Time: June 13th, 2016, AM 9:00-10:00
Location: Conference Room at the 1st floor, No. 1 Energy Building
Ning Chen (Science Division, Canadian Light Source)
Abstract
X-ray absorption spectroscopy (XAS) is an element specific local structure technique, including X-ray absorption fine structure (XAFS) and X-ray absorption near edge structure (XANES). As a molecular scale characterization technique, XAS has been widely used in material research for both crystalline and amorphous materials. The strength of XAS is not only because it is a powerful experimental based approach, more importantly the technique is supported by well-developed theory, making the technique playing its unique and irreplaceable role in material characterization, especially for those studies in which in-depth and precise understanding of the element specific local structure environment is required.
In this talk, discussion will be made regarding XAFS theory fundamental, application cases of Au/Pd bimetallic nanoparticle characterization (element coexisting mechanism), element site occupancy within crystalline material (case of single element type with two different oxidation states, occupying at two different crystallography sites), local structure related XANES finger print feature (case of amorphous material, but precursor of certain long range ordering), element local structure refinement (accuracy 0.02 ?), and the sensitivity of XANES (case of Fe K edge and Cd K edge). Theoretical XANES/EXAFS modeling have been used for all of these study cases, indicating that an XAS experiment should a theory (or hypothesis) guided experiment, and the effort of the post experiment data processing would be more effective if the effort turns to majorly verify, improve, and refine the existing structural model. With these aspects integrated, we will have the full power of XAS.
Introduction
Dr. Ning Chen is a staff scientist from Canadian Light Source (CLS), Canada, At CLS, Dr. Chen has involved in the design, installation, and commissioning the Hard X-ray MicroAnalysis (HXMA) beamline at CLS. In addition, He is an adjunct professor at the Department of Geological Sciences, University of Saskatchewan since 2003, and an adjunct professor at the School of Earth & Space Sciences, Peking University, China since 2014 and an adjunct professor at Université du Québec à Trois-Rivières since 2016. Currently his major role at CLS is responsible for the HXMA beamline operation, upgrade, and its XAFS user program. For the recent years he has made every effort to promote XAFS among researchers in material science across Canada and in China as well, providing courses and lectures, organizing and teaching XAFS workshops. He has also involved in the graduate programs at various universities in Canada, majorly form XAFS characterization perspective.
Dr. Chen received his B.Sc. in 1983 from the Department of Optics, Shandong University, China; M.Sc. in 1989 from the Beijing Institute of Environmental Features, former Ministry of Aerospace Industry, China; and Ph.D. in 2001 from the Department of Geological Sciences, University of Saskatchewan, Canada. He worked as postdoctoral fellowship and COGEMA research associate at CLS from 2001 to 2003. Since 2003 he became a staff scientist at CLS.
Contacts：Group 1502 Hui Sun (89161)