Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session Z37: Carbon Nanofoams and Composites |
Hide Abstracts |
Sponsoring Units: DCMP Chair: David Tomanek, Michigan State University Room: 705/707 |
Friday, March 7, 2014 11:15AM - 11:27AM |
Z37.00001: ABSTRACT WITHDRAWN |
Friday, March 7, 2014 11:27AM - 11:39AM |
Z37.00002: Dielectric characterization of multi-walled carbon nanotube nanocomposites as a function of ultraviolet exposure at microwave frequency Nathan Orloff, Christian J. Long, Kevin Twedt, Thomas Lam, Jabez McClelland, Jan Obrzut, J. Alexander Liddle We investigate multi-walled carbon nanotube epoxy composites as a function of ultraviolet exposure. As the epoxy is etched away from the composite, we found that the multi-walled carbon nanotubes form a thin conducting layer on the surface. We then characterize the multi-walled carbon nanotube composites by atomic force microscopy, lithium ion microscopy, and microwave cavity perturbation at each value of ultraviolet exposure. We perform our measurements on a set of neat samples made from a stoichiometric mixture bisphenol A epoxy resin and another set that contains a mass fraction of 3.5{\%} multi-walled carbon nanotubes. The samples were then exposed to ultraviolet radiation to etch the surface for different durations of time. At the 7.31 GHz, we measured the permittivity and loss tangent of the unexposed epoxy to be $\varepsilon \quad =$ 2.93$+$/-0.11 and tan$\delta =$ 0.029$+$/-0.002, respectively. The unexposed epoxy with a mass fraction of 3.5{\%} multi-walled carbon nanotubes had a permittivity of $\varepsilon $ $=$ 8.01$+$/-0.48 and loss tangent of tan$\delta =$0.144$+$/-0.011. [Preview Abstract] |
Friday, March 7, 2014 11:39AM - 11:51AM |
Z37.00003: Electric and Magnetic Polarizability Tensors of Carbon Nanotubes and Graphene Sheets with Different Morphologies: A Numerical Study Fernando Vargas-Lara, Jack F. Douglas, Ahmed Hassan, Edward Garboczi The addition of Carbon Nanotubes (CNTs) and Graphene Sheets (GSs) in polymeric melts affects the electromagnetic response of the resulting composites. This effect strongly depends on the shape of the CNTs and GSs. In this study, we explore how the morphology of individual CNTs and GSs immerse on a dielectric material is related to their electromagnetic signature. In the microwave region, the wavelength is much larger than the size of the CNTs or GSs. Hence, their electromagnetic response in the far field is determined by the electric polarizability tensor, the magnetic polarizability tensor, and the dielectric properties of the CNTs. To determine these properties, we first generate CNTs and GSs with different morphology via molecular dynamic simulations of coarse-grained models for CNTs and GSs, whose mechanical properties mimic the ones predicted by atomistic simulations and experiments. We, next compute the electric polarizability tensors of the aforementioned objects using the path integrator ZENO. Considering this information as a reference, we calculated the magnetic polarizability tensor using finite element calculations (low frequency 3D COMSOL simulations). We finally report these properties as well as their connection with other shape descriptors. [Preview Abstract] |
Friday, March 7, 2014 11:51AM - 12:03PM |
Z37.00004: Local curvature and relative stability of graphitic carbon nanostructures Jie Guan, Zhongqi Jin, David Tomanek We propose a way to estimate the relative stability of graphitic nanostructures including fullerenes, nanotubes and schwarzites using continuum elasticity theory. The key quantity is the local deformation energy with respect to graphene, which we determine by estimating the two principal radii of curvature at each lattice site using the Bertrand-Diquet-Puiseux theorem. We find an impressive level of agreement between strain energies based on local curvature and {\em ab initio} density functional calculations. We demonstrate that our approach correctly determines strain energy differences between nanotubes with different chiral indices (n,m) and zero Gaussian curvature, C$_n$ fullerenes with $20{\le}n{\le}72$ atoms and positive Gaussian curvature, and selected schwarzites with negative Gaussian curvature. In contrast to other methods, our approach correctly determines even the energy differences between different isomers of fullerenes such as C$_{28}$, C$_{36}$ and C$_{38}$. [Preview Abstract] |
Friday, March 7, 2014 12:03PM - 12:15PM |
Z37.00005: Static and dynamic response of bucky sponges Theyaraman Ramathasan, Mehmet Karakaya, Ramakrishna Podila, Chiara Daraio, Apparao Rao Here we present the static and dynamic mechanical behavior of a three dimensional, interconnected, carbon nanotube (CNT) based, spongy material termed the bucky sponge. We adopted a facile top-down synthesis approach by judiciously mixing carbon micro-fibers with CNTs to create bucky sponges with controlled porosity and density. Static and dynamic tests were performed using a customized setup based on geometric Moir\'{e} interferometry and high-speed microscopic imaging. In both quasi-static and dynamic experiments, the bucky sponges exhibited highly nonlinear foam-like stress-strain response with hysteretic dissipation. The energy dissipated at 80{\%} compressive strain is in the order of 500 kJ/m$^{\mathrm{3}}$, which is nearly 25 times more than the energy dissipated by commercial foams with similar densities. Dynamic unloading modulus of bucky sponges varies between 25-250 MPa depending on the maximum strain attained and they show exceptional resilience to impact by recovering more than 70{\%} of the deformation. Bucky sponges with tailored microstructure and mechanical properties have the potential to be used in applications requiring impact mitigation, vibration damping, and separating oil from water. [Preview Abstract] |
Friday, March 7, 2014 12:15PM - 12:27PM |
Z37.00006: Impact response of helically coiled carbon nanotube foams Chiara Daraio, Mehmet Karakaya, Ramakrishna Podila, Thevaraman Ramathasan, Apparao Rao We examined the dynamic response of helically coiled carbon nanotube (HCCNT) foams (K. Yang et al., \textit{Advanced Materials}~\textbf{20}, 179 (2008)) in an impact testing set up developed in our laboratory, which is based on geometric Moir\'{e} interferometry and high-speed microscopic imaging. Dynamic force and displacement histories were measured during the impact, from which the dynamic constitutive response was obtained. HCCNT foams exhibit nonlinear foam-like dynamic stress-strain response with an exceptional ability to mitigate impact forces and dissipate energy through hysteresis. The time-resolved image sequences obtained using high-speed microscopic imaging showed a progressive deformation in a preferred direction along the thickness of the foam during the impact. We attribute this finding to the inherent density gradient introduced in the foams during the chemical vapor deposition process. Due to their energy dissipative and cushioning characteristics, HCCNT foams can find potential use in impact mitigation, packaging and vibration damping applications. [Preview Abstract] |
Friday, March 7, 2014 12:27PM - 12:39PM |
Z37.00007: Energetics of Boron Doping of Carbon Pores Carlos Wexler, Alexander St. John, Matthew Connolly Carbon-based materials show promise, given their light weight, large surface areas and low cost for storage of hydrogen and other gases, e.g., for energy applications. Alas, the interaction of H2 and carbon, 4-5kJ/mol, is insufficient for room-temperature operation. Boron doping of carbon materials could raise the binding energy of H2 to 12-15kJ/mol. The nature of the incorporation of boron into a carbon structure has not been studied so far. In this talk we will address the energetics of boron incorporation into a carbon matrix via adsorption and decomposition of decaborane by first principles calculations. These demonstrate: (a) A strong adsorption of decaborane to carbon (70-80kJ/mol) resulting in easy incorporation of decaborane, sufficient for up to 10-20\% B:C at low decaborane vapour pressures. (b) Identification that boron acts as an electron acceptor when incorporated substitutionally into a graphene-like material, as expected due to its valence. (c) The electrostatic field near the molecule is responsible for ca. 2/3 of the enhancement of the H2-adsorbent interaction in aromatic compounds such as pyrene, coronene and ovalene. [Preview Abstract] |
Friday, March 7, 2014 12:39PM - 12:51PM |
Z37.00008: {\em Ab initio} study of novel carbon nanofoam structure as an anode material for Li secondary battery Hanjin Park, Sora Park, Seoung-Hun Kang, Young-Kyun Kwon Using ab inito density functional theory, we investigate the adsorption and diffusion properties of Li atoms on a new carbon nanostructure, which may be used as an anode of Li secondary battery. We focus on a special carbon nanofoam structure consisting of Schwarzite structures with negative Gaussian curvature as core parts, which are interconnected through (4,4) CNT segments. Considering the symmetry of the nanofoam structure, we find various Li adsorption sites exhibiting relatively large binding energies (${\agt}2.00$~eV). Based on these adsorption sites, we identify several diffusion paths on the outside or inside surface of the nanofoam structure and examine the diffusion barriers along the paths. Our results show that Li atom can diffuse almost freely due to its low energy barriers on both outside and inside surfaces. Finally, we also evaluate the energy gain tendency and the volume expansion as well as the average binding energy while adding Li atoms to estimate the Li-capacity and recyclability of the system, which are important characterisitics for anode materials. We conclude that the carbon nanofoam structure would be better as an anode material than graphite in Li capacity and volume expansion. [Preview Abstract] |
Friday, March 7, 2014 12:51PM - 1:03PM |
Z37.00009: Unusual conduction mechanism at graphitic carbon foam surfaces: An \textit{ab initio} study David Tomanek, Zhen Zhu, Zacharias G. Fthenakis, Jie Guan Using {\em ab initio} electronic structure and quantum conductance calculations, we identify an unusual conduction mechanism at the surface of a previously described graphitic carbon foam structure. The emergence of a new, topologically protected conduction band in this semiconducting system is intimately linked to the topology of the foam. In contrast to conduction bands of graphitic structures, which are related to nearest-neighbor interactions between $p_\perp$ orbitals normal to the surface, the new band responsible for metallic behavior derives from interactions between $p_\|$ orbitals lying in the surface plane. The conducting surface state occurs on bare and hydrogen-terminated surfaces and is thus unrelated to dangling bonds. We find that the conductance behavior can be further significantly modified by surface patterning. [Preview Abstract] |
Friday, March 7, 2014 1:03PM - 1:15PM |
Z37.00010: Thermal conductivity of one-, two- and three-dimensional sp2 carbon Luiz Felipe Pereira, Ivana Savic, Davide Donadio Carbon atoms can form structures in one, two and three dimensions due to their unique chemical versatility. In terms of thermal conductivity, carbon polymorphs cover a wide range from very low values with amorphous carbon to very high values with diamond, carbon nanotubes and graphene. Schwarzites are a class of three-dimensional fully covalent sp2-bonded carbon polymorphs, with the same local chemical environment as graphene and carbon nanotubes, but negative Gaussian curvature. We calculate the thermal conductivity of a (10,0) carbon nanotube, graphene and two schwarzites with different curvature, by molecular dynamics simulations based on the Tersoff empirical potential. We find that schwarzites present a thermal conductivity two orders of magnitude smaller than nanotubes and graphene. The reason for such large difference is explained by anharmonic lattice dynamics calculations, which show that phonon group velocities and mean free paths are much smaller in schwarzites than in nanotubes and graphene. Their reduced thermal conductivity, in addition to tunable electronic properties, indicate that schwarzites could pave the way towards all-carbon thermoelectric technology with high conversion efficiency. [Preview Abstract] |
Friday, March 7, 2014 1:15PM - 1:27PM |
Z37.00011: Adsorption-induced breathing in nanoporous carbon Matthew Connolly, Carlos Wexler In most adsorption studies it is assumed that the adsorbent conformation is not changed by the adsorption; this assumption underlies most conceptual and theoretical framework used for characterization of porous materials and of adsorption in general. Recently, the behavior of the solid has come under review: when a gas enters pores with sizes comparable with the range of the van der Walls forces an excess pressure or tension exists. Here we present a theoretical, computational and experimental demonstration of breathing (expansion) of graphene-like adsorbents (graphene oxide frameworks, GOFs): Molecular dynamics simulations show the potential for supercritical hydrogen to open new pores in carbons. Grand Canonical Monte Carlo perturbative calculations demonstrate a reduction of the free energy of strip-shaped pores with gas loading upon a conformational change that increases the net size of micropores. Experimentally, reversible pore expansion during adsorption was measured by x-ray scattering for GOFs. These breathing modes have significant consequences for medium- to high-pressure adsorption, with modified adsorption isotherms that may require re-interpretation of standard models. [Preview Abstract] |
Friday, March 7, 2014 1:27PM - 1:39PM |
Z37.00012: Strain effect on electronic properties of low-dimensional $\gamma$-graphyne : first principles study Hyeonsu Lee, Seoung-Hun Kang, Sora Park, Chang-Sun Lee, Young-Kyun Kwon Using first-principles calculations, we study the interplay between structural and electronic properties of $\gamma$-graphyne nanotubes ($\gamma$GNTs) consisting of hexagonal carbon rings and acetylenic linkages. We first identify the equilibrium structures of various $\gamma$GNTs classified in terms of chirality: $(n,0)$ denotes an armchair-type tube, whereas $(n,n)$ does a zigzag-type, in contrast with CNTs. Then their Young's moduli are calcuated to be a few hundreds in GPa, which are smaller than those of CNTs. We verify that all $\gamma$GNTs are intrinsic semicondutors with energy gap ($\alt 1.22$ eV) decreasing with tube diameter. It is, however, found that axial strain can significantly modifies the electronic structures of semiconducting $\gamma$GNTs. Very intriguingly, even semiconductor-metal transition occurs under compressive strain: all armchair $\gamma$GNTs, exept for (3,0) $\gamma$GNT with small diameter, become metallic, while only some types of zigzag $\gamma$GNTs metallic under compression. To explain the origin of such electronic structure modifications, we examine the effect of structural change on the band structures of two-dimensional $\gamma$-graphyne sheet under strains and match them with the band structure of $\gamma$GNTs using the zone-folding scheme. [Preview Abstract] |
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