Thermal decomposition of materials with layered structures

The kinetics of the isothermal dehydration of single crystals of vermiculite which have a layered structure, have been studied in vacuo of ~ 6.7 × 10⁻⁵ Pa by quartz crystal microbalance. A kinetic model is proposed for the process, which corresponds to gas diffusion from a semi-infinite medium with boundary conditions, and takes into consideration the mass transfer through the “solid-gas” interface. The kinetics can be described in terms of a quasilinear expression in the initial stages and as a first-order equation for greater times. From the experimental data the diffusion coefficients of the interlayer region have been estimated. The values obtained are in agreement with those measured by a quasi-elastic neutron-scattering method.