讲座人:   Klaus-Dieter Liss,澳大利亚核科学技术组织布拉格研究所高级研究员
时  间:    10月20日-22日下午 4:00-6:00
地  点:    材料学院 205 会议室
 
摘要:
系 列 讲 座 1:Neutron and X-rays: properties, sources, diffraction 
(时间:10月20日下午4:00-6:00)
An introductory overview is given on neutron and synchrotron radiation, discussing properties, complementarity, sources at large user facilities. A typical park of instrumentation is reviewed, as relevant for scattering studies elucidated in the following presentations. The concept of diffraction is elaborated in a modern representation, demonstrating the advantages to work in  eciprocal-space coordinates.
系列讲座2:Neutron based in-situ studies on materials under high temperature conditions
(时间:10月21日下午4:00-6:00)
Most of the microstructural information of materials at high temperature is still being obtained post mortem by the processing-quench-analysis method. The method is not only tedious and slow, but information may get lost during the quench process, as temperature driven stresses influence the microstructure or even phase transformations take place. Neutron diffraction, in contrast, can deliver in-situ information in real time from a large bulk average. The evolution of lattice parameters allows to probe for anisotropies and anomalies in thermal expansion and chemical segregation in each of the constituting or transforming phases, including intermediate structures. Sudden changes in peak width show recrystallization and intensity changes relate to the defect kinetics in the system. The negative scattering length in titanium makes neutron scattering particularly sensitive to ordering in its alloys. Sample systems are presented to demonstrate the generic features, which were measured mainly on metal systems, while outlook and literature are given into the field of ceramics.
系 列 讲 座 3:Thermo-mechanical processing in a synchrotron beam - The materials Oscilloscope
(时间:10月22日下午4:00-6:00)
Synchrotron high-energy X-rays of around 100 keV energy may show comparable bulk penetrations as neutrons. Scattering angles and beam cross sections are small, so that it is convenient to probe for in-situ processes in complex sample environment. Modern, fast 2-dimensional detectors allow to evaluate the morphology of the Debye Scherrer rings. The diffraction patterns can be streaked in time to deliver traces, similar to an oscilloscope. So-called Azimuthal-Angle/Time-plots allow to distinguish, formation of subgrains, grain rotation, recovery, recrystallization, grain growth, individually for each of the constituting phases. Examples are discussed on metallic systems at heating and on thermo-mechanic deformation.
 
To conclude, the presented diffraction work is pretty generic and can be applied to ceramic and functional materials in similar ways. A brief overview on studies regarding magnetic materials, energy storage materials and ceramics is risen to the wider community.
 
讲座人简介:Klaus–Dieter Liss博士是国际著名的中子衍射和同步辐射实验科学家,现任澳大利亚核科学技术组织布拉格研究所高级研究员(长期固定职位),中子衍射线站的首席科学家,中子衍射团队负责人,澳大利亚中子源实验线站顾问委员会委员,负责了澳大利亚中子源实验线站设计及其未来的升级发展,拥有中子衍射和同步辐射实验领域长达27年的研究经验,擅长利用中子衍射和同步辐射对材料结构进行精细研究和分析,成功负责了多达90个左右的中子衍射实验研究项目,并拥有该领域众多的重要成果。已发表国际学术期刊论文 80余篇,多次应邀在重要国际会议上做大会报告(Keynote),担任国际学术期刊《Textures, Stress and Microstructures》Co-editor,担任国际学术期刊《Advanced Engineering Materials》编委。