Nitrogen Flow Research Articles

Hysteresis loop variations induced by nitrogen flow rate in solution-based VO2 films

Hysteresis loop variations induced by nitrogen flow rate in solution-based VO2 films

Analysis of Nitrogen and Phosphorus Flows in a Rice-Growing Basin: The Case of the Maga Production Basin (Cameroon)

The availability of irrigation water has favored the development of agriculture in the Maga area, located in the Far North of Cameroon, with rice growing as the dominant agricultural activity. This activity is, however, known as a source of groundwater pollution through the infiltration of substances contained in inputs used for soil fertilization. The present study is a contribution to the analysis of the sources of contamination of the waters of the Maga rice basin by nitrogen and phosphate mineral compounds as well as the spatial distribution of these compounds. The monitoring of a network of fifteen wells and boreholes covering the rice-growing area during six campaigns made it possible to carry out the physicochemical characterization of subsurface and groundwater. The results obtained reveal that nitrates (NO3−) are present in water in low quantities, with averages per campaign ranging from 9.01 mg/L to 20.31 mg/L. On the other hand, ammonium (NH4+) and phosphates (PO43−) are in significant concentration. Their averages are of the order of 2.62 mg/L to 4.51 mg/L and then 0.65 mg/L to 5.58 mg/L for ammonium and phosphates, respectively. Mineral fertilizers used for soil amendment and degradation of organic matter, as well as the hydrolysis of minerals contained in the soil, contribute to the mineralization of water in the study area.

Synthesis and Characterization of Boron Nitride Thin Films Deposited by High-Power Impulse Reactive Magnetron Sputtering

In the present research, hexagonal boron nitride (h-BN) films were deposited by reactive high-power impulse magnetron sputtering (HiPIMS) of the pure boron target. Nitrogen was used as both a sputtering gas and a reactive gas. It was shown that, using only nitrogen gas, hexagonal-boron-phase thin films were synthesized successfully. The deposition temperature, time, and nitrogen gas flow effects were studied. It was found that an increase in deposition temperature resulted in hydrogen desorption, less intensive hydrogen-bond-related luminescence features in the Raman spectra of the films, and increased h-BN crystallite size. Increases in deposition time affect crystallites, which form larger conglomerates, with size decreases. The conglomerates’ size and surface roughness increase with increases in both time and temperature. An increase in the nitrogen flow was beneficial for a significant reduction in the carbon amount in the h-BN films and the appearance of the h-BN-related features in the lateral force microscopy images.

Modeling the Spatial Flows of Nitrogen: The Case of Xiamen

Rapid city expansion and intensive human activities have remarkably affected nitrogen flow, leading to increasingly intricate spatial heterogeneity of nitrogen flow. Focused on the temporal characteristics of nitrogen flow at certain city scales, the existing research has missed comprehensive grid-scale spatial models for nitrogen flow. To address this gap, this study develops a comprehensive spatial model for nitrogen flow by incorporating both natural and anthropic processes. Taking Xiamen as its research case, this study utilizes grid technology and spatial analysis to build a detailed spatial model for nitrogen flow at the grid scale. The results of spatial characteristics of Xiamen in 2015 revealed that hotspots of nitrogen input were primarily located in the surrounding areas outside and east of Xiamen, with the maximum nitrogen input reaching 20.07 × 104 kg/ha. However, the hotspots of nitrogen load in the atmosphere were concentrated in the urban center (i.e., Xiamen Island) and the nearby sea areas. The maximum nitrogen outputs can reach 18.32 × 104 kg/ha, which is 18 times the total nitrogen output to the water environment. Additionally, it was found that a significant gradient correlation exists between nitrogen flow and population density. These findings provide support for low-nitrogen spatial planning and emission reduction policymaking.

Bending response performance in nitrogen-doped reduced graphene oxide-PEDOT:PSS: The impact of nitrogen flow rate on the nitrogen doping configurations

Mechanical bending sensors play a pivotal role in various applications, from wearable devices to healthcare monitoring systems. The integration of nitrogen-doped reduced graphene oxide (NrGO) materials has emerged as a versatile approach, offering a promising avenue for enhancing the performances of these sensors. Various nitrogen doping configurations within the materials matrix have been found to profoundly influence the sensor's bending response. In this work, we identified that pyrrolic-N doping configurations were more dominant at lower nitrogen flow rates of 10 and 20 sccm, with the percentages of 52.9 and 48.7 %, respectively. These configurations exhibited a stable pattern of resistance changes in response to bending, particularly when subjected to bending angles of 55° and 65°. Despite some inconsistencies in bending response at lower bending angles, the sensors demonstrated heightened sensitivity, registering at 0.34 kPa. In contrast, sensors predominantly characterized by pyridinic-N configurations at 40 sccm maintained a consistent level of sensitivity across different bending angles, demonstrating remarkable stability and structural robustness, even after enduring 10,000 cycles. These findings indicated that pyridinic-N configurations play a critical role in enhancing sensor performance, ensuring reliable measurements across various mechanical deformations.

Research on Catalytic Pyrolysis Process of Coconut Coat of Tropical Agricultural and Forestry Wastes

The effects of reaction temperature, reaction time, heating rate, nitrogen flow rate, and catalyst quality on the oil yield and oxygen content in oil were investigated by using the single-factor principle. Too high and too low reaction temperature, nitrogen flow rate, heating rate, and reaction time improved the yield of bio-oil, but the oxygen content in bio-oil was higher. The reduction in catalytic dose is beneficial to the increase in oil yield but not conducive to the increase in aromatic compound content. The optimal reaction conditions were observed as a reaction temperature of 500 °C, a nitrogen flow rate of 110 mL/min, a heating rate of 20 °C/min, a reaction time of 15 min, a mass ratio of catalyst to coconut coat powder of 1, an oil yield of 4.97%, a water yield of 35.80%, and a solid yield of 30.78%. The gas yield was 28.45%, the oxygen content was 10.3%, and the aromatic compound content was 89.7%. The analysis of the catalytic cracking mechanism shows that most of the oxygen-containing compounds in bio-oil are generated into water and aromatic compounds by a catalytic cracking reaction at high temperature, thus removing oxygen.

Surface Transformation Of Ultrahigh-Temperature Ceramics HfB2-SiC-C(graphene) Under The Influence Of High-Speed Disossociated Nitrogen Jets

In order to study the promising potential of HfB2–30 vol % SiC ultrahigh-temperature ceramic materials modified with low amounts of reduced graphene oxide for the creation of aerospace equipment intended for use in N2-based atmospheres, the effect of high-speed dissociated nitrogen flow on it has been investigated. It has been established that under the chosen conditions of exposure during the stepwise increase of the anode power supply of plasma torch and, accordingly, the influencing heat flux, at certain parameters there is a sharp increase in the surface temperature from ~1750 to 2000-2100°C. At the same time, further increase of the heat flux has no obvious and proportional effect on the temperature of the sample surface, which may indicate its high catalyticity with respect to the reactions of surface recombination of atomic nitrogen. It is shown that the surface layers of the material undergo chemical transformation (removal of silicon-containing substances, formation of a new phase based on HfN), which is accompanied by a significant change in the microstructure (formation of dendrite-like structures), which affects the optical and catalytic characteristics of the surface.

Nutrient flows in biofloc-Nile tilapia culture: A semi-physical modelling approach

Biofloc culture systems potentially reduce the nutrient losses in aquaculture. However, knowledge of the nutrient flows in the system is not yet well-developed. This study deployed experimental data to develop a semi-physical model to understand the dynamics and flows of carbon (C), nitrogen (N), and phosphorus (P) in a biofloc-Nile tilapia-rearing system. The model involved eight process variables, which are pelleted feed A, C, N, P, fish, biofloc, periphyton, and water volume. Model calibration and validation were done under a Control-diet and High-NSP-diet, respectively. The diets differed by the type of starch in which the latter contains three times higher fibrous starch, called non-starch polysaccharides, than the former. Except for biofloc, the behaviour of the process variables fit the observations with a root mean square error (RMSE) of less than 30% of the corresponding average observations. The biofloc biomass was predicted using exponential growth model and results in a RMSE of 49% and 56% for the Control and High-NSP-diet, respectively. Scenario analyses, using the validated model, showed that the biofloc system generates less waste when the stocking density is doubled, which means double fish production and less nutrient losses. In terms of different diets, the high-NSP-diet resulted in more organic waste than the Control-diet. However, the amount of loss and unutilised C and P were similar which was mainly caused by the ability of biofloc and periphyton to assimilate more waste, especially C, in the High-NSP-diet.

Mechanical and Tribological Properties of Laminated (NbTaMoW)Nx Films.

Laminated (NbTaMoW)Nx films were prepared via co-sputtering. The sputtering variables were a substrate holder rotation speed of 2 and 10 rpm and a nitrogen flow ratio (fN2 = N2/(Ar + N2)) of 0.1, 0.2, and 0.4. The (NbTaMoW)Nx films fabricated at 30 rpm displayed columnar structures. The phase structures of the laminated (NbTaMoW)Nx films varied from multiple body-centered cubic phases to a nanocrystalline and a face-centered cubic phase as the fN2 increased from 0.1 to 0.2 and 0.4. The mechanical and tribological properties of the laminated (NbTaMoW)Nx films were evaluated. The laminated (NbTaMoW)Nx films deposited at an fN2 of 0.4 had hardnesses of 25.2 and 26.1 GPa when prepared at 2 and 10 rpm, respectively, lower than the value of 29.9 GPa for the columnar (NbTaMoW)Nx film prepared at an fN2 of 0.4 and 30 rpm. In contrast, the wear resistances of the laminated (NbTaMoW)Nx films were superior to those of the columnar (NbTaMoW)Nx films.

Synthesis of nanoporous carbon from Ulva lactuca activated by eggshell for CO2 capture: a novel approach to waste valorization.

Facing the daunting challenge of climate change, driven by escalating greenhouse gas concentrations, our research introduces an innovative solution for CO2 capture. We explore a novel nanoporous carbon derived from Ulva lactuca, activated with eggshell waste, spotlighting waste valorization in mitigating atmospheric CO2. Through a systematic methodology encompassing variable carbonization temperatures (700-900°C) and nitrogen flow rates (2-4ml/min), complemented by a suite of characterization techniques, we unveil the synthesis of this pioneering adsorbent. Our study not only presents a novel, sustainable pathway for CO2 capture but also demonstrates superior performance, particularly with the NC800-4 sample, achieving a CO2 capture capacity of 1.40mmol/g at 30°C, alongside demonstrating consistent adsorption efficiency over four successive adsorption/desorption cycles. This breakthrough underscores the potential of leveraging waste for environmental remediation, offering a dual solution to waste management and carbon capture, utilization, and storage (CCUS) applications.

Comparative experiments on the flow morphology of liquid nitrogen and water in perforated structured packing

Cryogenic distillation is the primary method for air separation, with corrugated plate packing as the main packing for heat and mass transfer between nitrogen and oxygen. The perforated structure on the corrugated plate packing can directly change the liquid distribution characteristics, thereby affecting the packing’s flow and mass transfer performance. Currently, the effect of perforated structure is mainly revealed by room temperature fluids such as water and air, while on the practical cryogenic fluids such as liquid nitrogen, it is seldom studied. In this study, the effects of perforation size ranging from 2 to 8 mm on the flow of water and liquid nitrogen on the perforated plates were investigated and compared by a high-speed camera. It was observed that water could hardly flow through the perforations, it completely covers the perforations, forming a continuous liquid film on the surface of the perforations. The expected role of perforations in redistributing water on the back side of the corrugated plate is relatively minor. While for liquid nitrogen, the presence of the perforated structure helps fluid redistribution on the back side of the plate, as it can easily flow through the perforations with diameters between 2 mm and 8 mm. It is found that when the perforation diameter exceeds 6 mm, liquid nitrogen will form suspended liquid droplets within the holes, which could be a risk of premature flooding. Under similar conditions, the wetting rate of liquid nitrogen reaches 86.90 % −99.48 %, higher than that of water which is about 10.26 % −78.82 %. The results show that perforations have quite different effects on the flow characters of water and liquid nitrogen due to their disparate physic properties.

Enhancing pipe chilldown with axial grooves filled with silicone sealant

This study proposes a method to accelerate the chilldown process in pipes using liquid nitrogen flow. Axial grooves were machined along the inner surface of the pipe and then filled with silicone sealant. This approach achieves a shorter chilldown time compared to previously proposed methods. Initial experiments involving pool boiling in liquid nitrogen were conducted to determine the optimal groove width and the ratio of groove-to-sealant area. The shortest chilldown time in pool boiling was achieved when the groove pitch was close to the capillary length. The effect of the copper-to-silicone sealant area ratio on the chilldown process was minimal. The shortest chilldown time was achieved with a surface that had a 2 mm pitch and a copper-to-silicone sealant area ratio of 0.25. The chilldown time was 1/4.4 of that of the bare surface. Pipes with different pitch and groove widths were tested in a flow chilldown experiment. Using the surface texture, the chilldown time of a stainless-steel pipe with an outer diameter of 1/2″ and a length of 120 mm from room temperature to the saturation temperature was reduced to a maximum of 1/3.6. The shortest cooling time is obtained at a groove pitch of 2 mm. In addition to the shorter cooling time, the amount of liquid nitrogen required for chilldown was also reduced.

Enhanced denitrification by sunlight–hematite: A neglected nitrogen flow pattern in red soil

Mineral-microbe interactions in the Earth's Critical Zone significantly influence elemental biogeochemical cycling and energy flow processes. This study addresses the key scientific question of how semiconducting minerals drive microbial nitrogen cycling. In the red soil environment, the presence of semiconducting minerals enhances the denitrification process mediated by facultative microorganisms (Pseudomonas aeruginosa PAO1) with denitrifying activity. Compared to darkness, light significantly enhanced the synergistic denitrification kinetic process of red soil and Pseudomonas aeruginosa PAO1 (1.87 times). Cyclic voltammetry shows that the P. aeruginosa PAO1-red soil synergistic system exhibits distinct redox peaks under light. The constant potential current curve and electrochemical impedance spectroscopy measurements reveal a high photocurrent density (1.0 μA/cm2) and minimal polarization resistance (102 Ω) under this condition. These findings confirm that the sunlight-red soil-P. aeruginosa PAO1 synergistic process has excellent electron generation and migration capacity, active redox reactions, and good electron compatibility. Additionally, the photoelectrons of semiconductive minerals in red soil profoundly impact the metabolic processes of microbial denitrification functional genes. Using real-time polymerase chain reaction (qPCR) gene array technology, the abundance of nitrogen metabolism functional genes in P. aeruginosa PAO1 increased by 200 % during the light-red soil synergistic process. Notably, denitrification-related genes (ureC, nirS1, gdhA, and nosZ2) were significantly upregulated. This study confirms that semiconducting minerals are involved in the nitrogen cycle pathway of microbial denitrification and supplements the theory of mineral-microbial synergistic element biogeochemical cycling in the natural environment.

Characterization of SiNx grown at different nitrogen flow and prediction of refractive index using artificial neural networks

SiNx films were grown on silicon substrates by Radio Frequency (RF) magnetron sputtering deposition. The effect of nitrogen flow on the structural and optical properties of the obtained films was investigated using X-ray diffraction, Scanning Electron Microscopy (SEM), UV–Vis–NIR spectrophotometer and spectroscopic ellipsometer, respectively. XRD spectra of the films showed that all films belong to amorphous structure. SEM photographs of SiNx films were analyzed. As a result of the analysis, it was observed that the surfaces of the films had a homogeneous and smooth structure as the nitrogen flow increased. The total and diffuse reflectance spectra of the films were measured and the energy band gaps of the films were determined using the Kubelka-Munk function by using the diffuse reflectance. It was observed that the energy band gap changed as the nitrogen percentage increased. The refractive index of all films was obtained as a function of temperature using a spectroscopic ellipsometer. In the second part of this study, we focused on predicting the temperature dependent refractive indices of the nitrogen flow-dependent films using Artificial Neural Networks (ANN). For the training of the ANN model, wavelength and temperature values from experimental data were used as input and refractive index as output parameters. The simulation and prediction results obtained from this model are compared with the experimental data and interpreted. It is concluded that the ANN approach is suitable for simulating and predicting the temperature dependent refractive index. The models successfully trained with ANN will be especially preferred for predicting the refractive indices of SiNx films, which cannot be measured experimentally, thus providing predictions in non-experimental ranges. In particular, the results obtained by focusing on the ability of the developed artificial neural network (ANN) models to predict the optical properties of SiNx films and their potential to provide information in non-experimental conditions, offer a new approach to quickly and effectively evaluate the optical properties of SiNx films. This approach reveals the importance of artificial intelligence-based methods in materials characterization studies.

Systematic approach for high piezoelectric AlN deposition

Aluminum nitride (AlN) is a wide band gap semiconductor with interesting piezoelectric properties for many applications, including micromechanical systems (MEMS), acoustic wave sensors or energy harvesting devices. The influence of DC reactive magnetron sputtering (DCRMS) deposition parameters on the structural, crystalline, and piezoelectric properties of AlN thin films are presented. The systematic approach of Design of Experiments (DoE) has been used to evaluate the role of magnetron power, nitrogen and argon flows on the deposition process and the film properties. Magnetron power and argon flow have resulted to be the parameters causing the most significant effects on the deposition rate. AlN films have been deposited with a high crystal quality, showing low values of FWHM (0.28) and c-axis orientation parallel oriented respect to the growth direction, as evidenced by X-ray diffraction (XRD) analysis and high-resolution transmission electron microscopy (HRTEM). These samples also showed a high piezoelectric coefficient (d33) of 5 pC/N for AlN thin films. This work highlights the importance of deposition parameters on the properties of the film and the important role that DoE play for its optimization with a minimum number of depositions.

Nitrogen use efficiencies, flows, and losses of typical dairy farming systems in Inner Mongolia

Dairy farming is a notable source of nitrogen (N) emissions, impacting both atmospheric and aquatic ecosystems, thus necessitating a detailed analysis of nutrient dynamics to curtail nutrient wastage. However, N flow variability and its environmental ramifications differ markedly among dairy farms, and a holistic understanding of these differences is lacking in Inner Mongolia, the biggest dairy production province in China. Utilizing data from 187 dairy farms and employing the NUFER-farm model, this study assessed N flows, N use efficiency (NUE), and N losses across four predominant dairy farming systems in Inner Mongolia. These systems include traditional pastoral dairy farms (PF), smallholder dairy farms with croplands (SF), industrial landless farms (IDF), and coupled dairy cattle and cropland-intensive farms (CDF). Our findings indicate considerable differences in N flows, NUE, and losses among the systems. On average, N deposition and N fertilizer were the primary N sources for PF and SF, respectively, whereas IDF and CDF derived over 90% of their N inputs from purchased feeds. PF and SF recycled all available manure N on-farm, whereas IDF and CDF recycled only approximately 36% of the total available manure N. N losses constituted 39–72% of total N outputs, with ammonia emissions accounting for 68–73% of total N losses across all farm types. In particular, PF had a higher N loss per kilogram of dairy product than other systems. Farm-level NUE ranged from 17 to 35%, with manure management practices showing significant variability, underscoring the potential for enhanced strategies to reduce N losses through improved manure treatment.

Effects of substrate temperature and bias voltage on mechanical and tribological properties of cosputtered (TiZrHfTa)Nx films

This study investigated the effects of substrate temperature and bias voltage on the mechanical and tribological properties of cosputtered (TiZrHfTa)Nx films. A substrate temperature ranging from room temperature to 400 °C, and a bias voltage ranging from 0 to −150 V were selected as the sputtering variables. A mixture gas with a nitrogen flow ratio (fN2 = N2/[N2 + Ar]) of 0.2 was used to fabricate nitride films. Nanoindentation and wear tests were conducted to assess the performance of the fabricated (TiZrHfTa)Nx films, which formed a single face-centered cubic structure. Increasing the substrate temperature resulted in grain growth, lattice shrinkage, and nonsignificant improvements in mechanical properties. Applying a bias voltage of −150 V to the substrate increased the hardness of the fabricated film to a peak of 32.7 GPa compared with that of 29.3 GPa for the film prepared in an electronically grounded state. The (Ti0.24Zr0.22Hf0.19Ta0.35)N0.66 film prepared at a bias voltage of 0 V and substrate temperature of 400 °C exhibited the optimal combination of mechanical and tribological properties (hardness, 30.0 GPa; elastic modulus, 325 GPa; and wear rate, 1.16 × 10−5 mm3/Nm).

Tracking Carbon and Ammonia Emission Flows of China's Nitrogen Fertilizer System: Implications for Domestic and International Trade.

China is the world's largest producer, consumer, and exporter of synthetic nitrogen (N) fertilizer. To assess the impact of domestic demand and international exports, we quantified the life-cycle CO2eq and ammonia (NH3) emissions by tracking carbon (C) and nitrogen (N) flows from coal/gas mining through ammonia production to N fertilizer production, application, and export. In 2020, China's N fertilizer system emitted 496.04 Tg of CO2eq and 3.74 Tg of NH3, with ammonia production and N fertilizer application processes contributing 36 and 85% of the life-cycle CO2eq and NH3 emissions, respectively. As the largest importers of N fertilizer, India, Myanmar, South Korea, Malaysia, and the Philippines collectively shifted 112.41 Tg of CO2eq. For every ton of N fertilizer produced and used in China, 16 t of CO2eq and 0.18 t of NH3 were emitted, compared to 9.7 t of CO2eq and 0.13 t of NH3 in Europe. By adopting currently available technologies, improving N fertilizer utilization efficiency and employing nitrification inhibitors could synergistically reduce CO2eq emissions by 20% and NH3 emissions by 75%, while energy transformation efforts would primarily reduce CO2eq emissions by 59%. The production of ammonia using green electricity or green hydrogen could significantly enhance the decarbonization of China's N fertilizer system.

Optimization of bio-oil production parameters from the pyrolysis of elephant grass (Pennisetum purpureum) using response surface methodology

Abstract The need to increase bio-oil yield from biomass and enhance its fuel properties has driven research into optimizing the pyrolysis process. This study investigated the influence of three key process parameters—temperature, heating rate, and nitrogen flow rate—on the pyrolysis of elephant grass (Pennisetum purpureum) in a fixed-bed reactor. Response surface methodology was used to study the impact of the aforementioned variables on bio-oil yield to improve its production efficiency. Proximate analysis of the biomass revealed 79.24 wt% volatile matter, 14.22 wt% fixed carbon, and 5.86% ash, with ultimate analysis showing 45.44% carbon, 5.59% hydrogen, and 40.95% oxygen. The high volatile matter content and favourable carbon and hydrogen percentages indicate that elephant grass is a viable energy source due to its potential for high bio-oil yield and energy content. The resulting bio-oil exhibited a higher heating value of 20.9 MJ/kg, indicating its suitability for various heating applications. A second-order regression model was developed for bio-oil yield, with optimal conditions identified as a temperature of 550°C, a heating rate of 17°C/min, and a nitrogen flow rate of 6 ml/min. The study achieved an optimal bio-oil yield of 59.03 wt%, and the model’s high R² value of 0.8683 from analysis of variance analysis confirmed its predictive accuracy. This research highlights elephant grass as a sustainable feedstock for bio-oil production, offering valuable insights into optimizing pyrolysis conditions to enhance bio-oil yield, thus advancing biofuel technology.

Investigation of mechanical morphological structural and electrochemical properties of PVD TiAlN coating: A detail experimental and its correlation with an analytical approach using the least square method

In this experimental investigation, a Physical Vapor Deposition (PVD) process was employed to deposit TiAlN coating onto a Si substrate. The nitrogen flow rate, bias voltage, and substrate-to-target distance were selected as input parameters, each with three different levels. The design of these input parameters was structured according to Taguchi's L9 Orthogonal Array (OA). Following deposition, the mechanical, microstructural, structural, and electrochemical properties of the TiAlN coating were meticulously characterized and analyzed to discern the influence of the selected parameters on its various properties. Microstructural analysis revealed a homogeneous structure throughout the film. Additionally, the mechanical properties of the film exhibited notable performance under the specified parameters. However, it was observed that no consistent trend could be identified across different properties concerning the applied parameters. To elucidate the complex relationships among these variables, the Least Squares Method (LSM) regression analysis technique was employed. This analytical approach facilitated the establishment of correlations among the diverse parameters, enhancing the understanding of their collective impact on the TiAlN coating properties. The understanding of analytical results will be useful for predicting the values between the two extremities to measure the performance parameters where the experimental results are not available.