DC Plasma Treatment Research Articles

Silver nanowire network for flexible transparent electrodes based on spray coating at a low DC electric field and plasma treatment

Flexible transparent electrodes have been fabricated successfully by using a metal nanowire network. Despite its higher conductivity and transparency, raw silver nanowire (AgNW) film suffers from the random arrangement and high surface roughness originating from the overlaps of a few tens of nanometer-thick AgNWs. In this work, a facile and environmentally friendly method is developed to form AgNW flexible transparent electrodes by spray coating at a low DC electric field (less than 6.0 V) and subsequent plasma treatment. The DC voltage, plasma power, and plasma treatment time of the AgNW network are optimized. The obtained electrodes fabricated by this technique exhibited excellent flexible, transparent, and flat junctions of AgNWs with a sheet resistance of 4.64 Ω · sq−1 and a specular transmittance of 87.3% at a wavelength of 550 nm. Furthermore, the AgNW electrodes are very flexible, highly durable, and moiré-free. The resistance remains almost unchanged over 500 cycles of mechanical deformation with a bending distance of 14 mm when its size is 20 × 20 mm. The as-prepared AgNW electrodes exhibited a root mean square roughness below 13.07 nm at a scan size of 5 × 5 μm. We propose that the improved properties can be attributed to the well-arranged AgNW network acheived by applying a DC electric field and a flat connection between the AgNW junctions induced by plasma treatment.

Surface modification of Cu/PS nanocomposite films: A comparative study of DC N2 plasma and Gamma radiation and their effects on the films' antibacterial activity

In this work we present a comparative study on the efficiency of surface modifications of Copper/Polystyrene (Cu/PS) nanocomposite films, induced by N2 DC plasma and gamma radiation to enhance their surfaces' antibacterial activity. Cu/PS nanocomposite films, with different concentrations of copper 0.4, 0.8 and 1 wt.%, were prepared by the solution casting method at room temperature. The samples were exposed to gamma with different radiation doses and N2 DC plasma for different treatment time. The structural and morphological properties of the samples were investigated before and after treatment by, water contact angle measurements, weight loss and scanning electron microscopy. The surface of the films were found to be more sensitive to N2 DC plasma than gamma radiation. The antibacterial properties of Cu/PS nanocomposite films against Staphylococcus aureus 15 have been evaluated by the optical density and colony forming unit's techniques. The results indicated that the N2 DC plasma treatment enhanced the antibacterial properties more than gamma radiation.

Effect of plasma oxidation parameters on physical properties of nanocrystalline nickel oxide thin films grown by two-step method: DC sputtering and plasma oxidation

Nanocrystalline nickel oxide (NiO) thin films were successfully grown on quartz substrates by two-step method. In the first step, nickel films were deposited on quartz substrates by DC magnetron sputtering technique. Then, the plasma oxidation of nickel films was used for preparation of nickel oxide. The effect of DC plasma power and treatment time on the structural, morphological and optical properties of the NiO films were investigated by different analyses. XRD results indicated that the plasma powers effectively influenced the structure of films, and the best crystallinity was obtained for plasma power of 15 w and treatment time of 20 min. The XPS, RBS and EDS analysis confirmed the presence of Ni and O elements. The FESEM and AFM images showed a granular structure with spherical shapes of grains. The optical band gap of the films synthesized under different plasma oxidation conditions was also discussed.

Fabrication of a Spherical Titanium Powder by Combined Combustion Synthesis and DC Plasma Treatment

AbstractCombustion synthesis is capable of producing many types of refractory and ceramic materials, as well as metals, with a relatively lower cost and shorter time frame than other solid state synthetic techniques. TiO2with Mg as reductant were dry mixed and hand compacted into a 60 mm diameter mold and then combusted under an Ar atmosphere. Depending on the reaction parameters (Mg concentration 2 ≤α≤ 4), the thermocouples registered temperatures between 1160°C and 1710°C · 3 mol of Mg gave the optimum results with combustion temperature (Tc) and combustion velocity (Uc) values of 1372°C and 0.26 cm/s respectively. Furthermore, this ratio also had the lowest oxygen concentration in this study (0.8 wt%). After combustion, DC plasma treatment was carried out to spheroidize the Ti powder for use in 3D printing. The characterization of the final product was performed using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and N/O analysis.

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.

Desizing of Starch Containing Cotton Fabrics Using Near Atmospheric Pressure, Cold DC Plasma Treatment

An attempt has been made to desize the starch containing grey cotton fabrics using the DC plasma with oxygen as the gaseous medium. Process conditions of the plasma reactor were optimized in terms of distance between the plates (3.2 cm), applied voltage (600 V) and applied pressure (0.01 bar) to obtain maximum desizing efficiency. No discolouration was observed in the hot water extracts of the desized sample in presence of iodine though relatively higher solvent extractable impurities (4.53 %) were observed in the plasma desized samples compared to acid desized samples (3.38 %). Also, significant weight loss, improvements in plasma desized samples were observed than that of grey fabrics in terms of drop absorbency.

Preparation and Characterization of LiMn2O4 Cathodes Surface‐Modified by DC Pulsed Plasma Treatment

AbstractA study of oxygen dc pulsed plasma irradiation treatment has been carried out on LiMn2O4 powder cathodes to enhance the electrochemical performances of lithium ion batteries. The samples have been characterized by X‐ray diffraction, scanning electron microscope, energy dispersion spectroscope and electrochemical measurements. It is found that after undergoing the plasma treatments, the sharp facets of LiMn2O4 particles become smooth due to plasma ion bombardment. The treated electrodes are partially covered by layers with high atomic percent of element F, indicating the reflow of binders. The electrochemical measurements are carried out under harsh conditions, including deep‐discharge at low cut‐off potential of 2 V and cycling at elevated temperature of 60 °C. The results reveal that moderate oxygen dc pulsed plasma treatment can improve the cycling stability of LiMn2O4 powder electrodes in the above mentioned conditions. The enhanced electrochemical performances are attributed to the dense protection layers on electrode surface, which reduce the capacity fading due to the Mn+2 ions dissolution.

GAS DISCHARGE STATIC CHARACTERISTICS IN PULSE REGIME

Савремени материјали, међународна научна конференција - Contemporary materials, International scientific conference,Савремени материјали 2010 - научна конференција у Бањој Луци

Wettability control on vertically-aligned multi-walled carbon nanotube surfaces with oxygen pulsed DC plasma and CO 2 laser treatments

This work presents a method to obtain control on wettability of vertically-aligned multi-walled carbon nanotube surfaces, using oxygen pulsed directly current plasma and CO 2 laser irradiation. Superhydrophilic surfaces were obtained by the oxygen pulsed DC plasma treatment to incorporate polar groups on VACNT. The CO 2 laser was used to irradiate the functionalized samples, at different power levels, in order to restore the superhydrophobic characteristic. Evaluation of polar and dispersive components of superficial energy was performed by Owens and Wendt method.

Production of geopolymers using glass produced from DC plasma treatment of air pollution control (APC) residues

Air pollution control (APC) residues are the hazardous waste produced from cleaning gaseous emissions at energy-from-waste (EfW) facilities processing municipal solid waste (MSW). APC residues have been blended with glass-forming additives and treated using DC plasma technology to produce a high calcium alumino-silicate glass. This research has investigated the optimisation and properties of geopolymers prepared from this glass. Work has shown that high strength geopolymers can be formed and that the NaOH concentration of the activating solution significantly affects the properties. The broad particle size distribution of the APC residue glass used in these experiments results in a microstructure that contains unreacted glass particles included within a geopolymer binder phase. The high calcium content of APC residues may cause the formation of some amorphous calcium silicate hydrate (C-S-H) gel. A mix prepared with S/L = 3.4, Si/Al = 2.6 and [NaOH] = 6 M in the activating solution, produced high strength geopolymers with compressive strengths of ∼130 MPa. This material had high density (2070 kg/m 3) and low porosity. The research demonstrates for the first time that glass derived from DC plasma treatment of APC residues can be used to form high strength geopolymer–glass composites that have potential for use in a range of applications.

On the fundamental mechanisms of active screen plasma nitriding

The nitriding mechanisms of conventional DC plasma treatments have been extensively studied and discussed, but no general agreement has been reached thus far. The sputtering and redeposition theory is among the most accepted ones but, even though this mechanism is feasible, its contribution to the nitriding effect is under question. Furthermore, the novel active screen plasma nitriding technique has been successful in treating samples left at floating potential, where sputtering can not be considered to play a major role. Therefore, it has been proposed that the material sputtered from the cathodic mesh of the active screen furnace (auxiliary cathode) and deposited onto the treated specimens is involved in the mass transfer of nitrogen. The contribution made by this transferred material is the focus of attention of the present study. The hardening effect on the treated specimens showed considerable correlation with the deposition layer, and the XRD analysis of this deposited material yielded possible FeN and Fe x N peaks. This finding supports the deposition of iron nitrides and their subsequent decomposition on the treated substrate as a mechanism of significance to the plasma nitriding treatments conducted in active screen experimental settings.

Polypropylene surface modification by active screen plasma nitriding

Here we describe the use of low energy plasma immersion with active screen as a convenient approach for polypropylene (PP) surface modification. Employing a stainless steel cathodic cage coated with carbon in order to prevent the sputtering of iron from the grid and its deposition onto the polymer sample, the physical chemical properties of PP surface could be effectively modified through the plasma-induced incorporation/formation of nitrogen- and oxygen-containing species. The areal densities of these elements depended on the plasma excitation source, as determined by Rutherford backscattering spectrometry (RBS). Newly formed C–O, C–N, and C O/O C–O/N–C O bonds along with C–C linkages from the PP backbone were identified at the near surface region of the specimens by X-ray photoelectron spectroscopy (XPS). The insertion of such polar reactive functionalities was further confirmed by a substantial decrease in the water contact angle upon plasma treatment. Scanning electron microscopy (SEM) analysis revealed that while no major changes in the morphology occur upon DC plasma treatments as compared to untreated samples, the use of pulsed plasma consistently leads to the formation of cracks at the surface. The herein reported approach is an attractive tool for environmental friendly low-cost surface engineering of novel materials.

Nitrogen and hydrogen plasma treatments of multiwalled carbon nanotubes

This article investigates plasma treatment of vertically aligned multiwall carbon nanotube (CNT) films in different plasma environments for modification of surface chemistry and morphology. The surfaces of the CNTs were functionalized with a pulsed dc plasma treatment, where the power was directly applied to the nanotube film in low pressure argon/nitrogen and argon/hydrogen backgrounds. Optical emission spectroscopy was used to detect atomic and molecular excitations in the gas mixtures as well as in pure gases in the vicinity of the CNT films. In situ x-ray photoelectron spectroscopy was performed on the treated samples to examine CNT surface chemistry after treatment. The analysis of CNT films after nitrogen and hydrogen treatment indicated formation of both CN and CH bonds, respectively. Correlations of the plasma characteristics to the surface chemistry and morphology of the CNT surfaces are discussed.

Comparative study of surface free energy and surface resistivity of polypropylene and polystyrene thin films after DC plasma treatment

30 o C, pressure 200 Pa). The effects of time (up to 110 s) and power (1 W or 5 W) of the treatment on the values of free energy (γs) of PS and PP samples and γS components — dispersive (γS D ) and polar (γS P ) ones — were determined. With prolonged time of interaction the values of γS and γS P increased, especially in the region of first 35—50 s, while γS D values kept the similar level during the whole time of exposure. The dependence of PP and PS surface resistance on the same parameters as above (time and power of interaction) has been also found. For both polymers this resistance decrease with prolonged time and growing power of exposure.

Surface modification of PMMA by DC glow discharge and microwave plasma treatment for the improvement of coating adhesion

PMMA shows poor adhesion for evaporated inorganic coatings. The DC and microwave plasma treatments can considerably increase free surface energy but an improvement of coating adhesion is, according to our results, only possible by the DC process. ATR spectroscopy has been applied to investigate the changed chemical structure of DC plasma-treated PMMA. Samples treated by microwave plasma did not show ATR alteration while XPS analysis indicated surface oxygen enrichment.

Oxygen plasma induced degradation of the surface of poly(styrene), poly(bisphenol-A-carbonate) and poly(ethylene terephthalate) as observed by soft X-ray absorption spectroscopy (NEXAFS)

Biaxially stretched poly(ethylene terephthalate) foils, poly(ethylene terephthalate) and poly(styrene) spin coated films as well as self-supporting poly(bisphenol-A-carbonate) films were analysed by surface sensitive near edge X-ray absorption fine structure spectroscopy (NEXAFS) before and after low pressure oxygen DC plasma treatments. The degradation effects of the treatment are discussed in a common way in terms of probable reaction pathways. The results are, when possible, cross-checked by XPS. NEXAFS analysis provides data on the phenyl ring, ester and carbonate group degradation in a straightforward manner. It can be shown that the phenyl rings in partially crystalline poly(ethylene terephthalate) are, in comparison, most effectively protected against plasma attack. In the case of poly(styrene), where the rings are located as side chains, they are most efficiently degraded.

Surface analysis of DC oxygen plasma treated or chromium evaporated poly(ethylene terephthalate) foils by soft X-ray absorption spectroscopy (NEXAFS)

Surface modified biaxially stretched poly(ethylene terephthalate) (PET) foils have been analysed by surface sensitive soft X-ray absorption (NEXAFS) spectroscopy. Generally, an orientation of polymer chain segments can be detected by a variation of the angle between the linearly polarized synchrotron light beam and the surface normal of the investigated sample (angle resolved NEXAFS spectroscopy). Biaxially stretched PET foils have been found to be characterized by angle dependent NEXAFS C and O K-edge spectra. This angle dependence was interpreted to be a result of a preferential orientation of the PET chain segments at the surface wherein the plane defined by the benzene ring is parallel to the surface plane. In the course of chromium deposition or low pressure O 2 DC plasma treatment that preferential orientation is continuously diminished. This is interpreted to be a structural effect of the respective treatment.

The Conversion of Czochralski Silicon from P-Type to N-Type by Hydrogen Plasma Enhanced Thermal Donor Formation

ABSTRACTOur experiments show a hydrogen plasma assisted creation of p-n junctions in p-type Cz silicon due to a hydrogen enhanced thermal donor (TD) formation at temperatures ≤450 °C. Applying DC or HF plasma treatments a conversion of p-type into n-type Cz silicon by TD formation occurs. One can distinguish one step processes (p-n junction formation appears just after the plasma exposure) and two step processes (p-n junction formation requires subsequent post hydrogenation annealing). The samples are studied by depth resolved spreading resistance probe (SRP), capacitance-voltage (CV) and Hall measurements. For the one step processes a kinetic model for hydrogen enhanced TD formation is presented.

Oxygen-free 6061 Aluminum Alloy Surface Produced in Ammonia Glow Discharge: An AES Spectrum

An oxygen-free 6061 aluminum surface was obtained for the first time in our knowledge in an ultrahigh vacuum (UHV) environment after ex situ ammonia dc plasma treatment. The specimen was first processed in an ammonia plasma chamber for 5 to 6 h then taken from the treatment chamber, mounted on a sample holder in air, and inserted into an UHV system through a sample transfer chamber. The sample was cleaned by 2.8 keV Ar+ ion bombardment for about 10 min to remove the oxide layer that had formed in air. A clean metallic aluminum Auger spectrum with no detectable oxygen peak was obtained under standard operating conditions with a Perkin-Elmer Physical Electronics 560 spectrometer. The kinetic energy of the Auger electrons was calibrated using sputter-cleaned Cu surfaces. The oxygen free Al surface is a key to thin film growth/deposition on aluminum or aluminum alloy surfaces.

Surface Modification of ALC by Low Temperature Plasma Treatment

A hydrophobic surface layer of sub-millimeter was obtained by low temperature DC plasma treatment of a porous building material (ALC) for a few minutes in a CHF3 atmosphere. The present modified surface layer of ALC showed, (a) the repellency against water droprets for a 20-40 minutes and (b) the reduction in water vapor adsorption quite less than a nonmodified sample.