Modification of surface properties of polypropylene (PP) film using DC glow discharge air plasma

The industrial use of polypropylene (PP) films is limited because of undesirable properties such as poor adhesion and printability. In the present study, a DC glow discharge plasma has been used to improve the surface properties of PP films and make it useful for technical applications. The change in hydrophilicity of modified PP film surface was investigated by contact angle (CA) and surface energy measurements as a function of exposure time. In addition, plasma-treated PP films have been subjected to an ageing process to determine the durability of the plasma treatment. Changes in morphological and chemical composition of PP 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 surface hydrophilicity has been improved due to the increase in the roughness and the introduction of oxygen-containing polar groups. The AFM observation on PP film shows that the roughness of the surface increased due to plasma treatment. Analysis of chemical binding states and surface chemical composition by XPS showed an increase in the formation of polar functional groups and the concentration of oxygen content on the plasma-processed PP film surfaces. T-peel and lap shear test for adhesion strength measurement showed that the adhesion strength of the plasma-modified PP films increased compared with untreated films surface.     

Preparation of ZnO nanopowders by thermal plasma and characterization of photo-catalytic property

Nano-sized zinc oxide (ZnO) powders were prepared via a thermal plasma process from micro-sized zinc powder while oxygen was employed as a reaction gas. Two different carrier gases, oxygen and argon, were evaluated and the flow rate of the reaction gas was controlled. The photo-catalytic activities of ZnO powders were evaluated by measuring the degradation of methylene blue (MB) in water under the UV and visible region. The prevailing goal of this study is to improve the photo-catalytic activity of nano-sized ZnO powders for the removal of environmental pollutants. The ZnO nanopowders were characterized by XRD, SEM, BET, and UV-vis spectrometry. Their mean crystallites sizes ranged from 26.5 nm to 48.6 nm. It was confirmed by a XRD analysis that the ZnO nanopowders had a high quality wurtzite structure. SEM and XRD results show that the size of the particles synthesized increased with an increase of the flow rate of the oxygen reaction gas. The powder obtained using the argon carrier gas with higher oxygen reaction gas flow rate was more rod-shape. The MB decomposition rates of the obtained ZnO nanopowders were studied under the UV and visible region. In the UV region, synthesized ZnO could decompose MB as well as commercial ZnO. However, in the visible region, the MB decomposition rate obtained using ZnO was much higher than that by commercial ZnO.     

Synthesis of nano-sized antimony-doped tin oxide (ATO) particles using a DC arc plasma jet

Nano-sized antimony-doped tin oxide (ATO) particles were synthesized using DC arc plasma jet. The precursors SnCl₄ and SbCl₅ were injected into the plasma flame in the vapor phase. ATO powder could conveniently be synthesized without any other post-treatment in this study. To control the doping amount of antimony in the ATO particles, the Sb/Sn molar ratio was used as an operating variable. To study the effect of carrier gas on the particle size, argon and oxygen gases were used. The results of XRD and TGA show that all Sb ions penetrated the SnO₂ lattice to substitute Sn ions. With the increased SbCl₅ concentration in source material, the Sb doping level was also increased. The size of the particles synthesized using the argon carrier gas was much smaller than that of the particles prepared using the oxygen carrier gas. For the argon gas, PSA results and SEM images reveal that the average particle size was 19 nm. However, for the oxygen gas, the average particle size was 31 nm.     

Long-distance oxygen plasma sterilization: Effects and mechanisms

The distribution of electrons, ions and oxygen radicals in long-distance oxygen plasma and the germicidal effect (GE) of Escherichia coli on the surface of medical poly(tetrafluoroethylene) (PTFE) film were studied. The quantity of protein leakage and the production of lipid peroxide in bacterial suspension as well as the state of DNA were measured after sterilization to analyse the inactivation mechanisms. The results showed that the concentration of electrons and ions decreased rapidly with increasing the distance from the center of induction coil, which approximated to 0 at 30 cm, whereas the concentration of oxygen radicals reduced slowly, i.e. decreased 30% within 40 cm. GE value reached 3.42 in the active discharge zone (0 cm) and exceeded 3.32 within 40 cm when plasma treatment parameters were set as follows: plasma rf power at 100 W, treatment time at 60 s and oxygen flux at 40 cm³/min. Fast etching action on cell membrane by electrons, ions and attacking polyunsaturation fatty acid (PUFA) in cell membrane by oxygen radicals are primary reasons of oxygen plasma sterilization in the active discharge and the afterglow zone, respectively. The GE of UV radiation in long-distance oxygen plasma is feebleness.     

Synthesis of nanocrystalline magnesium nitride (Mg3N2) powder using thermal plasma

Nanocrystalline magnesium nitride (Mg₃N₂) powder was synthesized from bulk magnesium by thermal plasma at atmospheric pressure. Magnesium vapor was generated through heating the bulk magnesium by DC plasma jet and reacted with ammonia gas. Injecting position and flow rates of ammonia gas were controlled to investigate an ideal condition for Mg₃N₂ synthesis. The synthesized Mg₃N₂ was cooled and collected on the chamber wall. Characteristics of the synthesized powders for each experimental condition were analyzed by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and thermogravity analysis (TGA). In absence of NH₃, magnesium metal powder was formed. The synthesis with NH₃ injection in low temperature region resulted in a formation of crystalline magnesium nitride with trigonal morphology, whereas the mixture of magnesium metal and amorphous Mg₃N₂ was formed when NH₃ was injected in high temperature region. Also, vaporization process of magnesium was discussed.     

Stability test and EXAFS characterization of plasma prepared Pd/HZSM-5 catalyst for methane combustion

Pd/HZSM-5 catalysts prepared via glow discharge plasma reduction followed by calcination thermally show excellent enhanced stability for methane combustion. EXAFS characterization confirms that argon glow discharge reduces Pd/HZSM-5 catalyst effectively at close to room temperature. After thermal calcination of argon plasma reduced Pd/HZSM-5 catalyst under air, specific tetragonal PdO species are formed. This kind of active PdO species keeps stable during methane combustion, which leads to the observed excellent stability of plasma prepared Pd/HZSM-5 catalyst. EXAFS characterization also shows argon plasma reduction can help to remove Cl, which has a negative effect on catalysts properties.     

Physical-morphological and chemical changes leading to an increase in adhesion between plasma treated polyester fibres and a rubber matrix

The effects of plasma treatment, used to increase adhesion strength between poly(ethylene terephtalate) (PET) fibres and a rubber matrix, were investigated and compared. Morphological changes as a result of atmospheric plasma treatment were observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Wettability analysis using a surface energy evaluation system (SEE system) suggested that the plasma treated fibre was more wetting towards a polar liquid. When treated, these fibres showed a new lamellar crystallization, as shown by a new melting peak using differential scanning calorimetry (DSC). X-ray photoelectron spectroscopy (XPS) has been used to study the chemical effect of inert (argon), active and reactive (nitrogen and oxygen) microwave-plasma treatments of a PET surface. Reactive oxygen plasma treatment by a de-convolution method shows new chemical species that drastically alter the chemical reactivity of the PET surface. These studies have also shown that the surface population of chemical species formed after microwave-plasma treatment is dependent on the plasma gas. All these changes cause better adhesion strength of the PET fibres to the rubber matrix.     

Morphological and surface compositional changes in poly(lactide-co-glycolide) tissue engineering scaffolds upon radio frequency glow discharge plasma treatment

Chemical functionalisation of polymeric scaffolds with functional groups such as amine could provide optimal conditions for loading of signalling biomolecules over the entire volume of the porous scaffolds. Three-dimensional (both surface and bulk) functionlisation of large volume scaffolds is highly desirable, but preferably without any change to the basic morphological, structural and bulk chemical properties of the scaffolds. In this work, we have carried out and compared treatments of poly(lactide-co-glycolide) tissue engineering scaffolds by two methods, that is, a wet chemical method using ethylenediamine and a glow discharge plasma method using heptylamine as a precursor. The samples thus prepared were analysed by scanning electron microscopy and X-ray photoelectron spectroscopy. The plasma treatment generated amide and protonated amine (NH⁺) groups which were present in the bulk and on the surface of the scaffold. Amination also occurred for the wet chemical treatments but the structural and chemical integrity were adversely affected.     

Plasma-induced graft-polymerization of polyethylene glycol acrylate on polypropylene substrates

A detailed study of argon plasma-induced graft-polymerization of polyethylene glycol acrylate (PEGA) on polypropylene (PP) substrates (membranes and films) is presented. The process consists of four steps: (a) plasma pre-activation of the PP substrates; (b) immersion in a PEGA solution; (c) argon plasma-induced graft-polymerization; (d) washing and drying of the samples. Influence of the solution and plasma parameters on the process efficiency evaluated in terms of amount of grafted polymer, coverage uniformity and substrates wettability, are investigated. The plasma-induced graft-polymerization of PEGA is then followed by sample weighting, water droplet adsorption time and contact angle measurements, attenuated total reflection infrared spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analyses. The stability of the obtained thin films was evaluated in water and in phosphate buffer saline (PBS) at 37 °C. Results clearly indicates that plasma-induced graft-polymerization of PEGA is a practical methodology for anti-fouling surface modification of materials.     

Simulation of the transport of sputtered atoms and effects of processing conditions

Sputter deposition is a complex process; it is obvious that the energy and direction of the particles arriving at the substrate is in close relation with the transport process from the target to the substrate, it is desirable to model this transport of atoms through the background gas. The transport of sputtered Ag atoms during sputter deposition through the gas phase in the facing targets sputtering system studied by Monte Carlo simulation is presented. The model calculates the flux of the atoms arriving at the substrate, their energy, direction and number of collisions they underwent. The dependence of the deposition rates of Ag atoms on the gas pressure and the distance between the targets and substrate were investigated.     

Effect of high energy ion irradiation on silicon substrate in a pulsed plasma device

We have performed an experimental analysis on the investigation of high energy ion beam irradiation on Si(1 0 0) substrates at room temperature using a low energy plasma focus (PF) device operating in methane gas. The surface modifications induced by the ion beams are characterized using standard surface science diagnostic tools, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), photothermal beam deflection, energy-dispersive X-ray (EDX) analysis and atomic force microscope (AFM) and the results are reported. In particular, it has been found that with silicon targets, the application of PF carbon ion beams results in the formation of a surface layer of hexagonal (6H) silicon carbide, with embedded self-organized step/terrace structures.     

Surface modification of the nanoparticles by an atmospheric room-temperature plasma fluidized bed

Using hexamethyldisiloxane (HMDSO) monomer, the magnetic nanoparticles (NPs) of nickel oxide (NiO) were modified by using an atmospheric room-temperature plasma fluidized bed (ARPFB). The plasma gas temperature of the ARPFB was not higher than 325 K, which was favorable for organic polymerization. The plasma optical emission spectrum (OES) of the gas mixture consisting of argon (Ar) and HMDSO was recorded by a UV-visible monochromator. The as-treated NPs were characterized by means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that the assembling NPs were isolated greatly after modified by the organosilicon polymer. Moreover, this treatment process changed the wettability of the NPs from super-hydrophilicity to super-hydrophobicity, and the contact angle (CA) of water on the modified NPs surface exceeded 150°. Therefore, the ARPFB is a prospective technology for the NPs surface modification according to the different requirements.     

Surface analytical studies of Ar-plasma etching of thin heptadecafluoro-1-decene plasma polymer films

An audio-frequency plasma polymerization set-up with a planar plasma source was used to deposit thin heptadecafluoro-1-decene (HDFD) plasma polymer films. The morphology and chemical structure of the films after deposition were compared with the state of the film after a subsequent Ar-plasma treatment by means of in situ Fourier transform infrared reflection absorbance spectroscopy (FT-IRRAS), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and atomic force microscopy (AFM) as well as contact angle measurements. The results revealed the correlation of wettability of the model Teflon-like films with change of surface chemistry and surface topography as a result of Ar-plasma treatment.     

Short-time plasma surface modification of HDPE powder in a Plasma Downer Reactor - process, wettability improvement and ageing effects

The effectiveness of improving the wettability of HDPE powders within less than 0.1 s by plasma surface modification in a Plasma Downer Reactor is investigated. A correlation is revealed between the XPS results (O/C-ratio) and the wettability (contact angle, polar surface tension by capillary rise method). The O₂-content in the plasma feed gas has been adjusted for best wettability properties. XPS results indicate the formation of CO and COOH functional groups on the powder surface. The O/C-ratio increased from 0.0 (no oxygen on the non-treated powder) up to 0.15 for the plasma treated HDPE powder surface. With pure O₂-plasma treatment, a water contact angle reduction from >90° (no water penetration into the untreated PE powder) down to 65° was achieved. The total surface free energy increased from 31.2 to 45 mN/m. Ageing of treated powders occurs and proceeds mostly within the first 7 days of storage. Contact angle measurements and O1s/O2s intensity ratio data support that ageing is mainly a diffusion-controlled process. Nevertheless, XPS results show the presence of oxygen functional groups even after 40 days, which explains why the powder is still dispersible in water without any addition of surfactants.     

Laser-produced plasma ion characteristics in laser ablation of lithium manganate

Laser ablation is widely used to assist in the fabrication of prototype lithium manganate (LiMn₂O₄) thin film structures for Li-ion battery electrodes via the pulsed laser deposition technique. However, films can be considerably Li and/or O deficient, depending the deposition conditions used. Here we present data on the ionic component of laser-produced plasma in laser ablation of lithium manganate with ns excimer laser. Plasma was monitored using an electrical Langmuir ion probe, in time-of-flight mode in conjunction with mass spectrometry to identify the dominant ionic species. Ablation in vacuum at ∼2.5 J cm⁻² revealed the plasma's ionic component was composed primarily of singly charged Li and Mn ions. The time-of-flight data indicates significant deceleration of the plasma when ablation is carried out in an oxygen background gas pressure of the order of 10 Pa. The implications for thin film growth are considered in terms of the possible gas phase interactions and/or thin film re-sputtering yield.     

Properties of Cu film and Ti/Cu film on polyimide prepared by ion beam techniques

Cu film and Ti/Cu film on polyimide substrate were prepared by ion implantation and ion beam assisted deposition (IBAD) techniques. Three-dimension white-light interfering profilometer was used to measure thickness of each film. The thickness of the Cu film and Ti/Cu film ranged between 490 nm and 640 nm. The depth profile, surface morphology, roughness, adhesion, nanohardness, and modulus of the Cu and Ti/Cu films were measured by scanning Auger nanoprobe (SAN), atomic force microscopy (AFM), and nanoindenter, respectively. The polyimide substrates irradiated with argon ions were analyzed by scanning electron microscopy (SEM) and AFM. The results suggested that both the Cu film and Ti/Cu film were of good adhesion with polyimide substrate, and ion beam techniques were suitable to prepare thin metal film on polyimide.     

Role of reactive gas in atmospheric plasma for cell attachment and proliferation on biocompatible poly ?-caprolactone film

This paper reports the surface modification of a biocompatible poly ?-caprolactone (PCL) film treated by atmospheric cold plasma (ACP) with reactive gases. The change in wettability and surface morphology of the PCL film after the plasma treatment with the reactive gases (Ar, H₂, N₂ and O₂) were determined using contact angle and surface roughness measurements. The chemical bonding states and molecular vibration modes of the activated organic groups on the polymer surface were examined by X-ray photoelectron spectroscopy and Fourier-transformation infrared techniques. The surface of the ACP-treated PCL films was also examined for their in vitro cell attachment and proliferation using human prostate epithelial cells (HPECs). The increase in the hydrophobicity of the Ar + H₂ plasma-treated PCL film resulted in a lower cell loading in the initial step of cell culture as well as a decrease in the level of cell attachment and proliferation compared with the pristine film. However, the hydrophilic properties of the Ar + N₂, Ar and Ar + O₂ plasma-treated PCL film improved the adhesion properties. Therefore, the Ar + N₂, Ar and Ar + O₂ plasma-treated PCL films showed a better cell distribution and growth than that of the pristine PCL film. The ACP-treated PCL film is potentially useful as a suitable scaffold in biophysics and bio-medical engineering applications.     

Influence of direct current plasma magnetron sputtering parameters on the material characteristics of polycrystalline copper films

Physical vapor processes using glow plasma discharge are widely employed in microelectronic industry. In particular magnetron sputtering is a major technique employed for the coating of thin films. This paper addresses the influence of direct current (DC) plasma magnetron sputtering parameters on the material characteristics of polycrystalline copper (Cu) thin films coated on silicon substrates. The influence of the sputtering parameters including DC plasma power and argon working gas pressure on the electrical and structural properties of the thin Cu films was investigated by means of surface profilometer, four-point probe and atomic force microscopy.     

Laser-induced forward transfer technique for maskless patterning of amorphous V2O5 thin film

A laser-induced forward transfer technique has been applied for the maskless patterning of amorphous V₂O₅ thin films. A sheet beam of a frequency doubled (SHG) Q-switched Nd:YAG laser was irradiated on a transparent glass substrate (donor), the rear surface of which was pre-coated with a vacuum-deposited V₂O₅ 180 nm thick film was either in direct contact with a second glass substrate (receiver) or a 0.14 mm air-gap was maintained between the donor film and the receiving substrate. Clear, regular stripe pattern of the laser-induced transferred film was obtained on the receiver. The pattern was characterized using X-ray diffraction (XRD), optical absorption spectroscopy, scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), atomic force microscopy (AFM), etc.     

Study on bacteria adherence properties of Mo surface-modified layer in Ti6Al4V alloy prepared by plasma surface alloying technique

Mo surface-modified layer in Ti₆Al₄V alloy was prepared using plasma surface alloying technique. Microstructure of the modified layer was analyzed using X-ray photoelectron spectroscopy (XPS), rough-meter and GDA750 glow discharge optical emission spectrometer. Phase composition of the Mo surface-modified layer was characterized by D/max 2500 X-ray diffraction. Results show that the Mo surface-modified layers consist of pure Mo surface layer with 〈1 1 0〉 and 〈2 1 1〉 orientations and diffusion layer. Mo 3d, O 1s, C 1s and Ti 2p, O 1s, C 1s XPS spectra are recorded at topsurface in the Mo-modified layer and titanium substrate respectively. Because of the different roughness and microstructure, the Mo surface-modified layer can to some extent inhibit bacteria adherence.