The as-deposited coating-substrate microstructure has been identified to substantially influence the high-cycle fatigue(HCF)behavior of Ni-based single-crystal(SX)superalloys at 900℃,but the impact of degraded micros...The as-deposited coating-substrate microstructure has been identified to substantially influence the high-cycle fatigue(HCF)behavior of Ni-based single-crystal(SX)superalloys at 900℃,but the impact of degraded microstructure on the HCF behavior remains unclear.In this work,a PtAl-coated third-generation SX superalloy with sheet specimen was thermal-exposed at 1100℃ with different durations and then subjected to HCF tests at 900℃.The influence of microstructural degradation on the HCF life and crack initiation were clarified by analyzing the development of microcracks and coating-substrate microstructure.Notably,the HCF life of the thermal-exposed coated alloy increased abnormally,which was attributed to the transformation of the fatigue crack initiation site from surface mi-crocracks to internal micropores compared to the as-deposited coated alloy.Although the nucleation and growth of surface microcracks occurred along the grain boundaries in the coating and the interdiffusion zone(IDZ)for both the as-deposited and the thermal-exposed coated alloys,remarkable differences of the microcrack growth into the substrate adjacent to the IDZ were observed,changing the crack initiation site.Specifically,the surface microcracks grew into the substrate through the cracking of the non-protective oxide layers in the as-deposited coated alloy.In comparison,the hinderance of the surface microcracks growth was found in the thermal-exposed coated al-loy,due to the formation of a protective Al_(2)O_(3) layer within the microcrack and theγ′rafting in the substrate close to the IDZ.This study will aid in improving the HCF life prediction model for the coated SX superalloys.展开更多
Nickel-based single-crystal(SX)superalloys are the key metallic materials of aeroengines.However,thermomechanical deformation always occurs during the directional solidification of SX superalloys,negatively influencin...Nickel-based single-crystal(SX)superalloys are the key metallic materials of aeroengines.However,thermomechanical deformation always occurs during the directional solidification of SX superalloys,negatively influencing the SX structure.Casting deformation is simulated in most of the previous studies,whereas the direct simulation of dendritic thermomechanical deformation has been largely ignored,resulting in a lack of comprehensive understanding of this process.In this study,we systematically investigate dendritic thermomechanical deformation with a model coupled with dendrite growth,fluid flow,and thermomechanical deformation behavior.Results reveal that the dendritic thermomechanical deformation-induced dendrite bending is not randomly distributed but is mainly concentrated on the casting surface.The dendritic thermal stress increases as dendrite grows and accumulates after dendrite bridging.Transverse thermal contraction mainly occurs at the edge of casting in the corner,and axial thermal contraction is larger than transverse contraction.The high-stress region of the primary dendrite trunk is mainly distributed below the dendrite bridging near the solidified part,and the stress along the transverse direction reaches its maximum value on the casting surface.Stress concentrated on the casting surface is mainly attributed to variations in transverse temperature gradients caused by heat dissipation on the lateral mold wall,and inconsistent constraints in the lateral mold walls.展开更多
Conventional polycrystalline LiMn_(2)O_(4)(PC-LMO)suffers from poor Li^(+)diffusion rates and structural instability,negatively affecting its electrochemical performance.Here,we design a single-crystal LMO cathode mat...Conventional polycrystalline LiMn_(2)O_(4)(PC-LMO)suffers from poor Li^(+)diffusion rates and structural instability,negatively affecting its electrochemical performance.Here,we design a single-crystal LMO cathode material using BaO flux(SC-LMOB)to address these issues.The BaO flux enables the fabrication of brick-like single-crystal particles,enhancing Li^(+)diffusion by shortening the diffusion path and increasing the unit cell volume.This process also reduces the specific surface area and stabilizes the crystal structure,effectively mitigating Mn dissolution and polarization.As a result,SC-LMOB exhibits ultra-high rate performance and superior structural stability,retaining 88.8%of its capacity at a 20 C discharge rate and achieving capacity retentions of 85.3%and 86.0%after 500 and 300 cycles at 1 C at room and elevated temperatures,respectively.This structural design offers a low-cost,scalable approach for fabricating single-crystal cathode materials with excellent performance.展开更多
Covalent organic frameworks(COFs)have demonstrated great potential in chromatographic separation because of unique structure and superior performance.Herein,single-crystal three-dimensional(3D)COFs with regular morpho...Covalent organic frameworks(COFs)have demonstrated great potential in chromatographic separation because of unique structure and superior performance.Herein,single-crystal three-dimensional(3D)COFs with regular morphology,good monodispersity and high specific surface area,were used as a stationary phase for high-performance liquid chromatography(HPLC).The single-crystal 3D COFs packed column not only exhibits high efficiency in separating hydrophobic molecules involving substituted benzenes,halogenated benzenes,halogenated nitrobenzenes,aromatic amines,aromatic hydrocarbons(PAHs)and phthalate esters(PAEs),but also achieves baseline separation of acenaphthene and acenaphthylene with similar physical and chemical properties as well as environmental pollutants,which cannot be quickly separated on commercial C18 column and a polycrystalline 3D COFs packed column.Especially,the column efficiency of 17303-24255 plates/m was obtained for PAEs,and the resolution values for acenaphthene and acenaphthylene,and carbamazepine(CBZ)and carbamazepine-10,11-epoxide(CBZEP)were 1.7and 2.2,respectively.This successful application not only confirmed the great potential of the singlecrystal 3D COFs in HPLC separation of the organic molecules,but also facilitates the application of COFs in separation science.展开更多
The poor electrochemical performance of all-solid-state batteries(ASSBs),which is assemblied by Ni-rich cathode and poly(ethylene oxide)(PEO)-based electrolytes,can be attributed to unstable cathodic interface and poo...The poor electrochemical performance of all-solid-state batteries(ASSBs),which is assemblied by Ni-rich cathode and poly(ethylene oxide)(PEO)-based electrolytes,can be attributed to unstable cathodic interface and poor crystal structure stability of Ni-rich cathode.Several coating strategies are previously employed to enhance the stability of the cathodic interface and crystal structure for Ni-rich cathode.However,these methods can hardly achieve simplicity and high efficiency simultaneously.In this work,polyacrylic acid(PAA)replaced traditional PVDF as a binder for cathode,which can achieve a uniform PAA-Li(LixPAA(0<x≤1))coating layer on the surface of single-crystal LiNi_(0.83)Co_(0.12)Mn_(0.05)O_(2)(SC-NCM83)due to H^(+)/Li^(+)exchange reaction during the initial charging-discharging process.The formation of PAA-Li coating layer on cathode can promote interfacial Li^(+)transport and enhance the stability of the cathodic interface.Furthermore,the partially-protonated surface of SC-NCM83 casued by H^(+)/Li^(+)exchange reaction can restrict Ni ions transport to enhance the crystal structure stability.The proposed SC-NCM83-PAA exhibits superior cycling performance with a retention of 92%compared with that(57.3%)of SC-NCM83-polyvinylidene difluoride(PVDF)after 200 cycles.This work provides a practical strategy to construct high-performance cathodes for ASSBs.展开更多
Benefited from its high process feasibility and controllable costs,binary-metal layered structured LiNi_(0.8)Mn_(0.2)O_(2)(NM)can effectively alleviate the cobalt supply crisis under the surge of global electric vehic...Benefited from its high process feasibility and controllable costs,binary-metal layered structured LiNi_(0.8)Mn_(0.2)O_(2)(NM)can effectively alleviate the cobalt supply crisis under the surge of global electric vehicles(EVs)sales,which is considered as the most promising nextgeneration cathode material for lithium-ion batteries(LIBs).However,the lack of deep understanding on the failure mechanism of NM has seriously hindered its application,especially under the harsh condition of high-voltage without sacrifices of reversible capacity.Herein,singlecrystal LiNi_(0.8)Mn_(0.2)O_(2) is selected and compared with traditional LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM),mainly focusing on the failure mechanism of Cofree cathode and illuminating the significant effect of Co element on the Li/Ni antisite defect and dynamic characteristic.Specifically,the presence of high Li/Ni antisite defect in NM cathode easily results in the extremely dramatic H2/H3 phase transition,which exacerbates the distortion of the lattice,mechanical strain changes and exhibits poor electrochemical performance,especially under the high cutoff voltage.Furthermore,the reaction kinetic of NM is impaired due to the absence of Co element,especially at the single-crystal architecture.Whereas,the negative influence of Li/Ni antisite defect is controllable at low current densities,owing to the attenuated polarization.Notably,Co-free NM can exhibit better safety performance than that of NCM cathode.These findings are beneficial for understanding the fundamental reaction mechanism of single-crystal Ni-rich Co-free cathode materials,providing new insights and great encouragements to design and develop the next generation of LIBs with low-cost and high-safety performances.展开更多
The magnetic field is an effective means to control the solidification structure and the defects of metal and semiconductor crystals.This work investigates the effects of Cusp magnetic field(CMF)and longitudinal magne...The magnetic field is an effective means to control the solidification structure and the defects of metal and semiconductor crystals.This work investigates the effects of Cusp magnetic field(CMF)and longitudinal magnetic field(LMF)on the stray-crystal formation in the platform regions during the directional solidification of single-crystal superalloy with the different cross section sizes.The application of CMF reduces the formation of platform stray-crystal,while LMF increases its generation.As the platform size increases,the stray-crystal ratio increases regardless of whether the magnetic fields are applied or not,the effectiveness of CMF increases,while that of LMF decreases.The reason that the effects of CMF and LMF on the platform stray-crystal formation could be attributed to the change of flow structure from the distribution characteristics of the thermoelectric magnetic force and the magnetic damping force near the liquid-solid interface.展开更多
Single-crystal Nickel-rich layered oxides has been recognized as one of the promising cathodes for nextgeneration lithium batteries on account of their high capacity,while its practical application was hindered by str...Single-crystal Nickel-rich layered oxides has been recognized as one of the promising cathodes for nextgeneration lithium batteries on account of their high capacity,while its practical application was hindered by structural instability and slow Li^(+) transfer kinetics.Herein,a surface-to-bulk engineered single-crystal LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)(Ni90) cathode,which features W-doped bulk and Li_(2)WO_(4) surface layer,was successfully achieved by a one-step high-valence W^(6+) modification.The as-obtained W-modified Ni90 delivers excellent cycling stability(89.8% capacity retention after 300 cycles at 0.5 C)and rate capability.The enhanced electrochemical performance was ascribed to the doped-W induced stabilized lattice oxygen,reduced Li^(+)/Ni^(2+) mixing and inhibited H2-H3 phase transition in the bulk,and Li_(2)WO_(4) layer generated stabilized cathode/electrolyte interface.In addition,the thinner LiF-rich cathode electrolyte interphase(CEI) on surface and smaller grain size for W-modified Ni90 benefit to its Li^(+) diffusion dynamics.The effect of high-valence W^(6+)on single-crystal Ni-rich cathode was firstly revealed in detail,which deepens the understanding of electrochemical behavior of Ni-rich cathode with high-valence cations modification,and provides clues for design of high-performance layered cathodes.展开更多
Single-crystal Ni-rich cathodes are a promising candidate for high-energy lithium-ion batteries due to their higher structural and cycling stability than polycrystalline materials.However,the phase evolution and capac...Single-crystal Ni-rich cathodes are a promising candidate for high-energy lithium-ion batteries due to their higher structural and cycling stability than polycrystalline materials.However,the phase evolution and capacity degradation of these single-crystal cathodes during continuous lithation/delithation cycling remains unclear.Understanding the mapping relationship between the macroscopic electrochemical properties and the material physicochemical properties is crucial.Here,we investigate the correlation between the physical-chemical characteristics,phase transition,and capacity decay using capacity differential curve feature identification and in-situ X-ray spectroscopic imaging.We systematically clarify the dominant mechanism of phase evolution in aging cycling.Appropriately high cut-off voltages can mitigate the slow kinetic and electrochemical properties of single-crystal cathodes.We also find that second-order differential capacity discharge characteristic curves can be used to identify the crystal structure disorder of Ni-rich cathodes.These findings constitute a step forward in elucidating the correlation between the electrochemical extrinsic properties and the physicochemical intrinsic properties and provide new perspectives for failure analysis of layered electrode materials.展开更多
Depending on the production process,copper(Cu)foils can be classified into two types,i.e.,rolled copper(r-Cu)foils and electrolytic copper(e-Cu)foils.Owing to their high electrical conductivity and ductility at low co...Depending on the production process,copper(Cu)foils can be classified into two types,i.e.,rolled copper(r-Cu)foils and electrolytic copper(e-Cu)foils.Owing to their high electrical conductivity and ductility at low cost,e-Cu foils are employed extensively in modern industries and account for more than 98%of the Cu foil market share.However,industrial e-Cu foils have never been single-crystallized due to their high density of grain boundaries,various grain orientations and vast impurities originating from the electrochemical deposition process.Here,we report a methodology of transforming industrial e-Cu foils into single crystals by facet copy from a single-crystal template.Different facets of both low and high indices are successfully produced,and the thickness of the single crystal can reach 500μm.Crystallographic characterizations directly recognized the single-crystal copy process,confirming the complete assimilation impact from the template.The obtained single-crystal e-Cu foils exhibit remarkably improved ductility(elongation-to-fracture of 105%vs.25%),fatigue performance(the average numbers of cycles to failure of 1600 vs.200)and electrical property(electrical conductivity of 102.6%of the international annealed copper standard(IACS)vs.98.5%)than original ones.This work opens up a new avenue for the preparation of single-crystal e-Cu foils and may expand their applications in high-speed,flexible,and wearable devices.展开更多
Sulfide all-solid-state lithium batteries(SASSLBs)with a single-crystal nickel-rich layered oxide cathode(LiNix-CoyMn_(1-x-y)O_(2),x≥0.8)are highly desirable for advanced power batteries owing to their excellent ener...Sulfide all-solid-state lithium batteries(SASSLBs)with a single-crystal nickel-rich layered oxide cathode(LiNix-CoyMn_(1-x-y)O_(2),x≥0.8)are highly desirable for advanced power batteries owing to their excellent energy density and safety.Nevertheless,the cathode material's cracking issue and its severe interfacial problem with sulfide solid electrolytes have hindered the further development.This study proposes to employ surface modification engineering to produce B-NCM cathode materials coated with boride nanostructure stabilizer in situ by utilizing NCM encapsulated with residual lithium.This approach enhances the electrochemical performance of SASSLBs by effectively inhibiting electrochemical-mechanical degradation of the NCM cathode material on cycling and reducing deleterious side reactions with the solid sulfide electrolyte.The B-NCM/LPSCl/Gr SASSLBs demonstrate impressive cycling stability,retaining 84.19%of its capacity after 500 cycles at 0.2 C,which represents a 30.13%increase vs.NCM/LPSCl/Gr.It also exhibits a specific capacity of 170.4 mAh/g during its first discharge at 0.1 C.This work demonstrates an effective surface engineering strategy for enhancing capacity and cycle life,providing valuable insights into solving interfacial problems in SASSLBs.展开更多
The effect of yttrium(Y)addition on the oxidation behavior of a Ni-based directionally solidified single-crystal superalloy is investigated in this study.Isothermal oxidation tests for samples with different levels of...The effect of yttrium(Y)addition on the oxidation behavior of a Ni-based directionally solidified single-crystal superalloy is investigated in this study.Isothermal oxidation tests for samples with different levels of Y addition are conducted at 1100℃ in air.The Y content of the samples is determined by the actual pickup amount obtained from an Inductively Coupled Plasma-Atomic Emission Spectrometry test.It is discovered that the addition of Y increases the oxide resistance by the scale of an adhesive double-layer oxide,which is composed of Al_(2)O_(3) and spinel Ni(Cr,Al)_(2)O_(4).With 70 ppm of Y addition,the oxidation mass gain decreases from 12.6 g/m^(2) for the alloy without Y addition to 5.3 g/m^(2),and the oxidation rate decreases significantly.In addition,the internal nitride disappears after Y doping because of an increase in oxidation scale adherence and a decrease in oxidation products.In this study,the alloy with 660 ppm Y addition demonstrates the best oxidation resistance.展开更多
Elevating the operating voltage is an effective approach to improve the reversible capacity of ultra-high nickel layered oxide cathode LiNi_(x)Co_(y)Mn_(z)O_(2)(NCM,x≥0.8)and solve the"range anxiety"confusi...Elevating the operating voltage is an effective approach to improve the reversible capacity of ultra-high nickel layered oxide cathode LiNi_(x)Co_(y)Mn_(z)O_(2)(NCM,x≥0.8)and solve the"range anxiety"confusion of electric vehicles.However,the undesirable surface reconstruction induced by the high cut-off voltage has a fatal impact on the thermodynamic stability of the material,inevitably leading to fast capacity degradation.Herein,a mechanical fusion aided by alcohol is suggested to create a stable olivine structure for the single-crystal(SC)ultrahigh-nickel cathode LiNi_(0.92)Co_(0.04)Mn_(0.04)O_(2).The addition of nanoparticles effectively bridges the void of SC-NCM,builds an ideal particle grading,and significantly raises the cost efficiency,as well as promotes the cycling stability and safety of the full cell.Remarkably,the layered/olivine mixture forms a perfect shield by lowering the surface area between the NCM cathode and electrolyte,hence mitigating side reactions and contributing to an incredibly thin and stable cathode/electrolyte interface.Furthermore,the thermodynamic stability of highly delithiated NCM is improved,as both the particle cracks and structural degradation are simultaneously postponed.Consequently,the maximum temperature of the single-crystal LiNi_(0.92)Co_(0.04)Mn_(0.04)O_(2)@LiFePO_(4)‖graphite pouch full cell is dramatically reduced from 599.4 to 351.4℃,and the full cell achieves 88.2%capacity retention after 800 cycles,demonstrating excellent thermal stability and cycling stability.This facile strategy provides a feasible technical reference for further exploiting the ultrahigh-capacity,highsafety,and long-life Ni-rich cathode for commercial application of lithium-ion batteries(LIBs).展开更多
Microscale stray grains(MSGs),which are composed of misoriented and fragmented high-ordered dendrite arms,small-sized equiaxed grains,and columnar grains,are a novel grain defect that occurs within the shrouds of sing...Microscale stray grains(MSGs),which are composed of misoriented and fragmented high-ordered dendrite arms,small-sized equiaxed grains,and columnar grains,are a novel grain defect that occurs within the shrouds of single-crystal(SC)blades made from Ni-based superalloy.State-of-the-art non-destructive testing methods are incapable of detecting this defect,resulting in a high-risk application of SC blades.This study aims to control this defect by systematically investigating directional solidification processing parameters,shroud dimensions,and rhenium(Re)content in the formation of MSG defects.The results reveal that the defect forms exclusively at the overhanging extremities of the upper shrouds on the back side of the blades that face the heater.Increasing the withdrawal rate reduces the occurrence of MSG defects.As the shroud dimensions increase,MSG defects appear in the transition area between the downward suspended extremity of the blade shroud and the side of the blade body,as well as near the corner of the downward suspended extremity of the shroud.The occurrence of MSG defects increases with increasing shroud dimensions.Varying Re content sharply decreases the formation of MSG defects.A concentration-attached Rayleigh-Taylor instability(RTI)superheating(CARTISH)model,considering solidification shrinkage,was proposed to comprehend the formation of MSG defects.Simulation results based on this model are consistent with the experimentally observed distribution and degree of MSG defects under different conditions.Effective control of the CARTISH is critical to managing MSG defects.展开更多
Catalysts for CO_(2)value-added conversion have been extensively explored,but there is still a lack of systematic design for catalysts that achieve efficient CO_(2)conversion under mild conditions.Herein,we explored a...Catalysts for CO_(2)value-added conversion have been extensively explored,but there is still a lack of systematic design for catalysts that achieve efficient CO_(2)conversion under mild conditions.Herein,we explored a mesoporous CeO_(2)single-crystal formed with the regulation of ionic liquids,which catalyzed the effective carbonylation reaction with CO_(2)under mild reaction conditions.By altering the synthetic environment,a series of uniform mesoporous CeO_(2)particles with atomically aligned single-crystal frameworks were constructed,which have different surface physicochemical properties and primary aggregation degree.The prepared mesoporous CeO_(2)single-crystal achieved efficient activation of CO_(2)and alcohols at 0.5 MPa CO_(2)and 100℃,and the CeO_(2)-IL-M catalyst shows optimal catalytic performance in the synthesis of ethylene carbonate with 46.22 mmol g^(–1)h^(–1),which was 50.6 times as high as that of the CeO_(2)obtained without ionic liquids.Subsequently,the catalytic pathway and mechanism of carbonylation reaction with CO_(2)on mesoporous CeO_(2)single-crystal were studied via React-IR spectra and C18O_(2)labeling experiments.The research provides a new strategy for controllable nanoscale assembly of mesoporous single-crystal materials and expands the application range of single-crystal materials,aiming to develop novel catalytic materials to meet industrial needs.展开更多
Based on the high-purity single-crystal tungsten nanowire firstly prepared by the metal-catalyzed vapor-phase reaction method, molecular dynamics method was used to calculate tensile stress-strain curves and simulate ...Based on the high-purity single-crystal tungsten nanowire firstly prepared by the metal-catalyzed vapor-phase reaction method, molecular dynamics method was used to calculate tensile stress-strain curves and simulate microscopic deformation structures of the single-crystal tungsten nanowires with different crystal orientations of 〈100〉, 〈110〉and 〈111〉, in order to reveal the effect of crystal orientation on their tensile mechanical properties and failure mechanisms. Research results show that all of the stress-strain curves are classified into four stages： elastic stage, damage stage, yielding stage and failure stage, where 〈100〉orientation has a special hardening stage after yielding and two descending stages. The crystal orientation has little effect on elastic modulus but great effect on tensile strength, yielding strength and ductility, depending on different atomic surface energies and principal sliding planes. The calculated values of elastic modulus are in good agreement with the tested values of elastic modulus.展开更多
The dynamic recrystallization behavior of single-crystal（SC） superalloy SR.R99 at low strain rate was investigated by high-temperature creep testing.The results show that dynamic recrystallization may take place aft...The dynamic recrystallization behavior of single-crystal（SC） superalloy SR.R99 at low strain rate was investigated by high-temperature creep testing.The results show that dynamic recrystallization may take place after the uncoated samples have been creep-tested in air at high temperature and low stress for a long time.Both the threshold temperature and strain for the dynamic recrystallization of SC superalloy SRR99 at low strain rate are lower than those for the static recrystallization.Dynamically recrystallized grains with the depth less than 15 μm are only located in the surface γ＇-free layers,and the recrystallized grains are well-developed grains without columnar y＇precipitates within them.The dynamic recrystallization behavior of SC superalloy SRR99 at low strain rate is mainly related to high-temperature oxidation.Suitable protective coating can effectively prevent the dynamic recrystallization of SC superalloy components in service.In addition,the dynamic recrystallization behavior of SC superalloy SRR99 at high strain rate was also studied by high-temperature compression testing.At high strain rate,a higher temperature and larger strain are needed for the occurrence of dynamic recrystallization than at low strain rate,and the recrystallized grains have cellular structures with an amount of columnar γ＇ precipitates within them.展开更多
Single-crystal Ni-rich cathode material LiNi0.88Co0.09Al0.03O2(SC) was synthesized by a high-temperature solid-state calcination method. Physicochemical properties of primary and delithiated SC samples were investigat...Single-crystal Ni-rich cathode material LiNi0.88Co0.09Al0.03O2(SC) was synthesized by a high-temperature solid-state calcination method. Physicochemical properties of primary and delithiated SC samples were investigated by X-ray diffractometry, X-ray photoelectron spectroscopy, and transmission electron microscopy. Electrochemical performance was characterized by long-term cycling, cyclic voltammetry, and in-situ impedance spectroscopy. The results indicated that high temperature rendered layered oxides to lose lithium/oxygen in the interior and exterior, and induced cationic disordering. Besides, the solid-phase synthesis process promoted phase transformation for electrode materials, causing the coexisting multi-phase in a single particle. High temperature can foster the growth of single particles, but it caused unstable structure of layered phase.展开更多
MCrAlY(M=Ni and/or Co)overlay coating is widely used as a protective coating against high temperature oxidation and corrosion.However,due to its big difference in chemical composition with the underlying superalloy,el...MCrAlY(M=Ni and/or Co)overlay coating is widely used as a protective coating against high temperature oxidation and corrosion.However,due to its big difference in chemical composition with the underlying superalloy,elements interdiffusion occurs inevitably.One of the direct results is the formation of interdiffusion zone(IDZ)and secondary reaction zone(SRZ)with a high density of fine topological closed-packed phases(TCPs),weakening dramatically the mechanical properties of the alloy substrate.It is by now the main problem of modern high-temperature metallic coatings,but there are still hardly any reports studying the formation,growth and transformation of IDZ and SRZ in deep,as well as the precipitation of TCPs.In this work,a typical NiCrAlY coating is deposited by arc ion plating on a single-crystal superalloy N5.Elements interdiffusion between them and its relationship on microstructure were clarified.Cr rather than Al from the coating diffuses into the alloy at high temperatures and segregates immediately beneath their interface,contributing largely to the formation of IDZ.Simultaneously,diffusion of Ni from the deep alloy to IDZ leads to the formation and continuous expansion of SRZ.展开更多
Chemical vapor deposition(CVD)-grown diamond films have been developed as irradiation-resistant materials to replace or upgrade current detectors for use in extreme radiation environments. However, their sensitivity i...Chemical vapor deposition(CVD)-grown diamond films have been developed as irradiation-resistant materials to replace or upgrade current detectors for use in extreme radiation environments. However, their sensitivity in practical applications has been inhibited by space charge stability issues caused by defects and impurities in pure diamond crystal materials. In this study, two high-quality CVD-grown single-crystal diamond(SCD) detectors with low content of nitrogen impurities were fabricated and characterized. The intrinsic properties of the SCD samples were characterized using Raman spectroscopy, stereomicroscopy, and X-ray diffraction with the rocking curve mode, cathode luminescence(CL), and infrared and ultraviolet-visible-near infrared spectroscopies. After packaging the detectors, the dark current and energy resolution under α particle irradiation were investigated. Dark currents of less than 5 pA at 100 V were obtained after annealing the electrodes, which is comparable with the optimal value previously reported. The detector that uses a diamond film with higher nitrogen content showed poor energy resolution, whereas the detector with more dislocations showed poor charge collection efficiency(CCE). This demonstrates that the nitrogen content in diamond has a significant effect on the energy resolution of detectors, while the dislocations in diamond largely contribute to the poor CCE of detectors.展开更多
基金financially supported by National Key Research and Development Program of China(No.2022YFB 3708100)the Science Center for Gas Turbine Project,China(No.P2021-A-IV-002-001)+1 种基金the National Natural Science Foundation of China(Nos.52331005 and 52201100)the State Key Laboratory for Advanced Metals and Materials,China(No.2024-Z02).
文摘The as-deposited coating-substrate microstructure has been identified to substantially influence the high-cycle fatigue(HCF)behavior of Ni-based single-crystal(SX)superalloys at 900℃,but the impact of degraded microstructure on the HCF behavior remains unclear.In this work,a PtAl-coated third-generation SX superalloy with sheet specimen was thermal-exposed at 1100℃ with different durations and then subjected to HCF tests at 900℃.The influence of microstructural degradation on the HCF life and crack initiation were clarified by analyzing the development of microcracks and coating-substrate microstructure.Notably,the HCF life of the thermal-exposed coated alloy increased abnormally,which was attributed to the transformation of the fatigue crack initiation site from surface mi-crocracks to internal micropores compared to the as-deposited coated alloy.Although the nucleation and growth of surface microcracks occurred along the grain boundaries in the coating and the interdiffusion zone(IDZ)for both the as-deposited and the thermal-exposed coated alloys,remarkable differences of the microcrack growth into the substrate adjacent to the IDZ were observed,changing the crack initiation site.Specifically,the surface microcracks grew into the substrate through the cracking of the non-protective oxide layers in the as-deposited coated alloy.In comparison,the hinderance of the surface microcracks growth was found in the thermal-exposed coated al-loy,due to the formation of a protective Al_(2)O_(3) layer within the microcrack and theγ′rafting in the substrate close to the IDZ.This study will aid in improving the HCF life prediction model for the coated SX superalloys.
基金financially sponsored by the National Natural Science Foundation of China(Nos.U2441268 and 52304406)the Natural Science Foundation of Shanghai,China(No.23TS1401900)+2 种基金the Science Foundation of Aeronautics(PSSFA),China(No.2024Z053057002)the Science and Technology Cooperation Program of Shanghai Jiao Tong University in Inner Mongolia Autonomous Region-Action Plan of Shanghai Jiao Tong University for“Revitalizing Inner Mongolia through Science and Technology”,ChinaLuwei Yang would like to thank the financial support from the Chinese Scholarship Council(No.202306230337).
文摘Nickel-based single-crystal(SX)superalloys are the key metallic materials of aeroengines.However,thermomechanical deformation always occurs during the directional solidification of SX superalloys,negatively influencing the SX structure.Casting deformation is simulated in most of the previous studies,whereas the direct simulation of dendritic thermomechanical deformation has been largely ignored,resulting in a lack of comprehensive understanding of this process.In this study,we systematically investigate dendritic thermomechanical deformation with a model coupled with dendrite growth,fluid flow,and thermomechanical deformation behavior.Results reveal that the dendritic thermomechanical deformation-induced dendrite bending is not randomly distributed but is mainly concentrated on the casting surface.The dendritic thermal stress increases as dendrite grows and accumulates after dendrite bridging.Transverse thermal contraction mainly occurs at the edge of casting in the corner,and axial thermal contraction is larger than transverse contraction.The high-stress region of the primary dendrite trunk is mainly distributed below the dendrite bridging near the solidified part,and the stress along the transverse direction reaches its maximum value on the casting surface.Stress concentrated on the casting surface is mainly attributed to variations in transverse temperature gradients caused by heat dissipation on the lateral mold wall,and inconsistent constraints in the lateral mold walls.
基金supported by National Key Research and Development Program of China(No.2021YFB3502000)the National Natural Science Foundation of China(Nos.22309207,52325405,U21A20284,52261135632,51874358 and 51772333)。
文摘Conventional polycrystalline LiMn_(2)O_(4)(PC-LMO)suffers from poor Li^(+)diffusion rates and structural instability,negatively affecting its electrochemical performance.Here,we design a single-crystal LMO cathode material using BaO flux(SC-LMOB)to address these issues.The BaO flux enables the fabrication of brick-like single-crystal particles,enhancing Li^(+)diffusion by shortening the diffusion path and increasing the unit cell volume.This process also reduces the specific surface area and stabilizes the crystal structure,effectively mitigating Mn dissolution and polarization.As a result,SC-LMOB exhibits ultra-high rate performance and superior structural stability,retaining 88.8%of its capacity at a 20 C discharge rate and achieving capacity retentions of 85.3%and 86.0%after 500 and 300 cycles at 1 C at room and elevated temperatures,respectively.This structural design offers a low-cost,scalable approach for fabricating single-crystal cathode materials with excellent performance.
基金the National Natural Science Foundation of China(No.22274021)Natural Science Foundation of Fujian Province(No.2022J01535)for financial support。
文摘Covalent organic frameworks(COFs)have demonstrated great potential in chromatographic separation because of unique structure and superior performance.Herein,single-crystal three-dimensional(3D)COFs with regular morphology,good monodispersity and high specific surface area,were used as a stationary phase for high-performance liquid chromatography(HPLC).The single-crystal 3D COFs packed column not only exhibits high efficiency in separating hydrophobic molecules involving substituted benzenes,halogenated benzenes,halogenated nitrobenzenes,aromatic amines,aromatic hydrocarbons(PAHs)and phthalate esters(PAEs),but also achieves baseline separation of acenaphthene and acenaphthylene with similar physical and chemical properties as well as environmental pollutants,which cannot be quickly separated on commercial C18 column and a polycrystalline 3D COFs packed column.Especially,the column efficiency of 17303-24255 plates/m was obtained for PAEs,and the resolution values for acenaphthene and acenaphthylene,and carbamazepine(CBZ)and carbamazepine-10,11-epoxide(CBZEP)were 1.7and 2.2,respectively.This successful application not only confirmed the great potential of the singlecrystal 3D COFs in HPLC separation of the organic molecules,but also facilitates the application of COFs in separation science.
基金the financial support from the National Natural Science Foundation of China(Nos.52034011 and 52204328)the Science and Technology Innovation Program of Hunan Province(2023RC305)the Changsha Municipal Natural Science Foundation(kq2202085)。
文摘The poor electrochemical performance of all-solid-state batteries(ASSBs),which is assemblied by Ni-rich cathode and poly(ethylene oxide)(PEO)-based electrolytes,can be attributed to unstable cathodic interface and poor crystal structure stability of Ni-rich cathode.Several coating strategies are previously employed to enhance the stability of the cathodic interface and crystal structure for Ni-rich cathode.However,these methods can hardly achieve simplicity and high efficiency simultaneously.In this work,polyacrylic acid(PAA)replaced traditional PVDF as a binder for cathode,which can achieve a uniform PAA-Li(LixPAA(0<x≤1))coating layer on the surface of single-crystal LiNi_(0.83)Co_(0.12)Mn_(0.05)O_(2)(SC-NCM83)due to H^(+)/Li^(+)exchange reaction during the initial charging-discharging process.The formation of PAA-Li coating layer on cathode can promote interfacial Li^(+)transport and enhance the stability of the cathodic interface.Furthermore,the partially-protonated surface of SC-NCM83 casued by H^(+)/Li^(+)exchange reaction can restrict Ni ions transport to enhance the crystal structure stability.The proposed SC-NCM83-PAA exhibits superior cycling performance with a retention of 92%compared with that(57.3%)of SC-NCM83-polyvinylidene difluoride(PVDF)after 200 cycles.This work provides a practical strategy to construct high-performance cathodes for ASSBs.
基金the National Natural Science Foundation of China(52070194,52073309,51902347,51908555)Natural Science Foundation of Hunan Province(2022JJ20069,2020JJ5741).
文摘Benefited from its high process feasibility and controllable costs,binary-metal layered structured LiNi_(0.8)Mn_(0.2)O_(2)(NM)can effectively alleviate the cobalt supply crisis under the surge of global electric vehicles(EVs)sales,which is considered as the most promising nextgeneration cathode material for lithium-ion batteries(LIBs).However,the lack of deep understanding on the failure mechanism of NM has seriously hindered its application,especially under the harsh condition of high-voltage without sacrifices of reversible capacity.Herein,singlecrystal LiNi_(0.8)Mn_(0.2)O_(2) is selected and compared with traditional LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM),mainly focusing on the failure mechanism of Cofree cathode and illuminating the significant effect of Co element on the Li/Ni antisite defect and dynamic characteristic.Specifically,the presence of high Li/Ni antisite defect in NM cathode easily results in the extremely dramatic H2/H3 phase transition,which exacerbates the distortion of the lattice,mechanical strain changes and exhibits poor electrochemical performance,especially under the high cutoff voltage.Furthermore,the reaction kinetic of NM is impaired due to the absence of Co element,especially at the single-crystal architecture.Whereas,the negative influence of Li/Ni antisite defect is controllable at low current densities,owing to the attenuated polarization.Notably,Co-free NM can exhibit better safety performance than that of NCM cathode.These findings are beneficial for understanding the fundamental reaction mechanism of single-crystal Ni-rich Co-free cathode materials,providing new insights and great encouragements to design and develop the next generation of LIBs with low-cost and high-safety performances.
基金supported by the National Natural Science Foundation of China(No.52373319)by the Independent Research and Development Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(SKLASS 2022-Z03).
文摘The magnetic field is an effective means to control the solidification structure and the defects of metal and semiconductor crystals.This work investigates the effects of Cusp magnetic field(CMF)and longitudinal magnetic field(LMF)on the stray-crystal formation in the platform regions during the directional solidification of single-crystal superalloy with the different cross section sizes.The application of CMF reduces the formation of platform stray-crystal,while LMF increases its generation.As the platform size increases,the stray-crystal ratio increases regardless of whether the magnetic fields are applied or not,the effectiveness of CMF increases,while that of LMF decreases.The reason that the effects of CMF and LMF on the platform stray-crystal formation could be attributed to the change of flow structure from the distribution characteristics of the thermoelectric magnetic force and the magnetic damping force near the liquid-solid interface.
基金National Key Research and Development Program of China (2022YFB2502103)National Natural Science Foundation of China (22279107, 22309153)Fundamental Research Funds for the Central Universities (20720230039)。
文摘Single-crystal Nickel-rich layered oxides has been recognized as one of the promising cathodes for nextgeneration lithium batteries on account of their high capacity,while its practical application was hindered by structural instability and slow Li^(+) transfer kinetics.Herein,a surface-to-bulk engineered single-crystal LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)(Ni90) cathode,which features W-doped bulk and Li_(2)WO_(4) surface layer,was successfully achieved by a one-step high-valence W^(6+) modification.The as-obtained W-modified Ni90 delivers excellent cycling stability(89.8% capacity retention after 300 cycles at 0.5 C)and rate capability.The enhanced electrochemical performance was ascribed to the doped-W induced stabilized lattice oxygen,reduced Li^(+)/Ni^(2+) mixing and inhibited H2-H3 phase transition in the bulk,and Li_(2)WO_(4) layer generated stabilized cathode/electrolyte interface.In addition,the thinner LiF-rich cathode electrolyte interphase(CEI) on surface and smaller grain size for W-modified Ni90 benefit to its Li^(+) diffusion dynamics.The effect of high-valence W^(6+)on single-crystal Ni-rich cathode was firstly revealed in detail,which deepens the understanding of electrochemical behavior of Ni-rich cathode with high-valence cations modification,and provides clues for design of high-performance layered cathodes.
文摘Single-crystal Ni-rich cathodes are a promising candidate for high-energy lithium-ion batteries due to their higher structural and cycling stability than polycrystalline materials.However,the phase evolution and capacity degradation of these single-crystal cathodes during continuous lithation/delithation cycling remains unclear.Understanding the mapping relationship between the macroscopic electrochemical properties and the material physicochemical properties is crucial.Here,we investigate the correlation between the physical-chemical characteristics,phase transition,and capacity decay using capacity differential curve feature identification and in-situ X-ray spectroscopic imaging.We systematically clarify the dominant mechanism of phase evolution in aging cycling.Appropriately high cut-off voltages can mitigate the slow kinetic and electrochemical properties of single-crystal cathodes.We also find that second-order differential capacity discharge characteristic curves can be used to identify the crystal structure disorder of Ni-rich cathodes.These findings constitute a step forward in elucidating the correlation between the electrochemical extrinsic properties and the physicochemical intrinsic properties and provide new perspectives for failure analysis of layered electrode materials.
基金financially supported by Guangdong Major Project of Basic and Applied Basic Research(No.2021B0301030002)the National Natural Science Foundation of China(No.52025023)the Key R&D Program of Guangdong Province(No.2020B010189001).
文摘Depending on the production process,copper(Cu)foils can be classified into two types,i.e.,rolled copper(r-Cu)foils and electrolytic copper(e-Cu)foils.Owing to their high electrical conductivity and ductility at low cost,e-Cu foils are employed extensively in modern industries and account for more than 98%of the Cu foil market share.However,industrial e-Cu foils have never been single-crystallized due to their high density of grain boundaries,various grain orientations and vast impurities originating from the electrochemical deposition process.Here,we report a methodology of transforming industrial e-Cu foils into single crystals by facet copy from a single-crystal template.Different facets of both low and high indices are successfully produced,and the thickness of the single crystal can reach 500μm.Crystallographic characterizations directly recognized the single-crystal copy process,confirming the complete assimilation impact from the template.The obtained single-crystal e-Cu foils exhibit remarkably improved ductility(elongation-to-fracture of 105%vs.25%),fatigue performance(the average numbers of cycles to failure of 1600 vs.200)and electrical property(electrical conductivity of 102.6%of the international annealed copper standard(IACS)vs.98.5%)than original ones.This work opens up a new avenue for the preparation of single-crystal e-Cu foils and may expand their applications in high-speed,flexible,and wearable devices.
基金support from the National Natural Science Foundation of China(Grant No.52374407)is gratefully acknowledged.
文摘Sulfide all-solid-state lithium batteries(SASSLBs)with a single-crystal nickel-rich layered oxide cathode(LiNix-CoyMn_(1-x-y)O_(2),x≥0.8)are highly desirable for advanced power batteries owing to their excellent energy density and safety.Nevertheless,the cathode material's cracking issue and its severe interfacial problem with sulfide solid electrolytes have hindered the further development.This study proposes to employ surface modification engineering to produce B-NCM cathode materials coated with boride nanostructure stabilizer in situ by utilizing NCM encapsulated with residual lithium.This approach enhances the electrochemical performance of SASSLBs by effectively inhibiting electrochemical-mechanical degradation of the NCM cathode material on cycling and reducing deleterious side reactions with the solid sulfide electrolyte.The B-NCM/LPSCl/Gr SASSLBs demonstrate impressive cycling stability,retaining 84.19%of its capacity after 500 cycles at 0.2 C,which represents a 30.13%increase vs.NCM/LPSCl/Gr.It also exhibits a specific capacity of 170.4 mAh/g during its first discharge at 0.1 C.This work demonstrates an effective surface engineering strategy for enhancing capacity and cycle life,providing valuable insights into solving interfacial problems in SASSLBs.
基金Supported by Preliminary Research Project of China (Grant No. J2019-Ⅵ-0023)
文摘The effect of yttrium(Y)addition on the oxidation behavior of a Ni-based directionally solidified single-crystal superalloy is investigated in this study.Isothermal oxidation tests for samples with different levels of Y addition are conducted at 1100℃ in air.The Y content of the samples is determined by the actual pickup amount obtained from an Inductively Coupled Plasma-Atomic Emission Spectrometry test.It is discovered that the addition of Y increases the oxide resistance by the scale of an adhesive double-layer oxide,which is composed of Al_(2)O_(3) and spinel Ni(Cr,Al)_(2)O_(4).With 70 ppm of Y addition,the oxidation mass gain decreases from 12.6 g/m^(2) for the alloy without Y addition to 5.3 g/m^(2),and the oxidation rate decreases significantly.In addition,the internal nitride disappears after Y doping because of an increase in oxidation scale adherence and a decrease in oxidation products.In this study,the alloy with 660 ppm Y addition demonstrates the best oxidation resistance.
基金the support from the Natural Science Foundation of Hunan Province,China(2024JJ7301)the science and technology innovation Program of Hunan Province(2024JK2097)+5 种基金the Project of the Scientific Research Fund of Hunan Provincial Education Department(No.22C0383)Changde Scientific and Technological Innovation Plan(CDKJJ20220517)Start-up Foundation for Doctors of Hunan University of Arts and Science(No.22BSQD22,21BSQD14 and 21BSQD15)Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Provincepartially supported by the Research Grants Council of the Hong Kong Special Administrative Region,China(PolyU152178/20E)the Innovation and Technology Commission of Hong Kong(MHP/080/22)。
文摘Elevating the operating voltage is an effective approach to improve the reversible capacity of ultra-high nickel layered oxide cathode LiNi_(x)Co_(y)Mn_(z)O_(2)(NCM,x≥0.8)and solve the"range anxiety"confusion of electric vehicles.However,the undesirable surface reconstruction induced by the high cut-off voltage has a fatal impact on the thermodynamic stability of the material,inevitably leading to fast capacity degradation.Herein,a mechanical fusion aided by alcohol is suggested to create a stable olivine structure for the single-crystal(SC)ultrahigh-nickel cathode LiNi_(0.92)Co_(0.04)Mn_(0.04)O_(2).The addition of nanoparticles effectively bridges the void of SC-NCM,builds an ideal particle grading,and significantly raises the cost efficiency,as well as promotes the cycling stability and safety of the full cell.Remarkably,the layered/olivine mixture forms a perfect shield by lowering the surface area between the NCM cathode and electrolyte,hence mitigating side reactions and contributing to an incredibly thin and stable cathode/electrolyte interface.Furthermore,the thermodynamic stability of highly delithiated NCM is improved,as both the particle cracks and structural degradation are simultaneously postponed.Consequently,the maximum temperature of the single-crystal LiNi_(0.92)Co_(0.04)Mn_(0.04)O_(2)@LiFePO_(4)‖graphite pouch full cell is dramatically reduced from 599.4 to 351.4℃,and the full cell achieves 88.2%capacity retention after 800 cycles,demonstrating excellent thermal stability and cycling stability.This facile strategy provides a feasible technical reference for further exploiting the ultrahigh-capacity,highsafety,and long-life Ni-rich cathode for commercial application of lithium-ion batteries(LIBs).
基金supported by the National Youth Talent Support Program,the National Science and Technology Major Project(No.HT-J2019-VI-0020-0136)the Excellent Youth Foundation of Shaanxi Province of China(No.2021JC-08)+1 种基金the Natural Science Basic Research Plan in Shaanxi Province of China(No.2022JQ-553)the China Postdoctoral Science Foundation(No.2021M692555).
文摘Microscale stray grains(MSGs),which are composed of misoriented and fragmented high-ordered dendrite arms,small-sized equiaxed grains,and columnar grains,are a novel grain defect that occurs within the shrouds of single-crystal(SC)blades made from Ni-based superalloy.State-of-the-art non-destructive testing methods are incapable of detecting this defect,resulting in a high-risk application of SC blades.This study aims to control this defect by systematically investigating directional solidification processing parameters,shroud dimensions,and rhenium(Re)content in the formation of MSG defects.The results reveal that the defect forms exclusively at the overhanging extremities of the upper shrouds on the back side of the blades that face the heater.Increasing the withdrawal rate reduces the occurrence of MSG defects.As the shroud dimensions increase,MSG defects appear in the transition area between the downward suspended extremity of the blade shroud and the side of the blade body,as well as near the corner of the downward suspended extremity of the shroud.The occurrence of MSG defects increases with increasing shroud dimensions.Varying Re content sharply decreases the formation of MSG defects.A concentration-attached Rayleigh-Taylor instability(RTI)superheating(CARTISH)model,considering solidification shrinkage,was proposed to comprehend the formation of MSG defects.Simulation results based on this model are consistent with the experimentally observed distribution and degree of MSG defects under different conditions.Effective control of the CARTISH is critical to managing MSG defects.
文摘Catalysts for CO_(2)value-added conversion have been extensively explored,but there is still a lack of systematic design for catalysts that achieve efficient CO_(2)conversion under mild conditions.Herein,we explored a mesoporous CeO_(2)single-crystal formed with the regulation of ionic liquids,which catalyzed the effective carbonylation reaction with CO_(2)under mild reaction conditions.By altering the synthetic environment,a series of uniform mesoporous CeO_(2)particles with atomically aligned single-crystal frameworks were constructed,which have different surface physicochemical properties and primary aggregation degree.The prepared mesoporous CeO_(2)single-crystal achieved efficient activation of CO_(2)and alcohols at 0.5 MPa CO_(2)and 100℃,and the CeO_(2)-IL-M catalyst shows optimal catalytic performance in the synthesis of ethylene carbonate with 46.22 mmol g^(–1)h^(–1),which was 50.6 times as high as that of the CeO_(2)obtained without ionic liquids.Subsequently,the catalytic pathway and mechanism of carbonylation reaction with CO_(2)on mesoporous CeO_(2)single-crystal were studied via React-IR spectra and C18O_(2)labeling experiments.The research provides a new strategy for controllable nanoscale assembly of mesoporous single-crystal materials and expands the application range of single-crystal materials,aiming to develop novel catalytic materials to meet industrial needs.
基金Projects(50374082,5071112018)supported by the National Natural Science Foundation of China
文摘Based on the high-purity single-crystal tungsten nanowire firstly prepared by the metal-catalyzed vapor-phase reaction method, molecular dynamics method was used to calculate tensile stress-strain curves and simulate microscopic deformation structures of the single-crystal tungsten nanowires with different crystal orientations of 〈100〉, 〈110〉and 〈111〉, in order to reveal the effect of crystal orientation on their tensile mechanical properties and failure mechanisms. Research results show that all of the stress-strain curves are classified into four stages： elastic stage, damage stage, yielding stage and failure stage, where 〈100〉orientation has a special hardening stage after yielding and two descending stages. The crystal orientation has little effect on elastic modulus but great effect on tensile strength, yielding strength and ductility, depending on different atomic surface energies and principal sliding planes. The calculated values of elastic modulus are in good agreement with the tested values of elastic modulus.
基金Project (2010ZF21007) supported by the Aeronautical Science Foundation of China
文摘The dynamic recrystallization behavior of single-crystal（SC） superalloy SR.R99 at low strain rate was investigated by high-temperature creep testing.The results show that dynamic recrystallization may take place after the uncoated samples have been creep-tested in air at high temperature and low stress for a long time.Both the threshold temperature and strain for the dynamic recrystallization of SC superalloy SRR99 at low strain rate are lower than those for the static recrystallization.Dynamically recrystallized grains with the depth less than 15 μm are only located in the surface γ＇-free layers,and the recrystallized grains are well-developed grains without columnar y＇precipitates within them.The dynamic recrystallization behavior of SC superalloy SRR99 at low strain rate is mainly related to high-temperature oxidation.Suitable protective coating can effectively prevent the dynamic recrystallization of SC superalloy components in service.In addition,the dynamic recrystallization behavior of SC superalloy SRR99 at high strain rate was also studied by high-temperature compression testing.At high strain rate,a higher temperature and larger strain are needed for the occurrence of dynamic recrystallization than at low strain rate,and the recrystallized grains have cellular structures with an amount of columnar γ＇ precipitates within them.
基金financial supports from the National Natural Science Foundation of China (51974368)the Fundamental Research Funds of the Central South University,China。
文摘Single-crystal Ni-rich cathode material LiNi0.88Co0.09Al0.03O2(SC) was synthesized by a high-temperature solid-state calcination method. Physicochemical properties of primary and delithiated SC samples were investigated by X-ray diffractometry, X-ray photoelectron spectroscopy, and transmission electron microscopy. Electrochemical performance was characterized by long-term cycling, cyclic voltammetry, and in-situ impedance spectroscopy. The results indicated that high temperature rendered layered oxides to lose lithium/oxygen in the interior and exterior, and induced cationic disordering. Besides, the solid-phase synthesis process promoted phase transformation for electrode materials, causing the coexisting multi-phase in a single particle. High temperature can foster the growth of single particles, but it caused unstable structure of layered phase.
基金the National Natural Science Foundation of China Nos.51671053 and 51801021the Ministry of Industry and Information Technology Project No.MJ-2017-J-99)。
文摘MCrAlY(M=Ni and/or Co)overlay coating is widely used as a protective coating against high temperature oxidation and corrosion.However,due to its big difference in chemical composition with the underlying superalloy,elements interdiffusion occurs inevitably.One of the direct results is the formation of interdiffusion zone(IDZ)and secondary reaction zone(SRZ)with a high density of fine topological closed-packed phases(TCPs),weakening dramatically the mechanical properties of the alloy substrate.It is by now the main problem of modern high-temperature metallic coatings,but there are still hardly any reports studying the formation,growth and transformation of IDZ and SRZ in deep,as well as the precipitation of TCPs.In this work,a typical NiCrAlY coating is deposited by arc ion plating on a single-crystal superalloy N5.Elements interdiffusion between them and its relationship on microstructure were clarified.Cr rather than Al from the coating diffuses into the alloy at high temperatures and segregates immediately beneath their interface,contributing largely to the formation of IDZ.Simultaneously,diffusion of Ni from the deep alloy to IDZ leads to the formation and continuous expansion of SRZ.
基金This work was financially supported by the Natural Science Foundation of Beijing,China(No.4192038)National Key Research and Development Program of China(Nos.2016YFE0133200 and 2018YFB0406501)European Union’s Horizon 2020 Research and Innovation Staff Exchange Scheme(No.734578).
文摘Chemical vapor deposition(CVD)-grown diamond films have been developed as irradiation-resistant materials to replace or upgrade current detectors for use in extreme radiation environments. However, their sensitivity in practical applications has been inhibited by space charge stability issues caused by defects and impurities in pure diamond crystal materials. In this study, two high-quality CVD-grown single-crystal diamond(SCD) detectors with low content of nitrogen impurities were fabricated and characterized. The intrinsic properties of the SCD samples were characterized using Raman spectroscopy, stereomicroscopy, and X-ray diffraction with the rocking curve mode, cathode luminescence(CL), and infrared and ultraviolet-visible-near infrared spectroscopies. After packaging the detectors, the dark current and energy resolution under α particle irradiation were investigated. Dark currents of less than 5 pA at 100 V were obtained after annealing the electrodes, which is comparable with the optimal value previously reported. The detector that uses a diamond film with higher nitrogen content showed poor energy resolution, whereas the detector with more dislocations showed poor charge collection efficiency(CCE). This demonstrates that the nitrogen content in diamond has a significant effect on the energy resolution of detectors, while the dislocations in diamond largely contribute to the poor CCE of detectors.
