Preparation of a\nSelf-Assembled Microwave Absorbing\nFilm Consisting of PDMS/Carbonyl Iron Powders/MWCNTs with Superhydrophobicity\nand Ductility

In this study, a self-assembled microwave absorbing film\nconsisting\nof polydimethylsiloxane (PDMS), carbonyl iron powders (CIPs), and\nmultiwalled carbon nanotubes (MWCNTs) with superhydrophobicity and\nductility was prepared. Microwave absorption materials can protect\naircraft from electromagnetic radars, but it is still a challenge\nto form a flexible covering skin for an airplane with a miniaturized\nbody and small curvature radius, and it is more susceptible to extreme\nweather conditions such as rain and snowl. To address the limitation\nof traditional absorbing materials, PDMS is chosen as the matrix material\nfor the film, profited by its great mechanical properties. Benefited\nby the addition of a multifunctional enhanced micronano filler including\nCIPs and MWCNTs, the film exhibits particle orientation anisotropy\nand stretching performance improvement, respectively. Simultaneously,\nas absorption fillers, the proportional relationship between them\ndirectly affects the impedance matching, absorbing performance, and\neven the superhydrophobicity of the film. After adjustment of the\nratio and conducting repeated experiments, we found that the film\nachieved great comprehensive performance under CIPs of 35 wt % and\nthe MWCNTs of 3 wt %. The minimum reflection loss (RL<sub>min</sub>) is −59 dB with the effective absorption bandwidth (EAB)\nof the film reaching 4.7 GHz at 1.0 mm. The radar cross section (RCS)\nreduction is 36.88 dB m<sup>2</sup> when the scattering angle is 0°.\nThe water contact angle (WCA) of the film reaches 155°, which\nsuggests superhydrophobic behavior. The maximum strain and tensile\nstrength of the film reach 0.63 and 35 MPa, respectively, indicating\nthat it exhibits great ductility and tensile strength. We present\na high-value method to fabricate a superhydrophobic and ductile electromagnetic\nwave (EMW) absorption film, which is meaningful and valuable considering\nits increasing demand as more low-altitude aircraft’s functional\ncovering skin.