Microscopic observations of ordering in dilute charged colloids

Ordering in dilute charged colloids is investigated using an optical reflection microscope, a video camera and an image processor. About six layers of colloidal crystal have been observed from the wall of the container. Grain boundaries, dislocations, voids and vacancies are observed along the depth of the colloidal crystal. The stable crystal structure and orientation of the crystal are identified and understood. The effect of the container wall on the ordering is analysed. The individual and collective motions of particles in the crystal are reported. The effect of aggregates on the crystalline order and the vibration of aggregates in the crystal are studied. The controversy over the inter-particle potential is addressed and the potential appears to have an attractive term like that in a Sogami potential.