Nitrogen Gas Pressure Research Articles

Relation between the nitrogen gas pressure and structure characteristics of WC–Ti(C, N)–Co graded cemented carbides

Abstract Nitrogen gas in the sintering atmosphere can adjust and optimize the graded microstructures of cemented carbides within the sintering cycle. In the present work, the effect of nitrogen gas pressure on the formation of graded zones is systematically studied in WC–Ti(C, N)–Co cemented carbides. The graded cemented carbides with the same composition have been sintered at 1450 °C for 2 h under different nitrogen gas pressure (from vacuum to 500 mbar). By introducing various nitrogen gas atmosphere, the evolution of characteristics (e.g. microstructure, phase distribution, composition distribution, and thickness of graded layer) at the near-surface area have been analyzed intuitively. Four different graded layers have been revealed with the changing of nitrogen gas pressure. The results describe the quantitative relationship between nitrogen gas pressure and the aforementioned characteristics in the different types of graded cemented carbides.

A novel method of preparing ultrafine ZnS particles from waste zinc–manganese batteries by evaporation–separation, sulfurization and inert gas condensation

This paper explores a novel method to produce ultrafine ZnS particles, a high value-added product, from waste zinc–manganese battery through evaporation–separation, sulfurization and inert gas condensation process. The heating temperature, condensation temperature, nitrogen gas pressure and condensation distance were identified as the main factors influencing the morphology of ZnS nanoparticles produced. Ultrafine ZnS particles can be prepared when the heating temperature is 873 K, the condensation temperature is 723 K and the nitrogen gas pressure is 1000–1500 Pa at the condensation distance of 30 cm. Size of ZnS particles was between 10 and 100 nm with average size of about 40 nm. Based on the scientific graphing and statistical analysis, the size of ZnS particles follows the log-normal distribution. This study not only provides the theoretical fundamentals for preparing ultrafine ZnS particles, but also provides a simple and efficient method to recycle the high value-added ZnS products from waste zinc–manganese batteries.

Modeling of bulk GaN crystal growth from gallium-sodium solution

Abstract A modeling approach for bulk GaN growth from gallium-sodium liquid solutions is suggested. The approach combines the thermodynamic theory of non-ideal solutions with kinetics of the chemical reactions proceeding at the free surface of the solution and at the GaN growth interface. The atomic nitrogen solubility in the solution is verified using available experimental data. The N-solubility and GaN growth rate are studied as a function of the sodium fraction in the solution and the nitrogen gas pressure. Growth of laboratory-scale (

High power diode laser nitriding of titanium in nitrogen gas filled simple acrylic box container: Microstructure, phase formation, hardness, dendrite and martensite solidification analyses

This work presents a detailed microstructure-property correlation of high power diode laser nitrided titanium based on its dendrite and martensite microstructures, structural phase and microhardness. For the laser nitrided titanium, cooling rate was estimated for the first time using empirical power law relationship by considering the martensite width and dendrite arm spacings and the results were validated by analytical thermal model. A processing window was formulated for laser gas nitriding of titanium by relating the experimental parameters such as laser processing parameters, nitrogen gas pressure and titanium nitride phases. The novelty of this work is demonstration of laser nitriding of titanium in laminar flow nitrogen gas environment using a simple acrylic container setup that avoids design and fabrication of a complex gas nozzle delivery system. In this setup, a thin transparent acrylic sheet was used as optical window instead of expensive quartz glass, to transmit high power diode laser beam at 980 nm wavelength to irradiate the substrate work piece in a closed container. This simple laser nitriding technique has created characteristic golden colored TiN surface with high surface hardness. Dendrite and martensite microstructures of the laser nitrided titanium were analyzed by optical and FESEM microscopy. EDAX analysis revealed the presence of nitrogen in laser nitrided titanium and X-ray diffraction confirmed the TiN phases. The microhardness of laser nitrided titanium is six times higher than its substrate.

Synthesis, Crystal Structure, and Luminescence Properties of a White-Light-Emitting Nitride Phosphor, Ca0.99Eu0.01AlSi4N7.

Colorless transparent single crystals of a new europium-doped calcium aluminum silicon nitride, Ca0.99Eu0.01AlSi4N7, were synthesized by heating a mixture of binary nitrides (Ca3N2, EuN, AlN, Si3N4, and Mg3N2) at 2150 °C under a nitrogen gas pressure of 0.85 MPa. The X-ray diffraction reflections from a single crystal were indexed with orthorhombic cell parameters a = 11.6819(3) Å, b = 21.0193(6) Å, and c = 4.91770(10) Å. The crystal structure was isomorphic to that of SrAlSi4N7:Eu (space group Pna21). One of the Ca/Eu sites was split into two sites of 4-fold and 8-fold nitrogen coordination. A white-light emission spectrum with two peaks at wavelengths of 498 and 614 nm was observed from the single crystals under 400 nm near-ultraviolet-light irradiation. The CIE1931 chromaticity of the white light was plotted at x = 0.378 and y = 0.429; the mean color-rendering index Ra was 81.

Experimental and theoretical investigation of the fluid behavior during polymeric fiber formation with and without pressure

The fabrication of polymeric micro/nanofibers is gaining attention due to their use in an array of applications including tissue engineering scaffolds, nanosensors, and fiber-reinforced composites. Despite their versatile nature, polymeric fibers are widely underutilized due to the lack of reliable, large-scale production techniques. Upon the discovery of centrifugal spinning and, recently, pressurized gyration techniques, new research directions have emerged. Here, we report a comprehensive study detailing the optimal conditions to significantly improve the morphology, homogeneity, and yield of fibers of varying diameters. A series of polymeric fibers was created using a 21 wt. % solution of polyethylene oxide in distilled water and the fluid behavior was monitored inside a transparent reservoir using a high-speed camera. Fabrication of the fibers took less than 1 s. Using centrifugal spinning, we studied the formation of the fibers at three different rotational speeds, and for pressurized gyration, one rotational speed was studied with three different nitrogen gas pressures. Using the pressurized gyration technique at a gas pressure of 0.3 MPa, there was significant improvement in the production yield of the fibers. We found a strong correlation between the variation of pressure and the rate of the solution leaving the reservoir with the improved morphology of the fibers. The use of reduced power techniques, like centrifugal spinning and pressured gyration, to yield high-quality nonwoven nanofibers and microfibers in large quantities is important due to their use in rapidly expanding markets.

A new catalyst (colemanite) for coal-to-liquid technology; a case study for the liquefaction of Elbistan Lignite: the effect of colemanite and Fe2O3 catalyst blending

In this study, the colemanite (a natural calcium borate mineral, NCBM) and Fe2O3 used as a catalyst on the liquefaction of Elbistan Lignite (EL, which has the most reserves in the east of Turkey). The liquefaction experiments were carried out at the reaction temperature of 400 °C, the reaction time of 90 min, the solvent/solid ratio of 3/1, stirring speed of 400 rpm, and initial nitrogen gas pressure of 20 bar. Fe2O3 and colemanite were together prepared as a new catalyst. Research has been made the recent observation that the highest liquefaction product yields, especially from a series of valuable fractions, obtained, with the highest mineral content of lignite. According to that model colemanite mixed with Fe2O3 to decide if the mineral content effect on total conversion if mineral substances added separately from coal. Fe2O3 selected as the most suitable catalyst type. To understand how to affect colemanite (as an economical catalyst source and also has high reserves in Turkey) as a catalyst on the liquefaction of EL with waste paper. The experiment conditions fixed and so compared due to the total conversion values. Unlike previous studies, this study was 67.1% of the total fluid conversion without catalyst, but this value increased to 77.6% when 15% NCBM catalyst was used. The total conversion was up to 83.8% with the catalyst concentration of 3% Fe2O3. On the other hand, when only 3% of Fe2O3 was used, the total conversion was only 75%. As a result, the mixture of NCBM and Fe2O3 increased the liquefaction efficiency by 15% by the synergistic effect.

Effect of Sodium Boron Hydride (NaBH4) on Waste Polyethylene Terephthalate Pyrolysis

Polyethylene terephthalate, which is used in many applications today, is very important in terms of nature and source in order to ensure recycling by appropriate methods after use. Because polyethylene terephthalate is a durable and long-lasting thermoplastic which is resistant to many environmental influences. Recovering residual plastics has become mandatory. In this study, the conversion of waste plastic to a new liquid fuel by polyethylene terephthalate (PET) pyrolysis method was investigated. Sodium boron hydride (NaBH4) was used as both catalyst and hydrogen donor in the pyrolysis experiments. Pyrolysis experiments were carried out in a batch reactor under catalytic and non-catalytic conditions, reaction time of 15-90 minutes, reaction temperature of 325-425 °C, solid/solvent ratio of 1/4 and initial nitrogen gas pressure of 20 bar. According to the results obtained, the most suitable reaction temperature was found to be 375-425 °C and the reaction time was 30 minutes. At the reaction times of 30 minutes, the maximum total conversion in non-catalytic conditions of waste polyethylene terephthalate samples was 53.1% at 400 °C reaction temperature and the highest oil + gas yield was 43.7% at 425 °C reaction temperature. In the pyrolysis of polyethylene terephthalate samples in the presence of sodium boron hydride, the maximum total conversion was 55.3% at 400 °C reaction temperature and the highest oil + gas yield was 44.6% at 425 °C reaction temperature. As a result, it can be argued that sodium boron hydride used in pyrolysis experiments of waste polyethylene terephthalate acts as both catalytic and hydrogen donor.

A Practical Synthesis of Ammonia from Nitrogen Gas, Samarium Diiodide and Water Catalyzed by a Molybdenum–PCP Pincer Complex

A practical method for ammonia synthesis is described. The reaction of atmospheric pressure of nitrogen gas with samarium diiodide as a reducing reagent and water as a proton source in the presence of a catalytic amount of a molybdenum trichloride complex bearing a PCP [1,3-bis(di-tert-butylphosphinomethyl)benzimidazol-2-ylidene]-type pincer ligand occurs under ambient conditions to afford ammonium sulfate after treatment with sulfuric acid.

Pure 2D-Nanopowders of Si2N2O by SHS under Nitrogen Pressure

Fine powders of pure Si2N2O were SHS-produced under pressure of nitrogen gas from mixtures doped with FeCl3 · 6H2O, and the influence of process conditions was explored by XRD and SEM/EDS. Pure 2D-nanopowders of Si2N2O were obtained in the presence of 15 × 10–3 M FeCl3 · 6H2O in green 3Si + SiO2 mixture at P(N2) = 5 MPa.

Dense AlON Ceramic by SHS under Nitrogen Gas Pressure

Dense AlON Ceramic by SHS under Nitrogen Gas Pressure

Influence of pressure of nitrogen gas on structure and thermoelectric properties of acid-treated PEDOT:PSS films

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most commonly investigated conductive polymer due to its unique thermoelectric properties. Several post treatments using various acids have been reported to improve the thermoelectric properties of PEDOT:PSS. In most articles, however, only the role of acids on the structure and thermoelectric properties of PEDOT:PSS were reported. In this article, we report the major role of the pressure of nitrogen gas (N2) on the structure and thermoelectric properties of PEDOT:PSS after treatment with various acids at optimized temperatures. After treatment with acids followed by N2 gas-passing, electrical conductivity enhances significantly. Therefore, N2 gas-passing after acid treatments results in higher thermoelectric properties than other traditional acid treatment methods. The enhancement in electrical conductivity is attributed to the removal of insulating PSS and the conformational change of the PEDOT chain. Furthermore, the pressure of N2 is responsible for the additional conformation of PEDOT chain, favoring the linear orientation of the PEDOT structure and resulting in an improvement of the electrical conductivity.

Influence of nitrogen partial pressure on optical properties of magnetron sputtered Al-Si-N thin films

Al-Si-N thin films were deposited on glass substrates at varying nitrogen partial pressure through magnetron sputtering. The effect of partial pressure of nitrogen gas in the gaseous mixture (argon and nitrogen) on the optical properties such as absorption coefficient, band gap energy, refractive index, extinction coefficient, dielectric constant of the film was investigated and correlation with structure was carried out. Nitrogen partial pressure has a considerable effect on the film microstructure and consequently on their optical properties. The transformation of the film from opaque to transparent is dependent on the partial pressure of nitrogen. The crystallite size decreases from 27 to 19 nm with the rise in partial pressure of nitrogen from 3 × 10−1 Pa to 6 × 10−1 Pa but again increases as the pressure reaches 7.5 × 10−1 Pa. Refractive index of Al-Si-N coatings shows normal dispersive behaviour. The transmittance, band gap energy, optical conductivity and dielectric constant of the films were also studied as a function of nitrogen partial pressure.

Effects of SnO<sub>2</sub>-SiO<sub>2</sub>-MgO-Bi<sub>2</sub>O<sub>3</sub>-Y<sub>2</sub>O<sub>3</sub> Additions on Liquid Phase Sintering Silicon Nitride

Si3N4 ceramics were sintered at relatively low temperature of 1400-1650 °C with additives from the SnO2-SiO2-MgO-Bi2O3-Y2O3 system. The degree of densification, α-β transformation, mass loss and microstructure were measured as a function of additives composition, sintering temperature, and nitrogen gas pressure. Specimen prepared from 3 mass% SnO2, 3 mass% SiO2, 3 mass% MgO, 6 mass% Bi2O3, and 5 mass% Y2O3 as the sintering additive could be sintered to almost full density at relatively low temperature as 1550 °C for 2 h under ambient pressure of nitrogen atmosphere. The α-β transformation was not completed at this condition. The mass loss was relatively high due to the evaporation of SiO2, MgO and Bi2O3. However, the resulted dense materials have high bending strength.

The possibility of using glycerin as the dielectric in pulse forming lines

In this paper, an approximately scaled coaxial test device is designed and constructed to study the breakdown characteristics of glycerin dielectric in pulse forming lines (PFLs). In the test device, factors affecting the breakdown strength of the glycerin are investigated, including polarity of high voltage, applied gas pressure, temperature, magnetic field, and the electrode surface characteristics. The time and temperature characteristics of the glycerin resistivity are investigated as well. The results show that glycerin has extremely high and stable resistivity, and its breakdown field strength is independent of the polarity of the applied electric field. As the nitrogen gas pressure is applied up to 2 MPa on the glycerin, the breakdown field strength is increased by 40%. When the temperature is changed from 10 to 55 °C, the breakdown field strength reduces from 310 to 165 kV/cm. It is also found that there is no effect on the breakdown field strength of glycerin on magnetic field under 1T. Moreover, the filling process of the glycerin PFL is investigated for exhausting the gas as far as possible. The glycerin PFL has been employed in pulsed power generators, and some breakdown problems in the practical application have been solved.

Effects of Ti Target Poisoning to Titanium Nitride Coating Fabricated by a Physical Vapor Deposition Technique

The DC magnetron sputtering is often used for fabricating thin hard coatings for a wide range of industrial applications. The technique allows using DC power for deposition low or non-conductive films from metal target without using expensive RF power for insulation target. However, the performance of DC reactive sputtering is affected significantly by a phenomenon namely target poisoning. When the target poisoning occurs, coating is formed not only on substrate surface but also on target surface, which results in the reduction of deposition rate and coating properties. This paper presents a study on poisoning of Ti target during TiN coating deposition in the Ar + N2atmosphere. Results showed that the target poisoning state is impressed dramatically by partial pressure and flow rate of nitrogen gas. In poisoning mode, the deposition rate was reduced significantly compared to that in the metal mode. In addition, the formed TiN coating exhibited a non-stoichiometric and low adhesion to the substrate.

Influence of Density Separation of Selected South African Coal Fines on the Products Obtained during Liquefaction Using Tetralin as a Solvent

The liquefaction of two South African discarded coal fines and their density separated (float) fractions were carried out under moderate conditions in a laboratory autoclave. Liquefaction tests were carried out on both discarded coal fines and their float fraction samples at temperatures ranging between 380 and 420 °C using tetralin as a solvent and an initial nitrogen gas pressure of 3 MPa. Oil samples produced from the liquefaction of coal fines discards and their float fractions were further characterized using gas chromatography–mass spectrometry (GC–MS) and nuclear magnetic resonance. The liquefaction test results showed that carbon conversions and oil yields were higher for the float fractions when compared to the discarded coal fines samples. The oil yields ranged from 24.4–37.2% (dry ash free (daf)) for the oil produced from the float fractions of the coal fines and 19.1–29.3% for oils produced from the coal fines (daf). The oil and the gas yields of the float fraction samples were higher when com...

Development and Validation of an Analytical Method Based on HPLC-ELSD for the Simultaneous Determination of Rosmarinic Acid, Carnosol, Carnosic Acid, Oleanolic Acid and Ursolic Acid in Rosemary.

The safety, efficacy and stability of natural antioxidants have been the focus of research in the food industry, with the aim of rapidly analyzing and controlling the quality of rosemary and its extracts, a novel analytical method involving high-performance liquid chromatography with evaporative light scattering detection (HPLC-ELSD) was developed for the simultaneous determination of rosmarinic acid, carnosol, carnosic acid, oleanolic acid and ursolic acid in rosemary. Chromatographic separation was conducted with gradient elution mode by using a Zorbax SB-C18 column (4.6 mm × 250 mm, 5 μm) with mobile phases of methanol and 0.6% acetic acid. The drift tube temperature of ELSD was 70 °C, and the pressure of nebulizer nitrogen gas was 40 Psi. The method developed has high sensitivity (with limits of detection from 1.3 to 8.6 μg/mL), acceptable linearity over the tested concentrations (with correlation coefficients from 0.991 to 0.999), good repeatability (with intra- and inter-day CV less than 3.1% for all analytes) and satisfactory accuracy (with recovery between 95.5% and 100.8%). The method has been demonstrated as a powerful tool for the functional ingredients analysis and quality control of rosemary and its extracts in a cost- and time-effective manner.

Aluminothermic Reduction Process Under Nitrogen Gas Pressure for Preparing High Nitrogen Austenitic Steels

The aluminothermic reduction casting process under nitrogen gas pressure to make austenitic Cr-Mn-N (Ni-free) and Cr-N (Ni/Mn-free) high nitrogen stainless steels was investigated. Thermodynamic simulation of the redox reaction depending on process parameters was performed. As a result, the optimal ratio of aluminum to oxygen in the initial powder mixture to obtain the highest yield of metal product with minimal aluminum nitride contamination was predicted to be slightly greater than the stoichiometric ratio of 1.125. Microstructures of aluminothermic 26Cr1N and 23Cr9Mn1N steels, prepared taking into account the results of thermodynamic simulation, were investigated by X-ray diffraction, metallography, and transmission electron microscopy. The as-cast microstructure was a pseudo-pearlite (layered ferrite-nitride mixture) in 26Cr1N steel and a ferrite-austenite with signs of discontinuous austenite decomposition in 23Cr9Mn1N steel. After hot forging and subsequent water quenching from 1200 °C, the microstructure was fully austenitic in both steels. Tensile tests of quenched 23Cr9Mn1N steel showed a combination of high strength (ultimate strength of 1324 MPa) and ductility (elongation of 27 pct). The results illustrate that the aluminothermic casting process for producing high nitrogen steel is competitive with the commonly used methods, such as pressure electroslag remelting, both in terms of cost and mechanical properties of manufactured steel.

Nitrogen Soft X-Ray Yield Optimization from UNU/ICTP PFF Plasma Focus Device

The aim of this research studying soft x-ray emission from United Nations University/International Centre for Theoretical Physics Plasma Fusion Facility (UNU/ICTP PFF) plasma focus device with nitrogen gas pressure changes and find the maximum value of soft x-ray yield by using the standard parameters of device and do optimization to obtain the combination of pressure and electrodes dimensions that gives the maximum value of soft x-ray yield. Many numerical experiments were carried out using Lee code and obtained the maximum value of soft x-ray yield 0.193J at pressure 1.9 Torr by using the standard parameters of device. We optimized the device and found the optimum combination of pressure and electrode dimensions (P0 = 0.5 Torr, z0 = 9 cm, a = 3.19 cm, b = 3.2 cm,) that gives the maximum value of soft x-ray yield Ysxr = 2.7 J without changing the energy of the device.