Keyword: boron nitride nanotubesBoron nitride nanotubes (BNNTs) are desired for their exceptional mechanical, electronic, thermal, structural, textural, optical, and quantum properties. Golberg [1] gives an excellent review of possible applications. To date, BNNTs have been grown by a number of techniques which can be divided roughly into two categories based on the class of material produced.One is the high temperature category in which energy is concentrated into a B or BN target at a level which can vaporize elemental boron. BNNTs form in the deposits of the liberated vapors. The energy is input by laser [2][3][4][5][6] or by arc discharge [7][8][9] . Only small quantities (mg's) of material have been produced by this method, but the tubes are high quality. They have one or just a few walls, and most importantly, the tube walls are low in defects and parallel to the axis of the nanotube. The second category is low temperature synthesis, between about 600 C and 1700 C, well below the vaporization temperature of pure boron (~4000 C). These low temperature synthesis methods can be further divided into two catagories. In the first category, ball-milled precursor powders of boron and catalyst are annealed in a nitrogen or ammonia gas atmosphere, sprouting nanostructures on their

Polymer/carbon nanotube films have been formed by the alternate adsorption of the polyelectrolyte poly(diallyldimethylammonium chloride) and single walled carbon nanotubes (SWNT) onto substrates. Atomic force and scanning electron microscopies indicated that the adsorbed SWNTs were mostly in the form of 5−10 nm bundles and that uniform substrate coverage occurred. Absorbance spectrophotometry (UV− vis−NIR) confirmed that the adsorption technique resulted in uniform film growth. Characterization of the adsorbed SWNTs by X-ray photoelectron, Raman, and UV−vis−NIR spectroscopies suggested that they have a core of well ordered nanotubes covered by a layer of oxidized carbon nanotubes.

The equations needed to correctly interpret both AC and DC conductivity results of single wall carbon nanotube (SWNT) polymer composites and the scaling of these results onto a single master curve are presented. Brief discussions on the factors that determine the critical volume fraction (/ c ) and the percolation exponent (t) are also given. The results for a series of SWNT-polyimide composites are presented and the parameters obtained from fitting these results are discussed. The critical volume fraction for electrical percolation of the present composite was about 0.0005. Results obtained from previous work on SWNT (MWNT)-polymer composites and other percolation systems and the modeling (interpretation) of these results are also discussed and compared.

While high shear alignment has been shown to improve the mechanical properties of single-wall carbon nanotube (SWNT)-polymer composites, this method does not allow for control over the electrical and dielectric properties of the composite and often results in degradation of these properties. Here, we report a novel method to actively align SWNTs in a polymer matrix, which permits control over the degree of alignment of the SWNTs without the side effects of shear alignment. In this process, SWNTs were aligned via AC field-induced dipolar interactions among the nanotubes in a liquid matrix followed by immobilization by photopolymerization under continued application of the electric field. Alignment of SWNTs was controlled as a function of magnitude, frequency, and application time of the applied electric field. The degree of SWNT alignment was assessed using optical microscopy and polarized Raman spectroscopy, and the morphology of the aligned nanocomposites was investigated by high-resolution scanning electron microscopy. The structure of the field induced aligned SWNTs was intrinsically different from that of shear aligned SWNTs. In the present work, SWNTs are not only aligned along the field, but also migrate laterally to form thick, aligned SWNT percolative columns between the electrodes. The actively aligned SWNTs amplify the electrical and dielectric properties of the composite. All of these properties of the aligned nanocomposites exhibited anisotropic characteristics, which were controllable by tuning the applied field parameters.

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