Nucleation strain-energy effects

Two-Component System with Isotropic Interfaces and Strain Energy Present. An example of this case is the solid-state precipitation of a 5-rich (i phase in an A-rich a-phase matrix. For steady-state nucleation, Eq. 19.16 again applies. However, for a generalized ellipsoidal nucleus, the expression for AQ will have the form of Eq. 19.28. Also, /3 must be replaced by an effective frequency, as discussed in Section 19.1.2. 

The effect of a dislocation line on dissolution nucleation has been attributed to the effect of their elastic strain energies on the chemical potential of the material nearby them (4). How ever this is a doubtful idea in both theory and practice. In theory the elastic energy of a screw dislocation line does not... 

Clem and Fisher (1958) use a similar treatment as above to derive the solid state nucleation kinetics for new phases at grain boundaries. They neglect orientation of the critical nucleus with respect to the host, strain energy, and coherency effects. Nucleation at the grain boundary interface removes boundary energy. Their treatment yields the following critical values ... 

The driving mechanisms for the island vertical correlation have been the subject of extensive studies over the past years. Because the buried islands produce a nonuniform strain field at the surface of the spacer layer, i.e. the regions above the islands are tensely strained while the regions in between islands remain compressed, exciting models have treated the island distribution at the spacer layer surface by considering the effect of such a strain field on surface diffusion [4] or on island nucleation [3]. Recent calculations have taken into account the effect of the elastic anisotropy of the materials [16], the surface energy [18] or the elastic interaction between the buried islands with newly deposited ones [19]. However, in all of the above models it was assumed that the surface of the spacer layer becomes perfectly flat before the deposition of a new layer. From the experimental point of view, this... 

The effect of particle-matrix interfacial free energy is often overlooked but is particularly important in the nucleation and coarsening of internal oxides. Consider the classical nucleation problem of forming a spherical nucleus. If strain is neglected, the free energy of formation of a nucleus of radius r is given by Equation (5.31),... 

Several expressions for the function/have been proposed by different authors based on different assumptions about the driving force for the enhancement of nucleation. The suggested driving forces include shear rate, recoverable strain, the first normal stress difference, the change in free energy induced by flow, the effect of the combination of shear rate and strain, etc. 

An epitaxial effect based on similar lattice parameters (McMillan 1979) presented a theoretical explanation for the favorable nucleating action of metals. Furthermore, mechanical strain was present at the substrate-glass interface, producing a high interfacial energy, as the coefficients of thermal expansion of the metal and the new nucleus were substantially different. As a result, catalyzation of nucleation could also be expected. 

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