Low Energy Ion Irradiation and Its Applicability to Mimic Materials - - PowerPoint PPT Presentation

Low Energy Ion Irradiation and Its Applicability to Mimic Materials Irradiation Damage from High Energy Protons

Weilin Jiang, David Senor Pacific Northwest National Laboratory HPT R&D Roadmap Workshop May 31 - June 1, 2017, Fermilab

Driving Force for Microstructural Changes Induced by MeV Ion Irradiation in Solids

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• 1. Nuclear energy deposition:

Elastic collision, damage cascades

• 2. Electronic energy deposition:

Electron excitation, ionization

• 3. Electron-phonon coupling:

Heat production, temperature increase

Emulation of Microstructural Features Using MeV Ion Irradiation and Thermal Annealing

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Benefits:  Accurate dose for emulation of material age  Accurate temperature for emulation of the location inside the material with a temperature gradient  Minimum or no radiological activation for immediate release and characterization of irradiated materials.  Implantation of impurity species into a pre-existing structure without thermal constraints.  Fast emulation of structural features within hours to days  Low cost Limitations:  High dose rate  Possible temperature shift

MeV Ion Irradiation to Emulate High Energy Proton Irradiated High Power Target Materials

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• Irradiation damage in HPT materials starts from production
• f point defects, followed by their accumulation and

interactions, leading to formation of defect clusters up to full amorphization.

• Point defects are produced mainly by irradiation of

spallation neutrons and ions, especially at low energies, which may be emulated by low energy ion irradiation.

• The effects of temperature and its possible gradient in HPT

materials may be emulated through post-irradiation thermal annealing at high temperatures, which may lead to formation of fractures and cracks.

• Gas bubbles and solid state precipitates in HPT materials

may be emulated by implanting the species.

• Each contributor may be emulated separately or in a

combined way to some extent.

Proposed Procedure to Emulate High Energy Proton Irradiated High Power Target Materials

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• To simplify data interpretation, start with highly oriented pyrolytic graphite (HOPG), pure

light metals or model alloys without grain boundaries, pores or high-level impurities, followed by polycrystalline materials with increasing levels of material complexities.

• Perform in-situ damage accumulation study of HOPG irradiated, for example, with H+ ions

and self-ions (C+) as a function of dose and temperature.

• Perform in-situ and ex-situ thermal annealing study of defect recovery and clustering.
• Perform in-situ HIM irradiation study of microstructural evolution in polycrystalline graphite.
• Perform microscopy study of HOPG and polycrystalline graphite implanted with H, He and

non-gaseous spallation/transmutation species (e.g., Li) and annealed at high temperatures to emulate microstructures for study of various features, including polycrystallization, amorphization, shrinking/swelling, creep, Mrozowski cracks, gas bubbles, and precipitates.

• Measure physical properties, including thermal conductivity, electrical conductivity, and

mechanical strength.

• Compare the emulated microstructures and properties with those of high energy proton

irradiated graphite and develop a fundamental understanding of the structure-property relationships, which may help assess and predict material performance.

Fundamental Processes of Ion-Solid Interactions in the MeV Energy Range

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INCIDENT BEAM Ion Implantation TARGET Rutherford Backscattering (RBS) Product of Nuclear Reaction (NRA) X-Ray (PIXE) -Ray (PIGE) Recoil Target Atom (ERDA)

Damage Peak

Ion Channeling and RBS/C

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From L. C. Feldman, et al., “Materials Analysis by Ion Channeling”

RBS/C and random spectra for 6H-SiC

Disorder Accumulation in -LiAlO2 at 573 K

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200 300 400 500 100 200 300 1000 500

Random Unimplanted

O Al

H

+/cm 2

3x10

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2x10

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1x10

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8x10

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6x10

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4x10

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2x10

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<001>-aligned

Scattering Yield Channel Number

LiAlO2 (001) 80 keV H2

+

60° off, 573 K

Al Depth (nm) 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6

Relative Al Disorder Dose (dpa)

LiAlO2 (001) 80 keV H2

+

60° off, 573 K

• Disorder on the Al sublattice saturates at levels of 0.3 and 0.5.
• No full amorphization occurs at the highest applied dose of 1 dpa.

Effect of Irradiation Temperature on Disordering Rate

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0.01 0.1 1 10 0.0 0.2 0.4 0.6 0.8 1.0

150 K 170 K 250 K 300 K 370 K 410 K 450 K 500 K 550 K

6H-SiC 2 MeV Au2+

Relative Si Disorder Dose (dpa)

Disordering rate decreases with increasing irradiation temperature due to simultaneous recovery

Thermal Recovery of Defects on Both Si and C Sublattices in Irradiated SiC

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20-min Isochronal Anneals

Similar recovery stages (I, II, III) on both Si and C sublattices

300 600 900 0.0 0.2 0.4 0.6 0.8 1.0

III II I

28Si(d,d)28Si

Au2+/nm2 0.40 0.20 0.15 0.10 0.06

Relative Si Disorder Annealing Temperature (K)

6H-SiC, 2 MeV Au2+, 170 K

300 600 900 0.0 0.2 0.4 0.6 0.8 1.0

III II I

12C(d,p)13C

Relative C Disorder

Li and H Out-diffusion in H+ Irradiated -LiAlO2

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• Material decomposition, Li diffusion and loss during irradiation
• H diffusion and release during thermal annealing

100 200 300 400 500 600 5 10

773 K 673 K 573 K 473 K 300 K Unimpl

Normalized Li Yield Depth (nm)

Polycrystalline -LiAlO2 80 keV H2

+

60° off, 1017 H+/cm2

100 200 300 400 500 600 2 4 6

300 K impl 573 K ann, 6h 673 K ann, 6h 773 K ann, 6h

Normalized H Yield Depth (nm)

Polycrystalline -LiAlO2 80 keV H2

+, 300 K

60° off, 1017 H+/cm2

During H+ Implantation During Thermal Annealing

Amorphization and Precipitate Formation

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• The precipitate in rectangular shape is identified as cubic LiAl5O8 with

zone axis [211] that is parallel to -LiAlO2 [100].

• Precipitates also show in triangular shape, which has a zone axis [111].
• Amorphization and gas bubbles near the surface are observed.

-LiAlO2 implanted to 1017 H+/cm2 at 773 K

STEM-EELS Mapping of Precipitates in 3C-SiC

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Formation of cubic Mg2Si and tetragonal MgC2 tetrahedra in Mg+ implanted 3C-SiC. 3C-SiC implanted to 9.6×1016 25Mg+/cm2 at 673 K and annealed at 1573 K for 12 h

Specifications and Capabilities

• Small beam size: < 0.1 nm
• High resolution: ≤ 0.35 nm
• Magnification: 100 – 1,000,000
• Field of view: 1 mm – 100 nm
• Depth of field: 5-7 times SEM
• RBS spatial resolution: ~10 nm
• Variable voltage: 5 – 30 kV
• Beam current: 1 fA – 25 pA
• No conductive coatings needed
• High surface sensitivity
• High image contrast
• Low Z imaging
• Backscattered ion imaging

Examples of Applications

• Nanostructures in nuclear

materials

• Precipitates, gas bubbles, grain

boundaries, cracks, interfaces, etc.

• Irradiation modification of material

structures using sub-nanometer He+ ion probe

The Column Source Tip Trimer

As an advanced instrument, HIM was developed and commercialized in 2007, providing cutting-edge imaging and chemical analysis with a sub-nanometer

• probe. One of the unique capabilities is

the in-situ study of microstructural evolution in bulk material at a microscopic site of choice under He+ ion irradiation.

Helium Ion Microscope (HIM) at PNNL/EMSL

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He Bubble Formation in -LiAlO2

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-LiAlO2 irradiated with 25 keV He+ at RT under HIM

(He+ ion projected range: 236 nm; max. 62.3 at.% He)

He Bubble Formation in a -LiAlO2 Grain under HIM

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Microstructural Evolution of Amorphous SiO2 Nanoparticles and LiAlO2 at a Void under HIM

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Mg+ and H+ Irradiated HOPG

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A C B D A C B D

0.78 MeV H+ 10 µm Al foil

400 800 1200 1600

A: Mg+ and H+ irradiated B: H+ irradiated C: Mg+ irradiated D: Non-irradiated

Graphite

1580 1360 A C B D

Raman Intensity (a.u.) Raman Shift (cm-1)

DLC D G G: Graphite peak at 1580 cm-1 D: Disorder peak at 1360 cm-1 DLC: Broad diamond like carbon peak ranging from 1100 to 1700 cm-1

A C B D HOPG