Synthesis of Metal Nano-Powders in Nonstationary Electrolysis Conditions

An increasing productivity of electrolytic method of metal powder manufacturing is very important for a lot of application. A perspective way of this is combination of pulse electrolysis with cathode vibration. Using vibrating cathode, one can obtain metal powders from dilute solutions, including electrolytes, sintering by anodic dissolution of metals and alloys. Such a possibility provides many electrolytes, but ammonia based is much of interest.

Copper powders, obtaining from anodic synthesized electrolytes, has prevailing fraction with particle size according to Microtrac analyzer data of about 110 nm (fig. 1). The shape of copper particles is polyhedral (fig. 1) with dendrite nano-wiskers. This result was obtained due to combination of pulse electrolysis with cathode vibration. Nickel powders, obtained in these conditions from ammonia complex electrolyte, have prevailing fraction of about 20 nm and spherical shape.

A productivity of copper powders in ammonia chloride electrolyte is 0.064 g/sm² per hour, that is much higher, than from sulphate one. We assume this is due to reduction of copper from [Cu(NH₃)₂]⁺complex, which equivalent mass is two times higher. It is interesting, that in ammonia electrolytes there is a way of copper powder formation near insoluble anode, such as graphite or platinum. This reaction is possible due to Cu(I) complex disproportion or generation of hydrazine by ammonia anodic oxidation.

Ammonia chloride electrolytes provide blocking effect for powder particle growth, which is strengthening by low frequency pulse electrolysis.

A method of electrolysis with vibrating cathode and anodic synthesized electrolyte was applied also for iron, and cadmium powders. All synthesized powders exhibit high activity in powder metallurgic processes, tribology systems and as electrode active materials of nickel-cadmium secondary cells.