Simple ternary eutectic system

The figure below shows such a polythermal projection of a simple ternary eutectic system without solid solution like the one represented by the figure above. 

Polythermal projections of the liquidus discussed in section 4.3.2. do not provide information on the compositions of solid phases if solid solutions or non-stoichiometric compounds are formed at equilibrium. For providing this information, the method of isothermal section is particularly useful. The following figure represents a simple ternary eutectic system with terminal solid solutions formed. 

Figure 3.29. Spatial view of the simple ternary eutectic system.

If we have a mixture AX-AY-BY, the composition of which is in Figure 3.35 shown by the figurative point Xi, the crystallization path at its cooling is completely similar as in the case of a simple ternary eutectic system. The component BY begins to crystallize first, the composition of the melt moves towards point Mi, where also component AX starts to crystallize. At the ensuing cooling, both the components fall out from the melt simultaneously and the composition of the melt moves on the boundary line etj — et2 from point Mi up to the eutectic point etj, where also component AY starts to crystallize and where also the whole system will solidify. 

The simple ternary eutectic system discussed above represents just a beginning to the general subject of ternary phase diagrams. Features such as solid... 

Figure 16.2. Some phase diagrams, (a) The water end of the system potassium chloride and water, (b) The water end of the system sodium chloride and water, (c) The water end of the system magnesium sulfate and water the heptahydrate goes to the mono at 150°C, and to anhydrous at 200°C. (d) /3-methylnaphthalene and /S-chloronaphthalene form solid solutions, (e) Mixtures of formamide and pyridine form a simple eutectic, (f) These mixtures form binary eutectics at the indicated temperatures and a ternary eutectic at mol fractions 0.392 dibenzyl, 0.338 diphenyl, and 0.27 naphthalene.

In the case of a mixture shown on Figure 3.32 by the figurative point X3, the situation is similar as in a simple eutectic ternary system. Starting with the crystallization of component C, the composition of the melt moves up to the point 5, where the component A4B begins to crystallize. At the ensuing cooling, the composition of the melt moves on the boundary line Pt—Ct up to the ternary eutectic point, where also component B crystallizes until the whole system solidifies. 

The binary compound BCX3 divides the AX-BX-CX2 and DX2-BX-CX2 ternary systems into four simple ternary subsystems. The crystallization paths of ternary mixtures end in one of the six ternary eutectic points E , where the ternary mixtures solidify. The crystallization path of any quaternary mixture follows the dotted boundary lines inside the concentration tetrahedron and ends in one of the two quaternary eutectic points Eq,. 

In the ternary system KF-K2T1F6-KBF4, the intermediate compound KsTiFy divides the system into two simple eutectic systems. The calculated coordinates of the two ternary eutectic points are ... 

As an example of calculation of the surface tension in the ternary system, KF-KCI-KBF4 is presented. The surface tension of this system was measured by Lubyova et al. (1997) using the maximum bubble pressure method. The system is a simple eutectic system experimentally attainable in the whole concentration triangle. 

AC or BC, which melts at a higher temperature than either of the pure elements (except for the InSb-Sb case). The binary phase diagram consists of two simple eutectic systems on either side of the compound (e.g., the A-AC and the AC-C systems). The third binary phase diagram represents solid-liquid equilibrium between elements from the same group. In Figure 1 the A-B portion of the ternary phase diagram is depicted as being isomorphous... 

Both the ternary systems are simple eutectic ones and the composition of the system is represented by the ionic fraction of one of the cations and one of the anions. In Figure 4.21 the ionic fraction of Li+ is varied along the X-axis, while the ionic fraction of F is varied along the 7-axis. 

Figure 2.19 Perspective drawing of a ternary system with a simple eutectic and no ternary compound. Reprinted, by permission, from Phase Diagrams for Ceramists, Vol. 1, p. 15. Copyright 1964, The American Ceramic Society.

The classification system described earlier is limited to the simplest kinds of individual melts and is not intended to include mixtures. However, molten mixtures of these different classes of compounds are often more practical solvents than the melts of the individual compounds, due to their much lower melting points and other favorable properties, and this system of classification can usually be extended to these mixtures. For example, the very popular molten LiCl-KCl eutectic mixture is simply a binary ionic melt, whereas molten NaN03-KN03-LiN03 is a ternary polyanionic melt. Interestingly, the equimolar molten mixture of the simple ionic salt NaCl (a) and the molecular compound A1C13 (d) produces a simple polyanionic salt melt (b) composed of Na+ and A1C14 ions ... 

Figure 11.6 shows an example of the phase diagram for a reactive system, in which a compound C is formed from components A and B. An isothermal cut and the polythermal projection are also shown. Such a phase diagram can be obtained via a reaction invariant projection of a higher-dimensional simple eutectic phase diagram. AS and BS are binary nonreactive eutectics, since their presence is not affected by the reaction, while ACSb and BCSa are ternary reactive eutectics. Similar... 

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