| A solid-state process has been developed for producing alumina bicrystals of controlled misorientation and is termed solid-state directed grain boundary assembly or SS-DGBA. Essentially, two single crystals with a known misorientation between them are diffusion bonded to a polycrystalline material of interest, and subsequently, they are allowed to grow through the polycrystal via templated grain growth (TGG) until their growth fronts collide and a grain boundary is formed. The results show that SS-DGBA is indeed a viable technique for processing bicrystals, and the development of a controlled misorientation tricrystal is even achieved by bonding three seed crystals to a polycrystalline source material. These specimens lend themselves to a wide variety of experiments and/or analyses that would offer a more fundamental understanding of materials and interfaces than the more general conclusions that are typically gained by studying polycrystalline materials alone. Although, one could examine individual grain boundaries in polycrystals with great detail, it is extremely unlikely one would be able to find the same grain boundary (perhaps aside from a few "special" boundaries) in two materials of different composition, and thus study the sole effect of a compositional change while maintaining a fixed grain boundary misorientation. Studying grain-boundary groove and triple junction (e.g., in the tricystals) configurations offer a relation between the specific interfacial energies involved in the junction. However, the theory used to interpret grain boundary grooves and triple junctions in which one or more of the interfaces involved has an anisotropic energy has not been fully appreciated in the literature. Consequently, an effort is made to understand this theory. In this process, new features of triple junctions are realized by finding triple junction configurations that satisfy the equilibrium conditions (i.e., the equilibrium conditions are solved).* (Abstract shortened by UMI.).;*This dissertation is compound (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Windows MediaPlayer or RealPlayer. |
