New Polymer Composite for Electromagnetic Shielding Applications

Scientists from NUST MISIS, South Ural State University and Joint Institute for Nuclear Research, together with colleagues from Egypt, Saudi Arabia and Belarus, have developed a new radar-absorbing polymer composite containing exfoliated graphite (EG)/barium aluminum hexaferrite (HF) fillers.

The new composite exhibits excellent magnetic and microwave properties. It can absorb 99.9% of incoming electromagnetic radiation, making it a promising absorber material for electromagnetic interference (EMI) shielding applications. The work was published in the Journal of Alloys and Compounds. The new composite has potential applications ranging from 5G networks to radar-absorbing coatings. The resulting material becomes undetectable in the microwave frequency range by effectively minimizing the intensity of reflected signals. Associate Professor Aleksey Trukhanov from the College of New Materials and Nanotechnologies at NUST MISIS stated: "High absorption coefficient was achieved by combining a magnetic dielectric filler (barium hexaferrite) and a diamagnetic conductive filler (nanographite). The novelty and level of interest in this concept are high (fundamentally a combination of powder fillers with different electrodynamic properties in the formation of functional composites). Today, the 'single-phase materials era' is coming to an end. It should be noted that extensive research has been conducted on the investigation of substituted barium hexaferrites to achieve this result. Therefore, complex studies were performed on the correlation between chemical composition, structural characteristics, and electrical, magnetic and microwave properties of a wide variety of solid hexaferrite solutions. The most suitable chemical compositions for composite synthesis were selected," Trukhanov explained. Polyvinylidene fluoride (PVDF) was used as the composite matrix. PVDF is a valuable polymer due to its chemical stability, resistance to organic solvents and higher elastic modulus compared to other polymers. PVDF was used to prepare the composite to overcome the main disadvantages of hexaferrite, such as brittleness and difficulty in processing into desired shapes. Scientists determined that the optimal weight percentage of HF and PVDF is 15 wt% PVDF + 85 wt% HF. EG concentration should not exceed 5 wt%. Higher concentrations can increase agglomeration and porosity in the finished material and produce incorrect measurements. The new composite can be used as an electromagnetic shield for incoming electromagnetic radiation with attenuation exceeding 99%. Source