chemical compatibility of structural materials with liquid li and sn-li · 2016. 6. 26. ·...

Chemical Compatibility of Structural Materials with Liquid Li and Sn-Li

S. Sharafat and N. M. Ghoniem

The University of California at Los Angeles (UCLA)Los Angeles, CA. 90095-1597, USA

APEX Meeting

Argonne National Laboratory

May 10-12, 2000

5/15/00 APEX - ANL-Meeting 2

PRESENTATION OUTLINE

• Data Base of Sn-Li:

– Thermo Physical Data for Sn

– Thermodynamic Data for Sn, Li-Sn

• Thermodynamics of Dissolved Solutes in Sn-Li

• Chemical Stability of Oxides, Carbides, Nitrides, and Hydrides.

• Uncertainties and Conclusions


Sn-Li Data Base

• An extensive database for Sn-Li has been compiled.• Database includes:

– Thermo Physical Properties:• Viscosity, Surface Tension, Heat Capacity, Compressibility,

etc…

– Thermodynamic Properties:• Enthalpy, Specific Heat, Entropy, Vapor Pressure.• Heat of dissociation, reaction enthalpies, ionization potentials

of various Tin-compounds.• Sn-H, Sn-O, Sn-C Systems.

• Full report is in preparation.


Vapor Pressure of Sn, Sn-Li 25, and Li

1.E-10

1.E-08

1.E-06

1.E-04

1.E-02

1.E+00

1.E+02

1.E+04

6 8 10 12 14

10-4/T (1/K)

Li[BCSS, 1984]

Sn[Kelly, 1935]

Li over Sn-Li25[APEX, 1999]

833 K1000 K1250 K


Sn-Li Phase Diagram

• For Sn-Li 25at.% the minimum operating temperature has to be 330oC to avoid formation of stableintermetallic compounds:

LiSn and Li2Sn5.

• Recent measurements* put the exact melting temperature at 334oC.

• Minimum operating temperature of the Sn-Li25 (at%) is 350oC.

*K. Natesan, W. E. Ruther, DOE/ER-0313/27

25 at.% Li


Chemical Activity of Li and Sn in Sn-Li

• Existence of stable intermetallics indicates low Li and Sn activity (aLi, aSn) in some temperature ranges.

• For Sn-Li the activities have been reported[1] at 1200oC:

[1] APEX-Interim Report, Nov. 1999

Li (at.%) Li-Activity Sn-Activity0.1 0.001 0.8950.2 0.003 0.7580.3 0.010 0.4860.4 0.020 0.3320.5 0.038 0.1940.6 0.078 0.0780.7 0.186 0.01550.8 0.354 0.002160.9 0.739 2.57E-05


Derivation of the Activity-Temperature-Composition Relationship for Li in Sn-Li

• Activity-temperature relationship for Sn-Li is expressed as:

ln aLi = A + B/T (1)

– Given activity-composition relationship for Sn-Li at 1200oC is:

ln aLi = - 8.1442 + 14.097 xLi - 11.371 xLi2 + 6.0259 xLi

3 (2)

– Given the activity-composition relationship for Pb-Li data [1]:(3)

• Determine coefficient B for Sn-Li using (1), (2), and (3):x_Li 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

A -0.52 -0.15 0.415 1.058 1.652 2.109 2.284 2.068 1.346B 769 222 -611 -1558 -2433 -3107 -3364 -3046 -1983

x_Li 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9A -0.52 -0.15 0.415 1.058 1.652 2.109 2.284 2.068 1.346

[1] Huberstey, JNM 247(1997)


Activity-Temperature-Composition Relationship for Li in Sn-Li

Li activity decreases with decreasing Li fraction and decreasing temperature.


Thermodynamics of Dissolved Solutes in Sn-Li

• Activity of solute (O, C, N, H) is calculated for saturated solutions under equilibrium conditions.

• For the chemical reaction:

where ∆fGo is the standard Gibbs Free Energy of formation given by:

∆fGo(Li2O) = RT ln Ke = RT ln { aLi2O/a2Li ·aO}

• The activity of oxygen and the other three non-metal solutes (C, N, H) can be calculated using the standard free energy of formation:

ln aO = {−∆fGo(Li2O)/RT} - 2 ln aLi

• Data for the Gibbs Free Energy of Formation of Li2O, Li2C2, Li3N were found in the JANAF tables.

OLiLiSnOLiSnLiOLiGo

f

2

)( 2

)()(2∆

→−+−


Gibbs Free Energy of Formation of Lithium-Salts*

∆G of Formation* (kJ/mol)Temp (K) Li2O LiH Li3N Li2C2

100 -592.392 -81.828 -150.597200 -584.794 -75.511 -140.16300 -561.875 -68.309 -128.417 -66.538400 -549.456 -60.718 -116.192 -69.576500 -536.272 -52.628 -102.781 -73.493600 -522.248 -44.103 -88.148 -78.066700 -508.198 -35.611 -73.556 -83.528800 -494.187 -27.233 -59.146 -89.782900 -480.247 -19.023 -45.008 -96.7451000 -466.401 -11.022 -31.203 -104.351100 -452.666 -3.261 -17.779 -112.5421200 -439.054 4.233 -4.769 -121.7751300 -425.574 11.441 7.799 -130.5131400 -412.23 18.345 -140.2251500 -399.026 24.929 -150.3821600 -385.961 -160.9621700 -358.681 -164.7691800 -328.002 -167.1921900 -297.541 -170.0252000 -267.29 -173.252

"JANAF Thermochemcial Tables," J. Phys. Chem. Ref. Data, Vol. 14, Suppl. 1, 1985

∆G(Li2O) = 5.109¥10-8 ¥ T3 - 1.286¥10-4¥T2

+ 2.282¥10-1 ¥ T - 6.208¥102

(100<T<2000 K)

∆G(LiH) = -1.474¥10-8 ¥ T3 + 3.285¥10-5 ¥ T2

+ 5.922 ¥10-2 ¥ T - 8.841 ¥101

(100<T<1500 K)

∆G(Li3N) = -3.549¥10-8 ¥ T3 + 8.109¥10-5 ¥ T2

+ 8.320 ¥10-2 ¥ T - 1.598 ¥102

(100<T<1300 K)

∆G(Li2C2) = 4.026¥10-8 ¥ T3 - 1.419¥0-4 ¥ T2

+ 7.573 ¥10-2 ¥ T - 7.956 ¥101

*JANAF-Tables (300<T<2000 K)

Polynomial Fits to ∆G (kJ/mol):


• Activity of O in saturated solutions: ln aO = {-∆fGo(Li2O)/RT} –2 ln aLi

Oxygen activity is low (ln aO is large and negative) throughout the composition and temperature range:Li2O formation is favored

Activity-Composition-Temperature Relationship of Li2O in Sn-Li

Oxygen activity increases with decreasing Li activity and withincreasing temperature (see Slide 15)

Activity-Temperature-Composition Relationship for Oxygen in Sn-Li


Activity-Composition-Temperature Relationship of Li2C2 in Sn-Li

Stable

Li2C2 Unstable

Stable Formation of Li2C2

(Dissolution of

Carbide Coatings)

Li2C2 Unstable

• Carbon activities increase above unity (from – to + with decreasing Li fraction)

• Hence Li2C2 is not stableand decomposes

• Activity of C for saturated solutions:

ln aC = {-∆fGo(Li2C2)/RT} –2 ln aLi

Activity-Temperature-Composition Relationship for Carbon in Sn-Li

Carbide-Coatings are resistant to dissolution


• Nitrogen activities are positive for almost all of the Li-fraction and temperature ranges of interest.

• Hence Li3N is not stable and decomposes

Stable

Li3N Unstable

Li3NFormation

Unstable Region(Li3N Formation Suppressed;

Nitride-Coatings are resistant to dissolution)

Activity-Composition-Temperature Relationship of Li3N in Sn-Li

• Activity of N for saturated solutions:

ln aN = {-∆fGo(Li3N)/RT} –2 ln aLi

Activity-Temperature-Composition Relationship for N in Sn-Li


• Hydrogen activities are positive for almost all of the Li-fraction and temperature ranges of interest.

• Hence LiH is not stable and decomposes

Unstable Region(LiH Formation Suppressed)

Stable

Activity-Composition-Temperature Relationship of LiH in Sn-Li

• Activity of H for saturated solutions:

ln aH = {-∆fGo(LiH)/RT} –2 ln aLi

Activity-Temperature-Composition Relationship for H in Sn-Li


0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

-60

-50

-40

-30

-20

-10

0

10

20

Ac tivity-Compos ition Relations hip For S a tura ted S o lutions

Lithium Fra c tion, xLi

ln a

ctiv

ity

T = 500oC

ln aLiln aO

ln aH ln aN

ln aC

Activity-Composition Relationship for Saturated Solutions of O, H, N, and C at 773 K

ln aLi

ln aO

ln aH

Non-metals formincreasingly stable salts(i.e.,Li2O)

Non-metals are increasingly in solution (Salts:LiH, Li2C2,Li3N dissolve)


0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

-60

-50

-40

-30

-20

-10

0

10

20

Ac tivity-Compos ition Relations hip For S a tura ted S o lutions

Lithium Fra c tion, xLi

ln a

ctiv

ity

T = 1000oC

ln aLiln aO

ln aH ln aN

ln aC

Activity-Composition Relationship for Saturated Solutions of O, H, N, and C at 1273 K

ln aLi

ln aO

ln aH

ln aLi

ln aH

Non-metals formincreasingly stable salts(i.e.,Li2O)

Non-metals are increasingly in solution (Salts:LiH, Li2C2,Li3N dissolve)


Thermodynamic Modeling of Chemical Stability of Coatings and Alloying Phases in Li and Sn-Li

• Assess the chemical viability of oxide coatings in liquid Sn-Li, based on the free energy (∆rG) changes of reactions :

where is the standard free energy of formation of the metal oxide, and is the solute (oxygen) free energy.

the oxide formation energies are taken from the JANAF tables (Slide 10)

however, the solute free energy has to be evaluated.

∆−−=∆

+−→−

)()()1(

)(

yxo

fOr

LiSnliquid

yx

OMGLiSnGyxG

xMLiSnOyOM

)( yxo

f OMG∆ )(___

LiSnGO −

)( yxo

f OMG∆

)(___

LiSnGO −


Solute Free Energies in Sn-Li

• Expression to evaluate the solute (oxygen) free energy in Sn-Li :

•where :

and: is the the partial free energy of dissolved lithium

*2

**

ln)(2)(

lnln

ln)(

OOLio

f

OOO

OO

xxRTLiGOLiG

xxRTaRT

aRTLiSnG

+−∆=

+=

=−

*Oa : oxygen activity at saturation

Ox : oxygen concentration*Ox : oxygen concentration at saturation

LiG___

)ln(___

LiLi aRTG =

Need the solubility data for non-metals in Sn-Li.Need the solubility data for non-metals in Sn-Li.


Solubility of Non-Metals in Sn-Li

• The solubility of oxygen is very low in Sn:

– At 536, 600, and 700°C the solubility limit are 6 ¥ 10-6, 2 ¥10-4, and 6 ¥ 10-4 at. %, respectively [1],

– and, the solubility of oxygen in Pb-Li is very low [2].

• Therefore, we take the solubility of oxygen in Sn-Li also to be very low and express it by the well established solubility expressions in Li [3]:

ln xO = 1.428 – 6659 (T/K)-1

ln xN = 2.976 – 4832 (T/K)-1

ln xC = – 1.100 – 5750 (T/K)-1

Of the four lithium salts (LiH, Li3N, Li2C2 , and Li2O) only Li2O is sufficiently stable to be formed in Sn-Li, the others decompose to saturated non-metal in solution:

[ is increasingly negative (see Slide 14-15) ]

Of the four lithium salts (LiH, Li3N, Li2C2 , and Li2O) only Li2O is sufficiently stable to be formed in Sn-Li, the others decompose to saturated non-metal in solution:

[ is increasingly negative (see Slide 14-15) ]LiG___

[1] T. N. Belford Trans. Faraday Soc. 61 (1965)

[2] M. G. Barker , Liquid Metal. Engr. (1984)

[3] p. Hubberstey, Liquid Metal Systems


Thermodynamic Modeling of Chemical Stability of Coatings in Sn-Li

• Because of the low oxygen solubility in Sn-Li, oxygen will be maintained at the saturated level (regardless of the purification);

• And, because the lithium salts LiH, Li3N, Li2C2 decompose readily (at xLi < 0.65; T=500oC), a simplified expression can be derived for the solute free energies:

which is valid for all four salts.

• The free energy change of reactions for all four salts ((LiH, Li3N, Li2C2 , and Li2O)* can now be expressed as:

*Replace Li2O with the other salts

)(2)()( 2 LiGOLiGLiSnG Lio

fO −∆=−

[ ]{ })()(2)(1

2 yxo

fLio

fr OMGLiSnGOLiGyx

G ∆−−−∆=∆

Slide#21GLi=RT ln aLi (Slide # 7,10)Slide#10


Gibbs Free Energy of Formation

• The free energy of formation of some oxides, carbides, and nitrides at 773 K [1].

[1] JANAF-Tables

Oxides ∆Gf(kJ/mol)Li2O -497.3Al2O3 -1432.6Cr2O3 -927.7Fe2O3 -617.4Sc2O3 -1679Y2O3 -1678.8La2O3 -1570.4Ce2O3 -1568.4B2O3 -1072.5SiO2 -770.3TiO2 -802.5ZrO2 -952.3HfO2 -974.1CeO2 -924.9NiO -168.9BeO -533.1MgO -517.4CaO -554.1LiAlO2 -1024.4LiCrO2 -809.2Li2Si2O5 -2183.5Li2SiO3 -1408.4Li4SiO4 -1963.1Li8SiO6 -2963.9

Nitrides ∆Gf(kJ/mol)BN -206.1AlN -219.2Si3N4 -489.1TiN -263.7ZrN -291.6VN -150.2TaN -187.6CrN -61.6

Carbides ∆Gf(kJ/mol)SiC -73TiC -175ZrC -189.4NbC -134.6TaC -141.3


Change in Gibbs Free Energy of Reaction of Oxides in Sn-Li at 773 K

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-500

-400

-300

-200

-100

0

100

200

300

400

S n-Li Compos ition (Li) (x10)

Gr (

kJ/m

ol)

Oxides G ibbs F re e E nergy of Reac tion in S n-Li a t 773 K

Al2O3 Cr2O3 Fe2O3 S c 2O3 Y2O3

∆

Increasingly

Unstable

(decomposition)

Increasingly

Stable Coating

Sn-Li 25

Sn-Li Composition (Li fraction)


0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-400

-300

-200

-100

0

100

200

300

400

ZrO2 HfO2 CeO2 NiO BeO


∆G (

kJ/m

ol)

Sn-Li (Li at% fraction)

Increasingly

Unstable

Increasingly

Stable Coating




0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-200

-150

-100

-50

0

50

100

150

200

250

300

La2O3 Ce2O3 B2O3 S iO2 TiO2

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9-200

-100

0

100

200

300

400

MgO CaO LiAlO2 LiCrO2 Li2S i2O5 ∆G

(kJ

/mol

)

∆G (

kJ/m

ol)

Sn-Li (Li at% fraction X 10)

Sn-Li (Li at% fraction X 10)Sn-Li Composition (Li fraction)



Change in Gibbs Free Energy of Reaction of Nitridesin Sn-Li at 773 K

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0

50

100

150

200

250

300

350

400

S n-Li Compos ition (Li) (x10)

Gr (

kJ/m

ol)

G ibbs F re e E nergy of Reac tion of Nitrides in Sn-Li a t 773 K

VN TaN CrN

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0

50

100

150

200

250

300

350

400

Sn-Li Compos ition (Li) (x10)

Gr (

kJ/m

ol)

Gibbs F ree Ene rgy of Reac tion of Nitrides in Sn-Li at 773 K

BN AlN S i3N4 TiN ZrN

∆

∆

Increasingly Stable

Coatings




Change in Gibbs Free Energy of Reaction of Carbides in Sn-Li at 773 K

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

0

50

100

150

200

250

300

S n -Li Compos ition (Li) (x10)

Gr (

kJ/m

ol)

G ibbs F re e E nergy of Reac tion of Carbides in Sn-Li a t 773 K

-S iCTiCZrCNbCTa C

β

∆

Increasingly

Unstable

Increasingly

Stable Coating



Stability of Oxides, Nitrides, and Carbides in Sn-Li at 773 K

qStability of Ceramic Coatings in Contact with Sn-Li 25 at.%at 773 K in Descending Order:

qNegative change in Gibbs free energy of reaction indicates unstable coating (decomposition).

Oxides ∆Gr

(kJ/mol)Sc2O3 290Y2O3 290LiAlO2 280Al2O3 270HfO2 245ZrO2 230La2O3 225Ce2O3 224CeO2 295Li2Si2O5 290CaO 285BeO 280MgO 255TiO2 75LiCrO2 65SiO2 40B2O3 -15Cr2O3 -100NiO -200Fe2O3 -370

Nitrides ∆Gr

(kJ/mol)ZrN 375TiN 340AlN 290BN 280TaN 260Si3N4 255VN 225CrN 130

Carbides ∆Gr

(kJ/mol)ZrC 230TiC 215TaC 180NbC 175SiC 115

5/15/00 APEX - ANL-Meeting 28-400 -300 -200 -100 0 100 200 300 400

Fe2O3NiO

Cr2O3B2O3 SiO2

LiCrO2TiO2

SiCCrN NbCTaCTiC

Ce2O3 La2O3

VNZrO2

ZrCHfO2 MgO

Si3N4TaN

Al2O3LiAlO2

BeOBN

CaO Sc2O3 Y2O3

Li2Si2O5AlN

CeO2 TiNZrN

∆Gr(kJ/mol)

∆Gr(kJ/mol) of Reaction at 773 K for Ceramics at Saturated Solutions in Sn-Li 25 at%

Increasingly StableUnstable


Uncertainties and Summary

• Uncertainties:– Extrapolation of Li-Activity Data from Pb-17Li– Lack of solubility data for non-metals in Sn-Li

• Summary:– Established Li-activities for the entire temperature and composition range.– Established solute (O, H, C, N) activities as a f (T,composition) in Sn-Li:

• Li2O: Oxygen activity is very low every where; Li2O formation is favored; very low dissolved oxygen.

• Li2C2: At high temperature (>1200oC) Li2C2 is stable down to low Li-fractions (xLi=0.10) à Carbide coatings should be resistant to dissolution in Sn-Li25 below 900oC.

• Li3N: At Li-fractions below 0.75 the formation of Li3N is suppressed over the entire temperature range (600 – 1500oC): à Nitride coatings should be resistant to dissolution even at high T in Sn-Li25.

• LiH: Hydrogen activities are positive for almost all Li-fractions and T-ranges. Hydride salt formation is suppressed (except for pure Li at low T<600oC)à For Sn-Li25 Tritium recovery should not pose a problem.


Conclusions

• Based on the low solubility of O, N, H, and C in Li, the following stability results are found for Oxide, Carbide, and Nitride Coatings in contact with Sn-Li (25at.%):

– Oxides:• Fe2O3, NiO, and Cr2O3 will decompose at 500oC.• These will possibly corrode.• All other oxides examined are stable.• At 500oC TiO2, SiO2, B2O3, LiCrO2, Li2Si2O5 are unstable at

high Li-fractions (xLi>0.2)

– Nitrides:• At 500oC all of the considered nitrides are stable.

– Carbides• All are stable (except for β-SiC in pure Li)


Ongoing Work

• More Accurate Thermodynamic Evaluations of Sn-Li on the basis of Phase Diagrams (CALPHAD method).

• Investigating the Compatibility of Alloying Elements in Metals.

• Erosion of Nozzles and High-Speed Zones (bends, contractions/expansions) due to formation of stable Li-compounds.

• Analysis of FLiBe Thermodynamics of Compatibility.

chemical compatibility of structural materials with liquid li and sn-li · 2016. 6. 26. ·...

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