Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session N32: Focus Session: Carbon Nanotubes: Composites and Applications |
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Sponsoring Units: DMP DPOLY Chair: Andrew Rinzler, University of Florida Room: Baltimore Convention Center 329 |
Wednesday, March 15, 2006 8:00AM - 8:36AM |
N32.00001: The Solid-State Fabrication, Structure, and Multifunctional Applications of Strong Carbon Nanotube Yarns and Transparent Sheets Invited Speaker: We describe novel methods for producing polymer-free carbon nanotube yarns and transparent sheets (self-assembled textiles), and describe their application as multifunctional materials. These fabrication methods are conducted at room temperature in the solid state for multi-walled carbon nanotubes, which are much cheaper to produce that our previously used single-walled carbon nanotube fibers. The yarns have a maximum failure strength of above 460 MPa (850 MPa after polymer infiltration), they are highly resistant to creep and to knot or abrasion-induced failure, and they provide a giant Poisson's ratio for stretch in the fiber direction. The nanotube textiles have higher gravimetric strength than the strongest steel sheet or the polymers used for ultralight air vehicles and proposed for solar sails. Applications evaluations are described for artificial muscles, thermal and light harvesting, energy storage, field-emission electron sources, electrically conducting appliques, three types of lamps and displays, and sensors. [Preview Abstract] |
Wednesday, March 15, 2006 8:36AM - 8:48AM |
N32.00002: Mechanical Reinforcement of Functionalized Carbon Nanotube-Polyethylene Polymer Composites Merlyn Pulikkathara, Valery Khabashesku Carbon nanotube-polymer composites are promising materials for a variety of applications including space exploration and the aerospace industry. In this work, we functionalized and fabricated a series of single walled carbon nanotube (SWNT) composite samples using medium density polyethylene (MDPE). The composites were made by shear mixing melt processing of MDPE with up to 1 wt.{\%} added pristine and functionalized SWNTs including fluoro (F), undecyl and urea SWNT-derivatives. The former two were prepared as described earlier, while the synthesis of the latter is a novel method that has been developed utilizing a solvent free reaction of fluoro-SWNT with molten urea. FTIR, Raman, and AFM data confirm that urea bonds covalently to the SWNT surface and displaces most of the fluorine. Initial tensile strength (TS) of the MDPE composites loaded with urea-F-SWNT reinforced 48{\%} and undecyl-functionalized SWNTs show unprecedented reinforcement up to 185{\%} compared to neat MDPE. These preliminary results show that these functionalized SWNT increased the mechanical strength in of MDPE composites. The FTIR, Raman, AFM, SEM, TEM, XPS, TGA, and TS data of studied materials will be presented. [Preview Abstract] |
Wednesday, March 15, 2006 8:48AM - 9:00AM |
N32.00003: Adhesion and Reinforcement in Carbon Nanotube Polymer Composite Chenyu Wei The temperature dependent adhesion behavior and reinforcement in carbon nanotube(CNT)-polymer (polyethylene) composite is studied through molecular dynamics (MD) simulations. The interfacial shear stress through van der Waals interactions is found to increase linearly with applied tensile strains along the nanotube axis direction, until the non-covalent bonds between CNTs and molecules break successively. A lower bound value about 46 MPa is found for the shear strength at low temperatures. Direct stress-strain calculations show significant reinforcements in the composite in a wide temperature range, with $\sim $ 200{\%} increase in the Young's modulus when adding 6.5{\%} volume ratio of short CNTs, and comparisons with the Halpin-Tsai formula are discussed. [Preview Abstract] |
Wednesday, March 15, 2006 9:00AM - 9:12AM |
N32.00004: Multi-scale Real-Space Characterization of Carbon Nanofiber Composites Benji Maruyama, Sirina Putthanarat, Lawrence Drummy, Richard Vaia, Jonathan Spowart, Carla Leer, Ferrie Van Hattum Good dispersion of the reinforcement phase in nanocomposites is recognized as critical to achieving material property goals. Hierarchical nanocomposite morphologies can be quantified by a combination of 1) Reciprocal space methods such as scattering, 2) Real space imaging such as AFM and TEM, and/or 3) Inference from established structure-property models. However, none of these techniques alone has proven satisfactory to quantitatively characterize nanocomposite morphologies across multiple length scales and link them to properties. Nor have they been adequate to define quality control metrics for dispersion. The current effort is devoted to characterizing dispersion in carbon nanofiber composites from the nano- to meso-scales (i.e., 10 nm - 10 mm) using the Multi-Scale Analysis of Area Fractions (MSAAF) technique of Spowart et al. This technique uses a fractal analysis of real space images to generate a homogeneous length scale (scale at which the statistical variability in concentration is at some threshold), and a fractal dimension characteristic of the dispersion over a wide range of length scales. This work is part of a larger effort to determine structure/property relations of complex materials systems. [Preview Abstract] |
Wednesday, March 15, 2006 9:12AM - 9:24AM |
N32.00005: Radial Elasticity of Nanotubes Ismael Palaci, Stephan Fedrigo, Harald Brune, Christian Klinke, Elisa Riedo The last decade has lead to the discovery of many nanostructures like nanotubes, nanowires or nanobelts. Industrial applications of these nanostructures need practical tools to characterize their optical, electrical or mechanical properties. Here we propose to use state of the art atomic force microscopy to characterize the radial elasticity of nanotubes of different diameters. The nanostructures were elastically strained in the radial direction by applying small indentation amplitudes. In the case of multiwalled carbon nanotubes, this method enables to extract the radial Young modulus from compliance measurements. We find 600 GPa for our smallest tubes with a radius $R$ = 2.2 nm. The values strongly decrease with increasing radii until they reach an asymptotic value of $30\pm 10$ GPa at $R\ge 4$ nm. The normal force vs. indentation curves are in qualitative agreement with molecular dynamics simulations. [Preview Abstract] |
Wednesday, March 15, 2006 9:24AM - 9:36AM |
N32.00006: Dissipation in suspended carbon nanotube oscillators P. Alex Greaney, Jeffrey C. Grossman The vibrational properties of doubly clamped suspended single walled carbon nanotubes are studied numerically using continuum, and atomistic methods. Of interest is the dissipation of energy in athermally excited modes. Simple continuum arguments may be used to bound the limits of energy dissipation that arise due to the scale of the nanotubes; however, more detailed atomistic descriptions are required to capture the dissipation due to coupling between phonon modes. This work has implication for the use of carbon nanotubes as high frequency resonators in nanomechanical systems. [Preview Abstract] |
Wednesday, March 15, 2006 9:36AM - 9:48AM |
N32.00007: Structure and Mechanical Properties of Model Nanotube Composites Andrew B. Schoch, Kenneth R. Shull, L. Catherine Brinson, Wesley R. Burghardt, Thomas O. Mason, Neil J. Kidner, Supaporn Wansom, Leta Y. Woo Thermoreversible gels based on solutions of acrylic triblock copolymers have been infused with multi-walled carbon nanotubes at various loadings. The fast transition between liquid and solid states allows for the nanotubes to be frozen into their positions. These composite materials exhibit distinct mechanical and electrical properties from the bulk gel. The storage modulus of the filled gels persists at temperatures well above the gel transition and signifies elasticity that comes solely from the nanotube inclusions. The magnitude of this additional elasticity at high temperatures increases dramatically with increasing nanotube volume fraction above a ``percolation'' threshold that is extremely low. Sensitivity to nanotube interactions is enhanced by the low background levels of gel elasticity above the gel transition temperature. Complementary alternating current impedance spectroscopy measurements were performed to asses the onset of electrical percolation in these systems. [Preview Abstract] |
Wednesday, March 15, 2006 9:48AM - 10:00AM |
N32.00008: \textit{In vivo} MRI of single-wall carbon nanohorns through magnetite nanoparticle attachment Jin Miyawaki, Masako Yudasaka, Hideto Imai, Hideki Yorimitsu, Hiroyuki Isobe, Eiichi Nakamura, Sumio Iijima Superparamagnetic magnetite (SPM) is used as a contrast agent in magnetic resonance imaging (MRI). Thus, the SPM-attachment to carbon nanotubes (CNTs) will enable to visualize motional behaviors of CNTs in the living body through MRI. We found that the strong attachment of the SPM nanoparticles (ca. 6 nm size) to one type of CNTs, single-wall carbon nanohorns (SWNHs), could be achieved through a deposition of iron acetate clusters on SWNHs in ethanol at room temperature, followed by heat-treatment in Ar. \textit{In vivo} MRI visualized that the SWNHs attached with the SPM nanoparticles accumulated in several organs of mice when injected into mice via tail veins. This simple method for the SPM-attaching on CNTs would facilitate the toxicity assessment of CNTs and the applications of CNTs in bioscience and biotechnology. [Preview Abstract] |
Wednesday, March 15, 2006 10:00AM - 10:12AM |
N32.00009: Sensor applications and spin-transport measurements in carbon nanotube nanocomposites J. Sanders, J. Gass, H. Srikanth, F.K. Perkins, E.S. Snow Vertical and horizontal carbon nanotubes have been grown at USF using CVD and PECVD techniques with Ni and Fe nanoparticle catalysts. At NRL we have used CVD to produce carbon nanotube networks on SiO$_{2}$/Si$^{++}$ substrates to build sensors for chemical and bio agents by measuring capacitance and conductance. Various chemical vapors are able to be sensed with a fast response and recovery as well as a high degree of selectivity. A microfluidic flow system has been developed to extend the sensing applications to biological analytes. It is also known that carbon nanotubes are excellent transmission channels for charge and spin transport. In addition to the biosensors, we will also report on our experiments probing charge and spin transport through nanotube networks using point contact Andreev reflection (PCAR) based on superconducting and ferromagnetic junctions. Work at USF supported by DARPA/ARO through grant {\#} W911NF-05-1-0354 [Preview Abstract] |
Wednesday, March 15, 2006 10:12AM - 10:24AM |
N32.00010: Characterisation of a Hydroxyapatite and Carbon Nanotube Bioceramic Composite C. Kealley, B. Ben-Nissan, A. van Riessen, M. Elcombe A biocompatible composite for bone replacement applications was investigated. The effects that the microstructure may have on the mechanical properties of the bioceramic have been assessed. Hydroxyapatite was prepared as reported previously[1] with 2, 5 and 10 wt{\%} of carbon nanotubes (CNTs) being incorporated during the production before hot isostatic pressing. Microstructural analysis of the composite has been undertaken by SEM/EDS, TEM/EDS, XRD and ND. The effects of concentration of the CNTs on the mechanical properties of the composite material have been determined. At 2 wt{\%} excellent densification has been achieved, and there is a significant improvement in Vickers Hardness and Young's Modulus. However, as expected fracture toughness is reduced. [1] Lewis, K., Kealley, C., Elcombe, M., van Riessen, A., and Ben-Nissan, B. (2005), J. Aust. Ceram. Soc., 41(2), p52-55. [Preview Abstract] |
Wednesday, March 15, 2006 10:24AM - 10:36AM |
N32.00011: The physical properties and possible applications of metal coated carbon nanotubes Engin Durgun, Sefa Dag, Salim Ciraci We show that Ti atoms can form a continuous coating of carbon nanotubes at various amounts of coverage. The circular cross section of the tubes changes to a square-like form, and the semiconducting tube becomes a ferromagnetic metal with high quantum ballistic conductance. Metallicity is induced not only by the metal-metal coupling, but also by the band gap closing of SWNT at the corners of the square. The magnetic properties of Ti coated tubes depend strongly on the geometry, amount of Ti coverage and also on the elastic deformation of the tube. While the magnetic moment can be pronounced significantly by the positive axial strain, it can decrease dramatically upon the adsorption of additional Ti atoms to the monolayer coting of the nanotube. Besides, electronic structure and spin- polarization near the Fermi level can also be modified by radial strain. On the other hand, it is found that Ti and V decorated carbon nanotubes of various radii and chirality can adsorb large amounts of hydrogen molecules and can be possible candidates for hydrogen storage applications. The other transtions metals like Fe, Co, Cr, and Mn cannot cover nanotube surface uniformly but can only be adsorbed in clustered forms. Depending on the geometry and amount of adsorption these systems can posses high polarization near Fermi level with variable magnetic moments which can be useful in spintronic devices. [Preview Abstract] |
Wednesday, March 15, 2006 10:36AM - 10:48AM |
N32.00012: Field Emission from Carbon Nanotubes: From Isolated Nanotubes to Matrix Cathodes. David Carey, Richard Smith, Ravi Silva The high aspect ratio and current carrying ability of carbon nanotubes (CNTs) make them an attractive material for electron sources. Field screening effects are known to occur at high nanotube densities and most large area field emission characteristics (FECs) reflect ensemble averages of the sites with the lowest effective potential barriers. We have studied the FECs and enhancement factor from isolated nanotubes mounted on high resolution manipulators within a scanning electron microscope. We have further developed an in-situ three terminal characterisation facility allowing estimates of the screening factor of the gate electrode and gate transparency. Measurements of the FEC of carbon nanotube -- polymer spin cast composites cathodes have also been made. A range of samples with arc discharge nanotube mass fractions up to 7 {\%} was prepared. Electron emission at low applied electric fields is observed. The transport and emission mechanism of the electrons is discussed in terms of a polymer coating that surrounds the nanotube and acts as a tunnel barrier. This gives rise to fluctuation induced tunnelling between the nanotubes which affects the field emission. The effects of the disordered percolation control network on the field emission along with prospects for applications are discussed. [Preview Abstract] |
Wednesday, March 15, 2006 10:48AM - 11:00AM |
N32.00013: Thermal Field Emission from a Single Carbon Nanotube Gongpu Zhao, Jian Zhang, Qi Zhang, Han Zhang, Tie Tang, Otto Zhou, Lu-Chang Qin Carbon nanotubes (CNTs) exhibit excellent characteristics in field-induced electron emission with high brightness, stable emission current, long service time and narrow energy distribution. But it is still not clear how carbon nanotubes behave under high electric field and high temperature. We have characterized the thermal field emission properties of an individual multiwalled carbon nanotube fabricated by a two step process. The characterization was conducted in the transition zone between thermionic emission and field emission. An approximation has been made to the Murphy-Good equation so that the temperature at the CNT apex can be extracted. The boundary of transition zone was determined experimentally by activating thermal field emission at various temperatures. We also show that higher temperature will improve the emission stability and remove disruptions in the emission current. [Preview Abstract] |
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