Nitrogen Ions Research Articles

Effect of fast electrons on emission properties of non-equilibrium nitrogen plasma in soft x-ray spectral range

Soft x-ray emission at 2.3–4.4 nm waveband in nitrogen plasma can be observed mostly from 2p-1s and 3p-1s resonant transitions. Ions of nitrogen in plasma emitting in necessary band have a high energy excited state in comparison with plasma temperature in experiments. Discharge and laser produced plasmas used in radiation sources often have non-equilibrium electron distributions with fast electrons. In this study the radiative properties of non-equilibrium nitrogen plasma with fast electrons are examined and the plasma conditions for optimal soft x-ray emission output in the water-window region are explored. Kinetic parameters for non-equilibrium plasma including major inelastic ion interaction processes, radiation characteristics are obtained in approach based on the Hartree-Fock-Slater quantum-statistical model and the distorted wave approximation. The presence of fast electrons in plasma at relatively small portions may have a significant influence on the ion level populations and the line emission intensities. Emission generation efficiency doubles at a temperature of 60 eV with 1% portion of fast electrons with respect to equilibrium plasma and the corresponding spectral efficiency jumps to 5.5%.

Structural and mechanical properties of tantalum thin films ected by nitrogen ion implantation

Tantalum bulk were implanted with nitrogen ions at different dose of [Formula: see text] ions/cm2 to [Formula: see text] ions/cm2 and at a energy 30 keV. The implanted samples were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), microhardness testing, friction coefficient measurements and wear mechanism study. Scanning electron microscopy (SEM) images were used to analyze the friction of samples. The XRD results confirmed that the increasing dose affects the formation of the TaN phase. Based on AFM images, the morphology and surface roughness change proportionally to grain size after implantation. It was found that hardness increases as energy increases. From the friction coefficient measurement, this coefficient decreases as energy increases. For the un-implanted sample, the wear mechanism has abrasion, and with increasing the energy, it shifts to being flake and sticky.

Effect of Filter Speed and Water Quality on Ammonia Removal in Groundwater Containing Iron, Manganese, and Ammonia at Low Temperature

In a groundwater plant we carried out a process operation test of biological removal of iron and manganese nitrification coupled with completely autotrophic ammonium removal over nitrite (CANON) (Fe(Ⅱ) 2.91-6.35 mg·L-1, Mn(Ⅱ) 0.47-0.98 mg·L-1, NH4+-N 1.15-2.26 mg·L-1) at low temperature (6-8℃), to explore the effects of filter speed and water quality on ammonia nitrogen removal. The results showed that the mature low-temperature biological filter column, which had been out of service for one month, was cultured for 40 days at a filtration rate of 2 m·h-1 and successfully started. In this process, when the water inlet concentration remained the same, the improved filter speed would reduce the efficiency of ammonia nitrogen capture by the filter column, increase the concentration of ammonia nitrogen in the depth of the filter layer, and improve the efficiency of ammonia nitrogen ions capture by anaerobic ammonia oxidation bacteria (AnAOB) in the depth of the filter layer, so that the ammonia nitrogen removed by CANON in the water increased, while the ammonia nitrogen removed by nitrification decreased. When the filter speed remained unchanged, the concentration of ammonia nitrogen in water was increased to make the ammonia nitrogen with higher concentration enter the filter layer, which increased the concentration of ammonia nitrogen in the zone where ammonia nitrogen and nitrous nitrogen coexist, and improved the net catching efficiency of AnAOB on ammonia nitrogen ions in the filter layer, thus resulting in an increase in ammonia nitrogen removed by CANON.

Investigation of nitrogen and iron co-doped TiO2 films synthesized in N2/CH4 via pulsed laser deposition technique

Nitrogen and iron ions co-doped titania films have been synthesized by PLD technique in nitrogen/methane (N2/CH4) (5:1) media at 1 mbar. Most of the samples are XRD amorphous but a certain amount of crystalline rutile is detected by Raman measurements. The presence of rutile phase only and its low crystallinity degree can be caused by nitrogen doping of oxide matrix. The most intensive VIS absorption and the lowest band gap values are observed for 5% Fe2O3 or Fe3O4 titania films that are supported by the highest nitrogen amount on the surface. The strongest photocatalysts in process of dichromate reduction under either UV or VIS irradiation are shown to be the films obtained from 5% iron oxide in titania target and synthesized at 550 °C as a result of optimal content of Ti–N and Ti–O–Fe structural fragments as revealed by XPS. The presence of Fe3+ and Fe2+ surrounded by oxygen as well as Fe–N bonds is confirmed by XPS data.

Modification of the microstructure and properties of martensitic steel during ultra-high dose high-intensity implantation of nitrogen ions

In this work, we report a study of the chemical and phase composition, structural modifications and mechanical properties of martensitic stainless steel surface layers modified by high-intensity nitrogen ion implantation using a high current beam of low-energy nitrogen ions. The effect of ultrahigh-dose implantation of nitrogen ions into steel using a high-intensity repetitively pulsed beam of nitrogen ions with a current of 0.6 A (at an ion energy of 1.2 keV) and a sample temperature of 500 °C is investigated. The fluence of ion irradiation in the range from 6 × 1021 ions/cm2 to 2.25 × 1021 ions/cm2 varied by changing the current density and implantation time. The studies performed using transmission electron microscopy and X-Ray diffraction analysis of the microstructure and phase composition of the implanted samples showed that the surface-doped layer formed up to 75 μm thick and contains ferrite, iron nitride Fe4N, and chromium nitride CrN (α-phase – 70.88 vol.%, γ'-Fe4N – 16.30 vol.%, CrN – 12.82 vol.%). The obtained values of the coherent scattering region size of the formed chromium nitride and iron nitride indicate a very high dispersion of the elements in the ion-doped layer substructure. The data on changes in the surface morphology and microhardness of the near-surface layers are presented.

Effective electron–hole separation over N‐doped TiO2 materials for improved photocatalytic reduction of 4‐nitrophenol using visible light

AbstractBACKGROUNDNitrogen‐doped titanium dioxide (TiO2) photocatalyst was synthesized successfully by a low temperature microwave‐assisted sol–gel method. Ethylenediamine was used as a source of nitrogen dopants to extend and improve the photoresponse of the materials to visible light. The photocatalysts were characterized by several techniques to determine the structural, textural and optical characteristics. The activity of the materials was tested in the photoreduction of 4‐nitrophenol (4‐NP) to 4‐aminophenol (4‐AP) under visible light.RESULTSThe results indicate that nitrogen ions were substitutedly doped into oxygen sites of the TiO2 lattice, resulting in band gap narrowing, which significantly promotes the visible light absorption of TiEN catalysts. When initial ethylenediamine concentration was increased, the content of nitrogen dopant and optical absorption in the visible region increased. Moreover, it was found that TiEN photocatalyst significantly enhances the photoreduction of 4‐NP in comparison to the bare TiO2.CONCLUSIONThe increased photocatalytic activity of TiEN new materials are predominantly related to a lower energy gap, enhanced visible light absorption, higher reactive surface area and improved charge separation of photoinduced electron–hole pairs. © 2020 Society of Chemical Industry

Formation of a Corrugated Surface on a Carbon Fiber under High-Fluence Irradiation with Nitrogen Ions

The behavior of the surface of carbon fibers based on polyacrylonitrile, which reinforce the KUP-VM composite, upon corrugation under high-fluence irradiation with $${\text{N}}_{2}^{ + }$$ ions with an energy of 15 and 30 keV and a temperature of the irradiated composite in the range from 100°C to 600°C is described and discussed. In contrast to irradiation with ions of noble gases, it is found that the main parameters of the corrugated structure, such as the tilt angles of corrugations and their fractions on the surface of a fiber, are practically independent of the composite temperature. The corrugation periodicity is hundreds of nanometers, as in the case of irradiation with neon and argon ions. In the case of using ion energies of 15 and 30 keV, the tilt angles are 30° and 40°, respectively. The difference between the temperature dependences of the tilt angle of the corrugations and their fraction on the fiber surface and similar dependences in the case of irradiation with noble gas ions is determined by the peculiarities of the dynamic annealing of radiation-induced damage in the fiber shell due to the chemical activity of nitrogen associated with the creation of C–N bonds and a larger proportion of the amorphous component.

Backward lasing of singly ionized nitrogen ions pumped by femtosecond laser pulses

We report on the observation of backward lasing at 391.4 nm of nitrogen ions pumped by linearly polarized intense femtosecond pulses at 800 nm. The strongly enhanced spectral intensity at 391.4 nm, as well as the amplification of an externally injected backward seeding pulse, confirm that the backward 391.4 nm signal is due to optical amplification in the gas plasma. Compared to the forward emission at 391.4 nm, the optimal backward emission is achieved at a lower gas pressure around 10 mbar, which is due to asymmetry of the backward and forward directions rooted in the traveling excitation geometry. This method, using the widely available 800 nm femtosecond pulses as a pump laser, provides a promising scheme for the generation of backward air laser, which holds a unique potential for optical remote sensing.

Enhanced photoelectrocatalytic degradation of organic pollutants using TiO2 nanotubes implanted with nitrogen ions

Nitrogen ions-implanted TiO2 nanotubes (TNTs) were prepared by the methods of ion implantation and electrochemical anodic oxidation. The prepared samples were applied in photoelectrocatalytic (PEC) oxidation of methyl blue, rhodamine B and bisphenol A. Compared with pure TNTs, morphology, crystallinity, chemical structure, photoelectric and PEC ability of doped samples were greatly promoted because of ion implantation. The experimental results propose that the electronic structure of TiO2 was modified because of the emergence of impurity states in the band gap by introducing nitrogen into the lattice, leading to the absorption of visible light. The synergy effects of tubular structures, doped nitrogen ions and the bias potential on the circuit are responsible for highly efficient and stable PEC activities induced by visible light and UV light. The doped TNTs prepared using the method of ion implantation could be applied to various areas, such as PEC water splitting and dye sensitized solar cells.

The spread of nitrogen compounds in an active groundwater exchange zone within a valuable natural ecosystem

The aim of the paper is to present a methodical approach for developing a hydrodynamic model of groundwater flow and transport of nitrogen compounds in the area covered by the precision farming system. The study area covers the part of the Vistula River floodplain terrace near Warsaw (Poland), in the vicinity of nature reserves: Wyspy Zawadowskie, Wyspy Świderskie and Łęgi Oborskie. The components of the water balance in the analysed area were determined using the HELP (Hydrologic Evaluation of Landfill Performance) model. In reference to the doses of mineral nitrogen used during precise fertilisation, the scenarios of the spread of nitrogen ions in the soil-water environment were detailed. The results were presented graphically in the form of hydroisohypses and isolines of nitrate and ammonium concentrations. The activity of overbank flows and the effect of the geological settings on the course of aquifer layers in the active exchange zone were taken into consideration when describing groundwater flow. This allowed us to indicate potential paths of intense nitrate migration resulting from the evolution of the fluvial environment. Moreover, “hydrogeological windows” have been identified, where contaminants can freely migrate to usable aquifer in the major groundwater basin.

Soil responses to manipulated precipitation changes: A synthesis of meta-analyses

Abstract. In the face of ongoing and projected precipitation changes, precipitation manipulation experiments (PMEs) have produced a wealth of data about the effects of precipitation changes on soils. In response, researchers have undertaken a number of synthetic efforts. Several meta-analyses have been conducted, each revealing new aspects of soil responses to precipitation changes. We synthesize the findings of 16 meta-analyses focused on the effects of decreased and increased precipitation on 42 soil response variables, covering a wide range of soil processes and examining responses of individual variables as well as more integrative responses of carbon and nitrogen cycles. We found a strong agreement among meta-analyses that decreased and increased precipitation inhibits and promotes belowground carbon and nitrogen cycling, respectively, while microbial communities are relatively resistant to precipitation changes. Much attention has been paid to fluxes and pools in carbon, nitrogen, and phosphorus cycles, such as gas emissions, soil carbon, soil phosphorus, extractable nitrogen ions, and biomass, but the rates of processes underlying these variables are less frequently covered in meta-analytic studies (e.g., rates of mineralization, fixation, and de/nitrification). Shifting scientific attention to these “processes” would, therefore, deepen the current understanding of the effects of precipitation changes on soil and provide new insights. By comparing meta-analyses focused on different variables, we provide here a quantitative and holistic view of soil responses to changes in precipitation.

Silicone-based modified layer obtained by low-energy nitrogen ion beam as diaphragm for environmental transmission electron microscope

Amorphous silicon carbonitride (a-SiCN) films were prepared with surface-modified layers of silicone resin and silicone grease, fabricated by low-energy nitrogen ion beam irradiation, for use as diaphragms in an environmental-cell transmission electron microscope (E-TEM). Conditions used during nitrogen ion irradiation for surface modification of silicone polymers were accelerating voltages of 0.8–1.5 kV, ion current densities of 0.70–2.10 μA/cm2, and ion doses of 4.8–8.0 × 1016 ions/cm2. The modified layers, obtained by etching the unmodified layers with hexane, were evaluated by X-ray photoelectron spectroscopy (XPS). The atomic ratio of nitrogen was higher in the modified layer using silicone grease than in the modified layer using silicone resin. The best thinnest and nitriding condition on the silicone grease was obtained through nitrogen ion irradiation using is the case of an accelerating voltage of 0.8 kV, an ion current density of 0.7 μA/cm2, and an ion dose of 4.8 ions/cm2. However, the silicone-grease-based modified layer exhibited much more deflection than the silicone-resin-based modified layer. This is thought to be because the non-modified layer of silicone resin is a tougher material than silicone grease.

The Interlayer Effects of Nitrogen Implantation in the TiN/N<sub>2</sub>- Film Synthesis on the NAK80 Steel

Nitrogen ions with an energy of 200keV were used for the investigation of the interlayer effects of nitrogen implantation in the TiN/N2-film synthesis on the NAK80 steel. The nitrogen ion plasmas formed a broad ion mixing area at the interface between TiN film and NAK80 substrate. The measured hardness indicates the well mixing of TiN film into the NAK80 substrate, which may have an effect on increasing the adhesion of the deposited film. The chemical components and micro-hardness of the filmed surface were measured. The micro-hardness of Rockwell C-scale (HRC) was increased from 40 to 61 after the films of TiN/N2 were synthesized on the NAK80 substrate, the increased micro-hardness is attributed to the metallurgical phase change and formation of amorphous crystal due to the nitrogen implantation.

Ion-Stimulated Chemisorption of Nitrogen on the Si(111) Surface

Nitriding of a silicon surface with a beam of low-energy (100–700 eV) nitrogen ions from a source with electronic excitation was studied. The density of the N+ flux on the nitrided sample was up to 4.0 μA/cm2. After the treatment, a silicon nitride monolayer film formed on the silicon surface, as evidenced by the results of profiling, calculation of the surface concentration, and energy shift of the Auger peak of silicon by 6.1 eV.

Ion implantation of copper oxide thin films; statistical and experimental results

Ion implantation is one of the interesting way to tune the electrical and optical properties of metal oxides. In this regard, doping copper oxide with nitrogen is of interest on account of its potential to enhance the properties of copper oxide. Herein, we have investigated the influence of nitrogen ion implantation on the properties of copper oxide thin films, prepared using DC magnetron sputtering. The crystal structure, surface morphology, and optical properties of pristine and ion implanted copper oxide were investigated by means of X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and UV–visible spectrophotometer. The results of XRD demonstrated a mixture of CuOCu2O and Cu2O (as dominant phase). Additionally, the ion implanted sample illustrated a lower grain compared to the pristine sample. An increase of 2–3 order was obtained in the internal strain upon implementation of nitrogen into the samples that could be ascribed to the formation of non-uniform grains and an increment in lattice imperfection.The results of surface micrographs demonstrated a remarkable change on the surface of samples and the appearance of interconnected holes after ion implementation. The band gap was tuned and increased from 2.27 to 2.36 eV upon ion implantation that is largely owing to the influence of the quantum size of copper oxide during implantation. Our results show that the nitrogen ion implantation (N-type doping) is a useful way to tune the properties of materials that are applicable for variety of photovoltaic and optoelectronic devices. Moreover, the 3-D surface micro-texture characteristics of pristine and nitrogen ion implanted copper oxide thin films were quantitatively investigated using AFM, fractal, and stereometric analyzes.

Nitrogen ion beam implantation for enhanced lipid accumulation of Scenedesmus obliquus in municipal wastewater

Breeding of high-lipid content microalgae in municipal wastewater is critical for large-scale microalgal biodiesel production. In this study, a strain of biodiesel promising microalga Scenedesmus obliquus with good stain resistance was obtained by N+ ion implantation, which was named as S1-A3. In the selenite enrichment (SE) medium, the lipid content of S1-A3 was up to 46.92%, which was increased by 24.1% than the original strain. Meanwhile, after 7 days of cultivation, the removal rates of TP,TN, NH4+-N and COD in wastewater attained 95.72%, 80.30%, 87.25% and 85.43% by S1-A3, respectively. S1-A3 had a good genetic stability in both municipal wastewater and SE medium, and its lipid production capacity was improved after four successive cultivation in wastewater. RAPD analysis showed that the mutant and the original strain were interspecific variations. Therefore, N+ ion implantation was proved to be an approach that can significantly improve the lipid content and adaptability of Scenedesmus obliquus.

Ammonia amendment promotes high rate lactate production and recovery from semi-continuous food waste fermentation

In this study, a reliable approach using ammonia nitrogen was proposed to increase lactate production during semi-continuous food waste (FW) fermentation under mesophilic conditions. Both free ammonia nitrogen (FAN) and ammonium ion (NH4+-N) were present in mesophilic reactors, with a wide FAN/NH4+-N ratio variation due to the intermittent pH control. The investigation of responsible mechanisms revealed that the increased production yield of LA was associated with the acceleration of solubilization, hydrolysis, glycolysis and acidification. The presence of FAN and NH4+-N in proper concentrations increased lactate production by 2.4 folds and recovered lactate production to 24.5 g COD/L from low rate control reactor (9.6 g COD/L) under mesophilic conditions. Furthermore, the microorganisms responsible for LA accumulation (Bavariicoccus, Enterococcus, Bifidobacterium and Corynebacterium) were selectively enriched, and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways associated with carbohydrate transport and LA production were enhanced in nitrogen fed reactors.

Phytoplankton in an urban river replenished by reclaimed water: Features, influential factors and simulation

Abstract Algal bloom control in rivers replenished by reclaimed water has drawn attentions. Aiming at precisely simulating and forecasting the algal density, a typical downstream urban river replenished by reclaimed water was monitored and investigated in aspects of the water quality, algal density, algal community. Parameters of water quality revealed the typical feature of reclaimed water, with high concentration of nitrogen. Algal density dropped gradually from spring to the late autumn, indicating that spring was of high risk of algal bloom. Chlorophyta and Bacillariophyta were identified as the dominant phyla, and Chlorella (belonged to Chlorophyta), Cyclotella (belonged to Bacillariophyta) and Coscinodiscus (belonged to Bacillariophyta) were the dominant species. Both statistical analysis and model simulation revealed that light intensity, nitrogen and metal ions were the influential factors of algal growth in the river. Simulation of the change of algal density using AutoRegressive Integrated Moving Average (ARIMA) model (0, 0, 15) was effective with all the simulated value in the 95% confidence interval, making it feasible to the practical forecast of algal bloom in urban rivers, especially those which are replenished by reclaimed water.

Experimental and computational study of visible light-induced photocatalytic ability of nitrogen ions-implanted TiO2 nanotubes**Project supported by the National Natural Science Foundation for Joint Fund Key Project of China (Grant No. U1865206), the National Science and Technology Major Project of China (Grant No. 2017-VII-0012-0107), the National Defense Science and Technology Key Laboratory Fund of China (Grant No. 614220207011802), and the Key

Nitrogen-doped TiO2 nanotubes (TNTs) were prepared by ion implantation and anodic oxidation. The prepared samples were applied in photocatalytic (PC) oxidation of methyl blue, rhodamine B, and bisphenol A under light irradiation. To explore the influence of doped ions on the band and electronic structure of TiO2, computer simulations were performed using the VASP code implementing spin-polarized density functional theory (DFT). Both substitutional and interstitial nitrogen atoms were considered. The experimental and computational results propose that the electronic structure of TiO2 was modified because of the emergence of impurity states in the band gap by introducing nitrogen into the lattice, leading to the absorption of visible light. The synergy effects of tubular structures and doped nitrogen ions were responsible for highly efficient and stable PC activities induced by visible and ultraviolet (UV) light.

Rotational-state-changing collisions between N2+ and Rb at low energies

We present a theoretical study of rotationally elastic and inelastic collisions between molecular nitrogen ions and Rb atoms in the sub-Kelvin temperature regime prevalent in ion-atom hybrid trapping experiments. The cross sections for rotational excitation and de-excitation collisions were calculated using quantum-scattering methods on ab-initio potential energy surfaces for the energetically lowest singlet electronic channel of the system. We find that the rotationally inelastic collision rates are at least an order of magnitude smaller than the charge-exchange rates found in this system, rendering inelastic processes a minor channel under the conditions of typical hybrid trapping experiments.