Abstract
Supercritical hydrothermal synthesis is a promising technology to produce nano-ZrO_2 due to its simple craft, short reaction time and low cost. In this paper, nano-ZrO_2 particles with an average particle size of 5.66-35.43 nm were successfully prepared by supercritical hydrothermal method. Meanwhile, the influences of reaction temperature, pressure, time, precursor concentration and pH value on the particle size distributions and surface topographies of nano-ZrO_2 were investigated under different conditions. Reaction time and precursor concentration were strong influencing factors of particle sizes and distributions. The reaction mechanisms of different crystal forms were controlled by pH value of the precursor. Under acidic conditions, soluble [Zr4(OH)_8(H_2O)_(16)]~(8+) was produced due to the hydrolysis of precursors, and the appearance of abundant monoclinic nucleus was triggered subsequent condensation of [Zr_4(OH)_8(H_2O)_(16)]~(8+). In-situ crystallization dominated the crystallization process and the tetragonal phase was formed by the rearrangement of the precursor structures. The intermediate product Zr(OH)_3NO_3 was detected under high pH conditions.
NSTL
Elsevier