Nanocomposites Based on Polyethylene and Nickel Ferrite: Preparation, Characterization, and Properties

Composite materials based on NiFe2O4 nanoparticles and polyethylene matrix have been synthesized by thermal decomposition to expand the application area of high-pressure polyethylene by filling it with nanoscale particles. The synthesized compositions were obtained in the form of a dark gray powder and compressed for further study According to TEM, the average particle size in composites was 2, 3, and 4 nm in samples with a filling of 10%, 20% and 30%. The concentration dependences of the specific electrical resistivity ρV, dielectric permittivity ε, saturation magnetization MS and the parameters of reflection and attenuation of microwave power of the obtained composites were investigated. The threshold for percolation in such materials is found to be within a concentration range of 20…30%. The electronic and atomic structure of composites was studied by methods of Mössbauer spectroscopy, X-ray diffraction and X-ray absorption spectroscopy. The closest atomic environment of nickel and iron in nanoparticles is close to that of crystalline NiFe2O4. The dependence of the nanoparticles size as well as the dependence of the number of tetrahedral or octahedral iron positions in nickel ferrite nanoparticles to their content in polyethylene matrix is established. It is shown that composite materials based on NiFe2O4 nanoparticles and polyethylene matrix can be used as components of electromagnetic compatibility systems.

Polymer Nanocomposite Containing Palladium Nanoparticles: Synthesis, Characterization, and Properties

Composite nanomaterials have been prepared through thermal decomposition of palladium diacetate. The composite contains palladium nanoparticles embedded in high-pressure polyethylene. The materials were studied by a number of different physico-chemical methods, such as transmission electron microscopy, X-ray diffraction, X-ray absorption spectroscopy, electron paramagnetic resonance, and EXAFS. The average size of the nanoparticles is 7.0 ± 0.5 nm. It is shown that with the decrease of metal content in the polymer matrix the average size of nanoparticles decreased from 7 to 6 nm, and the coordination number of palladium also decreased from 7 to 5.7. The mean size of palladium particles increases with the growing concentration of palladium content in the matrix. It is shown that the electrophysical properties of the material obtained depend on the filler concentration. The chemical composition of palladium components includes metallic palladium, palladium (III) oxide, and palladium dioxide. All samples have narrow lines (3-5 Oe) with a g factor of around two in the electron paramagnetic resonance (EPR) spectra. It is shown that EPR lines have uneven boarding by saturation lines investigation. The relaxation component properties are different for spectral components. It leads to the spectrum line width depending on the magnetic field value. At first approximation, the EPR spectra can be described as a sum of two Lorentzian function graphs, corresponding to the following two paramagnetic centers: one is on the surface, and one is inside the palladium particles. Some of the experimental characteristics were measured for the first time. The data obtained indicate interesting properties of palladium-based nanocomposites, which will be useful for obtaining products based on these materials.