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

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»

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

Immobilization of boron-rich compound on Fe3O4 nanoparticles: Stability and cytotoxicity

Magnetic nanoparticles based on Fe3O4 and their modifications of surface with therapeutic substances are of great interest, especially drug delivery for cancer therapy includes boron-neutron capture therapy. The results of boron-rich compound (carborane borate) attachment to previously aminated by (3-aminopropyl)-trimethoxysilane iron oxide nanoparticles are presented. Energy-dispersive X-ray analysis and Fourier transform infrared spectroscopy with attenuated total reflection (ATR) accessory confirmed change of nanoparticles elemental content after modification and formation of new bond between Fe3O4 and attached molecules. Scanning and transmission electron microscopy showed that Fe3O4 nanoparticles average size is 18.9 nm. Phase parameters were investigated by powder X-ray diffraction, Fe3O4 nanoparticles magnetic behavior was evaluated by Mössbauer spectroscopy. Chemical and colloidal stability was studied using simulated body fluid (phosphate buffer – PBS). Modified nanoparticles have excellent stability in PBS (pH = 7.4), characterized by X-ray diffraction, Mössbauer spectroscopy and dynamic light scattering. Fe3O4 biocompatibility was elucidated in-vitro using cultured mouse embryonic fibroblasts. The obtained results show the increasing of IC50 from 0.110 mg/ml for Fe3O4 to 0.405 mg/ml for Fe3O4-Carborane nanoparticles. Obtained data confirm biocompatibility and stability of synthesized nanoparticles and potential to use them in boron-neutron capture therapy

Isostatic Hot Pressed W–Cu Composites with Nanosized Grain Boundaries: Microstructure, Structure and Radiation Shielding Efficiency against Gamma Rays

Abstract: The W–Cu composites with nanosized grain boundaries and high effective density were fabricated using a new fast isostatic hot pressing method. A significantly faster method was proposed for the formation of W–Cu composites in comparison to the traditional ones. The influence of both the high temperature and pressure conditions on the microstructure, structure, chemical composition, and density values were observed. It has been shown that W–Cu samples have a polycrystalline well-packed microstructure. The copper performs the function of a matrix that surrounds the tungsten grains. The W–Cu composites have mixed bcc-W (sp. gr. Im 3 m) and fcc-Cu (sp. gr. Fm 3 m) phases. The W crystallite sizes vary from 107 to 175 nm depending on the sintering conditions. The optimal sintering regimes of the W–Cu composites with the highest density value of 16.37 g/cm3 were determined. Tungsten–copper composites with thicknesses of 0.06–0.27 cm have been fabricated for the radiation protection efficiency investigation against gamma rays. It has been shown that W–Cu samples have a high shielding efficiency from gamma radiation in the 0.276–1.25 MeV range of energies, which makes them excellent candidates as materials for radiation protection. © 2022 by the authorsLicensee MDPI, Basel, Switzerland.Ministry of Education and Science of the Russian Federation, Minobrnauka: 075-15-2020-926Funding: M.V.S. acknowledges financial support from the Ministry of Science and Higher Education of the Russian Federation within the framework of state support for the creation and development of World-Class Research Centers “Digital Biodesign and Personalized Healthcare” No. 075-15-2020-926

A Study of Ta2O5 Nanopillars with Ni Tips Prepared by Porous Anodic Alumina Through-Mask Anodization

The paper discusses the formation of Ta2O5 pillars with Ni tips during thin porous anodic alumina through-mask anodization on Si/SiO2 substrates. The tantalum nanopillars were formed through porous masks in electrolytes of phosphoric and oxalic acid. The Ni tips on the Ta2O5 pillars were formed via vacuum evaporation through the porous mask. The morphology, structure, and magnetic properties at 4.2 and 300 K of the Ta2O5 nanopillars with Ni tips have been studied using scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometry. The main mechanism of the formation of the Ta2O5 pillars during through-mask anodization was revealed. The superparamagnetic behavior of the magnetic hysteresis loop of the Ta2O5 nanopillars with Ni tips was observed. Such nanostructures can be used to develop novel functional nanomaterials for magnetic, electronic, biomedical, and optical nano-scale devices

Tribology properties investigation of the thermoplastic elastomers surface with the AFM lateral forces mode

Приведены результаты определения сил и коэффициентов трения между поверхностью модифицированных термоэластопластов и кремниевым наконечником зонда АСМ. Показана зависимость определяемых характеристик от скорости движения зонда. Выполнены исследования изменения Ктр в зависимости от количества циклов сканирования.The results of friction forces and friction coefficients (Ffr and Cfr) determination between the modified thermoplastic elastomers surfaces and the silicon tip of AFM probe are presented. The dependence of Ffr and Cfr on the probe speed is shown. A study of the changes in Cfr depending on the number of scan cycles was made.Работа выполнена при поддержке грантов РФФИ № 16-53-00178 и БРФФИ № Ф16Р-142

Distribution and luminescence characteristics of Ce3+Ce^{3+} ions in calcium hydroxyapatite

The luminescence characteristics of Ce³⁺ ions in calcium hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ have been studied under excitation within the 3.5-15 eV region. It has been found that in Ca₁₀(PO₄)₆(OH)₂ prepared in a reducing atmosphere, Ce³⁺ ions tend to occupy preferably high symmetry Ca(I) sites. The energies of all 5d crystal field levels of Ce³⁺ ions in Ca(I) sites have been determined. In addition to the 4f->5d excitation bands, the excitation spectrum of the Ce³⁺ emission shows a band with a maximum at 7.7 eV which is attributed to the host lattice absorption. The influence of the structural features of Ca₁₀(PO₄)₆(OH)₂ on the luminescent behavior of Ce³⁺ is discussed.Вивчено люмінесцентні властивості іонів Ce³⁺ у гідроксіапатиті кальцію Ca₁₀(PO₄)₆(OH)₂ при збудженні в області 3,5-15 еВ. Встановлено, що у Ca₁₀(PO₄)₆(OH)₂, одержаному у відновлювальному середовищі, іони Ce³⁺ виявляють тенденцію займати високосиметричні Са(І)-позиції. Визначено енергії всіх компонентів 5d-конфігурації іонів Ce³⁺ у позиціях Са(І). у спектрі збудження люмінесценції іонів Ce³⁺, крім 4f->5d смуг, також спостерігається смуга з максимумом 7,7 еВ, що обумовлена власним по- глинанням гідроксіапатиту кальцію. Обговорюється вплив структурних особливостей Ca₁₀(PO₄)₆(OH)₂ на люмінесцентні властивості іонів Ce³⁺.Изучены люминесцентные свойства ионов Ce³⁺ в гидроксиапатите кальция Ca₁₀(PO₄)₆(OH)₂ при возбуждении в области 3,5-15 эВ. Установлено, что в Ca₁₀(PO₄)₆(OH)₂, полученном в восстановительной среде, ионы Ce³⁺ проявляют тенденцию занимать высокосимметричные Са(l) позиции. Определены энергии всех компонентов 5d-конфигурации ионов Ce³⁺ в позициях Са(l). В спектре возбуждения люминесценции ионов Ce³⁺, помимо полос 4f->5d, также наблюдается полоса с максимумом 7,7 эВ, которая обусловлена собственным поглощением гидроксиапатита кальция. Обсуждается влияние структурных особенностей Ca₁₀(PO₄)₆(OH)₂ на люминесцентные свойства ионов Ce³⁺