Study On The New Process For Preparation Of Ultrafine Cobalt Powder By Chemical Reduction In Aqueous Solution

Cobalt has been widely used for its good physical, chemical and mechanical performance. The preparation of cobalt powder, however, is a very critical step. Researches on cobalt powder focus on the followings: ultrafine cobalt powder, nanometer cobalt powder, high-purity cobalt powder and so on. Ultrafine cobalt powder and nanometer cobalt powder are representative of cobalt powder, and so how to produce and use them is becoming a hot topic. The process in use to produce ultrafine cobalt powders are all complex and high energy cost. The size of them is more than 0.4μm, hence these products can not show their good performance. In this paper, a new and special chemical reduction method is applied to the preparation of ultrafine cobalt powder in aqueous solution. Firstly, the thermodynamic and kinetic possibility of preparation in aqueous solution is analysed. Secondly, in order to get the best reaction conditions, the factors such as temperature, concentration, and so on, are also studied. In addition, the methods of purification and collection are also studied, for they are important to ultrafine cobalt powder which is easily oxidated in water or air. Scanning electronic microscope and X-ray diffraction are used to observe the size, surface, crystal system, component of ultrafine cobalt powder. These experiments are studied for industry production in future. And the results are as the followings:The ultrafine cobalt powder with an average size 0.2~0.3μm is prepared by chemical reduction in aqueous solution;The thermodynamic possibility of preparation is proved by a lot of data;The speed of reaction and the size of product are affected by the temperature. The best temperature of reaction is 85℃;The concentration of hydrous hydrazine is very important. It is proved that the best concentration of it is 2.5 times of cobalt aqueous;The concentration of cobalt aqueous is also important and if it is too low, the reaction can not proceed completely. The beginning concentration of cobalt aqueous is 1.00mol/L;The reaction whether is complete or not depends on the time. Without enough time, the reaction can not complete, but with too long time, the sizes of products will increase. The best reaction time was 20 minutes;A little surfactant agent is employed to get the ultrafine cobalt powder with better size and smooth surface ;A magnified experiment is made for industry production in future and good result is gotten.