平板电极间胶体晶体在电场作用下的各向同性压缩

用直径 300 nm的聚苯乙烯微球配制不同浓度的胶体晶体溶液, 将其快速注入内表面镀有导电薄膜的玻璃样品池中, 形成 (111) 晶面平行于玻璃表面的面心立方单晶结构. 通过激光衍射Kossel线方法, 研究了不同体积分数的胶体晶体样品 及它们在均匀电场作用下晶体结构的变化. 实验发现, 随着电场强度的增加, 胶体晶体表现为各向同性的压缩. 胶体晶体在恒定电场下始终保持面心立方结构, 晶格常数随着电场强度的增加逐渐减小. 实验结果可用电场力、电流体力学作用力及颗粒间静电斥力共同解释: 电场力使带电微球克服静电斥力并沿电场反方向运动导致晶体压缩, 而由电场力作用引起的电流体力学液流产生的持续推力使垂直于电场平面上的胶体微球相互靠近. 本实验为天宫一号搭载科学实验的地基实验.关键词：胶体晶体Kossel衍射结构变化

Isotropic compression of colloidal crystal in electric field between plate electrode

Colloidal crystals composed of polystyrene micro-spheres (negatively charged, with a diameter of 300 nm) are fabricated by injecting aqueous suspensions of the micro-spheres with different volume fractions into sample cells which are made by gluing together two glass plates. Whose surfaces are coated with conductive films. The colloidal crystals have a face-centered-cubic structure with their (111) planes parallel to the surface of the sample cells. Laser diffraction is used to measure the structural changes of the colloidal crystals in an electric field. Structures of the colloidal crystals are characterized by using the Kossel-line method. It is found that the colloidal crystals are compressed isotropically in the electrical field. The lattice constants of the colloidal crystals decrease with the increase of the electric field, maintaining their face-centered-cubic structure. Results can be explained by the combined action of the electric field force, electrostatic repulsion and electrohydrodynamic force. The electric field makes all of the micro-spheres migrate to the positive plate of the sample cell and leads to a compression in the direction along the electric field. Then the electrohydrodynamic force produces an attractive interaction between the micro-spheres in the direction perpendicular to the electric field.
Keywords：colloidal crystalKossel linestructual changes