Photon Factory Activity Report 2005 #23 Part B (2006)
Materials Science

10C/2004G066

Structural Study of Nafion Film with Cu Ionby Small-Angle X-ray Scattering utilized with Anomalous X-ray dispersion EffectMasaaki SUGIYAMA*1, Takao
MITSUI2,1 Takashi SATO2, Yuji
SOEJIMA3, Kazuhiro 1HARA4,
5
1Hiroshi,
ORIHARA , Keiji ITOH , Kazuhiro MORI , Toshiharu FUKUNAGA
1
ResearchReactor Institute, Kyoto University, Osaka 590-0494, Japan
2
Graduate
Schoolof Engineering, Kyoto University, Kyoto 606-8501, Japan
3
Research and Development Center for Higher Education, Kyushu University, Fukuoka 810-8560,Japan4
Instituteof
EnvironmentalSystems,Kyushu
University, Fukuoka 812-8581, Japan
5
Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan

Experimental
Nafion 117 was used for the sample. Firstly, the Nafion
film was washed with HCl and ultra pure water to remove
remaining impurities. Then, the film was immersed into
the metal ion solution: we adopted two solutions, 0.1 M
CuCl2 aqueous solution (sample A) and 0.1 M CuCl2
ethanol solution (sample B). Finally, the samples wereencapsulated into the cell to prevent from the evaporationof the absorbed solvent.
The SAXS measurements sweeping the energy aroundthe Cu-K absorption edge were performed at BL10C ofPhoton Factory, synchrotron light facility in High Energy
Accelerator Research Organization (KEK), Tsukuba
Japan. The SAXS intensities were measured in the sweep
range of X-ray energy between 8.93-9.03 keV with anenergy step of 10 eV. The energy of the incident X-ray
was tuned with double monochromators of Si with aresolution δE/E=10-4. The scattering intensity wasaccumulated for 600 sec at each energy scanning step: thecorrections were made for absorption by the specimen
and for the decay of the orbit current of the synchrotron.

Intensity / a.u.

Results and discussion
As shown in Fig. 1, the scattering intensities of both
samples show enhancement just below the Cu-K
absorption edge (8.98 keV). It means that the scattering
contrast of the region including Cu ion becomes higher
because anomalous term of atomic form factor, f’, shows
negative divergence at the absorption edge. It isconsidered that the difference of the SAXS intensities andtheir enhancement between two samples originates fromthe difference of distributions of Cu ions in the samples.
The detailed analysis is now in progress.

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(a)

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Scattering vector / ÅIntensity / a.u

Introduction
Nafion film is used for a separator between electrodes
in a fuel cell. In the long term operation, the Nafion film
absorbs metal ions from an environment and its output
voltage deteriorates. In order to overcome this difficulty
and improve the electric property, we should know thedistribution of the metal ion in Nafon film.
Small-angle X-ray scattering (SAXS) is one of
powerful tools to observe a spatial fluctuation of electron
density with nano scale. However, it is difficult to findout the distribution of only a kind of atoms, such as Cu
ion, with a standard SAXS method. Here, we focus
attention on X-ray anomalous dispersion effect to solve
this problem: The anomalous atom drastically changes its
atomic form factor around the absorption edge. Therefore,
it is considered that the distribution of anomalous atoms
could be derived from the SAXS intensity using thiseffect. Based on this idea, we observed the change of theSAXS intensity of Nafion film with Cu ion by sweeping
the incident X-ray energy around the Cu-K absorptionedge.

0.6-1(b)

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Scattering vector / Å-1

Figure 1. SAXS intensities of samples A (a) and B (b).
Open and closed circle indicate the SAXS intensities at
8.96 keV and 8.98 keV, respectively. Cu-K absorption
edge is 8.98 keV.
*sugiyama@rri.kyoto-u.ac.jp

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