Search results for "conductivity"

High performance PA6/CNTs nanohybrid fibers prepared in the melt

2012

Commercial and home-made carbon nanotubes (CNTs) were plasma treated under oxygen atmosphere and then added to polyamide 6 (PA6) in order to prepare fibres by melt spinning. For comparison, pristine nanofillers were used too. The effect of functionalization and of filler characteristics on the morphological, rheological, mechanical and electrical properties of the fibres was studied by TEM and SEM, rheological measurements, tensile and electrical conductivity tests. The results demonstrated that the functionalization led to a better mechanical performance and the morphological analysis confirmed that the adhesion, the dispersion and the alignment of the nanotubes within the polymer matrix w…

Theory of nucleation and crystal growth of polymers in concentrated solutions

1974

ABSTRACT The process of crystallization in concentrated solutions depends strongly on the rate of crystallization and the rate of long range diffusion of the polymer chains. If the crystallization proceeds slowly compared to diffusion, this type of crystal nucleus will be formed for which the free energy of nucleation is smallest. By taking into account entropy effects which are characteristic for chain molecules one can show that the crystal with smallest free energy of nucleation is a crystal with almost regular chain folds on the surfaces. The influence of supercooling, concentration and molecular weight on the thickness and growth rate of such crystals is discussed. If the crystallizati…

FT-IR investigation of the state of iron (III) chloride clusters confined in AOT reverse micelles dispersed in carbon tetrachloride

2007

The state of the water-soluble salt iron(III) chloride in AOT reverse micelles dispersed in carbon tetrachloride has been investigated by FT-IR spectroscopy. Interestingly, while the entrapment of a lot of water-soluble inorganic salts in AOT reverse micelles requires preliminarily the presence of significant amounts of water within the micellar core, solubilization of FeCl3 occurs without the need to add water in the micellar solution reaching the very high solubility value, expressed as the maximum salt-to-surfactant molar ratio, of 1.30. The analysis of the spectral features of the investigated samples leads to hypothesize that iron(III) chloride is confined within the reverse micellar c…

MMX Chains and Molecular Species Containing Rh 2 n+ ( n = 4, 5, and 6) Units: Electrical Conductivity in Crystal Phase of MMX Polymers

2010

The control of the experimental conditions in the reaction of Rh 2 (O 2 CCH 3 ) 4 with halides allows the isolation of the novel dirhodium complexes K x [Rh 2 X(O 2 CCH 3 ) 4 ] x ·4xH 2 O (X = Br, 1·4H 2 O and I, 2·4H 2 O) [Rh 2 (O 2 CCH 3 ) 4 Cl] x H 2 O (3·H 2 O), [Rh 2 (O 2 CCH 3 )Cl] x ·4xH 2 O (3·4H 2 O), and {Rh 2 (O 2 CCH 3 ) 4 I 2 ]· 4H 2 0 (4·4H 2 O) containing Rh 2 n+ (n = 4, 5 and 6) units. The X-ray structure determination of compounds 1-4 reveals the presence of dirhodium units in different oxidation states. The polyanionic complexes 1·4H 2 O and 2·4H 2 O containing Rh 2 4+ units give zig-zag chains. In contrast, the partially oxidized complexes 3·H 2 O and 3·4H 2 O containing …

Variability of near-surface saturated hydraulic conductivity for the clay soils of a small Sicilian basin

2019

Abstract Proper characterization of saturated hydraulic conductivity, Ks, of clay soils in a hillslope or a basin is still a challenge for soil science. In this investigation, the clay soils of the Maganoce (Sicily, Italy) basin were sampled at 19 sampling sites by the BEST procedure of soil hydraulic characterization. More OM implied less compact conditions (decreasing dry soil bulk density; coefficient of determination, R2 = 0.67), more stability to water of the soil aggregates (increasing water stable aggregates; R2 = 0.83) and, consequently, higher Ks values (R2 = 0.54). Variability of Ks was lower in the steeper zones of the basin than in the flatter ones. A comparison with the Ks data…

Effective conductivity in association with model structure and spatial inhomogeneity of polymer/carbon black composites

1996

The relationship between effective conductivity and cell structure of polyethylene/carbon composites as well as between effective conductivity and spatial distribution of carbon black are discussed. Following Yoshida's model both structures can, in a way, be said to be intermediate between the well known Maxwell-Garnett (MG) and Bruggeman (BR) limiting structures. Using TEM photographs on composites with various carbon blacks we have observed that the larger is Garncarek's inhomogeneity measure H of two-dimensional (2D) representative distribution of the carbon black, the smaller is the effective conductivity of the composite.

Dynamics of confined polymer melts: Recent Monte Carlo simulation results

2000

The dynamic behavior of thin polymer films is studied by Monte Carlo simulations of a simplified lattice model. The film geometry is realized by two opposite hard walls whose distance is varied in the simulations. In the films the dynamics is accelerated with respect to the bulk, leading to a decrease of the extrapolated glass transition temperature with decreasing film thickness.

Underdamped soft phonon in orthorhombic BaTiO3

1990

Abstract Raman scattering measurements are reported in orthorhombic phase and through the orthorhombic-rhombohedral transition of BaTiO3. Spectra reveal the presence of an underdamped low frequency phonon which slightly softens with decreasing temperature and abruptly stiffens at the transition to the rhombohedral phase. Results are discussed in comparison with isomorphous KNbO3 and tetragonal BaTiO3 and are interpreted as due to a dominant displacive mechanism.

Functional Hybrid Materials Containing Polypyrrole and Polyoxometalate Clusters: Searching for High Conductivities and Specific Charges

2002

Atomic force microscopy study of conducting polymer films near electrode's edge or grown on microband electrode

2013

Abstract Polypyrrole (PPy) films of different thicknesses (within the range from 200 nm to 2.5 μm) were electrodeposited on two types of inhomogeneous substrates, single band and double-band Pt electrodes. Topographic images of the polymer layers were obtained by means of ex situ large-scale AFM technique to demonstrate how the propagation rates of the film growth above the electrode (in the normal direction to the electrode surface) and along the insulating surface surrounding the single- or double-band electrodes (in the horizontal direction) change with the deposition charge. It is proved that variations in the film thickness over the double band electrodes and progressive changes of the…