HAL Id: jpa-00219605
https://hal.archives-ouvertes.fr/jpa-00219605
Submitted on 1 Jan 1980
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
MÖSSBAUER SPECTRA OF IRON CONTAINING NAFION MEMBRANES
E. Bauminger, A. Levy, F. Labenski de Kanter, S. Ofer, C. Heintner-Wirguin
To cite this version:
E. Bauminger, A. Levy, F. Labenski de Kanter, S. Ofer, C. Heintner-Wirguin. MÖSSBAUER SPEC-
TRA OF IRON CONTAINING NAFION MEMBRANES. Journal de Physique Colloques, 1980, 41
(C1), pp.C1-329-C1-330. �10.1051/jphyscol:19801122�. �jpa-00219605�
JOURNAL DE PHYSIQUE
Colloque
C1,suppldment au n
O 1 ,Tome
41,janvier
1980,page
C1-329M~SSBAUER SPECTRA OF
I
RON CONTAIN1 NG NAFION MEMBRANESE.R. Bauminger, A. Levy, F. Labenski de Kanter, S . Ofer and C . Heitner-Wirquin
+
Racah I n s t i t u t e of Physics, the Hebrew University, Jemsalem, Israel.
*
Department of Inorganic and Analytical Chemistry, the Hebrew University, Jemsalem, Israel.Ion containing polymers have been i n t e n s i v e l y s t u d i e d i n r e c e n t years i n s o l u t i o n a s well a s i n t h e s o l i d s t a t e . The common property o f t h i s c l a s s of compounds i s t h e aggregation of t h e i o n s togeth- e r with t h e p o l a r solvent (water) i n t o c l u s t e r s o f various s i z e s i n t h e polymeric. matrix 111. Among t h e i o n containing polymers a r e a l s o t h e i o n ex- change membranes whose i n d u s t r i a l uses have r e c e n t - l y increased due t o improvement i n t h e i r proper- t i e s . One of t h e compn used membranes is Nafion
(perf luorosulfonic acid)
M6ssbauer experiments on Naf ion membranes co- ordinated w i t h f e r r i c c h l o r i d e have been performed i n o r d e r t o d i s t i n g u i s h between t h e d i f f e r e n t kinds of i r o n complexes, t o s t u d y t h e i r s t r u c t u r e and magnetic p r o p e r t i e s and t o estimate t h e s i z e o f t h e c l u s t e r s . For t h e s e measurements t h e hydrogen i o n s of t h e membranes were replaced by t e r v a l e n t i r o n
ions.
We r e p o r t h e r e t h e r e s u l t s o f measurements on t h r e e Nafion samples [provided by t h e courtesy of t h e P l a s t i c Department, Du Pont & Co.). One sample of equivalent weight 1100 (sample 1) was e q u i l i - b r a t e d i n a methanol s o l u t i o n and two samples o f equivalent weights of 1100 (sample 2) and of 1500
(sample 3) were e q u i l i b r a t e d i n aqueous s o l u t i o n s . The d e t a i l e d p r e p a r a t i o n s o f t h e s e membranes were previously described 121. S i m i l a r measurements have been c a r r i e d out on v i n y l p y r i d i n e copolymers by Meyer [31.
~ G s s b a u e r s p e c t r a o f sample 1 were measured between 0.05K and 80K and o f samples 2 and 3, be- tween 1.5K and 200K. Some of t h e s p e c t r a obtained with sample 1 a r e shown i n Fig. 1 , A t 85K t h e spectrum i s composed o f 2 doublets, one w i t h a quadrupole s p l i t t i n g o f 0.44t0.01 m / s and an i s o - n e r s h i f t o f 0.51+0.01 m/s, (isomer s h i f t s a r e
r e l a t i v e t o m e t a l l i c i r o n ) w i t h r e l a t i v e i n t e n s i t y of G O % , t h e o t h e r with a quadrupole s p l i t t i n g o f 1.68+-0.02 mm?s and an isomer s h i f t o f 0.56+0,02 m/s with r e l a t i v e i n t e n s i t y of %20%. A t 4,lK and
lower temperatures t h e r e l a t i v e i n t e n s i t y of t h e f i r s t doublet (subspectrum A) decreases and a mag- n e t i c a l l y s p l i t spectrum (subspectrum B) appears
i n s t e a d . Fig. 2 shows t h e d i s t r i b u t i o n i n t h e values o f t h e hyperfine f i e l d s i n subspectrum B.
I
VELOCITY (mm/sec)
Fig. 1.
-
~ S s s b a u e r s p e c t r a o f 5 7 ~ e i n Nafion, equi- l i b r a t e d with methanol. The s o l i d l i n e s a r e l e a s t squares computer f i t s t o t h e s p e c t r a , assuming 2 quadrupole doublets and a magnetically s p l i t spec- trum with a d i s t r i b u t i o n o f hyperfine f i e l d s given by N(H) = N ~ / [ ~ + [ ( H - H ~ ) / A H ] ~ ] , where AH i s d i f f - e r e n t f o r H>Ho and H<Ho.The r e l a t i v e i n t e n s i t y of t h e second quadru- pole s p l i t subspectrum (C) i s ~ 2 0 % a t a l l tempera- t u r e s . Subspectrum C i s a t t r i b u t e d t o iron-dimers
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19801122
C1-330 JOURNAL DE PHYSIQUE
w i t h a n t i f e r r o m a g n e t i c coupling and t o t a l s p i n ze- r o [4]. The temperature dependence o f s u b s p e c t r a A and B i s c h a r a c t e r i s t i c o f superparamagnetic p a r t i c l e s 151. Subspectra A and B correspond t o i r o n containing c l u s t e r s with non uniform s i z e s . A t each temperature, c l u s t e r s with s i z e s smaller than a c r i t i c a l s i z e y i e l d magnetically u n s p l i t s p e c t r a and c l u s t e r s l a r g e r than t h e c r i t i c a l s i z e , y i e l d magnetically s p l i t s p e c t r a .
o im 200 m w MO
HYPERFINE MUlETlC FIELD (KO )
Fig. 2.- D i s t r i b u t i o n o f hyperfine f i e l d s i n sam- p l e 1. The a r e a o f t h e r e c t a n g l e s r e p r e s e n t t h e i n t e n s i t i e s o f s u b s p e c t r a A.
Fig. 3 . - Ratio (%) between t h e i n t e n s i t y o f sub- spectrum A and t h e sum o f t h e i n t e n s i t i e s of sub- s p e c t r a A and B, a s a function of temperature.
The d i s t r i b u t i o n of t h e s i z e s o f t h e aggregates can be deduced from t h e d a t a i l l u s t r a t e d i n Fig. 3, using t h e formula derived by ~ e i l 161 f o r t h e r a t e a t which t h e magnetization changes d i r e c t i o n : f = f o expc-CV/kT). V is t h e volume o f t h e aggre- g a t e , f o and C a r e c o n s t a n t s c h a r a c t e r i s t i c o f t k e m a t e r i a l . Fig. 4 shows t h e d i s t r i b u t i o n o f t h e d i -
ues of f o and C a r e t h e same a s i n Fe2O3 [5], a
0
value o f ~ 2 0 A i s derived f o r d i n Fig. 4. A v a l -
0
ue of d=16A i s derived using t h e c o n s t a n t s given by Coey e t a l .
[ T I .
DIAMETER
Fig. 4 . - D i s t r i b u t i o n o f c l u s t e r diameters i n sample 1.
The s p e c t r a of samples 2 and 3 do n o t change between 4 . 1 and 1.5K and even a t 85K t h e y a r e com- posed o f t h r e e subspectra (A,B,C) w i t h t h e same parameters a s those o f sample 1, except t h a t t h e h y p e r f i n e f i e l d i s about 10% h i g h e r (58515 kOe).
The f a c t t h a t even a t 85K, p a r t o f t h e s p e c t r a is s p l i t , shows t h a t t h e s e samples contain i r o n ag-
o
gregates with d*80A. In sample 2, about 2/3 o f t h e i r o n i o n s which a r e n o t i n dimers, a r e i n ag-
o
g r e g a t e s with a diameter o f *80A and 1 / 3 of them
0
a r e smaller than 15A. In sample 3, about 50% have
0 0
diameters of %80A and %SO% a r e s m a l l e r than 15A.
Conclusions: In t h e Nafion samples examined two kinds o f i r o n s p e c i e s a r e present: (1) c l u s t e r s .
C2) dimers, In t h e sample e q u i l i b r a t e d with me- t h a n o l , t h e mean diameter o f t h e c l u s t e r s i s %20;.
I n t h e water e q u i l i b r a t e d samples, t h e r e a r e l a r g e
0 0
c l u s t e r s , (*80A) and small c l u s t e r s (115A).
REFERENCES
[ll
GIERKE, T.D., The Electrochemical Society Veeting, October 1977, A t l a n t a , Georgia.121 HEITNER-WIRGUIN, C . , Polymer
2
(1979) 371.[3] YEYER, C.T., J. de Physique,
37
(1976) C6-777.141 LECFWJ, R . , NICOLINI, C . , ABELEDO, C.R.,
FRANKEL, R.B., J. Chem. Phys.
59
(1973) 3138.[5] KUNDIG, W . , BOWEL, H., CONSTABARIS, G . , LINDnUIST, R.H., Phys. Rev. 142 (1966) 32.
16) N E ~ L , L . , Ann. Geophysique
5
(1949) 99.1 7 1 COEY, J . Y . , READMAN, P.W., Earth and Planetary Science L e t t e r s
21
(1973) 45.ameters o f t h e aggregates. Assuming t h a t t h e v a l -
