磁场调制的水基四氧化三铁磁流体的光学透射率

Magnetic Field-controlled Transmission of Aqueous Fe_3O_4 Ferrofluids

对水基四氧化三铁磁流体在缓变磁场中的透射率(稳态光透射率)进行了研究。结果表明,透射率随磁场的变化可分为3个(膜厚较小)或4个(膜厚较大)具有明显特征的阶段;膜厚的不同使得透射率在高磁场端的变化趋势完全不同。浓度的增大并不显著影响透射率对磁场的响应速率,但使透射率变化的各个特征阶段的结束磁场增大,同时使最终稳定的透射率降低。只要磁场不明显引起磁流体中粒子的团聚和成链,常规溶液对光的线性吸收定律在磁流体中仍然成立。结合纳米四氧化三铁粒子在磁场中的团聚过程,对透射率随磁场的变化表现出来的特征进行了解释。

The transmission of light in the aqueous ferrofluid films of Fe3O4 in slowly-changing magnetic fields was investigated.The results show that the evolution of transmission with the increase of magnetic fields can be divided into three（for small thickness of the film） or four（for larger thickness of the film） characteristic stages.Film thickness will cause differences in the evolution of the transmission under high magnetic fields.The concentration of magnetic fluids does not affect noticeably the responsive rate of the transmission to the external fields, but it increases the critical values of the field corresponding to each stage and decreases the final transmission. Beer＇ law for conventional solutions still applies to the magnetic fluids in low magnetic fields. Based on the agglomeration formation process of the magnetite particles in ferrofluid, the characteristics of light transmission of ferrofluids are explained.