Model of destruction of montmorillonite crystal structure in a microwave field

Abstract

We address amorphization of montmorillonite crystal structure. Powdered montmorillonite samples with an effective particle diameter D ≤ 630 µm were treated by microwave field with the frequency 2.45 GHz and power 750 W for ten minutes in different environments. The first sample was treated in an air environment, the second one in a humid environment. The third sample was a ceramic mass with 10% concentration of mixing water (with respect to the total mass). The model describing amorphization is based on results of X-ray analysis. Activation energies were evaluated for covalently and ionically bound oxygen ions, hydroxyl groups, and silicon (aluminum) ions. It is shown that the amorphization is carried out in four stages. In fractions of the energy consumption of the last stage the first one consumes 7 ÷ 9%, the second one takes 13 ÷ 15%, and the third one takes 49 ÷ 59%.

Thermostimulated crystal structure transformation of the polymineral clay submicron particles

“…The second endothermic effect (label b) in the temperature range of the sample from 570 to 870 K was due to the removal of crystallization water from montmorillonite and chlorite with partial amorphization of the ceramic mass [3,17]. A similar effect at lower temperatures was observed when the microwave field irradiated montmorillonite samples in a humid environment [18]. Heating from 870 to 1120 K did not cause visible changes in this range.…”