Porous Nanocrystalline Alloys Prepared by High Energy Ball Milling

Abstract

Several applications of new materials such as those related to electrocatalysis require large specific surfaces of the order of several m 2 /g for having good reaction kinetics. Although high energy ball milling is a useful technique to produce new metastable nanocrystalline alloys, the specific surface of these materials is usually less than 1m 2 /g due to cold welding of particles during the milling process. Nanophase materials prepared by the gas phase condensation technique do not have this drawback and their typical specific surfaces are usually of the order of 40-50m 2 /g. However, this fabrication technique does not allow fine adjustment of the chemical composition as in the case of ball milling. In this paper, we will describe new methods to increase the specific surface of ball milled nanocomposites and nanocrystalline alloys. These methods have been applied to improve the properties of hydrogen storage materials (nanocrystalline metal hydrides) and electrode materials for fuel cells.