Enhanced by Dielectric Barrier Discharge Plasma Pretreatment Irradiated by High-Intensity Pulsed Ion Beam

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 air-plasma 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 to 37.3 dB) in a frequency range of 50 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.     

Surface Treatment of Polyethylene Terephthalate Film Using Atmospheric Pressure Glow Discharge in Air

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     

Exploration to generate atmospheric pressure glow discharge plasma in air

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 ram.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.     

Investigation of Atmospheric Pressure Plasma Discharge and Its Application to Surface Modification of Blood-Filtering Material

Melt-blown polybutylene terephthalate (PBT) nonwoven materials treated by using plasma is regarded as one of the excellent materials to filter white blood cells (WBC) from blood.In this paper, dielectric barrier discharge (DBD) plasma source at an improved quasi-stable atmospheric pressure is achieved when discharge voltage, discharge current, and gap between the electrodes are carefully controlled. This plasma source has been used to modify the surface of PBT melt-blown nonwoven materials. Experimental results indicate that both the wettablity and permeation of treated PBT melt-blown nonwoven materials are greatly improved.     

Investigation into wideband electromagnetic stealth device based on plasma array and radar-absorbing materials

Manipulation of electromagnetic waves is essential to various microwave applications, and absorbing devices composed of low-pressure gas discharge tubes and radar-absorbing materials (RAM) can bring new solutions to broadband electromagnetic stealth. The microwave transmission method is used to measure the physical parameters of the plasma unit. The designed structure exhibits superior absorption performance and radar cross-section (RCS) reduction capability in the 2–18 GHz band, with unique absorption advantage in the S and C frequency bands. It is found that the combination of the plasma and the RAM can significantly broaden the absorption frequency band and improve the absorption performance with excellent synergistic stealth capability. Experimental and simulation results present that broadband, wide-angle, tunable electromagnetic wave absorption and RCS reduction can be achieved by adjusting the spatial layout of the combined plasma layer and the type of RAMs, which creates opportunities for microwave transmission and selective stealth of equipment. Therefore, the wave manipulation by combined plasma array and RAM provides a valuable reference for developing numerous applications, including radar antenna stealth, spatial filter, and high power microwave shielding.     

Research on corona discharge suppression of high-voltage direct-current transmission lines based on dielectric-film-covered conductor

Corona discharge suppression for high-voltage direct-current(HVDC) transmission lines at line terminals such as converter stations is a subject that requires attention. In this paper, a method based on a conductor covered with dielectric film is proposed and implemented through a bench-scale setup. Compared with the bare conductor, the corona discharge suppression effect of the dielectricfilm-covered conductor under positive polarity is studied from the composite field strength and ion current density using a line-plate experimental device. The influences of film thickness and film material on the corona discharge suppression effect are investigated. The charge accumulation and dissipation characteristics of different film materials are also studied. The results show that the conductor covered with dielectric film has excellent ability to inhibit corona discharge. The groundlevel composite field strength of the conductor covered with dielectric film is lower than its nominal field strength, and its ion current density is at the n A m~(-2) level. The corona threshold voltage can be promoted by increasing the film thickness, but the ability to inhibit corona discharge becomes weak.The larger the surface electric field strength, the more charge accumulated, but the faster the charge dissipation rate. Compared with polyvinyl chloride film, cross-linked polyethylene film has stronger charge accumulation ability and slower charge dissipation rate, which can better restrain the corona discharge of HVDC transmission lines.     

Improving the surface flashover performance of epoxy resin by plasma treatment:a comparison of fluorination and silicon deposition under different modes

This work treats the Al2O3-ER sample surface using dielectric barrier discharge fluorination(DBD-F),DBD silicon deposition(DBD-Si),atmospheric-pressure plasma jet fluorination(APPJ-F)and APPJ silicon deposition(APPJ-Si).By comparing the surface morphology,chemical components and electrical parameters,the diverse mechanisms of different plasma modification methods used to improve flashover performance are revealed.The results show that the flashover voltage of the DBD-F samples is the largest(increased by 21.2％at most),while the APPJ-F method has the worst promotion effect.The flashover voltage of the APPJ-Si samples decreases sharply when treatment time exceeds 180 s,but the promotion effect outperforms the DBD-Si method during a short modified time.For the mechanism explanation,firstly,plasma fluorination improves the surface roughness and introduces shallow traps by etching the surface and grafting fluorine-containing groups,while plasma silicon deposition reduces the surface roughness and introduces a large number of shallow traps by coating SiOx film.Furthermore,the reaction of the DBD method is more violent,while the homogeneity of the APPJ modification is better.These characteristics influence the effects of fluorination and silicon deposition.Finally,increasing the surface roughness and introducing shallow traps accelerates surface charge dissipation and inhibits flashover,but too many shallow traps greatly increase the dissipated rate and facilitate surface flashover instead.     

Influence of dielectric barrier discharge treatment on mechanical and dyeing properties of wool

Physical and chemical properties of wool surface significantly affect the absorbency,rate of dye bath exhaustion and fixation of the industrial dyes.Hence,surface modification is a necessary operation prior to coloration process in wool wet processing industries.Plasma treatment is an effective alternative for physiochemical modification of wool surface.However,optimum processing parameters to get the expected modification are still under investigation,hence this technology is still under development in the wool wet processing industries.Therefore,in this paper,treatment parameters with the help of simple dielectric barrier discharge plasma reactor and air as a plasma gas,which could be a promising combination for treatment of wool substrate at industrial scale were schematically studied,and their influence on the water absorbency,mechanical,and dyeing properties of twill woven wool fabric samples are reported.It is expected that the results will assist to the wool coloration industries to improve the dyeing processes.     

Properties of the acrylic acid polymers obtained by atmospheric pressure plasma polymerization

Plasma polymers of acrylic acid were obtained using an atmospheric pressure discharge system. The plasma polymerization reactor uses a dielectric barrier discharge, with the polyethylene terephthalate dielectric acting as substrate for deposition. The plasma was characterized by specific electrical measurements, monitoring the applied voltage and the discharge current. Based on the spatially resolved optical emission spectroscopy, we analyzed the distribution of the excited species in the discharge gap, specific plasma temperatures (vibrational and gas temperatures) being calculated with the Boltzmann plot method. The properties of the plasma polymer films were investigated by contact angle measurements, infrared and UV-Vis spectroscopy, scanning electron microscopy. The films produced by plasma polymerization at atmospheric pressure showed a hydrophilic character, in correlation with the strong absorbance of OH groups in the FTIR spectrum. Moreover, the surface of the plasma polymers at micrometric scale is smooth and free of defects without particular features.     

Electromagnetic Pulses Generated From Laser Target Interactions at Shenguang Ⅱ Laser Facility

Significant electromagnetic pulses(EMP) can be generated by the intensive laser irradiating solid targets in inertial confinement fusion(ICF). To evaluate the EMP intensity and distribution in and outside the laser chamber, we designed and fabricated a discone antenna with ultra-wide bands of over 10 GHz. The return loss(S11parameter) of this antenna was below-10 d B and could even achieve under-30 d B at 3.1 GHz. The EMP intensity in this study at80 cm and 40 cm away from the target chamber center(TCC) reached 400 k V/m and 2000 k V/m.The current results are expected to offer preliminary information to study physics regarding laser plasma interactions and will also lay experimental foundation for EMI shielding design to protect various diagnostics.     

Study on water treatment effect of dispersion discharge plasma based on flowing water film electrode

To improve the utilization rate of plasma active species,in this study,a closed non-uniform air gap is formed by a flowing water film electrode and a sawtooth insulating dielectric layer to realize the diffuse glow discharge in the atmosphere.Firstly,the electric field distribution characteristics of non-uniform air gap in the sawtooth dielectric layer are studied,and the influence of aspect ratio on the characteristics of diffuse discharge plasma is discussed.Subsequently,the effects of wire mesh,the inclination angle of the dielectric plate,and liquid inlet velocity on the flow characteristics of the water film electrode are analyzed.The results show that the non-uniform electric field distribution formed in the sawtooth groove can effectively inhibit the filamentous discharge,and the 1 mm flowing water film is directly used as the electrode,and high-active plasma is formed directly on the lower surface of the water film.In addition,a plasma flowing water treatment device is built to treat the methyl orange solution and observe its decolorization effect.The experimental results show that after 50 min of treatment,the decolorization rate of the methyl orange solution reaches 96％,which provides a new idea for industrial applications of wastewater treatment.     

Effect of Atmospheric Pressure Plasma and Subsequent Enzymatic Treatment on Flax Fabrics

The objective is to investigate the effect of atmospheric pressure dielectric barrier discharge (APDBD) plasma and subsequent cellulase enzyme treatment on the properties of flax fabrics. The changes of surface morphology and structure, physico-mechanical properties, hy?drophilicity, bending properties, whiteness, and dyeing properties of the treated substrate were investigated. The results indicated that atmospheric pressure dielectric barrier discharge plasma pre-treatment and subsequent cellulase enzyme treatment could diminish the hairiness of flax fab?rics, endowing the flax fabrics with good bending properties, water uptake and fiber accessibility while keeping their good mechanical properties compared with those treated with cellulase enzyme alone.     

On surface elementary processes and polymer surface modifications induced by double pulsed dielectric barrier discharge

In this paper, polyethylene terephthalate and polyethylene films were plasma treated using a dielectric barrier discharge (DBD), which presents a second current pulse with inverse polarity induced at the decreasing applied voltage flank in addition to the main current pulse. The surface modifications of polymer samples were pointed out by two complementary methods: the contact angle method and atomic force microscopy (AFM) technique. The influence of the voltage pulse parameters as width, falling rate and frequency on the secondary discharge formation was studied and correlated with polymer surface modifications. The plasma treatment is improved when the discharge is driven by a voltage pulses with very fast falling flank. After plasma treatment, roughness of the PE films is not considerably changed; only topographical modifications of PE treated samples being observed, while treated PET surfaces present an increased roughness and a new granular structure, with much smaller features compared to the pristine ones.     

A direct current glow discharge plasma source for inner surface modification of metallic tube

A dc glow discharge plasma source was developed for inner surface modification of metallic tubes with an inner diameter of 10 mm. A tungsten wire of 30 μm thick was stretched inside the tube to form coaxial electrodes. DC glow discharge plasma was generated inside the tube by applying a negative high dc voltage to the tube. It was found that the length of the cylindrical plasma bulk depends linearly on the applied voltage. The electron excitation temperature of Ar plasma was measured as 12830 ± 550 K by optical emission spectroscopy method. As a preliminary application, diamond-like carbon (DLC) films were deposited onto the inner surface of stainless steel tube of 100 mm in length and 10 mm in inner diameter by using CH₄/Ar mixture with 40% CH₄ at 40 Pa pressure. The chemical structure of the DLC film deposited on the substrate was analyzed by Raman spectroscopy. The integrated intensity ratio (I_D:I_G) was obtained as 1.62 from the Raman spectra. The thickness of the DLC film deposited on the substrate was estimated as 1.5 μm by scanning electron microscopy (SEM) observation.     

Improvement on Diamond Nucleation Treated by Pulsed Arc Discharge Plasma

A technique of improvement on diamond nucleation based on pulsed arc discharge plasma at atmospheric pressure was developed. The pulsed arc discharge was induced respectively by nitrogen, argon and methanol gas. After the arc plasma pretreatment, a nucleation density higher than 10^10 cm^-2 may be obtained subsequently in chemical vapor deposition (CVD) on a mirror-polished silicon substrate without any other mechanical treatment. The effects of the arc discharge plasma on the diamond nucleation were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR) and Raman spectroscopy. The enhancement of nucleation is postulated to be a result of the formation of carbonlike phase materials or nitrogenation on the substrate surface without surface defect produced by arc discharge.     

The effect of substrate holder size on the electric field and discharge plasma on diamond-film formation at high deposition rates during MPCVD

The effect of the substrate holder feature dimensions on plasma density(ne), power density(Qmw) and gas temperature(T) of a discharge marginal plasma(a plasma caused by marginal discharge) and homogeneous plasma were investigated for the microwave plasma chemical vapor deposition process. Our simulations show that decreasing the dimensions of the substrate holder in a radical direction and increasing its dimension in the direction of the axis helps to produce marginally inhomogeneous plasma. When the marginal discharge appears, the maximum plasma density and power density appear at the edge of the substrate. The gas temperature increases until a marginally inhomogeneous plasma develops. The marginally inhomogeneous plasma can be avoided using a movable substrate holder that can tune the plasma density, power density and gas temperature. It can also ensure that the power density and electron density are as high as possible with uniform distribution of plasma. Moreover, both inhomogeneous and homogeneous diamond films were prepared using a new substrate holder with a diameter of 30 mm. The observation of inhomogeneous diamond films indicates that the marginal discharge can limit the deposition rate in the central part of the diamond film. The successfully produced homogeneous diamond films show that by using a substrate holder it is possible to deposit diamond film at 7.2 μm h~(–1)at 2.5 kW microwave power.     

Surface Modification of Polyimide Film by Dielectric Barrier Discharge at Atmospheric Pressure

In this paper,polyimide(PI)films are modified using an atmospheric pressure plasma generated by a dielectric barrier discharge(DBD)in argon.Surface performance of PI film and its dependence on exposure time from 0 s to 300 s are investigated by dynamic water contact angle(WCA),field emission scanning electron microscopy(FESEM),and Fourier transform infrared spectroscopy in attenuated total multiple reflection mode(FTIR-ATR).The study demonstrates that dynamic WCA exhibits a minimum with 40 s plasma treatment,and evenly distributed nano-dots and shadow concaves appeared for 40 s and 12 s Ar plasma treatment individually.A short period of plasma modification can contribute to the scission of the imide ring and the introduction of C-O and C=O(-COOH)by detailed analysis of FTIR-ATR.     

Influence of air addition on surface modification of polyethylene terephthalate treated by an atmospheric pressure argon plasma brush

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.     

Insight into the remaining high surface energy of atmospheric DBD plasma-treated polyethylene web after three months' aging

In this paper, we report the modification of polyethylene(45 μm in thickness) webs through a roll-to-roll dielectric barrier discharge plasma treatment in an open atmospheric environment.Our work differs from the normal adopted corona discharge treatment at an atmospheric pressure, in that three monomers: allylamine, acrylic acid, and ethanol, are inlet into the discharge zone by argon(Ar) carrier gas. As a comparison, Ar plasma treatment is also carried out. We focus on the aging properties of treated plastics in the open air. It is found that the modified webs can retain the surface energy as high as 50.0?±?1 mN m~(-1) for more than three months. After characterization of the as-prepared and aged samples by the surface roughness, the wettability, and the chemical structure, the mechanism of retaining high surface energy is then presumed. We think that the initial high surface energy just after plasma treatment is correlated to the grafted functional groups, while the over 50.0 mN m~(-1) remaining surface energy after three month aging is due to the stable concentrations of oxygen-contained and nitrogencontained groups by post-reaction on the surfaces.     

Classification and uniformity optimization of mesh-plate DBD and its application in polypropylene modification

The classification of spatial characteristics and discharge modes of dielectric barrier discharge (DBD) are gaining increasing attention in industrial applications, especially in the field of surface treatment of materials. In this work, gray level histogram (GLH) and Fourier energy spectrum based on the digital image processing technology are applied to investigate the spatial structure and discharge mode of mesh-plate DBD. The coefficient of variation (CV) is calculated to describe the uniformity of the discharge. The results show that the discharge mode of mesh-plate DBD changes from periodic discharge to filamentary discharge when the applied voltage increases from 11–15 kV. Moreover, a more regular spatial structure is obtained under lower applied voltages during the discharge process. It is also found that the apertures of mesh electrodes which are below 1mm have smaller values of CV compared to plate electrodes, indicating more uniform discharge. Finally, polypropylene is treated by mesh-plate DBD for surface modification. The hydrophilicity is significantly improved as the water contact angle decreased by 64°, and the dyeing depth is also enhanced.