Freitag, 27. Januar 2017, 15:15 - 16:45 iCal
MATERIALS SCIENCE SEMINAR
"Atomistic modeling of pulsed laser interactions with metal targets in liquid environment", Cheng-Yu Shih (University of Virginia, Charlottesville, Virginia, USA)
Universität Wien, Chemische Institute, Seminarraum 2 (2124), 2. Stock
Währinger Straße 42, 1090 Wien
Vortrag
Laser ablation of metal target in liquid environment is actively used for generation of clean colloidal nanoparticles with unique shapes and functionalities, and has evolved over the last decade into a mature research field with a large and growing number of practical applications. While the challenges of increasing productivity and broadening the range of materials for which nanoparticles can be generated are successfully addressed by recent developments, the goal of achieving a narrow nanoparticle size distribution by direct one-step PLAL still remains elusive. The fundamental mechanisms responsible for the nanoparticle formation and the key processes that control the nanoparticle size distribution are still not fully understood. In particular, the bimodal size distributions, where the desired small nanoparticles coexist with larger (tens to hundreds of nanometers) ones, are commonly observed in PLAL experiments.
In this presentation, I will report the results of large-scale atomistic simulations aimed at revealing mechanisms of nanoparticle formation in PLAL and explaining the origin of the bimodal nanoparticle size distributions. The simulations are performed for Ag targets irradiated in water. Two distinct mechanisms of the nanoparticle formation are predicted in the simulations: (1) the nucleation and growth of small (mostly ? 10 nm) nanoparticles in the metal-water mixing region and (2) the formation of larger (tens of nm) nanoparticles through the breakup of the superheated molten metal layer triggered by the emergence of complex morphological features appearing due to the Rayleigh-Taylor instability of the interface between at the superheated metal layer and the supercritical water. The computational predictions are consistent with experimental observations of bimodal nanoparticle size distributions and the corresponding mechanistic insights may help in designing approaches aimed at minimizing the fraction of large nanoparticles.
Veranstalter
Institut für Physikalische Chemie, Universität Wien
Kontakt
Univ.-Prof. Dr. Wolfgang Kautek
Universität Wien
Institut für Physikalische Chemie
0043 664 60277 52470
wolfgang.kautek@univie.ac.at
Erstellt am Freitag, 20. Januar 2017, 10:55
Letzte Änderung am Dienstag, 24. Januar 2017, 15:10