Eurasian Journal of Physics and Functional Materials

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Vol 5, No 4 (2021)
169-180 1121

The effect of sapphire and bismuth single-crystal filters and their combinations on the quality of neutron radiographic images and neutron tomography data has been studied. The parameters of the contrast of the neutron image were analyzed depending on the monocrystalline filters. Neutron transmission spectra were obtained for sapphire and bismuth single crystals. Additionally, the effect of filters on the overall intensity of the thermal neutron beam and the background of gamma-rays was investigated. Based on the obtained data, we assume that a single-crystal sapphire filter can be most effectively used for radiographic and tomographic installations using thermal neutrons.

181-187 429

Neutron Resonance Capture Analysis (NRCA) is presently being developed at the Frank Laboratory of Neutron Physics (FLNP) to determine the elemental composition of samples. The NRCA is a nondestructive method that allows measuring objects’ bulk composition. The procedure is based on detecting neutron resonances in radiative capture and the measurement of the yield of reaction products in these resonances. The experiments are carried out at the Intense REsonance Neutron source (IREN). In this study, we applied the NRCA to investigate an archaeological object provided by the Museum and Exhibition Complex (MVK) "Volokolamsk Kremlin". The object was a women’s Old Believer cross (second half of the 17th century) found in the Moscow region, Volokolamsk district, the village of Chubarovo.

188-197 1040

The paper provides data on the peculiarity of change in the structure, structural phase changes and destructions in beryllium resulting from interaction with a near-wall plasma of fusion facilities. Beryllium resistance under conditions of ITER operation was evaluated, which considers factors leading to possible partial melting and erosion of panels of the ITER first wall. It presents the modelling of a heat s distribution in element (”finger”) of the first wall at ”normal” and ”increased” heat flux of the ITER operation.

198-210 452

This paper presents the experimental results on electron, ion temperatures and densities in a pulsed plasma accelerator. The values of electron densities and temperatures were computed using the methods of relative intensities of Hα and Hβ lines, Hβ Stark broadening, and the technique is based on Faraday cup beam current measurements. In this work, a linear optical spectrometer S-100 was used to acquire the emission spectra of hydrogen and air plasmas. In this spectrum, there are some lines due to Fe, Cu, N2, O2, and H2. The series of visible lines in the hydrogen atom spectrum are named the Balmer series. The spectral emissions of iron and copper occur throughout the gas breakdown and ignition of an arc discharge, during the erosion and sputtering of materials. The vacuum chamber and coaxial electrodes were made. The electron temperatures and densities in a pulsed plasma accelerator, measured via relative intensities of spectral lines and Stark broadening, at a charging voltage of a capacitor bank of 3 kV and a working gas pressure in a vacuum chamber of 40 mTorr, were 2.6 eV and 1.66 · 1016 cm−3 for hydrogen plasma. These results were compared with the Faraday cup beam current measurements. However, no match was found. Considering and analyzing this distinction, we concluded that the spectral method of plasma diagnostics provides more accurate results than electrical measurement. The theory of probe measurements can give approximate results in a moving plasma.

211-217 395

In this work, suitable pretreatment conditions have been studied to increase hydrogen production by dark fermentation of brewer’s grain (BG). All samples with different concentrations of raw materials were tested: treatment with sulfuric acid with a concentration of 1.5%, autoclaving at 121 C, purification from impurities by filtration, centrifugation and calibration of the pH of the medium to 7.5 units. The choice of acid hydrolysis is due to the fact that this type of pretreatment is the most suitable for the further commercialization of this technology. Also, pretreatment performs the task of suppressing methanogens and creating conditions for the life of hydrogen-producing bacteria. Experiments were carried out under mesophilic conditions ( 37 C) using wild-type and multiple mutant E. coli. The highest sugar yields were obtained at a 4% concentration of brewer’s grains and in the presence of a concentration of 1.5% sulfuric acid in the original substrate. The results of the experiments showed that brewer’s grains are a valuable product as a source of carbon and energy for microorganisms in the production of biohydrogen, as well as for the production of biomass for further production of value-added products. 

218-228 390

This paper studies deformation-stimulated features of radiative relaxation of self-trapped excitons and recombination assembly of exciton-like luminescence in RbI crystal. Methods of research were luminescence and thermal activation spectroscopy. The identity of the mechanism of manifestation of the X-ray luminescence, tunnel luminescence and thermally stimulated luminescence spectra were found in the elastically deformed RbI crystal, interpreted by the luminescence of self-trapped exciton, tunnel recharge of F′, VK -pairs and thermally stimulated recombination of e, VK -centres, respectively.
The temperatures of the maximum destruction peaks of thermally stimulated luminescence, their spectral composition and activation energies were determined experimentally, on the basis of which the mechanisms of recombination assembly of exciton-like luminescences in a RbI crystal were interpreted. Uniaxial elastic deformation leads to the effective formation of point radiation defects ( F′, HA, VK -centers) in comparison with an unbroken lattice, where the predominant mechanism is the association of interstitial atoms ( H -centres) with the formation of I3-centres.

229-235 959

The magnetic anisotropy energy and the stability of crystal modifications of D03 and L21 of Fe3Ga compounds are studied with the density functional theory methods. The magnetic anisotropy energy of the D03 structure is more than twice the same value for the L21 structure. The features in the electronic structure lead to the difference in the magnitude of spin-orbit interaction, explaining the found effect. The L21 structure is more thermodynamically stable in the entire range of the considered pressures. Under pressure, the considered crystal modifications of Fe3Ga lose their stability due to the appearance of imaginary frequencies in their phonon spectra.

236-244 892

Currently, dark fermentation is the most practically applicable for the implementation of biotechnological  roduction of hydrogen. However, this process has certain limiting factors, since a significant part of the substrates are converted into various metabolic products, but not into H2 . Therefore, it is necessary to develop optimal conditions for energy recovery in the form of gaseous molecular hydrogen. Various carbohydrate-containing raw materials for hydrogen production often require pretreatment before they can be used by microorganisms. Dilute acid pretreatment represents a promising way to increase biohydrogen production. However, during acid hydrolysis of carbohydrate-containing wastes, in addition to the released soluble sugars, inhibitors of enzymatic processing, such as furfural and 5-HMF, acetic and propionic acids, etc., can accumulate. In this regard, it is necessary to select the optimal conditions for the efficient production of biohydrogen. This study investigated the production of biohydrogen during the microbial fermentation of sugars in a dilute solution of a molasses-based acid hydrolyzate using Escherichia coli and a multiple mutant. The results of the experiments showed that molasses is a valuable product as a source of carbon and energy for microorganisms in the production of biohydrogen, as well as for the production of biomass for the further production of various products with high added value.

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ISSN 2522-9869 (Print)
ISSN 2616-8537 (Online)