In the work, the density of energy states in the valence band of metallic phase nanograins spherical shape with diameters from 1 to 50 nm was calculated. It was found that the energy distances between neighboring energy states in the valence band of metallic phase nanograins are from 0.1 to 2·10-6 eV for the above-mentioned diameter range. There are many orders larger distance, than characteristic for macroscopic-sized metal, the value of which is approximately 10-22 eV. The calculations show that in nanocomposites consisting of metallic phase nanograins with dimensions below 20 nm placed in a dielectric matrix with high resistivity, there is no characteristic for the macroscopic dimensions band conductivity at low temperatures. The results of the calculation of the distance between neighboring energetic states in the valence band of metallic phase nanograins are consistent with the values obtained experimentally.
In the paper, direct current conductivity of percolation channels in composite cellulose - insulating oil - water nanodrops, was analyzed. Number of nanodrops in macroscopic length channel (on the order of a few millimeters) is about 106. In such nanocomposites below the percolation threshold, direct current conduction takes place by electron tunneling between the potential wells generated by the nanoparticles of the conducting phase. On the basis of the tunneling mechanism, percolation channel resistance was calculated in which the nanoparticles are randomly distributed. Gauss probability distribution of the distances between neighboring nanodrops was used for the calculations. The standard deviation of the average distance between neighboring nanodrops was chosen as the disorder factor. It was established that the percolation channel resistance value is lowest in the case of regular distribution of the nanodrops. With the increase in disorder, which is characterized by an increase in the standard deviation value, the resistance of the percolation channel increases.
This paper presents the results of the AC conductivity of electrical pressboard production company Weidman with a water content from 0,6% to 7% by weight, impregnated with MIDEL 7131 synthetic ester. Frequency and temperature dependencies of the AC conductivity were determined. The Arrhenius plots were developed for the whole range of measurement frequencies, from which the activation energies of the AC conductivity were determined. It was found that changes in AC conductivity can be described by means of two activation energies. Each of these activation energies decreases with the increase of the measurement frequency. This may mean, in our view, that these differences are due to changes the environment occurring water nanoparticles. Some of the nanoparticles be are located in the environment cellulose material, while the other part - in the environment the MIDEL 7131 ester.
The article presents research on the percolation time of oil through the electrotechnical pressboard, which results in determining the statistical distribution of capillary radii, involved in the process of impregnation of paper-oil insulation. On the basis of the conducted research, a positive effect of pressboard calendering on its operation was detected.
Paper presents method of the percolation phenomenon visualization through modeling metal-dielectric type nanocomposite. Model was based on high voltage discharge in air between metallic discs modeling the metallic phase. A research station for visualization and simultaneous registration of percolation process was developed and built. Models have been executed in 2 dimension plane of randomly arranged metallic discs. The quantity of metal rings models different value of metal nanoparticles concentration. For different concentration of nanoparticles relationship of discharge voltage to metal concentration was determined.
The paper presented the method of visualization the phenomenon of percolation in the model of nanocomposite type metaldielectric, based on the occurrence of high voltage jumps in the air between metallic discs modeling the metallic nanoparticles. A research station for visualization and registration of the percolation process was developed and built. The models were made from metallic discs, randomly arranged on a plane for different values of „nanoparticles” concentration. The dependence of the jump voltage from the concentration was established. Visual images of percolation for different „nanoparticles” concentration were registered.
The paper presents investigated the dependencies of DC conductivity electrical pressboard impregnated insolating oil of moisture content and electric field strength. The studies were conducted for measuring temperature in the range of 20 °C to 80 °C and the electric field intensity in the range of 10 kV/m to 1000 kV/m. With approximate waveforms in double logarithmic coordinates conductivity depending on the intensity of the electric field exponential function determined coefficients of determination R2. The value of this ratio is close to unity, which provides high accuracy measurements of conductivity and the exact stability and temperature measurements. It was found that changes in the electric field intensity will decrease the activation energy of conductivity of about 0.01 eV, thus increasing the DC conductivity of about 1.5 times.
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