Plasma-activated water(PAW),as an extended form of cold atmospheric-pressure plasma,greatly expands the application of plasma-based technology.The biological effects of PAW are closely related to the aqueous reactive ...Plasma-activated water(PAW),as an extended form of cold atmospheric-pressure plasma,greatly expands the application of plasma-based technology.The biological effects of PAW are closely related to the aqueous reactive species,which can be regulated by the activation process.In this study,surface plasma-activated air(SAA)and a He+O_(2)plasma jet(Jet)were parallelly combined(the SAA+Jet combination)or sequentially combined(the SAA→Jet combination and the Jet→SAA combination)to prepare plasma-activated saline(PAS).The PAS activated by the combinations exhibited stronger bactericidal effects than that activated by the SAA or the Jet alone.The concentrations of H_(2)O_(2)and NO_(2)^(-)were higher in the PAS activated by the Jet→SAA combination,while ONOO^(-)concentrations were close in the three kinds of PAS and^(1)O_(2)concentrations were higher in the PAS activated by the SAA+Jet combination.The analysis of scavengers also demonstrated that H_(2)O_(2),^(1)O_(2),and ONOO^(-)in the PAS activated by the SAA+Jet combination,and^(1)O_(2)in the PAS activated by the Jet→SAA combination played critical roles in bactericidal effects.Further,the effective placement time of the three PAS varied,and the PAS activated by the Jet→SAA combination could also inactivate 2.6-log_(10)of MRSA cells after placement for more than 60 min.The regulation of reactive species in plasma-activated water via different combinations of plasma devices could improve the directional application of plasma-activated water in the biomedical field.展开更多
Plasma jet has extensive application potentials in various fields, which normally operates in a diffuse mode when helium is used as the working gas. However, when less expensive argon is used, the plasma jet often ope...Plasma jet has extensive application potentials in various fields, which normally operates in a diffuse mode when helium is used as the working gas. However, when less expensive argon is used, the plasma jet often operates in a filamentary mode. Compared to the filamentary mode, the diffuse mode is more desirable for applications. Hence, many efforts have been exerted to accomplish the diffuse mode of the argon plasma jet. In this paper, a novel single-needle argon plasma jet is developed to obtain the diffuse mode. It is found that the plasma jet operates in the filamentary mode when the distance from the needle tip to the central line of the argon stream(d) is short. It transits to the diffuse mode with increasing d. For the diffuse mode, there is always one discharge pulse per voltage cycle, which initiates at the rising edge of the positive voltage. For comparison, the number of discharge pulse increases with an increase in the peak voltage for the filamentary mode. Fast photography reveals that the plasma plume in the filamentary mode results from a guided positive streamer,which propagates in the argon stream. However, the plume in the diffuse mode originates from a branched streamer, which propagates in the interfacial layer between the argon stream and the surrounding air. By optical emission spectroscopy,plasma parameters are investigated for the two discharge modes, which show a similar trend with increasing d. The diffuse mode has lower electron temperature, electron density, vibrational temperature, and gas temperature compared to the filamentary mode.展开更多
This study proposes polyvinyl alcohol–potassium iodide(PVA–KI)as a novel gel chemical probe.The probe uses the reactions among PVA,KI,water,borax,and oxidative species to visualize the distribution of reactive speci...This study proposes polyvinyl alcohol–potassium iodide(PVA–KI)as a novel gel chemical probe.The probe uses the reactions among PVA,KI,water,borax,and oxidative species to visualize the distribution of reactive species.This method provides information regarding the distribution of reactive species by coloration on the gel surface.The effects of the surrounding gas phase on the distribution and diffusion of the reactive species are also investigated using the PVA–KI gel probe.Further,the relationship between the irradiation distance and reactive species diffusion is determined on the surface of the PVA–KI probe with and without plastic shielding.Adjusting the irradiation distance appropriately leads to an increase in the modified area as detected by the PVA–KI gel probe analysis.The relative concentration distributions of the reactive species are also obtained from visualized color distributions measured using a colorimeter.Furthermore,reactive species generation by long-scale line plasma is confirmed by the color reaction on the PVA–KI gel surface,with a greater area being covered by an atmospheric-pressure pulsed microwave line plasma source.展开更多
Acrylic polyurethane paint on the surface of 2A12 Al alloy was cleaned utilizing an atmospheric pressure plasma jet in this work.The dynamic evolution of the paint removal process during plasma treatment with time was...Acrylic polyurethane paint on the surface of 2A12 Al alloy was cleaned utilizing an atmospheric pressure plasma jet in this work.The dynamic evolution of the paint removal process during plasma treatment with time was explored through analysis of morphology and chemical states.The results showed that although the thickness of paint could be reduced effectively with an increase in cleaning time,the removal rate of paint gradually decreased with time.During the initial cleaning process range,its original smooth morphology of paint turned rugged quickly and was almost unchanged with further plasma treatment.Element and chemical state analysis showed that the content of C in the paint layer decreased obviously after plasma treatment.In contrast,the O content increased remarkably.The cleaning mechanism could be mainly attributed to the reaction between active O-containing species in air plasma and organic components in the paint.After removal of superficial organic matter,residue inorganic metal oxide substances aggregated on the base.The exposed metal oxides on the one hand elevated the superficial O content,but on the other hand hindered further plasma penetration,resulting in a gradual decrease in cleaning rate with cleaning time.Therefore,physical wiping was proposed to be incorporated with the plasma method and effective removal of paint was realized.展开更多
Electric field is an important parameter of plasma,which is related to electron temperature,electron density,excited species density,and so on.In this work,the electric field of an atmospheric pressure plasma jet is d...Electric field is an important parameter of plasma,which is related to electron temperature,electron density,excited species density,and so on.In this work,the electric field of an atmospheric pressure plasma jet is diagnosed by the electric field induced second harmonic(E-FISH)method,and the time-resolved electric field under different conditions is investigated.When positive pulse voltage is applied,the electric field has a peak of about 25 kV cm-1at the rising edge of the voltage pulse.A dark channel is left behind the plasma bullet and the electric field in the dark channel is about 5 kV cm-1.On the other hand,when negative pulse voltage is applied,the electric field has a peak of-16 kV cm-1when the negative voltage is increased to-8 kV.A relatively bright channel is left behind the plasma head and the electric field in this relatively bright channel is about-6 kV cm-1.When the pulse rising time increases from 60 to 200 ns,the peak electric field at both the rising edge and the falling edge of the voltage decreases significantly.When 0.5%of oxygen is added to the main working gas helium,the peak electric field at the rising edge is only about 15 kV cm-1.On the other hand,when 0.5%nitrogen is added,the peak electric field increases especially at the falling edge of the voltage pulse,where it increases reversely from-12 to-16 kV cm-1(the minus sign only represents the direction of electric field).展开更多
Surface hydrophilicity improvement of titanium(Ti)is of great significance for the applications of the important biomaterial.In this study,efficient hydrophilicity on the Ti surface is improved by an air plasma jet ge...Surface hydrophilicity improvement of titanium(Ti)is of great significance for the applications of the important biomaterial.In this study,efficient hydrophilicity on the Ti surface is improved by an air plasma jet generated by a microhollow cathode discharge(MHCD)geometry.Elementary discharge aspects of the plasma jet and surface characteristics of the Ti surface are investigated by varying dissipated power(P_(d)).The results show that the plasma jet can operate in a pulsed mode or a continuous mode,depending on P_(d).The plume length increases with Pdand air flow rate increasing.By optical emission spectroscopy,plasma parameters as a function of Pdare investigated.After plasma treatment,water contact angel(WCA)of the Ti sample decreases to a minimum value of 15°with Pdincreasing.In addition,the surface topography,roughness,and content of chemical composition are investigated by scanning electron microscopy(SEM),atomic force microscopy(AFM),and x-ray photoelectron spectroscopy(XPS)with Pdincreasing.The results show that Ti-O bond and O-H group on the Ti surface are beneficial to the improvement of the hydrophilicity of Ti surface.展开更多
Atmospheric pressure plasma jet shows great potential for polymer film processing. The electrode geometry is the key factor to determine discharge characteristics and film modification of jets. In this paper, we compa...Atmospheric pressure plasma jet shows great potential for polymer film processing. The electrode geometry is the key factor to determine discharge characteristics and film modification of jets. In this paper, we compared the discharge characteristics and the film modifications of atmospheric pressure plasma jets with needle-ring electrode(NRE) and doublering electrode(DRE). The results show that jet with NRE has stronger electric field intensity and higher discharge power,making it present more reactive oxygen particles and higher electron temperature, but its discharge stability is insufficient.In contrast, the jet with DRE has uniform electric field distribution of lower field intensity, which allows it to maintain stable discharge over a wide range of applied voltages. Besides, the modification results show that the treatment efficiency of PET film by NRE is higher than that by DRE. These results provide a suitable atmospheric pressure plasma jets device selection scheme for polymer film processing process.展开更多
Plasma jet triggered gas gap switch has obvious advantages in fast control switch.The development of the plasma in the ambient medium is the key factor affecting the triggering conduction of the gas switch.However,the...Plasma jet triggered gas gap switch has obvious advantages in fast control switch.The development of the plasma in the ambient medium is the key factor affecting the triggering conduction of the gas switch.However,the plasma jet process and its characteristic parameters are complicated and the existing test methods cannot fully characterize its development laws.In this work,a two-dimensional transient fluid calculation model of the plasma jet process of the gas gap switch is established based on the renormalization-group k-εturbulence equation.The results show that the characteristic parameters and morphological evolution of the plasma jet are basically consistent with the experimental results,which verifies the accuracy of the simulation model calculation.The plasma jet is a long strip with an initial velocity of 1.0 km·s-1and develops in both axial and radial directions.The jet velocity fluctuates significantly with axial height.As the plasma jet enters the main gap,the pressure inside the trigger cavity drops by80%,resulting in a rapid drop in the jet velocity.When the plasma jet head interacts with the atmosphere,the two-phase fluid compresses each other,generating a forward-propelled pressure wave.The plasma jet heads flow at high velocity,a negative pressure zone is formed in the middle part of the jet,and the pressure peak decreases gradually with height.As the value of the inlet pressure increases,the characteristic parameters of the plasma jet increase.The entrainment phenomenon is evident,which leads to an increase in the pressure imbalance of the atmospheric gas medium,leading to a significant Coanda effect.Compared with air,the characteristic parameters of a plasma jet in SF6are lower,and the morphological evolution is significantly suppressed.The results of this study can provide some insight into the mechanism of action of the switch jet plasma development process.展开更多
Sulfamethoxazole(SMX)is an antibiotic and widely present in aquatic environments,so it presents a serious threat to human health and sustainable development.A dielectric barrier discharge(DBD)plasma jet was utilized t...Sulfamethoxazole(SMX)is an antibiotic and widely present in aquatic environments,so it presents a serious threat to human health and sustainable development.A dielectric barrier discharge(DBD)plasma jet was utilized to degrade aqueous SMX,and the effects of various operating parameters(working gas,discharge power,etc)on SMX degradation performance were studied.The experimental results showed that the DBD plasma jet can obtain a relatively high degradation efficiency for SMX when the discharge power is high with an oxygen atmosphere,the initial concentration of SMX is low,and the aqueous solution is under acidic conditions.The reactive species produced in the liquid phase were detected,and OH radicals and O3were found to play a significant role in the degradation of SMX.Moreover,the process of SMX degradation could be better fitted by the quasi-first-order reaction kinetic equation.The analysis of the SMX degradation process indicated that SMX was gradually decomposed and 4-amino benzene sulfonic acid,benzene sulfonamide,4-nitro SMX,and phenylsulfinyl acid were detected,and thus three possible degradation pathways were finally proposed.The mineralization degree of SMX reached 90.04%after plasma treatment for 20 min,and the toxicity of the solution fluctuated with the discharge time but eventually decreased.展开更多
Helium plasma jets generated by micro-hollow cathode discharge(MHCD) with the squarewave power source of different polarities are investigated in this work. The effects of positive and negative polarity pulses on the ...Helium plasma jets generated by micro-hollow cathode discharge(MHCD) with the squarewave power source of different polarities are investigated in this work. The effects of positive and negative polarity pulses on the MHCD and plasma jet were compared, and the time-resolved optical emission spectra of excited species(N_(2)^(+) and O) were studied. The results confirm that the electric field is a key factor for the propagation of the jet during the rising edge of the positive current pulse, while the gas expansion is mainly important for the jet propagation during the current stable phase. The time-resolved spectra show that the generation of specie O in the jetdriven by the electric field is more efficient.展开更多
In this paper,we discuss the properties of ionization waves(IWs)in a multi-pulsed plasma jet while using the two-dimensional computational approach.The IWs are generated by application of three short negative pulses w...In this paper,we discuss the properties of ionization waves(IWs)in a multi-pulsed plasma jet while using the two-dimensional computational approach.The IWs are generated by application of three short negative pulses with a repetition frequency 12.5 MHz.The simulations are performed continuously during a single run while accounting for charges accumulated inside(surface charges)and outside(space charges)the tube.The plasma forming gas mixture(He/O2=99.8%/0.2%)is injected through the discharge tube into the surrounding humid air.We show that an IW can emerge from the tube exit at a pulse rising edge(as a negative IW)and at a falling edge of the same pulse(as a positive IW).It is demonstrated that remnants of the negative and positive charges play an essential role in the discharge evolution.The first pulse travels the shortest distance as it propagates through the initially non-ionized environment.The IWs developing during the second pulse essentially enlarge the plasma plume length.At the same time,the IWs generated by the third pulse eventually decay due to the remnants of charges accumulated during the previous pulses.Accumulated memory charges can lead to the IW extinction.展开更多
Atmospheric fluorocarbon plasma plays an important role in the surface modification of insulating materials like polymers.The existing fluorocarbon plasma is usually generated by dielectric barrier discharge,which has...Atmospheric fluorocarbon plasma plays an important role in the surface modification of insulating materials like polymers.The existing fluorocarbon plasma is usually generated by dielectric barrier discharge,which has a low concentration of reactive species and may cause insufficient surface fluorination.This work attempts to develop an atmospheric fluorocarbon plasma jet using a coaxial transmission line resonator by microwave discharge with locally enhanced electric field and high density.The gas temperature is reduced by pulse modulation technology.Three kinds of working gases,pure CF_(4),Ar/CF_(4)and He/CF_(4),are utilized to generate the atmospheric microwave fluorocarbon plasma jet.The discharge images,optical emission spectra,electron densities and gas temperatures are studied experimentally.The results show that the Ar/CF_(4)plasma jet has the best comprehensive performance,such as strong discharge intensity and controllable gas temperature.The electron density of the Ar/CF_4plasma jet has a magnitude of 10~(20)m^(-3),indicating a higher density than that of the frequently used dielectric barrier discharge.With the other conditions unchanged,the gas temperature at the end of the Ar/CF_(4)plasma jet can be reduced from 410.2 to 347.3 K by decreasing the duty cycle of the modulated pulse from 0.5 to 0.1.Thence,the microwave Ar/CF_(4)plasma jet is considered to be a promising fluorocarbon plasma source for surface fluorination of polymers.展开更多
在30kW级直流电弧等离子体喷射化学气相沉积(DC Arc P lasm a Jet CVD)设备上,采用Ar-H2-CH4混合气体,通过调节甲烷浓度以及控制其他沉积参数,在Mo衬底上沉积出微/纳米复合自支撑金刚石膜。实验表明,当微米金刚石膜层沉积结束后,在随后...在30kW级直流电弧等离子体喷射化学气相沉积(DC Arc P lasm a Jet CVD)设备上,采用Ar-H2-CH4混合气体,通过调节甲烷浓度以及控制其他沉积参数,在Mo衬底上沉积出微/纳米复合自支撑金刚石膜。实验表明,当微米金刚石膜层沉积结束后,在随后的沉积中,随着甲烷浓度的增加,金刚石膜表面的晶粒大小是逐渐减小的。当甲烷浓度达到20%以上时,金刚石膜生长面晶粒呈现菜花状的小晶团,膜体侧面已经没有了粗大的柱状晶,而是呈现出光滑的断口,对该层进行拉曼谱分析显示,位于1145 cm-1附近有一定强度的散射峰出现。这说明所沉积的晶粒全部变为纳米级尺寸。展开更多
An atmospheric pressure plasma jet(APPJ) in Ar with various grounded electrode arrangements is employed to investigate the effects of electrode arrangement on the characteristics of the APPJ.Electrical and optical met...An atmospheric pressure plasma jet(APPJ) in Ar with various grounded electrode arrangements is employed to investigate the effects of electrode arrangement on the characteristics of the APPJ.Electrical and optical methods are used to characterize the plasma properties.The discharge modes of the APPJ with respect to applied voltage are studied for grounded electrode positions of 10 mm,40 mm and 80 mm,respectively,and the main discharge and plasma parameters are investigated.It is shown that an increase in the distance between the grounded electrode and high-voltage electrode results in a change in the discharge modes and discharge parameters.The discharges transit from having two discharge modes,dielectric barrier discharge(DBD) and jet,to having three,corona,DBD and jet,with increase in the distance from the grounded to the high-voltage electrodes.The maximum length of the APPJ reaches 3.8 cm at an applied voltage of 8 kV.The discharge power and transferred charges and spectral line intensities for species in the APPJ are influenced by the positions of the grounded electrode,while there is no obvious difference in the values of the electron excited temperature(EET) for the three grounded electrode positions.展开更多
Through using a direct-current driven plasma jet operated underwater,degradation of methylene blue(MB)is investigated with air and oxygen used as working gases.With a low power voltage,a plasma plume extends from the ...Through using a direct-current driven plasma jet operated underwater,degradation of methylene blue(MB)is investigated with air and oxygen used as working gases.With a low power voltage,a plasma plume extends from the needle electrode,which is purple in air.It turns pink after it bridges the two electrodes.During the process,oxygen plasma remains white.Discharge operates in a pulsed mode or a continuous one,which depends on the magnitude of power voltage.For the pulsed mode,oxygen discharge has a shorter plume and a higher pulse frequency than air discharge under the same power voltage.For the same current of the continuous mode,both power and gap voltages of oxygen discharge are higher than those of air discharge.Moreover,MB degradation efficiency increases with increasing power voltage or initial concentration of MB solution.Compared with air discharge,oxygen discharge has a higher degradation efficiency with the same power voltage and treatment time.The pulsed oxygen discharge with power voltage of about 6.5 k V has the highest efficiency in degrading MB dye,reaching approximately 85.8%after 10 min treatment.As a comparison,after 10 min treatment in air discharge,the highest degradation efficiency is 63.7%,which appears in the continuous mode at a power voltage of 10.6 kV.Besides,optical spectra from the discharges are also compared for the two types of working gases.展开更多
In the present study,a coaxial transmission line resonator is constructed,which is always capable of generating cold microwave plasma jet plumes in ambient air in spite of using argon,nitrogen,or even air,respectively...In the present study,a coaxial transmission line resonator is constructed,which is always capable of generating cold microwave plasma jet plumes in ambient air in spite of using argon,nitrogen,or even air,respectively.Although the different kinds of working gas induce the different discharge performance,their ionization processes all indicate that the ionization enhancement has taken place twice in each pulsed periods,and the electron densities measured by the method of microwave Rayleigh scattering are higher than the amplitude order of 10^(18)m^(-3).The tail region of plasma jets all contain a large number of active particles,like NO,O,emitted photons,etc,but without O_(3).The formation mechanism and the distinctive characteristics are attributed to the resonance excitation of the locally enhanced electric fields,the ionization wave propulsion,and the temporal and spatial distribution of different particles in the pulsed microwave plasma jets.The parameters of plasma jet could be modulated by adjusting microwave power,modulation pulse parameters(modulation frequency and duty ratio),gas type and its flow rate,according to the requirements of application scenarios.展开更多
This study investigates the influence of two types of target,skin tissue and cell culture medium,with different permittivities on a k Hz helium atmospheric pressure plasma jet(APPJ)during its application for wound hea...This study investigates the influence of two types of target,skin tissue and cell culture medium,with different permittivities on a k Hz helium atmospheric pressure plasma jet(APPJ)during its application for wound healing.The basic optical-electrical characteristics,the initiation and propagation and the emission spectra of the He APPJ under different working conditions are explored.The experimental results show that,compared with a jet freely expanding in air,the diameter and intensity of the plasma plume outside the nozzle increase when it interacts with the pigskin and cell culture medium targets,and the mean velocity of the plasma bullet from the tube nozzle to a distance of 15 mm is also significantly increased.There are also multiple increases in the relative intensity of OH(A^(2)Σ→X^(2)Π)and O(3p^(5)S-3s^(5)S)at a position 15 mm away from nozzle when the He APPJ interacts with cell culture medium compared with the air and pigskin targets.Taking the surface charging of the low permittivity material capacitance and the strengthened electric field intensity into account,they make the various characteristics of He APPJ interacting with two different targets together.展开更多
Atmospheric pressure plasma jet(APPJ)was used to clean nitrogen-containing carbon films(C–N)fabricated by plasma-assisted chemical vapor deposition method employing the plasma surface interaction linear device at Sic...Atmospheric pressure plasma jet(APPJ)was used to clean nitrogen-containing carbon films(C–N)fabricated by plasma-assisted chemical vapor deposition method employing the plasma surface interaction linear device at Sichuan University(SCU-PSI).The properties of the contaminated films on the surface of pristine and He-plasma pre-irradiated tungsten matrix,such as morphology,crystalline structure,element composition and chemical structure were characterized by scanning electron microscopy,grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy.The experimental results revealed that the removal of C–N film with a thickness of tens of microns can be realized through APPJ cleaning regardless of the morphology of the substrates.Similar removal rates of 16.82 and 13.78μm min^(-1)were obtained for C–N films deposited on a smooth pristine W surface and rough fuzz-covered W surface,respectively.This is a remarkable improvement in comparison to the traditional cleaning method.However,slight surface oxidation was found after APPJ cleaning,but the degree of oxidation was acceptable with an oxidation depth increase of only 3.15 nm.Optical emission spectroscopy analysis and mass spectrometry analysis showed that C–N contamination was mainly removed through chemical reaction with reactive oxygen species during APPJ treatment using air as the working gas.These results make APPJ cleaning a potentially effective method for the rapid removal of C–N films from the wall surfaces of fusion devices.展开更多
Plasma spraying is an important enabling technology i n near-net-shaped process as well as many high-performance coating applicatio ns. Recently, it is being applied to rapid mould manufacturing to reduce develop ment...Plasma spraying is an important enabling technology i n near-net-shaped process as well as many high-performance coating applicatio ns. Recently, it is being applied to rapid mould manufacturing to reduce develop ment time and manufacturing cost. In this process, inputted powders are heated a nd accelerated by plasma jet, and impinge on master pattern or prototype to form ing a thick coating. Mould will be fabricated after backed-up with consolidated material and other post-treatments. Amongst numerous factors that affect the l ife and properties of mould made by this novel method, quality of coating is the most important one. However, the complex nature of the spray process results in a large number of processing parameters that must be controlled in order to obt ain optimum coatings. Traditional "trial and error" method is too time and cost consuming for the optimal processing parameters. Maybe modeling and diagnostics of process is the best way to ravel out the problems. It has been proved that pl asma-gas flowrate, power level and spray distance are the most critical variabl es. So flow visualization and diagnostics for plasma jet quality has become an i mportant task to obtain a repeatable and reliable plasma processing technology. Using enthalpy probe diagnostics, spectrometry and optical measurement, we can o btain the distribution of temperature field of plasma jet. These results can hel p us to design gun configuration and optimize processing parameters for high dep osition efficiency and good qualities of rapid mould manufacturing. Nevertheless , it is still very difficult to realize real-time diagnoses because of restrict of diagnosis condition and drawback of measurement approach. In our researches, a real-time data collection and image processing system for plasma jet with high temperature, velocity and compressed energy has been realiz ed by CCD sensor. In this paper, we firstly focus our attention on collection pr inciple and methods, and an effective method for collecting data in high tempera ture area is presented. Then a system of real-time data collection by CCD camer a is developed. Finally, fake color image processing is given to analyze the law of temperature field distribution under different conditions. The results are i mportant to realize the visualization of plasma spraying, and especially to furt her study on closed-loop feedback control of forming quality for plasma rapid m anufacturing process.展开更多
In this paper, a pulsed-dc CH_3OH/Ar plasma jet generated at atmospheric pressure is studied by laser-induced fluorescence(LIF) and optical emission spectroscopy(OES). A gas–liquid bubbler system is proposed to intro...In this paper, a pulsed-dc CH_3OH/Ar plasma jet generated at atmospheric pressure is studied by laser-induced fluorescence(LIF) and optical emission spectroscopy(OES). A gas–liquid bubbler system is proposed to introduce the methanol vapor into the argon gas, and the CH3OH/Ar volume ratio is kept constant at about 0.1%. Discharge occurs in a 6-mm needle-to-ring gap in an atmospheric-pressure CH_3OH/Ar mixture. The space-resolved distributions of OH LIF inside and outside the nozzle exhibit distinctly different behaviors. And, different production mechanisms of OH radicals in the needle-to-ring discharge gap and afterglow of plasma jet are discussed. Besides, the optical emission lines of carbonaceous species, such as CH, CN, and C_2 radicals, are identified in the CH_3OH/Ar plasma jet. Finally, the influences of operating parameters(applied voltage magnitude, pulse frequency, pulsewidth) on the OH radical density are also presented and analyzed.展开更多
基金supported by National Natural Science Foundation of China(No.51977174)。
文摘Plasma-activated water(PAW),as an extended form of cold atmospheric-pressure plasma,greatly expands the application of plasma-based technology.The biological effects of PAW are closely related to the aqueous reactive species,which can be regulated by the activation process.In this study,surface plasma-activated air(SAA)and a He+O_(2)plasma jet(Jet)were parallelly combined(the SAA+Jet combination)or sequentially combined(the SAA→Jet combination and the Jet→SAA combination)to prepare plasma-activated saline(PAS).The PAS activated by the combinations exhibited stronger bactericidal effects than that activated by the SAA or the Jet alone.The concentrations of H_(2)O_(2)and NO_(2)^(-)were higher in the PAS activated by the Jet→SAA combination,while ONOO^(-)concentrations were close in the three kinds of PAS and^(1)O_(2)concentrations were higher in the PAS activated by the SAA+Jet combination.The analysis of scavengers also demonstrated that H_(2)O_(2),^(1)O_(2),and ONOO^(-)in the PAS activated by the SAA+Jet combination,and^(1)O_(2)in the PAS activated by the Jet→SAA combination played critical roles in bactericidal effects.Further,the effective placement time of the three PAS varied,and the PAS activated by the Jet→SAA combination could also inactivate 2.6-log_(10)of MRSA cells after placement for more than 60 min.The regulation of reactive species in plasma-activated water via different combinations of plasma devices could improve the directional application of plasma-activated water in the biomedical field.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.51977057,11875121,and 11805013)the Natural Science Foundation of Hebei Province,China (Grant Nos.A2020201025 and A2022201036)+2 种基金the Funds for Distinguished Young Scientists of Hebei Province,China (Grant No.A2012201045)the Natural Science Interdisciplinary Research Program of Hebei University (Grant No.DXK202011)the Postgraduate’s Innovation Fund Project of Hebei University (Grant No.HBU2022bs004)。
文摘Plasma jet has extensive application potentials in various fields, which normally operates in a diffuse mode when helium is used as the working gas. However, when less expensive argon is used, the plasma jet often operates in a filamentary mode. Compared to the filamentary mode, the diffuse mode is more desirable for applications. Hence, many efforts have been exerted to accomplish the diffuse mode of the argon plasma jet. In this paper, a novel single-needle argon plasma jet is developed to obtain the diffuse mode. It is found that the plasma jet operates in the filamentary mode when the distance from the needle tip to the central line of the argon stream(d) is short. It transits to the diffuse mode with increasing d. For the diffuse mode, there is always one discharge pulse per voltage cycle, which initiates at the rising edge of the positive voltage. For comparison, the number of discharge pulse increases with an increase in the peak voltage for the filamentary mode. Fast photography reveals that the plasma plume in the filamentary mode results from a guided positive streamer,which propagates in the argon stream. However, the plume in the diffuse mode originates from a branched streamer, which propagates in the interfacial layer between the argon stream and the surrounding air. By optical emission spectroscopy,plasma parameters are investigated for the two discharge modes, which show a similar trend with increasing d. The diffuse mode has lower electron temperature, electron density, vibrational temperature, and gas temperature compared to the filamentary mode.
基金partially supported by the ZE Research Program IAE(No.ZE2021B-27)the joint usage/research program cLPS(No.21020)。
文摘This study proposes polyvinyl alcohol–potassium iodide(PVA–KI)as a novel gel chemical probe.The probe uses the reactions among PVA,KI,water,borax,and oxidative species to visualize the distribution of reactive species.This method provides information regarding the distribution of reactive species by coloration on the gel surface.The effects of the surrounding gas phase on the distribution and diffusion of the reactive species are also investigated using the PVA–KI gel probe.Further,the relationship between the irradiation distance and reactive species diffusion is determined on the surface of the PVA–KI probe with and without plastic shielding.Adjusting the irradiation distance appropriately leads to an increase in the modified area as detected by the PVA–KI gel probe analysis.The relative concentration distributions of the reactive species are also obtained from visualized color distributions measured using a colorimeter.Furthermore,reactive species generation by long-scale line plasma is confirmed by the color reaction on the PVA–KI gel surface,with a greater area being covered by an atmospheric-pressure pulsed microwave line plasma source.
基金supported by National Natural Science Foundation of China(No.U21A20438)the Foundation of Key Laboratory of Radiation Physics and Technology of the Ministry of Education(No.2021SCURPT03)。
文摘Acrylic polyurethane paint on the surface of 2A12 Al alloy was cleaned utilizing an atmospheric pressure plasma jet in this work.The dynamic evolution of the paint removal process during plasma treatment with time was explored through analysis of morphology and chemical states.The results showed that although the thickness of paint could be reduced effectively with an increase in cleaning time,the removal rate of paint gradually decreased with time.During the initial cleaning process range,its original smooth morphology of paint turned rugged quickly and was almost unchanged with further plasma treatment.Element and chemical state analysis showed that the content of C in the paint layer decreased obviously after plasma treatment.In contrast,the O content increased remarkably.The cleaning mechanism could be mainly attributed to the reaction between active O-containing species in air plasma and organic components in the paint.After removal of superficial organic matter,residue inorganic metal oxide substances aggregated on the base.The exposed metal oxides on the one hand elevated the superficial O content,but on the other hand hindered further plasma penetration,resulting in a gradual decrease in cleaning rate with cleaning time.Therefore,physical wiping was proposed to be incorporated with the plasma method and effective removal of paint was realized.
基金National Key Research and Development Program of China(No.2021YFE0114700)National Natural Science Foundation of China(Nos.52130701 and 51977096)。
文摘Electric field is an important parameter of plasma,which is related to electron temperature,electron density,excited species density,and so on.In this work,the electric field of an atmospheric pressure plasma jet is diagnosed by the electric field induced second harmonic(E-FISH)method,and the time-resolved electric field under different conditions is investigated.When positive pulse voltage is applied,the electric field has a peak of about 25 kV cm-1at the rising edge of the voltage pulse.A dark channel is left behind the plasma bullet and the electric field in the dark channel is about 5 kV cm-1.On the other hand,when negative pulse voltage is applied,the electric field has a peak of-16 kV cm-1when the negative voltage is increased to-8 kV.A relatively bright channel is left behind the plasma head and the electric field in this relatively bright channel is about-6 kV cm-1.When the pulse rising time increases from 60 to 200 ns,the peak electric field at both the rising edge and the falling edge of the voltage decreases significantly.When 0.5%of oxygen is added to the main working gas helium,the peak electric field at the rising edge is only about 15 kV cm-1.On the other hand,when 0.5%nitrogen is added,the peak electric field increases especially at the falling edge of the voltage pulse,where it increases reversely from-12 to-16 kV cm-1(the minus sign only represents the direction of electric field).
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51977057 and 11875121)the Natural Science Foundation of Hebei Province,China(Grant Nos.A2020201025 and A2022201036)+2 种基金the Natural Science Interdisciplinary Research Program of Hebei University,China(Grant Nos.DXK201908 and DXK202011)the Postgraduate’s Innovation Fund Project of Hebei Province,China(Grant Nos.CXZZBS2019023 and CXZZBS2019029)the Post-graduate’s Innovation Fund Project of Hebei University,China(Grant Nos.HBU2021ss063,HBU2021bs011,and HBU2022bs004)。
文摘Surface hydrophilicity improvement of titanium(Ti)is of great significance for the applications of the important biomaterial.In this study,efficient hydrophilicity on the Ti surface is improved by an air plasma jet generated by a microhollow cathode discharge(MHCD)geometry.Elementary discharge aspects of the plasma jet and surface characteristics of the Ti surface are investigated by varying dissipated power(P_(d)).The results show that the plasma jet can operate in a pulsed mode or a continuous mode,depending on P_(d).The plume length increases with Pdand air flow rate increasing.By optical emission spectroscopy,plasma parameters as a function of Pdare investigated.After plasma treatment,water contact angel(WCA)of the Ti sample decreases to a minimum value of 15°with Pdincreasing.In addition,the surface topography,roughness,and content of chemical composition are investigated by scanning electron microscopy(SEM),atomic force microscopy(AFM),and x-ray photoelectron spectroscopy(XPS)with Pdincreasing.The results show that Ti-O bond and O-H group on the Ti surface are beneficial to the improvement of the hydrophilicity of Ti surface.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11565003)the Jiangxi Province Academic Degree and Postgraduate Education and Teaching Reform Research Project (Grant No. JXYJG-2022-180)the Scientific Research Base Project of Gannan Normal University (Grant No. 22wdxt01)。
文摘Atmospheric pressure plasma jet shows great potential for polymer film processing. The electrode geometry is the key factor to determine discharge characteristics and film modification of jets. In this paper, we compared the discharge characteristics and the film modifications of atmospheric pressure plasma jets with needle-ring electrode(NRE) and doublering electrode(DRE). The results show that jet with NRE has stronger electric field intensity and higher discharge power,making it present more reactive oxygen particles and higher electron temperature, but its discharge stability is insufficient.In contrast, the jet with DRE has uniform electric field distribution of lower field intensity, which allows it to maintain stable discharge over a wide range of applied voltages. Besides, the modification results show that the treatment efficiency of PET film by NRE is higher than that by DRE. These results provide a suitable atmospheric pressure plasma jets device selection scheme for polymer film processing process.
基金supported by National Natural Science Foundation of China(No.52107142)。
文摘Plasma jet triggered gas gap switch has obvious advantages in fast control switch.The development of the plasma in the ambient medium is the key factor affecting the triggering conduction of the gas switch.However,the plasma jet process and its characteristic parameters are complicated and the existing test methods cannot fully characterize its development laws.In this work,a two-dimensional transient fluid calculation model of the plasma jet process of the gas gap switch is established based on the renormalization-group k-εturbulence equation.The results show that the characteristic parameters and morphological evolution of the plasma jet are basically consistent with the experimental results,which verifies the accuracy of the simulation model calculation.The plasma jet is a long strip with an initial velocity of 1.0 km·s-1and develops in both axial and radial directions.The jet velocity fluctuates significantly with axial height.As the plasma jet enters the main gap,the pressure inside the trigger cavity drops by80%,resulting in a rapid drop in the jet velocity.When the plasma jet head interacts with the atmosphere,the two-phase fluid compresses each other,generating a forward-propelled pressure wave.The plasma jet heads flow at high velocity,a negative pressure zone is formed in the middle part of the jet,and the pressure peak decreases gradually with height.As the value of the inlet pressure increases,the characteristic parameters of the plasma jet increase.The entrainment phenomenon is evident,which leads to an increase in the pressure imbalance of the atmospheric gas medium,leading to a significant Coanda effect.Compared with air,the characteristic parameters of a plasma jet in SF6are lower,and the morphological evolution is significantly suppressed.The results of this study can provide some insight into the mechanism of action of the switch jet plasma development process.
基金supported jointly by National Natural Science Foundation of China(Nos.U20A20372,51807046,51777206)the Natural Science Foundation of Anhui Province(Nos.2108085MD136,1908085MA29)。
文摘Sulfamethoxazole(SMX)is an antibiotic and widely present in aquatic environments,so it presents a serious threat to human health and sustainable development.A dielectric barrier discharge(DBD)plasma jet was utilized to degrade aqueous SMX,and the effects of various operating parameters(working gas,discharge power,etc)on SMX degradation performance were studied.The experimental results showed that the DBD plasma jet can obtain a relatively high degradation efficiency for SMX when the discharge power is high with an oxygen atmosphere,the initial concentration of SMX is low,and the aqueous solution is under acidic conditions.The reactive species produced in the liquid phase were detected,and OH radicals and O3were found to play a significant role in the degradation of SMX.Moreover,the process of SMX degradation could be better fitted by the quasi-first-order reaction kinetic equation.The analysis of the SMX degradation process indicated that SMX was gradually decomposed and 4-amino benzene sulfonic acid,benzene sulfonamide,4-nitro SMX,and phenylsulfinyl acid were detected,and thus three possible degradation pathways were finally proposed.The mineralization degree of SMX reached 90.04%after plasma treatment for 20 min,and the toxicity of the solution fluctuated with the discharge time but eventually decreased.
基金supported by National Natural Science Foundation of China (No. 11975047)。
文摘Helium plasma jets generated by micro-hollow cathode discharge(MHCD) with the squarewave power source of different polarities are investigated in this work. The effects of positive and negative polarity pulses on the MHCD and plasma jet were compared, and the time-resolved optical emission spectra of excited species(N_(2)^(+) and O) were studied. The results confirm that the electric field is a key factor for the propagation of the jet during the rising edge of the positive current pulse, while the gas expansion is mainly important for the jet propagation during the current stable phase. The time-resolved spectra show that the generation of specie O in the jetdriven by the electric field is more efficient.
基金supported by the Ministry of Science and Higher Education of the Russian Federation(No.075-15-2021-1026 of November 15,2021)jointly by the National Key Research and Development Plan of China(No.2021YFE0114700)。
文摘In this paper,we discuss the properties of ionization waves(IWs)in a multi-pulsed plasma jet while using the two-dimensional computational approach.The IWs are generated by application of three short negative pulses with a repetition frequency 12.5 MHz.The simulations are performed continuously during a single run while accounting for charges accumulated inside(surface charges)and outside(space charges)the tube.The plasma forming gas mixture(He/O2=99.8%/0.2%)is injected through the discharge tube into the surrounding humid air.We show that an IW can emerge from the tube exit at a pulse rising edge(as a negative IW)and at a falling edge of the same pulse(as a positive IW).It is demonstrated that remnants of the negative and positive charges play an essential role in the discharge evolution.The first pulse travels the shortest distance as it propagates through the initially non-ionized environment.The IWs developing during the second pulse essentially enlarge the plasma plume length.At the same time,the IWs generated by the third pulse eventually decay due to the remnants of charges accumulated during the previous pulses.Accumulated memory charges can lead to the IW extinction.
基金partly supported by National Natural Science Foundation of China(Nos.52207147 and 52177126)the Anhui Provincial Natural Science Foundation(Nos.2208085QE168 and 2108085ME180)the Anhui Provincial Natural Science Research Project of Higher Education(No.2022AH050301)。
文摘Atmospheric fluorocarbon plasma plays an important role in the surface modification of insulating materials like polymers.The existing fluorocarbon plasma is usually generated by dielectric barrier discharge,which has a low concentration of reactive species and may cause insufficient surface fluorination.This work attempts to develop an atmospheric fluorocarbon plasma jet using a coaxial transmission line resonator by microwave discharge with locally enhanced electric field and high density.The gas temperature is reduced by pulse modulation technology.Three kinds of working gases,pure CF_(4),Ar/CF_(4)and He/CF_(4),are utilized to generate the atmospheric microwave fluorocarbon plasma jet.The discharge images,optical emission spectra,electron densities and gas temperatures are studied experimentally.The results show that the Ar/CF_(4)plasma jet has the best comprehensive performance,such as strong discharge intensity and controllable gas temperature.The electron density of the Ar/CF_4plasma jet has a magnitude of 10~(20)m^(-3),indicating a higher density than that of the frequently used dielectric barrier discharge.With the other conditions unchanged,the gas temperature at the end of the Ar/CF_(4)plasma jet can be reduced from 410.2 to 347.3 K by decreasing the duty cycle of the modulated pulse from 0.5 to 0.1.Thence,the microwave Ar/CF_(4)plasma jet is considered to be a promising fluorocarbon plasma source for surface fluorination of polymers.
文摘在30kW级直流电弧等离子体喷射化学气相沉积(DC Arc P lasm a Jet CVD)设备上,采用Ar-H2-CH4混合气体,通过调节甲烷浓度以及控制其他沉积参数,在Mo衬底上沉积出微/纳米复合自支撑金刚石膜。实验表明,当微米金刚石膜层沉积结束后,在随后的沉积中,随着甲烷浓度的增加,金刚石膜表面的晶粒大小是逐渐减小的。当甲烷浓度达到20%以上时,金刚石膜生长面晶粒呈现菜花状的小晶团,膜体侧面已经没有了粗大的柱状晶,而是呈现出光滑的断口,对该层进行拉曼谱分析显示,位于1145 cm-1附近有一定强度的散射峰出现。这说明所沉积的晶粒全部变为纳米级尺寸。
基金supported by National Natural Science Foundation of China under Grant Nos.51377075 and 51677083
文摘An atmospheric pressure plasma jet(APPJ) in Ar with various grounded electrode arrangements is employed to investigate the effects of electrode arrangement on the characteristics of the APPJ.Electrical and optical methods are used to characterize the plasma properties.The discharge modes of the APPJ with respect to applied voltage are studied for grounded electrode positions of 10 mm,40 mm and 80 mm,respectively,and the main discharge and plasma parameters are investigated.It is shown that an increase in the distance between the grounded electrode and high-voltage electrode results in a change in the discharge modes and discharge parameters.The discharges transit from having two discharge modes,dielectric barrier discharge(DBD) and jet,to having three,corona,DBD and jet,with increase in the distance from the grounded to the high-voltage electrodes.The maximum length of the APPJ reaches 3.8 cm at an applied voltage of 8 kV.The discharge power and transferred charges and spectral line intensities for species in the APPJ are influenced by the positions of the grounded electrode,while there is no obvious difference in the values of the electron excited temperature(EET) for the three grounded electrode positions.
基金sponsored by National Natural Science Foundation of China (Nos. 11875121,11575050 and 51977057)the Midwest Universities Comprehensive Strength Promotion Project+3 种基金the Natural Science Foundation of Hebei Province,China (Nos. A2019201100 and A2016201042)College Hundred Outstanding Innovative Talent Support Program of Hebei Education Bureau (No. SLRC2017021)the 333 Talents Project of Hebei province,China (No. A2016005005)Post-graduate’s Innovation Fund Project of Hebei Province(Nos. CXZZBS2019023 and CXZZBS2019029)。
文摘Through using a direct-current driven plasma jet operated underwater,degradation of methylene blue(MB)is investigated with air and oxygen used as working gases.With a low power voltage,a plasma plume extends from the needle electrode,which is purple in air.It turns pink after it bridges the two electrodes.During the process,oxygen plasma remains white.Discharge operates in a pulsed mode or a continuous one,which depends on the magnitude of power voltage.For the pulsed mode,oxygen discharge has a shorter plume and a higher pulse frequency than air discharge under the same power voltage.For the same current of the continuous mode,both power and gap voltages of oxygen discharge are higher than those of air discharge.Moreover,MB degradation efficiency increases with increasing power voltage or initial concentration of MB solution.Compared with air discharge,oxygen discharge has a higher degradation efficiency with the same power voltage and treatment time.The pulsed oxygen discharge with power voltage of about 6.5 k V has the highest efficiency in degrading MB dye,reaching approximately 85.8%after 10 min treatment.As a comparison,after 10 min treatment in air discharge,the highest degradation efficiency is 63.7%,which appears in the continuous mode at a power voltage of 10.6 kV.Besides,optical spectra from the discharges are also compared for the two types of working gases.
基金supported by National Natural Science Foundation of China (Nos. 52177126 and 11575003)Anhui Province University Excellent Youth Foundation (No. gxyqzd2021104)
文摘In the present study,a coaxial transmission line resonator is constructed,which is always capable of generating cold microwave plasma jet plumes in ambient air in spite of using argon,nitrogen,or even air,respectively.Although the different kinds of working gas induce the different discharge performance,their ionization processes all indicate that the ionization enhancement has taken place twice in each pulsed periods,and the electron densities measured by the method of microwave Rayleigh scattering are higher than the amplitude order of 10^(18)m^(-3).The tail region of plasma jets all contain a large number of active particles,like NO,O,emitted photons,etc,but without O_(3).The formation mechanism and the distinctive characteristics are attributed to the resonance excitation of the locally enhanced electric fields,the ionization wave propulsion,and the temporal and spatial distribution of different particles in the pulsed microwave plasma jets.The parameters of plasma jet could be modulated by adjusting microwave power,modulation pulse parameters(modulation frequency and duty ratio),gas type and its flow rate,according to the requirements of application scenarios.
基金supported in part by the Scientific Innovation Practice Project of Postgraduates of Chang’an University(No.300103714007)the Fundamental Research Funds for the Central Universities(No.300102329301)National Natural Science Foundation of China(No.51677146)。
文摘This study investigates the influence of two types of target,skin tissue and cell culture medium,with different permittivities on a k Hz helium atmospheric pressure plasma jet(APPJ)during its application for wound healing.The basic optical-electrical characteristics,the initiation and propagation and the emission spectra of the He APPJ under different working conditions are explored.The experimental results show that,compared with a jet freely expanding in air,the diameter and intensity of the plasma plume outside the nozzle increase when it interacts with the pigskin and cell culture medium targets,and the mean velocity of the plasma bullet from the tube nozzle to a distance of 15 mm is also significantly increased.There are also multiple increases in the relative intensity of OH(A^(2)Σ→X^(2)Π)and O(3p^(5)S-3s^(5)S)at a position 15 mm away from nozzle when the He APPJ interacts with cell culture medium compared with the air and pigskin targets.Taking the surface charging of the low permittivity material capacitance and the strengthened electric field intensity into account,they make the various characteristics of He APPJ interacting with two different targets together.
基金funded by National Key Research, Development Program of China (No. 2017YFE0301305KYWX-002)Sichuan Science and Technology Program (No. 2021YFSY0015)
文摘Atmospheric pressure plasma jet(APPJ)was used to clean nitrogen-containing carbon films(C–N)fabricated by plasma-assisted chemical vapor deposition method employing the plasma surface interaction linear device at Sichuan University(SCU-PSI).The properties of the contaminated films on the surface of pristine and He-plasma pre-irradiated tungsten matrix,such as morphology,crystalline structure,element composition and chemical structure were characterized by scanning electron microscopy,grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy.The experimental results revealed that the removal of C–N film with a thickness of tens of microns can be realized through APPJ cleaning regardless of the morphology of the substrates.Similar removal rates of 16.82 and 13.78μm min^(-1)were obtained for C–N films deposited on a smooth pristine W surface and rough fuzz-covered W surface,respectively.This is a remarkable improvement in comparison to the traditional cleaning method.However,slight surface oxidation was found after APPJ cleaning,but the degree of oxidation was acceptable with an oxidation depth increase of only 3.15 nm.Optical emission spectroscopy analysis and mass spectrometry analysis showed that C–N contamination was mainly removed through chemical reaction with reactive oxygen species during APPJ treatment using air as the working gas.These results make APPJ cleaning a potentially effective method for the rapid removal of C–N films from the wall surfaces of fusion devices.
文摘Plasma spraying is an important enabling technology i n near-net-shaped process as well as many high-performance coating applicatio ns. Recently, it is being applied to rapid mould manufacturing to reduce develop ment time and manufacturing cost. In this process, inputted powders are heated a nd accelerated by plasma jet, and impinge on master pattern or prototype to form ing a thick coating. Mould will be fabricated after backed-up with consolidated material and other post-treatments. Amongst numerous factors that affect the l ife and properties of mould made by this novel method, quality of coating is the most important one. However, the complex nature of the spray process results in a large number of processing parameters that must be controlled in order to obt ain optimum coatings. Traditional "trial and error" method is too time and cost consuming for the optimal processing parameters. Maybe modeling and diagnostics of process is the best way to ravel out the problems. It has been proved that pl asma-gas flowrate, power level and spray distance are the most critical variabl es. So flow visualization and diagnostics for plasma jet quality has become an i mportant task to obtain a repeatable and reliable plasma processing technology. Using enthalpy probe diagnostics, spectrometry and optical measurement, we can o btain the distribution of temperature field of plasma jet. These results can hel p us to design gun configuration and optimize processing parameters for high dep osition efficiency and good qualities of rapid mould manufacturing. Nevertheless , it is still very difficult to realize real-time diagnoses because of restrict of diagnosis condition and drawback of measurement approach. In our researches, a real-time data collection and image processing system for plasma jet with high temperature, velocity and compressed energy has been realiz ed by CCD sensor. In this paper, we firstly focus our attention on collection pr inciple and methods, and an effective method for collecting data in high tempera ture area is presented. Then a system of real-time data collection by CCD camer a is developed. Finally, fake color image processing is given to analyze the law of temperature field distribution under different conditions. The results are i mportant to realize the visualization of plasma spraying, and especially to furt her study on closed-loop feedback control of forming quality for plasma rapid m anufacturing process.
基金supported by the National Natural Science Foundation of China(Grant Nos.11465013 and 11375041)the Natural Science Foundation of Jiangxi Province,China(Grant Nos.20151BAB212012 and 20161BAB201013)the International Science and Technology Cooperation Program of China(Grant No.2015DFA61800)
文摘In this paper, a pulsed-dc CH_3OH/Ar plasma jet generated at atmospheric pressure is studied by laser-induced fluorescence(LIF) and optical emission spectroscopy(OES). A gas–liquid bubbler system is proposed to introduce the methanol vapor into the argon gas, and the CH3OH/Ar volume ratio is kept constant at about 0.1%. Discharge occurs in a 6-mm needle-to-ring gap in an atmospheric-pressure CH_3OH/Ar mixture. The space-resolved distributions of OH LIF inside and outside the nozzle exhibit distinctly different behaviors. And, different production mechanisms of OH radicals in the needle-to-ring discharge gap and afterglow of plasma jet are discussed. Besides, the optical emission lines of carbonaceous species, such as CH, CN, and C_2 radicals, are identified in the CH_3OH/Ar plasma jet. Finally, the influences of operating parameters(applied voltage magnitude, pulse frequency, pulsewidth) on the OH radical density are also presented and analyzed.
