Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into...Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into the new β phase during the pulsed current-assisted aging process,and then the newly formed β phase is mainly transformed into the β_(t) phase,with occasional transition to new α_(p) phase,leading to a remarkable grain refinement,especially for the lamellarαs phases.In comparison to conventional aging treatment,the pulsed current-assisted aging approach achieves a significant enhancement in strength without degrading ductility,yielding an excellent mechanical property combination:a yield strength of 932 MPa,a tensile strength of 1042 MPa,and an elongation of 12.2%.It is primarily ascribed to the increased fraction of β_(t) phases,the obvious grain refinement effect,and the slip block effect induced by the multiple-variantαs colonies distributed within β_(t) phases.展开更多
Pulsed magnet technology is the only way to generate ultra-strong magnetic fields higher than 45 T so far.However,the inherently fast-changing field strength(typically on the order of 1000 T/s)poses significant challe...Pulsed magnet technology is the only way to generate ultra-strong magnetic fields higher than 45 T so far.However,the inherently fast-changing field strength(typically on the order of 1000 T/s)poses significant challenges for spectroscopic measurements which rely on time integration of signals to improve spectral qualities.In this work,we report high-sensitivity spectroscopic measurements under pulsed high magnetic fields employing the long flat-top pulsed magnetic field technique.By means of a multiple-capacitor power supply,we were able to generate pulsed high magnetic fields with controllable flat-top pulse width and field stabilities.By synchronizing spectroscopic measurements with the waveform of the flattop magnetic field,the integration time of each spectrum can be increased by up to 100 times compared with that of the conventional spectroscopic measurements under pulsed magnetic fields,thus enabling high-sensitivity spectroscopic measurements under ultra-strong pulsed magnetic fields.These findings promise an efficient way to significantly improve the performance and extend the application of optical measurements under pulsed high magnetic fields.展开更多
Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,...Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,including bubble,electromagnetic stirring,filtration separation,fluid flow,and sedimentation,often struggle with the removal of fine inclusions.Apart from these known methods,pulsed electric current(PEC),as an emerging technology,has demonstrated immense potential and environmental advantages.PEC offers adjustable current parameters and simple equipment,making it an attractive alternative to traditional methods.Its green energy-saving features and excellent results in regulating inclusion morphology and migration,as well as inhibiting submerged entry nozzle(SEN)clogging,make it a promising technology.In comparison to continuous current technology,PEC has shown significant advantages in regulating inclusions,not only improving purification efficiency but also demonstrating outstanding performance in flow stability and energy consumption.The ability of PEC to efficiently reduce inclusion numbers enhances the purity and quality of molten steel,improving its mechanical properties.Currently,the theoretical basis for controlling the movement of inclusions by current is mainly composed of three major theories:the double electric layer theory,electromagnetic force reverse separation theory,and electric free energy drive theory.These theories together form an important framework for researchers to understand and optimize the behavior of impurity movement controlled by electric current.Looking ahead,PEC is expected to pave the way for new solutions in directional regulation of inclusion migration,efficient inclusion removal,SEN clogging prevention,and the purification of molten steel.展开更多
The transition of hydrogen sourcing from carbon-intensive to water-based methodologies is underway,with renewable energy-powered proton exchange membrane water electrolysis(PEMWE)emerging as the preeminent pathway for...The transition of hydrogen sourcing from carbon-intensive to water-based methodologies is underway,with renewable energy-powered proton exchange membrane water electrolysis(PEMWE)emerging as the preeminent pathway for hydrogen production.Despite remarkable advancements in this field,confronting the sluggish electrochemical kinetics and inherent high-energy consumption arising from deteriorated mass transport within PEMWE systems remains a formidable obstacle.This impediment stems primarily from the hindered protons mass transfer and the untimely hydrogen bubbles detachment.To address these challenges,we harness the inherent variability of electrical energy and introduce an innovative pulsed dynamic water electrolysis system.Compared to constant voltage electrolysis(hydrogen production rate:51.6 m L h^(-1),energy consumption:5.37 kWh Nm-^(3)H_(2)),this strategy(hydrogen production rate:66 m L h^(-1),energy consumption:3.83 kWh Nm-^(3)H_(2))increases the hydrogen production rate by approximately 27%and reduces the energy consumption by about 28%.Furthermore,we demonstrate the practicality of this system by integrating it with an off-grid photovoltaic(PV)system designed for outdoor operation,successfully driving a hydrogen production current of up to 500 mA under an average voltage of approximately 2 V.The combined results of in-situ characterization and finite element analysis reveal the performance enhancement mechanism:pulsed dynamic electrolysis(PDE)dramatically accelerates the enrichment of protons at the electrode/solution interface and facilitates the release of bubbles on the electrode surface.As such,PDE-enhanced PEMWE represents a synergistic advancement,concurrently enhancing both the hydrogen generation reaction and associated transport processes.This promising technology not only redefines the landscape of electrolysis-based hydrogen production but also holds immense potential for broadening its application across a diverse spectrum of electrocatalytic endeavors.展开更多
Traditional heat treatment methods require a significant amount of time and energy to affect atomic diffusion and enhance the spheroidization process of carbides in bearing steel,while pulsed current can accelerate at...Traditional heat treatment methods require a significant amount of time and energy to affect atomic diffusion and enhance the spheroidization process of carbides in bearing steel,while pulsed current can accelerate atomic diffusion to achieve ultra-fast spheroidization of carbides.However,the understanding of the mechanism by which different pulse current parameters regulate the dissolution behavior of carbides requires a large amount of experimental data to support,which limits the application of pulse current technology in the field of heat treatment.Based on this,quantify the obtained pulse current processing data to create an important dataset that could be applied to machine learning.Through machine learning,the mechanism of mutual influence between carbide regulation and various factors was elucidated,and the optimal spheroidization process parameters were determined.Compared to the 20 h required for traditional heat treatment,the application of pulsed electric current technology achieved ultra-fast spheroidization of GCr15 bearing steel within 90 min.展开更多
BACKGROUND Atrial fibrillation,affecting approximately 33 million people globally,is the most common sustained arrhythmia,increasing risks of stroke,heart failure,and mortality.Pulmonary vein isolation via catheter ab...BACKGROUND Atrial fibrillation,affecting approximately 33 million people globally,is the most common sustained arrhythmia,increasing risks of stroke,heart failure,and mortality.Pulmonary vein isolation via catheter ablation is a key rhythm control strategy,with cryoballoon ablation(CBA)being a standard thermal method but associated with risks like phrenic nerve palsy(5%-10%),esophageal injury,and vein stenosis.Pulsed field ablation(PFA),a non-thermal technique using electrical pulses for selective electroporation,offers potential for shorter procedures and improved safety.Limited direct comparisons between PFA and CBA necessitate a systematic evaluation of their efficacy and safety.AIM To compare the procedural success,safety,and 1-year arrhythmia-free survival of PFA vs CBA for first-time pulmonary vein isolation in adults with paroxysmal or persistent atrial fibrillation.METHODS A Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant systematic review and metaanalysis was conducted,searching PubMed,EMBASE,Web of Science,and other databases up to August 2025 for comparative studies.Pooled mean difference for continuous outcomes and odds ratio(OR)for dichotomous outcomes were calculated using random-effects models.Study quality was assessed with the Newcastle-Ottawa Scale,heterogeneity with I2,and publication bias with funnel plots.RESULTS Seven studies(six cohorts,one randomized controlled trial)were included,with a mean age of approximately 66 years,59%-78%male,and high prevalence of hypertension and diabetes.PFA significantly reduced procedure time(mean difference=-15.24 minutes,95%CI:-16.63 to-13.85,P<0.00001;I2=89%),improved arrhythmia-free survival(OR=1.27,95%CI:1.04-1.55,P=0.02;I2=45%),and lowered phrenic nerve palsy risk(OR=0.17,95%CI:0.04-0.63,P=0.008;I2=0%).No significant differences were found in fluoroscopy time,cardiac tamponade,repeat ablation,or vascular complications.CONCLUSION PFA demonstrates shorter procedure times,reduced phrenic nerve palsy,and better arrhythmia control compared to CBA,with comparable safety profiles.However,evidence is limited by observational study designs,heterogeneity,and potential bias.Large-scale randomized controlled trials with extended follow-up are needed to confirm these findings and guide clinical practice.展开更多
Low-intensity pulsed ultrasound(LIPUS)is a non-invasive sonodynamic therapy that has been approved by the U.S.Food and Drug Administration for clinical use.Clinical trials have demonstrated that LIPUS ameliorates mild...Low-intensity pulsed ultrasound(LIPUS)is a non-invasive sonodynamic therapy that has been approved by the U.S.Food and Drug Administration for clinical use.Clinical trials have demonstrated that LIPUS ameliorates mild-to-moderate erectile dysfunction without adverse events.Histological analysis of the corpus cavernosum suggests that the therapeutic benefits of LIPUS may be attributed to alleviation of fibrosis,enhanced neovascularization,and promotion of innervation.Further investigations have revealed that LIPUS facilitates cavernous tissue repair through non-thermal mechanisms,including a cavitation effect,acoustic streaming,mass transfer enhancement,and direct mechanical stimulation.Mechanobiological transduction triggers molecular signaling cascades within endogenous cavernous cells,thereby stimulating cell proliferation,angiogenesis,extracellular matrix remodeling,and stem cell differentiation.Although LIPUS has the potential to induce cavernous rehabilitation in the treatment of erectile dysfunction,further investigations are necessary to elucidate the mechanisms via which LIPUS regulates each type of cavernous cell to determine the optimal parameters for this innovative therapy.展开更多
The kinetic characteristics of plasma-assisted oxidative pyrolysis of ammonia are studied by using the global/fluid models hybrid solution method.Firstly,the stable products of plasma-assisted oxidative pyrolysis of a...The kinetic characteristics of plasma-assisted oxidative pyrolysis of ammonia are studied by using the global/fluid models hybrid solution method.Firstly,the stable products of plasma-assisted oxidative pyrolysis of ammonia are measured.The results show that the consumption of NH_(3)/O_(2)and the production of N_(2)/H_(2)change linearly with the increase of voltage,which indicates the decoupling of nonequilibrium molecular excitation and oxidative pyrolysis of ammonia at low temperatures.Secondly,the detailed reaction kinetics mechanism of ammonia oxidative pyrolysis stimulated by a nanosecond pulse voltage at low pressure and room temperature is established.Based on the reaction path analysis,the simplified mechanism is obtained.The detailed and simplified mechanism simulation results are compared with experimental data to verify the accuracy of the simplified mechanism.Finally,based on the simplified mechanism,the fluid model of ammonia oxidative pyrolysis stimulated by the nanosecond pulse plasma is established to study the pre-sheath/sheath behavior and the resultant consumption and formation of key species.The results show that the generation,development,and propagation of the pre-sheath have a great influence on the formation and consumption of species.The consumption of NH_(3)by the cathode pre-sheath is greater than that by the anode pre-sheath,but the opposite is true for OH and O(1S).However,within the sheath,almost all reactions do not occur.Further,by changing the parameters of nanosecond pulse power supply voltage,it is found that the electron number density,electron current density,and applied peak voltages are not the direct reasons for the structural changes of the sheath and pre-sheath.Furthermore,the discharge interval has little effect on the sheath structure and gas mixture breakdown.The research results of this paper not only help to understand the kinetic promotion of non-equilibrium excitation in the process of oxidative pyrolysis but also help to explore the influence of transport and chemical reaction kinetics on the oxidative pyrolysis of ammonia.展开更多
In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 21...In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 2117.38 HV30,a 9.60%rise in fracture toughness from 9.06 to 9.93 MPa·m^(1/2),while the friction coefficient decreases from 0.63 to 0.47.Through the residual stress evolution,WC orientation change and the martensitic transformation of Co,and the internal enhancement mechanism of cryogenic combined with pulsed electric field treatment are revealed.The electron wind generated by the pulsed electric field can efficiently reduce the residual stress induced by cryogenic process.The evolution of residual stress promotes the base slip of WC,increasing the degree of{0001}orientation.In addition,the degree of martensitic transformation of Co intensifies,with the hcp-Co/fcc-Co ratio rising from 0.41%to 17.86%.The enhanced WC{0001}orientation and increased hcp-Co content contribute to significant improvements in hardness and wear resistance.This work provides a novel efficient enhancement strategy for ceramics and alloys,with the potential to be a mainstream strengthening method in the future.展开更多
In recent years,the effect of pulsed magnetic fields on improving the solidification structure of alloys has attracted significant attention.A GH4738 nickel-based alloy smelted using a self-designed 20-kg electromagne...In recent years,the effect of pulsed magnetic fields on improving the solidification structure of alloys has attracted significant attention.A GH4738 nickel-based alloy smelted using a self-designed 20-kg electromagnetic casting system was taken as the research object.Finite element software was used to numerically simulate the magnetic field intensity,distribution,and temperature field of the casting device.The effect of the pulsed magnetic field on the solidification process of the GH4738 alloy was studied by means of low-magnification microstructural analysis.The measured magnetic field shows that when the duty cycle is 20%,the pulse frequency is 50 Hz,the output current is in the range of 150–250 A,and the peak magnetic field intensity of the crucible center is 68–116 mT.The crucible temperature is heated to 600℃and the melt center solidification time is 12.844 s.The microstructural analysis of the ingot shows that its shrinkage hole is reduced from 130 to 100 mm,and the equiaxed crystal area is increased from 2275 to 3150 mm^(2).The solidification angle of the dendrite is changed under the action of the pulsed magnetic field,and the tilt angle is 45°.The results show that the pulsed magnetic field promotes the primary crystal core of the GH4738 alloy,improves the nucleation rate of the melt,reduces the size difference of the solidification structure between the center and the edge of the ingot,and improves the uniformity of the solidification structure.展开更多
The corrosion resistance of cobalt-based alloy cladding layers is crucial for the long-term reliability of materials in the nuclear power industry,where they are exposed to highly aggressive environmental conditions.A...The corrosion resistance of cobalt-based alloy cladding layers is crucial for the long-term reliability of materials in the nuclear power industry,where they are exposed to highly aggressive environmental conditions.A major challenge to their performance is the corrosion occurring at phase boundaries under harsh operating conditions.This study investigates the effects of pulsed magnetic field treatment(PMT)on improving corrosion resistance at phase boundaries,specifically at the carbide/matrix Co interface,and seeks to clarify the underlying mechanisms.Advanced characterization techniques,including scanning electron microscopy(SEM),in situ transmission electron microscopy(TEM),in situ scanning kelvin probe force microscopy(SKPFM),and density functional theory(DFT)calculations,were employed.PMT samples exhibited no interface corrosion cracking or carbide spalling and showed a significant reduction in corrosion depth.TEM analysis revealed reduced lattice distortion at phase boundaries and a partial transformation of face-centered cubic(FCC)Co to hexagonal closepacked(HCP)Co.The enhanced corrosion resistance at phase boundaries is attributed to changes in the electronic work function(EWF),as determined by SKPFM measurements and DFT calculations.展开更多
This paper describes an experimental study investigating the effects of sinusoidal pulsed injection on the combustion mode transition in a dual-mode supersonic combustor.The results are obtained under inflow condition...This paper describes an experimental study investigating the effects of sinusoidal pulsed injection on the combustion mode transition in a dual-mode supersonic combustor.The results are obtained under inflow conditions of 2.9 MPa stagnation pressure,1900 K stagnation temperature,and Mach number of 3.0.It has been observed that,at the same equivalence ratio,the combustion mode and flow field structure undergo irreversible changes from a weak combustion state to a strong combustion state at a specific pulsed jet frequency compared to steady jet.For steady jet,the combustion mode is dual-mode.As the frequency of the unsteady jet changes,the combustion mode also changes:it becomes a transition mode at frequencies of 171 Hz and 260 Hz,and a ramjet mode at 216 Hz.Combustion instability under steady jet manifests as a transition in flame stabilization mode.In contrast,under pulsed jet,combustion instability appears either as a transition in flame stabilization mode or as flame blow-off and flashback.The flow field oscillation frequency in the non-reacting flow is 171 Hz,which may resonate with the 171 Hz pulsed jet frequency,making the combustion oscillations most pronounced at this frequency.When the jet frequency is increased to 216 Hz,the combustion intensity significantly increases,and the combustion mode transfers to the ramjet mode.However,further increasing the frequency to 260 Hz results in a decrease in combustion intensity,returning to the transition mode.The frequency of the flow field oscillations varies with the coupling of the pulsed injection frequency,shock wave,and flame,and if the system reaches an unstable state,that is,pre-combustion shock train moves far upstream of the isolator during the pulsed jet period,strong combustion state can be achieved,and this process is irreversible.展开更多
Capacitor-based pulsed power supply(PPS)is widely used in fields related to electromagnetic launch,plasma,and materials'synthesis,modification and processing.As industrial applications place higher requirements on...Capacitor-based pulsed power supply(PPS)is widely used in fields related to electromagnetic launch,plasma,and materials'synthesis,modification and processing.As industrial applications place higher requirements on compact and portable pulsed power supplies,the National Key Laboratory of Transient Physics(NKLTP)recently developed a pulsed power supply consisting of a set of compact pulse-forming units(PFU),each with a capacitor energy storage of 220 kJ.This integrated PPS comes with a complete system configuration,a miniature compact structure,a high rate of repetition,and high power,with energy storage density exceeding 1.2 MJ/m^(3).This paper describes the device-level design of the unit,the system layout,the control system,the thermal management system,and the experimental results of the pulsed power supply.The experimental results verified the good reliability of the PPS at high repetition rates with each unit module delivering an output current of more than 100 kA.Additionally,flexible current pulse shapes can be formed by setting the charging voltage and the trigger sequence of the PFUs.The pulse forming network(PFN)developed from these PFUs was successfully applied to electromagnetic launch.展开更多
Type-II Dirac semimetal PtTe2is a promising candidate for various electronic device applications due to its high carrier mobility,high conductivity,and air stability.In this work,we report on the growth of large-scale...Type-II Dirac semimetal PtTe2is a promising candidate for various electronic device applications due to its high carrier mobility,high conductivity,and air stability.In this work,we report on the growth of large-scale PtTe_(2)films by the pulsed laser deposition(PLD)and the comparison of the magnetotransport properties with the PtTe2films grown by the chemical vapor deposition(CVD).The low-temperature Hall curves of the PLD-grown films exhibit a linear behavior,in contrast with the nonlinear characteristic of the Hall behavior observed in CVD-grown films,in which a defect gradient is introduced.Meanwhile,both PtTe2films show weak antilocalization at low temperatures,which is attributed to the strong spin–orbit coupling.展开更多
Synchrotron method of resonant X-ray reflectivity 2D mapping has been applied to study ultrathin epitaxial layers of WS_(2)grown by pulsed laser deposition on Al_(2)O_(3)(0001)substrates.The measurements were carried ...Synchrotron method of resonant X-ray reflectivity 2D mapping has been applied to study ultrathin epitaxial layers of WS_(2)grown by pulsed laser deposition on Al_(2)O_(3)(0001)substrates.The measurements were carried out across the L absorption edge of tungsten to perform depth-dependent element-selective analysis sensitive to potential chemical modification of the WS_(2)layer in ambient conditions.Despite the few monolayer thickness of the studied film,the experimentally measured maps of reflectance as a function of incident angle and photon energy turned out to be quite informative showing well-pronounced interference effects near W absorption edge at 10210 eV.The synchrotron studies were complemented with conventional non-resonant reflectance measurements carried out in the laboratory at a fixed photon energy corresponding to Cu Kαemission.The reconstruction of the depth and energy dependent scattering length density within the studied multilayers was carried out using the OpenCL empowered fitting software utilizing spectral shaping algorithm which does not rely on the pre-measured reference absorption spectra.A thin WO_(x) layer has been revealed at the surface of the WS_(2)layer pointing out to the effect of water assisted photo-oxidation reported in a number of works related to ultrathin layers of transition metal dichalcogenides.展开更多
The development of highly active and cost-effective catalysts for the full pH range of the hydrogen evolution reaction(HER)to meet the industrial application demands is an urgent challenge.In this work,the performance...The development of highly active and cost-effective catalysts for the full pH range of the hydrogen evolution reaction(HER)to meet the industrial application demands is an urgent challenge.In this work,the performance and structure–activityrelationships of CuIr alloys prepared by the pulsed laser ablation in liquid technique as full pH range HER catalysts wereinvestigated.Results indicated that Ir is doped into the Cu matrix as single atoms in CuIr-0.1,and CuIr-0.1 single-atom alloys(SAAs)exhibit superior HER performance and stability across the full pH range,with overpotentials of 135,203,and 172 mVat the current density of 10 mA/cm^(2)in acidic,neutral,and alkaline electrolytes,respectively.The enhanced performance ofCuIr-0.1 SAAs can be attributed to the abundant active sites and accelerated reaction kinetics brought about by the electroniceffects.This work successfully alloyed two immiscible metals to improve the catalytic performance,providing an avenue forthe development of highly efficient and versatile HER catalysts for industrial applications.展开更多
The complicated structure of electronic devices makes the conventional annealing method,which involves placing the entire device in a furnace,insufficient for achieving the desired quality.This issue is currently addr...The complicated structure of electronic devices makes the conventional annealing method,which involves placing the entire device in a furnace,insufficient for achieving the desired quality.This issue is currently addressed through the use of pulsed laser annealing,where a specific target layer is heated,preventing the overheating of other layers or the substrate.However,this method is only applicable to a very limited range of materials and requires very expensive,powerful pulsed laser sources.Herein,a novel approach for the selective local thermal treatment of thin films is proposed;in this method,short,powerful current pulses are applied to the target conductive layer.The application of two current pulses with a length of 1.5 s induced the crystallization of a 160-nm thick indium tin oxide(ITO)film,resulting in a sheet resistance of 8.68Ω·sq^(-1),an average visible light transmittance of 86.69%,and a figure of merit(FoM)of 293.61.This FoM is an order of magnitude higher than that of the as-prepared ITO film,and to the best of our knowledge,is among the highest reported values for the polycrystalline ITO films.Simulations have shown that even faster and more localized crystallization could be achieved by increasing the power of pulsed current.This novel annealing method is applicable to most semi-conductive or metallic thin films and requires only a relatively inexpensive pulsed current source,making it potentially more attractive than pulsed laser annealing.展开更多
In a pulsed plasma thruster,the voltage distribution between the electrodes is a key factor that influences the ionization process.However,few researchers have conducted in-depth studies of this phenomenon in the past...In a pulsed plasma thruster,the voltage distribution between the electrodes is a key factor that influences the ionization process.However,few researchers have conducted in-depth studies of this phenomenon in the past.Reported here are measurements of the voltage distribution between the plates of a parallel-plate pulsed plasma thruster under different discharge voltages,based on which the variations in the total circuit inductance and resistance as well as those between the plates are calculated.The results show that the time-averaged voltage across the plates accounts for 28.7%-50.4%of the capacitor voltage.As the capacitor initial voltage increases from 1250 V to 2000 V,the voltage across the plates rises,but its proportion relative to the capacitor voltage decreases.For every 250 V increase in the capacitor initial voltage,the average voltage proportion across the plates decreases by approximately 2%-3%.Additionally,the voltage proportion decreases gradually from the end near the propellant outward.The voltage distribution ratio between the plates is correlated with the proportions of the resistance and inductance between the plates relative to the total circuit.展开更多
Avoiding crystallization while maintaining the original microstructure and mechanical properties of the material are long-term goals of laser welding of Zr-based bulk metallic glass(BMG).In this paper,the effect of pu...Avoiding crystallization while maintaining the original microstructure and mechanical properties of the material are long-term goals of laser welding of Zr-based bulk metallic glass(BMG).In this paper,the effect of pulsed laser welding parameters on the microstructure,crystallization degree,and mechanical properties of Zr57Nb5Cu15.4Ni12.6Al10 BMG is investigated.Non-crystallized welding forming of a zirconium-based amorphous alloy is achieved by optimizing the process parameters of pulsed laser welding.The crystallization degree of Zr-based BMG is mainly determined by the welding speed and power.The welding depth and crystallization area fraction increase with an increase in the effective peak power density.The optimized welding process can effectively reduce the heat accumulation of the weld,thus avoiding crystallization.The flexural strength of the weld can be maintained at 96.5%of the matrix.展开更多
During direct chilling(DC)casting of ZK61 alloys,the primary and secondary cooling causes strong thermal gradients,which leads to the uneven crystallization rate and thermal contraction in different positions of the i...During direct chilling(DC)casting of ZK61 alloys,the primary and secondary cooling causes strong thermal gradients,which leads to the uneven crystallization rate and thermal contraction in different positions of the ingot.The consequences manifested appearance of heterogeneous grains,huge casting stresses,and even hot cracking flaws.In this paper,chemical and physical methods were integrated to produce large-scale magnesium(Mg)alloy ingots.A φ525 mm ZK61-RE alloy ingot that was refined,homogeneous,and free from hot cracking was obtained via the DC process coupled with a differential low frequency pulsed magnetic field(DLPM).The effects of rare earth(RE)and DLPM on the hot cracking tendency were investigated,and the mechanism of hot cracking formation and modification in largescale ingots was revealed.The findings indicate that the addition of moderate amounts of RE lessens the tendency of hot cracking in large-scale ZK61 alloy ingots.This is mainly attributed to the addition of RE increases the content of the second phase,thus enhancing the ability of the eutectic liquid phase to feed the cracking.With the introduction of DLPM,the grain sizes are significantly refined and homogenized,and there is no obvious hot cracking observed in the ingot.This is because the coupling of the DLPM provides a more homogeneous temperature field,leading to the synchronization of the solidification process,and the consequent reduction of the casting stress,thus reducing the driving force for the formation of hot cracking.In addition,the casting conditions are modified to enhance the ability of solidification feeding and the resistance to hot cracking.This work provides theoretical and practical references for the preparation of large-scale high-quality Mg alloy ingots.展开更多
基金National Key Research and Development Program of China(2021YFB3700801)。
文摘Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into the new β phase during the pulsed current-assisted aging process,and then the newly formed β phase is mainly transformed into the β_(t) phase,with occasional transition to new α_(p) phase,leading to a remarkable grain refinement,especially for the lamellarαs phases.In comparison to conventional aging treatment,the pulsed current-assisted aging approach achieves a significant enhancement in strength without degrading ductility,yielding an excellent mechanical property combination:a yield strength of 932 MPa,a tensile strength of 1042 MPa,and an elongation of 12.2%.It is primarily ascribed to the increased fraction of β_(t) phases,the obvious grain refinement effect,and the slip block effect induced by the multiple-variantαs colonies distributed within β_(t) phases.
基金financially supported by the National Key Research and Development Program of China(Grant No.2022YFA1602700)the National Natural Science Foundation of China(Grant No.12274159)。
文摘Pulsed magnet technology is the only way to generate ultra-strong magnetic fields higher than 45 T so far.However,the inherently fast-changing field strength(typically on the order of 1000 T/s)poses significant challenges for spectroscopic measurements which rely on time integration of signals to improve spectral qualities.In this work,we report high-sensitivity spectroscopic measurements under pulsed high magnetic fields employing the long flat-top pulsed magnetic field technique.By means of a multiple-capacitor power supply,we were able to generate pulsed high magnetic fields with controllable flat-top pulse width and field stabilities.By synchronizing spectroscopic measurements with the waveform of the flattop magnetic field,the integration time of each spectrum can be increased by up to 100 times compared with that of the conventional spectroscopic measurements under pulsed magnetic fields,thus enabling high-sensitivity spectroscopic measurements under ultra-strong pulsed magnetic fields.These findings promise an efficient way to significantly improve the performance and extend the application of optical measurements under pulsed high magnetic fields.
基金supported by the Fundamental Research Funds for the Central Universities(No.FRF-BD-23-01).
文摘Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,including bubble,electromagnetic stirring,filtration separation,fluid flow,and sedimentation,often struggle with the removal of fine inclusions.Apart from these known methods,pulsed electric current(PEC),as an emerging technology,has demonstrated immense potential and environmental advantages.PEC offers adjustable current parameters and simple equipment,making it an attractive alternative to traditional methods.Its green energy-saving features and excellent results in regulating inclusion morphology and migration,as well as inhibiting submerged entry nozzle(SEN)clogging,make it a promising technology.In comparison to continuous current technology,PEC has shown significant advantages in regulating inclusions,not only improving purification efficiency but also demonstrating outstanding performance in flow stability and energy consumption.The ability of PEC to efficiently reduce inclusion numbers enhances the purity and quality of molten steel,improving its mechanical properties.Currently,the theoretical basis for controlling the movement of inclusions by current is mainly composed of three major theories:the double electric layer theory,electromagnetic force reverse separation theory,and electric free energy drive theory.These theories together form an important framework for researchers to understand and optimize the behavior of impurity movement controlled by electric current.Looking ahead,PEC is expected to pave the way for new solutions in directional regulation of inclusion migration,efficient inclusion removal,SEN clogging prevention,and the purification of molten steel.
基金National Natural Science Foundation of China(No.52476192,No.52106237)Natural Science Foundation of Heilongjiang Province(No.YQ2022E027)。
文摘The transition of hydrogen sourcing from carbon-intensive to water-based methodologies is underway,with renewable energy-powered proton exchange membrane water electrolysis(PEMWE)emerging as the preeminent pathway for hydrogen production.Despite remarkable advancements in this field,confronting the sluggish electrochemical kinetics and inherent high-energy consumption arising from deteriorated mass transport within PEMWE systems remains a formidable obstacle.This impediment stems primarily from the hindered protons mass transfer and the untimely hydrogen bubbles detachment.To address these challenges,we harness the inherent variability of electrical energy and introduce an innovative pulsed dynamic water electrolysis system.Compared to constant voltage electrolysis(hydrogen production rate:51.6 m L h^(-1),energy consumption:5.37 kWh Nm-^(3)H_(2)),this strategy(hydrogen production rate:66 m L h^(-1),energy consumption:3.83 kWh Nm-^(3)H_(2))increases the hydrogen production rate by approximately 27%and reduces the energy consumption by about 28%.Furthermore,we demonstrate the practicality of this system by integrating it with an off-grid photovoltaic(PV)system designed for outdoor operation,successfully driving a hydrogen production current of up to 500 mA under an average voltage of approximately 2 V.The combined results of in-situ characterization and finite element analysis reveal the performance enhancement mechanism:pulsed dynamic electrolysis(PDE)dramatically accelerates the enrichment of protons at the electrode/solution interface and facilitates the release of bubbles on the electrode surface.As such,PDE-enhanced PEMWE represents a synergistic advancement,concurrently enhancing both the hydrogen generation reaction and associated transport processes.This promising technology not only redefines the landscape of electrolysis-based hydrogen production but also holds immense potential for broadening its application across a diverse spectrum of electrocatalytic endeavors.
基金supported by the National Key R&D Program of China(2020YFA0714900,2023YFB3709903)the National Natural Science Foundation of China(U21B2082,52474410)+6 种基金the Key R&D Program of Shandong Province,China(2023CXGC010406)the Scientific Research Special Project for First-Class Disciplines in Inner Mongolia Autonomous Region(YLXKZX-NKD-001)the International Science and Technology Cooperation Project of Higher Education Institutions in Inner Mongolia Autonomous Region(GHXM-002)the Natural Science Foundation of Inner Mongolia Autonomous Region of China(2024ZD06)the Technology Support Project for the Construction of Major Innovation Platforms in Inner Mongolia Autonomous Region(XM2024XTGXQ16)the Beijing Municipal Natural Science Foundation(2222065)the Fundamental Research Funds for the Central Universities(FRF-TP-22-02C2).
文摘Traditional heat treatment methods require a significant amount of time and energy to affect atomic diffusion and enhance the spheroidization process of carbides in bearing steel,while pulsed current can accelerate atomic diffusion to achieve ultra-fast spheroidization of carbides.However,the understanding of the mechanism by which different pulse current parameters regulate the dissolution behavior of carbides requires a large amount of experimental data to support,which limits the application of pulse current technology in the field of heat treatment.Based on this,quantify the obtained pulse current processing data to create an important dataset that could be applied to machine learning.Through machine learning,the mechanism of mutual influence between carbide regulation and various factors was elucidated,and the optimal spheroidization process parameters were determined.Compared to the 20 h required for traditional heat treatment,the application of pulsed electric current technology achieved ultra-fast spheroidization of GCr15 bearing steel within 90 min.
文摘BACKGROUND Atrial fibrillation,affecting approximately 33 million people globally,is the most common sustained arrhythmia,increasing risks of stroke,heart failure,and mortality.Pulmonary vein isolation via catheter ablation is a key rhythm control strategy,with cryoballoon ablation(CBA)being a standard thermal method but associated with risks like phrenic nerve palsy(5%-10%),esophageal injury,and vein stenosis.Pulsed field ablation(PFA),a non-thermal technique using electrical pulses for selective electroporation,offers potential for shorter procedures and improved safety.Limited direct comparisons between PFA and CBA necessitate a systematic evaluation of their efficacy and safety.AIM To compare the procedural success,safety,and 1-year arrhythmia-free survival of PFA vs CBA for first-time pulmonary vein isolation in adults with paroxysmal or persistent atrial fibrillation.METHODS A Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant systematic review and metaanalysis was conducted,searching PubMed,EMBASE,Web of Science,and other databases up to August 2025 for comparative studies.Pooled mean difference for continuous outcomes and odds ratio(OR)for dichotomous outcomes were calculated using random-effects models.Study quality was assessed with the Newcastle-Ottawa Scale,heterogeneity with I2,and publication bias with funnel plots.RESULTS Seven studies(six cohorts,one randomized controlled trial)were included,with a mean age of approximately 66 years,59%-78%male,and high prevalence of hypertension and diabetes.PFA significantly reduced procedure time(mean difference=-15.24 minutes,95%CI:-16.63 to-13.85,P<0.00001;I2=89%),improved arrhythmia-free survival(OR=1.27,95%CI:1.04-1.55,P=0.02;I2=45%),and lowered phrenic nerve palsy risk(OR=0.17,95%CI:0.04-0.63,P=0.008;I2=0%).No significant differences were found in fluoroscopy time,cardiac tamponade,repeat ablation,or vascular complications.CONCLUSION PFA demonstrates shorter procedure times,reduced phrenic nerve palsy,and better arrhythmia control compared to CBA,with comparable safety profiles.However,evidence is limited by observational study designs,heterogeneity,and potential bias.Large-scale randomized controlled trials with extended follow-up are needed to confirm these findings and guide clinical practice.
文摘Low-intensity pulsed ultrasound(LIPUS)is a non-invasive sonodynamic therapy that has been approved by the U.S.Food and Drug Administration for clinical use.Clinical trials have demonstrated that LIPUS ameliorates mild-to-moderate erectile dysfunction without adverse events.Histological analysis of the corpus cavernosum suggests that the therapeutic benefits of LIPUS may be attributed to alleviation of fibrosis,enhanced neovascularization,and promotion of innervation.Further investigations have revealed that LIPUS facilitates cavernous tissue repair through non-thermal mechanisms,including a cavitation effect,acoustic streaming,mass transfer enhancement,and direct mechanical stimulation.Mechanobiological transduction triggers molecular signaling cascades within endogenous cavernous cells,thereby stimulating cell proliferation,angiogenesis,extracellular matrix remodeling,and stem cell differentiation.Although LIPUS has the potential to induce cavernous rehabilitation in the treatment of erectile dysfunction,further investigations are necessary to elucidate the mechanisms via which LIPUS regulates each type of cavernous cell to determine the optimal parameters for this innovative therapy.
基金Fundamental Research Funds for the Central Universities(M23JBZY00050)National Natural Science Foundation of China(22278032)。
文摘The kinetic characteristics of plasma-assisted oxidative pyrolysis of ammonia are studied by using the global/fluid models hybrid solution method.Firstly,the stable products of plasma-assisted oxidative pyrolysis of ammonia are measured.The results show that the consumption of NH_(3)/O_(2)and the production of N_(2)/H_(2)change linearly with the increase of voltage,which indicates the decoupling of nonequilibrium molecular excitation and oxidative pyrolysis of ammonia at low temperatures.Secondly,the detailed reaction kinetics mechanism of ammonia oxidative pyrolysis stimulated by a nanosecond pulse voltage at low pressure and room temperature is established.Based on the reaction path analysis,the simplified mechanism is obtained.The detailed and simplified mechanism simulation results are compared with experimental data to verify the accuracy of the simplified mechanism.Finally,based on the simplified mechanism,the fluid model of ammonia oxidative pyrolysis stimulated by the nanosecond pulse plasma is established to study the pre-sheath/sheath behavior and the resultant consumption and formation of key species.The results show that the generation,development,and propagation of the pre-sheath have a great influence on the formation and consumption of species.The consumption of NH_(3)by the cathode pre-sheath is greater than that by the anode pre-sheath,but the opposite is true for OH and O(1S).However,within the sheath,almost all reactions do not occur.Further,by changing the parameters of nanosecond pulse power supply voltage,it is found that the electron number density,electron current density,and applied peak voltages are not the direct reasons for the structural changes of the sheath and pre-sheath.Furthermore,the discharge interval has little effect on the sheath structure and gas mixture breakdown.The research results of this paper not only help to understand the kinetic promotion of non-equilibrium excitation in the process of oxidative pyrolysis but also help to explore the influence of transport and chemical reaction kinetics on the oxidative pyrolysis of ammonia.
基金supported by the National Natural Science Foundation of China(Nos.U21A20399 and 52274407)Liaoning Province Applied Basic Research Program(No.2022JH2/101300212).
文摘In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 2117.38 HV30,a 9.60%rise in fracture toughness from 9.06 to 9.93 MPa·m^(1/2),while the friction coefficient decreases from 0.63 to 0.47.Through the residual stress evolution,WC orientation change and the martensitic transformation of Co,and the internal enhancement mechanism of cryogenic combined with pulsed electric field treatment are revealed.The electron wind generated by the pulsed electric field can efficiently reduce the residual stress induced by cryogenic process.The evolution of residual stress promotes the base slip of WC,increasing the degree of{0001}orientation.In addition,the degree of martensitic transformation of Co intensifies,with the hcp-Co/fcc-Co ratio rising from 0.41%to 17.86%.The enhanced WC{0001}orientation and increased hcp-Co content contribute to significant improvements in hardness and wear resistance.This work provides a novel efficient enhancement strategy for ceramics and alloys,with the potential to be a mainstream strengthening method in the future.
基金supported by National Natural Science Foundation of China(No.52074092)the Fundamental Research Funds for Inner Mongolia University of Science&Technology(No.2023QNJS007)+1 种基金Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(No.NJYT23115)the Inner Mongolia Natural Science Foundation(No.2022MS05039).
文摘In recent years,the effect of pulsed magnetic fields on improving the solidification structure of alloys has attracted significant attention.A GH4738 nickel-based alloy smelted using a self-designed 20-kg electromagnetic casting system was taken as the research object.Finite element software was used to numerically simulate the magnetic field intensity,distribution,and temperature field of the casting device.The effect of the pulsed magnetic field on the solidification process of the GH4738 alloy was studied by means of low-magnification microstructural analysis.The measured magnetic field shows that when the duty cycle is 20%,the pulse frequency is 50 Hz,the output current is in the range of 150–250 A,and the peak magnetic field intensity of the crucible center is 68–116 mT.The crucible temperature is heated to 600℃and the melt center solidification time is 12.844 s.The microstructural analysis of the ingot shows that its shrinkage hole is reduced from 130 to 100 mm,and the equiaxed crystal area is increased from 2275 to 3150 mm^(2).The solidification angle of the dendrite is changed under the action of the pulsed magnetic field,and the tilt angle is 45°.The results show that the pulsed magnetic field promotes the primary crystal core of the GH4738 alloy,improves the nucleation rate of the melt,reduces the size difference of the solidification structure between the center and the edge of the ingot,and improves the uniformity of the solidification structure.
基金financially supported by the National Key Research and Development Program of China(No.2020YFA0714900)the Joint Fund of the Ministry of Education(No.8091B012201)
文摘The corrosion resistance of cobalt-based alloy cladding layers is crucial for the long-term reliability of materials in the nuclear power industry,where they are exposed to highly aggressive environmental conditions.A major challenge to their performance is the corrosion occurring at phase boundaries under harsh operating conditions.This study investigates the effects of pulsed magnetic field treatment(PMT)on improving corrosion resistance at phase boundaries,specifically at the carbide/matrix Co interface,and seeks to clarify the underlying mechanisms.Advanced characterization techniques,including scanning electron microscopy(SEM),in situ transmission electron microscopy(TEM),in situ scanning kelvin probe force microscopy(SKPFM),and density functional theory(DFT)calculations,were employed.PMT samples exhibited no interface corrosion cracking or carbide spalling and showed a significant reduction in corrosion depth.TEM analysis revealed reduced lattice distortion at phase boundaries and a partial transformation of face-centered cubic(FCC)Co to hexagonal closepacked(HCP)Co.The enhanced corrosion resistance at phase boundaries is attributed to changes in the electronic work function(EWF),as determined by SKPFM measurements and DFT calculations.
基金supported by the Program of Key Laboratory of Cross-Domain Flight Interdisciplinary Technology,China(No.2023-ZY0205)。
文摘This paper describes an experimental study investigating the effects of sinusoidal pulsed injection on the combustion mode transition in a dual-mode supersonic combustor.The results are obtained under inflow conditions of 2.9 MPa stagnation pressure,1900 K stagnation temperature,and Mach number of 3.0.It has been observed that,at the same equivalence ratio,the combustion mode and flow field structure undergo irreversible changes from a weak combustion state to a strong combustion state at a specific pulsed jet frequency compared to steady jet.For steady jet,the combustion mode is dual-mode.As the frequency of the unsteady jet changes,the combustion mode also changes:it becomes a transition mode at frequencies of 171 Hz and 260 Hz,and a ramjet mode at 216 Hz.Combustion instability under steady jet manifests as a transition in flame stabilization mode.In contrast,under pulsed jet,combustion instability appears either as a transition in flame stabilization mode or as flame blow-off and flashback.The flow field oscillation frequency in the non-reacting flow is 171 Hz,which may resonate with the 171 Hz pulsed jet frequency,making the combustion oscillations most pronounced at this frequency.When the jet frequency is increased to 216 Hz,the combustion intensity significantly increases,and the combustion mode transfers to the ramjet mode.However,further increasing the frequency to 260 Hz results in a decrease in combustion intensity,returning to the transition mode.The frequency of the flow field oscillations varies with the coupling of the pulsed injection frequency,shock wave,and flame,and if the system reaches an unstable state,that is,pre-combustion shock train moves far upstream of the isolator during the pulsed jet period,strong combustion state can be achieved,and this process is irreversible.
基金financial support from the National Key Laboratory of Transient Physics,Nanjing University of Science and Technology(Grant No.6142604230101)Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant Nos.KYCX20_0321 and KYCX20_0322).
文摘Capacitor-based pulsed power supply(PPS)is widely used in fields related to electromagnetic launch,plasma,and materials'synthesis,modification and processing.As industrial applications place higher requirements on compact and portable pulsed power supplies,the National Key Laboratory of Transient Physics(NKLTP)recently developed a pulsed power supply consisting of a set of compact pulse-forming units(PFU),each with a capacitor energy storage of 220 kJ.This integrated PPS comes with a complete system configuration,a miniature compact structure,a high rate of repetition,and high power,with energy storage density exceeding 1.2 MJ/m^(3).This paper describes the device-level design of the unit,the system layout,the control system,the thermal management system,and the experimental results of the pulsed power supply.The experimental results verified the good reliability of the PPS at high repetition rates with each unit module delivering an output current of more than 100 kA.Additionally,flexible current pulse shapes can be formed by setting the charging voltage and the trigger sequence of the PFUs.The pulse forming network(PFN)developed from these PFUs was successfully applied to electromagnetic launch.
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1402404)the National Natural Science Foundation of China(Grant Nos.T2394473,624B2070,and 62274085)。
文摘Type-II Dirac semimetal PtTe2is a promising candidate for various electronic device applications due to its high carrier mobility,high conductivity,and air stability.In this work,we report on the growth of large-scale PtTe_(2)films by the pulsed laser deposition(PLD)and the comparison of the magnetotransport properties with the PtTe2films grown by the chemical vapor deposition(CVD).The low-temperature Hall curves of the PLD-grown films exhibit a linear behavior,in contrast with the nonlinear characteristic of the Hall behavior observed in CVD-grown films,in which a defect gradient is introduced.Meanwhile,both PtTe2films show weak antilocalization at low temperatures,which is attributed to the strong spin–orbit coupling.
基金supported by the Ministry of Science and Higher Education of the Russian Federation(agreement No.075-15-2021-1349)。
文摘Synchrotron method of resonant X-ray reflectivity 2D mapping has been applied to study ultrathin epitaxial layers of WS_(2)grown by pulsed laser deposition on Al_(2)O_(3)(0001)substrates.The measurements were carried out across the L absorption edge of tungsten to perform depth-dependent element-selective analysis sensitive to potential chemical modification of the WS_(2)layer in ambient conditions.Despite the few monolayer thickness of the studied film,the experimentally measured maps of reflectance as a function of incident angle and photon energy turned out to be quite informative showing well-pronounced interference effects near W absorption edge at 10210 eV.The synchrotron studies were complemented with conventional non-resonant reflectance measurements carried out in the laboratory at a fixed photon energy corresponding to Cu Kαemission.The reconstruction of the depth and energy dependent scattering length density within the studied multilayers was carried out using the OpenCL empowered fitting software utilizing spectral shaping algorithm which does not rely on the pre-measured reference absorption spectra.A thin WO_(x) layer has been revealed at the surface of the WS_(2)layer pointing out to the effect of water assisted photo-oxidation reported in a number of works related to ultrathin layers of transition metal dichalcogenides.
基金supported by the Natural Science Foundation of China(Nos.52022064 and 51971154).
文摘The development of highly active and cost-effective catalysts for the full pH range of the hydrogen evolution reaction(HER)to meet the industrial application demands is an urgent challenge.In this work,the performance and structure–activityrelationships of CuIr alloys prepared by the pulsed laser ablation in liquid technique as full pH range HER catalysts wereinvestigated.Results indicated that Ir is doped into the Cu matrix as single atoms in CuIr-0.1,and CuIr-0.1 single-atom alloys(SAAs)exhibit superior HER performance and stability across the full pH range,with overpotentials of 135,203,and 172 mVat the current density of 10 mA/cm^(2)in acidic,neutral,and alkaline electrolytes,respectively.The enhanced performance ofCuIr-0.1 SAAs can be attributed to the abundant active sites and accelerated reaction kinetics brought about by the electroniceffects.This work successfully alloyed two immiscible metals to improve the catalytic performance,providing an avenue forthe development of highly efficient and versatile HER catalysts for industrial applications.
基金supported by the National Key R&D Program of China(No.2021YFB2801600)the National Natural Science Foundation of China(Nos.52072060,52202164 and 52021001)the Natural Science Foundation of Sichuan(Nos.2023NSFSC1950 and 2022NSFSC1990).
文摘The complicated structure of electronic devices makes the conventional annealing method,which involves placing the entire device in a furnace,insufficient for achieving the desired quality.This issue is currently addressed through the use of pulsed laser annealing,where a specific target layer is heated,preventing the overheating of other layers or the substrate.However,this method is only applicable to a very limited range of materials and requires very expensive,powerful pulsed laser sources.Herein,a novel approach for the selective local thermal treatment of thin films is proposed;in this method,short,powerful current pulses are applied to the target conductive layer.The application of two current pulses with a length of 1.5 s induced the crystallization of a 160-nm thick indium tin oxide(ITO)film,resulting in a sheet resistance of 8.68Ω·sq^(-1),an average visible light transmittance of 86.69%,and a figure of merit(FoM)of 293.61.This FoM is an order of magnitude higher than that of the as-prepared ITO film,and to the best of our knowledge,is among the highest reported values for the polycrystalline ITO films.Simulations have shown that even faster and more localized crystallization could be achieved by increasing the power of pulsed current.This novel annealing method is applicable to most semi-conductive or metallic thin films and requires only a relatively inexpensive pulsed current source,making it potentially more attractive than pulsed laser annealing.
基金supported by the Beijing Natural Science Foundation(No.QY24166).
文摘In a pulsed plasma thruster,the voltage distribution between the electrodes is a key factor that influences the ionization process.However,few researchers have conducted in-depth studies of this phenomenon in the past.Reported here are measurements of the voltage distribution between the plates of a parallel-plate pulsed plasma thruster under different discharge voltages,based on which the variations in the total circuit inductance and resistance as well as those between the plates are calculated.The results show that the time-averaged voltage across the plates accounts for 28.7%-50.4%of the capacitor voltage.As the capacitor initial voltage increases from 1250 V to 2000 V,the voltage across the plates rises,but its proportion relative to the capacitor voltage decreases.For every 250 V increase in the capacitor initial voltage,the average voltage proportion across the plates decreases by approximately 2%-3%.Additionally,the voltage proportion decreases gradually from the end near the propellant outward.The voltage distribution ratio between the plates is correlated with the proportions of the resistance and inductance between the plates relative to the total circuit.
基金Supported by Guangdong Major Project of Basic and Applied Research,China(Grant No.2019B030302010)National Natural Science Foundation of China (Grant Nos.51735003,52205456)
文摘Avoiding crystallization while maintaining the original microstructure and mechanical properties of the material are long-term goals of laser welding of Zr-based bulk metallic glass(BMG).In this paper,the effect of pulsed laser welding parameters on the microstructure,crystallization degree,and mechanical properties of Zr57Nb5Cu15.4Ni12.6Al10 BMG is investigated.Non-crystallized welding forming of a zirconium-based amorphous alloy is achieved by optimizing the process parameters of pulsed laser welding.The crystallization degree of Zr-based BMG is mainly determined by the welding speed and power.The welding depth and crystallization area fraction increase with an increase in the effective peak power density.The optimized welding process can effectively reduce the heat accumulation of the weld,thus avoiding crystallization.The flexural strength of the weld can be maintained at 96.5%of the matrix.
基金Project supported by the Jiangxi Province Key Laboratory of Light Alloy(2024SSY05031)the National Natural Science Foundation of China(52061028)+1 种基金the National Key Research and Development Program of China(2021YFB3501001)the Major Research and Development Projects of Jiangxi Province(20223BBE51021,20213AAE02014)。
文摘During direct chilling(DC)casting of ZK61 alloys,the primary and secondary cooling causes strong thermal gradients,which leads to the uneven crystallization rate and thermal contraction in different positions of the ingot.The consequences manifested appearance of heterogeneous grains,huge casting stresses,and even hot cracking flaws.In this paper,chemical and physical methods were integrated to produce large-scale magnesium(Mg)alloy ingots.A φ525 mm ZK61-RE alloy ingot that was refined,homogeneous,and free from hot cracking was obtained via the DC process coupled with a differential low frequency pulsed magnetic field(DLPM).The effects of rare earth(RE)and DLPM on the hot cracking tendency were investigated,and the mechanism of hot cracking formation and modification in largescale ingots was revealed.The findings indicate that the addition of moderate amounts of RE lessens the tendency of hot cracking in large-scale ZK61 alloy ingots.This is mainly attributed to the addition of RE increases the content of the second phase,thus enhancing the ability of the eutectic liquid phase to feed the cracking.With the introduction of DLPM,the grain sizes are significantly refined and homogenized,and there is no obvious hot cracking observed in the ingot.This is because the coupling of the DLPM provides a more homogeneous temperature field,leading to the synchronization of the solidification process,and the consequent reduction of the casting stress,thus reducing the driving force for the formation of hot cracking.In addition,the casting conditions are modified to enhance the ability of solidification feeding and the resistance to hot cracking.This work provides theoretical and practical references for the preparation of large-scale high-quality Mg alloy ingots.
