TECHNOLOGY FOCUS - METALLURGY - Preferred Component: The catalytic metallic particles comprise a transition metal. They comprise nickel, copper, iron, tin, zinc or nickel-cobalt-copper alloy. They are self-supporting. The voids are spherical. They are channels, which are tubular and have platelet-like structures. The bulk region comprises a rare earth element or alloy. It comprises lanthanum or mischmetal. It comprises a transition metal element or alloy. It comprises nickel, titanium, magnesium or vanadium. It comprises copper, zinc, tin or iron. It comprises a component A and a component B, components A and B forming an alloy in which the atomic ratio of components A to B is 1:5, preferably 1:2. Component A comprises a rare earth element or transition metal. Component B comprises a transition metal. It comprises copper. The interface region and bulk region are formed upon activation of or etching a starting material, the activation inducing accelerated directed and preferential corrosion of the bulk region, the corrosion producing the interface region, the etching producing the interface region from the surface of the starting material.Preferred Dimension: The catalytic metallic particles have diameters of less than 50, preferably less than 30 Angstrom. The diameters of the spherical voids are less than 100 Angstrom. The channels have a cross-sectional dimension of 10-20 Angstrom, and a longitudinal dimension of greater than 20 Angstrom.Preferred Parameter: The volume fraction of the catalytic metallic particles in the interface region is greater than 30, preferably greater than 50%. The catalytic metallic particles vary in proximity from 2-300, preferably 50-100 Angstrom. The volume fraction of the voids in the interface region is greater than 10, preferably greater than 20%. The average diameter of the spherical voids is the same as the average diameter of the catalytic metallic particles. The atomic ratio of copper to component A is greater than or equal to0.1:1, preferably greater than or equal to0.3:1.