# Electromagnetic Radiation Shielding Using Carbon Nanotube and Nanoparticle Composites
## 4 CNT-Based Materials for Electromagnetic Interference (EMI) Shielding
[73] investigated the microwave attenuation of SiO\({}_{2}\)-matrix composites packed with various amounts of MWCNTs in the X-band frequency range (8.2-12.4 GHz) at temperatures ranging from 100 to 500 \({}^{\circ}\)C. The study found that electron movement within and between graphene layers in the MWCNT network significantly impacted the electrical conductivity, dielectric properties, and microwave-attenuation performance. Composites with 10 wt.% MWCNTs demonstrated electromagnetic interference shielding of 24.5 dB and a broad absorption bandwidth, indicating their promise as high-performance materials for microwave attenuation. CNT composites can be used as multi-spectral shielding materials and multifunctional materials. [PERSON] et al. [74] carefully examined the design and assessment of CNT-based materials for optical power limiters (OPLs). The study reviewed various OPL methods, types of optical power limiters, and OPL chromophores, highlighting CNTs' potential as broadband optical limiters due to their distinctive characteristics. Integrating CNTs with other organic and inorganic chromophores was highlighted to create synergistic effects, expanding the applications of optical materials across a broad range of frequencies. Materials for radiation attenuation often form composite materials. Metal powders such as lead, tin, and bismuth are mixed with poly(vinyl chloride) to create flexible matrices, which are then cut and layered to make protective clothing. Heavy metals like iron, zinc, bismuth, and gadolinium and less common metals like cerium, americium, and thallium, or salts can be incorporated into polymers to enhance the shielding effectiveness of carbon-nanostructured materials. Graphene is a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice. Graphene is known for its high electron density, high absorption coefficient, photoelectric absorption, mechanical strength, chemical stability, flexibility, and conformability [49; 75]. Combining PDMS, boron-based materials, and graphene with CNT hybrid fabric offers multiple benefits, such as joint shielding, enhanced structural integrity, optimized properties, and improved compatibility. Integrating component materials with diverse properties will further increase the shielding capabilities of host materials against radio waves and microwaves and higher-energy radiation like X-rays and gamma rays. Including graphene within the CNT fabric provides structural support and improves the mechanical properties, ensuring durability and integrity under radiation exposure. Adjusting the thickness and composition of this CNT hybrid fabric material can optimize and enhance its performance for different radiation environments. The materials used to form this hybrid material are biocompatible, making the entire hybrid material suitable for use in biomedical applications. Depositing or coating thin layers of graphene with the rest of the materials will enhance mechanical properties and functionalities while maintaining flexibility and conformability. However, creating materials with multiple components requires precise control over the coating process, including the deposition techniques, uniformity, and adhesion between layers. Achieving consistency and uniform coatings can be particularly challenging, especially for large-scale applications. The thickness or volume fraction of each component in the hybrid material is crucial to attain the desired shielding effectiveness. However, the increased weight and bulkiness of this material may limit its applications in certain industries, such as aerospace and healthcare. Moreover, this new hybrid CNT fabric material must meet regulatory requirements and standards for radiation-shielding materials, particularly in sectors like healthcare and nuclear energy.