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Influence of shielding gas and non-consumable electrode configuration on weld formation

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China Welding 2021年第4期30卷 17-24页

作者： Aleksandr Savinov Oleg Polesskiy Vladimir Lysak Pavel Krasikov artem Chudin Volgograd State Technical University Lenin av.28Volgograd400005Russia

The effect of the shielding gas composition and the cathode processing history on the weld formation quality during welding with a non-consumable electrode at high current was studied. The major reasons for pores, “waists” and undercuts formation during welding at high currents and speed are discrete melt movement to the solidification front due to the arc decline from the cathode axis and significant melt overhanging in the pool tail part caused by excessive peak pressure on the discharge axis. Cathode flow dispersion causes the lack of displacement of the molten metal which results in its laminar flow in the weld pool, uniform flow of the metal to the crystallization front and sound weld formation. The melt movement in the weld pool and eventually the welded joint quality is determined by the pressure distribution pattern on the welded metal surface and the anode spot lag from the electrode. It was demonstrated that non-consumable electrode configurations that provide arcing with a diffuse cathode spot and increased helium concentration in the inert atmosphere during welding with a conical electrode allow sound weld formation.

关键词： tungsten inert gas welding non-consumable electrode inert gas weld seam formation

Review of the relativistic magnetron

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Matter and Radiation at Extremes 2019年第6期4卷 44-62页

作者： Dmitrii Andreev artem Kuskov Edl Schamiloglu Department of Electrical and Computer Engineering University of New MexicoAlbuquerqueNew Mexico 87131-0001USA

The cavity magnetron is the most compact,efficient source of high-power microwave(HPM)*** imprint that the magnetron has had on the world is comparable to the invention of the nuclear ***-and low-power magnetrons are used in many applications,such as radar systems,plasma generation for semiconductor processing,and—the most common—microwave ovens for personal and industrial *** the invention of the magnetron in 1921 by Hull,scientists and engineers have improved and optimized magnetron technology by altering the geometry,materials,and operating conditions,as well as by identifying applications.A major step in advancing magnetrons was the relativistic magnetron introduced by Bekefi and Orzechowski at MIT(USA,1976),followed by the invention of the relativistic magnetron with diffraction output(MDO)by Kovalev and Fuks at the Institute of Applied Physics(Soviet Union,1977).The performance of relativistic magnetrons did not advance significantly thereafter until researchers at the University of Michigan and University of New Mexico(UNM)independently introduced new priming techniques and new cathode topologies in the 2000s,and researchers in Japan identified a flaw in the original Soviet MDO ***,the efficiency of the MDO has reached 92%with the introduction of a virtual cathode and magnetic mirror,proposed by Fuks and Schamiloglu at UNM(2018).This article presents a historical review of the progression of the magnetron from a device intended to operate as a high-voltage switch controlled by the magnetic field that Hull published in 1921,to the most compact and efficientHPMsource in the twenty-first century.

关键词： relativistic microwave mirror

Generation of synchronized x-rays and mid-infrared pulses by Doppler-shifting of relativistically intense radiation from near-critical-density plasmas

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Matter and Radiation at Extremes 2023年第2期8卷 6-13页

作者： Nikita A.Mikheytsev artem V.Korzhimanov Lobachevsky State University of Nizhny Novgorod 603022 Nizhny NovgorodRussia Federal Research Center Institute of Applied Physics of the Russian Academy of Sciences 603950 Nizhny NovgorodRussia

It is shown that when relativistically intense ultrashort laser pulses are reflected from the boundary of a plasma with a near-critical density,the Doppler frequency shift leads to generation of intense radiation in both the high-frequency(up to the x-ray)and low-frequency(mid-infrared)*** efficiency of energy conversion into the wavelength range above 3μm can reach several percent,which makes it possible to obtain relativistically intense pulses in the mid-infrared *** pulses are synchronized with high harmonics in the ultraviolet and x-ray ranges,which opens up opportunities for high-precision pump–probe measurements,in particular,laser-induced electron diffraction and transient absorption spectroscopy.

关键词： pump intense relativistic

High-spatial-resolution composition analysis of micro/nanostructures with a nanoscale compositional variation

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Nano Research 2023年第1期16卷 1090-1095页

作者： Meng Wang Xiaofeng Wang Zhican Zhou Feng Xia Haoran Zhang artem Shelaev Xinzheng Zhang Chuanfei Guo Jingjun Xu Qian Liu Chinese Academy of Sciences(CAS)Key Laboratory of Nanosystem and Hierarchical Fabrication CAS Center for Excellence in NanoscienceNational Center for Nanoscience and Technology&University of Chinese Academy of SciencesBeijing 100190China The MOE Key Laboratory of Weak-Light Nonlinear Photonics TEDA Applied Physics SchoolNankai UniversityTianjin 300457China Sino-German College of Intelligent Manufacturing Shenzhen Technology UniversityShenzhen 518118China Department of Materials Science and Engineering Southern University of Science and TechnologyShenzhen 518055China College of Physics Qingdao UniversityQingdao 26607China NT-MDT Co.Building 100 ZelenogradMoscow 124482Russia Institute of Physics Kazan Federal UniversityKazan 420008Russia Guangdong Provincial Key Laboratory of Functional Oxide Materials and Devices Southern University of Science and TechnologyShenzhen 518055China College of Material Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The composition of materials in a micro-/nano-devices plays a key role in determining their mechanical,physical,and chemical ***,for devices with a compositional change on nanoscale which can often be achieved by point-by-point direct writing technology using a focused ion beam(FIB),electron beam(EB),or laser beam(LB),but so far,nanoscale composition analysis of a large-area micro/nano structures with a variation composition remains a big challenge in cost,simpleness,and *** we present a feasible route to realize large-area composition analysis with nanoscale spatial resolution by using Raman *** experimentally verified the capability of this method by analyzing a complex Sn-SnOx system of a microscale grayscale mask with nanoscale spatial resolution of *** analyses using Auger electron spectroscopy,transmission electron microscopy,and atomic force microscopy indicated the effectiveness and practicality of our *** work opens up a way to analyze the composition of a large-area complex system at a nanoscale spatial resolution,and the method can be extended to many other material systems.

关键词： Raman spectroscopy nanoscale resolution composition analysis large-area

Crystal structure prediction at finite temperatures

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npj Computational Materials 2023年第1期9卷 306-313页

作者： Ivan A.Kruglov Alexey V.Yanilkin Yana Propad Arslan B.Mazitov Pavel Rachitskii artem R.Oganov Moscow Institute of Physics and Technology 9 Institutsky laneDolgoprudny 141700Russia Dukhov Research Institute of Automatics(VNIIA) Moscow 127055Russia Emerging Technologies Research Center XPANCEODubai Investment Park FirstDubaiUnited Arab Emirates Skolkovo Institute of Science and Technology Skolkovo Innovation Center30-1 Bolshoy blvdMoscow 121205Russia.

Crystal structure prediction is a central problem of crystallography and materials science, which until mid-2000s was consideredintractable. Several methods, based on either energy landscape exploration or, more commonly, global optimization, largely solvedthis problem and enabled fully non-empirical computational materials discovery. A major shortcoming is that, to avoid expensivecalculations of the entropy, crystal structure prediction was done at zero Kelvin, reducing to the search for the global minimum ofthe enthalpy rather than the free energy. As a consequence, high-temperature phases (especially those which are not quenchableto zero temperature) could be missed. Here we develop an accurate and affordable solution, enabling crystal structure prediction atfinite temperatures. Structure relaxation and fully anharmonic free energy calculations are done by molecular dynamics with aforcefield (which can be anything from a parametric forcefield for simpler cases to a trained on-the-fly machine learning interatomicpotential), the errors of which are corrected using thermodynamic perturbation theory to yield accurate results with full ab initioaccuracy. We illustrate this method by applications to metals (probing the P–T phase diagram of Al and Fe), a refractory covalentsolid (WB), an Earth-forming silicate MgSiO_(3) (at pressures and temperatures of the Earth’s lower mantle), and ceramic oxide HfO_(2).

关键词： prediction structure Crystal

Peculiarities of Ethylene Polymerization Reactions with Bis(imino)pyridyl Complexes of CoCl_(2) and FeCl_(2)

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Chinese Journal of Polymer Science 2024年第4期42卷 492-500页

作者： Laura A.Rishina Yury V.Kissin Svetlana S.Lalayan artem A.Antonov Vadim G.Krasheninnikov Alexander A.Gulin N.N.Semenov Federal Research Center for Chemical Physics Russian Academy of Sciences4 Kosygin St.Moscow119991Russia Department of Chemistry and Chemical Biology RutgersThe State University of New Jersey123 Bevier Rd.PiscatawayNJ08854USA Boreskov Institute of Catalysis Russian Academy of Sciences5 Lavrentieva Prosp.Novosibirsk630090Russia

The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. The complexes are converted into polymerization catalysts by reacting them either with polymethylalumoxane (MAO) or with a combination of Al(C2H5)2Cl and Mg(C4H9)2 at an [Al]:[Mg] ratio of ~3. Both MAO-activated complexes readily polymerize ethylene at 35 ℃ with the formation of linear, low molecular weight polymers with a narrow molecular weight distribution. The same complexes, when activated with the Al(C2H5)2Cl-Mg(C4H9)2 combination, form multi-center catalysts and generate polyethylenes with a broad molecular weight distribution.

关键词： Ethylene polymerization Bis(imino)pyridyl complexes of CoCl_(2)and FeCl_(2) Molecular-weight distribution Polymer chain structure

Synthesis ofγ-MnOOH nanorods by successive ionic layer deposition method and their capacitive performance

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Journal of Energy Chemistry 2017年第3期26卷 336-339页

作者： artem A.Lobinsky Valeri P.Tolstoy Department of Chemistry Saint-Petersburg State UniversityPeterhof198504 Saint-PetersburgRussian Federation

It was first shown in the present study that layers of manganite γ-Mn OOH can be deposited on the surface of a substrate by its multiple successive treatment by the solutions of MnSO;and K;S;O;using the successive ionic layer deposition（SILD） technique. Their analysis was carried out by the XRD, XPS, FT-IR,SEM and EDX methods. It has shown that the synthesized layers are formed by aggregates of nanorods up to 80–100 nm in length and approximately 8–10 nm in diameter. A probable sequence of chemical reactions leading to the formation of a layer of the given morphology is suggested. Testing of performance of supercapacitors with nickel foam electrodes incorporating the γ-Mn OOH layers in the 0.1 M KOH electrolyte at 1 A/g indicated the specific capacitance equal to 1120 F/g. After 1000 work cycles the observed degradation of this value was less than 3%.

关键词： Manganite Nanolayers SILD Supercapacitor

Gas-phase dehydration of glycerol over commercial Pt/γ-Al_2O_3 catalysts

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Chinese Journal of Chemical Engineering 2015年第7期23卷 1138-1146页

作者： Sergey Danov Anton Esipovich artem Belousov Anton Rogozhin Nizhny Novgorod State Technical University n.a. R.E. Alekseev Lobachevsky State University of Nizhni Novgorod National Research University

Gas-phase dehydration of glycerol to produce acmlein was investigated over commercial catalysts based on γ-Al2O3, viz. A-64, A-56,1-62, AP-10, AP-56, AP-64 and KR-104. To understand the effect of Cl anions, HCl-impregnated sup- ports have been investigated in the dehydration reaction of glycerol at 375 ℃. For comparison, various H-zeolites were also examined. It was found that the glycerol conversion over the solid acid catalysts was strongly dependent on their acidity and surface area. And the relationship between the catalytic activity and the acidity of the catalysts was discussed. The outstanding properties of Pt/γ-Al2O3 catalyst systems for the dehydration of glycerol were revealed. Pt/γ-Al2O3 catalyst （AP-64） showed the highest catalytic activity after 50 h of reaction with an acrolein selectivity of 65% at a conversion of glycerol of 90%. Based on these results, catalysts based on γ-Al2O3 appear to be most promising for gas phase dehydration of glycerol.

关键词： Glycerol Dehydration AcroleinZeolite Gamma alumina

All-optical generation of static electric field in a single metal-semiconductor nanoantenna

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Light(Science & Applications) 2023年第11期12卷 2350-2362页

作者： Yali Sun artem Larin Alexey Mozharov Eduard Ageev Olesia Pashina Filipp Komissarenko Ivan Mukhin Mihail Petrov Sergey Makarov Pavel Belov Dmitry Zuev School of Physics and Engineering ITMO UniversityLomonosova 9Saint Petersburg 191002Russia Center for Nanotechnologies Alferov UniversityKhlopina 8/3Saint Petersburg 194021Russia Higher School of Engineering Physics Peter the Great Saint Petersburg Polytechnic UniversityPolitekhnicheskaya 29Saint Petersburg 195251Russia

Electric field is a powerful instrument in nanoscale engineering,providing wide functionalities for control in various optical and solid-state *** development of a single optically resonant nanostructure operating with a charge-induced electrical field is challenging,but it could be extremely useful for novel nanophotonic ***,we show a resonant metal-semiconductor nanostructure with a static electric field created at the interface between its components by charge carriers generated via femtosecond laser *** study this field experimentally,probing it by second-harmonic generation signal,which,in our system,is time-dependent and has a non-quadratic signal/excitation power *** developed numerical models reveal the influence of the optically induced static electric field on the second harmonic generation *** also show how metal work function and silicon surface defect density for different charge carrier concentrations affect the formation of this *** estimate the value of optically-generated static electric field in this nanoantenna to achieve≈10^(8)V/*** findings pave the way for the creation of nanoantenna-based optical memory,programmable logic and neuromorphic devices.

关键词： antenna optical field