Search results for "CONDUCTIVITY"
showing 10 items of 1988 documents
Enhanced thermoelectric performance of PEDOT with different counter-ions optimized by chemical reduction
2014
This work reports on the synthesis of the intrinsically conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with several counter-ions, ClO4, PF6 and bis(trifluoromethylsulfonyl)imide (BTFMSI), by electro-polymerization and its thermoelectric properties. We show that, depending on the counter-ion size, the thermoelectric efficiency of PEDOT can be increased up to two orders of magnitude. A further chemical reduction with hydrazine optimizes the power factor (PF). By changing the counter-ions, we were able to increase the electrical conductivity (σ) of PEDOT by a factor of three, while the Seebeck coefficient remains at the same order of magnitude in the three polymers. The best…
Impedance spectroscopy characterization of functionalized alumina membranes
2005
Abstract Anodic alumina membranes have been impregnated with a protonic conductor either by immersion or by vacuum permeation of a saturated aqueous solution of CsHSO4 for different times. Synthetized salt, obtained through the reaction of cesium carbonate with sulphuric acid (in excess), contained a small quantity of Cs2SO4. Unmodified membranes consist of amorphous Al2O3 with a regular distribution of pores (average diameter: 200 nm) and are stable up to 850 °C. Long impregnation times caused partial dissolution of alumina, with formation of Al(HSO4)3 on the front surfaces as well as into pore walls. From the frequency dispersion of the impedance, the “macroscopic conductivity” of membran…
Reversible stimulus-responsive Cu(i) iodide pyridine coordination polymer
2015
We present a structurally flexible copper–iodide–pyridine-based coordination polymer showing drastic variations in its electrical conductivity driven by temperature and sorption of acetic acid molecules. The dramatic effect on the electrical conductivity enables the fabrication of a simple and robust device for gas detection. X-ray diffraction studies and DFT calculations allow the rationalisation of these observations.
Poling Induced Mass Transport in Thin Polymer Films
2013
In this study we report investigation of the polymer film morphology modifications during their corona poling for fabrication of nonlinear optically (NLO) active materials. We demonstrate that at certain poling conditions surface and spatial inhomogeneities in the poled area of the sample appear. Densities of the inhomogeinities depend on the strength of the poling field, the sample temperature during the poling, and the prepoling conditions. Optimization of the poling conditions directed toward avoiding surface modifications enables us to increase the overall observable effective nonlinearity of the sample up to 10 times. To investigate, understand, and eventually explain the formation of …
Equilibrium and transport properties of ion-exchange membranes
1984
Abstract Specific properties (ion-exchange capacity, water content, pore volume fraction) and transport properties (counterion transport number and electrical conductivity) have been measured in four commercial cation-exchange membranes loaded with a variety of cations of different nature and charge. Not surprisingly, equivalent conductances are lower than in free solution and transport numbers decrease with valency of the counterion. This behavior is explained by taking into account a “tortuosity factor”, due to a lengthening of the pores across the membrane, except for a membrane with a lower water content and for ions of higher charge, in which electrostatic interactions between mobile a…
Bio-based rigid high-density polyurethane foams as a structural thermal break material
2020
Abstract Sustainable development of building industry implies increasing usage of green materials. With this aim and for the intended application as a structural thermal break material, rigid high-density polyurethane foams have been manufactured using polyols derived from renewable resources - tall oil fatty acids. Thermal conductivity, compressive strength and stiffness of the foams of density ranging from ca. 100 to 680 kg/m3 have been determined. Comparison of the bio-based foams with reference foams derived from petrochemical resources demonstrated similar performance characteristics thus suggesting that bio-based foams can also serve as structural thermal break materials. Analytical m…
Correlations between Ion Conductivity and Polymer Dynamics in Hyperbranched Poly(ethylene oxide) Electrolytes for Lithium-Ion Batteries
2011
Poly(ethylene oxide)s with varying degrees of hyperbranching are effective at preventing the crystallization of PEO and lead to approximately a 100-fold increase in the Li-ion conductivity below 50 °C as compared with linear PEO. The Li-ion conductivities, which increase further upon permethylation of the hydroxyl termini, are found to correlate quantitatively with the fast segmental dynamics of PEO as measured by inelastic neutron scattering.
Tuning of interfacial charge transport in polyporphine/phthalocyanine heterojunctions by molecular geometry control for an efficient gas sensor
2022
Abstract Owing to high interfacial conductivity, organic heterostructures hold great promises to augment the electrical performances of electronic devices. In this endeavor, the present work reports fabrication of novel polyporphine/phthalocyanine heterostructures and investigates the modulation of charge transport induced by structural change of polyporphine and its implication on ammonia sensing properties. Polyporphines materials are electrosynthesized by oxidation of zinc(II) porphine monomer that corresponds to the fully unsubstituted porphyrin. At less-positive anodic potential, low conducting meso,meso-singly-linked type-1 polymer (pZnP-1) is formed in which a monomer unit stays orth…
Prediction method of electrical conductivity of nano-modified glass fibre reinforced plastics
2019
Glass fibre reinforced plastics (GFRP) is non-conductive construction material, however with carbon nanotubes (CNT) modifying it can get additional functionality due to its gained electrical conductivity. Main aim of the study is to check functionality of the prediction method of electrical conductivity of GFRP with nano-modified epoxy matrix using structural approach. GFRP composites under investigation were based on unidirectional (UD) Glass fiber and two matrixes modified with carbon nanotubes. Electrical conductivity of epoxy resin modified by CNT (concentrations < 1%) was modelled using structural approach. Electrical conductivity of unidirectional GFRP layer was measured experimentall…
Macroscopic persistent currents in YBa2Cu3O7
1988
Persistent currents in polycrystalline YBa2Cu3O7 rings have been investigated by measuring the spatial distribution of the magnetic flux trapped in field-cooled samples. The results unambiguously show that macroscopic persistent ring currents exist. The critical current density depends very sensitively on the sample quality, reachingj c ≈250 A/cm2 at 77 K for our best samples.