Mercury phase diagrams

High temperature superconductors (HTS), 23 814, 826, 829. See also Anisotropic HTS HTS entries applications of, 23 852-872 layered, 23 827, 840 magnetic phase diagram of, 23 838-842 p- and n-type, 23 838 structural anisotropy and fluxon line fragmentation in, 23 841 thallium- and mercury-based, 23 848-850... 

Mercury-cadmium-telluride is the principal semiconductor now being used in advanced infrared systems, both for military and other surveillance applications. Its preparation and use in infrared detectors and arrays was the subject of Volume 18 of this treatise. New generations of detectors and arrays require sophisticated epitaxial growth, which in turn requires precise phase diagram data. 

In order to gain a better understanding of the usefulness of phase diagrams, consider a cylinder in which temperature can be controlled and volume varied by injection or removal of mercury as shown in Figure 2-2. Figure 2-2A shows that a pure substance has been trapped in the... 

The importance of many-body interactions for accurate prediction of phase diagrams of rare gases has been demonstrated.87 A study on liquid mercury that uses an ab initio pair potential and a semiempirical many-body correction to produce an effective three-body potential that was able to predict the liquid-vapour phase diagram well,110 suggests that the main deficiency of the classical pair potential is the neglect of many-body effects. 

Table A-53 Measured enthalpies of dissolution of zinc and cadmium selenites in H2S04(aq, 1 50) and mercury selenites in HCl(aq, 1 35). The enthalpies of formation have been estimated from these data. The uncertainties stem from the original publication. The data for the compounds provided with an asterisk are given for information only as they do not seem to form under normal aqueous conditions cf. phase diagram studies reported in Chapter V).

A phase diagram is a map that indicates the areas of stability of the various phases as a function of external conditions (temperature and pressure). Pure materials, such as mercury, helium, water, and methyl alcohol are considered one-component systems and they have unary phase diagrams. The equilibrium phases in two-component systems are presented in binary phase diagrams. Because many important materials consist of three, four, and more components, many attempts have been made to deduce their multicomponent phase diagrams. However, the vast majority of systems with three or more components are very complex, and no overall maps of the phase relationships have been worked out. 

Solubilities and the physicochemical data related to these amalgams are readily available in the literature.62-65 Of these, sodium amalgam is of importance from the operational viewpoint of mercury cells. The phase diagram of sodium amalgam has been well established (see Fig. 10), and there are various compounds of... 

Pressure-temperature phase diagram of mercury with isochores at the... 

Because of the close relationship between the MNM transition and the vapor-liquid transition, it is to be expected that immiscibility in the mercury-helium system reaches up to the critical point, or even into the supercritical region. This expectation is confirmed by measurements of the phase diagram at very low helium concentrations and at pressures close to the critical pressure of pure mercury. The experiments extend up to 1610 °C and to pressures up to 3325 bar (Marceca et al., 1996). The p — T — X phase equilibrium surface obtained is qualitatively like the one shown schematically in Fig. 6.4 for a binary fiuid-fluid system of the first kind. The critical line starts at the critical point of pure mercury (Tc(l) = 1478 °C, Pc(l) = 1673 bar) and runs to higher temperatures and pressures as the helium composition X2 increases. 

Fig. 6.6. Isotherms in the (p—X2) plane of the mercury-helium phases diagram at 1490 C and 1518 C. Dot-dash curve is the critical line connecting critical points open circles), heavy solid lines represent solubility curves and are extrapolated (dashed curves) to p = 11 g cm". Coordinates of selected tie lines light solid lines) are given in Table 6.1.

Although prewetting transitions are inextricably connected with first-order wetting transitions, they have proven very difficult to observe experimentally for solid-vapor interfaces. The few systems for which the phenomenon has been observed include He films on cesium (Rutledge and Taborek, 1992), H2 films on rubidium (Cheng et al., 1993), mercury films on sapphire (Hensel and Yao, 1994 Yao and Hensel, 1996), and mercury films on niobium (Kozhevnikov et al., 1997). In these cases, complete prewetting phase diagrams were determined. 

Yao and Hensel (1996) determined the prewetting phase diagram of mercury on sapphire by reflecting light from a vertical sapphire-mercury vapor interface. To locate the prewetting line, reflectivity measurements could be performed at constant temperature while increasing the pressure of the vapor toward the bulk saturation value (p /) alternatively, at constant pressure as the temperature was reduced toward bulk satura-... 

Fig. 6.9. Prewetting phase diagram for mercury showing liquid-vapor coexistence curve and diameter together with line of prewetting transitions extending from to the prewetting critical point, The dashed extension of the prewetting line indicates loci of maximum two-dimensional compressibility in the supercritical range above Inset, Prewetting layer thicknesses estimated with a slab model as described in text.

Fig. 4.10 Pressure-temperature phase diagram of mercury with isochores at the indicated densities (Gotzlaff, 1988). 135...

Fig. 6.6 Isotherms in the (p — X2) plane of the mercury-helium phases diagram at 1490°C and 1518°C. 206...

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