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.     

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.     

Grafting Silane onto Silicate Glass Surface Treated by DBD in Air

Dielectric barrier discharge plasma in air was used to modify glass surface to induce the graft of silane onto the treated surface to increase the possibility of biomolecule immobilization. The plasma treated glass had been characterized by scanning electron microscopy （SEM）, Fourier transform infrared attenuated total reflection spectroscopy, X-ray photoelectron spectroscopy （XPS） and surface water contact angle measurement. The validity of grafting silane onto glass surface was approved by the analysis of water contact angle measurement, SEM and XPS. The grafted silane content was measured by visible absorption spectroscopy using acid Orange-7. It is shown that the grafting density of silane for glass samples increases significantly after plasma treatment.     

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.     

The Solubility of Natural Cellulose After DBD Plasma Treatment

Natural cellulose was treated by an atmospheidc DBD plasma. The solubility of cellulose in a diluted alkaline solution after the plasma treatment was investigated. The properties were characterized by X-ray photoelectron spectroscopy （XPS）, Fourier-transform infrared spectroscopy （FTIR） and scanning electron microscopy （SEM）. The results indicated that the surface of cellulose treated by the argon DBD plasma was significantly etched, and the relevant force of hydrogen bonding was decreased. This might be the essential reason for the solubility improvement of natural cellulose in the diluted alkaline solution. Through a comparison of two discharge modes, the atmospheric DBD plasma gun and the parallel plate capacitively coupled DBD plasma, it was found that the atmospheric DBD plasma gun was more effective in fragmentizing the cellulose due to its production of a high energy plasma based on its special structure.     

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.     

Studies of Wettability of Medical PVC by Remote Nitrogen Plasma

The effects of remote nitrogen plasma and nitrogen plasma on medical PVC＇s surface modification are studied. The surface properties are characterized by the contact angle measurement, X-ray photoelectron spectroscopy and scanning electron microscopy. Results show that the remote nitrogen plasma treatments modify the PVC surface in both morphology and composition and the treatment by the remote nitrogen plasma in PVC surface modification is more effective than that by the nitrogen plasma. Remote nitrogen plasma can modify the surface more uniformly. After the PVC surface is treated for 2 man by remote nitrogen plasma, the [w（O）＋ w （N）]/w （C）] value increases from 0.13 to 0.51 and the water contact angle decreases from 89° to 18 .     

Surface Roughness of Various Diamond-Like Carbon Films

Atomic force microscopy is used to estimate and compare the surface morphology of hydrogenated and hydrogen-free diamond-like carbon （DLC） films. The films were prepared by using DC magnetron sputtering of a graphite target, pulsed cathodic carbon arcs, electron cyclotron resonance （ECR）, plasma source ion implantation and dielectric barrier discharge （DBD）. The difference in the surface structure is presented for each method of deposition. The influences of various discharge parameters on the film surface properties are discussed based upon the experimental results. The coalescence process via the diffusion of adsorbed carbon species is responsible for the formation of hydrogen-free DLC films with rough surfaces. The films with surface roughness at an atomic level can be deposited by energetic ion impacts in a highly ionized carbon plasma. The hydrocarbon species dangling bonds created by atomic hydrogen lead to the uniform growth of at the a-C：H film surfaces of the ECR or DBD plasmas     

The Effects of Gas Composition on the Atmospheric Pressure Plasma Jet Modification of Polyethylene Films

Polyethylene（PE） films are treated using an atmospheric pressure plasma jet（APPJ） with He or He/O₂ gas for different periods of time.The influence of gas type on the plasma-polymer interactions is studied.The surface contact angle of the PE film can be effectively lowered to 58° after 20 s of He/O₂ plasma treatment and then remains almost unchanged for longer treatment durations,while,for He plasma treatment,the film surface contact angle drops gradually to 47° when the time reaches 120 s.Atomic force microscopy（AFM） results show that the root mean square（RMS） roughness was significantly higher for the He/O₂ plasma treated samples than for the He plasma treated counterparts,and the surface topography of the He/O₂plasma treated PE films displays evenly distributed dome-shaped small protuberances.Chemical composition analysis reveals that the He plasma treated samples have a higher oxygen content but a clearly lower percentage of-COO than the comparable He/O₂ treated samples,suggesting that differences exist in the mode of incorporating oxygen between the two gas condition plasma treatments.Electron spin resonance（ESR） results show that the free radical concentrations of the He plasma treated samples were clearly higher than those of the He/O₂ plasma treated ones with other conditions unchanged.     

Effect of Low-Frequency Power on Etching Characteristics of 6H-SiC in C4Fs/Ar Dual-Frequency Capacitively Coupled Plasma

Dry etching of 6H silicon carbide （6H-SiC） wafers in a C4Fs/Ar dual-frequency capacitively coupled plasma （DF-CCP） was investigated. Atomic force microscopy （AFM） and X-ray photoelectron spectroscopy （XPS） were used to measure the SiC surface structure and compositions, respectively. Optical emission spectroscopy （OES） was used to measure the relative concentration of F radicals in the plasma. It was found that the roughness of the etched SiC surface and the etching rate are directly related to the power of low-frequency （LF） source. At lower LF power, a smaller surface roughness and a lower etching rate are obtained due to weak bombardment of low energy ions on the SiC wafers. At higher LF power the etching rate can be efficiently increased, but the surface roughness increases too. Compared with other plasma dry etching methods, the DF-CCP can effectively inhibit CχFγ films＇ deposition, and reduce surface residues.     

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.     

Growth of Fluorocarbon Films by Low-Pressure Dielectric Barrier Discharge

Plasma polymerized fluorocarbon （FC） films have been deposited on silicon substrates from dielectric barrier discharge （DBD） plasma of C4Fs at room temperature under a pressure of 25～125 Pa. The effects of the discharge pressure and frequency of power supply on the films have been systematically investigated. FC films with a less cross linked structure may be formed at a relatively high pressure. Increase in the frequency of power supply leads to a significant increase in the deposition rate. Static contact angle measurements show that deposited FC films have a stable, hydrophobic surface property. All deposited films show smooth surfaces with an atomic surface roughness. The relationship between plasma parameters and the properties of the deposited FC films are discussed.     

Plasma-Assisted Chemical Vapor Deposition of Titanium Oxide Films by Dielectric Barrier Discharge in TiCl_4/O_2/N_2 Gas Mixtures

Low-pressure dielectric barrier discharge（DBD） TiCl4/O2and N2 plasmas have been used to deposit titanium oxide films at different power supply driving frequencies. A homemade large area low pressure DBD reactor was applied, characterized by the simplicity of the experimental set-up and a low consumption of feed gas and electric power, as well as being easy to operate. Atomic force microscopy, scanning electron microscopy, energy dispersive spectroscopy,and contact angle measurements have been used to characterize the deposited films. Experimental results show all deposited films are uniform and hydrophilic with a contact angle of about 15 o.Compared to titanium oxide films deposited in TiCl4/O2gas mixtures, those in TiCl4/O2/N2gas mixtures are much more stable. The contact angle of titanium oxide films in TiCl4/O2/N2gas mixtures with the addition of 50% N2 and 20% TiCl4 is still smaller than 20 o, while that of undoped titanium oxide films is larger than 64 owhen they are measured after one week. The low-pressure TiCl4/O2plasmas consist of pulsed glow-like discharges with peak widths of several microseconds, which leads to the uniform deposition of titanium oxide films. Increasing a film thickness over several hundreds of nm leads to the film’s fragmentation due to the over-high film stress. Optical emission spectra（OES） of TiCl4/O2DBD plasmas at various power supply driving frequencies are presented.     

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.     

Surface Modification of Polyethylene by Heparin for Improvement of Antithrombogenicity

The purpose of this paper was to enhance blood compatibility of polyethylene （PE） film. PE film pretreated by argon plasma was subjected to ultraviolet （UV） -induced graft polymerization with Acrylic acid（AAc） （AAc-grafted PE films, PE-g-PAAc） without photo-initiator, then heparin was covalently immobilized on the PE surface （PE-g-HPAAc）. The surface properties and microstructure of PE-g-PAAc and PE-g-HPAAc were studied by static contact angle measurement, atomic force microscope （AFM）, X-ray photoelectron spectroscopy （XPS） and Attenuated total reflectance Fourier transfer infrared spectroscopy （ATR-FTIR）. It was confirmed that AAc and heparin were successfully immobilized onto the surface of PE film. Results of platelet adhesion experiments indicated that the antithrombogenicity of the modified PE film was remarkably improved.     

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.     

The Effect of Air Plasma on Sterilization of Escherichia coli in Dielectric Barrier Discharge

In this work,a Dielectric Barrier Discharge (DBD) air plasma was used to sterilize Escherichia coli (E.coli) on the surface of medical Polyethylene Terephthalate (PET) film.The leakage of cellular DNA and protein by optical absorbance measurement at 260 nm and 280 nm,together with transmission electron microscopy (TEM) about cell morphology were performed after sterilization to analyse inactivation mechanisms.The results indicated that the DBD air plasma was very effective in E.coli sterilization.The plasma germicidal efficiency depended on the plasma treatment time,the air-gap distance,and the applied voltage.Within 5 min of plasma treatment,the germicidal efficiency against E.coli could reach 99.99%.An etching action on cell membranes by electrons,ions and radicals is the primary mechanism for DBD air plasma sterilization,which leads to the effusion of cellular contents (DNA and protein) and bacterial death.     

Synergistic Effect of Atmospheric Pressure Plasma Pre-Treatment on Alkaline Etching of Polyethylene Terephthalate Fabrics and Films

Dyeing of PET materials by traditional methods presents several problems.Plasma technology has received enormous attention as a solution for the environmental problems related with textile surface modifications,and there has been a rapid development and commercialization of plasma technology over the past decade.In this work,the synergistic effect of atmospheric pressure plasma on alkaline etching and deep coloring of dyeing properties on polyethylene terephthalate(PET)fabrics and films was investigated.The topographical changes of the PET surface were investigated by atomic force microscopy(AFM)images,which revealed a smooth surface morphology of the untreated sample whereas a high surface roughness for the plasma and/or alkaline treated samples.The effects of atmospheric pressure plasma on alkaline etching of the structure and properties of PET were investigated by means of differential scanning calorimetry(DSC),the main objective of performing DSC was to investigate the effect of the plasma pre-treatment on the T_g and T_m.Using a tensile strength tester YG065 H and following a standard procedure the maximum force and elongation at maximum force of PET materials was investigated.Oxygen and argon plasma pre-treatment was found to increase the PET fabric weight loss rate.The color strength of PET fabrics was increased by various plasma pre-treatment times.The penetration of plasma and alkaline reactive species deep into the PET structure results in better dyeability and leaves a significant effect on the K/S values of the plasma pre-treated PET.It indicated that plasma pre-treatment has a great synergistic effect with the alkaline treatment of PET.     

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.     

Cu Films Deposited by Unbalanced Magnetron Sputtering Enhanced by ICP and External Magnetic Field Confinement

Metallic copper（Cu） films were deposited on a Si （100） substrate by unbalanced magnetron sputtering enhanced by radio-frequency plasma and external magnetic field confinement. The morphology and structure of the films were examined by scanning electron microscopy （SEM）, atomic force microscope （AFM） and X-ray diffraction （XRD）. The surface average roughness of the deposited Cu films was characterized by AFM data and resistivity was measured by a four-point probe. The results show that the Cu films deposited with radio-frequency discharge enhanced ionization and external magnetic field confinement have a smooth surface, low surface roughness and low resistivity. The reasons may be that the radio-frequency discharge and external magnetic field enhance the plasma density, which further improves the ion bombardment effect under the same bias voltage conditions. Ion bombardment can obviously influence the growth features and characteristics of the deposited Cu films.