title: Ambient spark generation to synthesize carbon-encapsulated metal nanoparticles in continuous aerosol manner.
abstract: We report the use of spark generation in an inert gas atmosphere to synthesize carbon-encapsulated metal nanoparticles (CEMNs) in a continuous aerosol manner using a metal (nickel, cobalt, iron)-graphite carbon electrode configuration without the use of a vacuum. The spark-generated particles consisted of CEMNs and carbonaceous aggregated debris. The outer layer of the CEMNs showed parallel fringes (ordered graphitic nanostructures) while the debris consisted of disordered nanostructures. Electron and X-ray diffraction showed that both metal and graphite in the CEMNs were the pure elements except for iron-carbon, which contained a carbide phase. Based on the order of the activation energies for carbon diffusion into a metal: iron-carbon (10.5-16.5 kcal mol(-1)) < cobalt-carbon (34.7 kcal mol(-1)) approximately nickel-carbon (33.0-34.8 kcal mol(-1)), it was concluded that carbide particles form more easily from elemental iron than nickel or cobalt. The metal-to-carbon mass fractions of the spark-generated particles from nickel (anode)-carbon (cathode), cobalt-carbon, and iron-carbon spark configurations were 18.7, 28.3, and 11.2%, respectively, while the mass fractions for the configurations of metal (cathode)-carbon (anode) were 6.4, 9.1, and 4.3%, respectively. Similarly, the yield of CEMNs from the metal (anode)-carbon (cathode) electrodes was higher (54, 61, and 53%) than that of metal (cathode)-carbon (anode) electrodes (18, 30, and 18%).
authors.affiliation: Samsung Electronics Co., Ltd., Yongin, Republic of Korea.
authors.forename: Jeong Hoon
authors.initials: JH
authors.lastname: Byeon
authors.forename: Jae Hong
authors.initials: JH
authors.lastname: Park
authors.forename: Ki Young
authors.initials: KY
authors.lastname: Yoon
authors.forename: Jungho
authors.initials: J
authors.lastname: Hwang