| Abstrakt: |
The nickel–cobalt (NiCo) nanoparticles and NiCo nanocomposites are synthesized on graphene nanoplates (NiCo@GNP), on finely dispersed silica (Ni- Co@SiO2), on non-oxidized and oxidized multilayer carbon nanotubes (NiCo@NMLCNT, NiCo@OMLCNT) by means of the chemical coprecipitation of the nickel and cobalt carbonates from hydrazine hydrate. The presence of GNP, nickel, cobalt, SiO2, and MLCNT phases with a crystallite size of 15–30 nm is shown by x-ray phase analysis. The TEM images indicate that the size of metal particles reaches 20 nm, and their agglomerates have sizes up to 200 nm. As revealed by thermogravimetric methods, all the systems have an insignificant amount of chemically bound water, oxidation of the metal component occurs in the range from 600 to 800 K for each system individually. For the composite containing oxidized CNTs, the oxidation process of it upon heating is more intense that may be due to the smaller metal-particle size. The oxidation of such a system begins and ends at lower temperatures. The real and imaginary components of the complex dielectric and magnetic permeabilities of dispersed composites are determined by microwave interferometry methods. For composites containing MLCNT, the values ε', ε', μ', μ' are slightly higher in the microwave range. The differences in characteristics can be attributed to the additional processing of MLCNT and the presence of a large number of functional links on the surface. The real and imaginary components of the NiCo complex magnetic permeability significantly exceed the corresponding NiCo@GNP-composite values at high frequencies that may be due to the presence of the GNP in the nanostructured composites as well as NiCo particles. The electrical conductivity at low frequencies is higher for composites with unoxidized MLCNT. NiCo@GNP nanocomposites are sensitive to vapours of acetone, ammonia, and ethanol. The sensory properties of NiCo@GNP composites, when using ethyl alcohol vapours, are stable for many cycles. Composites of the PCTFE–NiCo@OMLCNT system have a percolation threshold of 0.07. The dependence of ε' at low frequencies reaches a value of 60, which indicates a significant separation surface area of the system components. [ABSTRACT FROM AUTHOR] |
