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W N Roy - One of the best experts on this subject based on the ideXlab platform.

  • computational analysis of the lattice Contribution to thermal Conductivity of single walled carbon nanotubes
    Journal of Materials Science, 2005
    Co-Authors: M Grujicic, Guoxin Cao, W N Roy
    Abstract:

    Molecular dynamics based heat-flux auto-correlation functions are combined with a Green-Kubo relation from the linear response theory to quantify the lattice Contribution to thermal Conductivity of single-walled carbon nanotubes with three different chiralities (screw symmetries). The interactions between carbon atoms within a nanotube are analyzed using the Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential. The results obtained show that, due to a long-term exponential-decay character of the heat-flux auto-correlation functions, converging values of the lattice thermal conductivities can be obtained using computational cells considerably smaller than the phonon mean free path. However, to obtain accurate values of the thermal Conductivity, a spectral Green-Kubo relation and a phonon-based extrapolation function are found to be instrumental for quantifying the thermal Conductivity Contribution of the long-wavelength phonons not allowed in the computational cells of a finite size. The results further show that chirality of the carbon nanotubes can affect the lattice Contribution to the thermal Conductivity by as much as 20%. Also, the simulation results of the effect of temperature on the thermal Conductivity clearly show a competition between an increase in the number of phonons and an increased probability for phonon scattering at higher temperatures.

Jani Kotakoski - One of the best experts on this subject based on the ideXlab platform.

  • Enhanced Tunneling in a Hybrid of Single-Walled Carbon Nanotubes and Graphene
    ACS nano, 2019
    Co-Authors: Yongping Liao, Kimmo Mustonen, Semir Tulić, Viera Skakalova, Sabbir A. Khan, Patrik Laiho, Qiang Zhang, Mohammad Reza Ahmadpour Monazam, Jani Kotakoski
    Abstract:

    Transparent and conductive films (TCFs) are of great technological importance. Their high transmittance, electrical Conductivity, and mechanical strength make single-walled carbon nanotubes (SWCNTs) a good candidate for the raw material for TCFs. Despite the ballistic transport in individual SWCNTs, electrical Conductivity of SWCNT networks is limited by low efficiency of charge tunneling between the tube elements. Here, we demonstrate that the nanotube network sheet resistance at high optical transmittance is decreased by more than 50% when fabricated on graphene. This is a comparable improvement as that obtained through gold chloride (AuCl3) doping. However, while Raman spectroscopy reveals substantial changes in spectral features of AuCl3 doped nanotubes, this does not occur with graphene. Instead, temperature-dependent transport measurements indicate that a graphene substrate reduces the tunneling barrier heights, while its parallel Conductivity Contribution is almost negligible. Finally, we show that...

M Grujicic - One of the best experts on this subject based on the ideXlab platform.

  • computational analysis of the lattice Contribution to thermal Conductivity of single walled carbon nanotubes
    Journal of Materials Science, 2005
    Co-Authors: M Grujicic, Guoxin Cao, W N Roy
    Abstract:

    Molecular dynamics based heat-flux auto-correlation functions are combined with a Green-Kubo relation from the linear response theory to quantify the lattice Contribution to thermal Conductivity of single-walled carbon nanotubes with three different chiralities (screw symmetries). The interactions between carbon atoms within a nanotube are analyzed using the Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential. The results obtained show that, due to a long-term exponential-decay character of the heat-flux auto-correlation functions, converging values of the lattice thermal conductivities can be obtained using computational cells considerably smaller than the phonon mean free path. However, to obtain accurate values of the thermal Conductivity, a spectral Green-Kubo relation and a phonon-based extrapolation function are found to be instrumental for quantifying the thermal Conductivity Contribution of the long-wavelength phonons not allowed in the computational cells of a finite size. The results further show that chirality of the carbon nanotubes can affect the lattice Contribution to the thermal Conductivity by as much as 20%. Also, the simulation results of the effect of temperature on the thermal Conductivity clearly show a competition between an increase in the number of phonons and an increased probability for phonon scattering at higher temperatures.

Yongping Liao - One of the best experts on this subject based on the ideXlab platform.

  • Enhanced Tunneling in a Hybrid of Single-Walled Carbon Nanotubes and Graphene
    ACS nano, 2019
    Co-Authors: Yongping Liao, Kimmo Mustonen, Semir Tulić, Viera Skakalova, Sabbir A. Khan, Patrik Laiho, Qiang Zhang, Mohammad Reza Ahmadpour Monazam, Jani Kotakoski
    Abstract:

    Transparent and conductive films (TCFs) are of great technological importance. Their high transmittance, electrical Conductivity, and mechanical strength make single-walled carbon nanotubes (SWCNTs) a good candidate for the raw material for TCFs. Despite the ballistic transport in individual SWCNTs, electrical Conductivity of SWCNT networks is limited by low efficiency of charge tunneling between the tube elements. Here, we demonstrate that the nanotube network sheet resistance at high optical transmittance is decreased by more than 50% when fabricated on graphene. This is a comparable improvement as that obtained through gold chloride (AuCl3) doping. However, while Raman spectroscopy reveals substantial changes in spectral features of AuCl3 doped nanotubes, this does not occur with graphene. Instead, temperature-dependent transport measurements indicate that a graphene substrate reduces the tunneling barrier heights, while its parallel Conductivity Contribution is almost negligible. Finally, we show that...

Igor Sevostianov - One of the best experts on this subject based on the ideXlab platform.

  • The effect of waviness of a helical inhomogeneity on its stiffness- and Conductivity Contribution tensors
    International Journal of Engineering Science, 2017
    Co-Authors: Anton Trofimov, Igor Sevostianov
    Abstract:

    Abstract The paper provides computational results for the stiffness- and Conductivity Contribution tensors of a helical carbon inhomogeneity embedded in an epoxy matrix. We analyze the effect of waviness of the fiber in a broad range of its variation. It is shown, in particular, that dependence of the components N 1111 and N 2222 of the stiffness Contribution tensor on the waviness parameter is almost the same as the one for the components K 11 and K 22 of the Conductivity Contribution tensor, respectively, implying certain cross-property connection. In contrast, the waviness- dependence of the components N 1122 and N 1212 is entirely different and is non-monotonic.

  • dipole moments property Contribution tensors and effective Conductivity of anisotropic particulate composites
    International Journal of Engineering Science, 2014
    Co-Authors: V I Kushch, Igor Sevostianov
    Abstract:

    The paper addresses the homogenization problem for a particulate composite with anisotropic constituents. Its specific goal is to bridge the gap between two different approaches to the problem of homogenization focusing on the anisotropic materials and to identify and discuss the key microstructural parameters affecting overall Conductivity of heterogeneous materials. The basic concepts of the homogenization theory including a consistent way of introducing the macroscopic field parameters are discussed and clarified. The exact explicit relations have been obtained between the dipole moments, property Contribution tensors and effective Conductivity of composite with phase anisotropy of the general type. A detailed comparison of the analytical expressions for the dipole moments obtained by the multipole expansion method and the independently derived expressions for the Conductivity Contribution tensors has been made between and their equivalence is shown for the matrix type composites with transversely isotropic constituents and spheroidal inhomogeneities. The numerical examples illustrate effect on the overall Conductivity of particulate composite of the properties of constituents, shape, volume content, spatial arrangement and orientation of particles.