Surface treatment of aluminum oxide and tungsten carbide powders by ion beam sputter deposition

Alumina and tungsten carbide powder were coated with gold and platinum by ion beam sputter deposition. For uniform deposition, the powder grains were agitated in a rotating conical vessel. It contained a sputter target which was irradiated by a beam of rare gas ions. Metal atoms sputtered from the target were deposited onto the powders. The amount of deposited noble metals was determined by means of atomic absorption spectrometry. It increased monotonically with the sputter ion fluence. Under the given conditions, up to 0.3 wt.% gold were deposited onto alumina, while tungsten carbide received up to 0.016 wt.% platinum. While alumina remained non-conductive, the electrical conductivity of tungsten carbide was increased up to a factor 4 by platinum deposition. Electrochemical measurements showed that the electrochemical activity of tungsten carbide was considerably enhanced by platinum deposition. This material may be used as an electrocatalyst.