11 results on '"Hong-Bo Zhou"'
Search Results
2. Characterization of the energetics and configurations of hydrogen in vacancy clusters in tungsten
- Author
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Yu-Hao Li, Guang-Hong Lu, Qing-Yuan Ren, Zhong-Zhu Li, Long Cheng, and Hong-Bo Zhou
- Subjects
Nuclear and High Energy Physics ,Materials science ,Hydrogen ,Thermal desorption spectroscopy ,Coordination number ,chemistry.chemical_element ,Condensed Matter Physics ,01 natural sciences ,Molecular physics ,010305 fluids & plasmas ,Perfect crystal ,chemistry ,Vacancy defect ,0103 physical sciences ,Cluster (physics) ,Molecule ,Shielding effect ,010306 general physics - Abstract
We have explored the retention of hydrogen (H) in tungsten (W) by investigating its dissolution and aggregation in vacancy clusters (VCs) using a first-principles method and thermodynamic models. The solution energy of a single H in the VCs is in the range of -0.99 ~ -0.64 eV, much lower than that at a mono-vacancy (~ -0.37 eV) and interstitial site (~ 1.01 eV) in W. Such a remarkable discrepancy is rationalized on the electronic interaction of H with its neighboring W atoms, which varies from repulsion to attraction with H moving from perfect crystal to vacancy/VCs. Specifically, the solution/trapping energies of H in VCs can be well categorized by the coordination number of its neighboring W atoms, i.e. the lower the coordination number of W, the stronger is the H-W attraction and the lower is the H solution/trapping energy. Furthermore, taking the V_9^m cluster as an example, it is observed that the multiple H atoms form a multilayer nested cage configuration at VCs surface initially, and then the stable H2 molecules form in the center of VCs. Interestingly, the pre-existed H atoms in VCs inner surface has a shielding effect on the H-W interaction, decreasing the electron density of the central region of VCs and facilitating the formation of H2 molecules. Moreover, the desorption temperatures of H in VCs are also predicted based on the Polanyi-Wigner equation, which are in good agreement with the available thermal desorption spectroscopy experiments. Our calculations provide a good reference to understand the influence of VCs on the retention and evolution of H in W.
- Published
- 2019
3. Towards understanding the influence of Re on H dissolution and retention in W by investigating the interaction between dispersed/aggregated-Re and H
- Author
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Hong-Bo Zhou, Guang-Hong Lu, Wenwen Wang, Fang-Fei Ma, and Yu-Hao Li
- Subjects
Nuclear and High Energy Physics ,Materials science ,Alloy ,Thermodynamics ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Crystallographic defect ,010305 fluids & plasmas ,0103 physical sciences ,engineering ,0210 nano-technology ,Dissolution - Abstract
We have investigated the effects of Re on the behaviors of H in W as well as their interaction with point defects using a first-principles method in combination with thermodynamic models. It is clearly found that the influence of Re on H is directly related to the distribution of Re in W. For the state of Re dispersed distribution, both a single Re and its complexes with point defects have very slight effect on H dissolution and retention in W. However, the influence of Re clusters (for the state of Re aggregation) on H is extraordinary stronger than that of a single Re. The retention of H in W can be significantly decreased by Re clusters, and their influences will be enhanced with the increasing of the number of Re atoms. This can be attributed to the electronic interaction between H and Re/W, in which the repulsion of Re–H is stronger than that of W–H. We have further examined the retention of H at different temperature in W based on the Polanyi–Wigner equation. It is found that a Re4-vacancy complex can only accommodate 4 H atoms at room temperature, ~33% lower than the maximum number of H atoms in a mono-vacancy. These results give a reasonable interpretation for the experimentally observed D retention significantly decreasing in damaged W–Re alloy in comparison with that in damaged pure W. Consequently, our calculations provide a good reference for evaluating the influence of Re on the performance of W-PFM.
- Published
- 2018
4. Behaviors of transmutation elements Re and Os and their effects on energetics and clustering of vacancy and self-interstitial atoms in W
- Author
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Huiqiu Deng, Ying Zhang, Shuo Jin, Hong-Bo Zhou, Guang-Hong Lu, and Yu-Hao Li
- Subjects
Nuclear and High Energy Physics ,Materials science ,Binding energy ,Nucleation ,chemistry.chemical_element ,02 engineering and technology ,Activation energy ,Rhenium ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Crystallographic defect ,010305 fluids & plasmas ,chemistry ,Chemical physics ,Vacancy defect ,0103 physical sciences ,Atom ,Osmium ,Atomic physics ,0210 nano-technology - Abstract
We investigate the behaviors of rhenium (Re) and osmium (Os) and their interactions with point defects in tungsten (W) using a first-principles method. We show that Re atoms are energetically favorable to disperse separately in bulk W due to the Re–Re repulsive interaction. Despite the attractive interaction between Os atoms, there is still a large activation energy barrier of 1.10 eV at the critical number of 10 for the formation of Os clusters in bulk W based on the results of the total nucleation free energy change. Interestingly, the presence of vacancy can significantly reduce the total nucleation free energy change of Re/Os clusters, suggesting that vacancy can facilitate the nucleation of Re/Os in W. Re/Os in turn has an effect on the stability of the vacancy clusters (V n ) in W, especially for small vacancy clusters. A single Re/Os atom can raise the total binding energies of V2 and V3 obviously, thus enhancing their formation. Further, we demonstrate that there is a strong attractive interaction between Re/Os and self-interstitial atoms (SIAs). Re/Os could increase the diffusion barrier of SIAs and decrease their rotation barrier, while the interstitial-mediated path may be the optimal diffusion path of Re/Os in W. Consequently, the synergistic effect between Re/Os and point defects plays a key role in Re/Os precipitation and the evolution of defects in irradiated W.
- Published
- 2017
5. A review of modelling and simulation of hydrogen behaviour in tungsten at different scales
- Author
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Charlotte Becquart, Guang-Hong Lu, and Hong-Bo Zhou
- Subjects
Nuclear and High Energy Physics ,Fusion ,Materials science ,Hydrogen ,Thermodynamics ,chemistry.chemical_element ,Tungsten ,Fusion power ,Condensed Matter Physics ,chemistry ,Thermal ,Liquid bubble ,Diffusion (business) ,Dissolution - Abstract
Tungsten (W) is considered to be one of the most promising plasma-facing materials (PFMs) for next-step fusion energy systems. However, as a PFM, W will be subjected to extremely high fluxes of low-energy hydrogen (H) isotopes, leading to retention of H isotopes and blistering in W, which will degrade the thermal and mechanical properties of W. Modelling and simulation are indispensable to understand the behaviour of H isotopes including dissolution, diffusion, accumulation and bubble formation, which can contribute directly to the design, preparation and application of W as a PFM under a fusion environment. This paper reviews the recent findings regarding the behaviour of H in W obtained via modelling and simulation at different scales.
- Published
- 2014
6. Towards suppressing H blistering by investigating the physical origin of the H–He interaction in W
- Author
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Shuo Jin, Hong-Bo Zhou, Guang-Hong Lu, Guang-Nan Luo, Ying Zhang, and Yue-Lin Liu
- Subjects
Nuclear and High Energy Physics ,Materials science ,Hydrogen ,Nucleation ,Noble gas ,chemistry.chemical_element ,Charge density ,Condensed Matter Physics ,Crystallographic defect ,chemistry ,Chemical physics ,Vacancy defect ,Redistribution (chemistry) ,Atomic physics ,Helium - Abstract
We investigate the physical origin of H–He interaction in W in terms of optimal charge density by calculating the energetics and diffusion properties using a first-principles method. On the one hand, we show a strong attraction between H and He in W originated from the charge density redistribution due to the presence of He, driving H segregation towards He. This can block the permeation of H into deeper bulk and thus suppress H blistering. On the other hand, we demonstrate that He, rather than H, energetically prefers to occupy the vacancy centre due to its closed-shell structure, which can block H2 formation at the vacancy centre. This is because He causes a redistribution of charge density inside the vacancy to make it ‘not optimal’ for the formation of H2 molecules, which can be treated as a preliminary nucleation of the H bubbles. We thus propose that H retention and blistering in W can be suppressed by doping the noble gas elements.
- Published
- 2010
7. Investigating behaviours of hydrogen in a tungsten grain boundary by first principles: from dissolution and diffusion to a trapping mechanism
- Author
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Ying Zhang, Guang-Nan Luo, Guang-Hong Lu, Hong-Bo Zhou, Yue-Lin Liu, and Shuo Jin
- Subjects
Nuclear and High Energy Physics ,Materials science ,Diffusion barrier ,Hydrogen ,chemistry.chemical_element ,Charge density ,Condensed Matter Physics ,chemistry ,Chemical physics ,Vacancy defect ,Interstitial defect ,Grain boundary ,Diffusion (business) ,Dissolution - Abstract
We have investigated the dissolution, segregation and diffusion of hydrogen (H) in a tungsten (W) grain boundary (GB) using a first-principles method in order to understand the GB trapping mechanism of H. Optimal charge density plays an essential role in such a GB trapping mechanism. Dissolution and segregation of H are directly associated with the optimal charge density, which can be reflected by the H solution and segregation energy sequence for the different interstitial sites. To occupy the optimal-charge-density site, H can be easily trapped by the W GB with the solution and segregation energy of −0.23 eV and −1.11 eV, respectively. Kinetically, such a trapping is easier to realize due to the much lower diffusion barrier of 0.13–0.16 eV from the bulk to the GB in comparison with the segregation energy, suggesting that it is quite difficult for the trapped H to escape out of the GB. However, the GB can hold no more than 2 H atoms because the isosurface of optimal charge density almost disappears with the second H atom in, leading to the conclusion that H2 molecule and thus H bubble cannot form in the W GB. Taking into account the lower vacancy formation energy in the GB as compared with the bulk, we propose that the experimentally observed H bubble formation in the W GB should be via a vacancy trapping mechanism.
- Published
- 2010
8. Characterization of the energetics and configurations of hydrogen in vacancy clusters in tungsten.
- Author
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Qing-Yuan Ren, Yu-Hao Li, Hong-Bo Zhou, Zhong-Zhu Li, L. Cheng, and Guang-Hong Lu
- Subjects
THERMAL desorption ,TUNGSTEN ,VACANCIES in crystals ,WATER clusters ,ELECTRON density ,HYDROGEN ,ATOMS - Abstract
We have explored the retention of hydrogen (H) in tungsten (W) by investigating its dissolution and aggregation in vacancy clusters (VCs) using a first-principles method and thermodynamic models. The solution energy of a single H in the VCs is in the range of −0.99 to −0.64 eV, much lower than that at a mono-vacancy (~ −0.37 eV) and interstitial site (~1.01 eV) in W. Such a remarkable discrepancy is rationalized on the electronic interaction of H with its neighboring W atoms, which varies from repulsion to attraction with H moving from perfect crystal to vacancy/VCs. Specifically, the solution/trapping energies of H in VCs can be well categorized by the coordination number of its neighboring W atoms, i.e. the lower the coordination number of W, the stronger the H–W attraction and the lower the H solution/trapping energy. Furthermore, taking the cluster as an example, it is observed that the multiple H atoms form a multilayer nested cage configuration at the VC surface initially, and then the stable H
2 molecules form in the center of the VCs. Interestingly, the pre-existing H atoms in the VC inner surface have a shielding effect on the H–W interaction, decreasing the electron density of the central region of the VCs and facilitating the formation of H2 molecules. Moreover, the desorption temperatures of H in the VCs are also predicted based on the Polanyi–Wigner equation, and are in good agreement with the available thermal desorption spectroscopy experiments. Our calculations provide a good reference to understand the influence of VCs on the retention and evolution of H in W. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
9. Towards understanding the influence of Re on H dissolution and retention in W by investigating the interaction between dispersed/aggregated-Re and H.
- Author
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Fang-Fei Ma, Wenwen Wang, Yu-Hao Li, Hong-Bo Zhou, and Guang-Hong Lu
- Subjects
DISSOLUTION (Chemistry) ,THERMODYNAMICS ,RHENIUM ,POINT defects ,TUNGSTEN compounds ,HELIUM ions - Abstract
We have investigated the effects of Re on the behaviors of H in W as well as their interaction with point defects using a first-principles method in combination with thermodynamic models. It is clearly found that the influence of Re on H is directly related to the distribution of Re in W. For the state of Re dispersed distribution, both a single Re and its complexes with point defects have very slight effect on H dissolution and retention in W. However, the influence of Re clusters (for the state of Re aggregation) on H is extraordinary stronger than that of a single Re. The retention of H in W can be significantly decreased by Re clusters, and their influences will be enhanced with the increasing of the number of Re atoms. This can be attributed to the electronic interaction between H and Re/W, in which the repulsion of Re–H is stronger than that of W–H. We have further examined the retention of H at different temperature in W based on the Polanyi–Wigner equation. It is found that a Re
4 -vacancy complex can only accommodate 4 H atoms at room temperature, ~33% lower than the maximum number of H atoms in a mono-vacancy. These results give a reasonable interpretation for the experimentally observed D retention significantly decreasing in damaged W–Re alloy in comparison with that in damaged pure W. Consequently, our calculations provide a good reference for evaluating the influence of Re on the performance of W-PFM. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
10. Mitigated blistering and deuterium retention in tungsten exposed to high-flux deuterium–neon mixed plasmas
- Author
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Guang-Hong Lu, Ying Zhang, Long Cheng, Hong-Bo Zhou, Bo Wang, Thomas Schwarz-Selinger, Yuan Yuan, G. De Temmerman, and Thomas Morgan
- Subjects
Nuclear and High Energy Physics ,Materials science ,Analytical chemistry ,chemistry.chemical_element ,Penetration (firestop) ,Plasma ,Tungsten ,Condensed Matter Physics ,01 natural sciences ,6. Clean water ,010305 fluids & plasmas ,Neon ,High flux ,chemistry ,Deuterium ,0103 physical sciences ,Atomic physics ,010306 general physics - Abstract
Surface morphology and deuterium retention in tungsten exposed at surface temperature of 550 K to mixed deuterium–neon plasmas of different neon concentrations are investigated. It is found that the addition of neon up to 20% mitigates blistering on the surface. Cross-section view of the surface shows the formation of pores near the surface in the depth less than 100 nm. Deuterium depth profile is featured by an enhanced deuterium concentration within a depth of 16 nm but a mitigated penetration in depth larger than 1 µ m. Deuterium retention is reduced by up to a factor of four. It is suggested the open pores formed in the surface serves as an escaping channel, mitigates deuterium penetration towards bulk and retention in the bulk.
- Full Text
- View/download PDF
11. Behaviors of transmutation elements Re and Os and their effects on energetics and clustering of vacancy and self-interstitial atoms in W.
- Author
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Yu-Hao Li, Hong-Bo Zhou, Shuo Jin, Ying Zhang, Huiqiu Deng, and Guang-Hong Lu
- Subjects
- *
NUCLEAR reactions , *POINT defects , *TUNGSTEN , *NUCLEATION , *OSMIUM , *RHENIUM - Abstract
We investigate the behaviors of rhenium (Re) and osmium (Os) and their interactions with point defects in tungsten (W) using a first-principles method. We show that Re atoms are energetically favorable to disperse separately in bulk W due to the Re–Re repulsive interaction. Despite the attractive interaction between Os atoms, there is still a large activation energy barrier of 1.10 eV at the critical number of 10 for the formation of Os clusters in bulk W based on the results of the total nucleation free energy change. Interestingly, the presence of vacancy can significantly reduce the total nucleation free energy change of Re/Os clusters, suggesting that vacancy can facilitate the nucleation of Re/Os in W. Re/Os in turn has an effect on the stability of the vacancy clusters (Vn) in W, especially for small vacancy clusters. A single Re/Os atom can raise the total binding energies of V2 and V3 obviously, thus enhancing their formation. Further, we demonstrate that there is a strong attractive interaction between Re/Os and self-interstitial atoms (SIAs). Re/Os could increase the diffusion barrier of SIAs and decrease their rotation barrier, while the interstitial-mediated path may be the optimal diffusion path of Re/Os in W. Consequently, the synergistic effect between Re/Os and point defects plays a key role in Re/Os precipitation and the evolution of defects in irradiated W. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
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