NANOSTRUCTURE BY DESIGN - SOLUTION-PHASE-PROCESSING ROUTES TO NANOCRYSTALLINE METALS, CERAMICS, INTERMETALLICS, AND COMPOSITES

Solution-phase processing affords nanoparticles and nanocomposites of a wide range of materials, including metals, alloys, intermetallics, a nd ceramics, with substantial control of particle size, particle morph ology, microstructure, and composite microstructure. The particle size of nanocrystalline Cu (nano-Cu) produced by the reduction of CuCl can be varied between 10-30 nm by changes in reducing agent and solvent, while that of nano-Al can be varied between 45-180 nm. The morphology of nano-AlN produced by nitridation of nano-Al can be varied from almo st entirely equiaxed to almost entirely whisker-like. Nanocrystalline nickel aluminides can be synthesized by reacting NiCl2 and LiAlH4 in o rganic solvents, followed by solid-state heating. When the reaction is performed in aromatic solvents the desired phase is obtained vith a p orous, highly sintered microstructure, while reactions performed in et hereal solvents yield nonsintered nickel aluminide particles in an amo rphous alumina matrix. Nanocrystalline composites of AlN and Al are pr epared by suspending the AlN particles in organic solvent, and perform ing solution-phase chemistry to produce nano-Al. (C) 1998 Elsevier Sci ence Ltd. All rights reserved.