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

NSRL in Hefei, China

The Storage Ring at NSRL

The beamline planned and Operated in NSRL 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 construction In Operation U1 X-ray lithography U7B XAFS U10A Photo-Chemistry U10B Time-Resolved Spectroscopy U12A Soft X-ray Microscopy U20 Photoelectron Spectroscopy

3-pole superconducting wiggler of 6T

Beam from bending magnet and superconducting wiggler

Monochromator of Si (111) double crystals

U7C XAFS station of NSRL

Side view of XAFS beamline at NSRL Superconducting Wiggler Experiment Hutch 1. Handle valve 2. Water cooling mask 3. Pressure valve 4. Fast control valve 5. Separating diaphragm 6. Beam stop 7. Pressure valve8. Absorption Be window9. Diaphragm 10. Pressure valve 11. Entry slit 12. Flux monitor13. Double crystal monochromator 14. Exit slit 15.Fluorescent screen 16. Beam stop

Q s1 Q s2 SR Sample Computer IEEE-488 Keithley 6517 Electrometer Keithley 6517 Electrometer Schematic diagram of detector system for charge measurement

Equivalent Circuit of Keithley 6517 Electrometer

XAFS Photon energy 5–12 keV Resolution 10 keV Flux 1× 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

Flux Intensity of U7C Beamline at the Sample Position of Hefei National Synchrotron Radiation Laboratory Photon Flux ( ph/s ) Energy ( eV )

X-ray absorption spectrum of K edge for Cu foil Cu foil (NSRL)  x ( Arb. Units ) Energy ( eV )

X-RAY ABSORPTION SPECTRUM OF K-EDGE FOR TiO 2 POWDER

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

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

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.

X-ray-absorption fine structure study on devitrification of ultrafine amorphous NiB alloy Phys.Rev.B63, (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.

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

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

1. 2 DTA profiles of NiB and NiP

1.3 XRD results of NiB with different annealed temperatures

XRD spectra of NiP at different temperature

1.4 XAFS results k 3  (k)-k function of NiB and NiP

Fitting results of NiB and NiP

Sample Annealing Pair Rj (nm) R0 (nm) N  T (10 -2 nm)  S (10 -2 nm)  E0 (eV) Temp Ni-B 25 o C Ni-Ni   Ni-B   Ni-P 25 o C Ni-Ni   Ni-P   Ni-B 300 o C Ni-Ni   Ni-B   Ni-P 300 o C Ni-Ni   Ni-P   Ni-B 500 o C Ni-Ni   Ni-B   Ni-P 500 o C Ni-Ni   Ni-P   Ni foil Ni-Ni Average distance Rj=R0+σs R’s error=  nm ，  T ’s error=  0.05  10-2 nm ，  S ’s error=  0.1  10-2 nm 。

Conclusion The XAFS results demonstrate that a fcc-like nanocrystalline Ni phase with a medium-range order is formed at 573 K where the first exothermic process is observed. The metastable intermediate states consist of the two phases, i.e., nanocrystalline Ni and crystalline Ni 3 B alloy.

We have noted that the  S of Ni-Ni shell significantly decreases from to 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 ( nm) of NiP sample is rather larger.

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

Significations The method of mechanical alloying can largely increase the solid solubility of immiscible Fe 100-x Cu x alloy. Unique electronic and magnetic properties for Fe-Cu system. The mechanism enhanced solubility of Fe-Cu alloy is not clear.

Structural transitions of mechanically alloyed Fe 100-x Cu x 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 Fe X Cu 100-X system induced by mechanical alloying. J.Phys. CM, 9, 11077(1997). Shiqiang Wei, Hiroyuki Oyanagi, Cuie Wen, Yuanzheng Yang, and Wenhan Liu.

Preparations Alloy omposition Fe 100-x Cu x 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.

k3  (k)-k function of Fe 100-x Cu x

RDFs of Fe 100-x Cu x alloys

Fitting results of the Fe 100-x Cu x samples

The structure parameters of Fe 100-x Cu x by fitting the Fe K-edge EXAFS spectra SampleBond type R(Å)  (Å) N E0E0 Fe powderFe-Fe 2.48    Fe 90 Cu 10 Fe-Fe 2.48    Fe-Cu 2.48    Fe 80 Cu 20 Fe-Fe 2.48    Fe-Cu 2.48    Fe 60 Cu 40 Fe-Fe 2.57    Fe-Cu 2.56    Fe 40 Cu 60 Fe-Fe 2.58    Fe-Cu 2.58    Fe 30 Cu 70 Fe-Fe 2.58    Fe-Cu 2.58    Fe 20 Cu 80 Fe-Fe 2.58    Fe-Cu 2.58   

The structure parameters of Fe100-xCux by fitting the Cu K-edge EXAFS spectra SampleBond type R(Å)  (Å) N E0E0 Fe 90 Cu 10 Cu-Cu 2.48    Cu-Fe 2.48    Fe 80 Cu 20 Cu-Cu 2.50    Cu-Fe 2.49    Fe 60 Cu 40 Cu-Cu 2.55    Cu-Fe 2.55    Fe 40 Cu 60 Cu-Cu 2.56    Cu-Fe 2.54    Fe 30 Cu 70 Cu-Cu 2.55    Cu-Fe 2.54    Fe 20 Cu 80 Cu-Cu 2.55    Cu-Fe 2.54    Cu powderCu-Cu 2.55   

Conclusions The local structures around Fe and Cu atoms depend on the initial composition. Fe 100-x Cu x solid solutions x  40, fcc-like structure x  20, bcc-like structure

The fitting results indicate that the MA Fe x Cu 100-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.

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