水溶液からの貴金属微粉末の還元生成

Abstract

Metal powder is one of the specific materials in the metal utilization. Powder metalluegy is wellknown since early times in the field of metallurgical processes. The particle size of the metal powder is approximately 0.1 mm. Recently, ultra fine powder and submicron powder have been used in various industries. Precious metal powders play an important role as electric conductive materials in the electronic industry. It is desirable for metal particles to be submicron in size and spherical in shape. This paper is a review of studies on the production of metal powder by the reduction of an aqueous solution with emphasis on hydrogen as the reductant. The production methods discussed include reductions by other gas (SO2) and reducible solutions as well as a disproportionation reaction that do not require a reduction agent. This review forcuses on the formation of submicron spherical particles. The formation of crystalic particles and thin film particles as well as the reduction mechanisms based on kinetic considerations are also discussed. It can be expected that hydrogen is a clean reducing agent which does not remain in the produced powder. In relation to use of hydrogen, the future of hydrogen as secondary energy was also discussed. Technical development of the use of hydrogen will be promote the realization of idea of [Hydrogen Economy]. And the technique using hydrogen will be placed under an obligation of [Hydrogen Economy].