This paper describes the realization of a homogeneous dielectric barrier discharge(DBD)in argon at atmospheric pressure.The effect of the morphology of the dielectric surface(especially the dielectric surface covered ...This paper describes the realization of a homogeneous dielectric barrier discharge(DBD)in argon at atmospheric pressure.The effect of the morphology of the dielectric surface(especially the dielectric surface covered by hollow ceramic beads(99%Al_(2)O_(3))with different diameters)on discharge is investigated.With different dielectrics,the argon DBD presents two discharge modes:a filamentary mode and a homogeneous mode.Fast photography shows that the filamentary mode operates in a streamer discharge,and the homogeneous mode operates in a Townsend discharge regime.It is found that a homogeneous discharge can be generated within a certain voltage range.The voltage amplitude range decreases,and the breakdown voltage increases with the increase in the mean diameter of the ceramic beads.Waveforms of the total current and optical emission signal present stochastic pulses per half voltage cycle for the filamentary mode,whereas there is one single hump per half voltage cycle for the homogeneous mode.In the homogeneous mode,the intensity of the optical emission decreases with the mean diameter of the ceramic beads.The optical emission spectrum is mainly composed of atomic lines of argon and the second positive system of molecular nitrogen.It reveals that the electron density decreases with the increasing mean diameter of the ceramic beads.The vibrational temperature increases with the increasing mean diameter of the ceramic beads.It is believed that a large number of microdischarges are formed,and smaller ceramic beads have a larger activation surface area and more point discharge.Electrons liberated in the shallow well and electrons generated from microdischarges can increase the secondary electron emission coefficient of the cathode and provide initial electrons for discharge continuously.Therefore,the breakdown electric field is reduced,which contributes to easier generation of homogeneous discharge.This is confirmed by the simulation results.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
Pattern formation is a very interesting phenomenon formed above a water anode in atmospheric pressure glow discharge.Up to now,concentric-ring patterns only less than four rings have been observed in experiments.In th...Pattern formation is a very interesting phenomenon formed above a water anode in atmospheric pressure glow discharge.Up to now,concentric-ring patterns only less than four rings have been observed in experiments.In this work,atmospheric pressure glow discharge above a water anode is conducted to produce diversified concentric-ring patterns.Results indicate that as time elapses,the number of concentric rings increases continuously and up to five rings have been found in the concentric-ring patterns.Moreover,the ring number increases continuously with increasing discharge current.The electrical conductivity of the anode plays an important role in the transition of the concentric patterns due to its positive relation with ionic strength.Hence,the electrical conductivity of the water anode is investigated as a function of time and discharge current.From optical emission spectrum,gas temperature and intensity ratio related with density and temperature of electron have been calculated.The various concentric-ring patterns mentioned above have been simulated at last with an autocatalytic reaction model.展开更多
An atmospheric pressure argon plasma brush with air addition is employed to treat polyethylene terephthalate(PET)surface in order to improve its hydrophilicity.Results indicate that the plasma plume generated by the p...An atmospheric pressure argon plasma brush with air addition is employed to treat polyethylene terephthalate(PET)surface in order to improve its hydrophilicity.Results indicate that the plasma plume generated by the plasma brush presents periodically pulsed current despite a direct current voltage is applied.Voltage-current curve reveals that there is a transition from a Townsend discharge regime to a glow one during one discharge period.Optical emission spectrum indicates that more oxygen atoms are produced in the plume with increasing air content,which leads to the better hydrophilicity of PET surface after plasma treatment.Besides,an aging behavior is also observed.The hydrophilicity improvement is attributed to the production of oxygen functional groups,which increase in number with increasing air content.Moreover,some grain-like structures are observed on the treated PET surface,and its mean roughness increases with increasing air content.These results are of great importance for the hydrophilicity improvement of PET surface with a large scale.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
Plasma jet is an important low-temperature plasma source in extensive application fields.To promote the production of active oxygen species,oxygen is often introduced into the inert working gas.However,the influence o...Plasma jet is an important low-temperature plasma source in extensive application fields.To promote the production of active oxygen species,oxygen is often introduced into the inert working gas.However,the influence of oxygen content on the discharge characteristics of an argon plasma jet is not clear.Aim to this status,an argon plasma jet in a singleelectrode geometry is employed to investigate the influence of oxygen concentration(CO)on discharge aspects.Results indicate that with increasing CO(≤0.6%),the plume transits from a diffuse morphology to a hollow structure.Electrical and optical measurements reveal that both discharge number per voltage cycle and pulse intensity alter with varying CO.Moreover,discharge morphologies of negative and positive discharges obtained by fast photograph also shift with varying CO.Besides,optical emission spectra are collected to investigate atomic CO,electron density,and electron temperature.The results mentioned above are explained qualitatively,which are believed to be of great significance for the applications of atmospheric pressure plasma jet.展开更多
Atmospheric pressure plasma jets can generate a remote plasma plume,which usually presents a conical or cylindrical morphology.Despite a few morphologies being observed,efforts should be made to obtain more plume stru...Atmospheric pressure plasma jets can generate a remote plasma plume,which usually presents a conical or cylindrical morphology.Despite a few morphologies being observed,efforts should be made to obtain more plume structures because streamer dynamics may be revealed from them.For this purpose,an argon plasma plume excited by a trapezoidal voltage is investigated,which presents two kinds of swells(a hollow swell and a diffuse swell)with increasing voltage amplitude(V).The results indicate that there are two positive discharges(Dand D)and one negative discharge(D)per voltage cycle for both of the swells.With increasing V,the inception voltage and discharge intensity increase for every positive discharge,while they decrease for the negative discharge.Fast photography reveals that the positive streamer(D)leaves different tracks in the two swells,which are curved in the hollow swell and randomly branched in the diffuse swell.The different tracks of Dare explained with the consideration of applied field strength and residual positive ions of D.The existence of residual positive ions is finally verified from optical emission spectra.展开更多
基金supported by National Natural Science Foundation of China(Nos.11875121,51977057,11575050,11875014)the Hebei Province Natural Science Foundation(No.A2022201036)。
文摘This paper describes the realization of a homogeneous dielectric barrier discharge(DBD)in argon at atmospheric pressure.The effect of the morphology of the dielectric surface(especially the dielectric surface covered by hollow ceramic beads(99%Al_(2)O_(3))with different diameters)on discharge is investigated.With different dielectrics,the argon DBD presents two discharge modes:a filamentary mode and a homogeneous mode.Fast photography shows that the filamentary mode operates in a streamer discharge,and the homogeneous mode operates in a Townsend discharge regime.It is found that a homogeneous discharge can be generated within a certain voltage range.The voltage amplitude range decreases,and the breakdown voltage increases with the increase in the mean diameter of the ceramic beads.Waveforms of the total current and optical emission signal present stochastic pulses per half voltage cycle for the filamentary mode,whereas there is one single hump per half voltage cycle for the homogeneous mode.In the homogeneous mode,the intensity of the optical emission decreases with the mean diameter of the ceramic beads.The optical emission spectrum is mainly composed of atomic lines of argon and the second positive system of molecular nitrogen.It reveals that the electron density decreases with the increasing mean diameter of the ceramic beads.The vibrational temperature increases with the increasing mean diameter of the ceramic beads.It is believed that a large number of microdischarges are formed,and smaller ceramic beads have a larger activation surface area and more point discharge.Electrons liberated in the shallow well and electrons generated from microdischarges can increase the secondary electron emission coefficient of the cathode and provide initial electrons for discharge continuously.Therefore,the breakdown electric field is reduced,which contributes to easier generation of homogeneous discharge.This is confirmed by the simulation results.
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financially supported by National Natural Science Foundation of China(Nos.11875121 and 51977057)Natural Science Interdisciplinary Research Program of Hebei University(Nos.DXK201908 and DXK202011)+2 种基金Natural Science Foundation of Hebei Province,China(Nos.A2020201025 and A2019201100)the financial support from Post-Graduate’s Innovation Fund Project of Hebei Province(Nos.CXZZBS2019023 and CXZZBS2019029)Post-Graduate’s Innovation Fund Project of Hebei University(Nos.HBU2021ss063 and HBU2021bs011)。
文摘Pattern formation is a very interesting phenomenon formed above a water anode in atmospheric pressure glow discharge.Up to now,concentric-ring patterns only less than four rings have been observed in experiments.In this work,atmospheric pressure glow discharge above a water anode is conducted to produce diversified concentric-ring patterns.Results indicate that as time elapses,the number of concentric rings increases continuously and up to five rings have been found in the concentric-ring patterns.Moreover,the ring number increases continuously with increasing discharge current.The electrical conductivity of the anode plays an important role in the transition of the concentric patterns due to its positive relation with ionic strength.Hence,the electrical conductivity of the water anode is investigated as a function of time and discharge current.From optical emission spectrum,gas temperature and intensity ratio related with density and temperature of electron have been calculated.The various concentric-ring patterns mentioned above have been simulated at last with an autocatalytic reaction model.
基金supported by National Natural Science Foundation of China(Nos.11875121,11575050 and51977057)the Midwest Universities Comprehensive Strength Promotion Project+4 种基金the Natural Science Foundation of Hebei Province,China(Nos.A2019201100,A2020201025)College Hundred Outstanding Innovative Talent Support Program of Hebei Education Bureau(No.SLRC2017021)Post-graduate’s Innovation Fund Project of Hebei Province(Nos.CXZZBS2019023,CXZZBS2019029)the Natural Science Interdisciplinary Research Program of Hebei University(No.DXK201908)Post-graduate’s Innovation Fund Project of Hebei University(No.HBU2021bs011)。
文摘An atmospheric pressure argon plasma brush with air addition is employed to treat polyethylene terephthalate(PET)surface in order to improve its hydrophilicity.Results indicate that the plasma plume generated by the plasma brush presents periodically pulsed current despite a direct current voltage is applied.Voltage-current curve reveals that there is a transition from a Townsend discharge regime to a glow one during one discharge period.Optical emission spectrum indicates that more oxygen atoms are produced in the plume with increasing air content,which leads to the better hydrophilicity of PET surface after plasma treatment.Besides,an aging behavior is also observed.The hydrophilicity improvement is attributed to the production of oxygen functional groups,which increase in number with increasing air content.Moreover,some grain-like structures are observed on the treated PET surface,and its mean roughness increases with increasing air content.These results are of great importance for the hydrophilicity improvement of PET surface with a large scale.
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 the National Natural Science Foundation of China(Grant Nos.51977057 and 11875121)the Natural Science Foundation of Hebei Province,China(Grant Nos.A2020201025 and A2019201100)+2 种基金the Natural Science Interdisciplinary Research Program of Hebei University(Grant Nos.DXK202011 and DXK201908)Post-graduate’s Innovation Fund Project of Hebei Province,China(Grant Nos.CXZZBS2019023 and CXZZBS2019029)Postgraduate’s Innovation Fund Project of Hebei University(Grant Nos.HBU2021ss063 and HBU2021bs011)。
文摘Plasma jet is an important low-temperature plasma source in extensive application fields.To promote the production of active oxygen species,oxygen is often introduced into the inert working gas.However,the influence of oxygen content on the discharge characteristics of an argon plasma jet is not clear.Aim to this status,an argon plasma jet in a singleelectrode geometry is employed to investigate the influence of oxygen concentration(CO)on discharge aspects.Results indicate that with increasing CO(≤0.6%),the plume transits from a diffuse morphology to a hollow structure.Electrical and optical measurements reveal that both discharge number per voltage cycle and pulse intensity alter with varying CO.Moreover,discharge morphologies of negative and positive discharges obtained by fast photograph also shift with varying CO.Besides,optical emission spectra are collected to investigate atomic CO,electron density,and electron temperature.The results mentioned above are explained qualitatively,which are believed to be of great significance for the applications of atmospheric pressure plasma jet.
基金supported by National Natural Science Foundation of China(Nos.51977057,11875121)the Natural Science Foundation of Hebei Province,China(Nos.A2020201025,A2019201100)+2 种基金the Natural Science Interdisciplinary Research Program of Hebei University(Nos.DXK201908,DXK202011)Post-graduate’s Innovation Fund Project of Hebei Province(Nos.CXZZBS2019023,CXZZBS2019029)Post-graduate’s Innovation Fund Project of Hebei University(Nos.HBU2021ss063,HBU2021bs011)。
文摘Atmospheric pressure plasma jets can generate a remote plasma plume,which usually presents a conical or cylindrical morphology.Despite a few morphologies being observed,efforts should be made to obtain more plume structures because streamer dynamics may be revealed from them.For this purpose,an argon plasma plume excited by a trapezoidal voltage is investigated,which presents two kinds of swells(a hollow swell and a diffuse swell)with increasing voltage amplitude(V).The results indicate that there are two positive discharges(Dand D)and one negative discharge(D)per voltage cycle for both of the swells.With increasing V,the inception voltage and discharge intensity increase for every positive discharge,while they decrease for the negative discharge.Fast photography reveals that the positive streamer(D)leaves different tracks in the two swells,which are curved in the hollow swell and randomly branched in the diffuse swell.The different tracks of Dare explained with the consideration of applied field strength and residual positive ions of D.The existence of residual positive ions is finally verified from optical emission spectra.
