STRUCTURAL STUDY OF SILICA PARTICLE DISPERSIONS BY ULTRA-SMALL-ANGLE X-RAY-SCATTERING

An ultra-small-angle x-ray-scattering study showed several orders of Bragg diffraction for an aqueous colloidal silica dispersion in a vertically held glass capillary, the first peak being at 150''. The same profile was observed when the capillary was rotated around its axis by (60×m)°(where m is an integer). A different profile was found at (30+60×m)°with the first peak at 85''. This showed that a bcc lattice was maintained with the (110) plane parallel to the capillary wall and with a lattice constant =3000, d110=2100, and d020=1500. The closest interparticle distance (2Dexp) was 2600 while the average distance from the overall concentration (2D0) was 2900, indicating the non-space-filling nature of the crystal. © 1995 The American Physical Society.