Design of composite materials for outgassing of implanted He M. J. - - PowerPoint PPT Presentation

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Design of composite materials for outgassing of implanted He M. J. - - PowerPoint PPT Presentation

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Design of composite materials for outgassing of implanted He M. J. Demkowicz MIT Department of Materials Science and Engineering, Cambridge, MA 02139 Sponsors: Acknowledgements: CMIME, an Energy Frontier Research A. Kashinath, D. Yuryev,

slide-1
SLIDE 1

Design of composite materials
 for outgassing of implanted He

  • M. J. Demkowicz

MIT Department of Materials Science and Engineering, Cambridge, MA 02139

Sponsors:

  • CMIME, an Energy Frontier Research

Center funded by DOE, Office of Science under Award Number 2008LANL1026

  • LANL LDRD program

Acknowledgements:

  • A. Kashinath, D. Yuryev,
  • P. Wang, J. Majewski, A. Misra,
  • X. Zhang, D. Bhattacharyya, …

ICTP-IAEA 2014 Trieste, Italy

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SLIDE 2

He-induced damage

  • S. Kajita et al., Nucl. Fus. 49, 095005 (2009)

He-implanted W, T=1000-2000K

Can we design a materials where this sort of damage does not occur?

slide-3
SLIDE 3

Nb Cu Free surface Design: channels for He outgassing Incident He Free surface Incident He No design: uncontrolled precipitation

Channels for continuous He outgassing

  • W. Z. Han et al., J. Nucl. Mater. 452, 57 (2014)
  • D. V. Yuryev et al., APL under review (2014)

Cu-Nb layered composites

slide-4
SLIDE 4

Outline

  • Modeling He precipitation in metal multilayers
  • Experimental validation of modeling results
  • Design of metal composites for He outgassing
slide-5
SLIDE 5

Misfit dislocation patterns at Cu-Nb interfaces

All Cu‐Nb interfaces in magnetron spu6ered composites have the same crystallography: {111}fcc || {110}bcc and <110>fcc || <111>bcc

<111> <110> <112> <110> <111> <112>

Cu Nb

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SLIDE 6

He trapping at Cu-Nb interfaces is quasi-static

!"! #$%$&%'! ()*+$&,$,-.&! /0! 12! 34(! 4-5526-.&! 78$**-&9! (&,"85$%"!

  • 35 keV He ions are implanted to

a dose of 1017/cm2 in 3 hours => 1 He atom reaches the vicinity of a trap every ~12 minutes

  • He migration energy at the

interface is ~0.1 eV => time to find the trap <1ns

  • Vacancy migration energy at the

interface is ~0.4 eV => time to equilibrate vacancy concentration <1s

[1] A. Y. Dunn et al, JNM 435 141 (2013); [2] K. Kolluri et al, PRB 84, 104102 (2011)

Trap

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SLIDE 7

Atomic-level modeling of He trapping


at a Cu-Nb interface using a custom-made EAM potential

  • A. Kashinath et al., PRL 110, 086101 (2013)

Iterative method for introducing He into interface: Outcome: He clusters grow at MDIs on Cu side of interface

  • There is a thermodynamic

driving force for clusters to coalesce, but the kinetics of coalescence is very slow.

  • He/vacancy ratio ≈ 1

Insert He into lowest energy location Remove Cu or Nb atoms until no negative vacancy energy sites remain Equilibrium He cluster

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SLIDE 8

Two modes of He cluster growth

  • A. Kashinath et al., PRL 110, 086101 (2013)
  • Cu
  • He
  • Nb

(a) 10 He (b) 15 He (c) 20 He (d) 40 He (e) 80 He

Along the interface Normal to the interface, into Cu layer

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SLIDE 9

<110>Cu || <111>N b (˚ A) <112>Cu || <112>N b (˚ A)

20 40 60 80 20 40 60 80 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8

Nb Cu

J/m2

Interface Energy (J/m2)

γHe-Cu 1.93 γHe-Nb 2.40 γCu-Nb Depends on location in the interface plane

Wetting Coefficient: W = γCu-Nb + γHe-Cu – γHe-Nb

Wetting

W > 0

Non-wetting

W < 0

Mechanism of interfacial He precipitation:


wetting at misfit dislocation intersections

“Heliophobic” W<0 “Heliophilic” W<0

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SLIDE 10

Outline

  • Modeling He precipitation in metal multilayers
  • Experimental validation of modeling results
  • Design of metal composites for He outgassing
slide-11
SLIDE 11
  • M. J. Demkowicz et al., Appl. Phys. Lett. 97, 161903 (2010)

Scales with interface area/vol. Depends on interface type: – Cu-Nb: 8.5 atoms/nm2 – Cu-Mo: 3.0 atoms/nm2 – Cu-V: 1.9 atoms/nm2

Critical He concentration to observe bubbles

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SLIDE 12

0.8 0.85 0.9 0.95 0.001 0.002 0.003 0.004 0.005 0.006

C u

  • V

C u

  • M
  • C

u

  • N

b

abcc / af cc

Areal density of MDIs (#/˚ A2)

! "

0.025 0.05 0.075 0.1 0.125 critical He concentration (#/˚ A2)

"

0.035 0.105 0.175 0.245 0.315 0.385 reduced critical dose (#/˚ A2) O−lattice TEM NR

Agreement between model, TEM, and NR

Kurdjumov-Sachs orientation relation, closest-packed interface planes

  • A. Kashinath et al., JAP 114, 043505 (2013)

Areal density, ρ, of heliophilic patches in Cu‐Nb Cu‐V

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SLIDE 13

Outline

  • Modeling He precipitation in metal multilayers
  • Experimental validation of modeling results
  • Design of metal composites for He outgassing
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SLIDE 14

Designing interfaces that outgas He

Interface composition and crystallography Precipitation of linear He channels with MDI pattern as a template

Model 2:

quantized Frank-Bilby equation + anisotropic elasticity

Model 2:

wetting of misfit dislocation intersections

BCC, abcc, {110} FCC, aFCC, {111}

θ

lmin l

Misfit dislocation intersections (MDIs) closely spaced in one direction and far apart in the perpendicular direction

  • D. V. Yuryev and M. J. Demkowicz, APL under review (2014)
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SLIDE 15

Two degrees of freedom: θ and ρ

BCC, abcc, {110} FCC, afcc, {111} θ

  • D. V. Yuryev and M. J. Demkowicz, APL under review (2014)

ρ=abcc/afcc

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SLIDE 16

lmin l

Design criteria

  • D. V. Yuryev and M. J. Demkowicz, APL under review (2014)

lmin < lmin

cut

l

lower < l < l upper

Criterion 2: Criterion 1:

lmin l (multiples of afcc)

(multiples of afcc)

Precipitates overlap along lmin prior to bubble-to-void transition

  • : channels sufficiently far

apart not to overlap

  • : channels sufficiently close

to getter He before it clusters

l

lower

l

upper

ρ=abcc/afcc

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SLIDE 17

l

upper

l

upper

tl fbind = R Ki = l

4 Kiafcc 5

6DHe < fbind

max =102

fbind <102

T‐tl envelopes where for K0=1032/m2s and different values of l

Rate theory model for He clustering

We chose: l

upper = 30

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SLIDE 18

Solution space

Sputter deposited CuV interfaces are good candidates for He outgassing

Cu‐V Pd‐Fe Pt‐Nb, Pt‐Ta ρ=abcc/afcc

  • D. V. Yuryev and M. J. Demkowicz, APL under review (2014)
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SLIDE 19

Designing interfaces that outgas He

<111> <110> <112> <110> <111> <112>

Cu Nb

heliophobic heliophilic Cu Nb He clusters

F

  • r

w a r d p r

  • b

l e m : m u l t i s c a l e m

  • d

e l i n g I n v e r s e p r

  • b

l e m : c

  • m

p u t a t i

  • n

a l d e s i g n

Model system: reliable simulation Atomic- level insight: precipitation mechanism ROM1: interface wetting Templated He precipitation: enables outgassing ROM 2: designer interface dislocation arrangement He resistant interface: could not have been found by “hit-or-miss” We6able regions Phase‐field model AnalyRcal model

We are here

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SLIDE 20

Conclusions

  • He precipitates on misfit dislocation intersections (MDIs) at interfaces in

fcc/bcc metal layered composites

  • Precipitation occurs by wetting of high energy regions of the interface,

which are located at MDIs

  • Layered composites containing interfaces that template He precipitation

into continuous channels have been designed and are now being synthesized and tested

  • Such composites may mitigate He-induced surface damage by providing

paths for He outgassing while maintaining cohesion across the interface