Coaxial plasma guns are a type of plasma source that produces plasma which propagates radially and axially controlled by the shape of the ground electrode, which has attracted much interest in several applications. In...Coaxial plasma guns are a type of plasma source that produces plasma which propagates radially and axially controlled by the shape of the ground electrode, which has attracted much interest in several applications. In this work, a 120° opening angle of CPG nozzle is used as a plasma gun configuration that operates at the energy of 150 J. The ionization of polyethylene insulator between the electrodes of the gun produces a cloud of hydrogen and carbon plasma.The triple Langmuir probe and Faraday cup are used to measure plasma density and plasma temperature. These methods are used to measure the on-axis and off-axis plasma divergence of the coaxial plasma gun. The peak values of ion densities measured at a distance of 25 mm on-axis from the plasma gun are(1.6±0.5)×10^(19)m^(-3)and(2.8±0.6)×10^(19)m^(-3)for hydrogen and carbon plasma respectively and the peak temperature is 3.02±0.5 eV. The mean propagation velocity of plasma is calculated using the transit times of plasma at different distances from the plasma gun and is found to be 4.54±0.25 cm/μs and 1.81±0.18 cm/μs for hydrogen and carbon plasma respectively. The Debye radius is obtained from the measured experimental data that satisfies the thin sheath approximation. The shot-to-shot stability of plasma parameters facilitates the use of plasma guns in laboratory experiments. These types of plasma sources can be used in many applications like plasma opening switches, plasma devices, and as plasma sources.展开更多
A novel emissive probe consisting of an oxide cathode coating is developed to achieve a low operating temperature and long service life.The properties of the novel emissive probe are investigated in detail,in comparis...A novel emissive probe consisting of an oxide cathode coating is developed to achieve a low operating temperature and long service life.The properties of the novel emissive probe are investigated in detail,in comparison with a traditional tungsten emissive probe,including the operating temperature,the electron emission capability and the plasma potential measurement.Studies of the operating temperature and electron emission capability show that the tungsten emissive probe usually works at a temperature of 1800 K-2200 K while the oxide cathode emissive probe can function at about 1200 K-1400 K.In addition,plasma potential measurements using the oxide cathode emissive probe with different techniques have been accomplished in microwave electron cyclotron resonance plasmas with different discharge powers.It is found that a reliable plasma potential can be obtained using the improved inflection point method and the hot probe with zero emission limit method,while the floating point method is invalid for the oxide cathode emissive probe.展开更多
To maintain the high-density plasma source in inductively coupled plasma(ICP),very high radiofrequency power is often delivered to the antenna,which can heat the dielectric windows near the antenna to high temperature...To maintain the high-density plasma source in inductively coupled plasma(ICP),very high radiofrequency power is often delivered to the antenna,which can heat the dielectric windows near the antenna to high temperature.This high temperature can modulate the plasma characteristics to a large degree.We thus study the effect of dielectric window temperature on plasma parameters in two different ICP structures based on COMSOL software.The distributions of various plasma species are examined at different dielectric window temperatures.The concentration of neutral gas is found to be largely modulated at high dielectric window temperature,which further affects the electron collision probability with neutrals and the electron temperature.However,the electron density profiles are barely affected by the dielectric window temperature,which is mainly concentrated at the center of the reactor due to the fixed power input and pressure.展开更多
Al2O3-r2O03/NiCoCrAIYTa coatings were prepared via atmosphere plasma spraying (APS). The microstructure and phase com- position of the coatings were analyzed by X-ray diffraction (XRD), scanning electron microsco...Al2O3-r2O03/NiCoCrAIYTa coatings were prepared via atmosphere plasma spraying (APS). The microstructure and phase com- position of the coatings were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser confocal scanning microsco- py (LSCM), and transmission electron microscopy (TEM). The dry frictional wear behavior of the coatings at 500℃ in static air was inves- tigated and compared with that of 0Cr25Ni20 steel. The results show that the coatings comprise the slatted layers of oxide phases, unmelted particles, and pores. The hot abrasive resistance of the coatings is enhanced compared to that of 0Cr25Ni20, and their mass loss is approxi- mately one-fifteenth that of 0Cr25Ni20 steel. The main wear failure mechanisms of the coatings are abrasive wear, fatigue wear, and adhe- sive wear.展开更多
Excitation( Texc ) and rotation( Trot ) temperatures were determined under different conditions for an oxygen-shielded argon microwave plasmsa torch source(OS-Ar-MPT). The Texc value, which was shown to be betwe...Excitation( Texc ) and rotation( Trot ) temperatures were determined under different conditions for an oxygen-shielded argon microwave plasmsa torch source(OS-Ar-MPT). The Texc value, which was shown to be between 4300 and 5250 K under different operating conditions, was calculated from the slope of the Boltzmann plot with Fe as the thermometric species. The Trot value, which was in the range of 2100-2500 K, was measured with OH molecular spectra. The influences of microwave power, flow rates of the support gas, cartier gas, and shielding gas, as well as the observation height on Texc and Trot were investigated and discussed. The detailed results of Texc and Trot provided a better understanding of the performance of an OS-ArMPT as a source for atomic emission spectrometry.展开更多
The chemical composition of alloys directly determines their mechanical behaviors and application fields. Accurate and rapid analysis of both major and minor elements in alloys plays a key role in metallurgy quality c...The chemical composition of alloys directly determines their mechanical behaviors and application fields. Accurate and rapid analysis of both major and minor elements in alloys plays a key role in metallurgy quality control and material classification processes. A quantitative calibration-free laser-induced breakdown spectroscopy(CF-LIBS) analysis method, which carries out combined correction of plasma temperature and spectral intensity by using a secondorder iterative algorithm and two boundary standard samples, is proposed to realize accurate composition measurements. Experimental results show that, compared to conventional CF-LIBS analysis, the relative errors for major elements Cu and Zn and minor element Pb in the copperlead alloys has been reduced from 12%, 26% and 32% to 1.8%, 2.7% and 13.4%, respectively.The measurement accuracy for all elements has been improved substantially.展开更多
A series of experiments were carried out to study the influence of low temperature plasma nitriding on the mechanical properties of AISI 420 martensitic stainless steel. Plasma nitriding experiments were carried out f...A series of experiments were carried out to study the influence of low temperature plasma nitriding on the mechanical properties of AISI 420 martensitic stainless steel. Plasma nitriding experiments were carried out for 15 h at 350℃ by means of DC- pulsed plasma in 25%N2+ 75%H2 atmosphere. The microstructure, phase composition, and residual stresses profiles of the nitrided layers were determined by optical microscopy and X-ray diffraction. The microhardness profiles of the nitridied surfaces were also studied. The fatigue life, sliding wear, and erosion wear loss of the untreated specimens and plasma nitriding specimens were determined on the basis of a rotating bending fatigue tester, a ball-on-disc wear tester, and a solid particle erosion tester. The results show that the 350℃ nitrided surface is dominated by c-Fe3N and ON, which is supersaturated nitrogen solid solution. They have high hardness and chemical stabilities. So the low temperature plasma nitriding not only increases the surface hardness values but also improves the wear and erosion resistance. In addition, the fatigue limit of AISI 420 steel can also be improved by plasma nitriding at 350℃ because plasma nitriding produces residual compressive stress inside the modified layer.展开更多
The distribution of nano-carbonitrides produced by the treatments of surface nanocrystallization and plasma electrolytic carbonitriding on a γ-TiAl was investigated by means of figure analysis. The skewness and kurto...The distribution of nano-carbonitrides produced by the treatments of surface nanocrystallization and plasma electrolytic carbonitriding on a γ-TiAl was investigated by means of figure analysis. The skewness and kurtosis of Gaussian shape distribution curves were studied and the effect of electrolyte temperature was determined. The usage of lower temperatures of the electrolyte is more suitable for achieving lower sizes of complex nano-carbonitrides. The surface roughness of treated samples was measured and it was observed that there is an optimum level of electrolyte temperature for surface roughness increase (difference between two measured data).展开更多
This study conducted experiments on producing inhaled medical nitric oxide (iNO) by pulsed arc discharge in dry and clean air under different discharge current. The concentration of NO and NO2 produced by air discha...This study conducted experiments on producing inhaled medical nitric oxide (iNO) by pulsed arc discharge in dry and clean air under different discharge current. The concentration of NO and NO2 produced by air discharge, as well as the change of the ratio of NO2/NO under different discharge current were investigated. Through the analysis of plasma emission spectrum, the relationship between discharge current and arc plasma temperature was studied. The results indicate that, as discharge current increases, the arc plasma temperature increases, which then leads to the increase of NO concentration, the decrease of NO2 concentration, and the rapid decrease of the ratio of NO2/NO. When the plasma temperature is 9000 K, the ratio of NO2/NO is approximately 60%, while when the plasma temperature varies between 10550 K and 11300 K, the NO2/NO ratio is within the range of 4.2% to 4.6%.展开更多
As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and elec...As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and electron temperature of the plasma device accurately, a laser Thomson scattering(LTS) system, which is generally recognized as the most precise plasma diagnostic method, has been established in our lab in Dalian University of Technology. The electron density has been measured successfully in the region of 4.5?×10^19m^-3 to7.1?×10^20m^-3 and electron temperature in the region of 0.18 eV to 0.58 eV. For comparison,an optical emission spectroscopy(OES) system was established as well. The results showed that the electron excitation temperature(configuration temperature) measured by OES is significantly higher than the electron temperature(kinetic electron temperature) measured by LTS by up to 40% in the given discharge conditions. The results indicate that the cascaded arc plasma is recombining plasma and it is not in local thermodynamic equilibrium(LTE). This leads to significant error using OES when characterizing the electron temperature in a non-LTE plasma.展开更多
This study deals with the investigation of Nd:YAG laser-assisted ablation and plasma formation of Ti at irradiance of 0.85 GW cm-2 under Ar and Ne environment at various pressures ranging from 10-120 Torr.Laser-induce...This study deals with the investigation of Nd:YAG laser-assisted ablation and plasma formation of Ti at irradiance of 0.85 GW cm-2 under Ar and Ne environment at various pressures ranging from 10-120 Torr.Laser-induced breakdown spectroscopy is used to evaluate plasma parameters,whereas quartz crystal microbalance is used for ablation yield measurements.The crater depth is evaluated by optical microscopy.The surface features are explored by scanning electron microscope(SEM) analysis and the micro-hardness is measured by a Vickers hardness tester.It is observed that the plasma parameters are higher in Ar than in Ne,and are strongly correlated with the ablation yield,ablation depth,surface features and hardness of laser-ablated Ti.These parameters increase with increasing the pressure of environmental gases,attain their maxima at 40 Torr for Ar and at 60 Torr for Ne.Afterwards,they show a decreasing trend up till a maximum pressure of 120 Torr.The maximum value of the electron temperature(Te) is5480 K,number density(ne) is 1.46 × 1018 cm-3,ablation depth is 184 μm,ablation yield is3.9 × 1015 atoms/pulse and hardness is 300 HV in the case of Ar atmosphere.SEM analysis reveals the growth of surface features,such as cones,ridges and pores,whose appearance is more distinct in Ar than Ne and is attributed to temperature,pressure and density gradients along with recoil pressure of the Ti plasma.展开更多
Inversion techniques are conducted based on the tangential x-ray crystal spectroscopy(TXCS)geometry on EAST to obtain the local profiles of ion temperature(Ti)and toroidal rotation velocity(vt).Firstly,local emissivit...Inversion techniques are conducted based on the tangential x-ray crystal spectroscopy(TXCS)geometry on EAST to obtain the local profiles of ion temperature(Ti)and toroidal rotation velocity(vt).Firstly,local emissivity profiles of the impurity argon are obtained using the asymmetrical Abel inversion.Then,the local vt and Ti profiles are calculated by considering the local emissivity profiles and the TXCS detailed geometry.In addition,how the changes in the vt profiles affect the accuracy in the Ti profiles is discussed in detail.It is also found that the lineintegrated Ti profiles are becoming less accurate with the increase in the radial gradient in the local vt profiles.Nonetheless,accurate Ti radial profiles are reconstructed after considering the effects of the emissivity and velocity,which are verified by comparing the inverted vt and Ti profiles with those local profile measurements from the Charge eXchange Recombination Spectroscopy(CXRS)on EAST.展开更多
Filtered cathodic vacuum arc(FCVA)deposition is regarded as an important technique for the synthesis of tetrahedral amorphous carbon(ta-C)films due to its high ionization rate,high deposition rate and effective filtra...Filtered cathodic vacuum arc(FCVA)deposition is regarded as an important technique for the synthesis of tetrahedral amorphous carbon(ta-C)films due to its high ionization rate,high deposition rate and effective filtration of macroparticles.Probing the plasma characteristics of arc discharge contributes to understanding the deposition mechanism of ta-C films on a microscopic level.This work focuses on the plasma diagnosis of an FCVA discharge using a Langmuir dualprobe system with a discrete Fourier transform smoothing method.During the ta-C film deposition,the arc current of graphite cathodes and deposition pressure vary from 30 to 90 A and from 0.3 to 0.9 Pa,respectively.The plasma density increases with arc current but decreases with pressure.The carbon plasma density generated by the arc discharge is around the order of10^(10)cm^(-3).The electron temperature varies in the range of 2-3.5 eV.As the number of cathodic arc sources and the current of the focused magnetic coil increase,the plasma density increases.The ratio of the intensity of the D-Raman peak and G-Raman peak(I_(D)/I_(G))of the ta-C films increases with increasing plasma density,resulting in a decrease in film hardness.It is indicated that the mechanical properties of ta-C films depend not only on the ion energy but also on the carbon plasma density.展开更多
A series of Ba8Ga16Si30 clathrate samples were prepared by arc melting, ball milling, acid washing, and spark plasma sintering (SPS). X-ray diffraction analysis revealed that the lattice of the Ba8Ga16Si30 samples e...A series of Ba8Ga16Si30 clathrate samples were prepared by arc melting, ball milling, acid washing, and spark plasma sintering (SPS). X-ray diffraction analysis revealed that the lattice of the Ba8Ga16Si30 samples expanded as the SPS temperature was increased from 400 to 750℃. Lattice contraction recurred when the SPS temperature was further increased in the range of 750-1000℃. This phenomenon can be explained by the variation of Ga content in the lattice. The thermoelectric figure of the merit ZT value of clathrates increased with the increase in SPS temperature and reached a maximum when the sample was subjected to SPS at 800℃. A further increase in SPS temperature did not contribute to the improvement of ZT. The variation of the lattice parameter a vs. SPS temperature T was similar to the variation ob-served in the ZT-T curve.展开更多
The contacting interface between the substrate and water-cooled base is vital to the substrate temperature during diamond films deposition by a DC (direct current) plasma jet. The effects of the solid contacting are...The contacting interface between the substrate and water-cooled base is vital to the substrate temperature during diamond films deposition by a DC (direct current) plasma jet. The effects of the solid contacting area,conductive materials and fixing between the substrate and the base were investigated without affecting the other parameters. Experimental results indicated that the preferable solid contacting area was more than 60% of total contacting areal; the particular Sn-Pb alloy was more suitable for conducting heat and the concentric fixing ring was a better setting for controlling the substrate temperature. The result was explained in terms of the variable thermal contact resistance at the interface between substrate and base. The diamond films were analyzed by scanning electron microscopy (SEM) for morphology, X-ray diffraction (XRD) for the intensity of characteristic spectroscopy and Raman spectroscopy for structure.展开更多
Layered Ni-rich cathode materials,LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622),are synthesized via solid reaction assisted with a plasma milling pretreatment,which is resulted in lowering sintering temperatures for solid p...Layered Ni-rich cathode materials,LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622),are synthesized via solid reaction assisted with a plasma milling pretreatment,which is resulted in lowering sintering temperatures for solid precursors.The plasma milling pretreated NCM622 cathode material sintered at 780℃(named as PM-780)demonstrates good cycling stability at both room and subzero temperatures.Specifically,the PM-780 cathode delivers an initial discharge capacity of 171.2 mAh g^(-1) and a high capacity retention of 99.7%after 300 cycles with current rate of 90 mA g^(-1) at 30℃,while stable capacities of 120.3 and 94.0 m Ah g^(-1) can be remained at-10℃and-20℃in propylene carbonate contained electrolyte,respectively.In-situ XRD together with XPS and SEM reveal that the NCM622 cycled at-10℃presented better structural stability and more intact interface than that of cathodes cycled at 30℃.It is also found that subzero temperatures only limit the discharge potential of NCM622 without destroying its structure during cycling since it still exhibits high discharge capacity at 30℃after cycled at subzero temperatures.This work may expand the knowledge about the low-temperature characteristics of layered cathode materials for Li-ion batteries and lay the foundation for its further applications.展开更多
Nitric oxide (NO) is increasingly being used in medical treatments of high blood pressure, acute respiratory distress syndrome and other illnesses related to the lungs. Currently a NO inhalation system consists of a...Nitric oxide (NO) is increasingly being used in medical treatments of high blood pressure, acute respiratory distress syndrome and other illnesses related to the lungs. Currently a NO inhalation system consists of a gas cylinder of N2 mixed with a high concentration of NO. This arrangement is potentially risky due to the possibility of an accidental leak of NO from the cylinder. The presence of NO in the air leads to the formation of nitric dioxide (NO2), which is toxic to the lungs. Therefore, an on-site generator of NO would be highly desirable for medical doctors to use with patients with lung disease. To develop the NO inhalation system without a gas cylinder, which would include a high concentration of NO, NAMIHIRA et al have recently reported on the production of NO from room air using a pulsed arc discharge. In the present work, the temperature of the pulsed arc discharge plasma used to generate NO was measured to optimize the discharge condition. The results of the temperature measurements showed the temperature of the pulsed arc discharge plasma reached about 10,000 K immediately after discharge initiation and gradually decreased over tens of microseconds. In addition, it was found that NO was formed in a discharge plasma having temperatures higher than 9,000 K and a smaller input energy into the discharge plasma generates NO more efficiently than a larger one.展开更多
The ion-to-electron temperature ratio is a good indicator of the processes involved in solar wind plasma entering and being transported inside Earth’s plasma sheet.In this study,we have demonstrated that patchy magne...The ion-to-electron temperature ratio is a good indicator of the processes involved in solar wind plasma entering and being transported inside Earth’s plasma sheet.In this study,we have demonstrated that patchy magnetic reconnection has the potential to preserve the ion-to-electron temperature ratio under certain conditions.If the charged particles are non-adiabatically accelerated no more than once in a single reconnection,the temperature ratio would be preserved;on the other hand,this ratio would not be preserved if they are accelerated multiple times.Consequently,under a northward interplanetary magnetic field(IMF)condition,the reconnection in the nonlinear phase of the Kelvin-Helmholtz instability is the dominant process for solar-originated plasma entering the Earth’s magnetosphere,and the ion-to-electron temperature ratio is preserved inside the plasma sheet.When the direction of the IMF is southward,the reflection of electrons from the magnetic mirror point,and subsequent multiple non-adiabatic accelerations at the reconnection site,are the primary reasons for the observed low ion-to-electron temperature ratio close to the Earth at midnight.While reconnections that occur in the night-side far tail might preserve the ratio,turbulence on the boundaries of the bursty bulk flows(BBFs)could change the ratio in the far tail through the violation of the frozen-in condition of the ions.The plateau in the contour of the calculated ion-to-electron temperature ratio in the down tail distance between 40 and 60 Earth radii may explain the strong correlation between the ion and electron temperatures in the outer central plasma sheet,which has not been clearly understood till date.展开更多
In order to understand the characteristics of breakdown process,plasma evolution and spectral emission in liquid jets laser-induced breakdown spectroscopy methods under the influence of the position variation between ...In order to understand the characteristics of breakdown process,plasma evolution and spectral emission in liquid jets laser-induced breakdown spectroscopy methods under the influence of the position variation between laser focus and gas–liquid interface,this work takes the plasma generated by laser-induced liquid jets as the object of study and discusses the changes in the spatial and temporal evolution characteristics and spectral radiation of the plasma when the position parameters between the laser focal point and the gas–liquid interface are different.The initial breakdown position is always between the front interface and the focus when the laser focus moves along the vertical direction of the interface,forming a phenomenon like’interface effect’.The relationship between laser pulse energy and breakdown probability exhibits a law similar to a‘hysteresis curve’in the study of breakdown threshold.In this work,plasma with smaller size,rounder shape,stronger radiation,higher temperature,and higher density can be produced when the focus position is in the liquid column 0.2 mm away from the front interface.Simultaneously,the spectral signal intensity and signal-to-back ratio of the characteristic peaks of target elements in water reach maximum values,and the spectral signal becomes more stable(relative standard deviation value reaches 2%).The Ca element’s ion radiation at 393.366 nm and atomic radiation at 422.673 nm are studied using narrow-band filtering imaging and time-space resolution spectroscopy.The findings demonstrate that the laws of ion and atomic radiation are not perfectly consistent in space and time.展开更多
基金supported by Bhabha Atomic Research Centre, Department of Atomic Energy, Government of IndiaDepartment of Atomic Energy, Government of India for financial assistance under DAE Doctoral Fellowship Scheme-2018。
文摘Coaxial plasma guns are a type of plasma source that produces plasma which propagates radially and axially controlled by the shape of the ground electrode, which has attracted much interest in several applications. In this work, a 120° opening angle of CPG nozzle is used as a plasma gun configuration that operates at the energy of 150 J. The ionization of polyethylene insulator between the electrodes of the gun produces a cloud of hydrogen and carbon plasma.The triple Langmuir probe and Faraday cup are used to measure plasma density and plasma temperature. These methods are used to measure the on-axis and off-axis plasma divergence of the coaxial plasma gun. The peak values of ion densities measured at a distance of 25 mm on-axis from the plasma gun are(1.6±0.5)×10^(19)m^(-3)and(2.8±0.6)×10^(19)m^(-3)for hydrogen and carbon plasma respectively and the peak temperature is 3.02±0.5 eV. The mean propagation velocity of plasma is calculated using the transit times of plasma at different distances from the plasma gun and is found to be 4.54±0.25 cm/μs and 1.81±0.18 cm/μs for hydrogen and carbon plasma respectively. The Debye radius is obtained from the measured experimental data that satisfies the thin sheath approximation. The shot-to-shot stability of plasma parameters facilitates the use of plasma guns in laboratory experiments. These types of plasma sources can be used in many applications like plasma opening switches, plasma devices, and as plasma sources.
基金Project supported by the National Natural Science Foundation of China (Grant No.11905076)S&T Program of Hebei (Grant No.SZX2020034)。
文摘A novel emissive probe consisting of an oxide cathode coating is developed to achieve a low operating temperature and long service life.The properties of the novel emissive probe are investigated in detail,in comparison with a traditional tungsten emissive probe,including the operating temperature,the electron emission capability and the plasma potential measurement.Studies of the operating temperature and electron emission capability show that the tungsten emissive probe usually works at a temperature of 1800 K-2200 K while the oxide cathode emissive probe can function at about 1200 K-1400 K.In addition,plasma potential measurements using the oxide cathode emissive probe with different techniques have been accomplished in microwave electron cyclotron resonance plasmas with different discharge powers.It is found that a reliable plasma potential can be obtained using the improved inflection point method and the hot probe with zero emission limit method,while the floating point method is invalid for the oxide cathode emissive probe.
基金financially supported by National Natural Science Foundation of China(NSFC)(Nos.12105035 and 11935005)Guangdong Basic and Applied Basic Research Foundation(No.2021B1515120018)+1 种基金the Fundamental Research Funds for the Central Universities(No.DUT21TD104)the Advanced Space Propulsion Laboratory of BICE and Beijing Engineering Research Center of Efficient and Green Aerospace Propulsion Technology(No.Lab ASP-2020-01)。
文摘To maintain the high-density plasma source in inductively coupled plasma(ICP),very high radiofrequency power is often delivered to the antenna,which can heat the dielectric windows near the antenna to high temperature.This high temperature can modulate the plasma characteristics to a large degree.We thus study the effect of dielectric window temperature on plasma parameters in two different ICP structures based on COMSOL software.The distributions of various plasma species are examined at different dielectric window temperatures.The concentration of neutral gas is found to be largely modulated at high dielectric window temperature,which further affects the electron collision probability with neutrals and the electron temperature.However,the electron density profiles are barely affected by the dielectric window temperature,which is mainly concentrated at the center of the reactor due to the fixed power input and pressure.
基金financially supported by the National High-tech Research and Development Program of China(No.2012AA03A513)the Fundamental Research Funds for the Central Universities(No.N140204001)the National Natural Science Foundation of China(Nos.51371044 and 51301037)
文摘Al2O3-r2O03/NiCoCrAIYTa coatings were prepared via atmosphere plasma spraying (APS). The microstructure and phase com- position of the coatings were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser confocal scanning microsco- py (LSCM), and transmission electron microscopy (TEM). The dry frictional wear behavior of the coatings at 500℃ in static air was inves- tigated and compared with that of 0Cr25Ni20 steel. The results show that the coatings comprise the slatted layers of oxide phases, unmelted particles, and pores. The hot abrasive resistance of the coatings is enhanced compared to that of 0Cr25Ni20, and their mass loss is approxi- mately one-fifteenth that of 0Cr25Ni20 steel. The main wear failure mechanisms of the coatings are abrasive wear, fatigue wear, and adhe- sive wear.
基金Supported by the Science and Technology Development Program of Jilin Province, P. R. China(No. 20010306-1).
文摘Excitation( Texc ) and rotation( Trot ) temperatures were determined under different conditions for an oxygen-shielded argon microwave plasmsa torch source(OS-Ar-MPT). The Texc value, which was shown to be between 4300 and 5250 K under different operating conditions, was calculated from the slope of the Boltzmann plot with Fe as the thermometric species. The Trot value, which was in the range of 2100-2500 K, was measured with OH molecular spectra. The influences of microwave power, flow rates of the support gas, cartier gas, and shielding gas, as well as the observation height on Texc and Trot were investigated and discussed. The detailed results of Texc and Trot provided a better understanding of the performance of an OS-ArMPT as a source for atomic emission spectrometry.
基金financially supported by the National Key Research and Development Program of China(No.2017YFA0304203)the Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(No.IRT13076)+3 种基金National Natural Science Foundation of China(Nos.61475093,61378047,61775125)the Shanxi‘1331 Project’Key Subjects Constructionthe Major Special Science and Technology Projects in Shanxi Province(No.MD2016-01)the State Key Lab of Power Systems for technical contribution and financial support
文摘The chemical composition of alloys directly determines their mechanical behaviors and application fields. Accurate and rapid analysis of both major and minor elements in alloys plays a key role in metallurgy quality control and material classification processes. A quantitative calibration-free laser-induced breakdown spectroscopy(CF-LIBS) analysis method, which carries out combined correction of plasma temperature and spectral intensity by using a secondorder iterative algorithm and two boundary standard samples, is proposed to realize accurate composition measurements. Experimental results show that, compared to conventional CF-LIBS analysis, the relative errors for major elements Cu and Zn and minor element Pb in the copperlead alloys has been reduced from 12%, 26% and 32% to 1.8%, 2.7% and 13.4%, respectively.The measurement accuracy for all elements has been improved substantially.
基金supported by National Natural Science Foundation of China(Nos.50171054 and 50671085)National High Technical Research and Development Programme of China(No.2007AA03Z521).
文摘A series of experiments were carried out to study the influence of low temperature plasma nitriding on the mechanical properties of AISI 420 martensitic stainless steel. Plasma nitriding experiments were carried out for 15 h at 350℃ by means of DC- pulsed plasma in 25%N2+ 75%H2 atmosphere. The microstructure, phase composition, and residual stresses profiles of the nitrided layers were determined by optical microscopy and X-ray diffraction. The microhardness profiles of the nitridied surfaces were also studied. The fatigue life, sliding wear, and erosion wear loss of the untreated specimens and plasma nitriding specimens were determined on the basis of a rotating bending fatigue tester, a ball-on-disc wear tester, and a solid particle erosion tester. The results show that the 350℃ nitrided surface is dominated by c-Fe3N and ON, which is supersaturated nitrogen solid solution. They have high hardness and chemical stabilities. So the low temperature plasma nitriding not only increases the surface hardness values but also improves the wear and erosion resistance. In addition, the fatigue limit of AISI 420 steel can also be improved by plasma nitriding at 350℃ because plasma nitriding produces residual compressive stress inside the modified layer.
基金funded by the National Elite Foundation of Iran and Iranian Nanotechnology Initia-tive is appreciated
文摘The distribution of nano-carbonitrides produced by the treatments of surface nanocrystallization and plasma electrolytic carbonitriding on a γ-TiAl was investigated by means of figure analysis. The skewness and kurtosis of Gaussian shape distribution curves were studied and the effect of electrolyte temperature was determined. The usage of lower temperatures of the electrolyte is more suitable for achieving lower sizes of complex nano-carbonitrides. The surface roughness of treated samples was measured and it was observed that there is an optimum level of electrolyte temperature for surface roughness increase (difference between two measured data).
基金supported by National Natural Science Foundation of China (No.50677026)the Graduates' Innovation Foundation of Huazhong University of Science and Technology of China (HF-08-11-2011-261)
文摘This study conducted experiments on producing inhaled medical nitric oxide (iNO) by pulsed arc discharge in dry and clean air under different discharge current. The concentration of NO and NO2 produced by air discharge, as well as the change of the ratio of NO2/NO under different discharge current were investigated. Through the analysis of plasma emission spectrum, the relationship between discharge current and arc plasma temperature was studied. The results indicate that, as discharge current increases, the arc plasma temperature increases, which then leads to the increase of NO concentration, the decrease of NO2 concentration, and the rapid decrease of the ratio of NO2/NO. When the plasma temperature is 9000 K, the ratio of NO2/NO is approximately 60%, while when the plasma temperature varies between 10550 K and 11300 K, the NO2/NO ratio is within the range of 4.2% to 4.6%.
基金supported by the National Magnetic Confinement Fusion Science Program of China(No.2013GB109005)the Fundamental Research Funds for the Central Universities(Nos.DUT15RC(3)072,DUT15TD44,DUT16TD13)
文摘As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and electron temperature of the plasma device accurately, a laser Thomson scattering(LTS) system, which is generally recognized as the most precise plasma diagnostic method, has been established in our lab in Dalian University of Technology. The electron density has been measured successfully in the region of 4.5?×10^19m^-3 to7.1?×10^20m^-3 and electron temperature in the region of 0.18 eV to 0.58 eV. For comparison,an optical emission spectroscopy(OES) system was established as well. The results showed that the electron excitation temperature(configuration temperature) measured by OES is significantly higher than the electron temperature(kinetic electron temperature) measured by LTS by up to 40% in the given discharge conditions. The results indicate that the cascaded arc plasma is recombining plasma and it is not in local thermodynamic equilibrium(LTE). This leads to significant error using OES when characterizing the electron temperature in a non-LTE plasma.
文摘This study deals with the investigation of Nd:YAG laser-assisted ablation and plasma formation of Ti at irradiance of 0.85 GW cm-2 under Ar and Ne environment at various pressures ranging from 10-120 Torr.Laser-induced breakdown spectroscopy is used to evaluate plasma parameters,whereas quartz crystal microbalance is used for ablation yield measurements.The crater depth is evaluated by optical microscopy.The surface features are explored by scanning electron microscope(SEM) analysis and the micro-hardness is measured by a Vickers hardness tester.It is observed that the plasma parameters are higher in Ar than in Ne,and are strongly correlated with the ablation yield,ablation depth,surface features and hardness of laser-ablated Ti.These parameters increase with increasing the pressure of environmental gases,attain their maxima at 40 Torr for Ar and at 60 Torr for Ne.Afterwards,they show a decreasing trend up till a maximum pressure of 120 Torr.The maximum value of the electron temperature(Te) is5480 K,number density(ne) is 1.46 × 1018 cm-3,ablation depth is 184 μm,ablation yield is3.9 × 1015 atoms/pulse and hardness is 300 HV in the case of Ar atmosphere.SEM analysis reveals the growth of surface features,such as cones,ridges and pores,whose appearance is more distinct in Ar than Ne and is attributed to temperature,pressure and density gradients along with recoil pressure of the Ti plasma.
基金supported by National Natural Science Foundation of China(Nos.12175278 and 12205072)the Comprehensive Research Facility for Fusion Technology Program of China(No.2018-000052-73-01-001228)+3 种基金Major Science and Technology Infrastructure Maintenance and Reconstruction Projects of the Chinese Academy of Sciences(2021),the University Synergy Innovation Program of Anhui Province(No.GXXT-2021-029)Anhui Provincial Key Research and Development Project(No.202104a06020021)Open Fund of the Magnetic Confinement Fusion Laboratory of Anhui Province(No.2021AMF01002)the National Magnetic Confinement Fusion Science Program of China(Nos.2019YFE03040000 and 2018YFE0303103).
文摘Inversion techniques are conducted based on the tangential x-ray crystal spectroscopy(TXCS)geometry on EAST to obtain the local profiles of ion temperature(Ti)and toroidal rotation velocity(vt).Firstly,local emissivity profiles of the impurity argon are obtained using the asymmetrical Abel inversion.Then,the local vt and Ti profiles are calculated by considering the local emissivity profiles and the TXCS detailed geometry.In addition,how the changes in the vt profiles affect the accuracy in the Ti profiles is discussed in detail.It is also found that the lineintegrated Ti profiles are becoming less accurate with the increase in the radial gradient in the local vt profiles.Nonetheless,accurate Ti radial profiles are reconstructed after considering the effects of the emissivity and velocity,which are verified by comparing the inverted vt and Ti profiles with those local profile measurements from the Charge eXchange Recombination Spectroscopy(CXRS)on EAST.
基金supported by the National Key Research and Development Program of China(No.2016YFB0101206)the Science and Technology Program of Wuhu(No.2021hg11)the Natural Science Foundation of the Anhui Higher Education in Institutions of China(No.2022AH050300)。
文摘Filtered cathodic vacuum arc(FCVA)deposition is regarded as an important technique for the synthesis of tetrahedral amorphous carbon(ta-C)films due to its high ionization rate,high deposition rate and effective filtration of macroparticles.Probing the plasma characteristics of arc discharge contributes to understanding the deposition mechanism of ta-C films on a microscopic level.This work focuses on the plasma diagnosis of an FCVA discharge using a Langmuir dualprobe system with a discrete Fourier transform smoothing method.During the ta-C film deposition,the arc current of graphite cathodes and deposition pressure vary from 30 to 90 A and from 0.3 to 0.9 Pa,respectively.The plasma density increases with arc current but decreases with pressure.The carbon plasma density generated by the arc discharge is around the order of10^(10)cm^(-3).The electron temperature varies in the range of 2-3.5 eV.As the number of cathodic arc sources and the current of the focused magnetic coil increase,the plasma density increases.The ratio of the intensity of the D-Raman peak and G-Raman peak(I_(D)/I_(G))of the ta-C films increases with increasing plasma density,resulting in a decrease in film hardness.It is indicated that the mechanical properties of ta-C films depend not only on the ion energy but also on the carbon plasma density.
基金supported by the National Natural Science Foundation of China(No.51072023)the National Science Foundation of US(No.DMR-0821284)the National Aeronautics and Space Administration of US(Nos.NNX10AM80H and NNX07AO30A)
文摘A series of Ba8Ga16Si30 clathrate samples were prepared by arc melting, ball milling, acid washing, and spark plasma sintering (SPS). X-ray diffraction analysis revealed that the lattice of the Ba8Ga16Si30 samples expanded as the SPS temperature was increased from 400 to 750℃. Lattice contraction recurred when the SPS temperature was further increased in the range of 750-1000℃. This phenomenon can be explained by the variation of Ga content in the lattice. The thermoelectric figure of the merit ZT value of clathrates increased with the increase in SPS temperature and reached a maximum when the sample was subjected to SPS at 800℃. A further increase in SPS temperature did not contribute to the improvement of ZT. The variation of the lattice parameter a vs. SPS temperature T was similar to the variation ob-served in the ZT-T curve.
基金the National Natural Science Foundation of China for the financial support under the contract Nos.50275076 and 50605032.
文摘The contacting interface between the substrate and water-cooled base is vital to the substrate temperature during diamond films deposition by a DC (direct current) plasma jet. The effects of the solid contacting area,conductive materials and fixing between the substrate and the base were investigated without affecting the other parameters. Experimental results indicated that the preferable solid contacting area was more than 60% of total contacting areal; the particular Sn-Pb alloy was more suitable for conducting heat and the concentric fixing ring was a better setting for controlling the substrate temperature. The result was explained in terms of the variable thermal contact resistance at the interface between substrate and base. The diamond films were analyzed by scanning electron microscopy (SEM) for morphology, X-ray diffraction (XRD) for the intensity of characteristic spectroscopy and Raman spectroscopy for structure.
基金supported by the National Natural Science Foundation of China(No.51671088,51621001,51822104 and 51831009)the Guangzhou Science and Technology Plan Projects(No.201904020018)the Fundamental Research Funds for the Central Universities in South China University of Technology(No.2019CG24)。
文摘Layered Ni-rich cathode materials,LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622),are synthesized via solid reaction assisted with a plasma milling pretreatment,which is resulted in lowering sintering temperatures for solid precursors.The plasma milling pretreated NCM622 cathode material sintered at 780℃(named as PM-780)demonstrates good cycling stability at both room and subzero temperatures.Specifically,the PM-780 cathode delivers an initial discharge capacity of 171.2 mAh g^(-1) and a high capacity retention of 99.7%after 300 cycles with current rate of 90 mA g^(-1) at 30℃,while stable capacities of 120.3 and 94.0 m Ah g^(-1) can be remained at-10℃and-20℃in propylene carbonate contained electrolyte,respectively.In-situ XRD together with XPS and SEM reveal that the NCM622 cycled at-10℃presented better structural stability and more intact interface than that of cathodes cycled at 30℃.It is also found that subzero temperatures only limit the discharge potential of NCM622 without destroying its structure during cycling since it still exhibits high discharge capacity at 30℃after cycled at subzero temperatures.This work may expand the knowledge about the low-temperature characteristics of layered cathode materials for Li-ion batteries and lay the foundation for its further applications.
基金the Industrial Technology Research Grant Program in '05 from the New Energy and Industrial Technology Development Organization (NEDO) of Japan
文摘Nitric oxide (NO) is increasingly being used in medical treatments of high blood pressure, acute respiratory distress syndrome and other illnesses related to the lungs. Currently a NO inhalation system consists of a gas cylinder of N2 mixed with a high concentration of NO. This arrangement is potentially risky due to the possibility of an accidental leak of NO from the cylinder. The presence of NO in the air leads to the formation of nitric dioxide (NO2), which is toxic to the lungs. Therefore, an on-site generator of NO would be highly desirable for medical doctors to use with patients with lung disease. To develop the NO inhalation system without a gas cylinder, which would include a high concentration of NO, NAMIHIRA et al have recently reported on the production of NO from room air using a pulsed arc discharge. In the present work, the temperature of the pulsed arc discharge plasma used to generate NO was measured to optimize the discharge condition. The results of the temperature measurements showed the temperature of the pulsed arc discharge plasma reached about 10,000 K immediately after discharge initiation and gradually decreased over tens of microseconds. In addition, it was found that NO was formed in a discharge plasma having temperatures higher than 9,000 K and a smaller input energy into the discharge plasma generates NO more efficiently than a larger one.
文摘The ion-to-electron temperature ratio is a good indicator of the processes involved in solar wind plasma entering and being transported inside Earth’s plasma sheet.In this study,we have demonstrated that patchy magnetic reconnection has the potential to preserve the ion-to-electron temperature ratio under certain conditions.If the charged particles are non-adiabatically accelerated no more than once in a single reconnection,the temperature ratio would be preserved;on the other hand,this ratio would not be preserved if they are accelerated multiple times.Consequently,under a northward interplanetary magnetic field(IMF)condition,the reconnection in the nonlinear phase of the Kelvin-Helmholtz instability is the dominant process for solar-originated plasma entering the Earth’s magnetosphere,and the ion-to-electron temperature ratio is preserved inside the plasma sheet.When the direction of the IMF is southward,the reflection of electrons from the magnetic mirror point,and subsequent multiple non-adiabatic accelerations at the reconnection site,are the primary reasons for the observed low ion-to-electron temperature ratio close to the Earth at midnight.While reconnections that occur in the night-side far tail might preserve the ratio,turbulence on the boundaries of the bursty bulk flows(BBFs)could change the ratio in the far tail through the violation of the frozen-in condition of the ions.The plateau in the contour of the calculated ion-to-electron temperature ratio in the down tail distance between 40 and 60 Earth radii may explain the strong correlation between the ion and electron temperatures in the outer central plasma sheet,which has not been clearly understood till date.
基金supported by Natural Science Foundation of Shandong Province(Nos.ZR201910290171 and ZR2019MD 016)National Key Research and Development Program of China(No.2016YFC0302101)National Natural Science Foundation of China(No.41976173)。
文摘In order to understand the characteristics of breakdown process,plasma evolution and spectral emission in liquid jets laser-induced breakdown spectroscopy methods under the influence of the position variation between laser focus and gas–liquid interface,this work takes the plasma generated by laser-induced liquid jets as the object of study and discusses the changes in the spatial and temporal evolution characteristics and spectral radiation of the plasma when the position parameters between the laser focal point and the gas–liquid interface are different.The initial breakdown position is always between the front interface and the focus when the laser focus moves along the vertical direction of the interface,forming a phenomenon like’interface effect’.The relationship between laser pulse energy and breakdown probability exhibits a law similar to a‘hysteresis curve’in the study of breakdown threshold.In this work,plasma with smaller size,rounder shape,stronger radiation,higher temperature,and higher density can be produced when the focus position is in the liquid column 0.2 mm away from the front interface.Simultaneously,the spectral signal intensity and signal-to-back ratio of the characteristic peaks of target elements in water reach maximum values,and the spectral signal becomes more stable(relative standard deviation value reaches 2%).The Ca element’s ion radiation at 393.366 nm and atomic radiation at 422.673 nm are studied using narrow-band filtering imaging and time-space resolution spectroscopy.The findings demonstrate that the laws of ion and atomic radiation are not perfectly consistent in space and time.