What is the relation between the oxygen content of a metal powder and its particle size?
Tantalum, niobium, tungsten and molybdenum metal powders pick up oxygen, when they are exposed to air. The quantity of oxygen pick up is directly proportional to the surface area of the powder. Thus the smaller the particle size of the powder, the higher is the pick up of oxygen. That is why fine powders with a large surface area have a higher oxygen content than coarse powders with a low surface area. In case of Ta and Nb powders with a particle size < 1 mm a minimum amount of oxygen on the surface of the powders is actually essential, because it hinders the self ignition in air. Nevertheless for handling fine Ta and Nb powders it is mandatory to avoid any electrostatic discharge during handling, e.g. filling or unloading.
