Key words: zinc oxide, cold sintering, recrystallization, solid-phase mobility in an aqueous medium, crystal size distribution, coalescence, surface spreading
An effect of mechanical pressure on the crystal size distribution during the treatment of zinc oxide in an aqueous medium in the presence of zinc acetate or ammonium chloride as activating additives was studied by analyzing scanning electron microscopy images. The results of ZnO cold sintering at 220—296 °C and its thermovaporous treatment (TVT) without applying mechanical pressure in an autoclave under similar conditions were compared. It was concluded that due to the presence of the additives in an aqueous medium, the hydration of the structure increased and the solid-phase mobility was activated, leading to the redistribution of the mass of crystals. Mechanical pressure during the cold sintering enhanced the effect of solid-phase mobility activation and led to the predominance of crystal coalescence in mass transfer. During the TVT with no mechanical pressure applied, surface spreading as the mass transfer mechanism prevailed. A scheme illustrating the effect of the aqueous medium on the mass transfer during the recrystallization of ZnO was proposed.
doi:10.34984/SCFTP.2021.16.1.002