viviana cristiglio (may 27th 2014)
TRANSCRIPT
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
4
Introduc6on Instrumenta6on Structure Dynamic Conclusion • QENS setup • Mul6-‐nozzle Aero. Lev.
• Benefits • Objec6ves
• Glassy state • Liquid state
• QENS • IXS
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
Introduc6on Instrumenta6on Structure Dynamic Conclusion • QENS setup • Mul6-‐nozzle Aero. Lev.
• Benefits • Objec6ves
• Glassy state • Liquid state
• QENS • IXS
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
Introduc6on Instrumenta6on Structure Dynamic Conclusion • QENS setup • Mul6-‐nozzle Aero. Lev.
• Benefits • Objec6ves
• Glassy state • Liquid state
• QENS • IXS
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
9
Introduc6on Instrumenta6on Structure Dynamic Conclusion • QENS setup • Mul6-‐nozzle Aero. Lev.
• Benefits • Objec6ves
• Glassy state • Liquid state
• QENS • IXS