Formation and structure of carbon nanocage structures produced by polymer pyrolysis and electron-beam irradiation
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Formation and structure of carbon nanocage structures produced by polymer pyrolysis and electron-beam irradiation Takeo Oku,a) Takanori Hirano, and Katsuaki Suganuma Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
Satoru Nakajima Department of Chemistry, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan (Received 10 May 1999; accepted 26 July 1999)
Carbon nanocapsules with SiC and Au nanoparticles were produced by thermal decomposition of polyvinyl alcohol at about 500 °C in Ar gas atmosphere. The formation mechanism of nanocapsules and a structural model for the nanocapsule/SiC interface were proposed. In addition, carbon clusters were formed at the surface of carbon nanocapsules, and carbon onions were produced by electron irradiation of amorphous carbon produced from polyvinyl alcohol. The present work indicates that the pyrolysis of polymer materials with clusters is a useful fabrication method for the mass production of carbon nanocapsules and onions at low temperatures compared to the ordinary arc discharge method.
I. INTRODUCTION
Carbon has various hollow-cage structures such as C60, giant fullerenes, nanocapsules, onions, nanopolyhedra, cones, cubes, and nanotubes.1–7 These structures show different physical properties and have the potential to allow the study of materials of low dimensionality within an isolated environment. Nanoclusters encapsulated within these carbon hollow-cage structures are intriguing for both scientific research and future device application such as cluster protection, nano-ballbearings, nano-optical-magnetic devices, catalysis, and biotechnology.8–11 Carbon nanocapsules filled with Au and LaC2 were reported,12 and various types of carbon nanocapsules incorporating clusters (such as Co, Fe, Ni, Cu, CrCx , MoO3, WCx , WO3, TiC, SiC, Pd, and other elements) have also been reported.4,7–11,13–21 Arc discharge22 is an ordinary method for the formation of the hollow-cage structures. However, it is hard to separate these cages from carbon soot, and the understanding of the formation process is difficult because of the coexistence of various carbon productions and of high-temperature annealing. The formation of carbon onions with a cage structure by electron-beam irradiation has also been reported,3,23–26 which is a useful method for the investigation of the formation mechanism by in situ direct observation.
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J. Mater. Res., Vol. 14, No. 11, Nov 1999 Downloaded: 19 Mar 2015
The purpose of the present work is twofold. The first is to prepare the carbon nanocapsules and onions at low temperatures by ordinary annealing and electron-beam irradiation without using the arc discharge method. In the present work, various clusters with polyvinyl alcohol were selected for the nanocapsule and onion formation. SiC, Ge, Fe, and Co nanoparticles with polyvinyl alcoh
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