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Ситников, Николай Николаевич

Организационные подразделения

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Институт лазерных и плазменных технологий

Стратегическая цель Института ЛаПлаз – стать ведущей научной школой и ядром развития инноваций по лазерным, плазменным, радиационным и ускорительным технологиям, с уникальными образовательными программами, востребованными на российском и мировом рынке образовательных услуг.

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Николай Николаевич

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The microstructure of rapidly quenched TiNiCu ribbons crystallized by isothermal and electropulse treatments
(2020) Sitnikov, N. N.; Shelyakov, A. V.; Khabibullina, I. A.; Visotina, E. A.; Ситников, Николай Николаевич; Шеляков, Александр Васильевич
© 2020 IOP Publishing Ltd. All rights reserved.The work is devoted to the study of the effect of isothermal and electropulse heat treatments on the structure of Ti50Ni25Cu25 (at.%) alloy with the shape-memory effect. The alloy was fabricated by rapid quenching from the liquid state (melt spinning technique) at the cooling rate of the melt of about 106 K/s in the form of a layered amorphous-crystalline ribbon with a thickness of 28 μm. To obtain a completely amorphous state, the ribbon thickness was reduced to 22 μm by means of electrochemical polishing. The alloy samples were subjected to the electropulse treatment (dynamic crystallization) by passing a single electric current pulse with a duration of 10 ms through the sample. The electron microscopy and X-ray diffraction studies have shown that electropulse treatment leads to a significant change in the crystalline structure being formed, in comparison with that obtained by isothermal crystallization. It was revealed that after dynamic crystallization, the microstructure of alloys in cross-section has a non-uniform distribution of crystals (grains) over the ribbon thickness. A structure of columnar crystals is formed near the ribbon surfaces, while individual crystals or grouped large crystals are present in the ribbon bulk. In addition, the columnar structure is textured.
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Layered Self-Healing Composite Material with an Internal Functional Layer Based on Borosiloxane
(2020) Khabibullina, I. A.; Mashchenko, V. I.; Mostovaya, K. S.; Vysotina, E. A.; Sitnikov, N. N.; Shelyakov, A. V.; Ситников, Николай Николаевич; Шеляков, Александр Васильевич
© 2020, Pleiades Publishing, Ltd.Abstract: Borosiloxane as a functional layer in multilayer self-healing composites is studied. The provisions and principles of self-healing in artificial materials are considered. It is substantiated that rapid self-healing requires at least two factors: directional mass transfer and self-adhesion of the boundaries brought into contact. Either fluid media or viscous-flow materials may act as self-healing materials. Borosiloxane is presented as a promising material of a self-healing viscous matrix in multilayer composites or sandwich panels. The addition of various fillers, e.g., fibers, to borosiloxane leads to a decrease in fluidity; owing to the low molecular weight, high diffusion of macromolecules ensuring high self-adhesion is maintained. The addition of polyester fibers to borosiloxane makes it possible to effectively control fluidity with the high diffusion rate and consequently the coalescence rate of the material surfaces brought into contact being maintained. Experimental samples of borosiloxane are obtained from synthetic rubbers during their interaction with boronic acid in a heated reaction vessel. The addition of 6 wt % polyester fibers ~3 mm long to the synthesized borosiloxane confines its spreading, preserves its shape owing to the stiffness of the fiber framework, and at the same time retains the properties of self-adhesion while the disconnected boundaries are brought into contact. The creation of ensembles from successive borosiloxane layers with different fluidity in one multilayer material allows providing the final composite material with high self-healing characteristics after a penetration defect is made. The effect of self-healing of the developed layered composite in the case of through puncture and cut is shown.
Только метаданные
Influence of copper content and thermal treatment on shape memory effect in rapidly quenched TiNiCu alloys
(2021) Borodako, K. A.; Shelyakov, A. V.; Sitnikov, N. N.; Zaletova, I. A.; Sevryukov, O. N.; Бородако, Кирилл Анатольевич; Шеляков, Александр Васильевич; Ситников, Николай Николаевич; Севрюков, Олег Николаевич
© 2021 Institute of Physics Publishing. All rights reserved.Amorphous alloys of the TiNi - TiCu system with a copper content of 25 to 40 at.% were prepared by planar flow casting at a melt cooling rate of 106 K/s. Crystallization of the alloys was carried out by isothermal annealing and by action of single electric pulse with a duration of 5 ms. Shape memory behavior and structure of the alloys was investigated by means of bending tests and X-ray phase analysis. It was found that increasing the copper content to above 30 at.% considerably reduces the plasticity and shape memory effect of the alloys. However, abrupt decreasing the annealing duration significantly improves the shape memory performance due to prevention of the formation of brittle Ti-Cu phases in the alloys structure.
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Layered nanostructured composites with self-healing effect based on plastic borosiloxane matrices
(2019) Khabibullina, I. A.; Mashchenko, V. I.; Sitnikov, N. N.; Ситников, Николай Николаевич
© Published under licence by IOP Publishing Ltd.This paper presents a layered composite material with an internal self-healing matrix based on borosiloxane compounds. The effects of self-healing in materials of various chemical nature (polymers, cements, ceramics, metals and composite materials) are considered and evaluated from the point of view of their practical application and the creation on their basis of self-healing composites. The properties and characteristics of borosiloxane are described. The prospects of using of borosiloxane as an internal self-healing matrix of layered or reinforced composites are shown. The effect of self-healing of the developed layered composite at breakdown and cut is demonstrated.
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Effect of Boric Acid on the Structure and Properties of Borosiloxanes
(2021) Mashchenko, V. I.; Khabibullina, I. A.; Chausov, D. N.; Spiridonov, V. V.; Sitnikov, N. N.; Shelyakov, A. V.; Ситников, Николай Николаевич; Шеляков, Александр Васильевич
© 2021, Pleiades Publishing, Ltd.Abstract: Borosiloxane materials obtained by mixing and thermostatting of hydroxyl-terminated polydimethylsiloxane and boric acid are studied. Samples synthesized at room temperature and at a temperature above 220°С are nontransparent rubberlike masses. Washing of boric acid yields single-phase transparent borosiloxanes demonstrating the rubberlike behavior. Studies are carried out using elemental analysis, dynamic light scattering, synchronous thermal analysis, and polarization optical microscopy. The viscoelastic properties of the samples are characterized by rheological methods and the ability of polymer ball-like samples to spread and rebound. It is shown that in initial states they contain boric acid microcrystalline inclusions that scatter visible light. An increase in the synthesis temperature and the presence of unreacted boric acid improve the elasticity of the materials and decrease their thermal stability. The content of boron in borosiloxane obtained at an increased temperature is an order of magnitude higher than that in borosiloxane synthesized at room temperature, whereas the radius of the effective hydrodynamic sphere is smaller by a factor of 5 than that in the high-temperature borosiloxane. The rheological properties of the tested samples are different. These materials show promise as components of multilayer self-healing and shock-absorbing composites and materials with controlled tackiness.
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Effect of Electric Pulse Treatment under Tensile Stress on the Properties of Rapidly Quenched Ti50Ni20Cu30 Alloy
(2021) Shelyakov, A. V.; Sitnikov, N. N.; Zaletova, I. A.; Borodako, K. A.; Шеляков, Александр Васильевич; Ситников, Николай Николаевич; Бородако, Кирилл Анатольевич
© 2021, Allerton Press, Inc.Abstract: Amorphous ribbons from a rapidly quenched alloy of the TiNi–TiCu quasi-binary system with copper content of 30 at % are crystallized via electric pulse treatment with variable durations of impact in the range of 1 to 100 ms at external tensile stress of up to 250 MPa. It is shown that the formed bimorph structure of columnar and coarse crystals is characterized by considerable differences when compared to a rapidly quenched alloy with 25 at % copper. An increase in tensile stress does not affect the phase composition or microstructure of the alloy, but it does lower the critical temperatures of martensitic transformation.
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INFLUENCE OF INITIAL STATE AND HEAT TREATMENT CONDITIONS ON THE STRUCTURE OF RAPIDLY-QUENCHED TiNiCu ALLOY
(2021) Dyadechko, A. A.; Zaletova, I. A.; Shelyakov, A. V.; Sitnikov, N. N.; Borodako, K. A.; Шеляков, Александр Васильевич; Ситников, Николай Николаевич; Бородако, Кирилл Анатольевич
© 2021, Pleiades Publishing, Ltd.Abstract: Amorphous-crystalline alloy of the TiNi–TiCu quasi-binary system with 25 at.% copper content is prepared in the form of thin ribbons by rapid quenching from a liquid state. Completely amorphous ribbons are obtained using electrochemical polishing. It is shown that the crystal structure prepared by high-speed electropulsing heat treatment differ significantly from that prepared by isothermal heat treatment. The initial ribbon crystallizes as column-like crystals growing from both surfaces of the ribbon and as large lens-like crystals in the volume of the ribbon. The structure of column-like crystals reproduces the morphology and texture of the original crystalline layer. Reducing the electropulsing time to 1 ms increases the fraction of column-like crystals while their height increases and the width decreases. After the amorphous ribbon is crystallized, the structures of column-like crystals on both surfaces have similar crystallographic orientations.
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Study of the Effect of Tensile Stress During Electric Pulse Treatment of Amorphous Rapidly Hardened Ti50Ni25Cu25 Alloys on Crystal Structure Formation
(2021) Ashmarin, A. A.; Sitnikov, N. N.; Zaletova, I. A.; Shelyakov, A. V.; Ситников, Николай Николаевич; Шеляков, Александр Васильевич
© 2021, Springer Science+Business Media, LLC, part of Springer Nature.The effect of a tensile stress during electric pulse heat treatment on crystal structure formation in amorphous rapidly hardened Ti50Ni25Cu25 alloys is studied. Amorphous ribbons are subjected to a 10-msec electric pulse treatment in a free condition and under a tensile stress of 5.9 and 29.7 MPa. Specimen structure is studied by optical and scanning electron microscopy, energy dispersive analysis, and differential scanning calorimetry. It is shown that amorphous ribbon crystallization under electric pulse treatment with a tensile load occurs primarily due to growth of surface columnar crystals from the ribbon surface into the depth and then from the internal part of a ribbon due to spherulite formation and growth.
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Effect of aluminum alloying on the structure and properties of rapidly quenched TiNiCu alloy
(2021) Shelyakov, A. V.; Sitnikov, N. N.; Zaletova, I. A.; Eroshenkov, S. A.; Sevryukov, O. N.; Шеляков, Александр Васильевич; Ситников, Николай Николаевич; Севрюков, Олег Николаевич
© 2021 Institute of Physics Publishing. All rights reserved.The efficiency of shape memory alloys for the MEMS technology has been recently demonstrated. Quasibinary intermetallic TiNi-TiCu alloys produced by rapid quenching from liquid phase in the form of thin (about 40 μm) ribbons are an attractive material for the fabrication of micro-actuators due to their narrow temperature hysteresis of the shape memory effect (SME) and relatively large recoverable strain. In order to broaden the functionality of SME microdevices, in this work we have alloyed TiNiCu containing 25 at.% copper with aluminum. The results have shown that alloying with 0.6 at.% Al increases the cast characteristics of the composition and favors its amorphization. Upon crystallization by isothermal annealing or electropulse treatment the resultant microstructure and SME properties of the Al containing alloy change but slightly in comparison with the original alloy however there is a significant shift (by more than 15°C) of the SME temperature range toward lower temperatures.
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Study of the Structure, Phase Transformations, and Shape Memory Effect in Amorphous-Crystalline TiNiCu Alloy
(2025) Shelyakov, A. V.; Sitnikov, N. N.; Khachatrian, D. A.; Zaletova, I. A.; Шеляков, Александр Васильевич; Ситников, Николай Николаевич; Хачатрян, Давид Арменович