Low-temperature Alloy Synthesis

Abstract

THE low temperature reduction of metal ions to the finely divided free metal by sodium borohydride reduction has been reported recently¹. In addition, the preparation of a number of inter-metallic compounds from mixed salt solutions using boiling hydrazine and hypophosphorous acid solutions as reducing agents has been accomplished². It was of interest to examine the sodium borohydride reduction of solutions of two metal ions as a possible method of low-temperature synthesis of finely divided solid solution alloys. Such materials would be of particular interest in catalyst investigations, where high-surface area alloys are often difficult to obtain. Work on such reactions have, therefore, been carried out, using metals where alloy formation might reasonably be expected with suitable preparative conditions. Those chosen for initial investigation were combinations of platinum–gold, platinum–iridium, and palladium–gold. All three metals form face-centred cubic lattices, have atomic radius ratios well within the Hume–Rothery limit, and form solid solutions with each other over the entire composition range.