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

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