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Individual CNTs (individual + cnt)

Distribution by Scientific Domains
Polymers and Materials Science100%

Selected Abstracts

Electrically Addressable Hybrid Architectures of Zinc Oxide Nanowires Grown on Aligned Carbon Nanotubes

ADVANCED FUNCTIONAL MATERIALS, Issue 15 2010
Jong G. Ok
Abstract The fabrication and characterization of hybrid architectures of ZnO nanowires (ZNWs) grown on organized carbon nanotubes (CNTs), by a two-step chemical vapor deposition (CVD) process involving CNT growth from a hydrocarbon source followed by ZNW growth using a Zn metal source, is reported. The ZNWs grow uniformly and radially from individual CNTs and CNT bundles, and the aligned morphology of the CNTs is not disturbed by the ZNW growth process. The nucleation and growth of ZnO crystals on CNTs are analyzed in relation to the classical vapor,solid mechanism. Importantly, the CNTs make uniform and distributed electrical contact to the ZNWs, with up to a 1000-fold yield advantage over conventional ZNW growth on a flat substrate. Hybrid ZNW/CNT sheets are fabricated by scalable CVD, rolling, and printing methods; and their electrical properties, which are governed by transport through the anisotropic CNT network, are characterized. Functional interaction between the ZNWs and CNTs is demonstrated by photoconductive behavior and photocurrent generation of the hybrid material under UV illumination. There is significant future opportunity to extend these processing methods to fabricate other functional oxides on CNTs, and to build devices that harness the attractive properties of ZNWs and CNTs with high volumetric efficiency over large areas. [source]

Tuning Nanotubes: Beam to String Transition of Vibrating Carbon Nanotubes Under Axial Tension (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2009
Mater.
On page 1753, the vibration properties of carbon nanotubes (CNTs) under axial tension are quantificationally studied by X. L. Wei et al. through a novel in situ method for precise and simultaneous measurement of the resonance frequency, the axial tension applied to individual CNTs, and the tube geometry. A gradual beam-to-string transition from multiwalled CNTs to singlewalled CNTs is observed; the CNTs can be tuned like a zither! [source]

Beam to String Transition of Vibrating Carbon Nanotubes Under Axial Tension

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2009
Xianlong Wei
Abstract State-of-the-art nanoelectromechanical systems have been demonstrated in recent years using carbon nanotube (CNT) based devices, where the vibration of CNTs is tuned by tension induced through external electrical fields. However, the vibration properties of CNTs under axial tension have not been quantitatively determined in experiments. Here, a novel in situ method for precise and simultaneous measurement of the resonance frequency, the axial tension applied to individual CNTs and the tube geometry is demonstrated. A gradual beam-to-string transition from multi-walled CNTs to single-walled CNTs is observed with the crossover from bending rigidity dominant regime to extensional rigidity dominant regime occur much larger than that expected by previous theoretical work. Both the tube resonance frequency under tension and transition of vibration behavior from beam to string are surprisingly well fitted by the continuum beam theory. In the limit of a string, the vibration of a CNT is independent of its own stiffness, and a force sensitivity as large as 0.25,MHz (pN),1 is demonstrated using a 2.2,nm diameter single-walled CNT. These results will allow for the designs of CNT resonators with tailored properties. [source]

Controlling the Morphology of Carbon Nanotube Films by Varying the Areal Density of Catalyst Nanoclusters Using Block-Copolymer Micellar Thin Films,

ADVANCED MATERIALS, Issue 17 2006
D. Bennett
The morphologies of carbon nanotube (CNT) thin films are controlled by varying the areal density of catalytic nanoclusters synthesized from a block-copolymer micellar thin film. The morphologies of the CNT films vary from a tangled and sparse arrangement of individual CNTs, through a transition region with locally bunched and self-aligned CNTs, to a rapid growth of thick vertical CNT films (see figure). [source]

Analysis and measurement of carbon nanotube dispersions: nanodispersion versus macrodispersion

POLYMER INTERNATIONAL, Issue 10 2010
Micah J Green
Abstract Because of their unique mechanical, optical, thermal and electrical properties, carbon nanotubes (CNTs) form the basis for a wide variety of multifunctional devices and materials; many of these applications require that CNTs be dispersed and processed in liquids such as organic solvents, polymer melts or surfactant solutions. One of the most problematic issues affecting the CNT research community is the lack of standards and uniform characterization methods for CNT dispersion. A 2005 NASA-NIST workshop aimed to address this issue and made a clear distinction between ,nanodispersion' of individual CNTs and ,macrodispersion' of CNT bundles. Unfortunately, this distinction has yet to percolate through the CNT dispersion literature. The present article seeks to elucidate and commend these concepts, identify the situations where this difference is most critical, note some scenarios where these concepts have been underutilized and posit experimental and computational characterization methods for quantifying the degree of nanodispersion. Particular attention is devoted to the controversial claims of complete nanodispersion and how such claims may be verified. Copyright © 2010 Society of Chemical Industry [source]