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报告主要介绍三方面工作
1、iDPC技术在轻元素成像中的应用及其最佳成像条件的探索
2、Bi2Te3基热电器件断裂机制的原位研究
3、重型燃气轮机中雀斑缺陷形成机制的探索
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二维材料是目前研究的热点。由于层间耦合效应和量子效应的减弱,大量新奇的物理现象在二维材料中被发现。其中,二维材料中的缺陷对其性能有直接的影响。理解本征缺陷的原子结构对二维材料功能器件的改进与性能提供具有重要意义。然而,只有少数几种二维材料在单层极限下在大气环境中是稳定,大部分新型二维材料,如单层铁电,单层铁磁,单层超导材料在大气环境下会迅速劣化,无法表征其本征缺陷。在这个报告中,我将报道定量衬度分析技术在二维材料缺陷表征中的应用,以及我们课题组搭建的大型氛围控制高通量生长与高精度表征联用系统的进展。我们利用该系统在直接观测二维敏感单层材料晶格原子结构与缺陷中取得的一些初步成果,包括单层WTe2的本征褶皱结构、点缺陷的分布,少层卤族铁磁反铁磁材料的直接CVD制备与无损表征,层状拓扑反铁磁绝缘体MnBi2Te4的自发表面重构现象等。
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镍基单晶高温合金是航空发动机高压涡轮叶片的重要制备材料,其微观结构特征是影响合金关键性能的重要因素。以一种新型第四代镍基单晶高温合金为对象,考察了合金铸态、热处理态和高温低应力蠕变过程中的微观结构演化特征。镍基单晶高温合金的铸态组织为“十字”的枝晶结构,枝晶间和枝晶干存在尺寸不均匀的粗大γ′相和γ/γ′相共晶组织。通过多步阶梯固溶处理,回溶粗大γ′相和γ/γ′相共晶组织并减小偏析,通过两步时效处理获得组织均匀、立方度好的γ′相。在1100℃/137MPa蠕变条件下,获得了合金在不同变形过程中γ′相的筏排化过程、位错网的演化规律,结合断口裂纹的扩展规律,明确了其微观结构演化与蠕变性能的关联关系。
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电镜选型如何实现降本增效?
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冷冻电子断层成像技术(Cryo-electron tomography,Cryo-ET)是一项高分辨、跨尺度的原位冷冻电镜技术,可以获得细胞和组织样品原位三维高分辨率超微结构、生物大分子的原位结构信息以及蛋白质机器原位相互作用信息。本技术流程基于最新冷冻聚焦离子束(Cryo-FIB),成功利用多种方法制备了生物含水切片样品,对比了常温和冷冻制样的区别,并总结了制样和数据收集过程中的一些技术难点和详细的解决方案,并对未来基于Cryo-FIB的Cryo-ET研究做了展望。
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冷冻电镜数据收集策略
时间:2022/08/08 11:44
164
常圣海,男,2005-2009...
高质量的冷冻电镜照片是获取高分辨三维重构结果的重要保证。本次报告将分享关于冷冻电镜数据收集过程中一些自己的心得和感悟,主要包括: K2相机和Falcon4相机重构结果的比较;SerialEM和EPU数据收集软件的对比等。
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跨尺度锂电池研究
时间:2022/08/08 11:18
162
黄建宇,燕山大学和湘潭大学教授...
高能量密度、长循环和高安全性锂电池的制备涉及到材料制备/表征,极片涂覆和电池组装等多尺度结构优化。因此电池设计是一个多尺度问题,任何一个环节出现问题都会导致电池劣化和失效。因此发展跨尺度锂电池表征技术尤为重要。近年来本研究组一直从事多尺度锂电池表征技术开发。在宏观层面,设计出原位光学表征技术,成功地在宏观尺度揭示固态电池锂枝晶生长和传输机制。在介观层面,开发出在FIB-SEM里面微米尺度电池,发现硫化物电解质电化学-力学耦合失效尺寸效应。在微观领域,结合透射电镜和探针显微镜(TEM-STM),实现了纳米材料的微观结构和性能的同步测量。利用TEM-STM平台,首次在电镜中构建了纳米电池,实现了对电化学反应的实时原位观测,开创了纳米电化学新领域。结合微机电加热系统,原子力显微镜和球差矫正环境电镜,利用TEM-STM平台可以实现温度、压力和气氛多场耦合条件下的原位电化学测量。本报告将介绍应用原位光学、FIB-SEM和TEM-STM平台在锂电池研究领域的最新研究成果。在纳米电池领域,发现锂嵌入硅导致粉化的尺寸效应。测定了锂、钠枝晶的力学性能,发现纳米锂、钠枝晶的强度比相应的体材强度高出200多倍。实现了锂枝晶的力-电耦合精准测量,揭示锂枝晶刺穿固态电解质机理。利用球差矫正环境电镜,实现了气体电池的原位测量。这些基础研究为开发高能量密度、高功率密度和长循环寿命锂电池提供了坚实的科学基础和技术路径。
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晶体变形过程中缺陷的形核及演化是组成这些缺陷的原子集体响应的动态过程。由于原有的原位实验技术分辨率长期局限于纳米尺度,导致人们对晶界变形的原子层次机理的认知强烈依赖于理论模型及计算机模拟,亟需原子层次原位实验证据澄清晶界塑性变形机制。本次报告主要介绍近年来团队在晶界变形机制研究的进展。主要是利用原创的实验技术,实现了多晶体系中晶界滑移、晶界原子扩散的原子层次动态观察。揭示出晶界滑移是通过晶界处原子相对滑移与原子短程扩散相互协调实现。研究晶界原子阵列合并消失、分裂出新原子阵列、原子迁移并插入晶体内部等多种新型的扩散机制。通过原位观察,发现晶界的产生及晶粒旋转的机制。
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Knowing the 3D atomic structures of materials or biomolecules is crucial for understanding their functions. X-ray diffraction is currently the most important technique for determination of 3D atomic structures, but requires large crystals which are often difficult to obtain. Electrons, similar to X-rays and neutrons, are powerful source for diffraction experiments. Due to the strong interactions between electrons and matter, crystals that are considered as powder in X-ray crystallography can be treated as single crystals by 3D electron diffraction methods [1]. This enables structure determination of materials and organic molecules from micron- to nanometer-sized 3D crystals that are too small for conventional X-ray diffraction. Furthermore, by taking the advantages of the unique properties of electron scattering, it is possible to determine the charge states of atoms/ions [2] and the absolute structure of chiral crystals [3].
Over the past decades, a number of 3D ED methods have been developed for structure determination. At the early stages of 3D ED method development, tilting of the crystal was done manually, while diffraction patterns were collected on negative film. It could take years before sufficient data were obtained and processed in order to determine the crystal structure. The computerization of TEMs and the development of CCD detectors allowed software to be developed that can semi-automatically collect 3D ED data in less than an hour [1]. Thanks to the recent advancement in CMOS and hybrid detector technology, it is now feasible to collect diffraction data in movie mode while continuously rotating the crystal (continuous rotation election diffraction, cRED, also known as MicroED [4] in structural biology). Benefiting from these technological advances, structure determination can now be accomplished within a few hours. Recently, fully automated serial rotation electron diffraction data collection and processing has been realized by our group [5].
By using 3D ED / MicroED methods, we have solved more than 200 novel crystal structures of small inorganic compounds [6] (including zeolite, MOF, COF and minerals) and biomolecules [7,8] (pharmaceuticals, small organic molecules, peptides and proteins) in the past 7 years. Recently, we have solved two novel protein [9,10] structures with 3D ED/MicroED and shown that it is feasible to use MicroED for structure based drug discovery [11]. We aim to further improve these methods, develop new methods and more importantly spread them to labs around the world.
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扫描电镜及电子背散射衍射在材料研究中的应用