Interphase boundaries

What of the corrosion resistance of new turbine-blade alloys like DS eutectics Well, an alloy like NiaAl-NisNb loses 0.05 mm of metal from its surface in 48 hours at the anticipated operating temperature of 1155°C for such alloys. This is obviously not a good performance, and coatings will be required before these materials are suitable for application. At lower oxidation rates, a more insidious effect takes place - preferential attack of one of the phases, with penetration along interphase boundaries. Obviously this type of attack, occurring under a break in the coating, can easily lead to fatigue failure and raises another problem in the use of DS eutectics. 

As we have already seen, when an alloy contains more of the alloying element than the host metal can dissolve, it will split up into two phases. The two phases are "stuck" together by interphase boundaries which, again, have special properties of their own. We look first at two phases which have different chemical compositions but the same crystal structure (Fig. 2.5a). Provided they are oriented in the right way, the crystals can be made to match up at the boundary. Then, although there is a sharp change in... 

Self-organization of polysiloxanes containing cyclic fragments into mono- and multilayer structures at interphase boundaries 99MI40. 

Replication of interphase boundaries under spinodal decomposition... 

Another kinetic jjhenomenon where Calm s critical waves can possibly be visualized and studied is the replication of interphase boundaries (IPB) illustrated in Figs. 8-10. Similarly to the replication of APBs. it can arise after a two-step quench of an initially uniform disordered alloy. First the alloy is quenched and annealed at temperature T in some two-phase state that can be either metastable or spinodally unstable with respect to phase separation. Varying the annealing time one can grow here precipitates ("droplets ) of a suitable size /. For sufficiently large /, the concentration c(r) within A-riched droplets is close to the equilibrium binodal value C(,(T ) (thin curve in Fig. 9). 

FIGURE 10.4 Coordinates of interphase boundaries and Gibbs surface. 

The solution of the problems of the first kind implies an in depth consideration of the formation of a multiblock copolymer macromolecule at the interphase boundary. This process may be described in the framework of the above-discussed physicochemical model as follows. 

The listed values V, if multiplied by N/2 (half the number of molecules) provide the energies of the nonlocal interaction components. To find the ground states, the values V should be compared in magnitude. Designate the orientational phases (2.3.25) by q0 X, q0 Y, qjVX, and qj Y. The corresponding interphase boundaries will then be described as follows ... 

I. Kaur and W. Gust Fundamentals of Grain and Interphase Boundary Diffusion, Ziegler, Stuttgart, 1988. 

Most local anesthetics exist in part in the cationic amphiphilic form (cf. p. 208). This physicochemical property favors incorporation into membrane interphases, boundary regions between polar and apolar domains. These are found in phospholipid membranes and also in ion-channel proteins. Some evidence suggests that Na+-channel blockade results from binding of local anesthetics to the channel protein. It appears certain that the site of action is reached from the cytosol, implying that the drug must first penetrate the cell membrane (p. 206). 

In the years since 1940, a voluminous literature has appeared on the subject of two-phase cocurrent gas-liquid flow. Most of the work reported has been done in restricted ranges of gas or liquid flow rates, fluid properties, and pipe diameter, and has usually been specific to horizontal or vertical pipe lines. The studies have in most instances been isothermal when two components were being considered nonisothermal cases were almost entirely single-component two-phase situations. Reports of investigations of two-phase two-component cocurrent flow where one component is being transferred across the interphase boundary are nearly nonexistent. 

The presence of surface tension has an important implication for the pressures across a curved interface and, as a consequence, for phase equilibria involving curved interphase boundaries. The equation that relates the pressure difference across an interface to the radii of curvature, known as the Laplace equation, is derived in Section 6.4, and the implications for phase equilibria are considered for some specific cases in Section 6.5. 

Numerical simulations of the coarsening of several particles are now possible, allowing the particles to change shape due to diffusional interparticle transport in a manner consistent with the local interphase boundary curvatures [17]. These studies display interparticle translational motions that are a significant phenomenon at high volume fractions of the coarsening phase. 

The system is at the temperature T and the 0 phase is essentially pure B, while the a phase contains a moderately low concentration of B so that Henry s law is obeyed. The average radius of the shell is (R) and the thickness of the thin shell is 6R, where 6R diffusion rate of B in the 0 phase is extremely slow and can be neglected in comparison to its diffusion rate in the a phase. Find an expression for the shrinkage rate of the shell and show that the shell will shrink at a rate inversely proportional to (R). Assume that the concentration of B in the a phase is maintained in local equilibrium with the 0 phase at both the inner and outer interphase boundaries between the shell and the 0 phase. Also, neglect any small volume changes that might occur. 

The reduced hardness and improved machinability are attributed primarily to the crack deflection process. It can be seen in Fig. 13.8 that the composite showed obvious particle pullout and significant crack deflection along interphase boundaries due to the weak interface bonding. The crack deflection mechanism (absorbing fracture energy and blunting crack tip) could lead to an increase in machinability. As described above, the thermal expansion... 

In this overview, we will first discuss how transmission electron microscopy (TEM) techniques can be used to determine the presence or absence of intergranular amorphous phases at interphase boundaries in structural... 

Wetting, non-wetting and dewetting behaviour of interphase boundaries in non-oxide ceramic composites... 

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