Total Gas Flow Rate Research Articles

Hydrogen plasma smelting reduction for fast production of green ferronickel

The production of ferronickel through conventional methods results in substantial CO2 emissions. To mitigate CO2 impact, using hydrogen gas as a reductant in Hydrogen Plasma Smelting Reduction (HPSR) shows great potential by overcoming thermodynamic and kinetic barriers. This study aimed to produce green ferronickel using the HPSR process. Results indicate that the feed must undergo calcination before HPSR process to ensure effective reduction. Green ferronickel can be produced rapidly through HPSR smelting in just 180 s, yielding Fe 70.64% and Ni 23.98%, with no carbon, sulfur and phosphorus detected, eliminating decarburization, desulfurization and dephosphorization steps. The green ferronickel product aligns with the thermodynamic calculations using FactSage 8.2. The process parameters of total gas flow rate and sample weight were investigated, revealing that the chemical composition of products is not significantly affected by total gas flow rate, whereas sample weight has a considerable impact. Therefore, green ferronickel production via HPSR shows great potential.

Improved surface morphology and reduced V-pits density of lattice-matched AlInN films grown by atmospheric pressure metalorganic chemical vapor deposition

AlInN has emerged as a promising material for advanced optoelectronic and electronic devices due to its unique properties. However, achieving AlInN layers with excellent surface morphology remains challenging. Here, Al0.83In0.17N layers lattice-matched to GaN/sapphire were grown by atmospheric-pressure metalorganic chemical vapor deposition at 875 °C. The lowest surface roughness measured by atomic force microscopy was 0.37 nm after optimizing the growth temperature and flux of precursors. The roughness value was constant in the range of 15–72 nm film thickness. Introducing a TMI pre-flow period before AlInN growth, further reduced roughness to 0.28 nm, although a graded inclusion of Ga into the AlInN near the GaN/AlInN interface was observed. This improved surface morphology was interpreted by the In-surfactant effect enriched by the pre-flow in the early stage of AlInN. Additionally, the V-pits density was as low as 2×105 cm−2, primarily due to high growth pressure and also influenced by relatively high growth temperature. Analysis of Al incorporation using second-order reaction model suggests that the severe parasitic reactions between TMA and NH3 at atmospheric pressure can be effectively eliminated by a high total gas flow rate of 72 slm, ensuring in-plane uniformity in surface morphology and relatively good crystalline quality.

Nanosecond pulsed gliding arc plasma for ammonia synthesis: better insight from discharge mode and vibrational temperature

Low-temperature plasma technology is a promising technological route to achieve green and efficient ammonia synthesis at ambient temperature and pressure. In this work, a Laval nozzle type gliding arc plasma reactor was designed for the direct synthesis of ammonia from N2 and H2 discharges ignited by a high voltage nanosecond pulsed power supply to investigate the effect of different electrode gaps, pulse voltages, and V N2:V H2 on ammonia synthesis. The nanosecond pulsed plasma discharges were characterized through oscilloscope and optical emission spectroscopy (OES). The maximum rate of NH3 synthesis was 538.12 μmol·h−1 at 1.5 mm electrode gap, 16 kV peak pulse voltage, 6 kHz pulse repetition frequency, 100 ns pulse width, 100 ns pulse rising edge, 100 ns pulse falling edge, and 200 mL·min−1 total gas flow rate with V N2:V H2 = 1:1. It was demonstrated that the discharge mode of the nanosecond pulsed gliding arc plasma can transit from a unipolar state to a bipolar state determined by the duty cycle accompanied with higher discharge power and vibrational temperature. Bipolar discharge mode is beneficial to improve the efficiency of plasma ammonia synthesis because of it can strengthen the plasma discharge and increase the vibrational temperature. The ammonia synthesis rate and N2 conversion rate increased with the increase of the discharge power and vibrational temperature.

Microwave plasma-assisted hydrogen production via conversion of CO2–CH4 mixture

A method concerning re-use of the main greenhouse gases: CO2 and CH4 at the same time producing value-added chemicals (H2 + CO) is presented in this paper. The method involves the methane dry reforming using an atmospheric pressure operated 915 MHz microwave plasma source with a swirl gas flow. The effect of the CO2 to CH4 flow rates ratio, the total gas flow rate and the absorbed microwave power on the volume concentration of the gaseous plasma component in the outlet gas (%), CO2 and CH4 conversion rate (%), hydrogen production rate (g h−1) and energy yield of hydrogen production (g kWh−1) was investigated experimentally. The recorded results of the CO2 and CH4 conversion rate were about 82% and 88%, respectively. The best results in terms of the hydrogen production rate and energy yield of hydrogen production were equal to 156 g h−1 and 24 g kWh−1, respectively.

Cryogenic DRIE processes for high-precision silicon etching in MEMS applications

Cryogenic deep reactive ion etching (Cryo DRIE) of silicon has become an enticing but challenging process utilized in front-end fabrication for the semiconductor industry. This method, compared to the Bosch process, yields vertical etch profiles with smoother sidewalls not subjected to scalloping, which are desired for many microelectromechanical systems (MEMS) applications. Smoother sidewalls enhance electrical contact by ensuring more conformal and uniform sidewall coverage, thereby increasing the effective contact area without altering contact dimensions. The versatility of the Cryo DRIE process allows for customization of the etch profiles by adjusting key process parameters such as table temperature, O2 percentage of the total gas flow rate (O2 + SF6), RF bias power and process pressure. In this work, we undertake a comprehensive study of the effects of Cryo DRIE process parameters on the trench profiles in the structures used to define cantilevers in MEMS devices. Experiments were performed with an Oxford PlasmaPro 100 Estrelas ICP-RIE system using positive photoresist SPR-955 as a mask material. Our findings demonstrate significant influences on the sidewall angle, etch rate and trench shape due to these parameter modifications. Varying the table temperature between −80 °C and −120 °C under a constant process pressure of 10 mTorr changes the etch rate from 3 to 4 μm min−1, while sidewall angle changes by ∼2°, from positive (<90° relative to the Si surface) to negative (>90° relative to the Si surface) tapering. Altering the O2 flow rate with constant SF6 flow results in a notable 10° shift in sidewall tapering. Furthermore, SPR-955 photoresist masks provide selectivity of 46:1 with respect to Si and facilitates the fabrication of MEMS devices with precise dimension control ranging from 1 to 100 μm for etching depths up to 42 μm using Cryo DRIE. Understanding the influence of each parameter is crucial for optimizing MEMS device fabrication.

Calculation of the required methanol consumption during the flow of wet hydrocarbon gas in a horizontal pipeline

One of the main problems that have to be solved during the development of hydrocarbon deposits is the formation of gas hydrates in pipelines. In this regard, the article presents a preventive method to struggle against the formation of gas hydrate deposits on the pipes inner walls associated with the supply of a hydrate formation inhibitor to the gas stream. The research was conducted on the basis of a mathematical model of the wet hydrocarbon gas flow in a horizontal pipeline. The research object is to determine the minimum required consumption of methanol, in which there is no formation of gas hydrate deposits on the channel inner walls. The practical significance of this study is that it is aimed at reducing the risks associated with the formation of gas hydrates in pipelines. The numerical implementation of a mathematical model of natural gas flow in a horizontal channel is based on a sequential solution of a system of four differential equations by the Runge-Kutta method of 4 orders of accuracy, followed by a search for sequential approximations of the minimum inhibitor flow rate, in which the "gas + water ↔ gas hydrate phase" transition process does not occur on the inner surface of the channel. The article presents a calculation of the proportion of a hydrate formation inhibitor in the liquid phase by solving a cubic equation using the Cardano method. Based on the computational experiments results, graphs were constructed and interpreted of the dependencies of the minimum inhibitor consumption on the soil temperature, inlet gas pressure, total water concentration in the gas flow, initial gas temperature and total gas flow rate.

Characterization of the Conversion of Benzene to Nitrosobenzene in a Helium Low-Temperature Plasma

The ionization of benzene (C6H6) through helium low-temperature plasma (He-LTP) offers a promising solution to the pervasive issue of its pollution in our daily lives. This study aimed to optimize the conditions for generating specific compounds, namely M+ and [M + 30]+, during the ionization of benzene in low-temperature plasma (LTP) with determination by mass spectrometry (MS). When the discharge voltage is 2.5 kV, a sample gas to discharge gas flow rate ratio of 2:3 is the best condition for generating M+ ions. When the discharge voltage is 3.5 kV, the gas flow rate ratio of 1:3 is the most suitable for generating [M + 30]+ ions. The LTP exhibits optimal ionization efficiency at a total gas flow rate of 40 mL/min. Additionally, we conducted a comparative analysis on the optical emission of benzene in the LTP which revealed the generation of free radicals associated with N, H, and O. The produced nitroso radical (ON•) combines with ionized benzene to yield the [M + 30]+ ion, identified to be nitrosobenzene. Notably, 95% conversion was achieved in the transformation from benzene to nitrosobenzene.

Effect of Gas Flow Rate and Ratio on Structure and Properties of Nitrogen-Doped Diamond-like Carbon Films

Diamond-like carbon (DLC) has attracted much attention due to its unique properties such as high chemical inertness, optical transparency, and high biocompatibility. In this study, the total gas flow rate was kept constant, while the ratio of reactive gases was varied to deposit nitrogen-doped diamond-like carbon thin films on glass substrates using radiofrequency plasma-enhanced chemical vapor deposition. The effects of the gas flow ratio on the composition, microstructure, surface morphology, and optical properties of the thin films were investigated through extended deposition times. It was found that with an increase in the nitrogen-to-methane gas flow ratio, the film surface became smoother and more compact. The maximum transmittance in the visible range reached 90%, and the highest and lowest transmittance in the same ultraviolet wavelength region differed by up to 25.62% among several sample groups. The optical bandgap decreased from 3.58 eV to 3.46 eV, contrary to the trend of the sp2 fraction variation. Compared with other studies, this study considered the preparation of nitrogen-doped diamondoids using a chemical vapor deposition method with a lesser total gas flow rate passed into it, which provides practical data reference value for the preparation of N-DLC.

A comparison between Claus and THIOPAQ sulfur recovery techniques in natural gas plants

A sulfur recovery process is one of the most important processes in the oil and gas industry to get rid of hydrogen sulfide (H2S) which is produced from the acid gas removal process of sour natural gas to convert it into sweet natural gas. Actual data from a gas field is used to obtain a realistic comparison between two sulfur recovery techniques, through which researchers and/or manufacturers can obtain information that will help them choose the most appropriate and cheapest method. A total feed acid gas flow rate of 5.1844 MMSCFD with an H2S concentration of 24.62% by mole percent was produced from amine acid gas removal units. Claus sulfur recovery technique is a traditional chemical process that uses thermal and catalytic reactors. Therefore, an acid gas enrichment unit is applied to increase the H2S concentration to approximately 50% mole to provide reliable and flexible operation in the thermal and catalytic reactors. Moreover, a tail gas treatment unit is applied to increase the overall conversion efficiency to 99.90% with the Claus technique instead of 95.08% without it to achieve high sulfur recovery and reliable operation through the conversion of carbonyl sulfide (COS) and mercaptans. Studies on the safety and simplicity of the Claus technique revealed many important hazards and a large number of transmitters (379) and control loops (128) in one Claus train. THIOPAQ sulfur recovery as a new technology is a biological desulfurization process that uses a natural mixture of sulfide-oxidizing bacteria. It is also a unique H2S removal process with an efficiency of 99.999%. In addition, studies on the safety and simplicity of the THIOPAQ technique have shown that the hazards, the number of transmitters (74), and the number of control loops (29) of a one THIOPAQ train are lower. The THIOPAQ technique showed higher efficiency, was safer, simpler, and had lower CAPEX and OPEX. This study was conducted using Aspen HYSYS V11 and actual data.

A Non-Matrix-Matched Calibration Method for In Situ Major and Trace Element Analysis of Scheelite by Nanosecond LA-ICP-MS.

In this work, a reliable and robust in situ non-matrix-matched calibration method is proposed for element composition determination in scheelite samples. With external calibration against the silicate glass standard reference material NIST SRM 610, the concentrations of both major elements (Ca and W) and trace elements (Si, Fe, Mo, Y, rare earth elements, etc.) in scheelite are determined using an ArF 193 nm excimer nanosecond laser ablation-inductively coupled plasma mass spectrometer (LA-ICP-MS). Here, the ablation was performed by hole drilling under a helium (He) environment using a laser spot size of 35 μm and a laser repetition of 5 Hz, and the aerosols were then transported to a quadrupole ICP-MS by a mixture of He and make-up gas argon (Ar) with a total gas flow rate of 1.6 L/min. Results showed that there was no apparent matrix effect between the NIST SRM 610 and scheelite by this proposed method. With internal standardization against W, the obtained concentrations of CaO and WO3 were found to yield an average matrix CaO/WO3 mass fraction ratio of 0.245 (2σ = 0.003, n = 19), which agreed well with the value of 0.243 (2σ = 0.002, n = 15) from electron probe microanalysis (EPMA). Furthermore, the accuracy of trace element analyses with this proposed non-matrix-matched calibration in situ method was evaluated by comparing the concentration results with those from bulk analysis by solution nebulizer ICP-MS (SN-ICP-MS). It was found that the quantification results from LA-ICP-MS and SN-ICP-MS were comparable, in particular showing a relative concentration bias of the total ∑REE+Y contents of less than 2%. This confirmed that scheelites can be accurately analyzed in situ by LA-ICP-MS without matrix-matched calibration standards. By using this developed in situ method, the element compositions in a series of scheelite samples from different W-associated deposits in China were successfully quantified, promising further genetic process investigation and associated geologic activities of the polymetallic resources.

Inhalation anesthesia in the cat: Development of cuff pressure when using nitrous oxide

During inhalation anesthesia with nitrous oxide in oxygen the pressure in the cuff of the endotracheal tube may increase due to diffusion of nitrous oxide into the cuff. The aim of the study was to investigate the development of cuff pressure during nitrous oxide anesthesia under clinical conditions in feline patients and to identify possible influencing factors such as tube size and gas flow rate. The prospective study included cats scheduled for inhalation anesthesia with nitrous oxide for a minimum duration of 60 minutes at the Department for Small Animals of the University of Leipzig. Cuff pressure was adjusted with a cuff manometer and its development was recorded. In total, the cuff pressure values of 24 cats were recorded. Animals were allocated into groups by tube size (ID 4.0 mm and ID 4.5 mm) and by fresh gas flow rate: low flow rate (0.6 l/min) and high flow rate (3 l/min). During anesthesia, cuff pressure increased over time, with statistical significance occurring from 45 minutes onwards in comparison to the initial cuff pressure (p=0.005). After 60 minutes, there was a mean cuff pressure increase of 3 cmH2O. Despite this moderate mean increase, highly variable pressure values up to 48 cmH2O in individual animals were recorded. No cat reached the termination criterion of 60 cmH2O cuff pressure. Effects of tube size (p=0.63) and flow rate (p=0.334) on the cuff pressure were not evident. After a period of 45 minutes of nitrous oxide administration, a significant increase in cuff pressure occurs in the cat. However, tube size and total gas flow rate do not seem to influence the cuff pressure development. When using nitrous oxide during inhalation anesthesia, regular cuff pressure evaluation and correction are necessary and hence recommended in feline patients. As individual pressure changes may be highly variable, no fixed recommendations for optimal management are possible.

Fabrication Method of Carbon-based Materials in CH4/N2 Plasma by RF-PECVD and Annealing Treatment for Laser Diodes

The present research addresses the synthesis of carbon materials thin films by RF-PECVD in N2/CH4 gas mixture. Carbon materials film was formed at 40/48 sccm of CH4/N2 of the total gas flow rate ratio CH4/CH4+N2 = 0.45 and 200/100 W HF/LF power at a deposition temperature of 350 oC and 1000 mTorr pressure. Then, post-annealing of carbon materials film took place at 400 oC by means of RTA under N2 flow. The formation of carbon nanostructures was investigated by scanning electron microscopy, energy dispersive X-ray, Raman spectroscopy, and atomic force microscopy, respectively. AFM shows that the films consisted of nanocrystalline grains. The surface morphology and structural characteristics of materials were studied as a gas flow function and substrate temperature. EDX results indicated the carbon presence, and Raman spectroscopy analysis revealed two broad bands: D-band 1381.64 cm−1 and G-band 1589.42 cm−1. The temperature-dependent post-annealing of carbon materials plays a key role in the graphite crystallites growth at high substrate temperatures. Our results indicate carbon materials incorporation for laser diode applications.

Catalytic Hydrogenation of Nitrate over Immobilized Nanocatalysts in a Multi-Phase Continuous Reaction System: System Performance, Characterization and Optimization

Nitrate catalytic reduction in a continuous system was studied in the presence of Pd-Cu macrostructured catalysts synthesized through a novel washcoating methodology of the pre-formed bimetallic powder catalyst. The present work aims to understand the behavior of the macrostructured bimetallic catalyst in the presence of different reaction conditions in order to achieve the design of an optimized facility that can produce the best catalytic results: maximum NO3− conversion with enhanced N2 selectivity. The residence time of the inlet solution and the catalyst concentration in the reactor proved to be the parameters that most influenced the conversion and selectivity due to the important role that these parameters play in the hydrodynamic conditions of the reactor. A higher loading of catalyst and lower inlet flow rates allow promoting a higher contact time between the three phases that participate in the reaction (G-L-S). The most efficient reaction conditions (three pieces of the macrostructured catalyst, liquid flow rate of 10 mL min−1, and a total gas flow rate of 200 Ncm3 min−1 (1:1 H2:CO2)) allowed obtaining an NO3− conversion of 51% with a corresponding N2 selectivity of 23%. Also, the conversion results strongly depended on the total gas flow rate used during the reaction since this assists the mixing between the three phases and promotes a greater contact that will contribute to enhanced catalytic results.

Enhancing molten tin methane pyrolysis performance for hydrogen and carbon production in a hybrid solar/electric bubbling reactor

Methane pyrolysis in liquid metals is a worth-developing process for CO2-free hydrogen production. This study investigates methane pyrolysis in molten tin and highlights the impact of several parameters on methane conversion (XCH4) in a novel hybrid solar/electric bubbling reactor. Temperature (1200–1300 °C), total inlet gas flow rate (Q0 = 0.25–0.5 NL/min), melt height (Him = 60-120-235 mm) and hybridization are addressed. Increasing the temperature from 1200 °C to 1300 °C (Q0 = 0.25 NL/min and Him = 120 mm) improves XCH4 (32% vs. 69%). Increasing Q0 from 0.25 to 0.5 NL/min (T = 1200 °C and Him = 120 mm) reduces XCH4 (19% vs. 9%). Doubling the melt height (Him from 60 to 120 mm) increases the residence time of bubbles, which increases XCH4 (7% vs. 19%). A customized sparger is also tested and shows little effect, probably because the holes are relatively large (1 mm diameter). An immersed bed of steel particles (0.2–0.4 mm diameter) instead shows improved results (XCH4 = 32%) at a relatively low temperature (1100 °C). Continuous reactor operation at 1300 °C without clogging is also confirmed. Analysis of carbon accumulated at melt surface during molten media methane pyrolysis reveals a tin-containing sheet-like structure.

Analysis of the outcome of blow-out operation in EAST manifold

Prior to equipment maintenance and “baking” operation, the Experimental Advanced Superconducting Tokamak (EAST) carries out a “blow-out” operation. Utilizing a manifold structure, pressurized nitrogen gas is driven into the Plasma Facing Components (PFCs)' cooling channels to eject residual cooling water. The “outcome” of the blow-out operation, the final steady-distribution of the gas-liquid two-phase in the manifold, significantly influences the efficiency, the time and energy cost of the subsequent drying process and indirectly shapes the quality of the vacuum environment required for plasma operation. In this context, this paper presents a theoretical analysis and simulation of the outcome of blow-out operation of EAST manifold. The analysis discusses three kinds of steady distribution state within a manifold branch: “Stagnant", “Two-phase flow", and “Near-dry flow". It is observed that stable “Two-phase flow” cannot be maintained when multiple branches flow concurrently due to the unstability of parallel flows. Thus, in such scenarios, the branch primarily exhibits only “Stagnant” and “Near-Dry” states. Furthermore, the total gas flow rate plays a significant role in determining the number of “Near-Dry” branches. Simulation provides specific quantities prediction of “Near-Dry” branches under varying gas volume flow rates. Finally, the theoretical analysis and simulation results is validated through experimental data. This study offers valuable insights for optimizing future blow-out operations of the EAST manifold.

Highly effective removal of perfluorooctanoic acid (PFOA) in water with DBD-plasma-enhanced rice husks

Adsorption is regarded as an efficient method to eliminate per- and polyfluoroalkyl substances from an aqueous solution. In the present investigation, an adsorbent based on rice husks (RHs) was successfully prepared by phosphoric acid (PA) activation and dielectric barrier discharge (DBD) plasma treatment, and it was used to adsorb perfluorooctanoic acid (PFOA) from water. The electrodes employed in the experiment were planar type. This research investigated RH surface properties and adsorption capacity before and after modification using DBD plasma. The results revealed that the He–O2 plasma modification introduced oxygen-containing functional groups and increased the PFOA removal efficiency. Increasing the oxygen content and total gas flow rate to 30 vol.% and 1.5 L/min, respectively, with 10 min of RH plasma treatment time at 100 W plasma discharge power enhanced the PFOA removal efficiency to 92.0%, while non-treated RH showed the removal efficiency of only 46.4%. The removal efficiency of the solution increased to 96.7% upon adjusting the pH to 4. The adsorption equilibrium isotherms fitted the Langmuir model, and the adsorption kinetic followed the pseudo-second-order model. The maximum adsorption capacity was 565 mg/g when the Langmuir isotherm model was applied.

Low-temperature fabrication of silicon nitride thin films from a SiH4+N2 gas mixture by controlling SiNx nanoparticle growth in multi-hollow remote plasma chemical vapor deposition

High-quality amorphous silicon nitride (SiNx) thin films were fabricated by the controlled growth of nanoparticles during SiH4+N2 multi-hollow remote plasma chemical vapor deposition (CVD) at low substrate temperature 100 °C. Measurements from quartz crystal microbalances showed that a higher amount of nanoparticle incorporation in the SiNx film corresponded to a higher ratio of N/Si in the film, implying that the nanoparticles were nitrided in the plasma phase. We controlled the size of the nanoparticles by tuning the gas flow ratio of N2/SiH4 and the total gas flow rate. Transmission electron microscopy and energy-dispersive X-ray spectroscopy showed that smaller nanoparticles in the plasma led to a higher ratio of N/Si in the film and a lower hydrogen content. We attribute these results to the low heat capacity and large specific surface area of the nanoparticles, which enabled active chemical reactions on their surface in the plasma.

In situ diagnostics of the Si etching structures profile in ICP SF6/C4F8 plasma: Macrostructures

In this work, we studied the influence of technological parameters of plasma chemical etching of silicon on silicon etching rate, photoresist etching rate, etching selectivity of silicon in relation to a photoresist, and sidewall angle of etched structures. It was found that the silicon etching rate increases with raising percentage of SF6 in the gas mixture (25%–50%), pressure (1–2.5 Pa), high-frequency (HF) power (1000–2000 W), and bias voltage module (15–75 V) and decreases with a raising total flow rate of the gas mixture (5–35 SCCM) due to the increasing passivation efficiency of the sample surface. The etching selectivity increases with a raising percentage of SF6 and pressure and decreases with the raising total gas flow rate, HF power, and bias voltage module due to different influences of technological parameters on the photoresist etching rate. In addition, based on the obtained results, a common regularity between the sidewall angle and the optical emission spectra was revealed. The method of in situ diagnostics was proposed, namely, controlling the sidewall angle by a ratio of emission intensities of a carbon line (517.1 nm) to a fluorine line (685.8 and 703.9 nm) designated as parameter X. It was found that the sidewall angle of etched structures takes certain values depending on the value of the X parameter. The ranges of X values at which the sidewall angle is acute, right, and obtuse were estimated. So, at values of X from ≈0.15 to ≈0.35, an acute angle (from 81° ± 0.5° to 89° ± 0.5°) is obtained; at X from ≈0.35 to ≈0.42, a right angle is obtained (90° ± 0.5°); and at X from ≈0.42 to ≈0.75, the values of the sidewall angle are in the range from 91° ± 0.5° to 94° ± 0.5°, no matter which technological parameters were set. Experiments were conducted for etching windows with linear dimensions from 0.5 × 20 to 2 × 20 mm.

Inductively coupled plasma etching of LiTaO3 in CHF3/Ar plasmas

CHF3/Ar plasma was used to etch LiTaO3 crystal by inductively coupled plasma technology. The etched crystals under different process parameters were analyzed by surface profilometer and characterized by atomic force microscopy and scanning electron microscope. It was shown that ICP power, RIE power, and total gas flow rate had similar effects on etching rate and selectivity, while Ar/(Ar + CHF3) gas ratio had opposite effects on etching rate and selectivity, with better etching rate and selectivity at the ratio of 0.2. Our work gives a fundamental instruction for the fabrication of LiTaO3 based devices.

Effect of Nitrogen Flow Rate on Microstructure and Optical Properties of Ta2O5 Coatings

Ta2O5 coatings were prepared on highly transparent quartz glass and silicon wafer substrates using RF magnetron sputtering technology. Different flow rates (10%, 15%, and 20%) of N2 were introduced during the sputtering process while keeping the total sputtering gas flow rate constant at 40 sccm. The effects of N2 flow rate on the phase structure, micro-morphology, elemental composition, and optical properties of Ta2O5 coatings were investigated. The coatings were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), electron energy spectroscopy (EDS), and spectrophotometry. The results show that the phase composition of the coating is an amorphous structure when the sputtering gases are pure argon and nitrogen-argon mixed gases, respectively. The coating after the passage of N2 is mainly composed of Ta, N, and O, which confirms that the deposited coating is a composite coating of Ta oxide and nitride. The EDS spectrum indicates that the ratio of O to Ta atoms in the composite coating is greater than the stoichiometric value of 2.5. It may be related to the deposition rate of Ta atoms during the preparation process. The optical properties show that the average transmittance of the composite coating is greater than 75% and the maximum light transmission is 78.03%. The transmittance in the visible range of Ta2O5 coatings prepared under nitrogen-argon mixed gas sputtering conditions is greater than that of those prepared under pure argon sputtering conditions. Finally, the coatings optical direct band gap Edg and indirect band gap Eig are obtained.