Surface XPS-investigations of tobacco leaves treated with low-temperature plasma

The tobacco leaves were treated with low-temperature plasma in Ar, N2, O2. and air atmospheres at different powers （60-130 W）. The surface-elemental components, their relative contents, and the functional groups of the surface components of the tobacco leaves were determined using XPS （X-ray photoelectron spectroscopy）. The experimental results showed that the percentage of the elements C, N, and O had changed considerably and a large number of polar functional groups containing oxygen atoms were incorporated into the components on the tobacco surfaces. The measurements of the surface contact angle showed that the surface contact angle of the modified tobacco leaves was 0 degree, whereas it was 110 degrees before the plasma treatment. These results indicate that the wettability of the modified tobacco leaves improved dramatically. This work may be significant for future researches on the surface modification of the tobacco leaves.     

Deposition of SiC_xH_yO_z thin film on epoxy resin by nanosecond pulsed APPJ for improving the surface insulating performance

Non-thermal plasma surface modification for epoxy resin(EP)to improve the insulation properties has wide application prospects in gas insulated switchgear and gas insulatedtransmission line.In this paper,a pulsed Ar dual dielectrics atmospheric-pressure plasma jet(APPJ)was used for Si C_xH_yO_zthin film deposition on EP samples.The film deposition was optimized by varying the treatment time while other parameters were kept at constants(treatment distance:10 mm,precursor flow rate:0.6 l min~(-1),maximum instantaneous power:3.08 k W and single pulse energy:0.18 m J).It was found that the maximum value of flashover voltages for negative and positive voltage were improved by 18%and 13%when the deposition time was3 min,respectively.The flashover voltage reduced as treatment time increased.Moreover,all the surface conductivity,surface charge dissipation rate and surface trap level distribution reached an optimal value when thin film deposition time was 3 min.Other measurements,such as atomic force microscopy and scanning electron microscope for EP surface morphology,Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy for EP surface compositions,optical emission spectra for APPJ deposition process were carried out to better understand the deposition processes and mechanisms.The results indicated that the original organic groups(C–H,C–C,C=O,C=C)were gradually replaced by the Si containing inorganic groups(Si–O–Si and Si–OH).The reduction of C=O in ester group and C=C in p-substituted benzene of the EP samples might be responsible for shallowing the trap level and then enhancing the flashover voltage.However,when the plasma treatment time was longer than 3 min,the significant increase of the surface roughness might increase the trap level depth and then deteriorate the flashover performance.     

Low Pressure DC Glow Discharge Air Plasma Surface Treatment of Polyethylene (PE) Film for Improvement of Adhesive Properties

The present work deals with the change in surface properties of polyethylene (PE) film using DC low pressure glow discharge air plasma and makes it useful for technical applications. The change in hydrophilicity of the modified PE film surface was investigated by measuring contact angle and surface energy as a function of exposure time. Changes in the morphological and chemical composition of PE films were analyzed by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The improvement in adhesion was studied by measuring T-peel and lap-shear strength. The results show that the wettability and surface energy of the PE film has been improved due to the introduction of oxygen-containing polar groups and an increase in surface roughness. The XPS result clearly shows the increase in concentration of oxygen content and the formation of polar groups on the polymer surface. The AFM observation on PE film shows that the roughness of the surface increased due to plasma treatment. The above morphological and chemical changes enhanced the adhesive properties of the PE film surfaces, which was confirmed by T-peel and lap-shear tests.     

Effect of Low-Pressure Nitrogen DC Plasma Treatment on the Surface Properties of Biaxially Oriented Polypropylene, Poly (Methyl Methacrylate) and Polyvinyl Chloride Films

In this study, commercial biaxially oriented polypropylene (BOPP), polyvinyl chloride (PVC) and poly (methyl methacrylate) (PMMA) films were treated with nitrogen plasma over different exposure times in a Pyrex tube surrounded by a DC variable magnetic field. The chemical changes that appeared on the surface of the samples were investigated using Fourier transform infrared (FT-IR) spectroscopy and attenuated total reflectance Fourier transform infrared (ATR- FTIR) spectroscopy after treatment for 2 min, 4 min and 6 min in a nitrogen plasma chamber. Effects of the plasma treatment on the surface topographies and contact angles of the untreated and plasma treated films were also analyzed by atomic force microscopy (AFM) and a contact angle measuring system. The results show that the plasma treated films become more hydrophilic with an enhanced wettability due to the formation of some new polar groups on the surface of the treated films. Moreover, at higher exposure times, the total surface energy in all treated films increased while a reduction in contact angle occurred. The behavior of surface roughness in each sample was completely different at higher exposure times.     

Plasma Treatment of Aluminum Using a Surface Barrier Discharge Operated in Air and Nitrogen: Parameter Optimization and Related Effects

This paper presents the results of aluminum surface treatment by diffuse coplanar surface barrier discharge. The goals are to study the effectiveness of the plasma treatment and the dependence of its efficiency on operation parameters, such as sample-to-electrode distance, treatment time or gas atmosphere. Three types of aluminum materials (bricks, sheets and thin films) were tested to ensure the reliability of the treatment. The changes in the surface properties were characterized by the surface free energy, atomic force microscopy, attenuated total reflectance Fourier transform infrared spectroscopy (ATR FTIR) and X-ray photoelectron spec- troscopy (XPS). The influence of aging effect on the treatment was also measured and discussed.     

Surface modification of SUS304 stainless steel by atmospheric pressure Ar/N2/O2 plasma

The surface characteristics of SUS304 stainless steel are investigated before and after surface modification by Ar/N₂/O₂ plasma under atmospheric pressure conditions. It was found that plasma treatment of a stainless steel plate has a significant effect on the wettability, contact angle, and free energy of the SUS304 surface. The contact angle and surface free energy were analyzed. The optimal surface modification parameters are a power of 1000 W, a torch-to-sample distance of 80 mm, a treatment time of 300 s, and an oxygen content of 1.5 wt%. Under these processing conditions, a contact angle of just 1.60° was obtained. The surface morphology, surface element composition, and surface roughness of the treated SUS304 specimens were examined using scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. The results show that the optimal surface modification conditions lead to the formation of fine, uniformly distributed crystallites in the SUS304 microstructure. Moreover, compared to the untreated surface, the treated surface had a significantly lower carbon content and a more uniform distribution of surface peaks.     

Comparison of glow argon plasma-induced surface changes of thermoplastic polymers

Modification of high-density polyethylene (PE), polytetrafluoroethylene (PTFE), polystyrene (PS), polyethyleneterephthalate (PET) and polypropylene (PP) by Ar plasma was studied. The amount of the ablated material was determined by gravimetry. Wettability of polymers after the plasma treatment was determined from the contact angle measurement. The changes in the surface morphology of polymers were observed using atomic force microscopy (AFM). Chemical structure of modified polymers was characterized by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Surface changes were also studied by the determination of electrokinetic potential (ζ-potential). It was found that under the plasma treatment the polymers are ablated and their surface morphology and roughness are changed dramatically. XPS measurements indicate an oxidation of the polymer surface. The plasma treatment results in a dramatic increase of the ζ-potential. EPR data show different radical amount present on the treated surface of all polymers. Most significant changes due to the degradation of polymer chains are observed on PTFE.     

Surface Treatment of Polypropylene Powders Using a Plasma Reactor with a Stirrer

A radio frequency argon plasma reactor with a stirrer was employed for the surface treatment of polypropylene (PP) powders. The changes in the superficial contact angle and the superficial composition of the un-treated and treated PP powders were analyzed by means of water contact angle (WCA) measurement, X-ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The water contact angle changed from the original value of 130.2° before plasma treatment to the value of 73.6° after treatment for 5 minutes. With the increase in plasma treating time, there were a decrease in the water contact angle and an increase in the content of oxygen containing polar functional groups (i.e., C-O, C=O and O-C=O). Both XPS and ATR-FTIR results indicated that the plasma treatment led to the formation of oxygen containing polar functional groups due to oxidation on the surface of the PP powders, and the trend of variation of the water contact angle with plasma treating time was related to the concentration of oxygen atom on the treated PP powders surface. Furthermore, the aging of the plasma-treated PP powders was investigated.     

Pulsed Plasma Polymerization of Perfluorooctyl Ethylene for Transparent Hydrophobic Thin Coatings

Herein we report on the deposition of transparent hydrophobic thin coatings by radio frequency plasma polymerization(PP) of perfluorooctyl ethylene(PFOE) in both pulsed and continuous wave(CW) modes.The chemical compositions of the resulting PP-PFOE coatings were confirmed by means of Fourier transform infrared spectroscopy(FT-IR) and X-ray photoelectron spectroscopy(XPS).The thicknesses and surface morphologies of the coatings were examined using surface plasmon resonance spectroscopy and atomic force microscopy.The surface wetting properties and optical transmittance were measured using a water contact angle goniometer and UV-vis spectroscopy.The FT-IR and XPS data showed that the PP-PFOE coatings deposited in the pulsed mode had a higher retention of CF_2 groups compared to those from the CW mode.While the water contact angle of the freshly deposited PP-PFOE from the pulsed mode showed a decrease from 120 degrees to 111 degrees in the first two days,it then remained almost unchanged up to 45 days.The UV-vis data indicated that a PP-PFOE coating 30.6 nm thick had a light transmittance above 90%in the UV and visible ranges.The deposition rates under various plasma conditions are also discussed.     

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.     

Argon/Hexamethyldisiloxane Plasma Effects on Poly Propylene Film Surface Properties

In this work a DC plasma reactor was used for deposition of plasma polymerized coating from hexamethyldisiloxane–Ar (35/65%) mixture on polypropylene films. Surface energy parameter have been calculated using Owens–Wendt approaches with the sessile drop method are used to obtain the dispersive γ^D and polar γ^P component of surface free energy. The surface morphology of samples were investigated using scanning electron microscope. Also the chemical properties and wetability of prepared samples were tested using Fourier transform infrared spectroscopy and contact angle measurement, respectively.     

Atmospheric Pressure Plasma Jet in Ar and O2/Ar Mixtures： Properties and High Performance for Surface Cleaning＊

An atmospheric pressure plasma jet generated in Ar and O2/Ar mixtures has been investigated by specially designed equipment with double power electrodes at 20~32 kHz, and their effects on the cleaning of surfaces have been studied. Properties of the jet discharge are studied by electrical diagnostics, including the waveform of discharge voltage, discharge current and the Q-V Lissajous figures. The optical emission spectroscopy is used to measure the plasma parameters, such as the excitation temperature and the gas temperature. It is found that the consumed power and the excitation temperature increase with increase of the discharge frequency. On the other hand, at the same discharge frequency, these parameters in O2/Ar mixture plasma are found to be much larger. The effect on surface cleaning is studied from the changes in the contact angle. For Ar plasma jet, the contact angle decreases with increase of the discharge frequency. For O2/Ar mixture plasma jet, the contact angle decreases with increase of discharge frequency up to 26 kHz, however, further increase of discharge frequency does not show further decrease in the contact angle. At the same discharge frequency, the contact angle after O2/Ar mixture plasma cleaning is found to be much lower compared to the case of pure Ar. From the results of quadrupole mass-spectrum analysis, we can identify more fragment molecules of CO and H2O in the emitted gases after O2/Ar plasma jet treatment compared with Ar plasma jet treatment, which are produced by the decomposition of surface organic contaminants during the cleaning process.     

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.     

Surface Sulfonation of Polyvinyl Chloride by Plasma for Antithrombogenicity

To enhance the blood compatibility of Polyvinyl Chloride (PVC) film, the film was modified by SO2/O2 gas plasma treatment. The effect of surface sulfonation of PVC treated by various SO2/O2 gas plasma depended on the volume ratio O2/(SO2 O2). When the volume ratio was 0.5, the effect of sulfonation was the best. Sulfonic acid groups were specifically and efficiently introduced onto the PVC surface, which was proved by X-ray photoelectron spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transfer Infrared (ATR-FTIR) spectroscopy. The surface microstructure of modified PVC film was studied with scanning electron microscopy (SEM). The antithrombogenicity of the samples was determined by the activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT) and plasma recalcification time (PRT) tests and platelet adhesion experiment. The results indicated that the antithrombogenicity of modified PVC was improved remarkably.     

The effect of atmospheric pressure glow discharge plasma treatment on the dyeing properties of silk fabric

In this study, the effects of plasma treatment parameters on surface morphology, chemical constituent, dyeability and color fastness of silk fabric were investigated. Atmospheric pressure glow discharge plasma generated with different applied voltages(0 kV to 45 kV) was used to treat the surface of silk fabrics. C I Natural Yellow 3 was used to dye untreated and plasmatreated silk fabrics. The physical analysis based on scanning electron microscopy showed that the surface of silk fabrics was affected by plasma treatment. The chemical analysis was investigated with x-ray photoelectron spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy. The results showed that the content of C 1s decreased with the increasing applied voltage, the content of N 1s and O 1s increased with the increasing applied voltage. The increasing K/S values represented that the dyeability of silk fabrics was improved after plasma treatment. The color fastness to dry and wet rubbing was decreased after plasma treatment.     

A low power 50 Hz argon plasma for surface modification of polytetrafluoroethylene

The characteristics of a low power 50 Hz argon plasma for surface treatment of polytetrafluoroethylene (PTFE) film is presented in this article. The current–voltage behavior of the discharge and time-varying intensity of the discharge showed that a DC glow discharge was generated in reversed polarity at every half-cycle. At discharge power between 0.5 and 1 W, the measured electron temperature and density were 2–3 eV and ∼10⁸ cm⁻³, respectively. The optical emission spectrum of the argon plasma showed presence of some 'impurity species' such as OH, N₂ and H, which presumably originated from the residual air in the discharge chamber. On exposure of PTFE films to the argon glow plasma at pressure 120 Pa and discharge power 0.5 to 1 W, the water contact angle reduced by 4% to 20% from the original 114° at pristine condition, which confirms improvement of its surface wettability. The increase in wettability was attributed to incorporation of oxygen-containing functional groups on the treated surface and concomitant reduction in fluorine as revealed by the XPS analysis and increase in surface roughness analyzed from the atomic force micrographs. Ageing upon storage in ambient air showed retention of the induced increase in surface wettability.     

Optical Spectroscopic Investigation of Ar/CH_3OH and Ar/N_2/CH_3OH Atmospheric Pressure Plasma Jets

Ar/CH3OH and Ar/N2/CH3OH plasma jets were generated at atmospheric pressure by dual-frequency excitations. Two different cases were studied with focus laid on the generation of CN radicals. In one case Ar gas passed through a bubbler with saturated methanol steam but without addition of N2 （Ar/CH3OH plasma）. In the other case N2 passed through the bubbler with saturated methanol steam （Ar/N2/CH3OH plasma）. The optical emission lines of CN radicals have been observed in these two cases of plasma discharges. The addition of N2 can significantly increase the optical emission intensity of CN bands.     

Cytocompatibility of Ar plasma treated and Au nanoparticle-grafted PE

Polyethylene (PE) was irradiated with inert Ar plasma, and the chemically active PE surface was grafted with Au nanoparticles. The composition and the structure of the modified PE surface were studied using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). Changes in the surface wettability were determined from the contact angle measured in a reflection goniometer. The changes in the surface roughness and morphology were followed by atomic force microscopy (AFM). The modified PE samples were seeded with rat vascular smooth muscle cells (VSMC) or mouse NIH 3T3 fibroblasts, and their adhesion and proliferation were studied. We found that plasma discharge and Au grafting lead to dramatic changes in the surface morphology and roughness of PE. The Au nanoparticles were found not only on the sample surface, but also in the sample interior up to the depth of about 100 nm. In addition, plasma modification of the PE surface, followed with grafting Au-nanoparticles, significantly increased the attractiveness of the PE surface for the adhesion and growth of VSMC, and particularly for mouse embryonic 3T3 fibroblasts.     

Plasma Modified Polypropylene Membranes as the Lithium-Ion Battery Separators

To reduce the thermal shrinkage of the polymeric separators and improve the safety of the Li-ion batteries,plasma treatment and plasma enhanced vapor chemical deposition（PECVD）of SiO_x-like are carried out on polypropylene（PP）separators,respectively.Critical parameters for separator properties,such as the thermal shrinkage rate,porosity,wettability,and mechanical strength,are evaluated on the plasma treated PP membranes.O₂ plasma treatment is found to remarkably improve the wettability,porosity and electrolyte uptake.PECVD SiO_x-like coatings are found to be able to effectively reduce the thermal shrinkage rate of the membranes and increase the ionic conductivity.The electrolyte-philicity of the Si Ox-like coating surface can be tuned by the varying O₂ content in the gas mixture during the deposition.Though still acceptable,the mechanical strength is reduced after PECVD,which is due to the plasma etching.     

Surface Activation of Plane and Curved Automotive Polymer Surfaces by Using a Fittable Multi-Pin DBD Plasma Source

In this work, surface activation of automotive polymers using atmospheric pressure plasmas was investigated. The aim was to increase the polar fraction of the surface energy of both plane and convex polymer devices with a radius in the range of 30 mm. For this purpose, a fittable low temperature atmospheric pressure plasma source based on capacitively coupled multi-pin electrodes was set up and applied. Each single electrode generates a treatment spot of approximately 2 cm2 with a tunable power density of up to 1.4 W/cm2. The surface energy was evaluated by contact angle measurements. After treatment at a low energy density of 1.01 J/cm2, the polar fraction of the surface energy of the investigated polymers was increased by a factor of 3.3 to 132, depending on the polymer materials. It was shown that by applying the presented fittable plasma source, this effect is independent of the surface radius of the polymer sample.