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The purpose of the work is to establish the possibility of obtaining expanded graphite of high purity (carbon content more than 99.5 % wt.) from flotation-enriched graphite (carbon content 94–97 % wt.) by combining into one process intercalation of graphite with a solution of potassium dichromate in concentrated sulfuric acid with subsequent hydrolysis, and chemical purification using solutions of ammonium bifluoride in sulfuric or hydrochloric acid and Trilon B in an alkaline buffer as purification reagents, and to confirm this possibility by quantum chemical calculations. It has been experimentally shown that combining oxidized graphite synthesis and its chemical purification into one process allows obtaining expanded graphite of high purity, with a carbon content of 99.75–99.85 % wt. The methods of X-ray diffraction and thermogravimetry show that the interaction of oxidized graphite (the residual compound of intercalation of graphite with sulfuric acid) with cleaning reagents does not reduce the ability to expand. The magnitude of the mass loss of oxidized graphite according to various variants of chemical post-cleaning and the temperature range of such loss remain practically unchanged. Quantum chemical calculations of the adsorption energy (∆Eads) of one molecule of Trilon B on the surface of a graphene-like plane (GLP), the complexation reaction of metal sulfates, the energy effect of the interaction of Trilon B with sulfates of alkaline earth metals in an aqueous solution, and with the participation of the surface of the graphene plane were carried out using the GAMESS (US) program by the density functional theory (DFT) method with the B3LYP functional and the 6-31G(d,p) basis set, taking into account the Grimme D3 dispersion correction within the PCM polarizable continuum. The results of the analysis of quantum chemical calculations indicate that the Trilon B molecule is better physically sorbed on the oxidized GLP (–412 kJ/mol) than on its native form (–188 kJ/mol). The values of the energy effect of the complexation of magnesium and calcium cations with Trilon B have a negative value both in an aqueous solution and in the presence of the oxidized form of GLP. This indicates the thermodynamic probability of this process, which is consistent with the experimental results. Regardless of the nature of the cation, its interaction with Trilon B is thermodynamically more likely in an aqueous solution than in the adsorbed state on the surface of oxidized GLP. [ABSTRACT FROM AUTHOR]

Laser-induced white emission of diamond was investigated under irradiation with a focused beam of an infrared laser diode. It is a surface-related coherent emission, characterized by an excitation threshold and an exponential dependence on pumping laser power. The mechanism of white emission is discussed in terms of multiphoton ionization of carbon atoms in an irradiated spot. The excitation power dependence of white emission intensity has demonstrated hysteresis loop behavior. This phenomenon could be useful in new broadband laser sources and optical information storage. [ABSTRACT FROM AUTHOR]

The research reveals the main reasons that prevent the extension of commercial apricot plantations in Ukraine and worldwide. This brief description includes eight cultivars from Ukrainian and foreign breeding programmes. The trials conducted in the Right-Bank subzone of the Western Forest Steppe of Ukraine. The plants from Ukrainian breeding programme 'Melitopolskyi Ranni?', 'Botsadivskyi', 'Siaivo', 'Kumir', 'Osoblyvyi Denysiuka', as well as the foreign one - 'Robada', 'Harogem', 'HJA-19', were distinguished by high adaptability to the complex of adverse overwintering factors in the above-mentioned region. These samples did not lose the acquired level of frost resistance under the influence of provoking thaws. A comprehensive assessment of drought resistance, based on water-holding capacity, turgor recovery degree, water deficiency, and leaves' hydration of the presented varieties, established that all variants of the experiment were not inferior to the best popular cultivars. According to the the biological feature of buds' formation at an early age, the cultivars 'Robada' and 'HJA-19' were characterized as early-fruiting. The yield and quality indicators for the 2021-2022 years of research were evaluated. Average fruit weight was noted in all samples, with the cultivar 'Siaivo' exceeding the average. To improve the assortment and enrich the apricot gene pool collections with the best samples suitable for cultivation in the Forest-Steppe Zone of Ukraine, according to the results of the study, the following researched cultivars were included in the collection of valuable samples of the common apricot gene pool of the Institute of Horticulture of the National Academy of Sciences of Ukraine: 'Melitopolskyi Ranni?,' 'Botsadivskyi,' 'Siaivo,' and 'Osoblyvyi Denysiuka'. These cultivars are sources of productivity and adaptability to abiotic factors of cultivation (winter and frost resistance, drought resistance). They are certified by the National Center of Plant Genetic Resources of Ukraine. [ABSTRACT FROM AUTHOR]

The efficiency of using electron beam welding in producing permanent joints of structural materials of all thicknesses and shapes is well-known. The work for the first time considers the possibility of using electron beam welding for the production of high-precision parts of optical system in cathode unit, providing the necessary parameters and their joining with electron beam gun insulator in future. The use of electron beam welding at the final stage of manufacturing cathode unit opens the opportunity of minimizing the number of further technological operations. It is noted that to create the welding technology, in which the operation of welding would become a final assembly operation, the development of new designs of welded joints and schemes for assembly of cathode unit are required. Due to a correct design of welding units and compliance with the accuracy of assembling for welding, it became possible to preserve geometric dimensions after electron beam welding and to provide the operational reliability of the design as a whole. 5 Ref., 6 Figures. [ABSTRACT FROM AUTHOR]