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Changing Complexions of Grain Boundaries

Martin P. Harmer and Shen J. Dillon, Lehigh University
Supported by the MRSEC Program of the NSF under award number DMR-0520425

In the manufacture of advanced ceramics, solids are created from powders by forming interfaces, called grain boundaries, between the different powder particles. For at least five decades, materials scientists have been puzzled by the speed with which grain boundaries move when materials such as alumina are processed to make ceramics. Under some conditions the boundaries move rather slowly and in others, they move 100,000 times faster. Our research has identified six distinct grain boundary 'complexions' in alumina that have characteristic speeds. A grain boundaries complexion can be controlled by chemistry and temperature. This new understanding of grain boundary complexions may also be applied to other systems to resolve longstanding problems and engineer new microstructures.