Materials Science and Engineering Location: Rodman Room-Thornton Hall
Add to Calendar 2022-08-15T12:00:00 2022-08-15T12:00:00 America/New_York Doctoral Dissertation Proposal: Chaobo Chen Multiscale modeling of laser ablation of metal targets in liquid   Committee: Professor Tao Sun (Materials Science and Engineering) - Chair Professor Ji Ma (Materials Science and Engineering) Professor Chris Paolucci (Chemical Engineering) Professor Sen Zhang (Chemistry) Professor Katharine Tibbetts (Chemistry, Virginia Commonwealth University) Professor Leonid Zhigilei (Materials Science and Engineering) - Advisor Abstract Rodman Room-Thornton Hall

Multiscale modeling of laser ablation of metal targets in liquid

 

Committee:

Professor Tao Sun (Materials Science and Engineering) - Chair

Professor Ji Ma (Materials Science and Engineering)

Professor Chris Paolucci (Chemical Engineering)

Professor Sen Zhang (Chemistry)

Professor Katharine Tibbetts (Chemistry, Virginia Commonwealth University)

Professor Leonid Zhigilei (Materials Science and Engineering) - Advisor

Abstract

Metal nanoparticles have practical applications in cancer treatments, drug delivery, solar energy harvesting, spectroscopy, and catalysis. One of the most promising methods for generating colloidal nanoparticles is the short pulse laser ablation in liquid (PLAL). This method yields chemically clean colloidal nanoparticles of high demand in the biomedicine and catalysis fields. Despite the practical importance, the understanding of the mechanisms responsible for the generation of nanoparticles in PLAL remains incomplete. The slow progress in this area is related to the highly nonequilibrium conditions and inherently multiscale nature of processes responsible for transforming the target material into nanoparticles. In this proposal, I will apply multiscale modeling methods to address the three key aspects of nanoparticle synthesis by PLAL: the mechanisms and dynamics of the laser-induced phase transformations in the target material, the effects of the liquid environment, and the laser interaction with the target undergoing the laser-induced phase transformations. These three aspects of PLAL will be addressed by undertaking five interrelated research tasks briefly outlined below.

The first task is to develop a comprehensive state-of-the-art model capable of describing the physics of laser interaction with the target, excitation of electrons, electron-phonon coupling, generation of stress waves in the target and liquid environment, phase transformations in the target and liquid, generation of cavitation bubbles, formation, cooling, and solidification of nanoparticles. The new parts to be integrated into the multiscale model are a compressible hydrodynamics model for simulating the long-range stress wave propagation in the liquid environment and an electromagnetic wave model capable of describing the interaction of the laser with a multiphase and highly heterogeneous ablation plume. Once the model is fully developed, it will be applied to investigating the thermodynamic conditions and kinetics of the nanoparticle formation in PLAL (Task 2), analysis of the effect of the spatial confinement by the liquid and supercritical fluid environments (Task 3), prediction of the temporally and spatially resolved optical properties of the target material excited by the laser pulse for comparison with the results of pump-probe experiments (Task 4), and exploration of the double-pulse irradiation regime for the enhanced productivity of the nanoparticle generation (Task 5). The choice of the research tasks is motivated by collaboration with experimental groups and focuses on improving the fundamental understanding of the PLAL mechanisms. The success of the proposed computational effort will contribute to the advancement of laser-based techniques for the production of chemically clean colloidal nanoparticles.

All interested persons are invited to attend.