PerspectiveMaterials Science

The Phase Behavior of Interfaces

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Science  08 Apr 2011:
Vol. 332, Issue 6026, pp. 182-183
DOI: 10.1126/science.1204204

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Summary

Common metal or ceramic objects are made up of many bonded micrometer-scale single crystals, or grains. Their interfaces, called grain boundaries, play a decisive role in determining the properties and processing of almost all engineering materials. Because of their structural and chemical complexities, the description of grain boundaries has lacked a satisfactory conceptual framework, and grain boundaries tend to be viewed as disordered regions with kinetically trapped structures. Recent work has shown that grain boundaries can be described as interface-stabilized phases (also called interphases or complexions) that are chemically and structurally distinct from any bulk phases (14). On page 206 of this issue, Baram et al. (5) extend our understanding of grain boundaries by examining interface structures that form between a gold particle in contact with metal oxide surfaces. They show that these nanoscale interface structures are equilibrium phases that obey thermodynamic rules analogous to those for bulk phases.