Direct-current(DC)arc plasma has great application values in the field of the chemical industry,but it has the problem of low energy efficiency.Facing the requirement for improving the energy efficiency of the arc,thi...Direct-current(DC)arc plasma has great application values in the field of the chemical industry,but it has the problem of low energy efficiency.Facing the requirement for improving the energy efficiency of the arc,this paper proposes a unique method of pulsed modulated arc(PMA).This method uses high-frequency pulses and reduces the arc current to improve the control of electron temperature.The electrical characteristics,optical characteristics and products are tested.The test results show that during the PMA process,all of the experimental results which include voltage,current and light will significantly increase.These results are analyzed from the perspective of functionality,repeatability and energy conversion.The analysis results show that although the PMA method does not show good parameter consistency,it has potential application prospects because it increases the energy conversion rate by 4.5%and 8%from the perspective of light and products,respectively.展开更多
Wheat(Triticum aestivum) seeds were treated with atmospheric pressure gliding arc discharge plasmas to investigate the effects on water absorption, seed germination rate, seedling growth and yield in wheat. The surfac...Wheat(Triticum aestivum) seeds were treated with atmospheric pressure gliding arc discharge plasmas to investigate the effects on water absorption, seed germination rate, seedling growth and yield in wheat. The surface architectures and functionalities of the seeds were found to modify due to plasma treatments. 6 min treatment was provided 95%–100% germination rate.For the treatment duration of 3 and 9 min the growth activity, dry matter accumulation, leaves chlorophyll contents, longest spikes, number of spikes/spikelet and total soluble protein content in shoots were improved. The grain yield of wheat was increased ~20% by 6 min treatment with H_2O/O_2 plasma with respect to control.展开更多
Atmospheric pressure air/Ar/H_2O gliding arc discharge plasma is produced by a pulsed dc power supply. An optical emission spectroscopic(OES) diagnostic technique is used for the characterization of plasmas and for id...Atmospheric pressure air/Ar/H_2O gliding arc discharge plasma is produced by a pulsed dc power supply. An optical emission spectroscopic(OES) diagnostic technique is used for the characterization of plasmas and for identifications of OH and O radicals along with other species in the plasmas. The OES diagnostic technique reveals the excitation Tx?≈?5550–9000 K, rotational Tr?≈?1350–2700 K and gas Tg?≈?850–1600 K temperatures, and electron density n?(1.1-1.9) ′101 4 cm^(-3) e under different experimental conditions. The production and destruction of OH and O radicals are investigated as functions of applied voltage and air flow rate. Relative intensities of OH and O radicals indicate that their production rates are increased with increasing Ar content in the gas mixture and applied voltage. nereveals that the higher densities of OH and O radicals are produced in the discharge due to more effective electron impact dissociation of H_2O and O_2 molecules caused by higher kinetic energies as gained by electrons from the enhanced electric field as well as by enhanced n e.The productions of OH and O are decreasing with increasing air flow rate due to removal of Joule heat from the discharge region but enhanced air flow rate significantly modifies discharge maintenance properties. Besides, Tgsignificantly reduces with the enhanced air flow rate. This investigation reveals that Ar plays a significant role in the production of OH and O radicals.展开更多
In agriculture production,plant health is threatened by pathogens parasitic on seeds;hence,it is necessary to disinfect harvested seeds before germination.In this study,a technique of gliding arc plasma treatment was ...In agriculture production,plant health is threatened by pathogens parasitic on seeds;hence,it is necessary to disinfect harvested seeds before germination.In this study,a technique of gliding arc plasma treatment was proposed and investigated.The experiment was conducted to treat Astragalus membranaceus(A.membranaceus)seeds that were artificially infected with Fusarium oxysporum(F.oxysporum).The plasma treatment duration varied from 30 s to 270 s.Direct and indirect treatments were compared to evaluate the inactivation efficiency of the F.oxysporum spores on the surface of seeds.The results indicated that the direct treatment behaved significantly better in disinfection than the indirect way.Meanwhile,experiments of the quantitative assessment of seed germination were also conducted,including the germination rate,the germination potential,and the germination index.The results showed that the inactivation efficiency increased as the plasma treatment time was extended.When the treatment time was90 s,the inactivation efficiency reached more than 98%.The plasma treatment of 270 s had a complete devitalization of F.oxysporum spores on the surface of the seeds.After the treatment of 30 s and 90 s,the seed germination parameters improved significantly.This study verified the inactivation efficacy of gliding arc discharge plasma under atmospheric pressure.The technique of gliding arc treatment shows advantages of energy saving and adaptation and has the potential to be utilized in industry.展开更多
Generation of atmospheric pressure homogeneous air plasma in a large gap(>4 mm)is a challenge.In this study,an atmospheric pressure homogeneous air plasma generated in a gap up to 10 mm is reported,which is based o...Generation of atmospheric pressure homogeneous air plasma in a large gap(>4 mm)is a challenge.In this study,an atmospheric pressure homogeneous air plasma generated in a gap up to 10 mm is reported,which is based on a three-electrode configuration,where a high-voltage(HV)electrode and a middle electrode form a surface dielectric barrier discharge(S-DBD),and together with the ground electrode form the main volume discharge.High-speed photographs confirm that the discharge in the main gap is homogeneous.The gas temperature of the plasma estimated from the N_(2)(C^(3)∏_(u)-B^(3)∏_(g))(Δv=-2)emission is about 320 K,which is close to room temperature.A detailed analysis shows that the discharge ignited between the HV electrode and the middle electrode is serving as an electron source,and the electrons deposited on the dielectric plate are due to the S-DBD along with the applied voltage generating a driving force,which results in a high concentration of seed electrons in the main gap and induces the homogeneous plasma.Further analysis shows that the electric field in the main gap is only about18.45 k V·cm^(-1),which is much lower than the typical breakdown electric field of 30 k V·cm^(-1)for atmospheric pressure air discharge.展开更多
Atmospheric pressure helium/water dielectric barrier discharge(DBD) plasma is used to investigate the generation of reactive species in a gas–liquid interface and in a liquid. The emission intensity of the reactive s...Atmospheric pressure helium/water dielectric barrier discharge(DBD) plasma is used to investigate the generation of reactive species in a gas–liquid interface and in a liquid. The emission intensity of the reactive species is measured by optical emission spectroscopy(OES)with different discharge powers at the gas–liquid interface. Spectrophotometry is used to analyze the reactive species induced by the plasma in the liquid. The concentration of OH radicals reaches 2.2 μm after 3 min of discharge treatment. In addition, the concentration of primary longlived reactive species such as H_2O_2, NO_3^- and O_3 are measured based on plasma treatment time.After 5 min of discharge treatment, the concentration of H_2O_2, NO_3^-, and O_3 increased from 0 mg?·?L^(-1) to 96 mg?·?L^(-1), 19.5 mg?·?L^(-1), and 3.5 mg?·?L^(-1), respectively. The water treated by plasma still contained a considerable concentration of reactive species after 6 h of storage. The results will contribute to optimizing the DBD plasma system for biological decontamination.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
A comparative study of radio-frequency atmospheric pressure glow discharge(rf APGD)generated in helium with and without dielectric electrodes to investigate the effect of electrodes insulation on electrical features o...A comparative study of radio-frequency atmospheric pressure glow discharge(rf APGD)generated in helium with and without dielectric electrodes to investigate the effect of electrodes insulation on electrical features of APGD is presented. In the α mode, both the rf APGDs remain volumetric, stable and uniform. In the γ mode, the APGD without dielectric electrodes shrinks into a constricted plasma column whereas APGD with dielectric electrodes remains stable and retains the same volume without plasma constriction even at higher densities of discharge current. A comparison of electrical features of both rf APGDs in normal and abnormal glow discharge regimes is presented. In both APGDs with and without dielectric electrodes,impedance measurements have been performed and compared with equivalent circuit models.The measured impedance data is found to be in good agreement with simulated data.展开更多
Non-thermal plasmas under atmospheric pressure are of great interest in polymer surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of Polyethylene terephthalate (...Non-thermal plasmas under atmospheric pressure are of great interest in polymer surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of Polyethylene terephthalate (PET) film surface for improving hydrophilicity using the non-thermal plasma generated by atmospheric pressure glow discharge (APGD) in air is conducted. The discharge characteristics of APGD are shown by measurement of their electrical discharge parameters and observation of light-emission phenomena, and the surface properties of PET before and after the APGD treatment are studied using contact angle measurement, x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It is found that the APGD is homogeneous and stable in the whole gas gap, which differs from the commonly filamentary dielectric barrier discharge (DBD). A short time (several seconds) APGD treatment can modify the surface characteristics of PET film markedly and uniformly. After 10 s APGD treatment, the surface oxygen content of PET surface increases to 39%, and the water contact angle decreases to 19°, respectively.展开更多
An improved self-consistent, multi-component, and one-dimensional plasma model for simulating atmospheric pressure argon glow discharge is presented. In the model, both the plasma hydrodynamics model and chemical mode...An improved self-consistent, multi-component, and one-dimensional plasma model for simulating atmospheric pressure argon glow discharge is presented. In the model, both the plasma hydrodynamics model and chemical model are considered. The numerical simulation is carried out for parallel-plate geometry with a separation of 0.06 cm. The results show that Ar plays a major role in the discharge, which is mainly produced by ground state excitation reaction. The electron temperature reaches its maximum in the cathode sheath but maintains a low value (0.23 eV) in bulk plasma. Elastic collision is the dominant volumetric electron energy loss in atmosphere argon glow discharge, which is negligible in low pressure argon glow discharge. The metastable step-wise ionization is the main mechanism for electron production to sustain the discharge. However, the highest contribution to electron production rate is ground state ionization reaction. The bremsstrahlung power density is related to electric voltage. With the increase of the electric voltage, the bremsstrahlung power density increases, namely, the strength of ultraviolet radiation spectrum enhances in the cathode sheath.展开更多
The surface dielectric barrier discharge(SDBD) plasma actuator has shown great promise as an aerodynamic flow control device. In this paper, the encapsulated electrode width of a SDBD actuator is changed to study the ...The surface dielectric barrier discharge(SDBD) plasma actuator has shown great promise as an aerodynamic flow control device. In this paper, the encapsulated electrode width of a SDBD actuator is changed to study the airflow acceleration behavior. The effects of encapsulated electrode width on the actuator performance are experimentally investigated by measuring the dielectric layer surface potential, time-averaged ionic wind velocity and thrust force. Experimental results show that the airflow velocity and thrust force increase with the encapsulated electrode width. The results can be attributed to the distinct plasma distribution at different encapsulated electrode widths.展开更多
In order to form an atmospheric-pressure plasma jet without airflow, a needle–ring electrode structure is proposed in this paper. When heteropolar potentials are applied to a needle and a ring, a marked electric fiel...In order to form an atmospheric-pressure plasma jet without airflow, a needle–ring electrode structure is proposed in this paper. When heteropolar potentials are applied to a needle and a ring, a marked electric field strength enhancement around the needle’s pointed end has been found. When the same potential is applied to both the needle and the ring, the lateral electric field strength for the needle can be weakened. By using the above two methods, an increase of the difference between the pointed end electric field strength and the lateral one is achieved and stable plasma jets are formed. A symmetrical space electric field distribution is established at the pointed end of the needles when several sets of heteropolar needle–ring electrodes are uniformly arranged, which is conducive to forming a uniform array plasma jet. Under DC discharge conditions, a safe and stable plasma jet of high density and an array plasma jet are successfully achieved.展开更多
In this work the effects of O_2 concentration on the pulsed dielectric barrier discharge in helium-oxygen mixture at atmospheric pressure have been numerically researched by using a one-dimensional fluid model in conj...In this work the effects of O_2 concentration on the pulsed dielectric barrier discharge in helium-oxygen mixture at atmospheric pressure have been numerically researched by using a one-dimensional fluid model in conjunction with the chosen key species and chemical reactions.The reliability of the used model has been examined by comparing the calculated discharge current with the reported experiments. The present work presents the following significant results. The dominative positive and negative particles are He_2^+ and O_2^-, respectively, the densities of the reactive oxygen species(ROS) get their maxima nearly at the central position of the gap, and the density of the ground state O is highest in the ROS. The increase of O_2 concentration results in increasingly weak discharge and the time lag of the ignition. For O_2 concentrations below 1.1%,the density of O is much higher than other species, the averaged dissipated power density presents an evident increase for small O_2 concentration and then the increase becomes weak. In particular,the total density of the reactive oxygen species reaches its maximums at the O_2 concentration of about 0.5%. This characteristic further convinces the experimental observation that the O_2 concentration of 0.5% is an optimal O_2/He ratio in the inactivation of bacteria and biomolecules when radiated by using the plasmas produced in a helium oxygen mixture.展开更多
Atmospheric pressure glow discharge(APGD) plasma in air has high application value. In this paper, the methods of generating APGD plasma in air are discussed, and the characteristics of dielectric barrier discharge(DB...Atmospheric pressure glow discharge(APGD) plasma in air has high application value. In this paper, the methods of generating APGD plasma in air are discussed, and the characteristics of dielectric barrier discharge(DBD) in non-uniform electric field are studied. It makes sure that APGD in air is formed by DBD in alternating current electric field with using the absorbing electron capacity of electret materials to provide initial electrons and to end the discharge progress. Through designing electric field to form two-dimensional space varying electric field and three-dimensional space varying electric field, the development of electron avalanches in airgap is suppressed effectively and a large space of APGD plasma in air is generated. Further,through combining electrode structures, a large area of APGD plasma in air is generated. On the other hand, by using the method of increasing the density of initial electrons, millimeter-gap glow discharge in atmospheric pressure air is formed, and a maximum gap distance between electrodes is 8 mm. By using the APGD plasma surface treatment device composed of contact electrodes, the surface modification of high polymer materials such as aramid fiber and polyester are studied and good effect of modifications is obtained. The present paper provides references for the researchers of industrial applications of plasma.展开更多
In this paper,the influence of voltage rising time on a pulsed-dc helium-air plasma at atmospheric pressure is numerically simulated.Simulation results show that as the voltage rising time increases from 10 ns to 30 n...In this paper,the influence of voltage rising time on a pulsed-dc helium-air plasma at atmospheric pressure is numerically simulated.Simulation results show that as the voltage rising time increases from 10 ns to 30 ns,there is a decrease in the discharge current,namely 0.052 A when the voltage rising time is 10 ns and 0.038 A when the voltage rising time is 30 ns.Additionally,a shorter voltage rising time results in a faster breakdown,a more rapidly rising current waveform,and a higher breakdown voltage.Furthermore,the basic parameters of the streamer discharge also increase with voltage rise rate,which is ascribed to the fact that more energetic electrons are produced in a shorter voltage rising time.Therefore,a pulsed-dc voltage with a short rising time is desirable for efficient production of nonequilibrium atmospheric pressure plasma discharge.展开更多
Dielectric barrier discharge(DBD) cold plasma at atmospheric pressure was used for preparation of copper nanoparticles by reduction of copper oxide(CuO). Power X-ray di?raction(XRD) was used to characterize the struct...Dielectric barrier discharge(DBD) cold plasma at atmospheric pressure was used for preparation of copper nanoparticles by reduction of copper oxide(CuO). Power X-ray di?raction(XRD) was used to characterize the structure of the copper oxide samples treated by DBD plasma. Influences of H2 content and the treating time on the reduction of copper oxide by DBD plasma were investigated. The results show that the reduction ratio of copper oxide was increased initially and then decreased with increasing H2 content, and the highest reduction ratio was achieved at 20% H2 content. Moreover, the copper oxide samples were gradually reduced by DBD plasma into copper nanoparticles with the increase in treating time. However, the average reduction rate was decreased as a result of the di?usion of the active hydrogen species. Optical emission spectra(OES) were observed during the reduction of the copper oxide samples by DBD plasma, and the reduction mechanism was explored accordingly. Instead of high-energy electrons, atomic hydrogen(H) radicals, and the heating e?ect, excited-state hydrogen molecules are suspected to be one kind of important reducing agents. Atmospheric-pressure DBD cold plasma is proved to be an efficient method for preparing copper nanoparticles.展开更多
The simultaneous removal of ethyl acetate, benzene and toluene with relatively low or high initial concentration is studied using a laboratory scale gliding arc gas discharge (GA) reactor. Good decomposition efficienc...The simultaneous removal of ethyl acetate, benzene and toluene with relatively low or high initial concentration is studied using a laboratory scale gliding arc gas discharge (GA) reactor. Good decomposition efficiencies are obtained which proves that the GA is effective for the treatment of volatile organic compounds (VOCs) with either low or high concentration. A theoretical decomposition mechanism is proposed based on detection of the species in the plasma region and analysis of the decomposition by-products. This preliminary investigation reveals that the GA has potential to be applied to the treatment of exhaust air during color printing and coating works, by either direct removal or combination with activated carbon adsorption/desorption process.展开更多
Matching optimization of resonant parameters among the high power inverters,low power transformers and plasma reactors have significant effects on the performance and output of the reactor array when applying the part...Matching optimization of resonant parameters among the high power inverters,low power transformers and plasma reactors have significant effects on the performance and output of the reactor array when applying the partitioned operation method.In this paper,the Matlab/Simulink electrical model was established based on the method of partitioned operation.The matching relation between resonant parameters is analyzed on the basis of experimental result.As a consequence,transformer leakage inductance and working frequency are the important parameters influencing the operational efficiency of system,leakage inductance of transformer should be adjusted based on the equivalent capacitance of plasma reactor to realize the matching optimization of resonant parameters.展开更多
基金supported by National Natural Science Foundation of China(No.52177135)the National Science and Technology Major Project of China(Nos.2017-Ⅲ-0007-0032,2019-Ⅲ-0013-0056)。
文摘Direct-current(DC)arc plasma has great application values in the field of the chemical industry,but it has the problem of low energy efficiency.Facing the requirement for improving the energy efficiency of the arc,this paper proposes a unique method of pulsed modulated arc(PMA).This method uses high-frequency pulses and reduces the arc current to improve the control of electron temperature.The electrical characteristics,optical characteristics and products are tested.The test results show that during the PMA process,all of the experimental results which include voltage,current and light will significantly increase.These results are analyzed from the perspective of functionality,repeatability and energy conversion.The analysis results show that although the PMA method does not show good parameter consistency,it has potential application prospects because it increases the energy conversion rate by 4.5%and 8%from the perspective of light and products,respectively.
基金Partial financial support has been provided by the Ministry of Science and Technology, Republic of Bangladesh: 39.00.0000.09.06.79.2017/2/98ESBangladesh Council for Scientific and Industrial Research (BCSIR) for providing Professor Abdullah Al-Muti Sharfuddin fellowship
文摘Wheat(Triticum aestivum) seeds were treated with atmospheric pressure gliding arc discharge plasmas to investigate the effects on water absorption, seed germination rate, seedling growth and yield in wheat. The surface architectures and functionalities of the seeds were found to modify due to plasma treatments. 6 min treatment was provided 95%–100% germination rate.For the treatment duration of 3 and 9 min the growth activity, dry matter accumulation, leaves chlorophyll contents, longest spikes, number of spikes/spikelet and total soluble protein content in shoots were improved. The grain yield of wheat was increased ~20% by 6 min treatment with H_2O/O_2 plasma with respect to control.
基金financial support has been provided by the University Grants Commission:A-663-5/52/UGC/Eng-9/2013 and A-670-5/52/UGC/Eng-4/2013,University of Rajshahi
文摘Atmospheric pressure air/Ar/H_2O gliding arc discharge plasma is produced by a pulsed dc power supply. An optical emission spectroscopic(OES) diagnostic technique is used for the characterization of plasmas and for identifications of OH and O radicals along with other species in the plasmas. The OES diagnostic technique reveals the excitation Tx?≈?5550–9000 K, rotational Tr?≈?1350–2700 K and gas Tg?≈?850–1600 K temperatures, and electron density n?(1.1-1.9) ′101 4 cm^(-3) e under different experimental conditions. The production and destruction of OH and O radicals are investigated as functions of applied voltage and air flow rate. Relative intensities of OH and O radicals indicate that their production rates are increased with increasing Ar content in the gas mixture and applied voltage. nereveals that the higher densities of OH and O radicals are produced in the discharge due to more effective electron impact dissociation of H_2O and O_2 molecules caused by higher kinetic energies as gained by electrons from the enhanced electric field as well as by enhanced n e.The productions of OH and O are decreasing with increasing air flow rate due to removal of Joule heat from the discharge region but enhanced air flow rate significantly modifies discharge maintenance properties. Besides, Tgsignificantly reduces with the enhanced air flow rate. This investigation reveals that Ar plays a significant role in the production of OH and O radicals.
文摘In agriculture production,plant health is threatened by pathogens parasitic on seeds;hence,it is necessary to disinfect harvested seeds before germination.In this study,a technique of gliding arc plasma treatment was proposed and investigated.The experiment was conducted to treat Astragalus membranaceus(A.membranaceus)seeds that were artificially infected with Fusarium oxysporum(F.oxysporum).The plasma treatment duration varied from 30 s to 270 s.Direct and indirect treatments were compared to evaluate the inactivation efficiency of the F.oxysporum spores on the surface of seeds.The results indicated that the direct treatment behaved significantly better in disinfection than the indirect way.Meanwhile,experiments of the quantitative assessment of seed germination were also conducted,including the germination rate,the germination potential,and the germination index.The results showed that the inactivation efficiency increased as the plasma treatment time was extended.When the treatment time was90 s,the inactivation efficiency reached more than 98%.The plasma treatment of 270 s had a complete devitalization of F.oxysporum spores on the surface of the seeds.After the treatment of 30 s and 90 s,the seed germination parameters improved significantly.This study verified the inactivation efficacy of gliding arc discharge plasma under atmospheric pressure.The technique of gliding arc treatment shows advantages of energy saving and adaptation and has the potential to be utilized in industry.
基金supported by National Natural Science Foundation of China(Nos.52130701,51977096,52277150,and12005076)the National Key Research and Development Program of China(No.2021YFE0114700)。
文摘Generation of atmospheric pressure homogeneous air plasma in a large gap(>4 mm)is a challenge.In this study,an atmospheric pressure homogeneous air plasma generated in a gap up to 10 mm is reported,which is based on a three-electrode configuration,where a high-voltage(HV)electrode and a middle electrode form a surface dielectric barrier discharge(S-DBD),and together with the ground electrode form the main volume discharge.High-speed photographs confirm that the discharge in the main gap is homogeneous.The gas temperature of the plasma estimated from the N_(2)(C^(3)∏_(u)-B^(3)∏_(g))(Δv=-2)emission is about 320 K,which is close to room temperature.A detailed analysis shows that the discharge ignited between the HV electrode and the middle electrode is serving as an electron source,and the electrons deposited on the dielectric plate are due to the S-DBD along with the applied voltage generating a driving force,which results in a high concentration of seed electrons in the main gap and induces the homogeneous plasma.Further analysis shows that the electric field in the main gap is only about18.45 k V·cm^(-1),which is much lower than the typical breakdown electric field of 30 k V·cm^(-1)for atmospheric pressure air discharge.
基金jointly supported by the Science Foundation of the Institute of Plasma Physics, the Chinese Academy of Sciences (No. DSJJ-14-YY02)National Natural Science Foundation of China (Grant Nos. 11475174 and 51777206)
文摘Atmospheric pressure helium/water dielectric barrier discharge(DBD) plasma is used to investigate the generation of reactive species in a gas–liquid interface and in a liquid. The emission intensity of the reactive species is measured by optical emission spectroscopy(OES)with different discharge powers at the gas–liquid interface. Spectrophotometry is used to analyze the reactive species induced by the plasma in the liquid. The concentration of OH radicals reaches 2.2 μm after 3 min of discharge treatment. In addition, the concentration of primary longlived reactive species such as H_2O_2, NO_3^- and O_3 are measured based on plasma treatment time.After 5 min of discharge treatment, the concentration of H_2O_2, NO_3^-, and O_3 increased from 0 mg?·?L^(-1) to 96 mg?·?L^(-1), 19.5 mg?·?L^(-1), and 3.5 mg?·?L^(-1), respectively. The water treated by plasma still contained a considerable concentration of reactive species after 6 h of storage. The results will contribute to optimizing the DBD plasma system for biological decontamination.
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.
基金partially supported by the Higher Education Commission Project No. 1852
文摘A comparative study of radio-frequency atmospheric pressure glow discharge(rf APGD)generated in helium with and without dielectric electrodes to investigate the effect of electrodes insulation on electrical features of APGD is presented. In the α mode, both the rf APGDs remain volumetric, stable and uniform. In the γ mode, the APGD without dielectric electrodes shrinks into a constricted plasma column whereas APGD with dielectric electrodes remains stable and retains the same volume without plasma constriction even at higher densities of discharge current. A comparison of electrical features of both rf APGDs in normal and abnormal glow discharge regimes is presented. In both APGDs with and without dielectric electrodes,impedance measurements have been performed and compared with equivalent circuit models.The measured impedance data is found to be in good agreement with simulated data.
文摘Non-thermal plasmas under atmospheric pressure are of great interest in polymer surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of Polyethylene terephthalate (PET) film surface for improving hydrophilicity using the non-thermal plasma generated by atmospheric pressure glow discharge (APGD) in air is conducted. The discharge characteristics of APGD are shown by measurement of their electrical discharge parameters and observation of light-emission phenomena, and the surface properties of PET before and after the APGD treatment are studied using contact angle measurement, x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It is found that the APGD is homogeneous and stable in the whole gas gap, which differs from the commonly filamentary dielectric barrier discharge (DBD). A short time (several seconds) APGD treatment can modify the surface characteristics of PET film markedly and uniformly. After 10 s APGD treatment, the surface oxygen content of PET surface increases to 39%, and the water contact angle decreases to 19°, respectively.
基金supported by the Major State Basic Research Development Program of China (973 Program) (No. 2011CB20941)Scientific Research Foundation of State Key Lab. of Power Transmission Equipment and System Security of China (No. 2007DA10512709102)+1 种基金National Natural Science Foundation of China (No. 51007096)the Fundamental Research Funds for the Central Universities of China(No. CDJZR10150001)
文摘An improved self-consistent, multi-component, and one-dimensional plasma model for simulating atmospheric pressure argon glow discharge is presented. In the model, both the plasma hydrodynamics model and chemical model are considered. The numerical simulation is carried out for parallel-plate geometry with a separation of 0.06 cm. The results show that Ar plays a major role in the discharge, which is mainly produced by ground state excitation reaction. The electron temperature reaches its maximum in the cathode sheath but maintains a low value (0.23 eV) in bulk plasma. Elastic collision is the dominant volumetric electron energy loss in atmosphere argon glow discharge, which is negligible in low pressure argon glow discharge. The metastable step-wise ionization is the main mechanism for electron production to sustain the discharge. However, the highest contribution to electron production rate is ground state ionization reaction. The bremsstrahlung power density is related to electric voltage. With the increase of the electric voltage, the bremsstrahlung power density increases, namely, the strength of ultraviolet radiation spectrum enhances in the cathode sheath.
基金supported by National Natural Science Foundation of China(No.11175037)National Natural Science Foundation for Young Scientists of China(No.11305017)Special Fund for Theoretical Physics(No.11247239)
文摘The surface dielectric barrier discharge(SDBD) plasma actuator has shown great promise as an aerodynamic flow control device. In this paper, the encapsulated electrode width of a SDBD actuator is changed to study the airflow acceleration behavior. The effects of encapsulated electrode width on the actuator performance are experimentally investigated by measuring the dielectric layer surface potential, time-averaged ionic wind velocity and thrust force. Experimental results show that the airflow velocity and thrust force increase with the encapsulated electrode width. The results can be attributed to the distinct plasma distribution at different encapsulated electrode widths.
基金supported by National Natural Science Foundation of China (No. 51577011)
文摘In order to form an atmospheric-pressure plasma jet without airflow, a needle–ring electrode structure is proposed in this paper. When heteropolar potentials are applied to a needle and a ring, a marked electric field strength enhancement around the needle’s pointed end has been found. When the same potential is applied to both the needle and the ring, the lateral electric field strength for the needle can be weakened. By using the above two methods, an increase of the difference between the pointed end electric field strength and the lateral one is achieved and stable plasma jets are formed. A symmetrical space electric field distribution is established at the pointed end of the needles when several sets of heteropolar needle–ring electrodes are uniformly arranged, which is conducive to forming a uniform array plasma jet. Under DC discharge conditions, a safe and stable plasma jet of high density and an array plasma jet are successfully achieved.
基金supported by the Fundamental Research Funds of Shandong University,China(No.2016JC016)
文摘In this work the effects of O_2 concentration on the pulsed dielectric barrier discharge in helium-oxygen mixture at atmospheric pressure have been numerically researched by using a one-dimensional fluid model in conjunction with the chosen key species and chemical reactions.The reliability of the used model has been examined by comparing the calculated discharge current with the reported experiments. The present work presents the following significant results. The dominative positive and negative particles are He_2^+ and O_2^-, respectively, the densities of the reactive oxygen species(ROS) get their maxima nearly at the central position of the gap, and the density of the ground state O is highest in the ROS. The increase of O_2 concentration results in increasingly weak discharge and the time lag of the ignition. For O_2 concentrations below 1.1%,the density of O is much higher than other species, the averaged dissipated power density presents an evident increase for small O_2 concentration and then the increase becomes weak. In particular,the total density of the reactive oxygen species reaches its maximums at the O_2 concentration of about 0.5%. This characteristic further convinces the experimental observation that the O_2 concentration of 0.5% is an optimal O_2/He ratio in the inactivation of bacteria and biomolecules when radiated by using the plasmas produced in a helium oxygen mixture.
文摘Atmospheric pressure glow discharge(APGD) plasma in air has high application value. In this paper, the methods of generating APGD plasma in air are discussed, and the characteristics of dielectric barrier discharge(DBD) in non-uniform electric field are studied. It makes sure that APGD in air is formed by DBD in alternating current electric field with using the absorbing electron capacity of electret materials to provide initial electrons and to end the discharge progress. Through designing electric field to form two-dimensional space varying electric field and three-dimensional space varying electric field, the development of electron avalanches in airgap is suppressed effectively and a large space of APGD plasma in air is generated. Further,through combining electrode structures, a large area of APGD plasma in air is generated. On the other hand, by using the method of increasing the density of initial electrons, millimeter-gap glow discharge in atmospheric pressure air is formed, and a maximum gap distance between electrodes is 8 mm. By using the APGD plasma surface treatment device composed of contact electrodes, the surface modification of high polymer materials such as aramid fiber and polyester are studied and good effect of modifications is obtained. The present paper provides references for the researchers of industrial applications of plasma.
基金supported by National Natural Science Foundation of China(NSFC) under Grant No.11465013the Natural Science Foundation of Jiangxi Province under Grant Nos.20151BAB212012 and 20161BAB201013part by the International Science and Technology Cooperation Program of China under Grant No.2015DFA61800
文摘In this paper,the influence of voltage rising time on a pulsed-dc helium-air plasma at atmospheric pressure is numerically simulated.Simulation results show that as the voltage rising time increases from 10 ns to 30 ns,there is a decrease in the discharge current,namely 0.052 A when the voltage rising time is 10 ns and 0.038 A when the voltage rising time is 30 ns.Additionally,a shorter voltage rising time results in a faster breakdown,a more rapidly rising current waveform,and a higher breakdown voltage.Furthermore,the basic parameters of the streamer discharge also increase with voltage rise rate,which is ascribed to the fact that more energetic electrons are produced in a shorter voltage rising time.Therefore,a pulsed-dc voltage with a short rising time is desirable for efficient production of nonequilibrium atmospheric pressure plasma discharge.
基金supported by National Natural Science Foundation of China(No.21173028)the Science and Technology Research Project of Liaoning Provincial Education Department of China(No.L2013464)the Scientific Research Foundation for the Doctor of Liaoning Province of China(No.20131004)
文摘Dielectric barrier discharge(DBD) cold plasma at atmospheric pressure was used for preparation of copper nanoparticles by reduction of copper oxide(CuO). Power X-ray di?raction(XRD) was used to characterize the structure of the copper oxide samples treated by DBD plasma. Influences of H2 content and the treating time on the reduction of copper oxide by DBD plasma were investigated. The results show that the reduction ratio of copper oxide was increased initially and then decreased with increasing H2 content, and the highest reduction ratio was achieved at 20% H2 content. Moreover, the copper oxide samples were gradually reduced by DBD plasma into copper nanoparticles with the increase in treating time. However, the average reduction rate was decreased as a result of the di?usion of the active hydrogen species. Optical emission spectra(OES) were observed during the reduction of the copper oxide samples by DBD plasma, and the reduction mechanism was explored accordingly. Instead of high-energy electrons, atomic hydrogen(H) radicals, and the heating e?ect, excited-state hydrogen molecules are suspected to be one kind of important reducing agents. Atmospheric-pressure DBD cold plasma is proved to be an efficient method for preparing copper nanoparticles.
基金Project (No. 50476058) supported by the National Natural ScienceFoundation of China
文摘The simultaneous removal of ethyl acetate, benzene and toluene with relatively low or high initial concentration is studied using a laboratory scale gliding arc gas discharge (GA) reactor. Good decomposition efficiencies are obtained which proves that the GA is effective for the treatment of volatile organic compounds (VOCs) with either low or high concentration. A theoretical decomposition mechanism is proposed based on detection of the species in the plasma region and analysis of the decomposition by-products. This preliminary investigation reveals that the GA has potential to be applied to the treatment of exhaust air during color printing and coating works, by either direct removal or combination with activated carbon adsorption/desorption process.
基金supported by National Key Technology Research and Development Program of the Ministry of Science and Technology of China(No.2013BAC06B02)Public Science and Technology Research Funds Projects of Ocean (No.201305027)+2 种基金National Natural Science Foundation of China(No.51877024)Liaoning Scientific Research Project of Department of Education of Liaoning Province(No.LZ2015007)High Level Talent Innovation Project of Dalian(No.2016RQ040)
文摘Matching optimization of resonant parameters among the high power inverters,low power transformers and plasma reactors have significant effects on the performance and output of the reactor array when applying the partitioned operation method.In this paper,the Matlab/Simulink electrical model was established based on the method of partitioned operation.The matching relation between resonant parameters is analyzed on the basis of experimental result.As a consequence,transformer leakage inductance and working frequency are the important parameters influencing the operational efficiency of system,leakage inductance of transformer should be adjusted based on the equivalent capacitance of plasma reactor to realize the matching optimization of resonant parameters.