Interface anisotropy

Interface anisotropy is another important parameter in multiphase fluids. This is mostly relevant to relate rheological properties with microstructure [192]. The interface anisotropy can be quantified using the interface tensor q j, defined as qy = fs i j where W ... 

The aim of this chapter is to develop and introduce a concept denoted as anisotropy in interfadal energies. This is crucial in understanding microstructure evolution of materials, and how the interface anisotropy influences the microstmc-tural evolution of materials. Particular attention is directed towards the interface-related topics, as many excellent reference materials are available that discuss the relationship between interface features and the resultant microstructures [5-7]. 

An enhanced understanding of the important role of the interface anisotropy on the microstructure evolution also raised a question on the conventional approach to the pore-boundary separation problem. It was noted that pores should remain at the... 

Although, to date, interface anisotropy has received less consideration in the study of microstructure evolution, it is dear that it plays a critical role in determining the final microstructure of materials. It can be said that a desirable microstructure could only be obtained by a dear understanding of interface anisotropy, and making proper use of it. Today, most theoretical developments relating to interface anisotropy and microstructure evolution remain qualitative in nature, due mainly to the lack of a database on the interface anisotropy of the materials in use. Hence, an extensive accumulation of these data, and a better refinement of theory, should further enhance the present understanding of the microstructure evolution of materials. 

Rohrer, G.S. (2005) Influence of interface anisotropy on grain growth and coarsening. Anna. Rev. Mater. Res., 35,99-126. 

In this subsection we discuss the experimental determination of interface anisotropy and show some typical results. For R/T multilayers, the R region is ordered magnetically at low temperature and from the energy viewpoint, the anisotropy eneigy per unit area can be written as... 

Figures 25 and 26 summarize the XK J X) for Dy/Co and Nd/Fe CMFs. In both of these figures, the slopes of kK JX) are negative and the intercepts are positive. Perera, O Shea and Fert have prepared DyNi/Mo (Perera et al. 1991) and R/Mo (R=Dy, Er) (Perera and O Shea 1991) multilayers and found similar AJT curves with negative slopes and positive intercepts as shown in fig. 27 for Er/Mo. This means that their PMA originates from the interface anisotropy. It is the single-ion anisotropy of R atoms and the anisotropic distribution of R and T atoms in the interface region which create the PMA.

In this respect, a theory that takes into account the deformation of one droplet (Doi and Ohta 1991) can be applied to describe the shear and normal stress transients. According to this model, blend morphology is characterized by a scalar (referring to a specific interfacial area) and a tensor (characterizing interface anisotropy). These parameters may be expressed in two equations—one describing the stresses of the interfacial structures and the other for the evaluation of the scalar and interface tensor. For immiscible blends with Newtonian or weakly viscoelastic fluids and an increase in shear, the droplets deform into fibrils while maintaining their initial diameter, d. In comparison, in a highly elastic matrix where droplet shape is... 

Equations [84] and [85] suggest that the droplet size in the steady state is essentially determined by competition of the interfacial tension and the viscous shear stress, as considered in the classical Taylor theory " for an instability criterion of a single droplet. However, the behavior of the normal stress difference (eqn [83b]) is not fully understood from this theory. Concerning this point, Doi and Ohta proposed a phenomenological model for the interface anisotropy and spedfic interfacial area in blends having the characteristic length determined only by the shear. The predictions of the Doi-Ohta model are consistent with the experimental observation (eqns [83]-[85]) as well as the scaling behavior observed for... 

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