Synthesis of (PVA/PEG: ZnO and Co3O4) Nanocomposites: Characterization and Gamma Ray Studies

Polymer blend (PVA/PEG) and its nanocomposites with constant ZnO and different ratios of Co3O4 NPs films synthesized using solution cast technique. The obtained products were identified by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Optical characteristics have been studied by UV-visible spectroscopy. FT-IR spectra confirmed of the produce the functional groups present in polymer nanocomposite systems. XRD analysis confirmed the formation nanocomposite films more crystalline from the polymeric matrix. SEM showed a powerful dispersion of ZnO and Co3O4 NPs on the surface of the polymeric matrix. The D.C electrical conductivity of the polymeric system (PVA/PEG) increases after addition of and Co3O4 NPs for all temperatures under test. D.C measurements indicate that all films having one activation energy, and that its value increases with the increase in the percentage of addition. The A.C electrical properties showed that the dielectric constant and dielectric loss for all films decreases with the increase of the electric field frequency, and that its values increase with the increasing of the wt.% of Co3O4 NPs. The (PVA/PEG) and its nanocomposite with ZnO and different wt.% of Co3O4 films have good linear attenuation coefficients for gamma ray radiation.

Preparation of single-layer coating polyester cotton composites with electric loss of their electromagnetic properties

In this paper, single-layer coated polyester–cotton composites were prepared using PU-2540 waterborne polyurethane resin as the adhesive, graphite and silicon carbide as functional particles, and adopting a coating technology on the plain polyester–cotton fabric. First, the single-layer graphite-coated polyester cotton composite was prepared with graphite as the functional particle, and the influence of graphite content on the reflection loss and shielding effectiveness was studied. When the applied electric field frequency is 1610 MHz and the graphite content is 40 wt%, the minimum reflection loss is −26 dB; when the applied electric field frequency is 39.9 MHz and the graphite content is 50 wt%, the maximum shielding effectiveness is 12 dB. Then the single-layer silicon carbide-coated polyester–cotton composite was prepared with silicon carbide as the functional particle, and the influence of silicon carbide content on the reflection loss and shielding effectiveness was studied. With the applied electric field in the range 500∼3000 MHz, the greater the content of silicon carbide, the smaller the reflection loss, the better the wave-absorbing ability, the larger the shielding effectiveness, and the better the shielding performance. Finally, the single-layer graphite/silicon carbide-coated polyester–cotton composites were prepared by doping graphite and silicon carbide in different proportions, and the influence of doping ratio on dielectric properties, reflection loss, and shielding effectiveness was investigated. The real part of the dielectric constant of the material was highest – that is, the polarization ability of the material was best when there were only graphite particles in the doping medium and the silicon carbide content was 0. The imaginary part of the dielectric constant and the tangent of loss angle of the material were the highest – that is, the loss and attenuation ability of the material were best – when the doping ratio of graphite to silicon carbide is 4:1. With the applied electric field in the range 500∼3000 MHz, and with increasing graphite content, the reflection loss of the material became smaller, showing an enhanced wave-absorbing property, and the shielding effectiveness of the material increased, showing an enhanced shielding performance.

Modified Morris-Lecar neuron model: Effects of very low frequency electric fields and of magnetic fields on the local and network dynamics of an excitable media

A Morris-Lecar neuron model is considered with Electric and Magnetic field effects where the electric field is a time varying sinusoid and magnetic field is simulated using an exponential flux memristor. We have shown that the exposure to electric and magnetic fields have significant effects on the neurons and have exhibited complex oscillations. The neurons exhibit a frequency-locked state for the periodic electric field and different ratios of frequency locked states with respect to the electric field frequency is also presented. To show the impact of the electric and magnetic fields on network of neurons, we have constructed different types of network and have shown the network wave propagation phenomenon. Interestingly the nodes exposed to both electric and magnetic fields exhibit more stable spiral waves compared to the nodes exhibited only to the magnetic fields. Also, when the number of layers are increased the range of electric field frequency for which the layers exhibit spiral waves also increase. Finally the noise effects on the field affected neuron network are discussed and multilayer networks supress spiral waves for a very low noise variance compared against the single layer network.

Dielectric losses under heat treatment of dispersed media

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.

XXIV Международный симпозиум Нанофизика и наноэлектроника", Нижний Новгород, 10-13 марта 2020 г. Влияние граничных условий на высокочастотную электропроводность тонкого проводящего слоя в продольном магнитном поле

The problem of the high-frequency conductivity of a thin conductive layer in a longitudinal magnetic field is solved in terms of kinetic approach taking into account diffuse-mirror boundary conditions. Specularity coefficients of layer surfaces are assumed to be different. An analytical expression is derived for dimensionless integral conductivity as a function of dimensionless parameters: layer thickness, electric field frequency, magnetic induction, chemical potential and surface specularity coefficients. The limiting cases of a degenerate and non-degenerate electron gas are considered. A comparative analysis of theoretical calculations with experimental data is carried out. The method to determine specularity coefficients and mean free path of charge carriers from the longitudinal magnetoresistance of a thin metal film is illustrated.

Precision Measurement and Comprehensive Analysis of Dielectrophoretic Crossover Behavior of Micro-Particles

To be one of the hottest topics recent years, a huge amount of diverse applications of the Dielectrophoresis (DEP) phenomenon have been discovered and published. The DEP force mainly comes from the difference in dielectric polarizability between the suspended particles and the suspending medium and it only occurs when the applied AC electric field is non-uniform in space. There are many important parameters that affect the magnitude, direction and the crossover frequency of the DEP force, such as the applied AC electric field frequency, electric field distribution, applied voltage, medium conductivity, particle permittivity, particle size, the electric double layer of particles and so on. Variation of each of the above mentioned parameters could cause great difference in the dielectrophoretic behavior of particles. People have made great efforts in quantifying the influence of them but there are still a lot of uncertain relations and mechanisms to be verified. Therefore, we present a comprehensive analysis of the crossover behavior of micro-particles due to DEP and several concurrent phenomena through both experiments and finite element simulations and provides an important foundation for further insight into electrical properties of micro-particles and for more advanced Lab-on-chip devices developments.

Dielectric Properties and Switching Processes of Barium Titanate–Barium Zirconate Ferroelectric Superlattices

This article is devoted to the investigation of the dielectric and repolarization properties of barium zirconate and barium titanate BaZrO3/BaTiO3 superlattices with a period of 13.322 nm on a monocrystal magnesium oxide (MgO) substrate. Synthesized superlattices demonstrated a ferroelectric phase transition at a temperature of approximately 393 °C, which is far higher than the Curie temperature of BaTiO3 thin films and bulk samples. The dielectric permittivity of the superlattice reached more than 104 at maximum. As the electric field frequency increased, the dielectric constant of the studied superlattice decreased over the entire study temperature range, but position of the maximum dielectric constant remained the same with changing frequency. The temperature dependence of the inverse dielectric permittivity 1/ε(T) for the studied samples shows that, in the investigated superlattice, both Curie–Weiss law and the law of “two” were followed. Additionally, the ε(T) dependences showed practically no temperature hysteresis with heating and cooling. Samples of synthesized superlattices had a relatively small internal bias field, which was directed from the superlattice towards the substrate.