O. V. Popkov

Fe-containing nanoparticles on the surface of silica microgranules

We have prepared nanomaterials consisting of SiO2 microgranules and Fe-containing nanoparticles on their surface and determined the size and composition of the nanoparticles. The nanoparticles are shown to have a core-shell structure (α-Fe core and γ-Fe2O3 shell). The α-Fe core and Fe2O3 shell are responsible, respectively, for the broad and narrow lines in the EMR spectrum of the nanoparticles. The magnetic properties of larger nanoparticles are dominated by the core, while those of smaller nanoparticles are dominated by the oxide shell.

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.

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.

Polymer nanocomposites: synthesis and physical properties

Gleb Yu. Yurkov1,2, Alexandr S. Fionov1,3, Oleg V. Popkov1, Igor D. Kosobudskii4, Nikolay A. Taratanov5 and Olga V. Potemkina5 1Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, 2Moscow Power Engineering Institute (Technical University), 3Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 4Department of Chemistry, Saratov State Technical University, 5Ivanovo Institute of State Fire Service of EMERCOM of Russia 1,2,3,4,5Russia

Degradation of physicomechanical properties of epoxy nanocomposites with carbon nanotubes upon heat and humidity aging

The dependence of the physicomechanical properties of epoxy nanocomposites subjected to heat and humidity aging on the type of covalently functionalized carbon nanotubes and on the uniformity of their distribution in the epoxy matrix was studied. Two types of carbon nanotubes were used: those modified with carboxy and amide groups. The elastic modulus, bending deflection, and ultimate bending strength for the initial epoxy nanocomposites with carbon nanotubes and for those subjected to heat and humidity aging were determined. The epoxy binders modified with carboxylated carbon nanotubes are more resistant to the action of aging factors. The presence of aggregates of carboxylated carbon nanotubes in the epoxy matrix positively influences the preservation of physicomechanical properties of the composite subjected to heat and humidity aging. Microscopic examination revealed structural features of the epoxy nanocomposite and their effect on the resistance of the composite to the heat and humidity aging.

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.

Composite tribological materials based on molybdenum disulfide nanoparticles and polytetrafluoroethylene microgranules

Tribological materials based on molybdenum disulfide nanoparticles localized on the surface of ultradispersed polytetrafluoroethylene were prepared. The composition and properties of the new composite materials were studied. Introduction of ultradispersed additives based on polytetrafluoroethylene with MoS2 and on polytetrafluoroethylene and nanodiamonds prepared by detonation synthesis (taken as reference samples) decreases the viscosity of MS-20 aviation oil. The dependence of the friction coefficient on the Sommerfeld number for the composites obtained was examined. Introduction of additives leads to a decrease in the friction coefficient with increasing linear sliding velocity, in contrast to the initial oil for which the trend is opposite. The dependence of the friction coefficient on the concentration of additives in the initial oil was demonstrated. Modification of polytetrafluoroethylene microgranules with 3 wt % MoS2 nanoparticles allows the amount of additive to the oil to be considerably reduced.

Composites based on SiO2 micrograins and cobalt-containing nanoparticles: Synthesis, structure, and magnetic properties

Cobalt-containing particles are synthesized on the surface of silicon dioxide micrograins prepared by the Stöber-Fink method. The composition and structure of nanoparticles are determined by transmission electron microscopy, X-ray diffraction analysis, and EXAFS. The average size of cobalt nanoparticles in the samples is found to be 14 ± 5 nm. The resulting composites are shown to be ferromagnetics with low specific magnetization values.

Magnetic ceramics based on nanoparticles of cobalt and silicon oxide obtained from polycarbosilane

Cobalt ferrite particles are produced in bulk polycarbosilane (PCS). Calcination of the composite to 800°C leads to transformation of PCS into amorphous silicon oxide, in the bulk of which cobalt ferrite nanoparticles are localized. Transmission electron microscopy (TEM) and X-ray phase analysis (XPA) demonstrate that cobalt ferrite nanoparticles have a cubic crystalline lattice. It is established that the average cobalt nanoparticle size is 20 nm. The obtained composite is characterized by ferromagnetic properties. The dynamics of coercive force variation with temperature increase makes it possible to assume that blocking temperature is slightly higher than room temperature.

Electrodynamic materials on the basis of the nanostructured composites

The technology of the production of the nanostructured composite materials on the basis of high pressure polyethylene, which contains the nanoparticles of different composition and structure, was developed. It is shown that variations in composition and concentration of nanoparticles lead to a change in the electrophysical parameters of materials and also characteristics of reflection and absorption in microwave range.