Surface modification of a polyester non-woven with a dielectric barrier discharge in air at medium pressure

In this paper, a polyester non-woven is plasma treated with a dielectric barrier discharge (DBD) in air at medium pressure (5.0 kPa) and at different discharge powers. Results show that an increasing power leads to a better plasma treatment of the sample. The barrier discharge is characterized by a voltage and current waveform, by a Lissajous figure and by Lichtenberg figures. The surface properties of the plasma treated samples are examined using X-ray photoelectron microscopy (XPS) and scanning electron microscopy (SEM). XPS analysis reveals that surface oxidation by the formation of oxygen-containing functional groups enhances the surface wettability. SEM analysis shows that the sample is not etched by the used barrier discharge. This is due to the low surface energy density of the DBD used in this paper. Therefore, a DBD in air at medium pressure provides an efficient modification of the chemical surface properties of textiles without destroying the physical structure.     

Effects of oxygen addition on physical properties of ZnO thin film grown by radio frequency reactive magnetron sputtering

We deposited a ZnO thin film on a microslide glass substrate at room temperature by employing the RF reactive magnetron sputtering process. Our results revealed that deposition rate decreases by increasing O₂/(Ar + O₂) ratio that was caused by two mechanisms. The first mechanism was the reduction of plasma density and, thus, argon ion density; caused by the addition of highly electronegative oxygen. While the second mechanism was target poisoning caused by the oxidation of the target. Additionally, at the O₂/(Ar + O₂) ratio of ∼0.3 and the help of XPS analysis the optimum stoichiometry of ZnO thin film (the highest binding energy and content fraction of O^I peak (O-Zn bond)) and the best polycrystallinity (the lowest FWHM with largest grain size) was found.     

Characteristics of copper oxide films deposited by PBII&D

Copper oxide films were deposited by plasma based ion implantation and deposition using a copper antenna as rf sputtering ion source. A gas mixture of Ar + O₂ was used as working gas. During the process, copper that was sputtered from the rf antenna reacted with oxygen and was deposited on a silicon substrate. The composition and the chemical state of the deposited films were analyzed by XPS. The structure of the films was detected by XRD. It is observed that Cu₂O film has been prepared on the Si substrate. It is found that the microstructure of the deposited film is amorphous for the applied voltage of − 5 kV. The surface layer of the deposited films is CuO. This is because the surface layer absorbs the oxygen from ambient air after the treated sample was removed from the vacuum chamber. An appropriate applied voltage, 2 kV under the present conditions, brings the lowest resistance. It is also seen that the maximum absorbance of the deposited films moves to a lower wavelength with increased applied voltage.     

Effect of humid air exposure between successive helium plasma treatments on PET foils

It is well known that helium plasmas can successfully alter the surface properties of polyethylene terephthalate (PET). However, the influence of humid (atmospheric) air exposure between successive helium plasma treatment steps has not been previously examined. In this work, PET foils are treated in successive short treatment steps of 5 s with a DBD operating in helium at medium pressure (5.0 kPa). Between every plasma treatment step, the samples are either kept in the plasma chamber at 5.0 kPa under helium atmosphere or are exposed to humid air at atmospheric pressure. The plasma-treated samples are examined using contact angle measurements and X-ray photoelectron spectroscopy (XPS). Results clearly show that exposure to humid air between successive helium plasma treatment steps leads to a larger decrease in water contact angle and a more pronounced oxygen incorporation. XPS results have shown that during each helium plasma treatment, O-C═O groups are introduced on the PET surfaces. However, when the samples are exposed to humid air between plasma treatments, also C-O groups are created on the PET surfaces. These C-O groups are mainly introduced during exposure to humid air: every helium plasma treatment creates surface radicals, which can in turn react with oxygen species present in the atmosphere during subsequent humid air exposure, leading to the incorporation of C-O groups.     

Extreme durability of wettability changes on polyolefin surfaces by atmospheric pressure plasma torch

In the present work three common polyolefins: high density polyethylene (HDPE), low density polyethylene (LDPE) and polypropylene (PP) have been treated with an atmospheric pressure air plasma torch (APPT) in order to improve their wettability properties. The variations in surface energy (γ_s), as well as the durability of the treatment are determined by means of contact angle measurements for different aging times after plasma exposure (up to 270 days) using five test liquids which cover a wide range of polarities. The introduction of new polar moieties (carbonyl, amine or hydroxyl) is confirmed by Fourier transform infrared spectroscopy in attenuated total multiple reflection mode (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Furthermore, scanning electron microscopy (SEM) provides information on the morphological changes and variation on surface roughness, revealing that smoother, lamellar and semispheric micrometric structures are created on the LDPE, HDPE and PP surfaces, respectively. Results show that APPT treatment enhances both the total and polar components of the γ_s under study, with an unprecedent stability (> 8 months) in time.     

Modification of polystyrene with a highly reactive cold oxygen plasma

Samples of biaxially oriented polystyrene (PS) were exposed to an extremely non-equilibrium oxygen plasma. The neutral gas kinetic temperature was 70 °C, the electron temperature was about 3 eV, the plasma density was about 2 × 10¹⁵ m^− 3, and the neutral oxygen atom density was 4 × 10²¹ m^− 3. The plasma was created with an electrodeless radiofrequency discharge and the samples were kept at a floating potential. The plasma treatment time was between 1 and 50 s. The samples were characterized by high-resolution X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), microbalance, and water contact-angle (WCA) measurements. The etching rate was found to be relatively independent of the treatment time, at about 9 nm/s. The corresponding probability for oxidation with O atoms was calculated from the known flux of O atoms onto the surface, and was close to 6 × 10^− 4. The AFM did not show any appreciable increase in the surface roughness due to the plasma treatment. Both the XPS and the WCA measurements showed a well-activated surface after just a second of plasma treatment. The rapid functionalization was explained by the huge flux of O atoms onto the sample surface. The tilting of the samples during the XPS characterization made it possible to conclude that the oxygen-containing functional groups were concentrated at the surface of the film, at a depth much smaller than that examined by XPS. The functional groups found using XPS were the standard C-O, O-C-O, C = O, O-C═O as well as -O-CO-O-. The appearance of functional groups with a high degree of oxidation, like carboxyl and carbonate, was attributed to the oxygen's interaction with the aromatic phenyl rings. The ageing results showed that the concentration of the oxygen functional groups did not change much, but the contact angle of the water drop increased moderately during the first day and remained almost unchanged after subsequent ageing.     

Incorporation of amino moieties through atmospheric pressure plasma: Relationship between precursor structure and coating properties

Parallel plates dielectric barrier discharge (DBD) at atmospheric pressure has been used to investigate the introduction of amino groups on a polypropylene substrate. For this purpose the plasma polymerization of aminopropyl triethoxysilane, trimethoxysilylpropyl ethylenediamine, allylamine, butylamine, ethylenediamine, and nitrogen/ammonia has been systematically studied and compared. The coatings have been characterized through wettability measurements, interferometry, labeling coupled with X-ray photoelectron spectroscopy, and IR spectroscopy. Significant hydrophilicity enhancement of the polypropylene substrate has been observed for butylamine, ethylenediamine or allylamine, with a surface energy up to 76 mN.m⁻¹. Higher reactivity in the plasma is observed for trimethoxysilylpropyl ethylenediamine which also gives rise to the maximum final amino group concentration of about 6 at.%. According to the choice of the precursor, surface properties can be tuned in terms of polarity, coating composition, and coating thickness.     

Low-temperature plasma carburizing of AISI 420 martensitic stainless steel: Influence of gas mixture and gas flow rate

Low-temperature plasma carburizing was studied aiming to determine the effect of the gas mixture and flow rate on the surface properties of AISI 420 martensitic stainless steel samples. Plasma carburizing was carried out for gas mixtures of 20% Ar + 80% H₂ comprising CH₄ contents between 0.25 and 1.00%, and gas flow rates ranging from 1.67 × 10^− 6 to 6.68 × 10^− 6 Nm³ s^− 1. The modified layers were characterized by confocal laser scanning microscopy, X-ray diffractometry and microhardness measurements. The plasma was also characterized by optical emission spectrometry. Results indicate the presence of a hard and thin outer layer and a carbon-enriched martensite diffusion layer. It is shown that gas mixture composition plays an important role in the process kinetics. Spectroscopic characterization of the glow discharge shows that the variation of the CH₄ content in the gas mixture leads to a variation of the emission lines intensity but does not significantly alter the relative peak intensities. It suggests a variation on the plasma density and no significant variation on the active species. It also indicates that, for the studied conditions, the emission spectroscopy cannot be applied as a tool for process control.     

Study of the surface modification of a Nylon-6,6 film processed in an atmospheric pressure air dielectric barrier discharge

A Nylon-6,6 film has been treated using an atmospheric pressure air dielectric barrier discharge (DBD). The resultant surface modifications were studied using X-ray photoelectron spectroscopy (XPS), contact angle measurement and secondary ion mass spectrometry (SIMS). The surface oxidation arising in the DBD discharge was found to arise in two stages: in the first stage, the creation of the carbon sites singly bonded to oxygen is dominant, the second stage leads to further conversion of such lightly oxidised carbons to those more heavily oxidised. The marked increase found in the hydrophilicity of the surface post-treatment is in the main believed to be associated with the earlier outcome. Partial recovery of the surface contact angle values is found for the treated samples following extended storage in ambient air. The final contact angle obtained for the treated samples was ∼50°, still reduced significantly from that of 83.5° for the untreated material.     

Synthesis and high temperature XRD studies of tantalum nitride thin films prepared by reactive pulsed dc magnetron sputtering

In the present work, the growth characteristics of tantalum nitride (TaN) thin films prepared on (1 0 0) Si substrates by reactive pulsed DC magnetron sputtering are investigated. XRD analyses indicated the presence of α-Ta and β-Ta in the films deposited in pure argon atmosphere, while β-TaN and fcc-TaN phases appeared for 2 sccm of nitrogen, and cubic TaN for 5-25 sccm of nitrogen in the sputtering gas mixture of argon and nitrogen at a substrate temperature of 773 K. The TaN films obtained with increasing substrate temperature and pulse width showed a change in the texture from [1 1 1] to [2 0 0] orientation. Atomic force microscopy (AFM) results indicated that the average surface roughness was low for films deposited in pure argon than for the films deposited in a mixed Ar + N₂ atmosphere. Nanocrystalline phase of the deposited material was identified from the high-resolution transmission electron microscopy (HRTEM) images. X-ray photoelectron spectroscopy (XPS) core level spectra confirmed the formation of TaN phase. The high temperature X-ray diffraction analysis of the optimized TaN thin film was performed in the temperature range 298-1473 K. The lattice parameter of the TaN films was found to increase from 4.383 to 4.393 Å on increasing the temperature from 298 to 823 K and it reduced to 4.345 Å at 1473 K. The thermal expansion coefficient value was found to be negative for the TaN films.     

The nanostructure, wear and corrosion performance of arc-evaporated CrBxNy nanocomposite coatings

The composition, nanostructure, tribological and corrosion behaviour of reactive arc evaporated CrB_xN_y coatings have been studied and compared to CrN. The CrB_xN_y coatings were deposited on a commercial Oerlikon Balzers RCS coating system employing 80:20 Cr:B targets. To vary the composition, the nitrogen fraction was adjusted (N₂ fraction = N₂/(Ar + N₂)) and a moderate bias voltage of − 20 V was applied during coating growth. The coating composition and nanostructure was determined using time-of-flight elastic recoil detection analysis (TOF-ERDA), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). Ball-on-disc dry sliding wear tests were conducted using an alumina ball counterface both at room temperature and at 500 °C with the relative humidity controlled at 20%. Potentiodynamic corrosion tests were undertaken in 3.5% NaCl aqueous solution. The wear tracks were examined using optical profilometry and scanning electron microscopy (SEM); the surface composition inside and outside of the wear tracks were investigated using Raman spectroscopy and XPS. All coatings exhibit nanocomposite structures and phase compositions which are in fair agreement with those expected from the equilibrium phase diagram. The lowest wear rate at room temperature and 500 °C was found for CrB_0.14N_1.14, which was shown to exhibit the highest hardness and possesses a nanocomposite nc-CrN/a-BN structure. CrB_0.12N_0.84 coatings showed the lowest passive current density in potentiodynamic corrosion tests.     

DBD treatment of polyethylene terephthalate: Atmospheric versus medium pressure treatment

In this paper, polyethylene terephthalate (PET) films are modified by a dielectric barrier discharge (DBD) in a helium/air mixture at medium (6.6 kPa) and atmospheric pressure. Surface analysis and characterization of the plasma-treated PET films is performed using contact angle measurements, X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). The polymer films, modified with the DBD at medium and atmospheric pressure, show a significant decrease in water contact angle due to the incorporation of oxygen-containing groups, such as C-O and O-C=O. Results also show that the surface treatment is uniform at micron scales, despite the fact that the discharge consists of a series of microdischarges. It is shown that at low energy densities (< ± 200 mJ/cm²), plasma treatment at medium pressure is more energy-efficient in incorporating oxygen functionalities than plasma treatment at atmospheric pressure. This effect could be induced by the larger diameter of the microdischarges at medium pressure than at atmospheric pressure (factor 3.92) and/or by the lower quenching of atomic oxygen in three-body collisions at medium pressure. The ageing behaviour of the plasma-treated PET films during storage in air is also studied in this paper. XPS results reveal that during the ageing process the induced oxygen-containing groups re-orientate into the bulk of the material. In this paper, it is shown that the ageing behaviour of the PET films is independent of the operating pressure used during plasma treatment.     

Deposition of silver ions onto DBD and DCSBD plasma treated nonwoven polypropylene

The aim of this work is plasma activation of nonwoven polypropylene (PP) using two different ambient air plasma sources: volume dielectric barrier discharge (DBD) and diffuse coplanar surface barrier discharge (DCSBD) and its functionalization by silver ion deposition.     

Reactive sputtering of TiOxNy coatings by the reactive gas pulsing process: Part II: The role of the duty cycle

The reactive gas pulsing process (RGPP) was used to deposit titanium oxynitride thin films by dc reactive magnetron sputtering. A titanium target was sputtered in a reactive atmosphere composed of Ar + O₂ + N₂. Argon and nitrogen gases were continuously introduced into the sputtering chamber whereas oxygen was injected with a well-controlled pulsing flow rate following a rectangular and periodic signal. A constant pulsing period T = 45 s was used for every deposition and the duty cycle α = t_ON/T was systematically changed from 0 to 100%. The operating conditions were investigated taking into account the poisoning phenomena of the target surface by oxygen and nitrogen. Kinetics of poisoning were followed from measurements of the total sputtering pressure and titanium target potential during the depositions. Deposition rate and optical transmittance of titanium oxynitride coatings were also analysed and correlated with the process parameters. Pulsing the oxygen flow rate with rectangular patterns and using suitable duty cycles, RGPP method allows working according to reversible nitrided-oxidised target conditions and leads to the deposition of a wide range of TiO_xN_y thin films, from metallic TiN to insulating TiO₂ compounds.     

Corrosion behavior and surface characterization of tantalum implanted TiNi alloy

TiNi shape memory alloy has been modified by Ta plasma immersion ion implantation technology to improve corrosion resistance. The results of the polarization tests show that the corrosion resistance of TiNi alloy in Ringer's solution at 310 K has been improved by the Ta ion implantation and the Ta/TiNi sample with a moderate incident dose of 1.5 × 10¹⁷ ions/cm² exhibits the best corrosion resistance ability. The surface characterization and chemical composition of the Ta/TiNi samples were determined by Auger electron spectroscopy (AES), Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) methods. AFM images reveal that compact aggregates of nano-grains uniformly disperse on the surface of the Ta/TiNi samples. AES and XPS analyses on the Ta/TiNi sample show that the component of the surface layer is mainly composed of TiO₂ and Ta₂O₅, which is benefit to the corrosion resistance ability and biocompatibility.     

Formation and microstructural characterisation of S-phase layers in Ni-free austenitic stainless steels by low-temperature plasma surface alloying

The feasibility of generating S-phase surface layers in nickel-free austenitic stainless steels by plasma surface alloying with nitrogen (at 430 °C), carbon (at 430 °C and 500 °C) and both carbon and nitrogen (at 430 °C) has been investigated. The structure, microstructure and composition of the plasma-alloyed surfaces were characterised by X-ray Diffraction (XRD), microscopy, Glow Discharge Optical Emission Spectroscopy (GDOES) and Transmission Electron Microscopy (TEM). The experimental results have demonstrated for the first time that the S-phase can be produced in the surface of nickel-free austenitic stainless steel by low-temperature plasma surface alloying. TEM analysis has revealed that when alloyed with carbon no precipitates can be found within the carbon-rich S-phase layer; however, when alloyed with nitrogen or both carbon and nitrogen some nitride precipitates (Mn₃N₂ and Cr₂N) were found within the nitrogen-rich S-phase layer. Based on experimental results, the response of Ni-free austenitic stainless steel to plasma surface alloying has been compared to the Ni-containing counterpart, and the role of nickel in the formation of S-phase in austenitic stainless steels has been discussed.     

Surface modification of poly(tetrafluoroethylene) by saddle field fast atom beam source

The surface of poly(tetrafluoroethylene) (teflon, PTFE) was treated by saddle field fast atom beam (FAB) source in hydrogen, helium and nitrogen with about 1 kV accelerating voltage, up to an estimated particle fluence of 10¹⁷ cm^− 2. The untreated and FAB-treated samples were characterised by XPS, Raman microspectroscopy, single pass topographic and multipass wear tests and water contact-angle measurements. According to XPS results, upon FAB-treatment the surface F/C value decreased drastically. Raman microspectroscopic measurements testified to the formation of a carbonised surface layer. The thickness of the graded, amorphous carbon-containing layer determined by in-depth Raman microspectroscopic analysis ranged between 5.5 ± 1 and 10.5 ± 1 μm. In addition to radiation damage, a decisive role of degradation induced by thermal effects and diffusion of reactive particles was suggested. The small scale wear resistance of the hydrogen and nitrogen FAB-treated samples improved in comparison with that of the untreated PTFE. The mean surface roughness increased for the treated samples in the order of N < He < H. Water contact-angle decreased upon FAB-treatment. The effect of increased wettability remained durable for at least three months.     

Aging of surface properties of ultra high modulus polyethylene fibers treated with He/O2 atmospheric pressure plasma jet

To investigate the relationship between aging of the treatment effect and the gas composition of atmospheric pressure plasma treatment, ultra high modulus polyethylene (UHMPE) fibers were selected as a model fiber to study the aging behavior of fiber surface treated by atmospheric pressure plasma jet (APPJ) with pure helium, helium + 1% oxygen, and helium + 2% oxygen. Atomic force microscopy showed increased surface roughness, while X-ray photoelectron spectroscopy revealed increased oxygen contents after the plasma treatments. The plasma treated fibers had lower contact angles and higher interfacial shear strengths to epoxy than those of the control fiber. Adding 1% of O₂ to helium increased effectiveness of the plasma in polymer surface modification and suppressed aging after the treatment, while adding 2% of O₂ had a negative effect on the APPJ modification results and accelerated aging. In addition, no significant difference in single fiber tensile strength was observed between the control and the plasma treated fibers.     

Hydrophobic over-recovery during aging of polyethylene modified by oxygen capacitively coupled radio frequency plasma: A new approach for stable superhydrophobic surface with high water adhesion

In this work, a new approach for the stable superhydrophobic surface with a high water adhesion has been found from an aging process at a high aging temperature of 90 °C during an aging time up to 24 h for the low density polyethylene (LDPE) modified by the oxygen capacitively coupled radio frequency plasma (CCP) under a radio frequency (RF) power of 200 W for an exposure time of 5 min. The plasma nanotexturing produced the nanofibrils array on the LDPE surface showing the contact angle of approximately 0°. During the aging process, the as-modified superhydrophilic LDPE surface underwent a hydrophobic over-recovery into the superhydrophobicity with a pinned water droplet showing the contact angle higher than 150°. A time-dependent contact angle model on the nanotextured surface was developed from the Cassie's equation for the heterogeneous surface containing different wetting patches, to describe the hydrophobic over-recovery due to the surface restructuring on the nanofibrils array. The stable superhydrophobicity with the high water adhesion was attributed to the CCP modified LDPE surface with the nanofibrils composed of the heterogeneous chemical compositions of polar and nonpolar chains/groups after the aging process.     

Surface characteristics and corrosion behavior of Ti-Al-Zr alloy implanted with Al and Nb

Ti-Al-Zr alloys were implanted with Al and Nb to doses ranging from 1 × 10¹⁷ to 1 × 10¹⁸ ions cm⁻². The valence states of element on the sample surfaces were analyzed by X-ray photoelectron spectroscopy (XPS). Glancing angle X-ray diffraction (GAXRD) was employed on the as-implanted specimens to understand phase formation. X-ray diffraction (XRD) measurement revealed α-Ti on Al-implanted samples and (α + β)-Ti on Nb-implanted samples. The tendency was observed in increasing corrosion resistance from α- toward (α + β)-phase. In deaerated 5 M HCl, the ion-implanted Ti-Al-Zr surface containing Nb-stabilized β-phase was spontaneously passive, while Al-implanted surface displaying an active/passive behavior. In the aerated solution with pH = 10, all the implanted surfaces are passive. Enhanced reoxidation was confirmed on implanted surfaces by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) analysis. The corrosion in the solution with pH = 10 was governed by a predominantly TiO₂ surface film. The cathodic kinetics was seen to affect the corrosion behavior in 5 M HCl.