Valentin I. Suslyaev

Interaction of microwave radiation with composites containing nanosized hexaferrite, multiferroics, carbon nanostructures and silicon binder

A new composite consisting of nanosized powders of hexaferrites BaFe12O19 (BaM), multiferroics Co1.6Zn1.4W+CaTiO3 (30%), carbon nanostructures (powder mixture of carbon nanotubes, fullerenes, squamous structures and amorphous carbon) and silicone binder absorbs microwaves. Varying the concentration of each component in the composite materials changes the characteristics of a coating from reflective to absorbing electromagnetic radiation. Adding a layer with multiferroics to a composite material significantly improves the coatings as protective layer from microwaves.

Properties of MWNT-Containing Polymer Composite Materials Depending on Their Structure

Carbon nanotubes (CNTs) are tubular structures composed of curved graphene sheets with diameter up to several tens of nanometers with typical length up to several micrometers. Singleand doublewall CNTs have diameters from 1.2 to ca. 3 nm and are usually packed in relatively dense structures (“ropes”). Multiwall carbon nanotubes can contain up to tens of concentrically aligned tubules and have diameter from 3-4 to tens of nanometers. Carbon nanotubes, both singleand multiwall, show outstanding mechanical and electrical properties [1, 2]. Nowadays CNTs are regarded as one of the key materials for development of various nanotechnology applications – new materials, sensors, actuators, field emitters etc. [3, 4, 5, 6]. In the last decade great effort was done in this field by many research groups, investigating structural, physical, mechanical, and electrical properties of CNTs.

Effective magnetic permeability of a composite material based on nanoscale hexaferrite particles

In this paper, an equation for the calculation of the effective magnetic permeability of nanosized particles on a two–layer sphere model has been derived. It is shown that the effective permeability of a two–layer sphere starts to decrease rapidly as it approaches the particle size to the nanometer range. The simulation of effective magnetic permeability of materials based on nanoscale powders synthesised hexaferrites Co0.6Zn1.4W and Co0.7Zn1.3W has been carried out. It has been proven necessary to adjust the formulas of compositional mixtures theory when they are used for calculation of effective permeability of the composite material based on nanosized hexaferrite powders.

Analysis and reoperation of the magnetic permeability spectra of textured composite based on Z-type hexaferrite by using Cramers-Kronig relations

The frequency dependences of the magnetic permeability of textured composite based on Ba3Co2,4Fe23,2O41 ferrite are given. The magnetic permeability spectra were obtained by coaxial method in the frequency range 0.01–18 GHz. The expert judgement on the spectra was made by using Cramers – Kronig relations. It was shown, that the Cramers – Kronig relations can be used to correct magnetic permeability measurements by reciprocal recalculation of the frequency dependences of the real and imaginary parts.

Quasi-optical 2D system for non-contact non-destructive testing of defects in natural and artificial crystals

The results of development the automated system of two-dimensional diagnostics of defects of crystalline materials are presented. Used technology imaging. The structural scheme of the system is given, its main blocks are indicated, the approbation process is described, the software of the system is described.

Effect of magnetic field treatment on the electromagnetic properties of polymer composite based on barium hexaferrite at microwave frequencies

Polymer composite materials are used in widely different areas of science and industry. It is possible to change electromagnetic properties of composite materials by external treatments. The present work focuses on the change of electromagnetic characteristics of barium polymer composite, which is exposed to the external magnetic field with different strength. Composite materials, containing 65 wt. % concentrations of barium hexaferrite (Z-type) powder with a linear size of less than 80u2005µm as fillers and epoxy resin as matrix were prepared. Reflection coefficients were measured by coaxial method at frequency range of 0.01 – 18u2005GHz. It was revealed that reflection coefficients of barium hexaferrite and epoxy resin composite are very sensitive to the values of external magnetic field. There is nonlinear dependence of the reflection coefficients on the values of external magnetic field. The optimum value of the strength of the external magnetic field was shown to be equal 4 mT. The Cramers-Kronig relations w...

Dielectric properties of marsh vegetation

The present work is devoted to the measurement of the dielectric properties of mosses and lichens in the frequency range from 500 MHz to 18 GHz. Subjects of this research were three species of march vegetation – moss (Dicranum polysetum Michx), groundcedar (Diphasiastrum complanatum (L.) Holub) and lichen (Cladonia stellaris). Samples of vegetation were collected in Tomsk region, Western Siberia, Russia. Complex dielectric permittivity was measured in coaxial section by Agilent Technologies vector network analyzer E8363B. Green samples was measured for some moisture contents from 100% to 3–5 % during a natural drying. The measurements were performed at room temperature, which remained within 21 ÷ 23 ° C. The frequency dependence of the dielectric constant for the three species of marsh vegetation differ markedly. Different parts of the complex permittivity dependency on moisture were fitted by line for all frequency points. Two break point were observed corresponding to the transition of water in the vegetation in various phase states. The complex permittivity spectra of water in the vegetation allow determining the most likely corresponding dielectric model of water in the vegetation by the method of hypothesis testing. It is the Debye’s model. Parameters of Debye’s model were obtained by numerical methods for all of three states of water. This enables to calculate the dielectric constant of water at any frequency range from 500 MHz to 18 GHz and to find the parameters of the dielectric model of the vegetation.