The influence of multilayer metal-carbon coatings composition with different arrangement of functional layers on their surface morphology

This research was supported by the grants of Belarussian Republican Foundation for Fundamental Research BRFFR № T17KIG-009

Friction coefficient obtained using AFM as a criterion of changes in the surface properties after low-temperature plasma treatment

This research was supported by the grant of Belarussian Republican Foundation for Fundamental Research BRFFR No.F17-118

Влияние параметров электролитического осаждения на структуру и микромеханические свойства пленок Ni–Fe

The correlation between the synthesis modes, chemical composition, crystal structure, surface microstructure, and also the mechanical properties of thin nanostructured Ni – Fe films has been studied. Thin Ni–Fe films on the Si with Au sublayer were obtained using electrolyte deposition with different current modes: direct current and three pulsed modes with pulse duration of 1 s, 10–3 and 10–5 s. It is shown that a decrease in the pulse duration to 10–5 s leads to an increase in the film elastic modulus and the hardness due to the small grain size and a large number of grain boundaries with increased resistance to plastic deformation. The effect of heat treatment at 100, 200, 300, and 400 °C on the surface microstructure and micromechanical properties of the films was investigated. An increase in grain size from 6 to 200 nm was found after heat treatment at 400 °C which, in combination with interfusion processes of the half-layer material, led to a significant decrease in hardness and elastic modulus. Ni–Fe films with improved mechanical properties can be used as coatings for microelectronic body for their electromagnetic protection.Проведены исследования корреляции между режимами синтеза, химическим составом, кристаллической структурой и микроструктурой поверхности, а также механическими свойствами тонких наноструктурированных пленок Ni–Fe. Тонкие пленки Ni–Fe были получены в различных режимах электролитического осаждения: в режиме постоянного тока и в импульсных режимах с длительностью импульса 1 с, 10–3 и 10–5 с. Показано, что уменьшение длительности импульса до 10–5 с приводит к увеличению модуля упругости и твердости пленок благодаря малому размеру зерна и, соответственно, большому количеству границ зерен с повышенным сопротивлением пластической деформации. Исследовано влияние термической обработки при T = 100, 200, 300 и 400 °С на микроструктуру поверхности и микромеханические свойства пленок. После термообработки при 400 °С наблюдалось увеличение размера зерна от 6 до 200 нм, что в сочетании с процессами взаимодиффузии материала подслоя и пленки привело к значительному снижению твердости и модуля упругости. Пленки Ni–Fe с улучшенными механическими свойствами могут быть использованы как покрытия корпусов микроэлектроники для электромагнитной их защиты

Electrochemical behaviour of Ti/Al2O3/Ni nanocomposite material in artificial physiological solution: Prospects for biomedical application

Inorganic-based nanoelements such as nanoparticles (nanodots), nanopillars and nanowires, which have at least one dimension of 100 nm or less, have been extensively developed for biomedical applications. Furthermore, their properties can be varied by controlling such parameters as element shape, size, surface functionalization, and mutual interactions. In this study, Ni-alumina nanocomposite material was synthesized by the dc-Ni electrodeposition into a porous anodic alumina template (PAAT). The structural, morphological, and corrosion properties were studied using x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and electrochemical techniques (linear sweep voltammetry). Template technology was used to obtain Ni nanopillars (NiNPs) in the PAAT nanocomposite. Low corrosion current densities (order of 0.5 μA/cm2) were indicators of this nanocomposite adequate corrosion resistance in artificial physiological solution (0.9% NaCl). A porous anodic alumina template is barely exposed to corrosion and performs protective functions in the composite. The results may be useful for the development of new nanocomposite materials technologies for a variety of biomedical applications including catalysis and nanoelectrodes for sensing and fuel cells. They are also applicable for various therapeutic purposes including targeting, diagnosis, magnetic hyperthermia, and drug delivery. Therefore, it is an ambitious task to research the corrosion resistance of these magnetic nanostructures in simulated body fluid. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Government Council on Grants, Russian FederationBelarusian Republican Foundation for Fundamental Research, BRFFR: Ф18Д-00720163522Funding: The work was performed with support of State Scientific and Technical Program “Nanotech” (ГБЦ No 20163522), Belarusian Republican Foundation for Fundamental Research (Grant No. Ф18Д-007), Act 211 of Government of Russian Federation (contract No. 02.A03.21.0011). Additionally, the work was partially supported by the Grant of World Federation of Scientists (Geneva, Switzerland)

Efficiency of Magnetostatic Protection Using Nanostructured Permalloy Shielding Coatings Depending on Their Microstructure

The effect of microstructure on the efficiency of shielding or shunting of the magnetic fluxby permalloy shields was investigated in the present work. For this purpose, the FeNi shieldingcoatings with different grain structures were obtained using stationary and pulsed electrodeposition.The coatings’ composition, crystal structure, surface microstructure, magnetic domain structure, andshielding efficiency were studied. It has been shown that coatings with 0.2–0.6μm grains have adisordered domain structure. Consequently, a higher value of the shielding efficiency was achieved,but the working range was too limited. The reason for this is probably the hindered movement of thedomain boundaries. Samples with nanosized grains have an ordered two-domain magnetic structurewith a permissible partial transition to a superparamagnetic state in regions with a grain size of lessthan 100 nm. The ordered magnetic structure, the small size of the domain, and the coexistenceof ferromagnetic and superparamagnetic regions, although they reduce the maximum value ofthe shielding efficiency, significantly expand the working range in the nanostructured permalloyshielding coatings. As a result, a dependence between the grain and domain structure and theefficiency of magnetostatic shielding was found

Electrochemical behaviour of Ti/Al2O3/Ni nanocomposite material in artificial physiological solution: Prospects for biomedical application

Inorganic-based nanoelements such as nanoparticles (nanodots), nanopillars and nanowires, which have at least one dimension of 100 nm or less, have been extensively developed for biomedical applications. Furthermore, their properties can be varied by controlling such parameters as element shape, size, surface functionalization, and mutual interactions. In this study, Ni-alumina nanocomposite material was synthesized by the dc-Ni electrodeposition into a porous anodic alumina template (PAAT). The structural, morphological, and corrosion properties were studied using x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and electrochemical techniques (linear sweep voltammetry). Template technology was used to obtain Ni nanopillars (NiNPs) in the PAAT nanocomposite. Low corrosion current densities (order of 0.5 μA/cm2) were indicators of this nanocomposite adequate corrosion resistance in artificial physiological solution (0.9% NaCl). A porous anodic alumina template is barely exposed to corrosion and performs protective functions in the composite. The results may be useful for the development of new nanocomposite materials technologies for a variety of biomedical applications including catalysis and nanoelectrodes for sensing and fuel cells. They are also applicable for various therapeutic purposes including targeting, diagnosis, magnetic hyperthermia, and drug delivery. Therefore, it is an ambitious task to research the corrosion resistance of these magnetic nanostructures in simulated body fluid. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Government Council on Grants, Russian FederationBelarusian Republican Foundation for Fundamental Research, BRFFR: Ф18Д-00720163522Funding: The work was performed with support of State Scientific and Technical Program “Nanotech” (ГБЦ No 20163522), Belarusian Republican Foundation for Fundamental Research (Grant No. Ф18Д-007), Act 211 of Government of Russian Federation (contract No. 02.A03.21.0011). Additionally, the work was partially supported by the Grant of World Federation of Scientists (Geneva, Switzerland)

Оптимизация излучающей катушки программно-аппаратного комплекса для исследования эффективности экранирования низкочастотного электромагнитного излучения

Optimization of the radiation coil of the hardware-software complex for studying the effectiveness of shielding of low-frequency electromagnetic radiation will make it possible to assess the effectiveness of shielding coatings at a higher level. This fact will make it possible to develop coatings with improved characteristics. The purpose of this work was to determine the optimal characteristics of the emitting coil which will ensure its stable operation and magnetic field strength in the frequency range up to 100 kHz.The parameters of the manufactured samples, such as inductance (L), active (R) and total resistance (Z), were obtained using an MNIPI E7-20 emittance meter. In practice, the coils with the optimal parameters calculated theoretically were connected to a current source and amplifier. To detect electromagnetic radiation, a multilayer inductor connected to a UTB-TREND 722-050-5 oscilloscope was used as a signal receiver.The results of measurements showed that the resistance of multilayer coils is approximately 1000 times higher than that of single-layer coils. Also, for multilayer coils, an avalanche-like increase in total resistance is observed starting from a frequency of 10 kHz, while for single-layer coils there is a uniform increase in total resistance over the entire frequency range up to 100 kHz.The paper presents results of research on the correlation of the performance of single-layer and multilayer inductors depending on their parameters in the frequency range from  20 Hz  to  100 kHz. Values of the voltage required to provide the magnetic field strength of 1, 5, 20 Oe at 25 Hz and 100 kHz have been calculated. After analyzing the data obtained, the optimal parameters of the inductor were found which ensure stable performance in the frequency range up to 100 kHz.Оптимизация излучающей катушки программно-аппаратного комплекса для исследования эффективности экранирования низкочастотного электромагнитного излучения позволит на более качественном уровне оценивать эффективность экранирующих покрытий. Данный факт даст возможность разрабатывать покрытия с улучшенными характеристиками. Целью данной работы являлось определение оптимальных характеристик излучающей катушки, которые обеспечат её стабильную работу и напряжённость магнитного поля в частотном диапазоне до 100 кГц.Параметры изготовленных образцов, такие как индуктивность, активное и общее сопротивление, были получены, используя измеритель иммитанса МНИПИ E7-20. На практике катушки с оптимальными параметрами, вычисленными теоретически, были подключены к источнику и усилителю тока. Для детектирования электромагнитного излучения в качестве приёмника сигнала использовалась многослойная катушка индуктивности, подключённая к осциллографу UTB-TREND 722-050-5.Результаты измерений показали, что сопротивление многослойных катушек приблизительно в 1000 раз больше сопротивления однослойных. Также у многослойных катушек наблюдается лавинообразный рост общего сопротивления, начиная с частоты 10 кГц, в то время как у однослойных катушек происходит равномерный рост общего сопротивления на всём диапазоне частот до 100 кГц. Представлены результаты исследований корреляции рабочих характеристик  однослойных  и многослойных  катушек  индуктивности  в  зависимости  от  их  параметров  в  частотном  диапазоне от 20 Гц до 100 кГц. Рассчитаны значения напряжения, необходимого для обеспечения напряжённости магнитного поля 1, 5, 20 Э при 25 Гц и 100 кГц. Проанализировав полученные данные, найдены оптимальные параметры катушки индуктивности, обеспечивающие стабильные рабочие характеристики в диапазоне частот до 100 кГц

The effect of heat treatment on the microstructure and mechanical properties of 2d nanostructured au/nife system

Nanostructured NiFe film was obtained on silicon with a thin gold sublayer via pulsed electrodeposition and annealed at a temperature from 100 to 400◦C in order to study the effect of heat treatment on the surface microstructure and mechanical properties. High-resolution atomic force microscopy made it possible to trace stepwise evolving microstructure under the influence of heat treatment. It was found that NiFe film grains undergo coalescence twice—at ~100 and ~300°C—in the process of a gradual increase in grain size. The mechanical properties of the Au/NiFe nanostructured system have been investigated by nanoindentation at two various indentation depths, 10 and 50 nm. The results showed the opposite effect of heat treatment on the mechanical properties in the near-surface layer and in the material volume. Surface homogenization in combination with oxidation activation leads to abnormal strengthening and hardening-up of the near-surface layer. At the same time, a nonlinear decrease in hardness and Young’s modulus with increasing temperature of heat treatment characterizes the internal volume of nanostructured NiFe. An explanation of this phenomenon was found in the complex effect of changing the ratio of grain volume/grain boundaries and increasing the concentration of thermally activated diffuse gold atoms from the sublayer to the NiFe film. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Funding: The work was supported by Act 211 Government of the Russian Federation, contract № 02.A03.21.0011

Combined Effect of Microstructure, Surface Energy, and Adhesion Force on the Friction of PVA/Ferrite Spinel Nanocomposites

Nanocomposite films based on spinel ferrite (Mg0.8Zn0.2Fe1.5Al0.5O4) in a PVA matrix were obtained. An increase in the spinel concentration to 10 wt.% caused an avalanche-like rise in roughness due to the formation of nanoparticle agglomerates. The lateral mode of atomic force microscopy (AFM) allowed us to trace the agglomeration dynamics. An unexpected result was that the composite with 6 wt.% of filler had a low friction coefficient in comparison with similar composites due to the successfully combined effects of low roughness and surface energy. The friction coefficient decreased to 0.07 when the friction coefficient of pure PVA was 0.72. A specially developed method for measuring nano-objects’ surface energy using AFM made it possible to explain the anomalous nature of the change in tribological characteristics. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.National University of Science and Technology, MISISAlex V. Trukhanov thanks NUST MISIS for support within the framework of the «Priority 2030»

Temperature induced structural and polarization features in BaFe12O19

We report the observation of a peculiar polarization behavior of BaFe12O19 in electric field where the linear polarization is detected at temperatures below 150 K whereas at higher temperatures a hysteresis-like polarization response is observed. At the same time, the performed neutron diffraction analysis shows no variations in crystal or magnetic structures with temperature. Based on the results of ab initio calculations we suggest the mechanism able to explain the experimentally observed behavior. We show that specific Fe atoms do not occupy the positions formally assigned to them by the conventional centrosymmetric P63/mmc (#194) space group (z = 0.25; 0.75) as these positions correspond to local energy maxima. Instead, these Fe atoms are shifted along the z-axis to positions z = 0.259 (0.241) and z = 0.759 (0.741), which correspond to local energy minima. To an inversion center move between these minima Fe atoms need to overcome an energy barrier. This barrier is rather insignificant for smaller volumes but it becomes larger for expanded volumes due to coupling between the displacements of these Fe atoms. Additionally, our analysis suggests that the non-centrosymmetric and polar P63mc (#186) space group could be appropriate for the description of the BaFe12O19 structure