Improved oxidation stability of carbon-coated Ni nanoparticles synthesized by one-step electrical wire explosion

Abstract

This study demonstrates a rapid one-step route to prepare high-purity carbon-coated Ni (Ni@C) nanoparticles via electrical wire explosion in methane gas used as a carbon source, and also investigates an oxidation stability of Ni@C nanoparticles. The Ni@C nanoparticles have smaller average particle size and narrower particle size distribution than the passivated Ni (Ni@P) nanoparticles and show positive dependence of carbon layer thickness on core Ni particle size. The thermal oxidation of Ni@C nanoparticles is closely related to the burn-off of protective carbon shells. From a thermogravimetry analysis to investigate the oxidation kinetics of Ni nanoparticles, the activation energy Ea for oxidation of Ni@C nanoparticles is determined to be 161.31–170.34 kJ mol−1, which is much higher than the Ea value (81.22 kJ mol−1) of Ni@P nanoparticles. This confirms that the carbon shell effectively prevents the active core Ni nanoparticles from high temperature oxidation in air.