Electromagnetic wave absorption properties of nanocrystalline Fe-based P/M sheets incorporating multi-walled carbon nanotubes

Nanocrystalline soft magnetic Fe73Si16B7Nb3Cu1 (at.%) powders were mixed with fine multi-walled carbon nanotube (MWNT) powders and polyurethane based binders. The mixtures were tape-cast, dried and then cold-rolled to form EM wave absorption sheets. The MWNT powders were added to the Fe-based powders up to 1 wt.% to improve the EM wave absorption properties. The processed sheets with 0.5 mm in thickness were cut into toroidal shape to measure the S-parameter, permeability, permittivity, and power loss at the high frequency of 10 MHz to 10 GHz. As a result, improved absorption properties were obtained from the sheets incorporating MWNT. The results were caused by the increase of dielectric loss of the absorption sheets, which was due to the addition of MWNT powder inducing a notable increase in complex permittivity.