Inert N2 Research Articles

Role of Information Feedback in Soil Nitrogen Management: Results from a Dynamic Simulation Game

Agricultural production depends on the consumption of nitrogen fertilizers, which are mostly produced by artificially fixing inert atmospheric N2 gas. Crops assimilate a fraction of the applied nitrogen (N) on farmlands, and the residual inorganic N in the soil solution is lost to the atmosphere and oceans, contributing to global climate change, water pollution and eutrophication. There is worldwide evidence indicating that N‐fertilizers are overused beyond profit‐maximizing levels, leading to dramatically low nitrogen use efficiencies. In this study, we focus on the problem of residual nitrogen accumulation on farmlands and the role of information feedback on fertilizer application rates. The vehicle is dynamic simulation and decision experimentation. Results of pilot experiments with students reveal that annual information feedback on farm profits and residual N help subjects adjust their rates towards economically meaningful quantities that do not create superfluous N losses. Because in real life, cause‐and‐effect between fertilizer rates and crop yields is confounded by various environmental factors, timely information on residual N may serve as a better cue for informing farmers' fertilizer decisions. When applied to farmer communities, the simulator is expected to facilitate learning about soil N accumulation and create the missing incentive for implementing regular soil analysis likely to lead towards more appropriate fertilizer rates. Copyright © 2017 John Wiley & Sons, Ltd.

Solution to Inverse Problem of Manufacturing by Surface Modification With Controllable Surface Integrity Correlated to Performance: A Case Study of Thermally Sprayed Coatings for Wear Performance

Inverse problem of manufacturing is studied under a framework of high performance manufacturing of components with functional surface layer, where controllable generation of surface integrity is emphasized due to its pivotal role determining final performance. Surface modification techniques capable of controlling surface integrity are utilized to verify such a framework of manufacturing, by which the surface integrity desired for a high performance can be more effectively achieved as reducing the material and geometry constraints of manufacturing otherwise unobtainable during conventional machining processes. Here, thermal spraying of WC–Ni coatings is employed to coat stainless steel components for water-lubricated wear applications, on which a strategy for direct problem from process to performance is implemented with surface integrity adjustable through spray angle and inert N2 shielding. Subsequently, multiple surface integrity parameters can be evaluated to identify the major ones responsible for wear performance by elucidating the wear mechanism, involving surface features (coating porosity and WC phase retention) and surface characteristics (microhardness, elastic modulus, and toughness). The surface features predominantly determine tribological behaviors of coatings in combination with the surface characteristics that are intrinsically associated with the surface features. Consequently, the spray process with improved N2 shielding is designed according to the desired surface integrity parameters for higher wear resistance. It is demonstrated that the correlations from processes to performance could be fully understood and established via controllable surface integrity, facilitating solution to inverse problem of manufacturing, i.e., realization of a material and geometry integrated manufacturing.

Highly Charged Protein Ions: The Strongest Organic Acids to Date

AbstractThe basicity of highly protonated cytochrome c (cyt c) and myoglobin (myo) ions were investigated using tandem mass spectrometry, ion–molecule reactions (IMRs), and theoretical calculations as a function of charge state. Surprisingly, highly charged protein ions (HCPI) can readily protonate non‐polar molecules and inert gases, including Ar, O2, and N2 in thermal IMRs. The most HCPIs that can be observed are over 130 kJ mol−1 less basic than the least basic neutral organic molecules known (tetrafluoromethane and methane). Based on theoretical calculations, it is predicted that protonated cyt c and myo ions should spontaneously lose a proton to vacuum for charge states in which every third residue is protonated. In this study, HCPIs are formed where every fourth residue on average is protonated. These results indicate that protein ions in higher charge states can be formed using a low‐pressure ion source to reduce proton‐transfer reactions between protein ions and gases from the atmosphere.

Highly Charged Protein Ions: The Strongest Organic Acids to Date

The basicity of highly protonated cytochrome c (cyt c) and myoglobin (myo) ions were investigated using tandem mass spectrometry, ion-molecule reactions (IMRs), and theoretical calculations as a function of charge state. Surprisingly, highly charged protein ions (HCPI) can readily protonate non-polar molecules and inert gases, including Ar, O2 , and N2 in thermal IMRs. The most HCPIs that can be observed are over 130 kJ mol-1 less basic than the least basic neutral organic molecules known (tetrafluoromethane and methane). Based on theoretical calculations, it is predicted that protonated cyt c and myo ions should spontaneously lose a proton to vacuum for charge states in which every third residue is protonated. In this study, HCPIs are formed where every fourth residue on average is protonated. These results indicate that protein ions in higher charge states can be formed using a low-pressure ion source to reduce proton-transfer reactions between protein ions and gases from the atmosphere.

Organic and inorganic sulphur compounds releases from high-pyrite coal pyrolysis in H2, N2 and CO2: Test case Chinese LZ coal

The effects of different atmospheres on the distribution of organic and inorganic sulphur compounds during high-pyrite coal pyrolysis were investigated. Sulphur compound releases were determined by atmospheric pressure-temperature programmed reduction (AP-TPR) “on-line” coupled with MS and AP-TPR “off-line” coupled with TD-GC/MS, which is a reliable technique for coal sulphur characterization. The results show that the decomposition of both organic and inorganic sulphur is different in the three applied atmospheres: H2, N2 and CO2. In H2, most sulphur from LZ coal is hydrogenated/reduced to H2S, decomposition of inorganic sulphur (pyrite and sulphates) has a great effect on the formation of H2S. It not only enhances the intensity of its m/z 34 signal but also shifts the peak maximum of its profile to a higher temperature, even without a returning to the base line. In inert N2 gas, as expected, hydrogenation of some sulphur compounds such as less-reactive di-aryl sulphur species and simple thiophenic structures are highly limited. The dominant peak of m/z 34 can also be related to the reduction of pyrite. In CO2, coal sulphur is mainly converted into SO2/SO, because CO2 is a more reactive gas and rather acts as an oxidizing agent. Decomposition of organic sulphonic acids occurs before 500°C and of sulphonics/sulphoxides after 500°C. The decomposition of sulphates and pyrite is better detectable in CO2 than in inert gas atmosphere. After 800°C char gasification in CO2 results in further decomposition of sulphur compounds and lower sulphur retention.

Self–Encapsulated Sb/C Nanocomposite with High Capacity and Stability As an Anode Material for Na-Ion Batteries

Li–ion batteries (LIBs) have been studied extensively in the past decades and become one of the most successful energy storage devices, which have rapidly penetrated into our lives. However, due to the limited supply and uneven global distribution of Li resources, the cost of LIBs may increase severely in the near future. Therefore, it is vital to develop more economical alternative energy storage system. In this regard, Na–ion batteries (SIBs) are attractive as promising alternative to LIBs due to the natural abundance of Na resources. Nevertheless, critical obstacles still exist for the commercialization of SIBs due to the lack of appropriate anode materials. Recently, Na-alloy type materials such as Sn and Sb have attracted attention due to their high theoretical specific capacity and low sodiation potential. In particular, Sb-based materials are very attractive as anode materials due to the low and suitable potentials for alloying/dealloying and high theoretical Na–storage capacity (660 mAh g-1) corresponding to formation of Na3Sb phase. However, these Na-alloy type materials can suffer from large volume change and resultant pulverization by the repeated alloying/dealloying processes. Although issues related to poor capacity retention of Na-alloy type materials caused by the large volume change during alloying/dealloying have been addressed using new binders and electrolyte additives, the practical application of Na-alloy type materials in SIBs is still challenge. In this study, a self–encapsulated Sb/C nanocomposite as an anode material for SIBs was successfully synthesized using the citric method followed by calcination process in an inert N2 atmosphere. In addition, effect of the content of carbon as a buffer layer on the electrochemical performance of the Sb/C nanocomposite electrode was investigated. The obtained results revealed that the Sb-C nanocomposite with an optimized Sb content of 50.87% exhibited the best electrochemical performance. The electrode showed almost 77.6% capacity retention of 585 mAh g-1 after 300 cycles of charge-discharge at the rate of C/10. Impressively, even at the high rate of 10 C, the specific capacity of 281 mAh g-1 ­was maintained. Furthermore, a full cell composed of Sb/C composite anode and NaCoO2 cathode exhibited satisfactory specific capacity and cyclability, which confirms the potential of Sn/C anode for high performance SIBs.

Determining the Chemical Composition of Corrosion Inhibitor/Metal Interfaces with XPS: Minimizing Post Immersion Oxidation.

An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, the focus is on metallic substrates immersed in acidic solutions containing organic corrosion inhibitors, as these systems can be particularly sensitive to oxidation following removal from solution. To minimize the likelihood of such degradation, samples are removed from solution within a glove box purged with inert gas, either N2 or Ar. The glove box is directly attached to the load-lock of the ultra-high vacuum X-ray photoelectron spectroscopy instrument, avoiding any exposure to the ambient laboratory atmosphere, and thus reducing the possibility of post immersion substrate oxidation. On this basis, one can be more certain that the X-ray photoelectron spectroscopy features observed are likely to be representative of the in situ submerged scenario, e.g. the oxidation state of the metal is not modified.

Determining the Chemical Composition of Corrosion Inhibitor/Metal Interfaces with XPS: Minimizing Post Immersion Oxidation

An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, the focus is on metallic substrates immersed in acidic solutions containing organic corrosion inhibitors, as these systems can be particularly sensitive to oxidation following removal from solution. To minimize the likelihood of such degradation, samples are removed from solution within a glove box purged with inert gas, either N2 or Ar. The glove box is directly attached to the load-lock of the ultra-high vacuum X-ray photoelectron spectroscopy instrument, avoiding any exposure to the ambient laboratory atmosphere, and thus reducing the possibility of post immersion substrate oxidation. On this basis, one can be more certain that the X-ray photoelectron spectroscopy features observed are likely to be representative of the in situ submerged scenario, e.g. the oxidation state of the metal is not modified.

Review on the high-temperature resistance of graphite in inert atmospheres

Temperature dependence of electrical resistivity of graphite materials at high temperatures up to 3000 °C was discussed on the bases of the published results on the measurements of resistivity of graphite rods and resistance of graphite heaters in high temperature furnace in inert atmospheres, Ar, N2 and He, and in vacuum. After passing through its minimum at around 1000 °C, resistance of graphite materials for most experimental conditions increases monotonically with increasing temperature up to 3000 °C. Due to extrinsic factors at certain experimental conditions in Ar atmosphere, however, a marked reduction in resistivity of the graphite rod above 2200 °C and also in resistance of the graphite heater above 2500 °C have been reported, no such resistance reduction having observed on the graphite heaters made from the same graphite material in N2 and He atmospheres, and under vacuum. The resistance reduction in Ar atmosphere at around 2000–2500 °C was supposed to be due to the formation of a short circuit by ionized Ar, which could be accelerated by the coexisted vaporized gases from the carbon materials loaded in the furnace to be heat-treated. The resistance reduction could be avoided by mixing more than 32% He in Ar.

N2 production via aerobic pathways may play a significant role in nitrogen cycling in upland soils

The importance of di-nitrogen (N2) production via aerobic pathways has been verified in a significant number of pure microbial strains. However, to date there are no reports confirming this in situ. In this study, we extracted micro-biota from three typical upland soils with variable properties and incubated them under aerobic and anaerobic conditions, with nitrate, to investigate whether N2 production occurred via aerobic pathways and the relative importance of it when compared with the N2 production via anaerobic pathways. Our results showed that N2 can be produced in soil extracts under aerobic conditions, and that the N2 produced via aerobic pathways equated to 29–51% of that produced via anaerobic pathways. Thus N2 production via aerobic pathways may play a significant role in soil nitrogen (N) cycling. Our results demonstrate that an O2 deficit may not to be a requirement for converting reactive N back into inert N2, and consequently this process may be more widespread in upland soils than currently thought.

Study of chemical vapour transport (CVT) grown WSe1.93 single crystals

In the present study, the single crystals of WSe1.93 were grown by chemical vapour transport (CVT) technique. Iodine was used as transporting agent. The purity and stoichiometry of the as-grown WSe1.93 single crystals were determined by energy dispersive analysis of X-ray (EDAX). The structural characterization was done by X-ray diffraction (XRD) technique. The scanning electron microscopy (SEM) of the as-grown single crystal surfaces showed that the crystal growth took place by layer growth mechanism. The thermogravimetric (TG), differential thermogravimetric (DTG) and differential thermal analysis (DTA) of as-grown WSe1.93 single crystal in inert N2 atmosphere showed two stages decomposition. The thermal parameters like activation energy (Ea), Arrhenius constant (A), enthalpy change (ΔH), the entropy change (ΔS) and the free energy change (Gibbs function) (ΔG) were calculated using Kissinger method. The optical bandgaps were determined from the optical absorption spectrum. The d.c. electrical resistivity measurements in the temperature range of 303–483K showed that the resistivity value decreases with increase of temperature, in line with semiconducting behavior. The p - type semiconducting nature of the sample was confirmed by Hall effect and thermoelectric power (TEP) measurements. The obtained results are discussed in details.

Flame Enhancement by Microwave-Induced Plasma: The Role of Major Bath Gas N2 Versus Ar

ABSTRACTA novel centralized microwave jet burner system is proposed here that can be used as a test platform to enable studies of plasma-assisted combustion (PAC) under various operation conditions and combustible mixtures. Spectroscopic characterizations of this burner are conducted using optical emission spectrum with methane/O2/N2 and methane/O2/Ar mixtures for comparison to distinguish the effects of the bath gas on flame enhancement and to delineate the flame enhancement mechanism of microwave induced plasma. The results show that the flame enhancement, by applying a nonequilibrium plasma, is more efficient when the dilution inert N2 in the air is replaced by Ar. The bath gas in the oxidizer stream plays an important role in the flame enhancement mechanism for the PAC system through more efficient direct impact of excited electrons on oxygen in the plasma and resulting in earlier initiation of the chain reactions through branched OH formation reactions in the flame.

Influence of stress on the properties of Ge nanocrystals in an SiO2 matrix

In this work, self-assembled Ge quantum dot (QD) formation in a dielectric matrix is explored. Of particular interest were their structural and optical properties, in order to understand the stress build-up in such a process and its impact on the material properties during processing. To this end, thin films consisting of (Ge + SiO2)/SiO2 multilayers grown by RF magnetron sputtering were deposited at room temperature. Annealing of such films at 873 K in inert N2 atmosphere produced, at the position of the Ge-rich SiO2 layers, a high lateral density (about 1012 cm−2) of Ge QDs with a good crystallinity. SiO2 spacer layers separated the adjacent Ge-rich layers, where the Ge QDs were formed with a diameter of about the size of the (Ge + SiO2) as-deposited layer thickness, and created a good vertical repeatability, confirmed by the appearance of a Bragg sheet in two-dimensional small-angle X-ray scattering patterns. The structural analysis, by wide-angle X-ray diffraction, grazing-incidence small-angle X-ray scattering and transmission electron microscopy, has shown that the described processing of the films induced large compressive stress on the formed QDs. Optical analysis by time-resolved photoluminescence (PL) revealed that the high density of crystalline Ge QDs embedded in the amorphous SiO2 matrix produced a strong luminescence in the visible part of the spectrum at 2–2.5 eV photon energy. It is shown that the decay dynamics in this energy range are very fast, and therefore the transitions that create such PL are attributed to matrix defects present in the shell surrounding the Ge QD surface (interface region with the matrix). The measured PL peak, though wide at its half-width, when analysed in consecutive short spectral segments showed the same decay dynamics, suggesting the same mechanism of relaxation.

Growth in the global N2 sink attributed to N fertilizer inputs over 1860 to 2000

Cropland expansion and fertilizer applications are among the most important substantial effects of human actions on the global nitrogen (N) cycle. However, questions remain over the fate of anthropogenic N inputs, particularly whether a significant fraction of N-based fertilizers have been lost to inert N2 or reactive N forms. Here, we combine natural N isotope constraints on the pre-industrial N cycle with global mass-balance modeling to investigate the role of cropland conversion on gaseous N emissions and hydrological N leaching fluxes. We estimate that cropland expansion has been accompanied by >9-fold increase in N input rates to cropping systems, roughly doubling the baseline N budget of the terrestrial biosphere. As a consequence, approximately 10 times more N is exported from modern croplands to the hydrosphere than in 1860, with a five-fold increase in cropland N gases emission to the atmosphere. Atmospheric NH3, NO, N2O and N2 fluxes increased from 8.6, 16.6, 11.7 and 31.9TgNyr−1, respectively, in 1860 to 17.7, 23.6, 15.2 and 39.7TgNyr−1, respectively, by 2000. Thus, the growth in N2 accounted for ~20% of cropland-driven N losses (dissolved plus gaseous pathways), with the remaining 80% exported as reactive N forms. Although the increase in N2 emissions has mitigated some of the unwanted side-effects of N fertilizer applications on human health, the economy, and climate change, this inert sink has been unable to keep pace with the increase in N inputs for enhanced food production. Our results imply that, unless new management steps are taken, an increasing fraction of N fertilizers will mobilize to reactive N forms in the global land, air and water systems, thus further accelerating the negative consequences of human modifications of the N cycle this century.

ROCker: accurate detection and quantification of target genes in short-read metagenomic data sets by modeling sliding-window bitscores

Functional annotation of metagenomic and metatranscriptomic data sets relies on similarity searches based on e-value thresholds resulting in an unknown number of false positive and negative matches. To overcome these limitations, we introduce ROCker, aimed at identifying position-specific, most-discriminant thresholds in sliding windows along the sequence of a target protein, accounting for non-discriminative domains shared by unrelated proteins. ROCker employs the receiver operating characteristic (ROC) curve to minimize false discovery rate (FDR) and calculate the best thresholds based on how simulated shotgun metagenomic reads of known composition map onto well-curated reference protein sequences and thus, differs from HMM profiles and related methods. We showcase ROCker using ammonia monooxygenase (amoA) and nitrous oxide reductase (nosZ) genes, mediating oxidation of ammonia and the reduction of the potent greenhouse gas, N2O, to inert N2, respectively. ROCker typically showed 60-fold lower FDR when compared to the common practice of using fixed e-values. Previously uncounted ‘atypical’ nosZ genes were found to be two times more abundant, on average, than their typical counterparts in most soil metagenomes and the abundance of bacterial amoA was quantified against the highly-related particulate methane monooxygenase (pmoA). Therefore, ROCker can reliably detect and quantify target genes in short-read metagenomes.

A modified biotrickling filter for nitrification-denitrification in the treatment of an ammonia-contaminated air stream.

A conventional biotrickling filter for airborne ammonia nitrification has been modified, by converting the liquid sump into a biological denitrifying reactor. The biotrickling filter achieves an average ammonia removal efficiency of 92.4%, with an empty bed retention time (EBRT) equal to 36s and an average ammonia concentration of 54.7mgNm-3 in the raw air stream. The denitrification reactor converts ammonia into inert gas N2, in addition to other important advantages connected to the alkaline character of the biochemical pathway of the denitrifying bacteria. Firstly, the trickling water crossing the denitrification reactor underwent a notable pH increase from 7.3 to 8.0 which prevented the acidic inhibition of the nitrifying bacteria due to the buildup of nitric and nitrous acids. Secondly, the pH increase created the ideal conditions for the autotrophic nitrifying bacteria. The tests proved that an ammonia removal efficiency of above 90% can be achieved with an EBRT greater than 30s and a volumetric load lower than 200g NH3m-3day-1. The results of the biofilm observation by using a scanning confocal laser microscope are reported together with the identification of degrading bacteria genera in the biotrickling filter. The efficiency of the plant and its excellent operational stability highlight the effectiveness of the synergistic action between the denitrification reactor and the biotrickling filter in removing airborne ammonia.

The Role of the Hydrogen Source on the Selective Production of γ-Valerolactone and 2-Methyltetrahydrofuran from Levulinic Acid.

A mechanistic study of the hydrogenation reaction of levulinic acid (LA) to 2-methyltetrahydrofuyran (MTHF) was performed using three different solvents under reactive H2 and inert N2 atmospheres. Under the applied reaction conditions, catalytic transfer hydrogenation and hydrogenation with molecular H2 were effective at producing high yields of γ-valerolactone. However, the conversion of this stable intermediate to MTHF required the combination of both hydrogen sources (the solvent and the H2 atmosphere) to achieve good yields. The reaction system with 2-propanol as solvent and Ni-Cu/Al2 O3 as catalyst allowed full conversion of LA and a MTHF yield of 80 % after 20 h reaction time at 250 °C and 40 bar of H2 (at room temperature). The system showed the same catalytic activity at LA feed concentrations of 5 and up to 30 wt%, and also when high acetone concentration at the beginning of the reaction were added, which confirmed the potential industrial applications of this solvent/catalyst system.

Characterization of Thin Film Dissolution in Water with in Situ Monitoring of Film Thickness Using Reflectometry.

Reflectometry was implemented as an in situ thickness measurement technique for rapid characterization of the dissolution dynamics of thin film protective barriers in elevated water temperatures above 100 °C. Using this technique, multiple types of coatings were simultaneously evaluated in days rather than years. This technique enabled the uninterrupted characterization of dissolution rates for different coating deposition temperatures, postdeposition annealing conditions, and locations on the coating surfaces. Atomic layer deposition (ALD) SiO2 and wet thermally grown SiO2 (wtg-SiO2) thin films were demonstrated to be dissolution-predictable barriers for the protection of metals such as copper. A ∼49% reduction in dissolution rate was achieved for ALD SiO2 films by increasing the deposition temperatures from 150 to 300 °C. ALD SiO2 deposited at 300 °C and followed by annealing in an inert N2 environment at 1065 °C resulted in a further ∼51% reduction in dissolution rate compared with the nonannealed sample. ALD SiO2 dissolution rates were thus lowered to values of wtg-SiO2 in water by the combination of increasing the deposition temperature and postdeposition annealing. Thin metal films, such as copper, without a SiO2 barrier corroded at an expected ∼1-2 nm/day rate when immersed in room temperature water. This measurement technique can be applied to any optically transparent coating.

Annealing effects on polycrystalline GaN using nitrogen and ammonia ambients

This paper describes effects of using post-annealing treatment in different conditions on the properties of polycrystalline GaN layer grown on m-plane sapphire substrate by electron beam (e-beam) evaporator. Without annealing, GaN surface was found to have a low RMS roughness with agglomeration of GaN grains in a specific direction and the sample consisted of gallium oxide (Ga2O3) material. When the post-annealing treatment was carried out in N2 ambient at 650 °C, initial re-crystallization of the GaN grains was observed while the evidence of Ga2O3 almost disappeared. As the NH3 annealing was conducted at 950 °C, more effect of re-crystallization occurred but with less grains coalescence. Three dominant XRD peaks of GaN in (101¯0), (0002) and (101¯1) orientations were evident. Near band edge (NBE) related emission in GaN was also observed. The significant improvement was attributed to simultaneous recrystallization and effective reduction of N deficiency density. The post-annealing in a mixture of N2 and NH3 ambient at 950 °C was also conducted, but has limited the effectiveness of the N atoms to incorporate on the GaN layer due to ‘clouding’ effect by the inert N2 gas. Further increase in the annealing temperature at 980 °C and 1100 °C, respectively caused severe deteriorations of the structural and optical properties of the GaN layer. Overall, this work demonstrated initial potential in improving polycrystalline GaN material in simple and inexpensive manner.

Ethylene/ethane permeation, diffusion and gas sorption properties of carbon molecular sieve membranes derived from the prototype ladder polymer of intrinsic microporosity (PIM-1)

Fine-tuning the microporosity of PIM-1 by heat treatment was applied to develop a suitable carbon molecular sieve membrane for ethylene/ethane separation. Pristine PIM-1 films were heated from 400 to 800°C under inert N2 atmosphere (<2ppm O2). At 400°C, PIM-1 self-cross-linked and developed polar carbonyl and hydroxyl groups due to partial dioxane splitting in the polymer backbone. Significant degradation occurred at 600°C due to carbonization of PIM-1 and resulted in 30% increase in cumulative surface area compared to its cross-linked predecessor. In addition, PIM-1-based CMS developed smaller ultramicropores with increasing pyrolysis temperature, which enhanced their molecular sieving capability by restricted diffusion of ethylene and ethane through the matrix due to microstructural carbon densification. Consequently, the pure-gas ethylene permeability (measured at 35°C and 2bar) decreased from 1600Barrer for the pristine PIM-1 to 1.3Barrer for the amorphous carbon generated at 800°C, whereas the ethylene/ethane pure-gas selectivity increased significantly from 1.8 to 13.