XAFS Studies in U7C XAFS Studies in U7C Wiggler Wiggler Beam-line of NSRL Beam-line of NSRL Shiqiang Wei, Xinyi Zhang Shiqiang Wei, Xinyi Zhang Hongwei Yang, and Faqiang Xu Hongwei Yang, and Faqiang Xu National Synchrotron Radiation La National Synchrotron Radiation La boratory boratory University of Science & Technology of University of Science & Technology of
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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.
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XAFS Studies in U7C Wiggler XAFS Studies in U7C Wiggler
Hongwei Yang, and Faqiang XuHongwei Yang, and Faqiang Xu
National Synchrotron Radiation LaboratoryNational Synchrotron Radiation LaboratoryUniversity of Science & Technology of ChinaUniversity of Science & Technology of China
Hefei, 230029, P.R.ChinaHefei, 230029, P.R.China
NSRL in Hefei, China
The Storage Ring at NSRL
The beamline planned and Operated in NSRL
U4 IR and Far IR SpectroscopyU7A LIGAU7B X-ray Diffraction and ScatteringU14 Atomic and Molecular SpectroscopyU18 Soft X-ray MCDU19 Surface PhysicsU25 Photo-Acoustic and Photo-Thermal SpectroscopyU27 Metrology and Spectral Radiation Standard
ConclusionThe 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 Ni3B alloy.
We have noted that the S of Ni-Ni shell signi
ficantly 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.
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 Fe100-xCux 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 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.
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.
k3(k)-k function of Fe100-xCux
4 8 12 16
-40
0
40
80
120
160
4 8 12 16
-40
0
40
80
120
160
(b)(a)
A
o
Fe90
Cu10
Fe20
Cu80
Fe30
Cu70
Fe40
Cu60
Fe60
cu40
Fe80
Cu20
Fe-Cu powder
Fe K-edge
k ( A-1 )
k3 (k
)
A
o
Cu K-edge
Fe90
Cu10
Fe80
Cu20
Fe60
Cu40
Fe40
Cu60
Fe30
Cu70
Fe20
Cu80
Fe-Cu powder
k3 (k
)
k ( A-1)
RDFs of Fe100-xCux alloys
0 2 4 6
500
1000
1500
2000
2500
3000
3500
0 2 4 6
500
1000
1500
2000
2500
3000
3500
o
Cu K-edge
Fe90
Cu10
Fe80
Cu20
Fe60
Cu40
Fe40
Cu60
Fe30
Cu70
Fe20
Cu80
Cu-Fe powderF
(r)
Distance( A )
(a) (b)
o
Fe90
Cu10
F(r
)
Distance( A )
Fe20
Cu80
Fe30
Cu70
Fe40
Cu60
Fe60
cu40
Fe80
Cu20
Fe-Cu powder
Fe K-edge
Fitting results of the Fe100-xCux samples
4 6 8 10 12 14-80
-40
0
40
80
120
160
4 6 8 10 12 14-80
-40
0
40
80
120
160
(a)
o
k( A-1 )
Fe-Cu powder
Fe40
Cu60
Fe30
Cu70
Fe20
Cu80
Fe60
Cu40
Fe80
Cu20
Fe90
Cu10
Fe K-edge
k3 (k
)
(b)
o
k( A-1)
Fe-Cu powder
Fe20
Cu80
Fe30
Cu70
Fe40
Cu60
Fe60
Cu40
Fe80
Cu20
Fe90
Cu10
Cu K-edge
k3 (k
)
The structure parameters of Fe100-xCux by fitting the Fe K-edge EXAFS spectra
Sample Bond type R(Å) (Å) N E0
Fe powder Fe-Fe 2.480.02 0.0700.005 8.00.5 2.97
Fe90Cu10 Fe-Fe 2.480.02 0.0780.005 7.60.5 -4.01
Fe-Cu 2.480.02 0.0800.005 0.70.3 -1.59
Fe80Cu20 Fe-Fe 2.480.02 0.0810.005 7.20.5 -2.01
Fe-Cu 2.480.02 0.0810.005 1.20.3 4.31
Fe60Cu40 Fe-Fe 2.570.02 0.0990.005 8.70.5 0.64
Fe-Cu 2.560.02 0.0990.005 3.50.3 -4.99
Fe40Cu60 Fe-Fe 2.580.02 0.0990.005 6.90.5 4.99
Fe-Cu 2.580.02 0.0990.005 5.60.5 2.63
Fe30Cu70 Fe-Fe 2.580.02 0.0980.005 5.70.5 4.96
Fe-Cu 2.580.02 0.0980.005 6.40.5 2.94
Fe20Cu80 Fe-Fe 2.580.02 0.0980.005 5.00.5 4.95
Fe-Cu 2.580.02 0.0980.005 7.10.5 3.45
The structure parameters of Fe100-xCux by fitting the Cu K-edge EXAFS spectra
Sample Bond type R(Å) (Å) N E0
Fe90Cu10 Cu-Cu 2.480.02 0.0780.005 1.50.3 -3.1
Cu-Fe 2.480.02 0.0730.005 6.70.5 -5.0
Fe80Cu20 Cu-Cu 2.500.02 0.0820.005 2.10.3 4.8
Cu-Fe 2.490.02 0.0810.005 6.20.5 4.0
Fe60Cu40 Cu-Cu 2.550.02 0.0890.005 7.10.5 2.7
Cu-Fe 2.550.02 0.0870.005 4.60.5 0.9
Fe40Cu60 Cu-Cu 2.560.02 0.0890.005 8.40.5 -3.9
Cu-Fe 2.540.02 0.0890.005 3.30.3 -4.3
Fe30Cu70 Cu-Cu 2.550.02 0.0890.005 9.70.5 -1.8
Cu-Fe 2.540.02 0.0890.005 2.30.3 -3.8
Fe20Cu80 Cu-Cu 2.550.02 0.0890.005 9.80.5 -2.1
Cu-Fe 2.540.02 0.0880.005 1.50.3 -4.6
Cu powder Cu-Cu 2.550.02 0.0890.005 12.00.5 0.4
Conclusions
The local structures around Fe and Cu atoms depend on the initial composition. Fe100-xCux solid solutions x40, fcc-like structure x20, bcc-like structure
• The fitting results indicate that the MA FexCu
100-x alloys with x40 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 x20. 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.