纳米Fe_3O_4磁性颗粒常温化学合成及外层结构研究

Solution synthesis of nano-magnetite particles at room temperature and out-layer structure pattern

研究纳米尺寸磁性颗粒常温液相合成化学及其颗粒外层氧化稳定性控制工艺和机理。以二价和三价混合铁盐和硫化钠(Na_2S)为原料,氨水为沉淀剂,用化学沉积的方法制备了稳定的四氧化三铁(Fe_3O_4)纳米颗粒,并通过XRD、TEM和振动磁强计对磁性颗粒进行了表征。结果表明,所合成的纳米Fe_3O_4颗粒纯度高、抗氧化性能好,颗粒形状为近圆形的多边形,粒径10~15nm。干燥过程不影响颗粒的纯度和粒度。在对颗粒进行了有机表面改性后,颗粒表面为亲油性。磁性检测结果显示,作分散用的表面活性剂会影响颗粒的磁学性能,样品S2的磁化强度达到21.67A/m,剩余磁化强度达到1.43A/m,保磁力达到17.00Gs。提出了单颗粒表面多层微观结构功能性和稳定性控制机理模型,对氧化防止和防团聚本质问题进行了分析。

The processes and mechanisms of synthesizing nanosized magnetite, out-layered structure and oxidation stability were investigated. Monodispersed,stabilized magnetite particles were successfully obtained by copreeipitation reaction from ferric and ferrous-iron,small amount of Na2S mixed aqueous solution neutralized by ammonia at room temperature. The obtained particles were characterized by XRD,TEM and magnetic measurements. X-ray powder diffraction pattern indicated that the product was pure magnetite. Transmission electron microscopy images showed that the particles were in shape of quasi-sphere polyhedron,with a size rang of 10-15nm. The drying procedure did not effected the particle size. Mag- netic measurement results revealed that the dispersing agent effeeted the particle magnetism. The as σ and coercive force of sample S2 were 21.67A/m, 1.43A/m and 17.00Gs, respectively. After being treated with organic agents, the obtained particles exhibited hydrophobic property. Based on the experimental and measured results,a sandwich model of single particle, consisting of a nanosized magnetic core and functional, stabilized out-layers, was presented. The intrinsic mechanisms of oxidation and agglomeration preventions were discussed.