羰基铁粉表面纳米钴修饰及其对磁流变液性能的影响

羰基铁粉作为制备磁流变液最重要的磁性材料,其表面特性将对所制备的磁流变体系的磁流变效应、化学稳定性和沉降稳定性产生很大的影响.因此,在磁流变液制备中,磁性颗粒的表面修饰必不可少,也是磁流变液研究的重要内容.本文采用化学沉积方法,首先在微米级羰基铁粉表面均匀镀上一层纳米级金属钴,然后再对表面进行其它处理,以试图改善磁性材料的表面均匀性、提高饱和磁化强度并增强磁流变效应.在pH=10左右的硼砂缓冲溶液介质中,采用次亚磷酸钠直接还原钴盐的方法将纳米级金属钴包覆在羰基铁粉的表面.对影响钴化学沉积过程的因素例如pH值、温度、溶液浓度等进行了实验研究,并对实验条件进行优化.采用XRD、热分析、SEM、XPS和原子发射光谱对处理后的颗粒样品进行观察、表征和成分测定.采用钴处理前后颗粒作为磁性粒子制备磁流变液,对其沉降稳定性和磁流变效应进行比较,得到较为满意的结果.

Carbonyl iron modified with nano cobalt and its magnetorheological effect

The properties of magnetorheological fluid(MRF),such as magnetorheological effect,chemical stability and sedimentation rate are greatly affected by the surface characteristics of carbonyl iron powder as a main magnetic material of MRF.It is essential to modify the surface of magnetic particles with surfactant in the preparation of MRF.In the present paper,micron carbonyl iron particles were firstly modified with nano cobalt by electroless plating,then coated with surfactant.The investigation attempted to improve surface characteristics of magnetic particles and to enhance effect of magnetorheological fluid.In the presence of pH10 borax buffer,cobaltous ions were reduced to deposit in the surface of carbonyl iron by sodium hypophosphite.The optimum conditions of plating were obtained by experimental.The carbonyl iron coated with nano cobalt was characterized by XRD,TG analysis,ICP-AES,XPS and SEM.The magnetorheological fluid which was prepared using iron coated cobalt exhibit better properties than one without cobalt coated.