Real Time Imaging Structural Transformation Dynamics of Materials
讲座名称：
Real Time Imaging Structural Transformation Dynamics of Materials
讲座时间：
2011-09-23
讲座人：
郑海梅
形式：
校区：
兴庆校区
实践学分：
讲座内容：
美国劳伦斯伯克利国家实验室首席研究员和主任科学家郑海梅博士将于9月23日到我校金属材料强度国家重点实验室微纳尺度材料与行为研究中心（CAMP-Nano）交流访问，届时将做精彩报告。
报告时间：2011年9月23日（周五）上午10:00
报告地点：材料学院/金属材料强度国家重点实验室215会议室
报告题目：Real Time Imaging Structural Transformation Dynamics of Materials
摘要：A critical challenge for the development of alternative energy resources is the inability to fabricate efficient and inexpensive energy conversion and storage devices. Any solution technologies rely on advanced functional materials. Understanding how materials grow, function, and transform dynamically at nanometer or atomic level is essential. In the first part of my talk, I will present our recent study on the phase transformation dynamics of copper sulfide nanocrystals. Copper sulfide has been studied extensively for solar cell applications and there are a number ofphases with the Cu:S ratio close to 2:1. Cu2S transforms from low- to high-chalcocite phase at 376 K (bulk). An understanding of the microscopic mechanisms of structural transformations is critical for controlling the metastability of the material and the long-term performance of the solar cell devices. We have been able to directly observe structural fluctuations within a single copper sulfide nanorod using an aberration-corrected transmission electron microscopy (TEM). We observed trajectories of structural transformations in individual nanocrystals with atomic resolution, which reveal an unprecedented level of details on the fluctuation dynamics, including nucleation, phase propagation,and pinning of structure domains by defects. The clear influence of the surface and interface energies on nucleation and pinning phenomena suggest strategies for stabilizing particular metastable structures. In the second part of the presentation, I will show our studies of growth trajectories of individual nanocrystals in solution using a microfabricatedliquid cell operating in a TEM. In situobservation of the dynamic growth of individual nanocrystals is expected to advance our understanding of nanocrystal growth mechanisms and future control of the solution processing of materials.
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