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Articoli di riviste sul tema "Ammonium nitrate particles":
1
Cheng, Chunlei, Zuzhao Huang, Chak K. Chan, Yangxi Chu, Mei Li, Tao Zhang, Yubo Ou et al. "Characteristics and mixing state of amine-containing particles at a rural site in the Pearl River Delta, China". Atmospheric Chemistry and Physics 18, n. 12 (29 giugno 2018): 9147–59. http://dx.doi.org/10.5194/acp-18-9147-2018.
Abstract (sommario):
Abstract. Particulate amines play an important role for the particle acidity and hygroscopicity and also contribute to secondary organic aerosol mass. We investigated the sources and mixing states of particulate amines using a single-particle aerosol mass spectrometer (SPAMS) during summer and winter 2014 at a rural site in the Pearl River Delta, China. Amine-containing particles accounted for 11.1 and 9.4 % of the total detected individual particles in summer and winter, respectively. Although the increase in amine-containing particle counts mostly occurred at night, no obvious correlations between amine-containing particles and ambient relative humidity (RH) were found during the sampling period. Among the three markers we considered, the most abundant amine marker was 74(C2H5)2NH2+, which was detected in 90 and 86 % of amine-containing particles in summer and winter, followed by amine marker ions of 59(CH3)3N+, and 86(C2H5)2NCH2+ which were detected in less than 10 % of amine-containing particles during sampling period. The amine-containing particles were characterized by high fractions of carbonaceous marker ions, carbon–nitrogen fragments, sulfate, and nitrate in both summer and winter. More than 90 % of amine-containing particles were found to be internally mixed with sulfate throughout the sampling period, while the percentage of amine particles containing nitrate increased from 43 % in summer to 69 % in winter. Robust correlations between the peak intensities of amines, sulfate, and nitrate were observed, suggesting the possible formation of aminium sulfate and nitrate salts. Interestingly, only 8 % of amine particles contained ammonium in summer, while the percentage increased dramatically to 54 % in winter, indicating a relatively ammonium-poor state in summer and an ammonium-rich state in winter. The total ammonium-containing particles were investigated and showed a much lower abundance in ambient particles in summer (3.6 %) than that in winter (32.6 %), which suggests the ammonium-poor state of amine-containing particles in summer may be related to the lower abundance of ammonia/ammonium in gas and particle phases. In addition, higher abundance of amines in ammonium-containing particles than that of ammonium in amine-containing particles suggests a possible contribution of ammonium–amine exchange reactions to the low abundance of ammonium in amine-containing particles at high ambient RH (72 ± 13 %) in summer. The particle acidity of amine-containing particles is estimated via the relative acidity ratio (Ra), which is defined as the ratio of the sum of the sulfate and nitrate peak areas divided by the ammonium peak area. The Ra was 326 ± 326 in summer and 31 ± 13 in winter, indicating that the amine-containing particles were more acidic in summer than in winter. However, after including amines along with the ammonium in the acidity calculation, the new Ra′ values showed no seasonal change in summer (11 ± 4) and winter (10 ± 2), which suggests that amines could be a buffer for the particle acidity of ammonium-poor particles.
2
Peng, Weihan, Cavan McCaffery, Niina Kuittinen, Topi Rönkkö, David R. Cocker e Georgios Karavalakis. "Secondary Organic and Inorganic Aerosol Formation from a GDI Vehicle under Different Driving Conditions". Atmosphere 13, n. 3 (8 marzo 2022): 433. http://dx.doi.org/10.3390/atmos13030433.
Abstract (sommario):
This study investigated the primary emissions and secondary aerosol formation from a gasoline direct injection (GDI) passenger car when operated over different legislative and real-world driving cycles on a chassis dynamometer. Diluted vehicle exhaust was photooxidized in a 30 m3 environmental chamber. Results showed elevated gaseous and particulate emissions for the cold-start cycles and higher secondary organic aerosol (SOA) formation, suggesting that cold-start condition will generate higher concentrations of SOA precursors. Total secondary aerosol mass exceeded primary PM emissions and was dominated by inorganic aerosol (ammonium and nitrate) for all driving cycles. Further chamber experiments in high temperature conditions verified that more ammonium nitrate nucleates to form new particles, forming a secondary peak in particle size distribution instead of condensing to black carbon particles. The results of this study revealed that the absorption of radiation by black carbon particles can lead to changes in secondary ammonium nitrate formation. Our work indicates the potential formation of new ammonium nitrate particles during low temperature conditions favored by the tailpipe ammonia and nitrogen oxide emissions from gasoline vehicles.
3
Hauglustaine, D. A., Y. Balkanski e M. Schulz. "A global model simulation of present and future nitrate aerosols and their direct radiative forcing of climate". Atmospheric Chemistry and Physics 14, n. 20 (21 ottobre 2014): 11031–63. http://dx.doi.org/10.5194/acp-14-11031-2014.
Abstract (sommario):
Abstract. The ammonia cycle and nitrate particle formation are introduced into the LMDz-INCA (Laboratoire de Météorologie Dynamique, version 4 – INteraction with Chemistry and Aerosols, version 3) global model. An important aspect of this new model is that both fine nitrate particle formation in the accumulation mode and coarse nitrate forming on existing dust and sea-salt particles are considered. The model simulates distributions of nitrates and related species in agreement with previous studies and observations. The calculated present-day total nitrate direct radiative forcing since the pre-industrial is −0.056 W m−2. This forcing corresponds to 18% of the sulfate forcing. Fine particles largely dominate the nitrate forcing, representing close to 90% of this value. The model has been used to investigate the future changes in nitrates and direct radiative forcing of climate based on snapshot simulations for the four representative concentration pathway (RCP) scenarios and for the 2030, 2050, and 2100 time horizons. Due to a decrease in fossil fuel emissions in the future, the concentration of most of the species involved in the nitrate–ammonium–sulfate system drop by 2100 except for ammonia, which originates from agricultural practices and for which emissions significantly increase in the future. Despite the decrease of nitrate surface levels in Europe and North America, the global burden of accumulation mode nitrates increases by up to a factor of 2.6 in 2100. This increase in ammonium nitrate in the future arises despite decreasing NOx emissions due to increased availability of ammonia to form ammonium nitrate. The total aerosol direct forcing decreases from its present-day value of −0.234 W m−2 to a range of −0.070 to −0.130 W m−2 in 2100 based on the considered scenario. The direct forcing decreases for all aerosols except for nitrates, for which the direct negative forcing increases to a range of −0.060 to −0.115 W m−2 in 2100. Including nitrates in the radiative forcing calculations increases the total direct forcing of aerosols by a factor of 1.3 in 2000, by a factor of 1.7–2.6 in 2030, by 1.9–4.8 in 2050, and by 6.4–8.6 in 2100. These results show that the agricultural emissions of ammonia will play a key role in the future mitigation of climate change, with nitrates becoming the dominant contributor to the anthropogenic aerosol optical depth during the second half of the 21st century and significantly increasing the calculated aerosol direct forcing. This significant increase in the influence that nitrate exerts on climate in the future will at the same time affect regional air quality and nitrogen deposition to the ecosystem.
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Myhre, G., e A. Grini. "Modelling of nitrate particles: importance of sea salt". Atmospheric Chemistry and Physics Discussions 6, n. 1 (22 febbraio 2006): 1455–80. http://dx.doi.org/10.5194/acpd-6-1455-2006.
Abstract (sommario):
Abstract. A thermo dynamical model for treatment of gas/aerosol partitioning of semi volatile inorganic aerosols has been implemented in a global chemistry and aerosol transport model (Oslo CTM2). The sulphur cycle and sea salt particles have been implemented earlier in the Oslo CTM2 and the focus of this study is on whether nitrate particles are formed as fine mode ammonium nitrate or react on existing sea salt particles. The model results show that ammonium nitrate particles play a non-negligible role in the total aerosol composition in certain industrialized regions and therefore have a significant local radiative forcing. On a global scale the aerosol optical depth of ammonium nitrate is relatively small due to limited availability of ammonia and reaction with sea salt particles. Inclusion of sea salt in the calculations reduces the aerosol optical depth and burden of ammonium nitrate particles by 25% on a global scale but with large regional variations.
5
Hauglustaine, D. A., Y. Balkanski e M. Schulz. "A global model simulation of present and future nitrate aerosols and their direct radiative forcing of climate". Atmospheric Chemistry and Physics Discussions 14, n. 5 (14 marzo 2014): 6863–949. http://dx.doi.org/10.5194/acpd-14-6863-2014.
Abstract (sommario):
Abstract. The ammonia cycle and nitrate particle formation have been introduced in the LMDz-INCA global model. Both fine nitrate particles formation in the accumulation mode and coarse nitrate forming on existing dust and sea-salt particles are considered. The model simulates distributions of nitrates and related species in agreement with previous studies and observations. The calculated present-day total nitrate direct radiative forcing since the pre-industrial is −0.056 W m−2. This forcing has the same magnitude than the forcing associated with organic carbon particles and represents 18% of the sulfate forcing. Fine particles largely dominate the nitrate forcing representing close to 90% of this value. The model has been used to investigate the future changes in nitrates and direct radiative forcing of climate based on snapshot simulations for the four Representative Concentration Pathway (RCP) scenarios and for the 2030, 2050 and 2100 time horizons. Due to a decrease in fossil fuel emissions in the future, the concentrations of most of the species involved in the nitrate-ammonium-sulfate system drop by 2100 except for ammonia which originates from agricultural practices and for which emissions significantly increase in the future. Despite the decrease of nitrate surface levels in Europe and Northern America, the global burden of accumulation mode nitrates increases by up to a factor of 2.6 in 2100. This increase in nitrate in the future arises despite decreasing NOx emissions due to increased availability of ammonia to form ammonium nitrate. The total aerosol direct forcing decreases from its present-day value of −0.234 W m−2 to a range of −0.070 to −0.130 W m−2 in 2100 based on the considered scenario. The direct forcing decreases for all aerosols except for nitrates for which the direct negative forcing increases to a range of −0.060 to −0.115 W m−2 in 2100. Including nitrates in the radiative forcing calculations increases the total direct forcing of aerosols by a factor of 1.3 in 2000, by a factor of 1.7–2.6 in 2030, by 1.9–4.8 in 2050 and by 6.4–8.6 in 2100. These results show that agricultural emissions of ammonia will play a key role in the future mitigation of climate change with nitrates becoming the dominant contributor to the anthropogenic aerosol optical depth during the second half of the XXIst century and significantly increasing the calculated aerosol direct forcing. This significant increase in the influence that nitrate exert on climate in the future will at the same time affect regional air quality and nitrogen deposition to the ecosystems.
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Schneider, Johannes, Stephan Mertes, Dominik van Pinxteren, Hartmut Herrmann e Stephan Borrmann. "Uptake of nitric acid, ammonia, and organics in orographic clouds: mass spectrometric analyses of droplet residual and interstitial aerosol particles". Atmospheric Chemistry and Physics 17, n. 2 (31 gennaio 2017): 1571–93. http://dx.doi.org/10.5194/acp-17-1571-2017.
Abstract (sommario):
Abstract. Concurrent in situ analyses of interstitial aerosol and cloud droplet residues have been conducted at the Schmücke mountain site during the Hill Cap Cloud Thuringia campaign in central Germany in September and October 2010. Cloud droplets were sampled from warm clouds (temperatures between −3 and +16 °C) by a counterflow virtual impactor and the submicron-sized residues were analyzed by a compact time-of-flight aerosol mass spectrometer (C-ToF-AMS), while the interstitial aerosol composition was measured by an high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). During cloud-free periods, the submicron out-of-cloud aerosol was analyzed using both instruments, allowing for intercomparison between the two instruments. Further instrumentation included black carbon measurements and optical particle counters for the aerosol particles as well as optical sizing instrumentation for the cloud droplets. The results show that, under cloud conditions, on average 85 % of the submicron aerosol mass partitioned into the cloud liquid phase. Scavenging efficiencies of nitrate, ammonium, sulfate, and organics ranged between 60 and 100 %, with nitrate having, in general, the highest values. For black carbon, the scavenging efficiency was markedly lower (about 24 %). The nitrate and ammonium mass fractions were found to be markedly enhanced in cloud residues, indicating uptake of gaseous nitric acid and ammonia into the aqueous phase. This effect was found to be temperature dependent: at lower temperatures, the nitrate and ammonium mass fractions in the residues were higher. Also, the oxidation state of the organic matter in cloud residues was found to be temperature dependent: the O : C ratio was lower at higher temperatures. A possible explanation for this observation is a more effective uptake and/or higher concentrations of low-oxidized water-soluble volatile organic compounds, possibly of biogenic origin, at higher temperatures. Organic nitrates were observed in cloud residuals as well as in the out-of-cloud aerosol, but no indication of a preferred partitioning of organic nitrates into the aqueous phase or into the gas phase was detected. Assuming the uptake of nitric acid and ammonia in cloud droplets will be reversible, it will lead to a redistribution of nitrate and ammonium among the aerosol particles, leading to more uniform, internally mixed particles after several cloud passages.
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Wu, Can, Cong Cao, Jianjun Li, Shaojun Lv, Jin Li, Xiaodi Liu, Si Zhang et al. "Different physicochemical behaviors of nitrate and ammonium during transport: a case study on Mt. Hua, China". Atmospheric Chemistry and Physics 22, n. 23 (13 dicembre 2022): 15621–35. http://dx.doi.org/10.5194/acp-22-15621-2022.
Abstract (sommario):
Abstract. To understand the chemical evolution of aerosols in the transport process, the chemistry of PM2.5 and nitrogen isotope compositions on the mountainside of Mt. Hua (∼1120 m above sea level, a.s.l.) in inland China during the 2016 summertime were investigated and compared with parallel observations collected at surface sampling site (∼400 m a.s.l.). The PM2.5 exhibited a high level at the mountain foot site (MF; average 76.0±44.1 µg m−3) and could be transported aloft by anabatic valley winds, leading to the gradual accumulation of daytime PM2.5 with a noon peak at the mountainside sampling site (MS). As the predominant ion species, sulfate exhibited nearly identical mass concentrations at both sites, but its PM2.5 mass fraction was moderately enhanced by ∼4 % at the MS site. The ammonium variations were similar to the sulfate variations, the chemical forms of both of which mainly existed as ammonium bisulfate (NH4HSO4) and ammonium sulfate ((NH4)2SO4) at the MF and MS sites, respectively. Unlike sulfate and ammonium, nitrate mainly existed as ammonium nitrate (NH4NO3) in fine particles and exhibited decreasing mass concentration and proportion trends with increasing elevation. This finding was ascribed to NH4NO3 volatilization, in which gaseous HNO3 from semi-volatile NH4NO3 subsequently reacted with dust particles to form nonvolatile salts, resulting in significant nitrate shifts from fine particles into coarse particles. Such scavenging of fine-particle nitrate led to an enrichment in the daytime 15N of nitrate at the MS site compared with to the MF site. In contrast to nitrate, at the MS site, the 15N in ammonium depleted during the daytime. Considering the lack of any significant change in ammonia (NH3) sources during the vertical transport process, this 15N depletion in ammonium was mainly the result of unidirectional reactions, indicating that additional NH3 would partition into particulate phases and further neutralize HSO4- to form SO42-. This process would reduce the aerosol acidity, with a higher pH (3.4±2.2) at the MS site and lower ones (2.9±2.0) at the MF site. Our work provides more insight into physicochemical behaviors of semi-volatile nitrate and ammonium, which will facilitate the improvement in the model for a better simulation of aerosol composition and properties.
8
Richardson, C. B., e R. L. Hightower. "Evaporation of ammonium nitrate particles". Atmospheric Environment (1967) 21, n. 4 (gennaio 1987): 971–75. http://dx.doi.org/10.1016/0004-6981(87)90092-8.
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Xu, Xiao Juan, Xu Dong Sun, Ya Qiu Liang e Wei Qiu. "Synthesis of Uniform Spherical Alumina Powders by Homogeneous Precipitation". Applied Mechanics and Materials 341-342 (luglio 2013): 100–104. http://dx.doi.org/10.4028/www.scientific.net/amm.341-342.100.
Abstract (sommario):
Uniform spherical alumina powders have been synthesized via homogeneous precipitation method from aluminum nitrate using urea as the precipitant. The amount of ammonium sulfate has a significant effect on morphology and particle size of the precursor powders. It was found that spherical particles can be obtained when the molar ratio of ammonium sulfate to aluminum nitrate is about 0.72 and the concentration of the aluminum nitrate is 0.005M. Spherical alumina particles with 400 nm in diameter were obtained by calcining the precursors at 1100°C for 4 hrs.
10
Hightower, R. L., e C. B. Richardson. "Evaporation of ammonium nitrate particles containing ammonium sulfate". Atmospheric Environment (1967) 22, n. 11 (gennaio 1988): 2587–91. http://dx.doi.org/10.1016/0004-6981(88)90492-1.
Tesi sul tema "Ammonium nitrate particles":
1
Boukhenane, Mohamed Lamine. "Développement de capteurs électroniques à base de matériaux nanocomposites conducteurs pour la mesure du nitrate d'ammonium particulaire". Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Lille Douai, 2020. http://www.theses.fr/2020MTLD0017.
Abstract (sommario):
La pollution atmosphérique par les particules fines (PM2,5) constitue un enjeu sanitaire et environnemental majeur. Avec une composition chimique présentant une grande variabilité, les particules fines (PM2,5) sont dominées par des sels d’ammonium (jusqu’à 40%), parmi eux, le nitrate d’ammonium. Ce dernier est formé majoritairement par la combinaison d’ammoniac, dont 80% des émissions en Europe proviennent des activités agricoles, avec de l’acide nitrique gazeux à température ambiante (<20°C). La mesure des particules de nitrate d’ammonium par les moyens habituels déployés pour la mesure des particules atmosphériques est une tâche lourde et coûteuse. En outre, les seuls capteurs optiques de particules qui existent n’informent en aucun cas sur la nature chimique des particules. Ainsi, l’objectif de cette thèse est de développer de nouveaux capteurs à faible coût capables de mesurer spécifiquement la concentration des particules de nitrate d’ammonium. La méthode de mesure repose sur la thermo-décomposition des particules de nitrate d’ammonium en acide nitrique gazeux et ammoniac. Ce dernier est quantifié à l’aide d’une couche sensible à base de matériaux nanocomposites conducteurs constitués de la polyaniline dopée (PANI), élément réactif, et d’une matrice en polyuréthane (PU). La concentration en ammoniac libéré est corrélée à la concentration massique des particules de nitrate d’ammonium. Les capteurs développés au cours de ce projet ont montré une réponse à l’ammoniac gazeux à des concentrations inférieures ou égales à 20 ppb avec une sensibilité de 0,35% ppb-1, ce qui répond aux objectifs attendus en air ambiant et permettrait d’envisager des mesures du nitrate d’ammonium particulaire. Les capteurs ont également démontré une bonne répétabilité et reproductibilité de leur réponse à ce gaz. L’impact de la température (23-50°C) et l’humidité relative (30%-90%) sur la sensibilité des capteurs à ce gaz est étudié afin d’évaluer la capacité des capteurs à mesurer l’ammoniac issu de la thermo-décomposition des particules de nitrate d’ammonium à des températures et à des taux d’humidité propices à leur décomposition. Certaines formulations de surfaces sensibles continuent de présenter des réponses concluantes à l’ammoniac même dans ces conditions particulières. Par ailleurs, les capteurs ont montré une sensibilité à l’acide nitrique gazeux seul à 50°C (-4,85% à 195ppb). Malgré cette interférence, les capteurs ont été capables de mesurer des concentrations en nitrate d’ammonium particulaire de l’ordre de 265 µg.m-3 avec une sensibilité de 1,82.10-3%.µg-1.m3 à 50°C. Ces résultats prometteurs démontrent la capacité des capteurs à mesurer le nitrate d’ammonium particulaire selon la méthode proposée. En revanche, l’interférence de l’acide nitrique gazeux pourrait réduire la sensibilité des capteurs à ces particulesAtmospheric pollution due to fine particles (PM2.5) is a major global health and environmental issue. Fine particles (PM2.5) exhibit high variability of their chemical composition which is dominated by ammonium salt (up to 40%), among them, ammonium nitrate. The latter is essentially formed by the combination, at room temperature (<20°C), of gaseous nitric acid with ammonia gas, which is mainly emitted by agricultural activities (over 80% of emissions in Europe). The determination of ammonium nitrate particles by the classical methods of atmospheric particles measurement is a high cost and heavy task. Moreover, atmospheric particles sensors that are currently available do not give any information on the chemical nature of the particles. Thus, the objective of this thesis is to develop new low-cost sensors able to measure specifically the concentration of ammonium nitrate particles. The measurement method is based on the thermal decomposition of ammonium nitrate particles into ammonia and nitric acid gas. The concentration of ammonia is measured using a sensitive layer based on conductive nanocomposite materials combining doped polyaniline and polyurethane matrix. Therefore, the concentration of the released ammonia is correlated to the mass concentration of ammonium nitrate particles. The sensors that are developed in this project showed a response to ammonia gas at concentrations as low as 20 ppb with a sensitivity of 0.35%.ppb-1, which corresponds to ammonia concentrations that are expected in ambient air and would allow the measurement of ammonium nitrate particles. The sensors also showed good repeatibility and reproductibility of their response to ammonia. The impact of temperature (23-50°C) and relative humidity (30%-90%) is also studied to assess the ability of the sensors to measure ammonia produced after the thermal decomposition of ammonium nitrate particles at temperatures and humidity that are favourable to their decomposition. Some sensitive materials showed a good response to ammonia gas even under these specific conditions. On the other hand, the sensors showed a response to gaseous nitric acid at 50°C (-4.85% at 195 ppb). Despite this interference, the sensors were able to measure ammonium nitrate particles at 50°C at concentrations in the order of 265 µg.m-3 with a sensitivitiy of 1.82.10-3%.µg-1.m3. These promising results demonstrate the ability of the sensors to measure ammonium nitrate particles through the proposed method. However, the interference of gaseous nitric acid could reduce the sensitivity of the sensors to these particles
2
Zhang, Jing. "Analyses of Atmospheric Pollutants in Atlanta and Hong Kong Using Observation-Based Methods". Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4768.
Abstract (sommario):
There are two parts in this study. The first part is to test the validity of the assumption of thermodynamic equilibrium between fine particulate (PM2.5) nitrate and ammonium and gas-phase nitric acid (HNO3(g)) and ammonia (NH3(g)). A rough estimation of the characteristic time to achieve thermodynamic equilibrium is first carried out, which suggests that PM2.5 and gas-phase species are in thermodynamic equilibrium. Then equilibrium is tested by calculating the equilibrium concentrations of HNO3(g) and NH3(g) implied by the PM2.5 inorganic composition, temperature and relative humidity observed at the Atlanta Supersite 1999 using ISORROPIA model.
The second part of this study is to analyze the ground-level ozone pollution precursor relationships in Hong Kong area. Characteristics of O3 precursors are explored. Trace gases NO and CO, VOCs, absorption coefficient, temperature and solar radiation are associated with the O3 formation. Specific VOC and VOC-sources that contribute most to the formation of photochemical smog are identified. The accuracy of pollutant emission inventories for Hong Kong and PRD region is also assessed. Combined with back trajectory information, dCO/dNOy is used to define whether O3 is locally or regionally occurred. An OBM is used to investigate the relative benefits of various emission-control strategies. Generally the formation of O3 throughout much of Hong Kong area is limited by VOC, in which reactive aromatics are dominant.
3
Taylor, Linda Lea. "Storage of Pine Tree Substrate Influences Plant Growth, Nitrification, and Substrate Properties". Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/40342.
Abstract (sommario):
Pine tree substrate (PTS) is a relatively new substrate for container crop production. There are no detailed studies that elucidate how storage time impacts PTS chemical, physical, and biological aspects. The objective of this research was to determine how PTS storage time influenced PTS chemical and physical properties, nitrification, and plant growth. Pine tree substrate was manufactured by hammer-milling chips of loblolly pine trees (Pinus taeda L.) through two screen sizes, 4.76 mm (PTS) and 15.9 mm amended with peat (PTSP). PTS and PTSP were amended with lime at five rates. A peat-perlite mix (PL) served as a control treatment. Prepared substrates were placed in storage bags and stored in an open shed in Blacksburg, Virginia. Subsamples were taken at 1, 42, 84, 168, 270, and 365 days. At each subsampling day, twelve 1-L containers were filled with each substrate. Six containers were left fallow and six were planted with marigold (Tagetes erecta L. â Inca Goldâ ) seedlings. Substrate was also collected from select treatments for Most Probable Number assays to estimate density of nitrifying microorganisms, and for chemical and physical property analyses. Pour-through extracts were collected from fallow containers at 0, 2, and 4 weeks, and from marigold containers at harvest for determination of pH, electrical conductivity, ammonium-N and nitrate-N. At harvest, marigold height, width, and dry weight were measured. At least 1 kgâ ¢m-3 lime for PTS, and 2 to 4 kgâ ¢m-3 lime for PTSP were needed to maintain pH values â ¥ 5.5 for 365 days. Bound acidity of unlimed PTS increased but cation exchange capacity for unlimed PTS and PTSP decreased over 365 days. Carbon to nitrogen ratio and bulk density values were unchanged over time in all treatments. There were minor changes in particle size distribution for limed PTS and unlimed and limed PTSP. Marigold growth in PTS and PTSP was â ¥ PL in all limed treatments, except at day 1. Nitrite-oxidizing microorganisms were present and nitrification occurred in PTS and PTSP at all subsampling days. Pine tree substrate is relatively stable in storage, but pH decreases, and lime addition may be necessary to offset this decrease.Ph. D.
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Yeh, Jia-Jau, e 葉佳昭. "On the Study of the Formation and Evolution of the Ammonium Nitrate Particles in the Controlled Environment". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/47194743887228223875.
Abstract (sommario):
碩士國立中央大學
環境工程研究所
82
Suspended particles has been the principal pollutant worsening the air quality in Taiwan. The major constituents are carbon contents, metal materials, water-soluble ions, and solidusts. Among these materials, the water-soluble ions occupied a significant proportion about 25 ~ 50% in the fine particles. Nonetheless, there are few studies on the effects of the temperature,relative humidity (RH), and light intensity of the environment during the formation and evolution of these particles. This work is focused on the generation and progression of the ammonium nitrate particles. Nitrogen dioxide, nitrous acid, and ammonium gas were injected into a continuous stirred tank reactor (CSTR) with artificial sunlight, controllable temperature, and RH. The reactants were converted into aerosol particles through a gas-to-particle process upon light incidence. The influences of the environmental factors on aerosol formation were investigated in this study. Based on the results, it was found that a good linear relationship existed between NO2 photolysis rate constant and light intensity. High temperature was beneficial to promote the production rate of the ammonium nitrate particles, whereas low temperature delayed their formations. The modal diameter (190nm) of the aerosol size distribution at 35℃ was larger than that (160nm) at 25℃ . The environment with low RH was harmful to the formation of the ammonium nitrate particles, the aerosol production rate reached the lowest under low temperature and RH. The increase of RH on the number of fine particles was helpful, especially at high value (74% in the study) the modal daimeter of the aerosol size distribution approached around 170 ~ 180nm compared with 150 ~ 160nm at low RH(10% in this work). Under the heterogeneous condensation of the ammonium nitrate particles, the modal diameter of the size distribution was increased from 150nm to 180nm which was probably due to the hygroscopic growth of the aerosol particles.
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Pimenta, João Manuel Rosa. "Micronização de partículas num jet mil". Master's thesis, 2013. http://hdl.handle.net/10316/38864.
Abstract (sommario):
Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra.O objectivo deste trabalho consiste no estudo e análise do processo de micronização de partículas num jet mill. Este tipo de moinho permite a micronização de partículas micrométricas sem qualquer contaminação pelos materiais de moagem. O projecto deste tipo de equipamento foi efectuado com o recurso à modelação simples de movimento de partículas, no interior de um escoamento, aplicado à separação ciclónica. Os resultados numéricos provaram que estávamos em condições de poder optimizar o projecto e construir um equipamento demonstrativo. A sua construção implicou também a selecção de materiais e o estudo comparativo com outros equipamentos congéneres. A validação experimental foi efectuada utilizando materiais como o nitrato de amónio e o carbonato de cálcio, sendo analisada a granulometria do material antes e após o processo de micronização, através de imagens obtidas num microscópio. Na realização dos ensaios, variou-se o número de jactos do jet mill e o tempo de funcionamento do processo, por forma a estabelecer perfis de funcionamento mais favoráveis à micronização das partículas. A componente energética do processo foi também considerada na análise efectuada. Os resultados comprovaram a validade do projecto efectuado e da sua construção. Demonstraram também que este tipo de equipamento se adequa mais à desaglomeração de partículas do que à sua micronização, quando se trata de partículas de escala micrométrica.
The aim of this work is the study and analyze of the process of micronization of particles in a jet mill. This type of milling allows the micronization of particles without any contamination by grinding materials. The design of this type of equipment has been carried out with the use of simple modeling of motion of particles within a flow, applied to the cyclonic separation. Numerical results proved that we were in a position to optimize the design and build a demonstrator equipment. Its construction also involved the selection of materials and the comparative study with other existing equipment. The experimental validation was carried out using materials such as ammonium nitrate and calcium carbonate, and the particle size of the material before and after the micronization process was analyzed through images obtained in a microscope. In the tests ranged, the number of jets and jet mill operating time of the process were optimized in order to establish the most favorable operation profiles for micronization of the particles. The energy component of the process was also considered in the analysis. The results confirmed the validity of the design and its construction. Also it was demonstrated that this type of equipment is more adequate to the deagglomeration of the particles than to their micronization, if the original particles are yet in a micrometer scale.
Capitoli di libri sul tema "Ammonium nitrate particles":
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Yokoyama, Seiji, e Katsuyoshi Saito. "Synthesis of Ultrafine Particles of Iron and Iron Nitride by Evaporation of Iron in Gas Mixtures of Argon and Ammonia or Argon and Nitrogen". In Materials Science Forum, 1047–50. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-462-6.1047.
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Amrousse, Rachid, Abderrahim Najah Elidrissi, Ahmed Bachar, Assia Mabrouk, Kainaubek Toshtay e Seitkhan Azat. "Nanosized Catalytic Particles for the Decomposition of Green Propellants as Substitute for Hydrazine". In Innovations and Applications of Hybrid Nanomaterials, 195–217. IGI Global, 2024. http://dx.doi.org/10.4018/979-8-3693-3268-9.ch009.
Abstract (sommario):
In the current chapter, the synthesis of nanosized catalytic particles posed a significant challenge, aimed at facilitating the thermal decomposition of various green propellants, such as hydroxylammonium nitrate (HAN) and ammonium dinitramide nitrate (ADN), with the intention of replacing conventional hydrazine as a monopropellant for satellite reaction control systems (RCS). This chapter delves into the methods employed for preparing catalytic nanoparticles and their impact on the thermal decomposition and combustion characteristics of these propellants. Additionally, the utilization of the developed systems combining {propellants + catalysts} in actual missions and within the industrial sector will be presented, thoroughly examined, and guided.
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Hildrew, Alan, e Paul Giller. "Running waters as ecosystems". In The Biology and Ecology of Streams and Rivers, 314–49. 2a ed. Oxford University PressOxford, 2023. http://dx.doi.org/10.1093/oso/9780198516101.003.0009.
Abstract (sommario):
Abstract Nutrients (mainly nitrogen and phosphorus) are essential for life. They are taken up and transformed by living things, while nutrients are mostly transported through catchments in solution (nitrogen) or mainly as particles (phosphorus). Plants require fixed (not molecular) nitrogen for growth, while transformations of nitrogen (largely N2, nitrous oxide, nitrate, nitrite and ammonium) are linked with the oxidation of organic matter, releasing energy to heterotrophic organisms. Phosphorus is less soluble and in clean waters is usually scarce (plants and microbes absorb it efficiently). Flow displaces nutrients downstream, creating a ‘spiral’ rather than a cycle. Streams reduce fixed nitrogen and release molecular nitrogen to the atmosphere but nutrient pollution increases leakage downstream and promotes the production of NO2. Agriculture is a source of nutrients, leading to a tension between food production and water security/climate change. Biotic vectors (e.g. animal migrations) transport nutrients across systems.
Atti di convegni sul tema "Ammonium nitrate particles":
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Bulgakov, Volodymyr, Ivan Holovach, Oleg Adamchuk, Adolfs Rucins e Aivars Aboltins. "Research in mineral fertiliser particle throwing distance from new centrifugal fertilizer spreader working tool". In 22nd International Scientific Conference Engineering for Rural Development. Latvia University of Life Sciences and Technologies, Faculty of Engineering, 2023. http://dx.doi.org/10.22616/erdev.2023.22.tf110.
Abstract (sommario):
The produced mineral fertiliser spreaders have the working width and productivity that do not satisfy today’s requirements in high-technology agricultural production. It refers also to the distance the mineral fertiliser particle can reach. We have developed a new centrifugal fertilizer spreading working tool with an inclined axis of rotation. It allows for increased distance of mineral particles at centrifugal spreading. The aim of the present research is to determine the throwing distance of the mineral particle from the spreading disc inclined to the horizon. The analytical research has been performed using the methods of modeling, mechanics and mathematics, as well as methods of calculation and computer modeling. In the result of the theoretical research differential equations were obtained describing throwing of the mineral fertiliser particles from the blades and their further distance after leaving the working tool. In the result of calculations new graphical dependences have been obtained of the throwing time from the blades and the distance the particles of different mineral fertilisers can reach, in particular ammonium nitrate, depending on the frequency of the disc rotation, angles of inclination to the horizontal plane, radius of feeding the mineral fertiliser particles, coefficient of friction along the surface of the disc etc. The obatined new analytical expressions and the developed graphical dependences allowed for determination of the working tool parameters that ensure maximal distance of mineral fertiliser particles at centrifugal spreading. The performed experimental investigations proved the correctness of the theoretical research and showed increased throwing distance at the used improved parameters of the new centrifugal working tool.
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Korotkikh, A. G., V. A. Arkhipov, I. V. Sorokin e E. A. Selikhova. "THERMAL BEHAVIOR AND IGNITION OF HIGH-ENERGY MATERIALS CONTAINING B, ALB2, AND TIB2". In 8TH INTERNATIONAL SYMPOSIUM ON NONEQUILIBRIUM PROCESSES, PLASMA, COMBUSTION, AND ATMOSPHERIC PHENOMENA. TORUS PRESS, 2020. http://dx.doi.org/10.30826/nepcap2018-2-14.
Abstract (sommario):
The paper presents the results of ignition and thermal behavior for samples of high-energy materials (HEM) based on ammonium perchlorate (AP) and ammonium nitrate (AN), active binder and powders of Al, B, AlB2, and TiB2. A CO2 laser with a heat flux density range of 90-200 W/cm2 was used for studies of ignition. The activation energy and characteristics of ignition for the HEM samples were determined. Also, the ignition delay time and the surface temperature of the reaction layer during the heating and ignition for the HEM samples were determined. It was found that the complete replacement of micron-sized aluminum powder by amorphous boron in a HEM sample leads to a considerable decrease in the ignition delay time by a factor of 2.2-2.8 at the same heat flux density due to high chemical activity and the difference in the oxidation mechanisms of boron particles. The use of aluminum diboride in a HEM sample allows one to reduce the ignition delay time of a HEM sample by a factor of 1.7-2.2. The quasi-stationary ignition temperature is the same for the AlB2-based and AlB12-based HEM samples.
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Garcia, E., L. Gan, R. Pilliar e T. Coyle. "Calcium Phosphate Coatings Produced by Solution Precursor Plasma Spray". In ITSC2005, a cura di E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2005. http://dx.doi.org/10.31399/asm.cp.itsc2005p0493.
Abstract (sommario):
Abstract Calcium phosphate (Ca-P) coatings have been used as surface coatings on porous metallic implants in dentistry and orthopaedics for the last twenty years. These Ca-P coatings, nominally hydroxyapatite (HA), have been shown to promote bone fixation and osteconductivity on Ti and Ti alloy substrates used for those purposes. Such coatings can be formed by different methods including plasma spray. In addition to the well known advantages of the plasma spray technique to deposit coatings, a new version of this technique, i.e. solution precursor plasma spray (SPPS), has been reported to produce submicron/nanocrystalline structured coatings. Nanocrystalline HA coatings may improve the resorption of the coating in the body, avoiding the irritant effect of large particles which may be seen in current thermal sprayed HA coatings. The main purpose of this work was to study the suitability of a sol-gel Ca-P solution precursor (calcium nitrate tetrahydrate and ammonium dihydrogen phosphate) as feedstock for the air plasma spray (APS) coating technique. We report on the formation and the characteristics of the coatings so formed on Ti6Al4V substrates. The presence of different Ca-P crystalline and amorphous phases was assessed by X-ray diffraction analysis. The X-ray photoelectron spectroscopy technique was used to characterize the surface chemical composition of the Ca-P coatings. The microstructural features of the coatings were characterized by scanning/transmission electron microscopy combined with image analysis in order to evidence the presence of submicron/nanocrystalline Ca-P features. Final results are discussed in terms of the spraying parameters. Abstract only; no full-text paper available.
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Miedema, Jan, Arjen Klein e Frans Zee. "Particle size distribution effect on burn rate of ammonium nitrate based propellant". In 31st Joint Propulsion Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1995. http://dx.doi.org/10.2514/6.1995-2714.
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Libersky, L. D. "Simulation of Void Collapse in Ammonium Nitrate Using a Meshfree Lagrangian Particle Method". In SHOCK COMPRESSION OF CONDENSED MATTER - 2003: Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter. AIP, 2004. http://dx.doi.org/10.1063/1.1780256.
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Endres, Derek, e Sandip Mazumder. "Computational Study of Pulsed Metal-Organic Chemical Vapor Deposition of Aluminum Nitride". In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-65525.
Abstract (sommario):
Particles of aluminum nitride (AlN) have been observed to form during epitaxial growth of AlN films by metal organic chemical vapor deposition (MOCVD). Particle formation is undesirable because particles do not contribute to the film growth, and are detrimental to the hydraulic system of the reactor. It is believed that particle formation is triggered by adducts that are formed when the group-III precursor, namely tri-methyl-aluminum (TMAl), and the group-V precursor, namely ammonia (NH3), come in direct contact in the gas-phase. Thus, one way to eliminate particle formation is to prevent the group-III and the group-V precursors from coming in direct contact at all in the gas-phase. In this article, pulsing of TMAl and NH3 is numerically investigated as a means to reduce AlN particle formation. The investigations are conducted using computational fluid dynamics (CFD) analysis with the inclusion of detailed chemical reaction mechanisms both in the gas-phase and at the surface. The CFD code is first validated for steady-state (non-pulsed) MOCVD of AlN against published data. Subsequently, it is exercised for pulsed MOCVD with various pulse widths, precursor gas flow rates, wafer temperature, and reactor pressure. It is found that in order to significantly reduce particle formation, the group-III and group-V precursors need to be separated by a carrier gas pulse, and the carrier gas pulse should be at least 5–6 times as long as the precursor gas pulses. The studies also reveal that with the same time-averaged precursor gas flow rates as steady injection (non-pulsed) conditions, pulsed MOCVD can result in higher film growth rates because the precursors are incorporated into the film, rather than being wasted as particles. The improvement in growth rate was noted for both horizontal and vertical reactors, and was found to be most pronounced for intermediate wafer temperature and intermediate reactor pressure.
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Korotkikh, A. G., V. A. Arkhipov, O. G. Glotov, I. V. Sorokin e E. A. Selikhova. "IGNITION, COMBUSTION, AND AGGLOMERATION OF HIGH-ENERGY MATERIALS BASED ON ALUMINUM AND BORON". In 8TH INTERNATIONAL SYMPOSIUM ON NONEQUILIBRIUM PROCESSES, PLASMA, COMBUSTION, AND ATMOSPHERIC PHENOMENA. TORUS PRESS, 2020. http://dx.doi.org/10.30826/nepcap2018-2-02.
Abstract (sommario):
The burning rate control of the high-energy materials (HEM) is mainly achieved by introducing the catalysts in composite solid propellant as well as by partial or complete replacement of ammonium perchlorate (AP) and ammonium nitrate by nitramines that change the equivalence ratio of formulation, or by varying the particle size of oxidizer and metal fuels. Promising metallic fuels are highly dispersed aluminum powders, which are characterized by different dispersity and passivation method, as well as bimetallic powders or mixtures of aluminum and other metals, their alloys, and metal powders with various coatings. In this study, the Al-based, Al/B-based, and Al/Fe-based HEM compositions have been used for comparative analysis of the ignition, combustion, and agglomeration characteristics. At the use of boron additive in the Al-based HEM, the ignition time is decreased by a factor of 1.2-1.4 and the burning rate is virtually unchanged as compared with that for the Al-based HEM. However, the agglomeration is significantly enhanced, which is manifested in the increase in the agglomerate particle content in condensed combustion products (CCP), increase in the agglomerate mean diameter, and increase in the unburned metal fraction in agglomerates.
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Endres, Derek, e Sandip Mazumder. "Numerical Investigation of Pulsed Chemical Vapor Deposition of Aluminum Nitride to Reduce Particle Formation". In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-65925.
Abstract (sommario):
Particles of aluminum nitride (AlN) have been observed to form during epitaxial growth of AlN films by metal organic chemical vapor deposition (MOCVD). Particle formation is undesirable because particles do not contribute to the film growth, and are detrimental to the hydraulic system of the reactor. It is believed that particle formation is triggered by adducts that are formed when the group-III precursor, namely tri-methyl-aluminum (TMAl), and the group-V precursor, namely ammonia (NH3), come in direct contact in the gas-phase. Thus, one way to eliminate particle formation is to prevent the group-III and the group-V precursors from coming in direct contact at all in the gas-phase. In this article, pulsing of TMAl and NH3 is numerically investigated as a means to reduce AlN particle formation. The investigations are conducted using computational fluid dynamics (CFD) analysis with the inclusion of detailed chemical reaction mechanisms both in the gas-phase and at the surface. The CFD code is first validated for steady-state (non-pulsed) MOCVD of AlN against published data. Subsequently, it is exercised for pulsed MOCVD with various pulse widths, precursor gas flow rates, wafer temperature, and reactor pressure. It is found that in order to significantly reduce particle formation, the group-III and group-V precursors need to be separated by a carrier gas pulse, and the carrier gas pulse should be at least 5–6 times as long as the precursor gas pulses. The studies also reveal that with the same time-averaged precursor gas flow rates as steady injection (non-pulsed) conditions, pulsed MOCVD can result in higher film growth rates because the precursors are incorporated into the film, rather than being wasted as particles. The improvement in growth rate was noted for both horizontal and vertical reactors, and was found to be most pronounced for intermediate wafer temperature and intermediate reactor pressure.
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Yan, Zheng, Tong Ti, Jing Shi-wei, Li Huan-yu, Liu Xuan, Gao Ya-dong e Nian Rui-xue. "A Movable Device of Explosives Detection". In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-66070.
Abstract (sommario):
This paper introduces a movable detection device for explosives hidden in wall. The device is composed of the 14MeV neutron generator, the silicon detector and Φ76mm×76mm LYSO detector. The γ spectra produced by the inelastic scattering interaction provide the relative counts of C, N, O, which are converted into chemical fractions to distinguish the explosives from the organic compounds. The device using associate particle method reduces the background 200–300 times. The 300g ammonium nitrate and TNT explosive simulated samples placed behind the 15cm-thick and 10cm-thick wall is detected by the device, respectively, when the neutron intensity is 1×107n/s. Compared with other methods, the experimental results show that the device with associate particle method has higher detection space resolution ability and explosives recognition ability. The device can provide the support for the detection of explosives.
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Liu, J., Z. Yang, L. Wang, S. Yan, J. Zhang e F. Lin. "Preparation and Characterization of Nickel Clad h-BN Composite Powders for Abradable Sealing Coating". In ITSC2008, a cura di B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima e G. Montavon. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2008. http://dx.doi.org/10.31399/asm.cp.itsc2008p1120.
Abstract (sommario):
Abstract Nickel clad hexagonal boron nitride (h-BN) powders were prepared by reducing nickel ions from a solution under hydrogen pressure in the presence of ammonia as a complexing agent, and plasma spraying was carried out to deposit the corresponding coating. The microstructure, morphology and phase composition of the powders and the coating were characterized by optical microscope (OM), Scanning Electronic Microscope (SEM) and X-ray Diffraction (XRD), respectively. The results show that alkali solution pretreatment and activation procession are necessary for acquiring a dense and uniform nickel coating on the surface of the h-BN particles, and the h-BN particles are distributed well throughout the coating with the porosity of about 26%, which indicate that the coating was potential for abradable sealing application.