Preparation of Unsupported Metal Particles

Less well dispersed metal powders are made by reducing solutions of salts with reducing agents such as formaldehyde (methanal), formic (methanoic) acid, hydrazine and the tetrahydridoborate (BH4 ) ion, ° although in this last case 

Metallic aerosols can be made by passing a massive amount of electricity through a thin wire by discharging a bank of capacitors, whereupon the wire explodes. The technique, to which the name deflagration has been applied, was pioneered (as were so many things) by Michael Faraday, who converted a gold wire into powder by using the current produced by a Leiden battery. 

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