Phase diagrams intermediate phases

Sponge mesophases are characterized by flow birefringence (giving anisotropic optical textures), yet they are isotropic at rest. They are typically viscous, though less so than bicontinuous cubic mesophases. Their mesostructures are closely related to the bicontinuous cubics. They often form at high (water) dilution, usually in regions of the phase diagram intermediate to lamellar and bicontinuous cubic mesophases. 

Figure 4.26 Sequence of phases observed on increasing solvent content, in a binary amphiphile-solvent system, representing a hypothetical phase diagram where phase transitions are controlled by solvent content only. Here a, b, c and d indicate intermediate phases (for example the bicontinuous cubic structure shown in Fig. 4.25d), L2 denotes the inverse micellar solution, Hn is the inverse hexagonal phase, L is the lamellar phase. Hi is the normal hexagonal phase and Li is the normal micellar phase. In practice, the full sequence of phases is rarely observed, and in reality the phase transitions depend on temperature as well as concentration...

A volatile oil contains a relatively large fraction of lighter and intermediate oomponents which vaporise easily. With a small drop in pressure below the bubble point, the relative amount of liquid to gas in the two-phase mixture drops rapidly, as shown in the phase diagram by the wide spacing of the iso-vol lines. At reservoir pressures below the bubble point, gas is released In the reservoir, and Is known as solution gas, since above the bubble point this gas was contained in solution. Some of this liberated gas will flow towards the producing wells, while some will remain in the reservoir and migrate towards the crest of the structure to form a secondary gas cap. 

Fig. 3.6. (a) The copper-nickel diagram is a good deal simpler than the lead-tin one, largely because copper and nickel are completely soluble in one another in the solid state. (b) The copper-zinc diagram is much more involved than the lead-tin one, largely because there are extra (intermediate) phases in between the end (terminal] phases. However, it is still an assembly of single-phase and two-phase fields. 

Fig. 16.6. A typical ceramic phase diagram that for alloys of SiOj with AljOj. The intermediate compound...

FIG. 4 Phase diagram of Langmuir monolayers at low and intermediate surface coverage (schematic). Not shown are the various phases on the condensed side at high surface coverage. 

FIG. 8 Phase diagram of a Langmuir monolayer in a model of grafted stiff Lennard-Jones chains. LE denotes a disordered expanded phase, LC-U a condensed phase with untilted chains, LC-NN and LC-NNN condensed phases with collective tilt towards nearest neighbors and next-nearest neighbors, respectively, and LC-mod a phase which has a superstructure and an intermediate direction of tilt. (From Stadler and Schmid [151].)... 

The phase-diagram (temperature vs concentration) for a eutectic two-component alloy shows at low temperatures a central two-phase region and two solid one-phase regions at low and high relative concentrations. At the eutectic temperature the liquid phase at an intermediate concentration can all of a sudden coexist with the two solid phases. Upon further increase of temperature, the liquidus lines open up a V-shaped liquid... 

By way of example, the Cu-Zn phase diagram shown in Fig. 20.42 exhibits a number of different intermediate phases (j8, 7, 6, etc.) and a number of peritectic reactions and a eutectoid reaction. In many instances it is not necessary to consider a complete phase diagram. Thus Fig. 20.43 illustrates the Al-rich end of the Al-Cu phase diagram and is used below in a discussion... 

Figure 2. Phase diagram for PEO-LiN(CF,S03)2 showing the eutectic equilibrum between PEO (Mw =4xI06) ant the 6 1 (salt wt. Fraction 0.52) intermediate compound. Compiled from C. I. abreche, I. Levesque, J. Prud homme, Macromolecule 1996, 29, 7795 and S. Lascaud, M. Perrier, A. Vallee, S. Besner, J. Prud homme, M. Armand, Macromolecules 1994, 27, 7469.

Alloys of lead and thallium have a structure based upon cubic closest packing from 0 to about 87-5 atomic percent thallium. The variation of the lattice constant with composition gives strong indication that ordered structures PbTl, and PbTl, exist. In the intermediate ranges, solid solutions of the types Pb(Pb,Tl)a and Pb(Pb,Tl)TlB exist. Interpretation of interatomic distances indicates that thallium atoms present in low concentration in lead assume the same valence as lead, about 2-14, and that the valence of thallium increases with increase in the mole fraction of thallium present, having the same value, about 2-50, in PbTls and PbTl, as in pure thallium. A theory of the structure of the alloys is presented which explains the observed phase diagram,... 

No phase diagram is available for the potassium-copper or potassium-silver systems. A diagram for the potassium-gold system shows the existence of four intermediate phases but later work shows that the phase identified as KAU4 1 diagram is in fact KAuj. 

No phase diagram is available for systems involving either Cu or Ag. The Rb-Au system shows three intermediate phases, although RbAu4 was later shown to be RbAus. No compound RbjAu has been observed corresponding to KjAu. 

The Li-Zn phase diagram shows the presence of eight intermediate phases. Later x-ray diffraction results confirm the existence of five intermediate RT phases " . Polymorphism is shown by the three compounds shown in the Li-Cd phase system, and this has confused the interpretation of x-ray diffraction patterns ". 

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