Grafen Nanoplatelet, Nano Gadolinyum Oksit ve Mikro Silika Jel Katkılı Epoksi Kompozitlerin Elektromanyetik Kalkanlama ve Akustik Özelliklerinin İncelenmesi

Abstract

These days, because of the increase in communication and complex electronic systems, electromagnetic interference can adversely affect the operation, protection of systems and human health, particularly in aviation, the defense industry, automotive and banking, where sensitive electronic systems are used. In order to prevent this situation, it is necessary to shield unwanted electromagnetic waves. Metals are generally used as shielding materials due to their reflective properties of electromagnetic waves. However, since metals are heavy materials and have low resistance to environmental conditions, there is a need to develop alternative shielding materials. Nanocomposite materials are used in many fields due to their light and flexible structures, their resistance to environmental conditions and their cost-effectiveness. Sound insulation in the automotive, aerospace and defense industries (vehicles, civil and military aircraft, missiles, etc.) has become important due to negative effects of noise on human health and comfort. Therefore, a material that has features of good sound absorber and electromagnetic sheilding effectiveness can be effective solution. It is known that the addition of graphene and its derivatives to various polymers used as a matrix enriches the mechanical, thermal, optical and electrical properties of the matrix. Compared to other graphene derivatives, graphene nanoplatelet (GNP) shows superior mechanical, thermal, electrical conductivity, optical properties and has two-dimensional large surface contact area that can interact with a polymer. Consequently, GNP-polymer nanocomposites are promising materials in industrial areas such as defense, automotive and energy. Epoxy resin is low cost thermoset polymer exhibit resistance to water, excellent corrosion and electrical insulation properties which is widely used in industry. However, since they have undesirable effects such as low impact resistance/strength, fillers such as graphene, GNP, carbon nanotubes (CNT) improve the undesired properties of epoxy. Addition of the low-cost inorganic fillers such as silica into the polymer is one of the effective ways to improve the performance of the polymer. Silica gel is a worthy sound insulation material due to its high surface area, porous structure, low thermal conductivity, and high flame resistance. The electrical insulation, thermal stability and mechanical properties of epoxy composites enhance due to the addition of silica gel particles, and can also improve the sound insulation property. Within the scope of thesis, electromagnetic shielding efficiency (SE) of graphene nanoplatelet (GNP) filled epoxy with different contents (0.5, 5 and 10 wt%) and magnetic nano gadolinium oxide (Gd2O3) particles filled epoxy nanocomposites (1, 5 and 10 wt%) nano composites were measured by a coaxial transmission line system. The measurements were performed in the range of frequencies from 30 MHz to 1.5 GHz and from 1.5 to 10 GHz. To determine the sound insulation properties in epoxy composites and the effects of filler type and filler content, the samples were preperad with silica gel micro particles (5, 10, 15 and 20 wt %), GNP (0.5, 5 and 10 wt%) and Gd2O3 nano particles (1 wt%). The sound transmission loss (TL) was measured by using an impedance tube in the range of frequencies from 100 to 1400 Hz and from 800 to 6400 Hz. The goal of this thesis is to evaulate the electromagnetic shielding and sound insulation performance of composites and determine the type and optimal content of filler to be used in epoxy matrix. The characterization of the filler materials and composites was made by means X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR) techniques. The transmission loss of the composites was significantly higher (35-45 dB at low frequencies and 35-55 dB at high frequencies); therefore they can be used as sound insulation materials. The shielding perfonmance of the composites could not be observed in the 30 MHz-1.5 GHz frequency range. The highest SE was found to be 11 dB in GNP -epoxy and Gd2O3-epoxy nanocomposites containing 10 wt % GNP and Gd2O3 at 1.62 GHz in the 1.5-10 GHz frequency range. The highest SE was found to be 11 dB in GNP -epoxy and Gd2O3-epoxy nanocomposites containing 10 wt % GNP and Gd2O3 at 1.62 GHz in the 1.5-10 GHz frequency range. The GNP -epoxy and Gd2O3-epoxy nanocomposites containing 10 wt % GNP and 1 wt% Gd2O3 exhibit an SE value of 8.5 dB at 8.5 GHz. The electrical conductivity increased as the GNP content increased, due to electrical resistance decrease. It was found that electrical resistance decrease and the electrical conductivity increases significantly in GNP-Gd2O3-epoxy nanocomposites.