Reduction of copper oxide powder by an inductively coupled thermal plasma

Additive manufacturing (AM) methods can be utilised to manufacture complex, custom Ti6Al4V components for medical implants. Infection at the bone-implant interface is a key reason for implant rejection. Advanced titanium implants with biocompatibility and antibacterial properties can be manufactured by modifying the titanium alloy with copper, which in small concentrations (< 1 at % copper) is a proven, non-toxic antibacterial agent. Copper can be embedded into the titanium implant during the AM process creating antibacterial functionality. In order to produce sufficiently fine metallic copper powder, copper oxide can be reduced, either by chemical reduction or thermal treatment methods. These include thermal decomposition or reduction of the oxide in the presence of a reactive gas at elevated temperatures. Making use of thermal treatment methods such as thermal plasma reduction, the process conditions can be tuned to manipulate the morphology and average particle size of the powders. The purpose of this study was to investigate the thermal plasma reduction of copper oxide to copper metal making use of the Tek-15 radio-frequency inductively coupled thermal plasma system at Necsa. In the presence of hydrogen, the black copper (II) oxide powder was converted to a dark red powder, while a yellow / orange coloured powder was obtained without hydrogen being present. A change in composition was observed using SEM-EDS and was confirmed by XRD analysis.