"Nanotechnology and nanomaterials"

Microwave properties of segregated composites with polyethylene and Fe20 Ni80 -decorated graphite nanoplatelets
Syvolozhskyi O.A, Lazarenko O.A., Vovchenko L.L., Matzui L.Yu., Oliynyk V.V., Ischenko O.V., Vakaliuk A.V.
Taras Shevchenko National University of Kyiv, Volodymyrs’ka str., 64/13, Kyiv, 01601, Ukraine 
E-mail: mail.olexiy@gmail.com

Creating a conductive filler network with a high local density significantly improves the properties of composites. Such composites are called segregated composite materials (SCM). These composites consist of polymer globules coated with nanofillers as a result of mechanical mixing and subsequent hot pressing. The use of SCM allows to reduce the amount of conductive filler. The branching of the conductive network creates conditions for good absorption of electromagnetic radiation (EMR) by such materials. Nowadays, most often carbon materials, such as carbon nanotubes and graphite nanoplatelets (GNPs) are used as fillers in polymer matrix. Incorporation of ferromagnetic metallic nanomaterials into polymer matrixes could be a good way to combine the advantages of magnetic metals as absorption materials and polymer materials (corrosion resistance, lightweight, high manufacturability). One way to combine carbon and metallic nanoparticles as a filler is growing FeNi alloy nanoparticles (Fe20Ni80) on graphite nanoplatelets (GNP) surface. FeNi alloy is widely used in applications such as EMR absorbers due to its remarkable magnetic properties, such as high saturation magnetization, high Curie temperature, low coercive force, high permeability and low magnetic anisotropy constant. 
This work presents the results of investigation of the characteristics of electromagnetic shielding of segregated composites with Fe20Ni80-decorated GNPs and ultra-high molecular weight polyethylene (UHMPE) in a frequency range 26-38 GHz. For this purpose, a series of samples of segregated GNP Fe20Ni80 /UHMPE composites with different concentrations of GNP- Fe20Ni80 (from 1.5 to 13.2 wt.%) was manufactured. The concentration dependencies of their transmission, reflection and absorption coefficients were investigated. The results of comparison of the investigated characteristics of GNP Fe20Ni80 /UHMPE composites with segregated GNP-UHMPE composites (containing no metal) are presented. It is shown that the SCM with GNPs decorated by Fe20Ni80 nanoparticles demonstrate to a significant improvement of EMR absorption properties of composites with segregated filler structure.