Electrical properties of composites in the vicinity of the percolation threshold

Foulger, Stephen H.

doi:10.1002/(sici)1097-4628(19990620)72:12<1573::aid-app10>3.0.co;2-6

Cited by 157 publications

(77 citation statements)

References 27 publications

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“…The cause for decreasing electronic conductivity with increasing RH is also understood as a consequence of water uptake; as the sample absorbs more water it swells, which weakens the electrical connections among carbon black particles within the percolated carbon black network. 38 Similar effects are seen by mechanically stretching composite materials containing carbon black, or by absorbing gases into composite films of carbon black and various soft hydrophobic polymers such as rubber (e.g. the "electronic nose").…”

Section: Resultsmentioning

confidence: 99%

“…This behavior is as expected for samples in which electronic conduction occurs along a percolated network, at a composition close to the percolation threshold. 38,40,41 Close inspection of the data for samples at 10 and 20 weigh percent carbon reveals that, for the same carbon content, electronic conduction is consistently lower for samples made from Nafion than for samples made from PVDF. There could be many reasons for this difference including differing degrees of carbon aggregation in the samples, and differences in polymer coating of individual carbon black particles for the two polymers.…”

Section: Resultsmentioning

confidence: 99%

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Quantifying Electronic and Ionic Conductivity Contributions in Carbon/Polyelectrolyte Composite Thin Films

Shetzline

Creager

2014

J. Electrochem. Soc.

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A method for independently obtaining electronic and ionic contributions to electrical conductivity in thin-film samples comprised of carbon black (CB) mixed with polymer electrolyte is reported. The method relies upon careful control of the nature of the contact between the sample and the current-carrying electrodes. Electronic conductivities are derived from currents obtained using electronically-conductive glassy carbon electrodes to contact the sample, whereas ionic conductivities are derived from currents obtained using ionically-conductive Nafion electrodes to contact the sample. Conditions under which the measured currents are free from interference from redox reactions at the electrodes and capacitive charging at electrode-electrolyte interfaces are discussed. Electrical conduction was studied in a series of composite carbon black/polymer samples under conditions of fixed temperature and variable relative humidity (RH). For samples containing 10-20 weight percent carbon black dispersed in Nafion, electronic conductivity was higher than ionic conductivity at all RH values tested (25-100% RH). Ionic conductivity increased with increasing RH in a manner consistent with expectation from prior studies on Nafion membranes, whereas electronic conductivity decreased with increasing RH due to water swelling and weakened electrical contacts among carbon particles in the network. Electrical conduction in materials may arise from motion in an electric field of electrons, ions, or both. For many materials the charge carrier identity is implicit; e.g. for metals and semimetals such as carbon, charge is understood to be carried by mobile electrons, whereas for electrolyte materials such as salts dissolved in solvents and most polymer electrolytes, charge is understood to be carried by mobile ions.1,2 Some materials have the very interesting property that they may transport charge via both ions and electrons; such materials are referred to as mixed ionic electronic conductors (MIECs).3-5 MIEC materials are critically important in many electrochemical technologies, for example in battery electrodes, 6-13 fuel-cell electrodes, [14][15][16] and in certain types of membrane reactor. 17-20A simple measurement of electrical resistance/conductance on a bulk sample, for example from the current obtained upon application of a potential difference between two points on the sample using current-carrying electrodes, can provide values for resistivity/conductivity but it does not provide information on the nature of the charge carrier(s). Four-point-probe (e.g. van der Pauw) measurements are useful for eliminating the influence of contact resistance at the current-carrying electrodes on the measured resistance but such measurements still do not distinguish whether charge is carried by electrons, ions, or both. For some special situations, e.g. doped semiconductors, information about charge-carrier identity may be obtained from the behavior of the sample in response to an external perturbation. For example, in the case of Hall-effect ...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Quantifying Electronic and Ionic Conductivity Contributions in Carbon/Polyelectrolyte Composite Thin Films

Shetzline

Creager

2014

J. Electrochem. Soc.

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“…At the same particle content, smaller particle size leads to lower interparticle distance and more chances for the formation of thermal conductive 'pathway' [21][22][23]. The particle size and content affect the interparticle distance and the stress state of the matrix polymer surrounding the voids.…”

Section: F S Wangmentioning

confidence: 99%

The effects of particle size and content on the thermal conductivity and mechanical properties of Al2O3/high density polyethylene (HDPE) composites

Zhang¹,

Cao²,

M.³

et al. 2011

Express Polym. Lett.

177

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Abstract. The influences of filler size and content on the properties (thermal conductivity, impact strength and tensile strength) of Al 2 O 3 /high density polyethylene (HDPE) composites are studied. Thermal conductivity and tensile strength of the composites increase with the decrease of particle size. The dependence of impact strength on the particle size is more complicated. The SEM micrographs of the fracture surface show that Al 2 O 3 with small particle size is generally more efficient for the enhancement of the impact strength, while the 100 nm particles prone to aggregation due to their high surface energy deteriorate the impact strength. Composite filled with Al 2 O 3 of 0.5 µm at content of 25 vol% show the best synthetic properties. It is suggested that the addition of nano-Al 2 O 3 to HDPE would lead to good performance once suitably dispersed.

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“…This critical value is known as the percolation threshold. In addition, close to the percolation threshold, the electrical properties show a nonlinear (critical) behaviour characterized by small variations in the physical parameters, such as temperature, composition or voltage, result in large variations of electrical properties [69].The percolation threshold for the electrical conductivity in polymer/CNTs nanocomposites shows the complex dependence on a variety of factors, including nanotube characteristics (aspect ratio, single-or multi-wall), and fabrication/processing conditions, which affect the filler's distribution and orientation and the filler-matrix interactions [70]. Figures 10 and 11 show the alternating current conductivity, at room temperature, as a function of frequency and the conductivity measured at 0.1 Hz respectively, for PTT nanocomposites with different MWCNTs content.…”

Section: Electrical Propertiesmentioning

confidence: 99%

Preparation and characterization of nanocomposites based on COOH functionalized multi-walled carbon nanotubes and on poly(trimethylene terephthalate)

Szymczyk¹,

Rosłaniec²,

Zenker³

et al. 2011

Express Polym. Lett.

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Poly(trimethylene terephthalate) nanocomposites containing COOH functionalized multi-walled nanotubes were synthesized with in situ polymerization method. The microstructure of the nanocomposites was studied by SEM, in terms of the dispersion state of the nanotubes and the polymer–nanotube interface. The thermal behaviour, mechanical properties and conductivity of these resultant PTT/MWCNTs nanocomposites were studied. The effect of the presence of MWCNTs on cold crystallization of PTT was monitored by dielectric spectroscopy. From thermal analysis study, it is found that the melting temperature and glass transition temperature are not significantly affected by the addition of MWCNTs. The crystallization temperature of PTT matrix is affected by the presence of CNTs. Nanocomposites have slightly higher degree of crystallinity than neat PTT and their thermo-oxidative stability is not significantly affected by the addition of MWCNTs. The study of the isothermal cold crystallization of amorphous PTT and its nanocomposites monitored by dielectric spectroscopy reveals that the presence of MWCNTs have influence on crystallization rate, especially at higher concentration (0.3 wt%). In comparison with neat PTT, the MWCNTs reinforced nanocomposites posses higher tensile strength and Young’s modulus at low MWCNTs loading (0.05–0.3 wt%). In addition, all nanocomposites show reduction of brittleness as compared to the neat PTT. The electrical percolation threshold was found between 0.3 and 0.4 wt% loading of MWCNTs

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Electrical properties of composites in the vicinity of the percolation threshold

Cited by 157 publications

References 27 publications

Quantifying Electronic and Ionic Conductivity Contributions in Carbon/Polyelectrolyte Composite Thin Films

Quantifying Electronic and Ionic Conductivity Contributions in Carbon/Polyelectrolyte Composite Thin Films

The effects of particle size and content on the thermal conductivity and mechanical properties of Al2O3/high density polyethylene (HDPE) composites

Preparation and characterization of nanocomposites based on COOH functionalized multi-walled carbon nanotubes and on poly(trimethylene terephthalate)

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