Oxidation corrosion of steels usually occurs in contact with the oxygen-contained environment, which is accelerated by high oxygen concentration and irradiation. The oxidation mechanism of steels is investigated by th...Oxidation corrosion of steels usually occurs in contact with the oxygen-contained environment, which is accelerated by high oxygen concentration and irradiation. The oxidation mechanism of steels is investigated by the adsorption/solution of oxygen atoms on/under body-centered-cubic(bcc) iron surfaces, and diffusion of oxygen atoms on the surface and in the near-surface region. Energetic results indicate that oxygen atoms prefer to adsorb at hollow and long-bridge positions on the Fe(100) and(110) surfaces, respectively. As the coverage of oxygen atoms increases, oxygen atoms would repel each other and gradually dissolve in the near-surface and bulk region. As vacancies exist, oxygen atoms are attracted by vacancies, especially in the near-surface and bulk region. Dynamic results indicate that the diffusion of O atoms on surfaces is easier than that into near-surface, which is affected by oxygen coverage and vacancies. Moreover, the effects of oxygen concentration and irradiation on oxygen density in the near-surface and bulk region are estimated by the Mc Lean’s model with a simple hypothesis.展开更多
We have systemically investigated the synergistic evolution of rhenium(Re)and irradiation defects in tungsten(W)-Re alloys under different temperatures and irradiation doses using object Kinetic Monte Carlo method.Our...We have systemically investigated the synergistic evolution of rhenium(Re)and irradiation defects in tungsten(W)-Re alloys under different temperatures and irradiation doses using object Kinetic Monte Carlo method.Our results revealed the underlying mechanism for the transition of Re effect on W from beneficial to harmful during the Re-defects evolution with the increase of irradiation dose,in which tem-perature always plays a critical role.On the one hand,Re will significantly promote the defect annihila-tion at low irradiation doses and high temperatures,thereby effectively reducing their sizes and number densities.This is due to the formation of stable Re-SIAs complexes that can be eliminated by the mobile vacancy-type defects,whereas the transition of the migration pattern of SIAs only plays a weak role in the defect recombination in W-Re system.On the other hand,with the increase of irradiation dose,Re will aggregate to form Re-rich clusters or even precipitates.Interestingly,the formation mechanism of Re-rich clusters is also dependent on temperature.At low temperatures,the interstitial-mediated mech-anism plays a crucial role in the Re-rich cluster formation,while at high temperatures,both SIA-type and vacancy-type defects will act as the transport carriers of Re to promote their clustering.Accordingly,the critical conditions for the transition of Re from beneficial to harmful and the formation of Re-rich clusters at different tem peratures and irradiation doses are given with the help of the phase diagram.Our work presents the temperature dependence of the synergy of Re and irradiation defects in W-Re in fusion-relevant environment,which provides a good reference for the development of radiation-resistant materials and the prediction of W performance in fusion reactors.展开更多
The effects of fast neutron irradiation on oxygen atoms in Czochralski silicon (CZ-Si) are investigated systemically by using Fourier transform infrared (FTIR) spectrometer and positron annihilation technique (PA...The effects of fast neutron irradiation on oxygen atoms in Czochralski silicon (CZ-Si) are investigated systemically by using Fourier transform infrared (FTIR) spectrometer and positron annihilation technique (PAT). Through isochronal annealing, it is found that the trend of variation in interstitial oxygen concentration ([Oi]) in fast neutrons irradiated CZ-Si fluctuates largely with temperature increasing, especially between 500 and 700℃. After the CZ-Si is annealed at 600℃, the V4 appearing as three-dimensional vacancy clusters causes the formation of the molecule-like oxygen clusters, and more importantly these dimers with small binding energies (0.1-1.0eV) can diffuse into the Si lattices more easily than single oxygen atoms, thereby leading to the strong oxygen agglomerations. When the CZ-Si is annealed at temperature increasing up to 700℃, three-dimensional vacancy clusters disappear and the oxygen agglomerations decompose into single oxygen atoms (O) at interstitial sites. Results from FTIR spectrometer and PAT provide an insight into the nature of the [Oi] at temperatures between 500 and 700℃. It turns out that the large fluctuation of [Oi] after short-time annealing from 500 to 700℃ results from the transformation of fast neutron irradiation defects.展开更多
Fe-Cr ferritic/martensitic(F/M)steels have been proposed as one of the candidate materials for the Generation IV nuclear technologies.In this study,a widely-used ferritic/martensitic steel,T91 steel,was irradiated by ...Fe-Cr ferritic/martensitic(F/M)steels have been proposed as one of the candidate materials for the Generation IV nuclear technologies.In this study,a widely-used ferritic/martensitic steel,T91 steel,was irradiated by 196-MeV Kr^(+)ions at 550℃.To reveal the irradiation mechanism,the microstructure evolution of irradiated T91 steel was studied in details by transmission electron microscope(TEM).With increasing dose,the defects gradually changed from black dots to dislocation loops,and further to form dislocation walls near grain boundaries due to the production of a large number of dislocations.When many dislocation loops of primary a0/2<111>type with high migration interacted with other defects or carbon atoms,it led to the production of dislocation segments and other dislocation loops of a0<100>type.Lots of defects accumulated near grain boundaries in the irradiated area,especially in the high-dose area.The grain boundaries of martensite laths acted as important sinks of irradiation defects in T91.Elevated temperature facilitated the migration of defects,leading to the accumulation of defects near the grain boundaries of martensite laths.展开更多
Remarkable room-temperature ferromagnetism was observed both in undoped and Cu-doped rutile TiO2 single crystals(SCs).To tune their magnetism,Ar ion irradiation was quantitatively performed on the two crystals in wh...Remarkable room-temperature ferromagnetism was observed both in undoped and Cu-doped rutile TiO2 single crystals(SCs).To tune their magnetism,Ar ion irradiation was quantitatively performed on the two crystals in which the saturation magnetizations for the samples were enhanced distinctively.The post-irradiation led to a spongelike layer in the near surface of the Cu-doped TiO2.Meanwhile,a new CuO-like species present in the sample was found to be dissolved after the post-irradiation.Analyzing the magnetization data unambiguously reveals that the experimentally observed ferromagnetism is related to the intrinsic defects rather than the exotic Cu ions,while these ions are directly involved in boosting the absorption in the visible region.展开更多
Ti_3AlC_2 samples are irradiated in advance by 3.5 MeV Fe-ion to the fluence of 1.0×10^(16) ion/cm^2,and then are implanted by 500 keV He-ion with the fluence of 1.0×10^(17) ion/cm^2 at room temperature....Ti_3AlC_2 samples are irradiated in advance by 3.5 MeV Fe-ion to the fluence of 1.0×10^(16) ion/cm^2,and then are implanted by 500 keV He-ion with the fluence of 1.0×10^(17) ion/cm^2 at room temperature.The irradiated samples are investigated by grazing incidence x-ray diffraction(GIXRD) and transmission electron microscopy(TEM).GIXRD results show serious structural distortion,but without amorphization in the irradiated samples.Fe-ion irradiation and He-ion implantation create much more serious structural distortion than single Fe-ion irradiation.TEM results reveal that there are a large number of defect clusters in the damage region,and dense spherical He bubbles appear in the He depositional region.It seems that the pre-damage does not influence the growth of He bubbles,but He-ion implantation influences the pre-created defect configurations.展开更多
To study the room-temperature stable defects induced by electron irradiation, commercial borosilicate glasses were irradiated by 1.2 MeV electrons and then ultraviolet(UV) optical absorption(OA) spectra were measu...To study the room-temperature stable defects induced by electron irradiation, commercial borosilicate glasses were irradiated by 1.2 MeV electrons and then ultraviolet(UV) optical absorption(OA) spectra were measured. Two characteristic bands were revealed before irradiation, and they were attributed to silicon dangling bond(E'-center) and Fe^3+species,respectively. The existence of Fe3+was confirmed by electron paramagnetic resonance(EPR) measurements. After irradiation, the absorption spectra revealed irradiation-induced changes, while the content of E'-center did not change in the deep ultraviolet(DUV) region. The slightly reduced OA spectra at 4.9 eV was supposed to transform Fe3+species to Fe^2+species and this transformation leads to the appearance of 4.3 eV OA band. By calculating intensity variation, the transformation of Fe was estimated to be about 5% and the optical absorption cross section of Fe2+species is calculated to be 2.2 times larger than that of Fe^3+species. Peroxy linkage(POL, ≡Si–O–O–Si≡), which results in a 3.7 eV OA band, is speculated not to be from Si–O bond break but from Si–O–B bond, Si–O–Al bond, or Si–O–Na bond break. The co-presence defect with POL is probably responsible for 2.9-eV OA band.展开更多
Titanium deuteride is an important nuclear material used in the field of nuclear technology, and further research is needed into TiD2 films irradiated by pulsed ion beams of the vacuum arc discharge with hydrogen. In ...Titanium deuteride is an important nuclear material used in the field of nuclear technology, and further research is needed into TiD2 films irradiated by pulsed ion beams of the vacuum arc discharge with hydrogen. In the current study, these irradiated TiD2 films have been investigated using scanning electronic microscopy and slow positron annihilation techniques. Both the thermal effect and irradiation defects of TiD2 films were studied, following their irradiation with mixed pulsed ion beams of titanium and hydrogen ions. It is found that the thermal effect is trivial on the irradiated surfaces, and the dominant effect is irradiation defects which can be enhanced by repetitive shots and is characterized by the inner diffusion of irradiation defects.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFE0302400 and 2017YFA0402803)the National Nature Science Foundation of China(Grant Nos.11735015,52071314,51871207,U1832206,12075274,U1967211,52171084)Hefei Advanced Computing Center。
文摘Oxidation corrosion of steels usually occurs in contact with the oxygen-contained environment, which is accelerated by high oxygen concentration and irradiation. The oxidation mechanism of steels is investigated by the adsorption/solution of oxygen atoms on/under body-centered-cubic(bcc) iron surfaces, and diffusion of oxygen atoms on the surface and in the near-surface region. Energetic results indicate that oxygen atoms prefer to adsorb at hollow and long-bridge positions on the Fe(100) and(110) surfaces, respectively. As the coverage of oxygen atoms increases, oxygen atoms would repel each other and gradually dissolve in the near-surface and bulk region. As vacancies exist, oxygen atoms are attracted by vacancies, especially in the near-surface and bulk region. Dynamic results indicate that the diffusion of O atoms on surfaces is easier than that into near-surface, which is affected by oxygen coverage and vacancies. Moreover, the effects of oxygen concentration and irradiation on oxygen density in the near-surface and bulk region are estimated by the Mc Lean’s model with a simple hypothesis.
基金This work is financially supported by the National Natu-ral Science Foundation of China(Nos.11905135,12075022 and 12192281)the National MCF Energy R&D Program(No.2018YFE0308103).
文摘We have systemically investigated the synergistic evolution of rhenium(Re)and irradiation defects in tungsten(W)-Re alloys under different temperatures and irradiation doses using object Kinetic Monte Carlo method.Our results revealed the underlying mechanism for the transition of Re effect on W from beneficial to harmful during the Re-defects evolution with the increase of irradiation dose,in which tem-perature always plays a critical role.On the one hand,Re will significantly promote the defect annihila-tion at low irradiation doses and high temperatures,thereby effectively reducing their sizes and number densities.This is due to the formation of stable Re-SIAs complexes that can be eliminated by the mobile vacancy-type defects,whereas the transition of the migration pattern of SIAs only plays a weak role in the defect recombination in W-Re system.On the other hand,with the increase of irradiation dose,Re will aggregate to form Re-rich clusters or even precipitates.Interestingly,the formation mechanism of Re-rich clusters is also dependent on temperature.At low temperatures,the interstitial-mediated mech-anism plays a crucial role in the Re-rich cluster formation,while at high temperatures,both SIA-type and vacancy-type defects will act as the transport carriers of Re to promote their clustering.Accordingly,the critical conditions for the transition of Re from beneficial to harmful and the formation of Re-rich clusters at different tem peratures and irradiation doses are given with the help of the phase diagram.Our work presents the temperature dependence of the synergy of Re and irradiation defects in W-Re in fusion-relevant environment,which provides a good reference for the development of radiation-resistant materials and the prediction of W performance in fusion reactors.
基金Project supported by the National Natural Science Foundation of China (Grant No 50872028)the Natural Science Foundation ofHebei Province,China (Grant No E2008000079)the Specialized Research Fund for the Doctoral Program of Higher Educationof China (Grant No 20050080006)
文摘The effects of fast neutron irradiation on oxygen atoms in Czochralski silicon (CZ-Si) are investigated systemically by using Fourier transform infrared (FTIR) spectrometer and positron annihilation technique (PAT). Through isochronal annealing, it is found that the trend of variation in interstitial oxygen concentration ([Oi]) in fast neutrons irradiated CZ-Si fluctuates largely with temperature increasing, especially between 500 and 700℃. After the CZ-Si is annealed at 600℃, the V4 appearing as three-dimensional vacancy clusters causes the formation of the molecule-like oxygen clusters, and more importantly these dimers with small binding energies (0.1-1.0eV) can diffuse into the Si lattices more easily than single oxygen atoms, thereby leading to the strong oxygen agglomerations. When the CZ-Si is annealed at temperature increasing up to 700℃, three-dimensional vacancy clusters disappear and the oxygen agglomerations decompose into single oxygen atoms (O) at interstitial sites. Results from FTIR spectrometer and PAT provide an insight into the nature of the [Oi] at temperatures between 500 and 700℃. It turns out that the large fluctuation of [Oi] after short-time annealing from 500 to 700℃ results from the transformation of fast neutron irradiation defects.
基金Project supported by Guangdong Major Project of Basic and Applied Basic Research(Grant No.2019B030302011)the National Natural Science Foundation of China(Grant Nos.U2032143,11902370,and 52005523)+2 种基金the International Science and Technology Cooperation Program of Guangdong Province,China(Grant No.2019A050510022)the China Postdoctoral Science Foundation(Grant Nos.2019M653173 and 2019TQ0374)the Heavy Ion Research Facility of Lanzhou(HIRFL).
文摘Fe-Cr ferritic/martensitic(F/M)steels have been proposed as one of the candidate materials for the Generation IV nuclear technologies.In this study,a widely-used ferritic/martensitic steel,T91 steel,was irradiated by 196-MeV Kr^(+)ions at 550℃.To reveal the irradiation mechanism,the microstructure evolution of irradiated T91 steel was studied in details by transmission electron microscope(TEM).With increasing dose,the defects gradually changed from black dots to dislocation loops,and further to form dislocation walls near grain boundaries due to the production of a large number of dislocations.When many dislocation loops of primary a0/2<111>type with high migration interacted with other defects or carbon atoms,it led to the production of dislocation segments and other dislocation loops of a0<100>type.Lots of defects accumulated near grain boundaries in the irradiated area,especially in the high-dose area.The grain boundaries of martensite laths acted as important sinks of irradiation defects in T91.Elevated temperature facilitated the migration of defects,leading to the accumulation of defects near the grain boundaries of martensite laths.
基金Project supported by the National Natural Science Foundation of China(Grant No.11575074)the Open Project of State Key laboratory of Crystal Material,Shandong University,China(Grant No.KF1311)+2 种基金the Open Project of Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education,Lanzhou University,China(Grant No.LZUMMM2012003)the Open Project of Key Laboratory of Beam Technology and Material Modification of Ministry of Education,Beijing Normal University,China(Grant No.201204)the Fundamental Research Funds for the Central Universities,China(Grant No.lzujbky-2015-240)
文摘Remarkable room-temperature ferromagnetism was observed both in undoped and Cu-doped rutile TiO2 single crystals(SCs).To tune their magnetism,Ar ion irradiation was quantitatively performed on the two crystals in which the saturation magnetizations for the samples were enhanced distinctively.The post-irradiation led to a spongelike layer in the near surface of the Cu-doped TiO2.Meanwhile,a new CuO-like species present in the sample was found to be dissolved after the post-irradiation.Analyzing the magnetization data unambiguously reveals that the experimentally observed ferromagnetism is related to the intrinsic defects rather than the exotic Cu ions,while these ions are directly involved in boosting the absorption in the visible region.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11405231 and 91426301
文摘Ti_3AlC_2 samples are irradiated in advance by 3.5 MeV Fe-ion to the fluence of 1.0×10^(16) ion/cm^2,and then are implanted by 500 keV He-ion with the fluence of 1.0×10^(17) ion/cm^2 at room temperature.The irradiated samples are investigated by grazing incidence x-ray diffraction(GIXRD) and transmission electron microscopy(TEM).GIXRD results show serious structural distortion,but without amorphization in the irradiated samples.Fe-ion irradiation and He-ion implantation create much more serious structural distortion than single Fe-ion irradiation.TEM results reveal that there are a large number of defect clusters in the damage region,and dense spherical He bubbles appear in the He depositional region.It seems that the pre-damage does not influence the growth of He bubbles,but He-ion implantation influences the pre-created defect configurations.
基金Project supported by the Fundamental Research Funds for the Central Universities of China(Grant No.lzujbky-2014-16)
文摘To study the room-temperature stable defects induced by electron irradiation, commercial borosilicate glasses were irradiated by 1.2 MeV electrons and then ultraviolet(UV) optical absorption(OA) spectra were measured. Two characteristic bands were revealed before irradiation, and they were attributed to silicon dangling bond(E'-center) and Fe^3+species,respectively. The existence of Fe3+was confirmed by electron paramagnetic resonance(EPR) measurements. After irradiation, the absorption spectra revealed irradiation-induced changes, while the content of E'-center did not change in the deep ultraviolet(DUV) region. The slightly reduced OA spectra at 4.9 eV was supposed to transform Fe3+species to Fe^2+species and this transformation leads to the appearance of 4.3 eV OA band. By calculating intensity variation, the transformation of Fe was estimated to be about 5% and the optical absorption cross section of Fe2+species is calculated to be 2.2 times larger than that of Fe^3+species. Peroxy linkage(POL, ≡Si–O–O–Si≡), which results in a 3.7 eV OA band, is speculated not to be from Si–O bond break but from Si–O–B bond, Si–O–Al bond, or Si–O–Na bond break. The co-presence defect with POL is probably responsible for 2.9-eV OA band.
文摘Titanium deuteride is an important nuclear material used in the field of nuclear technology, and further research is needed into TiD2 films irradiated by pulsed ion beams of the vacuum arc discharge with hydrogen. In the current study, these irradiated TiD2 films have been investigated using scanning electronic microscopy and slow positron annihilation techniques. Both the thermal effect and irradiation defects of TiD2 films were studied, following their irradiation with mixed pulsed ion beams of titanium and hydrogen ions. It is found that the thermal effect is trivial on the irradiated surfaces, and the dominant effect is irradiation defects which can be enhanced by repetitive shots and is characterized by the inner diffusion of irradiation defects.