Image: A schematic diagram of phase cancellation and microwave attenuation process. The fluffy structure of PANI/Fe ferrite composite can highly increase the transmission path of microwave, and the multiple reflections can enhance the microwave attenuation efficiency of the absorber. Thus, the microwave attenuation capability of PANI/Zn ferrite composites mainly comes from the enhanced effect of fluffy structure, multiple reflections, interfacial polarization, magnetic loss and dielectric loss. Moreover, if the relationship between the coating thickness and the frequency of incident microwaves matched well with the quarter-wave thickness criteria, the incident microwaves would vertically enter the absorber inside, as shown in this figure. Source: Honglong Xing
In a paper published in NANO, a group of researchers from Anhui University of Science and Technology have synthesized PANI/Zn ferrite composites which have shown excellent microwave absorption performance.
How to reduce electromagnetic pollution? How do these materials attenuate electromagnetic waves? A group of researchers from the School of Chemical Engineering at Anhui University of Science and Technology have synthesized Fe ferrite/PANI composites as efficient microwave absorbers to reduce or eliminate microwave pollution.
PANI/Zn ferrite composites were synthesized by a two-step hydrothermal and in-situ polymerization method. Zn ferrite was used to adjust the impedance matching and improve PANI magnetic loss capability. The synergy of fluffy structure, dielectric loss, magnetic loss, interfacial polarization and phase cancellation effect lead to the attenuation of microwave energy. Furthermore, the fluffy structure enhanced the microwave transmission path and attenuation efficiency. These factors make this composite a good microwave absorber and an ideal material in the electromagnetic wave absorption field.
Microwave absorption materials with reflection loss (RL) values less than -10 dB represent that 90% of microwave was absorbed. The minimum RL values of this composite can reach -54.4 dB with coating thickness of 1.4 mm. The bandwidth about RL below -10 dB was 4.8 GHz at 1.6 mm. The excellent microwave absorption performance of PANI/Zn ferrite composites suggested that it can be used as an excellent absorber with thin coating thickness, strong absorption and broad bandwidth.
Microwave absorption materials have been studied by many workers to reduce or eliminate microwave pollution. Because of rapid popularity and development of electronic devices, especially mobile phones, computers and wireless routers, microwave pollution has been intensified in recent years. These materials have great potential applications in information security, healthcare, electronic countermeasures and so on. The functional materials of PANI/Fe ferrite with lightweight, thin coating thickness, high efficiency and broadband absorption properties are also easy to synthesize, which is beneficial to industrial mass production.