Vol 59, No 1 (2023)

It is shown that, with the help of adsorption–catalytic deformation, it is possible to significantly change the composition of the skeletal nickel hydrogenation catalyst by changing the steric factor directly under the conditions of the chemical reaction. Various substances were tested as model compounds undergoing reduction: hydrogen peroxide, sodium maleate, and propen-2-ol-1. It is shown that, during the hydrogenation reaction, as a result of strong local overheating, the catalyst grain is deformed and the aluminum atoms that were previously in the bulk of this grain appear on the surface, after which aluminum becomes available for further leaching, while yielding additional hydrogen.

ES-103(1) microporous carbon adsorbent with specific micropore volume W0 = 0.80 cm3/g and pore width Х0 = 1.32 nm was prepared by thermochemical activation of wood waste in Н3РО4 at 1173 K. The specific BET surface of the adsorbent was SBET = 2115 m2/g. At 303 K and 20 MPa, the methane-adsorption capacity of the adsorbent reached ~22 wt %. In the main region of micropore fillings, the differential molar isosteric heats of methane adsorption gradually dropped from ~16 to 12 kJ/mol. To increase the energy of methane adsorption, it is necessary to use systems that provide a possibility additionally to increase the energy of adsorption due to the energy of adsorbate associating in micropores. At a pressure of 10 MPa, the methane volumetric density in ES-103(1) adsorbent compacted with a binder achieved 200 m3(NTP)/m3.

A comparative analysis of the composition and structure of freshly precipitated iron(III) hydroxide precipitates obtained from a sodium sulfate solution (400 mg/L) at pH 7 and 8 before and after the sorption of nickel ions on them was carried out. IR, Raman, and Mössbauer spectroscopy, as well as X-ray diffraction and thermal analyses, have shown that precipitates synthesized from a solution of iron(III) chloride are a two-line ferrihydrite with the gross formula Fe2O3⋅3H2O. It has been established that the sorption of nickel ions on these precipitates is not accompanied with chemisorption, i.e., the formation of mixed compounds between iron and nickel. Their doping with nickel ions also was not observed. It has been found that the ζ potential of ferrihydrite particles at pH < 5.4 has a positive value, whereas it becomes negative at pH > 5.4. The zero-charge point of the precipitate particles corresponds to pH 5.4.

The possibility of electrochemical formation of Al–Ni composite coatings from an aluminum suspension in an electrolyte based on a deep eutectic solvent has been studied. The composition of the electrolyte was proposed, and the influence of the aluminum content on the composition, structure, and morphology of the coating was studied.

Coatings obtained by high-power impulse magnetron sputtering (HIPIMS) were tested using a 64% Ti–16% C–14% Ni–6% Al target (42.5 at % Ti, 42.5 at % C, 7.5 at % Ni, 7.5 at % Al). The microstructure and composition of the coatings were studied using scanning electron microscopy, optical emission spectroscopy of a glow discharge, and X-ray phase analysis. Coatings were studied in terms of their hardness, modulus of elasticity, elastic recovery, resistance to elastic fracture strain, resistance to plastic deformation, friction coefficient and friction-slip wear resistance, resistance to shock-dynamic loading, as well as oxidation resistance. Field tests of coatings on the cutting tool were carried out. Properties of the coatings obtained by direct current and high-power pulse mode were compared. The results showed that the Ti–C–Ni–Al coatings had a dense homogeneous structure, a hardness of 12–26 GPa, an elastic modulus of 143–194 GPa, an elastic recovery of 66–90%, a low friction coefficient of 0.24–0.4, and high oxidation resistance at 800°C. The coating deposited according to the optimal regime confirmed its high practical efficiency during full-scale tests, reducing the cutting tool wear by ~25%.

In the present study, chitosan coatings modified with g-C3N4 were prepared for AZ91 magnesium alloy. The microstructure of the chitosan–g-C3N4 coatings, depending on the concentration of the particles of the modifying phase in the chitosan solution, was investigated by scanning electron microscopy and X-ray phase analysis. It was found that coatings prepared in suspension of chitosan containing more than 30 g/dm3 g-C3N4 exhibited a complete wettability with a sodium-phosphate buffer solution. Confocal microscopy established the degree of inhibition of E. coli biofilm formation on the surface of the prepared coatings. It was found by using linear voltammetry and electrochemical impedance spectroscopy that the modification of chitosan by the g-C3N4 particles led to an improvement in the protective properties of coatings.

Исследовано продольное (вдоль направления тока) перераспределение химического состава и дефектной структуры неоднородных оксидных слоев при окислении пленок на основе сплава системы Fe–Cr в условиях контактного наложения на пленку окисляющегося сплава электрического тока. Зарегистрировано активирующее действие внешнего электрического тока на оксидирование сплава. Оно проявляется (по сравнению с обычным термическим оксидированием) в росте средней скорости оксидирования, в неравномерном вдоль поверхности проводника перераспределении толщины, химического состава и дефектности поверхностного оксида. При смещении от отрицательного к положительному контакту наблюдается падение концентрации кислородных вакансий, упорядочение структуры и обогащение оксидного слоя хромом. При наложении внешнего тока концентрация хрома на межфазной границе метал-оксид постоянно возобновляется, что поддерживает интеркаляцию хрома из электродиффузионной зоны сплава в структуру межфазного оксида (предположительно железо-хромистой шпинели). При достижении предельной концентрации хрома в структуре шпинели, на границе раздела металл-оксид происходит выделение полуторной окиси хрома Cr₂O₃ в виде индивидуальной фазы.

Particles with an aluminum core and a hydroxide shell obtained by low-temperature (up to 100°C) oxidation of spherical aluminum micron particles with water are studied. Processes occurring upon heating these particles up to 750°C in a controlled gaseous atmosphere are analyzed. The composition and amount of released gas-phase products are studied, and their nature is determined. The transformation of the shell as a result of the phase transition of aluminum hydroxide to oxide is considered. The mechanism of formation of cracks as a result of thermal expansion of the core and shell during the heating of the particle is considered. Outcrops of aluminum onto the surface of the oxide shell after reaching the melting point of aluminum are noted. It is proposed to use aluminum extruded onto the surface for the formation of bonds between the particles upon executing 3D printing.

Using the random forest algorithm (RF), two models are obtained for predicting first-year corrosion losses K1 of aluminum in an open atmosphere in various regions of the world. The RF1 model was obtained using the combined databases of the international programs ISO CORRAG and MICAT and tests in Russia and is intended for evaluation of K1 in different types of atmosphere in different regions of the world. The model makes it possible to predict K1 only in the continental regions of the world. For all types of atmospheres, a comparison was made of the accuracy of the prediction of K1 according to the RF1 model and the dose-response function (DRF) presented in the ISO 9223 standard. For continental sites, a comparison of the reliability of the prediction is given by the RF2 model and the dose-response functions presented in ISO 9223 and the new DRF. It is shown that the reliability of predictions for both RF models is significantly better than using dose-response functions.