NOVELTY - Combinatorial libraries of supported metal-containing powders are prepared by preparing an array comprising dispersions; removing heat concurrently from each dispersion in the array to precipitate a dissolved metal from a solution onto a particulate support; and separating the particulate support from the solution for each dispersion in the array to yield an array comprising supported metal-containing powders.    USE - The process is used for forming combinatorial libraries (claimed) of supported metal-containing powders. The combinatorial libraries are used in conducting combinatorial research investigation, in particular w.r.t electrocatalysts for fuel cells.    ADVANTAGE - The process enables an effective combinatorial materials science research program for supported catalyst. It may be advantageously used in a process of generating data for an array of supported catalysts, e.g. supported electrocatalysts. The ability to provide relatively concentrated metal solutions allows for manipulation of smaller volumes of dispersions or suspensions, while still achieving relative high metal loadings, and preferably also relatively narrow particle size distributions.    DETAILED DESCRIPTION - The formation of combinatorial libraries of supported metal-containing powders includes preparing an array comprising dispersions each prepared by a process comprising dispersing a particulate support in a solution comprising a solvent and a dissolved metal, where a volumetric ratio of the particulate support to the solvent is greater than or equal to 1:10; removing heat concurrently from each dispersion in the array to precipitate the dissolved metal from the solution onto the particulate support; and after the removing step, separating the particulate support from the solution for each dispersion in the array to yield an array comprising supported metal-containing powders. Each of the powders comprises the particulate support and a precipitated metal.    DESCRIPTION OF DRAWING(S) - The figure is a TEM (sic) image of a carbon support with platinum alloy nanoparticles.    Carbon supported metal alloy electrocatalyst power particle (1)    Particulate support (2)    Deposits (3)