Papers by Keyword: Nitrogen Content

Abstract: Nitrocellulose (NC) has attracted great interest among researchers due to its extensive range of applications. Generally, NC with high nitrogen content is prepared from cotton, which is challenging to cultivate in Indonesia. Therefore, this study explored the potential of ramie and kenaf, materials that are known to have high-cellulose content and abundance in Indonesia, especially for NC production. In this research, cotton, ramie, and kenaf fibers were treated by using 17.5% (w/w) NaOH to obtain α-cellulose. The nitration process used a mixture of sulfuric acid (H₂SO₄) and nitric acid (HNO₃) with a ratio of 3:1 (v/v). The effect of cellulose-to-reagent on the nitrogen content in different weight ratios (1:50, 1:100, and 1:150) was investigated. The nitrogen content in NC was determined using the acetone insolubility test according to MIL-DTL-244C standards, FTIR spectroscopy, and elemental analyzer. The FTIR spectrum showed the presence of NO₂ groups in NC which confirmed a successful nitration process. In addition, the highest nitrogen content obtained from cotton, ramie, and kenaf fibers was 10.3%, 10.93% and 11.23%, respectively. Based on the research findings, ramie and kenaf fibers show great potential as raw materials for producing NC with higher nitrogen content compared to cotton.

Abstract: A comprehensive and systematic analysis of a large amount of experimental data was carried out, and, taking into account the available literature information, the mechanism of the process of grinding fibers of cellulose nitrate materials was revealed. The results obtained are of both scientific and practical interest, since the technological and rheological properties of the target products depend on the quality and nature of the grinding of fibrous materials. The combination of modern methods for studying the degree of dispersion, fractional composition, as well as the structure of fibrous materials during the grinding process, knowledge of the nature of the processing of fibers in various grinding units allow intensifying the grinding technology based on the created original technological scheme of the grinding process. The simulation of the grinding process of fibrous cellulose nitrate materials on the basis of experimental data, which allows predicting the properties of the target product and the creation of waste-free, resource-saving technology for producing materials with improved and adjustable characteristics, is carried out. The adequacy of the created model is shown.

Abstract: The melting of a 201 austenitic stainless steel was conducted in mushy zone for 0, 5, 10, 15 min under nitrogen atmosphere. The effect of the holding time on nitrogen content was investigated. The results showed that with the increase of holding time, the nitrogen content was significantly increased. It was found that the holding in mushy zone could avoid ferrite region during solidification, and facilitate the diffusion of nitrogen from liquid into austenite. Thermodynamic analysis demonstrates that the difference between the chemical potential of nitrogen in liquid and austenite provides the driving force for the nitrogen diffusion. It is concluded that melt holding in mushy zone is an effective way for increasing the nitrogen content in stainless steel, and thus provides a new method for the production of high nitrogen stainless steel.

Abstract: The effect of carbon and nitrogen contents on microstructure and the mechanism of precipitation of 18Cr18Mn steels at as-cast and aging treatment state were investigated by thermodynamics calculation, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results show that the increase in carbon and nitrogen contents promotes the precipitation of carbides and nitrides, respectively, inhibiting σ phase precipitation during solidification process. The rod-like σ phases present in 18Cr18Mn0.44N as-cast steel with 0.025%C. The coarse lamellar structure Cr₂₃C₆ phases with a space width of 0.34μm exist in 18Cr18Mn0.44N as-cast steel with 0.16%C. However, Cr₂₃C₆ and σ phase disappear in the interior of the grains and a small amount of nitrides exist only in grain boundaries of 18Cr18Mn0.72N0.020C as-cast steel. The precipitation of Cr₂₃C₆ and σ phases are greatly inhibited in high nitrogen austenitic stainless steels at 800°C aging treatment. Additionally, Cr₂N, the main precipitation phase, nucleates at austenitic grain boundary and grows towards inner grains with a lamellar morphology. Moreover, the quantity of Cr₂N increases and incubation time of it decreases as nitrogen or carbon content increasing.

Abstract: Nanohardness of chromium nitrid coatings deposited with DC magnetron from Cr target in the reactive atmosphere with various percentual contribution of nitrogen in Ar flow was investigated to determine the influence of nitrogen content and negative bias. The nanohardness of pure Cr coating was between 11 14 GPa and the addition of 50 % of nitrogen into Ar flow resulted in the increase of coating hardness up to ~ 22 GPa. The highest hardness of the studied CrN coatings of ~ 28 GPa was achieved at 700 W power, working pressure of 0.5 Pa with 50 % of nitrogen in Ar flow and negative bias of-30 V . The increase was ascribed to the formation of near-stoichiometric CrN compounds.

Abstract: In this study, nitrogen content greater than 0.9% of 18Cr18MnN austenitic stainless steel were prepared by high pressure reaction kettle. The relationships between nitrogen content and temperature, pressure were studied. The results show the nitrogen content in steel increases with increasing melting pressure, at air pressure 1.0MPa<P<1.4MPa, the increase of nitrogen content in steel is evident particularly. In the 1813k<T<1913k temperature range, the nitrogen content in steel decreases with the increasing temperature, there are differences in variation in the temperature range. When temperature is up to 1813K, nitrogen content can be as high as 1.075%. The best thermodynamic condition of melting a nitrogen content of 0.9% 18Mn18Cr austenitic stainless steel is: pressure and temperature are 1.32MPa, 1873k, respectively.

Abstract: Boron nitride(BN) fibres were synthesized by modified technique of Economy’s method. The products were characterized by X-ray diffraction (XRD), fourier transform infrared (FT-IR) absorption spectroscopy, field-emission scanning electron microscopy (FE-SEM), X-ray energy dispersive spectrum (EDS) and X-ray photoelectron spectroscopy (XPS). The results showed that BN fibers were mainly hexagonal boron nitride (h-BN) with diameters of 5-8 μm and the major compositions of BN fibers are B and N with a very small amount of O and C. At last, the chemical composition of samples were determined by the chemical analysis test method like GB/T 16555-2008 and GJB 507-1998.

Abstract: This study is concerning the influences of nitrogen content and aging precipitates on pitting corrosion resistance properties of high nitrogen austenitic stainless steel (HNS) through potentiodynamic polarization method. The microstructure of aged HNS is analized by scanning electron microscopy (SEM). The main results obtained are as follow: the formation of intergranular, cellular Cr₂N and intermetallic χ precipitates makes the depletion of Cr and Mo in the matrix and deteriorates the resistance to pitting corrosion in aged specimens. Cr₂N starts to precipitate in the form of lamellar structure to cellular precipitates, the pitting corrosion drops to about 0 V_SCE. HNSs perform the same tendency that the pitting corrosion potential firstly decreases then increases and reduce to the minimum value at nose temperature. All the pitting corrosion potential of HNS-B aged for 2h at different temperature presents more than that of HNS-A. The pitting corrosion resistance is mainly controlled by nitrogen content before great precipitates of cellular Cr₂N and intermetallic χ phase rich in Cr and Mo. It is also mainly controlled by the content and the type of precipitates after great precipitates of cellular Cr₂N.

Abstract: This paper investigated the relationship of the nuclear quadrupole resonance (NQR) signal amplitudes with nitrogen contents and frequencies of explosive simulants based on the NQR explosive detection principle. The NQR signals of urea, urotropine and sodium nitrite were detected by experiment at room temperature, and the signal spectra of the nitrogenous compounds with different weights were obtained. The results indicate that the NQR signal amplitudes of the same mimic are increasing linearly with the increase of weights under the same experimental conditions, meanwhile, the higher the frequency, the greater the signal amplitude. The NQR signal amplitudes of different mimics do not rely on the nitrogen contents, but depend on the other internal factors such as relaxation times, NQR frequencies and so on. The experimental data are consistent with the theoretical predictions. The results will be of value to the detection of NQR signals in explosives and the research on how to improve the signal-to-noise ratio (SNR).

Abstract: The behavior of nitrogen into the dissimilar joining metal between AISI 304 and AISI 316L Austenitic stainless steel during gas tungsten are welding process was investigated. Studied by using an arc nitrogen atmosphere – controlling in chamber. The relations between nitrogen content of the dissimilar weld metal and the welding parameters, such as the welding current, welding speed, welding arc length and penetration area of weld metals were also evaluated. The results show that the nitrogen content of the weld metals decreased with an increasing welding current, and increasing penetration areas of weld metal, but scarcely depends on the welding arc length. The nitrogen content of the weld metals increased with the welding speed, but decreased penetration areas of weld metals. The role of nitrogen content on the dissimilar weld metals stainless steel is further confirmed by the experimental microstructure, mechanical and corrosion behaviour of the weld metal.