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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. [ABSTRACT FROM AUTHOR]

The creation of new nanomaterials for absorbtion of electromagnetic radiation microwave range is an important direction in consequence of electromagnetic pollution of the environment. The aim of the paper was to develop and synthesize the polymer-filled systems based on the polychlorotrifluoroethylene and tin dioxide modified by nickel ferrite in order to study their electrophysical properties as potential materials absorbing electromagnetic radiation. NiFe2O4/SnO2 nanocomposites with a volume content of nickel ferrite on the surface of tin dioxide from 0.62 to 0.8 were synthesized by co-precipitation. Size of SnO2 and NiFe2O4 nanoparticles was determined by a transmission electron microscope and its about 30–50 nm and 15–30 nm, respectively. For the NiFe2O4/SnO2 nanocomposites the values of complex permittivity and complex permeability in the microwave range, values of conductivity at low frequencies were investigated. Maximum values of complex permittivity and complex permeability were found for NiFe2O4/SnO2 nanocomposites at the volume content of nickel ferrite 0.62. An increase was observed in the complex permittivity for the NiFe2O4/SnO2–polychlorotrifluoroethylene system, 2–3 times greater than the values related to the NiFe2O4/SnO2 nanocomposites. The electrical conductivity at low frequencies (100 Hz) of polymer composites increases by an order of magnitude with a decrease of the concentration of nickel ferrite on the surface of tin dioxide. It was found that the calculated absorption coefficient of an electromagnetic wave in the frequency range 1–41 GHz for NiFe2O4/SnO2 nanocomposites is about 2 times greater than that for nickel ferrite. It is shown that the creation of nanocomposites based on a conductive component modified by a magnetic component is more efficient for the processes of absorption of electromagnetic waves in the microwave range at optimal ratios of the values of the permittivity and permeability than pure ferrite. [ABSTRACT FROM AUTHOR]

In order to synthesize the polymer composite system of the PCTFE-CuS/ZnS, the nanodispersed ZnS was synthesized by hydrothermal method afterwards heterostructures of CuS/ZnS were obtained using ion-substitution mechanism. The concentration dependence of the real and the imaginary components of the complex dielectric permeability and electrical conductivity of synthesized samples were investigated. Obtained composites have high values of the dielectric permeability at high frequencies and conductivity at low frequencies. At 50 % (molar) substitution of Zn ions by Cu the percolation threshold was determined at the volumetric content of CuS about 0.06. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]