Local structure of cobalt nanoparticles synthesized by high heat flux plasma process

- Co-nanoparticles synthesized by a high flux plasma process.
- The morphology of the nanoparticles depends on the plasma current.
- The local structure of Co-nanoparticles studied by X-ray absorption spectroscopy.
- Production of CoO nanoparticles and Co-metal nanoparticles at low and high plasma currents.

We have used high heat flux plasma synthesis process to grow Co those for the morphology, stoichiometry and the local structure as a function of plasma current. We find that the nanoparticles produced by the thermal plasma method have different shapes and size distribution with the plasma current being a key parameter in controlling the formation of composition, morphology and crystalline structure. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements at Co K-edge have revealed formation of metal and metal oxide nanoparticles with the composition mainly depending on the arc current. While low plasma current appears to produce nanoparticles solely of CoO with a small amount of Co metal, the high plasma current tends to produce nanoparticles of CoO and Co3O4 oxides with increased amount of Co metal. The results are consistent with the morphological and structural analysis, showing nanoparticles of different shapes and size depending on the arc current.