Preparation of Fe–Si–Al intermetallic alloy and their composite coating for EM absorbing application in 6–18 GHz

An energy efficient and scalable process has been developed for the preparation of intermetallic Fe–Si–Al alloy particles. The preparation process involves initial homogenization & mechanical activation of elemental metal powders followed by vacuum annealing at elevated temperature ~ 650 °C. The physical properties of the as synthesized powders were investigated by means of X-ray Diffraction (XRD), Energy Dispersive Xray Flourence (EDXRF),Vibration Sample Magnetometer (VSM), Scanning Electron Microscope (SEM) and Particle Size Analyser. Composite coatings have been prepared by dispersing 30–60 wt% of Fe–Si–Al alloy in polyurethane (PU) resin. The effect of loading of Fe–Si–Al alloy on dielectric and electromagnetic (EM) properties of composites are studied in 6–18 GHz. A suitable formulation (50 wt% Fe–Si–Al) has been identified, wherein, proper combination of dielectric and magnetic loss of coating composite showed optimal microwave (MW) absorption in 6–18 GHz. The identified composite coating of thickness ~ 1.6 mm showed maximum Return Loss (RL) value ~  − 43 dB at 11.9 GHz and the loss values can exceed more than 10 dB within 6.5 to 16 GHz while varying thickness of coating from 1.2 to 2.2 mm. In the present study, microwave absorption properties of coatings are mainly credited to dielectric and magnetic loss values of the composites. The Fe-Si-Al filled resin composite with optimal loading of alloy particles can be a promising candidate for microwave absorbing coating applications.