Sm. Clarke et al., A DIFFRACTION TECHNIQUE TO INVESTIGATE THE ORIENTATIONAL ALIGNMENT OFANISOTROPIC PARTICLES - STUDIES OF CLAY UNDER FLOW, Europhysics letters, 35(3), 1996, pp. 233-238
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.