Stretchable carbonyl iron powder/polydimethylsiloxane composites for noise suppression in gigahertz bandwidth

Electromagnetic (EM) noise interference in high-frequency communication systems has attracted considerable attention. Flake-shaped iron-based alloy powder–polymer composites are the conventionally used EM noise suppressors; however, they exhibit low stretchability and cannot effectively suppress EM noise in the range of several gigahertz. The present study demonstrated the application of carbonyl iron powder (CIP)/polydimethylsiloxane (PDMS) composites as EM noise suppressors at 1–18 GHz. The CIP/PDMS composites presented excellent mechanical properties (rupture strength 6.57 MPa, elongation 71%) even at the maximum CIP content of 40 vol%. The tensile test results and finite element method (FEM) simulations revealed a lowering of the elongation with CIP loading content, which was attributed to the localized stress at the agglomerated CIPs. The spherical CIPs exhibited multicore shell interface structures with 2–300 nm ring gaps that were larger than the skin depth of pure iron. EM absorption characterization revealed that the magnetic loss tangent at 10 GHz increased linearly with increasing CIP content. Furthermore, the power loss at 10 GHz for the 40 vol% CIP/PDMS composite was 2.25 times higher than that for the 20 vol% CIP/PDMS composite. This indicated the effective suppression of EM noise in the gigahertz bandwidth with the addition of CIP.