DIELECTRIC PROPERTIES OF POLYVINYL ACETALS

1952 ◽  
Vol 30 (12) ◽  
pp. 940-947 ◽  
Author(s):  
B. L. Funt ◽  
T. H. Sutherland
Keyword(s):  
Dielectric Properties ◽  
Electrical Properties ◽  
Dielectric Relaxation ◽  
Relaxation Times ◽  
Dielectric Dispersion ◽  
Transition Temperatures ◽  
Free Energies ◽  
Frequency Range ◽  
Physical Picture ◽  
Electrical Relaxation

Measurements of dielectric dispersion in vinyl acetal and formal polymers were performed over the frequency range 0.050 to 100 kc. at temperatures between 25 and 135 °C. The results reflect the effects of internal plasticization on the electrical properties of the polymers. With increasing size of the substituent groups from formal to butyral the dispersion range is shifted to lower temperatures at a given frequency. Electrical relaxation times and transition temperatures were obtained and values of enthalpies, free energies, and entropies of activation were calculated. A tentative physical picture of the mechanism of dielectric relaxation in these polymers was also formulated.

scholarly journals Megahertz Dielectric Relaxation in the Nematic Phases of 4,4′-di-n-propyloxyazoxybenzene and 4,4′-di-n-pentyloxyazoxybenzene

1985 ◽  
Vol 40 (6) ◽  
pp. 627-631
Author(s):  
Nguyen X. Phuc ◽  
W. Otowski ◽  
J. Chruściel ◽  
H. Kresse ◽  
S. Urban ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Dielectric Relaxation ◽  
Homologous Series ◽  
Nematic Phase ◽  
Relaxation Times ◽  
Relaxation Processes ◽  
Frequency Range ◽  
The Third ◽  
Nematic Director ◽  
Nematic Phases

The dielectric properties of the third (3. OAOB) and fifth (5. OAOB) members of the PAA homologous series have been investigated in the frequency range from 0.1 to 12 MHz. Negative dielectric anisotropies have been obtained in the nematic phase of both substances. For the dielectric relaxation processes observed parallel to the nematic director, the relaxation times and activation energies have been estimated and discussed.

scholarly journals Dielectric Relaxation in Temperate Glaciers

1967 ◽  
Vol 6 (48) ◽  
pp. 897-909 ◽  
Author(s):  
P. W. F. Gribbon
Keyword(s):  
Dielectric Relaxation ◽  
Loss Factor ◽  
Relaxation Times ◽  
Frequency Range ◽  
Spreading Factor ◽  
Cold Surface ◽  
Relative Temperature ◽  
Low Frequencies ◽  
Glacial Ice ◽  
Impurity Ion

The dielectric relaxation ofnévéand glacial ice has been studied on two temperate glaciers in Greenland and France. Measurement of the capacitance and loss tangent in the audio-frequency range of thin parallel wires placed on the surface of a glacier gaveϵ′, the relative permittivity, andϵ″, the loss factor of thenévé. The relaxation time can be expressed in terms of the frequencyfmat the maximumϵ″ value of the Cole-Coleϵ″−ϵ′ diagram, and its variation with depth was derived from the Cole-Cole diagrams obtained for different wire separations.For wet 0°C. surface snow in Greenland,fm≈ 4 kHz. and decreased with the increase in density and form factor at greater depths, while for the low-density, cold surfacenévéin Francefm≈ 2 kHz. and increased with the increase in temperature at greater depths. All Cole-Cole diagrams showed both impurity-ion losses at low frequencies below 6 kHz., and a spreading factor of the distribution in relaxation times caused by the changes in the physical properties of the glacier with depth. Although the method could not measure temperatures absolutely, relative temperature differences and the position of the 0°C. isotherm were detected when a temperature gradient existed in a glacier.

scholarly journals Dielectric and Conduction Processes and Behaviours in Ni0.3Zn0.7Fe2O4

2016 ◽  
Vol 846 ◽  
pp. 311-317
Author(s):  
Mohd Noor Mat ◽  
M.K. Halimah ◽  
Wan Mohd Daud Wan Yusoff ◽  
H. Mansor ◽  
H. Nizam ◽  
...  
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Iron Oxide ◽  
Dielectric Properties ◽  
Dielectric Relaxation ◽  
Relaxation Process ◽  
Peak Frequency ◽  
Frequency Range ◽  
Dielectric Relaxation Process ◽  
Frequency Relaxation

Dielectric relaxation and conductivity of Ni0.3Zn0.7Fe2O4 (NZF) were studied in the frequency range between 0.01 Hz to 3 MHz and temperature range within 313 K to 473 K. The sample was prepared by mixing Zinc Oxide, Nickel Oxide and Iron Oxide and sintered at 1573 K for 10 hours long. Dielectric properties were studied using Novo Control Dielectric Spectrometer. Dielectric relaxation and conductivity phenomena were discussed using an empirical model to key out the dielectric relaxation process. Analyze peak frequency relaxation process consist of four slopes to explain the dielectric relaxation process. The conductivity of the sample indicates an activated process and activation energy of dc conductivity is 0.44 ± 0.01 eV.

scholarly journals Characteristics of Processes of Electrical Relaxation in Frozen Soils

1977 ◽  
Vol 19 (81) ◽  
pp. 675
Author(s):  
A.D. Frolov ◽  
B.V. Gusev
Keyword(s):  
Activation Energy ◽  
Dielectric Properties ◽  
Temperature Dependence ◽  
Relaxation Times ◽  
Frozen Soils ◽  
Electrical Relaxation ◽  
Basic Equations ◽  
Modified Theory

Abstract The results of measurements of dielectric properties of frozen soils are analysed on the basis of modified theory of dielectrics. The relaxational character of frequency and temperature dependence is shown and the basic equations are derived. The characteristics of distribution of relaxation times and effective relaxation times as depending on the temperatures are discussed. The values of activation energy are estimated.

scholarly journals Dielectric Relaxation in Temperate Glaciers

1967 ◽  
Vol 6 (48) ◽  
pp. 897-909
Author(s):  
P. W. F. Gribbon
Keyword(s):  
Dielectric Relaxation ◽  
Loss Factor ◽  
Relaxation Times ◽  
Frequency Range ◽  
Spreading Factor ◽  
Cold Surface ◽  
Relative Temperature ◽  
Low Frequencies ◽  
Glacial Ice ◽  
Impurity Ion

The dielectric relaxation of névé and glacial ice has been studied on two temperate glaciers in Greenland and France. Measurement of the capacitance and loss tangent in the audio-frequency range of thin parallel wires placed on the surface of a glacier gave ϵ′, the relative permittivity, and ϵ″, the loss factor of the névé. The relaxation time can be expressed in terms of the frequency fm at the maximum ϵ″ value of the Cole-Cole ϵ″−ϵ′ diagram, and its variation with depth was derived from the Cole-Cole diagrams obtained for different wire separations.For wet 0°C. surface snow in Greenland, fm ≈ 4 kHz. and decreased with the increase in density and form factor at greater depths, while for the low-density, cold surface névé in France fm ≈ 2 kHz. and increased with the increase in temperature at greater depths. All Cole-Cole diagrams showed both impurity-ion losses at low frequencies below 6 kHz., and a spreading factor of the distribution in relaxation times caused by the changes in the physical properties of the glacier with depth. Although the method could not measure temperatures absolutely, relative temperature differences and the position of the 0°C. isotherm were detected when a temperature gradient existed in a glacier.

Dielectric relaxation of nonionic microemulsion: influence of the salinity

2001 ◽  
Vol 79 (1) ◽  
pp. 49-58
Author(s):  
G Delbos ◽  
M Keita ◽  
T K Bose
Keyword(s):  
Dielectric Properties ◽  
Dielectric Relaxation ◽  
Relaxation Frequency ◽  
The Other ◽  
Spectral Amplitude ◽  
Microemulsion System ◽  
Frequency Range ◽  
Amplitude Increase ◽  
Nacl Concentration ◽  
Main Relaxation

Study of dielectric properties of a quaternary microemulsion system composed of water, oil, a nonionic surfactant, and an alcohol, in the frequency range 100 kHz – 15 GHz is reported as a function of salt (NaCl) concentration. Depending on the salinity, the decomposition of the dielectric spectra shows the presence of two or three main relaxation domains. The lower relaxation frequency and the corresponding spectral amplitude increase as a function of salinity. The other observed relaxation mechanisms are shown to be dipolar in origin.PACS No.: 97.22Gn

Dielectric Relaxation of Liquid Polyethyleneglycol on Addition of Polyvinylpyrrolidone

1993 ◽  
Vol 48 (12) ◽  
pp. 1229-1230
Author(s):  
M. Stockhausen ◽  
M. Abd-El-Rehim
Keyword(s):  
Dielectric Properties ◽  
Dielectric Relaxation ◽  
Relaxation Times ◽  
Molecular Solvents

Abstract The set of relaxation times describing the dynamic dielectric properties of liquid polyethyleneglycol 200 at 20 and 40 °C is found to be practically independent of the admixture of polyvinylpyrrolidone, though the viscosity is appreciably increased. This is compared to the rather similar behaviour of small molecular solvents.

scholarly journals Water Content Control to Improve Space Charge Storage in a Cork Derivative

2012 ◽  
Vol 730-732 ◽  
pp. 395-400
Author(s):  
M. Carmo Lança ◽  
Inês Cunha ◽  
João Paulo Marques ◽  
Eugen R. Neagu ◽  
Luis Gil ◽  
...  
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
Electrical Properties ◽  
Thermal Treatment ◽  
Dielectric Relaxation ◽  
Discharge Current ◽  
Absorption Rate ◽  
Charge Storage ◽  
Dielectric Relaxation Spectroscopy ◽  
Electrical And Dielectric Properties

The influence of humidity content on the electrical and dielectric properties of a composite made from recycled TetraPak® containers and granulated cork was studied. The material components have been dried before preparation and after the composite was conditioned by keeping the samples in a dry environment (desiccator) or in an oven at high temperature (70°C in air). The differences observed in electrical properties (investigated by isothermal charge and discharge current measurement) and dielectric properties (measured using dielectric relaxation spectroscopy) show that the thermal treatment at high temperature is more efficient on removing water and slows down the re-absorption rate.

Dielectric relaxation of lithium and sodium perchlorates in 1,2-dimethoxyethane and propylene carbonate

1981 ◽  
Vol 59 (7) ◽  
pp. 1051-1060 ◽  
Author(s):  
Hubert Cachet ◽  
Mohamed Fekir ◽  
Jean-Claude Lestrade
Keyword(s):  
Dielectric Properties ◽  
Ethyl Acetate ◽  
Dielectric Relaxation ◽  
Propylene Carbonate ◽  
Complex Permittivity ◽  
Ion Pairs ◽  
Conductivity Measurements ◽  
Frequency Range ◽  
Dielectric Data

The complex permittivity of LiClO4 and NaClO4 solutions in 1,2-dimethoxyethane (DME) has been measured in the frequency range 0.140–123.2 GHz. The data have been analysed according to a model for the reorientation of ion pairs given in a previous paper. The dielectric data are supplemented by conductivity measurements in a broad concentration range (10−4–1 mol/L) which evidence the large extent of salt association. The main result is that the solvation of Li+ and Na+ by DME cannot be described as simply as in the case of other solvents, such as tetrahydrofuran or ethyl acetate, as far as the dielectric properties are concerned: while the assumption of rigidly bound solvating molecules was acceptable for the latter solvents, some freedom in the reorientation of these molecules has to be taken into account for the case of DME. LiClO4 solutions in propylene carbonate (PC) + benzene and PC + DME mixtures have also been studied. The data, for the latter, can be qualitatively interpreted under the assumption that PC molecules take the place of DME molecules in the solvation sheath, even at low PC concentration.

Observation of Dielectric Peaks in Glassy Se70Te20Sn10 Alloy

2012 ◽  
Vol 329 ◽  
pp. 165-175 ◽  
Author(s):  
A. Sharma ◽  
N. Mehta
Keyword(s):  
Chalcogenide Glasses ◽  
Relaxation Times ◽  
Dielectric Dispersion ◽  
Dielectric Constants ◽  
Audio Frequency ◽  
Frequency Range ◽  
Glass Transition Region ◽  
Dipolar Relaxation ◽  
The Past ◽  
Frequency Dependences

The Temperature and Frequency Dependences of the Dielectric Constants () and Dielectric Loss (") Were Studied in Glassy Se70Te20Sn10Alloy in the Audio-Frequency Range below the Glass Transition Region. the Results Indicated that Dielectric Dispersion Occurred in Glassy Se70Te20Sn10Alloy. Well-Defined Dielectric Peaks Were Obtained in Glassy Se70Te20Sn10Alloy; these Are Rarely Observed in Chalcogenide Glasses. such Loss Peaks Were Not Observed in the Glassy Se80-xTe20SnxSystem in the past for Sn Concentrations of x ≤ 8. A Detailed Analysis of the Data Showed that the Results Could Be Explained in Terms of Dipolar Relaxation, with a Distribution of Relaxation Times, this Is Quite Expected in the Case of Chalcogenide Glasses.

Sign in / Sign up

Export Citation Format

Share Document