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

XAFS Studies in U7C Wiggler XAFS Studies in U7C Wiggler

Beam-line of NSRLBeam-line of NSRL

Shiqiang Wei, Xinyi ZhangShiqiang Wei, Xinyi Zhang

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

In construction

In Operation

U1 X-ray lithographyU7B XAFSU10A Photo-ChemistryU10B Time-Resolved SpectroscopyU12A Soft X-ray MicroscopyU20 Photoelectron Spectroscopy

3-pole superconducting wiggler of 6T

Beam from bending magnet and superco

nducting wiggler

Monochromator of Si (111) double crystals

U7C XAFS station of NSRL

Side view of XAFS beamline at NSRL

159

5

43

2

Front end Differential segment Monochromatic system

1

6

7

8

10

1112

13 14

16 17

18

SuperconductingWiggler

ExperimentHutch

1. Handle valve 2. Water cooling mask 3. Pressure valve 4. Fast control valve 5. Separating diaphragm6. Beam stop 7. Pressure valve 8. Absorption Be window 9. Diaphragm 10. Pressure valve11. Entry slit 12. Flux monitor 13. Double crystal monochromator 14. Exit slit 15.Fluorescent screen16. Beam stop

Huber 420Goniometer

Huber9011Motor

Controller

HeidenhanND261Angle

Display

MikeEncoder

Oriel 18011Mike

EncoderController

Keithley

6517

Electrometer

IEEE488 RS232 RS232IEEE488

Computer

Q2

Keithley

6517

Electrometer

IEEE488

SR Light Sample

Q1

Printer- Plotter

Si(111)

Double-Crystal

Monochromater

Controlled Systems of U7C XAFS Beamline and Station

Table 1 Main performance parameters of U7C stationTest Results

Ring energyCurrentReceived Angle (H×V)：

0.8 Gev160 mA1× 0.1 mrad2

Monochromator： Si(111)double crystalBeam size： 12× 1 mm2

Resolution (E/E)： 3× 10-4

Energy range： 4.113.0 keVDetect system： N2/Ar mixed gas

Keithley Model 6517Electrometer

Qs1 Qs2SR

Sample

Computer

IEEE-488

Keithley 6517Electrometer

Keithley 6517Electrometer

Schematic diagram of detector system for charge measurement

Equivalent Circuit of Keithley 6517 Electrometer

XAFSPhoton energy 5–12 keVResolution 10-4@12 keVFlux 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

4000 6000 8000 10000 12000 14000

109

108

Flux Intensity of U7C Beamline at the Sample PositionFlux Intensity of U7C Beamline at the Sample Position

of Hefei National Synchrotron Radiation Laboratoryof Hefei National Synchrotron Radiation Laboratory

Pho

ton

Flu

x (

ph/

s )

Energy ( eV )

8500 9000 9500 100000.0

0.5

1.0

1.5

2.0

X-ray absorption spectrum of K edge for Cu foilX-ray absorption spectrum of K edge for Cu foil

Cu foil (NSRL)

x (

Arb

. Uni

ts )

Energy ( eV )

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

10800 11200 11600 12000 12400

Ge powder

Energy ( eV )

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

Comparison for the XAFS spectra of Cu foilmeasured in BSRF, KEK and NSRL laboratory

8500 9000 9500 100000.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Comparisons for the XAFS spectra of Cu foil

measured in BSRF , K EK and NSRL laboratory

Cu foil (N SRL )

Cu foil (KE K)

Cu foil (BSRF)

mx

( A

rb.

Uni

ts )

Energy ( eV )

1 Annealed crystallization of 1 Annealed crystallization of Ni-B and Ni-P Ni-B and Ni-P nano-amorphous alloys 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, 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.

PreparationPreparation

Chemical method:

KBH4, 2 mol/LKBH4, 2 mol/L

Ni(CH3COO)2 Ni(CH3COO)2 4H2O, 0.25 mol/L 4H2O, 0.25 mol/L

ice-water bath and vigorously agitated by a ice-water bath and vigorously agitated by a

magnetic stirrer. magnetic stirrer.

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

100 200 300 400 500 600

230oC

380oC325oC

360oC

300oC

NiB

NiP

dH

/ d

T

temperature (oC)

1.2 DTA profiles of NiB and NiP

30 40 50 60 70oooooo o

oo

oooo

c-Nic-Ni

3B

+

o

+ o

+ooo

ooo

ooo

o

(111)

2.0

3 A

(301)

1.6

1 A

(230)

1.6

8 A

(122)

1.7

2 A

(200)

1.7

6 A

(221)

1.8

5 A

(112)

1.9

3 A

(031)

1.9

7 A

(102)

2.0

2 A

(211)

2.1

2 A

(201)

2.2

3 A

(121)

2.3

5 A

(2

10)

2.4

2 A

Inte

nsi

ty (

arb

. units

)

773 K

673 K

623 K

573 K

473 KNi-B (initial)

2 (degree)

1.3 XRD results of NiB with different annealed temperatures

XRD spectra of NiP at different temperature

30 40 50 60 70

0.1

76 n

m

0.1

94 n

m

0.2

03 n

m

0.2

14 n

m

773 K

573 K

523 K

Ni-P(initial)

Inte

nsit

y /

a.u

2 / degree

-100

-50

0

50

100

150

Ni-B

Ni-B (initial)

473 K

573 K

623 K

673 K

773 K

Ni foil

1601208040

k3 (k

)

k ( nm-1 )40 60 80 100 120 140 160

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

Ni-P (initial)

573 K

473 K

673 K

773 K

Ni foil

(k)

k ( nm-1 )

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

0

500

1000

1500

2000

2500

Ni-P ( initial )

473 K

573 K

673 K

773 K

Ni foil

1.00.80.60.40.2FT

Am

plitu

de (

a.u

. )

Distance / nm

0

500

1000

1500

2000

2500

Ni-B ( initial )

473 K573 K

623 K

673 K

773 K

Ni foil

1.00.80.60.40.2

FT A

mpl

itude

( a

.u. )

Distance / nm

40 60 80 100 120 140

-40

-20

0

20

40

60

80

773 K

673 K

573 K

473 K

NiB(initial)

Ni-B3

FITTINGEXPERIMENT

K3

(K)

K(nm-1)

50 100 150

0

20

40

60

80

573K

773K

Ni-P (initial)

Ni foil

k3 (k

)

k (nm-1)

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 oC Ni-Ni 0.274 0.2410.001 11.01.0 0.69 3.3 -0.2 Ni-B 0.218 0.2150.001 2.70.2 0.46 0.34 -4.7Ni-P 25 oC Ni-Ni 0.271 0.2430.001 10.01.0 0.60 2.8 -2.9 Ni-P 0.223 0.2150.001 1.60.2 0.40 0.80 5.3Ni-B 300 oC Ni-Ni 0.255 0.2430.001 9.91.0 0.60 1.1 -0.9 Ni-B 0.218 0.2150.001 2.60.2 0.60 0.34 5.0Ni-P 300 oC Ni-Ni 0.258 0.2420.001 10.11.0 0.63 1.6 -1.3 Ni-P 0.222 0.2150.001 0.80.2 0.49 0.65 8.7Ni-B 500 oC Ni-Ni 0.249 0.2450.001 10.81.0 0.70 0.39 1.6 Ni-B 0.217 0.2150.001 0.30.2 0.56 0.23 -5.0Ni-P 500 oC Ni-Ni 0.255 0.2430.001 10.41.0 0.60 1.25 -2.8 Ni-P 0.225 0.2190.001 0.60.2 0.40 0.56 7.6Ni foil Ni-Ni 0.249 12.0 0.74 Average distance Rj=R0+σs R’s error=0.001 nm ， T’s error=0.0510-2 nm ， S’s error=0.110-2 nm 。

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.

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