Too small particle diameters have negative properties as well. Nano particles
can penetrate directly through the skin and when inhaled can penetrate
very deep into the lungs. They will also diffuse through every component of
the equipment. This might cause short-circuits. The smallest particles are so
light that the are easily thrown away out of the melt pool. The flowability
of nano powders is also inferior. At last, the smaller the particles, the larger
their surface to volume ratio. They are more likely to inflame or even explode
if making contact with a reactive gas.