It was discovered that the specific surface area and magnetic susceptibility of Fe-dispersing single-walled carbon nanohorns (Fe-CNHs) were significantly increased without obvious destruction of CNH structures by oxidation in CO2 (10%) diluted with N-2 at 1000 degrees C. As-grown Fe-CNHs synthesized by a submerged arc discharge method had a specific surface area of 184 m(2)/g, and this surface area was raised to 500 m(2)/g by opening of pores upon this oxidation treatment. Under this condition, the carbon-based specific surface area are enhanced from 211 m(2)/g to 863 m(2)/g. Fe nanoparticles dispersing in Fe-CNHs were transformed into ferrimagnetic Fe3O4 nanoparticles without obvious change in their particle sizes and frames of CNHs. The magnetic susceptibility of the Fe-CNHs was increased by this oxidation, suggesting that their magnetic mobility could be improved. The structure of Fe-CNHs was stable against the extended oxidation duration in the CO2-N-2. In contrast to the oxidation in CO2-N-2, the oxidation in air resulted in the transformation of Fe nanoparticles into paramagnetic Fe2O3, and the excessive oxidation led to destructive of CNHs. (C) 2015 Elsevier B.V. All rights reserved.