In Situ Filling of Fe/Ni Oxide Nanowire into Carbon Nanotubes Doped with Nitrogen in CH₄/H₂/Air Plasma

Nitrogen-doped carbon nanotubes (N-CNTs) were synthesized using air as the nitrogen carrier gas and CH4 as the carbon source by plasma-enhanced chemical vapor deposition over a thin catalyst film of Fe50Ni50. Transmission electron microscopy and high resolution transmission electron microscopy measurements have indicated that the N-CNTs grew with a tip-type growth mode. When H2 was added to the CH4/air plasmas during the N-CNTs growth stage, it was found that Fe/Ni oxide nanowire was filled into the nanotube. However, without adding H2 in the CH4/air mixture plasma, only metal oxide nanoparticle was found on the tip of the N-CNT.