doi:10.1038/nindia.2014.23 Published online 18 February 2014
Researchers have produced a nanocomposite consisting of nickel–zinc–cobalt-ferrite nanoparticles contained within multiwalled carbon nanotubes. This nanocomposite can absorb microwave radiation, making it potentially useful for microwave shields that protect electronic devices from interfering microwave radiation produced by electromagnets1 .
Wireless electronic devices use microwaves to transmit and receive data. One such device is the cell phone — it emits and receives microwaves, which can disrupt the operation of nearby electronic gadgets, such as laptop computers. In addition, studies have shown that microwaves are harmful to human health. Most materials used to produce microwave shields are metallic, heavy and difficult to produce in bulk.
To develop a simple and effective microwave absorber, the researchers synthesized the nanocomposite by loading multiwalled carbon nanotubes with nickel–zinc–cobalt-ferrite nanoparticles. They then tested how effectively the nanocomposite absorbed microwaves. The nanocomposite exhibited sufficient absorption of electromagnetic energy in the microwave spectral region between 8 and 18 gigahertz. The nanocomposite significantly attenuated both the electric and magnetic energy of microwave radiation. Microwave attenuation increased with increasing nanocomposite thickness.
The nanocomposite exhibited higher microwave radiation attenuation than the ferrite nanoparticles alone or the multiwalled carbon nanotubes alone. "This nanocomposite can be used in paints and coatings on electronic devices to block interfering microwave radiation including in several defence mechanisms for developing stealth technology," says Sukhen Das, a senior author of the study.