INDEX ionic conductivity

Different from the critical radius, Mori et al. [89] proposed a concept of effective crystallographic index to maximize the oxide ionic conductivity of doped ceria. The index, I, is defined as... 

Na and K azides were detd in solns of varying concns by Petrikalns Ogrins (Ref 12).They also detd the density and refractive index for crystn Na and K azides. The ionic conductance of solid Li azide, as detd by Jacobs Tomkins (Ref 18), obeyed the general equation log k = log A - (E/2.303RT) where k is the specific conductivity in ohm-1 cm"1 A is a constant and E is activation energy in kcal/ mol. For Li azide log A 0.840, E is 19.1 and T, the temp range 300 370°K. The Raman Effect of crystn Li azide was detd by Kahovec Kohlrausch (Ref 14/, the observed frequency, 1368.7 cm-1, corresponded to the oscillation in a linear triatomic molecule. 

Chief among the interfacial properties of aqueous systems that suggest the occurrence of thermal anomalies are the following index of refraction, density, activation energy for ionic conductance, rates of surface reactions, surface tension, surface potentials, membrane potentials, heats of immersion, zeta potentials, rate of nucleation, viscous flow, ion activities, proton spin lattice relaxation times, optical rotation, ultrasonic velocity and absorption, sedimentation rates, coagulation rates, and dielectric properties. 

The changes in the film material with the current density, field, and temperature at which the films are made (in dilute, aqueous solution) and the changes which occur on subsequent annealing at temperatures of up to 200 C or so, represent large proportional changes in the concentration of mobile ions, that is, according to the usual theory, in the concentration of defects (interstitial metal ions and anion and cation vacancies). However, the absolute variations in terms of numbers of defects are probably small. Thus the variations in properties, which are not directly functions of defect concentrations, such as refractive index and density, are of the order of 1 %— not large for ordinary formation conditions—whereas the variations in those properties, such as ionic conductivity, electronic conductivity, and rate of dissolution in which are directly dependent on the concentra-... 

Experimental methods of investigating the ionic conduction process must start from some method of determining the thickness of the oxide, since the thickness must be known to determine the field. The rate of change of thickness determines the ionic current unless variations of composition occur, or ions of unusual valency are produced which result in chemical reactions at the interface in which hydrogen liberation accompanies oxide production. Most of the available methods are insufficiently reliable for satisfactory kinetic studies. Only the optical methods seem to be reasonably unequivocal. An optical thickness nD is usually found. If the oxide is shown to be uniform, a determination of the refractive index n gives D. Some optical techniques of high accuracy have been described elsewhere in detail. The technique of ellipsometry has recently been explored and some discussion will be given here. 

The thermal properties of the PILs including glass transition, Tg, melting point Tm, boihng point 7b, and chemical transformation or decomposition point, 7d, are given in Table 2. The physicochemical properties of density, p surface tension (for hqrrid—air interfaces), y viscosity, >7 refractive index, d and ionic conductivity, k, for the PILs are given in Table 3. In Tables 2 and 3, the PILs are grouped based... 

Table 3. Physicochemical Properties of Index (nj)), and Ionic Conductivity (K) ...

The dielectric constant, e, depends on temperature only to the extent that the density changes with temperature, eg, a sharp change at the melting temperature, Tm. Except for the influence of ionic conductivity at low frequencies or temperatures above I m. the dissipation factor and the loss index, e", are essentially constant for an ideal, nonpolar polymer, such as PTFE, with some minor exceptions due to branching and other perturbations in the molecular structure. 

To characterize the transport properties of in vitro BBB models, the solute permeability P of the in vitro BBB was determined by measuring the flux of the selected tracer. The most commonly used cell culture substrate consists of a porous membrane support submerged in the culture medium (Transwell apparatus). The Transwell system is characterized by a horizontal side-by-side or vertical diffusion system. During the experiment, the flux of tracers into the abluminal compartment of the Transwell system is recorded as a function of the time and the solute permeability P is calculated from the slope of the flux. The tracers used in the transport experiments are labeled by a fluorescent dye or isotope whose intensity can be measured quantitatively. Another index, transendothelial electrical resistance (TEER), or the ionic conductance of the monolayer, is also a measurement of the tightness of the in vitro BBB models. 

The ionic conductivity in the wet state of phosphorylated chitosan membranes prepared from the reaction of orthophosphoric acid and urea on the surface of chitosan membranes in AA -dimethylformamide was investigated by Wan et alP The authors observed that similarly to unmodified chitosan membranes phosphorylated chitosan membranes are hardly conductive in their dry states with conductivities between 10" and 10 S/cm. The entire conduction process occurs after the water incorporation increases the ionic conductivity values up to 10 and 10 S/cm depending on the phosphorus content in the sample. The best result of 1.2 x 10" S/cm was obtained with the sample containing 87.31 mg/m of phosphorus content. They also observed that the increase in the phosphorus content promotes a decrease in the crystallinity of phosphorylated chitosan membranes, an increase in the swelling index and not a significant loss of their tensile strength and thermal stability in comparison with the unmodified chitosan membranes. 

A method of characterising transport mechanisms in solid ionic conductors has been proposed which involves a comparison of a structural relaxation time, t, and a conductivity relaxation time, t . This differentiates between the amorphous glass electrolyte and the amorphous polymer electrolyte, the latter being a very poor conductor below the 7. A decoupling index has been defined where... 

Aqueous soap solutions can be obtained in three distinct forms, the sol form containing the ionic micelle, a clear gel, and a white opaque solid the curd. The sol and gel forms of various soaps have been examined by McBain and his co-workers and shown to differ only in elasticity and rigidity, whilst the electrical conductivity, refractive index, concentration of metallic ion and lowering of the vapour pressure are all identical, results to be anticipated on the fibrillar theory. The gel as we have seen is fibrillar in nature and the conversion of a gel into a curd is brought about by the removal of soap fi om solutions in the form of relatively coarse fibres, a process similar to crystallisation. The experiments of Laing and McBain... 

Ionic liquids are a class of solvents and they are the subject of keen research interest in chemistry (Freemantle, 1998). Hydrophobic ionic liquids with low melting points (from -30°C to ambient temperature) have been synthesized and investigated, based on 1,3-dialkyl imidazolium cations and hydrophobic anions. Other imidazolium molten salts with hydrophilic anions and thus water-soluble are also of interest. NMR and elemental analysis have characterized the molten salts. Their density, melting point, viscosity, conductivity, refractive index, electrochemical window, thermal stability, and miscibility with water and organic solvents were determined. The influence of the alkyl substituents in 1,2, 3, and 4(5)-positions on the imidazolium cation on these properties has been scrutinized. Viscosities as low as 35 cP (for l-ethyl-3-methylimi-dazolium bis((trifluoromethyl)sulfonyl)amide (bis(triflyl)amide) and trifluoroacetate) and conductivities as high as 9.6 mS/cm were obtained. Photophysical probe studies were carried out to establish more precisely the solvent properties of l-ethyl-3-methyl-imidazolium bis((trifluoromethyl)sulfonyl)amide. The hydrophobic molten salts are promising solvents for electrochemical, photovoltaic, and synthetic applications (Bon-hote et al., 1996). 

Long-wavelength refractive index [40,41] suggests a high frequency dielectric constant ex = a2 = 8.4, a value supported by recent measurement [42] and ab initio calculation [43], Ionic polarisability makes a significant contribution at low frequencies where, although measurement is presently inhibited by a high conductivity, s0 15 is recommended [43],... 

Refractive index detection allows an extremely wide latitude in the selection of the eluent type, eluent pH and the ionic strength. In principle, refractive index detection can be substituted for conductance or UV absorption detection in many separations. However, in early work, refractive detection was found to be only moderately sensitive and was considered to be somewhat interference-prone [71]. Minimum detectable quantities for common anion such as chloride nitrate, or sulfate were reported to be in the 20 ng to 50 ng range (compared with 1 to 5 ng for direct conductance detection). 

---