Morphology and Structure of Aerosol Carbon-Encapsulated Metal Nanoparticles from Various Ambient Metal−Carbon Spark Discharges

The morphology and structure of aerosol carbon encapsulated metal nanoparticles (CEMNs) of various transition metals (anode; Ti, Cu, Zn, Mo, Pd, W, Pt, or Au) formed by ambient spark discharge at the same electrical operating specifications were analyzed. CEMNs were produced with aggregated carbon particles, and their yields and sizes varied according to the metal-to-carbon fraction of each discharge relating to the ionization potential of the electrode material. Each encapsulated metal had natural crystallinity for all discharges, but carbon graphitization for the Mo-C and W-C configurations, which have relatively small differences in melting temperature between the materials, was particularly weak. An empty zone in the carbon shell was also detected in the CEMNs because of the difference in density between the molten and solid phases of the core metal during encapsulation.