Growth And Thermal Diffusion Mechanism Of Nanometal-materials By In-situ Synchrotron Radiation Technology

Controlled synthesis and property tailing of functional materials is an important research direction in today’s material science, the core issue of which is to examine materials during the dynamic process of preparation, structure, and to optimize and give guidance to the chemical and physical scale dynamics of functional materials at the atomic and nano levels. The study will contribute to the continuous innovation and update of our existing material and energy system and the satisfaction of needs of a variety of substances for human development. Synchrotron Radiation Large-scale scientific facility has been playing a significant part in basic research. With new methodologies, In situ synchrotron radiation experiment can effectively track the physical process of change in a real environment from the real-time, dynamic perspective and may launch a major breakthrough in the application of nano-technology and the solving of energy crisis. Based on USTC’s National Synchrotron Radiation Laboratory X-ray Experiment Station (U7B and U7C), this study has established and advanced a variety of new approaches(in-situ temperature-dependent XAFS technique and combination of UV-Vis-XFAS technique) For important and representative issues of the dynamics of model materials, such as: kinetics of initial nucleation of nanocrystals affecting its path late morphology and bimetallic nano-diffusion mechanism, the main results are shown as following:1. The initial nucleation mechanism path nanocrystals impact on the morphologyIn order to achieve controllable synthesis and manipulation of new functional materials with specific tailoring performance, we must make a full understanding of the reaction mechanism for the formation of nano-materials. Through many of research on nanomaterials nucleation and final-stage growth, the relationship between the early-stage nanocrystals path and the morphology of the final-stage growth has been barely studied. The second section of the paper work has constructed a coupling system combining situ synchrotron radiation XAFS and UV-Vis with an application on the research in situ growth mechanism of Pt nanomaterials with different morphologies. Firstly, we’ve realized the controlled synthesis of Pt nanocrystals particle morphology by controlling the path of chemical reduction reaction. By changing strength of reducing agent, we can converse the early-stage nucleation between two paths. There are two paths in the early-stage and middle-stage of reduction reaction the the formation of a linear ’PtnClx’ multimers under weak reducing agent and the formation of spherical zerovalent ’Ptn’ clusters under strong reducing conditions; by manipulating the two paths, we can realize the controlled nanocrystals control nanoparticles and nanowires morphology. Related research results have been published in "Journal of the American Chemical Society"[J. Am. Chem. Soc,134,9410(2012)]2. Thermal Diffusion in Bimetallic NanoparticlesThermally driven diffusion under nanoscale, which determines the rate and paths of chemical reaction and transformation of structure, has an extensive application in manufacturing nanoscale devices and improving materials. However, the present study of atomic scale diffusion generally stays in condensed matter physics, which acquires the theoretical simulated diffusion rate and diffusion mechanism by theoretical calculation and simulation. Constrained by technical means, there has been few understanding of authentic diffusion by experiment, and we knew little about the impacts of authentic diffusion on materials. We used time-resolved XAFS techniques to study the diffusion process of bimetallic core-shell structure.The third chapter investigates the mechanism of the diffusion of Cu@Au Core-Shell Structure with heterotherm driving by using variable temperature in situ XAFS. It in situ measurements evidence a dominant unidirectional diffusion route involving the migration of the Au shell atoms into the Cu core upon heating and forming a diffusion layer composed of substitutional CuAu-like intermetallic compounds. The presented results will provide more implications for manipulating the diffusion process, for example, by turning the structures or the composites in bimetallic systems. Related research results have been published in "ACSnano"[ACSnano8,1886(2014)]3. Dsigne and preparation of AuCunanocageDue to high specific surface area and little density and other characteristics of controlled structure, Hollow metal nanomaterials exhibit unique properties relative to bulk of a large size, which obtain much attentiond in catalysis, energy storage and Drug delivery.By manipulation of material parameters size, morphology, internal structure and composition the properties of hollow metal nanomaterials will change and optimize further. Chapter IV of the paper work is mainly the oil phase chemically synthesized material AuCu football nanostructures. By changing the volume of oil amine and tri-n-octylamine, and the temperature and other conditions, alkenyl synthesized AuCu football nanostructures with good porperties.