N2 Gas Flow Rate Research Articles

Role of growth parameters on structural and magnetic properties of Fe4N thin films grown by reactive magnetron sputtering

We studied the effect of growth parameters on the phase formation of Fe4N in a reactive sputtering process. The Fe4N phase formation was found to be extremely sensitive to N2 gas flow and sputter rate but not so much on the substrate temperature. But post-deposition annealing (PDA) time was found to be a critical parameter to get single phase Fe4N. As PDA time increases, the anti-bonding states characteristic of Fe4N start to diminish due to N out-diffusion. Signatures of such N diffusion process can also be seen from the Fe and N depth profiles. We found that the residual resistivity ratio was maximum for the optimized Fe4N films. Magnetization measurements were performed using bulk magnetization as well as polarized neutron reflectivity. We found that the magnetic moment of optimized Fe4N film was about 2.3 μB/atom at 15 K. Magnetic anisotropy measurements carried out using magneto optical-Kerr effect exhibit a rotatable anisotropy.

Changes of the Physical Properties of Sputtered InGaN Thin Films Under Small Nitrogen Gas Flow Variations

In this research work, InGaN triple compound was grown under low nitrogen gas flows by using the sputtering technique. The structural, optical and morphological characteristics of the InGaN compound have been studied in detail. X-ray diffraction (XRD) and Raman for structural analysis; absorption measurement technique for optical properties; scanning electron microscopy and atomic force microscopy (AFM) measurement techniques were used for the study of the morphological characteristics. In the XRD analysis, the film deposited at 0 sccm gas flow exhibits a (0002) peak of InN, (0002) and (10–11) peaks of GaN. Other films show dendritic structure. In the Raman analysis, the optical phonon modes of the InGaN compound are A1(LO) and E2(high). Optical band gaps are found to be 2.57 eV, 2.54 eV, 3.03 eV and 2.93 eV for 0–0.4–0.8–1.2 sccm, respectively. These changes are ascribed to the degraded crystallinity of the grown films at high nitrogen flow rates. The surface morphology of the InGaN films grown at 0 sccm displays clusters of near-spherical-shaped nanoparticles over the surface. In the results of the AFM, the surface topography of the InGaN thin films deposited with lower nitrogen content exhibited fewer grains on the surface, especially on 0.4 sccm gas flow rate. The number of grains increased with higher N2 gas flow rates. The surface roughness of the films decreased with increasing N2 gas flows. It is clear that surface morphology of the films depends on the gas flow rate very much. Due to their morphological properties, we can say that they are suitable structures for optoelectronic applications and friction applications in engineering. We can also say that films with a hexagonal crystal structure and different optical band gaps can be used in device applications such as LED, laser diode and power electronics.

Pyrolysis of orange bagasse: Comparative study and parametric influence on the product yield and their characterization

A pyrex glass semi-batch reactor was used for the pyrolysis of orange bagasse screened at 425 μm. The effect of temperature (350–600 °C), heating rate (25–100 °C min−1) and N2 gas flow rate (0.1–0.5 L min−1) on the product yield was observed. The highest pyrolysis oil yield of 35.53 wt. % was achieved at a temperature of 525 °C; at a constant heating rate and N2 gas flow rate of 75 °C min−1 and 0.2 L min−1. The H/C molar ratio of pyrolysis oil was 1.33 having an empirical formula of CH1.33O0.55 and an HHV of 21.72 MJ kg−1. The pyrolysis oil had a smoky odour with a dark brownish colour. The presence of different compounds like naphthenes, paraffin, olefins, aromatics, esters, acids, phenols, oxygenates, aldehydes and furans makes it complex and highly acidic in nature. The carbon distribution range of the pyrolysis oil lies from C2 to C18 which is similar to other liquid petroleum products. The biochar has an HHV of 27.67 MJ kg−1 because of the lower oxygen content than its parental biomass. The increase in the alkalinity (pH:8.1) of biochar finds application in neutralising soil acidity and improving crop yield.

Release Behavior of Arsenic during Pyrolysis of Two Chinese Coal Gangues

Release behaviors of arsenic (As) during pyrolysis of two Chinese coal gangues were studied in this report. The pyrolysis experiments were carried out in a temperature programmed tube furnace under N2 atmosphere with different temperature (200-1200 oC), residence time (0-50 min), heating rate (10-50 oC min-1) and N2 gas flow rate (100-500 cm3 min-1). The experiment results, under different pyrolysis conditions, indicate that the release ratio of As increases with increasing temperature, as well as residence time during pyrolysis of coal gangues. Besides that, higher heating rate during pyrolysis of coal gangues can stimulate the As release from coal gangue to some extent. The release ratio of As increases to a maximum and then decreases when the N2 gas flow rate is increased. The results imply that different modes of ocurrence of As exist in two coal gangues. The As release has positive relation with the volatile matter release. As is more easily released than coal gangue matrix during coal gangue pyrolysis.

P-Si(100)/InGaN thin film structure and investigation of its physical properties: N2 gas flow effect

Abstract In this study, effect of N2 gas flow rates on structural, optical and morphological properties of InGaN thin films grown by Radio Frequency Magnetron Sputtering (RFMS) method on p-Si (100) substrate have been investigated. X-ray diffraction (XRD) measurements confirmed that InGaN thin films have been successfully deposited and exhibited diffraction peak belong to (002) plane for each film. The surface roughness of InGaN thin films has been determined by using Atomic Force Microscopy (AFM) and the roughness value is about 13 nm with a maximum height of 36 nm and a maximum depth of 37 nm. The surface roughness value Rq\RMS value is 15 nm, which is almost consistent with the linear roughness value for 0 sccm. The energy band gap of the film was determined by using the optical reflectance spectra and the value of the band gap energy is found to be 2.01, 1.77 eV and 2.26 eV for 0 sccm, 1 sccm and 2 sccm N2 gas flow rates, respectively

Enhanced Photocatalytic Performance of Nitrogen-Doped TiO2 Nanotube Arrays Using a Simple Annealing Process

Nitrogen-doped TiO2 nanotube arrays (N-TNAs) were successfully fabricated by a simple thermal annealing process in ambient N2 gas at 450 °C for 3 h. TNAs with modified morphologies were prepared by a two-step anodization using an aqueous NH4F/ethylene glycol solution. The N-doping concentration (0–9.47 at %) can be varied by controlling N2 gas flow rates between 0 and 500 cc/min during the annealing process. Photocatalytic performance of as-prepared TNAs and N-TNAs was studied by monitoring the methylene blue degradation under visible light (λ ≥ 400 nm) illumination at 120 mW·cm−2. N-TNAs exhibited appreciably enhanced photocatalytic activity as compared to TNAs. The reaction rate constant for N-TNAs (9.47 at % N) reached 0.26 h−1, which was a 125% improvement over that of TNAs (0.115 h−1). The significant enhanced photocatalytic activity of N-TNAs over TNAs is attributed to the synergistic effects of (1) a reduced band gap associated with the introduction of N-doping states to serve as carrier reservoir, and (2) a reduced electron‒hole recombination rate.

Flow visualization of heavy oil in a packed bed using real-time neutron radiography

Neutron radiography can visualize heavy oil flows in metallic reactors used to upgrade heavy oils. Thus, we visualized heavy oil flows in a packed bed using real-time neutron radiography to support its capability and to offer basic experimental data necessary for verification and validation of numerical simulations. Atmospheric residue was used as the heavy oil sample and heavy oil and N2 gas were concurrently supplied into a packed bed from above a reactor simulating a trickle bed reactor. Reactor temperatures were set at either 100°C or 250°C to change heavy oil viscosity. The heavy oil flow rate was kept constant at 2.5 mL/min and the N2 gas flow rate was set at either 1 L/min or 3 L/min at 25°C. A series of neutron radiography experiments was conducted at the B-4 neutron imaging facility in the Kyoto University Research Reactor (KUR) with a thermal neutron flux of 5 × 107 n/cm2⋅s. We performed image processing for the neutron radiographs to calculate neutron beam attenuation and clarify flow behavior. Visualization results show differences in flow behavior depending on operating factors. Temperature had a particularly substantial effect on flow behavior because heavy oil viscosity depends strongly on temperature. The flows also showed different behaviors for 1 mm and 3 mm packed particle sizes because the void ratios in the packed bed, which were preliminarily observed by X-ray computational tomography (CT), change with particle size. Channeling flow was observed with 3 mm particles and a temperature of 250°C. Furthermore, this work suggests that neutron radiography can be used to investigate heavy oil flows in metallic reactors.

Synthesis of Tin Powders Using Dynamic CRN Method

Dynamic carbotermal reduction-nitridation (DCRN) is a new approach developed to produce more effective ceramic powder production than classical static system of carbothermal reduction-nitridation (CRN) method. In this new technique of DCRN, powder is produced in a moving system and production takes place at relatively lower temperatures and/or shorter times than CRN method. This study examines production of TiN powder by the DCRN method. The granules were prepared using TiO2 and carbon black powders in the stoichiometric ratio (C/TiO2=2). TiN powders of sub-micron were obtained in a graphite reactor from the prepared granules under N2 gas flow. The effects of various test parameters were investigated for TiN synthesis, such as temperatures of reaction (1350-1450°C), reaction time (0.5-3 h), N2 gas flow rate (60-120 L/h) and reactor rotation speed (2-6 rpm). The phases and microstructures of the powders were characterized by XRD, SEM and FESEM analyses.

Production of Bio-oil through Fast Pyrolysis of Baobab Waste Shells

The increasing demand for transportation fuel, due to increased urbanization, is now compounded by depleting and unstable crude oil reserves. Furthermore, the volatile market and the negative environmental impact of fossil fuels have driven the usage of biomass as a potential energy source. Of particular interest are biomass waste and baobab shells present an interesting option. The objective of this study is to produce bio oil by a fast pyrolysis process from baobab shells. The effect of reaction temperature, biomass particle size and fluidizing gas flow rate on the liquid product yield are investigated. The maximum liquid yield obtained was 36.6% at 500 OC at a N2 gas flowrate of 11.6 l/min and a particle size of less than 0.5 mm.

Valorization of Pine Needles by Thermal Conversion to Solid, Liquid and Gaseous Fuels in a Screw Reactor

The purpose of this study was to optimize the pyrolysis conditions to obtain maximum bio-oil yield from pine needles using a screw pyrolyzer for utilizing this abundantly available ligno-cellulosic biomass from pine forest as an alternate source of fuel. Pyrolysis was conducted in a pilot scale single screw reactor. Process parameters such as pyrolysis temperature, biomass particle size, solid residence time and gas flow rate were optimized by employing Taguchi’s L9 Orthogonal Array. Chemical characterization of bio-oil was conducted using gas chromatographic/mass spectroscopy (GC/MS) analysis. Fuel properties of bio-oil and biochar were determined using ASTM standard methods. Composition of product gas was determined by gas chromatography and higher heating value (HHV) was calculated theoretically. Results revealed that bio-oil yield was primarily influenced by pyrolysis temperature and biomass particle size. The optimum conditions for maximum bio-oil yield were—pyrolysis temperature of 500 °C, particle size of 1.25–2.0 mm, solid residence time of 15 min and N2 gas flow rate of 30 l h− 1(Gas flow velocity ∼ 0.33 m min−1). A maximum bio-oil yield of 28.98% was achieved at optimum conditions. Optimized conditions found in this experiment can be employed to continuous pyrolysis of pine needles for production of higher grade energy products like bio-oil, biochar and product gas through screw reactor.

Characterization of plasma polymerized organosilicon thin films deposited on 316L stainless steel

This study focused on the characterization of the organosilicon films deposited on 316L stainless steel (316L SS) substrate using a plasma polymerization process with hexamethyldisiloxane (HMDSO) precursor and different N2 gas flow rates. The organosilicon film had a C-rich composition as deposited using only HMDSO precursor. The nitrogen content of thin film consecutively increased with increasing N2 flow rate up to 15 sccm. The film deposition rate increased with increasing N2 flow rate. All films exhibited the smooth and pinhole free surfaces. Good adhesion property was obtained for each film after scratch test. Better biocompatibility and cell adhesion was observed for the nitrogen free organosilicon film as compared with that of the untreated 316L SS. Further enhancement of biocompatibility was found for those films with N2 addition. The best biocompatibility, highest transmittance, less hydrophobic surface, and excellent wear resistance were noted for the film grown under 5 sccm N2 flow rate. Such film performance makes it become a promising candidate as the surface coating layer on 316L SS for biomedical application.

Superimposition of high power impulse and middle frequency magnetron sputtering for fabrication of CrTiBN multicomponent hard coatings

The combination of superimposition and hybrid target powers using a superimposed high power impulse magnetron sputtering (HiPIMS) power and middle-frequency (MF) power system, together with the hybrid of direct-current (DC) and radio-frequency (RF) powers was adopted in this work to grow CrTiBN hard coatings. The flexibility of tailoring the chemical composition, phase, deposition rate, microstructure and mechanical properties of CrTiBN coatings through the feedback control of reactive N2 gas flow rate and the corresponding Ti target poisoning status by a plasma emission monitoring (PEM) system was successfully illustrated in this work. Both the peak current and peak power density of Ti target increased with increasing poisoning ratio, i.e., decreasing PEM set point. The 1.64 times higher deposition rate of CrTiBN films can be obtained when the Ti target status changes from poisoning (PEM set point 30%) to transition regime (PEM set point 70%). Fine and compact film microstructure, and a very smooth surface are fabricated for all films. Each coating shows a low coefficient of friction and low wear rate ranging from 0.46 to 0.49 and from 2.06 to 5.73 × 10−6 mm3 N−1m−1, respectively. The highest hardness of 34.1 GPa, adequate adhesion and wear resistance can be found for the CrTiBN coating as deposited at PEM set point of 40% and Ti target poisoning ratio of 60%.

STUDY ON ADHESION STRENGTH OF TIN COATED BIOMEDICAL TI-13ZR-13NB ALLOY

One of the crucial factors which determine the success of coated implantation and stability in the long run is the strength of adhesion between the coating and substrate. After implantation, a weakly adhered coating may delaminate and this might seriously restrict the implant’s effectiveness and longevity. Based on past studies, the quality of TiN coating is directly influenced by the process parameters. The objective of this research is to evaluate the effect of N2 gas flow rate on adhesion strength of biomedical grade Ti-13Zr-13Nb alloy. In this research, N2 gas flow rate of 100, 200 and 300 sccm were varied while the other parameters (substrate temperature and bias voltage) were fixed. The scratch testing method was used to examine the adhesion strength of the TiN coating. This research used the calibrated optical images to verify the total coating failures on the scratched coated samples. The results indicated that the micro droplet form on the TiN coating decreases as the flow rate of the N2 gas increases. In contrast, the TiN coating’s adhesion strength increases with the increase of N2 gas flow rate. It can be concluded that N2 gas flow rate was significant factor in improving the coating properties of TiN on Ti-13Zr-13Nb alloy.

Improved irradiation tolerance of reactive gas pulse sputtered TiN coatings with a hybrid architecture of multilayered and compositionally graded structures

This study investigates the improved irradiation tolerance of reactive gas pulse (RGP) sputtered TiN coatings which has hybrid architecture of multilayered and compositionally graded structures. The multilayered RGP-TiN coating is composed of hexagonal close-packed Ti phase and face-centred cubic TiN phase sublayers, where the former sublayer has a compositionally graded structure and the latter one maintains constant stoichiometric atomic ratio of Ti:N. After 100 keV He ion irradiation, the RGP-TiN coating exhibits improved irradiation resistance compared with its single layered (SL) counterpart. The size and density of He bubbles are smaller in the RGP-TiN coating than in the SL-TiN coating. The irradiation-induced surface blistering of the coatings shows a similar tendency. Meanwhile, the irradiation hardening and adhesion strength of the RGP-TiN coatings were not greatly affected by He irradiation. Moreover, the irradiation damage tolerance of the coatings can be well tuned by changing the undulation period number of N2 gas flow rate. Detailed analysis suggested that this improved irradiation tolerance could be related to the combined contribution of the multilayered and compositionally graded structures.

Predictive modelling and optimization of carbon fiber mechanical properties through high temperature furnace

Developments in carbon fiber mechanical properties are directly dependent on its manufacturing process, especially the thermal process of carbonization through a High Temperature (HT) furnace. These mechanical properties cannot be straightforwardly predicted experimentally since the thermal process involves complex parameters such as: (i) zones temperature, (ii) applied fiber tension, (iii) the N2 gas flow rate which is influenced by uncertain disturbances. The aim of this paper is to optimize the carbon fiber modulus based on the given range of tensile strength using a predictive modelling technique. The data collection of the carbonization thermal process is significantly costly and time consuming, hence we used a novel DOE method to minimize the number of required experiments. The carbon fiber with the highest and lowest tensile and modulus properties were initially analyzed by X-ray diffraction and Raman Spectroscopy, but no significant differences were observed that could account for the differences in measured mechanical and physical properties, thus a surrogate modelling approach was adopted. Four different mathematical methods were employed for modelling and compared with one another. These are (i) non-linear multivariable regression, (ii) Levenberg-Marquardt neural network algorithm, (iii) thin plate splines, and (iv) a convex hull technique. The results clearly showed that the convex hull technique has less error compared to the other tested methods. This method was selected to optimize the carbon fiber modulus based on the given range of tensile strength. Using the convex hull technique along with an evolutionary search (Genetic Algorithm) method, it is shown that the modulus of carbon fiber can be optimized for any given range of tensile strength, providing an optimum set of control parameters are chosen during the process.

Facile synthesis of silicon nitride nanowires with flexible mechanical properties and with diameters controlled by flow rate

Ultralong Si3N4 nanowires (NWs) were successfully synthesized with size controlled in N2 gas by using an efficient method. The diameters of the Si3N4 NWs increased when the flow rate of N2 gas increased, with average diameters of 290 nm from flow rates of 100 ml/min, 343 nm from flow rates of 200 ml/min and 425 nm from flow rates of 400 ml/min. Young’s modulus was found to rely strongly on the diameters of the Si3N4 NWs, decreasing from approximately 526.0 GPa to 321.9 GPa; as the diameters increased from 360 nm to 960 nm. These findings provide a promising method for tailoring these mechanical properties of the NWs in a controlled manner over a wide range of Young’s modulus values. Vapour-liquid-solid (VLS) mechanisms were used to model the growth of Si3N4 NWs on the inner wall of an alumina crucible and on the surface of the powder mixture. Alumina may be an effective mediator of NW growth that plays an important role in controlling the concentrations of Si-containing reactants to support the growth of NWs on the inner wall of the alumina crucible. This approach offers a valuable means for preparing ultralong Si3N4 NWs doped with Al with unique properties.

Pyrolysis of Alternanthera philoxeroides (alligator weed): Effect of pyrolysis parameter on product yield and characterization of liquid product and bio char

In the present work, fast pyrolysis of Alternanthera philoxeroides was evaluated with a focus to study the chemical and physical characteristics of bio-oil produced and to determine its practicability as a transportation fuel. Pyrolysis of A.philoxeroides was conducted inside a semi batch quartz glass reactor to determine the effect of different operating conditions on the pyrolysis product yield. The thermal pyrolysis of A. philoxeroides were performed at a temperature range from 350 to 550 °C at a constant heating rate of 25 °C/min & under nitrogen atmosphere at a flow rate of 0.1 L/min, which yielded a total 40.10 wt.% of bio-oil at 450 °C. Later, some more sets of experiments were also performed to see the effect on pyrolysis product yield with change in operating conditions like varying heating rates (50 °C/min, 75 °C/min & 100 °C/min) and different flow rates of nitrogen (0.2, 0.3, 0.4 & 0.5 L/min). The yield of bio-oil during different heating rate (25, 50, 75 and 100 °C/min) was found to be more (43.15 wt.%) at a constant heating rate of 50 °C/min with 0.2 L/min N2 gas flow rate and at a fixed pyrolysis temperature of 450 °C. The High Heating Value (HHV) value of bio-oil (8.88 MJ/kg) was very less due to presence of oxygen in the biomass. However, the high heating value of bio-char (20.41 MJ/kg) was more, and has the potential to be used as a solid fuel. The thermal degradation of A. philoxeroides was studied in TGA under inert atmosphere. The characterization of bio-oil was done by elemental analyser (CHNS/O analyser), FT-IR, & GC/MS. The char was characterized by elemental analyser (CHNS/O analysis), SEM, BET and FT-IR techniques. The chemical characterization showed that the bio-oil could be used as a transportation fuel if upgraded or blended with other fuels. The bio-oil can also be used as feedstock for different chemicals. The bio-char obtained from A. philoxeroides can be used for adsorption purposes because of its high surface area.

Characterization of a Microwave-Induced Atmospheric-Pressure Ar–N2Plasma Pencil

A microwave-induced atmospheric-pressure plasma pencil was developed with an Ar–N2 gas mixture supplied to a coaxial transmission line. High-frequency simulation showed sufficient high electric field at the tip of the inner conductor, which resulted to automatic plasma ignition and a stable operation. The dependence of the characteristics of the plasma pencil from Ar and N2 gas flow rates was extensively studied. At moderate Ar gas flow rates, the plasma pencil can be operated at several tens of watts to achieve a near room-temperature and centimeter-long Ar–N2 plasma plume with OH and NO radicals as active species. Optical emission spectroscopy was also used to determine the vibrational and rotational temperatures of the plasma pencil. The vibrational temperature of N2 from the second positive system (2PS) can be obtained at moderate gas flow rates, since there was a good linear fitting with the Boltzmann distribution. At these gas flow rates, the vibrational and rotational temperatures of N2 from 2PS were found to be 0.42 and 0.29 eV, respectively.

Morphological, microstructural, and photoluminescence characterization of heterogeneous/homogeneous TeO2 nanostructures based on effect of different N2 gas flow rates

TeO2 nanowires with diameters ranging from a few tens to hundreds of nanometers and lengths of a few tens of micrometers were prepared by thermal evaporation of Te powder with a Co catalyst. Initially, bead-like γ-TeO2 nanoparticles on the surface of pre-formed thick TeO2 nanowires were heterogeneously formed. Subsequently, uniform thin TeO2 nanowires without the γ-TeO2 phase were homogeneously synthesized by changing only the inlet N2 gas flow rates and keeping other process parameters constant. The morphological and microstructural evolution of the two different nanomaterials was examined by X-ray diffraction, energy-dispersive X-ray spectrometry, and scanning and transmission electron microscopy. The optical properties of the nanomaterials were also investigated using photoluminescence spectroscopy. The emission peaks in the PL measurement without the supply of N2 gas showed a synergetic effect between (1) bead-like orthorhombic γ-TeO2 nanoparticles that show two specific emission bands at 388 nm and 590 nm; and (2) uniform tetragonal TeO2 nanowires that show a characteristic emission band at 440 nm. In contrast, the pure tetragonal TeO2 nanostructures synthesized under a N2 gas flow rate of 2 standard liters per minute flow rate revealed a red-shifted emission band at 450 nm compared to heterogeneous structures of the same composition. The origins of the growth and emission mechanisms in the different TeO2 structures are also discussed.

Consequences of N2 gas flow variation on properties of zirconium oxide-nitride films

Zirconium oxide-nitride films was prepared by RF reactive magnetron sputtering in presence of helium, oxygen and nitrogen gases. The N2 gas flow rate was varied for each consecutive run of sputtering at values of 66, 72, 78, 84, and 90 sccm respectively. Zirconium oxide-nitride films showed structural variation in evolution of various textures as detected by X-ray diffraction. It showed good transmission values above 50% for all samples. Wettability studies of zirconium oxide-nitride films was done by contact angle goniometer. All samples depict hydrophobic behaviour as all films have contact angle values above 90° and as nitrogen gas flow rate increases, the films roughness as well as contact angle increases. Tribological test is done on zirconium oxide-nitride films coated on aluminium, brass and mild steel pins, which give excellent wear resistance compared to uncoated pins.