The results of a study of the microwave emission effect (power 700 W, frequency 2.45 GHz) on the structural changes in natural clay particles with effective diameters D≤630 μm are presented. The influence of the irradiation time (10 and 20 min) and the environment in the microwave chamber (atmospheric air and air saturated with water vapor) on the structural changes occurring in the particles were traced. During the first 10 min, capillary water was completely removed and agglomeration was carried out by attaching single dispersed particles (diffusion limited aggregation model). At the second stage (10-20 min), the already formed agglomerates grew (cluster-cluster aggregation model). A complex of independent optical-physical methods was used to analyze weak structural changes, including X-ray diffraction analysis, colorimetry and wavelet analysis. This approach increased the information content and reliability of measurements, quantitatively characterizing the structural responses in disperse clay systems. In the air, the removal of capillary water was accompanied by agglomerations of particles and polymorphic transformations of oxides: montmorillonite was completely decomposed and amorphous phases, in particular CaCO3, crystallized. The composition of the environment in the microwave chamber affected the type of phase transformations in iron compounds: iron-aluminum silicate (Fe2Al4Si5O18) was formed in the air; magnetite Fe.Fe2O4 (Fe3O4) appeared in the water vapor medium. The carried-out studies with the developed set of experimental methods indicated the possibility of regulating the processes of structure formation in dispersed clay systems by optimizing the regimes of exposure to microwave radiation.
Influence of microwave radiation on structure changes of montmorillonite particles was studied on a montmorillonite clay sample. Multi-scale long-range processes were induced in the nature-occurring aluminosilicates by microwave radiation of low and medium power (2.45 Hz, 750 W, 10 min). Powdered samples treated with microwave radiation demonstrated reduction of the relative intensity of diffraction peaks and reduction of interplanar spacing of montmorillonite lattice (d001 * from 1.220 to 0.945 nm, d001 from 0.642 to 0.627 nm, d002 from 0.318 to 0.314 nm and d003 from 0.214 to 0.213 nm). The effect was due to extraction of water molecules contained in three-layer packages. Water extraction occurred stepwise with the temperature rise which pointed on long-range processes with a delayed effect. Heating of powdered samples up to 200 °С resulted in the destruction of half of the montmorillonite lattice volume; at 400 °С about 70% of the lattice was destroyed. Fragments of lattice cells formed agglomerates via two-step mechanism. The degree of agglomeration was proportional to the montmorillonite sample amorphicity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.