HU Yue, ZHANG Tong, GUAN Mingjun, ZHANG Yi, CHEN Kelong, BAI Xuefeng, WANG Zhiyong

(AECC Beijing Institute of Aeronautical Material, Beijing 100095, China)

Abstract:  Carbonyl iron powders (CIP) are important electromagnetic materials due to their high magnetic loss and high magneto-conductivity. However, the high specific area and high chemical activity of CIP makes them to be easily corroded in salt water and hence cannot satisfy the growing requirements of long-term service in marine environment. Herein, a CIP/SiO₂ core-shell structure was developed by using modified Stöber method. Through two-step coating procedure, SiO₂ coating with uniform thickness of ~500 nm was deposited on the CIP particles. The CIP/SiO₂ exhibited permittivity of 7.5-8.0 in frequency range of 1-18 GHz, which was lower than that of the uncoated CIP (8.7-9.1). The reflectivity decreased from -23.2 dB to -25.6 dB. The effective absorbing band (EAB) was broadened from 7.7 GHz to 8.3 GHz, indicating that microwave property of the CIP/SiO₂ was enhanced as compared with the uncoated CIP. Corrosion test in NaCl solution indicated that the CIP/SiO₂ had higher corrosion resistance than the uncoated one and the high corrosion resistance was still retended after the CIP/SiO₂ coating was abraded or scratched.

Key words:  silica coating; corrosion resistance; carbonyl iron powders