The Experts below are selected from a list of 213 Experts worldwide ranked by ideXlab platform

Uttandaraman Sundararaj - One of the best experts on this subject based on the ideXlab platform.

  • copper nanowire polystyrene nanocomposites lower percolation threshold and higher emi shielding
    Composites Part A-applied Science and Manufacturing, 2011
    Co-Authors: Mohammed H Alsaleh, Genaro A Gelves, Uttandaraman Sundararaj
    Abstract:

    Abstract A highly Conductive with exceptional electromagnetic interference (EMI) shielding capabilities copper nanowire (CuNW)/Polystyrene (PS) composite Powder was formulated by solution processing. We used a dilution process where the Conductive Powder was then dry mixed with pure PS Powder to prepare composites with lower CuNW concentration. The composite parts were prepared by compression molding. The electrical percolation threshold of the composite prepared by the dilution process followed by the compression molding was only 0.24 vol.% CuNW. Electron micrographs indicated that the Conductive Powder formed a segregated network within the polymer matrix. The EMI shielding effectiveness (SE) results showed that in the X-band frequency range, a 210 μm film made of PS composite containing 1.3 vol.% CuNW has an EMI SE of 27 dB and PS with 2.1 vol.% CuNW has an EMI SE of 35 dB. For 1.3 vol.% and 2.1 vol.% CuNW composites, contribution of absorption to the overall shielding was ∼54% of the overall EMI SE.

  • Copper nanowire/polystyrene nanocomposites: Lower percolation threshold and higher EMI shielding
    Composites Part A-applied Science and Manufacturing, 2010
    Co-Authors: Mohammed H. Al-saleh, Genaro A Gelves, Uttandaraman Sundararaj
    Abstract:

    Abstract A highly Conductive with exceptional electromagnetic interference (EMI) shielding capabilities copper nanowire (CuNW)/Polystyrene (PS) composite Powder was formulated by solution processing. We used a dilution process where the Conductive Powder was then dry mixed with pure PS Powder to prepare composites with lower CuNW concentration. The composite parts were prepared by compression molding. The electrical percolation threshold of the composite prepared by the dilution process followed by the compression molding was only 0.24 vol.% CuNW. Electron micrographs indicated that the Conductive Powder formed a segregated network within the polymer matrix. The EMI shielding effectiveness (SE) results showed that in the X-band frequency range, a 210 μm film made of PS composite containing 1.3 vol.% CuNW has an EMI SE of 27 dB and PS with 2.1 vol.% CuNW has an EMI SE of 35 dB. For 1.3 vol.% and 2.1 vol.% CuNW composites, contribution of absorption to the overall shielding was ∼54% of the overall EMI SE.

Eugene A. Olevsky - One of the best experts on this subject based on the ideXlab platform.

  • Contribution of Electric Current into Densification Kinetics during Spark Plasma Sintering of Conductive Powder
    Journal of the American Ceramic Society, 2015
    Co-Authors: Elena V Aleksandrova, Aleksandra M. Ilyina, E. G. Grigoryev, Eugene A. Olevsky
    Abstract:

    The shrinkage kinetics of a Conductive material (copper Powder) under spark plasma sinter-forging conditions in the presence and absence of the electric current passing directly through the specimen is investigated from both experimental and theoretical points of view. The experiments on the current-assisted and current-insulated spark plasma sinter-forging are conducted using specially developed spark plasma sintering tooling which has a number of particular features. The tooling enables direct temperature measurement at the free lateral surface of a Powder sample as well as the simultaneous insitu measurement of the radius and height of a porous cylindrical sample during spark plasma sinter-forging, rendering conditions of bi-axial dilatometry. The continuum theory of sintering-based constitutive model of free upsetting (hot forging with free lateral surface) is refined taking into account the obtained experimental data on the current-insulated mode of spark plasma sinter-forging. It is shown that the model framework traditionally utilized for the description of hot deformation of Powder materials is not suitable for the simulation of the considered current-assisted spark plasma sintering modes. Thus, the necessity of the development of new, specific to spark plasma sintering, constitutive models taking into account the direct contributions of electric current into mass transfer, is demonstrated.

Elena V Aleksandrova - One of the best experts on this subject based on the ideXlab platform.

  • Contribution of Electric Current into Densification Kinetics during Spark Plasma Sintering of Conductive Powder
    Journal of the American Ceramic Society, 2015
    Co-Authors: Elena V Aleksandrova, Aleksandra M. Ilyina, E. G. Grigoryev, Eugene A. Olevsky
    Abstract:

    The shrinkage kinetics of a Conductive material (copper Powder) under spark plasma sinter-forging conditions in the presence and absence of the electric current passing directly through the specimen is investigated from both experimental and theoretical points of view. The experiments on the current-assisted and current-insulated spark plasma sinter-forging are conducted using specially developed spark plasma sintering tooling which has a number of particular features. The tooling enables direct temperature measurement at the free lateral surface of a Powder sample as well as the simultaneous insitu measurement of the radius and height of a porous cylindrical sample during spark plasma sinter-forging, rendering conditions of bi-axial dilatometry. The continuum theory of sintering-based constitutive model of free upsetting (hot forging with free lateral surface) is refined taking into account the obtained experimental data on the current-insulated mode of spark plasma sinter-forging. It is shown that the model framework traditionally utilized for the description of hot deformation of Powder materials is not suitable for the simulation of the considered current-assisted spark plasma sintering modes. Thus, the necessity of the development of new, specific to spark plasma sintering, constitutive models taking into account the direct contributions of electric current into mass transfer, is demonstrated.

Ndy N. Ekere - One of the best experts on this subject based on the ideXlab platform.

  • effect of particle size ratio on the conducting percolation threshold of granular Conductive insulating composites
    Journal of Physics D, 2004
    Co-Authors: Da He, Ndy N. Ekere
    Abstract:

    In this paper, we apply Monte Carlo simulation to investigate the Conductive percolation threshold of granular composite of Conductive and insulating Powders with amorphous structure. We focus on the effect of insulating to Conductive particle size ratio λ = di/dc on the conducting percolation threshold pc (the volume fraction of the Conductive Powder). Simulation results show that, for λ = 1, the percolation threshold pc lies between simple cubic and body centred cubic site percolation thresholds, and that as λ increases the percolation threshold decreases. We also use the structural information obtained by the simulation to study the nonlinear current–voltage characteristics of composite with solid volume fraction of Conductive Powder below pc in terms of electron tunnelling for nanoscale Powders, dielectric breakdown for microscale or larger Powders, and pressing induced conduction for non-rigid insulating Powders.

  • Effect of particle size ratio on the conducting percolation threshold of granular Conductive–insulating composites
    Journal of Physics D, 2004
    Co-Authors: Da He, Ndy N. Ekere
    Abstract:

    In this paper, we apply Monte Carlo simulation to investigate the Conductive percolation threshold of granular composite of Conductive and insulating Powders with amorphous structure. We focus on the effect of insulating to Conductive particle size ratio λ = di/dc on the conducting percolation threshold pc (the volume fraction of the Conductive Powder). Simulation results show that, for λ = 1, the percolation threshold pc lies between simple cubic and body centred cubic site percolation thresholds, and that as λ increases the percolation threshold decreases. We also use the structural information obtained by the simulation to study the nonlinear current–voltage characteristics of composite with solid volume fraction of Conductive Powder below pc in terms of electron tunnelling for nanoscale Powders, dielectric breakdown for microscale or larger Powders, and pressing induced conduction for non-rigid insulating Powders.

Michael J Reece - One of the best experts on this subject based on the ideXlab platform.