Synthesis of absorbing coating based on magnetorheological gel with controllable electromagnetic wave absorption properties

Abstract

Owing to the increasingly complicated electromagnetic environment and changeable battleground, it is especially urgent to study electromagnetic wave absorbing coating with enhanced absorbing capacity and adaptive ability. Magnetorheological gel (MRG) is prepared by mixing magnetic particles with high viscosity polymer matrix. Under magnetic field, these magnetic particles move to form columnar or chains, which allows electromagnetic (EM) waves to penetrate and scatter along the chains. Accordingly, the MRG-based coating that absorbs electromagnetic waves was successfully synthesized. Moreover, flower-like carbonyl iron particles (FCIPs), as the filled magnetic particles, were prepared by in situ method. We studied the effect of magnetic field, particle concentration and matrix curing on electromagnetic (EM) absorbing properties of the MRG-based coating. With the purpose to test absorption performance of the MRG-based coating under different magnetic field intensity, a device that regulates the magnetic field is essential. Thus, we built the device that contains permanent magnet, frame, lifting table. From the results, magnetic field can make absorption peak frequency (APF) move toward high frequency. The amount of shifting to high frequency increases as the magnetic field increases. The magnetic-induced frequency offsets of four samples with different mass fractions (40 wt%, 50 wt%, 60 wt%, 70 wt%) are 2.88 GHz, 1.26 GHz, 1.52 GHz and 0.64 GHz from 0 to 300 mT, respectively. Meanwhile, a suitable magnetic field is beneficial for the coating to absorb more electromagnetic waves. This characteristic of MRG will make it have a wide application prospect in real-time electromagnetic protection and electromagnetic stealth.