Abstract:

Structure transformation and neck growth during the heat and sintering process of two TiO₂ nanoparticles were investigated using molecular dynamics (MD) simulations. Based on the space meshing of the system and analysis of neighboring meshes, a neck atom identification model was developed. The model was successfully applied to identify neck atoms. Combined with the surface atom identification model previously developed by the authors, atoms in the system were further classified and the characteristics of the classified atoms were simulated and analyzed. The results show that sintering occurs when the temperature is above 573 K, the neck area increases with increasing sintering temperature, and it is mostly occupied by interior atoms. Surface atoms occupy less neck area and they are less sensitive to sintering temperature variation. The average displacement of neck atoms is larger than that of surface and interior atoms of the mother particles and O atoms are more active in migration than Ti atoms in the neck. Meanwhile, displacement of outside neck atoms is larger than that of inside neck atoms, meaning that neck growth mainly depends on the motion of outside neck atoms. The proposed model is stable and effective, and it provides fundamental information to analyze nanostructures in different zones.

Key words: Nano particle, Molecular dynamics, Sintering process, Sintered neck, TiO₂