N2 Flow Rate Research Articles

Modelling of titanium oxynitride films for decorative coating by using response surface methodology

In this work, titanium oxynitride films were deposited on SS316L and Si-wafer substrates using reactive DC magnetron sputtering. An experimental design and statistical analysis were applied for the thin film coating. The experiment software (Design-Expert Software) was used to design the deposition parameters, including the plasma current density (10-25 mA/cm2) and N2 gas flow rate (20–60 sccm) by maintaining O2 gas flow rate. Response surface methodology based on a central composite design was used to empirically model the influence of the plasma current density (I) and N2 (N) flow rate on the CIE colour system of titanium oxynitride thin films. The model fitting equations for two colour channels (a* and b*) were obtained and represented by a* = –26.65 + 0.67N + 2.92I + 0.02NI – 0.01N2 – 0.12I2 and b* = 4.83 – 1.05N + 1.72I – 0.02NI + 0.02N2 – 0.03I2. In addition, the effects of current density and N2 flow rate on the chemical composition of TiON films were investigated by X-ray photoelectron spectroscopy (XPS). The titanium 2p (Ti2p) spectra indicated that the TiON and TiO2 structures depended on the deposition parameters. Additionally, the increase in N2 flow rate and current density affected the increase of the TiN structure. Cytotoxicity was performed on the Ti sheet and the TiON film on SS316L by assessing the cellular response to L929 fibroblast cells. The result shows that the TiON film on SS316L exhibits good biocompatibility with the L929 fibroblast cells.

Numerical integration strategies of PFR dynamic models with axial dispersion and variable superficial velocity: the case of CO2 capture by a solid sorbent

In order to integrate mole balances (partial differential equations) of an Axial Dispersion Plug Flow Reactor (ADPFR) model, the overall superficial velocity is usually considered constant, a hypothesis which fits well only null or negligible variations of volumetric flow rate, e.g. feeding flow strongly diluted by inert species. This work proposes a numerical-integration approach (based on the method of lines) for ADPFR dynamic modelling, applied to simulate the CO2 capture in an isothermal-isobaric packed bed, made of purposely synthesized and experimentally characterized CaO-mayenite sorbent particles. This approach proved to be suitable for both constant and variable superficial velocity with respect to time and space. With the latter option, velocity profiles agreed with simulated reactive phenomena, while discrepancies between solutions from the two options became increasingly evident as dilution of inlet CO2 decreased. N2 flow rate and CO2 mole balances obtained from numerical-integrations with variable superficial velocity appeared as the most physicochemically reasonable.

Low-loss single-photon NbN microwave resonators on Si

We present coplanar waveguide (CPW) microwave resonators with exceptionally low loss produced from NbN sputtered on Si. The NbN films are deposited with a modest RF substrate bias during reactive DC magnetron sputtering at a substrate temperature of 250 °C and can achieve a critical temperature as high as 15 K depending on the N2 flow rate. We measure the internal quality factors (Qi) of two such resonators at high-powers near saturation and report high-power quality factors in excess of 1.2 × 106 at 200 mK and 3.5 × 105 at 2 K. We also measure the temperature-dependent frequency shift at high power levels and the quality factor at single-photon power levels. From these measurements, we find a low-power (average photon number less than one) Qi value of 4.2 × 105 at 200 mK, which is consistent with a system limited by two-level-system loss.

Effect of N2 and O2 on OH radical production in an atmospheric helium microwave plasma jet

UV-pulsed laser cavity ringdown spectroscopy of the hydroxyl radical OH(A–X) (0–0) band in the wavelength range of 306–310 nm was employed to determine absolute number densities of OH in the atmospheric helium plasma jets generated by a 2.45 GHz microwave plasma source. The effect of the addition of molecular gases N2 and O2 to He plasma jets on OH generation was studied. Optical emission spectroscopy was simultaneously employed to monitor reactive plasma species. Stark broadening of the hydrogen Balmer emission line (Hβ) was used to estimate the electron density ne in the jets. For both He/N2 and He/O2 jets, ne was estimated to be on the order of 1015 cm−3. The effects of plasma power and gas flow rate were also studied. With increase in N2 and O2 flow rates, ne tended to decrease. Gas temperature in the He/O2 plasma jets was elevated compared to the temperatures in the pure He and He/N2 plasma jets. The highest OH densities in the He/N2 and He/O2 plasma jets were determined to be 1.0 × 1016 molecules/cm3 at x = 4 mm (from the jet orifice) and 1.8 × 1016 molecules/cm3 at x = 3 mm, respectively. Electron impact dissociation of water and water ion dissociative recombination were the dominant reaction pathways, respectively, for OH formation within the jet column and in the downstream and far downstream regions. The presence of strong emissions of the bands in both He/N2 and He/O2 plasma jets, as against the absence of the emissions in the Ar plasma jets, suggests that the Penning ionization process is a key reaction channel leading to the formation of in these He plasma jets.

Mechanical and Tribological Properties of CrN Coated Inconel X750

Three CrN coatings were deposited on the Inconel X750 through the metal vapor vacuum arc ion implantation and the magnetic filtered cathodic vacuum arc deposition system (MEVVA-FCVA) with the N2 flow rates of 10, 50, and 100 sccm, respectively. The surface morphologies and cross-section morphologies of the CrN coatings were obtained through scanning electron microscopy (SEM) and an optical profilometer. The microstructures of the coatings were characterized through X-ray diffraction (XRD). The hardness and the elastic modulus of the coatings were tested by a nano-hardness tester. The adhesion strength and friction coefficients were investigated through scratch tests and ball-on-disk tests and the wear tracks were tested by the optical profilometer. The experimental results indicate that the CrN coating deposited on the Inconel X750 substrate displays a uniform thickness and a smooth surface. The mechanical properties behaves well as the N2 flow rate varies. The CrN coating significantly reduces the friction coefficient fluctuation and improves the antiadhesion and anti-wear properties of the Inconel X750.

SNS Josephson Junctions With Tunable Ta–N Barriers

We report on the fabrication and characterization of Nb/Ta-N/Nb Josephson junctions grown by room temperature magnetron sputtering on 150-mm diameter Si wafers. Junction characteristics depend upon the Ta-N barrier composition, which was varied by adjusting the N2 flow during film deposition. Higher N 2 flow rates raise the barrier resistance and increase the junction critical current. This work demonstrates the viability of Ta-N as an alternative barrier to aluminum oxide, with the potential for large scale integration.

Continuous Growth of Buffer/Drift Epitaxial Stack Based on 4H-SiC by Quick Change of N<sub>2 </sub>Flow Rate under High Growth Rate Condition

N-type 4H-SiC homo-epitaxial films were grown under high growth rate condition by high speed wafer rotation vertical CVD tool, and dependence on N2 flow rate for in-wafer distribution of thickness and carrier concentration was investigated. By adjusting only the N2 flow rate from 0.33 to 130 sccm, average carrier concentration of the SiC film was controlled within a range from 3 x 1015 to 1 x 1018 cm-3, while maintaining good in-wafer uniformity less than ±7.0%. Average growth rate higher than 54 μm/h and in-wafer uniformity less than ±3.1% were maintained and no dependence for thickness distribution on N2 flow rate was observed. Buffer/drift epitaxial stack using quick change of N2 flow rate was fabricated, and the crystalline quality and steepness of N concentration at buffer/drift interface were also investigated. The epitaxial stack showed lower defect density compared with single drift layer and showed steep interface between buffer layer and drift layer.

Low temperature retorting of Jordanian oil shales using semi-continuous apparatus

Two oil shales from Jordan, El-Lajjun (EL) in the centre of the country and Isfir Al-Mahata (IA) in the south, have been analysed by elemental analysis, XRF, XRD, FTIR, TGA and 13C NMR. Both oil shales have high S contents and atomic H/C ratios. The calorific value of EL (1630 ± 10 kcal/kg) was similar to that of IA (1571 ± 13 kcal/kg). IA has higher moisture content (7.1 ± 0.3 wt% db) than EL shale (0.7 ± 0.2 wt% db); higher CaCO3 content (XRF, XRD) and lower P content (XRF, XRD). FTIR and 13C NMR indicated a high content of aliphatics for both oil shales, especially for IA shale. These oil shales have been pyrolysed at 300 °C and 320 °C for 7, 14 and 21 days under a constant flow rate of N2. The lower-temperature, long-time reaction yields and analyses of the products were compared with those obtained from the standard Fischer Assay method (520 °C for 90 min). EL oil shale was less reactive than IA oil shale, particularly at lower reaction time. For both oil shales, as the reaction time increased from 7 to 21 days, the oil yield increased to 83–90 wt% of the Fischer Assay oil yield.Fischer assay and lower-temperature, long-time reaction products were analysed using gas chromatography-mass spectrometry (GC–MS) and 1H NMR. The GC–MS results for both shales showed that all the reaction products were similar and of high aliphatic content. Higher diesel fraction was obtained for 21 day reactions at 320 °C. Homologous series of sulfur-containing organic compounds (thiophenes and benzothiophenes) were present in considerable amounts in both EL and IA reaction products. The 1H NMR measurements suggested that the Fischer assay and long-time, lower-temperature reaction products all had high aliphatic content, matching the results obtained from GC–MS measurements.

A DoE–TOPSIS meta-model for parametric optimization of silicon carbonitride (SiCN) thin film deposition process

Silicon carbonitride (SiCN) thin films were deposited on p-type Si(100) substrate by thermal chemical vapour deposition process using SiC and Si3N4 nanopowder as the source, and mixture of N2 and H2 as precursor gases. For the experimental design, Taguchi’s L25 orthogonal array was used considering H2 flow rate, N2 flow rate and deposition temperature as the input deposition parameters, while taking into account, ID/IG ratio, hardness and Young’s modulus as the responses. Design of experiments integrated with technique for order of preference by similarity to ideal solution (TOPSIS) method was applied to develop a corresponding meta-model so as to obtain the optimal parametric combination of the deposition process with respect to the computed TOPSIS score. It was found that optimal parametric combination of H2 flow rate as 60 sccm, N2 flow rate as 100 sccm and deposition temperature as 1300 °C results in improved values of ID/IG ratio, hardness and Young’s modulus. The microstructure, chemical bonding and mechanical properties of SiCN thin films were characterized using Atomic force microscopy, Raman spectroscopy and nano-indentation techniques. As the developed meta-model is solely based on the analysis of the data obtained from experimentation, it is more practical and immune of introducing any additional parameter in the analysis. Moreover, the developed surface plots will further help the process engineer in selecting the most suitable combination of deposition parameters for achieving desirable responses.

Optimization of the Condition of Palm Frond Torrefaction Process by Utilizing Liquid Torrefaction Product as Pre-treatment for Improve Product Quality

Abstract Palm frond can be converted to solid fuel using torrefaction process as an alternative energy source. Torrefaction is the process to convert the biomass into solid fuel at a temperature range of 200-300oC in inert condition. Calorific value is the most important response in solid fuel. The aim of this research is to obtain the optimum condition of palm fronds torrefaction statistically was used Response Surface Methodology. Torrefaction of palm frond on fixed bed a horizontal reactor which is equipped with horizontal condenser and condensate trap with the condition process such as the temperature (225-275oC), time (15-45 min), and N2 flow rate (50-150 ml/min). This research methodology consist of drying, washing with liquid product of torrefaction, torrefaction, and analysis. The response variables were mass yield, calorific value, energy yield, and proximate. Design Expert Trial Version 7.0 Software was used for optimization of condition process with desirability. The optimized condition process were temperature of 275oC, time of 44 minute, and N2 flow rate of 50 ml/min. Keywords: solid fuel, design expert, optimization, palm frond, torrefaction

Effect of N2 shielding gas flow rate on microstructure and weld surface corrosion resistance of high nitrogen steel by laser-arc hybrid welding

In order to investigate the microstructure of welded joint and corrosion resistance of the weld surface of high nitrogen steel, a laser-arc hybrid welding process was used for welding high nitrogen steel in this paper. The Ar + CO2 mixed gas was used as the shielding gas above the weldment, N2 was used as the shielding gas under the weldment. The microstructure of welded joint and corrosion resistance of the weld surface of high nitrogen steel were studied by changing the flow rate of N2. The results showed that all of the welded joints have an excellent macroscopic appearance, weld nitrogen content increases with increasing N2 flow, the microstructure of welded joints are austenite and a small amount of delta-ferrite, the higher the nitrogen flow, the tinier the dendrite of ferrite is. Compared with the weld arc zone, the dendrite of ferrite of the weld laser zone is finer. As the nitrogen flow rate increases, the pitting potential of L1–L4 increase, and the corrosion resistance become better. Nitrogen pores appear in the weld of the L5 group, and a large number of pitting pits appears around the nitrogen pores, which significantly reduce the corrosion resistance. The corrosion resistance of the weld arc zone is not affected by nitrogen flow, the dendrites of ferrite in the weld arc zone are peeled from the crystal structure. Compared with the surface of the weld laser zone, the corrosion resistance of the weld arc zone is worse.

Effects of substrate self-bias and nitrogen flow rate on non-polar AlN film growth by reactive sputtering

The effects of the N2 gas flow ratio and the substrate self-bias of reactive sputtering on the polarity of AlN film on various planar sapphire substrates were investigated to obtain a non-polar oriented AlN film. On a c-plane sapphire substrate, substrate self-bias enhanced c-plane AlN growth and Al termination at the surface, as confirmed by X-ray diffraction (XRD) and time-of-flight low-energy atom scattering spectroscopy. In addition, the AlN film deposited at an N2 gas:Ar sputtering gas ratio of 14% with substrate self-bias had high crystallinity with an XRD ω-rocking curve of 17 arcsec for the 0002 diffraction. In contrast, the AlN films on a- and r-plane sapphire substrates had semi-polar and non-polar plane orientations, respectively. However, on the a-plane sapphire substrate, the c-plane-orientated AlN phase was also observed, which was increased under substrate self-bias condition and an N2 flow rate below 30%. Preferable conditions for non-polar AlN growth by reactive sputtering were non-substrate self-bias and a high N2 flow rate of 30% or more.

A low-temperature and short-annealing process for metal oxide thin film transistors using deep ultraviolet light for roll-to-roll processing

Solution-processed metal oxide semiconductors have superior electron mobility and stability than solution-processed organic semiconductors. However, their fabrication requires a very-high-temperature and long-time annealing process. In this study, we utilized deep ultraviolet (DUV) light to decrease both the temperature and time of the annealing process. High external energy is required to break the organic bonds in a metal oxide film, which is generally supplied by a high-temperature annealing process carried out for a long duration.Alternatively, the required high energy can be supplied more efficiently by irradiating the metal oxide film with DUV light for a shorter duration. In this work, we used DUV light whose peaks at 172 nm instead of the generally used mercury lamp, peaking at 254 and 185 nm. Owing to this difference, thin film transistors (TFTs) could be fabricated on silicon wafers at a lower temperature and shorter duration as compared to the conditions used in previous studies. Various conditions, such as the heating temperature, duration of DUV irradiation, and N2 flow rate, were optimized to control the heating temperature so as to achieve a mobility of 4.44 cm2/V·s and on–off ratio of 2 × 107, which are much higher than those of a transistor annealed at 300 °C for 30 min (mobility, 1.31 cm2/V·s and on–off ratio, 7 × 105).

Chitin derived biochar as an alternative adsorbent to treat colored effluents containing methyl violet dye

Chitin was used to prepare an alternative, eco–friendly and low–cost adsorbent by a simple pyrolysis process. The adsorbent, named chitin derived biochar, was characterized and applied to treat colored effluents containing methyl violet dye (MV). Pyrolysis using N2 flow rate of 0.25 L min−1, heating rate of 10 °C min−1 until 800 °C was suitable to prepare a chitin derived biochar with good characteristics. Chitin derived biochar presented surface area of 275.0 m2 g−1. The MV adsorption on the chitin derived biochar was favored in alkaline conditions and ambient temperature. The adsorption process presented fast kinetics and, the maximum adsorption capacity was higher than 1000 mg g−1. Chitin derived biochar can be used for 7 consecutive adsorption/desorption cycles maintaining the same adsorption capacity. Also, the material was suitable to treat colored effluents, reaching color removal percentage of 95%. In brief, it was demonstrated that chitin derived biochar is a low–cost and efficient material to treat colored effluents.

Microstructural Characterization and Formation Mechanism of Nitrided Layers on Aluminum Substrates by Thermal Plasma Nitriding

Nitrided layers on 6082 aluminum alloy substrates and 1060 aluminum substrates are formed at atmospheric pressure using thermal nitrogen plasma, which only takes seconds to form a millimeter-level layer. The nitrided layers are composed of aluminum nitride (AlN) and aluminum solid solution phases. Microstructures in these nitrided layers can be divided into three regions from bottom to top: the transition region, the dendrite region, and the lamella region. These regions are formed in sequence. The formation mechanisms and processes of the three regions are discussed in detail. Furthermore, we found that Al melt is transported upward through the voids and the capillaries in the AlN structures, and reacts with N plasma in the melt surface. The growth of the AlN structures promotes this transport. With the increase of N2 flow rates from 1 L/min to 7.5 L/min, both the hardness and the wear resistance of the nitrided layers are improved, and the nitrided layer becomes thicker.

Effect of Ar:N2 flow rate on morphology, optical and electrical properties of CCTO thin films deposited by RF magnetron sputtering

Abstract Calcium copper titanate (CCTO) thin films were deposited on indium tin oxide (ITO) substrates using radio frequency (RF) magnetron sputtering, at selected Ar:N 2 flow rates (1:1, 1:2, 1:4, and 1:6 sccm) at ambient temperature. The effect of Ar:N 2 flow rate on the morphology, optical and electrical properties of the CCTO thin films were investigated using FESEM, XRD, AFM, Hall effect measurement, and UV–Vis spectroscopy. It was confirmed by XRD analysis that the thin films were produced is CCTO with cubic crystal structure. As the flow rate of Ar:N 2 increased up to 1:6 sccm, the thin film thickness reduced from 87 nm to 35 nm while the crystallite size of CCTO thin film decreased from 27 nm to 20 nm. Consequently, the surface roughness of thin film was halved from 8.74 nm to 4.02 nm. In addition, the CCTO thin films deposited at the highest Ar:N 2 flow rate studied, at 1:6 sccm; are having the highest sheet resistivity (13.27 Ω/sq) and the largest optical energy bandgap (3.68 eV). The results articulate that Ar:N 2 flow rate was one of the important process parameters in RF magnetron sputtering that could affect the morphology, electrical properties and optical properties of CCTO thin films.

Innovative utilization of refractory iron ore via suspension magnetization roasting: A pilot-scale study

In this study, an innovative suspension magnetization roasting (SMR) technology was developed and utilized for the recovery of iron from a typical refractory iron ore. The effects of the roasting temperature, CO reducing gas flow rate, N2 fluidizing gas flow rate, and feeding rate on the iron recovery were investigated. Under the optimal roasting conditions, a continuous and stable pilot scale SMR test was conducted for 72 h, and a staged grinding and staged low-intensity magnetic separation (LIMS) process was designed to upgrade the roasted product. The results showed that with the appropriate SMR conditions — a roasting temperature of 520 °C, CO flow rate of 4.0 m3/h, N2 flow rate of 2.0 m3/h, and feeding rate of 100 kg/h — an iron concentrate with a total iron grade (TFe) of 60.18% and iron recovery of 90.17% could be obtained. Compared to the traditional process of shaft furnace magnetization roasting (SFMR) followed by LIMS, the novel technique developed here could improve the TFe and iron recovery of the iron concentrate by 12–14% and 17–22%, respectively, with well-functioning equipment. During the SMR process, hematite and siderite were transformed into magnetite, which enhanced the magnetism of the iron minerals. The utilization of the SMR method has the potential to provide a significant technological advance in the field of refractory iron ore recovery in China and globally.

Effects of deposition parameters on structures and photoluminescence of MoO3-x nanomaterials grown by CVD

MoO3-x nanomaterials were synthesized on Si substrate deposited with gold film in hot filaments assisted chemical vapor deposition system using low cost precursors MoO3 and N2. The characterization results indicate that the structures of MoO3-x nanomaterials transfer from nanoparticles to nanosheets with the reduction of N2 flow rate and growth time, which results from the weakening diffusion of MoO3-like molecules in gas environment. Furthermore, the photoluminescence (PL) of MoO3-x nanomaterials was studied at room temperature. The PL results indicate that the MoO3-x nanomaterials emit ultraviolet, blue, green, red and near-infrared light, and the MoO3-x nanosheets generate stronger PL emission than the MoO3-x nanoparticles. These multi-PL bands are related to the bandgap of MoO3, the transition between the sub-bands related to Mo5+ defects and oxygen vacancies, and the transition between the intermediate and valence bands, respectively. The strong PL emission of MoO3-x nanosheets is associated with the enhancement of oxygen vacancies due to more surfaces and edges of nanosheets. Our results provide an effective method of controlling the structures of molybdenum oxide nanomaterials and contribute to the development of next-generation optoelectronic devices based on molybdenum oxide nanomaterials.

Mechanical Properties and Corrosion Resistance of NbTiAlSiZrNx High-Entropy Films Prepared by RF Magnetron Sputtering.

In this study, we designed and fabricated NbTiAlSiZrNx high-entropy alloy (HEA) films. The parameters of the radio frequency (RF) pulse magnetron sputtering process were fixed to maintain the N2 flux ratio at 0%, 10%, 20%, 30%, 40%, and 50%. Subsequently, NbTiAlSiZrNx HEA films were deposited on the 304 stainless steel (SS) substrate. With an increasing N2 flow rate, the film deposited at a RN of 50% had the highest hardness (12.4 GPa), the highest modulus (169 GPa), a small roughness, and a beautiful color. The thicknesses of the films were gradually reduced from 298.8 nm to 200 nm, and all the thin films were of amorphous structure. The electrochemical corrosion resistance of the film in a 0.5 mol/L H2SO4 solution at room temperature was studied and the characteristics changed. The HEA films prepared at N2 flow rates of 10% and 30% were more prone to corrosion than 304 SS, but the corrosion rate was lower than that of 304 SS. NbTiAlSiZrNx HEA films prepared at N2 flow rates of 20%, 40%, and 50% were more corrosion-resistant than 304 SS. In addition, the passivation stability of the NbTiAlSiZrNx HEA was worse than that of 304 SS. Altogether, these results show that pitting corrosion occurred on NbTiAlSiZrNx HEA films.

Microstructural evolution of high quality AlN grown by PAMBE under different growth conditions

The morphological evolution of AlN microstructures by varying the growth temperature and Al/N flux ratio on Si (1 1 1) substrate via plasma-assisted molecular beam epitaxy has been investigated. The transformations in microstructures of AlN grown along the c-plane were explored as a function of N2-flow rate, growth temperature and Al-flux. The structural analysis carried out using high resolution X-ray diffraction reveals single crystalline quality with reduced full widths at half maximum value of 15 arcmin corresponding to a screw dislocation density of 8.5 × 108 cm−2. The topographical study of AlN grown by modulating growth conditions revealed an average surface roughness of 6.9 nm. It was exemplified that interplay between higher growth temperature and nitrogen flow rate is desired to prevent condensation of metallic Al on the surface. Also, the AlN pertaining less screw dislocation density leads to lower dark current which can be fruitful for various optoelectronic applications like vacuum-UV photodetectors.