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In focus - surface-active materialsИнформационные сообщени

Коллоидно-химические свойства водной дисперсии прополиса, полученной методом замены растворителя

Mixing an alcoholic extract of propolis with distilled water or aqueous solution, which model seawater composition, give rise to aqueous dispersions with or without emulsifier. High dispersion stability is attained at hydrophylic-lipophylic balance equaled 13.9 using sorbitan oleate and polyoxyethylene sorbitan monooleate (Polysorbate-80) as a binary emulsifier. The initial particle size of dispersions is almost identical regardless of the presence of the emulsifier or water salinity. However, in the latter case a dispersion with essentially narrow size distribution is formed and, as a result, the dispersion is more resistant to coagulation and phase separation. Apparently, the main contribution to the stability of the aqueous propolis dispersion is made by the structural-mechanical barrier, which is formed by a thick adsorption layer of the hydrated nonionic surfactant.Смешением спиртового раствора прополиса с дистиллированной водой или водным раствором, моделирующим состав морской воды, получены его дисперсии, в том числе в присутствии эмульгатора. Наибольшая устойчивость дисперсии достигается при использовании в качестве эмульгатора смеси сорбитанолеат/полисорбат-80 со значением гидрофильно-липофильного баланса 13.9. Исходный размер частиц дисперсии практически одинаков вне зависимости от присутствия ПАВ и минерализации среды, однако в последнем случае получается более монодисперсная и потому более устойчивая к коагуляции и расслоению дисперсия. Основной вклад в устойчивость водной дисперсии прополиса, по-видимому, вносит структурно-механический барьер, который образован толстым адсорбционным слоем неионогенного ПАВ, сольватированного водой

Эмульсии пикеринга и их применение при получении полимерных наноструктурированных материалов

In this article both types of Pickering emulsions – oil/water and water/oil – and their applications in the synthesis of different polymers have been considered. Pickering emulsions are dispersions stabilized by solid particles adsorbed at oil-water interface instead of conventional emulsifier. The influence of various solid particles, their amount and interaction on emulsions formation, stability and morphology with various suspended solid particles have been considered. Phase inversion phenomena and factors (such as wettability of solid particles) affecting them have been described. The interest to Pickering emulsions for the last decade is highly fueled by eco-friendly and cost-effective manufacture of hybrid polymer particles and nanocomposites with supracolloidal structures. The Pickering emulsion polymerization or suspension polymerization allows preparing in situ reinforced nanostructural polymer composites, unusual latexes and microcapsules with unique properties.Эмульсии Пикеринга представляют собой дисперсии, стабилизированные твердыми частицами, закрепленными на границе масло–вода, вместо обычных эмульгаторов. Здесь рассматривается их образование, стабильность и морфология в присутствии твердых частиц разной природы. Большой интерес к эмульсиям Пикеринга за последние десятилетия проявляется в связи с перспективами экологически чистого и экономичного производства гибридных полимерных частиц и нанокомпозитов с супрамолекулярной коллоидной структурой. Эмульсионная или суспензионная полимеризация в эмульсиях Пикеринга позволяет получать in situ усиленные наноструктурированные полимерные композиты, необычные латексы и микрокапсулы с уникальными свойствами

One-loop effective action in N=2{\cal N}=2 supersymmetric massive Yang-Mills theory

We consider the ${\cal N}=2$ supersymmetric theory of the massive Yang-Mills field formulated in the ${\cal N}=2$ harmonic superspace. The various gauge-invariant forms of writing the mass term in the action (in particular, using the Stueckelberg superfield), which result in dual formulations of the theory, are presented. We develop a gauge-invariant and explicitly supersymmetric scheme of the loop off-shell expansion of the superfield effective action. In the framework of this scheme, we calculate gauge-invariant and explicitly ${\cal N}=2$ supersymmetric one-loop counterterms including new counterterms depending on the Stueckelberg superfield. Component structure of one of these counterterms is analyzed.Comment: 18, pages, Accepted for publication in Theor. Math. Phy

In focus - surface-active materials

In focus - surface-active material

Rheological behaviour of aqueous montmorillonite dispersions from the tagansky deposit

The article considers results of rheological studies of dilute aqueous dispersions of montmorillonite near the sol-gel transition. Results of dynamic light scattering, rotational viscometry, and adsorption data reveal the presence of a critical concentration of the structure formation, which is strongly influenced by the electrolyte (NaCl) concentration in the dispersion. Bentonite dispersion behaves differently with respect to the NaCl content near the critical concentration just before and after it. When we have a smaller particle concentration in the dispersion, extreme dependence of the strength and viscosity characteristics on the NaCl concentration is evident, while monotonic dependence exists at high particle concentration up to attaining the maximal value of the gel tensile strength. The critical concentration obtained from viscometry data is close to the theoretical value obtained for the simplified model in the approximation of hard spheres

Pickering emulsions and their use in production of polymer nanostructured materials

In this article both types of Pickering emulsions – oil/water and water/oil – and their applications in the synthesis of different polymers have been considered. Pickering emulsions are dispersions stabilized by solid particles adsorbed at oil-water interface instead of conventional emulsifier. The influence of various solid particles, their amount and interaction on emulsions formation, stability and morphology with various suspended solid particles have been considered. Phase inversion phenomena and factors (such as wettability of solid particles) affecting them have been described. The interest to Pickering emulsions for the last decade is highly fueled by eco-friendly and cost-effective manufacture of hybrid polymer particles and nanocomposites with supracolloidal structures. The Pickering emulsion polymerization or suspension polymerization allows preparing in situ reinforced nanostructural polymer composites, unusual latexes and microcapsules with unique properties

Colloid-chemical properties of aqueous propolis dispersion prepared by the solvent diffusion method

Mixing an alcoholic extract of propolis with distilled water or aqueous solution, which model seawater composition, give rise to aqueous dispersions with or without emulsifier. High dispersion stability is attained at hydrophylic-lipophylic balance equaled 13.9 using sorbitan oleate and polyoxyethylene sorbitan monooleate (Polysorbate-80) as a binary emulsifier. The initial particle size of dispersions is almost identical regardless of the presence of the emulsifier or water salinity. However, in the latter case a dispersion with essentially narrow size distribution is formed and, as a result, the dispersion is more resistant to coagulation and phase separation. Apparently, the main contribution to the stability of the aqueous propolis dispersion is made by the structural-mechanical barrier, which is formed by a thick adsorption layer of the hydrated nonionic surfactant

Development of Technology for D eposition of Thick Copper Layers onto Ceramic Substrates Applied in Power Electronics

Received: 23.06.22. Revised: 19.07.22. Accepted: 19.07.22. Available online: 26.07.22.The technology of a two-layer metallization coating on ceramic substrates made of aluminum nitride and oxide was developed.The resulting copper coatings are characterized by a strong adhesive bond with the base and low electrical resistance (at the level of 3·10–6 Ohm·cm).For high-quality adhesion, the optimum annealing temperature was 1000 °C.The basic element of the design of a power module is a metallized ceramic substrate. In this work, the formation of metallization coatings by the method of thermal transfer of metallization pastes (Mo-Mn-Si + binder) for alumina and aluminum nitride ceramics was carried out. The fixing of the metallization coating on the ceramic substrate was performed by firing at a temperature of 1320 °C. The subsequent deposition of the copper layer was carried out by the method of cold gas-dynamic spraying (CGDS) followed by annealing of the deposited coating. For high-quality adhesion, the optimum annealing temperature was 1000 °C.The work was funded by the State task of Ministry of Science and Higher Education of Russia (project no. FSUN-2020-0008)