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47 results on '"Mikheev, K."'

11. Laser-induced graphene and its modification with polypyrrole for increasing microsupercapacitor capacitance

Author

null Mikheev G. M., null Bulatov D. L., null Zonov R. G., null Syugaev A. V., and null Mikheev K. G.

Abstract

Laser-induced graphene (LIG) films were synthesized by line-by-line scanning of cw CO2 laser focused radiation on the surface of industrial polyimide film as a result of pyrolysis of its near-surface layer. The structure of the synthesized film material is shown to be heterogeneous in thickness by Raman spectroscopy. The results of the study of the effect of the laser power and the distance between the lines on the specific electrical capacitance c of the synthesized material in aqueous solution of sulfuric acid are presented. It is shown that modification of LIG with polypyrrole (PPy) allows to increase c up to 60 mF/cm2. PPy-modified LIG films were used to make a prototype of a flexible film microsupercapacitor with an area of 8 cm2, using a gel electrolyte based on sulfuric acid and polyvinyl alcohol, with a 230 mF capacitance. Keywords: laser-induced graphene, electric capacitance, polypyrrole, microsupercapacitor.

Published
2023

19. The effect of line-by-line laser scanning on the properties of laser-induced graphene

Author

null Mikheev G. M., null Bulatov D. L., null Syugaev A. V., null Zonov R. G., and null Mikheev K. G.

Abstract

Technology of polyimide (PI) film carbonization by direct laser treatment attracts much attention due to the versatility and ease of obtaining the carbon material, laser-induced graphene (LIG), used in the creation of various sensors and functional devices. In this work LIG film structures are obtained by line-by-line scanning of a cw CO2 laser beam over the surface of the PI film. The synthesized carbon film material is studied by optical and scanning electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. It is shown that the Raman spectra of a single LIG line and a set of overlapping LIG lines significantly differ from each other. It is found that multiple laser scanning of the PI film leads to a marked decrease in the number of defects in the LIG structure as well as to a significant decrease in the specific surface resistance of the synthesized film material. The results obtained can be used in the synthesis of LIG film structures with improved characteristics. Keywords: laser-induced graphene, polyimide film, line-by-line laser scanning.

Published
2022

20. Optical Harmonics Generation under the Interaction of Intense (up to 1014 W/cm2) Mid-Infrared Femtosecond Laser Radiation of a Fe:ZnSe Laser System with a Dense Laminar Gas Jet.

Author

Rumiantsev, B. V., Mikheev, K. E., Pushkin, A. V., Migal, E. A., Stremoukhov, S. Yu., and Potemkin, F. V.

Subjects
*LASER beams, *HARMONIC generation, *FEMTOSECOND lasers, *ENERGY consumption, *GASES, *RADIATION
Abstract

Low-order (fifth, seventh, and ninth) harmonics have been generated under the interaction of intense (I ~ 1014 W/cm2) femtosecond mid-infrared radiation of a laser system based on a Fe:ZnSe crystal (wavelength is 4.55 μm, pulse duration by the FWHM level of intensity is 160 fs, and the pulse energy is up to 3.5 mJ) with an argon jet (pressure is up to 10 bar) in the tunneling ionization regime (Keldysh parameter is ). The maximum energy efficiencies of the 5th, 7th, and 9th harmonic generation are 2 × 10–7, 6 × 10‒9, and 3 × 10–10, respectively. It has been established that nonlinear effects of propagation of generating radiation under an increase in the pressure of the gas jet begin to significantly affect the process of generation. [ABSTRACT FROM AUTHOR]

Published
2022
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43. Effect of the nature of an extractant on the composition and properties of lipids extracted from peat.

Author

Mal'tseva, E., Mikheev, K., Yudina, N., Burkova, V., and Il'ina, A.

Abstract

The effect of an extractant on the yield of lipids depending on the moisture content of peat was studied. A maximum yield of lipids was obtained upon extraction with a mixture of methyl tert-butyl ether and ethanol in a ratio of 1: 1. It was found that the use of an ethyl acetate-ethanol or methyl tert-butyl ether-ethanol solvent mixture led to a decrease in the acid and peroxide numbers of lipids regardless of the moisture content of peat. The antioxidant activity of lipids increased with the moisture content of peat. [ABSTRACT FROM AUTHOR]

Published
2012
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46. Enhanced saturable absorption in the laser-treated free-standing carbon nanotube films

Author

Vanyukov, V. V., Mikheev, K. G., Nasibulin, A. G., Svirko, Y., Mikheev, G. M., University of Eastern Finland, Udmurt Federal Reseatch Center of the Ural Branch of the Russian Academy of Sciences, Department of Chemistry and Materials Science, Aalto-yliopisto, and Aalto University

Subjects
Physics::Optics
Abstract

We demonstrate an increase of optical transmittance and saturable absorption of laser-treated free-standing single-walled carbon nanotube (SWNT) films. The combined acid and low-power non-destructive laser treatment ensures an enhancement of linear transmittance across the visible range and double-digit increase of the saturable absorption of femtosecond laser radiation at 795 nm. The saturable absorption coefficient and the ratio of saturable to non-saturable losses increase by 26% and 35%, correspondingly, while the saturation intensity decreases by 20% because of the treatment. Our analysis indicates that with the performed treatment one can significantly improve the nonlinear optical properties of free-standing SWNT-based ultrafast saturable absorbers.

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