Ternary M_(n+1)AX_n phases with layered hexagonal structures, as candidate materials used for next-generation nuclear reactors, have shown great potential in tolerating radiation damage due to their unique combination...Ternary M_(n+1)AX_n phases with layered hexagonal structures, as candidate materials used for next-generation nuclear reactors, have shown great potential in tolerating radiation damage due to their unique combination of ceramic and metallic properties. However, M_(n+1)AX_n materials behave differently in amorphization when exposed to energetic neutron and ion irradiations in experiment. We first analyze the irradiation tolerances of different M_(n+1)AX_n(MAX) phases in terms of electronic structure, including the density of states(DOS) and charge density map. Then a new method based on the Bader analysis with the first-principle calculation is used to estimate the stabilities of MAX phases under irradiation. Our calculations show that the substitution of Cr/V/Ta/Nb by Ti and Si/Ge/Ga by Al can increase the ionicities of the bonds,thus strengthening the radiation tolerance. It is also shown that there is no obvious difference in radiation tolerance between M_(n+1)AC_n and M_(n+1)AN_n due to the similar charge transfer values of C and N atoms. In addition, the improved radiation tolerance from Ti_3AlC_2 to Ti_2AlC (Ti_3AlC_2 and Ti_2AlC have the same chemical elements), can be understood in terms of the increased Al/TiC layer ratio. Criteria based on the quantified charge transfer can be further used to explore other M_(n+1)AX_n phases with respect to their radiation tolerance, playing a critical role in choosing appropriate MAX phases before they are subjected to irradiation in experimental test for future nuclear reactors.展开更多
Nanostructured materials with abundant defect sinks show good radiation tolerance due to their efficient absorption of irradiation-induced interstitials and vacancies.However,the poor thermal stability and limited siz...Nanostructured materials with abundant defect sinks show good radiation tolerance due to their efficient absorption of irradiation-induced interstitials and vacancies.However,the poor thermal stability and limited size of such nanomaterials severely limit their practical applications.Herein,we report a novel flexible free-standing network-structured hybrid consisting of amorphous carbon encapsulated nickel nanocrystals anchored on a single-wall carbon nanotube scaffold with excellent radiation tolerance up to 5 dpa at 673 K and exceptional thermal stability up to 1073 K.The nano-scale Ni-SWCNT network with abundant Ni-SWCNT interfaces and grain boundaries provides effective sinks and fast transportation channels for defects,which effectively absorb irradiation-induced defects and improved the irradiation tolerance.Furthermore,the formation of a low-energy Ni-C interface and surface thermal grooves significantly reduces the system free energy and increased thermal stability.The amorphous carbon layer produces an external compressive radial stress that inhibits Ni grain boundaries from migrating,which greatly improves the thermal stability of the hybrid by pinning GBs at grooves between grains and facilitates the annihilation of irradiation-induced defects at the sinks.This work provides a new strategy to improve the thermal stability and radiation tolerance of nano-materials used in an irradiation environment.展开更多
Objectire To evaluate the radiation tolerance of the reconstructive flaPs used following radicalexcision of oro - maxillofacial tumors. methods The survival and radiation response of 88 flaps (preoperative 14and posto...Objectire To evaluate the radiation tolerance of the reconstructive flaPs used following radicalexcision of oro - maxillofacial tumors. methods The survival and radiation response of 88 flaps (preoperative 14and postoperative 74) in 82 patients were reviewed. Results The survival rate of 14 flaps done on preradiatedareas was 85.7% (12/14), markedly inferior to that of the flaps receiving postoperative radiation (98.6%, 73/74). Therate of radiation response of the flaps (35.1%) was signofcantly lower than that of the normal oral mucosasurrounding the flap (83.8%, P<0.01). Conclusion The good radiation tolerability of the transplants followingtumors excision pointed to the salety of its postoperative radiotherapy.展开更多
Radiation-tolerant materials are widely desired in nuclear reactors. High-entropy alloys(HEAs) exhibiting superior mechanical performance and swelling tolerance are being considered as next-generation nuclear structur...Radiation-tolerant materials are widely desired in nuclear reactors. High-entropy alloys(HEAs) exhibiting superior mechanical performance and swelling tolerance are being considered as next-generation nuclear structural materials. However, an understanding of HEAs irradiation tolerance at an atomic scale is still lacking. In this study, the atomic scale irradiation response of AlCoCrFeNi_(2.1), composed of face-centered cubic(FCC) phase and B2 phase, has been systematically investigated at 298 and 723 K. The bubble volume ratio of the B2 phase is much larger than that of the FCC phase under the same irradiation conditions, and hence, the FCC phase has superior swelling tolerance than the B2 phase. Also, order-disorder transformation occurred in both L12and B2 phases. The different irradiation responses between the FCC and B2 phases, depend firstly on composition and secondly on crystal structure. The higher compositional complexity and complicated atomic-level lattice environment of the FCC phase contribute to better radiation performance than B2 phase. The results pave a way for exploring radiation-tolerant structural high-entropy alloys.展开更多
We report first-principles results of the point defect properties in a V-Ta-Cr-W high-entropy alloy(HEA)with the body-centered cubic(bcc)structure.Different from the widely-investigated face-centered cubic(fcc)HEAs,th...We report first-principles results of the point defect properties in a V-Ta-Cr-W high-entropy alloy(HEA)with the body-centered cubic(bcc)structure.Different from the widely-investigated face-centered cubic(fcc)HEAs,the local lattice distortion is more pronounced in bcc ones,which has a strong influence on the defect properties and defect evolution under irradiation.Due to the large size of Ta,the exchange between vacancies and Ta exhibits lower energy barriers.On the other hand,interstitial dumbbells containing V and Cr possess lower formation energies.These defect energetics predicts an enrichment of V and Cr and a depletion of Ta andWin the vicinity of defect sinks.Besides,we find that interstitial dumbbells favor the[110]orientation in the HEA,instead of[111]direction in most nonmagnetic bcc metals,which helps to slow down interstitial diffusion significantly.Consequently,the distribution of migration energies for vacancies and interstitials exhibit much larger overlap regions in the bcc HEA compared to fcc HEAs,leading to the good irradiation resistance by enhancing defect recombination.Our results suggest that HEAs with the bcc structure may bear excellent irradiation tolerance due to the particular defect properties.展开更多
Tungsten(W)as plasma facing material(PFM)needs to face an unprecedented harsh environment in the fusion reactor,which puts forward high requirements for its radiation tolerance.Among the many challenges,the rapid accu...Tungsten(W)as plasma facing material(PFM)needs to face an unprecedented harsh environment in the fusion reactor,which puts forward high requirements for its radiation tolerance.Among the many challenges,the rapid accumulation of helium(He)atoms to form numerous bubbles or even“fuzzy”nanostructure leads to swelling and embrittlement of W matrix and seriously shorten its service life,which is one of the most serious problems faced by PFM-W at present.In this review,we summarize the recent works on the nanochannel W films with high surface-to-volume ratio deposited by magnetron sputter-ing,and the behaviors of He in the nanochannel W films at different fusion-related irradiation environment.Experimental and simulation results showed that the nanochannel W films have better radiation tolerance performance in managing He behaviors than that of commercial bulk W.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.91226202 and 91426304)
文摘Ternary M_(n+1)AX_n phases with layered hexagonal structures, as candidate materials used for next-generation nuclear reactors, have shown great potential in tolerating radiation damage due to their unique combination of ceramic and metallic properties. However, M_(n+1)AX_n materials behave differently in amorphization when exposed to energetic neutron and ion irradiations in experiment. We first analyze the irradiation tolerances of different M_(n+1)AX_n(MAX) phases in terms of electronic structure, including the density of states(DOS) and charge density map. Then a new method based on the Bader analysis with the first-principle calculation is used to estimate the stabilities of MAX phases under irradiation. Our calculations show that the substitution of Cr/V/Ta/Nb by Ti and Si/Ge/Ga by Al can increase the ionicities of the bonds,thus strengthening the radiation tolerance. It is also shown that there is no obvious difference in radiation tolerance between M_(n+1)AC_n and M_(n+1)AN_n due to the similar charge transfer values of C and N atoms. In addition, the improved radiation tolerance from Ti_3AlC_2 to Ti_2AlC (Ti_3AlC_2 and Ti_2AlC have the same chemical elements), can be understood in terms of the increased Al/TiC layer ratio. Criteria based on the quantified charge transfer can be further used to explore other M_(n+1)AX_n phases with respect to their radiation tolerance, playing a critical role in choosing appropriate MAX phases before they are subjected to irradiation in experimental test for future nuclear reactors.
基金financial support from the Ministry of Science and Technology of China(Nos.2017YFA0700702 and 2017YFA0700705)the National Natural Science Foundation of China(Nos.52073290,51927803,52130209,52188101,12075141,and 11427904)+1 种基金the Science Foundation of Shenyang National Laboratory for Materials Science,Distinguished Young Scholars Foundation of Liaoning Scientific Committee(2023JH6/100500004)Carbon Neutrality Foundation of Shenyang Scientific Committee(21-108-9-01).
文摘Nanostructured materials with abundant defect sinks show good radiation tolerance due to their efficient absorption of irradiation-induced interstitials and vacancies.However,the poor thermal stability and limited size of such nanomaterials severely limit their practical applications.Herein,we report a novel flexible free-standing network-structured hybrid consisting of amorphous carbon encapsulated nickel nanocrystals anchored on a single-wall carbon nanotube scaffold with excellent radiation tolerance up to 5 dpa at 673 K and exceptional thermal stability up to 1073 K.The nano-scale Ni-SWCNT network with abundant Ni-SWCNT interfaces and grain boundaries provides effective sinks and fast transportation channels for defects,which effectively absorb irradiation-induced defects and improved the irradiation tolerance.Furthermore,the formation of a low-energy Ni-C interface and surface thermal grooves significantly reduces the system free energy and increased thermal stability.The amorphous carbon layer produces an external compressive radial stress that inhibits Ni grain boundaries from migrating,which greatly improves the thermal stability of the hybrid by pinning GBs at grooves between grains and facilitates the annihilation of irradiation-induced defects at the sinks.This work provides a new strategy to improve the thermal stability and radiation tolerance of nano-materials used in an irradiation environment.
文摘Objectire To evaluate the radiation tolerance of the reconstructive flaPs used following radicalexcision of oro - maxillofacial tumors. methods The survival and radiation response of 88 flaps (preoperative 14and postoperative 74) in 82 patients were reviewed. Results The survival rate of 14 flaps done on preradiatedareas was 85.7% (12/14), markedly inferior to that of the flaps receiving postoperative radiation (98.6%, 73/74). Therate of radiation response of the flaps (35.1%) was signofcantly lower than that of the normal oral mucosasurrounding the flap (83.8%, P<0.01). Conclusion The good radiation tolerability of the transplants followingtumors excision pointed to the salety of its postoperative radiotherapy.
基金supported by financial support from the National Natural Science Foundation of China(Nos.51771201 and 52071124)the Key Project of Natural Science Foundation of Tianjin(No.20JCZDJC00440)+1 种基金the National Key Research and Development Program(No.2018YFB0703402)the Open Research Fund from the State Key Laboratory of Rolling and Automation,Northeastern University(No.2020RALKFKT002)。
文摘Radiation-tolerant materials are widely desired in nuclear reactors. High-entropy alloys(HEAs) exhibiting superior mechanical performance and swelling tolerance are being considered as next-generation nuclear structural materials. However, an understanding of HEAs irradiation tolerance at an atomic scale is still lacking. In this study, the atomic scale irradiation response of AlCoCrFeNi_(2.1), composed of face-centered cubic(FCC) phase and B2 phase, has been systematically investigated at 298 and 723 K. The bubble volume ratio of the B2 phase is much larger than that of the FCC phase under the same irradiation conditions, and hence, the FCC phase has superior swelling tolerance than the B2 phase. Also, order-disorder transformation occurred in both L12and B2 phases. The different irradiation responses between the FCC and B2 phases, depend firstly on composition and secondly on crystal structure. The higher compositional complexity and complicated atomic-level lattice environment of the FCC phase contribute to better radiation performance than B2 phase. The results pave a way for exploring radiation-tolerant structural high-entropy alloys.
基金This work was supported financially by the Project of the City University of Hong Kong(No.9610425)the Research Grants Council of Hong Kong(No.21200919).
文摘We report first-principles results of the point defect properties in a V-Ta-Cr-W high-entropy alloy(HEA)with the body-centered cubic(bcc)structure.Different from the widely-investigated face-centered cubic(fcc)HEAs,the local lattice distortion is more pronounced in bcc ones,which has a strong influence on the defect properties and defect evolution under irradiation.Due to the large size of Ta,the exchange between vacancies and Ta exhibits lower energy barriers.On the other hand,interstitial dumbbells containing V and Cr possess lower formation energies.These defect energetics predicts an enrichment of V and Cr and a depletion of Ta andWin the vicinity of defect sinks.Besides,we find that interstitial dumbbells favor the[110]orientation in the HEA,instead of[111]direction in most nonmagnetic bcc metals,which helps to slow down interstitial diffusion significantly.Consequently,the distribution of migration energies for vacancies and interstitials exhibit much larger overlap regions in the bcc HEA compared to fcc HEAs,leading to the good irradiation resistance by enhancing defect recombination.Our results suggest that HEAs with the bcc structure may bear excellent irradiation tolerance due to the particular defect properties.
基金financially supported by the National Natural Science Fund for Excellent Young Scholars (Grant No. 11522543)the National Natural Science Foundation of China (Grant Nos. 11905058,11935011 and 11475129)+1 种基金the Natural Science Foundation of Hubei Province,China (Grant Nos. 2020CFA041 and 2016CFA080)the Fundamental Research Funds for the Central Universities
文摘Tungsten(W)as plasma facing material(PFM)needs to face an unprecedented harsh environment in the fusion reactor,which puts forward high requirements for its radiation tolerance.Among the many challenges,the rapid accumulation of helium(He)atoms to form numerous bubbles or even“fuzzy”nanostructure leads to swelling and embrittlement of W matrix and seriously shorten its service life,which is one of the most serious problems faced by PFM-W at present.In this review,we summarize the recent works on the nanochannel W films with high surface-to-volume ratio deposited by magnetron sputter-ing,and the behaviors of He in the nanochannel W films at different fusion-related irradiation environment.Experimental and simulation results showed that the nanochannel W films have better radiation tolerance performance in managing He behaviors than that of commercial bulk W.
