Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session A17: Focus Session: Carbon Nanotubes & Related Materials: Growth, Separation, and Assembly |
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Sponsoring Units: DMP Chair: Andrew Rinzler, University of Florida Room: 102AB |
Monday, March 2, 2015 8:00AM - 8:12AM |
A17.00001: Modulating diameter of single-walled carbon nanotubes in alcohol catalytic chemical vapor deposition Rong Xiang, Kehang Cui, Hua An, Xiao Chen, Shohei Chiashi, Shigeo Maruyama Modulating the diameter of a single walled carbon nanotube (SWNT) is essential for its applications in optical and electronic devices. We demonstrate that the average diameter of vertically aligned SWNTs can be successfully reduced from 2.5 to 1.2 nm by changing catalyst component ratio in a Co/Mo bimetallic system, no matter the catalyst is dip-coated or spray-coated onto a substrate. Meanwhile, the diameter can be further reduced after replacing the conventional ethanol carbon source by acetonitrile. Recently, Cu is found to be effective in reducing diameter in alcohol catalytic chemical vapor deposition, and sub-1-nm SWNTs are achieved using this novel Co/Cu combination. Diameter modulation is confirmed by Raman spectroscopy, optical absorption spectroscopy and transmission electron microscopy. The structure and element distribution in Co/Cu catalyst is also investigated. [Preview Abstract] |
Monday, March 2, 2015 8:12AM - 8:24AM |
A17.00002: Ethanol decomposition on transition metal nanoparticles during carbon nanotube growth: ab initio molecular dynamics study Yasushi Shibuta, Kohei Shimamura, Tomoya Oguri, Rizal Arifin, Fuyuki Shimojo, Shu Yamaguchi The growth mechanism of carbon nanotubes (CNT) has been widely discussed both from experimental and computational studies. Regarding the computational studies, most of the studies focuses on the aggregation of isolate carbon atoms on the catalytic metal nanoparticle, whereas the initial dissociation of carbon source molecules should affect the yield and quality of the products [1]. On the other hand, we have studied the dissociation process of carbon source molecules on the metal surface by the ab initio molecular dynamics simulation [2,3]. In the study, we investigate the ethanol dissociation on Pt and Ni clusters by ab initio MD simulations to discuss the initial stage of CNT growth by alcohol CVD technique. [1] Y. Shibuta, Diamond and Related Materials, 20 (2011) 334-338. [2] T. Oguri, K. Shimamura, Y. Shibuta, F. Shimojo, S. Yamaguchi, J. Phys. Chem. C 117 (2013) 9983. [3] T. Oguri, K. Shimamura, Y. Shibuta, F. Shimojo, S. Yamaguchi, Chem. Phys. Lett., 595-596 (2014) 185. [Preview Abstract] |
Monday, March 2, 2015 8:24AM - 8:36AM |
A17.00003: Advanced Synthesis of Spinnable MWCNT Forests by RF-Induction Heating Enhanced CVD Process Anvar Zakhidov, William Holmes We demonstrate here an advanced method to effectively grow tall multi-wall carbon nanotubes (MWCNT) vertically oriented forests which are highly spinnable. Heating of the Fe catalyst is achieved extremely fast by RF induction heating using coils outside the quartz tube. This method and the new apparatus designed and presented in this paper allow separate control over the temperature of the substrate and the temperature of the incoming gases. In addition to temperature control, the fast T-ramping of the substrate preserves the catalyst nanoclusters from Ostwald ripening and other growth quenching effects such as carbon overgrowth of the catalyst. We show that the parametric sweet spot or bell curve of substrate spinnability can be increased significantly with this improved RF-CVD method. The catalyst nanoclusters also show a wide band of density arrangements that very positively effect spinnability and the drawing ratio. Drawing ratios can vary from 2 meters to 12 meters of sheets drawn from only 1cm of forest. RF-CVD method allows to grow fast (in several minuts) higher CNT forests at higher temperature of synthesis up to 800 K, and obtain dry-spinable CNTs, Characterization results of the samples created in the newRF-CVD system will be presented and compared to previous CNT sheet samples by conventional three-zone resistive heating CVD to measure the extent of property improvements of the CNT sheets and forests. Specifics of the experimental system will be addressed in detail and future property improvements and applications explored. [Preview Abstract] |
Monday, March 2, 2015 8:36AM - 9:12AM |
A17.00004: Carbon Nanotubes: On the Origin of Helicity Invited Speaker: Avetik Harutyunyan The mechanism of helicity formation of carbon nanotubes still remains elusive that hinders their applications. Current explanations mainly rely on the planar interrelationship between the structure of nanotube and corresponding facet of catalyst in 2D geometry that could amend the structure of grown carbon layer, specifically due to the epitaxial interaction. Yet, the structure of carbon nanotube and circumference of the rims assume involvement of more than one facet i.e. it is 3D problem. By aiming this problem we find that the nanotube nucleation is initiated by cap formation via evolving of graphene embryo across the adjacent facets of catalyst particle. As a result the graphene embryos incorporate in their hexagonic network various polygons to accommodate the curved 3D geometry that initiates cap formation following by elongation of the circumferential rims. Based on these results, also on the census of nanotube caps and the fact that given cap fit only one nanotube wall, we consider carbon cap responsible for the helicity of carbon nanotube. This understanding could provide new avenues towards engineering particles to explicitly accommodate certain helicities via exploitation of the angular distribution of catalyst adjacent facets. Our recent progresses in production of carbon nanotubes, nanotube reinforced composites and their potential applications also will be presented. [Preview Abstract] |
Monday, March 2, 2015 9:12AM - 9:24AM |
A17.00005: Carbon Nanotube-Graphene Nanoscroll Hybrid Structures Oleg Martynov, Sinchul Yeom, Marc Bockrath Graphene nanoscrolls (GNS) are a spiral one-dimensional tubular form of graphitic carbon [1]. Recently a number of methods have been devised to produce GNS; however, they suffer from low yield and poor controllability. Consequently, GNS provide a relatively unexplored system with some theoretically promising and unique properties [2][3][4]. We will discuss our progress towards GNS synthesis using a wet process modeled after Xie et al [5], producing a GNS from single or multilayer graphene on an Si/SiO2 substrate. We propose a novel method to produce a nested multiwalled carbon nanotube (MWCNT)-nanoscroll structure using aligned MWCNT transfer onto exfoliated graphene. Latest progress and measurements on these MWCNT-nanoscroll hybrids will be presented. [1] S. Braga et al., Nano Lett., 4 (5), pp 881-884 (2004). [2] V. Coluci et al., Phys. Rev. B 75, 125404 (2007). [3] X. Shi et al., Appl. Phys. Lett. 95, 163113 (2009). [4] M. Fogler et al., Phys. Rev. B 81, 161408(R) (2010). [5] X. Xie et al., Nano Lett. , 9 (7), pp 2565-2570 (2009). [Preview Abstract] |
Monday, March 2, 2015 9:24AM - 9:36AM |
A17.00006: Advanced Multifunctional Properties of Aligned Carbon Nanotube-Epoxy Composites from Carbon Nanotube Aerogel Method Thang Tran, Peng Liu, Zeng Fan, Nigel Ngern, Hai Duong Unlike previous methods of making carbon nanotube (CNT) thin films, aligned CNT thin films in this work are synthesized directly from CNT aerogels in a CVD process. CH$_{4}$/H$_{2}$/He gases and ferrocene/thiophene catalysts are mixed and reacted in the reactor at 1200 $^{\circ}$C to form CNT aerogel socks. By pulling out the socks with a metal rod, CNT thin films with 15-nm diameter MWNTs are aligned and produced continuously at a speed of a few meters per minute. The number of the aligned CNT thin film layers/ thickness can also be controlled well. The as-synthesized aligned CNT films are further condensed by acetone spray and post-treated by UV light. The aligned CNT films without any above post-treatment have a high electrical conductivity of 400S/cm. We also develop aligned CNT-epoxy composites by infiltrating epoxy into the above aligned CNT thin films using Vacuum Assisted Resin Transfer Molding~(VARTM) method. Our cost-effective fabrication method of the aligned CNT films is more advanced for developing the composites having CNT orientation control. The mechanical, electrical and optical properties of the aligned CNT epoxy composites are measured. About 2{\%} of the aligned CNTs can enhance significantly the electrical conductivity and hardness of aligned CNT-epoxy composite films. Effects of morphologies, volume fraction, and alignment of the CNTs on the advanced multifunctional properties of the aligned CNT-epoxy composites are also quantified. [Preview Abstract] |
Monday, March 2, 2015 9:36AM - 9:48AM |
A17.00007: Crystallographic growth and alignment of carbon nanotubes on few-layer graphene Aram Arash, Patrick D. Hunley, Mohsen Nasseri, Mathias J. Boland, Abhishek Sundararajan, Bethany M. Hudak, Beth S. Guiton, Douglas R. Strachan Hybrid carbon nanotube and graphene structures are emerging as an exciting material system built from a common sp2 carbon backbone. Such hybrid systems have promise for use in improving the performance of energy storage and high-speed electronic applications. Towards the attainment of such hybrid materials, the catalytic growth and crystallographic alignment of these integrated structures are investigated along with the atomic-scale features of their interfaces. The catalytic activity of nanoparticles to form carbon nanotubes on the surface of few-layer graphene is tuned through precise feedstock application. Through careful materials synthesis, the interfaces of these hybrid carbon nanotube -- graphene systems are investigated through ultra-high resolution electron microscopy. [Preview Abstract] |
Monday, March 2, 2015 9:48AM - 10:00AM |
A17.00008: Scaled Synthesis of Boron Nitride Nanotubes, Nanoribbons, and Nanococoons Using Direct Feedstock Injection into an Extended-Pressure, Inductively-Coupled Thermal Plasma Aidin Fathalizadeh, Thang Pham, William Mickelson, Alex Zettl A variable pressure (up to 10 atm) powder or gas injection inductively coupled plasma system has been developed and used to produce high-quality boron nitride nanotubes (BNNTs) at continuous production rates of 35 g/h. Under suitable conditions, collapsed BN nanotubes (i.e., nanoribbons), and closed shell BN capsules (i.e., nanococoons) are also obtained. The process is adaptable to a large variety of feedstock materials. [Preview Abstract] |
Monday, March 2, 2015 10:00AM - 10:12AM |
A17.00009: Electronic and optoelectronic devices based on chirality-enriched wafer-scale single-wall carbon nanotube thin films Weilu Gao, Xiaowei He, Lijuan Xie, Qi Zhang, Erik Haroz, Stephen K. Doorn, Junichiro Kono The unique and rich material properties of single-wall carbon nanotubes (SWCNTs) make them attractive for nano-electronic and optoelectronic applications. Slight changes in tube diameter and wrapping angle, defined by the chirality indices ($n$,$m$), can dramatically modify the bandstructure, which can be utilized for designing devices with tailored properties. However, it remains to be a challenge to fabricate macroscopic, single-chirality devices. Here, we introduce a simple way of producing chirality-enriched wafer-scale SWCNT films by combining recently developed solution-based polymer-modified sorting method\footnote{C. Y. Khripin {\it et al.}, JACS \textbf{18}, 6822 (2013)} and vacuum filtration. The produced thin films can be easily transferred onto any substrate to have a CMOS compatible wafer. We fabricated a transistor of (6,5)-enriched SWCNTs with an on/off ratio $>$10$^3$. Large-scale photothermoelectric-effect-based and photovoltaic-effect-based photodetectors made of (6,6)- and (6,5)-enriched films, respectively, will also be discussed. [Preview Abstract] |
Monday, March 2, 2015 10:12AM - 10:24AM |
A17.00010: Single Chirality Resolution Separation of Single-Wall Carbon Nanotubes up to 1.7+ nm in Diameter using Aqueous Two-Phase Extraction Jeffrey Fagan The recent development of aqueous two-phase extraction (ATPE) as a method for separating single-wall carbon nanotubes (SWCNTs) provides a scalable method for isolating many individual species of SWCNT via solution processing. In this presentation I will demonstrate that the ability of ATPE is not limited to the separation of small diameter SWCNTs $<$ 1nm, but enables the extraction of single metallic and semiconducting SWCNT species from plasma torch, laser ablation, electric arc and even large diameter CVD grown SWCNTs. The separation range of the technique thus extends to the isolation of individual species of nanotubes up to at least 1.7 nm in diameter, a dramatic improvement beyond previous SWCNT separation methods. Optical characterization of the refined populations, and analysis of the order of (n,m) extraction with respect to the mechanism underlying the ATPE method will be presented. [Preview Abstract] |
Monday, March 2, 2015 10:24AM - 10:36AM |
A17.00011: Molecular Dynamics Study of Surfactant Self-Assembly on Single-Walled Carbon Nanotubes (SWCNTs) Frederick Phelan Jr. Single-walled carbon nanotubes (SWNCTs) are materials with structural, electronic and optical properties that make them attractive for a myriad of advanced technology applications. Increased adaptation of these materials requires advancement in separation techniques which enables them to be sorted with increased reliability into monodisperse fractions with respect to length and chirality. Most separation techniques currently in use rely on dispersion of tubes in aqueous solution using surfactants. This results in a colloidal mixture in which tubes are packed and individually dispersed in a surfactant shell. Understanding the structure and properties of the SWCNT-surfactant complex at the molecular level, and how this is affected by chirality, will help to improve separations processes. In this work, we study the structure and properties of SWCNT-surfactant colloidal complexes using all-atom molecular dynamics. Self-assembled structures are computed for a number of combinations SWCNT/surfactant, and also, co-surfactant mixtures for the bile salt surfactant sodium deoxycholate (DOC) and the anionic surfactant sodium dodecyl sulfate (SDS). From the radial distribution function we estimate the size of the SWCNT hydration layer, and use that information to compute the buoyant densities of unfilled tubes for a number of concentrations. Estimates of the change in hydrodynamic radius with increased surfactant packing and the binding energies of the individual surfactants are also obtained. [Preview Abstract] |
Monday, March 2, 2015 10:36AM - 10:48AM |
A17.00012: Integration of Nanotubes, Etch Tracks, and Nanoribbons in Crystallographic Alignment Mathias J. Boland, D. Patrick Hunley, Abhishek Sundrarajan, Mohsen Nasseri, Douglas R. Strachan Three nanomaterial components, carbon nanotubes (CNTs), few-layer graphene (FLG), and etch tracks exposing insulating SiO$_{\mathrm{2}}$ regions, are integrated to form crystallographically-aligned nanoscale systems. These integrated systems consist of CNTs grown across nanogap etch tracks and nanoribbons formed within the FLG films as a result of chemical vapor deposition (CVD) processing. Each nanoscale component is aligned along the underlying graphene lattice, resulting in their orientations being locked into precise values, with CNTs maintaining alignment even after crossing etch tracks. The growth of aligned CNTs across nanogap etch tracks and nanoribbons suggests that integrated formations can be achieved by growing CNTs directly over nanogap etch tracks and nanoribbons. This is supported by calculations of the vibrational energy of CNTs indicating that they should be capable of maintaining atomic registry with an underlying graphene lattice as they grow across a typical etch track, in agreement with our experimental results. Thus, this work is relevant to the integration of semiconducting, conducting, and insulating nano-materials all together into precise nano-electronic systems. [Preview Abstract] |
Monday, March 2, 2015 10:48AM - 11:00AM |
A17.00013: High stability of faceted nanotubes and fullerenes of multi-phase layered phosphorus: A computational study Jie Guan, Zhen Zhu, David Tomanek We present a paradigm in constructing very stable, faceted nanotube and fullerene structures by laterally joining nanoribbons or patches of different planar phosphorene phases. Our {\em ab initio} density functional calculations indicate that these phases may form very stable, non-planar joints. Unlike fullerenes and nanotubes obtained by deforming a single-phase planar monolayer at substantial energy penalty, we find faceted fullerenes and nanotubes to be nearly as stable as the planar single-phase monolayers. The resulting rich variety of polymorphs allows to tune the electronic properties of phosphorene nanotubes (PNTs) and fullerenes not only by the chiral index, but also by the combination of different phosphorene phases. In selected PNTs, a metal-insulator transition may be induced by strain or changing the number of walls. [Preview Abstract] |
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