# Electromagnetic Radiation Shielding Using Carbon Nanotube and Nanoparticle Composites
## 4 CNT-Based Materials for Electromagnetic Interference (EMI) Shielding  
CNTs are being extensively developed for EMI shielding and a large volume of literature is available. Figure 2 depicts an electromagnetic wave approaching a conductive shielding material, with the primary mechanisms of EMI shielding labeled: reflection (or multiple reflections) and absorption. Many different research efforts have explored the use of CNT films for electromagnetic shielding, with studies demonstrating the effectiveness of incorporating multi-wall carbon nanotubes (MWCNTs) into composites to enhance electrical conductivity and achieve high shielding effectiveness [52; 53; 54; 55]. Studies conducted by [PERSON] et al. [54], [PERSON] et al. [55], [PERSON] et al. [53], and [PERSON] et al. [56] provide a representative summary of the advancements in the EMI-shielding effectiveness of CNT-based composites. [PERSON] et al. [54] investigated the use of MWCNTs in conjunction with polypropylene (PP) to fabricate conductive textiles with enhanced shielding effectiveness against electromagnetic waves. They evaluated the mechanical properties, surface resistivity, and electromagnetic shielding effectiveness (EMSE) of their PP/MWCNT-coated yarns and woven fabrics through a series of standardized testing methods, including ASTM standards for tensile testing and JIS standards for surface resistivity measurements. Their research examined the influence of the MWCNT content and processing parameters on the mechanical properties, electrical conductivity, and EMSE of PP/MWCNT composites. The findings suggest that incorporating MWCNTs enhances both the mechanical strength and electrical conductivity, with an optimal MWCNT content of 5 wt%. Additionally, the study highlights the significance of processing parameters such as the coiling speed and lamination angle in achieving optimal EMSE. This comprehensive evaluation underscores the potential of PP/MWCNT composites in developing advanced conductive textiles for effective electromagnetic shielding. [PERSON] et al. [55] specifically examined how the addition of ferrite nanoparticles to CNT films could improve their efficiency in attenuating electromagnetic waves across a broad frequency range. They employed a straightforward and scalable process for synthesizing ferrite-decorated CNT films, enhancing their potential for practical applications. Techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and electromagnetic interference shielding effectiveness (EMI SE) were used to characterize the structural and shielding properties of the fabricated films. Ferrite-decorated CNT films provided higher EMI-shielding effectiveness than pristine CNT films. The high electrical conductivity of CNTs and the magnetic properties of ferrite nanoparticles led to the improved absorption and reflection of electromagnetic waves. Their research highlights the potential of composite films for use in advanced electromagnetic shielding applications. [PERSON] et al. [53] evaluated the effectiveness of high-loading CNT/poly(allylamine hydrochloride) (PAH) nanocomposite coatings applied to fabrics for electromagnetic interference (EMI) shielding. They implemented a capillarity-assisted assembly technique to fabricate these coatings, offering precise control over CNT deposition and orientation on the fabric substrate. This method allowed for significantly increased CNT loading while maintaining the softness and flexibility of the fabric. Their findings demonstrated that high-loading CNT/PAH nanocomposite coatings exhibited promising EMI-shielding effectiveness, blocking up to 92% of incident electromagnetic radiation, while preserving the material flexibility, softness, and air permeability. However, the study also identified potential challenges in scaling up the fabrication process for industrial applications and emphasized the need for further optimization for different fabric types and thicknesses as areas for future research.