Basic magnetic properties of magnetoactive elastomers of mixed content

The results of theoretical and experimental investigations of the polymer composites that belong to a class of magnetoactive elastomers with mixed magnetic content (MAEs-MC) are presented. The fundamental distinction of such composites from ordinary magnetoactive elastomers is that the magnetic filler of MAEs-MC comprises both magnetically soft (MS) particles of size 3-5 m and magnetically hard (MH) particles whose size is an order of magnitude greater. Since MH particles of the magnetic filler are mixed into a composition in a non-magnetised state, this can ensure preparation of samples with fairly homogeneous distribution of the filler. The 'initiation' process of a synthesised MAE-MC is done by its magnetisation in a strong magnetic field that imparts to the sample unique magnetic and mechanical properties. In this work, it is shown that the presence of MS particles around larger MH particles, firstly, causes an augmentation of magnetic moments, which the MH particles acquire during initiation, and secondly, enhances the magnetic susceptibility and remanent magnetisation of MAEs-MC. These magnetic parameters are evaluated on the basis of the macroscopic magnetostatics from the experimental data of spatial scanning of the field over the space around MAEs-MC made in the shape of a spheroid. A set of samples with a fixed MH and varying MS volume contents that are initiated in two different fields, is used. The developed mesoscopic model of magnetic interactions between the MH and MS phases is able to explain the experimentally observed dependencies of the magnetic parameters on the concentration of the MS phase. The problem is solved numerically under the assumption that the elastic matrix of MAEs-MC is rigid, i.e. the mutual displacements of the particles are negligible. The model helps to elucidate the interaction of the magnetic phases and to establish that the MS phase plays thereby a dual role. On the one hand, the MS phase screens out the field acting inside MH particles, and on the other hand, it forms mesoscopic magnetic bridges between adjoining MH particles, which in turn enhance their field. The combined interplay of these contributions defines the resulting material properties of MAEs-MC on the macroscopic scale. © 2020 The Author(s). Published by IOP Publishing Ltd

Modeling the magnetostriction effect in elastomers with magnetically soft and hard particles

We analyze theoretically the field-induced microstructural deformations in a hybrid elastomer, that consists of a polymer matrix filled with a mixture of magnetically soft and magnetically hard spherical microparticles. These composites were introduced recently in order to obtain a material that allows the tuning of its properties by both, magnetically active and passive control. Our theoretical analysis puts forward two complementary models: a continuum magnetomechanical model and a bead-spring computer simulation model. We use both approaches to describe qualitatively the microstructural response of such elastomers to applied external fields, showing that the combination of magnetically soft and hard particles may lead to an unusual magnetostriction effect: either an elongation or a shrinking in the direction of the applied field depending on its magnitude. This behavior is observed for conditions (moderate particle densities, fields and deformations) under which the approximations of our models (linear response regime, negligible mutual magnetization between magnetically soft particles) are physically valid. © The Royal Society of Chemistry.Deutsche Forschungsgemeinschaft, DFG: OD 18/24-1Russian Foundation for Basic Research, RFBR: 19-52-12028, 19-52-12045, 17-41-590160Government Council on Grants, Russian FederationP. A. S. and S. S. K. acknowledge support by the DFG grant OD 18/24-1, by the Act 211 of the Government of the Russian Federation, contract No. 02.A03.21.0006, and by the FWF START-Projekt Y 627-N27. S. S. K. also acknowledges RFBR Grant 19-52-12028. O. V. S. and Yu. L. R. acknowledge support by RFBR projects 17-41-590160 and 19-52-12045, respectively. Computer simulations were carried out at the Vienna Scientific Cluster

Features of Formation of Crystallographic Texture in Cells of Spacing Grid at their Stamping

The structural and textural heterogeneity of thin-walled tubes of Zr-1% Nb alloy used for stamping of the cells of the spacing grid (SG) was studied. It was found, that structure and texture of thin-walled tubes corresponds to incomplete recrystallization. During the increasing of recrystallization degree, the variation of crystal structure parameters of Nb solid solution i

First-principles Calculation of the Formation Energy in MgO-CaO Solid Solutions

The electronic structure and total energy were calculated for ordered and disordered MgO-CaO solid solutions within the multiple scattering theory in real space and the local density approximation. Based on the dependence of the total energy on the unit cell volume the equilibrium lattice parameter and formation energy were determined for different solution compositions. The formation energy of the solid solutions is found to be positive that is in agreement with the experimental phase diagram, which shows a miscibility gap.Comment: 11 pages, 3 figure

Complex Estimation of Strength Properties of Functional Materials on the Basis of the Analysis of Grain-Phase Structure Parameters

The technique allows analysis using grain-phase structure of the functional material to evaluate its performance, particularly strength properties. The technique is based on the use of linguistic variable in the process of comprehensive evaluation. An example of estimating the strength properties of steel reinforcement, subject to special heat treatment to obtain the desired grain-phase structure

МАКРОКАЛОРИМЕТРИЧЕСКИЙ МЕТОД В ГИДРОБИОЛОГИИ: ОПИСАНИЕ ПИЛОТНОЙ МОДЕЛИ ПРИБОРА И ЕЁ ВОЗМОЖНОСТЕЙ

В Институте биологии южных морей НАНУ создан действующий опытный образец дифференциально-проточного макрокалориметра, позволяющего прямо измерять биогенные тепловые потоки в многосуточных экспериментах. Разработанный прибор позволяет в режиме реального времени снимать и передавать на компьютер информацию об изменениях температуры в сосудах и биологическом объекте. Используемые электроды могут помещаться как в воду, так и внутрь биологического объекта. Использование одновременно двух электродов позволяет оценивать разность температур внутри объекта и в экспериментальном сосуде, что расширяет возможности интерпретации получаемых данных. Описаны установка, её использование, возможности применения.A pilot model of differencial-flow macrocalorimeter was made in the Institute of the Biology of the Southern Seas (IBSS), which allows to measure biogenic heat flows several days in a row. This device allows registering temperature changes in vessels and biological objects and transferring this data to the computer. The simultaneous usage of two sensors (in the vessel and in the biological object) gives a better interpretation of the data received. The description of the device, its test results and the possibilities of its utilization are presented in this report

THE ACCURACY INVESTIGATION OF THE HIGH POSITION OF THE ROAD COVERAGE SURFACE WITH THE DIFFERENT GEODESIC DEVICES’ APPLICATION

Introduction. The updated wording of the rulebooks SP apply instead of the SNiP for the road construction last time, in which the accuracy requirements of the device bases and pavements is greatly increased. To ensure high requirements to the accuracy of vertical position of the structural layers of bases and covers roads there is a need of application of modern surveying instruments (precision optical levels and electronic total stations with different accuracy). Materials and methods. The research of the vertical position accuracy (unevenness) of the coating roads surface in IV category at the constructive layers’ device is observed with the road vehicles without an automatic system of vertical heights and with the leveling step through 10 m. Results. The calculated statistical characteristics and parameters for the deviations’ distribution of the amplitudes on the pavements’ surface elevation, which are obtained according to the measurement results, are used on the N-3 optical level and on the TRIMBLE M3 electronic total station. Discussion and conclusion. The standard deviations’ values of the amplitude, which are obtained by the N-3 optical level’s usage and by the electronic total station’s usage, remain on the same accuracy order. Therefore, the usage of the electronic total stations for the accuracy ensuring is planned also on the vertical position of their bases and pavements

Energy sustainability performance of the regional economy

The results of the study of the dynamics of energy intensity of gross regional product of the Sverdlovsk region for the period 1996 - 2003 years. and projections for the period up to 2015. The principal possibility of growth performance of the regional economy, without a significant increase in the consumption of primary fuel