Reactive Gas Flow Rate Research Articles

Effect of N2 reactive gas flow rate on the structural, optical and wettability properties of silicon carbon oxynitride thin films

In the current research, the silicon carbon oxynitride (SiCON) thin film was deposited on the silicon (Si) substrate by radio frequency (RF) reactive magnetron sputtering method. To comprehensively assess the impact of nitrogen flux rate on thin film characteristics, a suite of advanced analytical methods was utilized. The GIXRD analysis confirmed that the SiCON thin film is amorphous in structure. Additionally, Raman spectroscopy detected no graphite nanocrystals within the film. Ellipsometry measurements further showed that the refractive index of the thin films rises with increased nitrogen flux in the reactive gas, indicating a direct correlation between nitrogen concentration during deposition and optical properties. Based on the designs made with McLeod's software, the amount of reflection can be reduced up to 5.7 % at the wavelength of 4 μm and up to 8.5 % in the wavelength range of 3–5 μm for an optimal thickness thin film. The atomic force microscopy (AFM) examination revealed that the surface roughness of the thin films decreases as the nitrogen flux in the reactive gas mixture increases. Additionally, measurements of the water contact angle (WCA) indicated that the SiCON thin films exhibit a hydrophilic state.

Optimization and test of a ring-ring typed atmospheric pressure plasma jet for optical fabrication

In recent years, the atmospheric pressure plasma jet (APPJ) has gained considerable attention in the field of optical fabrication because the chemical etching approach offers the advantage of avoiding mechanical damage to workpieces. This paper presents the development of an atmospheric pressure plasma machining system with a ring-ring typed APPJ, which exhibits several favorable characteristics. It has a relatively low processing temperature, no electrode corrosion, no plasma contamination, and a long discharge plume, etc. Optimization of the dimensional parameters and analysis of reactive gas flow rate are conducted through experimental investigations. Comparative experiments are carried out with the commonly used needle-ring typed APPJ, revealing significant improvements of the ring-ring typed APPJ, i.e., a fourfold increase in machining distance, a tenfold increase in machining efficiency, and a 58% enhancement in the stability of the material volumetric removal rate. Furthermore, on-line temperature monitoring of the footprint has been achieved due to the specific traits of the extended discharge plume. Fabrication experiments are conducted to demonstrate the significant correlation between the temperature and material removal rate, which shows the possibility of improving the accuracy of optical fabrication based on the ring-ring typed APPJ.

Continuous Synthesis of Diazo Acetonitrile: From Experiments to Physical and Grey‐Box Modeling

AbstractDiazo compounds are gathering interest for their potential in promoting greener synthesis routes. We investigate, at a lab‐scale, the continuous synthesis of diazo acetonitrile (DAN) using a micro‐structured flow reactor and a flow reaction calorimeter. Data concerning DAN formation in the former, and relative to reaction heat and gas flow rate in the latter, are collected. We present a physical and a grey‐box model, both of which are calibrated to our data. Compared to the physical model, the grey‐box approach allows to better incorporate the complex chemical reaction pathways of DAN.

Dissolution behavior and kinetic investigation of 〖Ca〗^(2+) in the dissolution of colemanite in propionic acid presence saturated with synthetic flue gas

Colemanite (〖2CaO.3B〗_2 O_3.5H_2 O) is a calcium borate mineral and can be expressed as the primary material of industrial production of boric acid. Boric acid is one of the most essential raw materials obtained by solving colemanite ore in acidic solutions and gases. The dissolution behavior and kinetics of 〖Ca〗^(2+) in a solution of colemanite in a propionic acid solution saturated with synthetic flue gas were examined. In this context; the effects of particle size, reaction temperature, acid concentration, solid-liquid ratio and synthetic flue gas flow rate parameters were investigated. According to the experimental data, it was observed that the amount of 〖Ca〗^(2+) passing to the solution increased with the increase of the reaction temperature, acid concentration and gas flow rate, and with the decrease in solid-liquid ratio and grain size. Experimental results were analyzed by homogeneous and heterogeneous models using the Statistica package program, and it was determined that the dissolution of 〖Ca〗^(2+) in solution complies with the “Avrami” model. The activation energy (E) was found as 〖26.83 kJ.mol〗^(-1) and the Arrhenius constant (A) was found as 〖8.9*10〗^3.

Structure optimisation of cathode parallel polar plate PEMFC based on topology optimisation

Polar plate design can directly affect the performance of the proton exchange membrane fuel cell(PEMFC). A novel topology parallel polar plate design is proposed to improve cell performance. We used the sparse nonlinear optimisation (SNOPT) algorithm to freely evolve the 2D model and obtain the output material factor distribution map. While keeping the height of the gas diffusion layer constant, the channel height is stretched proportionally to the output material factor to obtain 3D models. By analyzing the mass transfer, water management, and cell performance, the results indicate that increasing the selection range of material output factors is beneficial for the diffusion of reactive gases, reducing pressure loss, and improving cell performance. Reducing the selection range of material output factors helps increase the reaction gas flow rate and enhancing drainage performance. The optimisation model with lower limits benefits oxygen diffusion, increasing gas flow rate and pressure loss, and has little impact on drainage. Case 6 performs well in mass transfer and drainage performance, and the pressure loss is relatively small. The quantitative evaluation shows that Case 6 has an improvement of 22.2% compared to the parallel polar plate and 26.5% compared to the serpentine polar plate in cell efficiency.

Selective strategy of reactive hysteresis loop for coatings on alloy substrates with different moduli

The structure and properties of nitride films, such as titanium nitride (TiN), depend on the reactive gas (N2) flow rates, which are normally selected according to the reactive hysteresis loops. Film-substrate adhesion depends on the properties of the films and substrates. A selective strategy for the reactive gas flow rate within the hysteresis loop was investigated by characterizing the structure, properties, and failure mechanisms of TiN films on Ti6Al4 V titanium alloy (TC4) and 4Cr5MoSiV1 hot-work die steel (H13). The hysteresis loop of the titanium (Ti) target potential as a function of the N2 flow rate was measured, and flow rates in different sputtering modes were used to prepare TiN films using plasma-enhanced magnetron sputtering. As the N2 flow rate increased from 5 cm3/min, 10 cm3/min, 15 cm3/min to 20 cm3/min, from the metallic mode to the compound mode, the morphologies of the films changed from loose to dense, the phase structures changed from TiN0.3 (002) to TiN (111), (200), and (220), and the nano-hardness and elastic moduli increased. Applying a Rockwell normal load, asymmetric circular cracks appeared and became significant for TiN/TC4 as the N2 flow rate increased to 15–20 cm3/min; cracks were only observed in TiN/H13 at an N2 flow rate of 20 cm3/min. Applying normal and shear scratch stresses, the TiN films peeled off from the TC4, except for TiN, with an N2 flow rate of 10 cm3/min, indicating that the adhesion between TiN and TC4 was weak. No peel-off chips were observed in the scratch morphologies of TiN/H13, indicating excellent adhesion between the films and H13 substrate. Circular cracks appeared in the scratch morphology of TiN0.3, indicating that cohesion had broken within the film. The possible failure mechanism was the large difference in the elastic moduli and hardness of TiN and TC4, which led to TC4 elastic and plastic deformation much earlier than in TiN films. According to numerical simulation, the interfacial tensile stress of TiN/TC4 under a normal load was higher, and the interfacial strain near the indentation edges was larger than that of TiN/H13. Considering the comprehensive properties, a reactive flow rate near the critical point such as 15 cm3/min for TiN/TC4 should be used for the nitride film on a low-hardness and low-modulus substrate; in the compound mode stage, 20 cm3/min for TiN/H13 should be used for the nitride film on a high-hardness and high-modulus substrate.

Investigation of silicon carbon oxynitride thin film deposited by RF magnetron sputtering

In this research, silicon carbon oxynitride (SiCON) thin films were deposited on silicon substrate by a radio frequency magnetron sputtering method. The effect of methane reactive gas flow rate on the structural, morphological, optical, and mechanical properties of the thin films was evaluated by using of grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) , field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), fourier transform infrared spectroscopy (FTIR), ellipsometry and nano-indentation methods. The results of the GIXRD proved the formation of an amorphous structure in the thin films. Also, the Raman spectroscopy results determined the absence of graphite nanocrystals in the thin film structure. FE-SEM revealed the formation of a thin film with a smooth, dense and crack-free surface. AFM results showed that SiCON thin film is formed with very low surface roughness in the RMS range of 0.73 nm to 4.39 nm. The results of the ellipsometry analysis indicated that the refractive index of the thin film was changed during increase of the CH4 reactive gas flow rate in the of 1.4 to 1.61 at 4 µm. According to the nano-indentation results, sample N10-C20-R1 has the highest hardness and Young's modulus equals 22.7 GPa and 231.6 GPa, respectively.

Rapid determination of titanium in human urine by inductively coupled plasma-tandem mass spectrometry

To establish an inductively coupled plasma-tandem mass spectrometry(ICP-MS/MS) method to determinate the titanium(Ti) in human urine samples rapidly. By comparing different gas mode, ~(47)Ti was selected as the analysis element. Injecting NH_3 to the collision/reaction cell, swept by mass spectrum to determine the optimal mass spectrum conditions with the mass number of Q1=47, Q2=149(Ti ammonia hexamer). The mass spectrometry conditions of internal standard elements, integration time, reaction gas flow rate and data processing method and so on were optimized. Ti had a good linear between 0.1-5.00 μg/L under the optimal analytical conditions. The detection limit was 0.1 μg/L. The RSDs of intra-day and inter-day were less than 10%, and the average recoveries were 93.7%-112.2%. The result of Seronorm Trace Elements Urine L-2 met the acceptable range. The method is rapid, simple, accuracy, and suitable for the rapid analysis of titanium in human urine.

Controllable preparation of boron nitride microspheres and their epoxy-based thermoconductive composites

How to prepare spherical boron nitride (BN) particle with different size is an extremely challenging work. In this paper, the controllable preparation of spherical BN particle from nanospheres to microsphere was realized by changing the synthesis temperature of trimethyl borate (B(OMe)3) and ammonia. The spherical precursor (SP) with high oxygen content was obtained first, and then it was heated under flowing ammonia atmosphere to form stable boron nitride microspheres (BNMS). The BNMS exhibits onion-like cavitation structure with a diameter of 0.8–3.4 μm. The effects of the lower reaction temperature (700–825 °C) and gas flow rate on the spherical precursor are discussed. A possible mechanism is proposed to explain the formation of precursors and the appearance of onion-like structure. It is believed that the formation of microsphere is due to the deposition and growth of BO species during the flow process of nanosphere. In addition, the effect of the addition of BNMS on the thermal conductivity of epoxy resin (EP) composites was investigated.

Single-cell ICP-MS for studying the association of inorganic nanoparticles with cell lines derived from aquaculture species

The current research deals with the use of single-cell inductively coupled plasma-mass spectrometry (scICP-MS) for the assessment of titanium dioxide nanoparticle (TiO2 NP) and silver nanoparticle (Ag NP) associations in cell lines derived from aquaculture species (sea bass, sea bream, and clams). The optimization studies have considered the avoidance of high dissolved background, multi-cell peak coincidence, and possible spectral interferences. Optimum operating conditions were found when using a dwell time of 50 μs for silver and 100 μs for titanium. The assessment of associated TiO2 NPs by scICP-MS required the use of ammonia as a reaction gas (flow rate at 0.75 mL min−1) for interference-free titanium determinations (measurements at an m/z ratio of 131 from the 48Ti(NH)(NH3)4 adduct). The influence of other parameters such as the number of washing cycles and the cell concentration on accurate determinations by scICP-MS was also fully investigated. Cell exposure trials were performed using PVP-Ag NPs (15 and 100 nm, nominal diameter) and citrate-TiO2 NPs (5, 25, and 45 nm, nominal diameter) at nominal concentrations of 10 and 50 μg mL−1 for citrate-TiO2 NPs and 5.0 and 50 μg mL−1 for PVP-Ag NPs. Results have shown that citrate-TiO2 NPs interact with the outer cell membranes, being quite low in the number of citrate-TiO2 NPs that enters the cells (the high degree of aggregation is the main factor which leads to the aggregates being in the extracellular medium). In contrast, PVP-Ag NPs have been found to enter the cells.Graphical abstract

Continuous Flow Synthesis of Esomeprazole via Asymmetric Sulfoxidation

In this paper, an expeditious and efficient continuous flow process for the synthesis of esomeprazole is described. The asymmetric sulfoxidation was achieved in optimized continuous reaction equipment under a mild condition to provide esomeprazole in 98% yield and 98% ee. For a more efficient reaction, an inert gas was introduced into the homogeneous reaction process, and the residence time in the flow system was markedly reduced (from 2 h in batch to 48 s in flow) because of an enhanced mixing effect. The effects of the reaction equipment, gas and liquid flow rate, reagent equivalents, reaction temperature, system concentration, solvent, and pressure have been investigated successively. To reveal the versatility and applicability of the reaction procedure, a scale-up strategy of continuous oxidation was employed to obtain nearly 20 g of product with a total productivity of 5.6 g/h. Ultimately, esomeprazole sodium was obtained with 99.8% purity and 99.6% ee following a simplified salt formation operation.

Highly efficient and atomic scale polishing of GaN via plasma-based atom-selective etching

Plasma-based atom-selective etching (PASE) of GaN is conducted to realize the highly efficient planarization of the GaN surface. Inductively coupled plasma with high temperature and high concentration of radicals is used as the source of PASE. The non-toxic carbon tetrafluoride is chosen over chlorine as the reaction gas, and the volatility of the etching products will be improved at high temperatures in the PASE of GaN. After 2 min of PASE, the GaN surface roughness is reduced from Sa 135.8 nm to Sa 0.527 nm. The material removal rate of PASE of GaN is measured to be 93.01 μm/min, thousands of times higher than that of the conventional chemical mechanical polishing method. The crystal structure of the GaN subsurface is well-ordered without any damage or defects. PASE is thus proven to be a non-destructive etching method. In this study, the effects of radio frequency power and reaction gas flow rate on PASE are also investigated. Surface temperature and concentration of radicals are found to be the critical factors in the PASE of GaN.

State-of-the-Art Developments in Advanced Hard Ceramic Coatings Using PVD Techniques for High-Temperature Tribological Applications

Hard and wear-resistant coatings created utilizing physical vapor deposition (PVD) techniques are extensively used in extreme tribological applications. The friction and wear behavior of coatings vary significantly with temperature, indicating that advanced coating concepts are essential for prolonged load-bearing applications. Many coating concepts have recently been explored in this area, including multicomponent, multilayer, gradient coatings; high entropy alloy (HEA) nitride; and functionally modified coatings. In this review, we highlighted the most significant findings from ongoing research to comprehend crucial coating properties and design aspects. To obtain enhanced tribological properties, the microstructure, composition, residual stress, hardness, and HT oxidation resistance are tuned through doping or addition of appropriate materials at an optimized level into the primary coatings. Such improvements are achieved by optimizing PVD process parameters such as input power, partial pressure, reactive gas flow rates, substrate bias, and temperature. The incorporation of ideal amounts of Si, Cr, Mo, W, Ag, and Cu into ternary and quaternary coatings, as well as unique multilayer designs, considerably increases the tribological performance of the coatings. Recent discoveries show that not only mechanical hardness and fracture toughness govern wear resistance, but also that oxidation at HT plays a significant role in the lubrication or wear failure of coatings. The tribo-induced metal oxides and/or Magnéli phases concentrated in the tribolayer are the key governing factors of friction and wear behavior at high temperatures. This review includes detailed insights into the advancements in wear resistance as well as various failure mechanisms associated with temperature changes.

Magnetron Sputtered Thin Films Based on Transition Metal Nitride: Structure and Properties

Transition metal nitride (TMN) thin films exhibit outstanding physical, chemical, and mechanical properties, making them best suitable for a wide variety of applications. The most commonly used technique to produce metal nitride thin films with specific properties at optimum conditions is magnetron sputtering. Considering this, this review begins with advancements in the sputtering process from basic diode sputtering to the most commonly used pulsed magnetron sputtering. Further, the literature on several TMNs deposited via magnetron sputtering is summarized, referring to several articles that have been published during the last decades. The main emphasis lies on nitride‐based thin films’ structural, morphological, and mechanical aspects for various applications. In addition, the influence of reactive gas flow rate, substrate temperature, layer thickness, postannealing temperature, substrate bias voltage, protective layers, the sputtering technique adopted, etc. on the quality and performance of the thin films is also focused. The overall review work can be beneficial for the students and researchers in understanding the basic sputtering phenomenon with its advancements, the relationship between deposition parameters and surface properties, and to know the current research trend for exploring several research gaps in the literature.

Reactive simulation of gas-catalyst thermochemical properties in a pilot-plant catalytic MTO fluidized bed

The methanol-to-olefin (MTO) process enables economical production of light olefins thus decreases the reliance on petroleum resources. The reactive multiphase flow patterns and reaction behaviors inside pilot-plant MTO fluidized reactor are numerically simulated with multiphase particle-in-cell model. Based on the model validation, the thermochemical properties of catalytic particle (e.g., heat transfer coefficient (HTC), temperature) and gas phase thermal characteristics are comprehensively investigated with the discussion on several crucial operating parameters. The results reveal that large HTC of catalyst particle is located in the crucial reaction zone and freeboard zone. The HTC of catalyst material covers a range of 50 to 150 W/(m2·K). Gas-solid hydrodynamics and gas concentrations exhibit spatial non-uniform distribution. Moreover, the reactant gas flow rate is more positively sensitive to the product distributions and gas thermal properties. Enlarging the reaction pressure significantly enhances the heat transfer. The vertical dispersion coefficient of catalyst is two orders of magnitude larger than the horizontal ones.

Modeling Isothermal Reduction of Iron Ore Pellet Using Finite Element Analysis Method: Experiments & Validation

Iron ore pellet reduction experiments were performed with pure hydrogen (H2) and mixtures with carbon monoxide (CO) at different ratios. For direct reduction processes that switch dynamically between reformed natural gas and hydrogen as the reductant, it is important to understand the effects of the transition on the oxide reduction kinetics to optimize the residence time of iron ore pellets in a shaft reactor. Hence, the reduction rates were studied by varying experimental parameters such as the temperature (800, 850 & 900 °C), reactant gas flow rate (100, 150 & 200 cm3/min), pellet size and composition of the reactant gas mixture. The rate of reduction was observed to increase with an increase in temperature and reactant gas flow rate, but it decreased with an increase in pellet size. SEM greyscale analysis was performed to analyze the porosity and phase composition of partially reduced pellets. The porosity of the pellets was observed to increase from 0.3 for unreacted pellet to 0.42 for a completely reduced pellet. Energy-dispersive X-ray spectroscopy (EDAX) analysis was performed to identify the phases observed in the SEM images. The fraction of iron phase was observed to increase from the shell region of the pellet to the core region with an increase in the degree of reduction. A 2D-axisymmetric numerical model was developed on COMSOL Multiphysics, and it was validated using the conversion (X) vs. time curves obtained from each experiment. The model was able to accurately predict the total time needed for the complete conversion of a single iron ore pellet for multiple experiments. Effects of changes in the porosity and tortuosity of the pellet on the model were also studied and the rate of reduction was observed to be sensitive to changes in both porosity and tortuosity. The SEM analysis and the model results show that tortuosity is higher for pellets reduced with H2 than for pellets reduced with H2-CO gas mixtures.

(Digital Presentation) Fabrication and Characterization for Vanadium Oxynitride Thin Films By Magnetron Sputtering

Vanadium oxynitride (VNxOy, x+y=1) is a metallic compound between vanadium oxides (VO, V2O3, V2O5) and vanadium nitride (VN) which would have interesting properties and functions that potentially can be supplied for different applications. In this study, vanadium nitride and oxynitride thin films were obtained by reactive magnetron sputtering using vanadium targets, Ar as plasma carrier, and a mix of N2 and O2 as reactive gas. The ratio of mass flow between the two gases is maintained around O2:N2=1:20 during the process. To obtain crystalline phases of oxynitrides a post rapid thermal annealing (RTP) in Ar atmosphere at 600ºC and 700ºC for 5 minutes was done. The purpose of the study is to define the effect of the magnetron sputtering parameters, such as reactive gas flow rates, and annealing temperature on the composition, microstructure, and optical properties of the obtained vanadium oxynitride thin films. The characterization of obtained films includes the examination of thickness and morphology by the surface profiler and SEM; identifying crystal structures and further microstructural vibration modes of molecular polarizability by X-ray diffraction and Raman spectroscopy, respectively; evaluation of the chemical composition of films by XPS analysis; assessing of optical transmittance, reflectance, and absorbance by the UV-visible- NIR spectrometer. Experimental data reveal that the annealed films can be oxynitrides when the oxygen flow rate is below 0.25 sccm and the ratio of oxygen/nitrogen ≤1/20. The annealed vanadium oxynitride films in terms of their properties are closer to vanadium nitrides than to oxides: more metallic than semi-conductive with dark appurtenance and high optical absorbance across the spectrum between 200 and 900 nm. The optical absorbance reaches almost 90% around 300 nm and then slowly reduces to 70% at 900 nm. Thus, these films could be good optical shields. For practical usage, the deposition of O2:N2=1/20, O2<0.25 sccm, and 600ºC annealing are recommended because of the truly low transmittance (<10%) through films.

Comparative Study on the Influence of Reactive Gas Flow Rate on the Growth and Properties of P-doped TiAlN Coatings Prepared by DcMS and HiPIMS

Comparative Study on the Influence of Reactive Gas Flow Rate on the Growth and Properties of P-doped TiAlN Coatings Prepared by DcMS and HiPIMS

Electrode reaction properties using a reactant gas addition method in a commercial 100 cm2 class solid oxide fuel cell

This work investigates the reaction characteristics of the anode and cathode by overpotential analyses in 100 cm2 class planar anode-supported SOFCs. The reactant gas addition (RA) technique was applied to analyse the overpotential, which uses the reactant gas flow rate and partial pressure as parameters due to their variation upon adding a reactant species to an electrode. The anodic overpotential was determined to be made up of mass transfer-induced overpotentials of H2 and H2O species. The H2O species account for the majority of the anodic overpotential at the measured current range i.e., 0–150 mA cm−2. Thus, the anodic reaction is under an extreme H2O-induced mass-transfer resistance compared with H2. The RA method showed that the cathodic overpotential was mainly due to a deficiency of O2 species in the mass transfer through the gas phase rather than the solid phase. Furthermore, both cathodic and anodic overpotentials depended on gas flow rate and utilisation, indicating a significant gas-phase mass transfer effect.

Bipolar high‐power impulse magnetron sputtering synthesis of high‐entropy carbides

AbstractIn this study, we report high‐entropy carbides synthesis with reactive bipolar high‐power impulse magnetron sputtering (HiPIMS). Uncontrolled microstructure and stoichiometry development with reactive gas flow rate are major limitations of conventional direct current (DC) and radio frequency (RF) magnetron sputtering of multicomponent carbides. With HiPIMS these chemically disordered crystals structurally and compositionally transform from a carbon‐deficient metallic (C/M &lt; 1), to a stoichiometric ceramic zone (C/M ∼ 1), and to a nanocomposite embodiment (C/M &gt; 1), as a function of the carbon content during HiPIMS deposition. X‐ray diffraction, X‐ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and nanoindentation hardness measurements are combined to demonstrate the three regions of synthesis domain. HiPIMS provides access to metallic, ceramic, and composite carbides with great control over the microstructure and stoichiometry, which is elusive in case of conventional DC and RF magnetron sputtering. Notably, the stoichiometric ceramic zone maintains a constant carbon to metal ratio (C/M ∼ 1) over an extended amount of methane flow before transitioning to a nanocomposite microstructure (C/M &gt; 1). The transition zone breadth depends on materials affinity for carbon that correlates with valence electron concentration (VEC). As such, synthesis conditions for new high‐entropy carbides can be understood and predicted based on VEC.