Special grain boundary

When any deviation from the perfect crystal requires any of the macroscopic DOFs to be mediated, the related boundary can be termed the macroscopic grain boundary. Typical examples are general grain boundaries and special grain boundaries such as coincident site lattice (CSL) boundaries and twins. However, when only the micro-... 

The obvious application of microfocus Raman spectroscopy is the measurement of individual grains, inclusions, and grain boundary regions in polycrystalline materials. No special surface preparation is needed. Data can be obtained from fresh fracture surfeces, cut and polished surfaces, or natural surfeces. It is also possible to investigate growth zones and phase separated regions if these occur at a scale larger than the 1-2 pm optical focus limitation. 

Palumbo, G. and Aust, K.T. (1992) Special properties of S grain boundaries, in Materials Interfaces Atomic-level Structure and Properties, eds. Wolf, D. and Yip, S. (Chapman Hall, London) p. 190. 

Fig. 8 reveals that under the assumption of reasonable values for the adjustable parameters in Eq. (7) the theoretical predictions compare well to the experimental data. The very different behaviour of special and non-special boundaries reflects an influence of grain boundary structure on grain boundary migration mechanism. In particular, impurities not only may have an effect on migration by impurity drag, but also by changing grain boundary structure itself. This was shown recently by Udler and Seidman in a Monte Carlo... 

D. A. Molodov, U. Czubayko, G. Gottstein and L. S. Shvindlerman, Mobility of <111> tilt grain boundaries in the vicinity of the special misorientation S7 in bicrystals of pure aluminium, Scripta metull. mater. 32 529 (1995). 

Bubble Nucleation in a Liquid Phase The above classical nucleation theory can be easily extended to melt nucleation in another melt. It can also be extended to melt nucleation in a crystal but with one exception. Crystal grains are usually small with surfaces or grain boundaries. Melt nucleation in crystals most likely starts on the surface or grain boundaries, which is similar to heterogeneous nucleation discussed below. Homogeneous nucleation of bubbles in a melt can be treated similarly using the above procedures. Because of special property of gases, the equations are different from those for the nucleation of a condensed phase, and are hence summarized below for convenience. 

D. Turnbull. Grain boundary and surface diffusion. In J.H. Holloman, editor, Atom Movements, pages 129-151, Cleveland, OH, 1951. American Society for Metals. Special Volume of ASM. 

However, Plateau s laws are not obeyed by the grain boundary structure in the special polycrystal in Fig. 15.15. To achieve local equilibrium at all grain junctions, so that Plateau s laws are obeyed, the faces of each grain must be curved [31]. A boundary structure in which all junctions obey Plateau s laws is presented in Fig. 15.16, which shows a polycrystal consisting of six grains that meet at four vertices. Each grain fully occupies one face of the polycrystal. As in Fig. 15.15,... 

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