Numerical simulations of sonochemical production and oriented aggregation of BaTiO₃ nanocrystals

Numerical simulations of sonochemical production and oriented attachment of BaTiO₃ nanocrystals are performed in aqueous solution with pH 14. It is suggested that most significant effect of ultrasound is the dissolution of Ti-based gel in aqueous solution. It results in the dissolution-precipitation mechanism in the production of BaTiO₃ nanoparticles, while with mechanical stirring without ultrasound it is the in situ mechanism that BaTiO₃ is gradually formed on Ti-based gel. The oriented attachment of spherical BaTiO₃ nanocrystals occurs by van der Waals torque (Casimir torque). Large aggregates of nanocrystals do not attach with each other as the repulsive double layer interaction is stronger for larger aggregates. For smaller spherical nanocrystals, the alignment of the crystal axes is less accurate due to more significant rotational Brownian motion of the nanocrystals.