Excellent electromagnetic interference shielding characteristics of a unidirectionally oriented thin multiwalled carbon nanotube/polyethylene film

In this study, we synthesized oriented multiwalled carbon nanotube (CNT)/polyethylene (PE) composite films and investigated their electromagnetic interference (EMI) shielding properties. The oriented CNT sheet structure was prepared by stacking CNT webs produced by a dry spinning technique with a CNT forest. In a near-field EMI attenuation measurement by a microstrip line method, composite films with a CNT fraction higher than 2 wt% showed a high attenuation that exceeded 50 dB at 10 GHz. This high attenuation was due to the enhanced magnetic anisotropy of the oriented CNTs and the encapsulated catalyst-derived cementite nanoparticles. This is the first report of high magnetic anisotropy in an oriented CNT structure for noise attenuation in a transmission line. In a far-field EMI shielding measurement by a coaxial tube method, the EMI shielding effectiveness (SE) significantly increased as the number of CNT web layers increased. A CNT/PE film with a high CNT fraction was found to have a high specific EMI SE of 0.6 dB/μm. The oriented CNT/PE composite film has great potential as a promising EMI material that demonstrates high shielding efficiency performance with low CNT loading.