A. S. Fionov

Electrical and Magnetic Properties of Nanomaterials Containing Iron or Cobalt Nanoparticles

We have prepared nanocomposites consisting of narrowly sized metal-containing nanoparticles embedded in a polyethylene matrix and have established conditions for the fabrication of thick films and bulk materials from the synthesized polymer powders. Dielectric permittivity and resistivity measurements demonstrate that the electrical properties of the nanocomposites depend significantly on the nanoparticle size and content.The microwave absorption and permittivity of the materials are shown to vary little in a broad frequency range. The magnetization (including the remanent one) of the cobalt-containing nanomaterials is higher than that of the iron-containing samples.

Creation and physical properties of the molybdenum-containing polyethylene-based nanomaterials

The thermal decomposition of molybdenum carbonyl is employed for the creation of the composite nanomaterial that represents molybdenum-containing nanoparticles stabilized in the high-pressure polyethylene matrix. The resulting nanomaterials are studied using the transmission electron microscopy, X-ray phase analysis, and electron paramagnetic resonance. The experiments show that the Mo-containing nanoparticles have a mean size of 3–5 nm and consist of several components (Mo, MoC, MoO3, and MoO2). The concentration dependences of the electrophysical properties of the synthesized nanomaterials are analyzed.

Study of structure and properties of polymer composites based on polytetrafluoroethylene and cobalt nanoparticles

This work discusses the study of structure and properties of composites based on polytetrafluoroethylene (PTFE) and filler, which is a composite material of cobalt nanoparticles and ultrafine polytetrafluoroethylene (UF PTFE). Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray phase analysis (XRF) are applied for complex investigation into the properties of the obtained composite materials, such as specific energy absorption rate, thermal resistance and internal orientational stresses, thermophysical properties, and dielectric permeability. It is demonstrated that the obtained composite materials are superior to the initial matrix—PTFE. The magnetic study of the composite materials confirms the occurrence of metal nanoparticles and their interaction with the polymer matrix.

Synthesis and physicochemical properties of composites for electromagnetic shielding applications: a polymeric matrix impregnated with iron- or cobalt-containing nanoparticles

Abstract. Magnetic, magnetic resonance, and structural properties of iron and cobalt nanoparticles embedded in a polyethylene matrix were studied. The materials were prepared by thermal decomposition of cobalt or iron formate in a polyethylene melt in mineral oil and contained from 2 to 40% wt. of metal. Transmission electron microscopy data indicate that the average diameter of particles is up to 8.0 nm. According to extended x-ray absorption fine structure and Mössbauer spectroscopy studies, the particles comprise a metallic core and nonmetallic shell which is chemically bound to the surrounding matrix. Electrophysical and magnetic properties of the materials prepared were studied along with their reflection and attenuation factors in the super high frequency band. The materials were found to be suitable for use in electromagnetic shielding.

Electric Conductivity of Composite Materials Based on Phenylon Matrices and Nickel Particles

Nanocomposites based on nickel-containing particles and phenylon matrices have been developed and investigated. The size and compositions of the particles are determined. The conductivity of composite polymer materials containing nickel particles is studied in the vicinity of the percolation threshold. It is found that, below this threshold, the experimental dependence of the electric conductivity on the content of nickel nanoparticles in these materials differs from the dependence calculated in accordance with the percolation theory.

Broadband radio-absorbing materials based on porous composites with carbon nanotubes

The reflection coefficient of an electromagnetic wave has been theoretically studied as a function of the thickness of a material and its dielectric properties. Samples based on spheroplastics with noncovalently modified carbon nanotubes have been obtained. The radio-engineering and electrophysical properties of these composites are discussed as well. The prospects for applying porous nanocomposites with carbon nanotubes in the fabrication of radio-absorbing materials are also shown.

The investigation of effect of thin films conductivity on the acoustic waves in structures containing piezoelectric plates

The fractional change in velocity and attenuation of the zero-order acoustic wave with shear-horizontal polarization propagating in “YX LiNbO3 - air gap - conducting film deposited of glass surface” are experimentally investigated. The possibility of determination of film conductivity in such structure by the noncontact methods is demonstrated.

Composite material based on iron-containing nanoparticles for applications in the problems of electromagnetic compatibility

The decomposition of iron formate is used to synthesize composite materials that represent ironcontaining nanoparticles localized in the high-pressure-polyethylene matrix with the concentration of the iron-containing component ranging from 10 to 40 wt %. The composition and structure of the materials are comprehensively analyzed using the transmission electron microscopy, X-ray phase analysis, Mössbauer spectroscopy, and electronic magnetic resonance. Electrophysical and magnetic properties of the synthesized materials and the coefficients of reflection and attenuation in the centimeter-wavelength range are studied. It is demonstrated that the composite materials can be used to provide electromagnetic compatibility, noise immunity, radio shielding, and protection of biological objects against electromagnetic radiation.

The permittivity of phenylone-based composites with nickel particles

Composites consisting of a phenylone matrix and nickel-bearing particles are fabricated. The permittivity of composites with nickel particles near the percolation threshold is studied. The experimental dependence of the permittivity on the bulk content of nickel nanoparticles in a composite below this threshold is found to be different from that calculated using the percolation theory.

Composite materials on basis of NiFe 2 O 4 nanoparticles and polyethylene matrix

The composite materials on the basis of NiFe₂O₄ nanoparticles and polyethylene matrix have been synthesized. The concentration dependences of volume resistivity εV, permittivity ε, saturation magnetization σS and reflection and attenuation factors have been investigated. It has been determined that percolation threshold in these materials had been located at the concentration interval 20...30 of weight %. It has been shown that the composites on the basis of NiFe₂O₄ nanoparticles and polyethylene matrix might be used as the components of gradient radio absorbing coatings.