in-situ TEM observations of irradiation damage in boron carbide

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in-situ TEM observations of irradiation damage in boron

carbide

Guillaume Victor, Yves Pipon, Nathalie Moncoffre, Nicolas Bérerd, Claude

Esnouf, Thierry Douillard, Aurélie Gentils

To cite this version:

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In situ TEM observations of irradiation damage in

boron carbide

G. Victor1_{, Y. Pipon}1_{, N. Moncoffre}1_{, N. Bérerd}1_{, C. Esnouf}2_{, T. Douillard}2_{, A. Gentils}3

1 _{Université de Lyon, UCBL, Institut de Physique Nucléaire de Lyon, Villeurbanne, France} 2_{Université de Lyon, INSA de Lyon, MATEIS UMR CNRS 5510, Villeurbanne, France} 3_{CSNSM, Université Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, Orsay, France}

Main results

Experimental protocole

General Background

Observations - Conclusion

→ Lamella preparation using the Focused Ion Beam (FIB) technique

→ Observe the formation of ballistic damage induced by heavy ions (Au+₎

irradiation

→ Observe the crystallographic orientation effects on the damage formation → Identify the amorphisation threshold (comparison with recent results of D.

Gosset et al.*)

Aim of the study

B4C structure

Sodium Fast Reactor

Acknowledgments The authors wish to thank the NEEDS Project for financial support and all the JANNuS-Orsay technical staff for their

assistance during the irradiation 1.3x1015_at.cm-2_{(∼ 2 dpa)}

3.5x1015_at.cm-2_{(∼ 4 dpa)}

4x1015_at.cm-2_{(∼6 dpa)}

Irradiation of lamella L2 (Bright field)

*Reference: D. Gosset et al., Nucl. Instr. Meth. Phys. Res. Sect. B, 365 (2015) 300-304

Generation IV Sodium Fast reactor (SFR)

Neutron absorber: Boron carbide B4C

Behavior under irradiation: role of ballistic and electronic damage

Lamella L1 EELS measurement

(lamella thickness t)

tL1∼ Small to 150 nm tL2∼ 80 nm

→ Crystallographic orientation analysis by TKD

SEM E-T SE imaging

Lamella L2

→ Distribution of the Z0sample direction with respect to crystal reference system → Each color corresponds to a different grain orientation

TEM in-situ observations performed on the grain

G (black circle EBSD) GL1: random orientation GL2: [1-210] // Au+beam

→ 1 MeV Au+_{ions at RT}

→ Fluence: from 1x1013_{to 4x10}15_at.cm-2

Irradiation conditions simulated by SRIM:

1

3

2

Bright field image of the lamella L1 after irradiation 1.3x1015_at.cm-2_{(∼ 2 dpa)} Unirradiated (0 dpa) 1x1014_at.cm-2_{(∼ 0.1 dpa)} 2x1014_at.cm-2_{(∼0.4 dpa)} Damage formation: 0 to 2x1014_at.cm-2_{: 0 to 0.4 dpa}

Local curvature of the sample due to an important stress induced in the material

1

1x1015_at.cm-2_{: ∼ 1.6 dpa}

Growth of the « black dots » until observation of larger stress field of : → Dislocation loops ∼ 20 nm

3

1.2x1014_at.cm-2 _{: ∼ 0.2 dpa}

Appearance of « black dots »

2 2.5x1015 _{< φ < 4x10}15_at.cm-2 _: 4 < x < 6 dpa Amorphisation threshold 4 Random orientation [1-210] Diffraction patterns:

- In the area observed in-situ under constant electron beam irradiation -1

- In a thick part of the lamella (∼ 150 nm) -2

- In a thin part of the lamella (< 100 nm) -3

0 50 100 150 200 250 300 350 400 Depth (nm) Au+_Rp 1,3x1014 at.cm-2 1x1015 at.cm-2 4x1015 at.cm-2 d p a Im p la n te d i o n s ( a .u .) 0 1 2 3 4 5 6 7 Rp = 190 ± 50 nm tL1< Rp tL2< Rp tL2 tL1 max Irradiation of lamella L1:

Damage (dpa) and Au+_{ions implantation profiles}

No crystallographic orientation effect:

→ defects created homogeneously in the whole lamella, whatever the grain orientation

Effect of the electron beam :

→ Self-healing of the material under electron beam combined with the ballistic effect of the ion beam

Effect of the ion implantation:

→ Amorphisation at fluences 2-3x lower when presence of Au atoms: