Ratio Of NH3 Research Articles

Characteristics of Silicon Nitride Films Deposited by Cat-CVD at a Low Temperature (100 ℃)

Silicon nitride (SiNx) films for use as gate dielectric layers in thin-film transistors (TFTs) were deposited by catalytic chemical vapor deposition (Cat-CVD) at a low substrate temperature (100 ºC). Filament geometry, spacing between the filament and the substrate, and process pressure were optimized to deposit reliable dielectric films at 100 ºC. Silane (SiH4), ammonia (NH3) and hydrogen (H2) were used as source gases, and the flow ratios of NH3 / SiH4 and H2 / SiH4 were varied from 10 to 60 and from 20 to 200, respectively. An in-situ chemical annealing was performed by using H2 during the deposition process. As a result, SiNx films having a composition close to stoichiometry, having an electrical resistivity of 1012 ohm∙cm and a breakdown field strength of 7 MV/cm, were obtained. These films are believed to be applicable to TFTs on plastic substrates.

Enhanced nitrogen deposition over China

China is experiencing intense air pollution caused in large part by anthropogenic emissions of reactive nitrogen. These emissions result in the deposition of atmospheric nitrogen (N) in terrestrial and aquatic ecosystems, with implications for human and ecosystem health, greenhouse gas balances and biological diversity. However, information on the magnitude and environmental impact of N deposition in China is limited. Here we use nationwide data sets on bulk N deposition, plant foliar N and crop N uptake (from long-term unfertilized soils) to evaluate N deposition dynamics and their effect on ecosystems across China between 1980 and 2010. We find that the average annual bulk deposition of N increased by approximately 8 kilograms of nitrogen per hectare (P < 0.001) between the 1980s (13.2 kilograms of nitrogen per hectare) and the 2000s (21.1 kilograms of nitrogen per hectare). Nitrogen deposition rates in the industrialized and agriculturally intensified regions of China are as high as the peak levels of deposition in northwestern Europe in the 1980s, before the introduction of mitigation measures. Nitrogen from ammonium (NH4(+)) is the dominant form of N in bulk deposition, but the rate of increase is largest for deposition of N from nitrate (NO3(-)), in agreement with decreased ratios of NH3 to NOx emissions since 1980. We also find that the impact of N deposition on Chinese ecosystems includes significantly increased plant foliar N concentrations in natural and semi-natural (that is, non-agricultural) ecosystems and increased crop N uptake from long-term-unfertilized croplands. China and other economies are facing a continuing challenge to reduce emissions of reactive nitrogen, N deposition and their negative effects on human health and the environment.

Dimethylamine and ammonia measurements with ion chromatography during the CLOUD4 campaign

Abstract. The CLOUD project investigates the influence of galactic cosmic rays on the nucleation of new particles in an environmental chamber at CERN. Dimethylamine (DMA) was injected intentionally into the CLOUD chamber to reach atmospherically relevant levels away from sources (up to 100 pptv) in order to study its effect on nucleation with sulphuric acid and water at 278 K. Quantification of DMA and also background ammonia (NH3) was performed with ion chromatography (IC). The IC method used together with the sampling line developed for CLOUD in order to measure NH3 and DMA at low pptv levels is described; the overall sampling efficiency of the method is discussed; and, finally, mixing ratios of NH3 and DMA measured during CLOUD4 are reported.

Correlation between photo response and nanostructures of silicon quantum dots in annealed Si-rich nitride films

Synthesis and characterization of silicon quantum dots (Si QDs) materials are carried out. The Si QDs were prepared from a hydrogenated silicon rich nitride film that is deposited by the plasma enhanced chemical vapor deposition process with a gas mixture of SiH4 and NH3 at flow ratios from 0.5 to 2. The Si QDs can be precipitated from the hydrogenated silicon rich nitride film by a high temperature annealing. The optimum density of the Si QDs precipitated amounts to 6.4×1012cm−2, as calculated from transmission electron microscope images, for flow ratio of SiH4 versus NH3 at 2, and particle sizes less than 6nm. The dots density within the film becomes concentrated when the flow ratio of SiH4 versus NH3 increases. The intensity of photo response increases drastically when the dots density becomes large.

Facile hydrothermal synthesis of polyhedral Fe3O4 nanocrystals, influencing factors and application in the electrochemical detection of H2O2

Polyhedral Fe3O4 nanocrystals have been successfully synthesized by a facile hydrothermal technique, employing FeSO4·7H2O, N2H4 and NH3·H2O as the reactants without the assistance of any surfactant. The phase of the as-obtained Fe3O4 was characterized by X-ray powder diffraction (XRD) and further proved by Rietveld refinement of XRD data. Energy dispersive spectrometry (EDS) and scanning electron microscopy (SEM) were used for the composition and morphology analyses of the final product. Some factors influencing the formation of polyhedral Fe3O4 nanocrystals were systematically investigated, including the reaction temperature and time, and the original volume ratio of NH3·H2O/N2H4·H2O. It was found that the as-prepared Fe3O4 polyhedra exhibited a good electrochemical property in 0.1M phosphate buffer solution (PBS) with pH 7.0 and could be prepared into an electrochemical sensor for the detection of H2O2. The linear response range of the sensor was 10.0×10−6 to 140.0×10−6M and a sensitivity was 11.05μA/mM. Furthermore, the room-temperature magnetic property of the product was also investigated.

Chemical Vapor Deposition of Cobalt Nitride and its Application as an Adhesion-Enhancing Layer for Advanced Copper Interconnects

An interlayer of face centered cubic (fcc) Co4N has demonstrated significant improvements in adhesion between copper and diffusion barrier layers. This fcc phase of Co4N was prepared by chemical vapor deposition (CVD) using bis(N-tert-butyl-N′-ethyl-propionamidinato)cobalt(II) and a reactant mixture of NH3 and H2 at substrate temperatures from 100 to 180°C. The Co/N atomic ratio and the phase of cobalt nitride film can be modified by adjusting the ratio of NH3 and H2 in the gas feedstock. The cobalt nitride films prepared by CVD are smooth, highly conformal, and stable against intermixing with copper up to at least 400°C. This fcc cobalt nitride material has very strong adhesion to copper due to the small lattice mismatch (−1 to 2%) between fcc-Co4N and fcc Cu. Copper wires should be stabilized against failure by electromigration when fcc cobalt nitride interlayers are placed between the copper and surrounding diffusion barriers.

Atmospheric ammonia measurements in Houston, TX using an external-cavity quantum cascade laser-based sensor

Abstract. In order to improve the current understanding of the dynamics of ammonia (NH3) in a major industrial and urban area, intensive measurements of atmospheric NH3 were conducted in Houston during two sampling periods (12 February 2010–1 March 2010 and 5 August 2010–25 September 2010). The measurements were performed with a 10.4-μm external cavity quantum cascade laser (EC-QCL)-based sensor employing conventional photo-acoustic spectroscopy. The mixing ratio of NH3 ranged from 0.1 to 8.7 ppb with a mean of 2.4 ± 1.2 ppb in winter and ranged from 0.2 to 27.1 ppb with a mean of 3.1 ± 2.9 ppb in summer. The larger levels in summer probably are due to higher ambient temperature. A notable morning increase and a mid-day decrease were observed in the diurnal profile of NH3 mixing ratios. Motor vehicles were found to be major contributors to the elevated levels during morning rush hours in winter. However, changes in vehicular catalytic converter performance and other local or regional emission sources from different wind directions governed the behavior of NH3 during morning rush hours in summer. There was a large amount of variability, particularly in summer, with several episodes of elevated NH3 mixing ratios that could be linked to industrial facilities. A considerable discrepancy in NH3 mixing ratios existed between weekdays and weekends. This study suggests that NH3 mixing ratios in Houston occasionally exceeded previous modeling predictions when sporadic and substantial enhancements occurred, potentially causing profound effects on particulate matter formation and local air quality.

Experimental studies on removal capacity of carbon dioxide by a packed reactor and a spray column using aqueous ammonia

The absorption of carbon dioxide into ammonia aqueous solution using packed reactor and spray column was investigated. The removal efficiencies were evaluated over ranges of main operating variables, including CO2 inlet concentration, gas flow rate, liquid flow rate, concentration of ammonia and temperature. Experimental results showed that the suitable reaction temperatures are 40�� and 35�� for spray column and packed reactor respectively, and the mole ratio of NH3 to CO2 is a key parameter and plays an important role on CO2 removal efficiency. Compared with the absorption of CO2 in the spray column, the CO2 removal efficiency in the packed reactor shows superior performance. © 2010 Elsevier Ltd. All rights reserved

Plasma Diagnostics for NH3 Plasmas Using a Quartz Sensor at Various Pressures

A novel plasma diagnostic method using a quartz sensor (Q-sensor) was applied to the analysis of NH3 plasmas at various pressures of 19.6–131.0 Pa. The change in the gas composition of the NH3 plasmas was derived from the change in the Q-sensor output through pressure normalization because the pressure-normalized Q-sensor output depends on the molecular weight and viscosity of the measured gas. The change in the gas composition of the NH3 plasmas agrees with the results obtained from the gas analysis using a quadrupole mass spectrometer (QMS): the plasma gas composition includes high-density H2 and low-density N2. The dissociation ratio of NH3 was compared with measurements obtained using the Q-sensor and QMS, which indicates that Q-sensor measurement is useful as a method of plasma diagnostics for obtaining the gas composition of NH3 plasmas at 19.6–131.0 Pa.

Preparation of Acicular Basic Magnesium Carbonate by the Activation Product of Chrysotile Asbestos Tailing

Chrysotile asbestos tailing was broken down into active magnesium oxide and silicon dioxide by roasting. The activation product of Chrysotile as raw materials was used to prepare acicular basic magnesium carbonate by the carbon–ammonia method. The effect of the carbonization temperature, aging temperature, aging time, and the mole ratio of NH3•H2O and Mg2+ were studied on the form and percent conversion of the acicular basic magnesium carbonate. The structure, thermal properties and crystal morphology of the sample were analyzed by XRD analysis, thermal analysis and optical microscope, respectively. The results show that acicular basic magnesium carbonate prepared at the best conditions: carbonization temperature is at 50°C, aging temperature is at 70°C, aging time is for 4-5 hours, and the molar ratio of NH3•H2O and Mg2+ is 2:1. In this condition, the formation rate of specula basic magnesium carbonate is more than 82%. Its chemical formula which is 4MgCO3•Mg(OH)2•4H2O is obtained by XRD and thermal analysis, and the aspect ratio of the sample of the acicular basic magnesium carbonate was about 30 which was tested by optical microscope.

HNCO hydrolysis performance in urea-water solution thermohydrolysis process with and without catalysts

The thermolysis of urea-water solution and its product, HNCO hydrolysis is investigated in a dual-reactor system. For the thermal decomposition below about 1073 K, the main products are ammonia (NH3) and isocyanic acid (HNCO) whereas at higher temperatures the oxidation processes take effect and the products include a low concentration of nitric oxide (NO) and nitrous oxide (N2O). The gas HNCO is quite stable and a high yield of HNCO is observed. The ratio of NH3 to HNCO increases from approximately 1.2 to 1.7 with the temperature. The chemical analysis shows that H radical is in favor of HNCO hydrolysis by instigating the reaction HNCO+H·→·NH2+CO and high temperature has positive effect on H radical. The hydrolysis of HNCO over an alumina catalyst made using a sol-gel process (designated as γ-Al2O3) is investigated. The conversion of HNCO is high even at the high space velocities (6×105 h−1) and low temperatures (393–673 K) in the tests with catalysts, which enhances HNCO hydrolysis and raises the ratio of NH3 to HNCO to approximately 100. The pure γ-Al2O3 shows a better catalytic performance than CuO/γ-Al2O3. The addition of CuO not only reduces the surface area but also decreases the Lewis acid sites which are recognized to have a positive effect on the catalytic activity. The apparent activation energy of the hydrolysis reaction amounts to about 25 kJ/mol in 393–473 K while 13 kJ/mol over 473 K. The overall hydrolysis reaction rate on catalysts is mainly determined by external and internal mass-transfer limitations.

Solvent-Free One-Pot Synthesis of high performance silica/epoxy nanocomposites

High performance silanized silica/epoxy nanocomposites were prepared through mixing epoxy, tetraethyl orthosilicate (TEOS), (3-aminopropyl)trimethoxysilane (APTMS) and ammonia solution at 50 °C. This all-in-one “Solvent-Free One-Pot Synthesis” results in nanocomposites with uniform dispersion of oval shaped silica nanoparticles and strong adhesion between silica and epoxy matrix. The influence of the synthesis conditions, such as molar ratio of NH3:TEOS, aging time, curing process and silica content on the thermal mechanical properties of nanocomposites were studied. The silanized silica/epoxy nanocomposite prepared in this study exhibits better thermal mechanical property in comparison with neat epoxy, non-functionalized silica/epoxy and commercialized silica/epoxy systems. The prepared nanocomposite with 3 wt% silanized silica exhibits 20%, 17% and 6% improvements on flexural, tensile and storage modulus over those of neat epoxy, respectively.

Atmospheric aerosol formation and its growth during the cold season in India

The effects of molecular diffusivity of H2SO4 and NH3 vapours on nucleated particles of SO 2−4 and NO −3 species are reported. Condensation sink and source rate of H2SO4 and NH3 vapours, growth rates and ratios of real to apparent nucleation rates are calculated for SO –4 and NO −3 aerosols using fractional contributions of them in total aerosol size-distribution during the measurement period at Pune, reported in Chate and Pranesha (2004). The percentage of nucleated SO 2−4 and NO −3 aerosols of mid-point diameter 13 nm are 2% and 3% respectively of the total particles (13 nm ≤ D p ≤ 750 nm) for both H2SO4 and NH3 diffusion. In the diameter range 75 nm ≤ D p ≤ 133 nm, it is 48% and 45% of SO 2−4 and NO −3 aerosols, respectively for NH3 diffusion and 43% and 36% of SO 2−4 and NO −3 for H2SO4 diffusion. Increase in percentage of nucleated particles of these species corresponding to mid-point diameter 133 nm around 0900 h IST is significantly higher than that of mid-point diameter 13 nm and it is due to photo-chemical nucleation, coagulation and coalescence among nucleated clusters. The ratios of real to apparent formation rates for SO 2−4 and NO −3 aerosols are 12% and 11% respectively, corresponding to mid-point diameter 13 nm, 17% and 13%, for midpoint diameter 133 nm and 12% and 9.5%, for mid-point diameter 750 nm. The results indicate that nucleation involving H2SO4 and acidic NH3 diffusion on SO 2−4 and NO −3 particles is the most relevant mechanism in this region.

Extraction of valuable metals from low-grade nickeliferous laterite ore by reduction roasting-ammonia leaching method

Nickel and cobalt were extracted from low-grade nickeliferous laterite ore using a reduction roasting-ammonia leaching method. The reduction roasting-ammonia leaching experimental tests were chiefly introduced, by which fine coal was used as a reductant. The results show that the optimum process conditions are confirmed as follows: in reduction roasting process, the mass fraction of reductant in the ore is 10%, roasting time is 120 min, roasting temperature is 1 023–1 073 K; in ammonia leaching process, the liquid-to-solid ratio is 4:1(mL/g), leaching temperature is 313 K, leaching time is 120 min, and concentration ratio of NH3 to CO2 is 90 g/L:60 g/L. Under the optimum conditions, leaching efficiencies of nickel and cobalt are 86.25% and 60.84%, respectively. Therefore, nickel and cobalt can be effectively reclaimed, and the leaching agent can be also recycled at room temperature and normal pressure.

Effects of the solar eclipse on 15 January 2010 on the surface O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;, NO, NO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, NH&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;, CO mixing ratio and the meteorological parameters at Thiruvanathapuram, India

Abstract. In this paper, we present the effect of total solar eclipse on surface O3, NO, NO2, NH3, CO mixing ratio and the meteorological parameters on 15 January 2010 at Thiruvanathapuram, India. On the day of total solar eclipse (i.e., 15 January 2010), the decrease in mixing ratio of surface O3 and NO2 is observed after the beginning of the solar eclipse events (11:15 to 15:30). Decrease in surface O3 may be due to decreased efficiency of the photochemical ozone formation, whereas, mixing ratio of NO and NH3 have been changed following the night time chemistry. Surface O3 reduced to 20.3 ppb after 22 min of full phase of the eclipse. During the solar eclipse period, the ambient temperature and wind speed have decreased, whereas, relative humidity has increased as expected.

Direct-Liquid-Injection Chemical Vapor Deposition of Nickel Nitride Films and Their Reduction to Nickel Films

Smooth and continuous films of nickel nitride (NiNx) with excellent step coverage were deposited from a novel nickel amidinate precursor, Ni(MeC(NtBu)2)2, and either ammonia (NH3) or a mixture of NH3 and hydrogen (H2) gases as co-reactants. The reactants were injected together in direct-liquid-injection chemical vapor deposition (DLI-CVD) processes at substrate temperatures of 160−200 °C. Depending on the ratio of NH3 to H2 gases during deposition, the Ni:N atomic ratio in DLI-CVD NiNx films could be varied from ∼3:1 to ∼15:1, having either a cubic nickel structure or a mixture of hexagonal Ni3N and cubic Ni4N crystal structures with an incorporation of nitrogen as low as 6%. The chemical vapor deposition (CVD) growth rates of NiNx could be increased to more than 5 nm/min. The CVD films were smooth and continuous, and they had ∼100% step coverage in high-aspect-ratio (>50:1) holes. The as-deposited NiNx films had resistivities as low as ∼50 μΩ cm for film thicknesses of ∼25 nm. Annealing of the films in H2 at 160 °C or hydrogen plasma treatment at room temperature removed the nitrogen and led to pure nickel films.

The annual ammonia budget of fertilised cut grassland – Part 2: Seasonal variations and compensation point modeling

Abstract. The net annual NH3 exchange budget of a fertilised, cut grassland in Central Switzerland is presented. The observation-based budget was computed from semi-continuous micrometeorological fluxes over a time period of 16 months and using a process-based gap-filling procedure. The data for emission peak events following the application of cattle slurry and for background exchange were analysed separately to distinguish short-term perturbations from longer-term ecosystem functioning. A canopy compensation point model of background exchange is parameterised on the basis of measured data and applied for the purposes of gap-filling. The data show that, outside fertilisation events, grassland behaves as a net sink for atmospheric NH3 with an annual dry deposition flux of −3.0 kg N ha−1 yr−1, although small NH3 emissions by the canopy were measured in dry daytime conditions. The median Γs ratio in the apoplast (=[NH4+]/[H+]) estimated from micrometeorological measurements was 620, equivalent to a stomatal compensation point of 1.3 μg NH3 m−3 at 15 °C. Non-stomatal resistance to deposition Rw was shown to increase with temperature and decrease with surface relative humidity, and Rw values were among the highest published for European grasslands, consistent with a relatively high ratio of NH3 to acid gases in the boundary layer at this site. Since the gross annual NH3 emission by slurry spreading was of the order of +20 kg N ha−1 yr−1, the fertilised grassland was a net NH3 source of +17 kg N ha−1 yr−1. A comparison with the few other measurement-based budget values from the literature reveals considerable variability, demonstrating both the influence of soil, climate, management and grassland type on the NH3 budget and the difficulty of scaling up to the national level.

Variations in Mixing Ratios of Ambient Ammonia, Nitric Oxide and Nitrogen Dioxide in Different Environments of India

° 38'N, 77 ° 10'E; 220m m.s.l.), India (Figure 1) during July 2009. Delhi, the capital city of India, located in the northern part of India. It is one of the ten most polluted cities of the world and third most polluted city of the country having numerous industries in and around the city. The total number of registered vehicles in the city Abstract Mixing ratios of ambient NH3, NO and NO2 were measured over three different environments viz Delhi, Dibrugarh and Thiruvananthapuram during 2009-10 to study their diurnal variations, concentration and source strength. The average mixing ratio of NH 3 over Delhi, Dibrugarh and Thiruvananthapuram were recorded as 13.24 ± 0.39, 13.46 ± 2.52 and 12.65 ± 1.51 ppb respectively. The average mixing ratio of NO2 was recorded as 12.69 ± 0.39 with maxima of 20.22 ppb and minima of 0.75 ppb over Delhi whereas, the mixing ratio of ambient NO 2 ranges from 0.65 to 3.65 ppb and 0.83 to 3.02 over Dibrugarh and Thiruvananthapuram respectively. The mixing ratio of NO and NO2 varying significantly at all the three locations except NH 3 might be due to source strength and meteorological conditions of the locations. Result reveals that the mixing ratio of ambient NH 3 is positively correlated with ambient temperature (r 2 = 0.872) and NO2 (r 2 = 0.975) over Delhi whereas non-significant at other locations.

Controlled Growth of Lead Oxide Nanosheets, Scrolled Nanotubes, and Nanorods

PbO2 nanosheets, scrolled nanotubes, and nanorods have been selectively synthesized on lead foil with a convenient hydrothermal approach by simply modifying the reaction conditions. The presence of ammonia plays a key role in the preparation of PbO2 nanosheets, while the volume ratio of NH3 to H2O and reaction temperature have a significant influence on the shapes and sizes of the PbO2 product. The formation mechanism of the PbO2 nanostructures was discussed. The samples were characterized using X-ray powder diffraction, energy dispersive X-ray spectrometry, transmission electron microscopy, and scanning electron microscopy.

Impact of Point Defects on the Luminescence Properties of (Al,Ga)N

Threading dislocations (TDs) in (Al,In,Ga)N semiconductors are known to affect the luminescence efficiency of near-band-edge (NBE) emissions in bulk films and quantum structures. However, the principal role of point defects such as vacancies on the luminescent properties has not been fully understood. In this article, impacts of point defects on the luminescence quantum efficiency of NBE emissions and on the intensity of deep emission bands will be described, based on the results of steady-state and time-resolved photoluminescence (TRPL) and positron annihilation measurements. The room temperature nonradiative lifetime (τNR) of the NBE excitonic photoluminescence (PL) peak in polar (0001) and (000-1) , nonpolar (11-20) and (10-10), and zincblende (001) GaN layers prepared by various growth techniques was shown to increase with the decrease in concentration or size of Ga vacancies (VGa) and with the decrease in gross concentration of point defects including complexes, leading to an increase in the NBE PL intensity. As the edge TD density decreased, the concentration or size of VGa tended to decrease and τNR tended to increase. However, there existed remarkable exceptions. The results indicate that the nonradiative recombination process is governed not by single point defects, but by certain defects introduced with the incorporation of VGa, such as VGa-defect complexes. Similar relations were found in AlxGa1-xN alloy films grown by metalorganic vapor phase epitaxy: i. e. τNR at room temperature increased with the decrease in the concentration of cation vacancies (VIII) and with the decrease in gross concentration of point defects. In addition to nonradiative processes, the VIII concentration was found to correlate with the intensity ratio of characteristic deep emission band to the NBE emission (Ideep/INBE). For example, Ideep/INBE at low temperature for the deep emission bands at 4.6, 3.8, and 3.1 eV of AlN epilayers grown by NH3-source molecular beam epitaxy had a linear correlation with the concentration or size of Al vacancies (VAl). Since the relative intensities of 3.1 eV and 3.8 eV bands increased remarkably with lowering the supply ratio of NH3 to Al (V/III ratio) and growth temperature (Tg), they were assigned to originate from VAl-O as well as VAl-shallow donor complexes. The VAl concentration could be decreased by adjusting the V/III ratio and Tg. In the case of AlxGa1-xN alloys, the concentration or size of VIII and Ideep/INBE at 300 K increased simultaneously with the increase in x up to approximately 0.7. Similar to the case for GaN and AlN, the deep emission band was assigned as being due to the emission involving VIII-O complexes.