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DC Conductivity (dc + conductivity)

Distribution by Scientific Domains
Polymers and Materials Science66%
Physics and Astronomy33%

Selected Abstracts

Effect of Multiwall Carbon Nanotubes on Electrical and Dielectric Properties of Yttria-Stabilized Zirconia Ceramic

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2006
Sui-Lin Shi
MWCNT/3Y-TZP (3 mol% yttria-stabilized tetragonal polycrystalline zirconia) composites with different multiwall carbon nanotube (MWCNT) contents were prepared by the spark plasma sintering technique. The effect of MWCNT addition on the electrical and dielectric properties of the composites at room temperature was studied. The experimental results showed that the DC conductivity of the composites demonstrated a typical percolation behavior with a very low percolation threshold between 1.0 and 2.0 wt% MWCNT content, and the dielectric constant was greatly increased when the MWCNT concentration was close to the percolation threshold, which was attributed to dielectric relaxation, the space charge polarization effect, and the percolation effect. [source]

Glass Transition Temperature Depression at the Percolation Threshold in Carbon Nanotube,Epoxy Resin and Polypyrrole,Epoxy Resin Composites

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2005
Sophie Barrau
Abstract Summary: The glass transition temperatures of conducting composites, obtained by blending carbon nanotubes (CNTs) or polypyrrole (PPy) particles with epoxy resin, were investigated by using both differential scanning calorimetry (DSC) and dynamical mechanical thermal analysis (DMTA). For both composites, dc and ac conductivity measurements revealed an electrical percolation threshold at which the glass transition temperature and mechanical modulus of the composites pass through a minimum. DC conductivity, ,dc, as a function of the conducting filler concentration of the CNT, (,) and PPy, (,) epoxy resin composites. [source]

Optically driven Mott-Hubbard systems out of thermodynamic equilibrium

ANNALEN DER PHYSIK, Issue 12 2009
A. Lubatsch
Abstract We consider the Hubbard model at half filling, driven by an external, stationary laser field. This stationary, but periodic in time, electromagnetic field couples to the charge current, i.e. it induces an extra contribution to the hopping amplitude in the Hubbard Hamiltonian (photo-induced hopping). We generalize the dynamical mean-field theory (DMFT) for nonequilibrium with periodic-in-time external fields, using a Floquet mode representation and the Keldysh formalism. We calculate the non-equilibrium electron distribution function, the density of states and the optical DC conductivity in the presence of the external laser field for laser frequencies above and below the Mott-Hubbard gap. The results demonstrate that the system exhibits an insulator-metal transition as the frequency of the external field is increased and exceeds the Mott-Hubbard gap. This corresponds to photo-induced excitations into the upper Hubbard band. [source]

Dielectric Relaxation in CaO,Bi2O3,B2O3 Glasses

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2010
Koushik Majhi
Glasses in the system CaO,Bi2O3,B2O3 (in molar ratio) have been prepared using melt-quenching route. Ion transport characteristics were investigated for this glass using electric modulus, ac conductivity and impedance measurements. The ac conductivity was rationalized using Almond,West power law. Dielectric relaxation has been analyzed based on the behavior of electric modulus behavior. The activation energy associated with the electrical relaxation determined from the electric modulus spectra was found to be 1.76 eV, close to that the activation energy for dc conductivity (1.71 eV) indicating that the same species took part in both the processes. The stretched exponent , (0.5,0.6) is invariant with temperature for the present glasses. [source]

Homes relation in the attractive Hubbard model in d = ,

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2006
M. Bak
Abstract Lack of the recognized theory of high-temperature superconductivity (HTS) has led to an intense experimental and theoretical search for some universal relationships, which might unravel the physics behind the HTS. One of the most known is so called Uemura relation, ,s(0) , Tc, where ,s is superfluid density and Tc is the superconducting transition temperature. Recently Homes et al. [Nature 430, 539 (2004)] reported a new universal scaling relation, ,s , ,dc(Tc) · Tc, where ,dc(T ) is dc conductivity. In the present paper Homes relation is investigated theoretically in the limit of infinite dimensions in the second order perturbation theory. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Electromagnetic interference shielding by using conductive polypyrrole and metal compound coated on fabrics

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 8 2002
C. Y. Lee
Abstract Electromagnetic interference (EMI) shielding materials of complex type of conductive polypyrrole (PPy) as an intrinsically conducting polymer and silver-palladium (AgPd) metal compound coated on woven or non-woven fabrics are synthesized. From dc conductivity and SEM photographs of PPy/fabric complexes, we discuss charge transport mechanism and the homogeneity of coating on the fabrics. The EMI shielding efficiency of PPy/fabric and AgPd/fabric complexes is in the range of 8,,,80 dB depending on the conductivity and the additional Ag vacuum evaporation. The highest EMI shielding efficiency of PPy/fabric complexes vacuum-evaporated by Ag is ,80 dB, indicating potential materials for military uses. We propose that PPy/fabrics are excellent RF and microwave absorber because of the relatively high absorbance and low reflectance of the materials. Copyright © 2002 John Wiley & Sons, Ltd. [source]