Nanostructure photodetectors,as the core component of optoelectronic devices,are mainly focused on the precise preparation of mixed-component nano-heterostructures and the realization of zero power consumption devices...Nanostructure photodetectors,as the core component of optoelectronic devices,are mainly focused on the precise preparation of mixed-component nano-heterostructures and the realization of zero power consumption devices.Herein,we successfully fabricated n-GaN/p-ZnTe core/shell nanopillar array and realized self-power ultraviolet/violet photodetection.The radial heterojunction nanodevice reveals high light-dark current ratio of 104 at 0 V bias,indicating effective carriers’separation.And more,by integrating plasmonic effect,the responsivity and detectivity of the Au nanoparticles decorated device are increased from 3.85 to 148.83 mA/W and 4.45×1011 to 2.33×1012 Jones under 325 nm UV light irradiation.While the rise and the fall time are decreased 1.3 times and 6.8 times under 520 nm visible light irradiation at 0 V bias.The high photocurrent gain is derived from that the oscillating high-energy hot electrons in Au nanoparticles spontaneously inject into the ZnTe conduction band to involve the photodetection process.This work presents an effective route to prepare high-performance self-power photodetector and provides a promising blueprint to realize different functional photoelectronic devices based on core/shell nanostructure.展开更多
Thanks to its excellent high-temperature performance and moderate density,Ti_(2) AlNb-based alloy is con-sidered to be a new generation of high-temperature structural material in the aerospace field.However,its applic...Thanks to its excellent high-temperature performance and moderate density,Ti_(2) AlNb-based alloy is con-sidered to be a new generation of high-temperature structural material in the aerospace field.However,its application is restricted currently due to the limitations of traditional processing methods.Recently,our group first successfully prepared this alloy with an unconventional approach named wire-based in-situ additive manufacturing(AM)technology,and great mechanical performance has been obtained.The unbalanced thermal process of AM easily causes inconsistent or undesired microstructures,as well as mechanical properties.Therefore,in this study,we further carried out post-heat treatment research on the as-printed sample so as to optimize its mechanical performance.Results show that theα2-phase will precipitate from the as-deposited samples(B2/β+O)after solution treatment(ST),while all precipitates were dissolved to the B2/β-matrix when the solution temperature was 1100℃.The aging treatment(AT)promoted a great number of O-phases precipitated and led to an increase in its proportion.With the increase in aging temperature,the tensile strength decreased(995 to 821 MPa)gradually coupling the increase of fracture strain(1.65%to 2.12%),while the aging duration time did not show an obvious ef-fect on its performance.In addition,after proper heat treatment,the high temperature(650℃)tensile strength of the samples was as high as 818 and 792 MPa.This research not only promotes the develop-ment of Ti_(2) AlNb-based alloy fabricated through in-situ AM,but also facilitates its further application in the aerospace field.展开更多
For the first time,this work comprehensively studied the effectiveness of precipitation hardening achieved by aging treatment in improving the tensile superelasticity of NiTi alloys fabricated by elec-tron beam wire-f...For the first time,this work comprehensively studied the effectiveness of precipitation hardening achieved by aging treatment in improving the tensile superelasticity of NiTi alloys fabricated by elec-tron beam wire-feed additive manufacturing(EBAM),which possesses inherent advantages in producing dense and oxidation-free structures.Aging treatments under three temperatures(450,350,and 250℃)and different durations were conducted,and the resultant performance of tensile superelasticity,together with the corresponding evolution of precipitation and phase transformation behavior were investigated for the EBAM-fabricated NiTi alloys.Results showed that by appropriate aging treatment,EBAM fabricated NiTi alloys could achieve excellent recovery rates of approximately 95%and 90%after the 1st and 10th load/unload cycle for a maximum tensile strain of 6%,which were almost the highest achieved so far by AM processed NiTi alloys and close to those of some conventional NiTi alloys.The improvement of tensile superelasticity benefited from the fine and dispersive Ni4Ti3 precipitates,which could be introduced by aging at 350℃ for 4 h or at 250℃ for 200 h.Moreover,the large amount of Ni4Ti3 precipitates would promote the intermediate R-phase transformation and bring a two-stage or three-stage transformation sequence,which depended on whether the distribution of the precipitation was homogeneous or not.This work could provide guidance for the production of NiTi alloys with good tensile superelasticity by EBAM or other additive manufacturing processes.展开更多
Three ice cores recovered from the Himalayas (i.e. the East Rongbuk Glacier and the Far East Rongbuk Glacier at Mt. Qomolangma (Everest), and the Dasuopu Glacier at Xixiabangma) show a sharp decline in the accumulatio...Three ice cores recovered from the Himalayas (i.e. the East Rongbuk Glacier and the Far East Rongbuk Glacier at Mt. Qomolangma (Everest), and the Dasuopu Glacier at Xixiabangma) show a sharp decline in the accumulation rates since the 1950s, which is consistent with the precipitation fluctuation over India and the low northern latitude zone (5°-35癗). Correspondingly, an increasing trend is observed for the ice core accumulations from the central and northern Qinghai-Tibetan Plateau (i.e. the Xiao Dongkemadi Glacier in the central Tanggula Mountains, the Guliya Ice Cap in the western Kunlun Mountains, and the Dunde Ice Cap in the Qilian Mountains) since the 1950s, which is consistent with the precipitation fluctuation over the middle-high northern latitude zone (35°-70°N). However, the variation magnitude of the high-elevation ice core accumulations is more significant than that of precipitation at the low-eleva- tion places, suggesting its extra sensitivity of high-elevation areas to climatic change.展开更多
For the first time we investigate the basal thermal condition in the upper area of Jima Yangzong Glacier, the headstream of Yarlung Zangbo River, using ground-penetrating radar techniques. With common offset and commo...For the first time we investigate the basal thermal condition in the upper area of Jima Yangzong Glacier, the headstream of Yarlung Zangbo River, using ground-penetrating radar techniques. With common offset and common mid-point surveys we analyze the radar velocities in ice with respect to cold-temperate ice transition surface(0.1751 ± 0.0028 m ns^(-1)) and ice-bedrock interface(0.1657 ± 0.0033 m ns^(-1)), indicating a radar velocity of 0.1410 ± 0.0154 m ns^(-1) for the temperate ice layer(16.6 ± 1.8 m). We estimate that the temperate ice layer has a water content of around 6 % ± 4 %, suggesting that the Jima Yangzong Glacier, previously known as continental-type, now possibly becomes polythermal.展开更多
Directed energy deposition has been used to repair superalloy components in aero engines and gas turbines.However,the microstructure and properties are generally inhomogeneous in components because of the different pr...Directed energy deposition has been used to repair superalloy components in aero engines and gas turbines.However,the microstructure and properties are generally inhomogeneous in components because of the different processing histories.Here,the microstructures and wear behavior of different zones(substrate,HAZ,and deposit)are investigated for the IC10 directionally solidified superalloy repaired by the directed energy deposition process.It is found that the microstructure of the deposited layers is strongly textured with a<001>-fiber texture in the building direction,and the texture intensity is continuously increased along the building direction.Two kinds ofγ’phase(primary and secondaryγ’phase)can be found in the heat-affected zone(HAZ),and the average size of primaryγ’phase is smaller than that in the substrate due to liquation.In the deposit layers,the size ofγ’phase is much smaller than those in the substrate and the primaryγ’phase of HAZ;both size and the fraction of theγ’phase decreases with the increase of building height.The wear rate of the substrate is the smallest,indicating the best wear resistance;while the wear rate of HAZ is the largest,indicating the worst wear resistance in the repaired sample.The wear rates in the deposit layers increase from the bottom to the top zones,showing a decreasing wear resistance.Abrasive wear is found to be the dominant wear mechanism of the repaired alloy,and the resistance to which is closely related to the fraction ofγ’phase in the microstructure.The understanding of the influence of microstructure on wear resistance allows for a more informed application of inhomogeneous superalloy components repaired by directed energy deposition in industry.展开更多
基金the National Natural Science Foundation of China(Nos.62075041,62375049,and 62335003)the Basic Research Program of Jiangsu Province(No.BK20222007).
文摘Nanostructure photodetectors,as the core component of optoelectronic devices,are mainly focused on the precise preparation of mixed-component nano-heterostructures and the realization of zero power consumption devices.Herein,we successfully fabricated n-GaN/p-ZnTe core/shell nanopillar array and realized self-power ultraviolet/violet photodetection.The radial heterojunction nanodevice reveals high light-dark current ratio of 104 at 0 V bias,indicating effective carriers’separation.And more,by integrating plasmonic effect,the responsivity and detectivity of the Au nanoparticles decorated device are increased from 3.85 to 148.83 mA/W and 4.45×1011 to 2.33×1012 Jones under 325 nm UV light irradiation.While the rise and the fall time are decreased 1.3 times and 6.8 times under 520 nm visible light irradiation at 0 V bias.The high photocurrent gain is derived from that the oscillating high-energy hot electrons in Au nanoparticles spontaneously inject into the ZnTe conduction band to involve the photodetection process.This work presents an effective route to prepare high-performance self-power photodetector and provides a promising blueprint to realize different functional photoelectronic devices based on core/shell nanostructure.
基金financially supported by the National Natural Sci-ence Foundation of China(No.51875309)the Beijing Municipal Natural Science Foundation(CN)(No.3222008).
文摘Thanks to its excellent high-temperature performance and moderate density,Ti_(2) AlNb-based alloy is con-sidered to be a new generation of high-temperature structural material in the aerospace field.However,its application is restricted currently due to the limitations of traditional processing methods.Recently,our group first successfully prepared this alloy with an unconventional approach named wire-based in-situ additive manufacturing(AM)technology,and great mechanical performance has been obtained.The unbalanced thermal process of AM easily causes inconsistent or undesired microstructures,as well as mechanical properties.Therefore,in this study,we further carried out post-heat treatment research on the as-printed sample so as to optimize its mechanical performance.Results show that theα2-phase will precipitate from the as-deposited samples(B2/β+O)after solution treatment(ST),while all precipitates were dissolved to the B2/β-matrix when the solution temperature was 1100℃.The aging treatment(AT)promoted a great number of O-phases precipitated and led to an increase in its proportion.With the increase in aging temperature,the tensile strength decreased(995 to 821 MPa)gradually coupling the increase of fracture strain(1.65%to 2.12%),while the aging duration time did not show an obvious ef-fect on its performance.In addition,after proper heat treatment,the high temperature(650℃)tensile strength of the samples was as high as 818 and 792 MPa.This research not only promotes the develop-ment of Ti_(2) AlNb-based alloy fabricated through in-situ AM,but also facilitates its further application in the aerospace field.
基金This work was financially supported by the Tribology Science Fund of the State Key Laboratory of Tribology(No.SKLT2022C20)the National Natural Science Foundation of China(Nos.51875309 and 51905310)the Natural Science Foundation of Shandong Province(No.ZR2020YQ39).
文摘For the first time,this work comprehensively studied the effectiveness of precipitation hardening achieved by aging treatment in improving the tensile superelasticity of NiTi alloys fabricated by elec-tron beam wire-feed additive manufacturing(EBAM),which possesses inherent advantages in producing dense and oxidation-free structures.Aging treatments under three temperatures(450,350,and 250℃)and different durations were conducted,and the resultant performance of tensile superelasticity,together with the corresponding evolution of precipitation and phase transformation behavior were investigated for the EBAM-fabricated NiTi alloys.Results showed that by appropriate aging treatment,EBAM fabricated NiTi alloys could achieve excellent recovery rates of approximately 95%and 90%after the 1st and 10th load/unload cycle for a maximum tensile strain of 6%,which were almost the highest achieved so far by AM processed NiTi alloys and close to those of some conventional NiTi alloys.The improvement of tensile superelasticity benefited from the fine and dispersive Ni4Ti3 precipitates,which could be introduced by aging at 350℃ for 4 h or at 250℃ for 200 h.Moreover,the large amount of Ni4Ti3 precipitates would promote the intermediate R-phase transformation and bring a two-stage or three-stage transformation sequence,which depended on whether the distribution of the precipitation was homogeneous or not.This work could provide guidance for the production of NiTi alloys with good tensile superelasticity by EBAM or other additive manufacturing processes.
基金This work was supported by the KnowledgeInnovation Projects of the Chinese Academy of Sciences (CAS) (Grant Nos. KZCX1-1-10-02 and KZCX2-108 and 301)the Cold and Arid Regions Environmental and Engineering Research Institute of the CAS (Grant No. CACX
文摘Three ice cores recovered from the Himalayas (i.e. the East Rongbuk Glacier and the Far East Rongbuk Glacier at Mt. Qomolangma (Everest), and the Dasuopu Glacier at Xixiabangma) show a sharp decline in the accumulation rates since the 1950s, which is consistent with the precipitation fluctuation over India and the low northern latitude zone (5°-35癗). Correspondingly, an increasing trend is observed for the ice core accumulations from the central and northern Qinghai-Tibetan Plateau (i.e. the Xiao Dongkemadi Glacier in the central Tanggula Mountains, the Guliya Ice Cap in the western Kunlun Mountains, and the Dunde Ice Cap in the Qilian Mountains) since the 1950s, which is consistent with the precipitation fluctuation over the middle-high northern latitude zone (35°-70°N). However, the variation magnitude of the high-elevation ice core accumulations is more significant than that of precipitation at the low-eleva- tion places, suggesting its extra sensitivity of high-elevation areas to climatic change.
基金supported by the Polar Atmospheric Science Field Base of CAMS(2016Z005)National Natural Science Foundation of China(41425003)National Fundamental Research Project(973)of China(2007CB411503)
文摘For the first time we investigate the basal thermal condition in the upper area of Jima Yangzong Glacier, the headstream of Yarlung Zangbo River, using ground-penetrating radar techniques. With common offset and common mid-point surveys we analyze the radar velocities in ice with respect to cold-temperate ice transition surface(0.1751 ± 0.0028 m ns^(-1)) and ice-bedrock interface(0.1657 ± 0.0033 m ns^(-1)), indicating a radar velocity of 0.1410 ± 0.0154 m ns^(-1) for the temperate ice layer(16.6 ± 1.8 m). We estimate that the temperate ice layer has a water content of around 6 % ± 4 %, suggesting that the Jima Yangzong Glacier, previously known as continental-type, now possibly becomes polythermal.
基金financial support to this work from the Tribology Science Fund of the State Key Laboratory of Tribology(SKLT2020C09)National Natural Science Foundation of China(No.51675303)National Key Research and Development Program of China(2017YFB1103300)。
文摘Directed energy deposition has been used to repair superalloy components in aero engines and gas turbines.However,the microstructure and properties are generally inhomogeneous in components because of the different processing histories.Here,the microstructures and wear behavior of different zones(substrate,HAZ,and deposit)are investigated for the IC10 directionally solidified superalloy repaired by the directed energy deposition process.It is found that the microstructure of the deposited layers is strongly textured with a<001>-fiber texture in the building direction,and the texture intensity is continuously increased along the building direction.Two kinds ofγ’phase(primary and secondaryγ’phase)can be found in the heat-affected zone(HAZ),and the average size of primaryγ’phase is smaller than that in the substrate due to liquation.In the deposit layers,the size ofγ’phase is much smaller than those in the substrate and the primaryγ’phase of HAZ;both size and the fraction of theγ’phase decreases with the increase of building height.The wear rate of the substrate is the smallest,indicating the best wear resistance;while the wear rate of HAZ is the largest,indicating the worst wear resistance in the repaired sample.The wear rates in the deposit layers increase from the bottom to the top zones,showing a decreasing wear resistance.Abrasive wear is found to be the dominant wear mechanism of the repaired alloy,and the resistance to which is closely related to the fraction ofγ’phase in the microstructure.The understanding of the influence of microstructure on wear resistance allows for a more informed application of inhomogeneous superalloy components repaired by directed energy deposition in industry.