Enhancement of radio-absorbing properties and thermal conductivity of polysiloxane-based magnetorheological elastomers by the alignment of filler particles

A design for the fabrication of more effective, thin, light-weight radio-absorbers (RAs) based on magnetorheological elastomers (MREs) is demonstrated. Carbonyl iron (CI) particles were incorporated into polydimethylsiloxane matrix either homogeneously (isotropic) or with preferential orientation into chain-like structures (anisotropic). The reflection coefficient (R) of MRE-based single-layer metal-backed RAs was calculated on the basis of transmission line theory. The results show that the orientation of CI particles strongly enhances the permittivity of the systems, while preserving their permeability, which ultimately manifests itself in enhanced absorption of electromagnetic (EM) energy and reduced thickness of RAs. Thus, RAs based on anisotropic MREs are characterized by superior EM shielding capability in the microwave frequency range compared to their isotropic analogues, which offers great practical as well as economic advantages. Moreover, the thermal conductivity of both types of RAs was investigated, since efficient energy dissipation is important to prevent heat build-up under a radio-absorbing shield and thus to extend the service life of the protected device.Internal Grant Agency of Tomas Bata University in Zlin [IGA/CPS/2016/008]; Grant Agency of the Czech Republic [14-32114P]; Ministry of Education, Youth and Sports of the Czech Republic-Program NPU I [LO1504]; Operational Program Research and Development for Innovations - European Regional Development Fund (ERDF); project CPS-strengthening research capacity [CZ.1.05/2.1.00/19.0409