Ar Gas Plasma Research Articles

Enhancement of S-scheme heterojunction hematite and titanium dioxide nanocomposite by plasma treatment in the photocatalytic membrane for hydrogen separation

This work evaluated the performance of the photocatalytic membrane reactor (PMR) for hydrogen and oxygen separation. The PMR was conducted in a 500-ml reactor under solar light simulated by a mercury arc lamp (250 W). Hematite (α-Fe2O3) was deposited on titanium dioxide (TiO2) by sol-gel method on the Ti foil while palladium (Pd) was deposited on the other side. The sample surface was modified by argon (Ar) gas plasma treatment at 50 W for 10 min. The S-scheme heterojunction photocatalyst was characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy, and UV–vis spectroscopy. The charge carrier transport of photocatalysts was also analyzed. The photocatalytic activity was significantly improved by plasma treatment. The band gap energy decreased from 1.88 eV to 1.77 eV, and the average crystalline was reduced from 21.62 ± 4.79 nm to 21.34 ± 5.63 nm. The photocatalytic activity of fabricated materials for hydrogen production was evaluated in multi-cycle experiments. The highest hydrogen production rate of 1346.19 µmol h−1 was observed for the Ar plasma-treated heterojunction α-Fe2O3 and TiO2 nanocomposite sample (α-Fe2O3 @TiO2-P). After 5 cycles, the photocatalyst reaction of α-Fe2O3 @TiO2-P under solar light irradiation showed high stability for H2 production of 85.24 % compared to the first cycle. The S-scheme was photogenerated of charge transferred of type S-scheme mechanism between α-Fe2O3 and TiO2 under solar light. This work provides insight to enhance hydrogen production through the modification of the S-scheme photocatalyst membrane. The improved photocatalytic performance of the fabricated material suggests the effectiveness of the proposed Ar plasma treatment strategy to enhance the photoactivity for H2 production via water splitting.

Surface Roughness Influence on Tribological Behavior of HiPIMS DLC Coatings

The application of diamond-like carbon (DLC) coatings in dry machining of difficult-to-machine materials has been gaining popularity due to high inertness, low coefficient of friction (COF), and high hardness of these coatings. Although the effect of surface roughness on the tribological properties of DLC coatings is of paramount importance, usually it is overlooked and coatings performance analysis was accomplished generally on highly polished substrates. The generation of polished surfaces is a time-consuming, labor-intensive process and, in most cases, not feasible for the industry due to its high cost. This article focuses on determining the effect of substrate (cemented carbide, WC-Co) surface roughness on the load-bearing capacity and tribological properties of DLC coatings deposited by High Power Impulse Magnetron Sputtering (HiPIMS) in Ne–Ar gas plasma. The DLC films were deposited onto WC-Co substrates with three different surface roughness profiles and their tribological performance were evaluated using a reciprocating tribotest. The high surface roughness resulted in increased wear rate due to high levels of asperities and increased potential for premature delamination of the coatings, while also causing severe damage to the counterbody due to inhibition of transfer film formation.

Renewal of Lead Battery Electrodes Using a Plasma—Chemical Processing Method

The increasing use of renewable energy sources increases the need for electricity storage systems. In this work, the possibility of renewing worn-out battery Pb electrodes by applying Ar and O2 gas plasma in a magnetron vacuum system was investigated. As shown by the SEM results of the surface of Pb electrodes, after exposure to O2 plasma, the surface of Pb electrodes consists of irregularly shaped microstructures. Analyzing the XRD results revealed that the spectrum peaks of the Pb4O3SO4 compound are more pronounced in the case of the electrodes of the worn battery than those electrodes that were exposed to Ar and O2 gas plasma. It was observed that the process of renewing Pb electrodes in Ar and O2 plasma has a positive effect. This effect is also confirmed by the results of EDS studies, as the chemical compounds that inhibit the charge/discharge process are reduced, and the percentage of pure lead increases from 68.2% (in the case of worn electrodes) to 81–82% (when the worn electrodes were processed using Ar and O2 plasma).

Effect of Microstructural and Tribological Behaviors of Sputtered Titanium Carbide Thin Film on Copper Substrate

Titanium carbide (TiC) thin films were deposited by radio frequency magnetron sputtering (RFMS) onto a copper substrate by using Argon (Ar) gas plasma at a gas flow rate of 10.0 sccm. The effect of time and temperature at a constant RF power on the structural and tribological properties were respectively investigated by atomic force spectroscopy (AFM), X-ray Diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, optical microscopy (OM), scanning electron microscopy (SEM) and tribological measurements. All films were tested to have crystal structures with the preferential plane (111) and dominant plane (200) grain orientations. Thus, plane (111) has phase identification of Cu(Cu16Ti)0.23 for some samples, whereas plane (200) has a phase identification of Cu(Cu0.997Ti0.003) and Cu(Cu0.923Ti0.077) for other samples. The lowest thin film roughness of 19.797 nm was observed in the sample, with RF power, sputtering time, and a temperature of 200 W, for two hours and 80 °C, respectively. The FTIR spectra of TiC films formed under different sputtering times (2-3 h) and temperatures (80 °C-100 °C) on Cu substrates at a constant sputtering power of 200 W in the range of 5000-500 cm-1. The peaks at 540 cm-1, 780 cm-1, and 1250 cm-1 are presented in the FTIR spectra and the formation of a Ti-C bond was observed. On the other hand, a sample was revealed to have the lowest wear volume of 5.1 × 10-3 mm3 while another sample was obtained with the highest wear volume of 9.3 × 10-3 mm3.

Spatio-temporal measurements Ar 2p1 excitation rates and optical emission spectroscopy by capacitively coupled Ar and Ne mixed gas plasma

Spatio-temporal measurements Ar 2p1 excitation rates and optical emission spectroscopy by capacitively coupled Ar and Ne mixed gas plasma

Study the electron field emission properties of plasma-based reduction of graphene oxide (GO): An ex-situ plasma approach

Vacuum-based electron emission devices requires fast and low turn-on field processes. Graphene oxide (GO) can be a perfect candidate for field electron emission applications. In this work, we have prepared graphene oxide (GO) via modified Hummer's method and treated it with dense plasma of argon gas (Ar). The surface morphology of the prepared GO reveals the growth of the stacked-layer and large surface area flakes of GO. Raman spectra reveals the high defective growth of GO. The impurities in the GO are due to the incorporation of oxygen moieties. For enhancing the field emission properties, the GO thin films were treated with a dense plasma of Ar gas at 50, 100, 150 and 200 W. Raman spectra strongly indicates the removal of oxygen moieties and formation of defects and vacancies in the sheet of plasma-treated GO. The field emission properties drastically improved in the scenario of plasma-treated GO field emitters. The turn-on and threshold fields were reduced after plasma treatment in comparison with pristine GO field emitters. The reduction in the turn-on and threshold fields is due to the enhancement in the edge effects, protrusion formation and modification in structural properties. The emission current density was drastically enhanced in the 200 W plasma-treated GO field emitters. The emission stability test was performed for a 600 min at 3 V / μ m applied electric field. The stability was enhanced with plasma power and shows the minimum current fluctuation. The field enhancement factor also improved after plasma treatment and for 200 W treated β becomes 3 times the pristine GO. We have also implemented the orthodox emission hypothesis test, which was qualified by the prepared pristine and plasma-treated GO field emitters due to the f e x t r values belonging in the acceptable range. Conclusively, Ar gas plasma-treated GO field emitters can be useful for emission applications in vacuum devices.

The Influences of Non-Volatile Surface Compound Layer on the Dry Etching of Borosilicate Glass

In the dry etching of borosilicate glass (BSG), the process gas reacts with the impurities of borosilicate glass and forms a non-volatile compound layer on the surface. This surface compound layer (SCL) makes it difficult to control the surface morphology and device structure dimension with precision and significantly influences the etch rate. We examined the influence of SCL on the etch rate of quartz and BSG and discussed its etching mechanism depending on the thickness of the SCL. The formation of SCL was dominated by both the plasma gas composition and substrate material, and the etching regime can be defined by the thickness of the SCL. A thin SCL was formed on the BSG by CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /Ar gas plasma etching, and the etch rate was suppressed by the SCL. A significantly thin SCL was formed on the quartz specimens under in same etching conditions, and a direct etching reaction was occurred. As the ratio of physical etching gas (Ar) increased, both the ion energy flux and the physical ion bombardment increased and consequently improved the etch rate. The SCL plays the role of an F radical supplier, while the thick SCL reduces the etch rate because it takes time for the etchants to transit from the surface to the interface. The SCL acts as a barrier in the etching reaction, which could be adjusted by the regulation of the etching gas composition or the plasma parameters, such as the inductive power and the bias power of the RIE reactor. [2021-0071]

Enhancement of Electrical Properties of Sol-Gel Indium-Tin-Oxide Films by Microwave Irradiation and Plasma Treatment.

We proposed the enhancement of the electrical properties of solution-processed indium–tin–oxide (ITO) thin films through microwave irradiation (MWI) and argon (Ar) gas plasma treatment. A cost- and time-effective heat treatment through MWI was applied as a post-deposition annealing (PDA) process to spin-coated ITO thin films. Subsequently, the sheet resistance of MWI ITO thin films was evaluated before and after plasma treatment. The change in the sheet resistance demonstrated that MWI PDA and Ar plasma treatment significantly improved the electrical properties of the ITO thin films. Furthermore, X-ray photoelectron spectroscopy and X-ray diffraction analyses showed that the electrical properties of the ITO thin films were enhanced by the increase in oxygen vacancies due to the ion bombardment effect of high-energy plasma ions during Ar plasma treatment. Changes in the band gap structure of the ITO thin film due to the ion bombardment effect were also analyzed. The combination of MWI PDA and Ar plasma treatment presents new possibilities for improving the high-conductivity sol–gel ITO electrode.

Modification of surface α-Fe2O3/TiO2 photocatalyst nanocomposite with enhanced photocatalytic activity by Ar gas plasma treatment for hydrogen evolution

In this work, hematite (α-Fe2O3) deposited on anatase TiO2 was modified by plasma treatment and studied. α-Fe2O3/TiO2 was successfully synthesized using sol-gel precipitation methods and the surface was modified by argon (Ar) gas plasma treatment to increase photocatalyst nanocomposite activity. The effect of Ar-plasma treatment times from 5 to 20 min at DC glow discharge powers of 50 watts was investigated. The crystal structures, surface morphology, optical properties were characterization by using X-ray Diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), UV–vis spectrometry (UV–Vis), X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL) and electrochemical impedance spectroscopy (EIS). After plasma treatment, the crystalline phase of TiO2 form changed from pure anatase to a mixture of anatase and rutile phases. The particle size was reduced from 25 to 20 nm. The band gap energy decreased from approximately 2.18 eV to 1.84 eV and exhibited a wider absorption edge under visible light irradiation (400–700 nm). Ar-plasma modification of the surface showed the attribution of oxygen vacancies and Ti3+. The plasma treatment improved the heterojunction photocatalyst to enhance the photocatalytic activity under visible light for H2 evolution. The best photocatalytic activity for H2 evolution rate was obtained at 1.25 mmol h-1 for α-Fe2O3/TiO2-10 photocatalyst compared to α-Fe2O3/TiO2-untreated (0.13 mmol h-1). The plasma treatment on photocatalyst materials showed long-term stability and excellent separation of the photogenerated charge carriers.

XPS Studies of the SiO2 Substrates and Thermoelectric Thin Films of Sn/Sn+SnO2 under the Effects of the Different Thermal Treatments

Multilayered thermoelectric Sn/Sn+SnO2 thin films were prepared using KJL DC/RF magnetron sputtering system under Ar gas plasma on the SiO2 substrates. The thicknesses of the fabricated thin films were found using Filmetrics UV thickness measurement system. The fabricated thin films were annealed at different temperatures for one hour to tailor the thermoelectric properties. In this study, unannealed, annealed at 150 and 300°C samples were characterized using Thermo Fisher XPS system brought to the Alabama A&M University by the NSF-MRI support. X-ray Photoelectron Spectroscopy (XPS), also known as Electron Spectroscopy for Chemical Analysis (ESCA) is a type of analysis used for characterization of various surface materials. XPS is mostly known for the characterization of thin films-which are coatings that have been deposited onto a substrate and may be comprised of many different materials to alter or enhance the substrate’s performance. XPS analysis provides information for composition, chemical states, depth profile, imaging and thickness of thin film. This paper focuses on the application of XPS techniques in thin film research for Sn/Sn+SnO2 multilayered thermoelectric system and SiO2 substrates annealed at different temperatures. Since SiO2 substrates were used during the deposition of the multilayer thin films, we would like to perform detailed XPS studies on the SiO2 substrates. SiO2 substrates is being used with many researchers, this manuscript will be good reference for the researchers using SiO2 substrates. Thermal treatment of the substrates and the multilayered thin films has caused some changes of the XPS characterization including binding energy, depth profile, peak value and FWHM. The treatment effects were discussed and compared to each other.

Surface modification of FO membrane by plasma-grafting polymerization to minimize protein fouling

The aim of this study was to compared the effect of two plasma gases, Argon (Ar) and carbon dioxide (CO2), in the acrylic acid (AAc) grafting modification of a commercial cellulose triacetate (CTA) membrane to improve water flux and anti-protein fouling properties in forward osmosis (FO) for protein recovery application. The successful grafting polymerization was evaluated by measuring the grafting yield and water contact angle, X-ray photoelectron spectroscopy (XPS) analysis, Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) analysis. The contact angle of the CTA membrane was decreased from 64.0° to 37.1° and 36.4° by CO2 and Ar plasma gas treatment, respectively, which indicated an increase in hydrophilicity. The FO experiments were carried out in a lab-scale filtration apparatus. The effects of interfacial characteristics between membrane surfaces and model protein and polysaccharide foulants on flux decline and reversibility of foulants were compared. Ar gas was able to provide more free radicals and plasma electrons on the membrane surfaces, thus it was more effective than CO2 in increasing water flux and also decreased reverse salt flux and fouling tendency. The modified membranes had excellent anti-protein fouling properties, which makes them suitable for protein recovery applications. Using the Ar plasma modified membranes, tuna protein was concentrated from 4.5 % to 10.7 %, and excellent maintenance of water flux was achieved.

ZnO thin films synthesis by RF magnetron sputtering deposition

Investigation of ZnO thin films synthesis using RF magnetron sputtering deposition in the Ar/O2 plasma gas mixture at different O2 composition and at different growth temperatures is presented. The effect growth process on structural (morphology and orientation films, grain sizes, lattice parameters) and optical (transmittance, absorption, refractive index, photoluminescence) properties are examined. It is shown that synthesized ZnO thin films at a temperature from 200 to 300 °C are polycrystal and textured. Notice that ZnO thin films, which are synthesized using pure Ar plasma gas, are porosity. The optical transmittance and absorption spectra have an absorption edge near 380 nm. The PL spectra of synthesized ZnO films show exciton peaks at 370-400 nm and the wide emission at the yellow and red spectral regions.

Electrical, thermal and optical characteristics of plasma torch

Non thermal argon plasma needle at atmospheric pressure was constructed. The experimental set up was based on simple and low cost electric components that generate electrical field sufficiently high at the electrodes to ionize various gases which flow at atmospheric pressure. A high AC power supply was used with 9.6kV peak to peak and 33kHz frequency. The plasma was generated using two electrodes. The voltage and current discharge waveform were measured. The temperature of Ar gas plasma jet at different gas flow rate and distances from the plasma electrode was also recorded. It was found that the temperature increased with increasing frequency to reach the maximum value at 15 kHz, and that the current leading the voltage, which demonstrates the capacitive character of the discharge. The electron temperature was measured at about 0.61 eV, and we calculated the electron number density to be 4.38×1015 cm-3.

Modulating the concentrations of reactive oxygen and nitrogen species and oxygen in water with helium and argon gas and plasma jets

We employed UV–vis spectroscopy to monitor real-time changes in the oxygen tension and concentration of reactive oxygen and nitrogen species (RONS) in deionized (DI) water during treatments with helium (He) and argon (Ar) gas plasma jets. He and Ar gas jets are both shown to de-oxygenate DI water with He being more efficient than Ar, whilst the plasma jets deliver and regulate the concentrations of hydrogen peroxide (H2O2), nitrite (NO2−) and nitrate (NO3−) in DI water. The H2O2 and NO3− production efficiency varied between He and Ar plasma jets, but was similar for NO2−. Whilst DI water fully equilibrated with ambient air prior to treatment (de-oxygenated by both plasma jets) when DI water was first de-oxygenated by an inert gas jet treatment, both plasma jets were found to be capable of oxygenating DI water. These insights were then used to show how different combinations of plasma jet and inert gas jet treatments can be used to modulate O2 tension and RONS chemistry. Finally, potential further improvements to improve control in the use of plasma jets in regulating O2 and RONS are discussed.

Sidewall chemistry of nano-contact patterns in C4F8 + CH2F2 + O2 + Ar inductively coupled plasmas

In this study, silicon dioxide contact holes were etched with C4F8 + CH2F2 + O2 + Ar gas plasmas, and the characteristics of the etching residue thereby generated inside the nanopatterns were investigated. The chemical composition of the etching residue formed on the sidewalls of the nano-contact patterns in the gas chemistry was investigated at various oxygen partial pressures by performing in situ Ar sputtering and X-ray photoelectron microscopy at different take-off angles. To investigate the effect of the plasma-active species (polymerizing radicals and charged species) on the formation of the etching residue, plasma diagnostics were conducted via optical emission spectroscopy and Langmuir probe measurements. It was found that as the oxygen content of the plasma increased, the thickness of the fluorocarbon (FC) polymer layer formed on the sidewalls of the nanopatterns decreased with a reduction in the FC polymer deposition rate of the plasma. In addition, at higher aspect ratios, the FC polymer layer showed a lower fluorine content.

Effect of Ar, O2, and N2 Plasma on the Growth and Composition of Vanadium Oxide Nanostructured Thin Films

AbstractVanadium oxide nanostructured thin films (NTFs) are synthesized using plasma assisted sublimation process (PASP) in different gases' Ar, O2, and N2 plasma (AP, OP, and NP) and O2 gas (OG) ambient. Morphological studies conducted via electron microscopy reveal nanostrips, nanoflakes, nanorods, and nanoparticles organized as clusters for OP, OG, AP, and NP respectively. X‐ray photoelectron spectroscopy (XPS) studies show that samples OP and OG are composed of α‐V2O5, whereas AP and NP are composed of V6O13 along with V2O5. The relative percentages calculated using XPS data show that in AP, V6O13, and V2O5 are 38 and 62%, respectively. These percentages change to 48% for V6O13 and 52% for V2O5 in NP. The V6O13/V2O5 ratio is lower in AP than NP. This increment of V6O13 in NP is due to presence of more reductive species in N2 plasma than Ar plasma. Since N2 plasma contains species like N*, , etc. it leads to the formation of NO2, N2O, etc. Raman spectra indicate the surface of the sample NP consisting of both V6O13 and V2O5, agreeing with the X‐ray diffraction (XRD) and XPS results. Studies demonstrate that plasma ambient during synthesis process affects both morphology and composition of deposited vanadium oxide NTFs.

Step-Down dc-dc Converter for Low Temperature Plasma

This paper presents a step down converter with a high speed rectifier and filter for Argon plasma torches. Buck circuit with a high frequency pulse width modulation control and very fast MOSFET transistor were used for switching. For Argon (Ar) gas Plasma Torches, and by increasing the pulse width, the average output voltage has modified from 80 V up to 100 V. The frequency of the designed step down converter was steady at 20 KHz.

High Frequency High Power Full Bridge Converter for Plasma Torches

This paper presents a full bridge converter with a high speed rectifier and filter for plasma torches. Full bridge circuit with high frequency pulse width modulation control is used and high frequency transformer to insulate is adopted. For Argon (Ar) gas Plasma Torches, and by increasing the pulse width the average power consumption has modified from 1KW to 5.6KW (positive load). For Nitrogen (N2) gas Plasma Torches, and by increasing the pulse width the average power consumption has reduced from 7.7KW down to 3KW (negative load). For the Plasma Torches load the frequency of converter was steady at 50KHz.

Capture of dengue viruses using antibody-integrated graphite-encapsulated magnetic beads produced using gas plasma technology.

Despite significant advances in medicine, global health is threatened by emerging infectious diseases caused by a number of viruses. Dengue virus (DENV) is a mosquito-borne virus, which can be transmitted to humans via mosquito vectors. Previously, the Ministry of Health, Labour and Welfare in Japan reported the country's first domestically acquired case of dengue fever for almost 70 years. To address this issue, it is important to develop novel technologies for the sensitive detection of DENV. The present study reported on the development of plasma-functionalized, graphite-encapsulated magnetic nanoparticles (GrMNPs) conjugated with anti-DENV antibody for DENV capture. Radiofrequency wave-excited inductively-coupled Ar and ammonia gas plasmas were used to introduce amino groups onto the surface of the GrMNPs. The GrMNPs were then conjugated with an antibody against DENV, and the antibody-integrated magnetic beads were assessed for their ability to capture DENV. Beads incubated in a cell culture medium of DENV-infected mosquito cells were separated from the supernatant by applying a magnetic field and were then washed. The adsorption of DENV serotypes 1–4 onto the beads was confirmed using reverse transcription-polymerase chain reaction, which detected the presence of DENV genomic RNA on the GrMNPs. The methodology described in the present study, which employed the plasma-functionalization of GrMNPs to enable antibody-integration, represents a significant improvement in the detection of DENV.

A study of adhesive improvement of a Cr-Ni alloy layer on a liquid crystal polymer (LCP) surface

Abstract To improve adhesion of an alloy plating layer made from chromium (Cr) and nickel (Ni), surface modification effects produced by low pressure nitrogen (N 2 ), oxygen (O 2 ), or argon (Ar) gas plasmas on a liquid crystal polymer (LCP) film were analyzed with X-ray photoelectron spectroscopy (XPS). Furthermore, we focused on motion of the LCP main chains caused by macro-Brownian motion and found that reducing the glass-transition temperature of liquid crystalline by annealing further improves adhesion between the alloy plating layer and LCP.