Preparation of functional fluid dispersing ultrafine particles and its optical property

我们成功地制备了钛酸钡微粒稳定分散在煤油中的介电液。该流体表现出电流变现象，例如在电场下粘度增加。此外，已经报道了在电场下仅使用介电流体的薄流体膜作为潜在的光快门。快门作用是由于钛酸钡团簇在电场作用下形成可见光的瑞利散射引起的。对于煤油基流体，在接通电场后形成簇的响应时间为10 ms的量级;然而，在断开电场后钛酸钡簇消失的衰减时间更大，为几秒。此外，还制备了磁铁矿微粒稳定分散的煤油基磁流体。本文研究了电磁场作用下介质和磁流体混合物薄膜中的光散射。该薄膜在无电场条件下可透过可见光。在薄膜上施加电场后，薄膜的透过率迅速下降，这一现象可以用电场作用下形成的介电团簇引起的瑞利散射来解释。在关闭场之后，在没有电场的情况下恢复到透射率的衰减时间比打开场之后的响应时间大得多;然而，磁场和电场的使用允许缩短衰减时间。

We have successfully prepard dielectric fluids in which barium titanate fine particles are stably dispersed in kerosene. The fluids show Electrorheological phenomena such as an increase of viscosity under an electric field. Furthermore, a thin fluid film that uses only a dielectric fluid under an electric field has been reported as a potential light shutter. The shutter action is caused by Rayleigh scattering of visible light due to the formation of barium titanate clusters under the electric field. The response time for the formation of the clusters after switching on the electric field is in the order of 10ms for kerosene-based fluids ; however, the decay time for the disappearance of barium titanate clusters after switching off the field is larger, several seconds. In addition, kerosene-based magnetic fluids with magnetite fine particles stably dispersed have been also prepared. Light scattering in a thin film of a mixture of dielectric and magnetic fluids has been studied under both electric and magnetic fields. The film can transmit visible light in no electric field. When an electric field is applied across the film, the transmittance decreased rapidly.The phenomenon is explained by Rayleigh scattering due to the dielectric clusters formed under the field. The decay time to return to the transmittance at no electric field after switching off the field is much larger than the response time after switching on the field ; however, the usage of a magnetic as well as an electric field allows the decay time to be shortened.