This article is the first to apply wire-feed electron beam additive manufacturing in vacuum to fabricate a part from a complex nickel-based superalloy with directional structure on a stainless steel ...substrate. It is shown that the determining factor for the formation of parts with directional structure is the local metallurgy conditions implemented in electron beam additive manufacturing. These conditions are the magnitude and direction of the temperature gradient as well as the geometry (shape) of the solidification front in the molten pool. The substrate effect (both chemical and structural) on the composition and structure of the part material is cancelled out at a distance not exceeding 8.0 mm from the substrate. Thus, the proposed 3D printing method is quite acceptable for the manufacturing of parts from heat-resistant nickel alloys with directional structure on substrates made of less expensive materials.
Promising New Salt of Oseltamivir Kalashnikov, A. I.; Sonina, E. G.; Kulagina, D. A. ...
Pharmaceutical chemistry journal,
09/2021, Letnik:
55, Številka:
6
Journal Article
Recenzirano
Odprti dostop
A synthetic method for the promising new drug oseltamivir ethoxysuccinate is described in detail. Various conditions for obtaining the target substance are considered. Its complete physicochemical ...characteristics are given. The obtained agent is shown to be effective against influenza virus A (H1N1)pdm09.
Combined technologies based on the use of concentrated energy fluxes, including low-temperature plasma and a pulsed electron beam, is currently considered to be an effective approach for surface ...modification of metals and alloys, cermet and ceramic materials. The purpose of the paper is to identify and analyze the patterns of changes in the elemental and phase composition, the state of the defective substructure, and mechanical properties of industrial steel Gr1J03502 subjected to combined treatment that includes plasma deposition of a powder coating based on the Ni-Cr-B-Si system and irradiation with an intense pulsed electron beam. The results obtained by optimizing the mode of the substrate surface fusion and the mode of powder deposition onto the molten surface of the substrate using low-temperature plasma generators of the original design are presented. It has been found that the optimum melting mode of the substrate surface is implemented with the following parameters of the plant: the feed rate is Vп = 50 … 150 mm/min, the distance is h1 = 30…100 mm, the scanning frequency is ω = 50 min−1, β = 75 … 90°, the amplitude is 90 … 100 mm, the plasmatron voltage is 160 V, the current strength is Im = 100 … 120 А. The optimal spraying conditions of the powders are as follows: h1 = 30÷50 mm; h2 = 100÷120 mm; β = 75÷90°; α = 45÷50°; ω = 50 min−1; Um = 140÷160 В; IS = 350÷400A; Im = 80÷100 A; GH (sprayed powder consumption) 0.8÷1 g/s. The characteristics of a plasma jet generated by an electric arc plasmatron are presented. The parameters of the electron beam are as follows: the energy of accelerated electrons is 18 keV, the energy density of the electron beam is 20 J/cm2 and 40 J/cm2, the pulse duration of the electron beam is 200 μs, the pulse repetition rate is 0.3 s−1, and the number of pulses is 10. It has been shown that plasma spraying of a powder coating leads to formation of a high relief surface containing micro and macropores, microcracks, and particles of the sprayed powder. Subsequent treatment of the modified surface with an intense pulsed electron beam of a submillisecond duration in the melting mode of the surface layer is accompanied by smoothing of the coating surface, saturation of the crystalline lattice of the steel surface with Ni, Cr, B, and Si atoms, formation of submicron-sized dendritic crystallization cells, precipitation of nanosized particles of the second phase, and formation of a quenching (martensitic) steel structure. Together, these transformations of the structure and phase composition of the material have led to a multiple increase in the microhardness of the surface layer with a thickness of up to 1500 mm.
•It has been shown that a combined modification of the surface layer of Gr1J03502 steel, including plasma spraying of a powder coating of the Ni-Cr-B-Si system and the subsequent irradiation with an intense pulsed electron beam, leads to formation of boride (CrB, Fe2B), silicide (FeSi), and carbide (Cr7C3) particles of iron and chromium.•Moreover, formation of an island structure has been found in the molten surface layer after the crystallization.•The islands containing refractory inclusions are separated by regions having the structure of high-speed dendritic crystallization of the submicron-sized range•The thickness of the total hardened layer, the microhardness of which is 4.6-6.5 times greater than the microhardness of the original steel, reaches 1500 μm.
The investigations of the surface physicochemical and biological properties of polylactic acid modified by silver, argon and carbon ion implantation to doses of 1 × 1014, 1 × 1015 and 1 × 1016 ...ion/cm2 and energies of 20 keV (for C+ and Ar+) and 40 keV (for Ag2+) are described. X-ray photoelectron spectroscopy revealed that chemical bond ratio in polylactic acid is alternated indicating that different chemical processes take place depending on the implanted ion kind. Chemical reactions that occur during ion implantation of polylactic acid are proposed. X-ray diffraction analysis shows the degree of crystallinity decrease for all the ion types that leads to microhardness and elastic modulus decreasing. Silver is established to form metal nanoparticle into subsurface layer of polylactic acid with the average size of 2–3 nm. It was shown by atomic force microscopy that the higher irradiation doses the lower the surface roughness of polylactic acid that results in hydrophilicity improvement. The cytotoxicity investigation on three individual donor macrophages shows that Ag-implanted polylactic acid has no negative impact on the immune system cells and can be very promising material for biomedical application.
•PLA chemical bond ratio is alternated after ion implantation.•Chemical reactions that occur during ion implantation of PLA are proposed.•Implanted silver forms 2–3 nm size metal nanoparticle into the subsurface layer of PLA.•Surface roughness of PLA decreases with the dose enhancing•Ag-implanted polylactic acid has no negative impact on the immune system cells.
—
The results of numerical simulation of a multiple-beam X-band klystron have been presented. The analysis of a new principle of constructing the interaction space that allows us to provide a high ...efficiency value without using second harmonic resonators has been given. The results of an experimental study of the developed 25-beam KIU-283 klystron with a peak power of 3.0 MW at a frequency of 9300 MHz with an electronic efficiency of 58% have been presented.
Abstract
The article discusses the issues of reducing the size of the cooling unit of the antenna of a radar station by improving the gas-dynamic processes occurring in the air-cooling unit. The ...results of the experimental studies of the gas flow in a plate-fin heat exchanger, being blown by one axial fan are presented. The feasibility of changing the number of axial fans for organizing a more uniform flow around the heat-exchange surfaces has been determined by calculation and theoretical methods. The calculation results are confirmed by experimental studies of the air flow in the segment of the heat exchanger, which is provided by a smaller fan.
The obtained results show that using an electron beam wire feed process makes it possible to manufacture axially symmetric articles which metal strength is close to this of conventionally made ones. ...However, it is necessary to optimize the process parameters and thus provide forming the desired microstructure with or without the anisotropy.
The results of photon Doppler velocimetry of ejecta from shock-loaded metal samples are reported. The experiments have been performed with tin and lead samples of a given thickness and a given ...surface roughness. The direct numerical simulation of the process of mass ejection from the surface of shock-loaded samples is performed for conditions close to experimental by the smoothed particle hydrodynamics method. The areal density and initial velocity distribution of the volume density of ejecta are determined. Using these results, we calculate the time dependence of the profile of the volume density at the expansion of the formed dust cloud to air. Applying an approach based on the transport equation for the correlation function of the scattered field, the main parameters of the velocity distribution of ejecta, areal density of ejecta, etc. are reconstructed from spectral photon Doppler velocimetry data. The experimentally observed temporal dynamics of spectra, which is caused by the drag of dust in air, is described at an appropriately chosen size dispersion of dust particles. The masses of ejecta reconstructed from experimental data are in agreement with the smoothed particle hydrodynamics results.
Evolution of microstructure, elemental and phase composition of dense zirconia-based composite under irradiation with electron beam were investigated. Tetragonal zirconia-based composite reinforced ...by 5 wt% alumina nanofibers and 0.5 wt% single-walled carbon nanotubes was prepared by spark plasma sintering at a temperature of 1500°C. Irradiation of the composite was carried out with a low-energy pulsed electron beam of submillisecond duration in the following mode: beam energy density 15 J·cm−2; pulse duration 200 μs; pulse repetition rate 0.3 s−1; pulses quantity 10, 20, 30 and 40; residual gas pressure (argon) in the working camera 10−2 Pa. It has been established that electron beam treatment leads to the formation of modified multilayered surface, the thickness of which varies from 6 to 40 μm. Redistribution of Al atoms in the modified surface layer was detected. The phase evolution dependent on the quantity of irradiation pulses and manifested in the crystalline structure of material.
The formation of martensitic α′ and α′′ phases in Ti-6Al-4V titanium alloy subjected to low energy high current pulsed electron beam (LEHCPEB) treatment with an energy density of 12–25 J/cm2 was ...revealed by X-ray diffraction and transmission electron microscopy. It was substantiated that the strain-induced phase transformation is the dominant mechanism underlying the deformation behavior of the melted surface layer of the titanium alloy samples during nanoindentation and scratch testing. It was found that the reverse transformation of the α′′ phase into the more close-packed α phase is responsible for the softening of the uppermost surface layer of the samples subjected to LEHCPEB treatment. The development of the direct and reverse α′′→α→α′′ martensitic transformations in the uppermost surface layer resulted in the improvement in elastic recovery of the treated Ti-6Al-4V samples after scratching.
Display omitted
•LEHCPEB treatment leads to formation of α′ and α″ phases in melted surface layer of Ti-6Al-4V alloy.•Strain-induced phase transformations occur during nanoindentation and scratching.•α→α″ martensitic transformation results in increasing elastic recovery of scratch groove.
PDF
