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    Investigation of the Dielectric Properties of Graphite and Carbon Black-Filled Composites as Electromagnetic Interference Shielding Coatings
    (Mdpi, 2023) Gumus, Emre; Yagimli, Mustafa; Arca, Emin
    The main purpose of electromagnetic interference (EMI) shielding coatings is the insulation of sensitive devices and protect people from electromagnetic field exposure due to its effects on the human body. This paper investigates the dielectric properties, and electromagnetic shielding performances of graphite and carbon black (CB) filled epoxy matrix composites produced by the mechanical mixing method. The sample compositions were created at rates ranging from 1 to 7 wt%. Samples were analyzed by Vector Network Analyzer (VNA) using the coaxial method in the range of 1-14 GHz, including L band, S band, C band, X band and partially Ku band. After determining the scattering parameters with VNA, AC conductivity, absorption, reflection and total shielding efficiency values were calculated. At high frequencies, almost all the samples showed higher AC conductivity. CB-filled samples show higher AC conductivity than graphite-filled samples. The total shielding efficiency (SET) of the graphite-added samples (19-21 dB) is slightly higher than the carbon black-added samples (8-17 dB). Distinct filling ratios in graphite-added samples result in closer shielding behavior in contrast to carbon black-added samples. However, higher shielding efficiency is observed as the CB filler ratio increases. The shielding efficiencies of the samples with both types of filling materials vary little depending on the frequency. Reflection is the main mechanism of the shielding efficiency, which constitutes the majority of total efficiency for all types of samples.
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    Mathematical modelling of sound transmission loss (STL) in metallic and graphite based coatings
    (Taylor & Francis Ltd, 2022) Yalcin, G. E.; Ergin Esen, Hande; Yağımlı, Mustafa; Arca, Emin
    This study aimed to investigate the relationship between the sound transmission loss (STL) properties and surface morphologies of metallic-based and graphite-based coatings. Aluminium (22 mu m average particle size (APS) and 12 mu m APS), copper (12 mu m APS), silver (14 mu m APS) as conductive metal pigments and graphite (18 mu m APS) as a semi-conductive pigment were used to create coatings and STL properties were measured with an in-house designed sound wave modulation device. Laser beams with different carrier wavelengths were used in the experiment, for which the wavelength with the highest R-2 and number of significant variables was used to create a mathematical model to help in measuring the sound transmission loss properties. Surface tension energy, conductivity, permeability, reflectivity, concentration and the type of pigment were found to be significant in determining the STL properties.