Piezoactive porous polyvinylidene fluoride films obtained by melt extrusion followed by isometric annealing, uniaxial stretching, and thermal fixation have been studied. It is shown that two ...competing orientational processes occur under the uniaxial extension of the annealed films: the polymorphic transition of the nonpolar crystalline α-phase to the polar piezoactive β-phase and the formation of a porous structure. It has been established that the degree of orientation of the extruded films is a key factor determining the efficiency of both processes. The thermally stimulated depolarization method has been used to study the dipole relaxation in the oriented structure of the films and to determine the activation energy of the investigated processes. The films have been polarized by a corona discharge and a high-voltage contact method; the dependences of the piezoelectric modulus on the polarization conditions have been obtained. The maximum piezoelectric modulus
d
31
= 30.1 pC/N has been reached in the films polarized in a corona discharge field.
The effect of the annealing temperature on the characteristics of hard elastic polypropylene samples obtained by annealing of extruded films and having an oriented lamellar structure is studied. It ...is established using the methods of X-ray scattering and differential scanning calorimetry that the lamellae thickness, the large period, and the degree of orientation of the folded lamellae increase with an increase in the annealing temperature, which is accompanied by an increase in the melting temperature and enthalpy. Porous films are obtained by uniaxial extension of the annealed samples in the orientation direction. It is shown that the porosity and permeability of the porous films increase with an increase in the annealing temperature, owing to an increase in the number and sizes of the through channels. The mechanical characteristics (strength, elastic modulus, and break elongation) of the hard elastic and porous films are measured, and their relationship with changes in the structure and orientation of the samples, depending on the annealing temperature, is established.
Measurements in microwave electrotechnology Kalganova, S; Vasinkina, E; Alekseev, V ...
Journal of physics. Conference series,
12/2018, Letnik:
1124, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The classification of measurements in microwave electrical engineering is given, which takes into account all measurements at different stages of creation and operation of both a microwave electrical ...installation and its individual elements
The manufacturing process of poly(vinylidene fluoride) microporous films containing through flow channels and permeable to liquids has been elaborated. The process is based on polymer melt extrusion ...with subsequent stages of annealing, uniaxial extensions (“cold” and “hot” drawing), and thermal stabilization. The effect of orientation parameters (melt draw ratio and extension degrees) on overall porosity, permeability, morphology, and content of polar piezoactive
β
-phase in crystalline structure of the films was investigated by filtration porosimetry, sorptometry, scanning electron microscopy, X-ray scattering, and mechanical properties measurements. It is shown that the through pores were formed by a percolation mechanism. It is observed that permeability and the
β
-phase content increased with the growth of extension degree at the pore formation stages but the portion of
β
-crystallites decreased with increasing melt draw ratio at extrusion, which permitted to regulate the combination of through permeability and piezoactivity values by variation of the preparation process parameters.
Polyvinylidene f luoride porous films containing through channels have been prepared for the first time. The films have been obtained via melt extrusion followed by annealing, uniaxial extension, and ...thermal fixation. Uniaxial extension has been carried out in two stages (“cold” and “hot” drawing) at room and elevated temperature, respectively. The effect of orientation efforts during formation of the porous structure of films on the overall porosity, permeability for liquids, the content of piezoactive β- phase in the crystalline part of sample, and piezo modulus
d
31
has been studied. The formation of through channels occurs via a percolation mechanism at the overall porosity of 23%. Under uniaxial extension of films, the pore formation competes with the polymorphic α → β transition. The conditions of porous film preparation allowing one to attain the maximum through permeability and piezo modulus values have been determined.
A method to produce microporous polyvinylidene fluoride films characterized by a high content of a piezoactive crystalline phase and a developed relief surface is elaborated. The porous films are ...obtained in the process based on melt extrusion with subsequent isometric annealing and uniaxial extension. It is found that the samples have an oriented lamellar structure containing both α- and β-modifications of the crystallites. The effect of temperature and degree of uniaxial extention of the annealed films on the characteristics of the porous samples, that is, the content of the piezoactive crystalline β-phase, overall porosity, breakdown voltage and the piezoelectric modulus is studied.
The paper concerns to the so-called “Muscovy crown” (“corona moscoviae”) of Polish kings that existed in the 17th century. This insignia emerged in Rzeczpospolita during the Russian Time of Troubles, ...having until then belonged to the Tsar's treasury in Moscow Kremlin. The adherents of False Dmitry I took it in 1606, upon which it turned up in possession of King Sigismund III and his heirs. It appears that the “Muscovy crown” was made in England for Tsar Ivan the Terrible as a symbol of the Astrakhan Khanate, which had been annexed by the Russian State in 1556. Contemporary evidence from various sources, including diplomatic ones, points to the possibility of the crown being delivered as a token of strengthening trade relations between Moscow and London, where the Moscow company was functioning in this period. The crown was not taken as a gift, it was bought for a large sum. The article includes a detailed survey of English, Polish and Russian sources, both primary and indirect, while looking into the mode of use of such insignia at the court of Russian Tsars and grand princes. The article also mentions, together with Monomach's cap and Kazan cap, both of which are now kept in the Moscow Kremlin, the now-lost first Siberian and Astrakhan caps, the latter of which is identified with the object of study. The crown is also compared to the Eastern and Western jewelry traditions of the time. The article is prefaced with a brief narration of the circumstances in which the insignia had got the name it was since called in Polish historical writings. The author concludes with a hypothesis on why this crown and other similar to it were commissioned from foreign jewelers. This question, however, demands further research, as does the character of the insignia's use at the court of Polish kings.
This paper is devoted to the history and controversies surrounding the outstanding representative of Russian medieval literature from the late 14th century, the famous Zadonshchina. This work ...glorifies the military victory of the united forces of the Russian troops, led by Grand Prince Dmitry Donskoy, over the Tatar army on 8 September 1380, at Kulikovo Field near the Don River. This article presents arguments in favor of a Ryazan origin of the Zadonshchina text; furthermore, the article offers an explanation of the presence in the text of two “protagonists,” Grand Prince Dmitry Ivanovich and his cousin, Vladimir Andreyevich the Bold, Prince of Serpukhov. The joint rule of the “brothers” was a result of deaths caused by the plague in the Moscow ruling house, which took the dynasty to the brink of extinction. This feature of the political situation is reflected in the Zadonshchina text.
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