Effect Of Nitrogen Content Research Articles

The Effect of Nitrogen Content on Archaeal Diversity in an Arctic Lake Region.

The function of Arctic soil ecosystems is crucially important for the global climate, and nitrogen (N) is the major limiting nutrient in these environments. This study assessed the effects of changes in nitrogen content on archaeal community diversity and composition in the Arctic lake area (London Island, Svalbard). A total of 16S rRNA genes were sequenced to investigate archaeal community composition. First, the soil samples and sediment samples were significantly different for the geochemical properties and archaeal community composition. Thaumarchaeota was an abundant phylum in the nine soil samples. Moreover, Euryarchaeota, Woesearchaeota, and Bathyarchaeota were significantly abundant phyla in the three sediment samples. Second, it was found that the surface runoff caused by the thawing of frozen soil and snow changed the geochemical properties of soils. Then, changes in geochemical properties affected the archaeal community composition in the soils. Moreover, a distance-based redundancy analysis revealed that NH4+–N (p < 0.05) and water content were the most significant factors that correlated with the archaeal community composition. Our study suggests that nitrogen content plays an important role in soil archaeal communities. Moreover, archaea play an important role in the carbon and nitrogen cycle in the Arctic lake area.

Effect of Ammonia Activation and Chemical Vapor Deposition on the Physicochemical Structure of Activated Carbons for CO2 Adsorption

Focusing on the bottlenecks of traditional physical activation method for the preparation of activated carbons (ACs), we established a simple and scalable method to control the physicochemical structure of ACs and study their CO2 adsorption performance. The preparation is achieved by ammonia activation at different volume fractions of ammonia in the mixture (10%, 25%, 50%, 75%, and 100%) to introduce the nitrogen-containing functional groups and form the original pores and subsequent chemical vapor deposition (CVD) at different deposition times (30, 60, 90, and 120 min) to further adjust the pore structure. The nitrogen content of ACs-0.1/0.25/0.5/0.75/1 increases gradually from 2.11% to 8.84% with the increase of ammonia ratio in the mixture from 10% to 75% and then decreases to 3.02% in the process of pure ammonia activation (100%), during which the relative content of pyridinium nitrogen (N-6), pyrrolidine (N-5), and graphite nitrogen (N-Q) increase sequentially but nitrogen oxygen structure (N-O) increase continuously. In addition, ACs-0.5 and ACs-0.75, with a relatively high nitrogen content (6.37% and 8.84%) and SBET value (1048.65 m2/g and 814.36 m2/g), are selected as typical samples for subsequent CVD. In the stage of CVD, ACs-0.5-60 and ACs-0.75-90, with high SBET (1897.25 and 1971.57 m2/g) value and an appropriate pore-size distribution between 0.5 and 0.8 nm, can be obtained with the extension of deposition time from 60 to 90 min. The results of CO2 adsorption test indicate that an adsorption capacity of ACs-0.75-90, at 800 mmHg, is the largest (6.87 mmol/g) out of all the tested samples. In addition, the comparison of CO2 adsorption performance of tested samples with different nitrogen content and pore structure indicates that the effect of nitrogen content seems to be more pronounced in this work.

Effect of nitrogen content on microstructure, mechanical properties, and corrosion behaviour of coarse-grained heat-affected zone of nitrogen-containing austenitic stainless steel

AbstractThe microstructures and properties of austenitic stainless steel with varying nitrogen content after welding thermal simulation were investigated. The results indicate that the nitrogen fraction has a considerable influence on the phase composition and properties. Low nitrogen fraction leads to formation of δ-ferrite. After a welding thermal cycle, the number of annealing twins of high nitrogen-containing steel decreases, M23C6 precipitates, and fine M23C6 are observed. For low nitrogen-containing steel, large-size M23C6 and elongated δ-ferrite are formed, which deteriorate the ductility. Meanwhile, equilibrium phase calculations also reveal the inhibiting effect of nitrogen on M23C6 and δ-ferrite. Furthermore, susceptibility to intergranular attack by 10 % oxalic acid solution was detected, and the synergistic effect of coherent twin boundaries, M23C6, and δ-ferrite leads to low resistance to corrosion for low nitrogen-containing steel.

Fabrication of Porous Carbon with Controllable Nitrogen Doping as Anode for High‐Performance Potassium‐Ion Batteries

AbstractPotassium‐ion batteries (PIBs) are a potential alternative for lithium‐ion batteries (LIBs) due to the abundant reserves of potassium and the low redox potential of K+/K. Nonetheless, the practical application of PIBs is hampered by the fact that K+ has a large ion radium and cannot smoothly and reversibly insert/extract into the existing electrode materials. Herein, a series of nitrogen‐doped porous carbon materials with varied N content are synthesized and the effect of nitrogen content on the performance of PIBs is investigated. It is demonstrated that the N content is not in direct proportion to the K‐storage capacity of porous carbon considering the irregular change of specific surface area. Porous carbon with 12.44 at% N content (NPC‐2) exhibits the best performance among the synthesized samples on account of its large specific surface area associated with the superior porous structure as well as abundant defects. It delivers a high reversible capacity of 385 mAh g−1 at 0.05 A g−1, remarkable rate performance of 218 mAh g−1at 2 A g−1, and long‐term cycling stability maintaining 242 mAh g−1 after 800 cycles at 0.5 A g−1. The quantitative kinetics analysis verify that the K‐storage mechanism is mainly dominated by surface‐driven capacitive controlled process, which explains the superior rate capability. The theoretical simulation of different types of nitrogen adsorption and density of states (DOS) prove that pyridinic‐N and pyrrolic‐N exhibit higher affinity to K atoms and thus N‐doping is beneficial to the adsorption of K+ on the surface of electrode. This work provides a basic reference for the subsequent development of carbon anode materials for potassium‐ion batteries.

Urea as a single denaturing agent in deproteinisation of natural rubber latex

This paper describes the utilisation of urea as a single chemical agent to obtain deproteinised high ammoniated natural rubber latex (HA-NRL). The role of urea in HA-NRL deproteinisation was further investigated by employing two different concentrations of urea solution which are low (0.01–0.05%) and high (1.0–5.0%) concentrations. The study assessed the potential usage of urea as a single denaturing agent in the presence of neither stabilising agent nor additives during the deproteinisation process. The effect of different urea concentrations on properties of deproteinised NRL was further scrutinised by using sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE), nitrogen content analysis, extractable protein (EP) content, Zeta potential, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and physical strength. The presence of residual urea is pertinent as the concentration of urea increases while contributing to the increase of total nitrogen content in the resultant film. Leaching the film with hot water is sufficient to remove the residual urea as supported by an ATR-FTIR analysis. Initial exploratory data analysis of low and high urea concentrations on the effect of nitrogen content, EP, surface charge properties of latex and green strength of the deproteinised NRL were evaluated and their relation to each factor was further discussed. Based on the initial findings, urea was observed to be less effective as a single denaturant. Nonetheless, the properties of the deproteinised HA-NRL treated with urea were revealed to be markedly influenced by the urea concentration.

Effect of Nitrogen Content in Tunneling Dielectric on Cell Properties of 3-D NAND Flash Cells

The effect of band engineering by controlling nitrogen content in the tunneling dielectric of the 3-D NAND flash cells is investigated by comparing various cell properties of the two devices. These measured devices have the same device dimensions and different nitrogen contents. The device with higher nitrogen content shows larger trap density profile and improved erase characteristics. After the same P/E cycling stress, the device with higher nitrogen content shows larger increase of trap density and more significant degradation in its erase characteristics. The electrons stored in the device with higher nitrogen content more easily escape through the trap-assisted tunneling mechanism due to higher trap density, resulting in worse retention characteristics at room temperature.

Effects of SCF content, injection speed, and CF content on the morphology and tensile properties of microcellular injection‐molded CF/PP composites

Carbon fiber/polypropylene composite foams were prepared by microcellular injection molding using nitrogen as a foaming agent. The effects of nitrogen content, injection speed, and CF content on the morphology and tensile properties of the composite foams were investigated. A three‐layer structure was formed in the microcellular foams: the skin layer was solid, the intermediate layer contained stretched cells parallel to the flow direction, and the core layer consisted of spherical cells. The average cell diameter of the machine direction decreased from 41 to 34 μm as the nitrogen content increased from 0.5 to 1 wt%, increased from 34 to 43 μm as the injection speed increased from 50 to 150 mm/s, and decreased from 34 to 25 μm as the CF content increased from 10 to 30 wt%. Thus, the microcellular structure was improved by increasing the nitrogen and CF content and by decreasing the injection speed. Furthermore, when the CF content increased from 10 to 30 wt%, the Young's modulus of the solids and foams increased by 78% and 113%, respectively. Thus, the Young's modulus of the foams improved by 35% due to the improvement in the cellular structure. POLYM. ENG. SCI., 59:1371–1380 2019. © 2019 Society of Plastics Engineers

Heterogeneous Fenton-Like Degradation of p-Nitrophenol over Tailored Carbon-Based Materials

Activated carbon (AC), carbon xerogel (XG), and carbon nanotubes (CNT), with and without N-functionalities, were prepared. Catalysts were obtained after impregnation of these materials with 2 wt.% of iron. The materials were characterized in terms of N2 adsorption at −196 °C, elemental analysis (EA), and the pH at the point of zero charge (pHPZC). The p-nitrophenol (PNP) degradation and mineralization (assessed in terms of total organic carbon–TOC–removal) were evaluated during adsorption, catalytic wet peroxidation (CWPO), and Fenton process. The textural and chemical properties of the carbon-based materials play an important role in such processes, as it was found that the support with the highest surface area -AC- presents the best performance in adsorption, whereas the materials with the highest mesopore surface area -XG or Fe/XG- lead to best removals by oxidation processes (for XG it was achieved 39.7 and 35.0% and for Fe/XG 45.4 and 41.7% for PNP and TOC, respectively). The presence of N-functionalities increases such removals. The materials were reused in consecutive cycles: the carbon-based materials were deactivated by hydrogen peroxide, while the catalysts showed high stability and no Fe leaching. For the support with superior performances -XG-, the effect of nitrogen content was also evaluated. The removals increase with the increase of the nitrogen content, the maximum removals (81% and 65% for PNP and TOC, respectively) being reached when iron supported on a carbon xerogel doped with melamine was used as catalyst.

A nonradical reaction-dominated phenol degradation with peroxydisulfate catalyzed by nitrogen-doped graphene

Nitrogen doping is a common approach for functionalization of graphene to generate active sites for catalytic reactions. However, the effect of nitrogen content and species within nitrogen-doped graphene (NG) on catalytic phenol oxidation remains largely unaddressed, especially for the peroxidisulfate (PDS) system. In this work, graphene (G), NH3•H2O-reduced graphene (NG-NH3), and N2H4-reduced graphene (NG-N2H4) with different nitrogen contents were synthesized, and their catalytic abilities in inducing PDS was evaluated. The degradation results indicated that nitrogen doping improved the catalytic ability of G and NG-NH3 shows a higher catalytic ability than NG-N2H4, even though they have similar nitrogen contents. Based on the XPS spectra, among all the doped nitrogen species, the graphitic N made the greatest contribution to the catalytic activity. The scavenger and electron paramagnetic resonance results imply a major contribution of a nonradical mechanism in the NG-PDS-phenol reaction system. Finally, the hydroquinone and p-hydroxybenzoic acid were identified as two intermediate products during the degradation. The decrease in total organic carbon concentration (TOC) after reaction confirmed that phenol was mineralized partially in CO2. These findings will guide the applications of NG as a catalyst and enrich our understanding of the PDS-phenol reaction system.

Influence of the nitrogen content in the gas mixture on elemental composition of Zr1−xAlxN thin coating, its microhardness and friction coefficient

Abstract The effect of nitrogen content in a gas mixture during pulsed magnetron sputtering on the elemental composition, microhardness, and friction coefficient of Zr1−xAlxN thin coating was studied. The N content in Zr1−xAlxN thin coatings doubles with a double decrease in Al content in the case of an increase in the nitrogen content in the gas mixture over 10% was found. The Zr content in Zr1−xAlxN thin coatings increases slightly, when the nitrogen content in the gas mixture increases to 40%. The nitrogen content in the gas mixture to a greater extent affects the N content in Zr1−xAlxN thin coating. When the nitrogen content in the gas mixture exceeds 15%, Zr1−xAlxN thin coating is formed with a close to stoichiometric elemental composition, maximum micro-hardness, and minimum friction coefficient.

Inert Gas Atomization of High‐Nitrogen TRIP‐Steels

High nitrogen steels with transformation induced plasticity (TRIP) effect have been recently developed within the framework of the project CRC799. These steels are utilized in a form of powder for the needs of this project. Therefore, the current study focuses on the powder production of high nitrogen steels via inert gas atomization process. Specifically, the role of nitrogen content in determination of the basic powder properties and its behavior on the atomization process are investigated. Additionally, the effects of several other process parameters, such as temperature of the melt and gas to metal ratio are discussed. Thereby, the effect of nitrogen content on the median particle size is not confirmed. Meanwhile, an increase in the spraying temperature and a rise in gas to metal ratio lead to a slight decrease in the median particle size. Nitrogen content in the powder is technologically controlled by the atmosphere above the melt before the spraying process. At last, nitrogen shows a significant impact on the phase composition of powder, by stabilizing the austenite phase. The results thus obtained are of high interest for the future application of the designed steels in the powder form.

Effect of nitrogen content on physical properties of glass fiber reinforced polyamide 6 prepared by microcellular injection molding

The aim of the study was to determine the effect of the amount of nitrogen dosed in supercritical state to polymer melt on structure and physical properties of large-scale molded pieces from polyamide PA 6 GF30, obtained in the process of microcellular injection molding with gas dosage using MuCell® method. Apart from the reduction of the density at a level of about 15 % for samples with the highest nitrogen content, the increase of the impact resistance of samples PA 6 GF30 was observed. The other investigated mechanical properties were maintained at a good level.

Theoretical and experimental study on the effect of nitrogen content on the thermal characteristics of nitrocellulose under low heating rates

The thermal behavior of nitrocellulose (NC) with different nitrogen contents has been widely investigated in previous works. However, most of the experiments were carried out under high heating rates, a situation in which it is difficult to capture minor changes during the thermal decomposition process. In the present study, the thermal characteristics of NC with different nitrogen contents were theoretically and experimentally investigated using a CALVET heat flux calorimeter C80 at heating rates from 0.2 to 0.8 °C/min. Before thermal analysis, the results of high-precision scanning electron microscopy showed that more cracks and coarser surfaces were detected on NC fibers with higher nitrogen contents. It was found that a “turning point” was detected on the heat flow curves of NC with higher nitrogen contents. Furthermore, the heat flow curves of NC transformed from “bell shape” to “right triangles” with increases in the nitrogen content, which suggested that NC with high nitrogen contents exhibited autocatalysis characteristics under low heating rates. This characteristic was also confirmed by the isothermal experiment results that showed the autocatalytic properties became increasingly obvious by increasing the isothermal temperature. Moreover, the relevant chemical kinetic and thermodynamic parameters were obtained. The heat of the reaction (ΔH) increased and the activation energy values in the initial stages of NC decomposition decreased as the nitrogen content was increased. Furthermore, the critical explosion temperature (Tb), which is as an important parameter to evaluate the thermal hazard of NC, decreased by elevating the nitrogen content.

Effects of Nitrogen Content on the Structure and Mechanical Properties of (Al0.5CrFeNiTi0.25)Nx High-Entropy Films by Reactive Sputtering.

In this study, (Al0.5CrFeNiTi0.25)Nx high-entropy films are prepared by a reactive direct current (DC) magnetron sputtering at different N2 flow rates on silicon wafers. It is found that the structure of (Al0.5CrFeNiTi0.25)Nx high-entropy films is amorphous, with x = 0. It transforms from amorphous to a face-centered-cubic (FCC) structure with the increase of nitrogen content, while the bulk Al0.5CrFeNiTi0.25 counterpart prepared by casting features a body-centered-cubic (BCC) phase structure. The phase formation can be explained by the atomic size difference (δ). Lacking nitrogen, δ is approximately 6.4% for the five metal elements, which is relatively large and might form a BCC or ordered-BCC structure, while the metallic elements in this alloy system all have a trend to form nitrides like TiN, CrN, AlN, and FeN. Therefore, nitride components are becoming very similar in size and structure and solve each other easily, thus, an FCC (Al-Cr-Fe-Ni-Ti)N solid solution forms. The calculated value of δ is approximately 23% for this multicomponent nitride solid solution. The (Al0.5CrFeNiTi0.25)Nx films achieve a pronounced hardness and a Young’s modulus of 21.45 GPa and 253.8 GPa, respectively, which is obviously much higher than that of the as-cast Al0.5CrFeNiTi0.25 bulk alloys.

Effect of nitrogen content on the crack growth behavior in the Fe-N alloy at high temperatures via molecular dynamics simulations

In this work, the influence of nitrogen content on the crack propagation behavior in Iron-Nitrogen (Fe-N) nano-crystalline was studied at high temperatures using molecular dynamics (MD). The semi-empirical Modified Embedded Atom Method (MEAM) potential function was utilized to model the interatomic interactions. The results revealed that at higher temperature of 900 K and 1100 K, more slip systems are activated resulting in the crack tip blunting ahead of crack tip and void nucleation and growth. Moreover, the results showed that the deformation mechanism and fracture behavior are significantly altered owing to the initial nitrogen concentration. The simulated results indicated the slow crack propagation at low nitrogen content of 0.1 wt.%. Detailed analysis confirmed that nitrogen concentration has a significant effect on the crack propagation. At high nitrogen content (0.51 wt.%), the crack growth increased by changing the crack propagation path.

Effect of nitrogen contents on the microstructure and mechanical properties of V-Ti microalloyed steels for the forging of crankshafts

The microstructure and mechanical properties of vanadium-titanium microalloyed crankshaft steels with two different nitrogen concentrations were studied. The increasing nitrogen not content only refined the austenite grain size but also facilitated the formation of intragranular ferrite (IGF) idiomorphs. The V-Ti-N steel has a better combination of strength, plasticity and toughness than that of the V-Ti steel. Increasing the nitrogen content also facilitated the precipitation of V(C, N) particles in ferrite, which significantly strengthened it. This outcome remedied the strength reduction caused by the decrease in the pearlite volume fraction. The IGF idiomorphs can deform along with the outside pearlite compatibly and restrain the crack growth in pearlite while in tensile deformation. As a result, the plasticity is significantly improved from the increase of the IGF idiomorphs. Moreover, the effective grain size can be refined by the increase of the IGF idiomorphs, which improves the toughness.

Single- and Dual-Stage High-Purity Oxygen Production Using Silver-Exchanged Titanosilicates (Ag-ETS-10)

High-purity (>99.5%) O2 production from air with silver-exchanged titanosilicates (Ag-ETS-10) using multiple single- and dual-stage vacuum swing adsorption (VSA) cycle configurations was investigated through process simulation, and optimization. Model predictions for the Skarstrom cycle were validated through experiments and an O2 purity of 98.3 ± 0.5% with a corresponding recovery of 10.6% was achieved. Oxygen purity-recovery Pareto fronts for the Skarstrom cycle and 6-step cycle with pressure equalization (PE) and heavy product pressurization (HPP) with dry air as the feed were obtained. The optimization predicted 82.0% O2 recovery with a product purity of 99.5% for a 6-step cycle with PE and HPP and dry air feed stream. The effect of nitrogen content in the feed on the performance indicators was also studied. Operating conditions for various cycle configurations were optimized through nondominated sorting genetic algorithm technique to achieve low total energy consumption (592.4 kWh/tonne O2) and high ...

Synergistic Effect of Nitrogen and Refractory Material on TiN Formation and Equiaxed Grain Structure of Ferritic Stainless Steel

The effect of nitrogen content on the formation of an equiaxed solidification structure of Fe-16Cr steel was investigated. Moreover, two different kinds of refractory materials, i.e., alumina and magnesia, were employed to control the type of oxide inclusion. The characteristics of TiN(-oxide) inclusions were quantitatively analyzed in both molten steel and solidified samples. When the melting was carried out in the alumina refractory, the grain size continuously decreased with increasing nitrogen content. However, a minimum grain size was observed at a specific nitrogen content (approx. 150 ppm) when the steel was melted in the magnesia refractory. Most of the single TiN particles had a cuboidal shape and fine irregularly shaped particles were located along the grain boundary due to the microsegregation of Ti at the grain boundary during solidification. The type of TiN-oxide hybrid inclusion was strongly affected by the refractory material where Al2O3-TiN and MgAl2O4-TiN hybrid-type inclusions were obtained in the alumina and magnesia refractory experiments, respectively. The formation of oxide inclusions was well predicted by thermochemical computations and it was commonly found that oxide particles were initially formed, followed by the nucleation and growth of TiN. When the nitrogen content increased, the number density of TiN linearly increased in the alumina refractory experiments. However, the number of TiN exhibits a maximum at about [N] = 150 ppm, at which a minimum grain size was obtained in the magnesia refractory experiments. Therefore, the larger the number density of TiN, the smaller the primary grain size after solidification. The number density of TiN in the steel melted in the magnesia refractory was greater than that in the steel melted in the alumina refractory at given Ti and N contents, which was due to the lower planar lattice disregistry of MgAl2O4-TiN interface rather than that of Al2O3-TiN interface. When ∆TTiN (= difference between the TiN precipitation temperature and the liquidus of the steel) was 20 K to 40 K, the number density of effective TiN was maximized and thus, the grain size was minimized after solidification. Finally, although most of the TiN particles were smaller than 1 μm in the molten steel samples irrespective of the nitrogen content, TiN particles larger than 10 μm were observed in the solidified samples when the nitrogen content was greater than 150 ppm. The growth of TiN particles during melting and solidification was well predicted by the combinatorial simulation of the ‘Ostwald ripening model’ based on the Lifshitz–Slyozov–Wagner theory in conjunction with the ‘Diffusion controlled model’ using Ohnaka’s microsegregation equation.

The Effect of Nitrogen Contents on the Corrosion and Nano-Mechanical Properties of Arc Ion Plated Ti–Al–Si–N Layers

The Effect of Nitrogen Contents on the Corrosion and Nano-Mechanical Properties of Arc Ion Plated Ti–Al–Si–N Layers

Assessing Constitutive Models for Prediction of High-Temperature Flow Behavior with a Perspective of Alloy Development

The utility of different constitutive models describing high-temperature flow behavior has been evaluated from the perspective of alloy development. Strain compensated Arrhenius model, modified Johnson–Cook (MJC) model, model D8A and artificial neural network (ANN) have been used to describe flow behavior of different model alloys. These alloys are four grades of SS 316LN with different nitrogen contents ranging from 0.07 to 0.22%. Grades with 0.07%N and 0.22%N have been used to determine suitable material constants of the constitutive equations and also to train the ANN model. While the ANN model has been developed with chemical composition as a direct input, the MJC and D8A models have been amended to incorporate the effect of nitrogen content on flow behavior. The prediction capabilities of all models have been validated using the experimental data obtained from grades containing 0.11%N and 0.14%N. The comparative analysis demonstrates that ‘N-amended D8A’ and ‘N-amended MJC’ are preferable to the ANN model for predicting flow behavior of different grades of 316LN. The work provides detailed insights into the usual statistical error analysis technique and frames five additional criteria which must be considered when a model is analyzed from the perspective of alloy development.