In order to generate high quality ion beams through the stable radiation pressure acceleration(RPA) of the near critical density(NCD) target, we propose a new type of target where an ultra-thin high density(HD) layer ...In order to generate high quality ion beams through the stable radiation pressure acceleration(RPA) of the near critical density(NCD) target, we propose a new type of target where an ultra-thin high density(HD) layer is attached to the front surface of an NCD target, which has a preferable self-supporting property in the RPA experiments than the ultra-thin foil target. It is found that in one-dimensional particle-in-cell(PIC) simulation, by the block of the HD layer in the new target,there emerges the hole-boring process rather than propagation in the NCD layer when the intense laser pulse impinges on this target. As a result, a typical RPA structure that the compressed electron layer overlaps the ion layer as a whole is formed and a high quality ion beam is obtained, e.g., a circularly polarized laser pulse with normalized amplitude a_0= 120 impinges on this new target and a 1.2 GeV monoenergetic ion beam is generated through the RPA of the NCD layer. Similar results are also found in the two-dimensional PIC simulation.展开更多
The work investigates influence of the electrolyte conductivity on the onset of partial contact glow discharge electrolysis(CGDE)in a water electrolysis.Critical current density(CCD)and breakdown voltage were measured...The work investigates influence of the electrolyte conductivity on the onset of partial contact glow discharge electrolysis(CGDE)in a water electrolysis.Critical current density(CCD)and breakdown voltage were measured together with in situ observation of hydrogen bubble behavior,whose influence has not been focused on.For a fixed current during normal electrolysis,hydrogen coalescence adjacent to cathode surface was invigorated at a lower conductivity.Photographic analyses elucidated the hydrogen coalescence characteristics by quantifying size and population of detached hydrogen bubbles.The CCD increased about 104% within given range of conductivity(11.50-127.48 mS·cm^(-1))due to impaired bubble coalescence,which delays hydrogen film formation on the cathode.Meanwhile,decreasing trend of breakdown voltage was measured with increased conductivity showing maximum drop of 74%.It is concluded that onset of partial CGDE is directly affected by hydrodynamic bubble behaviors,whereas the electrolyte conductivity affects the bubble formation characteristics adjacent to cathode electrode.展开更多
Apparent critical current density(j_(Ac)^(a))of garnet all-solid-state lithium metal symmetric cells(ASSLSCs)is a fundamental parameter for designing all-solid-state lithium metal batteries.Nevertheless,how much the p...Apparent critical current density(j_(Ac)^(a))of garnet all-solid-state lithium metal symmetric cells(ASSLSCs)is a fundamental parameter for designing all-solid-state lithium metal batteries.Nevertheless,how much the possible maximum apparent current density that a given ASSLSC system can endure and how to reveal this potential still require study.Herein,a capacity perturbation strategy aiming to better measure the possible maximum j_(Ac)^(a)is proposed for the first time.With garnet-based plane-surface structure ASSLSCs as an exemplification,the j_(Ac)^(a)is quite small when the capacity is dramatically large.Under a perturbed capacity of 0.001 mA h cm^(-2),the j_(Ac)^(a)is determined to be as high as 2.35 mA cm^(-2)at room temperature.This investigation demonstrates that the capacity perturbation strategy is a feasible strategy for measuring the possible maximum j_(Ac)^(a)of Li/solid electrolyte interface,and hopefully provides good references to explore the critical current density of other types of electrochemical systems.展开更多
The empirically reported values of the critical current density (<i>j<sub>c</sub></i>) of Bi-2212 as 2.4 × 10<sup>5</sup> (<i>j<sub>c</sub></i><sub&g...The empirically reported values of the critical current density (<i>j<sub>c</sub></i>) of Bi-2212 as 2.4 × 10<sup>5</sup> (<i>j<sub>c</sub></i><sub>1</sub>;Sample 1) and 1.0 × 10<sup>6</sup> A/cm<sup>2</sup> (<i>j<sub>c</sub></i><sub>2</sub>;Sample 2) are intriguing because both of them correspond to the <i>same</i> values of the temperature <i>T</i> = 4.2 K and the applied magnetic field <i>H</i> = 12 × 10<sup>4</sup> G. This difference is conventionally attributed to such factors—not all of which are quantifiable—as the geometry, dimensions and the nature of dopants and the manners of preparation of the samples which cause their granular structures, grain boundaries, alignment of the grains and so on to differ. Based on the premise that the chemical potential <i>μ</i> subsumes most of these features, given herein is a novel explanation of the said results in terms of the values of <i>μ</i> of the two samples. This paper revisits the problem that was originally addressed in [Malik G.P., Varma V.S. (2020) WJCMP, 10, 53-70] in the more accurate framework of a subsequent paper [Malik G.P., Varma V.S. (2021) JSNM, 34, 1551-1561]. Besides, it distinguishes between the contributions of the electro-electron (<i>e-e</i>) and the hole-hole (<i>h-h</i>) pairs to <i>j<sub>c</sub></i>—a feature to which no heed was paid earlier. The essence of our findings is that the <i>j<sub>c</sub></i>s of the two samples differ because they are characterized by different values of the <i>primary</i> variables <i>μ<sub>i</sub></i><sub> </sub>and <img src="Edit_e1b831e9-dc51-4c3b-bd84-fa905e3e62b5.png" alt="" />, where <img src="Edit_1f775a80-30ab-447d-861f-afb4ba8fba6a.png" alt="" /> is the effective mass of a charge-carrier and <i>m<sub>e</sub></i><sub> </sub>is the free-electron mass and <i>i</i> = 1 and 2 denote Sample 1 and Sample 2, respectively. In the scenario of the charge-carriers being <i>predominantly h-h</i> pairs, the values of these parameters are estimated to be: <i>μ</i><sub>1</sub> ≈ 12.3 meV, <i>η</i><sub>1</sub> ≈ 0.58;<i>μ</i><sub>2</sub> ≈ 22.7 meV, <i>η</i><sub>2</sub> ≈ 0.94. Following from these and similar estimates when the charge-carriers are <i>e-e</i> pairs, given below for each sample are the detailed results for the values of the <i>secondary</i> variables viz. the number density of the charge-carriers and their critical velocity, the number of occupied Landau levels and the magnetic interaction parameter.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
Cubic phase Li7La3Zr2O12(LLZO),a member of the Li–Garnet family,is a promising solid electrolyte and has been widely studied in recent years.However,LLZO samples prepared via conventional ambient air sintering report...Cubic phase Li7La3Zr2O12(LLZO),a member of the Li–Garnet family,is a promising solid electrolyte and has been widely studied in recent years.However,LLZO samples prepared via conventional ambient air sintering reported in the published literature often contain large grains with lower than desired(<94%)relative density.In this study,a non-contact method of co-firing with mother powder method is proposed to prepare high-quality Ta-doped LLZO–MgO composite ceramics.By sintering at 1150℃for 5 h,the ceramics can reach relative density of 98.2%,conductivity of 5.17×10^-4 S cm^-1 at 25℃and fracture strength of 150 MPa.The sintered samples have uniform fine-grained microstructure and high critical current densities of 0.75–0.95 mA cm-2 at room temperature in Li–Li symmetry cell with Au modification.In addition,systematic sintering experiments and characterizations are conducted to explore the function of MgO in inhibiting the Ta-LLZO grain growth and its existing form inside the composite ceramics.展开更多
High critical current density(>10^(6)A/cm^(2))is one of major obstacles to realize practical applications of the currentdriven magnetization reversal devices.In this work,we successfully prepared Pd/CoZr(3.5 nm)/Mg...High critical current density(>10^(6)A/cm^(2))is one of major obstacles to realize practical applications of the currentdriven magnetization reversal devices.In this work,we successfully prepared Pd/CoZr(3.5 nm)/MgO thin films with large perpendicular magnetic anisotropy and demonstrated a way of reducing the critical current density with a low out-of-plane magnetic field in the Pd/CoZr/MgO stack.Under the assistance of an out-of-plane magnetic field,the magnetization can be fully reversed with a current density of about 10^(4)A/cm^(2).The magnetization reversal is attributed to the combined effect of the out-of-plane magnetic field and the current-induced spin-orbital torque.It is found that the current-driven magnetization reversal is highly relevant to the temperature owing to the varied spin-orbital torque,and the current-driven magnetization reversal will be more efficient in low-temperature range,while the magnetic field is helpful for the magnetization reversal in high-temperature range.展开更多
The rocking curve of Tl-2212 thin films in Fig.2 of our original paper[1]should be replaced with the following new one.Accordingly,in the fifth paragraph of Section 3 of the original paper,the statement“The full widt...The rocking curve of Tl-2212 thin films in Fig.2 of our original paper[1]should be replaced with the following new one.Accordingly,in the fifth paragraph of Section 3 of the original paper,the statement“The full width at half maximum(FWHM)of the(0012)peak of the Tl-2212 phase is about 0.24°”should be“The full width at half maximum(FWHM)of the(0012)peak of the Tl-2212 phase is about 0.42°”.展开更多
Utilization of novel materials,particularly high-T_(c)(critical temperature)superconductors,is essential to pursue the United Nations’Sustainable Goals,as well as to meet the increasing worldwide demand for clean and...Utilization of novel materials,particularly high-T_(c)(critical temperature)superconductors,is essential to pursue the United Nations’Sustainable Goals,as well as to meet the increasing worldwide demand for clean and carbon-free electric power technologies.Superconducting magnets are beneficial in several real-life applications including transportation,energy production,magnetic resonance imaging(MRI),and drug delivery systems.To achieve high performance,one must develop uniform,large-grain,infiltration-growth(IG)processed bulk YBa_(2)Cu_(3)O_(y)(Y-123)super-magnets.In this study,we report the magnetic and microstructural properties of a large-grain,top-seeded,IG-processed Y-123 pellet,which is 20 mm in diameter and 6 mm in height;the pellet is produced utilizing liquid Yb-123+Ba_(3)Cu_(5)O_(8) as the liquid source.All the samples cut from the top of the bulk exhibit a sharp superconducting transition(approximately 1 K wide)with the onset T_(c) of approximately 90 K.However,in the samples cut from the bottom surface,the onset T_(c) values slightly decreased to between 88 and 90 K,although still exhibiting a sharp superconducting transition.The top and bottom samples exhibited the highest remnant value of J_(c)(critical current density)at 77 K H//c-axis of 50 and 55 kA/cm^(2),respectively.The remnant J_(c) and irreversibility field values significantly fluctuated,being fairly low in some bottom samples.Scanning electron microscopy identified nanometer size Y-211(Y2BaCuO5)secondary-phase particles dispersed in the Y-123 matrix.Energy-dispersive spectroscopy clarified that the decreased both T_(c) and J_(c) for the bottom samples were attributed to liquid phase dispersion within the Y-123 phase.展开更多
The paper presents fabrication and characterization of spark plasma sintered textured(001) MgB_(2)with a record degree of orientation of about 40% and 16% by high-energy ultra-sonication and slip casting in high magne...The paper presents fabrication and characterization of spark plasma sintered textured(001) MgB_(2)with a record degree of orientation of about 40% and 16% by high-energy ultra-sonication and slip casting in high magnetic field(12 T) and 0 T magnetic field, respectively.Structural characterization was performed by X-ray diffraction, and electron microscopy. The analysis revealed unexpected preferred orientation also in the MgO secondary phase due to the epitaxial growth of(111) MgO on(001) MgB_(2). The influence of oriented microstructure on the superconducting characteristics expressed by critical current density(J_(c)), irreversibility field(H_(irr)), and on the pinning properties were assessed. High anisotropy versus sample orientation in applied magnetic field, H, was observed for J_(c), Hirr, pinning activation energy(U^(*))extracted from relaxation measurements. The zero-field critical current, J_(c0)and F_(p),maxare weakly or not dependent on the direction of H,while the other indicated parameters are significantly influenced. Results enable control of superconducting parameters by further optimization of microstructure through MgB_(2) texturing as a novel and viable strategy for development of bulk MgB2with enhanced properties when taking advantage of its anisotropy.展开更多
The doping effects of transition metals(TMs = Mn, Co, Ni, and Cu) on the superconducting critical parameters are investigated in the films of iron selenide(Li,Fe)OHFe Se. The samples are grown via a matrix-assisted hy...The doping effects of transition metals(TMs = Mn, Co, Ni, and Cu) on the superconducting critical parameters are investigated in the films of iron selenide(Li,Fe)OHFe Se. The samples are grown via a matrix-assisted hydrothermal epitaxy method. Among the TMs, the elements of Mn and Co adjacent to Fe are observed to be incorporated into the crystal lattice more easily. It is suggested that the doped TMs mainly occupy the iron sites of the intercalated(Li,Fe)OH layers rather than those of the superconducting Fe Se layers. We find that the critical current density J_(c) can be enhanced much more strongly by the Mn dopant than the other TMs, while the critical temperature T_(c) is weakly affected by the TM doping.展开更多
The effect of cold high pressure densification(CHPD)on anisotropy of the critical current density(Jc)in《in situ》single core binary and alloyed MgB2 tapes has been determined as a function of temperatures at 4.2 K,20...The effect of cold high pressure densification(CHPD)on anisotropy of the critical current density(Jc)in《in situ》single core binary and alloyed MgB2 tapes has been determined as a function of temperatures at 4.2 K,20 K and 25 K as well as at applied magnetic fields up to 19 T.The study includes binary and C4H6O5(malic acid)doped MgB2 tapes before and after CHPD.It is remarkable that the CHPD process not only improved the Jc values,in particular at the higher magnetic fields,but also decreased the anisotropy ratio,Г=JC^///JC^⊥In binary MgB2 tapes,the anisotropy factor F increases with higher aspect ratios,even after applying CHPD.In malic acid(C4H6O5)doped tapes,however,the application of CHPD leads only to small enhancements ofГ,even for higher aspect ratios.This is attributed to the higher carbon content in the MgB2 filaments,which in turn is a consequence of the reduced chemical reaction path in the densified filaments.At all applied field values,it was found that CHPD processed C4H6O5 doped tapes exhibit an almost isotropic behavior.This constitutes an advantage in view of industrial magnet applications using wires with square or slightly rectangular configuration.展开更多
Photoreflectance(PR)spectroscopy is a powerful and non-destructive experimental technique to explore interband transitions of semiconductors.In most PR systems,the photon energy of the pumping beam is usually chosen t...Photoreflectance(PR)spectroscopy is a powerful and non-destructive experimental technique to explore interband transitions of semiconductors.In most PR systems,the photon energy of the pumping beam is usually chosen to be higher than the bandgap energy of the sample.To the best of our knowledge,the highest energy of pumping laser in reported PR systems is 5.08 eV(244 nm),not yet in the vacuum ultraviolet(VUV)region.In this work,we report the design and construction of a PR system pumped by VUV laser of 7.0 eV(177.3 nm).At the same time,dual-modulated technique is applied and a dual channel lock-in-amplifier is integrated into the system for efficient PR measurement.The system’s performance is verified by the PR spectroscopy measurement of well-studied semiconductors,which testifies its ability to probe critical-point energies of the electronic band in semiconductors from ultraviolet to near-infrared spectral region.展开更多
The terahertz band,a unique segment of the electromagnetic spectrum,is crucial for observing the cold,dark universe and plays a pivotal role in cutting-edge scientific research,including the study of cosmic environmen...The terahertz band,a unique segment of the electromagnetic spectrum,is crucial for observing the cold,dark universe and plays a pivotal role in cutting-edge scientific research,including the study of cosmic environments that support life and imaging black holes.High-sensitivity superconductor–insulator–superconductor(SIS)mixers are essential detectors for terahertz astronomical telescopes and interferometric arrays.Compared to the commonly used classical Nb/AlO_(x)/Nb superconducting tunnel junction,the Nb/AlN/NbN hybrid superconducting tunnel junction has a higher energy gap voltage and can achieve a higher critical current density.This makes it particularly promising for the development of ultra-wideband,high-sensitivity coherent detectors or mixers in various scientific research fields.In this paper,we present a superconducting SIS mixer based on Nb/AlN/NbN parallel-connected twin junctions(PCTJ),which has a bandwidth extending up to490 GHz–720 GHz.The best achieved double-sideband(DSB)noise temperature(sensitivity)is below three times the quantum noise level.展开更多
In the applications of superconducting materials,the critical current density J_(c)(B)is a crucial performance parameter.The conventional method of measuring J_(c)(B)of bulk superconductor is magnetization method.Howe...In the applications of superconducting materials,the critical current density J_(c)(B)is a crucial performance parameter.The conventional method of measuring J_(c)(B)of bulk superconductor is magnetization method.However,there are errors in the estimation of J_(c)(B)in the lower field,and the estimation is not applicable in the region where the magnetic field reverses.In this paper,J_(c)(B)of the bulk superconductor is determined by the hysteresis and magnetostriction loops with artificial neural network(ANN),respectively.Compared with double‐output ANN,the critical current density obtained by single‐output ANN is more accurate.Finally,the prediction results given by the hysteresis and magnetostriction loops are discussed.展开更多
The critical current density(Jc)of the body centered cubic(bcc)V0.6Ti0.4 alloy enhances significantly after the addition of rare earth Gd as the latter is immiscible in the matrix[S.Paul,et.al,IEEE Trans.Appl.Supercon...The critical current density(Jc)of the body centered cubic(bcc)V0.6Ti0.4 alloy enhances significantly after the addition of rare earth Gd as the latter is immiscible in the matrix[S.Paul,et.al,IEEE Trans.Appl.Supercond.31,5(2021)].Very low solubility of Gd in other bcc elements like Ta and Nb is also well known[Jr.KA Gschneidner in Prog Sci Technol Rare Earths,vol.1,pp.222–258,1964&M Neuberger,et.al in Handbook of Electronic Materials,Vol 4,1972].We use these facts to find the effect of adding 1 at.%Gd into the Nb0.6Ti0.4 and Ta0.4Ti0.6 alloys on the superconducting properties e.g.,the transition temperature(Tc),Jc,flux pinning force density(Fp)and the microstructure.In spite of Gd being ferromagnetic,the Tc in these alloys change only marginally(increase by 0.3 K in Ta0.4Ti0.6 and decrease by 0.15 K in Nb0.6Ti0.4 after Gd addition.The Jc(H?1 T,T=4 K)increases by 5 and 1.5 times respectively in the Gd containing Nb0.6Ti0.4 and Ta0.4Ti0.6 alloys,which is quite small as compared to the increase observed in the V0.6Ti0.4(20 times)system.With Gd addition,the grain size reduces approximately by 65%and 10%respectively in Nb0.6Ti0.4 and Ta0.4Ti0.6.Our analysis indicates that grain boundaries are the major flux line pinning centres in these alloys and the role of Gd in increasing the Jc depends on the effectiveness of Gd in reducing the grain size.The grain boundary density depends strongly on the distribution of Gd precipitates,which is quite different from each other for two alloy systems under study.Moreover,our results suggest that the addition of Gd to commercial Nb‐Ti(Nb0.37Ti0.63)alloy is a new promising route for achieving higher Jc values.展开更多
The number of vehicles that a road network can carry is limited.When the limit is exceeded,the network system is not able to function effectively.In this paper,an updated cellular automaton model for grid networks wit...The number of vehicles that a road network can carry is limited.When the limit is exceeded,the network system is not able to function effectively.In this paper,an updated cellular automaton model for grid networks with all-way stop-controlled intersections is proposed to simulate the network level critical density and carrying capacity under different conditions,which essentially indicates the limit number of vehicles that the network can handle before going into gridlock.In the proposed model,two update rules,including lane-changing and the longitudinal location update,are adopted to describe the vehicle’s movements on road segments according to the driving condition on the road and the vehicle’s direction in the downstream intersection.The vehicle’s movements in intersection areas are prioritized based on vehicle’s position,so as to prevent collisions within the intersection area.The simulation results show that an increase in network size is able to expand the carrying capacity of a road network,whereas the expansion rate is lower than the change rate in the network size.The carrying capacity is also associated with the structure of road network.The carrying capacity is inversely proportional to the number of intersections,and proportional to the length of the road in the network.Also,optimizing the origin-destination(O-D)distribution can increase the carrying capacity of an urban road network.展开更多
Garnet-type oxide is one of the most promising solid-state electrolytes(SSEs)for solid-state lithium-metal batteries(SSLMBs).However,the Li dendrite formation in garnet oxides obstructs the further development of the ...Garnet-type oxide is one of the most promising solid-state electrolytes(SSEs)for solid-state lithium-metal batteries(SSLMBs).However,the Li dendrite formation in garnet oxides obstructs the further development of the SSLMBs seriously.Here,we report a high-performance garnet oxide by using AlN as a sintering additive and Li as an anode interface layer.AlN with high thermal conductivity can promote the sintering activity of the garnet oxides,resulting in larger particle size and higher relative density.Moreover,Li3N with high ionic conductivity formed at grain boundaries and interface can also improve Li-ion transport kinetics.As a result,the garnet oxide electrolytes with AlN show enhanced thermal conductivity,improved ionic conductivity,reduced electronic conductivity,and increased critical current density(CCD),compared with the counterpart using Al_(2)O_(3) sintering aid.In addition,Li symmetric cells and Li|LiFePO_(4)(Li|LFP)half cells using the garnet electrolyte with the AlN additive exhibit good electrochemical performances.This work provides a simple and effective strategy for high-performance SSEs.展开更多
Superconducting thin films are widely used in superconducting quantum interferometers,microwave devices,etc.The electrical performance of a superconducting thin film is often affected by structural deformation or stre...Superconducting thin films are widely used in superconducting quantum interferometers,microwave devices,etc.The electrical performance of a superconducting thin film is often affected by structural deformation or stress.Based on four-point bending of a Cu-Be beam,we constructed a device that could apply uniaxial,uniform.compressive strain to a superconducting thin film at both room temperature and the temperature of liquid nitrogen.The thin film was placed into a slot carved in the Cu-Be beam.We optimized the size of this slot via numerical simulation.Our results indicated that the slot width was optimal when it was same as the width of the Cu-Be beam.Notably,the sample bended hardly after machining two slits along width direction on both sides of the slot.A YBa2Cu3O7-δSrTiO3(YBCO-STO)film was used as an example.It was loadedby the aforementioned device to determine its electrical characteristics as functions of the uniaxial-uniform-compressive strain.The optimized design allowed the sample to be compressed to a larger strain without breaking it.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11365020,11475026,11565022,and 11547304)the Science and Technology Program of Gansu Province of China(Grant No.1606RJZA090)+2 种基金the Fundamental Research Funds for the Higher Education Institutions of Gansu Province of China(2012)the Foundation of Northwest Normal University(Grant Nos.NWNU-LKQN-14-9 and NWNU-LKQN-16-3)partially supported by the Fundamental Research Funds for the Central Universities of China
文摘In order to generate high quality ion beams through the stable radiation pressure acceleration(RPA) of the near critical density(NCD) target, we propose a new type of target where an ultra-thin high density(HD) layer is attached to the front surface of an NCD target, which has a preferable self-supporting property in the RPA experiments than the ultra-thin foil target. It is found that in one-dimensional particle-in-cell(PIC) simulation, by the block of the HD layer in the new target,there emerges the hole-boring process rather than propagation in the NCD layer when the intense laser pulse impinges on this target. As a result, a typical RPA structure that the compressed electron layer overlaps the ion layer as a whole is formed and a high quality ion beam is obtained, e.g., a circularly polarized laser pulse with normalized amplitude a_0= 120 impinges on this new target and a 1.2 GeV monoenergetic ion beam is generated through the RPA of the NCD layer. Similar results are also found in the two-dimensional PIC simulation.
基金sponsored by the Korean Ministry of Science and ICT(MSIT)supported by nuclear Research&Development program grant funded by the National Research Foundation(NRF)(2021M2D1A1084838)。
文摘The work investigates influence of the electrolyte conductivity on the onset of partial contact glow discharge electrolysis(CGDE)in a water electrolysis.Critical current density(CCD)and breakdown voltage were measured together with in situ observation of hydrogen bubble behavior,whose influence has not been focused on.For a fixed current during normal electrolysis,hydrogen coalescence adjacent to cathode surface was invigorated at a lower conductivity.Photographic analyses elucidated the hydrogen coalescence characteristics by quantifying size and population of detached hydrogen bubbles.The CCD increased about 104% within given range of conductivity(11.50-127.48 mS·cm^(-1))due to impaired bubble coalescence,which delays hydrogen film formation on the cathode.Meanwhile,decreasing trend of breakdown voltage was measured with increased conductivity showing maximum drop of 74%.It is concluded that onset of partial CGDE is directly affected by hydrodynamic bubble behaviors,whereas the electrolyte conductivity affects the bubble formation characteristics adjacent to cathode electrode.
基金the financial support from the Natural Science Foundation for Distinguished Young Scholars of Hunan Province(2020JJ2047)the science and technology innovation Program of Hunan Province(2022RC3048)+2 种基金the Program of Huxiang Young Talents(2019RS2002)the Innovation-Driven Project of Central South University(2020CX027)the Fundamental Research Funds for the Central Universities of Central South University(2021zzts0125)。
文摘Apparent critical current density(j_(Ac)^(a))of garnet all-solid-state lithium metal symmetric cells(ASSLSCs)is a fundamental parameter for designing all-solid-state lithium metal batteries.Nevertheless,how much the possible maximum apparent current density that a given ASSLSC system can endure and how to reveal this potential still require study.Herein,a capacity perturbation strategy aiming to better measure the possible maximum j_(Ac)^(a)is proposed for the first time.With garnet-based plane-surface structure ASSLSCs as an exemplification,the j_(Ac)^(a)is quite small when the capacity is dramatically large.Under a perturbed capacity of 0.001 mA h cm^(-2),the j_(Ac)^(a)is determined to be as high as 2.35 mA cm^(-2)at room temperature.This investigation demonstrates that the capacity perturbation strategy is a feasible strategy for measuring the possible maximum j_(Ac)^(a)of Li/solid electrolyte interface,and hopefully provides good references to explore the critical current density of other types of electrochemical systems.
文摘The empirically reported values of the critical current density (<i>j<sub>c</sub></i>) of Bi-2212 as 2.4 × 10<sup>5</sup> (<i>j<sub>c</sub></i><sub>1</sub>;Sample 1) and 1.0 × 10<sup>6</sup> A/cm<sup>2</sup> (<i>j<sub>c</sub></i><sub>2</sub>;Sample 2) are intriguing because both of them correspond to the <i>same</i> values of the temperature <i>T</i> = 4.2 K and the applied magnetic field <i>H</i> = 12 × 10<sup>4</sup> G. This difference is conventionally attributed to such factors—not all of which are quantifiable—as the geometry, dimensions and the nature of dopants and the manners of preparation of the samples which cause their granular structures, grain boundaries, alignment of the grains and so on to differ. Based on the premise that the chemical potential <i>μ</i> subsumes most of these features, given herein is a novel explanation of the said results in terms of the values of <i>μ</i> of the two samples. This paper revisits the problem that was originally addressed in [Malik G.P., Varma V.S. (2020) WJCMP, 10, 53-70] in the more accurate framework of a subsequent paper [Malik G.P., Varma V.S. (2021) JSNM, 34, 1551-1561]. Besides, it distinguishes between the contributions of the electro-electron (<i>e-e</i>) and the hole-hole (<i>h-h</i>) pairs to <i>j<sub>c</sub></i>—a feature to which no heed was paid earlier. The essence of our findings is that the <i>j<sub>c</sub></i>s of the two samples differ because they are characterized by different values of the <i>primary</i> variables <i>μ<sub>i</sub></i><sub> </sub>and <img src="Edit_e1b831e9-dc51-4c3b-bd84-fa905e3e62b5.png" alt="" />, where <img src="Edit_1f775a80-30ab-447d-861f-afb4ba8fba6a.png" alt="" /> is the effective mass of a charge-carrier and <i>m<sub>e</sub></i><sub> </sub>is the free-electron mass and <i>i</i> = 1 and 2 denote Sample 1 and Sample 2, respectively. In the scenario of the charge-carriers being <i>predominantly h-h</i> pairs, the values of these parameters are estimated to be: <i>μ</i><sub>1</sub> ≈ 12.3 meV, <i>η</i><sub>1</sub> ≈ 0.58;<i>μ</i><sub>2</sub> ≈ 22.7 meV, <i>η</i><sub>2</sub> ≈ 0.94. Following from these and similar estimates when the charge-carriers are <i>e-e</i> pairs, given below for each sample are the detailed results for the values of the <i>secondary</i> variables viz. the number density of the charge-carriers and their critical velocity, the number of occupied Landau levels and the magnetic interaction parameter.
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financially supported by the National Key R&D Program of China under Grant No.2018YFB0905400,Corning Incorporatedthe National Natural Science Foundation of China under Grant No.51772315,No.51432010
文摘Cubic phase Li7La3Zr2O12(LLZO),a member of the Li–Garnet family,is a promising solid electrolyte and has been widely studied in recent years.However,LLZO samples prepared via conventional ambient air sintering reported in the published literature often contain large grains with lower than desired(<94%)relative density.In this study,a non-contact method of co-firing with mother powder method is proposed to prepare high-quality Ta-doped LLZO–MgO composite ceramics.By sintering at 1150℃for 5 h,the ceramics can reach relative density of 98.2%,conductivity of 5.17×10^-4 S cm^-1 at 25℃and fracture strength of 150 MPa.The sintered samples have uniform fine-grained microstructure and high critical current densities of 0.75–0.95 mA cm-2 at room temperature in Li–Li symmetry cell with Au modification.In addition,systematic sintering experiments and characterizations are conducted to explore the function of MgO in inhibiting the Ta-LLZO grain growth and its existing form inside the composite ceramics.
基金supported by the ISF-NSFC Joint Research Project of International Cooperation and Exchanges(Grant No.51961145305)the National Natural Science Foundation of China(Grant Nos.52171191 and 51771145)+1 种基金the Shaanxi Key Program for International Science and Technology Cooperation Projects(Grant No.2021KWZ-12)the Youth Innovation Team of Shaanxi Universities
文摘High critical current density(>10^(6)A/cm^(2))is one of major obstacles to realize practical applications of the currentdriven magnetization reversal devices.In this work,we successfully prepared Pd/CoZr(3.5 nm)/MgO thin films with large perpendicular magnetic anisotropy and demonstrated a way of reducing the critical current density with a low out-of-plane magnetic field in the Pd/CoZr/MgO stack.Under the assistance of an out-of-plane magnetic field,the magnetization can be fully reversed with a current density of about 10^(4)A/cm^(2).The magnetization reversal is attributed to the combined effect of the out-of-plane magnetic field and the current-induced spin-orbital torque.It is found that the current-driven magnetization reversal is highly relevant to the temperature owing to the varied spin-orbital torque,and the current-driven magnetization reversal will be more efficient in low-temperature range,while the magnetic field is helpful for the magnetization reversal in high-temperature range.
文摘The rocking curve of Tl-2212 thin films in Fig.2 of our original paper[1]should be replaced with the following new one.Accordingly,in the fifth paragraph of Section 3 of the original paper,the statement“The full width at half maximum(FWHM)of the(0012)peak of the Tl-2212 phase is about 0.24°”should be“The full width at half maximum(FWHM)of the(0012)peak of the Tl-2212 phase is about 0.42°”.
基金This work was presented at the International Conference on Carbon Materials and Nanotechnology,Osaka,Japan(JICCMAN 2020)which was held during June 30–July 1 of 2020 as an online summit.This work was delivered as an oral presentation and was acknowledged with the Outstanding Young Researcher Award.
文摘Utilization of novel materials,particularly high-T_(c)(critical temperature)superconductors,is essential to pursue the United Nations’Sustainable Goals,as well as to meet the increasing worldwide demand for clean and carbon-free electric power technologies.Superconducting magnets are beneficial in several real-life applications including transportation,energy production,magnetic resonance imaging(MRI),and drug delivery systems.To achieve high performance,one must develop uniform,large-grain,infiltration-growth(IG)processed bulk YBa_(2)Cu_(3)O_(y)(Y-123)super-magnets.In this study,we report the magnetic and microstructural properties of a large-grain,top-seeded,IG-processed Y-123 pellet,which is 20 mm in diameter and 6 mm in height;the pellet is produced utilizing liquid Yb-123+Ba_(3)Cu_(5)O_(8) as the liquid source.All the samples cut from the top of the bulk exhibit a sharp superconducting transition(approximately 1 K wide)with the onset T_(c) of approximately 90 K.However,in the samples cut from the bottom surface,the onset T_(c) values slightly decreased to between 88 and 90 K,although still exhibiting a sharp superconducting transition.The top and bottom samples exhibited the highest remnant value of J_(c)(critical current density)at 77 K H//c-axis of 50 and 55 kA/cm^(2),respectively.The remnant J_(c) and irreversibility field values significantly fluctuated,being fairly low in some bottom samples.Scanning electron microscopy identified nanometer size Y-211(Y2BaCuO5)secondary-phase particles dispersed in the Y-123 matrix.Energy-dispersive spectroscopy clarified that the decreased both T_(c) and J_(c) for the bottom samples were attributed to liquid phase dispersion within the Y-123 phase.
基金financial support from MCI-UEFISCDI Romania, the projects PN030101 (21 N/2019), 5PTE/2020 – BIOTEHKER, and POC 37_697 no. 28/01.09.2016 REBMAT。
文摘The paper presents fabrication and characterization of spark plasma sintered textured(001) MgB_(2)with a record degree of orientation of about 40% and 16% by high-energy ultra-sonication and slip casting in high magnetic field(12 T) and 0 T magnetic field, respectively.Structural characterization was performed by X-ray diffraction, and electron microscopy. The analysis revealed unexpected preferred orientation also in the MgO secondary phase due to the epitaxial growth of(111) MgO on(001) MgB_(2). The influence of oriented microstructure on the superconducting characteristics expressed by critical current density(J_(c)), irreversibility field(H_(irr)), and on the pinning properties were assessed. High anisotropy versus sample orientation in applied magnetic field, H, was observed for J_(c), Hirr, pinning activation energy(U^(*))extracted from relaxation measurements. The zero-field critical current, J_(c0)and F_(p),maxare weakly or not dependent on the direction of H,while the other indicated parameters are significantly influenced. Results enable control of superconducting parameters by further optimization of microstructure through MgB_(2) texturing as a novel and viable strategy for development of bulk MgB2with enhanced properties when taking advantage of its anisotropy.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0303003 and 2016YFA0300300)the National Natural Science Foundation of China(Grant Nos.11834016 and 11888101)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB33010200 and XDB25000000)the Strategic Priority Research Program and Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(Grant Nos.QYZDY-SSW-SLH001 and QYZDY-SSW-SLH008)。
文摘The doping effects of transition metals(TMs = Mn, Co, Ni, and Cu) on the superconducting critical parameters are investigated in the films of iron selenide(Li,Fe)OHFe Se. The samples are grown via a matrix-assisted hydrothermal epitaxy method. Among the TMs, the elements of Mn and Co adjacent to Fe are observed to be incorporated into the crystal lattice more easily. It is suggested that the doped TMs mainly occupy the iron sites of the intercalated(Li,Fe)OH layers rather than those of the superconducting Fe Se layers. We find that the critical current density J_(c) can be enhanced much more strongly by the Mn dopant than the other TMs, while the critical temperature T_(c) is weakly affected by the TM doping.
基金This work was supported by the Australian Research Council(Grant No.LP160101784)A.K.thanks the Researchers Supporting Project(RSP-2019/127)King Saud University,Riyadh,Saudi Arabia for the support.This work was performed in part at the Queensland node of the Australian National Fabrication Facility,a company established under the National Collaborative Research Infrastructure Strategy to provide nano-and microfabrication facilities for Australia's researchers.M.M.acknowledges an internal funding project of the University of Osijek(ZUP-2018).
文摘The effect of cold high pressure densification(CHPD)on anisotropy of the critical current density(Jc)in《in situ》single core binary and alloyed MgB2 tapes has been determined as a function of temperatures at 4.2 K,20 K and 25 K as well as at applied magnetic fields up to 19 T.The study includes binary and C4H6O5(malic acid)doped MgB2 tapes before and after CHPD.It is remarkable that the CHPD process not only improved the Jc values,in particular at the higher magnetic fields,but also decreased the anisotropy ratio,Г=JC^///JC^⊥In binary MgB2 tapes,the anisotropy factor F increases with higher aspect ratios,even after applying CHPD.In malic acid(C4H6O5)doped tapes,however,the application of CHPD leads only to small enhancements ofГ,even for higher aspect ratios.This is attributed to the higher carbon content in the MgB2 filaments,which in turn is a consequence of the reduced chemical reaction path in the densified filaments.At all applied field values,it was found that CHPD processed C4H6O5 doped tapes exhibit an almost isotropic behavior.This constitutes an advantage in view of industrial magnet applications using wires with square or slightly rectangular configuration.
基金Project supported by the National Development Project for Major Scientific Research Facility of China(Grant No.ZDYZ2012-2)the National Natural Science Foundation of China(Grant No.11874350)CAS Key Research Program of Frontier Sciences(Grant Nos.ZDBS-LY-SLH004 and XDPB22)。
文摘Photoreflectance(PR)spectroscopy is a powerful and non-destructive experimental technique to explore interband transitions of semiconductors.In most PR systems,the photon energy of the pumping beam is usually chosen to be higher than the bandgap energy of the sample.To the best of our knowledge,the highest energy of pumping laser in reported PR systems is 5.08 eV(244 nm),not yet in the vacuum ultraviolet(VUV)region.In this work,we report the design and construction of a PR system pumped by VUV laser of 7.0 eV(177.3 nm).At the same time,dual-modulated technique is applied and a dual channel lock-in-amplifier is integrated into the system for efficient PR measurement.The system’s performance is verified by the PR spectroscopy measurement of well-studied semiconductors,which testifies its ability to probe critical-point energies of the electronic band in semiconductors from ultraviolet to near-infrared spectral region.
基金Project supported in part by the National Key Research and Development Program of China(Grant Nos.2023YFA1608201 and 2023YFF0722301)the National Natural Science Foundation of China(Grant Nos.11925304,12020101002,12333013,12273119,and 12103093)supported by grant from the Russian Science Foundation(Grant No.23-7900019)。
文摘The terahertz band,a unique segment of the electromagnetic spectrum,is crucial for observing the cold,dark universe and plays a pivotal role in cutting-edge scientific research,including the study of cosmic environments that support life and imaging black holes.High-sensitivity superconductor–insulator–superconductor(SIS)mixers are essential detectors for terahertz astronomical telescopes and interferometric arrays.Compared to the commonly used classical Nb/AlO_(x)/Nb superconducting tunnel junction,the Nb/AlN/NbN hybrid superconducting tunnel junction has a higher energy gap voltage and can achieve a higher critical current density.This makes it particularly promising for the development of ultra-wideband,high-sensitivity coherent detectors or mixers in various scientific research fields.In this paper,we present a superconducting SIS mixer based on Nb/AlN/NbN parallel-connected twin junctions(PCTJ),which has a bandwidth extending up to490 GHz–720 GHz.The best achieved double-sideband(DSB)noise temperature(sensitivity)is below three times the quantum noise level.
基金support from the National Natural Science Foundation of China(Grant Nos.U2241267,12172155 and 11872195).
文摘In the applications of superconducting materials,the critical current density J_(c)(B)is a crucial performance parameter.The conventional method of measuring J_(c)(B)of bulk superconductor is magnetization method.However,there are errors in the estimation of J_(c)(B)in the lower field,and the estimation is not applicable in the region where the magnetic field reverses.In this paper,J_(c)(B)of the bulk superconductor is determined by the hysteresis and magnetostriction loops with artificial neural network(ANN),respectively.Compared with double‐output ANN,the critical current density obtained by single‐output ANN is more accurate.Finally,the prediction results given by the hysteresis and magnetostriction loops are discussed.
文摘The critical current density(Jc)of the body centered cubic(bcc)V0.6Ti0.4 alloy enhances significantly after the addition of rare earth Gd as the latter is immiscible in the matrix[S.Paul,et.al,IEEE Trans.Appl.Supercond.31,5(2021)].Very low solubility of Gd in other bcc elements like Ta and Nb is also well known[Jr.KA Gschneidner in Prog Sci Technol Rare Earths,vol.1,pp.222–258,1964&M Neuberger,et.al in Handbook of Electronic Materials,Vol 4,1972].We use these facts to find the effect of adding 1 at.%Gd into the Nb0.6Ti0.4 and Ta0.4Ti0.6 alloys on the superconducting properties e.g.,the transition temperature(Tc),Jc,flux pinning force density(Fp)and the microstructure.In spite of Gd being ferromagnetic,the Tc in these alloys change only marginally(increase by 0.3 K in Ta0.4Ti0.6 and decrease by 0.15 K in Nb0.6Ti0.4 after Gd addition.The Jc(H?1 T,T=4 K)increases by 5 and 1.5 times respectively in the Gd containing Nb0.6Ti0.4 and Ta0.4Ti0.6 alloys,which is quite small as compared to the increase observed in the V0.6Ti0.4(20 times)system.With Gd addition,the grain size reduces approximately by 65%and 10%respectively in Nb0.6Ti0.4 and Ta0.4Ti0.6.Our analysis indicates that grain boundaries are the major flux line pinning centres in these alloys and the role of Gd in increasing the Jc depends on the effectiveness of Gd in reducing the grain size.The grain boundary density depends strongly on the distribution of Gd precipitates,which is quite different from each other for two alloy systems under study.Moreover,our results suggest that the addition of Gd to commercial Nb‐Ti(Nb0.37Ti0.63)alloy is a new promising route for achieving higher Jc values.
基金the Zhejiang Provincial Natural Science Foundation of China(LY18E080021)the Project of Science and Technology of the Department of Transportation of Hubei Province,China(2017-538-4-9)the National Science Foundation,USA(1137732)。
文摘The number of vehicles that a road network can carry is limited.When the limit is exceeded,the network system is not able to function effectively.In this paper,an updated cellular automaton model for grid networks with all-way stop-controlled intersections is proposed to simulate the network level critical density and carrying capacity under different conditions,which essentially indicates the limit number of vehicles that the network can handle before going into gridlock.In the proposed model,two update rules,including lane-changing and the longitudinal location update,are adopted to describe the vehicle’s movements on road segments according to the driving condition on the road and the vehicle’s direction in the downstream intersection.The vehicle’s movements in intersection areas are prioritized based on vehicle’s position,so as to prevent collisions within the intersection area.The simulation results show that an increase in network size is able to expand the carrying capacity of a road network,whereas the expansion rate is lower than the change rate in the network size.The carrying capacity is also associated with the structure of road network.The carrying capacity is inversely proportional to the number of intersections,and proportional to the length of the road in the network.Also,optimizing the origin-destination(O-D)distribution can increase the carrying capacity of an urban road network.
基金supported by the National Key R&D Program of China (2018YFA0704200 and 2017YFE0129500)the National Natural Science Foundation of China (51861135311, U1832213 and 51721005)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences (XDB25000000)the Key Research Program of Frontier Sciences of Chinese Academy of Sciences (QYZDJ-SSWJSC026)
基金the National Key R&D Program of China(No.2019YFA0210600)the National Natural Science Foundation of China(No.21805185)+2 种基金Shanghai Science and Technology Plan(No.21DZ2260400)Shanghai Rising-Star Program(No.20QA1406600)Center for High-resolution Electron Microscopy,SPST of ShanghaiTech University(No.EM02161943)for support.
文摘Garnet-type oxide is one of the most promising solid-state electrolytes(SSEs)for solid-state lithium-metal batteries(SSLMBs).However,the Li dendrite formation in garnet oxides obstructs the further development of the SSLMBs seriously.Here,we report a high-performance garnet oxide by using AlN as a sintering additive and Li as an anode interface layer.AlN with high thermal conductivity can promote the sintering activity of the garnet oxides,resulting in larger particle size and higher relative density.Moreover,Li3N with high ionic conductivity formed at grain boundaries and interface can also improve Li-ion transport kinetics.As a result,the garnet oxide electrolytes with AlN show enhanced thermal conductivity,improved ionic conductivity,reduced electronic conductivity,and increased critical current density(CCD),compared with the counterpart using Al_(2)O_(3) sintering aid.In addition,Li symmetric cells and Li|LiFePO_(4)(Li|LFP)half cells using the garnet electrolyte with the AlN additive exhibit good electrochemical performances.This work provides a simple and effective strategy for high-performance SSEs.
基金the National Natural Science Foundation of China(Grants 11622217,11872196,and11902130)the Fundamental ResearchFunds for the Central Universities(Grant lzujbky-2018-9).
文摘Superconducting thin films are widely used in superconducting quantum interferometers,microwave devices,etc.The electrical performance of a superconducting thin film is often affected by structural deformation or stress.Based on four-point bending of a Cu-Be beam,we constructed a device that could apply uniaxial,uniform.compressive strain to a superconducting thin film at both room temperature and the temperature of liquid nitrogen.The thin film was placed into a slot carved in the Cu-Be beam.We optimized the size of this slot via numerical simulation.Our results indicated that the slot width was optimal when it was same as the width of the Cu-Be beam.Notably,the sample bended hardly after machining two slits along width direction on both sides of the slot.A YBa2Cu3O7-δSrTiO3(YBCO-STO)film was used as an example.It was loadedby the aforementioned device to determine its electrical characteristics as functions of the uniaxial-uniform-compressive strain.The optimized design allowed the sample to be compressed to a larger strain without breaking it.