The Casulli's difference scheme was introduced into the three-dimensional ocean model in the present paper, and the wind-driven current and thermohaline current were simulated. The results show that, southwesterly...The Casulli's difference scheme was introduced into the three-dimensional ocean model in the present paper, and the wind-driven current and thermohaline current were simulated. The results show that, southwesterly monsoon in summer induces a clockwise circulation in the Beibu Gulf, and the density gradient induces a counter-clockwise one; but the density current is more intense than the wind- driven one in summer, espeially in surface layer. In addition, the northeasterly monsoon in winter in- duces a counter-clockwise circulation. The simulated results don't support the traditional condusion that there is a clockwise circulation in the Beibu Gulf in summer and a counter-clockwise one in winter, but support the statement that a counterclockwise circulation exists in the Beibu Gulf all year round.展开更多
In this paper, the characteristics of density current under the action of waves are described with the help of flume experiment and theoretical analysis. The study shows that turbid water under the action of the waves...In this paper, the characteristics of density current under the action of waves are described with the help of flume experiment and theoretical analysis. The study shows that turbid water under the action of the waves can present three types of motion, i. e. significant stratification, fragile stratification and strong mixing. The motion gf turbid;,ater presents significant stratification when (H/D)/root Delta rho/rho less than or equal to 4.5, generally this state is known as density current. The formulas of motion velocity, thickness, and discharge of density current moving on horizontal bottom are derived by use of basic equations such as momemtum equation, equation of energy conservation and continuity equation of fluid. The time-average velocity and the thickness of density current under the action of waves have a relationship with such parameters as relative density (Delta rho/rho), wave height (H), and water depth (D). When these parameters are determined, the time-average thickness and motion velocity of density current are also determined. The relative thickness of density current (D-t/D) decreases with the increase of Delta rho/rho and increases with the increase of H/D. On the other hand, the motion velocity of density current increases with the increase of Delta rho/rho and decreases with the increase of the relative thickness (D-t/D) of density current. It is shown that the calculated results are in agreement with those of the flume experiment.展开更多
The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-...The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-heterostructured nanoporous CoFe/CoFe_(2)O_(4) and CeO_(2−x),in situ grown on nickel foam(NF),holds great promise as a high-efficient bifunctional electrocatalyst(named R-CoFe/Ce/NF)for water splitting.Experimental characterization verifies surface reconstruction from CoFe alloy/oxide to highly active CoFeOOH during in situ electrochemical polarization.By virtues of three-dimensional nanoporous architecture and abundant electroactive CoFeOOH/CeO_(2−x) heterostructure interfaces,the R-CoFe/Ce/NF electrode achieves low overpotentials for oxygen evolution(η_(10)=227 mV;η_(500)=450 mV)and hydrogen evolution(η_(10)=35 mV;η_(408)=560 mV)reactions with high normalized electrochemical active surface areas,respectively.Additionally,the alkaline full water splitting electrolyzer of R-CoFe/Ce/NF||R-CoFe/Ce/NF achieves a current density of 50 mA·cm^(−2) only at 1.75 V;the decline of activity is satisfactory after 100-h durability test at 300 mA·cm^(−2).Density functional theory also demonstrates that the electron can transfer from CeO_(2−x) by virtue of O atom to CoFeOOH at CoFeOOH/CeO_(2−x) heterointerfaces and enhancing the adsorption of reactant,thus optimizing electronic structure and Gibbs free energies for the improvement of the activity for water splitting.展开更多
Electrically assisted forming(EAF)is a reliable method of reducing the deformation resistance of metallic materials and enhancing their formability.In this study,the mechanical properties and microstructure of Al_(0.5...Electrically assisted forming(EAF)is a reliable method of reducing the deformation resistance of metallic materials and enhancing their formability.In this study,the mechanical properties and microstructure of Al_(0.5)CoCrFeNi high-entropy alloy(HEA)under electrically assisted compression(EAC)were investigated.The results showed that the flow stress decreased with increasing current density in the EAC.Specifically,the flow curves exhibited S-shaped softening at a higher current density,which was dominated by the non-uniform distribution of the Joule heating temperature during EAC.When the flow stress was fixed at 500 MPa and 80 A·mm^(−2),compressible deformation amounts of 63.7%were observed at a strain rate of 1 s−1,indicating full compression of Al_(0.5)CoCrFeNi HEA at low-stress levels.Based on the microstructure,the flowability of Al_(0.5)CoCrFeNi HEA was improved during EAC,and the flow direction shifted from 45°to the horizontal direction.The current density,which influences the Joule heating temperature and strain rate,synergistically affects the stacking fault energy(SFE)and critical resolved shear stress(CRSS),which affect the tendency for twinning behavior.Thererfore,deformation nanoscale twins(DTs)were observed,indicating a shift in the deformation mechanisms from dislocation slip domination to a mixed pattern of dislocation slip and twinning.This study confirmed the deformability of Al_(0.5)CoCrFeNi HEA during EAC and provided an experimental foundation and theoretical support for the formation of HEAs.展开更多
Retaining satisfactory electrocatalytic performance under high current density plays a crucial role in industrial water splitting but is still limited to the enormous energy loss because of insufficient exposure of ac...Retaining satisfactory electrocatalytic performance under high current density plays a crucial role in industrial water splitting but is still limited to the enormous energy loss because of insufficient exposure of active sites caused by the blocked mass/charge transportation at this condition.Herein,we present a freestanding lamellar nanoporous Ni-Co-Mn alloy electrode(Lnp-NCM)designed by a refined variant of the“dealloying-coarsening-dealloying”protocol for highly efficient bifunctional electrocatalyst,where large porous channels distribute on the surface and small porous channels at the interlayer.With its 3D lamellar architecture regulating,the electrocatalytic properties of the electrodes with different distances between lamellas are compared,and faster energy conversion kinetics is achieved with efficient bubble transport channels and abundant electroactive sites.Note that the optimized sample(Lnp-NCM4)is expected to be a potential bifunctional electrocatalyst with low overpotentials of 258 and 439 mV at high current densities of 1000 and 900 mA·cm^(-2)for hydrogen and oxygen evolution reactions(HER and OER),respectively.During overall water splitting in a two-electrode cell with Lnp-NCM4 as cathode and anode,it only needs an ultralow cell voltage of 1.75 V to produce 100 mA·cm^(-2)with remarkable long-term stability over 50 h.This study on lamellar nanoporous electrode design approaches industrial water splitting requirements and paves a way for developing other catalytic systems.展开更多
Recently,it has been observed that during the operation of an inductively coupled plasma(ICP),a luminescent target(BAM,BaMgAl10O17:Eu)can interact with the plasma beam and emit blue light.After excluding the influence...Recently,it has been observed that during the operation of an inductively coupled plasma(ICP),a luminescent target(BAM,BaMgAl10O17:Eu)can interact with the plasma beam and emit blue light.After excluding the influence of ultraviolet(UV)and electromagnetic wave radiation,the results indicate that the BAM target may undergo luminescent excitation due to collisions with electrons and ions.This led us to investigate the physical mechanism behind this plasma luminescence excitation phenomenon.A spectrometer was used to record the luminescent spectroscopy and peak light intensity.Under excitation by argon plasma,the BAM material emits a continuum spectrum from 400 nm to 550 nm,with the peak light intensity located at 462.58 nm,which is the same as the spectrum excited by UV torchlight.To identify the relationship between the plasma parameters and the luminescent intensity,Langmuir and Faraday probes were employed to determine the local plasma parameters such as electron density,electron temperature,and current density.After normalizing the peak light intensity to the plasma parameters,the most interesting point is that the current density is linearly correlated with the luminescent light intensity.To verify the repeatability and lifetime of the plasma-luminescence interaction,a 600 s lifetime test was conducted in a 200 W ICP discharge environment.The maximum difference for the peak light strength of the luminescent spectrum is 6.5%.From a voltage bias experiment and a theoretical derivation,we initially identified that bombardment by ions plays the dominant role in the luminescence excitation process,which also explains the mechanism by which the current density is proportional to the luminescence intensity.This new finding leads us to reconsider the possibility of applying this plasma luminescence phenomenon to optical plasma diagnostics.The BAM light intensity can potentially be used to predict the current density of a plasma beam for large-area two-dimensional(2D)measurements and can capture high spatial resolution in a single test.We believe that this method may lead to high-efficiency,spatially resolved plasma current density measurement.展开更多
Photoelectrochemical(PEC)water splitting holds significant promise for sustainable energy harvesting that enables efficient conversion of solar energy into green hydrogen.Nevertheless,achievement of high performance i...Photoelectrochemical(PEC)water splitting holds significant promise for sustainable energy harvesting that enables efficient conversion of solar energy into green hydrogen.Nevertheless,achievement of high performance is often limited by charge carrier recombination,resulting in unsatisfactory saturation current densities.To address this challenge,we present a novel strategy for achieving ultrahigh current density by incorporating a bridge layer between the Si substrate and the NiOOH cocatalyst in this paper.The optimal photoanode(TCO/n-p-Si/TCO/Ni)shows a remarkably low onset potential of 0.92 V vs.a reversible hydrogen electrode and a high saturation current density of 39.6 mA·cm^(-2),which is about 92.7%of the theoretical maximum(42.7 mA·cm^(-2)).In addition,the photoanode demonstrates stable operation for 60 h.Our systematic characterizations and calculations demonstrate that the bridge layer facilitates charge transfer,enhances catalytic performance,and provides corrosion protection to the underlying substrate.Notably,the integration of this photoanode into a PEC device for overall water splitting leads to a reduction of the onset potential.These findings provide a viable pathway for fabricating highperformance industrial photoelectrodes by integrating a substrate and a cocatalyst via a transparent and conductive bridge layer.展开更多
The large current density of electrochemical CO_(2)reduction towards industrial application is challenging.Herein,without strong acid and reductant,the synthesized BiVO_(4)with abundant oxygen vacancies(Ovs)exhibited ...The large current density of electrochemical CO_(2)reduction towards industrial application is challenging.Herein,without strong acid and reductant,the synthesized BiVO_(4)with abundant oxygen vacancies(Ovs)exhibited a high formate Faradaic efficiency(FE)of 97.45%(-0.9 V)and a large partial current density of-45.82 mA/cm^(2)(-1.2 V).The good performance benefits from the reconstruction of BiVO_(4)to generate active metal Bi sites,which results in the electron redistribution to boost the OCHO∗formation.In flow cells,near industrial current density of 183.94 mA/cm^(2)was achieved,with the FE of formate above 95%from 20mA/cm^(2)to 180mA/cm^(2).Our work provides a facily synthesized BiVO_(4)precatalyst for CO_(2)electroreduction.展开更多
A finite equilibrium current density arises in the anomalous Hall effect(AHE)as a result of time-reversal symmetry breaking,affecting both the differential current density and total current.In this paper,we illustrate...A finite equilibrium current density arises in the anomalous Hall effect(AHE)as a result of time-reversal symmetry breaking,affecting both the differential current density and total current.In this paper,we illustrate the equilibrium current density in a ribbon-shaped system within the AHE regime,consisting of two sets of counterpropagating channels arranged in a zebra stripes pattern.While the middle channels are susceptible to scattering,the edge channels remain relatively robust.Despite this difference,all channels exhibit the same differential current density when subjected to a differential voltage across the two ends of the ribbon.When a differential voltage is applied to both sides of the ribbon,it results in a snaking pattern of differential current density forming across it.Furthermore,in a four-terminal device comprising the ribbon and two normal leads,it is found that Hall conductance is independent of ribbon width within certain scattering strengths due to the differences in robustness between middle and edge channels.These findings disclose the details of the AHE transport in a finite-sized system under weak scattering.展开更多
Lattice-strain engineering has demonstrated its capability to influence the electronic structure and catalytic performance of electrocatalysts.Herein,we present a facile method for inducing thermal strain in cobalt/mo...Lattice-strain engineering has demonstrated its capability to influence the electronic structure and catalytic performance of electrocatalysts.Herein,we present a facile method for inducing thermal strain in cobalt/molybdenum nitride rod-shaped structures(denoted Co/Mo_(2)N)via ammonia-assisted reduction,which effectively modulating the HER performance.The optimized Co/Mo_(2)N-500,characterized by 3%tensile lattice strain,demonstrates exceptional HER activity with lower overpotentials of140 mV and 184 mV at high current density of 1000 mA cm^(-2)in alkaline freshwater and seawater electrolytes,respectively.Co/Mo_(2)N also exhibits excellent long-term durability even at a high current density of 300 mA cm^(-2),surpassing its counterparts and benchmark Pt/C catalyst.Density functional theory calculations validate that the tensile strain optimizes the d-band states,water dissociation,and hydrogen adsorption kinetics of the strained Mo_(2)N in Co/Mo_(2)N,thereby improving its catalytic efficacy.This work provides valuable insights into controlling lattice strain to develop highly efficient electrocatalysts towards advanced electrocatalytic applications.展开更多
Garnet-type solid-state batteries(SSBs)are considered to be one of the most promising candidates to realize next-generation lithium metal batteries with high energy density and safety.However,the dendrite-induced shor...Garnet-type solid-state batteries(SSBs)are considered to be one of the most promising candidates to realize next-generation lithium metal batteries with high energy density and safety.However,the dendrite-induced short-circuit and the poor interfacial contact impeded the practical application.Herein,interface engineering to achieve low interfacial resistance without high temperature calcination was developed,which Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO)was simply coated with complex hydride(Li_(4)(BH_(4))_(3)I(3L1L))in various mass ratios n(Li_(4)(BH_(4))_(3)I)-(100−n)LLZTO(10≤n≤40).The interfacial conductivity increases by more than three orders of magnitude from 8.29×10^(−6)S·cm^(−1)to 1.10×10^(−2)S·cm^(−1).Symmetric Li cells exhibit a high critical current density(CCD)of 4.0 mA·cm^(−2) and an excellent cycling stability for 200 h at 4.0 mA·cm^(−2).SSBs with polymeric sulfur-polyacrylonitrile(SPAN)cathode achieve a high discharge capacity of 1149 mAh·g^(−1) with a capacity retention of 91%after 100 cycles(0.2 C).This attempt guides a simple yet efficient strategy for obtaining a stable Li/LLZTO interface,which would promote the development of solid-state batteries.展开更多
The high-entropy alloy(HEA)superconductor,Ta_(1/6)Nb_(2/6)Hf_(1/6)Zr_(1/6)Ti_(1/6)(Ta-Nb-Hf-Zr-Ti),is systematically studied to examine changes in superconducting critical properties,critical temperature(T_(c)),critic...The high-entropy alloy(HEA)superconductor,Ta_(1/6)Nb_(2/6)Hf_(1/6)Zr_(1/6)Ti_(1/6)(Ta-Nb-Hf-Zr-Ti),is systematically studied to examine changes in superconducting critical properties,critical temperature(T_(c)),critical cur-rent density(J_(c)),and upper critical field(H_(c2)),concerning thermal treatment conditions.Annealing condi-tion affects Jc more significantly than T_(c)and H_(c2),with a large improvement of flux pinning force density(F_(p)).The Jc of bare sample is reduced to 10 A cm^(-2)at an applied magnetic field of approximately 1.5 T,whereas the sample annealed at 550℃for 12 h exhibits J_(c)>100 kA cm^(-2)up to around 4 T.Furthermore,the Vickers hardness(HVIT)of the Ta-Nb-Hf-Zr-Ti HEA superconductor notably increases from∼384 to 528 HVIT following a 24-h annealing at 500℃.These results demonstrate that thermal annealing is a powerful process to optimize both the superconducting and mechanical properties of high-entropy alloy superconductors.展开更多
The Nd:TiO_(2 )PEO coatings were formed in a phosphate-based electrolyte with the addition of Nd_(2)O_(3 )under the current density of 150,200,250 and 300 m A/cm^(2).SEM results showed that the micropores decreased on...The Nd:TiO_(2 )PEO coatings were formed in a phosphate-based electrolyte with the addition of Nd_(2)O_(3 )under the current density of 150,200,250 and 300 m A/cm^(2).SEM results showed that the micropores decreased on quantity and increased on scale with the increasing current density.AFM results revealed that the roughness of the coatings increased with the increasing current density.Phase and composition analysis showed that the Nd:TiO_(2) coatings were mainly composed of anatase and rutile phase.And the anatase phase content has reached the maximum value at the current density of 250 m A/cm^(2).XPS results indicated that Ti2p spin-orbit components of the Nd:TiO_(2) coatings are shifted towards higher binding energy,compared with the pure TiO_(2) coating,suggesting that some of the Nd^(3+)ions are combined with TiO_(2) lattice and led to dislocation.Photocatalytic test showed that the photocatalytic activity of Nd:TiO_(2) coatings varied in the same pattern with the anatase content variation in Nd:TiO_(2) coatings.The photocatalytic experiment results show that the photocatalytic activity of Nd:TiO_(2) coatings can be greatly enhanced with moderate amount of Nd^(3+).However,excessive amount of Nd^(3+)does not have an effective impact on the photoctalytic activity improvement.展开更多
The electrolysis of water powered by renewable energy sources offers a promising method of"green hydrogen"production,which is considered to be at the heart of future carbon-neutral energy systems.In the past...The electrolysis of water powered by renewable energy sources offers a promising method of"green hydrogen"production,which is considered to be at the heart of future carbon-neutral energy systems.In the past decades,researchers have reported a number of hydrogen evolution reaction(HER)electrocatalysts with activity comparable to that of commercial Pt/C,but most of them are tested within a small current density range,typically no more than 500 mA cm^(-2).To realize the industrial application of hydrogen production from water electrolysis,it is essential to develop high-efficiency HER electrocatalysts at high current density(HCD≥500 mA cm^(-2)).Nevertheless,it remains challenging and significant to rational design HCD electrocatalysts for HER.In this paper,the design strategy of HCD electrocatalysts is discussed,and some HCD electrocatalysts for HER are reviewed in seven categories(alloy,metal oxide,metal hydroxide,metal sulfide/selenide,metal nitride,metal phosphide and other derived electrocatalysts).At the end of this article,we also pro-pose some viewpoints and prospects for the future development and research directions of HCD electrocatalysts for HER.展开更多
Many magnetohydrodynamic stability analyses require generation of a set of equilibria with a fixed safety factor q-profile while varying other plasma parameters.A neural network(NN)-based approach is investigated that...Many magnetohydrodynamic stability analyses require generation of a set of equilibria with a fixed safety factor q-profile while varying other plasma parameters.A neural network(NN)-based approach is investigated that facilitates such a process.Both multilayer perceptron(MLP)-based NN and convolutional neural network(CNN)models are trained to map the q-profile to the plasma current density J-profile,and vice versa,while satisfying the Grad–Shafranov radial force balance constraint.When the initial target models are trained,using a database of semianalytically constructed numerical equilibria,an initial CNN with one convolutional layer is found to perform better than an initial MLP model.In particular,a trained initial CNN model can also predict the q-or J-profile for experimental tokamak equilibria.The performance of both initial target models is further improved by fine-tuning the training database,i.e.by adding realistic experimental equilibria with Gaussian noise.The fine-tuned target models,referred to as fine-tuned MLP and fine-tuned CNN,well reproduce the target q-or J-profile across multiple tokamak devices.As an important application,these NN-based equilibrium profile convertors can be utilized to provide a good initial guess for iterative equilibrium solvers,where the desired input quantity is the safety factor instead of the plasma current density.展开更多
Within the framework of achieving global carbon neutrality,utilizing electrocatalytic water splitting to produce“green hydrogen”holds significant promise as an effective solution.The strategic development of economi...Within the framework of achieving global carbon neutrality,utilizing electrocatalytic water splitting to produce“green hydrogen”holds significant promise as an effective solution.The strategic development of economic,efficient,and robust anode oxygen evolution reaction(OER)catalysts is one of the imminent bottlenecks for scalable application of electrolyzing water into hydrogen and oxygen,particularly under actual yet harsh operating conditions such as large current density(LCD).In this review,we intend to summarize the advances and challenges in the understanding of the electrocatalytic OER at LCD.Initially,the impact of LCD on the electron transfer,mass transportation efficiency and catalyst stability is identified and summarized.Furthermore,five basic principles for catalyst design,namely the dimension of the materials,surface chemistry,creation of electron transfer pathways,synergy among nano-,micro-,and macroscale structures,and catalyst-support interaction,are systematically discussed.Specifically,the correlation between the synergistic function of the multiscale structures and the catalyst-support interaction is highlighted to direct improvements in catalyst efficiency and durability at the LCD.Finally,an outlook is prospected to further our understanding of these topics and provide related researchers with potential research areas.展开更多
Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density o...Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.展开更多
Al/conductive coating/α-Pb O2-Ce O2-Ti O2/β-PbO 2-MnO 2-WC-Zr O2 composite electrode material was prepared on Al/conductive coating/α-PbO 2-Ce O2-Ti O2 substrate by electrochemical oxidation co-deposition technique...Al/conductive coating/α-Pb O2-Ce O2-Ti O2/β-PbO 2-MnO 2-WC-Zr O2 composite electrode material was prepared on Al/conductive coating/α-PbO 2-Ce O2-Ti O2 substrate by electrochemical oxidation co-deposition technique. The effects of current density on the chemical composition, electrocatalytic activity, and stability of the composite anode material were investigated by energy dispersive X-ray spectroscopy（EDXS）, anode polarization curves, quasi-stationary polarization（Tafel） curves, electrochemical impedance spectroscopy（EIS）, scanning electron microscopy（SEM）, and X-ray diffraction（XRD）. Results reveal that the composite electrode obtained at 1 A/dm2 possesses the lowest overpotential（0.610 V at 500 A/m2） for oxygen evolution, the best electrocatalytic activity, the longest service life（360 h at 40 °C in 150 g/L H2SO4 solution under 2 A/cm2）, and the lowest cell voltage（2.75 V at 500 A/m2）. Furthermore, with increasing current density, the coating exhibits grain growth and the decrease of content of Mn O2. Only a slight effect on crystalline structure is observed.展开更多
AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs double-barrier resonant tunneling diodes （DBRTDs） grown on a semi-insulated GaAs substrate with molecular beam epitaxy is demonstrated. By sandwiching the In0.1 Ga0.9 As layer betwee...AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs double-barrier resonant tunneling diodes （DBRTDs） grown on a semi-insulated GaAs substrate with molecular beam epitaxy is demonstrated. By sandwiching the In0.1 Ga0.9 As layer between GaAs layers, potential wells beside the two sides of barrier are deepened, resulting in an increase of the peak-to-valley current ratio （PVCR） and a peak current density. A special shape of collector is designed in order to reduce contact resistance and non-uniformity of the current;as a result the total chrrent density in the device is increased. The use of thin barriers is also helpful for the improvement of the PVCR and the peak current density in DBRTDs. The devices exhibit a maximum PVCR of 13.98 and a peak current density of 89kA/cm^2 at room temperature.展开更多
Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxid...Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxide coatings formed on magnesium alloys are mainly composed of MgO and MgAl2O4 phases;in addition,the content of MgO increases with increasing the current density.The morphology and surface roughness of the coatings were characterized by confocal laser scanning microscopy (CLSM).The results show that the surface roughness(Ra)decreases with increasing the current density.Moreover,the electrochemical corrosion results prove that the MgO coating produced in the electrolyte Na2SiO3 at current density of 5 A/cm 2 shows the best corrosion resistance.展开更多
基金This study was supported by the Youth Ocean Sience Funds of State Oceanic Administration under contract No. 97301.
文摘The Casulli's difference scheme was introduced into the three-dimensional ocean model in the present paper, and the wind-driven current and thermohaline current were simulated. The results show that, southwesterly monsoon in summer induces a clockwise circulation in the Beibu Gulf, and the density gradient induces a counter-clockwise one; but the density current is more intense than the wind- driven one in summer, espeially in surface layer. In addition, the northeasterly monsoon in winter in- duces a counter-clockwise circulation. The simulated results don't support the traditional condusion that there is a clockwise circulation in the Beibu Gulf in summer and a counter-clockwise one in winter, but support the statement that a counterclockwise circulation exists in the Beibu Gulf all year round.
文摘In this paper, the characteristics of density current under the action of waves are described with the help of flume experiment and theoretical analysis. The study shows that turbid water under the action of the waves can present three types of motion, i. e. significant stratification, fragile stratification and strong mixing. The motion gf turbid;,ater presents significant stratification when (H/D)/root Delta rho/rho less than or equal to 4.5, generally this state is known as density current. The formulas of motion velocity, thickness, and discharge of density current moving on horizontal bottom are derived by use of basic equations such as momemtum equation, equation of energy conservation and continuity equation of fluid. The time-average velocity and the thickness of density current under the action of waves have a relationship with such parameters as relative density (Delta rho/rho), wave height (H), and water depth (D). When these parameters are determined, the time-average thickness and motion velocity of density current are also determined. The relative thickness of density current (D-t/D) decreases with the increase of Delta rho/rho and increases with the increase of H/D. On the other hand, the motion velocity of density current increases with the increase of Delta rho/rho and decreases with the increase of the relative thickness (D-t/D) of density current. It is shown that the calculated results are in agreement with those of the flume experiment.
基金sponsored by the National Natural Science Foundation of China(Nos.5210125 and 52375422)the Science Research Project of Hebei Education Department(No.BJK2023058)the Natural Science Foundation of Hebei Province(Nos.E2020208069,B2020208083 and E202320801).
文摘The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-heterostructured nanoporous CoFe/CoFe_(2)O_(4) and CeO_(2−x),in situ grown on nickel foam(NF),holds great promise as a high-efficient bifunctional electrocatalyst(named R-CoFe/Ce/NF)for water splitting.Experimental characterization verifies surface reconstruction from CoFe alloy/oxide to highly active CoFeOOH during in situ electrochemical polarization.By virtues of three-dimensional nanoporous architecture and abundant electroactive CoFeOOH/CeO_(2−x) heterostructure interfaces,the R-CoFe/Ce/NF electrode achieves low overpotentials for oxygen evolution(η_(10)=227 mV;η_(500)=450 mV)and hydrogen evolution(η_(10)=35 mV;η_(408)=560 mV)reactions with high normalized electrochemical active surface areas,respectively.Additionally,the alkaline full water splitting electrolyzer of R-CoFe/Ce/NF||R-CoFe/Ce/NF achieves a current density of 50 mA·cm^(−2) only at 1.75 V;the decline of activity is satisfactory after 100-h durability test at 300 mA·cm^(−2).Density functional theory also demonstrates that the electron can transfer from CeO_(2−x) by virtue of O atom to CoFeOOH at CoFeOOH/CeO_(2−x) heterointerfaces and enhancing the adsorption of reactant,thus optimizing electronic structure and Gibbs free energies for the improvement of the activity for water splitting.
基金supported by the National Natural Science Foundation of China(Nos.52305349,52305423 and 51635005)CGN-HIT Advanced Nuclear and New Energy Research Institute(No.CGN-HIT202305).
文摘Electrically assisted forming(EAF)is a reliable method of reducing the deformation resistance of metallic materials and enhancing their formability.In this study,the mechanical properties and microstructure of Al_(0.5)CoCrFeNi high-entropy alloy(HEA)under electrically assisted compression(EAC)were investigated.The results showed that the flow stress decreased with increasing current density in the EAC.Specifically,the flow curves exhibited S-shaped softening at a higher current density,which was dominated by the non-uniform distribution of the Joule heating temperature during EAC.When the flow stress was fixed at 500 MPa and 80 A·mm^(−2),compressible deformation amounts of 63.7%were observed at a strain rate of 1 s−1,indicating full compression of Al_(0.5)CoCrFeNi HEA at low-stress levels.Based on the microstructure,the flowability of Al_(0.5)CoCrFeNi HEA was improved during EAC,and the flow direction shifted from 45°to the horizontal direction.The current density,which influences the Joule heating temperature and strain rate,synergistically affects the stacking fault energy(SFE)and critical resolved shear stress(CRSS),which affect the tendency for twinning behavior.Thererfore,deformation nanoscale twins(DTs)were observed,indicating a shift in the deformation mechanisms from dislocation slip domination to a mixed pattern of dislocation slip and twinning.This study confirmed the deformability of Al_(0.5)CoCrFeNi HEA during EAC and provided an experimental foundation and theoretical support for the formation of HEAs.
基金supported by the National Natural Science Foundation of China(No.52101251)the Science Research Project of Hebei Education Department(No.BJK2023058)the Natural Science Foundation of Hebei Province(Nos.E2020208069 and B2020208083).
文摘Retaining satisfactory electrocatalytic performance under high current density plays a crucial role in industrial water splitting but is still limited to the enormous energy loss because of insufficient exposure of active sites caused by the blocked mass/charge transportation at this condition.Herein,we present a freestanding lamellar nanoporous Ni-Co-Mn alloy electrode(Lnp-NCM)designed by a refined variant of the“dealloying-coarsening-dealloying”protocol for highly efficient bifunctional electrocatalyst,where large porous channels distribute on the surface and small porous channels at the interlayer.With its 3D lamellar architecture regulating,the electrocatalytic properties of the electrodes with different distances between lamellas are compared,and faster energy conversion kinetics is achieved with efficient bubble transport channels and abundant electroactive sites.Note that the optimized sample(Lnp-NCM4)is expected to be a potential bifunctional electrocatalyst with low overpotentials of 258 and 439 mV at high current densities of 1000 and 900 mA·cm^(-2)for hydrogen and oxygen evolution reactions(HER and OER),respectively.During overall water splitting in a two-electrode cell with Lnp-NCM4 as cathode and anode,it only needs an ultralow cell voltage of 1.75 V to produce 100 mA·cm^(-2)with remarkable long-term stability over 50 h.This study on lamellar nanoporous electrode design approaches industrial water splitting requirements and paves a way for developing other catalytic systems.
基金partly supported by National Natural Science Foundation of China(Nos.52302464 and 52177128)supported by the Key Scientific Research Project for Institutions of Higher Education of Henan Province(No.22B140002).
文摘Recently,it has been observed that during the operation of an inductively coupled plasma(ICP),a luminescent target(BAM,BaMgAl10O17:Eu)can interact with the plasma beam and emit blue light.After excluding the influence of ultraviolet(UV)and electromagnetic wave radiation,the results indicate that the BAM target may undergo luminescent excitation due to collisions with electrons and ions.This led us to investigate the physical mechanism behind this plasma luminescence excitation phenomenon.A spectrometer was used to record the luminescent spectroscopy and peak light intensity.Under excitation by argon plasma,the BAM material emits a continuum spectrum from 400 nm to 550 nm,with the peak light intensity located at 462.58 nm,which is the same as the spectrum excited by UV torchlight.To identify the relationship between the plasma parameters and the luminescent intensity,Langmuir and Faraday probes were employed to determine the local plasma parameters such as electron density,electron temperature,and current density.After normalizing the peak light intensity to the plasma parameters,the most interesting point is that the current density is linearly correlated with the luminescent light intensity.To verify the repeatability and lifetime of the plasma-luminescence interaction,a 600 s lifetime test was conducted in a 200 W ICP discharge environment.The maximum difference for the peak light strength of the luminescent spectrum is 6.5%.From a voltage bias experiment and a theoretical derivation,we initially identified that bombardment by ions plays the dominant role in the luminescence excitation process,which also explains the mechanism by which the current density is proportional to the luminescence intensity.This new finding leads us to reconsider the possibility of applying this plasma luminescence phenomenon to optical plasma diagnostics.The BAM light intensity can potentially be used to predict the current density of a plasma beam for large-area two-dimensional(2D)measurements and can capture high spatial resolution in a single test.We believe that this method may lead to high-efficiency,spatially resolved plasma current density measurement.
基金supported by Multi-Year Research Grants from the University of Macao(MYRG-GRG2023-00010-IAPME,MYRG-GRG2024-00038-IAPME,MYRG2022-00026-IAPME)the Science and Technology Development Fund(FDCT)from Macao SAR(0023/2023/AFJ,0050/2023/RIB2,006/2022/ALC,0087/2024/AFJ,0111/2022/A2).
文摘Photoelectrochemical(PEC)water splitting holds significant promise for sustainable energy harvesting that enables efficient conversion of solar energy into green hydrogen.Nevertheless,achievement of high performance is often limited by charge carrier recombination,resulting in unsatisfactory saturation current densities.To address this challenge,we present a novel strategy for achieving ultrahigh current density by incorporating a bridge layer between the Si substrate and the NiOOH cocatalyst in this paper.The optimal photoanode(TCO/n-p-Si/TCO/Ni)shows a remarkably low onset potential of 0.92 V vs.a reversible hydrogen electrode and a high saturation current density of 39.6 mA·cm^(-2),which is about 92.7%of the theoretical maximum(42.7 mA·cm^(-2)).In addition,the photoanode demonstrates stable operation for 60 h.Our systematic characterizations and calculations demonstrate that the bridge layer facilitates charge transfer,enhances catalytic performance,and provides corrosion protection to the underlying substrate.Notably,the integration of this photoanode into a PEC device for overall water splitting leads to a reduction of the onset potential.These findings provide a viable pathway for fabricating highperformance industrial photoelectrodes by integrating a substrate and a cocatalyst via a transparent and conductive bridge layer.
基金financially supported by the Fundamental Research Funds for the Central Universities of Central South University(No.2022ZZTS0579).
文摘The large current density of electrochemical CO_(2)reduction towards industrial application is challenging.Herein,without strong acid and reductant,the synthesized BiVO_(4)with abundant oxygen vacancies(Ovs)exhibited a high formate Faradaic efficiency(FE)of 97.45%(-0.9 V)and a large partial current density of-45.82 mA/cm^(2)(-1.2 V).The good performance benefits from the reconstruction of BiVO_(4)to generate active metal Bi sites,which results in the electron redistribution to boost the OCHO∗formation.In flow cells,near industrial current density of 183.94 mA/cm^(2)was achieved,with the FE of formate above 95%from 20mA/cm^(2)to 180mA/cm^(2).Our work provides a facily synthesized BiVO_(4)precatalyst for CO_(2)electroreduction.
基金supported by the National Natural Science Foundation of China(Grant No.12304062)supported by the National Natural Science Foundation of China(Grant No.12074107)+1 种基金the Program of Outstanding Young and Middle-aged Scientific and Technological Innovation Teams of Colleges and Universities in Hubei Province(Grant No.T2020001)the Innovation Group Project of the Natural Science Foundation of Hubei Province of China(Grant No.2022CFA012)。
文摘A finite equilibrium current density arises in the anomalous Hall effect(AHE)as a result of time-reversal symmetry breaking,affecting both the differential current density and total current.In this paper,we illustrate the equilibrium current density in a ribbon-shaped system within the AHE regime,consisting of two sets of counterpropagating channels arranged in a zebra stripes pattern.While the middle channels are susceptible to scattering,the edge channels remain relatively robust.Despite this difference,all channels exhibit the same differential current density when subjected to a differential voltage across the two ends of the ribbon.When a differential voltage is applied to both sides of the ribbon,it results in a snaking pattern of differential current density forming across it.Furthermore,in a four-terminal device comprising the ribbon and two normal leads,it is found that Hall conductance is independent of ribbon width within certain scattering strengths due to the differences in robustness between middle and edge channels.These findings disclose the details of the AHE transport in a finite-sized system under weak scattering.
基金supported by the Hunan Joint International Laboratory of Advanced Materials and Technology for Clean Energy(2020CB1007)Fundamental Research Funds for the Central Universities and Guangxi Key Laboratory of Information Materials and Guilin University of Electronic Technology,China(231002-K)+4 种基金Natural Science Foundation of Guangxi Zhuang Autonomous Region(2022GXNSFAA035467)Guangxi Science and Technology Program(Guike AD21220067)National Natural Science Foundation of China(22369002)Nationally Funded Postdoctoral Researcher Program(GZC20230756)China Postdoctoral Science Foundation(2024M750858)。
文摘Lattice-strain engineering has demonstrated its capability to influence the electronic structure and catalytic performance of electrocatalysts.Herein,we present a facile method for inducing thermal strain in cobalt/molybdenum nitride rod-shaped structures(denoted Co/Mo_(2)N)via ammonia-assisted reduction,which effectively modulating the HER performance.The optimized Co/Mo_(2)N-500,characterized by 3%tensile lattice strain,demonstrates exceptional HER activity with lower overpotentials of140 mV and 184 mV at high current density of 1000 mA cm^(-2)in alkaline freshwater and seawater electrolytes,respectively.Co/Mo_(2)N also exhibits excellent long-term durability even at a high current density of 300 mA cm^(-2),surpassing its counterparts and benchmark Pt/C catalyst.Density functional theory calculations validate that the tensile strain optimizes the d-band states,water dissociation,and hydrogen adsorption kinetics of the strained Mo_(2)N in Co/Mo_(2)N,thereby improving its catalytic efficacy.This work provides valuable insights into controlling lattice strain to develop highly efficient electrocatalysts towards advanced electrocatalytic applications.
基金This study was financially supported by the National Natural Science Foundation of China(Nos.52171180,51802154,and 51971065)the National Science Fund for Distinguished Young Scholars(No.51625102)+3 种基金the Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-07-E00028)the Fundamental Research Funds for the Central Universities(No.NG2022005)the Open Fund for Graduate Innovation Base in Nanjing University of Aeronautics and Astronautics(No.xcxjh20210612)partially supported by the Fundamental Research Funds for the Central Universities,NS2021043.
文摘Garnet-type solid-state batteries(SSBs)are considered to be one of the most promising candidates to realize next-generation lithium metal batteries with high energy density and safety.However,the dendrite-induced short-circuit and the poor interfacial contact impeded the practical application.Herein,interface engineering to achieve low interfacial resistance without high temperature calcination was developed,which Li_(6.4)La_(3)Zr_(1.4)Ta_(0.6)O_(12)(LLZTO)was simply coated with complex hydride(Li_(4)(BH_(4))_(3)I(3L1L))in various mass ratios n(Li_(4)(BH_(4))_(3)I)-(100−n)LLZTO(10≤n≤40).The interfacial conductivity increases by more than three orders of magnitude from 8.29×10^(−6)S·cm^(−1)to 1.10×10^(−2)S·cm^(−1).Symmetric Li cells exhibit a high critical current density(CCD)of 4.0 mA·cm^(−2) and an excellent cycling stability for 200 h at 4.0 mA·cm^(−2).SSBs with polymeric sulfur-polyacrylonitrile(SPAN)cathode achieve a high discharge capacity of 1149 mAh·g^(−1) with a capacity retention of 91%after 100 cycles(0.2 C).This attempt guides a simple yet efficient strategy for obtaining a stable Li/LLZTO interface,which would promote the development of solid-state batteries.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MIST)(Nos.2021R1A2C2010925,RS-2023-00240326,and RS-2023-00220471)Basic Science Research Program through the NRF of Korea funded by the Ministry of Education(Nos.NRF-2019R1F1A1055284 and NRF-2021R1I1A1A01043885).
文摘The high-entropy alloy(HEA)superconductor,Ta_(1/6)Nb_(2/6)Hf_(1/6)Zr_(1/6)Ti_(1/6)(Ta-Nb-Hf-Zr-Ti),is systematically studied to examine changes in superconducting critical properties,critical temperature(T_(c)),critical cur-rent density(J_(c)),and upper critical field(H_(c2)),concerning thermal treatment conditions.Annealing condi-tion affects Jc more significantly than T_(c)and H_(c2),with a large improvement of flux pinning force density(F_(p)).The Jc of bare sample is reduced to 10 A cm^(-2)at an applied magnetic field of approximately 1.5 T,whereas the sample annealed at 550℃for 12 h exhibits J_(c)>100 kA cm^(-2)up to around 4 T.Furthermore,the Vickers hardness(HVIT)of the Ta-Nb-Hf-Zr-Ti HEA superconductor notably increases from∼384 to 528 HVIT following a 24-h annealing at 500℃.These results demonstrate that thermal annealing is a powerful process to optimize both the superconducting and mechanical properties of high-entropy alloy superconductors.
基金Supported by the Open Project Foundation of Industrial Perception and Intelligent Manufacturing Equipment Engineering Research Center of Jiangsu Province (No. ZK220504)the Open Project Foundation of High-tech Key Laboratory of Agricultural Equipment and Intelligence of Jiangsu Province (No. MAET202104)+1 种基金the Open Project Foundation of Jiangsu Wind Power Engineering Technology Center (No. ZK220302)the Qing Lan Project of Jiangsu Province,China。
文摘The Nd:TiO_(2 )PEO coatings were formed in a phosphate-based electrolyte with the addition of Nd_(2)O_(3 )under the current density of 150,200,250 and 300 m A/cm^(2).SEM results showed that the micropores decreased on quantity and increased on scale with the increasing current density.AFM results revealed that the roughness of the coatings increased with the increasing current density.Phase and composition analysis showed that the Nd:TiO_(2) coatings were mainly composed of anatase and rutile phase.And the anatase phase content has reached the maximum value at the current density of 250 m A/cm^(2).XPS results indicated that Ti2p spin-orbit components of the Nd:TiO_(2) coatings are shifted towards higher binding energy,compared with the pure TiO_(2) coating,suggesting that some of the Nd^(3+)ions are combined with TiO_(2) lattice and led to dislocation.Photocatalytic test showed that the photocatalytic activity of Nd:TiO_(2) coatings varied in the same pattern with the anatase content variation in Nd:TiO_(2) coatings.The photocatalytic experiment results show that the photocatalytic activity of Nd:TiO_(2) coatings can be greatly enhanced with moderate amount of Nd^(3+).However,excessive amount of Nd^(3+)does not have an effective impact on the photoctalytic activity improvement.
文摘The electrolysis of water powered by renewable energy sources offers a promising method of"green hydrogen"production,which is considered to be at the heart of future carbon-neutral energy systems.In the past decades,researchers have reported a number of hydrogen evolution reaction(HER)electrocatalysts with activity comparable to that of commercial Pt/C,but most of them are tested within a small current density range,typically no more than 500 mA cm^(-2).To realize the industrial application of hydrogen production from water electrolysis,it is essential to develop high-efficiency HER electrocatalysts at high current density(HCD≥500 mA cm^(-2)).Nevertheless,it remains challenging and significant to rational design HCD electrocatalysts for HER.In this paper,the design strategy of HCD electrocatalysts is discussed,and some HCD electrocatalysts for HER are reviewed in seven categories(alloy,metal oxide,metal hydroxide,metal sulfide/selenide,metal nitride,metal phosphide and other derived electrocatalysts).At the end of this article,we also pro-pose some viewpoints and prospects for the future development and research directions of HCD electrocatalysts for HER.
基金supported by National Natural Science Foundation of China (Nos. 12205033, 12105317, 11905022 and 11975062)Dalian Youth Science and Technology Project (No. 2022RQ039)+1 种基金the Fundamental Research Funds for the Central Universities (No. 3132023192)the Young Scientists Fund of the Natural Science Foundation of Sichuan Province (No. 2023NSFSC1291)
文摘Many magnetohydrodynamic stability analyses require generation of a set of equilibria with a fixed safety factor q-profile while varying other plasma parameters.A neural network(NN)-based approach is investigated that facilitates such a process.Both multilayer perceptron(MLP)-based NN and convolutional neural network(CNN)models are trained to map the q-profile to the plasma current density J-profile,and vice versa,while satisfying the Grad–Shafranov radial force balance constraint.When the initial target models are trained,using a database of semianalytically constructed numerical equilibria,an initial CNN with one convolutional layer is found to perform better than an initial MLP model.In particular,a trained initial CNN model can also predict the q-or J-profile for experimental tokamak equilibria.The performance of both initial target models is further improved by fine-tuning the training database,i.e.by adding realistic experimental equilibria with Gaussian noise.The fine-tuned target models,referred to as fine-tuned MLP and fine-tuned CNN,well reproduce the target q-or J-profile across multiple tokamak devices.As an important application,these NN-based equilibrium profile convertors can be utilized to provide a good initial guess for iterative equilibrium solvers,where the desired input quantity is the safety factor instead of the plasma current density.
基金support of the Fundamental Research Funds for the Central Universities(Grant No.40120631)National Natural Science Foundation of China(Grant No.52202291)for the support+2 种基金Dr.C.Chen acknowledges the financial support of Natural Science Foundation of Hubei Province(Grant No.2022CFB388)the Natural Science Foundation of Hainan Province of China(Grant No.623MS068)J.Wang thanks Singapore MOE for support of research conducted at the National University of Singapore(Tier 1,A-8000186-01-00).
文摘Within the framework of achieving global carbon neutrality,utilizing electrocatalytic water splitting to produce“green hydrogen”holds significant promise as an effective solution.The strategic development of economic,efficient,and robust anode oxygen evolution reaction(OER)catalysts is one of the imminent bottlenecks for scalable application of electrolyzing water into hydrogen and oxygen,particularly under actual yet harsh operating conditions such as large current density(LCD).In this review,we intend to summarize the advances and challenges in the understanding of the electrocatalytic OER at LCD.Initially,the impact of LCD on the electron transfer,mass transportation efficiency and catalyst stability is identified and summarized.Furthermore,five basic principles for catalyst design,namely the dimension of the materials,surface chemistry,creation of electron transfer pathways,synergy among nano-,micro-,and macroscale structures,and catalyst-support interaction,are systematically discussed.Specifically,the correlation between the synergistic function of the multiscale structures and the catalyst-support interaction is highlighted to direct improvements in catalyst efficiency and durability at the LCD.Finally,an outlook is prospected to further our understanding of these topics and provide related researchers with potential research areas.
基金Project(51371039)supported by the National Natural Science Foundation of China
文摘Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.
基金Projects(51004056,51004057)supported by the National Natural Science Foundation of ChinaProject(KKZ6201152009)supported by the Opening Foundation of Key Laboratory of Inorganic Coating Materials,Chinese Academy of Sciences+2 种基金Project(2010ZC052)supported by the Applied Basic Research Foundation of Yunnan Province,ChinaProject(20125314110011)supported by the Specialized Research Fund for the Doctoral Program of Higher Education,ChinaProject(2010247)supported by Analysis&Testing Foundation of Kunming University of Science and Technology,China
文摘Al/conductive coating/α-Pb O2-Ce O2-Ti O2/β-PbO 2-MnO 2-WC-Zr O2 composite electrode material was prepared on Al/conductive coating/α-PbO 2-Ce O2-Ti O2 substrate by electrochemical oxidation co-deposition technique. The effects of current density on the chemical composition, electrocatalytic activity, and stability of the composite anode material were investigated by energy dispersive X-ray spectroscopy（EDXS）, anode polarization curves, quasi-stationary polarization（Tafel） curves, electrochemical impedance spectroscopy（EIS）, scanning electron microscopy（SEM）, and X-ray diffraction（XRD）. Results reveal that the composite electrode obtained at 1 A/dm2 possesses the lowest overpotential（0.610 V at 500 A/m2） for oxygen evolution, the best electrocatalytic activity, the longest service life（360 h at 40 °C in 150 g/L H2SO4 solution under 2 A/cm2）, and the lowest cell voltage（2.75 V at 500 A/m2）. Furthermore, with increasing current density, the coating exhibits grain growth and the decrease of content of Mn O2. Only a slight effect on crystalline structure is observed.
文摘AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs double-barrier resonant tunneling diodes （DBRTDs） grown on a semi-insulated GaAs substrate with molecular beam epitaxy is demonstrated. By sandwiching the In0.1 Ga0.9 As layer between GaAs layers, potential wells beside the two sides of barrier are deepened, resulting in an increase of the peak-to-valley current ratio （PVCR） and a peak current density. A special shape of collector is designed in order to reduce contact resistance and non-uniformity of the current;as a result the total chrrent density in the device is increased. The use of thin barriers is also helpful for the improvement of the PVCR and the peak current density in DBRTDs. The devices exhibit a maximum PVCR of 13.98 and a peak current density of 89kA/cm^2 at room temperature.
基金Project(20080505)supported by Science and Technology Department of Jilin Province,China
文摘Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxide coatings formed on magnesium alloys are mainly composed of MgO and MgAl2O4 phases;in addition,the content of MgO increases with increasing the current density.The morphology and surface roughness of the coatings were characterized by confocal laser scanning microscopy (CLSM).The results show that the surface roughness(Ra)decreases with increasing the current density.Moreover,the electrochemical corrosion results prove that the MgO coating produced in the electrolyte Na2SiO3 at current density of 5 A/cm 2 shows the best corrosion resistance.
