Yeni Tasarım Nanokompozit Kaplamalar ile Ekranlama ve Biyofiziksel Özelliklerin Araştırılması ve Geliştirilmesi
Özet
Due to the development of electronic technology and telecommunications in recent years, the presence and effect of unwanted signals, which are considered as electromagnetic pollution, to which people and devices are exposed, have increased considerably. In order to reduce the impact of electromagnetic signals on the environment, the shielding method using conductive materials is the most commonly used method. Metals are generally used as materials due to their high conductivity properties. However, as a material, the negativities such as the high density of metal, the inflexibility of their structure, their difficulty in processing and the fact that they are open to corrosion make it necessary to turn to alternative materials instead of these materials. In this context, in order to benefit from their small density, low cost, easy shaping and flexible structure, the design of polymer-based, nanotechnological materials has become important today.
In this thesis, first of all, new design, polymer-based, nanocomposite materials doped with CNT and graphene in different mass ratios were prepared. These composites can be applied in spray and gel phases on different types of fabrics. In the studies carried out within the scope of the thesis, the fabric produced with natural linen material without any screening feature and the SG fabric with self-screening feature (commercially sold in the market) produced with special techniques were studied. The main purpose is to provide a high-level shielding feature by applying a new design nano-composite coating to a non-shielding material. On the other hand, increasing the current shielding efficiency value of materials with shielding feature has been determined as a secondary objective.
In the first phase of the study, the interactions of different fabric samples coated with unique nanocomposites with electromagnetic wave (EMD) (1.5 – 10.0 GHz), nUV-VIS-nIR (350 - 700 nm) were investigated. As a target, the shielding properties were tried to be developed in a controlled manner by associating the electromagnetic shielding effectiveness of the samples with the nano structures determined as a result of SWAXS (X-Ray Small and Wide Angle Scattering) analysis.
According to the preliminary findings, when linen fabric samples without EMD shielding effect were coated with 3% wt CNT encoded nanocomposite, it caused an increase in the EMD absorption in 1.5 – 10.0 GHz range and giving a shielding effectiveness feature of approximately 9 dB (@9.5 GHz). As a result of the coating process, it was determined that the transmittance of electromagnetic waves in the wavelength range of 350 - 700 nm (near UV, visible and near IR) was reduced and the absorption property increased with the same coating material.
While the volumetric nanoparticles existing in the natural structure of the linen fabric have a radius of 97.7 ± 0.9 Å, after the coating process, the nanomorphologies transformed into the core shell model and reached a radius of 75.7 ± 0.1 Å in spherical form. In other words, it has been determined that the coating material can diffuse into the porous structure and fill the porous structure, forming smaller sized nano morphologies with high electron density. When CSC material containing Ag pigments available in the market is applied to linen material, it has been observed that it provides approximately 65 dB (@9.5 GHz) shielding to the fabric.
In the next stages, CSC material, which was systematically doped with CNT and graphene at different rates (by mass), was applied on linen and SG fabric and measurements were carried out. It has been determined that the most stable nanocomposites are obtained with CSC 5%wt CNT and the non-shielding linen fabric has a shielding efficiency of approximately 80-85 dB in the 1.5-10 GHz range.
It has been determined that the most stable nanocomposites are obtained with CSC 5% wt, and the non-screening linen fabric has a shielding efficiency of approximately 80 - 85 dB in the 1.5-10 GHz range. On the other hand, it has been determined that the shielding property of SG fabric, which has a pre-screening feature, has been improved from 65 dB to ~105 dB shielding values (at the rate of ~62%).
Rg (Girration Radius), 3D structure models and distance distributions of nano-formations were investigated in order to determine the nanostructures of the samples with SAXS analysis and to make analogies with the shielding values. Micro-scale structures formed on the surface of the nanocomposite material due to CNT and graphene doping were also observed with SEM measurements before and after the coating of the samples.
In the continuation of the study, it was determined that the achived shielding property for linen CSC 5% CNT with samples prepared at different times was not random.
In addition, it is foreseen that nano composite coatings can be used in many applications that may be in human contact, and antimicrobial researches with the Disc Diffusion Method were also carried out within the scope of this thesis study. In this context, Candida albicans, E.coli and S. Aureus (fungus and bacteria) were studied.
As a result, it has been shown that while significant improvements have been made in the shielding properties of substrate fabrics with the original nano-composite materials prepared and applied as a coating in this thesis, on the other hand, it has been shown that "bioactive properties" can be added to the "designed coating materials", which also prevents bacterial and fungal growth.
