Multi-component transition group metal borides(MMB_(2))have become a research hotspot due to their new composition design concepts and superior properties compared with conventional ceramics.Most of the current method...Multi-component transition group metal borides(MMB_(2))have become a research hotspot due to their new composition design concepts and superior properties compared with conventional ceramics.Most of the current methods,however,are complicated and time-consuming,the mass production remains a chal-lenge.Herein,we proposed a new high-efficiency strategy for synthesis of MMB_(2)using molten aluminum as the medium for the first time.The prepared Al-containing multi-component borides(TiZrHfNbTa)B_(2)microcrystals had a homogeneous composition with a hexagonal AlB_(2)structure and ultra-high hardness value of∼35.3 GPa,which was much higher than data reported in the literature and the rule of mix-ture estimations.Furthermore,combined with the First-principles calculation results,we found that the Poisson’s ratio(v)values exhibit a clearly ascending trend from 0.17 at VEC=3.5 to 0.18 at VEC=3.4,then to 0.201 at VEC=3.2 with the increasing of Al content.This indicates that the intrinsic toughness of multi-component boride microcrystals is obviously enhanced by the trace-doped Al elements.Besides,the fabricated Al-containing multi-component boride microcrystals have superior oxidation activation en-ergy and structural stability.The enhanced oxidation resistance is mainly attributed to the formation of a protective Al2 O3 oxide layer and the lattice distortion,both of which lead to sluggish diffusion of O_(2).These findings propose a new unexplored avenue for the fabrication of MMB_(2)materials with supe-rior comprehensive performance including ultra-hardness and intrinsically improved thermo-mechanical properties.展开更多
The unique structure and exceptional properties of two-dimensional(2D)materials offer significant potential for transformative advancements in semiconductor industry.Similar to the reliance on wafer-scale single-cryst...The unique structure and exceptional properties of two-dimensional(2D)materials offer significant potential for transformative advancements in semiconductor industry.Similar to the reliance on wafer-scale single-crystal ingots for silicon-based chips,practical applications of 2D materials at the chip level need large-scale,high-quality production of 2D single crystals.Over the past two decades,the size of 2D single-crystals has been improved to wafer or meter scale,where the nucleation control during the growth process is particularly important.Therefore,it is essential to conduct a comprehensive review of nucleation control to gain fundamental insights into the growth of 2D single-crystal materials.This review mainly focuses on two aspects:controlling nucleation density to enable the growth from a single nucleus,and controlling nucleation position to achieve the unidirectionally aligned islands and subsequent seamless stitching.Finally,we provide an overview and forecast of the strategic pathways for emerging 2D materials.展开更多
Transition-metal monosilicide RhGe has been reported to exhibit weak itinerant ferromagnetism,superconductivity,and topological properties.In this study,we report the high-pressure growth of high-quality RhGe single c...Transition-metal monosilicide RhGe has been reported to exhibit weak itinerant ferromagnetism,superconductivity,and topological properties.In this study,we report the high-pressure growth of high-quality RhGe single crystals up to millimeter size using a flux method.Transport measurements reveal metallic behavior in RhGe from 2 K to 300 K with Fermi liquid behavior at low temperatures.However,no superconductivity was observed with variations in the Ge composition.Magnetic characterizations indicate that RhGe exhibits paramagnetic behavior between 2 K and 300 K.The high-quality and large-size RhGe single crystals pave the way for further investigation of their topological properties using spectroscopic techniques.展开更多
Polysynthetic twinned(PST)TiAl single crystal specifically refers to a fully lamellar TiAl single crystal with parallel phase interfaces and twin interfaces grown by directional solidification.In this paper,PST single...Polysynthetic twinned(PST)TiAl single crystal specifically refers to a fully lamellar TiAl single crystal with parallel phase interfaces and twin interfaces grown by directional solidification.In this paper,PST single crystals with different phase ratios are obtained by annealing at specific temperatures and holding times.The results show that the diffusion rates of Ti and Al elements at various temperatures directly trigger and propel the surface recrystallization and variation in the internal phase ratio.When the temperature is lower than 1448 K,the diffusion rate of Ti is obviously higher than that of Al,which causes one denseα_(2)recrystallized layer to form on the surface of TiAl single crystals.Meanwhile,as more Ti elements migrate to the surface,theα_(2)phase ratio inside the TiAl single crystal thereby decreases.When the temperature exceeds 1448 K,the diffusion rate of Al gradually reverses to exceed that of Ti,which forms the surface sandwiched recrystallization dominated byγphase and simultaneously increasesα_(2)phase ratio inside the TiAl single crystal.The variation in the two-phase ratio directly induces a significant change in the lamellae thickness,which exhibits different tensile behaviors of PST-TiAl single crystal.When theα_(2)phase content is less than 20%,widerγlamellae make it easier for dislocations to be activated within its lamellae and continuously move across theγ/α_(2)interfaces,thereby obtaining better tensile plasticity.As theα_(2)phase content exceeds 30%,finerγlamellae inhibit the dislocation initiation,resulting in the fracture occurrence of TiAl single crystal before yielding.No matter how the phase ratio changes,the crack preferentially initiates withinα_(2)lamellae.However,the crack propagation follows different paths based on variousγlamella thicknesses.The fracture mode of PST-TiAl single crystal also changes from shear fracture along slip bands within theγlamella to brittle fracture along the{1¯100}planes withinα_(2)lamella.展开更多
Although three-dimensional metal halide perovskites are promising candidates for direct X-ray detection,the ion migration of perovskites seriously affects the detector stability.Herein,face-/edge-shared 3D heterometal...Although three-dimensional metal halide perovskites are promising candidates for direct X-ray detection,the ion migration of perovskites seriously affects the detector stability.Herein,face-/edge-shared 3D heterometallic glycinate hybrid perovskitoid Pb_(2)CuGly_(2)X_(4)(Gly=-O_(2)C-CH_(2)-NH_(2);X=Cl,Br)single crystals(SCs),in which the adjacent lead halide layers are linked by large-sized Cu(Gly)_(2)pillars,are synthesized in water.The Cu(Gly)_(2)pillars in combination with face-/edge-shared inorganic skeleton are found able to synergistically suppress the ion migration,delivering a high ion migration activation energy(Ea)of 1.06 eV.The Pb_(2)CuGly_(2)Cl_(4)SC X-ray detector displays extremely low dark current drift of 1.20×10^(-9)nA mm^(-1)s^(-1)V^(-1)under high electric field(120 V mm^(-1))and continuous X-ray irradiation(2.86 Gy),and a high sensitivity of 9,250μC Gy^(-1)cm^(-2)is also achieved.More excitingly,the Pb_(2)CuGly_(2)Cl_(4)nanocrystal can be easily dispersed in water and directly blade-coated on thin-film transistor(TFT)array substrate,and the obtained Pb_(2)CuGly_(2)Cl_(4)-based TFT array detector offers an X-ray imaging capability with spatial resolution of 2.2 lp mm^(-1).展开更多
The(010)-oriented substrates of β-Ga_(2)O_(3) are endowed with the maximum thermal conductivity and fastest homoepi-taxial rate,which is the preferred substrate direction for high-power devices.However,the size of(01...The(010)-oriented substrates of β-Ga_(2)O_(3) are endowed with the maximum thermal conductivity and fastest homoepi-taxial rate,which is the preferred substrate direction for high-power devices.However,the size of(010)plane wafer is critically limited by die in the commercial edge-defined film-fed growth(EFG)method.It is difficult to grow the β-Ga_(2)O_(3) crystal with(010)principal face due to the(100)and(001)are cleavage planes.Here,the 2-inch diameter(010)principal-face β-Ga_(2)O_(3) sin-gle crystal is successfully designed and grown by improved EFG method.Unlike previous reported techniques,the single crys-tals are pulled with[001]direction,and in this way the(010)wafers can be obtained from the principal face.In our experi-ments,tree-like defects(TLDs)in(010)principal-face bulk crystals are easy to generate.The relationship between stability of growth interface and origin of TLDs are thoroughly discussed.The TLDs are successfully eliminated by optimizing growth condi-tions.The high crystalline quality of(010)-oriented substrates are comprehensive demonstrated by full width at half maximum(FWHM)with 50.4 arcsec,consistent orientation arrangement of(010)plane,respectively.This work shows that the(010)-ori-ented substrates can be obtained by EFG method,predicting the commercial prospects of large-scale(010)-oriented β-Ga_(2)O_(3) substrates.展开更多
In contrast to research on active sites in nanomaterials,lithium tantalate single crystals,known for their exceptional optical properties and long-range ordered lattice structure,present a promising avenue for in-dept...In contrast to research on active sites in nanomaterials,lithium tantalate single crystals,known for their exceptional optical properties and long-range ordered lattice structure,present a promising avenue for in-depth exploration of photocatalytic reaction systems with fewer constraints imposed by surface chemistry.Typically,the isotropy of a specific facet provides a perfect support for studying heteroatom doping.Herein,this work delves into the intrinsic catalytic sites for photocatalytic nitrogen fixation in iron-doped lithium tantalate single crystals.The presence of iron not only modifies the electronic structure of lithium tantalate,improving its light absorption capacity,but also functions as an active site for the nitrogen adsorption and activation.The photocatalytic ammonia production rate of the iron-doped lithium tantalate in pure water is maximum 26.95μg cm^(−2)h^(−1),which is three times higher than that of undoped lithium tantalate.The combination of first-principles simulations with in situ characterizations confirms that iron doping promotes the rate-determining step and changes the pathway of hydrogenation to associative alternating.This study provides a new perspective on in-depth investigation of intrinsic catalytic active sites in photocatalysis and other catalytic processes.展开更多
Sulfide-based all-solid-state lithium batteries suffer from electrochemo-mechanical damage to Ni-rich oxide-based cathode active materials(CAMs),primarily caused by severe volume changes,results in significant stress ...Sulfide-based all-solid-state lithium batteries suffer from electrochemo-mechanical damage to Ni-rich oxide-based cathode active materials(CAMs),primarily caused by severe volume changes,results in significant stress and strain,causes micro-cracks and interfacial contact loss at potentials>4.3 V(vs.Li/Li^(+)).Quantifying micro-cracks and voids in CAMs can reveal the degradation mechanisms of Ni-rich oxidebased cathodes during electrochemical cycling.Nonetheless,the origin of electrochemical-mechanical damage remains unclear.Herein,We have developed a multifunctional PEG-based soft buffer layer(SBL)on the surface of carbon black(CB).This layer functions as a percolation network in the single crystal LiNi_(0.83)Co_(0.07)Mn_(0.1)O_(2)and Li_(6)PS_(5)Cl composite cathode layer,ensuring superior ionic conductivity,reducing void formation and particle cracking,and promoting uniform utilization of the cathode active material in all-solid-state lithium batteries(ASSLBs).High-angle annular dark-field STEM combined with nanoscale X-ray holo-tomography and plasma-focused ion beam scanning electron microscopy confirmed that the PEG-based SBL mitigated strain induced by reaction heterogeneity in the cathode.This strain produces lattice stretches,distortions,and curved transition metal oxide layers near the surface,contributing to structural degradation at elevated voltages.Consequently,ASSLBs with a LiNi_(0.83)Co_(0.07)Mn_(0.1)O_(2)cathode containing LCCB-10(CB/PEG mass ratio:100/10)demonstrate a high areal capacity(2.53 mAh g^(-1)/0.32 mA g^(-1))and remarkable rate capability(0.58 mAh g^(-1)at 1.4 mA g^(-1)),with88%capacity retention over 1000 cycles.展开更多
The deformation and fracture of a third-generation single crystal superalloy during in-situ tension at room temperature were investigated at multiple scales by scanning electron microscope,electron back-scattered diff...The deformation and fracture of a third-generation single crystal superalloy during in-situ tension at room temperature were investigated at multiple scales by scanning electron microscope,electron back-scattered diffractometer,and transmission electron microscope to reveal the deformation and fracture mechanism during tension.The proportion of low angle boundaries(LABs)with angles from 2.5°to 5.5°increases during tension.The change in LABs is particularly pronounced after elongation over 7%.The initiation of microcracks is caused by{111}<110>slip systems.After initiation,the crack size along the stress direction increases whereas the size extension along slip systems is suppressed.The fracture mode of the alloy is quasi-cleavage fracture and the slip lines near the fracture are implicit at room temperature.展开更多
The microstructure of single crystal superalloy is relatively simple,consisting primarily ofγdendrites andγ/γ′eutectics.During the directional solidification process of Ni-based single crystal superalloys,withdraw...The microstructure of single crystal superalloy is relatively simple,consisting primarily ofγdendrites andγ/γ′eutectics.During the directional solidification process of Ni-based single crystal superalloys,withdrawal rate is a critical parameter affecting the spatial distribution ofγ/γ′eutectic along gravity direction.The results show that theγ/γ′eutectic fraction of the upper platform surface is always higher than that of the lower one,regardless of withdrawal rate.As the withdrawal rate decreases,there is a significant increase inγ/γ′eutectic fraction on the upper surface,while it decreases on the lower surface.The upward accumulation ofγ/γ′eutectic becomes more severe as the withdrawal rate decreases.It is also found that the percentage of Al+Ta is positively correlated with theγ/γ′eutectic fraction.Thermo-solute convection of Al and Ta solutes in the solidification front is the prime reason for the non-uniform distribution of eutectic.The non-uniform distribution ofγ/γ′eutectic cannot be eliminated even after subsequent solution heat treatment,resulting in excess eutectic on the upper surface and thus leading to the scrapping of the blade.展开更多
Lead magnesium niobate-lead titanate(PMN-PT)piezoelectric single crystals are widely utilized due to their outstanding performance,with varying compositions significantly impacting their properties.While application o...Lead magnesium niobate-lead titanate(PMN-PT)piezoelectric single crystals are widely utilized due to their outstanding performance,with varying compositions significantly impacting their properties.While application of PMN-PT in high-power settings is rapidly evolving,material parameters are typically tested under low signal conditions(1 V),and effects of different PT(PbTiO_(3))contents on the performance of PMN-PT single crystals under high-power conditions remain unclear.This study developed a comprehensive high-power testing platform using the constant voltage method to evaluate performance of PMN-PT single crystals with different PT contents under high-power voltage stimulation.Using crystals sized at 10 mm×3 mm×0.5 mm as an example,this research explored changes in material parameters.The results exhibit that while trend of the parameter changes under high-power excitation was consistent across different PT contents,degree of the change varied significantly.For instance,a PMN-PT single crystal with 26%(in mol)PT content exhibited a 25%increase in the piezoelectric coefficient d_(31),a 13%increase in the elastic compliance coefficient s_(11)^(E),a 17%increase in the electromechanical coupling coefficient k_(31),and a 73%decrease in the mechanical quality factor Q_(m) when the power reached 7.90 W.As the PT content increased,the PMN-PT materials became more susceptible to temperature influences,significantly reducing the power tolerance and more readily reaching the depolarization temperatures.This led to loss of piezoelectric performance.Based on these findings,a clearer understanding of impact of PT content on performance of PMN-PT single crystals under high-power applications has been established,providing reliable data to support design of sensors or transducers using PMN-PT as the sensitive element.展开更多
The lattice parameter,measured with sufficient accuracy,can be utilized to evaluate the quality of single crystals and to determine the equation of state for materials.We propose an iterative method for obtaining more...The lattice parameter,measured with sufficient accuracy,can be utilized to evaluate the quality of single crystals and to determine the equation of state for materials.We propose an iterative method for obtaining more precise lattice parameters using the interaction points for the pseudo-Kossel pattern obtained from laser-induced X-ray diffraction(XRD).This method has been validated by the analysis of an XRD experiment conducted on iron single crystals.Furthermore,the method was used to calculate the compression ratio and rotated angle of an LiF sample under high pressure loading.This technique provides a robust tool for in-situ characterization of structural changes in single crystals under extreme conditions.It has significant implications for studying the equation of state and phase transitions.展开更多
Organic semiconductor materials have shown unique advantages in the development of optoelectronic devices due to their ease of preparation,low cost,lightweight,and flexibility.In this work,we explored the application ...Organic semiconductor materials have shown unique advantages in the development of optoelectronic devices due to their ease of preparation,low cost,lightweight,and flexibility.In this work,we explored the application of the organic semiconductor Y6-1O single crystal in photodetection devices.Firstly,Y6-1O single crystal material was prepared on a silicon substrate using solution droplet casting method.The optical properties of Y6-1O material were characterized by polarized optical microscopy,fluorescence spectroscopy,etc.,confirming its highly single crystalline performance and emission properties in the near-infrared region.Phototransistors based on Y6-1O materials with different thicknesses were then fabricated and tested.It was found that the devices exhibited good visible to near-infrared photoresponse,with the maximum photoresponse in the near-infrared region at 785 nm.The photocurrent on/off ratio reaches 10^(2),and photoresponsivity reaches 16 mA/W.It was also found that the spectral response of the device could be regulated by gate voltage as well as the material thickness,providing important conditions for optimizing the performance of near-infrared photodetectors.This study not only demonstrates the excellent performance of organic phototransistors based on Y6-1O single crystal material in near-infrared detection but also provides new ideas and directions for the future development of infrared detectors.展开更多
For emerging renewable and sustainable energy technologies,single crystal materials have become key materials to enhance electrocatalytic performance because of their atomic-level ordered structures and tailorable sur...For emerging renewable and sustainable energy technologies,single crystal materials have become key materials to enhance electrocatalytic performance because of their atomic-level ordered structures and tailorable surface and interfacial properties.Various single crystal types,including metals,semiconductors,ceramics,organics,and nanocrystals,exhibit superior catalytic selectivity and stability in reactions such as water splitting and carbon/nitrogen cycles,benefiting from high electrical conductivity,tunable energy bands,and active sites with high surface energy.Through surface modification,interfacial atomic doping,and heterostructure construction,the distribution of active sites,electronic structure,and mass transport can be precisely regulated,significantly optimizing the catalytic kinetics of single crystal materials.In situ characterizations elucidate catalytic mechanisms at the atomic scale,while emerging methods like AI-assisted synthesis and bio-template directed growth offer pathways to overcome bottlenecks in the precision and cost of single crystal preparation.In addressing stability challenges in complex environments,strategies such as organic-inorganic hybridization and gradient interface design effectively mitigate interfacial instability.Future research should focus on cross-scale structural regulation and multidisciplinary integration to facilitate the transition of single crystal electrocatalysts from fundamental research to industrial applications,enabling efficient energy conversion.展开更多
To enhance the high-temperature oxidation resistance and mechanical properties of a secondgeneration nickel-based superalloy,various concentrations of lanthanum(La)ranging from 5.0×10^(-5)wt.%to 3.4×10^(-4)w...To enhance the high-temperature oxidation resistance and mechanical properties of a secondgeneration nickel-based superalloy,various concentrations of lanthanum(La)ranging from 5.0×10^(-5)wt.%to 3.4×10^(-4)wt.%are added to the alloy.The microstructure of the nickel-based single crystal superalloy with trace of La was examined by means of SEM,EDS and TEM.Results show the addition of La decreases the segregation of elements and increases the amount ofγ/γ′eutectics of the as-cast alloy,and in the interdendritic region,the growth of eutectics is accompanied by the growth of strip clusters composed of Ni_(5)La and Ni_(3)Ta.As the La content in the alloy increases,the proportion of Ni_(5)La in the cluster increases.After heat treatment,incipient melting occurs in the cluster regions,leading to an increase in microporosity compared to the original as-cast samples.Furthermore,the heat treatment alters the shape of the clusters from a strip morphology to an elliptical one,and it changes their composition from Ni_(5)La and Ni_(3)Ta to a combination of Ni_(5)La,Ni_(3)Ta,and MC carbides.展开更多
The effects of synthesis conditions,especially the heating rate,on the reaction kinetics of Ni-rich cathodes were systematically studied.The growth rate of Ni-rich oxide increases continuously as the heating rate incr...The effects of synthesis conditions,especially the heating rate,on the reaction kinetics of Ni-rich cathodes were systematically studied.The growth rate of Ni-rich oxide increases continuously as the heating rate increases.Ab initio molecular dynamics simulations demonstrate that a high heating rate induces anabatic oscillations,indicating a decrease in thermodynamic stability and a tendency for the crystal surface to undergo reconstruction.The presence of an intermediate phase at the grain boundary amplifies atomic migration-induced interface fusion and consequently augments crystal growth kinetics.However,the excessively high heating rate aggravates the Li+/Ni2+mixing in the Ni-rich cathode.The single-crystal Ni-rich cathode exhibits enhanced structural/thermal stability but a decreased specific capacity and rate performance compared with its polycrystalline counterpart.展开更多
Due to the high hardness and low fracture toughness of the single crystal silicon(SCS),it is highly susceptible to microscopic cracks and subsurface damage during processing.In this paper,we propose to adjust the mech...Due to the high hardness and low fracture toughness of the single crystal silicon(SCS),it is highly susceptible to microscopic cracks and subsurface damage during processing.In this paper,we propose to adjust the mechanical properties of SCS by cold plasma jet,and systematically investigate the influences of the plasma on material deformation and damage mechanisms by nanoscratch tests.The results indicate that the plasma can increase the critical normal force for the plastic-brittle(P-B)conversion of SCS.Compared with the ordinary nanoscratch test,the critical force for P-B conversion of plasma-assisted scratching at 1μm/s can increase from 43.6 to 66.4 mN.Increasing the scratching speed under ordinary conditions can enhance the plastic deformability of SCS to some extent,but its effect is not as effective as that of plasma;in addition,the increased scratching speed causes the shear bands(SBs)to lack time to propagate,so the quantity of SBs under plasma-assisted scratching at 10μm/s is reduced compared to 1μm/s.From subsurface damage topographies,the highly localized amorphous SBs cause the generation of subsurface cracks.The cold plasma can alleviate cracks on the scratched subsurface of SCS by introducing multiple SBs and stacking faults.This paper may provide a novel strategy for high-efficiency and low-damage ultra-precision machining of hard and brittle materials.展开更多
The effects of temperature and Re content on the mechanical properties,dislocation morphology,and deformation mechanism of γ-γ′phases nickel-based single crystal superalloys are investigated by using the molecular ...The effects of temperature and Re content on the mechanical properties,dislocation morphology,and deformation mechanism of γ-γ′phases nickel-based single crystal superalloys are investigated by using the molecular dynamics method through the model of γ-γ′phases containing hole defect.The addition of Re makes the dislocation distribution tend towards the γ phase.The higher the Re content,the earlier theγphase yields,while the γ′phase yields later.Dislocation bends under the combined action of the applied force and the resistance of the Re atoms to form a bend point.The Re atoms are located at the bend points and strengthen the alloy by fixing the dislocation and preventing it from cutting the γ′phase.Dislocations nucleate first in the γ phase,causing theγphase to deform plastically before the γ′phase.As the strain increases,the dislocation length first remains unchanged,then increases rapidly,and finally fluctuates and changes.The dislocation lengths in the γ phase are larger than those in the γ′phase at different temperatures.The dislocation length shows a decreasing tendency with the increase of the temperature.Temperature can affect movement of the dislocation,and superalloys have different plastic deformation mechanisms at low,medium and high temperatures.展开更多
Arising from the increasing demand for electric vehicles(EVs),Ni-rich LiNi_(x)Co_(y)Mn_(z)O_(2)(NCM,x+y+z=1,x≥0.8)cathode with greatly increased energy density are being researched and commercialized for lithium-ion ...Arising from the increasing demand for electric vehicles(EVs),Ni-rich LiNi_(x)Co_(y)Mn_(z)O_(2)(NCM,x+y+z=1,x≥0.8)cathode with greatly increased energy density are being researched and commercialized for lithium-ion batteries(LIBs).However,parasitic crack formation during the discharge–charge cycling process remains as a major degradation mechanism.Cracking leads to increase in the specific surface area,loss of electrical contact between the primary particles,and facilitates liquid electrolyte infiltration into the cathode active material,accelerating capacity fading and decrease in lifetime.In contrast,Ni-rich NCM when used as a single crystal exhibits superior cycling performances due to its rigid mechanical property that resists cracking during long charge–discharge process even under harsh conditions.In this paper,we present comparative investigation between single crystal Ni-rich LiNi_(0.92)Co_(0.04)Mn_(0.04)O_(2)(SC)and polycrystalline Ni-rich LiNi_(0.92)Co_(0.04)Mn_(0.04)O_(2)(PC).The relatively improved cycling performances of SC are attributed to smaller anisotropic volume change,higher reversibility of phase transition,and resistance to crack formation.The superior properties of SC are demonstrated by in situ characterization and battery tests.Consequently,it is inferred from the results obtained that optimization of preparation conditions can be regarded as a key approach to obtain well crystallized and superior electrochemical performances.展开更多
To investigate the microstructure and creep properties of a hot corrosion resistant Ni-based single crystal superal oy containing different hafnium(Hf)additions(0-0.4wt.%),creep test was performed at 980℃/200 MPa.Opt...To investigate the microstructure and creep properties of a hot corrosion resistant Ni-based single crystal superal oy containing different hafnium(Hf)additions(0-0.4wt.%),creep test was performed at 980℃/200 MPa.Optical microscopy,scanning electron microscopy,electron probe micro analysis(EPMA),and transmission electron microscopy were employed to analyze the microstructure differences.With the increase of Hf,the creep rupture life of the alloys at 980℃/200 MPa gradually increases.Microstructure analysis reveals that Hf promotes the transformation of carbide morphology from script to rod-like and finally to blocky.Upon the addition of Hf,there is an increase in the volume fraction of blocky MC carbides,along with an elevation in the partitioning ratio of Cr and Mo elements.Concurrently,theγ/γ′interfacial dislocation spacing undergoes a reduction.It is found that script carbides are more likely to cause stress concentration in high temperature creep,leading to nucleation and propagation of microcracks.The formation mechanism of blocky MC carbides is related to the increase in precipitation temperature and lattice constant,and its beneficial impact on creep resistance is also investigated based on the analysis of the creep test results.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52271033 and 52071179)the Key program of National Natural Science Foundation of China(No.51931003)+2 种基金Natural Science Foundation of Jiangsu Province,China(No.BK20221493)Jiangsu Province Leading Edge Technology Basic Research Major Project(No.BK20222014)Foundation of“Qinglan Project”for Colleges and Universities in Jiangsu Province.
文摘Multi-component transition group metal borides(MMB_(2))have become a research hotspot due to their new composition design concepts and superior properties compared with conventional ceramics.Most of the current methods,however,are complicated and time-consuming,the mass production remains a chal-lenge.Herein,we proposed a new high-efficiency strategy for synthesis of MMB_(2)using molten aluminum as the medium for the first time.The prepared Al-containing multi-component borides(TiZrHfNbTa)B_(2)microcrystals had a homogeneous composition with a hexagonal AlB_(2)structure and ultra-high hardness value of∼35.3 GPa,which was much higher than data reported in the literature and the rule of mix-ture estimations.Furthermore,combined with the First-principles calculation results,we found that the Poisson’s ratio(v)values exhibit a clearly ascending trend from 0.17 at VEC=3.5 to 0.18 at VEC=3.4,then to 0.201 at VEC=3.2 with the increasing of Al content.This indicates that the intrinsic toughness of multi-component boride microcrystals is obviously enhanced by the trace-doped Al elements.Besides,the fabricated Al-containing multi-component boride microcrystals have superior oxidation activation en-ergy and structural stability.The enhanced oxidation resistance is mainly attributed to the formation of a protective Al2 O3 oxide layer and the lattice distortion,both of which lead to sluggish diffusion of O_(2).These findings propose a new unexplored avenue for the fabrication of MMB_(2)materials with supe-rior comprehensive performance including ultra-hardness and intrinsically improved thermo-mechanical properties.
基金supported by the National Natural Science Foundation of China(12322406,12404208)the National Key R&D Program of China(2022YFA1403503)+2 种基金China Postdoctoral Science Foundation(2024M750970)the Science and Technology Program of Guangzhou(SL2024A04J00033)the Scientific Research lnnovation Project of Graduate School of South China Normal University.
文摘The unique structure and exceptional properties of two-dimensional(2D)materials offer significant potential for transformative advancements in semiconductor industry.Similar to the reliance on wafer-scale single-crystal ingots for silicon-based chips,practical applications of 2D materials at the chip level need large-scale,high-quality production of 2D single crystals.Over the past two decades,the size of 2D single-crystals has been improved to wafer or meter scale,where the nucleation control during the growth process is particularly important.Therefore,it is essential to conduct a comprehensive review of nucleation control to gain fundamental insights into the growth of 2D single-crystal materials.This review mainly focuses on two aspects:controlling nucleation density to enable the growth from a single nucleus,and controlling nucleation position to achieve the unidirectionally aligned islands and subsequent seamless stitching.Finally,we provide an overview and forecast of the strategic pathways for emerging 2D materials.
基金supported by the National Key Research&Development Program of China(Grant Nos.2023YFA1406000,2022YFA1403800,2021YFA1400300,and 2023YFA1406500)the National Natural Science Foundation of China(Grant Nos.12474002,22171283,12425403,12261131499,12304268,and 12274459)the China Postdoctoral Science Foundation(Grant Nos.2023M730011 and 2023M743741).
文摘Transition-metal monosilicide RhGe has been reported to exhibit weak itinerant ferromagnetism,superconductivity,and topological properties.In this study,we report the high-pressure growth of high-quality RhGe single crystals up to millimeter size using a flux method.Transport measurements reveal metallic behavior in RhGe from 2 K to 300 K with Fermi liquid behavior at low temperatures.However,no superconductivity was observed with variations in the Ge composition.Magnetic characterizations indicate that RhGe exhibits paramagnetic behavior between 2 K and 300 K.The high-quality and large-size RhGe single crystals pave the way for further investigation of their topological properties using spectroscopic techniques.
基金supported by the National Natural Science Foundation of China(NSFC)under Grant Nos.52288102,52322101,92163215,52174364,52101143,U23A20542the Fundamental Research Funds for the Central Universities under Grant No.30922010202+1 种基金the 100 Talents Plan of Hebei Province under Grant No.E2020100005the Natural Science Foundation of Hebei Province under Grant No.E2022203109.
文摘Polysynthetic twinned(PST)TiAl single crystal specifically refers to a fully lamellar TiAl single crystal with parallel phase interfaces and twin interfaces grown by directional solidification.In this paper,PST single crystals with different phase ratios are obtained by annealing at specific temperatures and holding times.The results show that the diffusion rates of Ti and Al elements at various temperatures directly trigger and propel the surface recrystallization and variation in the internal phase ratio.When the temperature is lower than 1448 K,the diffusion rate of Ti is obviously higher than that of Al,which causes one denseα_(2)recrystallized layer to form on the surface of TiAl single crystals.Meanwhile,as more Ti elements migrate to the surface,theα_(2)phase ratio inside the TiAl single crystal thereby decreases.When the temperature exceeds 1448 K,the diffusion rate of Al gradually reverses to exceed that of Ti,which forms the surface sandwiched recrystallization dominated byγphase and simultaneously increasesα_(2)phase ratio inside the TiAl single crystal.The variation in the two-phase ratio directly induces a significant change in the lamellae thickness,which exhibits different tensile behaviors of PST-TiAl single crystal.When theα_(2)phase content is less than 20%,widerγlamellae make it easier for dislocations to be activated within its lamellae and continuously move across theγ/α_(2)interfaces,thereby obtaining better tensile plasticity.As theα_(2)phase content exceeds 30%,finerγlamellae inhibit the dislocation initiation,resulting in the fracture occurrence of TiAl single crystal before yielding.No matter how the phase ratio changes,the crack preferentially initiates withinα_(2)lamellae.However,the crack propagation follows different paths based on variousγlamella thicknesses.The fracture mode of PST-TiAl single crystal also changes from shear fracture along slip bands within theγlamella to brittle fracture along the{1¯100}planes withinα_(2)lamella.
基金financially supported by the National Natural Science Foundation of China (62004089,62374053, 62474187 and 12235006)the Special Zone Support Program for Outstanding Talents of Henan University+4 种基金the Shenzhen Basic Research Program (JCYJ20220818101612027)the Guangdong Basic and Applied Basic Research Foundation (2024A1515012494)the Henan Province Postdoctoral Science Foundation (J23029Y)the Natural Science Foundation of Henan Province (232300420412)the Science and Technology Tackling Project of Henan Province (242102210160)
文摘Although three-dimensional metal halide perovskites are promising candidates for direct X-ray detection,the ion migration of perovskites seriously affects the detector stability.Herein,face-/edge-shared 3D heterometallic glycinate hybrid perovskitoid Pb_(2)CuGly_(2)X_(4)(Gly=-O_(2)C-CH_(2)-NH_(2);X=Cl,Br)single crystals(SCs),in which the adjacent lead halide layers are linked by large-sized Cu(Gly)_(2)pillars,are synthesized in water.The Cu(Gly)_(2)pillars in combination with face-/edge-shared inorganic skeleton are found able to synergistically suppress the ion migration,delivering a high ion migration activation energy(Ea)of 1.06 eV.The Pb_(2)CuGly_(2)Cl_(4)SC X-ray detector displays extremely low dark current drift of 1.20×10^(-9)nA mm^(-1)s^(-1)V^(-1)under high electric field(120 V mm^(-1))and continuous X-ray irradiation(2.86 Gy),and a high sensitivity of 9,250μC Gy^(-1)cm^(-2)is also achieved.More excitingly,the Pb_(2)CuGly_(2)Cl_(4)nanocrystal can be easily dispersed in water and directly blade-coated on thin-film transistor(TFT)array substrate,and the obtained Pb_(2)CuGly_(2)Cl_(4)-based TFT array detector offers an X-ray imaging capability with spatial resolution of 2.2 lp mm^(-1).
基金support by the fund of the National Natural Science Foundation of China(NSFC)(Grant No.U23A20358,51932004)Key-Area Research and Development Program of Guangdong Province(Grant No.2020B010174002)+3 种基金Natural Science Foundation of Shandong Province(Grant No.ZR2023ZD05,2022TSGC2120)the Shenzhen Fundamental Research Program(Grant No.GJHZ20220913142605011)the 111 Project 2.0(Grant No.BP2018013)Laboratory Construction and Management Research Project of Shandong University(Grant No.sy20233203)。
文摘The(010)-oriented substrates of β-Ga_(2)O_(3) are endowed with the maximum thermal conductivity and fastest homoepi-taxial rate,which is the preferred substrate direction for high-power devices.However,the size of(010)plane wafer is critically limited by die in the commercial edge-defined film-fed growth(EFG)method.It is difficult to grow the β-Ga_(2)O_(3) crystal with(010)principal face due to the(100)and(001)are cleavage planes.Here,the 2-inch diameter(010)principal-face β-Ga_(2)O_(3) sin-gle crystal is successfully designed and grown by improved EFG method.Unlike previous reported techniques,the single crys-tals are pulled with[001]direction,and in this way the(010)wafers can be obtained from the principal face.In our experi-ments,tree-like defects(TLDs)in(010)principal-face bulk crystals are easy to generate.The relationship between stability of growth interface and origin of TLDs are thoroughly discussed.The TLDs are successfully eliminated by optimizing growth condi-tions.The high crystalline quality of(010)-oriented substrates are comprehensive demonstrated by full width at half maximum(FWHM)with 50.4 arcsec,consistent orientation arrangement of(010)plane,respectively.This work shows that the(010)-ori-ented substrates can be obtained by EFG method,predicting the commercial prospects of large-scale(010)-oriented β-Ga_(2)O_(3) substrates.
基金supported by Natural Science Foundation of Shandong Province(Nos.ZR2022YQ42,ZR2021JQ15,ZR2021QE011,ZR2021ZD20,2022GJJLJRC-01)Innovative Team Project of Jinan(No.2021GXRC019)the National Natural Science Foundation of China(Nos.52022037,52202366).
文摘In contrast to research on active sites in nanomaterials,lithium tantalate single crystals,known for their exceptional optical properties and long-range ordered lattice structure,present a promising avenue for in-depth exploration of photocatalytic reaction systems with fewer constraints imposed by surface chemistry.Typically,the isotropy of a specific facet provides a perfect support for studying heteroatom doping.Herein,this work delves into the intrinsic catalytic sites for photocatalytic nitrogen fixation in iron-doped lithium tantalate single crystals.The presence of iron not only modifies the electronic structure of lithium tantalate,improving its light absorption capacity,but also functions as an active site for the nitrogen adsorption and activation.The photocatalytic ammonia production rate of the iron-doped lithium tantalate in pure water is maximum 26.95μg cm^(−2)h^(−1),which is three times higher than that of undoped lithium tantalate.The combination of first-principles simulations with in situ characterizations confirms that iron doping promotes the rate-determining step and changes the pathway of hydrogenation to associative alternating.This study provides a new perspective on in-depth investigation of intrinsic catalytic active sites in photocatalysis and other catalytic processes.
基金supported by the Hainan Province Science and Technology Special Fund(ZDYF2021SHFZ232,ZDYF2023GXJS022)the Hainan Province Postdoctoral Science Foundation(300333)the National Natural Science Foundation of China(21203008,21975025,12274025,22372008)。
文摘Sulfide-based all-solid-state lithium batteries suffer from electrochemo-mechanical damage to Ni-rich oxide-based cathode active materials(CAMs),primarily caused by severe volume changes,results in significant stress and strain,causes micro-cracks and interfacial contact loss at potentials>4.3 V(vs.Li/Li^(+)).Quantifying micro-cracks and voids in CAMs can reveal the degradation mechanisms of Ni-rich oxidebased cathodes during electrochemical cycling.Nonetheless,the origin of electrochemical-mechanical damage remains unclear.Herein,We have developed a multifunctional PEG-based soft buffer layer(SBL)on the surface of carbon black(CB).This layer functions as a percolation network in the single crystal LiNi_(0.83)Co_(0.07)Mn_(0.1)O_(2)and Li_(6)PS_(5)Cl composite cathode layer,ensuring superior ionic conductivity,reducing void formation and particle cracking,and promoting uniform utilization of the cathode active material in all-solid-state lithium batteries(ASSLBs).High-angle annular dark-field STEM combined with nanoscale X-ray holo-tomography and plasma-focused ion beam scanning electron microscopy confirmed that the PEG-based SBL mitigated strain induced by reaction heterogeneity in the cathode.This strain produces lattice stretches,distortions,and curved transition metal oxide layers near the surface,contributing to structural degradation at elevated voltages.Consequently,ASSLBs with a LiNi_(0.83)Co_(0.07)Mn_(0.1)O_(2)cathode containing LCCB-10(CB/PEG mass ratio:100/10)demonstrate a high areal capacity(2.53 mAh g^(-1)/0.32 mA g^(-1))and remarkable rate capability(0.58 mAh g^(-1)at 1.4 mA g^(-1)),with88%capacity retention over 1000 cycles.
文摘The deformation and fracture of a third-generation single crystal superalloy during in-situ tension at room temperature were investigated at multiple scales by scanning electron microscope,electron back-scattered diffractometer,and transmission electron microscope to reveal the deformation and fracture mechanism during tension.The proportion of low angle boundaries(LABs)with angles from 2.5°to 5.5°increases during tension.The change in LABs is particularly pronounced after elongation over 7%.The initiation of microcracks is caused by{111}<110>slip systems.After initiation,the crack size along the stress direction increases whereas the size extension along slip systems is suppressed.The fracture mode of the alloy is quasi-cleavage fracture and the slip lines near the fracture are implicit at room temperature.
基金Shenzhen Science and Technology Program(JSGG20220831092800001)。
文摘The microstructure of single crystal superalloy is relatively simple,consisting primarily ofγdendrites andγ/γ′eutectics.During the directional solidification process of Ni-based single crystal superalloys,withdrawal rate is a critical parameter affecting the spatial distribution ofγ/γ′eutectic along gravity direction.The results show that theγ/γ′eutectic fraction of the upper platform surface is always higher than that of the lower one,regardless of withdrawal rate.As the withdrawal rate decreases,there is a significant increase inγ/γ′eutectic fraction on the upper surface,while it decreases on the lower surface.The upward accumulation ofγ/γ′eutectic becomes more severe as the withdrawal rate decreases.It is also found that the percentage of Al+Ta is positively correlated with theγ/γ′eutectic fraction.Thermo-solute convection of Al and Ta solutes in the solidification front is the prime reason for the non-uniform distribution of eutectic.The non-uniform distribution ofγ/γ′eutectic cannot be eliminated even after subsequent solution heat treatment,resulting in excess eutectic on the upper surface and thus leading to the scrapping of the blade.
基金Research and Development Project on Voltage Sensors by China Southern Power Grid Digital Research Institute(210000KK52220017)。
文摘Lead magnesium niobate-lead titanate(PMN-PT)piezoelectric single crystals are widely utilized due to their outstanding performance,with varying compositions significantly impacting their properties.While application of PMN-PT in high-power settings is rapidly evolving,material parameters are typically tested under low signal conditions(1 V),and effects of different PT(PbTiO_(3))contents on the performance of PMN-PT single crystals under high-power conditions remain unclear.This study developed a comprehensive high-power testing platform using the constant voltage method to evaluate performance of PMN-PT single crystals with different PT contents under high-power voltage stimulation.Using crystals sized at 10 mm×3 mm×0.5 mm as an example,this research explored changes in material parameters.The results exhibit that while trend of the parameter changes under high-power excitation was consistent across different PT contents,degree of the change varied significantly.For instance,a PMN-PT single crystal with 26%(in mol)PT content exhibited a 25%increase in the piezoelectric coefficient d_(31),a 13%increase in the elastic compliance coefficient s_(11)^(E),a 17%increase in the electromechanical coupling coefficient k_(31),and a 73%decrease in the mechanical quality factor Q_(m) when the power reached 7.90 W.As the PT content increased,the PMN-PT materials became more susceptible to temperature influences,significantly reducing the power tolerance and more readily reaching the depolarization temperatures.This led to loss of piezoelectric performance.Based on these findings,a clearer understanding of impact of PT content on performance of PMN-PT single crystals under high-power applications has been established,providing reliable data to support design of sensors or transducers using PMN-PT as the sensitive element.
基金National Natural Science Foundation of China(12102410)Fund of National Key Laboratory of Shock Wave and Detonation Physics(JCKYS2022212005)。
文摘The lattice parameter,measured with sufficient accuracy,can be utilized to evaluate the quality of single crystals and to determine the equation of state for materials.We propose an iterative method for obtaining more precise lattice parameters using the interaction points for the pseudo-Kossel pattern obtained from laser-induced X-ray diffraction(XRD).This method has been validated by the analysis of an XRD experiment conducted on iron single crystals.Furthermore,the method was used to calculate the compression ratio and rotated angle of an LiF sample under high pressure loading.This technique provides a robust tool for in-situ characterization of structural changes in single crystals under extreme conditions.It has significant implications for studying the equation of state and phase transitions.
基金Supported by the National Key Research and Development Program of China(2021YFB2012601)National Natural Science Foundation of China(12204109)+1 种基金Science and Technology Innovation Plan of Shanghai Science and Technology Commission(21JC1400200)Higher Education Indus⁃try Support Program of Gansu Province(2022CYZC-06)。
文摘Organic semiconductor materials have shown unique advantages in the development of optoelectronic devices due to their ease of preparation,low cost,lightweight,and flexibility.In this work,we explored the application of the organic semiconductor Y6-1O single crystal in photodetection devices.Firstly,Y6-1O single crystal material was prepared on a silicon substrate using solution droplet casting method.The optical properties of Y6-1O material were characterized by polarized optical microscopy,fluorescence spectroscopy,etc.,confirming its highly single crystalline performance and emission properties in the near-infrared region.Phototransistors based on Y6-1O materials with different thicknesses were then fabricated and tested.It was found that the devices exhibited good visible to near-infrared photoresponse,with the maximum photoresponse in the near-infrared region at 785 nm.The photocurrent on/off ratio reaches 10^(2),and photoresponsivity reaches 16 mA/W.It was also found that the spectral response of the device could be regulated by gate voltage as well as the material thickness,providing important conditions for optimizing the performance of near-infrared photodetectors.This study not only demonstrates the excellent performance of organic phototransistors based on Y6-1O single crystal material in near-infrared detection but also provides new ideas and directions for the future development of infrared detectors.
基金supported by National Natural Science Foundation of China(No.52202366)Taishan Scholar Project of Shandong Province(tstp20240515,tsqn202312217)+1 种基金Natural Science Foundation of Shandong Province(China,No.2025HWYQ-050,ZR2021QE011,ZR2022QH072,ZR2021QE284)the King Abdullah University of Science and Technology,the Center of Excellence for Renewable Energy and Storage Technologies.
文摘For emerging renewable and sustainable energy technologies,single crystal materials have become key materials to enhance electrocatalytic performance because of their atomic-level ordered structures and tailorable surface and interfacial properties.Various single crystal types,including metals,semiconductors,ceramics,organics,and nanocrystals,exhibit superior catalytic selectivity and stability in reactions such as water splitting and carbon/nitrogen cycles,benefiting from high electrical conductivity,tunable energy bands,and active sites with high surface energy.Through surface modification,interfacial atomic doping,and heterostructure construction,the distribution of active sites,electronic structure,and mass transport can be precisely regulated,significantly optimizing the catalytic kinetics of single crystal materials.In situ characterizations elucidate catalytic mechanisms at the atomic scale,while emerging methods like AI-assisted synthesis and bio-template directed growth offer pathways to overcome bottlenecks in the precision and cost of single crystal preparation.In addressing stability challenges in complex environments,strategies such as organic-inorganic hybridization and gradient interface design effectively mitigate interfacial instability.Future research should focus on cross-scale structural regulation and multidisciplinary integration to facilitate the transition of single crystal electrocatalysts from fundamental research to industrial applications,enabling efficient energy conversion.
基金funded by the National Science and Technology Major Project of China(Grant No.J2019-Ⅵ-0023-0139)。
文摘To enhance the high-temperature oxidation resistance and mechanical properties of a secondgeneration nickel-based superalloy,various concentrations of lanthanum(La)ranging from 5.0×10^(-5)wt.%to 3.4×10^(-4)wt.%are added to the alloy.The microstructure of the nickel-based single crystal superalloy with trace of La was examined by means of SEM,EDS and TEM.Results show the addition of La decreases the segregation of elements and increases the amount ofγ/γ′eutectics of the as-cast alloy,and in the interdendritic region,the growth of eutectics is accompanied by the growth of strip clusters composed of Ni_(5)La and Ni_(3)Ta.As the La content in the alloy increases,the proportion of Ni_(5)La in the cluster increases.After heat treatment,incipient melting occurs in the cluster regions,leading to an increase in microporosity compared to the original as-cast samples.Furthermore,the heat treatment alters the shape of the clusters from a strip morphology to an elliptical one,and it changes their composition from Ni_(5)La and Ni_(3)Ta to a combination of Ni_(5)La,Ni_(3)Ta,and MC carbides.
基金funded by the National Natural Science Foundation of China(No.22379052)Taishan Scholars of Shandong Province,China(No.tsqnz20221143)。
文摘The effects of synthesis conditions,especially the heating rate,on the reaction kinetics of Ni-rich cathodes were systematically studied.The growth rate of Ni-rich oxide increases continuously as the heating rate increases.Ab initio molecular dynamics simulations demonstrate that a high heating rate induces anabatic oscillations,indicating a decrease in thermodynamic stability and a tendency for the crystal surface to undergo reconstruction.The presence of an intermediate phase at the grain boundary amplifies atomic migration-induced interface fusion and consequently augments crystal growth kinetics.However,the excessively high heating rate aggravates the Li+/Ni2+mixing in the Ni-rich cathode.The single-crystal Ni-rich cathode exhibits enhanced structural/thermal stability but a decreased specific capacity and rate performance compared with its polycrystalline counterpart.
基金Supported by National Natural Science Foundation of China(Grant No.52475430)the Fundamental Research Funds for the Central Universities(Grant No.DUT23YG118).
文摘Due to the high hardness and low fracture toughness of the single crystal silicon(SCS),it is highly susceptible to microscopic cracks and subsurface damage during processing.In this paper,we propose to adjust the mechanical properties of SCS by cold plasma jet,and systematically investigate the influences of the plasma on material deformation and damage mechanisms by nanoscratch tests.The results indicate that the plasma can increase the critical normal force for the plastic-brittle(P-B)conversion of SCS.Compared with the ordinary nanoscratch test,the critical force for P-B conversion of plasma-assisted scratching at 1μm/s can increase from 43.6 to 66.4 mN.Increasing the scratching speed under ordinary conditions can enhance the plastic deformability of SCS to some extent,but its effect is not as effective as that of plasma;in addition,the increased scratching speed causes the shear bands(SBs)to lack time to propagate,so the quantity of SBs under plasma-assisted scratching at 10μm/s is reduced compared to 1μm/s.From subsurface damage topographies,the highly localized amorphous SBs cause the generation of subsurface cracks.The cold plasma can alleviate cracks on the scratched subsurface of SCS by introducing multiple SBs and stacking faults.This paper may provide a novel strategy for high-efficiency and low-damage ultra-precision machining of hard and brittle materials.
基金Project supported by the Xi’an Science and Technology Plan Project of Shaanxi Province of China(Grant No.23GXFW0086).
文摘The effects of temperature and Re content on the mechanical properties,dislocation morphology,and deformation mechanism of γ-γ′phases nickel-based single crystal superalloys are investigated by using the molecular dynamics method through the model of γ-γ′phases containing hole defect.The addition of Re makes the dislocation distribution tend towards the γ phase.The higher the Re content,the earlier theγphase yields,while the γ′phase yields later.Dislocation bends under the combined action of the applied force and the resistance of the Re atoms to form a bend point.The Re atoms are located at the bend points and strengthen the alloy by fixing the dislocation and preventing it from cutting the γ′phase.Dislocations nucleate first in the γ phase,causing theγphase to deform plastically before the γ′phase.As the strain increases,the dislocation length first remains unchanged,then increases rapidly,and finally fluctuates and changes.The dislocation lengths in the γ phase are larger than those in the γ′phase at different temperatures.The dislocation length shows a decreasing tendency with the increase of the temperature.Temperature can affect movement of the dislocation,and superalloys have different plastic deformation mechanisms at low,medium and high temperatures.
基金supported by the Technology Innovation Program(RS-2023-00256202Development of MLCB design and manufacturing process technology for board mounting)funded By the Ministry of Trade,Industry&Energy(MOTIE,Korea)+2 种基金supported by the Technology Innovation Program(or Industrial Strategic Technology Development Program-Public-private joint investment semiconductor R&D program(K-CHIPS)to foster high-quality human resources)(RS-2023-00237003,High selectivity etching technology using cryoetch)funded By the Ministry of Trade,Industry&Energy(MOTIE,Korea)supported by 2022 Research Grant from Kangwon National University(No.202203080001)supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(RS-2023-00280367).
文摘Arising from the increasing demand for electric vehicles(EVs),Ni-rich LiNi_(x)Co_(y)Mn_(z)O_(2)(NCM,x+y+z=1,x≥0.8)cathode with greatly increased energy density are being researched and commercialized for lithium-ion batteries(LIBs).However,parasitic crack formation during the discharge–charge cycling process remains as a major degradation mechanism.Cracking leads to increase in the specific surface area,loss of electrical contact between the primary particles,and facilitates liquid electrolyte infiltration into the cathode active material,accelerating capacity fading and decrease in lifetime.In contrast,Ni-rich NCM when used as a single crystal exhibits superior cycling performances due to its rigid mechanical property that resists cracking during long charge–discharge process even under harsh conditions.In this paper,we present comparative investigation between single crystal Ni-rich LiNi_(0.92)Co_(0.04)Mn_(0.04)O_(2)(SC)and polycrystalline Ni-rich LiNi_(0.92)Co_(0.04)Mn_(0.04)O_(2)(PC).The relatively improved cycling performances of SC are attributed to smaller anisotropic volume change,higher reversibility of phase transition,and resistance to crack formation.The superior properties of SC are demonstrated by in situ characterization and battery tests.Consequently,it is inferred from the results obtained that optimization of preparation conditions can be regarded as a key approach to obtain well crystallized and superior electrochemical performances.
基金financially supported by the National Key Research and Development Program of China (No.2021YFA1600603)the National Science and Technology Major Project (No.J20191-VI-0010-0124)the National Natural Science Foundation of China (No.52071219)。
文摘To investigate the microstructure and creep properties of a hot corrosion resistant Ni-based single crystal superal oy containing different hafnium(Hf)additions(0-0.4wt.%),creep test was performed at 980℃/200 MPa.Optical microscopy,scanning electron microscopy,electron probe micro analysis(EPMA),and transmission electron microscopy were employed to analyze the microstructure differences.With the increase of Hf,the creep rupture life of the alloys at 980℃/200 MPa gradually increases.Microstructure analysis reveals that Hf promotes the transformation of carbide morphology from script to rod-like and finally to blocky.Upon the addition of Hf,there is an increase in the volume fraction of blocky MC carbides,along with an elevation in the partitioning ratio of Cr and Mo elements.Concurrently,theγ/γ′interfacial dislocation spacing undergoes a reduction.It is found that script carbides are more likely to cause stress concentration in high temperature creep,leading to nucleation and propagation of microcracks.The formation mechanism of blocky MC carbides is related to the increase in precipitation temperature and lattice constant,and its beneficial impact on creep resistance is also investigated based on the analysis of the creep test results.
