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This chapter provides an overview of the dielectric and magnetic properties of transformer oil-based magnetic fluids as unique materials with potential utilization in the field of technology as insulating and cooling media. The main idea of incorporating magnetic nanoparticles in transformer oil is the improvement of its insulating and cooling properties, thus achieving better conditions for its wide application in power engineering technology. Here, we review some selected dielectric, magnetic and structural properties of transformer oil based magnetic fluids reported in recent years, including our latest research results.

The electronic properties and phase transition of β(C11b)-WGe2 and α(C23)-WGe2 phases were investigated via x-ray emission spectroscopy method and first-principles calculations. The analysis of the comparison of the partial energy distributions of the valence electrons of the β(C11b)-WGe2 and α(C23)-WGe2 phases was also studied. The transformation of interatomic bonds during the polymorphic transition α(C23)-WGe2→β(C11b)-WGe2 under comprehensive compression was proposed. The first-principles calculations showed that the phase transition from the α(C23)-WGe2 phase to the β(C11b)-WGe2 phase occurs under high pressure. Furthermore, the electronic structure calculations indicate that the considered phases are metallic in nature. The results have revealed that the fine-structure peculiarities of the WLβ 5- and GeKβ 2-emission bands match well with the main peaks of the partial densities of the W d- and Ge p- electronic states for the both phases.

In this study, the nonlinear dynamics of nanoparticle concentration in a colloidal suspension (nanofluid) were theoretically studied under the action of a light field with constant intensity by considering concentration convection. The heat and nanoparticle transfer processes that occur in this case are associated with the phenomenon of thermal diffusion, which is considered to be positive in our work. Two exact analytical solutions of a nonlinear Burgers-Huxley-type equation were derived and investigated, one of which was presented in the form of a solitary concentration wave. These solutions were derived considering the dependence of the coefficients of thermal conductivity, viscosity, and absorption of radiation on the nanoparticle concentration in the nanofluid. Furthermore, an expression was obtained for the solitary wave velocity, which depends on the absorption coefficient and intensity of the light wave. Numerical estimates of the concentration wave velocity for a specific nanofluid—water/silver—are given. The results of this study can be useful in the creation of next-generation solar collectors.

It is known that ferrofluids typically respond to magnetic fields and can be manipulated by such external fields. The particle assembly in magnetic nanofluids can be induced even by a direct current (dc) electric field. An experimental study of magnetic colloidal particles and their changes induced by an external electric field in a ferrofluid based on 2 transformer oils with different concentrations of nanoparticles is presented. By small-angle neutron scattering (SANS), we show the influence of the electric field intensity and the concentration on magnetic nanoparticle aggregates.

Relevance. The development of measures to prevent possible negative environmental, economic and social problems in forest ecosystems should be based on objective information, which may be provided by the process of landscape-environmental planning. Purpose. Analysis of the conflicts of nature use from anthropogenic activity in forest ecosystems to develop measures optimization of environmental management in the process of landscape-ecological planning. Methods. The assessment of conflicts of nature use in forest ecosystems was carried at the test site of the tract "Zarudska Dacha" of Lyubovytsi forestry of the Malinsky district of Zhytomyr region according to the author's method of landscape-ecological planning. Results. Based on the results of the inventory and evaluation phase of landscape-ecological planning, we have obtained information about the landscape differentiation of the test area, internal and external sources of environmental conflicts, their boundaries, and intensity. The study of the structure of forestry has shown that the sources of conflict are predominantly forest areas and settlements landscapes. The assessment of intensity of the conflicts has shown that medium-intensity conflicts prevail in the territory. Based on the information of matrices of the conflict measures to optimize the use of nature in forest ecosystems have been developed. Conclusions. For optimization of nature use in forest ecosystems, it is recommended: restoration of plantations, control of rational use of forest resources, reduction of the volumes of use of the chemical means on the adjacent fields, organized garbage collection, controlled recreation, etc.

The light induced mechanism of bubble clusters formation has been investigated experimentally. It was detected the accumulation of bubbles in the cluster in the light field in almost horizontal closed cell The shape and dimensions of the cluster match the mode structure of the laser spot. The nature of the phenomenon is based on the existence of the thermocapillary forces, which push a suspension of bubbles in a heated area, as well as there are the adhesion forces. The light induced bubble clusters are formed in the case of free-surface liquids also. The dynamical bubble cluster foundation is described on the liquid surface. It is shown that the presence of inhomogeneous heat radiation, effective interaction of bubbles with each other (in the case of free surface) and with the surface of a solid body (closed cells) may lead to the formation of stable bubble clusters at the developed convection.

We study the theory of the dynamics of the concentration of nanoparticles in a liquid-phase environment under the influence of a light field. An exact solution for the nonlinear diffusion equation was found in the form of switching waves. It is shown that under the conditions of a stationary and nonlinear temperature coefficient of thermal conductivity in the medium, nanofluids become bistable. A comparative analysis of linear and non-linear approaches to solving the diffusion equation is given.

It was described the photoelectric element on the basis of thin sandwich metal-ferroelectric-metal system. The effect was observed in doped lithium niobate crystal with two electrodes of different metals. The current value increases dramatically when you reduce the thickness of the crystal. The effect is observed only in doped lithium niobate crystals and has a maximum for concentrations of impurities of iron around 0.3 weight. % . This paper proposed thermal model of the investigated phenomena resulting from field contact potential difference on the borders of section of metal-ferroelectric material. The results obtained can be used to develop radiation receivers, as well as in the interpretation of experimental results on studying the properties of sandwiched metalferroelectric-metal structure.

Photorefractive scattering occurs in rhodium-doped lithium niobate crystals irradiated by coherent light. The photorefractive scattering has both wide-angle and selective components. The results of experimental investigation of selective photorefractive scattering in LiNbO3:Rh crystals and calculation of the spatial structure of scattering are reported. The selective scattering is regarded as a kind of a frequency-degenerate fourwave vector interaction.

We conduct a theoretical study ofthe dynamics of the concentration of nanoparticles in liquid-phase media under the influence of a laser light field. An exact solution of the nonlinear diffusion equation in the form of switching wavesis found. It is shown that, in the conditions of a fixed temperature and a nonlinear medium thermal conductivity, nanofluid becomes bistable.

Experiments for estimation of influence of microplasma parameters in ZrO2 – coating properties were performed with using of fractional-factorial design of the experiments. Regression equations for determination of the parameters significance and a selection of conditions for a deposition of coatings with specified properties were obtained. Possibility of deposition of ZrO2 - Y2O3 coating with tetragonal phase content 90 wt.% and more without cubic phase content by microplasma spraying was shown. Conditions of microplasma ZrO2-coating spraying with high content of tetragonal phase (93-95%) and porosity (1,3-1,8%) were established. Measurement of microplasma sprayed ZrO2-coating spots has established that the spots have an elliptical shape. Size of major and lateral axis (and also sprayed hill altitude) depends on spray parameters, mainly on amperage and spray distance. Microplasma sprayed ZrO2-coating can be applied for repair of small local defects on thermo barrier coatings and a deposition of zirconia electrolyte layer in solid oxide fuel cell.

Development of thermal spraying of quasicrystalline coatings is connected with development of new powders for produced from alloyed quasicrystalline alloys. Powders of AlCuFe alloyed by Cr and Sc were produced by high – pressure water atomization of melt. Phase composition, microstructure, morphology, flowability of the powders were investigated. Resistance of powders to oxidation in air was studied using thermography. It was determined that doping of AlCuFe – alloy by 0,265 and 0,440 at.% Sc and by 8 at.% Cr significantly increases in them content of quasicrystalline phases. Annealing of AlCuFeCr at 550°C leads to transformation quasicrystalline phase into crystalline approximant of decagonal quasicrystalline phase.

Electrodynamic of thermo-EMF models in sandwich structure metal-ferroelectric-metal is analysed.

Lithium niobate crystals are a perspective material for the optical information storage and processing. The photorefractive properties of the lithium niobate crystal depend strongly on the kind of the dopants. The study of the photorefractive light scattering (PRLS) in the LiNbO3 crystals with various additives allows to gain information of the processes taking place in the crystals. This problem is solved using models describing the experimental results. This paper presents new experimental results of PRLS intensity kinetics in the LiNbO3:Rh crystal and proposes also a model within the framework of which the experiment data are explained.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In the paper, the non-linear optical effect of the Gaussian beam self-action in the microheterogeneous medium is theoretically considered taking into account the electrostriction and thermo-diffusion non-linearity.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The photoinduced changes of optical constants in As 2 S 3 films were experimentally studied according to the wave length of initiating radiation at different exposure temperatures. It was determined that the irradiation leads not only to shift but also to change in a slope of the Urbach absorption margin. It was shown that the basic experimental relationships describing the photoinduced changes of optical constants conform with a model of heterogenous medium with a local heating of microareas.

Lithium niobate is a perspective material for recording of the polarization-phase holograms in the optical systems of information processing and storage. In this work, the direct and back photorefraction scattering in LiNbO 3 crystals with iron and rhodium as alloying additives have been studied. When comparing the photorefraction scattering in LiNbO 3 :Rh and LiNbO 3 :Fe it was established that a kind of additive has influence on both quantitative characteristics of the photorefraction scattering in lithium niobate and on its nature. The selective component in back scattering in LiNbO 3 :Fe has been found.

The thermocapillary mechanism of nonlinearity of two-component medium (aerosol, mocroemulsion) is investigated, in which case the drift of particles in temperature field is due to the temperature dependence of the surface tension coefficient of the phase interface. Redistribution of particles concentration therewith changes the local index of refraction (absorption) of the medium, providing in such a way the presence of nonzero coefficient of efficient cubic nonlinearity. In terms of linear nonequilibrium thermodynamics, the variation of dielectric permeability of two-component medium exposed to action of incident radiation is caused by two fluxes: thermal JT and concentration JC, which in general case are thermodynamically mixed and are determined by kinetic coefficients Lij. In the case of weakly absorbing medium, the expression is obtained for the efficient coefficient of cubic nonlinearity. The experimental investigation of the thermocapillary nonlinearity was conducted in the bubble medium in two regimes: at laser radiation self-action and dynamic hologram recording. The generated hologram was of amplitude-phase character, but due to relatively large size of bubbles, the grid of the extinction coefficient was prevailing.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Ring-shaped photoinduced light scattering in pure and iron-doped lithium niobate crystals is found and studied under irradiation by a laser beam directed perpendicularly to the optic axis of the crystal. The scattering is observed in the directions of both reflected and transmitted pump beams. The structure and kinetics of the reported photorefractive scattering suggest that the phase-matching condition should be fulfilled in the vector interaction of the pump and scattered beams.

This paper presents the results of an experimental study of photoinduced light scattering in a LiNbO3:Rh crystal. Angle-selective scattering is regarded as a variety of four-wave frequency-degenerate vector mixing. © 2004 Optical Society of America