Reactive Gas Flow Rate Research Articles

Confirmation of40Ar+related product ions in the octopole reaction cell of an ICP-QMS/QMS with18O2enriched oxygen as the reaction cell gas

40Ar+ related product ions in an octopole reaction cell (ORC) were observed with an inductively coupled plasma tandem quadrupole mass spectrometer (ICP-QMS/QMS). In order to simplify the ion composition of the plasma, the carrier gas was directly connected to the torch injector, i.e. without introduction of the sample solution. The m/z of the first QMS was set to 40 permitting the passage of 40Ar+. Isotope enriched oxygen gas (18O2) was used as the reaction gas in order to separate the spectra of O3+ and Ar2O2+. The intensities of the ions produced in the ORC were measured by the second QMS. As the products of the reactions among 40Ar+ ions and 18O2 molecules in the ORC, the following ions were observed: 18O+, 18O2+, 18O3+, 18O4+, 40Ar18O+, 40Ar18O2+, 40Ar218O2+, and 40Ar18O22+. At a reaction gas flow rate of 0.3 mL min−1, the ionic species with the highest signal intensity was 18O2+, followed by 40Ar+ and 18O+. The maximum signal intensities of different product ions were obtained at different flow rates of the reaction gas. A lower flow rate of the reaction gas benefited the production of 40Ar18O+ and 18O3+, while a higher flow rate of the reaction gas benefited the production of 40Ar18O2+ and 40Ar218O2+. The maximum transfer efficiency from 40Ar+ to the resulting ionic species was 91%, 2.0%, and 0.12% for 18O2+, 18O+, and 40Ar18O+, respectively. The maximum transfer efficiency to the other investigated ionic species was less than 0.023%. By using 18O2 as the reaction gas, the mechanisms of 40Ar+ resulted ionic species interfering with the measurement of 32S16O+ were confirmed. The results showed that the contributions of 16O3+ and 40Ar2O2+ were almost equivalent to each other.

Optimization of process parameters to achieve spectrally selective TiAlC/TiAlCN/TiAlSiCN/TiAlSiCO/TiAlSiO high temperature solar absorber coating

TiAlC/TiAlCN/TiAlSiCN/TiAlSiCO/TiAlSiO tandem absorber was deposited on stainless steel substrate by using four cathode reactive direct current unbalanced magnetron sputtering system. The reactive gas flow rates (C2H2, N2 and O2) and thicknesses of each individual layers were varied to obtain the selective properties of the tandem absorber. The detailed effects of reactive gas flow rates and thicknesses of the individual layers on the optical properties were studied by using UV–vis–NIR spectrophotometer. Guiding factor in optimizing various process parameters was to achieve low reflectance in the solar spectrum region and high reflectance in the infrared region. The change in growth rate of the tandem absorber with reactive gas flow rate was studied using the thickness data, target voltage and target current. These results indicate a decrease in the growth rate of each individual layer of the tandem absorber with an increase in the flow rates of the reactive gases. The changes in bonding structure and chemical composition with reactive gas flow rates were studied by X-ray photoelectron spectroscopy. The optimized tandem absorber deposited on stainless steel substrate shows absorptance of 0.960 and emittance of 0.15. The thicknesses of the optimized individual layers were ∼62, 18, 20, 16, 27nm, respectively.

Model-Based Analysis of Carbon Corrosion in Start-up/Shutdown, Fuel Starvation, and Voltage Reversal of a Polymer Electrolyte Fuel Cell

Support carbon corrosion has been identified as a major degradation source in a polymer electrolyte fuel cell. Start-up/Shutdown (SUSD) [1], fuel starvation [1], and voltage reversal [2] are widely-known conditions that can trigger non-negligible carbon corrosion in the anode or cathode. SUSD carbon corrosion is associated with current reversal while there is no external load. As a comparison, fuel starvation due to nitrogen blanketing and/or water droplets in an operating cell also can result in similar current reversal. The region with current reversal, i.e., a proton flux from the cathode to the anode, features extremely severe hydrogen depletion in the anode and occurrence of carbon corrosion in the opposite cathode. Differently, the voltage reversal occurs in one or a few cells (not all) in a stack. Those cells show negative cell voltages under extended reversal, but the overall current is flowing as usual thanks to the other normal cells in the stack. The voltage reversal leads to carbon corrosion in the anode, as compared to carbon corrosion in the cathode for current reversal. The local potential for carbon corrosion could be much more severe in an extended voltage reversal than that in SUSD. This paper/presentation will elucidate the fundamental differences of these three carbon corrosion scenarios with model simulation and analysis. The models [3, 4] will also be used to perform comprehensive parametric studies, aiming to understand the impacts from key design and operating parameters including pseudo-capacitance, selective oxygen evolution reaction (OER) catalysis, reactant gas flow rate, temperature, membrane hydration state, and current load drawn from the stack. It is anticipated to shed light on the otherwise confusing carbon corrosion scenarios in a polymer electrolyte fuel cell and the fundamental ideas for alleviation strategies. For example, in the fuel starvation induced carbon corrosion, the simulation indicates that the decreasing cell voltage due to diluted hydrogen concentration appears to limit the local potential in the cathode and associated carbon corrosion. In the SUSD carbon corrosion, pseudo-capacitance from Pt oxidation may raise another concern in parallel to carbon corrosion. In general, a reduced temperature or enhanced OER activity is helpful in reducing carbon corrosion.

Reducing Polarization Using Novel Carbon Support in Polymer Electrolyte Fuel Cells

1. Introduction Fibrous carbon nanomaterials are expected to be appropriate Pt support materials. Their small diameter and long length contribute to the formation of large specific surface areas. Fibrous carbon materials have few inside internal pores, and their surface areas are due to the outside of the fibers. The fibrous structure is expected to facilitate both the smooth supply of fuel gases and the discharge of water. Carbon nanofilaments(CNFs) are fibrous carbon materials that have a cup-stack primary structure with graphene edges on the filament surface. The edges on the outer surfaces of CNFs are expected to act as support sites for highly dispersed Pt particles. Marimo-like carbon (MC)(1) comprises many CNFs that are interwoven to form a spherical secondary shape. We studied the relation between preparation conditions and properties of the formed Pt nanoparticles and revealed the effects of the microstructure of catalyst layers using MC 2. Experimental MC was synthesized by CVD using a fixed-bed flow-type reactor. An oxidized diamond-supported Ni catalyst was placed at the center of the reactor, and heated to the reaction temperature, after which a reactant gas was fed into the reactor in a stream of Ar at a flow rate of 30 mL min-1. The reaction temperature was maintained at 823 K for 10 h, and the CH4 reactant gas flow rate was 30 mL min-1. An MC supported Pt catalyst(Pt/MC) was prepared using the nanocolloidal solution method(2). Carbon materials were added to the solution before Pt particles were generated. Pt particles were directly deposited from the solution onto the surfaces of carbon materials. Pt/MC was used as the membrane electrode assembly (MEA) with different catalyst inks (I/C = 0.14) produced from the carbon supported Pt catalyst (Pt/C, I/C = 0.46). The surface area of the electrode was 5×5 cm2, and the amount of Pt in the electrode was 5 mg (0.2 mg cm-2). The I-V measurements were conducted at 353 K. Humidified hydrogen gas (200 ml min-1, 100 % RH at 353 K) was supplied to the anode and humidified air (200 ml min-1, 100 % RH at 353 K) was supplied to the cathode. The durability of the fuel cell was estimated using an accelerated degradation test (ADT). Electrodes were conditioned by potential cycling at a scan rate of 200 mV s-1 over a range of 50 -1200 mV vs. RHE. 3. Results and discussion Before ADT (0 cycle), the MEA using the Pt/C showed higher performance than the Pt/MC. The oxygen reduction reaction activities of Pt/MC were 41.9 A g-1 (mass activity) and 58.9 mA cm-2 (specific activity) and those of Pt/C were 83.9 A g-1 and 76.9 mA cm-2. The Pt/C exhibited two times better performance than Pt/MC before ADT. However, after 500 cycles of ADT, Pt/MC exhibited the same performance as Pt/C and even better performance after 1000-2000 cycles. From this result, the cause of low performance using Pt/MC was perhaps determined to be the shortage breaking in the fuel cell during this operation. The mechanism of this behavior under cell operating conditions was not clear, but the good cell performance was confirmed shen using Pt/MC. Pt/MC exhibited high durability under ADT conditions. This result reveals that MC has superior oxidation-resistant properties under ADT conditions. MC comprises carbon nanofilaments, which have a graphene stacked structure. Only the edges of graphene sheets can be oxidized, the inside of graphene cannot be oxidized. Thus, the graphene structure is more stable against oxidation and decomposition compared with an amorphous structure. The unique structure of MC results in superior electrochemical properties. (1) K. Nakagawa, H. Oda, A. Yamashita, M. Okamoto, Y. Sato, H. Gamo, M. Nishitani-Gamo, K. Ogawa, T. Ando, J. Mater. Sci, 44 (2009) 221. (2) M. Eguchi, S. Yamamoto, M. Kikuchi, K. Uno, Y. Kobayashi, M. Nishitani-Gamo, T. Ando, Journal of Surface Finishing Society of Japan, 62 (2011) 179.

Tribological behavior of TiN films depositid by reactive magnetron sputtering under low pressure

The effect of deposition conditions on the tribological behavior of titanium nitride thin films produced by reactive magnetron sputtering has been studied. Dependences of the hardness, the width of the friction track, the friction coefficient, and the volume wear of the TiN films on the N2 reactive gas flow rate have been obtained. Conditions of deposition under which the coatings with the best tribological characteristics are formed have been determined.

Phenomenological study of iron and lanthanum magnetron co-sputtering using two reactive gases

Abstract Due to their tunability, oxynitride perovskites are mainly studied for new applications as smart devices. The miniaturization of such component has led to thin film synthesis and reactive magnetron sputtering from metallic targets is an efficient way for such objective. However, co-sputtering in two reactive gases involves complex mechanisms, and studies are usually dedicated to highly reactive element (Ti, Si, Nb, Al, Zr). We purpose a phenomenological study of lanthanum and iron co-sputtering in Ar/O 2 /N 2 atmosphere. In a first step, single target sputtering with one and two reactive gases has been studied. Elemental and compound sputtering modes have been determined. La target exhibits a clear hysteresis behavior while Fe shows a reversible one as a function of the reactive gas flow rate. In a second step, La and Fe targets have been co-sputtered using one or two reactive gases. In each case, the mechanisms involved are mainly driven by La target, with a shift of the hysteresis loop to higher gas flow rate. Then, a two dimensional diagram is purposed with delimitation of sputtering regimes, depending on reactive flow rate (N 2 and O 2 ). Finally, two LaFeO 3 − x N x multilayers have been synthesized with two initial atmospheres (Ar/O 2 ratio are 21/7 and 21/1 sccm) where nitrogen is introduced step by step. SIMS analysis and voltage measurements during sputtering, deposition rate, electrical resistivity and UV–visible measurements show that nitrogen incorporation can be roughly controlled choosing the atmosphere composition. Selected conditions have been determined to deposit oxynitride perovskite thin films with an optimized nitrogen content to tune the film optical properties, with Ar/O 2 /N 2 ratio of 21/1/6.

Influence of Temperature and Pressure on the Performance of Proton Exchange Membrane Fuel Cell

Proton Exchange Membrane (PEM) fuel cells are having high efficiency and working at low temperature and atmospheric pressure. The operating parameters like temperature, pressure, mass flow rate and humidity of reactant gases, are greatly affecting the performance of the fuel cells. In this paper, the optimum values of the operating temperature and pressure of the PEM fuel cell were found numerically. A single channel PEM fuel cell with active area of 60 mm2 was modeled and analyzed using COMSOL software package. The fuel cell was operated at different temperatures of 40°C, 50°C, 60°C, 70°C and 80°C corresponding to the operating pressures of 0.5 bar, 1 bar, 1.5 bar and 2.0 bar. The current density values of the fuel cell corresponding to the different cell voltages were obtained for all 20 different combinations of the above pressures and temperatures. From the results, it was found that the maximum power density was obtained at the operating pressure of 2 bar and operating temperature of 40°C corresponding the cell potential of 0.35 V. The optimum values of the operating parameters like temperature, pressure and cell potential of PEM fuel cell were found numerically.

Study of hysteresis behavior in reactive sputtering of cylindrical magnetron plasma**Project supported by the Department of Science and Technology, Government of India and Council of Scientific and Industrial Research, India.

In order to make sufficient use of reactive cylindrical magnetron plasma for depositing compound thin films, it is necessary to characterize the hysteresis behavior of the discharge. Cylindrical magnetron plasmas with different targets namely titanium and aluminium are studied in an argon/oxygen and an argon/nitrogen gas environment respectively. The aluminium and titanium emission lines are observed at different flows of reactive gases. The emission intensity is found to decrease with the increase of the reactive gas flow rate. The hysteresis behavior of reactive cylindrical magnetron plasma is studied by determining the variation of discharge voltage with increasing and then reducing the flow rate of reactive gas, while keeping the discharge current constant at 100 mA. Distinct hysteresis is found to be formed for the aluminium target and reactive gas oxygen. For aluminium/nitrogen, titanium/oxygen and titanium/nitrogen, there is also an indication of the formation of hysteresis; however, the characteristics of variation from metallic to reactive mode are different in different cases. The hysteresis behaviors are different for aluminium and titanium targets with the oxygen and nitrogen reactive gases, signifying the difference in reactivity between them. The effects of the argon flow rate and magnetic field on the hysteresis are studied and explained.

Nanocrystalline silicon embedded in silicon suboxide synthesized in high-density inductively coupled plasma

A two-phase material system of nanocrystalline silicon (nc-Si) embedded in a dielectric matrix of silicon suboxide (SiOx) is fundamentally and technologically significant for the photonic and photovoltaic device such as light emission diode and solar cells. nc-Si in amorphous SiOx has been synthesized by means of the low-frequency (460 kHz) inductively coupled plasma (LFICP) of SiH4 + CO2 + H2 without the common route of high hydrogen dilution. The chemical composition, microstructures and optical properties of the complex material system are tuned by the reactive gas flow rate ratio of CO2/SiH4. nc-Si embedded in amorphous SiOx due to the phase separation are observed by means of SEM and TEM characterization tools. The crystalline volume fraction in nc-SiOx:H is determined by the density of the embedded nc-Si particles and the occurrence of the a-SiOx encapsulating shell layer. The bond configuration analysis shows the concurrent oxygenation and dehydrogenation process with the incorporation of oxygen. The underlying mechanism in forming the two-phase complex material system and the phase evolution with the reactive gas flow rate ratio are discussed in terms of the unique features of the utilized high-density LFICP.

Electrical transport property of zirconium oxynitride thin film deposited by magnetron sputtering process

Zirconium oxynitride thin films were deposited on the sapphire substrate by DC magnetron sputtering process, which was performed in argon/oxygen/nitrogen mixture gases with various flow rates of reactive gases (N2+O2). It was observed from XRD, Raman and XPS results that oxygen had a great effect not only on the composition but also on the structure of zirconium oxynitride films. Moreover, the electrical behavior of zirconium oxynitride thin film was investigated and correlated with their compositional and structural properties. For samples deposited at relatively low flow rate, the 2D–3D process dominates the electrical transport mechanism in a weakly localized regime. When the samples deposited at a relatively high-flow rate, the electronic transport is governed by thermal activation at the high temperatures. While a crossover from thermal activation conduction to Mott’s variable hopping conduction (VRH) was observed at the lower temperature range. The experimental results demonstrate that the addition of a small amount of oxygen into the zirconium nitride films can be an effective way to optimize the compositional, structural as well as electrical conduction properties of zirconium oxynitride thin films.

The role of pulse length in target poisoning during reactive HiPIMS: application to amorphous HfO2

In conventional reactive magnetron sputtering, target poisoning frequently leads to an instability that requires the reactive gas flow rate to be actively regulated to maintain a constant composition of the deposited layers. Here we demonstrate that the pulse length in high power impulse magnetron sputtering (HiPIMS) is important for determining the surface conditions on the target that lead to poisoning. By increasing the pulse length, a smooth transition can be achieved from a poisoned target condition (short pulses) to a quasi-metallic target condition (long pulses). Appropriate selection of pulse length eliminates the need for active regulation, enabling stable reactive magnetron sputter deposition of stoichiometric amorphous hafnium oxide (HfO2) from a Hf target. A model is presented for the reactive HiPIMS process in which the target operates in a partially poisoned mode with a distribution of oxide on its surface that depends on the pulse length.

Improving the stoichiometry of RF-sputtered amorphous alumina thin films by thermal annealing

Abstract High quality alumina thin films were deposited on glass substrate by reactive radio-frequency sputtering. The deposition process and rate were controlled by radio-frequency power and reactive gas (oxygen) flow rate. The relationships between O/Al ratio contents and the structural, electrical resistivity and optical parameters of the films were investigated. The O/Al of the films varied with change in oxygen flow ratio, power density and post deposition annealing. The structure and phase of the films were unaltered as the deposition parameters and post deposition annealing up to 573 K were varied. O/Al of 1.5 was obtained at oxygen flow ratio of 11%, radio-frequency power of 250 W and post deposition annealing of 573 K. The sheet resistance of the films were all very high but the same within experimental uncertainties. The optical parameters (transmittance, refractive index and extinction coefficient) of the films varied considerably and depended on the films' stoichiometry.

Photo-catalytic destruction of ethylene using microwave discharge electrodeless lamp

A double tube type microwave discharge electrodeless lamp was employed to investigate the photo-catalytic decomposition of ethylene gas, an important VOC species. The anatase TiO2 film photo-catalyst balls prepared by a low pressure metal organic chemical vapor deposition method were used. In addition, the advantages of microwave/UV/TiO2 photo-catalysts hybrid process were analyzed. The removal performance was examined under different conditions with different initial ethylene concentrations, gas residence times and oxygen concentrations. At all microwave powers tested, UV-C exhibited much larger irradiance than UV-A and UV-B. The degradation efficiency of ethylene increased with increasing microwave intensity, with decreasing inlet concentration, and with decreasing reaction gas flow rate. Taking the energy cost into account, residence time should be determined considering inlet concentration, volume of degradation, capacity of devices, and admitted costs. Microwave intensity was shown to be a critical operation variable for the photo-catalytic degradation of ethylene, required to be determined depending on initial ethylene concentration.

Element Determination in Pharmaceuticals Using Direct Solid Analysis-Electrothermal Vaporization Inductively Coupled Plasma Optical Emission Spectrometry

A solid sampling electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP OES) method for determination of As, Cd, Cr, Cu, Mn, Mo, Ni, Pb, Pd, Pt, Rh, Ru and V in pharmaceuticals is proposed. Tricyclic pharmaceuticals were directly analyzed due to their difficult decomposition with acids. Pyrolysis and vaporization temperature, sample mass, and reaction gas (Freon) flow rate were evaluated. The effect of organic and inorganic compounds was evaluated for matrix matching. The limits of detection ranged from 0.04 µg g−1 (Cu) to 107 µg g−1 (As) and the relative standard deviation was lower than 10%. The investigated elements were not detected in the analyzed samples with the exception of Cr in cyclobenzaprine hydrochloride. Since there was no certified reference materials available for metals and metalloids in pharmaceuticals, the accuracy of the method was evaluated by an independent technique and by analyte recovery. Inductively coupled plasma mass spectrometry was employed for analyte determination after sample decomposition by microwave induced combustion. The agreement of the results found by both techniques was better than 87% and analyte recoveries ranged from 91 to 103%.

Sputtering Deposition of VO$lt;inf$gt;2$lt;/inf$gt; Film Using Plasma Emission Monitor as Reactive Gas Flow Rate Feedback Control

Monoclinic VO2 film was deposited on quartz substrate by reactive sputtering using the plasma emission monitor (PEM) system as reactive gas flow rate feedback control. Relationship between oxygen flow rate and plasma emission intensity was studied. It was found that single-phase VO2(M) could be obtained steadily at specific relative emission intensity (REI), which were determined as 0.6-0.65, 0.65 and 0.6 for total deposition pressure of 0.8 Pa, 0.5 Pa and 0.2 Pa, respectively. XRD measurement indicated that the deposited VO2 films were strongly oriented of (011) and the XPS measurements verified stoichiometry of the films as VO2.02. Optical transmission measurement of VO2 film exhibited an abrupt change of transmittance from 81% to 16% as VO2 film switched from semiconductor state to metallic state, at transition temperature of 66℃.

Structural and ellipsometric study on tailored optical properties of tantalum oxynitride films deposited by reactive sputtering

Oxynitride materials, which offer the possibility of merging oxide and nitride properties, are increasingly studied for this reason. This paper focuses on assessing the optical properties of tantalum oxynitride thin films deposited by pure tantalum target sputtering in an Ar/O2/N2 reactive atmosphere. First, by changing the oxygen to reactive gas flow rate ratio, and using thermal post-treatment, we deposited films with elemental compositions studied by Rutherford backscattering spectroscopy, ranging from a nitride (close to Ta3N5) to an oxide (close to Ta2O5) with various structures analyzed by x-ray diffraction. Their optical properties were investigated in depth by spectroscopic ellipsometry and UV-visible spectroscopy. For the ellipsometry investigation, we propose a model combining the Tauc–Lorentz law and additional Lorentz oscillator: the first contribution is linked to a semi-conductor or insulator film matrix, and the second one to the presence of conductive TaN crystals. Ellipsometry thus appears as a powerful tool to investigate complex materials such as tantalum oxynitrides. Moreover, we demonstrated that using this deposition method we were able to finely tune the film refractive index from 3.4 to 2.0 (at 1.96 eV) and the optical band gap, specifically from 1.3 to 2.7 eV.

Ion-neutral gas reactions in a collision/reaction cell in inductively coupled plasma mass spectrometry: Correlation of ion signal decrease to kinetic rate constants

Reaction gas flow rate dependent Ar2+ and Ar+ signals are correlated to fundamental kinetic rate coefficients. A simple calculation, assuming that gas exits the reaction cell due only to effusion, is described to estimate the gas pressure in the reaction cell. The value of the product of the kinetic rate constant and the ion residence time in the reaction cell can be determined from experimental measurement of the decrease in an ion signal as a function of reaction gas flow rate. New kinetic rate constants are determined for the reaction of CH3F with Ar+ and Ar2+.

상압 플라즈마-촉매 하이브리드 반응기를 통한 CO2와 CH4의 전환처리

The conversion reaction of methane and carbon dioxide at an atmospheric pressure plasma reactor filled with Ni-Al2O3 and Ni-MgAl2O4 catalyst was performed. Effects of various process parameters such as the applied electric power, reaction gas flow rate, reactor temperature, mixing ratio of reactants and the presence of the catalyst on the reaction between methane and carbon dioxide were analyzed. From the analysis of the contribution of the catalyst in the reaction step, even if the tem- perature raised to 400 ℃, there was no spontaneous catalytic conversion of methane and carbon dioxide without plasma discharges. When the catalysts for the conversion of methane and carbon dioxide would be adopted to the plasma reactor, the careful selection of suitable catalysts and process parameters should be essential.

Preparation and characterization of Ba(ZrxTi1−x)O3 thin films for high-frequency applications

Ba(ZrxTi1−x)O3 (BZT) thin films were deposited on a (100)MgO substrate by RF-magnetron reactive sputtering using metal targets. In this paper, a model of the reactive sputtering process using a metal composite target at different reactive gas flow rates is presented. 500-nm-thick BZT thin (x = 0.26) films for high frequency performance showed a single perovskite phase and a high crystallinity on the MgO substrate with only a (001)/(100) orientation at an optimum reactive gas flow rate in Ar + O2. The BZT films had a stoichiometric Ba/Ti ratio and epitaxially grew on the MgO substrate. They showed a dense microstructure without cracks or voids. Their low capacitance and loss tangent showed little dispersion at 1–18 GHz. These results indicated that we succeeded in depositing high-quality and potentially tunable ferroelectric BZT films for high-frequency applications by RF-magnetron reactive sputtering using metal targets.

On the Positive Effect of CO during Start/Stop in High-Temperature Polymer Electrolyte Fuel Cells

The influence of CO in the fuel gas on cathode carbon corrosion during start/stop cycles in high temperature polymer electrolyte fuel cells (HT-PEFC) was investigated. The fuel cell underwent simulated start/stop cycles with a constant time interval, reactant gas flow rate and temperature by switching between H2/CO mixtures and O2 at the fuel electrode. The results reveal that increasing amounts of CO in the fuel gas reduce the amount of carbon corrosion at the air electrode. Therefore, HT-PEFC operation with CO containing fuel has the benefit of mitigating start/stop induced degradation effects.