title: Superior Electrochemical Properties of Nanofibers Composed of Hollow CoFe2 O4 Nanospheres Covered with Onion-Like Graphitic Carbon.
abstract: Nanofibers composed of hollow CoFe2 O4 nanospheres covered with onion-like carbon are prepared by applying nanoscale Kirkendall diffusion to the electrospinning process. Amorphous carbon nanofibers embedded with CoFe2 @onion-like carbon nanospheres are prepared by reduction of the electrospun nanofibers. Oxidation of the CoFe2 -C nanofibers at 300 °C under a normal atmosphere produces porous nanofibers composed of hollow CoFe2 O4 nanospheres covered with onion-like carbon. CoFe2 nanocrystals are transformed into the hollow CoFe2 O4 nanospheres during oxidation through a well-known nanoscale Kirkendall diffusion process. The discharge capacities of the carbon-free CoFe2 O4 nanofibers composed of hollow nanospheres and the nanofibers composed of hollow CoFe2 O4 nanospheres covered with onion-like carbon are 340 and 930 mA h g(-1) , respectively, for the 1000th cycle at a current density of 1 A g(-1) . The nanofibers composed of hollow CoFe2 O4 nanospheres covered with onion-like carbon exhibit an excellent rate performance even in the absence of conductive materials.
authors.affiliation: Department of Materials Science and Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-713 (Republic of Korea).
authors.forename: Young Jun
authors.initials: YJ
authors.lastname: Hong
authors.affiliation: Department of Materials Science and Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-713 (Republic of Korea).
authors.forename: Jung Sang
authors.initials: JS
authors.lastname: Cho
authors.affiliation: Department of Materials Science and Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-713 (Republic of Korea). yckang@korea.ac.kr.
authors.forename: Yun Chan
authors.initials: YC
authors.lastname: Kang
keywords: energy storage materials; hollow nanospheres; nanostructures; onion-like carbon; synthesis design