Corrosion Resistance and Wave Absorbing Property of Carbonyl Iron Powder Coating with Alumina by Atomic Layer Deposition

To improve the corrosion resistant capability and electromagnetic performance of carbonyl iron powders (CIPs), alumina thin films were coated on carbonyl iron powder by atomic layer deposition (ALD) using trimethylaluminum and water as precursors. Original and modified carbonyl iron powder was characterized comprehensively via scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analyzer (TGA), Fourier Transform infrared spectroscope (FTIR), and vector network analyzer. The results indicated that nano-alumina films were conformably grown on the surface of carbonyl iron powders via ALD, forming an excellent core-shell CIP/alumina structure. Compared to the original sample, thermal stability and corrosion resistance of the modified carbonyl iron powders were greatly improved. Antioxidation capability of CIPs was found enhanced with the increase of alumina coating thickness, and the maximum antioxidation temperature can exceed 550 degrees C. It was also found that the complex permittivity of core-shell CIP/alumina decreased greatly while the complex permeability was almost the same. Therefore, the electromagnetic parameters and microwave absorption properties of the modified CIPs was also improved.