Monazite is a phosphate mineral which contains a significant amount of rare earth elements (REE) with thorium (Th) and a low concentration of uranium (U). The radioactive components of monazite, Th and U, make it an unattractive source of REE due to the added cost associated with radioactive waste handling. The mineral is also chemically inert requiring the use of corrosive reagents at elevated temperatures to effectively extract REEs. According to thermodynamic calculations, monazite dissociation into oxides of REE and phosphorus (P) is favourable at temperatures greater than 1000°C, while the reverse reaction occurs well below a 1000°C. Rapid cooling is required to prevent the reverse reaction. Achieving these high temperatures, with rapid heating and cooling, is possible by means of thermal plasma treatment such as a radio frequency plasma. This type of plasma system offers superior control of plasma/particle interaction, quenching rates and plasma gas composition. The objective of this study was to determine the parameters for dissociation of the monazite under various conditions to reduce its chemical inertness. Dark and grey powders were obtained under reducing conditions, while lighter powder formed in the presence of an oxygen plasma with increase particle circularity observed after plasma treatment. While SEM-EDS analysis indicated no notable change in powder composition after plasma treatment, dissolution tests proved that monazite was not only more reactive, but also more susceptible chemical reaction after treatment.

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The environmental impact was assessed for the spheroidisation process to compare its advantages versus mining titanium from the ground. Energy consumption was used to compare the environmental impact. With the introduction of spheroidisation at Necsa, there was a need to investigate the environmental impact of the process. The environmental impact of plasma spheroidisation making use of the 15 kW Tekna plasma system was investigated. Environmental impact assessment is part of a bigger study to investigate the holistic impact of the spheroidisation of titanium powder at Necsa. The study was carried out using ASTM standards, ensuring that the results from the experiments are acceptable. The primary focus of the paper was the 15-kW spheroidisation system. The energy consumption of the reconditioning of titanium alloys was compared to conventionally producing titanium. The role spheroidisation plays in the additive manufacturing lifecycle was also assessed. This life cycle assessment also included the other processes in additive manufacturing to give an overview of how the spheroidisation process can fit in and improve the additive manufacturing value stream.

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.