The conventional electromagnetic interface (EMI) shielding materials include applying metal-based shielding materials, but metals are heavy and have a tendency to corrode.
The conducting plastics and coatings have good potential for EMI-shielding materials. There are two types of conductive coatings: intrinsic conductive polymer and composite conductive coating. The intrinsic conductive polymers include polyaniline, polypyrrole, and polypydine. Their poor processing ability and chemical toxicity limit their applications.
The composite conductive coatings consist of electromagnetic absorbents (EMA) and coating matrix. Typical EMI absorbents, such as ferromagnetic metal oxides, carbon clusters,
silicon carbide like materials, are widely applied to EMI-shielding coating. However, there are still numerous drawbacks, such as oxidation and corrosion of metal-like absorbents, inadequate conductive of carbon-like absorbents, inferior dispersing power and bonding strength with coatings, narrow frequency range shielding, and thick and heavy coating layer .
In recent years, as EM shielding, conductive polymeric composites filled with carbon fibers have been used.
They have many advantages because they combine their good mechanical, chemical stability properties of matrix to significant reinforcing effects of fillers: their low density, which makes them suitable for lightweight shielding materials and their ease of forming by extrusion or injection molding, which makes them suitable to be processed in batches.
These materials could have a wide range of applications in military, industrial, and commercial fields. For example, they can be used as casings for computers and television sets to shield electromagnetic waves and thus make them work safely. However, an obvious weakness of the shielding materials filled with carbon fibers is that the conductivity of carbon fibers is much lower than the metal; so a greater volume fraction of carbon fibers is needed in order to provide the same shielding effect. Therefore, in order to decrease the amount of carbon fibers
content and still retain a good shielding effect, a layer of metal is usually plated on the surface of fibers. Nickel and copper are the two main metals used as coatings. Nickel is generally preferred because of its stability and copper is preferred because of the readiness with which it is oxidized .
With the recent improvements in nanotechnology, it is expected to exploit the promising nanomaterials to overcome the aforementioned drawbacks and to develop EMI-shielding coating
with high shielding efficiency, broadband frequency, light and thin coating layer, and chemical stability as well as user-friendly attributes .
The nanoscale design and engineering of multifunctional materials and devices is based on a new type of carbon composites: carbon nanotubes composites. These are moving a
large number of research activities to thriving and remarkable number of industrial products. A large number of these research activities are focused on, but not limited to, the studies of
multifunctional composites based on carbon materials as EMIshielding materials.
This Reesearch yields a review and an outlook for a new generation of nanomaterials for electromagnetic shielding. It provides a description of epoxy composites loaded with carbon nanotubes.
Carbon nanotubes are an allotropic form of graphite with amazing properties. The combination of the matrix and the filler gives a light, strong, highly conducting material, which could be used as an electromagnetic shield in several ways, including coating, paint, and glue.
The Research shows the principal physical parameters, especially the dielectric properties. The dc and ac studies of the behavior of the nanocomposites and their modeling help in obtaining a better understanding of the physical properties and the ways to obtain high-performance nanocomposites.
Lastly some results of the measurement of shielding effectiveness have been illustrated. Quantifying nanofiller dispersion, distribution, orientations, and aspect ratio is crucial to the understanding of the property–structure relationship.
The aspect ratio is the most important parameter. Its high value is essential for good conductivity, mechanical property, and high shielding effectiveness of nanocomposites. It has a strong influence on several CNT properties. It is possible to confirm that CNTs could be used for the fabrication of effective electromagnetic materials on the basis of the epoxy resin. However,
before these materials can find widespread commercialization, studies and modeling are needed to improve the performance of CNT-based nanocomposites and to solve difficulties such as higher interfacial interactions with polymers, optimization of fabrication processes, and well dispersion into the matrix.
This Research takes into account only carbon nanotubes, but it is important to remark that a large number of investigations are being carried out currently on graphene and magnetic nanoparticles.
They could become a novel potential filler to use in the matrix for nanocomposites for electromagnetic shielding in the coming years.
