The long-period-stacking-ordered(LPSO)structure affects the mechanical,corrosion and hydrolysis properties of Mg alloys.The current work employs high angle annular dark field-scanning transmission electron microscopy(...The long-period-stacking-ordered(LPSO)structure affects the mechanical,corrosion and hydrolysis properties of Mg alloys.The current work employs high angle annular dark field-scanning transmission electron microscopy(HAADF-STEM)and atom probe tomography(APT)to investigate the structural and local chemical information of LPSO phases formed in Mg-Ni-Y/Sm ternary alloys after extended isothermal annealing.Depending on the alloying elements and their concentrations,Mg-Ni-Y/Sm develops a two-phase LPSO+α-Mg structure in which the LPSO phase contains defects,hybrid LPSO structure,and Mg insertions.HAADF-STEM and APT indicate non-stoichiometric LPSO with incomplete Ni_(6)(Y/Sm)_(8) clusters.In addition,the APT quantitatively determines the local composition of LPSO and confirms the presence of Ni within the Mg bonding layers.These results provide insight into a better understanding of the structure and hydrolysis properties of LPSO-Mg alloys.展开更多
Aluminum-based alloys play a key role in modern engineering and are widely used in construction components in aircraft, automobiles and other means of transportation due to their light weight and superior mechanical p...Aluminum-based alloys play a key role in modern engineering and are widely used in construction components in aircraft, automobiles and other means of transportation due to their light weight and superior mechanical properties. Introduction of different nano-structure features can improve the service and the physical properties of such alloys. An improvement of an Al-based alloy has been performed based on the understanding of the relationships among compositions, processing, microstructural characteristics and properties. Knowledge of the decomposition process of the microstructure during the precipitation reaction is particularly important for future technical developments. The objective of this study is to investigate the nano-scale chemical composition in the Al-Cu, Al-Li and Al-Li-Cu alloys during the early stage of the precipitation sequence and to describe whether this compositional difference correlates with variations in the observed precipitation kinetics. Investigation of the fine scale segregation effects of dilute solutes in aluminum alloys which were experienced different heat treatments by using atom probe tomography has been achieved. The results show that an Al-1.7 at.% Cu alloy requires a long ageing time of approximately 8 h at 160°C to allow the diffusion of Cu atoms into Al matrix. For the Al-8.2 at.% Li alloy, a combination of both the natural ageing condition (48 h at room temperature) and a short artificial ageing condition (5 min at 160°C) induces increasing on the number density of the Li clusters and hence increase number of precipitated particles. Applying this combination of natural ageing and short artificial ageing conditions onto the ternary Al-4 at.% Li-1.7 at.% Cu alloy induces the formation of a Cu-rich phase. Increasing the Li content in the ternary alloy up to 8 at.% and increasing the ageing time to 30 min resulted in the precipitation processes ending with δ' particles. Thus the results contribute to the understanding of Al-alloy design.展开更多
Mssbauer spectrum and three dimensional atom probes（3DAP） were combined to investigate the mechanism of cementite dissolution in a cold-drawn eutectoid steel at a true strain of 2.89.The experimental results suggest...Mssbauer spectrum and three dimensional atom probes（3DAP） were combined to investigate the mechanism of cementite dissolution in a cold-drawn eutectoid steel at a true strain of 2.89.The experimental results suggest that the dislocations play an important role in the dissolution of the cementite by sweeping across the nano-scaled cementite,and transferring carbon from cementite to ferrite inducing cementite decomposition.The mechanism of cementite dissolution in the steel is discussed in association with the investigation of nonstoichiometric cementite structure after heavy deformation.展开更多
Granulitic lunar meteorites offer rare insights into the timing and nature of igneous,metamorphic and impact processes in the lunar crust.Accurately dating the different events recorded by these materials is very chal...Granulitic lunar meteorites offer rare insights into the timing and nature of igneous,metamorphic and impact processes in the lunar crust.Accurately dating the different events recorded by these materials is very challenging,however,due to low trace element abundances (e.g.Sm,Nd,Lu,Hf),rare micrometerscale U-Th-bearing accessory minerals,and disturbed Ar-Ar systematics following a multi-stage history of shock and thermal metamorphism.Here we report on micro-baddeleyite grains in granulitic mafic breccia NWA 3163 for the first time and show that targeted microstructural analysis (electron backscatter diffraction) and nanoscale geochronology (atom probe tomography) can overcome these barriers to lunar chronology.A twinned (-90°/<401>) baddeleyite domain yields a 232Th/208Pb age of 4328 ± 309 Ma,which overlaps with a robust secondary ion mass spectrometry (SIMS) 207Pb/206Pb age of 4308± 18.6 Ma and is interpreted here as the crystallization age for the igneous protolith of NWA 3163.A second microstructural domain,< 2 mm in width,contains patchy overprinting baddeleyite and yields a Th-Pb age of 2175± 143 Ma,interpreted as dating the last substantial impact event to affect the sample.This finding demonstrates the potential of combining microstructural characterization with nanoscale geochronology when resolving complex P-T-t histories in planetary materials,here yielding the oldest measured crystallization age for components of lunar granulite NWA 3163 and placing further constraints on the formation and evolution of lunar crust.展开更多
β-Nb is a typical second phase in Zr-Nb-based alloys used as fuel claddings in water-cooled nuclear reactors. The segregation of alloying element Fe may affect the corrosion resistance of Zr-Nb-based alloys. In this ...β-Nb is a typical second phase in Zr-Nb-based alloys used as fuel claddings in water-cooled nuclear reactors. The segregation of alloying element Fe may affect the corrosion resistance of Zr-Nb-based alloys. In this work, the Fe segregation at the interface between β-Nb phase and a-Zr matrix in Zr-2.5Nb alloy was studied using atom probe tomography and focused ion beam. The results suggested that the Fe concentration was much lower than Nb concentration in a-Zr matrix, while Fe selectively segregated at the β-Nb/a-Zr phase interface, leading to a Fe concentration peak at some interfaces. The peak Fe concentration varied from 0.4 to 1.2 at.% and appeared at the position where Zr concentration was approximately equal to Nb concentration. The selective segregation of Fe should be affected by the heat treatment and structure defects induced by cold rolling.展开更多
Three-dimensional distribution of solute elements in an Mg–Zn–Gd alloy during ageing process is quantitatively characterized by three-dimensional atom probe(3DAP) tomography. Based on the radius distribution functio...Three-dimensional distribution of solute elements in an Mg–Zn–Gd alloy during ageing process is quantitatively characterized by three-dimensional atom probe(3DAP) tomography. Based on the radius distribution function, it is found that Zn–Gd solute pairs in Mg matrix appear mainly at two peaks at early stage of ageing, and the separation distance between Zn and Gd atoms could be well rationalized by the first-principle calculation. Moreover, the fraction of Zn–Gd solute pairs increases first and then decreases due to the precipitation of long-period stacking ordered(LPSO) structures. Both the composition of the structural unit in LPSO structure and the solute enrichment around it are quantified. It is found that Zn and Gd elements are synchronized in the LPSO structure, and solute segregation of pure Zn or Gd is not observed at the transformation front of the LPSO structure in this alloy. In addition, the crystallography of transformation front is further determined by 3DAP data.展开更多
We present a precise measurement of a weak radio frequency electric field with a frequency of ■3 GHz employing a resonant atomic probe that is constituted with a Rydberg cascade three-level atom, including a cesium g...We present a precise measurement of a weak radio frequency electric field with a frequency of ■3 GHz employing a resonant atomic probe that is constituted with a Rydberg cascade three-level atom, including a cesium ground state |6S(1/2)〉,an excited state |6P(3/2)〉, and Rydberg state |nD(5/2)〉. Two radio frequency(RF) electric fields, noted as local and signal fields, couple the nearby Rydberg transition. The two-photon resonant Rydberg electromagnetically induced transparency(Rydberg-EIT) is employed to directly read out the weak signal field having hundreds of k Hz difference between the local and signal fields that is encoded in the resonant microwave-dressed Rydberg atoms. The minimum detectable signal fields of ESmin= 1.36 ± 0.04 mV/m for 2.18 GHz coupling |68D(5/2)〉→ |69P(3/2)〉 transition and 1.33 ± 0.02 mV/m for 1.32 GHz coupling |80D(5/2)〉→ |81P(3/2)〉 transition are obtained, respectively. The bandwidth dependence is also investigated by varying the signal field frequency and corresponding -3 dB bandwidth of 3 MHz is attained. This method can be employed to perform a rapid and precise measurement of the weak electric field, which is important for the atom-based microwave metrology.展开更多
An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy （AFM） here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two hig...An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy （AFM） here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two high precision microtranslators. When silicon probe and carbon nanotube are very close, several tens voltage is applied between them. And carbon nanotube is divided and attached to the end of silicon probe, which mainly due to the arc welding function. Comparing with the arc discharge method before, the new method here needs no coat silicon probe with metal film in advance, which can greatly reduce the fabrication＇s difficulty. The fabricated carbon nanotube probe shows good property of higher aspect ratio and can more accurately reflect the true topography of silicon grating than silicon probe. Under the same image drive force, carbon nanotube probe had less indentation depth on soft triblock copolymer sample than silicon probe. This showed that carbon nanotube probe has lower spring constant and less damage to the scan sample than silicon probe.展开更多
We have investigated the two-dimensional （2D） atom localization via probe absorption in a coherently driven four-level atomic system by means of a radio-frequency field driving a hyperfine transition. It is found th...We have investigated the two-dimensional （2D） atom localization via probe absorption in a coherently driven four-level atomic system by means of a radio-frequency field driving a hyperfine transition. It is found that the detecting probability and precision of 2D atom localization can be significantly improved via adjusting the system parameters. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization.展开更多
In the present paper, we investigate the behavior of two-dimensional atom localization in a five-level M-scheme atomic system driven by two orthogonal standing-wave fields. We find that the precision and resolution of...In the present paper, we investigate the behavior of two-dimensional atom localization in a five-level M-scheme atomic system driven by two orthogonal standing-wave fields. We find that the precision and resolution of the atom localization depends on the probe field detuning significantly. And because of the effect of the microwave field, an atom can be located at a particular position via adjusting the system parameters.展开更多
In this paper, three different tips are employed, i.e., the carbon nanotube tip, monocrystalline silicon tip and silicon nitride tip. Resorting to atomic force microscope （AFM）, they are used for measuring the surfa...In this paper, three different tips are employed, i.e., the carbon nanotube tip, monocrystalline silicon tip and silicon nitride tip. Resorting to atomic force microscope （AFM）, they are used for measuring the surface roughness of indium tin oxide （ITO） film and the immunoglobulin G （IgG） proteins within the scanning area of 10 μm×10 μm and 0.5 μm×0.5 μm, respectively. Subsequently, the scanned surface of the ITO film and IgG proteins are analyzed by using fractal dimension. The results show that the ffactal dimension measured by carbon nanotube tip is biggest with the highest frequency components and the most microscopic information. Therefore, the carbon nanotube tip is the ideal measuring tool for measuring super-smooth surface, which will play a more and more important role in the high-resolution imaging field.展开更多
We investigate the effect of aging temperature on precipitation behavior and mechanical properties of an Al-7.6Zn-2.7Mg-2.0Cu-0.1Zr-0.07Ti(wt.%)alloy by evaluating the matrix’s microhardness,electrical resistivity,an...We investigate the effect of aging temperature on precipitation behavior and mechanical properties of an Al-7.6Zn-2.7Mg-2.0Cu-0.1Zr-0.07Ti(wt.%)alloy by evaluating the matrix’s microhardness,electrical resistivity,and tensile properties:additionally,employing X-ray diffraction(XRD),differential scanning calorimetry(DSC),transmission electron microscopy(TEM),and atom-probe tomography(APT)to charac-terize this alloy.The nanoprecipitates forming under peak-aging conditions vary with aging temperature,forming coherent GPI zones at 80℃,GPII zones with minorη’at 120-150℃,andη’/ηwith minor GP zones at 180-220℃.GPI and GPII zones forming at 80-150℃ contain similar concentrations of solute atoms(11Zn-9Mg-(<1.0)Cu(at.%)),whereas theη’/ηnanoprecipitates forming at 180℃ contain larger concentrations of solute atoms(28Zn-24Mg-3.4Cu(at.%)).The strength of the peak-aged alloy decreases with increasing aging temperature owing to the increasing size and decreasing number density of the nanoprecipitates.Under peak-aging conditions,precipitation strengthening originates mainly from dislo-cation shearing at 80-150℃ and from Orowan bypassing at temperatures above 180℃.The shearable to non-shearable transition of the nanoprecipitates at 180℃ reduces the strain hardening rate,thereby decreasing the alloy’s ductility.展开更多
Multiple precipitating species in a 2.2 GPa grade precipitation-hardened martensitic stainless steel with balanced ductility were characterized at atomic scale by atom probe tomography.The results indicated that the c...Multiple precipitating species in a 2.2 GPa grade precipitation-hardened martensitic stainless steel with balanced ductility were characterized at atomic scale by atom probe tomography.The results indicated that the clustering of solute atoms was promoted with progressive aging treatments.(Cr,Mo)-rich carbide(M_(2)C)precipitated at the linear dislocations in the as-aged steels.Obvious segregation of Cr,Mo,and C at phase boundaries favored the precipitation of carbide and caused the formation of Cr-lean domains.Spinodal decomposition of martensitic matrix during aging led to the substantial precipitation of fine Cr-rich(α′Cr)phase.Compared with the first aging treated samples,a synergistic enhancement of both strength and ductility of the secondary aging treated(SAT)samples was primarily ascribed to the enhanced precipitation of Cr-rich phase.Additionally,Ni-rich filmy reversed austenite precipitated at the lath boundary,which was beneficial to the ductility of SAT samples.展开更多
The redistribution of C and N atoms during cryogenic treatment is crucial for the microstructure evolution and properties of high nitrogen martensitic steel.Here,the distinct redistribution behavior of C and N atoms i...The redistribution of C and N atoms during cryogenic treatment is crucial for the microstructure evolution and properties of high nitrogen martensitic steel.Here,the distinct redistribution behavior of C and N atoms in a martensitic stainless steel with 0.3 wt%C and 0.5 wt%N after cryogenic treatment were investigated by the atom probe tomography.Carbon clusters begin to form after cryogenic treatment at-60℃and gradually increase with the decrease of cryogenic treatment temperature.While Mo–N and Cr–N pairs are homogeneously distributed in the matrix even after cryogenic treatment at-120℃,and then form enrichment phenomenon when the cryogenic temperature is deeply lowered to-190℃.It is found that the distinct redistributions of C and N atoms are associated with the different interaction energy between substitutional atoms and them.The stronger interaction between Cr,Mo atoms and N delays the segregation of N during the cryogenic treatment.Finally,the mechanical properties results confirmed that the deep lower cryogenic treatment is a promising method to improve the hardness and strength in the high nitrogen martensitic stainless steel.展开更多
基金the financial support provided by ANR(Project ANR-22-PEHY-0007)DGA(French Direction Générale des Armées,2018600045)Région Nouvelle Aquitaine(agreement 2018–1R10126).
文摘The long-period-stacking-ordered(LPSO)structure affects the mechanical,corrosion and hydrolysis properties of Mg alloys.The current work employs high angle annular dark field-scanning transmission electron microscopy(HAADF-STEM)and atom probe tomography(APT)to investigate the structural and local chemical information of LPSO phases formed in Mg-Ni-Y/Sm ternary alloys after extended isothermal annealing.Depending on the alloying elements and their concentrations,Mg-Ni-Y/Sm develops a two-phase LPSO+α-Mg structure in which the LPSO phase contains defects,hybrid LPSO structure,and Mg insertions.HAADF-STEM and APT indicate non-stoichiometric LPSO with incomplete Ni_(6)(Y/Sm)_(8) clusters.In addition,the APT quantitatively determines the local composition of LPSO and confirms the presence of Ni within the Mg bonding layers.These results provide insight into a better understanding of the structure and hydrolysis properties of LPSO-Mg alloys.
文摘Aluminum-based alloys play a key role in modern engineering and are widely used in construction components in aircraft, automobiles and other means of transportation due to their light weight and superior mechanical properties. Introduction of different nano-structure features can improve the service and the physical properties of such alloys. An improvement of an Al-based alloy has been performed based on the understanding of the relationships among compositions, processing, microstructural characteristics and properties. Knowledge of the decomposition process of the microstructure during the precipitation reaction is particularly important for future technical developments. The objective of this study is to investigate the nano-scale chemical composition in the Al-Cu, Al-Li and Al-Li-Cu alloys during the early stage of the precipitation sequence and to describe whether this compositional difference correlates with variations in the observed precipitation kinetics. Investigation of the fine scale segregation effects of dilute solutes in aluminum alloys which were experienced different heat treatments by using atom probe tomography has been achieved. The results show that an Al-1.7 at.% Cu alloy requires a long ageing time of approximately 8 h at 160°C to allow the diffusion of Cu atoms into Al matrix. For the Al-8.2 at.% Li alloy, a combination of both the natural ageing condition (48 h at room temperature) and a short artificial ageing condition (5 min at 160°C) induces increasing on the number density of the Li clusters and hence increase number of precipitated particles. Applying this combination of natural ageing and short artificial ageing conditions onto the ternary Al-4 at.% Li-1.7 at.% Cu alloy induces the formation of a Cu-rich phase. Increasing the Li content in the ternary alloy up to 8 at.% and increasing the ageing time to 30 min resulted in the precipitation processes ending with δ' particles. Thus the results contribute to the understanding of Al-alloy design.
基金supported by the National Natural Science Foundation of China(No.50371057)
文摘Mssbauer spectrum and three dimensional atom probes（3DAP） were combined to investigate the mechanism of cementite dissolution in a cold-drawn eutectoid steel at a true strain of 2.89.The experimental results suggest that the dislocations play an important role in the dissolution of the cementite by sweeping across the nano-scaled cementite,and transferring carbon from cementite to ferrite inducing cementite decomposition.The mechanism of cementite dissolution in the steel is discussed in association with the investigation of nonstoichiometric cementite structure after heavy deformation.
基金a postdoctoral fellowship supported by Hatch Ltd.NSERC Discovery Grants awarded to D.E.M and K.T.Tsupported by Royal Society Research Grant RG160237 awarded to J.R.D+1 种基金a Department of Museum Volunteers Acquisitions & Research Fund awarded to K.T.Tpartly supported by a grant from the Instrumentation and Facilities Program, Division of Earth Sciences, National Science Foundation
文摘Granulitic lunar meteorites offer rare insights into the timing and nature of igneous,metamorphic and impact processes in the lunar crust.Accurately dating the different events recorded by these materials is very challenging,however,due to low trace element abundances (e.g.Sm,Nd,Lu,Hf),rare micrometerscale U-Th-bearing accessory minerals,and disturbed Ar-Ar systematics following a multi-stage history of shock and thermal metamorphism.Here we report on micro-baddeleyite grains in granulitic mafic breccia NWA 3163 for the first time and show that targeted microstructural analysis (electron backscatter diffraction) and nanoscale geochronology (atom probe tomography) can overcome these barriers to lunar chronology.A twinned (-90°/<401>) baddeleyite domain yields a 232Th/208Pb age of 4328 ± 309 Ma,which overlaps with a robust secondary ion mass spectrometry (SIMS) 207Pb/206Pb age of 4308± 18.6 Ma and is interpreted here as the crystallization age for the igneous protolith of NWA 3163.A second microstructural domain,< 2 mm in width,contains patchy overprinting baddeleyite and yields a Th-Pb age of 2175± 143 Ma,interpreted as dating the last substantial impact event to affect the sample.This finding demonstrates the potential of combining microstructural characterization with nanoscale geochronology when resolving complex P-T-t histories in planetary materials,here yielding the oldest measured crystallization age for components of lunar granulite NWA 3163 and placing further constraints on the formation and evolution of lunar crust.
基金supported by the National Natural Science Foundation of China (No. 51171102)
文摘β-Nb is a typical second phase in Zr-Nb-based alloys used as fuel claddings in water-cooled nuclear reactors. The segregation of alloying element Fe may affect the corrosion resistance of Zr-Nb-based alloys. In this work, the Fe segregation at the interface between β-Nb phase and a-Zr matrix in Zr-2.5Nb alloy was studied using atom probe tomography and focused ion beam. The results suggested that the Fe concentration was much lower than Nb concentration in a-Zr matrix, while Fe selectively segregated at the β-Nb/a-Zr phase interface, leading to a Fe concentration peak at some interfaces. The peak Fe concentration varied from 0.4 to 1.2 at.% and appeared at the position where Zr concentration was approximately equal to Nb concentration. The selective segregation of Fe should be affected by the heat treatment and structure defects induced by cold rolling.
基金supported by a Grant-in-Aid for Scientific Research on Innovative Areas,‘‘Synchronized Long-Period Stacking Ordered Structure’’,from the Ministry of Education,Culture,Sports,Science and Technology,Japan(No.23109006)Fundamental Research Funds for the Central Universities(No.FRFTP-17-003A1)
文摘Three-dimensional distribution of solute elements in an Mg–Zn–Gd alloy during ageing process is quantitatively characterized by three-dimensional atom probe(3DAP) tomography. Based on the radius distribution function, it is found that Zn–Gd solute pairs in Mg matrix appear mainly at two peaks at early stage of ageing, and the separation distance between Zn and Gd atoms could be well rationalized by the first-principle calculation. Moreover, the fraction of Zn–Gd solute pairs increases first and then decreases due to the precipitation of long-period stacking ordered(LPSO) structures. Both the composition of the structural unit in LPSO structure and the solute enrichment around it are quantified. It is found that Zn and Gd elements are synchronized in the LPSO structure, and solute segregation of pure Zn or Gd is not observed at the transformation front of the LPSO structure in this alloy. In addition, the crystallography of transformation front is further determined by 3DAP data.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFA0304203)the National Natural Science Foundation of China(Grant Nos.61475090,61675123,61775124,and 11804202)+1 种基金the State Key Program of National Natural Science of China(Grant Nos.11434007 and 61835007)Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(Grant No.IRT 17R70)。
文摘We present a precise measurement of a weak radio frequency electric field with a frequency of ■3 GHz employing a resonant atomic probe that is constituted with a Rydberg cascade three-level atom, including a cesium ground state |6S(1/2)〉,an excited state |6P(3/2)〉, and Rydberg state |nD(5/2)〉. Two radio frequency(RF) electric fields, noted as local and signal fields, couple the nearby Rydberg transition. The two-photon resonant Rydberg electromagnetically induced transparency(Rydberg-EIT) is employed to directly read out the weak signal field having hundreds of k Hz difference between the local and signal fields that is encoded in the resonant microwave-dressed Rydberg atoms. The minimum detectable signal fields of ESmin= 1.36 ± 0.04 mV/m for 2.18 GHz coupling |68D(5/2)〉→ |69P(3/2)〉 transition and 1.33 ± 0.02 mV/m for 1.32 GHz coupling |80D(5/2)〉→ |81P(3/2)〉 transition are obtained, respectively. The bandwidth dependence is also investigated by varying the signal field frequency and corresponding -3 dB bandwidth of 3 MHz is attained. This method can be employed to perform a rapid and precise measurement of the weak electric field, which is important for the atom-based microwave metrology.
基金This project is supported by National Natural Science Foundation of China (No.50205006).
文摘An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy （AFM） here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two high precision microtranslators. When silicon probe and carbon nanotube are very close, several tens voltage is applied between them. And carbon nanotube is divided and attached to the end of silicon probe, which mainly due to the arc welding function. Comparing with the arc discharge method before, the new method here needs no coat silicon probe with metal film in advance, which can greatly reduce the fabrication＇s difficulty. The fabricated carbon nanotube probe shows good property of higher aspect ratio and can more accurately reflect the true topography of silicon grating than silicon probe. Under the same image drive force, carbon nanotube probe had less indentation depth on soft triblock copolymer sample than silicon probe. This showed that carbon nanotube probe has lower spring constant and less damage to the scan sample than silicon probe.
基金the National Natural Science Foundation of China(Grant No.11205001)the National Basic Research Program of China(Grant No.2010CB234607)the Postdoctoral Science Foundation of Anhui University,China
文摘We have investigated the two-dimensional （2D） atom localization via probe absorption in a coherently driven four-level atomic system by means of a radio-frequency field driving a hyperfine transition. It is found that the detecting probability and precision of 2D atom localization can be significantly improved via adjusting the system parameters. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60768001 and 10464002)
文摘In the present paper, we investigate the behavior of two-dimensional atom localization in a five-level M-scheme atomic system driven by two orthogonal standing-wave fields. We find that the precision and resolution of the atom localization depends on the probe field detuning significantly. And because of the effect of the microwave field, an atom can be located at a particular position via adjusting the system parameters.
基金National Natural Science Foundation of China(No.50605012).
文摘In this paper, three different tips are employed, i.e., the carbon nanotube tip, monocrystalline silicon tip and silicon nitride tip. Resorting to atomic force microscope （AFM）, they are used for measuring the surface roughness of indium tin oxide （ITO） film and the immunoglobulin G （IgG） proteins within the scanning area of 10 μm×10 μm and 0.5 μm×0.5 μm, respectively. Subsequently, the scanned surface of the ITO film and IgG proteins are analyzed by using fractal dimension. The results show that the ffactal dimension measured by carbon nanotube tip is biggest with the highest frequency components and the most microscopic information. Therefore, the carbon nanotube tip is the ideal measuring tool for measuring super-smooth surface, which will play a more and more important role in the high-resolution imaging field.
基金financially supported by the Industrial Strategic Technology Development Program(No.10062304)funded by the Ministry of Trade,Industry,and Energy(MOTIE,Republic of Korea)the Main Research Program(Nos.PNK8370&PNK8650)funded by the Korea Institute of Materials Science(KIMS,Republic of Korea)+6 种基金a National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(No.RS-2023-00217415)performed at the Northwestern University Center for Atom-Probe Tomography(NUCAPT)The LEAP tomo-graph at NUCAPT was purchased and upgraded with grants from the NSF-MRI(No.DMR-0420532)ONRDURIP(Nos.N00014-0400798,N00014-0610539,N00014-0910781,N00014-1712870)programssupport from the MRSEC program(No.NSF DMR-1720139)the Materials Research Center,SHyNE Re-source(No.NSF ECCS-1542205)the Initiative for Sustainability and Energy(ISEN)at Northwestern University.We thank the Cen-ter for University-wide Research Facilities(CURF)at Jeonbuk Na-tional University and Institute of Next-generation Semiconductor convergence Technology(INST)at DGIST for their assistance with the experiments.We also thank Prof.Dieter Isheim and Dr.Amir Farkoosh for their helpful discussions concerning APT analyses.
文摘We investigate the effect of aging temperature on precipitation behavior and mechanical properties of an Al-7.6Zn-2.7Mg-2.0Cu-0.1Zr-0.07Ti(wt.%)alloy by evaluating the matrix’s microhardness,electrical resistivity,and tensile properties:additionally,employing X-ray diffraction(XRD),differential scanning calorimetry(DSC),transmission electron microscopy(TEM),and atom-probe tomography(APT)to charac-terize this alloy.The nanoprecipitates forming under peak-aging conditions vary with aging temperature,forming coherent GPI zones at 80℃,GPII zones with minorη’at 120-150℃,andη’/ηwith minor GP zones at 180-220℃.GPI and GPII zones forming at 80-150℃ contain similar concentrations of solute atoms(11Zn-9Mg-(<1.0)Cu(at.%)),whereas theη’/ηnanoprecipitates forming at 180℃ contain larger concentrations of solute atoms(28Zn-24Mg-3.4Cu(at.%)).The strength of the peak-aged alloy decreases with increasing aging temperature owing to the increasing size and decreasing number density of the nanoprecipitates.Under peak-aging conditions,precipitation strengthening originates mainly from dislo-cation shearing at 80-150℃ and from Orowan bypassing at temperatures above 180℃.The shearable to non-shearable transition of the nanoprecipitates at 180℃ reduces the strain hardening rate,thereby decreasing the alloy’s ductility.
基金This work was financially supported by the National“13th Five-year Plan”high-tech Research and Development Program of China(YE-17T60270B).
文摘Multiple precipitating species in a 2.2 GPa grade precipitation-hardened martensitic stainless steel with balanced ductility were characterized at atomic scale by atom probe tomography.The results indicated that the clustering of solute atoms was promoted with progressive aging treatments.(Cr,Mo)-rich carbide(M_(2)C)precipitated at the linear dislocations in the as-aged steels.Obvious segregation of Cr,Mo,and C at phase boundaries favored the precipitation of carbide and caused the formation of Cr-lean domains.Spinodal decomposition of martensitic matrix during aging led to the substantial precipitation of fine Cr-rich(α′Cr)phase.Compared with the first aging treated samples,a synergistic enhancement of both strength and ductility of the secondary aging treated(SAT)samples was primarily ascribed to the enhanced precipitation of Cr-rich phase.Additionally,Ni-rich filmy reversed austenite precipitated at the lath boundary,which was beneficial to the ductility of SAT samples.
基金supported by the National Natural Science Foundation of China(No.51871212)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDC04000000)+1 种基金the Major Scientific and Technological Projects of Jiangxi Province(No.20194ABC28011)the Project to Strengthen Industrial Development at the Grass-roots Level(TC190A4DA/35)。
文摘The redistribution of C and N atoms during cryogenic treatment is crucial for the microstructure evolution and properties of high nitrogen martensitic steel.Here,the distinct redistribution behavior of C and N atoms in a martensitic stainless steel with 0.3 wt%C and 0.5 wt%N after cryogenic treatment were investigated by the atom probe tomography.Carbon clusters begin to form after cryogenic treatment at-60℃and gradually increase with the decrease of cryogenic treatment temperature.While Mo–N and Cr–N pairs are homogeneously distributed in the matrix even after cryogenic treatment at-120℃,and then form enrichment phenomenon when the cryogenic temperature is deeply lowered to-190℃.It is found that the distinct redistributions of C and N atoms are associated with the different interaction energy between substitutional atoms and them.The stronger interaction between Cr,Mo atoms and N delays the segregation of N during the cryogenic treatment.Finally,the mechanical properties results confirmed that the deep lower cryogenic treatment is a promising method to improve the hardness and strength in the high nitrogen martensitic stainless steel.
