Real-time 3D imaging of nuclear structural materials at high - - PowerPoint PPT Presentation

Real-time 3D imaging of nuclear structural materials at high temperature

• Dr. Dong LIU

EPSRC Postdoctoral Research Fellow 1851 Exhibition Brunel Research Fellow Junior Research Fellow at Mansfield College Department of Materials, University of Oxford, UK Research Affiliate Lawrence Berkeley Lab, UC Berkeley, USA

Content

• What is in situ x-ray computed tomography
• Deformation and fracture
• Examples for in situ mechanical testing with x-rays:
• Porous graphite composites (nuclear application)
• Ceramic-based composites (aero application)
• Electronic devices (communications, radars…)

What is x-ray computed tomography

Contrast

• Different absorption

in different materials Higher atomic number  more absorption

• Phase contrast from

abrupt boundaries (more complex)

• Tomography – Radiograph
• X-rays are like light in that they are

electromagnetic waves, but they are more energetic, so they can penetrate many materials.

Tomography – “X-ray Vision”

https://commons.wikimedia.org/wiki/ File:UPMCEast_CTscan.jpg https://commons.wikimedia.org/w iki/File:3d_CT_scan_animation.gif

• CT completely eliminates the superimposition of

images of structures outside the area of interest.

• Inherent high-contrast resolution, differences

between tissues that differ in physical density by less than 1% can be distinguished.

Tomography – Rotating Beam

Tomography – Rotating Sample

Tomography – Reconstruction

Back-Projection Method Slice-by-slice

Tomography – Reconstruction

Back-Projection Method

Tomography – Reconstruction

• Scan an object when it is static to obtain its 3D

structure only

• Take a scan when an event is happening:
• Chemical reaction
• Physical loading
• …

In situ XCT

Cracks may not be visible to a the human eye…

• Too small
• Hidden deep in material

They can propagate catastrophically…

How things break: deformation and fracture

‘Fracture mechanics’

The Liberty Ships

The Liberty ship S.S. Schenectady, which, in 1943, failed before leaving the shipyard.

(Reprinted with permission of Earl R. Parker, Brittle Behavior of Engineering Structures, National Academy of Sciences, National Research Council, John Wiley & Sons, New York, 1957.)

• Ductile to brittle transition of

metals

• Square hatch corners increase

stress concentration

• Steel sheet were welded rather

than riveted

• Local defects and discontinuities in

the welds

• …

DeHavilland Comet Disasters

Design flaws, including dangerous stresses at the corners of the square avionics windows and installation methods, were ultimately identified. Full-scale cyclic internal pressurisation test of the fuselage in a water tank of the aircraft G-ALYU removed from service

• In addition to design improvement, ‘better’ materials (higher

strength and toughness, lighter in weight..) have been developed, e.g. composite materials have seen an significant increase in various applications, e.g. nuclear and aero

• There is a need to understand the 3D microstructure and defects

in a material prior to its application

• Where can we do such experiments?
• Lab-based x-ray machines (x-ray tubes)

• An electron gun – 90 keV
• A 100 MeV linear accelerator
• A 100 MeV – 3 GeV booster

synchrotron (158 m in circumference).

• Electrons then travel at 3 GeV (near

the speed of light) around a storage ‘ring’ (~561 m)

• 48 sided polygon
• Sudden change of direction causes

the electrons to emit an bright beam (electro-magnetic radiation) to be used for experiments

• X-ray to far infrared

Synchrotron radiation sources

10 billion times brighter than the sun.

• US:
• SSRL and LCLS at SLAC National Accelerator Laboratory
• APS at Argonne National Laboratory
• ALS at Lawrence Berkeley National Laboratory
• NSLS at Brookhaven National Laboratory
• …
• UK:
• Diamond Light Source, Rutherford Appleton Laboratory
• …
• Europe:
• European Synchrotron Radiation Facility, France
• Swiss Light source, Switzerland
• …

Synchrotron radiation sources

Diamond Light Source

I12 Beamline Storage ring

“Where does this bit go?”

Cast Iron

Limpet Shell

Limpet Shell

Limpet Shell - Cracked

What to do after the experiment?

5 days of experiments generated 8TB of data!

• Reconstruction
• Comparison with Models
• Deformation Analysis

(3D image tracking algorithms)

The UK has 15 operational nuclear fission reactors at seven plants (14 advanced gas- cooled reactors (AGR) and one pressurised water reactor (PWR)), as well as a nuclear reprocessing plant at Sellafield.

Nuclear-grade Graphite

• Graphite has been widely used as a moderator, reflector and fuel matrix in various

types of nuclear reactors, such as gas cooled reactor (e.g. AGR, MAGNOX), Russian RBMK reactors, high temperature gas cooled reactor (Dragon, Peach Bottom, AVR, THTR-300, Fort St. Vain, HTTR, HTR-10 ) etc.

• Gilsocarbon graphite is used as moderators and structural components in operating

Advanced Gas-cooled Reactors (AGRs) in the UK; Life-limiting as it is not replaceable.

Nuclear-grade Graphite

Filler particle

Micro-scale Mrozowski cracks

100 µm

• Micro- and Nano- scale

500 µm 500 µm

Filler Binder

Threshold image

• Macro-scale

Microstructure

• Manufacture route

Gilsonite coke

Calcination (~1300°) Milled and sized

Filler and flour Coal tar pitch Green article Baked article Nuclear graphite

Baking at ~800° Re-impregnated with pitch Baking Graphitisation (~3000°C) Cooled Moulded Hot mixed

Multi-scale Characterisation: RT & HT

Room temperature Elevated temperature Crystal bonding Lattice strain Macro-scale deformation 3D microstructure

10 µm

High temperature mechanical tests

• Heating type: laser, lamp, induction,

current…

• Furnace (controlled environment + loading

cell)

• Microscopy chamber based (combined

with laser heating or hot stage)

• Indentation kit with temperature option…

Challenges

• Temperature control / measurement;

displacement measurement; strain distribution.

• Need to be able to ‘see’ the sample during

deformation and fracture.

• …

In situ high temperature tomography

• Beamline 8.3.2, Advanced Light Source (LBNL); Hot cell with

capability of heating up to ~2300°C; Vacuum: up to 10-3 torr;

• Gas environment: inert - Ar or N2, oxidizing - air
• Maximum tensile load: 2 kN; LVDT extension measurements;

test volume: 0.5 cm3

Hotcell

In situ high temperature tomography

Schematic of the setup and operation

Graphite

Graphite sample rollers Loading jig Alignment and in situ control of crack growth

• Flexural strength and fracture toughness
• Flexural strength increases with temperature
• Failure strain is larger at high temperature
• Fracture toughness increases with temperature between ambient and 1000C

In situ high temperature tomography

400 800 1200 10 20 30 40

Flexural strength

Flexural strength (MPa) Temperature (C)

Average values

0.0 0.5 1.0 1.5 2.0 500 1000 1500

amax J (J/m

2)



a (mm)

20C

Jmax

1000C 650C

• D. Liu & R. O. Ritchie et al. Nature Communications, 2017

0.0 0.5 1.0 1.5 2.0 500 1000 1500

III II IV JQ (J/m

2)

a (mm) I

• In situ crack growth: rising J-R curve

In situ high temperature tomography

• 3D segmentation of a crack at 1000°C
• Interaction between filler

particles and strain field

• 3D maximum principal strain overlay (DVC)
• D. Liu & R. O. Ritchie et al. Nature Communications, 2017

• Toughening mechanisms

In situ high temperature tomography

Crack deflection

Microcracks\ unmicrocracked material

crack tip uncracked ligament bridges crack tip uncracked ligament bridges

Constraint micro-cracking Uncracked-Ligament Bridging

• Less micro-cracking at HT
• More bifurcation at HT

• Raman spectra provide the ‘figure print’ of the various forms of carbon

In situ high temperature Raman spectroscopy

• G band shift changes with strain/temperature

500 1000 1500 2000 2500 3000

D* D

Intensity (a.u.)

Wavenumber (cm

• 1)

G

Wavenumber (cm-1) Intensity (a.u.)

200°C 400°C 600°C 800°C

G

G band: crystalline; D band: disorder

• D. Liu & R. O. Ritchie et al. Nature Communications, 2017

1550 1560 1570 1580 1590 20 40 60 Counts

G peak position (cm

• 1)

20C 800C

500 1000 1500 1550 1555 1560 1565 1570 1575 1580 1585

G peak_centre position change with temperature Linear Fit of peaks I

I H Slope = -0.02460.00037

ΔG 1400°C 20°C 1581cm-1 ΔT 1551cm-1

In situ high temperature Raman Spectroscopy

• 121 measurements in each map; four maps in total.
• The same area was measured at RT and 800°C
• The histogram on the right shows that at RT there is large

variation of the G peak shift (strain) and at 800°C this variation is reduced

• In situ Raman spectroscopy at high temperature indicate that

there is residual stress relaxation in this material

• D. Liu & R. O. Ritchie et al. Nature Communications, 2017

Diamond Anvil Cell

Yang et al, Nanowires – Fundamental Research, Chapter 23, 2011

• DAC was used to apply pressure on the graphite sample;
• Ruby grains to give indication of the stress while the Raman spectra of the graphite is monitored;
• Relaxation of residual stress contributes to increased resistance to micro-cracking at HT

In situ Raman spectroscopy at high temperature

• Convert G peak shift to stress
• D. Liu & R. O. Ritchie et al. Nature Communications, 2017

Relaxation of local tensile stresses!

• Assisted the closure of nano-cracks;
• Reduced the amount of micro-cracking...

The mechanism for higher strength and fracture toughness at elevated temperature

• D. Liu & R. O. Ritchie et al. Nature Communications, 2017

Key messages

• The high temperature behaviour of

Gilsocarbon nuclear graphite has been investigated at different length-scales by X-ray computed tomography and Raman spectroscopy.

• It exhibits higher flexural/tensile strength and fracture toughness at elevated temperatures.
• This is attributed to

the relaxation of residual stresses that were ‘frozen-in’ during manufacture

… and others

Ma Main n limiting ng fact ctor: r: SiC therm hermal co cond nduc uctivity

GaN-on-SiC commercial microwave electronics

Int nteg egra rate e di diamond nd with h GaN allows rea ealisation n of ul ultra ra-hi

• high

h power er el elec ectro ronic devices es

X-r

• ray

ay com computed tom tomograp aphy on

• n elect

ctron

• nic

c device ces

Si-substrate AlGaN/GaN Step 1. MOCVD Si-substrate AlGaN/GaN Substrate Step 2. Mount on carrier wafer AlGaN/GaN Substrate Step 3. Remove Si substrate AlGaN/GaN Substrate Step 5. Diamond seeding Diamond AlGaN/GaN Substrate Step 6. Deposition of 100µm Diamond AlGaN/GaN Substrate Step 4. Dielectric layer deposition Diamond AlGaN/GaN Step 7. Remove Carrier wafer

• Large diamond seeding

particles:

• < 0.5 µm in size.
• Small diamond seeding

particles:

• < 50 nm in size.
• Both as-made GaN-on-

diamond samples, and those annealed at 825°C, a typical condition used for ohmic contact formation, were studied.

X-r

• ray

ay com computed tom tomograp aphy on

• n elect

ctron

• nic

c device ces

Liu et al, Proceeding of CS-ManTech, 2017

Mic icros

• structu

cture: :

Small diamond see eeding parti rticle 400 00 µm

1 µm GaN Top surface Diamond

• No fea

eatures ures were ere obs bserv rvabl ble e on the he GaN surface

• No thro

hroug ugh-ho h-holes or r da dark rk do dots

• FIB cro

ross-s

• sect

ctioning ng re revealed ed un uniform rmly bo bonded ded GaN-di

• diamond

nd int nterf erface ce without ut voids ds

X-r

• ray

ay com computed tom tomograp aphy on

• n elect

ctron

• nic

c device ces

Liu et al, Impact of Diamond Seeding on the Microstructural Properties and Thermal Stability of GaN-on-Diamond Wafers for High-Power Electronic Devices, Scripta Materialia, 2017

1 µm 10 10 µm

• Foc
• cus ion
• n beam milling

revea ealing the cros ross-s

• sec

ecti tion

• n of
• f

Ga GaN-d N-diamon

• nd str

tructu ture re

• Viewed

ed in SEM EM on

• n a sample

ti tilt t of 52° 2°

• Voi
• ids at th

the Ga GaN/ N/diamon

• nd

inter erface undern erneath a ty typical dark rk dot

• t

GaN aN Diam iamon

• nd

X-r

• ray

ay com computed tom tomograp aphy on

• n elect

ctron

• nic

c device ces

Liu et al, Impact of Diamond Seeding on the Microstructural Properties and Thermal Stability of GaN-on-Diamond Wafers for High-Power Electronic Devices, Scripta Materialia, 2017

X-r

• ray

ay com computed tom tomograp aphy on

• n elect

ctron

• nic

c device ces

Examp mple of f a defe fecte ted mate terial due to to inapprop

• priate

te seeding

Key messages

In situ x-ray computed tomography is a powerful tool to study the damage and fracture of materials, non-destructive testing and a lot more!

Acknowledgements

D.L. acknowledges the EPSRC fellowship grant: EP/N004493/1 D.L. acknowledges the Royal Commission for the Exhibition of 1851 Research Fellowship grant D.L. acknowledges EPSRC Grant (EP/M02833X/1) for the use of Zeiss Xradia 510

Oxford Materials, UK

• Mr. Phil Earp, Dr. Selim Barhli, Dr. Yelena Vertyagina, Prof. James Marrow

Lawrence Berkeley National Laboratory, US

• Dr. Bernd Gludovatz, Mr. Jon Ell, Dr. Claire Acevedo, Dr. Dula Parkingson, Dr. Harold Barnard, Dr. Alastair MacDowell,
• Prof. Robert Ritchie

Centre for Device Thermography and Reliability, Bristol

• Dr. James Pomeroy, Mr. Culhum Middleton, Dr. Maire Power, Prof. Martin Kuball
• Dr. Oliver Lord (Royal Society Research Fellow, Bristol)