Solute region

In aging, the alloy is heated below the solvus to permit precipitation of fine particles of a second phase 9 (CuAl ). The solvus represents the boundary on a phase diagram between the soHd-solution region and a region consisting of a second phase in addition to the soHd solution. 

In addition to this work on the / phase, both the thermodynamic and kinetic properties of the terminal solid-solution region, which extends to about 9 atom% lithium at 423 °C, were also investigated in detail [36]. 

The binary system lead-thallium shows an unusual type of phase diagram. Fig. 1, taken from Hansen (1936), represents in the main the results obtained by Kumakow Pushin (1907) and by Lewkonja (1907). The liquidus curve in the wide solid-solution region has a maximum at about 63 atomic percent thallium. The nature of this maximum has not previously been made clear. 

The linear velocity of the liquid developing under the effect of this force is zero directly at the solid surface, and increases to some maximum value v at the distance X = 8o from the surface. Solution regions farther out lack the excess charges that could come under the effect of the external electric field hence, there is no further increase in liquid velocity (Fig. 31.4). When the layer (Sg) is much thinner than the capillary radius, 5g r, the assumption can be made that the bulk of the solution moves with a uniform velocity v. 

In the simple case of electrostatic attraction alone, electrolyte ions can approach to a distance given by their primary solvation sheaths, where a monomolecular solvent layer remains between the electrode and the solvated ions. The plane through the centres of the ions at maximum approach under the influence of electrostatic forces is called the outer Helmholtz plane and the solution region between the outer Helmholtz plane and the electrode surface is called the Helmholtz or compact layer. Quantities related to the outer Helmholtz plane are mostly denoted by symbols with the subscript 2. 

The description of the double layer reported in Figures 3 and 22 is only approximate the composition of the electrode/solution region is somewhat more complex. The double layer has been studied in most detail for a mercury electrode immersed in an aqueous solution. According to Gouy-Chapman-Stem there are several layers of solution in contact with the electrode, see Figure 25. 

Approximately ten years ago, it was first reported by Haertling and Land (jj that optical transparency was achieved in a ferroelectric ceramic material. This material was, in reality, not just one composition but consisted of a series of compositions in the lanthanum modified lead zirconate-lead titanate (PLZT) solid solution region. The multiplicity of compositions, each with different mechanical, electrical and electrooptic properties has led to a decade of study in defining the chemical and structural nature of these materials in understanding the phenomena underlying their optical and electrooptic properties and in evaluating the practicality of the large number of possible applications (2-12),... 

PLZT Compositional System. The solid solution region which forms the basis of the PLZT materials is a series of compositions resulting from the complete miscibility of lead zirconate and lead titanate (commonly designated at PZT) in each other. Modifications to the PZT system by the addition of lanthanum oxide has a marked beneficial effect upon several of the basic properties of the material such as decreased coercive field and increased dielectric constant, electromechcuiical coupling coef-... 

So far we have established in a qualitative way the importance of the metal properties on the characteristics of the interfacial region through two properties, the relation of Omvs. pzc and the capacitance of the double layer. What is next At this point it would be good to obtain a detailed model of the metal region and then determine—now in a quantitative way—the influence of the metal on the interfacial properties, similarly to the procedure followed when studying the solution region (Section 6.6.1). 

In the PIT range Shinoda observed an isotropic liquid phase called the surfactant phase (31) the general features of the micellar solution regions are illustrated in Figure 3. The influence of several factors on the size of the various regions has been amply described (32, 33). 

Figure 6. General features of the isotropic solution regions in a system water, hydrocarbon, and nonionic emulsifier with an oxyethyl-ene chain length of about 4. The numbers 1-6 show the regions at increasing temperatures.

An example of the concentration profiles of the oxidized species O, calculated for different times and corresponding to the application of a constant potential under linear diffusion conditions, is shown in Fig. 1.20. The electrode reaction at the interface leads to the depletion of species O at the solution region adjacent to the electrode surface. As the time increases, the layer in the solution affected by the diffusive mass transport becomes thicker, which indicates that linear diffusion is unable to restore the initial situation (for a more detailed discussion on concentration profiles and their relation with the current, see Sects. 2.2.1 and 2.2.2). 

If the overall composition lies within one of the solid solution regions, the aUoy will exist as the corresponding solid solution. 

Figure E3.6b, which plots the solution of Eq. E3.6-23 for three n values, also indicates the four solution regions.

Avery common occurrence is that, in the liquid phase, the components are completely miscible, whereas in the sohd phase, the components are only partially miscible, usually in small ranges around the pure components. This is illustrated in Fig. 10. Except for the single-phase sohd solution regions in the vicinity of the pure solid components, this diagram is similar to Fig. 10 of Chapter 8. It shows a eutectic, which freezes to a mixture of fine crystals of the two solid solutions. These three coexisting phases are represented by a horizontal line on the phase diagram. 

Because the kinetic and mass-transport phenomena occur in a thin region adjacent to the electrode surface, this area is treated separately from the bulk solution region. Since kinetic effects are manifested within 100 A of the electrode surface, the resulting overpotential is invariably incorporated in the boundary conditions of the problem. Mass transport in the boundary layer is often treated by a separate solution of the convective diffusion equation in this region. Continuity of the current can then be imposed as a matching condition between the boundary layer solution and the solution in the bulk electrolyte. Frequently, Laplace s equation can be used to describe the potential distribution in the bulk electrolyte and provide the basis for determining the current distribution in the bulk electrolyte. 

Figure 36.1 Ideal dilute solution regions for liquid-liquid mixture (solution) A/B.

As seen from Fig. 6 at 305°C the values of partial molar enthalpy for different runs of hydrogen desorption have a large deviation probably because of a proximity to critical temperature, thus it is difficult to determine the phase boundaries. The critical temperature for the existence of ZrMn2 hydride phase estimated by different authors is 277-327 °C [8] and 318°C [15], The plot of the AHdes. -C could be divided into three parts the hydrogen a-solid solution region (0pi transition (0.6p2 transition (1.0[Pg.353]

Many electrical double-layer and adsorption models have been proposed to account for experimental data dealing with the adsorption of ions on oxides. Stern suggested separation of the solution region near the surface into two parts, the first consisting of a layer of... 

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