Nanocrystalline MgO powder materials prepared by sol-gel studied by X-ray diffraction and electron microscopy

Abstract

Materials with MgO nanocrystallites were prepared by sol-gel synthesis. Alcogels were dried either supercritically at 538 K or in supercritical CO2. Conventional drying was also applied. Structure studies were performed by X-ray diffraction, scanning and transmis- sion electron microcopies. Nitrogen adsorption/desorption measurements were also per- formed. Calcination of dry gels at 723 K under vacuum yielded MgO nanocrystallites. In the studied materials the presence of the amorphous phase was observed. It is also stated that MgO nanocrystallites are immersed in an amorphous matrix. Morphology of supercritically dried samples is similar; rough surface of powder particles is observed. Powder particles of conventionally dried sample are more compact. Size of MgO crystallites is generally similar for all samples and equal to about 7 nm despite the drying conditions of alcogels. The specific surface area and the volume of mesopores are the great- est for the sample supercritically dried at 538 K.