Browsing by Author "Davis, Virginia Angelica"

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    Fibers of aligned single-wall carbon nanotubes and process for making the same
    (2006-10-24) Smalley, Richard E.; Saini, Rajesh Kumar; Sivarajan, Ramesh; Hauge, Robert H.; Davis, Virginia Angelica; Pasquali, Matteo; Ericson, Lars Martin; Rice University; United States Patent and Trademark Office
    The present invention involves fibers of highly aligned single-wall carbon nanotubes and a process for making the same. The present invention provides a method for effectively dispersing single-wall carbon nanotubes. The process for dispersing the single-wall carbon nanotubes comprises mixing single-wall carbon nanotubes with 100% sulfuric acid or a superacid, heating and stirring under an inert, oxygen-free environment. The single-wall carbon nanotube/acid mixture is wet spun into a coagulant to form the single-wall carbon nanotube fibers. The fibers are recovered, washed and dried. The single-wall carbon nanotubes were highly aligned in the fibers, as determined by Raman spectroscopy analysis.
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    Method and apparatus for determining the length of single-walled carbon nanotubes
    (2005-11-08) Pasquali, Matteo; Davis, Virginia Angelica; Stepanek-Basset, Ingrid; Parra-Vasquez, Nicholas A. G.; Hauge, Robert H.; Rice University; United States Patent and Trademark Office
    The present invention is directed to at least one method and at least one apparatus for determining the length of single-wall carbon nanotubes (SWNTs). The method generally comprises the steps of: dispersing a sample of SWNTs into a suitable dispersing medium to form a solvent-suspension of solvent-suspended SWNTs; determining the mean SWNT diameter of the solvent-suspended SWNTs; introducing the solvent-suspended SWNTs into a viscosity-measuring device; obtaining a specific viscosity for the SWNT solvent-suspension; and determining the length of the SWNTs based upon the specific viscosity by solving, for example, the Kirkwood-Auer equation corrected by Batchelor's formula for the drag on a slender cylinder for “L,” to determine the length of the SWNTs. The apparatus generally comprises: a SWNT sample introduction mechanism; a dispersal chamber; a SWNT radius-determination chamber; and a viscosity determining chamber, wherein the SWNT sample introduction mechanism, the dispersal chamber, the SWNT radius-determination chamber, and the viscosity determination chamber are each operatively connected to at least one of the others.
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    Phase behavior and rheology of single-walled carbon nanotubes (SWNTs) in superacids with application to fiber spinning
    (2006) Davis, Virginia Angelica; Pasquali, Matteo; Smalley, Richard E.
    This dissertation describes the first discovery and characterization of a SWNT liquid crystalline phase. The protonation of SWNTs in superacids enables their dispersion at concentrations up to 12% vol. (10% wt.); this concentration is an order of magnitude higher than has been achieved for pristine SWNTs in any other solvent. The dispersed SWNTs behave as rigid rods; with increasing concentration the dispersions transition from a dilute phase of Brownian non-interacting rods, to a semidilute phase in which rod rotation is inhibited, to a biphasic regime where an isotropic phase coexists with a liquid crystalline phase, and finally to a single phase liquid crystal. This phase behavior was determined using a combination of rheology, optical microscopy, and differential scanning calorimetry. For monodisperse rods interacting only through hard rod repulsion, the phase boundaries are only a function of the rods' aspect ratio. For SWNTs in superacids, the phase transitions are also affected by the extent of SWNT protonation as well as aspect ratio polydispersity. SWNT protonation has significant effects on the concentration at which the system becomes biphasic, the liquid crystalline morphology, and the response of the system to non-solvents. In contrast, SWNT protonation has little effect on the concentration at which the system becomes a single liquid crystalline phase; this transition appears to be primarily controlled by SWNT polydispersity. The ability to form a lyotropic nematic SWNT liquid crystal directly impacts the development of applications requiring macroscopic assemblies of highly aligned SWNTs. Highly aligned macroscopic SWNT fibers ranging from 30 to 100 mum in diameter and up to 100 m in length have been produced by solution spinning liquid crystalline SWNT-102% H2SO4 dispersions. The direct impact of liquid crystalline phase behavior and liquid crystal morphology on fiber microstructure was demonstrated by producing fibers from SWNTs dispersed in 102% H2SO4 and ClSO3H. The results of this research provide a key example of how liquid crystalline phase behavior can be used to facilitate the development of macroscopic structures comprised of anisotropic nanomaterials.
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    Single-wall carbon nanotube alewives- process for making- and compositions thereof
    (2007-10-30) Smalley, Richard E.; Saini, Rajesh Kumar; Sivarajan, Ramesh; Hauge, Robert H.; Davis, Virginia Angelica; Pasquali, Matteo; Ericson, Lars Martin; Kumar, Satish; Veedu, Sreekumar Thaliyil; Rice University; United States Patent and Trademark Office
    The present invention involves alewives of highly aligned single-wall carbon nanotubes (SWNT), process for making the same and compositions thereof. The present invention provides a method for effectively making carbon alewives, which are discrete, acicular-shaped aggregates of aligned single-wall carbon nanotubes and resemble the Atlantic fish of the same name. Single-wall carbon nanotube alewives can be conveniently dispersed in materials such as polymers, ceramics, metals, metal oxides and liquids. The process for preparing the alewives comprises mixing single-wall carbon nanotubes with 100% sulfuric acid or a superacid, heating and stirring, and slowly introducing water into the single-wall carbon nanotube/acid mixture to form the alewives. The alewives can be recovered, washed and dried. The properties of the single-wall carbon nanotubes are retained in the alewives.