SiO_(2)包覆羰基铁粉及其涂层的耐腐蚀性能

Carbonyl Iron Powders with Silica Coating and Long-time Corrosion Resistance

羰基铁粉(CIP)在功能涂料、电磁流变材料等领域有着重要应用前景。然而,羰基铁粉的耐腐蚀性较差,在湿热及海洋环境使用时,会发生严重的粉体腐蚀,造成材料性能失效。通过改进的Stober方法对羰基铁粉表面进行水解包覆,在羰基铁粉表面制备均匀致密的SiO_(2)厚包覆层。实验结果表明,通过"有机-无机"两步包覆过程,可以实现羰基铁粉表面的均匀致密包覆,包覆层厚度约为500 nm。与未包覆的羰基铁粉相比,包覆后的羰基铁粉介电常数实部由8.7-9.1下降至7.5-8.0,最低反射率由-23.2 d B降至-25.6 d B,有效吸收带宽由7.7 GHz提升为8.3 GHz。采用包覆后的复合粉体制成涂层样品,其耐盐水腐蚀性能显著提升,而且在打磨、刻划后仍保持了优异的耐腐蚀能力,在耐腐蚀功能涂料、软磁材料等领域有重要应用前景。

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/SiO_(2)core-shell structure was developed by using modified St?ber method.Through two-step coating procedure,SiO_(2)coating with uniform thickness of~500 nm was deposited on the CIP particles.The CIP/SiO_(2)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/SiO_(2)was enhanced as compared with the uncoated CIP.Corrosion test in NaCl solution indicated that the CIP/SiO_(2)had higher corrosion resistance than the uncoated one and the high corrosion resistance was still retended after the CIP/SiO_(2)coating was abraded or scratched.