Evolution of phase morphology in dispersed clay systems under the microwave irradiation

TL;DR

This study investigates how microwave irradiation influences the structural evolution of natural clay particles, revealing phase transformations and agglomeration processes depending on exposure time and environment, with implications for controlling clay structure formation.

Contribution

It introduces a comprehensive optical-physical analysis approach to quantitatively characterize structural changes in clay under microwave treatment, highlighting environmental effects on phase transformations.

Findings

Capillary water is removed within 10 minutes, leading to particle agglomeration.

Extended irradiation (10-20 min) promotes growth of agglomerates and phase transformations.

Environmental conditions influence phase formation, such as iron compounds transforming into different phases.

Abstract

The results of a study of the effect of microvolume emission (power 700 W, frequency 2.45 GHz) on the structural changes in natural clay particles are presented. The influence of the irradiation time (10 and 20 minutes) and the environment in the microwave chamber (atmospheric air and air saturated with water vapor) on the structural changes occurring in the particles was traced. During the first 10 minutes, capillary water is completely removed and agglomeration is carried out by attaching single dispersed particles (diffusion limited aggregation model). At the second stage (10-20 minutes), already formed agglomerates (cluster-cluster aggregation model) are growing. A complex of independent optical-physical methods was used to analyze weak structural changes. It includes X-ray phase analysis, colorimetry and wavelet analysis. This approach has made it possible to increase the information content and reliability of measurements, quantitatively characterize the structural responses in disperse clay systems. In the air, the removal of capillary water is accompanied by agglomerations of particles and polymorphic transformations of oxides: montmorillonite is completely decomposed, amorphous phases crystallize. The composition of the environment in the microwave chamber affects the type of phase transformations in iron compounds: iron-alumina is formed in air, magnetite appear in the water vapor medium. The studies carried out using the developed set of experimental methods indicate the possibility of regulating the processes of structure formation in disperse clay systems by optimizing the regimes of exposure to microwave radiation.