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Zhi-min Dang - One of the best experts on this subject based on the ideXlab platform.

  • dielectric properties of reduced graphene oxide polypropylene composites with ultralow Percolation Threshold
    Polymer, 2013
    Co-Authors: Dongrui Wang, Zhi-min Dang, Xiaoman Zhang, Jun Zhao, Guohua Hu
    Abstract:

    In this paper, we report the preparation and dielectric properties of reduced graphene oxide/polypropylene (rGO/PP) composites with an ultralow Percolation Threshold as low as 0.033 vol%. This value is the lowest among those that have been reported in graphene-filled composites. The rGO/PP composites were prepared through a latex technique, which consists of an in-situ chemical reduction of graphene oxide in PP latex and a subsequent filtration. Scanning electron microscopy and X-ray diffraction measurements demonstrate that the homogeneous dispersion of rGO nanosheets in the PP matrix was realized. A blue shift in Raman G band of the rGO nanosheets was observed in the rGO/PP composites, indicating the strong interaction between the rGO filler and the PP matrix. In the frequency range from 10(2) Hz to 10(7) Hz, the rGO/PP composites showed an insulator-to-conductor Percolation transition as the increase of the rGO loading. Near the Percolation Threshold, the dielectric permittivity of the rGO/PP composites underwent a significant change of three orders of magnitude. Moreover, the permittivity was found to be temperature dependent.

  • influence of aspect ratio of carbon nanotube on Percolation Threshold in ferroelectric polymer nanocomposite
    Applied Physics Letters, 2007
    Co-Authors: Zhi-min Dang, Meijuan Jiang, Haiping Xu
    Abstract:

    Multiwall carbon nanotube (MWNT) with different aspect ratio (AR) was dispersed into ferroelectric polyvinylidene fluoride (PVDF) to fabricate the MWNT/PVDF nanocomposites. An increase of dielectric constant with increasing the AR value was observed in the MWNT/PVDF composites. Meanwhile, the result showed that the change of Percolation Threshold displayed the same rule with that of critical exponent, and both of them increased with increase of AR in some extent, which provides an effective and simple way to describe the dielectric transition of practical composites in the neighborhood of Percolation Threshold with the scaling theory.

  • dielectric behavior of a metal polymer composite with low Percolation Threshold
    Applied Physics Letters, 2006
    Co-Authors: Yunjia Li, Man Xu, Junqiang Feng, Zhi-min Dang
    Abstract:

    Stainless steel fiber (SSF)/poly(vinylidene fluoride) composite is prepared via simple blending and hot pressing route. The dependence of the dielectric properties of the composite on both volume fraction of the fillers and frequency is investigated. The Percolation Threshold of the composite, 9.4vol% (0.094 volume fraction), is much lower than that of the common two phase metal particle-polymer composite. A dielectric constant of 427 is observed at 50Hz with 10vol% of SSF. Large enhancements of the ac conductivity and loss tangent are also observed near the Percolation Threshold. The dielectric properties are explained by Percolation theory while the dielectric anomalies are attributed to the high slenderness ratio of the SSF fillers.

  • Carbon nanotube composites with high dielectric constant at low Percolation Threshold
    Applied Physics Letters, 2005
    Co-Authors: Lan Wang, Zhi-min Dang
    Abstract:

    In this letter, the dielectric properties of the untreated multiwall carbon-nanotubes/poly(vinylidene fluoride) (MWNT/PVDF) composites are studied. Towards low frequencies, the dielectric constant of a composite with about 2.0 vol% of MWNT increases rapidly and the value of the dielectric constant is as high as 300. However, by a calculation, the Percolation Threshold of the MWNT/ PVDF composites is only 1.61 vol% (0.0161 volume fraction) of MWNT. Both the large aspect ratio and the high conductivity of the MWNT may lead to the low Percolation Threshold of the MWNT/PVDF composites. For the Percolation composite, the dielectric loss value is always less than 0.4, irrespective of the frequency. Therefore, the experimental results suggest that the dielectric properties of MWNT/PVDF composites may be improved significantly without the chemical functionalization to carbon nanotubes.

  • dielectric behavior and dependence of Percolation Threshold on the conductivity of fillers in polymer semiconductor composites
    Applied Physics Letters, 2004
    Co-Authors: Zhi-min Dang, Yihe Zhang, S C Tjong
    Abstract:

    Polymer-semiconductor PVDF∕LNO (polyvinylidene fluoride∕Li doped NiO) composites were fabricated via simple blending and hot-molding technique. The dielectric behavior of such composites was studied over broad frequency. The results revealed the dependence of Percolation Threshold on the conductivity of LNO filler in the composites. And the conductivity of the LNO fillers played an important role on the dielectric properties and critical exponents of the PVDF∕LNO composites. High dielectric constants and low conductivities of the composites were observed near the Percolation Threshold. Finally, critical exponents were also used to explain the experimental results, and provided useful information for understanding the resultant dielectric properties.

Jing Li - One of the best experts on this subject based on the ideXlab platform.

  • correlations between Percolation Threshold dispersion state and aspect ratio of carbon nanotubes
    Advanced Functional Materials, 2007
    Co-Authors: Jing Li, Wing Sze Chow, Chi Kai To, Ben Zhong Tang
    Abstract:

    Critical factors that determine the Percolation Threshold of carbon nanotube (CNT)-reinforced polymer nanocomposites are studied. An improved analytical model is developed based on an interparticle distance concept. Two dispersion parameters are introduced in the model to correctly reflect the different dispersion states of CNTs in the matrix—entangled bundles and well-dispersed individual CNTs. CNT–epoxy nanocomposites with different dispersion states are fabricated from the same constituent materials by employing different processing conditions. The corresponding Percolation Thresholds of the nanocomposites vary over a wide range, from 0.1 to greater than 1.0 wt %, and these variations are explained in terms of dispersion parameters and aspect ratios of CNTs. Important factors that control the Percolation Threshold of nanocomposites are identified based on the comparison between modeling data and experimental results.

  • Percolation Threshold of conducting polymer composites containing 3d randomly distributed graphite nanoplatelets
    Composites Science and Technology, 2007
    Co-Authors: Jing Li
    Abstract:

    An improved analytical model is developed based on the average interparticle distance (IPD) concept to predict the Percolation Threshold of conducting polymer composites containing disc-shaped nanoparticles with high aspect ratios. Two different conditions were taken into account in the model in terms of particle distribution, namely two- and three-dimensional random orientations. A 10 nm interparticle distance is adopted as the electrical conducting criterion according to the tunneling mechanism, and the Percolation Threshold is estimated as a function of geometric shape of the nanoparticle. A parametric study suggests that the thickness and diameter of fillers are important factors that determine the Percolation Threshold of conducting nanocomposites. The accuracy and the applicability of the present IPD model are verified by comparing with several existing models and experimental data for graphite nanoplatelet reinforced polymer nanocomposites. It is shown that the current model presents much better agreement with experimental results than existing models.

  • Percolation Threshold of conducting polymer composites containing 3D randomly distributed graphite nanoplatelets
    Composites Science and Technology, 2007
    Co-Authors: Jing Li, Jang-kyo Kim
    Abstract:

    An improved analytical model is developed based on the average interparticle distance (IPD) concept to predict the Percolation Threshold of conducting polymer composites containing disc-shaped nanoparticles with high aspect ratios. Two different conditions were taken into account in the model in terms of particle distribution, namely two- and three-dimensional random orientations. A 10 nm interparticle distance is adopted as the electrical conducting criterion according to the tunneling mechanism, and the Percolation Threshold is estimated as a function of geometric shape of the nanoparticle. A parametric study suggests that the thickness and diameter of fillers are important factors that determine the Percolation Threshold of conducting nanocomposites. The accuracy and the applicability of the present IPD model are verified by comparing with several existing models and experimental data for graphite nanoplatelet reinforced polymer nanocomposites. It is shown that the current model presents much better agreement with experimental results than existing models. ?? 2006 Elsevier Ltd. All rights reserved.

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

  • relationship between electromechanical response and Percolation Threshold in carbon nanotube poly vinylidene fluoride composites
    Carbon, 2013
    Co-Authors: A Ferreira, M. T. Martínez, Alejandro Ansoncasaos, L E Gomezpineda, S Lancerosmendez
    Abstract:

    Abstract This paper reports on the piezoresistive response of carbon nanotube/poly(vinylidene fluoride), CNT/PVDF, composites prepared with different CNT types with and without functionalization, via in situ-generated diazonium compounds. The results show that for a CNT concentration close to the Percolation Threshold, tunneling is the main mechanism responsible for the electrical response, leading also to a significant increase of the piezoresistance of the composites. Interestingly, this fact is independent of the CNT type or functionalization, as well as of the Percolation Threshold concentration. In this way, a close relationship between the Percolation Threshold and the piezoresistive response was demonstrated. The electromechanical response, as characterized by the gauge factor, reach values up to 3.9, being among the largest obtained for thermoplastic composites and demonstrating the suitability of these materials for sensor applications.

  • Relationship between electromechanical response and Percolation Threshold in carbon nanotube/poly(vinylidene fluoride) composites
    Carbon, 2013
    Co-Authors: A Ferreira, M. T. Martínez, A. Ansón-casaos, L. E. Gómez-pineda, Filipe Vaz, Senentxu Lanceros-méndez
    Abstract:

    This paper reports on the piezoresistive response of carbon nanotube/poly(vinylidene fluoride), CNT/PVDF, composites prepared with different CNT types with and without functionalization, via in situ-generated diazonium compounds. The results show that for a CNT concentration close to the Percolation Threshold, tunneling is the main mechanism responsible for the electrical response, leading also to a significant increase of the piezoresistance of the composites. Interestingly, this fact is independent of the CNT type or functionalization, as well as of the Percolation Threshold concentration. In this way, a close relationship between the Percolation Threshold and the piezoresistive response was demonstrated. The electromechanical response, as characterized by the gauge factor, reach values up to 3.9, being among the largest obtained for thermoplastic composites and demonstrating the suitability of these materials for sensor applications. © 2013 Elsevier Ltd. All rights reserved.

O Quadrat - One of the best experts on this subject based on the ideXlab platform.

  • electrical conductivity of carbon fibres polyester resin composites in the Percolation Threshold region
    European Polymer Journal, 2002
    Co-Authors: Jarmila Vilcakova, Petr Saha, O Quadrat
    Abstract:

    Abstract The electrical conductivity of composites of a polyester resin filled with short carbon fibres has been investigated with a special attention to the properties in the Percolation Threshold region. A very low Percolation Threshold (0.7–0.8 vol% of the filler) was confirmed. In contrast to S-shaped curves calculated according to the Percolation theory of composites of globular particles, the experimental conductivity vs. fibre content dependence, after a steep increase in the Percolation region, increased almost linearly. This atypical behaviour was explained by a different mechanism of formation of fibrous and globular conducting structures above the Percolation Threshold. An increase in scatter of conductivity values observed at Percolation Threshold as a consequence of great fluctuation of fibre arrangement manifested itself also in the conductivity–temperature dependences.

  • Electrical conductivity of carbon fibres/polyester resin composites in the Percolation Threshold region
    European Polymer Journal, 2002
    Co-Authors: Jarmila Vilcakova, Petr Saha, O Quadrat
    Abstract:

    Abstract The electrical conductivity of composites of a polyester resin filled with short carbon fibres has been investigated with a special attention to the properties in the Percolation Threshold region. A very low Percolation Threshold (0.7–0.8 vol% of the filler) was confirmed. In contrast to S-shaped curves calculated according to the Percolation theory of composites of globular particles, the experimental conductivity vs. fibre content dependence, after a steep increase in the Percolation region, increased almost linearly. This atypical behaviour was explained by a different mechanism of formation of fibrous and globular conducting structures above the Percolation Threshold. An increase in scatter of conductivity values observed at Percolation Threshold as a consequence of great fluctuation of fibre arrangement manifested itself also in the conductivity–temperature dependences.

S Lancerosmendez - One of the best experts on this subject based on the ideXlab platform.

  • relationship between electromechanical response and Percolation Threshold in carbon nanotube poly vinylidene fluoride composites
    Carbon, 2013
    Co-Authors: A Ferreira, M. T. Martínez, Alejandro Ansoncasaos, L E Gomezpineda, S Lancerosmendez
    Abstract:

    Abstract This paper reports on the piezoresistive response of carbon nanotube/poly(vinylidene fluoride), CNT/PVDF, composites prepared with different CNT types with and without functionalization, via in situ-generated diazonium compounds. The results show that for a CNT concentration close to the Percolation Threshold, tunneling is the main mechanism responsible for the electrical response, leading also to a significant increase of the piezoresistance of the composites. Interestingly, this fact is independent of the CNT type or functionalization, as well as of the Percolation Threshold concentration. In this way, a close relationship between the Percolation Threshold and the piezoresistive response was demonstrated. The electromechanical response, as characterized by the gauge factor, reach values up to 3.9, being among the largest obtained for thermoplastic composites and demonstrating the suitability of these materials for sensor applications.