Synthesis of carbon nanocapsules containing Fe produced by discharge in ethanol

概要

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We attempted to synthesize Fe filled carbon nanocapsules with a narrow size distribution and high magnetization by a discharge in ethanol. Most of the particles found in the as-synthesized soot were less than 40 nm in diameter. High-resolution transmission electron microscope measurements revealed that particles had a core − shell structure and their shells are composed with some graphite layers. Occasionally, carbon particle without any cores were found as impurities. Selected area electron diffraction and temperature dependent magnetization indicated that α-Fe and γ-Fe nanoparticles were encapsulated in carbon cages and they were single crystals. Fe3C also existed in the soot. After the temperature cycle measurement of magnetization went up to 680 ℃, the nanocapsules showed an increase in magnetization at 10 kOe from 77 emu/g to 100 emu/g owing to a phase transition from γ-Fe to α-Fe, however, the graphite shells of some nanocapsules seemed to be deformed. An annealing treatment at 500 ℃ on the as-synthesized soot was able to increase the magnetization at 10 kOe to 92 emu/g without any deformations of graphite shells.
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