GRAIN-BOUNDARY COMPONENT IN W-GA COMPOSITES - A WAY TOWARDS SKELETON STRUCTURES

Nanostructured materials consist of crystalline and grain-boundary com ponents. In the simplest case, both components are chemically identica l. Here, we present the results of a study of a system consisting of a crystalline component built by A atoms (tungsten) and a grain boundar y component of B atoms (gallium). Within this system, component B is i n a disordered state. Most likely, it exhibits an amorphouslike struct ure, and coats the tungsten crystals uniformly with a constant thickne ss, thus forming a Ga skeleton structure. The noncrystalline gallium s eems to undergo no first-order structural phase transitions, e.g., no first-order melting transition was noted when the composite was below, at, or above the equilibrium melting point of Ga. The properties of g allium as a grain-boundary component differ significantly from those o f crystalline and amorphous bulk gallium. [S0163-1829(98)03038-0].