Phase diagram of a binary system

Figure 7 A schematic phase diagram of a binary system...

Because there is an added term, the composition, binary systems are inherently more complex than unary systems. In order to completely represent the phase diagram of a binary system a three dimensional pressure-temperature-composition (P-T-x) diagram can be constructed. However, it is a more common... 

The phase diagram of a binary system as shown below is effectively two simple eutectic diagrams linked together. Therefore there are two eutectic points in this kind of the system. A maximum point appears on the liquidus, which is the melting point of the congruently-melting compound. 

Also, formation of a solid solution is often considered to be a prerequisite for the occurrence of a chemical compound layer, with the latter being a result of supersaturation of the former. In fact, however, these are two concurrent, competing processes, if both solid solutions and chemical compounds are present on the phase diagram of a binary system. In any... 

Exact laws governing the sequence of occurrence of compound layers in a particular reaction couple have not so far been established. What is available is a few empirical rules predicting this sequence at a probability level of about 60 to 90 %. These are based either (i) on the structure of the equilibrium phase diagram of a binary system or (ii) on the thermodynamic properties of its compounds. 

Fig. 11.7. Isobaric phase diagram of a binary system where the following reaction takes place A + B — C resulting in (a) a congruent melting compound and (b) an incongruent melting compound.

FIG. 141, Schematic phase diagram of a binary system with a miscibility gap (curve/), with indicated region of spinodal decomposition (curve s). 

Fig. 10-6. (a) Phase diagram of a binary system with a lower critical point solid line, binodal (or cloud-point curve) dashed line, spinodal C, Critical point, (b) Composition dependence of AGe at T = To. 

The G-M method for predicting the phase diagram of a binary system on activated carbon is based on the equation... 

Construction of the Phase Diagram of a Binary System A-B with Ideal Solid Solution... 

Figure 11.25 Schematic phase diagram of a binary system surfactant/water. Inverse hexagonal phase Hn, lamellar phase Lo, hexagonal phase Hj, isotropic (cubic) phases a, b, c, d.

A very simple model is now introduced to illustrate how a eutectic reaction may occur and to map out the phase diagram of a binary system in which a eutectic reaction occurs. We assume the freezing temperature of A Ta > Tb and the eutectic temperature Tg = 940 K as shown in Figure 12.15. 

Typical phase diagram of a binary system with complete liquid and solid solubility. The first-to-freeze component will have composition Cl. The rejected B component will be pushed ahead of the solidification front and, if convectively mixed with the remaining melt, the solid will become richer in 6 as the process continues. 

Figure 9.1 Phase diagram of a binary system A-B. The solid line represents a region where Phase A and Phase B are not miscible...

As mentioned earlier, texture observation cannot always be counted on to produce an unambiguous determination of the type of mesophase present. It can happen that similar textures are observed with two LC states separated by a phase transition. It is advisable, therefore, to use this method in conjunction with other types of characterization such as miscibility tests. Sackman and his school at Halle have produced a classification scheme for LMMLCs based on the criterion of complete miscibility of identical phases. " Isomorphous LCs are considered as equivalent and characterized by the same symbol. Therefore, the mesophases of a new compound can be positively identified by isomorphy with known mesophases of reference compounds. Assuming that the method is applicable to LCPs, the type of mesophase can be determined by establishing the isobaric temperature-composition phase diagram of a binary system composed of the polymer and a reference compound. Such diagrams can be generated from thermal data or, because of the various optical features characteristic of each mesophase... 

Figure 4 Schematic phase diagram of a binary system, consisting of a polymer and a solvent of marginal thermodynamic quality. The miscibility gap is shaded. Indicated in the graph is how the compositions of the working point (WP) can be reached either by cooling a homogeneous feed solution (FD, route A) or by adding pure solvent (extracting agent, EA) to a concentrated feed solution (FD, route B). The system demixes into a polymer-rich gel phase (GL) and a polymer-lean sol phase (SL).

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