257 results on '"William J. Weber"'
Search Results
2. Electron diffraction radial distribution function analysis of amorphous boron carbide synthesized by ion beam irradiation and chemical vapor deposition
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Yanwen Zhang, Natale J. Ianno, Ryusuke Nakamura, George Peterson, Michael Nastasi, Manabu Ishimaru, and William J. Weber
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Diffraction ,Materials science ,Ion beam ,Electron diffraction ,Materials Chemistry ,Ceramics and Composites ,Analytical chemistry ,Chemical vapor deposition ,Thin film ,Homonuclear molecule ,Ion ,Carbide - Abstract
Amorphous boron carbide (a-BxC) networks consist of light elements, and their low atomic scattering factors makes structural analysis by x-ray diffraction difficult. Electron diffraction has an advantage of detecting the light elements, because of the strong interaction between the matter and electrons. We prepared a-BxC by ion beam technologies and plasma-enhanced chemical vapor deposition, and characterized their structures via atomic pair-distribution functions derived from electron diffraction intensity profiles. It was found that a pentagonal pyramid is the most favorable cluster in a-B4C generated by ion irradiation, while C C homonuclear bonds were formed in the deposited a-BxC thin film. X-ray photoemission spectroscopy revealed that the a-BxC thin film possesses more carbon than B4C, which is responsible for the formation of the homonuclear bonds.
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- 2022
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3. Origin of increased helium density inside bubbles in Ni(1−x)Fe alloys
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Xing Wang, Yong Zhang, F. Granberg, Ke Jin, Flyura Djurabekova, William J. Weber, Kai Nordlund, Di Chen, Karren L. More, Hongbin Bei, and Y.Q. Wang
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010302 applied physics ,Materials science ,Mechanical Engineering ,Metals and Alloys ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Molecular dynamics ,chemistry ,Mechanics of Materials ,Chemical physics ,0103 physical sciences ,General Materials Science ,Irradiation ,Dislocation ,Solubility ,0210 nano-technology ,Material properties ,Embrittlement ,Helium ,Stacking fault - Abstract
Due to virtually no solubility, He atoms implanted or created inside materials tend to form bubbles, which are known to damage material properties through embrittlement. Higher He density in nano-sized bubbles was observed both experimentally and computationally in Ni ( 100 − x ) Fex-alloy samples compared to Ni. The bubbles in the Ni ( 100 − x ) Fex-alloys were observed to be faceted, whereas in elemental Ni they were more spherical. Molecular dynamics simulations showed that stacking fault structures formed around bubbles at maximum He density. Higher Fe concentrations stabilize stacking fault structures, suppress evolution of dislocation network around bubbles and suppress complete dislocation emission, leading to higher He density.
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- 2021
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4. Coupled effects of electronic and nuclear energy deposition on damage accumulation in ion-irradiated SiC
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Yanwen Zhang, Eva Zarkadoula, William J. Weber, Lauren Nuckols, Miguel L. Crespillo, and Chen Xu
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010302 applied physics ,Range (particle radiation) ,Materials science ,Polymers and Plastics ,Metals and Alloys ,Analytical chemistry ,02 engineering and technology ,Dissipation ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Ion ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Ceramics and Composites ,Silicon carbide ,Irradiation ,0210 nano-technology ,Spectroscopy ,Single crystal ,Deposition (law) - Abstract
Coupling between electronic and nuclear energy dissipation in ion-irradiated, single crystal 4H-SiC has been investigated using Si, Ti, and Ni ions over a range of energies at 300 K, and irradiation damage accumulation is characterized using Rutherford backscattering spectroscopy in channeling geometry. The damage production rate from nuclear energy loss (Sn) is observed to decrease with increasing electronic energy loss (Se) of the incident ions. A dynamic threshold (Se,th) in electronic energy loss is determined for each ion species, which defines two regions: i) Se > Se,th, where electronic energy dissipation fully suppresses damage production due to nuclear energy loss along incident ion paths, and ii) Se
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- 2020
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5. Effects of Au 2+ Irradiation Induced Damage in a High-Entropy Pyrochlore Oxide Single Crystal
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Candice Kinsler-Fedon, Lauren Nuckols, Christopher Nelson, Zehui Qi, Qing Huang, David Mandrus, Yanwen Zhang, William J. Weber, and Veerle Keppens
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- 2022
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6. Effects of Au2+ irradiation induced damage in a high-entropy pyrochlore oxide single crystal
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Candice Kinsler-Fedon, Lauren Nuckols, Christopher T. Nelson, Zehui Qi, Qing Huang, David Mandrus, Yanwen Zhang, William J. Weber, and Veerle Keppens
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Mechanics of Materials ,Mechanical Engineering ,Metals and Alloys ,General Materials Science ,Condensed Matter Physics - Published
- 2022
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7. Laser Doppler vibrometry for piezoelectric coefficient (d33) measurements in irradiated aluminum nitride
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Hongbin Sun, Eva Zarkadoula, Miguel L. Crespillo, William J. Weber, Vivek Rathod, Steven J. Zinkle, and Pradeep Ramuhalli
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Metals and Alloys ,Electrical and Electronic Engineering ,Condensed Matter Physics ,Instrumentation ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Published
- 2022
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8. Understanding effects of chemical complexity on helium bubble formation in Ni-based concentrated solid solution alloys based on elemental segregation measurements
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Xing Wang, Ke Jin, Chun Yin Wong, Di Chen, Hongbin Bei, Yongqiang Wang, Maxim Ziatdinov, William J. Weber, Yanwen Zhang, Jonathan Poplawsky, and Karren L. More
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Nuclear and High Energy Physics ,Nuclear Energy and Engineering ,General Materials Science - Published
- 2022
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9. Deformation mechanisms in single crystal Ni-based concentrated solid solution alloys by nanoindentation
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Liuqing Yang, Youxing Chen, Jimmie Miller, William J. Weber, Hongbin Bei, and Yanwen Zhang
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2022
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10. Two regimes of ionization-induced recovery in SrTiO3 under irradiation
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Haizhou Xue, Yanwen Zhang, William J. Weber, and Eva Zarkadoula
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010302 applied physics ,Range (particle radiation) ,Materials science ,Mechanical Engineering ,Metals and Alloys ,02 engineering and technology ,Electron ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Molecular physics ,Ion ,Coupling (electronics) ,Molecular dynamics ,Mechanics of Materials ,Ionization ,0103 physical sciences ,General Materials Science ,Irradiation ,0210 nano-technology ,Excitation - Abstract
Irradiation of pre-damaged SrTiO3 with 2 MeV He, 1.2 MeV C, 5 MeV C and 12 MeV O ions reveals two regimes of ionization-induced recovery. For C and O ions, with electronic energy loss between 1.6 and 3 keV/nm, recovery cross-sections range from 0.27 to 0.38 nm2, and molecular dynamics confirms recovery related to ionization-induced thermal spikes via electron-phonon coupling. At lower electronic energy losses, recovery cross-sections decrease to about 5.5 × 10−4 nm2 for 2 MeV He ions and 1.0 × 10−5 nm2 for 200 keV electrons, which suggests recovery associated with local electronic excitation processes.
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- 2019
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11. Multi-axial and multi-energy channeling study of disorder evolution in ion-irradiated nickel
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Gihan Velisa, Chenyang Lu, Yanwen Zhang, William J. Weber, Ke Jin, Hongbin Bei, Zhe Fan, and Lumin Wang
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Nuclear and High Energy Physics ,Materials science ,Nuclear Energy and Engineering ,Transmission electron microscopy ,General Materials Science ,Crystal structure ,Irradiation ,Single crystal ,Crystallographic defect ,Molecular physics ,Ion ,Stacking fault ,Black spot - Abstract
To better understand defect structure and the evolution of irradiation-induced damage in single crystal Ni, in situ Rutherford backscattering spectroscopy in channeling geometry (RBS/C) is performed along the , , and axes with different probing beam energies. The RBS/C data reveal that damage evolution occurs in three steps. The first step at low doses (up to 0.09 dpa), characterized by a linear increase with dose, is related to the formation of point defects and small clusters. The second step in the intermediate dose range (0.09–0.4 dpa) shows a sublinear increase in disorder to saturation. This sublinear increase is due to the growth of defect clusters resulting from the interaction of irradiation-induced defects with already existing damage from previous ion impacts. The third step at high doses (0.4–13.39 dpa) exhibits a surprising decrease in the disorder level, which may be attributed to defect evolution from black spot defects to large dislocation loops that leads to strain relaxation. In addition, the damage extends much deeper than the predicted depths and is attributed to a long-range defect migration effect confirmed by transmission electron microscopy (TEM) observations. Although similar damage evolution trends have been observed along all channeling directions, the disorder accumulation is largest along the and axes than observed along axis. This “preferential” disordering process along and suggests that more defects are shielded by the atomic rows than the two other axes. The co-existence of both uncorrelated displaced lattice atoms and dislocation loops in Ni irradiated at 1 ions/nm 2 is revealed by the energy-dependent RBS/C studies along all three axes. In contrast, dislocation loops and stacking fault tetrahedral are simultaneously present in the crystal structure of Ni irradiated at 100 ions/nm 2 that is consistent with previous molecular dynamics simulations and TEM observations.
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- 2019
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12. Irradiation effects of medium-entropy alloy NiCoCr with and without pre-indentation
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Gihan Velisa, Yanwen Zhang, Pengyuan Xiu, William J. Weber, Chenyang Lu, Ke Jin, Qing Peng, Fei Gao, Hongbin Bei, Lumin Wang, and Tai ni Yang
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Nuclear and High Energy Physics ,Void (astronomy) ,Materials science ,High entropy alloys ,Stacking ,02 engineering and technology ,Atmospheric temperature range ,021001 nanoscience & nanotechnology ,01 natural sciences ,010305 fluids & plasmas ,Nuclear Energy and Engineering ,Indentation ,0103 physical sciences ,General Materials Science ,Irradiation ,Composite material ,Dislocation ,0210 nano-technology ,Stacking fault - Abstract
Medium entropy alloy NiCoCr draws great attention due to its excellent strength-ductility trade-off mechanical behavior. Its irradiation behavior at elevated temperatures has been investigated using ion beam irradiation in a temperature range of 420–580°Cand transmission electron microscopy. Irradiation induced stacking fault tetrahedra were only observed at 420 °C. With increasing irradiation temperature, all stacking fault tetrahedra vanished, while the size of voids and dislocation loops increased significantly. Nanoindentation-induced structural complexities, including dislocations, stacking faults and twins helped to reduce void swelling. However, at the elevated temperatures, NiCoCr is still much more susceptible to void swelling compared to high entropy alloys such as NiCoFeCrMn and NiCoFeCrPd.
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- 2019
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13. Defect evolution in Ni and NiCoCr by in situ 2.8 MeV Au irradiation
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Christopher M. Barr, Karren L. More, Khalid Hattar, Yanwen Zhang, William J. Weber, Ke Jin, Hongbin Bei, and Xing Wang
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Nuclear and High Energy Physics ,Materials science ,Alloy ,Analytical chemistry ,engineering.material ,Dark field microscopy ,law.invention ,Nuclear Energy and Engineering ,Transmission electron microscopy ,law ,Microscopy ,Scanning transmission electron microscopy ,engineering ,General Materials Science ,Irradiation ,Electron microscope ,Solid solution - Abstract
The evolution of radiation-induced defects in Ni and the single-phase concentrated solid solution alloy, NiCoCr, were investigated during in situ 2.8 MeV Au ion irradiation and post-irradiation analysis using transmission electron microscopy. Compared to Ni, both the size and area density of defect clusters decreased in NiCoCr under the same irradiation conditions, suggesting that the chemical complexity, i.e., randomness of lattice site occupations, of NiCoCr suppressed radiation-induced damage. One-dimensional glide of defect clusters was observed in Ni but not in the NiCoCr alloy. The structural nature of small defect clusters in NiCoCr were further investigated using high-angle annular dark field scanning transmission electron microscopy.
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- 2019
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14. Temperature-dependent defect accumulation and evolution in Ni-irradiated NiFe concentrated solid-solution alloy
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Gihan Velisa, William J. Weber, Miguel L. Crespillo, Ke Jin, Yanwen Zhang, Zhe Fan, and Hongbin Bei
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Nuclear and High Energy Physics ,Materials science ,Structural material ,Annealing (metallurgy) ,High entropy alloys ,Alloy ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Rutherford backscattering spectrometry ,01 natural sciences ,010305 fluids & plasmas ,Nuclear Energy and Engineering ,Irradiated materials ,Chemical physics ,0103 physical sciences ,engineering ,General Materials Science ,Irradiation ,0210 nano-technology ,Solid solution - Abstract
Temperature significantly affects defect migration and evolution in irradiated materials. However, the effects of temperature on defect evolution in concentrated solid-solution alloys (CSAs), including high entropy alloys, are not well understood, despite their potential as structural materials in advanced nuclear reactors. As an important model system of these CSAs, equiatomic Ni50Fe50 (NiFe) was selected to understand the effects of temperature on defect evolution during irradiation and subsequent thermal annealing. Specifically, defect accumulation and evolution in NiFe alloy under Ni-ion irradiation at 150, 300, and 500 K were studied, and the irradiated specimens were subsequently annealed at higher temperatures. Rutherford backscattering spectrometry along the channeling direction was employed to study damage accumulation and evolution before and after each irradiation and annealing experiment. Here we show that more defects survive and accumulate at 150 K, but more importantly defects can migrate to deeper depths at this low irradiation temperature. Irradiation-induced damage at 150 and 300 K does not recover substantially after post-irradiation annealing at 500 K, but dramatic recovery is observed after post-irradiation annealing at 700 K, indicating an onset temperature of defect recovery between 500 and 700 K. The migration of irradiation-induced defects upon annealing is closely related to the mobility and stress state arising from the surviving defects. With the consideration of five stages of defect recovery in conventional dilute alloys, the underlying mechanisms for temperature-dependent defect accumulation and evolution in NiFe CSA are discussed.
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- 2019
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15. Effects of electron-phonon coupling and electronic thermal conductivity in high energy molecular dynamics simulations of irradiation cascades in nickel
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Eva Zarkadoula, German D. Samolyuk, and William J. Weber
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Materials science ,General Computer Science ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Crystallographic defect ,0104 chemical sciences ,Ion ,Coupling (electronics) ,Computational Mathematics ,Nickel ,Molecular dynamics ,Thermal conductivity ,chemistry ,Mechanics of Materials ,Vacancy defect ,Cluster (physics) ,General Materials Science ,0210 nano-technology - Abstract
The two-temperature model has been applied to investigate the effects of the electronic subsystem on 150 keV Ni ion cascades in nickel using molecular dynamics simulation. We explore the effects of the magnitude of the electron-phonon coupling and the electronic thermal conductivity on defect production and cluster formation. It has been found that stronger electron-phonon coupling allows larger and more rapid energy feedback to the atomic subsystem, leading to reduction of number of point defects and suppression of the formation of larger defect clusters. It was observed that larger electronic thermal conductivity results in slightly increased number of point defects and larger size vacancy clusters. The latter takes place because of suppression of point defects recombination in faster cooling areas of initial damage.
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- 2019
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16. Channeling analysis in studying ion irradiation damage in materials containing various types of defects
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Yanwen Zhang, Haizhou Xue, Gihan Velisa, Taini Yang, Hongbin Bei, William J. Weber, Lumin Wang, and Ke Jin
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Nuclear and High Energy Physics ,Materials science ,Scattering ,Intermetallic ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Crystallographic defect ,Molecular physics ,Spectral line ,010305 fluids & plasmas ,Amorphous solid ,Ion ,Nuclear Energy and Engineering ,visual_art ,0103 physical sciences ,visual_art.visual_art_medium ,General Materials Science ,Ceramic ,Irradiation ,0210 nano-technology - Abstract
Ion channeling is a powerful quantitative technique for studying ion-irradiation induced defect evolution in single crystalline materials. An iterative procedure to determine dechanneling yields has been developed for decades, serving as a major method for analyzing experimental channeling data. The applicability of such procedure is, however, generally limited to the crystalline damage with only point defects and local amorphous domains. For the other cases, such as irradiated metals, the assumption of direct-backscattering free has usually been made. In the present study, Ni, TiAl, MgO, and SrTiO3 single crystals are selected as four model materials, representing metals, intermetallic alloys, and ceramic compounds with different defect evolution processes under irradiation, to investigate the fidelity of applying dechanneling analysis on various types of defects. The pure dechanneling assumption is shown oversimplified in Ni irradiated with low fluence self-ions and may result in error on the derived damage profile. Moreover, the iterative procedure of dechanneling analysis is shown valid for more general situations than the randomly distributed atoms, including those not exhibiting a peak in channeling spectra. The disappearance of damage peak in channeling spectra is attributed to the combined effects of small (but non-zero) scattering factor, long-range damage effects, and non-ignorable damage level in pristine crystals. Furthermore, the ratio of direct backscattering to dechanneling areas provides information on defect configurations in the materials containing a well-defined damage peak in channeling spectra. The contribution from dechanneling sources increases from SrTiO3, TiAl, to MgO, according to the derived scattering and dechanneling factors.
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- 2019
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17. Role of electronic energy loss on defect production and interface stability: Comparison between ceramic materials and high-entropy alloys
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Yanwen Zhang, Chinthaka Silva, Timothy G. Lach, Matheus A. Tunes, Yufan Zhou, Lauren Nuckols, Walker L. Boldman, Philip D. Rack, Stephen E. Donnelly, Li Jiang, Lumin Wang, and William J. Weber
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General Materials Science - Published
- 2022
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18. Role of chemical disorder on radiation-induced defect production and damage evolution in NiFeCoCr
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Yufan Zhou, Gihan Velişa, Saro San, Miguel L. Crespillo, Zhe Fan, Hongbin Bei, William J. Weber, Pengyuan Xiu, Lumin Wang, Filip Tuomisto, Wai-Yim Ching, and Yanwen Zhang
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Nuclear and High Energy Physics ,Nuclear Energy and Engineering ,General Materials Science - Published
- 2022
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19. Light emission of self-trapped excitons from ion tracks in silica glass: Interplay between Auger recombination, exciton formation, thermal dissociation, and hopping
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Joseph T. Graham, Miguel L. Crespillo, Fernando Agulló-López, and William J. Weber
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Polymers and Plastics ,Metals and Alloys ,Ceramics and Composites ,Electronic, Optical and Magnetic Materials - Published
- 2022
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20. Engineering defect energy landscape of CoCrFeNi high-entropy alloys by the introduction of additional dopants
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Shijun Zhao, Yanwen Zhang, and William J. Weber
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Nuclear and High Energy Physics ,Nuclear Energy and Engineering ,General Materials Science - Published
- 2022
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21. Multiscale characterization of irradiation behaviour of ion-irradiated SiC/SiC composites
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Gerd Duscher, S. Agarwal, Y.Y. Zhao, William J. Weber, Miguel L. Crespillo, and Yutai Katoh
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010302 applied physics ,Materials science ,Polymers and Plastics ,Electron energy loss spectroscopy ,Metals and Alloys ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,stomatognathic system ,chemistry ,Transmission electron microscopy ,0103 physical sciences ,Volume fraction ,Ceramics and Composites ,symbols ,Fiber ,Irradiation ,Dislocation ,Composite material ,0210 nano-technology ,Raman spectroscopy ,Carbon - Abstract
The irradiation tolerance of SiC/SiC composites was studied using 10 MeV Au ion irradiations at 350 °C, for surface doses between 1 and 50 displacements per atom (dpa). Atomic force microscopy and optical profilometry revealed irradiation-induced axial and radial shrinkage of SiC-fibers. At 50 dpa, net fiber shrinkage reached 2.8 ± 0.3%. We conclude that the primary cause of SiC-fiber shrinkage in SiC/SiC composites is the irradiation-induced loss of pre-existing carbon packets, which had occupied 2–3% fiber volume in unirradiated state. A compelling evidence of the carbon packet loss was revealed using a combination of state-of-art conventional transmission electron microscopy (TEM), high resolution TEM, energy-filtered TEM and electron energy loss spectroscopy. The carbon packet volume fraction decreased with increasing dose, reaching near-complete loss after 50 dpa. Carbon packet loss was further confirmed using Raman spectroscopy where the carbon D and G peaks disappeared after irradiation. In contrast, irradiation-induced swelling of 1 ± 0.5% was observed in the matrix after 50 dpa. The study also shows that up to 50 dpa, the multilayer pyrolytic-carbon (PyC) interface in the composite is highly irradiation tolerant as it maintained its morphology, graphitic nature and showed no signs of amorphization. Additionally, Raman spectroscopy revealed a saturation of TEM invisible disorder at 1 dpa for both ultra-fine grains of the fiber and the larger SiC-matrix grains. However, TEM visible extended defect formation such as dislocation loops were only detected in the larger matrix grains, thereby revealing a potential role of grain size on defect accumulation in SiC.
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- 2018
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22. Primary radiation damage: A review of current understanding and models
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Robert S Averback, David Simeone, Francois Willaime, Kai Nordlund, Sergei L. Dudarev, A. E. Sand, Steven J. Zinkle, Lorenzo Malerba, Tomoaki Suzudo, R. E. Stoller, Florian Banhart, William J. Weber, F. Granberg, Helsinki Institute of Physics (HIP), Helsingin yliopisto = Helsingfors universitet = University of Helsinki, The University of Tennessee [Knoxville], Oak Ridge National Laboratory [Oak Ridge] (ORNL), UT-Battelle, LLC, Department of Materials Science Engineering lillinois, Japan Atomic Energy Agency, Structural Materials, Institute of Nuclear Materials Science, Centre d'Etude de l'Energie Nucléaire (SCK-CEN), Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Service de recherches de métallurgie physique (SRMP), Département des Matériaux pour le Nucléaire (DMN), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Culham Centre for Fusion Energy (CCFE), CEA- Saclay (CEA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Université Paris-Saclay, and Department of Physics
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Nuclear and High Energy Physics ,MOLECULAR-DYNAMICS SIMULATIONS ,dpa ,VACANCY-LIKE DEFECTS ,02 engineering and technology ,Binary collision approximation ,THRESHOLD DISPLACEMENT ENERGIES ,114 Physical sciences ,01 natural sciences ,ATOMIC-DISPLACEMENT ,Displacement (vector) ,COMPUTER-SIMULATION ,Topological defect ,BINARY-COLLISION APPROXIMATION ,0103 physical sciences ,Atom ,Radiation damage ,General Materials Science ,Statistical physics ,NI-BASED ALLOYS ,010306 general physics ,Mixing (physics) ,[PHYS]Physics [physics] ,Physics ,Thermal spike ,CASCADE DAMAGE ,Displacement cascades ,021001 nanoscience & nanotechnology ,TEMPERATURE-DEPENDENCE ,Nuclear Energy and Engineering ,Particle ,ION-SOLID INTERACTIONS ,Defect production ,0210 nano-technology ,Event (particle physics) - Abstract
Scientific understanding of any kind of radiation effects starts from the primary damage, i.e. the defects that are produced right after an initial atomic displacement event initiated by a high-energy particle. In this Review, we consider the extensive experimental and computer simulation studies that have been performed over the past several decades on what the nature of the primary damage is. We review both the production of crystallographic or topological defects in materials as well as radiation mixing, i.e. the process where atoms in perfect crystallographic positions exchange positions with other ones in non-defective positions. All classes of materials except biological materials are considered. We also consider the recent effort to provide alternatives to the current international standard for quantifying this energetic particle damage, the Norgett-Robinson-Torrens displacements per atom (NRT-dpa) model for metals. We present in detail new complementary displacement production estimators ("athermal recombination corrected dpa", arc-dpa) and atomic mixing ("replacements per atom", rpa) functions that extend the NRT-dpa, and discuss their advantages and limitations. (C) 2018 The Authors. Published by Elsevier B.V.
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- 2018
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23. Interstitial migration behavior and defect evolution in ion irradiated pure nickel and Ni-xFe binary alloys
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Fei Gao, Qing Peng, Haizhou Xue, Hongbin Bei, Liang-Liang Niu, Yanwen Zhang, Feifei Zhang, Lumin Wang, Chenyang Lu, Miguel L. Crespillo, Ke Jin, Gihan Velisa, Taini Yang, Pengyuan Xiu, and William J. Weber
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010302 applied physics ,Nuclear and High Energy Physics ,Void (astronomy) ,Materials science ,Mean free path ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Ion ,Nickel ,Nuclear Energy and Engineering ,chemistry ,Chemical physics ,Vacancy defect ,Interstitial defect ,0103 physical sciences ,General Materials Science ,Irradiation ,0210 nano-technology ,Solid solution - Abstract
Transition from long-range one-dimensional to short-range three-dimensional migration modes of interstitial defect clusters greatly reduces the damage accumulation in single-phase concentrated solid solution alloys under ion irradiation. A synergetic investigation with experimental, computational and modeling approaches revealed that both the resistance to void swelling and the delay in dislocation evolution in Ni-Fe alloys increased with iron concentration. This was attributed to the gradually increased sluggishness of defect migration, which enhances interstitial and vacancy recombination. Transition from long-range one-dimensional defect motion in pure nickel to short-range three-dimensional motion in concentrated Ni-Fe alloys is continuum, not abrupt, and within an iron concentration range up to 20%. The gradual transition process can be quantitatively characterized by the mean free path of the interstitial defect clusters.
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- 2018
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24. Isolated oxygen vacancies in strontium titanate shine red: Optical identification of Ti3+ polarons
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Miguel L. Crespillo, Fernando Agulló-López, Joseph T. Graham, Yanwen Zhang, and William J. Weber
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Materials science ,Annealing (metallurgy) ,Oxide ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Polaron ,01 natural sciences ,Crystallographic defect ,Oxygen ,Ion ,chemistry.chemical_compound ,chemistry ,Chemical physics ,0103 physical sciences ,Strontium titanate ,General Materials Science ,010306 general physics ,0210 nano-technology ,Luminescence - Abstract
Oxide perovskites exhibit fascinating physical properties that identify them as key materials for the next generation of oxide-based functional electronic devices, as well as for catalysis and photochemistry applications. In strontium titanate, substantial efforts have been devoted to elucidate the role of oxygen vacancies and localized electronic states, such as polarons, on those properties. A new model is presented that assigns a definitive red luminescence signature at 2.0 eV to Ti3+ polarons trapped at isolated oxygen vacancies. This emission provides an unequivocal identification for the oxygen vacancies, which allows monitoring their creation and annealing by a variety of physio-chemical treatments. Ionoluminescence with energetic (MeV) ion beams enables such identification by combining the sensitivity and resolution of spectroscopic techniques with their in situ character, as well as controlled incorporation of point defects, such as oxygen vacancies. Alternative models assigning the blue luminescence emission at 2.8 eV to oxygen vacancies are not supported by the experimental results. Therefore, oxygen vacancies shine red and not blue, as previously proposed.
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- 2018
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25. Radiation-induced extreme elastic and inelastic interactions in concentrated solid solutions
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William J. Weber, Matthew F. Chisholm, Pengfei Zhai, Jie Liu, Patrick Kluth, Ritesh Sachan, Hongbin Bei, Yanwen Zhang, Daniel Schauries, Christina Trautman, and Mohammad W. Ullah
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010302 applied physics ,Materials science ,Mechanical Engineering ,Alloy ,02 engineering and technology ,Dissipation ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Ion ,Mechanics of Materials ,Structural stability ,0103 physical sciences ,lcsh:TA401-492 ,Tetrahedron ,engineering ,lcsh:Materials of engineering and construction. Mechanics of materials ,General Materials Science ,Irradiation ,0210 nano-technology ,Stacking fault ,Solid solution - Abstract
One of the biggest challenges in the radiation induced defect science is to understand the complex nature of ion-atom interactions under highly extreme conditions. Here, we report the irradiation induced non-equilibrium defect formation in NiCoCr single phase concentrated solid solution alloy due to (i) the extreme inelastic and (ii) the coupled inelastic and elastic ion-atom interactions. These two conditions are achieved at 5 and 30 μm penetration depths along the paths of swift heavy ions (1.542 GeV Bi). In general, the irradiation induced damage consists of interstitial-type dislocation loops and vacancy-type stacking fault tetrahedra (SFT). Near the surface (~5 μm) where electronic energy loss is dominating (~62.5 keV nm−1), the atomic motion primarily results in the formation of SFT. A noticeable increase of dislocation loop formation is observed at 30 μm near the maximum energy deposition from elastic interactions (~4.9 keV nm−1), as compared to the near surface region (~0.06 keV nm−1). Insights on the complex electronic and atomic correlations of extreme energy deposition and dissipation on defect dynamics and structural stability may pave the way for new design principles of radiation–tolerant structural alloys. Keywords: Concentrated solid solution alloys, Swift heavy ions, Ion-irradiation, Defects, Electronic energy-loss
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- 2018
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26. Local structure of NiPd solid solution alloys and its response to ion irradiation
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Hongbin Bei, Yanwen Zhang, Ke Jin, Changyong Park, Mohammad W. Ullah, Shijun Zhao, Yang Tong, Haizhou Xue, William J. Weber, Rong Huang, Gihan Velisa, and Fuxiang Zhang
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Materials science ,Mechanical Engineering ,Metals and Alloys ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Local structure ,Ion ,Mechanics of Materials ,0103 physical sciences ,Materials Chemistry ,Physical chemistry ,Irradiation ,010306 general physics ,0210 nano-technology ,Solid solution - Published
- 2018
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27. GeV ion irradiation of NiFe and NiCo: Insights from MD simulations and experiments
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German D. Samolyuk, Pengfei Zhai, Jie Liu, Aleksi A. Leino, Ritesh Sachan, Hongbin Bei, Yanwen Zhang, William J. Weber, F. Granberg, and Department of Physics
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TRACKS ,Materials science ,Polymers and Plastics ,ALLOYS ,chemistry.chemical_element ,02 engineering and technology ,Electronic structure ,Molecular dynamics ,114 Physical sciences ,01 natural sciences ,Molecular physics ,Nickel alloys ,Ion ,Bismuth ,Thermal conductivity ,Swift heavy ion ,EXCITATION ,0103 physical sciences ,010306 general physics ,TEMPERATURE ,DISPLACEMENT CASCADES ,ENERGY-RANGE ,Scanning/transmission electron microscopy (STEM) ,Lattice ,Metals and Alloys ,021001 nanoscience & nanotechnology ,MOLECULAR-DYNAMICS SIMULATION ,Crystallographic defect ,ELECTRONS ,Electronic, Optical and Magnetic Materials ,chemistry ,Heat transfer ,Ceramics and Composites ,Defects ,METALS ,0210 nano-technology ,Solid solution - Abstract
Concentrated solid solution alloys have attracted rapidly increasing attention due to their potential for designing materials with high tolerance to radiation damage. To tackle the effects of chemical complexity in defect dynamics and radiation response, we present a computational study on swift heavy ion induced effects in Ni and equiatomic Ni -based alloys (Ni50Fe50, Ni50Co50) using two-temperature molecular dynamics simulations (2T-MD). The electronic heat conductivity in the two-temperature equations is parameterized from the results of first principles electronic structure calculations. A bismuth ion (1.542 GeV) is selected and single impact simulations performed in each target. We study the heat flow in the electronic subsystem and show that alloying Ni with Co or Fe reduces the heat dissipation from the impact by the electronic subsystem. Simulation results suggest no melting or residual damage in pure Ni while a cylindrical region melts along the ion propagation path in the alloys. In Ni50Co50 the damage consists of a dislocation loop structure (d = 2 nm) and isolated point defects, while in Ni50Fe50, a defect cluster (d = 4 nm) along the ion path is, in addition, formed. The simulation results are supported by atomic-level structural and defect characterizations in bismuth-irradiated Ni and Ni50Fe50. The significance of the 2T-MD model is demonstrated by comparing the results to those obtained with an instantaneous energy deposition model without consideration of e-ph interactions in pure Ni and by showing that it leads to a different qualitative behavior.
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- 2018
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28. Synergistically-enhanced ion track formation in pre-damaged strontium titanate by energetic heavy ions
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Ritesh Sachan, Christina Trautmann, William J. Weber, Yanwen Zhang, Eva Zarkadoula, and Haizhou Xue
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Materials science ,Polymers and Plastics ,Ion track ,Metals and Alloys ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Rutherford backscattering spectrometry ,01 natural sciences ,Molecular physics ,Electronic, Optical and Magnetic Materials ,Amorphous solid ,Ion ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Scanning transmission electron microscopy ,Ceramics and Composites ,Strontium titanate ,Irradiation ,010306 general physics ,0210 nano-technology ,Single crystal - Abstract
Latent ion tracks created by energetic heavy ions (12 MeV Ti to 946 MeV Au) in single crystal SrTiO3 are investigated using Rutherford backscattering spectrometry and scanning transmission electron microscopy. The results demonstrate that pre-existing irradiation damage, introduced via elastic collision processes, interacts synergistically with the electronic energy deposition from energetic heavy ions to enhance formation of latent ion tracks. The average amorphous cross-section increases with the level of pre-damage and is linearly proportional to the electronic energy loss of the ions, with a slope dependent on the pre-damage level. For the highest energy ions (629 MeV Xe and 946 MeV Au), the tracks are continuous over the pre-damaged depth, but become discontinuous beyond the pre-damaged region. This work provides new understanding and insights on ion-solid interactions that significantly impact the interpretation of latent track formation processes, models of amorphization, and the fabrication of electro-ceramic devices.
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- 2018
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29. Effect of atomic order/disorder on vacancy clustering in concentrated NiFe alloys
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William J. Weber, Dilpuneet S. Aidhy, A. Harms, Mohammad Arman Ullah, and Debajit Chakraborty
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010302 applied physics ,Atomic order ,Materials science ,General Computer Science ,General Physics and Astronomy ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Kinetic energy ,01 natural sciences ,Computational Mathematics ,Molecular dynamics ,Mechanics of Materials ,Chemical physics ,Vacancy defect ,0103 physical sciences ,Tetrahedron ,General Materials Science ,Random structure ,0210 nano-technology ,Cluster analysis ,Stacking fault - Abstract
Using molecular dynamics simulations, we elucidate the effect of atomic structure on vacancy clustering in ordered (L10) and random NiFe. Based on our simulations, we predict the vacancy evolution to be in complete contrast between the two systems. While large vacancy clusters, i.e., stacking fault tetrahedra (SFT) are formed in the random structure, no clustering is observed in the ordered-L10 structure. Similar simulations are performed on L10-CuAu and L10-TiAl to understand whether SFT formation is generic in L10 structures, or is specific to NiFe. Both materials show SFT formation, thereby highlighting specific defect energetics in L10 NiFe that lead to the lack of vacancy clustering. We elucidate that L10-NiFe has unique thermodynamic and kinetic defect energetics, i.e., antisite energies, vacancy sublattice preference, and directional migration energy barriers that collectively lead to the lack of vacancy clustering. Understanding such defect energetics could open avenues to prevent defect clustering in the vision towards development of radiation-tolerant concentrated alloys for nuclear reactor applications.
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- 2018
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30. Revealing ionization-induced dynamic recovery in ion-irradiated SrTiO3
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Gihan Velisa, William J. Weber, Yanwen Zhang, Elke Wendler, and Haizhou Xue
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Range (particle radiation) ,Materials science ,Polymers and Plastics ,Kinetics ,Metals and Alloys ,02 engineering and technology ,Electron ,021001 nanoscience & nanotechnology ,01 natural sciences ,Fluence ,Molecular physics ,Electronic, Optical and Magnetic Materials ,Ion ,chemistry.chemical_compound ,chemistry ,Ionization ,0103 physical sciences ,Ceramics and Composites ,Strontium titanate ,Irradiation ,010306 general physics ,0210 nano-technology - Abstract
The lack of fundamental understanding on the coupled effects of energy deposition to electrons and atomic nuclei on defect processes and irradiation response poses a significant roadblock for the design and control of material properties. In this work, SrTiO3 has been irradiated with various ion species over a wide range of ion fluences at room temperature with a goal to deposit different amounts of energy to target electrons and atomic nuclei by varying the ratio of electronic to nuclear energy loss. The results unambiguously show a dramatic difference in behavior of SrTiO3 irradiated with light ions (Ne, O) compared to heavy ions (Ar). While the damage accumulation and amorphization under Ar ion irradiation are consistent with previous observations and existing models, the damage accumulation under Ne irradiation reveals a quasi-saturation state at a fractional disorder of 0.54 at the damage peak for an ion fluence corresponding to a dose of 0.5 dpa; this is followed by further increases in disorder with increasing ion fluence. In the case of O ion irradiation, the damage accumulation at the damage peak closely follows that for Ne ion irradiation up to a fluence corresponding to a dose of 0.5 dpa, where a quasi-saturation of fractional disorder level occurs at about 0.48; however, in this case, the disorder at the damage peak decreases slightly with further increases in fluence. This behavior is associated with changes in kinetics due to irradiation-enhanced diffusional processes that are dependent on electronic energy loss and the ratio of electronic to nuclear energy dissipation. These findings are critical for advancing the fundamental understanding of ion-solid interactions and for a large number of applications in oxide electronics where SrTiO3 is a foundational material.
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- 2018
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31. Stability of vacancy-type defect clusters in Ni based on first-principles and molecular dynamics simulations
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Shijun Zhao, Yanwen Zhang, and William J. Weber
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010302 applied physics ,Materials science ,Mechanical Engineering ,Metals and Alloys ,02 engineering and technology ,Type (model theory) ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Stability (probability) ,Ab initio molecular dynamics ,Condensed Matter::Materials Science ,Molecular dynamics ,Mechanics of Materials ,Chemical physics ,Vacancy defect ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,Tetrahedron ,General Materials Science ,Chemical stability ,Atomic physics ,0210 nano-technology ,Stacking fault - Abstract
Using first-principles calculations based on density-functional theory, the energetics of different vacancy-type defects, including voids, stacking fault tetrahedra (SFT) and vacancy loops, in Ni are investigated. It is found that voids are more stable than SFT at 0 K, which is also the case after taking into account the volumetric strains. By carrying out ab initio molecular dynamics simulations at temperatures up to 1000 K, direct transformations from vacancy loops and voids into SFT are observed. Our results suggest the importance of temperature effects in determining thermodynamic stability of vacancy clusters in face-centered cubic metals.
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- 2018
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32. Irradiation-induced defect formation and damage accumulation in single crystal CeO2
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Yanwen Zhang, Joseph T. Graham, and William J. Weber
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010302 applied physics ,Nuclear and High Energy Physics ,Materials science ,Analytical chemistry ,Nucleation ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Rutherford backscattering spectrometry ,01 natural sciences ,Crystallographic defect ,Fluence ,Ion ,symbols.namesake ,Nuclear Energy and Engineering ,0103 physical sciences ,symbols ,General Materials Science ,Irradiation ,0210 nano-technology ,Raman spectroscopy ,Single crystal - Abstract
The accumulation of irradiation-induced disorder in single crystal CeO2 has been investigated over a wide range of ion fluences. Room temperature irradiations of epitaxial CeO2 thin films using 2 MeV Au2+ ions were carried out up to a total fluence of 1.3 × 1016 cm−2 Post-irradiation disorder was characterized using ion channeling Rutherford backscattering spectrometry (RBS/C) and confocal Raman spectroscopy. The Raman measurements were interpreted by means of a phonon confinement model, which employed rigid ion calculations to determine the phonon correlation length in the irradiated material. Comparison between the dose dependent changes in correlation length of the Raman measurements and the Ce disorder fraction from RBS/C provides complementary quantitative details on the rate of point and extended defect formation on the Ce and O sub-lattices over a broad range of ion fluences. Raman measurements, which are significantly more sensitive than RBS/C at low doses, reveal that the nucleation rate of defects is highest below 0.1 displacements per atom (dpa). Comparison between Raman and RBS/C measurements suggests that between 0.1 and 10 dpa the damage evolution is characterized by modest growth of point defects and/or small clusters, while above 10 dpa the preexisting defects rapidly grow into extended clusters and/or loops.
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- 2018
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33. Coupled electronic and atomic effects on defect evolution in silicon carbide under ion irradiation
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Shuo Zhang, Xue-Lin Wang, Yanwen Zhang, Ritesh Sachan, Christopher Ostrouchov, William J. Weber, Haizhou Xue, Peng Liu, Tie Shan Wang, and Eva Zarkadoula
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010302 applied physics ,Materials science ,Annealing (metallurgy) ,Ionic bonding ,02 engineering and technology ,Electron ,Dissipation ,021001 nanoscience & nanotechnology ,01 natural sciences ,Ion ,chemistry.chemical_compound ,chemistry ,Ionization ,0103 physical sciences ,Silicon carbide ,General Materials Science ,Irradiation ,Atomic physics ,0210 nano-technology - Abstract
Understanding energy dissipation processes in electronic/atomic subsystems and subsequent non-equilibrium defect evolution is a long-standing challenge in materials science. In the intermediate energy regime, energetic particles simultaneously deposit a significant amount of energy to both electronic and atomic subsystems of silicon carbide (SiC). Here we show that defect evolution in SiC closely depends on the electronic-to-nuclear energy loss ratio (Se/Sn), nuclear stopping powers (dE/dxnucl), electronic stopping powers (dE/dxele), and the temporal and spatial coupling of electronic and atomic subsystem for energy dissipation. The integrated experiments and simulations reveal that: (1) increasing Se/Sn slows damage accumulation; (2) the transient temperatures during the ionization-induced thermal spike increase with dE/dxele, which causes efficient damage annealing along the ion trajectory; and (3) for more condensed displacement damage within the thermal spike, damage production is suppressed due to the coupled electronic and atomic dynamics. Ionization effects are expected to be more significant in materials with covalent/ionic bonding involving predominantly well-localized electrons. Insights into the complex electronic and atomic correlations may pave the way to better control and predict SiC response to extreme energy deposition.
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- 2017
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34. Evolution of irradiation-induced strain in an equiatomic NiFe alloy
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Hongbin Bei, William J. Weber, Mohammad W. Ullah, Neila Sellami, Yanwen Zhang, Aurélien Debelle, Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11)
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[PHYS]Physics [physics] ,010302 applied physics ,Diffraction ,Materials science ,Strain (chemistry) ,Mechanical Engineering ,Alloy ,Relaxation (NMR) ,Metals and Alloys ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Crystallographic defect ,Molecular physics ,Ion ,Crystallography ,Mechanics of Materials ,0103 physical sciences ,engineering ,General Materials Science ,Irradiation ,Dislocation ,0210 nano-technology - Abstract
International audience; The evolution of irradiation-induced atomic strain in an equiatomic NiFe concentrated solid-solution alloy is investigated using both atomistic simulations and x-ray diffraction analysis. The irradiations are performed using 1.5 MeV Ni ions to fluences ranging from 1 × 1013 to 1 × 1014 cm− 2. The irradiation simulations are carried out by overlapping 5 keV Ni recoils cascades up to a total of 300 recoils. An increase of volumetric strain is observed at low dose, which is associated with production of point defects and small clusters. Relaxation of strain occurs at higher doses, when large defect clusters, e.g., dislocation loops, dominate.
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- 2017
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35. Diffusion of point defects near stacking faults in 3C-SiC via first-principles calculations
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Bin Liu, William J. Weber, Jianqi Xi, Fenglin Yuan, and Yanwen Zhang
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010302 applied physics ,Annihilation ,Materials science ,Condensed matter physics ,Mechanical Engineering ,Metals and Alloys ,Stacking ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Crystallographic defect ,Crystallography ,Mechanics of Materials ,Interstitial diffusion ,0103 physical sciences ,General Materials Science ,Irradiation ,Diffusion (business) ,0210 nano-technology ,human activities ,Stacking fault - Abstract
First-principles calculations are used to investigate diffusion of point defects near stacking faults in 3C-SiC and to identify the migration mechanisms. Compared with the energy barriers for defects in the bulk, the migration barriers for both Si and C vacancies and Si interstitials near the stacking fault are found to decrease. For C interstitials, the energy barriers increase depending on the electronic localization in the stacking fault region. The lower barriers for Si interstitial diffusion near the faults may be responsible for the enhanced defect annihilation observed under irradiation in 3C-SiC with high densities of stacking faults.
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- 2017
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36. Effects of electronic excitation on cascade dynamics in nickel–iron and nickel–palladium systems
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William J. Weber, Eva Zarkadoula, and German D. Samolyuk
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inorganic chemicals ,010302 applied physics ,Materials science ,Mechanical Engineering ,Dynamics (mechanics) ,Metals and Alloys ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Molecular dynamics ,Nickel ,chemistry ,Mechanics of Materials ,Cascade ,Chemical physics ,0103 physical sciences ,Electronic effect ,General Materials Science ,Irradiation ,Atomic physics ,0210 nano-technology ,Excitation ,Palladium - Abstract
Using molecular dynamics simulations and the two-temperature model, we provide a comparison of the surviving damage from single ion irradiation events in nickel-based alloys, for cascades with and without taking into account the effects of the electronic excitations. We find that including the electronic effects impacts the amount of the resulting damage and the production of isolated defects. Irradiation of nickel–palladium systems results in larger numbers of defects compared to nickel–iron systems, with similar numbers of isolated defects. We additionally investigate the mass effect on the two-temperature model in molecular dynamics simulations of cascades.
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- 2017
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37. Irradiation-induced damage evolution in concentrated Ni-based alloys
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Mohammad W. Ullah, Miguel L. Crespillo, Gihan Velisa, Yanwen Zhang, Hongbin Bei, Haizhou Xue, Ke Jin, and William J. Weber
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010302 applied physics ,Range (particle radiation) ,Materials science ,Polymers and Plastics ,Metals and Alloys ,Analytical chemistry ,02 engineering and technology ,Radiation ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Fluence ,Electronic, Optical and Magnetic Materials ,Ion ,Crystallography ,Molecular dynamics ,0103 physical sciences ,Ceramics and Composites ,Irradiation ,0210 nano-technology ,Spectroscopy - Abstract
Understanding the effects of chemical complexity from the number, type and concentration of alloying elements in single-phase concentred solid-solution alloys (SP-CSAs) on defect dynamics and microstructure evolution is pivotal for developing next-generation radiation-tolerant structural alloys. A specially chosen set of SP-CSAs with different chemical complexity (Ni 80 Fe 20 , Ni 80 Cr 20 and Ni 40 Fe 40 Cr 20 ) are investigated using 1.5 MeV Mn ions over a wide fluence range, from 2 × 10 13 to 1 × 10 16 ions cm −2 at room temperature. Based on an integrated study of Rutherford backscattering spectroscopy in channeling geometry and molecular dynamics simulations, the results demonstrate that Ni 40 Fe 40 Cr 20 is more radiation tolerant than Ni 80 Fe 20 , Ni 80 Cr 20 and elemental Ni in the low fluence regime. While chemical complexity of this set of SP-CSAs is clearly demonstrated to affect defect evolution through suppressed defect production and enhanced recombination at early stages, the effect of the mixed ferro- and anti-ferromagnetic interactions is not the only controlling factor responsible for the improved radiation performance. The observed strong alloying effect on defect evolution is attributed to the altered defect migration mobilities of defect clusters in these alloys, an intrinsic characteristic of the complex energy landscapes in CSAs.
- Published
- 2017
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38. Effects of the electron-phonon coupling activation in collision cascades
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William J. Weber, German D. Samolyuk, and Eva Zarkadoula
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Nuclear and High Energy Physics ,Chemistry ,Metallurgy ,Electron phonon coupling ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Collision ,01 natural sciences ,Molecular physics ,Ion ,Coupling (electronics) ,Condensed Matter::Materials Science ,Molecular dynamics ,Nuclear Energy and Engineering ,0103 physical sciences ,Electronic effect ,General Materials Science ,010306 general physics ,0210 nano-technology - Abstract
Using the two-temperature (2T-MD) model in molecular dynamics simulations, we investigate the condition of switching the electronic stopping term off when the electron-phonon coupling is activated in the damage production due to 50 keV Ni ion cascades in Ni and equiatomic NiFe. Additionally, we investigate the effect of the electron-phonon coupling activation time in the damage production. We find that the switching condition has negligible effect in the produced damage, while the choice of the activation time of the electron-phonon coupling can affect the amount of surviving damage.
- Published
- 2017
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39. Amorphization due to electronic energy deposition in defective strontium titanate
- Author
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Yanwen Zhang, Haizhou Xue, Peng Liu, Eva Zarkadoula, William J. Weber, and Ke Jin
- Subjects
Materials science ,Polymers and Plastics ,Ion track ,Metals and Alloys ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,Molecular physics ,Electronic, Optical and Magnetic Materials ,Amorphous solid ,Ion ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Ceramics and Composites ,Strontium titanate ,Stopping power (particle radiation) ,Thin film ,Atomic physics ,010306 general physics ,0210 nano-technology ,Single crystal - Abstract
The synergistic interaction of electronic energy loss by ions with ion-induced defects created by elastic nuclear scattering processes has been investigated for single crystal SrTiO3. An initial pre-damaged defect state corresponding to a relative disorder level of 0.10–0.15 sensitizes the SrTiO3 to amorphous track formation along the ion path of 12 and 20 MeV Ti, 21 MeV Cl and 21 MeV Ni ions, where Ti, Cl and Ni ions otherwise do not produce amorphous or damage tracks in pristine SrTiO3. The electronic stopping power threshold for amorphous ion track formation is found to be 6.7 keV/nm for the pre-damaged defect state studied in this work. These results suggest the possibility of selectively producing nanometer scale, amorphous ion tracks in thin films of epitaxial SrTiO3.
- Published
- 2017
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40. Radiation-induced segregation on defect clusters in single-phase concentrated solid-solution alloys
- Author
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Fei Gao, Ning Gao, Yanwen Zhang, Pengyuan Xiu, Chenyang Lu, Yan Dong, Taini Yang, William J. Weber, Hongbin Bei, Ke Jin, Lumin Wang, and Kai Sun
- Subjects
010302 applied physics ,Materials science ,Polymers and Plastics ,High entropy alloys ,Electron energy loss spectroscopy ,Alloy ,Metals and Alloys ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Fluence ,Electronic, Optical and Magnetic Materials ,Ion ,Crystallography ,Transmission electron microscopy ,0103 physical sciences ,Ceramics and Composites ,engineering ,Irradiation ,0210 nano-technology ,Solid solution - Abstract
A group of single-phase concentrated solid-solution alloys (SP-CSAs), including NiFe, NiCoFe, NiCoFeCr, as well as a high entropy alloy NiCoFeCrMn, was irradiated with 3 MeV Ni 2+ ions at 773 K to a fluence of 5 × 10 16 ions/cm 2 for the study of radiation response with increasing compositional complexity. Advanced transmission electron microscopy (TEM) with electron energy loss spectroscopy (EELS) was used to characterize the dislocation loop distribution and radiation-induced segregation (RIS) on defect clusters in the SP-CSAs. The results show that a higher fraction of faulted loops exists in the more compositionally complex alloys, which indicate that increasing compositional complexity can extend the incubation period and delay loop growth. The RIS behaviors of each element in the SP-CSAs were observed as follows: Ni and Co tend to enrich, but Cr, Fe and Mn prefer to deplete near the defect clusters. RIS level can be significantly suppressed by increasing compositional complexity due to the sluggish atom diffusion. According to molecular static (MS) simulations, “disk” like segregations may form near the faulted dislocation loops in the SP-CSAs. Segregated elements tend to distribute around the whole faulted loop as a disk rather than only around the edge of the loop.
- Published
- 2017
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41. Two-temperature model in molecular dynamics simulations of cascades in Ni-based alloys
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Eva Zarkadoula, German D. Samolyuk, and William J. Weber
- Subjects
010302 applied physics ,Coupling ,Materials science ,Mechanical Engineering ,Metals and Alloys ,chemistry.chemical_element ,02 engineering and technology ,Electron ,021001 nanoscience & nanotechnology ,01 natural sciences ,Crystallographic defect ,Molecular physics ,Ion ,Nickel ,Molecular dynamics ,chemistry ,Mechanics of Materials ,0103 physical sciences ,Materials Chemistry ,Electronic effect ,Irradiation ,Atomic physics ,0210 nano-technology - Abstract
In high-energy irradiation events, energy from the fast moving ion is transferred to the system via nuclear and electronic energy loss mechanisms. The nuclear energy loss results in the creation of point defects and clusters, while the energy transferred to the electrons results in the creation of high electronic temperatures, which can affect the damage evolution. We perform molecular dynamics simulations of 30 keV and 50 keV Ni ion cascades in nickel-based alloys without and with the electronic effects taken into account. We compare the results of classical molecular dynamics (MD) simulations, where the electronic effects are ignored, with results from simulations that include the electronic stopping only, as well as simulations where both the electronic stopping and the electron-phonon coupling are incorporated, as described by the two temperature model (2T-MD). Our results indicate that the 2T-MD leads to a smaller amount of damage, more isolated defects and smaller defect clusters.
- Published
- 2017
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42. Ab initio molecular dynamics simulations of low energy recoil events in MgO
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William J. Weber, B.A. Petersen, Bin Liu, and Yong Zhang
- Subjects
Physics ,Nuclear and High Energy Physics ,Chemical substance ,Oxide ,Charge (physics) ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Displacement (vector) ,Nuclear physics ,chemistry.chemical_compound ,Molecular dynamics ,Recoil ,Nuclear Energy and Engineering ,chemistry ,visual_art ,0103 physical sciences ,Threshold displacement energy ,visual_art.visual_art_medium ,General Materials Science ,Ceramic ,010306 general physics ,0210 nano-technology - Abstract
Low-energy recoil events in MgO are studied using ab intio molecular dynamics simulations to reveal the dynamic displacement processes and final defect configurations. Threshold displacement energies, Ed, are obtained for Mg and O along three low-index crystallographic directions, [100], [110], and [111]. The minimum values for Ed are found along the [110] direction consisting of the same element, either Mg or O atoms. Minimum threshold values of 29.5 eV for Mg and 25.5 eV for O, respectively, are suggested from the calculations. For other directions, the threshold energies are considerably higher, 65.5 and 150.0 eV for O along [111] and [100], and 122.5 eV for Mg along both [111] and [100] directions, respectively. These results show that the recoil events in MgO are partial-charge transfer assisted processes where the charge transfer plays an important role. There is a similar trend found in other oxide materials, where the threshold displacement energy correlates linearly with the peak partial-charge transfer, suggesting this behavior might be universal in ceramic oxides.
- Published
- 2017
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43. Non-radiative luminescence decay with self-trapped hole migration in strontium titanate: Interplay between optical and transport properties
- Author
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William J. Weber, Miguel L. Crespillo, Fernando Agulló-López, Yanwen Zhang, and Joseph T. Graham
- Subjects
Annihilation ,Materials science ,Exciton ,02 engineering and technology ,Activation energy ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Ion ,chemistry.chemical_compound ,chemistry ,Strontium titanate ,General Materials Science ,Density functional theory ,0210 nano-technology ,Luminescence ,Excitation - Abstract
A novel model for the non-radiative decay of self-trapped excitons (STEs) in the advanced functional oxide SrTiO3 is proposed and supported by experimental observations. The study is based on the initial ionoluminescence stage for STE emission at 2.5 eV, and its dependence on temperature and electronic excitation rate under energetic heavy-ion irradiation. For all temperatures, this initial stage reaches rapidly a quasi-steady level, and then decreases as induced-structural damage increases. The quasi-steady luminescence exhibits a linear dependence on the excitation rate, suggesting a constant efficiency for STEs formation. An activation energy of 55 meV, essentially independent of the incident ion mass and energy of projectile-ion, is deduced from an Arrhenius-type relationship with irradiation temperature. This energy is in good agreement with experimental values, measured for non-radiative STE decay under ns-laser pulse excitation, and reasonably consistent with density functional theory calculations for migration of self-trapped holes (STHs) described by a small-polaron adiabatic hopping model. A new mechanism dealing with a non-radiative contribution to the STE transition is discussed, consisting of STH migration through thermally-activated hopping and annihilation with the STE-electron. Luminescence kinetics from the chromium intrinsic impurity strongly supports this model, being consistent with the annihilation of Cr3+ centers through recombination with migrating STHs.
- Published
- 2021
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44. Effects of recoil spectra and electronic energy dissipation on defect survival in 3C-SiC
- Author
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Ju Li, William J. Weber, Miguel L. Crespillo, Yang Yang, Yanwen Zhang, Eva Zarkadoula, and Lauren Nuckols
- Subjects
Coupling ,Elastic scattering ,Recoil ,Materials science ,Physics::Plasma Physics ,General Materials Science ,Dissipation ,Electronic energy ,Single crystal ,Molecular physics ,Spectral line ,Ion - Abstract
The coincidence of electronic and damage energy dissipation from energetic ions to an atomic lattice can significantly affect damage production along the ion trajectory due to spatial overlap of inelastic and elastic processes. Damage production and disordering in single crystal 3C-SiC from 5 MeV Si and 10 MeV Au ions is investigated using ion-channeling experiments. While defects are created by damage energy dissipation via elastic scattering, electronic energy dissipation via electron-phonon coupling decreases defect survival along the ion trajectory for Si ions. The more energetic recoil spectrum for 10 MeV Au ions leads to weaker spatial coupling of electronic and damage energy dissipation processes, and damage production is only weakly affected.
- Published
- 2021
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45. Effects of Fe concentration on the ion-irradiation induced defect evolution and hardening in Ni-Fe solid solution alloys
- Author
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Jonathan D. Poplawsky, William J. Weber, Yanwen Zhang, Wei Guo, Chenyang Lu, Ke Jin, Mohammad W. Ullah, Lumin Wang, and Hongbin Bei
- Subjects
010302 applied physics ,Materials science ,Polymers and Plastics ,Metals and Alloys ,Analytical chemistry ,02 engineering and technology ,Atom probe ,Nanoindentation ,021001 nanoscience & nanotechnology ,01 natural sciences ,Fluence ,Electronic, Optical and Magnetic Materials ,law.invention ,Ion ,Crystallography ,Transmission electron microscopy ,law ,0103 physical sciences ,Ceramics and Composites ,Hardening (metallurgy) ,Irradiation ,0210 nano-technology ,Solid solution - Abstract
Understanding alloying effects on the irradiation response of structural materials is pivotal in nuclear engineering. To systematically explore the effects of Fe concentration on the irradiation-induced defect evolution and hardening in face-centered cubic Ni-Fe binary solid solution alloys, single crystalline Ni-xFe (x = 0–60 at%) alloys have been grown and irradiated with 1.5 MeV Ni ions. The irradiations have been performed over a wide range of fluences from 3 × 1013 to 3 × 1016 cm−2 at room temperature. Ion channeling technique has shown reduced damage accumulation with increasing Fe concentration in the low fluence regime, which is consistent to the results from molecular dynamic simulations. No irradiation-induced compositional segregation was observed in atom probe tomography within the detection limit, even in the samples irradiated with high fluence Ni ions. Transmission electron microscopy analyses have further demonstrated that the defect size significantly decreases with increasing Fe concentration, indicating a delay in defect evolution. Furthermore, irradiation induced hardening has been measured by nanoindentation tests. Ni and the Ni-Fe alloys have largely different initial hardness, but they all follow a similar trend for the increase of hardness as a function of irradiation fluence.
- Published
- 2016
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46. Combined effects of radiation damage and He accumulation on bubble nucleation in Gd2Ti2O7
- Author
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William J. Weber, Yanwen Zhang, Haizhou Xue, Caitlin A. Taylor, Yongqiang Wang, Miguel L. Crespillo, J. Wen, Maulik K. Patel, and Jeffery A. Aguiar
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010302 applied physics ,Nuclear and High Energy Physics ,Materials science ,Radiochemistry ,Pyrochlore ,Bubble nucleation ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,Amorphous solid ,Nuclear Energy and Engineering ,chemistry ,Chemical physics ,0103 physical sciences ,engineering ,Radiation damage ,General Materials Science ,Nuclide ,Liquid bubble ,0210 nano-technology ,Helium - Abstract
Pyrochlores have long been considered as host phases for long-term immobilization of radioactive waste nuclides that would undergo α-decay for hundreds of thousands of years. This work utilizes ion-beam irradiations to examine the combined effects of radiation damage and He accumulation on bubble formation in Gd2Ti2O7 over relevant waste-form timescales. Helium bubbles are not observed in pre-damaged Gd2Ti2O7 implanted with 2 × 1016 He/cm2, even after post-implantation irradiations with 7 MeV Au3+ at 300, 500, and 700 K. However, He bubbles with average diameters of 1.5 nm and 2.1 nm are observed in pre-damaged (amorphous) Gd2Ti2O7 and pristine Gd2Ti2O7, respectively, after implantation of 2 × 1017 He/cm2. The critical He concentration for bubble nucleation in Gd2Ti2O7 is estimated to be 6 at.% He.
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- 2016
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47. Ab initio study of point defects near stacking faults in 3C-SiC
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Yanwen Zhang, William J. Weber, Jianqi Xi, and Bin Liu
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010302 applied physics ,Materials science ,General Computer Science ,Silicon ,Condensed matter physics ,Band gap ,Stacking ,Ab initio ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Electronic structure ,021001 nanoscience & nanotechnology ,01 natural sciences ,Crystallographic defect ,Computational Mathematics ,Crystallography ,chemistry ,Mechanics of Materials ,0103 physical sciences ,General Materials Science ,Density functional theory ,0210 nano-technology ,Stacking fault - Abstract
Interactions between point defects and stacking faults in 3C-SiC are studied using an ab initio method based on density functional theory. The results show that the discontinuity of the stacking sequence considerably affects the configurations and behavior of intrinsic defects, especially in the case of silicon interstitials. The existence of an intrinsic stacking fault (missing a C-Si bilayer) shortens the distance between the tetrahedral-center site and its second-nearest-neighboring silicon layer, making the tetrahedral silicon interstitial unstable. Instead of a tetrahedral configuration with four C neighbors, a pyramid-like interstitial structure with a defect state within the band gap becomes a stable configuration. In addition, orientation rotation occurs in the split interstitials that has diverse effects on the energy landscape of silicon and carbon split interstitials in the stacking fault region. Furthermore, our analyses of ionic relaxation and electronic structure of vacancies show that the built-in strain field, owing to the existence of the stacking fault, makes the local environment around vacancies more complex than that in the bulk.
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- 2016
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48. Amorphization resistance of nano-engineered SiC under heavy ion irradiation
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William J. Weber, Haizhou Xue, Yanwen Zhang, Manabu Ishimaru, Steven Shannon, and Kenta Imada
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010302 applied physics ,Nuclear and High Energy Physics ,Materials science ,technology, industry, and agriculture ,Analytical chemistry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Heavy ion irradiation ,Ion ,Carbide ,Crystallography ,chemistry.chemical_compound ,stomatognathic system ,chemistry ,Materials Science(all) ,Nuclear Energy and Engineering ,Relative resistance ,0103 physical sciences ,Nano ,Silicon carbide ,General Materials Science ,Irradiation ,0210 nano-technology ,Single crystal - Abstract
Silicon carbide (SiC) with a high-density of planar defects (hereafter, ‘nano-engineered SiC’) and epitaxially-grown single-crystalline 3C-SiC were simultaneously irradiated with Au ions at room temperature, in order to compare their relative resistance to radiation-induced amorphization. It was found that the local threshold dose for amorphization is comparable for both samples under 2 MeV Au ion irradiation; whereas, nano-engineered SiC exhibits slightly greater radiation tolerance than single crystalline SiC under 10 MeV Au irradiation. Under 10 MeV Au ion irradiation, the dose for amorphization increased by about a factor of two in both nano-engineered and single crystal SiC due to the local increase in electronic energy loss that enhanced dynamic recovery.
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- 2016
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49. Bubble formation and lattice parameter changes resulting from He irradiation of defect-fluorite Gd2Zr2O7
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J. Wen, Jeffery A. Aguiar, Haizhou Xue, Maulik K. Patel, Yanwen Zhang, William J. Weber, Caitlin A. Taylor, Yongqiang Wang, and Miguel L. Crespillo
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010302 applied physics ,Materials science ,Polymers and Plastics ,Metals and Alloys ,Pyrochlore ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,Fluence ,Electronic, Optical and Magnetic Materials ,Ion ,Lattice constant ,chemistry ,0103 physical sciences ,Ceramics and Composites ,engineering ,Radiation damage ,Irradiation ,Liquid bubble ,0210 nano-technology ,Helium ,Nuclear chemistry - Abstract
Pyrochlores have long been considered as potential candidates for advanced ceramic waste-forms for the immobilization of radioactive waste nuclides. This work provides evidence that Gd2Zr2O7, often considered the most radiation tolerant pyrochlore, could be susceptible to radiation damage in the form of bubble nucleation at the highest He doses expected over geological time. Ion irradiations were utilized to experimentally simulate the radiation damage and He accumulation produced by alpha-decay. Samples were pre-damaged using 7 MeV Au3+ to induce the pyrochlore to defect-fluorite phase transformation, which would occur due to alpha-recoil damage within several hundred years of storage in a Gd2Zr2O7 waste form. These samples were then implanted to various He concentrations in order to study the long-term effects of He accumulation. Helium bubbles 1-3 nm in diameter were observed in TEM at a concentration of 4.6 at.% He. Some bubbles remained isolated, while others formed chains 10-30 nm in length parallel to the surface. GIXRD measurements showed lattice swelling after irradiating pristine Gd2Zr2O7 with 7 MeV Au3+ to a fluence of 2.2 x 10(15) Au/cm(2). An increase in lattice swelling was also measured after 2.2 x 10(15) Au/cm(2) + 2 x 10(15) He/cm(2) and 2.2 x 10(15) Au/cm(2) + 2 x 10(16) He/cm(2). A decrease in lattice swelling was measured after irradiation with 2.2 x 1015 Au/cm2 + 2 x 1017 He/cm2, the fluence where bubbles and bubble chains were observed in TEM. Bubble chains are thought to form in order to reduce lattice strain normal to the surface, which is produced by the Au and He irradiation damage. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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- 2016
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50. Effects of compositional complexity on the ion-irradiation induced swelling and hardening in Ni-containing equiatomic alloys
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Ke Jin, Chenyang Lu, Yong Zhang, Jun Qu, William J. Weber, Hongbin Bei, and L. M. Wang
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Materials science ,Alloy ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,01 natural sciences ,Ion ,Materials Science(all) ,0103 physical sciences ,medicine ,General Materials Science ,Irradiation ,010302 applied physics ,Mechanical Engineering ,Metallurgy ,technology, industry, and agriculture ,Metals and Alloys ,Quinary ,Nanoindentation ,equipment and supplies ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Nickel ,chemistry ,Mechanics of Materials ,engineering ,Hardening (metallurgy) ,Swelling ,medicine.symptom ,0210 nano-technology - Abstract
The impact of compositional complexity on the ion-irradiation induced swelling and hardening is studied in Ni and six Ni-containing equiatomic alloys with face-centered cubic structure. The irradiation resistance at the temperature of 500 °C is improved by controlling the number and, especially, the type of alloying elements. Alloying with Fe and Mn has a stronger influence on swelling reduction than does alloying with Co and Cr. The quinary alloy NiCoFeCrMn, with known excellent mechanical properties, has shown 40 times higher swelling tolerance than nickel.
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- 2016
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