10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Investigation of Collisional Growth Rate of Titania Nanoparticles at High Flame Temperatures Through Molecular Dynamics Simulations
GIRISH SHARMA, Rajan K. Chakrabarty, Pratim Biswas, Washington University in St Louis
Abstract Number: 288 Working Group: Aerosol Physics
Abstract Nanoparticles are synthesized extensively using high-temperature flame and furnace aerosol reactors (1000-2200 K). At such high temperatures, the particles collide with each other and coagulate to form larger particles. Kinetic theory of gases is widely used to calculate the coagulation coefficient in the free molecular regime at high temperatures. This theory is verified both experimentally and through modeling, but only at ambient temperatures. Ideally, a correction factor accounting for the inter-particle forces should be incorporated. Previously reported modeling studies, performed at ambient temperatures, have shown that this correction factor can be greater or less than 1. This depends on the dominance of attractive or repulsive forces, which are material dependent. Moreover, at very high temperatures, nanoparticles have high thermal energy, and therefore instead of colliding and sticking, they can bounce back after collision, or even fragment the nanoparticle.
In this work, the aim is to investigate the coagulation correction factor for nanoparticle collisions for titania at high temperatures in free molecular regime. To achieve this, molecular dynamics (MD) simulations are performed. First, a realistic atomic model of the collision event for two titania nanoparticles is developed. Then, in the presence of interaction forces, particle trajectories are simulated over time. These different particle trajectories are then related to calculate the collisional correction factor. Following this, the effect of particle size, particle charge, functional groups, and particle temperature on collisional correction factor will be investigated. The insights on the physics of titania nanoparticle collisions, and the role played by interaction forces will be presented.