On the nature of grain boundary structures in nanophase materials

A significant fraction of the atoms in nanophase materials are associated with grain boundaries. Hence, the nature of the grain boundary structures in these materials is interesting in its own right as well as ultimately important to the properties of nanophase materials. Considerable uncertainty has surrounded the atomic structure of nanophase boundaries, but recent experiments have shed some light on these interesting structures. These investigations have included direct HREM observations combined with image simulations, as well as Raman spectroscopy and SANS. The emerging picture is one of nanophase boundaries that are not dissimilar in structure to those normally encountered in conventional polycrystals. The connections between this picture, of nanophase materials as ultrafine grained polycrystals, and experimental observations on these materials are discussed.