Silicon-29 NMR self-diffusion and chemical-exchange studies of concentrated sodium silicate solutions

For the first time, self-diffusion of silicate species in a highly condensed silicate solution has been investigated. Self-diffusion coefficients in the range of 5.8 x 10(-11) m(2) s(-1) (for the Q(4) units) to 1.9 x 10(-10) m(2) s(-1) (for the Q(1) units) were obtained. Upper limits to chemical-exchange rates between silicate units have been determined. The exchange processes are not fast enough to average the self-diffusion coefficients between the various units on the timescale of the relevant stimulated echo experiment, though they may reduce the observed differences in D-self.