Aiming at inhibiting the irreversible P2–O2 phase transition of conventional P2-type cathode materials at high voltage and enhancing the cycling stability of sodium-ion batteries,in this article,based on a strategy o...Aiming at inhibiting the irreversible P2–O2 phase transition of conventional P2-type cathode materials at high voltage and enhancing the cycling stability of sodium-ion batteries,in this article,based on a strategy of adjusting the Na^(+)ion occupancy within the crystal structure,Na_(0.67)Ni_(0.33)Mn_(0.67–x)Fe_(x)O_(2)(NM–x Fe,x=0.10,0.15,0.20)cathode materials were synthesized by high shear mixer(HSM)-assisted co-precipitation method and evaluated the electrochemical performance at high voltage(4.35 V).The optimal sample NM–0.15Fe exhibits an initial discharge capacity of 130.8 mAh/g(0.1 C),with exceptional retention of 95.9%after 100 cycles(1 C).XRD analysis reveals that Fe intercalation promotes the more amount of Nae-similar occupation;the Nae/Naf ratio equals 1.93 for NM–0.15Fe versus 1.62 for NM,which enhances Na^(+)diffusion kinetics,as confirmed by GITT tests.Through characterizations of in situ XRD,XPS,HRTEM,CV,etc.,it is illustrated that the Fe^(3+)intercalation can effectively disrupt the Na^(+)/vacancy ordering and inhibit the harmful P2–O2 phase transition,and then improve the cycling stability of the cathode.DFT calculations disclose that intercalated Fe can reduce the electron densities of adjacent transition metallic elements,generating more repulsive forces impacted on sodium and consequently appearance of more Nae sites,leading to a lower Na^(+)diffusion energy barrier.Such strategy of modulating Na occupation sites in crystal structure is conducive to the development of low-cost and high-performance layered cathode materials for sodium-ion batteries.展开更多
Ta/NiFe film is deposited on Si substrate precoated with SiO_2 by magnetron sputtering.SiO_2/Ta interface and Ta_5Si_3 standard sample are investigated by using X-ray photoelectron spectroscopy (XPS) and peak decompos...Ta/NiFe film is deposited on Si substrate precoated with SiO_2 by magnetron sputtering.SiO_2/Ta interface and Ta_5Si_3 standard sample are investigated by using X-ray photoelectron spectroscopy (XPS) and peak decomposition technique.The results show that there is a thermodynamically favorable reaction at the SiO_2/Ta interface:37Ta+15SiO_2=5Ta_5Si_3+6Ta_2O_5.The more stable products Ta_5Si_3 and Ta_2O_5 may be beneficial to stop the diffusion of Cu into SiO_2.展开更多
A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatm...A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatments,wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt.In order to perform a comparison with conventional Ni Al and(Ni,Pt)Al coatings,the cyclic oxidation performance of the Ni Re Pt Al coating was evaluated at 1100 and 1150℃.We observed that the oxidation resistance of the Ni Re Pt Al coating was significantly improved by the greater presence of the residualβ-Ni Al phase in the outer layer and the lesser outward-diffusion of Mo from the substrate.In addition,the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate,where the thickness of the second reaction zone(SRZ)in the substrate alloy decreased by 25%.The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed,in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.展开更多
NiCrAlY coatings are widely applied on various alloy components to enhance oxidation and/or corrosion resistance at high temperatures.However,elements interdiffusion occurs between them due to composition difference.A...NiCrAlY coatings are widely applied on various alloy components to enhance oxidation and/or corrosion resistance at high temperatures.However,elements interdiffusion occurs between them due to composition difference.Although various diffusion barriers(DBs)are reported,this problem is still far from completely solved as most ceramic barriers suffer from poor adherence,while the metallic barriers play a limited role.In this study,NiCrAlY coating was deposited onto a second-generation single-crystal superalloy by arc ion plating.A novel simple method is provided to address elements interdiffusion.By pre-oxidation at a moderate temperature,a thin scale of Ni(Co)O forms at the alloy surface.It transforms to be an alumina/NiCoCr alloy/alumina sandwich by an in-situ reaction with the overlaying NiCrAlY coating and the alloy substrate at high service temperatures,which offers good barrier ability in conjunction with strong adhesion.In the presence of such an alumina/alloy/alumina DB,the NiCrAlY coating provides high resistance to oxidation and scale spallation for the alloy substrate.展开更多
Beryllium carbide is used in inertial confinement fusion(ICF)capsule ablation material due to its low atomic number,low opacity,and high melting point properties.We used the method of climbing image nudged elastic ban...Beryllium carbide is used in inertial confinement fusion(ICF)capsule ablation material due to its low atomic number,low opacity,and high melting point properties.We used the method of climbing image nudged elastic band(CINEB)to calculate the diffusion barrier of copper atom in the crystal of beryllium and beryllium carbide.The diffusion barrier of copper atom in crystal beryllium is only 0.79 eV,and the barrier in beryllium carbide is larger than 2.85 eV.The three structures of beryllium carbide:anti-fluorite Be2C,Be2C-Ⅰ,and Be2C-Ⅲhave a good blocking effect to the diffusion of copper atom.Among them,the Be2C-Ⅲstructure has the highest diffusion barrier of 6.09 eV.Our research can provide useful help for studying Cu diffusion barrier materials.展开更多
The effect of LPPS Ni_3Al-Y_2O_3 diffusion barrier layer on interdiffusion of elements between coating and substrate has been investigated.It was found that the retardation of interdiffusion is related to the amount o...The effect of LPPS Ni_3Al-Y_2O_3 diffusion barrier layer on interdiffusion of elements between coating and substrate has been investigated.It was found that the retardation of interdiffusion is related to the amount of oxide in the diffusion barrier layer.The retardation is not remark- able when the content of Y_2O_3 is 8 wt-%,whereas the diffusion of Al,Co or Cr has all been notably retarded when the content of Y_2O_3 reaches 30 wt-%.The retardation effect of diffu- sion barrier is different for different elements such as Al,Co or Cr.展开更多
To advance the application of layered oxide cathodes in fast-charging sodium-ion batteries,it is crucial to not only suppress irreversible phase transitions but also improve the rate capability of cathode materials an...To advance the application of layered oxide cathodes in fast-charging sodium-ion batteries,it is crucial to not only suppress irreversible phase transitions but also improve the rate capability of cathode materials and optimize Na^(+)diffusion kinetics to ensure high capacity output at various charge-discharge rates.In this research,the targeted F-substitution with a heavy ratio in oxygen anion layer optimizes the Na^(+)diffusion path and electronic conductivity of the material,thereby decreasing the Na^(+)diffusion barrier and imparting high-rate performance.At a 20 C rate,the cathode achieves a capacity of over 80 mAh g^(-1)with stable cycling performance.Additionally,the dual rivet effect between the transition metal layer and oxygen layer prevents significant phase transitions during charge/discharge within the 2-4.2 V range for the modified cathode.As a result,the F-substituted oxygen anion layer improved Na^(+)diffusion,electronic conductivity,and crystal plane structure stability,which led to the development of a highperformance,fast-charging sodium-ion battery(SIB),opening new avenues for commercial applications.展开更多
An important challenge facing K-ion batteries lies in exploring earth-abundant and safe cathode materials that can provide high capacity with high migration rate of K ions.Here,we propose a simple and efficient method...An important challenge facing K-ion batteries lies in exploring earth-abundant and safe cathode materials that can provide high capacity with high migration rate of K ions.Here,we propose a simple and efficient method for searching potential K cathode materials with first principles calculations.Our screening is based on combinations of weight capacity,K ion occupation ratio,volume change per K,and valence limit.With this screening method we predicted a series of potential K ions cathodes with favorable electrochemical performance,such as K_(2)VPO_(4)CO_(3)-like structures with 1 D diffusion channels,3 D channel structures K_(2)CoSiO_(4),layered materials KCoO_(2),KCrO_(2),KVF_(4) and K_(5)V_(3)F_(14),and others.These potential cathodes have small volume changes,suitable voltage,and high capacity,with small diffusion barriers.They may be useful in K-ion batteries with high energy density and rate performance.展开更多
Tungsten nitride(W_(x)N)thin films with good crystalline structure,high quality and relatively low resistivity were deposited by hot filament chemical vapor deposition(HFCVD)technique at different mixtures of N2 and A...Tungsten nitride(W_(x)N)thin films with good crystalline structure,high quality and relatively low resistivity were deposited by hot filament chemical vapor deposition(HFCVD)technique at different mixtures of N2 and Ar gases.Experimental data demonstrate that different N_(2) contents in gas mixture strongly affect microstructure,phase formation,texture morphology and resistivity of the W_(x)N films.According to X-ray diffraction(XRD)patterns,the growth of tungsten nitride films promotes δ-WN phase for lower N_(2) contents in gas mixture.At higher N_(2) contents,a phase transition is observed in the tungsten nitride films.Both hexagonal δ-WN and cubic β-W_(2)N phases coexist,and WN phase approximately disappears with N_(2) contents in the gas mixture increasing.Scanning electron microscope(SEM)images for deposited films at lower N_(2) contents in gas mixture indicate a definite dense columnar nanostructure.The electrical resistivity results exhibit a significant drop for the W_(x)N thin films with N_(2) contents in the mixed gas increasing.The changes in N_(2) content in gas mixture are found to be responsible for variation in the film resistivity values.Thus,the deposited tungsten nitride thin film at higher N_(2) contents in gas mixture has noncolumnar microstructure and lower resistivity,which may be used as a superior diffusion barrier.展开更多
In this work,a modified approach for preparing CVD SiC fiber-reinforced superalloy matrix composites was rationally developed.The composites were fabricated by vacuum hot pressing(VHP)process using precursor wires coa...In this work,a modified approach for preparing CVD SiC fiber-reinforced superalloy matrix composites was rationally developed.The composites were fabricated by vacuum hot pressing(VHP)process using precursor wires coated with(Al+Al2O3)diffusion barrier layers and GH4169 superalloy coatings.BNi-7 brazing filler metals were introduced on the surface of precursor wires in order to decrease the temperature of the VHP process.It was found that the VHP temperature was reduced by about 100℃,and the melting,diffusion,nucleation and growth processes of BNi-7 fillers at 900?C motivated the recrystallization and plastic flow of the matrix under the increasing pressure,thereby a compact composite composed of intact SiC fibers and fine equiaxial grain structure superalloy matrix was achieved.Meanwhile,the elements were distributed homogeneously among the fibers in the composite and no interfacial reactions occurred.This method provides a new insight for designing and manufacturing high-quality composites in practical engineering.展开更多
A novel Re modifiedβ-(Ni,Pt)Al coating was prepared on a Mo-rich Ni_3 Al-based single crystal(SC)superalloy by electro-deposition of Re/Pt dual films and low-activity aluminizing.The isothermal oxidation behavior of ...A novel Re modifiedβ-(Ni,Pt)Al coating was prepared on a Mo-rich Ni_3 Al-based single crystal(SC)superalloy by electro-deposition of Re/Pt dual films and low-activity aluminizing.The isothermal oxidation behavior of the Re modifiedβ-(Ni,Pt)Al coating and traditionalβ-(Ni,Pt)Al coating was comparatively studied at 1100℃.Apparent spallation of oxide scale was found on the surface of traditionalβ-(Ni,Pt)Al coating after 300 h isothermal exposure,which mainly resulted from the evaporation of Mo-containing oxides.It is further found that the outward diffusion of Mo from the SC substrate was effectively inhibited in the Re modifiedβ-(Ni,Pt)Al coating by forming theσ-MoRe phase both at the coating/superalloy interface and grain boundaries.It is also revealed that the addition of Re can stabilise Mo to form theσ-MoRe phase,allowing the improved oxidation resistance of the Re modifiedβ-(Ni,Pt)Al coating.展开更多
Sodium(Na)metal batteries with a high volumetric energy density that can be operated at high rates are highly desirable.However,an uneven Na-ion migration in bulk Na anodes leads to localized deposition/dissolution of...Sodium(Na)metal batteries with a high volumetric energy density that can be operated at high rates are highly desirable.However,an uneven Na-ion migration in bulk Na anodes leads to localized deposition/dissolution of sodium during high-rate plating/stripping behaviors,followed by severe dendrite growth and loose stacking.Herein,we engineer the Na hybrid anode with sodiophilic Na_(3)Bi-penetration to develop the abundant phase-boundary ionic transport channels.Compared to intrinsic Na,the reduced adsorption energy and ion-diffusion barrier on Na_(3)Bi ensure even Na^(+)nucleation and rapid Na^(+)migration within the hybrid electrode,leading to uniform deposition and dissolution at high current densities.Furthermore,the bismuthide enables compact Na deposition within the sodiophilic framework during cycling,thus favoring a high volumetric capacity.Consequently,the obtained anode was endowed with a high current density(up to 5 mA∙cm^(−2)),high areal capacity(up to 5 mA∙h∙cm^(−2)),and long-term cycling stability(up to 2800 h at 2 mA∙cm^(−2)).展开更多
Internal reformation of low steam methane fuel is important for the high efficiency and low cost operation of solid oxide fuel cell. Understanding and overcoming carbon deposition is crucial for the technology develop...Internal reformation of low steam methane fuel is important for the high efficiency and low cost operation of solid oxide fuel cell. Understanding and overcoming carbon deposition is crucial for the technology development. Here a multi-physics model is established for the relevant experimental cells. Balance of electrochemical potentials for the electrochemical reactions, generic rate expression for the methane steam reforming, dusty gas model in a form of Fick＇s model for anode gas transport are used in the model. Excellent agreement between the theoretical and experimental current-voltage relations is obtained, demonstrating the validity of the proposed theoretical model. The steam reaction order in low steam methane reforming reaction is found to be 1. Detailed information about the distributions of physical quantities is obtained by the numerical simulation. Carbon deposition is analyzed in detail and the mechanism for the coking inhibition by operating current is illustrated clearly. Two expressions of carbon activity are analyzed and found to be correct qualitatively, but not quantitatively. The role of anode diffusion layer on reducing the current threshold for carbon removal is also explained. It is noted that the current threshold reduction may be explained quantitatively with the carbon activity models that are only qualitatively correct.展开更多
Internal reformation of low steam methane fuel is highly beneficial for improving the energy efficiency and reducing the system complexity and cost of solid oxide fuel cells(SOFCs).However,anode coking for the Ni-base...Internal reformation of low steam methane fuel is highly beneficial for improving the energy efficiency and reducing the system complexity and cost of solid oxide fuel cells(SOFCs).However,anode coking for the Ni-based anode should be prevented before the technology becomes a reality.A multi-physics fully coupled model is employed to simulate the operations of SOFCs fueled by low steam methane.The multi-physics model produces I-V relations that are in excellent agreement with the experimental results.The multi-physics model and the experimental non-coking current density deduced kinetic carbon activity criterion are used to examine the effect of operating parameters and the anode diffusion barrier layer on the propensity of carbon deposition.The interplays among the fuel utilization ratio,current generation,thickness of the barrier layer and the cell operating voltage are revealed.It is demonstrated that a barrier layer of 400μm thickness is an optimal and safe anode design to achieve high power density and non-coking operations.The anode structure design can be very useful for the development of high efficiency and low cost SOFC technology.展开更多
A method of preparing continuous（Al＋Al2O3）-coated SiC fiber reinforced nickel matrix composite was presented,in which the diffusion between SiC fiber and nickel matrix could be prevented.Magnetron sputtering is use...A method of preparing continuous（Al＋Al2O3）-coated SiC fiber reinforced nickel matrix composite was presented,in which the diffusion between SiC fiber and nickel matrix could be prevented.Magnetron sputtering is used to deposit Ni coating on the surface of the（Al＋Al2O3）-coated SiC fiber in preparation of the precursor wires.It is shown that the deposited Ni coating combines well with the（Al＋Al2O3） coating and has little negative effect on the tensile strength of（Al＋Al2O3）-coated SiC fiber.Solid-state diffusion bonding process is employed to prepare the（Al＋Al2O3）-coated SiC fiber reinforced nickel matrix with 37% fibers in volume.The solid-state diffusion bonding process is optimized and the optimum parameters are temperature of 870,pressure of 50 MPa and holding time of 2 h.Under this condition,the precursor wires can diffuse well,composite of full density can be formed and the（Al＋Al2O3） coating is effective to restrict the reaction between SiC fiber and nickel matrix.展开更多
Lithium metal batteries are emerging as a strong candidate in the future energy storage market due to its extremely high energy density.However,the uncontrollable lithium dendrites and volume change of lithium metal a...Lithium metal batteries are emerging as a strong candidate in the future energy storage market due to its extremely high energy density.However,the uncontrollable lithium dendrites and volume change of lithium metal anodes severely hinder its application.In this work,the porous Cu skeleton modified with Cu_(6)Sn_(5)layer is prepared via dealloying brass foil following a facile electroless process.The porous Cu skeleton with large specific surface area and high electronic conductivity effectively reduces the local current density.The Cu_(6)Sn_(5)can react with lithium during the discharge process to form lithiophilic Li_(7)Sn_(2)in situ to promote Li-ions transport and reduce the nucleation energy barrier of lithium to guide the uniform lithium deposition.Therefore,more than 300 cycles at 1 mA cm^(−2)are achieved in the half-cell with an average Coulombic efficiency of 97.5%.The symmetric cell shows a superior cycle life of more than 1000 h at 1 mA cm^(−2)with a small average hysteresis voltage of 16 mV.When coupled with LiFePO_(4)cathode,the full cell also maintains excellent cycling and rate performance.展开更多
Restorative cell-based therapies for experimental brain injury, such as stroke and traumatic brain injury,substantially improve functional outcome. We discuss and review state of the art magnetic resonance imaging met...Restorative cell-based therapies for experimental brain injury, such as stroke and traumatic brain injury,substantially improve functional outcome. We discuss and review state of the art magnetic resonance imaging methodologies and their applications related to cell-based treatment after brain injury. We focus on the potential of magnetic resonance imaging technique and its associated challenges to obtain useful new information related to cell migration, distribution, and quantitation, as well as vascular and neuronal remodeling in response to cell-based therapy after brain injury. The noninvasive nature of imaging might more readily help with translation of cell-based therapy from the laboratory to the clinic.展开更多
Tantalum nitride （TAN） thin films are achieved on Si（111） and SS317L substrates by cathodic vacuum arc technique, which is rarely reported in the literature. The crystal structure, composition and surface morpholo...Tantalum nitride （TAN） thin films are achieved on Si（111） and SS317L substrates by cathodic vacuum arc technique, which is rarely reported in the literature. The crystal structure, composition and surface morphology of the films are characterized by x-ray diffraction （XRD）, x-ray photoelectron spectroscopy （XPS）, auger electron spectroscopy, and atomic force microscopy, respectively. The influence of substrate negative bias on crystal structure, composition, surface morphology of the TaN films is systematically studied. At the substrate bias of 0 V and -50 V, the amorphous TaN film is obtained. As the bias increases to -100 V, cubic TaN phase can be found. Stoichiometric TaN with hexagonal lattice preferred （300） orientation is prepared at a bias of -200 V. Combine the XRD and XPS results, the binding energy value of 23.6eV of Ta 4f（7/2） is contributed to hexagonal TaN. Compared to other techniques, TaN thin films fabricated by cathodic vacuum arc at various substrate biases show different microstructures.展开更多
Ce is prone to catastrophic oxidation at room temperature and its oxidation resistance is difficult to be improved by alloying.Herein,we found that the oxidation resistance of active metal Ce can be significantly impr...Ce is prone to catastrophic oxidation at room temperature and its oxidation resistance is difficult to be improved by alloying.Herein,we found that the oxidation resistance of active metal Ce can be significantly improved by the addition of 20 at.%Ga.Focused ion beam lift-out technique and scanning transmission electron microscopy analysis disclosed that a discontinuous Ga-rich layer was generated beneath the oxide layer in the coarse-grained Ce-Ga alloy.The Ga-rich layer formed by selective oxidation of Ce acts as a diffusion barrier for Ce outward diffusion and ceases the O/M interfacial reaction when a critical concentration of Ga(75 at.%)is reached.After nanocrystallization,uniform distribution of Ga was achieved.After oxidation,a relatively continuous Ga-rich layer was formed which further enhanced the oxidation resistance.The introduction of noble elements combining with nanocrystallization may provide a novel strategy for the protection of metals with high activity and poor oxidation resistance.展开更多
In thermoelectric(TE)devices,the interfacial reliability greatly influenced devices’durability and power output.For skutterudites(SKD)devices,TE legs and electrodes are bonded together with diffusion barrier layer(DB...In thermoelectric(TE)devices,the interfacial reliability greatly influenced devices’durability and power output.For skutterudites(SKD)devices,TE legs and electrodes are bonded together with diffusion barrier layer(DBL).At elevated temperatures,DBL react with SKD matrix or electrode to generate complex interfacial microstructures,which often accompanies evolutions of the thermal,electrical and mechanical properties at the interfaces.In this work,a finite element model containing the interfacial microstructure characteristics based on the experimental results was built to analyze the interfacial stress state in the skutterudite-based TE joints.A single-layer model was applied to screen out the most important parameters of the coefficient of thermal expansion(CTE)and the modulus of DBL on the first principle stress.The multilayer model considering the interfacial microstructures evolution was built to quantitively simulate the stress state of the TE joints at different aging temperatures and time.The simulation results show that the reactive CoSb2 layer is the weakest layer in both SKD/Nb and SKD/Zr joints.And by prolonging the aging time,the thickness of the reaction layer continuously increased,leading to a significant raising of the interfacial stress.The tensile testing results of the SKD/Nb joints match the simulation results well,consolidating accuracy and feasibility of this multilayer model.This study provides an important guidance on the design of DBL to improve the TE joints’mechanical reliability,and a common method to precisely simulate the stress condition in other coating systems.展开更多
基金supported by Jing-Jin-Ji Regional Integrated Environmental Improvement,National Science and Technology Major Project(Nos.2024ZD1200303).
文摘Aiming at inhibiting the irreversible P2–O2 phase transition of conventional P2-type cathode materials at high voltage and enhancing the cycling stability of sodium-ion batteries,in this article,based on a strategy of adjusting the Na^(+)ion occupancy within the crystal structure,Na_(0.67)Ni_(0.33)Mn_(0.67–x)Fe_(x)O_(2)(NM–x Fe,x=0.10,0.15,0.20)cathode materials were synthesized by high shear mixer(HSM)-assisted co-precipitation method and evaluated the electrochemical performance at high voltage(4.35 V).The optimal sample NM–0.15Fe exhibits an initial discharge capacity of 130.8 mAh/g(0.1 C),with exceptional retention of 95.9%after 100 cycles(1 C).XRD analysis reveals that Fe intercalation promotes the more amount of Nae-similar occupation;the Nae/Naf ratio equals 1.93 for NM–0.15Fe versus 1.62 for NM,which enhances Na^(+)diffusion kinetics,as confirmed by GITT tests.Through characterizations of in situ XRD,XPS,HRTEM,CV,etc.,it is illustrated that the Fe^(3+)intercalation can effectively disrupt the Na^(+)/vacancy ordering and inhibit the harmful P2–O2 phase transition,and then improve the cycling stability of the cathode.DFT calculations disclose that intercalated Fe can reduce the electron densities of adjacent transition metallic elements,generating more repulsive forces impacted on sodium and consequently appearance of more Nae sites,leading to a lower Na^(+)diffusion energy barrier.Such strategy of modulating Na occupation sites in crystal structure is conducive to the development of low-cost and high-performance layered cathode materials for sodium-ion batteries.
文摘Ta/NiFe film is deposited on Si substrate precoated with SiO_2 by magnetron sputtering.SiO_2/Ta interface and Ta_5Si_3 standard sample are investigated by using X-ray photoelectron spectroscopy (XPS) and peak decomposition technique.The results show that there is a thermodynamically favorable reaction at the SiO_2/Ta interface:37Ta+15SiO_2=5Ta_5Si_3+6Ta_2O_5.The more stable products Ta_5Si_3 and Ta_2O_5 may be beneficial to stop the diffusion of Cu into SiO_2.
基金the Key-Area Research and Development Program of Guangdong Province(2019B010936001)financially supported by the National Natural Science Foundation of China(Grant Nos.51671202 and 51301184)。
文摘A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatments,wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt.In order to perform a comparison with conventional Ni Al and(Ni,Pt)Al coatings,the cyclic oxidation performance of the Ni Re Pt Al coating was evaluated at 1100 and 1150℃.We observed that the oxidation resistance of the Ni Re Pt Al coating was significantly improved by the greater presence of the residualβ-Ni Al phase in the outer layer and the lesser outward-diffusion of Mo from the substrate.In addition,the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate,where the thickness of the second reaction zone(SRZ)in the substrate alloy decreased by 25%.The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed,in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.
基金financially supported by the National Natural Science Foundation of China(No.51671053)the Natural Science Foundation of Liaoning Province of China(No.2019-ZD-0264)the Ministry of Industry and Information Technology Project(No.MJ-2017-J-99)。
文摘NiCrAlY coatings are widely applied on various alloy components to enhance oxidation and/or corrosion resistance at high temperatures.However,elements interdiffusion occurs between them due to composition difference.Although various diffusion barriers(DBs)are reported,this problem is still far from completely solved as most ceramic barriers suffer from poor adherence,while the metallic barriers play a limited role.In this study,NiCrAlY coating was deposited onto a second-generation single-crystal superalloy by arc ion plating.A novel simple method is provided to address elements interdiffusion.By pre-oxidation at a moderate temperature,a thin scale of Ni(Co)O forms at the alloy surface.It transforms to be an alumina/NiCoCr alloy/alumina sandwich by an in-situ reaction with the overlaying NiCrAlY coating and the alloy substrate at high service temperatures,which offers good barrier ability in conjunction with strong adhesion.In the presence of such an alumina/alloy/alumina DB,the NiCrAlY coating provides high resistance to oxidation and scale spallation for the alloy substrate.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974253 and 11774248)the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(Grant No.2017YFA0303600)
文摘Beryllium carbide is used in inertial confinement fusion(ICF)capsule ablation material due to its low atomic number,low opacity,and high melting point properties.We used the method of climbing image nudged elastic band(CINEB)to calculate the diffusion barrier of copper atom in the crystal of beryllium and beryllium carbide.The diffusion barrier of copper atom in crystal beryllium is only 0.79 eV,and the barrier in beryllium carbide is larger than 2.85 eV.The three structures of beryllium carbide:anti-fluorite Be2C,Be2C-Ⅰ,and Be2C-Ⅲhave a good blocking effect to the diffusion of copper atom.Among them,the Be2C-Ⅲstructure has the highest diffusion barrier of 6.09 eV.Our research can provide useful help for studying Cu diffusion barrier materials.
文摘The effect of LPPS Ni_3Al-Y_2O_3 diffusion barrier layer on interdiffusion of elements between coating and substrate has been investigated.It was found that the retardation of interdiffusion is related to the amount of oxide in the diffusion barrier layer.The retardation is not remark- able when the content of Y_2O_3 is 8 wt-%,whereas the diffusion of Al,Co or Cr has all been notably retarded when the content of Y_2O_3 reaches 30 wt-%.The retardation effect of diffu- sion barrier is different for different elements such as Al,Co or Cr.
基金supported by the National Natural Science Foundation of China(Nos.22178221,22208221)the Shenzhen Science and Technology Program(Nos.JCYJ20220818095805012,JCYJ20230808105109019)+2 种基金the Natural Science Foundation of Guangdong Province(Nos.2024A1515011078,2024A1515011507)the Scientific Foundation for Youth Scholars of Shenzhen University(868-000001032522,827-0001004)the Instrumental Analysis Center of Shenzhen University for the assistance with the Electron Microscope technical support。
文摘To advance the application of layered oxide cathodes in fast-charging sodium-ion batteries,it is crucial to not only suppress irreversible phase transitions but also improve the rate capability of cathode materials and optimize Na^(+)diffusion kinetics to ensure high capacity output at various charge-discharge rates.In this research,the targeted F-substitution with a heavy ratio in oxygen anion layer optimizes the Na^(+)diffusion path and electronic conductivity of the material,thereby decreasing the Na^(+)diffusion barrier and imparting high-rate performance.At a 20 C rate,the cathode achieves a capacity of over 80 mAh g^(-1)with stable cycling performance.Additionally,the dual rivet effect between the transition metal layer and oxygen layer prevents significant phase transitions during charge/discharge within the 2-4.2 V range for the modified cathode.As a result,the F-substituted oxygen anion layer improved Na^(+)diffusion,electronic conductivity,and crystal plane structure stability,which led to the development of a highperformance,fast-charging sodium-ion battery(SIB),opening new avenues for commercial applications.
基金supported by the National Key R&D Program of China(Grant No.2016YFA0200400)the National Natural Science Foundation of China(Grant No.11504123 and No.51627805)。
文摘An important challenge facing K-ion batteries lies in exploring earth-abundant and safe cathode materials that can provide high capacity with high migration rate of K ions.Here,we propose a simple and efficient method for searching potential K cathode materials with first principles calculations.Our screening is based on combinations of weight capacity,K ion occupation ratio,volume change per K,and valence limit.With this screening method we predicted a series of potential K ions cathodes with favorable electrochemical performance,such as K_(2)VPO_(4)CO_(3)-like structures with 1 D diffusion channels,3 D channel structures K_(2)CoSiO_(4),layered materials KCoO_(2),KCrO_(2),KVF_(4) and K_(5)V_(3)F_(14),and others.These potential cathodes have small volume changes,suitable voltage,and high capacity,with small diffusion barriers.They may be useful in K-ion batteries with high energy density and rate performance.
文摘Tungsten nitride(W_(x)N)thin films with good crystalline structure,high quality and relatively low resistivity were deposited by hot filament chemical vapor deposition(HFCVD)technique at different mixtures of N2 and Ar gases.Experimental data demonstrate that different N_(2) contents in gas mixture strongly affect microstructure,phase formation,texture morphology and resistivity of the W_(x)N films.According to X-ray diffraction(XRD)patterns,the growth of tungsten nitride films promotes δ-WN phase for lower N_(2) contents in gas mixture.At higher N_(2) contents,a phase transition is observed in the tungsten nitride films.Both hexagonal δ-WN and cubic β-W_(2)N phases coexist,and WN phase approximately disappears with N_(2) contents in the gas mixture increasing.Scanning electron microscope(SEM)images for deposited films at lower N_(2) contents in gas mixture indicate a definite dense columnar nanostructure.The electrical resistivity results exhibit a significant drop for the W_(x)N thin films with N_(2) contents in the mixed gas increasing.The changes in N_(2) content in gas mixture are found to be responsible for variation in the film resistivity values.Thus,the deposited tungsten nitride thin film at higher N_(2) contents in gas mixture has noncolumnar microstructure and lower resistivity,which may be used as a superior diffusion barrier.
基金financially supported by the National Natural Science Foundation of China(No.51371170)。
文摘In this work,a modified approach for preparing CVD SiC fiber-reinforced superalloy matrix composites was rationally developed.The composites were fabricated by vacuum hot pressing(VHP)process using precursor wires coated with(Al+Al2O3)diffusion barrier layers and GH4169 superalloy coatings.BNi-7 brazing filler metals were introduced on the surface of precursor wires in order to decrease the temperature of the VHP process.It was found that the VHP temperature was reduced by about 100℃,and the melting,diffusion,nucleation and growth processes of BNi-7 fillers at 900?C motivated the recrystallization and plastic flow of the matrix under the increasing pressure,thereby a compact composite composed of intact SiC fibers and fine equiaxial grain structure superalloy matrix was achieved.Meanwhile,the elements were distributed homogeneously among the fibers in the composite and no interfacial reactions occurred.This method provides a new insight for designing and manufacturing high-quality composites in practical engineering.
基金financially supported by the National Science and Technology Major Project(Nos.2017-VI-0010-0081 and 2017-VI-0002-0072)the National Natural Science Foundation of China(Nos.51590894 and 51901107)+1 种基金the Beijing Natural Science Foundation(No.2194078)the“111 Project”(No.B17002)。
文摘A novel Re modifiedβ-(Ni,Pt)Al coating was prepared on a Mo-rich Ni_3 Al-based single crystal(SC)superalloy by electro-deposition of Re/Pt dual films and low-activity aluminizing.The isothermal oxidation behavior of the Re modifiedβ-(Ni,Pt)Al coating and traditionalβ-(Ni,Pt)Al coating was comparatively studied at 1100℃.Apparent spallation of oxide scale was found on the surface of traditionalβ-(Ni,Pt)Al coating after 300 h isothermal exposure,which mainly resulted from the evaporation of Mo-containing oxides.It is further found that the outward diffusion of Mo from the SC substrate was effectively inhibited in the Re modifiedβ-(Ni,Pt)Al coating by forming theσ-MoRe phase both at the coating/superalloy interface and grain boundaries.It is also revealed that the addition of Re can stabilise Mo to form theσ-MoRe phase,allowing the improved oxidation resistance of the Re modifiedβ-(Ni,Pt)Al coating.
基金supported by the National Natural Science Foundation of China (21938005 and 21776197)Key Laboratory of Coal Science and Technology, Education Ministry and Shanxi Province, Taiyuan University of Technology
文摘Sodium(Na)metal batteries with a high volumetric energy density that can be operated at high rates are highly desirable.However,an uneven Na-ion migration in bulk Na anodes leads to localized deposition/dissolution of sodium during high-rate plating/stripping behaviors,followed by severe dendrite growth and loose stacking.Herein,we engineer the Na hybrid anode with sodiophilic Na_(3)Bi-penetration to develop the abundant phase-boundary ionic transport channels.Compared to intrinsic Na,the reduced adsorption energy and ion-diffusion barrier on Na_(3)Bi ensure even Na^(+)nucleation and rapid Na^(+)migration within the hybrid electrode,leading to uniform deposition and dissolution at high current densities.Furthermore,the bismuthide enables compact Na deposition within the sodiophilic framework during cycling,thus favoring a high volumetric capacity.Consequently,the obtained anode was endowed with a high current density(up to 5 mA∙cm^(−2)),high areal capacity(up to 5 mA∙h∙cm^(−2)),and long-term cycling stability(up to 2800 h at 2 mA∙cm^(−2)).
基金This work was supported by the National Basic Research Program of China （No.2012CB215405）, the National Natural Science Foundation of China （No.11374272）, and the Specialized Research Fund for the Doctoral Program of Higher Education （No.20123402110064）.
文摘Internal reformation of low steam methane fuel is important for the high efficiency and low cost operation of solid oxide fuel cell. Understanding and overcoming carbon deposition is crucial for the technology development. Here a multi-physics model is established for the relevant experimental cells. Balance of electrochemical potentials for the electrochemical reactions, generic rate expression for the methane steam reforming, dusty gas model in a form of Fick＇s model for anode gas transport are used in the model. Excellent agreement between the theoretical and experimental current-voltage relations is obtained, demonstrating the validity of the proposed theoretical model. The steam reaction order in low steam methane reforming reaction is found to be 1. Detailed information about the distributions of physical quantities is obtained by the numerical simulation. Carbon deposition is analyzed in detail and the mechanism for the coking inhibition by operating current is illustrated clearly. Two expressions of carbon activity are analyzed and found to be correct qualitatively, but not quantitatively. The role of anode diffusion layer on reducing the current threshold for carbon removal is also explained. It is noted that the current threshold reduction may be explained quantitatively with the carbon activity models that are only qualitatively correct.
基金supported by the National Natural Science Foundation of China (No.11574284 abd No.11774324)the National Basic Research Program of China (No.2012CB215405)Collaborative Innovation Center of Suzhou Nano Science and Technology
文摘Internal reformation of low steam methane fuel is highly beneficial for improving the energy efficiency and reducing the system complexity and cost of solid oxide fuel cells(SOFCs).However,anode coking for the Ni-based anode should be prevented before the technology becomes a reality.A multi-physics fully coupled model is employed to simulate the operations of SOFCs fueled by low steam methane.The multi-physics model produces I-V relations that are in excellent agreement with the experimental results.The multi-physics model and the experimental non-coking current density deduced kinetic carbon activity criterion are used to examine the effect of operating parameters and the anode diffusion barrier layer on the propensity of carbon deposition.The interplays among the fuel utilization ratio,current generation,thickness of the barrier layer and the cell operating voltage are revealed.It is demonstrated that a barrier layer of 400μm thickness is an optimal and safe anode design to achieve high power density and non-coking operations.The anode structure design can be very useful for the development of high efficiency and low cost SOFC technology.
文摘A method of preparing continuous（Al＋Al2O3）-coated SiC fiber reinforced nickel matrix composite was presented,in which the diffusion between SiC fiber and nickel matrix could be prevented.Magnetron sputtering is used to deposit Ni coating on the surface of the（Al＋Al2O3）-coated SiC fiber in preparation of the precursor wires.It is shown that the deposited Ni coating combines well with the（Al＋Al2O3） coating and has little negative effect on the tensile strength of（Al＋Al2O3）-coated SiC fiber.Solid-state diffusion bonding process is employed to prepare the（Al＋Al2O3）-coated SiC fiber reinforced nickel matrix with 37% fibers in volume.The solid-state diffusion bonding process is optimized and the optimum parameters are temperature of 870,pressure of 50 MPa and holding time of 2 h.Under this condition,the precursor wires can diffuse well,composite of full density can be formed and the（Al＋Al2O3） coating is effective to restrict the reaction between SiC fiber and nickel matrix.
基金supported by the National Natural Science Foundation of China(52072173)the Jiangsu Province Outstanding Youth Fund(BK20200016)the International Cooperation of Jiangsu Province(SBZ2022000084)
文摘Lithium metal batteries are emerging as a strong candidate in the future energy storage market due to its extremely high energy density.However,the uncontrollable lithium dendrites and volume change of lithium metal anodes severely hinder its application.In this work,the porous Cu skeleton modified with Cu_(6)Sn_(5)layer is prepared via dealloying brass foil following a facile electroless process.The porous Cu skeleton with large specific surface area and high electronic conductivity effectively reduces the local current density.The Cu_(6)Sn_(5)can react with lithium during the discharge process to form lithiophilic Li_(7)Sn_(2)in situ to promote Li-ions transport and reduce the nucleation energy barrier of lithium to guide the uniform lithium deposition.Therefore,more than 300 cycles at 1 mA cm^(−2)are achieved in the half-cell with an average Coulombic efficiency of 97.5%.The symmetric cell shows a superior cycle life of more than 1000 h at 1 mA cm^(−2)with a small average hysteresis voltage of 16 mV.When coupled with LiFePO_(4)cathode,the full cell also maintains excellent cycling and rate performance.
基金supported by NIH grants RO1 NS64134 and RO1 NS 48349
文摘Restorative cell-based therapies for experimental brain injury, such as stroke and traumatic brain injury,substantially improve functional outcome. We discuss and review state of the art magnetic resonance imaging methodologies and their applications related to cell-based treatment after brain injury. We focus on the potential of magnetic resonance imaging technique and its associated challenges to obtain useful new information related to cell migration, distribution, and quantitation, as well as vascular and neuronal remodeling in response to cell-based therapy after brain injury. The noninvasive nature of imaging might more readily help with translation of cell-based therapy from the laboratory to the clinic.
文摘Tantalum nitride （TAN） thin films are achieved on Si（111） and SS317L substrates by cathodic vacuum arc technique, which is rarely reported in the literature. The crystal structure, composition and surface morphology of the films are characterized by x-ray diffraction （XRD）, x-ray photoelectron spectroscopy （XPS）, auger electron spectroscopy, and atomic force microscopy, respectively. The influence of substrate negative bias on crystal structure, composition, surface morphology of the TaN films is systematically studied. At the substrate bias of 0 V and -50 V, the amorphous TaN film is obtained. As the bias increases to -100 V, cubic TaN phase can be found. Stoichiometric TaN with hexagonal lattice preferred （300） orientation is prepared at a bias of -200 V. Combine the XRD and XPS results, the binding energy value of 23.6eV of Ta 4f（7/2） is contributed to hexagonal TaN. Compared to other techniques, TaN thin films fabricated by cathodic vacuum arc at various substrate biases show different microstructures.
基金supported by the National Natural Science Foundation of China(No.52101107)the China Postdoctoral Science Foundation(No.2021M703274)CNNC’s 2021 young talents scientific research project(No.75)。
文摘Ce is prone to catastrophic oxidation at room temperature and its oxidation resistance is difficult to be improved by alloying.Herein,we found that the oxidation resistance of active metal Ce can be significantly improved by the addition of 20 at.%Ga.Focused ion beam lift-out technique and scanning transmission electron microscopy analysis disclosed that a discontinuous Ga-rich layer was generated beneath the oxide layer in the coarse-grained Ce-Ga alloy.The Ga-rich layer formed by selective oxidation of Ce acts as a diffusion barrier for Ce outward diffusion and ceases the O/M interfacial reaction when a critical concentration of Ga(75 at.%)is reached.After nanocrystallization,uniform distribution of Ga was achieved.After oxidation,a relatively continuous Ga-rich layer was formed which further enhanced the oxidation resistance.The introduction of noble elements combining with nanocrystallization may provide a novel strategy for the protection of metals with high activity and poor oxidation resistance.
基金National Key Research and Development Program of China(2018YFB0703600)National Natural Science Foundation of China(51572282,51632010,11572050)Youth Innovation Promotion Association CAS。
文摘In thermoelectric(TE)devices,the interfacial reliability greatly influenced devices’durability and power output.For skutterudites(SKD)devices,TE legs and electrodes are bonded together with diffusion barrier layer(DBL).At elevated temperatures,DBL react with SKD matrix or electrode to generate complex interfacial microstructures,which often accompanies evolutions of the thermal,electrical and mechanical properties at the interfaces.In this work,a finite element model containing the interfacial microstructure characteristics based on the experimental results was built to analyze the interfacial stress state in the skutterudite-based TE joints.A single-layer model was applied to screen out the most important parameters of the coefficient of thermal expansion(CTE)and the modulus of DBL on the first principle stress.The multilayer model considering the interfacial microstructures evolution was built to quantitively simulate the stress state of the TE joints at different aging temperatures and time.The simulation results show that the reactive CoSb2 layer is the weakest layer in both SKD/Nb and SKD/Zr joints.And by prolonging the aging time,the thickness of the reaction layer continuously increased,leading to a significant raising of the interfacial stress.The tensile testing results of the SKD/Nb joints match the simulation results well,consolidating accuracy and feasibility of this multilayer model.This study provides an important guidance on the design of DBL to improve the TE joints’mechanical reliability,and a common method to precisely simulate the stress condition in other coating systems.
