CONDUCTIVITY AT ALTERNATING CURRENT OF THIN FILMS OF POLYCHLOROPRENE FORMED IN ELECTRIC FIELD

The temperature dependences of conductivity at alternating current (a frequency of 1 kHz) were studied for thin polychloroprene films formed from a solution on metal electrodes having different polarities: anode, cathode and zero potential. It was found that the nature and form of the temperature dependence of the conductivity of the investigated polymer film depends on the method of sample formation. Temperature regions of maximum conductivity were detected. The realization of the heating cycle followed by the film cooling in a limited region between the electrodes under the action of an alternating electric field leads to an increase in the specific conductivity and a shift of the extreme values to the region of lower temperatures. This effect is manifested to the greatest extent for films formed at the cathode. The process of heating and subsequent cooling is of hysteresis nature both for permittivity and for the dielectric loss tangent. The dependence of dielectric loss tangent on permittivity in a rather wide temperature range is inversely proportional. During the analysis of temperature dependences the mechanism of conductivity was studied for polychloroprene thin films at direct and alternating current. The determined activation energies of the polymeric system conductivity change enable concluding that the mechanisms of electric conductivity at direct and alternating current are of similar nature. The extreme values of permittivity may be due to structural alterations in the process of heating. This is confirmed by the data on the temperature dependence of dielectric loss tangent. In order to explain conductivity at direct current a model of dipole traps is offered.

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Computational method of determining dielectric-loss tangent for thin films

Measurement Techniques ◽

10.1007/bf00865003 ◽

1987 ◽

Vol 30 (10) ◽

pp. 1011-1013

Author(s):

E. M. Tolstopyatov

Keyword(s):

Thin Films ◽

Dielectric Loss ◽

Loss Tangent ◽

Dielectric Loss Tangent ◽

Computational Method

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Analysis of the temperature-frequency effect on dielectric losses in a grain medium

Proceedings of Irkutsk State Technical University ◽

10.21285/1814-3520-2021-6-733-740 ◽

2022 ◽

Vol 25 (6) ◽

pp. 733-740

Author(s):

M. Yu. Buzunova

Keyword(s):

Dielectric Loss ◽

Electric Field ◽

Mechanical Activation ◽

External Electric Field ◽

Loss Tangent ◽

Dielectric Loss Tangent ◽

Dielectric Losses ◽

Frequency Range ◽

Dielectric Parameters ◽

Dielectric Characteristics

The aim of the study is to determine the influence of the thermal effect on dielectric losses in grain mass subject to bruising during drying and storage on the example of wheat across a wide external electric field frequency range. The study of the electrophysical characteristics of a dispersed medium comprising mechanically activated wheat grains takes into account the effect of the degree of breakage on the dielectric parameters of the studied medium. The studies were carried out on experimental samples having different degrees of mechanical activation of particles, which ranged in size from from 50 to 1000 μm. Variations in the dielectric loss tangent were studied using the dielectric method across a wide temperature-frequency range. Studies of variations in dielectric properties were carried out for wheat sam-ples subjected to grinding according to the mechanical activation method at temperatures varying from 20°C to 255°C with a constant heating rate of 0.7 deg / min. During the course of the experiment, the frequency of the external electric field was varied from 25 Hz to 1∙106 Hz. Dielectric constant and dielectric loss tangent calculations were carried out using data on electrical capacity and conductivity obtained using an E7-20 immittance meter and a measuring cell in the form of a flat capacitor. An analysis of variations in these dielectric characteristics was also performed. The obtained stable correlation of the dielectric loss tangent with the frequency of external electric impact and the degree of heating of the samples was most pronounced for finely dispersed samples (particle size 50 μm). Variations in dielectric characteristics are most significant when the frequency decreases to 100 Hz and below. The study of variations in the main dielectric parameters can be used to prevent self-heating and ignition of the grain mass during storage, as well as for selecting the most efficient energy-saving drying mode.

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Study on Temperature Characteristics of Ceramic Materials for Piezoelectric Actuators and Model Modification

Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University ◽

10.1051/jnwpu/20193751011 ◽

2019 ◽

Vol 37 (5) ◽

pp. 1011-1017

Author(s):

Nan Liu ◽

Zhenming Liu ◽

Xinrui Gong ◽

Xinyuan Huang ◽

Chunyou Xiong

Keyword(s):

Dielectric Loss ◽

Electric Field ◽

Loss Tangent ◽

Coercive Field ◽

Dielectric Loss Tangent ◽

Strong Electric Field ◽

Ceramic Materials ◽

Loading Test ◽

Residual Polarization ◽

Maximum Polarization

The performance of piezoelectric actuator ceramics under strong electric field(20 kV/cm) and variable temperature (30~150℃) were tested on a piezoelectric ceramic thermo-electro-mechanical multi-field loading test bench. The variation of hysteresis loop, strain loop, free capacitor and dielectric loss tangent with temperature was analyzed. A mathematical model of displacement characteristics of ceramic materials considering temperature effect is established, and the accuracy of the model is verified. The results show that the hysteresis loops become slender with the increasing of temperature, while the residual polarization, maximum polarization and coercive field decrease. The effect of the temperature on the residual polarization and coercive field is stronger than that on maximum polarization. The strain loop presents a typical butterfly curve, and the negative strain decreases gradually to 0.12% with the increasing of temperature. In the unipolar electric field, the residual polarization varies slightly with the increasing of temperature, and the maximum polarization increases about 40%. The piezoelectric constant of the material increases linearly. The free capacitor and dielectric loss tangent increases continuously. The higher the temperature, the greater the increase.

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Improvement of dielectric loss tangent of Al2O3 doped Ba0.5Sr0.5TiO3 thin films for tunable microwave devices

Journal of Applied Physics ◽

10.1063/1.1638615 ◽

2004 ◽

Vol 95 (3) ◽

pp. 1416-1419 ◽

Cited By ~ 101

Author(s):

K. B. Chong ◽

L. B. Kong ◽

Linfeng Chen ◽

L. Yan ◽

C. Y. Tan ◽

...

Keyword(s):

Thin Films ◽

Dielectric Loss ◽

Loss Tangent ◽

Dielectric Loss Tangent ◽

Microwave Devices ◽

Tunable Microwave

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ELECTRORHEOLOGICAL BEHAVIOR OF SUSPENSIONS BASED ON POLYDIMETHYLSILOXANE FILLED WITH HALLOYSITE

IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA ◽

10.6060/tcct.20186106.5682 ◽

2018 ◽

Vol 61 (6) ◽

pp. 41 ◽

Cited By ~ 2

Author(s):

Nikita M. Kuznetsov ◽

Sergey I. Belousov ◽

Natalya P. Bessonova ◽

Sergey N. Chvalun

Keyword(s):

Electrical Conductivity ◽

Dielectric Loss ◽

Electric Field ◽

Water Content ◽

Loss Tangent ◽

Rheological Behavior ◽

Dielectric Loss Tangent ◽

Shear Stresses ◽

Storage And Loss Moduli ◽

Frequency Dependences

The rheological behavior at 20 °С of electrorheological fluids based on silicone oil filled with halloysite nanotubes with different water content was studied. Flow and viscosity curves, storage and loss moduli were measured using a cylinder-cylinder rotary viscometer. The frequency dependences of electrical conductivity and dielectric loss tangent were obtained by dielectric spectroscopy. When an electric field is applied to the samples, their rheological behavior changes - the values of the yield stress increase. In this case, the viscosity curves exhibit an elastic behavior at low shear stresses and exhibit a Newtonian flow when the yield point is overcome. The frequency dependences of the storage and loss moduli confirm the results obtained on the flow curves. The electric field intensity influence on the magnitude of the electrorheological effect was also investigated. The effect of water presence on electrorheological and electrophysical properties was shown. Electrorheological fluid with a small amount of water exhibits a better response to the electric field application, as evidenced by higher values of the yield stresses in comparison with the sample containing drained filler. The small water content does not have a strong effect on the electrical conductivity of the systems under study, but its presence significantly changes the form of the dielectric loss tangent - the contribution of the electrical conductivity to the relaxation processes is significant, and the nature of the relaxation transitions changes due to the different polarizabilities of the wet and dried filler. This work demonstrates the prospects of using nanoscaled fillers with a high aspect ratio as the dispersed phase for electrorheological fluids.Forcitation:Kuznetsov N.M., Belousov S.I., Bessonova N.P., Chvalun S.N. Electrorheological behavior of suspensions based on polydimethylsiloxane filled with halloysite. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 6. P. 41-47

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Electrophysical properties of mixtures of mineral oil and synthetic ester dielectric liquid

Safety and Reliability of Power Industry ◽

10.24223/1999-5555-2021-14-2-132-141 ◽

2021 ◽

Vol 14 (2) ◽

pp. 132-141

Author(s):

M. N. Lyutikova ◽

S. M. Korobeynikov ◽

A. A. Konovalov

Keyword(s):

Dielectric Loss ◽

Breakdown Voltage ◽

Loss Tangent ◽

Dielectric Loss Tangent ◽

Kinematic Viscosity ◽

Mineral Oil ◽

Flash Point ◽

Power Transformers ◽

Synthetic Ester ◽

Insulating Properties

Power transformers are key equipment in power generation, transmission, and distribution systems. The reliability of power transformers is based on the performance of the insulation system, which includes solid cellulose insulation and a liquid dielectric. Modern power engineering requires liquid insulation to have excellent insulating properties, high fire resistance, and biodegradability. Mineral oil that has been in use for over 100 years does not meet certain requirements. Therefore, various methods of enhancing the insulating properties of the oil are currently being considered, including mixing it with other liquid dielectrics, which have excellent properties. Synthetic and natural esters are considered as alternative fluids.This article discusses the possibility of enhancing the insulating characteristics of mineral oil with a high content of aromatic hydrocarbons (for example, T-750 oil) by mixing it with synthetic ester Midel 7131. Assessment is given of insulating parameters of the resulting mixtures with an ester fraction in mineral oil from 0% to fifty%. The main characteristics of the mixtures are described, such as density, kinematic viscosity, flash point, dielectric loss tangent, relative dielectric permittivity, breakdown voltage, and moisture content. It is shown that with an increase in the proportion of ester, some parameters of the obtained insulating liquid improve (flash point, dielectric constant, breakdown voltage), while values of other parameters (density, kinematic viscosity, dielectric loss tangent) with an ester content of more than 10% in the mixture do not meet the requirements for mineral oils.

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Method of calculating the dielectric loss tangent of binary systems

Journal of Engineering Physics ◽

10.1007/bf00872513 ◽

1987 ◽

Vol 52 (3) ◽

pp. 310-312

Author(s):

G. N. Dul'nev ◽

D. P. Volkov ◽

M. V. Dobrochasov

Keyword(s):

Dielectric Loss ◽

Loss Tangent ◽

Dielectric Loss Tangent ◽

Binary Systems

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Dielectric and electrical properties of Cr substituted Mg ferrites

Journal of Bangladesh Academy of Sciences ◽

10.3329/jbas.v39i1.23652 ◽

2015 ◽

Vol 39 (1) ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

AKM Zakaria ◽

Faizun Nesa ◽

MA Saeed Khan ◽

SM Yunus ◽

NI Khan ◽

...

Keyword(s):

Dielectric Constant ◽

Dielectric Loss ◽

Loss Tangent ◽

Dielectric Loss Tangent ◽

Lattice Parameter ◽

Activation Energies ◽

X Ray Diffraction ◽

Constant E ◽

Cr Concentration ◽

Academy Of Sciences

The spinel ferrites MgCrxFe2-xO4 (0.0 ? × ?1.0) were prepared through the solid state reaction using conventional ceramic method at 1300°C in air. The homogeneous phase of the ferrite samples was observed from the X-ray diffraction study. Lattice parameter of the samples was found to decrease with increasing Cr concentration in the system obeying Vegards law. The ac electrical resistivity, measured as a function of temperature, decreases with the increase of temperature indicating the semiconducting nature of all the samples. The activation energies were calculated and found to decrease with increasing Cr content. The lower activation energies are associated with higher electrical conductivity. With the increase of temperature, dielectric constant (e`) and dielectric loss tangent are observed to be increased; while with the increase of frequency, dielectric constant (e`) and dielectric loss tangent decrease for all the samples.Journal of Bangladesh Academy of Sciences, Vol. 39, No. 1, 1-12, 2015

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