TEM-HRTEM study on the dehydration process of nanostructured Mg-Ca hydroxide into Mg-Ca oxide

Abstract

The dehydration process from Mg0.97Ca0.03 (OH)(2) nanoparticles (brucite type hexagonal structure) to Mg0.97Ca0.03 (periclase type cubic structure) was studied by Transmission Electron Microscopy (TEM-HRTEM), Electron Diffraction (SAED), Electron Energy Loss Spectroscopy (EELS) and image analysis. The transformation process was monitored in function of the reaction time applying 200 and 300 KV. Changes in porosity were possible to observe only during the irradiation with 200 KV. Depending on the irradiation time, the changes were gradual, producing an increase from the particle's edge towards the inner region. Different stages were observed, corresponding to the amount of water extracted from the particle, until finally a decrease in porosity and particle shrinkage occurs, coinciding with the formation of the Mg-Ca oxide.