Abstract:

Microwave applications, a shielding material must have conductive and magnetic characteristics. Traditionally, heavy-weight magnetic/ nonmagnetic metallic materials were used as the shielding material which can be replaced by light-weight polymers and sp2 -hybridized carbon allotropes such as graphene, CNTs and fullerenes. Polyaniline composites with MWCNT, carbon fiber and graphene possessing core-shell morphology have been reported to have EM shielding effectiveness of 37, 31 and 39 dB respectively in the Ku frequency band. The graphene incorporated composite demonstrates better shielding result as compared to other fillers due to moderate electrical conductivity and large surface area. In case of metallic conductors, the shielding mainly dominated by reflection, and the reflected wave can still interact with other devices. As the electromagnetic wave absorption is related to the losses in the materials, magnetic materials such as soft ferrite and ferrite composites are widely used in shielding applications. At higher frequencies, these materials cannot function as good microwave absorbers because the permeability of these materials decreases due to the eddy current losses induced by electromagnetic waves. As the natural resonance frequency of uniaxial anisotropic materials is proportional to their anisotropy fields, it is possible to use hard ferrites and their composites having large anisotropy as a microwave absorber. Strontium hexaferrite (SrFe12O19) is one such example with wide applications such as magnetic storage media, permanent magnets and microwave absorber being chemically inert, with large magnetization, anisotropic properties and having high frequencies response. Recently, Strontium hexaferrite (SrF) has been reported with promising microwave absorbing characteristics due to a high magnetic loss in highfrequency band, but high density and corrosion sensitivity limit its application.

Description:

Magnetic Filler, PEDOT/Graphene Composite, Microwave applications, shielding material, magnetic characteristics, heavy-weight magnetic, nonmagnetic metallic materials