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

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.

scholarly journals Dielectric losses under heat treatment of dispersed media

2021 ◽  
Vol 24 (6) ◽  
pp. 1223-1231
Author(s):  
M. Yu. Buzunova
Keyword(s):  
Heat Treatment ◽  
Dielectric Loss ◽  
Electric Field ◽  
External Electric Field ◽  
Dielectric Losses ◽  
Loss Angle ◽  
Field Frequency ◽  
Dielectric Characteristics ◽  
Dielectric Loss Angle ◽  
Electric Field Frequency

The purpose of the paper is to study the dependence of dielectric losses of mechanically activated grain crops on example of wheat under heat treatment on temperature and external electric field frequency as well as to examine the effect of particle size of fine grain samples on grain electrophysical characteristics and dielectric losses. Experimental samples of dispersed systems with particle sizes in the range from 50 to 1000 μm are prepared by the method of mechanical activation. The temperature dependence of the dielectric loss angle tangent is measured using the dielectric method over a wide frequency range. The dependence of the dielectric loss angle tangent tgδ of mechanically activated wheat samples with the different degrees of particle dispersion in a wide temperature range from 20°C to 250°C with a heating rate of 0.7 deg/min is studied. It is found out that the external electric field frequency varies in the range from 25 Hz to 106 Hz. Electric capacitance and conductivity are measured using an E7-20 immitance meter and a specially designed measuring cell. Dielectric characteristics are calculated. Experimental data are presented in the form of graphs and diagrams. We have determined the correlation of the tangent of the dielectric loss angle tgδ with the frequency of the external electric field and temperature, which is most characteristic for fine samples. The most finely dispersed samples with a particle size of less than 50 microns are shown to have high electrical activity. Increase in the dielectric permittivity and the tangent of the dielectric loss angle is most noticeable at the frequencies below 100 Hz. The study of dielectric characteristics allows to choose an effective energy-saving drying mode of the crop under study.

An Investigation of the Effect of Laser Radiation on the Dielectric Parameters of Polymethyl Methacrylate

2018 ◽  
Vol 45 (5) ◽  
pp. 205-207
Author(s):  
Z.S. Torshkhoeva ◽  
A.S. Akhriev ◽  
B.I. Kunizhev
Keyword(s):  
Laser Radiation ◽  
Dielectric Loss ◽  
Dielectric Permittivity ◽  
Laser Pulse ◽  
Polymethyl Methacrylate ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Pulse Treatment ◽  
Dielectric Parameters ◽  
Temperature Range

The effect of laser radiation on the dielectric parameters of polymethyl methacrylate at a frequency of 50 kHz in the 170–420 K temperature range was investigated. It was shown that the laser pulse treatment of specimens leads to considerable changes in their dielectric permittivity and dielectric loss tangent.

scholarly journals Investigation of the dielectric properties of copolymers based on 2,3,4,5,6-pentafluorostyrene, styrene, 4-fluoro-α-methylstyrene and α-methylstyrene

2019 ◽  
Vol 60 (12) ◽  
pp. 87-90
Author(s):  
Ignat S. Dolgin ◽  
◽  
Pyotr P. Purygin ◽  
Yury P. Zarubin ◽  
◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Signal Generator ◽  
Frequency Signal ◽  
Current Frequency ◽  
Dielectric Characteristics ◽  
Methyl Styrene

Three new copolymers based on fluorine-containing derivatives of styrene and α-methylstyrene were obtained. According to the results of the previous stages of the study, copolymers based on styrene derivatives have improved dielectric properties compared to polystyrene and a copolymer of styrene and α-methyl styrene. The dielectric constant ε and dielectric loss tangent tanδ were measured for the initial and synthesized samples of styrene – α-methyl styrene copolymer at Samara Electromechanical Plant OJ-SC (Samara city, Russia). All measurements of dielectric characteristics were carried out at an alternating current frequency of 10 GHz on a pressed copolymer tablet with a diameter of 10 and a thickness of 3 mm. During the experiment, a measuring stand was used, consisting of a high-frequency signal generator G4-83, an electronically counting frequency meter Ch3-54 with a frequency converter YaZCh-43, a measuring amplifier U2-4; low-frequency signal generator G3-109; measuring unit FKDG 418151.002. The results obtained indicate high values of the dielectric constant. For samples of copolymers of α-methylstyrene – 4-fluoro-α-methylstyrene and styrene – 4-fluoro-α-methylstyrene, values of 4.63 and 4.21, respectively, were obtained. These dielectric permittivity values are superior not only to samples previously obtained during the experiment, but also to some other compounds that are widely used in industry. In particular, the dielectric constant of lavsan, which is used in the manufacture of capacitors, is 3.1-3.3. The improved dielectric constant values are probably related to the high-quality composition of the copolymer. Samples of the copolymer containing 4-fluoro-α-methylstyrene are significantly superior to the copolymer with 2,3,4,5,6-pentafluorostyrene for this characteristic. The values of the dielectric loss tangent are in the range from 8.74∙10−4 to 37.4∙10−4. Given the dielectric characteristics of the synthesized copolymers, we can conclude that there are good prospects for the use of fluorine-containing styrene copolymers. The obtained values of permittivity and dielectric loss tangent indicate a good possible competitiveness of new materials based on new copolymers. In the future, it is planned to study a number of other physicochemical properties of these materials in order to obtain the most complete spectrum of their characteristics.

scholarly journals Диэлектрическая спектроскопия пленок VO-=SUB=-2-=/SUB=-:Ge

2019 ◽  
Vol 45 (11) ◽  
pp. 44
Author(s):  
А.В. Ильинский ◽  
Р.А. Кастро ◽  
А.А. Кононов ◽  
М.Э. Пашкевич ◽  
И.О. Попова ◽  
...  
Keyword(s):  
Dielectric Loss ◽  
Dielectric Permittivity ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Complex Impedance ◽  
High Sensitivity ◽  
Circuit Diagram ◽  
Frequency Range ◽  
Cole Diagram ◽  
Additional Maximum

AbstractThe frequency dependencies of complex impedance $$\dot {Z}$$ , dielectric permittivity ε, and dielectric loss tangent tanδ of thin (1400 Å ) films V_1 –_ x Ge_ x O_2 (for x = 0 and 0.03) are studied in the frequency range of 10‒10^6 Hz at 300 K. It is found that, at x = 0, the frequency dependence of tanδ has a maximum at a frequency of 100 kHz, whereas at x = 0.03 an additional maximum in the region of 10 kHz is detected. Also, the Cole–Cole diagram of VO_2:Ge films acquires a feature in the form of an additional semicircle. Owing to the extremely high sensitivity of the dielectric spectroscopy method, the proposed equivalent circuit diagram of the sample allowed detecting the existence of two sets of VO_2 nanocrystallites in the V_0.97Ge_0.03O_2 film, including Ge-doped nanocrystallites and practically nondoped ones.

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

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.

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

2018 ◽  
Vol 13 (1) ◽  
pp. 75-92 ◽  
Author(s):  
N. N. Komova
Keyword(s):  
Thin Films ◽  
Dielectric Loss ◽  
Electric Field ◽  
Temperature Dependence ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Extreme Values ◽  
Alternating Current ◽  
Limited Region ◽  
Temperature Dependences

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.

scholarly journals ELECTRORHEOLOGICAL BEHAVIOR OF SUSPENSIONS BASED ON POLYDIMETHYLSILOXANE FILLED WITH HALLOYSITE

2018 ◽  
Vol 61 (6) ◽  
pp. 41 ◽  
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

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

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.

Method of calculating the dielectric loss tangent of binary systems

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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