Sr-substituted ABO_3 perovskite oxides such as La_(0.6) Sr_(0.4 )Mn_(O3-δ)(LSM) and La_(0.6) Sr_(0.4) FeO_(3-δ)(LSF) are widely used as oxygen electrode materials in solid oxide cells. The substituted Sr is not adeq...Sr-substituted ABO_3 perovskite oxides such as La_(0.6) Sr_(0.4 )Mn_(O3-δ)(LSM) and La_(0.6) Sr_(0.4) FeO_(3-δ)(LSF) are widely used as oxygen electrode materials in solid oxide cells. The substituted Sr is not adequately stable under the operating conditions, because of the surface segregation of Sr. Herein, we focused on investigating the relationship between the local geometric structure due to Sr substitution and stability of LSM and LSF. We characterized the local geometric structure of Sr atoms via X-ray absorption spectroscopy. A greater Debye-Waller factor and a longer bond length of both the second and third Sr-O shells were observed in LSF, which demonstrates that LSF has a higher local structural disorder and that Sr in LSF requires less energy to segregate. After 20 h of heat treatment in the presence of a Fe-Cr alloy interconnect, the Sr/La molar ratio on LSF was observed to be much larger than that on LSM. This result unequivocally suggests that Sr in LSF is not as stable as in LSM, and the reaction between Sr and Cr accelerates the Sr surface segregation in LSF.展开更多
The oxidation behavior of a nickel-based superalloy at 1000°C in air was investigated through X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy analysis. A series of oxides, incl...The oxidation behavior of a nickel-based superalloy at 1000°C in air was investigated through X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy analysis. A series of oxides, including external oxide scales（Cr_2O_3,（TiO_2 ＋ Mn Cr_2O_4）） and internal oxides（Al_2O_3,Ti N）, were formed on the surface or sub-surface of the substrate at 1000°C in experimental still air. The oxidation resistance of the alloy was dependent on the stability of the surface oxide layer. The continuity and density of the protective Cr_2O_3 scale were affected by minor alloying elements such as Ti and Mn. The outermost oxide scale was composed of TiO_2 rutile and Mn Cr_2O_4 spinel, and the growth of TiO_2 particles was controlled by the outer diffusion of Ti ions through the pre-existing oxide layer. Severe internal oxidation occurred beneath the external oxide scale, consuming Al and Ti of the strength phase γ′（Ni_3（Al,Ti）） and thereby severely deteriorating the surface mechanical properties. The depth of the internal oxidation region was approximately 35 μm after exposure to experimental air at 1000°C for 80 h.展开更多
The atom-economical C-F insertion chemistry is emerged as a promising technology for the synthesis of various fluorinated scaffolds,which have wide applications both in the academic and the industrial com-munities.The...The atom-economical C-F insertion chemistry is emerged as a promising technology for the synthesis of various fluorinated scaffolds,which have wide applications both in the academic and the industrial com-munities.The past three years have witnessed rapid developments in this field.This highlight provides an overview on the evolution according to the fluorinating agents used.展开更多
The effect of sulphide(Na2S)concentration(SC)on the corrosion and cavitation erosion behaviours of a cast nickel aluminium bronze(NAB)in 3.5% NaCl solution is investigated in this study.The results show that when the ...The effect of sulphide(Na2S)concentration(SC)on the corrosion and cavitation erosion behaviours of a cast nickel aluminium bronze(NAB)in 3.5% NaCl solution is investigated in this study.The results show that when the SC exceeds 50 ppm,the hydrogen evolution reaction dominates the cathodic process,and a limiting current region appears in the anodic branch of the polarisation curve due to the formation of a copper sulphide film,which is a diffusion-controlled process.After longterm immersion,the increased mass loss rate of NAB with the sulphide additions of 20 and 50 ppm is attributed to the less protective films,which contains a mixture of copper oxides and sulphides.Moreover,NAB undergoes severe localised corrosion(selective phase corrosion,SPC)at the β’phases and eutectoid microstructureα+κⅢ.By comparison,NAB undergoes general corrosion and a copper sulphide film is formed in 100 and 200 ppm sulphide solutions.Cavitation erosion greatly increases the corrosion rate of NAB in all solutions and causes a negative potential shift in 3.5%NaCl solution due to the film destruction.However,a positive potential shift occurs in the solutions with SC higher than 50 ppm due to the accelerated mass transfer of the cathodic process.The cavitation erosion mass loss rate of NAB increases with the increase of SC.The occurrence of severe SPC decreases the phase boundary cohesion and causes brittle fracture under the cavitation impact.The corrosion-enhanced erosion is the most predominant factor for the cavitation erosion damage when the SC exceeds 50 ppm.展开更多
Accelerator-based ion-beam irradiation has been widely used to mimic the effects of neutron radiation damage in nuclear reactors.However,ion radiation is most often monodisperse in the incoming ions’momentum directio...Accelerator-based ion-beam irradiation has been widely used to mimic the effects of neutron radiation damage in nuclear reactors.However,ion radiation is most often monodisperse in the incoming ions’momentum direction,leading to excessive polarization in defect distribution,while the scattering under neutron irradiation is often more isotropic and has less radiation-induced polarization.Mitigation of the excess-polarization as well as the damage non-uniformity artifact might be crucial for making the simulation of neutron radiation by ion-beam radiation more realistic.In this work,a general radiation polarization theory in treating radiation as external polar stimuli is established to understand the natural material responses in different contexts,and the possibility to correct the defect polarization artifact in ion-beam irradiation.Inspired by Magic Angle Spinning in Nuclear Magnetic Resonance,we present a precise sample spinning strategy to reduce the point-defect imbalance effect in ion-beam irradiation.It can be seen that with optimized surface inclination angle and the axis of sample rotation,the vacancy-interstitial population imbalance,as well as the damage profile non-uniformity in a designated region in the target are both reduced.It is estimated that sample spinning frequency on the order of kHz should be sufficient to scramble the ion momentum monodispersity for commonly taken ion fluxes and dose rates,which is experimentally feasible.展开更多
基金supported by the ‘‘The Strategic Priority Research Program’’ of the Chinese Academy of Sciences(No.XDA02040601)the Key Project of Science and Technology of Shanghai(No.15DZ1200100)
文摘Sr-substituted ABO_3 perovskite oxides such as La_(0.6) Sr_(0.4 )Mn_(O3-δ)(LSM) and La_(0.6) Sr_(0.4) FeO_(3-δ)(LSF) are widely used as oxygen electrode materials in solid oxide cells. The substituted Sr is not adequately stable under the operating conditions, because of the surface segregation of Sr. Herein, we focused on investigating the relationship between the local geometric structure due to Sr substitution and stability of LSM and LSF. We characterized the local geometric structure of Sr atoms via X-ray absorption spectroscopy. A greater Debye-Waller factor and a longer bond length of both the second and third Sr-O shells were observed in LSF, which demonstrates that LSF has a higher local structural disorder and that Sr in LSF requires less energy to segregate. After 20 h of heat treatment in the presence of a Fe-Cr alloy interconnect, the Sr/La molar ratio on LSF was observed to be much larger than that on LSM. This result unequivocally suggests that Sr in LSF is not as stable as in LSM, and the reaction between Sr and Cr accelerates the Sr surface segregation in LSF.
基金financial support of Science and Technology Program of Jiangsu Province (Nos. BE2015144 and BE2015145)
文摘The oxidation behavior of a nickel-based superalloy at 1000°C in air was investigated through X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy analysis. A series of oxides, including external oxide scales（Cr_2O_3,（TiO_2 ＋ Mn Cr_2O_4）） and internal oxides（Al_2O_3,Ti N）, were formed on the surface or sub-surface of the substrate at 1000°C in experimental still air. The oxidation resistance of the alloy was dependent on the stability of the surface oxide layer. The continuity and density of the protective Cr_2O_3 scale were affected by minor alloying elements such as Ti and Mn. The outermost oxide scale was composed of TiO_2 rutile and Mn Cr_2O_4 spinel, and the growth of TiO_2 particles was controlled by the outer diffusion of Ti ions through the pre-existing oxide layer. Severe internal oxidation occurred beneath the external oxide scale, consuming Al and Ti of the strength phase γ′（Ni_3（Al,Ti）） and thereby severely deteriorating the surface mechanical properties. The depth of the internal oxidation region was approximately 35 μm after exposure to experimental air at 1000°C for 80 h.
基金The Tertiary Education Scientific Research Project of Guangzhou Municipal Education Bureau(No.202235305)is gratefully acnowledged for financial support.
文摘The atom-economical C-F insertion chemistry is emerged as a promising technology for the synthesis of various fluorinated scaffolds,which have wide applications both in the academic and the industrial com-munities.The past three years have witnessed rapid developments in this field.This highlight provides an overview on the evolution according to the fluorinating agents used.
基金financially supported by the National Natural Science Foundation of China (Nos.51601058 and 51879089)the Fundamental Research Funds for the Central Universities of P.R.China (No.2018B59614)+1 种基金the Natural Science Foundation of Jiangsu Province (BK20191161),the Changzhou Sci & Tech Program (Grant No.CJ20180045)the first group of 2011 plan of China’s Jiangsu province (Grant No.[2013] 56) (Cooperative Innovational Center for Coastal Development & Protection)
文摘The effect of sulphide(Na2S)concentration(SC)on the corrosion and cavitation erosion behaviours of a cast nickel aluminium bronze(NAB)in 3.5% NaCl solution is investigated in this study.The results show that when the SC exceeds 50 ppm,the hydrogen evolution reaction dominates the cathodic process,and a limiting current region appears in the anodic branch of the polarisation curve due to the formation of a copper sulphide film,which is a diffusion-controlled process.After longterm immersion,the increased mass loss rate of NAB with the sulphide additions of 20 and 50 ppm is attributed to the less protective films,which contains a mixture of copper oxides and sulphides.Moreover,NAB undergoes severe localised corrosion(selective phase corrosion,SPC)at the β’phases and eutectoid microstructureα+κⅢ.By comparison,NAB undergoes general corrosion and a copper sulphide film is formed in 100 and 200 ppm sulphide solutions.Cavitation erosion greatly increases the corrosion rate of NAB in all solutions and causes a negative potential shift in 3.5%NaCl solution due to the film destruction.However,a positive potential shift occurs in the solutions with SC higher than 50 ppm due to the accelerated mass transfer of the cathodic process.The cavitation erosion mass loss rate of NAB increases with the increase of SC.The occurrence of severe SPC decreases the phase boundary cohesion and causes brittle fracture under the cavitation impact.The corrosion-enhanced erosion is the most predominant factor for the cavitation erosion damage when the SC exceeds 50 ppm.
基金C.R.,P.H.,and Z.Z.acknowledge the support from the Strategic Priority Research Program of the Chinese Academy of Sciences under grant no.XDA02040100C.R.acknowledges the support from the scholarship from China Scholarship Council.J.L.acknowledges support from the US DOE Office of Nuclear Energy’s NEUP Program under grant no.DE-NE0008827+1 种基金Y.L.acknowledges the National Natural Science Foundation of China under grant nos.11975018 and 11775254the National Magnetic Confinement Fusion Energy Research Project under grant no.2018YEF0308100。
文摘Accelerator-based ion-beam irradiation has been widely used to mimic the effects of neutron radiation damage in nuclear reactors.However,ion radiation is most often monodisperse in the incoming ions’momentum direction,leading to excessive polarization in defect distribution,while the scattering under neutron irradiation is often more isotropic and has less radiation-induced polarization.Mitigation of the excess-polarization as well as the damage non-uniformity artifact might be crucial for making the simulation of neutron radiation by ion-beam radiation more realistic.In this work,a general radiation polarization theory in treating radiation as external polar stimuli is established to understand the natural material responses in different contexts,and the possibility to correct the defect polarization artifact in ion-beam irradiation.Inspired by Magic Angle Spinning in Nuclear Magnetic Resonance,we present a precise sample spinning strategy to reduce the point-defect imbalance effect in ion-beam irradiation.It can be seen that with optimized surface inclination angle and the axis of sample rotation,the vacancy-interstitial population imbalance,as well as the damage profile non-uniformity in a designated region in the target are both reduced.It is estimated that sample spinning frequency on the order of kHz should be sufficient to scramble the ion momentum monodispersity for commonly taken ion fluxes and dose rates,which is experimentally feasible.
