Fe_3O_4纳米晶的粒径控制合成、表征及其吸波性能

Size-controlled Synthesis,Characterization and Microwave Absorption Efficiency of Fe_3O_4 Nanocrystallines

采用十二烷基磺酸钠和聚乙二醇作为保护剂，成功地制备出Fe3O4纳米晶．通过改变实验条件，可在10～200nm范围内有效调控Fe3O4纳米晶的粒径．采用X射线衍射仪、透射电子显微镜和扫描电子显微镜等对样品的微观结构、粒径和形貌进行了分析．结果表明，所得尖晶石型Fe3O4纳米晶粒径均匀，形貌均为球形．利用振动样品磁场计测量了不同粒径样品的磁性能．结果显示，粒径小时，随着粒径的增加，Fe3O4的饱和磁化强度Ms逐渐增加，但当粒径增加到80nm时，Ms达到最大值；随着粒径的减小，矫顽力也随之减小．利用矢量网络分析仪对不同粒径样品的电磁性能和吸波性能进行了研究，结果表明，当Fe3O4纳米晶的粒径小于100nm时，吸波性能良好，其中，粒径为20nm的样品吸收峰的峰值在8GHz附近达到了-32dB．

Fe3O4 nanocrystallines were successfully prepared by using the mixed surfactants of SDS and PEG as the protective reagents. The sizes of the nanoparticles can be varied from 10 to 200 nm by adjusting the experimental conditions. The microstructure, size and morphology of the products were investigated in detail by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and scanning electron microscopy （SEM）. The results indicate that uniform spinel Fe3O4 nanospheres were achieved. Magnetic studies on the samples with different sizes reveal that when the size of product is below 80 nm, the saturation magnetization （M） increases as the particle size increases, where the coercive force （Hc） decreases as the particle size decreases. Both of electromagnetic performance and microwave adsorption property of Fe3O4 nanocrystallines with different sizes were measured by a vector network analyzer（VNA） technique in the frequency region of 2-18 GHz. The results indicate that when the sizes of the samples are below 100 nm, Fe3O4 nanocrystallines exhibit a better microwave adsorption property. For example, the reflection loss is up to 32 dB for the sample with the nanoparticle size of 20 nm.