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Main achievements in 2023The development of technology of plasma spraying of silicide coatings to protect zirconium alloys from oxidationI.B. Gnesin, D.V. Prokhorov, N.I. Gnesina, B.A. Gnesin, V.I. Vnukov, M.I. Karpov, I.S. Zheltyakova, T.S. Stroganova et al. Within fundamental pilot work towards creating accident-tolerant nuclear fuel, a laboratory (scalable) technology for applying silicide coatings on zirconium alloys was developed. As a result of this work, a molybdenum silicide coating was successfully applied on a zirconium-based alloy (E110) by atmospheric plasma spraying for the first time. Coatings based on the binary eutectic Mo5Si3 + MoSi2 were deposited onto the surface of E110 alloy sheets. The features of the structure and phase composition of the coatings after deposition and their evolution as a result of isothermal annealing at 1300 °C were studied. The kinetics of the diffusion interaction between the coating and the base material was investigated. The possibility of successfully protecting a zirconium alloy from oxidation at 1100 °C in the air by the complex deposition of a molybdenum silicide coating was experimentally shown. The effectiveness of this coating against oxidation was confirmed by heat resistance tests. 
Figure 1. Appearance of the samples after the heat resistance test: fully protected by the coating (a); partially protected by the coating (b); uncoated (c).
Publication: Gnesin I.B., Prokhorov D.V., Gnesina N.I., Nekrasov A.N., Gnesin B.A., Vnukov V.I., Karpov M.I., Zheltyakova I.S., Stroganova T.S. On the Plasma Spraying of Silicide Coatings to Protect Zirconium Alloys from Oxidation (2023) Journal of Surface Investigation, 17 (5), pp. 1065 - 1073 DOI: 10.1134/S102745102305018X The study was carried out with the financial support of the Russian Foundation for Basic Research and Rosatom State Corporation within the framework of scientific project no. 20-21-00137. Engineering Sciences, branches The development of new physical principles for the construction of THz phase shiftersK.R. Dzhikirba, I.V. Kukushkin, V.M. Muravev et al. The THz frequency range (100 GHz - 3 THz) remains one of the least investigated ranges of the electromagnetic spectrum. Nevertheless, this frequency range has a number of distinctive features that make its exploration crucial for a number of sectors of the civil and military industry. The most important applications of sub-THz electronics include the creation of a phased array, where the radiation direction can be quickly changed using applied voltage. Today, centimeter-wavelength phased arrays are widely used in radiolocation, ground-to-space communications, advanced satellite internet systems, Earth remote sensing, and radio vision for security systems. Higher-frequency sub-THz phased arrays are also beginning to find various civil and military applications. For example, the possibility of using millimeter phased arrays is relevant in the new generation of 6G wireless communication systems. Nowadays, the sub-THz range provides one or two orders of magnitude higher spatial resolution and data transmission rate for radars and ground-to-space communication systems. A new mechanism for constructing packaged semiconductor phase shifters was developed and studied at ISSP RAS. These systems use the relativistic plasmonic effect, which is realized in 2D-electronic systems with high conductivity. In this case, an important property of semiconductors is used: the ability to adjust system parameters, e.g., the phase of transmitted radiation, by applying voltage to the microstructure gate. The most important advantage of the technology is that it is implemented on the basis of GaAs semiconductor technology. This enables easy scaling of the number of phase shifters on a semiconductor wafer, thus creating arrays of any size. This approach is particularly attractive for creating a new generation of phased arrays.  
Figure 1. Developed phased array system and its characteristics: dependencies of a change in the phase on the voltage on the gate and the frequency.
Publication: Dzhikirba, K.R. Demonstration of the plasmonic THz phase shifter at room temperature / K.R. Dzhikirba, A. Shuvaev, D. Khudaiberdiev, I.V. Kukushkin, V.M. Muravev // Applied Physics Letters. – 2023. – Vol. 123, Iss. 5. – P. 52104. – DOI:10.1063/5.0160612 RSF project no. 19-72-30003 Physical Sciences, branch 1.3.2.5. “Physics of Nano- and Heterostructures, Mesoscopic Physics” A novel method for deposition of gas-tight SiC coatingsS.L. Shikunov, A.V. Kaledin, I.A. Shikunova, B.B. Straumal, V.N. Kurlov A novel method for the deposition of gas-tight silicon carbide protective coatings based on the direct interaction of carbon formed during the high-temperature pyrolytic decomposition of hydrocarbon molecules with a silicon melt contained in the surface layer of the material to be coated and/or silicon vapor, the source of which is the silicon melt placed in the thermal zone of a furnace, was developed. The effective protection of such materials as SiC-C-Si and SiC-C-MoSi2 ceramics (Fig. 1), carbon–carbon composite materials (CCCMs) (Fig. 2), structural graphite, and refractory metals and metal alloys by this coating was experimentally demonstrated. The tests showed the high thermal oxidation and thermal shock stability of the protective coating, as well as its good adhesion to the substrate. 
Figure 1. Structure of a SiC-C-MoSi2 ceramic composite material with a protective SiC coating at different magnifications.
 
Figure 2. Structure of a CCCM with a protective SiC coating at different magnifications.
Publication: Shikunov, S. Novel Method for Deposition of Gas-Tight SiC Coatings / S. Shikunov, A. Kaledin, I. Shikunova, B. Straumal, V. Kurlov // Coatings. – 2023. – Vol. 13, Iss. 2. – P. 354. – DOI:10.3390/coatings13020354 State task: “Physics and Technologies of New Materials and Prospective Structures, no. 122040600127-3” Physical Sciences, branch 1.3.2.10. “Physical Materials Science and Physics of Defects” Spin chaos of exciton polaritons in a magnetic fieldS.S. Gavrilov, N.N. Ipatov, V.D. Kulakovskii The spin properties of exciton polaritons in a micropillar cavity placed in a static magnetic field and excited by a resonant light wave were studied theoretically. Owing to the Zeeman effect, a nonlinear polariton system has two branches of optical response that are characterized by opposite circular polarizations. An indirect mechanism of polarization reversal was predicted, according to which the current state of the system undergoes a transition to dynamical chaos and then the alternative spin state is established spontaneously. Such spin switches mediated by a chaotic stage can proceed in both directions near the same critical excitation amplitude, so that the sign of the circular polarization of the cavity radiation is directly determined by the intensity of the optical pump. Therefore, the predicted mechanism allows one to implement a controlled two-way switch of the polarization of the micropillar cavity radiation.  Publication: S. S. Gavrilov, N. N. Ipatov, and V. D. Kulakovskii. Spin Chaos of Exciton Polaritons in a Magnetic Field. JETP Lett. 118(9), pp. 637-643 (2023) DOI: 10.1134/S002136402360310X RSF project no. 23-22-00455 Physical Sciences, branches Practical implementation of prototypes of superconducting neuronsA.S. Ionin, N.S. Shuravin, L.N. Karelina, A.N. Rossolenko, M.S. Sidel’nikov, S.V. Egorov, V.V. Bol’ginov et al. Prototypes of superconducting neurons were fabricated and studied for the first time. They were single- or two-junction interferometers, part of the circuit of which was shunted by an additional inductance (sigma neuron and Gauss neuron, respectively). The samples were designed in the form of multilayer thin-film interferometers located over a thick superconducting screen. That provided conditions close to earlier theoretical models. To fabricate the samples, an eight-stage technological process was used, which had been developed and implemented in the Laboratory of Superconductivity at ISSP RAS. The subject of study was the transfer function of the sample. It was shown that the transfer functions of the samples, which were the dependence of the output magnetic flux on the input magnetic flux, generally corresponded to the theoretical predictions. However, an effect of the direct transfer of an input signal to the measuring circuit was found, which was due to the emergence of circulating supercurrents in the screen as a response to the input signal. It was shown that the transfer function of a Gauss neuron could be modified due to the interaction with the measuring circuit. The results confirmed the possibility of implementing superconducting neural networks and indicated ways for improving superconducting neurons.  
Figure 1. Micrographs of the implemented sigma (a) and Gauss (b) neurons.
Publications:
RSF project no. 23-72-00053 Physical Sciences, branch 1.3.2.8. “Quantum Macrophysics, Bose-Einstein Condensates, Superconductivity” Novel carbon fibre/titanium compositesS.T. Mileiko, A.A. Kolchin, I.D. Petukhov, N.A. Prokopenko, V. Yu. Malyshev (The work is carried out in cooperation with UMATEX, Rosatom.) The Cu coating of carbon fibre fabricated by UMATEX has allowed the research group from ISSP RAS to develop a novel method for producing carbon fibre/titanium composites. In contrast to the method for producing a carbon/titanium composite previously developed at ISSP RAS, firstly, the novel method does not require a special intermediate matrix for infiltrating the carbon fibre (this essentially simplifies the technology); secondly, it prevents the formation of titanium carbide on the fibre surface (this, in particular, follows from observations of the microstructure of the composite - Fig. 1); thirdly, as a result, the strength (up to 1700 MPa) and Young’s modulus (up to 200 GPa) of the new-generation composite bring its characteristics closer to those of good steel at a density of about 5 g/cm3. There is no analogue of this type of structural materials. 
Figure 1. Microstructure of the reinforcing layer of the carbon/titanium composite.
With proper development of the work, the use of this type of composites instead of metal alloys (titanium or steel) will significantly improve the characteristics of flying apparatuses, primarily, supersonic aircraft, as well as deep-sea vehicles. The method is now patented (RU 2 818 920) and will be disclosed in a paper accepted for publication in Russian journal Deformation and Fracture of Materials. RSF project no. 23-19-00419 Physical Sciences, branch 1.3.2.10. “Physical Materials Science and Physics of Defects” Synthesis of superconducting zirconium trihydride under high hydrogen pressureV.E. Antonov, V.I. Kulakov, V.D. Muzalevsky, N.S. Orlov, A.V. Palnichenko, Y.M. Shulga Previously unknown zirconium trihydride ZrH3 and trideuteride ZrD3 with hexagonal close-packed (hcp) metal lattices were synthesized at ISSP RAS at a hydrogen/deuterium pressure of 9 GPa and a temperature of 873 K using toroid-type high-pressure chambers with a large reaction volume. In contrast to many new hydrides synthesized in diamond anvil cells in recent years, relatively massive (about 25 mg each) samples of ZrH3 and ZrD3 were retained and studied at atmospheric pressure. This made it possible to experimentally determine their chemical composition and superconducting transition temperatures Tc = 11.6 K and 9.5 K, respectively (see Fig. 1). The normal isotope effect (a lower Tc value for the compound with a heavier hydrogen isotope) distinguishes zirconium trihydride from previously studied superconducting metal hydrides with an atomic ratio of H/Me ≤ 3.75, which all showed an inverse isotope effect. The inverse isotope effect in superconductivity of metal hydrides was discovered more than 40 years ago, but its commonly accepted explanation turned out to be incorrect [V.E. Antonov et al., J. Alloys Compd. 905 (2022) 164208]. The results for hcp-ZrH3 demonstrated that this effect is not an intrinsic property of hydrides with H/Me ≤ 3.75.  Figure 1. Temperature dependencies of the ac magnetic susceptibility χ = χ' – iχ'' in the vicinity of the superconducting transition in powdered hcp-ZrH3 and hcp-ZrD3 samples containing a certain amount of non-superconducting ZrH2 and ZrD2 phases. The real part χ' and imaginary part χ'' of the susceptibility are shown in the upper and lower panels, respectively. The measurements were carried out in a drive magnetic field with an amplitude of 3.5 mOe and a frequency of 1.5 kHz. The temperatures Tc of the onset of the superconducting transition were determined from the position of the extra-loss peak in the χ''(T) dependencies.
Publication: Kuzovnikov, M.A. Synthesis of superconducting hcp-ZrH3 under high hydrogen pressure / M.A. Kuzovnikov, V.E. Antonov, V.I. Kulakov, V.D. Muzalevsky, N.S. Orlov, A.V. Palnichenko, Y.M. Shulga // Physical Review Materials. – 2023. – Vol. 7, Iss. 2. – P. 24803. – DOI:10.1103/PhysRevMaterials.7.024803 State task: “Coherent States, Dynamics, and Phase Transitions in Liquids and Solids, no. 122040600126-6” RFBR project no. 20-02-00638 Physical Sciences, branch 1.3.2.2. “Structural Studies of Condensed Media, Relationship between the Structure and Properties” Thermally stable concentrated solutions of molecular hydrogen in lithium silicate glassV.S. Efimchenko, M.A. Korotkova, K.P. Meletov et al. Materials for hydrogen storage should release absorbed hydrogen at temperatures of -10÷100 °С and pressures close to normal ones to be used in practice. In the present work, the effect of lithium cations on the thermal stability of hydrogen solutions in the Li2O·6SiO2 glass was experimentally studied for the first time. The kinetics of decomposition of solutions containing 0.39 and 0.25 mole of molecular hydrogen was investigated by Raman spectroscopy under isothermal annealing and thermal desorption of hydrogen. The activation energy of hydrogen release from the surface glass layer Ea=(0.419±0.019) eV/H2 determined by means of Raman spectroscopy turned out to be higher than Ea=(0.16±0.02) eV/Н2, which had been obtained earlier for a hydrogen solution in silica glass, indicating the enhancement of the interaction between hydrogen molecules and glass atoms. This resulted in the higher decay time constant τ = 3220 sec at room temperature compared to τ = 3 sec for hydrogen solutions in pure silica glass. It was shown by the thermal desorption method that weak hydrogen diffusion in the lithium silicate glass additionally increased the time constant of solution decomposition to τ ≈ 16000 sec at room temperature.   Figure 1. (Left panel) Inset: spectrum of the hydrogenated lithium silicate glass at different time intervals. Main figure: change in the intensity and position of the H2 stretching line with time at 308 K. (Right panel) Time constants in Arrhenius coordinates.
Publication: Efimchenko, V.S. Thermally Stable Concentrated Solutions of Molecular Hydrogen in Bulk Lithium Silicate Glass / V.S. Efimchenko, M.A. Korotkova, K.P. Meletov, S. Buchner // Journal of Physical Chemistry C. – 2023. – Vol. 127, Iss. 28. – P. 13538–13546. – DOI:10.1021/acs.jpcc.3c02644 RSF project no. 23-23-00426 Physical Sciences, branch 1.3.2.10. “Physical Materials Science and Physics of Defects” A method for producing ZnSe:Cr single crystals for active and passive components of near-IR lasersN.N. Kolesnikov, D.N. Borisenko, A.V. Timonina, D.S. Denisenko, E.B. Borisenko A novel method has been proposed for producing ZnSe single crystals uniformly doped with chromium (Fig. 1) with a Cr concentration of 1016-1020 cm-3 for use in the optics (Fig. 2) of near-IR lasers applied in range finding equipment.  Figure 1. ZnSe:Cr single crystal (Cr concentration of 6×1018 cm-3) cleaved along (110) parallel to the growth direction.
 
Figure 2. Laser optics made of single-crystal ZnSe:Cr: passive modulator (SESAM-type saturable absorber) on the left and active laser components on the right. Polished blanks without coatings are shown.
The method was developed based on a previously created method for doping ZnSe crystals with Cr [1] and includes the synthesis of CrSe and the growth of single crystals by vertical zone melting under inert gas pressure. The technological parameters of the process were selected based on the results of an experimental study of the effective coefficients of Cr distribution in ZnSe at various dopant concentrations [2] that was carried out for the first time. The method has significant advantages over existing methods for producing ZnSe:Cr by ion implantation or diffusion of Cr into ZnSe polycrystals. These methods do not provide uniform doping throughout the volume of laser components; moreover, the limiting concentrations of Cr are usually lower. The method developed at ISSP RAS makes it possible to grow single crystals with a Cr content of up to 1020 cm-3, with the radial distribution of Cr being almost absent. This enables the manufacturing of uniformly doped products. Publications:
State task: “Physics and Technologies of New Materials and Prospective Structures, no. 122040600127-3” Physical Sciences, branch 1.3.5.6. “New Optical Materials, Optical Photonics Components, Integrated Optics, Holography, Nanophotonics, Metamaterials, and Metasurfaces” The quantum Hall Bogoliubov interferometerV.S. Khrapai A novel type of an electron interferometer in the integer quantum Hall effect regime containing a grounded superconducting terminal has been proposed. This geometry allows one to control the amplitudes of the Andreev and normal scattering of sub-gap Bogoliubov quasi-particles with the Aharonov–Bohm phase, as well as with the constrictions defining the interferometer loop (Fig. 1). The conductance matrix of such a three-terminal NSN interference device exhibits a much richer behavior compared to its two-terminal Fabry–Pérot counterpart, which is illustrated by the non-trivial behavior of non-local charge and heat transport (Fig. 2). A single edge version of the interferometer enables full on-demand control of the electron-hole superposition, including resonant enhancement of arbitrary small Andreev reflection probability up to 1. This makes it possible to use the Bogoliubov interferometer as a building block in future more complex interference setups. 
Figure 1. Model of the interferometer. The Bogoliubov interferometer is a Fabry–Pérot-type interferometer based on edge channels formed by two constrictions (1 and 2) and a superconducting terminal inside (S). The matrices of propagation along the edge corresponding to scattering in the constrictions, flights along the edge, and scattering by regions with an induced proximity effect are denoted with letters with circumflex.
Figure 2. Non-local electrical and thermal conductances. Color maps of non-local electrical conductance (a, b) and thermal conductance (c) as a function of the Aharonov–Bohm phase and the reflection coefficient in the constrictions. Cross-cut of the map at fixed R=0.25 (d).
Publication: Khrapai, V. Quantum Hall Bogoliubov interferometer / V. Khrapai // Physical Review B. – 2023. – Vol. 107, Iss. 24. – P. L241401. – DOI:10.1103/PhysRevB.107.L241401 RSF project no. 22-12-00342 Physical Sciences, branch 1.3.2.5. “Physics of Nano- and Heterostructures, Mesoscopic Physics” |
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