Ar Addition Research Articles

CO2, Ar, and He dilution effects on combustion dynamics and characteristics in a laboratory-scale combustor

This study aimed to investigate the impact of CO2, Ar, and He addition on combustion instability under varying acoustic frequencies, dynamic pressure amplitudes, and light emission intensities. Experiments involved using pure methane as fuel at a 1.0 equivalence ratio, with three distinct acoustic frequencies. The burner operated at 5 kW, and the combustion chamber was excited at frequencies of 90 Hz, 160 Hz, and 320 Hz. It was observed that with dilution, the temperatures decreased more from the burner exit temperature to the exhaust section. As the oxygen concentration in the oxidizer decreases in Ar, He, and CO2 dilution, CO emissions increase, but CO2 emissions decrease. The addition of Ar, He, and CO2 causes an effect that reduces the flame temperature and brightness while causing the flame length to extend due to the diluting effect. While a decrease in instability was observed in He-Ar-CO2 dilution in 20 % oxygen, instability increased again in the three 19 % cases. It is observed that mixtures under the diluent effect approach the blowoff limit due to the increase in ignition delay. It has been determined that the addition of diluent increases the tendency for the flame to go out, especially due to the thermal effect. The methane fuel with an 18 % oxygen concentration in the oxidizer of Ar remained below lean extinction limits, undergoing blowoff. The temperature was measured as 1156 K at 21 % oxygen concentration, 584 K at 19 % oxygen concentration for carbon dioxide, 877 K for Helium, and finally 777 K for argon. In the case of pure air for the combustion of methane, CO emissions were measured at 140 ppm. Average CO levels at 20 % oxygen concentration in the oxidizer are 1254 ppm, 356 ppm, and 308 ppm with carbon dioxide, argon, and helium, respectively. The study also shows that an increase in O2 in oxidizing air leads to a decrease in CO emissions, while an increase in He/Ar/CO2 gases leads to an increase in CO emissions. Regarding NOX emissions, undiluted conditions measured a value of 14 ppm. NOX emission levels approached 0 ppm in all dilution cases and achieved its goal.

Effectiveness of Noble Gas Addition for Plasma Synthesis of Ammonia in a Dielectric Barrier Discharge Reactor

Non-thermal plasma driven ammonia synthesis has great potential for future industrial applications due to its low theoretical energy requirements. To achieve technological advancement and environmental sustainability, it is crucial to boost the energy yield in plasma-assisted ammonia synthesis. Therefore, optimizing energy transfer and utilization are key strategies for enhancing energy efficiency. In this study, dielectric barrier discharge driven by a nanosecond pulsed power supply is used to enhance plasma-assisted ammonia synthesis by controlling the energy transfer through the addition of noble gases. It was found that the addition of noble gases changed the plasma characteristics, significantly improved the uniformity of the discharge, and achieved a high energy yield for ammonia synthesis. The effects of additive amounts of argon (Ar) and helium (He), as well as the pulse parameters including the pulse voltage, pulse repetition frequency, pulse width, and pulse rise time on the energy yield of ammonia synthesis are discussed. The inclusion of noble gases expanded the pathway for gas-phase reactions, with the active components of critical reactions examined through optical emission spectra. This analysis revealed an increased presence of both N2+ and N2* particles in the reaction’s rate-limiting step, attributed to the addition of noble gases. Finally, a zero-dimensional (0D) plasma chemical kinetic model was established to investigate the influence of Ar addition on the reaction mechanism of ammonia synthesis.

Plasma-induced methane catalytic cracking: Effects of experimental conditions

Low-carbon conversion of hydrocarbon fuels and feedstocks, as well as the macroscopic production of H2, are central focus in the advancement of high-value and efficient conversion of CH4. The effects of Ar addition ratio, discharge power and temperature on the results of plasma methane cracking were investigated on a dielectric barrier discharge (DBD) plasma experimental system. The results show that the addition of Ar can improve the methane conversion, and the optimal ratio of CH4 conversion to H2 production after the effect is CH4: Ar = 1:1, at which the methane conversion reaches 49.62% and the H2 selectivity reaches 52.66%. The plasma at 25 °C can make the methane conversion close to the effect of catalytic cracking at 600 °C, while the H2 selectivity is lower, the H2 generation is 32.59% lower than the latter, and the products have more C2–C4 hydrocarbon impurities. The solid byproduct resulting from the DBD plasma cracking of methane primarily consisted of carbon black, possessing an average particle size of 62.21 nm. The incorporation of Ar and the amplification of power augment the CH* radical intensities, which suggests both conditions contribute positively to the dissociation of the CH4 molecule.

Kinetic Modeling Analysis of Ar Addition to Atmospheric Pressure N2-H2 Plasma for Plasma-Assisted Catalytic Synthesis of NH3.

Zero-dimensional kinetic modeling of atmospheric pressure Ar-N2-H2 nonthermal plasma was carried out to gain mechanistic insights into plasma-assisted catalytic synthesis of ammonia. Ar dilution is a common technique for tailoring plasma discharge properties and has been shown to enhance NH3 formation when added to N2-H2 plasma. The kinetic model was developed for a coaxial dielectric barrier discharge quartz wool-packed bed reactor operating at near room temperature using a kHz-frequency plasma source. With 30% Ar mixed in a 1:1 N2-H2 plasma at 760 Torr, we find that NH3 production is dominated by Eley-Rideal (E-R) surface reactions, which heavily involve surface NHx species derived from N and H radicals in the gas phase, while the influence of excited N2 molecules is negligible. This is contrary to the commonly proposed mechanism that excited N2 molecules created by Penning excitation of N2 by Ar(4s) and Ar(4p) play a significant role in assisting NH3 formation. Our model shows that the enhanced NH3 formation upon Ar dilution is unlikely due to the interactions between Ar and H species, as excited Ar atoms have a weak effect on H radical formation through H2 dissociation compared to electrons. We find that excited Ar atoms contribute to 28% of the N radical production in the gas phase via N2 dissociation, while the rest are dominated by electron-impact dissociation. Furthermore, Ar species play a negligible role in the product NH3 dissociation. N2 conversion sensitivity analyses were carried out for electron number density (ne) and reduced electric field (E/N), and contributions from Ar to gas-phase N radical production were quantified. The model can provide guidance on potential reasons for observing enhanced NH3 formation upon Ar dilution in N2-H2 plasma beyond changes in the discharge characteristics.

Plasma-catalytic CO2 methanation over Ni supported on MCM-41 catalysts: Effect of metal dispersion and process optimization

Catalytic carbon dioxide (CO2) conversion technologies can be important components in carbon capture, storage and utilization for CO2 mitigation and possible future economic activity and have gained significant attention globally in past decades. Electrified non-thermal plasma (NTP) catalysis enables CO2 hydrogenation into value-added chemicals under mild conditions. If the hybrid process is coupled with renewable energy and green hydrogen, it can be the promising solution to address the energy and carbon emission challenges. To enhance the energy efficiency of NTP-catalytic systems, bespoke catalyst design and process optimization are necessary. Here, using Ni catalysts supported on mesoporous MCM-41 and NTP-catalytic CO2 methanation as the model systems, the effects of Ni metal dispersion, argon (Ar) addition and residence time on the NTP catalysis were also studied. The findings show that (i) increased metal dispersion alone did not lead to significant enhancement in the performance of NTP catalysis (e.g., CH4 production rate: 31.4 × 10−5 mol/(s·gNi) for 42.6 % Ni dispersion vs. 26.8 × 10−5 mol/(s·gNi) for 25.1 % dispersion), (ii) Ar addition to the system led to the decreased methane production rate (e.g., CH4 selectivity decreased by ∼19 % due to the increase in Ar addition to the system from 5 to 50 mL/min), and (iii) optimization of the residence time could improve the performance of NTP-catalytic CO2 methanation (i.e., an extension of the residence time to 0.69 s resulted in the higher CO2 conversion of 72.7 % and CH4 selectivity of 95.9 % at 9.6 kV than that at 0.49 s and 11 kV).

Study of apparent effective ionization coefficient in CO2 and Ar gas mixtures

Ar:CO2 gas mixtures have recently received research interest due to the possibly beneficial effects of Ar addition to CO2 for CO2 conversion using electrical discharges. For any gas discharge, knowledge of fundamental parameters, such as the effective ionization coefficient, is necessary to optimize the efficiency of the discharge for a particular application. The reduced apparent effective ionization coefficient αea/N is a measure of total ionization. αea/N is influenced by electron impact ionization, electron attachment and also by charge transfer reaction, Penning ionization, and photoionization. This study determined the αea/N of Ar:CO2 gas mixtures in the pressure range of 10–800 Torr and reduced electric field strength E/N range of 40–1200 Td utilizing a steady-state non-self-sustaining Townsend discharge. Experimental results were compared with calculations of Boltzmann equation solver BOLSIG+. Differences between measurements and calculations increased with decreasing CO2 content in the mixture down to 20%, and the differences were highest at low E/N values (below 150 Td). As the simple modification of the model, contribution of ionization of CO2 by Penning transfer from Ar* 3p53d excited states (13.86 eV) was added to the BOLSIG+ calculations, which resulted in good fit of the experimental measurements. Comparison of CO2 addition to Ar with the addition of O2 or N2 revealed that ionization of CO2 or O2 from Ar* 3p53d excited states influences ionization in Ar:CO2 and Ar:O2 mixtures but not in Ar:N2 mixtures, due to the different ionization energies of CO2, O2, and N2.

Effect of Anthropogenic Aerosol Addition on Phytoplankton Growth in Coastal Waters: Role of Enhanced Phosphorus Bioavailability.

Atmospheric deposition can supply nutrients to induce varying responses of phytoplankton of different sizes in the upper ocean. Here, we collected surface and subsurface chlorophyll a maximum (SCM) seawaters from the Yellow Sea and East China Sea to conduct a series of onboard incubation experiments, aiming to explore the impact of anthropogenic aerosol (AR, sampled in Qingdao, a coastal city in Northern China) addition on phytoplankton growth using schemes with (unfiltered seawater, UFS) and without (filtered seawater, FS) microsized (20–200 μm) cells. We found that AR addition stimulated phytoplankton growth obviously, as indicated by chlorophyll a (Chl a) in surface incubations, and had stimulatory or no effects in SCM incubations, which was related to nutrient statuses in seawater. The high ratio of nitrogen (N) to phosphorus (P) in the AR treatments demonstrated that P became the primary limiting nutrient. The alkaline phosphatase activity (APA), which can reflect the rate at which dissolved organic P (DOP) is converted into dissolved inorganic P, was 1.3–75.5 times higher in the AR treatments than in the control, suggesting that AR addition increased P bioavailability in the incubated seawater. Dinoflagellates with the capacity to utilize DOP showed the dominant growth in the AR treatments, corresponding to the shift in phytoplankton size structure toward larger cells. Surprisingly, we found that nanosized (2–20 μm) and picosized (0.2–2 μm) Chl a concentrations in UFS were generally higher than those in FS. The APA in UFS was at least 1.6 times higher than in FS and was proportional to the contribution of microsized cells to the total Chl a, suggesting that microsized cells play an important role in the increase in APA, which contributes to the growth of nanosized and picosized phytoplankton. Current work provides new insight into the increase of P bioavailability induced by atmospheric deposition and resultant ecological effect in coastal waters.

P‐11: Effects of Ar Dilution on N2O/SiH4 PECVD for the Growth of Silicon Oxide Thin Films with Improved Breakdown Voltage Characteristics

In order to obtain a robust gate dielectric, the nitrogen atom incorporation in the silicon oxide thin film has been investigated in much prior study in recent years. Silicon oxide thin film deposition is mainly performed using SiH4‐N2O plasma by the Plasma enhanced chemical vapor deposition (PECVD) system. Reducing the N2O/SiH4 gas flow ratio increases the nitrogen content in the film. However, the film uniformity dramatically deteriorates as the N2O/SiH4 ratio is decreased and this issue makes the low N2O/SiH4 ratio condition a challenging area for the process condition. In this study, to overcome this problem Argon (Ar) addition was employed to the low N2O/SiH4 ratio plasma and we found that Ar not only allows the thin film to be uniformly deposited by increasing the plasma density due to the penning effect, but also increases Si‐N bond especially under the ratio of 10:1 condition. Even though the silicon oxide thin film was deposited with low N2O/SiH4 gas flow rate, the film uniformity and breakdown voltage characteristics dramatically improved by Ar dilution. In addition, LTPS p‐channel TFT was fabricated by utilizing the improved silicon oxide thin film as a gate dielectric layer and it showed excellent electrical characteristics. This work would be one of the most practical solutions for robust gate dielectric deposition.

Study on physicochemical characteristics, solidification and utilisation of tannery sludge gasification ash

Gasification is an attractive method for tannery sludge (TS) disposal because of its advantages: volume reduction, stabilisation, harmlessness, and energy recovery. TS reduction ash (AR) and TS oxidation ash (AO), simulated from a downdraft fixed bed gasifier (DFBG) and an updraft fixed bed gasifier (UFBG), were investigated on their physicochemical characteristics, solidification behaviour, and value-added utilisation. Results showed that the main mineral matters in AR and AO consisted of Fe-oxids and Fe–Cr compounds, and the DFBG was more suitable for TS gasification than the UFBG because of the lower content of Cr(Ⅵ) in AR. With the addition of waste glass bottles (WGB), the ash fusion temperatures (AFTs) and leaching concentrations of heavy metals in AR and AO decreased significantly, and the heavy metals in AR and AO were successfully immobilised by the wrapping effect of the molten WGB. Moreover, gasification ash, as an auxiliary material for rock wool, reduced the AFTs and viscosity coefficient of the main chemical compositions in rock wool. With the addition of AR, the occurrence of Fe-containing compounds and the extremely low risk of leaching toxicity of heavy metals were observed. The maximum addition proportion of gasification ash was dependent on the maximum content of Fe2O3 allowed in the raw materials of rock wool, and its addition ratio must be below 15%.

High-crystallinity single-walled carbon nanotube aerogel growth: Understanding the real-time catalytic decomposition reaction through floating catalyst chemical vapor deposition

In this study, high-purity single-walled carbon nanotubes (SWCNTs) are synthesized with additional carrier gas through floating catalyst chemical vapor deposition. The presence of Ar during the SWCNT aerogel formation affects to the precursor decomposition and to the formation of different reactive hydrocarbons. Furthermore, the concentration of produced various carbon species is sensitive to the carrier gas compositions. The in-situ sampling methods prove the thermodynamic pathway for the hydrocarbon cracking during carbon nanotube (CNT) aerogel formation process. The addition of Ar promoted the formation of reactive hydrocarbon species, such as CH3, CH4, and C2H4/CO, to improve CNT morphology and graphitization. Ar has improved purity of CNTs compared to when only H2 is used. The synthesized CNTs were narrow in size, and the diameter decreased from 1.8 to 1.2 nm with the carrier gas composition (Rx) according to Ar addition. The IG/ID ratio of the CNTs changed from 78 to 3 at R0.1 and R0.57, respectively. Furthermore, the purity also increased to approximately 10% from 78% to 91% depending on Rx.

Plasma-assisted ammonia synthesis in a packed-bed dielectric barrier discharge reactor: effect of argon addition

The effect of argon (Ar) addition on plasma-assisted ammonia (NH3) synthesis in a packed-bed dielectric barrier discharge (DBD) reactor is investigated in this work. Both higher normalized NH3 concentration and N2 conversion are achieved by adding Ar to N2–H2 plasma. The 18.6% increment of normalized NH3 concentration and 15% increment of N2 conversion are realized with 30 vol.% Ar addition compared with the case of N2–H2 plasma only, indicating that Ar addition would contribute to NH3 formation. The mechanisms of NH3 synthesis with Ar addition are proposed based on electrical characteristics and electron energy distribution function of the N2–H2–Ar plasma. The intensity of microdischarges, mean electron energy and quantity of energetic electrons increase upon Ar addition. Hence, the electron-impact reactions would be enhanced upon Ar addition. Meanwhile, the effective capacitance of the plasma reactor is improved, which suggests Ar addition contributes to achieve fully-bridged plasma discharge and transfer energy into chemical process in plasma. Moreover, the presence of Ar introduces Penning excitation and ionization reactions in N2-H2 plasma, which would benefit N2 conversion and then accelerate NH3 formation as well.

첨가당을 달리한 아로니아(Aronia melanocarpa)청의 품질 특성 연구

This study examined the characteristics of aronia cheong prepared with the addition of sugar (AR_SU), sugar and oligosaccharide (AR_SO), and oligosaccharide (AR_OL) over 90 days. The soluble solid content of AR_SU was the highest among the samples and remained constant throughout the storage period, but that of AR_OL gradually decreased. The acidity increased significantly on the 90th day compared to the 30th day of storage, with the highest increase in AR_OL. L, a, and b values of all samples decreased during storage. The tannin content of AR_SU increased during storage, but there was no significant difference between the levels at 60 days and 90 days. The tannin content of AR_OL decreased continuously, but it was significantly higher than AR_SU and AR_SO. However, the tannin content of all three samples decreased by 1/3rd to 1/2 at day 90, compared with the samples at day 0. The anthocyanin content decreased in all samples during the storage period. The ABTS radical scavenging activity of AR_SU and AR_OL increased by the 60th day, but decreased slightly on the 90th day, while it increased continuously in AR_SO. In the sensory evaluation test, flavor, astringency, and sourness were higher in the decreasing order of AR_OL, AR-SO, AR_SU, and sweetness, in the decreasing order of AR_SU, AR_SO, AR_OL. AR_SU was very sweet, and AR_OL had a weak sweet taste, but a strong unattractive flavor. So, the overall preference was the highest for AR_OL. Based on the above results, the addition of AR_SO is recommended to increase the consumption of aronia which has potential health benefits.

EUCALYPTUS GRANDIS X EUCALYPTUS UROPHYLLA GROWTH CURVE IN DIFFERENT SITE CLASSIFICATIONS, CONSIDERING RESIDUAL AUTOCORRELATION

Brazil is a major producer in the timber sector, mainly with the use of wood from species of the genus Eucalyptus, with 26.1% of planted forests located in Minas Gerais. Researchers and manufacturers have been searching for techniques with the objective of making full use of these forests, with a primary focus on greater growth. A modeling of growth curves is an alternative for the estimation of oral production andan important aid tool for the researcher's decision making. Growth curves are commonly studied by nonlinear regression models, which have important assumptions that if not met should be added to the model. The present work aims to select among nonlinear Logistic, Gompertz and von Bertalany regression models the most suitable to describe the growth in wood volume of Eucalyptus urophylla x Eucalyptus grandis hybrids in three Forest Site categories, including whether assumption deviations are required. Methods were executed by the Gauss-Newton iterative method implemented in nls() and it gnls() functions of the R software. Determination coecient, Akaike information criterion (AICc) and Residual Standard Deviation (RSD) were used as selection evaluators of the best model. The results demonstrate that for all site categories, the Gompertz model with addition of autoregressive parameters AR (1) is the most appropriate to describe the growth in wood volume of Eucalyptus urophylla x Eucalyptus grandis hybrids. The addition of the rst-order autoregressive parameter does not aect the quality of t, but it is the correct procedure. Site I, which presents the largest trees according to pre-dened variations, recorded 308 m3/ha of wood volume, followed by 286 m3/ha and 263 m3/ha for Sites II and III, respectively. The time for Site III to reach the maximum point of volume growth is between the fourth and sixth year, while the other sites are more precocious, reaching this point between the second and third year.

Effect of adding different concentrations of L-arginine to Tris-yolk extender on the quality of sub-fertile ejaculates in buffalo.

To investigate the effect of supplementation of L-arginine (AR) on sub-fertile buffalo-bulls' ejaculates, 25 ejaculates of poor motility (40 to 55%) were collected by artificial vagina from 5 buffalo-bulls and extended with Tris-yolk extender (1:10) supplemented with different concentrations of AR (0, 3, 4, 5, and 6mM). Semen was cooled gradually to 4°C within 2h and incubated at 4°C for additional 2h. Incubated semen samples were evaluated by computer-assisted semen analysis. Results showed that addition of 5mM AR increased (P < 0.05) total sperm motility and rapid progressive motility percentages, while decreased (P < 0.05) non-motile sperm and static sperm percentages compared with AR-free (control) extender. Increasing the AR level to 6mM increased (P < 0.05) the percentages of sperm progressive motility and rapid and slow progressive motilities, while decreased (P < 0.05) the non-progressive sperm motility percentages compared with AR-free extender. Supplementation of 5mM AR improved (P < 0.05) sperm straight linear, curve linear, and average path velocities (36 ± 0.13, 20.6 ± 5.3, and 33.2 ± 8.5, respectively) in comparing with control and other AR treatments. Addition of AR (5 and 6mM) improved (P < 0.05) the percentages of vitality (89.8 ± 1.9 and 80.0 ± 3.4, respectively), normality (44.3 ± 3.6 and 44.8 ± 1.5, respectively), and functional sperm (20.4 ± 8.6 and 21.0 ± 0.61, respectively), and decreased abnormal neck and tail percentages compared with AR-free extender. All AR levels decreased (P < 0.05) the abnormal neck and tail percentages. Addition of all AR levels had no significant (P > 0.05) effect on the activity of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase in semen extender. Supplementation of Tris-yolk extender with L-arginine (5 or 6mM) can improve sperm motility, velocity, vitality, and functional sperm and can decrease tail and neck abnormalities of sub-fertile buffalo ejaculate after 4h incubation at cool temperature.

Effect of Diluent Addition on Combustion Characteristics of Methane/Nitrous Oxide Inverse Tri-Coflow Diffusion Flames

ABSTRACT The purpose of this study is to examine the dilution effect on combustion characteristics of methane/nitrous oxide inverse tri-coflow diffusion flame through the addition of various dilution gases. Two diluents, namely carbon dioxide and argon, were used. To scrutinize the overall combustion characteristics, the effects of dilution on flame appearance and pollution emissions were calculated numerically and observed experimentally. In terms of flame appearance, with increasing the central oxidizer flow rate, the flame became an inner-oxidizer-injected flame structure and then converted to a double flame structure. When 40% Ar and 20% CO2 were added to the oxidizer individually, a liftoff edge flame was formed at high central oxidizer flow rate. This theoretical prediction provided a fast and preliminary explanation of the various flame structures and concurred with the trend of IDF formation observed in the experiment. Regarding the flue gas emission, the addition of Ar in CH4/N2O diffusion flame can effectively reduce the yield of CO, whereas the addition of CO2 leads to an increase of CO concentration in the flue gas. Simulation results indicated that for Ar addition, the production of NOx is dominated by the inert effect at dilution levels lower than 40%, whereas the thermal/diffusion effect dominates at dilution levels higher than 40%. CO formation is mainly dominated by the thermal/diffusion effect. In CO2 dilution, NOx formation is dominated by the inert and chemical effects at dilution levels lower than 40%. However, at dilution levels higher than 40%, the chemical effect is more dominant. Thus, CO formation is dominated mainly by the chemical effect.

Experimental study on the metal transfer control by using pulsed Ar addition in CO2 arc welding process: studies on pulsed gas MAG welding

ABSTRACT CO2 gas-shielded arc welding, which is widely used in the industrial world, has been recognized as an efficient and economical GMA welding process. However, its characteristic repelled transfer produces a large amount of spatter which results in costly cleanup and, thus, practical methods to overcome this weakness have been highly demanded. In the series of this study, ‘Pulsed Gas MAG’ welding was proposed as a new approach to reducing spatter, in which Ar gas pulses were periodically injected into CO2 shielding gas so that gas composition of arc atmosphere was largely modified in a very short period of time and a metal droplet formed at the electrode tip during CO2 atmosphere was released before repelled transfer had occurred. In this report, the influence of parameters of Ar gas injections, such as frequencies, average gas flow rates and gas injection periods, on the metal transfer was investigated. It was found that synchronous metal transfer stimulated by pulsed Ar gas injections was achieved at any frequencies from 35 to 65 Hz under the conditions of gas injection periods longer than 4 ms and of Ar gas volumes larger than approximately 1mL/pulse. This is because Ar gas injections below these critical levels resulted in lack of time for arc shape changes and metal drop detachment. From these experimental results, a model to explain the metal transfer phenomena was developed. The amount of spatter was reduced to the levels as low as that of the conventional MAG welding with 80 %Ar +20 %CO2 shielding gas mix and penetration profiles were round shape like those obtained in CO2 arc welding.

Gliding arc plasma reforming of toluene for on-board hydrogen production

Hydrogen is considered as a clean and promising fuel, and hydrogen production on-board has attracted widespread research attention. In this work, a gliding arc discharge (GAD) plasma reactor was utilized to reform toluene at room temperature and atmosphere pressure. The performance of hydrogen production through oxidative reforming with toluene as raw material under different input power, oxygen to carbon molecular ratio (O/C), residence time and argon addition was investigated. The optimal yields of H2 and CO (48.6% and 44.3%) were obtained under the condition of the input power of 32 W, the O/C of 0.68, the residence time of 18.4 s and 10 vol% Ar addition. By analyses of spectrum lines and GC-MS, the plasma reforming mechanism of toluene was proposed. It is believed that N2(B3Πg) and Ar* could increase the formation of reactive oxygen species (O+, O (1D), O and so on), and N2(B3Πg) could impact directly the reforming of toluene.

Experimental study on the metal transfer control by using pulsed Ar addition in CO2 arc welding process

Experimental study on the metal transfer control by using pulsed Ar addition in CO2 arc welding process

VUV Spectral Irradiance Measurements in H2/He/Ar Microwave Plasmas and Comparison with Solar Data

Abstract Microwave plasmas with H2 and H2/rare gas mixtures are convenient sources of VUV radiation for laboratory simulations of astrophysical media. We recently undertook an extensive study to characterize microwave plasmas in an H2/He gas mixture in order to optimize a VUV solar simulator over the 115–170 nm spectral range. In this paper, we extend our investigation to the effect of the addition of Ar into H2/He plasma on the VUV spectral irradiance. Our study combines various optical diagnostics such as a VUV spectrometer and optical emission spectroscopy. Quantitative measurements of the spectral irradiance and photons flux in different mixtures are accomplished using a combination of VUV spectrometry and chemical actinometry. Results show that the Ar addition into H2/He plasma largely affects the predominant emissions of the hydrogen Lyα line (121.6 nm) and H2 (B1Σu–X1Σg) band (150–170 nm). While a microwave plasma with 1.4% H2/He is required to mimic the entire VUV solar spectrum in the 115–170 nm range, the combination with 1.28% H2/35% Ar/He is the best alternative to obtain a quasi-monochromatic spectrum with emission dominated by the Lyα line. The maximum of the spectral irradiance is significantly higher in the ternary mixtures compared to the binary mixture of 1.4% H2/He. Further Ar increase yielded lower spectral irradiance and absolute photon fluxes. Our measured spectral irradiances are compared to VUV solar data in the 115–170 nm range, emphasizing the use of microwave plasmas in astrophysical studies and laboratory simulations of planetary atmospheres.

Effects of Ar Addition to O2 Plasma on Plasma-Enhanced Atomic Layer Deposition of Oxide Thin Films

A method for significantly increasing the growth rates (GRs) of high- k oxide thin films grown via plasma-enhanced atomic layer deposition (PE-ALD) by enhancing the plasma density through the addition of Ar gas to the O2 plasma oxidant was developed. This approach led to improvements of ∼60% in the saturation GRs of PE-ALD ZrO2, HfO2, and SiO2. Furthermore, despite the significantly higher GR enabled by PE-ALD, the mechanical and dielectric properties of the PE-ALD oxide films were similar or even superior to those of films grown via the conventional O2 plasma process. Optical emission spectroscopy analyses in conjunction with theoretical calculation of the electron energy distribution function revealed that adding Ar gas to the O2 plasma increased the density of high-energy electrons, thereby generating more O2 plasma species, such as ions and radicals, which played a key role in improving the GRs and the properties of the films. This promising approach is expected to facilitate the high-volume manufacturing of films via PE-ALD, especially for use as gate insulators in thin-film transistor-based devices in the display industry.