LouisHENNETCNRS-CEMHTI

(ConditionExtrêmes etMatériaux,HauteTempérature etirradiation)1davenuedelarecherche Scientifique

45071OrléansFrance

louis.hennet@cnrs-orleans.fr

Invert glasses

Invert glasses

Invert glasses

Glassmodifiers

Glassformers

Howtoquenchthesamplerapidely ?

Inmostofthecases,theyareobtainedusingfastquenching

Fewinvertglassescanbeobtainedwithaclassicalquench:C12A7:Ca12Al14O33

1/Rollerquenching

Quenchrate~105 K/s (PbO)80-(SiO2)20

L.G.Aldermanetal,Phys.Chem.Chem.Phys.15,8506(2013)

Coe College Physics Department,Warwick

Laser1

Laser2

Opticalpyrometers

Videocameras

Mirror

Mirror

Sphericalsample(1-4mm)

Levitator

Gas

AerodynamiclevitationandCO2 laserheating

Levitator

300K/s

500K/s

700K/s

Cooling rates(CaAl2O4)300-700K/sTheratedependsonthesamplesize

Ca12Al14O33 (C12A7)

CaAl2O4(CA)

CA2

C3A

x

T,K (CaO)x-(Al2O3)1-x

Example:CaO– Al2O3 phasediagram

Withconventionalmethods:Narrowvitreousdomainaroundtheeutectic.

UsinglevitationtechniquesExtensionofthevitreousdomainto:0.37<x<0.75(difficultbelow0.4)

Ca3Al2O6(C3A)

=invertglass

CaAl2O4(CA)

=invertglass

Ca2Al6O11 (C2A3)

• Silicateglasses• witharatioglassmodifier/former>1.

Whatistheroleplayedbythemodifier?– Binaryoxides:SiO2-MOwithM=Ca,Mg

• Aluminate glasses:Whatexplaintheglassformingabilityinthatcase?

RoleofAl– Aluminates:Al2O3-CaO

• FewwordsonthesystemSiO2-Al2O3-CaO

Outline

SiO2-CaOcompositions

D.C.KasemanetalJ.Phys.Chem.B,119,8440(2015)

Glassformingsystemupto63%ofCaO

42mol%≤CaO≤61mol%

29SiNMR-MASspectraProgressiveshiftofthecenterofgravity

(increasingchemicalshift)

Q0 Q1

Q3 Q4Q2

NBO

ProgressivereplacementQ2,Q3species Q0,Q1

Glassesmadeusingaerodynamiclevitation

Invertglasses

Progressiveincreaseofthedensity

ThisincreaseinpackingdensityininvertglassesisconsistentwiththeprogressivereplacementofthesilicatenetworkdominatedbyQ3 andQ2 specieswithtightlypackedcorner- andedge-sharingCaO6polyhedra intheglassstructure

Influenceonproperties

Samescenario:

At50%,theglassstructureisdominatedbychainsofQ2 tetrahedra interspersedwiththoseofCaO6octahedra.ByincreasingtheCaO contenttheQ2 tetrahedralchainsareprogressivelyreplacedbyQ1 dimers andQ0 monomers.Theglassstructurerepolymerizes viaformationofpercolatingdomainsofcornerandedge-sharingCaO6octahedra withrelativelystrongCa-Obondsthatincreasestherigidityofthestructure.

Progressiveincreaseoftg

MgO

NBO Tg

S.Senetal,J.Phys.Chem.B2009,113,15243−15248.

50mol%≤MgO ≤67mol%

SiO2

Glassesmadeusingaerodynamiclevitation

Glassformingsystemupto63%ofMgO

29SiNMR-MASspectra

SiO2-MgOcompositions

Q0

Q4

Aluminates:Al2O3-MO

Intermediate Modifiers

Al2O3 CaOSrOBaO

M=Ca,Sr,Ba

Glassformingregion(withlevitation)

Notraditionalglassformer

M.Licheronetal,J.Non-Cryst.Solids3572796–2801(2011)

Howisexplainedtheglassformingability?

NMRCA:CA0.50:AlO4(96.5%),AlO5(3.5%)– Q4C12A7:CA0.39:AlO4(100%)– Q3-Q4C3A:CA0.25:AlO4(100%)– Q2

Neuvilleetal.,Am.Min.95,1580–1589(2010)

Aluminates:Al2O3-CaO

Poeetal,Science,259,786(1993)

Glasses

CaAl2O4

Ca12Al14O33

Ca3Al2O6

27Al3QMASNMRspectra

Alontetrahedralsites.Al2O3 playsaroleofnetworkformer

T(r)=4prr0g(r)

CNarecalculatedusingaGaussianfittoT(r)

rAl-O CAl-O rCa-O CCa-O

X-rays 1.81 Å 4.5 2.32 Å 4.5-5.5Neutrons 1.82 Å 4.4 2.34 Å 3.9-5.4

CaAl2O4 glass: 1.76Å 4.0

Liquid Glass

Al-O

Ca-O O-O Al-AlCa-CaAl-Ca

J.W.E.Drewittetal,J.Phys.Cond.Mat.,23155101(2011)

Al-O

Ca-O

O-OAl-Al,Al-Ca,Ca-Ca

Structurefactor

Pairdistributionfunction

1.78Å2.30Å

4.50

3.90-5.5

1.75Å2.29Å

4.13

6.20

rAl-O

OAln

rCa-O

OCan

Exp. MD

J.W.E.Drewittetal,J.Phys.Cond.Mat.,23155101(2011)

Thespectrameasuredonglassesaresimilartothoseotthecorrespondingreferences

CA:AlinQ4C12A7:MixtureQ4,Q3C3A:AlinQ2

NBOwiththeCaOcontent

XANESattheAlKabsorptionedge

Q2 Q4

IncreaseofQ3andQ2speciesalsovisiblewithRamanspectroscopy

Shiftofthebandat780cm-1

Neuville etalAmericanMineralogist,95,1580(2010)

0

0.4

0.8

1.2

1.6

2

2.4

1560 1580 1600 1620 1640 1660 1680 1700

Nor

mal

ized

Int

ensi

ty

E (eV)

2050K1950K

300K

CaAl2O

4

Tl=1878K

1500K

a

b

c d800K

1750K

e

CA=CaAl2O4

Crystalandliquid=>[4]Alwith4BO

AlV

Neuville etalAmericanMineralogist,93,228-234(2008)

AlKedge

Increaseof[5]AlwithincreasingT(AsobservedbyNMR)

0

0.5

1

1.5

4050 4100 4150 4200

Nor

mal

ized

Int

ensi

ty

E (eV)

1950K Liquid

CaAl2O

4 T

l=1878K

Ca3Al

2O

6 T

l=1930K

300K Crystal

0.1

0.2

0.3

0.4

4038 4040 4042 4044

1950K Liquid

CaAl2O

4

300K Cristal

0.6

0.7

0.8

0.9

1

1.1

4036 4038 4040 4042

1950K Liquid

Ca3Al2O

6

300K Cristal

CA:Ca6-7foldcoordinationwithapre-edgeat4041.1eVandnochangewithtemperature

C3A:cubic,Ca6foldcoordinationwithoutpre-edgeatRTandwithasmallpre-edgeat1950K– PerfectCaO6intheglass.

C3A(Ca3Al2O6)

CA=(CaAl2O4)

XANESattheCalciumKabsorptionedge

åå ==ba

ababba

abbaba,,

)()()( QSwQSbbccQF

Isotope % bc (fm)natCa --- 4.70 40Ca 96.941 4.80 42Ca 0.657 3.36 43Ca 0.135 -1.56 44Ca 2.086 1.42 46Ca 0.004 3.6048Ca 0.187 0.39

(coherentscatteringlengths)

Totalinterferencefunction:

NDwithIsotopicsubstitution(NDIS)Principle:

Possibletomodifybychangingwiththeuseofisotopes

abw ba ,b

OAlCa ,,, =ba

Wemade3samples:• natCaAl2O4• 44CaAl2O4• Mixtureofthetwo(50/50)

Inthisstudy,weusednatCaand44Cab contrast=3.28fm

úúú

û

ù

êêê

ë

é×úúú

û

ù

êêê

ë

é

=úúú

û

ù

êêê

ë

é

)()()(

121212

)()()(

44244

2

22

22

44 QQQS

bcbcbcbcbcbc

QSQSQS

x

CaCaCa

CaCa

mixCamixCa

natCanatCamix

nat

dd

[ ] [ ]1)(1)()( -+-= QSbcQSbcQ CaOOOCaAlAlAlCad

)(QSCaCa

[ ] [ ] [ ]1)(21)(1)()( 2222 -+-+-= QSbbccQSbcQSbcQ AlOOAlOAlOOOOAlAlAlAlxd

44

4444 )()()(

bbQFbQFbQ

nat

natnatx

--

=D

[ ] [ ] [ ] [ ]1)(1)(21)(1)( 2222 -+-+-+-= QSQSbbccQSbcQSbc CaCaAlOOAlOAlOOOOAlAlAlAl h

[ ] [ ] [ ]1)(1)(1)( -+-+-= QSbcQSbcQS CaAlAlAlCaOOOCaCa ggh)()()( 44 QFQFQ natCa -=D ( )24422 bbc natCa -=h

( )442 bbc natCa -=g

Sαβ(Q) functionswithα, β ≠ Ca haveidenticalweightingsandcanthereforebeeliminatedbytakingthedifferencefunction

ItisalsopossibletoeliminatethepartialsfunctionsSCaO(Q) andSCaAl(Q) bytakingthedifferencefunction

Finally,byinvertingthematrixequation

itispossibletoextractthe3functions:

Gls:GlassyCaAl2O4Liq:LiquidCaAl2O4

Differencefunctions

J.W.E.Drewittetal Phys.Rev.Lett.,109235501(2012)

DGx :Al-O,O-O,Al-Al,Ca-CadGx :Al-O,O-O,Al-Al

DGCa :Ca-O,Ca-AlCa-Ca

dGCa :Ca-O,Ca-Al

Al-O

O-O

Ca-O

Ca-O

Ca-Al

Ca-Al

rAl-O 1.77Å 1.75Å

rO-O 1.88Å

OAln 4.2 4.0IVAl+VAl(20%) IVAl

fewVIAl*

Liquid Glass1st peak(Al-O)

2nd peak(O-O)

Al-O-Al 107.99° 109.81°

rCa-O 2.30Å 2.37ÅOCan 6.0 (MD:6.2) 6.5

1st peak(Ca-O)

Realspacedifferencefunctions

Differences: )(),( QGQG xx Dd

Lowcontributionofcation-cationpairs

Differences: )(),( QGQG CaCa dD

Al-OetO-O

Ca-O

ThemeanCa-Cadistancesforcorner-,edge-,andface-sharingpolyhedraare4.40,3.74,and3.41Å,respectively.ThesimulatedfunctionhasasinglepeakatrCaCa3:81andyieldsacomparablecoordinationnumberofCNCa=4.9

3.594.41Å CNCa=5.22

Formationintheglassofbranchedchainsinvolvingedge- andface-sharinglinkages.

Ca-Cacorrelations

Al2O3 doesnotformaglassbyitselfwhichmaybeexplainedsimplyasduetoinsufficientoxygenatomsbeingavailabletoformatetrahedrally connectedAlO4 networkandAlO6.

WhenCaOisaddedtoAl2O3 ,itincreasestheO:Alratiowhilemaintainingchargebalancesuchthat,at50:50CaO:Al2O3 (CaAl2O4)enoughoxygenatomsarepresenttoformafullyconnectedAl-Otetrahedralnetwork.

Onquenching,theAlO5 polyhedrareorganizetoformaglassnetworkmadepredominantlyfromcornersharingAlO4 tetrahedra.InthisprocessthereisaremovalofAl-centerededge-sharingmotifs(Al06).

SnapshottakenfromtheMDsimulationsat2500K

SomeconsiderationsontheglassformingabilityofCA

Thecalciumatomsthenlocatethemselvesinthevoidsbetweenthetetrahedra.

Snapshotsillustratingthelargestclustersofedge-sharingCa-centeredpolyhedra intheMDsimulations.

Liquid Glass

TheCa-O coordinationnumbershowsasmallincreasefrom6.0(2)to6.4(2),andthereisalargechangeintheconnectivityoftheCa-centeredpolyhedra withtheformationintheglassofbranchedchainsinvolvingedge- andface-sharinglinkages.

J.W.E.Drewittetal Phys.Rev.Lett.,109235501(2012)

0

0.5

1

1.5

4050 4100 4150 4200

Nor

mal

ized

Int

ensi

ty

E (eV)

1950K Liquid

CaAl2O

4 T

l=1878K

Ca3Al

2O

6 T

l=1930K

300K Crystal

0.1

0.2

0.3

0.4

4038 4040 4042 4044

1950K Liquid

CaAl2O

4

300K Cristal

0.6

0.7

0.8

0.9

1

1.1

4036 4038 4040 4042

1950K Liquid

Ca3Al2O

6

300K Cristal

CA:Ca6-7foldcoordinationwithapre-edgeat4041.1eVandnochangewithtemperature

C3A:cubic,Ca6foldcoordinationwithoutpre-edgeatRTandwithasmallpre-edgeat1950K– PerfectCaO6intheglass.

C3A(Ca3Al2O6)

CA=(CaAl2O4)

XANESattheCalciumKabsorptionedge

0

0.5

1

1.5

2

1540 1560 1580 1600 1620 1640 1660 1680 1700

Nor

mal

ized

Int

ensi

ty

E (eV)

1950K1830K

300K

Ca3Al

2O

6

Tl=1930K

1000K

a

b'

c d e

C3A=Ca3Al2O6

Crystal=>Alin4foldcoordinationwith2BridgingOxygen,Q2 speciesNochangeobservedwithincreasingtemperature.AlinQ2

Neuville etalAmericanMineralogist,93,228-234(2008)

XANESattheAlKabsorptionedge

AsforCA,wemadeneutrondiffractionwithisotopicsubstitution.

Moleculardynamics(MD)simulationandreverseMonteCarlo(RMC)refinementmethodswereemployedtoobtainadetailedatomisticmodeloftheliquidstructure.

J.W.E.Drewittetal Phys.Rev.B.,109235501(2012)

The further addition of CaO does not give rise to highercoordinated aluminum atoms but rather broadly maintainsthe AlO4 motifs while increasing the number of NBOatoms in the network (Al in Q2).

As the number of NBO atoms increases, the rigidity and stability of the network willdecrease, which would suggest a steady weakening of its glass-forming ability.However, the network may still, to a certain extent, be stabilized by the increasednumber of Ca atoms occupying voids in the network.

The composition of 75% CaO studied here appears to be the upper limit of the glassforming region for the CaO-Al2O3 system.The results demonstrate that a significant number of unconnected AlO4 monomersand Al2O7 dimers which do not belong to an infinitely connected cluster arealready present.The number of these isolated units is expected to increase as the CaO contentincreases further.

CaO

SiO2

Al2O3

CA33.17

CA50.0

CA0.50

Notation:CAx.y

x=%SiO2y=%Al2O3100-x-y=%CaO

R=CaO/Al2O3

R=1R=3

Invertglassarea

Aluminosilicates:SiO2-Al2O3-CaO

CA0.25

R=1.57

CA0.39

AlinQ4

AlinQ2

Invertglasses(R>1)

Si/Almixing