Homophase interface

Interfaces may also be classified broadly into homophase interfaces and heterophase interfaces. A homophase interface separates two regions of the same phase, whereas a heterophase interface separates two dissimilar phases. Crystal/vapor and crys-tal/liquid interfaces are heterophase interfaces. Crystal/crystal interfaces can be either homophase or heterophase. Examples of crystal/crystal homophase interfaces are illustrated in Figs. B.2, B.4, and B.5. Examples of heterophase crystal/crystal interfaces are shown in Figs. B.6 and B.7. Figure B.6o shows an interface between f.c.c. and h.c.p. crystals where the small mismatch between close-packed lll fcc... 

For crystalline-crystalline interfaces we further discriminate between homophase and heterophase interfaces. At a homophase interface, composition and lattice type are identical on both sides, only the relative orientation of the lattices differ. At a heterophase interface two phases with different composition or/and Bravias lattice structure meet. Heterophase interfaces are further classified according to the degree of atomic matching. If the atomic lattice is continuous across the interface, we talk about a fully coherent interface. At a semicoherent interface, the lattices only partially fit. This is compensated for by periodic dislocations. At an incoherent interface there is no matching of lattice structure across the interface. 

The modem method for quantifying the goodness of fit between two adjacent grains in a pure poly crystalline substance (homophase interfaces) or in a multiphase solid (heterophase interfaces) counts the number of lattice points (not... 

Grain boundaries in single-phase materials, defined as homophase interfaces, are regions separating grains of... 

Preferential precipitation of detrimental phases at homophase interfaces by heterogeneous nucleation. 

However, the column can also be operated in reverse by filling it with toluene and adjusting the principal interface at the bottom of the column. Then water is the dispersed phase and would break into drops at the feed point at the top of the column. These drops descend in the toluene phase and, at the bottom of the column, coalesce to a water homophase that is below the toluene phase. When needed, the principal interface can be adjusted somewhere between top and bottom of the column, whereby the heavier liquid is dispersed above and the lighter liquid below the principal interface. How is it decided which of the two liquids should be dispersed Understanding the flow and mass transfer processes in the extractor, which are analysed in this chapter, provides the answer. At this point, only the important factors are listed thus, the dispersed phase should be ... 

Fig. 9.24 Basic phenomena of drop coalescence at a horizontal interface. The drop has to reach the interface. A thin layer of the continuous phase remains between the drop and the interface. The thin layer has to drain until it breaks up. Then the drop can flow into its homophase. Mostly, the drainage process is the time-determining step of this process. 

Homophase crystal/crystal interfaces are often called grain boundaries. It is customary to classify such boundaries as either small-angle grain boundaries or large-angle grain boundaries. 

All sharp crystal/crystal homophase and heterophase interfaces can be classified as coherent, semicoherent, and incoherent. The structural features of these interfaces can be revealed by constructing them using a series of operations which always starts with a reference structure. 

Grain boundaries are the most important type of homophase solid-solid interfaces. An example of crystalline heterophase interfaces with high relevance for technological applications are semiconductor heterostructures. 

Role of Crain Boundary Structure and Interface Energy at Homophase and Heterophase Interfaces Differences in structure and energy result from the creation of a solid-state interface... 

The aim of a separator vessel is to give the coalescence process the neeessary time and ereate conditions for satisfactory phase separation. The elassical approach is to use an overall residence time eriterion, which allows the drops to (1) reach a bulk interface by sedimentation and (2) coalesce with this bulk interface, forming a single homophase. One seeks to minimize any events contributing to drop break-up. 

The primary effect of wetting is related to the existence of a slow mode characterized by a soft dispersion of its relaxation rate, whereas the upper part of the spectrum remains more or less the same as in a homophase system (see insets of Fig. 8.5). The elementary mode of fluctuations of the degree of order is localized at the phase boundary between the wetting layer and the bulk phase and it corresponds to fiuctuations of the thickness of the central part of the slab. The next mode, which is also localized at the nematic-isotropic interface, represents fluctuations of the position of the core. The relaxation rates of these two modes are the same as long as the two wetting layers are effectively uncoupled. 

Next, let us consider the non-stationary kinetics of the postpolymerization in the dark. Since, as was noted before, the contribution of the homophaseous process into the total process under the postpolymerization process should be insufficient, we analyzed only the kinetics in the interface layer assuming that w = In the dark period Vim = 0, and... 

Grain boundary is the interface between two grains. When these two grains are of the same material, the boundary is called a homophase boundary when they are of different materials, then it is a heterophase boundary. Often, there are other phases that are only a few nanometers thick and can be present between the grains of two different materials in such case, the grain boundary represents three phases. These phases may be crystalline or amorphous. The presence or absence of a third phase has important ramifications on processing, electrical properties, and creep of the material concerned. 

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