Nanocrystalline materials

Abstract

Nanocrystalline materials (NCM) are single-phase or multiphase polycrystals, the crystal size of which is of the order of a few (typically 1–10) nanometers, so that about 50 vol. % of the material consists of grain or interphase boundaries. These materials are of interest for the following reasons. (i) NCM seem to exhibit an atomic structure which differs from the two known solid-state structures: the crystalline state (with long-range order) and the glassy state (with short-range order). The presently available experimental evidence suggests that the atoms situated in the grain or interphase boundaries of NCM represent a new solid-state structure with a random atomic arrangement. (ii) The properties of NCM differ from the properties of glasses and/or crystals with the same chemical composition. Hence, NCM may be utilized technologically. (iii) NCM seem to permit the alloying of components which are immiscible in the solid and/or molten state such as metals and ionics or metals and polymers. The resulting alloys could be candidates for new and technologically attractive properties.