Модель Ізінга для опису магнітних властивостей елементів системи керування авіаційним двигуном

The creation of competitive engines is impossible without the development and implementation of new materials and design and technological solutions. At present, in the engines, nickel alloys obtained by directional crystallization are widely used, including monocrystalline, granular alloys. The use of various composite materials, permanent joints from dissimilar materials is constantly expanding, extensive research is being carried out to create a structure from monolithic ceramics and intermetallic compounds. The successful introduction of unconventional materials is impossible without a thorough study of their structural strength, magnetic properties, features of deformation, and destruction, taking into account the specifics of these materials when developing the design and manufacturing technology of a part or engine unit. The article discusses a software package for the optimal design of control system elements for aircraft gas turbine engines using a description of their magnetic properties. Due to the modular structure of the optimization program, various optimization procedures and calculation programs can be used. It was determined that, for the Ising model, the formation of domains with a given spread of spins at a temperature T and a vector of magnetic induction B is calculated array element using a random number generator. The number of tests L depends on the size of the sample. In the Ising model, all parts of the N*N system are contenders for testing. So, Step corresponds to the number of Monte Carlo steps. Since the parts are selected once on average, it is possible to select one particle several times or not to select it at all. Therefore, the Step value should be significantly greater than one. For a convenient implementation of a certain model, its application with a graphical magnetization interface with a different number of iterations has been considered. When executing the command file, the following should be performed: building a geometric model, building a finite element mesh, applying loads, calculating the stress-strain state (SSS), displaying the results.

Magneto-optical properties of two-layer film systems based on Fe and Cr

The results of the investigation of two-layer Fe/Cr systems using the magneto-optical Kerr effect (MOKE) are presented in this paper. The samples were obtained by thermal evaporation in a vacuum with a thickness of individual layers from 2 nm to 50 nm. It was found that the presence of the Cr layer significantly affects the values of the coercivity and the Kerr angle. At a substrate temperature of 450 K, the value of the coercivity is almost half that of the same sample obtained at room temperature of the substrate. In addition, the influence of the order of deposition of layers, as well as the effect of a thin gold protective layer on the parameters measured by the Kerr method, is shown. These studies have shown that the MOKE can be used as an additional method for studying the composition of multilayer systems, granular alloys and spin-valve systems, using specific software methods.

Symmetrized Maxwell–Garnett Approximation as an Effective Method for Studying Nanocomposites

The symmetrized Maxwell-Garnett (SMG) approximation is considered as the most optimal method of an effective medium for the description of nanocomposite structures. This approximation takes into account the microstructure of the sample, which makes it possible to calculate the metal-dielectric system. Thus, SMG describes with good accuracy the structure of the nanocomposite. Besides, this approximation is applicable for granular alloys consisting of metal components. As a result, this technique can be considered as a universal approximation to describe a wide class of nanostructured materials. At the same time, this article discusses various methods of effective environment. In these methods, the metal component of nanocomposites and the dielectric matrix are replaced by an effective medium with effective permittivity εeff. It is necessary that the particles (granules) in such structures be small in comparison with the wavelength of electromagnetic radiation incident on the sample. Based on this, the spectral dependences of the transverse Kerr effect (TKE) in magnetic nanocomposites were calculated with (CoFeZr)(Al2O3) structure as an example at different concentrations of the magnetic component. The simulation was carried out at small and large concentrations (below and above the percolation threshold). The spectral dependences were obtained taking into account the form factor of nanoparticles and the quasi-classical size effect. Besides, the authors note and discuss in this paper the contribution of various mechanisms that affect the type of spectra of the transverse Kerr effect. Using the symmetrized Maxwell-Garnett approximation, the effective values of the granule size of the nanocomposites under study were found, and the tensor of effective dielectric permittivity (TEDP) was calculated. The obtained TEDP values allowed to simulate the spectral dependences of the magneto-optical transverse Kerr effect. The authors discuss and draw conclusions about the features of the obtained spectral dependences in both the visible and infrared regions of the spectrum. In addition, the practical and fundamental importance of the obtained results is noted. The importance of effective medium methods for the study of optical, transport and magneto-optical properties of magnetic nanocomposites is shown.

MAGNETIC NANOMATERIALS AND NANOSTRUCTURES. TRENDS OF DEVELOPMENT

There are analyzed creation and development of magnetic nanomaterials and nanostructures, films with a columnar type of crystal structure, multilayer film structures, nanocomposites, granular alloys and nanowires. The methodics of obtaining, structure, magnetic and magnetoresistive properties of three types of nanowires – multilayered and granular ones and the ones of spin-valve type are discussed. It is shown that multilayer film coatings with very thin (< 1 nm) alternating magnetic and nonmagnetic layers behave like films of granular alloys. It is emphasized that the films of granular Cu–Co alloys were first obtained at the Scientific and Practical Materials Research Center of the National Academy of Sciences of Belarus by the method of electrolytic deposition without subsequent annealing, as is the case with other methods for their preparation. As prepared Cu–Co films are superparamagneties. That is, they demonstrate ferromagnetic below blocking temperature, which is dependent on the size of cobalt clusters in diamagnetic matrix of copper. The granulated nanowires, firstly obtained by us, exhibit similar behavior. Special attention is paid to the analysis of obtaining and properties of multilayered films of the spin-valve type. The trends in the development of materials science are predicted, which will allow creating new materials with a high level of quality and specified properties, what will allow expanding the area of export of such materials and products from them in the future.

Phase Transformation in Granular Alloys of Cu2S-Ni3S2-Na2S System

The effect of Na2S on the phase composition and microstructure of tempered Cu2S-Ni3S2 alloys was studied by X-ray diffraction, optical microscopy and electron probe microanalysis (EPMA). It was found that quick crystallization of the sulfide melt leads to separation into two phases - Ni3S2 and a solid solution of Cu2S with Na2Cu4S5, moreover, nickel is concentrated in large particles and copper – in small ones. In contrast to the fine dendrite solidification of granular Cu2S-Ni3S2 alloys, in the ternary system there is a well-defined two-phase microstructure with rounded borders of the interface. Friability and a low microhardness of Cu2S - Na2Cu4S5 solid solution provide an autodecomposition of the sulfides melt by quenching into water (granulation). The degree of separation of copper and nickel depends on the overheating temperature and a quantity of Na2S in melt. The results can be used to hydrometallurgical processing of copper-nickel convert matt.