The Synthesis of Metalcarbon Nanocomposite Ni / C on the Basis of Polyacrylonitrile

Metalcarbon nanocomposites based on polyacrylonitrile and nickel chloride are synthesized under the influence of infrared heat. The resulting materials represent a system of carbon matrix formed during the carbonization of PAN, and distributed in it nickel nanoparticles. The average size of the nanoparticles in the nanocomposite was 15-25 nm. It was found that the distribution of nickel nanoparticles sizes is determined by temperature synthesis nanocomposite. Thus with increasing temperature, the predominant average particle size of the metal increases, and the distribution is spread and shifted toward larger sizes. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3360

Влияние вида РЗЭ на структуру и каталитическую активность титанатов Ln2Ti2O7

The influence of the Ln type on the crystal, local structure, and catalytic properties of Ln2Ti2O7 titanates (Ln = Pr, Sm, Gd, Tb, Dy, Yb) was studied. It was shown that Pr2Ti2O7 powder has a monoclinic structure of layered perovskite, and the other Ln2Ti2O7 samples (Ln = Sm, Gd, Tb, Dy, Yb) have cubic pyrochlore one. It was found that the catalytic activity of Ln titanates in the reaction of propane cracking increases with a decrease in the Ln ionic radius. Anomalous activity of Gd2Ti2O7 was detected.Исследовано влияние вида РЗЭ на кристаллическую, локальную структуру и каталитические свойства титанатов Ln2Ti2O7 (Ln = Pr, Sm, Gd, Tb, Dy, Yb). Показано, что порошок Pr2Ti2O7 имеет моноклинную структуру слоистого первоскита, а остальные образцы Ln2Ti2O7 (Ln = Sm, Gd, Tb, Dy, Yb) - кубического пирохлора. Установлено, что каталитическая активность титанатов РЗЭ в реакции крекинга пропана увеличивается с уменьшением ионного радиуса РЗЭ. Обнаружена аномальная активность Gd2Ti2O7

Magnetization Dynamics in Proximity-Coupled Superconductor-Ferromagnet-Superconductor Multilayers

© 2020 American Physical Society. In this work, magnetization dynamics is studied in superconductor-ferromagnet-superconductor three-layered films in a wide frequency, field, and temperature ranges using the broad-band ferromagnetic resonance measurement technique. It is shown that in the presence of both superconducting layers and of superconducting proximity at both superconductor-ferromagnet interfaces a massive shift of the ferromagnetic resonance to higher frequencies emerges. The phenomenon is robust and essentially long-range: It has been observed for a set of samples with the thickness of ferromagnetic layer in the range from tens up to hundreds of nanometers. The resonance frequency shift is characterized by proximity-induced magnetic anisotropies: By the positive in-plane uniaxial anisotropy and by the drop of magnetization. The shift and the corresponding uniaxial anisotropy grow with the thickness of the ferromagnetic layer. For instance, the anisotropy reaches 0.27 T in experiment for a sample with a 350-nm-thick ferromagnetic layer, and about 0.4 T in predictions, which makes it a ferromagnetic film structure with the highest anisotropy and the highest natural resonance frequency ever reported. Various scenarios for the superconductivity-induced magnetic anisotropy are discussed. As a result, the origin of the phenomenon remains unclear. Application of the proximity-induced anisotropies in superconducting magnonics is proposed as a way for manipulations with a spin-wave spectrum

Effect of the Chemical and Phase Composition of Nanocrystalline Gadolinium Complex Oxides on the Propane Cracking Process

Abstract: Effect of the chemical composition and crystal structure type of gadolinium complex oxides on their catalytic activity is studied. It is shown that nanocrystalline powders Gd2Ti2O7, Gd2Zr2O7, and Gd2Hf2O7 form highly symmetrical face-centered сubic crystal structures having localized (in Gd2Ti2O7) and delocalized (in Gd2Zr2O7 and Gd2Hf2O7) oxygen vacancies. At the same time, low-symmetrical crystal structures are formed in Gd2(WO4)3 (the monoclinic structure) and Gd2(МоO4)3 (a mixture of monoclinic and rhombic structures). Catalytic runs show that formation of the cubic structure contributes to an increase in the degree of conversion of propane and causes a shift in cracking temperatures to lower values. Formation of this type of nanocrystalline oxides facilitates the dehydrogenation reaction with propylene selectivity up to 80% at temperatures up to 700 К. Formation of the mixture of monoclinic and rhombic structures in Gd2(МоO4)3 leads to a shift in the degree of conversion to the catalytic temperature range of 700–900 К, in which the dehydrogenation reaction predominates (80%). In the case of the monoclinic structure of Gd2(WO4)3 in the same cracking temperature ranges the process of degradation occurs in parallel; this decreases propylene selectivity to 50% and promotes an increase in the yield of ethylene to 30%. © 2020, Pleiades Publishing, Ltd

Magnetization Dynamics in Proximity-Coupled Superconductor-Ferromagnet-Superconductor Multilayers

In this work, magnetization dynamics is studied in superconductor-ferromagnet-superconductor three-layered films in a wide frequency, field, and temperature ranges using the broad-band ferromagnetic resonance measurement technique. It is shown that in the presence of both superconducting layers and of superconducting proximity at both superconductor-ferromagnet interfaces a massive shift of the ferromagnetic resonance to higher frequencies emerges. The phenomenon is robust and essentially long-range: it has been observed for a set of samples with the thickness of ferromagnetic layer in the range from tens up to hundreds of nanometers. The resonance frequency shift is characterized by proximity-induced magnetic anisotropies: by the positive in-plane uniaxial anisotropy and by the drop of magnetization. The shift and the corresponding uniaxial anisotropy grow with the thickness of the ferromagnetic layer. For instance, the anisotropy reaches 0.27 T in experiment for a sample with a 350-nm-thick ferromagnetic layer, and about 0.4 T in predictions, which makes it a ferromagnetic film structure with the highest anisotropy and the highest natural resonance frequency ever reported. Various scenarios for the superconductivity-induced magnetic anisotropy are discussed. As a result, the origin of the phenomenon remains unclear. Application of the proximity-induced anisotropies in superconducting magnonics is proposed as a way for manipulations with a spin-wave spectrum.peerReviewe

Rearrangement in the local, electronic and crystal structure of europium titanates under reduction and oxidation

We studied powder samples of europium titanates Eu1−x2+Eux3+TiO3+x/2 prepared by sol-gel and coprecipitation methods with subsequent thermal treatment of precursors at different conditions (reducing or oxidizing atmosphere, temperature, exposure time). We have revealed a radical rearrangement in the local, electronic and crystal structure of europium titanates depending on synthesis conditions. The combination of synchrotron X-ray diffraction (s-XRD), X-ray absorption (XANES and EXAFS), infrared and Raman spectroscopies supplemented by photoluminescence and simultaneous thermal analysis was used in our study. It is shown that the combined XANES and thermogravimetric analysis gives clear evidence of a change in the oxidation state of europium cations from Eu2+ to Eu3+. The comparison of s-XRD, XANES, and EXAFS data allowed us to explain the local structure rearrangement during the phase transition from cubic perovskite Eu2+TiO3 (space group Pm3¯m) to pyrochlore phase Eu23+Ti2O7 (space group Fd3¯m) through intermediate layered perovskite Eu23+Ti2O7 with monoclinic structure (space group P21) under annealing in oxidizing atmosphere. The Raman spectroscopy study pointed to significant changes in the local structure of the anionic sublattice upon the observed phase transitions. The analysis of luminescence spectra has shown that Eu3+ cations occupy positions with low local site symmetry in all synthesized compounds regardless of the type of the crystal structure. © 2020 Elsevier B.V

Neutralizing activity of sera from sputnik v-vaccinated people against variants of concern (VOC: B.1.1.7, B.1.351, P.1, B.1.617.2, B.1.617.3) and Moscow endemic SARS-CoV-2 variants

Since the beginning of the 2021 year, all the main six vaccines against COVID-19 have been used in mass vaccination companies around the world. Virus neutralization and epidemiological efficacy drop obtained for several vaccines against the B.1.1.7, B.1.351 P.1, and B.1.617 genotypes are of concern. There is a growing number of reports on mutations in receptor-binding domain (RBD) increasing the transmissibility of the virus and escaping the neutralizing effect of antibodies. The Sputnik V vaccine is currently approved for use in more than 66 countries but its activity against variants of concern (VOC) is not extensively studied yet. Virus-neutralizing activity (VNA) of sera obtained from people vaccinated with Sputnik V in relation to internationally relevant genetic lineages B.1.1.7, B.1.351, P.1, B.1.617.2, B.1.617.3 and Moscow endemic variants B.1.1.141 (T385I) and B.1.1.317 (S477N, A522S) with mutations in the RBD domain has been assessed. The data obtained indicate no significant differences in VNA against B.1.1.7, B.1.617.3 and local genetic lineages B.1.1.141 (T385I), B.1.1.317 (S477N, A522S) with RBD mutations. For the B.1.351, P.1, and B.1.617.2 statistically significant 3.1-, 2.8-, and 2.5-fold, respectively, VNA reduction was observed. Notably, this decrease is lower than that reported in publications for other vaccines. However, a direct comparative study is necessary for a conclusion. Thus, sera from “Sputnik V”-vaccinated retain neutralizing activity against VOC B.1.1.7, B.1.351, P.1, B.1.617.2, B.1.617.3 as well as local genetic lineages B.1.1.141 and B.1.1.317 circulating in Moscow. © 2021 by the authors. Licensee MDPI, Basel, Switzerland