Viviana Cristiglio (May 27th 2014)

Probing materials at ILL: an overview of structure inves7ga7on with neutrons

Viviana CRISTIGLIO Instrument Scien6st at the Ins6tut Laue Langevin

-‐ Neutrons science at high T -‐  Carbon nanotubes -‐  Li ba=eries

Industrial materials, Energy

The liquid state is fundament state of the ma=er and is an essen6al stage for various technological applica1ons

Metallurgy Op6c fibers Aerospace propulsion

Why do we need HT?

Glass making : from liquid to glass by quenching Design of new glasses : Storing nuclear waste

Food and drink Chemistry, Pharmaceu6cs, Cosme6cs

Structure of Liquids by diffrac6on

Unlike crystals, the structural informa6on for liquids and glasses is described in terms of:

1.  Probabilis6c atomic distribu6on func6ons.

2.  Mean atomic distribu6on around each chemical species given by the Pair Distribu6on Func6on g(r).

g(r) is the probability to find an atom at a distance r from another taken at the origin

Interatomic distances

Coordina6on number

Spa6al distribu6on of atoms or

molecules in the system

Crystalline solids

Equilibrium posi6ons

Well defined Bragg peaks

Amorphous

Distribu6on of equilibrium

posi6ons

No Bragg peaks

Structure of Crystalline and Amorphous Solids

Diffusive Mo6ons Internal Dynamics

Structural informa7on Collec6ve dynamics

Coherent

σcoh 4π

Incoherent

σinc 4π

Sca=ering cross sec6on σ = σcoh + σinc

Coherent and Incoherent ScaAering

More sensi6ve to light elements (H, Li, Bo) But

Isotopic subs6tu6on () H/D exchange

Complexity in the data interpreta6on à Mul6-‐techniques approach

Why neutrons are useful for liquids?

neutrons

X-‐rays

Bragg law

Radioactive waste disposal

Aqueous Solutions in Confined Systems

Underground Research Laboratory at Meuse Haute-‐Marne, ANDRA, French Na6onal Agency for the

Management of Radioac6ve Waste

Clays have wide environmental applications, but particularly in waste disposal

Radioactive waste disposal

SiO2 (Network former)

Si-‐O Strong bond

Al2O3 (Intermediate element)

Ca/Mg/Na-‐O (Network modifier)

Al-‐O Less strong

bond

+ +

4 Bridging oxygens 3 Bridging oxygens Strong liquid Fragile liquid

Alumino-‐silicates Ca/Mg/Na -‐ Al2O3 -‐ SiO2

Alumino-‐silicates Ca/Mg/Na -‐ Al2O3 -‐ SiO2

© Britannica

© D. Neuville

Etna, Sicily

Crust and mantle forma6on, magma6c ocean

Candidate for waste storage

New class of cements

ü Maintain the purity of the sample

ü Access very high temperatures (> 3000°C)

ü Absence of heterogeneous nuclea6on

ü Easy access to metastable states

ü Undercooling (Several hundreds degrees below the mel6ng point)

Aerodynamic levita7on

r (Å)

g(r)

Glass

Ca-‐O correla6on less pronounced Difficult to solve the Ca-‐O because its mostly composed by O-‐O (50%of the total g(r)) Molecular dynamics model for experimental data interpreta6on

Ca-‐O

Liquid

r (Å)

Pair Distribu6on Func6on:

From Molecular Dynamics calcula6ons

Liquid CA (SiO2 = 0)

Diffusion coefficient: D [1

0-‐10

m2 s

-‐1]

1000/T [K]

Arrhenius plot

1-‐ Si atoms have a lower self diffusion

2-‐ Si

SiO4 tetrahedra

O, Ca

Dcoherent When SiO2

Introduc6on Instrumenta6on Structure Dynamic Conclusion •  QENS setup •  Mul6-‐nozzle Aero. Lev.

•  Benefits •  Objec6ves

• Glassy state • Liquid state

• QENS • IXS

What is the common point between: Volcanic lava, Magma, Silicate melt, Glass ?

• Amorphous material • Disordered at the atomic length scale • Very high temperature • SiO2 -‐ Al2O3 -‐ CaO

How the viscosity of a volcanic lava changes with temperature? With its chemical composi6on?

© Britannica

© Britannica

© D. Neuville

Etna, Sicily

The liquid state is also an essential stage for various technological applications:

Metallurgy Op6c fibers

• Design of new glasses (storing nuclear waste,…)

Applica6ons

Aerospace propulsion

3

Crust and mantle forma6on, magma6c ocean

Calcium AluminoSilicate (CAS)

SiO2 (Network former)

Tetrahedral

Si-‐O Strong bond

Al2O3 (Intermediate element)

CaO (Network modifier)

Tetrahedral

Al-‐O Less strong bond >>

+ +

4 Bridging oxygens

3 Bridging oxygens

Strong liquid Fragile liquid

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Objec6ves of this thesis (1)

Two furnaces, same principle! • High temperatures • Silicate Melts

Important to be able to study the proper6es of high temperature liquids:

First objec1ve of this thesis: Develop and Combine different techniques on large scale instruments in order to study the structure and dynamics of high temperature liquids.

ESRF

ILL

5





Objec6ves of this thesis (2)

Monitor the evolu1on of viscosity η Study the dynamics

Neutron and X-‐ray Inelas6c Sca=ering

Angell Plot

Study the structure (Neutron and X-‐ray Diffrac6on)

The microscopic mechanisms approaching the glass transition are still not well understood: Rapid change in the

dynamical proper6es like the viscosité ( η )

Correlate Structure and Dynamics?

Add strong glass former “SiO2”

+

6





The common principle is to apply a force to counteract the gravity

G

F

Various levita7on techniques have been developed

Levita7on techniques

Electromagne6c field

Electrosta6c field

Acous6c wave

Gas flow Gas film levita6on

Aerodynamic levita1on

Possible to reach very high liquid temperatures (>3000°C) No container effect These methods maintain the sample purity Easy access to the supercooled state

Advantages :

(few hundred degrees below the mel6ng point)

Limita6ons for QENS

X-‐rays:

Diffrac6on Inelas6c Sca=ering

o  Flux of X-‐ray >> Flux of Neutrons

o  Current configura6on: Half of the sample is s6ll masked by the nozzle.

Neutrons:

Diffrac6on

Inelas6c Sca=ering

1. Bigger diameter 2. Levitated completely outside the nozzle

Sample:

Diameter ∼ 2.7 mm

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Science

Viviana Cristiglio (May 27th 2014)