Papers by Keyword: Nitrous Oxide

Abstract: The AQUASONIC project is aimed to develop a sounding rocket including a hybrid propulsion system based on the propellant combination nitrous oxide and polyethylene. It takes place in the frame of the STERN (Student Experimental Rockets) programme founded by the German Space Agency (DLR) in order to promote students in the area of launch vehicles. Main element of the project is the AQUASONIC rocket, which shall reach a flight altitude of 5-6 km and a velocity of MACH 1. All major activities like design, manufacturing, verification and, finally, the launch campaign will be performed by students. The rocket shall be launched at Esrange Space Centre (Sweden) in 2016. Thus, students are able to apply their skills and knowledge to a real project like it is conducted by the space industry or research organisations.

Abstract: Nitrous oxide has recently entered violently the arena of space propulsion and gained interest, due to its high energy and gasification potential and despite its low oxygen content as an oxidizing chemical and its instability over some 600 C. However, its physical and chemical instability soon proved to be a potential hazard and led to a renewed interest in the study of its behavior as a fluid. In the present contribution computer simulation of the liquid phase flow of the nitrous oxide under high pressure is used to predict and avoid the cavitation into the feeding line tract of rocket engines, specifically of the compound rocket engines feeding line. The method involves a substantially simplified 1-D description of the fluid motion with sufficiently accurate determination of cavitation risk where the feeding duct suffers blunt variations of the cross area or steep turns and corners involving sensible static pressure variations of the fluid. A means of avoiding dangerous behaviors of the nitrous oxide is thus developed that could increase safety margins during the handling of this quite unpredictable oxidizer for the compound, combined or hybrid rocket engines.

Abstract: In this work, effects of post-deposition annealing (PDA) time (15, 30, and 45 min) in nitrous oxide ambient on Y₂O₃ film deposited on Si substrate using RF-magnetron sputtering have been systematically studied. Y₂O₃/Si system subjected to PDA time at 15 and 30 min has demonstrated a negative flatband voltage shift but a change to positive flatband voltage shift was observed when PDA time was prolonged to 45 min. The shift from negative to positive flatband voltage with enhancement of PDA time could be related to the accumulation of nitrogen in the Y₂O₃ gate that acted as negatively trap charge. It was perceived that sample subjected to PDA time at 30 min has demonstrated the best leakage current density-breakdown voltage (J-V_B) characteristic. A correlation between the J-V_B characteristics with effective oxide charge, slow trap density, interface trap density, and total interface trap density has been discussed.

Abstract: In this work, structural, optical and electrical properties of nitrogen doped (N-doped) cupric oxide (CuO) thin films deposited on <100> orientated n-type silicon, glass and polyethylene terephthalate substrates using reactive radio frequency sputtering system were investigated. X-ray diffraction results revealed that all films exhibited monoclinic CuO(-111) and have only slightly different structural properties for various substrates. Field effect scanning electron microscopy shown N-doped CuO on Si and glass are denser than on PET substrates and all have nanotriangle-like structure morphologies. The N-doped CuO thin films have an indirect band gap of around 1.30 eV. The resistively, carrier concentration and hall mobility of the N-doped CuO thin film on glass were 1.05 kΩ.cm, 6.70 x 10¹⁴ cm^-3 and 8.86 cm²/V-s respectively. Furthermore, palladium formed ohmic contact characteristics for N-doped CuO on glass and PET but exhibited schottky contact characteristics for N-doped CuO on Si.

Abstract: In this paper, hexaaluminate oxides LaMAl₁₂O_19-σ were prepared by using M=Cu ,Ce and Zn as active components to substitute Al in the hexaaluminate lattice by co-precipitation method. The structure and properties of LaMAl₁₁O_19-σ catalyst was characterized with XRD and BET. The results showed LaCuAl₁₁O_19-σ exhibited significant high catalytic activity for the decomposition reaction of N₂O. Under the simulated in situ condition, LaCuAl₁₁O_19-σ also indicated significant catalytic activity and stability, with N₂O conversion of 90% at 635°C.

Abstract: N2O emissions have been increasing in recent years due to intensive agricultural practices. This study was conducted to evaluate N2O emissions from a subtropical paddy field of south China with closed static chamber and a gas chromatograph in situ in the second crop season. Gas samples were taken simultaneously from rice-involved and rice-free plots. It showed that diurnal variation of N2O emission was more regular at the booting stage. The diurnal mean N2O flux of rice-involved plot was higher than that of rice-free plot during flooding time but lower during the drying time. It showed no significant correlation between N2O flux and temperature. The N2O flux was affected by soil water regime. Rice paddy field in growing season is a N2O source to atmosphere.

Abstract: The decompositon of ethylenediamine (EDA) in supercritical water oxidation (SCWO) were investigated. The experiments were conducted in an isothermal and vertical continuous plug-flow reactor at 375-500°C, 25 MPa, residence time of 2-80 s, and excess oxygen of 150%. It was found that yields of nitrous oxide, nitrogen, and the denitrification rate increased as temperature and residence time increased. The kinetics for denitrification of EDA was described by a rate law involving first order reaction. The results calculated from kinetics equation reconciled the experimental data.

Abstract: Nitrous oxide (N₂O) is the fourth most prevalent greenhouse gas in the atmosphere after carbon dioxide (CO₂), methane (CH₄), and water vapor. This gas contributes most significantly to global warming since it decomposes with great difficulty in the atmosphere, even in low concentrations. Emissions of N₂O gas are known to have an impact 310 times greater than the impact of CO₂ on global warming. According to the Intergovernmental Panel on Climate Change, N₂O concentration in the atmosphere has increased by 46 ppb (17%) since 1750, and continues to increase. A biofilter works by draining the contaminated air flow through a porous medium in which contaminants in the air flow are adsorbed by biofilms; these contaminants are then oxidized to produce biomass, CO₂, H₂O, nitrate (NO₃^-), and sulfate (SO₄^2-). In addition, the biofilter supports the growth of microorganisms present in the porous medium. This research was conducted to investigate the performance of two types of a compost-based filter medium in 9 hours N₂O biofiltration, with N₂O flow rate variations and variations in water content levels of the filter medium. A biofiltration experiment was conducted to evaluate the effects of selected parameters on N₂O removal efficiency. The results showed that goat manure-based compost was more effective in reducing N₂O compared with cow manure-based compost, with the highest efficiency of 70.1%.

Abstract: _{Subscript text}The kinetic model for simulating the mechanism of the promoted effect of methanol on the NOxOUT process has been established and it mainly includes the optimal sub-mechanisms respectively for the NOxOUT process and the chemical reaction of methanol. The oxygen concentration does not obviously influence the maximum NO reduction efficiency in the range of 1-6 %, but the temperature window is overall shifted to lower temperature zone with oxygen concentration increased. Meanwhile, the mole ratio of urea to nitric oxide by a factor of 2 should be maintained between 1.5 and 2 from both the efficiency and running cost view. Also, ample residence time of 300/T-400/T s must be guaranteed for the reduction occurring thoroughly. Methanol does not compromise the maximum NO reduction efficiency and broadens the temperature window towards low temperature zone. The promoted mechanism of methanol on the NO_xOUT process is the abundant OH formation through the methanol regenerative reaction of CH₂OH/CH₃O+H2O=CH₃OH+OH and methanol should be maintained at 50-100 ppm for an obvious promoted effect. During the co-injection of methanol and urea, the “ammonia slip” is depressed, especially at 1173 K where the promoted effect on NO reduction is obvious, but emission of nitrous oxide is also markedly increased at this temperature.

Abstract: SiC power MOSFETs are attractive electronic power switches for innovative power supply and motor drive solutions. The paper discusses this statement and specifies market segments offering the best chances for a commercialization. Due to well-known difficulties in achieving adequate channel conductivity, a lot of SiC-MOSFET publications focus on the channel mobility. However, for a power MOSFET this is only one important parameter affecting the performance. Other characteristics have to be considered too for an honest evaluation: transfer characteristics and blocking capability over the standard operation temperature range, handling of gate oxide stress and related reliability issues, capability of paralleling, dynamic stability, body diode characteristics, reproducibility of the fabrication process and device size. Various attempts have been made in recent years in order to address these features. Approaches differ in the use of different crystal orientations and polytypes, accumulation or inversion channel, implanted or epitaxially grown channels and novel oxidation techniques. Worldwide a trend to the planar DIMOS concept can be observed. Our present results are shown for a power SiC MOSFET designed for 10 A / 1200 V. Key data are a specific on-resistance of 12 m1cm2, the desired low but positive increase of the onresistance with temperature, static avalanche (20 mA DC @1574 V), short-circuit stability at 600 V for 20 9s and robust switching behavior.