Synthesis of carbon encapsulated non-ferromagnetic metal nanoparticles

Graphite (graphene) encapsulated metal (GEM) nanoparticles are a core-shell structured composite material. Contrary to the fast development of ferromagnetic GEM, the non-ferromagnetic core-shell structure was rarely studied, although these materials are potentially useful in many applications, such as thermal dissipation, electromagnetic wave absorption and radioactive waste disposal. In this study, non-ferromagnetic carbon encapsulated metal (CEM), i.e., core metals without graphite-catalyzing capability, were successfully synthesized with two new crucible designs. The new designs can effectively increase or decrease the thermal efficiency of the arc for high or low melting metals, respectively, thereby controlling the carbon-to-metal vapor ratio at an adequate value. Preliminary results showed that non-ferromagnetic metals, e.g. Mo and Cu, can be encapsulated by these two new setups. The percentage of well-encapsulated nanoparticles has been improved from negligible to about 4–6%. Additionally, a new centrifugal purification method was also developed to gather the non-ferromagnetic Mo- and Cu-CEM nanoparticles, which cannot be collected by a strong magnetic field. The new synthesis setups are proven to be feasible, and effective; they should be easily adapted to the synthesis of other CEM nanoparticles with various core metals.

► Using an arc-discharge method to synthesize non-ferromagnetic CEM nanoparticles.
► Cu-CEM and Mo-CEM are successfully synthesized with the two new crucible designs.
► The carbon-to-metal ratio is the key to the synthesis of non-ferromagnetic CEM nanoparticles.
► Two-step mechanism model has been proved invaluable to this work.