Nucleation and growth of He bubbles at different annealing temperatures T≤1023 K in stain- less steels HR-2 and SS321,implanted with He^+(40-70 keV.1×10^(16)-6× 10^(17) He^+/cm^2),were ohserved under TEM.T=...Nucleation and growth of He bubbles at different annealing temperatures T≤1023 K in stain- less steels HR-2 and SS321,implanted with He^+(40-70 keV.1×10^(16)-6× 10^(17) He^+/cm^2),were ohserved under TEM.T=0.45T_m seems to be a transition temperature.The He bubbles continue mainly their nucleation at 0.3T_m< T<0.45T_m,and grow predominantly at T≥0.45T_m,due probably to migration and coalescence by surface diffusion of metal atoms around the bubbles.The apparent activation energies for the growth are found to he 0.41 and 0.31 eV for HR-2 and SS321 respectively.The bubble density in HR-2 is greater than that in SS321 within whole measuring temperature range,and the onset temperature of rapid swelling is also higher.It is believed that the resistance of HR-2 to He is superior to that fo SS321.展开更多
Bubble evolution in low energy and high dose He-implanted 6H-SiC upon thermal annealing is studied. The （0001）-oriented 6H-SiC wafers are implanted with 15keV helium ions at a dose of 1×10^17 cm^-2 at room temp...Bubble evolution in low energy and high dose He-implanted 6H-SiC upon thermal annealing is studied. The （0001）-oriented 6H-SiC wafers are implanted with 15keV helium ions at a dose of 1×10^17 cm^-2 at room temperature. The samples with post-implantation are annealed at temperatures of 1073, 1173, 1273, and 1473K for 30rain. He bubbles in the wafers are examined via cross-sectional transmission electron microscopy （XTEM） analysis. The results present that nanoscale bubbles are almost homogeneously distributed in the damaged layer of the as-implanted sample, and no significant change is observed in the He-implanted sample after 1073 K annealing. Upon 1193 K annealing, almost full recrystallization of He-implantation-induced amorphization in 6H-SiC is observed. In addition, the diameters of He bubbles increase obviously. With continually increasing temperatures to 1273K and 1473 K, the diameters of He bubbles increase and the number density of lattice defects decreases. The growth of He bubbles after high temperature annealingabides by the Ostwald ripening mechanism. The mean diameter of He bubbles located at depths of 120-135 nm as a function of annealing temperature is fitted in terms of a thermal activated process which yields an activation energy of 1.914＋0.236eV.展开更多
This study reports the response of helium(He)ion irradiation on binary-phase structured alloy V_(34)Ti_(25)Cr_(10)Ni_(30)Pd1.The alloy consists of a VCr matrix with nano-sized TiNi precipitates and a B2 TiNi matrix wi...This study reports the response of helium(He)ion irradiation on binary-phase structured alloy V_(34)Ti_(25)Cr_(10)Ni_(30)Pd1.The alloy consists of a VCr matrix with nano-sized TiNi precipitates and a B2 TiNi matrix with nano-sized VCr precipitates.VCr is chemical-disordered and TiNi has a B2-ordered structure.The alloy was subjected to 400 keV He ion irradiation with a fluence of 1×10^(17)ions cm^(−2)at 450℃.The results show He bubbles within the chemical-disordered VCr matrix exhibit a near-spherical shape with a smaller size and higher density compared to that in chemical-ordered TiNi phase with a larger size,lower density,and faceted shape.This indicates the chemical-disordered VCr phase effectively suppresses He accumulation compared to the B2-ordered TiNi phase,emphasizing the dominance of chemical struc-tures in He bubble formation.The calculation of density functional theory(DFT)shows that Ti and Ni have lower vacancy formation energy than that of V and Cr,respectively,which results in the increased vacancy production in TiNi.Consequently,He bubbles in TiNi have a larger bubble size consistent with experimental observations of radiation-induced Ni segregation.These findings elucidate the roles of or-dered and disordered chemical structures in He bubble evolution,offering insights for the development of gas ion irradiation-resistant materials.展开更多
The He production rate(i.e.,He/dpa)in nuclear reactors strongly affects the degradation of material prop-erties.This is an important but not yet fully understood issue.Here,the effect of He/dpa on bubble char-acterist...The He production rate(i.e.,He/dpa)in nuclear reactors strongly affects the degradation of material prop-erties.This is an important but not yet fully understood issue.Here,the effect of He/dpa on bubble char-acteristics in Fe9Cr1.5W0.4Si ferrite-martensitic(F/M)steel was in situ studied during 400 keV Fe^(+)and 30 keV He^(+)dual-beam irradiation at 723 K with three ratios of 100,500,and 2500 appm He/dpa and subsequent stepwise annealing using transmission electron microscopy(TEM).He/dpa strongly affected the bubble characteristics.During irradiation,the higher the He/dpa,the smaller the size of irradiated bubbles,but the higher their density.However,He/dpa didn’t affect the final saturation size of irradiated bubbles for all three cases,which was-2.2 nm.During annealing,high He/dpa caused large,immobile,dense polyhedral bubbles with a wider bubble size distribution,while low He/dpa caused small,low-mobility,and relatively low-density spherical bubbles.It was found that the higher the He/dpa ratio,the greater the swelling during irradiation and annealing,and annealing further enhanced the swelling.Moreover,the tunnel structure was first found in body-centered cubic(BCC)F/M steel during in-situ irra-diation.The current work provides valuable and potential insights for further understanding the He/dpa effects in materials serving in different nuclear reactors.展开更多
To improve the mechanical properties of the Y_(2)O_(3)-added W alloy,Mo and Zr were independently added to a sample of W-Y_(2)O_(3).In this study,the effects of minor additions of elemental Mo and Zr on He bubble form...To improve the mechanical properties of the Y_(2)O_(3)-added W alloy,Mo and Zr were independently added to a sample of W-Y_(2)O_(3).In this study,the effects of minor additions of elemental Mo and Zr on He bubble formation in the Y_(2)O_(3)added W alloys were investigated at 773 K,973 K,and 1173 K,where the maximum irradiation fluence of the samples using 5 keV He ions was 1.8×10^(21) He m^(−2).He bubbles were observed at all temperatures for both alloys;however,the irradiation fluences at which He bubbles could be observed differed at each temperature.With increase in irradiation temperature,the He irradiation fluence for which the formation of He bubbles could be observed decreased.At the relatively low temperature of 773 K,the void swelling in the W-Mo-Y_(2)O_(3)and W-Zr-Y_(2)O_(3)alloys was slightly lower than that of W-Y_(2)O_(3)alloy.However,at high temperature of 973 K and 1173 K,the He irradiation resistances of both W-Mo-Y_(2)O_(3)and W-Zr-Y_(2)O_(3)were worse than that of W-Y_(2)O_(3).The addition of Zr enhanced the interaction between vacancies and He,enhancing the formation of He bubbles.However,the addition of Mo coarsened the Y_(2)O_(3)particles,reducing the suppression of vacancy cluster formation due to the dispersion of Y_(2)O_(3)particles.It is,therefore,necessary to fully consider mechanical properties and T-retention in addition to the irradiation resistance of He to select an alloy as the plasma-facing material for fusion applications.展开更多
To investigate the surface damage of a material by He ions,a dispersion-strengthened W-1wt%TiC alloy was irradiated by 5-keV He ions at 773 K,973 K,and 1173 K up to an ion dose of 1.8×10^(21)He m−2,respectively.N...To investigate the surface damage of a material by He ions,a dispersion-strengthened W-1wt%TiC alloy was irradiated by 5-keV He ions at 773 K,973 K,and 1173 K up to an ion dose of 1.8×10^(21)He m−2,respectively.No He bubble formation was observed under transmission electron microscopy at any temperature for He doses less than 1.5×10^(20)He m^(−2).When this dose was exceeded,He bubbles grew and void swelling increased with increasing irradiation doses.Naturally,the growth of He bubbles and the void swelling became more pronounced with increasing irradiation temperatures.Compared to the published data on commercially available pure W,the formation of He bubbles was suppressed by TiC particles in the W-TiC alloy,especially at low doses.展开更多
文摘Nucleation and growth of He bubbles at different annealing temperatures T≤1023 K in stain- less steels HR-2 and SS321,implanted with He^+(40-70 keV.1×10^(16)-6× 10^(17) He^+/cm^2),were ohserved under TEM.T=0.45T_m seems to be a transition temperature.The He bubbles continue mainly their nucleation at 0.3T_m< T<0.45T_m,and grow predominantly at T≥0.45T_m,due probably to migration and coalescence by surface diffusion of metal atoms around the bubbles.The apparent activation energies for the growth are found to he 0.41 and 0.31 eV for HR-2 and SS321 respectively.The bubble density in HR-2 is greater than that in SS321 within whole measuring temperature range,and the onset temperature of rapid swelling is also higher.It is believed that the resistance of HR-2 to He is superior to that fo SS321.
基金Supported by the National Natural Science Foundation of China under Grant No 11475229
文摘Bubble evolution in low energy and high dose He-implanted 6H-SiC upon thermal annealing is studied. The （0001）-oriented 6H-SiC wafers are implanted with 15keV helium ions at a dose of 1×10^17 cm^-2 at room temperature. The samples with post-implantation are annealed at temperatures of 1073, 1173, 1273, and 1473K for 30rain. He bubbles in the wafers are examined via cross-sectional transmission electron microscopy （XTEM） analysis. The results present that nanoscale bubbles are almost homogeneously distributed in the damaged layer of the as-implanted sample, and no significant change is observed in the He-implanted sample after 1073 K annealing. Upon 1193 K annealing, almost full recrystallization of He-implantation-induced amorphization in 6H-SiC is observed. In addition, the diameters of He bubbles increase obviously. With continually increasing temperatures to 1273K and 1473 K, the diameters of He bubbles increase and the number density of lattice defects decreases. The growth of He bubbles after high temperature annealingabides by the Ostwald ripening mechanism. The mean diameter of He bubbles located at depths of 120-135 nm as a function of annealing temperature is fitted in terms of a thermal activated process which yields an activation energy of 1.914＋0.236eV.
基金supported by the National Magnetic Con-finement Fusion Energy Research Project from the Ministry of Science and Technology of China(No.2022YFE03030004 and 2019YFE03120003)the National Natural Science Foundation of China(No.12275010,12275176,12275001,12335017,11921006,U21B2082,U22B2064 and U20B2025)+3 种基金the Beijing Municipal Natural Science Foundation(No.1222023)the Shenzhen Science and Technology Program(No.RCYX20210609103904028)Engang Fu acknowledges the support from the Science Fund or Creative Research Groups of NSFC,the Ion Beam Materials Laboratory(IBML)and Electron Microscopy Laboratory(EML)the High-performance Computing Platform(HPC)at Peking University.Xing Liu acknowledges the discussion with Prof.Ning Gao and Dr.Yifan Zhang.
文摘This study reports the response of helium(He)ion irradiation on binary-phase structured alloy V_(34)Ti_(25)Cr_(10)Ni_(30)Pd1.The alloy consists of a VCr matrix with nano-sized TiNi precipitates and a B2 TiNi matrix with nano-sized VCr precipitates.VCr is chemical-disordered and TiNi has a B2-ordered structure.The alloy was subjected to 400 keV He ion irradiation with a fluence of 1×10^(17)ions cm^(−2)at 450℃.The results show He bubbles within the chemical-disordered VCr matrix exhibit a near-spherical shape with a smaller size and higher density compared to that in chemical-ordered TiNi phase with a larger size,lower density,and faceted shape.This indicates the chemical-disordered VCr phase effectively suppresses He accumulation compared to the B2-ordered TiNi phase,emphasizing the dominance of chemical struc-tures in He bubble formation.The calculation of density functional theory(DFT)shows that Ti and Ni have lower vacancy formation energy than that of V and Cr,respectively,which results in the increased vacancy production in TiNi.Consequently,He bubbles in TiNi have a larger bubble size consistent with experimental observations of radiation-induced Ni segregation.These findings elucidate the roles of or-dered and disordered chemical structures in He bubble evolution,offering insights for the development of gas ion irradiation-resistant materials.
基金supported by the National Natural Science Foun-dation of China(No.U1967211)the National Science Fund for Distinguished Young Scholars of China(No.12225506).
文摘The He production rate(i.e.,He/dpa)in nuclear reactors strongly affects the degradation of material prop-erties.This is an important but not yet fully understood issue.Here,the effect of He/dpa on bubble char-acteristics in Fe9Cr1.5W0.4Si ferrite-martensitic(F/M)steel was in situ studied during 400 keV Fe^(+)and 30 keV He^(+)dual-beam irradiation at 723 K with three ratios of 100,500,and 2500 appm He/dpa and subsequent stepwise annealing using transmission electron microscopy(TEM).He/dpa strongly affected the bubble characteristics.During irradiation,the higher the He/dpa,the smaller the size of irradiated bubbles,but the higher their density.However,He/dpa didn’t affect the final saturation size of irradiated bubbles for all three cases,which was-2.2 nm.During annealing,high He/dpa caused large,immobile,dense polyhedral bubbles with a wider bubble size distribution,while low He/dpa caused small,low-mobility,and relatively low-density spherical bubbles.It was found that the higher the He/dpa ratio,the greater the swelling during irradiation and annealing,and annealing further enhanced the swelling.Moreover,the tunnel structure was first found in body-centered cubic(BCC)F/M steel during in-situ irra-diation.The current work provides valuable and potential insights for further understanding the He/dpa effects in materials serving in different nuclear reactors.
基金The study is financially supported by JSPS KAKENHI(Grant No.JP20K03900).
文摘To improve the mechanical properties of the Y_(2)O_(3)-added W alloy,Mo and Zr were independently added to a sample of W-Y_(2)O_(3).In this study,the effects of minor additions of elemental Mo and Zr on He bubble formation in the Y_(2)O_(3)added W alloys were investigated at 773 K,973 K,and 1173 K,where the maximum irradiation fluence of the samples using 5 keV He ions was 1.8×10^(21) He m^(−2).He bubbles were observed at all temperatures for both alloys;however,the irradiation fluences at which He bubbles could be observed differed at each temperature.With increase in irradiation temperature,the He irradiation fluence for which the formation of He bubbles could be observed decreased.At the relatively low temperature of 773 K,the void swelling in the W-Mo-Y_(2)O_(3)and W-Zr-Y_(2)O_(3)alloys was slightly lower than that of W-Y_(2)O_(3)alloy.However,at high temperature of 973 K and 1173 K,the He irradiation resistances of both W-Mo-Y_(2)O_(3)and W-Zr-Y_(2)O_(3)were worse than that of W-Y_(2)O_(3).The addition of Zr enhanced the interaction between vacancies and He,enhancing the formation of He bubbles.However,the addition of Mo coarsened the Y_(2)O_(3)particles,reducing the suppression of vacancy cluster formation due to the dispersion of Y_(2)O_(3)particles.It is,therefore,necessary to fully consider mechanical properties and T-retention in addition to the irradiation resistance of He to select an alloy as the plasma-facing material for fusion applications.
基金the auspices of the NIFS Collaboration Research Program(Grant No.NIFS17KLPF055).
文摘To investigate the surface damage of a material by He ions,a dispersion-strengthened W-1wt%TiC alloy was irradiated by 5-keV He ions at 773 K,973 K,and 1173 K up to an ion dose of 1.8×10^(21)He m−2,respectively.No He bubble formation was observed under transmission electron microscopy at any temperature for He doses less than 1.5×10^(20)He m^(−2).When this dose was exceeded,He bubbles grew and void swelling increased with increasing irradiation doses.Naturally,the growth of He bubbles and the void swelling became more pronounced with increasing irradiation temperatures.Compared to the published data on commercially available pure W,the formation of He bubbles was suppressed by TiC particles in the W-TiC alloy,especially at low doses.
