Abstract/Details

Electron diffraction and microscopy study of nanotubes and nanowires


2007 2007

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Abstract (summary)

Carbon nanotubes have many excellent properties that are strongly influenced by their atomic structure. The realization of the ultimate potential of carbon nanotubes in technological applications necessitates a precise control of the structure of as-grown nanotubes as well as the identification of their atomic structures. Transmission electron microscopy (TEM) is a technique that can deliver this by combining the high resolution imaging and electron diffraction simultaneously. In this study, a new catalyst system (the Co/Si) was investigated in the production of single-walled carbon nanotubes (SWNTs) by laser ablation. It was discovered that the Co/Si mixture as a catalyst was as successful as the Ni/Co in the synthesis of SWNTs. The isolated individual SWNTs were examined by using nanobeam electron diffraction for the structure identification and it was found that carbon nanotubes grown by this catalyst mixture tend to be slightly more metallic.

The electron diffraction technique has been refined to establish a new methodology to determine the chirality of each shell in a carbon nanotube and it has been applied to determine the atomic structure of double-walled carbon nanotubes (DWNT), few-walled carbon nanotubes (FWNT) and multi-walled carbon nanotubes (MWNT). We observed that there is no strong correlation in the structure of two adjacent shells in DWNTs. Several FWNTs and MWNTs have been examined by our new electron diffraction method to determine their atomic structures and to test the efficiency and the reliability of this method for structure identification. We now suggest that a carbon nanotube of up to 25 shells can be studied and the chirality of each shell can be identified by this new technique. The guidelines for the automation of such procedure have been laid down and explained in this work.

The atomic structure of tungsten disulfide (WS2) nanotubes was studied by using the methods developed for the structure determination of carbon nanotubes. The WS2 nanotubes are another example of the tube forming ability of the layered structures and a member of the family of inorganic fullerene-like structures. These nanotubes are much larger in diameter than carbon nanotubes. The tubes studied here have helicities less than 18° and usually have near zigzag structure.

The short-range order (SRO) in the atomic structure of carbon soot produced by laser ablation was investigated using electron diffraction and radial distribution function (RDF) analysis. The effects of the furnace temperature and the metal catalyst on the SRO in the carbon soot were also studied. It was discovered that the SRO structure is the same for all carbon soot samples studied and is very similar to that of amorphous carbon. These techniques were also applied to determine the atomic structure of amorphous boron nanowires. We found out that the atomic structure of these boron nanowires agree well with the previously reported structure of bulk amorphous boron.

Indexing (details)


Subject
Condensation
Classification
0611: Condensation
Identifier / keyword
Pure sciences; Atomic structure; Multiwalled carbon nanotubes; Nanotubes; Nanowires
Title
Electron diffraction and microscopy study of nanotubes and nanowires
Author
Deniz, Hakan
Number of pages
221
Publication year
2007
Degree date
2007
School code
0153
Source
DAI-B 68/11, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780549325444
Advisor
Qin, Lu-Chang
Committee member
Karwowski, Hugon; Lopez, Rene; McNeil, Laurie; Washburn, Sean
University/institution
The University of North Carolina at Chapel Hill
Department
Physics & Astronomy
University location
United States -- North Carolina
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3289068
ProQuest document ID
304840972
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/304840972/abstract
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