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The Comparative Study of the Structure and Phase Composition of Ni-Based Coatings Modified by Plasma Jet or Electron Beam

100%
Alontseva D., Russakova A., Krasavin A.
Acta Physica Polonica A
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2016
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vol. 129
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issue 4
838-841
EN
The paper deals with the results of the comparative study into the structure and phase composition, as well as some properties (microhardness, corrosion resistance) of Ni-based powder coatings before and after their modification by DC electron beam or DC pulse plasma jet, according to the modes recommended on the basis of model calculations of the temperature profiles at irradiation. The transmission electron microscopy and X-ray analysis have revealed that irradiation leads to an increase in the volume fraction of reinforcing nanosized intermetallic components in the coatings. There were established certain similarities and differences in the structure and properties of the coatings modified by different types of irradiation. The microhardness of the irradiated coatings has increased in both cases along with the growth of the volume fraction of the CrNi₃ particle phase. However, it was found that the diffusion zone in the coatings modified by plasma jet is higher than that of the coatings modified by electron irradiation. The coating surface melted by the electron beam has a marked reduction of its roughness and better homogenization of the microstructure therefore demonstrating better adhesion and corrosion resistance.
2
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Modification of Ni-Based Plasma Detonation Coatings by a Low-Energy DC E-Beam

100%
Alontseva D., Krasavin A., Pogrebnjak A., Russakova A.
Acta Physica Polonica A
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2013
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vol. 123
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issue 5
867-870
EN
The paper presents the study of Ni-based coatings deposited by plasma detonation onto a steel substrate after direct current low-energy electron beam irradiation and proposes explicit parameters of the electron beam for modification of coatings by irradiation. The choice of irradiation modes is based on the calculation of the temperature profile in the Ni-Fe two-layer absorbents using numerical simulation methods. It was found that the exposure of coatings to irradiation according to the recommended modes leads to the evolution of the structural-phase state of coatings and substantial improvement of performance properties of modified surfaces. The wear resistance of modified surfaces increases 3 times, the microhardness increases on the average 25%.
3
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Formation of Dislocation Structure in LiF Crystals Irradiated with Swift Heavy Ions under Oblique Incidence

100%
Russakova A., Akilbekov A., Dauletbekova A., Baizhumanov M.
Acta Physica Polonica A
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2014
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vol. 125
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issue 6
1257-1260
EN
The structural modifications of LiF irradiated with swift heavy ions under oblique angles have been investigated using AFM, SEM, chemical etching, nanoindentation and optical absorption spectroscopy. LiF crystals were irradiated under incidence angles of 30 and 70 degrees with 2.2 GeV Au (fluence 5 × 10^{11} ions cm^{-2}) and 150 MeV Kr ions (fluence 10^{12}-10^{14} ions cm^{-2}). Structural study on sample cross-sections shows that two damage regions, (1) nanostructured zone and (2) dislocation rich zone, which are typical for irradiations at normal incidence, appear also in samples irradiated under oblique angles. However in the latter case a more complex structure is formed that leads to stronger ion-induced hardening.
4
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Synthesis, Structure, and Catalytic Activity of Au/Poly(ethylene terephthalate) Composites

100%
Mashentseva A., Borgekov D., Zdorovets M., Russakova A.
Acta Physica Polonica A
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2014
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vol. 125
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issue 6
1263-1267
EN
A standard technique of electroless gold deposition was modified by changing the composition of Ag-based activation solution. This allows preparation of two types of poly(ethyleneterephthalate) (PET) track etched membranes coated entirely with gold after 1, 5, and 24 h of reaction at 4°C. After dissolving the polymer template, gold nanotubes with outer diameter of 70-80 nm were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Reduction of p-nitrophenol to p-aminophenol by sodium borohydride was used to investigate the catalytic activity of as-prepared Au/PET membrane. All experiments were carried out for five consecutive cycles and rate constant of the pseudo-first-order reaction was calculated. It was found that Au/Ag/PET composites prepared after activation for 3 min in Ag-based solution (with potassium sodium tartrate as reducing agent) more effective catalyst (k=0.087 min^{-1}) was obtained when the Au/PET samples activated with ammonia silver nitrate solution (k=0.041 min^{-1}).
5
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Modeling of Processes Taking Place during Powder Coating Treatment by an Electron Beam or a Plasma Jet

100%
Alontseva D., Krasavin A., Kolesnikova T., Russakova A.
Acta Physica Polonica A
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2014
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vol. 125
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issue 6
1275-1279
EN
This paper considers the problem of finding the temperature field in two-layer metallic materials heated by a moving source of radiation. It describes developed by the authors numerical method for solving the problem of heating a two-layer plate by a moving axially symmetric surface heat source with regard to the function of distribution of the power density of the beam for which the program of computation in C^{++} was implemented. The calculation results were used for selecting the optimal parameters (speed and power density of the source) of modifying radiation of protective powder coatings on steel substrates.
6
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Temperature Dependent Catalytic Activity of Ag/PET Ion-Track Membranes Composites

76%
Borgekov D., Mashentseva A., Kislitsin S., Kozlovskiy A., Russakova A., Zdorovets M.
Acta Physica Polonica A
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2015
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vol. 128
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issue 5
871-874
EN
Electroless deposition has been used to coat finely porous polyethylene terephthalate (PET) track-etched membranes with silver, forming silver nanotubes within the pores with inner and outer diameters of 60 and 100 nm. The sample's X-ray diffraction pattern shows a face-centered cubic crystalline phase of silver with the lattice constant 4.0838 nm. The average size of silver nanoclusters, as obtained from the scanning electron microscopy analysis is about 30 nm which is consistent with the X-ray diffraction results. The temperature dependent catalytic activity of prepared composites is demonstrated for two model reactions such as reduction of 4-nitrophenol (4-NP) and decomposition of hydrogen peroxide. Apparent constant rates and activation energy as well as reusability of catalysts were determined. The developed composite catalyst could be used consecutively for several runs without any damages for 4-NP reduction. For hydrogen peroxide reaction decomposition the reaction rate of the second cycle is reduced 2.4 times. Moreover, the second reuse reduced conversion of H₂O₂ to 54.7% suggests removal of active Ag centers during the first cycle of testing.
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