Change of Electrical Properties of Rubber and Gutta-Percha during Storage under Water

1931 ◽  
Vol 4 (1) ◽  
pp. 39-53
Author(s):  
Harvey L. Curtis ◽  
Arnold H. Scott
Keyword(s):  
Dielectric Constant ◽  
Direct Current ◽  
Power Factor ◽  
Marked Change ◽  
Dielectric Constants ◽  
The Other ◽  
Time Interval ◽  
Electrical Measurements ◽  
Copper Salts ◽  
Gutta Percha

Abstract A number of samples of rubber and gutta-percha were stored under water for about seven years and electrical measurements made on them periodically to determine the effect of aging on the resistivity, dielectric constant, and power factor. The dielectric constant was measured under three different conditions, namely, 60 cycles alternating current, pulsating direct currentusing 0.6 second charge with 0.1 second discharge, and pulsating direct current using the same time of charge with 1 second discharge. In all cases the dielectric constants increased with time unless failure was approached. A sample was considered to have failed when measurement of its capacitance became impracticable. The changes of the resistivity and power factor varied from sample to sample. The approach of failure was first indicated by the resistivity. When a curve was plotted with time the sample had been under observation as abscissa and resistance of the samples as ordinates, the curves of the sample which failed showed a break or marked change in direction several months before actual failure occurred. With similar curves for power factor and direct-current dielectric constant, breaks occurred at a later time. The time interval between the break in the resistivity curve and the breaks in the other curves was a function of the rate of decrease of the resistivity. These facts indicate that the failure of a sample is the result of its decrease in resistivity. This decrease in resistivity has been ascribed to the formation of fine holes through the material. This explanation was confirmed by the microscopic examination of microtome sections of the samples which failed. These sections showed fern-like figures projecting into the rubber. All of the samples that failed were in the form of tubes, with water electrodes both inside and outside the tubes. Some copper salts were inadvertently allowed to form inside the tubes. The catalytic action of these copper salts accelerated the aging, and probably changed its character.

Epitaxial Growth and Anisotropic Dielectric Properties of La-Doped Bi4Ti3O12 Thin Films

2007 ◽  
Vol 124-126 ◽  
pp. 177-180
Author(s):  
Jang Sik Lee ◽  
Q.X. Jia
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Bottom Electrode ◽  
Dielectric Constants ◽  
The Other ◽  
Field Range ◽  
Anisotropic Dielectric ◽  
Dielectric Nonlinearity ◽  
La Doped

To investigate the anisotropic dielectric properties of layer-structured bismuth-based ferroelectrics along different crystal directions, we fabricate devices along different crystal orientations using highly c-axis oriented Bi3.25La0.75Ti3O12 (BLT) thin films on (001) LaAlO3 (LAO) substrates. Experimental results have shown that the dielectric properties of the BLT films are highly anisotropic along different crystal directions. The dielectric constants (1MHz at 300 K) are 358 and 160 along [100] and [110], respectively. Dielectric nonlinearity is also detected along these crystal directions. On the other hand, a much smaller dielectric constant and no detectable dielectric nonlinearity in a field range of 0-200 kV/cm are observed for films along [001] when c-axis oriented SRO is used as the bottom electrode.

Effect of Temperature and Frequency on the Dielectric Constant, Power Factor, and Conductivity of Compounds of Purified Rubber and Sulfur

1934 ◽  
Vol 7 (2) ◽  
pp. 342-370 ◽  
Author(s):  
A. H. Scott ◽  
A. T. McPherson ◽  
Harvey L. Curtis
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Power Factor ◽  
Water Soluble ◽  
Effect Of Temperature ◽  
General Character ◽  
Soluble Salts ◽  
Electrical Measurements ◽  
Separate Paper ◽  
Rubber Compounds

Abstract The electrical measurements given in this paper differ from those previously reported by the authors and by other investigators in that they were made on specimens prepared from purified rubber. The purification, which involved the removal of proteins, resins, and water-soluble salts, affected all the electrical properties to some extent, but did not alter the general character of the variation in electrical properties with composition, temperature, or frequency. The results of the present investigation afford comprehensive data on the electrical properties of rubber-sulfur compounds, and may form a basis for designing rubber compounds for specific electrical uses. They also demonstrate the inadequacy of the simple numerical coefficients that are sometimes employed to evaluate the changes in the electrical properties with temperature and frequency. A discussion of the results from the standpoint of modern dielectric theory is not included in the present paper, but is contemplated for a separate paper.

scholarly journals Dielectric constants of solids at high frequencies and the influence of water of crystallization on dielectric constant

1937 ◽  
Vol 158 (893) ◽  
pp. 182-198 ◽  
Keyword(s):  
Dielectric Constant ◽  
Experimental Error ◽  
Dielectric Constants ◽  
The Other ◽  
High Frequencies ◽  
Influence Of Water

The determination of the dielectric constant of one constituent of a mixture, when the dielectric constants of the other component and the mixture itself are known, has been a problem which has been given much attention for many years. The familiar Clausius-Mossotti relationship for the dielectric constant of any substance is: ε-1/(ε + 2) d = A, where ε is the dielectric constant of the substance, d the density, and A a constant depending upon the polarizability of the molecule. This relation was developed independently by Clausius, Mossotti, Lorenz, Lorentz, Rayleigh, and Debye; but even in the case of pure liquids deviations well outside the experimental error have been found.

Studies in the Vulcanization of Rubber. V. Dielectric Constant and Power Factor of Vulcanized Rubber

1932 ◽  
Vol 5 (3) ◽  
pp. 367-383
Author(s):  
Donald W. Kitchin
Keyword(s):  
Dielectric Constant ◽  
Sulfur Content ◽  
Power Factor ◽  
Dielectric Behavior ◽  
Dielectric Constants ◽  
Low Dielectric ◽  
Vulcanized Rubber ◽  
Wide Range ◽  
Hard State ◽  
Critical Experiment

Abstract 1. Power factor and dielectric constant data have been given for vulcanized rubber samples tested over a wide range of composition, temperature, and frequency. 2. The real identity of the agents responsible for the peculiar dielectric behavior is not known. It seems probable that these agents are the rubber-sulfur molecules themselves. because the effects increase, under proper conditions, directly with per cent combined sulfur. 3. The effect of increasing sulfur content on the dielectric behavior is complex; it modifies not only these supposed agents themselves, but also the stiffness of their environment. Moreover, at a given sulfur content the agents are not identical but differ widely in relaxation time, and therefore in ability to respond; and with progressive addition of sulfur, the rubber does not increase continuously in stiffness, but, at a composition which depends on the temperature, passes rather abruptly from a soft to a hard state. 4. The temperature at which the transition from one state to the other occurs increases almost linearly with the sulfur content from −90° to +90° C. 5. In the soft state the behavior of vulcanized rubber with respect to compressibility, thermal expansion, dielectric constant, and power factor, and probably other properties, resembles that of a viscous liquid; in the hard state, that of a solid. 6. Rubber with less than 2 per cent combined sulfur shows low dielectric constant and power factor over the whole temperature and frequency range investigated; hard rubber, only at room temperature, where its rigidity restricts the response to the field. 7. Hard rubber, although not an electret, can hold an electric charge for 24 hours or more. The low dielectric constants of high-sulfur rubber samples found in measurements with a ballistic galvanometer were due to the disparity between its period of about one second and the long discharge periods of the samples. This led to the idea of dipole compensation shown to be incorrect by the high temperature results. 8. At temperatures sufficiently high to permit free response, the dielectric constant increases with sulfur content over the whole range. 9. If a dipole mechanism is involved, addition of sulfur to more than half the double bonds does not cause the dipole moment of the molecules to vanish owing to compensation. 10. The power factor of vulcanized rubber sheets decreases on stretch. 11. The data neither prove nor disprove a dipole mechanism. A critical experiment to settle this question is still wanting.

Removal of Particles From the Surface of a Droplet

2008 ◽  
Author(s):  
N. Aubry ◽  
P. Singh ◽  
S. Nudurupati ◽  
M. Janjua
Keyword(s):  
Dielectric Constant ◽  
Electric Field ◽  
Strong Electric Field ◽  
Dielectric Constants ◽  
The Other ◽  
Uniform Electric Field ◽  
Drop Deformation ◽  
Ambient Fluid ◽  
Dielectrophoretic Force ◽  
Different Types

We present a technique to concentrate particles on the surface of a drop, separate different types of particles, and remove them from the drop by subjecting the drop to a uniform electric field. The particles are moved under the action of the dielectrophoretic force which arises due to the non-uniformity of the electric field on the surface of the drop. Experiments show that depending on the dielectric constants of the fluids and the particles, particles aggregate either near the poles or near the equator of the drop. When particles aggregate near the poles and the dielectric constant of the drop is greater than that of the ambient fluid, the drop deformation is larger than that of a clean drop. In this case, under a sufficiently strong electric field the drop develops conical ends and particles concentrated at the poles eject out by a tip streaming mechanism, thus leaving the drop free of particles. On the other hand, when particles aggregate near the equator, it is shown that the drop can be broken into three major droplets, with the middle droplet carrying all particles and the two larger sized droplets on the sides being free of particles. The method also allows us to separate particles for which the sign of the Clausius-Mossotti factor is different, making particles of one type aggregate at the poles and of the second type aggregate at the equator. The former are removed from the drop by increasing the electric field strength, leaving only the latter inside the drop.

Dielectric Constant, Power Factor, and Conductivity of the System Rubber-Calcium Carbonate

1942 ◽  
Vol 15 (4) ◽  
pp. 879-894
Author(s):  
Arnold H. Scott ◽  
Archibald T. McPherson
Keyword(s):  
Dielectric Constant ◽  
Calcium Carbonate ◽  
Natural Rubber ◽  
Power Factor ◽  
Loss Tangent ◽  
Direct Relationship ◽  
Dielectric Constants ◽  
Constant Power ◽  
Dielectric Constant And Loss

Abstract The results obtained in this investigation indicate that either the formula developed by Wiener (Formula 7) or the exponent formula (Formula 9) may be used for the computation of the dielectric constants of mixtures of calcium carbonate and rubber. Formula 7 may be preferred, since it gives some indication of the shape of the particles and state of dispersion of the powder. There was little difference between values of the dielectric constant and loss tangent at 1 kilocycle per second and at 100 kilocycles per second. The change of the loss tangent with the content of calcium carbonate was not large, but a direct relationship between loss tangent and percentage of calcium carbonate was indicated. The 1-minute-conductivity values increased continuously with increasing content of calcium carbonate when Vistanex was used as the base, but passed through a minimum when natural rubber was used.

scholarly journals Progress in Traceable Nanoscale Capacitance Measurements Using Scanning Microwave Microscopy

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 820
Author(s):  
François Piquemal ◽  
José Morán-Meza ◽  
Alexandra Delvallée ◽  
Damien Richert ◽  
Khaled Kaja
Keyword(s):  
Uncertainty Budget ◽  
Dielectric Constants ◽  
Electrical Measurements ◽  
Capacitance Measurements ◽  
Uncertainty Sources ◽  
Microwave Microscopy ◽  
Calibration Methods ◽  
Combined Uncertainty ◽  
Calibration Samples ◽  
Scanning Microwave Microscopy

Reference samples are commonly used for the calibration and quantification of nanoscale electrical measurements of capacitances and dielectric constants in scanning microwave microscopy (SMM) and similar techniques. However, the traceability of these calibration samples is not established. In this work, we present a detailed investigation of most possible error sources that affect the uncertainty of capacitance measurements on the reference calibration samples. We establish a comprehensive uncertainty budget leading to a combined uncertainty of 3% in relative value (uncertainty given at one standard deviation) for capacitances ranging from 0.2 fF to 10 fF. This uncertainty level can be achieved even with the use of unshielded probes. We show that the weights of uncertainty sources vary with the values and dimensions of measured capacitances. Our work offers improvements on the classical calibration methods known in SMM and suggests possible new designs of reference standards for capacitance and dielectric traceable measurements. Experimental measurements are supported by numerical calculations of capacitances to reveal further paths for even higher improvements.

scholarly journals Comment on “investigation of dielectric constants of water in a nano-confined pore” by H. Zhu, F. Yang, Y. Zhu, A. Li, W. He, J. Huang and G. Li, RSC Adv., 2020, 10, 8628

RSC Advances ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 5179-5181
Author(s):  
Sayantan Mondal ◽  
Biman Bagchi
Keyword(s):  
Dielectric Constant ◽  
Dielectric Constants ◽  
Static Dielectric Constant ◽  
Inherent Anisotropy ◽  
Nanoconfined Water

Neglects of inherent anisotropy and distinct dielectric boundaries may lead to completely erroneous results. We demonstrate that such mistakes can give rise to gross underestimation of the static dielectric constant of cylindrically nanoconfined water.

scholarly journals Effect of Co-Inoculation of Bacillus sp. Strain with Bacterial Endophytes on Plant Growth and Colonization in Tomato Plant (Solanum lycopersicum)

2021 ◽  
Vol 12 (2) ◽  
pp. 480-490
Author(s):  
Ahsanul Salehin ◽  
Ramesh Raj Puri ◽  
Md Hafizur Rahman Hafiz ◽  
Kazuhito Itoh
Keyword(s):  
Plant Growth ◽  
Solanum Lycopersicum ◽  
Plant Growth Promotion ◽  
Tomato Plant ◽  
Growth Promotion ◽  
Growth Parameters ◽  
The Other ◽  
Time Interval ◽  
Bacillus Sp ◽  
F 33

Colonization of a biofertilizer Bacillus sp. OYK strain, which was isolated from a soil, was compared with three rhizospheric and endophytic Bacillus sp. strains to evaluate the colonization potential of the Bacillus sp. strains with a different origin. Surface-sterilized seeds of tomato (Solanum lycopersicum L. cv. Chika) were sown in the sterilized vermiculite, and four Bacillus sp. strains were each inoculated onto the seed zone. After cultivation in a phytotron, plant growth parameters and populations of the inoculants in the root, shoot, and rhizosphere were determined. In addition, effects of co-inoculation and time interval inoculation of Bacillus sp. F-33 with the other endophytes were examined. All Bacillus sp. strains promoted plant growth except for Bacillus sp. RF-37, and populations of the rhizospheric and endophytic Bacillus sp. strains were 1.4–2.8 orders higher in the tomato plant than that of Bacillus sp. OYK. The plant growth promotion by Bacillus sp. F-33 was reduced by co-inoculation with the other endophytic strains: Klebsiella sp. Sal 1, Enterobacter sp. Sal 3, and Herbaspirillum sp. Sal 6., though the population of Bacillus sp. F-33 maintained or slightly decreased. When Klebsiella sp. Sal 1 was inoculated after Bacillus sp. F-33, the plant growth-promoting effects by Bacillus sp. F-33 were reduced without a reduction of its population, while when Bacillus sp. F-33 was inoculated after Klebsiella sp. Sal 1, the effects were increased in spite of the reduction of its population. Klebsiella sp. Sal 1 colonized dominantly under both conditions. The higher population of rhizospheric and endophytic Bacillus sp. in the plant suggests the importance of the origin of the strains for their colonization. The plant growth promotion and colonization potentials were independently affected by the co-existing microorganisms.

DIELECTRIC CONSTANT AND SEEBECK COEFFICIENT FOR SEMICONDUCTORS: THERMODYNAMIC AND DFT STUDIES

2013 ◽  
Vol 12 (06) ◽  
pp. 1350057 ◽  
Author(s):  
HSIU-YA TASI ◽  
CHAOYUAN ZHU
Keyword(s):  
Boundary Condition ◽  
Dielectric Constant ◽  
Seebeck Coefficient ◽  
Gas Phase ◽  
Present Method ◽  
Dielectric Constants ◽  
Semiconductor Materials ◽  
Electronic Polarizability ◽  
Seebeck Coefficients ◽  
Good Agreement

Dielectric constants and Seebeck coefficients for semiconductor materials are studied by thermodynamic method plus ab initio quantum density functional theory (DFT). A single molecule which is formed in semiconductor material is treated in gas phase with molecular boundary condition and then electronic polarizability is directly calculated through Mulliken and atomic polar tensor (APT) density charges in the presence of the external electric field. This electronic polarizability can be converted to dielectric constant for solid material through the Clausius–Mossotti formula. Seebeck coefficient is first simulated in gas phase by thermodynamic method and then its value divided by its dielectric constant is regarded as Seebeck coefficient for solid materials. Furthermore, unit cell of semiconductor material is calculated with periodic boundary condition and its solid structure properties such as lattice constant and band gap are obtained. In this way, proper DFT function and basis set are selected to simulate electronic polarizability directly and Seebeck coefficient through chemical potential. Three semiconductor materials Mg 2 Si , β- FeSi 2 and SiGe are extensively tested by DFT method with B3LYP, BLYP and M05 functionals, and dielectric constants simulated by the present method are in good agreement with experimental values. Seebeck coefficients simulated by the present method are in reasonable good agreement with experiments and temperature dependence of Seebeck coefficients basically follows experimental results as well. The present method works much better than the conventional energy band structure theory for Seebeck coefficients of three semiconductors mentioned above. Simulation with periodic boundary condition can be generalized directly to treat with doped semiconductor in near future.

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