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 treatment of simulated wastewater containing Reactive Red 195 using zero-valent iron/activated carbon （ZVI/AC）, microwave discharge electrodeless lamp/sodium hypochlorite （MDEL/NaCIO） and th...A comparative study of treatment of simulated wastewater containing Reactive Red 195 using zero-valent iron/activated carbon （ZVI/AC）, microwave discharge electrodeless lamp/sodium hypochlorite （MDEL/NaCIO） and the combination of ZVI/AC- MDEL/NaCIO was conducted. The preliminary results showed the two steps method of ZVI/AC-MDEL/NaCIO had much higher degradation efficiency than both single steps. The final color removal percentage was nearly up to 100% and the chemical oxygen demand reduction percentage was up to approximately 82%. The effects of operational parameters, including initial pH value of simulated wastewater, ZVI/AC ratio and particle size of ZVI were also investigated. In addition, from the discussion of synergistic effect between ZVI/AC and MEDL/NaCIO, we found that in the ZVI/AC-MEDL/NaCIO process, ZVI/AC could break the azo bond firstly and then MEDLfNaCIO degraded the aromatic amine products effectively. Reversing the order would reduce the degradation efficiency.展开更多
The luminescent properties of microwave discharge electrodeless mercury lamp（MDEL-Hg） which was ignited within the resonant cavity and photolysis of hydrogen sulfide with low concentration were studied in this paper...The luminescent properties of microwave discharge electrodeless mercury lamp（MDEL-Hg） which was ignited within the resonant cavity and photolysis of hydrogen sulfide with low concentration were studied in this paper.Experiment results indicated that the Interior MDEL-Hg could be made the best of energy utihzation and the efficiency of photolysis of H2S was very significant under the experimental conditions with the initial H2S concentration of 7.9 mg m^-1.With residence time of 1.5 s,the removal efficiency of hydrogen sulfide was 91%,the absolute removal amount（ARA） was 3.24μg s^-1 and the energy consumption was 58.23 mg（kWh）^-1.展开更多
Reactions between CH_4 and CO_2 under the action of continuous microwave discharge at atmospheric pressure were studied in a special homemade reactor. The main products were CO and H2, while acetylene and ethylene wer...Reactions between CH_4 and CO_2 under the action of continuous microwave discharge at atmospheric pressure were studied in a special homemade reactor. The main products were CO and H2, while acetylene and ethylene were also found in the products. Experimental results show that conversions of CH4 and CO2 could be higher than 90% without the presence of any catalyst. Effects of CO2/CH4 molar ratio and total flow rate of the feed gas on the reaction were also investigated.展开更多
The microwave （MW） transmission method is employed to measure both the plasma density and the plasma decay time in the hollow cathode discharge （HCD） in argon at low pressure. The plasma density in DC-driven or pu...The microwave （MW） transmission method is employed to measure both the plasma density and the plasma decay time in the hollow cathode discharge （HCD） in argon at low pressure. The plasma density in DC-driven or pulsed HCD is on the order of 1012 cm-3, which can block the X-band MW effectively. In the case of pulsed HCD, the MW transmittance shows the same waveform as the pulsed current during the rising edge if the driving frequency is low, but with a longer delay during the falling edge. The MW transmittance reaches a constant low level when the driving frequency is high enough. The plasma decay time in the HCD system is measured to be about 100 μs around a pressure of 120 Pa. The ambipolar diffusion is considered to be the major mechanism in the decay process.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
Atmospheric lower-power pulsed microwave argon cold plasma jets are obtained by using coaxial transmission line resonators in ambient air.The plasma jet plumes are generated at the end of a metal wire placed in the mi...Atmospheric lower-power pulsed microwave argon cold plasma jets are obtained by using coaxial transmission line resonators in ambient air.The plasma jet plumes are generated at the end of a metal wire placed in the middle of the dielectric tubes.The electromagnetic model analyses and simulation results suggest that the discharges are excited resonantly by the enhanced electric field of surface plasmon polaritons.Moreover,for conquering the defect of atmospheric argon filamentation discharges excited by 2.45-GHz of continued microwave,the distinctive patterns of the plasma jet plumes can be maintained by applying different gas flow rates of argon gas,frequencies of pulsed modulator,duty cycles of pulsed microwave,peak values of input microwave power,and even by using different materials of dielectric tubes.In addition,the emission spectrum,the plume temperature,and other plasma parameters are measured,which shows that the proposed pulsed microwave plasma jets can be adjusted for plasma biomedical applications.展开更多
Different discharge morphologies in atmospheric Ar and He plasmas are excited by using a pulsed microwave hairpin resonator.Ar plasmas form an arched plasma plume at the opened end of the hairpin,whereas He plumes gen...Different discharge morphologies in atmospheric Ar and He plasmas are excited by using a pulsed microwave hairpin resonator.Ar plasmas form an arched plasma plume at the opened end of the hairpin,whereas He plumes generate only a contracted plasmas in between both tips of metal electrodes.Despite this different point,their discharge processes have three similar characteristics:(i)the ionization occurs at the main electrode firstly and then develops to the slave electrode,(ii)during the shrinking stage the middle domain of the discharge channels disappears at last,and(iii)even at zero power input(in between pulses)a weak light region always exists in the discharge channels.Both experimental results and electromagnetic simulations suggest that the discharge is resonantly excited by the local enhanced electric fields.In addition,Ar ionization and excitation energies are lower than those of He,the effect of Ar gas flow is far greater than that of He gas,and the contribution of accelerated electrons only locates at the domain with the strongest electric fields.These reasons could be used to interpret the different characteristic plume morphologies of the proposed atmospheric Ar and He plasmas.展开更多
Abstract： This paper presents a review of a beamed energy propulsion rocket, the Microwave Rocket, WlllCn proauces propmslve thrust from millimeter-wave beams transferred from the ground. The thrust is generated thro...Abstract： This paper presents a review of a beamed energy propulsion rocket, the Microwave Rocket, WlllCn proauces propmslve thrust from millimeter-wave beams transferred from the ground. The thrust is generated through millimeter-wave discharge driven in a cylindrical thruster. As a high-power millimeter-wave generator, a Gyrotron is promising as the beam source. The salient benefit of Microwave Rockets is the resultant drastic cost reduction of mass transportation into space. We have already conducted launch experiments and have achieved continuous thrust generation under multi-pulse operation. Recently, a long-distance beam transfer system has been developed. Ignition tests have been conducted. The physics of the millimeter-wave discharge remain unclear. Additional studies using exoerimentation and calculations must be conducted to optimize the thrust generation.展开更多
In this study, growth of mirror-like ultra-nanocrystalline diamond（UNCD） films by a facile hybrid CVD approach was presented. The nucleation and deposition of UNCD films were conducted in microwave plasma CVD（MPCVD...In this study, growth of mirror-like ultra-nanocrystalline diamond（UNCD） films by a facile hybrid CVD approach was presented. The nucleation and deposition of UNCD films were conducted in microwave plasma CVD（MPCVD） and direct current glow discharge CVD（DC GD CVD） on silicon substrates, respectively. A very high nucleation density（about 1×10^11 nuclei cm^-2） was obtained after plasma pretreatment. Furthermore, large area mirrorlike UNCD films of Φ 50 mm were synthesized by DC GD CVD. The thickness and grain size of the UNCD films are 24 μm and 7.1 nm, respectively. In addition, the deposition mechanism of the UNCD films was discussed.展开更多
Diverse interactions between microwaves and irradiated media provide a solid foundation for identifying novel organization pathways for energy flow.In this study,a high-energy-site phenomenon and targeted-energy trans...Diverse interactions between microwaves and irradiated media provide a solid foundation for identifying novel organization pathways for energy flow.In this study,a high-energy-site phenomenon and targeted-energy transition mechanism were identified in a particular microwave heating(MH)process.Intense discharges were observed when microwaves were imposed on irregularly sized SiC particles,producing tremendous heat that was 8-fold the amount generated in the discharge-free case.Energy efficiency was thereby greatly improved in the electricity-microwaves-effective heat transition.Meanwhile,the dispersed microwave field energy concentrated in small sites,where local temperatures could reach 2000℃–4000℃,with the energy density reaching up to 4.010^(5) W/kg.This can be called a high-energy site phenomenon which could induce further processes or reactions enhancement by coupling effects of heat,light,and plasma.The whole process,including microwave energy concentration and intense site-energy release,shapes a targeted-energy transition mechanism that can be optimized in a controlled manner through morphology design.In particular,the discharge intensity,frequency,and high-energy sites were strengthened through the fabrication of sharp nano/microstructures,conferring twice the energy efficiency of untreated metal wires.The microwave-induced high-energy sites and targeted energy transition provide an important pathway for high-efficiency energy deployment and may lead to promising applications.展开更多
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supported by the Major Projects on Control and Rectification of Water Body Pollution (Water Special Project) (No.2009ZX07010-001,2008ZX07526-001)the National Basic Research Program (973) of China (No.2008CB418201)
文摘A comparative study of treatment of simulated wastewater containing Reactive Red 195 using zero-valent iron/activated carbon （ZVI/AC）, microwave discharge electrodeless lamp/sodium hypochlorite （MDEL/NaCIO） and the combination of ZVI/AC- MDEL/NaCIO was conducted. The preliminary results showed the two steps method of ZVI/AC-MDEL/NaCIO had much higher degradation efficiency than both single steps. The final color removal percentage was nearly up to 100% and the chemical oxygen demand reduction percentage was up to approximately 82%. The effects of operational parameters, including initial pH value of simulated wastewater, ZVI/AC ratio and particle size of ZVI were also investigated. In addition, from the discussion of synergistic effect between ZVI/AC and MEDL/NaCIO, we found that in the ZVI/AC-MEDL/NaCIO process, ZVI/AC could break the azo bond firstly and then MEDLfNaCIO degraded the aromatic amine products effectively. Reversing the order would reduce the degradation efficiency.
基金supported by the Shanghai Natural Science Foundation(No.07ZR14004)
文摘The luminescent properties of microwave discharge electrodeless mercury lamp（MDEL-Hg） which was ignited within the resonant cavity and photolysis of hydrogen sulfide with low concentration were studied in this paper.Experiment results indicated that the Interior MDEL-Hg could be made the best of energy utihzation and the efficiency of photolysis of H2S was very significant under the experimental conditions with the initial H2S concentration of 7.9 mg m^-1.With residence time of 1.5 s,the removal efficiency of hydrogen sulfide was 91%,the absolute removal amount（ARA） was 3.24μg s^-1 and the energy consumption was 58.23 mg（kWh）^-1.
文摘Reactions between CH_4 and CO_2 under the action of continuous microwave discharge at atmospheric pressure were studied in a special homemade reactor. The main products were CO and H2, while acetylene and ethylene were also found in the products. Experimental results show that conversions of CH4 and CO2 could be higher than 90% without the presence of any catalyst. Effects of CO2/CH4 molar ratio and total flow rate of the feed gas on the reaction were also investigated.
基金Project supported by the National Natural Science Foundation of China(Grant No.11005009)
文摘The microwave （MW） transmission method is employed to measure both the plasma density and the plasma decay time in the hollow cathode discharge （HCD） in argon at low pressure. The plasma density in DC-driven or pulsed HCD is on the order of 1012 cm-3, which can block the X-band MW effectively. In the case of pulsed HCD, the MW transmittance shows the same waveform as the pulsed current during the rising edge if the driving frequency is low, but with a longer delay during the falling edge. The MW transmittance reaches a constant low level when the driving frequency is high enough. The plasma decay time in the HCD system is measured to be about 100 μs around a pressure of 120 Pa. The ambipolar diffusion is considered to be the major mechanism in the decay process.
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 by the National Natural Science Foundation of China(Grant Nos.11105002 and 61170172)the Natural Science Foundation of Anhui Province,China(Grant Nos.1408085QA16 and 1408085ME101)+1 种基金the China Postdoctoral Science Foundation(Grant No.2014M551788)the Open-end Fund of State Key Laboratory of Advanced Electromagnetic Engineering and Technology(HUST),China(Grant No.GZ1301)
文摘Atmospheric lower-power pulsed microwave argon cold plasma jets are obtained by using coaxial transmission line resonators in ambient air.The plasma jet plumes are generated at the end of a metal wire placed in the middle of the dielectric tubes.The electromagnetic model analyses and simulation results suggest that the discharges are excited resonantly by the enhanced electric field of surface plasmon polaritons.Moreover,for conquering the defect of atmospheric argon filamentation discharges excited by 2.45-GHz of continued microwave,the distinctive patterns of the plasma jet plumes can be maintained by applying different gas flow rates of argon gas,frequencies of pulsed modulator,duty cycles of pulsed microwave,peak values of input microwave power,and even by using different materials of dielectric tubes.In addition,the emission spectrum,the plume temperature,and other plasma parameters are measured,which shows that the proposed pulsed microwave plasma jets can be adjusted for plasma biomedical applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11575003 and 51607003)
文摘Different discharge morphologies in atmospheric Ar and He plasmas are excited by using a pulsed microwave hairpin resonator.Ar plasmas form an arched plasma plume at the opened end of the hairpin,whereas He plumes generate only a contracted plasmas in between both tips of metal electrodes.Despite this different point,their discharge processes have three similar characteristics:(i)the ionization occurs at the main electrode firstly and then develops to the slave electrode,(ii)during the shrinking stage the middle domain of the discharge channels disappears at last,and(iii)even at zero power input(in between pulses)a weak light region always exists in the discharge channels.Both experimental results and electromagnetic simulations suggest that the discharge is resonantly excited by the local enhanced electric fields.In addition,Ar ionization and excitation energies are lower than those of He,the effect of Ar gas flow is far greater than that of He gas,and the contribution of accelerated electrons only locates at the domain with the strongest electric fields.These reasons could be used to interpret the different characteristic plume morphologies of the proposed atmospheric Ar and He plasmas.
文摘Abstract： This paper presents a review of a beamed energy propulsion rocket, the Microwave Rocket, WlllCn proauces propmslve thrust from millimeter-wave beams transferred from the ground. The thrust is generated through millimeter-wave discharge driven in a cylindrical thruster. As a high-power millimeter-wave generator, a Gyrotron is promising as the beam source. The salient benefit of Microwave Rockets is the resultant drastic cost reduction of mass transportation into space. We have already conducted launch experiments and have achieved continuous thrust generation under multi-pulse operation. Recently, a long-distance beam transfer system has been developed. Ignition tests have been conducted. The physics of the millimeter-wave discharge remain unclear. Additional studies using exoerimentation and calculations must be conducted to optimize the thrust generation.
基金supported by the program of international S&T cooperation(Agreement No.S2015ZR1100)
文摘In this study, growth of mirror-like ultra-nanocrystalline diamond（UNCD） films by a facile hybrid CVD approach was presented. The nucleation and deposition of UNCD films were conducted in microwave plasma CVD（MPCVD） and direct current glow discharge CVD（DC GD CVD） on silicon substrates, respectively. A very high nucleation density（about 1×10^11 nuclei cm^-2） was obtained after plasma pretreatment. Furthermore, large area mirrorlike UNCD films of Φ 50 mm were synthesized by DC GD CVD. The thickness and grain size of the UNCD films are 24 μm and 7.1 nm, respectively. In addition, the deposition mechanism of the UNCD films was discussed.
基金supported by the Natural Science Foundation of Shandong Province(Grant No.ZR2019MEE035)the Key Research and Development Plan of Shandong Province(Grant No.2019GSF109091)+1 种基金the Young Scholars Program of Shandong University(Grant No.2018WLJH75)the International Clean Energy Talent Program(iCET 2019).
文摘Diverse interactions between microwaves and irradiated media provide a solid foundation for identifying novel organization pathways for energy flow.In this study,a high-energy-site phenomenon and targeted-energy transition mechanism were identified in a particular microwave heating(MH)process.Intense discharges were observed when microwaves were imposed on irregularly sized SiC particles,producing tremendous heat that was 8-fold the amount generated in the discharge-free case.Energy efficiency was thereby greatly improved in the electricity-microwaves-effective heat transition.Meanwhile,the dispersed microwave field energy concentrated in small sites,where local temperatures could reach 2000℃–4000℃,with the energy density reaching up to 4.010^(5) W/kg.This can be called a high-energy site phenomenon which could induce further processes or reactions enhancement by coupling effects of heat,light,and plasma.The whole process,including microwave energy concentration and intense site-energy release,shapes a targeted-energy transition mechanism that can be optimized in a controlled manner through morphology design.In particular,the discharge intensity,frequency,and high-energy sites were strengthened through the fabrication of sharp nano/microstructures,conferring twice the energy efficiency of untreated metal wires.The microwave-induced high-energy sites and targeted energy transition provide an important pathway for high-efficiency energy deployment and may lead to promising applications.
