采用化学共沉淀法制备了油酸包覆Fe3O4磁性颗粒,经过非离子表面活性剂的二次包覆后,将其均匀分散于具有优良耐高温性能的PAO合成油中,制成了合成油基Fe3O4磁性液体,将该磁性液体在大气环境中进行170 ℃长时间加热处理,对其密度、粘度、饱和磁化强度及挥发速率进行了测试,并用透射电镜进行形貌观察.结果表明：磁性颗粒呈球形,粒径在10 nm左右;合成油基Fe3O4磁性液体随加热时间的延长,密度缓慢增加并逐渐趋于平缓,粘度快速增加,饱和磁化强度变幅仅为0.4%,挥发速率逐渐下降.

The magnetic particles of Fe3O4 covered with oleic acid were prepared by common chemical coprecipitation method.Covered by the second kind of surfactant,the particles were dispersed in PAO synthetic-oil which has excellent high temperature resistance.In this way,the stable Fe3O4 based magnetic fluid was obtained.The TEM investigation showed that the shape of the particles was nearly spherical and the mean particle size was about 10 nm.The changes of density,viscosity,saturation magnetization and volatilizing rate of the magnetic fluid sample were tested after the sample was heat treated at 170 ℃ for 20 d and the results showed that the density increased slowly,viscosity increased rapidly,the change of saturation magnetization was 0.4%,and the volatilizing rate decreased gradually.