Ultrasound driven aggregation—A novel method to assemble ceramic nanoparticles

Nanoparticle (NP) aggregations could enhance performance of the materials in many ways. Ultrasonication has been demonstrated as an effective and cost-efficient method to aggregate NPs. However, the aggregation mechanism remains unclear, which delays the development of assembling NPs with ultrasound. This letter investigates aggregation mechanism of zirconia NPs using molecular dynamics (MD) simulation. The aggregation is demonstrated by melting and subsequent quenching of the local atoms around impact facets between NPs. Value of the critical velocity is one-third of that estimated based on complete melting in literature. The partial melting mechanism explains experimental phenomena observed in literature successfully, and therefore is validated as a more realistic mechanism to predict NP aggregation. Furthermore, the work proves that ceramic NPs, despite of their low diffusivity, could be aggregated through ultrasonication, which provides a convenient manufacturing method to assemble ceramic NPs.