Ammonia NH3 Research Articles

STUDY OF AIR POLLUTANTS, PART (1): AMMONIA AND DUST EMISSIONS PATTERNS INSIDE POULTRY HOUSES

The poultry production sector in most Arabian countries has a great development due to economic trends and policy shifts occurring during the last years. Hence, there is an urgent need to quantify ammonia NH3 and dust inside poultry houses to obtain a real vision of ammonia emission both inside and outside poultry houses. The present research work aims to assess and study the pattern of emission of both ammonia and dust inside poultry houses. The familiar smell of ammonia (NH3) can be noticed from poultry houses. Also, many parts of the poultry farms produce ammonia either when they are not well managed or when the workers agitate the litter. Results of calculations have been compared with measurement and analysis of ammonia generated and emitted from a variety of holds of poultry in a previous study, where the results showed that the concentration and the rate of emission of ammonia varies with each location, size and type of house poultry, the internal temperature, air relative humidity, air velocity, time of day and age of birds. The results also indicated that the ammonia volatilization rate depends primarily on the surface of emission- emission-surface temperature - the difference in the concentration of ammonia emission between the surface and the surrounding air. This requires detecting its presence and a measure to indicate different levels of ammonia inside the house.

Synthesis of the Long-Sought Unsubstituted Aminodiboranate Na(H3B−NH2−BH3) and Its N-Alkyl Analogs

Reduction of ammonia borane, NH(3) x BH(3), with Na or NaNH(2) in refluxing tetrahydrofuran (thf) affords the new compound, the unsubstituted aminodiboranate Na(BH(3)-NH(2)-BH(3)) (1a). Similar N-alkyl- and N,N-dialkylaminodiboranate salts, Na(H(3)B-NHMe-BH(3)) (1b), Na(H(3)B-NHEt-BH(3)) (1c), Na(H(3)B-NMeEt-BH(3)) (1d), Na[H(3)B-N(C(4)H(8))-BH(3)] (1e), and Na[H(3)B-N(C(5)H(10))-BH(3)] (1f), where N(C(4)H(8)) = pyrrolido and N(C(5)H(10)) = piperido, have also been prepared, along with their adducts with dioxane Na[H(3)B-NRR'-BH(3)](diox)(x) where x = 0.5 or 1.0 (2a-f). Crystal structures of 2b, 2c, and 2e are reported. Treatment of ErCl(3) with Na(H(3)B-NH(2)-BH(3)) in thf affords the new erbium complex Er(H(3)B-NH(2)-BH(3))Cl(2)(thf)(3), 3, which has been crystallographically characterized. (1)H and (11)B NMR spectra of the new compounds are reported.

Structure, acidity and activity of CuO x/WO x–ZrO 2 catalyst for selective catalytic reduction of NO by NH 3

A series of CuO x /WO x –ZrO 2 catalysts were synthesized by impregnating different amounts of copper on the coprecipitated WO x –ZrO 2 support and were characterized by XRD, BET, XPS, NH 3/NO chemisorption, NH 3-TPO and NH 3-SCR activity measurements. A wide temperature range (200–320 °C) in which NO conversion exceeds 80% is achieved on the 10 wt.% CuO x /WO x –ZrO 2 catalyst. The activity and selectivity of the catalysts for ammonia oxidation and NH 3-SCR reaction are determined by the strength and amount of Lewis acid sites and Brønsted acid sites, which are adjusted by the formation of WO x –ZrO 2 solid solutions and the addition of copper oxides. Two different reaction routes, “ammonia–NO 2 route” at low temperatures (<200 °C) and “amine–NO/NO 2” at high temperatures (>250 °C), are presented for SCR reaction over CuO x /WO x –ZrO 2 catalysts.

High-speed Growth and Characterization of Polycrystalline AlN Layers by High Temperature Chemical Vapor Deposition (HTCVD)

In this paper, AlN synthesis is achieved by High Temperature CVD which consists of a graphite susceptor heated by induction in a home-built vertical cold-wall reactor working at low pressure. The reactants used are ammonia NH3 and aluminium chlorides AlClx species formed in situ via Cl2 reaction with high purity Al wire. AlN films were deposited on a 55 mm diameter graphite susceptor between 1200{degree sign}C and 1600{degree sign}C. The influence of deposition temperature on growth rate, surface morphology, grain size and crystalline state is presented. Growth rates of up to 230 µm.h-1 were reached. AlN layers were characterized by SEM, X-ray Diffraction, Raman spectroscopy and Optical Profilometry.

Influence of total pressure and precursors flow rates on the growth of aluminium nitride by high temperature chemical vapor deposition (HTCVD)

AbstractIn order to achieve AlN bulk growth, HTCVD chlorinated process is investigated. High growth rate and high crystalline quality are targeted for AlN films grown on (0001) 4H SiC at 1750 °C. The precursors used are ammonia NH3 and aluminium chlorides AlClx species formed in situ by action of Cl2 on high purity Al wire. Influence of total pressure, Cl2 flow rate and NH3 flow rate on AlN growth rate, crystalline state and microstructure are presented. Growth rates of up to 200 μm.h–1 have been reached for polycrystalline layers. Thermodynamic calculations were carried out and correlated to the experimental results. As‐grown AlN layers were characterized by SEM and X‐ray Diffraction. Surface morphology was studied by SEM and FEG‐SEM and crystallographic orientations were obtained by X‐ray diffraction on θ/2θ. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Influence of the N/Al Ratio in the Gas Phase on the Growth of AlN by High Temperature Chemical Vapor Deposition (HTCVD)

In order to achieve AlN bulk growth, HTCVD chlorinated process is investigated. High growth rate and high crystalline quality are targeted for AlN films grown on (0001) 4H SiC at 1750°C. The precursors used are ammonia NH3 and aluminium chlorides AlClx species formed in situ by action of Cl2 on high purity Al wire. Influences of N/Al ratio in the gas phase on growth rate, crystalline state and microstructure are presented. Growth rates of up to 200 µm/h have been reached for polycrystalline layers. Thermodynamic calculations were carried out and correlated to the experimental results. As-grown AlN layers were characterized by SEM and X-ray Diffraction. Surface morphology is studied by SEM and FEG-SEM and crystallographic orientations were obtained by X-ray diffraction on θ/2θ.

Growth of Thick AlN Layers by High Temperature CVD (HTCVD)

To achieve AlN bulk growth, HTCVD chlorinated process is investigated. High growth rate and high crystalline quality are targeted for AlN films grown on (0001) α-Al2O3 and (0001) 4H or 6H SiC substrates between 1100 °C and 1750 °C. The precursors used are ammonia NH3 and aluminium chlorides AlClx species formed in situ by action of Cl2 on high purity Al wire. Both influences of temperature and carrier gas on microstructure, crystalline state and growth rate are presented. Growth rates higher than 190 μm.h-1 have been reached. Thermodynamic calculations were carried out to understand the chemistry of AlN deposition. AlN layers were characterized by SEM and θ/2θ X-Ray Diffraction. Their epitaxial relationships with substrates were deduced from pole figures obtained by X-Ray diffraction on a texture goniometer.

ND-stretching vibrational energy relaxation of NH2D in liquid-to-supercritical ammonia studied by femtosecond midinfrared spectroscopy

Femtosecond midinfrared pump-probe spectroscopy was carried out to explore the dynamics of vibrational energy relaxation of NH(2)D in fluid ammonia NH(3). The ND-stretching fundamental of the partially deuterated solute NH(2)D was excited by femtosecond pulses centered at 2450 cm(-1), and both the ground-state bleach and the anharmonically shifted transient absorption of the same vibration was probed. The temperature of the sample was varied between 230 and 450 K, while the pressure was tuned from 10 to 1500 bar, thereby entering both the liquid and the supercritical phase of the fluid solution. The density and temperature dependence of the ND-stretching lifetime suggests that hydrogen bonding is of negligible importance for vibrational energy relaxation. Rather, the energy transfer dynamics can be understood qualitatively in terms of a simple Landau-Teller description for vibrational energy relaxation using molecular dynamics simulations to estimate the spectral density of the fluctuating forces exerted by a weakly interacting Lennard-Jones solvent (NH(3)) onto the vibrationally excited solute (NH(2)D).

Investigation of the structure of carbon-nitrogen compounds

Carbon nitride is synthesized in the form of g-C3N4 and β-C3N4 with the use of two methods: (i) thermal decomposition of a mixture of sodium and potassium thiocyanates and (ii) interaction of carbon tetrachloride CCl4 with ammonia NH3. The carbon-nitrogen phases thus synthesized are investigated using electron microscopy, X-ray powder diffraction, IR spectroscopy, and mass spectrometry.

Determination of ammonia emission rates from a tunnel ventilated chicken house using passive samplers and a Gaussian dispersion model

Atmospheric deposition can provide a significant fraction of the nitrogen loading to coastal waters. The Delmarva Peninsula, on the eastern shore of the Chesapeake Bay, is a region with intense poultry production that may supply a significant source of atmospheric ammonia (NH3). There is a need to quantify ammonia NH3 from representative growing methods in this region in order to more accurately estimate agricultural NH3 emissions and to develop best management practices. In this study, NH3 emissions were determined at an 18,600-bird tunnel-ventilated chicken house using a modified sampling grid (a planar arrangement normal to the length of the house) with Ogawa passive samplers to characterize the emission plume downwind from the house. This improvement in the sampling strategy, compared to a previous study, simplified the inverse Gaussian plume analysis which improved the confidence in the emission factors. In this study, a total of four separate plume characterizations were conducted over the final 3 weeks of the 6-week broiler grow-out cycle. The mean emission factor observed at the tunnel-ventilated house, 0.13 g NH3–N/bird-day, was an order of magnitude lower than that previously observed at a nearby side-wall ventilated house. Although not all growing variables were measured, the large difference in emission factors between the two ventilation regimes suggest that modern, tunnel-ventilated houses may result in a significant decrease in NH3 emissions compared with traditional growing methods. This variability in emission factors underscores the need for characterizing chicken houses under various conditions and determining the factors that control these atmospheric emissions.

Effect of thermal annealing and nitrogen content on amorphous silicon thin‐film crystallization

AbstractWe study the influence of high‐temperature annealing (1100–1200 °C) on the crystallization of nitrogen‐doped silicon films deposited by LPCVD (low‐pressure chemical vapor deposition) at low temperature (465 °C) from disilane Si2H6 and ammonia NH3. Scanning electron microscopy (SEM) and X‐ray diffraction, studies of films are used to analyze crystallinity evolution and grain orientations. Results show the transformation of films deposited in amorphous phase to a typically polycrystalline structure after high‐temperature annealing with a large grain size exceeding 1 μm. The structural properties are strongly influenced by the annealing conditions and the nitrogen ratio in each film. It is shown that the film crystallinity increases with the duration of annealing, and that the nitrogen content inhibits the crystallization phenomena. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Collisional excitation of doubly deuterated ammonia ND$_\mathsf{2}$H by helium

Context. Doubly deuterated ammonia has been found in various dense interstellar environments. Aims. We extend our previous study of singly deuterated ammonia NH 2 D collisional excitation by helium to doubly deuterated ammonia ND 2 H. Methods. The presence of two deuterium atoms in the system modifies the symmetry and the expansion coefficients of the intermolecular potential energy surface. We establish the corresponding collision equations. Results. Cross sections are calculated in the coupled-state (CS) approximation and collisional rate coefficients are given between 5 and 100 K, a range of temperatures that is relevant to interstellar conditions. Conclusions. These results may be used to interpret the available millimeter and submillimeter observations of ND 2 H.

Collisional excitation of monodeuterated ammonia NH2D by helium

Context. Observations of deuterated molecules are useful probes of the physical and chemical conditions in star-forming regions. However their detailed interpretation is hampered by the lack of knowledge of the corresponding collisional rate coefficients. Aims. We extend our previous study of ammonia collisional excitation by helium to monodeuterated ammonia NH2D, which has been found to be abundant in a variety of environments. Methods. We introduce the principal isotopic effects in the collisional equations by calculating the relevant angular dependence of the intermolecular potential energy surface. Results. Cross sections are calculated in the coupled states approximation, and collisional rate coefficients are given from 5 to 100 K, a range of temperatures that is relevant in the interstellar medium. Conclusions. These results allow to include justifiable collisional excitation rate coefficients of NH2D by He in the analysis of the emitted radiation for the first time

Atomic Layer Deposition of NbN and Nb(Si)N for Metal Electrodes

Niobium nitride NbN and niobium silicon nitride Nb(Si)N were deposited by Atomic Layer Deposition (ALD) from niobium pentachloride NbCl5, silicon tetrachloride SiCl4, and ammonia NH3. It was shown that low resistivity NbN can be more readily processed by ALD than low resistivity TaN using just NH3 as reducing agent. Silicon could be uniformly added into the NbN structure, and increase in silicon content increased the resistivity of the films due to silicon incorporation as silicon nitride. A successful scale-up onto 200 mm wafer was performed for both processes.

Ammonium Toxicity at High pH in a Marine Bioassay Using Corophium volutator

Two forms of ammonium exist in water: un-ionized ammonia NH3 and ionized ammonium NH4+. The toxicity to many aquatic organisms is primarily attributed to the NH3 (un-ionized) species, with the NH4+ ion (ionized) species being relatively less toxic. The pH level influences the degree of ionization. It is therefore very important that quality criteria be derived for total ammonium levels at several pH values in order to allow correct interpretation of the sediment bioassay with Corophium volutator. The responses of Corophium to total ammonium were studied in a series of pH-controlled experiments. The LC50 of total ammonium showed a significant decrease with increasing pH, in both water-only and sediment experiments. The results indicated a combined NH4+ and NH3 toxicity at pH levels less than 8.3. The results can be used to set pH-dependent water quality criteria for total ammonium in overlying water in a 10-day sediment bioassay with Corophium volutator.

Le satellite Encelade source d'ions N + dans la magnétosphère de Saturne

The first pass of the Cassini probe in the vicinity of Saturn, above the E-ring, demonstrated a plasma consisting of water group ions (H +, O +, OH +, H 2O +) with a small N + ion component (3%). Using a simple model for the transport of magnetospheric ions, we show that the N + ions can be traced back to the Enceladus satellite. Such a result can be explained by the existence in this icy satellite, supposed to be still geologically active, of volatile components such as ammonia NH 3, or by the previous implantation of N + ions of external origin on its surface. To cite this article: M. Bouhram et al., C. R. Physique 6 (2005).

Interaction between the silyl and silylen centres in the deposits prepared by pulsed laser ablation of silicon monoxide and ammonia, methylamine and dimethylamine

Silicon suboxide films were prepared by TEA CO2 pulsed laser ablation (PLA) of the silicon monoxide target in the Kr atmosphere. The deposits were examined by means of Fourier transformed infrared spectroscopy (FTIR), electron paramagnetic resonance spectroscopy (EPR) and X-ray photoelectron spectroscopy (XPS). The generated point defects in the films – mostly silyl ≡Si· (E’ center) and silylen =Si: – were allowed to react with the gaseous ammonia NH3, methylamine MeNH2 and dimethylamine Me2NH after the ablation. As a result, the functional groups ≡SiNHxMey (x+y=2) were formed. The reactivity of the deposits are due to silyl ≡Si· and silylen =Si: radicals as deduced by comparison of the initial concentration of the silyl radicals (5.3–9.8×1019 /g, EPR) – and the newly formed -(Si)NH bonds (3.6×1019 /g, FTIR). The observed absorption bands ν(SiH) at 2223, 2214 and 2220 cm-1 could be assigned to =(O2)Si(H)NH2, =(O2)Si(H)NHMe and =(O2)Si(H)NMe2 species. The singlet line in EPR spectrum of the native deposit before exposition is due to the silyl radical with free valence on the silicon backbonded via oxygen and another silicon atom. After exposition either to NH3 or MeNH2 the silyl concentration rapidly decreased to several % of its original value.

Studies of high-temperature phase transition, electrical conductivity, and dielectric relaxation in (NH4)H2PO4 single crystal

Optical observation, differential scanning calorimetry, thermogravimetric analysis, and differential thermogravimetric measurements have been carried out on (NH4)H2PO4 single crystal in the temperature range of 30–250°C. The results show that the crystal starts to decompose at around 160°C. Upon heating, ammonia NH3 escapes from the surface of the crystal gradually with the production of phosphoric acid. The measured ac impedance data are analyzed as a function of frequency in the temperature range between 40 and 150°C. The frequency dependence of conductivity follows Jonscher’s dynamical law with the relation σ(ω)=σ(0)+Bωn, where ω is the frequency of the applied ac electric field and B is a constant. The obtained values of the exponent n decrease from 1 to 0.25 as the temperature is raised. The electrical conduction at low temperatures below 70°C is attributed to the hopping of proton on O–H–O hydrogen bonds among hydrogen vacancies. The activation energy of the migration is 0.12eV in this extrinsic region. At temperatures between 70 and 97°C, additional defects are created by breaking the stronger hydrogen bond in ammonium groups. The activation energy of defect formation and migration of proton among defects is 0.83eV. At temperatures above 97°C, ammonium ions in the crystal are proposed to have the contribution to the electrical conduction with an activation energy of 3.01eV.

The influence of impregnating pH on the postnatal and steam reforming characteristics of a Co-Ni/Al 2O 3 catalyst

Bimetallic alumina supported Co-Ni catalysts were prepared by impregnation under low (2) and high (8) pH values. Support dissolution due to acid attack appeared to be responsible for the low BET surface area for catalyst obtained at pH 2. However, this low-pH catalyst possesses higher dispersion and superior metal surface area. This is ascribed to the charged-induced migration of metal cations towards the grain centre where adsorption sites are located as a result of the formation of positively charged alumina surface at low pH. Ammonia NH 3-TPD analysis showed that the surface of both catalysts was populated with weak Lewis acid sites though a higher site concentration was found on the high-pH catalyst. TEM images further revealed an eggyolk profile for the catalyst impregnated at pH 2 with metal species located in the particle interior; while in the catalyst synthesised at pH 8, the impregnant metal is concentrated around the external surface of the particle. XRD analysis of the catalysts before and after reduction indicates that the basic catalyst was more difficult to reduce probably because of higher metal aluminate content. This was further confirmed by the lower degree of reduction shown for this catalyst during the thermogravimetric TPR–TPO runs. Solid-state kinetic data of the catalyst calcination, reduction and oxidation conformed with the Avrami–Erofeev model. In particular, the ratios of the associated kinetic rate constants for calcination and oxidation parallel those obtained for the deactivation and steam reforming constants, respectively, in both catalysts. Thus, it may be possible to have an a priori knowledge of the comparative reaction and deactivation behaviour of different catalysts from the temperature-programmed kinetics of their nascent solid states.

Desorption behaviours from metal–N–H systems synthesized by ball milling

Three metal amides LiNH 2, NaNH 2 and Mg(NH 2) 2 were synthesized by ball milling the metal hydrides under gaseous ammonia NH 3 at room temperature. The decomposition behaviours from these metal amides were investigated by thermal desorption mass spectroscopy and thermogravimetry analysis methods. The results showed that LiNH 2 decomposed at T > 230 ° C and was transformed into the imide Li 2NH with emitting NH 3, while Mg(NH 2) 2, decomposed at T > 180 ° C and was transformed into MgNH and finally into Mg 3N 2 with emitting NH 3 within 500 ° C. Then, a new metal–N–H system composed of Mg(NH 2) 2 and LiH with a molar ratio of 3:8 was designed by ball milling treatment and examined the hydrogen storage properties. The results showed that this system could reversibly absorb/desorb a large amount of hydrogen ( ∼ 7 wt.%) at a moderate temperature and pressure, which was better than the system of LiNH 2 and LiH for hydrigen storage.