Smart Materials Design for Electromagnetic Interference Shielding Applications

This chapter introduces the basis of electromagnetic interference shielding theory, techniques for characterizing electromagnetic materials, and the application of studying the electromagnetic properties of materials. The main topics include theoretical shielding effectiveness calculation and its measurement, Shielding Mechanism of E-Field and H-Field, absorption and reflection loss, interfacial and orientation polarization, electronic and atomic polarization, characterization methodology, Nicholson-Ross-Weir technique, short circuit line technique electrical properties, electrical permittivity, and magnetic permeability, and dielectric measurement techniques. In addition, the field method is used to analyze the electromagnetic field. This chapter introduced the concept of microwave shield and described its characteristics to achieve the ideal shield. Next, the basic physics that coordinates the interaction between the material and the electromagnetic field is described in detail. Subsequently, we analyze the general properties of typical electromagnetic materials such as dielectric materials, semiconductors, conductors, magnetic materials, and artificial materials. The last part of this chapter introduces the latest developments in EMI shielding materials in various structural forms, as well as future challenges and guidelines for finding material solutions for next-generation shielding applications. Indeed, advanced materials and process technology are the keys to successful EMI shielding. 

In the modern technological era, various electronic devices are being widely used in proportion to the fast-growing demand in society. These devices have created electronic pollutions such as electronic noise, electromagnetic interference (EMI), and radiofrequency interference (RFI), leading to improper functioning of electronic devices. In view of mitigating these detrimental effects, strong EMI shielding materials are required. In recent years, carbon composite foams have attracted worldwide interest due to their outstanding properties such as lightweight, interconnected porosity, high surface area, excellent corrosion resistance, superior electrical and thermal properties that are highly useful for suppressing electromagnetic noises. In this chapter, several carbon foam preparation methods, such as the foaming method, pressure release method, template method, etc., are described. The effect of precursors like pitches, resins, polymers, and biodegradable materials on the microstructure, electrical, and EMI shielding properties of carbon composite foams have been studied. The influences of different fillers such as CNT, graphene, MXene, metals, and magnetic materials on the electrical conductivity and EMI shielding properties of carbon composite foams have been deeply reviewed. The EMI shielding, density, and thickness of carbon composite foam with various loading of fillers are summarized in tables in this chapter, which will provide readers with useful information. In the last section, current challenges and future research directions of this growing field are also discussed. 

We have seen a rapid surge in the growth and subsequent drive-in scaling down electronic interfaces with intelligent electronic devices. Any electronic gadget that transmits, distributes, or uses electrical energy produces electromagnetic interference (EMI), which has harmful effects on device performance, human health, and the surrounding environment. This increase in unrestricted EM pollution can also affect human well-being and the surrounding environment if proper shielding is not provided. Therefore, there is an increasing demand for EMI shielding materials due to the rapid increase in EM radiation sources. EMI shielding materials must have the capability to absorb and reflect EM radiation at very high frequencies and act as a shield against the penetration of radiation through them. The polymer matrices are generally electrically insulating; therefore, they cannot provide shielding against EM radiations. Thus, the use of electrically conducting fillers enables the path in polymer composites to shield the EM radiations. This chapter covers the up‐to‐date research activities targeting EMI shielding based on thermoplastic, and thermoset polymer nanocomposites (PNCs) reinforced with carbon-based nanostructures (CBNS). The first section of this chapter gives a brief overview of the fundamentals of EMI shielding, theoretical aspects of shielding, and different strategies for controlling EM radiations. Other synthesis methods are discussed in the next section, which deals with the preparation of PNCs. Comprehensive justification of potential materials for controlling EMI is also described with nanocomposites based on thermoplastic and thermoset polymer matrices incorporated within CBNS, magnetic, dielectric, and hybrid materials. The synergistic effects of the hybrid fillers may render tunable electrical conductivity and electrical percolation phenomenon in nanocomposites.

Interference and chaos among the various electromagnetic signals are becoming the primary challenge of the current era that relies on wireless communication. Electromagnetic pollution is the overabundance of electromagnetic radiation emitted by electronic devices, like cell phones, cordless phones, Wi-Fi routers, or Bluetooth-enabled equipment, and our relationship with these devices has become more and more intimate. The potential effects of electromagnetic pollution, both in terms of its interaction with electronic devices as well as biological species, are serious concerns for the research community. EMI shielding reduces electromagnetic interference among the electronic components. Therefore, protection from such harmful radiations must be acquired by either blocking or shielding these unavoidable severe electromagnetic radiations. Metals have been typically used as the material of choice for shielding applications, but heavy weight, corrosion susceptibility, and cumbersome processing methods make them unsuitable for both researchers and users. Alternatively, polymer nanocomposites have gained tremendous attention as electromagnetic interference (EMI) shielding materials owing to their facile synthesis, ease of processing, and low cost. Different thermoplastic and thermoset polymer matrices have been explored for the development of lightweight composite material for EMI shielding applications. Among the thermoplastic polymers, thermoplastic polyurethanes (TPU) have attracted a great deal of recognition due to their combination of properties, such as flexibility, stretchability, transparency, good wear and weather resistance, better abrasion and chemical resistance, and better mechanical properties. Although graphene and carbon nanotubes have been explored as conducting fillers in polyurethane matrix for the development of EMI shields, no reports are available using a combination of these fillers along with magnetic nanoparticles in thermoplastic polyurethane matrix. 

This chapter gives a brief oversight of the preparation, characterization, and electromagnetic interference shielding studies of conducting polymer and MWCNT composites. The different approaches have been implemented to fabricate composites, which are used as EMI shielding materials. The key emphasis has been given to PEDOT conducting polymer, which is synthesized via emulsion polymerization. The topographical and chemical analyses of polymer composite samples were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermo gravimetric analysis, and Raman spectroscopy. The dielectric and electromagnetic shielding measurements of the polymer composites were conducted by a vector network analyzer. In addition, PEDOT/MWCNT coated polyurethane foam usage as an antistatic material has also been discussed in this chapter.

Graphene is composed of a single atomic layer of carbon with excellent mechanical, electrical, and optical properties. It can be widely used in the areas of physics, chemistry, energy, information, equipment manufacturing, and electromagnetic interference shielding. This chapter described the concepts, structures, properties, manufacturing methods, and applications of graphene composites in shielding against electromagnetic interference. The continuous 3D conductive array of graphene composites can effectively improve the electronic and ionic transmission of the material. Therefore, adding graphene oxide to the composite material will significantly improve the performance of the material for better conduction and EMI shielding. This chapter summarizes the latest developments in the electromagnetic shielding performance of graphene composites and highlights their prospects.

Electromagnetic interference (EMI) disturbs the working of electronic and electrical equipment used in aerospace, military, and many more areas. This disturbance leads to the complete failure of equipment and it is also very dangerous to human beings, especially radiation created by mobile phones. The considerable development in materials has been achieved with the fabrication of the shield in the form of composite sheets, paints, coatings, etc. Now, there is a need to fabricate flexible materials to achieve intricate shapes and structures to provide excellent EMI shielding in a wide frequency range. In addition to EM pollution, society is also dealing with pollution created by solid waste like fly ash. The disposal of fly ash has become a challenge due to its astounding amount produced in coal thermal power plants. This research work demonstrates the usage of fly ash to fabricate advanced composites for electromagnetic shielding applications. This chapter will throw some light on the electromagnetic shielding mechanism, EMI shielding measurement methods, fabrication of smart materials for shielding application in the designing of conducting polypyrrole nanocomposites, polyurethane composites, and cement paint composite using fly ash along with other magnetic/dielectric reinforcement to develop material offering optimized electromagnetic shielding properties. Moreover, these composites are further tested for other characterization techniques. These developed smart materials not only find a solution for the utilization of fly ash but also offer excellent shielding effectiveness in a wide frequency range. 

EMI is a 20th-century radiation pollution that not only results in various health hazards but also weakens the electronic system's performance. With the rapid global development in various fields, this problem is increasing consistently. To ensure the uninterrupted performance of electronic gadgets and avoid the effects on human health, EMI shielding has become a necessity. In the recent past, a large number of materials having a wide range of conductivity and good electromagnetic attributes have been exploited for EMI shielding applications. Initially used metallic shields, due to their high cost & weight, corrosion propensity, and reflection-based shielding, have been replaced by various types of materials. Among them, intrinsically conducting polymers (ICPs) like polyaniline, polythiophene, polypyrrole, etc., and their composites with various types of conductive and/or magnetic fillers have played a significant role. Among all the conducting polymers, polyaniline has been studied the most due to its special properties like moderately high conductivity, ease of synthesis, proton doping, low cost, and high environmental stability. Most of the developments related to EMI shielding have been focused on the synthesis of new materials with high shielding effectiveness (SE). For this purpose, polyaniline and its composites have been widely explored due to its appropriate properties. But the commercial use of polyaniline for EMI shielding applications has always been hampered due to its infusibility and limited processability. Also, limited work has been done for the fabrication of polyaniline composites in the form of sheets that have sufficient SE along with improved thermal and mechanical stability. The work presented in this chapter is based on the fabrication of lightweight, thin sheets of polyaniline composites for EMI shielding application in the X-band of microwave range (8.2-12.4 GHz). The polyaniline-CFnovolac (PACN) composite sheets thus obtained were finally tested for EMI shielding applications using vector network analyzer (VNA) in the X-band of microwave range. Characterization of all the composites and/or their sheets was done by UV-vis, FT-IR, SEM, TGA, electrical conductivity (standard four-probe method), flexural strength, and flexural modulus measurements.

A study was made to design a copolymer of aniline and o-toluidine and its composite with carbon fiber (CF) in making PANIoTCFN sheets for controlling electromagnetic interference. PANIoTTCFN composite synthesized by emulsion polymerization was physically blended with different proportions of novolac resin to prepare a composite sheet by hot press compression moulding. In-situ incorporation of carbon fiber into the copolymer during the synthesis leads to the formation of composites with improved mechanical, thermal, electrical, and shielding properties. Structural and morphological studies were carried out by FTIR, XRD, and SEM. PANIoTCFN composite sheets with 50 % loading of novolac resin have a flexural strength of 52.4 MPa and exhibited shielding effectiveness of 26 dB at a thickness of 1.48 mm of the composite sheet, which reveals that these composite sheets can be used for EMI shielding applications. 

Advancement in modern electronic devices needs special requirements such as compact size, lightweight, and easy processing ability for the new innovative systems. This chapter describes the fundamentals of porous MXene composites (foams and aerogels) with the aim of inhibiting electromagnetic (EM) pollution. The first article that elucidated the EM shielding capabilities of MXene composites demonstrated superior performances to those of the existing materials, owing to their metallic conductivity, large surface area, surface modifiability, and ease of processability. Various approaches have been used to attenuate EM waves, including the application of laminate, porous, and hybrid structures. Among these, the porous morphology can contribute to the design of the absorption-dominant EM shield. Herein, the variations in electrical conductivity, mechanical stability, and electromagnetic interference shielding effectiveness (EMI SE) were explored with the use of a porous morphology. Subsequently, the theoretical and experimental results were analyzed to obtain new insights into the shielding mechanisms. This chapter will provide an overview of porous MXene composite materials and future challenges and strategies to design hybrid materials for next-generation EMI shielding applications.

For an effective EMI shielding, materials should have high electrical conductivity as EMI attenuation is a sum of relfection, absorption, and multiple relfections which requires the existence of mobile charge carriers (electrons or holes), electric and/or magnetic dipoles, usually provided by materials having high dielectric constants (ε) or magnetic permeability (μ) and the large surface area or interface area. Until now, a metal shroud was the material of choice as an EMI shield. However, metal fillers add additional weight and are susceptible to corrosion, making them less desirable. Therefore, we have focused on new emerging two-dimensional 2D nanomaterials that are light in weight and have a low cost. Here, the focus is to address the challenges in their synthesis especially transition metal carbides (MXenes), MoS2, functionalized graphene/ferromagnetic conducting polymer composites, and their fabrication for EMI reductions. These articles also evaluate and explain the recent progress explicitly and underline the complex interplay of its intrinsic properties of 2D nanostructured materials (MXene, MoS2, Graphene/ferromagnetic polymer composite) as a potential candidate for EMI shielding and evaluate their electromagnetic compatibility. The chapter will cover the facets related to a newly emerging area of EMI shields in the automotive industry, especially lithium-ion battery-operated electric vehicles and self-driving cars, high-speed wireless communication devices, and next-generation mobile phones with 4G and 5G technology.

For the first time, the capability of red mud waste has been explored for the development of advanced synthetic radiation shielding aggregate and radiation shielding concrete. Red mud, an aluminium industry waste, consists of multicomponent and multi-elemental characteristics. Approximately two tons of red mud are generated for every ton of aluminium production. There are about 85 alumina plants all over the world, thus leading to the generation of about 77 million tons of highly alkaline waste annually. The major mineral content of red mud waste includes hematite, anatase, and cancrinite, thus making red mud waste the most suitable multicomponent resource material for developing multi phases containing shielding aggregate. Further, these multi-elements in the red mud are present in the form of oxide, oxy-hydroxide, and hydroxides, having low as well as high atomic number elements, namely sodium, iron, titanium compounds, respectively, and are non-toxic in nature. The concrete possessing specific gravity higher than 2600 kg/m3 is known as heavyweight concrete, and aggregate with specific gravities higher than 3000 kg/m3 is called heavyweight aggregate as per TS EN 206-1 (2002). The shielding aggregate contains both naturally occurring as well as some of the artificial aggregate. The natural aggregate includes hematite, magnetite, limonite barite, etc., which are nonreplenishable and are useful for many other important applications, and the artificial aggregate includes the use of iron shots and steel filing and in some cases, lead shots, etc. The use of lead shots makes the material toxic in nature, therefore, there is a need to avoid the use of lead-based materials for shielding applications, as it ranks second in the list of hazardous materials. Apart from toxicity associated with lead, the low melting point of lead is also prohibitive as the shielding concrete should be preferably heat and fire-resistant. Further, all the natural minerals inherently contain only a single shielding phase, therefore, conventionally shielding concretes are developed by a combination of various natural minerals, which leads to an inhomogeneous radiation shielding matrix in the developed conventional radiation shielding concrete. In view of the above, there is an urgent need to develop advanced non-toxic synthetic shielding aggregate capable of providing homogeneous radiation shielding matrix preferably obviating the use of toxic lead and conventional non-replenishable natural minerals resources. In this chapter, aluminium industrial waste, i.e., red mud, has been utilized. Chemical formulation and mineralogical designing of the red mud has been done by ceramic processing using appropriate reducing agents and additives. The chemical analysis, SEM microphotographs, and XRD analysis confirm the presence of multi-component, multi shielding, and multi-layered phases in developed advanced synthetic radiation shielding aggregate. The maximum density of developed synthetic aggregate is found to be 4.16 g/cc. The mechanical properties, namely aggregate impact value, aggregate crushing value, and aggregate abrasion value, have been evaluated and was compared with hematite ore aggregate and found to be an excellent material useful for making advanced radiation shielding concrete for the construction of nuclear power plants and other radiation installations.

For the first time, the development and design mix of novel radiation shielding concrete using innovative red mud-based synthetic shielding aggregates have been carried out in which the heavy density shielding aggregates are developed using red mud and are basically ceramic materials consisting of shielding phases, namely barium silicate (san-bornite), barium iron titanium silicate (bafertisite), barium aluminium silicate, iron titanium oxide (pseudorutile), barium titanate, barium iron titanium oxide, barium aluminium oxide, and magnetite, which are multi-elemental, multi phases, multi-layered crystal structures, therefore, they are excellent shielding materials.

The radiation shielding concrete was made using developed synthetic shielding aggregates adopting IS 10262-2009 standard for grade designation of M-30 concrete. The reference hematite ore concrete and developed concrete tested for radiation shielding attenuation properties for gamma rays using 137Cs (of photon energy 662 keV) and 241Am (of photon energy 60 keV) were found to possess highly effective shielding properties. The developed novel design mix concrete achieved an attenuation factor of 5.8 as compared to 5.1 attenuation factor for reference hematite ore concrete. The developed radiation shielding concrete using red mud-based synthetic shielding aggregates possess a broad application spectrum ranging from the construction of diagnostic X-ray, CT scanner rooms, and storing radioactive waste to nuclear power plants.