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Microstructure Probing of Nanostrutured and Nano Materials

讲座标题:Microstructure Probing of Nanostrutured and Nano Materials

主讲人: Ke Han博士(US National High Magnetic Field Laboratory)

讲座时间:2016-11-16 10:00

讲座地点:务实楼202会议室

讲座语言:英语

主办单位:环化学院


讲座内容:

Nanostructured materials have a variety of unique functional and structural properties such as giant magnetoresistance, ultrahigh hardness and new combinations of conductivity/strength. Such new properties depend on both the size of the structure, K, and nature of the surface and interface structures. On the other hand, as the K is decreased, non-equilibrium phases can form in the materials. The interfaces and surfaces may serve as the nucleation sites of both defects and reactions, and for formation of both stable and metastable phases, etc., which control the properties of the multilayers. Also the scale of the structures is such that they are amenable to large-scale atomistic simulation as well as experiment. To link the microstructure, simulation and properties, transmission electron microscopy is recognized as a powerful tool for providing direct evidence on detailed structural information, such as crystallography, growth morphology, composition and phase identification, lattice distortion and even atomic positions. This talk exemplifies studies of nanostructured and nano materials using various TEM, high resolution TEM (HRTEM), and scanning TEM (STEM)  techniques. These selected cases include the characterizations of: (a) periodicity and scale of the structure, (b) solid solution formed at interfaces due to the intermixing, and (c) non-equilibrium phases including amorphous phases and nanoparticles. Microscale and some atomic scale information can be obtained by both selected area diffraction pattern (SADP) and conventional TEM images, whereas local atomic structure investigations need the HRTEM and STEM approaches in combination with imaging simulation. Both SADP and HRTEM imaging techniques can be used to estimate the magnitude of the local strains and how they are distributed along the interfaces and surface. Moreover, these techniques are able to reveal the local metastable phases or unusual atomic arrangements which are usually identified with respect to the bulk materials.


主讲人概况:


Han got his Master of Science degree from Beijing University of Science and Technology and his doctoral degree from University of Oxford. In 1992, Han started to work at the National High Resolution Electron Microscopy Center in the Netherlands. In 1995, Han moved to Los Alamos National Laboratory in New Mexico, USA. After he joined US National High Magnetic Field Laboratory (MagLab) in 1999, Han became the group leader for materials development and characterization in magnet science technology division in MagLab. Since 2000, he has advised/supervised fourteen graduate students and postdocs. All of them have started working in the field as professions. Between 2010 and 2014, he also hosted four visiting scientists who were supported by Chinese Scholar Council. All these young scientists created new collaboration opportunities that had not previously existed between their home institutes and MagLab.

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