PIE-Laser Based Properties Measurements

David Hurley - INLStephen Reese - INLFarhad Farzbod – INLMarat Khafizov – INLRobert Schley – INLRory Kennnedy – INLJianliang Lin – CSMS. Phillpot / A. Chernatynskiy– UFClarrisa Yablinski - UWSubhash Shinde – SNLHeng Ban - USU

Outline

• Two new laser-based instruments are being designed

• Thermal conductivity microscope

• Mechanical Properties Microscope

• Physics based description of instruments

• Several examples of measurements made on surrogate materials

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• A photon first interacts with the electrons− Electronic and optical properties

• Electronic energy is then converted into heat − Thermal properties

• Thermal expansion (acoustic waves)− Mechanical properties

Motivation• Optical methods are appealing because they can be performed remotely• Optical methods are extremely reproducible • Optical methods have high spatial and temporal resolution

Laser Interaction with Materials

Laser Based Properties Measurements

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Thermal Properties

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Measurement of Thermal Properties – physics description

Phase profile slope = 1/LD

• We have developed a spatially resolved thermal conductivity probe for – investigating individual microstructure features– investigating thin damage layers caused by irradiation

• This approach excites a harmonic thermal wave by a localized pump beam and measures its profile using a localized probe beam

• By combining frequency and spatial domain scan we can extract thermal conductivity (applicable to constant thermal load)

Scan probeThermal wave

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Hurley et al., J. Appl. Phys. 107, 023521 (2001)Khafizov and Hurley, J. Appl. Phys. 110, 083525 (2011)

Example 1 – Thermal anisotropy (atomic bonding)

Phase lag (degrees)

-55

-5

x1

x310 kHz

1 kHz

Phase lag (degrees)

x1

x3

x1

x3

Scan Distance (m)

• Lateral resolution is related to the optical spot size (~1m)

• Depth resolution is related to modulation frequency (1 MHz→100nm)

• Quartz is trigonal and exhibits thermal anisotropy in the plane of the sample

The profile shows conjugate relationship between changes in position and changes in

frequency

Phase contour reveals thermally anisotropic nature of substrate for kilohertz range

modulation

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• Thermal conductivity of UO2 strongly depends on radius• Electrons/phonons/photons are the energy carriers• Thermal conductivity related to ability to transport kinetic energy• In UO2 phonons are primary heat carrier

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Example 2 – The influence of microstructure

Specular

Diffuse

Hot s

ide

Cold side

Nanochannel Boundary

Hot s

ide

Cold side

Internal Grain Boundary

Phonon-phonon scattering

Phonon-defect scattering

Connect microstructure to thermal transport

• Irradiation induced defects that influence thermal conductivity– Fission products– Stoichiometry changes– Dislocation loops– Grains boundaries

• Separate effects studies are important

• High burnup structure at the rim of UO2 fuel pellet exhibits submicron grains with nearly defect free intragrain regions

J. Noirot et al., J. Nucl. Mater. 372, 318 (2008)

• Understand the role of grain boundaries on thermal transport • Two approaches

– Single boundary (Atomistic Simulations)– Many boundaries (Boltzmann Transport Equation)

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Ceria thin film grown on Si substrate using pulsed unbalanced magnetron sputteringGrain size ~ 450 nm

-10 -5 0 5 10-3

-2.5

-2

-1.5

-1

-0.5

0Al/CSM#10: T=300K km=7.36 kf=24.5 ks=156

Distane (m)

phas

e

1 kHz10 kHz100 kHz

KCeO2=7.4 W/mK

• Nanocrystalline thin film has conductivity of 7.4 W/mK much lower than the bulk 15.6 W/mK

• Thermal conductivity in thin film is reduced due to grain boundary scattering

Thermal transport in nanocrystalline ceria thin filmsMetal film is deposited on top of ceria to

ensure strong optical absorption

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Temperature dependent conductivity of ceria samplesParameterize phonon-mean free path

0 50 100 150 200 250 3000

10

20

30

40

50

60

70

80

Temperature (K)

Ther

mal

Con

duct

ivity

(W/m

K)

pelletthin film

• Thermal conductivity of ceria pellet continues to be dominated by ph-ph interactions down to 100 K• Thermal conductivity in thin film is strongly affected by grain boundary scattering to high temperatures

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Grain boundary conductance

• Much lower value than suggested by molecular dynamics modeling in UO2 (0.30 GW/m2K)• For multi-component systems need to include the effect of defect segregation, and stoichiometry

variations near grain boundary

Molecular Dynamics

T. Watanabe et al., J. Nucl. Mater. 375, 388 (2008)

0 50 100 150 200 250 300 3500

20

40

60

80

Temperature (K)

Ther

mal

Con

duct

ivity

(W/m

K)

dTTT 111

0

0 50 100 150 200 250 300 3500

0.01

0.02

0.03

Temperature (K)

GB

Con

duct

ance

(GW

/m2 K

)

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Thermal transport across a single interface

45

-5

-55

-110

nmProfilometry

101100

111

101100

111

HRTEM EELS

4.5 nm O

Si

Fabrication

Interface Characterization

Axes Alignment EBSD

• Original goal: to study transport across Σ29 grain boundary in Si - Silicon has similar optical properties as UO2, the experimental methodology for one material can be

applied to the other- Thermal transport across grain boundaries in silicon has been modeled extensively enabling direct and

immediate comparison of experiment and theory• Interface characterization reveals a 4.5 nm SiO2 layer

D. Hurley, M. Khafizov, J. Appl. Phys. 109,083504 (2011)

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Thermal diffusion across vertical interface

D. Hurley, M. Khafizov, S. Shinde, J. Appl. Phys. 109,083504 (2011)

• Conductance across single Si/SiO2 interface is 0.43 GW/m2K• Conductance across both interfaces and SiO2 layer is 0.11 GW/m2K

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Thermal conductance of interface

• Molecular dynamics simulation using Stillinger Weber interatomic potential

• Transmission of individual longitudinal acoustic phonons (primary source) is modeled

• From calculated transmission coefficients conductance is 0.13 GW/m2K

• Experimentally measured conductance 0.11 GW/m2K

• Overall good agreement between model and experiment– SW potentials generally overestimate

the conductivity

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New Thermal Conductivity Microscope

Lab-based instrument Preliminary design

Mechanical Properties

Laser Ultrasound (brief overview)

Laser generation

Propagation • Elastic and microstructure• Bulk wave velocity – elastic constants

(volumetric)• SAW dispersion - corrosive film thickness

(surface)

Laser detection• Interferometric/holographic • Knife edging

• Electronic and optical properties• For NDE applications in metals typically

thermoelastic• Laser ablation can be used to generate larger

amplitude signal

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Shear

Longitudinal

SAW

Pulse or chopped laser beam

Thermoelastic generation (i.e. nondestructive)

• Far field directivity pattern for bulk shear and longitudinal waves is due to mode conversion at the surface. Very little energy travels along the epicentral direction.

• 70% of energy goes into SAW and 30% into bulk waves• Well defined directivity pattern of shear wave can be exploited for locating flaws

Arrival Time (ns)

Nor

mal

ized

Dis

plac

emen

t

— Experiment— Greens function

Isotropic homogeneous

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Time (ms)

Nor

mal

ized

Am

plitu

de

High temperature elastic properties: Inconel 617Tube Furnace

)21)(1()1(

,

EM

GV

MV sl

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Elastic Constants of Radiological Materials: U-Moly

• RERTR surrogate fuel• Single crystal at RT is orthorhombic – 9 elastic constants• Isotropic if Polycrystalline w/ random orientation• Fuel plate is rolled and may have considerable texture

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Anisotropic Elastic Properties

Grain Boundary

200 µm × 200 µm

Acoustic Wave perspectiveLoad Frame perspective

• Multiple orientations – important waste issues for radiological materials• Nice if we could determine all elastic constants using a single measurement

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Resonant Ultrasound Spectroscopy (RUS)

Inverse problem- Go from spectrum to elastic constants- Turns out that solution is not unique

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In situ changes in microstructure

Using simulation we can predict the relationship between the polycrystalline elastic constants and the evolving microstructure … the appeal of RUS is that it can provide a crucial validation metric for this modeling approach

441211 ,, CCC

Initial Annealed

Temperature (°C)

Freq

uenc

y (k

Hz)

111

101Evolution of microstructure 001

Heat

Polycrystal plasticity model provides the initial dislocation density for the phase field model

A phase field grain growth simulation determines the defect driven grain growth

Averaged elastic constants are measured and computationally determined as a function of time

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Laser RUS in high radiation environment: Gamma tube facility at ATR

In situ laser ultrasonic measurements of Inconel in the high gamma radiation field at ATR showing the sample temperature and resonant frequencies of a split vibration mode as

irradiation was increased by (3 times) placing fuel rods closer to the sample.

Example of moving from the lab to real life

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Mechanical Properties Microscope

Solid Model Rendering Prototype -mockup facility

Thanks!