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XAFS Studies in U7C Wiggler Beam-line of NSRL Shiqiang Wei, Xinyi Zhang

XAFS Studies in U7C Wiggler Beam-line of NSRL Shiqiang Wei, Xinyi Zhang Hongwei Yang, and Faqiang Xu National Synchrotron Radiation Laboratory University of Science & Technology of China Hefei, 230029, P.R.China. NSRL in Hefei, China. The Storage Ring at NSRL.

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XAFS Studies in U7C Wiggler Beam-line of NSRL Shiqiang Wei, Xinyi Zhang

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  1. XAFS Studies in U7C Wiggler Beam-line of NSRL Shiqiang Wei, Xinyi Zhang Hongwei Yang, and Faqiang Xu National Synchrotron Radiation Laboratory University of Science & Technology of China Hefei, 230029, P.R.China

  2. NSRL in Hefei, China

  3. The Storage Ring at NSRL

  4. The beamline planned and Operated in NSRL In construction U4 IR and Far IR Spectroscopy U7A LIGA U7B X-ray Diffraction and Scattering U14 Atomic and Molecular Spectroscopy U18 Soft X-ray MCD U19 Surface Physics U25 Photo-Acoustic and Photo-Thermal Spectroscopy U27 Metrology and Spectral Radiation Standard In Operation U1 X-ray lithography U7B XAFS U10A Photo-Chemistry U10B Time-Resolved Spectroscopy U12A Soft X-ray Microscopy U20 Photoelectron Spectroscopy

  5. 3-pole superconducting wiggler of 6T

  6. Beam from bending magnet and superconducting wiggler

  7. Monochromator of Si (111) double crystals

  8. U7C XAFS station of NSRL

  9. Superconducting Wiggler Experiment Hutch Side view of XAFS beamline at NSRL 1. Handle valve 2. Water cooling mask 3. Pressure valve 4. Fast control valve 5. Separating diaphragm 6. Beam stop 7. Pressure valve 8. Absorption Be window 9. Diaphragm 10. Pressure valve 11. Entry slit 12. Flux monitor 13. Double crystal monochromator 14. Exit slit 15.Fluorescent screen 16. Beam stop

  10. Schematic diagram of detector system for charge measurement Sample Qs1 SR Qs2 Keithley 6517 Electrometer Keithley 6517 Electrometer IEEE-488 Computer

  11. Equivalent Circuit of Keithley 6517 Electrometer

  12. XAFS Photon energy 5–12 keV Resolution 10-4@12 keV Flux 1× 1010 photons/sec • K edge Z=22∼33 • L edge Z=52∼73 • Transmission Fluorescence • In situ measurements U7C of XAFS station open for users in Dec. 1999

  13. Photon Flux ( ph/s ) 9 10 8 10 4000 6000 8000 10000 12000 14000 Energy ( eV ) Flux Intensity of U7C Beamline at the Sample Position of Hefei National Synchrotron Radiation Laboratory

  14. 2.0 Cu foil (NSRL) 1.5 1.0 x ( Arb. Units ) m 0.5 0.0 8500 9000 9500 10000 Energy ( eV ) X-ray absorption spectrum of K edge for Cu foil

  15. X-RAY ABSORPTION SPECTRUM OF K-EDGE FOR TiO2 POWDER

  16. X-RAY ABSORPTION SPECTRA OF K-EDGE FOR Ge POWDER

  17. APPLICATIONS of U7C XAFS STATION 1 Annealed crystallization of Ni-B and Ni-P nano-amorphous alloys

  18. Significations • TM-M type Ultrafine amorphous alloy (TM=Ni, Co, Fe; M=B, P) have the high ratio of surface atoms and amorphous structure. • Applications in ferrofluid, catalysts and magnetic recording materials.

  19. X-ray-absorption fine structure study on devitrification of ultrafine amorphous NiB alloy Phys.Rev.B63, 224201(2001). Shiqiang Wei, Hiroyuki Oyanagi, Xinyi Zhang, Wenhan Liu, • Annealed crystallization of ultrafine amorphous NiB alloy studied by XAFS Journal of Synchrotron Radiation, 8, 566(2001). Shiqiang Wei, Zhongrui Li, Shilong Yin, Xinyi Zhang.

  20. Preparation Chemical method: KBH4, 2 mol/L Ni(CH3COO)2  4H2O, 0.25 mol/L ice-water bath and vigorously agitated by a magnetic stirrer.

  21. 1.1 Catalytic activities of nano-amorphous Ni-B and Ni-P for Benzene Hydrogenation

  22. 1.2 DTA profiles of NiB and NiP

  23. 1.3 XRD results of NiB with different annealed temperatures

  24. XRD spectra of NiP at different temperature

  25. 1.4 XAFS results k3(k)-k function of NiB and NiP

  26. Fitting results of NiB and NiP

  27. Sample Annealing Pair Rj (nm) R0 (nm) N T (10-2 nm) S(10-2 nm) E0 (eV) Temp Ni-B 25 oC Ni-Ni 0.274 0.2410.001 11.01.0 0.69 3.3 -0.2 Ni-B 0.218 0.2150.001 2.70.2 0.46 0.34 -4.7 Ni-P 25 oC Ni-Ni 0.271 0.2430.001 10.01.0 0.60 2.8 -2.9 Ni-P 0.223 0.2150.001 1.60.2 0.40 0.80 5.3 Ni-B 300 oC Ni-Ni 0.255 0.2430.001 9.91.0 0.60 1.1 -0.9 Ni-B 0.218 0.2150.001 2.60.2 0.60 0.34 5.0 Ni-P 300 oC Ni-Ni 0.258 0.2420.001 10.11.0 0.63 1.6 -1.3 Ni-P 0.222 0.2150.001 0.80.2 0.49 0.65 8.7 Ni-B 500 oC Ni-Ni 0.249 0.2450.001 10.81.0 0.70 0.39 1.6 Ni-B 0.217 0.2150.001 0.30.2 0.56 0.23 -5.0 Ni-P 500 oC Ni-Ni 0.255 0.2430.001 10.41.0 0.60 1.25 -2.8 Ni-P 0.225 0.2190.001 0.60.2 0.40 0.56 7.6 Ni foil Ni-Ni 0.249 12.0 0.74 Average distance Rj=R0+σs R’s error=0.001 nm，T’s error=0.0510-2 nm，S’s error=0.110-2 nm。

  28. Conclusion The XAFS results demonstrate that a fcc-like nanocrystalline Ni phase with a medium-range order is formed at 573K where the first exothermic process is observed. The metastable intermediate states consist of the two phases, i.e., nanocrystalline Ni and crystalline Ni3B alloy.

  29. We have noted that the S of Ni-Ni shell significantly decreases from 0.033 to 0.0029 nm, after NiB being annealed at the temperature of 773 K. The structural parameters of NiB sample is almost the same as that of Ni foil. Nevertheless, the S (0.0125 nm) of NiP sample is rather larger.

  30. 2 Structural transitions for immiscible Fe-Cu system induced by mechanical alloying

  31. Significations The method of mechanical alloying can largely increase the solid solubility of immiscible Fe100-xCux alloy. Unique electronic and magnetic properties for Fe-Cu system. The mechanism enhanced solubility of Fe-Cu alloy is not clear.

  32. Structural transitions of mechanically alloyed Fe100-xCux • system studied by X-ray absorption fine structure • Physica B, 305, 135(2001) • Shiqiang Wei, Wensheng Yan, Yuzhi Li, Wenhan Liu, • Jiangwei Fan, and Xinyi Zhang • Metastable structures of immiscible FeXCu100-X system • induced by mechanical alloying. • J.Phys. CM, 9, 11077(1997). • Shiqiang Wei, Hiroyuki Oyanagi, Cuie Wen, • Yuanzheng Yang, and Wenhan Liu.

  33. Preparations Alloy omposition Fe100-xCux x= 0, 10, 20, 40, 60, 80, 100. WC balls to the mixed Fe-Cu powder 10 to 1. MA milling rate: about 210 r/min.

  34. k3(k)-k function of Fe100-xCux

  35. RDFs of Fe100-xCux alloys

  36. Fitting results of the Fe100-xCux samples

  37. The structure parameters of Fe100-xCux by fitting the Fe K-edge EXAFS spectra

  38. The structure parameters of Fe100-xCux by fitting the Cu K-edge EXAFS spectra

  39. Conclusions The local structures around Fe and Cu atoms depend on the initial composition. Fe100-xCux solid solutions x40, fcc-like structure x20, bcc-like structure

  40. The fitting results indicate that the MA FexCu100-x alloys with x40 are inhomogeneous supersaturated solid solutions, and there are a fcc Fe-rich and a fcc Cu-rich regions in solid solutions. For lower Cu concentrations with x20. The evolution of the FT intensities and structural parameters of Fe atoms is identical with those of Cu atoms. This result suggests that the Cu atoms be almost homogeneously incorporated into the bcc Fe-Cu phase.

  41. Thanks for Attendance

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