Structure of Frilled Carbon Nanowires Synthesized by Sulfur-assisted Chemical Vapor Deposition
- PDF / 818,599 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 89 Downloads / 217 Views
Structure of Frilled Carbon Nanowires Synthesized by Sulfur-assisted Chemical Vapor Deposition Tadashi Mitsui, Takashi Sekiguchi, Mikka Nishitani-Gamo1, Yafei Zhang2 and Toshihiro Ando2 Nanomaterials Laboratory, National Institute for Materials Science (NIMS) Sengen 1-2-1, Tsukuba, Ibaraki 305-0047, Japan 1 Insititute of Applied Physics and Center for Tsukuba Advanced Research Alliance (TARA), University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8577, Japan 2 Core Research for Evolution Science and Technology (CREST) of Japan Science and Technology Cooperation (JST), c/o Advanced Materials Laboratory, NIMS Namiki 1-1, Tsukuba, Ibaraki, 305-0044, Japan ABSTRACT Effects of hydrogen sulfide on the structure of carbon nanotubes (CNTs) were studied using high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). The CNTs were synthesized with an iron thin-film catalyst by microwave plasma-assisted CVD on the diamond substrate. The HRTEM images revealed that essentially all of the CNTs obtained in this study were multiwall (MWCNT). The addition of H2S resulted in nanotubes with split skins as cornhusks and/or frills. Electron energy loss spectra of the cornhusks indicated that they consist of sp2, sp3 and amorphous carbon phase. The spectra revealed that the sp3 to sp2 ratio at the points where cornhusks divide from the main stem was more than that at the edge of the cornhusks. No evidence of sulfur incorporation into the MWCNTs grown with the H2S addition was found. We speculate that the chemical nature of sulfur on the CNT growth yields such anomalous structure.
INTRODUCTION Carbon nanotubes [1] have a great potential for industrial applications, such as field mission electron source [2], actuator [3], nanometer scale sheath or device [4-6], hydrogen storage [7, 8], etc. For hydrogen storage in particular, single-wall carbon nanotubes (SWCNTs) are more advantageous than multi-wall CNTs because SWCNTs have a large surface area of graphite sheets. Dillon and co-workers [9] have published a further review on this subject. In order to make the SWCNTs fit for the practical application in hydrogen storage, mass synthesis methods are indispensable. However, any mass synthesis methods of CNTs always produce both multi-wall and single-wall CNTs, various fullerenes, and amorphous carbon. A new methodology for the synthesis of desired CNTs is required. Some groups have reported that annealing processes such as high-energy electron beam or laser beam irradiation cause structural changes in CNTs. Ajayan and co-workers [10, 11] have observed the structure changes which are caused by oxidation and annealing using high-resolution transmission electron microscopy (HRTEM). Wei and co-workers [12] have studied the structural transition from MWCNTs to carbon onion and then to diamond by laser Z3.10.1
irradiation. But these annealing processes are not practical for obtaining a desired structure with a high yield. Other approaches were reported for obtaining CNTs from CNTs-containing carb
Data Loading...
