Supercritical hydrothermal synthesis of zirconia nanoparticles from zirconium basic carbonate

Zirconia nanoparticles were synthesized by using the supercritical hydrothermal method from zirconium basic carbonate, which is insoluble in water at ambient temperature. The diameters of these nanoparticles were 10–20 nm. They contained both tetragonal and monoclinic phases. A long treatment in supercritical water induced the phase transition from the tetragonal phase to the monoclinic phase with the desorption of carbonate ions. These results indicated that the carbonate ions absorbed on the surface works as a stabilizer of the unstable tetragonal phase. The process developed here allows us to bypass wastewater treatment along with the product refining because byproducts are only water and carbon dioxide.