A DIFFRACTION TECHNIQUE TO INVESTIGATE THE ORIENTATIONAL ALIGNMENT OFANISOTROPIC PARTICLES - STUDIES OF CLAY UNDER FLOW

Measurement of the orientation distribution of anisotropic particles i s of considerable interest. The free energy of such materials depends strongly on the relative orientation of the particles and will effect the order-to-disorder transitions associated with liquid-crystal phase s and alignment under the influence of external fields. This paper ill ustrates the use of a diffraction technique that measures the full ori entation distribution of anisotropic crystalline particles in a fluid. Neutron diffraction data for dispersions of plate-like particles in p ipe flow are presented and the changes in orientational order with flo w and shape are described. This technique gives data about orientation which is decoupled from effects of both inter-particle order and the shape of the particles. Wider applications of this method, which provi des order parameters for liquid crystals to arbitrary high order, are discussed.