Mechanisms of recovery of radiation damage based on the interaction - PowerPoint PPT Presentation

Mechanisms of recovery of radiation damage based on the interaction of quodons with crystal defects Vladimir Dubinko NSC Kharkov Institute of Physics and Technology, Kharkov, Ukraine

OUTLINE 1. Driving forces of microstructure evolution 2. Void growth and shrinkage: MD simulation 3. Radiation-induced solubility limit: Focuson concept 4. Experimental evidence for the radiation-induced annealing of voids and dislocation loops 5. Theoretical estimates: the need for quodons 6. Quodon definition and discovery 7. Experimental evidence 8. Applications in physics of radiation effects: Swelling saturation and reduction with increasing irradiation dose Self-organization of voids Electron-plastic effect Outstanding problems

Radiation-induced void swelling × − 1.2 MeV Cr 3+ → Ni (600 o C, ~25 dpa) 3 7 10 dpa s / DOSE ATE:

Driving forces of microstructure evolution Perfect crystal a Thermal treatment SIA D c v Void PKA Crowdion Focuson γω ⎧ ⎫ 2 Dc th ⎨ ⎬ exp VAC _ v 0 ⎩ ⎭ kTR Crystal with ED Irradiation _ D i c b i _ SIA Void Void D v c PKA Crowdion v GB Focuson _ VAC _ _ E ( ( ) ) ≈ 0 Φ irr d Dc K bl E , E R vR F F v E F

HISTORY “For many years already we study the void swelling in reactor materials, but to solve the problem one should know how the void shrink rather than grow…” Ilya Naskidashvilly, Winter School, Bakuriani, Georgia1980 20 years later…

MD simulation of point defects production in the vicinity of extended defects Schematic representation of point defect Illustration of the final stages of collision cascade formation near a void. developments in the bulk (left) and near the void (right) at PKA energy 1 keV. N. P. Lazarev, V. I. Dubinko, Radiat. Eff. Def. Solids 158 (2003) 803 100 Number of displaced atoms Near Void Vacancies 10 80 FP in bulk In Bulk Number of defects Interstitials 60 5 40 20 0 0 10 100 1000 10 100 1000 PKA Energy, eV PKA Energy, eV In contrast to the Frenkel pair production in the bulk, the collision events in the vicinity of extended defects results in a biased formation of vacancies due to the lower energy barrier involved

Radiation-induced solubility limit 1 ( ) ( ) ( ) = + eq th irr c T , K c T c T , K 0.1 v v v VACANCY CONCENTRATION Ee = 1 MeV 0.01 1 . 10 3 ⎛− ⎞ f ( ) E ⎜ ⎟ = 1 . 10 4 th v exp c T ⎜ ⎟ v 1 . 10 5 ⎝ ⎠ k T B 1 . 10 6 ( ) 0 1 . 10 7 ( ) Kbl E ≈ Φ irr SD F d c T , K E , E 1 . 10 8 ( ) v v F D T , K E 1 . 10 9 v F 1 . 10 10 1 . 10 11 SD ⎛ ⎞ ( ) E E v F E ∫ ⎜ ⎟ Φ = 1 . 10 12 SD F E , E ln x ln x dx ⎜ ⎟ v F SD ⎝ ⎠ E 1 . 10 13 v 1 0.2 0.4 0.6 0.8 HOMOLOGICAL TEMPERATURE = + Thermal equilibrium SD f m E E E Self-diffusion Radiation-induced equilibrium v v v activation energy Total equilibrium Steady-state

Radiation-induced reduction in the void swelling V.I. Dubinko, A.G. Guglya, E. Melnichenko, R. Vasilenko, EMRS 2008, Journal of Nuclear Materials, 385 (2009) 228-230 Cr 3+ → Ni (600 o C, ~25 dpa) + Cr 3+ → Cr 3+ → Ni (600 o C, ~25 dpa) Ni (525 o C, ~25 dpa) Cr 3+ → Ni (600 o C, ~25 dpa) + Cr 3+ → 10 21 ions/m 2 ION FLUENCE Ni (450 o C, ~25 dpa) − − = × DOSE RATE 3 1 K 7 10 s

Radiation-induced void shrinkage Experiment 3.0 1 - Cr3+ (1,2 MeV, 600oC, 1017ion/cm2) 50 Void density, x 1015 cm-3 2.8 48 2 - Cr3+ (600oC + 525oC ) 1 - Cr3+ (600oC) 46 2.6 3 - Cr3+ (600oC + 450oC) 2 - Cr3+ (600oC + 525oC) Void diamiter, nm 44 2.4 42 3 - Cr3+ (600oC + 450oC) 40 2.2 38 2.0 36 34 1.8 32 1.6 30 28 1.4 26 1.2 24 22 1.0 20 1 2 3 1 2 3 Tipe of irradiation Tipe of irradiation 1 - C3+ (600oC) 7 2 - Cr3+ (600oC + 525oC) Swelling, % 3 - Cr3+ (600oC + 450oC) 6 5 − − = × 4 DOSE RATE 3 1 K 7 10 s 3 2 1 1 2 3 Tipe of irradiation

Proton irradiation of nickel samples (Dubinko, Guglya, 2009) 600 o C, 3 dpa H + (30 keV) - Ni, 600 o C, + 3 dpa, (10 18 ion/cm 2 450 o C, 6 dpa

Proton irradiation of nickel samples (Dubinko, Guglya, 2009) 5.0 10 20 Swelling, % 4.5 Void size, nm 9 18 4.0 8 16 -3 16 cm 3.5 7 14 3.0 6 Void density, x 10 12 2.5 5 10 2.0 4 8 3 1.5 6 2 1.0 4 1 0.5 2 0 0 0.0 0.0 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 2.0 18 ion/cm 2 18 ion/cm 2 18 ion/cm 2 Dose, x 10 Dose, x 10 Dose, x 10 Dose dependence of void size (a), void density (b) and swelling (c) in nickel irradiated by H+ ions ( 30 keV, 3 dpa (1018 ion/cm2)) at 600 оС and 450 оС .

Radiation damage and electron radiation induced recovery in ZnTe Lu, Niu, Wang Radiation Effects and Defects in Solids, 116 (1991) 81 - 94 3,5 and 7 keV Ar ion irradiation produced defects in ZnTe crystals and their annealing are investigated using transmission electron microscopy. The defects are identified to be densely distributed small dislocation loops. Under electron beam irradiation (80-200 keV), these dislocation loops are seen to reduced in density considerably. This electron beam induced defect annealing is explained qualitatively in terms of the non- radiative recombination of excited electron on the defects

Radiation-induced void shrinkage theory [ ] dR 1 ( ) = − − V V V eq , Z D c Z D c Z D c T K v v v i i i v v v dt R 20 Temperature dependence of the 15 Void growth/shrinkage rate VOID GROWTH RATE, nm/h 10 in Ni for different ranges of 5 breather propagation. 0 0 − − = × DOSE 3 1 K 7 10 s 5 RATE 10 700 800 900 1000 1100 1200 TEMPERATURE (K) Breather range 10000 b Breather range 10000 b Breather range 1000 b Breather range 1000 b Focuson range 10 b ("classical" limit) Focuson range 10 b ("classical" limit)

Quodon definition As the incident focuson energy is dispersed but the available kinetic energy still far exceeds that of phonons, atoms experience large displacements from their equilibrium positions. Propagation of the corresponding lattice vibrations may be governed by nonlinear forces. This may result in formation of vibrational particle-like solitons, called discrete breathers (DBs) or quodons (QODs). According to molecular dynamic simulations, the DBs are mobile, highly anharmonic longitudinal vibrations that are sharply localized in longitudinal direction and practically across one atomic distance in the transverse direction. The main difference between focusons and breathers (quodons) is that the latter are stable against thermal motion.

Discrete breathers can move and transport coherently energy through the lattice: Interaction of moving discrete breathers with vacancies, J Cuevas, 1 JFR Archilla, B S´anchez-Rey, FR Romero, 2005 Energy density plot for the interaction moving breather–vacancy. The particle to the right of the vacancy is located at n = 0. In (a), the moving breather is reflected and the vacancy moves backwards, in (b) the breather is transmitted and the vacancy moves backwards.

F.M. Russell, J.C. Eilbeck, Evidence for moving breathers in a layered crystal insulator at 300 K , Europhysics Letters 78, 10004, 2007. Ejection of atoms at a crystal surface caused by energetic breathers which have travelled more than 10 7 unit cells in atomic chain directions. The breathers were created by bombardment of a crystal face with heavy ions. This effect was observed at 300K in the layered crystal muscovite, which has linear chains of atoms for which the surrounding lattice has C2 symmetry.

Swelling saturation and void ordering Breather Dissolution of a void in the “interstitial” position Micrographs of bcc void lattices following ion due to the absorption of breathers coming from irradiation in molybdenum, (111) projection larger distances as compared to “regular” voids [J.H. Evans, in Patterns, Defects and Materials [V. Dubinko, Nuclear Inst. and Methods in Instabilities, 1990]. Physics Research, 2009]

SUMMARY #1 � Vacancy voids have been produced in Ni by 1.2 MeV Cr ion irradiation at 873 o K up to the ion fluence of 10 21 ions m -2 � Irradiation of specimens containing voids at 798 o K and 723 o K has resulted in the radiation-induced annealing of voids . � The experimental results may be explained in the framework of the rate theory taking into account the interaction of voids with long-propagating discrete breathers - quodons.

Outstanding problem: How to observe quodons in conventional MD ? The energy relaxation simulations in Cu at T = 1 K, Lazarev, Dubinko, 2003

INVESTIGATION OF THE ELECTRON-PLASTIC EFFECT • In 60-70th of the last century a pioneering study was made on the effect of electron beam on plastic deformation of some hcp and fcc metals. However, the underlying mechanisms of the observed effects are still a subject of debates. • In the present paper, we report on the effect of electron beam of (0.5 MeV energy and 5 х 1013 с m-2s-1 density) on plastic deformation of polycrystalline aluminum (99,5%) and copper (99,5%) under uniaxial deformation at a rate of 1.6x10-4s-1 at room temperature.