纳米Fe_3O_4颗粒的制备及磁性能

采用X-ray衍射、高能X-ray衍射、透射电子显微镜及振动样品磁量计等表征手段,研究了不同制备工艺对Fe3O4纳米粒子的平均晶粒尺寸及磁性能的影响.结果表明多元醇方法所制备的Fe3O4粉体平均粒径为32 nm,其饱和磁化强度为6.8×10-3A/m(该值比块体Fe3O4的饱和磁化强度约降低了8%),剩磁Mr=4.2×10-3A/m,矫顽力Hc=1.43×10-2T;通过共沉淀方法得到的Fe3O4粉体平均粒径显著减小为7 nm,但是其饱和磁化强度也明显降低为3.3×10-4A/m,比块体Fe3O4的饱和磁化强度减小约96%,剩磁及矫顽力也下降为零.这是由于小尺寸效应导致出现超顺磁现象,说明Fe...

Synthesis and Magnetization Characteristics of Fe_3O_4 Nanoparticles

The effect of preparation process on the particle sizes and magnetization characteristics of Fe3O4 nanoparticles was characterized by XRD, high-energy XRD, TEM and vibrating sample magnetometer. It was indicated that the average particle size is 32 nm and 7 nm as the results of polyol method and co-precipitation process, respectively. The powdered Fe3O4 nanoparticle samples prepared by two methods showed that the saturated magnetization, remanent magnetization Mr, coercive force Hc are 6.8 × 10^-3 A/m (8% lower than that of bulk samples), 4.2 × 10^-3 A/m, 1.43 × 10^-2 T and 3.3 × 10^-4 A/m (about 96% lower than that of bulk samples), 0.0 A/m, 0.0 T, respectively. All these reveal that the size effect causes the occurrence of superparamagnetism, and that the particle size and magnetization characteristics of powdered Fe3O4 relate closely to its preparation process.