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PULSED LASER AS NEW TOOLS FOR CONTROLLED NANOMANUFACTURING AND SCIENTIFIC RESEARCH IN SOLUTION-BASED CHEMICAL SYNTHESIS
thesisposted on 21.06.2022, 13:38 authored by Siyu LiuSiyu Liu
Pulsed lasers are studied as new tools to realize competitive nanomanufacturing. The capabilities of pulsed lasers as promising tools for research, design, manufacturing, and control rely on the flexibility due to the great variety of operation parameters, and the inherent precision in aspects of time, spatial resolution, and energy input. As new tools, the fundamental understanding and technological capabilities of pulsed laser-induced chemical synthesis were explored in this dissertation research. In order to study the capabilities of pulsed laser in controlled synthesis, a thermal model was developed to predict the local temperature change due to the very short period of irradiation by a pulsed laser. And combining with the classical Gibbs free energy theories, a set of guidelines were developed for precision control for pulsed laser-induced chemical synthesis. Zinc oxide crystals were studied as an example case, showing the relationship between the wide range variables of pulsed laser including repetition rate, energy area density, power density, irradiation duration, etc. and the material structures of deposited crystals in aspects of crystal density, size, shape, crystalline properties, surface morphologies, growth rate, etc. Mechanisms from thermodynamic and kinetic aspects were explored. Pulsed laser-induced different heating conditions were found to separate two crystallization processes with different energy barriers, one dominated by a burst of nucleation and the other dominated by crystal growth through particle aggregation. For the study of the fundamental mechanisms in crystallization, pulsed laser initiated and controlled the crystallization in its early stage, and the crystal evolution were observed and analyzed by transmission electron microscopy (TEM). Crystal growth from intermediate monomers was first studied by an electron beam under the condition without precursor solution environment, providing crucial process information of crystal evolution, indicating multistage processes by continuous mass and phase transfer among intermediate monomers. This dissertation shows the capabilities of pulsed laser in realizing precision control for the targeted synthesis in nanomanufacturing, providing unique insight to crystallization mechanisms, and extending prospects to scientific research of other energy beam induced processes.
Manufacturing of Self-Powered Nanosensor Systems by Pulsed Laser Processing
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