chapter  7
8 Pages

## The Formation and Interfacial Structure of Silica Sols

Experimental Details . . . . . . . . . . . . . . . . . . . . . . . . 58

Results and Discussion . . . . . . . . . . . . . . . . . . . . . . 58

Small-Angle Neutron Scattering . . . . . . . . . . . . . . 58

Ultracentrifugation Studies . . . . . . . . . . . . . . . . . . 60

PCS Studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

29Si NMR Spectroscopy of Colloidal

Silica. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . 64

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Several techniques, including small-angle neutron scattering (SANS), ultracentrifugation, photon corre-

lation spectroscopy, and 29Si NMR spectroscopy, were used to investigate the nature of the oxide-water

interface of silica sols and its significance in the formation and growth of colloidal particles in aqueous

solution. These studies were performed with a range of commercial silica sols of different diameters in

the range 7-30 nm. When the diameter is small the sols contain a significant proportion of oligomeric silicate species that may be associated at the surface of the particles. For sols of the largest diameter,

the relative proportion of oligomers is much smaller. In all the sols the core of the particles has a highly

condensed Si-O-Si structure.