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1

Generation of nanopores during desorption of NH3 from Mg(NH3)6Cl2.  

PubMed

It is shown that nanopores are formed during desorption of NH3 from Mg(NH3)6Cl2, which has been proposed as a hydrogen storage material. The system of nanopores facilitates the transport of desorbed ammonia away from the interior of large volumes of compacted storage material. DFT calculations show that there exists a continuous path from the initial Mg(NH3)6Cl2 material to MgCl2 that does not involve large-scale material transport. Accordingly, ammonia desorption from this system is facile. PMID:16390099

Hummelshøj, Jens S; Sørensen, Rasmus Zink; Kustova, Marina Yu; Johannessen, Tue; Nørskov, Jens K; Christensen, Claus Hviid

2006-01-11

2

Pillared smectite modified with carbon and manganese as catalyst for SCR of NO x with NH 3 . Part II. Temperature?programmed studies  

Microsoft Academic Search

Temperature?programmed desorption (TPD) and surface reaction (TPSR), and additionally FTIR spectroscopy of adsorbed NO molecules\\u000a were used to characterise surface sites on pillared smectites modified with carbon and manganese. Much higher adsorption of\\u000a NH3 than NO was found, but acidic pre?treatment increased NO sorption to comparable values as well as catalytic performance in\\u000a SCR of NOx. In this case formation

L. Chmielarz; R. Dziembaj; T. Grzybek; J. Klinik; T. ?ojewski; D. Olszewska; A. W?grzyn

2000-01-01

3

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

4

Conductance-Based Temperature Programmed Desorption with Single Defect Resolution  

NASA Astrophysics Data System (ADS)

The controlled functionalization of nanotubes and graphene requires methods of chemically attacking these inert surfaces and of removing unwanted oxidation damage. The appeal of reversible chemistries is rarely achieved: the degraded electrical properties of reduced graphene oxide compared to pristine graphene indicates residual damage that remains poorly understood. Using a high temperature, UHV apparatus to perform electrical measurements in situ, we investigate the thermal desorption of adducts that can restore conductivity in oxidized nanographites. The majority of our measurements are accomplished using SWCNTs, due to their enhanced sensitivity to even single point defects. Discrete conductance jumps accompanying the removal of different types of adducts provide a characterization method that directly distinguishes the relative electronic effects of phenolic, epoxide, and carboxylic defects. The electronic measurements complement more traditional, temperature programmed desorption from bulk material, which is insensitive to electronic disorder.

Pan, Deng; Sims, Patrick C.; Corso, Brad L.; Collins, Philip G.

2011-03-01

5

Reversible hydrogen adsorption on MoS sub 2 studied by temperature-programmed desorption and temperature-programmed reduction  

Microsoft Academic Search

The adsorption and desorption of hydrogen on MoSâ were studied using a combination of temperature-programmed desorption (TPD) and temperature-programmed reduction (TPR) with a control of the maximum temperature. Reversible hydrogen adsorption was observed in the temperature range of 375-500 K. MoSâ samples reduced in hydrogen at different temperatures behaved distinctively towards reversible hydrogen adsorption. The amount of the reversible hydrogen

X. S. Li; Q. Xin; X. X. Guo; P. Grange; B. Delmon

1992-01-01

6

The oxidized soot surface: Theoretical study of desorption mechanisms involving oxygenated functionalities and comparison with temperature programed desorption experiments  

Microsoft Academic Search

The desorption mechanism for oxygenated functionalities on soot is investigated by quantum mechanical calculations on functionalized polycyclic aromatic hydrocarbon (PAH) models and compared with recently published temperature programed desorption-mass spectrometry results. Substituents on PAHs of increasing size (up to 46 carbon atoms in the parent PAH) are chosen to reproduce the local features of an oxidized graphenic soot platelet. Initially,

Gianluca Barco; Andrea Maranzana; Giovanni Ghigo; Mauro Causà; Glauco Tonachini

2006-01-01

7

Interactions of NH3, Coadsorbed with PF3, on Ru(001).  

National Technical Information Service (NTIS)

NH3, coadsorbed with PF3, on Ru(001) has been studied by temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS shows that the P-F stretching frequency decreases in the presence of NH3. This is explained by t...

Y. Zhou Z. M. Liu J. M. White

1990-01-01

8

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

9

Reactivity of propylene carbonate toward metallic lithium. Temperature programmed desorption study  

Microsoft Academic Search

This paper presents temperature programmed desorption (TPD) data for perdeuterated propylene carbonate (PC-dâ) condensed at cryogenic temperatures on Li films vapor deposited onto polycrystalline (poly) Au and Ag foils and represents an extension of previous work involving the reactivity of tetrahydrofuran (THF) toward Li supported on Ag(poly). The findings suggest that the product of the reaction between PC and metallic

Guorong Zhuang; Gary Chottiner; Daniel A. Scherson; Ernest B. Yeager

1995-01-01

10

Automatic apparatus for catalyst characterization by temperature-programmed reduction\\/desorption\\/oxidation  

Microsoft Academic Search

An apparatus is described for the automatic quantitative registration of reduction, desorption\\/adsorption, and oxidation phenomena which occur when a catalyst sample is heated or cooled under temperature programming in a flowing gas that contains either hydrogen or oxygen as the reactive component. The design considerations and the automation scheme are fully discussed. A typical example of the characterization of a

H. Boer; W. J. Boersma; N. Wagstaff

1982-01-01

11

Determining desorption pre-exponential factors from temperature-programmed desorption spectra when the surface is nonuniform  

SciTech Connect

To find desorption pre-exponential factors from temperature-programmed desorption (TPD) spectra, we develop procedures using both the TPD spectra and their derivatives. First, an approximate method is derived using peak temperatures. This method is formally identical with one used for determining pre-exponential factors and desorption activation energies when desorptions are energetically uniform. The method can be used when the pre-exponential factor is constant. We next develop an iterative process that also uses peak temperatures, and again is usable when the pre-exponential factor is constant. This iterative approach should give more exact values of pre-exponential factors than the approximate approach. Using the first derivatives of TPD spectra over the entire range of temperatures leads to a second iterative process. This last procedure allows determination of energy-dependent pre-exponential factors. 8 refs., 13 figs.

Brown, L.F.; Chemburkar, R.M.

1991-03-15

12

Encapsulation of Gases in Zeolite 3A and Temperature Programmed Desorption of the Trapped Gases  

Microsoft Academic Search

Gases (Ar, N? and CO?) were encapsulated in zeolite 3A at high temperature (350ºC) and pressure (maximum pressure obtained from a gas cylinder). Temperature programmed desorption (TPD), with a linear temperature schedule, was applied to study the kinetics of the release of the trapped gases. The TPD spectra for argon show two peaks ( a large peak at about 350ºC

Yun-cheung Chan

1976-01-01

13

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

14

Investigation of a Co-MgO-ZSM catalyst by temperature-programmed reduction, temperature-programmed desorption, and IR spectroscopy  

Microsoft Academic Search

The 32% Co-3% MgO-ZSM (SiO2\\/Al2O3=38) system has been studied by means of temperature-programmed reduction, temperature-programmed desorption, and IR spectroscopy. The data from temperature-programmed reduction show that cobalt exists on the surface of the catalyst in the form of Co2+, CoO, Co3O4, and CoO·MgO solid solutions. Reduction of the sample results in the formation of a very inhomogeneous surface with four

A. Yu. Krylova; A. L. Lapidus; S. D. Sominskii; L. F. Rar; A. Zukal; J. Ratkousky; M. Jancalkova; V. I. Yakerson

1992-01-01

15

Monte Carlo simulations of temperature-programmed and isothermal desorption from single-crystal surfaces  

SciTech Connect

The kinetics of temperature-programmed and isothermal desorption have been simulated with a Monte Carlo model. Included in the model are the elementary steps of adsorption, surface diffusion, and desorption. Interactions between adsorbates and the metal as well as interactions between the adsorbates are taken into account with the Bond-Order-Conservation-Morse-Potential method. The shape, number, and location of the TPD peaks predicted by the simulations is shown to be sensitive to the binding energy, coverage, and coordination of the adsorbates. In addition, the occurrence of lateral interactions between adsorbates is seen to strongly effect the distribution of adsorbates is seen to strongly effect the distribution of adsorbates on the surface. Temperature-programmed desorption spectra of a single type of adsorbate have been simulated for the following adsorbate-metal systems: CO on Pd(100); H{sub 2} on Mo(100); and H{sub 2} on Ni(111). The model predictions are in good agreement with experimental observation. TPD spectra have also been simulated for two species coadsorbed on a surface; the model predictions are in qualitative agreement with the experimental results for H{sub 2} coadsorbed with strongly bound atomic species on Mo(100) and Fe(100) surfaces as well as for CO and H{sub 2} coadsorbed on Ni(100) and Rh(100) surfaces. Finally, the desorption kinetics of CO from Pd(100) and Ni(100) in the presence of gas-phase CO have been examined. The effect of pressure is seen to lead to an increase in the rate of desorption relative to the rate observed in the absence of gas-phase CO. This increase arises as a consequence of higher coverages and therefore stronger lateral interactions between the adsorbed CO molecules.

Lombardo, S.J. (California Inst. of Tech., Pasadena, CA (USA). Dept. of Chemical Engineering Lawrence Berkeley Lab., CA (USA))

1990-08-01

16

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

17

Microsystem with integrated capillary leak to mass spectrometer for high sensitivity temperature programmed desorption  

SciTech Connect

Temperature programmed desorption (TPD) is a method for obtaining information about quantities and binding properties of adsorbed species on a surface. A microfabricated flow system for TPD with an integrated capillary leak to a mass spectrometer is presented. The use of an integrated capillary leak minimizes dead volumes in the system, resulting in increased sensitivity and reduced response time. These properties make the system ideal for TPD experiments in a carrier gas. With CO desorbing from platinum as model system, it is shown that CO desorbing in 10{sup 5} Pa of argon from as little as 0.5 cm{sup 2} of platinum foil gives a clear desorption peak. By using the microfabricated flow system, TPD experiments can be performed in a carrier gas with a sensitivity approaching that of TPD experiments in vacuum.

Quaade, Ulrich J.; Jensen, Soeren; Hansen, Ole

2004-10-01

18

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

19

Simulation Analysis of the NH3-H2O Two-Stage Desorption Type Absorption Refrigerator Driven by Low Grade Waste Heat  

NASA Astrophysics Data System (ADS)

Recently, from a view point of the environmental protection, NH3-H2O absorption refrigerator attracts attention in the field of the refrigeration and the air conditioning. Since NH3-H2O absorption refrigerators can produce below zero degree products, this type of refrigerators have many usages in the refrigeration. This paper describes the two-stage desorption type absorption refrigerator driven by waste heat of co-generation system. There are two absorption cycles which are operated under the condition of the different pressure and the solution concentration in this absorption refrigerator. It becomes essential to clarify the characteristics of this absorption refrigerator since the operating conditions are changed through out the year in the co-generation system. Particularly, in this paper, we investigate the effects of evaporating temperature of ammonia and cooling water temperature for the performance of this absorption refrigerator by simulation analysis. Through out the research, it is shown that COP can be improved when evaporating temperature is higher or cooling water temperature is lower. In addition to this, it is obtained that the necessary temperature of hot water becomes lower in such condition. As a result, the effectiveness of using this absorption refrigerator under the operating condition of which hot watertemperatureis90?100[°C] and evaporating temperature is -10?- 20 [°C] is clarified

Takei, Toshitaka; Kimijima, Shinji; Saito, Kiyoshi; Kawai, Sunao

20

Study of chemisorption and hydrogenation of 1-butene on platinum by temperature-programmed desorption  

SciTech Connect

The temperature-programmed desorption (TPD) chromatograms of 1-butene from platinum black comprised four peaks, A, B, C, and D, with peak maxima at about 265, 390, 580, and higher than 770 K, respectively. Peak A was identified to be 1-butene with a trace amount of n-butane. Peaks B and C were the mixtures of 1-butene and propylene. Peak D was methane. The methane and propylene were formed from chemisorbed 1-butene by decomposition as the temperature was raised during the subsequent TPD. The reactivities of various types of chemisorbed hydrogen previously detected by TPD were also investigated with regard to the hydrogenation of 1-butene. Two types of chemisorbed hydrogen, presumed to be present on the surface in the form of hydrogen atoms chemisorbed on top of platinum atoms and in the bridge form of molecular hydrogen, were found to react with 1-butene.

Tsuchiya, S.; Yoshioka, N.

1984-05-01

21

Temperature-programmed reduction and temperature-programmed desorption studies of CuO\\/ZrO 2 catalysts  

Microsoft Academic Search

Copper\\/zirconia catalysts were prepared by an impregnation method. The reducibility and characteristics of the supported copper oxide catalysts with various copper loadings were revealed and determined by H2-TPR, CO-TPR, XRD and O2-TPD, respectively. Five H2-TPR peaks could be observed. In conjunction with the observations by X-ray diffraction (XRD), three temperature-programmed reduction (TPR) peaks with lower peak temperatures (namely, ?1, ?2

Ren-xian Zhou; Tie-ming Yu; Xiao-yuan Jiang; Fang Chen; Xiao-ming Zheng

1999-01-01

22

Initial adsorption and C-incorporation of organosilanes at Si(0 0 1) investigated by temperature-programmed desorption  

NASA Astrophysics Data System (ADS)

Temperature-programmed desorption (TPD) has been used to study the initial adsorption and C-incorporation of organosilanes [monomethylsilane (MMS), dimethylsilane (DMS) and trimethylsilane (TMS)] at Si(0 0 1) surfaces. Hydrogen was the only desorbing species observed in the TPD spectra from organosilanes. Organosilane molecules adsorb dissociatively on the Si(0 0 1) surfaces at room temperature. TPD spectra from DMS- and TMS-adsorbed Si surfaces present carbon-related hydrogen (H 2) desorption peaks from the initial adsorption. The carbon-incorporation ratio was found to be larger in the order of TMS > DMS > MMS, with the sticking probability of molecules being almost identical for the three organosilane molecules.

Senthil, K.; Suemitsu, M.

2005-04-01

23

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

24

The Influence of Ultraviolet Irradiation on the Surface Chemistry of Ztetraol Magnetic Hard Disk Lubricant: a Combined Temperature Programed Desorption and X-Ray Photoelectron Spectroscopic Study  

Microsoft Academic Search

Magnetic hard disks coated with ztetraol lubricant were characterized with temperature programed desorption (TPD) and X-ray\\u000a photoelectron spectroscopy (XPS). Ztetraol was found to have two adsorbed states, with desorption temperatures of ~650 and ~950 K.\\u000a The complete removal of the low temperature state by solvent extraction identified it as due to the mobile lubricant. Desorption\\u000a of the CF3 mass fragment was observed only

Paul M. Jones; Alexei Merzikline; Xiaoping Yan; Lei Li; Lang Dinh; Michael Stirniman; Huan Tang

25

Characteristics of copper ion exchanged mordenite catalyst deactivated by HCl for the reduction of NO x with NH 3  

Microsoft Academic Search

The deactivation characteristics of copper ion exchanged mordenite type zeolite catalyst (CuHM) by HCl for the reduction of NOx, particularly from an incinerator with NH3, have been investigated over a fixed bed flow reactor system. X-ray absorption near edge spectroscopy (XANES), extended X-ray absorption fine structure (EXAFS), synchrotron radiation X-ray diffraction (SR-XRD), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption

Jin Woo Choung; In-Sik Nam

2006-01-01

26

Hydrogen absorption and temperature programmed desorption (TPD) studies of iron- and chromium-substituted ZrV/sub 2/  

SciTech Connect

The hydrogen absorption proterties of the alloys Zr(V/sub 1-x/Cr/sub x/)/sub 2/, x = 0.4 and 0.5, were studied at 450/sup 0/C from 10/sup -3/ atm to 10 atm. the alloy ZrV/sub 0.8/Cr/sub 1.2/ was studied at 350/sup 0/, 400/sup 0/, and 450/sup 0/C from 10/sup -3/ atm to 10 atm, and from these data partial molar enthalpies and entropies of solution were calculated for several hydride compositions. A free energy against cell volume plot of the cubic chromium-containing materials compared with earlier data on hexagonal as well as cubic iron-substituted alloys shows that electronic factors are probably more important than structural factors in determining the free energies of the ternary Zr(V/sub 1-x/B/sub x/)/sub 2/ systems. Temperature-programmed desorption (TPD) of several hydride compositions in the systems ZrV/sub 1.6/Fe/sub 0.4/H/sub y/ and ZrV/sub 1.2/Cr/sub 0.8/H/sub y/ revealed two distinct peaks. The TPD results appear to correlate with changes in the pressure-composition isotherms when plotted on a log-log plot. These changes may be related to thermodynamic changes in the desorption of hydrogen. The so called trapping model (Pfeiffer and Wipf, 1976; Flanagan, Wulff, and Bowerman, 1980) is presented as a possible explanation of the observed TPD behavior. 7 figures, 2 tables.

Mendelsohn, M.H.; Gruen, D.M.

1981-01-01

27

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

28

Dosimeter-Type NOx Sensing Properties of KMnO4 and Its Electrical Conductivity during Temperature Programmed Desorption  

PubMed Central

An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT) for NOx storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2) during the short-term thermal NOx release.

Gro?, Andrea; Kremling, Michael; Marr, Isabella; Kubinski, David J.; Visser, Jacobus H.; Tuller, Harry L.; Moos, Ralf

2013-01-01

29

Quantification of lateral repulsion between coadsorbed CO and N on Rh(100) using temperature-programmed desorption, low-energy electron diffraction, and Monte Carlo simulations  

NASA Astrophysics Data System (ADS)

Temperature programmed desorption of CO coadsorbed with atomic N on Rh(100), reveals both long- and short-range interactions between adsorbed CO and N. For CO desorption from Rh(100) at low coverage we find an activation energy Ea of 137+/-2 kJ/mol and a preexponential factor of 1013.8+/-0.2 s-1. Coadsorption with N partially blocks CO adsorption and destabilizes CO by lowering Ea for CO desorption. Destabilization at low N coverage is explained by long-range electronic modification of the Rh(100) surface. At high N and CO coverage, we find evidence for a short-range repulsive lateral interaction between COads and Nads in neighboring positions. We derive a pairwise repulsive interaction ?CO-NNN=19 kJ/mol for CO coadsorbed to a c(2×2) arrangement of N atoms. This has important implications for the lateral distribution of coadsorbed CO and N at different adsorbate coverages. Regarding the different lateral interactions and mobility of adsorbates, we propose a structural model which satisfactorily explains the observed effects of atomic N on the desorption of CO. Dynamic Monte Carlo simulations were used to verify the experimentally obtained value for the CO-N interaction, by using the kinetic parameters and interaction energy derived from the temperature-programmed desorption experiments.

van Bavel, A. P.; Hopstaken, M. J. P.; Curulla, D.; Niemantsverdriet, J. W.; Lukkien, J. J.; Hilbers, P. A. J.

2003-07-01

30

A Study of Ethanol Reactions over Pt\\/CeO 2 by Temperature-Programmed Desorption and in Situ FT-IR Spectroscopy: Evidence of Benzene Formation  

Microsoft Academic Search

The reaction of ethanol over unreduced and H2-reduced 1 wt% Pt\\/CeO2 has been investigated primarily by temperature-programmed desorption (TPD) and in situ Fourier transform infrared spectroscopy (FT-IR). Steady state reactions have been conducted to provide information regarding the kinetics of the above reaction. Characterisation of the catalyst has been achieved through the use of XPS and titration of surface metal

Anna Yee; Scott J. Morrison; Hicham Idriss

2000-01-01

31

The CO + NH 3 coadsorption over Re(0001) studied by optical second harmonic generation  

NASA Astrophysics Data System (ADS)

The coadsorption of CO and NH 3 on Re(0001) was investigated utilizing the optical second harmonic generation (SHG) technique. The results were compared to temperature programmed desorption (TPD) and work function change measurements (??). It was found that the enhancement of the SHG due to ammonia is quenched very efficiently in the presence of small CO coverages. A quenching cross section by CO of the second harmonic response of the metal substrate due to ammonia adsorbates, is defined to be 100 ± 10 Å2. This extreme sensitivity of the SHG signal to the presence of CO adsorbed with NH 3 is in sharp contrast to both ?? and TPD measurements. These results present only a minor effect of CO on the ?? and TPD of ammonia on Re(0001). It is concluded that unlike the local contribution to the SHG signal generally assumed for separate adsorbates, the quenching by CO is a nonlocal effect. Moreover, the electronic interactions which govern the SHG from the NH 3-rhenium system, are very different from the interactions which lead to the TPD and ?? data. At ammonia preadsorption on the surface, the effect of the same amount of coadsorbed CO is largely reduced. This observation is discussed in terms of possible islanding mechanisms driven by the postadsorbed CO.

Rosenzweig, Z.; Asscher, M.; Wittenzellner, C.

1990-12-01

32

A novel co-precipitation method for preparation of Mn--Ce/TiO2 composites for NOx reduction with NH3 at low temperature.  

PubMed

Mn--Ce/TiO2 catalyst prepared by a novel co-precipitation method was used in this study for low-temperature selective catalytic reduction (SCR) of NOx with ammonia. The catalyst showed high activity and good SO2 resistance. The NO conversion on the catalyst increased to 100% when 700 ppm of SO2 flowed in, and reached 60.8% in 2.5 h. The characterized results indicated that the catalyst prepared by the new method had good dispersion of the active phase, uniform micro-size particles and large Brunauer-Emmett-Teller surface. The temperature programmed reduction and temperature programmed desorption experiments showed that the improvement in SCR activity on the Mn--Ce/TiO2 catalyst might be due to the increase of active oxygen species and the enhancement of NH3 chemisorption, both of which were conducive to NH3 activation. PMID:23393985

Sheng, Zhongyi; Hu, Yufeng; Xue, Jianming; Wang, Xiaoming; Liao, Weiping

2012-01-01

33

In situ supported MnO(x)-CeO(x) on carbon nanotubes for the low-temperature selective catalytic reduction of NO with NH3.  

PubMed

The MnO(x) and CeO(x) were in situ supported on carbon nanotubes (CNTs) by a poly(sodium 4-styrenesulfonate) assisted reflux route for the low-temperature selective catalytic reduction (SCR) of NO with NH(3). X-Ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), H(2) temperature-programmed reduction (H(2)-TPR) and NH(3) temperature-programmed desorption (NH(3)-TPD) have been used to elucidate the structure and surface properties of the obtained catalysts. It was found that the in situ prepared catalyst exhibited the highest activity and the most extensive operating-temperature window, compared to the catalysts prepared by impregnation or mechanically mixed methods. The XRD and TEM results indicated that the manganese oxide and cerium oxide species had a good dispersion on the CNT surface. The XPS results demonstrated that the higher atomic concentration of Mn existed on the surface of CNTs and the more chemisorbed oxygen species exist. The H(2)-TPR results suggested that there was a strong interaction between the manganese oxide and cerium oxide on the surface of CNTs. The NH(3)-TPD results demonstrated that the catalysts presented a larger acid amount and stronger acid strength. In addition, the obtained catalysts exhibited much higher SO(2)-tolerance and improved the water-resistance as compared to that prepared by impregnation or mechanically mixed methods. PMID:23282798

Zhang, Dengsong; Zhang, Lei; Shi, Liyi; Fang, Cheng; Li, Hongrui; Gao, Ruihua; Huang, Lei; Zhang, Jianping

2013-02-01

34

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

35

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

36

Low Temperature Catalyst for NH3 Removal.  

National Technical Information Service (NTIS)

Air revitalization technologies maintain a safe atmosphere inside spacecraft by the removal of C02, ammonia (NH3), and trace contaminants. NH3 onboard the International Space Station (ISS) is produced by crew metabolism, payloads, or during an accidental ...

O. Melendez O. Monje

2013-01-01

37

Determination of the adsorption heat of n-hexane and n-heptane on zeolites beta, L, 5A, 13X, Y and ZSM-5 by means of quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA)  

Microsoft Academic Search

Measurements of temperature-programmed desorption and adsorption of n-hexane and n-heptane under quasi-equilibrium conditions (QE-TPDA) were performed for several zeolites in TPD apparatus equipped with a TCD detector. One-step adsorption profiles for zeolites X and Y and two-step adsorption profiles for beta, L, 5A and ZSM-5 were observed. Approximate adsorption isobars calculated from the QE-TPDA profiles did not depend on the

Wac?aw Makowski; ?ukasz Ogorza?ek

2007-01-01

38

Low Temperature Catalyst for NH3 Removal  

NASA Technical Reports Server (NTRS)

Air revitalization technologies maintain a safe atmosphere inside spacecraft by the removal of C02, ammonia (NH3), and trace contaminants. NH3 onboard the International Space Station (ISS) is produced by crew metabolism, payloads, or during an accidental release of thermal control refrigerant. Currently, the ISS relies on removing NH3 via humidity condensate and the crew wears hooded respirators during emergencies. A different approach to cabin NH3 removal is to use selective catalytic oxidation (SCO), which builds on thermal catalytic oxidation concepts that could be incorporated into the existing TCCS process equipment architecture on ISS. A low temperature platinum-based catalyst (LTP-Catalyst) developed at KSC was used for converting NH3 to H20 and N2 gas by SCO. The challenge of implementing SCO is to reduce formation of undesirable byproducts like NOx (N20 and NO). Gas mixture analysis was conducted using FTIR spectrometry in the Regenerable VOC Control System (RVCS) Testbed. The RVCS was modified by adding a 66 L semi-sealed chamber, and a custom NH3 generator. The effect of temperature on NH3 removal using the LTP-Catalyst was examined. A suitable temperature was found where NH3 removal did not produce toxic NO, (NO, N02) and N20 formation was reduced.

Monje, Oscar; Melendez, Orlando

2013-01-01

39

Bonding of NH3 to Cu  

NASA Technical Reports Server (NTRS)

Bagus et al. (1984) have studied the chemisorption of NH3 at the on-top site of Cu(100), using a cluster model, Cu5(1,4)NH3. On the basis of the value of the NH3 chemisorption energy obtained, it was concluded that NH3 chemisorbs directly above a Cu atom. In order to consider also other sites, Al(111) was substituted for Cu(100). Chemisorption on Al can be quite different from a transition metal, however, and questions arise regarding the suitability of the choice of the Al model. Thus, in this note, NH3 into hollows is considered for Cu(111). Attention is given to the conduction of self-consistent field calculations, problems of site determination, and the consideration of electrostatic interaction.

Bauschlicher, C. W., Jr.

1985-01-01

40

Plasma-assisted CuO/CeO2/TiO2-?-Al2O3 catalysts for NO + CH4 reaction and NO temperature programmed desorption studies  

NASA Astrophysics Data System (ADS)

The removal of NO and CH4 has been studied with a hybrid system integrating plasma activation and four Cu-based catalysts. The best catalytic performance was observed for catalysts obtained from CuO/CeO2/TiO2/?-Al2O3.The efficiency of NO removal decreased with the order: 12%CuO/10%CeO2/15%TiO2/?-Al2O3 > 12%CuO/15%TiO2/?-Al2O3 > 12%CuO/?-Al2O3 > 12% CuO/TiO2. Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD) Temperature-programmed reduction (H2-TPR) and NO temperature-programmed desorption (NO-TPD) experiments were carried out to gain insight into the synergetic effects with the catalysts. The results revealed that copper species existed as bulk CuO crystalline for all the catalysts, H2-TPR suggested that the Cu2+ incorporated TiO2 or CeO2 lattice and crystalline CuO might be the most active component for NO removal, and NO-TPD studies indicated that 12%CuO/10%CeO2/15%TiO2/?-Al2O3 catalyst had lower NO desorption temperature and larger peak area, which seemed to be responsible for the better catalytic activity over NO + CH4 reactions than other catalysts.

Li, Huijuan; Jiang, Xiaoyuan; Zheng, Xiaoming

2013-09-01

41

Mn-CeOx/Ti-PILCs for selective catalytic reduction of NO with NH3 at low temperature.  

PubMed

Titanium-pillared clays (Ti-PILCs) were obtained by different ways from TiCl4, Ti(OC3H7)4 and TiOSO4, respectively. Mn-CeO(x)/)Ti-PILCs were then prepared and their activities of selective catalytic reduction (SCR) of NO with NH3 at low-temperature were evaluated. Mn-CeO(x)/Ti-PILCs were characterized by X-ray diffraction, N2 adsorption, Fourier transform infrared spectroscopy, thermal analysis, temperature-programmed desorption of ammonia and H2-temperature-programmed reduction. It was found that Ti-pillar tend to be helpful for the enlargement of surface area, pore volume, acidity and the enhancement of thermal stability for Mn-CeO(x)/Ti-PILCs. Mn-CeO(x)/Ti-PILCs catalysts were active for the SCR of NO. Among three resultant Mn-CeO(x)/Ti-PILCs, the catalyst from TiOSO4 showed the highest activity with 98% NO conversion at 220 degrees C, it also exhibited good resistance to H2O and SO2 in flue gas. The catalyst from TiCl4 exhibited the lowest activity due to the unsuccessful pillaring process. PMID:22655365

Shen, Boxiong; Ma, Hongqing; Yao, Yan

2012-01-01

42

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

43

TES/Aura L2 Ammonia (NH3) Nadir (TL2NH3N)  

TES/Aura L2 Ammonia (NH3) Nadir (TL2NH3N) News:  TES News ... Level:  L2 Instrument:  TES/Aura L2 Ammonia Spatial Coverage:  5.3 x 8.5 km nadir ... Data: TES Order Tool Parameters:  Ammonia Order Data:  Reverb:   Order Data ...

2013-12-18

44

TES/Aura L2 Ammonia (NH3) Nadir (TL2NH3NS)  

TES/Aura L2 Ammonia (NH3) Nadir (TL2NH3NS) News:  TES News ... Level:  L2 Platform:  TES/Aura L2 Ammonia Spatial Coverage:  5.3 x 8.5 km nadir ... Data: TES Order Tool Parameters:  Ammonia Order Data:  Reverb:   Order Data ...

2013-12-18

45

Diode laser saturation spectroscopy of NH3  

NASA Technical Reports Server (NTRS)

Saturation of molecular transitions using a tuneable diode laser was demonstrated for the first time using a standing-wave cavity configuration with an f/8 beam focussed at the sample. Observed saturation effects in NH3 transitions near 888/cm include sub-Doppler (Lamb-dip) resonances at line center.

Jennings, D. E.

1978-01-01

46

Epitaxial Formation of Adsorbed Multilayers as Studied by ESDIAD: NH3 Adsorption on Top of Chemisorbed CO on Nickel Crystal Surfaces,  

National Technical Information Service (NTIS)

The epitaxial growth of an adsorbed layer of NH3 on top of chemisorbed CO on Ni(111) and Ni(110) surfaces was studied using ESDIAD. A strong interaction yielding an activation energy for NH3 desorption of 12 kcal/mol was observed. This interaction, possib...

A. M. Lanzillotto M. J. Dresser M. D. Alvey J. T. Yates

1987-01-01

47

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

NASA Astrophysics Data System (ADS)

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 NH3 sample, the main species ejected are NH3, H2, and N2, where the hydrogen and nitrogen increase with laser fluence. This increase in N2 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 H2 and N2 in the mass spectrometer, consistent with the very small mass loss during the experiment and with a <5% decrease in the NH3 infrared absorption bands spectroscopy after a fluence of ~3 × 1019 photons/cm2. The results imply that ammonia-ice mixtures in the outer solar system are relatively stable under solar irradiation.

Loeffler, M. J.; Baragiola, R. A.

2010-12-01

48

Development of ultralow energy (1-10 eV) ion scattering spectrometry coupled with reflection absorption infrared spectroscopy and temperature programmed desorption for the investigation of molecular solids.  

PubMed

Extremely surface specific information, limited to the first atomic layer of molecular surfaces, is essential to understand the chemistry and physics in upper atmospheric and interstellar environments. Ultra low energy ion scattering in the 1-10 eV window with mass selected ions can reveal extremely surface specific information which when coupled with reflection absorption infrared (RAIR) and temperature programmed desorption (TPD) spectroscopies, diverse chemical and physical properties of molecular species at surfaces could be derived. These experiments have to be performed at cryogenic temperatures and at ultra high vacuum conditions without the possibility of collisions of neutrals and background deposition in view of the poor ion intensities and consequent need for longer exposure times. Here we combine a highly optimized low energy ion optical system designed for such studies coupled with RAIR and TPD and its initial characterization. Despite the ultralow collision energies and long ion path lengths employed, the ion intensities at 1 eV have been significant to collect a scattered ion spectrum of 1000 counts/s for mass selected CH2(+). PMID:24517785

Bag, Soumabha; Bhuin, Radha Gobinda; Methikkalam, Rabin Rajan J; Pradeep, T; Kephart, Luke; Walker, Jeff; Kuchta, Kevin; Martin, Dave; Wei, Jian

2014-01-01

49

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

50

Temperature Programmed Desorption Study of Graphene Oxide  

Microsoft Academic Search

Graphene oxide is an electrical insulator that shows potential for use in nanoscale electronic devices. An understanding of the thermal stability of graphene oxide sheets is important since the electrical, chemical, and mechanical properties of graphene oxide will change as it is reduced at elevated temperatures. In this study, graphene oxide films were grown by deposition of an aqueous solution

Nicholas Clark; Daniel Field; Simona Rieman; Carl Ventrice; Inhwa Jung; Dongxing Yang; Richard Piner; Rodney Ruoff

2009-01-01

51

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

52

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

53

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

54

Absorption in the troughs of the far infrared spectra of NH 3 and mixtures of NH 3 and H 2  

Microsoft Academic Search

The absorption coefficients in the troughs between the J-multiplets of the far infrared rotation-inversion spectrum of NH3 and NH3 broadened by H2 were measured at 296K in the region from about 65–230 cm?1. Wave numbers were selected in the troughs that are removed from nearby weak absorption lines, and measurements of the absorption versus the density of NH3 and of

George Birnbaum; Andrew Buechele; Tian Jiang; Glen S. Orton; Zoran Hadzibabic; Griffith R. John

2000-01-01

55

Absorption by pure NH 3 and NH 3–H 2 mixtures in the 5 ?m window region  

Microsoft Academic Search

Absorption by pure NH3 and NH3–H2 mixtures in the 5?m transparency region was studied at room temperature using two different set-ups. Measurements were made for various density conditions in order to deduce pressure normalized absorption coefficients due to line-wing contributions. The results obtained from the two experiments are in good agreement and demonstrate that the NH3 line wings are significantly

D. Bailly; G. Birnbaum; A. Buechele; P.-M. Flaud; J.-M. Hartmann

2004-01-01

56

Ab initio potential energy surfaces of Ar-NH3 for different NH3 umbrella angles  

NASA Astrophysics Data System (ADS)

Four ab initio potential energy surfaces of the van der Waals system argon-ammonia are computed for the following four different HNH ('umbrella') angles of ammonia: 100 deg, 106.67 deg, 113.34 deg, and 120 deg. These potentials have been obtained by Heitler-London short-range calculations and from multipole-expanded dispersion and induction long-range contributions. A Tang-Toennies-like damping is applied to the long-range energy. Each surface is given analytically in the form of a spherical harmonic expansion through l = 7, where the expansion functions depend on the polar angles of the argon atom with respect to the principal axes of NH3. The expansion coefficients are represented by functions depending on the distance between the monomers. The potential for the equilibrium HNH angle 106.67 deg is applied to the computation of interaction virial coefficients in which quantum effects are included.

Bulski, M.; Wormer, P. E. S.; van der Avoird, A.

1991-01-01

57

Effect of the Mn oxidation state and lattice oxygen in Mn-based TiO2 catalysts on the low-temperature selective catalytic reduction of NO by NH3.  

PubMed

TiO2-supported manganese oxide catalysts formed using different calcination temperatures were prepared by using the wet-impregnation method and were investigated for their activity in the low-temperature selective catalytic reduction (SCR) of NO by NH3 with respect to the Mn valence and lattice oxygen behavior. The surface and bulk properties of these catalysts were examined using Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and temperature-programmed desorption (TPD). Catalysts prepared using lower calcination temperatures, which contained Mn4+ displayed high SCR activity at low temperatures and possessed several acid sites and active oxygen. The TPD analysis determined that the Brönsted and Lewis acid sites in the Mn/TiO2 catalysts were important for the low-temperature SCR at 80-160 and 200-350 degrees C, respectively. In addition, the available lattice oxygen was important for attaining high NO to NO2 oxidation at low temperatures. Implications: Recently, various Mn catalysts have been evaluated as SCR catalysts. However, there have been no studies on the relationship of adsorption and desorption properties and behavior of lattice oxygen according to the valence state for manganese oxides (MnO(x)). Therefore, in this study, the catalysts were prepared by the wet-impregnation method at different calcination temperatures in order to show the difference of manganese oxidation state. These catalysts were then characterized using various physicochemical techniques, including BET, XRD, TPR, and TPD, to understand the structure, oxidation state, redox properties, and adsorption and desorption properties of the Mn/TiO2 catalysts. PMID:23019822

Lee, Sang Moon; Park, Kwang Hee; Kim, Sung Su; Kwon, Dong Wook; Hong, Sung Chang

2012-09-01

58

Diffusion measurements of CO, HNCO, H2CO, and NH3 in amorphous water ice  

NASA Astrophysics Data System (ADS)

Context. Water is the major component of the interstellar ice mantle. In interstellar ice, chemical reactivity is limited by the diffusion of the reacting molecules, which are usually present at abundances of a few percent with respect to water. Aims: We want to study the thermal diffusion of H2CO, NH3, HNCO, and CO in amorphous water ice experimentally to account for the mobility of these molecules in the interstellar grain ice mantle. Methods: In laboratory experiments performed at fixed temperatures, the diffusion of molecules in ice analogues was monitored by Fourier transform infrared spectroscopy. Diffusion coefficients were extracted from isothermal experiments using Fick's second law of diffusion. Results: We measured the surface diffusion coefficients and their dependence with the temperature in porous amorphous ice for HNCO, H2CO, NH3, and CO. They range from 10-15 to 10-11 cm2 s-1 for HNCO, H2CO, and NH3 between 110 K and 140 K, and between 5-8 × 10-13 cm2 s-1 for CO between 35 K and 40 K. The bulk diffusion coefficients in compact amorphous ice are too low to be measured by our technique and a 10-15 cm2 s-1 upper limit can be estimated. The amorphous ice framework reorganization at low temperature is also put in evidence. Conclusions: Surface diffusion of molecular species in amorphous ice can be experimentally measured, while their bulk diffusion may be slower than the ice mantle desorption kinetics.

Mispelaer, F.; Theulé, P.; Aouididi, H.; Noble, J.; Duvernay, F.; Danger, G.; Roubin, P.; Morata, O.; Hasegawa, T.; Chiavassa, T.

2013-07-01

59

NH3 column abundances over Lauder, New Zealand  

NASA Technical Reports Server (NTRS)

Gaseous NH3 has been observed in the atmosphere over central New Zealand with infrared absorption spectra. The amount of NH3 shows marked variability, which is strongly correlated with time of day and season. The pattern is similar to data obtained in Denver, Colorado, but is much more variable than data from Hampton, Virginia. The rapid variability indicates a residence time of 8 hours in some cases.

Murcray, Frank J.; Goldman, Aaron; Matthews, Andrew; Johnston, Paul; Rinsland, Curtis

1989-01-01

60

Absorption in the troughs of the far infrared spectra of NH3 and mixtures of NH3 and H2.  

NASA Astrophysics Data System (ADS)

The absorption coefficients in the troughs between the J-multiplets of the far infrared rotation-inversion spectrum of NH3 and NH3 broadened by H2 were measured at 296 K in the region from about 65-230 cm-1. Wave numbers were selected in the troughs that are removed from nearby weak absorption lines, and measurements of the absorption versus the density of NH3 and of H2 verified that the absorption was due to the wings of distant rather than nearby spectral lines. These measurements were compared with computations of the absorption arising from binary collisions of NH3-NH3 and NH3-H2 for uncoupled Lorentz lines. Except at the lowest and highest frequencies, the measured continuum absorption in the troughs was less than the computed absorption, a discrepancy that increased with increasing frequency. An improved representation of the measured absorption was obtained by fitting the Rosenkrantz line shape with the Ben-Reuven formulation of the line coupling coefficient of the inversion J-doublets. The application of these results to the spectrum of Jupiter shows clear differences between the spectrum of the above model and the Lorentz line shape, with the largest differences occurring in the dearest troughs.

Birnbaum, G.; Buechele, A.; Jiang, T.; Orton, G. S.; Hadzibabic, Z.; John, G. R.

2000-01-01

61

High Pressure Study of NH3 - H2 System  

NASA Astrophysics Data System (ADS)

We have conducted exploratory studies in NH_3-H2 system up to 10 GPa at 300K with 5-50 mol % of NH_3. Raman measurements and visual observations revealed the tendency for phase separation of individual components. At low pressures below 1.2 GPa the equilibrium of the NH_3- and H_2- rich fluids was observed. Mutual solubilities of species are low and estimated from the intensities of their stretching vibrations. The frequency of H-H vibron in fluid NH_3- rich phase is significantly lower in comparison to that in pure H_2. In H_2- rich fluid phase and at low pressures, H-H vibrons and rotons are much sharper that those of pure H2 possibly due to the collisonal effects of NH3 molecules. Upon pressure increase the system undergoes a sequence of the phase transions which closely folows that of individual components. Spectra of the solid phases found in the studied pressure range could be identified as those of pure ammonia and hydrogen, i.e. clathrate formation has not been observed. *Supported by NSF DMR-9304028 and NASA NAGW-1722.

Lazor, P.; Hemley, R. J.; Mao, H. K.

1996-03-01

62

Rotation/precession of NH 3 groups in Hofmann clathrates  

NASA Astrophysics Data System (ADS)

Vibrational spectra, crystallography and rotational spectra of the Hofmann clathrate Ni(NH 3) 2Ni(CN) 4 · 2C 6D 6 are all consistent with the displacement of the N atom during the free rotation of the NH 3 groups. Molecular dynamics calculations using a slightly modified universal force field reproduce the measured inelastic neutron scattering spectrum and crystal structure. An examination of the H and N atom trajectories from a simulation show that the NH 3 rotation is best described as a rigid rotor in which the H3 triangle turns around the Ni?N axis whilst the Ni?N axis precesses round the crystallographic z-direction.

Neumann, Marcus; Kearley, Gordon J.

1997-02-01

63

Urban NH3 levels and sources in a Mediterranean environment  

NASA Astrophysics Data System (ADS)

Urban NH3 concentrations were mapped in Barcelona (Spain) by means of passive samplers (dosimeters). Average NH3 levels were 9.5 ?g m-3 in summer and 4.4 ?g m-3 in winter, higher than those reported in other urban background sites in Europe, this being especially notable in summer. During this season, values were significantly higher at urban background than at traffic sites, probably indicating the impact of emissions from biological sources, such as humans, sewage systems and garbage containers. Thus, the volatilization of NH3 from the aerosol phase seems to be significant enough during summer to dominate over traffic emissions. Conversely, in winter levels were higher at traffic sites, suggesting a contribution from vehicle emissions. Indeed, NH3 levels decreased by 55% with increasing distance (50 m) to the direct emissions from traffic. A significant correlation between NH3 concentrations averaged for the different districts of the city and the number of waste containers per hm2 was also obtained, highlighting the necessity for controlling and reducing the emissions from garbage collection systems. The urban topography of the Barcelona historical city centre, characterised by narrow streets with a high population density, seemed to exert a strong influence on NH3 levels, with levels reaching up to 30 ?g m-3 as a consequence of limited dispersion and ventilation conditions. The impact of the sewage system emissions was also detected with an increase of levels when measuring immediately above the source, even though further studies are required to evaluate the relevance of these emissions.

Reche, Cristina; Viana, Mar; Pandolfi, Marco; Alastuey, Andrés; Moreno, Teresa; Amato, Fulvio; Ripoll, Anna; Querol, Xavier

2012-09-01

64

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

65

On the inversion spectra of NH3 and ND3  

Microsoft Academic Search

When the dipole-dipole interaction energy of two polar molecules is comparable to their thermal energy during a binary collision, there is a net orientation of the two dipoles towards each other. The impact theory for the inversion bands of NH3 and ND3 is investigated in order to assess the implications of such orienting collisions. This is done by retaining cross

D. R. A. McMahon

1976-01-01

66

NH3 Temperatures of Infrared Dark Cloud Cores  

NASA Astrophysics Data System (ADS)

We will observe a sample of 63 Infrared Dark Cloud cores in NH3 (1,1), (2,2) and (3,3). Our goal is to measure the temperatures of these star-forming cores. If the quiescent cores are indeed pre-stellar high-mass cores, they ought to be much colder than the active star-forming cores.

Jackson, James; Chambers, Edward; Finn, Susanna

2009-04-01

67

Hydrogen generation behaviors of NaBH4-NH3BH3 composite by hydrolysis  

NASA Astrophysics Data System (ADS)

In this work, NH3BH3 (AB) is used to induce hydrogen generation during NaBH4 (SB) hydrolysis in order to reduce the use of catalysts, simplify the preparation process, reduce the cost and improve desorption kinetics and hydrogen capacity as well. xNaBH4-yNH3BH3 composites are prepared by ball-milling in different proportions (from x:y = 1:1 to 8:1). The experimental results demonstrate that all composites can release more than 90% of hydrogen at 70 °C within 1 h, and their hydrogen yields can reach 9 wt% (taking reacted water into account). Among them, the composites in the proportion of 4:1 and 5:1, whose hydrogen yields reach no less than 10 wt%, show the best hydrogen generation properties. This is due to the impact of the following aspects: AB additive improves the dispersibility of SB particles, makes the composite more porous, hampers the generated metaborate from adhering to the surface of SB, and decreases the pH value of the composite during hydrolysis. The main solid byproduct of this hydrolysis system is NaBO2·2H2O. By hydrolytic kinetic simulation of the composites, the fitted activation energies of the complexes are between 37.2 and 45.6 kJ mol-1, which are comparable to the catalytic system with some precious metals and alloys.

Xu, Yanmin; Wu, Chaoling; Chen, Yungui; Huang, Zhifen; Luo, Linshan; Wu, Haiwen; Liu, Peipei

2014-09-01

68

Studies of elastic e-NH3 collisions  

NASA Technical Reports Server (NTRS)

Differential and momentum-transfer cross sections for the elastic scattering of electrons by NH3 have been obtained for collision energies of between 2.5 and 20 eV using the fixed-nuclei static-exchange approximation of the Schwinger variational principle. At intermediate and large scattering angles, good agreement is found between calculated and relative experimental cross sections. The differential cross sections reveal evidence of a weak d-wave enhancement around 8 eV.

Pritchard, H. P.; Lima, M. A. P.; Mckoy, V.

1989-01-01

69

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

70

Advanced ammonia (NH3) monitoring system for industrial applications  

NASA Astrophysics Data System (ADS)

The present paper describes an Electro-Optical Monitoring System developed for the real time in-situ monitoring of Ammonia (NH3) emissions, at very low concentrations in air, well below the hazardous levels. Ammonia is the starting chemical for almost all industrially produced nitrogen compounds and is therefore one of the most important inorganic raw materials. Due to its unique chemical and physical characteristics, the Ammonia (NH3) anhydrous gas is used in various industrial applications such as: Air Conditioning, Refrigeration (including space shuttles), Agriculture and Chemical Processing. NH3 gas, being a highly irritant toxic and flammable gas with a pungent odor detectable by human perception at 53 ppm, has a TLV-TWA of 25 ppm (TLV-STEL of 35 ppm) and a lower explosive limit (LEL) of 15% in air. Being extremely corrosive and irritating to the skin, eyes, nose and respiratory tract, (irritation begins at 130 - 200 ppm), exposures to high concentrations (above 2500 ppm) are life threatening, thus early detection of Ammonia at concentrations up to 50 ppm is essential to prevent its toxic influence. Existing detection methods for NH3 rely mainly on chemical sensors and analytical methods that require the gas to be sampled and introduced into the detection system via a probe, compared to various standards (for determining the concentration) and the result is not always reflecting the actual gas concentration. The emerging optical open path remote sensing technology that analyzes the specific 'finger print' absorption characteristics of NH3 in various narrow spectral bands, specifically in the UV solar blind band, is discussed including the rationale of the detection algorithm and system design. The system offers warning and alarm signals set at the above low concentration detection sensitivity, (10 - 50 ppm(DOT)m) thus providing reliable Ammonia detection over an air path from 3 (including air-duct applications) to 400 ft (1 - 120 m). Typical installations of Ammonia Monitoring Systems, field and laboratory test data are discussed, including spectral cross sensitivity analysis with interfering chemicals and changing environmental conditions (heat, humidity).

Spector, Oded; Jacobson, Esther

1999-12-01

71

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

72

Adsorption, diffusion, dewetting, and entrapment of acetone on Ni(111), surface-modified silicon, and amorphous solid water studied by time-of-flight secondary ion mass spectrometry and temperature programmed desorption  

NASA Astrophysics Data System (ADS)

Interactions of acetone with the silicon surfaces terminated with hydrogen, hydroxyl, and perfluorocarbon are investigated; results are compared to those on amorphous solid water (ASW) to gain insights into the roles of hydrogen bonds in surface diffusion and hydration of acetone adspecies. The surface mobility of acetone occurs at ~60 K irrespective of the surface functional groups. Cooperative diffusion of adspecies results in a 2D liquid phase on the H- and perfluorocarbon-terminated surfaces, whereas cooperativity tends to be quenched via hydrogen bonding on the OH-terminated surface, thereby forming residues that diffuse slowly on the surface after evaporation of the physisorbed species (i.e., 2D liquid). The interaction of acetone adspecies on the non-porous ASW surface resembles that on the OH-terminated Si surface, but the acetone molecules tend to be hydrated on the porous ASW film, as evidenced by their desorption during the glass-liquid transition and crystallization of water. The roles of micropores in hydration of acetone molecules are discussed from comparison with the results using mesoporous Si substrates.

Souda, Ryutaro

2011-10-01

73

Cs5Sn9(OH)·4NH3.  

PubMed

The title compound, penta-caesium nona-stannide hydroxide tetra-ammonia, crystallized from a solution of CsSnBi in liquid ammonia. The Sn9 (4-) unit forms a monocapped quadratic anti-prism. The hydroxide ion is surrounded by five caesium cations, which form a distorted quadratic pyramidal polyhedron. A three-dimensional network is formed by Cs-Sn [3.8881?(7)?Å to 4.5284?(7)?Å] and Cs-NH3 [3.276?(7)-3.636?(7)?Å] contacts. PMID:24940189

Friedrich, Ute; Korber, Nikolaus

2014-06-01

74

Cs5Sn9(OH)?4NH3  

PubMed Central

The title compound, penta­caesium nona­stannide hydroxide tetra­ammonia, crystallized from a solution of CsSnBi in liquid ammonia. The Sn9 4? unit forms a monocapped quadratic anti­prism. The hydroxide ion is surrounded by five caesium cations, which form a distorted quadratic pyramidal polyhedron. A three-dimensional network is formed by Cs—Sn [3.8881?(7)?Å to 4.5284?(7)?Å] and Cs—NH3 [3.276?(7)–3.636?(7)?Å] contacts.

Friedrich, Ute; Korber, Nikolaus

2014-01-01

75

Sensing Mechanisms for Carbon Nanotube Based NH3 Gas Detection  

SciTech Connect

There has been an argument on carbon nanotube (CNT) based gas detectors with a field-effect transistor (FET) geometry: do the response signals result from charge transfer between adsorbed gas molecules and the CNT channel and/or from the gas species induced Schottky barrier modulation at the CNT/metal contacts? To differentiate the sensing mechanisms, we employed three CNTFET structures, i.e., (1) the entire CNT channel and CNT/electrode contacts are accessible to NH3 gas; (2) the CNT/electrode contacts are passivated with a Si3N4 thin film, leaving the CNT channel open to the gas and, in contrast, (3) the CNT channel is covered with the film, while the contacts are open to the gas. We suggest that the Schottky barrier modulation at the contacts is the dominant mechanism from room temperature to 150°C. At higher temperatures, the charge transfer process contributes to the response signals. There is a clear evidence that the adsorption of NH3 on the CNT channel is facilitated by environmental oxygen.

Peng, Ning; Zhang, Qing; Chow, Chee L.; Tan, Ooi K.; Marzari, Nicola N.

2009-03-31

76

Fast Reactions NO(+)(H2O)(n) + NH3 yields NH4(+)(H2O)(n-1) + HNO2, n equals 1-3, and NO(+)NH3 + NH3 yields NH4(+) + ONNH2.  

National Technical Information Service (NTIS)

An afterglow technique has been utilized to measure the reaction NO(+).H2O+NH3 yields NH4(+)+HNO2 quantitatively and to observe qualitatively similar reactions of the ions NO(+).(H2O)2 and NO(+).(H2O)3 with NH3. The experiment was straightforward, N2 gas ...

F. C. Fehsenfeld E. E. Ferguson

1970-01-01

77

Study on treating of NH3–N wastewater by membrane technology in a pilot plant  

Microsoft Academic Search

Reverse osmosis (RO) and activated zeolite and three types of tertiary treatment pilot systems were evaluated to treat the effluents of secondary sedimentation tank of spandex waste water. For RO system, when NH3–N concentration of RO influent was less than 28 mg\\/l, NH3–N concentration of RO effluent was below 1 mg\\/l; when NH3–N concentration was 62 mg\\/l, the NH3–N removal

Yanbin Yun; Xinxin Zhang; Yili Wang

2011-01-01

78

Removal of high concentrations of NH3 by a combined photoreactor and biotrickling filter system  

Microsoft Academic Search

Average emission levels as high as 800 ppmv NH3 have often been found during the anaerobic fermentation process. At these levels, NH3 is regarded as an environmental toxic compound. High concentrations of NH3 gas are difficult to treat in a single treatment process, suggesting that, in terms of economic cost and treatment performance, a coupled system may be a feasible

Li-Chun Wu; Cheng-Lang Kuo; Ying-Chien Chung

2011-01-01

79

A semiconducting metal oxide sensor array for the detection of NO x and NH 3  

Microsoft Academic Search

In many fossil fuel burning systems, NOx emissions are minimized by a selective catalytic reduction (SCR) technique where NH3 is injected into the flue gas stream to react with NOx to form environmentally safe gases, such as nitrogen and water vapor. Unfortunately, this process is usually incomplete, resulting in either NOx emissions or excess NH3 (NH3 slip). Therefore, a critical

Brent T. Marquis; John F. Vetelino

2001-01-01

80

Réduction catalytique sélective de NO par NH3 en présence d'oxygène sur zéolithes NaY échangées au cuivre  

NASA Astrophysics Data System (ADS)

A series of Cu-NaY, prepared by ion-exchange and impregnation, was characterized by temperature programmed reduction (TPR) and oxidation (TPO) and also tested for the selective catalytic reduction (SCR) of NO by NH3 in an oxygen rich atmosphere, and in the NH3 oxidation. From the TPR profiles, the amount of isolated Cu2+ species, [Cu-O-Cu]2+ dimer species and CuO aggregates were evaluated. The TPO of Cu^+-NaY issued from the reduction of Cu2+-NaY by NH3, shows that NO alone cannot perform the reoxidation of Cu+ to Cu2+ below 873 K, but this reaction is enhanced in the presence of NO/O2 with respect to O2 alone. The SCR of NO with NH3 in 3% O2 leads to three peaks in the NO conversion curve, when conducted in the temperature programmed reaction mode. The first peak is a transient effect due to the impossible regeneration of Cu+ to Cu2+. As soon as the reoxydation of Cu+ to Cu2+ become feasible by NO/O2, the reaction starts (second peak) and would be related to the presence of copper in supercages. The formation of N2O in this temperature range occurs in the presence of copper oxide aggregates. The final conversion, at high temperature leads to 100% conversion of NO and is due to a better oxidation of Cu+ by NO/O2 and O2 alone. In this latter temperature range, the formation of N2O comes mainly from the reaction between NO and NH3 in the sodalite cavities but also from the oxidation of NH3. Une série de catalyseurs Cu-NaY, préparés par échange et imprégnation, a été caractérisée par réduction (TPR) et oxsydation (TPO) en température programmée et a été testée en réduction catalytique sélective (SCR) de NO par NH3 et en oxydation de NH3. La TPR a permis d'évaluer les différentes espèces cuivre présentes (Cu2+, [Cu-O-Cu]2+, CuO) dans les solides préparés. La TPO de Cu^+-NaY, obtenu par réduction de Cu2+-NaY par NH3 montre que NO seul ne réoxyde pas Cu+ en Cu2+ en dessous de 873 K, et que cette réaction est favorisée en présence de NO/O2 par rapport à O2 seul. En SCR de NO par NH3 en présence de 3 % O2 trois pics de conversion de NO sont observés si la réaction est réalisée en température programmée. Le premier pic de conversion vers 420 K est un phénomène transitoire en raison de l'impossibilité de réoxyder Cu+ en Cu2+ dans ce domaine de température . La deuxième vague vers 500 K apparaît dès que la réoxydation par le mélange NO/O2 devient possible et serait due à la présence de Cu en supercages. La formation de N2O dans cette zone de température se produit en présence d'agrégats d'oxyde de cuivre dans le solide. Enfin dès que la réoxydation de l'ensemble des ions Cu+ est possible, la conversion en NO devient totale pour des températures supérieures à 610 K. La formation de N2O dans ce dernier domaine de température provient principalement de la réaction entre NO et NH3 dans les cages sodalites mais aussi de l'oxydation de NH3.

Delahay, G.; Kieger, S.; Neveua, B.; Coq, B.

1999-03-01

81

(C4H3SCH2NH3)2(CH3NH3)Pb2I7: non-centrosymmetrical crystal structure of a bilayer hybrid perovskite.  

PubMed

The analysis of the crystal structure of (C4H3SCH2NH3)2(CH3NH3)Pb2I7, displaying a well-ordered acentric inorganic Pb2I7(3-) bilayer, is reported, and compared to the related monolayer hybrid perovskite. PMID:12357824

Zhu, Xu-Hui; Mercier, Nicolas; Riou, Amédée; Blanchard, Philippe; Frère, Pierre

2002-09-21

82

Intervalence Transfer in the Dimer ((NH3)5RuII(4,4'-bpy)RuIII(NH3)5)(5+),  

National Technical Information Service (NTIS)

We have reinvestigated the solvent dependence of the intervalence absorption band energy in the mixed-valence dimer (NH3)5Ru(4,4'-bipyridine)Ru(NH3)5)5+. From the new results we conclude that: 1) There is a considerable contribution to the apparent band e...

J. T. Hupp T. J. Meyer

1987-01-01

83

Synthesis, DTA, IR and Raman spectra of penthylenediammonium hexachlorostannate NH3(CH2)5NH3SnCl6.  

PubMed

The Raman and IR spectra of NH3(CH2)5NH3SnCl6 have been measured at ambient temperature. It is shown that the cations in the compound assume a symmetry lower than C2v. Combination bands observed in the 2100-1800 cm(-1) region in the IR spectrum of NH3(CH2)5NH3SnCl6 indicate that the compound contains the C-NH3 grouping, the bands are discussed and their assignment are suggested. No evidence of existence of hydrogen bonding is found from the infrared spectrum in the region of 2800-3200 cm(-1); anions and cations are found not connected by hydrogen bonding and are therfore isolated. The Raman spectrum of anions can be interpreted in terms of disordered groups, not clearly showing the predicted splitting of bands. PMID:11765786

Ouasri, A; Elyoubi; Guedira, T; Rhandour, A; Mhiri, T; Daoud, A

2001-11-01

84

Observational constraints on solar nebula nitrogen chemistry - N2/NH3  

NASA Technical Reports Server (NTRS)

Observations of N2(+) and NH2 in Comet Halley and N2H(+) and NH3 in nine Galactic star-forming regions are used to determine the average N2/NH3 abundance ratio in these objects. For Comet Halley, N2/NH3 of about 0.1 is found, and for the quiescent gas in a sample of star-forming regions, N2/NH3 of about 170 +/- 100. The cometary N2/NH3 ratio corrected for gas-phase elemental nitrogen depletion in Comet Halley indicates that the gas component in the comet-forming region of the solar nebula was N2/NH3 of about 4. It is concluded that more realistic models which include condensation fractionation effects are required before the N2 and NH3 abundances in comet volatiles can be related to star-forming regions.

Womack, Maria; Wyckoff, Susan; Ziurys, L. M.

1992-01-01

85

DRIFT Study of CuO-CeO2-TiO2 Mixed Oxides for NOx Reduction with NH3 at Low Temperatures.  

PubMed

A CuO-CeO2-TiO2 catalyst for selective catalytic reduction of NOx with NH3 (NH3-SCR) at low temperatures was prepared by a sol-gel method and characterized by X-ray diffraction, Brunner-Emmett-Teller surface area, ultraviolet-visible spectroscopy, H2 temperature-programmed reduction, scanning electron microscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). The CuO-CeO2-TiO2 ternary oxide catalyst shows excellent NH3-SCR activity in a low-temperature range of 150-250 °C. Lewis acid sites generated from Cu(2+) are the main active sites for ammonia activation at low temperature, which is crucial for low temperature NH3-SCR activity. The introduction of ceria results in increased reducibility of CuO species and strong interactions between CuO particles with the matrix. The interactions between copper, cerium and titanium oxides lead to high dispersion of metal oxides with increased active oxygen and enhanced catalyst acidity. Homogeneously mixed metal oxides facilitate the "fast SCR" reaction among Cu(2+)-NO, nitrate (coordinated on cerium sites) and ammonia (on titanium sites) on the CuO-CeO2-TiO2 catalyst at low temperatures. PMID:24848157

Chen, Lei; Si, Zhichun; Wu, Xiaodong; Weng, Duan

2014-06-11

86

NH3 formation and destruction during the gasification of coal in oxygen and steam.  

PubMed

This study was conducted to investigate the formation and destruction of NH3 during the gasification of coal in atmospheres containing O2 and steam. A Victorian brown coal was gasified in a novel bench-scale fluidized-bed/ fixed-bed reactor at 800 degrees C in atmospheres containing 2000 ppm O2, 15% H2O, or 2000 ppm O2 + 15% H2O. A NH3 standard gas was also used to study the destruction of NH3 in the gas phase and through gas-solid interactions. Sand, char, and coal ash were all found to enhance the destruction of NH3. An atmosphere containing O2 alone does not favor the conversion of char-N into NH3 but favors the destruction of NH3 through various mechanisms. The introduction of H2O into the gasification system greatly favors the conversion of char-N into NH3 and inhibits the destruction of NH3. The formation and destruction of NH3 in an atmosphere containing 15% H20 was similar to that in an atmosphere containing 15% H20 and 2000 ppm 02, indicating the dominant effects of steam in the formation and destruction of NH3 in a gasifier. PMID:17822124

Mckenzie, Lachlan J; Tian, Fu-Jun; Li, Chun-Zhu

2007-08-01

87

A model of nitrogen isotope fractionation during leaf-atmosphere NH3(g) exchange  

NASA Astrophysics Data System (ADS)

To date, the isotopic composition of NH3(g) in the atmosphere has been ascribed to two processes: volatilization from soils that generates isotopically depleted ammonia and precipitation events that scavenge isotopically enriched ammonium and deposit it to the land surface, leaving residual, isotopically depleted ammonia aloft. Here, we present a mathematical model describing nitrogen isotope fractionation during exchange between NH3(aq) in leaves and NH3(g) in the atmosphere. Two approaches are used to derive the model. The first is a classical, substitution-based method that yields only the equilibrium solution. The second is a matrix-based method that also yields the complete solution. With both approaches, the model predicts that efflux of NH3(g) from leaves isotopically depletes atmospheric NH3(g), whereas uptake isotopically enriches residual atmospheric NH3(g). When there is bidirectional exchange of NH3(g) (i.e., when atmospheric NH3(g) is close to the foliar NH3(g) compensation point), the model predicts that atmospheric NH3(g) can become either isotopically enriched or depleted. These results suggest that exchange between NH3(aq) in leaves and NH3(g) in the atmosphere contributes to variation in the nitrogen isotopic composition of NH3(g) in the atmosphere as well as organic nitrogen in plants, and should be considered in analyses of the distribution of nitrogen isotopes at natural abundance and tracer levels. Thus, the model may be useful for distinguishing between multiple sources and sinks for ammonia in the atmosphere, studying processes within the atmospheric reactive nitrogen cycle, and interpreting records of the isotopic composition of nitrogen-containing atmospheric gases (e.g., N2O) and particles (e.g., NH4+ and NO3- aerosols). In addition, the matrix-based modeling approach that is introduced may be useful for quantifying isotope dynamics in other complex systems in which the classical approach for determining equilibrium solutions becomes unwieldy, or dynamics are of particular interest.

Johnson, J. E.; Field, C. B.; Berry, J. A.

2012-12-01

88

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

89

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

90

Reduction Kinetics of Graphene Oxide Determined by Temperature Programmed Desorption  

Microsoft Academic Search

Graphene oxide, which is an electrical insulator, shows promise for use in several technological applications such as dielectric layers in nanoscale electronic devices or as the active region of chemical sensors. In principle, graphene oxide films could also be used as a precursor for the formation of large-scale graphene films by either thermal or chemical reduction of the graphene oxide.

Carl Ventrice; Nicholas Clark; Daniel Field; Heike Geisler; Inhwa Jung; Dongxing Yang; Richard Piner; Rodney Ruoff

2009-01-01

91

Analyte separation utilizing temperature programmed desorption of a preconcentrator mesh  

DOEpatents

A method and system for controllably releasing contaminants from a contaminated porous metallic mesh by thermally desorbing and releasing a selected subset of contaminants from a contaminated mesh by rapidly raising the mesh to a pre-determined temperature step or plateau that has been chosen beforehand to preferentially desorb a particular chemical specie of interest, but not others. By providing a sufficiently long delay or dwell period in-between heating pulses, and by selecting the optimum plateau temperatures, then different contaminant species can be controllably released in well-defined batches at different times to a chemical detector in gaseous communication with the mesh. For some detectors, such as an Ion Mobility Spectrometer (IMS), separating different species in time before they enter the IMS allows the detector to have an enhanced selectivity.

Linker, Kevin L. (Albuquerque, NM); Bouchier, Frank A. (Albuquerque, NM); Theisen, Lisa (Albuquerque, NM); Arakaki, Lester H. (Edgewood, NM)

2007-11-27

92

Ultrasensitive gaseous NH3 sensor based on ionic liquid-mediated signal-on electrochemiluminescence.  

PubMed

This work reports that ammonia (NH(3)) can be used as an efficient co-reactant for tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL) in ionic liquids (ILs), on the basis of which a signal-on ECL sensor for directly detecting gaseous NH(3) has been developed. The NH(3) ECL sensor has a very high sensitivity, with a detection limit of 10 ppt NH(3) (at signal-to-noise ratio of 3) without any preconcentration. The high sensitivity is mainly due to the zero ECL background of Ru(bpy)(3)(2+) in the ILs, strong co-reactant ECL activity of NH(3), and high solubility of NH(3) in imidazolium-based ILs. Additionally, the ECL sensor shows an excellent selectivity against common interfering gases and a wide linear response range from 10 ppt to 10 ppm. PMID:22728516

Chen, Lichan; Huang, Danjun; Zhang, Yuanjin; Dong, Tongqing; Zhou, Chen; Ren, Shuyan; Chi, Yuwu; Chen, Guonan

2012-08-01

93

TECHNICAL DESIGN NOTE: NH3-TPD measurements using a zeolite-based sensor  

NASA Astrophysics Data System (ADS)

A novel method for NH3-TPD measurements based on impedance spectroscopy (IS), denoted as IS-TPD, is presented. It applies a highly sensitive zeolite-based NH3-sensor instead of gas chromatography used in the conventional NH3-TPD. The zeolite samples were coated in the form of a thick-film on a directly heated inter-digital electrode (ide) chip. Altogether this set-up allows to substantially reduce the sample mass and to minimize temperature gradients.

Rodríguez-González, Luz; Simon, Ulrich

2010-02-01

94

Solid–gas equilibrium in chemical heat pumps: the NH 3–CoCl 2 system  

Microsoft Academic Search

The design of heat transfer equipment used in chemical heat pumps requires a knowledge of the temperature at which heat is produced during the synthesis reaction and the temperature at which it is used during the decomposition reaction. The existing equilibrium data in the literature for the reaction, CoCl2·2NH3+4NH3=CoCl2·6NH3 was obtained at pressures of 1 atm or less. Data at

Josée Trudel; Sophie Hosatte; Marten Ternan

1999-01-01

95

Density dependence of the 5 micron infrared spectrum of NH3  

Microsoft Academic Search

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

Camille Chapados; Gordon L. Bjoraker; George Birnbaum

1990-01-01

96

Ternary nucleation of H2SO4, NH3, and H2O in the atmosphere  

Microsoft Academic Search

Classical theory of binary homogeneous nucleation is extended to the ternary system H2SO4-NH3-H2O. For NH3 mixing ratios exceeding about 1 ppt, the presence of NH3 enhances the binary H2SO4-H2O nucleation rate by several orders of magnitude. The Gibbs free energies of formation of the critical H2SO4-NH3-H2O cluster, as calculated by two independent approaches, are in substantial agreement. The finding that

P. Korhonen; M. Kulmala; A. Laaksonen; Y. Viisanen; R. McGraw; J. H. Seinfeld

1999-01-01

97

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

NASA Astrophysics Data System (ADS)

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 the adsorbed NH3. Various physisorption, molecular and dissociative adsorption configurations are discussed.

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

2009-02-01

98

Comparison of preparation methods for ceria catalyst and the effect of surface and bulk sulfates on its activity toward NH3-SCR.  

PubMed

A series of CeO2 catalysts prepared with sulfate (S) and nitrate (N) precursors by hydrothermal (H) and precipitation (P) methods were investigated in selective catalytic reduction of NOx by NH3 (NH3-SCR). The catalytic activity of CeO2 was significantly affected by the preparation methods and the precursor type. CeO2-SH, which was prepared by hydrothermal method with cerium (IV) sulfate as a precursor, showed excellent SCR activity and high N2 selectivity in the temperature range of 230-450 °C. Based on the results obtained by temperature-programmed reduction (H2-TPR), transmission infrared spectra (IR) and thermal gravimetric analysis (TGA), the excellent performance of CeO2-SH was correlated with the surface sulfate species formed in the hydrothermal reaction. These results indicated that sulfate species bind with Ce(4+) on the CeO2-SH catalyst, and the specific sulfate species, such as Ce(SO4)2 or CeOSO4, were formed. The adsorption of NH3 was promoted by these sulfate species, and the probability of immediate oxidation of NH3 to N2O on Ce(4+) was reduced. Accordingly, the selective oxidation of NH3 was enhanced, which contributed to the high N2 selectivity in the SCR reaction. However, the location of sulfate on the CeO2-SP catalyst was different. Plenty of sulfate species were likely deposited on CeO2-SP surface, covering the active sites for NO oxidation, which resulted in poor SCR activity in the test temperature range. Moreover, the resistance to alkali metals, such as Na and K, was improved over the CeO2-SH catalyst. PMID:24140528

Chang, Huazhen; Ma, Lei; Yang, Shijian; Li, Junhua; Chen, Liang; Wang, Wei; Hao, Jiming

2013-11-15

99

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

100

Structural study of the hydrogen-bonded 1-naphthol.(NH3)2 cluster  

NASA Astrophysics Data System (ADS)

The structure of the 1-naphthol.(NH3)2 cluster was investigated by rotational coherence spectroscopy (RCS), mass selective one- and two-color resonant two-photon ionization (R2PI) experiments and ab initio calculations. RCS measurements yielded rotational constants of 1-naphthol.(NH3)2 as A=1197, B=500, and C=413 MHz, as well as those for several isotopomers. The counterpoise-corrected second-order Møller-Plesset perturbation theory (MP2) method predicts two isomers A and B. Both structures have hydrogen bonded naphthol-OH...NH3...NH3 chains, with the second NH3 bent above the proximal aromatic ring and pointing towards the ?-electron system and have nearly the same binding energy. The experimental rotational constants agree better with those calculated for structure B. The B3LYP and PW91 density functional methods also predict two isomers A, B with the rotational constants of B in acceptable agreement with experiment. Based on two-color R2PI experiments using low ionization frequency to suppress cluster fragmentation, the S1<--S0 electronic origin region of the 1-naphthol.(NH3)(2-4) cluster series was reassigned, in agreement with the work of Dedonder-Lardeux et al. [Phys. Chem. Chem. Phys. 3, 4316 (2001)]. In one-color experiments, the 1-naphthol.(NH3)3 cluster fragments with nearly 100% efficiency into the 1-naphthol.(NH3)2+ mass channel.

Tanner, Christian; Henseler, Debora; Leutwyler, Samuel; Connell, Leslie L.; Felker, Peter M.

2003-05-01

101

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...

102

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

103

Ultrafast and sensitive room temperature NH3 gas sensors based on chemically reduced graphene oxide  

NASA Astrophysics Data System (ADS)

Ultrafast and sensitive room temperature NH3 gas sensors based on chemically reduced graphene oxide (rGO) are demonstrated in this work. rGO, which was prepared via the reduction of graphene oxide by pyrrole, exhibited excellent responsive sensitivity and selectivity to ammonia (NH3) gas. The high sensing performance of these rGO sensors with resistance change as high as 2.4% and response time as fast as 1.4 s was realized when the concentration of NH3 gas was as low as 1 ppb. Furthermore, the rGO sensors could rapidly recover to their initial states with IR illumination. The devices also showed excellent repeatability and selectivity to NH3. These rGO sensors, with low cost, low power, and easy fabrication, as well as scalable properties, showed great potential for ultrasensitive detection of NH3 gas in a wide variety of fields.

Hu, Nantao; Yang, Zhi; Wang, Yanyan; Zhang, Liling; Wang, Ying; Huang, Xiaolu; Wei, Hao; Wei, Liangmin; Zhang, Yafei

2014-01-01

104

Fluxes of NH3 and CO2 over upland moorland in the vicinity of agricultural land  

NASA Astrophysics Data System (ADS)

Intensive field measurements of NH3 and CO2 exchange were made over a wet heathland in the vicinity (<500 m) of sheep pastures in the Cairngorm mountains of Scotland for a two-week period in the summer. Fluxes of NH3 were determined using the aerodynamic gradient method with a 3-height continuous denuder system; fluxes of CO2 were determined using eddy correlation, while sensible and latent heat fluxes were determined by both methods. Few studies have measured NH3 and CO2 fluxes simultaneously, making these measurements relevant to compare exchange dynamics. Both NH3 and CO2 exchanged bidirectionally, in response to a combination of biological (foliar, soil) and physico-chemical controls (solubility). NH3 was deposited rapidly to leaf surfaces, although during warm, dry daytime conditions periods of emission occurred, explained by the existence of a compensation point concentration for NH3. By contrast, CO2 followed a characteristic pattern of absorption during the day associated with net photosynthesis and emission at night. Both gases showed net uptake from the atmosphere, at 30 ?mol NH3 m-2 d-1 and 74 mmol CO2 m-2 d-1. In southeast winds, NH3 emissions from the sheep pasture caused a significant advection error to the measured fluxes (>10%). Corrections were applied using a local-scale dispersion-exchange model. The analysis highlights how advection modifies the classical one-dimensional inferential resistance approach. It is concluded that ecosystems in the vicinity of agricultural land receive more dry deposition than would be estimated using NH3 concentration monitoring and standard inferential models. In the present study, this effect represented an overall increase in total NH3 deposition of 32%.

Milford, Celia; Hargreaves, Ken J.; Sutton, Mark A.; Loubet, Benjamin; Cellier, Pierre

2001-10-01

105

X-ray, thermal and vibrational studies of two structural phases transition in hexylenediammonium pentachlorobismuthate (III) [NH3(CH2)6NH3]BiCl5  

NASA Astrophysics Data System (ADS)

[NH3(CH2)6NH3]BiCl5 crystal has been studied by means of X-ray diffraction, DSC and vibrational spectroscopy techniques. The X-ray powder study showed that the crystal exhibits two phase transitions near 286 K and 326 K as it was indicated by crystallography analysis: ?(P212121, Z = 4 at 223 K) ? ?(P21/n, Z = 8 at 308 K) ? ?(Pnma, Z = 4 at 373 K). The DSC analysis (on heating and cooling) confirm the existence of these phase transitions at 291/286 K and 326/325 K and indicate that ? ? ? phase transition is of first-order character, but ? ? ? one is of weak first-order type. Infrared and Raman spectra which interpreted at room temperature indicated that the [NH3(CH2)6NH3]BiCl5 structure was consisted of isolated (BiCl52-)n units composed of distorted BiCl63-octahedra. Raman spectroscopy at various temperatures showed that both anionic and cationic motions contribute to the complex transition mechanisms. The character order-disorder of ? ? ? phase transition is undoubtedly related to the change in dynamical state of +NH(CH)6NH3+ cations which are performing some kind of reorientational or rotational motions above 298 K.

Ouasri, A.; Jeghnou, H.; Rhandour, A.; Mazzah, A.; Roussel, P.

2012-11-01

106

Tetra-amminelithium triamminelithium tris-ulfide, [Li(NH3)4][Li(NH3)3S3  

PubMed Central

The title compound, [Li(NH3)4]+[Li(NH3)3S3]?, an ammo­niate of the previously unknown lithium tris­ulfide, was obtained from the reaction of lithium and sulfur in liquid ammonia. The asymmetric unit consists of two crystallographically independent formula units. The [Li(NH3)4]+ cations are close to regular LiN4 tetra­hedra. The anions contain LiSN3 tetra­hedra; the S—S—S bond angles are 110.43?(5) and 109.53?(5)°. In the crystal, the components are linked by multiple N—H?S hydrogen bonds. A weak N—H?N hydrogen bond is also present.

Guentner, Christian; Korber, Nikolaus

2012-01-01

107

Transformation from chemisorption to physisorption with tube diameter and gas concentration: Computational studies on NH3 adsorption in BN nanotubes  

NASA Astrophysics Data System (ADS)

Using first-principles computations, we studied NH3 adsorption on a series of zigzag (n,0) single-walled BN nanotubes (BNNTs) and the effect of gas coverage. Tube diameter and NH3 coverage play important roles on the tube-NH3 interaction. Chemisorption of a single NH3 molecule on top of B site is energetically preferable for all the tubes studied, but the adsorption energy decreases sharply with increasing tube diameter, and then gradually approaches the value for NH3 physisorption on BN graphene layer. On the sidewall of (10,0) BNNT, NH3 molecules prefer to pair arrangement on top of B and N atoms opposite in the same hexagon. At low coverages, NH3 molecules are partly chemically bound to BNNTs. With the increase of NH3 coverage, hydrogen bonds form between the adsorbed NH3 molecules or between the NH3 molecules and N atoms in BNNTs. When the coverage reaches 25%, the chemisorption of NH3 transforms to physisorption completely. NH3 adsorption does not modify the overall band structures of BNNTs, irrespective of NH3 coverage, but the band gap is narrowed due to the NH3-tube coupling and tube deformation.

Li, Yafei; Zhou, Zhen; Zhao, Jijun

2007-11-01

108

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

109

Matrix Isolation Spectroscopy and Nuclear Spin Conversion of NH3 and ND3 in Solid Parahydrogen  

NASA Astrophysics Data System (ADS)

We present matrix isolation infrared absorption spectra of NH3 and ND3 trapped in solid parahydrogen (pH2) at temperatures around 1.8 K. We used the relatively slow nuclear spin conversion (NSC) of NH3 and ND3 in freshly deposited pH2 samples as a tool to assign the sparse vibration-inversion-rotation (VIR) spectra of NH3 in the regions of the -2, -4, 2-4, -1, and -3 bands and ND3 in the regions of the -2, -4, -1, and -3 fundamentals. Partial assignments are also presented for various combination bands of NH3. Detailed analysis of the -2 bands of NH3 and ND3 indicates that both isotopomers are nearly free rotors; that the vibrational energy is blue-shifted by 1-2%; and that the rotational constants and inversion tunneling splitting are 91-94% and 67-75%, respectively, of the gas-phase values. The line shapes of the VIR absorptions are narrow (0.2-0.4 cm-1) for upper states that cannot rotationally relax and broad (>1 cm-1) for upper states that can rotationally relax. We report and assign a number of NH3-induced infrared absorption features of the pH2 host near 4150 cm-1, along with a cooperative transition that involves simultaneous vibrational excitation of a pH2 molecule and rotation-inversion excitation of NH3. The NSCs of NH3 and ND3 were found to follow first-order kinetics with rate constants at 1.8 K of k = 1.88(16) - 10-3 s-1 and k = 1.08(8) - 10-3 s-1, respectively. These measured rate constants are compared to previous measurements for NH3 in an Ar matrix and with the rate constants measured for other dopant molecules isolated in solid pH2.

Ruzi, Mahmut; Anderson, David T.

2013-10-01

110

Concentration-dependent NH 3 deposition processes for moorland plant species with and without stomata  

NASA Astrophysics Data System (ADS)

Currently, in operational modelling of NH 3 deposition a fixed value of canopy resistance ( Rc) is generally applied, irrespective of the plant species and NH 3 concentration. This study determined the effect of NH 3 concentration on deposition processes to individual moorland species. An innovative flux chamber system was used to provide accurate continuous measurements of NH 3 deposition to Deschampsia cespitosa (L.) Beauv., Calluna vulgaris (L.) Hull, Eriophorum vaginatum L., Cladonia spp., Sphagnum spp., and Pleurozium schreberi (Brid.) Mitt. Measurements were conducted across a wide range of NH 3 concentrations (1-140 ?g m -3). NH 3 concentration directly affects the deposition processes to the vegetation canopy, with Rc, and cuticular resistance ( Rw) increasing with increasing NH 3 concentration, for all the species and vegetation communities tested. For example, the Rc for C. vulgaris increased from 14 s m -1 at 2 ?g m -3 to 112 s m -1 at 80 ?g m -3. Diurnal variations in NH 3 uptake were observed for higher plants, due to stomatal uptake; however, no diurnal variations were shown for non-stomatal plants. Rc for C. vulgaris at 80 ?g m -3 was 66 and 112 s m -1 during day and night, respectively. Differences were found in NH 3 deposition between plant species and vegetation communities: Sphagnum had the lowest Rc (3 s m -1 at 2 ?g m -3 to 23 at 80 ?g m -3), and D. cespitosa had the highest nighttime value (18 s m -1 at 2 ?g m -3 to 197 s m -1 at 80 ?g m -3).

Jones, M. R.; Leith, I. D.; Raven, J. A.; Fowler, D.; Sutton, M. A.; Nemitz, E.; Cape, J. N.; Sheppard, L. J.; Smith, R. I.

111

Shock-excited NH3 (3, 3) masers in the NGC 6334 star-forming region  

NASA Technical Reports Server (NTRS)

We report the discovery of four NH3 (3, 3) masers in the NGC 6334 star formation region. The masers are found in two of the seven far-infrared continuum sources where high-mass star formation is taking place in this molecular cloud. These masers occur at the ends of high-velocity molecular outflows; no maser emission was found near regions without high-velocity outflows. The NH3 masers are not associated with any other type of maser. These results confirm that the NH3 (3, 3) masers are caused by shocks and probably mark the location where the molecular outflow jet impinges upon the ambient medium.

Kraemer, Kathleen E.; Jackson, James M.

1995-01-01

112

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

113

Dependence of Time-Dependent Dielectric Breakdown Lifetime on NH3-Plasma Treatment in Cu Interconnects  

NASA Astrophysics Data System (ADS)

The time-dependent dielectric breakdown (TDDB) between adjacent Cu wires was investigated. TDDB lifetime strongly depends on the conditions of the chemical mechanical polishing (CMP) surface and of NH3-plasma treatment prior to cap nitride deposition. The condition of NH3-plasma treatment was evaluated in detail. The TDDB lifetime is strongly dependent on the substrate temperature and the duration of NH3-plasma treatment but is independent of the pressure and power. Excessive NH3-plasma treatment degrades the TDDB lifetime. Hillocks on the Cu surface appear abruptly as the substrate temperature rises. The optimum treatment conditions are 10-30 s for a substrate temperature of 360°C, and 10 s for a substrate temperature of 400°C.

Noguchi, Junji; Ohashi, Naofumi; Yamaguchi, Hizuru; Takeda, Ken-ichi

2005-07-01

114

Rotational tunneling of ammonia in (NH3)K3C60  

NASA Astrophysics Data System (ADS)

The rotational dynamics of NH3 in the ammoniated fulleride (NH3)K3C60 are studied by the inelastic neutron scattering technique. Well-defined excitations appear in the low-energy spectra at 1.5 K as a broad band centered at ~350 ?eV with shoulders at ~240 and 590 ?eV. The temperature dependence of their intensities, energies, and widths is consistent with their assignment to rotational tunneling transitions of the NH3 molecule. The estimated barrier of the threefold hindrance potential to rotation of the H atoms about the K-N axis is ~5.7 meV. The existence of minority hindering sites with both larger (~8 meV) and smaller (~2 meV) torsional barriers shows that orientational disorder effects survive in (NH3)K3C60 even at low temperatures.

Margadonna, Serena; Prassides, Kosmas; Brown, Craig M.; Shimoda, Hideo; Iwasa, Yoshihiro; Casalta, Hélène

1999-12-01

115

Indirect measurement of N-14 quadrupolar coupling for NH3 intercalated in potassium graphite  

NASA Technical Reports Server (NTRS)

A method for indirect measurement of the nuclear quadrupolar coupling was developed and applied to NH3 molecules in the graphite intercalation compound K(NH3)4.3C24, which has a layered structure with alternating carbon and intercalant layers. Three triplets were observed in the H-1 NMR spectra of the compound. The value of the N-14 quadrupolar coupling constant of NH3 (3.7 MHz), determined indirectly from the H-1 NMR spectra, was intermediate between the gas value of 4.1 MHz and the solid-state value of 3.2 MHz. The method was also used to deduce the (H-1)-(H-1) and (N-14)-(H-1) dipolar interactions, the H-1 chemical shifts, and the molecular orientations and motions of NH3.

Tsang, T.; Fronko, R. M.; Resing, H. A.

1987-01-01

116

Cross sections for direct and dissociative ionization of NH3 and CS2 by electron impact  

NASA Technical Reports Server (NTRS)

A crossed electron beam-molecular beam collision geometry is used to measure cross sections for the production of positive ions by electron impact on NH3 and CS2. Ionization cross-section data for NH3 and the values of various cross sections are presented, as well as ionization efficiency curves for CS2. Considerable differences are found between the various results on NH3. The present values are close to the data of Djuric et al. (1981). The semiempirical calculations of Hare and Meath (1987) differ considerably in the absolute values of cross sections. Discrepancies were observed in comparisons of cross sections of other fragment ions resulting from the ionization and dissociate ionization of NH3.

Rao, M. V. V. S.; Srivastava, S. K.

1991-01-01

117

Characterization by temperature programmed reduction  

Microsoft Academic Search

Fresh and used EUROCAT Oxide-2 catalyst made up of V2O5, WO3 and TiO2 with SiO2, Al2O3 and CaO as main additives have been studied by means of temperature programmed reduction (TPR). As in the EUROCAT Oxide-1 project (V2O5\\/TiO2 catalysts) for similar conditions similar profiles were obtained in the different laboratories. In contrast to the V2O5\\/TiO2 catalysts (EUROCAT Oxide-1 project), where

M. A Reiche; M Maciejewski; A Baiker

2000-01-01

118

New Cation-Diffusing Phase of (CH3NH3)5Bi2Cl11  

NASA Astrophysics Data System (ADS)

A new phase transition of (CH3NH3)5Bi2Cl11 was found at 520 K by proton NMR and differential thermal analysis. By the phase transition, the activation energy of translational diffusion of CH3NH3+ cation was reduced from 83 kJ/mol to 29 kJ/mol. Rotational motion of the cation in the low-temperature phase is also discussed.

Nagatomo, Shigenori; Takeda, Sadamu; Yamaguchi, Kizashi; Iwata, Makoto; Ishibashi, Yoshihiro

1995-02-01

119

Radiation Damage and Recovery in Polarized 14NH3 Ammonia Targets at Jefferson Lab  

NASA Astrophysics Data System (ADS)

Dynamically nuclear polarized solid ammonia offers an attractive combination of high polarization, comparatively high dilution factor and high radiation damage resistance as a target material in electron scattering experiments. Polarized 14NH3, provided by the University of Virginia Polarized Target Group, was used as target material in two simultaneous experiments at Thomas Jefferson National Accelerator Facility in the spring of 2009. Target polarization performance for both experiments is discussed, as is previously unseen behavior in irradiated 14NH3.

Maxwell, J. D.

2011-01-01

120

Concentration-dependent NH 3 deposition processes for mixed moorland semi-natural vegetation  

NASA Astrophysics Data System (ADS)

Dry deposition modelling typically assumes that canopy resistance ( Rc) is independent of ammonia (NH 3) concentration. An innovative flux chamber system was used to provide accurate continuous measurements of NH 3 deposition to a moorland composed of a mixture of Calluna vulgaris (L.) Hull, Eriophorum vaginatum L. and Sphagnum spp. Ammonia was applied at a wide range of concentrations (1-100 ?g m -3). The physical and environmental properties and the testing of the chamber are described, as well as results for the moorland vegetation using the 'canopy resistance' and 'canopy compensation point' interpretations of the data. Results for moorland plant species demonstrate that NH 3 concentration directly affects the rate of NH 3 deposition to the vegetation canopy, with Rc and cuticular resistance ( Rw) increasing with increasing NH 3 concentrations. Differences in Rc were found between night and day: during the night Rc increases from 17 s m -1 at 10 ?g m -3 to 95 s m -1 at 80 ?g m -3, whereas during the day Rc increases from 17 s m -1 at 10 ?g m -3 to 48 s m -1 at 80 ?g m -3. The lower resistance during the day is caused by the stomata being open and available as a deposition route to the plant. Rw increased with increasing NH 3 concentrations and was not significantly different between day and night (at 80 ?g m -3 NH 3 day Rw=88 s m -1 and night Rw=95 s m -1). The results demonstrate that assessments using fixed Rc will over-estimate NH 3 deposition at high concentrations (over ˜15 ?g m -3).

Jones, M. R.; Leith, I. D.; Fowler, D.; Raven, J. A.; Sutton, M. A.; Nemitz, E.; Cape, J. N.; Sheppard, L. J.; Smith, R. I.; Theobald, M. R.

121

A study of a bubble absorber using a plate heat exchanger with NH 3–H 2O, NH 3–LiNO 3 and NH 3–NaSCN  

Microsoft Academic Search

There is a continuous research effort being carried out worldwide on the development of absorption cooling systems with the objective of increasing their performance, one important area is the search for more efficient heat exchangers and alternative working fluids that can improve the performance of NH3–H2O and H2O–LiBr that are commonly used in commercial absorption refrigeration machines. In this work

J. Cerezo; R. Best; R. J. Romero

2011-01-01

122

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...

123

On the Interaction of CO and NH3 with BH3 and BF3  

NASA Technical Reports Server (NTRS)

BH3CO, BF3CO, BH3NH3, and BF3NH3 have been studied using density functional theory (DFT). The computed geometries are in reasonable agreement with experiment. BF3CO is found to be weakly bound. The binding energies of BH3CO, BH3NH3 , and BF3NH3 have also been computed using the coupled cluster singles and doubles level of theory, including a perturbational estimate of the connected triples [CCSD(T)]. These CCSD(T) calculations are performed using correlation consistent polarized-valence triple-zeta basis sets. These are expected to be the most accurate binding energies to date. The DFT binding energies are in good agreement with those obtained at the CCSD(T) level. The bonding is analyzed using the constrained space orbital variation (CSOV) technique. In addition to analyzing the bonding in BH3CO, BH3NH3, and BF3NH3, the CSOV approach is used to study why the bonding in BF3CO is so weak.

Bauschlicher, Charles W., Jr.; Ricca, Alessandra; Langhoff, Stephen R. (Technical Monitor)

1994-01-01

124

Superconductivity in (NH3)yCs0.4FeSe  

NASA Astrophysics Data System (ADS)

Alkali-metal-intercalated FeSe materials, (NH3)yM0.4FeSe (M: K, Rb, and Cs), have been synthesized using the liquid NH3 technique. (NH3)yCs0.4FeSe shows a superconducting transition temperature (Tc) as high as 31.2 K, which is higher by 3.8 K than the Tc of nonammoniated Cs0.4FeSe. The Tcs of (NH3)yK0.4FeSe and (NH3)yRb0.4FeSe are almost the same as those of nonammoniated K0.4FeSe and Rb0.4FeSe. The Tc of (NH3)yCs0.4FeSe shows a negative pressure dependence. A clear correlation between Tc and lattice constant c is found for ammoniated metal-intercalated FeSe materials, suggesting a correlation between Fermi-surface nesting and superconductivity.

Zheng, Lu; Izumi, Masanari; Sakai, Yusuke; Eguchi, Ritsuko; Goto, Hidenori; Takabayashi, Yasuhiro; Kambe, Takashi; Onji, Taiki; Araki, Shingo; Kobayashi, Tatsuo C.; Kim, Jungeun; Fujiwara, Akihiko; Kubozono, Yoshihiro

2013-09-01

125

H2CO and H110? observations towards NH3 sources  

NASA Astrophysics Data System (ADS)

We observed the H2CO(110-111) absorption lines and H110? radio recombination lines (RRL) toward 180 NH3 sources using the Nanshan 25-m radio telescope. In our observation, 138 sources were found to have H2CO lines and 36 have H110? RRLs. Among the 138 detected H2CO sources, 38 sources were first detected. The detection rates of H2CO have a better correlation with extinction than with background continuum radiation. Line center velocities of H2CO and NH3 agree well. The line width ratios of H2CO and NH3 are generally larger than unity and are similar to that of 13CO. The correlation between column densities of H2CO and extinction is better than that between NH3 and extinction. These line width relation and column density relation indicate H2CO is distributed on a larger scale than that of NH3, being similar to the regions of 13CO. The abundance ratios between NH3 and H2CO were found to be different in local clouds and other clouds.

Yuan, Ye; Esimbek, Jarken; Zhou, Jian Jun; Tang, Xin Di; Wu, Gang; Ma, Ying Xiu

2014-04-01

126

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

127

SEASONAL NH3 EMISSION ESTIMATES FOR THE EASTERN UNITED STATES BASED ON AMMONIUM WET CONCENTRATIONS AND AN INVERSE MODELING METHOD  

EPA Science Inventory

Significant uncertainty exists in the magnitude and variability of ammonia (NH3) emissions. NH3 emissions are needed as input for air quality modeling of aerosols and deposition of nitrogen compounds. Approximately 85% of NH3 emissions are estimated to come from agricultural ...

128

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

129

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.

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

2013-01-01

130

Pharmacological profile of the thyroid hormone receptor antagonist NH3 in rats.  

PubMed

NH3 is a thyroid hormone receptor (TR) antagonist that inhibits binding of thyroid hormones to their receptor and that inhibits cofactor recruitment. It was active in a tadpole tail resorption assay, with partial agonist activity at high concentrations. We determined the effect of NH3 on the cholesterol-lowering, thyroid stimulating hormone (TSH)-lowering, and tachycardic action of thyroid hormone (T(3)) in rats. Cholesterol-fed, euthyroid rats were treated for 7 days with NH3, and a dose response (46.2-27,700 nmol/kg/day) was determined. We also determined the effect of two doses of T(3) on the NH3 dose-response curve. NH3 decreased heart rate modestly starting at 46.2 nmol/kg/day, but the effect was lost at >2920 nmol/kg/day. At 27,700 nmol/kg/day, tachycardia was seen, suggesting partial agonist activity. NH3 increased plasma cholesterol to a maximum of 27% at 462 nmol/kg/day. At higher doses, cholesterol was reduced, suggesting partial agonist activity. Plasma TSH was increased from 46.2 to 462 nmol/kg/day NH3, but at higher doses, this effect was lost, and partial agonist effects were apparent. T(3) at 15.4 and 46.2 nmol/kg/day increased heart rate, reduced cholesterol, and reduced plasma TSH. NH3 inhibited the cholesterol-lowering, TSH-lowering and tachycardic effects of 15.4 nmol/kg/day T(3), but much of the effect was lost at >924 nmol/kg/day doses. NH3 had no effect on the cholesterol-lowering action of 46.2 nmol/kg/day T(3), but it inhibited the tachycardic and TSH suppressant effects up to the 924 nmol/kg/day dose. Single doses of 462 and 27,700 nmol/kg caused no TR inhibitory effects. In conclusion, NH3 has TR antagonist properties on T(3)-responsive parameters, but it has partial agonist properties at higher doses. PMID:17440037

Grover, Gary J; Dunn, Celeste; Nguyen, Ngoc-Ha; Boulet, Jamie; Dong, Gao; Domogauer, Jason; Barbounis, Peter; Scanlan, Thomas S

2007-07-01

131

Structural, electronic, bonding, and elastic properties of NH3BH3: a density functional study.  

PubMed

The structural, electronic, bonding, and elastic properties of the low-temperature orthorhombic phase of NH(3)BH(3) are studied by means of first-principles total energy calculations based on the pseudopotential method. The calculated structural parameters of NH(3)BH(3) are found to be in good agreement with the experimental values. From the band structure calculations, the compound is found to be an indirect bandgap insulator with the bandgap of 5.65 eV (5.90 eV) with LDA(GGA) along the ?-Z direction. The Mulliken bond population and the charge density distributions are used to analyze the chemical bonding in NH(3)BH(3) . The study reveals that B-H bonds are more covalent than N-H bonds. The elastic constants are predicted for ambient as well as pressures up to 6 GPa, from which theoretical values of all the related mechanical properties such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and anisotropy factors are calculated. It is found that NH(3)BH(3) is mechanically stable at ambient and also external pressures up to 6 GPa. As pressure increases all the calculated elastic moduli of NH(3)BH(3) increase, indicating that the compound becomes more stiffer and hard under pressure. From the ratio of shear modulus to bulk modulus (G/B), we conclude NH(3)BH(3) to be ductile in nature, and the ductility increases with pressure. The present results confirm the experimentally observed less plastic nature of the low-temperature phase of NH(3)BH(3) . PMID:21425297

Lingam, Ch Bheema; Babu, K Ramesh; Tewari, Surya P; Vaitheeswaran, G

2011-06-01

132

Bibliography of Sources of Thermodynamic Data for the Systems: CO2+NH3+H2O, CO2+H2S+H2O, H2S+NH3+H2O, and CO2+NH3+H2S+H2O.  

National Technical Information Service (NTIS)

Contained herein is a bibliography of sources of experimental and correlated thermodynamic data for the systems CO2 + NH3 + H2O, CO2 + H2S + H2O, H2S + NH3 + H2O, and CO2 + NH3 + H2S + H2O. The types of data in this bibliography include all types of equil...

R. N. Goldberg D. K. Steckler

1985-01-01

133

Temperature-Programmed Reduction and XRD Studies of Ammonia-Treated Molybdenum Oxide and Its Activity for Carbazole Hydrodenitrogenation  

Microsoft Academic Search

The change structure and composition of molybdenum nitride catalysts with cooling in a stream of ammonia or helium gas after NH3 treating was determined using temperature-programmed reduction (TPR) and X-ray powder diffraction analyses. The relationship between the molybdenum species and the catalytic activities of the molybdenum nitride catalysts for the hydrodenitrogenation (HDN) of carbazole was discussed. MoO2, ?-Mo2N, and Mo

M. Nagai; Y. Goto; A. Miyata; M. Kiyoshi; K. Hada; K. Oshikawa; S. Omi

1999-01-01

134

Investigation of NH3 emissions from new technology vehicles as a function of vehicle operating conditions.  

PubMed

The objective of this study was to measure ammonia (NH3) emissions from modern technology vehicles since information is scarce aboutthis importantsource of particulate matter (PM) precursors. Test variables included the emission level to which the vehicle was certified, the vehicle operating conditions, and catalyst age. Eight vehicles with low-emission vehicle (LEV) to super-ultralow-emission vehicle (SULEV) certification levels were tested over the Federal Test Procedure (FTP75), a US06 cycle, a hot running 505, a New York City Cycle (NYCC), and a specially designed Modal Emissions Cycle (MEC01v7) using both as-received and bench-aged catalysts. NH3 emissions in the raw exhaust were measured by tunable diode laser (TDL) absorption spectroscopy. The results show that NH3 emissions depend on driving mode and are primarily generated during acceleration events. More specifically, high NH3 emissions were found for high vehicle specific power (VSP) events and rich operating conditions. For some vehicles, NH3 emissions formed immediately after catalyst light-off during a cold start. PMID:14620808

Huai, Tao; Durbin, Thomas D; Miller, J Wayne; Pisano, John T; Sauer, Claudia G; Rhee, Sam H; Norbeck, Joseph M

2003-11-01

135

Nitrogen conversion in relation to NH3 and HCN during microwave pyrolysis of sewage sludge.  

PubMed

The nitrogen conversions in relation to NH3 and HCN were investigated during microwave pyrolysis of sewage sludge. The nitrogen distributions and evolution of nitrogen functionalities in the char, tar, and gas fractions were conducted. The results suggested that the thermal cracking of protein in sludge produced three important intermediate compounds, including the amine-N, heterocyclic-N, and nitrile-N compounds. The deamination of amine-N compounds resulted from labile proteins cracking led to the formation of NH3 (about 7.5% of SS-N) between 300 and 500 °C. The cracking of nitrile-N and heterocyclic-N compounds in the tars from the dehydrogenation and polymerization of amine-N generated HCN (6.6%) from 500 to 800 °C, respectively. Moreover, the ring-opening of heterocyclic-N in the char and tar contributed to the release of NH3 accounting for about 18.3% of SS-N with the temperature increasing from 500 to 800 °C. Specifically, the thermal cracking of amine-N, heterocyclic-N and nitrile-N compounds contributed to above 80% of the total (HCN+NH3) productions. Consequently, it might be able to reduce the HCN and NH3 emissions through controlling the three intermediates production at the temperature of 500-800 °C. PMID:23477529

Tian, Yu; Zhang, Jun; Zuo, Wei; Chen, Lin; Cui, Yanni; Tan, Tao

2013-04-01

136

NH3 Abatement in Fluidized Bed Co-Gasification of RDF and Coal  

NASA Astrophysics Data System (ADS)

Gasification of wastes may come out as an alternative technology to produce a gas with many potential applications, from direct burning in a boiler or motor to the production of synthetic chemicals and hydrogen. High tar production and high operational costs are preventing gasification wider dissemination. Besides these problems, the presence of NH3 in the syngas may have a negative impact as it can be converted into nitrogen oxides if the gas is further burnt. To reduce NH3 formation it is required a full understanding of how operational parameters contribute to the formation/reduction of this pollutant. A full studyon the effect of fuel composition, temperature and equivalence ratio on the formation of NH3 is given. Experimental results are compared to theoretical ones obtained with FactSage software. It is also analyzed the effect of feedstock mineral matterin NH3 release during gasification. Toaccomplish a significant decrease in the release of NH3, different catalysts and sorbents were tested with the aim of achieving high energy conversions and low environmental impact.

Gulyurtlu, I.; Pinto, Filomena; Dias, Mário; Lopes, Helena; André, Rui Neto; Cabrita, I.

137

An investigation on NH 3 emissions and particulate NH 4+-NO 3- formation in East Asia  

NASA Astrophysics Data System (ADS)

In this study, the accuracy of NH 3 emissions in East Asia is evaluated by a comparison of measured and predicted NH 4NO 3 concentrations. For the prediction of particulate NH 4NO 3 concentrations, this study uses the USEPA Models-3/Community Multi-scale Air Quality (Models-3/CMAQ) model. The measurement data are collected from 4 ground-based stations (Beijing, Shanghai, Qingdao, and Kangwha) and ACE-ASIA C130 Flights #6, #7, and #10. The four ground-based stations and air flight tracks are located in and around the Yellow Sea in East Asia. According to the results, the predicted fine-mode NH 4+concentrations are 1.2-3.8 times overestimated compared to those measured on the mass basis, and fine-mode NO 3- concentrations are 1.9-7.6 times overestimated on the mass basis. It is also revealed in this study that aberrantly high predicted fine-mode NO 3- concentrations in East Asia can be attributed to the overestimated NH 3 emissions. The predicted gas-phase NH 3 concentrations and estimated NH 3 emissions are likely to be 1.2-3.8 times overestimated in East Asia on the mass basis. Therefore, it is recommended that approximately 20-75% reduced NH 3 emission fields should be used in future modeling studies for East Asia.

Kim, J. Y.; Song, C. H.; Ghim, Y. S.; Won, J. G.; Yoon, S. C.; Carmichael, G. R.; Woo, J.-H.

138

Dynamics of gas phase Ne(*) + NH3 and Ne(*) + ND3 Penning ionisation at low temperatures.  

PubMed

Two isotopic chemical reactions, Ne(*) + NH3, and Ne(*) + ND3, have been studied at low collision energies by means of a merged beams technique. Partial cross sections have been recorded for the two reactive channels, namely, Ne(*) + NH3 ? Ne + [Formula: see text] + e(-), and Ne(*) + NH3 ? Ne + [Formula: see text]+ H + e(-), by detecting the [Formula: see text] and [Formula: see text] product ions, respectively. The cross sections for both reactions were found to increase with decreasing collision energy, Ecoll, in the range 8 ?eV < Ecoll < 20 meV. The measured rate constant exhibits a curvature in a log(k)-log(Ecoll) plot from which it is concluded that the Langevin capture model does not properly describe the Ne(*) + NH3 reaction in the entire range of collision energies covered here. Calculations based on multichannel quantum defect theory were performed to reproduce and interpret the experimental results. Good agreement was obtained by including long range van der Waals interactions combined with a 6-12 Lennard-Jones potential. The branching ratio between the two reactive channels, [Formula: see text], is relatively constant, ? ? 0.3, in the entire collision energy range studied here. Possible reasons for this observation are discussed and rationalized in terms of relative time scales of the reactant approach and the molecular rotation. Isotopic differences between the Ne(*) + NH3 and Ne(*) + ND3 reactions are small, as suggested by nearly equal branching ratios and cross sections for the two reactions. PMID:24985633

Jankunas, Justin; Bertsche, Benjamin; Jachymski, Krzysztof; Hapka, Micha?; Osterwalder, Andreas

2014-06-28

139

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

140

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

141

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

142

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

143

Neutron quasielastic scattering by (CH3NH3)5Bi2Cl11  

NASA Astrophysics Data System (ADS)

(CH3NH3)+-cation rotation in crystalline (CH3NH3)5Bi2Cl11 was studied by the QNS. The following (no doubt simplified) models were considered: 1. All cations are equivalent and rotate as a whole around C-N axes 2. Majority of cations behave as in point (1) and the remaining ones do not move (for the neutron observation window). 3. All CH3 groups rotate, whereas all NH3 groups do not move. The QNS measurements exclude the possibilities (1) and (3). A transition at ca. 160-170 K was confirmed in the measurements, as connected with an increase of the quasielastic component intensity observed via a dip of the EISF.

Jakubas, R.; Janik, J. A.; Krawczyk, J.; Mayer, J.; Stanek, T.; Steinsvoll, O.

1998-04-01

144

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.

2012-01-01

145

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

146

NH2 fluorescence efficiencies and the NH3 abundance in Comet Halley  

NASA Technical Reports Server (NTRS)

If NH3 is the dominant source of the NH2 observed in comet spectra, then the NH3 abundance can in principle be accurately determined. Fluorescence efficiencies for the (0, v-prime/2/, O) to (0, 0, 0) progression of NH2 bands are calculated for NH2 bands likely to be observed in the 4500-8200-A region of comets. The results differ from previous determinations of the NH2 band fluorescence efficiencies by factors in the range 1.4-5.9, leading t6o significant changes in previously reported NH2 production rates in comets. A recalculation of the NH3/H2O abundance ratio in Comet Halley gives about (0.5 + or - 0.2) percent in better agreement with the Giotto ion-mass-spectrometer results of Allen et al (1987).

Tegler, Stephen; Wyckoff, Susan

1989-01-01

147

Resonance enhanced multiphoton ionization (2+1) in NH 3 using linearly and circularly polarized light  

NASA Astrophysics Data System (ADS)

A pulsed tunable dye laser is used for (2 + 1) REMPI in NH 3 via its C' state with ? 2 = 2. The spectra, in the 3040-3062 Å range, originate in 300 K NH 3. Both circular and linear laser polarization is used. The results are interpreted via the formalism of McClain and Harris. Because (a) we prepare pure light polarization, (b) the transition symmetry is known, and (c) individual rotational lines are resolved, the interpretation is clear and analysis yields molecular invariants that are otherwise difficult to obtain. Comparison is made with a similar treatment for alkyl iodides in which individual lines were not resolved. Alternatively, the same NH 3 transitions are also observed via the optogalvanic effect in a discharge. Because the REMPI process occurs mainly at the focus of the laser, spatially resolved diagnostics are possible.

Lee, Seong-Poong; Rothe, Erhard W.; Reck, G. P.

1988-10-01

148

Quantum IR line list of NH3 and isotopologues for ISM and dwarf studies  

NASA Astrophysics Data System (ADS)

Ammonia (NH3) was the first polyatomic molecule observed in the ISM. Its importance in interstellar molecules is only second to CO because its rovibrational spectroscopic signature can be used very effectively at deducing the conditions of the interstellar environment such as temperature and density, and because it is found in so many different interstellar objects in a wide temperature range. However, experimental determination of NH3 IR spectra is extremely difficult due to the large-amplutide inversion vibration, and the existing HITRAN2008 database for NH3 is limited in temperature, coverage, completeness, and accuracy. With rapid progress in theoretical chemistry and computational resources, now we are able to generate a highly reliable/accurate IR line list of NH3 (and its isotopologues) for astronomical studies. Exact quantum rovibrational computations on an empirically refined potential energy surface (with nonadiabatic corrections included) have achieved accuracies of 0.02-0.05 cm-1 (for line position) and better than 85-95% (for line intensity) for both NH3 and 15NH3 spectra. The unique feature of our work is that our predictions are essentially as accurate as reproducing existing measurements, suitable for synthetic simulation of various astrophysical environments or objects. The reliabilty and accuracy of our predictions for missing bands and higher energies computed on HSL-2 (Fig. 1) have been proved by the most recent high-resolution experiments and extended up to 7000 cm-1. See Huang et al. 2008, Huang et al. 2011, & Sung et al. 2012 for more details.

Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.; Sung, Keeyoon; Brown, Linda R.

2013-03-01

149

NH3 Survey Observation of Massive Star-Forming Region W 43  

NASA Astrophysics Data System (ADS)

We consider the properties of giant molecular cloud complexes in the star-forming region W 43 with a resolution of several pc scale, and discuss their relations to the evolutionary stages of massive star formation. We performed a NH3 (J , K) = (1, 1), (2, 2), and (3, 3) inversion-line survey with the Hokkaido University 11-m telescope. Among 51 observed positions, selected based on integrated intensity maps of 13CO (J = 1-0), these three emissions were detected from 21, 8, and 5 positions, respectively. The integrated intensity of the NH3 (J , K) = (1, 1) line was found to be proportional to the far-infrared luminosity, estimated from IRAS data. The rotation temperatures were deduced to be ˜ 15-20 K at eight observed positions. In addition, the upper limits were estimated for 13 positions, which include the relatively low temperatures below 14 K at two positions with a relatively high fractions of NH3 for 13CO and with a low far-infrared luminosity. We derived the ortho-to-para abundance ratio of NH3. From the population distribution between the ortho- and para-levels of NH3, we also derived temperatures of ˜ 6-12 K, which may be interpreted as the temperatures when NH3 molecules were formed. We discuss the relevance of the present results of our observations to the massive star-formation process and the current status of the W 43 region while taking into account previous observations of other indicators of massive star formation. It is shown that the complexes contain several regions in different evolutionary stages, or with the distinct characteristics of star formation within a timescales shorter than the lifetime of massive stars.

Nishitani, Hiroyuki; Sorai, Kazuo; Habe, Asao; Hosaki, Keita; Watanabe, Yoshimasa; Ohishi, Yukie; Motogi, Kazuhito; Minamidani, Tetsuhiro; Fujimoto, Masayuki Y.

2012-04-01

150

Sequential growth simulation of (NH 3) n clusters ( n = 2-8) in ultracold superfluid environment  

NASA Astrophysics Data System (ADS)

The growth of ammonia cluster (NH 3) n ( n = 2-8) in He droplets was studied using a polarizable potential assuming ultrafast heat dissipation and preventing the rearrangement of cluster structures. Energies, structures and isomer statistical distributions were obtained showing that a few high energy isomers may form with a probability similar to low energy ones and that ammonia clusters behave differently from (H 2O) n for n ? 5. Guide by our theoretical analysis, we suggest the need for re-interpreting recent experimental IR spectra of (NH 3) n in He droplets for 5 ? n ? 8.

Patrone, Marta; Mella, Massimo

2011-09-01

151

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

152

NH3 sensor based on CSA doped PANi-SnO2 nanohybrid  

NASA Astrophysics Data System (ADS)

The PANi-SnO2 hybrid nanocomposite based thin films doped with 10-50 wt % CSA were deposited on the glass substrates using the spin coating technique. The sensor response in relation to the CSA doping concentration and the gas concentration has been systematically studied. A significant sensitivity (91%) towards 100 ppm NH3 operating at room temperature is observed for the 30 wt % CSA doped PANi-SnO2 nanohybrid. The sensing mechanism of CSA doped PANi-SnO2 materials to NH3 was presumed to be the effect of p-n heterojunctions.

Khuspe, G. D.; Navale, S. T.; Chougule, M. A.; Mulik, R. N.; Godse, P. R.; Sen, Shashwati; Patil, V. B.

2014-04-01

153

"NH3 and PH3 Line Parameters: The 2000 HITRAN Update and New Results"  

SciTech Connect

The line parameters of ammonia and phosphine have been revised using new results for line positions, intensities and line widths. The improvements for NH3 in the HITRAN 2000, containing some 29084 lines (corresponding to more than twice the number of lines present in the 1996 HITRAN database for this molecule) involved replacing pure-rotational and infrared transitions from 0 to 5294 cm-1 with new calculations. This update focuses on the 0-3700 cm-1 spectral range of the 14NH3 isotopomer. New PH3 parameters available from 770 to 2156 cm-1 for future updates are described and contrasted with the parameters in HITRAN 2000.

Kleiner, I; Tarrago, G.; Cottaz, C; Sagui, L; Brown, L.R.; Poynter, R. L.; Pickett, H M.; Chen, P; Pearson, J C.; Sams, Robert L.; Blake, G A.; Matsuura, S; Nemtchinov, V; Varanasi, Prasad; Fusina, L; Di Lonardo, G

2003-11-01

154

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

155

Ultraviolet-gas phase and -photocatalytic synthesis from CO and NH3. [photolysis products  

NASA Technical Reports Server (NTRS)

Ammonium cyanate is identified as the major product of the photolysis of gaseous NH3-CO mixtures at 206.2 or 184.9 nm. Lesser amounts of urea, biurea, biuret semicarbazide, formamide and cyanide are observed. A series of 18 reactions underlying the formation of photolysis products is presented and discussed. Photocatalytic syntheses of C-14-urea, -formamide, and -formaldehyde are carried out through irradiation of (C-14)O and NH3 in the presence of Vycor, silica gel, or volcanic ash shale surfaces. The possible contributions of the relevant reactions to the abiotic synthesis of organic nitrogen compounds on Mars, the primitive earth, and in interstellar space are examined.

Hubbard, J. S.; Voecks, G. E.; Hobby, G. L.; Ferris, J. P.; Williams, E. A.; Nicodem, D. E.

1975-01-01

156

Structural and reactivity studies on the ternary system guanine\\/methionine\\/ trans -[PtCl 2 (NH 3 )L] (L=NH 3 , quinoline): implications for the mechanism of action of nonclassical trans -platinum antitumor complexes  

Microsoft Academic Search

The present model study explores the chemistry of methionine complexes and ternary methionine-guanine adducts formed by trans-[PtCl2(NH3)2] (1) and antitumor trans-[PtCl2(NH3)quinoline] (2) using 1D (1H, 195Pt) and 2D NMR spectroscopy. Compound 2 was substitution inert in reactions with N-acetyl-lmethionine [AcMet(H)]. Reactions of trans-[PtCl(NO3)(NH3)quinoline] (5) (\\

Ulrich Bierbach; Nicholas Farrell

1998-01-01

157

Effects of NO 2 and NH 3 from road traffic on epiphytic lichens  

Microsoft Academic Search

The results of a survey aimed at investigating whether NO2 and NH3 emitted by road traffic can influence lichen diversity, lichen vitality and the accumulation of nitrogen in lichen thalli are reported. For this purpose, distance from a highway in a rural environment of central Italy was regarded as the main parameter to check this hypothesis. The results of the

L. Frati; E. Caprasecca; S. Santoni; C. Gaggi; A. Guttova; S. Gaudino; A. Pati; S. Rosamilia; S. A. Pirintsos; S. Loppi

2006-01-01

158

Ferroelectric domain structure of (CH3NH3)5Bi2Brll single crystals  

Microsoft Academic Search

Ferroelectric domain structure of (CH3, NH3)5 Bi2 Br11 single crystals was revealed using nematic liquid crystal decoration and scanning electron microscopy. The domain boundaries observed on the c-surface of the crystal were found to be parallel to the b-orthorhombic axis and this direction was found to be an easy direction of domain growth.

M. Po?omska; L. Szcze?niak; R. Jakubas; K.-P. Meyer; H. Blumtritt

1989-01-01

159

10 Years of NH3 Variability over the US Measured by AIRS  

NASA Astrophysics Data System (ADS)

Atmospheric InfraRed Sensor provides twice daily and nearly global coverage of tropospheric compositions due to AIRS wide swaths. With longer than 10 years of data records, these measurements have been used not only for daily monitoring purposes but also for inter-annual variability and short-term trend studies. We have developed a new daily and global tropospheric ammonia product from AIRS measurements. AIRS NH3 is retrieved from an add-on module to the AIRS operational codes; and this module uses the Optimal Estimation (OE) technique. Using OE method, the retrieved products provide sensitivity properties, in addition to NH3 concentrations, e.g., the Averaging Kernels (AKs), error covariance matrices, and the Degrees Of Freedom for Signal (DOFS). Globally, AIRS captures NH3 emissions from biogenic and anthropogenic activities over many emission regions. We will focus in this presentation the ammonia distribution over the US, and will particularly emphasize its variability in the last 10 years. Validation examples using in situ measurements for AIRS NH3 will also be presented.

Warner, J. X.; Wei, Z.; Strow, L. L.

2013-12-01

160

Gas sensor for CO and NH3 using polyaniline\\/CNTs composite at room temperature  

Microsoft Academic Search

We fabricated a gas sensor for the detection of a carbon monoxide (CO) and ammonia (NH3) gas using single walled carbon nano tubes (SWNTs) and polyaniline(PANI) composite. The SWNTs were dispersed in sodium dodecyl sulfate (SDS) and were applied over the electrodes of an interdigitated electrodes (DDEs) by photolithography. By using this method, the active area for gas sensing can

Inho Kim; Ki-Young Dong; Byeong-Kwon Ju; Hyang Hee Choi

2010-01-01

161

Sensing characteristics of a novel NH3-nitrided Schottky-diode hydrogen sensor  

Microsoft Academic Search

A novel NH3-nitrided Schottky-diode hydrogen sensor has been successfully fabricated. Measurements have been performed to investigate the sensitivity, stability and response speed of the sensor at different temperatures and hydrogen concentrations. It can respond to hydrogen variation very quickly and can give significant response even at low hydrogen concentration. The studied device exhibits high sensitivity of 350% at 300 °C

W. M. Tang; P. T. Lai; J. P. Xu; C. L. Chan

2004-01-01

162

The detailed isotope effect in the F + NH 3 AND F + ND 3 reactions  

NASA Astrophysics Data System (ADS)

Arrested relaxation infrared chemiluminescence measurements show that the reaction of fluorine atoms with ND 3 channels a much larger fraction of the available exoergicity into DF product vibration than the analogous NH 3 reaction channels into HF vibration. This result is interpreted by a mechanism involving competition between direct abstraction and formation of an intermediate complex.

Slaon, J. J.; Watson, D. G.; Williamson, J.

1980-09-01

163

Laboratory Tests of NH 3\\/CO2 Cascade System for Supermarket Refrigeration  

Microsoft Academic Search

The development of a laboratory test rig of an NH3\\/CO2 cascade system is presented in this paper along with a theoretical model that simulates the performance of the system. The system solution under investigation replicates a medium size supermarket in Sweden, it is designed to fulfil the general requirements of the supermarket and operate within its temperature boundaries. Several possibilities

SAMER SAWALHA; JÖRGEN ROGSTAM; PER-OLOF NILSSON

164

Characterization of a high pressure, high temperature modification of ammonia borane (BH3NH3)  

NASA Astrophysics Data System (ADS)

At elevated pressures (above 1.5 GPa) dihydrogen bonded ammonia borane, BH3NH3, undergoes a solid-solid phase transition with increasing temperature. The high pressure, high temperature (HPHT) phase precedes decomposition and evolves from the known high pressure, low temperature form with space group symmetry Cmc21 (Z = 4). Structural changes of BH3NH3 with temperature were studied at around 6 GPa in a diamond anvil cell by synchrotron powder diffraction. At this pressure the Cmc21 phase transforms into the HPHT phase at around 140 °C. The crystal system, unit cell, and B and N atom position parameters of the HPHT phase were extracted from diffraction data, and a hydrogen ordered model with space group symmetry Pnma (Z = 4) subsequently established from density functional calculations. However, there is strong experimental evidence that HPHT-BH3NH3 is a hydrogen disordered rotator phase. A reverse transition to the Cmc21 phase is not observed. When releasing pressure at room temperature to below 1.5 GPa the ambient pressure (hydrogen disordered) I4mm phase of BH3NH3 is obtained.

Nylén, Johanna; Eriksson, Lars; Benson, Daryn; Häussermann, Ulrich

2013-08-01

165

Linelists for ammonia NH3, NH2D, ND2H, and ND3 (Coudert+, 2006)  

NASA Astrophysics Data System (ADS)

Linelists with calculated line positions and line intensities for ammonia (NH3) molecule and its three deuterated variants NH2D, ND2H, and ND3 with quadrupole coupling hyperfine splittings. Lines in linelists are formatted as in the JPL data base (Pickett, Poynter, Cohen et al. 1998, J. Quant. Spectrosc. Radiat. Transfer, 60, 883). (4 data files).

Coudert, L. H.; Roueff, E.

2005-11-01

166

Kinetics of gas-liquid reaction between NO and Co(NH3)6(2+).  

PubMed

Wet ammonia desulphurization process can be retrofitted for combined removal of SO2 and NO from the flue gas by adding soluble cobalt(II) salts into the aqueous ammonia solutions. The Co(NH3)6(2+) formed by ammonia binding with Co2+ is the active constituent of scrubbing NO from the flue gas streams. A stirred vessel with a plane gas-liquid interface was used to measure the chemical absorption rates of nitric oxide into the Co(NH3)6(2+) solution under anaerobic and aerobic conditions separately. The experiments manifest that the nitric oxide absorption reaction can be regarded as instantaneous when nitric oxide concentration levels are parts per million ranges. The gas-liquid reaction becomes gas film controlling as Co(NH3)6(2+) concentration exceeds 0.02 mol/l. The NO absorption rate is proportional to the nitric oxide inlet concentration. Oxygen in the gas phase is favorable to the absorption of nitric oxide. But it is of little significance to increase the oxygen concentration above 5.2%. The NO absorption rate decreases with temperature. The kinetic equation of NO absorption into the Co(NH3)6(2+) solution under aerobic condition can be written as. PMID:15869841

Long, Xiang-li; Xiao, Wen-De; Yuan, Wei-kang

2005-08-31

167

[H3N(CH2)7NH3]8(CH3NH3)2Sn(IV)Sn(II)12I46- a mixed-valent hybrid compound with a uniquely templated defect-perovskite structure.  

PubMed

The incorporation of H(3)N(CH(2))(7)NH(3) with CH(3)NH(3)SnI(3) resulted in the formation of a mixed-valent and semiconducting (Eg = 0.84 eV) organic-based perovskite, [H(3)N(CH(2))(7)NH(3)](8)(CH(3)NH(3))(2)Sn(iv)Sn(ii)(12)I(46), with a unique 3D defect-perovskite structure with ordered vacancies at the Sn and I sites. PMID:15614368

Guan, Jun; Tang, Zhongjia; Guloy, Arnold M

2005-01-01

168

Photochemistry of NH3, CH4 and PH3. Possible applications to the Jovian planets.  

PubMed

Photolysis of NH3 at 185 nm in the presence of a two-fold excess of CH4 results in the loss of about 0.25 mole of CH4 per mole of NH3 decomposed (delta CH4/delta NH3). The loss arises from the abstraction of hydrogen atoms from CH4 by photolytically generated hot hydrogen atoms, the presence of which is established by the constancy of delta CH4/delta NH3 between 298 and 156 K and by the quenching of the abstraction reaction when either H2 or SF6 is added. From the latter result, it can be concluded that NH3 photolysis in the H2-abundant atmosphere of Jupiter is not responsible for the presence of the carbon compounds observed there such as ethane, acetylene, and hydrogen cyanide, but may have had a role in the early atmosphere of Titan. Photolysis of PH3 with a 206 nm light source gives P2H4, which in turn is converted to a red-brown solid (P4?). The course of the photolysis is not changed appreciably when the temperatures is lowered to 157 K except that the concentration of P2H4 increases. The presence of H2 has no effect on the P2H4 yield. Photolysis of 9:1 NH3:PH3 gives a rate of decomposition of PH3 that is comparable with that observed by the direct photolysis of PH3. Comparable amounts of P2H4 and the red-brown solid are also observed. The mechanisms of these photochemical reactions together with their implications to the atmospheric chemistry of Jupiter are discussed. The structures of the compounds responsible for the wide array of colors e.g., brown, red and white, observed in the atmosphere of Jupiter have been the subject of extensive speculation. One theory suggests that these colors are due to organic materials formed by the action of either solar ultraviolet light or electric discharges on mixtures of CH4, NH3 and NH4HS in the Jovian atmosphere (Ponnamperuma, 1976; Khare et al., 1978). An alternative hypothesis is that the colors are due to inorganic compounds resulting from the photolysis of NH4HS and PH3 (Lewis and Prinn, 1970; Prinn and Lewis, 1975). In this paper we will summarize our experiments which were designed to test some of these hypotheses. PMID:7162800

Ferris, J P; Morimoto, J Y; Benson, R; Bossard, A

1982-09-01

169

Development and types of passive samplers for monitoring atmospheric NO2 and NH3 concentrations.  

PubMed

Numerous passive samplers based on the "Palmes-tube" have been developed for ambient air monitoring. In each case, the diffusion path length and/or cross-sectional area are modified to achieve the desired sampling rate. "Tube-type" samplers are low sensitivity samplers suitable for long-term monitoring, whereas the "badge-type" samplers have faster sampling rates suited to short-term monitoring. In the U.K., diffusion tubes are widely used for monitoring nitrogen dioxide (NO2) and ammonia (NH3). The open-ended diffusion tubes are prone to positive bias caused by incursion of wind eddies, leading to a shortening of the diffusion path. By using a porous membrane at the inlet, wind incursion is prevented, but an additional diffusion resistance is imposed and it is necessary to calibrate the tubes against a reference method to obtain an effective sampling rate. For NO2 sampling, positive bias also arises from the reaction of NO with O3 within the sampler. The interference from the chemical reaction is severe close to NO sources, with errors up to 30% for curbside locations when using the "tube-type" sampler. In rural areas, where NO concentrations are small relative to NO2, these errors are small. In some implementations, there is also a negative bias over long sampling periods caused by the degradation of trapped NO2. The low sampling rates of diffusion tubes make them too uncertain for use at background NH3 concentrations (<1 microg NH3 m(-3)) where they significantly overestimate concentrations. Badge-type samplers such as the "Willems badge" samplers permit accurate sampling at low ambient NH3 concentrations, but suffer from saturation at high concentrations and sensitivity to wind speed. A passive sampler optimised for monthly measurements of NH3 is reported here, together with its application in the U.K. National Ammonia Monitoring Network. PMID:12805844

Tang, Y S; Cape, J N; Sutton, M A

2001-10-01

170

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

171

Nucleobases and prebiotic molecules in organic residues produced from the ultraviolet photo-irradiation of pyrimidine in NH(3) and H(2)O+NH(3) ices.  

PubMed

Although not yet identified in the interstellar medium (ISM), N-heterocycles including nucleobases-the information subunits of DNA and RNA-are present in carbonaceous chondrites, which indicates that molecules of biological interest can be formed in non-terrestrial environments via abiotic pathways. Recent laboratory experiments and ab initio calculations have already shown that the irradiation of pyrimidine in pure H(2)O ices leads to the formation of a suite of oxidized pyrimidine derivatives, including the nucleobase uracil. In the present work, NH(3):pyrimidine and H(2)O:NH(3):pyrimidine ice mixtures with different relative proportions were irradiated with UV photons under astrophysically relevant conditions. Liquid- and gas-chromatography analysis of the resulting organic residues has led to the detection of the nucleobases uracil and cytosine, as well as other species of prebiotic interest such as urea and small amino acids. The presence of these molecules in organic residues formed under abiotic conditions supports scenarios in which extraterrestrial organics that formed in space and were subsequently delivered to telluric planets via comets and meteorites could have contributed to the inventory of molecules that triggered the first biological reactions on their surfaces. PMID:22519971

Nuevo, Michel; Milam, Stefanie N; Sandford, Scott A

2012-04-01

172

C60-mediated hydrogen desorption in Li-N-H systems.  

PubMed

Hydrogen desorption from a LiH + NH(3) mixture is very difficult due to the formation of the stable LiNH(4) compound. Using cluster models and first-principles theory, we demonstrate that the C(60) molecule can in fact significantly improve the thermodynamics of ammonia-mediated hydrogen desorption from LiH due to the stabilization of the intermediate state, LiNH(4). The hydrogen desorption following the path of LiNH(4)-C(60) ? LiNH(3)-C(60) + 1/2H(2) is exothermic. Molecular dynamic simulations show that this reaction can take place even at room temperature (300 K). In contrast, the stable LiNH(4) compound cannot desorb hydrogen at room temperature in the absence of C(60). The introduction of C(60) also helps to restrain the NH(3) gas which is poisonous in proton exchange membrane fuel cell applications. PMID:23138595

Qian, Zhao; Li, Sa; Pathak, Biswarup; Araújo, C Moysés; Ahuja, Rajeev; Jena, Puru

2012-12-01

173

C60-mediated hydrogen desorption in Li-N-H systems  

NASA Astrophysics Data System (ADS)

Hydrogen desorption from a LiH + NH3 mixture is very difficult due to the formation of the stable LiNH4 compound. Using cluster models and first-principles theory, we demonstrate that the C60 molecule can in fact significantly improve the thermodynamics of ammonia-mediated hydrogen desorption from LiH due to the stabilization of the intermediate state, LiNH4. The hydrogen desorption following the path of LiNH4-C60 ? LiNH3-{{C}}_{6 0}+\\frac{1}{2}{{H}}_{2} is exothermic. Molecular dynamic simulations show that this reaction can take place even at room temperature (300 K). In contrast, the stable LiNH4 compound cannot desorb hydrogen at room temperature in the absence of C60. The introduction of C60 also helps to restrain the NH3 gas which is poisonous in proton exchange membrane fuel cell applications.

Qian, Zhao; Li, Sa; Pathak, Biswarup; Moysés Araújo, C.; Ahuja, Rajeev; Jena, Puru

2012-12-01

174

New syntheses and structural characterization of NH3BH2Cl and (BH2NH2)3 and thermal decomposition behavior of NH3BH2Cl.  

PubMed

New convenient procedures for the preparation of ammonia monochloroborane (NH(3)BH(2)Cl) and cyclotriborazane [(BH(2)NH(2))(3)] are described. Crystal structures have been determined by single-crystal X-ray diffraction. Strong H···Cl···H bifurcated hydrogen bonding and weak N-H···H dihydrogen bonding are observed in the crystal structure of ammonia monochloroborane. When heated at 50 °C or under vacuum, ammonia monochloroborane decomposes to (NH(2)BHCl)(x), which was characterized by NMR, elemental analysis, and powder X-ray diffraction. Redetermination of the crystal structure of cyclotriborazane at low temperature by single-crystal X-ray diffraction analysis provides accurate hydrogen positions. Similar to ammonia borane, cyclotriborazane shows extensive dihydrogen bonding of N-H···H and B-H···H bonds with H(?+)···H(?-) interactions in the range of 2.00-2.34 Å. PMID:23215030

Lingam, Hima K; Wang, Cong; Gallucci, Judith C; Chen, Xuenian; Shore, Sheldon G

2012-12-17

175

Observations of NH3 and H2O in the Pelican Nebula hotspot  

NASA Astrophysics Data System (ADS)

Observations of NH3 and H2O in the direction of the Pelican Nebula hotspot are presented. Observations of the (J, K) = (1, 1) and (2, 2) transitions of NH3 have resolved the cloud into two condensations, each of about 1.2 pc in size. The line velocities vary by about 2 km/sec over the region, although no obvious systematic gradients which would indicate that the cloud is rotating, collapsing or expanding are found. Instead, these velocity differences are interpreted as due to two spatially separated clouds which lie close to one another. An H2O maser was found in the more intense of these peaks which is apparently not associated with any near-infrared emission. The ammonia observations were used to derive rotation temperatures of about 12 K, densities of 500-2500/cu cm and a cloud mass of about 90 solar masses.

Willson, R. F.; Leblanc, D.; Leblanc, J.

1983-06-01

176

Calculations on the rate of the ion-molecule reaction between NH3(+) and H2  

NASA Technical Reports Server (NTRS)

The rate coefficient for the ion-molecule reaction NH3(+) + H2 yields NH4(+) + H has been calculated as a function of temperature with the use of the statistical phase space approach. The potential surface and reaction complex and transition state parameters used in the calculation have been taken from ab initio quantum chemical calculations. The calculated rate coefficient has been found to mimic the unusual temperature dependence measured in the laboratory, in which the rate coefficient decreases with decreasing temperature until 50-100 K and then increases at still lower temperatures. Quantitative agreement between experimental and theoretical rate coefficients is satisfactory given the uncertainties in the ab initio results and in the dynamics calculations. The rate coefficient for the unusual three-body process NH3(+) + H2 + He yields NH4(+) + H + He has also been calculated as a function of temperature and the result found to agree well with a previous laboratory determination.

Herbst, Eric; Defrees, D. J.; Talbi, D.; Pauzat, F.; Koch, W.

1991-01-01

177

On the reaction CH2O + NH3 Yields CH2NH + H2O  

NASA Technical Reports Server (NTRS)

We study the energetics of CH2O + NH3-Yields CH2NH + H2O in the gas phase at the B3LYP and CCSD(T)levels. This reaction is shown to have a sizeable barrier. Ionization of NH3 reduces the barrier to about 5 kcal/mol. We also show that in water, a proton catalyzed mechanism yields no barriers in excess of the reaction endothermicity. Since this reaction has been proposed as one of the steps in interstellar synthesis of glycine, the simplest amino acid, this work suggests that the formation of amino acids is occurring in and/or on interstellar water ice grains, and not in the gas phase.

Walch, Stephen P.; Bauschlicher, Charles W., Jr.; Ricca, Alessandra; Bakes, E. L. O.; Arnold, James (Technical Monitor)

2000-01-01

178

H2S and NH3 Removal by Silent Discharge Plasma and Ozone Combo-System  

Microsoft Academic Search

Treatment of H2S and NH3 using the non-thermal plasma (NTP) methods was investigated. Two NTP systems were used in this study, one consisting of a multi-cell plate-to-wire reactor (PTW), and the other consisting of an ozonization chamber and the multi-cell PTW reactor. Each cell of the PTW reactor had a sheet of copper foil embedded in dielectric layers as its

Hongbin Ma; Paul Chen; Roger Ruan

2001-01-01

179

The structure, ordering and equation of state of ammonia dihydrate (nh 3 · 2h 2o)  

Microsoft Academic Search

We present the first ab initio simulations of the low-pressure phase of ammonia dihydrate (NH3 · 2H2O), ADH I, a likely constituent of many volatile-rich solid bodies in the outer Solar System (e.g., Saturn’s moons). Ordered monoclinic (space group P21) and orthorhombic (space group P212121) variants of the experimentally observed cubic cell (space group P213) may be constructed, with fully

A. D. Fortes; I. G. Wood; J. P. Brodholt; L. Vo?adlo

2003-01-01

180

The structure, ordering and equation of state of ammonia dihydrate (nh3 . 2h2o)  

Microsoft Academic Search

We present the first ab initio simulations of the low-pressure phase of ammonia dihydrate (NH3 . 2H2O), ADH I, a likely constituent of many volatile-rich solid bodies in the outer Solar System (e.g., Saturn's moons). Ordered monoclinic (space group P21) and orthorhombic (space group P212121) variants of the experimentally observed cubic cell (space group P213) may be constructed, with fully

A. D. Fortes; I. G. Wood; J. P. Brodholt; L. Vocadlo

2003-01-01

181

The circumstellar structure of IRAS 16293-2422 - (C-18)O, NH3, and CO observations  

Microsoft Academic Search

Interferometric observations of the (C-18)O and (C-12)O J = 1-0 transitions, and the NH3 (1, 1) and (2, 2) transitions toward the young far-IR source IRAS 16293-2422 are presented. The data reveal elongated gas structures which are aligned perpendicular to the axis of a bipolar outflow and to the local magnetic field direction. By combining the interferometric data with single-dish

Lee G. Mundy; H. A. Wootten; Bruce A. Wilking

1990-01-01

182

Electrical Conduction of Silicon Nitride Films Deposited by SiH4NH3 Reaction  

Microsoft Academic Search

The electrical conduction of silicon nitride films deposited pyrolytically on silicon substrates by the reaction of silane (SiH4) and ammonia (NH3) is caused by the Pool-Frenkel mechansim at room temperature and by the tunnel mechanism at a temperature of 208 K. When the deposition temperature is 850°C, the electrical conductivity of the films at room temperature and 208 K decreases

Yutaka Misawa; Hideyuki Yagi

1976-01-01

183

Negative ion photoelectron spectroscopy of the negative cluster ion H?(NH3)1  

Microsoft Academic Search

The negative ion photoelectron spectrum of the negative cluster ion H? (NH3)1 has been recorded with 2.540 eV photons. This negative cluster ion was prepared in a supersonic nozzle-ion source involving the injection of electrons into an expanding jet. While the spectrum is dominated by a broadened peak centered at 1.430±0.019 eV, there is also a small feature centered at

J. V. Coe; J. T. Snodgrass; C. B. Freidhoff; K. M. McHugh; K. H. Bowen

1985-01-01

184

SYNTHESIS AND INTRAMOLECULAR EXCITED STATE ELECTRON TRANSFER OF [Co(NH3)5CEPHALEXIN] COMPLEX  

Microsoft Academic Search

[Co(NH3)5-cephalexin] has been synthesized and characterized by elemental analyses, IR and UV-Visible spectroscopy as well as photochemical and thermal studies. The electronic spectrum of the complex in DMF shows two bands at 358 and 267 nm, which are assigned to intraligand charge transfer and ?-?* transitions, respectively. The fluorescence of the cephalexin is quenched by excited state electron transfer to Co(III).

Ahmed H. Osman

2002-01-01

185

High NH2D\\/NH3 ratios in protostellar cores  

Microsoft Academic Search

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

Jennifer Hatchell

2003-01-01

186

CH3NH3PbI(3-x)(BF4)x: molecular ion substituted hybrid perovskite.  

PubMed

A molecular ion (BF4(-)) substituted hybrid perovskite CH3NH3PbI(3-x)(BF4)x is synthesized. The substituted perovskite shows significant enhancement in electrical conductivity at low frequencies and improved photoresponse under AM1.5 illumination as compared to the perovskite (CH3NH3PbI3). PMID:25020198

Nagane, Satyawan; Bansode, Umesh; Game, Onkar; Chhatre, Shraddha; Ogale, Satishchandra

2014-07-29

187

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...

188

Vibrational analysis of ag 3(PO 2NH) 3, na 3(PO 2NH) 3.H 2O, na 3(PO 2NH) 3.4H 2O, [C(NH 2) 3] 3(PO 2NH) 3.H 2O and (nh 4) 4(PO 2NH) 4.4H 2O  

NASA Astrophysics Data System (ADS)

FT IR and FT Raman spectra of Ag 3(PO 2NH), (Compound I), Na 3(PO 2NH) 3.H 2O (Compound II), Na 3(PO 2NH) 3.4H 2O (Compound III), [C(NH 2) 3] 3(PO 2NH) 3.H 2O (Compound IV) and (NH 4) 4(PO 2NH) 4.4H 2O (Compound V) are recorded and analyzed on the basis of the anions, cations and water molecules present in each of them. The PO 2NH - anion ring in compound I is distorted due to the influence of Ag + cation. Wide variation in the hydrogen bond lengths in compound III is indicated by the splitting of the v2 and v3 modes of vibration of water molecules. The NH 4 ion in compound V occupies lower site symmetry and exhibits hindered rotation in the lattice. The correlations between the symmetric and asymmetric stretching vibrations of P?N?P bridge and the P?N?P bond angle have also been discussed.

John, Annamma; Philip, Daizy; Stock, Norbert; Schnick, Wolfgang; Devanarayanan, S.

2001-04-01

189

Constraints on the NH3 and PH3 distributions in the Great Red Spot  

NASA Technical Reports Server (NTRS)

Medium resolution (10 A) UV spectra were obtained for the Great Red Spot (GRS) and South Tropical Zone (STZ) of Jupiter using the low dispersion mode of the IUE spectrometers at wavelengths from 1900-2200 A. The scans were carried out to determine the coloring agent for the GRS to improve the database for developing photochemical models of the feature. The wavelengths were selected to cover the absorption features of NH3 and PH3. The resulting data were interpreted using a vertically inhomogeneous Rayleigh scattering radiative transfer model. Various NH3 concentrations were explored in an effort to fit the data, taking into account changes which would occur at different atmospheric pressure levels and due to the projected temperature fields. A forbidden NH3/forbidden H2 mixing ratio that was calculated at the 80-125 mbar pressure level in the GRS was enhanced by 3-10 percent relative to the STZ. An upper limit was obtained for the mixing ratio of PH3 in the GRS that is significantly lower than previously predicted concentrations, implying that vertical transport in the GRS is not much greater than in adjacent regions.

Wagener, R.; Caldwell, J.; Owen, T.

1986-01-01

190

Carbamic acid and carbamate formation in NH{3}:CO{2} ices - UV irradiation versus thermal processes  

NASA Astrophysics Data System (ADS)

Context: We study carbamic acid [ NH{2}COOH] and ammonium carbamate [ NH{2}COO-] [ NH{4}+] formation in interstellar ice analogs. Aims: We demonstrate how carbamic acid [ NH{2}COOH] and ammonium carbamate [ NH{2}COO-] [ NH{4}+] can be formed from both thermal reactions and energetic photons in an NH{3}:CO{2} ice mixture. Methods: Infrared and mass spectroscopy are used to monitor NH{3}:CO{2} ice mixture evolution during both warming and VUV photon irradiation. Results: Carbamic acid and ammonium carbamate can be produced thermally in a 1:1 ratio from NH{3} and CO{2} above 80 K. They can be also formed in a 28:1 ratio by less efficient processes such as energetic photons. Our study and its results provide fresh insight into carbamic acid formation in interstellar ices. Conclusions: We demonstrate that care is required to separate irradiation-induced reactivity from purely thermal reactivity in ices in which ammonia and carbon dioxide are both present. From an interstellar chemistry point of view, carbamic acid and ammonium carbamate are readily produced from the ice mantle of a typical interstellar grain and should therefore be a detectable species in molecular clouds.

Bossa, J. B.; Theulé, P.; Duvernay, F.; Borget, F.; Chiavassa, T.

2008-12-01

191

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

192

Reactivity of HNCO with NH 3 at low temperature monitored by FTIR spectroscopy: formation of NH 4+OCN -  

NASA Astrophysics Data System (ADS)

The reactivity of isocyanic acid (HNCO) with solid ammonia (NH 3) was first studied at 10 K, using FTIR spectroscopy. The ammonium isocyanate (NH 4+OCN -) is formed from a reaction between HNCO and NH 3. Vibrational band assignments for NH 4+OCN - have been given. On the other hand, when HNCO is adsorbed on amorphous NH 3 film, the reaction does not occur. Warming up of this sample at 90 K induces the NH 4+OCN - formation. Quantum calculations showed that the solvation of NH 3 directly bonded to HNCO by at least three NH 3 molecules plays a major role in the NH 4+OCN - formation process and confirmed the spontaneous character of this reaction.

Raunier, S.; Chiavassa, T.; Marinelli, F.; Allouche, A.; Aycard, J. P.

2003-01-01

193

Melting phase relations in the system H2O - NH3 at high pressure  

NASA Astrophysics Data System (ADS)

The density models of Uranus and Neptune constrained by their gravitational moments from Voyager mission suggest that mantles of these planets may be predominantly comprised of water (H2O), methane (CH4), and ammonia (NH3). The impurities in pure water would greatly influence the phase relations in the water-rich system expected in the icy mantle, which must be known to construct a plausible planetary model. One of important effects of the impurity is on the liquidus temperature (Tliq), since it decides the actual presence of solid phase within the icy mantle. In order to determine Tliq in H2O-rich region of the H2O - CH4 - NH3 ternary system, the melting phase relations in the H2O - CH4 and H2O - NH3 systems must be accurately known. However, previous melting experiments on each binary system were limited to several gigapascals, thus need to be explored to higher P-T conditions for application in interiors of Uranus and Neptune. We have investigated high-pressure (P) and -temperature (T) melting phase relations in the H2O - NH3 system based on a combination of visual observation and angle-dispersive x-ray diffraction (XRD) measurements at BL10XU, SPring-8. High-P-T conditions were generated in an externally-resistive heated diamond anvil cell (DAC). Starting material was 20wt% NH3 aqueous solution whose composition was checked via Tliq of the solution measured in a DAC at near atmospheric pressure. The aqueous solution was loaded into a gold-lined hole in a preindented rhenium gasket in order to insulate the sample from rhenium. Pressure was determined from the unit-cell volume of gold liner. Melting and freezing of the sample were detected by monitoring disappearance/appearance of diffraction peaks of solid and diffuse scattering of liquids, as well as observing melting/crystallization of crystal grains under microscope. Up to 20 GPa at room temperature, in addition to ice VII, diffraction peaks of bcc-like phase, which is most likely to be the reported phase VI of ammonia monohydrate (AMH VI), were observed, although the diffraction peaks were either too broad or too few to specify its structure. When temperature was raised until diffuse scattering appeared, the diffraction peaks of AMH VI disappeared, indicating ice VII is the liquidus phase. Newly obtained Tliq were higher than all the exiting melting curves of pure H2O determined in externally-heated DAC by 50 K at 15 GPa at minimum. This contradicts the previous reports that the H2O - NH3 system is eutectic, i.e. Tliq of our sample should be lower than the melting temperature of the H2O end member. We will discuss possible sources for this discrepancy. We also propose a new phase diagram of the system H2O - NH3 and possible implications for the structure of the icy planets.

Sugimura, E.; Hirose, K.; Komabayashi, T.; Ohishi, Y.; Hirao, N.; Dubrovinsky, L. S.

2012-12-01

194

Temperature-Programmed Reduction and HDS Activity of Sulfided Transition Metal Catalysts: Formation of Nonstoichiometric Sulfur  

Microsoft Academic Search

Sulfided alumina-supported transition metal catalysts have been studied using temperature-programmed reduction (TPR). The H2 and H2S concentrations were determined simultaneously and the major processes occurring were discriminated, namely reduction of oxidic and sulfidic species and desorption of H2S. Because of the high maximum reduction temperature and the high hydrogen partial pressure applied, a complete description of all species was acquired,

P. J. Mangnus; A. Riezebos; A. D. Vanlangeveld; J. A. Moulijn

1995-01-01

195

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

196

Vehicle specific power approach to estimating on-road NH3 emissions from light-duty vehicles.  

PubMed

NH3 emissions from motor vehicles have been the subject of a number of recent studies due to their potential impact on ambient particulate matter (PM). Highly time-resolved NH3 emissions can be measured and correlated with specific driving events utilizing a tunable diode laser (TDL). It is possible to incorporate NH3 emissions with this new information into models that can be used to predict emissions inventories from vehicles. The newer generation of modal models are based on modal events, with the data collected at second-by-second time resolution, unlike the bag-based emission inventory models such as EMFAC and MOBILE. The development of an NH3 modal model is described in this paper. This represents one of the first attempts to incorporate vehicle NH3 emissions into a comprehensive emissions model. This model was used in conjunction with on-road driving profiles to estimate the emissions of SULEV, ULEV, and LEV vehicles to be 9.4 +/- 4.1, 21.8 +/- 5.2, and 34.9 +/- 6.0 mg/mi, respectively. We also implement this new NH3 model to predict and evaluate the NH3 emission inventory in the South Coast air basin (SoCAB). PMID:16475340

Huai, Tao; Durbin, S Thomas D; Younglove, Ted; Scora, George; Barth, Matthew; Norbeck, Joseph M

2005-12-15

197

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

198

High sensitivity detection of NO2 and NH3 in air using chemical vapor deposition grown graphene  

NASA Astrophysics Data System (ADS)

We show that graphene films synthesized by chemical-vapor-deposition enables detection of trace amounts of nitrogen dioxide (NO2) and ammonia (NH3) in air at room temperature and atmospheric pressure. The gas species are detected by monitoring changes in electrical resistance of the graphene film due to gas adsorption. The sensor response time was inversely proportional to the gas concentration. Heating the film expelled chemisorbed molecules from the graphene surface enabling reversible operation. The detection limits of ~100 parts-per-billion (ppb) for NO2 and ~500 ppb for NH3 obtained using our device are markedly superior to commercially available NO2 and NH3 detectors.

Yavari, Fazel; Castillo, Eduardo; Gullapalli, Hemtej; Ajayan, Pulickel M.; Koratkar, Nikhil

2012-05-01

199

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

200

Phase Transition in (CH3NH3)3Bi2Br9 Single Crystal  

NASA Astrophysics Data System (ADS)

The successive phase transitions in (CH3NH3)3Bi2Br9 (MABB) single crystal have been investigated by measuring of dielectric and elastic dispersion and Brillouin and Raman scattering. Softening of the elastic constant c66 and critical slowing down of the order parameter, which belongs to the Eg representation, have been found in the phase I. No optical soft mode has been observed. The phase transition from the phase I to the phase II has been discussed by the Landau theory.

Iwata, Makoto; Eguchi, Masahito; Ishibashi, Yoshihiro; Sasaki, Shigeo; Shimizu, Hiroyasu; Kawai, Taketoshi; Shimanuki, Shigetaka

1993-09-01

201

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

202

M dependence in the analysis of NH3-He microwave double resonance experiments  

NASA Technical Reports Server (NTRS)

New close-coupled calculations of laboratory-frame, m-dependent cross sections for rotational excitation in NH3-He collisions are used to examined the validity of using degeneracy averaged values in the analysis of four-level double resonance experiments. It is found that the proper use of m-dependent cross sections and absorption probabilities produces only minor changes in the calculated Delta I/I (the fractional change in the signal absorption intensity when pumping radiation is applied) and does not, therefore, resolve the discrepancies between theoretical and experimental values that were noted in previous studies.

Davis, S. L.; Green, S.

1983-01-01

203

Femtosecond two-photon ionization of fluid NH3 at 9.3 eV  

NASA Astrophysics Data System (ADS)

Liquid and supercritical ammonia (NH3) is photo-ionized at an energy of 9.3 eV with 100-fs duration pulses at a wavelength of 266 nm. The ionization involves two photons and generates fully solvated electrons via the conduction band of the solvent within the time resolution of the experiment. The dynamics of their ensuing geminate recombination is followed in real time with femtosecond near-infrared (IR) probe pulses. The recombination mechanism can be understood as an ion-pair mediated reaction. The electron survival probability is found to be in quantitative agreement with the classical Onsager theory for the initial recombination of ions.

Urbanek, Janus; Dahmen, Annika; Torres-Alacan, Joel; Vöhringer, Peter

2013-03-01

204

H2O/Ni(100) and NH3/Ni(100) - A computational approach  

NASA Technical Reports Server (NTRS)

The adsorption of NH3 and H2O on the Ni(100) is treated using a cluster model. The adsorption is found to have only a small effect on the HXH angle. Rotation about the principal ligand axis requires virtually no energy. Ligand tilts of 15 deg are found to require small amounts of energy, leading to the suggestion that the ESDIAD signal is a result of excited tilting modes, not a change in the HXH angle. For H2O additional bending modes are considered and all are found to be quite flat in energy.

Bauschlicher, C. W., Jr.

1985-01-01

205

On the nature of the interaction in donor-acceptor van der Waals complexes: BH 3…CO, BF 3…CO, BH 3…NH 3 and BF 3…NH 3  

Microsoft Academic Search

Ab initio calculations at the MP2\\/6–31G?? level have been carried out to analyze the nature of the interaction in BH3…CO, BF3…CO, BH3…NH3 and BF3…NH3 van der Waals complexes. There is a good correlation between charge transfer, as measured by a method based on the expansion of the MOs of a complex system in terms of the MOs of its fragments,

V. M. Rayón; J. A. Sordo

1998-01-01

206

Application of Temperature Dependent Computerized Control of Desorption for Catalyst Surface Characterization.  

National Technical Information Service (NTIS)

The dissertation discusses the applications of temperature-programmed desorption and its limits in the characterisation of catalyst surfaces and in heterogeneous catalysis. Further, the quantitative information of the TPD spectra is critically reviewed. (...

E. Morales de Leguizamon

1984-01-01

207

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

PubMed

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

Dong, Ki-Young; Choi, Jinnil; Lee, Yang Doo; Kang, Byung Hyun; Yu, Youn-Yeol; Choi, Hyang Hee; Ju, Byeong-Kwon

2013-01-01

208

NMR study of monomethylammonium cation in (CH3NH3)5Bi2Cl11 ferroelectric polycrystal.  

PubMed

Spin-lattice relaxation times T1 and T1p are determined for protons in three polycrystals (CH3NH3)5Bi2Cl11, (CD3NH3)5Bi2Cl11 and (CH3ND3)5Bi2Cl11. The temperature dependencies of the relaxation times obtained for (CH3NH3)5Bi2Cl11 and (CD3NH3)5Bi2Cl11 are interpreted as a result of correlated motions of the three-proton groups of the monomethylammonium cation. The minimum of the T1p relaxation time is explained as a result of the oscillations of the symmetry axis of the whole cation. PMID:10378430

Medycki, W

1999-05-01

209

Effects of NH 3 Plasma Treatment of the Substrate on Metal Organic Chemical Vapor Deposition of Copper Films  

NASA Astrophysics Data System (ADS)

Surface modification by NH3 plasma treatment enabled selective copper (Cu) chemical vapor deposition (CVD) andchanged the structure of the deposited Cu film. After NH3 plasma treatment of the substrate, Cu nucleation was suppressedon borophosphosilicate glass (BPSG), while Cu films were formed on TiN. NH3 plasma treatment was not as effective as N2 plasma treatment in inducing the selectivity. The lower efficiency of the NH3 plasma in inducing the selectivitycan be explained by the generation of NH++ or H species. A Cu film deposited on plasma-treated TiN showed larger grainsand enhanced (111) preferential orientation compared with that deposited on untreated TiN, which could be explained in termsof surface energy minimization.

Kim, Young; Jung, Donggeun; Kim, Dong; Min, Suk-Ki

1998-08-01

210

High resolution NH3 studies of nearby star-forming regions  

NASA Astrophysics Data System (ADS)

Stars form within dense molecular cores. These cores are often embedded within larger structures, such as clumps and filaments, particularly in clustered star-forming environments. Indeed, large-scale maps of the continuum emission from dust have revealed the ubiquity of filaments in star-forming regions. The condensation and fragmentation of cores within larger structures is therefore a critical step in the star formation process, but continuum data alone do not provide key information, such as the gas kinematics, needed to discern between evolutionary scenarios. I will present new results from large NH3 studies of nearby star-forming regions, including Taurus and Serpens South. While NH3 primarily traces high density gas, sensitive observations over Serpens South reveal extensive, low brightness emission between the prominent cores and filaments, and show directly the frequently (but not invariably) sharp transitions between turbulent and quiescent gas in the high density regions. I will discuss the hierarchical structure of the dense gas in Serpens South, with comparisons between two- and three-dimensional analysis, and analyze the importance of thermal fragmentation in the filaments and cores over a range of physical scales.

Friesen, Rachel

2014-07-01

211

Decomposition of NH3 and H2 on ZrB2 (0001) surface  

NASA Astrophysics Data System (ADS)

Group III nitride semiconductors (AlN, GaN, InN, and their alloys) are important materials for applications in solid-state lighting, optoelectronics, and photovoltaics. However, the lack of lattice--matched substrates for their growth results in less than optimal material quality. In the last decade, zirconium diboride (ZrB2) has been demonstrated as a promising substrate for GaN growth because of its similar lattice constant and thermal expansion properties when compared to the nitride. Moreover, the high electrical conductivity of ZrB2 makes it desirable for many GaN-based device applications. In this talk, we present results of density functional theory calculations for the reactivity of the ZrB2(0001) surface towards the N precursor, NH3, and the carrier gas, H2, commonly used in metal organic chemical vapor deposition and molecular beam epitaxy of nitrides. Two different terminations of ZrB2(0001) surface, the Zr and B terminations, are considered and assessed in terms of their catalytic properties toward NH3 and H2 decomposition. The theoretical results are analyzed in connection with our recent XPS and RAIRS measurements.

Walkosz, Weronika; Manandhar, Kedar; Trenary, Michael; Zapol, Peter

2012-02-01

212

HCN and NH3 formation during coal/char gasification in the presence of NO.  

PubMed

Understanding the conversion of coal-N during gasification is an important part of the development of gasification-based power generation technologies to reduce NO(x) emissions from coal utilization. This study investigated the conversion of coal-N in the presence of NO during the gasification of three rank-ordered coals and their chars in steam and low-concentration O(2). Our results show that NO can be incorporated into the char structure during gasification. The inherent char-N and the N incorporated into the char from NO-char reactions behave very similarly during gasification. During the gasification in steam, significant amounts of HCN and NH(3) can be formed from the incorporated N structure in char, especially for the relatively "aged" chars, mainly due to the availability of abundant H radicals on the char surface during the gasification in steam. During the gasification in 2000 ppm O(2), the formation of HCN or NH(3) from the N structures in char, including those incorporated into the char from the NO-char reactions, was not a favored route of reaction mainly due to the lack of H on char surface in the presence of O(2). PMID:20415414

Lin, Jian-Ying; Zhang, Shu; Zhang, Lian; Min, Zhenhua; Tay, Huiling; Li, Chun-Zhu

2010-05-15

213

A theoretical analysis of the reaction between CN radicals and NH3.  

PubMed

The reaction between CN radicals and NH3 molecules has been studied experimentally over an unusually wide range of temperature (25-716 K). Below 295 K, the rate constant exhibits a strong negative dependence on temperature; that is, it increases sharply as the temperature is lowered. The present work analyses the kinetics of this reaction theoretically, both to explain this unusual temperature-dependence and to identify the major products of the reaction--which have not been well established by experiment. Quantum chemical calculations at the CCSD(T) theoretical level show that the minimum energy path for reaction proceeds: (a) first, via a potential well, which is 39.3 kJ mol(-1) below the energy of the separated reactants, when allowance is made for zero-point energies, corresponding to a quite strongly bound NC-NH3 complex, and (ii) then over a 'submerged' barrier with a crest 10.9 kJ mol(-1) below the energy of the reactants to the products HCN + NH2. These ab initio calculations also demonstrate that there is no low energy path to the products NCNH2 + H. The dynamics of the main reaction have been further investigated using the two transition state model of Klippenstein and co-workers, in which transition state theory is applied at the selected E, J microcanonical level. The rate constants calculated for temperatures between 25 and 200 K are in excellent agreement with the experimental values. PMID:19774278

Talbi, Dahbia; Smith, Ian W M

2009-10-14

214

Re-analysis of ammonia spectra: Updating the HITRAN 14NH3 database  

NASA Astrophysics Data System (ADS)

The data incorporated in the HITRAN database for 14NH3 are analyzed using a comprehensive and consistent set of quantum numbers, empirical lower energy levels and the BYTe variationally calculated line list as reference points. Labelings are checked to ensure that they obey both the usual selection rules and the HITRAN labeling formalisms; the problems identified are corrected where possible. Further assignments are brought into question by combination difference (CD) checking of implied upper energy levels. The CD analysis yields an 89% complete 14NH3 energy level list up to 6610 cm-1 and J=21, self-consistent to 0.1 cm-1. In combination with the 1723 previously unassigned and unlabeled lines in HITRAN a total of 2529 problem lines were identified for re-analysis. The compiled energy level list was used to label and assign the set of problem transitions, resulting in a total of 249 new assignments and a further 368 new labelings. Assignment by comparison with the reference line list resulted in 111 further new line assignments and 14 new labelings. Intensities are checked against recent measurements and BYTe. New intensities are proposed for the ?2 band with new intensities and line positions for the 2?2-?2 and new line lists are created for the ?2-?2, ?2-?4 and ?4-?4 bands. BYTe band intensities are analyzed to identify other regions of missing intensity.

Down, Michael J.; Hill, Christian; Yurchenko, Sergei N.; Tennyson, Jonathan; Brown, Linda R.; Kleiner, Isabelle

2013-11-01

215

The production of NH(A 3Pi i) through photodissociative excitation of NH3  

NASA Technical Reports Server (NTRS)

The NH(A-X) emission produced by photodissociation of NH3 is examined using a line emission source in the 600-1340 A region. It is observed that the production of the NH(A 3Pi i) photofragment involves a spin-forbidden transition. Fluorescence spectra of NH3 are derived and analyzed. The relationship between fluorescence cross sections and fluorescence count rates and gas pressure is studied. The fluorescence cross sections of NH(A-X) are calculated as 2.1 x 10 to the -22nd, 3.1 x 10 to the -22nd, 3.0 x 10 to the -21st, 1.5 x 10 to the -20th, and 3.4 x 10 to the -20th sq cm for the primary photon wavelength of 1239, 1184, 1065, 1037, and 976 A, respectively; and the corresponding fluorescence quantum yields are 0.00002, 0.00003, 0.0012, 0.0085, and 0.015.

Wu, C. Y. Robert

1987-01-01

216

NH3 and NH2 in the coma of Comet Brorsen-Metcalf  

NASA Technical Reports Server (NTRS)

Evidence consistent with NH3 ice in the nucleus of Comet Brorsen-Metcalf as the source of the NH2 observed in the comet coma is presented. The distribution of NH2 is symmetric and shows no evidence for jet structure at the 3-sigma significance level above background emission. An azimuthal average of the NH2 image produces an NH2 surface brightness profile for Comet Brorsen-Metcalf which yields a factor of about-10 improvement in the signal-to-noise ratio over previous 1D long-slit NH2 observations, and provides a significant constraint on the NH2 photodissociation time scale in comets. A Monte Carlo simulation of the comet coma, assuming that NH2 is the primary source of NH2, is described and compared with the observations. For an observed production rate, Q(H2O) is approximately equal to 7 x 10 exp 28 molecules/s, collisional effects on the NH3 and NH2 outflow had at most an approximately 10-percent effect on the NH2 surface brightness profile. Because Comet Brorsen-Metcalf showed no significant dust or gas production rate variability, it is argued that steady state conditions best match the comet at the time of the observations.

Tegler, Stephen C.; Burke, Luke F.; Wyckoff, Susan; Womack, Maria; Fink, Uwe; Disanti, Michael

1992-01-01

217

Structure cristalline et etude par spectrometrie de vibration (IR et Raman) du bis(ethylenediammonium) diphosphate (NH 3(CH 2) 2NH 3) 2 · P 2O 7  

NASA Astrophysics Data System (ADS)

Classical methods extensively known for the synthesis of inorganic condensed phosphates are used to give compounds that are intermediate between inorganic and organic. We prepared the title compound to examine the possibility of using, in this new field, the ion exchange resin and Boullé's methods. Chemical preparation, crystal structure, and vibrational studies are given for a new diphosphate. The bis(ethylenediammonium) diphosphate salt is monoclinic with the unit cell dimensions a = 8.724(1), b = 13.511(2), c = 10.039(1)Å, ? = 96.25(1)°, V = 1176.3(5)Å 3, Dm = 1.673Mg m -3, D x = 1.684Mg m -3, ? = 2.163 mm -1, space group C2 c with Z = 4. The structure was solved by the Patterson method and refined to a final R value of 0.059 for 2602 observed independent reflections. The P sbnd O(L) sbnd P bridge is symmetrical with a P sbnd O(L) distance of 1.570(1)Åand a POP angle of 141.94(7)°. The P 2O 4-7 anions are located around the twofold axis. The ethylenediammonium dications have a trans configuration. Half of them, having a crystallographic inversion center, are located in channels delimited by the diphosphate anions. The others, located around the twofold axis, are sandwiched along the c axis between two diphosphate anions. The cohesion and the stability of the atomic arrangement result from the N sbnd H···O hydrogen bonds. The IR and Raman spectra of [NH 3(CH) 2NH 32 · P 2O 7 are recorded and analyzed. From the spectra it is inferred that the P 2O 4-7 anion has a C2 symmetry in the crystal; all the POP modes (stretching and bending) are active in IR and Raman.

Kamoun, Slaheddine; Jouini, Amor; Daoud, Abdelaziz

1992-07-01

218

The influence of mixing between NH 3 and NO for a De-NOx reaction in the SNCR process  

Microsoft Academic Search

The objective of this study was to determine the mixing effect on De-NOx in the selective non-catalytic reduction (SNCR) process using NH3 as a reductant. A bench scale reactor set-up was used to perform experimental investigations on the mixing in the SNCR process, using an injection of NH3, with or without an air injection, into the bulk gas. Mixing between

Gang-Woo Lee; Byung-Hyun Shon; Jeong-Gun Yoo; Jong-Hyeon Jung; Kwang-Joong Oh

2008-01-01

219

Regeneration of initial activity of a pitch-based ACF for NO–NH 3 reaction at ambient temperature  

Microsoft Academic Search

The reactivity of adsorbed NO (including NO2) and NH3 in the presence of 4.0% oxygen in He was examined over a pitch-based ACF calcined at 800°C. Regeneration at 30°C by 4% O2 in He without NH3 was found to be optimum for the recovery of the initial activity with complete removal of NO within 3h, with minimum leaks of adsorbed

Isao Mochida; Masahiro Kishino; Shizuo Kawano; Kinya Sakanishi; Yozo Korai; Akinori Yasutake; Masaaki Yoshikawa

1998-01-01

220

The G305 star-forming complex: wide-area molecular mapping of NH3 and H2O masers  

NASA Astrophysics Data System (ADS)

We present wide-area radio (12 mm) Mopra telescope observations of the complex and rich massive star-forming region G305. Our goals are to determine the reservoir for star formation within G305 using NH3 to trace the dense molecular content, and thus the gas available to form stars; estimate physical parameters of detected NH3 clumps (temperature, column density, mass, etc.); locate current areas of active star formation via the presence of H2O and methanol masers and the distribution of young stellar objects (YSOs) and ultra-compact HII regions associated with this region. This paper details the NH3 (J, K), (1,1), (2,2) and (3,3) inversion transition and 22 GHz H2O maser observations. We observed a ~ region with ~2 arcmin angular resolution and a sensitivity of ~60 mK per 0.4kms-1 channel. We identify 15 NH3 (1,1), 12 NH3 (2,2) and 6 NH3 (3,3) clumps surrounding the central HII region. The sizes of the clumps vary between <2.6 and 10.1 pc; the average kinetic temperature of the gas is 25K. We calculate clump masses of and find the total molecular mass of the complex to be . We note the positions of 56 star formation tracers, and discover a high degree of correlation with detected NH3 clumps. We have detected 16 H2O masers and find they correlate with the detected ammonia clumps. In general, they are found closer to the NH3 clump cores than star formation tracers of later evolutionary stages.

Hindson, L.; Thompson, M. A.; Urquhart, J. S.; Clark, J. S.; Davies, B.

2010-11-01

221

Ultra-Thin High Quality Oxynitride Formed by NH3 Nitridation and High Pressure O2 Re-oxidation  

Microsoft Academic Search

In this paper, a novel technique to engineer the nitrogen profile in an ultra-thin silicon nitride-oxide gate stack is presented. It was found that the re-oxidation of silicon nitride, formed by NH3-nitridation, in a vertical high pressure (VHP) O2 furnace effectively moves the nitrogen-rich layer toward the top interface by growing pure oxide underneath. The impact of NH3 nitridation temperature

T. Y. Luo; V. H. C. Watt; H. N. Al-Shareef; G. A. Brown; A. Karamcheti; M. D. Jackson; H. R. Huff; B. Evans; D. L. Kwong

2000-01-01

222

New reduction pathways for ctc-[PtCl2(CH3CO2)2(NH3)(Am)] anticancer prodrugs.  

PubMed

Reduction of anticancer prodrugs such as ctc-[PtCl(2)(CH(3)CO(2))(2)(NH(3))(Am)] can yield three products in addition to the expected cis-[PtCl(2)(NH(3))(Am)]. A possible explanation is that reduction proceeds by several pathways where in addition to the loss of two axial ligands, one axial (acetato) and one equatorial (chlorido) ligand, or two equatorial ligands are eliminated. PMID:20198227

Nemirovski, Alina; Vinograd, Inbal; Takrouri, Khuloud; Mijovilovich, Ana; Rompel, Annette; Gibson, Dan

2010-03-21

223

The photolysis of NH3 in the presence of substituted acetylenes - A possible source of oligomers and HCN on Jupiter  

NASA Technical Reports Server (NTRS)

An NMR spectral study is presently conducted of NH3 photolysis in the presence of substituted acetylenes with NMR spectra and gas chromatography. Quantum yields and percentage conversions to products are reported. It is shown that acetylenic hydrocarbons generated during methane photolysis in Jupiter's stratosphere can react with radicals formed by NH3 photolysis to yield nonvolatile, yellow-brown polymers, alkylnitriles, and in due course, HCN, as observed on Jupiter.

Ferris, James P.; Jacobson, Richard R.; Guillemin, Jean C.

1992-01-01

224

A two-color infrared-vacuum ultraviolet laser pulsed field ionization photoelectron study of NH3.  

PubMed

We have observed fully rotationally resolved transitions of the photoelectron vibrational bands 2(4), 2(5), 1(1)2(1), and 1(1)2(3) for ammonia cation (NH3+) by two-color infrared (IR)-vacuum ultraviolet (VUV)- pulsed field-ionization photoelectron (PFI-PE) measurements. By preparing an intermediate rovibrational state of neutral NH(3) with a known parity by IR excitation followed by VUV-PFI-PE measurements, we show that the photoelectron parity can be determined unambiguously. The IR-VUV-PFI-PE measurement of the 2(4) band clearly reveals the formation of both even and odd l states for the photoelectrons, where l is the orbital angular momentum quantum number. This observation is consistent with the conclusion that the lack of inversion symmetry for NH3 and NH3+ allows odd/even l mixings, rendering the production of both odd and even l states for the photoelectrons. Evidence is also found, indicating that the photoionization transitions with DeltaK=0 are strongly favored compared to that with DeltaK=3. For the 2(5), 1(1)2(1), and 1(1)2(3) bands, only DeltaK=0 transitions for the production of even l photoelectron states from the J'K'=2(0) rotational level of NH3(nu1=1) are observed. The preferential formation of even l photoelectron states for these vibrational bands is attributed to the fact that the DeltaK=0 transitions for the formation of odd l photoelectron states from the 2(0) rotational level of NH3(nu1=1) are suppressed by the constraint of nuclear-spin statistics. In addition to information obtained on the photoionization dynamics of NH3, this experiment also provides a more precise value of 3232+/-10 cm-1 for the nu1+ (N-H stretch) vibrational frequency of NH3+. PMID:16164295

Bahng, Mi-Kyung; Xing, Xi; Baek, Sun Jong; Ng, C Y

2005-08-22

225

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

NASA Astrophysics Data System (ADS)

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.

Wang, I.-Shun; Lin, Yi-Ting; Huang, Chi-Hsien; Lu, Tseng-Fu; Lue, Cheng-En; Yang, Polung; Pijanswska, Dorota G.; Yang, Chia-Ming; Wang, Jer-Chyi; Yu, Jau-Song; Chang, Yu-Sun; Chou, Chien; Lai, Chao-Sung

2012-03-01

226

Influence of H 2\\/NH 3 mixtures on the composition of SiCNYO and SiCNAl(O) nanopowders  

Microsoft Academic Search

We performed pyrolysis of SiCNAlH and SiCNYOH nanopowder precursors under a reactive atmosphere (Ar\\/NH3\\/H2) with various compositions of ammonia (NH3) and dihydrogen (H2) to diminish C content, which is deleterious for thermal stability and sintering of the powders. This paper continues a previous work on the fabrication of an Si3N4\\/SiC composite without free C by studying the effect of H2

Sirine Chehaidi; Vincent Salles; Sylvie Foucaud; Alexandre Maitre; Paul Goursat

2011-01-01

227

Process Modeling of an Advanced NH3 Abatement and Recycling Technology in the Ammonia-Based CO2 Capture Process.  

PubMed

An advanced NH3 abatement and recycling process that makes great use of the waste heat in flue gas was proposed to solve the problems of ammonia slip, NH3 makeup, and flue gas cooling in the ammonia-based CO2 capture process. The rigorous rate-based model, RateFrac in Aspen Plus, was thermodynamically and kinetically validated by experimental data from open literature and CSIRO pilot trials at Munmorah Power Station, Australia, respectively. After a thorough sensitivity analysis and process improvement, the NH3 recycling efficiency reached as high as 99.87%, and the NH3 exhaust concentration was only 15.4 ppmv. Most importantly, the energy consumption of the NH3 abatement and recycling system was only 59.34 kJ/kg CO2 of electricity. The evaluation of mass balance and temperature steady shows that this NH3 recovery process was technically effective and feasible. This process therefore is a promising prospect toward industrial application. PMID:24850444

Li, Kangkang; Yu, Hai; Tade, Moses; Feron, Paul; Yu, Jingwen; Wang, Shujuan

2014-06-17

228

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

229

NH3, H2S, and the Radio Brightness Temperature Spectra of the Giant Planets  

NASA Technical Reports Server (NTRS)

Recent radio interferometer observations of Neptune enable comparisons of the radio brightness temperature (T(sub B)) spectra of all four giant planets. This comparison reveals evidence for fundamental differences in the compositions of Uranus' and Neptune's upper tropospheres, particularly in their ammonia (NH3) and hydrogen sulfide (H2S) mixing ratios, despite those planets' outward similarities. The tropospheric abundances of these constituents yield information about their deep abundances, and ultimately about the formation of the planets from the presolar nebula (Atreya et al.). Figures 1, 2, 3, and 4 show the T(sub B) spectra of Jupiter, Saturn, Uranus, and Neptune, respectively, from 0.1 to tens of cm wavelength. The data shown are collected from many observers. Data for Jupiter, Saturn, and Uranus are those cataloged by de Pater and Massie (1985), plus the Saturn Very Large Array (VLA) data by Grossman et al. Figure 3, Uranus, shows only data acquired since 1973. Before 1973 Uranus' T(sub B) increased steadily as its pole moved into view, causing significant scatter in those data. Neptune data at greater than 1 cm, all taken at the VLA, are collected from de Pater and Richmond, de Pater et al., and Hofstadter. For a variety of reasons, such as susceptibility to source confusion, single-dish data at those wavelengths are much noisier than the more reliable VLA data and have been ignored. Single-dish data by Griffin and Orton shortward of 0.4 cm are shown, along with the Owens Valley Radio Observatory (interferometer) datum at 0.266 cm by Muhleman and Berge. Spectra of Jupiter, Saturn, and Neptune share certain gross characteristics. In each spectrum, T(sub B) at 1.3 cm is approximately 120-140 K, less than approximately 30 K different from that at 0.1 cm. All three spectra show a break in slope at or near 1.3 cm, with T(sub B) increasing fairly rapidly with wavelength longward of 1.3 cm. Visible and IR spectroscopy show that NH3, whose strong inversion spectrum peaks at appropximately 1.3 cm, is an important tropospheric species at Jupiter and Saturn. Its signature on the Jovian radio spectrum is obvious, causing the prominent "hole" at 1.3 cm. At Saturn it is more subdued but is the source of that spectrum's change in slope at 1.3 cm. Radiative transfer models of Jupiter and Saturn with near-solar deep NH3 abundances agree well with the data (e.g., de Pater).

Spilker, Thomas R.

1995-01-01

230

Vibrational infrared spectrum of NH 3 adsorbed on MgO(100). I. Ab initio calculations  

NASA Astrophysics Data System (ADS)

The perturbed cluster approach, previously devoted to the calculation of the stable adsorption site and energy for ammonia adsorbed on MgO(100), is used to determine the frequency and the intensity of the main peaks associated with the normal vibrational modes of the admolecule. The ab initio model based on a cluster embedded in an array of point charges is then compared to the perturbed cluster approach and used to investigate different molecular orientations and associations on the surface in order to give an interpretation to the occurrence of the infrared signals. Six normal modes for each admolecule are calculated due to the removing of internal degeneracy by adsorption. The characteristics of the calculated spectrum are compared to the experimental infrared data and it is shown that the set of selected situations is able to explain almost every band in the spectrum without implication of NH 3 dissociation on the surface.

Allouche, A.; Corà, F.; Girardet, C.

1995-12-01

231

Nontemplate synthesis of CH3NH3PbBr3 perovskite nanoparticles.  

PubMed

To date, there is no example in the literature of free, nanometer-sized, organolead halide CH3NH3PbBr3 perovskites. We report here the preparation of 6 nm-sized nanoparticles of this type by a simple and fast method based on the use of an ammonium bromide with a medium-sized chain that keeps the nanoparticles dispersed in a wide range of organic solvents. These nanoparticles can be maintained stable in the solid state as well as in concentrated solutions for more than three months, without requiring a mesoporous material. This makes it possible to prepare homogeneous thin films of these nanoparticles by spin-coating on a quartz substrate. Both the colloidal solution and the thin film emit light within a narrow bandwidth of the visible spectrum and with a high quantum yield (ca. 20%); this could be advantageous in the design of optoelectronic devices. PMID:24387158

Schmidt, Luciana C; Pertegás, Antonio; González-Carrero, Soranyel; Malinkiewicz, Olga; Agouram, Said; Mínguez Espallargas, Guillermo; Bolink, Henk J; Galian, Raquel E; Pérez-Prieto, Julia

2014-01-22

232

Double core hole creation and subsequent Auger decay in NH3 and CH4 molecules.  

PubMed

Energies of the hollow molecules CH(4)(2+) and NH(3)(2+) with double vacancies in the 1s shells have been measured using an efficient coincidence technique combined with synchrotron radiation. The energies of these states have been determined accurately by high level electronic structure calculations and can be well understood on the basis of a simple theoretical model. Their major decay pathway, successive Auger emissions, leads first to a new form of triply charged ion with a core hole and two valence vacancies; experimental evidence for such a state is presented with its theoretical interpretation. Preedge 2-hole-1-particle (2h-1p) states at energies below the double core-hole states are located in the same experiments and their decay pathways are also identified. PMID:21231301

Eland, J H D; Tashiro, M; Linusson, P; Ehara, M; Ueda, K; Feifel, R

2010-11-19

233

Investigation of the stability of Co-doped apatite ionic conductors in NH 3  

NASA Astrophysics Data System (ADS)

Hydrogen powered solid oxide fuel cells (SOFCs) are of enormous interest as devices for the efficient and clean production of electrical energy. However, a number of problems linked to hydrogen production, storage and transportation are slowing down the larger scale use of SOFCs. Identifying alternative fuel sources to act as intermediate during the transition to the full use of hydrogen is, therefore, of importance. One excellent alternative is ammonia, which is produced on a large scale, is relatively cheap and has the infrastructure for storage and transportation already in place. However, considering that SOFCs operate at temperatures higher than 500 °C, a potential problem is the interaction of gaseous ammonia with the materials in the cathode, anode and solid electrolyte. In this paper, we extend earlier work on high temperature reactions of apatite electrolytes with NH 3 to the transition metal (Co) doped systems, La 9.67Si 5CoO 26 and La 10(Si/Ge) 5CoO 26.5. A combination of PXRD, TGA and XAFS spectroscopy data showed a better structural stability for the silicate systems. Apatite silicates and germanates not containing transition metals tend to substitute nitride anions for their interstitial oxide anions, when reacted with NH 3 at high temperature and, consequentially, lower the interstitial oxide content. In La 9.67Si 5CoO 26 and La 10(Si/Ge) 5CoO 26.5 reduction of Co occurs as a competing process, favouring lower levels of nitride-oxide substitution.

Headspith, D. A.; Orera, A.; Slater, P. R.; Young, N. A.; Francesconi, M. G.

2010-12-01

234

Characterizing the excess electron of Li(NH3)4  

NASA Astrophysics Data System (ADS)

Small lithium ammonia clusters are model systems for the dissociation of metals into solvated cations and electrons in ammonia. Metal-ammonia solutions display a complex behavior with increasing metal concentration including a phase change from a paramagnetic to a metallic diamagnetic phase, and small clusters should be useful models in the low concentration regime, where one may expect the ammoniated electron to show a behavior similar to that of the hydrated electron. Yet, even in the low concentration regime the nature of the ammoniated electron is still controversial with cavity models supported by optical and density measurements whereas localized radical models have been invoked to explain magnetic measurements. Small clusters can shed light on these open questions, and in particular the Li-NH3 tetramer represents the smallest cluster with a complete solvation shell for the Li+ cation. In view of the controversies about the character of the excess electron, the first question investigated is whether different theoretical characterizations of the ``excess electron'' lead to different conclusions about it. Only small differences are found between orbital-based and spin density-based and between self-consistent-field and coupled-cluster-based methods. Natural orbitals from equation-of-motion coupled-cluster calculations are then used to analyze the excess electron's distribution of Li(NH3)4 with particular emphasis on the portion of the excess electron's density that is closely associated with the N atoms. Three different comparisons show that only about 6% of the excess electron's density are closely associated with the atoms, with about 1% being closely associated with any N atom, and that the electron is best characterized as a Rydberg-like electron of the whole cluster. Finally, it is shown that in spite of the small amount of density close to the N atoms, the spin-density at the N nuclei is substantial, and that the magnetic observations can plausibly be explained within the cavity model.

Sommerfeld, Thomas; Dreux, Katelyn M.

2012-12-01

235

Hydrogen bonding induced proton exchange reactions in dense D2-NH3 and D2-CH4 mixtures  

NASA Astrophysics Data System (ADS)

We have investigated high-pressure behaviors of simple binary mixtures of NH3 and D2 to 50 GPa and CH4 and D2 to 30 GPa using confocal micro-Raman spectroscopy. The spectral data indicate strong proton exchange reactions occur in dense D2-NH3 mixture, producing different isotopes of ammonia such as NH3, NH2D, NHD2, and ND3. In contrast, the proton exchange process in dense D2-CH4 mixture is highly limited, and no vibration feature is apparent for deuterated methane. The vibrational modes of H2 isotopes in D2-NH3 are blue shifted from those of pure H2 isotopes, whereas the modes of D2-CH4 show overall agreement with those in pure D2 and CH4. In turn, this result advocates the presence of strong repulsion and thereby internal pressure in D2-NH3 mixture, which are absent in D2-CH4. In fact, the bond length of hydrogen molecules in D2-NH3, calculated from the present spectral data, is shorter than that observed in pure hydrogen - supporting the enhanced intermolecular interaction in the mixture. Comparing the present spectral results with those previously observed in D2-H2O mixtures further suggests that the strength of repulsive interaction or the magnitude of internal pressure in the mixtures is proportional to the strength of hydrogen bonding in H2O, NH3, and CH4 in decreasing order. Hence, we suggest that the proton exchange is assisted by hydrogen bonding in these molecules.

Borstad, Gustav M.; Yoo, Choong-Shik

2014-01-01

236

Competition Between Co(NH3)63+ and Inner Sphere Mg2+ Ions in the HDV Ribozyme  

PubMed Central

Divalent cations play critical structural and functional roles in many RNAs. While the hepatitis delta virus (HDV) ribozyme can undergo self-cleavage in the presence of molar concentrations of monovalent cations, divalent cations such as Mg2+ are required for efficient catalysis under physiological conditions. Moreover, the cleavage reaction can be inhibited with Co(NH3)63+, an analog of Mg(H2O)62+. Here, the binding of Mg2+ and Co(NH3)63+ to the HDV ribozyme are studied by Raman microscopic analysis of crystals. Raman difference spectra acquired at different metal ion conditions reveal changes in the ribozyme. When Mg2+ alone is introduced to the ribozyme, inner sphere coordination of Mg(H2O)x2+ (x?5) to non-bridging PO2? oxygen, and changes in base stretches and phosphodiester group conformation are observed. In addition, binding of Mg2+ induces deprotonation of a cytosine assigned to the general acid C75, consistent with solution studies. When Co(NH3)63+ alone is introduced, deprotonation of C75 is again observed, as are distinctive changes in base vibrational ring modes and phosphodiester backbone conformation. In contrast to Mg2+ binding, Co(NH3)63+ binding does not perturb PO2? group vibrations, consistent with its ability to make only outer sphere contacts. Surprisingly, competitive binding studies reveal that Co(NH3)63+ ions displace some inner sphere-coordinated magnesium species, including ions coordinated to PO2? groups or the N7 of a guanine, likely G1 at the active site. These observations contrast with the tenet that Co(NH3)63+ ions displace only outer sphere magnesium ions. Overall, our data support two classes of inner sphere Mg2+-PO2? binding sites: sites that Co(NH3)63+ can displace, and others it cannot.

Gong, Bo; Chen, Jui-Hui; Bevilacqua, Philip C.; Golden, Barbara L.; Carey, Paul R.

2009-01-01

237

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

238

Phase polymorphism of novel [Ru(NH3)6](ClO4)3—Comparison with [Ru(NH3)6](BF4)3. Part II  

NASA Astrophysics Data System (ADS)

[Ru(NH3)6](ClO4)3 undergoes two phase transitions at: TC1=290.3 K and TC2=74.8 K , thus exhibits three crystalline phases in the temperature range of 5-310 K. For the detected phase transitions, thermal effects were determined. Fourier transform far- and middle-infrared spectra (FT-FIR and FT-MIR), recorded at 8-350 K, suggest that reorientational motions of the NH3 ligands are very fast (?R?10-12 s above TC1) and are significantly slowed down below TC2. X-ray single crystal diffraction (XRSCD) measurements revealed that in the high temperature phase (above TC1) the compound belongs to the cubic Fm3¯m (No. 225) space group, whereas in the intermediate phase the unit cell parameter doubles and the space group is Ia3¯(No. 206). 1H NMR studies revealed that the following reorientational motions are liberated during heating: three-fold reorientation of NH3 ligands, three-fold reorientation of the entire [Ru(NH3)6]3+ cation, and isotropic reorientation of this cation. In the high temperature phase I the cations perform isotropic reorientations with the estimated activation energy equal to ca. 30.1 kJ mol-1. Comparison with adequate results obtained earlier for [Ru(NH3)6](BF4)3 and for other similar compounds was made and general regularities were drawn.

Do??ga, Diana; Mikuli, Edward; Górska, Natalia; Inaba, Akira; Ho?derna-Natkaniec, Krystyna; Nitek, Wojciech

2013-08-01

239

Ce-Ti amorphous oxides for selective catalytic reduction of NO with NH3: confirmation of Ce-O-Ti active sites.  

PubMed

The amorphous Ce-Ti mixed oxides were reported to be catalysts for selective catalytic reduction of NO(x) with NH(3), in which Ce and not Ti acts as their solvent in spite of the fact that Ce is low in content. The amorphous catalysts were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) equipped with selective area electron diffraction (SAED). The Ce-Ti amorphous oxide shows higher activity than its crystalline counterpart at lower temperatures. Moreover, the presence of small CeO(2) crystallites as for the impregnated sample is deleterious to activity. The Ce-O-Ti short-range order species with the interaction between Ce and Ti in atomic scale was confirmed for the first time to be the active site using temperature programmed reduction with H(2) (H(2)-TPR), in situ FTIR spectra of NO adsorption, X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine-structure (XAFS). Lastly, the Ce-O-Ti structure was directly observed by field-emission TEM (FETEM). PMID:22888951

Li, Ping; Xin, Ying; Li, Qian; Wang, Zhongpeng; Zhang, Zhaoliang; Zheng, Lirong

2012-09-01

240

Global analytical potential energy surface for the electronic ground state of NH3 from high level ab initio calculations.  

PubMed

The analytical, full-dimensional, and global representation of the potential energy surface of NH(3) in the lowest adiabatic electronic state developed previously (Marquardt, R.; et al. J. Phys. Chem. B 2005, 109, 8439–8451) is improved by adjustment of parameters to an enlarged set of electronic energies from ab initio calculations using the coupled cluster method with single and double substitutions and a perturbative treatment of connected triple excitations (CCSD(T)) and the method of multireference configuration interaction (MRCI). CCSD(T) data were obtained from an extrapolation of aug-cc-pVXZ results to the basis set limit (CBS), as described in a previous work (Yurchenko, S.N.; et al. J. Chem. Phys 2005, 123, 134308); they cover the region around the NH3 equilibrium structures up to 20,000 hc cm(–1). MRCI energies were computed using the aug-cc-pVQZ basis to describe both low lying singlet dissociation channels. Adjustment was performed simultaneously to energies obtained from the different ab initio methods using a merging strategy that includes 10,000 geometries at the CCSD(T) level and 500 geometries at the MRCI level. Characteristic features of this improved representation are NH3 equilibrium geometry r(eq)(NH(3)) ? 101.28 pm, ?(eq)(NH(3)) ? 107.03°, the inversion barrier at r(inv)(NH(3)) ? 99.88 pm and 1774 hc cm(–1) above the NH(3) minimum, and dissociation channel energies 41,051 hc cm(–1) (for NH(3) ? ((2)B(2))NH(2) + ((2)S(1/2))H) and 38,450 hc cm(–1) (for NH(3) ? ((3)?(–))NH +((1)?(g)(+))H(2)); the average agreement between calculated and experimental vibrational line positions is 11 cm(–1) for (14)N(1)H(3) in the spectral region up to 5000 cm(–1). A survey of our current knowledge on the vibrational spectroscopy of ammonia and its isotopomers is also given. PMID:23688044

Marquardt, Roberto; Sagui, Kenneth; Zheng, Jingjing; Thiel, Walter; Luckhaus, David; Yurchenko, Sergey; Mariotti, Fabio; Quack, Martin

2013-08-15

241

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

242

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

243

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

244

Desorption kinetics from a surface derived from direct imaging of the adsorbate layer.  

PubMed

There are numerous indications that adsorbed particles on a surface do not desorb statistically, but that their spatial distribution is important. Evidence almost exclusively comes from temperature-programmed desorption, the standard method for measuring desorption rates. However, this method, as a kinetics experiment, cannot uniquely prove an atomic mechanism. Here we report a low-energy electron microscopy investigation in which a surface is microscopically imaged while simultaneously temperature-programmed desorption is recorded. The data show that during desorption of oxygen molecules from a silver single crystal surface, islands of oxygen atoms are present. By correlating the microscopy and the kinetics data, a model is derived that includes the shapes of the islands and assumes that the oxygen molecules desorb from the island edges. The model quantitatively reproduces the complex desorption kinetics, confirming that desorption is affected by islands and that the often used mean-field treatment is inappropriate. PMID:24834863

Günther, S; Mente?, T O; Niño, M A; Locatelli, A; Böcklein, S; Wintterlin, J

2014-01-01

245

Desorption kinetics from a surface derived from direct imaging of the adsorbate layer  

NASA Astrophysics Data System (ADS)

There are numerous indications that adsorbed particles on a surface do not desorb statistically, but that their spatial distribution is important. Evidence almost exclusively comes from temperature-programmed desorption, the standard method for measuring desorption rates. However, this method, as a kinetics experiment, cannot uniquely prove an atomic mechanism. Here we report a low-energy electron microscopy investigation in which a surface is microscopically imaged while simultaneously temperature-programmed desorption is recorded. The data show that during desorption of oxygen molecules from a silver single crystal surface, islands of oxygen atoms are present. By correlating the microscopy and the kinetics data, a model is derived that includes the shapes of the islands and assumes that the oxygen molecules desorb from the island edges. The model quantitatively reproduces the complex desorption kinetics, confirming that desorption is affected by islands and that the often used mean-field treatment is inappropriate.

Günther, S.; Mente?, T. O.; Niño, M. A.; Locatelli, A.; Böcklein, S.; Wintterlin, J.

2014-05-01

246

Doping effect on the adsorption of NH3 molecule onto graphene quantum dot: From the physisorption to the chemisorption  

NASA Astrophysics Data System (ADS)

The adsorption of ammonia molecule onto a graphene hexagonal flake, aluminum (Al) and boron (B) doped graphene flakes (graphene quantum dots, GQDs) are investigated using density functional theory. We found that NH3 molecule is absorbed to the hollow site through the physisorption mechanism without altering the electronic properties of GQD. However, the adsorption energy of NH3 molecule onto the Al- and B-doped GQDs increases with respect GQD resulting chemisorption. The adsorption of NH3 onto the Al-doped and B-doped GQDs makes graphene locally buckled, i.e., B- doped and Al-doped GQDs are not planar. The adsorption mechanism onto a GQD is different than that of graphene. This study reveals important features of the edge passivation and doping effects of the adsorption mechanism of external molecules onto the graphene quantum dots.

Seyed-Talebi, Seyedeh Mozhgan; Beheshtian, J.; Neek-amal, M.

2013-09-01

247

Structural and optical properties of Zn3N2 films prepared by magnetron sputtering in NH3—Ar mixture gases  

NASA Astrophysics Data System (ADS)

Zinc nitride films were prepared by RF magnetron sputtering a metallic zinc target in NH3—Ar mixture gases on glass substrate at room temperature. The effects of NH3 ratio on the structural and optical properties of the films were examined. X-ray diffraction (XRD) analysis indicates that the films are polycrystalline and have a preferred orientation of (321). An indirect optical band gap increased from 2.33 to 2.70 eV when the NH3 ratio varied from 5% to 25%. The photoluminescence (PL) spectrum shows two emission peaks; the peak located at 437 nm is attributed to the incorporation of oxygen, and the other at 459 nm corresponds to the intrinsic emission.

Jiangyan, Wu; Jinliang, Yan; Wei, Yue; Ting, Li

2012-04-01

248

Effects of PbCl2 on selective catalytic reduction of NO with NH3 over vanadia-based catalysts.  

PubMed

The effects of PbCl2 on the selective catalytic reduction of NO with NH3 over vanadia-based catalysts were studied with BET, XRD, SEM, XPS, NH3-TPD, NH3 chemisorption, FT-IR and catalytic activity measurements. The results showed that PbCl2 deactivated the catalysts to a very high extent. The doping of PbCl2 could decrease the surface acidity, especially that of Brønsted acid sites. XPS characterization reveals that the presence of PbCl2 resulted in the transformation of V(5+) into V(4+), which decreased the reducibility of vanadia species. Based on the analysis of physical and chemical properties of the catalysts, the PbCl2-poisoning mechanism model of the vanadia-based SCR catalysts was proposed. PMID:24794983

Jiang, Ye; Gao, Xiang; Zhang, Yongxin; Wu, Weihong; Song, Hao; Luo, Zhongyang; Cen, Kefa

2014-06-15

249

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

NASA Technical Reports Server (NTRS)

The tropospheric abundances of NH3 and PH3 in Jupiter's Great Red Spot (GRS) are presently determined on the basis of a group of Voyager IRIS spectra, and compared with those of the surrounding South Tropical Zone (STZ) obtained from another two groups of IRIS spectra, in order to characterize the GRS's chemistry and dynamics. Although the GRS is believed to be a region of strong vertical transport, NH3 depletion is surprisingly found to occur below the tropopause within the GRS. Since one of the STZ's selections has a temperature-pressure profile similar to that of the GRS below the 300 mbar level, condensation cannot explain the low NH3 abundance in the GRS.

Griffith, Caitlin A.; Bezard, Bruno; Owen, Tobias; Gautier, Daniel

1992-01-01

250

Superconducting phases in (NH3)yMxFeSe1-zTez (M = Li, Na, and Ca)  

NASA Astrophysics Data System (ADS)

Superconducting phases of (NH3)yMxFeSe1-zTez have been synthesized by the intercalation of metal atoms (M: Li, Na, Ca) into FeSe and FeSe0.5Te0.5 using a low-temperature liquid NH3 technique. The superconducting transition temperature (Tc) is 31.5 K for Na-doped FeSe, and for Li-, Na-, and Ca-doped FeSe0.5Te0.5 it is 26, 22, and 17 K, respectively. The 31.5 K superconducting is the superconducting phase in ammoniated Na-doped FeSe. The Tc is lower than that (onset Tc = 46 K) of the superconducting phase reported previously. The reason why the Tc of this phase is lower is discussed based on the structure. The pressure dependences of Tc in the (NH3)yNa0.5FeSe and (NH3)yNa0.4FeSe0.5Te0.5 samples have been measured and a negative pressure dependence is observed; i.e., a decrease in lattice constant c leads to a decrease in Tc, consistent with the behavior of (NH3)yCs0.4FeSe reported previously by our group. Furthermore, the magnetic behavior of (NH3)yNa0.4FeSe0.5Te0.5 has been fully investigated at different applied magnetic fields (H) to determine the critical magnetic field. This is a successful metal intercalation into FeSe1-zTez (z?0) and an observation of superconductivity.

Sakai, Yusuke; Zheng, Lu; Izumi, Masanari; Teranishi, Kazuya; Eguchi, Ritsuko; Goto, Hidenori; Onji, Taiki; Araki, Shingo; Kobayashi, Tatsuo C.; Kubozono, Yoshihiro

2014-04-01

251

Laboratory IR Studies of Ion-Irradiated Ices Containing H_2O, CO_2 and NH_3  

NASA Astrophysics Data System (ADS)

Acid-base reactions in irradiated ices containing molecules such as H_2O, CO_2, and NH_3 are one scheme we are examining for the formation of species whose spectra could match the unidentified 6.8 micron interstellar ice feature in NGC 7548 IRS9 and RAFGL 7009S. Similar reactions could be important on the icy surfaces of some satellites. We have examined the reaction of NH_3 with a layer of carbonic acid, H_2CO_3, and identified the formation of carbamic acid. In this experiment, a layer of NH_3 is condensed at 18K and covered with a layer of H_2O + CO_2 ice. During irradiation, H_2CO_3 is formed in the H_2O + CO_2 ice layer (JGR 96, E2, 17,541, 1991). During slow warming the NH_3 diffuses through and reacts with the carbonic acid. The spectrum evolves into a stable set of features near 250 K. The features are identified as carbamic acid, NH_3COO (Spectrochimica Acta, accepted, 1998). The spectrum of carbamic acid is a good match with the 6.8 micron band, but since carbamic acid also contains a strong 7.7 micron band, it is not a good candidate for the interstellar feature. Additional ice experiments in which NH_3 is intimately mixed with H_2O and CO_2 result in a weaker 7.7 micron component. In progress are studies where similar reactions are done on a magnesium silicate surface.

Moore, M. H.; Khanna, R. K.

1998-09-01

252

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

253

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.

2011-01-01

254

The Bonding of NO2, NH3, and CH2NY to Models of a (10,0) Carbon Nanotube  

NASA Technical Reports Server (NTRS)

We have studied the bonding of NO2, NH3, and CH2NH to a (10,O) carbon nanotube using the MP2 and ONIOM methods with extended basis sets. We find bond strengths of 3.5, 3.6. and 6.3 kcal/mol for NO2, NH3, and CH2NH, respectively, using the ONIOM method with the high accuracy part treated at the MP2/aug-CC-pVTZ level and the remainder of the CNT approximated at the UFF level and including an estimate of basis set superposition error using the counterpoise method.

Walch, Stephen P.

2004-01-01

255

Substituent effects in X?C?C?H⋯NH 3 (or OH 2, FH) hydrogen bonding  

NASA Astrophysics Data System (ADS)

MP2/6-31g(p,d) calculations were performed on the C?H⋯N (or O, F) hydrogen bonding between 18 substituted X?C?C?H and NH3, H2O, and HF. It was found that the Hammett-type correlation was applicable to the above systems, which indicated that the field/inductive and resonance effects could both affect the X?C?C?H⋯NH 3 (or H 2O, HF) hydrogen bonding.

Chen, Rong; Zhang, Ke-Chun; Liu, Lei; Li, Xiao-Song; Guo, Qing-Xiang

2001-04-01

256

Dielectric Dispersion in (CH3NH3)5Bi2X11 (X=Cl, Br) Single Crystals  

NASA Astrophysics Data System (ADS)

The temperature dependences of dielectric dispersion in (CH3NH3)5Bi2Cl11 and (CH3NH3)5Bi2Br11 single crystals, which undergo the para-ferroelectric phase transition (I?II) at 307 K and 311.5 K, respectively, were measured near the phase transition point in the frequency range from 1 MHz to 1 GHz. The dielectric dispersion exhibited was found to be of the Debye-type. The critical slowing down was observed near the phase transition point.

Iwata, Makoto; Ishibashi, Yoshihiro

1990-12-01

257

Laser induced fluorescence and absorption measurements of NO in NH3\\/O2 and CH4\\/air flames  

Microsoft Academic Search

Laser diagnostics have been used to probe NO in atmospheric pressure flames. Laser induced fluorescence techniques (LIF) were used to measure relative concentration profiles of NO at fuel equivalence ratios ?=1.28, 1.50, and 1.81 in NH3\\/O2\\/N2 flames and ?=1.7 and 1.8 in CH4\\/air\\/O2 flames. Laser absorption measurements were made to derive an absolute concentration of NO in a lean NH3\\/O2\\/N2

Mau-Song Chou; Anthony M. Dean; David Stern

1983-01-01

258

Cooperative nitrogen insertion processes: Thermal transformation of NH3 on a Si(100) surface  

NASA Astrophysics Data System (ADS)

The thermal behavior of an ammonia-covered Si(100) surface is investigated by infrared spectroscopy and density functional methods. Upon adsorption at room temperature, (Si)NH2 and Si-H species are formed on the surface. Comparison of the vibrational studies with density functional calculations suggests that the (Si)NH2 structures are preferentially located on the same side along the silicon dimer row on a (2×1) reconstructed Si(100) surface, although a mixture of different long-range configurations is likely formed. Decomposition of these (Si)NH2 species is observed to start at temperatures as low as 500K . Theoretical predictions of the vibrational modes indicate that at this point, the spectrum is composed of a combination of (Si)2NH and (Si)3N vibrational signatures, which result from insertion of N into Si-Si bonds. Our computational study of the formation of (Si)2NH structures indicates that subsurface insertion is more feasible if the strain imposed during the insertion in a Si dimer is attenuated by a (Si)2NH structure already inserted in the neighboring dimer along the same silicon dimer row. This cooperative reaction lowers the energetic requirements for subsurface insertion, providing a theoretical explanation for the mechanism of thermal decomposition of NH3 on Si(100) and for other systems where subsurface migration is observed experimentally.

Rodríguez-Reyes, J. C. F.; Teplyakov, A. V.

2007-08-01

259

Thermal decomposition of NH 3 on the Si(1 0 0) surface  

NASA Astrophysics Data System (ADS)

The adsorption and thermal reaction of NH 3 on the Si(1 0 0) surface are investigated by high-resolution core-level photoemission spectroscopy using synchrotron radiation. The existence of different reaction products and their chemical bonding configurations at different substrate temperatures are revealed from N 1s and Si 2p core-level spectra. We clearly identified a series of Si-NH 2, Si 2?NH and Si 3?N species in N 1s spectra indicating a successive N-H bond dissociation during thermal decomposition. The depth distribution and the population changes of each N species with annealing suggest that (i) the intermediate Si 2?NH species include insertion into the back-bond site between the first and the second Si layers as well as bridging Si dimer site and (ii) the fully dissociated N atoms are incorporated into the Si subsurface layers first. At a high temperature above 900 K, the incorporated N atoms partly segregate back to the surface to form stoichiometric silicon nitride patches. The Si 2p core levels consistently show progressive changes in subnitride formation and the liberation of H atom upon increase of annealing temperature. The implication of the present result on the proposed reaction mechanism is discussed.

Kim, Jeong Won; Yeom, Han Woong

2003-12-01

260

Phase Transitions in (CH3NH3)4InBr7  

NASA Astrophysics Data System (ADS)

Measurements of the dielectric constant, the DTA signal and the linear thermal expansion, optical observation of domain structure and X-ray examination of (CH3NH3)4InBr7 have been carried out over a temperature range from 25°C to 180°C. It is found that the crystal undergoes phase transitions at 171°C (T1) and 141°C (T2), and is ferroelastic below T1. The crystal at room temperature belongs to monoclinic P2/n with lattice parameters: a{=}16.854(6) Å, b{=}7.731(6) Å, c{=}16.756(9) Å and ?{=}103.22(2)°. When the symmetry is approximated as to be pseudo-orthorhombic by taking a'{=}a+c, b'{=}b and c'{=}c-a (?'{=}90.34(11)°), the domain structure observed below T1 is deduced from the strain-compatibility relations for the domain boundaries by taking account of the symmetry change from mmm to 2/m at T1. At T2 no change of domain configuration has been detected.

Miyazaki, Akio; Irokawa, Katsumi; Komukae, Masaru; Osaka, Toshio; Makita, Yasuharu

1991-11-01

261

DFT based study of transition metal nano-clusters for electrochemical NH3 production.  

PubMed

Theoretical studies of the possibility of producing ammonia electrochemically at ambient temperature and pressure without direct N2 dissociation are presented. Density functional theory calculations were used in combination with the computational standard hydrogen electrode to calculate the free energy profile for the reduction of N2 admolecules and N adatoms on transition metal nanoclusters in contact with an acidic electrolyte. This work has established linear scaling relations for the dissociative reaction intermediates NH, NH2, and NH3. In addition, linear scaling relations for the associative reaction intermediates N2H, N2H2, and N2H3 have been determined. Furthermore, correlations between the adsorption energies of N, N2, and H have been established. These scaling relations and the free energy corrections are used to establish volcanoes describing the onset potential for electrochemical ammonia production and hence describe the potential determining steps for the electrochemical ammonia production. The competing hydrogen evolution reaction has also been analyzed for comparison. PMID:23598667

Howalt, J G; Bligaard, T; Rossmeisl, J; Vegge, T

2013-05-28

262

Enhanced localization of tunneling of the NH 3 umbrella mode in nano-cage fullerene  

NASA Astrophysics Data System (ADS)

The infrared bar-spectrum of a single ammonia molecule encapsulated in nano-cage C 60 fullerene molecule is modeled using the site inclusion model successfully applied to analyze spectra of CO 2 isotopologues isolated in rare gas matrix. Calculations show that NH 3 can rotate freely on a sphere of radius 0.184 Å around the site center of the nano-cage and spin freely about its C 3 symmetry axis. In the static field inside the cage degenerate ?3 and ?4 vibrational modes are blue shifted and split. When dynamic coupling with translational motion is considered, the spectral signature of the ?2 mode is modified with a higher hindering barrier (2451 cm -1), an effective reduced mass (6.569 g mol -1) and a longer tunneling time (55594 ps) for the fundamental level compared to gas-phase values (2047 cm -1), (2.563 g mol -1) and (20.85 ps). As a result this mode is red shifted. Moreover, simulation shows that the changes in the bar-spectrum of the latter mode can be used to probe the temperature of the surrounding media in which fullerene is observed.

Lakhlifi, Azzedine; Dahoo, Pierre R.

2011-07-01

263

Quasielastic neutron scattering of -NH3 and -BH3 rotational dynamics in orthorhombic ammonia borane  

SciTech Connect

Neutrons scattering techniques are ideally suited to directly probe H in materials due to the large incoherent scattering cross-section of hydrogen atom, and have been invaluable in providing direct insight into the local fluctuations and large amplitude motions in AB. Dihydrogen bonding may have a significant affect on materials to be used to store hydrogen for fuel-cell powered applications. We have noticed a trend of low temperature release of H2 in materials composed of hydridic and protonic hydrogen. This phenomenon has caught our attention and motivated our interest to gain more insight into dihydrogen bonding interactions in AB. We present results from a thorough Quasielastic Neutron Scattering (QENS) investigation of diffusive hydrogen motion in NH311BH3 and ND311BH3 to obtain (1) a direct measure of the rotational energy barriers the protonated species and (2) a confirmation of the 3-site jump model for rotational motion. The amplitude of the energy barrier of rotation of BH3 and NH3 determined by QENS are compared to those determined for BD3 and ND3 determined by 2H NMR studies.

Hess, Nancy J.; Hartman, Michael R.; Brown, Craig; Mamontov, Eugene; Karkamkar, Abhijeet J.; Heldebrant, David J.; Daemen, Luke L.; Autrey, Thomas

2008-06-27

264

Photochemical reactions in interstellar grains photolysis of CO, NH3, and H2O  

NASA Technical Reports Server (NTRS)

The interstellar grains are currently considered to be the basic building blocks of comets and, possibly, meteorites. To test this theory, 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 10 K, with concomitant irradiation with vacuum UV. The results of the HPLC and IR analyses of the nonvolatile residue formed by photolysis at 10 K are compared with those observed at 77 K and 298 K. Some of the compounds that may be present on the surfaces of interstellar dust particles have been identified, and some specific predictions concerning the types of molecular species present in comets could be drawn. The results also suggest that photochemical reactions may have been important for the formation of meteorite components. The implication of the findings to the questions of the source of organic matter on earth and the origin of life are discussed.

Agarwal, V. K.; Ferris, J. P.; Schutte, W.; Greenberg, J. M.; Briggs, R.

1985-01-01

265

Spectral intensities in the nu(sub 1) band of NH3  

NASA Technical Reports Server (NTRS)

Intensities have been measured for individual transitions in the Q and R branches of the nu(sub 1) band of NH3 using a difference-frequency laser spectrometer. The data yield an integrated band strength of S(sup 0 sub v) = 219.36 +/- 1.03/sq cm/MPa at 297 K, corresponding to a transition moment of absolute value of mu(sub v) = 8.535(20) x 10(exp -32) C x m, and a Herman-Wallis correction factor,(1 + alpha(sub J)m), where alpha(sub J) = 0.0209(20). The intensities of a few lines for K greater than or equal to 7 were noticeably perturbed by a perpendicular Coriolis interaction with 2nu(sub 4)(E, l = 2), so were excluded from the fit. A small sample of nu(sub 3) band lines occurring in the nu(sub 1) band scans also yields a rough estimate of the nu(sub 3) band intensity with evident irregular perturbations.

Pine, A. S.; Dang-Nhu, M.

1993-01-01

266

The electronic structure of organic-inorganic hybrid compounds: (NH4)2CuCl4, (CH3NH3)2CuCl4 and (C2H5NH3)2CuCl4  

NASA Astrophysics Data System (ADS)

Hybrid organic-inorganic compounds are an intriguing class of materials that have been experimentally studied over the past few years because of a potential broad range of applications. The electronic and magnetic properties of three organic-inorganic hybrid compounds with compositions (NH4)2CuCl4, (CH3NH3)2CuCl4 and (C2H5NH3)2CuCl4 are investigated for the first time with density functional theory plus on-site Coulomb interaction. A strong Coulomb interaction on the copper causes a relatively weak exchange coupling within the layers of the octahedral network, in good agreement with experiment. The character of the exchange interaction (responsible for magnetic behavior) is analyzed. The calculations reveal that (C2H5NH3)2CuCl4 has the strongest Jahn-Teller (JT) distortion in comparison with the two other compounds. The easy axis of magnetization is investigated, showing a weak anisotropic interaction between inter-layer Cu2+ ions in the (C2H5NH3)2CuCl4 structure. Orbital ordering is concluded from our partial density of states calculations: a cooperation of the JT distortion with an antiferro-distortive pattern.

Zolfaghari, P.; de Wijs, G. A.; de Groot, R. A.

2013-07-01

267

Association of Electroactive Counterions with Polyelectrolytes. 5. Electrostatic Binding of Ru(NH3)6(3+) and Co(NH3)6(3+) to Polyacrylates. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

The spontaneous association of M(NH3)6(3+) complexes (M = Ru, Co) with polyacrylate anions (PAAs) in aqueous solution was investigated by means of cyclic and rotating disk voltammetry at graphite electrodes. Equilibrium constants, Kb, for the association ...

R. Jiang F. C. Anson

1992-01-01

268

Fe2O3 particles as superior catalysts for low temperature selective catalytic reduction of NO with NH3.  

PubMed

Fe2O3 particle catalysts were experimentally studied in the low temperature selective catalytic reduction (SCR) of NO with NH3. The effects of reaction temperature, oxygen concentration, [NH3]/[NO] molar ratio and residence time on SCR activity were studied. It was found that Fe2O3 catalysts had high activity for the SCR of NO with NH3 in a broad temperature range of 150-270 degrees C, and more than 95% NO conversion was obtained at 180 degrees C when the molar ratio [NH3]/[NO] = 1, the residence time was 0.48 seconds and O2 volume fraction was 3%. In addition, the effect of SO2 on SCR catalytic activity was also investigated at the temperature of 180 degrees C. The results showed that deactivation of the Fe2O3 particles occurred due to the presence of SO2 and the NO conversion decreased from 99.2% to 58% in 240 min, since SO2 gradually decreased the catalytic activity of the catalysts. In addition, X-ray diffraction, Thermogravimetric analysis and Fourier transform infrared spectroscopy were used to characterize the fresh and deactivated Fe2O3 catalysts. The results showed that the deactivation caused by SO2 was due to the formation of metal sulfates and ammonium sulfates on the catalyst surface during the de-NO reaction, which could cause pore plugging and result in suppression of the catalytic activity. PMID:24649679

Wang, Xiaobo; Gui, Keting

2013-12-01

269

Neural Network Based Recognition, of CO and NH3 Reducing Gases, Using a Metallic Oxide Gas Sensor Array  

Microsoft Academic Search

An analysis of single gases using non-selective sensor elements is presented. It contains two steps: At first, the sensor is submitted in different gases (CO and NH3) of progressive increasing concentration and its characteristic responses are collected for each gas, each concentration and for each sensor element. In order to do the recognition, the signals of sensor output, are transformed

Georgios Tsirigotis; Laure Berry; Maria Gatzioni

2003-01-01

270

Tropospheric Reactions of H+(NH3)m(H2O)n with Pyridine and Picoline,  

National Technical Information Service (NTIS)

Rate constants for the reactions of H+(NH3) sub m (H2O) sub n with pyridine and all three picolines have been measured for m + n 5. The rate constants were found to be large for all m and n studied. The reactions proceed by proton transfer, with an undete...

A. A. Viggiano R. A. Morris F. Dale J. F. Paulson

1988-01-01

271

Ammonium formate decomposition over Au/TiO2: a unique case of preferential selectivity against NH3 oxidation.  

PubMed

The unique selectivity of Au/TiO2 for converting ammonium formate to CO2 in the presence of excess O2 and H2O without oxidising NH3 up to 300 °C is reported. The catalyst is highly stable and selective even after severe hydrothermal aging. PMID:24846456

Sridhar, Manasa; Peitz, Daniel; van Bokhoven, Jeroen Anton; Kröcher, Oliver

2014-07-01

272

Low-temperature SCR of NO x with NH 3 over activated carbon fiber composite-supported metal oxides  

Microsoft Academic Search

In previous works, the authors were involved in the preparation and optimization of Nomex-based activated carbon fibers (ACFs) monoliths and their use as catalytic supports of manganese oxides for the selective catalytic reduction (SCR) of NOx with NH3 at low temperature. Thus, a low density monolith made of carbonized Nomex™ rejects was fabricated and submitted to different surface conditioning treatments

Gregorio Marbán; Raquel Antuña; Antonio B Fuertes

2003-01-01

273

Hydrogen-bonding in the pyrimidineNH3 van der Waals complex: experiment and theory.  

PubMed

The pyrimidineNH3 van der Waals complex has been studied using a combination of resonant two-photon ionisation (R2PI) spectroscopy, ab initio molecular orbital calculations and multidimensional Franck-Condon analysis. The R2PI spectrum is assignable to a single stable conformer in which the ammonia molecule binds via two hydrogen bonds within the plane of the ring, in a location which minimises repulsion between the ammonia nitrogen lone pair and that of the second, more remote pyrimidine nitrogen in the 3 position on the opposite side of the ring. Ground state estimated CCSD(T) interaction energies were extrapolated to the complete basis set limit: these calculations found the dissociation energy of the most stable conformer, ?B, to be 20% larger than that of a second in-plane conformer, ?A, in which the ammonia forms a similar pseudo five-membered ring, bridging the nitrogen at the 1 position with the carbon at the 2 position. This conformation in turn was found to have a dissociation energy 35% larger than that of a ?-complex in which the ammonia binds above the plane of the aromatic ring. The results of multidimensional Franck-Condon simulations based on ab initio ground and excited state CASSCF and RICC2 geometry optimisations and vibrational frequency calculations showed good agreement with experiment. It is postulated that longer-range electrostatic interactions between the ammonia lone pair and the more distant of the two ring nitrogens on the pyrimidine, play a key role in determining which of the two in-plane structures is the more stable and which, therefore, is responsible for all of the spectral features observed in the R2PI spectrum. PMID:24910315

Gosling, M P; Cockett, M C R

2014-07-21

274

Comparing approaches to correct for respiratory motion in NH3 PET-CT cardiac perfusion imaging  

PubMed Central

Aim Respiratory motion affects cardiac PET-computed tomography (CT) imaging by reducing attenuation correction (AC) accuracy and by introducing blur. The aim of this study was to compare three approaches for reducing motion-induced AC errors and evaluate the inclusion of respiratory motion correction. Materials and methods AC with a helical CT was compared with averaged cine and gated cine CT, as well as with a pseudo-gated CT, which was produced by applying PET-derived motion fields to the helical CT. Data-driven gating was used to produce respiratory-gated PET and CT images, and 60 NH3 PET scans were attenuation corrected with each of the CTs. Respiratory motion correction was applied to the gated and pseudo-gated attenuation-corrected PET images. Results Anterior and lateral wall intensity measured in attenuation-corrected PET images generally increased when PET-CT alignment improved and decreased when alignment degraded. On average, all methods improved PET-CT liver and cardiac alignment, and increased anterior wall intensity by more than 10% in 36, 33 and 25 cases for the averaged, gated and pseudo-gated CTAC PET images, respectively. However, cases were found where alignment worsened and severe artefacts resulted. This occurred in more cases and to a greater extent for the averaged and gated CT, where the anterior wall intensity reduced by more than 10% in 21 and 24 cases, respectively, compared with six cases for the pseudo-gated CT. Application of respiratory motion correction increased the average anterior and inferior wall intensity, but only 13% of cases increased by more than 10%. Conclusion All methods improved average respiratory-induced AC errors; however, some severe artefacts were produced. The pseudo-gated CT was found to be the most robust method.

O'Doherty, Michael J.; Barrington, Sally F.; Morton, Geraint; Marsden, Paul K.

2013-01-01

275

Tracing the evolutionary stage of Bok globules: CCS and NH3  

NASA Astrophysics Data System (ADS)

Aims: We investigate a previously proposed correlation between the chemical properties and the physical evolutionary stage of isolated low-mass star-forming regions. The NNH3/NCCS abundance ratio has been proposed to be a potentially useful indicator of the evolutionary stage of cloud cores, and we study its applicability for isolated Bok globules. Methods: We searched for CCS(21-10) emission in 42 Bok globules both with and without signs of current star formation. A set of NH3 measurements was compiled from measurements available in the literature and from our own observations. The abundance ratio of both molecules is discussed with respect to the evolutionary stage of the objects and in the context of chemical models. Results: We determine the NNH3/NCCS ratio for 18 Bok globules and find that it is moderately high and roughly similar across all evolutionary stages from starless and prestellar cores towards internally heated cores harboring protostars of Class 0, Class I, or later. We do not find any Bok globules with extremely high CCS abundances analogous to carbon-chain producing regions in dark cloud cores. The observed range of NNH3/NCCS implies that all of the observed Bok globules are in a relatively evolved chemical state. Based on observations obtained with the 100-m telescope of the MPIfR (Max-Planck-Institut für Radioastronomie) at Effelsberg and the 64-m Parkes radio telescope. The Parkes radio telescope is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.

Marka, C.; Schreyer, K.; Launhardt, R.; Semenov, D. A.; Henning, Th.

2012-01-01

276

Composition of Ta 2O 5 stacked films on N 2O- and NH 3-nitrided Si  

NASA Astrophysics Data System (ADS)

The composition and microstructure of rf sputtered 20 nm Ta 2O 5 on N 2O or NH 3 Rapid Thermal Nitrided (RTN) Si substrates have been investigated by X-ray photoelectron spectroscopy. RTN at 800 and 850 °C is effective to suppress active oxidation of Si. There is no evidence for the presence of SiO 2 at Si interface. A lightly nitrided surface is established in both cases without a formation of detectable oxynitride layer at Si. A layered nature of the films is observed, with stoichiometric tantalum pentoxide at and close to the films' surface. In the depth, the films are mixed ones whose composition depends on the nitridation ambient. N 2O treatment stimulates oxidation processes during the film deposition while NH 3 nitridation results to a less effective oxidation and produces Ta-silicate like film. The correlation between the composition of the interfacial regions and the nitridation gas is also discussed. The results suggest that hydrogen, as a component of nitridation ambient, plays significant role in the reactions controlling the exact composition of the deposited Ta 2O 5, activating reactions with nitrogen. Nitrogen related reactions likely occur with NH 3 processing but do not with N 2O one. The presence of nitrogen feature is not detected in N 2O-samples spectra at all. In the integration perspective, preliminary RTN of Si in N 2O or NH 3 could be a suitable way to produce layered Ta 2O 5-based films with more or less presence of tantalum silicate with a trace of nitrogen, either only at the interface with Si (N 2O-process) or in the whole film (NH 3-process).

Atanassova, E.; Spassov, D.; Paskaleva, A.; Kostov, K.

2006-12-01

277

Thermal desorption of CO from Mo(110)  

NASA Astrophysics Data System (ADS)

Adsorption of CO on Mo(110) has been studied by temperature programmed desorption (TPD), photoelectron spectroscopy, and Monte-Carlo simulations. Carbon monoxide is partly dissociated when adsorbed on this surface at ambient temperatures. Two desorption regions, 250-400 K (molecular adsorption) and 850-1100 K (dissociative adsorption) are observed in the TPD spectra. Molecular species were identified by orbitals present in the photoemission measurements. It was found that the desorption signal corresponding to dissociative adsorption saturates rapidly for CO exposures below 1L, whereas the desorption intensity corresponding to molecular adsorption increases with exposure up to about 5L. Interpretation of desorption data is generally not straight forward due to the dependence of several properties of the surface and absorbed species. Therefore, the experimental data for the molecular adsorption region has been compared to Monte-Carlo simulations. The algorithm proposed by Meng and Weinberg [1] was employed. The presence of dissociated species on the surface has been modeled. Two different adsorption sites, "on-top" and "bridge" sites, was considered. Three different near neighbor interactions on the bcc(110) surface have been included. [1] B.Meng and W.H. Weinberg, J. Chem. Phys. 100, 5280 (1994).

Raaen, S.; Juel, M.

2003-03-01

278

Orientational ordering of alkali ammonia clusters in ammoniated alkali fullerides (NH3)K3C60 and (ND3)K3C60  

NASA Astrophysics Data System (ADS)

Synchrotron x-ray diffraction measurements of (NH3)K3C60 and (ND3)K3C60 have revealed a structural phase transition at Ts~=150 K. The low-temperature phase has a unit cell derived by doubling the unit lattice vectors of high-temperature phase, and is characterized as an orientationally ordered state of the K-NH3 pair at the octahedral site of the C60 lattice. At 100 KNH3 pairs lie, which is related to the ordering of K-NH3 pair.

Ishii, K.; Watanuki, T.; Fujiwara, A.; Suematsu, H.; Iwasa, Y.; Shimoda, H.; Takenobu, T.; Mitani, T.

1999-09-01

279

Determining Surface-Adsorbate Binding Energies from Collision-Induced Desorption Experiments.  

NASA Astrophysics Data System (ADS)

The work in this dissertation details the determination of surface-adsorbate bond energies from collision-induced desorption experiments. The collision-induced desorption experiment utilizes an intense, nearly monoenergetic beam of neutral, noble gas atoms to desorb surface bound molecules into the gas phase. A general equation derived from classical mechanics is used to calculate a physisorption or chemisorption bond energy from the threshold energy required to desorb an adsorbate from the surface. The first system studied in this dissertation is the collision-induced desorption of CH_4 physisorbed to Ni{111 } by energetic Ar atoms. A theory is presented to extract the bond energy for this system using a one -dimensional square well to model the Ni-CH_4 interaction. The threshold for desorption scales with the fraction of energy transferred from Ar to CH _4 along the direction of the surface normal. This model calculates the CH_4/Ni {111} bond energy to be 120 meV which is close to experimental value of 126 meV. The second investigation involves the collision -induced desorption of NH_3 chemisorbed on Pt{111}. The absolute cross sections for NH_3 desorption at 0.25 ML were measured by x-ray photoelectron spectroscopy as a function of Ar kinetic energy and incident angle. The threshold desorption energy, 1.95 eV, was independent of the Ar angle of incidence and suggests a strong lateral corrugation in the NH_3/Pt {111} interaction potential. The collision model calculates the NH_3/Pt {111} binding energy to be 1.45 eV. The third system probed by collision-induced desorption was the di-sigma configuration of rm C_2H_4 chemisorbed to Pt{111} at 90 K. An energetic Xe beam was used to desorb rm C_2H_4 and the threshold energy for desorption, 5.2 eV, was independent of the Xe angle of incidence. The model calculates the di-sigma binding energy to be 2.1 eV and predicts that rm C_2H_4 desorbs from the surface in a planar configuration. From this result a thermal desorption mechanism involving a radical intermediate for ethylene was proposed. This mechanism may provide new insight into the hydrogenation of olefins on metals surfaces.

Szulczewski, Gregory John

1995-01-01

280

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

281

Effect of Hydrostatic Pressure on the Phase Transitions in Ferroelectric (CH3NH3)5Bi2Cl11 (MAPCB) and (CH3NH3)5Bi2Br11 (MAPBB)  

NASA Astrophysics Data System (ADS)

Effect of hydrostatic pressure on the phase transitions and dielectric anomalies has been studied for ferroelectric (CH3NH3)5Bi2Cl11 (MAPCB) and (CH3NH3)5Bi2Br11 (MAPBB) in a pressure range up to about 650 MPa. The Curie temperatures T c (311 K in MAPCB, 307 K in MAPBB at 0 MPa) increase with increasing pressure with initial pressure coefficients (dT c/dp)p=0 of 0.063 K/MPa and 0.060 K/MPa for MAPCB and MAPBB, respectively. In MAPCB, the temperature at which the dielectric constant shows a diffuse anomaly (around 160 K at 0 MPa) increases linearly with increasing pressure with a rate of 0.057 K/MPa. The dielectric anomaly becomes more and more diffusive as pressure increases.

Gesi, Kazuo; Iwata, Makoto; Ishibashi, Yoshihiro

1995-07-01

282

Temperature-programmed desorption and photoluminescence studies of thorium dioxide surface states  

Microsoft Academic Search

A mass spectroscopic study of the species desorbed from oxygen- or hydrogen-treated thorium dioxide and photoluminescence studies suggested that the fully hydrated thorium dioxide surface contains three anionic species: oxide lattice ions, hydroxyl ions, and vacancies. The stepwise mechanism of dehydration of the surface is analyzed and its relationship to acid-base properties of the surface and catalytic activity discussed.

M. Breysse; B. Claudel; L. Faure; M. Guenin

1979-01-01

283

Temperature-programmed desorption and photoluminescence studies of thorium dioxide surface states  

SciTech Connect

A mass spectroscopic study of the species desorbed from oxygen- or hydrogen-treated thorium dioxide and photoluminescence studies suggested that the fully hydrated thorium dioxide surface contains three anionic species: oxide lattice ions, hydroxyl ions, and vacancies. The stepwise mechanism of dehydration of the surface is analyzed and its relationship to acid-base properties of the surface and catalytic activity discussed.

Breysse, M.; Claudel, B.; Faure, L.; Guenin, M.

1979-06-01

284

Thermal Desorption Treatment.  

National Technical Information Service (NTIS)

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

D. Oberacker P. Lafornara P. dePercin

1991-01-01

285

Effect of Methionine Sulfoximine on the Accumulation of Ammonia in C(3) and C(4) Leaves : The Relationship between NH(3) Accumulation and Photorespiratory Activity.  

PubMed

Additions of methionine sulfoximine (MSX), an inhibitor of glutamine synthetase (GS), result in an increase in NH(3) in seedling leaves of C(3) (wheat [Triticum aestivum cv. Kolibri] and barley [Hordeum vulgare var Perth]) and C(4) (corn [Zea mays W6A x W182E] and sorghum [Sorghum Vulgare var MK300]) plants. NH(3) accumulation is higher in C(3) (about 17.8 micromoles per gram fresh weight per hour) than in C(4) (about 4.7 micromoles) leaves. Under ideal conditions, when photosynthesis is not yet inhibited by the accumulation of NH(3), the rate of NH(3) accumulation is about 16% of the apparent rate of photosynthesis. A maximum accumulation of NH(3) was elicited by 2.5 millimolar MSX and was essentially independent of the addition of NO(3) (-) during either the growth or experimental period. When O(2) levels in the air were reduced to 2%, MSX resulted in some accumulation of NH(3) (6.0 micromoles per gram fresh weight per hour). At these levels of NH(3), there was no significant inhibition of rates of CO(2) fixation. There was also a minor, but significant, accumulation of NH(3) in corn roots treated with MSX. Inhibitors of photorespiration (isonicotinic hydrazide, 70 millimolar; 2-pyridylhydroxymethanesulfonic acid, 20 millimolar) or transaminase reactions (aminooxyacetate, 1 millimolar) inhibited the accumulation of NH(3) in both C(3) and C(4) leaves. These results support the hypothesis that GS is important in the assimilation of NH(3) in leaves and that the glycine-serine conversion is a major source of that NH(3). PMID:16662781

Martin, F; Winspear, M J; Macfarlane, J D; Oaks, A

1983-01-01

286

The infrared and Raman spectra of ethylammonium hexafluorosilicate [C2H5NH3]2SiF6.  

PubMed

The X-rays powder diffraction pattern of [C2H5NH3]2SiF6 was obtained and indexed on the basis of a hexagonal unit cell. The vibrational spectra (IR and Raman) of this compound were recorded and discussed in relation to the above-mentioned crystal structure. The vibrational spectra of the cations indicate that they are disordered and hydrogen bonded to the anions. On the opposite, the Raman spectrum of the anions could be interpreted in terms of ordered groups. The combination bands observed in the 2300-1800 cm(-1) spectral region in the IR spectrum indicate that this compound may contain C-NH3 groups. PMID:12685910

Ouasri, Ali; Rhandour, Ali; Dhamelincourt, Marie-Claire; Dhamelincourt, Paul; Mazzah, Ahmed

2003-01-15

287

Improved memory characteristics by NH3-nitrided GdO as charge storage layer for nonvolatile memory applications  

NASA Astrophysics Data System (ADS)

Charge-trapping memory capacitor with nitrided gadolinium oxide (GdO) as charge storage layer (CSL) is fabricated, and the influence of post-deposition annealing in NH3 on its memory characteristics is investigated. Transmission electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction are used to analyze the cross-section and interface quality, composition, and crystallinity of the stack gate dielectric, respectively. It is found that nitrogen incorporation can improve the memory window and achieve a good trade-off among the memory properties due to NH3-annealing-induced reasonable distribution profile of a large quantity of deep-level bulk traps created in the nitrided GdO film and reduction of shallow traps near the CSL/SiO2 interface.

Liu, L.; Xu, J. P.; Ji, F.; Chen, J. X.; Lai, P. T.

2012-07-01

288

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

289

Electronic and magnetic properties of an organic multiferroic: (C2H5NH3)2CuCl4  

NASA Astrophysics Data System (ADS)

(C2H5NH3)2CuCl4 was proposed to be a ferroelectric material with dominant ferromagnetic interactions. Using first-principles calculations we find that the insulating state and in-plane ferromagnetism induced by d-d orbital order can be expressed well by generalized gradient approximation (GGA) at ambient pressure. While the Jahn Teller distortion (JTD) is suppressed under critical pressure of 4 GPa, as a result the new d orbital order leads to in-plane antiferromagnetism. Meanwhile the conventional GGA gives a wrong metal state. Our results suggest that (C2H5NH3)2CuCl4 is a strong correlated charge transfer insulator, while the depress of JTD by pressure changes it to a Mott Hubbard insulator.

Ding, Jun; Li, HaiSheng; Wen, LiWei; Kang, XiuBao; Li, HaiDong; Zhang, JianMin

2013-11-01

290

Adsorption of NH 3 onto activated carbon prepared from palm shells impregnated with H 2SO 4  

Microsoft Academic Search

Adsorption of ammonia (NH3) onto activated carbons prepared from palm shells impregnated with sulfuric acid (H2SO4) was investigated. The effects of activation temperature and acid concentration on pore surface area development were studied. The relatively large micropore surface areas of the palm-shell activated carbons prepared by H2SO4 activation suggest their potential applications in gas adsorption. Adsorption experiments at a fixed

Jia Guo; Wang Sheng Xu; Yan Lin Chen; Aik Chong Lua

2005-01-01

291

Growth Characterization of Low-Temperature MOCVD GaN---Comparison between N2H4 and NH3---  

Microsoft Academic Search

The reaction mechanisms of the low-temperature growth of GaN using TMG (trimethylgallium) and two different nitrogen sources, i.e., N2H4 and NH3, are presented. Quite the same temperature dependence of the growth rate for both N sources was found, suggesting that the transport and decomposition of TMG are growth-rate limiting. A different behavior between the two N sources, on the other

Shinji Fujieda; Masashi Mizuta; Yoshishige Matsumoto

1987-01-01

292

Evidence that Fungal MEP Proteins Mediate Diffusion of the Uncharged Species NH3 across the Cytoplasmic Membrane  

PubMed Central

Methylammonium and ammonium (MEP) permeases of Saccharomyces cerevisiae belong to a ubiquitous family of cytoplasmic membrane proteins that transport only ammonium (NH4+ + NH3). Transport and accumulation of the ammonium analog [14C]methylammonium, a weak base, led to the proposal that members of this family were capable of energy-dependent concentration of the ammonium ion, NH4+. In bacteria, however, ATP-dependent conversion of methylammonium to ?-N-methylglutamine by glutamine synthetase precludes its use in assessing concentrative transport across the cytoplasmic membrane. We have confirmed that methylammonium is not metabolized in the yeast S. cerevisiae and have shown that it is little metabolized in the filamentous fungus Neurospora crassa. However, its accumulation depends on the energy-dependent acidification of vacuoles. A ?vph1 mutant of S. cerevisiae and a ?vma1 mutant, which lack vacuolar H+-ATPase activity, had large (fivefold or greater) defects in the accumulation of methylammonium, with little accompanying defect in the initial rate of transport. A vma-1 mutant of N. crassa largely metabolized methylammonium to methylglutamine. Thus, in fungi as in bacteria, subsequent energy-dependent utilization of methylammonium precludes its use in assessing active transport across the cytoplasmic membrane. The requirement for a proton gradient to sequester the charged species CH3NH3+ in acidic vacuoles provides evidence that the substrate for MEP proteins is the uncharged species CH3NH2. By inference, their natural substrate is NH3, a gas. We postulate that MEP proteins facilitate diffusion of NH3 across the cytoplasmic membrane and speculate that human Rhesus proteins, which lie in the same domain family as MEP proteins, facilitate diffusion of CO2.

Soupene, Eric; Ramirez, Robert M.; Kustu, Sydney

2001-01-01

293

Measurement of Dielectric Constant Near 170 K in (CH3NH3)5Bi2Cl11 Single Crystal  

NASA Astrophysics Data System (ADS)

Measurement of the dielectric constant and optical observation of domain structure in (CH3NH3)5Bi2Cl11 have been carried out in the temperature range including 170 K, which has been regarded as a transition temperature. No indication of any phase transition was obtained near 170 K. Temperature dependence of the dielectric constant in this temperature range has been explained applying the Landau theory.

Iwata, Makoto; Ishibashi, Yoshihiro

1992-12-01

294

Selective grafting of amine groups on polyethylene by means of NH 3 ?H 2 RF glow discharges  

Microsoft Academic Search

Plasma treatments in Radio Frequency Glow Discharges fed with NH3?H2 mixtures have been performed for modifying polyethylene surfaces. Treatment kinetics and the role of species present in the\\u000a glow have been investigated. Actinometric Optical Emission Spectroscopy has been utilized as a plasma diagnostic technique.\\u000a Electron Spectroscopy for Chemical Analysis has been utilized for studying surface composition of treated substrates, which

Pietro Favia; Marco Vito Stendardo; Riccardo d'Agostino

1996-01-01

295

Measurements of Line Positions and Intensities of 14NH_3 in the 1.5 ?m Region  

NASA Astrophysics Data System (ADS)

In the atmosphere of outer planets, low mass brown dwarfs, and possibly extrasolar planets, ammonia (NH_3) is one of the major opacity sources particularly in the 1.5 ?m region (the H-band). However, the spectroscopic information of NH_3 in the region is completely missing in the HITRAN database. NH_3 has four infrared active fundamental modes, with the well-known inversion doubling for {?_2} band, in addition to the usual vibrational degeneracies. Its strong bands, {?_1}, {?_3} and 2{?_4}, dominate the spectrum at 3 ?m, while their corresponding overtone and combination bands (e.g., 2{?_1}, 2{?_3}, {?_1}+{?_3}, {?_1}+2{?_4} and {?_3}+2{?_4}) are prominent in the 1.5 ?m region. As part of an effort to provide a complete set of NH_3 spectroscopic information in the 1.5 ?m region, we are analyzing the laboratory spectra recorded at various temperatures (200 - 299 K) with the McMath-Pierce Fourier transform spectrometer (FTS) on Kitt Peak Observatory in Arizona. Line positions and strengths have been measured from the laboratory spectra, from which lower state energies and quantum assignments are being determined by adopting intensity ratios at two different temperatures and combination differnces. A theoretical IR linelist built upon the recent HSL-2 potential energy surface (nonadiabatic corrections included) is complementarily used for the quantum assignments. Preliminary results are presented for {?_1}+{?_3}, 2{?_3}, {?_1}+2{?_4} and {?_3}+{2?_4} bands and compared with those from early work available. X. Huang, D.W. Schwenke, and T.J. Lee J. Chem. Phys. 134, (2011) 044320/044321 The research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology and the Ames Research Center under contracts with National Aeronautics and Space Administration.

Sung, Keeyoon; Brown, Linda R.; Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.

2011-06-01

296

Orientational disorder in Ni(NH_3)_6I_2. Evidence for rotation-translation coupling  

Microsoft Academic Search

Patterson and Fourier analysis of neutron diffraction data of cubic Ni(HN3)6I2 taken at T = 295 K and T = 35 K show a planar proton density distribution with four maxima at the corners of a square. We show that this observation is the consequence of a coupled rotational-translational motion of the NH3 group in a two-dimensional anharmonic single particle

P. Schiebel; A. Hoser; W. Prandl; G. Heger; P. Schweiss

1993-01-01

297

Transport, Optical, and Magnetic Properties of the Conducting Halide Perovskite CH 3NH 3SnI 3  

Microsoft Academic Search

A low-temperature (T ? 100°C) solution technique is described for the preparation of polycrystalline and single crystal samples of the conducting halide perovskite, CH3NH3SnI3. Transport, Hall effect, magnetic, and optical properties are examined over the temperature range 1.8-300 K, confirming that this unusual conducting halide perovskite is a low carrier density p-type metal with a Hall hole density, 1\\/RHe ?

D. B. Mitzi; C. A. Feild; Z. Schlesinger; R. B. Laibowitz

1995-01-01

298

Violet InGaN\\/GaN Light Emitting Diodes Grown by Molecular Beam Epitaxy Using NH3  

Microsoft Academic Search

GaN and InGaN alloys were grown on c-plane sapphire substrates by molecular beam epitaxy using NH3. This allows realizing light emitting diodes (LEDs) based on InGaN\\/GaN single heterostructures. The forward voltage is 3.6 V at 20 mA. The room temperature electroluminescence exhibits a strong emission at 405 nm. The I V characteristics were studied as a function of the temperature.

Nicolas Grandjean; Jean Massies; Mathieu Leroux; Philippe Lorenzini

1998-01-01

299

EIS study of the effect of high levels of NH 3 on the deformation of polyester-coated galvanised steel at different relative humidities  

Microsoft Academic Search

The effect of NH3 on the deformation of polyester-coated galvanised steel at different relative humidities (RHs) was investigated using electrochemical impedance spectroscopy. Measurements were performed on specimens which had been tested in accelerated gaseous corrosion test. For this purpose the samples were subjected to NH3 gas for 16 and 24 days in atmospheric test cells with adjusted RH from 60

? Dehri; H Sözüsa?lam; M Erbil

2003-01-01

300

Effect of High NH3 Input Partial Pressure on Hydride Vapor Phase Epitaxy of InN Using Nitrided (0001) Sapphire Substrates  

NASA Astrophysics Data System (ADS)

The influence of the source gas supply sequence prior to growth and the NH3 input partial pressure (PoNH3) on the nucleation of InN islands during the initial stages of hydride vapor phase epitaxy on a nitrided (0001) sapphire substrate was investigated. The crystalline quality of the InN layer after subsequent lateral growth was also examined. When NH3 was flowed prior to growth, single-crystal hexagonal InN islands formed. When InN was grown with a higher PoNH3, the number of InN islands decreased remarkably while their diameter increased. The crystalline quality of InN grown on the hexagonal islands with a high PoNH3 significantly improved with increasing growth time. A strong PL spectrum was observed only from InN layers grown with a high PoNH3. It was thus revealed that an NH3 preflow and a high PoNH3 are effective for producing InN with high crystalline quality and good optical and electrical properties.

Togashi, Rie; Yamamoto, Sho; Karlsson, K. Fredrik; Murakami, Hisashi; Kumagai, Yoshinao; Holtz, Per-Olof; Koukitu, Akinori

2013-08-01

301

Improved characteristics for MOHOS memory with oxygen-rich GdO as charge storage layer annealed by NH3  

NASA Astrophysics Data System (ADS)

Characteristics of metal-oxide-high-k-oxide-silicon (MOHOS) memories with oxygen-rich or oxygen-deficient GdO as charge storage layer annealed by NH3 or N2 are investigated. Transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction are used to analyze the cross-sectional quality, composition and crystallinity, respectively, of the stacked gate dielectric with a structure of Al/Al2O3/GdO/SiO2/Si. The MOHOS capacitor with oxygen-rich GdO annealed in NH3 exhibits a good trade-off among its memory properties: large memory window (4.8 V at ±12 V, 1 s), high programming speed (2.6 V at ±12 V/100 ?s), good endurance and retention properties (window degradation of 5 % after 105 program/erase cycles and charge loss of 18.6 % at 85 °C after 10 years, respectively) due to passivation of oxygen vacancies, generation of deep-level traps in the grain boundaries of the GdO layer and suppression of the interlayer between GdO and SiO2 by the NH3 annealing.

Liu, Lu; Xu, J. P.; Chen, J. X.; Lai, P. T.

2013-10-01

302

Biological gas channels for NH3 and CO2: evidence that Rh (Rhesus) proteins are CO2 channels.  

PubMed

Physiological evidence from our laboratory indicates that Amt/Mep proteins are gas channels for NH3, the first biological gas channels to be described. This view has now been confirmed by structural evidence and is displacing the previous belief that Amt/Mep proteins were active transporters for the NH4+ ion. Still disputed is the physiological substrate for Rh proteins, the only known homologues of Amt/Mep proteins. Many think they are mammalian ammonium (NH4+ or NH3) transporters. Following Monod's famous dictum, "Anything found to be true of E. coli must also be true of elephants" [Perspect. Biol. Med. 47(1) (2004) 47], we explored the substrate for Rh proteins in the unicellular green alga Chlamydomonas reinhardtii. C. reinhardtii is one of the simplest organisms to have Rh proteins and it also has Amt proteins. Physiological studies in this microbe indicate that the substrate for Rh proteins is CO2 and confirm that the substrate for Amt proteins is NH3. Both are readily hydrated gases. Knowing that transport of CO2 is the ancestral function of Rh proteins supports the inference from hematological research that a newly evolving role of the human Rh30 proteins, RhCcEe and RhD, is to help maintain the flexible, flattened shape of the red cell. PMID:16563833

Kustu, S; Inwood, W

2006-01-01

303

Star-forming regions of the Aquila rift cloud complex. II. Turbulence in molecular cores probed by NH3 emission  

NASA Astrophysics Data System (ADS)

Aims: We intend to derive statistical properties of stochastic gas motion inside the dense, low-mass star-forming molecular cores that are traced by NH3(1, 1) and (2, 2) emission lines. Methods: We use the spatial two-point autocorrelation (ACF) and structure functions calculated from maps of the radial velocity fields. Results: The observed ammonia cores are characterized by complex intrinsic motions of stochastic nature. The measured kinetic temperature ranges between 8.8 K and 15.1 K. From NH3 excitation temperatures of 3.5-7.3 K, we determine H2 densities with typical values of nH2~ (1-6) × 104 cm-3. The ammonia abundance, X = [NH3]/[H2], varies from 2 × 10-8 to 1.5 × 10-7. We find oscillating ACFs, which eventually decay to zero with increasing lags on scales of 0.04 ? ? ? 0.5 pc. The current paradigm supposes that the star-formation process is controlled by the interplay between gravitation and turbulence with the latter preventing molecular cores from a rapid collapse due to their own gravity. Thus, oscillating ACFs may indicate a damping of the developed turbulent flows surrounding the dense but less turbulent core, a transition to dominating gravitational forces and, hence, to gravitational collapse. Appendix A is available in electronic form at http://www.aanda.org

Levshakov, S. A.; Henkel, C.; Reimers, D.; Wang, M.

2014-07-01

304

Improved characteristics for MOHOS memory with oxygen-rich GdO as charge storage layer annealed by NH3  

NASA Astrophysics Data System (ADS)

Characteristics of metal-oxide-high- k-oxide-silicon (MOHOS) memories with oxygen-rich or oxygen-deficient GdO as charge storage layer annealed by NH3 or N2 are investigated. Transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction are used to analyze the cross-sectional quality, composition and crystallinity, respectively, of the stacked gate dielectric with a structure of Al/Al2O3/GdO/SiO2/Si. The MOHOS capacitor with oxygen-rich GdO annealed in NH3 exhibits a good trade-off among its memory properties: large memory window (4.8 V at ±12 V, 1 s), high programming speed (2.6 V at ±12 V/100 ?s), good endurance and retention properties (window degradation of 5 % after 105 program/erase cycles and charge loss of 18.6 % at 85 °C after 10 years, respectively) due to passivation of oxygen vacancies, generation of deep-level traps in the grain boundaries of the GdO layer and suppression of the interlayer between GdO and SiO2 by the NH3 annealing.

Liu, Lu; Xu, J. P.; Chen, J. X.; Lai, P. T.

2014-06-01

305

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

306

Platinum(IV) analogues of AMD473 (cis-[PtCl2(NH3)(2-picoline)]): preparative, structural, and electrochemical studies.  

PubMed

The preparation and oxidation of the anticancer drug AMD473, cis-[PtCl2(NH3)(2-pic)] (2-pic = 2-methylpyridine), has been investigated. cis-[PtCl2(NH3)(2-pic)] is readily oxidized with peroxide to give the trans-dihydroxoplatinum(IV) complex cis,trans,cis-[PtCl2(OH)2(NH3)(2-pic)]. The crystal structure of this complex reveals that it is highly strained as a result of a steric clash between the methyl group of the 2-picoline ligand and an axial hydroxo ligand, with the Pt-N-C angle adjacent to this clash opened up to an unprecedented 138.6(6) degrees . Attempts at converting the dihydroxoplatinum(IV) complex to dichloro and diacetato analogues were unsuccessful with reaction with HCl leading to loss and protonation of the 2-picoline ligand to form the salt (2-picH)[PtCl5(NH3)] and the platinum(II) complex cis-[PtCl2(NH3)(2-pic)], both confirmed by crystallography. Electrochemical studies revealed that cis,trans,cis-[PtCl2(OH)2(NH3)(2-pic)] is reduced more readily (-714 mV vs Ag/AgCl) than its pyridine analogue cis,trans,cis-[PtCl2(OH)2(NH3)(pyridine)] (-770 mV vs Ag/AgCl) consistent with the steric clash in the former complex destabilizing the platinum(IV) oxidation state. PMID:16878941

Battle, Andrew R; Choi, Robin; Hibbs, David E; Hambley, Trevor W

2006-08-01

307

Ultrasensitive detection of DNA in diluted serum using NaBH4 electrooxidation mediated by [Ru(NH3)6]3+ at indium-tin oxide electrodes.  

PubMed

There is a crucial need for simple and highly sensitive techniques to detect DNA in complicated biological samples such as serum. Here we present an ultrasensitive electrochemical DNA sensor using (i) single DNA hybridization with peptide nucleic acid (PNA), (ii) selective binding of [Ru(NH(3))(6)](3+) to hybridized DNA, (iii) fast NaBH(4) electrooxidation mediated by [Ru(NH(3))(6)](3+), and (iv) low background currents of NaBH(4) at indium-tin oxide (ITO) electrodes. The [Ru(III)(NH(3))(5)NH(2)](2+) formed from [Ru(III)(NH(3))(6)](3+) in borate buffer (pH 11.0) is readily electrooxidized to both [Ru(IV)(NH(3))(5)NH(2)](3+) and Ru complex with a higher oxidation state. In the absence of [Ru(NH(3))(6)](3+) bound to the DNA-sensing ITO electrodes, the oxidation currents of NaBH(4) are very low. However, in the presence of [Ru(NH(3))(6)](3+), the oxidation currents of NaBH(4) are highly enhanced due to electron mediation of the oxidized Ru complexes. The significant enhancement in the electrocatalytic activity of sensing electrodes after [Ru(NH(3))(6)](3+) binding facilitates to obtain high signal-to-background ratios. PNA and ethylenediamine on DNA-sensing electrodes significantly decrease [Ru(NH(3))(6)](3+) binding, also allowing for high signal-to-background ratios. The oxidation charges of NaBH(4) obtained from chronocoulometry are highly reproducible. All combined effects enable the detection of DNA with a detection limit of 1 fM in ten-fold diluted human serum. The simple and fast detection procedure and the ultrasensitivity make this approach highly promising for practical DNA detection. PMID:20085331

Das, Jagotamoy; Lee, Jeong-Ah; Yang, Haesik

2010-05-01

308

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

309

Photon Stimulated Desorption  

NASA Astrophysics Data System (ADS)

The combination of the X-ray standing wave (XSW) technique and photon stimulated desorption (PSD) offers the possibility to investigate both the atomic structure as well as the mechanisms leading to the X-ray induced desorption of ions from the sample surface. Here, we present a review of surface systems studied by the XSW-PSD technique along with a brief description of the basic differences in XSW data evaluation when desorbing ions are used as secondary signal. We show how direct and indirect desorption processes can be identified and that even site-specific desorption cross-sections may be determined with this method.

Flege, Jan Ingo; Schmidt, Thomas; Falta, Jens; Hille, Alexander; Materlik, Gerhard

2013-01-01

310

Highly Sensitive NH3 Detection Based on Organic Field Effect Transistors with Tris(pentafluorophenyl)Borane as Receptor  

PubMed Central

We have increased organic field-effect transistor (OFET) NH3 response using tris-(pentafluorophenyl)borane (TPFB) as receptor. OFETs with this additive detect concentrations of 450 ppb v/v, with a limit of detection of 350 ppb, the highest sensitivity yet from semiconductor films; in comparison, when triphenylmethane (TPM) and triphenylborane (TFB) were used as an additive, no obvious improvement of sensitivity was observed. These OFETs also show considerable selectivity with respect to common organic vapors, and stability to storage. Furthermore, excellent memory of exposure was achieved by keeping the exposed devices in a sealed container stored at ?30°C, the first such capability demonstrated with OFETs.

Huang, Weiguo; Besar, Kalpana; LeCover, Rachel; Rule, Ana Maria; Breysse, Patrick N.; Katz, Howard E.

2012-01-01

311

Optical And Structural Properties Of Hydrogenated ZnO Thin Films And Their Application For NH3 Gas Sensors  

NASA Astrophysics Data System (ADS)

Measurements of the optical and structural properties of ZnO thin films (ZnO:H) deposited by magnetron sputtering in an Ar+H2 atmosphere have been performed. The optical band gap, Eopt, and the Urbach band tail width were calculated. The influence of the substrate temperature on the resistivity, optical band gap and structural properties has been studied. A discussion of the influence of Ts on the properties is presented. The sensitivity of ZnO films to exposure to NH3 has been measured by the quartz crystal microbalance method.

Dimova-Malinovska, D.; Lazarova, V.; Angelov, O.; Nichev, H.

2007-04-01

312

An AlGaAs-GaAs quantum cascade laser operating with a thermoelectric cooler for spectroscopy of NH 3  

NASA Astrophysics Data System (ADS)

A new design of AlGaAs-GaAs quantum cascade laser (QCL) operating at a wavelength around 11.2 ?m is reported. An improved injection region and increased barrier height in the active region have enabled high temperature operation with reduced temperature dependence of the threshold current. The laser has been employed at temperatures up to 244 K (accessible with a thermoelectric cooler) for spectroscopy of gas phase NH 3, using the injected current pulse to linearly tune a single mode of its multi-mode Fabry-Perot output through an absorption line of the gas.

Garcia, M.; Normand, E.; Stanley, C. R.; Ironside, C. N.; Farmer, C. D.; Duxbury, G.; Langford, N.

2003-10-01

313

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

Microsoft Academic Search

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

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

2006-01-01

314

Ferroelastic Domain of (CH3NH3)4InCl7 and Its Phase Transitions  

NASA Astrophysics Data System (ADS)

Optical observation of domain structure, differential thermal analysis, dielectric and dilatometric measurements of (CH3NH3)4InCl7 have been carried out over a temperature range from 25°C to 200°C. It has been found that the crystal undergoes phase transitions at 194°C (T1) and 190°C (T2), and is ferroelastic below T1. Taking account of the strain-compatibility relations for domain boundaries, it is suggested from the result of optical observation that the crystal symmetry is mmm, 2/m and 2/m in order of descending temperature.

Miyazaki, Akio

1992-06-01

315

Effect of internal bias field on domain switching in (CH3NH3)5Bi2Br11 crystal  

NASA Astrophysics Data System (ADS)

In this report we investigate the microscopic features of 180° domain wall dynamics and relate its dynamics to the defect structure in unipolar methylammonium bromobismuthate, (CH3NH3)5Bi2Br11, single crystal. The switching and spontaneous backswitching processes have been studied by observation of domain structure by using nematic liquid crystal method and by switching current registration. We found a two-step relaxation decay of polarization induced by Eb; the fast one decays on the time scale of milliseconds, while the slow one lasts over seconds. In the late-time regime, the stretched-exponential function was used as an empirical fit of relaxation data.

Matyjasek, K.; Rogowski, R. Z.

2006-04-01

316

Sequential bond energies of Pt +(NH 3) x ( x=1–4) determined by collision-induced dissociation and theory  

Microsoft Academic Search

The sequential bond energies of Pt+(NH3)x (x=1–4) are determined by collision-induced dissociation (CID) with Xe using guided-ion beam tandem mass spectrometry. Analysis of the kinetic energy-dependent cross sections includes consideration of multiple ion–neutral collisions, the internal energies of the complexes, and the dissociation lifetimes. We obtain the following 0K bond energies in eV (kJ\\/mol): 2.84±0.12 (274±12), 2.71±0.10 (261±10), 0.80±0.05 (77±5),

R. Liyanage; M. L. Styles; R. A. J. O’Hair; P. B. Armentrout

2003-01-01

317

Laboratory measurements of the 7. 5-9. 38-mm absorption of gaseous ammonia (NH3) under simulated Jovian conditions  

SciTech Connect

An attempt is made to infer the abundance and distribution of ammonia from RF emission measurements more accurately than heretofore, on the basis of the results of laboratory measurements for the mm-wave opacity of gaseous ammonia under simulated Jovian atmosphere conditions. The measurements were conducted at various frequencies in the 32-40 GHz range at 2 atm and 203 K; the atmospheric mixture was 88.34 percent H2, 9.81 percent He, and 1.85 percent NH3. Experimental results are found to be readily modeled by the Gross (1955) line-shape factor, rather than that of Van Vleck and Weisskopf (1945). 15 refs.

Joiner, J.; Steffes, P.G.; Jenkins, J.M. (Georgia Institute of Technology, Atlanta (USA))

1989-10-01

318

Structure of cis -[Pt(NH 3 )(2-picoline)] 2+ and DNA adduct and its bonding characteristics  

Microsoft Academic Search

Several methods including molecular mechanics, molecular dynamics, ONIOM that combines quantum chemistry with molecular mechanics\\u000a and standard quantum chemistry are used to study the configuration and electron structures of an adduct of the DNA segment\\u000a d(ATACATG*G*TACATA)d(TATGTACCATGTAT) with cis-[Pt(NH3)(2-Picoline)]2+. The investigation shows that the configuration optimized by ONIOM is similar to that determined by NMR. Strong chemical\\u000a bonds between Pt of

Muxin Jia; Kai Liu; Zuoyin Yang; Guangju Chen

2004-01-01

319

Laboratory measurements of the 7.5-9.38-mm absorption of gaseous ammonia (NH3) under simulated Jovian conditions  

NASA Technical Reports Server (NTRS)

An attempt is made to infer the abundance and distribution of ammonia from RF emission measurements more accurately than heretofore, on the basis of the results of laboratory measurements for the mm-wave opacity of gaseous ammonia under simulated Jovian atmosphere conditions. The measurements were conducted at various frequencies in the 32-40 GHz range at 2 atm and 203 K; the atmospheric mixture was 88.34 percent H2, 9.81 percent He, and 1.85 percent NH3. Experimental results are found to be readily modeled by the Gross (1955) line-shape factor, rather than that of Van Vleck and Weisskopf (1945).

Joiner, Joanna; Steffes, Paul G.; Jenkins, Jon M.

1989-01-01

320

The conformational equilibrium of CH 3CH 2CH 2NH 3+: Raman study in solution and ab initio calculations  

NASA Astrophysics Data System (ADS)

Temperature-dependent Raman measurements of n-propylammonium chloride solutions in water, concentrated hydrochloric acid and methanol yield experimental gauche-trans enthalpy differences of 0.21 ± 0.13, 0.51 ± 0.26 and 0.37 ± 0.11 kcal mol -1, respectively. Raman spectra in different aqueous solutions show that the gauche-trans equilibrium in solution is affected by the total chloride concentration. The gauche-trans enthalpy difference for CH 3CH 2CH 2NH 3+ is found by 4-31G ab initio calculations to be 0.26 kcal mol -1.

Hagemann, Hans; Bill, Hans; Mareda, Jiri

1989-05-01

321

The application of a new, simple interference technique to the determination of growth concentration gradients of the layer perovskite NH 3(CH 2) 3NH 3CdCl 4  

NASA Astrophysics Data System (ADS)

A description of a new simple microscopic interference technique is given using a Mach-Zehnder set-up in front of a microscope objective, which enables the direct visualization of concentration gradients and concentration profiles in the solution surrounding a crystal during growth from a temperature and flow controlled bulk solution. The performance and applicability of the technique is compared with the achievements obtained with the help of single and double exposure holograms during direct observation or after reconstruction of single holograms and sandwich holograms. All techniques use coherent lasers as a light source. The performance of these techniques is demonstrated on the example of concentration profiles during growth and dissolution of single crystals up to 10×10×2 mm 3 of the layer perovskite NH 3(CH 2) 3NH 3CdCl 4 from an aqueous solution in an unstirred thermostated cell. The resulting concentration profiles are analysed with the help of the solubility curve and the dependence of the refractive index of the solution on concentration and temperature.

Van Dam, J. C.; Mischgofsky, F. H.

1987-09-01

322

Evidences of the origin of N2O in the high-temperature NH3 oxidation over Pt-Rh gauze.  

PubMed

Transient isotopic experiments reveal that the mechanism of N2O formation in the high-temperature NH3 oxidation over Pt-Rh gauze involves the reaction of adsorbed ammonia intermediate species (NHx) and NO. PMID:14765216

Pérez-Ramírez, Javier; Kondratenko, Evgueni V

2004-02-21

323

Triggering N2 Uptake via Redox Induced Expulsion of Coordinated NH3 and N2 Silylation at Trigonal Bipyramidal Iron  

PubMed Central

The biological reduction of nitrogen to ammonia may occur via one of two predominant pathways in which nitrogenous NxHy intermediates including hydrazine (N2H4), diazene (N2H2), nitride (N3-) and imide (NH2-) may be involved. To test the validity of hypotheses concerning iron’s direct role in the stepwise reduction of N2, iron model systems are needed. Such systems can test the chemical compatibility of iron with various proposed NxHy intermediates, and the reactivity patterns of such species. Here we describe a TBP (SiPR3)Fe-L scaffold (SiPR3 represents [Si(o-C6H4PR2)3]?; R = Ph and iPr) where the apical site is occupied by nitrogenous ligands such as N2, N2H4, NH3 and N2R. The system accommodates terminally bound N2 in the three formal oxidation states (iron(0), +1, and +2). N2 uptake is demonstrated via displacement of its reduction partners NH3 and N2H4, and N2 functionalizaton is illustrated via electrophilic silylation.

Lee, Yunho; Mankad, Neal P.

2010-01-01

324

Computational study of Al- or P-doped single-walled carbon nanotubes as NH3 and NO2 sensors  

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) calculations were carried out to analyze the electronic and structural properties of pristine and aluminum or phosphorus doped (8,0) single walled carbon nanotube (SWCNT) as a sensor for the detection of nitrogen dioxide (NO2) and ammonia (NH3). The binding energies, equilibrium gas-nanotube distances, the amounts of charge transfer and molecular orbital schemes as well as the density of states have been calculated and used to interpret the mechanism of gas adsorption on the surface of nanotubes. In agreement with the experimental data, our results show considerable binding energy and energy gap alteration due to the adsorption of NO2 on pristine SWCNT. The results reveal that the doping of both Al and P atoms increase the capability of the nanotube for the adsorption of NO2, and the effect is more significant for the Al-doped nanotube. The Al-doped nanotube can also be considered as a good sensor for NH3 due to its high binding energy, considerable amount of charge transfer and energy band gap alteration.

Azizi, Khaled; Karimpanah, Mohammad

2013-11-01

325

[Rb(18-crown-6)][Rb([2.2.2]-cryptand)]Rb2Sn9?5NH3  

PubMed Central

The crystal structure of the title compound, poly[[(4,7,13,16,21,24-hexa­oxa-1,10-diaza­bicyclo­[8.8.8]hexa­cosa­ne)rubidium] [[(1,4,7,10,13,16-hexa­oxacyclo­octa­deca­ne)rubidium]di-?-rubidium-?-nona­stannide] penta­ammonia], {[Rb(C18H36N2O6)][Rb3Sn9(C12H24O6)C12H24O6)]·5NH3}n represents the first ammoniate of a Zintl anion together with two different chelating substances, namely 18-crown-6 and [2.2.2]-cryptand. The involvement of these large mol­ecules in the crystal structure of [Rb(18-crown-6)][Rb([2.2.2]-cryptand)]Rb2Sn9·5NH3 leads to the formation of a new structural motif, namely one-dimensionally extended double strands running parallel to [100] and built by Sn9 4? cages and Rb+ cations. The double strands are shielded by 18-crown-6 and [2.2.2]-cryptand. The cations are additionally coordin­ated by ammonia mol­ecules. One of the four independent Rb+ cations is disordered over two sets of sites in a 0.74?(2):0.26?(2) ratio.

Gaertner, Stefanie; Korber, Nikolaus

2011-01-01

326

Using Hot Emission Spectra in Generating Line Lists of Molecules (NH3, CH4) for Astrophysical Applications  

NASA Astrophysics Data System (ADS)

Spectra of cool stars, brown dwarfs and extrasolar planets (exoplanets) contain a dense forest of lines from hot molecules. Examples include CH4 and NH3 in brown dwarfs and CH4 in `hot Jupiter' exoplanets. These observations present challenges to astronomers, who typically use databases such as HITRAN intended for room-temperature applications, to model the spectral energy distributions. We have used a novel technique to combine `hot' emission spectra recorded for a range of sample temperatures (300 -- 1400°C) in order to deduce empirical lower state energies of the emitted lines. We have applied this method to NH3 in the 740 -- 2100 cm-1 range which includes the ?2 and the ?4 fundamental modes and in the 1650 -- 4000 cm-1 range which includes the ?1 and ?3 fundamental modes. We have estimated empirical lower state energies and our values have been incorporated into the line lists along with line positions and calibrated line intensities. This method is currently being extended to CH4. Our results can be used directly for the simulation of astronomical spectra. Hargreaves, R. J., Li, G., and Bernath, P. F. Astrophys. J. 735 (2011) 111. Hargreaves, R. J., Li, G., and Bernath, P. F. J. Quant. Spectrosc. Radiat. Transfer, (2012) in press.

Hargreaves, R. J.; Michaux, L.; Li, G.; Beale, C.; Irfan, M.; Bernath, P. F.

2012-06-01

327

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

328

Detection of interstellar NH3 in the far-infrared - Warm and dense gas in Orion-KL  

NASA Technical Reports Server (NTRS)

Results of an investigation are presented which show the detection of the (J,K) = a(4,3)-s(3,3) rotation-inversion transition of ammonia at 124.6 microns toward the center of the Orion-KL region. The line is found to be in emission and has a FWHM greater than or equal to 30 km/s, while the far-IR ammonia line emission probably comes mainly from the 'hot core', a compact region of warm, very dense gas previously identified by the radio inversion lines of NH3. The a(4,3)-s(3,3) line is very optically thick and it is determined that radiative excitation of the (4,3) NH3 level by far-IR emission from dust within the source can be ruled out. It is concluded that the (4,3) level is probably collisionally excited and the gas in the hot core region is warmer than the dust. Densities of approximately 10 to the 7th/cu cm are high enough to explain the observations, while shock heating by the mass outflow from IRc2 may account for the high gas temperatures in the hot core region.

Townes, C. H.; Genzel, R.; Watson, D. M.; Storey, J. W. V.

1983-01-01

329

[Emission of CH4, N2O and NH3 from vegetable field applied with animal manure composts].  

PubMed

Greenhouse gas (GHG) emission from vegetable land is of great concern recently because agriculture land is one of the major sources contributing to global GHG emission. In this study, an experiment of Lactuca sativa L. land applied with different animal manure composts was carried out in a greenhouse vegetable land located in the surburb of Beijing to monitor the emission of GHG (CH4 and N2O) and ammonia in situ, and to analyze the affecting factors of GHG and ammonia emission. Results showed that the emission factors (EFs) of CH4 from Treatment NRM, RM and CF were 0.2%, 0.027% and 0.004%, respectively,the EFs of N2O from these three treatments were 0.18%, 0.63% and 0.74%, respectively, and the EFs of ammonia were 2.00%, 3.98% and 2.53%, respectively. CH4 emission flux was significantly affected by soil temperature and humidity, while N2O emission flux was related to soil temperature, surface temperature and humidity. The emission fluxes of CH4, N2O and NH3 were significantly affected by soil moisture, but there was little relation between CH4, N2O and NH3 emissions and the ambient temperature in the greenhouse. PMID:24881375

Wan, He-Feng; Zhao, Chen-Yang; Zhong, Jia; Ge, Zhen; Wei, Yuan-Song; Zheng, Jia-Xi; Wu, Yu-Long; Han, Sheng-Hui; Zheng, Bo-Fu; Li, Hong-Mei

2014-03-01

330

Uranus and Neptune structure models with ab initio EOS data for CH4, NH3, and H2O  

NASA Astrophysics Data System (ADS)

Uranus and Neptune are supposed to be rich in ices in their deep interiors as their mean density closely resembles that of liquid water. Moreover, highly super-solar abundances of CH4 and CO, indicative of internal water, have been observed in their atmospheres. We here compare ab initio equations of state for CH4, NH3, and H2O and apply them to compute ice-rich, adiabatic internal structure models of Uranus and Neptune. The explicit consideration of the light ices CH4 and NH3 allows us to put tighter constraints on the minimum H/He abundance in their deep interior, which was found to be non-zero in all previous Uranus and in most of the Neptune models that were based on water as a proxy for ices. In particular, we investigate if hydrogen in the deep interior can solely be a result of assumed Carbon sedimentation (diamond rain), as an alternative scenario to the early accretion of H/He containing material during the formation of the planets. We conclude by discussing the deep internal H/He abundance in light of rock-rich and warmer-than-adiabatic interiors, which has been suggested to explain Uranus' low intrinsic luminosity. Our models serve to better understand the formation and bulk composition of Neptune-sized planets.

Nettelmann, Nadine; Fortney, Jonathan; Hamel, Sebastien; Bethkenhagen, Mandy; Redmer, Ronald

2014-05-01

331

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...

332

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

333

Improved optical response for N-doped anatase TiO 2 films prepared by pulsed laser deposition in N 2\\/NH 3\\/O 2 mixture  

Microsoft Academic Search

Nanostructured N-doped TiO2 films in anatase phase were prepared by laser ablation of titanium target in N2\\/O2 and NH3\\/N2\\/O2, respectively. The films were deposited on glass substrates which were heated to 400°C. The as-deposited films were characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and atomic force microscope (AFM). Nitrogen doping is more efficient when adding a little NH3 into

Peng Xu; Lan Mi; Pei-Nan Wang

2006-01-01

334

A pilot field-scale study on biotrickling filter treatment of NH 3 -containing odorous gases from organic waste composting plants  

Microsoft Academic Search

The use of a biotrickling filter was investigated for a pilot field-scale elimination of NH3 gas and other odorous gases from a composting plant in Tongzhou District, Beijing. The inlet gas flow rate was 3500 m3\\/h and NH3 concentration fluctuated between 2.76–27.84 mg\\/m3, while the average outlet concentration was 1.06 mg\\/m3 with an average of 94.9% removal. Critical volumetric loading

Nian-tao Xue; Qun-hui Wang; Chuan-fu Wu; Xiao-hong Sun; Wei-min Xie

2010-01-01

335

Effect of NH 3 flow rate on m-plane GaN growth on m-plane SiC by metalorganic chemical vapor deposition  

Microsoft Academic Search

This paper reports a study of the effect of NH3 flow rate on m-plane GaN growth on m-plane SiC with an AlN buffer layer. It is found that a reduced NH3 flow rate during m-plane GaN growth can greatly improve the recovery of in situ optical reflectance and the surface morphology, and narrow down the on-axis (101¯0) X-ray rocking curve

Qian Sun; Christopher D. Yerino; Yu Zhang; Yong Suk Cho; Soon-Yong Kwon; Bo Hyun Kong; Hyung Koun Cho; In-Hwan Lee; Jung Han

2009-01-01

336

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

337

Solid-state changes in ligand-to-metal charge-transfer spectra of (NH3)5Ru(III)(2,4-dihydroxybenzoate) and (NH3)5Ru(III)(xanthine) chromophores.  

PubMed

Five distorted-octahedral complexes containing (NH3)5Ru(III)L ions, where L = 2,4-dihydroxybenzoate or a xanthine, have been studied using a combination of X-ray crystallography, solution and polarized single-crystal electronic absorption spectroscopy, and first principles electronic structure computational techniques. Both yellow (2) and red (3) forms of the complex (NH3)5Ru(III)L, where L = 2,4-dihydroxybenzoate, as well as three xanthine complexes in which L = hypoxanthine-kappaN(7) (4), 7-methylhypoxanthine-kappaN(9) (5), and 1,3,9-trimethylxanthine-kappaN(7) (6) were examined. In the solid state, some of these complexes exhibit split low-energy ligand-to-metal charge-transfer (LMCT) bands. Traditional solid-state effects, such as ligand pi-pi overlap or hydrogen bonding that might lead to splitting of electronic absorption bands, were probed in an attempt to identify the origins of these unusual observations. For comparison, companion studies were carried out for spectroscopically normal reference complexes of the same ligands. Time-dependent density-functional theory (TD-DFT) calculations, employing modified B3LYP-type functionals with increased contributions of exact exchange, attribute the color change in the crystalline complexes 2 and 3 to pi(ligand) --> Ru[d(pi)] LMCT bands which, in the red form (3), arise from ligand donor pi-orbitals split by strongly overlapping phenyl moieties in centrosymmetric (NH3)5Ru(III)(2,4-dihydroxybenzoate) dimers. Complex 5 does not show split visible absorptions, whereas both the polarizations and energies of the split visible absorptions shown by 4 and 6 also suggest assignment as LMCT. No support is found for relating the split absorptions of 4 and 6 to the details of pi-pi xanthine overlap in the solid state; indeed, complex 4 enjoys considerably less pi-stacking overlap than does 5. We feel compelled to attribute the split absorptions in crystalline 4 and 6 to the emergence of a LMCT transition originating in the carbonyl lone pair, potentially deriving intensity from the significant intramolecular N-H...O hydrogen bonding present in both 4 and 6 (but not in 5). The electronic structure calculations suggest an O(n) --> Ru[d(sigma*)] LMCT transition; however, this novel assignment must be considered tentative. PMID:18837549

Krogh-Jespersen, Karsten; Stibrany, Robert T; John, Elizabeth; Westbrook, John D; Emge, Thomas J; Clarke, Michael J; Potenza, Joseph A; Schugar, Harvey J

2008-11-01

338

Ammonia, cyclohexane, nitrogen and water adsorption capacities of an activated carbon impregnated with increasing amounts of ZnCl 2, and designed to chemisorb gaseous NH 3 from an air stream  

Microsoft Academic Search

The adsorption capacity of ZnCl2-impregnated activated carbon (AC) for NH3 is reported in terms of stoichiometric ratio of reaction (NH3 per ZnCl2). This ratio depends on the testing conditions used. Compared to the ratio obtained under dry conditions, the ratio is higher under humid conditions or increased NH3 concentrations. The linear increase of the NH3 capacity with increasing loading of

H. Fortier; P. Westreich; S. Selig; C. Zelenietz; J. R. Dahn

2008-01-01

339

a Study of the Two-Halide Superexchange Interaction in the Compounds (NH3(CH2)(N)NH3) Copper-X for N = 2, 3, 4, and 5 and X = CHLORINE(4) and CHLORINE(2)BROMINE(2)  

NASA Astrophysics Data System (ADS)

Results of magnetic susceptibility and magnetization measurements on the eclipsed layered compounds (NH(,3)(CH(,2))(,n)NH(,3)) CuX for n = 2 and 4 with X = Cl(,4) and for n = 2 with X = Cl(,2)Br(,2) are presented. The intralayer and interlayer superexchange values for the three compounds were found to be J/k = 23.0K (+OR-) 0.5K, J'/k = -13.7K (+OR-) 0.5K; J/k = 13.0K (+OR-) 0.2K, J'/k = -1.5K (+OR-) 0.2K; and J/k = 15.0K (+OR-) 1.0K, J'/k = -31.0K (+OR-) 1.0K respectively. These values along with those for the n = 3 and 5 members of the above Cl(,4) series were used to obtain the first direct measurement of the two-halide superexchange interaction in a transition metal. Strong evidence is presented that the halide-halide overlap is the primary factor in determining the strength of the superexchange interaction through a two-halide bridge rather than the cation-cation separation as has previously been suggested. A Rayleigh-Schrodinger perturbation calculation is also presented on a four-center, four-electron cluster which represents a linear two-halide superexchange bridge. The results of the calculation support the experimental findings that the critical parameter involved in the two-halide superexchange is the interaction between the intervening diamagnetic anions.

Snively, Leslie Orin

340

Structure cristalline du cyclotétraphosphate triple de lithium sodium et d'éthylène diammonium trihydrate NaLi[NH 3?(CH 2) 2?NH 3]P 4O 12.3H 2O  

NASA Astrophysics Data System (ADS)

Classical methods extensively used for the synthesis of inorganic condensed phosphates are known to give compounds that are intermediate between inorganic and organic. We prepared the title compound to examine the possibility of using, in this new field, the ion exchange resin method. The cyclotetraphosphate is the first condensed phosphate associated with the ethylenediammonium ion and mixed monovalent cations. We describe its chemical preparation and crystal structure. The orthorhombic unit cell has the following dimensions: a = 13.135(3) Å, b = 7.737(2) Å, c = 15.478(4) Å, V = 1573(2)Å 3, Dm = 2.020 g/cm 3, Dx = 1.951 g/cm 3, ? = 0.297 mm -1, space group is Pcca with Z = 4. The crystal structure has been solved by using 2005 unique reflections with a final R value of 0.043 ( Rw = 0.045). The principal feature of this compound lies in its linear atomic arrangement of the monovalent cations with different coordination polyhedra. The lithium cation is statistically distributed on two general positions with 0.5 occupancy, or moves very rapidly between these two positions. The P 4O 4-12 ring anion is located around the twofold axis. The cohesiveness and the stability of the crystal result from two kinds of weak hydrogen bonds: N?H---O and O(W)?H---O. The structure of this compound is compared to that of Na 2[NH 3?(CH 2) 2?NH 3]P 4O 12.2H 2O; half the sodium positions are occupied by lithium cations.

Bdiri, Mohamed; Jouini, Amor

1989-12-01

341

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

342

Characterisation of CuMFI catalysts by temperature programmed desorption of NO and temperature programmed reduction. Effect of the zeolite Si\\/Al ratio and copper loading  

Microsoft Academic Search

Copper MFI zeolites with different Si\\/Al ratios and different copper loadings, prepared by ion exchange, were characterised by XRD, H2-TPR and NO TPD. The results indicated the existence of diverse copper species in CuMFI catalysts, such as isolated CU2+, Cu+ ions and CuO species, whose concentrations depends on the catalyst Si\\/Al ratio and copper loading. In underexchanged catalysts (catalysts with

C. Torre-Abreu; M. F. Ribeiro; C. Henriques; G. Delahay

1997-01-01

343

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

344

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

345

CO(2) Laser Absorption Coefficients for Determining Ambient Levels of O(3), NH(3), and C(2)H(4).  

PubMed

A carbon dioxide laser source was used to determine absorption coefficients for dilute absorber-air mixtures at wavelengths corresponding to several vibration-rotation lines in each branch of the 00 degrees 1-02 degrees 0 band at 9.4 microm and the 00 degrees 1-10 degrees 0 band at 10.4 microm. For all samples the total pressure was 1 atm and the temperature was 300 K; the concentrations ranged from 10 ppm (parts per million by volume) to 357 ppm for NH(3) and C(2)H(4), and from 10 ppm to 80 ppm for O(3). The absorption coefficients are tabulated, and the use of selected laser lines in monitoring ambient concentrations is discussed. PMID:20134799

Patty, R R; Russwurm, G M; McClenny, W A; Morgan, D R

1974-12-01

346

Optical Absorption in Band-Edge Region of ( CH3NH3)3Bi2I9 Single Crystals  

NASA Astrophysics Data System (ADS)

Optical absorption spectra were measured around the band edge in ( CH3NH3)3Bi2I9 single crystals. In the very thin crystals, an intrinsic exciton band appears clearly at 2.51 eV at low temperatures, and the absorption peak remains even at room temperature reflecting a large binding energy of more than 300 meV. The exciton band does not show a discontinuous shift near the temperature where the methylammonium ions induce a structural phase transition. This fact indicates that the exciton states are independent of the methylammonium ions. The origin of the exciton band is examined on the basis of the annealing effect on the absorption bands in vacuum-evaporated films. The lower energy tail of the exciton band obeys the Urbach rule between 78 and 350 K. The detailed analysis by the Urbach rule reveals that the exciton-phonon interaction in the present system is relatively strong.

Kawai, Taketoshi; Ishii, Atsuko; Kitamura, Takako; Shimanuki, Shigetaka; Iwata, Makoto; Ishibashi, Yoshihiro

1996-05-01

347

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.

348

Reactions of [NH3+*, H2O] with carbonyl compounds: a McLafferty rearrangement within a complex?  

PubMed

The reactions of the water solvated ammonia radical cation [NH(3)(+*), H(2)O] with a variety of aldehydes and ketones were investigated. The reactions observed differ from those of low energy aldehydes and ketones radical cations, although electron transfer from the keto compound to ionized ammonia is thermodynamically allowed within the terbody complexes initially formed. The main process yields an ammonia solvated enol with loss of water and an alkene. This process corresponds formally to a McLafferty fragmentation within a complex. With aldehydes, another reaction can take place, namely the transfer of the hydrogen from the CHO group to ammonia, leading to the proton bound dimer of ammonia and water, and to the NH(4)(+) cation. Comparison between the available experimental results leads to the conclusion that the McLafferty fragmentation occurs within the terbody complex initially formed, with no prior ligand exchange, the water molecule acting as a spectator partner. PMID:15234355

van der Rest, G; Jensen, L B; Abdel-Azeim, S; Mourgues, P; Audier, H E

2004-07-01

349

Molecular dynamics of the methylammonium cation in [CH3NH3]5Bi2Cl11.  

PubMed

The 1H relaxation times T1 of methylammonium in chlorobismuthate(III) were measured in the temperature range from 50 to 270 K with a SXP 4/100 Bruker pulse spectrometer at 55.2 MHz. It was found that the T1 temperature dependence has three minima. The individual relaxation rates of the three-proton groups can be described by the O'Reilly and Tsang formula. The results obtained from the fitting procedure, using the typical Woessner formula for complex compounds, allow to conclude that the low-temperature minimum is due to the relaxation of all CH3 groups and the other two minima are due to the relaxation of two and four NH3 groups, respectively. This assignment is based on the X-ray results showing that methylammonium cations are differently bonded in this crystal. PMID:7827971

Medycki, W; Pi?lewski, N; Jakubas, R

1993-09-01

350

Specific Heat and Phase Transition Phenomena in (CH3NH3)5Bi2Cl11  

NASA Astrophysics Data System (ADS)

Specific heat of (CH3NH3)5Bi2Cl11 was measured by adiabatic calorimetry between 13 K and 325 K. A typical second-order type of anomaly was observed at 307.4 K. The enthalpy and entropy of transition were determined as 3.06 kJ mol-1 and 10.6 J K-1 mol-1, respectively. A broad hump in the curve of specific heat was found around 160 K. Its contribution was estimated as the excess specific heat extending from about 100 K to 200 K over an assumed normal base line, which results in the values of enthalpy and entropy as 1.57 kJ mol-1 and 9.85 J K-1 mol-1, respectively. The phase transition in the crystal was discussed in connection with such specific heat anomalies.

Iwata, Makoto; Tojo, Takeo; Atake, Tooru; Ishibashi, Yoshihiro

1994-10-01

351

Kinetics of ferroelectric switching in unipolar (CH3NH3)5Bi2Br11 crystal  

NASA Astrophysics Data System (ADS)

Ferroelectric switching in unipolar (CH3NH3)5Bi2Br11 crystal has been studied by optical observation of the domain structure in low electric fields and switching current registration in high fields. We discuss investigations on the temporal behaviour of the electric polarization in static electric fields as well as polarization decay after removal of the electric field. The backswitching process appears to have a correlation to a defect-induced internal field in the crystal. For the interpretation of experimental data we utilize the classical nucleation and growth model of phase transformation (e.g. Avrami-Kolmogorov theory). An analysis assuming a statistical distribution of the characteristic domain growth times is proposed to explain and to find the functional form of the experimental data.

Rogowski, R. Z.; Matyjasek, K.; Jakubas, R.

2005-12-01

352

Comparative NH 3-sensing characteristic studies of PANI/TiO II nanocomposite thin films doped with different acids  

NASA Astrophysics Data System (ADS)

Polyaniline/titanium dioxide (PANI/TiO II) nanocomposite thin films were synthesized by in-situ self-assembly method, which were doped with p-toluene sulphonic acid (p-TSA) and hydrochloric acid (HCl), respectively. The thin films were characterized by using UV-Vis absorption spectroscopy and scanning electron microscope (SEM), and the NH 3 gas sensitive properties of the thin films were investigated at room temperature. The results showed that the PANI/TiO II thin film doped with HCl was superior to that doped with p-TSA in terms of response-recovery characteristics. The surface morphology characterization of the thin films were performed to explain the different gas-sensing properties.

Tai, Huiling; Jiang, Yadong; Xie, Guangzhong; Yu, Junsheng; Ying, Zhihua; Chen, Xuan

2008-03-01

353

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

354

Two mixed-NH3/amine platinum (II) anticancer complexes featuring a dichloroacetate moiety in the leaving group  

NASA Astrophysics Data System (ADS)

Two mixed-NH3/amine platinum (II) complexes of 3-dichoroacetoxylcyclobutane-1, 1-dicarboxylate have been prepared in the present study and characterized by elemental analysis and IR, HPLC-MS and 1H, 13C-NMR. The complexes exist in equilibrium between two position isomeric forms and undergo hydrolysis reaction in aqueous solution, releasing the platinum pharmacophores and dichloroacetate which is a small-molecular cell apoptosis inducer. Both complexes were evaluated for in vitro cytotoxic profile in A549, SGC-7901 and SK-OV-3 caner cells as well as in BEAS-2B normal cells. They exhibit markedly cytoxicity toward cancer cells by selectively inducing the apoptosis of cancer cells, whereas leaving normal cells less affected. They have also the ability to overcome the resistance of SK-OV-3 cancer cells to cisplatin. Our findings offer an alternative novel way to develop platinum drugs which can both overcome the drug resistance and selectively target tumor cells.

Liu, Weiping; Su, Jia; Jiang, Jing; Li, Xingyao; Ye, Qingsong; Zhou, Hongyu; Chen, Jialin; Li, Yan

2013-08-01

355

Effect of dissolved oxygen on etching process of Si(111)in 2.5% NH 3 solution  

NASA Astrophysics Data System (ADS)

Etching processes of Si(111) in 2.5% NH 3 solution (pH 12) were examined with attention to the effect of oxygen dissolved in the solution. Atomic force microscopy observation showed that many etch pits were formed on the surface in the solution containing dissolved oxygen at high concentrations. In contrast, the surface was atomically flattened by removing dissolved oxygen from the solution. Infrared absorption spectroscopy revealed that the surface was hydrogen-terminated after treatment with the solutions with and without dissolved oxygen, and that dissolved oxygen degraded the homogeneity of the surface. It was also found that dissolved oxygen lowered the etching rate of Si(111) in the solution.

Fukidome, Hirokazu; Matsumura, Michio

2000-09-01

356

Rh proteins vs Amt proteins: an organismal and phylogenetic perspective on CO2 and NH3 gas channels.  

PubMed

Rh (Rhesus) proteins are homologues of ammonium transport (Amt) proteins. Physiological and structural evidence shows that Amt proteins are gas channels for NH(3), but the substrate of Rh proteins, be it CO2 as shown in green alga, or NH3/NH4+ as shown in mammalian cells, remains disputed. We assembled a large dataset generated of Rh and Amt to explore how Rh originated from and evolved independently of Amt relatives. Analysis of this rich data implies that Rh was split from Amt first to emerge in archaeal species. The Rh ancestor underwent divergence and duplication along speciation, leading to neofunctionalization and subfunctionalization of the Rh family. The characteristic organismal distribution of Rh vs. Amt reflects their early separation and subsequent independent evolution: they coexist in microbes and invertebrates but do not in fungi, vascular plants or vertebrates. Rh gene-duplication was prominent in vertebrates: while epithelial RhBG/RhCG displayed strong purifying selection, erythroid Rh30 and RhAG experienced different episodes of positive selection in each of which adaptive evolution occurred at certain time points and in a few codon sites. Mammalian Rh30 and RhAG were subject to particularly strong positive selection in some codon sites in the lineage from rodents to human. The grounds of this adaptive evolution may be driven by the necessity to increase the surface/volume ratio of biconcave erythrocytes for facilitative gas diffusion. Altogether, these results are consistent with Rh proteins not being the orthologue of Amt proteins but having gained the function for CO2/HCO3- transport, with important roles in systemic pH regulation. PMID:16564193

Peng, J; Huang, C H

2006-01-01

357

Emissions of NO and NH3 from a Typical Vegetable-Land Soil after the Application of Chemical N Fertilizers in the Pearl River Delta  

PubMed Central

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.

Li, Dejun

2013-01-01

358

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

359

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

360

Influence of bulking agents on CH4, N2O, and NH3 emissions during rapid composting of pig manure from the Chinese Ganqinfen system.  

PubMed

Mismanagement of the composting process can result in emissions of CH4, N2O, and NH3, which have caused severe environmental problems. This study was aimed at determining whether CH4, N2O, and NH3 emissions from composting are affected by bulking agents during rapid composting of pig manure from the Chinese Ganqinfen system. Three bulking agents, corn stalks, spent mushroom compost, and sawdust, were used in composting with pig manure in 60 L reactors with forced aeration for more than a month. Gas emissions were measured continuously, and detailed gas emission patterns were obtained. Concentrations of NH3 and N2O from the composting pig manure mixed with corn stalks or sawdust were higher than those from the spent mushroom compost treatment, especially the sawdust treatment, which had the highest total nitrogen loss among the three runs. Most of the nitrogen was lost in the form of NH3, which accounts for 11.16% to 35.69% of the initial nitrogen. One-way analysis of variance for NH3 emission showed no signi?cant differences between the corn stalk and sawdust treatments, but a signi?cant difference was noted between the spent mushroom compost and sawdust treatments. The introduction of sawdust reduced CH4 emission more than the corn stalks and spent mushroom compost. However, there were no significant differences among the three runs for total carbon loss. All treatments were matured after 30 d. PMID:24711356

Sun, Xiang-Ping; Lu, Peng; Jiang, Tao; Schuchardt, Frank; Li, Guo-Xue

2014-04-01

361

Influence of bulking agents on CH4, N2O, and NH3 emissions during rapid composting of pig manure from the Chinese Ganqinfen system*  

PubMed Central

Mismanagement of the composting process can result in emissions of CH4, N2O, and NH3, which have caused severe environmental problems. This study was aimed at determining whether CH4, N2O, and NH3 emissions from composting are affected by bulking agents during rapid composting of pig manure from the Chinese Ganqinfen system. Three bulking agents, corn stalks, spent mushroom compost, and sawdust, were used in composting with pig manure in 60 L reactors with forced aeration for more than a month. Gas emissions were measured continuously, and detailed gas emission patterns were obtained. Concentrations of NH3 and N2O from the composting pig manure mixed with corn stalks or sawdust were higher than those from the spent mushroom compost treatment, especially the sawdust treatment, which had the highest total nitrogen loss among the three runs. Most of the nitrogen was lost in the form of NH3, which accounts for 11.16% to 35.69% of the initial nitrogen. One-way analysis of variance for NH3 emission showed no significant differences between the corn stalk and sawdust treatments, but a significant difference was noted between the spent mushroom compost and sawdust treatments. The introduction of sawdust reduced CH4 emission more than the corn stalks and spent mushroom compost. However, there were no significant differences among the three runs for total carbon loss. All treatments were matured after 30 d.

Sun, Xiang-ping; Lu, Peng; Jiang, Tao; Schuchardt, Frank; Li, Guo-xue

2014-01-01

362

Low Dislocation Densities of Nitride-Based Light-Emitting Diodes with a Preflow of NH3 Source before Growth of AlN Buffer Layer  

NASA Astrophysics Data System (ADS)

In this study, the AlN buffer layer grown on c-plane sapphire (Al2O3) substrates by metal--organic chemical vapor deposition (MOCVD) was controlled by a preflow of the NH3 source. With the treatment of NH3 preflow, the monolayer of AlN was formed on the surface of a sapphire substrate by the decomposition of the NH3 source and Al2O3 substrate. It was found that the density of threading dislocations significantly decreased owing to the abatement of lattice mismatch between a GaN layer and a sapphire substrate. At an injection current of 350 mA, the light output intensity of the light-emitting diode (LED) with NH3 preflow was increased by 14.1% compared with that of a conventional LED. On the other hand, LEDs with NH3 preflow treatment could endure electrostatic discharge (ESD) surges up to -3000 V and caused a low rate of light output degradation at a high ambient temperature.

Wang, Chun-Kai; Chiou, Yu-Zung; Sun, De-Jun; Chiang, Tsung-Hsun

2013-01-01

363

Electronic and Excitonic Structures of Inorganic-Organic Perovskite-Type Quantum-Well Crystal (C4H9NH3)2PbBr4  

NASA Astrophysics Data System (ADS)

The electronic and excitonic structures of an inorganic-organic perovskite-type quantum-well crystal (C4H9NH3)2PbBr4 have been investigated by optical absorption, photoluminescence, electroabsorption, two-photon absorption, and magnetoabsorption spectroscopies. Excitons in (C4H9NH3)2PbBr4 are of the Wannier-type, and ns (n? 2) excitons form an ideal two-dimensional Wannier exciton system. The binding energy, longitudinal--transverse splitting energy, and exchange energy of 1s excitons have been determined to be 480, 70 and 31 meV, respectively. These high values originate from both a strong two-dimensional confinement and the image charge effect. These values are larger than those in (C6H13NH3)2PbI4, owing to the smaller dielectric constant of the well layer in (C4H9NH3)2PbBr4 than that in (C6H13NH3)2PbI4. The seemingly unusual electric-field dependence of excitons resonance is also reasonably understood by taking the image charge effect into account.

Tanaka, Kenichiro; Takahashi, Takayuki; Kondo, Takashi; Umeda, Kenichi; Ema, Kazuhiro; Umebayashi, Tsutomu; Asai, Keisuke; Uchida, Kazuhito; Miura, Noboru

2005-08-01

364

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

365

Theoretical study of the hydrogen release mechanism from a lithium derivative of ammonia borane, LiNH 2BH 3-NH 3BH 3  

NASA Astrophysics Data System (ADS)

Ammonia borane and lithium amidoborane proved to have potential as efficient hydrogen storage materials. Although a combination of both compounds, LiNH 2BH 3-NH 3BH 3 has been shown to have even better hydrogen release characteristics, the inherent process was not clear. We determined the reaction mechanism of H 2 release from LiNH 2BH 3-NH 3BH 3 using computational quantum chemistry methods (MP2 and CCSD(T) methods and aug-cc-pVnZ basis sets). The energy barrier for H 2 release becomes lower than in pure LiNH 2BH 3 or NH 3BH 3 in agreement with experiment. Relevant transition structures are analyzed in detail and the initial formation of a cyclic adduct is likely responsible for the strong reduction of energy barriers.

Swinnen, Saartje; Nguyen, Vinh Son; Nguyen, Minh Tho

2011-11-01

366

Interplay of Hydrogen-Bond and Coordinate Covalent-Bond Interactions in Self-Assembly of NH3 Molecules on the Si(001) Surface  

NASA Astrophysics Data System (ADS)

An exchange of hydrogen-bond and coordinate covalent-bond (dative-bond) interactions is found to play a critical role in the self-assembly of NH3 molecules on the Si(001) surface. An NH3 molecule in the height of ˜3 10Å above the surface is attracted toward the preadsorbed NH2 moiety through the long-range H-bond interaction. Within ˜3Å, the H-bond interaction becomes repulsive, and instead the dative bond with the buckled-down Si atom governs the adsorption process. The interplay of the two interactions induces the clustering and the zigzag feature of the dissociatively adsorbed NH3 molecules on the Si(001) surface.

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

2008-06-01

367

The enhancement for SCR of NO by NH3 over the H2 or CO pretreated Ag/?-Al2O3 catalyst.  

PubMed

H2 or CO pretreatment had been processed on the Ag/?-Al2O3 catalyst which significantly enhanced its NH3-SCR activity. The main purpose of this study was to prove that the impacts of pretreatment on silver species caused the enhancement. XRD, UV-vis, XPS, in situ FTIR and NO-TPD results showed the relationship between pretreatment, Ag species, NOX adsorption and NOX conversion. Extra nitrates were adsorbed on the Ag clusters which were produced by the pretreatment, thereby enhancing the activity. The reactivities between NO and NH3 had been studied. The difference between CO-pretreatment and H2-pretreatment had also been discussed. Furthermore, the durability and stability of the pretreated sample were tested. Therefore, a modified Ag2O/Al2O3 catalyst for NH3-SCR was researched. PMID:24831955

Yu, Lemeng; Zhong, Qin; Zhang, Shule

2014-06-28

368

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

NASA Technical Reports Server (NTRS)

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 independent 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 constrasted with those for the corresponding reactions of H and OH with PH3.

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

1983-01-01

369

Birefringence, X-ray and neutron diffraction measurements on the structural phase transitions of (CH 3NH 3) 2 MnCl 4 and (CH 3NH 3) 2FeCl 4  

NASA Astrophysics Data System (ADS)

We used optical birefringence, X-ray and neutron diffraction methods with single crystals to study the structural phase transitions of the perowskite-type layer structures of (CH 3NH 3) 2MeCl 4 with Me=Mn, Fe. The Mn-compound shows the following structural transitions at 394 K — a continuous order-disorder phase transition from tetragonal symmetry {I4}/{mmm} to orthorhombic space group Abma ( Cmca in reference 10); at 257 K — a discontinuous transition to a second tetragonal modification; at 95 K — a discontinuous transition to a monoclinic phase. For the Fe-compound the corresponding transition temperatures are 328 K and 231 K, respectively. A low temperature monoclinic phase could not be observed. The lattice parameters of the different modifications were determined as a function of temperature. The temperature dependent course of the order parameter has been investigated for the order—disorder transition. For both compounds, all the methods used gave the same value for the critical exponent of ? = 0.315.

Knorr, K.; Jahn, I. R.; Heger, G.

1974-07-01

370

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

371

Optical Properties of Electron Trapped Center in Layered Ionic Crystals (CH3NH3)2CdCl4 and (C2H5NH3)2CdCl4 Irradiated with X-Rays at 15 K  

NASA Astrophysics Data System (ADS)

New optical absorption bands (IR bands) were found at around 10˜20 kcm-1 besides absorption band of Cl2- molecular center in two-dimensional crystals of (CH3NH3)2CdCl4 and (C2H5NH3)2CdCl4 irradiated with X-rays at 15 K. The absorption intensities increase with the X-ray dosage in proportion to that of the Cl2- center and decrease at temperatures higher than 25 K for (CH3NH3)2CdCl4 and 35 K for (C2H5NH3)2CdCl4 accompanying the decrease of Cl2-. The both bands are also bleached by the light irradiation on the IR bands at 15 K. The IR bands are assigned to an electron center where an electron is trapped by an alkylammonium head in the neighborhood of a Cl- vacancy.

Yoshinari, Takehisa; Matsuyama, Tomochika; Yamaoka, Hitoshi; Aoyagi, Kiyoshi

1989-11-01

372

Experimental (FT-IR and FT-RS) and theoretical (DFT) studies of molecular structure and internal modes of [Mn(NH 3) 6](NO 3) 2  

Microsoft Academic Search

Fourier-transform Raman and infrared spectra of [Mn(NH3)6](NO3)2 were recorded and interpreted by comparison with respective theoretical spectra calculated using DFT method. The [Mn(NH3)6]2+ cation equilibrium geometry with C1 symmetry, harmonic vibrational frequencies, infrared and Raman scattering intensities were determined using B3LYP\\/LAN2LTZ+\\/6-311+G(d,p) level of theory. The band assignment was based on potential energy distribution (PED) of normal modes. The computations of

Kacper Dru?bicki; Edward Mikuli

2010-01-01

373

Improved Determination of the 10-00 Rotational Frequency of NH3D+ from the High-resolution Spectrum of the ?4 Infrared Band  

NASA Astrophysics Data System (ADS)

The high-resolution spectrum of the ?4 band of NH3D+ has been measured by difference frequency IR laser spectroscopy in a multipass hollow cathode discharge cell. From the set of molecular constants obtained from the analysis of the spectrum, a value of 262817 ± 6 MHz (±3?) has been derived for the frequency of the 10-00 rotational transition. This value supports the assignment to NH3D+ of lines at 262816.7 MHz recorded in radio astronomy observations in Orion-IRc2 and the cold prestellar core B1-bS.

Doménech, J. L.; Cueto, M.; Herrero, V. J.; Tanarro, I.; Tercero, B.; Fuente, A.; Cernicharo, J.

2013-07-01

374

Partial pressures and nature of products. Application to the photolysis of PH 3 and NH 3 in the atmosphere of jupiter and saturn  

NASA Astrophysics Data System (ADS)

The photolysis of mixtures of gases containing NH 3 or PH 3 presents important differences mainly due to the strength of the X-H bond. On some examples, these differences are evidenced and the consequences for mixtures of gases containing these two compounds are shown: the photolysis of ammonia and ethylene mainly gives ethyl-, butyl- and hexylamine whereas the photolysis of phosphine and ethylene leads to ethyl- and vinylphosphine. When gaseous mixtures of NH 3, PH 3 and ethylene are photolyzed together, the presence of phosphine dramatically decreases the formation of nitrogen derivatives. The relevance of such lab studies to the atmospheres of Jupiter and Saturn is discussed.

Guillemin, J.-C.; El Chaouch, S.; Bouayad, A.; Janati, T.

375

Partial pressures and nature of products. Application to the photolysis of PH3 and NH3 in the atmosphere of Jupiter and Saturn.  

PubMed

The photolysis of mixtures of gases containing NH3 or PH3 presents important differences mainly due to the strength of the X-H bond. On some examples, these differences are evidenced and the consequences for mixtures of gases containing these two compounds are shown: the photolysis of ammonia and ethylene mainly gives ethyl-, butyl- and hexylamine whereas the photolysis of phosphine and ethylene leads to ethyl- and vinylphosphine. When gaseous mixtures of NH3, PH3 and ethylene are photolyzed together, the presence of phosphine dramatically decreases the formation of nitrogen derivatives. The relevance of such lab studies to the atmospheres of Jupiter and Saturn is discussed. PMID:11605639

Guillemin, J C; El Chaouch, S; Bouayad, A; Janati, T

2001-01-01

376

Pyroelectric and Dilatometric Studies on the Low Temperature Ferroelectric Phase Transition of (CH3NH3)5Bi2Br11  

NASA Astrophysics Data System (ADS)

The results of the linear thermal expansion studies on (CH3NH3)5Bi2Br11 single crystals in the temperature range 60-340 K are presented. The thermal anomaly in the vicinity of 77 K is assigned to the phase transition classified as close to first order type. The pyroelectric measurements of (CH3NH3)5Bi2Br11 were carried out in the range of 45-320 K along the a- and c-axis. The step-like change in the spontaneous polarization along the a-axis at 77 K indicates a discontinuous character of ferroelectric transition.

Dziedzic, J.; Mróz, J.; Jakubas, R.

2006-09-01

377

The relationship between NH3 emissions from a poultry farm and soil NO and N2O fluxes from a downwind forest  

NASA Astrophysics Data System (ADS)

Intensive livestock farms emit large concentrations of NH3, most of which is deposited very close to the source. The presence of trees enhances the deposition. Rates to downwind forests can exceed 40 kg N ha-1 y-1. The steep gradient in large NH3 concentrations of 34.3±20.4, 47.6±24.9, 21.7±16.8 µg NH3 m3 at the edge of a forest 15, 30 and 45 m downwind of the farm to near background concentrations within 270 m downwind (1.15±0.7 µg NH3 m3) provides an ideal site to study the effect of different rates of atmospheric NH3 concentrations and inferred deposition on biological and chemical processes under similar environmental conditions. We have investigated the effect of different NH3 concentrations and implied deposition rates on the flux of NO and N2O from soil in a mixed woodland downwind of a large poultry farm (160 000 birds) in Scotland, which has been operating for about 40 years. Measurements were carried out for a 6 month period, with hourly NO flux measurements, daily N2O fluxes close to the farm and monthly at all sites, and monthly cumulative wet and dry N deposition. The increased NH3 and NH4+ deposition to the woodland increased emissions of NO and N2O and soil available NH4+ and NO3- concentrations. Average NO and N2O fluxes measured 15, 25 and 45 m downwind of the farm were 111.2±41.1, 123.3±40.7, 38.3±28.8 µg NO-N m-2 h-1 and 9.9±7.5, 34.3±33.3 and 21.2±6.1 µg N2O-N m-2 h-1, respectively. At the background site 270 m downwind the N2O flux was reduced to 1.75±2.1 µg N2O-N m-2 h-1. NO emissions were significantly influenced by seasonal and daily changes in soil temperature and followed a diurnal pattern with maximum emissions approximately 3 h after noon. For N2O no consistent diurnal pattern was observed. Changes in soil moisture content had a less clear effect on the NO and N2O flux. In spite of the large NO and N2O emissions accounting for >3% of the N deposited to the woodland downwind of the farm, extrapolation to the entire British poultry flock suggests that these NH3 emissions contribute to less than 0.5% and 0.02%, respectively of the total annual UK NOx and N2O emissions.

Skiba, U.; Dick, J.; Storeton-West, R.; Lopez-Fernandez, S.; Woods, C.; Tang, S.; Vandijk, N.

2006-08-01

378

Fast temperature programmed sensing for micro-hotplate gas sensors  

Microsoft Academic Search

We describe an operating mode of a gas sensor that greatly enhances the capability of the device to determine the composition of a sensed gas. The device consists of a micromachined hotplate with integrated heater, heat distribution plate, electrical contact pads, and sensing film. The temperature programmed sensing (TPS) technique uses millisecond timescale temperature changes to modify the rates for

R. E. Cavicchi; J. S. Suehle; K. G. Kreider; M. Gaitan; P. Chaparala

1995-01-01

379

Characterization of nickel loaded mordenite catalysts by temperature programmed reduction  

Microsoft Academic Search

Temperature programmed reduction (TPR) has been used to study the redox behavior of Ni(II) ions in nickel sodium mordenite (NiNaM) and decationated nickel mordenite (NiHM). The TPR profiles suggest that Ni(II) ions occupy nonequivalent sites with different cooridination states in the mordenite. The reducibility of Ni(II) depends strongly on the zeolite acidity.

Z. Popova; R. Dimitrova; Chr Dimitrova; G. Wendt

1989-01-01

380

Temperature programmed reduction of silica supported nickel catalysts  

Microsoft Academic Search

Nickel oxide promoted catalysts are prepared by simple precipitation, precipitation from homogeneous solution and impregnation methods and their reduction behavior is monitored with temperature programmed reduction (TPR) technique. The effect of different parameters such as metal loading, method of preparation and heat treatment temperature are also observed on the reducibility of the catalysts. It is observed that reduction temperature increases

M. Afzall; C. R. Theocharis; S. Karim

1993-01-01

381

High-Pressure Temperature-Programmed Reduction of Sulfided Catalysts  

Microsoft Academic Search

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

Franck Labruyère; Michel Lacroix; Daniel Schweich; Michèle Breysse

1997-01-01

382

Cerium dioxide crystallite sizes by temperature-programmed reduction  

Microsoft Academic Search

Yao and Yao recently reported that the temperature-programmed reduction (TPR) traces of unsupported ceria show two peaks, which are associated with surface capping oxide ions and bulk ions, respectively. The work reported here has confirmed their qualitative relationship between the magnitude of the capping oxide peak and BET surface areas of the ceria specimens. Furthermore, the observed quantity of hydrogen

M. F. L. Johnson; J. Mooi

1987-01-01

383

Temperature programmed reduction studies of nonpyrophoric Raney nickel catalysts  

Microsoft Academic Search

Temperature programmed reduction studies have revealed that the surface of nonpyrophoric Raney nickel catalysts is covered by readily reduceable nonstoichiometric metaloxygen structures. A method is suggested to calculate kinetic reaction parameters on the basis of analyzing the shape of one of the TPR curves.

A. B. Fasman; S. D. Mikhailenko; E. V. Leongard; T. A. Khodareva; A. I. Lyashenko

1989-01-01

384

Kinetics of hydrogen adsorption and desorption on Si(100) surfaces  

NASA Astrophysics Data System (ADS)

The kinetics of molecular hydrogen reactions at the Si (100) surface has been studied by simulation to extract the physics underlying two unexpected experimental observations: apparently first-order desorption kinetics and an increase in sticking probability with hydrogen coverage. At a partially H-terminated Si(100) surface, each Si dimer assumes an unoccupied dimer (UOD), singly occupied dimer (SOD), or doubly occupied dimer (DOD) structure. In our hydrogen reaction model based on an inter-dimer mechanism, a site consisting of an adjacent pair of a DOD and a UOD (DOD/UOD) is a key component for the desorption and adsorption kinetics of hydrogen at the Si(100) surface. To simulate reaction kinetics of both reactions, DU (D: DOD, U: UOD) and SS (S: SOD) pathways are proposed: DU pathway claims that the adsorption as well as desorption of hydrogen takes place at common sites having a cis-configured SOD/SOD pair that is transformed transiently from a DOD/UOD pair by H(D) diffusion. Thus the adsorption obeys the so-called 4H mechanism, but the desorption obeys the 2H mechanism. SS pathway claims that the adsorption occurs at sites having a UOD/UOD pair, and the desorption occurs at sites having a cis-configured SOD/SOD pair that is generated by diffusion of isolated SODs. To simulate temperature-programmed-desorption spectra and sticking probability vs coverage curves, thermo-statistics for a lattice-gas system characterized with parameters for hydrogen pairing and dimer clustering is used to evaluate equilibrium populations of DOD/UOD pairs and isolated SODs. The model simulation based on the above reaction model successfully reproduces all of the complicated, coverage dependent adsorption and desorption reactions of hydrogen at Si(100) surfaces. Specifically, at high coverage above 0.1 ML majority of the adsorption and desorption proceed along the DU pathway. Hence, it is suggested that the adsorption and desorption in the high coverage regime are not microscopically reversible. On the other hand, at low coverages below 0.1 ML, the simulation shows up that the majority of adsorption proceeds along the SS pathway, and the desorption by the DU pathway. Since both reactions obey the 2H mechanism, it is suggested that the desorption and adsorption in the low coverage regime are microscopically reversible.

Narita, Yuzuru; Inanaga, Shoji; Namiki, Akira

2013-06-01

385

Indium nitride surface structure, desorption kinetics and thermal stability  

NASA Astrophysics Data System (ADS)

Unique physical properties such as small effective mass, high electron drift velocities, high electron mobility and small band gap energy make InN a candidate for applications in high-speed microelectronic and optoelectronic devices. The aim of this research is to understand the surface properties, desorption kinetics and thermal stability of InN epilayers that affect the growth processes and determine film quality as well as device performance and life time. We have investigated the structural properties, the surface desorption kinetics, and the thermal stability using Auger electron spectroscopy (AES), x-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), high resolution electron energy loss spectroscopy (HREELS), and temperature programmed desorption (TPD). Investigations on high pressure chemical vapor deposition (HPCVD)-grown InN samples revealed the presence of tilted crystallites, which were attributed to high group V/III flux ratio and lattice mismatch. A study of the thermal stability of HPCVD-grown InN epilayers revealed that the activation energy for nitrogen desorption was 1.6+/-0.2 eV, independent of the group V/III flux ratio. Initial investigations on the ternary alloy In0.96Ga0.04N showed single-phase, N-polar epilayers using XRD and HREELS, while a thermal desorption study revealed an activation energy for nitrogen desorption of 1.14 +/- 0.06 eV. HREELS investigations of atomic layer epitaxy (ALE)-grown InN revealed vibrational modes assigned to N-N vibrations. The atomic hydrogen cleaned InN surface also exhibited modes assigned to surface N-H without showing In-H species, which indicated N-polar InN. Complete desorption of hydrogen from the InN surface was best described by the first-order desorption kinetics with an activation energy of 0.88 +/- 0.06 eV and pre-exponential factor of (1.5 +/- 0.5) x105 s-1. Overall, we have used a number of techniques to characterize the structure, surface bonding configuration, thermal stability and hydrogen desorption kinetics of InN and In0.96Ga0.04N epilayers grown by HPCVD and ALE. High group V/III precursors ratio and lattice mismatch have a crucial influence on the film orientation. The effects of hydrogen on the decomposition add to the wide variation in the activation energy of nitrogen desorption. Presence of surface defects lowers the activation energy for hydrogen desorption from the surface.

Acharya, Ananta

386

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

387

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)]. 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

388

Monte Carlo study of a compressible pseudospin model for (CH3NH3)5Bi2Cl11  

NASA Astrophysics Data System (ADS)

A two-sublattice peudospin model with distance-dependent interaction parameters is constructed for the ferroelectric phase transition at 307 K and for the isomorphous anomaly at 180 K in pentakis (methylammonium) undecachlorodibismuthate (III) (CH3NH3)5Bi2Cl11. A series of Monte Carlo simulations involving continuous degrees of freedom of deformation is performed for the model. The critical temperatures turn out about 23% lower than those resulting from the mean-field treatment for the three-dimensional fcc lattice in the absence of coupling with strain. An upward shift in the critical temperature then is found due to the coupling with the strain. The multiple histogram method is used to obtain the theoretical predictions for the temperature dependence of the spontaneous polarization, dielectric susceptibility, and specific heat. The existence of a narrow peak in the specific heat and the ratio of the Curie constants close to 4 are confirmed. Evidence is given of the usefulness of the Monte Carlo method with fairly small simulation boxes for the studies of isomorphous anomalies.

Kuchta, B.; Carpentier, P.; Jakubas, R.; ZajaÇ, W.; Zieli?ski, P.

2001-06-01

389

Sub-doppler spectroscopy of the ?2 band of NH 3 using microwave modulation sidebands of CO 2 laser lines  

NASA Astrophysics Data System (ADS)

Microwave modulation sidebands of CO 2 laser lines were used for sub-Doppler saturation spectroscopy in the ?2 fundamental of NH 3. Fifteen transitions were observed and their positions were determined with an absolute frequency accuracy of typically ±100 kHz. The intensities of the observed Lamb dips and crossover dips could be shown to be consistent with theory. In addition, the electronic quadrupole hyperfine splittings due to the 14N nucleus on five transitions were resolved. From this the quadrupole coupling constant eqQ in the ?2 state was determined as ( eqQ) ( v2=1, s) = -4442 ± 156 kHz and ( eqQ) ( v2=1, a) = -4329 ± 375 kHz for the lower and upper inversion levels, respectively. The observed increase of 296 kHz in the magnitude of eqQ upon vibrational excitation could be shown to be consistent with its dependence on hybridization and ionicity of the N?H bond.

Magerl, Gottfried; Schupita, Walter; Frye, Joan M.; Kreiner, Welf A.; Oka, Takeshi

1984-09-01

390

Deposition of GaN films on (1 1 1) Si substrates by alternate supply of TMG and NH 3  

NASA Astrophysics Data System (ADS)

GaN films were grown on (1 1 1) Si substrates at 1000 °C by separate admittances of trimethylgallium (TMG) and ammonia (NH 3). To achieve high quality GaN films, the optimization in growth temperature and layer thickness of AlN buffer layer between GaN film and Si substrate is required. Cross-sectional transmission electron microscopic observations of the GaN/(1 1 1)Si samples show a nearly parallel orientation relationship between the (0 0 0 1) planes of GaN film and the (1 1 1) planes of Si substrate. Room temperature photoluminescence spectra of high quality GaN films show a strong near band edge emission and a weak yellow luminescence. The achievement of high quality GaN films on (1 1 1) Si substrates is believed to be attributed to enhancement in surface mobilities of the adsorbed surface species and adequate accommodation of lattice mismatch between high temperature AlN buffer layer and Si substrate.

Gong, Jyh-Rong; Yeh, Ming-Fa; Tsai, Yu-Li

2004-01-01

391

Two mixed-NH3/amine platinum (II) anticancer complexes featuring a dichloroacetate moiety in the leaving group.  

PubMed

Two mixed-NH3/amine platinum (II) complexes of 3-dichoroacetoxylcyclobutane-1, 1-dicarboxylate have been prepared in the present study and characterized by elemental analysis and IR, HPLC-MS and (1)H, (13)C-NMR. The complexes exist in equilibrium between two position isomeric forms and undergo hydrolysis reaction in aqueous solution, releasing the platinum pharmacophores and dichloroacetate which is a small-molecular cell apoptosis inducer. Both complexes were evaluated for in vitro cytotoxic profile in A549, SGC-7901 and SK-OV-3 cancer cells as well as in BEAS-2B normal cells. They exhibit markedly cytotoxicity toward cancer cells by selectively inducing the apoptosis of cancer cells, whereas leaving normal cells less affected. They have also the ability to overcome the resistance of SK-OV-3 cancer cells to cisplatin. Our findings offer an alternative novel way to develop platinum drugs which can both overcome the drug resistance and selectively target tumor cells. PMID:23955304

Liu, Weiping; Su, Jia; Jiang, Jing; Li, Xingyao; Ye, Qingsong; Zhou, Hongyu; Chen, Jialin; Li, Yan

2013-01-01

392

GaN materials growth by MOVPE in a new-design reactor using DMHy and NH 3  

NASA Astrophysics Data System (ADS)

Thin films of GaN were grown on template substrates of 4-?m-thick GaN layers on sapphire substrates by low-pressure metal organic vapour-phase epitaxy (LP-MOVPE) in a new-design reactor with the shape T. Wide range of growth temperature from 520 to 1100 °C was explored. At low temperature growth between 550 and 690 °C, dimethylhydrazine (DMHy) was used as source of atomic nitrogen while ammonia (NH 3) was used at high temperature growth (1000-1100 °C). At low temperature micro-Raman spectroscopy revealed a significant relaxation of the selection rules for the scattering by the optical phonons in the films grown at lower temperatures. Variation of the intensity ratio for E 2H and E 1 phonon modes has been attributed to changes in the structural quality of the films grown at different temperatures. At high temperature, the quality of GaN layers were comparable to that of the substrate before growth.

Gautier, S.; Sartel, C.; Ould-Saad, S.; Martin, J.; Sirenko, A.; Ougazzaden, A.

2007-01-01

393

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

PubMed Central

Summary 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.

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

2014-01-01

394

Organic chemistry of NH3 and HCN induced by an atmospheric abnormal glow discharge in N2-CH4 mixtures  

NASA Astrophysics Data System (ADS)

The formation of the chemical products produced in an atmospheric glow discharge fed by a N2-CH4 gas mixture has been studied using Fourier Transform InfraRed (FTIR) and Optical Emission Spectrometry (OES). The measurements were carried out in a flowing regime at ambient temperature and pressure with CH4 concentrations ranging from 0.5% to 2%. In the recorded emission spectra the lines of the second positive system CN system and the first negative system of N2 were found to be the most intensive but atomic H?, H?, and C (247 nm) lines were also observed. FTIR-measurements revealed HCN and NH3 to be the major products of the plasma with traces of C2H2. These same molecules have been detected in Titan's atmosphere and the present experiments may provide some novel insights into the chemical and physical mechanisms prevalent in Titan's atmosphere with these smaller species believed to be the precursors of heavier organic species in Titan's atmosphere and on its surface.

Horvath, G.; Krcma, F.; Polachova, L.; Klohnova, K.; Mason, N. J.; Zahoran, M.; Matejcik, S.

2011-01-01

395

Effect of native and NH3 plasma-functionalized polymeric membranes on the gene expression profiles of primary hepatocytes.  

PubMed

Little is known about how cells respond to different biomaterials at the molecular level. Biomaterials could stimulate specific cellular responses at the molecular level, such as activation of signalling pathways that control gene activity involved in the maintenance, growth and functional regeneration of liver tissue in vitro. This aspect is an important step in liver tissue engineering. Currently, there are no data available concerning the modulation of cellular genomic response by using synthetic membranes in a bioartificial system. For the first time we investigated gene expression profiles of primary hepatocytes cultured on different substrates: collagen sandwich, native and NH(3) plasma-grafted PEEK-WC-PU membranes. Gene expression in cell suspension prepared after cell isolation was used as a control. Generally, microarray data revealed that the expression of the majority of genes remained unchanged compared to the control. Among 31 000 genes, 52 were significantly changed: 20 were upregulated and 32 downregulated. There were similar changes in gene expression of hepatocytes cultured in the membranes and collagen sandwich. However, some genes involved in the cell proliferation and functional metabolic pathways are more expressed in cells cultured on the membranes and especially on the functionalized ones. Both membranes sustained liver functions at the molecular level, demonstrating their suitability for the reconstruction of liver and as a toxicogenomic tool to predict the liver response to novel drugs. PMID:21751426

Pavlica, Sanja; Schmitmeier, Stephanie; Gloeckner, Pia; Piscioneri, Antonella; Peinemann, Frank; Krohn, Knut; Siegmund-Schulz, Michaela; Laera, Stefania; Favia, Pietro; Bartolo, Loredana De; Bader, Augustinus

2012-06-01

396

Observation of ultrafast NH3 (Ã) state relaxation dynamics using a combination of time-resolved photoelectron spectroscopy and photoproduct detection.  

PubMed

The ultrafast excited state relaxation of ammonia is investigated by resonantly exciting specific vibrational modes of the electronically excited NH(3) (Ã) state using three complementary femtosecond (fs) pump-probe techniques: time-resolved photoelectron, ion-yield and photofragment translational spectroscopy. Ammonia can be seen as a prototypical system for studying non-adiabatic dynamics and therefore offers a benchmark species for demonstrating the advantages of combining the aforementioned techniques to probe excited state dynamics, whilst simultaneously illuminating new aspects of ammonia's photochemistry. Time-resolved photoelectron spectroscopy (TRPES) provides direct spectroscopic evidence of ?* mediated relaxation of the NH(3) (Ã) state which manifests itself as coupling of the umbrella (?(2)) and symmetric N-H stretch (?(1)) modes in the photoelectron spectra. Time-resolved ion yield (TRIY) and time-resolved photofragment translation spectroscopy (TRPTS) grant a measure of the dissociation dynamics through analysis of the H and NH(2) photodissociation co-fragments. Initial vibrational level dependent TRIY measurements reveal photoproduct formation times of between 190 and 230 fs. Measurement of H-atom photoproduct kinetic energies enables investigation into the competition between adiabatic and non-adiabatic dissociation channels at the NH(3) (Ã)/NH(3) (X?) conical intersection and has shown that upon non-adiabatic dissociation into NH(2) (X?) + H, the NH(2) (X[combining tilde]) fragment is predominantly generated with significant fractions of internal vibrational energy. PMID:22499282

Evans, Nicholas L; Yu, Hui; Roberts, Gareth M; Stavros, Vasilios G; Ullrich, Susanne

2012-08-14

397

Superhydrophobic pure silver surface with flower-like structures by a facile galvanic exchange reaction with [Ag(NH3)2]OH.  

PubMed

Superhydrophobic pure silver film composed of flower-like microstructures built by interconnected silver nanoplates on a copper plate without any modification was prepared by a facile galvanic exchange reaction between the aqueous [Ag(NH3)2]OH and the copper plate, giving rise to a contact angle as high as 157 degrees . PMID:18535710

Cao, Zongwei; Xiao, Debao; Kang, Longtian; Wang, Zhongliang; Zhang, Shuxiao; Ma, Ying; Fu, Hongbing; Yao, Jiannian

2008-06-21

398

Reinterpretation of the vibrational spectroscopy of the medicinal bioinorganic synthon c,c,t-[Pt(NH3) 2Cl 2(OH) 2].  

PubMed

The Pt(IV) complex c,c,t-[Pt(NH3)2Cl2(OH)2] is an important intermediate in the synthesis of Pt(IV) anticancer prodrugs and has been investigated as an anticancer agent in its own right. An analysis of the vibrational spectroscopy of this molecule was previously reported (Faggiani et al., Can. J. Chem. 60:529, 1982), in which crystallographic determination of the structure of the complex permitted a site group approach. The space group, however, was incorrectly assigned. In the present study we have redetermined at high resolution crystal structures of c,c,t-[Pt(NH3)2Cl2(OH)2] and c,c,t-[Pt(NH3)2Cl2(OH)2]·H2O2, which makes possible discussion of the effect of hydrogen bonding on the N-H and O-H vibrational bands. The correct crystallographic site symmetry of the platinum complex in the c,c,t-[Pt(NH3)2Cl2(OH)2] structure is used to conduct a new vibrational analysis using both group-theoretical and modern density functional theory methods. This analysis reveals the nature and symmetry of the "missing band" described in the original publication and suggests a possible explanation for its disappearance. PMID:24515615

Johnstone, Timothy C; Lippard, Stephen J

2014-06-01

399

Modified Two-Step Deposition Method for High-Efficiency TiO2/CH3NH3PbI3 Heterojunction Solar Cells.  

PubMed

Hybrid organic-inorganic perovskites (e.g., CH3NH3PbI3) are promising light absorbers for the third-generation photovoltaics. Herein we demonstrate a modified two-step deposition method to fabricate a uniform CH3NH3PbI3 capping layer with high-coverage and thickness of 300 nm on top of the mesoporous TiO2. The CH3NH3PbI3 layer shows high light-harvesting efficiency and long carrier lifetime over 50 ns. On the basis of the as-prepared film, TiO2/CH3NH3PbI3 heterojunction solar cells achieve a power conversion efficiency of 10.47% with a high open-circuit voltage of 948 mV, the highest recorded to date for hole-transport-material-free (HTM-free) perovskite-based heterojunction cells. The efficiency exceeding 10% shows promising prospects for the HTM-free solar cells based on organic lead halides. PMID:24830329

Shi, Jiangjian; Luo, Yanhong; Wei, Huiyun; Luo, Jianheng; Dong, Juan; Lv, Songtao; Xiao, Junyan; Xu, Yuzhuan; Zhu, Lifeng; Xu, Xin; Wu, Huijue; Li, Dongmei; Meng, Qingbo

2014-06-25

400

Regeneration of field-spent activated carbon catalysts for low-temperature selective catalytic reduction of NO x with NH 3  

Microsoft Academic Search

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

Jong-Ki Jeon; Hyeonjoo Kim; Young-Kwon Park; Charles H. F. Peden; Do Heui Kim

2011-01-01

401

Can the Inversion-Vibration Problem in the nu_4 and 2nu_2 States of NH_3 BE Solved to Experimental Accuracy?  

Microsoft Academic Search

The problem of coupling between a large amplitude motion state and a small amplitude vibration state remains an area of considerable interest and few conclusions in molecular physics. The nu_4 and 2nu_2 states of NH_3 provide an excellent opportunity to study the coupling of large and small amplitude motions in an inversion system where the quantum mechanics have been worked

J. C. Pearson; S. Yu; B. J. Drouin; O. Pirali; M.-A. Martin; M. Vervloet; D. Balcon; C. P. Endres

2010-01-01

402

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.

2012-01-01

403

Thermolysis, nonisothermal decomposition kinetics, specific heat capacity and adiabatic time-to-explosion of [Cu(NH3)4](DNANT)2 (DNANT= dinitroacetonitrile).  

PubMed

A new energetic copper complex of dinitroacetonitrile (DNANT), [Cu(NH3)4](DNANT)2, was first synthesized through an unexpected reaction. The thermal decomposition of [Cu(NH3)4](DNANT)2 was studied with DSC and TG/DTG methods. The gas products were analyzed through a TG-FTIR-MS method. The nonisothermal kinetic equation of the exothermic process is d?/dT = 10(10.92)/?4(1 - ?)[-ln(1 - ?)](3/4) exp(-1.298 × 10(5)/RT). The self-accelerating decomposition temperature and critical temperature of thermal explosion are 217.9 and 221.0 °C. The specific heat capacity of [Cu(NH3)4](DNANT)2 was determined with a micro-DSC method, and the molar heat capacity is 512.6 J mol(-1) K(-1) at 25 °C. Adiabatic time-to-explosion of Cu(NH3)4(DNANT)2 was also calculated to be about 137 s. PMID:24476567

Zhang, Yu; Wu, Hao; Xu, Kangzhen; Zhang, Wantao; Ren, Zhaoyu; Song, Jirong; Zhao, Fengqi

2014-02-20

404

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

405

Models, predictions, and experimental measurements of far-infrared NH 3 -laser dynamics and comparisons with the Lorenz-Haken model  

Microsoft Academic Search

Dynamics of the intensity and optical field amplitude of a coherently pumped far-infrared NH3-laser are measured and characterized. The experimental findings in certain parameter ranges closely follow the dynamics of the Lorenz model and its generalization for laser systems. Similarities and some specific differences are found in geometrical or statistical characterizations of the attractors. The experimental results are also consistent

C. O. Weiss; R. Vilaseca; N. B. Abraham; R. Corbalán; E. Roldán; G. J. de Valcárcel; J. Pujol; U. Hübner; D. Y. Tang

1995-01-01

406

Production of Positive Ions and Electrons in Collisions of 1-25 KeV Protons and Hydrogen Atoms with Co, CO2, CH4, and NH3.  

National Technical Information Service (NTIS)

Cross sections are reported for the production of slow, positive-ions (sigma(+)) and electrons (sigma(-)) in collisions of 1-25 keV protons and hydrogen atoms with CO, CO2, CH4, and NH3. For H(+) bombardment sigma(-) is the total ionization cross section,...

R. J. McNeal

1970-01-01

407

Surface modification of pitch-based spherical activated carbon by CVD of NH 3 to improve its adsorption to uric acid  

NASA Astrophysics Data System (ADS)

Surface chemistry of pitch-based spherical activated carbon (PSAC) was modified by chemical vapor deposition of NH 3 (NH 3-CVD) to improve the adsorption properties of uric acid. The texture and surface chemistry of PSAC were studied by N 2 adsorption, pH PZC (point of zero charge), acid-base titration and X-ray photoelectron spectroscopy (XPS). NH 3-CVD has a limited effect on carbon textural characteristics but it significantly changed the surface chemical properties, resulting in positive effects on uric acid adsorption. After modification by NH 3-CVD, large numbers of nitrogen-containing groups (especially valley-N and center-N) are introduced on the surface of PSAC, which is responsible for the increase of pH PZC, surface basicity and uric acid adsorption capacity. Pseudo-second-order kinetic model can be used to describe the dynamic adsorption of uric acid on PSAC, and the thermodynamic parameters show that the adsorption of uric acid on PSAC is spontaneous, endothermic and irreversible process in nature.

Liu, Chaojun; Liang, Xiaoyi; Liu, Xiaojun; Wang, Qin; Zhan, Liang; Zhang, Rui; Qiao, Wenming; Ling, Licheng

2008-08-01

408

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

409

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

410

Calorimetric, spectroscopic and structural investigations of phase polymorphism in [Ru(NH3)6](BF4)3. Part I  

NASA Astrophysics Data System (ADS)

Four crystalline phases of the coordination compound [Ru(NH3)6](BF4)3 are identified by adiabatic calorimetry. Three phase transitions, one at TC3(IV?III)=30.7 K, the second at TC2(III?II)=91.7 K (both accompanied by comparable entropy changes 3.0 and 3.1 J K-1 mol-1, respectively) and the third at TC1(II?I)=241.6 K (accompanied by an entropy change of 8.1 J K-1 mol-1) were discovered. X-ray single crystal diffraction (at 293 K) demonstrates that phase I is a highly dynamic disordered cubic phase (Fm3¯m, No. 225) with two types of BF4- anions differing in a degree of disorder. In phase II (at 170 K) the structure remains cubic (Ia3¯, No. 206), with two different types of cations and four different types of anions. Splitting of certain IR bands connected with NH3 ligands at the observed phase transitions suggests a lowering of the symmetry of the [Ru(NH3)6]3+ complex cation. Both NH3 ligands and BF4- anions perform fast reorientations (?R?10-12 s), which are significantly slowed down below the phase transition at TC3. 1H NMR studies led to estimate the values of the activation energy of NH3 ligands reorientation in the phases II and I as equal to ˜8 kJ mol-1. In phase I the whole hexammineruthenium(III) cations reorientation as a tumbling process can be noticed. The activation energy value of this motion is ˜24 kJ mol-1. 19F NMR studies give the values of the activation energy of BF4- anions reorientation as ˜6 kJ mol-1. Above the phase transition temperature half of BF4- anions perform a tumbling motion with Ea?8 kJ mol-1.

Do??ga, Diana; Mikuli, Edward; Inaba, Akira; Górska, Natalia; Ho?derna-Natkaniec, Krystyna; Nitek, Wojciech

2013-01-01

411

Temperature-programmed reduction of Ni-Mo oxides  

Microsoft Academic Search

Temperature-programmed reduction (TPR) has been employed to study Ni-Mo mixed oxides which were previously used as model hydrodesulphurization (HDS) catalysts, using compositions ranging from pure MoO3 to pure NiO. An assignment of TPR signals to the different bulk phases was attempted. Good agreement between TPR spectra and structural data obtained previously from X-ray and electron diffraction was observed. TPR traces

Joaquín L. Brito; Jorge Laine; Kerry C. Pratt

1989-01-01

412

High-performance temperature-programmed microfabricated gas chromatography columns  

Microsoft Academic Search

This paper reports the first development of high-performance, silicon-glass micro-gas chromatography (?GC) columns having integrated heaters and temperature sensors for temperature programming, and integrated pressure sensors for flow control. These 3-m long, 150-?m wide and 250-?m deep columns, integrated on a 3.3 cm square die, were fabricated using a silicon-on-glass dissolved wafer process. Demonstrating the contributions to heat dissipation from

Masoud Agah; Joseph A. Potkay; Gordon Lambertus; Richard Sacks; Kensall D. Wise

2005-01-01

413

An analytical potential energy function to model protonated peptide soft-landing experiments. The CH3NH3+/CH4 interactions.  

PubMed

To model soft-landing of peptide ions on surfaces, it is important to have accurate intermolecular potentials between these ions and surfaces. As part of this goal, ab initio calculations at the MP2/aug-cc-pVTZ level of theory, with basis set superposition error (BSSE) corrections, were performed to determine both the long-range attractive and short-range repulsive potentials for CH(4) interacting with the -NH(3)(+) group of CH(3)NH(3)(+). Potential energy curves for four different orientations between CH(4) and CH(3)NH(3)(+) were determined from the calculations to obtain accurate descriptions of the interactions between the atoms of CH(4) and those of -NH(3)(+). A universal analytic function was not found that could accurately represent both the long-range and short-range potentials for collision energies as high as those obtained in surface-induced-dissociation (SID) experiments. Instead, long-range and short-range analytic potentials were developed separately, by simultaneously fitting the four ab initio potential energy curves with a sum of two-body interactions between the atoms of CH(4) and -NH(3)(+), and then connecting these long-range and short-range two-body potentials with switching functions. Following a previous work [J. Am. Chem. Soc., 2002, 124, 1524], these two-body potentials may be used to describe the interactions of the N and H atoms of the -NH(3)(+) group of a protonated peptide ion with the H and C atoms of alkane-type surfaces such as alkyl thiol self-assembled monolayers and H-terminated diamond. Accurate short-range and long-range potentials are imperative to model protonated peptide ion soft-landing experiments. The former controls the collision energy transfer, whereas the latter describes the binding of the ion to the surface. A comparison of the ab initio potential energy curves for CH(3)NH(3)(+)/CH(4) with those for NH(4)(+)/CH(4) shows that they give nearly identical two-body interactions between the atoms of -NH(3)(+) and those of CH(4), showing that the smaller NH(4)(+)/CH(4) system may be used to obtain the two-body potentials. A comparison of the four ab initio potential energy curves reported here for CH(3)NH(3)(+)/CH(4), with those given by the AMBER and CHARMM molecular mechanical potentials, show that these latter potentials "roughly" approximate the long-range attractions, but are grossly in error for the short-range repulsions. The work reported here illustrates that high-level ab initio calculations of intermolecular potentials between small model molecules may be used to develop accurate analytical intermolecular potentials between peptide ions and surfaces. PMID:18665306

Deb, Bipasha; Hu, Wenfang; Song, Kihyung; Hase, William L

2008-08-21

414

Influence of ceria modification on the properties of TiO2-ZrO2 supported V2O5 catalysts for selective catalytic reduction of NO by NH3.  

PubMed

TiO(2)-ZrO(2) (hereafter denoted as Ti-Zr) supported V(2)O(5) catalysts with different loadings of CeO(2) were synthesized, and their physicochemical properties were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), in situ Fourier transform infrared spectroscopy (in situ FT-IR) and temperature-programmed reduction (TPR). Their catalytic activities toward the NO(x) reduction reaction with NH(3) were tested. We found that with the addition of CeO(2), more NO was removed in a wide temperature range of 220-500 °C. As the CeO(2) content was increased from 10% to 20% (i.e., the molar ratio of Ce to Ti-Zr), NO conversion increased significantly; after that, increasing CeO(2) content, however, decreased NO conversion. In particular, the addition of CeO(2) to V(2)O(5)/Ti-Zr suppressed the coke deposition and rendered a stable and high catalytic activity. The characterization results indicated that: (1) the deposited vanadium and cerium oxides were highly dispersed over the Ti-Zr support, and in addition to ZrV(2)O(7), a common binary compound observed in V(2)O(5)/Ti-Zr, CeVO(4) and Ce(3)ZrO(8) was formed upon increasing CeO(2) content; (2) the introduction of CeO(2) to V(2)O(5)/Ti-Zr sample promoted the redox ability of the resulting catalysts; and (3) the Ce-containing catalysts possessed the greater amount of surface acidic and active intermediate. PMID:22464542

Zhang, Yaping; Zhu, Xiaoqiang; Shen, Kai; Xu, Haitao; Sun, Keqin; Zhou, Changcheng

2012-06-15

415

Desorption from interstellar grains  

NASA Technical Reports Server (NTRS)

Different desorption mechanisms from interstellar grains are considered to resolve the conflict between the observed presence of gaseous species in molecular clouds and their expected depletion onto grains. The physics of desorption is discussed with particular reference to the process of grain heating and the specific heat of the dust material. Impulsive heating by X-rays and cosmic rays is addressed. Spot heating of the grains by cosmic rays and how this can lead to desorption of mantles from very large grains is considered. It is concluded that CO depletion on grains will be small in regions with A(V) less than five from the cloud surface and n(H) less than 10,000, in agreement with observations and in contrast to expectations from pure thermal equilibrium. Even in very dense and obscured regions and in the absence of internal ultraviolet sources, the classical evaporation of CO or N2 and O2-rich mantles by cosmic rays is important.

Leger, A.; Jura, M.; Omont, A.

1985-01-01

416

Adsorption, desorption, and diffusion of nitrogen in a model nanoporous material. I. Surface limited desorption kinetics in amorphous solid water.  

PubMed

The adsorption and desorption kinetics of N2 on porous amorphous solid water (ASW) films were studied using molecular beam techniques, temperature programed desorption (TPD), and reflection-absorption infrared spectroscopy. 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 indicating 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, approximately 0.5 microm). 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. PMID:18020658

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

2007-11-14

417

Exciton Self-Trapping in Two-Dimensional System of (C 2H 5NH 3) 2CdCl 4 Single Crystal  

NASA Astrophysics Data System (ADS)

The exciton-phonon interaction in a two-dimensional (C2H5NH3)2CdCl4 single crystal was studied by investigating the low energy tail of the first exciton absorption band in the temperature range of 100 440 K. The tail spectrum for different temperatures obeys the Urbach rule with small steepness parameters. From the analysis of those tails, it is determined that the steepness coefficient ?0 is 0.60 and the exciton-phonon coupling constant g is 2.1. These indicate that the exciton-phonon interaction in (C2H5NH3)2CdCl4 is strong and the free exciton relaxes to the self-trapped exciton state. The electronic nature of the excitonic transition is discussed on the basis of the results in the present work.

Ohnishi, Akimasa; Tanaka, Ken-ichi; Yoshinari, Takehisa

1999-01-01

418

SO2 and NH3 gas adsorption on a ternary ZnO/CuO/CuCl2 impregnated activated carbon evaluated using combinatorial methods.  

PubMed

Ternary libraries of 64 ZnO/CuO/CuCl(2) impregnated activated carbon samples were prepared on untreated or HNO(3)-treated carbon and evaluated for their SO(2) and NH(3) gas adsorption properties gravimetrically using a combinatorial method. CuCl(2) is shown to be a viable substitute for HNO(3) and some compositions of ternary ZnO/CuO/CuCl(2) impregnated carbon samples prepared on untreated carbon provided comparable SO(2) and NH(3) gas removal capacities to the materials prepared on HNO(3)-treated carbon. Through combinatorial methods, it was determined that the use of HNO(3) in this multigas adsorbent formulation can be avoided. PMID:22126267

Romero, Jennifer V; Smith, Jock W H; Sullivan, Braden M; Croll, Lisa M; Dahn, J R

2012-01-01

419

Nature of the Low-Temperature Dielectric Anomalies in (CH 3NH 3) 5Bi 2X 11 (X: Cl, Br)  

NASA Astrophysics Data System (ADS)

The low-temperature dielectric anomalies of two isomorphic ferroelectrics (CH3NH3)5Bi2Cl11 (MAPCB) and (CH3NH3)5Bi2Br11 (MAPBB) have been studied in detail. The anomaly in the dielectric constant of MAPBB at 77 K shows a thermal hysteresis along all three crystallographic axes. The broad peak of the dielectric constant along the a-direction of MAPCB around 160 K becomes flatter and more diffuse as pressure increases. It is concluded that the 77 K anomaly in MAPBB represents a first-order phase transition whereas the 160 K anomaly in MAPCB is an over-critical phenomenon of an isomorphous transition.

Gesi, Kazuo; Iwata, Makoto; Ishibashi, Yoshihiro

1996-01-01

420

Classical and quantum molecular dynamics of cation in (CH3NH3)3 Sb2Br9 polycrystal as studied by 1H NMR.  

PubMed

1H spin-lattice relaxation times and second moments were determined for polycrystalline (CH3NH3)3Sb2Br9 sample in a wide range of temperature (5-200 K) at 24.6 and 55.2 MHz. 2H NMR spectra of (CD3NH3)3Sb2Br9 were recorded between 5 K and room temperature. The relaxation time is interpreted as a result of motion of two different non-equivalent types of monomethylammonium cations occurring at the 2:1 propor