The aim of this work was to determine the anisotropy of the electrophysical and mechanical properties of rubber reinforced with a hybrid filler CNTs&CB (carbon nanotubes and carbon black) as a function of CNT content and the technological parameters of the production process. A significant difference in electrical conductivity (σ) and dielectric permittivity (ε) in three perpendicular directions was found for CNT concentrations ranging from 0 to 0.007 in volume fraction. The highest values of σ and ε were observed in the calendering direction, with slightly lower values in the perpendicular direction. This effect was attributed to the orientation of polymer molecules and CNTs along the direction of movement during calendering, as well as the disruption of the cluster structure in the transverse direction. Although the calculated percolation threshold values of the investigated system differed slightly, a correlation was observed between the mechanical and electrophysical properties of CNTs&CB rubber. This correlation enables rubber products to be designed with optimal properties tailored to the desired direction.

Синтез композитів графенові нанопластини/(Ni-Co) та їхні властивості

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.

Hybrid composites of carbon component/nanosized FeCo particles were synthesized from solution by the co-precipitation method (multiwalled carbon nanotubes, graphene nanoplates, carbon black and carbon fiber were used as the carbon component, and the presence of phases of carbon substrates, cobalt, iron and its oxide forms was found. FeCo nanoparticles with sizes from 5 nm form agglomerates of 50–100 nm on the surface of carbon substrates; the localization of metal particles is characteristic of each substrate, which is associated with the distribution of active functional groups on the surface. The dielectric behavior of the composites in the microwave range and at low frequencies has been studied. It has been shown that carbon fiber/FeCo composites with ?? and ?" significantly exceeding the values of individual components have a significant interface between the components in the composite and a more uniform distribution of metal particles on the surface of carbon fiber compared to other substrates. All the composites obtained have pronounced magnetic properties and thermally stable to a temperature of 250 °C. The frequency dependences of absorption and reflection coefficients in the range from 1 to 40 GHz for the composites obtained are calculated. Several absorption mechanisms are realized simultaneously in the composites (absorption above -12 dB), which makes them an attractive component for creating effective electromagnetic radiation absorbers for different ranges.