Search

The results of studies of wear resistance and tribological properties of experimental single carbide hard alloys grades with modified Co-Mo-Ti binders upon conditions of friction without lubricant on stainless steel are presented. All the data obtained were compared with similar parameters for the basic alloy VK8 (Co-Mo), on the basis of which the experimental grades were developed. Tribological tests were performed on tribometer which implemented a scheme of friction "pin on disk" at constant sliding speed and normal load values with artificially heated tribo contact zone. Studies have found that partial substitution of cobalt in a binder by Mo and Ti has led to a decrease in average friction rates. It was established that the greatest wear resistance and the best tribological characteristics were obtained for specimens of experimental grade 2.22 (5,65%Co+1,8%Mo+0,6%Ti). The process of friction for this pin material was characterized by the formation of secondary structures with high shielding properties, reducing of the adhesive interaction of materials, low volume wear intensity, minimal friction coefficient, as well as the least roughness of friction tracks on the counter body (disk). An increase in the proportion of molybdenum in the binder of more than 5% reduced the wear resistance of the experimental grades in comparison with the basic alloy VK8.

It is shown that when counterpropagating laser beams are incident on an array of parallel single-walled carbon nanotubes, strong interaction of waves is possible, accompanied by the amplification of one of the waves at the expense of another, more intense pump wave. The interaction is most efficient when the condition of phase matching of the incident waves and the slow plasmon polariton wave formed because of the laser-induced metallisation of nanotubes is satisfied. The dependence of the the signal wave gain on the geometric parameters of the array and the wave characteristics of the incident waves is studied numerically. A range of phase detuning values is found, in which the gain changes weakly near its maximum value.

Aerated concrete is actively used in energy efficient construction, mainly as a masonry material for vertical load-bearing structures. At the same time, the creation of a closed thermal contour of the building, which is the basis of modern energy saving requirements, is rational by the use of aerated concrete in load-bearing horizontal structures that require reinforcement. Traditionally bar reinforcement is ineffective in aerated concrete due to low specific adhesion at the contact of the reinforcement with concrete and significantly less than that of heavy concrete, the distribution capacity of concrete around a rod, which evenly transforms concrete stress to bar extension, the consequence of which is the significant bar understress while pulling it in concrete. The authors’ research in the field of rationalization of reinforcing elements that are effective in cellular concrete, aimed at increasing the contact surface of the reinforcing element with concrete while maintaining the original steel consumption, makes it possible to recommend tape reinforcement for use in reinforced aerated concrete structures. Punched steel tapes equal to the bar reinforcement of the cross-sectional area, but having developed lateral surface, provide an increase in the adhesion strength of the reinforcement and preventing its pulling. The article presents the results of a numerical study of stress-strain state in reinforced aerated concrete beam with rectangular section, reinforced with the proposed tape reinforcement in comparison with traditional bar reinforcement

A study of the electroluminescence of asymmetric InAs/InAs1 – ySby/InAsSbP light-emitting diode heterostructures with a molar fraction of InSb in the ternary solid solution in the active region y = 0.15 and y = 0.16 in the temperature range 4.2–300 K is reported. It is found on the basis of experimental data that a staggered type-II heterojunction is formed at the InAs1 – ySby/InAs0.41Sb0.28P0.40 heterointerface. It is shown that interfacial radiative transitions at the type-II heterointerface make a dominant contribution in the temperature range of 4.2–180 K. This enables minimization of the temperature dependence of the operating wavelength of a light-emitting diode.

To change or repair sliding gates, steel ladles are installed in horizontal position, in which they are heated to keep a working temperature of lining. Peculiarities of a steel ladle heating in horizontal position considered. Description of the lining heating process presented, necessity of elaboration a method of its numeral simulation justified. The method should enable to make studies of influence of various methods of burner location on the ladle cover and torch parameters on efficiency of heating for a particular ladle and time available for the heating. A method of mathematical simulation of heat- and mass-exchange processes of lining heating in nonstationary conditions described. Based on examples of various variants of torch power calculation, dynamics of a ladle walls heating was shown. Results of calculation of temperature distribution over a ladle lining presented, as well as the map of gases flow in the ladle volume for various parameters of torch and heating process stages. Taking into consideration, that calculation costs related to simulation of nonstationary ladle heating are very high, a simplified one-dimensional model of calculation of lining heating process was elaborated. In the model correction factors are used, obtained as a result of numeral simulation. The model enables to make calculations in real time conditions and to use them for control at a practical steel ladle heating in horizontal position at a modern automized heating facility.

Analytical expressions are presented, and, through them, the analysis of component parts of the electrical resistance of injection microdisk lasers is carried out depending on the size of the microdisk resonator, parameters of the substrate, and configuration of the contact to it.

The effect of laser radiation with a wavelength near 1.55 µm on the photoluminescence properties of “nitrogen-vacancy” (NV) color centers in diamond has been studied experimentally. The effect of radiation of an infrared laser on the charge state of color centers redistributes the spectral intensity of photoluminescence in the ensemble of NV centers. In the case of neutral NV centers, the quenching of photoluminescence reaching about 60% has been observed. A feature of the laser excitation of NV centers by this method is the absence of competition with stimulated emission and two-photon excitation, which is observed with an increase in the power of infrared radiation at other wavelengths.

In the article, the authors present a method of constrained bending of sheet parts with curvilinear sides by the elastic media. They describe the process of constrained bending and the scheme of the experiment. After the first transition, a part with thinning in the radius and high side springing is obtained. The second transition, on a low-height rigging, a wave of excess material is first formed in the radius zone, which settles on the contour of the mandrel with a set of thickness. The stages of forming a semi-finished product are given. The experiment showed the feasibility of constrained bending of curved sides, wall thickness measurements showed that the second transition results in a thickening of the part wall. Finite element modeling of a constrained bend is performed to study the effect of excess of the Board on the thickening in the bending zone. Numerical studies of deformation processes have been carried out. An example of a diagram of the part thickness change for various deformation stages as a result of numerical studies is given. Dependence of part height exceeding with loss of stability during shaping is established. Examples of defects - folds are given.

The incorporation and activation of arsenic from tris(dimethylamino)arsine in CdTe layers grown by metal-organic chemical vapor deposition from dimethylcadmium and diisopropyltellurium on GaAs substrates are investigated. The incorporation of arsenic into CdTe depends on the crystallographic orientation of the layers and increases in the series (111)B → (100) → (310). The arsenic concentration in the CdTe layers is proportional to the tris(dimethylamino)arsine flow rate at a power of 1.4 and increases with decreasing diisopropyltellurium/dimethylcadmium ratio from 1.4 to 0.5. After deposition, the CdTe:As layers have p-type conductivity with an arsenic concentration of 1 × 1017–7 × 1018 cm–3 and a hole concentration of 2.7 × 1014–4.6 × 1015 cm–3, respectively; the fraction of electrically active arsenic does not exceed ~0.3%. After annealing in argon (250–450°C), the highest hole concentration is 1 × 1017 cm–3, and the arsenic activation efficiency is ~4.5%. The ionization energy of arsenic determined from the temperature dependence of the hole concentration is in the range of 98–124 meV. The low-temperature photoluminescence spectra of the layers have an emission peak with an energy of ~1.51 eV, which can be attributed to donor–acceptor recombination, where AsTe is an acceptor with an ionization energy of ~90 meV.

The peculiarity of planar quantum magnetotransport in the type II broken-gap p-GaInAsSb/p-InAs heterostructures at high magnetic fields has been investigated. The structure of the hybridized energy spectrum of a two-dimensional semimetal channel at a single type II broken-gap heterointerface was considered in dependence on the composition of the quaternary solid solution. A transition from a conducting state to a dielectric state (quantum insulator) for a 2D-semimetal channel at the heteroboundary was observed in quantizing magnetic fields under the condition of simultaneous filling of the first Landau levels for 2D-electron and interface hole states.

In this work the problem of free convection of the Newtonian poorly stratified liquid in the cell warmed up from left and cooled from right with the heat-insulated horizontal boarders is presented. Liquid with small concentration of salt and initial linear stratification on cell height is considered. The model of double diffusion in a Boussinesq approximation is applied to model the process. The problem is solved both in two - and three-dimensional statement by means of a control volume method and a SIMPLE algorithm. It is shown that vortex structures at the layered mode of convection have quasi-two-dimensional character.

We report on the electroluminescent and I–V characteristics of the n-InAs/n-InAsSb/p-InAsSbP heterostructure grown by metalorganic vapor-phase epitaxy. In the spectral range of 0.23–0.29 eV, the high-intensity electroluminescence at a temperature of T = 77 K has been observed. The position of the maximum of the main emission band ( $$h\nu $$ ~ 0.24 eV) has shown a noticeable blue shift with increasing forward bias. Based on the investigations, a conclusion about the existence of a type-II staggered heterojunction at the InAs0.84Sb0.16/InAs0.32Sb0.28P0.40 heterointerface has been drawn, which is confirmed by the calculated energy band diagram.

A new way of producing custom blocks for external electron beam therapy is described. The blocks are made of steel or lead grit uniformly distributed in epoxy resin. The proposed technique is user-friendly, inexpensive, and based on non-toxic materials.

The paper studies the interaction between surgical catgut and silver nanoparticles depending on the fiber surface treatment and time of exposure (1 and 24 hours) in Ag-containing gels. After a 24-hour exposure, the maximum sorption capacity is observed on polished catgut for silver nanoparticles ranging in size from 1 to 10 nm. After this time period, the sorption capacity of silver nanoparticles on unpolished catgut occurs in Agcontaining gel within the whole size range, mainly from 1 to 5 nm, when silver nanoparticles are obtained by cavitation and diffusion photoreduction. At the same time, the incubation period of 1 hour in Argogel does not provide the potentially effective concentration of silver nanoparticles on the fiber surface.

Magnetic properties and high-frequency impedance of nanocrystalline Fe73.5Si16.5B6Nb3Cu1 ribbons are studied in a high-temperature range of 300 to 723 K. The exchange-coupled state of nanocrystallites was found to be destructed at a temperature of about 530 K, which is substantially lower than the Curie temperature of the amorphous phase that is close to 635 K. It was found that, at an ac frequency of above 5 MHz, the marked magnetoimpedance effect (more than 50% for the magneoimpedance ratio in the case of complete impedance) is observed over the whole temperature range under study. This similar behavior can be essential in designing special-purpose magnetic field sensors intended for high-temperature applications.

We discuss the effect of self-heating on performance of injection microdisk lasers operating in continuous-wave (CW) regime at room and elevated temperature. A model is developed that allows one to obtain analytical expressions for the peak optical power limited by the thermal rollover effect, the corresponding injection current and excess temperature of the device. The model predicts, there exists the maximum temperature of microlaser operation in CW regime and the minimum mircrodisk diameter, at which CW lasing is possible. The model allows one to determine the dependence of the device characteristics on its diameter and the inherent parameters, such as thermal resistance, electrical resistance, non-radiative recombination and characteristic temperature of the threshold current. It is found that a rapid growth of the threshold current density with decreasing the diameter (which takes place even in the absence of the self-heating effect) is the main internal reason leading to the dependence of the temperature characteristics of the mirodisk laser on its size. In the calculations, we used a set of parameters extracted from experiments with InGaAs quantum dot microdisk lasers. The simulation results (in particular, the light-current curve and the dependence of the minimum microdisk diameter on ambient temperature) comply well with the measured dependences.

Methods for determining the dependence of the lateral-scan coordinate on the A-scan number from tomographic images of test samples are investigated and techniques for compensating for horizontal distortions of tomographic images caused by uneven speed of the probing-beam displacement are proposed. An opal-glass Ronchi ruling and an inclined flat surface of the volume-scattering plate were used as test samples.

The results of experiments aimed at fabricating and studying the properties of photodetector structures based on single-layer graphene produced by chemical vapor deposition are presented. The configuration of a Ta2O5 vertical microcavity with a resonance wavelength of about 850 nm and a lower dielectric SiO2/Ta2O5 distributed Bragg reflector is taken as the base structure. The conditions for the transfer and fabrication of mesas in the graphene layer on the microcavity surface are optimized. The diagnostics by Raman spectroscopy of the structural quality of graphene after fabrication of the mesas in the graphene layer and contact pads are indicative of the single-layer structure of graphene with a low intensity of features in its spectrum, responsible for imperfection of the structure. The photocurrent is measured under local optical pumping.

AlGaAs/GaAs microdisk lasers with InAs/InGaAs quantum dots have been transferred to the surface of a silicon wafer using an indium solder. The microlasers have a common electric contact deposited on top of the residual n+-GaAs substrate and individual addressing is ensured by placing the microdisks with the p contact down onto separate contact pads formed on silicon. No effect of a non-native substrate on the electrical, threshold, thermal, and spectral characteristics has been established. The microdisks can operate in continuous-wave regime without forced cooling at a threshold current density of ~0.7 kA/cm2. The lasing wavelength is stable (

Gold nanoparticles are promising radiosensitizers for proton radiotherapy. However, the physical mechanisms of gold nanoparticles radiosensitization remain unclear. In the present study, the Geant4 toolkit was used to estimate by the Monte-Carlo simulation the changes (1) in the contribution of primary and secondary particles to the absorbed dose, (2) in the dose-averaged linear energy transfer, and (3) in the relative biological effectiveness of a 150 MeV proton beam caused by the addition of 50 mg/mL of gold nanoparticles to the irradiated water phantom. In the presence of gold nanoparticles no significant changes in the absorbed dose and the Bragg peak position were found, at the same time a redistribution of the contribution of secondary particles to the absorbed dose was recorded. An increase in the contributions from protons (~16%), recoil nuclei (~58%), α-particles (~400%), deuterons (~900%), tritons (~3000%), and photons (~7000%) was observed ~10 mm beyond the Bragg peak. The contribution of the secondary electrons decreased by ~35%. This redistribution led to ~5-fold increase in the dose-averaged linear energy transfer at the distal edge of the Bragg curve; this, in turn, may cause the ~1.4−2.2-fold increase in the relative biological effectiveness within this region. Thus, it is critically important to take into account the presence of gold nanoparticles when dosimetric planning proton radiotherapy in order to avoid unwanted damage to the normal tissues around the tumor.

The feasibility of detecting the emission of a microdisk laser with a diameter of 23 μm with an active region based on InGaAs/GaAs quantum well-dots using a nearby photodetector (100 × 4000 μm) with a similar active region is demonstrated. For continuous lasing, a pump current of 20 mA, and a distance between the faces of the microlaser and the photodetector of about 100 μm, a photocurrent of ~10 μA was obtained, which corresponds to a photodetector sensitivity of ~0.9 μA/μW.

A model is developed that makes it possible to analytically determine the threshold current of a microdisk laser with consideration for its self-heating as a function of the ambient temperature and the microlaser diameter. It is shown that there exists a minimum microdisk diameter determined by self-heating, up to which continuous-wave lasing can be reached at a given temperature. Another manifestation of the self-heating effect is the existence of the ultimate working temperature, which is lower, the smaller the microlaser diameter. Reasonable agreement between the predictions of the model and the available experimental data is shown.

The operation speed of microdisk lasers with quantum dots working at room temperature without thermal stabilization has been experimentally examined, and the widest modulation bandwidth of microdisks with various diameters has been calculated. It was shown that taking into account the effect of self-heating of a microlaser at high bias currents, which is manifested in a decrease of the ultimate operation speed and in an increase in the current at which the widest modulation bandwidth is reached, enables a good description of the experimental data. The self-heating most strongly affects microlasers with a small diameter (less than 20 μm).

Purpose: The radiotherapy methods using heavy charged particles become popular nowadays due to its high efficiency in treatment of oncological patients. On the other side, the practical application of such particles is deeply connected to the influence of secondary radiation, which is a result of nuclear collisions, that can affect the patients’ tissues and organs outside the treatment field. Doses in the out-of-field volumes should be considered from the standpoint of radiological protection. In this study we perform mathematical simulations of the absorbed dose in various organs under the prostate irradiation with carbon ion beam and compared these dose values with existing reference values from CT procedures, and known radiological protection recommendations against current practice of clinical use of carbon ions. Material and methods: The simulation tool is general application Monte-Carlo code FLUKA widely used for ionizing radiation transport modeling and simulations in radiological protection field. The patient model is one of the most detailed voxelized anthropomorphic phantom Vishum. During the simulation the absorbed dose of segmented organs has been assessed under the spread-out Bragg peak of carbon ions uniformly covering the prostate with the physical dose. The resulted dose in organs is normalized to the prostate dose. This is the qualitative assessment of radiation treatment procedure which allowed us to analyze the out-of-field doses in distant organs from the viewpoint of radiological protection in ion beam therapy, following existing ICRP Publication 127 guidelines. Results: The results show that the levels of dose due to prostate irradiation in the regimes widely used in the world practice are two level of magnitude lower than dose levels under the full body CT examination, and are comparable to the aircraft crew doses. Conclusion: Thus, the obtained results might be interested from the risks assessment point of view, including the secondary radiation-induced cancers or other observable or expected treatment effects.

—This article presents the results of an experiment on the processes of scattering of ions and neutral atoms on targets from polished tungsten obtained using a neutral particle facility. The neutral particle facility is a laboratory instrument designed to study the processes of reflection and scattering of charged particles and neutral atoms on the surfaces of targets made of various materials. The facility allows one to record the energy and angular distributions of secondary particles formed as a result of the interaction of a stream of ions of different energies or neutral atoms with a target installed at different angles.

The design and technology for the fabrication of an asymmetric stepped InAs/InAs1 –ySby/InAsSbP heterostructure with an ultimate InSb content (up to y = 0.17) in the narrow-gap active region by vapor-phase epitaxy from metal-organic compounds are developed. The electroluminescence characteristics of long-wavelength LEDs based on the proposed heterostructure, which emits in the spectral range of 4.6–5.3 μm, are studied. A linear decrease in the quantum efficiency of the electroluminescence with increasing InSb content in the active layer of the LEDs obtained is revealed. The advantage of using the asymmetric heterostructure for fabricating LEDs with a working wavelength of more than 4.5 μm is shown.

The results of comparative analysis of the spectral and threshold characteristics of room-temperature injection microdisk lasers of the spectral range 1.2×× μm with different active regions, notably, InGaAsN/GaAs quantum wells or InAs/InGaAs/GaAs quantum dots are presented. It is found that microlasers of a comparable size with quantum wells possess a larger laser generation threshold when compared with microlasers with quantum dots. At the same time, the latter are characterized by a noticeably smaller fraction of emitted power corresponding to laser modes. The jump to lasing via an excited-state optical transition is also characteristic for them. Microdisk lasers based on InGaAsN alloy do not have these disadvantages.

—This work studies the effect of heat treatment on the magnetoimpedance (MI) effect of soft magnetic Co68.5Fe4Si15B12.5 amorphous ribbons prepared by melt quenching on a rotating wheel. It was found that after heat treatments at temperatures of 100°C and higher there occur irreversible changes of MI over a wide range of excitation ac frequencies. A change in the magnetoimpedance response to the action of elastic tensile stresses is shown to be related to the change in the sign of saturation magnetostriction coefficient (λS), which results from the heat treatment.

It is demonstrated that microdisk lasers about 10 μm in diameter with an active region based on InAs/InGaAs quantum dots synthesized on GaAs substrates can be used for biodetection. Chimeric monoclonal antibodies against the CD20 protein that are covalently attached to the surface of microdisk lasers operating in an aqueous medium under optical pumping and room temperature were used as detectable objects. It is shown that the addition of secondary antibodies leads to an increase in the threshold power of laser generation, as well as to an increase in the full width at half maximum (FWHM) of the resonance laser line.

This work is devoted to the numerical research of free convection by a Newtonian anomalous thermoviscous fluid in a flat cell. The cell is heated from below, cooled from above; and the lateral boundaries are heat insulated. The viscosity anomaly of the fluid is modeled by the Gaussian function of temperature and is characterized by two parameters. A flow regime with isolated convective cells separated by a region of high viscosity, the so-called viscous barrier, was detected at a certain set of control parameters. For these flow regimes, current lines, heat fluxes, temperature fields, and contours of the components of the velocity vector of the fluid are given.

Funding Information: V.N. thanks the Russian Foundation for Basic Research (RFBR project No. 19-32-60040) for PDMS/MW membrane fabrication and optical measurements. V.F. thanks the Russian Foundation for Basic Research (RFBR project No. 19-32-60037) for the support of the MBE growth. V.N. and F.K. thank the support from the Russian Foundation for Basic Research (grant 20-32-90182) for electrical measurements. V.N., F.K., R.I. and I.M. thank the Russian Scientific Foundation (RSF project No. 20-19-00256) for chemical treatment of PDMS. V.N., V.F., A.M., F.K. and K.S. thank the Ministry of Science and Higher Education of the Russian Federation (FSRM-2020-0005) for the general support. E.M. thanks the Basic Research Program at the National Research University Higher School of Economics (HSE University) in 2021 for optical measurements. N.A.-M. and M.T. thank ITN Marie Curie project INDEED (grant No. 722176) for GaPAs NW/PDMS membrane investigation. This work received financial support from Partenariats Hubert Curien Kolmogorov project No. 43784UJ and Indo French Centre for the Promotion of Advanced Research (CEFIPRA) Project No. 6008-1. A.G.N. acknowledges the Russian Scientific Foundation (RSF project No. 21-72-20050) for synthesis of SWCNTs. Funding Information: Funding: V.N. thanks the Russian Foundation for Basic Research (RFBR project No. 19-32-60040) for PDMS/MW membrane fabrication and optical measurements. V.F. thanks the Russian Foundation for Basic Research (RFBR project No. 19-32-60037) for the support of the MBE growth. V.N. and F.K. thank the support from the Russian Foundation for Basic Research (grant 20-32-90182) for electrical measurements. V.N., F.K., R.I. and I.M. thank the Russian Scientific Foundation (RSF project No. 20-19-00256) for chemical treatment of PDMS. V.N., V.F., A.M., F.K. and K.S. thank the Ministry of Science and Higher Education of the Russian Federation (FSRM-2020-0005) for the general support. E.M. thanks the Basic Research Program at the National Research University HigherSchool of Economics (HSE University) in 2021 for optical measurements. N.A.-M. and M.T. thank ITN Marie Curie project INDEED (grant No. 722176) for GaPAs NW/PDMS membrane investigation. This work received financial support from Partenariats Hubert Curien Kolmogorov project No. 43784UJ and Indo French Centre for the Promotion of Advanced Research (CEFIPRA) Project No. 6008-1. A.G.N. acknowledges the Russian Scientific Foundation (RSF project No. 21-72-20050) for synthesis of SWCNTs. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. We demonstrate flexible red light-emitting diodes based on axial GaPAs/GaP heterostruc-tured nanowires embedded in polydimethylsiloxane membranes with transparent electrodes involv-ing single-walled carbon nanotubes. The GaPAs/GaP axial nanowire arrays were grown by molecular beam epitaxy, encapsulated into a polydimethylsiloxane film, and then released from the growth substrate. The fabricated free-standing membrane of light-emitting diodes with contacts of single-walled carbon nanotube films has the main electroluminescence line at 670 nm. Membrane-based light-emitting diodes (LEDs) were compared with GaPAs/GaP NW array LED devices processed directly on Si growth substrate revealing similar electroluminescence properties. Demonstrated membrane-based red LEDs are opening an avenue for flexible full color inorganic devices.

In the last decades, significant efforts have been devoted to developing semiconductors III-V lasers on silicon substrates, due to the prospects for the implementation of the high-speed lasers for optical communication systems integrated with silicon electronics and transistor logic. Low-threshold ridge-waveguide and microdisk/microring lasers based on AlGaAs heterostructures with self-organizing quantum dots In(Ga)As grown on Si substrates were demonstrated [1] , [2] . However, lasers synthesized on silicon are still inferior to analogs grown on native substrates (GaAs) [3] , due to higher defect densities caused by differences in polarity, lattice constants and coefficients thermal expansion of III-V materials and silicon. The epitaxial growth of laser heterostructures on native substrates (e.g. GaAs) and subsequent transfer of ready-made microlasers to silicon can help to avoid problems associated with monolithic integration of III-V and Si. Ring and disk microlasers have attracted more and more attention and are considered as promising sources of emission for inter-chip data transmission. The advantages of such microcavities are the high Q-factor of the whispering gallery (WG) modes, small size and, accordingly, low threshold currents and power consumption. In this work we study integration of InAs/GaAs quantum dot microdisk lasers on silicon either retaining the native substrate or separating from the substrate using a sacrificial layer.

We demonstrate a record low threshold current density of 250 A/cm2 in a quantum dot microdisk laser with a 31-μm diameter operating at room temperature in continuous wave regime without temperature stabilization. This low threshold current density is very close to the transparency current density estimated in broad-area edge-emitting lasers made of the same epitaxial wafer.

Uniform arrays of the InSb quantum dots with a surface density of nQD = 2 × 109 cm–2 were obtained by liquid phase epitaxy on a matrix layer based on a multicomponent InGaAsSb solid solution lattice-matched with the GaSb substrate. The change in the composition of the cationic part of the matrix by using the epitaxial matrix layer allowed to lower the temperature of the epitaxy to T = 430°C and determined the shape of a typical InSb quantum dot in the form of a truncated cone with average values of height h = 3 nm and diameter d = 30 nm, which corresponded to the aspect ratio L = h/d = 0.1.

We have studied arsenic incorporation from tris(dimethylamino)arsine into epitaxial Hg1– xCdxTe (x ~ 0.4) layers grown by the metalorganic chemical vapor deposition interdiffused multilayer process (MOCVD-IMP) on GaAs (310), (100), and (111)B substrates. CdTe was grown from dimethylcadmium and diethyltellurium vapors, and HgTe, from diisopropyltellurium and mercury vapors. Arsenic incorporation into the layers has been shown to depend on the crystallographic orientation of their growth, increasing in the order (111)B < (100) < (310). The addition of tris(dimethylamino)arsine during CdTe sublayer growth in an excess of diethyltellurium has been shown to have no significant effect on the macroscopic composition of the HgCdTe layers. The arsenic-doped HgCdTe layers have p-type conductivity. The fraction of electrically active arsenic in the layers depends on its concentration and rises from 15 to 85% in going from the (111)B to (100) and to (310) orientation. Additional two-step annealing ensures a near 100% arsenic activation in the HgCdTe layers.

Asymmetric n-InAs/InAs(1 – y)Sby/p-InAsSbP heterostructures with a narrow-gap active layer and a composition range y = 0.09–0.16 were grown by vapor phase epitaxy from metalorganic compounds. Room-temperature electroluminescence was observed at a wavelength of up to λ = 5.1 μm at a spectral maximum. The study of low-temperature electroluminescence spectra provided the possibility to establish the existence of two radiative recombination channels caused by the nature of the InAsSb/InAsSbP heterointerface. The effect produced by the chemistry of the active layer on the composition of the grown barrier layer and the formation of the InAsSb/InAsSbP heterojunction with an increase in the antimony content in the InAsSb solid solution was demonstrated.

—The paper presents the results of studying the strength properties of surfaces of nanomodified polymer composites based on a polyethylene matrix formed at high pressures (100–800 MPa) in the manufacture of experimental samples from melt by direct extrusion. The changes in static and dynamic sclerometric hardness are measured. We used optical microscopy to assess variations in the deformed layers at the microscale.

When producing castings of wide-interval magnesium alloys, their structure is the factor that most decisively affects a complex of mechanical, manufacturing, and operational properties. The specified structure of alloys of the Mg–Al–Zn system is impossible without using the melt modification operation in the smelting manufacturing process. In this work, the results of studying the modification of the ML5 magnesium alloy by different substances are presented. The influence of introducing magnesite into the melt in an amount of 0.4–0.45 wt % at 720–740°C, as well as the influence of melt blowing by oxygen-free carbon-bearing gases at the same temperature on the structure of the alloy and conservation duration of the modification effect is investigated. The latter is especially important in the large-scale and mass production of small castings made of alloys of the Mg–Al–Zn–Mn system when the melt pouring process is prolonged. It is shown that the use of oxygen-free carbon-bearing gases to modify the ML5 alloy provides the attainment of the level of mechanical properties of castings elevated by the 15–20% level of mechanical properties of castings when compared with the standard one according to GOST (State Standard) 2856–79. The conservation efficiency of the duration of the modifying effect by the conventional method (magnesite) is compared with using oxygen-free carbon-bearing gases. It is shown that the modification effect by magnesite is retained no longer than 30–40 min, while, when using oxygen-free carbon-bearing gas, it is no shorter than 4 h, which makes it possible to perform the prolonged pouring of a melt over molds.

Microdisk lasers 10–30 μm in diameter operating at room temperature without thermal stabilization and with an active region based on nanostructures of hybrid dimensionality—quantum wells–dots—are investigated. High-frequency measurements of the microlaser response are performed in the direct small-signal modulation mode, which makes it possible to establish the parameters of the operating speed and analyze their dependence on the microlaser diameter. It is found that the K factor is (0.8 ± 0.2) ns, which corresponds to optical losses of ~6 cm–1, and no regular dependence on the diameter is observed. It is found that the low-frequency component of the damping coefficient of relaxation oscillations is inversely proportional to the diameter. This character of the dependence evidences a decrease in the carrier lifetime in small-diameter microcavities, which can be associated with the prevalence of nonradiative recombination on their side walls.

We report a method of femtosecond laser-induced vitrification of crystalline tracks laser-written in glasses with different crystallization ability including lanthanum borogermanage, barium titanium silicate and lithium niobium silicate glasses. We have found that crystalline tracks consisting of nonlinear optical LaBGeO5 and BaTi2Si2O8 phases corresponding to glass-forming compositions could be readily amorphized by the femtosecond beam, whereas the laser-induced vitrification of a track consisting of LiNbO3 crystalline phase possessing a non-glass-forming composition is more complicated but also possible. The suggested technique provides reversibility of femtosecond laser-induced space-selective crystallization of glasses and thus extends the functionality of the direct laser writing of crystal-in-glass architectures that is important for the fabrication of novel integrated optical components and devices.

The aggregate stability of silver nanoparticles (Ag – NPs) in a gel composition is estimated. It is established that during long-term storage (for 3 years), a decrease in the number of nanoparticles with sizes of 1–5 and 5–10 nm and a significant increase in the number of nanoparticles with sizes of 10–15 nm are observed. At the same time, the fraction of silver nanoparticles with sizes greater than 30 nm is less than 5%.

It has been shown that the nature of the support (MFI zeolite, aluminum–magnesium hydrotalcite, stabilized ceria, neodymia) has a significant effect on the stability of Ni and Ni–Co catalysts for partial oxidation of methane to synthesis gas and a less significant effect on the stability of the catalysts for dry reforming of methane to synthesis gas. It has been found that aluminum–magnesium hydrotalcite is the most advantageous support for nickel catalysts, because it reliably provides a high synthesis gas yield in partial oxidation and dry reforming of methane, whereas the MFI zeolite is a stable and selective support for Ni–Co catalysts for dry reforming of methane.

Oxygen plays a crucial role in photocatalytic oxidation as an electron acceptor. Quantification of its adsorption appears to be a useful, although underestimated supplement in characterization of photocatalytic materials. Oxygen adsorption on TiO2 nanopowders was experimentally measured within the pressure interval from 10 to 760 mm Hg using standard equipment. The method of accurate measurement of adsorption capacity of photocatalyst powders was developed in the study. The apparent desorption effect of UV-irradiation on oxygen observed under ambient conditions was attributed to the sample free space measurement error caused by the thermal effect.