New Details to Relaxation Dynamics of Dielectric Composite Materials Comprising Longitudinally Opened Carbon Nanotubes

© 2017 American Chemical Society. The difference between intact and longitudinally opened multiwalled carbon nanotubes (referred to as CNT and OCNT) has been studied in their application as conductive filler in polymer composite materials. The dielectric properties have been studied in a broad frequency range at the temperatures varying from 293 K through 373 K. Introduction of as little as 0.5% and 1.0% of the conductive filler dramatically increased both parts of the complex permittivity. The percolation threshold is registered at ∼1.5% filling fraction. The main frequency dispersion of the dielectric permittivity lies in the low frequency end of the tested spectrum: from 10 2 Hz through 10 4 Hz. At equal filling fractions, the permittivity of the OCNT-based samples exceeds that of the intact CNT-based samples. The relaxation dynamics is largely affected by the nanoscale geometry of the filler: the temperature dependence of such parameters as dielectric strength, activation energy, and relaxation time demonstrated significant difference between the charge transfer mechanism in the CNT-based and OCNT-based samples. The obtained activation energy is 150 and 85 kJ/mol for materials comprising CNTs and OCNTs, respectively. The relaxation mechanism is complex, and the exact factors behind the macroscopic dielectric properties of the tested materials cannot be singled out with certainty. Several experimental data points suggest that the individual nanotubes, not their aggregates, play the major role in the observed electrical properties of the composites. At the low loading fractions, we attained the highest dielectric strength values among all the data reported by the present day for the CNT/polymer host systems

Conductivity in disordered structures: Verification of the generalized Jonschers law on experimental data

The generalized Jonschers law for complex conductivity (derived earlier) is tested on available experimental data. We suggest some criteria, which are used for verification of the analytical expression describing the data related to complex conductivity. It is shown that the generalized Jonschers law is suitable for description of the electrode polarization phenomenon. © 2012 American Institute of Physics

Water structure analysis considering dielectric spectrum in microwave range

In this paper the analysis of the water dielectric spectrum in the relaxation (1 cm) and microwave (100 mu) range on the basis of the theoretical results presented in Ref. was made. The absorption spectrum in the microwave range as well as the relaxation spectrum are shown to be the results of the orientational polarization. In the framework of the existing water structure models this result corresponds to the models in which one assume two types of the molecules for the fixed time moment. They are the molecules having a hydrogen bonds and ones free from them. Free molecules either can be located in the voids or can make the exchange between the clasters. In the analysis suggested we do not use the definite water structure model. The dielectric spectrum parameters allow us estimate the value of the abnormal water expansion within the freezing process. Our results agree well with the experimental data

Study of electret state in polylactic acid with nanosized filler by dielectric spectroscopy

© 2016 Author(s).Dielectric spectroscopy method was implemented to study electret state in both polylactic acid and its composites with nano-sized aerosil. Two components of the activation energy for the dielectric relaxation process, related to glass transition and segmental mobility of the macromolecules, were obtained. The lifetime and thermal stability of the electret state increased due to the addition of the filler. The optimal SiO2 content for negative corona electrets was found to be 4 wt. %

Study of polylactic acid electret by dielectric spectroscopy

© 2016 AIP Publishing LLC.Correlation between the electret and dielectric properties of the PLA samples charged at different conditions was studied. Electret state of polylactic acid characterized by macromolecule segmental orientation is reflected on dielectric spectra that were used to calculate relaxation energy

Dielectric spectroscopy of amino alcohols at low temperatures

© 2016 Pleiades Publishing, Ltd. The dielectric properties of three vicinal amino alcohols are studied at temperatures in the range of -140-70°C and the frequency interval of 0.1 Hz to 1 MHz. The temperature dependences of the observed relaxation processes indicate both glass transition and melting processes. The relatively high conductivity of the samples was considered from the viewpoint of proton conductivity through a network of hydrogen bonds of amino alcohol molecules

SOVIET-INDIAN RELATIONS (1955 - 1971): THE BIRTH OF A FRIENDSHIP

The most important stage in the relations between the USSR and India is the second half of the 1950s and the 1960s, when the systemic factors led to the transformation of the two states into natural strategic allies. The article studies the evolution of Soviet and Indian foreign policies and the impact of exogenous and endogenous factors on their strategies. The analysis of unique, special and universal aspects of the general strategy of two states reveals their geo-economic and geopolitical interests and conditions which promoted or limited the realization of these interests. All key subsystems of bilateral relations (political, economic, military-political and culturalcivilizational) are studied in their correlations. The analysis of the political parameters covers the summits, political consultations on a broad range of issues, cooperation between the USSR and India at the global and regional levels. The article focuses on the analysis of the global changes that largely determined the evolution of the Soviet-Indian relations. The significance of the formation of all-party consensus in India on foreign policy (from the middle of the 1950-s) is stressed. This concord concerns the main directions and macro objects, while there are differences in the methods of their achievement, which is linked both with different political and ideological platforms and with global changes in the world system. The analysis of Soviet-Indian economic relations covers the growth of trade turnover and changes in its structure, cooperation in the field of heavy industry and energy, the supply of Soviet machinery and equipment. Close military-political ties that is the cornerstone of the present bilateral relations originated in this period. At the same time it is necessary to point out the relative closeness of two countries in the sphere of cultural life (notwithstanding enormous differences of Russian and Indian civilizations): spiritualism as en immanent element of both cultures opposes materialism and consumerism of the developed world and multinational and multiconfessional composition of both countries brings them closer

Conductivity in disordered structures: Verification of the generalized Jonscher's law on experimental data

The generalized Jonscher's law for complex conductivity (derived earlier) is tested on available experimental data. We suggest some criteria which are used for verification of the analytical expression describing the data related to complex conductivity. It is shown that the generalized Jonscher's law is suitable for description of the electrode polarization phenomenon

Water structure analysis considering dielectric spectrum in microwave range

In this paper the analysis of the water dielectric spectrum in the relaxation (1 cm) and microwave (100 mu) range on the basis of the theoretical results presented in Ref. was made. The absorption spectrum in the microwave range as well as the relaxation spectrum are shown to be the results of the orientational polarization. In the framework of the existing water structure models this result corresponds to the models in which one assume two types of the molecules for the fixed time moment. They are the molecules having a hydrogen bonds and ones free from them. Free molecules either can be located in the voids or can make the exchange between the clasters. In the analysis suggested we do not use the definite water structure model. The dielectric spectrum parameters allow us estimate the value of the abnormal water expansion within the freezing process. Our results agree well with the experimental data