The continued optimization of technologically advanced ceramics, such as bone implants, computer components, and thermal barrier coatings, is necessary to continue the improvement of their lifetimes, effectiveness, and energy efficiencies. Properties of polycrystalline ceramics can be controlled by varying processing conditions. In order to fully understand the morphological development of grains in polycrystalline material during processing, one must understand the structure and movement of their grain boundaries, both individually and as a group. For many materials, the average group behavior has been measured, but little is known about the qualities of individual boundaries, which comprise a wide range of geometries and misorientations. A more complete understanding of the structure and motion of a collection of interfaces can only be obtained by creating and studying a range of individual interfaces with known misorientations. Many methods currently exist for creating one – or a few – isolated grain boundaries, also called "bicrystals," in a sample. However, this then represents only a tiny fraction of the grain boundaries present in advanced polycrystals and until now, there has been no method for creating a wide and representative collection of bicrystals within a single ceramic sample. This research project involves the development of an experimental method that results in hundreds of ceramic island-grain bicrystals on a single sample in order to facilitate combinatorial studies of a wide range of interfaces. These samples could then be used to observe correlations such as interface structure vs. misorientation, kinetic behavior vs. misorientation, and relative surface energy by measurement of dihedral angle relative to misorientation. Additionally, changes in samples that have been chemically doped or annealed under different conditions could be compared. A clear understanding of these relationships is expected to shed light on bulk polycrystalline behavior and therefore provide more complete understanding of the energetic and kinetic properties and characteristics of interfaces in ceramics and therefore more opportunities to control and improve bulk polycrystalline ceramics.
|Advisor:||Glaeser, Andreas M.|
|Commitee:||Gronsky, Ronald, Wenk, Hans-Rudolf|
|School:||University of California, Berkeley|
|Department:||Materials Science & Engineering|
|School Location:||United States -- California|
|Source:||DAI-B 74/07(E), Dissertation Abstracts International|
|Subjects:||Engineering, Materials science|
|Keywords:||Alumina, Bicrystals, Ceramics, Interfaces, Sapphire, Surfaces|
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