A novel structure of Ferro-Aluminum based sandwich composite for magnetic and electromagnetic interference shielding

Highlights: • A novel sandwich composite with Fe/FeAl/Fe structure was prepared. • Al element in Fe–Al reaction layer shows a gradient distribution. • The composite improves EMI shielding effectiveness due to multiple reflections. • Sandwich composite shunts magnetic field twice to increase shielding effectiveness. A novel Ferro-Aluminum based sandwich composite for magnetic and electromagnetic interference shielding was designed and fabricated by hot pressing and subsequent diffusion treatment. The microstructure evolution of sandwich composite was characterized. Magnetic and electromagnetic interference shielding properties and mechanisms of the composites were also investigated. Sandwich composite is obtained with pure iron/Fe–Al alloy layer/pure iron structure and the Fe–Al/Fe interface shows good bonding. Al elemental content in reaction layer presents gradient distribution and the Al-riched brittle phase turns into ductile phase with diffusion time increasing. The electromagnetic shielding effectiveness of sandwich composite is higher than that of pure iron plate and increases with diffusion time extension, reaching 70 – 80 dB at the frequency of 30 KHz – 1.5 GHz. The multiple reflection loss in Fe–Al gradient layer is the primary contribution to the shielding effectiveness improvement of sandwich composite. The magnetic shielding effectiveness of sandwich composite can amount to 10 dB, about 2.5 times of that of pure iron plate. Fe–Al intermetallic layer, as non-magnetic spacer, is added between two iron plates and the permeable layer in sandwich composite can shunt magnetic field twice to improve shielding effectiveness.