chapter, many of which we shall not even mention. For example, pressure as well as temperature has been used as an experimental variable to study volume effects. Dielectric constants, indices of refraction, and nuclear magnetic resonsance (NMR) spectra are used, as well as mechanical relaxations, to monitor the onset of the glassy state. X-ray, electron, and neutron diffraction are used to elucidate structure along with electron microscopy. It would take us too far afield to trace all these different techniques and the results obtained from each, so we restrict ourselves to discussing only a few types of experimental data. Our failure to mention all sources of data does not imply that these other techniques have not been employed to good advantage in the study of the topics contained herein. 

Dielectric Film Deposition. Dielectric films are found in all VLSI circuits to provide insulation between conducting layers, as diffusion and ion implantation (qv) masks, for diffusion from doped oxides, to cap doped films to prevent outdiffusion, and for passivating devices as a measure of protection against external contamination, moisture, and scratches. Properties that define the nature and function of dielectric films are the dielectric constant, the process temperature, and specific fabrication characteristics such as step coverage, gap-filling capabihties, density stress, contamination, thickness uniformity, deposition rate, and moisture resistance (2). Several processes are used to deposit dielectric films including atmospheric pressure CVD (APCVD), low pressure CVD (LPCVD), or plasma-enhanced CVD (PECVD) (see Plasma technology). 

Uses. l-Methyl-2-pyrrohdinone is a dipolar aprotic solvent. It has a high dielectric constant and is a weak proton acceptor. AH of its commercial uses involve its strong and frequendy selective solvency. It has replaced other solvents of poorer stabiUty, higher vapor pressures, greater dammabiUties, and greater toxicides. 

The formation of acids from heteroatoms creates a corrosion problem. At the working temperatures, stainless steels are easily corroded by the acids. Even platinum and gold are not immune to corrosion. One solution is to add sodium hydroxide to the reactant mixture to neutralize the acids as they form. However, because the dielectric constant of water is low at the temperatures and pressure in use, the salts formed have low solubiHty at the supercritical temperatures and tend to precipitate and plug reaction tubes. Most hydrothermal processing is oxidation, and has been called supercritical water oxidation. 

Because of its low dielectric constant, Hquid hydrogen sulfide is a poor solvent for ionic salts, eg, NaCl, but it does dissolve appreciable quantities of anhydrous AlCl, ZnCl2, FeCl, PCl, SiCl, and SO2. Liquid hydrogen sulfide or hydrogen sulfide-containing gases under pressure dissolve sulfur. At equihbrium H2S pressure, the solubihty of sulfur in Hquid H2S at —45, 0, and 40°C is 0.261, 0.566, and 0.920 wt %, respectively (98). The equiHbria among H2S, H2S, and sulfur have been studied (99,100). 

Reactions. Supercritical fluids are attractive as media for chemical reactions. Solvent properties such as solvent strength, viscosity, diffusivity, and dielectric constant may be adjusted over the continuum of gas-like to Hquid-like densities by varying pressure and temperature. Subsequently, these changes can be used to affect reaction conditions. A review encompassing the majority of studies and apphcations of reactions in supercritical fluids is available (96). 

HF is a colourless volatile liquid and an oligomeric H-bonded gas (HF), whereas the heavier HX are colourless diatomic gases at room temperature. Some molecular and bulk physical properties are summarized in Table 17.10. The influence of H bonding on the (low) vapour pressure, (long) liquid range and (high) dielectric constant of HF have already been discussed... 

Now, we should ask ourselves about the properties of water in this continuum of behavior mapped with temperature and pressure coordinates. First, let us look at temperature influence. The viscosity of the liquid water and its dielectric constant both drop when the temperature is raised (19). The balance between hydrogen bonding and other interactions changes. The diffusion rates increase with temperature. These dependencies on temperature provide uS with an opportunity to tune the solvation properties of the liquid and change the relative solubilities of dissolved solutes without invoking a chemical composition change on the water. 

The use of SCFs as solvents influences the reacting system because it is possible to dramatically change the density of the fluid with small perturbations of temperature and pressure and, in such a way, greatly affect the density-dependent bulk properties such as the dielectric constant, solubility and diffu-sibility of these compressible fluids. 

Water in its supercritical state has fascinating properties as a reaction medium and behaves very differently from water under standard conditions [771]. The density of SC-H2O as well as its viscosity, dielectric constant and the solubility of various materials can be changed continuously between gas-like and liquid-like values by varying the pressure over a range of a few bars. At ordinary temperatures this is not possible. For instance, the dielectric constant of water at the critical temperature has a value similar to that of toluene. Under these conditions, apolar compounds such as alkanes may be completely miscible with sc-H2O which behaves almost like a non-aqueous fluid. 

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