Currently artificial carbonaceous materials dominate microwave electromagnetics in many respects. This is mainly because of the electromagnetic (EM) properties of these materials can be tailored in a wide range by choosing appropriate carbon allotropes, whose morphology and physical properties strongly depend on the structure at the atomic level.
We present the comparative study of EM interference shielding effectiveness (EMI SE) in Ka-band (26-37 GHz) provided by (i) epoxy resin composites filled with low concentration (0.25-0.5 wt.%) of carbons of high surface area (such as single-walled and multi-walled carbon nanotubes, exfoliated graphite, carbon black, activated carbon, etc); (ii) micro structured carbon foams with cell size from 100 to 500 microns and (iii) nano-thin pyrolytic carbon (PyC) and a few-layered graphene films, 5-240 nm thick.
All investigated materials demonstrate high EMI SE in microwave range. In practice epoxy based composites are beneficial when the flexibility and process ability is crucial. Carbon foams are almost not transparent to microwaves when density is higher than 0.054 g/cm3, highly conducting (at the level of CNT-based polymer composites containing 5-10 wt. % of nanocarbon additives) and 26-7.5 times lighter than epoxy composites. Ultralow (thousands times lower than carbon foams) weight of PyC films makes them especially attractive for application in satellite and airplane communication systems. Moreover, PyC films can be deposited on both dielectric and metal substrates of any shape and/or size by using conventional and inexpensive chemical vapor deposition technology.
The epoxy/carbon composites, carbon foam and carbonaceous thin films provide us with a material platform to design smart coatings and structures for advanced electromagnetics.
