NUCLEATION AND GROWTH OF CUBIC ICE IN LiCl.n D2O GLASSES

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NUCLEATION AND GROWTH OF CUBIC ICE IN LiCl.n D2O GLASSES

A. Elarby Aouizerat, J. Jal, J. Dupuy, P. Chieux, A. Wright, R. Parreins

To cite this version:

A. Elarby Aouizerat, J. Jal, J. Dupuy, P. Chieux, A. Wright, et al.. NUCLEATION AND GROWTH

OF CUBIC ICE IN LiCl.n D2O GLASSES. Journal de Physique Colloques, 1982, 43 (C9), pp.C9-205-

C9-208. �10.1051/jphyscol:1982936�. �jpa-00222465�

N U C L E A T I O N AND GROWTH OF C U B I C I C E I N L i C 1 , n D 2 0 GLASSES A. Elarby Aouizerat, J.F. Jal, J. Dupuy, P. Chieux*, A. right* and R. Parreins**

De'partement de Physique des Mate'riaux, L. A. 172, Lyon ViZZeurbanne, France

* I n s t i t u t Laue-Langevin, 156X, 38 0 4 2 GrenobZe Cedex, France

**Laboratoire de Physique des Me'taux, UniversZte' du Languedoc, !4onontpeZZier, France

RBsumB

-

On a dtudie par diffusion de neutrons la nucleation contr6lee de la glace dans les Qchantillons vitreux m6tastables LiC1.n D20. On a pr6cis6 les conditions de formation de la glace cubique Ic et de sa transformation en glace hexagonale. La structure de la phase ddsordonnee restante a &tQ utilisQe pour obtenir la concentration de la matrice vitreuse durant les diverses Qta- pes de la prQcipitation. On a observ6 une modification importante de la struc- ture desordonn6e pendant la nuclQation.

Abstract - The controlled nucleation of ice in metastable LiC1.n Dz0 glassy samples has been followed by neutron scattering. The conditions were determi- ned for cubic ice Ic nucleation as well as for its transformation to hexagonal ice. The structure of the remaining disordered phase has been used to follow the glassy or supercooled matrix concentration along the various steps of the precipitation. A strong modification of the disordered structure is observed in the nucleation stage.

Concentrated ionic solutions of LiCl in Hz0 or D20 present a low temperature glassy state with a glass transition temperature Tg around 139K (H20) or 142K (DzO). This Tg value is concentration dependent at very high salt concentrations i.e.above the eutectic composition. The same trend is observed in other aqueous solutions of MX or lfX2 salts [I]. At salt mole fractions between about9 %to 14 %, the LiC1.n D20 glasses are metastable and various low temperature immiscibility domains have been postulated in the past [2,3]. The phase diagram given in Fig. 1 is, however, now generally ac-

cepted. Its main feature is the repre- sentation of the homogeneous nucleation temperature Th for ice crystallization as a function of concentration as ob- tained from microemulsion experiments [ 4 ] . A metastability criterion (Th

-

Tg) /Tg is thus defined and confirms the trend to ice crystallization at lower concentrations.

1

Small angle neutron scattering experi- _{- .} ments have given a direct insight into the structural aspects of the crystal- lization process. In agreement with

7 : ⁷ : : ? , ? a ! wl

, O

+

^{k ; I i h.}

10 20 tl

mole % LiCl C'

d' s.

0:

b l

Fig. 1

hat has been observed recently on some igh temperature cordierite glasses [5]

he nucleation and growth of the ice rys~allites in the metastable domain epends on the thermal history of the mple. In particular, the annealing E the sample at temperatures just elow Tg allows the control of the

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1982936

C9-206 JOURNAL DE PHYSIQUE

n u c l e i s i z e s and t h e i n t r o d u c t i o n of p e r i o d i c i t y e f f e c t s i n t h e i r d i s t r i b u t i o n [6].

E l e c t r i c a l c o n d u c t i v i t y measurements have a l s o proved t o be a very s e n s i t i v e method f o r t h e d e t e c t i o n of t h e f i r s t s t a g e s of t h e n u c l e a t i o n and t h e sample c h a r a c t e r i z a - t i o n . The c o n d i t i o n s of e q u i v a l e n t annealing treatment have i n t h i s way been d e t e r - mindd f o r d i f f e r e n t s a l t concentrations[7].

2. Comments on t h e s t r u c t u r e of t h e d i s o r d e r e d m a t r i x . The s t r u c t u r e f a c t o r of c o n c e n t r a t e d s o l u t i o n s of LiCl i n D20 h a s a l r e a d y been i n v e s t i g a t e d i n d e t a i l [ 9 , lo]. Non-corrected i n t e n s i t y c u r v e s such a s seen ' 0 2 4 6 k(fi~) on t h e f i g u r e 2, bottom, a r e s u f f i c i e n t f o r our pur-

pose. I d e n t i c a l p a t t e r n s have been obtained i n t h e l i q u i d s t a t e a t raom temperature (we n o t e t h a t t h e Fig. 2 low a n g l e belongs t o t h e background).

1 . I d e n t i f i c a t i o n of t h e I c e Phases.- A t c o n c e n t r a t i o n s around o r lower t h a n 8 % (mole f r a c t i o n LiCl/LiCl + D20) t h e s t a b i l i t y c r i t e r i o n i s l a r g e and c r y s t a l l i z a t i o n i s unavoidable f o r cooling r a t e s of about one degree p e r second ( i - e . l i q u i d Nitrogen quench). It has been observed by neutron d i f f r a c t i o n on t h e high f l u x powder d i f f r a c - tometer D2 a t I.L.L. Grenoble t h a t under t h o s e circumstances it i s t h e hexagonal i c e I h which i s formed.

A t high-e-r--concentration , around 10 %, t h e m e t a s t a b i l i t y index i s weaker and c r y s t a l - l i z a t i o n i s n o t d e t e c t e d d u r i n g t h e quench. The nu-

A c h a r a c t e r i s t i c f e a t u r e of t h o s e curves ( s e e f i g u r e 3 ) i s t h a t t h e main peak of t h e s t r u c - t u r e i s much more c o n c e n t r a t i o n dependent i n t h e g l a s s y s t a t e a t 13YK t h a n a t room temperature.

The temperature e f f e c t s on t h e peak p o s i t i o n seem of o p p o s i t e s i g n s on each s i d e of a concen-

k(Aill

2 0 ^{, A T-20°C , ,}

^{:A: : ,-;}

t r a t i o n of about 14 %. This allows a f a s t iden-

*,~;,39K

t i f k a t i o n of t h e microscopic s t r u c t u r e of t h e ^{1 9} remaining d i s o r d e r e d phase along w i t h every

s t e p of t h e c r y s t a l l i z a t i o n p r o c e s s . The crys- ^{1 6} ₉ 10 1 1 12 13 14 15 16

t a l l i n e i c e peaks a r e s u f f i c i e n t l y rcr-ote from Moles % L E I . D ~ O

t h e d i s o r d e r e d s t r u c t u r e main peak a s not t o i n t e r f e r e .

F i g . 3

c l e a t i o n and growth of t h e i c e i s c o n t r o l l e d by t h e sample thermal t r e a t m e n t and i n p a r t i c u l a r , by t h e c h o i c e of t h e annealing c o n d i t i o n s . The f i r s t crys- t a l l i t e s corresponding t o a volume f r a c t i o n of one p a r t per thousand, a r e d e t e c t e d a few degrees above Tg and i t w i l l r e q u i r e s e v e r a l degrees more t o achi- eve f u l l i c e p r e c i p i t a t i o n [8]. The i n t e r m e d i a t e s t a g e s of t h e p r o c e s s a r e e a s i l y f r o z e n , i f n e c e s s a r y . The i c e h a s now t h e c u b i c I c s t r u c t u r e ( s e e F i g . 2) w i t h a v e r y s l i g h t I h contamination depending on t h e thermal h i s t o r y . The t r a n s i t i o n temperature from I c t o I h and i t s sharpness depend on t h e sample thermal t r e a t m e n t . For c o n c e n t r a t i o n of 10 % and 10.5 % t h e y occur around 152-160 K.

A rough e s t i m a t e of t h e s i z e of t h e c r y s t a l l i t e s i s made from t h e FWHM of some c h a r a c t e r i s t i c d i f f r a c t i o n peaks [ll]

.

There i s a c o r r e l a t i o n between t h e c u b i c s t r u c t u r e and small s i z e s , say < 200 8 .

1(103)

5

l o 5

lo-

A t t h e mole f r a c t i o n of 8 Z i t i s found t h a t t h e peak p o s i t i o n of t h 6 remaining d i s o r d e r e d phase corresponds t o t h e 16.5 % c o n c e n t r a t i o n , i . e . t h e composition of LiC1.5 D2C(as r e a d on Yigure 3 from a peak p o s i t i o n of 2.05

LlCl . D 2 0

c70:L

A

^t36K

concentration of the disordered phase is

~(a-l)

^A. amealed A O non-annealed

retained to values lower than 16.5 %,

which means that all the free water is not I 2.1 LiCL D,O

ture main peak shifts progressively

K (A-'1 up to a concentration near 16.5 %

( A )

which i s attained at a temperature

2.1 - LtCL D 2 0 where the crystallites become larger

yet involved in the precipitation. ^-/;

1

^5.01

I

A 14 - 2.0-

- i

-

I - /

I

At the concentration of 14 % there is no detectable ice crystallization and an ex-

tremely small change of the disordered 10

,

^, ,

l3;

structure peak position with temperature. %

P-

However, at that concentration, the tempe-

,--LI--..---- ^,

^{--,,f 200}

rature and concentration effects play in C r - r -

opposite direction and a careful data ana- 100

lysis should be made before deciding defi- 140 150 160 nitely that no change occurs in the disor- T ( " K )

dered matrix.

Fig. 5

and the transition from cubic to he- xagonal ice starts (see figure 4).

300

At the concentration of 10.5 % has -200 been studied the effect of annealing

at 139K on the structural properties.

Annealing tends to favor small ice nu-

Quantitative estimates of the volume of ice precipitated are presently being made in order to make a quantitative correlation between the microscopic concentration change of the matrix as detected here and the amount of ice formed, at every inter- mediate step of the process.

140 150 160 clei and the cubic phase and shifts to pK ) higher temperature the transition to

larger crystallites sizes (Figure 5).

This trend is in agreement with the Fig. 4 visible light transmission experiments

1121. It is again seen that as long as the nuclei are small (i.e. less than about

200 8) and the cubic ohase favored. the

3. The first stages of the nucleation as observed from the structure of the disordered matrix.

For the non annealed 10 % concentration significant modifications in the glassy - structure at temperatures (143K) near Tg, before any crystallization is detected have been observed (see Figure 6). In a first approximation the structure change might be described as a 10 % drop in in-

-1 0 tensity which is extremely difficult to

interpret by a simple density effect in the thermal treatment. One must think of +(143K(lh)-136K) a more orofound structural modification.

-201 I I I I and indeed a small peak shift correspon- 0

2

4 k ding to a concentration change from 10 to

1 1 % is observed (see Figure 4). The sys- tem behaves as if part of the water mole- Fig. 6 cules had disappeared from the scattering

C9-208 JOURNAL DE PHYSIQUE

pattern, but were not yet regrouped in detectable ice crystallites.

In summary, an analysis of the disordered structure of the glassy or supercooled matrix gives very interesting complementary informations on the process of ice precipitation in the LiCl D 0 system. It permits the confirmation of the kinetics of ice precipitation of the thermal treatment. Under the conditions of cubic ice 2 formation, the precipitation seems to be completed only when the transformation to the hexagonal phase or to the large crystallites has started. A strong modification of the disordered structure is observed in the nucleation stage. This effect should be further investigated since it raises important questions on the low temperature structural and dynamical properties of this system [13].

References

[I]

Angell C.A., Sare J.E., J. Chem. Phys. z(3) (1970) 1058-1068.

21 Angell C.A., Sare J.E., J. Chem. Phys. 49 (1968) 1713.

33 Hsich S.Y., Gammon R.W., Macedo P.B., tlztrose C. J., J. Chem. Phys. - 56 (1972) 1663.

[4] Kanno H., Angell C.A., J. Phys. Chem. 31 (1977) 2639 ;

Angell C.A., Sare J.E., Donnella J., ::z~arlane D.R., J. Phys. Chem.

85

⁽¹⁹⁸¹⁾

1461.

[5] Wright A., Talbot J., Fender B.E.F., Nature

277

(1979) 366.

[s]

Dupuy J., Chieux P., Calemczuk R., Jal J.F., Ferradou C., Wright A., Angell C.A., Narure 296 (1982) 138.

[7] Angell

m.,

MacFarlane D.R., J. Phys. Chem. (to appear).

p]

Elarby A., Jal J.F., Dupuy J., Chieux P., Wright A., Parreins R., J. Physique

-

Lettres 43 (1982) L-355.

[ 9

] Narten AZ., Vaslow F., Levy H.A., J. Chem. Phys. z(11)(1973) 5017.

[lo]

Newsome J.R., Neilson G.W., Enderby J.E., J. Phys. C - 13 (1960) L923

[lljArnold G.P., Finch E.D., Rabideau S.W., Wenzel R.G., J. Chem. Phys. - 49 (10) (1966) 4365.

[12] Ferradou C., Reports No 1 and No 2.

[13] Baianu I.C., Boden N., Lightowlers D., Itortimer M., Chem. Phys. Lett. %(I) (1978) 169.