Vacancy trapping mechanism for hydrogen bubble formation in metal

Liu, Yue Lin; Zhang, Ying; Zhou, Hong-Bo; Lu, Guang Hong; Liu, Feng; Luo, Guang–Nan

doi:10.1103/physrevb.79.172103

Cited by 282 publications

(220 citation statements)

References 30 publications

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“…Furthermore, the detrapping energy of the defect site has been found to be dependent on the number of hydrogen isotopes bound to the tungsten defects site. This behaviour is somehow quite general, since it has been found by DFT for vacancies [14][15][16][17][18][19], dislocations [21] and grain boundaries [21,22] in tungsten, and it has been recently included in MRE model codes by Schmid et al [23] and Hodille et al [9]. The latter implementation used in the present work, called MHIMS-Reservoir [9], can be summarized with the potential energy diagrams of figure 4.…”

Section: Mre Models: Single Trap-multi-detrapping Energymentioning

confidence: 52%

Retention and release of hydrogen isotopes in tungsten plasma-facing components: the role of grain boundaries and the native oxide layer from a joint experiment-simulation integrated approach

et al. 2017

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Fusion fuel retention (trapping) and release (desorption) from plasma-facing components are critical issues for ITER and for any future industrial demonstration reactors such as DEMO. Therefore, understanding the fundamental mechanisms behind the retention of hydrogen isotopes in first wall and divertor materials is necessary. We developed an approach that couples dedicated experimental studies with modelling at all relevant scales, from microscopic elementary steps to macroscopic observables, in order to build a reliable and predictive fusion reactor wall model. This integrated approach is applied to the ITER divertor material (tungsten), and advances in the development of the wall model are presented. An experimental dataset, including focused ion beam scanning electron microscopy, isothermal desorption, temperature programmed desorption, nuclear reaction analysis and Auger electron spectroscopy, is exploited to initialize a macroscopic rate equation wall model. This model includes all elementary steps of modelled experiments: implantation of fusion fuel, fuel diffusion in the bulk or towards the surface, fuel trapping on defects and release of trapped fuel during a thermal excursion of materials. We were able to show that a single-trap-type single-detrapping-energy model is not able to reproduce an extended parameter space study of a polycrystalline sample exhibiting a single desorption peak. It is therefore justified to use density functional theory to guide the initialization of a more complex model. This new model still contains a single type of trap, but includes the density functional theory findings that the detrapping energy varies as a function of the number of hydrogen isotopes bound to the trap. A better agreement of the model with experimental results is obtained when grain boundary defects are included, as is consistent with the polycrystalline nature of the studied sample. Refinement of this grain boundary model is discussed as well as the inclusion in the model Nuclear Fusion

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Section: Mre Models: Single Trap-multi-detrapping Energymentioning

confidence: 52%

Retention and release of hydrogen isotopes in tungsten plasma-facing components: the role of grain boundaries and the native oxide layer from a joint experiment-simulation integrated approach

et al. 2017

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“…12,14 To determine the most stable site for a single He atom in perfect or defective Ti 3 AlC 2 , we calculate the solution energy for a He atom at different sites. The solution energy for a He atom in Ti 3 AlC 2 with and without a vacancy is defined as 22,23…”

Section: Resultsmentioning

confidence: 99%

“…This result is in good agreement with the previous theoretical predictions and experimental measurements. 6,22 Additionally, it is important to note that the solution energy of He in an Al vacancy is lower than that of a C vacancy, which implies that the Al vacancy exhibits stronger trapping for He than the C vacancy.…”

Section: Resultsmentioning

confidence: 99%

New insight into the helium-induced damage in MAX phase Ti3AlC2 by first-principles studies

Bai

Zha

et al. 2015

The Journal of Chemical Physics

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In the present work, the behavior of He in the MAX phase Ti 3 AlC 2 material is investigated using first-principle methods. It is found that, according to the predicted formation energies, a single He atom favors residing near the Al plane in Ti 3 AlC 2 . The results also show that Al vacancies are better able to trap He atoms than either Ti or C vacancies. The formation energies for the secondary vacancy defects near an Al vacancy or a C vacancy are strongly influenced by He impurity content. According to the present results, the existence of trapped He atoms in primary Al vacancy can promote secondary vacancy formation and the He bubble trapped by Al vacancies has a higher tendency to grow in the Al plane of Ti 3 AlC 2 . The diffusion of He in Ti 3 AlC 2 is also investigated. The energy barriers are approximately 2.980 eV and 0.294 eV along the c-axis and in the ab plane, respectively, which means that He atoms exhibit faster migration parallel to the Al plane. Hence, the formation of platelet-like bubbles nucleated from the Al vacancies is favored both energetically and kinetically. Our calculations also show that the conventional spherical bubbles may be originated from He atoms trapped by C vacancies. Taken together, these results are able to explain the observed formation of bubbles in various shapes in recent experiments. This study is expected to provide new insight into the behaviors of MAX phases under irradiation from electronic structure level in order to improve the design of MAX phase based materials. C 2015 AIP Publishing LLC. [http://dx

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“…In other words, the tensile stress promoted structure stability, whereas the compressive stress promoted structure instability. The vacant space for S occupation will be smaller because of the compression, leading to higher energy [33]. Furthermore, the relative values of the total energy at the TIS were larger than those of the total energy at the OIS.…”

Section: Stability and Charge Density Distribution Under Stressmentioning

confidence: 94%

Stress effects on stability and diffusion behavior of sulfur impurity in nickel: A first-principles study

Dong

Zhang

Liu

et al. 2014

Computational Materials Science

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a b s t r a c tA systematic investigation regarding the effect of stress on the stability and diffusion behavior of S impurity in Ni was carried out via first-principles methods. A comparison of the formation energy of S in Ni indicated that S more easily forms as a solution atom with increasing S concentration in Ni supercells, but the binding energy showed that as the concentration of S that dissolved into Ni increased, the structure became less stable. The diffusion barrier via the octahedral-tetrahedral-octahedral site path was always lower than that via the octahedral-octahedral site path. The diffusion barrier of single S decreased with increase in tensile stress. S diffusion accelerated under applied tensile stress, which was disadvantageous in suppressing S retention in Ni. These results implied that even at a low concentration, dissolved S still had a tendency of precipitating from the Ni matrix, to further increase the stability of the system.

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Vacancy trapping mechanism for hydrogen bubble formation in metal

Cited by 282 publications

References 30 publications

Retention and release of hydrogen isotopes in tungsten plasma-facing components: the role of grain boundaries and the native oxide layer from a joint experiment-simulation integrated approach

Retention and release of hydrogen isotopes in tungsten plasma-facing components: the role of grain boundaries and the native oxide layer from a joint experiment-simulation integrated approach

New insight into the helium-induced damage in MAX phase Ti3AlC2 by first-principles studies

Stress effects on stability and diffusion behavior of sulfur impurity in nickel: A first-principles study

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