268 results on '"Cluster dynamics"'
Search Results
2. Mechanistic nuclear fuel performance modeling of uranium nitride
- Author
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Rizk, Jason T., Cooper, Michael W.D., Simon, Pierre-Clément A., Schneider, Anton J., Andersson, David A., Novascone, Stephen R., and Matthews, Christopher
- Published
- 2025
- Full Text
- View/download PDF
3. Cluster dynamics study on nano damage of RPV steels under proton irradiation at 290°C.
- Author
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Wan, Qiangmao, Shu, Guogang, Tang, Jiaxuan, Pang, Jianjun, Chen, Lisha, Wang, Duan, Lin, Hui, Ding, Hui, Xu, Chi, Wu, Shi, and Fu, Baoqin
- Subjects
PRESSURE vessels ,TRANSMISSION electron microscopy ,DISLOCATION density ,EMBRITTLEMENT ,NUCLEATION ,DISLOCATION loops - Abstract
Irradiation-induced defects such as dislocation loops, cavities or solute clusters and chemical composition segregation of reactor pressure vessel (RPV) steel are the root causes of irradiation embrittlement. Combining two nucleation mechanisms, namely, the uniform nucleation and non-uniform nucleation of solute clusters (such as Cu-rich phase), a cluster kinetic simulation was established based on the reaction rate theory, and the co-evolution of matrix damage and Cu-rich phase in low-copper RPV steel was simulated under irradiation. And the average size and number density of defective clusters and solute clusters were established with irradiation dose. Compared with the average size and number density of dislocation loops observed by transmission electron microscopy (TEM) of proton irradiated RPV steel at 290°C, the verification results show that the cluster dynamics model considering both the nucleation mechanism of interstitial dislocation loops and vacancy clusters can well simulate the irradiation damage behavior of materials. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
4. Influence of Source Term Algorithm on Irradiation Induced Microstructure Evolution Based on Cascade Collision Defect Database by Cluster Dynamics Method
- Author
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WANG Dongjie#, PAN Caifu#, WU Shi, HE Xinfu, DOU Yankun, YANG Wen
- Subjects
cluster dynamics ,source term ,pka spectrum ,cascade collision defect database ,sampling algorithm ,Nuclear engineering. Atomic power ,TK9001-9401 ,Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Under irradiation of high-energy particles (neutrons or ions), cascade collisions continue to occur in nuclear materials, producing a large number of vacancy clusters and interstitial clusters. These defect clusters will undergo reactions such as diffusion, aggregation, recombination, and annihilation, forming important microstructures such as voids and dislocation loops. Cluster dynamics (CD) method is one of the important methods for simulating the microstructure evolution of nuclear materials under high-energy particle irradiation. The source term (i.e., the average size distribution of huge number of cascade collision defect clusters) is key input of the CD method. In the classical CD method, the source term is usually obtained by empirical fitting, and the maximum cluster in the source term usually only contains several vacancies or interstitials. According to recent studies on cascade collision simulations based on molecular dynamics (MD) methods, cascade collisions corresponding to high-energy primary knocked atom (PKA) can form clusters with dozens or even hundreds of vacancies or interstitials. So, the initial defect information obtained at the atomic level was not fully utilized in traditional CD simulations. With the development of molecular dynamics, cascade collision defect databases have been greatly enriched. Combined with PKA energy spectrum, it is enough to obtain more reasonable source term. The PKA spectrum is generally a quasi-continuous spectrum, and the number of energy groups is usually tens or hundreds. However, the MD cascade collision defect database usually only contains about ten energy values, which is much smaller than the former. If the MD cascade collision defect database is to be used rationally, a mapping rule from a quasi-continuous spectrum to a finite number of discrete energy values must be determined. In view of this, based on probability theory and the principle of proximity, fully considering the changing characteristics of the PKA spectrum curve, five sampling algorithms were proposed for obtaining discrete values of cascade energy from the quasi-continuous PKA energy spectrum. Based on the probability of discrete values of cascade energy, the defect cluster size distribution in the cascade collision defect database was weighted, grouped, fitted, and a relatively smooth continuous size distribution curve was obtained as the source term of the CD method. In order to test the rationality of the source term algorithms, the CD method was used to simulate the low-dose neutron irradiation of pure tungsten experiment in the HFIR reactor, and compared the defect cluster information. The results are consistent with the experimental data. Since there are differences in the size distribution of defect clusters after irradiation simulation with the five algorithms, after analysis, it is believed that the fifth source term algorithm is the most reasonable. In addition, the shortcomings of the current source term algorithm and CD model used and improvement that can be expected in the future were also summarized.
- Published
- 2024
- Full Text
- View/download PDF
5. 基于级联碰撞缺陷数据库的源项对辐照微结构 演化影响团簇动力学模拟研究.
- Author
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王东杰, 潘才富, 吴 石, 贺新福, 豆艳坤, and 杨 文
- Abstract
Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2024
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- View/download PDF
6. Cluster dynamics and firms' strategies – an integrative framework.
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Ostapenko, Svitlana, Africano, Ana Paula, and Meneses, Raquel
- Abstract
Purpose: This study aims to systematise the links between firms' strategies (corporate and business) and the cluster dynamics (through the cluster life cycle [CLC] perspective) and propose an integrative framework bridging firms' strategic behaviour and cluster dynamics (CLC). Design/methodology/approach: The methodology used is an integrative literature review, which provides a distinctive form of research. Findings: The study identifies several links between firms' strategies (corporate and business) and the cluster dynamics (CLC), namely: (1) firms' strategies as a triggering factor of cluster evolution; (2) firms' strategies and path's decline; (3) firms' strategies and cluster's renewal; (4) resilience strategies and the cluster life cycle; and (5) cluster's features and firms' strategies. Research limitations/implications: This study contributes to developing strategic management theory and cluster theory by bridging firms' strategies and cluster dynamics (CLC). It proposes a new conceptualisation of the impact of cluster dynamics on firms' strategic choices – firstly, it proposes a specific approach to identify the CLC; and secondly, it develops an integrative framework model that relates firms' strategies and each stage of the CLC. These are theoretical tools relevant for further advancements in this area of research, as they can be applied in studies of different clusters for validation, something that was not done. Practical implications: The integrative framework is expected to be helpful to company managers, allowing them to design better strategies that account for dynamic cluster environments. Originality/value: This study aims to fill this gap in the literature by systematising the links between firms' strategies (corporate and business) and the cluster dynamics (CLC). [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
7. Cluster dynamics study on nano damage of RPV steels under proton irradiation at 290°C
- Author
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Qiangmao Wan, Guogang Shu, Jiaxuan Tang, Jianjun Pang, Lisha Chen, Duan Wang, Hui Lin, and Hui Ding
- Subjects
reactor pressure vessels ,cluster dynamics ,proton irradiation ,dislocation loops ,solute clusters ,General Works - Abstract
Irradiation-induced defects such as dislocation loops, cavities or solute clusters and chemical composition segregation of reactor pressure vessel (RPV) steel are the root causes of irradiation embrittlement. Combining two nucleation mechanisms, namely, the uniform nucleation and non-uniform nucleation of solute clusters (such as Cu-rich phase), a cluster kinetic simulation was established based on the reaction rate theory, and the co-evolution of matrix damage and Cu-rich phase in low-copper RPV steel was simulated under irradiation. And the average size and number density of defective clusters and solute clusters were established with irradiation dose. Compared with the average size and number density of dislocation loops observed by transmission electron microscopy (TEM) of proton irradiated RPV steel at 290°C, the verification results show that the cluster dynamics model considering both the nucleation mechanism of interstitial dislocation loops and vacancy clusters can well simulate the irradiation damage behavior of materials.
- Published
- 2024
- Full Text
- View/download PDF
8. Assessing the Impact of Science and Technology Parks on Firm Profitability: A Comparative Study of On-Cluster and Off-Cluster Dynamics.
- Author
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Al-kfairy, Mousa
- Subjects
- *
INFORMATION technology parks , *REGIONAL development , *COMPARATIVE studies , *ECONOMIC development , *PROFITABILITY - Abstract
Science and Technology Parks (STPs) are pivotal in driving regional development, primarily through fostering innovation and enhancing regional wealth. However, the impact of STPs on regional development remains a contentious topic with inconclusive findings. This study digs into the contribution of STPs to the profitability of firms by conducting a comparative analysis of profitability and salary data between firms located within these parks (on-cluster) and those outside them (off-cluster). The research adopts a two-pronged approach: initially, it examines firm profitability and employee salaries at an aggregate level to understand the overall economic impact of STPs. Following this, it models the various factors that influence firm profitability, offering a nuanced understanding of the dynamics at play. The findings are revealing - being located within an STP (on-cluster) appears to significantly boost a firm's profitability, but only up to a certain size of the cluster. This suggests that the benefits of being in an STP diminish beyond a certain scale. At a more granular, micro level, the study finds that a firm's previous innovation output has a positive impact on its profitability. This underscores the importance of continuous innovation for sustained economic success within these clusters. Conversely, a larger firm size seems to negatively impact profitability within STPs, indicating a potential strategy for growing firms to relocate off-cluster to mitigate this effect. For firms operating outside STPs (off-cluster), the scenario differs. Here, innovation plays a partial role in influencing profitability, and interestingly, the size of the firm does not significantly impact its profitability. This distinction between on- and off-cluster firms highlights the unique economic ecosystems fostered by STPs and their varied effects on firm performance. Overall, this study contributes to the ongoing debate on the role of STPs in regional development, offering new insights into how these entities affect firm profitability and suggesting potential strategies for firms operating within and outside these parks. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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9. Effects of interstitial cluster mobility on dislocation loops evolution under irradiation of austenitic steel
- Author
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Yan, Xin-Hua, Sun, Lu, Zhou, Du, Xie, Teng, Peng, Chang, Yang, Ye-Xin, Chen, Li, and Tong, Zhen-Feng
- Published
- 2024
- Full Text
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10. Oxidative Dehydrogenation of Cyclohexane by Cu vs Pd Clusters: Selectivity Control by Specific Cluster Dynamics
- Author
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Halder, Avik, Ha, Mai‐Anh, Zhai, Huanchen, Yang, Bing, Pellin, Michael J, Seifert, Sönke, Alexandrova, Anastassia N, and Vajda, Stefan
- Subjects
cluster dynamics ,cyclohexane oxidative dehydrogenation ,deposited clusters ,selectivity control ,size-selected subnanometer clusters ,Inorganic Chemistry ,Physical Chemistry (incl. Structural) ,Chemical Engineering ,Organic Chemistry - Published
- 2020
11. A Simple Model of Knowledge Percolation
- Author
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Bagnoli, Franco, de Bonfioli Cavalcabo’, Guido, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Chopard, Bastien, editor, Bandini, Stefania, editor, Dennunzio, Alberto, editor, and Arabi Haddad, Mira, editor
- Published
- 2022
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12. The role of irradiation-enhanced interstitial diffusion in over-pressurizing fission gas bubbles in UO2.
- Author
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Cooper, M.W.D., Matthews, C., and Andersson, D.A.
- Subjects
- *
FISSION gases , *GAS dynamics , *NUCLEAR fuels , *LOW temperatures , *HIGH temperatures - Abstract
Fission gas bubbles in UO 2 nuclear fuel have been observed to exhibit pressures in excess of the equilibrium bubble pressure; however, the cause of bubble over-pressurization has not yet been demonstrated. The mechanical interaction between a bubble and the surrounding matrix or grain boundary depends on the internal pressure of the bubble and local stress state, such that over-pressurized bubbles are thought to be responsible for fragmentation and pulverization, when exposed to a temperature ramp. Here, we investigate the role of U interstitials, produced through irradiation, in over-pressurizing bubbles by using a combined molecular dynamics (MD) and cluster dynamics approach. Firstly, the energies for the capture of interstitials and vacancies by bubbles have been determined from MD as a function of the ratio of gas atoms to vacancies that make up the bubble. Secondly, these reaction energies have been implemented in the cluster dynamics code Centipede to predict bubble over-pressurization as a function of temperature for typical fission rates. It was found that there is a transition from low pressure bubbles (at high temperatures) to high pressure bubbles (at lower temperatures). The cause of this behavior was shown to be the creation of irradiation-induced interstitials that are highly mobile relative to vacancies at low temperature; whereas, vacancies are sufficiently mobile at high temperatures to limit bubble pressures. This result supports the hypothesis that over-pressurized bubbles form during steady-state operation and that this behavior is highly sensitive to the local pellet temperature. [ABSTRACT FROM AUTHOR]
- Published
- 2025
- Full Text
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13. Revealing the role of oxygen on the defect evolution of electron-irradiated tungsten: A combined experimental and simulation study.
- Author
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Hu, Zhiwei, Yang, Qigui, Jomard, François, Desgardin, Pierre, Genevois, Cécile, Joseph, Jérôme, Olsson, Pär, Jourdan, Thomas, and Barthe, Marie-France
- Subjects
- *
BODY-centered cubic metals , *POSITRON annihilation , *DOPPLER broadening , *DENSITY functional theory , *POSITRONS , *TUNGSTEN - Abstract
The evolution of Frenkel pairs has been studied experimentally and theoretically in tungsten, a Body-Centered Cubic metal. We used positron annihilation spectroscopy to characterize vacancy defects induced by electron irradiation in two sets of polycrystalline tungsten samples at room temperature. Doppler Broadening spectrometry showed that some positrons were trapped at pure single vacancies with a lower concentration than expected. At the same time, positron annihilation lifetime spectroscopy revealed that positrons are annihilated in unexpected states with a lifetime 1.44–1.64 times shorter than that of single vacancy (200 ps), namely unidentified (X) defects. Secondary ions mass spectrometry detected a significant concentration of oxygen in these samples, of the same order of magnitude as electron-induced single vacancy. In addition, Cluster dynamics simulated defect behaviors under experimental conditions, and Two-component density functional theory was used to calculate defect annihilation characteristics that are difficult to obtain in experiments. Finally, by combining the theoretical data, we simulated the positron signals and compared them with the experimental data. This enabled us to elucidate the interactions between oxygen and Frenkel Pairs. The X defects were identified as oxygen-vacancy complexes formed during irradiation, as oxygen is mobile in tungsten at room temperature, and can be trapped in a vacancy, while its binding to self-ion atoms leads to their immobilization thus reducing defect recombination. Therefore, we anticipate oxygen to play an important role in the evolution of tungsten microstructure under irradiation. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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- View/download PDF
14. In-Situ TEM study of microstructural evolution in proton irradiated single crystal UO2 under high-temperature annealing.
- Author
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Bawane, Kaustubh, Kamboj, Anshul, Jin, Miaomiao, Minaruzzaman, Md, Alshannaq, Mutaz, Rickert, Karl, Mann, J. Matthew, Teng, Fei, Childs, Mason, Shao, Lin, Hurley, David H., Zhang, Yongfeng, Khafizov, Marat, and Kombaiah, Boopathy
- Subjects
- *
DISLOCATION loops , *TRANSMISSION electron microscopy , *FREE surfaces , *URANINITE , *TEMPERATURE effect - Abstract
Understanding microstructural changes in nuclear fuels under different irradiation conditions is important as it directly affects thermal, oxidation and mechanical properties and thereby reactor safety and longevity. This work focuses on the effect of temperature on the evolution of extended defects in uranium dioxide. In-situ transmission electron microscopy (TEM) annealing of proton irradiated UO 2 was performed at different temperatures: 900 °C, 1100 °C and 1300 °C, 1 hour for each temperature. Microstructural evolution in terms of dislocation loops and voids were captured using in-situ TEM during annealing at different temperatures. Post-annealing at each temperature, detailed characterization using rel-rod dark field, bright field, and underfocus-overfocus imaging in TEM were used to identify faulted loops, perfect dislocation loops, and voids, respectively. Dislocation loops showed migration, disappearance, coalescence and loop-line interactions which significantly contributed to the recovery process during annealing at temperatures of 1100 °C and 1300 °C. Small voids were observed at 900 °C (diameter ∼ 0.5–1.5 nm) and grew rapidly during 1300 °C annealing (diameter ∼ 1–3 nm). Void growth was attributed to vacancy absorption, Ostwald ripening and void coalescence mechanisms. Extensive void growth was unique to in-situ TEM annealing due to free surface effect as ex-situ annealing confirmed negligible TEM resolvable (> 0.5 nm) voids at 1300 °C. The dislocation loops and voids behavior during in-situ TEM annealing were compared with rate theory and cluster dynamics predictions. [Display omitted] [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
15. Cluster dynamics modeling of hydrogen retention and desorption in tungsten with saturation and multi-trapping effect of sinks
- Author
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Xiaoru Chen, Yuanyuan Zhang, Liuming Wei, Qirong Zheng, Chuanguo Zhang, and Yonggang Li
- Subjects
tungsten ,deuterium ,cluster dynamics ,retention ,thermal desorption ,Nuclear and particle physics. Atomic energy. Radioactivity ,QC770-798 - Abstract
Hydrogen (H) retention and desorption in tungsten (W)-based plasma-facing materials are still not well understood, largely due to the limitations of ex-situ observations in experimental detection methods like thermal desorption spectroscopy (TDS). In order to reveal the fundamental mechanisms behind H retention and desorption, we developed a cluster dynamics model, IRadMat-TDS, for theoretical modeling of depth distribution and TDS of deuterium (D) in polycrystalline W. The model newly includes the saturated absorption and emission of D in inherent sinks like grain boundaries (GBs), as well as the multi-trapping effect of D in various types of GBs with different trapping energies. The simulated TDS spectra are in agreement with experimental ones. For polycrystalline W under D ion irradiation within keV-energy range, two typical thermal desorption peaks in TDS at around 490 and 550 K are explicitly attributed to D emission from GBs and vacancies, respectively. And GBs play a major role in D retention. Moreover, the broad peaks in TDS come from the convolution of multi-trapping of D in sinks with different types of trapping sites rather than a single-site approximation.
- Published
- 2024
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16. The roles of intermediaries in upgrading of manufacturing clusters: Enhancing cluster absorptive capacity.
- Author
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Karlsen, Asbjørn, Lund, Henrik B, and Steen, Markus
- Subjects
INDUSTRY 4.0 ,INDUSTRIAL clusters - Abstract
Specialized clusters rely on common knowledge resources and extra-cluster linkages, but how such resources develop over time is unclear. A case in point is how extra-cluster linkages are integrated into intra-cluster networks and the role of different cluster actors in enhancing cluster absorptive capacity. The paper explores the role of cluster intermediaries in linking clusters to external knowledge sources and contributing to knowledge dissemination among cluster firms. This perspective is relevant as manufacturing firms are facing rapid changes in technology, such as those associated with 'Industry 4.0'. Two manufacturing clusters in Norway are studied regarding cluster absorptive capacities and the role of cluster intermediaries. The authors derive two types of cluster intermediaries with different kinds of service provision well-adjusted to the firm structure. Cluster intermediaries in both cluster contexts can assist firms in tracking and adapting to rapid technological developments. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
17. Modeling mesoscale fission gas behavior in UO2 by directly coupling the phase field method to spatially resolved cluster dynamics
- Author
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Dong-Uk Kim, Sophie Blondel, David E. Bernholdt, Philip Roth, Fande Kong, David Andersson, Michael R. Tonks, and Brian D. Wirth
- Subjects
Phase-field method ,Cluster dynamics ,Multi-scale simulation ,MOOSE framework ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
Abstract Fission gas release within uranium dioxide nuclear fuel occurs as gas atoms diffuse through grains and arrive at grain boundary (GB) bubbles; these GB bubbles grow and interconnect with grain edge bubbles; and grain edge tunnels grow and connect to free surfaces. In this study, a hybrid multi-scale/multi-physics simulation approach is presented to investigate these mechanisms of fission gas release at the mesoscale. In this approach, fission gas production, diffusion, clustering to form intragranular bubbles, and re-solution within grains are included using spatially resolved cluster dynamics in the Xolotl code. GB migration and intergranular bubble growth and coalescence are included using the phase field method in the MARMOT code. This hybrid model couples Xolotl to MARMOT using the MultiApp and Transfer systems in the MOOSE framework, with Xolotl passing the arrival rate of gas atoms at GBs and intergranular bubble surfaces to MARMOT and MARMOT passing evolved GBs and bubble surface positions to Xolotl. The coupled approach performs well on the two-dimensional simulations performed in this work, producing similar results to the standard phase field model when Xolotl does not include fission gas clustering or re-solution. The hybrid model performs well computationally, with a negligible cost of coupling Xolotl and MARMOT and good parallel scalability. The hybrid model predicts that intragranular fission gas clustering and bubble formation results in up to 70% of the fission gas being trapped within grains, causing the increase in the intergranular bubble fraction to slow by a factor of six. Re-solution has a small impact on the fission gas behavior at 1800 K but it has a much larger impact at 1000 K, resulting in a twenty-times increase in the concentration of single gas atoms within grains. Due to the low diffusion rate, this increase in mobile gas atoms only results in a small acceleration in the growth of the intergranular bubble fraction. Finally, the hybrid model accounts for migrating GBs sweeping up gas atoms. This results in faster intergranular bubble growth with smaller initial grain sizes, since the additional GB migration results in more immobile gas clusters reaching GBs.
- Published
- 2022
- Full Text
- View/download PDF
18. Revealing the governing factors for long-term radiation damage evolution in multi-principal elemental alloys through atomistically-informed cluster dynamics
- Author
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Yaoxu Xiong, Jun Zhang, Shihua Ma, Biao Xu, and Shijun Zhao
- Subjects
High-entropy alloys ,Multi-principal elemental alloys ,Defect evolution ,Cluster dynamics ,Radiation damage ,Thermodynamics and kinetics ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
Multi-principal elemental alloys (MPEAs) exhibit unusual mechanical properties and irradiation resistance. It has been reported that the irradiation tolerance of MPEAs originates from the long-term defect evolution stage rather than the ballistic collision phase. However, understanding the long-term evolution of MPEAs is exceptionally challenging due to intrinsic chemical disorder. In this work, we apply atomistically-informed cluster dynamics to study defect evolution in MPEAs for the first time, which enables us to elucidate the critical features responsible for the irradiation performance of MPEAs. With suitable irradiation parameters, our obtained cluster size distributions are in good agreement with experiments. We further discuss the influences of defect migration energy heterogeneity, cluster geometry, and temperature on the produced defect cluster forms. Our results suggest that the small clusters during the collision phase in MPEAs suppress the formation of large-sized defect clusters in the long term. Contrary to the common belief, a broader migration energy distribution due to chemical disorder cannot reduce the maximal defect cluster size but increase the proportion of small clusters. Our results thus reveal that the major role of chemical complexity in MPEAs is to modify the growth mechanism of clusters by promoting small cluster formation and suppressing overall defect diffusivities.
- Published
- 2023
- Full Text
- View/download PDF
19. Assessment of the precipitation kinetics of Al3Sc and Al3Li in binary alloys using an improved cluster dynamics model.
- Author
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Cui, Senlin
- Subjects
- *
BINARY metallic systems , *PRECIPITATION (Chemistry) kinetics , *PHASE equilibrium , *DATABASE design , *DATABASES - Abstract
Precipitation is a natural phenomenon that is known to play an important role in the strengthening of Al–Li alloys. Cluster dynamics is powerful and effective in modeling the precipitation kinetics of precipitates in heat-treatable metallic materials, especially in the early stage. In this work, a cluster dynamics model with cluster mobility is further developed by redefining the effective monomer diffusivity for self-consistently modeling multicomponent and multiphase precipitation. The precipitation kinetic data for Al 3 Sc in Al–Sc binary alloys and Al 3 Li in Al–Li binary alloys are systematically reviewed and evaluated. The metastable fcc_A1/Al 3 Li two-phase equilibria are reoptimized using the split four sublattice compound energy formalism to accommodate both the related phase equilibrium measurements and precipitation kinetic measurements. One set of precipitation kinetic parameters is respectively assessed for each of the two precipitate phases. The improved cluster dynamics model, together with the assessed model parameters, can reasonably reproduce the reliable experimental precipitation kinetic data of the two phases. The model parameter determination includes extensive sensitivity studies to use physically reasonable values, and the present work also studies the use of cluster mobility in modeling the early stage precipitation kinetics. The present work indicates that the obtained model parameters can be used to develop the fundamental informative CALPHAD-type precipitation kinetic database. [Display omitted] • Improved cluster dynamics model with cluster mobility for multicomponent and multiphase precipitation. • Newly defined effective monomer diffusivity for both diffusion-limited and kinetic-limited growth. • Critical review and assessment of Al 3 Sc and Al 3 Li precipitation kinetic data in binary alloys. • Cluster dynamics precipitation kinetic parameters for Al 3 Sc and Al 3 Li in binary alloys. • Discussion of precipitation kinetic database development in the frame of CALPHAD approach. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
20. Cluster dynamics modeling of niobium and titanium carbide precipitates in α -Fe and γ -Fe.
- Author
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Korepanova, Nadezda, Gu, Long, éľ™, 顾, Dima, Mihai, Xu, Hushan, and ĺľ, ç'šçŹŠ
- Subjects
- *
TITANIUM carbide , *NIOBIUM , *CEMENTITE , *NIOBIUM compounds , *MONOMERS , *IRON clusters , *AUSTENITE - Abstract
Kinetic behaviors of niobium and titanium carbide precipitates in iron are simulated with cluster dynamics. The simulations, carried out in austenite and ferrite for niobium carbides, and in austenite for titanium carbide, are analyzed for dependences on temperature, solute concentration, and initial cluster distribution. The results are presented for different temperatures and solute concentrations, compared to experimental data available. They show little impact of initial cluster distribution beyond a certain relaxation time and that highly dilute alloys with monomers only present a significantly different behavior from denser alloys or ones with different initial cluster distributions. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
21. The influence of pressure on the acoustic cavitation in saturated CO2-expanded N, N-dimethylformamide
- Author
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Hanyang Gao, Kunkun Pei, Guoxin Hu, Wenxing Liu, Aihua Meng, Hongcheng Wang, Huifeng Shao, and Wenxin Li
- Subjects
CO2-expanded liquid ,Ultrasonic cavitation ,Cluster dynamics ,Pressure pulse ,Excess enthalpy ,Surface free energy ,Chemistry ,QD1-999 ,Acoustics. Sound ,QC221-246 - Abstract
CO2-expanded organic solvent is a kind of important fluid medium and has broad applications in chemical industry, environmental protection and other fields. Ultrasonic cavitation in gas expanded liquids (GXLs) is conducive to enhancing mass transfer and producing many exciting phenomena. In this paper, the ultrasonic cavitations and streaming in the saturated CO2-expanded liquid N, N-dimethylformamide (DMF) at 4.2 MPa and 5.2 MPa are observed by a high-speed camera. The cavitation intensity and time trace of pressure pulses are recorded using a PZT hydrophone. The influences of gas–liquid equilibrium pressure and ultrasonic power on the cluster dynamics of transient and stable cavitation are examined. The excess molar enthalpies required for CO2 dissociation from DMF are calculated by Peng-Robinson equations of state and the change of surface free energy of CO2-expanded DMF is predicted. The results show that the excess enthalpy of the mixture is one of the key factors to control ultrasonic cavitation at high pressurized conditions, while the surface tension is the key factor for low pressure. As the increase of applied ultrasonic power, the formation and collapsing frequency of bubble clusters increases, and the amplitude and cyclic frequency of pressure pulse are enhanced. The transient cavitation intensity increases as it reaches a maximum value at a certain ultrasonic power and then decreases. The change trends of stable cavitation intensity under different pressures are basically same. It can be concluded from the evidence that ultrasonic cavitation in CO2-expanded DMF is affected by the combined effect of compression and substitution: compression depresses the nucleation and growth of bubbles, while the high solubility of CO2 in DMF is conducive to the generation of bubbles in cavitation.
- Published
- 2022
- Full Text
- View/download PDF
22. Correlated proton-electron hole dynamics in protonated water clusters upon extreme ultraviolet photoionization
- Author
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Vendrell, Oriol [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); The Hamburg Centre for Ultrafast Imaging, Hamburg (Germany)]
- Published
- 2016
- Full Text
- View/download PDF
23. Void Swelling Screening Criteria for Stainless Steels in PWR Systems
- Author
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Davidsaver, Sarah, Fyfitch, Steve, Brimbal, Daniel, McKinley, Joshua, Amberge, Kyle, Jackson, John H., editor, Paraventi, Denise, editor, and Wright, Michael, editor
- Published
- 2019
- Full Text
- View/download PDF
24. Modeling mesoscale fission gas behavior in UO2 by directly coupling the phase field method to spatially resolved cluster dynamics.
- Author
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Kim, Dong-Uk, Blondel, Sophie, Bernholdt, David E., Roth, Philip, Kong, Fande, Andersson, David, Tonks, Michael R., and Wirth, Brian D.
- Subjects
CRYSTAL grain boundaries ,NUCLEAR fuels ,COALESCENCE (Chemistry) ,THERMAL conductivity ,RESIDUAL stresses - Abstract
Fission gas release within uranium dioxide nuclear fuel occurs as gas atoms diffuse through grains and arrive at grain boundary (GB) bubbles; these GB bubbles grow and interconnect with grain edge bubbles; and grain edge tunnels grow and connect to free surfaces. In this study, a hybrid multi-scale/multi-physics simulation approach is presented to investigate these mechanisms of fission gas release at the mesoscale. In this approach, fission gas production, diffusion, clustering to form intragranular bubbles, and re-solution within grains are included using spatially resolved cluster dynamics in the Xolotl code. GB migration and intergranular bubble growth and coalescence are included using the phase field method in the MARMOT code. This hybrid model couples Xolotl to MARMOT using the MultiApp and Transfer systems in the MOOSE framework, with Xolotl passing the arrival rate of gas atoms at GBs and intergranular bubble surfaces to MARMOT and MARMOT passing evolved GBs and bubble surface positions to Xolotl. The coupled approach performs well on the two-dimensional simulations performed in this work, producing similar results to the standard phase field model when Xolotl does not include fission gas clustering or re-solution. The hybrid model performs well computationally, with a negligible cost of coupling Xolotl and MARMOT and good parallel scalability. The hybrid model predicts that intragranular fission gas clustering and bubble formation results in up to 70% of the fission gas being trapped within grains, causing the increase in the intergranular bubble fraction to slow by a factor of six. Re-solution has a small impact on the fission gas behavior at 1800 K but it has a much larger impact at 1000 K, resulting in a twenty-times increase in the concentration of single gas atoms within grains. Due to the low diffusion rate, this increase in mobile gas atoms only results in a small acceleration in the growth of the intergranular bubble fraction. Finally, the hybrid model accounts for migrating GBs sweeping up gas atoms. This results in faster intergranular bubble growth with smaller initial grain sizes, since the additional GB migration results in more immobile gas clusters reaching GBs. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
25. Multi-scale simulation of radiation damage accumulation and subsequent hardening in neutron-irradiated α-Fe
- Author
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Capolungo, Laurent [Georgia Inst. of Technology, Georgia Tech., Metz (France)]
- Published
- 2015
- Full Text
- View/download PDF
26. Multi-scale fracture probability analysis of tungsten monoblocks under fusion conditions
- Author
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M.A. Oude Vrielink, J.A.W. van Dommelen, and M.G.D. Geers
- Subjects
Crystal plasticity ,Tungsten ,Nuclear fusion ,Failure probability ,Neutron irradiation ,Cluster dynamics ,Nuclear engineering. Atomic power ,TK9001-9401 - Abstract
Plasma facing components inside future nuclear fusion reactors are subjected to a high heat load and intense irradiation conditions. Using advanced computational material models, several problems can be solved that reflect tungsten monoblocks under fusion relevant loading scenarios. This allows for the identification of the conditions under which material failure is probable. The material model and parameters are identified such that the mechanical behaviour is in accordance with the homogenized behaviour of a previously developed crystal plasticity model on the microscopic scale. The heterogeneous stress field that follows is analysed in order to assess the probability of material failure, which is typically reflected by unstable crack propagation. Since fracture is an inherently multi-scale problem, critical regions are analysed in detail by means of a representative volume element. The resulting analysis reveals that in case the stress relaxation in the monoblock under the applied static heat load is complete, the probability of unstable crack propagation can reach values close to 35%. Finally, the impact of prolonged neutron irradiation is simulated by means of a cluster dynamics model. Although irradiation drastically increases the brittleness of tungsten, its impact on the overall monoblock performance remains limited.
- Published
- 2021
- Full Text
- View/download PDF
27. An overview: multiscale simulation in understanding the radiation damage accumulation of reactor materials.
- Author
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Chen, Dandan, He, Xinfu, Chu, Genshen, He, Xiao, Jia, Lixia, Wang, Zhaoshun, Yang, Wen, and Hu, Changjun
- Subjects
- *
NUCLEAR reactor materials , *RADIATION damage , *MOLECULAR dynamics , *MULTISCALE modeling , *SIMULATION methods & models , *CONSTRUCTION materials - Abstract
The reactor is an extreme environment of high temperature, high pressure, and high radiation dose. Damage accumulates in structural materials over service time. It will eventually lead to material failure, such as hardening, embrittlement, and swelling. The radiation damage accumulation is an inherent, complex, and multiscale process, which has been studied extensively with multiscale modeling and simulation methods. The rapid development of high-performance computing makes it possible to accurately operate multiscale simulation for the microstructure evolution of irradiated reactor materials. The European Union, the USA, and China have put great effort into this, and many related works have been carried out. This paper first outlines the basic application of multiscale modeling and simulation technology in understanding the effects of radiation on reactor structural materials. Then, some relevant projects carried out by the USA, the European Union, and China in recent years are summarized. Next, the paper focuses on three widely used simulation techniques at different scales: molecular dynamics, kinetic Monte Carlo, and cluster dynamics. For each method, some key developments in algorithms and computer implementations are reviewed. Finally, the comparison between them is discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
28. Investigation of cluster property in the riser of circulating fluidized bed with a wide particle size distribution.
- Author
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Liu, Xiaohuan, Wang, Shuai, Yang, Shiliang, and Wang, Hua
- Subjects
- *
PARTICLE size distribution , *RISER pipe , *CLUSTERING of particles - Abstract
In this work, the cluster dynamics in the riser of a pilot-scale circulating fluidized bed with the presence of wide particle size distribution (PSD) are numerically simulated via the multiphase particle-in-cell (MP-PIC) approach. Specifically, the gas and solid motions are tracked in the Eulerian and Lagrangian frameworks, respectively. The gas-solid numerical model is firstly validated with the experimental data. Then, the spatial distribution of particle clusters together with the cluster dynamics (velocity, length, aspect ratio) in the bed operating with different parameters are explored. The results demonstrate the ability of the MP-PIC model on predicting the important features of the cluster in the riser. Clusters mainly distribute in the lower part of the riser. The closer of the cluster to the riser wall, the larger vertical length, and larger aspect ratio appear. Moreover, the presence of riser outlet and solid inlet slightly affects the spatial distribution, the size and aspect ratio of clusters in the riser. The superficial gas velocity has an obvious impact on the cluster volume and the cluster vertical length, while the PSD width significantly affects the horizontal length and the aspect ratio. The results obtained in this work provide meaningful insights regarding the cluster dynamics in the riser, which will be beneficial to the deep understanding of this specific structure in the practical operation. [Display omitted] • Effect of PSD width on the cluster dynamics in a CFB riser is investigated. • Clusters close to the wall leads to large vertical length and aspect ratio. • Inlet and outlet of the riser affect the size and aspect ratio of clusters. • Superficial gas velocity highly affects the cluster volume and vertical length. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
29. Spatially-resolved cluster dynamics modeling of irradiation growth.
- Author
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Maron, Matthew, Li, Yang, Lalani, Inam, Baker, Kristopher, Flores, Benjamin Ramirez, Black, Thomas, Hollenbeck, James, Ghoniem, Nasr, and Po, Giacomo
- Subjects
- *
CRYSTAL models , *DISLOCATION loops , *SINGLE crystals , *REACTION-diffusion equations , *FINITE element method , *TRANSMISSION electron microscopy , *NEUTRON irradiation , *IRRADIATION - Abstract
We develop here a spatially resolved, three-dimensional continuum model coupling cluster dynamics (SR-CD) and crystal plasticity to investigate irradiation growth in zirconium. The model uses scale separation to divide the population of the irradiation cluster into mobile and immobile families. Small interstitial and vacancy clusters are modeled using anisotropic reaction–diffusion equations. Among the immobile clusters, an atomistically-informed vacancy cluster to vacancy loop transition is taken into account. The coupling between the evolution equation of CD and the plastic deformation of the material is two-fold, with stress-informed bias factors and local inelastic strains computed from the evolution of the evolving cluster population. The numerical implementation of the model utilizes the finite element method to analyze both single-crystal and polycrystalline samples. The growth strains that are computed align well with the experimental data provided by Carpenter for single-crystal Zr. Furthermore, the transformation of a vacancy cluster into a complete vacancy loop, occurring at a size of 14 nm, is in agreement with experimental observations and atomistic simulations. The density, size, and growth rate of the dislocation loops, denoted as 〈 c 〉 and 〈 a 〉 , also exhibit good agreement with transmission electron microscopy (TEM) analysis of irradiated Zr and its alloys. Our findings demonstrate that there is a spatial correlation between the growth of these dislocation loops and growth strains, significantly influenced by the crystal size. To explain the expansion of the 〈 a 〉 axis and the contraction of the 〈 c 〉 axis in irradiated Zr, it is necessary to consider the diffusion anisotropy difference (DAD) of mobile interstitial species. We show that the PWR Kearns parameters, specifically f r = 0.63, f t = 0.32, f a = 0.05, confer enhanced irradiation resistance to Zr along the principal directions when compared to single crystals. Additionally, reducing the grain size to nanograins further enhances the resistance to irradiation-induced growth, particularly along the direction with the highest volume fraction of basal poles [0001]. • The SR-CD and crystal plasticity model accurately predicts growth strains in Zr. • There is a spatially correlated growth of dislocation loops. • Growth strains in single crystals are influenced by crystal size. • A vacancy cluster transformation is necessary to describe breakaway growth. • Textured polycrystals and nanograins show enhanced irradiation growth resistance. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
30. Machine learning method to determine concentrations of structural defects in irradiated materials.
- Author
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Johnson, Landon, Malone, Walter, Rizk, Jason, Chen, Renai, Gibson, Tammie, Cooper, Michael W.D., and Craven, Galen T.
- Subjects
- *
RADIOACTIVE substances , *MATERIALS science , *COMPUTATIONAL complexity , *URANIUM , *NITRIDES - Abstract
The formation and subsequent growth of structural defects in an irradiated material can strongly influence the material's performance in technological and industrial applications. Predicting how the growth of defects affects material performance is therefore a pressing problem in materials science. One common computational approach that is used to examine defect growth is cluster dynamics, a method which employs a system of mean-field rate equations to track the time evolution of concentrations of individual defect types. However, the computational complexity of performing cluster dynamics can limit its practical implementation, specifically in the context of exploring a broad set of physical conditions corresponding to, for example, different temperatures and pressures. Here, we present a machine learning approach to circumvent the computational challenges of performing cluster dynamics while maintaining high accuracy in the prediction of defect concentrations. Our method is illustrated on the nuclear material uranium nitride but is broadly applicable to other materials. The developed data-driven method is shown to accurately capture complex correlations between material properties, temperature, irradiation conditions, and the concentration of defects. [Display omitted] [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
31. Evolution of dislocation loops in irradiated α-Uranium: An atomistically-informed cluster dynamics investigation.
- Author
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Mazumder, Sanjoy Kumar, Yao, Tiankai, and El-Azab, Anter
- Subjects
- *
DISLOCATION loops , *NEUTRON irradiation , *POINT defects , *BINDING energy , *MOLECULAR dynamics , *URANIUM , *METAL clusters - Abstract
An atomistically-informed mean field cluster dynamics model has been developed to investigate the nucleation and growth of prismatic loops in irradiated α -Uranium. TEM analysis of neutron irradiated α -Uranium shows the evolution of self-interstitial atom and vacancy loops on (010) and (100) crystallographic planes, respectively, resulting in an anisotropic lattice swelling of its face-centered orthorhombic crystal. To provide model parameters, the crystallography of loops and the binding energy of point defects to these loops were studied using an angular dependent EAM potential and classical molecular dynamics (MD) simulations. Furthermore, using the bond-boost hyperdynamics method, the anisotropic diffusion of interstitials and vacancies in α -Uranium was investigated. The mechanisms of point defect diffusion and the associated migration energies were reported and compared with previous DFT studies. The energetics and kinetic quantities mentioned above were used in the cluster dynamics model to predict the cluster density as a function of dose rate, dose and temperature and the results were compared to the reported neutron irradiation experiments. The model predictions reveal an accumulation of small sized vacancy loops along with a population of large and growing self-interstitial loops, which closely corresponds to the TEM observations. [Display omitted] [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
32. Cluster Dynamics in a Circulating Fluidized Bed
- Author
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Breault, R
- Published
- 2006
33. Global Heteroclinic Rebel Dynamics Among Large 2-Clusters in Permutation Equivariant Systems.
- Author
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Fiedler, Bernold, Haugland, Sindre W., Kemeth, Felix P., and Krischer, Katharina
- Subjects
- *
VECTOR fields , *PERMUTATIONS , *ORBIT method , *CLUSTER algebras , *SYNCHRONIC order , *EQUILIBRIUM - Abstract
We explore equivariant dynamics under the symmetric group SN of all permutations of N elements. Specifically we study one-parameter vector fields, up to cubic order, which commute with the standard real (N-1)-dimensional irreducible representation of SN. The parameter is the linearization at the trivial 1-cluster equilibrium of total synchrony. All equilibria are cluster solutions involving up to three clusters. The resulting global dynamics is of gradient type: all bounded solutions are cluster equilibria and heteroclinic orbits between them. In the limit of large N, we present a detailed analysis of the web of heteroclinic orbits among the plethora of 2-cluster equilibria. Our focus is on the global dynamics of 3-cluster solutions with one rebel cluster of small size. These solutions describe slow relative growth and decay of 2-cluster states. For N→∞, the limiting heteroclinic web defines an integrable\emph{rebel flow} in the space of 2-cluster equilibrium configurations. We identify and study the seven qualitatively distinct global rebel flows which arise in this setting. Applications include oscillators with all-to-all coupling, and electrochemistry. For illustration we consider synchronization clusters among N complex Stuart-Landau oscillators with complex linear global coupling. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
34. Simulation of Cu precipitation in Fe-Cu dilute alloys with cluster mobility
- Author
-
Senlin Cui, Mahmood Mamivand, and Dane Morgan
- Subjects
Cu-rich precipitates ,Fe-Cu dilute alloys ,Cluster dynamics ,Coagulation ,Reactor pressure vessel steels ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
Cu-rich precipitates formation is associated with the precipitation hardening of Fe-Cu based steels and the embrittlement of reactor pressure vessel steels under neutron irradiation. The accurate modeling of the time evolution of Cu-rich precipitates is therefore of fundamental importance for the design of Fe-Cu based steels and the prediction of the irradiation induced shift of the ductile to brittle transition temperature of reactor pressure vessels. This work applies cluster dynamics with mobile Cu monomers and clusters to model Cu precipitation in dilute Fe-Cu alloys at several temperatures. Optimized model parameters can be used to simulate the mean radius, number density, volume fraction, and matrix composition evolution during isothermal annealing with reasonable accuracy. The possible reduction of the mobility of Cu-rich clusters due to additional alloying elements in Fe-Cu based steels is discussed.
- Published
- 2020
- Full Text
- View/download PDF
35. A model for suspension of clusters of particle pairs.
- Author
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Mecherbet, Amina
- Subjects
- *
CLUSTERING of particles , *RADIUS (Geometry) , *STOKES flow , *DISTANCES - Abstract
In this paper, we consider N clusters of pairs of particles sedimenting in a viscous fluid. The particles are assumed to be rigid spheres and inertia of both particles and fluid are neglected. The distance between each two particles forming the cluster is comparable to their radii 1/N 1 N $ \frac{1}{N}$ while the minimal distance between the pairs is of order N−1/2. We show that, at the mesoscopic level, the dynamics are modelled using a transport-Stokes equation describing the time evolution of the position x and orientation ξ of the clusters. Under the additional assumption that the minimal distance is of order N−1/3, we investigate the case where the orientation of each cluster is initially correlated to its position. In this case, a local existence and uniqueness result for the limit model is provided. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
36. Nonclassical nucleation towards separation and recycling science: Iron and aluminium (Oxy)(hydr)oxides.
- Author
-
Lukić, Miodrag J., Gebauer, Denis, and Rose, Andrew
- Subjects
- *
NUCLEATION , *ALUMINUM , *IRON , *OXIDES , *SUPERSATURATION - Abstract
Separation, analysis and recycling technologies are of high interest for our modern societies, where colloidal iron and aluminium (hydr)oxides have important applications. However, there are significant gaps in the fundamental understanding of how these phases form in real systems. Classical nucleation theory cannot account for many experimental observations, and there is a dichotomy between the chemistry of hydrolysing/condensating systems and the physical notion of supersaturation. Reviewing parts of the established and recent literature, we demonstrate that concepts of nonclassical nucleation pathways can overcome these issues. This broader, chemistry-based conceptual framework has a high potential for advancing current applications, and developing new strategies towards separation, analysis and recycling applications, which seem to be urgently required for the future. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
37. Cluster dynamics simulations of tritium and helium diffusion in lithium ceramics.
- Author
-
Roy, Ankit, Sassi, Michel, Pitike, Krishna Chaitanya, Lanza, Mark S., Casella, Andrew M., Senor, David J., Matthews, Christopher, Andersson, David A., and Devanathan, Ram
- Subjects
- *
TRITIUM , *HELIUM , *CERAMICS , *THERMAL conductivity - Abstract
Tritium (T) and He diffusion in LiAlO 2 and LiAl 5 O 8 phases influences the performance of tritium producing burnable absorber rods (TPBARs) by affecting the gas release, swelling and thermal conductivity of Li-bearing ceramic pellets. Frenkel pair defects and clusters created by irradiation can attract T and He interstitials and form clusters of the type H e i x L i , H e i x A l , H e i x O , T i x L i , T i x A l and T i x O , 1 ≤ x ≤ 4 in a Li, Al or O vacancy site (notation denotes x He or T atoms in a 1 Li, 1 Al or 1 O vacant site). The concentration and mobility of each of these clusters collectively contribute to the diffusion of the He and T gases in LiAlO 2 and LiAl 5 O 8. In this work, free energy cluster dynamics simulations implemented in the Centipede code, are used to obtain the concentration and diffusivities of these clusters which are then used to calculate the total diffusivity of T and He gases in LiAlO 2 and LiAl 5 O 8. The results show that diffusivity of T is at least one order of magnitude higher in LiAlO 2 as compared to that in LiAl 5 O 8 whereas He diffusion is 2–13 orders of magnitude higher in LiAlO 2 as compared to that in LiAl 5 O 8. There is a higher concentration of highly diffusive species (T interstitials and T i 03 L i for the case of tritium and H e i 01 L i , H e i 02 L i and H e i 03 L i for the case of He) in LiAlO 2 than in LiAl 5 O 8 which increase the total diffusion of T and He in LiAlO 2. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
38. Multi-scale Cluster Dynamics modelling of Guinier–Preston zone formation in binary Al–Cu alloys.
- Author
-
Stegmüller, Tobias and Haider, Ferdinand
- Subjects
- *
MONTE Carlo method , *BINARY metallic systems , *ALUMINUM-zinc alloys , *MULTISCALE modeling , *DENSITY functional theory , *DYNAMICS , *COPPER-titanium alloys - Abstract
We developed a multi-scale model for the prediction of precipitation kinetics of binary alloys and present its application to the formation of Guinier–Preston zones (GPZ) in Al-rich binary Al–Cu alloys. The approach is covering three length scales: (i) Starting from density functional theory (DFT) calculations a Cluster Expansion (CE) for the binary Al–Cu system on the fcc lattice is constructed. Based on the obtained CE (ii) a lattice Monte Carlo (MC) sampling technique, known as the overlapping distribution method, is used to calculate cluster free energies of precipitate clusters. Finally (iii) a meso-scale Cluster Dynamics (CD) model is constructed by taking the cluster free energies as input. The result is a fast, parameter free method that is able to predict the evolution of precipitate size distributions. To validate the model kinetic MC simulations on the precipitation of GPZ are conducted. The results agree well with those obtained by our model. When comparing our results to experimental data a problem of time scaling arises, which is discussed in the results section. Image 1 • A model for the prediction of GPZ precipitation in Al–Cu alloys is constructed. • The approach includes DFT, Cluster Expansion, Monte Carlo and Cluster Dynamics. • The model's results show a good comparability to results from kinetic Monte Carlo. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
39. Effect of the Temperature Change of Material Test Reactor on Calibration of Cluster Dynamics for Neutron Irradiation Pure Iron.
- Author
-
Gokhman, O. R. and Kondria, М. S.
- Subjects
NEUTRON irradiation ,MATERIALS testing ,TEMPERATURE effect ,NUCLEAR reactor materials ,IRON - Abstract
luster dynamics (CD) simulation is used to study the effect of the temperature T change of reactor pressure vessel (RPV) on the evolution of vacancy clusters (VC) and self-interstitial atom clusters (SIAC) in neutron irradiation pure iron in material test reactor (MTR) BR-2 (Mol, Belgium). During operation time of BR-2, T increases from 300 K to 573 K in the first 19 hours, does not change in the next 370 hours and decreases then to 373 K in the last 7 hours. The time evolution of concentrations of single vacancies, C1v, single self-interstitial atoms, C1i, of VC, Cnv, and SIAC, Cni, in pure iron under neutron irradiation in the MTR BR-2 for neutron flux of 1.39 × 10
– 7 dpa/s in the range fluence from 0.026 to 0.19 dpa are determined by CD simulation for approach on the constant T as well as with taking into account T change of RPV. Then the dose dependences of number density and mean size of SIAC are calculated. The new calibration of defect structure model has been performed from the comparison of experimental transmission electron microscopy (TEM) data and CD simulation results. It was found the migration energy of a vacancy in iron which provides the best coincidence of experimental data and CD results. The difference between predictions of CD model on dose dependences of the number density and mean size with the constant temperature and model with taking into account the change temperature at the beginning and at the end of operation time of MTR BR-2 has been analyzed. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
40. Вплив зміни температури на початку та наприкінці опромінення в науково-дослідному реакторі на нейтронну крихкість α-заліза
- Author
-
Гохман, О. Р., Кондря, М. С., and Тадеуш, О. Х.
- Subjects
NEUTRON irradiation ,NUCLEAR pressure vessels ,RESEARCH reactors ,POSITRON annihilation ,NUCLEAR reactors ,NUCLEAR research ,ORDINARY differential equations - Abstract
Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2019
- Full Text
- View/download PDF
41. Molecular dynamics study of propylene carbonate based concentrated electrolyte solutions for lithium ion batteries.
- Author
-
Mynam, Mahesh, Ravikumar, Bharath, and Rai, Beena
- Subjects
- *
PROPYLENE carbonate , *MOLECULAR dynamics , *ELECTROLYTE solutions , *LITHIUM-ion batteries , *THERMAL stability - Abstract
Abstract Concentrated electrolytes have displayed enhanced thermal and reactive stabilities, thus enabling development of safer lithium ion batteries (LIBs). Computational studies of the concentrated electrolytes are required to get better understanding of the physical phenomena responsible for the enhanced properties. Motivated by the improved cycle life of the LIBs made of propylene carbonate (PC) based concentrated electrolytes, we probe PC-LiPF 6 (lithium hexafluorophosphate) electrolyte system for a range of concentrations up to 4 mol/kg using molecular dynamics simulation. Structural and dynamic properties of the system are affected by the salt concentration. Electrolyte tend to form contact-ion-pairs and multi-ion complexes at high concentration, thereby impacting the transport properties such as diffusivity and ionic conductivity. The rate of formation and disintegration of multi-ion complexes increases with concentration. Change in the molecular structure of the solution, especially composition of the lithium ion coordination shell, explains the improved stability features of the concentrated electrolytes reported in literature. Highlights • Salt concentration affects structural/dynamic properties of electrolyte. • Rise in concentration leads to formation of complexes of various sizes. • Multi-ion-complexes of net charge ranging from −2 to 2 are formed. • Long-range ordering in the solution is observed at high concentration. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
42. Study of xenon evolution in UO[formula omitted] using multi-grain cluster dynamics modeling.
- Author
-
Bai, He, Hu, Changjun, Zhu, Yuhan, and Chen, Dandan
- Subjects
- *
FISSION gases , *GAS dynamics , *LONG-Term Evolution (Telecommunications) , *THERMAL conductivity , *XENON , *NUCLEAR reactors - Abstract
The behavior of fission gas is a key issue for the performance of UO 2 fuel, which is the most widely used fuel type in GEN-III reactors. Fission gas will lead to lower thermal conductivity and affect the microstructure of fuel, gradually cause swelling and other phenomena. It seriously affects the performance and safety of nuclear reactor. The numerical simulation method based on physical model is an important means to study fission gas. In this paper, in order to study the key parameters affecting the behavior and evolution of fission gas xenon in UO 2 fuel, a multi-grain parallel cluster dynamics model is designed and implemented. The model can describe the multi-grain structure characteristics of UO 2 , and establish the correlation for the physical process of intra- and inter-granular bubbles. Furthermore, the model is extended to a larger temporal and spacial scale through parallelization, so as to simulate the fission gas behavior closer to the actual situation, and expand the applicable conditions and range of the model. Based on the modeling work, the long-term evolution processes of xenon under different initial grain radius and temperature conditions are analyzed, the results show that the initial grain radius has a much bigger effect on the inter-granular gas concentration than the intra-granular gas, while temperature has a large effect on both intra- and inter-granular gas concentrations. The model and analysis results provide theoretical support for understanding fission gas behavior and improving UO 2 fuel performance. • The intra-granular and inter-granular correlation model was established, and the grain growth process was concerned. • Design and implement a multi-grain parallel CD model. • The key parameters affecting the evolution of fission gas xenon in UO 2 fuel were studied. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
43. Evolution of dislocation loops and voids in post-irradiation annealed ThO2: A combined in-situ TEM and cluster dynamics investigation.
- Author
-
Mazumder, Sanjoy Kumar, Bawane, Kaustubh, Mann, J. Matthew, French, Aaron, Shao, Lin, He, Lingfeng, and El-Azab, Anter
- Subjects
- *
DISLOCATION loops , *POINT defects , *DISCONTINUOUS precipitation , *OSTWALD ripening , *THORIUM dioxide , *HIGH temperatures , *ANNEALING of metals - Abstract
The effect of isochronal annealing on the evolution of dislocation loop and void population in proton irradiated ThO 2 has been investigated. Post-irradiation annealing in other actinide oxides like UO 2 shows significant loop coarsening. ThO 2 samples were irradiated with 2 MeV protons up to a dose of 0.1 dpa at 600 °C. Post-irradiation isochronal annealing was performed at 600, 800, 1000 and 1100 °C for 1 h at each temperature using in-situ TEM. Only faulted 1/3<111> type dislocation loops were observed, and their sizes and distribution were characterized. The population of self-interstitial atom (SIA) dislocation loops did not show any significant growth and coarsening. Additionally, nanometric voids were observed at annealing temperatures of 1000 and 1100 °C. Using cluster dynamics (CD), we have studied the nucleation and growth of point defects and defect clusters, i.e., SIA prismatic dislocation loops and nanometric and sub-nanometric voids in proton irradiated ThO 2. The CD model was further utilized to predict the growth and coarsening of loops and voids during isochronal annealing at the experimental and higher temperatures. The model did not predict significant SIA loop growth which closely corresponds to the TEM observations. CD predicted SIA loop coarsening is insignificant even at high annealing temperature of 1500 °C because the model only considers the growth of defect clusters by absorption of like point defects, i.e., SIA loops absorb interstitials and voids absorb vacancies, and cannot account for their migration and coalescence due to elastic interaction. The CD model also predicts the evolution of nanometric voids having mean size within the error bounds of TEM observations. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
44. Simplified atomistic based kinetic model for swelling prediction.
- Author
-
Yanilkin, Alexey
- Subjects
- *
FAST reactors , *HETEROGENOUS nucleation , *PREDICTION models , *DIFFUSION coefficients - Abstract
In this paper, simplified kinetics with several self-consistent models is proposed for swelling prediction. It is based on the rate theory and atomistic simulation, while focusing on the description of experimentally observed bubbles and voids evolution and swelling. In this way, several models are proposed. They include the self-consistent accounting for the vacancy diffusion coefficient and the formation energy, models of heterogeneous bubbles nucleation, interstitial cluster sink and spatial inhomogeneity of sinks. Parametrized model shows the reasonable agreement with experimental data on AISI CW 316 steel, irradiated at various temperatures and doses in fast reactor EBR-II. The influence of interstitial cluster sink and dislocation annealing on temperature dependence of swelling is discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
45. Safety Monitoring of Materials and Components of Nuclear Power Plants
- Author
-
Gokhman, A., Bergner, F., Shunin, Yuri N., editor, and Kiv, Arnold E., editor
- Published
- 2012
- Full Text
- View/download PDF
46. Constant Chemical Potential-Quantum Mechanical-Molecular Dynamics simulations of the Graphene-electrolyte double layer
- Author
-
Nicodemo Di Pasquale, Aaron R. Finney, Joshua D. Elliott, Paola Carbone, and Matteo Salvalaglio
- Subjects
interfaces ,electrical double layers ,Condensed Matter - Materials Science ,quantum mechanical calculations ,cluster dynamics ,General Physics and Astronomy ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,classical force fields ,electrolytes ,Physical and Theoretical Chemistry ,molecular dynamics - Abstract
We present the coupling of two frameworks -- the pseudo-open boundary simulation method known as constant potential Molecular Dynamics simulations (C$\mu$MD), combined with QMMD calculations -- to describe the properties of graphene electrodes in contact with electrolytes. The resulting C$\mu$QMMD model was then applied to three ionic solutions (LiCl, NaCl and KCl in water) at bulk solution concentrations ranging from 0.5 M up to 6 M in contact with a charged graphene electrode. The new approach we are describing here provides a simulation protocol to control the concentration of the electrolyte solutions while including the effects of a fully polarizable electrode surface. Thanks to this coupling, we are able to accurately model both the electrode and solution side of the double layer and provide a thorough analysis of the properties of electrolytes at charged interfaces, such as the screening ability of the electrolyte and the electrostatic potential profile. We also report the calculation of the integral electrochemical double layer capacitance in the whole range of concentrations analysed for each ionic species, while the QM simulations provide access to the differential and integral quantum capacitance. We highlight how subtle features, such as the adsorption of potassium at the interface or the tendency of the ions to form clusters, emerge from our simulations, contribute to explaining the ability of graphene to store charge and suggest implications for desalination., Comment: 28 pages, 10 figures
- Published
- 2022
47. Cluster dynamics simulation of the flux effect for neutron irradiated pure iron.
- Author
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Kondria, M. and Gokhman, A.
- Subjects
- *
NEUTRON flux , *NEUTRON irradiation , *DYNAMICS , *NEUTRON temperature , *IRON , *FLUX (Energy) - Abstract
The effect of flux in a wide range from 1.39×10−10 to 1.39 ×10−3 dpa/s has been studied by the cluster dynamics (CD) simulation for pure iron neutron irradiated at a temperature of 300°C for the two fluences. The critical flux values which mark the regimes of flux dependence of average size, number density and irradiation induced hardening for vacancy clusters (VC) and self-interstitial atoms clusters (SIAC) are found. It was found that the effect of neutron irradiation on average size of SIAC was similar for low and high fluxes in the case of the same fluence. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
48. Atomistic modeling of α’ precipitation in Fe-Cr alloys under charged particles and neutron irradiations: Effects of ballistic mixing and sink densities.
- Author
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Soisson, Frédéric, Meslin, Estelle, and Tissot, Olivier
- Subjects
- *
ATOMISM , *PRECIPITATION (Chemistry) , *CHROMIUM alloys , *DIFFUSION , *MONTE Carlo method - Abstract
The α′ precipitation in Fe-Cr alloys under electron, neutron and ion irradiations is modelled by cluster dynamics and atomistic kinetic Monte Carlo simulations. The former method provides the evolution of the density of point defect sinks. This density is then introduced in the Monte Carlo which models the diffusion of point defects and atoms. By comparison with previous studies, this provides a better description of the evolution of point defect concentrations and therefore of the balance between two competing irradiation effects: the acceleration of diffusion and the ballistic mixing. The prediction of the model is in agreement with existing atomic-scale experiments already reported after electron, ion and neutron irradiations or obtained for the present study. Irradiation is found to accelerate the precipitation by orders of magnitude, except for the case of ion irradiation at high doses rates, where the simulations predict a ballistic dissolution of α′ precipitates. According to our model, this dissolution is mainly due to a high sink density, which reduces the concentrations of point defects and limits the acceleration of diffusion. This effect may be reinforced by carbon contamination, which reduces the mobility of point defects. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
49. Modeling microstructural evolution in irradiated materials with cluster dynamics methods: A review.
- Author
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Kohnert, Aaron A., Wirth, Brian D., and Capolungo, Laurent
- Subjects
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MICROSTRUCTURE , *NUCLEAR energy , *MONOMERS , *TEMPERATURE effect , *MOLECULAR dynamics - Abstract
As both the design of material systems for nuclear energy applications and the number of reactor designs being proposed increase the need for material models predicting the evolution of microstructures as a function of chemistry, texture, grain size, precipitate content, etc., and irradiation conditions is steadily increasing. This manuscript aims at presenting a review of the different cluster dynamics modeling schemes that have emerged worldwide over the past decade(s). Further, the manuscript also critically discusses limitations in existing approaches and identifies potential routes for future developments. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
50. On the transfer of cascades from primary damage codes to rate equation cluster dynamics and its relation to experiments.
- Author
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Jourdan, T. and Crocombette, J.-P.
- Subjects
- *
DISPLACEMENT (Mechanics) , *RATE laws (Chemistry) , *MONTE Carlo method , *FRACTURE mechanics , *ASYMPTOTIC homogenization - Abstract
Transferring displacement cascades from primary damage codes to rate equation cluster dynamics (RECD) is not straightforward, due to the inability of RECD to treat spatial correlations explicitly. A method, called “sphere homogenization kinetic Monte Carlo” (SHKMC), has been proposed to produce a effective source term from a cascade database. This paper reviews the method and a few applications. SHKMC is based on a modified kinetic Monte Carlo algorithm to keep track of the homogenization process of defects within cascades. The crucial parameter is the homogenization distance, which is not an intrinsic parameter of cascades but which is given by RECD simulations. SHKMC leads to a time-varying source term, even under constant irradiation flux. RECD with such a source term is able to reproduce reference kinetic Monte Carlo calculations of microstructure evolution under cascade conditions. It is also possible to provide a spatially-dependent source term for the simulation of ion irradiations. As an example, irradiation of iron with 10 MeV Fe ions is discussed. Analysis of the source term shows that the fraction of mono-defects is close to the fraction of freely-migrating defects determined experimentally and that it significantly varies with depth. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
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