Browsing by Author "Chiang, Wan-Ting"

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    Characterization of fluorinated carbon nanotubes
    (2000) Chiang, Wan-Ting; Margrave, John L.
    Reaction temperatures and time are probed to get the optimal fluorination conditions in order to produce C2F carbon nanotubes. Possible fluorotube structures are optimized with molecular mechanics calculation. Results show that fluorines would like to add along the circumference of the tubes instead of going down the tube axis. The (1,4) isomer has the lower total steric energy (TSE) between the two proposed fluorotube structures, but the energy difference is small. Scanning tunneling microscopy has been used for atomic scale imaging of the fluorotubes. Significant band features are seen on fluorotubes, not on pristine carbon nanotubes. Butylated tubes have also been investigated by STM imaging. Instead of bands, relatively large, distinct features with spacing of about 50 A are observed. Both theoretical and experimental results indicated the (1,4) isomer with bands around the tubes should be the preferred structure.
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    Gas-phase process for purifying single-wall carbon nanotubes and compositions thereof
    (2006-08-15) Smalley, Richard E.; Hauge, Robert H.; Chiang, Wan-Ting; Yang, Yuemei; Smith, Kenneth A.; Kittrell, Carter W.; Gu, Zhenning; Rice University; United States Patent and Trademark Office
    The present invention relates to an all gas-phase process for the purification of single-wall carbon nanotubes and the purified single-wall carbon nanotube material. Known methods of single-wall carbon nanotube production result in a single-wall carbon nanotube product that contains single-wall carbon nanotubes in addition to impurities including residual metal catalyst particles and amounts of small amorphous carbon sheets that surround the catalyst particles and appear on the sides of the single-wall carbon nanotubes and “ropes” of single-wall carbon nanotubes. The purification process removes the extraneous carbon as well as metal-containing residual catalyst particles. The process comprises oxidation of the single-wall carbon nanotube material, reduction and reaction of a halogen-containing gas with the metal-containing species. The oxidation step may be done dry or in the presence of water vapor. The present invention provides a scalable means for producing high-purity single-wall carbon nanotube material.
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    Macroscopic ordered assembly of carbon nanotubes
    (2004-09-14) Smalley, Richard E.; Colbert, Daniel T.; Smith, Kenneth A.; Walters, Deron A.; Casavant, Michael J.; Huffman, Chad; Yakobson, Boris I.; Hauge, Robert H.; Saini, Rajesh Kumar; Chiang, Wan-Ting; Rice University; United States Patent and Trademark Office
    The present invention is directed to the creation of macroscopic materials and objects comprising aligned nanotube segments. The invention entails aligning single-wall carbon nanotube (SWNT) segments that are suspended in a fluid medium and then removing the aligned segments from suspension in a way that macroscopic, ordered assemblies of SWNT are formed. The invention is further directed to controlling the natural proclivity of nanotube segments to self assemble into ordered structures by modifying the environment of the nanotubes and the history of that environment prior to and during the process. The materials and objects are “macroscopic” in that they are large enough to be seen without the aid of a microscope or of the dimensions of such objects. These macroscopic, ordered SWNT materials and objects have the remarkable physical, electrical, and chemical properties that SWNT exhibit on the microscopic scale because they are comprised nanotubes, each of which is aligned in the same direction and in contact with its nearest neighbors. An ordered assembly of closest SWNT also serves as a template for growth of more and larger ordered assemblies. An ordered assembly further serves as a foundation for post processing treatments that modify the assembly internally to specifically enhance selected material properties such as shear strength, tensile strength, compressive strength, toughness, electrical conductivity, and thermal conductivity.
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    Process for purifying single-wall carbon nanotubes and compositions thereof
    (2004-06-22) Smalley, Richard E.; Hauge, Robert H.; Chiang, Wan-Ting; Rice University; United States Patent and Trademark Office
    The present invention relates to a process for the purification of single-wall carbon nanotubes and the purified single-wall carbon nanotube material. Known methods of single-wall carbon nanotube production result in a single-wall carbon nanotube product that contains single-wall carbon nanotubes in addition to impurities including residual metal catalyst particles and amounts of small amorphous carbon sheets that surround the catalyst particles and appear on the sides of the single-wall carbon nanotubes and “ropes” of single-wall carbon nanotubes. The purification process removes the extraneous carbon as well as metal-containing residual catalyst particles. The process employs steps including a gas-phase oxidation of the amorphous carbon and subsequent liquid-phase reaction of a halogen-containing acid with the metal-containing species. Optionally, the single-wall carbon nanotube material may be annealed dry or in the presence of moisture. The present invention provides a scalable means for producing high-purity single-wall carbon nanotube material.