PIE-Laser Based Properties Measurements

1. PIE-Laser Based Properties Measurements David Hurley - INL Stephen Reese - INL Farhad Farzbod – INL Marat Khafizov – INL Robert Schley – INL Rory Kennnedy – INL Jianliang Lin – CSM S. Phillpot/ A. Chernatynskiy– UF ClarrisaYablinski - UW SubhashShinde – SNL Heng Ban - USU

2. 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 ATR – NSUF User Week, 2012

3. Laser Based Properties Measurements 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 • 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 ATR – NSUF User Week, 2012

4. Thermal Properties ATR – NSUF User Week, 2012

5. 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) Measurement of Thermal Properties – physics description Thermal wave Phase profile slope = 1/LD Scan probe Hurley et al., J. Appl. Phys. 107, 023521 (2001) Khafizov and Hurley, J. Appl. Phys. 110, 083525 (2011) ATR – NSUF User Week, 2012

6. -5 Phase lag (degrees) x1 x3 -55 x1 x3 1 kHz Phase lag (degrees) x1 x3 10 kHz Scan Distance (m) Example 1 – Thermal anisotropy (atomic bonding) Phase contour reveals thermally anisotropic nature of substrate for kilohertz range modulation The profile shows conjugate relationship between changes in position and changes in frequency • Lateral resolution is related to the optical spot size (~1m) • Depth resolution is related to modulation frequency (1 MHz→100nm) • Quartz is trigonal and exhibits thermal anisotropy in the plane of the sample ATR – NSUF User Week, 2012

7. Example 2 – The influence of microstructure • 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 • Phonon-phonon scattering • Phonon-defect scattering ATR – NSUF User Week, 2012

8. 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 • Understand the role of grain boundaries on thermal transport • Two approaches • Single boundary (Atomistic Simulations) • Many boundaries (Boltzmann Transport Equation) J. Noirot et al., J. Nucl. Mater. 372, 318 (2008) ATR – NSUF User Week, 2012

9. Thermal transport in nanocrystalline ceria thin films Metal film is deposited on top of ceria to ensure strong optical absorption KCeO2=7.4 W/mK Ceria thin film grown on Si substrate using pulsed unbalanced magnetron sputtering Grain size ~ 450 nm • 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 ATR – NSUF User Week, 2012

10. Temperature dependent conductivity of ceria samples Parameterize phonon-mean free path • 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 ATR – NSUF User Week, 2012

11. Grain boundary conductance Molecular Dynamics • 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 T. Watanabe et al., J. Nucl. Mater. 375, 388 (2008) ATR – NSUF User Week, 2012

12. Thermal transport across a single interface • 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) ATR – NSUF User Week, 2012

13. Thermal diffusion across vertical interface • Conductance across single Si/SiO2 interface is 0.43 GW/m2K • Conductance across both interfaces and SiO2 layer is 0.11 GW/m2K D. Hurley, M. Khafizov, S. Shinde, J. Appl. Phys. 109,083504 (2011) ATR – NSUF User Week, 2012

14. 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 ATR – NSUF User Week, 2012

15. New Thermal Conductivity Microscope Lab-based instrument Preliminary design

16. Mechanical Properties

17. Laser Ultrasound (brief overview) Laser generation • Electronic and optical properties • For NDE applications in metals typically thermoelastic • Laser ablation can be used to generate larger amplitude signal Propagation • Elastic and microstructure • Bulk wave velocity – elastic constants (volumetric) • SAW dispersion - corrosive film thickness (surface) Laser detection • Interferometric/holographic • Knife edging ATR – NSUF User Week, 2012

18. Pulse or chopped laser beam SAW Longitudinal Shear Thermoelastic generation (i.e. nondestructive) Isotropic homogeneous —Experiment —Greens function Normalized Displacement Arrival Time (ns) • 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 ATR – NSUF User Week, 2012

19. High temperature elastic properties: Inconel 617 Tube Furnace Normalized Amplitude Time (ms) ATR – NSUF User Week, 2012

20. 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 ATR – NSUF User Week, 2012

21. Grain Boundary 200 µm × 200 µm Anisotropic Elastic Properties Load Frame perspective Acoustic Wave perspective   • Multiple orientations – important waste issues for radiological materials • Nice if we could determine all elastic constants using a single measurement ATR – NSUF User Week, 2012

22. Resonant Ultrasound Spectroscopy (RUS) • Inverse problem • Go from spectrum to elastic constants • Turns out that solution is not unique ATR – NSUF User Week, 2012

23. Initial Annealed 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 Averaged elastic constants are measured and computationally determined as a function of time 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 ATR – NSUF User Week, 2012

24. Example of moving from the lab to real life 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. ATR – NSUF User Week, 2012

25. Mechanical Properties Microscope Solid Model Rendering Prototype -mockup facility

26. Thanks!