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

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.

Gamma induced changes in Makrofol/CdSe nanocomposite films

In our present work, we applied ex-situ casting procedure to prepare a nanocomposite (NCP) from Makrofol polycarbonate (PC) and CdSe nanoparticles. The CdSe nanoparticles were prepared by thermolysis procedure in the presence of N2 gas flow. Rietveld refinement of x-ray data illustrated that the CdSe accustoms cubic zinc blend structure of a 6.057 Å lattice parameter and 2 nm typical grain size. Samples from the prepared NCP were exposed to γ dosages (20-250 kGy). The modifications induced in the NCP films owing to γ dosages have been studied. The γ irradiation (50-250 kGy) causes the crosslinks that reduces the optical bandgap from 4.15 to 3.81 eV; associated with an increase in dielectric parameters and refractive index. This is attributed to the increase of the mass fraction of the disordered regions as specified by XRD. The PC-CdSe NCP was found to have reaction to color modification which makes it suitable in saleable reproduction on printing press.

Исследования диэлектрических свойств нефтяных дисперсных систем в зависимости от соотношения асфальтосмолистых веществ

The degree of influence of the electromagnetic field on oil dispersed systems depends on the dielectric properties of these systems, in particular oil. Dielectric properties of oil depend on the content of high molecular weight polar components: asphaltenes and resins. In this regard, a study was carried out of the dielectric properties of oil in the radio-frequency range, depending on the content of asphalt-resinous substances in it. The obtained results of experimental studies show the correlation of dielectric parameters with the ratio of the content of resins and asphaltenes in oil.

Dielectric Relaxation Studies of Hydrogen Bonded Complexes of Benzamide and Acetamide with 4-substituted Phenols Using X-band Microwave Frequency

At 308 K, using a 9.37 GHz dielectric relaxation setup, dielectric studies of hydrogen bonded complexes of benzamide and acetamide with 4-fluorophenol, 4-bromophenol, 4-chlorophenol, and 4-iodophenol in benzene were performed. Various dielectric parameters (such as ??, ??, ?0, and ??) were tested. The steric interactions of the proton donor determined the group rotation relaxation time t(2), whereas the significance of Higasi’s single frequency method for multiple relaxation time t(1) was determined by the hydrogen bonding power of the phenolic hydrogen. The presence of a 1:1 complex system between the prepared samples, as well as a charge transfer between the free hydroxyl group of phenols and the carbonyl group of amides was confirmed by the fact that the relaxation time and molar free energy activation of the 1:1 molar ratio were greater than some other higher molar ratios (i.e. 3:1, 2:1, 1:2, 1:3).

Improving photoluminescence, optical and electrical characteristics of PMMA films with gamma irradiation

Polymeric materials are macromolecules, essentially a combination of numerous repeated subunits. Polymers are innovative and advanced materials that currently have a strong impact on our daily lives. In recent years, polymer use has been prominent due to the materials’ distinctive properties; thus, they entered different fields of science, technology and industrial-biomedical applications.The improvement of photoluminescence, optical and electrical characteristics of non-conducting Poly(methyl methacrylate) (PMMA) films was studied. Upon gamma irradiation of various doses, the photophysical and electrical properties of PMMA films were investigated using photoluminescence spectroscopy, ultraviolet–visible (UV-Vis) spectroscopy and the LCR Meter Bridge Circuit technique. The fluorescent response improved the photoluminescence (PL) spectral emission peaks according to gamma values. Strong fluorescence peaks appeared with the highest gamma dose. The UV–Vis results revealed a significant red-shift in the absorption edge as gamma doses increased. This shift exhibits a continuous decrease in the energy band gap values (from 3.50 to 2.60 eV for direct transition and from 3.05 to 1.55 eV for indirect transition). This was due to the formation of carbon clusters, which led to an increase in the electrical conductivity and improved the dielectric parameters of the irradiated PMMA films. Among a variety of measurements presented and discussed in the present study, the electrical measurements showed improved electrical characteristics of gamma-irradiated PMMA films.

APPLICATION OF nonPLANAR MICROSTRIP MICROWAVE STRUCTURES FOR gauging the DIELECTRIC PARAMETERS OF LIQUIDS AND SOLID MATERIALS

В данной статье отражаются основные результаты компьютерного моделирования, практической реализации и применения непланарной микрополосковой периодической СВЧ структуры в качестве преобразовательного элемента в задачах контроля диэлектрических параметров материалов и веществ. Основными достоинствами подобной реализации датчика являются большая чувствительность и относительно небольшие линейные размеры по сравнению с аналогичными, реализованными на основе планарных СВЧ структур. Помимо этого, благодаря непланарной форме микрополосковой линии расширяется диапазон областей применения СВЧ датчиков. This article reflects the main results of computer modeling, practical implementation and application of a nonplanar microstrip periodic microwave structure as transducer in the problems of gauging the dielectric parameters of materials and substances. The main advantages of such a sensor implementation are high sensitivity and relatively small linear dimensions in comparison with similar ones based on planar microwave structures. In addition, due to the nonplanar shape of the microstrip line, the range of applications for microwave sensors is expanded.

Study of Dielectric, Polarization Properties of Cyclopentanol and Their Solutions in Cyclopentane by a New Variation Method

Results of calculating the theoretical principles of the variational method for measuring the dielectric parameters of polar liquids: cyclopentanol and its solutions in cyclopentane have been shown in the paper. Their dielectric constant ξ' and dielectric losses ξ'' are calculated. Solutions to the equations were found and a graphical solution method and an automated method for calculating ξ' and ξ'' were developed on the basis of this method. Comparison with the results of other methods revealed that these indicators are at the same time minimal within 1.5–2.0%.