Function Of Plasma Treatment Time Research Articles

Bulk Polymerization of Acrylic Acid Using Dielectric-Barrier Discharge Plasma in a Mesoporous Material.

This research investigated a non-thermal, dielectric-barrier discharge (DBD) plasma-based approach to prepare poly(acrylic acid) (PAA) from acrylic acid in its liquid state at atmospheric temperature and pressure. Neither additives nor solvents were needed, and the polymerization was accomplished both as a film and inside a sheet of mesoporous paper. All prepared samples were characterized and the DBD plasma-initiated kinetics were analyzed for the polymerization of acrylic acid. Using FTIR semi-quantitative analysis, the degree of polymerization was monitored, and the reaction followed an overall second-order kinetic model with respect to the DBD-initiated polymerization. Additionally, the application of a PAA-modified paper as a water retention cloth or 'wet wipe' was investigated. The results showed that the PAA-modified paper substrates using DBD plasma increased water retention as a function of plasma treatment time.

Flux enhancement of cellulose nitrate membrane through plasma assisted route for waste and mud water treatment

AbstractFouling of polymeric membranes is a common problem due to its hydrophobic nature. Plasma assisted surface modification of polymeric membranes are immensely popular method in particular for the improvement of antifouling and adhesive properties. The effect of low‐pressure nitrogen plasma on surface morphology, hydrophilicity, structure, permeate flux and ageing effect for the cellulose nitrate polymer membrane are studied in the present work. The cylindrical Langmuir probe and optical emission spectroscopy are used to characterize the plasma. The macro void creation and pore enlargement effects have been observed from scanning electron microscopy images due to the surface etching of the membrane after plasma treatment. The atomic force microscopy analysis shows a prominent enhancement of the surface roughness of the plasma treated membrane. Wettability of membrane is studied as a function of plasma treatment time for treated and untreated membrane. From the contact angle measurement, it is found that the hydrophilicity of the plasma treated membranes increases with plasma treatment time. From gravity filtration process, the enhancement of permeate flux for both waste water and mud water are observed after plasma treatment. The ageing mechanism of the treated membranes is investigated for 30 days for different plasma treatment time. The hydrophobic recovery of plasma treated membranes is significant for initial ageing period of 7 days, after that it has shown almost stable in nature. A theoretical model is developed to study the hydrophilic recovery of plasma treated membranes. It is observed that the experimental results show a very good agreement with the theoretical results.

Improved Surface Properties of Copper/PolyMethylMethacrylate nanocomposite films using DC O2 Plasma

Films of Polymethylmethacrylate with copper nanofiller were prepared and treated with low temperature oxygen DC glow discharge plasma. FTIR spectroscopy, AFM, water contact angle (WCA) measurements and UV-Vis spectroscopy were used to detect the produced chemical, morphological and optical changes as a function of plasma treatment time. The FTIR spectra, showed a decreasing value of the main characterizing signals of the composite films in addition to the creation of an oxygen containing functional group. The surface morphology of the treated samples was altered according to the increased values of the average surface roughness, obtained from the AFM images. The WCA also, decreased noticeably with increasing treatment time. The UV-Vis spectroscopic analysis showed a decreasing value of the optical absorption in the wave length range 190-270 nm which is an indication to the loss of carbonyl group. The value direct and inddirect optical band gap decreased with treatment time meanwhile, values of the band tail width were significantly increased.

Plasma surface modification of P(VDF-TrFE): Influence of surface chemistry and structure on electronic charge injection

Reactive ion plasma treatments have been used to alter the high field electrical properties of organic dielectrics via a grafting process of chemical species within the plasma to the surface of the dielectric. This study determines the effect of a CF4/O2 plasma based processing procedure on polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] on low and high field electrical performance. Plasma treatment in conjunction with a thermal annealing procedure is analyzed in the following ways: X-ray Photoelectron Spectroscopy to determine the changes in surface chemistry of films post plasma treatment, optical profilometry to measure evolution in surface topology, water contact angle to track surface polarity as a function of plasma treatment time, and current-voltage measurements at low and high-fields to capture the electrical behavior of the films. The results indicate that plasma treatment causes the chemical modification of P(VDF-TrFE) surface through the addition of carbonyl (C=O) groups, as well as oxygen and fluorine based moieties (CF-O, C-O) which are dependent on processing condition. Contact angle with water shows an increase as a function of plasma treatment time from ∼84° to 111° in plasma treated films, indicating decreased surface polarity after plasma treatment. Finally, plasma treatment decreases film resistivity by one order of magnitude, from 8.0 × 1011 Ω m in untreated control samples to 0.8 × 1011 Ω m, as well as resulted in enhanced Schottky emission caused by decreased Schottky barrier height. Modeling I(V) data using both a surface limited (Schottky) and bulk limited (Poole-Frenkel) approaches suggest that conduction in P(VDF-TrFE) thin films results from Schottky emission and is dependent on the chemical environment of the metal/dielectric contact. This study ultimately demonstrates the ability to alter the electrical properties by plasma surface treatment and also the importance of surface chemistry in organic dielectrics to control conduction through the material for high energy and power applications.

A new approach for orientation-controlled growth of CNTs: an in-depth analysis on the role of oxygen plasma treatment to catalyst

In this paper, a novel and easy technique is proposed for orientation controlled growth of MWNTs. The results indicate that when CNT growth was carried over the substrate, not treated with plasma, horizontal network of MWNTs was formed. Plasma treatment to the substrate prior to CNTs growth led to formation of vertically aligned MWNTs. An in situ growth as a function of plasma treatment time reveals the mechanism behind this flip process. All experiments were performed under atmospheric pressure. At every step during time-dependent growth process, CNTs were characterized using FESEM, HRTEM, and Raman spectroscopy. Iron sputtered silicon substrate was also investigated to validate the excellent formation of as-grown vertical CNTs and also to analyze the role of oxygen plasma behind the orientation-controlled growth. The as-grown CNTs over the iron sputtered silicon substrate with or without plasma treatment were characterized by FESEM and AFM. The successful orientation-controlled growth of CNTs was achieved.

Surface oxidation effect on the electrical behaviour of Bi2Te2Se nanoplatelets

Charge transport in topological insulators is notably influenced by moisture and air in the surrounding environment. At present, however, little is known about the detailed composition of the oxidized surface and its impact on the electrical characteristics of these materials. Here, we investigate the surface oxide formation on the topological insulator Bi2Te2Se (BTS) and how this affects its electrical behavior. While ambient exposure of BTS nanoplatelets predominantly creates surface hydroxyl groups, oxygen plasma treatment yields a compact, few-nanometer thick surface oxide layer. The plasma causes p-type doping, accompanied by a decrease of the effective platelet thickness, the interplay of which is manifested in a resistance maximum as a function of plasma treatment time. It is furthermore demonstrated that the structural integrity of the plasma-derived surface oxide is sufficient to enable its use as a gate insulator layer in combination with a top gate.

Enhancement of gas sensor response of nanocrystalline zinc oxide for ammonia by plasma treatment

Abstract The effect of oxygen plasma treatment on nanocrystalline ZnO thin film based gas sensor was investigated. ZnO thin films were synthesized on alkali-free glass substrates by a sol–gel process. ZnO thin films were treated with oxygen plasma to change the number of vacancies/defects in ZnO. The effect of oxygen plasma on the structural, electrical, optical and gas sensing properties was investigated as a function of plasma treatment time. The results suggest that the microstructure and the surface morphology can be tuned by oxygen plasma treatment. The optical transmission in the visible range varies after the oxygen plasma treatment. Moreover, it is found that the oxygen plasma has significant impact on the electrical properties of ZnO thin films indicating a variation of resistivity. The oxygen plasma treated ZnO thin film exhibits an enhanced sensing response towards NH 3 in comparison with that of the as-deposited ZnO sensor. When compared with the as-deposited ZnO film, the sensing response was improved by 50% for the optimum oxygen plasma treatment time of 8 min. The selectivity of 8 min plasma treated ZnO sensor was also examined for an important industrial gas mixture of H 2 , CH 4 and NH 3 .

Surface Functionalization of Macroporous Polymeric Materials by Treatment with Air Low Temperature Plasma

Polystyrene/divinylbenzene (PS-DVB) macroporous monoliths obtained using highly concentrated emulsions as templates show a superhydrophobic behaviour, restricting their potential technological applications, especially those related to adhesion and wetting. Air plasma treatments were carried out in order to modulate wetting properties, modifying the surface chemical composition of macroporous polystyrene/divinylbenzene materials. The superhydrophobic behaviour was rapidly suppressed by air plasma treatment, greatly reducing the water contact angle, from approximately 150 degrees to approximately 90 degrees, in only 10 seconds of treatment. The new surface chemical groups, promoted by plasma active species, were characterized by surface analysis techniques with different depth penetration specificity (contact angle, XPS, FTIR and SEM). Results demonstrated that very short treatment times produced different chemical functionalities, mainly C-O, C=O, O-C=O and C-N, which provide the materials with predominantly acidic surface properties. However, plasma active species did not penetrate deeply through the interconnected pores of the material. FTIR analysis evidenced that the new hydrophilic surface groups promoted by plasma active species are in a negligibly concentration compared to bulk chemical groups, and are located in a very thin surface region on the PS-DVB monolith surface (significantly below 2 microm). XPS analysis of treated monoliths revealed a progressive increase of oxygen and nitrogen content as a function of plasma treatment time. However, oxidation of the PS-DVB monoliths surface prevails over the incorporation of nitrogen atoms. Finally, SEM studies indicated that the morphology of the plasma treated PS-DVB does not significantly change even for the longest air plasma treatment time studied (120 s).

산소 플라즈마 처리한 탄소나노튜브의 표면상태와 전계방출 특성

Multi-walled carbon nanotubes (MWCNTs) were synthesized using catalytic chemical vapor deposition (CVD) method. Oxygen plasma treatment was applied to modify surface state of the CNTs synthesized for improvement of field emission performance. Surface state of the plasma treated CNTs was studied by X-ray photoelectron spectroscopy (XPS). The surface states of the CNTs were changed as a function of plasma treatment time. The oxygen related carbon shift was moved toward higher binding energy with the plasma treatment time. This result implies that the oxygen plasma treatment changes the surface state effectively. While any shift in carbon 1s peak was not detected for the as grown CNTs, oxygen related carbon shift was detected for the plasma treated CNTs. Carbon shift implies that closed CNT tips were opened by the oxygen plasma and reacted with oxygen species. Since the field emission occurs at pentagons or dangling bonds of the CNT tips, the increase of carbon-oxygen bonds plays an important role in field emission behavior by increasing the number of electron emission sites resulting in improvement of the field emission performance.

Effect of Glow-Discharge Air Plasma Treatment on Wettability of Synthetic Polymers

Main aim of this study was focused on characterization of the effect of microwave air plasma treatment on wettability of synthetic polymer surfaces. Wettability of solid polymer surfaces polyethylene, polypropylene, polystyrene (PE, PP, PS) was followed as a function of plasma treatment time. For evaluation the equilibrium contact angles of wetting as well as dynamic contact angles of wetting were determined by means of sessile drop and Wilhelmy plate methods. Free surface energy (SFE) of studied samples were calculated from the experimentally determined contact angles using Fowkes and van Oss, Chaudhury and Good (vOCG) approaches. It was found that with prolonged treatment time the total surface free energy of PE was two times increased from 23 mJ/m2 to 45 mJ/m2 after 360 s plasma treatment time (calculated for W and EG as wetting liquids). Similar effect was found for all studied polymers. With respect to the dispersive and polar components of the total surface free energy the vigorous effect was found for polar component, for which it was increased from 7 mJ/m2 to 20 mJ/m2.

Biocidal Activity of Plasma Modified Electrospun Polysulfone Mats Functionalized with Polyethyleneimine-Capped Silver Nanoparticles

The incorporation of silver nanoparticles (AgNPs) into polymeric nanofibers has attracted a great deal of attention due to the strong antimicrobial activity that the resulting fibers exhibit. However, bactericidal efficacy of AgNP-coated electrospun fibrous mats has not yet been demonstrated. In this study, polysulfone (PSf) fibers were electrospun and surface-modified using an oxygen plasma treatment, which allowed for facile irreversible deposition of cationically charged polyethyleneimine (PEI)-AgNPs via electrostatic interactions. The PSf-AgNP mats were characterized for relative silver concentration as a function of plasma treatment time using ICP-MS and changes in contact angle. Plasma treatment of 60 s was the shortest time required for maximum loss of bacteria (Escherichia coli) viability. Time-dependent bacterial cytotoxicity studies indicate that the optimized PSf-AgNP mats exhibit a high level of inactivation against both gram negative bacteria, Escherichia coli, and gram positive bacteria, Bacillus anthracis and Staphylococcus aureus.

Corrosion protection of a thin aluminium layer deposited on polyester

Organosilicon plasma polymer layers were deposited by surface dielectric barrier discharge (DBD) at atmospheric pressure, in an attempt to enhance the corrosion protection of a reflective aluminium (Al) layer applied on a polyester (PET) fabric. A number of tests were carried out to characterize the improvement of corrosion resistance – namely sodium carbonate (Na 2CO 3), water vapor and Kesternich tests – as a function of plasma treatment time, type of carrier gas, admixture of oxygen, amount of hexamethyldisiloxane (HMDSO) precursor supplied to plasma and post-plasma-treatment heating. Moreover, plasma-deposited protective films were characterized by the scanning electron microscopy (SEM), infrared spectroscopy (DRIFT FTIR), and X-ray photoelectron spectroscopy (XPS). While aluminium was consumed in the Na 2CO 3 corrosive solution within a few minutes for the untreated surface, the optimally performing plasma polymerized layers revealed an extraordinary corrosion resistance. Furthermore, the best protective organosilicon coatings showed only a 1–2% absolute reduction of reflection compared to the untreated fabric, over the complete solar spectrum (250–2500 nm).

Surface modification of spin-coated high-density polyethylene films by argon and oxygen glow discharge plasma treatments

Thin spin coated films of high-density polyethylene (HDPE) were modified by argon and oxygen radio frequency glow discharge plasma. The modified polymer surfaces were characterised by in situ X-ray photoelectron spectroscopy (XPS), contact angle measurements and time-of-flight secondary ion mass spectrometry (TOF-SIMS). In contrast to other reports of argon-plasma treated polymer substrates, we have been able to treat HDPE films with argon-plasma without oxygen incorporation, as measured with in situ XPS. However, exposure to air of argon-plasma treated surfaces leads to incorporation of oxygen (and some nitrogen) species. Properties such as amount of oxygen incorporation as a function of plasma treatment time, oxygen saturation levels, ageing and modification depth were studied.