A study of the swelling of n-butylammonium vermiculite in water by neutron diffraction

Abstract

The swelling of an n-butylammonium vermiculite in solutions of n-butylammonium chloride has been studied as a function of temperature, hydrostatic pressure, uniaxial pressure, and the concentration of the soaking solution, by neutron diffraction. On heating the swollen clays a transition to the crystalline phase takes place at a well defined temperature, which depends on the external electrolyte concentration. The application of hydrostatic pressure induces macroscopic swelling of the vermiculite in the region of 1 kbar. The transition is completely reversible and also depends on temperature. — The dependence of interparticle distance on applied uniaxial pressure varies semiquantitatively with ionic strength in a similar way to the forces between mica plates in electrolyte solution. — Approximate dimensions of the Stern layer have been obtained from isotopic substitution of the counterion. The Stern layer is 5.5 ± 1 Å thick.