## 1 Introduction  
Electromagnetic interference (EMI) shielding has become an increasingly important area of research due to the increase of electronic device usage in our daily lives. With the rising demand for electronic and telecommunication devices [1], as well as the increasing concern over EMI on human health and safety, the need for effective shielding materials has become paramount [2]. Recent studies have determined the effects of electromagnetic waves on the human body [3; 4; 5; 6]. These negative effects can be avoided by isolating places where people use sensitive electronic devices are located. For example, International Commission on Non-Ionizing Radiation Protection (ICNIRP) provides guidelines and recommendations for limiting human exposure to electromagnetic fields in the frequency range of 0 Hz to 300 GHz. Their guidelines cover both occupational and public exposure and are based on scientific research and expert consensus. International Electrotechnical Commission (IEC) publishes standards related to the safety and effectiveness of electrical and electronic devices, including limits on human exposure to electromagnetic radiation. Institute of Electrical and Electronics Engineers (IEEE) has developed standards, such as IEEE C95.1, which provides guidelines for safety levels with respect to human exposure to electric, magnetic and electromagnetic fields. The 1-14 GHz frequency range is commonly referred to as the microwave frequency range. It includes a range of electromagnetic waves with relatively high frequencies and shorter wavelengths compared to radio waves and lower-frequency signals. This range includes L-band (1-2 GHz), S-band (2-4 GHz), C-band (4-8 GHz), X-band (8-12 GHz) and partial Ku-band (12-18 GHz). These bands are used for telecommunications (communication systems, microwave links, satellite communication, radar systems etc. ), wireless networks (Wi-Fi, Bluetooth, microwave-based wireless local area networks etc. ), aerospace and defense (aircraft navigation, weather monitoring, target detection, surveillance etc. ), medical imaging, scientific research (spectroscopy, radio astronomy etc. ), industrial applications (microwave heating, drying, sterilization etc.) and automotive radar (collision avoidance systems, adaptive cruise control etc.) [7]. When an electromagnetic wave penetrates a material, the wave can be transmitted, absorbed, or reflected, depending on the properties of the material and the characteristics of the wave. Transmission occurs when the wave passes through the material without being attenuated. This can occur if the material has a low impedance and is of the same order of magnitude as the wave impedance [8]. Absorption occurs when the energy of the wave is dissipated within the material. This is typically due to the resistive losses of the material, which convert the electromagnetic energy into heat. The amount of absorption depends on the conductivity of the material and the frequency of the wave [9; 10]. Reflection occurs when the wave is reflected into the medium from which it originated. This can occur if the shielding material has a high impedance and is not of the same order of magnitude as the wave impedance. The reflection coefficient, which is a measure of the amount of energy reflected, depends on the difference in impedance between the material and the medium [11]. EMI shielding can be provided by using metallic products, such as copper, silver, iron, nickel, etc., that have effectiveness due to high electrical conductivity [12; 13]. When metals are used for these applications, some characteristics such as high density, poor corrosion resistance and forming difficulty must be dealt with [14]. Among the various materials being investigated for electromagnetic shielding, carbon-based materials, such as graphite, carbon black, carbon fiber, carbon nanotube and graphene, have shown great promise due to their high electrical conductivity, low density, easy processing and low cost [15; 16].