Ammonia Flow Research Articles

Pathogenicity of CsRV2 and CdPBV1 in Callinectes danae: An Imminent Concern for Crab Production in Brazil.

Understanding the pathogenicity of viral infections in aquatic organisms is vital due to their substantial impact on aquaculture and wild populations. This study assessed the pathogenicity of Callinectes sapidus Reovirus 2 in Callinectes danae and its effects on the metabolic, immunological and behavioural parameters. CsRV2-negative specimens were divided into CsRV2 inoculum (n = 10) and saline injection (n = 15). After 14 days, all the crabs that received the inoculum tested positive for CsRV2. However, 11 crabs from the control group also tested positive and were subsequently considered an additional experimental group. The cumulative mortality in the group challenged reached 70% after 14 days. RT-PCR revealed Callinectes danae Portunibunyavirus 1 presence in CsRV2-injected crabs, explaining heightened mortality. Ammonia flow remained unaffected, but oxygen consumption was significantly impacted (p < 0.05) by CsRV2 and coinfection, suggesting increased metabolic energy expenditure. The coinfection caused an increase in the proportion of crabs with reflex impairment as a likely consequence of physiological exhaustion. Additionally, there was a trend toward reducing the number of granulocytes in coinfected crabs, indicating that granulocytes may be more affected by coinfection. These findings demonstrate the pathogenicity of CsRV2 in C. danae, with coinfection exacerbating metabolic, behavioural and immunological changes, increasing mortality.

Simulation study on the cavitation flow characteristics of liquid ammonia in the nozzle under high-pressure injection conditions

In this study, a non-isothermal compressible cavitating flow simulation model for liquid ammonia in high-pressure injector, accounting for the phase change properties, was established. The model was validated using experimental data from existing literature. The cavitation phase change process of liquid ammonia within the injector nozzle was investigated, and the differences in cavitation distribution between ammonia and diesel were explored. The results indicate that with increasing injection pressure, the vapor volume fraction of ammonia increases linearly, while that of diesel fuel shows a rapid initial rise followed by a decelerating trend. In terms of flow coefficient, ammonia is lower than diesel, though the two values converge at higher injection pressures. Under low injection pressure, the heat absorbed by the cavitation phase change of ammonia exceeded the heat generated by the high-speed friction of ammonia flow against the nozzle wall, leading to a temperature drop at the nozzle inlet. Conversely, at high injection pressure, the temperature of ammonia on the nozzle wall increases by more than 20 K, resulting in a rapid rise in saturated vapor pressure and significantly intensifying the cavitation effect. Compared to ammonia, diesel experienced a higher temperature rise within the nozzle but exhibited smaller variations in saturated vapor pressure, making the temperature effect on cavitation less pronounced. Diesel’s higher density and viscosity resulted in lower flow velocities compared to ammonia, leading to more developed cavitation in the lower wall region of the nozzle and creating a higher pressure region on the upper wall of the nozzle, which was more distant from the nozzle inlet and inhibited cavitation development there. The research results provide theoretical support for the design of liquid ammonia injectors.

Position-dependent degradation and damage mechanisms of Inconel 600 in an ammonia gas flow environment at elevated temperatures

With an aim to use ammonia as a direct fuel in gas turbines, an investigation on the degradation of materials used in the turbine components in the ammonia flow environment is important. The present work investigated the surface reaction and degradation of Inconel 600 placed at different positions inside a furnace in the direction of ammonia flow at 400 °C to 600 °C. Severe surface damage and degradation was identified. The effect of specimen position on the extent of degradation and the damage mechanisms were elucidated utilizing XRD, TEM, and Optical Emission Spectroscopy (OES).

Ammonia adiabatic two-phase flow patterns in the horizontal tube

The manuscript reports the experimental study results dealing with the ammonia two-phase flow pattern observations in the transparent horizontal tube of ID 7.5 mm with a saturation temperature of 15 to 65°C, mass velocity of 50 to 160 kg·m−2s−1 and vapour quality of 0.1 to 0.8. Stratified-wavy, annular-wave and annular smooth patterns have been identified based on analyses of camera images. The annular-wavy pattern was not distinguished in the previous ammonia studies at low saturation temperatures (Lima et al., 2009; Gao et al., 2021). Transitions between stratified-wavy and annular-wavy and between annular-wavy and smooth annular patterns occur at constant interfacial vapour momentum flux. This observation aligns with Hewitt and Roberts's (1969) suggestions for vertical steam-water flows. It does not match the existing iterations of Taitel and Dukler's (1976) map, which accurately predicts the transition of HFC fluids and partly the low-temperature ammonia tests. Implementing newly developed transitions between the two-phase ammonia flow patterns in the horizontal tubes updated and validated the existing hydraulic and heat transfer correlations. The most significant among them is an update to the Müller-Steinhagen and Heck's (1986) model in predicting adequately the ammonia frictional pressure losses in the horizontal tube for the broad range of boundary conditions.

Ammonia two-phase flow patterns and condensation in the inclined smooth tubes

The paper reports the experimental study of the two-phase ammonia flow patterns and condensation in the upward and downward inclined tubes. The two-phase patterns have been studied by the photography method in the transparent quartz tube of ID 7.5 mm at the inclination of −90 to 90°, saturation temperature of 35–65 °C, mass velocity of 40–160 kg m−2 s−1 and vapour quality of 0.1–0.8. The Hewitt and Roberts (1969) [19] upward pattern map in interfacial momentum flux coordinates compiled for the high-pressure steam water flows was compared with the obtained ammonia patterns, showing satisfactory qualitative correspondence. However, the transition lines quantitatively are not accurate for ammonia, especially in churn-to-slug cases. Matching the two-phase patterns and ammonia condensation HTC identified in the prior study for the smooth tubes of ID 8 and 11 mm, a so-called forced convective condensation (flow velocity dependent) domination line has been clearly shown for the upward and downward flows. This line splits the boundary conditions, providing similar condensation HTC for the horizontal and upward/downward flows independently on the expected pattern and with the essentially reduced HTC at the upward/downward configuration. The existence of the HTC maximum for the ammonia flow at the inclination of −30° was proved and quantified experimentally for the broad range of boundary conditions in the ID 8 and 11 mm tubes. Matching the identified condensation HTC and the observed flow patterns allows us to conclude that the condensation HTC maximum is mainly determined by the change of stratified-wavy pattern on a smooth stratified one.

A novel solar tower simulator for hydrogen regeneration by thermo-catalytic cracking of Ammonia: Energy, Exergy, and CFD investigations

This paper presents a novel concept of a central solar tower-based hydrogen regeneration system by thermo-catalytic cracking of ammonia. This includes a closed volumetric receiver for ammonia heating and cracking, a 2.45 kWe high-concentration radiation source, and an air-cooling system for the radiation source. The thermodynamic analysis shows that the net solar-to-hydrogen generation efficiency, first law efficiency, and exergy efficiency are 31 %, 82 %, and 79.8 %, respectively, for the optical efficiency of 35 %, the conversion efficiency of 99 %, and the waste heat recovery fraction of 20 %. The simulations with an ammonia flow rate of 1 kg/hr and flux concentration of 1200 Suns show the regeneration of 1.27 kg H2/day at Jodhpur and 1.57 kg H2/day at Ladakh. Monte Carlo ray tracing simulations revealed that the developed radiation source provides an average flux of ∼ 2 MW/m2 onto a spot size of 20 mm with an efficiency of about 31 %. Reynolds-averaged Navier Stokes-based analyses are used to design a novel air-cooling system for the radiation source. The computations show that (a) an unequal distribution of air mass flow rates at the front mḟ and back mḃ, should be preferred with mḟ>mḃ, and (b) for a total mass flowrate of 0.1 kg/s with mḟmḃ = 4, the maximum surface temperature of reflectors and Xe-arc lamps is less than 315 K and 610 K, respectively. The investigations revealed the feasibility of the concept and provided valuable insight for the planned experimental assessment and scale-up of the solar tower simulator.

On Morphology of Aluminum-Gallium Nitride Layers Grown by Halide Vapor Phase Epitaxy: The Role of Total Reactants' Pressure and Ammonia Flow Rate.

The focus of this study was the investigation of how the total pressure of reactants and ammonia flow rate influence the growth morphology of aluminum-gallium nitride layers crystallized by Halide Vapor Phase Epitaxy. It was established how these two critical parameters change the supersaturation levels of gallium and aluminum in the growth zone, and subsequently the morphology of the produced layers. A halide vapor phase epitaxy reactor built in-house was used, allowing for precise control over the growth conditions. Results demonstrate that both total pressure and ammonia flow rate significantly affect the nucleation and crystal growth processes which have an impact on the alloy composition, surface morphology and structural quality of aluminum-gallium nitride layers. Reducing the total pressure and adjusting the ammonia flow rate led to a notable enhancement in the homogeneity and crystallographic quality of the grown layers, along with increased aluminum incorporation. This research contributes to a deeper understanding of the growth mechanisms involved in the halide vapor phase epitaxy of aluminum-gallium nitride, and furthermore it suggests a trajectory for the optimization of growth parameters so as to obtain high-quality materials for advanced optoelectronic and electronic applications.

Supported chromium nitride: A new catalyst for oxidative desulfurization of liquid fuel

Desulfurization of fuel is very important for our sound health and environment; oxidative desulfurization (ODS) can be one of the solutions. In this work, ODS or oxidation of thiophenic S-compounds was done firstly with a CrN catalyst, dispersed on carbon, which was prepared via pyrolysis of a MOF (composed of Cr2O3 and melamine), even without ammonia flow. Of note, ODS has been very seldom studied with Cr-based catalysts, so far. One CrN@carbon (named CrN@C-6) was highly effective in ODS with very low Ea (which is not far from that of simple diffusion in the liquid phase). Additionally, the catalyst showed rapid kinetics even at low temperatures (for example, 96 % of dibenzothiophene (1000 mg/L) was oxidized in 30 min at 60 °C; 83 % dibenzothiophene oxidation was possible at 30 °C in 60 min). The oxidation mechanism over the CrN@C-6 catalyst was interpreted with radical scavengers and electron spin resonance; the ODS was carried out through a non-radical mechanism probably through Cr-peroxo species. Calculation also supported that the Cr-nitride was more effective than Cr-oxide (that can be a representative Cr-based catalyst for ODS) in both H2O2 adsorption and ODS. The effective ODS catalysis could be explained with the contribution of well-dispersed active CrN with the electronegative nitrogen atom of the CrN and the high porosity of the catalyst. Finally, the invented CrN@C-6 can be suggested as a promising catalyst for ODS based on its remarkable activity even at low temperatures and ready recyclability (after simple solvent washing).

In-situ synthesis of BN/Al18B4O33 heterogeneous core-shell nanowires with different BN shell thicknesses and the microstructure evolution mechanism

A simple method was developed for the controllable synthesis of novel BN-coated aluminum borate (Al18B4O33) heterogeneous core-shell nanowires using Al4B2O9 nanowhiskers as rigid templates. This method allows the fabrication of Al18B4O33 nanowires with BN coatings of different thicknesses. The phases, microstructures, and chemical compositions of the samples were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and other characterization techniques. The heterogeneous core-shell nanowires of BN/Al18B4O33 had diameters and tube lengths of 35–60 nm and 400–600 nm, respectively, and the thickness of the BN cladding shell was between 2 and 7 nm. The concentration of B* volatilized on the whisker surface could be controlled by varying the ammonia flow rate, which in turn regulated the thickness of the BN cladding layer. The thickness of the BN cladding changed more significantly when the ammonia flow rate was varied at the Al4B2O9 nanowhisker's decomposition temperature. The experimental results show that the BN on the BN/Al18B4O33 heterogeneous core-shell structured nanowires conforms to the vapor–solid (VS) growth mechanism.

Dapagliflozin Stimulates Renal Ammonia Excretion in Rats

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are drugs that induce glycosuria and are used to treat type 2 diabetes mellitus, moreover it has also been used in other conditions such as heart failure and atherosclerosis. However, little is known about the effects of these drugs on renal function. Considering that the maintenance of acid-base balance is closely related to renal physiology, in this study we evaluated the influence of chronic use of dapagliflozin on global renal function and urinary excretion of ammonia and titratable acids. Objective: To evaluate global renal function and urinary acid excretion (ammonia and titratable acid) in male Wistar rats chronically treated with dapagliflozin. Methods: 3-month-old male Wistar rats were randomized to control (C) and dapagliflozin (D) groups. Animals in group D received dapagliflozin (3 mg/kg, gavage) for 4 weeks. All animals were given food and water ad libitum throughout the experimental protocol. At 4 months of age, animals were placed in metabolic cages for 24-hour urine collection followed by blood sampling. Plasma concentrations of creatinine, sodium, potassium, urea, pH, pCO2, and bicarbonate were evaluated. The following were also evaluated: body weight, water intake, urine flow, and excretion of ammonia, titratable acids, glucose, and protein. Protocol approved by CEUA-UNIFESP number: 5985180423. Values expressed as mean ± standard error; number of animals per group: 6. Results: No significant changes were observed in blood gas parameters: pH (C: 7.33±0.043; D: 7.36±0.027), pCO2 (C: 53.30±2.40; D: 52.67±3.63 mmHg) and HCO3− (C: 27.07±1.31; D: 29.75±1.72 mEq/L) and no significant changes in plasma creatinine concentration (C: 0.41±0.04; D: 0.40±0.04mg/dl), Na+ (C: 144±0.47; D: 137±2.04 mmol/l) and K+ (C: 4.30±0.21; D: 4.16±0.20 mmol/l). We observed a significant increase in urine flow (C: 0.027±0.006; D: 0.068±0.005 mL/min/kg), possibly associated with intense glycosuria (C: 0.017±0.005; D: 8.97±0.51 g/24h). The significant increase in plasma urea concentration (C: 39.17±2.57; D: 48.83±1.27 mg/dL) and proteinuria (C: 11.04±0.30; D: 15.79±0.56 mg/24h) may indicate some renal impairment. Considering the marked increase in urinary excretion of ammonia (C: 0.65±0.05; D: 3.49±2.31 mEq/24h) and titratable acids (C: 0.180±0.036; D: 0.628±0.078 mEq/24h), we can conclude that the drug-induced glycosuria may lead to biochemical adaptations to maintain blood glucose levels within the normal range, at the expense of increased metabolic acid production. However, further experiments are needed to confirm this hypothesis. CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Ammonia-enriched biogas as an alternative fuel in diesel engines: Combustion, performance and emission analysis

This study investigates the potential of ammonia as a secondary fuel in diesel engines, amidst the rising interest in alternative fuels and the growth of electric vehicles. Unlike hydrogen, with its higher flammability and safety concerns, ammonia offers a viable, sustainable fuel source. A single-cylinder diesel engine was utilized to assess engine performance and combustion characteristics using ammonia gaseous blends. Ammonia was combined with biogas to mitigate its corrosive effects and compensate for its lower heating value. Th entire best conducted with constant ammonia flow rate of 30 LPM. Diesel was mixed with biogas in compositions of 10 LPM, 20 LPM and 30 LPM, and tested under engine loads of 25%, 50%, 75%, and 100%. The blend with the highest ammonia concentration (B30B3) exhibited the largest heat release rate, highlighting a strong correlation between ammonia content and heat release levels. This is attributed to the premixed combustion phase and the accelerated flame speed associated with ammonia. An increase in ammonia content resulted in higher brake thermal efficiency and reduced brake specific fuel consumption. All ammonia-inclusive blends showed a decrease in hydrocarbon and carbon monoxide emissions, with the lowest emissions observed in the B30B3 blend. However, the high flammability of biogas in the B30B3 blend, compared to diesel, and enhanced fuel atomization, led to increased nitrogen Oxides formation. The results clearly indicate that combination of ammonia along with the biogas enhances the combustion and reduces greenhouse gas emissions. Findings of this study provides valuable insights into the use of ammonia as a sustainable alternative in diesel engines, offering a improved balance between combustion efficiency and environmental impact.

Enhancing the blue GaN laser diodes by modifying the first barrier structure and adjusting the growth conditions of quantum wells

The structure of the first barrier (FB) of quantum wells was modified from the single-layer GaN to the GaN-InGaN-GaN composite structure. Experiments have shown that the composite first barrier can improve the crystal quality of the quantum wells, which increase the luminous power and reduce the stress accumulation before the InGaN quantum well. Furthermore, the composite first barrier can reduce the polarized electric fields and suppress the impact of quantum confinement Stark effect (QCSE) on the luminescence properties of the quantum wells. The growth conditions of the InGaN/GaN quantum wells were studied. Both the growth rate and the ammonia flow are related to the incorporation of In in InGaN quantum wells and the formation of In clusters. These two parameters have optimal values when the other one is fixed. After optimizing the growth rate and the ammonia flow, the internal quantum efficiency of the quantum wells was finally improved from 24.14 % to a commercial level of 77.2 %.

Ammonia single-phase and two-phase frictional pressure losses in horizontal smooth and straight inner-grooved tubes

The experimental study of single-phase and two-phase frictional pressure losses has been performed with ammonia flow in stainless steel smooth tubes (internal diameter of 5.5 mm and 8.5 mm) and six straight inner-grooved aluminium tubes with different nominal diameters (7.15 to 13.3 mm), length (0.45 to 2.0 mm) and thickness (0.35 to 0.8) of fins. Single-phase test boundary conditions correspond to Reynolds numbers of 1000 to 20,000. Two-phase tests have been carried out at saturation temperature of 45 to 65 °C, mass velocity of 50 to 210 kg·m−2s−1 and vapour quality of 0.1 to 0.9. Comparison of obtained test data with the existing frictional losses approaches shows that the Blasius model is appropriate to single-phase flows in smooth tubes, and Müller-Steinhagen and Heck's (1986) model is most accurate in predictions of two-phase frictional losses in smooth tubes. Existing approaches of single-phase frictional pressure loss predictions in the pipes and channels with longitudinal fins (Carnavos, 1980; Edwards and Jensen, 1994) are not adequately suited to the ammonia test points obtained in the considered straight inner-grooved tubes. A new semi-empirical model has been proposed, based on generalisation around the revealed geometric dimensionless factor, which accurately describes friction pressure losses in the considered inner-finned profiles. The simplest homogeneous model for defining two-phase friction pressure losses, using McAdams et al.'s (1942) recommendation for mixture dynamic viscosity definition and a new model of single-phase friction factor, best fit both quantitatively and qualitatively to ammonia two-phase test points in most of the considered straight inner-grooved tubes.

Development of a smart powering system with ammonia fuel cells and internal combustion engine for submarines

The current limitations of hydrogen storage technology in submarines have prompted the need for alternative solutions. One promising option is the use of ammonia, a readily stored fuel. This paper presents an innovative, integrated system that runs on ammonia and does not rely on atmospheric air. The system combines Direct Ammonia Fuel Cell (DAFC) stack and an Internal Combustion Engine (ICE) technology to generate power, freshwater, and cooling. The system also recovers waste heat and utilizes it efficiently to produce these useful outputs. The study further aims to assess the system's performance using energy and exergy analysis methods and to conduct a parametric analysis to examine the impact of parameters and operating conditions on system efficiency. In the developed integrated system, the quantities of net power produced, cooling provided, and freshwater flow rate produced under specified conditions are 4069 kW, 589.5 kW, and 1.269 kg/s, respectively. Its energy and exergy efficiency were found to be 38.58% and 44.77%, respectively. The analysis study also obtains that increasing the ammonia flow rate supplied to the ICE and the steam flow rate provided to the turbine, as well as the reference temperature, could potentially improve both energetic and exergetic efficiencies.

A Hydrogen Production System Based on Ammonia Combustion Heat: Graded Decomposition and Parameter Analysis

This study introduces a hydrogen production system that utilizes the heat from ammonia combustion for graded decomposition. About 17% of the ammonia undergoes combustion to provide heat for the subsequent decomposition of the remaining ammonia. To enhance economic efficiency and reduce costs, a design combining precious and non-precious metals is employed, aiming to decrease the usage of precious metal catalysts without compromising decomposition efficiency. Considering the required temperatures for the two catalysts, high and low-temperature decomposers are established to achieve cascaded energy utilization in the flue gas. The preheating temperature of ammonia before entering the decomposer plays a crucial role in both ammonia decomposition efficiency and the system’s fuel consumption. Following optimization, the system yields 493.6kg/h of hydrogen with an inlet ammonia flow rate of 4000kg/h. Concurrently, the discharge temperature of the flue gas decreases to 378.59K, effectively utilizing a substantial portion of the energy. This study introduces a novel approach to designing an ammonia decomposition system using ammonia combustion as a heat source, and it serves as a reference for subsequent optimization.

Nitrogen-doped carbon nanotubes for self-powered memristive systems

Memristive devices are one of the promising candidates for creating neuromorphic systems due to the possibility of multilevel switching, low operating voltages and high scalability. However, as with any passive element, the memristor requires an external bias voltage to operate, which requires the inclusion of a power source in the circuit. In this regard, of great interest are works on the creation of self-powered memristive systems consisting of connecting in series a memristor and a nanogenerator that converts the energy of the external environment into electrical energy [1, 2]. Such a memristive system has a high potential for applications in aerospace and implantable electronics. At the moment, the first self-powered memristive and sensor systems based on metal oxides and piezoelectric nanogenerators (PENG) have already been developed [2]. The main problems in this area are to reduce the size of the nanogenerator and to match the output parameters of the nanogenerator and the input parameters of the memristor. In the framework of this work, these problems are being resolved by creating a self-powered memristive system based on nitrogen-doped carbon nanotubes (N-CNTs). Previously, we studied the memristive properties of N-CNTs and showed that nanotubes demonstrate reproducible multilevel switching with a resistance ratio in the high- and low-resistance states (HRS/LRS) of about 4⋅105 [3, 4]. It was found that the memristive effect in N-CNTs is due to the incorporation of nitrogen atoms into the nanotube structure and the formation of an internal piezoelectric field [4]. As part of further studies, it was found that an array of vertically aligned N-CNTs is a promising material for creating PENG: the generated output voltage is hundreds of mV and the current generated by single nanotube reaches hundreds of nA [5]. The results obtained allow us to speak about the possibility of developing a self-powered memristive system by connecting in series a memristor and PENG based on N-CNTs. To optimize the output characteristics of the PENG, in particular, the amplitude of the generated voltage, and the input switching voltage of the N-CNT-based memristor, studies were carried out to increase the piezoelectric response and reduce the switching voltage of the N-CNT resistance by changing the concentration of the dopant nitrogen in the nanotube growth process. It was found that it is necessary to grow N-CNTs with a doping nitrogen concentration of up to 12% and a high aspect ratio of length to diameter (more than 60) to create PENG with an output voltage of up to 2 V. These N-CNT parameters are provided at a low growth temperature (500–550 C°) and high ratio of acetylene and ammonia flows (1:5 - 1:6). On the contrary, the N-CNTs with a small aspect ratio (less than 30) and doping nitrogen concentrations of 4–6% are required for the manufacture of memristors with a minimum switching voltage (about 2 V), These N-CNT parameters are provided by increasing the growth temperature to 615 C° and reduction in growth time. The obtained results can be used in the development of self-powered memristive and sensor systems based on nitrogen-doped carbon nanotubes.

Control of nitrogen defects in carbon nanotubes for self-powered memristive systems

Recent studies show that the additional introduction of heteroatoms into the structure of CNTs makes it possible to change their electronic and physical properties [1]. Of great interest is the process of doping CNTs with nitrogen atoms [2]. The introduction of nitrogen defects into a lattice of carbon atoms makes it possible to modify the CNT structure up to the demonstration of anomalous properties that are not appropriate for this material [3]. It has been shown that multi-walled N-CNTs can exhibit memristive and piezoelectric properties [4]. The parameters of CNTs during synthesis can be controlled by the plasma enhanced chemical vapor deposition (PECVD) method. The addition of ammonia (NH3) to the carbonaceous gas in the PECVD process allows CNTs to be doped directly during growth. At the same time, the dopant concentration and the type of nitrogen defects have a significant effect on the properties of CNTs. The memristive properties of CNTs have already been sufficiently studied [5], however, for their application in self-powered systems, additional studies of the parameters of the piezoelectric module of N-CNTs are required. The aim of this work is to study the effect of ammonia flow on the concentration, type of nitrogen defects, and the value of the piezoelectric modulus during growth of CNTs by the PECVD. Silicon (100) substrates were used as samples with films of a buffer (Mo, 100 nm) sublayer and a catalytic layer (Ni, 15 nm). CNTs were grown at a temperature of 550 °C in an atmosphere of acetylene (C2H2, 35 sccm) and NH3. The C2H2 flow was kept constant, while the NH3 flow was changed in the C2H2:NH3 ratio from 1:1 to 1:10. Based on the obtained SEM images, it was found that with an increase in the ratio of C2H2:NH3 flowes, an increase in the density of nanotubes in the array were observed. This occurs due to more active growth of N-CNTs on small nickel catalytic centers due to the accelerated process of hydrogen desorption and its binding with ions in ammonia plasma, which leads to an increase in the growth rate of nanotubes on smaller catalytic centers. Thus, the area of the catalytic center is one of the limiting factors of the growth rate and allows one to control the aspect ratio and density of CNTs in the array. An analysis of the XPS spectra showed that with an increase in the ratio of C2H2:NH3 flows from 1:1 to 1:10, a nonlinear change in the concentration of the nitrogen dopant in N-CNTs from 8.4 to 12 at % is also observed. This led to a nonlinear change in the piezoelectric modulus of nanotubes from 8.7 to 20.6 pm/V and a change in their memristive properties. It has been established that an increase in the concentration of doping nitrogen leads to an increase in the piezoelectric modulus of N-CNTs, which is the source of the memristive effect. The obtained results can be used in the development of energy-efficient piezoelectric nanogenerators based on an array of vertically aligned N-CNTs for autonomous memristive systems.

Pulsed-Mode Metalorganic Vapor-Phase Epitaxy of GaN on Graphene-Coated c-Sapphire for Freestanding GaN Thin Films.

We report the growth of high-quality GaN epitaxial thin films on graphene-coated c-sapphire substrates using pulsed-mode metalorganic vapor-phase epitaxy, together with the fabrication of freestanding GaN films by simple mechanical exfoliation for transferable light-emitting diodes (LEDs). High-quality GaN films grown on the graphene-coated sapphire substrates were easily lifted off by using thermal release tape and transferred onto foreign substrates. Furthermore, we revealed that the pulsed operation of ammonia flow during GaN growth was a critical factor for the fabrication of high-quality freestanding GaN films. These films, exhibiting excellent single crystallinity, were utilized to fabricate transferable GaN LEDs by heteroepitaxially growing InxGa1-xN/GaN multiple quantum wells and a p-GaN layer on the GaN films, showing their potential application in advanced optoelectronic devices.

Recent Research on Indium-Gallium-Nitride-Based Light-Emitting Diodes: Growth Conditions and External Quantum Efficiency

The optimization of the synthesis of III-V compounds is a crucial subject in enhancing the external quantum efficiency of blue LEDs, laser diodes, quantum-dot solar cells, and other devices. There are several challenges in growing high-quality InGaN materials, including the lattice mismatch between GaN and InGaN causing stress and piezoelectric polarization, the relatively high vapor pressure of InN compared to GaN, and the low level of incorporation of indium in InGaN materials. Furthermore, carrier delocalization, Shockley–Read–Hall recombination, auger recombination, and electron leakage in InGaN light-emitting diodes (LEDs) are the main contributors to efficiency droop. The synthesis of high-quality III-V compounds can be achieved by optimizing growth parameters such as temperature, V/III ratios, growth rate, and pressure. By reducing the ammonia flow from 200 sccm to 50 sccm, increasing the growth rate from 0.1 to 1 m/h, and lowering the growth pressure from 250 to 150 Torr, the external quantum efficiency of III-V compounds can be improved at growth temperatures ranging from 800 °C to 500 °C. It is crucial to optimize the growth conditions to achieve high-quality materials. In addition, novel approaches such as adopting a microrod crystal structure, utilizing the piezo-phototronic effect, and depositing AlN/Al2O3 on top of the P-GaN and the electron-blocking layer can also contribute to improving the external quantum efficiency. The deposition of a multifunctional ultrathin layers of AlN/Al2O3 on top of the P-GaN can enhance the peak external quantum efficiency of InGaN blue LEDs by 29%, while the piezo-phototronic effect induced by a tensile strain of 2.04% results in a 183% increase in the relative electroluminescence intensity of the LEDs. This paper also discusses conventional and inverted p-i-n junction structures of LEDs.

426 Forages Containing Plant Secondary Compounds Can Improve Digestibility, Rumen Ammonia and Rumen Metabolites of Pasture: an in Vitro Continuous Culture Case Study

Abstract Forages containing plant secondary metabolites (PSM) have been investigated for use in reducing nitrogen waste in feedlot and dairy cattle diets but use as supplements to grazing beef cattle to capture the positive effects of PSM is unclear. Here we investigate potential improvement in rumen digestibility and metabolome, rumen ammonia production and flow from feed protein due to PSM bioactivity in forages used to supplement pasture grass using in vitro methods. Can PSM-containing forages offer a practical way to improve range nutrition and provide delivery of phytochemical benefits? Phytochemical- containing forages birdsfoot trefoil (BFT), sainfoin (SAN), small burnet (SMB) and cicer milkvetch (CMV) supplemented grass pasture diets (200 g/kg of DM). In vitro true dry matter digestibility was determined using 2-stage in vitro methods. Randomly assigned diets of PAS supplemented with one of the PSM-containing forage diets (PAS+X) or not supplemented (PAS) were randomly applied to in vitro dual flow continuous culture (CC) vessels inoculated with grazing beef cow rumen fluid as a metabolic host. For 2-stage digestibility, SMB digestibility exceeded that of CMV, followed by BFT and SAN. The grass diet (PAS) was the least digestible (Table 1). Saponin was detected in CMV samples, which is a new finding. For CC, compared with PAS, minimum culture pH for PAS+CMV was highest (P &amp;lt; 0.02) but no differences were observed in pH between PAS, and PAS+BFT and PAS+SAN. Compared with PAS, the molar proportion of the fatty acid propionate increased with PAS+CMV(P = 0.03) in contrast to the acetate- to- propionate ratio found highest for PAS and decreased for all diets with supplementation of PSM forages. Concentration of rumen NH3–N flow to rumen fluid per gram of protein intake was lower (P &amp;lt; 0.01) with PAS+CMV and PAS+SMB, compared with grass only. Feeding CMV and SMB to grazing cattle may improve nutrient utilization, metabolome, and environmental sustainability of beef cattle production by improving diet digestibility and reducing ammonia waste.