Morphology stability

K. Sekimoto, R. Oguma, K. Kawasaki. Morphological stability analysis of partial wetting. Ann Phys 776 359-392, 1987. 

L. Biihler, S. H. Davis. Flow induced changes of the morphological stability in directional solidification localized morphologies. J Crystal Growth 756 629, 1998 Y.-J. Chen, S. H. Davis, Directional solidification of a binary alloy into a cellular convective flow (unpublished). Applied Math Technical Report No. 9708, Northwestern University, Evanston, IL 60208. 

S. Coriell, R. Sekerka. Effect of convective flow on morphological stability. Physico-Chem Hydrodyn 2 281, 1981. 

In contrast to materials of low molecular mass, polymeric emitters possess the advantage that they can be easily worked into transparent films with a low degree of scattering. In addition, they show a higher morphological stability than that of vapor-deposited low molecular weight compounds (low tendency toward recrystallization). 

The morphological stability of initially smooth electrodeposits has been analyzed by several authors [48-56]. In a linear stability analysis, the current distribution on a low-amplitude sinusoidal surface is found as an expansion around the distribution on the flat surface. The first order current distribution is used to calculate the rate of amplification of the surface corrugation. A plot of amplification rate versus mode number or wavelength separates the regimes of stable and unstable fluctuation and... 

Morphological stability means that all materials, regardless of their chromo-phores and whether they are used because of their photophysical, photochemical, or redox properties, should be able to form stable glasses (or alternatively single... 

Hydrated Acidic Polymers. Hydrated acidic polymers are, by far, the most commonly used separator materials for low-temperature fuel cells. Their typical nanoseparation (also see Section 1) leads to the formation of interpenetrating hydrophobic and hydrophilic domains the hydrophobic domain gives the membrane its morphological stability, whereas the hydrated hydrophilic domain facilitates the conduction of protons. Over the past few years, the understanding of the microstructure of these materials has been continuously growing, and this has been crucial for the improved understanding of the mechanism of proton conduction and the observed dependence of the conductivity on solvent (water and methanol) content and temperature. 

Film thickness can govern the morphology, stability, and surface-chemical expression of polymeric thin films. NIST researchers developed a process for producing gradients, termed flow coating, which is a modified blade-casting technique [3-5]. How coater instrumentation and the flow coating process are illustrated in Fig. 2. To create the library, a dilute solution of polymer in solvent (1-5% mass fraction) is injected into the gap between a doctor blade positioned over a flat substrate... 

If we predict morphological changes based on the analyses of interface states, on the R versus A/u/kT relations for the three models of growth mechanism, and on the morphological stability of interfaces, as discussed in Sections 3.2-3.9,... 

W. W. Mullins and R. F. Sekerka, Morphological stability of a particle growing by diffusion or heat flow, J. Appl. Phys., 34,1963, 323-9... 

T. Kuroda, T. Irisawa, and A. Ookawa, Growth of a polyhedral crystal and its morphological stability,/. Crystal Growth, 42,1977,41-6... 

Nickel Essential trace element Chicks and rats raised on deficient diet show impaired liver function and morphology stabilizes coiled ribosomes. Active metal in several hydrogenases and plant ureases Very toxic to most plants, moderately so to mammals carcinogenic. Local industrial pollutant of air and water. 

Figure 7-5. Explanation of morphological stability of the invariant boundaries (interfaces) of AO during the oxidation process, j">j, i = A r,e. ...

The Morphological Stability of Boundaries During Metal Oxidation... 

Although Chapter 11 is especially devoted to the morphological stability of solid-solid interfaces during reaction, it is necessary in the context of alloy oxidation to... 

Figure 10-17. Morphological stability of interface AB/B during the heterogeneous reaction A+B = AB. Since nb(1)

Figure 10-18. Crystal AO in an oxygen potential gradient and the morphological stability of its interfaces. Since V//A(t)

Let us finally comment on the morphological stability of the boundaries during metal oxidation (A + -02 = AO) or compound formation (A+B = AB) as discussed in the previous chapters. Here it is characteristic that the reaction product separates the reactants. 1 vo interfaces are formed and move. The reaction resistance increases with increasing product layer thickness (reaction rate 1/A J). The boundaries of these reaction products are inherently stable since the reactive flux and the boundary velocity point in the same direction. The flux which causes the boundary motion pushes the boundary (see case c) in Fig. 11-5). If instabilities are occasionally found, they are not primarily related to diffusional transport. The very fact that the rate of the diffusion controlled reaction is inversely proportional to the product layer thickness immediately stabilizes the moving planar interface in a one-... 

Note that we have assumed the vacancies to be ideally diluted. We can then introduce a perturbation of the planar boundary, z = A +0(x,y,t), and define °(x,y) = Cartesian coordinates perpendicular to z. In this way, the morphological stability becomes a two-dimensional problem. Since we also assume that local equilibrium prevails at both interfaces (surfaces), the boundary conditions are... 

This system of (nonlinear) differential equations cannot be solved analytically. It does, however, contain the answer to our basic question of whether or not 90/91 is positive or negative, which means whether the perturbation 0 decreases or increases with time. Thus, the negative sign on 0 defines the (initial) morphological stability. 

All three approaches have been worked out. It has been demonstrated [R.F, Sekerka (1967)] that they lead to the same conclusions concerning the initial morphological stability. However, they must differ with respect to the morphological evolution and the selection of growth modes at later times. 

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