Bulletin of the Russian Academy of Sciences: Physics最新文献

The authors study the effect of changes in the transparency of magnetic emulsions with deformable droplets of submicrometer size under the influence of magnetic field. The effect the orientation and strength of the magnetic field and the concentration of microdroplets have on the amplitude of transparency changes is revealed. Experimental data on the field dependence of the magneto-optical effect and its dependence on the angle of the magnetic field’s orientation are compared via calculations in an approximation of anomalous diffraction. The possibility of determining interphase tension in magnetic emulsions is analyzed by studying the relaxation of optical effects.

The features of the magnetic susceptibility of a magnetic fluid with a non-magnetic filler were experimentally studied. It was determined that the dependence of the magnetic susceptibility on the concentration of the non-magnetic filler has features. The explanation of the detected effects is based on the assumption of the influence of surface forces on the processes of relaxation of the magnetic moment of magnetic particles. It was also found that the dependences of the magnetic susceptibility of a magnetic fluid with a non-magnetic filler on the strength of the external magnetic field differ from similar dependences for the magnetic fluid without a filler.

Magnetoactive, also known as magnetorheological, elastomer is a composite material based on an elastic polymer filled with magnetic particles. The specifics of its deformation under the influence of magnetic fields have been the subject of this research. For instance, in non-homogeneous fields the degree of strain may reach hundreds of percent whereas magnetized samples containing high-coercivity (hard magnetic) components can suffer deformations occurring in a complex way. In addition to that, a sample responds to an external field with an increased roughness of its surface thus becoming more hydrophobic. The material also increases its stiffness by ten folds. These facts suggest that this elastomeric composite may be considered potentially useful for such areas as robotics and controllable damping units.

This paper presents the results of studying the features of the formation of structural lattices in thin layers of colloids in an electric field directed perpendicular to the plane of the layer, as well as under the additional influence of a magnetic field. New results were obtained about the dependence of the threshold (critical) value of the electric field strength corresponding to the formation of a labyrinthine structure on the strength of an additionally applied magnetic field, layer thickness, and temperature. The dependences of the formation time of the structure under study on temperature and the strength of the additionally applied magnetic field were characterized. A thermally induced phenomenon of the formation of a labyrinthine structure in a magnetic colloid in the subcritical region of the applied electric field strength under additional exposure to laser radiation was discovered.

The authors describe a controlled oscillatory RLC circuit in which a cell with a layer of magnetodielectric liquid is used as a capacitor element. The possibility of creating a self-tuning inductive-capacitive element based on a thin layer of magnetodielectric liquid is discussed. It is shown that changing the properties of a magnetodielectric liquid in electric and magnetic fields allows the creation of adjustable inductive-capacitive converters.

Magnetic properties of magnetic polymer composite materials were studied. Monodisperse and bidisperse theoretical models considering interparticle dipole–dipole interactions were verified using experimental data. It was determined that the bidisperse approximation well describe the experimental results for real polydisperse composites.

A theoretical model and a method for its approximation analysis are developed to study circulation flows arising in a channel with a nonuniform alternating rotating magnetic field. This channel contains a nonmagnetic fluid into which a cloud of a ferrofluid is injected, the particles of which are distributed along the channel according to the Gaussian law. It is assumed that the right end of the channel is blocked to simulate a thrombosed vessel. The main goal of the study is to develop a scientific basis for increasing the efficiency of transport of thrombolytic drugs in thrombosed blood vessels using magnetic stimulation.

A photonic crystal was created using a magnetic fluid–epoxy resin composite. The amplitude–frequency characteristics of the reflection coefficient of electromagnetic radiation in the microwave range from the resulting structure were experimentally studied. The possibility of using magnetic composites to create controlled photonic crystals was demonstrated.

A theoretical study was made of the increase in the magnetization of a suspension of noninteracting magnetic particles with time after switching on an external constant uniform magnetic field. It was found that the characteristic relaxation time of the process is the same at the initial stage and at the final stage of reaching the equilibrium value of the magnetization and has a minimum in the region of intermediate times.

A study was made of the dynamics of nonmagnetic droplets in magnetic fluids in microchannels with the flow-focusing configuration under the action of an inhomogeneous magnetic field of a ring magnet. Two types of multiphase systems were investigated: nonmagnetic emulsions “oil in water,” “water in oil,” and “water in oil in water,” as well as magnetic oil-in-water emulsions in which the magnetic fluid was used as the continuous phase. Characterization was made of the dependences of the sizes of the generated nonmagnetic inclusions on the flow rate of the continuous magnetic phase and on the displacement of the magnetic field source relative to the dispersed phase supply connector horizontally along the channel axis are obtained.