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1

Decomposition of NH3 on Ir(100): A Temperature Programmed Desorption Study A. K. Santra, B. K. Min, C. W. Yi, Kai Luo, T. V. Choudhary, and D. W. Goodman*  

E-print Network

Decomposition of NH3 on Ir(100): A Temperature Programmed Desorption Study A. K. Santra, B. K. Min 27, 2001 Ammonia adsorption has been studied on an Ir(100) surface in the temperature range 100-410 K. In contrast to previous studies on Ir(111), approximately 12% of the chemisorbed ammonia undergoes stepwise

Goodman, Wayne

2

A dynamic calibration technique for temperature programmed desorption spectroscopy  

NASA Astrophysics Data System (ADS)

A novel, rapid and accurate calibration procedure as a means for quantitative gas desorption measurement by temperature programmed desorption (TPD) spectroscopy is presented. Quantitative measurement beyond the linear regime of the instrument is achieved by associating an instantaneous calibrated molar flow rate of gas to the detector response. This technique is based on fundamental methods, and is independently verified by comparison to the hydrogen desorption capacity of a known standard metal hydride with known stoichiometry. The TPD calibration procedure described here may be used for any pure gas, and the accuracy is demonstrated for the specific case of hydrogen.

Hurst, K. E.; Heben, M. J.; Blackburn, J. L.; Gennett, T.; Dillon, A. C.; Parilla, P. A.

2013-02-01

3

DFT study of ammonia desorption from the GaN(0001) surface covered with a NH3/NH2 mixture  

NASA Astrophysics Data System (ADS)

Properties of the GaN(0001) surface, fully covered by a mixture of NH3 molecules and NH2 radicals, were investigated by DFT simulations. It is shown that for extremely low ammonia content, the Fermi level at the surface is at valence band maximum (VBM), then at the 25% ammonia in coverage it is depinned, moving upward in the bandgap to reach conduction band minimum (CBM) at higher ammonia percentages. It is shown that the 25% ammonia in the coverage is corresponding to a flat band configuration in accordance with ECR arguments. The stability of the mixed NH2/NH3 coverage with respect to detachment of ammonia molecules or molecular hydrogen was also investigated. It was shown that high ammonia fraction leads to instability of the coverage due to detachment of ammonia or of molecular hydrogen. The instability point is reached for 36% and 41% fraction of ammonia in the coverage for desorption of molecular hydrogen and ammonia, respectively. The energy barrier for detachment of molecular hydrogen is consistently higher since the H2 molecule has to be created first in the course of desorption process. The ammonia is simply detached in the molecular form so that the high energy intermediate configuration is absent.

Kempisty, Pawel; Strak, Pawel; Sakowski, Konrad; Krukowski, Stanislaw

2014-10-01

4

Temperature-Programmed Desorption of Oxalate from the Goethite Surface  

SciTech Connect

The TPD-FTIR technique was used to investigate the relative thermal stabilities and decomposition reactions of different oxalate complexes adsorbed on the dry goethite surface. The measurements showed that important differences in coordination have a considerable impact on the thermal stability of the surface complexes. Three important stages of desorption were identified from both TPD (Figure 1) and FTIR data in the 300-900 K range. Stage I (300-440 K) corresponds to the desorption of weakly-bound oxalate molecules with decomposition pathways characteristic of oxalic acid. Stage II (440-520 K) corresponds to the dehydration of key surface OH2 groups responsible in stabilizing hydrogen-bonded surface complexes. These species can either decompose via typical oxalic acid decomposition pathways or convert to metal-bonded surface complexes. Finally, Stage III (520-660 K) corresponds to the thermal decomposition of all metal-bonded oxalate complexes, proceeding through a two-electron reduction pathway that converts oxalate to CO2. Experiments in the absence of oxalate were used to assess the contributions from dehydration, dehydroxylation and decarbonation reactions from the goethite bulk.

Boily, Jean F.

2007-08-31

5

Temperature programmed desorption from LiAlO 2 treated with H 2  

NASA Astrophysics Data System (ADS)

Temperature programmed desorption (TPD) measurements have been made of H 2O and H 2 desorption from LiAlO 2 treated at 923 K with He-H 2 mixtures containing 990, 495, and 247 vppm H 2. Desorptions were into sweep gases of pure He and into He-H 2 mixtures. The H 2O and H 2 desorption peaks were shown to be the sums of first order subpeaks which had reproducible desorption activation energy and pre-exponential terms. For H 2O desorption, the activation energies were 96, 117, and 134 kJ/mol (23, 28, and 32 kcal/mol). (Earlier work had identified an additional peak with an activation energy of 75 kJ/mol (18 kcal/mol.) Enhancement of desorption of H 2O by H 2 in the sweep gas was confirmed. The enhancement results not from modifying the activation energies and pre-exponential terms for the various sites but from changes in the populations of sites participating in the desorption process so that sites with lower activation energies are increasingly involved. For those runs with He as the sweep gas, desorption of H 2 could be observed. The subpeaks involved had activation energies within approximately 4 kJ/mol (1 kcal/mol) higher than the analogous peaks for H 2O desorption.

Fischer, Albert K.

1992-09-01

6

Temperature programmed desorption and infrared spectroscopic studies of thin water films on MgO(100)  

E-print Network

such as physisorption versus chemi- sorption and the orientation of water molecules in the first few monolayers deserveTemperature programmed desorption and infrared spectroscopic studies of thin water films on MgO(100 Abstract Thin water (D2O) films on MgO(100) surfaces have been studied. Water was deposited at 115 K

Reisler, Hanna

7

Intermittent temperature-programmed desorption study of perovskites used for catalytic purposes  

NASA Astrophysics Data System (ADS)

A differential desorption technique, called intermittent temperature-programmed desorption (ITPD), was used to give new insights into the properties of La 1- xSr xCo 0.8Fe 0.2O 3 perovskites as a contribution to improve their performances with respect to various important application fields such as catalysis, electrocatalysis and solid oxide fuel cells (SOFC). Both ITPD and interrupted TPD (carried out at different heating rates) evidenced two distinct oxygen adsorbed states, desorbing at temperatures lower than 400 °C, corresponding to less than 5% of a compact monolayer of oxide ions. The first one, for low desorption temperatures (lower than 290 °C) exhibits a heat of adsorption (? H) distribution from 101 to 121 kJ mol -1. The second one, for higher desorption temperatures (between 290 and 400 °C) corresponds to ? H = 146 ± 4 kJ mol -1. Additionally, for temperatures higher than 400 °C, we observed a continuous desorption of oxygen species, probably originating from the sub-surface or semi-bulk, with an associated activation energy of desorption ?175 kJ mol -1.

Gaillard, F.; Joly, J. P.; Boréave, A.; Vernoux, P.; Deloume, J.-P.

2007-04-01

8

TEMPERATURE-PROGRAMMED DESORPTION: PRINCIPLES, INSTRUMENT DESIGN, AND DEMONSTRATION WITH NAALH4  

SciTech Connect

This article is a brief introduction to temperature-programmed desorption (TPD), an analytical technique devised to analyze, in this case, materials for their potential as hydrogen storage materials. The principles and requirements of TPD are explained and the different components of a generic TPD apparatus are described. The construction of a modified TPD instrument from commercially available components is reported together with the control and acquisition technique used to create a TPD spectrum. The chemical and instrumental parameters to be considered in a typical TPD experiment and the analytical utility of the technique are demonstrated by the dehydrogenation of titanium-doped NaAlH{sub 4} by means of thermally programmed desorption.

Stowe, A; Ragaiy Zidan, R

2006-11-07

9

Effects of surface coordination on the temperature-programmed desorption of oxalate from goethite  

SciTech Connect

The temperature-programmed desorption (TPD) of weakly-bound, hydrogen-bonded and metal-bonded oxalate complexes at the goethite surface was investigated in the 300-900 K range with concerted Fourier Transform Infrared (FTIR) measurements (TPD-FTIR). These reactions took place with the concomitant dehydroxylation reaction of goethite to hematite and decarbonation of bulk-occluded carbonate. The measurements revealed three important stages of desorption. Stage I (300-440 K) corresponds to the desorption of weakly-and/or un-bound oxalate molecules in the goethite powder with a thermal decomposition reaction pathway characteristic of oxalic acid. Stage II (440-520 K) corresponds to a thermally-driven dehydration of hydrogen-bonded surface complexes, leading to a partial desorption via oxalic acid thermal decomposition pathways and to a partial conversion to metal-bonded surface complexes. This latter mechanism led to the increase in FTIR bands characteristic of these complexes. Finally, Stage III (520-660 K) corresponds to the thermal decomposition of the metal-bonded oxalate complex, proceeding through a 2 electron reduction pathway.

Boily, Jean F.; Szanyi, Janos; Felmy, Andrew R.

2007-11-15

10

Molecular Hydrogen Formation on Low Temperature Surfaces in Temperature Programmed Desorption Experiments  

E-print Network

The study of the formation of molecular hydrogen on low temperature surfaces is of interest both because it allows to explore elementary steps in the heterogeneous catalysis of a simple molecule and because of the applications in astrochemistry. Here we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations and the activation energies of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results can thus be used to evaluate the formation rate of H_2 on dust grains under the actual conditions present in interstellar clouds.

G. Vidali; V. Pirronello; L. Li; J. Roser; G. Manico; R. Mehl; A. Lederhendler; H. B. Perets; J. R. Brucato; O. Biham

2007-08-13

11

Molecular Hydrogen Formation on Low Temperature Surfaces in Temperature Programmed Desorption Experiments  

E-print Network

The study of the formation of molecular hydrogen on low temperature surfaces is of interest both because it allows to explore elementary steps in the heterogeneous catalysis of a simple molecule and because of the applications in astrochemistry. Here we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations and the activation energies of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results can thus be used to evaluate the formation rate of H_2 on dust grains under the actual conditions...

Vidali, G; Li, L; Roser, J; Manico, G; Mehl, R; Lederhendler, A; Perets, H B; Brucato, J R; Biham, O

2007-01-01

12

Analysis of molecular hydrogen formation on low-temperature surfaces in temperature programmed desorption experiments.  

PubMed

The study of the formation of molecular hydrogen on low-temperature surfaces is of interest both because it enables the exploration of elementary steps in the heterogeneous catalysis of a simple molecule and because of its applications in astrochemistry. Here, we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments, beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations, and the energy barriers of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results are used in order to evaluate the formation rate of H2 on dust grains under the actual conditions present in interstellar clouds. It is found that, under typical conditions in diffuse interstellar clouds, amorphous silicate grains are efficient catalysts of H2 formation when the grain temperatures are between 9 and 14 K. This temperature window is within the typical range of grain temperatures in diffuse clouds. It is thus concluded that amorphous silicates are good candidates to be efficient catalysts of H2 formation in diffuse clouds. PMID:17988107

Vidali, G; Pirronello, V; Li, L; Roser, J; Manicó, G; Congiu, E; Mehl, H; Lederhendler, A; Perets, H B; Brucato, J R; Biham, O

2007-12-13

13

Temperature-Programmed Desorption Observation of Graphene-on-Silicon Process  

NASA Astrophysics Data System (ADS)

With its industrial adaptability, graphene-on-silicon (GOS), formed by ultrahigh-vacuum annealing of a SiC thin film on a silicon substrate, is attracting recent attention. Little is known, however, about the growth mechanism of GOS. We demonstrate in this paper that temperature-programmed-desorption spectroscopy of deuterium (D2-TPD) can be a powerful in-situ probe to investigate the surface chemistry during formation of epitaxial graphene (EG) on SiC crystals. Using the D2-TPD, the surface stoichiometry and the back-bonds of the surface atoms, including their dependence on the crystallographic orientations [Si(111), Si(100), and Si(110)] can be obtained. Difference in the growth mechanism of GOS among the orientations is discussed based on the results.

Abe, Shunsuke; Handa, Hiroyuki; Takahashi, Ryota; Imaizumi, Kei; Fukidome, Hirokazu; Suemitsu, Maki

2011-07-01

14

Catalytic reduction of CO with hydrogen sulfide. 4. Temperature-programmed desorption of methanethiol on anatase, rutile, and sulfided rutile  

SciTech Connect

The interaction of methanethiol with anatase, rutile, and sulfided rutile was studied by temperature-programmed desorption. Dissociative adsorption occurs on rutile but is insignificant on anatase. Decomposition products are dominated by H/sub 2/ on rutile and by CH/sub 4/ on sulfided rutile. In both cases desorption occurs between 500 and 775 K. The 5- and 4-coordinate sites on the (110) face of rutile are proposed as the active sites for decomposition. The dominance of methane on a sulfided surface is attributed to the relatively large supply of highly mobile surface hydrogen atoms.

Beck, D.D.; White, J.M.; Ratcliffe, C.T.

1986-07-03

15

New method for the temperature-programmed desorption (TPD) of ammonia experiment for characterization of zeolite acidity: a review.  

PubMed

In this review, a method for the temperature-programmed desorption (TPD) of ammonia experiment for the characterization of zeolite acidity and its improvement by simultaneous IR measurement and DFT calculation are described. First, various methods of ammonia TPD are explained, since the measurements have been conducted under the concepts of kinetics, equilibrium, or diffusion control. It is however emphasized that the ubiquitous TPD experiment is governed by the equilibrium between ammonia molecules in the gas phase and on the surface. Therefore, a method to measure quantitatively the strength of the acid site (?H upon ammonia desorption) under equilibrium-controlled conditions is elucidated. Then, a quantitative relationship between ?H and H0 function is proposed, based on which the acid strength ?H can be converted into the H0 function. The identification of the desorption peaks and the quantitative measurement of the number of acid sites are then explained. In order to overcome a serious disadvantage of the method (i.e., no information is provided about the structure of acid sites), the simultaneous measurement of IR spectroscopy with ammonia TPD, named IRMS-TPD (infrared spectroscopy/mass spectrometry-temperature-programmed desorption), is proposed. Based on this improved measurement, Brønsted and Lewis acid sites were differentiated and the distribution of Brønsted OH was revealed. The acidity characterized by IRMS-TPD was further supported by the theoretical DFT calculation. Thus, the advanced study of zeolite acidity at the molecular level was made possible. Advantages and disadvantages of the ammonia TPD experiment are discussed, and understanding of the catalytic cracking activity based on the derived acidic profile is explained. PMID:23868494

Niwa, Miki; Katada, Naonobu

2013-10-01

16

Temperature programed desorption of C{sub 2}H{sub 4} from pure and graphite-covered Pt(111)  

SciTech Connect

Ethylene adsorption on Pt(111) at 95 K was studied by temperature programed desorption (TPD), low energy electron diffraction (LEED), and x-ray photoelectron spectroscopy. Ethylene desorbs reversibly at 112 K and irreversibly at 255 and 280 K. It is generally accepted that annealing of ethylene adsorbed on Pt(111) to 300 K results in a dehydrogenation to ethylidyne through an ethylidene intermediate. This was observed by a hydrogen desorption peak at 300 K. Also, hydrogenation of the adsorbed ethylene was observed by a small ethane desorption peak at 300 K. Upon heating to 700 K, the ethylidyne species will further dehydrogenate to carbidic carbon species with hydrogen desorption peaks at 460 and 640 K. If the carbidic species is heated to higher temperatures (up to 1000 K), it will further dehydrogenate and form graphitic islands which will accumulate by Ostwald ripening in larger islands at the step edges of the surface. After annealing the sample to 1000 K, a statistically distributed 8x8 superstructure of these graphite islands is achieved, as interpreted from A pattern in the LEED data. The TPD results indicate that ethylene adsorption on Pt(111) results in the formation of graphitic islands upon heating to 1000 K, contrary to previous conjectures of formation of a full graphite monolayer.

Vermang, B.; Juel, M.; Raaen, S. [Physics Department, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim (Norway)

2007-11-15

17

The effect of oxygen vacancies on the binding interactions of NH3 with rutile TiO2(110) -1×1  

SciTech Connect

A series of NH3 temperature-programmed desorption (TPD) spectra was taken after the NH3 dose at 70 K on rutile TiO2(110)-1×1 surfaces with the oxygen vacancy (VO) concentrations of ~0% (p-TiO2) and 5% (r-TiO2), respectively, to study the effect of VO’s on the desorption energy of NH3 as a function of the coverage, ?. Our results show that at zero coverage limit, the desorption energy of NH3 on r-TiO2 is 115 kJ/mol, which is 10 kJ/mol less than that on p-TiO2. The desorption energy from the Ti4+ sites decreases with increasing ? due to the repulsive NH3 - NH3 interactions and approaches ~ 55 kJ/mol upon the saturation of Ti4+ sites (? = 1 monolayer, ML) on both p- and r-TiO2. The absolute saturation coverage is determined to be about 10% smaller on r-TiO2 than that on p-TiO2. Further, the trailing edges of the NH3 TPD spectra on the hydroxylated TiO2(110) (h-TiO2) appear to be the same as that on r-TiO2 while those on oxidized TiO2(110) (o-TiO2) shift to higher temperatures. We present the detailed analysis of the results and reconcile the observed differences based on the repulsive adsorbate-adsorbate interactions between neighboring NH3 molecules and the surface charge associated with the presence of VO’s. Besides NH3, no other reaction products are observed in the TPD spectra.

Kim, Boseong; Li, Zhenjun; Kay, Bruce D.; Dohnalek, Zdenek; Kim, Yu Kwon

2012-11-21

18

Adsorption and reaction of formic acid on NiO(lOO) films on Mo(l00): Temperature programmed desorption and high resolution electron  

E-print Network

Adsorption and reaction of formic acid on NiO(lOO) films on Mo(l00): Temperature programmed desorption and high resolution electron energy loss spectroscopy studies Charles M. Truong, Ming-Cheng Wu-3255 (Received 24 June 1992;accepted8 September1992) Adsorption and reaction of formic acid on well-defined Ni

Goodman, Wayne

19

UV-Raman spectroscopy, X-ray photoelectron spectroscopy, and temperature programmed desorption studies of model and bulk heterogeneous catalysts  

SciTech Connect

X-ray photoelectron spectroscopy (XPS) and Temperature Programmed Desorption (TPD) have been used to investigate the surface structure of model heterogeneous catalysts in ultra-high vacuum (UHV). UV-Raman spectroscopy has been used to probe the structure of bulk model catalysts in ambient and reaction conditions. The structural information obtained through UV-Raman spectroscopy has been correlated with both the UHV surface analysis and reaction results. The present day propylene and ethylene polymerization catalysts (Ziegler-Natta catalysts) are prepared by deposition of TiCl{sub 4} and a Al(Et){sub 3} co-catalyst on a microporous Mg-ethoxide support that is prepared from MgCl{sub 2} and ethanol. A model thin film catalyst is prepared by depositing metallic Mg on a Au foil in a UHV chamber in a background of TiCl{sub 4} in the gas phase. XPS results indicate that the Mg is completely oxidized to MgCl{sub 2} by TiCl{sub 4} resulting in a thin film of MgCl{sub 2}/TiCl{sub x}, where x = 2, 3, and 4. To prepare an active catalyst, the thin film of MgCl{sub 2}/TiCl{sub x} on Au foil is enclosed in a high pressure cell contained within the UHV chamber and exposed to {approx}1 Torr of Al(Et){sub 3}.

Tewell, Craig R.

2002-08-19

20

Characterization of Lewis acid sites on the (100) surface of beta-AlF3: Ab initio calculations of NH3 adsorption.  

PubMed

The current study employs hybrid-exchange density functional theory to show that the Lewis base, NH(3), binds to the beta-AlF(3) (100) surface with a binding energy (BE) of up to -1.96 eV per molecule. This is characteristic of a strong Lewis acid. The binding of NH(3) to the surface is predominately due to electrostatic interactions. There is only a small charge transfer from the NH(3) molecule to the surface. The BE as a function of coverage is computed and used to develop a lattice Monte Carlo model which is used to predict the temperature programed desorption (TPD) spectrum. Comparison with experimental TPD studies of NH(3) from beta-AlF(3) strongly suggests that these structural models and binding mechanisms are good approximations to those that occur on real AlF(3) surfaces. PMID:18554039

Bailey, C L; Wander, A; Mukhopadhyay, S; Searle, B G; Harrison, N M

2008-06-14

21

Thermal stability of water and hydroxyl on the surface of the Moon from temperature-programmed desorption measurements of lunar analog materials  

NASA Astrophysics Data System (ADS)

The adsorption of molecular water onto lunar analog materials was investigated under ultra-high vacuum with the goal to better understand the thermal stability and evolution of water on the lunar surface. Temperature-programmed desorption (TPD) experiments show that lunar-analog basaltic-composition glass is hydrophobic, with water-water interactions dominating over surface chemisorption. This suggests that lunar agglutinates will tend not to adsorb water at temperatures above where water clusters and multilayer ice forms. The basalt JSC-1A lunar mare analog, which is a complex mixture of minerals and glass, adsorbs water above 180 K with an adsorption profile that extends to 400 K, showing evidence for a continuum of water adsorption sites. Bancroft albite adsorbs more water, more strongly, than JSC-1A, with a well-defined desorption peak near 225 K. This suggests that mineral surfaces will adsorb more water than mare or mature (glassy, agglutinate rich) surfaces and may explain the association of water with fresh feldspathic craters at high latitudes. The activation energies for the thermal desorption of water from these materials were determined, and along with values from the literature, used to model the grain-to-grain migration of water within the lunar regolith. These models suggest that a combination of recombinative desorption of hydroxyl along with molecular desorption of water and its subsequent migration within and out of the regolith may explain observed diurnal variations in the distribution of water and hydroxyl on the illuminated Moon.

Hibbitts, C. A.; Grieves, G. A.; Poston, M. J.; Dyar, M. D.; Alexandrov, A. B.; Johnson, M. A.; Orlando, T. M.

2011-05-01

22

Adsorption and decomposition of nickelocene on Ag(1 0 0): a high-resolution electron energy loss spectroscopy and temperature programmed desorption study  

NASA Astrophysics Data System (ADS)

Nickelocene adsorption and decomposition on the Ag(1 0 0) surface were studied with temperature programmed desorption and high resolution electron energy loss spectroscopy. At monolayer coverages on the relatively inert Ag(1 0 0) surface at 175 K, nickelocene physisorbs molecularly, with its molecular axis perpendicular to the surface plane. Nickelocene begins decomposing to adsorbed cyclopentadienyl and nickel at 225 K. Molecular desorption is only observed from multilayer material, at 210 K, or from the first monolayer if adjacent surface sites for decomposition are not available. The cyclopentadienyl decomposes through disproportionation to cyclopentadiene, which desorbs, and adsorbed nickel and carbon fragments on the Ag(1 0 0) surface with a maximum at 525 K.

Pugmire, D. L.; Woodbridge, C. M.; Boag, N. M.; Langell, M. A.

2001-02-01

23

Thermomagnetic Torque in Nh3  

E-print Network

June 1970) A study of the thermomagnetic torque (Scott effect) in NH3 is reported. The small posi- tive Scott torque is measured as a function of magnetic field for absolute pressures of 0.028, 0.043, 0.048, 0.057, and 0.078 Torr. At maximum torque..., the magnetic field Hp for each pressure P is given by Hp ?-b(P+a), where a=-4. 4&&10 3 Torr and b=3. 18&&103 Oe/Torr. INTRODUCTION In 1967 Scott, Sturner, and Williamson' opened an exciting new field with the discovery of a thermo- magnetic torque on a...

Adair, Thomas W.; McClurg, G. R.

1970-01-01

24

5, 25832605, 2008 Stomatal NH3  

E-print Network

grass species such as Phleum pratense and Lolium multiflorum had NH3 compensation points below species (Lolium perenne, Festuca pratensis and Dactylis glomerata) had sufficiently high NH3 compensation

Paris-Sud XI, Université de

25

Measurement of the Reversible Hydrogen Storage Capacity of Milligram Ti-6A1-4V Alloy Samples with Temperature Programmed Desorption and Volumetric Techniques  

SciTech Connect

We report the results of a study using temperature programmed desorption (TPD) and a volumetric sorption technique to measure the hydrogen storage capacity of the Ti-6Al-4V alloy. Samples of various sizes and surface treatments were studied to obtain a statistically meaningful value for the maximum hydrogen storage capacity, as well as to understand the effect of sample size, sample oxidation, and hydrogen charging conditions on the measured capacity. We find a maximum reversible hydrogen storage capacity of {approx} 3.76 wt% with hydrogen exposures near ambient temperature and pressure. This value is higher than any reported in the literature previously, possibly due to the utilization of very small particles and rapid hydrogen exposures, which allow for equilibration times of approximately 1 h. Comparison of a variety of samples indicates that the measured hydrogen capacity is affected by surface oxidation. Samples generated in a strongly oxidizing environment exhibit decreased hydrogen uptake. The implications of these results are discussed with regards to previously reported capacity values in the literature.

Blackburn, J. L.; Parilla, P. A.; Gennett, T.; Hurst, K. E.; Dillon, A. C.; Heben, M. J.

2007-01-01

26

Temperature-programmed desorption investigation of the adsorption and reaction of butene isomers on Pt(111) and ordered Pt-Sn surface alloys  

SciTech Connect

The influence of alloyed Sn on the chemistry of C{sub 4} butene isomers, including 1-butene, cis-2-butene, and isobutene, chemisorbed on Pt(111) was investigated by temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and low-energy electron diffraction (LEED). Pt-Sn alloy chemistry was probed by investigation of two ordered surface alloys formed when Sn atoms were incorporated within the topmost layer on a Pt(111) substrate. All three butenes undergo decomposition on Pt(111) during TPD which accounts for 50-60% of the chemisorbed monolayer. Alloying Sn into the surface causes a large reduction in the reactivity of the surface, and the fraction of the chemisorbed layer which decomposes is decreased to 3-7% on the (2 x 2) alloy, and no decomposition occurs on the ({radical}3 x {radical}3)R30{degree} alloy. The strong reduction of decomposition on these two surface alloys may be due to the elimination of adjacent pure Pt 3-fold hollow sites. No large changes occur in the coverage of chemisorbed monolayer of butenes in the presence of up to 33% of a monolayer of alloyed Sn, showing that the adsorption ensemble requirement for chemisorption of these alkenes on Pt(111) and the two Sn/Pt(111) alloys is at most a few Pt atoms. 39 refs., 15 figs., 1 tab.

Tsai, Y.L.; Koel, B.E. [Univ. of Southern California, Los Angeles, CA (United States)] [Univ. of Southern California, Los Angeles, CA (United States)

1997-04-10

27

Surface characterization of oxygen-functionalized multi-walled carbon nanotubes by high-resolution X-ray photoelectron spectroscopy and temperature-programmed desorption  

NASA Astrophysics Data System (ADS)

Multi-walled carbon nanotubes were exposed either to nitric acid or to an oxygen plasma to synthesize oxygen-containing functional groups which were characterized by high-resolution X-ray photoelectron spectroscopy (XPS). The C 1s spectra revealed that the treatment with nitric acid mainly resulted in the formation of carboxylic (COOR) and phenolic (C sbnd OR) groups, whereas the plasma treatment led to a higher amount of carbonyl (C dbnd O) groups. Furthermore, the nitric acid treatment yielded a 60% higher surface oxygen concentration compared to the plasma treatment, and created a minor amount of nitrogen-containing functional groups. Thus, the nitric acid treatment was found to be more effective in creating acidic functional groups. The presence and the thermal stability of these groups was also investigated by temperature-programmed desorption (TPD). The release of carbon dioxide was detected at about 350 and 450 °C, indicating the decomposition of COOR groups. The C dbnd O groups were more stable decomposing even above 600 °C. In addition, ammonia was adsorbed as probe molecule followed by TPD to derive the amount and the acidity of the carboxylic and phenolic groups.

Xia, Wei; Wang, Yuemin; Bergsträßer, Ralf; Kundu, Shankhamala; Muhler, Martin

2007-10-01

28

Regeneration of field-spent activated carbon catalysts for low-temperature selective catalytic reduction of NOx with NH3  

SciTech Connect

In the process of producing liquid crystal displays (LCD), the emitted NOx is removed over an activated carbon catalyst by using selective catalytic reduction (SCR) with NH3 at low temperature. However, the catalyst rapidly deactivates primarily due to the deposition of boron discharged from the process onto the catalyst. Therefore, this study is aimed at developing an optimal regeneration process to remove boron from field-spent carbon catalysts. The spent carbon catalysts were regenerated by washing with a surfactant followed by drying and calcination. The physicochemical properties before and after the regeneration were investigated by using elemental analysis, TG/DTG (thermogravimetric/differential thermogravimetric) analysis, N2 adsorption-desorption and NH3 TPD (temperature programmed desorption). Spent carbon catalysts demonstrated a drastic decrease in DeNOx activity mainly due to heavy deposition of boron. Boron was accumulated to depths of about 50 {mu}m inside the granule surface of the activated carbons, as evidenced by cross-sectional SEM-EDX analysis. However, catalyst activity and surface area were significantly recovered by removing boron in the regeneration process, and the highest NOx conversions were obtained after washing with a non-ionic surfactant in H2O at 70 C, followed by treatment with N2 at 550 C.

Jeon, Jong Ki; Kim, Hyeonjoo; Park, Young-Kwon; Peden, Charles HF; Kim, Do Heui

2011-10-15

29

Temperature-programmed decomposition desorption of mercury species over activated carbon sorbents for mercury removal from coal-derived fuel gas  

SciTech Connect

The mercury (Hg{sup 0}) removal process for coal-derived fuel gas in the integrated gasification combined cycle (IGCC) process will be one of the important issues for the development of a clean and highly efficient coal power generation system. Recently, iron-based sorbents, such as iron oxide (Fe{sub 2}O{sub 3}), supported iron oxides on TiO{sub 2}, and iron sulfides, were proposed as active mercury sorbents. The H{sub 2}S is one of the main impurity compounds in coal-derived fuel gas; therefore, H{sub 2}S injection is not necessary in this system. HCl is also another impurity in coal-derived fuel gas. In this study, the contribution of HCl to the mercury removal from coal-derived fuel gas by a commercial activated carbon (AC) was studied using a temperature-programmed decomposition desorption (TPDD) technique. The TPDD technique was applied to understand the decomposition characteristics of the mercury species on the sorbents. The Hg{sup 0}-removal experiments were carried out in a laboratory-scale fixed-bed reactor at 80-300{sup o}C using simulated fuel gas and a commercial AC, and the TPDD experiments were carried out in a U-tube reactor in an inert carrier gas (He or N{sub 2}) after mercury removal. The following results were obtained from this study: (1) HCl contributed to the mercury removal from the coal-derived fuel gas by the AC. (2) The mercury species captured on the AC in the HCl{sup -} and H{sub 2}S-presence system was more stable than that of the H{sub 2}S-presence system. (3) The stability of the mercury surface species formed on the AC in the H{sub 2}S-absence and HCl-presence system was similar to that of mercury chloride (HgClx) species. 25 refs., 12 figs., 1 tab.

M. Azhar Uddin; Masaki Ozaki; Eiji Sasaoka; Shengji Wu [Okayama University, Okayama (Japan). Faculty of Environmental Science and Technology

2009-09-15

30

Thermal desorption of circumstellar and cometary ice analogs  

NASA Astrophysics Data System (ADS)

Context. Thermal annealing of interstellar ices takes place in several stages of star formation. Knowledge of this process comes from a combination of astronomical observations and laboratory simulations under astrophysically relevant conditions. Aims: For the first time we present the results of temperature programmed desorption (TPD) experiments with pre-cometary ice analogs composed of up to five molecular components: H2O, CO, CO2, CH3OH, and NH3. Methods: The experiments were performed with an ultra-high vacuum chamber. A gas line with a novel design allows the controlled preparation of mixtures with up to five molecular components. Volatiles desorbing to the gas phase were monitored using a quadrupole mass spectrometer, while changes in the ice structure and composition were studied by means of infrared spectroscopy. Results: The TPD curves of water ice containing CO, CO2, CH3OH, and NH3 present desorption peaks at temperatures near those observed in pure ice experiments, volcano desorption peaks after water ice crystallization, and co-desorption peaks with water. Desorption peaks of CH3OH and NH3 at temperatures similar to the pure ices takes place when their abundance relative to water is above ~3% in the ice matrix. We found that CO, CO2, and NH3 also present co-desorption peaks with CH3OH, which cannot be reproduced in experiments with binary water-rich ice mixtures. These are extensively used in the study of thermal desorption of interstellar ices. Conclusions: These results reproduce the heating of circumstellar ices in hot cores and can be also applied to the late thermal evolution of comets. In particular, TPD curves represent a benchmark for the analysis of the measurements that mass spectrometers on board the ESA-Rosetta cometary mission will perform on the coma of comet 67P/Churyumov-Gerasimenko, which will be active before the arrival of Rosetta according to our predictions.

Martín-Doménech, R.; Muñoz Caro, G. M.; Bueno, J.; Goesmann, F.

2014-04-01

31

NH3-TPD-MS study of Ce effect on the surface of Mn- or Fe-exchanged zeolites for selective catalytic reduction of NOx by ammonia  

NASA Astrophysics Data System (ADS)

The selective catalytic reduction (SCR) of NOx with NH3 is considered to be a promising technique for the efficient reduction of highly detrimental NOx emitted from diesel engine vehicles to N2. This study was focused on a series of catalysts with ZSM-5 as support, prepared by Mn- or Fe-exchange followed by wet impregnation of Ce, or Fe or Mn. These catalysts were characterized by temperature-programmed desorption coupled with a mass spectrometer using ammonia (NH3-TPD-MS). Specifically, NH3-TPD-MS was used as a means of identifying the various strengths of acid sites and their relative abundance in an attempt to explain the effect of the catalyst surface acid sites on DeNOx activity. Acid sites with adsorption energies ranging from 47.0 to 75.6 kJ/mol were detected for all of the catalysts. For the same concentration of exchanged metal it was found that the DeNOx activity depends strongly on the type of metal. Furthermore, the acid site strength and distribution depend on the active metal and correlate with the observed DeNOx catalyst activity. Additionally, SEM metal mapping images confirmed the presence of well dispersed active metal on the surface of all catalysts. The catalysts with bimetallic active phase were stable and demonstrated high NOx conversion over a broad temperature range. Impregnation of metal-exchanged zeolites with Ce enhanced the low temperature NOx conversion. Observed differences of activity between the various catalysts of this study may be due to the formation of new ammonia activation sites. The ammonia desorption profile during the elevation of temperature was correlated to the DeNOx activity.

Stanciulescu, M.; Bulsink, P.; Caravaggio, G.; Nossova, L.; Burich, R.

2014-05-01

32

NH{sub 3} adsorption and decomposition on Ir(110): A combined temperature programmed desorption and high resolution fast x-ray photoelectron spectroscopy study  

SciTech Connect

The adsorption and decomposition of NH{sub 3} on Ir(110) has been studied in the temperature range from 80 K to 700 K. By using high-energy resolution x-ray photoelectron spectroscopy it is possible to distinguish chemically different surface species. At low temperature a NH{sub 3} multilayer, which desorbs at {approx}110 K, was observed. The second layer of NH{sub 3} molecules desorbs around 140 K, in a separate desorption peak. Chemisorbed NH{sub 3} desorbs in steps from the surface and several desorption peaks are observed between 200 and 400 K. A part of the NH{sub 3ad} decomposes into NH{sub ad} between 225 and 300 K. NH{sub ad} decomposes into N{sub ad} between 400 K and 500 K and the hydrogen released in this process immediately desorbs. N{sub 2} desorption takes place between 500 and 700 K via N{sub ad} combination. The steady state decomposition reaction of NH{sub 3} starts at 500 K. The maximum reaction rate is observed between 540 K and 610 K. A model is presented to explain the occurrence of a maximum in the reaction rate. Hydrogenation of N{sub ad} below 400 K results in NH{sub ad}. No NH{sub 2ad} or NH{sub 3ad}/NH{sub 3} were observed. The hydrogenation of NH{sub ad} only takes place above 400 K. On the basis of the experimental findings an energy scheme is presented to account for the observations.

Weststrate, C.J.; Bakker, J.W.; Rienks, E.D.L.; Lizzit, S.; Petaccia, L.; Baraldi, A.; Vinod, C.P.; Nieuwenhuys, B.E. [Leids Instituut voor Chemisch Onderzoek, Universiteit Leiden, P.O. Box 9502, Einsteinweg 55, 2333 CC Leiden (Netherlands); Sincrotrone Trieste, Strada Statale 14 km 163.5, I-34012 Basovizza (Italy); Physics Department and Center of Excellence for Nanostructured Materials, Trieste University, Via Valerio 2, I-34127 Trieste (Italy); Laboratorio TASC-INFM, Strada Statale 14 Km 163.5, I-34012 Trieste (Italy); Leids Instituut voor Chemisch Onderzoek, Universiteit Leiden, P.O. Box 9502, Einsteinweg 55, 2333 CC Leiden (Netherlands); Schuit Institute of Catalysis, Technische Universiteit Eindhoven, P.O. Box 5600 MB, Eindhoven (Netherlands)

2005-05-08

33

Photolysis of solid NH3 and NH3-H2O mixtures at 193 nm.  

PubMed

We have studied UV photolysis of solid ammonia and ammonia-dihydrate samples at 40 K, using infrared spectroscopy, mass spectrometry, and microgravimetry. We have shown that in the pure NH(3) sample, the main species ejected are NH(3), H(2), and N(2), where the hydrogen and nitrogen increase with laser fluence. This increase in N(2) ejection with laser fluence explains the increase in mass loss rate detected by a microbalance. In contrast, for the ammonia-water mixture, we see very weak signals of H(2) and N(2) in the mass spectrometer, consistent with the very small mass loss during the experiment and with a <5% decrease in the NH(3) infrared absorption bands spectroscopy after a fluence of ~3 × 10(19) photons/cm(2). The results imply that ammonia-ice mixtures in the outer solar system are relatively stable under solar irradiation. PMID:21142307

Loeffler, M J; Baragiola, R A

2010-12-01

34

The Inverse Modeling of NH3 Bidirectional Fluxes in CMAQ for NH3 Emission Estimates in the East United States  

NASA Astrophysics Data System (ADS)

NH3 bidirectional exchange is an important mechanism to control soil acidification and nitrification in biogeochemical cycles, and to affect emission/deposition processes of NH3 in atmospheric Chemistry Transport Models (CTMs). The latter is key to estimating NH3 emissions as well as ambient NH3 concentrations. However, current CTMs do not include NH3 bidirectional exchange because of the high uncertainties in parameterizations of such mechanism and a lack of observations for evaluation. Our study on the evaluation of NH3 using both surface and space based observations suggested the possibility that bidirectional exchange of NH3 might reduce the bias and error between model vs observation in North Carolina summer by improving estimated NH3 vertical profiles. With recent in-situ and satellite observations over North Carolina region and NH3 bidirectional exchange mechanism, we will assess NH3 emissions using inverse modeling techniques. The forward model, Community Multiscale Air Quality (CMAQ, v 5.0) model with NH3 bidirectional exchange was run for 12 km Continent Unites States (CONUS) domain from June 1st - August 31st, 2009. NH3 bidirectional fluxes from fertilizer applications were estimated using soil ammonium and pH from specific fertilizer application and management practices output from USDA agro-ecosystem model, Environmental Policy Integrated Climate (EPIC). We used inverse modeling approaches to optimize CMAQ NH3 concentration with surface observations such as Carolina Ammonia Monitoring Network (CAMNet) and Ammonia Monitoring Network (AMoN), and CMAQ Representative Volume Mixing Ratio (RVMR) with Topospheric Emission Spectrometer (TES) RVMR. A new NH3 emission estimate is compared with previous estimates. We also demonstrate how bidirectional exchange mechanism affects ambient NH3 vertical structure in the surface boundary layer, NH3 deposition velocity, and its atmospheric lifetime.

Jeong, G.; Bash, J. O.; Henze, D. K.

2011-12-01

35

Theoretical and experimental analysis of ammonia ionic clusters produced by 252Cf fragment impact on an NH3 ice target.  

PubMed

Positive and negatively charged ammonia clusters produced by the impact of (252)Cf fission fragments (FF) on an NH(3) ice target have been examined theoretical and experimentally. The ammonia clusters generated by (252)Cf FF show an exponential dependence of the cluster population on its mass, and the desorption yields for the positive (NH(3))(n)NH(4)(+) clusters are 1 order of magnitude higher than those for the negative (NH(3))(n)NH(2)(-) clusters. The experimental population analysis of (NH(3))(n)NH(4)(+) (n = 0-18) and (NH(3))(n)NH(2)(-) (n = 0-8) cluster series show a special stability at n = 4 and 16 and n = 2, 4, and 6, respectively. DFT/B3LYP calculations of the (NH(3))(0)(-)(8)NH(4)(+) clusters show that the structures of the more stable conformers follow a clear pattern: each additional NH(3) group makes a new hydrogen bond with one of the hydrogen atoms of an NH(3) unit already bound to the NH(4)(+) core. For the (NH(3))(0)(-)(8)NH(2)(-) clusters, the DFT/B3LYP calculations show that, within the calculation error, the more stable conformers follow a clear pattern for n = 1-6: each additional NH(3) group makes a new hydrogen bond to the NH(2)(-) core. For n = 7 and 8, the additional NH(3) groups bind to other NH(3) groups, probably because of the saturation of the NH(2)(-) core. Similar results were obtained at the MP2 level of calculation. A stability analysis was performed using the commonly defined stability function E(n)(-)(1) + E(n)(+1) - 2E(n), where E is the total energy of the cluster, including the zero point correction energy (E = E(t) + ZPE). The trend on the relative stability of the clusters presents an excellent agreement with the distribution of experimental cluster abundances. Moreover, the stability analysis predicts that the (NH(3))(4)NH(4)(+) and the even negative clusters [(NH(3))(n)NH(2)(-), n = 2, 4, and 6] should be the most stable ones, in perfect agreement with the experimental results. PMID:16913675

Fernandez-Lima, F A; Ponciano, C R; Chaer Nascimento, M A; da Silveira, E F

2006-08-24

36

Thermal desorption of circumstellar and cometary ice analogs  

E-print Network

Thermal annealing of interstellar ices takes place in several stages of star formation. Knowledge of this process comes from a combination of astronomical observations and laboratory simulations under astrophysically relevant conditions. For the first time we present the results of temperature programmed desorption (TPD) experiments with pre-cometary ice analogs composed of up to five molecular components: H2 O, CO, CO2, CH3 OH, and NH3 . The experiments were performed with an ultra-high vacuum chamber. A gas line with a novel design allows the controlled preparation of mixtures with up to five molecular components. Volatiles desorbing to the gas phase were monitored using a quadrupole mass spectrometer, while changes in the ice structure and composition were studied by means of infrared spectroscopy. The TPD curves of water ice containing CO, CO2, CH3 OH, and NH3 present desorption peaks at temperatures near those observed in pure ice experiments, volcano desorption peaks after water ice crystallization, and...

Martín-Doménech, Rafael; Bueno, Juan; Goesmann, Fred

2014-01-01

37

Condensation and Vaporization Studies of CH3OH and NH3 Ices: Major Implications for Astrochemistry  

NASA Technical Reports Server (NTRS)

In an extension of previously reported work on ices containing H20, CO, CO2, SO2, H2S, and H2, We present measurements of the physical and infrared spectral properties of ices containing CH30H and NH3.The condensation and sublimation behavior of these ice systems is discussed and surface binding energies are presented for all of these molecules. The surface binding energies can be used to calculate the residence times of the molecules on grain surfaces as a function of temperature. It is demonstrated that many of the molecules used to generate radio maps of and probe conditions in dense clouds, for example CO and NH3, will be significantly depleted from the gas phase by condensation onto dust grains. Attempts to derive total column densities solely from radio maps that do not take condensation effects into account may vastly underestimate the true column densities of any given species. Simple CO condensation onto and vaporization off of grains appears to be capable of explaining the observed 87 of gas phase CO in cold, dense molecular cores. This is not the case for NH3, however, where thermal considerations alone predict that all of the NH3 should be condensed onto grains. The fact that some gas phase NH3 is observed indicates that additional desorption processes must be involved. The surface binding energies of CH3OH, in conjunction with this molecule's observed behavior during warm up in H2O-rich ices, is shown to provide an explanation of the large excess of CH3OH seen in many warm, dense molecular cores. The near-infrared spectrum and associated integrated band strengths of CH3OH-containing ice are given, as are middle infrared absorption band strengths for both CH3OH and NH3.

Sandford, Scott A.; Allamandola, Louis J.

1993-01-01

38

Condensation and vaporization studies of CH3OH and NH3 ices: major implications for astrochemistry.  

PubMed

In an extension of previously reported work on ices containing H2O, CO, CO2, SO2, H2S, and H2, we present measurements of the physical and infrared spectral properties of ices containing CH3OH and NH3. The condensation and sublimation behavior of these ice systems is discussed and surface binding energies are presented for all of these molecules. The surface binding energies can be used to calculate the residence times of the molecules on grain surfaces as a function of temperature. It is demonstrated that many of the molecules used to generate radio maps of and probe conditions in dense clouds, for example CO and NH3, will be significantly depleted from the gas phase by condensation onto dust grains. Attempts to derive total column densities solely from radio maps that do not take condensation effects into account may vastly underestimate the true column densities of any given species. Simple CO condensation onto and vaporization off of grains appears to be capable of explaining the observed depletion of gas phase CO in cold, dense molecular cores. This is not the case for NH3, however, where thermal considerations alone predict that all of the NH3 should be condensed onto grains. The fact that some gas phase NH3 is observed indicates that additional desorption processes must be involved. The surface binding energies of CH3OH, in conjunction with this molecule's observed behavior during warm up in H2O-rich ices, is shown to provide an explanation of the large excess of CH3OH seen in many warm, dense molecular cores. The near-infrared spectrum and associated integrated band strengths of CH3OH-containing ice are given, as are middle infrared absorption band strengths for both CH3OH and NH3. PMID:11540092

Sandford, S A; Allamandola, L J

1993-11-10

39

Condensation and vaporization studies of CH3OH and NH3 ices: Major implications for astrochemistry  

NASA Technical Reports Server (NTRS)

In an extension of previously reported work on ices containing H2O, CO, CO2, SO2, H2S, and H2, we present measurements of the physical and infrared spectral properties of ices containing CH3OH and NH3. The condensation and sublimation behavior of these ice systems is discussed and surface binding energies are presented for all of these molecules. The surface binding energies can be used to calculate the residence times of the molecules on grain surfaces as a function of temperature. It is demonstrated that many of the molecules used to generate radio maps of and probe conditions in dense clouds, for example CO and NH3, will be significantly depleted from the gas phase by condensation onto dust grains. Attempts to derive total column densities solely from radio maps that do not take condensation effects into account may vastly underestimate the true column densities of any given species. Simple CO condensation onto and vaporization off of grains appears to be capable of explaining the observed depletion of gas phase CO in cold, dense molecular cores. This is not the case for NH3, however, where thermal considerations alone predict that all of the NH3 should be condensed onto grains. The fact that some gas phase NH3 is observed indicates that additional desorption processes must be involved. The surface binding energies of CH3OH, in conjunction with this molecule's observed behavior during warm up in H2O-rich ices, is shown to provide an explanation of the large excess of CH3OH seen in many warm, dense molecular cores. The near-infrared spectrum and associated integrated band strengths of CH3OH-containing ice are given, as are middle infrared absorption band strengths for both CH3OH and NH3.

Sandford, Scott A.; Allamandola, Louis J.

1993-01-01

40

NH3 observations of southern cold cores  

NASA Astrophysics Data System (ADS)

We propose an NH3 spectral line study of southern massive star formation sources that have been mapped in millimetre continuum emission using the SIMBA bolometer on the SEST. Following a multiwavelength investigation into these cores, using followup and existing submillimetre continuum observations as well as archival infrared data, we have drawn spectral energy distribution (SED) diagrams for the cores. SED profiling reveals source specific parameters such as their temperature and luminosity. Analysis of our SED fits indicates a differentiation in temperature for cores devoid of methanol maser sources and/or UC HII regions compared to those associated with these objects. This has led us to propose that this temperature differentiation is indicative of an evolutionary sequence for the cores in our sample. We now need an independent determination of the temperature of the cores in order to test the robustness of our SED fits and hypotheses drawn from these fits. A systematic determination of the temperature of all the cores in the sample will allow determination of the temperature and subsequent analysis of cores without enough data to SED profile. Ammonia is an excellent molecular cloud thermometer and is perfectly suited to this work.

Hill, Tracey; Cunningham, Maria; Burton, Michael; Minier, Vincent

2008-04-01

41

Quantum state-resolved study of NH 3 photodesorbed from GaAs(1 0 0)  

NASA Astrophysics Data System (ADS)

The laser-induced desorption of ammonia from GaAs(1 0 0)-(4 × 6) has been studied using (2 + 1)-photon REMPI as a state-specific probe. Ammonia and its deuterated sibling exhibit surprisingly large isotope effects in their relative cross sections for photodesorption from GaAs. This finding has led to the proposition of a vibrationally mediated UV photodesorption model. We find that NH 3 desorbs with a mean translational energy, < Etrans>, of 300 K, a rotational temperature of about 520 K, and vibrational excitation in the ?2 mode corresponding to about 930 K.

Nessler, W.; Bornscheuer, K.-H.; Kolasinski, K. W.; Hasselbrink, E.

1995-06-01

42

NH3-Promoted Ligand Lability in Eleven-Vertex Rhodathiaboranes.  

PubMed

The reaction of the 11-vertex rhodathiaborane, [8,8-(PPh3)2-nido-8,7-RhSB9H10] (1), with NH3 affords inmediately the adduct, [8,8,8-(NH3)(PPh3)2-nido-8,7-RhSB9H10] (4). The NH3-Rh interaction induces the labilization of the PPh3 ligands leading to the dissociation product, [8,8-(NH3)(PPh3)-nido-8,7-RhSB9H10] (5), which can then react with another molecule of NH3 to give [8,8,8-(NH3)2(PPh3)-nido-8,7-RhSB9H10] (6). These clusters have been characterized in situ by multielement NMR spectroscopy at different temeperatures. The variable temperature behavior of the system demonstrates that the intermediates 4-6 are in equilibrium, involving ligand exchange processes. On the basis of low intensity signals present in the (1)H NMR spectra of the reaction mixture, some species are tentatively proposed to be the bis- and tris-NH3 ligated clusters, [8,8-(NH3)2-nido-8,7-RhSB9H10] (7) and [8,8,8-(NH3)3-nido-8,7-RhSB9H10] (8). After evaporation of the solvent and the excess of NH3, the system containing species 4-8 regenerates the starting reactant, 1, thus closing a stoichiometric cycle of ammonia addition and loss. After 40 h at room temperature, the reaction of 1 with NH3 gives the hydridorhodathiaborane, [8,8,8-(H)(PPh3)2-nido-8,7-RhSB9H9] (2), as a single product. The reported rhodathiaboranes show reversible H3N-promoted ligand lability, which implies weak Rh-N interactions, leading to a rare case of metal complexes that circumvent "classical" Werner chemistry. PMID:25382790

Calvo, Beatriz; Roy, Beatriz; Macías, Ramón; Artigas, Maria Jose; Lahoz, Fernando J; Oro, Luis A

2014-12-01

43

Diatomics-in-molecules treatment of NH3  

Microsoft Academic Search

The diatomics-in-molecules method is applied to calculate the ground state potential-energy surface of NH3 by using both the selection of atomic states and the diatomic input data previously employed in a successful DIM description of the low-lying valence states of NH3. It appears that the diatomic information is transferable from one DIM model to the other one only in a

R. Polák; J. Vojtík

1989-01-01

44

A Sensitive Survey of Ammonia (NH3) in Comets  

NASA Astrophysics Data System (ADS)

Being the fully reduced form of nitrogen, ammonia (NH3) is a key molecule for understanding the nitrogen chemistry in comets and to properly characterize the primordial conditions under which these icy bodies formed. Yet, its abundance has not been well characterized, even though NH3 is a major reservoir of volatile nitrogen in comets. To date the abundance has been directly measured in only 10 comets, all at radio and infrared wavelengths. This small sample is largely due to the difficulty in measuring emission from NH3 since its emission is normally weak, can be affected by terrestrial extinction, and (without sufficient spectral resolution) is not resolved from other volatile cometary emissions. In this paper, we present a search for NH3 in seven comets using archival data acquired by our Team using the NIRSPEC instrument at the Keck-2 telescope and the CSHELL instrument at the NASA Infrared Telescope Facility, both atop Mauna Kea, HI. Using an updated fluorescence model that is based on millions of ammonia spectral lines (Villanueva et al., in prep.), we present relative abundances of NH3 with respect to H2O. We find the relative abundance of NH3/H2O varies from 0.3% to 1.6% in these seven comets, and we compare this indicator with other properties measured for these comets (isotopic fractionation and mixing ratios of selected primary volatiles). We gratefully acknowledge support from NASA’s Postdoctoral Program (LP), the NASA Astrobiology Institute (PI MJM), NASA’s Planetary Astronomy (PI GLV; PI MJM; PI DiSanti) and Planetary Atmospheres (PI DiSanti, PI Villanueva) programs, and from NSF Planetary Astronomy program (PI BPB).

Magee-Sauer, Karen P.; Villanueva, G. L.; Bonev, B. P.; Paganini, L.; DiSanti, M. A.; Mumma, M. J.

2012-10-01

45

Quantifying Dry NH 3 Deposition to an Ombrotrophic Bog from an Automated NH 3 Field Release System  

Microsoft Academic Search

Providing an accurate estimate of the dry component of N deposition to low N background, semi-natural habitats, such as bogs and upland moors dominated by Calluna vulgaris is difficult, but essential to relate nitrogen deposition to effects in these communities. To quantify the effects of NH3 inputs to moorland vegetation growing on a bog at a field scale, a field

Ian D. Leith; Lucy J. Sheppard; David Fowler; J. Neil Cape; Matt Jones; Alan Crossley; Ken J. Hargreaves; Y. Sim Tang; Mark Theobald; Mark R. Sutton

2004-01-01

46

Kinetics of the NH3 and CO2 solid-state reaction at low temperature.  

PubMed

Ammonia and carbon dioxide play an important role in both atmospheric and interstellar ice chemistries. This work presents a theoretical and experimental study of the kinetics of the low-temperature NH3 and CO2 solid-state reaction in ice films, the product of which is ammonium carbamate (NH4(+)NH2COO(-)). It is a first-order reaction with respect to CO2, with a temperature-dependent rate constant fitted to the Arrhenius law in the temperature range 70 K to 90 K, with an activation energy of 5.1 ± 1.6 kJ mol(-1) and a pre-exponential factor of 0.09-0.08(+1.1) s(-1). This work helps to determine the rate of removal of CO2 and NH3, via their conversion into ammonium carbamate, from atmospheric and interstellar ices. We also measure first-order desorption energies of 69.0 ± 0.2 kJ mol(-1) and 76.1 ± 0.1 kJ mol(-1), assuming a pre-exponential factor of 10(13) s(-1), for ammonium carbamate and carbamic acid, respectively. PMID:25198107

Noble, J A; Theule, P; Duvernay, F; Danger, G; Chiavassa, T; Ghesquiere, P; Mineva, T; Talbi, D

2014-11-21

47

The first thiosilicate from solution: synthesis and crystal structure of (NH4)2[SiS3(NH3)].2NH3.  

PubMed

The ammonolysis of SiS(2) in liquid ammonia yields crystalline (NH(4))(2)[SiS(3)(NH(3))].2NH(3), which contains [SiS(3)(NH(3))](2-) as a derivative of the ortho-thiosilicate anion SiS(4)(4-). PMID:19421590

Meier, Martin; Korber, Nikolaus

2009-03-01

48

First NH3 detection of the Orion Bar  

Microsoft Academic Search

Odin has successfully observed three regions in the Orion A cloud, i.e. Ori KL, Ori S and the Orion Bar, in the 572.5 GHz rotational ground state line of ammonia, ortho-NH3 (J,K) = (1,0) -> (0,0), and the result for the Orion Bar represents the first detection in an ammonia line. Several velocity components are present in the data. Specifically,

B. Larsson; R. Liseau; P. Bergman; P. Bernath; J. H. Black; R. S. Booth; V. Buat; C. L. Curry; P. Encrenaz; E. Falgarone; P. Feldman; M. Fich; H. G. Florén; U. Frisk; M. Gerin; E. M. Gregersen; J. Harju; T. Hasegawa; L. E. B. Johansson; S. Kwok; A. Lecacheux; T. Liljeström; K. Mattila; G. F. Mitchell; L. H. Nordh; M. Olberg; G. Olofsson; L. Pagani; R. Plume; I. Ristorcelli; Aa. Sandqvist; F. v. Schéele; N. F. H. Tothill; K. Volk; C. D. Wilson; Å. Hjalmarson

2003-01-01

49

Catalytic reduction of CO with hydrogen sulfide. 3. Study of adsorption of O/sub 2/, CO, and CO coadsorbed with H/sub 2/S on anatase and rutile using Auger electron spectroscopy and temperature-programmed desorption  

SciTech Connect

In O/sub 2/ and CO adsorption on anatase, only one weakly bound molecular desorption state was observed. For CO on rutile, there was a strongly bound and a weakly bound state. For O/sub 2/ rutile, a weakly bound state and two strongly chemisorbed states were observed. These strongly bound states are associated with the surface lattice anion vacancies produced on rutile (110). The amount of chemisorption in one of the strongly bound oxygen desorption states is correlated with the initial rate of irreversible adsorption of H/sub 2/S on rutile. Coadsorption of CO and H/sub 2/S indicates that strongly chemisorbed CO interacts with strongly chemisorbed H/sub 2/S to yield intermediates which desorb as CH/sub 3/SH and CH/sub 4/ at T approx. 800 K. At higher temperatures the surface sulfide concentration dominates the -SH concentration, explaining the dominance of COS in the product mixture. Implications of commercial hydrodesulfurization catalysts are discussed.

Beck, D.D.; White, J.M.; Ratcliffe, C.T.

1986-07-03

50

Preparation of highly active manganese oxides supported on functionalized MWNTs for low temperature NOx reduction with NH3  

NASA Astrophysics Data System (ADS)

Manganese oxide catalysts (MnOx) supported on functionalized multi-walled carbon nanotubes (FMWNTs) for low temperature selective catalytic reduction (LTSCR) of nitrogen oxides (NOx) with NH3 in the presence of excess O2 were prepared by the incipient wetness impregnation method. These catalysts were characterized by N2 adsorption, Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and H2-temperature programmed reduction (H2-TPR) methods. The effects of reaction temperature, MnOx loading, calcination temperature and calcination time were investigated. The presence of surface nitrate species under moderate calcination conditions may play a favorable role in the LTSCR of NOx with NH3. Under the reaction conditions of 200 °C, 1 bar, NO = NH3 = 900 ppm, O2 = 5 vol%, GHSV = 30,000 h-1 and 12 wt% MnOx, NOx conversion and N2 selectivity were 97% and 99.5%, respectively. The SCR activity was reduced in the presence of 100 ppm SO2 and 2.5 vol% H2O from 97% to 92% within 6 h at 200 °C, however such an effect was shown to be reversible by exposing the catalyst to a helium flow for 2 h at 350 °C due to thermal decomposition of ammonium sulphate salts.

Pourkhalil, Mahnaz; Moghaddam, Abdolsamad Zarringhalam; Rashidi, Alimorad; Towfighi, Jafar; Mortazavi, Yadollah

2013-08-01

51

First NH3 detection of the Orion Bar  

NASA Astrophysics Data System (ADS)

Odin has successfully observed three regions in the Orion A cloud, i.e. Ori KL, Ori S and the Orion Bar, in the 572.5 GHz rotational ground state line of ammonia, ortho-NH3 (J,K) = (1,0) -> (0,0), and the result for the Orion Bar represents the first detection in an ammonia line. Several velocity components are present in the data. Specifically, the observed line profile from the Orion Bar can be decomposed into two components, which are in agreement with observations in high-J CO lines by Wilson et al. (\\cite{wilson01}). Using the source model for the Orion Bar by these authors, our Odin observation implies a total ammonia abundance of NH3/H2 = 5x 10-9. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation has been the industrial prime contractor.

Larsson, B.; Liseau, R.; Bergman, P.; Bernath, P.; Black, J. H.; Booth, R. S.; Buat, V.; Curry, C. L.; Encrenaz, P.; Falgarone, E.; Feldman, P.; Fich, M.; Florén, H. G.; Frisk, U.; Gerin, M.; Gregersen, E. M.; Harju, J.; Hasegawa, T.; Johansson, L. E. B.; Kwok, S.; Lecacheux, A.; Liljeström, T.; Mattila, K.; Mitchell, G. F.; Nordh, L. H.; Olberg, M.; Olofsson, G.; Pagani, L.; Plume, R.; Ristorcelli, I.; Sandqvist, Aa.; Schéele, F. v.; Tothill, N. F. H.; Volk, K.; Wilson, C. D.; Hjalmarson, Å.

2003-05-01

52

Laboratory simulations of pre-cometary ice processes: thermal desorption, UV and X-ray irradiation.  

NASA Astrophysics Data System (ADS)

The formation of ice mantles on pre-cometary dust grains was simulated experimentally under ultrahigh vacuum conditions. An ice mixture containing H2O, CO, CO2, CH3OH, and NH3 was deposited at 8 K. The ice layer was either irradiated by UV or X-rays, or warmed up in a controlled way. The ice was monitored by infrared spectroscopy in transmittance and the species in the gas phase were detected by quadrupole mass spectroscopy (QMS). The temperature programmed desorption (TPD) of a complex ice mixture with up to five molecular components can aid to interpret the data collected by mass spectrometers on board cometary missions like Rosetta during the flyby. The irradiation experiments led to the formation of many photo-products. We will focus on those made by irradiation of ices containing H2S to study the formation of the detected sulfurbearing species in comets, such as S2.

Muñoz Caro, G. M.; Bueno-López, J.; Jiménez-Escobar, A.; Cruz-Diaz, G. A.; Chen, Y.-J.; Ciaravella, A.; Cecchi-Pestellini, C.; Goesmann, F.

2012-09-01

53

Prospects for producing ultracold NH3 molecules by sympathetic cooling: A survey of interaction potentials  

Microsoft Academic Search

We investigate the possibility of producing ultracold NH3 molecules by sympathetic cooling in a bath of ultracold atoms. We consider the interactions of NH3 with alkali-metal and alkaline-earth-metal atoms, and with Xe, using ab initio coupled-cluster calculations. For Rb-NH3 and Xe-NH3 we develop full potential energy surfaces, while for the other systems we characterize the stationary points (global and local

Piotr S. Zuchowski; Jeremy M. Hutson

2008-01-01

54

Experimental Binding Energies for the Metal Complexes [Mg(NH3)n](2+), [Ca(NH3)n](2+), and [Sr(NH3)n](2+) for n = 4-20 Determined from Kinetic Energy Release Measurements.  

PubMed

A supersonic source of clusters has been used to prepare neutral complexes of ammonia in association with a metal atom. From these complexes the following metal-containing dications have been generated: [Mg(NH3)n](2+), [Ca(NH3)n](2+), and [Sr(NH3)n](2+), and for n in the range 4-20, kinetic energy release measurements following the evaporation of a single molecule have been undertaken using a high resolution mass spectrometer. Using finite heat bath theory, these data have been transformed into binding energies for individual ammonia molecules attached to each of the three cluster systems. In the larger complexes (n > 6) the results exhibit a consistent trend, whereby the experimental binding energy data for all three metal ions are very similar, suggesting that the magnitude of the charge rather than charge density influences the strength of the interaction. From a comparison with data recorded previously for (NH3)nH(+) it is found that the 2+ charge on a metal ion has an effect on the binding energy of molecules in complexes containing up to 20 solvent molecules. Although subject to comparatively large experimental errors, the results recorded for Ca(2+) and Sr(2+) when n ? 6 show evidence for the formation of an inner solvation shell containing up to 6 molecules. However, Mg(2+) exhibits relatively low binding energies when n = 5 and 6, which suggests that a second shell starts to form before there are 6 ammonia molecules bound to the metal ion. This conclusion is supported by DFT calculations and it is proposed that these complexes could take the form [Mg(NH3)4(NH3)](2+) when n = 5 and either [Mg(NH3)4(NH3)2](2+) or [Mg(NH3)5(NH3)](2+) when n = 6. In each case, additional molecules are hydrogen bonded to one or more molecules in the inner solvation shell. PMID:24964399

Bruzzi, E; Raggi, G; Parajuli, R; Stace, A J

2014-09-18

55

Elevated CO2 decreases the Photorespiratory NH3 production but does not decrease the NH3 compensation point in rice leaves.  

PubMed

The exchange of gaseous NH3 between the atmosphere and plants plays a pivotal role in controlling the global NH3 cycle. Photorespiration generates NH3 through oxygenation instead of carboxylation by the CO2-fixing enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). The future increase in the atmospheric CO2 concentration, [CO2], is expected to reduce plant NH3 production by suppressing RuBisCO oxygenation (Vo). We measured the net leaf NH3 uptake rate (FNH3) across NH3 concentrations in the air (na) ranging from 0.2 to 1.6 nmol mol(-1) at three [CO2] values (190, 360 and 750 µmol mol(-1)) using rice plants. We analyzed leaf NH3 gas exchange using a custom-made whole-leaf chamber system, and determined the NH3 compensation point (?), a measure of potential NH3 emission, as the x-intercept of the linear relationship of FNH3 as a function of na. Our ? values were lower than those reported for other plant species. ? did not decrease under elevated [CO2], although leaf NH4 (+) content decreased with decreasing Vo at higher [CO2]. This was also the case for ? estimated from the pH and NH4 (+) concentration of the leaf apoplast solution (?'). ?' of rice plants, grown at elevated [CO2] for months in a free-air CO2 enrichment facility, was also not decreased by elevated [CO2]. These results suggest that suppression of RuBisCO oxygenation by elevated [CO2] does not decrease potential leaf NH3 emission in rice plants. PMID:24951312

Miyazawa, Shin-Ichi; Hayashi, Kentaro; Nakamura, Hirofumi; Hasegawa, Toshihiro; Miyao, Mitsue

2014-09-01

56

Production of NH4+ and OCN- ions by the interaction of heavy-ion cosmic rays with CO-NH3 interstellar ice  

NASA Astrophysics Data System (ADS)

In the interstellar medium, high-energy cosmic rays are able to penetrate deeply into molecular clouds, resulting in the ionization and dissociation of condensed molecules on ice-grain surfaces, which in turn leads to the desorption of a number of species. The interpretation of interstellar data requires qualitative and quantitative studies of the molecular species formed in several processes. In this work, the interaction of cosmic rays with CO-NH3 ice is simulated by the bombardment of ˜65-MeV heavy ions (masses of ˜100 u) on frozen gases. Positive and negative ions ejected from the ice surface as a consequence of the impact are analysed through time-of-flight mass spectrometry. The dependence of the ion desorption yield on the sample temperature (which varies/increases with time) has been used to discuss the emission process of the desorbed ions, especially near ice sublimation temperatures (˜30 K for CO at 10-8 mbar); at these temperatures, HCO+, NO+, NH3OH+ and NH3CO+ are formed and emitted. For temperatures in the 40 to 65 K range, mass spectra of positive ions are dominated by the NH4+ ion peak, similarly to what occurs for a pure frozen NH3 target. Concerning the mass spectra of negative ions, the total yield of negative ions at T = 25 K is found to be about 20 times lower than that of positive ions. Before CO sublimation, CN-bearing species are formed, among which the cyanide ions CN- and OCN- are by far the most abundant species. These findings support the idea that NH4+ and OCN- ions are efficiently formed by the interaction of cosmic rays with CO-NH3 ices.

Martinez, R.; Bordalo, V.; da Silveira, E. F.; Boechat-Roberty, H. M.

2014-11-01

57

Relativistic GW calculations on CH3NH3PbI3 and CH3NH3SnI3 Perovskites for Solar Cell Applications  

NASA Astrophysics Data System (ADS)

Hybrid AMX3 perovskites (A = Cs, CH3NH3; M = Sn, Pb; X = halide) have revolutionized the scenario of emerging photovoltaic technologies, with very recent results demonstrating 15% efficient solar cells. The CH3NH3PbI3/MAPb(I1-xClx)3 perovskites have dominated the field, while the similar CH3NH3SnI3 has not been exploited for photovoltaic applications. Replacement of Pb by Sn would facilitate the large uptake of perovskite-based photovoltaics. Despite the extremely fast progress, the materials electronic properties which are key to the photovoltaic performance are relatively little understood. Density Functional Theory electronic structure methods have so far delivered an unbalanced description of Pb- and Sn-based perovskites. Here we develop an effective GW method incorporating spin-orbit coupling which allows us to accurately model the electronic, optical and transport properties of CH3NH3SnI3 and CH3NH3PbI3, opening the way to new materials design. The different CH3NH3SnI3 and CH3NH3PbI3 electronic properties are discussed in light of their exploitation for solar cells, and found to be dominantly due to relativistic effects. These effects stabilize the CH3NH3PbI3 material towards oxidation, by inducing a deeper valence band edge. Relativistic effects, however, also increase the material band-gap compared to CH3NH3SnI3, due to the valence band energy downshift (~0.7 eV) being only partly compensated by the conduction band downshift (~0.2 eV).

Umari, Paolo; Mosconi, Edoardo; de Angelis, Filippo

2014-03-01

58

Relativistic GW calculations on CH3NH3PbI3 and CH3NH3SnI3 perovskites for solar cell applications.  

PubMed

Hybrid AMX3 perovskites (A = Cs, CH3NH3; M = Sn, Pb; X = halide) have revolutionized the scenario of emerging photovoltaic technologies, with very recent results demonstrating 15% efficient solar cells. The CH3NH3PbI3/MAPb(I(1-x)Cl(x))3 perovskites have dominated the field, while the similar CH3NH3SnI3 has not been exploited for photovoltaic applications. Replacement of Pb by Sn would facilitate the large uptake of perovskite-based photovoltaics. Despite the extremely fast progress, the materials electronic properties which are key to the photovoltaic performance are relatively little understood. Density Functional Theory electronic structure methods have so far delivered an unbalanced description of Pb- and Sn-based perovskites. Here we develop an effective GW method incorporating spin-orbit coupling which allows us to accurately model the electronic, optical and transport properties of CH3NH3SnI3 and CH3NH3PbI3, opening the way to new materials design. The different CH3NH3SnI3 and CH3NH3PbI3 electronic properties are discussed in light of their exploitation for solar cells, and found to be dominantly due to relativistic effects. These effects stabilize the CH3NH3PbI3 material towards oxidation, by inducing a deeper valence band edge. Relativistic effects, however, also increase the material band-gap compared to CH3NH3SnI3, due to the valence band energy downshift (~0.7?eV) being only partly compensated by the conduction band downshift (~0.2?eV). PMID:24667758

Umari, Paolo; Mosconi, Edoardo; De Angelis, Filippo

2014-01-01

59

Studies of the electrodeposition of palladium from baths based on [Pd(NH 3 ) 2 X 2 ] salts. I. [Pd(NH 3 ) 2 Cl 2 ] baths  

Microsoft Academic Search

Spectroscopic techniques are used to confirm the chemistry of solutions of [Pd(NH3)2Cl2] in aqueous NH4Cl at various pH. In addition, potential sweep and step methods at rotating and stationary disc electrodes (both vitreous carbon and freshly plated palladium) are used to investigate palladium deposition from a standard electroplating bath, [Pd(NH3)2Cl2] in NH4Cl\\/NH3 (pH 8.9). The relative importance of oxygen reduction,

R. Le Penven; W. Levason; D. Pletcher

1990-01-01

60

Adsorption states of the self-assembly of NH3 molecules on the Si(001) surface  

Microsoft Academic Search

Adsorption states of the self-assembly of NH3 molecules on the Si(001) surface are investigated using density-functional theory calculations. H-bond interactions between incoming and adsorbed NH3 molecules produce a strong attractive potential field for the incoming molecules. Induced by the H bonds, physisorption states are formed on the adsorbed NH3. Molecular adsorption states are formed on a buckled-down Si atom near

Yong-Sung Kim; Ja-Yong Koo; Hanchul Kim

2009-01-01

61

Accurate Potential Energy Surface, Rovibrational Energy Levels, and Transitions of Ammonia C_{3v} Isotopologues: ^{14}NH_3, ^{15}NH_3, ^{14}ND_3 and ^{14}NT_3  

Microsoft Academic Search

A further refined, global potential energy surface (PES) is computed for the C_{3v} symmetry isotopologues of ammonia, including ^{14}NH_3, ^{15}NH_3, ^{14}ND_3 and ^{14}NT_3. The refinement procedure was similar to that used in our previously reported PES, but now extends to higher J energy levels and other isotopologues. Both the diagonal Born-Oppenheimer correction and the non-adiabatic correction were included. J=0-6 rovibrational

Xinchuan Huang; David W. Schwenke; Timothy J. Lee

2009-01-01

62

Prospects for producing ultracold NH_{3} molecules by sympathetic cooling: A survey of interaction potentials  

Microsoft Academic Search

We investigate the possibility of producing ultracold NH3 molecules by\\u000asympathetic cooling in a bath of ultracold atoms. We consider the interactions\\u000aof NH3 with alkali-metal and alkaline-earth atoms, and with Xe, using ab initio\\u000acoupled-cluster calculations. For Rb-NH3 and Xe-NH3 we develop full potential\\u000aenergy surfaces, while for the other systems we characterize the stationary\\u000apoints (global and local

Jeremy M. Hutson

2008-01-01

63

Calculated spectroscopic and electric properties of the alkali metal-ammonia complexes from Kn-NH3 to Frn-NH3 (n=0,+1)  

NASA Astrophysics Data System (ADS)

The newly developed Stuttgart small-core scalar relativistic pseudopotentials for the alkali metals are used to study spectroscopic and electric properties of the heavier alkali metal-ammonia complexes from Kn-NH3 to Frn-NH3 (n=0,+1) at the second-order Møller-Plesset (MP2) and coupled cluster [CCSD(T)] levels of theory. Equilibrium geometries and dissociation energies computed at the MP2 level are in reasonable agreement with their CCSD(T) counterparts, whereas for the dipole polarizabilities MP2 is not performing well overestimating significantly electron correlation effects. The bond distances increase monotonically with increasing mass of the metal atom as relativistic effects are small in these systems. However, the dipole polarizabilities are more sensitive to such effects and we find a decrease in this property from Cs-NH3 to Fr-NH3. Combination of CCSD(T) harmonic frequencies and MP2 anharmonic corrections obtained from a perturbative vibrational treatment leads to fundamental frequencies in good agreement with experimental results obtained by Süzer and Andrews [J. Am. Chem. Soc. 109, 300 (1986)]. We also present the results of variational calculations with a three-dimensional vibrational Hamiltonian, making use of CCSD(T) potential energy and electric dipole moment surfaces. Complexation of NH3 to the metal causes a strong infrared intensification of the symmetric NH3 stretching mode in the neutral complexes, which is absent in the charged species.

Lim, Ivan S.; Botschwina, Peter; Oswald, Rainer; Barone, Vincenzo; Stoll, Hermann; Schwerdtfeger, Peter

2007-09-01

64

Time Resolved Measurement of Ecosystem-Atmosphere NH3 Exchange Using the Eddy Covariance Technique  

NASA Astrophysics Data System (ADS)

Quantifying ammonia fluxes between the land surface and atmosphere is required for effective control of air quality, improving agricultural practices, and understanding natural ecosystem function. Ammonia (NH3) is emitted in large but uncertain amounts from animal agriculture, in lesser amounts from imperfect use of nitrogen fertilizers in crop agriculture, from catalytic converters used on automobiles and other energy related industrial processes, and exchanged between the ecosystem and atmosphere by natural ecosystem processes on vast spatial scales. To address the need for accurate, time-resolved NH3 flux measurements, we have developed an eddy covariance (EC) instrument for direct measurements of NH3 flux. EC flux measurements of NH3 were not previously possible because instruments were not sufficiently sensitive at high frequencies required to capture rapid variations in surface layer NH3 concentrations. To overcome this hurdle we combined a tunable-diode-laser (TDL) spectrometer with a fast-response NH3 sampling inlet and automated pulse-response calibration system. Laboratory tests of the inlet system demonstrate that the response to 10 ppb step in NH3 concentration is well described by a double exponential model with (1/e) times of 0.3 (85% response) and 1.5 (15% response) seconds. This response combined with a routinely measured instrument stability of ~ 0.1 ppb (on 30 minute timescales) indicates that the instrumental contribution to noise in NH3 flux measurements is ~ 0.2 umol NH3 m-2 hr-1, sufficient to stringently test models for NH3 exchange under most conditions. Recent results of field work to verify the instrument performance and observe examples of NH3 exchange will be presented.

Fischer, M. L.; Littlejohn, D.

2005-12-01

65

Effects of atmospheric ammonia (NH 3) on terrestrial vegetation: a review  

Microsoft Academic Search

At the global scale, among all N (nitrogen) species in the atmosphere and their deposition on to terrestrial vegetation and other receptors, NH3 (ammonia) is considered to be the foremost. The major sources for atmospheric NH3 are agricultural activities and animal feedlot operations, followed by biomass burning (including forest fires) and to a lesser extent fossil fuel combustion. Close to

S. V Krupa

2003-01-01

66

Effects of NH3 flow rate on the thermal plasma synthesis of AlN nanoparticles  

NASA Astrophysics Data System (ADS)

Aluminium nitride (AlN) nanoparticles were synthesized by using a non-transferred arc plasma. A pellet of micro-sized aluminium (Al) powders was evaporated by using an argon-nitrogen thermal plasma flame, and ammonia (NH3) was introduced into the reactor as a reactive gas. The flow rate of NH3 was controlled from 5 to 25 L/min at a fixed input power of 10.2 kW. In experiments, unreacted Al powder was found at low NH3 flow rates at 5 and 10 L/min. The size and the crystallinity of the synthesized AlN particles increased with increasing flow rate of NH3 until 20 L/min. The maximum particle size of AlN nanoparticle was about 100 nm at a 20 L/min NH3 flow rate. At an excessive flow rate of NH3 of 25 L/min, however, the size and the crystallinity of AlN were decreased. In order to analyze the experimental results for the thermal plasma synthesis of AlN nanoparticles, we carried out numerical simulations on the thermal plasma. The vortex flow of the thermal plasma near the Al pellet was gradually enhanced with increasing NH3 flow rate from 10 to 20 L/min. The strength of the vortex flow, however, was decreased at the highest NH3 flow rate of 25 L/min.

Kim, Tae-Hee; Choi, Sooseok; Park, Dong-Wha

2013-11-01

67

Final Report On-Road Motor Vehicle Emissions including NH3,  

E-print Network

Final Report On-Road Motor Vehicle Emissions including NH3, SO2 and NO2 Contract No. 07-319 October contract no. 07-319 On-Road Motor Vehicle Emissions including NH3, SO2 and NO2 by the University of Denver

Denver, University of

68

SEASONAL NH 3 EMISSIONS FOR ANNUAL 2001 CMAQ SIMULATION: INVERSE MODEL ESTIMATION AND EVALUATION  

EPA Science Inventory

The formation of ammonium nitrate aerosols is often limited by ammonia (NH3), and sulfate aerosols are predominantly in the form of ammonium sulfate. While NH3plays a central role in the prediction of nitrate and sulfate aerosols, inherent uncertainty exist...

69

Low and room temperature photoabsorption cross sections of NH 3 in the UV region  

Microsoft Academic Search

Using synchrotron radiation as a continuum light source, we have measured the absolute absorption cross sections of NH3 with a spectral bandwidth (FWHM) of 0.5 Å. The photoabsorption cross sections of NH3 have been measured from 1750 to 2250 Å under temperature conditions of 295, 195, and 175 K. Significant temperature effects in the absorption threshold region which are mainly

F. Z Chen; D. L Judge; C. Y. Robert Wu; John Caldwell

1998-01-01

70

Pore Sealing by NH3 Plasma Treatment of Porous Low Dielectric Constant Films  

E-print Network

Pore Sealing by NH3 Plasma Treatment of Porous Low Dielectric Constant Films Hua-Gen Peng,a Dong-silsesquioxane-based dielectric film by NH3 plasma treatment. Depth-profiled beam positronium anni- hilation lifetime spectroscopy identified by the curtailment of positronium escape into vacuum through the surface. Among plasma treatments

Gidley, David

71

Exploring and rationalising effective n-doping of large area CVD-graphene by NH3.  

PubMed

Despite the large number of papers on the NH3 doping of graphene, the achievement of stable n-doped large area CVD (chemical vapor deposition) graphene, which is intrinsically p-doped, is still challenging. A control of the NH3 chemisorption and of the N-bond configuration is still needed. The feasibility of a room temperature high pressure NH3 treatment of CVD graphene to achieve n-type doping is shown here. We use and correlate data for (a) sheet resistance, R(sh), and the Hall coefficient, R(H), in van der Pauw configuration, acquired in real time during the NH3 doping of CVD-graphene on a glass substrate, (b) optical measurements of the effect of doping on the graphene Van Hove singularity point at 4.6 eV in the dielectric function spectra by spectroscopic ellipsometry, and of (c) N-bond configuration by XPS to better understand and, finally, control the NH3 doping of graphene. The discussion is focused on the thermal and time stability of the n-doping after air exposure. A chemical rationale is provided for the NH3 n-doping based on the interaction of (i) NH3 with intrinsic oxygen functionalities and defects of CVD graphene and of (ii) C-NH2 doping centers with acceptor species present in the air. PMID:24413594

Bianco, G V; Losurdo, M; Giangregorio, M M; Capezzuto, P; Bruno, G

2014-02-28

72

Photosynthesis of Quercus suber is affected by atmospheric NH3 generated by multifunctional agrosystems.  

PubMed

Montados are evergreen oak woodlands dominated by Quercus species, which are considered to be key to biodiversity conservation and ecosystem services. This ecosystem is often used for cattle breeding in most regions of the Iberian Peninsula, which causes plants to receive extra nitrogen as ammonia (NH(3)) through the atmosphere. The effect of this atmospheric NH(3) (NH(3atm)) on ecosystems is still under discussion. This study aimed to evaluate the effects of an NH(3atm) concentration gradient downwind of a cattle barn in a Montado area. Leaves from the selected Quercus suber L. trees along the gradient showed a clear influence of the NH(3) on ?(13)C, as a consequence of a strong limitation on the photosynthetic machinery by a reduction of both stomatal and mesophyll conductance. A detailed study of the impact of NH(3atm) on the photosynthetic performance of Q. suber trees is presented, and new mechanisms by which NH(3) affects photosynthesis at the leaf level are suggested. PMID:24150034

Pintó-Marijuan, Marta; Da Silva, Anabela Bernardes; Flexas, Jaume; Dias, Teresa; Zarrouk, Olfa; Martins-Loução, Maria Amélia; Chaves, Maria Manuela; Cruz, Cristina

2013-12-01

73

Synthesis, crystal structures and properties of the trimetaphosphimates NaBa(PO 2NH) 3, KSr(PO 2NH) 3?4H 2O, and NH 4Sr(PO 2NH) 3?4H 2O  

NASA Astrophysics Data System (ADS)

The three double salts sodium barium tri- ?-imidocyclotriphosphate, NaBa(PO 2NH) 3 ( 1), potassium strontium tri- ?-imidocyclotriphosphate tetrahydrate, KSr(PO 2NH) 3?4H 2O ( 2), and ammonium strontium tri- ?-imidocyclotriphosphate tetrahydrate, NH 4Sr(PO 2NH) 3?4H 2O ( 3), were synthesized by combining equimolar aqueous solutions of Na 3(PO 2NH) 3?4H 2O, K 3(PO 2NH) 3, or (NH 4) 3(PO 2NH) 3?H 2O, respectively, with the corresponding alkaline earth nitrate. In case of compound 1, suitable single crystals for X-ray crystal structure determination were solely obtained using gel crystallization in gelatine gels. The structures of 2 and 3 were found to be isotypic. All crystal structures were solved by single-crystal X-ray methods ( 1: C2/m, a=1084.5(2), b=1025.0(2), c=796.2(2) pm, ?=115.18(3)°, Z=4, R=0.023; 2: P2/n, a=1087.2(2), b=1049.6(2), c=1191.2(2) pm, ?=111.98(3)°, Z=4, R=0.025; 3: P2/n, a=1088.4(2), b=1048.5(2), c=1196.9(2) pm, ?=111.43(3)°, Z=4, R=0.025). In both structure types, the P 3N 3 rings of the trimetaphosphimate ions exhibit a chair conformation. In the crystal, the trimetaphosphimate ions act as mono and bidentate ligands of the alkali ions, and additionally as tridentate ones in case of the alkaline earth ions. Besides the oxygen atoms, the nitrogen atoms of the (PONH)33- rings contribute to the coordination of the cations as well. In 2 and 3, crystal water molecules complete the coordination of the metal ions. Extended hydrogen bonding reinforces the three-dimensional interconnection of the ions and the crystal water molecules in the structures of all three compounds.

Correll, Sascha; Sedlmaier, Stefan; Schnick, Wolfgang

2005-10-01

74

Role of the support on the behavior of Ag-based catalysts for NH3 selective catalytic oxidation (NH3-SCO)  

NASA Astrophysics Data System (ADS)

In this work four supports with different textural properties (Al2O3, SiO2, NaY and TiO2) are used to evaluate the formation of different silver species and their effect on the NH3-SCO performance. Characterization analyses have shown that the predominant Ag0 species and the oxidized Ag species (Ag+ and Agn?+) are located on the four catalysts with different ratio of Ag0/oxidized Ag. Small Ag0 particle with high dispersion which is obtained on 10 wt% Ag/Al2O3 (5 nm, Ag0 ratio = 97.7%) shows an excellent catalytic performance for SCO reaction at low temperatures (a complete NH3 conversion at 180 °C and a high N2 selectivity of 89%). In addition, a certain amount of oxidized Ag species formed on the catalysts, especially for the NaY and SiO2 support, as well as the surface acidity of catalysts have also been found to play an important role in the enhanced N2 selectivity above 140 °C by promoting iSCR reaction involving NO as an intermediate for N2 formation. A model to relate the silver species with the performance of NH3-SCO is proposed, which is very significant for the further optimization of the catalyst (e.g. choosing a suitable support) for NH3-SCO reaction and its practical application in the future.

Qu, Zhenping; Wang, Hui; Wang, Shudong; Cheng, Hao; Qin, Yuan; Wang, Zhong

2014-10-01

75

PREPARATION, CRYSTAL STRUCTURE AND CARACTERIZATION OF INORGANIC-ORGANIC HYBRID PEROVSKITE [NH3-(CH2)10-NH3] ZnCl4  

E-print Network

PREPARATION, CRYSTAL STRUCTURE AND CARACTERIZATION OF INORGANIC-ORGANIC HYBRID PEROVSKITE [NH3-(CH2-461" #12;( Day, P. and Ledsham, R.D.1982; Zangar, H. et al., 1989). The class of hybrid materials is very. INTRODUCTION In recent years, layered hybrid organic-inorganic compounds have attracted much attention due

Paris-Sud XI, Université de

76

3-D agricultural air quality modeling: Impacts of NH3/H2S gas-phase reactions and bi-directional exchange of NH3  

NASA Astrophysics Data System (ADS)

Accurately simulating the transport and fate of reduced nitrogen (NHx = ammonia (NH3) + ammonium (NH4+))- and sulfur-containing compounds emitted from agricultural activities represents a major challenge in agricultural air quality modeling. In this study, the Community Multiscale Air Quality (CMAQ) modeling system is further developed and improved by implementing 22 ammonia (NH3)/hydrogen sulfide (H2S) related gas-phase reactions and adjusting a few key parameters (e.g., emission potential) for bi-directional exchange of NH3 fluxes. Several simulations are conducted over the eastern U.S. domain at a 12-km horizontal resolution for January and July 2002 to examine the impacts of those improved treatments on air quality. The 5th generation mesoscale model (MM5) and CMAQ predict an overall satisfactory and consistent performance with previous modeling studies, especially for 2-m temperature, 2-m relative humidity, ozone (O3), and fine particulate matter (PM2.5). High model biases exist for precipitation in July and also dry/wet depositions. The updated model treatments contribute to O3, NHx, and PM2.5 by up to 0.4 ppb, 1.0 ?g m-3, and 1.0 ?g m-3 in January, respectively, and reduce O3 by up to 0.8 ppb and contribute to NHx and PM2.5 by up to 1.2 and 1.1 ?g m-3 in July, respectively. The spatial distributions of O3 in both months and sulfur dioxide (SO2) in January are mainly affected by inline dry deposition velocity calculation. The spatial distributions of SO2 and sulfate (SO42-) in July are affected by both inline dry deposition velocity and NH3/H2S reactions. The variation trends of NH3, NHx, ammonium nitrate (NH4NO3), PM2.5 and total nitrogen (TN) are predominated by bi-directional exchange of NH3 fluxes. Uncertainties of NH3 emission potentials and empirical constants used in the bi-directional exchange scheme may significantly affect the concentrations of NHx and PM2.5, indicating that a more accurate and explicit treatment for those parameters should be considered in the future work.

Wang, Kai; Zhang, Yang

2014-12-01

77

Formation and excretion of NH 3 ?NH 4 + . new aspects of an old problem  

Microsoft Academic Search

Summary The proximal tubule cell is the major site of renal ammoniagenesis. Glutamine is the major substrate. Deamidation by mitochondrial glutaminase yields glutamate? and NH4+ (not NH3, as traditionally taught). A second NH4+ ion is obtained by deamination of glutamate? to 2-oxo-glutarate2?. NH4+ preferentially enters the tubule lumen primarily, but probably not exclusively, by non-ionic diffusion of NH3. For each

S. Silbernagl; D. Scheller

1986-01-01

78

Global distributions, time series and error characterization of atmospheric ammonia (NH3) from IASI satellite observations  

NASA Astrophysics Data System (ADS)

Ammonia (NH3) emissions in the atmosphere have increased substantially over the past decades, largely because of intensive livestock production and use of fertilizers. As a short-lived species, NH3 is highly variable in the atmosphere and its concentration is generally small, except near local sources. While ground-based measurements are possible, they are challenging and sparse. Advanced infrared sounders in orbit have recently demonstrated their capability to measure NH3, offering a new tool to refine global and regional budgets. In this paper we describe an improved retrieval scheme of NH3 total columns from the measurements of the Infrared Atmospheric Sounding Interferometer (IASI). It exploits the hyperspectral character of this instrument by using an extended spectral range (800-1200 cm-1) where NH3 is optically active. This scheme consists of the calculation of a dimensionless spectral index from the IASI level1C radiances, which is subsequently converted to a total NH3 column using look-up tables built from forward radiative transfer model simulations. We show how to retrieve the NH3 total columns from IASI quasi-globally and twice daily above both land and sea without large computational resources and with an improved detection limit. The retrieval also includes error characterization of the retrieved columns. Five years of IASI measurements (1 November 2007 to 31 October 2012) have been processed to acquire the first global and multiple-year data set of NH3 total columns, which are evaluated and compared to similar products from other retrieval methods. Spatial distributions from the five years data set are provided and analyzed at global and regional scales. In particular, we show the ability of this method to identify smaller emission sources than those previously reported, as well as transport patterns over the ocean. The five-year time series is further examined in terms of seasonality and interannual variability (in particular as a function of fire activity) separately for the Northern and Southern Hemispheres.

Van Damme, M.; Clarisse, L.; Heald, C. L.; Hurtmans, D.; Ngadi, Y.; Clerbaux, C.; Dolman, A. J.; Erisman, J. W.; Coheur, P. F.

2014-03-01

79

Photochemical reactions in interstellar grains photolysis of co, NH 3 , and H 2 O  

Microsoft Academic Search

A simulation of the organic layer accreted onto interstellar dust particles was prepared by slow deposition of a CO:NH3:H2O gas mixture on an Al block at 10K, with concomitant irradiation with vacuum UV. The residues were analyzed by GC-MS, HPLC, and near IR; a reaction pathway leading from NH3 to complex alcohol, fatty acid, and amide products in 27 stages

V. K. Agarwal; W. Schutte; J. M. Greenberg; J. P. Ferris; R. Briggs; Steven Connor; C. P. E. M. Van de Bult; F. Baas

1985-01-01

80

Mechanisms for sealing of porous low-k SiOCH by combined He and NH3 plasma treatment  

E-print Network

Mechanisms for sealing of porous low-k SiOCH by combined He and NH3 plasma treatment Juline Shoeba surface sites to accelerate the reactions responsible for pore sealing. NH3 plasma treatment completes

Kushner, Mark

81

Evaluation of a regional air-quality model with bidirectional NH3 exchange coupled to an agroecosystem modelecosystem model  

EPA Science Inventory

Atmospheric ammonia (NH3) is the primary atmospheric base and an important precursor for inorganic particulate matter and when deposited NH3 contributes to surface water eutrophication, soil acidification and decline in species biodiversity. Flux measurement...

82

Ultraviolet Absorption Spectroscopy Measurement of Trace NH3 in Gases Containing High Concentration of SO2  

NASA Astrophysics Data System (ADS)

In heavy oil-burning thermal power plants, NH3 injection is frequently used to neutralize SOx in flue gas. In order to ascertain the neutralization effect the concentration of NH3 must be measured in the presence of high concentration of SO2. Ultraviolet absorption spectroscopy in the 200-225 nm wavelength region is the most sensitive method to measure SO2 and NH3. However, as the absorption bands of SO2 and NH3 overlap, accurate determination of the SO2 absorption is needed to detect the absorption due to trace NH3. The nonlinear dependence of the absorption coefficient on the concentration, which appeared for absorption coefficients of ?>0.05 cm-1, is taken into account using a third order polynomial approximation in order to accurately determine the SO2 absorption. An analysis procedure based on this approximation was developed. Results showed that NH3 concentrations of about 4 ppm can be detected in the presence of SO2 concentrations of about 1000 ppm.

Fukuchi, Tetsuo; Ninomiya, Hideki

83

DFT study of NH3 adsorption on pristine, Ni- and Si-doped graphynes  

NASA Astrophysics Data System (ADS)

The electronic sensitivity of pristine, Ni- and Si-doped graphynes to ammonia (NH3) molecule was investigated using density functional theory, including dispersion correction. It was found that NH3 is weakly adsorbed on the sheet, releasing energy of 2.9-4.4 kcal/mol, and the electronic properties of the sheet are not significantly changed. Although both Ni-doping and Si-doping make the sheet more reactive and sensitive to NH3, Si-doping seems to be a better strategy to manufacture NH3 chemical sensors because of higher sensitivity. Our calculations show that the HOMO/LUMO gap of the Si-doped sheet is significantly decreased from 2.13 to 1.46 eV after the adsorption of NH3, which may increase the electrical conductance of the sheet. Therefore, the doped sheet might convert the presence of NH3 molecules to electrical signals. Moreover, the shorter recovery time of the Si-doped sheet is because of the middle adsorption energy of 39.3 kcal/mol in comparison with 55.1 kcal/mol for the Ni-doped sheet.

Peyghan, Ali Ahmadi; Rastegar, Somayeh F.; Hadipour, Nasser L.

2014-06-01

84

Improvement of thermal stability of nickel silicide film using NH3 plasma treatment  

NASA Astrophysics Data System (ADS)

In this study, the effects of NH3 plasma pre-treatment on the characteristics of NiSi films were investigated. Nickel film was deposited on a Si(100) substrate by meal-organic chemical vapor deposition (MOCVD) using Ni(iPr-DAD)2 as a Ni precursor and NH3 gas as a reactant. Before the Ni deposition, silicon substrate was treated by NH3 plasma with various flow rates to adjust the amount of inserted hydrogen and nitrogen atoms. The Ni films showed a considerable low sheet resistance around 12 ?/?, irrespective of the NH3 plasma pre-treatment conditions. The sheet resistance of the all Ni films was decreased after annealing at 500 °C due to formation of a low resistive NiSi phase. NiSi films with a high flow rate of NH3 plasma pre-treatment exhibited a lower sheet resistance and smoother interface between NiSi and the Si substrate than the low flow rate of the NH3 plasma pre-treated NiSi films because lots of nitrogen atoms incorporated at grain boundary of NiSi which result in reduce total surface/interface energy of NiSi and enhancement interface characteristics.

Park, Jingyu; Jeon, Heeyoung; Kim, Hyunjung; Jang, Woochool; Kim, Jinho; Kang, Chunho; Yuh, Junhan; Jeon, Hyeongtag

2014-09-01

85

Synthesis, structure and spectroscopic investigations of two new organic-inorganic hybrids NH3(C6H4)2NH3CuCl4 and NH3(C6H4)2NH3HgCl4  

NASA Astrophysics Data System (ADS)

Two metal organic-inorganic hybrid compounds, NH3(C6H4)2NH3CuCl4, 1, and NH3(C6H4)2NH3HgCl4, 2, have been synthesized and structurally characterized by single-crystal X-ray diffraction. The two compounds crystallize in the monoclinic space groups P21/c and C2/c, respectively, with a = 14.3774 (7), b = 7.3472 (4), c = 7.1669 (3), ? = 96.589 (3)°, Z = 2 and R1 = 0.037 for 1, and a = 6.2986 (4), b = 18.2911 (12), c = 28.5854 (17), ? = 91.836 (2)°, Z = 8 and R1 = 0.049 for 2. The organic-inorganic layered perovskite structure of compound 1 features well-ordered sheets of corner-sharing distorted CuCl6 octahedra, due to the presence of Jahn-Teller effect in the d9 electronic system of Cu(II), separated by layers of benzidinium cations. The structure of compound 2 consists of anionic parallel layers built up from discrete tetrahedral HgCl42- species, alternating with layers of organic molecules [NH3(C6H4)2NH3]2+. The structures of the two compounds are stabilized by an extensive network of N-H...C1 hydrogen bonds. These compounds are also investigated by IR spectroscopy.

Belhouchet, M.; Wamani, W.; Mhiri, T.

2010-11-01

86

New insights into the diurnal variability of animal NH3 emissions using in-situ, satellite and aloft observations  

NASA Astrophysics Data System (ADS)

Ammonia (NH3) is the primary atmospheric base and an important precursor for inorganic particulate matter. NH3 deposition contributes to surface water eutrophication, soil acidification and decline in species biodiversity. Despite its importance in atmospheric chemistry and the nitrogen biogeochemical cycle, the magnitude and temporal dynamics of NH3 emissions remain uncertain in regional and global scale models. This uncertainty stems from the lack of routine ambient NH3 observations and the complexity of NH3 emission sources. We will combine satellite, in-situ, and aircraft observations with model sensitivities to develop and evaluate process based improvements in NH3 emissions from animal production activities. First, we will show that initial model evaluations of ambient NH3 estimates using TES satellite and in-situ Carolina Ammonia Monitoring Network (CAMNet) observations paired in space and time indicated that the Community Multi-scale Air Quality (CMAQ) and GEOS-Chem overestimated CAMNet NH3 observations but underestimated TES observations. An evaluation of the differences in the timing of the measurement techniques indicated that the model errors are due to the dynamics of the temporal NH3 emissions, predominately from animal production. This was confirmed qualitatively using hourly in-situ NH3 observations. Then, a mechanistic NH3 animal emissions conceptual model was developed and implemented for use in both CMAQ and GEOS-Chem models. Finally, we will present improvements in model evaluations of gaseous NH3, NO3 aerosol concentrations and NH4 wet deposition against network, TES satellite and aircraft observations.

Bash, J. O.; Henze, D. K.; Zhu, L.; Jeong, G.; Walker, J. T.; Nowak, J. B.; Neuman, J. A.; Cady-Pereira, K. E.; Shephard, M. W.; Luo, M.; Pinder, R. W.

2013-12-01

87

Movement of NH3 through the human urea transporter B: a new gas channel  

PubMed Central

Aquaporins and Rh proteins can function as gas (CO2 and NH3) channels. The present study explores the urea, H2O, CO2, and NH3 permeability of the human urea transporter B (UT-B) (SLC14A1), expressed in Xenopus oocytes. We monitored urea uptake using [14C]urea and measured osmotic water permeability (Pf) using video microscopy. To obtain a semiquantitative measure of gas permeability, we used microelectrodes to record the maximum transient change in surface pH (?pHS) caused by exposing oocytes to 5% CO2/33 mM HCO3? (pHS increase) or 0.5 mM NH3/NH4+ (pHS decrease). UT-B expression increased oocyte permeability to urea by >20-fold, and Pf by 8-fold vs. H2O-injected control oocytes. UT-B expression had no effect on the CO2-induced ?pHS but doubled the NH3-induced ?pHS. Phloretin reduced UT-B-dependent urea uptake (Jurea*) by 45%, Pf* by 50%, and (??pHS*)NH3 by 70%. p-Chloromercuribenzene sulfonate reduced Jurea* by 25%, Pf* by 30%, and (?pHS*)NH3 by 100%. Molecular dynamics (MD) simulations of membrane-embedded models of UT-B identified the monomeric UT-B pores as the main conduction pathway for both H2O and NH3 and characterized the energetics associated with permeation of these species through the channel. Mutating each of two conserved threonines lining the monomeric urea pores reduced H2O and NH3 permeability. Our data confirm that UT-B has significant H2O permeability and for the first time demonstrate significant NH3 permeability. Thus the UTs become the third family of gas channels. Inhibitor and mutagenesis studies and results of MD simulations suggest that NH3 and H2O pass through the three monomeric urea channels in UT-B. PMID:23552862

Musa-Aziz, Raif; Enkavi, Giray; Mahinthichaichan, P.; Tajkhorshid, Emad; Boron, Walter F.

2013-01-01

88

Advection of NH3 over a pasture field and its effect on gradient flux measurements  

NASA Astrophysics Data System (ADS)

Deposition of atmospheric ammonia (NH3) to semi-natural ecosystems leads to serious adverse effects, such as acidification and eutrophication. A step in quantifying such effects is the measurement of NH3 fluxes over semi-natural and agricultural land. However, measurement of NH3 fluxes over vegetation in the vicinity of strong NH3 sources is challenging, since NH3 emissions are highly heterogeneous. Indeed, under such conditions, local advection errors may alter the measured fluxes. In this study, local advection errors (?Fz,adv) were estimated over a 14 ha grassland field, which was successively cut and fertilised, as part of the GRAMINAE integrated Braunschweig experiment. The magnitude of ?Fz,adv was determined up to 810 m downwind from farm buildings emitting between 6.2 and 9.9 kg NH3 day-1. The GRAMINAE experiment provided a unique opportunity to compare two methods of estimating ?Fz,adv: one inference method based on measurements of horizontal concentration gradients, and one based on inverse dispersion modelling with a two-dimensional model. Two sources of local advection were clearly identified: the farm NH3 emissions leading to positive ?Fz,adv ("bias towards emissions") and field NH3 emissions, which led to a negative ?Fz,adv ("bias towards deposition"). The local advection flux from the farm was in the range 0 to 27 ng NH3 m-2 s-1 at 610 m from the farm, whereas ?Fz,adv due to field emission was proportional to the local flux, and ranged between -209 and 13 ng NH3 m-2 s-1. The local advection flux ?Fz,adv was either positive or negative depending on the magnitude of these two contributions. The modelled and inferred advection errors agreed well. The inferred advection errors, relative to the vertical flux at 1 m height, were 52% on average, before the field was cut, and less than 2.1% when the field was fertilised. The variability of the advection errors in response to changes in micrometeorological conditions is also studied. The limits of the 2-D modelling approach are discussed.

Loubet, B.; Milford, C.; Hensen, A.; Daemmgen, U.; Erisman, J.-W.; Cellier, P.; Sutton, M. A.

2009-07-01

89

The role of NH 3 atmosphere in preparing nitrogen-doped TiO 2 by mechanochemical reaction  

NASA Astrophysics Data System (ADS)

NH 3 atmosphere in ball milling plays an important role in preparing TiO 2-XN X by a simple mechanochemical reaction. The results show that the structure transformation of titania milled in NH 3 is greatly delayed compared with that in air. The specific surface area of titania milled in NH 3 for 2 h is two times larger than that in air. It was also found that titania prepared in NH 3 has obvious absorbance for visible light. Mechanochemical milling in NH 3 atmosphere offers a new route to prepare TiO 2-XN X with high surface area.

Liu, Gang; Li, Feng; Chen, Zhigang; Lu, Gao Qing; Cheng, Hui-Ming

2006-01-01

90

Experimental verification of the high pressure crystal structures in NH3BH3.  

PubMed

A detailed high-pressure study on NH3BH3 has been carried out using in situ synchrotron X-ray diffraction (XRD) and Raman scattering with a diamond anvil cell up to 20 and 33 GPa, respectively. The Rietveld refinement based on the XRD pattern and analysis of Raman data indicate two first-order phase transitions from the ambient pressure I4 mm structure (?-NH3BH3) to a high pressure Cmc21 phase (?-NH3BH3) at 2.14 GPa, and further into a monoclinic P21 (Z = 2) phase (?-NH3BH3) at 9.67 GPa. Fitting the measured volumetric compression data to the third order Birch-Murnaghan equation of state reveals a bulk modulus of B0 = 9.9 ± 0.5 and 17.0 ± 3.0 GPa (with fixed B0 (') = 4) for the ?-NH3BH3 below and above 5 GPa, respectively. Still, with the splitting of the NBH rock mode in Raman experiment, it is concluded that a second-order isostructural phase transition occurs at 5 GPa. By analyzing the dihydrogen bonding framework, the origin of the isostructural phase transition is attributed to the number of dihydrogen bondings per molecule in the Cmc21 phase increasing from 12 to 14 at 5 GPa. PMID:24985654

Huang, Yanping; Huang, Xiaoli; Zhao, Zhonglong; Li, Wenbo; Jiang, Shuqing; Duan, Defang; Bao, Kuo; Zhou, Qiang; Liu, Bingbing; Cui, Tian

2014-06-28

91

Mesoscopic CH3NH3PbI3/TiO2 heterojunction solar cells.  

PubMed

We report for the first time on a hole conductor-free mesoscopic methylammonium lead iodide (CH(3)NH(3)PbI(3)) perovskite/TiO(2) heterojunction solar cell, produced by deposition of perovskite nanoparticles from a solution of CH(3)NH(3)I and PbI(2) in ?-butyrolactone on a 400 nm thick film of TiO(2) (anatase) nanosheets exposing (001) facets. A gold film was evaporated on top of the CH(3)NH(3)PbI(3) as a back contact. Importantly, the CH(3)NH(3)PbI(3) nanoparticles assume here simultaneously the roles of both light harvester and hole conductor, rendering superfluous the use of an additional hole transporting material. The simple mesoscopic CH(3)NH(3)PbI(3)/TiO(2) heterojunction solar cell shows impressive photovoltaic performance, with short-circuit photocurrent J(sc)= 16.1 mA/cm(2), open-circuit photovoltage V(oc) = 0.631 V, and a fill factor FF = 0.57, corresponding to a light to electric power conversion efficiency (PCE) of 5.5% under standard AM 1.5 solar light of 1000 W/m(2) intensity. At a lower light intensity of 100W/m(2), a PCE of 7.3% was measured. The advent of such simple solution-processed mesoscopic heterojunction solar cells paves the way to realize low-cost, high-efficiency solar cells. PMID:23043296

Etgar, Lioz; Gao, Peng; Xue, Zhaosheng; Peng, Qin; Chandiran, Aravind Kumar; Liu, Bin; Nazeeruddin, Md K; Grätzel, Michael

2012-10-24

92

Thermal Durability of Cu-CHA NH3-SCR Catalysts for Diesel NOx Reduction  

SciTech Connect

Multiple catalytic functions (NOx conversion, NO and NH3 oxidation, NH3 storage) of a commercial Cu-zeolite urea/NH3-SCR catalyst were assessed in a laboratory fixed-bed flow reactor system after differing degrees of hydrothermal aging. Catalysts were characterized by using x-ray diffraction (XRD), 27Al solid state nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM) / energy dispersive X-ray (EDX) spectroscopy to develop an understanding of the degradation mechanisms during catalyst aging. The catalytic reaction measurements of laboratory-aged catalysts were performed, which allows us to obtain a universal curve for predicting the degree of catalyst performance deterioration as a function of time at each aging temperature. Results show that as the aging temperature becomes higher, the zeolite structure collapses in a shorter period of time after an induction period. The decrease in SCR performance was explained by zeolite structure destruction and/or Cu agglomeration, as detected by XRD/27Al NMR and by TEM/EDX, respectively. Destruction of the zeolite structure and agglomeration of the active phase also results in a decrease in the NO/NH3 oxidation activity and the NH3 storage capacity of the catalyst. Selected laboratory aging conditions (16 h at 800oC) compare well with a 135,000 mile vehicle-aged catalyst for both performance and characterization criteria.

Schmieg, Steven J.; Oh, Se H.; Kim, Chang H.; Brown, David B.; Lee, Jong H.; Peden, Charles HF; Kim, Do Heui

2012-04-30

93

NH3 molecular doping of silicon nanowires grown along the [112], [110], [001], and [111] orientations  

PubMed Central

The possibility that an adsorbed molecule could provide shallow electronic states that could be thermally excited has received less attention than substitutional impurities and could potentially have a high impact in the doping of silicon nanowires (SiNWs). We show that molecular-based ex-situ doping, where NH3 is adsorbed at the sidewall of the SiNW, can be an alternative path to n-type doping. By means of first-principle electronic structure calculations, we show that NH3 is a shallow donor regardless of the growth orientation of the SiNWs. Also, we discuss quantum confinement and its relation with the depth of the NH3 doping state, showing that the widening of the bandgap makes the molecular donor level deeper, thus more difficult to activate. PMID:22709657

2012-01-01

94

Photoacoustic system for NH3 detection in a selective catalytic reactor  

NASA Astrophysics Data System (ADS)

A new instrument specifically developed for measuring NH3 concentrations at the inlet and outlet of an SCR reactor is described. It is based on the photoacoustic technique and can perform an online and in-situ n-point measurement grid. The major problem is the severe interference of CO2 combustion gas that absorbs at the same wavelength used for NH3, lowering the sensitivity of the technique. A 13CO2 tunable laser emitting at three wavelengths has been used in order to evaluate simultaneously the CO2 and NH3 concentration. The integrated measurements have been done by a simple differential absorption technique by using a pyroelectric detector; the spatially resolved measurements have been carried out through the analysis of the acoustic wave generated by the laser beam and collected by four microphones perpendicularly disposed. Experimental tests on a 35 MW industrial plant and comparison with traditional sampling methods are presented.

Pintus, Nice; Carrer, Isabella; Del Corno, Ada; Fiorina, Lorenzo; Zanzottera, Eugenio

1995-09-01

95

Structural, elastic, and electronic properties of orthorhombic NH 3BH 3: An ab initio study  

NASA Astrophysics Data System (ADS)

At the generalized gradient approximation (GGA), the elastic constants of the orthorhombic phase of NH 3BH 3 were calculated with plane-wave pseudo-potential method. Our calculation showed that the orthorhombic phase NH 3BH 3 is a loose and brittle material, as well as hard to be deformed, also we calculated the elastic anisotropies and the Debye temperatures from the elastic constants. And from the band structure and density of state (DOS), we concluded that NH 3BH 3 is a wide-gap semiconductor and the band gap is almost 6.0 eV. The bonds between N atoms and H atoms show a strong covalent characteristic, B atoms and H atoms form ironic bonds, and so as to the B-N bonds. Electrons from the B atoms are absorbed by the H atoms around the B atoms, and the H atoms display electronegativity.

Song, Qi; Hou, Yu-Qing; Li, Li-Sha; Jiang, Zhen-Yi; Zhou, Bo; Zhang, Xiao-Dong

2012-02-01

96

Unusual defect physics in CH3NH3PbI3 perovskite solar cell absorber  

NASA Astrophysics Data System (ADS)

Thin-film solar cells based on Methylammonium triiodideplumbate (CH3NH3PbI3) halide perovskites have recently shown remarkable performance. First-principle calculations show that CH3NH3PbI3 has unusual defect physics: (i) Different from common p-type thin-film solar cell absorbers, it exhibits flexible conductivity from good p-type, intrinsic to good n-type depending on the growth conditions; (ii) Dominant intrinsic defects create only shallow levels, which partially explain the long electron-hole diffusion length and high open-circuit voltage in solar cell. The unusual defect properties can be attributed to the strong Pb lone-pair s orbital and I p orbital antibonding coupling and the high ionicity of CH3NH3PbI3.

Yin, Wan-Jian; Shi, Tingting; Yan, Yanfa

2014-02-01

97

Engineering analysis of an NH3-air alkaline fuel cell system for vehicular applications  

NASA Astrophysics Data System (ADS)

The use of a hydrogen air alkaline fuel cell in a vehicle with liquid anhydrous ammonia as the hydrogen storage medium was examined. In the system analyzed here, hydrogen is supplied to the fuel cell by the catalytic cracking of liquid anhydrous ammonia, making the total system an indirect NH3 air fuel cell system. It was found that the endothermicity of the NH3 cracking reaction is supplied by combustion of the anode vent gas after utilizing 80% of the hydrogen electrochemically resulting in a minimal efficiency penalty. Laboratory scale examinations were made of the ammonia cracking reaction and the power characteristics of an alkaline fuel cell running on cracked ammonia and air. Single cell and bicell testing indicated system thermal efficiencies of 48 to 60% (based on L.H.V. of NH3) can be achieved at power densities of 1 to 2.6 kW/sq m using currently known electrode technology in a bipolar design.

Ross, P. N., Jr.

1982-06-01

98

Density dependence of the 5 micron infrared spectrum of NH3  

NASA Technical Reports Server (NTRS)

Measurements of dilute mixtures of NH3 in H2 were made in the window region 1900-2100/cm of the NH3 spectrum to determine is behavior with increasing pressure of H2. The spectra of pure H2, pure NH3, and mixtures of the two, in the total pressure range from 2.38 to 8.17 atm at 309 K, were obtained with a 975-cm white-cell. Synthetic spectra were calculated using precise line strengths, line positions, and a Lorentz profile. The experimental and calculated spectra are in reasonably good agreement, except that the former is super-imposed on a rather flat background not given by the calculation. A possible mechanism for this background is suggested.

Chapados, Camille; Bjoraker, Gordon L.; Birnbaum, George

1990-01-01

99

Partial phase diagram for the system NH3-H2O - The water-rich region  

NASA Technical Reports Server (NTRS)

Phase boundaries of the H2O-NH3 system for (NH3)/x/(H2O)/1-x/ have been determined with diamond-anvil cells for mixtures in two composition ranges: (1) for x in the range from 0 to 0.3, at pressures up to 4 GPa at 21 C, and (2) for x in the range from 0.46 to 0.50, at pressures up to 5 GPa from 150 to 400 K. Phases were identified visually with a microscope and polarized optics. The NH3.2(H2O) phase is strongly anisotropic with a much smaller refractive index than that of ice VII and cracks in two nonperpendicular networks. NH3.H2O has a refractive index closer to that of Ice VII and does not appear to form cracks. Both phases are colorless. Phase boundaries were determined on both increasing and decreasing pressures, and compositions of the ammonia ices were determined by estimating relative amounts of water and ammonia ices at known overall compositions. For low-ammonia compositions (x equal to or less than 0.15), the following assemblages succedd one another as pressure increases: liquid; liquid and Ice VI (at 1.0 + GPa); liquid and Ice VII (at 2.1 GPa); Ice VII and NH3.H2O (at 3.5 GPa). For x in the range from 0.15 to 0.30, the water ice and liquid fields are replaced by the NH3.2(H2O) and liquid field at pressures down to 1.0 GPa and lower.

Johnson, M. L.; Schwake, A.; Nicol, M.

1984-01-01

100

Complex Actions of Thyroid Hormone Receptor Antagonist NH-3 on Gene Promoters in Different Cell Lines  

PubMed Central

It is desirable to obtain new antagonists for thyroid hormone (TRs) and other nuclear receptors (NRs). We previously used X-ray structural models of TR ligand binding domains (LBDs) to design compounds, such as NH-3, that impair coactivator binding to activation function 2 (AF-2) and block thyroid hormone (triiodothyronine, T3) actions. However, TRs bind DNA and are transcriptionally active without ligand. Thus, NH-3 could modulate TR activity via effects on other coregulator interaction surfaces, such as activation function (AF-1) and corepressor binding sites. Here, we find that NH-3 blocks TR-LBD interactions with coactivators and corepressors and also inhibits activities of AF-1 and AF-2 in transfections. While NH-3 lacks detectable agonist activity at T3-activated genes in GC pituitary cells it nevertheless activates spot 14 (S14) in HTC liver cells with the latter effect accompanied by enhanced histone H4 acetylation and coactivator recruitment at the S14 promoter. Surprisingly, T3 promotes corepressor recruitment to target promoters. NH-3 effects vary; we observe transient recruitment of N-CoR to S14 in GC cells and dismissal and rebinding of N-CoR to the same promoter in HTC cells. We propose that NH-3 will generally behave as an antagonist by blocking AF-1 and AF-2 but that complex effects on coregulator recruitment may result in partial/mixed agonist effects that are independent of blockade of T3 binding in some contexts. These properties could ultimately be utilized in drug design and development of new selective TR modulators. PMID:18930112

Shah, Vanya; Nguyen, Phuong; Nguyen, Ngoc-Ha; Togashi, Marie; Scanlan, Thomas S.; Baxter, John D.; Webb, Paul

2014-01-01

101

Liquid Phase Deposition Of Thin Titanium Dioxide Films For NH3 Detection  

NASA Astrophysics Data System (ADS)

TiO2 thin films are prepared by a new method called Liquid Phase Deposition (LDP). The layers are obtained by the reaction between the metal fluorocomplex and boric acid in aqueous solution. The morphology of the films and the composition are investigated by scanning electron microscopy (SEM) and x-ray photoelectron spectrometry (XPS). The sorption properties of TiO2 film to NH3 are measured by the Quartz Crystal Microbalance (QCM) method. A correlation between NH3 concentration and the sorption ability of as-deposited and annealed samples is obtained.

Georgieva, V.; Stefchev, P.; Stefanov, P.; Spassov, L.; Raicheva, Z.; Ivanova, K.

2007-04-01

102

Global distributions and trends of atmospheric ammonia (NH3) from IASI satellite observations  

NASA Astrophysics Data System (ADS)

Ammonia (NH3) emissions in the atmosphere have strongly increased in the past decades, largely because of the intensive livestock production and use of fertilizers. As a short-lived species, NH3 is highly variable in the atmosphere and its concentration is generally small, except in and close to local source areas. While ground-based measurements are possible, they are challenging and sparse. Advanced infrared sounders in orbit have recently demonstrated their capability to measure NH3, offering a new tool to refine global and regional budgets. In this paper we describe an improved retrieval scheme of NH3 total columns from the measurements of the Infrared Atmospheric Sounding Interferometer (IASI). It exploits the hyperspectral character of this instrument by using an extended spectral range (800-1200 cm-1) where NH3 is optically active. This scheme consists of the calculation of a dimensionless spectral index from the IASI level1C radiances, which is subsequently converted to a total NH3 column using look-up-tables built from forward radiative transfer model simulations. We show how to retrieve the NH3 total columns from IASI quasi-globally and twice daily, above both land and sea, without large computational resources and with an improved detection limit. The retrieval also provides error characterization on the retrieved columns. Five years of IASI measurements (1 November 2007 to 31 October 2012) have been processed to acquire the first global and multiple-year dataset of NH3 total columns, which are evaluated and compared to similar products from other retrieval methods. Spatial distributions from the five years dataset are provided and analyzed at global and regional scales. We show in particular the ability of this method to identify smaller emission sources than those reported previously, as well as transport patterns above sea. The five year time series is further examined in terms of seasonality and inter-annual variability (in particular as a function of fire activity) separately for the Northern and Southern Hemispheres.

Van Damme, M.; Clarisse, L.; Heald, C. L.; Hurtmans, D.; Ngadi, Y.; Clerbaux, C.; Dolman, A. J.; Erisman, J. W.; Coheur, P. F.

2013-09-01

103

Modeling of Jupiter's millimeter wave emission utilizing laboratory measurements of ammonia (NH3) opacity  

NASA Technical Reports Server (NTRS)

The techniques used to make laboratory measurements of the millimeter wave opacity from gaseous ammonia under simulated Jovian conditions are described. The results are applied to a radiative transfer model, which is used to compute Jupiter's millimeter wavelength emission. The absorptivity of gaseous NH3 is measured to reduce one of the largest uncertainties in modeling Jupiter's millimeter wave emission. Several other millimeter wave opacity sources are examined. New expressions are given for computing the absorptivity of NH3, H2O, cloud condensates, and pressure-induced absorption. Jupiter's reliable millimeter wavelength observations are compared with synthetic emission spectra which utilize these new absorption expressions.

Joiner, Joanna; Steffes, Paul G.

1991-01-01

104

Ground-based FTIR measurements of NH3 total columns and comparison with IASI data  

NASA Astrophysics Data System (ADS)

Atmospheric ammonia (NH3) dominates global emissions of total reactive nitrogen. It has an impact on human health, as a precursor of fine particulate matter, and on Earth's ecosystems, via deposition. The main source of global NH3 emissions is agriculture, the remaining ones being the oceans, natural vegetation, humans, wild animals and biomass burning. The global atmospheric budget of NH3 is still very uncertain in chemical models, highlighting the critical need for satellite and ground-based observations. We present, for the first time, time-series (2009 - 2011) of NH3 total columns obtained from ground-based FTIR measurements. These observations are performed at Reunion Island (21°S, 55°E), one of the two subtropical stations, in Southern Hemisphere, of the ground-based Network for the Detection of Atmospheric Composition Change (NDACC) equipped with FTIR instruments. The seasonal and inter-annual variabilities of ammonia observed at Reunion Island from the ground are compared to the ones derived from recent IASI data obtained with a new retrieval method based on the calculation of a Hyperspectral Range Index.

Vigouroux, Corinne; De Mazière, Martine; Desmet, Filip; Hermans, Christian; Langerock, Bavo; Scolas, Francis; Van Damme, Martin; Clarisse, Lieven; Coheur, Pierre-François

2013-04-01

105

Estimation of NH3 Bi-Directional Flux from Managed Agricultural Soils  

EPA Science Inventory

The Community Multi-Scale Air Quality model (CMAQ v4.7) contains a bi-directional ammonia (NH3) flux option that computes emission and deposition of ammonia derived from commercial fertilizer via a temperature dependent parameterization of canopy and soil compensation ...

106

Parametrization of electron impact ionization cross sections for CO, CO2, NH3 and SO2  

NASA Technical Reports Server (NTRS)

The electron impact ionization and dissociative ionization cross section data of CO, CO2, CH4, NH3, and SO2, measured in the laboratory, were parameterized utilizing an empirical formula based on the Born approximation. For this purpose an chi squared minimization technique was employed which provided an excellent fit to the experimental data.

Srivastava, Santosh K.; Nguyen, Hung P.

1987-01-01

107

Spin transport in CH3NH3PbI3  

NASA Astrophysics Data System (ADS)

Organometal trihalide perovskites with the general formula (CH3NH3)PbX3 (X is Cl, I and/or Br) have a composition dependent tunable band gap and long electron-hole diffusion length, which is not only being hotly studied for usage in hybrid solar cells, but also has potential application in organic spintronics. In this work, we prepared CH3NH3PbI3-coated Fe3O4 granular films. CH3NH3PbI3 behaves effectively as a spacer to decouple the Fe3O4 particles and spin-preserved transporting matrix. The magnetoresistance of Fe3O4 particles has been significantly enhanced after CH3NH3PbI3 coating, which is about -6% at 300 K and -10.8% at 150 K under a magnetic field of 10 kOe, about 3 times larger than the values of pure Fe3O4 (-1.9% at 300 K and -3.4% at 150 K).

Xu, Qingyu; Liu, Er; Qin, Sai; Shi, Shan; Shen, Kai; Xu, Mingxiang; Zhai, Ya; Dong, Shuai

2014-10-01

108

Infrared multi-line NH3 laser and its application for pumping an InSb laser  

Microsoft Academic Search

In this paper, infrared (IR) emissions from a TE CO2 laser pumped NH3 laser are reported. 38 IR laser lines were obtained from a CO2 9R(30) line pumped NH3:N2 mixture by cooling a NH3 laser tube, and 13 lines of them were new emission lines as far as we know. Four Q-branch lines were included and the others belonged to

N. Yamabayashi; T. Yoshida; K. Miyazaki; K. Fujisawa

1979-01-01

109

Low energy structural dynamics and constrained libration of Li(NH3)4, the lowest melting point metal.  

PubMed

The lattice and molecular dynamics for the solid phases of the lowest melting-point metal, Li(NH3)4, are determined by incoherent inelastic neutron scattering. Measurements of internal molecular displacements and distortions of the Li(NH3)4 units have been modelled and assigned using density functional theory calculations for the solid and molecular system. Inelastic neutron scattering measurement allow for the first determination of NH3 librational transitions. PMID:24988060

Seel, A G; Zurek, E; Ramirez-Cuesta, A J; Ryan, K R; Lodge, M T J; Edwards, P P

2014-09-25

110

A Deuterium NMR Spectroscopic Study of Solid BH(3)NH(3).  

PubMed

Deuterium nuclear magnetic resonance (NMR) powder spectra and spin-lattice relaxation times (T(1)) are used to measure the deuterium quadrupolar coupling constants (QCCs) chi(BD) and chi(ND) and to investigate the molecular reorientation of the BD(3) and ND(3) groups in solid deuterated borane monoammoniate, BD(3)NH(3) and BH(3)ND(3), respectively. In the high-temperature, tetragonal, phase (above 225 K) the following Arrhenius parameters are obtained from the temperature-dependent T(1): E(a) = 5.9 +/- 0.5 kJ/mol and tau(infinity) = 1.1 x 10(-)(13) s for BD(3)NH(3); E(a) = 7.3 +/- 0.8 kJ/mol and tau(infinity) = 4.4 x 10(-)(14) s for BH(3)ND(3). In the low-temperature, orthorhombic, phase the following parameters are obtained: E(a) = 26.4 +/- 1.4 kJ/mol and tau(infinity) = 1.2 x 10(-)(17) s for BD(3)NH(3); E(a) = 13.7 +/- 0.9 kJ/mol and tau(infinity) = 5.7 x 10(-)(15) s for BH(3)ND(3). Here tau(infinity) is proportional to the inverse of the usual Arrhenius preexponential factor, A. Deuterium line shape measurements for the low-temperature phase of BD(3)NH(3) yield E(a) = 25 +/- 2 kJ/mol and tau(infinity) = 4.7 x 10(-)(19) s. These dynamic factors indicate that the molecule is probably undergoing whole molecule rotation above the phase transition but the BH(3) and NH(3) groups are undergoing uncorrelated motion in the low-temperature phase. Deuterium quadrupolar coupling constants of 105 +/- 10 and 200 +/- 10 kHz were determined for BD(3)NH(3) and BH(3)ND(3), respectively. Molecular orbital (MO) calculations (CI(SD)/6-31G(d,p)//MP2/6-31G(d,p)) for the isolated molecule yield values of 143 and 255 kHz. MO calculations also show that the deuterium quadrupolar coupling constants chi(BD) and chi(ND) are relatively insensitive to all molecular structural parameters except the B-H and N-H bond lengths, respectively. It is suggested that the large decrease in the QCC on going from the gas phase to the solid state may be due to a slight lengthening of the B-H and N-H bonds, possibly a result of attractive B-H.H-N interactions. PMID:11671032

Penner, Glenn H.; Chang, Y. C. Phillis; Hutzal, Jennifer

1999-06-14

111

Nitrogen doping of nanoporous WO3 layers by NH3 treatment for increased visible light photoresponse.  

PubMed

Nanoporous WO(3) layers were grown by electrochemical anodization of W in a fluoride containing electrolyte. These layers were exposed to a thermal treatment in NH(3) to achieve nitrogen doping of the material. The morphology, crystal structure, composition and photoresponse of pure and nitrogen doped WO(3) were compared using scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and photoelectrochemical measurements. The results clearly show that successful nitrogen doping into WO(3) layers can be achieved by controlling the temperature and time during the NH(3) treatment. Most importantly, it is demonstrated that for the nitrogen doped WO(3) layers the photocurrent is significantly enhanced in the visible light region. PMID:20154369

Nah, Yoon-Chae; Paramasivam, Indhumati; Hahn, Robert; Shrestha, Nabeen K; Schmuki, Patrik

2010-03-12

112

Nitrogen doping of nanoporous WO3 layers by NH3 treatment for increased visible light photoresponse  

NASA Astrophysics Data System (ADS)

Nanoporous WO3 layers were grown by electrochemical anodization of W in a fluoride containing electrolyte. These layers were exposed to a thermal treatment in NH3 to achieve nitrogen doping of the material. The morphology, crystal structure, composition and photoresponse of pure and nitrogen doped WO3 were compared using scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and photoelectrochemical measurements. The results clearly show that successful nitrogen doping into WO3 layers can be achieved by controlling the temperature and time during the NH3 treatment. Most importantly, it is demonstrated that for the nitrogen doped WO3 layers the photocurrent is significantly enhanced in the visible light region.

Nah, Yoon-Chae; Paramasivam, Indhumati; Hahn, Robert; Shrestha, Nabeen K.; Schmuki, Patrik

2010-03-01

113

Substrate-controlled band positions in CH3NH3PbI3 perovskite films.  

PubMed

Using X-ray and ultraviolet photoelectron spectroscopy, the surface band positions of solution-processed CH3NH3PbI3 perovskite thin films deposited on an insulating substrate (Al2O3), various n-type (TiO2, ZrO2, ZnO, and F:SnO2 (FTO)) substrates, and various p-type (PEDOT:PSS, NiO, and Cu2O) substrates are studied. Many-body GW calculations of the valence band density of states, with spin-orbit interactions included, show a clear correspondence with our experimental spectra and are used to confirm our assignment of the valence band maximum. These surface-sensitive photoelectron spectroscopy measurements result in shifting of the CH3NH3PbI3 valence band position relative to the Fermi energy as a function of substrate type, where the valence band to Fermi energy difference reflects the substrate type (insulating-, n-, or p-type). Specifically, the insulating- and n-type substrates increase the CH3NH3PbI3 valence band to Fermi energy difference to the extent of pinning the conduction band to the Fermi level; whereas, the p-type substrates decrease the valence band to Fermi energy difference. This observation implies that the substrate's properties enable control over the band alignment of CH3NH3PbI3 perovskite thin-film devices, potentially allowing for new device architectures as well as more efficient devices. PMID:25209217

Miller, Elisa M; Zhao, Yixin; Mercado, Candy C; Saha, Sudip K; Luther, Joseph M; Zhu, Kai; Stevanovi?, Vladan; Perkins, Craig L; van de Lagemaat, Jao

2014-10-28

114

Role of NH3 and NH4+ transporters in renal acid-base transport  

PubMed Central

Renal ammonia excretion is the predominant component of renal net acid excretion. The majority of ammonia excretion is produced in the kidney and then undergoes regulated transport in a number of renal epithelial segments. Recent findings have substantially altered our understanding of renal ammonia transport. In particular, the classic model of passive, diffusive NH3 movement coupled with NH4+ “trapping” is being replaced by a model in which specific proteins mediate regulated transport of NH3 and NH4+ across plasma membranes. In the proximal tubule, the apical Na+/H+ exchanger, NHE-3, is a major mechanism of preferential NH4+ secretion. In the thick ascending limb of Henle's loop, the apical Na+-K+-2Cl? cotransporter, NKCC2, is a major contributor to ammonia reabsorption and the basolateral Na+/H+ exchanger, NHE-4, appears to be important for basolateral NH4+ exit. The collecting duct is a major site for renal ammonia secretion, involving parallel H+ secretion and NH3 secretion. The Rhesus glycoproteins, Rh B Glycoprotein (Rhbg) and Rh C Glycoprotein (Rhcg), are recently recognized ammonia transporters in the distal tubule and collecting duct. Rhcg is present in both the apical and basolateral plasma membrane, is expressed in parallel with renal ammonia excretion, and mediates a critical role in renal ammonia excretion and collecting duct ammonia transport. Rhbg is expressed specifically in the basolateral plasma membrane, and its role in renal acid-base homeostasis is controversial. In the inner medullary collecting duct (IMCD), basolateral Na+-K+-ATPase enables active basolateral NH4+ uptake. In addition to these proteins, several other proteins also contribute to renal NH3/NH4+ transport. The role and mechanisms of these proteins are discussed in depth in this review. PMID:21048022

Verlander, Jill W.

2011-01-01

115

Effect of NH3-plasma treatment and CMP modification on TDDB improvement in Cu metallization  

Microsoft Academic Search

Time-dependent dielectric breakdown (TDDB) between Cu interconnects is investigated. TDDB lifetime strongly depends on the surface condition of the Cu interconnect and surrounding pTEOS. A NH3-plasma treatment prior to cap-pSiN deposition on Cu interconnect improved the dielectric breakdown lifetime (TBD) over cap-pSiN deposition only. The plasma treatment also has the beneficial effect of suppressing wiring resistance increase during pSiN deposition.

Junji Noguchi; Naofumi Ohashi; Tomoko Jimbo; Hizuru Yamaguchi; Ken-ichi Takeda; Kenji Hinode

2001-01-01

116

An accurate global potential energy surface, dipole moment surface, and rovibrational frequencies for NH3  

Microsoft Academic Search

A global potential energy surface (PES) that includes short and long range terms has been determined for the NH3 molecule. The singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations and the internally contracted averaged coupled-pair functional electronic structure methods have been used in conjunction with very large correlation-consistent basis sets, including diffuse functions. Extrapolation

Xinchuan Huang; David W. Schwenke; Timothy J. Lee

2008-01-01

117

Equilibrium inversion barrier of NH3 from extrapolated coupled-cluster pair energies  

Microsoft Academic Search

The basis-set convergence of singlet and triplet pair energies of coupled-cluster theory including single and double excitations is accelerated by means of extrapolations based on the distinct convergence behaviors of these pairs. The new extrapolation procedure predicts a nonrelativistic Born-Oppenheimer inversion barrier of 1767 ± 12 cm ?1 for NH3 .A n effective one-dimensional, vibrationally averaged barrier of 2021 ±

Wim Klopper; Claire C. M. Samson; György Tarczay; Attila G. Császár

2001-01-01

118

SIMPLE DESIGN FOR AUTOMATION OF TUNGSTEN(VI) OXIDE TECHNIQUE FOR MEASUREMENT OF NH3, AND HNO3  

EPA Science Inventory

The tungstic acid technique for collection and analysis of NH3 and HNO3 concentrations in the ambient air has been automated in a simple and cost-effective design. The design allows complete separation of HNO3 and NH3 during detection. Unattended operation in field trials has bee...

119

Si-H bond production by NH 3 adsorption on Si(111): An UPS study  

NASA Astrophysics Data System (ADS)

The adsorption of NH 3 on Si(111) has been examined using essentially ultraviolet photoemission spectroscopy (UPS) between room temperature (RT) and 400°C. In this domain NH 3 molecules chemisorb dissociatively on some surface sites as deduced from the observation of Si-H monohydride units at 5.4 eV below EF. Other species labeled NH X ( X=1, 2 or 3), characterized by two NH 3 induced orbitals at 4.9 and 10.6 eV, are also adsorbed at RT with a saturation coverage ?1/3 monolayer for a 10 L (1 L=10 -6 Torr s) exposure. A strong S 2 surface state decrease results from adsorptions. With increasing substrate temperature the adsorption of the nitrided NH X species gradually decreases until 300°C where mainly Si-H bonds are observable. No direct conclusive assignment could be given by UPS about the exact nature of the NH X units, but XPS N 1s binding energy (BE) data give arguments for partly dissociated species (NH 2 or NH). The nitride formation starts to develop only above 300°C as evidenced by both a rapid XPS nitrogen coverage increase and new Si-N UPS features in this domain.

Kubler, L.; Hlil, E. K.; Bolmont, D.; Gewinner, G.

1987-05-01

120

Exploring High-Velocity NH_3(6,6) Emission at the Center of our Galaxy  

E-print Network

Using the NH\\3 (6,6) transition, which samples dense ($\\sim 10^{5}$) molecular gas with an energy above ground of 412 K, we find hot gas at high velocities (--142 to --210 km s$^{-1}$) associated with the central 2 pc of the Galactic center. This material may be either infalling gas due to shocks or tidal stripping, or possibly gas swept from the nuclear region. We identify two high-velocity features, which we call the Southern Runner and the Cap, and correlate these features with others detected in various molecular observations of the Galactic center. The characteristic linewidths of the Southern Runner and Cap, 10 -- 15 \\kms, are similar to those of other hot Galactic center clouds. The estimated H$_{2}$ masses of these clouds are 4$\\times 10^{3}$ M$\\sol$ and 2$\\times 10^{3}$ M$\\sol$, consistent with the masses of the western streamer and northern ridge, NH\\3 (6,6) emission features detected within the central 10 pc at lower velocities. Three possible explanations for this emission are discussed assuming that they lie at the Galactic center, including sweeping by the supernova remnant Sgr A East, infall and/or shock from the circumnuclear disk (CND), and stripping from the central rotating low-velocity NH\\3 (6,6) cloud.

Jennifer L. Donovan; Robeson M. Herrnstein; Paul T. P. Ho

2006-05-11

121

Development and evaluation of optical fiber NH3 sensors for application in air quality monitoring  

NASA Astrophysics Data System (ADS)

Ammonia is a major air pollutant emitted from agricultural practices. Sources of ammonia include manure from animal feeding operations and fertilizer from cropping systems. Sensor technologies with capability of continuous real time monitoring of ammonia concentration in air are needed to qualify ammonia emissions from agricultural activities and further evaluate human and animal health effects, study ammonia environmental chemistry, and provide baseline data for air quality standard. We have developed fiber optic ammonia sensors using different sensing reagents and different polymers for immobilizing sensing reagents. The reversible fiber optic sensors have detection limits down to low ppbv levels. The response time of these sensors ranges from seconds to tens minutes depending on transducer design. In this paper, we report our results in the development and evaluation of fiber optic sensor technologies for air quality monitoring. The effect of change of temperature, humidity and carbon dioxide concentration on fiber optic ammonia sensors has been investigated. Carbon dioxide in air was found not interfere the fiber optic sensors for monitoring NH3. However, the change of humidity can cause interferences to some fiber optic NH3 sensors depending on the sensor's transducer design. The sensitivity of fiber optic NH3 sensors was found depends on temperature. Methods and techniques for eliminating these interferences have been proposed.

Huang, Yu; Wieck, Lucas; Tao, Shiquan

2013-02-01

122

Formation of a passivating CH3NH3PbI3/PbI2 interface during moderate heating of CH3NH3PbI3 layers  

NASA Astrophysics Data System (ADS)

Layers of CH3NH3PbI3 are investigated by modulated surface photovoltage spectroscopy (SPV) during heating in vacuum. As prepared CH3NH3PbI3 layers behave as a p-type doped semiconductor in depletion with a band gap of 1.5 eV. After heating to 140 °C the sign of the SPV signals of CH3NH3PbI3 changed concomitant with the appearance of a second band gap at 2.36 eV ascribed to PbI2, and SPV signals related to charge separation from defect states were reduced after moderate heating.

Supasai, T.; Rujisamphan, N.; Ullrich, K.; Chemseddine, A.; Dittrich, Th.

2013-10-01

123

Characterizing the influence of highways on springtime NO2 and NH3 concentrations in regional forest monitoring plots.  

PubMed

Highways are major sources of nitrogen dioxide (NO2) and ammonia (NH3). In this study, springtime NO2 and NH3 concentrations were measured at 17 Ontario Forest Biomonitoring Network (OFBN) plots using passive samplers. Average springtime NO2 concentrations were between 1.3 ?g m(-3) and 27 ?g m(-3), and NH3 concentrations were between 0.2 ?g m(-3) and 1.7 ?g m(-3), although concentrations measured in May (before leaf out) were typically twice as high as values recorded in June. Average NO2 concentrations, and to a lesser extent NH3, could be predicted by road density at all radii (around the plot) tested (500 m, 1000 m, 1500 m). Springtime NO2 concentrations were predicted for a further 50 OFBN sites. Normalized plant/lichen N concentrations were positively correlated with estimated springtime NO2 and NH3 concentrations. Epiphytic foliose lichen richness decreased with increasing NO2 and NH3, but vascular plant richness was positively related to estimated springtime NO2 and NH3. PMID:24747347

Watmough, Shaun A; McDonough, Andrew M; Raney, Shanel M

2014-07-01

124

Estimation of NH3 emissions from a naturally ventilated livestock farm using local-scale atmospheric dispersion modelling  

NASA Astrophysics Data System (ADS)

Agricultural livestock represents the main source of ammonia (NH3) in Europe. In recent years, reduction policies have been applied to reduce NH3 emissions. In order to estimate the impacts of these policies, robust estimates of the emissions from the main sources, i.e. livestock farms are needed. In this paper, the NH3 emissions were estimated from a naturally ventilated livestock farm in Braunschweig, Germany during a joint field experiment of the GRAMINAE European project. An inference method was used with a Gaussian-3D plume model and with the Huang 3-D model. NH3 concentrations downwind of the source were used together with micrometeorological data to estimate the source strength over time. Mobile NH3 concentration measurements provided information on the spatial distribution of source strength. The estimated emission strength ranged between 6.4±0.18 kg NH3 d-1 (Huang 3-D model) and 9.2±0.7 kg NH3 d-1 (Gaussian-3D model). These estimates were 94% and 63% of what was obtained using emission factors from the German national inventory (9.6 kg d-1 NH3). The effect of deposition was evaluated with the FIDES-2D model. This increased the emission estimate to 11.7 kg NH3 d-1, showing that deposition can explain the observed difference. The daily pattern of the source was correlated with net radiation and with the temperature inside the animal houses. The daily pattern resulted from a combination of a temperature effect on the source concentration together with an effect of variations in free and forced convection of the building ventilation rate. Further development of the plume technique is especially relevant for naturally ventilated farms, since the variable ventilation rate makes other emission measurements difficult.

Hensen, A.; Loubet, B.; Mosquera, J.; van den Bulk, W. C. M.; Erisman, J. W.; Dämmgen, U.; Milford, C.; Löpmeier, F. J.; Cellier, P.; Mikuška, P.; Sutton, M. A.

2009-12-01

125

VUV Photolysis of NH_3: a Matrix Isolation Study of the Molecular Interactions Between Amidogen Radical and Ammonia Molecules  

NASA Astrophysics Data System (ADS)

The presence of NH_3 in the interstellar medium is very promising in terms of possible exobiologically-relevant reactions. This is the reason why numerous laboratory investigations on reactions involving NH_3 were carried out in the context of astrochemistry. Among other reactions, the photolysis of NH_3 was widely investigated. IR spectroscopy in solid phase as well as in rare-gas matrices suggested the formation of NH_2 radicals. In most of these experiments, samples containing NH_3 were prepared at cryogenic temperatures and further irradiated. On the other hand, since the penetration of the photons inside the solid ices as well as inside matrices is limited, the concentration of the photoproducts is weak, thus hindering possible secondary reaction studies. Furthermore, in addition with ice-grain irradiations, in the interstellar clouds, the gaseous species may be subjected to irradiation during their condensation on ice grains. In order to reproduce this effect, instead of irradiating samples obtained by condensation of NH_3 or NH_3/Ne gases at low temperatures, we carried experiments in which irradiation was carried out during the sample deposition. Thus, the amidogen radical and complexes between this radical and ammonia molecules were prepared and isolated in a neon matrix. The formation of (NH_2)(NH_3), (NH_2)(NH_3)_2 and (NH_2)(NH_3)_3 was clearly established thanks to the comparison between the theoretical and the experimental vibrational frequencies. Thus, such ammonia-containing aggregates may be formed in the interstellar clouds. These complexes, as solvated radicals, may further react with carbon- and oxygen-containing species present on the surface of ice grains. Such reactions may be a first step toward the formation of prebiotic molecules.

Krim, L.; Zins, E. L.

2013-06-01

126

Structural Study on Cubic-Tetragonal Transition of CH3NH3PbI3  

NASA Astrophysics Data System (ADS)

The cubic-tetragonal phase transition of CH3NH3PbI3 was investigated by single crystal X-ray diffractometry. The crystal structure was refined at five temperatures in the teragonal phase. The PbI6 octahedron rorates around the c-axis alternatively to construct the SrTiO3-type tetragonal structure. A methylammonium ion is partially orderd; 24 disordered states in the cubic phase are reduced to 8. With decreasing temperature, the rotation angle of the octahedron increases monotonically, which indicates it is an order parameter of the cubic-tetragonal transition.

Kawamura, Yukihiko; Mashiyama, Hiroyuki; Hasebe, Katsuhiko

2002-07-01

127

An Innovative Measurement for Testing the Nanocatalyst Degradation Efficiency of NH3  

NASA Astrophysics Data System (ADS)

This study develops a low-cost, fast and innovative measurement method for testing the efficiency of photocatalysts in the degradation of gaseous concentrations. In the past, photocatalyst tests of catalyst response to gases mainly relied on measurement with either GC/MS (Gas Chromatography/Mass Spectrometer) or FTIR (Fourier Transform Infrared Spectroscopy), to monitor the reaction process. However, these two instruments are very expensive, and the processes are complicated and time-consuming. The major devices of the measurement method developed by this study are UV/VIS spectrophotometer and quartz cuvettes. The experimental procedures are not only simple but fast. In the experiment, a gas of a specific concentration is first injected into an enclosed quartz cuvette. The cuvette is then placed in the UV/VIS spectrophotometer to carry out tests to obtain an absorption spectrum. Thus, a calibration curve of UV light absorbance intensity vs. various gaseous concentrations can also be obtained using the same method. The degradation efficiency of the different photocatalysts is to be measured. Quartz plates are coated with two different types of TiO2 nanocatalysts. The coated plates are then placed in separate cuvettes. After injecting NH3 into a quartz cuvette, the cuvette is then put under the UV light irradiation to perform the degradation experiment. Afterwards, the cuvette is transferred to the UV/VIS spectrophotometer for testing. The absorbance intensity of the absorption spectra is then compared with the calibration curves. Based on the change of the gaseous concentration, the degradation efficiency of the photocatalyst is determined. The experimental results reveal that the self-made TiO2 nanocatalyst has excellent degradation efficiency towards NH3. When NH3 is exposed to UV irradiation for 60 minutes, the gaseous concentration can be reduced to 10.35% of the original concentration. However, the commercial TiO2 nanocatalyst can only reduce the gaseous concentration to 50.2% of the original concentration. In addition, the degradation reaction rate constant of the self-made TiO2 nanocatalyst towards NH3 is as high as 0.029 min-1.

Jwo, C. S.; Chen, D. M.; Chang, H.; Chen, J. Z.; Tien4, D. C.

2006-10-01

128

Natural bond orbital analysis of molecular interactions Theoretical studies of binary complexes of HF, H2O, NH3, O2, F2, CO, and CO2 with HF, H2O, and NH3  

Microsoft Academic Search

Ab initio molecular orbital theory and natural bond orbital analysis were applied to the binary complexes of HF, H2O, NH3, N2, O2, F2, CO and CO2 with HF, H2O and NH3. Both hydrogen-bonded and nonhydrogen-bonded structures were found for complexes involving N2, O2, F2, CO, and CO2; these structures were defined by NBO analysis of charge transfer, which is generally

A. E. Reed; F. Weinhold; L. A. Curtiss; D. J. Pochatko

1986-01-01

129

Natural bond orbital analysis of molecular interactions: Theoretical studies of binary complexes of HF, H2O, NH3, N2, O2, F2, CO, and CO2 with HF, H2O, and NH3  

Microsoft Academic Search

The binary complexes of HF, H2O, NH3, N2, O2, F2, CO, and CO2 with HF, H2O, and NH3 have been studied by abinitio molecular orbital theory and natural bond orbital (NBO) analysis. Most of the complexes involving N2, O2, F2, CO, and CO2 are found to have both hydrogen-bonded and non-hydrogen-bonded structures. The NBO analysis provides a consistent picture of

Alan E. Reed; Frank Weinhold; Larry A. Curtiss; David J. Pochatko

1986-01-01

130

Oxidation of methane by Methylomicrobium album and Methylocystis sp. in the presence of H2S and NH 3.  

PubMed

Oxidation of methane by methanotrophs, Methylomicrobium album and Methylocystis sp., was measured at several initial concentrations of H2S and NH3 in the headspace of stoppered flasks, at the same initial concentration of methane as sole carbon and energy source: 15 % (v/v). No effect was observed at 0.01 % (v/v) H2S and 0.025 % (v/v) NH3 in gas phase but over 0.05 and 0.025 % (v/v), respectively, they inhibited the oxidation of methane. The effect of H2S was stronger in Methylocystis sp. and both microorganisms were similarly affected by NH3. Depending on their concentrations in gas phase, H2S and NH3 can thus affect the rate of oxidation of methane and biomass growth of both methanotrophs. PMID:24068504

Cáceres, Manuel; Gentina, Juan C; Aroca, Germán

2014-01-01

131

Detection of a CO and NH3 gas mixture using carboxylic acid-functionalized single-walled carbon nanotubes  

PubMed Central

Carbon nanotubes (CNT) are extremely sensitive to environmental gases. However, detection of mixture gas is still a challenge. Here, we report that 10 ppm of carbon monoxide (CO) and ammonia (NH3) can be electrically detected using a carboxylic acid-functionalized single-walled carbon nanotubes (C-SWCNT). CO and NH3 gases were mixed carefully with the same concentrations of 10 ppm. Our sensor showed faster response to the CO gas than the NH3 gas. The sensing properties and effect of carboxylic acid group were demonstrated, and C-SWCNT sensors with good repeatability and fast responses over a range of concentrations may be used as a simple and effective detection method of CO and NH3 mixture gas. PMID:23286690

2013-01-01

132

Mobilities of NH4+(NH3)n clusters in helium from 100 K to 298 K  

NASA Astrophysics Data System (ADS)

A variable temperature-selected ion flow drift tube (VT-SIFDT) has been used to measure the mobilities of NH4+(NH3)n clusters drifting in He. The mobilities have been measured for n=0-2 at 298 K, n=0-3 at 200 K, and n=0-5 at 100 K, marking the first mobilities experiments for these clusters below room temperature. The reduced mobilities measured at 298 K are compared to the previous SIFDT results of Krishnamurthy et al. [J. Chem. Phys. 106, 530 (1997)] for n=0-2. While the current results compare quite favorably for n=0-2, there is a discrepancy for n=3 which is addressed by current 100 K and 200 K data where these species are thermally stable. The trends in the mobilities from 100 K to 298 K as a function of E/N and effective temperature reveal that the repulsive part of the He-NH4+(NH3)n interaction potential is sampled predominantly for n=1-5. However, the attractive part of the potential is accessed at the lowest temperatures for He-NH4+.

Midey, Anthony J.; Viggiano, A. A.

2001-04-01

133

Impact of atmospheric NH 3 deposition on plant growth and functioning — a case study with Brassica oleracea L  

Microsoft Academic Search

Brassica oleraceaL. (curly kale) was exposed to 0, 2, 4, 6 and 8?l l?1NH3during one week and the impact on growth and N compounds was determined. Exposure to NH3increased shoot biomass production at 2 and 4?l l?1, but resulted in an inhibition of shoot and root growth at 6 and 8?l l?1. Shoot to root ratio was not affected up

Ana Castro; Ineke Stulen; Luit J. De Kok

134

Immobilization of enzyme and antibody on ALD-HfO2-EIS structure by NH3 plasma treatment  

PubMed Central

Thin hafnium oxide layers deposited by an atomic layer deposition system were investigated as the sensing membrane of the electrolyte-insulator-semiconductor structure. Moreover, a post-remote NH3 plasma treatment was proposed to replace the complicated silanization procedure for enzyme immobilization. Compared to conventional methods using chemical procedures, remote NH3 plasma treatment reduces the processing steps and time. The results exhibited that urea and antigen can be successfully detected, which indicated that the immobilization process is correct. PMID:22401350

2012-01-01

135

DECHLORINATION OF PCBS, CAHS, HERBICIDES AND PESTICIDES NEAT AND IN SOILS AT 25&DEG;C USING NA/NH3. (R829421E01)  

EPA Science Inventory

Na/NH3 reductions have been used to dehalogenate polychlorinated biphenyls (PCBs), chlorinated aliphatic hydrocarbons (CAHs) and pesticides at diffusion controlled rates at room temperature in model compound studies in both dry NH3 and when water was adde...

136

Phase transitions in [Co(NH3)6](ClO4)3 investigated by neutron scattering methods  

NASA Astrophysics Data System (ADS)

[Co(NH3)6](ClO4)3 was investigated by neutron scattering methods in the temperature range of 20-290 K. Neutron powder diffraction revealed that the crystal structure does not change at the TC2 and TC3 phase transitions. High temperature phases are orientationally disordered. QENS study showed that NH3 ligands perform rapid reorientational motion around their 3-fold axes in a wide temperature range. However, below TC3 some excess of elastic scattering is observed, which can be explained by the assumption that only half of the NH3 groups reorient fast enough to contribute to the QENS broadening, whereas the remaining NH3 groups reorient more slowly. The activation energy for NH3 jumps, estimated from the temperature dependence of QENS broadening, is small but comparable with the results obtained for other hexaammine complexes. Quantum chemical calculation, carried out on the basis of DFT for isolated [Co(NH3)6]3+ cation and ClO4- anion, and experimental (IR, RS, IINS) spectra are in good agreement.

Hetma?czyk, ?ukasz; Górska, Natalia; Hetma?czyk, Joanna; Mikuli, Edward; Natkaniec, Ireneusz

2013-02-01

137

NH4+-NH3 removal from simulated wastewater using UV-TiO2 photocatalysis: effect of co-pollutants and pH.  

PubMed

The main objective of the present study was to investigate the efficiency of titanium dioxide (TiO2) assisted photocatalytic degradation (PCD) process for the removal of ammonium-ammonia (NH4(+)-NH3) from the aqueous phase and in the presence of co-pollutants thiosulfate (S2O3(2-)) and p-cresol (C6H4CH3OH) under varying mixed conditions. For the NH4(+)-NH3 only PCD experiments, results showed higher NH4 -NH3 removal at pH 12 compared to pH 7 and 10. For the binary NH4(+)-NH3/S2O3(2-) studies the respective results indicated a significant lowering in NH4(+)-NH3 PCD in the presence of S2O32- at pH 7/12 whereas at pH 10 a marked increase in NH4(+)-NH3 removal transpired. A similar trend was noted for the p-cresol/NH4(+)-NH3 binary system. Comparing findings from the binary (NH4(+)-NH3/S2O3(2-) and p-cresol/NH4(+)-NH3) and tertiary (NH4(+)-NH3/S2O3(2-)/p-cresol) systems, at pH 10, showed fastest NH4(+)-NH3 removal transpiring for the tertiary system as compared to the binary systems, whereas both the binary systems indicated comparable NH4(+)-NH3 removal trends. The respective details have been discussed. PMID:20540426

Vohra, M S; Selimuzzaman, S M; Al-Suwaiyan, M S

2010-05-01

138

Trends of NO-, NO 2-, and NH 3-emissions from gasoline-fueled Euro-3- to Euro-4-passenger cars  

NASA Astrophysics Data System (ADS)

Vehicular emissions of reactive nitrogen compounds (RNCs) such as nitric oxide (NO), nitrogen dioxide (NO 2), and ammonia (NH 3) have a substantial impact on urban air quality. NO and NO 2 support the photochemical formation of ozone, and NH 3 is involved in the atmospheric formation of secondary aerosols. Vehicular NO is mainly formed during combustion, whereas NO 2 and NH 3 are both secondary pollutants of the catalytic converter systems. Herein we report on tail-pipe RNC emissions of gasoline-fueled Euro-3- and Euro-4-passenger cars at transient driving from 0 to 150 km h -1. Two sets of 10 in-use vehicles with comparable engine size and mileage were studied with time-resolved chemical ionization-mass spectrometry (CI-MS). Each vehicle was tested in 7 different driving cycles including the legislative European (EDC) and the US FTP-75 driving cycles. Mean emission factors (EFs) for different traffic situations are reported and effects of cold start, velocity, acceleration, and deceleration are discussed. Furthermore, critical operating conditions supporting the de novo formation of NH 3 have been identified. In the EDC, mean NO- and NH 3-EFs of 57±26 and 16±12 mg km -1 were obtained for Euro-3-vehicles; those of the Euro-4-technology were lower by about 25% and 33% at the levels of 43±46 and 10±7 mg km -1, respectively. NO 2 emissions of the investigated three-way catalyst (TWC) vehicles accounted for <1% of the detected RNCs, whereas NH 3 was found to be the dominant RNC for most vehicle conditions. Molar NH 3 proportions varied from about 0.4-0.8, as soon as catalyst light-off occurred. NO was found in large excess only during the cold-start period. Catalyst light-off is indicated by a fast transition from NO- to NH 3-rich exhaust. Velocity and acceleration had pronounced effects on the RNC emission characteristics. Mean velocity-dependent EFs for NO and NH 3 varied by about one order of magnitude from 10 to 74 and 15 to 161 mg km -1 for Euro-3-vehicles and from 12 to 44 and 7 to 144 mg km -1 for the Euro-4 fleet. We conclude that the investigated Euro-3- and Euro-4-vehicles are mainly operated under slightly reducing conditions, where the NH 3 emissions dominate over those of the NO. Under these conditions, both vehicle fleets on an average fulfilled the valid Euro-3 and Euro-4 limits for nitrogen oxides (NO x) of 150 and 80 mg km -1, respectively (as NO 2 equivalents).

Heeb, Norbert V.; Saxer, Christian J.; Forss, Anna-Maria; Brühlmann, Stefan

139

High NH2D/NH3 ratios in protostellar cores  

E-print Network

Observations of low mass protostars which probe small enough size scales to be within likely CO depletion regions show the highest [NH2D]/[NH3] ratios yet measured, of 4--33%. These molecular D/H ratios are higher than those measured on larger scales, showing that deuterium fractionation increases towards protostellar cores. As in cold clouds, such high ratios can be produced by gas-phase ion-molecule chemistry in the presence of depletion. Grain surface chemistry is less likely to explain the deuterium enhancement, as it would require higher fractionation in ices than current models predict. The link between accretion, depletion and high molecular deuterium fractionation is strongly supported.

Jennifer Hatchell

2003-02-27

140

Distinguishing and identifying hydrogens in an NH 3 group by I.R. spectroscopy  

NASA Astrophysics Data System (ADS)

Combined low temperature isotopic dilution and polarized i.r. measurements have been performed on single crystal specimens of sulfamic acid, +H 3N?SO 3-, containing 5% D with respect to H. The three isotropically isolated ?ND bands observed in these spectra at 2302.5, 2313 and 2324 cm -1 were polarized along different crystallograpkic axes, which allowed to assign them to specific hydrogen positions in the crystal and in the NH 3 groups. Comparison of neutron diffraction and vibrational frequency data shows that, despite the differences in N?H?O hydrogen angles, of all the geometric parameters the N⋯O distance only seems to correlate with the isolated N-D stretching frequencies.

Keresztury, Gábor

1986-03-01

141

Quantum dynamics study of H +NH3?H2+NH2 reaction  

NASA Astrophysics Data System (ADS)

We report in this paper a quantum dynamics study for the reaction H +NH3?NH2+H2 on the potential energy surface of Corchado and Espinosa-Garcia [J. Chem. Phys. 106, 4013 (1997)]. The quantum dynamics calculation employs the semirigid vibrating rotor target model [J. Z. H. Zhang, J. Chem. Phys. 111, 3929 (1999)] and time-dependent wave packet method to propagate the wave function. Initial state-specific reaction probabilities are obtained, and an energy correction scheme is employed to account for zero point energy changes for the neglected degrees of freedom in the dynamics treatment. Tunneling effect is observed in the energy dependency of reaction probability, similar to those found in H +CH4 reaction. The influence of rovibrational excitation on reaction probability and stereodynamical effect are investigated. Reaction rate constants from the initial ground state are calculated and are compared to those from the transition state theory and experimental measurement.

Zhang, Xu Qiang; Cui, Qian; Zhang, John Z. H.; Han, Ke Li

2007-06-01

142

An accurate global potential energy surface, dipole moment surface, and rovibrational frequencies for NH3  

NASA Astrophysics Data System (ADS)

A global potential energy surface (PES) that includes short and long range terms has been determined for the NH3 molecule. The singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations and the internally contracted averaged coupled-pair functional electronic structure methods have been used in conjunction with very large correlation-consistent basis sets, including diffuse functions. Extrapolation to the one-particle basis set limit was performed and core correlation and scalar relativistic contributions were included directly, while the diagonal Born-Oppenheimer correction was added. Our best purely ab initio PES, denoted "mixed," is constructed from two PESs which differ in whether the ic-ACPF higher-order correlation correction was added or not. Rovibrational transition energies computed from the mixed PES agree well with experiment and the best previous theoretical studies, but most importantly the quality does not deteriorate even up to 10300cm-1 above the zero-point energy (ZPE). The mixed PES was improved further by empirical refinement using the most reliable J =0-2 rovibrational transitions in the HITRAN 2004 database. Agreement between high-resolution experiment and rovibrational transition energies computed from our refined PES for J =0-6 is excellent. Indeed, the root mean square (rms) error for 13 HITRAN 2004 bands for J =0-2 is 0.023cm-1 and that for each band is always ?0.06cm-1. For J =3-5 the rms error is always ?0.15cm-1. This agreement means that transition energies computed with our refined PES should be useful in the assignment of new high-resolution NH3 spectra and in correcting mistakes in previous assignments. Ideas for further improvements to our refined PES and for extension to other isotopolog are discussed.

Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.

2008-12-01

143

An accurate global potential energy surface, dipole moment surface, and rovibrational frequencies for NH(3).  

PubMed

A global potential energy surface (PES) that includes short and long range terms has been determined for the NH(3) molecule. The singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations and the internally contracted averaged coupled-pair functional electronic structure methods have been used in conjunction with very large correlation-consistent basis sets, including diffuse functions. Extrapolation to the one-particle basis set limit was performed and core correlation and scalar relativistic contributions were included directly, while the diagonal Born-Oppenheimer correction was added. Our best purely ab initio PES, denoted "mixed," is constructed from two PESs which differ in whether the ic-ACPF higher-order correlation correction was added or not. Rovibrational transition energies computed from the mixed PES agree well with experiment and the best previous theoretical studies, but most importantly the quality does not deteriorate even up to 10 300 cm(-1) above the zero-point energy (ZPE). The mixed PES was improved further by empirical refinement using the most reliable J=0-2 rovibrational transitions in the HITRAN 2004 database. Agreement between high-resolution experiment and rovibrational transition energies computed from our refined PES for J=0-6 is excellent. Indeed, the root mean square (rms) error for 13 HITRAN 2004 bands for J=0-2 is 0.023 cm(-1) and that for each band is always NH(3) spectra and in correcting mistakes in previous assignments. Ideas for further improvements to our refined PES and for extension to other isotopolog are discussed. PMID:19063558

Huang, Xinchuan; Schwenke, David W; Lee, Timothy J

2008-12-01

144

Why is N···Be distance of NH3H(+)···DBeH shorter than that of NH3D(+)···HBeH? Paradoxical geometrical isotope effects for partially isotope-substituted dihydrogen-bonded isotopomers.  

PubMed

The partial isotope substitution for the change of geometrical parameters, interaction energies, and nuclear magnetic shielding tensors (?) of dihydrogen-bonded NH3X(+)···YBeH (X, Y?=?H, D, and T) systems is analyzed. Based on the theoretical calculation, the distance between heavy atoms RN···Be of NH3H(+) ···DBeH is clearly found to be shorter than that in NH3D(+)···HBeH. Such apparently paradoxical geometrical isotope effect (GIE) on RN···Be is revealed by the cooperative effect of two kinds of (1) primary covalent-bonded GIE and (2) secondary dihydrogen-bonded one. We have demonstrated that (1) the covalent bond lengths become shorter by heavier isotope-substitution and (2) the dihydrogen-bonded distance RX···Y becomes shorter by heavier Y and lighter X isotope-substitution due to the difference of electronic structure reflected by the nuclear distribution. We have also found that interaction energy of NH3H(+)···DBeH is stronger than that of NH3D(+)···HBeH and isotopic deshielding effect of magnetic shielding becomes large in lighter isotope. PMID:24323845

Udagawa, Taro; Tachikawa, Masanori

2014-02-01

145

The tropospheric abundances of NH3 and PH3 in Jupiter's Great Red Spot, from Voyager IRIS observations.  

PubMed

To investigate the chemistry and dynamics of Jupiter's Great Red Spot (GRS), the tropospheric abundances of NH3 and PH3 in the GRS are determined and compared to those of the surrounding region, the South Tropical Zone (STZ). These gases well up from deep in the atmosphere, and, in the upper troposphere, are depleted by condensation (in the case of NH3), chemical reactions, and UV photolysis. At Jupiter's tropopause, the chemical lifetimes of NH3 and PH3 are comparable to the time constant for vertical transport over the atmospheric scale height. The distributions of these gases are therefore diagnostic of the rate of vertical transport in the upper troposphere and lower stratosphere. Three groups of Voyager IRIS spectra are analyzed, two of the STZ and one of the GRS. The two groups of STZ spectra are defined on the basis of their radiances at 602 and 226 cm-1, which reflect, respectively, the temperature near 150 mbar and the cloud opacity in the 300-600 mbar region. One selection of STZ spectra is chosen to have the same radiance as does the GRS at 226 cm-1. The other STZ selection has a significantly greater radiance, indicative of reduced cloudiness. Variations in the abundances of NH3 and PH3 are determined within the STZ, as a background for our studies of the GRS. Within the uncertainty of our measurements (-55% and +75%), the PH3 mixing ratio at 600 mbar is 3 x 10(-7), the same for all three selections. The NH3 mixing ratio profile in the pressure region between 300 and 600 mbar is the same within error (-25% and +50% at 300 mbar) for both STZ selections. In the GRS, however, NH3 is significantly depleted at 300 mbar, with an abundance of 25% that derived for the STZ selections. Since the GRS is believed to be a region of strong vertical transport, our finding of a depletion of NH3 below the tropopause within the GRS is particularly unexpected. One of the STZ selections has a temperature-pressure profile similar to that of the GRS below the 300-mbar level; therefore, condensation at this level does not easily explain the low NH3 abundance in the GRS. All samples are taken at essentially the same latitude; photolysis and/or charged particle precipitation is probably not directly responsible either. The observed NH3 depletion may have a dynamical origin or result from some unidentified chemical processes at work in the GRS. PMID:11540935

Griffith, C A; Bezard, B; Owen, T; Gautier, D

1992-01-01

146

Validation of flux measurements with artificial sources: simulating CH4 from cows and NH3 emissions from medium plot scales  

NASA Astrophysics Data System (ADS)

Mitigation of ammonia (NH3) emissions with detrimental environmental effects as well as of greenhouse gas emissions (GHG: CO2, N2O, CH4) are key challenges faced by the agricultural production sector. While NH3 originates mainly from polluted surfaces, e.g. after slurry application, the main source for CH4 emissions are cows and other ruminating animals, representing point sources. There are two widespread state-of-the-art techniques to determine agricultural emissions: eddy covariance (EC) flux measurements and Lagrangian stochastic (LS) dispersion modelling, namely the WindTrax (WT) model. Whereas GHG emissions can be measured with both techniques, NH3 emissions are usually not feasible with EC measurements due to the stickiness of NH3 molecules on surfaces. In addition, point sources render difficulties for the interpretation of EC flux data. We tested the EC technique and the WT model using artificial sources with known gas release rates. i) The effect of a point source on EC fluxes was investigated by placing an artificial CH4 source with known release rate upwind of the EC tower at two different heights and during different wind conditions. ii) The WT model was checked with a NH3 release grid of 314 m2 of known source strength. Ambient NH3 concentrations were measured by open path DOAS systems and impinger sampling. The CH4 concentration timeseries influenced by the point source showed a similar pattern as in the presence of cows upwind of the EC system. CH4 release rates from the point source were reproduced by the EC flux measurement with stationary background conditions only. The experiments with the NH3 release showed that WT performs well for emission determination, even in complex terrain (asphalt surrounded by grassland) with associated micrometeorology, given a realistic description of the vertical profile of wind velocity. Calculated gas recoveries ranged between 73 to 105%. Such a result is encouraging considering the immanent uncertainties from a NH3 experiment (variable background concentration, relatively small downwind concentrations, NH3 interception on ground/tubing).

Sintermann, Jörg; Felber, Raphael; Häni, Christoph; Ammann, Christof; Neftel, Albrecht

2014-05-01

147

Superconductivity and phase instability of NH3-free Na-intercalated FeSe1-zSz  

NASA Astrophysics Data System (ADS)

The discovery of ThCr2Si2-type AxFe2-ySe2 (A=K, Rb, Cs and Tl) with Tc ~30?K make much progress in iron-based superconducting field, but their multiple-phase separations are disadvantageous for understanding the origin. On the other hand, for small alkali metals, studies on (Li,Na)FeCu(S,Se)2 and NaFe2-?S2 show that these compounds possess CaAl2Si2-type structure, implying that ThCr2Si2-type structure is unstable for small alkali metal-intercalated FeSe under high temperature. Here we report a new intercalate Na0.65(1)Fe1.93(1)Se2 with Tc ~37?K, synthesized by low-temperature ammonothermal method. The notable finding is that the Na0.65(1)Fe1.93(1)Se2 shows a ThCr2Si2-type structure, which is the first instance of small-sized alkali metal intercalates without NH3 co-intercalation. Besides, the NH3-poor Na0.80(4)(NH3)0.60Fe1.86(1)Se2 and NH3-rich phase with Tcs at 45 and 42?K are identified by tuning the concentration of Na-NH3 solutions. The modulation of interlayer spacing reveals the versatile evolution of structural stability and superconductivity in these intercalates.

Guo, Jiangang; Lei, Hechang; Hayashi, Fumitaka; Hosono, Hideo

2014-08-01

148

High Resolution Infrared and Microwave Spectra of NH3-HCCH and NH3-OCS Complexes: Studies of Weak C-H\\cdotsN Hydrogen Bond and Electric Multipole Interactions  

NASA Astrophysics Data System (ADS)

C-H\\cdotsN weak hydrogen bond is of much current interest. We report the first high resolution infrared spectroscopic study of a prototypical C-H\\cdotsN bonded system, i.e. NH3-HCCH, at the vicinity of the ?4 band of NH3. The spectrum has been recorded using an infrared spectrometer equipped with an astigmatic multipass cell aligned for 366 passes and a room temperature external cavity quantum cascade laser at the 6 ?m region. The perpendicular band spectrum of symmetric top rotor observed is consistent with the previous microwave and infrared studies at 3 ?m. We also extended the previous microwave measurement to higher J and K. For the related NH3-OCS complex, microwave spectrum of J up to 6 and infrared spectrum at the vicinity of the ?4 band of NH3 have been recorded and analyzed for the first time. Comparison has been made with the previously studied isoelectronic complexes such as NH3-N2O and NH3-CO2. The source of the difference will be discussed with the aid of ab initio calculations. G.T. Fraser, K.R. Leopold, and W. Klemperer, J. Chem. Phys. 80(4), 1423, (1984) G. Hilpert, G.T. Fraser, and A.S. Pine, J. Chem. Phys. 105(15), 6183, (1996) G.T. Fraser, D.D. Nelson, JR., G.J. Gerfen, and W. Klemperer, J. Chem. Phys. 83(11), 5442, (1985) G.T. Fraser, K.R. Leopold, and W. Klemperer, J. Chem. Phys. 81(6), 2577, (1984)

Liu, Xunchen; Xu, Yunjie

2011-06-01

149

Validation of model calculation of ammonia deposition in the neighbourhood of a poultry farm using measured NH 3 concentrations and N deposition  

NASA Astrophysics Data System (ADS)

Substantial emission of ammonia (NH 3) from animal houses and the related high local deposition of NH 3-N are a threat to semi-natural nitrogen-deficient ecosystems situated near the NH 3 source. In Denmark, there are regulations limiting the level of NH 3 emission from livestock houses near N-deficient ecosystems that are likely to change due to nitrogen (N) enrichment caused by NH 3 deposition. The models used for assessing NH 3 emission from livestock production, therefore, need to be precise, as the regulation will affect both the nature of the ecosystem and the economy of the farmer. Therefore a study was carried out with the objective of validating the Danish model used to monitor NH 3 transport, dispersion and deposition from and in the neighbourhood of a chicken farm. In the study we measured NH 3 emission with standard flux measuring methods, NH 3 concentrations at increasing distances from the chicken houses using passive diffusion samplers and deposition using 15N-enriched biomonitors and field plot studies. The dispersion and deposition of NH 3 were modelled using the Danish OML-DEP model. It was also shown that model calculations clearly reflect the measured NH 3 concentration and N deposition. Deposition of N measured by biomonitors clearly reflected the variation in NH 3 concentrations and showed that deposition was not significantly different from zero ( P < 0.05) at distances greater than 150-200 m from these chicken houses. Calculations confirmed this, as calculated N deposition 320 m away from the chicken farm was only marginally affected by the NH 3 emission from the farm. There was agreement between calculated and measured deposition showing that the model gives true estimates of the deposition in the neighbourhood of a livestock house emitting NH 3.

Sommer, S. G.; Østergård, H. S.; Løfstrøm, P.; Andersen, H. V.; Jensen, L. S.

150

Thermal desorption spectroscopy from the surfaces of metal-oxide-semiconductor nanostructures  

NASA Astrophysics Data System (ADS)

An experimental setup, which combines direct heating and temperature measurement of metal nanofilms allowing temperature programmed desorption experiments is described. This setup enables the simultaneous monitoring of the thermal desorption flux from the surface of chemi-electric devices and detection of chemically induced hot charge carriers under UHV conditions. This method is demonstrated for the case of water desorption from a Pt/SiO2-n-Si metal-oxide-semiconductor nanostructure.

Meyburg, Jan Philipp; Nedrygailov, Ievgen I.; Hasselbrink, Eckart; Diesing, Detlef

2014-10-01

151

Observation of DCl and upper limit to NH3 on Venus  

NASA Astrophysics Data System (ADS)

To search for DCl in the Venus atmosphere, a spectrum near the D35Cl (1-0) R4 line at 2141.54 cm-1 was observed using the CSHELL spectrograph at NASA IRTF. Least square fitting to the spectrum by a synthetic spectrum results in a DCl mixing ratio of 17.8 ± 6.8 ppb. Comparing to the HCl abundance of 400 ± 30 ppb (Krasnopolsky [2010a] Icarus, 208, 314-322), the DCl/HCl ratio is equal to 280 ± 110 times the terrestrial D/H = 1.56 × 10-4. This ratio is similar to that of HDO/H2O = 240 ± 25 times the terrestrial HDO/H2O from the VEX/SOIR occultations at 70-110 km. Photochemistry in the Venus mesosphere converts H from HCl to that in H2O with a rate of 1.9 × 109 cm-2 s-1 (Krasnopolsky [2012] Icarus, 218, 230-246). The conversion involves photolysis of HCl; therefore, the photochemistry tends to enrich D/H in HCl and deplete in H2O. Formation of the sulfuric acid clouds may affect HDO/H2O as well. The enriched HCl moves down by mixing to the lower atmosphere where thermodynamic equilibriums for H2 and HCl near the surface correspond to D/H = 0.71 and 0.74 times that in H2O, respectively. Time to establish these equilibriums is estimated at ˜3 years and comparable to the mixing time in the lower atmosphere. Therefore, the enriched HCl from the mesosphere gives D back to H2O near the surface. Comparison of chemical and mixing times favors a constant HDO/H2O up to ˜100 km and DCl/HCl equal to D/H in H2O times 0.74. Ammonia is an abundant form of nitrogen in the reducing environments. Thermodynamic equilibriums with N2 and NO near the surface of Venus give its mixing ratio of 10-14 and 6 × 10-7, respectively. A spectrum of Venus near the NH3 line at 4481.11 cm-1 was observed at NASA IRTF and resulted in a two-sigma upper limit of 6 ppb for NH3 above the Venus clouds. This is an improvement of the previous upper limit by a factor of 5. If ammonia exists at the ppb level or less in the lower atmosphere, it quickly dissociates in the mesosphere and weakly affects its photochemistry.

Krasnopolsky, Vladimir

2012-05-01

152

Emission factor of ammonia (NH3) from on-road vehicles in China: tunnel tests in urban Guangzhou  

NASA Astrophysics Data System (ADS)

Ammonia (NH3) is the primary alkaline gas in the atmosphere that contributes to formation of secondary particles. Emission of NH3 from vehicles, particularly gasoline powered light duty vehicles equipped with three-way catalysts, is regarded as an important source apart from emissions from animal wastes and soils, yet measured emission factors for motor vehicles are still not available in China, where traffic-related emission has become an increasingly important source of air pollutants in urban areas. Here we present our tunnel tests for NH3 from motor vehicles under ‘real world conditions’ in an urban roadway tunnel in Guangzhou, a central city in the Pearl River Delta (PRD) region in south China. By attributing all NH3 emissions in the tunnel to light-duty gasoline vehicles, we obtained a fuel-based emission rate of 2.92 ± 0.18 g L-1 and a mileage-based emission factor of 229.5 ± 14.1 mg km-1. These emission factors were much higher than those measured in the United States while measured NO x emission factors (7.17 ± 0.60 g L-1 or 0.56 ± 0.05 g km-1) were contrastingly near or lower than those previously estimated by MOBILE/PART5 or COPERT IV models. Based on the NH3 emission factors from this study, on-road vehicles accounted for 8.1% of NH3 emissions in the PRD region in 2006 instead of 2.5% as estimated in a previous study using emission factors taken from the Emission Inventory Improvement Program (EIIP) in the United States.

Liu, Tengyu; Wang, Xinming; Wang, Boguang; Ding, Xiang; Deng, Wei; Lü, Sujun; Zhang, Yanli

2014-05-01

153

Effect of residual H2O on epitaxial AlN film growth on 4H-SiC by alternating doses of TMA and NH3  

NASA Astrophysics Data System (ADS)

An epitaxial AlN film was synthesized on 4H-SiC using alternate doses of trimethyl aluminum (TMA) and anhydrous ammonia (a-NH3) at 540 °C. The growth per cycle (GPC) at the temperature was limited to 0.27 Å/cycle under the minute amount of residual H2O. The formation of an inert Al-O-Al bond generated by the recombinative desorption of two Al-OH species to produce H2O has been proposed as a possible reason for the low deposition rate. By eliminating any present moisture in the reactor system, the GPC increased to 1.5 Å/cycle. The suppression of the OH group generation at 540 °C made it possible to deposit nearly stoichiometric AlN film which has the crystallinity with the preferred orientation along the (0 0 0 1) direction on 4H-SiC templates. The measured RMS surface roughness was comparable to that achieved by molecular beam epitaxy (MBE).

Perng, Ya-Chuan; Kim, Taeseung; Chang, Jane P.

2014-09-01

154

Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants  

PubMed Central

Background In plants, nitrate (NO3-) nutrition gives rise to a natural N isotopic signature (?15N), which correlates with the ?15N of the N source. However, little is known about the relationship between the ?15N of the N source and the 14N/15N fractionation in plants under ammonium (NH4+) nutrition. When NH4+ is the major N source, the two forms, NH4+ and NH3, are present in the nutrient solution. There is a 1.025 thermodynamic isotope effect between NH3 (g) and NH4+ (aq) which drives to a different ?15N. Nine plant species with different NH4+-sensitivities were cultured hydroponically with NO3- or NH4+ as the sole N sources, and plant growth and ?15N were determined. Short-term NH4+/NH3 uptake experiments at pH 6.0 and 9.0 (which favours NH3 form) were carried out in order to support and substantiate our hypothesis. N source fractionation throughout the whole plant was interpreted on the basis of the relative transport of NH4+ and NH3. Results Several NO3--fed plants were consistently enriched in 15N, whereas plants under NH4+ nutrition were depleted of 15N. It was shown that more sensitive plants to NH4+ toxicity were the most depleted in 15N. In parallel, N-deficient pea and spinach plants fed with 15NH4+ showed an increased level of NH3 uptake at alkaline pH that was related to the 15N depletion of the plant. Tolerant to NH4+ pea plants or sensitive spinach plants showed similar trend on 15N depletion while slight differences in the time kinetics were observed during the initial stages. The use of RbNO3 as control discarded that the differences observed arise from pH detrimental effects. Conclusions This article proposes that the negative values of ?15N in NH4+-fed plants are originated from NH3 uptake by plants. Moreover, this depletion of the heavier N isotope is proportional to the NH4+/NH3 toxicity in plants species. Therefore, we hypothesise that the low affinity transport system for NH4+ may have two components: one that transports N in the molecular form and is associated with fractionation and another that transports N in the ionic form and is not associated with fractionation. PMID:21575190

2011-01-01

155

Open-path Atmospheric N2O, CO, and NH3 Measurements Using Quantum Cascade Laser Spectroscopy  

NASA Astrophysics Data System (ADS)

We develop a compact, mid-infrared quantum cascade (QC) laser based sensor to perform high precision measurements of N2O and CO simultaneously. Since CO is a good tracer of anthropogenic emissions, simultaneous measurements of CO and N2O allow us to correlate the sources of N2O emissions. The thermoelectrically (TE) cooled, and continuous wave QC laser enables room-temperature and unattended operation. The laser is scanned over the absorption features of N2O and CO near 4.54 ?m by laser current modulation. A novel cylindrical multi-pass optical cell terminated at the (N/2)th spot is used to simplify the optical configuration by separating the laser and TE cooled detector. Our systems are open-path and non-cryogenic, which avoids vacuum pump and liquid nitrogen. This configuration enables a future design of a non-intrusive, compact (shoe box size), and low-power (10W) sensor. Wavelength modulation spectroscopy (WMS) is used to enhance measurement sensitivity. Higher-harmonic detection (4f and 6f) is performed to improve the resolution between the nearly overlapping N2O and CO lines. Relevant atmospheric N2O and CO concentration is measured, with a detection limit of 0.3 ppbv for N2O and 2 ppbv for CO for 1 s averaging in terms of noise. We also develop an open-path high sensitivity atmospheric ammonia (NH3) sensor using a very similar instrument design. A 9.06 ?m QC laser is used to probe absorption features of NH3. Open-path detection of NH3 is even more beneficial due to the surface absorption effect of NH3 and its tendency to readily partition into condensed phases. The NH3 sensor was deployed at the CALNEX 2010 field campaign. The entire system was stable throughout the campaign and acquired data with 10 s time resolution under adverse ambient temperatures and dusty conditions. The measurements were in general agreement with other NH3 and trace gases sensors. Both the N2O/CO and NH3 sensors will be deployed in a local eddy-covariance station to examine long term stability and detection limit in the field. Future sensor applications include characterizing urban and agricultural N2O and NH3 emission sources and quantifying their respective fluxes.

Sun, K.; Khan, A.; Miller, D. J.; Rafferty, K.; Schreiber, J.; Puzio, C.; Portenti, M.; Silver, J.; Zondlo, M. A.

2010-12-01

156

Formation of uranium and cerium nitrides by the reaction of carbides with NH 3 and N 2/H 2 stream  

NASA Astrophysics Data System (ADS)

UC or CeC 2 were converted into U 2N 3 or CeN by the use of NH 3 or an N 2/H 2 gas mixture. A stream of NH 3 works not only as a nitriding agent but also as a carbon clearing agent due to its high nitriding and hydriding activities. When the carbide is converted into nitride, carbon is liberated. Some experiments were performed in order to examine the role of the carbon activity of carbon materials (amorphous carbon or graphite) in the formation of CH 4.

Nakagawa, Takashi; Matsuoka, Hirotaka; Sawa, Masaji; Hirota, Masayuki; Miyake, Masanobu; Katsura, Masahiro

1997-08-01

157

Metal complexes of the carbonic anhydrase inhibitor methazolamide (Hmacm). Crystal structure of the Zn(macm)2(NH3)2. Anticonvulsant properties of the Cu(macm)2(NH3)3(H2O).  

PubMed

Complexes of Co(II), Cu(II), and Zn(II) with deprotonated methazolamide and ammonia are synthesized and characterized. The complex Zn(macm)2(NH3)2 crystallizes in the monoclinic C2/c space group with a = 13.468(1), b = 6.759(1), c = 23.014(2) A, beta = 90.27(1), and Z = 4. The structure was refined to R = 0.049 (Rw = 0.053). The Zn(II) ion is coordinated to two deprotonated sulfonamido nitrogen atoms of the macm- ligand and two nitrogen atoms of the ammonia ligands in a distorted tetrahedron. The Zn(macm)2(NH3)2 complex is shown to be a simple model for the methazolamide inhibition of CA. EHMO calculations applied to fractional coordinates of the Zn(macm)2(NH3)2 complex indicate that the atomic orbitals of the Zn do not contribute to HOMO and LUMO of the complex. The characteristics of the Cu(macm)2(NH3)3(H2O) as an anticonvulsant agent are tested. PMID:7876839

Alzuet, G; Casanova, J; Ramirez, J A; Borrás, J; Carugo, O

1995-02-15

158

Catalytic NO reduction with NH 3 over carbons modified by acid oxidation and by metal impregnation and its kinetic studies  

Microsoft Academic Search

The catalytic effects of carbon in NO reduction with NH3 at low temperatures (<200°C) were examined using mineral matter free carbon derived from phenol–formaldehyde resin. The carbon was found to have little catalytic activity in the reaction, in contrary to other previous studies. The activity was considerably enhanced by oxidation with nitric acid and exceedingly enhanced upon impregnation with Cu

Li-Yeh Hsu; Hsisheng Teng

2001-01-01

159

Design of a pulsed valve for high-pressure NH3 injection into supersonic beam\\/mass spectrometry  

Microsoft Academic Search

A novel design of a pulsed valve for high-pressure injection of NH3 for supersonic jet expansions is presented. This valve can operate up to 200-atm reservoir pressure at 180 °C with a pulse width down to 100 ?s. This valve has been designed so that the solenoid core is not in contact with the carrier fluid so that it can

Ho Ming Pang; David M. Lubman

1988-01-01

160

Improvement in electrical characteristics of HfO2 gate dielectrics treated by remote NH3 plasma  

NASA Astrophysics Data System (ADS)

We report the structural and electrical characteristics of hafnium oxide (HfO2) gate dielectrics treated by remote NH3 plasma under various radio-frequency (RF) powers at a low temperature. Significant increase of effective dielectric constant (keff), decrease of capacitance equivalent thickness (CET), reduction in leakage current density, and suppression of the interfacial layer thickness were observed with the increase of the RF power in the remote NH3 plasma treatment. The effects of hydrogen passivation and depassivation on the HfO2/Si interface due to the remote NH3 plasma treatment were also observed by the variation of photoluminescence (PL) intensity, indicating that the PL measurement is applicable to probe the interfacial properties. An ultrathin interfacial layer (˜0.3 nm), a high keff, (20.9), a low leakage current density (9 × 10-6 A/cm2), and a low CET (1.9 nm) in the nitrided HfO2 film were achieved, demonstrating that the nitridation process using remote NH3 plasma under a high RF power at a low temperature is a promising way to improve in electrical properties of high-K gate dielectrics.

Huang, Li-Tien; Chang, Ming-Lun; Huang, Jhih-Jie; Lin, Hsin-Chih; Kuo, Chin-Lung; Lee, Min-Hung; Liu, Chee Wee; Chen, Miin-Jang

2013-02-01

161

Operational Characteristics of Effective Removal of H2S and NH3 Waste Gases by Activated Carbon Biofilter  

Microsoft Academic Search

Simultaneous removal of hydrogen sulfide (H2S) and am- gases. monia (NH3) gases from gaseous streams was studied in a biofilter packed with granule activated carbon. Extensive studies, including the effects of carbon (C) source on the growth of inoculated microorganisms and gas removal efficiency, product analysis, bioaerosol emission, pressure drop, and cost evaluation, were conducted. The results indicated that molasses

Ying-Chien Chung; Yu-Yen Lin; Ching-Ping Tseng

2004-01-01

162

NH3 formation and utilization in regenerationof Pt/Ba/Al2O3 NOx storage-reduction catalyst with H2  

SciTech Connect

The nature of H2 regeneration of a model Pt/Ba/Al2O3 LNT catalyst was investigated with specific focus on intra-catalyst formation and utilization of NH3 and its role in catalyst regeneration. In-situ measurements of the transient intra-catalyst species (H2, NH3, N2, NOx) distributions at different temperatures were used to detail the reaction evolution along the catalyst axis. Comparison of the species transients identifies unique individual natures for the reductant (H2), inert product (N2) and intermediate-reductant product (NH3) which readily explain the conventional effluent species sequence as an integral effect. The data demonstrates that NH3 is created on similar timescales as the N2 product inside the catalyst, but consumed as aggressively as H2 reductant along the catalyst. This spatiotemporal NH3 behavior experimentally confirms that Intermediate-NH3 regeneration pathway is active. Analysis at 200 and 325 C indicates equivalent local NOx storage, H2 consumption and regeneration effectiveness, but differing NH3/N2 ratio, suggesting a temperature-dependence of partitioning between Direct-H2 and Intermediate-NH3 regeneration pathways. Further experimental and numerical work is needed to more clearly understand the partitioning between the possible regeneration pathways. Nevertheless, the experimental data show that intermediate NH3 plays a significant role in LNT catalyst regeneration.

Partridge Jr, William P [ORNL; Choi, Jae-Soon [ORNL

2009-01-01

163

Phase transitions in the ferroelectric crystals [CH3NH3]5Bi2Cl11 and [CH3NH3]5Bi2Br11 studied by the nonlinear dielectric effect  

NASA Astrophysics Data System (ADS)

The real part of the complex electric permittivity at low frequencies and at several biasing fields (between 0 and 5×105V/m ) has been measured in ferroelectric crystals [CH3NH3]5Bi2Cl11 (MAPCB) and [CH3NH3]5Bi2Br11 (MAPBB) in the temperature range covering the temperature of the ferroelectric phase transitions. Comparative measurements for the known triglycine sulphate (NH2CH2COOH)3H2SO4 crystal have been used as a test of the validity and of possible errors in the determination of the ferroelectric equation of state by the method applied. The estimates of the critical parameters TC , ? , and ? then have been evaluated for MAPCB and MAPBB on the basis of the Widom-Griffiths scaling hypothesis. Complementary pyroelectric measurements of the spontaneous polarization providing the critical exponent ? are in accordance with the parameters obtained.

Szklarz, P.; Ga??zka, M.; Zieli?ski, P.; Bator, G.

2006-11-01

164

[NH3, N2O, CH4 and CO2 emissions from growing process of caged broilers].  

PubMed

To obtain Ammonia and greenhouse gas (GHG) emission factors of caged broilers, ammonia (NH3), methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions of broilers aged 0 d to 42 days were monitored in caged broilers production systems located in Shandong province. Gas concentrations of incoming and exhaust air streams were measured by using INNOVA 1312 multi-gas monitor with multi-channel samplers. Building ventilation rates were determined by on site FANS (Fan Assessment Numeration System) measurement systems. The NH3 emission factors showed a trend of increase at the beginning and then decreased with the broiler ages. The NH3 emission rates were 8.5 to 342.1 mg x (d x bird)(-1) and the average daily emission rate was 137.9 mg x (d x bird)(-1) [48.6 g x (d x AU)(-1)] over the 42-d period. The GHGs emission rates were 19.5-351.9 mg x (d x bird)(-1) with an average of 154.5 mg x (d x bird)(-1) [54.4 g x (d x AU)(-1)] for CH4, and 2.2- 152.9 g x (d x bird)(-10 with an average of 65.9 g x (d x bird)(-1) [23.2 kg x (d x AU)(-1)] for CO2. No emission of N2O was observed. The CH4 and CO2 emission rates increased with the increase of broilers ages. The total NH3 emission over the 42 d growing period averaged (5.65 +/- 1.02) g x (bird x life cycle)(-1). The NH3 emission contribution in different growth phase to the total emission were 33.6% in growth phase 1 (0-17 day, GP1), 36.4% in GP2 (18-27 days), and 29.9% in GP3 (28-42 days), respectively. The NH3 emission in GP2 was significantly higher than emission in GP1 and GP3. CH4 and CO2 cumulative emission rates were (6.30 +/- 0.16) g x (bird(-1) x life cycle)(-1) and (2.68 +/- 0.18) kg x (bird x life cycle)(-1), respectively. The cumulative emission rates of CH4 and CO2 in GP3 were significantly higher than emission rates in GP2 and in GP1, accounting for 50% of total emissions. The results of this study could provide the data support for mitigation of gas emission from broilers production. PMID:23947019

Zhou, Zhong-Kai; Zhu, Zhi-Ping; Dong, Hong-Min; Chen, Yong-Xing; Shang, Bin

2013-06-01

165

State selected ion-molecule reactions by a coincidence technique. XV. Hydrogen atom abstraction as an electron jump followed by proton transfer in the ND + 3 (v)+NH3 and NH + 3 (v)+ND3 reactions  

NASA Astrophysics Data System (ADS)

The effects of the vibrational excitation of the ?2 mode of ND+3 (v) and NH+3 (v) on the three channels of their reaction with NH3 and ND3, respectively, are investigated up to v=12 in the center-of-mass kinetic energy range from 0.9 to 4.5 eV by use of the TESICO technique. The ratio (?) of the hydrogen/deuterium atom abstraction cross section over the competing deuteron/proton transfer cross section has a maximum systematically at a vibrational level (vmax ) slightly higher than that giving maximum Franck-Condon factor (vFC ) for the neutralization of ND+3 (v)/NH+3 (v). A new reaction model based on a nonadiabatic transition theory and the potential energy surface calculated for the ammonia dimer cation is proposed to explain the experimental results. The hydrogen/deuterium atom abstraction reaction is interpreted as a near resonant electron jump at larger intermolecular separation followed by proton/deuteron transfer which proceeds on the ``electron (charge)-transferred'' potential surface.

Tomoda, Shinji; Suzuki, Shinzo; Koyano, Inosuke

1988-12-01

166

Thermal decomposition pathway and desorption study of isopropanol and tert-butanol on Si(100)  

NASA Astrophysics Data System (ADS)

Thermal decomposition pathway and desorption of isopropanol (IPA) and tert-butanol on Si(100) were studied using temperature programed desorption. Adsorbed alcohols studied were decomposed into atomic hydrogen and alkoxy on the surface. During heating the sample up to 1000 K, acetone, propylene, and hydrogen were desorbed as decomposition products of IPA on Si(100). Desorption pathways of IPA on Si(100) were largely consistent with those on metal surfaces: beta-hydride elimination reaction to acetone and C-O scission to propylene. For tert-butanol, which has no beta-hydrogen, isobutene and hydrogen were observed as main desorption products. copyright 2002 American Vacuum Society.

Kim, Jaehyun; Kim, Kwansoo; Yong, Kijung

2002-09-01

167

Deposition of silicon nitride from SiCl4 and NH3 in a low pressure RF plasma  

NASA Technical Reports Server (NTRS)

Silicon nitride coatings were deposited in a low-pressure (1-10 Torr) RF plasma from SiCl4 and NH3 in the presence of argon onto stainless martensitic steel grounded and floating substrates at 300 C and 440 C respectively. The heating of the substrates depends mainly on the position and the induced RF power. The coatings were identified as silicon nitride by X-ray investigation and were found to contain chlorine by energy-dispersive analysis of X-rays. The growth rate, the microhardness and the chlorine concentration of the coatings were determined as a function of the total gas pressure, the RF power input and the NH3-to-SiCl4 ratio. It was observed that the coatings on the floating substrates have higher deposition rates and are of superior quality.

Ron, Y.; Raveh, A.; Carmi, U.; Inspektor, A.; Avni, R.

1983-01-01

168

Hall mobility in tin iodide perovskite CH3NH3SnI3: Evidence for a doped semiconductor  

NASA Astrophysics Data System (ADS)

CH3NH3SnI3 is a metal halide perovskite that shows metallic conductivity over a wide temperature range, although ab initio calculations and optical absorption indicate that its band structure is consistent with that of an intrinsic semiconductor. Hall effect measurements of as-grown crystals give a hole concentration of about 9×1017 cm-3 with rather high Hall mobility of about 200 cm2 V-1 s-1 at 250 K. Artificial hole doping enhances the electrical conductivity of the crystals without influencing mobility. These observations indicate that the electronic structure in stoichiometric CH3NH3SnI3 can be described as that of an intrinsic semiconductor with a wide valence band. This situation leads to metal-like conduction with even a trace amount of spontaneous hole doping in the as-grown crystal.

Takahashi, Yukari; Hasegawa, Hiroyuki; Takahashi, Yukihiro; Inabe, Tamotsu

2013-09-01

169

Photocarrier recombination dynamics in perovskite CH3NH3PbI3 for solar cell applications.  

PubMed

Using time-resolved photoluminescence and transient absorption measurements at room temperature, we report excitation-intensity-dependent photocarrier recombination processes in thin films made from the organo-metal halide perovskite semiconductor CH3NH3PbI3 for solar-cell applications. The photocarrier dynamics are well described by a simple rate equation including single-carrier trapping and electron-hole radiative recombination. This result provides clear evidence that the free-carrier model is better than the exciton model for interpreting the optical properties of CH3NH3PbI3. The observed large two-carrier recombination rate suggests the promising potential of perovskite semiconductors for optoelectronic device applications. Our findings provide the information about the dynamical behaviors of photoexcited carriers that is needed for developing high-efficiency perovskite solar cells. PMID:25075458

Yamada, Yasuhiro; Nakamura, Toru; Endo, Masaru; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

2014-08-20

170

Effect of tube radius on the exohedral chemical functionalization of boron-nitride zigzag nanotubes with NH3  

NASA Astrophysics Data System (ADS)

The interaction between zigzag BNNTs with chirality index n=3-10 and ammonia has been studied at the level of B3LYP/6-31G*. Ammonia can be chemically adsorbed on (3,0) to (7,0) BNNTs and physically adsorbed on other studied BNNTs. From NBO analysis charge transfer occur from NH3 to BNNTs and change in the natural electron configuration of B atom of BNNTs at adsorption site for the (3,0) and (4,0) BNNTs cases is larger than others. The DOS result show that after functionalization of BNNTs with NH3 molecules electronic properties of tubes are largely preserved and can be viewed as some kind of harmless modification. Electronic analysis revealed that the interaction of zigzag BNNTs with ammonia is more electrostatic (ionic) in nature, rather than the sole covalent and electrostatic nature increased with increasing of tube diameter.

Zahedi, Ehsan

2012-09-01

171

Water desorption from nanostructured graphite surfaces.  

PubMed

Water interaction with nanostructured graphite surfaces is strongly dependent on the surface morphology. In this work, temperature programmed desorption (TPD) in combination with quadrupole mass spectrometry (QMS) has been used to study water ice desorption from a nanostructured graphite surface. This model surface was fabricated by hole-mask colloidal lithography (HCL) along with oxygen plasma etching and consists of a rough carbon surface covered by well defined structures of highly oriented pyrolytic graphite (HOPG). The results are compared with those from pristine HOPG and a rough (oxygen plasma etched) carbon surface without graphite nanostructures. The samples were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The TPD experiments were conducted for H2O coverages obtained after exposures between 0.2 and 55 langmuir (L) and reveal a complex desorption behaviour. The spectra from the nanostructured surface show additional, coverage dependent desorption peaks. They are assigned to water bound in two-dimensional (2D) and three-dimensional (3D) hydrogen-bonded networks, defect-bound water, and to water intercalated into the graphite structures. The intercalation is more pronounced for the nanostructured graphite surface in comparison to HOPG surfaces because of a higher concentration of intersheet openings. From the TPD spectra, the desorption energies for water bound in 2D and 3D (multilayer) networks were determined to be 0.32 ± 0.06 and 0.41 ± 0.03 eV per molecule, respectively. An upper limit for the desorption energy for defect-bound water was estimated to be 1 eV per molecule. PMID:24018989

Clemens, Anna; Hellberg, Lars; Grönbeck, Henrik; Chakarov, Dinko

2013-12-21

172

The role of NH3 and hydrocarbon mixtures in GaN pseudo-halide CVD: a quantum chemical study.  

PubMed

The prospects of a control for a novel gallium nitride pseudo-halide vapor phase epitaxy (PHVPE) with HCN were thoroughly analyzed for hydrocarbons-NH3-Ga gas phase on the basis of quantum chemical investigation with DFT (B3LYP, B3LYP with D3 empirical correction on dispersion interaction) and ab-initio (CASSCF, coupled clusters, and multireference configuration interaction including MRCI+Q) methods. The computational screening of reactions for different hydrocarbons (CH4, C2H6, C3H8, C2H4, and C2H2) as readily available carbon precursors for HCN formation, potential chemical transport agents, and for controlled carbon doping of deposited GaN was carried out with the B3LYP method in conjunction with basis sets up to aug-cc-pVTZ. The gas phase intermediates for the reactions in the Ga-hydrocarbon systems were predicted at different theory levels. The located ?-complexes Ga…C2H2 and Ga…C2H4 were studied to determine a probable catalytic activity in reactions with NH3. A limited influence of the carbon-containing atmosphere was exhibited for the carbon doping of GaN crystal in the conventional GaN chemical vapor deposition (CVD) process with hydrocarbons injected in the gas phase. Our results provide a basis for experimental studies of GaN crystal growth with C2H4 and C2H2 as auxiliary carbon reagents for the Ga-NH3 and Ga-C-NH3 CVD systems and prerequisites for reactor design to enhance and control the PHVPE process through the HCN synthesis. PMID:25316343

Gadzhiev, Oleg B; Sennikov, Peter G; Petrov, Alexander I; Kachel, Krzysztof; Golka, Sebastian; Gogova, Daniela; Siche, Dietmar

2014-11-01

173

Enhanced electroluminescence of silicon-rich silicon nitride light-emitting devices by NH 3 plasma and annealing treatment  

Microsoft Academic Search

Silicon-rich silicon nitride (SRSN) films were deposited on p-type silicon substrates using a conventional plasma-enhanced chemical vapor deposition (PECVD) system. Before deposition, silicon substrate was pre-treated by NH3 plasma in the PECVD system. And devices with metal–insulator–semiconductor (MIS) structure were fabricated using indium tin oxides (ITO) as anode and aluminum (Al) film as cathode. It was found that after 1100°C

Dongsheng Li; Jianhao Huang; Deren Yang

2009-01-01

174

Evaluating 4 years of atmospheric ammonia (NH3) over Europe using IASI satellite observations and LOTOS-EUROS model results  

NASA Astrophysics Data System (ADS)

Monitoring ammonia (NH3) concentrations on a global to regional scale is a challenge. Due to the limited availability of reliable ground-based measurements, the determination of NH3 distributions generally relies on model calculations. Novel remotely sensed NH3burdens provide valuable insights to complement traditional assessments for clear-sky conditions. This paper presents a first quantitative comparison between Atmospheric Sounding Interferometer (IASI) satellite observations and LOTOS-EUROS model results over Europe and Western Russia. A methodology to account for the variable retrieval sensitivity of the measurements is described. Four years of data (2008-2011) highlight three main agricultural hot spot areas in Europe: the Po Valley, the continental part of Northwestern Europe, and the Ebro Valley. The spatial comparison reveals a good overall agreement of the NH3 distributions not only in these source regions but also over remote areas and over sea when transport is observed. On average, the measured columns exceed the modeled ones, except for a few cases. Large discrepancies over several industrial areas in Eastern Europe and Russia point to underestimated emissions in the underlying inventories. The temporal analysis over the three hot spot areas reveals that the seasonality is well captured by the model when the lower sensitivity of the satellite measurements in the colder months is taken into account. Comparison of the daily time series indicates possible misrepresentations of the timing and magnitude of the emissions. Finally, specific attention to biomass burning events shows that modeled plumes are less spread out than the observed ones. This is confirmed for the 2010 Russian fires with a comparison using in situ observations.

Van Damme, M.; Wichink Kruit, R. J.; Schaap, M.; Clarisse, L.; Clerbaux, C.; Coheur, P.-F.; Dammers, E.; Dolman, A. J.; Erisman, J. W.

2014-08-01

175

CH3NH3PbI3 perovskite/fullerene planar-heterojunction hybrid solar cells.  

PubMed

All-solid-state donor/acceptor planar-heterojunction (PHJ) hybrid solar cells are constructed and their excellent performance measured. The deposition of a thin C60 fullerene or fullerene-derivative (acceptor) layer in vacuum on a CH3 NH3 PbI3 perovskite (donor) layer creates a hybrid PHJ that displays the photovoltaic effect. Such heterojunctions are shown to be suitable for the development of newly structured, hybrid, efficient solar cells. PMID:23775589

Jeng, Jun-Yuan; Chiang, Yi-Fang; Lee, Mu-Huan; Peng, Shin-Rung; Guo, Tzung-Fang; Chen, Peter; Wen, Ten-Chin

2013-07-19

176

Heat recovery system to power an onboard NH 3-H 2O absorption refrigeration plant in trawler chiller fishing vessels  

Microsoft Academic Search

This paper is concerned with the design, modelling and parametric analysis of a gas-to-thermal fluid heat recovery system from engine exhausts in a trawler chiller fishing vessel to power an NH3-H2O absorption refrigeration plant for onboard cooling production. Synthetic oil was used as heat transfer fluid and recirculated. The major components of the system are fluid-to-solution and gas-to-fluid heat exchangers.

José Fernández-Seara; Alberto Vales; Manuel Vázquez

1998-01-01

177

Metal-Oxide-Semiconductor Characteristics of NH3-Nitrided N2O-Annealed Oxides Fabricated at Reduced Pressure  

NASA Astrophysics Data System (ADS)

In this paper, a new technique, namely, the fabrication of NH3-nitrided N2O-annealed oxides (NNO) under reduced pressure, is presented to attain the desired nitrogen concentrations and profiles that eventually improve the hot-carrier lifetime and high immunity to boron penetration. The proposed NNO dielectrics fabricated at reduced pressure (<550 Torr) showed excellent hot-carrier lifetimes and barrier properties to boron penetration without any adverse effects on the electrical properties and reliability.

Yoon, Giwan; Epstein, Yefim

2000-04-01

178

A cluster DFT study of NH3 and NO adsorption on the (MoO2)2+/HZSM-5 surface: Lewis versus Brønsted acid sites  

NASA Astrophysics Data System (ADS)

A systematic DFT study was carried out to investigate NH3 and NO adsorption on both Lewis and Brønsted acid sites of (MoO2)2+/HZSM-5 catalyst by using cluster models. The adsorption energy results indicate that NH3 could strongly adsorb on both Lewis and Brønsted acid sites in the form of coordinated NH3 and NH4+, respectively, whereas NO represents poorer adsorption ability. It is also found that Lewis and Brønsted acid sites are competitive energetically for NH3 adsorption. According to the difference in the proposed mechanisms for NH3 adsorption on different acid sites, particular attention has been focused on the first dissociation of coordinated NH3 for Lewis acid site and the effect of Mo site on the introduction of NO for Brønsted acid site. For the coordinated NH3 on Lewis acid site, the more electron donation from NH3 is, the greater its adsorption stability is and the higher active its H atoms are. In addition, DOS results show that stability of the H atoms is enhanced by interacting with framework oxygen and especially the H atoms chemical-bonded with framework oxygen. For the NH4+ on Brønsted acid site, reduced-state Mo5+ holds stronger reducibility and oxidizability than terminal oxygen, which is suggested to play a key role in adsorption and activation of NOx together with the adsorbed NH4+.

Yan, Zhifeng; Zuo, Zhijun; Li, Zhe; Zhang, Jinshan

2014-12-01

179

Ternary homogeneous nucleation of H2SO4, NH3, and H2O under conditions relevant to the lower troposphere  

NASA Astrophysics Data System (ADS)

Ternary homogeneous nucleation (THN) of H2SO4, NH3 and H2O has been used to explain new particle formation in various atmospheric regions, yet laboratory measurements have failed to reproduce atmospheric observations. Here, we report laboratory observations of THN made under conditions relevant to the lower troposphere (H2SO4 of 106-107 cm-3, NH3 of 0.08-20 ppbv, and 288 K). Our observations show that NH3 can enhance atmospheric H2SO4 aerosol nucleation and the enhancement factor (EF) in nucleation rate due to NH3 increases linearly with increasing NH3 and increases exponentially with decreasing H2SO4 and RH. The critical clusters of ternary homogeneous nucleation contain 3-5 molecules of H2SO4, 1-4 molecules of H2O, and only 1 molecule of NH3. The composition of H2SO4 and H2O in critical clusters and the threshold of H2SO4 concentrations required for the unit nucleation rate both do not vary in the presence and absence of NH3. These observations can be directly used to improve aerosol nucleation models to correctly assess how man-made SO2 and NH3 affect aerosol formation and CCN production at the global scale.

Benson, D.; Markovich, A.; Lee, S.-H.

2010-09-01

180

Ternary homogeneous nucleation of H2SO4, NH3, and H2O under conditions relevant to the lower troposphere  

NASA Astrophysics Data System (ADS)

Ternary homogeneous nucleation (THN) of H2SO4, NH3 and H2O has been used to explain new particle formation in various atmospheric regions, yet laboratory measurements of THN have failed to reproduce atmospheric observations. Here, we report first laboratory observations of THN made under conditions relevant to the lower troposphere ([H2SO4] of 106-107 cm-3, [NH3] of 0.08-20 ppbv, and a temperature of 288 K). Our observations show that NH3 can enhance atmospheric H2SO4 aerosol nucleation and the enhancement factor (EF) in nucleation rate (J) due to NH3 (the ratio of J measured with vs. without NH3) increases linearly with increasing [NH3] and increases with decreasing [H2SO4] and RH. Two chemical ionization mass spectrometers (CIMS) are used to measure [H2SO4] and [NH3], as well as possible impurities of amines in the nucleation system. Aerosol number concentrations are measured with a water condensation counter (CPC, TSI 3786). The slopes of Log J vs. Log [H2SO4], Log J vs. Log RH, and Log J vs. Log [NH3] are 3-5, 1-4, and 1, respectively. These slopes and the threshold of [H2SO4] required for the unity nucleation vary only fractionally in the presence and absence of NH3. These observations can be used to improve aerosol nucleation models to assess how man-made SO2 and NH3 affect aerosol formation and CCN production at the global scale.

Benson, D. R.; Yu, J. H.; Markovich, A.; Lee, S.-H.

2011-05-01

181

Degradation of SO 2, NO 2 and NH 3 leading to formation of secondary inorganic aerosols: An environmental chamber study  

NASA Astrophysics Data System (ADS)

We have examined the interactions of gaseous pollutants and primary aerosols that can produce secondary inorganic aerosols. The specific objective was to estimate degradation rates of precursor gases (NH 3, NO 2 and SO 2) responsible for formation of secondary inorganic aerosols. A Teflon-based outdoor environmental chamber facility (volume 12.5 m 3) was built and checked for wall losses, leaks, solar transparency and ability to simulate photochemical reactions. The chamber was equipped with state-of-the-art instrumentation to monitor concentration-time profiles of precursor gases, ozone, and aerosol. A total of 14 experimental runs were carried out for estimating the degradation of precursor gases. The following initial conditions were maintained in the chamber: NO 2 = 246 ± 104 ppb(v), NH 3 = 548 ± 83 ppb(v), SO 2 = 238 ± 107 ppb(v), O 3 = 50 ± 11 ppb(v), PM 2.5 aerosol = 283438 ± 60524 No./litre. The concentration-time profile of gases followed first-order decay and were used for estimating degradation rates (NO 2 = 0.26 ± 0.15 h -1, SO 2 = 0.31 ± 0.17 h -1, NH 3 = 0.35 ± 0.21 h -1). We observed that degradation rates showed a statistical significant positive correlation (at 5% level of significance) with the initial PM 2.5 levels in the chamber (coefficient of correlation: 0.63 for NO 2; 0.62 for NH 3 and 0.51 for SO 2), suggesting that the existing surface of the aerosol could play a significant role in degradation of precursor gases. One or more gaseous species can be adsorbed on to the existing particles and these may undergo heterogeneous or homogeneous chemical transformation to produce secondary inorganic aerosols. Through correlation analysis, we have observed that degradation rates of precursor gases were dependent on initial molar ratio of (NH 3)/(NO 2 + SO 2), indicative of ammonia-rich and ammonia-poor situations for eventual production of ammonium salts.

Behera, Sailesh N.; Sharma, Mukesh

2011-08-01

182

Desorption From Interstellar Ices  

E-print Network

The desorption of molecular species from ice mantles back into the gas phase in molecular clouds results from a variety of very poorly understood processes. We have investigated three mechanisms; desorption resulting from H_2 formation on grains, direct cosmic ray heating and cosmic ray induced photodesorption. Whilst qualitative differences exist between these processes (essentially deriving from the assumptions concerning the species-selectivity of the desorption and the assumed threshold adsorption energies, E_t) all three processes are found to be potentially very significant in dark cloud conditions. It is therefore important that all three mechanisms should be considered in studies of molecular clouds in which freeze-out and desorption are believed to be important. Employing a chemical model of a typical static molecular core and using likely estimates for the quantum yields of the three processes we find that desorption by H_2 formation probably dominates over the other two mechanisms. However, the physics of the desorption processes and the nature of the dust grains and ice mantles are very poorly constrained. We therefore conclude that the best approach is to set empirical constraints on the desorption, based on observed molecular depletions - rather than try to establish the desorption efficiencies from purely theoretical considerations. Applying this method to one such object (L1689B) yields upper limits to the desorption efficiencies that are consistent with our understanding of these mechanisms.

J. F. Roberts; J. M. C. Rawlings; S. Viti; D. A. Williams

2007-08-24

183

Lattice potential energy and standard molar enthalpy in the formation of 1—dodecylamine hydrobromide (1-C12H25NH3·Br)(s)  

NASA Astrophysics Data System (ADS)

This paper reports that 1-dodecylamine hydrobromide (1-C12H25NH3·Br)(s) has been synthesized using the liquid phase reaction method. The lattice potential energy of the compound 1-C12H25NH3·Br and the ionic volume and radius of the 1-C12H25NH3+ cation are obtained from the crystallographic data and other auxiliary thermodynamic data. The constant-volume energy of combustion of 1-C12H25NH3·Br(s) is measured to be ?cUmo(1-C12H25NH3·Br, s) = -(7369.03±3.28) kJ·mol-1 by means of an RBC-II precision rotating-bomb combustion calorimeter at T = (298.15±0.001) K. The standard molar enthalpy of combustion of the compound is derived to be ?cHmo(1-C12H25NH3·Br, s) = -(7384.52±3.28) kJ·mol-1 from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound is calculated to be ?fHmo(1-C12H25NH3·Br, s)=-(1317.86±3.67) kJ·mol-1 from the standard molar enthalpy of combustion of the title compound and other auxiliary thermodynamic quantities through a thermochemical cycle.

Liu, Yu-Pu; Di, You-Ying; Dan, Wen-Yan; He, Dong-Hua; Kong, Yu-Xia; Yang, Wei-Wei

2011-02-01

184

THERMAL DESORPTION TREATMENT  

EPA Science Inventory

Thermal desorption is an ex situ means to physically separate volatile and some semivolatile contaminants from soil, sediments, sludges, and filter cakes. or wastes containing up to 10% organics or less, thermal desorption can be used alone for site remediation. t also may find a...

185

Sub-ppm NH3 sensor for control of de-nitrification process using diode laser spectroscopy  

NASA Astrophysics Data System (ADS)

Diode laser absorption spectroscopy (DLAS) has become an important analytical technique for highly sensitive and specific gas concentration measurements as it is reliable, fast and accurate. In this work a diode laser sensor has been developed to monitor ammonia at sub-ppm in 1510-nm region. The system was designed to control the de-nitrification process with selective catalytic reduction (SCR) abatement system. To ensure that NOx is reacted completely and to avoid secondary pollution resulted from ammonia slip, it is essential to monitor emissions of ammonia for controlling the amount of NH3 injection. NH3 concentration is demanded not to exceed 5ppm, preferably 2-3ppm. In order to provide enough sensitivity, the sensor uses DLAS with wavelength modulation as AC detection of absorption line derivatives, at frequencies where the laser noise is reduced, coupled with coherent electronic detection techniques. Experiment results demonstrate that the sensor with the second-harmonic detection shows in-situ, continuous measurements with low detection limit (60 ppb), fast response (<1s) and long-term stability all of which is difficult to obtain with conventional techniques such as wet chemical analysis, non-dispersive infrared (NDIR). In addition, the influence of water vapor on ammonia measurements due to line broadening effects is investigated. A real-time spectrum analysis algorithm is developed. The systematic measurement error is corrected by means of the line width measurements based on fast pattern correlation analysis of second-harmonic line shape. This offers the advantage of accurate NH3 concentration measurement even though the moisture content is above 40%.

Gu, Haitao; Liu, Lipeng; Li, Ying; Chen, Ren; Wen, Luhong; Wang, Jian

2008-12-01

186

Effect of the vibrational excitation on the non-radiative deactivation rate of the S 1 state of p-cresol(NH 3) complex  

NASA Astrophysics Data System (ADS)

The effect of the CH 3 group on the lifetime of the S 1 state of the p-cresol(NH 3) complex was investigated by means of REMPI, LIF, DF spectroscopy and abinitio calculations. At variance with PhOH(NH 3) for which vibrational-mode specificity was reported, the lifetime of the S 1 state of the p-cresol(NH 3) complex decreases monotonically upon vibrational excitation indicating that randomization of energy takes place at low excitation energy. This result is analyzed as the consequence of a stronger coupling of the complex intermolecular modes with those of the CH 3 group.

Oldani, A. N.; Mobbili, M.; Marceca, E.; Ferrero, J. C.; Pino, G. A.

2009-03-01

187

Infrared photodissociation spectroscopy of Mg +(NH 3) n ( n=3-6): direct coordination or solvation through hydrogen bonding  

NASA Astrophysics Data System (ADS)

The infrared photodissociation spectra of mass-selected Mg +(NH 3) n ( n=3-6) are measured and analyzed with the aid of density functional theory calculations. No large frequency reduction is observed for the NH stretches of ammonia, suggesting that either all the ammonia molecules coordinate directly to the Mg + ion or an additional ammonia in the second shell bridges two ammonias in the first shell through hydrogen bonds. Four or possibly five ammonia molecules are allowed to occupy the first shell, in striking contrast to the closure of the first shell in Mg +(H 2O) 3.

Ohashi, Kazuhiko; Terabaru, Kazutaka; Inokuchi, Yoshiya; Mune, Yutaka; Machinaga, Hironobu; Nishi, Nobuyuki; Sekiya, Hiroshi

2004-07-01

188

Quasi-one-dimensional antiferromagnetism in (CH3NH3)MnCl3 . 2H2O  

Microsoft Academic Search

(CH3NH3)MnCl3?2H2O, MMC, contains chains of cis-[MnCl4(H2O)2] octahedra corner-linked via single Cl atoms. These chains are very similar to those in CsMnCl3?2H2O, CMC, but more widely separated by the larger cations. We have measured the magnetic susceptibilities of MMC between ?1 and 100 K at 80 Hz and its heat capacity between ?1 and 20 K. Susceptibilities above ?10 K are

Satoru Simizu; Jiing-Yann Chen; S. A. Friedberg

1984-01-01

189

Qualifying composition dependent p and n self-doping in CH3NH3PbI3  

NASA Astrophysics Data System (ADS)

We report the observation of self-doping in perovskite. CH3NH3PbI3 was found to be either n- or p-doped by changing the ratio of methylammonium halide (MAI) and lead iodine (PbI2) which are the two precursors for perovskite formation. MAI-rich and PbI2-rich perovskite films are p and n self-doped, respectively. Thermal annealing can convert the p-type perovskite to n-type by removing MAI. The carrier concentration varied as much as six orders of magnitude. A clear correlation between doping level and device performance was also observed.

Wang, Qi; Shao, Yuchuan; Xie, Haipeng; Lyu, Lu; Liu, Xiaoliang; Gao, Yongli; Huang, Jinsong

2014-10-01

190

Application of a diffusion-desorption rate equation model in astrochemistry.  

PubMed

Desorption and diffusion are two of the most important processes on interstellar grain surfaces; knowledge of them is critical for the understanding of chemical reaction networks in the interstellar medium (ISM). However, a lack of information on desorption and diffusion is preventing further progress in astrochemistry. To obtain desorption energy distributions of molecules from the surfaces of ISM-related materials, one usually carries out adsorption-desorption temperature programmed desorption (TPD) experiments, and uses rate equation models to extract desorption energy distributions. However, the often-used rate equation models fail to adequately take into account diffusion processes and thus are only valid in situations where adsorption is strongly localized. As adsorption-desorption experiments show that adsorbate molecules tend to occupy deep adsorption sites before occupying shallow ones, a diffusion process must be involved. Thus, it is necessary to include a diffusion term in the model that takes into account the morphology of the surface as obtained from analyses of TPD experiments. We take the experimental data of CO desorption from the MgO(100) surface and of D2 desorption from amorphous solid water ice as examples to show how a diffusion-desorption rate equation model explains the redistribution of adsorbate molecules among different adsorption sites. We extract distributions of desorption energies and diffusion energy barriers from TPD profiles. These examples are contrasted with a system where adsorption is strongly localized--HD from an amorphous silicate surface. Suggestions for experimental investigations are provided. PMID:25302396

He, Jiao; Vidali, Gianfranco

2014-01-01

191

The desorption of H2CO from interstellar grains analogues  

NASA Astrophysics Data System (ADS)

Context. Much of the formaldehyde (H2CO) is formed from the hydrogenation of CO on interstellar dust grains, and is released in the gas phase in hot core regions. Radio-astronomical observations in these regions are directly related to its desorption from grains. Aims: We study experimentally the thermal desorption of H2CO from bare silicate surfaces, from water ice surfaces and from bulk water ice in order to model its desorption from interstellar grains. Methods: Temperature-programmed desorption experiments, monitored by mass spectrometry, and Fourier transform infrared spectroscopy are performed in the laboratory to determine the thermal desorption energies in: (i.) the multilayer regime where H2CO is bound to other H2CO molecules; (ii.) the submonolayer regime where H2CO is bound on top of a water ice surface; (iii.) the mixed submonolayer regime where H2CO is bound to a silicate surface; and (iv.) the multilayer regime in water ice, where H2CO is embedded within a H2O matrix. Results: In the submonolayer regime, we find the zeroth-order desorption kinetic parameters ?0 = 1028 mol cm-2 s-1 and E = 31.0 +/-0.9 kJ mol-1 for desorption from an olivine surface. The zeroth-order desorption kinetic parameters are ?0 = 1028 mol cm-2 s-1 and E = 27.1 +/-0.5 kJ mol-1 for desorption from a water ice surface in the submonolayer regime. In a H2CO:H2O mixture, the desorption is in competition with the H2CO + H2O reaction, which produces polyoxymethylene, the polymer of H2CO. This polymerization reaction prevents the volcano desorption and co-desorption from happening. Conclusions: H2CO is only desorbed from interstellar ices via a dominant sub-monolayer desorption process (E = 27.1 +/ - 0.5 kJ mol-1). The H2CO which has not desorbed during this sub-monolayer desorption polymerises upon reaction with H2O, and does not desorb as H2CO at higher temperature.

Noble, J. A.; Theule, P.; Mispelaer, F.; Duvernay, F.; Danger, G.; Congiu, E.; Dulieu, F.; Chiavassa, T.

2012-07-01

192

Hydrothermal synthesis and characterization of organically templated zincophosphites with two- and three-dimensional structures, [CH 3CH(NH 3)CH 2NH 3]·[Zn 2(HPO 3) 3]·H 2O and [H 3N(CH 2) 6NH 3]·[Zn 3(HPO 3) 4  

NASA Astrophysics Data System (ADS)

Two organically templated zincophosphites, [CH 3CH(NH 3)CH 2NH 3]·[Zn 2(HPO 3) 3]·H 2O ( 1) and [H 3N(CH 2) 6NH 3]·[Zn 3(HPO 3) 4] ( 2) were hydrothermally synthesized and characterized by single-crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic system, space group P2 1/c with cell parameters: a=9.9875(13) Å, b=10.3402(11) Å, c=14.4373(16) Å, ?=102.093°, and Z=4. It possesses a layered architecture and organic template molecules located between the inorganic layers forming hydrogen bonds. The inorganic layers, which consist of four-, eight-membered rings, are constructed of alternating ZnO 4 tetrahedra and [HPO 32-] pseudo-pyramid by sharing vertices. Each four-membered ring is capped by a [HPO 32-] pseudo-pyramid. The 1,2-diammonium-propane template molecules are located above the eight-membered rings. Compound 2 crystallizes in the orthorhombic system, space group Pbcn with cell parameters: a=8.8754(14) Å, b=16.667(3) Å, c=13.864(2) Å, and Z=4. It is built up from three-dimensional Zn/P/O frameworks. Corner-linked ZnO 4 tetrahedra and [HPO 32-] pseudo-pyramids form four-, six-, eight-membered rings and 12-membered ring channels. 1,6-diaminohexane cations are located in the 12-membered ring channel systems. Two compounds were characterized by IR spectroscopy, and differential thermal and thermogravimetric analyses.

Fu, Wensheng; Shi, Zhan; Zhang, Dong; Li, Guanghua; Dai, Zhimin; Chen, Xiaobo; Feng, Shouhua

2003-08-01

193

Depletion region effect of highly efficient hole conductor free CH3NH3PbI3 perovskite solar cells.  

PubMed

The inorganic-organic perovskite is currently attracting a lot of attention due to its use as a light harvester in solar cells. The large absorption coefficients, high carrier mobility and good stability of organo-lead halide perovskites present good potential for their use as light harvesters in mesoscopic heterojunction solar cells. This work concentrated on a unique property of the lead halide perovskite, its function simultaneously as a light harvester and a hole conductor in the solar cell. A two-step deposition technique was used to optimize the perovskite deposition and to enhance the solar cell efficiency. It was revealed that the photovoltaic performance of the hole conductor free perovskite solar cell is strongly dependent on the depletion layer width which was created at the TiO2-CH3NH3PbI3 junction. X-ray diffraction measurements indicate that there were no changes in the crystallographic structure of the CH3NH3PbI3 perovskite over time, which supports the high stability of these hole conductor free perovskite solar cells. Furthermore, the power conversion efficiency of the best cells reached 10.85% with a fill factor of 68%, a Voc of 0.84 V, and a Jsc of 19 mA cm(-2), the highest efficiency to date of a hole conductor free perovskite solar cell. PMID:24736900

Aharon, Sigalit; Gamliel, Shany; El Cohen, Bat; Etgar, Lioz

2014-06-14

194

Study of the chemistry of NH 3 on aluminum nitride and oxynitride under steady-state conditions using external-reflection infrared spectroscopy  

Microsoft Academic Search

Polarization-modulated Fourier-transform infrared reflection absorption spectroscopy has been applied to the characterization of thin films of AlN and Al oxynitride (‘AlON’) on NiAl(111) and to the observation of surface chemical processes under steady-state conditions in a static NH3 ambient of up to 200Torr. AlN films, grown by dosing NiAl(111) with NH3 at ?1230K, are found to be structurally inhomogeneous and

V. M. Bermudez

1999-01-01

195

The effect of ALD-Zno layers on the formation of CH3NH3PbI3 with different perovskite precursors and sintering temperatures.  

PubMed

ZnO films deposited by atomic layer deposition at 70 °C were used to fabricate perovskite solar cells, and a conversion efficiency of 13.1% was obtained. On the ZnO layer, CH3NH3PbI3 was formed at room temperature using CH3NH3I and PbCl2 precursors, which is in contrast to the reported results. PMID:25302343

Dong, Xu; Hu, Hongwei; Lin, Bencai; Ding, Jianning; Yuan, Ningyi

2014-10-23

196

Growth of CH3NH3PbI3 cuboids with controlled size for high-efficiency perovskite solar cells.  

PubMed

Perovskite solar cells with submicrometre-thick CH3NH3PbI3 or CH3NH3PbI3-xClx active layers show a power conversion efficiency as high as 15%. However, compared to the best-performing device, the average efficiency was as low as 12%, with a large standard deviation (s.d.). Here, we report perovskite solar cells with an average efficiency exceeding 16% and best efficiency of 17%. This was enabled by the growth of CH3NH3PbI3 cuboids with a controlled size via a two-step spin-coating procedure. Spin-coating of a solution of CH3NH3I with different concentrations follows the spin-coating of PbI2, and the cuboid size of CH3NH3PbI3 is found to strongly depend on the concentration of CH3NH3I. Light-harvesting efficiency and charge-carrier extraction are significantly affected by the cuboid size. Under simulated one-sun illumination, average efficiencies of 16.4% (s.d.?±?0.35), 16.3% (s.d.?±?0.44) and 13.5% (s.d.?±?0.34) are obtained from solutions of CH3NH3I with concentrations of 0.038?M, 0.050?M and 0.063 M, respectively. By controlling the size of the cuboids of CH3NH3PbI3 during their growth, we achieved the best efficiency of 17.01% with a photocurrent density of 21.64?mA?cm(-2), open-circuit photovoltage of 1.056?V and fill factor of 0.741. PMID:25173829

Im, Jeong-Hyeok; Jang, In-Hyuk; Pellet, Norman; Grätzel, Michael; Park, Nam-Gyu

2014-11-01

197

Improved reliability of AlGaN-GaN HEMTs using an NH3 plasma treatment prior to SiN passivation  

Microsoft Academic Search

A passivation method has been developed which reduces the degradation of AlGaN-GaN high electron mobility transistor (HEMT) electrical properties caused by extended dc bias or microwave power operation. The key aspect of this passivation technique is exposure to a low-power NH3 plasma prior to SiN deposition. Devices fabricated with the NH3 treatment prior to SiN passivation show minimal gate lag

Andrew P. Edwards; Jeffrey A. Mittereder; Steven C. Binari; D. Scott Katzer; David F. Storm; Jason A. Roussos

2005-01-01

198

Development and uncertainty analysis of a high-resolution NH3 emissions inventory and its implications with precipitation over the Pearl River Delta region, China  

NASA Astrophysics Data System (ADS)

Detailed NH3 emission inventories are important to understand various atmospheric processes, air quality modeling studies, air pollution management, and related environmental and ecological issues. A high-resolution NH3 emission inventory was developed based on state-of-the-science techniques, up-to-date information, and advanced expert knowledge for the Pearl River Delta region, China. To provide model-ready emissions input, this NH3 emissions inventory was spatially allocated to 3 km × 3 km grid cells using source-based spatial surrogates with geographical information system (GIS) technology. For NH3 emissions, 9 source categories and 45 subcategories were identified in this region, and detailed spatial and temporal characteristics were investigated. Results show that livestock is by far the most important NH3 emission source by contributing about 61.7% of the total NH3 emissions in this region, followed by nitrogen fertilizer applications (~23.7%) and non-agricultural sources (~14.6%). Uncertainty analysis reveals that the uncertainties associated with different sources vary from source to source and the magnitude of the uncertainty associated with a specific source mainly depends on the degree of accuracy of the emission factors and activity data as well as the technique used to perform the estimate. Further studies should give priority to the hog, broiler, goose subsectors of the livestock source and N fertilizer application source in order to reduce uncertainties of ammonia emission estimates in this region. The validity of the NH3 emissions inventory is justified by the trend analysis of local precipitation compositions, such as pH values, the Ca2++NH4+/SO42-+ NO3- ratios, and NH4+ concentrations which are directly or indirectly related to NH3 emissions.

Zheng, J. Y.; Yin, S. S.; Kang, D. W.; Che, W. W.; Zhong, L. J.

2012-08-01

199

Observations of the Partitioning of Trace Acids During CalNex, Bakersfield: HONO, HCl and Oxalic Acid in an NH3-rich Environment  

Microsoft Academic Search

The 2010 California Research at the Nexus of Air Quality and Climate Change (CalNex) field campaign supersite in Bakersfield, CA, presented an opportunity to investigate the gas-particle partitioning of trace atmospheric species in a low-sulphur high-NH3 environment. With the demand for cleaner energy, atmospheric S levels are expected to continue to decrease across North America, while restrictions on NH3 emissions

T. C. Vandenboer; M. Z. Markovic; J. Sanders; X. Ren; J. G. Murphy

2010-01-01

200

The nature of the dense core population in the Pipe Nebula: A survey of NH3, CCS, and HC5N molecular line emission  

E-print Network

Recent extinction studies of the Pipe Nebula (d=130 pc) reveal many cores spanning a range in mass from 0.2 to 20.4 Msun. These dense cores were identified via their high extinction and comprise a starless population in a very early stage of development. Here we present a survey of NH3 (1,1), NH3 (2,2), CCS (2_1,1_0), and HC5N (9,8) emission toward 46 of these cores. An atlas of the 2MASS extinction maps is also presented. In total, we detect 63% of the cores in NH3 (1,1) 22% in NH3 (2,2), 28% in CCS, and 9% in HC5N emission. We find the cores are associated with dense gas (~10^4 cm-3) with 9.5 < T_k < 17 K. Compared to C18O, we find the NH3 linewidths are systematically narrower, implying that the NH3 is tracing the dense component of the gas and that these cores are relatively quiescent. We find no correlation between core linewidth and size. The derived properties of the Pipe cores are similar to cores within other low-mass star-forming regions: the only differences are that the Pipe cores have weaker NH3 emision and most show no current star formation as evidenced by the lack of embedded infrared sources. Such weak NH3 emission could arise due to low column densities and abundances or reduced excitation due to relatively low core volume densities. Either alternative implies that the cores are relatively young. Thus, the Pipe cores represent an excellent sample of dense cores in which to study the initial conditions for star formation and the earliest stages of core formation and evolution.

J. M. Rathborne; C. J. Lada; A. A. Muench; J. F. Alves; M. Lombardi

2007-08-27

201

Wagging motion of hydrogen-bonded wire in the excited-state multiple proton transfer process of 7-hydroxyquinoline·(NH3)3 cluster.  

PubMed

In this work, the dynamics of hydrogen bonds (as well as the hydrogen-bonded wire) in excited-state tautomerization of 7-hydroxyquinoline·(NH3)3 (7HQ·(NH3)3) cluster has been investigated by using time-dependent density functional theory (TDDFT). It shows that upon an excitation, the hydrogen bond between -OH group in 7-hydroxyquinoline (7HQ) and NH3 moiety would extremely strengthened in S1 state, which could effectively facilitate the releasing of the proton from the phenolic group of 7HQ moiety to the hydrogen-bonded wire and the forming an Eigen-like cationic wire (NH3···NH4(+)···NH3) in the cluster. To fulfill the different optimal angles of NH4(+) in the wire, a wagging motion of hydrogen-bonded wire would occur in excited state. Moreover, the wagging motion of the hydrogen-bonded wire would effectively promote excited-state proton transfer reaction. As the results, an excited-state multiple proton transfer (ESMPT) mechanism containing two concerted and asymmetrical processes has been proposed for the proton transfer dynamics of 7HQ·(NH3)3 cluster. PMID:23673244

Liu, Yu-Hui; Lan, Sheng-Cheng; Li, Chun-Ran

2013-08-01

202

Activities of CeO2/TiO2 catalyst for SCR of NO with NH3 at low temperature according to operating conditions  

NASA Astrophysics Data System (ADS)

A catalyst based on CeO2/TiO2 was prepared by the impregnation method, and its activities for low temperature selective catalytic reduction (SCR) of NO with NH3 were investigated at temperature from 373 to 573 K. As the cerium oxide loading was increased until 40 wt. %, NO conversion of CeO2/TiO2 catalyst increased significantly, whereas that of the catalyst with 50 wt. % cerium oxide loading decreased due to the change of the main phase. The effects of the operating conditions were also studied at various gas hourly space velocities (GHSV), reaction temperatures, O2 concentrations and NH3/NO ratios. The reaction temperature has a greater effect on the activity of the catalyst than the GHSV. The lattice oxygen of CeO2 contributes to the SCR of NO with NH3 at low O2 concentration. When an excess NH3 concentration, further NH3 addition could not improve the NO conversion efficiency due to the limited amount of adsorption sites. The experimental results showed that the best CeO2/TiO2 catalyst yielded more than 92% NO conversion at 523 K at a space velocity of 10,000 h-1. The reaction orders of NO, NH3, and O2 were determined to be 1, 0, and 0.5, respectively, and the apparent activation energy was calculated to be 32.5 kJ/mol.

Shin, Min-Chul; Cha, Jin-Sun; Shin, Byeongkil; Chun, Ho Hwan; Lee, Heesoo

2013-01-01

203

Thermal desorption of 3He from T@C 60  

NASA Astrophysics Data System (ADS)

The interaction of recoil tritium (T), with an initial kinetic energy of 2.7 MeV with C 60 molecules, is studied in a 6Li( n, ?) T activated homogenized compound matrix of Li 2CO 3 and C 60. Liquid scintillation spectrometry coupled with high pressure liquid chromatography (HPLC) revealed endohedral T insertion into the fullerene cage upon extraction of the fullerene species into the organic phase. Solid state temperature programmed desorption profiles of the activated compound target showed the desorption of 3He gas (as a ?- decay product from T) from the endohedral T@C 60 at 882 °C. The deconvoluted evolved gas analysis-mass spectral (EGA-MS) data provided a 25% probability of T@C 60 formation upon nuclear activation of the compound target. The non-isothermal kinetics of the tritium desorption, studied as a function of temperature, revealed the process to be diffusion controlled.

Sahoo, Rashmi R.; Patnaik, Archita

2001-11-01

204

Experimental and theoretical investigation of homogeneous gaseous reaction of CO2(g) + nH2O(g) + nNH3(g) ? products (n = 1, 2).  

PubMed

Decreasing CO2 emissions into the atmosphere is key for reducing global warming. To facilitate the CO2 emission reduction efforts, our laboratory conducted experimental and theoretical investigations of the homogeneous gaseous reaction of CO2(g) + nH2O(g) + nNH3(g) ? (NH4)HCO3(s)/(NH4)2CO3(s) (n = 1 and 2) using Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy and ab initio molecular orbital theory. Our FTIR-ATR experimental results indicate that (NH4)2CO3(s) and (NH4)HCO3(s) are formed as aerosol particulate matter when carbon dioxide reacts with ammonia and water in the gaseous phase at room temperature. Ab initio study of this chemical system suggested that the reaction may proceed through formation of NH3·H2O(g), NH3·CO2(g), and CO2·H2O(g) complexes. Subsequent complexes, NH3·H2O·CO2 and (NH3)2·H2O·CO2, can be formed by adding gaseous reactants to the NH3·H2O(g), NH3·CO2(g), and CO2·H2O(g) complexes, respectively. The NH3·H2O·CO2 and (NH3)2·H2O·CO2 complexes can then be rearranged to produce (NH4)HCO3 and (NH4)2CO3 as final products via a transition state, and the NH3 molecule acts as a medium accepting and donating hydrogen atoms in the rearrangement process. Our computational results also reveal that the presence of an additional water molecule can reduce the activation energy of the rearrangement process. The high activation energy predicted in the present work suggests that the reaction is kinetically not favored, and our experimental observation of (NH4)HCO3(s) and (NH4)2CO3(s) may be attributed to the high concentrations of reactants increasing the reaction rate of the title reactions in the reactor. PMID:22900762

Li, Zhuangjie; Zhang, Baoquan

2012-09-13

205

Thermodynamics on hydride vapor phase epitaxy of AlN using AlCl3 and NH3  

NASA Astrophysics Data System (ADS)

A thermodynamic analysis on hydride vapor phase epitaxy (HVPE) of AlN using AlCl3 and NH3 was performed. Regardless of the carrier gas used, partial pressures of Al-containing gaseous species [AlCl3, AlCl2, AlCl and (AlCl3)2] in equilibrium with AlN are significantly low in the temperature range of 500-1500 °C when the input V/III ratio is above 1. This means that the driving force for AlN growth (?PAl) becomes almost equal to the input partial pressure of AlCl3, which is quite different from HVPE of GaN. The good agreement between the calculated and experimental growth rates shows that HVPE of AlN is thermodynamically controlled.

Kumagai, Y.; Takemoto, K.; Kikuchi, J.; Hasegawa, T.; Murakami, H.; Koukitu, A.

206

Electron-Temperature Dependence of the Recombination of NH4(+)((NH3)(sub n) Ions with Electrons  

NASA Technical Reports Server (NTRS)

The two-body recombination of NH4(+)(NH3)(sub 2,3) cluster-ions with electrons has been studied in an afterglow experiment in which the electron temperature T, was elevated by radio-frequency heating from 300 K up to 900 K. The recombination coefficients for the n = 2 and n = 3 cluster ions were found to be equal, alpha(sub 2, sup(2)) = alpha(sub 3, sup(2)) = (4.8 +/- 0.5) x 10(exp - 6)cu cm/s, and to vary with electron temperature as T(sub c, sup -0.65) rather than to be nearly temperature-independent as had been inferred from measurements in microwave-heated plasmas.

Skrzypkowski, M. P.; Johnson, R.

1997-01-01

207

Photolysis products of CO, NH3 aND H2O and their significance to reactions on interstellar grains  

NASA Technical Reports Server (NTRS)

With the increase in evidence that interstellar grains are the basic building blocks of comets and with the realization that comet collisions with the earth have probably occured at a much higher frequency than earlier assumed it may be presumed that interstellar dust chemistry played an important role in the early chemistry of the earth. As a part of the study of the photochemical processes taking place on interstellar grains the photolysis of mixtures of CO, NH3 and H2O was performed at 10 K, 77K and 298K. The reaction products were determined by GC/MS and HPLC analysis to be lactic acid, glycolic acid, hydroxyacetamide, urea, biuret, oxamic acid, oxamide, glyceric acid and glyceramide. Ethylene glycol and glycerol were also detected but is is not clear at present whether these are true photoproducts or contaminants. The mechanism of formation of these molecules are discussed as well as their possible significance to the origins of life.

Ferris, J. P.

1986-01-01

208

A theoretical investigation of gaseous absorption by water droplets from SO2-HNO3-NH3-CO2-HCl mixtures  

NASA Technical Reports Server (NTRS)

A physical-chemical model is developed and used to investigate gaseous absorption by water droplets from trace gas mixtures. The model is an extension of that of Carmichael and Peters (1979) and includes the simultaneous absorption of SO2, NH3, HNO3, CO2, and HCl. Gas phase depletion is also considered. Presented results demonstrate that the absorption behavior of raindrops is strongly dependent on drop size, fall distance, trace gas concentrations, and the chemical and physical properties of the constituents of the mixture. In addition, when gas phase depletion is considered, the absorption rates and equilibrium values are also dependent on the precipitation rate itself. Also, the trace constituents liquid phase concentrations may be a factor of six or more lower when gas depletion is considered then when the depletion is ignored. However, the hydrogen ion concentration may be insensitive to the gas phase depletion.

Adewuyi, Y. G.; Carmichael, G. R.

1982-01-01

209

Macroporous WO3 thin films active in NH3 sensing: role of the hosted Cr isolated centers and Pt nanoclusters.  

PubMed

Macroporous WO(3) films with inverted opal structure were synthesized by one-step procedure, which involves the self-assembly of the spherical templating agents and the simultaneous sol-gel condensation of the semiconductor alkoxide precursor. Transition metal doping, aimed to enhance the WO(3) electrical response, was carried out by including Cr(III) and Pt(IV) centers in the oxide matrix. It turned out that Cr remains as homogeneously dispersed Cr(III) centers inside the WO(3) host, while Pt undergoes reduction and aggregation to form nanoclusters located at the oxide surface. Upon interaction with NH(3), the electrical conductivity of transition metal doped-WO(3) increases, especially in the presence of Pt dopant, resulting in outstanding sensing properties (S = 110 ± 15 at T = 225 °C and [NH(3)] = 74 ppm). A mechanism was suggested to explain the excellent electrical response of Pt-doped films with respect to the Cr-doped ones. This associates the easy chemisorption of ammonia on the WO(3) nanocrystals, promoted by the inverted opal structure, with the catalytic action exerted by the surface Pt nanoclusters on the N-H bond dissociation. The overall results indicate that in Pt-doped WO(3) films the effects of the macroporosity positively combine with the electrical sensitization promoted by the metal nanoclusters, thus providing very lightweight materials which display high functionality even at relatively low temperatures. We expect that this synergistic effect can be exploited to realize other functional hierarchical metal oxide structures to be used as gas sensors or catalysts. PMID:21425840

D'Arienzo, Massimiliano; Armelao, Lidia; Mari, Claudio Maria; Polizzi, Stefano; Ruffo, Riccardo; Scotti, Roberto; Morazzoni, Franca

2011-04-13

210

Emissions of NO and NH3 from a typical vegetable-land soil after the application of chemical N fertilizers in the Pearl River Delta.  

PubMed

Cropland soil is an important source of atmospheric nitric oxide (NO) and ammonia (NH3). Chinese croplands are characterized by intensive management, but limited information is available with regard to NO emissions from croplands in China and NH3 emissions in south China. In this study, a mesocosm experiment was conducted to measure NO and NH3 emissions from a typical vegetable-land soil in the Pearl River Delta following the applications of 150 kg N ha(-1) as urea, ammonium nitrate (AN) and ammonium bicarbonate (ABC), respectively. Over the sampling period after fertilization (72 days for NO and 39 days for NH3), mean NO fluxes (± standard error of three replicates) in the control and urea, AN and ABC fertilized mesocosms were 10.9±0.9, 73.1±2.9, 63.9±1.8 and 66.0±4.0 ng N m(-2) s(-1), respectively; mean NH3 fluxes were 8.9±0.2, 493.6±4.4, 144.8±0.1 and 684.7±8.4 ng N m(-2) s(-1), respectively. The fertilizer-induced NO emission factors for urea, AN and ABC were 2.6±0.1%, 2.2±0.1% and 2.3±0.2%, respectively. The fertilizer-induced NH3 emission factors for the three fertilizers were 10.9±0.2%, 3.1±0.1% and 15.2±0.4%, respectively. From the perspective of air quality protection, it would be better to increase the proportion of AN application due to its lower emission factors for both NO and NH3. PMID:23527173

Li, Dejun

2013-01-01

211

Effects of pollutant concentration ratio on the simultaneous removal of NH3, H2S and toluene gases using rock wool-compost biofilter.  

PubMed

The biological treatment of a tri-component mixed waste gas system in BRC1 and BRC2 biofilters packed with rock wool-compost media was studied. The model gases were NH(3), H(2)S and toluene. The gases were fed initially at about 50-55 ppm each. H(2)S was found to have the shortest start-up while toluene had the longest. Under two different NH(3):H(2)S:toluene concentration ratios of 250:120:55 and 120:220:55 (in ppm) for BRC1 and BRC2, the removal efficiencies of NH(3), H(2)S and toluene were found to be affected by their respective loading rate. On the other hand, toluene removal was observed to be inhibited at H(2)S concentration of 220 ppm as well. Almost complete removal of NH(3) and H(2)S was achieved when loading rate was applied up to 16.14 g-NH(3)/(m(3) bed h) and 36.09 g-H(2)S/(m(3) bed h), respectively. The maximum elimination capacity for NH(3) was determined to be 23.67 g-NH(3)/(m(3) bed h) at 78.6% removal efficiency and for H(2)S, 38.50 g-H(2)S/(m(3) bed h) at 68.1% removal efficiency. The maximum toluene elimination capacity was 30.75 g-toluene/(m(3) bed h) at 87.9% removal efficiency when the concentration of NH(3):H(2)S:toluene was 250:120:55 in BRC1, and was 16.60 g-toluene/(m(3) bed h) at 45.5% removal efficiency when the concentration of NH(3):H(2)S:toluene was 120:220:55 in BRC2. The pressure drops along both columns were low and the ratio of bed compactions over biofilter height was observed to be less than 0.02. PMID:17714863

Galera, Melvin Maaliw; Cho, Eulsaeng; Tuuguu, Enkhdul; Park, Shin-Jung; Lee, Changhee; Chung, Wook-Jin

2008-04-01

212

Internal Rotation in CF3ICdotsNH3 and CF3I\\cdotsN(CH3)_3 Probed by Cp-Ftmw Spectroscopy  

NASA Astrophysics Data System (ADS)

The pure rotational spectra of CF3ICdotsNH3 and CF3I\\cdotsN(CH3)_3 have been measured by chirped-pulse, Fourier transform microwave (CP-FTMW) spectroscopy between 7 and 18.5 GHz. Both molecules are generated by supersonic expansion of a gas sample containing a small percentage of each precursor in a balance of argon. The spectra of both complexes are consistent with {C}3v prolate symmetric top structures. The observed spectrum of CF3ICdotsNH3 displays evidence for internal rotation of NH3 about the principal axis. More than one hundred transitions of CF3ICdotsNH3 have been assigned to the internal rotor {A} state allowing rotational, centrifugal distortion constants and a nuclear quadrupole coupling constant for the iodine atom to be determined for this state. Measurements performed using a Balle-Flygare FTMW spectrometer further allow determination of a nuclear quadrupole coupling constant for the 14N nucleus. Many transitions in the spectrum of the CF3ICdots15NH3 isotopologue have also been measured and the length of the halogen bond between the iodine and nitrogen atoms has been determined. Measurements of hyperfine components in nine different J''?J' transitions of CF3I\\cdotsN(CH3)_3 have allowed assignment of the spectrum of this complex to determine rotational, centrifugal distortion and nuclear quadrupole coupling constants.

Walker, N. R.; Stephens, S. L.; Legon, A. C.

2011-06-01

213

Atomic oxygen diffusion on and desorption from amorphous silicate surfaces.  

PubMed

Surface reactions involving atomic oxygen have attracted much attention in astrophysics and astrochemistry, but two of the most fundamental surface processes, desorption and diffusion, are not well understood. We studied diffusion and desorption of atomic oxygen on or from amorphous silicate surfaces under simulated interstellar conditions using a radio-frequency dissociated oxygen beam. Temperature programmed desorption (TPD) experiments were performed to study the formation of ozone from reaction of atomic and molecular oxygen deposited on the surface of a silicate. It is found that atomic oxygen begins to diffuse significantly between 40 K and 50 K. A rate equation model was used to study the surface kinetics involved in ozone formation experiments. The value of atomic oxygen desorption energy has been determined to be 152 ± 20 meV (1764 ± 232 K). The newly found atomic oxygen desorption energy, which is much higher than the well-accepted value, might explain the discrepancy in abundance of molecular oxygen in space between observations and chemical models. PMID:24434834

He, Jiao; Jing, Dapeng; Vidali, Gianfranco

2014-02-28

214

PREDICTION OF RETENTION TIMES IN TEMPERATURE PROGRAMMED MULTICHROMATOGRAPHY  

EPA Science Inventory

The calculation of retention times for temperature programmed serially liked capillary gas chromatography columns is demonstrated. quations are derived for tbe verification of operating conditions via internal standards and for the precise calculation of ad-point pressure corresp...

215

Prediction of Retention Times in Temperature-Programmed Multichromatography.  

National Technical Information Service (NTIS)

The calculation of retention times for temperature programmed serially linked capillary gas chromatography columns is demonstrated. Equations are derived for the verification of operating conditions via internal standards and for the precise calculation o...

L. H. Wright, J. F. Walling

1991-01-01

216

Stability domains of water ices in the NH3 - H2O system: experimental results and thermodynamic modelling  

NASA Astrophysics Data System (ADS)

The ammonia compound decreases very significantly the melting curve of water ices. This property is of fundamental importance in planetology because it constrains the nature of the icy mantle within icy moons of the giant planets (1,2). That is why many experimental studies have been conducted for understanding the binary system H2O - NH3 in the temperature - pressure space (1-6). The most surprising effect of the ammonia compound is that it decreases the melting temperature of the ice polymorphs down to 180 K at the eutectic temperature (1,2). This effect has been observed throughout the pressure domain relevant for icy moons from 0 to 1 GPa. In this paper, a review of these efforts, in addition to new results, obtained by the authors with a sapphire anvil cell in the domains where experimental data were lacking (8), will be presented. A thermodynamic description that uses the chemical potential approach can be used for describing the pure water system (7,9). However, most studies that have used this approach were clearly focused on describing the melting curves of the water phase diagram. A new formulation has recently been proposed (9), which allows to compute phase equilibria in the whole P-T domain where ice polymorphs are encountered. In this work, the model has been improved by incorporating the ice II polymorph, and by describing more accurately the behaviour of the binary liquid mixture which is close to a regular symmetric solution (10). This model has been validated in the pure water domain by checking that all stability domains of the ice polymorphs (Ih, II, III, V, and VI) were predicted with an accuracy better than 1%. A very good reproduction of the stability domain of ice Ih in the H2O-NH3 phase diagram is also achieved. It will be shown that the thermodynamic approach allows to predict the stability of each ice polymorphs whatever the pressure and temperature are, in very good agreement with the available experimental data. It appears that the stability domain of some polymorphs, such as ice II and ice V, enlarges with the ammonia concentration, whereas that of ice III diminishes with NH3 concentration, and this phase is expected to disappear above 10 %wt of ammonia in the system. For each polymorph, a whole description of stability domains and melting surfaces will be presented. Implications for the occurrence of liquid oceans within the largest moons will also be briefly discussed. Ref. : 1. Hogenboom et al., Icarus, 1997. 2. Grasset and Pargamin, Planet. Space Sci., 2005. 3. Croft et al., Icarus, 1988. 4. Johnson and Nicol, J. Geoph. Res., 1987. 5Kargel, Icarus, 1992. 6. Leliwa-Kopystynski et al., Icarus, 2002. 7. Chizhov and Nagornov, J. Appl. Mech. Techn. Phys. 1991. 8. Choukroun M., PhD thesis, 2007. 9. Choukroun and Grasset, J. Chem. Phys, 2007. 10.Wood and Fraser, Oxford Univ. Press, 1977.

Grasset, O.; Choukroun, M.

2009-12-01

217

Inkjet Printing and Instant Chemical Transformation of a CH3 NH3 PbI3 /Nanocarbon Electrode and Interface for Planar Perovskite Solar Cells.  

PubMed

A planar perovskite solar cell that incorporates a nanocarbon hole-extraction layer is demonstrated for the first time by an inkjet printing technique with a precisely controlled pattern and interface. By designing the carbon plus CH3 NH3 I ink to transform PbI2 in?situ to CH3 NH3 PbI3 , an interpenetrating seamless interface between the CH3 NH3 PbI3 active layer and the carbon hole-extraction electrode was instantly constructed, with a markedly reduced charge recombination compared to that with the carbon ink alone. As a result, a considerably higher power conversion efficiency up to 11.60?% was delivered by the corresponding solar cell. This method provides a major step towards the fabrication of low-cost, large-scale, metal-electrode-free but still highly efficient perovskite solar cells. PMID:25255744

Wei, Zhanhua; Chen, Haining; Yan, Keyou; Yang, Shihe

2014-11-24

218

Rotational excitation of symmetric top molecules by collisions with atoms: Close coupling, coupled states, and effective potential calculations for NH3-He  

NASA Technical Reports Server (NTRS)

The formalism for describing rotational excitation in collisions between symmetric top rigid rotors and spherical atoms is presented both within the accurate quantum close coupling framework and also the coupled states approximation of McGuire and Kouri and the effective potential approximation of Rabitz. Calculations are reported for thermal energy NH3-He collisions, treating NH3 as a rigid rotor and employing a uniform electron gas (Gordon-Kim) approximation for the intermolecular potential. Coupled states are found to be in nearly quantitative agreement with close coupling results while the effective potential method is found to be at least qualitatively correct. Modifications necessary to treat the inversion motion in NH3 are discussed.

Green, S.

1976-01-01

219

The reaction NH2 + PH3 yields NH3 + PH2 - Absolute rate constant measurement and implication for NH3 and PH3 photochemistry in the atmosphere of Jupiter  

NASA Astrophysics Data System (ADS)

The rate constant is measured over the temperature interval 218-456 K using the technique of flash photolysis-laser-induced fluorescence. NH2 radicals are produced by the flash photolysis of ammonia highly diluted in argon, and the decay of fluorescent NH2 photons is measured by multiscaling techniques. For each of the five temperatures employed in the study, the results are shown to be indepenent of variations in PH3 concentration, total pressure (argon), and flash intensity. It is found that the rate constant results are best represented for T between 218 and 456 K by the expression k = (1.52 + or - 0.16) x 10 to the -12th exp(-928 + or - 56/T) cu cm per molecule per sec; the error quoted is 1 standard deviation. This is the first determination of the rate constant for the reaction NH2 + PH3. The data are compared with an estimate made in order to explain results of the radiolysis of NH3-PH3 mixtures. The Arrhenius parameters determined here for NH2 + PH3 are then contrasted with those for the corresponding reactions of H and OH with PH3.

Bosco, S. R.; Brobst, W. D.; Nava, D. F.; Stief, L. J.

1983-10-01

220

The Jahn-Teller effect and orientational order in (CnH2n+1NH3)2CuCl4, n=1, 2, 3  

Microsoft Academic Search

Crystal optical and X-ray diffraction studies show that the high-temperature phase I of the perovskite-type layer-compounds (CnH2n+1NH3)2CuCl4 with n=1, 2, 3 is Jahn-Teller distorted orthorhombic with space group Bbcm (D2h18). As a consequence, the order of the CnH2n+1NH3 group leads to two configurations, realised in a monoclinic phase II with space group P21\\/c (C2h5) and an orthorhombic phase III with

I. R. Jahn; K. Knorr; J. Ihringer

1989-01-01

221

Thermal effects on CH$_3$NH$_3$PbI$_3$ perovskite from ab-initio molecular dynamics simulations  

E-print Network

We present a molecular dynamics simulation study of CH$_3$NH$_3$PbI$_3$ based on forces calculated from density functional theory. The simulation were performed on model systems having 8 and 27 unit cells, and for a total simulation time of 40 ps in each case. Analysis of the finite size effects, in particular the mobility of the organic component, suggests that the smaller system is over correlated through the long range electrostatic interaction. In the larger system this finite size artifact is relaxed producing a more reliable description of the anisotropic rotational behavior of the methyl ammonium molecules. The thermal effects on the optical properties of the system were also analyzed. The HOMO-LUMO energy gap fluctuates around its central value with a standard deviation of approximately 0.1 eV. The projected density of states consistently place the Fermi level on the $p$ orbitals of the I atoms, and the lowest virtual state on $p$ orbitals of the Pb atoms throughout the whole simulation trajectory.

Carignano, Marcelo A; Hutter, Jürg

2014-01-01

222

Density functional theory analysis of structural and electronic properties of orthorhombic perovskite CH3NH3PbI3.  

PubMed

The organic-inorganic hybrid perovskite CH3NH3PbI3 is a novel light harvester, which can greatly improve the solar-conversion efficiency of dye-sensitized solar cells. In this article, a first-principle theoretical study is performed using local, semi-local and non-local exchange-correlation approximations to find a suitable method for this material. Our results, using the non-local optB86b + vdWDF functional, excellently agree with the experimental data. Thus, consideration of weak van der Waals interactions is demonstrated to be important for the accurate description of the properties of this type of organic-inorganic hybrid materials. Further analysis of the electronic properties reveals that I 5p electrons can be photo-excited to Pb 6p empty states. The main interaction between the organic cations and the inorganic framework is through the ionic bonding between CH3 and I ions. Furthermore, I atoms in the Pb-I framework are found to be chemically inequivalent because of their different chemical environments. PMID:24296525

Wang, Yun; Gould, Tim; Dobson, John F; Zhang, Haimin; Yang, Huagui; Yao, Xiangdong; Zhao, Huijun

2014-01-28

223

An analytical approach to evaluate the performance of graphene and carbon nanotubes for NH3 gas sensor applications.  

PubMed

Carbon, in its variety of allotropes, especially graphene and carbon nanotubes (CNTs), holds great potential for applications in variety of sensors because of dangling ?-bonds that can react with chemical elements. In spite of their excellent features, carbon nanotubes (CNTs) and graphene have not been fully exploited in the development of the nanoelectronic industry mainly because of poor understanding of the band structure of these allotropes. A mathematical model is proposed with a clear purpose to acquire an analytical understanding of the field-effect-transistor (FET) based gas detection mechanism. The conductance change in the CNT/graphene channel resulting from the chemical reaction between the gas and channel surface molecules is emphasized. NH3 has been used as the prototype gas to be detected by the nanosensor and the corresponding current-voltage (I-V) characteristics of the FET-based sensor are studied. A graphene-based gas sensor model is also developed. The results from graphene and CNT models are compared with the experimental data. A satisfactory agreement, within the uncertainties of the experiments, is obtained. Graphene-based gas sensor exhibits higher conductivity compared to that of CNT-based counterpart for similar ambient conditions. PMID:24991510

Akbari, Elnaz; Arora, Vijay Kumar; Enzevaee, Aria; Ahmadi, Mohamad T; Saeidmanesh, Mehdi; Khaledian, Mohsen; Karimi, Hediyeh; Yusof, Rubiyah

2014-01-01

224

The lineshapes of infrared-microwave two-photon transitions in the ?2 band of 15NH 3  

NASA Astrophysics Data System (ADS)

The lineshapes of the ssR(4, 2), ssQ(6, 4), and aaP(2, 1) transitions in the ?2 band of 15NH 3 were recorded at several pressures by means of a computer-coupled infrared laser microwave two-photon spectrometer. The lowest pressure lineshapes were Gaussian to high precision with Doppler widths within 0.1% of the calculated values. Plots of Lorentz widths vs. pressure obtained by assuming the lineshapes to be Voigt profiles gave negative intercepts. The data were reanalyzed under the assumptions of the soft-collision and hard-collision models of collisional narrowing. The resulting pressure-broadening parameters are 16.6, 18.1, and 16.5 MHz/Torr for the ssR(4, 2), ssQ(6, 4), and aaP(2, 1) transitions, respectively. These values are comparable to pressure-broadening parameters for inversion transitions in the ground state, but they are significantly larger than corresponding values for inversion transitions in the v2 = 1 state. This comparison is explained as being the result of a larger contribution from adiabatic reorientation and/or phase-changing collisions to the pressure-broadening of the infrared transitions than to the inversion transitions in either state. The limiting low-pressure values of the center frequencies of the transitions are reported and the pressure shifts in the center frequencies are given. Collisional-narrowing parameters for the three transitions are estimated.

Shabestary, N.; Sandholm, S. T.; Schwendeman, R. H.

1985-10-01

225

Thermal Assisted Oxygen Annealing for High Efficiency Planar CH3NH3PbI3 Perovskite Solar Cells  

PubMed Central

We report investigations on the influences of post-deposition treatments on the performance of solution-processed methylammonium lead triiodide (CH3NH3PbI3)-based planar solar cells. The prepared films were stored in pure N2 at room temperature or annealed in pure O2 at room temperature, 45°C, 65°C and 85°C for 12?hours prior to the deposition of the metal electrodes. It is found that annealing in O2 leads to substantial increase in the power conversion efficiencies (PCEs) of the devices. Furthermore, strong dependence on the annealing temperature for the PCEs of the devices suggests that a thermally activated process may underlie the observed phenomenon. It is believed that the annealing process may facilitate the diffusion of O2 into the spiro-MeOTAD for inducing p-doping of the hole transport material. Furthermore, the process can result in lowering the localized state density at the grain boundaries as well as the bulk of perovskite. Utilizing thermal assisted O2 annealing, high efficiency devices with good reproducibility were attained. A PCE of 15.4% with an open circuit voltage (VOC) 1.04?V, short circuit current density (JSC) 23?mA/cm2, and fill factor 0.64 had been achieved for our champion device. PMID:25341527

Ren, Zhiwei; Ng, Annie; Shen, Qian; Gokkaya, Huseyin Cem; Wang, Jingchuan; Yang, Lijun; Yiu, Wai-Kin; Bai, Gongxun; Djurisic, Aleksandra B.; Leung, Wallace Woon-fong; Hao, Jianhua; Chan, Wai Kin; Surya, Charles

2014-01-01

226

NH3 Survey of the Vela-C and Vela-D Dust Cores Selected by BLAST  

NASA Astrophysics Data System (ADS)

The Balloon-borne Large Aperture Submillimeter Telescope (BLAST; Pascale et al. 2008) is the closest precursor of the Herschel Space Observatory. During its second Long Duration Ballon flight in 2006, BLAST mapped about 50 square degrees in the Vela Molecular Ridge (VMR) at a sensitivity of <~1 solar mass. The continuum observations were carried out simultaneously at 250, 350, and 500 micron, i.e., at the peak (or very near it) of the cold cores SED. Thus the VMR cores found by BLAST represent an excellent sample of dense cores in which to study the initial conditions for star formation and the earliest phases of core evolution. The combination of (sub)mm and molecular line observations is a powerful method to determine the dynamical state of starless cores detected at submm wavelengths. Therefore, we propose coordinated observations of NH3(1,1) and (2,2), with the Parkes telescope, and of various molecular tracers with the Mopra telescope, of this sample.

Olmi, Luca; Burton, Michael; Giannini, Teresa; Lorenzetti, Dario; Massi, Fabrizio; Elia, Davide; de Luca, Massimo

2009-04-01

227

Dynamics study of the OH + NH3 hydrogen abstraction reaction using QCT calculations based on an analytical potential energy surface  

NASA Astrophysics Data System (ADS)

To understand the reactivity and mechanism of the OH + NH3 ? H2O + NH2 gas-phase reaction, which evolves through wells in the entrance and exit channels, a detailed dynamics study was carried out using quasi-classical trajectory calculations. The calculations were performed on an analytical potential energy surface (PES) recently developed by our group, PES-2012 [Monge-Palacios et al. J. Chem. Phys. 138, 084305 (2013)], 10.1063/1.4792719. Most of the available energy appeared as H2O product vibrational energy (54%), reproducing the only experimental evidence, while only the 21% of this energy appeared as NH2 co-product vibrational energy. Both products appeared with cold and broad rotational distributions. The excitation function (constant collision energy in the range 1.0-14.0 kcal mol-1) increases smoothly with energy, contrasting with the only theoretical information (reduced-dimensional quantum scattering calculations based on a simplified PES), which presented a peak at low collision energies, related to quantized states. Analysis of the individual reactive trajectories showed that different mechanisms operate depending on the collision energy. Thus, while at high energies (Ecoll ? 6 kcal mol-1) all trajectories are direct, at low energies about 20%-30% of trajectories are indirect, i.e., with the mediation of a trapping complex, mainly in the product well. Finally, the effect of the zero-point energy constraint on the dynamics properties was analyzed.

Monge-Palacios, M.; Corchado, J. C.; Espinosa-Garcia, J.

2013-06-01

228

Thermal Assisted Oxygen Annealing for High Efficiency Planar CH3NH3PbI3 Perovskite Solar Cells.  

PubMed

We report investigations on the influences of post-deposition treatments on the performance of solution-processed methylammonium lead triiodide (CH3NH3PbI3)-based planar solar cells. The prepared films were stored in pure N2 at room temperature or annealed in pure O2 at room temperature, 45°C, 65°C and 85°C for 12?hours prior to the deposition of the metal electrodes. It is found that annealing in O2 leads to substantial increase in the power conversion efficiencies (PCEs) of the devices. Furthermore, strong dependence on the annealing temperature for the PCEs of the devices suggests that a thermally activated process may underlie the observed phenomenon. It is believed that the annealing process may facilitate the diffusion of O2 into the spiro-MeOTAD for inducing p-doping of the hole transport material. Furthermore, the process can result in lowering the localized state density at the grain boundaries as well as the bulk of perovskite. Utilizing thermal assisted O2 annealing, high efficiency devices with good reproducibility were attained. A PCE of 15.4% with an open circuit voltage (VOC) 1.04?V, short circuit current density (JSC) 23?mA/cm(2), and fill factor 0.64 had been achieved for our champion device. PMID:25341527

Ren, Zhiwei; Ng, Annie; Shen, Qian; Gokkaya, Huseyin Cem; Wang, Jingchuan; Yang, Lijun; Yiu, Wai-Kin; Bai, Gongxun; Djuriši?, Aleksandra B; Leung, Wallace Woon-Fong; Hao, Jianhua; Chan, Wai Kin; Surya, Charles

2014-01-01

229

Thermal Assisted Oxygen Annealing for High Efficiency Planar CH3NH3PbI3 Perovskite Solar Cells  

NASA Astrophysics Data System (ADS)

We report investigations on the influences of post-deposition treatments on the performance of solution-processed methylammonium lead triiodide (CH3NH3PbI3)-based planar solar cells. The prepared films were stored in pure N2 at room temperature or annealed in pure O2 at room temperature, 45°C, 65°C and 85°C for 12 hours prior to the deposition of the metal electrodes. It is found that annealing in O2 leads to substantial increase in the power conversion efficiencies (PCEs) of the devices. Furthermore, strong dependence on the annealing temperature for the PCEs of the devices suggests that a thermally activated process may underlie the observed phenomenon. It is believed that the annealing process may facilitate the diffusion of O2 into the spiro-MeOTAD for inducing p-doping of the hole transport material. Furthermore, the process can result in lowering the localized state density at the grain boundaries as well as the bulk of perovskite. Utilizing thermal assisted O2 annealing, high efficiency devices with good reproducibility were attained. A PCE of 15.4% with an open circuit voltage (VOC) 1.04 V, short circuit current density (JSC) 23 mA/cm2, and fill factor 0.64 had been achieved for our champion device.

Ren, Zhiwei; Ng, Annie; Shen, Qian; Gokkaya, Huseyin Cem; Wang, Jingchuan; Yang, Lijun; Yiu, Wai-Kin; Bai, Gongxun; Djuriši?, Aleksandra B.; Leung, Wallace Woon-Fong; Hao, Jianhua; Chan, Wai Kin; Surya, Charles

2014-10-01

230

Quasi-one-dimensional antiferromagnetism in (CH3NH3)MnCl3?2H2O  

NASA Astrophysics Data System (ADS)

(CH3NH3)MnCl3?2H2O, MMC, contains chains of cis-[MnCl4(H2O)2] octahedra corner-linked via single Cl atoms. These chains are very similar to those in CsMnCl3?2H2O, CMC, but more widely separated by the larger cations. We have measured the magnetic susceptibilities of MMC between ˜1 and 100 K at 80 Hz and its heat capacity between ˜1 and 20 K. Susceptibilities above ˜10 K are well described by models of the antiferromagnetic linear Heisenberg chain with S=5/2, g=2.00, and J1/k=-3.01 K, very nearly the same intrachain coupling as in CMC. Below TN =4.12 K weak interchain interactions (˜6×10-3?J1?) produce long-range AF order in three dimensions with preferred spin alignment along or near the a axis. The linear chains in MMC are more nearly independent than those in CMC.

Simizu, Satoru; Chen, Jiing-Yann; Friedberg, S. A.

1984-03-01

231

Origin of the visible-light photoactivity of NH3-treated TiO2: Effect of nitrogen doping and oxygen vacancies  

NASA Astrophysics Data System (ADS)

N-doped and oxygen-deficient TiO2 photocatalysts were obtained by heating commercial TiO2 in NH3 atmosphere, followed by a postcalcination process. Catalysts were characterized by X-ray diffraction (XRD), N2-sorption BET surface area, X-ray photoelectron spectroscopy (XPS), Elemental analysis (EA), UV/vis diffuse reflectance spectroscopy (DRS), Electron spin resonance (ESR) and Photoluminescence (PL). It shows that the NH3-heat-treatment of TiO2 resulted in not only nitrogen doping but also creation of oxygen vacancies with optical absorption in visible-light region. The postcalcination achieved several beneficial effects including dramatic removal of surface amino species, a rapid decrease in surface Ti3+ species, and a low recombination rate of photogenerated carriers on the co-doped TiO2. The photocatalytic measurement was carried out by the degradation of gas-phase benzene under visible light irradiation. At steady state, the photocatalytic conversion rate of benzene over the postannealed catalyst was 35.8%, accompanied by the yield of 115 ppmv CO2, which was much higher than that on the NH3-treated TiO2 before postcalcination or the H2-treated TiO2 catalysts. Results show that the visible-light activity of the NH3-treated TiO2 is attributed to a synergistic effect of substitutional nitrogen species and oxygen vacancies in TiO2.

Chen, Yilin; Cao, Xiaoxin; Lin, Bizhou; Gao, Bifen

2013-01-01

232

Comparison of the Cardiac MicroPET Images Obtained Using [(18)F]FPTP and [(13)N]NH3 in Rat Myocardial Infarction Models.  

PubMed

The short half-life of current positron emission tomography (PET) cardiac tracers limits their widespread clinical use. We previously developed a (18)F-labeled phosphonium cation, [(18)F]FPTP, that demonstrated sharply defined myocardial defects in a corresponding infarcted myocardium. The aim of this study was to compare the image properties of PET scans obtained using [(18)F]FPTP with those obtained using [(13)N]NH3 in rat myocardial infarction models. Perfusion abnormality was analyzed in 17 segments of polar map images. The myocardium-to-liver and myocardium-to-lung ratios of [(18)F]FPTP were 10.48 and 2.65 times higher, respectively, than those of [(13)N]NH3 in images acquired 30 min after tracer injection. The myocardial defect size measured by [(18)F]FPTP correlated more closely with the hypoperfused area measured by quantitative 2,3,5-triphenyltetrazolium chloride staining (r = 0.89, P < 0.01) than did [(13)N]NH3 (r = 0.84, P < 0.01). [(18)F]FPTP might be useful as a replacement for the myocardial agent [(13)N]NH3 in cardiac PET/CT applications. PMID:25313324

Kim, Dong-Yeon; Kim, Hyeon Sik; Jang, Hwa Youn; Kim, Ju Han; Bom, Hee-Seung; Min, Jung-Joon

2014-10-01

233

Mesoscopic TiO2/CH3NH3PbI3 perovskite solar cells with new hole-transporting materials containing butadiene derivatives.  

PubMed

Two new triphenylamine-based hole-transporting materials (HTMs) containing butadiene derivatives are employed in CH3NH3PbI3 perovskite solar cells. Up to 11.63% of power conversion efficiency (PCE) has been achieved. Advantages such as easy synthesis, low cost and relatively good cell performance exhibit a possibility for commercial applications in the future. PMID:24841233

Lv, Songtao; Han, Liying; Xiao, Junyan; Zhu, Lifeng; Shi, Jiangjian; Wei, Huiyun; Xu, Yuzhuan; Dong, Juan; Xu, Xin; Li, Dongmei; Wang, Shirong; Luo, Yanhong; Meng, Qingbo; Li, Xianggao

2014-07-01

234

Efficient and stable CH3NH3PbI3-sensitized ZnO nanorod array solid-state solar cells  

NASA Astrophysics Data System (ADS)

We report for the first time the use of a perovskite (CH3NH3PbI3) absorber in combination with ZnO nanorod arrays (NRAs) for solar cell applications. The perovskite material has a higher absorption coefficient than molecular dye sensitizers, gives better solar cell stability, and is therefore more suited as a sensitizer for ZnO NRAs. A solar cell efficiency of 5.0% was achieved under 1000 W m-2 AM 1.5 G illumination for a solar cell with the structure: ZnO NRA/CH3NH3PbI3/spiro-MeOTAD/Ag. Moreover, the solar cell shows a good long-term stability. Using transient photocurrent and photovoltage measurements it was found that the electron transport time and lifetime vary with the ZnO nanorod length, a trend which is similar to that in dye-sensitized solar cells, DSCs, suggesting a similar charge transfer process in ZnO NRA/CH3NH3PbI3 solar cells as in conventional DSCs. Compared to CH3NH3PbI3/TiO2 solar cells, ZnO shows a lower performance due to more recombination losses.

Bi, Dongqin; Boschloo, Gerrit; Schwarzmüller, Stefan; Yang, Lei; Johansson, Erik M. J.; Hagfeldt, Anders

2013-11-01

235

Efficient and stable CH3NH3PbI3-sensitized ZnO nanorod array solid-state solar cells.  

PubMed

We report for the first time the use of a perovskite (CH3NH3PbI3) absorber in combination with ZnO nanorod arrays (NRAs) for solar cell applications. The perovskite material has a higher absorption coefficient than molecular dye sensitizers, gives better solar cell stability, and is therefore more suited as a sensitizer for ZnO NRAs. A solar cell efficiency of 5.0% was achieved under 1000 W m(-2) AM 1.5 G illumination for a solar cell with the structure: ZnO NRA/CH3NH3PbI3/spiro-MeOTAD/Ag. Moreover, the solar cell shows a good long-term stability. Using transient photocurrent and photovoltage measurements it was found that the electron transport time and lifetime vary with the ZnO nanorod length, a trend which is similar to that in dye-sensitized solar cells, DSCs, suggesting a similar charge transfer process in ZnO NRA/CH3NH3PbI3 solar cells as in conventional DSCs. Compared to CH3NH3PbI3/TiO2 solar cells, ZnO shows a lower performance due to more recombination losses. PMID:24100947

Bi, Dongqin; Boschloo, Gerrit; Schwarzmüller, Stefan; Yang, Lei; Johansson, Erik M J; Hagfeldt, Anders

2013-12-01

236

Synthesis, structure, and photovoltaic property of a nanocrystalline 2H perovskite-type novel sensitizer (CH3CH2NH3)PbI3  

PubMed Central

A new nanocrystalline sensitizer with the chemical formula (CH3CH2NH3)PbI3 is synthesized by reacting ethylammonium iodide with lead iodide, and its crystal structure and photovoltaic property are investigated. X-ray diffraction analysis confirms orthorhombic crystal phase with a?=?8.7419(2) Å, b?=?8.14745(10) Å, and c?=?30.3096(6) Å, which can be described as 2?H perovskite structure. Ultraviolet photoelectron spectroscopy and UV-visible spectroscopy determine the valence band position at 5.6?eV versus vacuum and the optical bandgap of ca. 2.2?eV. A spin coating of the CH3CH2NH3I and PbI2 mixed solution on a TiO2 film yields ca. 1.8-nm-diameter (CH3CH2NH3)PbI3 dots on the TiO2 surface. The (CH3CH2NH3)PbI3-sensitized solar cell with iodide-based redox electrolyte demonstrates the conversion efficiency of 2.4% under AM 1.5?G one sun (100?mW/cm2) illumination. PMID:22738298

2012-01-01

237

Structural characterization, thermal, dielectric and vibrational properties of tris(allylammonium) hexabromoantimonate(III), (C 3H 5NH 3) 3SbBr 6  

NASA Astrophysics Data System (ADS)

The novel inorganic-organic hybrid material, allylammonium hexabromoantimonate(III), ( C3H5NH3) 3SbBr6, has been synthesized and its structure has been determined by means of the single-crystal X-ray diffraction studies at five temperatures (273, 248, 220, 170 and 100 K). At room temperature the compound crystallizes in the monoclinic space group, C2/ m. Its crystal structure is composed of the discrete SbBr63- anions and three non-equivalent allylammonium, ( C3H5NH3) +, cations. In ( C3H5NH3) 3SbBr6 three solid-solid structural phase transitions are detected: a continuous one at 260/256 K (on heating-cooling) from phase I to II, a discontinuous one at 227/208 K (II?III) and another discontinuous at 197/191 K (III?IV). The electric properties of the compound have been measured in a wide temperature region (150-300 K). Temperature-dependent vibrational properties in the frequency region 3500-500 cm -1 have been reviewed. Possible mechanisms of the phase transitions in ( C3H5NH3) 3SbBr6 are discussed on the basis of the presented results.

P?owa?, I.; Bia?o?ska, A.; Jakubas, R.; Bator, G.; Zarychta, B.; Baran, J.

2010-09-01

238

An Experimental Study of Single Suspended H2so4\\/nh3\\/h2o-aerosols : Atmospheric Relevance of Letovicite  

Microsoft Academic Search

Aerosols in the atmosphere have a large effect on the radiative balance of the earth due to their scattering and absorbing properties. Some aerosols can also act as cloud con- densation nuclei (CCN) of cirrus clouds which play an important role for the global climate. The influence of NH3 and H2SO4 containing aerosols on cirrus formation are discussed. The thermodynamic

C. A. Colberg; U. K. Krieger; B. Luo; H. Wernli; Th. Peter

2002-01-01

239

Study of the structure, energetics, and vibrational properties of small ammonia clusters (NH3)n (n = 2-5) using correlated ab initio methods.  

PubMed

Equilibrium geometries, interaction energies, and harmonic frequencies of (NH3)n isomers (n = 2-5) have been computed using correlated calculations (MP2) in conjunction with Dunning's aug-cc-pVXZ (X = D, T, Q) basis sets and the Counterpoise procedure. Whenever available, literature values for the binding energy and geometry of dimers and trimers agree well with our data. Low lying isomers for (NH3)4 and (NH3)5 have been found to have similar binding energies (roughly 16 and 20 kcal/mol for the tetramer and pentamer, respectively), perhaps suggesting the presence of a very smooth energy landscape. Using BSSE corrected forces or freezing the monomer structure to its gas phase geometry have been found to have only a weak impact on the energetic and structural properties of the clusters. The effect of zero-point energy (ZPE) on the relative stability of the clusters has been estimated using harmonic frequencies. The latter also highlighted the presence of vibrational fingerprints for the presence of double acceptor ammonia molecules. Many-body effects for (NH3)n isomers (n = 2-4) have been investigated to explore the possibility of building a pairwise interaction model for ammonia. In the frame of the work presented, we have found the 3-body effect to account for 10-15% of the total interaction energy, whereas the 4-body effects may be neglected as first approximation. PMID:17004733

Janeiro-Barral, Paula E; Mella, Massimo

2006-10-01

240

On the Surface Formation of NH3 and HNCO in Dark Molecular Clouds - Searching for Wöhler Synthesis in the Interstellar Medium  

NASA Astrophysics Data System (ADS)

Despite its potential to reveal the link between the formation of simple species and more complex molecules (e.g., amino acids), the nitrogen chemistry of the interstellar medium (ISM) is still poorly understood. Ammonia (NH _{3}) is one of the few nitrogen-bearing species that have been observed in interstellar ices toward young stellar objects (YSOs) and quiescent molecular clouds. The aim of the present work is to experimentally investigate surface formation routes of NH _{3} and HNCO through non-energetic surface reactions in interstellar ice analogues under fully controlled laboratory conditions and at astrochemically relevant cryogenic temperatures. This study focuses on the formation of NH _{3} and HNCO in CO-rich (non-polar) interstellar ices that simulate the CO freeze-out stage in interstellar dark cloud regions, well before thermal and energetic processing start to become predominant. Our work confirms the surface formation of ammonia through the sequential addition of three hydrogen/deuterium atoms to a single nitrogen atom at low temperature. The H/D fractionation of the formed ammonia is also shown. Furthermore, we show the surface formation of solid HNCO through the interaction of CO molecules with NH radicals - one of the intermediates in the formation of solid NH _{3}. Finally, we discuss the implications of HNCO in astrobiology, as a possible starting point for the formation of more complex prebiotic species.

Fedoseev, Gleb; Lamberts, Thanja; Linnartz, Harold; Ioppolo, Sergio; Zhao, Dongfeng

241

Quasi-classical trajectory study of the role of vibrational and translational energy in the Cl(2P) + NH3 reaction.  

PubMed

A detailed state-to-state dynamics study was performed to analyze the effects of vibrational excitation and translational energy on the dynamics of the Cl((2)P) + NH(3)(v) gas-phase reaction, effects which are connected to such issues as mode selectivity and Polanyi's rules. This reaction evolves along two deep wells in the entry and exit channels. At low and high collision energies quasi-classical trajectory calculations were performed on an analytical potential energy surface previously developed by our group, together with a simplified model surface in which the reactant well is removed to analyze the influence of this well. While at high energy the independent vibrational excitation of all NH(3)(v) modes increases the reactivity by a factor ?1.1-2.9 with respect to the vibrational ground-state, at low energy the opposite behaviour is found (factor ? 0.4-0.9). However, when the simplified model surface is used at low energy the independent vibrational excitation of all NH(3)(v) modes increases the reactivity, showing that the behaviour at low energies is a direct consequence of the existence of the reactant well. Moreover, we find that this reaction exhibits negligible mode selectivity, first because the independent excitation of the N-H symmetric and asymmetric stretch modes, which lie within 200 cm(-1) of each other, leads to reactions with similar reaction probabilities, and second because the vibrational excitation of the reactive N-H stretch mode is only partially retained in the products. For this "late transition-state" reaction, we also find that vibrational energy is more effective in driving the reaction than an equivalent amount of energy in translation, consistent with an extension of Polanyi's rules. Finally, we find that the non-reactive events, Cl((2)P)+NH(3)(v) ? Cl((2)P) + NH(3)(v'), lead to a great number of populated vibrational states in the NH(3)(v') product, even starting from the NH(3)(v = 0) vibrational ground state at low energies, which is unphysical in a quantum world. This result is interpreted on the basis of non-conservation of the ZPE per mode. PMID:22526719

Monge-Palacios, M; Corchado, J C; Espinosa-Garcia, J

2012-05-28

242

Ab initio based potential energy surface and kinetics study of the OH + NH3 hydrogen abstraction reaction  

NASA Astrophysics Data System (ADS)

A full-dimensional analytical potential energy surface (PES) for the OH + NH3 --> H2O + NH2 gas-phase reaction was developed based exclusively on high-level ab initio calculations. This reaction presents a very complicated shape with wells along the reaction path. Using a wide spectrum of properties of the reactive system (equilibrium geometries, vibrational frequencies, and relative energies of the stationary points, topology of the reaction path, and points on the reaction swath) as reference, the resulting analytical PES reproduces reasonably well the input ab initio information obtained at the coupled-cluster single double triple (CCSD(T)) = FULL/aug-cc-pVTZ//CCSD(T) = FC/cc-pVTZ single point level, which represents a severe test of the new surface. As a first application, on this analytical PES we perform an extensive kinetics study using variational transition-state theory with semiclassical transmission coefficients over a wide temperature range, 200-2000 K. The forward rate constants reproduce the experimental measurements, while the reverse ones are slightly underestimated. However, the detailed analysis of the experimental equilibrium constants (from which the reverse rate constants are obtained) permits us to conclude that the experimental reverse rate constants must be re-evaluated. Another severe test of the new surface is the analysis of the kinetic isotope effects (KIEs), which were not included in the fitting procedure. The KIEs reproduce the values obtained from ab initio calculations in the common temperature range, although unfortunately no experimental information is available for comparison.

Monge-Palacios, M.; Rangel, C.; Espinosa-Garcia, J.

2013-02-01

243

Spontaneous gradual accumulation of hexagonally-aligned nano-silica on gold nanoparticles embedded in stabilized zirconia: a pathway from catalytic to NH3-sensing performance.  

PubMed

The present study highlights the influence of nano-impurities on the catalytic/sensing performance of nano-structured Au sensing-electrodes (SEs) housed in a quartz reactor and operated at high temperature over a long period of time. The planar sensor, made from a nano-structured Au-SE on a polished-polycrystalline (pp) yttria-stabilized zirconia (YSZ) substrate exhibited initially negligible electromotive force (emf) response to each of the examined gases (CO, CH(4), C(3)H(8), C(3)H(6), NO(x) and NH(3); 400 ppm each) at 700 °C in the presence of 5 vol.% oxygen and 5 vol.% water vapor. Such a poor emf response was attributed to the excellent gas-phase oxidation/reduction ability of Au nanoparticles embedded in the YSZ substrate at high temperature. The response of the planar sensor made up of nano-structured Au-SE was monitored for about 75 days at 700 °C. As a result of this long-term monitoring, we detected the appearance of highly sensitive and selective NH(3) gas-sensing properties after 45-75 days of sensor operation. Detailed observation of the morphology and composition of the as-fabricated nano-structured Au-SE after 75 days operation at 700 °C revealed the gradual accumulation of hexagonally-aligned SiO(2) nano-impurities on the surface of the Au nanoparticles. The NH(3) sensing mechanism of the YSZ-based sensor using the spontaneously-formed composite (nano-Au + nano-SiO(2))-SE is therefore proposed to be based on a strong acid-base interaction between gaseous NH(3) and SiO(2) nano-impurities, followed by spillover of adsorbed NH(3) towards the nano-Au/pp-YSZ interface. PMID:21494733

Plashnitsa, Vladimir V; Elumalai, Perumal; Fujio, Yuki; Kawaguchi, Toshikazu; Miura, Norio

2011-05-01

244

Adsorption, Desorption, and Diffusion of Nitrogen in a Model Nanoporous Material: I. Surface Limited Desorption Kinetics in Amorphous Solid Water  

SciTech Connect

The adsorption and desorption kinetics of N2 on porous amorphous solid water (ASW) films were studied using molecular beam techniques, temperature programmed desorption (TPD), and reflection-absorption infrared spectroscopy (RAIRS). The ASW films were grown on Pt(111) at 23 K by ballistic deposition from a collimated H2O beam at various incident angles to control the film porosity. The experimental results show that the N2 condensation coefficient is essentially unity until near saturation, independent of the ASW film thickness. This means that N2 transport within the porous films is rapid. The TPD results show that the desorption of a fixed dose of N2 shifts to higher temperature with ASW film thickness. Kinetic analysis of the TPD spectra shows that a film thickness rescaling of the coverage dependent activation energy curve results in a single master curve. Simulation of the TPD spectra using this master curve results in a quantitative fit to the experiments over a wide range of ASW thicknesses (up to 1000 layers, ~0.5 mm). The success of the rescaling model indicates that N2 transport within the porous film is rapid enough to maintain a uniform distribution throughout the film on a time scale faster than desorption.

Zubkov, Tykhon; Smith, R. Scott; Engstrom, Todd R.; Kay, Bruce D.

2007-11-14

245

Nanostructured Pt(NH(3))(4)Cl(2)/SiO(2) for nanomedicine: catalytic degradation of DNA in cancer cells.  

PubMed

In vivo suppression of glioblastoma multiforme (GBM) in Wistar rats using silica-shelled biocatalytic Pt(NH(3))(4)Cl(2) nanoparticles is reported. These nanoparticles were synthesized by a sol-gel technique and characterized by SEM and HRTEM imaging. We confirmed morphological uniformity (30 nm) and surface acidity of the nanoparticles, respectively, by TEM imaging and FTIR spectral analysis. Interestingly, treatment of Wistar rats intraperitoneally inoculated with C(6) cells using the biocatalysts resulted in considerable tumor shrinkage. Efficiency of the biocatalyst to shrink a tumor is superior to that by the commercial cytotoxic agent cisplatin. The tumor suppression property of Pt(NH(3))(4)Cl(2) nanoparticles is attributed to catalytic damage of DNA in C(6) cells. PMID:22110876

López, Tessy; Islas, Emma Ortíz; Alvarez Lemus, Mayra A; González, Richard Donald

2011-01-01

246

Enhanced NH3 gas sensing properties of a QCM sensor by increasing the length of vertically orientated ZnO nanorods  

NASA Astrophysics Data System (ADS)

Vertically aligned ZnO nanorods were directly synthesised on a gold electrode of quartz crystal microbalance (QCM) by a simple low-temperature hydrothermal method for a NH3 gas sensing application. The length of vertically aligned ZnO nanorods was increased to purpose enhancement in the gas sensing response of the sensor. The length of ZnO nanorods increased with an increase in growth time. The growth time of ZnO nanorods was systematically varied in the range of 1-4 h to examine the effect of the length of the ZnO nanorods on the gas sensing properties of the fabricated sensors. The gas sensing properties of sensors with different ZnO nanorods lengths was examined at room temperature for various concentrations of NH3 (50-800 ppm) in synthetic air. Enhancement in gas sensing response by increasing the length of ZnO nanorods was observed.

Minh, Vu Anh; Tuan, Le Anh; Huy, Tran Quang; Hung, Vu Ngoc; Quy, Nguyen Van

2013-01-01

247

Long-range balanced electron- and hole-transport lengths in organic-inorganic CH3NH3PbI3.  

PubMed

Low-temperature solution-processed photovoltaics suffer from low efficiencies because of poor exciton or electron-hole diffusion lengths (typically about 10 nanometers). Recent reports of highly efficient CH3NH3PbI3-based solar cells in a broad range of configurations raise a compelling case for understanding the fundamental photophysical mechanisms in these materials. By applying femtosecond transient optical spectroscopy to bilayers that interface this perovskite with either selective-electron or selective-hole extraction materials, we have uncovered concrete evidence of balanced long-range electron-hole diffusion lengths of at least 100 nanometers in solution-processed CH3NH3PbI3. The high photoconversion efficiencies of these systems stem from the comparable optical absorption length and charge-carrier diffusion lengths, transcending the traditional constraints of solution-processed semiconductors. PMID:24136965

Xing, Guichuan; Mathews, Nripan; Sun, Shuangyong; Lim, Swee Sien; Lam, Yeng Ming; Grätzel, Michael; Mhaisalkar, Subodh; Sum, Tze Chien

2013-10-18

248

Photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 in the VUV region  

NASA Technical Reports Server (NTRS)

Using synchrotron radiation as a continuum light source, the photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 have been measured from their respective ionization thresholds to 1060 A. The vibrational constants associated with the nu(2) totally symmetric, out-of-plane bending vibration of the ground electronic state of PH3(+) have been obtained. The cross sections and quantum yields for producing neutral products through photoexcitation of these molecules in the given spectral regions have also been determined. In the present work, autoionization processes were found to be less important than dissociation and predissociation processes in NH3, PH3, and C2H4. Several experimental techniques have been employed in order to examine the various possible systematic errors critically.

Xia, T. J.; Chien, T. S.; Wu, C. Y. Robert; Judge, D. L.

1991-01-01

249

Applications of tunable diode laser spectroscopy for the detection of exhaled endogenous gases: CO, NH3, CH4, N20, and CO2  

NASA Astrophysics Data System (ADS)

Tunable diode laser spectroscopy (TDLS) is proposed for content measurements of trace gases like CO, carbon-dioxide, NH3, CH4, NO, NO2 in human and animal's exhalation. High sensitivity and wide dynamic range of the method ensure fast detection of these gases at ppb level and within the accuracy better than 10%. One-expiration sample is enough to reach these parameters. There is no need for any preliminary preparations of tested samples. Some pairs of the gases, for instance, CO and carbon-dioxide, NH3 and carbon- dioxide, or CO and nitrous oxide, can be measured simultaneously by one laser providing complex studies. The high sensitive gas analysis could provide necessary background to the noninvasive diagnostics in a wide variety of medical problems. Perspectives of the TDLS methods in application to medicine diagnostics are demonstrated by the first results of exhalation tests.

Kouznetsov, Andrian I.; Stepanov, Eugene V.

1996-04-01

250

Pure and Sn, Ga and Mn-doped ZnO gas sensors working at different temperatures for formaldehyde, humidity, NH 3 , toluene and CO  

Microsoft Academic Search

ZnO and Sn-, Ga- and Mn-doped ZnO nanoparticles were prepared by a coprecipitation method, and characterized by scanning electron\\u000a microscopy (SEM), energy dispersive spectra (EDS), X-ray diffraction (XRD) and Raman spectra. The gas sensing properties were\\u000a studied using formaldehyde, relative humidity, NH3, toluene and CO as the probes. The results show that all particles have wurtzite ZnO phase, though Sn–ZnO

Ning Han; Haidi Liu; Xiaofeng Wu; Dongyan Li; Linyu Chai; Yunfa Chen

2011-01-01

251

First detection of NH3 (10 -> 00) from a low mass cloud core. On the low ammonia abundance of the rho Oph A core  

Microsoft Academic Search

Odin has successfully observed the molecular core rho Oph A in the 572.5 GHz rotational ground state line of ammonia, NH3 (JK = 10 -> 00). The interpretation of this result makes use of complementary molecular line data obtained from the ground (C17O and CH3OH) as part of the Odin preparatory work. Comparison of these observations with theoretical model calculations

R. Liseau; B. Larsson; A. Brandeker; P. Bergman; P. Bernath; J. H. Black; R. Booth; V. Buat; C. Curry; P. Encrenaz; E. Falgarone; P. Feldman; M. Fich; H. Florén; U. Frisk; M. Gerin; E. Gregersen; J. Harju; T. Hasegawa; Å. Hjalmarson; L. Johansson; S. Kwok; A. Lecacheux; T. Liljeström; K. Mattila; G. Mitchell; L. Nordh; M. Olberg; G. Olofsson; L. Pagani; R. Plume; I. Ristorcelli; Aa. Sandqvist; F. v. Schéele; G. Serra; N. Tothill; K. Volk; C. Wilson

2003-01-01

252

Full Printable Processed Mesoscopic CH3NH3PbI3/TiO2 Heterojunction Solar Cells with Carbon Counter Electrode  

NASA Astrophysics Data System (ADS)

A mesoscopic methylammonium lead iodide (CH3NH3PbI3) perovskite/TiO2 heterojunction solar cell is developed with low-cost carbon counter electrode (CE) and full printable process. With carbon black/spheroidal graphite CE, this mesoscopic heterojunction solar cell presents high stability and power conversion efficiency of 6.64%, which is higher than that of the flaky graphite based device and comparable to the conventional Au version.

Ku, Zhiliang; Rong, Yaoguang; Xu, Mi; Liu, Tongfa; Han, Hongwei

2013-11-01

253

Air Pollution Grant Ideas Possible air pollutants to study: SO2, H2S, NO2, NH3, CO, CO2, O3.  

E-print Network

Air Pollution Grant Ideas Possible air pollutants to study: SO2, H2S, NO2, NH3, CO, CO2, O3 to the formation of ground-level ozone, and fine particle pollution, NO2 is linked with a number of adverse effects) not currently easy to find and buy in USA, simple plastic tube, cap and steel mesh. (ii) Chemical education side

Short, Daniel

254

Formation of Graphitic-C3N4 and ?-C3N4 Fine Particles by DC Arc Discharge in NH3 Gas  

NASA Astrophysics Data System (ADS)

Graphitic-C3N4 (AAA stacking mode) and ?-C3N4 fine particles were successfully formed by dc arc discharge in NH3 gas. Synthesized particles were studied by transmission electron microscopy. Graphitic-C3N4 particles were observed on the graphite or independently in a dispersed state on the collodion film, with an average diameter of 15 nm. ?-C3N4 fine particles were observed in a coagulated form with an average diameter of 30 nm.

Okazaki, Tsugio; Tosaka, Kazuo

2005-11-01

255

Nickel oxide electrode interlayer in CH3 NH3 PbI3 perovskite/PCBM planar-heterojunction hybrid solar cells.  

PubMed

This study successfully demonstrates the application of inorganic p-type nickel oxide (NiOx ) as electrode interlayer for the fabrication of NiOx /CH3 NH3 PbI3 perovskite/PCBM PHJ hybrid solar cells with a respectable solar-to-electrical PCE of 7.8%. The better energy level alignment and improved wetting of the NiOx electrode interlayer significantly enhance the overall photovoltaic performance. PMID:24687334

Jeng, Jun-Yuan; Chen, Kuo-Cheng; Chiang, Tsung-Yu; Lin, Pei-Ying; Tsai, Tzung-Da; Chang, Yun-Chorng; Guo, Tzung-Fang; Chen, Peter; Wen, Ten-Chin; Hsu, Yao-Jane

2014-06-25

256

Dielectric Properties of the (CH3NH3)5Bi2(1- x)Sb2xCl11 Mixed Crystals  

NASA Astrophysics Data System (ADS)

The (CH3NH3)5Bi2(1-x)Sb2xCl11 crystals were examined from the point of view of their applicability in pyroelectric detectors. It was shown that they can be useful so far as the construction of infrared detectors is concerned due to high values of both their pyroelectric coefficient and figure of merit p/sqrt? which are both comparable with those of triglycine sulphate crystals.

Mróz, J.; Dziedzic, J.; Pykacz, H.

2006-10-01

257

INTERACTION OF LASER RADIATION WITH MATTER: IR multiphoton dissociation of trichlorosilane induced by pulsed CO2 and NH3 laser radiation  

Microsoft Academic Search

The IR multiphoton dissociation of trichlorosilane (SiHCl3) molecules irradiated by pulses from CO2 and NH3 lasers is studied. The dependences of dissociation yield on the frequency and energy density of laser radiation, as well as on the parent pressure of SiHCl3, are determined. It is found that HCl and a solid precipitate, probably with a common chemical formula (SiCl2)n, are

V. M. Apatin; Vladimir B. Laptev; Evgenii A. Ryabov

2003-01-01

258

Regulation of Nitrification by Benzotriazole, oNitrophenol, m-Nitroaniline and Dicyandiamide and Pattern of NH3 Emissions from Citronella Field Fertilized with Urea  

Microsoft Academic Search

Nitrification inhibitors areuseful for reducing fertilizer related environmentalpollution. Use of such nitrification inhibitors as,benzotriazole, o-nitrophenol, m-nitroaniline anddicyandiamide has effectively regulated nitrification in acitronella (Cymbopogon winterianus Jowitt.) fieldfertilized with urea. At 450 kg N ha-1 yr-1, there wassubstantially higher accumulation of NH+4-N in thesoil. Proper placement (5 cm below soil surface) offertilizers have minimized NH3 emissions even fromnitrification inhibitor treated urea

K. Puttanna; N. M. Nanje Gowda; E. V. S. Prakasa Rao

2001-01-01

259

Determination of the uptake of [Pt(NH 3) 4](NO 3) 2 by grass cultivated on a sandy loam soil and by cucumber plants, grown hydroponically  

Microsoft Academic Search

Two cultivation experiments were carried out in order to answer the question to what extent platinum can enter the food chain by accumulation in plants, when the platinum is present in a bio-available form: (i) cucumber plants (Cucumis sativus) were grown hydroponically in nutrient solutions containing [Pt(NH3)4](NO3)2 (from 0.5 to 50 ?g Pt\\/l solution); and (ii) a water-soluble platinum compound

Dominique Verstraete; Jörgen Riondato; Jordy Vercauteren; Frank Vanhaecke; Luc Moens; Richard Dams; Marc Verloo

1998-01-01

260

Spin–Lattice Relaxation in Dilute Gases. III. 1H Relaxation in NH3 and 19F Relaxation in BF3  

Microsoft Academic Search

Spin–lattice relaxation times have been measured for the protons in gaseous NH3 and for the fluorine nuclei in gaseous BF3 as a function of temperature and pressure in the dilute gas region. The measured temperature dependences are as predicted for relaxation resulting from a spin–rotation interaction. Cross sections for the relaxation are calculated and from them it is deduced that

R. L. Armstrong; T. A. J. HANRAIIANt

1968-01-01

261

CALCULS DES PROPRIETÉS THERMODYNAMIQUES ET DE TRANSPORT DES PLASMAS Ar-N2 ET Ar-NH3 À LA PRESSION ATMOSPH~RIQUE  

Microsoft Academic Search

RESUME: Les propriétés thermodynamiques et de transport de mélanges Ai-N2 et Ai-NH3 pour la synthèse de nitrure d'aluminium par arc transféré plasma sont calculées. Dans le cas de vapeur d'aluminium métallique en présence de plasma d'azote ou d'ammoniac, une approche thermodynamique donne les conditions de composition initiale et de température qui conduisent à de bonnes conditions expérimentales pour la réaction

M.-F. ELCHINGER; B. PATEYRON; G. DELLUC; P. FAUCHAIS

262

A novel model to predict the physical state of atmospheric H2SO4\\/NH3\\/H2O aerosol particles  

Microsoft Academic Search

The physical state of the tropospheric aerosol is largely unknown despite its importance for cloud formation and for the aerosol's radiative properties. Here we use detailed microphysical laboratory measurements to perform a systematic global modelling study of the physical state of the H2SO4\\/NH3\\/H2O aerosol, which constitutes an important class of aerosols in the free troposphere. The Aerosol Physical State Model

C. A. Colberg; B. P. Luo; H. Wernli; T. Koop; Th. Peter

2003-01-01

263

A novel model to predict the physical state of atmospheric H2SO4\\/NH3\\/H2O aerosol particles  

Microsoft Academic Search

The physical state of tropospheric aerosol particles is largely unknown despite its importance for cloud formation and for the aerosols' radiative properties. Here we show the first systematic global modelling study of the physical state of the H2SO4\\/NH3\\/H2O aerosol, which constitutes an important class of aerosols in the free troposphere. The Aerosol Physical State Model (APSM) developed here is based

C. A. Colberg; B. P. Luo; H. Wernli; T. Koop; Th. Peter

2002-01-01

264

An ambient experimental study of phase equilibrium in the atmospheric system: Aerosol H +, NH 4+, SO 2-4, NO 3--NH 3(g), HNO 3(g)  

NASA Astrophysics Data System (ADS)

A major simplification in the quantitative modeling of the atmospheric impact of the major aerosol and gaseous sulfur and nitrogen compounds would result from demonstration of phase equilibrium between the gases NH 3, HNO 3 and the appropriate aerosol-phase ionic or molecular species in the ambient atmosphere. The phase diagram of the (NH 4) 2SO 4-H 2SO 4-H 2O and NH 4NO 3-H 2O systems have been recently refined by experimental measurements and preliminary calculations of the mixed nitrate-sulfate system have also been made. Experiments to test the applicability of existing phase equilibria considerations to the ambient atmosphere have been designed and conducted based on newly devised techniques for continuous determination of gaseous NH 3 with time resolution < 5 min and unambiguous speciation of nitric acid and aerosol nitrate with time resolution of ~ 15 min. Preliminary results suggest that during a daytime period with aerosol composition approximating a letovicite-NH 4NO 3 mixture, observed products of NH 3 (g) and HNO 3(g) concentrations agreed very well with the equilibrium constant calculated for the ammonium nitrate-NH 3(g), HNO 3(g) equilibrium. During a night-time period, the predicted ammonia concentrations, based on bulk aerosol composition data, were much lower and nitric acid concentrations much higher, respectively, than the observed values. The error sources in the measured and calculated values do not appear to account for the apparent deviations from gas-phase concentrations based on the droplet-pH controlling bisulfate-sulfate equilibrium.

Tanner, Roger L.

265

Internal rotation and halogen bonds in CF3I···NH3 and CF3I···N(CH3)3 probed by broadband rotational spectroscopy.  

PubMed

The rotational spectra of CF(3)I···NH(3) and CF(3)I···N(CH(3))(3) are measured between 6.7 and 18 GHz using a chirped-pulse Fourier transform microwave spectrometer. Transitions in each spectrum are assigned to A and E species associated with ground and excited internal rotor states respectively. Rotational constants, B(0), centrifugal distortion constants, D(J), D(Jm), D(JKm), nuclear quadrupole coupling constants of the (14)N and (127)I atoms, ?(aa)(N) and ?(aa)(I), are determined for each complex. D(JK) is additionally determined for CF(3)I···NH(3). Results are presented for both (14)N and (15)N-substituted isotopologues. All data are consistent with C(3v) symmetric top structures for both complexes. The nuclear quadrupole coupling constants of iodine are determined to be -2230.030(83) MHz and -2241.61(17) MHz in CF(3)I···(14)NH(3) and CF(3)I···(14)N(CH(3))(3) respectively. The data are interpreted through a model that accounts for the internal dynamics of the complexes in order to determine the length of the halogen bond between the iodine and nitrogen atoms, r(N···I). Values of r(N···I) are thus determined to lie in the ranges 3.054 Å > r(N···I) > 3.034 Å and 2.790 Å > r(N···I) > 2.769 Å for CF(3)I···NH(3) and CF(3)I···N(CH(3))(3) respectively. PMID:21997343

Stephens, Susanna L; Walker, Nicholas R; Legon, Anthony C

2011-12-14

266

Full Printable Processed Mesoscopic CH3NH3PbI3/TiO2 Heterojunction Solar Cells with Carbon Counter Electrode  

PubMed Central

A mesoscopic methylammonium lead iodide (CH3NH3PbI3) perovskite/TiO2 heterojunction solar cell is developed with low-cost carbon counter electrode (CE) and full printable process. With carbon black/spheroidal graphite CE, this mesoscopic heterojunction solar cell presents high stability and power conversion efficiency of 6.64%, which is higher than that of the flaky graphite based device and comparable to the conventional Au version. PMID:24185501

Ku, Zhiliang; Rong, Yaoguang; Xu, Mi; Liu, Tongfa; Han, Hongwei

2013-01-01

267

Applications of tunable diode laser spectroscopy for the detection of exhaled endogenous gases: CO, NH3, CH4, N20, and CO2  

Microsoft Academic Search

Tunable diode laser spectroscopy (TDLS) is proposed for content measurements of trace gases like CO, carbon-dioxide, NH3, CH4, NO, NO2 in human and animal's exhalation. High sensitivity and wide dynamic range of the method ensure fast detection of these gases at ppb level and within the accuracy better than 10%. One-expiration sample is enough to reach these parameters. There is

Andrian I. Kouznetsov; Eugene V. Stepanov

1996-01-01

268

Efficient perovskite solar cells based on low-temperature solution-processed (CH3NH3)PbI3 perovskite/CuInS2 planar heterojunctions  

PubMed Central

In this work, the solution-processed CH3NH3PbI3 perovskite/copper indium disulfide (CuInS2) planar heterojunction solar cells with Al2O3 as a scaffold were fabricated at a temperature as low as 250°C for the first time, in which the indium tin oxide (ITO)-coated glass instead of the fluorine-doped tin oxide (FTO)-coated glass was used as the light-incidence electrode and the solution-processed CuInS2 layer was prepared to replace the commonly used TiO2 layer in previously reported perovskite-based solar cells. The influence of the thickness of the as-prepared CuInS2 film on the performance of the ITO/CuInS2(n)/Al2O3/(CH3NH3)PbI3/Ag cells was investigated. The ITO/CuInS2(2)/Al2O3/(CH3NH3)PbI3/Ag cell showed the best performance and achieved power conversion efficiency up to 5.30%. PMID:25278818

2014-01-01

269

Synthesis, characterization and application of Y3Fe5O12 nanocatalyst for green production of NH3 using magnetic induction method (MIM)  

NASA Astrophysics Data System (ADS)

Y3Fe5O12 (YIG) was prepared through sol-gel technique and sintered at three different temperatures (1000-1200?C). Various characterizations on the morphological and structural properties of produced YIG have been done as to understand the potential of this unique magnetic type nanomaterial to be used in the catalyst application for ammonia synthesis at ambient or green production environment. YIG catalyst exposed under magnetic induction of 0.1 T produced about 242.56?mol/h.g-cat yield of ammonia (NH3) at freezing reaction temperature of 0?C. About 95.88% improvements of NH3 yield is produced in comparison with the absence of magnetic induction reaction condition (10?mol/h.g-cat). Synthesis at 25?C yielded reduction about 0.90% lower than the synthesis at 0?C temperature. Thus, it is proven that the temperature engaged the dominant roles in affecting the catalytic effect of YIG catalyst for NH3 production. Further parametric studies should be conducted as to explore the robustness of YIG catalyst for new route of ammonia production until the commercial scale-up could be achieved.

Razak, Jeefferie Abd; Sufian, Suriati; Ku Shaari, Ku Zilati; Puspitasari, Poppy; Hoe, Tshai Kim; Yahya, Noorhana

2012-09-01

270

First detection of NH3 (10 -> 00) from a low mass cloud core. On the low ammonia abundance of the rho Oph A core  

NASA Astrophysics Data System (ADS)

Odin has successfully observed the molecular core rho Oph A in the 572.5 GHz rotational ground state line of ammonia, NH3 (JK = 10 -> 00). The interpretation of this result makes use of complementary molecular line data obtained from the ground (C17O and CH3OH) as part of the Odin preparatory work. Comparison of these observations with theoretical model calculations of line excitation and transfer yields a quite ordinary abundance of methanol, X(CH3OH)= 3 x 10-9. Unless NH3 is not entirely segregated from C17O and CH3OH, ammonia is found to be significantly underabundant with respect to typical dense core values, viz. X(NH3) = 8 x 10-10. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation has been the industrial prime contractor. and based on observations collected with the Swedish ESO Submillimeter Telescope, SEST, in La Silla, Chile.

Liseau, R.; Larsson, B.; Brandeker, A.; Bergman, P.; Bernath, P.; Black, J. H.; Booth, R.; Buat, V.; Curry, C.; Encrenaz, P.; Falgarone, E.; Feldman, P.; Fich, M.; Florén, H.; Frisk, U.; Gerin, M.; Gregersen, E.; Harju, J.; Hasegawa, T.; Hjalmarson, Å.; Johansson, L.; Kwok, S.; Lecacheux, A.; Liljeström, T.; Mattila, K.; Mitchell, G.; Nordh, L.; Olberg, M.; Olofsson, G.; Pagani, L.; Plume, R.; Ristorcelli, I.; Sandqvist, Aa.; Schéele, F. v.; Serra, G.; Tothill, N.; Volk, K.; Wilson, C.

2003-05-01

271

Efficient perovskite solar cells based on low-temperature solution-processed (CH3NH3)PbI3 perovskite/CuInS2 planar heterojunctions.  

PubMed

In this work, the solution-processed CH3NH3PbI3 perovskite/copper indium disulfide (CuInS2) planar heterojunction solar cells with Al2O3 as a scaffold were fabricated at a temperature as low as 250°C for the first time, in which the indium tin oxide (ITO)-coated glass instead of the fluorine-doped tin oxide (FTO)-coated glass was used as the light-incidence electrode and the solution-processed CuInS2 layer was prepared to replace the commonly used TiO2 layer in previously reported perovskite-based solar cells. The influence of the thickness of the as-prepared CuInS2 film on the performance of the ITO/CuInS2(n)/Al2O3/(CH3NH3)PbI3/Ag cells was investigated. The ITO/CuInS2(2)/Al2O3/(CH3NH3)PbI3/Ag cell showed the best performance and achieved power conversion efficiency up to 5.30%. PMID:25278818

Chen, Chong; Li, Chunxi; Li, Fumin; Wu, Fan; Tan, Furui; Zhai, Yong; Zhang, Weifeng

2014-01-01

272

Mechanism of N2O formation during the low-temperature selective catalytic reduction of NO with NH3 over Mn-Fe spinel.  

PubMed

The mechanism of N2O formation during the low-temperature selective catalytic reduction reaction (SCR) over Mn-Fe spinel was studied. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and transient reaction studies demonstrated that the Eley-Rideal mechanism (i.e., the reaction of adsorbed NH3 species with gaseous NO) and the Langmuir-Hinshelwood mechanism (i.e., the reaction of adsorbed NH3 species with adsorbed NOx species) both contributed to N2O formation. However, N2O selectivity of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism was much less than that through the Eley-Rideal mechanism. The ratio of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism remarkably increased; therefore, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the decrease of the gas hourly space velocity (GHSV). As the gaseous NH3 concentration increased, N2O selectivity of NO reduction over Mn-Fe spinel increased because of the promotion of NO reduction through the Eley-Rideal mechanism. Meanwhile, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the increase of the gaseous NO concentration because the formation of NH on Mn-Fe spinel was restrained. Therefore, N2O selectivity of NO reduction over Mn-Fe spinel was related to the GHSV and concentrations of reactants. PMID:25105802

Yang, Shijian; Xiong, Shangchao; Liao, Yong; Xiao, Xin; Qi, Feihong; Peng, Yue; Fu, Yuwu; Shan, Wenpo; Li, Junhua

2014-09-01

273

Interstellar ice analogs: band strengths of H$_2$O, CO$_2$, CH$_3$OH, and NH$_3$ in the far-infrared region  

E-print Network

We measure the band strengths in the far-infrared region of interstellar ice analogs of astrophysically relevant species, such as H$_2$O, CO$_2$, CH$_3$OH, and NH$_3$, deposited at low temperature (8-10 $\\mathrm{K}$), followed by warm-up, to induce amorphous-crystalline phase transitions when relevant. The spectra of pure H$_2$O, NH$_3$, and CH$_3$OH ices have been measured in the near-, mid- and far-infrared spectroscopic regions using the Interstellar Astrochemistry Chamber (ISAC) ultra-high-vacuum setup. In addition, far-infrared spectra of NH$_3$ and CO$_2$ were measured using a different set-up equipped with a bolometer detector. Band strengths in the far-infrared region were estimated using the corresponding near- and mid-infrared values as a reference. We also performed theoretical calculations of the amorphous and crystalline structures of these molecules using solid state computational programs at density functional theory (DFT) level. Vibrational assignment and mode intensities for these ices were p...

Giuliano, B M; Martín-Doménech, R; Dartois, E; Caro, G M Muñoz

2014-01-01

274

Kinetics of absorption and transformation of CO2 to Nesquehonite in the Mg-NH3 system  

NASA Astrophysics Data System (ADS)

Mineral sequestration of CO2 is one of the safer options in the portfolio of available Carbon Storage and Sequestration (CCS) stratagems. To date, numerous efforts were made to optimize the absorption of CO2 using various media. For example, Satoshi K et al. proposed a pH-swing CO2 mineralization process recycling ammonium chloride to lower the costs of the operation. However, few studies have concerned CO2 absorption kinetics under low CO2 partial pressure. Such lacks of knowledge of absorption rate makes it difficult to estimate the scale and cost of absorption devices and to determine the quantity of stock material supply in industrial settings. The purpose of this research is to investigate the rate and kinetic controlling factors for CO2 absorption and mineralization in MgCl2-NH3 solutions. CO2 absorption experiments were carried out at 298 K in solutions of different compositions (0.05~0.2molL-1 MgCl2) to measure the reaction kinetics using a wetted wall column setup similar to those reported in Pacheco (1998) and Victor (2011). The solution chemistry was maintained at conditions where brucite precipitation was not allowed. The absorption solution was then cycled between the column and a jacked glass reactor with its pH maintained constant, and the transmittance at 546 nm was monitored in real-time. Magnesium concentration was analyzed by ICP-AES with interval sampling. Preliminary results indicate that initial concentration of Mg in solution has little effect on CO2 absorption. Although CO2 absorption rate increased slightly over time with increasing ammonia addition, pH appeared to be the dominant controlling factor. The higher the solution pH was, the faster the absorption rate increased. Upon reaching saturation, nesquehonite precipitated to lower the transmittance, leading to rapid addition of aqueous ammonia. However, precipitation of nesquehonite unexpectedly showed little influence on CO2 absorption, suggesting that the interaction between aqueous CO2 and OH- or ammonium ions in liquid film may be the rate limit step during the absorption process, further implying that the gas-liquid interaction barrier should be treated seriously in order to optimize CO2 capture efficiency. Due to the low gas-liquid reaction area (0.005 m2L-1), it takes long time (2~3 hours) to dissolve enough CO2 for nesquehonite to reach supersaturation. The typical absorption rates under these experimental conditions are between 0.000668 mol s-1m-2 (pH=8.74, pCO2= 15495Pa, 298K) and 0.001997 mol s-1m-2 (pH=9.16, pCO2= 15403Pa, 298K).; Schematic diagram for the CO2 absorption system

Zhu, C.; Zhao, L.; Ji, J.; Jun, C.; Teng, H.

2012-12-01

275

High-pressure temperature-programmed reduction of sulfided catalysts  

SciTech Connect

Temperature-programmed reduction (TPR) of solids materials is a widely used technique of characterization in heterogeneous catalysis. So far all studies dealing with this technique have been carried out at ambient or subambient pressure. Because most catalytic processes are performed at higher hydrogen pressures, the impact of this technique could be enhanced by the development of a new generation of equipment working under conditions approaching those used in reality. This work describes a new experimental temperature-programmed reduction set-up working at hydrogen pressures above 1 atm. Basic hydrodynamic considerations have been employed for correcting the signal from the variations of the residence time distribution of the molecules in the reactor. Model and industrial sulfide catalysts were studied at various pressures. When the raw signals are suitably corrected, it appears that the hydrogen pressure does not influence the TPR patterns. 25 refs., 7 figs.

Labruyere, F.; Lacroix, M.; Breysse, M. [Institut de Recherches sur la Catalyse, Villeurbanne (France)] [and others] [Institut de Recherches sur la Catalyse, Villeurbanne (France); and others

1997-04-15

276

Ammonia emissions in the United States, European Union, and China derived by high-resolution inversion of ammonium wet deposition data: Interpretation with a new agricultural emissions inventory (MASAGE_NH3)  

NASA Astrophysics Data System (ADS)

We use the adjoint of a global 3-D chemical transport model (GEOS-Chem) to optimize ammonia (NH3) emissions in the U.S., European Union, and China by inversion of 2005-2008 network data for NH4+ wet deposition fluxes. Optimized emissions are derived on a 2° × 2.5° grid for individual months and years. Error characterization in the optimization includes model errors in precipitation. Annual optimized emissions are 2.8 Tg NH3-N a-1 for the contiguous U.S., 3.1 Tg NH3-N a-1 for the European Union, and 8.4 Tg NH3-N a-1 for China. Comparisons to previous inventories for the U.S. and European Union show consistency (˜±15%) in annual totals but some large spatial and seasonal differences. We develop a new global bottom-up inventory of NH3 emissions (Magnitude And Seasonality of Agricultural Emissions model for NH3 (MASAGE_NH3)) to interpret the results of the adjoint optimization. MASAGE_NH3 provides information on the magnitude and seasonality of NH3 emissions from individual crop and livestock sources on a 0.5° × 0.5° grid. We find that U.S. emissions peak in the spring in the Midwest due to corn fertilization and in the summer elsewhere due to manure. The seasonality of European emissions is more homogeneous with a well-defined maximum in spring associated with manure and mineral fertilizer application. There is some evidence for the effect of European regulations of NH3 emissions, notably a large fall decrease in northern Europe. Emissions in China peak in summer because of the summertime application of fertilizer for double cropping.

Paulot, F.; Jacob, D. J.; Pinder, R. W.; Bash, J. O.; Travis, K.; Henze, D. K.

2014-04-01

277

Dry deposition of nitrogen compounds (NO2, HNO3, NH3), sulfur dioxide and ozone in west and central African ecosystems using the inferential method  

NASA Astrophysics Data System (ADS)

This work is part of the IDAF program (IGAC-DEBITS-AFRICA) and is based on the long-term monitoring of gas concentrations (1998-2007) established at seven remote sites representative of major African ecosystems. Dry deposition fluxes were estimated by the inferential method using on the one hand surface measurements of gas concentrations (NO2, HNO3, NH3, SO2 and O3) and on the other hand modeled exchange rates. Dry deposition velocities (Vd) were calculated using the big-leaf model of Zhang et al. (2003b). The bidirectional approach is used for NH3 surface-atmosphere exchange (Zhang et al., 2010). Surface and meteorological conditions specific to IDAF sites have been used in the models of deposition. The seasonal and annual mean variations of gaseous dry deposition fluxes (NO2, HNO3, NH3, O3 and SO2) are analyzed. Along the latitudinal transect of ecosystems, the annual mean dry deposition fluxes of nitrogen compounds range from -0.4 to -0.8 kg N ha-1 yr-1 for NO2, from -0.7 to -1.0 kg N ha-1 yr-1 for HNO3 and from -0.7 to -8.3 kg N ha-1 yr-1 for NH3 over the study period (1998-2007). The total nitrogen dry deposition flux (NO2+HNO3+NH3) is more important in forests (-10 kg N ha-1 yr-1) than in wet and dry savannas (-1.6 to -3.9 kg N ha-1 yr-1). The annual mean dry deposition fluxes of ozone range between -11 and -19 kg ha-1 yr-1 in dry and wet savannas, and -11 and -13 kg ha-1 yr-1 in forests. Lowest O3 dry deposition fluxes in forests are correlated to low measured O3 concentrations, lower by a factor of 2-3, compared to other ecosystems. Along the ecosystem transect, the annual mean of SO2 dry deposition fluxes presents low values and a small variability (-0.5 to -1 kg S ha-1 yr-1). No specific trend in the interannual variability of these gaseous dry deposition fluxes is observed over the study period.

Adon, M.; Galy-Lacaux, C.; Delon, C.; Yoboue, V.; Solmon, F.; Kaptue Tchuente, A. T.

2013-11-01

278

G-G base-pairing in nucleobase adducts of the anticancer drug cis-[PtCl2(NH3)(2-picoline)] and its trans isomer.  

PubMed

cis-[PtCl2(NH3)(2-picoline)] (AMD473) is a sterically-hindered anticancer complex with a profile of chemical and biological activity that differs significantly from that of cisplatin. Adducts of AMD473 with neutral 9-ethylguanine (9-EtGH) and anionic (N1-deprotonated) 9-ethylguanine (9-EtG) as perchlorate and nitrate salts, and also a nitrate salt of the trans isomer (AMD443), were prepared and their structures determined by X-ray crystallography: cis-[Pt(NH3)(2-pic)(9-EtGH)2](ClO4)2 (1).2H(2)OMe(2)CO, cis-[Pt(NH3)(2-pic)(9-EtGH)2](NO3)2 (2).2H2O, cis-[Pt(NH3)(2-pic)(9-EtGH)(9-EtG)]NO3 (3),3.5 H2O, trans-[Pt(NH3)(2-pic)(9-EtGH)(9-EtG)]NO3 (4).8H2O. In all cases, platinum coordination is through N7 of neutral (1, 2) and anionic (3, 4) guanine. In each complex, the guanine bases are arranged in the head-to-tail conformation. In complex 1, there is an infinite array of six-molecule cycles, based on both hydrogen bonding and pi-pi stacking of the 2-picoline and guanine rings. Platinum(II) coordinated at N7 acidifies the N1 proton of neutral 9-ethylguanine (pKa = 9.57) to give pKa1 = 8.40 and pKa2 = 8.75 for complex 2, and pKa1 = 7.77 and pKa2 = 9.00 for complex 4. In complexes 3 and 4, three intermolecular hydrogen bonds are formed between neutral and deprotonated guanine ligands involving O6, N1 and N2 sites. Unusually, both of the platinated guanine bases of complexes 3 and 4 participate in this triple G triple bond G hydrogen bonding. This is the first report of X-ray crystal structures of nucleobase adducts of the promising anticancer drug AMD473. PMID:15880542

McGowan, Geraldine; Parsons, Simon; Sadler, Peter J

2005-07-18

279

Temperature-programmed reduction and HDS activity of sulfided transition metal catalyst: Formation of nonstoichiometric sulfur  

SciTech Connect

Sulfided alumina-supported transition metal catalysts have been studied using temperature-programmed reduction (TPR). The H{sup 2} and H{sub 2}S concentrations were determined simultaneously and the major processes occurring were discriminated, namely reduction of oxidic and sulfidic species and desorption of H{sub 2}S. Because of the high maximum reduction temperature and the high hydrogen partial pressure applied, a complete description of all species was acquired, except for the Cr and Mn catalysts which could not be reduced below 1270 K. After sulfiding at 673 K, TPR of alumina-supported transition metals showed that several types of sulfur were present, viz. (i) sulfur species with a stoichiometry in agreement with bulk thermodynamics, indicated as stoichiometric sulfur, (ii) a nonstochiometric sulfur species (S{sub x}) which was present in excess of the S/Me ratio based on bulk thermodynamics (not identical to elemental sulfur since it is present after purging at 673 K), (iii) S-H groups, and (iv) adsorbed H{sub 2}S. The mechanism of S{sub x} formation is discussed. The amounts of nonstoichiometric sulfur mainly depended on the type of transition metal and the pretreatment procedure. The influence of the reducibility of the stoichiometric and nonstoichiometric sulfur species on the hydrodesulfurization activity is discussed. The results presented indicate that chemisorption measurements may depend on the pretreatment of sulfided catalysts. 26 refs., 13 figs., 4 tabs.

Mangnus, P.J.; Riezebos, A.; Langeveld, A.D. van; Moulijn, J.A. [Univ. of Asterdam (Netherlands)] [Univ. of Asterdam (Netherlands)

1995-01-01

280

Deconstructing Desorption Electrospray Ionization: Independent Optimization of Desorption and Ionization by Spray Desorption Collection  

NASA Astrophysics Data System (ADS)

Spray desorption collection (SDC) and reflective electrospray ionization (RESI) were used to independently study the desorption and ionization processes that together comprise desorption electrospray ionization (DESI). Both processes depend on several instrumental parameters, including the nebulizing gas flow rate, applied potential, and source geometries. Each of these parameters was optimized for desorption, as represented by the results obtained by SDC, and ionization, as represented by the results obtained by RESI. The optimized conditions were then compared to the optimization results for DESI. Our results confirm that optimal conditions for desorption and ionization are different and that in some cases the optimized DESI conditions are a compromise between both sets. The respective results for DESI, RESI, and SDC for each parameter were compared across the methods to draw conclusions about the contribution of each parameter to desorption and ionization separately and then combined within DESI. Our results indicate that desorption efficiency is (1) independent of the applied potential and (2) the impact zone to inlet distance, and that (3) gas pressure settings and (4) sprayer to impact zone distances above optimal for DESI are detrimental to desorption but beneficial for ionization. In addition, possible interpretations for the observed trends are presented.

Douglass, Kevin A.; Jain, Shashank; Brandt, William R.; Venter, Andre R.

2012-11-01

281

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction  

SciTech Connect

Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on the development of novel bimetallic dispersed catalysts for temperature-programmed liquefaction. The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular that can be used in low precursors concentrations (< 1 %) but exhibit high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. The major technical approaches are, first, to prepare the desired heteronuclear organometallic molecules as catalyst precursors that contain covalently bound, two different metal atoms and sulfur in a single molecule. Such precursors will generate finely dispersed bimetallic catalysts such as Fe-Mo, Co-Mo and Ni-Mo binary sulfides upon thermal decomposition. The second major technical approach is to perform the liquefaction of coals unpregnated with the organometallic precursors under temperature-programmed conditions, where the programmed heat-up serves as a step for both catalyst activation and coal pretreatment or preconversion. Two to three different complexes for each of the Fe-Mo, Co-Mo, and Ni-Mo combinations will be prepared. Initial catalyst screening tests will be conducted using a subbituminous coal and a bituminous coal. Effects of coal rank and solvents will be examined with the selected bimetallic catalysts which showed much higher activity than the dispersed catalysts from conventional precursors.

Song, Chunshan; Schobert, H.H.

1993-02-01

282

Study of the Thermal Decomposition of Some Components of Biomass by Desorption Mass Spectrometry  

NASA Astrophysics Data System (ADS)

The investigation of thermal transformations of lignin samples have been carried out using temperature programmed desorption mass spectrometry method (TPD-MS). Main stages and products of lignin pyrolysis have been identified. The first stages (Tmax = 230 °C and Tmax = 300 °C) are attributed to thermal transformations of lignin peripheral polysaccharide fragments such as hemicellulose and cellulose respectively. The second stage (Tmax = 335 °C) is associated with desorption of lignin structural elements in the molecular forms as a result of depolymerization processes of polymeric blocks of lignin. The third stage (Tmax = 370 °C) correspond to a deeper decomposition of lignin and characterized by desorption of smaller structural fragments in molecular forms (m/z = 110, pyrocatechol). Pressure-temperature curves of pyrolysis of lignin samples have been analyzed.

Palianytsia, Borys; Kulik, Tetiana; Dudik, Olesia; Cherniavska, Tetiana; Tonkha, Oksana

283

Investigating the influences of SO2 and NH3 levels on isoprene-derived secondary organic aerosol formation using conditional sampling approaches  

NASA Astrophysics Data System (ADS)

Filter-based PM2.5 samples were chemically analyzed to investigate secondary organic aerosol (SOA) formation from isoprene in a rural atmosphere of the southeastern US influenced by both anthropogenic sulfur dioxide (SO2) and ammonia (NH3) emissions. Daytime PM2.5 samples were collected during summer 2010 using conditional sampling approaches based on pre-defined high and low SO2 or NH3 thresholds. Known molecular-level tracers for isoprene SOA formation, including 2-methylglyceric acid, 3-methyltetrahydrofuran-3,4-diols, 2-methyltetrols, C5-alkene triols, dimers, and organosulfate derivatives, were identified and quantified by gas chromatography coupled to electron ionization mass spectrometry (GC/EI-MS) and ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS). Mass concentrations of six isoprene low-NOx SOA tracers contributed to 12-19% of total organic matter (OM) in PM2.5 samples collected during the sampling period, indicating the importance of the hydroxyl radical (OH)-initiated oxidation (so-called photooxidation) of isoprene under low-NOx conditions that leads to SOA formation through reactive uptake of gaseous isoprene epoxydiols (IEPOX) in this region. IEPOX-derived SOA tracers were enhanced under high-SO2 sampling scenarios, suggesting that SO2 oxidation increases aerosol acidity of sulfate aerosols needed for enhancing heterogeneous oxirane ring-opening reactions of IEPOX. No clear associations between isoprene SOA formation and high and low NH3 conditional samples were found. Furthermore, weak correlations between aerosol acidity and mass of IEPOX SOA tracers suggests that IEPOX-derived SOA formation might be modulated by other factors as well in addition to aerosol acidity. Positive correlations between sulfate aerosol loadings and IEPOX-derived SOA tracers for samples collected under all conditions indicates that sulfate aerosol could be a surrogate for surface area in the uptake of IEPOX onto preexisting aerosols.

Lin, Y.-H.; Knipping, E. M.; Edgerton, E. S.; Shaw, S. L.; Surratt, J. D.

2013-02-01

284

Investigating the influences of SO2 and NH3 levels on isoprene-derived secondary organic aerosol formation using conditional sampling approaches  

NASA Astrophysics Data System (ADS)

Filter-based PM2.5 samples were chemically analyzed to investigate secondary organic aerosol (SOA) formation from isoprene in a rural atmosphere of the southeastern US influenced by both anthropogenic sulfur dioxide (SO2) and ammonia (NH3) emissions. Daytime PM2.5 samples were collected during summer 2010 using conditional sampling approaches based on pre-defined high and low SO2 or NH3 thresholds. Known molecular-level tracers for isoprene SOA formation, including 2-methylglyceric acid, 3-methyltetrahydrofuran-3,4-diols, 2-methyltetrols, C5-alkene triols, dimers, and organosulfate derivatives, were identified and quantified by gas chromatography coupled to electron ionization mass spectrometry (GC/EI-MS) and ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS). Mass concentrations of six isoprene low-NOx SOA tracers contributed to 12-19% of total organic matter (OM) in PM2.5 samples collected during the sampling period, indicating the importance of the hydroxyl radical (OH)-initiated oxidation (so-called photooxidation) of isoprene under low-NOx conditions that lead to SOA formation through reactive uptake of gaseous isoprene epoxydiols (IEPOX) in this region. The contribution of the IEPOX-derived SOA tracers to total organic matter was enhanced by 1.4% (p = 0.012) under high-SO2 sampling scenarios, although only weak associations between aerosol acidity and mass of IEPOX SOA tracers were observed. This suggests that IEPOX-derived SOA formation might be modulated by other factors simultaneously, rather than only aerosol acidity. No clear associations between isoprene SOA formation and high or low NH3 conditional samples were found. Positive correlations between sulfate aerosol loadings and IEPOX-derived SOA tracers for samples collected under all conditions indicates that sulfate aerosol could be a surrogate for surface accommodation in the uptake of IEPOX onto preexisting aerosols.

Lin, Y.-H.; Knipping, E. M.; Edgerton, E. S.; Shaw, S. L.; Surratt, J. D.

2013-08-01

285

Direct microscopic observation of Oswald ripening along a faceted bridge for the layer perovskite (C 3H 7NH 3) 2CuCl 4 in aqueous solution  

NASA Astrophysics Data System (ADS)

Simultaneous growth and dissolution has been observed of two extremely thin platelets of the layer perovskite bis-(propylammonium) copper(II) tetrachloride (C 3H 7NH 3) 2CuCl 4 from a thermostated aqueous solution. From the details of the experiment it is concluded that the event took place at or near the saturation concentration of the solution, so that the event is an example of Oswald ripening. The origin of a faceted bridge between the two initially free floating, separate platelets is explained on the basis of crystal movement and face stability.

Mischgofsky, F. H.

1983-12-01

286

Preparation of Single Phase Films of CH3NH3Pb(I1-xBrx)3 with Sharp Optical Band Edges  

E-print Network

?inorganic perovskite (CH3NH3PbI3?xClx) solar cells now show photovoltaic (PV) performance1?4 approaching 18%,5,6 and high charge-carrier mobilities.7 Perovskite films have also shown promising photoluminescence quantum efficiencies (PLQEs) of more than 70% and lasing... energetic disorder as the exponential decay of the absorption below the bandgap with a characteristic energy, the Urbach energy (Eu), and has been used to study the perovskite materials system.16 The Received: June 27, 2014 Accepted: July 9, 2014 Published...

Sadhanala, Aditya; Deschler, Felix; Thomas, Tudor H; Dutton, Siân E.; Goedel, Karl C.; Hanusch, Fabian C.; Lai, May L.; Steiner, Ullrich; Bein, Thomas; Docampo, Pablo; Cahen, David; Friend, Richard H.

2014-07-09

287

Manifestation of a thermochromic phase transition in electronic spectra of C3H7NH3CuCl3 crystals  

NASA Astrophysics Data System (ADS)

The temperature evolution of absorption spectra of isopropylammonium trichlorocuprate (C3H7NH3CuCl3) crystals was investigated in the energy range 1.77-2.48 eV. It was established that the optical absorption edge was described by the Urbach rule and resulted from exciton-phonon interaction. A comparatively strong exciton-phonon interaction was associated with a band produced by self-trapped excitons. Analysis of the temperature dependences for the Urbach-rule parameters confirmed the existence of a thermochromic phase transition at 325 K.

Korchak, Yu. M.; Fedor, B. S.; Polovynko, I. I.; Rudyk, V. P.

2012-05-01

288

Characteristics of vanadia on the surface of V 2O 5\\/Ti-PILC catalyst for the reduction of NO x by NH 3  

Microsoft Academic Search

A series of vanadia catalysts impregnated on titania pillared interlayered clays (Ti-PILCs) were prepared to identify the characteristics of vanadia on the surface of Ti-PILC for the selective catalytic reduction (SCR) of NO by NH3. V2O5\\/Ti-PILC exhibited superior performance as a novel SCR catalyst compared to conventional catalysts including V2O5\\/TiO2 and V2O5\\/Al2O3. NO removal activity over the supported vanadia catalyst

Ho Jeong Chae; In-Sik Nam; Sung-Won Ham; Suk Bong Hong

2004-01-01

289

New insights from comprehensive on-road measurements of NOx, NO2 and NH3 from vehicle emission remote sensing in London, UK  

NASA Astrophysics Data System (ADS)

In this paper we report the first direct measurements of nitrogen dioxide (NO2) in the UK using a vehicle emission remote sensing technique. Measurements of NO, NO2 and ammonia (NH3) from almost 70,000 vehicles were made spanning vehicle model years from 1985 to 2012. These measurements were carefully matched with detailed vehicle information data to understand the emission characteristics of a wide range of vehicles in a detailed way. Overall it is found that only petrol fuelled vehicles have shown an appreciable reduction in total NOx emissions over the past 15-20 years. Emissions of NOx from diesel vehicles, including those with after-treatment systems designed to reduce emissions of NOx, have not reduced over the same period of time. It is also evident that the vehicle manufacturer has a strong influence on emissions of NO2 for Euro 4/5 diesel cars and urban buses. Smaller-engined Euro 4/5 diesel cars are also shown to emit less NO2 than larger-engined vehicles. It is shown that NOx emissions from urban buses fitted with Selective Catalytic Reduction (SCR) are comparable to those using Exhaust Gas Recirculation for Euro V vehicles, while reductions in NOx of about 30% are observed for Euro IV and EEV vehicles. However, the emissions of NO2 vary widely dependent on the bus technology used. Almost all the NOx emission from Euro IV buses with SCR is in the form of NO, whereas EEV vehicles (Enhanced Environmentally friendly Vehicle) emit about 30% of the NOx as NO2. We find similarly low amounts of NO2 from trucks (3.5-12t and >12t). Finally, we show that NH3 emissions are most important for older generation catalyst-equipped petrol vehicles and SCR-equipped buses. The NH3 emissions from petrol cars have decreased by over a factor of three from the vehicles manufactured in the late 1990s compared with those manufactured in 2012. Tables of emission factors are presented for NOx, NO2 and NH3 together with uncertainties to assist the development of new emission inventories.

Carslaw, David C.; Rhys-Tyler, Glyn

2013-12-01

290

Solvent effects on the metal-to-ligand charge transfer transition of the complex [Ru(NH3)5(Pyrazine)]2+  

NASA Astrophysics Data System (ADS)

In this work the solvent effects on the structure and metal-to-ligand charge transfer (MLCT) transition of the complex [Ru(NH3)5(Pyrazine)]2+ was investigated in aqueous solution, using the hybrid Density Functional Theory/Effective Fragment Potential Hamiltonian (DFT/EFP/MD) approach. The MLCT transition causes a large charge separation in the complex and produces a dipole moment variation of 8.3 ± 1.1 Debye upon excitation in solution and causes a large red-shift of 0.55 ± 0.15 eV. The solvatochromic shift can be attributed to the large charge separation accompanying the MLCT transition in solution.

Chagas, Marcelo A.; Rocha, Willian R.

2014-09-01

291

The role of isolated Cu(2+) location in structural stability of Cu-modified SAPO-34 in NH3-SCR of NO.  

PubMed

In this study, three different methods (ion exchange, wet mixing and impregnation) were employed to prepare Cu-modified SAPO-34 molecular sieves. All these freshly prepared catalysts showed excellent activities towards the selective catalytic reduction (SCR) of NO with NH3 (NH3-SCR) no matter which preparation method was used. However, hydrothermal ageing significantly reduced the catalytic activities of those catalysts prepared by the wet-mixing and impregnation methods, respectively. The results of X-ray powder diffraction, H2-TPR and electron paramagnetic resonance measurements for these catalysts suggested that the decrease in catalytic activity may be attributed to the migration of Cu(2+) ion to the centre of the hexagonal prism (site III), the formation of CuxOy and the collapse of the molecular framework during hydrothermal ageing. The degrees of structural collapse of each Cu-modified molecular sieve were different, probably due to Cu(2+) species in different sites (in the ellipsoidal cavity (site I) for ion-exchange sample, near the eight-ring window (site IV) for the wet-mixing and impregnation samples). Cu(2+) located at site I was more stable than that located at site IV. PMID:25413111

Yan, Chundi; Cheng, Hao; Yuan, Zhongshan; Wang, Shudong

2015-01-01

292

Elementary steps of the catalytic NOx reduction with NH3: Cluster studies on reaction paths and energetics at vanadium oxide substrate  

NASA Astrophysics Data System (ADS)

We consider different reaction scenarios of the selective catalytic reduction (SCR) of NO in the presence of ammonia at perfect as well as reduced vanadium oxide surfaces modeled by V2O5(010) without and with oxygen vacancies. Geometric and energetic details as well as reaction paths are evaluated using extended cluster models together with density-functional theory. Based on earlier work of adsorption, diffusion, and reaction of the different surface species participating in the SCR we confirm that at Brønsted acid sites (i.e., OH groups) of the perfect oxide surface nitrosamide, NH2NO, forms a stable intermediate. Here adsorption of NH3 results in NH4 surface species which reacts with gas phase NO to produce the intermediate. Nitrosamide is also found as intermediate of the SCR near Lewis acid sites of the reduced oxide surface (i.e., near oxygen vacancies). However, here the adsorbed NH3 species is dehydrogenated to surface NH2 before it reacts with gas phase NO to produce the intermediate. The calculations suggest that reaction barriers for the SCR are overall higher near Brønsted acid sites of the perfect surface compared with Lewis acid sites of the reduced surface, examined for the first time in this work. The theoretical results are consistent with experimental findings and confirm the importance of surface reduction for the SCR process.

Gruber, M.; Hermann, K.

2013-12-01

293

Asymmetric Environmental Effects on the Structure and Vibrations of cis-[Pt(NH3)2Cl2] in Condensed Phases.  

PubMed

We report the structural and vibrational properties of anticancer drug cisplatin (cis-[Pt(NH3)2Cl2]) in gas phase, in solid phase, and in aqueous solution using density functional theory (DFT) calculations, quantum mechanical/molecular mechanical (QM/MM) molecular dynamics, and effective normal modes analysis. In contrast with the gas-phase case, asymmetric hydrogen bonding environments are found in both solid phase and aqueous solution. It is shown that the discrepancy of the molecular geometry between previous gas phase calculations and the X-ray crystal structure can be resolved by considering intermolecular hydrogen bonds in the calculations of solid phase. In addition, our simulations in solid phase and aqueous solution reveal that asymmetric environmental effects lead to several spectral features observed in experiments, such as the blue-shift in the N-H stretching region and the frequency splitting of NH3 symmetric deformation modes. Furthermore, a similar decoupling and localization of several vibrational modes of cisplatin is found in solid phase and aqueous solution, in comparison to those of O-H stretching modes of water molecules in liquid water [ J. Phys. Chem. Lett. 2013 , 4 ( 19 ), 3245 - 3250 ]. PMID:25144652

Zhang, Chao; Naziga, Emmanuel Baribefe; Guidoni, Leonardo

2014-10-01

294

Peroxido complexes of vanadium(V) as ligands. Crystal structures of [Cd(NH3)6][{VO(O2)2(OH)}2{?-Cd(NH3)4}] and [{VO(O2)2(Im)}2{?-Cu(Im)4}] (Im = Imidazole).  

PubMed

Two novel heterometallic complexes [Cd(NH3)6][{VO(O2)2(OH)}2{?-Cd(NH3)4}] (2) and [{VO(O2)2(Im)}2{?-Cu(Im)4}] (3) (Im = imidazole) containing peroxidovanadium complexes as metalloligands were prepared and characterized by spectral methods. X-ray single-crystal analysis revealed the presence of unique trinuclear complexes in the crystal structures of 2 and 3. The structure of 2 contains an anionic complex, whose two {VO(O2)2(OH)}(2-) ions are interconnected by a {?-Cd(NH3)4}(2+) group. Compound 3 is a trinuclear neutral complex comprising two {VO(O2)2(Im)}(-) ions and a single bridging {?-Cu(Im)4}(2+) group. The bonding via an equatorial OH(-) ligand in 2 and via a doubly bonded apical oxygen atom in 3 represents coordination modes previously unobserved for diperoxidovanadium complexes. Compared with complex 2, density functional theory studies reported decreased Cu-?-O bond orders and increased ?-O-V bond orders in 3, in accordance with the expected Jahn-Teller distortion of the latter complex. PMID:24801123

Bystrický, Roman; Antal, Peter; Tatiersky, Jozef; Schwendt, Peter; Gyepes, Róbert; Žák, Zdirad

2014-05-19

295

Implementation of New TPD Analysis Techniques in the Evaluation of Second Order Desorption Kinetics of Cyanogen from Cu(001)  

SciTech Connect

The interactions of cyanide species with a copper (001) surface were studied with temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Adsorbed cyanide species (CN{sub (a)}) undergo recombinative desorption evolving molecular cyanogen (C{sub 2}N{sub 2}). As the adsorbed CN species charge upon adsorption, mutually repulsive dipolar interactions lead to a marked desorption energy reduction with increasing CN{sub (a)} coverages. Two new TPD analysis approaches were developed, which used only accurately discernible observables and which do not assume constant desorption energies, E{sub d}, and pre-exponential values, v. These two approaches demonstrated a linear variation of E{sub d} with instantaneous coverage. The first approach involved an analysis of the variations of desorption peak asymmetry with initial CN coverages. The second quantitative approach utilized only temperatures and intensities of TPD peaks, together with deduced surface coverages at the peak maxima, also as a function of initial surface coverages. Parameters derived from the latter approach were utilized as initial inputs for a comprehensive curve fit analysis technique. Excellent fits for all experimental desorption curves were produced in simulations. The curve fit analysis confirms that the activation energy of desorption of 170-180 kJ/mol at low coverage decreases by up to 14-15 kJ/mol at CN saturation.

Hinch, B.J.; Senanayake, S.; Ciftlikli, E.Z.; Lee, E.Y.M.; Lallo, J.; Rangan, S.

2010-12-21

296

Observations of the Partitioning of Trace Acids During CalNex, Bakersfield: HONO, HCl and Oxalic Acid in an NH3-rich Environment  

NASA Astrophysics Data System (ADS)

The 2010 California Research at the Nexus of Air Quality and Climate Change (CalNex) field campaign supersite in Bakersfield, CA, presented an opportunity to investigate the gas-particle partitioning of trace atmospheric species in a low-sulphur high-NH3 environment. With the demand for cleaner energy, atmospheric S levels are expected to continue to decrease across North America, while restrictions on NH3 emissions are still in preliminary stages. Despite the absence of significant sulphur emissions contributing to particulate matter (PM) formation, California’s San Joaquin Valley still experiences some of the worst air quality in the continental US. Partitioning of other trace gases may become more important in low sulphur regions; here we report our observations of HONO, HCl and oxalic acid partitioning. Observations of the water-soluble composition of atmospheric gases and fine particulate matter (PM2.5) were made with an Ambient Ion Monitor - Ion Chromatography (AIM-IC) system from University Research Glassware (Chapel Hill, NC). The AIM-IC was fitted with a newly designed impactor inlet that minimizes gas and particle losses prior to collection by a wet wall parallel plate denuder and super saturated steam condensation chamber, respectively, situated at a height of 4.5 m for this study. Observations of NH3 indicated ambient levels typically in excess of 10 ppb, up to 60 ppb, and all observed inorganic aerosol was found to be completely neutralized throughout the campaign by NH4+. Mixing ratios of HONO showed excellent agreement with concurrent measurements made by a LOPAP instrument from University of Miami, maximizing during the night at values in the range of 1 - 1.5 ppb. On several nights, particulate NO2- mass loadings in the range of 0.2 ?g m-3 (equivalent to 0.1 ppb HONO) were observed by the AIM-IC. The diurnal pattern of HCl showed maximum mixing ratios of 0.2 - 0.3 ppb occurring near 13:00 PST, and near zero values at night. Intermittent bursts of Cl- were also detected, however the Cl- present in PM2.5 was significantly less than that present as HCl. These online observations are some of the few to date describing simultaneous measurements of both gas and particle phase reservoirs of chlorine as HCl/Cl-. The diurnal pattern of oxalic acid showed maximum mixing ratios less than 0.1 ppb near 16:00 PST and near zero values at night. The presence of oxalate in PM2.5 was observed throughout the campaign with mass loadings in the range of 0 - 0.2 ?g m-3 also maximizing during the day.

Vandenboer, T. C.; Markovic, M. Z.; Sanders, J.; Ren, X.; Murphy, J. G.

2010-12-01

297

n-alkanes on Pt(111) and on C(0001)/Pt(111): Chain Length Dependence of Kinetic Desorption Parameters  

SciTech Connect

We have measured the desorption of seven small n-alkanes (CNH2N+2, N = 1-4, 6, 8, 10) from the Pt(111) and C(0001) surfaces by temperature programmed desorption. We compare these results to our recent study of the desorption kinetics of these molecules on MgO(100) [J. Chem. Phys. 122, 164708 (2005)]. There we showed an increase in the desorption pre-exponential factor by several orders of magnitude with increasing n-alkane chain length and a linear desorption energy scaling with a small y-intercept value. We suggest that the significant increase in desorption prefactor with chain length is not particular to the MgO(100) surface, but is a general effect for desorption of the small n-alkanes. This argument is supported by statistical mechanical arguments for the increase in the entropy gain of the molecules upon desorption. In this work, we demonstrate that this hypothesis holds true on both a metal surface and a graphite surface. We observe an increase in prefactor by five orders of magnitude over the range of n-alkane chain lengths studied here. On each surface, the desorption energies of the n-alkanes are found to increase linearly with the molecule chain length and have a small y-intercept value. Prior results of other groups have yielded a linear desorption energy scaling with chain length that has unphysically large y-intercept values. We demonstrate that by allowing the prefactor to increase according to our model, a reanalysis of their data resolves this y-intercept problem to some degree.

Tait, Steven L.; Dohnalek, Zdenek; Campbell, Charles T.; Kay, Bruce D.

2006-12-21

298

The Release of Trapped Gases from Amorphous Solid Water Films: II. “Bottom-Up” Induced Desorption Pathways  

SciTech Connect

In this (Paper II) and the preceding companion paper (Paper I) we investigate the mechanisms for the release of trapped gases from underneath of amorphous solid water (ASW) films. In Paper I, we focused on the low coverage (pressure) regime where the release mechanism is controlled by crystallization-induced cracks formed in the ASW overlayer. In that regime the results were largely independent of the particular gas underlayer. Here in Paper II, we focus on the high coverage (pressure) regime where new desorption pathways become accessible prior to ASW crystallization. In contrast to the results for the low coverage regime (Paper I), the release mechanism is a function of the multilayer thickness and composition, displaying dramatically different behavior between Ar, Kr, Xe, CH4, N2, O2, and CO. Two primary desorption pathways are observed. The first occurs between 100 and 150 K and manifests itself as sharp, extremely narrow desorption peaks. Temperature programmed desorption is utilized to show that abrupt desorption bursts are due to pressure induced structural failure of the ASW overlyaer. The second pathway occurs at low temperature (typically <100 K) where broad desorption peaks are observed. Desorption through this pathway is attributed to diffusion through pores and connected pathways formed during ASW deposition. The extent of desorption and the lineshape of the low temperature desorption peak are dependent on the substrate on which the gas underlayer is deposited. Angle dependent ballistic deposition of the ASW is used vary the porosity of overlayer and confirm that the low temperature desorption pathway is due to porosity that is inherent in the ASW overlayer during deposition.

May, Robert A.; Smith, R. Scott; Kay, Bruce D.

2013-03-14

299

Thermal reaction and desorption behaviors of 2,5-diiodothiophene on clean and passivated Au surfaces  

NASA Astrophysics Data System (ADS)

Thermal reactions and desorption behaviors of 2,5-diiodothiophene on Au were studied with temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES). Diiodo-substituted hetero-cyclic molecules are an important precursor molecule for photochemical production of conjugated polymers. This paper describes the surface reactions and multilayer structure of 2,5-diiodothiophene in the absence of photon irradiation. 2,5-Diiodothiophene adsorbs molecularly on Au at 100 K. At 200-300 K, the C-I bond of the molecule dissociates producing atomic iodine. The C-I bond cleavage appears to induce further dissociation of the thiophene ring structure. The iodine species desorb at 600-750 K from the surface. The dissociated carbon and sulfur remain on the Au surface even at 800 K. The desorption of thin multilayers occurs at ˜220 K. During the desorption of these layers, a clustering process seems to occur. The desorption of thick multilayer occurs at ˜235 K.

Liu, Guangming; Ryoo, Kunkul; Kim, Seong H.

2007-07-01

300

The poisoning effect of Na and K on Mn/TiO2 catalyst for selective catalytic reduction of NO with NH3: A comparative study  

NASA Astrophysics Data System (ADS)

Mn/TiO2 catalyst is of high activity for low temperature selective catalytic reduction (SCR) of NO with NH3. And the deposition of alkali metal would lead to the deactivation of Mn/TiO2 catalyst. In this paper, the poisoning effect of Na and K on Mn/TiO2 was investigated based on experimental and theoretical study. It was found that K had a stronger poisoning effect than that of Na. The bad performance of K-Mn/TiO2 may be due to its small surface area, high crystallinity, weak surface acidity, low content of Mn4+ and chemisorbed oxygen, and bad redox ability. The interpretation of the experimental results is supported by DFT calculations.

Guo, Rui-tang; Wang, Qing-shan; Pan, Wei-guo; Zhen, Wen-long; Chen, Qi-lin; Ding, Hong-lei; Yang, Ning-zhi; Lu, Chen-zi

2014-10-01

301

Effective hole extraction using MoOx-Al contact in perovskite CH3NH3PbI3 solar cells  

NASA Astrophysics Data System (ADS)

We report an 11.4%-efficient perovskite CH3NH3PbI3 solar cell using low-cost molybdenum oxide/aluminum (i.e., MoOx/Al) as an alternative top contact to replace noble/precious metals (e.g., Au or Ag) for extracting photogenerated holes. The device performance of perovskite solar cells using a MoOx/Al top contact is comparable to that of cells using the standard Ag top contact. Analysis of impedance spectroscopy measurements suggests that using 10-nm-thick MoOx and Al does not affect charge-recombination properties of perovskite solar cells. Using a thicker (20-nm) MoOx layer leads to a lower cell performance caused mainly by a reduced fill factor. Our results suggest that MoOx/Al is promising as a low-cost and effective hole-extraction contact for perovskite solar cells.

Zhao, Yixin; Nardes, Alexandre M.; Zhu, Kai

2014-05-01

302

Dielectric properties and electrical conductivity of the hybrid organic-inorganic polyvanadates (H3N(CH2)4NH3)[V6O14  

NASA Astrophysics Data System (ADS)

Plate-like crystals of the polyvanadate (H3N(CH2)4NH3)[V6O14] have been synthesized via an hydrothermal treatment. X-ray powder diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, electron spin resonance and complex impedance spectroscopy were used to analyze the hybrid material. The frequency dependence of AC conductivity at different temperatures indicates that the CBH model is the probable mechanism for the AC conduction behavior. The conductivity was measured by complex impedance spectroscopy which is equal to 31.10-3 ?-1 m-1 at 443 K. The Arrhenius diagram is not linear, it presents a rupture situated at 357 K and the activation energies' average values are 0.22 eV and 0.14 eV, deduced from the Arrhenius relation.

Nefzi, H.; Sediri, F.; Hamzaoui, H.; Gharbi, N.

2012-06-01

303

An analysis of the semiscale MOD-2C S-NH-3 test using the TRAC-PF1 computer program  

SciTech Connect

A calculation was performed using the TRAC-PF1/MOD1 computer program to simulate a small break, loss-of-coolant experiment where the high-pressure injection was not used to mitigate the fuel rod temperature excursion. This experiment, designated the S-NH-3 Test, simulated a 0.5% cold-leg break in a PWR and was one of a series of tests, conducted in the Semiscale Mod-2C test facility. The primary purpose for doing the calculation was to evaluate the capability of the TRAC-PF1 code to calculate the thermal-hydraulic response observed in the experiment. The evaluation employs the comparison of selected code-calculated system responses with the test data. Conclusions and recommendations on improving the quality of the calculation are included.

Driskell, W.E.; Kullberg, C.M.

1987-03-01

304

Application of NH3-Annealed and Wet-Oxidized Chemical-Vapor-Deposited SiO2 Single-Layer Films to Tunnel Oxides of Flash Memories  

NASA Astrophysics Data System (ADS)

I report here the application of NH3-annealed, wet-oxidized chemical vapor deposited (CVD) SiO2 single-layer films to the tunnel oxide of flash memories. The films exhibit good Fowler-Nordheim tunneling characteristics under the use conditions of flash memories. Trapped charges in the films are reduced to an allowable level. Stress induced leakage current (SILC) is as low as that of conventional thermal oxides, which is a result of reducing the E' centers in the films. These characteristics suggest that the films could be an alternative to thermal oxides, which is favorable for achieving three-dimensional structural flash memories that have a significantly larger bit density.

Kobayashi, Takashi

2008-10-01

305

Ion-orbital coupling in Car-Parrinello calculations of hydrogen-bond vibrational dynamics: Case study with the NH3-HCl dimer  

NASA Astrophysics Data System (ADS)

We have performed Car-Parrinello molecular dynamics (CPMD) calculations of the hydrogen-bonded NH3-HCl dimer. Our main aim is to establish how ionic-orbital coupling in CPMD affects the vibrational dynamics in hydrogen-bonded systems by characterizing the dependence of the calculated vibrational frequencies upon the orbital mass in the adiabatic limit of Car-Parrinello calculations. We use the example of the NH3-HCl dimer because of interest in its vibrational spectrum, in particular the magnitude of the frequency shift of the H-Cl stretch due to the anharmonic interactions when the hydrogen bond is formed. We find that an orbital mass of about 100 a.u. or smaller is required in order for the ion-orbital coupling to be linear in orbital mass, and the results for which can be accurately extrapolated to the adiabatic limit of zero orbital mass. We argue that this is general for hydrogen-bonded systems, suggesting that typical orbital mass values used in CPMD are too high to accurately describe vibrational dynamics in hydrogen-bonded systems. Our results also show that the usual application of a scaling factor to the CPMD frequencies to correct for the effects of orbital mass is not valid. For the dynamics of the dimer, we find that the H-Cl stretch and the N-H-Cl bend are significantly coupled, suggesting that it is important to include the latter degree of freedom in quantum dynamical calculations. Results from our calculations with deuterium-substitution show that both these degrees of freedom have significant anharmonic interactions. Our calculated frequency for the H-Cl stretch using the Becke-exchange Lee-Yang-Parr correlation functional compares reasonably well with a previous second-order Møller-Plesset calculation with anharmonic corrections, although it is low compared to the experimental value for the dimer trapped in a neon-matrix.

Ong, S. W.; Lee, B. X. B.; Kang, H. C.

2011-09-01

306

A novel model to predict the physical state of atmospheric H2SO4/NH3/H2O aerosol particles  

NASA Astrophysics Data System (ADS)

The physical state of the tropospheric aerosol is largely unknown despite its importance for cloud formation and for the aerosol's radiative properties. Here we use detailed microphysical laboratory measurements to perform a systematic global modelling study of the physical state of the H2SO4/NH3/H2O aerosol, which constitutes an important class of aerosols in the free troposphere. The Aerosol Physical State Model (APSM) developed here is based on Lagrangian trajectories computed from ECMWF (European Centre for Medium Range Weather Forecasts) analyses, taking full account of the deliquescence/efflorescence hysteresis. As input APSM requires three data sets: (i) deliquescence and efflorescence relative humidities from laboratory measurements, (ii) ammonia-to-sulfate ratios (ASR) calculated by a global circulation model, and (iii) relative humidities determined from the ECMWF analyses. APSM results indicate that globally averaged a significant fraction (17-57%) of the ammoniated sulfate aerosol particles contain solids with the ratio of solid-containing to purely liquid particles increasing with altitude (between 2 and 10 km). In our calculations the most abundant solid is letovicite, (NH4)3H(SO4)2, while there is only little ammonium sulfate, (NH4)2SO4. Since ammonium bisulfate, NH4HSO4, does not nucleate homogeneously, it can only form via heterogeneous crystallization. As the ammonia-to-sulfate ratios of the atmospheric H2SO4/NH3/H2O aerosol usually do not correspond to the stoichiometries of known crystalline substances, all solids are expected to occur in mixed-phase aerosol particles. This work highlights the potential importance of letovicite, whose role as cloud condensation nucleus (CCN) and as scatterer of solar radiation remains to be scrutinized.

Colberg, C. A.; Luo, B. P.; Wernli, H.; Koop, T.; Peter, Th.

2003-07-01

307

Ab initio calculation of the NH,,3 -...-NH,,3 -  

E-print Network

-consistent-field method supplemented with perturbative configuration interaction calculations of second and third orders progress in the cooling of neutral atoms in the dilute gas phase. Experiments at ul- tralow temperatures field.11 The magnetically trapped species are cooled by elastic collisions with a cold helium buffer gas

308

Double functions of porous TiO2 electrodes on CH3NH3PbI3 perovskite solar cells: Enhancement of perovskite crystal transformation and prohibition of short circuiting  

NASA Astrophysics Data System (ADS)

In order to analyze the crystal transformation from hexagonal PbI2 to CH3NH3PbI3 by the sequential (two-step) deposition process, perovskite CH3NH3PbI3 layers were deposited on flat and/or porous TiO2 layers. Although the narrower pores using small nanoparticles prohibited the effective transformation, the porous-TiO2 matrix was able to help the crystal transformation of PbI2 to CH3NH3PbI3 by sequential two-step deposition. The resulting PbI2 crystals in porous TiO2 electrodes did not deteriorate the photovoltaic effects. Moreover, it is confirmed that the porous TiO2 electrode had served the function of prohibiting short circuits between working and counter electrodes in perovskite solar cells.

Murugadoss, Govindhasamy; Mizuta, Gai; Tanaka, Soichiro; Nishino, Hitoshi; Umeyama, Tomokazu; Imahori, Hiroshi; Ito, Seigo

2014-08-01

309

Morphological structure of atmospheric aerosols on the basis of laboratory studies of single levitated H2SO4/NH3/H2O aerosol particles  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols are of high interest due to their radiative properties, their possible role as CCNs and heterogeneous chemical processes on their surfaces. However, heterogeneous reactions on solid aerosol surfaces or ice surfaces are not well understood. In general heterogeneous chemistry on solid atmospheric particles can be influenced by liquid films on these particles. Thereby diffusion kinetics and solubility are influenced by the sample morphology, such as polycrystallinity, impurities at grain boundaries or at the junctions where three grains meet, and porosity. Therefore morphological considerations of atmospheric aerosols on the basis of laboratory studies of single levitated H2SO4/NH3/H2O aerosol particles are accomplished in this study. The experiments are performed in an electrodynamic particle trap. Four analytical tools provide independent information on the aerosol composition, structure and morphology. Apart from the morphology, deliquescence and efflorescence relative humidities (DRH and ERH) of H2SO4/NH3/H2O aerosol particles, as well as the water uptake and drying behavior, are studied. In general the thermodynamic data of the present work is in good agreement to previous work. The observed solid phases are letovicite and ammonium sulfate, which often exist as mixed-phase (solid/liquid) particles. Ammonium bisulfate did not nucleate under the conditions of our experiments. Moreover, solid aerosol particles crystallized from liquid NH4HSO4/H2O droplets, show occasionally a complex three-step-deliquescence behavior with intermediate phase transitions. This observation suggests that a new, hitherto unknown phase is detected during the experiments. In supporting experiments the new phase is identified as ammonium bisulfate monohydrate. Mixed phase particles crystallize in different morphologies and tend to form inclusion-particles. The liquid is either completely shielded from the gas phase or stored in several open cavities, with the liquid for example located between grain boundaries of single crystals or in pores with concave surfaces. The exact morphology, i.e. the degree of how much the remaining liquid is shielded by the solid, differs not only from aerosol particle to aerosol particle but also from efflorescence to efflorescence. Depending on the shielding degree water-uptake can take place prior to deliquescence or not. Apparently even particles, which were assumed to be purely solid, show a slight water-uptake approximately 2-3 % in RH before the actual DRH. The reason for this what we call pre-deliquescence is probably also morphology related, e.g. cavities between single crystals filled with a liquid or pores with concave surfaces. Based on the results and implications of this work we can provide a morphological concept which could possibly be transferred to a wide spectrum of atmospheric aerosol.

Colberg, C. A.; Krieger, U. K.; Peter, Th.

2003-04-01

310

Influence of counter-ions on the crystal structures of DNA decamers: binding of [Co(NH3)6]3+ and Ba2+ to A-DNA.  

PubMed Central

A-DNA is a stable alternative right-handed double helix that is favored by certain sequences (e.g., (dG)n.(dC)n) or under low humidity conditions. Earlier A-DNA structures of several DNA oligonucleotides and RNA.DNA chimeras have revealed some conformational variation that may be the result of sequence-dependent effects or crystal packing forces. In this study, four crystal structures of three decamer oligonucleotides, d(ACCGGCCGGT), d(ACCCGCGGGT), and r(GC)d(GTATACGC) in two crystal forms (either the P6(1)22 or the P2(1)2(1)2(1) space group) have been analyzed at high resolution to provide the molecular basis of the structural difference in an experimentally consistent manner. The study reveals that molecules crystallized in the same space group have a more similar A-DNA conformation, whereas the same molecule crystallized in different space groups has different (local) conformations. This suggests that even though the local structure is influenced by the crystal packing environments, the DNA molecule adjusts to adopt an overall conformation close to canonical A-DNA. For example, the six independent CpG steps in these four structures have different base-base stacking patterns, with their helical twist angles (omega) ranging from 28 degrees to 37 degrees. Our study further reveals the structural impact of different counter-ions on the A-DNA conformers. [Co(NH3)6]3+ has three unique A-DNA binding modes. One binds at the major groove side of a GpG step at the O6/N7 sites of guanine bases via hydrogen bonds. The other two modes involve the binding of ions to phosphates, either bridging across the narrow major groove or binding between two intra-strand adjacent phosphates. Those interactions may explain the recent spectroscopic and NMR observations that [Co(NH3)6]3+ is effective in inducing the B- to A-DNA transition for DNA with (G)n sequence. Interestingly, Ba2+ binds to the same O6/N7 sites on guanine by direct coordinations. Images FIGURE 4 PMID:8527670

Gao, Y G; Robinson, H; van Boom, J H; Wang, A H

1995-01-01

311

Crystal structures, lattice potential energies, and thermochemical properties of crystalline compounds (1-C(n)H(2n+1)NH3)2ZnCl4(s) (n = 8, 10, 12, and 13).  

PubMed

As part of our ongoing project involving the study of (1-C(n)H(2n+1)NH(3))(2)MCl(4)(s) (where M is a divalent metal ion and n = 8-18), we have synthesized the compounds (1-C(n)H(2n+1)NH(3))(2)ZnCl(4)(s) (n = 8, 10, 12, and 13), and the details of the structures are reported herein. All of the compounds were crystallized in the monoclinic form with the space group P2(1)/n for (1-C(8)H(17)NH(3))(2)ZnCl(4)(s), P21/c for (1-C(10)H(21)NH(3))(2)ZnCl(4)(s), P2(1)/c for (1-C(12)H(25)NH(3))(2)ZnCl(4)(s), and P2(1)/m for (1-C(13)H(27)NH(3))(2)ZnCl(4)(s). The lattice potential energies and ionic volumes of the cations and the common anion of the title compounds were obtained from crystallographic data. Molar enthalpies of dissolution of the four compounds at various molalities were measured at 298.15 K in the double-distilled water. According to Pitzer's theory, molar enthalpies of dissolution of the title compounds at infinite dilution were obtained. Finally, using the values of molar enthalpies of dissolution at infinite dilution (?(s)H(m)(?)) and other auxiliary thermodynamic data, the enthalpy change of the dissociation of [ZnCl(4)](2-)(g) for the reaction [ZnCl(4)](2-)(g)? Zn(2+)(g) + 4Cl(-)(g) was obtained, and then the hydration enthalpies of cations were calculated by designing a thermochemical cycle. PMID:21995326

Liu, Yupu; Di, Youying; He, Donghua; Zhou, Qian; Dou, Jianmin

2011-11-01

312

Molecular desorption of methyl halides from GaAs(110): The role of lateral dipole--dipole interaction between adsorbates  

SciTech Connect

Temperature programmed desorption (TPD) spectra of CH[sub 3]X (X=Cl, Br, I) from GaAs(110) were recorded with a heating rate of 5 K/s for coverages from less than 0.1 to 2 ML, where methyl halides desorb molecularly, i.e., without dissociation. The shapes of the TPD spectra are strongly coverage dependent with the peak temperature of desorption decreasing with increasing coverage, especially for the submonolayer region. A model incorporating dipole--dipole repulsive interactions between the adsorbed molecules and which was previously proposed for the desorption of adsorbed molecules from metal surfaces has been employed to fit our TPD spectra. The fit gives the activation energy, effective dipole moment, and effective polarizability for the adsorbate. The resulting dipole moment and polarizability are less than the gas-phase molecular values, suggesting the importance of an ordered adsorption orientation. [copyright] [ital 1994][ital American] [ital Institute] [ital of] [ital Physics].

Lu, P.; Lasky, P.J.; Yang, Q.; Wang, Y.; Osgood, R.M. Jr. (Columbia Radiation Laboratory, Columbia University, New York, New York 10027 (United States))

1994-12-01

313

Mapping Observations of the Horsehead Nebula and the NGC 2023 Region in the NH3 (1,1),(2,2) and (3,3) Lines with the Nobeyama 45 m Telescope  

NASA Astrophysics Data System (ADS)

We performed mapping observations of the Horsehead Nebula and the NGC 2023 region in the NH3 (1,1), (2,2) and (3,3) lines. We identified five dense cores (Cores A to E), and estimated the masses and kinetic temperatures of the cores by analyzing the NH3 lines. For all the cores, the temperature tends to increase in the outer parts, suggesting heating due to the ionized gas from IC 434. Core B is discovered by this work and indicates a sign of infalling motion.

Ohashi, S.; Kitamura, Y.; Akashi, T.

2013-10-01

314

Selective Etching of Magnetic Tunnel Junction Materials Using CO/NH3 Gas Mixture in Radio Frequency Pulse-Biased Inductively Coupled Plasmas  

NASA Astrophysics Data System (ADS)

The etch characteristics of magnetic tunneling junction (MTJ) materials and the etch selectivity over W have been investigated using RF pulse-biased conditions in addition to the continuous wave (CW) bias condition with a CO/NH3 gas combination in an inductively coupled plasma system. By using a time-averaged substrate DC bias voltage condition for the RF pulse biasing, the etch rates of MTJ materials for the RF pulse-biased conditions were generally similar to those etched using the CW RF bias condition even though the etch rates were slightly decreased with decreasing the duty percentage of the RF pulse biasing. However, the use of the RF pulse biasing improved the etch selectivity of the MTJ materials over mask materials such as W. When the surface roughness and the residual thickness remaining on the etched surface of the MTJ material such as CoFeB were investigated by using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively, it was clear that the use of the RF pulse biasing instead of CW RF biasing also decreased the residual thickness and the surface roughness. This is believed to be related to the formation of a more uniform chemically reacted layer on the etch CoFeB surface during the RF pulse-biased etching condition.

Jeon, Min Hwan; Kim, Hoe Jun; Che Yang, Kyung; Kang, Se Koo; Kim, Kyong Nam; Yeom, Geun Young

2013-05-01

315

Electrical properties, phase transitions and conduction mechanisms of the [(C2H5)NH3]2CdCl4 compound  

NASA Astrophysics Data System (ADS)

The [(C2H5)NH3]2CdCl4 hybrid material was prepared and its calorimetric study and electric properties were investigated at low temperature. The X-ray powder diffractogram has shown that the compound is crystallized in the orthorhombic system with Abma space group, and the refined unit cell parameters are a=7.546 Å, b=7.443 Å, and c=21.831 Å. The calorimetric study has revealed two endothermic peaks at 216 K and 357 K, which are confirmed by the variation of fp and ?dc as a function of temperature. The equivalent circuit based on the Z-View-software was proposed and the conduction mechanisms were determined. The obtained results have been discussed in terms of the correlated barrier hopping model (CBH) in phase I (low temperature (OLT)), non-overlapping small polaron tunneling model (NSPT) in phase II (room temperature (ORT)) and the overlapping large polaron tunneling model in phase III (high temperature (OHT)). The density of localized states NF(E) at the Fermi level and the binding energy Wm were calculated. The variation of the dielectric loss log(??) with log(?) was found to follow the empirical law, ??=B ?m(T).

Mohamed, C. Ben; Karoui, K.; Saidi, S.; Guidara, K.; Rhaiem, A. Ben

2014-10-01

316

Femtosecond time-resolved transient absorption spectroscopy of CH3NH3PbI3 perovskite films: evidence for passivation effect of PbI2.  

PubMed

CH3NH3PbI3 perovskite layered films deposited on substrates with and without a titania support structure have been prepared and studied using time-resolved femtosecond transient absorption (fs-TA) spectroscopy in the visible light range (450-800 nm). The electron injection dynamics from the photoexcited perovskite layers to the neighboring film structures could be directly monitored via the transient bleaching dynamics of the perovskite at ?750 nm and thus systematically studied as a function of the layer-by-layer architecture. In addition, for the first time we could spectrally distinguish transient bleaching at ?750 nm from laser-induced fluorescence that occurs red-shifted at ?780 nm. We show that an additional bleach feature at ?510 nm appears when PbI2 is present in the perovskite film. The amplitudes of the PbI2 and perovskite TA peaks were compared to estimate relative amounts of PbI2 in the samples. Kinetic analysis reveals that perovskite films with less PbI2 show faster relaxation rates than those containing more PbI2. These fast dynamics are attributed to charge carrier trapping at perovskite grain boundaries, and the slower dynamics in samples containing PbI2 are due to a passivation effect, in line with other recently reported work. PMID:25145978

Wang, Lili; McCleese, Christopher; Kovalsky, Anton; Zhao, Yixin; Burda, Clemens

2014-09-01

317

Mechanical properties of hybrid organic-inorganic CH3NH3BX3 (B = Sn, Pb; X = Br, I) perovskites for solar cell absorbers  

NASA Astrophysics Data System (ADS)

The crystal structures, elastic and anisotropic properties of CH3NH3BX3 (B = Sn, Pb; X = Br, I) compounds as solar cell absorber layers are investigated by the first-principles calculations. The type and strength of chemical bond B-X are found to determine the elastic properties. B-X bonds and the organic cations are therefore crucial to the functionalities of such absorbers. The bulk, shear, Young's modulus ranges from 12 to 30 GPa, 3 to 12 GPa, and 15 to 37 GPa, respectively. Moreover, the interaction among organic and inorganic ions would have negligible effect for elastic properties. The B/G and Poisson's ratio show it would have a good ductile ability for extensive deformation as a flexible/stretchable layer on the polymer substrate. The main reason is attributed to the low shear modulus of such perovskites. The anisotropic indices AU, AB AG, A1, A2, and A3 show ABX3 perovskite have very strong anisotropy derived from the elastic constants, chemical bonds, and symmetry.

Feng, Jing

2014-08-01

318

Efficient planar perovskite solar cells based on 1.8 eV band gap CH3NH3PbI2Br nanosheets via thermal decomposition.  

PubMed

Hybrid organometallic halide perovskite CH3NH3PbI2Br (or MAPbI2Br) nanosheets with a 1.8 eV band gap were prepared via a thermal decomposition process from a precursor containing PbI2, MABr, and MACl. The planar solar cell based on the compact layer of MAPbI2Br nanosheets exhibited 10% efficiency and a single-wavelength conversion efficiency of up to 86%. The crystal phase, optical absorption, film morphology, and thermogravimetric analysis studies indicate that the thermal decomposition process strongly depends on the composition of precursors. We find that MACl functions as a glue or soft template to control the initial formation of a solid solution with the main MAPbI2Br precursor components (i.e., PbI2 and MABr). The subsequent thermal decomposition process controls the morphology/surface coverage of perovskite films on the planar substrate and strongly affects the device characteristics. PMID:25118565

Zhao, Yixin; Zhu, Kai

2014-09-01

319

Structure of duplex DNA containing the cisplatin 1,2-{Pt(NH3)2}[superscript 2]+-d(GpG) crosslink at 1.77 [Angstrom] resolution  

E-print Network

We report the 1.77-Å resolution X-ray crystal structure of a dodecamer DNA duplex with the sequence 5?-CCTCTGGTCTCC-3? that has been modified to contain a single engineered 1,2-cis-{Pt(NH3)2}2+-d(GpG) cross-link, the major ...

Todd, Ryan C.

320

Selective Catalytic Reduction (SCR) of nitric oxide with ammonia using Cu-ZSM-5 and Va-based honeycomb monolith catalysts: effect of H2 pretreatment, NH 3-to-NO ratio, O2, and space velocity  

E-print Network

In this work, the steady-state performance of zeolite-based (Cu-ZSM-5) and vanadium-based honeycomb monolith catalysts was investigated in the selective catalytic reduction process (SCR) for NO removal using NH 3. The aim was to delineate the effect...

Gupta, Saurabh

2004-09-30

321

Analysis of the Activation and Heterolytic Dissociation of H2 by Frustrated Lewis Pairs: NH3/BX3 (X = H, F, and Cl)  

SciTech Connect

We present results of our computational study aimed at understanding the mechanism of H2 activation and heterolytic dissociation by 'frustrated' Lewis pairs (FLPs). We studied the pairs of ammonia (NH3) with BH3, BF3, and most extensively, BCl3. While these pairs are capable of forming a strong dative bond, electronic structure theories make it possible to explore the potential surface in regions away from the dative complex relevant to H2 activation by frustrated Lewis pairs. We analyzed in great detail the changes that occur along the minimum energy path between the FLP and the product ion pair complex. For X = Cl, the mechanism involves a precursor complex, H3N-H2-BCl3, with a B-H-H angle of {approx}80{sup o} and nearly linear N-H-H angle. At the transition state (TS), the H2 bond is weakened but not broken, and the BCl3 moiety has undergone significant pyramidal distortion. As such, the FLP is prepared to accept the incipient proton and hydride ion on the product-side. The interaction energy of the H2 with the acid/base pair and the different contributions for the precursor and TS complex from an energy decomposition analysis expose the dominant factors affecting the reactivity. We find that structural reorganization of precursor complex plays a significant role in the 'activation' and that charge-transfer interactions are the dominant stabilizing force in the activated complex. The electric field clearly has a role in polarizing H2, but its contribution to the overall interaction energy seems to be smaller. Our detailed study of the nature of the bonding and the different types of interaction between the prototypical Lewis pair and H2 provides insight into the important components that should be taken into account when designing related systems to activate hydrogen.

Camaioni, Donald M.; Ginovska-Pangovska, Bojana; Schenter, Gregory K.; Kathmann, Shawn M.; Autrey, Thomas

2012-07-05

322

Effects of gaseous NH(3) and SO(2) on the concentration profiles of PCDD/F in flyash under post-combustion zone conditions.  

PubMed

The influence of gaseous ammonia and sulphur dioxide on the formation of 2378-substituted PCDD/F on a reference flyash from a municipal waste incinerator has been investigated using a laboratory scale fixed-bed reactor. The reference flyash samples (BCR-490) was reacted under a simulated flue gas stream at temperatures of 225 and 375°C for 96h. The experiments were carried out in two series: first with simulated flue gas alone, and then with injection of NH(3) or SO(2) gas into the flue gas just before the reactor inlet. It was found that the injection of gaseous ammonia into the flue gas could decrease the concentration of both PCDD and PCDF by 34-75% from the solid phase and by 21-40% from the gas phase. Converting the results to I-TEQ values, it could reduce the total I-TEQ values of PCDD and PCDF in the sum of the flyash and exhaust flue gas by 42-75% and 24-57% respectively. The application of SO(2) led to 99% and 93% reductions in the PCDD and PCDF average congener concentrations, respectively in the solid phase. In the gas phase, the total reductions were 89% and 76% for PCDD and PCDF, respectively. Moreover, addition of SO(2) reduced the total I-TEQ value of PCDD and PCDF in the flyash and exhaust flue gas together by 60-86% and 72-82% respectively. Sulphur dioxide was more effective than ammonia in suppressing PCDD/F formation in flyash under the conditions investigated. PMID:22429934

Hajizadeh, Yaghoub; Onwudili, Jude A; Williams, Paul T

2012-07-01

323

Experimental investigation of aminoacetonitrile formation through the Strecker synthesis in astrophysical-like conditions: reactivity of methanimine (CH2NH), ammonia (NH3), and hydrogen cyanide (HCN)  

NASA Astrophysics Data System (ADS)

Context. Studing chemical reactivity in astrophysical environments is an important means for improving our understanding of the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. Laboratory simulations of the reactivity of ice analogs provide important insight into the reactivity in these environments. Here, we use these experimental simulations to investigate the Strecker synthesis leading to the formation of aminoacetonitrile in astrophysical-like conditions. The aminoacetonitrile is an interesting compound because it was detected in SgrB2, hence could be a precursor of the smallest amino acid molecule, glycine, in astrophysical environments. Aims: We present the first experimental investigation of the formation of aminoacetonitrile NH2CH2CN from the thermal processing of ices including methanimine (CH2NH), ammonia (NH3), and hydrogen cyanide (HCN) in interstellar-like conditions without VUV photons or particules. Methods: We use Fourier Transform InfraRed (FTIR) spectroscopy to monitor the ice evolution during its warming. Infrared spectroscopy and mass spectroscopy are then used to identify the aminoacetonitrile formation. Results: We demonstrate that methanimine can react with -CN during the warming of ice analogs containing at 20 K methanimine, ammonia, and [NH4+ -CN] salt. During the ice warming, this reaction leads to the formation of poly(methylene-imine) polymers. The polymer length depend on the initial ratio of mass contained in methanimine to that in the [NH4+ -CN] salt. In a methanimine excess, long polymers are formed. As the methanimine is progressively diluted in the [NH4+ -CN] salt, the polymer length decreases until the aminoacetonitrile formation at 135 K. Therefore, these results demonstrate that aminoacetonitrile can be formed through the second step of the Strecker synthesis in astrophysical-like conditions.

Danger, G.; Borget, F.; Chomat, M.; Duvernay, F.; Theulé, P.; Guillemin, J.-C.; Le Sergeant D'Hendecourt, L.; Chiavassa, T.

2011-11-01

324

A novel model to predict the physical state of atmospheric H2SO4/NH3/H2O aerosol particles  

NASA Astrophysics Data System (ADS)

The physical state of tropospheric aerosol particles is largely unknown despite its importance for cloud formation and for the aerosols' radiative properties. Here we show the first systematic global modelling study of the physical state of the H2SO4/NH3/H2O aerosol, which constitutes an important class of aerosols in the free troposphere. The Aerosol Physical State Model (APSM) developed here is based on Lagrangian trajectories computed from ECMWF (European Centre for Medium Range Weather Forecasts) analyses, taking full account of the deliquescence/efflorescence hysteresis. As input APSM requires three data sets: (i) deliquescence and efflorescence relative humidities from laboratory measurements, (ii) ammonia-to-sulfate ratios (ASR) calculated by a global circulation model, and (iii) relative humidities determined from the ECMWF analyses. APSM results indicate that globally averaged a significant fraction (17-57%) of the ammoniated sulfate aerosol particles contain solids with the ratio of solid-containing to purely liquid particles increasing with altitude (between 2 and 10 km). In our calculations the most abundant solid is letovicite, (NH4)3H(SO4)2, while there is only little ammonium sulfate, (NH4)2SO4. Since ammonium bisulfate, NH4HSO4, does not nucleate homogeneously, it can only form via heterogeneous crystallization. As the ammonia-to-sulfate ratios of the atmospheric aerosol usually do not correspond to the stoichiometries of known crystalline substances, all solids are expected to occur in mixed-phase aerosol particles. This work highlights the global importance of letovicite, whose role as cloud condensation nucleus (CCN) and as scatterer of solar radiation remains to be scrutinized.

Colberg, C. A.; Luo, B. P.; Wernli, H.; Koop, T.; Peter, Th.

2002-12-01

325

Laboratory study on new particle formation from the reaction OH + SO2: influence of experimental conditions, H2O vapour, NH3 and the amine tert-butylamine on the overall process  

NASA Astrophysics Data System (ADS)

Nucleation experiments starting from the reaction of OH radicals with SO2 have been performed in the IfT-LFT flow tube under atmospheric conditions at 293±0.5 K for a relative humidity of 13-61%. The presence of different additives (H2, CO, 1,3,5-trimethylbenzene) for adjusting the OH radical concentration and resulting OH levels in the range (4-300)·105 molecule cm-3 did not influence the nucleation process itself. The number of detected particles as well as the threshold H2SO4 concentration needed for nucleation was found to be strongly dependent on the counting efficiency of the used counting devices. High-sensitivity particle counters allowed the measurement of freshly nucleated particles with diameters down to about 1.5 nm. A parameterization of the experimental data was developed using power law equations for H2SO4 and H2O vapour. The exponent for H2SO4 from different measurement series was in the range of 1.7-2.1 being in good agreement with those arising from analysis of nucleation events in the atmosphere. For increasing relative humidity, an increase of the particle number was observed. The exponent for H2O vapour was found to be 3.1 representing a first estimate. Addition of 1.2·1011 molecule cm-3 or 1.2·1012 molecule cm-3 of NH3 (range of atmospheric NH3 peak concentrations) revealed that NH3 has a measureable, promoting effect on the nucleation rate under these conditions. The promoting effect was found to be more pronounced for relatively dry conditions. NH3 showed a contribution to particle growth. Adding the amine tert-butylamine instead of NH3, the enhancing impact for nucleation and particle growth appears to be stronger.

Berndt, T.; Stratmann, F.; Sipilä, M.; Vanhanen, J.; Petäjä, T.; Mikkilä, J.; Grüner, A.; Spindler, G.; Mauldin, R. Lee, III; Curtius, J.; Kulmala, M.; Heintzenberg, J.

2010-03-01

326

An Experimental Study of Single Suspended H2so4/nh3/h2o-aerosols : Atmospheric Relevance of Letovicite  

NASA Astrophysics Data System (ADS)

Aerosols in the atmosphere have a large effect on the radiative balance of the earth due to their scattering and absorbing properties. Some aerosols can also act as cloud con- densation nuclei (CCN) of cirrus clouds which play an important role for the global climate. The influence of NH3 and H2SO4 containing aerosols on cirrus formation are discussed. The thermodynamic and kinetic behavior of the H2SO4/NH3/H2O-system at atmospheric conditions is poorly understood. The reason for this uncertainty is that thermodynamic models are mainly based on experimental data obtained at room tem- perature and that the conditions at which aerosols crystallize cannot be predicted re- liably. Hence, laboratory experiments are needed to improve our knowledge of the chemical and physical state of inorganic aerosols in the atmosphere. In the present work laboratory measurements of individual H2SO4/NH3/H2O-aerosols in an electrodynamic particle trap are performed. The trap is located in a thermally in- sulated chamber where the relative humidity (RH), the total pressure and temperature are controlled. The DC-Voltage is used as a direct measure for the mass of the parti- cles. The radii of liquid droplets are determined by Mie-phase-function-analysis and RMS-deviation measurements of the intensity fluctuations provide information on the aerosol morphology. Raman-spectroscopy is used to identify liquid and solid parti- cles chemically. These four analytical tools provide independent information on the aerosol composition and structure. The thermodynamic behavior of single suspended particles is examined for different stoichiometries at different temperatures and relative humidities. The deliquescence and efflorescence relative humidities (DRH and ERH), as well as the water uptake and loss are studied. In general the thermodynamic data of the present work is in good agreement to the model with Clegg et al. [1998] and existing experimental data. The observed solid phases are, surprisingly letovicite and ammonium sulfate, which often exist as mixed-phase (solid/liquid) particles. Ammonium bisulfate is not de- tected in the electrodynamic trap. Moreover the results suggest that a new, hitherto unknown phase is observed during the experiments. In supporting experiments the new phase is identified as ammonium bisulfate monohydrate. Efflorescence usually takes place at RH < 30%. The exact ERH values, however, de- pend on the liquid particle stoichiometry. Furthermore, it is observed that different 1 solids as well as solids and remaining liquid can coexist. In addition these mixed par- ticles crystallize in different morphologies and tend to form inclusion-particles with embedded liquid cavities, for example as veins filled with a liquid between single crystals or pores with concave surfaces. Laboratory results are applied to the atmosphere in a model that uses two input param- eters: NH+/SO24 -ratios of a GCM-study by Adams et al. [1999] and global RH-values - 4 determined from ECMWF-data by Wernli [2001]. NH+/SO24 -ratios and RH-values - 4 are followed along trajectories, calculated from ECMWF-data Wernli [2001]. In the present work a new model which combines the three data-sets is developed. Results indicate that a significant fraction of the ammoniate sulfate aerosols contain solids over large regions in the whole atmosphere, most likely in the form of letovicite. Be- cause of the varying stoichiometries of atmospheric aerosols it is expected that they form multiphase aerosols upon crystallization. The three major implications of the present work are: Crystalline ammoniated sulfate particles, especially letovicite, are very likely to occur throughout the whole atmosphere. These aerosols are not expected to be pure solids but mixtures of one or more solids and a remaining liquid. The morphologies of these aerosols are probably very diverse and complex and, hence, not easily predictable. Based on the experiments of this work letovicite appears to be an atmospherically very important phase whereas most earlier studies discuss only the relevance

Colberg, C. A.; Krieger, U. K.; Luo, B.; Wernli, H.; Peter, Th.

327

Trapping in water - an important prerequisite for complex reactivity in astrophysical ices: the case of acetone (CH3)2C = O and ammonia NH3  

NASA Astrophysics Data System (ADS)

Water is the most abundant compound in interstellar and cometary ices. Laboratory experiments on ice analogues have shown that water has a great influence on the chemical activity of these ices. In this study, we investigated the reactivity of acetone-ammonia ices, showing that water is an essential component in chemical reactions with high activation energies. In a water-free binary ice, acetone and ammonia do not react due to high activation energy, as the reactants desorb before reacting (at 120 and 140 K, respectively). By contrast, our study shows that under experimental conditions of ˜150 K, this reaction does occur in the presence of water. Here, water traps reactants in the solid phase above their desorption temperatures, allowing them to gather thermal energy as the reaction proceeds. Using infrared spectroscopy and mass spectrometry associated with isotopic labelling, as well as quantum chemical calculations, 2-aminopropan-2-ol (2HN-C(CH3)2-OH) was identified as the acetone-ammonia reaction product. The formation of this product may represent the first step towards formation of 2-aminoisobutyric acid (AIB) in the Strecker synthesis. The activation energy for the formation of 2-aminopropan-2-ol was measured to be 42 ± 3 kJ mol-1, while its desorption energy equalled 61.3 ± 0.1 kJ mol-1. Our work demonstrates that astrophysical water, rather than being a non-thermally reactive species, is crucial for the evolution of complex chemistry occurring in the Universe.

Fresneau, Aurélien; Danger, Grégoire; Rimola, Albert; Theule, Patrice; Duvernay, Fabrice; Chiavassa, Thierry

2014-10-01

328

Lateral interactions in the desorption kinetics of weakly adsorbed species: unexpected differences in the desorption of C 4 alkenes and alkanes from Ag(110) due to oriented ?-bonding of the alkenes  

NASA Astrophysics Data System (ADS)

Temperature programmed desorption (TPD), X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure (NEXAFS) techniques were used to compare the desorption kinetics of butanes and butenes. Even though these molecules are weakly adsorbed and of similar molecular weight, alkane desorption shows evidence of weak attractive intermolecular interactions, whereas alkenes show clear evidence for moderately strong repulsive interactions in desorption. This behavior is contrary to the weak attractive intermolecular interactions expected for both the butanes and the butenes based on theories of physical adsorption, since the second virial coefficients for both in the gas phase are negative below 550 K. Adsorption of the alkenes clearly introduces repulsive intermolecular forces that are not present in the gas phase. The origin of these intermolecular forces is revealed by NEXAFS measurements for the alkenes, which show a strong orientation of the double bond axis parallel to the surface, indicative of weak directional bonding between the surface and the alkene. It appears that this preferred orientation caused by the surface alters the intermolecular forces between colliding pairs of alkenes, leading to the repulsive interactions that produce the decrease in the activation energy for desorption with increasing alkene coverage. This effect does not occur for butane, whose weak intermolecular interactions in the adsorbed layer are consistent with the predictions for physical adsorption.

Pawela-Crew, Jacquelyn; Madix, Robert J.

1995-09-01

329

Interaction of Acetone with Single Wall Carbon Nanotubes at Cryogenic Temperatures: A Combined Temperature Programmed  

E-print Network

charge transfer or polarization was found. Carbon black was used to model amorphous carbonaceous impurities present in as-produced SWCNTs. Desorption of acetone from carbon black revealed two peaks at 140 desorption from SWCNTs was peak at 300 K that was not observed for carbon black. Care should be taken when

Borguet, Eric

330

Desorption of uranium from amidoxime fiber adsorbent  

SciTech Connect

An amidoxime fibrous adsorbent is contacted with uranium-enriched seawater (10 ppm); about 10 mg uranium is loaded per 1 g dry fiber. Then the rate and yield of uranium desorption from the fiber are determined with various eluents. Acid solutions are superior to alkali carbonate solutions as eluents. With a 0.1 mol[center dot]L[sup [minus]1] HCl solution, desorption is completed in 2 hours regardless of the presence of uranium in the leaching solution up to 15 ppm ([approx]6 [times] 10[sup [minus]5]mol[center dot]L[sup [minus]1]). Serial operation of the adsorption-desorption cycle four times does not affect desorption efficiency, but the addition of heavy metal ions to the eluent at a level of 1.8 [times] 10[sup [minus]3]mol[center dot]L[sup [minus]1] significantly decreases desorption efficiency. 13 refs., 5 figs., 1 tab.

Goto, Akira; Morooka, Shigeharu; Fukamachi, Masakazu; Kusakabe, Katsuki (Kyushu Univ., Fukuoka (Japan)); Kago, Tokihiro (Towa Univ., Fukuoka (Japan))

1993-10-01

331

Laboratory study on new particle formation from the reaction OH + SO2: influence of experimental conditions, H2O vapour, NH3 and the amine tert-butylamine on the overall process  

NASA Astrophysics Data System (ADS)

Nucleation experiments starting from the reaction of OH radicals with SO2 have been performed in the IfT-LFT flow tube under atmospheric conditions at 293±0.5 K for a relative humidity of 13-61%. The presence of different additives (H2, CO, 1,3,5-trimethylbenzene) for adjusting the OH radical concentration and resulting OH levels in the range (4-300) ×105 molecule cm-3 did not influence the nucleation process itself. The number of detected particles as well as the threshold H2SO4 concentration needed for nucleation was found to be strongly dependent on the counting efficiency of the used counting devices. High-sensitivity particle counters allowed the measurement of freshly nucleated particles with diameters down to about 1.5 nm. A parameterization of the experimental data was developed using power law equations for H2SO4 and H2O vapour. The exponent for H2SO4 from different measurement series was in the range of 1.7-2.1 being in good agreement with those arising from analysis of nucleation events in the atmosphere. For increasing relative humidity, an increase of the particle number was observed. The exponent for H2O vapour was found to be 3.1 representing an upper limit. Addition of 1.2×1011 molecule cm-3 or 1.2×1012 molecule cm-3 of NH3 (range of atmospheric NH3 peak concentrations) revealed that NH3 has a measureable, promoting effect on the nucleation rate under these conditions. The promoting effect was found to be more pronounced for relatively dry conditions, i.e. a rise of the particle number by 1-2 orders of magnitude at RH = 13% and only by a factor of 2-5 at RH = 47% (NH3 addition: 1.2×1012 molecule cm-3). Using the amine tert-butylamine instead of NH3, the enhancing impact of the base for nucleation and particle growth appears to be stronger. Tert-butylamine addition of about 1010 molecule cm-3 at RH = 13% enhances particle formation by about two orders of magnitude, while for NH3 only a small or negligible effect on nucleation in this range of concentration appeared. This suggests that amines can strongly influence atmospheric H2SO4-H2O nucleation and are probably promising candidates for explaining existing discrepancies between theory and observations.

Berndt, T.; Stratmann, F.; Sipilä, M.; Vanhanen, J.; Petäjä, T.; Mikkilä, J.; Grüner, A.; Spindler, G.; Mauldin, R. Lee, III; Curtius, J.; Kulmala, M.; Heintzenberg, J.

2010-08-01

332

On the nature of the structural and magnetic phase transitions in the layered perovskite-like (CH3NH3)2[Fe(II)Cl4].  

PubMed

In view of renewed interest in multiferroic for molecular systems, we re-examine the structural and magnetic properties of the potentially ferroic layered perovskite-like (CH3NH3)2[Fe(II)Cl4] due to its high-temperature magnetic ordering transition. The structures from several sets of diffraction data of single crystals consist of square-grid layers of corner-sharing FeCl6 octahedra and changes from the high-symmetry I4/mmm (T > 335 K) to the low-symmetry Pccn (T < 335 K). In the former the iron and bridging chlorine atoms are within the layer and the organic cations sit in the middle of each square grid, while in the latter the octahedra are tilted in pairs, two in and two out, progressively by up to 12° and the nitrogen atoms follow their motion to be nearer to the two-in pairs. Crystals are stable up to 450 K and display three phase transitions, two structural at 332 and 233 K and one magnetic at 95 K. The temperature dependences of the dc magnetization (zero-field and field-cooling modes) in different applied fields (10-10,000 Oe) on several aligned single crystals independently reveal a hidden-canted antiferromagnetic ground state of at least four sublattices and not the reported canted antiferromagnetic ground state. A metamagnetic critical field of only 200 Oe transforms it to a canted antiferromagnet. The estimated canting angle is 1.4° in zero field, and it folds to ca. 2.8° in a field of 50 kOe at 2 K. The easy axis is along 010, the hard axis is along 100, and the intermediate and canting axis is 001. Using the available extracted parameters the phase diagram has been constructed. This study provides evidence of a complex and intricate manifestation of the orientation, temperature, and field dependence of the interplay between anisotropy and coherent lengths, which would need further studies. PMID:24471961

Han, Jing; Nishihara, Sadafumi; Inoue, Katsuya; Kurmoo, Mohamedally

2014-02-17

333

Reactions of uranium atoms with ammonia: infrared spectra and quasi-relativistic calculations of the U:NH3, H2N--UH, and HN==UH2 complexes.  

PubMed

Ammonia molecules interact with U atoms, and the resulting U:NH3 complex rearranges upon visible irradiation to form the H2N--UH and HN==UH2 molecules in excess argon. These products are identified by functional group frequencies, 15NH3 and ND3 isotopic shifts, and comparison to frequencies calculated by using density functional theory. The N==U pi bond in HN==UH2 is enhanced by partial triple-bond character through N(2p) to U(5f) conjugation, which is comparable to that found in the analogous HN==ThH2 molecule. These products also form complexes with additional ammonia molecules in the matrix. The interesting higher-energy N[triple chemical bond]UH3 complex is not formed. PMID:18767108

Wang, Xuefeng; Andrews, Lester; Marsden, Colin J

2008-01-01

334

Direct microscopic observation of Oswald ripening along a faceted bridge for the layer perovskite (C3H7NH3)2CuCl4 in aqueous solution  

Microsoft Academic Search

Simultaneous growth and dissolution has been observed of two extremely thin platelets of the layer perovskite bis-(propylammonium) copper(II) tetrachloride (C3H7NH3)2CuCl4 from a thermostated aqueous solution. From the details of the experiment it is concluded that the event took place at or near the saturation concentration of the solution, so that the event is an example of Oswald ripening. The origin

F. H. Mischgofsky

1983-01-01

335

trans-[Ru(NO)(NH3)4(py)](BF4)3.H2O encapsulated in PLGA microparticles for delivery of nitric oxide to B16-F10 cells: Cytotoxicity and phototoxicity.  

PubMed

The NO donor trans-[Ru(NO)(NH(3))(4)(py)](BF(4))(3).H(2)O (py=pyridine) was loaded into poly-lactic-co-glycolic acid (PLGA) microparticles using the double emulsification technique. Scanning electron microscopy (SEM) and dynamic light scattering revealed that the particles are spherical in shape, have a diameter of 1600nm, and have low tendency to aggregate. The entrapment efficiency was 25%. SEM analysis of the melanoma cell B16-F10 in the presence of the microparticles containing the complex trans-[Ru(NO)(NH(3))(4)(py)](BF(4))(3).H(2)O (pyMP) showed that the microparticles were adhered to the cell surface after 2h of incubation. The complex with concentrations lower than 1x10(-4)M did not show toxicity in B16-F10 murine cells. The complex in solution is toxic at higher concentrations (>1x10(-3)M), with cell death attributed to NO release following the reduction of the complex. pyMP is not cytotoxic due to the lower bioavailability and availability of the entrapped complex to the medium and its reducing agents. However, pyMP is phototoxic upon light irradiation. The phototoxicity strongly suggests that cell death is due to NO release from trans-[Ru(NO)(NH(3))(4)(py)](3+). This work shows that pyMP can serve as a model for a drug delivery system carrying the NO donor trans-[Ru(NO)(NH(3))(4)(py)](BF(4))(3).H(2)O, which can release NO locally at the tumor cell by irradiation with light only. PMID:18215422

Gomes, Anderson J; Barbougli, Paula A; Espreafico, Enilza M; Tfouni, Elia

2008-04-01

336

Effect of Ce doping of TiO2 support on NH3-SCR activity over V2O5-WO3/CeO2-TiO2 catalyst.  

PubMed

CeO2-TiO2 composite supports with different Ce/Ti molar ratios were prepared by a homogeneous precipitation method, and V2O5-WO3/CeO2-TiO2 catalysts for the selective catalytic reduction (SCR) of NOx with NH3 were prepared by an incipient-wetness impregnation method. These catalysts were characterized by means of BET, XRD, UV-Vis, Raman and XPS techniques. The results showed that the catalytic activity of V2O5-WO3/TiO2 was greatly enhanced by Ce doping (molar ratio of Ce/Ti=1/10) in the TiO2 support. The catalysts that were predominantly anatase TiO2 showed better catalytic performance than the catalysts that were predominantly fluorite CeO2. The Ce additive could enhance the surface adsorbed oxygen and accelerate the SCR reaction. The effects of O2 concentration, ratio of NH3/NO, space velocity and SO2 on the catalytic activity were also investigated. The presence of oxygen played an important role in NO reduction. The optimal ratio of NH3/NO was 1/1 and the catalyst had good resistance to SO2 poisoning. PMID:25288555

Cheng, Kai; Liu, Jian; Zhang, Tao; Li, Jianmei; Zhao, Zhen; Wei, Yuechang; Jiang, Guiyuan; Duan, Aijun

2014-10-01

337

Ab initio Quantum Chemical Studies of Reactions in Astrophysical Ices. Reactions Involving CH3OH, CO2, CO, HNCO in H2CO/NH3/H2O Ices  

NASA Technical Reports Server (NTRS)

While reactions between closed shell molecules generally involve prohibitive barriers in the gas phase, prior experimental and theoretical studies have demonstrated that some of these reactions are significantly enhanced when confined within an icy grain mantle and can occur efficiently at temperatures below 100 K with no additional energy processing. The archetypal case is the reaction of formaldehyde (H2CO) and ammonia (NH3) to yield hydroxymethylamine (NH2CH2OH). In the present work we have characterized reactions involving methanol (CH3OH), carbon dioxide (CO2), carbon monoxide (CO), and isocyanic acid (HNCO) in search of other favorable cases. Most of the emphasis is on CH3OH, which was investigated in the two-body reaction with one H2CO and the three-body reaction with two H2CO molecules. The addition of a second H2CO to the product of the reaction between CH3OH and H2CO was also considered as an alternative route to longer polyoxymethylene polymers of the -CH2O- form. The reaction between HNCO and NH3 was studied to determine if it can compete against the barrierless charge transfer process that yields OCN(-) and NH4(+). Finally, the H2CO + NH3 reaction was revisited with additional benchmark calculations that confirm that little or no barrier is present when it occurs in ice.

Woon, David E.

2006-01-01

338

Monte Carlo evaluation of thermal desorption rates  

SciTech Connect

The recently reported method for computing thermal desorption rates via a Monte Carlo evaluation of the appropriate transition state theory expression (J. E. Adams and J. D. Doll, J. Chem. Phys. 74, 1467 (1980)) is extended, by the use of importance sampling, so as to generate the complete temperature dependence in a single calculation. We also describe a straightforward means of calculating the activation energy for the desorption process within the same Monte Carlo framework. The result obtained in this way represents, for the case of a simple desorptive event, an upper bound to the true value.

Adams, J.E.; Doll, J.D.

1981-05-01

339

Plasma Desorption Mass Spectrometry: Coming of Age.  

ERIC Educational Resources Information Center

Discusses the history and development of Plasma Desorption Mass Spectrometry to determine molecular weights and structures of proteins and polymers. Outlines theory, instrumentation, and sample preparation commonly used. Gives several examples of resulting spectra. (ML)

Cotter, Robert J.

1988-01-01

340

Thermal Desorption Analysis Applied to Materials Characterization.  

National Technical Information Service (NTIS)

Thermal desorption analysis is used to characterize the outgassing properties of both vacuum envelope materials and the hydrided sources and targets in neutron generators employing erbium deuteride films and erbium tritide target. (ERA citation 05:002698)

T. K. Mehrhoff

1979-01-01

341

The influence of potassium doping on hydrogen adsorption on carbon nanocone material studied by thermal desorption and photoemission  

NASA Astrophysics Data System (ADS)

Hydrogen adsorption/desorption on potassium doped carbon nanocones was studied by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy. TPD shows that the hydrogen storage was enhanced by up to 40% after potassium doping. Hydrogen adsorption on K-modified carbon nanocone material seems more stable than that on the undoped material. The XPS results indicate that there is charge transfer from potassium to carbon. The C 1s binding energy increases with increased potassium doping and the peak becomes wider. These binding energy shifts may be explained by work function changes related to potassium doping. The K 2p spectra indicate that there are two different local environments for potassium on the carbon cone material.

Yu, Xiaofeng; Raaen, Steinar

2013-04-01

342

Surface Electronic Spectra Detected by Atomic Desorption  

SciTech Connect

Using continuously tunable laser excitation of KI we measure the velocity profiles and the yield of desorbing hyperthermal iodine atoms as a function of photon energy. Based on the theoretical model of desorption we demonstrate that these spectra display a signature of a surface exciton and constitute a new sensitive method of surface specific desorption spectroscopy. Our results demonstrate that creation of surface excitions can be a much more general phenomenon than was previously thought based on extant spectroscopic measurements.

Joly, Alan G.; Beck, Kenneth M.; Henyk, Matthias; Hess, Wayne P.; Sushko, Petr V.; Shluger, Alexander L.

2003-10-10

343

Transformation of Paraffins to Improve the Octane Number of the Cracked Naphtha Over Ni\\/HZSM-5 Catalyst  

Microsoft Academic Search

Paraffins in the cracked naphtha can be transformed into aromatics and isoparaffin to improve the octane number. In this article, a series of Ni\\/HZSM-5 bifunctional catalysts were prepared and were characterized by temperature-programmed desorption of NH3 (NH3-TPD), FT-IR analysis with adsorbed pyridine as well as by x-ray powder diffraction analysis. The monolayer dispersion threshold value of Ni on HZSM-5 was

C. Yin; R. Zhao; H. Zhao; Y. Xu; C. Liu

2007-01-01

344

Molecular Desorption from Dust in Star-Forming Regions  

Microsoft Academic Search

The chemistry of collapsing protostellar cores has been reassessed so as to include the effects of desorption of molecular species from grain mantles. Several desorption mechanisms have been considered, including the mechanism by which desorption occurs as a result of H2 formation on the grains. Although the desorption time-scale is typically larger than the free-fall time, the desorption processes may

K. Willacy; J. M. C. Rawlings; D. A. Williams

1994-01-01

345

Determination of the Arrhenius Activation Energy Using a Temperature-Programmed Flow Reactor.  

ERIC Educational Resources Information Center

Describes a novel method for the determination of the Arrhenius activation energy, without prejudging the validity of the Arrhenius equation or the concept of activation energy. The method involves use of a temperature-programed flow reactor connected to a concentration detector. (JN)

Chan, Kit-ha C.; Tse, R. S.

1984-01-01

346

Temperature-programmed combustion studies of coal and maceral group concentrates  

Microsoft Academic Search

Temperature-programmed combustion profiles of coals and their maceral group concentrates were obtained by thermogravimetric analysis in air at a heating rate of 15 K min?1. The maceral group concentrates were prepared by density separation of demineralized, micronized coal samples. Particle size had a significant effect on combustion profiles, with increased complexity in terms of the number of peaks observed for

Jimmy B. Milligan; K. Mark Thomas; John C. Crelling

1997-01-01

347

Coordination preferences of the alkali cations sodium and caesium in the mixed-cationic Zintl ammoniate Cs3.2Na0.8Ge9·5.3NH3.  

PubMed

The involvement of two different alkali cations in the nonagermanide ammoniate Cs3.2Na0.8Ge9·5.3NH3 [tricaesium sodium nonagermanide-ammonia (1/5.3)] provides insights into the coordination behaviour of ammonia towards sodium and caesium cations within one compound and represents the first mixed-cationic solvate structure of nonagermanide tetraanions. The compound crystallizes in the monoclinic space group P21/m and, with the presence of pseudomerohedral twinning, mixed-cation sites and disordering of the nonagermanide cage anions, features a combination of crystallographic challenges which could all be resolved during the refinement. PMID:25370102

Gärtner, Stefanie; Suchentrunk, Christof; Korber, Nikolaus

2014-11-15

348

A straight forward route for the development of metal-organic frameworks functionalized with aromatic -OH groups: synthesis, characterization, and gas (N2, Ar, H2, CO2, CH4, NH3) sorption properties.  

PubMed

A facile and general methodology for the development of metal-organic frameworks (MOFs) functionalized with pendant, aromatic hydroxyl (-OH) groups is presented. Extensive gas-sorption studies in representative and important MOFs functionalized with free aromatic -OH groups such as the IRMOF-8 and DUT-6 (or MOF-205), denoted here as 1 and 2, revealed a high CO(2)/CH(4) selectivity for 1 (13.6 at 273 K and 1 bar) and a high NH(3) uptake of 16.4 mol kg(-1) at 298 K and 1 bar for 2. PMID:23301595

Spanopoulos, Ioannis; Xydias, Pantelis; Malliakas, Christos D; Trikalitis, Pantelis N

2013-01-18

349

{[M(NH3)6][Ag4M4Sn3Se13]}? (M=Zn, Mn): Three-dimensional chalcogenide frameworks constructed from quaternary metal selenide clusters with two different transition metals  

NASA Astrophysics Data System (ADS)

Herein we report solvothermal syntheses of two new three-dimensional chalcogenide frameworks {[M(NH3)6][Ag4M4Sn3Se13]}n (M=Zn (1), Mn (2)), which consist of quaternary metal selenide clusters with two different transition metals. The compounds represent the first Ag-Zn/Mn-Sn-Se based quaternary anionic frameworks. The optical studies show that the band gaps for 1 and 2 are 2.09 eV and 1.71 eV, respectively. Moreover, the photoelectrochemical study indicates that compound 1 displays n-type semiconducting behaviour and is photoactive under visible light illumination (?>400 nm).

Xiong, Wei-Wei; Miao, Jianwei; Li, Pei-Zhou; Zhao, Yanli; Liu, Bin; Zhang, Qichun

2014-10-01

350

Identification and characterization of monomeric, volatile SiCl3NH2 as product of the reaction between SiCl4 and NH3: an important intermediate on the way to silicon nitride?  

PubMed

We studied the reaction of SiCl(4) with NH(3) by mass spectrometry and IR spectroscopy. By means of mass spectrometry, SiCl(3)NH(2) was for the first time identified as an intermediate generated in significant amounts in the course of the reaction. In additional experiments, SiCl(3)NH(2) was formed as a stable gaseous product of the ammonolysis of SiCl(4), and the product was identified and characterized in detail by IR spectroscopic methods (gas phase and matrix isolation) in combination with quantum-chemical calculations. The calculations also gave access to important thermodynamical data. PMID:12645028

Himmel, Hans-Jörg; Schiefenhövel, Nils; Binnewies, Michael

2003-03-17

351

Development of laser sensing device both NH3 at 1.53?m and NO2 at 3.46?m at the same instant using laser absorption spectrometry  

NASA Astrophysics Data System (ADS)

This paper reports on a trace gas monitor using a dual wavelength coherent light source. The laser spectrometer is based on difference frequency generation (DFG) techniques in a periodically poled lithium niobate (PPLN) crystal, naturally having two laser sources (i.e., signal and pump laser sources) in it. A newly proposed idea is to use residual signal DFB-LD power to tune to NH3 absorption lines around at 1.536 ?m when the DFG output wavelengths are accessed at 3.46 ?m. In the experiments, the signal DFB-LD was carefully tune the wavelength guided by HITRAN database in order to select appropriate mid-IR absorption lines of NO2, while the DFB-LD can detect simultaneously NH3 absorption lines. As results, both gaseous species were detected successfully with the same multi-pass optical cell in one DFG spectrometer scheme. Spectroscopic data both in near-IR and in mid-IR region, simulating flue gas condition are discussed in detail.

Wake, Kouichi; Ono, Takuro; Tanoue, Satoru; Ohtani, Nobuyoshi; Yamaguchi, Shigeru; Endo, Masamori; Nanri, Kenzo; Morita, Takakazu; Fujioka, Tomoo

2005-03-01

352

Spatiotemporal distribution of NOx storage and impact on NH3 and N2O selectivities during lean/rich cycling of a Ba-based lean NOx trap catalyst  

SciTech Connect

We summarize results from an investigation of the spatiotemporal distribution of NO{sub x} storage and intermediate gas species in determining the performance of a fully formulated, Ba-based, lean NO{sub x} trap catalyst under lean/rich cycling conditions. By experimentally resolving spatiotemporal profiles of gas composition, we found that stored NO{sub x} was significantly redistributed along the monolith axis during the rich phase of the cycle by release and subsequent downstream re-adsorption. Sulfur poisoning of upstream NO{sub x} storage sites caused the active NO{sub x}-storage zone to be displaced downstream. This axial displacement in turn influenced rich-phase NO{sub x} release and re-adsorption. As sulfur poisoning increased, NH3 slip at the catalyst exit also increased due to its formation closer to the catalyst outlet and decreased exposure to downstream oxidation by surface oxygen. N{sub 2}O formation was found to be associated with nitrate reduction rather than oxidation of NH3 by stored oxygen. We propose that the observed evolution of N{sub 2}O selectivity with sulfation can be explained by changes in the spatiotemporal distribution of NO{sub x} storage resulting in either increased or decreased number of precious-metal sites surrounded by nitrates.

Choi, Jae-Soon [ORNL; Partridge Jr, William P [ORNL; Pihl, Josh A [ORNL; Kim, Miyoung [ORNL; Koci, Petr [Institute of Chemical Technology, Prague, Czech Republic; Daw, C Stuart [ORNL

2012-01-01

353

Detecting Chemical Hazards with Temperature-Programmed Microsensors: Overcoming Complex Analytical Problems with Multidimensional Databases *  

NASA Astrophysics Data System (ADS)

Complex analytical problems, such as detecting trace quantities of hazardous chemicals in challenging environments, require solutions that most effectively extract relevant information about a sample's composition. This review presents a chemiresistive microarray-based approach to identifying targets that combines temperature-programmed elements capable of rapidly generating analytically rich data sets with statistical pattern recognition algorithms for extracting multivariate chemical fingerprints. We describe the chemical-microsensor platform and discuss its ability to generate orthogonal data through materials selection and temperature programming. Visual inspection of data sets reveals device selectivity, but statistical analyses are required to perform more complex identification tasks. Finally, we discuss recent advances in both devices and algorithms necessary to deal with practical issues involved in long-term deployment. These issues include identification and correction of signal drift, challenges surrounding real-time unsupervised operation, repeatable device manufacturability, and hierarchical classification schemes designed to deduce the chemical composition of untrained analyte species.

Meier, Douglas C.; Raman, Baranidharan; Semancik, Steve

2009-07-01

354

APPLICATION OF THERMAL DESORPTION TECHNOLOGIES TO HAZARDOUS WASTE SITES  

EPA Science Inventory

Thermal desorption is a separation process frequently used to remediate many Superfund sites. hermal desorption technologies are recommended and used because of (1) the wide range of organic contaminants effectively treated, (2) availability and mobility of commercial systems, an...

355

APPLICATION OF THERMAL DESORPTION TECHNOLOGIES TO HAZARDOUS WASTE SITES  

EPA Science Inventory

Thermal desorption is a separation process frequently used to remediate many Superfund sites. Thermal desorption technologies are recommended and used because of (1) the wide range of organic contaminants effectively treated, (2) availability and mobility of commercial systems, ...

356

Enhanced desorption of 2,4,6 Trinitrotoluene  

E-print Network

requires that the 'TNT be desorbed and transferred into the aqueous phase. The purpose of this research was to study the influence of surfactants on the desorption of TNT. Furthermore, a comparison of the desorption enhancement capabilities of synthetic...

Aturaliye, Upul Anuruddha

2012-06-07

357

THERMAL DESORPTION OF PETROLEUM CONTAMINATED SOILS  

EPA Science Inventory

The U.S. Environmental Protection Agency recently funded a study which addresses the treatment of soils contaminated by petroleum hydrocarbons using low temperature thermal desorption (LTTD). he proposed paper will summarize some of the results of that study. TTD has become a maj...

358

Mercury compounds characterization by thermal desorption.  

PubMed

The ability to accurately determine metal mercury content and identify different mercury species in solid samples is essential for developing remediation and control strategies. The aim of the present study is to characterize mercury compounds based on thermal desorption. For this purpose a series of samples was prepared and the operational parameters-heating velocity, carrier gas-were optimized. Fifteen commercial mercury compounds were analyzed for use as fingerprints. The results of the study show that the identification of mercury species by the method of thermal desorption is possible. The temperature of desorption increased according to the following order HgI2desorption curve shows that recoveries of 79-104% for HgS can be estimated. The proposed method represents a significant step forward in direct mercury analysis in solid samples. PMID:23953477

Rumayor, M; Diaz-Somoano, M; Lopez-Anton, M A; Martinez-Tarazona, M R

2013-09-30

359

THE SORPTION AND DESORPTION OF IODINE  

Microsoft Academic Search

Adsorption isothernas were measured for various substances for iodine in ; carbon tetrachloride at 20 deg C. Sorption of radioiodine by these solids from ; the gas phase was also measured at 200 deg C; exchange of the radioiodine with ; inactive iodine has shown considerable differences in behavior; thermal ; desorption is not easily accomplished. The results are discussed

F. Hudswell; E. Furby; J. G. Simons; K. L. Wilkinson

1960-01-01

360

Computational simulation characteristics desorption in TPS aggregates  

NASA Astrophysics Data System (ADS)

The article describes the modified model of desorption in a continuously operating apparatus in fluidized bed, which allows for a refined timing warm adsorbent particles of spherical shape at a flow of hot air to equalize the temperature along the radius of granules and assess relevant energy costs.

Goldaev, Sergey; Khushvaktov, Alisher

2014-08-01

361

The potential for and challenges of detecting chemical hazards with temperature-programmed microsensors  

Microsoft Academic Search

Several recent demonstrations of the abilities of micro-electromechanical systems (MEMS)-based microsensor technology to detect hazardous compounds and their simulants in a variety of background conditions are presented. In each case, two pairs of conductometric metal oxide sensors (TiO2 and SnO2) produced via chemical vapor deposition are operated using temperature-programmed sensing (TPS). NIST microdevices can utilize this operating mode to sample

D. C. Meier; J. K. Evju; Z. Boger; B. Raman; K. D. Benkstein; C. J. Martinez; C. B. Montgomery; S. Semancik

2007-01-01

362

Method of enhancing selective isotope desorption from metals  

DOEpatents

This invention relates generally to the field of gas desorption from metals; and, more particularly, to a method of enhancing the selective desorption of a particular isotope of a gas from metals. Enhanced selective desorption is especially useful in the operation of fusion devices.

Knize, R.J.; Cecchi, J.L.

1983-07-26

363

Isothermal and isobaric desorption of carbon dioxide by purge  

Microsoft Academic Search

Adsorption and desorption constitute the two most basic steps in all pressure swing adsorption (PSA) processes for gas separation. The desorption steps are the primary energy-consuming steps in the PSA process. They also dictate the overall separation efficiency. Isothermal and isobaric desorption of carbon dioxide was experimentally evaluated by purging adsorbent columns saturated with pure carbon dioxide with pure hydrogen,

Shivaji Sircar; Timothy C. Golden

1995-01-01

364

Lindane Adsorption-Desorption on Chitin in Sea Water  

Microsoft Academic Search

The adsorption and desorption processes by solid materials are important in determining the movement and fate of pesticide compounds in aquatic systems. Chitin is one of the constituents of natural organic matter and may serve as a model organic phase for studying the pesticide adsorption-desorption in marine systems. The lindane adsorption-desorption to chitin has been studied as a function of

M. Gonzalez-davila; J. Perez-Peña; J. M. Santana-casiano

1992-01-01

365

Isoparaffin production by aqueous phase processing of sorbitol over the Ni\\/HZSM-5 catalysts: Effect of the calcination temperature of the catalyst  

Microsoft Academic Search

Ni\\/HZSM-5 catalysts calcined at different temperatures were used in the isoparaffin production by aqueous phase processing of sorbitol and characterized by N2 physical adsorption, temperature-programmed reduction (H2-TPR), temperature-programmed desorption of ammonia (NH3-TPD) and Raman techniques. The effect of calcination temperature of the catalysts on the catalytic performance for the reaction was investigated. The activity test results indicated that the maximal

Qing Zhang; Ke Qiu; Bing Li; Ting Jiang; Xinghua Zhang; Longlong Ma; Tiejun Wang

2011-01-01

366

Reversibility, Dopant Desorption, and Tunneling in the Temperature-Dependent Conductivity of Type-Separated, Conductive Carbon Nanotube Networks  

SciTech Connect

We present a comprehensive study of the effects of doping and temperature on the conductivity of single-walled carbon nanotube (SWNT) networks. We investigated nearly type-pure networks as well as networks comprising precisely tuned mixtures of metallic and semiconducting tubes. Networks were studied in their as-produced state and after treatments with nitric acid, thionyl chloride, and hydrazine to explore the effects of both intentional and adventitious doping. For intentionally and adventitiously doped networks, the sheet resistance (R{sub s}) exhibits an irreversible increase with temperature above {approx}350 K. Dopant desorption is shown to be the main cause of this increase and the observed hysteresis in the temperature-dependent resistivity. Both thermal and chemical dedoping produced networks free of hysteresis. Temperature-programmed desorption data showed that dopants are most strongly bound to the metallic tubes and that networks consisting of metallic tubes exhibit the best thermal stability. At temperatures below the dopant desorption threshold, conductivity in the networks is primarily controlled by thermally assisted tunneling through barriers at the intertube or interbundle junctions.

Barnes, T. M.; Blackburn, J. L.; van de Lagemaat, J.; Coutts, T. J.; Heben, M. J.

2008-09-01

367

Synthesis and structural characterization of two cobalt phosphites: 1-D (H 3NC 6H 4NH 3)Co(HPO 3) 2 and 2-D (NH 4) 2Co 2(HPo 3) 3  

NASA Astrophysics Data System (ADS)

Two new cobalt phosphites, (H 3NC 6H 4NH 3)Co(HPO 3) 2 ( 1) and (NH 4) 2Co 2(HPO 3) 3 ( 2), have been synthesized and characterized by single-crystal X-ray diffraction. All the cobalt atoms of 1 are in tetrahedral CoO 4 coordination. The structure of 1 comprises twisted square chains of four-rings, which contain alternating vertex-shared CoO 4 tetrahedra and HPO 3 groups. These chains are interlinked with trans-1,4-diaminocyclohexane cations by hydrogen bonds. The 2-D structure of 2 comprises anionic complex sheets with ammonium cations present between them. An anionic complex sheet contains three-deck phosphite units, which are interconnected by Co 2O 9 to form complex layers. Magnetic susceptibility measurements of 1 and 2 showed that they have a weak antiferromagnetic interaction.

Cheng, Chi-Chang; Chang, Wei-Kuo; Chiang, Ray-Kuang; Wang, Sue-Lein

2010-02-01

368

Comment on "Density functional theory analysis of structural and electronic properties of orthorhombic perovskite CH3NH3PbI3" by Y. Wang et al., Phys. Chem. Chem. Phys., 2014, 16, 1424-1429.  

PubMed

Yun Wang et al. used density functional theory (DFT) to investigate the orthorhombic phase of CH3NH3PbI3, which has recently shown outstanding properties for photovoltaic applications. Whereas their analysis of ground state properties may represent a valuable contribution to understanding this class of materials, effects of spin-orbit coupling (SOC) cannot be overlooked as was shown in earlier studies. Moreover, their discussion on optical properties may be misleading for non-DFT-experts, and the nice agreement between experimental and calculated band gap is fortuitous, stemming from error cancellations between SOC and many-body effects. Lastly, Bader charges suggest potential problems during crystal structure optimization. PMID:24671474

Even, J; Pedesseau, L; Katan, C

2014-05-14

369

Near-band-edge optical responses of solution-processed organic-inorganic hybrid perovskite CH3NH3PbI3 on mesoporous TiO2 electrodes  

NASA Astrophysics Data System (ADS)

We studied the near-band-edge optical responses of solution-processed CH3NH3PbI3 on mesoporous TiO2 electrodes, which is utilized in mesoscopic heterojunction solar cells. Photoluminescence (PL) and PL excitation spectra peaks appear at 1.60 and 1.64 eV, respectively. The transient absorption spectrum shows a negative peak at 1.61 eV owing to photobleaching at the band-gap energy, indicating a direct band-gap semiconductor. On the basis of the temperature-dependent PL and diffuse reflectance spectra, we clarified that the absorption tail at room temperature is explained in terms of an Urbach tail and consistently determined the band-gap energy to be ˜1.61 eV at room temperature.

Yamada, Yasuhiro; Nakamura, Toru; Endo, Masaru; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

2014-03-01

370

The tropospheric gas composition of Jupiter's north equatorial belt (NH3, PH3, CH3D, GeH4, H2O) and the Jovian D/H isotropic ratio  

NASA Technical Reports Server (NTRS)

The gas composition of the troposphere of Jupiter in the clearest regions of the North Equatorial Belt (NEB) was derived from the Voyager 1 IRIS data. The infrared spectrum for this homogeneous cloud free region was modeled to infer altitude profiles for NH3, PH3, GeH4 and H2O. The Profiles for NH3 and PH3 were found to be depleted in the upper troposphere but otherwise in agreement with their solar values at the 1 bar level. The mole fraction for CH3D was determined to be 3.5(+1.0 or -1.3) x 10 to the minus 7th power. The GeH4 mole fraction of 7+ or -2 x 10 to the minus 10th power at the 2 to 3 bar level is a factor of 10 lower than the solar value. The H2O mole fraction is approximately 1 x 0.00001 at the 2.5 bar level and is increasing to approximately 3 x 0.00001 at 4 bars where it is a factor of 30 lower than solar. Using IRIS infrared values for the mole fractions of CH3D and CH4 a value of D/H = 3.6(+1.0 or -1.4)x 0.00001 is derived. Assuming this Jovian D/H ratio is representative of the protosolar nebula, and correcting for chemical galactic evolution, yields a value of 5.5 - 9.0 x 0.00001 for the primordial D/H ratio and an upper limit of 1.8 to 2.4 x 10 to the minus 31st power cu cm for the present day baryon density.

Kunde, V.; Hanel, R.; Maguire, W.; Gautier, D.; Baluteau, J. P.; Marten, A.; Chedin, A.; Husson, N.; Scott, N.

1982-01-01

371

Robust removal of heavy metals from water by intercalation chalcogenide [CH3NH3]2xMnxSn3-xS6·0.5H2O  

NASA Astrophysics Data System (ADS)

The intercalation chalcogenide, [CH3NH3]2xMnxSn3-xS6·0.5H2O (x = 0.5-1.1) (CMS), was synthesized by simply hydrothermal method, which exhibited excellent adsorption properties for the removal of Cd2+/Pb2+. CNS analysis, SEM-EDX, ICP-OES, TG-DTG, XPS, N2 physical-adsorption and XRD were used to characterize the crystal structure, chemical composition and micro-morphologies of CMS material. The results indicated that the CH3NH3+ ions intercalated between the layers can exchange with heavy metal ions in the solution. The pH effect on Cd2+/Pb2+ adsorption was slight and the suitable pH value for Cd2+/Pb2+ removal by CMS materials was between 2 to 7. The equilibrium times were 7 h for 200 mg/L Cd2+ and 2 h for 400 mg/L Pb2+, respectively, and the adsorption kinetics was in agreement with pseudo-second-order kinetic model. The adsorption capacities of the CMS for Cd2+ and Pb2+ were 515 mg/g for Cd2+ and 1053 mg/g at 20 °C, respectively. The Freundlich isotherm was applied to describe the adsorption process, which fit the experimental dates well. Competitive adsorption results showed that the presence of 1 M Na+, Ca2+ or Mg2+ exerted slightly inhibiting effect on Cd2+/Pb2+ adsorption. The reaction temperature also affected the adsorption capacity of CMS. The adsorbed CMS can be considered as an excellent permanent waste form without the risk of lease of heavy metals.

Li, Jian-Rong; Wang, Xu; Yuan, Baoling; Fu, Ming-Lai; Cui, Hao-Jie

2014-11-01

372

Thermal desorption of petroleum contaminated soils  

SciTech Connect

The US Environmental Protection Agency recently funded a study which addresses the treatment of soils contaminated by petroleum hydrocarbons using low temperature thermal desorption (LTTD). The proposed paper will summarize some of the results of that study. LTTD has become a major petroleum contaminated soil remediation technology. The paper will define LTTD and discuss fundamental thermal desorption mechanisms such as hydrocarbon vapor pressure, steam stripping and soil characteristics. Full-scale LTTD equipment such as asphalt kilns, rotary dryers, thermal screws and indirect fired calciners will be described. Typical off-gas treatment equipment such as afterburners, baghouses, wet scrubbers, carbon and condensation/recovery will also be discussed. Full-scale LTTD performance data, such as hydrocarbon destruction efficiency, carbon monoxide and particulate stack concentrations, and soil total petroleum hydrocarbon residuals will be summarized.

Troxler, W.L.; Yezzi, J.J.; Cudahy, J.J.; Rosenthal, S.I.

1992-01-01

373

Desorption of hexachlorobiphenyl from selected particulate matter  

E-print Network

amounts of the HCBP. This is speculated to be a function of particle structure, organic carbon content of the particles, and HCBP's hydrophobic and lipophilic nature. Two mathematical models were developed considering sorption and desorption... to be first order processes. The model successfully predicted stripping HCBP from water as well as a 300 m J~l sand suspension. However, as the system became more complex ? 2 particle types--the models broke down. It was concluded that sorption...

Rorschach, Reagan Cartwright

2012-06-07

374

Reaction kinetics for the oxygen hydrogenation process on Pt(111) derived from temperature-programmed XPS  

NASA Astrophysics Data System (ADS)

Oxygen hydrogenation under ultra high vacuum conditions at the platinum surface was explored using temperature-programmed X-ray photoelectron spectroscopy. Through modeling of the oxygen consumption, information on the reaction kinetics was obtained indicating that the reaction rate of the oxygen hydrogenation process depends on the hydrogen diffusion and on the lifetime of hydroxyl intermediates. The reaction rate is, however, enhanced when an autocatalytic process stabilizes the hydroxyl intermediates through hydrogen bonding to neighboring water molecules. The overall activation energy for the hydrogenation of atomic oxygen to form water was determined to be 0.20 eV with a frequency factor of only 103 s- 1.

Näslund, Lars-Åke

2013-12-01

375

Temperature-programmed reaction in zeolites. I. The decomposition of Fe(CO)/sub 5/  

SciTech Connect

The nonisothermal kinetics of the decomposition of iron pentacarbonyl adsorbed on type Y zeolite have been studied. The spectra of the temperature-programmed reaction was recorded from the evolution of CO with a linear change in temperature. With a decrease in Fe(CO)/sub 5/ content in the specimen additional distinguishable maxima appear in the high-temperature region for high coverages, which is probably associated with the competition between the monomolecular and bimolecular decomposition of Fe(CO)/sub 5/. The high-temperature maxima are assigned to the successive release of CO molecules from Fe(CO)/sub 5/ fragments.

Zakharov, A.N.; Vanegas Fetekua, K.Kh.; Romanovskii, B.V.

1988-04-01

376

Novel devices for solvent delivery and temperature programming designed for capillary liquid chromatography.  

PubMed

Analyses in chromatographic systems able to save mobile and stationary phases without reducing efficiency and resolution are of current interest. These advantages regarding savings have challenged us to develop a system dedicated to miniaturized liquid chromatography. This paper reports on the development of a high-pressure syringe-type pump, an oven able to perform isothermal and temperature programming and a software program to control these chromatographic devices. The experimental results show that the miniaturized system can generate reproducible and accurate temperature and flow rate. The system was applied to the separation of statins and tetracylines and showed excellent performance. PMID:24838528

Coutinho, Lincoln Figueira Marins; Nazario, Carlos Eduardo Domingues; Monteiro, Alessandra Maffei; Lanças, Fernando Mauro

2014-08-01

377

Ambient pressure laser desorption and laser-induced acoustic desorption ion mobility spectrometry detection of explosives.  

PubMed

The development of fast, mobile, and sensitive detection systems for security-relevant substances is of enormous importance. Because of the low vapor pressures of explosives and improvised explosive devices, adequate sampling procedures are crucial. Ion mobility spectrometers (IMSs) are fast and sensitive instruments that are used as detection systems for explosives. Ambient pressure laser desorption (APLD) and ambient pressure laser-induced acoustic desorption (AP-LIAD) are new tools suitable to evaporate explosives in order to detect them in the vapor phase. Indeed, the most important advantage of APLD or AP-LIAD is the capability to sample directly from the surface of interest without any transfer of the analyte to other surfaces such as wipe pads. A much more gentle desorption, compared to classical thermal-based desorption, is possible with laser-based desorption using very short laser pulses. With this approach the analyte molecules are evaporated in a very fast process, comparable to a shock wave. The thermal intake is reduced considerably. The functionality of APLD and AP-LIAD techniques combined with a hand-held IMS system is shown for a wide range of common explosives such as EGDN (ethylene glycol dinitrate), urea nitrate, PETN (pentaerythritol tetranitrate), HMTD (hexamethylene triperoxide diamine), RDX (hexogen), tetryl (2,4,6-trinitrophenylmethylnitramine), and TNT (trinitrotoluene). Detection limits down to the low nanogram range are obtained. The successful combination of IMS detection and APLD/AP-LIAD sampling is shown. PMID:24116702

Ehlert, Sven; Walte, Andreas; Zimmermann, Ralf

2013-11-19

378

The influence of step geometry on the desorption characteristics of O2, D2, and H2O from stepped Pt surfaces  

NASA Astrophysics Data System (ADS)

We have compared the desorption characteristics of O2, D2, and H2O from the Pt(533) surface to the Pt(553) surface using temperature programmed desorption. Both surfaces consist of four atom wide (111) terraces interrupted by monoatomic steps of the different step geometries: (100) versus (110), respectively. We find that desorption is influenced significantly by the presence of step sites and the geometry of those sites. In general, molecules and atoms are thought to be bound more strongly to step sites than to terrace sites. Our D2 desorption data from Pt(553) provide an anomalous counterexample to this common belief since D atoms on this surface appear to be bound stronger by terrace sites. We also show that it is not possible to say a priori which step geometry will bind atoms or molecules stronger: recombinatively desorbing O atoms are bound stronger to (100) sites, whereas H2O molecules are bound stronger to (110) sites. Furthermore, the amount of adatoms or molecules that are affected by the presence of steps varies for the different species, as is evident from the various step: terrace ratios of ~1:1.3 for O2 (O), ~1:3 for D2 (D), and ~1:1 for H2O. This indicates that, in contrast to deuterium, more oxygen atoms and water molecules are affected by the presence of steps than would be expected on geometrical arguments alone.

van der Niet, Maria J. T. C.; den Dunnen, Angela; Juurlink, Ludo B. F.; Koper, Marc T. M.

2010-05-01

379

Desorption of hydrogen and carbon monoxide from Ni(100), Ni(100)p(2 × 2)S, and Ni(100)c(2 × 2)S surfaces  

NASA Astrophysics Data System (ADS)

The adsorption and desorption of hydrogen and carbon monoxide from Ni(100), Ni(100)p(2 × 2)S and Ni(100)c(2 × 2)S were investigated by temperature programmed desorption. The presence of sulfur reduced values of the kinetic parameters which characterized hydrogen recombination from E = 21.3 {kcal}/{gmole} and v = 5 × 10 -2{cm2}/{atom· s} on clean Ni(100) to ˜10 {kcal}/{gmole} and 3 × 10 -8{cm2}/{atom· s} on the c(2 × 2) surface. The low values of the activation energy and pre-exponential factor for hydrogen desorption from sulfurized Ni(100) surfaces correlate with the peaked spatial distribution of desorbing hydrogen observed by others. The low v values appear to originate from severe steric hindrance to hydrogen recombination on these surfaces. Surface sulfur reduced the amount of carbon monoxide adsorbed in the state characteristic of the clean Ni(100) surface while enhancing additional peaks at lower temperatures. Desorption spectra of CO on the clean, p(2 × 2), and c(2 × 2) surfaces suggested that the primary binding site for carbon monoxide on clean Ni(100) is the four-fold hollow rather than the on top site.

Johnson, S.; Madix, R. J.

1981-06-01

380

Probing adsorbed water on lunar regolith materials using thermal and non-thermal desorption (Invited)  

NASA Astrophysics Data System (ADS)

Results from the Moon Mineralogy Mapper (M3) on the Chandrayaan-1 spacecraft, the Visual and Infrared Mapping Spectrometer (VIMS) on Cassini during its flyby of the moon in 1999, and the extended mission for the Deep Impact Spacecraft (EPOXI) have recently implicated the existence of hydroxyl and water on the Moon. More recently, the potential presence of water on and within the surface regolith material of the Moon was somewhat validated by the Lunar Crater Observation and Sensing Satellite (LCROSS) impact event. LCROSS examined ejecta from a permanently-shadowed crater in the southern polar region, whereas the spacecraft observations characterized optical features in the 2-3.5 micron region throughout the polar and equatorial regions on the sunlit side. These optical features are thought to be indicative of hydroxyl and/or water-bearing materials with concentrations between 10 - 1000 parts per million and possibly higher. Though the source(s) of the hydroxyl and water is (are) not known, their formation via solar wind proton irradiation has been strongly suggested. There is precedent in the literature for proton irradiation-induced defect production and hydroxyl formation in silicates and some minerals. However, there are actually no reports that clearly indicate that proton irradiation leads to the formation of molecular water. We report our recent experimental probes of the desorption kinetics and binding energies of water adsorbed on minerals such as anorthosite, albite and a standard JSC1A lunar stimulant material. The temperature programmed desorption profiles clearly indicate the presence of chemisorbed water for all materials studied. The chemisorbed water requires intrinsic surface and grain boundary defects. We also report a combined low-energy (5-100 eV) electron and 5 keV proton (D+) beam bombardment study of anorthosite, albite and JSC-1A. Low-energy electron stimulated production and desorption of H3O+ (and DH2O+ after D+ bombardment) does occur, however, this involves the intrinsic water bound to surface defects and terminal -OH groups. Ion-beam bombardment does produce terminal -OH (OD) sites as expected, however, we do not observe ion-beam induced production of molecular water. Though molecular water formation is not induced via electronic excitations brought about by solar particle impact events, it may be produced via a thermally-induced recombinative desorption process. This seems to require temperatures well above the high temperatures (400K) reached as a result of solar irradiation and may also require trapped hydrogen.

Orlando, T. M.; McLain, J.; Poston, M.; Greives, G.; Alexandrov, A.; Dyar, M. D.; Hibbitts, C.

2010-12-01

381

Chitosan (polysaccharide) Cationic polyelectrolyte (NH3  

E-print Network

.3) Selective deposition Rich amine groups (DNA, protein, cell adhesion) Good interface material MEMS technology deposition and biofunctionalization Packaging - Polycarbonate packaging material - Leak free packaging and electrical inputs/outputs Pyrex chip, SU-8/PDMS microfluidics Package fixture Leak free microfluidics

Rubloff, Gary W.

382

Desorption kinetics of hydrophobic organic contaminants from marine plastic pellets.  

PubMed

This study investigated the desorption behavior of polychlorinated biphenyls (PCBs) from marine plastic pellets. Long-term desorption experiments were conducted using field-collected polyethylene (PE) pellets. The results indicate that the desorption kinetics highly depends on the PE-water partition coefficients of PCB congeners. After 128 d of the experiment, the smallest congener considered (CB 8) had desorbed nearly completely (98%), whereas major fractions (90-99%) of highly chlorinated congeners remained in the pellets. An intraparticle diffusion model mostly failed to reproduce the desorption kinetics, whereas an aqueous boundary layer (ABL) diffusion model well approximated the data. The desorption half-lives are estimated to 14 d to 210 years for CB 8 to CB 209 in an actively stirred solution (ABL thickness: 30 ?m). Addition of methanol to water enhanced the desorption to a large extent. A need for further work to explore roles of organic matter in facilitating solute transfer is suggested. PMID:23906473

Endo, Satoshi; Yuyama, Masaki; Takada, Hideshige

2013-09-15

383

Thermal desorption mass spectrometer for mass metrology  

NASA Astrophysics Data System (ADS)

This article presents a device for the study of physisorbed elements on polished surfaces (diameter ?56 mm) of the kind used in mass metrology. The technique is based on mass spectrometry of molecules desorbed after heating under vacuum of the analyzed surface. We describe a first application of the device to study current and future mass standards in order to understand how their surface reactivity depends on storage conditions, cleaning processes, and polishing methods. Surface contamination analysis by thermal desorption mass spectrometry to examine the effect of cleaning on pure iridium is given as an example.

Silvestri, Z.; Azouigui, S.; Bouhtiyya, S.; Macé, S.; Plimmer, M. D.; Pinot, P.; Tayeb-Chandoul, F.; Hannachi, R.

2014-04-01

384

Hydrogen Storage Properties of New Hydrogen-Rich BH3NH3-Metal Hydride (TiH2, ZrH2, MgH2, and/or CaH2) Composite Systems  

SciTech Connect

Ammonia borane (AB = NH3BH3) is one of the most attractive materials for chemical hydrogen storage due to its high hydrogen contents of 19.6 wt.%, however, impurity levels of borazine, ammonia and diborane in conjunction with foaming and exothermic hydrogen release calls for finding ways to mitigate the decomposition reactions. In this paper we present a solution by mixing AB with metal hydrides (TiH2, ZrH2, MgH2 and CaH2) which have endothermic hydrogen release in order to control the heat release and impurity levels from AB upon decomposition. The composite materials were prepared by mechanical ball milling, and their H2 release properties were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The formation of volatile products from decomposition side reactions, such as borazine (N3B3H6) was determined by mass spectrometry (MS). Sieverts type pressure-composition-temperature (PCT) gas-solid reaction instrument was adopted to observe the kinetics of the H2 release reactions of the combined systems and neat AB. In situ 11B MAS-NMR revealed a destabilized decomposition pathway. We found that by adding specific metal hydrides to AB we can eliminate the impurities and mitigate the heat release.

Choi, Young Joon; Xu, Yimin; Shaw, Wendy J.; Ronnebro, Ewa

2012-04-19

385

A multiple system of high-mass YSOs surrounded by disks in NGC 7538 IRS1 . Gas dynamics on scales of 10-700 AU from CH3OH maser and NH3 thermal lines  

NASA Astrophysics Data System (ADS)

Context. It has been claimed that NGC 7538 IRS1 is a high-mass young stellar object (YSO) with 30 M?, surrounded by a rotating Keplerian disk, probed by a linear distribution of methanol masers. The YSO is also powering a strong compact Hii region or ionized wind, and is driving at least one molecular outflow. The axis orientations of the different structures (ionized gas, outflow, and disk) are, however, misaligned, which has led to the different competing models proposed to explain individual structures. Aims: We investigate the 3D kinematics and dynamics of circumstellar gas with very high linear resolution, from tens to 1500 AU, with the ultimate goal of building a comprehensive dynamical model for what is considered the best high-mass accretion disk candidate around an O-type young star in the northern hemisphere. Methods: We used high-angular resolution observations of 6.7 GHz CH3OH masers with the EVN, NH3 inversion lines with the JVLA B-Array, and radio continuum with the VLA A-Array. In particular, we employed four different observing epochs of EVN data at 6.7 GHz, spanning almost eight years, which enabled us to measure line-of-sight (l.o.s.) accelerations and proper motions of CH3OH masers, besides l.o.s. velocities and positions (as done in previous works). In addition, we imaged highly excited NH3 inversion lines, from (6,6) to (13,13), which enabled us to probe the hottest molecular gas very close to the exciting source(s). Results: We confirm previous results that five 6.7 GHz maser clusters (labeled from "A" to "E") are distributed over a region extended N-S across ?1500 AU, and are associated with three components of the radio continuum emission. We propose that these maser clusters identify three individual high-mass YSOs in NGC 7538 IRS1, named IRS1a (associated with clusters "B" and "C"), IRS1b (associated with cluster "A"), and IRS1c (associated with cluster "E"). We find that the 6.7 GHz masers distribute along a line, with a regular variation in VLSR with position, along the major axis of the distribution of maser cluster "A" and the combined clusters "B" + "C". A similar VLSR gradient (although shallower) is also detected in the NH3 inversion lines. Interestingly, the variation in VLSR with projected position is not linear but quadratic for both maser clusters. We measure proper motions for 33 maser features, which have an average amplitude (4.8 ± 0.6 km s-1) similar to the variation in VLSR across the maser cluster, and are approximately parallel to the clusters' elongation axes. By studying the time variation in the maser spectrum, we also derive l.o.s. accelerations for 30 features, with typical amplitude of ~ 10-3-10-2 km s-1 yr-1. We modeled the masers in both clusters "A" and "B" + "C" in terms of an edge-on disk in centrifugal equilibrium. Based on our modeling, masers of clusters "B" + "C" may trace a quasi-Keplerian ~1 M?, thin disk, orbiting around a high-mass YSO, IRS1a, of up to ?25 M?. This YSO dominates the bolometric luminosity of the region. The disk traced by the masers of cluster "A" is both massive (?16 M? inside a radius of ?500 AU) and thick (opening angle ?45°), and the mass of the central YSO, IRS1b, is constrained to be at most a few M?. Towards cluster "E", NH3 and 6.7 GHz masers trace more quiescent dynamics than for the other clusters. The presence of a radio continuum peak suggests that the YSO associated with the cluster "E", IRS1c, may be an ionizing, massive YSO as well. Conclusions: We present compelling evidence that NGC 7538 IRS1 is forming not just one single high-mass YSO, but consists of a multiple system of high-mass YSOs, which are surrounded by accretion disks and are probably driving individual outflows. This new model naturally explains all the different orientations and disk/outflow structures proposed for the region in previous models. Table 2 and Appendix A are ava

Moscadelli, L.; Goddi, C.

2014-06-01

386

High efficiency solid-state sensitized solar cell-based on submicrometer rutile TiO2 nanorod and CH3NH3PbI3 perovskite sensitizer.  

PubMed

We report a highly efficient solar cell based on a submicrometer (~0.6 ?m) rutile TiO2 nanorod sensitized with CH3NH3PbI3 perovskite nanodots. Rutile nanorods were grown hydrothermally and their lengths were varied through the control of the reaction time. Infiltration of spiro-MeOTAD hole transport material into the perovskite-sensitized nanorod films demonstrated photocurrent density of 15.6 mA/cm(2), voltage of 955 mV, and fill factor of 0.63, leading to a power conversion efficiency (PCE) of 9.4% under the simulated AM 1.5G one sun illumination. Photovoltaic performance was significantly dependent on the length of the nanorods, where both photocurrent and voltage decreased with increasing nanorod lengths. A continuous drop of voltage with increasing nanorod length correlated with charge generation efficiency rather than recombination kinetics with impedance spectroscopic characterization displaying similar recombination regardless of the nanorod length. PMID:23672481

Kim, Hui-Seon; Lee, Jin-Wook; Yantara, Natalia; Boix, Pablo P; Kulkarni, Sneha A; Mhaisalkar, Subodh; Grätzel, Michael; Park, Nam-Gyu

2013-06-12

387

Neonization method for stopping, mean excitation energy, straggling, and for total and differential ionization cross sections of CH4, NH3, H2O and FH by impact of heavy projectiles  

NASA Astrophysics Data System (ADS)

We propose a neonization method to deal with molecules composed by hydrides of the second row of the periodic table of elements: CH4, NH3, OH2 and FH. This method describes these ten-electron molecules as dressed atoms in a pseudo-spherical potential. We test it by covering most of the inelastic collisional magnitudes of experimental interest: ionization cross sections (total, single and double differential), stopping power, energy-loss straggling and mean excitation energy. To this end, the neonization method has been treated with different collisional formalisms, such as the continuum-distorted-wave-eikonal-initial-state, the first order Born, and the shell-wise local plasma approximations. We show that the present model reproduces the different empirical values with high reliability in the intermediate to high-energy region. We also include the expansion of the spherical wave functions in terms of Slater-type orbitals and the analytic expression for the spherical potentials. This makes it possible in the future to tackle present neonization strategy with other collisional models.

Montanari, C. C.; Miraglia, J. E.

2014-01-01

388

A 3D metal halide framework in the organic-inorganic compound (H 3N(CH 2) 2SS(CH 2) 2NH 3) 3Pb 5I 16  

NASA Astrophysics Data System (ADS)

A novel organic-inorganic hybrid compound, namely (H 3N(CH 2) 2SS(CH 2) 2NH 3) 3Pb 5I 16, was synthesized from the reaction of lead iodide, cystamine chloride, and concentrated hydriodic acid in ethanol under solvothermal condition. According to the results of X-ray single crystal structural analysis, its 3D inorganic framework was constructed from lead iodide octahedra in corner-, edge- or face-sharing mode, which can be considered as connected staircase-like sheets. Disordered cystamine molecules are located both in the cages defined between two consecutive steps of the staircase-like network and in the channels formed by 10 adjacent bridged PbI 6 octahedra. The formation and high stability of such a unique 3D metal halide network can be partly attributed to the unusual weak interactions between disulfides and iodides ( d(S⋯I) ? 3.55 Å) in the structure. Monoclinic, space group: C2/ c, a = 35.396(2) Å, b = 8.984(1) Å, c = 22.623(2) Å, ? = 120.66(2)°, V = 6188.1(9) Å 3, Z = 4.

Louvain, Nicolas; Mercier, Nicolas

2008-10-01

389

The spin-wave theory of the susceptibility of Heisenberg antiferromagnetics: Application to a quadratic layer antiferromagnet K 2MnF 4 and comparison with (C 2H 5NH 3) 2CuCl 4  

NASA Astrophysics Data System (ADS)

Low-temperature magnetic susceptibilities of quasi-two-dimensional antiferromagnet K 2MnF 4 are reanalyzed by the use of renormalized spin-wave (RSW) theory. For the parallel susceptibility ??, the formula is obtained as ?? ? Q/{1+(1+ ?-2 d) Q}, where Q is a quantity which is essentially proportional to ?? given by the free spin-wave (FSW) approximation, and ? and d the anisotropy parameters. The second termin the denominator represents a contribution from the spin-wave interaction. A good agreement with the experiemental data is obtained up to near TN by using this formula. For the perpendicular susceptibility, we adopt the quadratic part with RSW energy ? k(T) as unpertubed part of the Hamiltonian and the Zeeman term as the perturbation. The second order perturbation energy has been calculated using the canonical transformation which eliminates the terms of the first and third degree with respect to the Boson operators. Up to the terms of ¢(1/S 2), the result agrees partially with that of Oguchi. It is shown that the correction terms have a form of double summation with respect to wave numbers or fourfold integral and are not so small compared to the term of ¢(1/S). Finally, the different situation of (C 2H 5NH 3) 2CuCl 4, a nearly two-dimensional ferromagnet with very weak interlayer antiferromagnetic coupling, is discussed in a comparative way with the case of K 2MnF 4.

Tsuru, Kazuo; Uryû, Norikiyo

1983-01-01

390

ATRAZINE DESORPTION KINETICS FROM A FRESH-WATER SEDIMENT  

EPA Science Inventory

Research has shown that the sorption and desorption of neutral organic compounds to soils and sediments occurs in two stages, with an initial rapid sorption/desorption phase (usually less than an hour) followed by a slower phase that can last for several months to years for very ...

391

THERMAL DESORPTION...NOW YOU'RE COOKIN'  

EPA Science Inventory

Thermal desorption includes a number of ex situ processes that use either direct or indirect heat exchange to heat a waste material to volatilize organic materials. hermal desorption systems typically operate at soil treatment temperatures in the range of 400 to 600 degrees F to ...

392

Integrated field emission array for ion desorption  

SciTech Connect

An integrated field emission array for ion desorption includes an electrically conductive substrate; a dielectric layer lying over the electrically conductive substrate comprising a plurality of laterally separated cavities extending through the dielectric layer; a like plurality of conically-shaped emitter tips on posts, each emitter tip/post disposed concentrically within a laterally separated cavity and electrically contacting the substrate; and a gate electrode structure lying over the dielectric layer, including a like plurality of circular gate apertures, each gate aperture disposed concentrically above an emitter tip/post to provide a like plurality of annular gate electrodes and wherein the lower edge of each annular gate electrode proximate the like emitter tip/post is rounded. Also disclosed herein are methods for fabricating an integrated field emission array.

Resnick, Paul J; Hertz, Kristin L; Holland, Christopher; Chichester, David; Schwoebel, Paul

2013-09-17

393

Properties of Sm 2O 3–ZrO 2 composite oxides and their catalytic performance in isosynthesis  

Microsoft Academic Search

Sm2O3 doped ZrO2-based catalysts (Sm2O3–ZrO2 composite oxide) were prepared by co-precipitation and their physical properties (texture and structure) and chemical properties (acid–base and redox) were characterized with the methods of N2 adsorption–desorption isotherm, powder X-ray diffraction, Raman spectroscopy, NH3 and CO2 temperature programmed desorption and H2 temperature programmed reduction. The catalytic performances of the catalysts (activity and selectivities) were evaluated

Yingwei Li; Dehua He; Zhihui Zhu; Qiming Zhu; Boqing Xu

2007-01-01

394

D2 sticking coefficient and desorption rate on various forms of water ice films under interstellar conditions  

NASA Astrophysics Data System (ADS)

Gas-grain interactions play a key role in the formation of molecular hydrogen in the ISM. An experimental facility named FORMOLISM (Molecular Formation in the Interstellar Medium) has recently been developed in our laboratory in order to investigate the catalytic role played by the grain in the chemical reaction producing H2 in conditions similar to the interstellar medium. A differentially pumped atomic beam of H or D is directed to surface sample which can be cooled down to 8K, in the centre of an ultra high vacuum chamber (<10-10 mBar). Temperature-Programmed Desorption experiments (TPD) can be performed and the desorbing molecules can be selectively probed in their individual (v, J) levels, thanks to the (2+1) Resonance Enhanced Multi-photon Ionisation (REMPI) method. Ions are detected by using a Time-Of-Flight mass spectrometer. Our experiment gives access to fast reactions mechanisms that can not be probed in conventional TPD experiments. REMPI coupling with TOF detection and atomic dosing can be performed simultaneously. In order to determine H and H2 interaction on water ice surfaces, we are conducting a detailed study of D2 adsorbed on different forms of water ice films using both TPD and REMPI techniques. The ice morphology is controlled by changing vapour deposition temperature and subsequent annealing. Variations of D2 sticking coefficients and desorption rate with surface temperature are compared in high density amorphous water ice, and low density amorphous water ice of different porosity.

Amiaud, L.; Baouche, S.; Dulieu, F.; Fillion, J.-H.; Momeni, A.; Lemaire, J.-L.

2004-12-01

395

Catalytic oxidation of propylene--7. Use of temperature programmed reoxidation to characterize. gamma. -bismuth molybdate  

SciTech Connect

Temperature-programed reoxidation of propylene-reduced ..gamma..-Bi/sub 2/MoO/sub 6/ revealed a low-temperature peak (LTP) at 158/sup 0/C and a high-temperature peak (HTP) at 340/sup 0/C. Auger spectroscopy and X-ray diffraction of reduced and partially or completely reoxidized bismuth molybdate showed that at the LTP, molybdenum(IV) is oxidized to molybdenum(VI) and bismuth, from the metallic state to an oxidation state between zero and three, and that the HTP is associated with the complete oxidation of bismuth to bismuth(III). Activity tests for propylene oxidation showed lower acrolein formation on the catalyst, on which only the LTP was reoxidized than on catalysts on which both peaks were reoxidized. The reoxidation kinetics of the catalyst under conditions corresponding to the LTP showed an activation energy of 22.9 kcal/mole below 170/sup 0/C and near zero above 170/sup 0/C; the break in the Arrhenius plot of reoxidation of the catalyst under conditions corresponding to the HTP was at 400/sup 0/C, with activation energies of 46 kcal/mole at lower and near zero at higher temperatures. Propylene oxidation was apparently rate-limited by the HTP reoxidation process below 400/sup 0/C and by allylic hydrogen abstraction above 400/sup 0/C.

Uda, T.; Lin, T.T.; Keulks, G.W.

1980-03-01

396

The kinetics of CO desorption from Ni(110)  

NASA Astrophysics Data System (ADS)

The kinetics of CO desorption from clean Ni(110) have been measured by thermal desorption mass spectrometry (TDMS) using the method of variation of heating rates. Analysis of the desorption spectra gives the coverage dependence of the preexponential factor ?d, and the activation energy Ed, of the desorption rate constant. For 0desorption kinetics. The experimental results for ?d(?) are compared with those predicted for desorption by three precursor mechanisms and for desorption of a lattice gas with lateral interactions.

Feigerle, C. S.; Desai, S. R.; Overbury, S. H.

1990-07-01

397

More realistic soil cleanup standards with dual-equilibrium desorption.  

PubMed

The desorption of contaminants from soils/sediments is one of the most important processes controlling contaminant transport and environmental risks. None of the currently adopted desorption models can accurately quantify desorption at relatively low concentrations; these models often overestimate the desorption and thus the risks of hydrophobic organic chemicals, such as benzene and chlorinated solvents. In reality, desorption is generally found to be biphasic, with two soil-phase compartments. A new dual-equilibrium desorption (DED) model has been developed to account for the biphasic desorption. This model has been tested using a wide range of laboratory and field data and has been used to explain key observations related to underground storage tank plumes. The DED model relates the amount of a chemical sorbed to the aqueous concentration, with simple parameters including octanol-water partition coefficient, solubility, and fractional organic carbon; thus, it is the only biphasic model, to date, that is based on readily available parameters. The DED model can be easily incorporated into standard risk and transport models. According to this model, many regulatory standards of soils and sediments could be increased without increasing the risks. PMID:11916120

Chen, W; Kan, A T; Newell, C J; Moore, E; Tomson, M B

2002-01-01

398

Testosterone sorption and desorption: Effects of soil particle size.  

PubMed

Soils contain a wide range of particles of different diameters with different mobility during rainfall events. Effects of soil particles on sorption and desorption behaviors of steroid hormones have not been investigated. In this study, wet sieve washing and repeated sedimentation methods were used to fractionate the soils into five ranges. The sorption and desorption properties and related mechanisms of testosterone in batch reactors filled with fractionated soil particles were evaluated. Results of sorption and desorption kinetics indicate that small soil particles have higher sorption and lower desorption rates than that of big ones. Thermodynamic results show the sorption processes are spontaneous and exothermal. The sorption capacity ranks as clay>silt>sand, depending mainly on specific surface area and surface functional groups. The urea control test shows that hydrogen bonding contributes to testosterone sorption onto clay and silt but not on sand. Desorption tests indicate sorption is 36-65% irreversible from clay to sand. Clays have highest desorption hysteresis among these five soil fractions, indicating small particles