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Dive into the research topics where L. I. Kravets is active.

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Featured researches published by L. I. Kravets.


Desalination | 2002

Water permeability of poly(ethylene) terephthalate track membranes modified in plasma

S. N. Dmitriev; L. I. Kravets; Vladimir Sleptsov; Vera M. Elinson

Abstract The properties of poly(ethylene) terephthalate track membranes (PET TM) subjected to effect of plasma of the RF-discharge in air have been investigated. The influence of conditions of a plasma treatment on the surface properties and hydrodynamic characteristics of the membranes has been studied. It has been found that the effect of the air plasma on the membranes studied results in a formation of asymmetric track membranes with a higher flow rate; the structure and chemical composition of their superficial layer are changed. It was shown that the presence of the modified layer on the membrane surface caused changing in their hydrodynamic characteristics — the water permeability of the membranes, processed in plasma, in a greater degree depends upon pH of a filtered solution.


High Energy Chemistry | 2009

Modification of properties of polymer membranes by low-temperature plasma treatment

L. I. Kravets; S. N. Dmitriev; A. B. Gil’man

The results of investigations into the use of low-temperature plasma for modification of porous polymer membranes are summarized. The basic lines of research in this area are considered. It is shown that plasma treatment is a quite effective tool for both improving the properties of existing polymer membranes and manufacturing new composite membranes with unique characteristics.


Surface & Coatings Technology | 2003

Production of asymmetric track membranes by gas-discharge method

L. I. Kravets; S. N. Dmitriev; Vladimir Sleptsov; Vera M. Elinson

An investigation of the structure and surface of poly(ethylene) terephthalate (PET) track membranes (TM) treated with a plasma RF-discharge in non-polymerizing gases has been performed. It was arranged that the effect of non-polymerizing gas plasma on the TM results in etching a surface layer of the membranes. The membrane pore size and the shape change in this case. It is shown that it is possible to change the structure of track membranes directly by gas-discharge etching. Depending on the choice of discharge parameters, it is possible to achieve etching conditions either in part of the channel or along the whole length of the pore channels. In both cases membranes with asymmetric pores are formed, which possess a higher porosity and flow rate.


Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms | 1995

Particle track detection and relaxation transitions in polymer

P.Yu. Apel; A. Yu. Didyk; B.I. Fursov; L. I. Kravets; V.G. Nesterov; G.S. Zhdanov

Abstract The sensitivity of polymeric track detectors is influenced by the registration temperature, i.e. the temperature of the polymer at the moment of the particle impact. Here, temperature effects on registration were considered in terms of molecular mobility and relaxation transitions. An attempt was made to find a correlation between the formation of heavy particle tracks in polypropylene (PP) and known transitions in this polymer. The track etch rate was measured as function of temperature in the range between 77 and 373 K. The obtained results were compared with radiothermoluminescence curves and thermally stimulated currents used for detecting charges in molecular mobility. It was found that the increase of the track etch rate with decreasing registration temperature seems to correlate with γ and glass transitions. The decrease of the track etch rate at the irradiation temperatures below 130 K can be assigned to the situation when oxidation is prohibited but some structure reparation reactions still take place. The heating of irradiated PP samples at the temperatures above ca. 340 K leads to a dramatic increase of damage in heavy ion tracks which can be associated with another transition occurring in semicrystalline polyolefins.


International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements | 1990

Track structure in some heavy-ion irradiated plastic films

P.Yu. Apel; A. Yu. Didyk; L. I. Kravets; V.I. Kuznetsov

Abstract The changes occurring in thin polyethylene terephthalate (PETP), polycarbonate (PC) and polypropylene (PP) films irradiated with heavy ions have been investigated. The track etching properties were studied in the submicroscopic diameter range of 1–60 nm. The method of absorption spectroscopy in ultraviolet (u.v.) and infrared (i.r.) regions, viscosimetry of polymer solution and sol-gel analysis were used to investigate radiation chemical processes in the polymers. It has been found that in all three polymers both the chain rupture and cross-linking processes occur simultaneously. The chain ruptures predominate in the track core with a diameter of several nanometers. The cross-linking process takes place in the vicinity of the track core at radii of up to 30–50 nm and appears most clearly in PETP where cross-linking events prevail over the destruction at large distances from the ion path.


Radiation Measurements | 1995

PLASMA MODIFICATION OF POLYETHYLENETEREPHTHALATE TRACK MEMBRANES

S. N. Dmitriev; L. I. Kravets; N.V. Simakina; V.V. Sleptsov

An investigation of the properties of polyethyleneterephthalate track membranes (PETP TMs) treated with the gaseous plasma discharge has been performed. The effect of plasma of inorganic gases showed a considerable change of the membrane surface properties. The sedimentation of the plasma polymerized films of organic compounds improves the physical, chemical and medicobiological performances of the PETP TMs and extends their applicability.


Materials Science Forum | 2010

Polymer Composite Nanomembranes with Asymmetry of Conductivity

L. I. Kravets; S. N. Dmitriev; G. Dinescu; V. Satulu; A. B. Gilman; M. Yablokov

This paper describes a structure and electrotransport properties of poly(ethylene terephthalate) track membrane (PET TM) modified by plasma of thiophene. It is shown that the deposition of the polymer on the track membrane surface by plasma polymerization of thiophene in case of forming a semipermeable layer results in creation of composite nanomembrane having in electrolyte solutions of asymmetry of conductivity - a rectification effect. It is caused by presence in the membrane of two layers with various functional groups, and also by changing of the pore geometry. Such type membranes can be used for creation of chemical and biochemical sensors.


Radiation Measurements | 1997

Registration temperature effect in polymers: Physico-chemical aspects

P.Yu. Apel; A. Yu. Didyk; B.I. Fursov; L. I. Kravets; V.G. Nesterov; L.I Samoilova; G.S. Zhdanov

Abstract Registration temperature effect in two different polymers - poly(ethylene terephthalate) (PET) and polypropylene (PP) films - is investigated. Temperature effects on track formation are considered in terms of molecular mobility and relaxation transitions. The track eth rate is measured as a function of irradiation temperature in the range of 77 to 373 K. The obtained results are compared with the radical yields, radiothermoluminescence curves and thermally stimulated currents measured with the aim of detecting changes in the mobility of macromolecules and radiolysis intermediates. It is found that the change of the track etch rate with changing registration temperature correlates with γ- and glass transitions in PP and with β-and glass transitions in PET.


Radiation Measurements | 2003

On the determination of and content in human tissues

B.M Bolotov; A.Ch Gaitinov; A.I Polyakov; Yu. T. Chuburkov; V.P. Perelygin; T. P. Drobina; L. I. Kravets; S. N. Timokhin; J.M Mietelski; Z. Szeglowski; R.I. Petrova; T Ruskov

Abstract The growing concentration of man-made Pu in natural environment—water, soil, plants and food can provide the serious danger for all kind of animals and especially for mankind. Actually, as it has been established recently, Pu is accumulated during the whole life and the dangerous concentrations are estimated to be 10 −12 – 10 −13 g of Pu/g of human tissues. We warn that now the average concentration of Pu in human body is not less that 10 −14 g/g and much higher for some “hot” regions in Europe and Asia. Here we present the data on 239 Pu and also 241 Am in human hair (Semipalatinsk region area) and in human gall stones of some samples from more “quiet” regions—Minsk (Belarus) and Krakow (Poland). At the measurements of 239 Pu concentration in human hair and gall stones it has been found that it varies from 10 −13 up to 3×10 −12 g/g for south part of heavily damaged Semipalatinsk nuclear bomb test site region. Further possible improvement of neutron–gamma activation analysis—up to the level of 10 −15 g/g of Pu in human tissues, based on application of ultra clean chemicals and track detectors and on selective extraction of U out of electroplated Pu layers in flow of chlorides at high temperatures are discussed. Such upgrading the method can allow one to use the specimens of human tissues as small, as 0.1– 0.2 g in the routine Pu analysis.


Russian Journal of Electrochemistry | 2011

Synthesis of bilayer composite nanomembranes with conductivity asymmetry

L. I. Kravets; S. N. Dmitriev; V.A. Altynov; V. Satulu; B. Mitu; G. Dinescu

The structure and electrochemical properties of polyethylene terephthalate track membranes modified in acetylene plasma are studied. It is found that polymer deposition on the track membrane surface using acetylene polymerization in plasma results in the case of formation of a semipermeable layer covering pores in formation of a composite nanomembrane featuring asymmetry of conductivity in solutions of electrolytes: a rectifying effect similar to that of a p-n junction in semiconductors. It is shown that the observed effect of conductivity asymmetry is caused by a significant decrease in the diameter of pores in the plasma-deposited polymer layer and a change in the pore geometry, same as existence of an interface between the initial membrane and polymer layer that have a different concentration of carboxyl groups in the surface layer. The impedance spectroscopy method allowed obtaining information on ion transfer in the studied membranes.

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S. N. Dmitriev

Joint Institute for Nuclear Research

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A. B. Gilman

Russian Academy of Sciences

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Vera M. Elinson

Moscow State Aviation Technological University

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Vladimir Sleptsov

Moscow State Aviation Technological University

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P.Yu. Apel

Joint Institute for Nuclear Research

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A. B. Gil’man

Russian Academy of Sciences

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A. Yu. Didyk

Joint Institute for Nuclear Research

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M. Yu. Yablokov

Russian Academy of Sciences

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Alexander Drachev

Russian Academy of Sciences

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V. A. Altynov

Joint Institute for Nuclear Research

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