Surface Modification of Polyethylene (PE) Films Using Dielectric Barrier Discharge Plasma at Atmospheric Pressure

Modification of the surface properties of polyethylene （PE） films is studied using air dielectric barrier discharge at atmospheric pressure. The treated samples are examined by Water contact angle measurements, Fourier transform infrared attenuated total reflection spectroscopy （FTIR-ATR）, X-ray photoelectron spectroscopy （XPS） and scanning electron microscopy （SEM）. With the increase in treating time, the water contact angle changes from 93.2° before treatment to a minimum of 53.3° after a treatment for 50 s. Both ATR and XPS results show some oxidized species are introduced into the sample surface by the plasma treatment and the tendency of the water contact angle with the treating time is the same as that of oxygen concentration on the treated sample surface. SEM result shows the surface roughness of PE samples increases with the treatment time increasing.

Experimental Study on Surface Dielectric Barrier Discharge Plasma Actuator with Different Encapsulated Electrode Widths for Airflow Control at Atmospheric Pressure

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.

Diagnosis of Electronic Excitation Temperature in Surface Dielectric Barrier Discharge Plasmas at Atmospheric Pressure

The electronic excitation temperature of a surface dielectric barrier discharge （DBD） at atmospheric pressure has been experimentally investigated by optical emission spectroscopic measurements combined with numerical simulation. Experiments have been carried out to deter- mine the spatial distribution of electric field by using FEM software and the electronic excitation temperature in discharge by calculating ratio of two relative intensities of atomic spectral lines. In this work, we choose seven Ar atomic emission lines at 415.86 nm [（3s^23p^5）5p →（3s^23p^5）4s] and 706.7 nm, 714.7 nm, 738.4 nm, 751.5 nm, 794.8 nm and 800.6 nm [（3s^23p^5）4p → （3s^23p^5）4s] to estimate the excitation temperature under a Boltzmann approximation. The average electron energy is evaluated in each discharge by using line ratio of 337.1 nm （N2（C^3Пu →B3Пg）） to 391.4 nm （N2^＋（B2 ∑u^＋→ ∑g^＋））. Furthermore, variations of the electronic excitation tempera- ture are presented versus dielectric thickness and dielectric materials. The discharge is stable and uniform along the axial direction, and the electronic excitation temperature at the edge of the copper electrode is the largest. The corresponding average electron energy is in the range of 1.6- 5.1 eV and the electric field is in 1.7-3.2 MV/m, when the distance from copper electrode varies from 0 cm to 6 cm. Moreover, the electronic excitation temperature with a higher permittivity leads to a higher dissipated electrical power.

Surface Treatment of Polypropylene Films Using Dielectric Barrier Discharge with Magnetic Field

Atmospheric pressure non-thermal plasma is of interest for industrial applications. In this study, polypropylene （PP） films are modified by a dielectric barrier discharge （DBD） with a non-uniform magnetic field in air at atmospheric pressure. The surface properties of the PP films before and after a DBD treatment are studied by using contact angle measurement, atomic force microscopy （AFM） and X-ray photoelectron spectroscopy （XPS）. The effect of treatment time on the surface modification with and without a magnetic field is investigated. It is found that the hydrophilic improvement depends on the treatment time and magnetic field. It is also found that surface roughness and oxygen-containing groups are introduced onto the PP film surface after the DBD treatment. Surface roughness and oxygen-containing polar functional groups of the PP films increase with the magnetic induction density. The functional groups are identified as C-O, C=O and O-C=O by using XPS analysis. It is concluded that the hydrophilic improvement of PP films treated with a magnetic field is due to a greater surface roughness and more oxygen-containing groups.

Improving the Interfacial Mechanical Property of Fiber Reinforced Cement with Dielectric Barrier Discharge 2: Morphological and Compositional Changes of the Fiber Surface

The morphological and compositional changes of the PP fibers pretreated with dielectric barrier discharge (DBD)are investigated with SEM, XPS and IR. The result shows that the etching effect is the main reason for the improvement of the result of pull-out test of the fibercement composite reported in a previous paper and the oxidation of the fiber surface also favors the adhesion between the fiber and the matrix.

Wire-to-Plate Surface Dielectric Barrier Discharge and Induced Ionic Wind

The electrical and mechanical characteristics of the wire-to-plate surface dielectric barrier discharge and the induced ionic wind are investigated experimentally.The different temporal behaviors in positive and negative half-cycles are studied by time-resolved images.It is shown that the discharge and the light emission are generally stronger in the positive half cycle.The discharge is inhomogeneous and propagates in streamer mode;however,in the negative half-cycle,the discharge appears visually uniformly and operates in the diffuse mode.The surface discharge can produce ionic wind about several m/s above the dielectric surface.There exists an optimal width of the grounded electrode to produce a larger plasma area or active wind region.Increasing of the applied voltage or normalized dielectric constant leads to a larger wind velocity.The performance of ionic wind on flow control is visualized by employing a smoke stream.

Surface Modification of Fluororubber Using Atmospheric Pressure Dielectric Barrier Discharge(DBD)

Fluoride rubber F2311 film, an alternating copolymer of CF2-CFC1 （CTFE） and CH2-CF2 （VF2） components, was treated by atmospheric pressure dielectric barrier discharge （DBD） in air. The surface structure, topography and surface chemistry of the treated F2311 films were characterized by contact angle measurement, atomic force microscopy （AFM）, and X-ray photoelectron spectroscopy （XPS）, respectively. The experimental results showed that a short time air plasma treatment led to morphological, wettability and chemical changes in the F2311 films. The surface hydrophilicity increased greatly after the plasma treatment, the static water contact angle decreased from 98.6° to 32°, and oxygen containing groups （C=O, O-C=O, etc. ） were introduced. Atomic force microscopy revealed that plasma produced by DBD etched F2311 films obviously. The roughness of the samples increased remarkably with the formation of peaks and valleys on the treated surfaces. The increased surface wettability may be correlated with both the introduction of hydrophilic groups due to air plasma oxidation of the surface and the change in surface morphology etched by DBD.

Characteristics of Coaxial Dielectric Barrier Discharge at an Atmospheric Pressure with a Swirling Gas Argon/Oxygen Mixture for the Surface Modification of Polyester Fiber Cord

Abstract A newly developed coaxial dielectric barrier discharge reactor with a length of 1000 mm at an atmospheric pressure was used for plasma treatment of polyester fiber cord in a roll-to-roll manner. In this reactor, swirling mixture gases of oxygen of about 1% and argon with a flow rate of 1.5 L/rain to 2.7 L/min ensured the gas usage sparing, discharge uniformity and efficient fiber surface modification. The water contact angle and surface morphology of the treated fiber were measured. The results show that the surface oxygenation is mainly responsible for the wettability improvement of the fiber cord when passing through the plasma zone at a linear speed of 3 m/min to 8 m/rain. The specimens of modified-polyester fiber reinforced rubber composite were also prepared for the interracial shear strength tests. Furthermore, the effect of adding oxygen into argon discharge on the fiber surface oxidation was correlated with optical emission spectroscopy. Finally, the effect of adding oxygen into argon discharge on the kinetic processes of the active species generation were also analyzed.

Electrical model and experimental analysis of a double spiral structure surface dielectric barrier discharge

A surface dielectric barrier discharge (SDBD) can discharge at atmospheric pressure and produce a large area of low-temperature plasma.An SDBD plasma reactor based on the double spiral structure is introduced in this paper.To study the discharge mechanism of SDBD,an equivalent circuit model was proposed based on the analysis of the micro-discharge process of SDBD.Matlab/Simulink is used to simulate and compare the voltage-current waves,Lissajous and discharge power with the experimental results.The consistency of the results verifies the validity of the SDBD equivalent circuit model.Maxwell software based on the finite elements method is used to analyze the electrostatic field distribution of the device,which can better explain the relationship between the discharge image and the electrostatic field distribution.The combination of equivalent circuit simulation and electrostatic field simulation can provide better guidance for optimizing a plasma generator.Finally,the device is used to treat PM2.5 and formaldehyde.The test results show that the degradation rate of PM2.5 can reach 78% after 24 min,and formaldehyde is about 31.5% after 10m in of plasma treatment.

Surface treatment of titanium dioxide nanopowder using rotary electrode dielectric barrier discharge reactor

Titanium dioxide(Ti O_(2))nanopowder(P-25;Degussa AG)was treated using dielectric barrier discharge(DBD)in a rotary electrode DBD(RE-DBD)reactor.Its electrical and optical characteristics were investigated during RE-DBD generation.The treated TiO_(2)nanopowder properties and structures were analyzed using x-ray diffraction(XRD)and Fourier-transform infrared spectroscopy(FTIR).After RE-DBD treatment,XRD measurements indicated that the anatase peak theta positions shifted from 25.3°to 25.1°,which can be attributed to the substitution of new functional groups in the TiO_(2)lattice.The FTIR results show that hydroxyl groups(OH)at 3400 cm-1 increased considerably.The mechanism used to modify the TiO_(2)nanopowder surface by air DBD treatment was confirmed from optical emission spectrum measurements.Reactive species,such as OH radical,ozone and atomic oxygen can play key roles in hydroxyl formation on the TiO_(2)nanopowder surface.

Improving the energy efficiency of surface dielectric barrier discharge devices for plasma nitric oxide conversion utilizing active flow control

Improving energy efficiency in plasma NO removal is a critical issue.When the surface dielectric barrier discharge(SDBD)device is considered as a combination of multiple plasma actuators,the induced plasma aerodynamic effect cannot be ignored,which can affect the mass transfer,then affect the chemical reactions.Five SDBD devices with different electrode arrangements are studied for NO conversion.They correspond to different flow patterns.We find that the energy efficiency in an SDBD device with a common structure(Type 1)is 28%lower than that in SDBD devices with a special arrangement(Types 2–5).Two reasons may explain the results.First,fewer active species are produced in Type 1 because the development of discharge is hindered by the mutually exclusive electric field forces caused by the symmetrically distributed charged particles.Second,the plasma wind induced by the plasma actuator can enhance the mass and heat transfer.The mixing of reactants and products is better in Types 2–5 than Type 1 due to higher turbulence kinetic energy.

The effects of gas flow pattern on the generation of ozone in surface dielectric barrier discharge

Ozone production utilizing surface dielectric barrier discharge（SDBD） was experimental studied for different flow patterns considering the influences of transversal flow, lateral flow and different lateral flow positions. Results show that the flow patterns have a remarkable impact on the ozone yield by affecting the uniformity and turbulence of gas flow. Meanwhile, distributing the O2 flow rate according to the intensity of the plasma reaction would also increase the generation efficiency of SDBD for ozone production. By improving the uniformity and introducing the lateral flow to the transversal flow, the highest ozone yield was obtained in flow pattern ‘F’. In this case, the ozone yield increased by 28.4% to 131 g kWh-1 from 102.8 g k Wh-1 in flow pattern ‘A’.

Study on the Generation Characteristics of Dielectric Barrier Discharge Plasmas on Water Surface

A new contact glow discharge electrode employed in this study. Because of the strong field the electrode and the water surface, glow discharge on the surface of water was designed and strength in the small air gap formed by plasmas were generated and used to treat waste water. The electric field distribution of the designed electrode model was simulated by MAXWELL 3D~ simulation software, and the discharge parameters were measured. Through a series of experiments, we investigated the impact of optimal designs, such as the dielectric of the electrode, immersion depths, and curvature radii of the electrode on the generation characteristics of plasmas. In addition, we designed an equipotential multi-electrode configuration to treat a Methyl Violet solution and observe the discoloration effect. The experimental and simulation results indicate that the designed electrodes can realize glow discharge with a relative low voltage, and the generated plasmas covered a large area and were in stable state. The efficiency of water treatment is improved and optimized with the designed electrodes.

Study on the transition from filamentary discharge to diffuse discharge by using a dielectric barrier surface discharge device

Discharge characteristics have been investigated in different gases under different pressures using a dielectric barrier surface discharge device. Electrical measurements and optical emission spectroscopy are used to study the discharge, and the results obtained show that the discharges in atmospheric pressure helium and in low-pressure air are diffuse, while that in high-pressure air is filamentary. With decreasing pressure, the discharge in air can transit from filamentary to diffuse one. The results also indicate that corona discharge around the stripe electrode is important for the diffuse discharge. The spectral intensity of N＋ （391.4nm） relative to N2 （337.1 nm） is measured during the transition from diffuse to filamentary discharge. It is shown that relative spectral intensity increases during the discharge transition. This phenomenon implies that the averaged electron energy in diffuse discharge is higher than that in the filamentary discharge.

Improving Hydrophobicity of Glass Surface Using Dielectric Barrier Discharge Treatment in Atmospheric Air

Non-thermal plasmas under atmospheric pressure are of great interest in industrial applications, especially in material surface treatment. In this paper, the treatment of a glass surface for improving hydrophobicity using the non-thermal plasma generated by dielectric barrier discharge （DBD） at atmospheric pressure in ambient air is conducted, and the surface properties of the glass before and after the DBD treatment are studied by using contact angle measurement, surface resistance measurement and wet flashover voltage tests. The effects of the applied voltage and time duration of DBD on the surface modification are studied, and the optimal conditions for the treatment are obtained. It is found that a layer of hydrophobic coating is formed on the glass surface after spraying a thin layer of silicone oil and undergoing the DBD treatment, and the improvement of hydrophobicity depends on DBD voltage and treating time. It seems that there exists an optimum treating time for a certain applied voltage of DBD during the surface treatment, The test results of thermal aging and chemical aging show that the hydrophobic layer has quite stable characteristics. The interaction mechanism between the DBD plasma and the glass surface is discussed. It is concluded that CHa and large molecule radicals can react with the radicals in the glass surface to replace OH, and the hydrophobicity of the glass surface is improved accordingly.

Optimization of Dielectric Barrier Discharge Process for Decolorization of Reactive Blue 19 by Means of Response Surface Methodology

The decolorization of reactive blue 19(RB-19)as a model dye from aqueous solutions has been studied by means of the dielectric barrier discharge(DBD)process.The independent parameters of input power,initial dye concentration and initial pH value were evaluated respectively.Experimental data were optimized by means of a 33 factorial design and response surface methodology(RSM).The dye was quickly removed during the treatment,yielding 96.9%of decolorization efficiency under optimized conditions.Therefore,the total organic carbon(TOC)and chemical oxygen demand(CODcr)results indicated that only the chromophore was destroyed rather than completed oxidation.This was confirmed with UV-vis and tertiary butanol assessments during the DBD treatment.

Square grid pattern with direction-selective surface discharges in dielectric barrier discharge

A new phenomenon that a filament discharged only once instead of twice in a cycle of the applied voltage is observed in a square grid pattern in a dielectric barrier discharge(DBD)with a larger gas gap,which is named intermittent discharge.Its spatiotemporal dynamics and the formation mechanism are studied by the multiple photomultiplier tubes and an intensified charge-coupled device.Corresponding to the positions of spots in the picture with an exposure time of 40 ms,there are some bright spots(discharge spots)and black spots(non-discharged spots)in the instantaneous image with an exposure time of 10μs(a half cycle of the applied voltage).There are at least two bright spots around one black spot and vice versa.The surface discharges(SDS)can be observed between any two adjacent spots.The intensity of the SDSbetween the bright spot and the black spot is 2.5 times greater than that between two adjacent bright spots,which indicates that the SDSare directional-selective.The intermittent discharge with positive(negative)current polarity changes to that with negative(positive)current polarity,after it sustains up to 14 voltage cycles at the longest.The spatial distribution of the electric field component is calculated through COMSOL software to solve the Poisson equation numerically.It is found that the inhomogeneous distribution of surface electric field is caused by the inhomogeneous distribution of wall charges,which leads to direction-selective SDS.The intermittent discharge is formed by the competition between the direction-selective SDSand volume discharges(VDS)in DBD.This is the reason why the intermittent discharge is generated.

Electrical modeling of dielectric barrier discharge considering surface charge on the plasma modified material

We present the variations of electrical parameters of dielectric barrier discharge(DBD)when the DBD generator is used for the material modification,whereas the relevant physical mechanism is also elaborated.An equivalent circuit model is applied for a DBD generator working in a filament discharging mode,considering the addition of epoxy resin(EP)as the plasma modified material.The electrical parameters are calculated through the circuit model.The surface conductivity,surface potential decay,trap distributions and surface charge distributions on the EP surface before and after plasma treatments were measured and calculated.It is found that the coverage area of micro-discharge channels on the EP surface is increased with the discharging time under the same applied AC voltage.The results indicate that the plasma modified material could influence the ignition of new filaments in return during the modification process.Moreover,the surface conductivity and density of shallow traps with low trap energy of the EP samples increase after the plasma treatment.The surface charge distributions indicate that the improved surface properties accelerate the movement and redistribution of charge carriers on the EP surface.The variable electrical parameters of discharge are attributed to the redistribution of deposited surface charge on the plasma modified EP sample surface.

Hollow hexagonal pattern with surface discharges in a？dielectric barrier discharge

The hollow hexagonal pattern involved in surface discharges is firstly investigated in a？dielectric barrier discharge system. The spatiotemporal structures of the pattern are studied using an intensified charge-coupled device and photomultiplier. Instantaneous images taken by an intensified charge-coupled device and optical correlation measurements show that the surface discharges are induced by volume discharges. The optical signals indicate that the discharge filaments constituting the hexagonal frame discharge randomly at the first current pulse or the second pulse, once？or twice. There is no？interleaving of several sub-lattices, which indicates that the ‘memory＇ effect is no longer in force due to surface discharges. By using the emission spectrum method, both the molecule vibration temperature？and electron density of the surface discharges are larger than that of the volume discharges.

Characterization and Properties of Electroless Nickel Plated Poly (ethylene terephthalate) Nonwoven Fabric Enhanced by Dielectric Barrier Discharge Plasma Pretreatment

In order to develop a more economical pretreatment method for electroless nickel plating, a dielectric barrier discharge （DBD） plasma at atmospheric pressure was used to improve the hydrophilicity and adhesion of poly （ethylene terephthalate） （PET） nonwoven fabric. The properties of the PET nonwoven fabric including its liquid absorptive capacity （WA）, aging behavior, surface chemical composition, morphology of the surface, adhesion strength, surface electrical resistivity and electromagnetic interference （EMI）- shielding effectiveness （SE） were studied. The liquid absorptive capacity （WA） increased due to the incorporation of oxygen-containing and nitrogen-containing functional groups on the surface of PET nonwoven fabric after DBD airplasma treatment. The surface morphology of the nonwoven fibers became rougher after plasma treatment. Therefore, the surface was more prone to absorb tin sensitizer and palladium catalyst to form an active layer for the deposition of electroless nickel. SEM and X-ray diffraction （XRD） measurements indicated that a uniform coating of nickel was formed on the PET nonwoven fabric. The average EMI-SE of Ni-plating of PET nonwoven fabric maintained a relatively stable value （38.2 dB to 37.3 dB） in a frequency range of 50 MHz to 1500 MHz. It is concluded that DBD is feasible for pretreatment of nonwoven fabric for electroless nickel plating to prepare functional material with good EMI-SE properties.