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Oxide layers on Mg97Y2Zn1 magnesium alloy with strengthening LPSO-phase were formed by plasma electrolytic oxidation (PEO) in bipolar mode with frequency variation of forming current pulses (50 and 500 Hz) and addition of sodium aluminate or sodium silicate to alkali phosphate fluoride electrolyte. Microstructure, chemical and phase composition, corrosion and mechanical properties of the oxide layers formed were investigated. With increasing current frequency for both electrolytes, an increase in homogeneity of the oxide layers structure and a decrease in their porosity and fracturing at constant thickness were recorded. The oxide layers formed at 500 Hz even with some decrease in hardness have better adhesive strength and 2 orders of magnitude higher short-term corrosion resistance values. PEO of Mg-alloy with LPSO-phase in the electrolyte with addition of sodium aluminate in combination with increased pulse frequency (500 Hz) allows forming the best-quality uniform oxide layer with high hardness, adhesive strength and corrosion resistance properties. The use of electrolyte with addition of sodium silicate reduced the adhesive strength by 1.5 times and brought down the long-term corrosion resistance of oxide layers by an order of magnitude, as compared with the electrolyte with sodium aluminate. The reason for a significant improvement in the complex of protective properties of the oxide layers with an increase in the current pulse frequency is supposed to be a decrease in the power and duration of individual microarc discharges with simultaneous increase in their number per unit oxidized area.

An important goal of materials science is the development of copper powders, which are used as catalysts in reactors based on fluidization bed technology. These reactors are more economical and efficient than the reactors with fixed catalytic layer. However, such reactors put special requirements to the catalysts. The catalyst should be stable in the temperature fields, have high thermal conductivity and wear resistance, certain shapes and sizes of the active particles. Сopper powders with approximately the same average particle size, but with different internal structures and surface morphologies were obtained by electrolytic method in this work. A comparative analysis of the results of exposure to temperature fields was also performed. The heating of powders was carried out in a differential scanning calorimeter (X -DSC 7000). Investigations of surface morphology and phase composition changes of the copper powders particles were performed using scanning electron microscopy and X-ray diffraction. It has been shown that particles with different initial structures and morphologies have similar morphological and phase transformations in the process of annealing in air (sintering and loss of particles faceting, the growth of whiskers and oxidation, the formation of cavities inside and pores on the surface). Nevertheless, for the icosahedral small particles of copper, there is an increased release of energy during the heating in DSC, and this energy activates and accelerates structuralphase transformations in the particles. By authors' opinion, this can be related to particular features of the internal structure and morphology of their surface.Keywords: copper, copper powder, icosahedral small particles, thermal treatment, differential scanning calorimetry. Особенности поведения электролитических медных порошков различных морфологических форм в температурных поляхОвечкина Т. А., Грызунова Н. Н. † , Викарчук А. А., Грызунов А. М., Денисова А. Г.Тольяттинский государственный университет, ул. Белорусская 14 б, 445020, Тольятти, Россия Важной задачей материаловедения является создание материалов в виде медных порошков, которые могут приме-няться в качестве катализаторов для реакторов, работающих по технологии псевдоожиженного слоя. Они являются более экономичными и эффективными, чем реакторы с неподвижным слоем катализатора. Однако, такие реакторы предъявляют особые требования к катализатору. Катализаторы должны быть стабильны в температурных полях, об-ладать высокой теплопроводностью и износостойкостью, иметь определенные формы и размеры активных частиц. В данной работе электролитическим методом были получены медные порошки с примерно одинаковым средним размером частиц, формой близкой к сферической, но разной внутренней структурой и морфологией поверхности. Проведен сравнительный анализ результатов воздействия на них температурных полей. Температурные исследо-вания осуществлялись в дифференциальном сканирующем калориметре (X -DSC 7000). Исследование изменений морфологии поверхности и фазового состава частиц порошков пр...

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