Microwave shielding effectiveness study of composites materials and coating based ongraphene, MWCNT and biochar.

In this thesis the basic theory of shielding effectiveness is described in Chapter 1, where only approximate solutions are presented to compute the shielding effectiveness of metallic shields. The purpose of this chapter is to introduce the basic concepts of the electromagnetic waves shielding that will be recalled in Chapter 2, where all the actually used methods to measure the shielding effectiveness of materials are described. This chapter is a kind of selection guide that allows the reader to choose the best method for measuring the shielding effectiveness of its material. Only two of these methods are standardized, because the research of new materials able to shield the electromagnetic waves is relatively new. In Chapter 3 the characterized ma-terials are described: they are, for instance, dispersions in an epoxy resin of multiwalled carbon nanotubes (MWCNT) or biochar powder. The developed system able to mix the powders with-out having air bubbles inside the epoxy resin is also thoroughly described. In the Chapter 3 end, the possibility to test the obtained composites with a standard coaxial holder is investigated. The result of the measurements is reported in Chapter 4, while the utility of the characterized composites as electromagnetic shielding materials is discussed in Chapter 5.