The effect of hydrolysis duration on the phase composition, texture, aggregation and agglomeration of ZrO$_2$ nanoparticles

In this work, a number of ZrO$_2\cdot n$H$_2$O and ZrO$_2$ samples were synthesized by direct precipitation and hydrolysis with different duration (36 and 61 h) followed by neutralization and thermal treatment. The prepared samples were analyzed using DT-TGA, PXRD, N$_2$ physisorption and LD methods. The dependence of the size of crystallites and secondary particles, phase composition, texture, and particle morphology on the amount of zirconium hydrolyzed to form $m$-ZrO$_2$ is shown. The possibility of regulating the phase composition of ZrO$_2$ has been established while maintaining the specific surface area (110 – 120 m$^2$/g), as well as creating a hierarchical system of micro-mesopores. The mechanism of the ZrO$_2\cdot n$H$_2$O formation during hydrolysis and precipitation is considered. The size of the critical nucleus is estimated (1.5 – 2 nm).