Corrosion Resistant Enhancement Of Carbonyl Iron Powder Electromagnetic Wave Absorber With Polymer Material

Carbonyl iron powder（CI）is a type of widely applied magnetic material.However,it is active metal and easily erodes and fails in corrosive environments.Exploration of methods and techniques to improve their corrosion resistance never ceases.This thesis discussed two different approaches to improve the corrosion resistance of CI.One method was to chemically couple stable water-resistant polymer material maleic anhydride grafted polypropylene（PP-g-mah）as a protective layer on the flake carbonyl iron powder（FCI）by chemical grafting method,which enhanced the corrosion resistance and hydrophobicity of FCI.The coating thickness was adjusted by the tuning amount of coupling agent aminopropyltriethoxysilane（APTES）.The thermal stability,electrochemical corrosion resistance,hydrophobic properties,and magnetic properties of the coated CI were studied by thermogravimetric analysis,electrochemical impedance spectroscopy,Tafel test,cyclic voltammetry test,contact angle test,and vibration magnetometer.After the FCI particles were coated by PP-g-mah with stable natural barrier effect,the corrosion current(J_corr)decreased from 13.37μA/cm~2 to 4.74μA/cm~2,and the corrosion rate decreased from 0.1554 mm/Y to 0.05507 mm/Y.Meanwhile,the hydrophobicity of PP-g-mah modified FCI particles can be used to prepare superhydrophobic flexible surfaces,which provided new idea for the preparation of corrosion resistant and superhydrophobic FCI-based composites.Another method was to copolymerize two monomers（trimethylolpropane trimethacrylate（TMPTMA）and 2-perfluorooctylethyl methacrylate（17FMA））around CI by in-situ polymerization to form dense polymer layer to enhance its corrosion resistance and tune the microwave absorption properties.The coating thickness was controlled by adjusting the amount of monomer.The influence of the coating on the thermal stability,chemical resistance,electrochemical corrosion resistance and microwave absorption properties of CI were investigated by thermogravimetric analysis,electrochemical impedance spectroscopy,cyclic voltammetry,Tafel test,and electromagnetic parameter test.The corrosion current density(J_corr)of CI particles decreased from 14.73μA/cm~2 to4.374μA/cm~2,and the corrosion rate decreased from 0.1712 mm/Y to 0.05084 mm/Y after coating.In terms of microwave absorption performance,the maximum value of reflection loss（R_L）increased from-41.33 d B to-45.21 d B,and the maximum effective absorption bandwidth EAB（below-10 d B）value of the sample increased from 7.45 GHz to 7.96 GHz.