Вивчено склад, електрофізичні та магнітні властивості масивів залізовмісних волокнистих вуглецевих нанокомпозитів (ЗВВНК), синтезованих з використанням методів газофазного піролітичного розкладу ацетилену та термокаталітичного осадження вуглецю в присутності каталізаторутворюючого залізовмісного концентрату. У складі ЗВВНК виявлено вуглецеві нановолокна та багатостінні вуглецеві нанотрубки (зовнішній діаметр 10-100 нм, довжина 100-1000 нм), а також нанокристалічні фази магнетиту, кремнезему, графіту, карбіду заліза, середній розмір яких, обчис

The electrophysical studies indicate a significant difference between the properties at low frequencies of Ni-Co and GNP/(Ni-Co). In the area of ultra-high frequency the characteristics have similar values, which are due to the relaxation phenomena.The resulting nanocomposites can be promising for use in energy conversion devices, catalysis, gas sensor, screening, and magnetic devices.

The single-domain nanoparticles of NiCo, NiCo on the surface of graphene (NiCo@GNP) and NiCo on the surface of silica dioxide (NiCo@SiO 2) are synthesized. Their crystalline structure, surface morphology and magnetic characteristics of nanoparticle are investigated. It is shown that the magnetization curve of the nanoparticles ensembles in the form, which is distinctive for superparamagnets, and its calculations within the framework of the Langevin's paramagnetism theory are satisfactorily consistent with the experimental results. The laws of particle size distribution in ensembles are established using the method of magnetic granulometry.

Metal-containing nanocomposites containing nanoparticles of organic and inorganic materials, attract considerable attention of specialists in recent years due to a large number of possible applications. NiCo nanoparticles have been obtained on the surface of unoxidized and oxidized multiwall carbon nanotubes (MWCNT) by chemical precipitation of the corresponding carbonates from a solution of hydrazine hydrate at a temperature of 350 K. Oxidation of MWCNT was carried out in a solution of potassium dichromate and sulfuric acid. The purpose of this work is to synthesize composites of MWCNT/NiCo and to find differences in their electrophysical properties dependent on the nature of the MWCNT surface. The transmission electron microscopic and radiographic studies showed the presence of phases composites with the size of crystallites of 20-30 nm. The packing density of agglomerates of metal particles is higher in composites with unoxidized MWCNT. The metal particles are arranged on the surface of MWCNT more evenly and in shape more close to spherical in composites with oxidized MWCNT. The method of thermogravimetric analysis shows that the process of composites oxidation during heating for a composite containing oxidized MWCNT is more intense. It indicates a smaller particle size of metals. The real and imaginary components of the complex dielectric and magnetic permeabilities of the disperse composites was determined by the methods of ultrahigh-frequency interferometry. The corresponding values are somewhat higher for composites containing oxidized MWCNT in the ultrahigh-frequency range. The values of imaginary magnetic permeability are higher by 18 % for unoxidized MWCNT composites at low frequencies. The electrical conductivity at low frequencies is 2.9 and 1.6 Ohm-1 •cm-1 for composites containing unoxidized and oxidized MWCNTs, respectively.

The composites of epoxy resin-expanded graphite(EG)-vermiculite and epoxy resin-expanded graphite-perlite were obtained and their electrophysical properties were analysed at low frequencies and in the microwave range. High values (> 30) of real and imaginary components of the complex permittivity for both systems were achieved with a content of EG of less than 2 wt. %. The values of the percolation threshold and critical index of systems were defined: for a system with vermiculite the percolation transition (φ c = 0.0018); and for a system with perlite (φ c =0.0039). The method of impedance spectroscopy (10-2-10 6 Hz) shows that for all investigated composites there is no dependence of electrical conductivity to frequency, but up to a value of 10 3 Hz, indicating a low level of ionic conductivity. It was found that the difference in electrophysical characteristics of two systems with the same content of the expanded graphite arises due to the nature of the surface of the dielectric components. The best indicators, namely, the lower percolation threshold and the achievement of maximum electrical conductivity values at lower EG, are in the system with vermiculite. It is due to the hydrophobic properties of the surface the filler particles, as well as the effect of the flow of a dielectric particle of vermiculite by a suspension of an epoxy resin-EG, while the particles perlite is impregnated with it. Changing the content of such dielectric ingredients allows us to expand the functionality of composites when used for shielding from electromagnetic fields.

Nanocomposites containing components with semiconductor, ferroelectric, and ferromagnetic properties have attracted considerable attention of specialists due to the range of possible applications, including catalysis and electrocatalysis, electrode materials for solar and fuel cells, capacitors, electrical and biosensors, anti-corrosion coatings and much more. In recent years, both fundamental and applied interest in this direction of research is due to the possibility of creating a new type of controlled microwave devices and tools. The aim of the work is to develop methods for the synthesis of nanostructured NiCo composites based on BaTiO3 and TiO2, as well as to find the differences and regularities of their physicochemical properties. Two series of samples with different content of NiCo nanoparticles based on titanium oxide (TiO2) and barium titanate (BaTiO3) were obtained. NiCo particles were obtained by the method of chemical precipitation of nickel and cobalt carbonates in equal parts from a hydrazine hydrate solution at the temperature of 350 K. The results of X-ray phase analysis indicate the chemical purity of the obtained samples. The values of ε′, ε″ at a frequency of 9 GHz for the NiCo/BaTiO3 system are twice as high compared to NiCo/TiO2 for the corresponding values of the NiCo content, which is due to the higher values of ε′, ε″ of the initial barium titanate. Electrical conductivity of NiCo/BaTiO3 system changes by six orders of magnitude, which indicates the formation of a continuous percolation cluster of metal particles on the surface of dielectric BaTiO3 particles. The composites are heat-resistant up to 630K, as shown by the method of thermogravimetry and pronounced magnetic properties. The program for calculating frequency dependences of reflection and absorption coefficients in a complex form has been developed. EMF absorption for composites from the radiation frequency and the position of the minima of these characteristics, which agree satisfactorily with the experiment. The obtained composites can be promising components for obtaining composite systems and paints for protection against electromagnetic radiation.

Polymeric construction materials based on epoxy resin, carbon fillers, such as graphene nanoplates (GNP), carbon nanotubes (CNT) and fillers of inorganic nature – perlite, vermiculite, sand with improved electrophysical characteristics have been developed. The electrophysical propertieгs of composites obtained in various ways which differ according to the principle of injecting components have been investigated. GNP were obtained in two ways. Size distribution of GNP obtained by electrochemical method is 50 to 150 nm. The average particle size is up to 100 nm. It occurs that these particles tend to aggregate as it is shown by the method of dynamic light scattering. The GNP obtained by dispersing thermally expanded graphite in water in a rotary homogenizer have a particle size distribution of 400 to 800 nm if very small particles and large aggregates are absent. The second method of obtaining GNP is less energy consuming and requires fewer manufacturing cycles, so it is more cost-effective. Obtaining composites using aqueous suspensions of GNP is environmentally friendly. Due to the hydrophobic properties of its surface the electrical conductivity of the system which uses vermiculite is higher than one of that which uses perlite for composites with CNT and GNP. It has been found that the difference of electrophysical characteristics between two systems which contain the same amount of carbon filler is caused by the nature of the surface of dielectric components – sand. By changing the content of dielectric ingredients can expand the functionality of composites if use them for shielding from electromagnetic fields.

The properties of composites based on polychlorotryfluoroene with graphene containing 5 % (wt.) obtained by electrochemical dispergasion of graphite electrodes were researched. It is shown that the conductivity of the initial graphene that is determined by the impedance spectroscopy method is caused by the mainly electronic component. The concentration dependence of conductivity at low frequencies and real and imaginary components of the complex dielectric permeability at a frequency of 9 GHz composites significantly changes in the concentration range of 0,25-1%, that is stimulated by the presence of percolation threshold with graphene content of 0,45 %. The critical indexes of the percolation theory were calculated for the system.