Influence of Alkalis and Aging Time on the Electric and Dielectric Behaviours
of Geopolymers
Colloque Géopolymère – Nîmes 10/11 Octobre 2012
Jaroslav Merlar, Guillaume Renaudin, Arnaud Poulesquen, Fabien Frizon, Christine Taviot-Guého, Fabrice Leroux
ICCF, UMR CNRS n°6296, Université Blaise Pascal CEA, DEN, DTCD/SPDE/ LP2C and LCF1, Marcoule
Outline of the presentation: Geopolymer characterization Chemical composition and Long range order DRX
Some backgrounds in Electrochemical Impedance Spectroscopy Equivalent circuit Model and CPE
Nyquist representation and spectra refinement Impedance vs. T Activation Energy of Alkalis-Geopolymer Associated Fractal dimension
Dielectric behavior Cole-Cole and Argand representations
Relaxation Time of Alkalis-Geopolymer Pair Distribution Function Some first results
Conclusion
Geopolymer characterization
metakaolin Na1 Na2 K1 K2 Cs1 Cs2
Wt % Mol % Mol % Mol % Mol % Mol % Mol % Mol %
SiO2 54.4 63.2 SiO2 24.6 31.9 SiO2 26.1 35.8 SiO2 23.5 29.1
Al2O3 38.4 26.3 Al2O3 8.7 10.4 Al2O3 9.0 11.6 Al2O3 8.5 10.5
TiO2 1.6 1.4 Na2O 10.4 9.6 K2O 9.5 11.4 Cs2O 8.9 10.2
Fe2O3 1.3 0.6 TiO2 0.2 0.1 Na2O 0.3 0.1 Na2O 0.3 0.1
K2O 0.6 0.5 Fe2O3 0.2 0.2 TiO2 0.2 0.3 TiO2 0.3 0.3
MgO 0.2 0.3 K2O 0.2 0.2 Fe2O3 0.2 0.3 Fe2O3 0.2 0.2
Na2O 0.2 0.2 SO3 0.1 < 0.1 SO3 0.2 < 0.1 K2O 0.2 0.2
CaO 0.1 0.1 CaO 0.1 0.1 CaO 0.2 0.1 SO3 0.2 < 0.1
H2O* 1.9 7.4 MgO 0.1 0.1 MgO 0.1 0.1 CaO 0.1 0.1
ZrO2 < 0.1 < 0.1 ZrO2 < 0.1 < 0.1 MgO 0.1 0.1
Cs2O < 0.1 < 0.1 Cs2O < 0.1 < 0.1 ZrO2 < 0.1 < 0.1
H2O* 55.4 47.4 H2O* 54.3 40.3 H2O* 57.7 49.1
Al:Si 1:1.41 1:1.53 Al:Si 1:1.45 1:1.54 Al:Si 1:1.38 1:1.39
Al:M 1:1.19 1:0.92 Al:M 1:1.06 1:0.98 Al:M 1:1.05 1:0.97
Elemental chemical composition of the metakaolin used for the syntheses and the geopolymer samples determined by X-ray fluorescence and thermogrametric analysis
Mineralogical composition of the polymer samples extracted from Rietveld analyses
Phase Na1 (wt %)
Na2 (wt %)
K1 (wt %)
K2 (wt %)
Cs1 (wt %)
Cs2 (wt %)
Anatase TiO2
0.8 0.8 0.8 0.6 0.4 0.4
Quartz SiO2
5.6 5.0 5.7 5.1 3.6 3.9
Paragonite 2M1 NaAl3Si3O10(OH)2
4.2 3.4 - - - -
Trona Na2CO3·NaHCO3·2H2O
- 5.3 - - - -
Muscovite KAl3Si3O10(OH)2
- - 5.6 4.3 - -
Pollucite Cs2Al2Si4O12·2H2O
- - - - - 3.0
Geopolymer part 89.4 85.5 87.9 90.0 96.0 92.7
Rietveld plots relative to Cs1 sample (left) and Cs2 sample (right). Experimental and calculated patterns (a), difference curve (b) and Bragg peak position of silicon (c1; 5 wt % of internal standard), anatase TiO2 (c2), quartz SiO2 (c3) and pollucite Cs2Al2Si4O12·2H2O (c4).
Principle Application of a potential of weak sinosoidal signal Analysis of the recorded current (amplitude and dephasage) Re and Im parts of the complex impedance Z*. Frequency sweep in usually large frequency domain (here comes the Spectroscopic term of the method)
Some backgrounds in Electrochemical Impedance Spectroscopy
0 0 00
exp( )( )( ) exp( ) cos sin
( ) exp( )
E j tEZ Z j Z j
I I j t j
*( )
( ) '( ) ''( ) cos( ( )) sin( ( ))( )
S
UZ Z jZ j
I
)(
)(
)()(
1)(
*
*
**
*
I
U
C
j
YZ
PP
S
0
*
00
*
)(
)()('')(')(
C
C
C
jY
CZ
jj
PP
S
)(''
)('
)('
)(''))(tan(
Z
Z
0 1000 2000 3000
0
-1000
-2000
-3000
Z''
()
Z' ()
Experimental curve
Fitted curve
Impedance formalism
0 Hz∞ Hz
Equivalent circuit Model and CPE
0 10000 20000 30000 40000
0
-10000
-20000
-30000
-40000
0 1000 2000 30000
-1000
-2000
-3000
Z''
()
Z' ()
Z''
()
Z' ()
Experimental data
Fitted data (high frequencies)
Fitted data (low frequencies)
0.0 3.0x10-4
6.0x10-4
9.0x10-4
0.0
3.0x10-4
6.0x10-4
9.0x10-4
Y''
(S)
Y' (S)
Experimental data
Fitted data
Admittance formalism
0 Hz ∞ Hz
Z ’’
Z’
Nyquist representation and spectra refinement of Alkalis Geopolymer
The case of K-geopolymer
255 K 259 K
264 K 271 K
277 K 283 K
292 K
Resistivity vs. T Activation Energy of Alkalis-Geopolymer
Log
(s.T
) (S
.cm
-1.K
)
1000/T
Linear behaviour over a small T domain 3.4 < 1000/T < 4 Irreversible regime loss of conductive species and/or conductive path
Why: TGA
Resistivity vs. T Activation Energy of Alkalis-Geopolymer
Log
(s.T
) (S
.cm
-1.K
)
1000/T
s.T = S0.e-Ea/kT
Log (s.T) = Log s0 – Loge.Ea/kT
Ea = 0.53 eV
Ea = 0.46 eV
Ea = 0.31 eV
Ea = 0.66 eV
Ea = 0.48 eV
Ea = 0.32 eV
Associated Fractal dimension Lo
g K
1000/T
n
n = 1 – (2q/p) n = (Ds – 1)/2 From quasi-Euclidian to more fractal when T ↑
11
The dynamic range of Dielectric Spectroscopy Dielectric spectroscopy is sensitive to relaxation processes
in an extremely wide range of characteristic times ( 10 5 - 10 -12 s)
Broadband Dielectric Spectroscopy
Porous materials and colloids
Clusters Single droplets and pores
Glass forming liquids
Macromolecules
10-2 10-4 100 102 104 106 108 1010 1012
Time Domain Dielectric Spectroscopy
f (Hz) 10-6
Water
ice
Dielectric behavior Cole-Cole and Argand representations
Cs1
Na1
’
’ ’’
’’ M’’
M’’ M’
M’
M* = M’+jM” = 1/* = j..Z* (j2 = -1)
(M’ – (M - Ms)/2)2 + M”2 = ((M - Ms)/2)
2
DM = M - Ms is the dielectric relaxation strength
M’ ’
’’ M’’
Other representations Ta
n
Log f Log f
Tan
Cs1 Na1
Relaxation at peak maximum, .t = 1 Very different relaxation frequency dependences
tan = ’’/’ = M’’/M’
Relaxation Time of Alkalis-Geopolymer
Log
f
1000/T
Arrhenius representation: linear dependence
f = f0. e-Er/RT
Logf = Logf0 –Er/RT.Loge
Correlation Ea vs Er
Er (
eV)
Ea (eV)
Cs1
Na1
K1
Cs2
Na2
K2
Analyse de la fonction de distribution de paires (PDF)
Analyse de matériaux nano-granulaires, amorphes, de liquide
G(Å
-2)
à partir de données de diffusion des rayons X haute résolution collectées sur un diffractomètre de laboratoire (λ Ag = 0.5608 Å)
Accès directement: • à la distribution des distances
interatomiques, à différentes échelles
• à la taille des grains
Conclusion
Conductive and dielectric behavior Linear behavior below RT Effect of alkali and ageing on Ea and Er Less and less correlation between Ea and Er from Na Cs High frequency relaxation time Na Cs Mobility vs. Dielectric relaxation strength
Merci de votre attention