Wireless communication technologies are used in an increasing number of electronic devices. This also makes electromagnetic interference (EMI) an ever-growing problem and leads to a need for high-performance EMI shielding materials. Freestanding films are a commonly used form factor for this. The films need to be thin and low-weight but provide effective shielding and high mechanical strength.

Yan-Jun Wan, Peng-Li Zhu, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, and colleagues have developed an ultrathin densified carbon nanotube (CNT) film with good mechanical properties and high EMI shielding effectiveness. The team first prepared a raw CNT film using a floating catalyst chemical vapor deposition (FCCVD) method. This film contains impurities such as amorphous carbon and catalyst residues. These impurities were removed using high-temperature and acid treatments. This process improves CNT–CNT attraction and leads to densification of the films. The thickness of CNT decreases significantly from ca. 5.4 μm to ca. 1.8 μm, and the surface becomes smoother and develops a metallic sheen.

The densified, purified CNT films have good tensile strength, high electrical conductivity, and high EMI shielding efficiency. The films are stable at high temperatures and in humid, acidic, or basic environments. According to the researchers, this could lead to applications in, e.g, wearable electronics or 5G communication.

• Ultrathin Densified Carbon Nanotube Film with “Metal-like” Conductivity, Superior Mechanical Strength, and Ultrahigh Electromagnetic Interference Shielding Effectiveness,
  Yan-Jun Wan, Xiao-Yun Wang, Xing-Miao Li, Si-Yuan Liao, Zhi-Qiang Lin, You-Gen Hu, Tao Zhao, Xiao-Liang Zeng, Chun-Hong Li, Shu-Hui Yu, Peng-Li Zhu, Rong Sun, Ching-Ping Wong,
  ACS Nano 2020.
  https://doi.org/10.1021/acsnano.0c06971