Synthesis and physicochemical properties of composites for electromagnetic shielding applications: a polymeric matrix impregnated with iron- or cobalt-containing nanoparticles G.Yu. Yurkov; A.S. Fionov; A.V. Kozinkin; Yu.A. Koksharov; Y.A. Ovtchenkov; D.A. Pankratov; O.V. Popkov; V.G. Vlasenko; Yu.A. Kozinkin; M.I. Biryukova; V.V. Kolesov; S.V. Kondrashov; N.A. Taratanov; V.M. Bouznik //Journal of Nanophotonics. 2012. V.6, Iss.1, 061717 (December 05, 2012)
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.
The possibility of combination of properties specific for metals and polymers in a single material, as well as control of these properties by means of concentration variations, has been studied for a while. Different polymers can be used as the matrix in such a material, e.g., polyethylene, polypropylene, polytetrafluoroethylene, and others. These polymers exert relatively high thermal resistance, unique rheological properties and high dielectric strength and they are chemically inert and easily processable, which allows one to form items of any desired shape and size from them. It is also important that these polymers are produced using well-studied methods.
Impregnation of polymer matrices with metal-containing nanoparticles allows creation of materials with interesting magnetic, electrophysical, and performance properties. A major advantage of composite materials, including nanocomposites, is the possibility of combination of conductivity, dielectric and magnetic properties in a single material, i.e., such materials combine properties of both the filler and the matrix. Besides that, it is possible to control magnetic and electrophysical properties of a nanocomposite by varying composition, size and concentration of the embedded nanoparticles. In particular, impregnation of dielectric polymers with carbon nanotubes, metal-containing fillers, results in formation of composites with enhanced conductivity compared to the pristine polymer matrix. The listed sources indicate that electric properties of composites depend on composition, shape, size, and concentration of the filler.
The goal of this work was creation of new composite materials composed of the low-density polyethylene (LDPE) matrix impregnated with iron- or cobalt-containing nanoparticles. Composition, electrophysical and magnetic properties of the materials prepared were studied. Such new nanocomposites could be used in electromagnetic shielding applications.
A technology for small-scale production of nanostructured materials based on cobalt- and iron-containing nanoparticles has been developed. Structural analysis results indicate that the nanoparticles have a complex structure: the cobalt-containing particles are composed of hcp metallic cobalt and cobalt carbide, whereas the iron-containing particles are composed of iron oxides.
The investigations of the static magnetization and the microwave resonance absorption have showed that Co nanoparticles in a polyethylene matrix display a set of interesting properties. First of all, it is enhanced (in comparison with the bulk value) magnetic moment per atom. Secondly, it is the record blocking temperature, notably higher than the room temperature. The high blocking temperature points to high magnetic anisotropy, which can be apparently related with surface effects. Basic electrophysical properties of the materials prepared have been studied; the materials are efficient for use in electromagnetic shielding applications.