CAREER: Atomic Structure and Growth of Nano-Particles

这份职业计划的重点是纳米级原子聚集体的结构。这是一个重要的问题，因为胚胎团簇或颗粒形成于相变的早期阶段，而团簇结构影响相变和组织演变。此外，金属颗粒是重要的工业催化剂，纳米颗粒是纳米技术的基石。这一提议将开发基于新的纳米区域电子衍射(NED)技术的结构表征和原子分辨率成像的新方法，该技术涉及纳米尺寸的相干平行电子束。NED允许记录单个颗粒的衍射图，以确定三维结构。这一结果将有助于理解纳米粒子中的原子结构。将使用改进的分析型超高电压扫描透射电子显微镜来开发现场能力。这种分析能力将对研究双金属纳米颗粒的合金化和相分离非常有用。通过将实验与分子动力学模拟进行比较，将获得关于粒子结构的见解。该项目的一个目标是利用结构知识作为生长的反馈，以改善纳米粒子的性能。所研究的材料包括纳米银的模型体系和共晶的银/铜体系。以后的研究将集中在Ag/Fe和Fe/Pt磁性合金，以及催化铂/Ru结构与性能的关联。研究将与教育在多个层面上相结合。该项目将开发新的方法，利用纳米尺寸的平行电子相干光束来确定原子排列。这项技术是通用的，原则上适用于单个大分子。待开发的现场能力将通过材料微量分析中心(CMM)向更广泛的社区提供。所获得的知识将被纳入纳米结构表征教学，并通过讲习班和学校用于外联活动。该项目的一个重要方面是以基于网络的研究软件和教程的形式为试图将纳米科学纳入其课程的教育工作者创造研究和教育工具。将在这里开发的教材还将通过向学生介绍分子衍射的概念来填补当前材料科学教育的空白。研究生和本科生研究人员将通过实践研讨会、会议和纳米科学具体项目的合作来接受培训。

This career proposal focuses on the structure of nano-scale atomic aggregates. The problem is important because embryonic clusters or particles form at the early stage of phase transformations and the cluster structure affects the phase transformation and microstructure evolution. Furthermore, metal particles are important industrial catalyst and nanoparticles are the building blocks for nanotechnology. This proposal will develop new approaches to structure characterization and atomic resolution imaging based on the new nano-area electron diffraction (NED) technique involving a nanometer-sized coherent beam of parallel electrons. NED allows diffraction patterns to be recorded from individual particles for 3-D structure determination. The results will contribute to the understanding of atomic structure in nanoparticles. In-situ capabilities will be developed using a modified analytical UHV scanning transmission electron microscope. The analytical capability will be very useful for studying alloying and phase separation in bimetallic nanoparticles. Insight about particle structure will be obtained by comparing experiment with molecular dynamics simulations. A goal of the project is to use the structural knowledge as a feedback to growth to improve the properties of the nano-particles. Materials to be studied include the model system of Ag nanoparticles and the eutectic Ag/Cu system. Later study will focus on magnetic alloys of Ag/Fe and Fe/Pt, and catalytic Pt/Ru to correlate structure with properties.The research will be integrated with education at several levels. This project will develop novel methods that make use of a nanometer-sized coherent beam of parallel electrons to determine atomic arrangements. The technique is general, and in principle, applicable to individual macromolecules. The in-situ capabilities to be developed will be available through the Center for Microanalysis of Materials (CMM) to the broader community. Knowledge gained will be incorporated for teaching nanostructure characterization and used for outreach activities through workshops and schools. An important aspect of the project is the creation of research and education tools in the form of web-based research software and tutorials for educators who seek to incorporate nanoscience in their own curricula. The teaching materials to be developed here will also fill a gap in current materials science education by introducing students to the concept of molecular diffraction. Graduate and undergraduate researchers will be trained through hands-on workshops, conferences and collaboration on nanoscience specific projects.