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Sample records for air n2 o2

  1. Orbital tuning of deep ice cores using O2/N2 of trapped air

    NASA Astrophysics Data System (ADS)

    Kawamura, K.; Aoki, S.; Nakazawa, T.

    2014-12-01

    The chronology of the first Dome Fuji deep ice core (80,000-340,000 yr BP) was established by orbital tuning of measured O2/N2 ratios in trapped air to the past local summer insolation at the drill site (Kawamura et al., 2007). The O2/N2 ratios found in ice cores are generally lower than atmospheric ratio because of size-dependent molecular fractionation during bubble close-off. The magnitude of this gas fractionation appears to be influenced by snow metamorphism when the layer was originally at the surface, which in turn is controlled by local summer insolation (Fujita et al., 2009). The O2/N2 record has little 100,000-yr periodicity (strongest in climatic records), suggesting insignificant climatic influence in the orbital tuning. Agreement of the O2/N2 chronology with U-Th radiometric chronology of speleothems (within ~2000 yr) suggests that O2/N2 and summer insolation are indeed in phase. However, it may not be common to all ice cores that O2/N2 signal only records local summer insolation. For example, the GISP2 ice core (Greenland) has clear imprint of abrupt climate changes in the O2/N2 record, indicating climatic (non-insolation) signal in the record and the possibility of phase variability of O2/N2 relative to the past insolation (Suwa and Bender, 2008). Here we present new O2/N2 record from the second Dome Fuji ice core with significant improvements in ice core storage practice and mass spectrometry. In particular, the ice core had been stored at about -50 ˚C until the air extraction except during transportations, which prevent fractionation due to gas loss during the core storage. The precision of the new O2/N2 data set is improved by a factor of 3 over the previous data, and we do not observe outliers (there were 15% outliers in the previous data). Clear imprint of local insolation is recognizable in the new O2/N2, which would enable us to generate a chronology with accuracy of ~2000 yr towards older periods. Samples from the first core after long

  2. A systematic study of Rayleigh-Brillouin scattering in air, N2, and O2 gases

    NASA Astrophysics Data System (ADS)

    Gu, Ziyu; Ubachs, Wim

    2014-09-01

    Spontaneous Rayleigh-Brillouin scattering experiments in air, N2, and O2 have been performed for a wide range of temperatures and pressures at a wavelength of 403 nm and at a 90° scattering angle. Measurements of the Rayleigh-Brillouin spectral scattering profile were conducted at high signal-to-noise ratio for all three species, yielding high-quality spectra unambiguously showing the small differences between scattering in air, and its constituents N2 and O2. Comparison of the experimental spectra with calculations using the Tenti S6 model, developed in the 1970s based on linearized kinetic equations for molecular gases, demonstrates that this model is valid to high accuracy for N2 and O2, as well as for air. After previous measurements performed at 366 nm, the Tenti S6 model is here verified for a second wavelength of 403 nm, and for the pressure-temperature parameter space covered in the present study (250-340 K and 0.6-3 bars). In the application of the Tenti S6 model, based on the transport coefficients of the gases, such as thermal conductivity κ, internal specific heat capacity cint and shear viscosity η, as well as their temperature dependencies taken as inputs, values for the more elusive bulk viscosity ηb for the gases are derived by optimizing the model to the measurements. It is verified that the bulk viscosity parameters obtained from previous experiments at 366 nm are valid for wavelengths of 403 nm. Also for air, which is treated as a single-component gas with effective gas transport coefficients, the Tenti S6 treatment is validated for 403 nm as for the previously used wavelength of 366 nm, yielding an accurate model description of the scattering profiles for a range of temperatures and pressures, including those of relevance for atmospheric studies. It is concluded that the Tenti S6 model, further verified in the present study, is applicable to LIDAR applications for exploring the wind velocity and the temperature profile distributions of the

  3. Accurate age scale of the Dome Fuji ice core, Antarctica from O2/N2 ratio of trapped air

    NASA Astrophysics Data System (ADS)

    Kawamura, K.; Aoki, S.; Nakazawa, T.; Suzuki, K.; Parrenin, F.

    2012-04-01

    Chronology of the first Dome Fuji deep ice core (core length: 2,500 m, ice thickness: 3,035 m) for the age range from 80 kyr to 340 kyr ago was established by orbital tuning of measured O2/N2 ratios in trapped air to local summer insolation, with precision better than about 2,000 years (Kawamura et al., 2007). The O2/N2 ratios found in polar ice cores are slightly lower than the atmospheric ratio because of size-dependent molecular fractionation during bubble close-off. The magnitude of this gas fractionation is believed to be governed by the magnitude of snow metamorphism when the layer was originally at the surface, which in turn is controlled by local summer insolation (Fujita et al., 2009). A strong advantage of the O2/N2 chronology is that there is no need to assume a lag between climatic records in the ice core and orbital forcings, becacuse O2/N2 ratios record local insolation through physical processes. Accuracy of the chronology was validated by comparing the O2/N2 chronology with U-Th radiometric chronology of speleothem records (Cheng et al., 2009) for the ends of Terminations II, III and IV, as well as several large climatic events, for which both ice-core CH4 and speleothem δ18O (a proxy for precipitation) show abrupt shifts as seen in the last glacial period. All ages from O2/N2 and U-Th chronology agreed with each other within ~2,000 yr. The O2/N2 chronology permits comparisons between Antarctic climate, greenhouse gases, astronomically calculated orbital parameters, and radiometrically-dated sea level and monsoon records. Here, we completed the measurements of O2/N2 ratios of the second Dome Fuji ice core, which reached bedrock, for the range from 2,400 to 3,028 m (320 - 700 kyr ago) at approximately 2,000-year time resolution. We made significant improvements in ice core storage practices and mass spectrometry. In particular, the ice core samples were stored at about -50 ° C until the air extraction, except during short periods of transportation

  4. Inactivation of Escherichia coli Cells in Aqueous Solution by Atmospheric-Pressure N2, He, Air, and O2 Microplasmas

    PubMed Central

    Zhou, Renwu; Zhang, Xianhui; Bi, Zhenhua; Zong, Zichao; Niu, Jinhai; Song, Ying; Yang, Size

    2015-01-01

    Atmospheric-pressure N2, He, air, and O2 microplasma arrays have been used to inactivate Escherichia coli cells suspended in aqueous solution. Measurements show that the efficiency of inactivation of E. coli cells is strongly dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N2 and He microplasma arrays, air and O2 microplasma arrays may be utilized to more efficiently kill E. coli cells in aqueous solution. The efficiencies of inactivation of E. coli cells in water can be well described by using the chemical reaction rate model, where reactive oxygen species play a crucial role in the inactivation process. Analysis indicates that plasma-generated reactive species can react with E. coli cells in water by direct or indirect interactions. PMID:26025895

  5. Air content and O2/N2 tuned chronologies on local insolation signatures in the Vostok ice core are similar

    NASA Astrophysics Data System (ADS)

    Lipenkov, V.; Raynaud, D.; Loutre, M.-F.; Duval, P.; Lemieux-Dudon, B.

    2009-04-01

    An accurate chronology of ice cores is needed for interpreting the paleoclimatic record and understanding the relation between insolation and climate. A new domain of research in this area has been initially stimulated by the work of M. Bender (2002) linking the record of O2/N2 ratio in the air trapped in the Vostok ice with the local insolation. More recently, it has been proposed that the long-term changes in air content, V, recorded in ice from the high Antarctic plateau is also dominantly imprinted by the local summer insolation (Raynaud et al., 2007). The present paper presents a new V record from Vostok, which is compared with the published Vostok O2/N2 record for the same period of time (150-400 ka BP) by using the same spectral analysis methods. The spectral differences between the two properties and the possible mechanisms linking them with insolation through the surface snow structure and the close-off processes are discussed. The main result of our study is that the two experimentally independent local insolation proxies lead to absolute (orbital) time scales, which agree together within a standard deviation of 0.6 ka. This result strongly adds credibility to the air content of ice and the O2 to N2 ratio of the air trapped in ice as equally reliable and complementary tools for accurate dating of existing and future deep ice cores. References: M. Bender, Orbital tuning chronology for the Vostok climate record supported by trapped gas composition, Earth and Planetary Science Letters 204(2002) 275-289. D. Raynaud, V. Lipenkov, B. Lemieux-Dudon, P. Duval, M.F. Loutre, N. Lhomme, The local insolation signature of air content in Antarctic ice: a new step toward an absolute dating of ice records, Earth and Planetary Science Letters 261(2007) 337-349.

  6. Decomposition of Methylene Blue by using an Atmospheric Plasma Jet with Ar, N2, O2, or Air

    NASA Astrophysics Data System (ADS)

    Takemura, Yuichiro; Yamaguchi, Naohiro; Hara, Tamio

    2013-05-01

    We have performed experiments on the decomposition of methylene blue by using an atmospheric plasma jet with various working gases. The decomposition efficiencies of Ar, N2, and O2 plasmas are almost equivalent; on the other hand, the rate of methylene blue decomposition by air plasma is lower than those by the other plasmas. From the absorption spectra, it has been found that HONO (nitrous acid) is produced by air plasma-liquid reactions. It has been clarified by a series of experiments, where oxygen concentration in N2 plasma is varied, that the concentration of HONO increases and the rate of methylene blue decomposition degrades with increasing oxygen gas flow rate. Furthermore, the presence of nitrate ions and nitrite ions was confirmed by ion chromatography and pH measurement.

  7. A convenient N2-CCl4 mixture plasma treatment to improve TiO2 photocatalytic oxidation of aromatic air contaminants under both UV and visible light

    NASA Astrophysics Data System (ADS)

    Hu, Shaozheng; Li, Fayun; Fan, Zhiping

    2013-12-01

    A convenient N2-CCl4 mixture plasma treatment to improve TiO2 photocatalytic oxidation of aromatic air contaminants under both UV and visible light was reported. X-ray diffraction (XRD), N2 adsorption, UV-vis spectroscopy, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) were used to characterize the prepared TiO2 catalysts. The microstructures of the TiO2 catalysts were preserved after plasma treatments. Chlorine ions did not doped into TiO2 lattice but located on TiO2 surface via the coordination with Ti4+ sites. The doping N content of prepared TiO2 catalyst increased obviously by using this N2-CCl4 mixture plasma method. The activities were tested in the photocatalytic oxidation of benzene and toluene under both UV and visible light. Chlorine radicals which formed under illumination are effective in oxidizing aromatic side groups, but ineffective in reactions with the aromatic ring.

  8. HIGH PRECISION ISOTOPE RATIO MASS SPECTROMETRY METHOD FOR MEASURING THE O2/N2 RATIO OF AIR

    EPA Science Inventory

    Studies of the distribution of O2 in air will inform us about critical problems in the global carbon cycle which are not readily accessed by other measurements, including the rate of seasonal net production in the oceans on a hemispheric scale, the rate at which the oceans are ta...

  9. Effects of Atmospheric-Pressure N2, He, Air, and O2 Microplasmas on Mung Bean Seed Germination and Seedling Growth.

    PubMed

    Zhou, Renwu; Zhou, Rusen; Zhang, Xianhui; Zhuang, Jinxing; Yang, Size; Bazaka, Kateryna; Ken Ostrikov, Kostya

    2016-01-01

    Atmospheric-pressure N2, He, air, and O2 microplasma arrays have been used to investigate the effects of plasma treatment on seed germination and seedling growth of mung bean in aqueous solution. Seed germination and growth of mung bean were found to strongly depend on the feed gases used to generate plasma and plasma treatment time. Compared to the treatment with atmospheric-pressure O2, N2 and He microplasma arrays, treatment with air microplasma arrays was shown to be more efficient in improving both the seed germination rate and seedling growth, the effect attributed to solution acidification and interactions with plasma-generated reactive oxygen and nitrogen species. Acidic environment caused by air discharge in water may promote leathering of seed chaps, thus enhancing the germination rate of mung bean, and stimulating the growth of hypocotyl and radicle. The interactions between plasma-generated reactive species, such as hydrogen peroxide (H2O2) and nitrogen compounds, and seeds led to a significant acceleration of seed germination and an increase in seedling length of mung bean. Electrolyte leakage rate of mung bean seeds soaked in solution activated using air microplasma was the lowest, while the catalase activity of thus-treated mung bean seeds was the highest compared to other types of microplasma. PMID:27584560

  10. Effects of Atmospheric-Pressure N2, He, Air, and O2 Microplasmas on Mung Bean Seed Germination and Seedling Growth

    PubMed Central

    Zhou, Renwu; Zhou, Rusen; Zhang, Xianhui; Zhuang, Jinxing; Yang, Size; Bazaka, Kateryna; (Ken) Ostrikov, Kostya

    2016-01-01

    Atmospheric-pressure N2, He, air, and O2 microplasma arrays have been used to investigate the effects of plasma treatment on seed germination and seedling growth of mung bean in aqueous solution. Seed germination and growth of mung bean were found to strongly depend on the feed gases used to generate plasma and plasma treatment time. Compared to the treatment with atmospheric-pressure O2, N2 and He microplasma arrays, treatment with air microplasma arrays was shown to be more efficient in improving both the seed germination rate and seedling growth, the effect attributed to solution acidification and interactions with plasma-generated reactive oxygen and nitrogen species. Acidic environment caused by air discharge in water may promote leathering of seed chaps, thus enhancing the germination rate of mung bean, and stimulating the growth of hypocotyl and radicle. The interactions between plasma-generated reactive species, such as hydrogen peroxide (H2O2) and nitrogen compounds, and seeds led to a significant acceleration of seed germination and an increase in seedling length of mung bean. Electrolyte leakage rate of mung bean seeds soaked in solution activated using air microplasma was the lowest, while the catalase activity of thus-treated mung bean seeds was the highest compared to other types of microplasma. PMID:27584560

  11. Prediction of the dielectric strength for c-C4F8 mixtures with CF4, CO2, N2, O2 and air by Boltzmann equation analysis

    NASA Astrophysics Data System (ADS)

    Li, Xingwen; Zhao, Hu; Jia, Shenli; Murphy, Anthony B.

    2014-10-01

    The dielectric strength of c-C4F8, and mixtures of c-C4F8 with CF4, CO2, N2, O2 and air, is studied through solution of the Boltzmann equation. The reduced ionization coefficient α/N and reduced attachment coefficient η/N are calculated, allowing the reduced effective ionization coefficient (α-η)/N and the critical reduced electric field strength (E/N)cr (the reduced electric field for which (α-η)/N = 0), to be determined. A high value of (E/N)cr for an electronegative gas, such as those considered here, indicates good insulating properties. It is found that c-C4F8-N2 and c-C4F8-air have very similar (E/N)cr values, higher than those of the other three mixtures, and superior even to that of pure SF6 for c-C4F8 concentrations above 80%. Comparison of the results obtained for c-C4F8 and c-C4F8-N2 with experimental values from the literature supports the validity of the approach taken here and the parameters used.

  12. Key insights into the reacting kinetics of atmospheric pressure plasmas using He +N2 /O2 /CO2 /H2 O/Air mixtures

    NASA Astrophysics Data System (ADS)

    Murakami, Tomoyuki

    2015-09-01

    A zero dimensional kinetic chemistry computational modeling to identify the important collisional mechanisms and the dominant species in atmospheric pressure plasmas has been developed. This modeling provides an enhanced capability to tailor wide variety of reactive intermediates/species in atmospheric pressure plasmas using He +N2 /O2 /CO2 /H2 O/Air mixtures. The influence of the gas constituent, the gas temperature and the excitation frequency (kHz-, RF-, Pulsed-working) on the complex reacting chemical kinetics is clarified. This work also focuses on the benchmarking between the predictive outputs of this computer-based simulations and the diverse experimental diagnostics with particular emphasis on reactive oxygen/nitrogen intermediates/species. This work was partly supported by KAKENHI Grant Number 24561054.

  13. Production of N2O/+/ by reaction of metastable O2/+/ ions with N2

    NASA Technical Reports Server (NTRS)

    Ajello, J. M.; Rayermann, P.

    1975-01-01

    Photoionization mass spectrometry examination of the production of N2O(+) was undertaken to determine whether N2(+) or O2(+) ions are responsible for onset of N2O(+). It appears that the N2(+) ion does not contribute significantly to the production of N2O(+) in this experiment. Therefore, it is clear that excited O2(+) is responsible for the formation of N2O(+) near the appearance potential of these ions.

  14. Prostaglandin release from isolated rabbit cerebral cortex micro-vessels--comparison of 6-keto PGF1 alpha and PGE2 release from micro-vessels incubated in 100% O2, room air and 95% N2:5% CO2.

    PubMed

    Rodrigues, A M; Gerritsen, M E

    1984-01-01

    Prostaglandin release from microvessels isolated from the rabbit cerebral cortex was determined under three different atmospheric conditions: 100% O2 ("O2") room air, and 95% N2:5% CO2 ("N2-CO2"). Initial studies with homogenates prepared from rabbit cerebral microvessels (RCMV) indicated two pathways of enzymatic PGH2 transformation, namely PGI2 synthase and GSH-dependent PGH-PGE isomerase. We measured the release of the principal products of these pathways, 6-keto PGF1 alpha and PGE2 from freshly prepared RCMV. The release of 6-keto PGF1 alpha exceeded that of PGE2 in all three protocols. RCMV incubated in "N2-CO2" exhibited a reduction in the release of 6-keto PGF1 alpha compared to room air or "O2" incubated RCMV, evident at 30-60 min of incubation. No significant differences in the release of PGE2 were observed among the three incubation protocols. In all three incubation protocols the ratio of 6-keto PGF1 alpha to PGE2 did not differ during the initial 10 minutes of each incubation. After 30 to 60 min of incubation, this ratio did not change from the "O2" or room air treated RCMV, but decreased significantly for the "N2-CO2" treated group. To determine the reversibility of the apparent "N2-CO2" induced decline in 6-keto PGF1 alpha release, microvessels were removed from the nitrogen atmosphere and incubated in room air. Release was measured during the initial 10 min following reintroduction to room air and was compared to room air pretreated controls treated in an identical manner.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6431653

  15. Strain-induced extinction of hydrogen-air counterflow diffusion flames - Effects of steam, CO2, N2, and O2 additives to air

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Northam, G. B.; Wilson, L. G.

    1992-01-01

    A fundamental study was performed using axisymmetric nozzle and tubular opposed jet burners to measure the effects of laminar plug flow and parabolic input velocity profiles on the extinction limits of H2-air counterflow diffusion flames. Extinction limits were quantified by 'flame strength', (average axial air jet velocity) at blowoff of the central flame. The effects of key air contaminants, on the extinction limits, are characterized and analyzed relative to utilization of combustion contaminated vitiated air in high enthalpy supersonic test facilities.

  16. O2 Herzberg State Reaction with N2: A Possible Source of Stratospheric N2O

    NASA Technical Reports Server (NTRS)

    Slanger, Tom G.; Copeland, Richard A.

    1997-01-01

    The goal of this one-year investigation was to determine whether N2O is formed in atmospherically significant quantities by the reaction of vibrationally excited levels of the O2((A3 Sigma(sub u)(sup +)) state with nitrogen. O2(A3 Sigma(sub u)(sup +)) is made throughout the upper stratosphere in considerable amounts by solar photoabsorption, and only a very small reactive yield is necessary for this mechanism to be a major N2O source. By long-term 245-252 nm irradiation of O2/N2 mixtures on- and off-resonance with absorption lines in the O2(A3 Sigma(sub u)(sup +) - X3 Sigma(sub g)(sup -)) transition, followed by N2O analysis by frequency-modulated diode laser absorption spectroscopy, we determined an upper limit for the N2O yield of the candidate reaction. This limit, 3 x 10(exp -5), eliminates O2(A3 Sigma(sub u)(sup +)) + N2 as a significant channel for the generation of stratospheric N2O. In further measurements, we established that N2O is stable under our photolysis conditions, showing that the small amounts of ozone generated from the reaction of O2(A) and O2 do not indirectly lead to destruction of N2O.

  17. Air- and N2-Broadening Coefficients and Pressure-Shift Coefficients in the C-12(O2-16) Laser Bands

    NASA Technical Reports Server (NTRS)

    Devi, V. Malathy; Benner, D. Chris; Smith, Mary Ann H.; Rinsland, Curtis P.

    1998-01-01

    In this paper we report the pressure broadening and the pressure-induced line shift coefficients for 46 individual rovibrational lines in both the (12)C(16)O2, 00(sup 0)1-(10(sup 0)0-02(sup 0)0)I, and 00(sup 0)1-(10(sup 0)0-02(sup 0)0)II, laser bands (laser band I centered at 960.959/cm and laser band II centered at 1063.735/cm) determined from spectra recorded with the McMath-Pierce Fourier transform spectrometer. The results were obtained from analysis of 10 long-path laboratory absorption spectra recorded at room temperature using a multispectrum nonlinear least-squares technique. Pressure effects caused by both air and nitrogen have been investigated. The air-broadening coefficients determined in this study agree well with the values in the 1996 HITRAN database; ratios and standard deviations of the ratios of the present air-broadening measurements to the 1996 HITRAN values for the two laser bands are: 1.005(15) for laser band I and 1.005(14) for laser band II. Broadening by nitrogen is 3 to 4% larger than that of air. The pressure-induced line shift coefficients are found to be transition dependent and different for the P- and R-branch lines with same J" value. No noticeable differences in the shift coefficients caused by air and nitrogen were found. The results obtained are compared with available values previously reported in the literature.

  18. Characterization and Oxidation Behaviour of Al2O3 Coating Deposited on Ti-Al-Nb Alloy in Air and in 9%O2 + 0.2%HCl + 0.08%SO2 + N2 Atmosphere

    NASA Astrophysics Data System (ADS)

    Małecka, Joanna

    2015-02-01

    The paper presents research results of isothermal oxidation of Ti-46Al-7Nb-0.7Cr-0.1Si-0.1Ni intermetallic alloy with Al2O3 coating. Oxidation was carried out in air and in the atmosphere with the content 9%O2 + 0.2%HCl + 0.08%SO2 + N2 at 750 °C. Mass changes of the specimens were recorded after 50, 100, 300 and 500 hours. The surface morphology of the oxidized samples were studied using Scanning Electron Microscopy (SEM), Wavelength Dispersive Spectroscopy (WDS) and Energy Dispersive Spectroscopy (EDS). The results obtained showed that the corrosion resistance of the examined alloy is better in air. The oxidation in the atmosphere of 9%O2 + 0.2%HCl + 0.08%SO2 + N2 causes the formation of eruptions of Al2O3 and TiO2 mixture, however, in air the forming oxide layer is suppressed by the deposited protective Al2O3 coating.

  19. Mixed Matrix Membranes for O2/N2 Separation: The Influence of Temperature

    PubMed Central

    Fernández-Barquín, Ana; Casado-Coterillo, Clara; Valencia, Susana; Irabien, Angel

    2016-01-01

    In this work, mixed matrix membranes (MMMs) composed of small-pore zeolites with various topologies (CHA (Si/Al = 5), LTA (Si/Al = 1 and 5), and Rho (Si/Al = 5)) as dispersed phase, and the hugely permeable poly(1-trimethylsilyl-1-propyne) (PTMSP) as continuous phase, have been synthesized via solution casting, in order to obtain membranes that could be attractive for oxygen-enriched air production. The O2/N2 gas separation performance of the MMMs has been analyzed in terms of permeability, diffusivity, and solubility in the temperature range of 298–333 K. The higher the temperature of the oxygen-enriched stream, the lower the energy required for the combustion process. The effect of temperature on the gas permeability, diffusivity, and solubility of these MMMs is described in terms of the Arrhenius and Van’t Hoff relationships with acceptable accuracy. Moreover, the O2/N2 permselectivity of the MMMs increases with temperature, the O2/N2 selectivities being considerably higher than those of the pure PTMSP. In consequence, most of the MMMs prepared in this work exceeded the Robeson’s upper bound for the O2/N2 gas pair in the temperature range under study, with not much decrease in the O2 permeabilities, reaching O2/N2 selectivities of up to 8.43 and O2 permeabilities up to 4,800 Barrer at 333 K. PMID:27196937

  20. Potential energy surface of triplet N2O2

    NASA Astrophysics Data System (ADS)

    Varga, Zoltan; Meana-Pañeda, Rubén; Song, Guoliang; Paukku, Yuliya; Truhlar, Donald G.

    2016-01-01

    We present a global ground-state triplet potential energy surface for the N2O2 system that is suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation. The surface is based on multi-state complete-active-space second-order perturbation theory/minimally augmented correlation-consistent polarized valence triple-zeta electronic structure calculations plus dynamically scaled external correlation. In the multireference calculations, the active space has 14 electrons in 12 orbitals. The calculations cover nine arrangements corresponding to dissociative diatom-diatom collisions of N2, O2, and nitric oxide (NO), the interaction of a triatomic molecule (N2O and NO2) with the fourth atom, and the interaction of a diatomic molecule with a single atom (i.e., the triatomic subsystems). The global ground-state potential energy surface was obtained by fitting the many-body interaction to 54 889 electronic structure data points with a fitting function that is a permutationally invariant polynomial in terms of bond-order functions of the six interatomic distances.

  1. Potential energy surface of triplet N2O2.

    PubMed

    Varga, Zoltan; Meana-Pañeda, Rubén; Song, Guoliang; Paukku, Yuliya; Truhlar, Donald G

    2016-01-14

    We present a global ground-state triplet potential energy surface for the N2O2 system that is suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation. The surface is based on multi-state complete-active-space second-order perturbation theory/minimally augmented correlation-consistent polarized valence triple-zeta electronic structure calculations plus dynamically scaled external correlation. In the multireference calculations, the active space has 14 electrons in 12 orbitals. The calculations cover nine arrangements corresponding to dissociative diatom-diatom collisions of N2, O2, and nitric oxide (NO), the interaction of a triatomic molecule (N2O and NO2) with the fourth atom, and the interaction of a diatomic molecule with a single atom (i.e., the triatomic subsystems). The global ground-state potential energy surface was obtained by fitting the many-body interaction to 54 889 electronic structure data points with a fitting function that is a permutationally invariant polynomial in terms of bond-order functions of the six interatomic distances. PMID:26772574

  2. Effects of N2-O2 and CO2-O2 Tensions on Growth of Fungi Isolated from Damaged Flue-Cured Tobacco 1

    PubMed Central

    Yang, H.; Lucas, G. B.

    1970-01-01

    Ten fungi, Aspergillus niger, A. flavus, A. ochraceus, A. ruber, A. repens, A. amstelodami, Alternaria tenuis, Penicillium brevi-compactum, Cladosporium herbarum, and Chaetomium dolicotrichum, were isolated from moldy flue-cured tobacco and grown in various mixtures of N2-O2 or CO2-O2. A 1 to 5% concentration of O2 in an N2 atmosphere caused the greatest change in growth of the nine species, and a 10 to 20% concentration of O2 for A. flavus. All species, except A. amstelodami and A. ruber, grew faster in air than in mixtures containing 10% O2. High O2 concentrations generally inhibited furrow production in the mycelial mats. In an atmosphere of 5 to 40% O2 in the N2 atmosphere, furrows formed in mycelial mats between 5 and 40% O2 in the species except for A. ruber, A. repens, and A. amstelodami, which produced none in any concentration. As O2 decreased below 20%, spore production was progressively decreased, colony color faded to white, and cleistothecia formation was suppressed. In CO2-O2 mixtures radial growth of all species increased with each quantitative decrease of CO2. All species except A. niger grew faster in air than in 10% CO2. In contrast to N2-O2 mixtures, the fungi formed furrows, sporulation and cleistothecial formation were suppressed, and colony color changed to white in higher O2 concentrations. PMID:5461786

  3. Influence of heliox, oxygen, and N2O-O2 breathing on N2 bubbles in adipose tissue.

    PubMed

    Hyldegaard, O; Madsen, J

    1989-05-01

    Bubbles in rat adipose tissue were studied at 1 bar after decompression from an exposure to air at 3.3 bars (absolute) for 4 h. During air breathing the bubbles grew throughout the observation period. During heliox (80:20) breathing they shrank and eventually disappeared from view. If the breathing gas was changed from heliox back to air or to N2O-O2 (80:20) while the bubbles still had an appreciable size, they started growing again. If the change to N2O was done after or a few minutes before a bubble disappeared from view, it did not reappear. During breathing of 100% O2, most bubbles containing N2 initially grew and then maintained their size for a while before diminishing. However, some bubbles did not start shrinking during the 2-3-h observation period. The relevance of the findings to heliox treatment of CNS decompression sickness after air dives is discussed. PMID:2741253

  4. Efficiency of Collisional O2 + N2 Vibrational Energy Exchange.

    PubMed

    Garcia, E; Kurnosov, A; Laganà, A; Pirani, F; Bartolomei, M; Cacciatore, M

    2016-03-01

    By following the scheme of the Grid Empowered Molecular Simulator (GEMS), a new O2 + N2 intermolecular potential, built on ab initio calculations and experimental (scattering and second virial coefficient) data, has been coupled with an appropriate intramolecular one. On the resulting potential energy surface detailed rate coefficients for collision induced vibrational energy exchanges have been computed using a semiclassical method. A cross comparison of the computed rate coefficients with the outcomes of previous semiclassical calculations and kinetic experiments has provided a foundation for characterizing the main features of the vibrational energy transfer processes of the title system as well as a critical reading of the trajectory outcomes and kinetic data. On the implemented procedures massive trajectory runs for the proper interval of initial conditions have singled out structures of the vibrational distributions useful to formulate scaling relationships for complex molecular simulations. PMID:26292835

  5. N2/O2/H2 Dual-Pump Cars: Validation Experiments

    NASA Technical Reports Server (NTRS)

    OByrne, S.; Danehy, P. M.; Cutler, A. D.

    2003-01-01

    The dual-pump coherent anti-Stokes Raman spectroscopy (CARS) method is used to measure temperature and the relative species densities of N2, O2 and H2 in two experiments. Average values and root-mean-square (RMS) deviations are determined. Mean temperature measurements in a furnace containing air between 300 and 1800 K agreed with thermocouple measurements within 26 K on average, while mean mole fractions agree to within 1.6 % of the expected value. The temperature measurement standard deviation averaged 64 K while the standard deviation of the species mole fractions averaged 7.8% for O2 and 3.8% for N2, based on 200 single-shot measurements. Preliminary measurements have also been performed in a flat-flame burner for fuel-lean and fuel-rich flames. Temperature standard deviations of 77 K were measured, and the ratios of H2 to N2 and O2 to N2 respectively had standard deviations from the mean value of 12.3% and 10% of the measured ratio.

  6. Effect of He-O2, O2, and N2O-O2 breathing on injected bubbles in spinal white matter.

    PubMed

    Hyldegaard, O; Møller, M; Madsen, J

    1991-01-01

    Injected air bubbles in spinal white matter in the rat were studied at 1 bar after decompression from an exposure to air at 3.1 bar (absolute) for 4 h. During air breathing all injected bubbles grew for the first 2 h of the observation period. Thereafter three of nine bubbles began to shrink and one of them disappeared. During breathing of heliox (80:20) bubbles consistently shrank and disappeared from view. If the breathing gas was changed from heliox to N2O-O2 (80:20), while bubbles still had an appreciable size, they started growing again. If the change to N2O-O2 was done after a bubble disappeared from view, it did not reappear. During breathing of 100% oxygen, all bubbles initially grew. Subsequently they all shrank and disappeared at about the same time after gas shift, as during heliox breathing. The effect of heliox treatment on CNS decompression sickness after air dives is discussed. PMID:1746064

  7. Discharge Kinetics of N2-O2 Laser Generated Plasma Channels

    NASA Astrophysics Data System (ADS)

    Ladouceur, Harold; Baronavski, Andrew; Petrova, Tzvetelina

    2006-10-01

    We study both experimentally and theoretically the effects of recombination and attachment of different N2--O2 gas compositions upon the plasma channel dynamics at one atmosphere. The time-dependent DC electrical conductivity technique [1] has been applied to determine the electron density decay. The rate constants have been determined from the electron balance equation by curve fitting of voltage-time measurements over the decay time interval. The measured electron density decay time for air is hundreds of nanoseconds while for pure nitrogen it is much longer, about 2 μs. For air, we derive an attachment rate ηair=1.39x10^7;s-1 and an electron-ion recombination rate βair=1.02x10-8;cm^31pts-1. In order to investigate in details the kinetics of N2--O2 gas mixture we developed a time-dependent collisional-radiative model based upon the numerical solution of the electron Boltzmann equation for the electron energy distribution function. It is coupled with the time-dependent balance equations of electrons, atomic and molecular ions under consideration, and various nitrogen and oxygen species in ground and excited states. The validity of the model was verified by comparison of the swarm parameters derived from the model with experimental parameters for pure oxygen, pure nitrogen, and air. [1] H.D. Ladouceur at al., Optics Communications, 189 (2001) 107 * NRL-NRC Postdoc

  8. O2/n2 Measurements On Polar Ice Cores With A New On-line Extraction Technique

    NASA Astrophysics Data System (ADS)

    Huber, C.; Leuenberger, M.

    We developed a new on-line extraction and analysis technique for bubble air trapped in ice cores. The technique is based on our continuous flow analysis (CFA) melt system which has been successfully used for in situ analysis of chemical substances on several European drilling projects in Antarctica (EPICA) and Greenland (GRIP). A piece of ice (up to 1 m long, cross-section typically 2 × 2 cm) is continuously melted and the air is subsequently separated from the meltwater into a helium flux. The helium-air mixture is then analyzed in a Delta Plus XL isotope ratio mass spectrometer where the isotopic ratios of the major atmospheric gases nitrogen (N2), oxygen (O2) and argon (Ar) and the elemental ratios O2/N2 and Ar/N2 can be measured. Nitrogen (15N) and oxygen (18O) isotope measurements of standard air admixed to a water flux by a bubble generator with subsequent degassing proved to be as pre- cise as conventional off-line extraction devices. First results of ice measurements are promising. 15N and 18O can be measured with a precision better than 0.05 permil and 0.1 permil respectively for a resolution of 2 - 3 cm. Therefore, we suppose that this technique has the potential to measure the ratio of oxygen to nitrogen (O2/N2). The stable isotope composition of the main air components in ice core bubbles en- compass a wealth of important information regarding abrupt temperature shifts, and variations of the global ice volume as well as marine and terrestrial biological ac- tivities. O2/N2 or 13C in combination with CO2 is used to determine oceanic and terrestrial carbon sources and sinks. Direct atmospheric O2/N2 monitoring started in the late 1980's. Recent modeling studies show that present O2/N2 measurements lead to more consistent results than today's available 13C values. However, reliable firn or archive tank data do not extend further back in time than 1977. Therefore, it is of great interest to study O2/N2 in the firn as well as in the neighboring ice. The

  9. Formation of NOx from N2 and O2 in catalyst-pellet filled dielectric barrier discharges at atmospheric pressure.

    PubMed

    Sun, Qi; Zhu, Aimin; Yang, Xuefeng; Niu, Jinhai; Xu, Yong

    2003-06-21

    At temperatures above 350 degrees C, significant amounts of NOx formed from N2 and O2 have been observed in Cu-ZSM-5 catalyst-pellet filled dielectric barrier discharges, indicating the necessity of using low-temperature performance in all plasma-catalytic processes for removal of air pollutants. PMID:12841270

  10. Physisorption of N2, O2, and CO on Fully Oxidized TiO2(110)

    SciTech Connect

    Dohnalek, Zdenek; Kim, Jooho; Bondarchuk, Oleksander A.; White, J. M.; Kay, Bruce D.

    2006-03-30

    Physisorption of N2, O2 and CO was studied on fully oxidized TiO2(110) using beam reflection and temperature programmed desorption (TPD) techniques. Sticking coefficients for all three molecules are nearly equal (0.75 ± 0.05) and approximately independent of coverage suggesting that adsorption occurs via a precursor mediated mechanism. Excluding multilayer coverages, the TPD spectra for all three adsorbates exhibit three distinct coverage regimes that can be interpreted in accord with previous theoretical studies of N2 adsorption. At low coverages (0 to 0.5 N2/Ti4+), N2 molecules bind head-on to five-coordinated Ti4+ ions. The adsorption occurs preferentially on the Ti4+ sites that do not have neighboring adsorbates. This arrangement minimizes the repulsive interactions between the adsorbed molecules along the Ti4+ rows resulting in a relatively small shift of the TPD peak (105 → 90 K) with increasing coverage. At higher N2 coverages (0 to 1.0 N2/Ti4+) the nearest-neighbor Ti4+ sites become occupied. The close proximity of the adsorbates results in strong repulsion thus giving rise to a significant shift of the TPD leading edges (90 → 45 K) with increasing coverage. For N2/Ti4+ > 1, an additional low temperature peak (~ 43 K) is present and is ascribed to N2 adsorption on bridge-bonded oxygen rows. The results for O2 and CO are qualitatively similar. The repulsive adsorbate-adsorbate interactions largest for CO, most likely due to aligned CO dipole moments. The coverage dependent binding energies of O2, N2, and CO are determined by inverting TPD profiles.

  11. Investigation of N2O Production from 266 and 532 nm Laser Flash Photolysis of O3/N2/O2 Mixtures

    NASA Technical Reports Server (NTRS)

    Estupinan, E. G.; Nicovich, J. M.; Li, J.; Cunnold, D. M.; Wine, P. H.

    2002-01-01

    Tunable diode laser absorption spectroscopy has been employed to measure the amount of N2O produced from laser flash photolysis of O3/N2/O2 mixtures at 266 and 532 nm. In the 532 nm photolysis experiments very little N2O is observed, thus allowing an upper limit yield of 7 x 10(exp -8) to be established for the process O3 + N2 yield N2O + O2, where O3 is nascent O3 that is newly formed via O(3P(sub J)) + O2 recombination (with vibrational excitation near the dissociation energy of O3). The measured upper limit yield is a factor of approx. 600 smaller than a previous literature value and is approximately a factor of 10 below the threshold for atmospheric importance. In the 266 nm photolysis experiments, significant N2O production is observed and the N2O quantum yield is found to increase linearly with pressure over the range 100 - 900 Torr in air bath gas. The source of N2O in the 266 nm photolysis experiments is believed to be the addition reaction O(1D(sub 2)) + N2 + M yields (k(sub sigma)) N2O + M, although reaction of (very short-lived) electronically excited O3 with N2 cannot be ruled out by the available data. Assuming that all observed N2O comes from the O(1D(sub 2)) + N2 + M reaction, the following expression describes the temperature dependence of k(sub sigma) (in its third-order low-pressure limit) that is consistent with the N2O yield data: k(sub sigma) = (2.8 +/- 0.1) x 10(exp -36)(T/300)(sup -(0-88+0.36)) cm(sup 6) molecule(sup -2)/s, where the uncertainties are 2(sigma) and represent precision only. The accuracy of the reported rate coefficients at the 95% confidence level is estimated to be 30 - 40% depending on the temperature. Model calculations suggest that gas phase processes initiated by ozone absorption of a UV photon represent about 1.4% of the currently estimated global source strength of atmospheric N2O. However, these processes could account for a significant fraction of the oxygen mass-independent enrichment observed in atmospheric N2O, and

  12. The Effects of Flame Structure on Extinction of CH4-O2-N2 Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Du, J.; Axelbaum, R. L.; Gokoglu, S. (Technical Monitor)

    1996-01-01

    The effects of flame structure on the extinction limits of CH4-O2-N2 counterflow diffusion flames were investigated experimentally and numerically by varying the stoichiometric mixture fraction Z(sub st), Z(sub st) was varied by varying free-stream concentrations, while the adiabatic flame temperature T(sub ad) was held fixed by maintaining a fixed amount of nitrogen at the flame. Z(sub st) was varied between 0.055 (methane-air flame) and 0.78 (diluted- methane-oxygen flame). The experimental results yielded an extinction strain rate K(sub ext) of 375/s for the methane-air flame, increasing monotonically to 1042/s for the diluted-methane-oxygen flame. Numerical results with a 58-step Cl mechanism yielded 494/s and 1488/s, respectively. The increase in K(sub ext) with Z(sub st) for a fixed T(sub ad) is explained by the shift in the O2 profile toward the region of maximum temperature and the subsequent increase in rates for chain-branching reactions. The flame temperature at extinction reached a minimum at Z(sub st) = 0.65, where it was 200 C lower than that of the methane-air flame. This significant increase in resistance to extinction is seen to correspond to the condition in which the OH and O production zones are centered on the location of maximum temperature.

  13. Calculated vibrational populations of O2 Herzberg states in the mixture of CO2, CO, N2, O2 gases

    NASA Astrophysics Data System (ADS)

    Kirillov, A. S.

    2014-05-01

    Calculated in (Kirillov, 2014) constants are applied for simulations of vibrational populations of Herzberg states in mixtures of O2 with CO2, CO, N2 gases for laboratory conditions. Results show very important role of electronic-vibrational processes in redistribution of electronic excitation energy among vibrational levels. It is shown that the interaction between O2(A‧3Δu) and O2 causes effective production O2(c1Σu-,v = 0) observed in laboratory conditions. The inclusion of the interaction between O2(A‧3Δu) and CO2 molecules may explain high intensities of Herzberg II system observed in laboratory experiments with high CO2 concentrations and registered in the nightglow of Venusian atmosphere.

  14. Dielectric breakdown properties of N2-O2 mixtures by considering electron detachments from negative ions

    NASA Astrophysics Data System (ADS)

    Zhao, Hu; Lin, Hui

    2016-07-01

    The paper analyzes the dielectric breakdown properties of N2-O2 mixtures at different O2 concentrations and gas pressures, taking into account electron detachments from negative ions. The reduced effective ionization coefficients α(eff)/N in N2-O2 mixtures at different O2 concentrations and gas pressures were calculated and analyzed, by considering electron detachments. The critical reduced electric fields (E/N)cr and the critical electron temperature Tb were then determined. The result indicates a clear enhancement of α(eff)/N by collisional detachments, which causes a reduction in the (E/N)cr. In addition, a synergistic effect in the N2-O2 mixture was also observed in both (E/N)cr and Tb. The value of Tb was decreased by the increase of pd product, however, Tb tended to be constant at relatively high pd products.

  15. Ignition and Combustion of Pulverized Coal and Biomass under Different Oxy-fuel O2/N2 and O2/CO2 Environments

    NASA Astrophysics Data System (ADS)

    Khatami Firoozabadi, Seyed Reza

    This work studied the ignition and combustion of burning pulverized coals and biomasses particles under either conventional combustion in air or oxy-fuel combustion conditions. Oxy-fuel combustion is a 'clean-coal' process that takes place in O2/CO2 environments, which are achieved by removing nitrogen from the intake gases and recirculating large amounts of flue gases to the boiler. Removal of nitrogen from the combustion gases generates a high CO2-content, sequestration-ready gas at the boiler effluent. Flue gas recirculation moderates the high temperatures caused by the elevated oxygen partial pressure in the boiler. In this study, combustion of the fuels took place in a laboratory laminar-flow drop-tube furnace (DTF), electrically-heated to 1400 K, in environments containing various mole fractions of oxygen in either nitrogen or carbon-dioxide background gases. The experiments were conducted at two different gas conditions inside the furnace: (a) quiescent gas condition (i.e., no flow or inactive flow) and, (b) an active gas flow condition in both the injector and furnace. Eight coals from different ranks (anthracite, semi-snthracite, three bituminous, subbituminous and two lignites) and four biomasses from different sources were utilized in this work to study the ignition and combustion characteristics of solid fuels in O2/N2 or O2/CO2 environments. The main objective is to study the effect of replacing background N2 with CO2, increasing O2 mole fraction and fuel type and rank on a number of qualitative and quantitative parameters such as ignition/combustion mode, ignition temperature, ignition delay time, combustion temperatures, burnout times and envelope flame soot volume fractions. Regarding ignition, in the quiescent gas condition, bituminous and sub-bituminous coal particles experienced homogeneous ignition in both O2/N 2 and O2/CO2 atmospheres, while in the active gas flow condition, heterogeneous ignition was evident in O2/CO 2. Anthracite, semi

  16. Electron transport coefficients in the mixtures of H2O with N2, O2, CO2 and dry air for the optimization of non-thermal atmospheric pressure plasmas

    NASA Astrophysics Data System (ADS)

    Ruíz-Vargas, G.; Yousfi, M.; de Urquijo, J.

    2010-11-01

    This paper presents the simultaneous measurement and calculation of the electron drift velocity in binary and ternary mixtures of N2, O2, CO2 with H2O. The main aim of this study has been the generation of a self-consistent set of validated collision cross sections that explain thoroughly the dependence of the electron drift velocity in the above pure gases and their mixtures. In doing this, changes to the collision cross section set for H2O had to be made, while all other cross section sets remained unchanged. It is worth mentioning that only a few experiments had been performed before dealing with water mixtures. The electron drift velocities in the binary and ternary mixtures under study show the effects of negative differential conductivity, and this has been explained thoroughly in terms of the collision cross sections and electron distribution functions through a multi-term Boltzmann code. It is important to note that two-term codes fail to predict the dependence of the drift velocity at low water concentrations and low E/N values. Calculated values of longitudinal and transverse diffusion coefficients, mean energies and distribution functions are also given over the E/N range 0.1 Td-2 kTd (1 Td = 10-17 V cm2).

  17. Laboratory measurements of the O+/2D/ + N2 and O+/2D/ + O2 reaction rate coefficients and their ionospheric implications

    NASA Technical Reports Server (NTRS)

    Johnsen, R.; Biondi, M. A.

    1980-01-01

    Rate coefficients which have been measured at thermal energies for the charge transfer reactions of metastable O+/2D/ ions with N2 and O2 are reported. It is found that at an effective temperature of about 550 K, k(n2) = (8 + or - 2) x 10 to the -10 cu cm/sec and k(O2) = (7 + or - 2) x 10 to the -10 cu cm/sec. Drift tube-mass spectrometer measurements employ the reaction He(+) + O2 as the source of metastable O+ ions, showing that the ions produced in this manner are in the 2D state rather than the 2P state, a possible alternative identification. Finally, consideration is given to the ionospheric implications of the laboratory measurements.

  18. Fiber-Optic Determination of N2, O2, and Fuel Vapor in the Ullage of Liquid-Fuel Tanks

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet

    2008-01-01

    A fiber-optic sensor system has been developed that can remotely measure the concentration of molecular oxygen (O2), nitrogen (N2), hydrocarbon vapor, and other gases (CO2, CO, H2O, chlorofluorocarbons, etc.) in the ullage of a liquid-fuel tank. The system provides an accurate and quantitative identification of the above gases with an accuracy of better than 1 percent by volume (for O2 or N2) in real-time (5 seconds). In an effort to prevent aircraft fuel tank fires or explosions similar to the tragic TWA Flight 800 explosion in 1996, OBIGGS are currently being developed for large commercial aircraft to prevent dangerous conditions from forming inside fuel tanks by providing an inerting gas blanket that is low in oxygen, thus preventing the ignition of the fuel/air mixture in the ullage. OBIGGS have been used in military aircraft for many years and are now standard equipment on some newer large commercial aircraft (such as the Boeing 787). Currently, OBIGGS are being developed for retrofitting to existing commercial aircraft fleets in response to pending mandates from the FAA. Most OBIGGS use an air separation module (ASM) that separates O2 from N2 to make nitrogen-enriched air from compressed air flow diverted from the engine (bleed air). Current OBIGGS systems do not have a closed-loop feedback control, in part, due to the lack of suitable process sensors that can reliably measure N2 or O2 and at the same time, do not constitute an inherent source of ignition. Thus, current OBIGGS operate with a high factor-of-safety dictated by process protocol to ensure adequate fuel-tank inerting. This approach is inherently inefficient as it consumes more engine bleed air than is necessary compared to a closed-loop controlled approach. The reduction of bleed air usage is important as it reduces fuel consumption, which translates to both increased flight range and lower operational costs. Numerous approaches to developing OBIGGS feedback-control sensors have been under

  19. Removal of NO in NO/N2, NO/N2/O2, NO/CH4/N2, and NO/CH4/O2/N2 systems by flowing microwave discharges.

    PubMed

    Hueso, José L; Gonzalez-Elipe, Agustín R; Cotrino, José; Caballero, Alfonso

    2007-02-15

    In this paper, continuing previous work, we report on experiments carried out to investigate the removal of NO from simulated flue gas in nonthermal plasmas. The plasma-induced decomposition of small concentrations of NO in N2 used as the carrier gas and O2 and CH4 as minority components has been studied in a surface wave discharge induced with a surfatron launcher. The reaction products and efficiency have been monitored by mass spectrometry as a function of the composition of the mixture. NO is effectively decomposed into N2 and O2 even in the presence of O2, provided always that enough CH4 is also present in the mixture. Other majority products of the plasma reactions under these conditions are NH3, CO, and H2. In the absence of O2, decomposition of NO also occurs, although in that case HCN accompanies the other reaction products as a majority component. The plasma for the different reaction mixtures has been characterized by optical emission spectroscopy. Intermediate excited species of NO*, C*, CN*, NH*, and CH* have been monitored depending on the gas mixture. The type of species detected and their evolution with the gas composition are in agreement with the reaction products detected in each case. The observations by mass spectrometry and optical emission spectroscopy are in agreement with the kinetic reaction models available in literature for simple plasma reactions in simple reaction mixtures. PMID:17286359

  20. Numerical simulations of turbulent premixed H2/O2/N2 flames with complex chemistry

    NASA Technical Reports Server (NTRS)

    Baum, M.; Poinsot, T. J.; Haworth, D. C.

    1992-01-01

    Premixed stoichiometric H2/O2/N2 flames propagating in two-dimensional turbulence were studied using direct numerical simulation (simulations in which all fluid and thermochemical scales are fully resolved) including realistic chemical kinetics and molecular transport. Results are compared with earlier zero-chemistry (flame sheet) and one-step chemistry simulations. Consistent with the simpler models, the turbulent flame with realistic chemistry aligns preferentially with extensive strain rates in the tangent plane and flame curvature probability density functions are close to symmetric with near-zero means. By contrast to simple-chemistry results with non-unity Lewis numbers (ratio of thermal to species diffusivity), local flame structure does not correlate with curvature but rather with tangential strain rate. Turbulent straining results in substantial thinning of the flame relative to the steady unstrained laminar case. Heat release and H2O2 contours remain thin and connected ('flamelet-like') while species including H-atom and OH are more diffuse. Peak OH concentration occurs well behind the peak heat-release zone. The feasibility of incorporating realistic chemistry into full turbulence simulations to address issues such as pollutant formation in hydrocarbon-air flames is suggested.

  1. Regional differences in the δO2/N2 records from East Antarctica over the last interglacial

    NASA Astrophysics Data System (ADS)

    Bazin, L.; Landais, A.; Masson-Delmotte, V.; Kageyama, M.; Paillard, D.; Bopp, L.; Ritz, C.; Leuenberger, M.

    2013-12-01

    Ice cores are the only climate archives offering samples of past atmosphere. The air is trapped at around 100 m under the surface, where the snow is compacted into ice. During this process, multiple influences may modify the air composition as the quantity of insolation received at the surface impacts snow metamorphism and hence air trapping conditions at the basis of the firn (top ~100m of the ice sheet). Analyses of trapped air in ice cores thus give us information on both local and global scales. In this study, we focus on temporal variations of elemental and isotopic composition of oxygen from East Antarctic ice cores. On the one hand, the δ18Oatm, uniformly distributed in the atmosphere, is known to be related to the hydrological cycle and the vegetation cover (Landais et al., 2010), and can be linked to the precession variations. The δO2/N2, on the other hand, appears to be influenced by the local insolation, probably because of modification of the snow structure affecting pore close-off. These two quantities have largely been used as orbital tuning tools for dating purposes in several ice cores from Antarctica (Bender 2002, Suwa et Bender 2008, Kawamura et al., 2007, Dreyfus et al., 2007,Landais et al., 2012, Bazin et al., 2013). Still, gaps in our understanding of the exact mechanisms explaining the δ18Oatm and δO2/N2 variations lead to quite large uncertainties when using these proxies as tie-points for dating purposes. In this study, we use several ice core records in low accumulation rate sites of East Antarctica to decipher global and local effects on the δO2/N2 records. First, we present a compilation of δO2/N2 measurements of the Dome F, Vostok and Dome C ice cores over the last interglacial period. While Dome F and Vostok data were corrected for gas loss during several years of storage at -25°C, new measurements of the air isotopic composition on the Dome C ice core were performed on well-conserved ice (-50°C). Different δO2/N2 mean levels

  2. O(2)And N(2)O Activation By Bi-, Tri-, And Tetranuclear Cu Clusters in Biology

    SciTech Connect

    Solomon, E.I.; Sarangi, R.; Woertink, J.S.

    2009-06-04

    Copper-cluster sites in biology exhibit unique spectroscopic features reflecting exchange coupling between oxidized Cu's and e (-) delocalization in mixed valent sites. These novel electronic structures play critical roles in O 2 binding and activation for electrophilic aromatic attack and H-atom abstraction, the 4e (-)/4H (+) reduction of O 2 to H 2O, and in the 2e (-)/2H (+) reduction of N 2O. These electronic structure/reactivity correlations are summarized.

  3. O2 and N2O activation by Bi-, Tri-, and tetranuclear Cu clusters in biology.

    PubMed

    Solomon, Edward I; Sarangi, Ritimukta; Woertink, Julia S; Augustine, Anthony J; Yoon, Jungjoo; Ghosh, Somdatta

    2007-07-01

    Copper-cluster sites in biology exhibit unique spectroscopic features reflecting exchange coupling between oxidized Cu's and e (-) delocalization in mixed valent sites. These novel electronic structures play critical roles in O 2 binding and activation for electrophilic aromatic attack and H-atom abstraction, the 4e (-)/4H (+) reduction of O 2 to H 2O, and in the 2e (-)/2H (+) reduction of N 2O. These electronic structure/reactivity correlations are summarized below. PMID:17472331

  4. Generating Breathable Air Through Dissociation of N2O

    NASA Technical Reports Server (NTRS)

    Zubrin, Robert; Frankie, Brian

    2006-01-01

    A nitrous oxide-based oxygen-supply system (NOBOSS) is an apparatus in which a breathable mixture comprising 2/3 volume parts of N2 and 1/3 volume part of O2 is generated through dissociation of N2O. The NOBOSS concept can be adapted to a variety of applications in which there are requirements for relatively compact, lightweight systems to supply breathable air. These could include air-supply systems for firefighters, divers, astronauts, and workers who must be protected against biological and chemical hazards. A NOBOSS stands in contrast to compressed-gas and cryogenic air-supply systems. Compressed-gas systems necessarily include massive tanks that can hold only relatively small amounts of gases. Alternatively, gases can be stored compactly in greater quantities and at low pressures when they are liquefied, but then cryogenic equipment is needed to maintain them in liquid form. Overcoming the disadvantages of both compressed-gas and cryogenic systems, the NOBOSS exploits the fact that N2O can be stored in liquid form at room temperature and moderate pressure. The mass of N2O that can be stored in a tank of a given mass is about 20 times the mass of compressed air that can be stored in a tank of equal mass. In a NOBOSS, N2O is exothermically dissociated to N2 and O2 in a main catalytic reactor. In order to ensure the dissociation of N2O to the maximum possible extent, the temperature of the reactor must be kept above 400 C. At the same time, to minimize concentrations of nitrogen oxides (which are toxic), it is necessary to keep the reactor temperature at or below 540 C. To keep the temperature within the required range throughout the reactor and, in particular, to prevent the formation of hot spots that would be generated by local concentrations of the exothermic dissociation reaction, the N2O is introduced into the reactor through an injector tube that features carefully spaced holes to distribute the input flow of N2O widely throughout the reactor. A NOBOSS

  5. Turbulence in Supercritical O2/H2 and C7H16/N2 Mixing Layers

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth; Okong'o, Nora

    2003-01-01

    This report presents a study of numerical simulations of mixing layers developing between opposing flows of paired fluids under supercritical conditions, the purpose of the study being to elucidate chemical-species-specific aspects of turbulence. The simulations were performed for two different fluid pairs O2/H2 and C7H16/N2 at similar reduced initial pressures (reduced pressure is defined as pressure divided by critical pressure). Thermodynamically, O2/H2 behaves more nearly like an ideal mixture and has greater solubility, relative to C7H16/N2, which departs strongly from ideality. Because of a specified smaller initial density stratification, the C7H16/N2 layers exhibited greater levels of growth, global molecular mixing, and turbulence. However, smaller density gradients at the transitional state for the O2/H2 system were interpreted as indicating that locally, this system exhibits enhanced mixing as a consequence of its greater solubility and closer approach to ideality. These thermodynamic features were shown to affect entropy dissipation, which was found to be larger for O2/H2 and concentrated in high-density-gradient-magnitude regions that are distortions of the initial density-stratification boundary. In C7H16/N2, the regions of largest dissipation were found to lie in high-density-gradient-magnitude regions that result from mixing of the two fluids.

  6. Infrared spectroscopic parameters of COF2, SF6, ClO, N2, and O2

    NASA Technical Reports Server (NTRS)

    Rinsland, Curtis P.; Goldman, Aaron; Flaud, Jean-Marie

    1992-01-01

    The status of the middle infrared spectroscopy of selected atmospheric trace gases, COF2, SF6, ClO, N2, and O2 is reviewed. Emphasis is placed on improved sets of spectroscopic parameters that have been included in the 1991 and 1992 versions of the HITRAN database.

  7. Charge transfer coefficients for the O+/2D/ + N2 and O+/2D/ + O2 excited ion reactions at thermal energy. [from ionospheric observations

    NASA Technical Reports Server (NTRS)

    Johnsen, R.; Biondi, M. A.

    1980-01-01

    An investigation of the reactions of metastable O(+) ions and O2 using drift tube-mass spectrometer techniques is presented. It was shown that ordinary charge transfer is the dominant reaction branch in both cases; it occurs with large rate coefficients, k(N2) = (8 + or - 2) x 10 to the -10th cu cm/s and k(O2) = (7 + or - 2) x 10 to the -10th cu cm/s, at an effective ion temperature of about 550 K. The reaction He(+) + O2 is used as a source of metastable O(+) ions, and evidence is presented that the O(+) ions so produced are in the 2D state rather than the 2P state. The results are compared with previous measurements, and inferences drawn from ionospheric observations.

  8. Absolute intensity and polarization of rotational Raman scattering from N2, O2, and CO2

    NASA Technical Reports Server (NTRS)

    Penney, C. M.; St.peters, R. L.; Lapp, M.

    1973-01-01

    An experimental examination of the absolute intensity, polarization, and relative line intensities of rotational Raman scattering (RRS) from N2, O2, and CO2 is reported. The absolute scattering intensity for N2 is characterized by its differential cross section for backscattering of incident light at 647.1 nm, which is calculated from basic measured values. The ratio of the corresponding cross section for O2 to that for N2 is 2.50 plus or minus 5 percent. The intensity recent for N2, O2, and CO2 are shown to compare favorably to values calculated from recent measurements of the depolarization of Rayleigh scattering plus RRS. Measured depolarizations of various RRS lines agree to within a few percent with the theoretical value of 3/4. Detailed error analyses are presented for intensity and depolarization measurements. Finally, extensive RRS spectra at nominal gas temperatures of 23 C, 75 C, and 125 C are presented and shown to compare favorably to theoretical predictions.

  9. The calculation of quenching rate coefficients of O2 Herzberg states in collisions with CO2, CO, N2, O2 molecules

    NASA Astrophysics Data System (ADS)

    Kirillov, A. S.

    2014-01-01

    The removal rates of Herzberg states of molecular oxygen O2(cΣu-, v = 0-16), O2(AΔu, v = 0-11), O2(AΣu+, v = 0-10) in the collisions with ground-state CO2, CO, N2, O2 molecules are calculated according to analytical expressions. The study includes a consideration of intramolecular electron energy transfers without and with vibrational excitation of target molecules and intermolecular processes. The preliminary calculations show important role of electronic-vibrational energy transfer processes in the quenching O2(AΣu+, v) + CO2; O2(cΣu-, v) + CO2, CO, N2; O2(AΔu, v) + O2. Reasonable agreement of the calculated rate coefficients with data of laser experimental measurements is obtained.

  10. Helicity in Supercritical O2/H2 and C7H16/N2 Mixing Layers

    NASA Technical Reports Server (NTRS)

    Okongo, Nora; Bellan, Josette

    2004-01-01

    This report describes a study of databases produced by direct numerical simulation of mixing layers developing between opposing flows of two fluids under supercritical conditions, the purpose of the study being to elucidate chemical-species-specific aspects of turbulence, with emphasis on helicity. The simulations were performed for two different fluid pairs -- O2/H2 and C7H16/N2 -- at similar values of reduced pressure.

  11. Fast gas heating in N2/O2 mixtures under nanosecond surface dielectric barrier discharge: the effects of gas pressure and composition

    PubMed Central

    Nudnova, M. M; Kindysheva, S. V; Aleksandrov, N. L; Starikovskii, A. Yu

    2015-01-01

    The fractional electron power quickly transferred to heat in non-equilibrium plasmas was studied experimentally and theoretically in N2/O2 mixtures subjected to high electric fields. Measurements were performed in and after a nanosecond surface dielectric barrier discharge at various (300–750 Torr) gas pressures and (50–100%) N2 percentages. Observations showed that the efficiency of fast gas heating is almost independent of pressure and becomes more profound when the fraction of O2 in N2/O2 mixtures increases. The processes that contribute towards the fast transfer of electron energy to thermal energy were numerically simulated under the conditions considered. Calculations were compared with measurements and the main channels of fast gas heating were analysed at the gas pressures, compositions and electric fields under study. It was shown that efficient fast gas heating in the mixtures with high fraction of O2 is due to a notable contribution of heat release during quenching of electronically excited N2 states in collisions with O2 molecules and to ion–ion recombination. The effect of hydrocarbon addition to air on fast gas heating was numerically estimated. It was concluded that the fractional electron power transferred to heat in air, as a first approximation, could be used to estimate this effect in lean and stoichiometric hydrocarbon–air mixtures. PMID:26170431

  12. Enhanced O-2 Selectivity versus N-2 by Partial Metal Substitution in Cu-BTC

    SciTech Connect

    Sava Gallis, Dorina F.; Parkes, Marie V.; Greathouse, Jeffery A.; Zhang, Xiaoyi; Nenoff, Tina M.

    2015-03-24

    Here, we describe the homogeneous substitution of Mn, Fe, and Co at various levels into a prototypical metal organic framework (MOP), namely Cu-BTC (HKUST-1), and the effect of that substitution on preferential gas sorption. Using a combination of density functional theory (DFT) calculations, postsynthetic metal substitutions, materials characterization, and gas sorption testing, we demonstrate that the identity of the metal ion has a quantifiable effect on their oxygen and nitrogen sorption properties at cryogenic temperatures. An excellent correlation is found between O-2/N-2 selectivities determined experimentally at 77 K and the difference in O-2 and N-2 binding energies calculated from DFT modeling data: Mn > Fe Co >> Cu. Room temperature gas sorption studies were also performed and correlated with metal substitution. The Fe-exchanged sample shows a significantly higher nitrogen isosteric heat of adsorption at temperatures close to ambient conditions (273-298 K) as compared to all other metals studied, indicative of favorable interactions between N-2 and coordinatively unsaturated Fe metal centers. Interestingly, differences in gas adsorption results at cryogenic and room temperatures are evident; they are explained by comparing experimental results with DFT binding energies (0 K) and room temperature Grand Canonical Monte Carlo simulations.

  13. Enhanced O2 selectivity versus N2 by partial metal substitution in Cu-BTC

    DOE PAGESBeta

    Sava Gallis, Dorina F.; Parkes, Marie V.; Greathouse, Jeffery A.; Zhang, Xiaoyi; Nenoff, Tina M.

    2015-03-05

    Here we describe the homogeneous substitution of Mn, Fe and Co at various levels into a prototypical metal-organic framework (MOF), namely Cu-BTC (HKUST-1), and the effect of that substitution on preferential gas sorption. Using a combination of density functional theory (DFT) calculations, postsynthetic metal substitutions, materials characterization, and gas sorption testing, we demonstrate that the identity of the metal ion has a quantifiable effect on their oxygen and nitrogen sorption properties at cryogenic temperatures. An excellent correlation is found between O2/N2 selectivities determined experimentally at 77 K and the difference in O2 and N2 binding energies calculated from DFT modelingmore » data: Mn > Fe > Co > Cu. Room temperature gas sorption studies were also performed and correlated with metal substitution. The Fe-exchanged sample shows a significantly higher nitrogen isosteric heat of adsorption at temperatures close to ambient conditions (273 K - 298 K) as compared to all other metals studied, indicative of favorable interactions between N2 and coordinatively unsaturated Fe metal centers. Furthermore, differences in gas adsorption results at cryogenic and room temperatures are evident; they are explained by comparing experimental results with DFT binding energies (0 K) and room temperature Grand Canonical Monte Carlo simulations.« less

  14. Turbulent piloted partially-premixed flames with varying levels of O2/N2: stability limits and PDF calculations

    NASA Astrophysics Data System (ADS)

    Juddoo, Mrinal; Masri, Assaad R.; Pope, Stephen B.

    2011-12-01

    This paper reports measured stability limits and PDF calculations of piloted, turbulent flames of compressed natural gas (CNG) partially-premixed with either pure oxygen, or with varying levels of O2/N2. Stability limits are presented for flames of CNG fuel premixed with up to 20% oxygen as well as CNG-O2-N2 fuel where the O2 content is varied from 8 to 22% by volume. Calculations are presented for (i) Sydney flame B [Masri et al. 1988] which uses pure CNG as well as flames B15 to B25 where the CNG is partially-premixed with 15-25% oxygen by volume, respectively and (ii) Sandia methane-air (1:3 by volume) flame E [Barlow et al. 2005] as well as new flames E15 and E25 that are partially-premixed with 'reconstituted air' where the O2 content in nitrogen is 15 and 25% by volume, respectively. The calculations solve a transported PDF of composition using a particle-based Monte Carlo method and employ the EMST mixing model as well as detailed chemical kinetics. The addition of oxygen to the fuel increases stability, shortens the flames, broadens the reaction zone, and shifts the stoichiometric mixture fraction towards the inner side of the jet. It is found that for pure CNG flames where the reaction zone is narrow (∼0.1 in mixture fraction space), the PDF calculations fail to reproduce the correct level of local extinction on approach to blow-off. A broadening in the reaction zone up to about 0.25 in mixture fraction space is needed for the PDF/EMST approach to be able to capture these finite-rate chemistry effects. It is also found that for the same level of partial premixing, increasing the O2/N2 ratio increases the maximum levels of CO and NO but shifts the peak to richer mixture fractions. Over the range of oxygenation investigated here, stability limits have shown to improve almost linearly with increasing oxygen levels in the fuel and with increasing the contribution of release rate from the pilot.

  15. Characterization of Water Coordination to Ferrous Nitrosyl Complexes with fac-N2O, cis-N2O2, and N2O3 Donor Ligands.

    PubMed

    McCracken, John; Cappillino, Patrick J; McNally, Joshua S; Krzyaniak, Matthew D; Howart, Michael; Tarves, Paul C; Caradonna, John P

    2015-07-01

    Electron paramagnetic resonance (EPR) experiments were done on a series of S = (3)/2 ferrous nitrosyl model complexes prepared with chelating ligands that mimic the 2-His-1-carboxylate facial triad iron binding motif of the mononuclear nonheme iron oxidases. These complexes formed a comparative family, {FeNO}(7)(N2Ox)(H2O)3-x with x = 1-3, where the labile coordination sites for the binding of NO and solvent water were fac for x = 1 and cis for x = 2. The continuous-wave EPR spectra of these three complexes were typical of high-spin S = (3)/2 transition-metal ions with resonances near g = 4 and 2. Orientation-selective hyperfine sublevel correlation (HYSCORE) spectra revealed cross peaks arising from the protons of coordinated water in a clean spectral window from g = 3.0 to 2.3. These cross peaks were absent for the {FeNO}(7)(N2O3) complex. HYSCORE spectra were analyzed using a straightforward model for defining the spin Hamiltonian parameters of bound water and showed that, for the {FeNO}(7)(N2O2)(H2O) complex, a single water conformer with an isotropic hyperfine coupling, Aiso = 0.0 ± 0.3 MHz, and a dipolar coupling of T = 4.8 ± 0.2 MHz could account for the data. For the {FeNO}(7)(N2O)(H2O)2 complex, the HYSCORE cross peaks assigned to coordinated water showed more frequency dispersion and were analyzed with discrete orientations and hyperfine couplings for the two water molecules that accounted for the observed orientation-selective contour shapes. The use of three-pulse electron spin echo envelope modulation (ESEEM) data to quantify the number of water ligands coordinated to the {FeNO}(7) centers was explored. For this aspect of the study, HYSCORE spectra were important for defining a spectral window where empirical integration of ESEEM spectra would be the most accurate. PMID:26090963

  16. Efficient vibrational Raman conversion in O2 and N2 cells by use of superfluorescence seeding

    NASA Technical Reports Server (NTRS)

    Zhang, Barry; Lempert, Walter R.; Miles, R. B.; Diskin, Glenn

    1993-01-01

    We report first-Stokes vibrational conversion efficiency of 21 percent and 35 percent, respectively, in high-pressure O2- and N2-stimulated Raman cells. Broadband superfluorescence is employed to seed these Raman cells, significantly increasing the conversion efficiences with no measured effect on the Raman spectrum. The addition of helium buffer gas reduces competition from stimulated Brillouin scattering and improves the pulse-to-pulse stability and spatial mode quality by increasing the thermal conductivity. Further improvement of the spatial mode quality is achieved by use of gentle heating on the bottom of the cell to induce convection.

  17. Laser diagnostics of pulverized coal combustion in O2/N2 and O2/CO2 conditions: velocity and scalar field measurements

    NASA Astrophysics Data System (ADS)

    Balusamy, Saravanan; Kamal, M. Mustafa; Lowe, Steven M.; Tian, Bo; Gao, Yi; Hochgreb, Simone

    2015-05-01

    Optical diagnostic techniques are applied to a 21 kW laboratory-scale pulverized coal-methane burner to map the reaction zone during combustion, in mixtures with varying fractions of O2, N2 and CO2. Simultaneous Mie scatter and OH planar laser-induced fluorescence (PLIF) measurements have been carried out to study the effect of the oxidizer/diluent concentrations as well as the coal-loading rate. The spatial distribution of soot is captured using laser-induced incandescence (LII). Additionally, velocity profiles at selected axial locations are measured using the pairwise two-dimensional laser Doppler velocimetry technique. The OH PLIF images capture the reaction zones of pilot methane-air flames and the variation of the coal flame structure under various O2/CO2 compositions. Coal particles devolatilize immediately upon crossing the flame interface, so that the Mie scatter signal almost vanishes. Increasing coal-loading rates leads to higher reaction rates and shorter flames. LII measurements show that soot is formed primarily in the wake of remaining coal particles in the product regions. Finally, differences in the mean and RMS velocity field are explained by the combined action of thermal expansion and the changes in particle diameter between reacting and non-reacting flows.

  18. CO oxidation at nickel centres by N2O or O2 to yield a novel hexanuclear carbonate.

    PubMed

    Horn, Bettina; Limberg, Christian; Herwig, Christian; Feist, Michael; Mebs, Stefan

    2012-08-25

    Reaction of a nickel(0) carbonyl complex, K(2)[L(tBu)NiCO](2), with N(2)O generates a cyclic carbonate compound composed of six [Ni(II)(CO(3))K](+) units. The same product can also be obtained using O(2) as the oxidant in a solid-state/gas reaction. These conversions represent unique examples of a nickel-bound CO oxidation by N(2)O and O(2), respectively. PMID:22785444

  19. Etch Properties of Amorphous Carbon Material Using RF Pulsing in the O2/N2/CHF3 Plasma.

    PubMed

    Jeon, Min Hwan; Park, Jin Woo; Yun, Deok Hyun; Kim, Kyong Nam; Yeom, Geun Young

    2015-11-01

    The amorphous carbon layer (ACL), used as the hardmask for the etching of nanoscale semi-conductor materials, was etched using O2/CHF3 in addition to O2/N2 using pulsed dual-frequency capacitively coupled plasmas, and the effects of source power pulsing for different gas combinations on the characteristics of the plasmas and ACL etching were investigated. As the etch mask for ACL, a patterned SiON layer was used. The etch rates of ACL were decreased with the decrease of pulse duty percentage for both O2/N2 and O2/CHF3 due to decrease of the reactive radicals, such as F and O, with decreasing pulse duty percentage. In addition, at the same pulse duty percentage, the etch selectivity of ACL/SiON with O2/CHF3 was also significantly lower than that with O2/N2. However, the etch profiles of ACL with O2/CHF3 was more anisotropic and the etch profiles were further improved with decreasing the pulse duty percentage than those of ACL with O2/N2. The improved anisotropic etch profiles of ACL with decreasing pulse duty percentage for O2/CHF3 were believed to be related to the formation of a more effective passivation layer, such as a thick fluorocarbon layer, on the sidewall of the ACL during the etching with O2/CHF3, compared to the weak C-N passivation layer formed on the sidewall of ACL when using O2/N2. PMID:26726555

  20. Infrared spectroscopy at high temperature : N2- and O2-broadening coefficients in the ν4 band of CH4

    NASA Astrophysics Data System (ADS)

    Fissiaux, Laurent; Populaire, Jean-Claude; Blanquet, Ghislain; Lepère, Muriel

    2015-11-01

    In the present work, we have developed a high-temperature absorption cell for infrared spectroscopy. This absorption cell can contain gases of the room temperature up to 650 K without temperature gradient. The construction of the cell and its technical features are described in detail in this paper. In order to demonstrate the feasibility and the interest of the cell, we have measured the N2-, O2- and air-broadening coefficients of, respectively, six and three absorption lines in the ν4 band of methane at four temperatures (350, 425, 500, 575 K). The measurements of these coefficients was realized with a tunable diode-laser spectrometer. The line parameters were obtained by fitting to the experimental profile the Voigt line shape and the Rautian and Galatry models taking into account the collisional narrowing. For these lines, the n parameter of the temperature dependence has been determined.

  1. Tuning Effect of N2 on Atmospheric-Pressure Cold Plasma CVD of TiO2 Photocatalytic Films

    NASA Astrophysics Data System (ADS)

    Di, Lanbo; Li, Xiaosong; Zhao, Tianliang; Chang, Dalei; Liu, Qianqian; Zhu, Aimin

    2013-01-01

    To deposit TiO2 films through plasma CVD, the partial pressure ratio of O2 to TiCl4 should be greater than the stoichiometric ratio (pO2/pTiCl4 > 1). However, this may lead to the formation of powder instead of film on the substrate when using volume dielectric barrier discharge (volume-DBD) at atmospheric pressure. In this study, by adding N2 into the working gas Ar, TiO2 photocatalytic films were successfully fabricated in the presence of excess O2 (pO2/pTiCl4 = 2.6) by using a wire-to-plate atmospheric-pressure volume-DBD. The tuning effect of N2 on the deposition of TiO2 film was studied in detail. The results showed that by increasing the N2 content, the deposition rate and particle size of the TiO2 film were reduced, and its photocatalytic activity was enhanced. The tuning mechanism of N2 is further discussed.

  2. K-shell photoabsorption coefficients of O2, CO2, CO, and N2O

    NASA Technical Reports Server (NTRS)

    Barrus, D. M.; Blake, R. L.; Burek, A. J.; Chambers, K. C.; Pregenzer, A. L.

    1979-01-01

    The total photoabsorption coefficient has been measured from 500 to 600 eV around the K edge of oxygen in gases O2, CO2, CO, and N2O by means of a gold continuum source and crystal spectrometer with better than 1-eV resolution. The cross sections are dominated by discrete molecular-orbital transitions below the K-edge energy. A few Rydberg transitions were barely detectable. Broad shape resonances appear at or above the K edge. Additional broad, weak features above the K edge possibly arise from shake up. Quantitative results are given that have about 10% accuracy except on the very strong peaks. All the measured features are discussed in relation to other related measurements and theory.

  3. Direct N2H4/H2O2 Fuel Cells Powered by Nanoporous Gold Leaves

    PubMed Central

    Yan, Xiuling; Meng, Fanhui; Xie, Yun; Liu, Jianguo; Ding, Yi

    2012-01-01

    Dealloyed nanoporous gold leaves (NPGLs) are found to exhibit high electrocatalytic properties toward both hydrazine (N2H4) oxidation and hydrogen peroxide (H2O2) reduction. This observation allows the implementation of a direct hydrazine-hydrogen peroxide fuel cell (DHHPFC) based on these novel porous membrane catalysts. The effects of fuel and oxidizer flow rate, concentration and cell temperature on the performance of DHHPFC are systematically investigated. With a loading of ~0.1 mg cm−2 Au on each side, an open circuit voltage (OCV) of 1.2 V is obtained at 80°C with a maximum power density 195 mW cm−2, which is 22 times higher than that of commercial Pt/C electrocatalyst at the same noble metal loading. NPGLs thus hold great potential as effective and stable electrocatalysts for DHHPFCs. PMID:23230507

  4. Nonstationary effects in ozone generation by barrier discharges in N2/O2 mixtures

    NASA Astrophysics Data System (ADS)

    Zosimov, A. V.; Lunin, V. V.; Samoilovich, V. G.; Abramovskaya, E. A.; Mankelevich, Yu. A.; Poroykov, A. Yu.; Rakhimova, T. V.; Voloshin, D. G.

    2016-08-01

    The yield of ozone in barrier discharges in oxygen-nitrogen mixtures containing 0.001 to 40% of nitrogen is investigated experimentally. Phenomena of the nonstationarity of processes of ozone generation that differ from the known ozone-zero phenomenon (OZP) apparent in the reduced efficiency of ozone generation in very high purity oxygen at long periods (from hours to tens of hours) of ozonator operation are found. It is established that the characteristic times (from minutes to tens of minutes) of ozone attaining stationary values after changes in the discharge parameters indicate slow adjustment of the surface condition of insulators and thus the heterogeneous decay of ozone to more rapidly changing flows of neutral and charged particles from gas discharge plasma on the surfaces of dielectrics. The possibility of such a scenario is confirmed using a new analytical approach and numerical calculations of the plasma-chemical kinetics of N2/O2 mixtures presented in the accompanying theoretical study.

  5. Electron ionization dynamics of N2 and O2 molecules: Velocity-map imaging

    NASA Astrophysics Data System (ADS)

    Bull, James N.; Lee, Jason W. L.; Vallance, Claire

    2015-02-01

    This paper reports a crossed-beam velocity-map imaging study into the electron ionization dynamics of jet-cooled N2 and O2 molecules at electron collision energies from 35 to 100 eV. The use of velocity-map imaging detection provides insight into the detailed ionization dynamics through the dimension of the product ion kinetic energy associated with impulsive dissociation. In particular, "mesoscopic" cross sections corresponding to ionization from manifolds of energetically close states converging to the same dissociation asymptote are reported for a number of single-ionization channels. In addition, a range of double-ionization cross sections have been characterized, including those yielding X2 2 + dications. These are found to be in excellent agreement with other cross sections determined in coincidence measurements. This agreement supports a meaningful and accurate determination of the single-ionization channels.

  6. Temperature Dependence of the Collisional Removal of O2(A(sup 3)Sigma(sup +)(sub u), upsilon=9 ) with O2 and N2

    NASA Technical Reports Server (NTRS)

    Hwang, Eunsook S.; Copeland, Richard A.

    1997-01-01

    The temperature dependence of the collisional removal of O2 molecules in the upsilon = 9 level of the A(sup 3)Sigma(sup +)(sub u) electronic state has been studied for the colliders O2 and N2, over the temperature range 150 to 300 K. In a cooled flow cell, the output of a pulsed dye laser excites the O2 to the upsilon = 9 level of the A(sup 3)Sigma(sup +)(sub u) state, and the output of a time-delayed second laser monitors the temporal evolution of this level via a resonance-enhanced ionization. We find the u thermally averaged removal cross section for O2 collisions is constant (approx. 10 A(sup 2)) between room temperature and 200 K, then increases rapidly with decreasing temperature, doubling by 150 K. In contrast, the N2 cross section at 225 K is approx. 8% smaller and gradually increases to a value at 150 K that is approx. 60% larger than the room temperature value. The difference between the temperature dependence of the O2 and N2 collision cross section implies that the removal by oxygen becomes more important at the lower temperatures found in the mesosphere, but removal by N2 still dominates.

  7. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    NASA Astrophysics Data System (ADS)

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-08-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

  8. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    PubMed Central

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-01-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate. PMID:26235671

  9. H2, N2, and O2 metabolism by isolated heterocysts from Anabaena sp. strain CA.

    PubMed Central

    Smith, R L; Kumar, D; Zhang, X K; Tabita, F R; Van Baalen, C

    1985-01-01

    Metabolically active heterocysts isolated from wild-type Anabaena sp. strain CA showed high rates of light-dependent acetylene reduction and hydrogen evolution. These rates were similar to those previously reported in heterocysts isolated from the mutant Anabaena sp. strain CA-V possessing fragile vegetative cell walls. Hydrogen production was observed with isolated heterocysts. The ratio of C2H4 to H2 produced ranged from 0.9 to 1.2, and H2 production exhibited unique biphasic kinetics consisting of a 1 to 2-min burst of hydrogen evolution followed by a lower, steady-state rate of hydrogen production. This burst was found to be dependent upon the length of the dark period immediately preceding illumination and may be related to dark-to-light ATP transients. The presence of 100 nM NiCl2 in the growth medium exerted an effect on both acetylene reduction and hydrogen evolution in the isolated heterocysts from strain CA. H2-stimulated acetylene reduction was increased from 2.0 to 3.2 mumol of C2H4 per mg (dry weight) per h, and net hydrogen production was abolished. A phenotypic Hup- mutant (N9AR) of Anabaena sp. strain CA was isolated which did not respond to nickel. In isolated heterocysts from N9AR, ethylene production rates were the same under both 10% C2H2-90% Ar and 10% C2H2-90% H2 with or without added nickel, and net hydrogen evolution was not affected by the presence of 100 nM Ni2+. Isolated heterocysts from strain CA were shown to have a persistent oxygen uptake of 0.7 mumol of O2 per mg (dry weight) per h, 35% of the rate of whole filaments, at air saturating O2 levels, indicating that O2 impermeability is not a requirement for active heterocysts. PMID:3921524

  10. In Situ Multi-Species (O2, N2, Fuel, Other) Fiber Optic Sensor for Fuel Tank Ullage

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet

    2007-01-01

    A rugged and compact fiber optic sensor system for in situ real-time measurement of nitrogen (N2), oxygen (O2), hydrocarbon (HC) fuel vapors, and other gases has been developed over the past several years at Glenn Research Center. The intrinsically-safe, solid-state fiber optic sensor system provides a 1% precision measurement (by volume) of multiple gases in a 5-sec time window. The sensor has no consumable parts to wear out and requires less than 25 W of electrical power to operate. The sensor head is rugged and compact and is ideal for use in harsh environments such as inside an aircraft fuel tank, or as a feedback sensor in the vent-box of an on-board inert gas generation system (OBIGGS). Multiple sensor heads can be monitored with a single optical detection unit for a cost-effective multi-point sensor system. The present sensor technology is unique in its ability to measure N2 concentration directly, and in its ability to differentiate different types of HC fuels. The present sensor system provides value-added aircraft safety information by simultaneously and directly measuring the nitrogen-oxygen-fuel triplet, which provides the following advantages: (1) information regarding the extent of inerting by N2, (2) information regarding the chemical equivalence ratio, (3) information regarding the composition of the aircraft fuel, and (4) by providing a self-consistent calibration by utilizing a singular sensor for all species. Using the extra information made available by this sensor permits the ignitability of a fuel-oxidizer mixture to be more accurately characterized, which may permit a reduction in the amount of inerting required on a real-time basis, and yet still maintain a fire-safe fuel tank. This translates to an increase in fuel tank fire-safety through a better understanding of the physics of fuel ignition, and at the same time, a reduction in compressed bleed air usage and concomitant aircraft operational costs over the long-run. The present fiber

  11. Conversion of photosynthetic products in the light in CO2-free O 2 and N 2 in leaves of Zea mays L. and Phaseolus vulgaris L.

    PubMed

    Lewanty, Z; Maleszewski, S

    1976-01-01

    After 10 min illumination of segments of bean (Phaseolus vulgaris L.) or maize (Zea mays L.) leaves in air with (14)CO2, the atmosphere was changed to CO2-free O2 or N2 and conversion of photosynthetic products in the light was investigated. The experiments have shown that after the (14)CO2 assimilation period the bean leaves contain the pool of weakly fixed (14)C (WF-(14)C) which is converted into stable products during the subsequent period of illumination in CO2-free N2. In O2 atmosphere the WF-(14)C pool is initially the main source of CO2 evolved. The marked decrease in radioactivity of sucrose and starch during illumination of bean leaves in O2 atmosphere indicates that these compounds were also the source of CO2 evolved in the light. The total amount of previously fixed (14)C remained almost on the same level during illumination of maize leaves in N2 as well as in O2. However, oxygen changed the distribution of (14)C in photosynthetic products, which is suggested to be the consequence of the photorespiration process in maize. PMID:24424758

  12. Collisional Removal of OH (X (sup 2)Pi, nu=7) by O2, N2, CO2, and N2O

    NASA Technical Reports Server (NTRS)

    Knutsen, Karen; Dyer, Mark J.; Copeland, Richard A.

    1996-01-01

    Collisional removal rate constants for the OH (X 2PI, nu = 7) radical are measured for the colliders O2, CO2, and N2O, and an upper limit is established for N2. OH(nu = 4) molecules, generated in a microwave discharge flow cell by the reaction of hydrogen atoms with ozone, are excited to v = 7 by the output of a pulsed infrared laser via direct vibrational overtone excitation. The temporal evolution of the P = 7 population is probed as a function of the collider gas partial pressure by a time-delayed pulsed ultraviolet laser. Fluorescence from the B 21 + state is detected in the visible spectral region.

  13. The effect of N2/+/ recombination on the aeronomic determination of the charge exchange rate coefficient of O/+//2D/ with N2

    NASA Technical Reports Server (NTRS)

    Torr, D. G.; Orsini, N.

    1978-01-01

    The Atmosphere Explorer (AE) data are reexamined in the light of new laboratory measurements of the N2(+) recombination rate coefficient alpha. The new measurements support earlier measurements which yielded values of alpha significantly lower than the AE values. It is found that the values for alpha determined from the satellite data can be reconciled with the laboratory measurements, if the charge exchange rate coefficient for O(+)(2D) with N2 is less than one-quarter of that derived in the laboratory by Rutherford and Vroom (1971).

  14. Quantum Cascade Laser Measurements of Line Intensities, N2-, O2- and Ar- Collisional Broadening Coefficients of N2O in the ν3 Band Near 4.5 µm.

    PubMed

    Es-Sebbar, Et-Touhami; Deli, Meriem; Farooq, Aamir

    2016-06-01

    This study deals with precise measurements of absolute line intensities, N2-, O2- and Ar- collisional broadening coefficients of N2O in the P-branch of the ν3 vibrational band near 4.5 µm. Collisional broadening coefficients of N2O-air are derived from the N2- and O2- broadening contributions by considering an ideal atmospheric composition. Studies are performed at room temperature for 10 rotational transitions over 2190-2202 cm(-1) spectral range using a distributed-feedback quantum cascade laser. To retrieve spectroscopic parameters for each individual transition, measured absorption line shape is simulated within Voigt and Galatry profiles. The obtained results compare well with previous experimental data available in the literature: the discrepancies being less than 4% for most of the probed transitions. The spectroscopic data reported here are very useful for the design of sensors used to monitor the abundance of N2O in earth's atmosphere. PMID:27091906

  15. Effects of N2-O2 Gas Mixture Ratio on Microorganism Inactivation in Low-Pressure Surface Wave Plasma

    NASA Astrophysics Data System (ADS)

    Zhao, Ying; Ogino, Akihisa; Nagatsu, Masaaki

    2011-08-01

    In this study, the effect of N2/O2 gas mixture ratio on low-pressure surface wave plasma inactivation of spore-forming bacteria was investigated. It was experimentally confirmed from the quadrupole mass spectrometry measurements that the spores were etched by atomic oxygen via converting the hydrogen atoms constituting microorganisms into H2O and the carbon into CO2. On the basis of results of plasma diagnostics by optical emission spectroscopy and the results of inactivation efficiency by colony-forming units and scanning electron microscope, we found that although there is the highest ultraviolet (UV) emission intensity in pure N2 plasma and the highest etching efficiency in 90% O2/10% N2 plasma, the inactivation rate of microorganisms was not so efficient. The best inactivation result was obtained in 30-80% O2 gas mixture ratios after 60 s plasma irradiation. The present results indicated that more efficient inactivation is achieved by the synergetic effects between atomic oxygen etching and the vacuum ultraviolet (VUV)/UV emission by combining both effects via optimizing N2/O2 gas mixture ratio.

  16. Temperature dependence of the rate coefficient for charge exchange of metastable O/+//2D/ with N2. [in atmosphere

    NASA Technical Reports Server (NTRS)

    Torr, M. R.; Torr, D. G.

    1980-01-01

    Using a data base of aeronomical parameters measured on board the Atmosphere Explorer-C satellite, temperature dependence of the reaction rate coefficient is deduced for the charge exchange of O(+)(2D) with N2. The results indicate the Explorer values determined over the temperature range from 700 to 1900 K are not in conflict with laboratory measurements made at higher temperatures.

  17. Opposed jet burner studies of hydrogen combustion with pure and N2, NO-contaminated air

    NASA Technical Reports Server (NTRS)

    Guerra, Rosemary; Pellett, Gerald L.; Northam, G. Burton; Wilson, Lloyd G.

    1987-01-01

    A counterflow diffusion flame formed by an argon-bathed tubular-opposed jet burner (OJB) was used to determine the 'blowoff' and 'restore' combustion characteristics for jets of various H2/N2 mixtures and for jets of air contaminated by NO (which normally occurs in high-enthalpy airflows supplied to hypersonic test facilities for scramjet combustors). Substantial divergence of 'blowoff' and 'restore' limits occurred as H2 mass flux, M(H)2, increased, the H2 jet became richer, and the M(air)/M(H2 + N2) ratio increased from 1 to 3 (molar H2/O2 from 1 to 16). Both OJB limits were sensitive to reactant composition. One to six percent NO in air led to significant N2-corrected decreases in the M(H2) values for 'blowoff' (2-8 percent) and 'restore' (6-12 percent) for mole fractions of H2 ranging from 0.5 to 0.95. However, when H2/O2 was held constant, all N2-corrected changes in M(H2) were negligible.

  18. Measurements of the O+ plus N2 and O+ plus O2 reaction rates from 300 to 900 K

    NASA Technical Reports Server (NTRS)

    Chen, A.; Johnsen, R.; Biondi, M. A.

    1977-01-01

    Rate coefficients for the O(+) + N2 atom transfer and O(+) + O2 charge transfer reactions are determined at thermal energies between 300 K and 900 K difference in a heated drift tube mass spectrometer apparatus. At 300 K the values K(O(+) + N2) = (1.2 plus or minus 0.1) x 10 to the negative 12 power cubic cm/sec and k(O(+) + O2) = (2.1 plus or minus 0.2) x 10 to the negative 11 power cubic cm/sec were obtained, with a 50% difference decrease in the reaction rates upon heating to 700 K. These results are in good agreement with heated flowing afterglow results, but the O(+) + O2 thermal rate coefficients are systematically lower than equivalent Maxwellian rates inferred by conversion of nonthermal drift tube and flow drift data.

  19. Photocatalytic inactivation efficiency of anatase Nano-TiO(2) Sol on the H(9) N(2) avian influenza virus.

    PubMed

    Cui, Haixin; Jiang, Jianfang; Gu, Wei; Sun, Changjiao; Wu, Donglai; Yang, Tao; Yang, Guochen

    2010-01-01

    This study was conducted to investigate efficiency of TiO(2) nanomaterial as a novel environment-friendly disinfectant to control avian influenza (AI) by its photochemical sterilization ability. Anatase nano-TiO(2) sol, a neutral, viscous aqueous colloid of 1.6% TiO(2) , was synthesized from peroxotitanic acid solution according to the Ichinose method. Transmission electron microscope images showed that the TiO(2) particles were spindle-shaped with an average size of 50 nm. X-ray diffraction patterns revealed that the crystal phase of TiO(2) particles was anatase type with photocatalytic effect. A photocatalytic film of nano-TiO(2) sol was tested as a means of inactivating H(9) N(2) avian influenza virus (AIV). Inactivation capabilities were examined with 365nm ultraviolet (UV) radiation under black light by adjusting the UV intensity, the UV irradiation time and the quantity of AIV. The titer change of AIV was determined by hemagglutination tests. Cytopathic effect of Madin Darby canine kidney (MDCK) cells was monitored by inverted fluorescence microscope. The results showed that anatase nano-TiO(2) sol significantly inactivated AIV under UV irradiation of 365nm. The inactivation of AIV viruses reached up to 100%. Therefore, anatase nano-TiO(2) sol is a potentially environment-friendly antivirus agent to prevent AI. PMID:20553405

  20. Synthesis and characterization of different MnO2 morphologies for lithium-air batteries

    NASA Astrophysics Data System (ADS)

    Choi, Hyun-A.; Jang, Hyuk; Hwang, Hyein; Choi, Mincheol; Lim, Dongwook; Shim, Sang Eun; Baeck, Sung-Hyeon

    2014-09-01

    Manganese dioxide (MnO2) was synthesized in the forms of nanorods, nanoparticles, and mesoporous structures and the characteristics of these materials were investigated. Crystallinities were studied by x-ray diffraction and morphologies by scanning and transmission electron microscopy. Average pore sizes and specific surface areas were analyzed using the Barret-Joyner-Halenda and Brunauer-Emmett-Teller methods, respectively. Samples were also studied by cyclic voltammetry using 1M aqueous KOH solution saturated with either O2 or N2 as electrolytes to investigate their ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) activities. Of the samples produced, mesoporous MnO2 exhibited the highest ORR and OER catalytic activities. Mesoporous MnO2 supported on a gas diffusion layer was also used as a catalyst on the air electrode (cathode) of a lithium-air battery in organic electrolyte. The charge-discharge behavior of mesoporous MnO2 was investigated at a current density 0.2 mAcm-2 in a pure oxygen environment. Mesoporous MnO2 electrodes showed stable cycleability up to 65 cycles at a cell capacity of 700 mAhg-1.

  1. Experimental study of NO2 reduction in N2/Ar and O2/Ar mixtures by pulsed corona discharge.

    PubMed

    Zhu, Xinbo; Zheng, Chenghang; Gao, Xiang; Shen, Xu; Wang, Zhihua; Luo, Zhongyang; Cen, Kefa

    2014-11-01

    Non-thermal plasma technology has been regarded as a promising alternative technology for NOx removal. The understanding of NO2 reduction characteristics is extremely important since NO2 reduction could lower the total NO oxidation rate in the plasma atmosphere. In this study, NO2 reduction was experimentally investigated using a non-thermal plasma reactor driven by a pulsed power supply for different simulated gas compositions and operating parameters. The NO2 reduction was promoted by increasing the specific energy density (SED), and the highest conversion rates were 33.7%, 42.1% and 25.7% for Ar, N2/Ar and O2/Ar, respectively. For a given SED, the NO2 conversion rate had the order N2/Ar>Ar>O2/Ar. The highest energy yield of 3.31g/kWh was obtained in N2/Ar plasma and decreased with increasing SED; the same trends were also found in the other two gas compositions. The conversion rate decreased with increasing initial NO2 concentration. Furthermore, the presence of N2 or O2 led to different reaction pathways for NO2 conversion due to the formation of different dominating reactive radicals. PMID:25458679

  2. The reaction of N/2D/ with O2 as a source of O/1D/ atoms in aurorae

    NASA Technical Reports Server (NTRS)

    Rusch, D. W.; Sharp, W. E.; Gerard, J.-C.

    1978-01-01

    The source of O(1D) atoms in the auroral ionosphere is investigated using sounding rocket data. Previously, it has been shown that the conventional sources of O(1D) atoms in the aurora, dissociative recombination of O2(plus) and electron impact excitation of atomic oxygen, fail to explain the measured 6300 A volume emission rate profile. It is suggested that the atom-atom interchange reaction of N(2D) with O2 can be the major source of auroral 6300 A emission if O(1D) is created with high efficiency.

  3. Pressure broadening of the 2.5 THz H(Cl-35) rotational line by N2 and O2

    NASA Technical Reports Server (NTRS)

    Park, K.; Chance, K. V.; Nolt, I. G.; Radostitz, J. V.; Vanek, M. D.; Jennings, D. A.; Evenson, K. M.

    1991-01-01

    The pressure broadening coefficients of the 2.5 THz rotation line of H(Cl-35) by N2 and O2, for application to the analysis of far infrared spectra obtained in the stratosphere, are reported. The broadening coefficients were measured in absorption at 296 and 201 L using a tunable far infrared spectrometer. Results show that at room temperature the N2 pressure broadening coefficient is 0.0669 +/-0.0021/cm/atm (2sigma), with a temperature coefficient B of 0.58 +/-0.02.

  4. Unraveling the importance of surface association to the formation of molecules in a recombining N_2 / O_2 plasma

    NASA Astrophysics Data System (ADS)

    Zijlmans, R.; Welzel, S.; Gabriel, O.; van Helden, J. H.; Ropcke, J.; Schram, D. C.; Engeln, R.

    2008-07-01

    mainly on the gas phase formation of NO, but recognize the importance of the surfaces of the plasma reactor. Also Castillo et al. (2005) conclude in their studies that mainly heterogeneous processes are responsible for the formation of NO. To unravel the contribution of surface related processes to the total kinetics in a low pressure recombining plasma created from mixtures of N_2 and O_2, we measured the abundance of the stable molecules NO, N_2O and NO_2 in the plasma by means of IRMA, which is an IR tunable diode laser absorption system (Ropcke et al. 2000), and mass spectrometry (N_2 and O_2). A simulation, developed in CHEMKIN (2004), is used to investigate the effect of radical-surface interactions on the conversion of the feedstock gases. 2. RESULTS A plasma expansion is created from a flow of 3000 standard cubic centimeters per minute (sccm) argon through a cascaded arc plasma source. A total power of 5 kW (I = 75 A) is used to create the Ar plasma in the arc channel of the source. This plasma expands from the exit of the arc channel into the reactor, which is kept at a pressure of p = 20 Pa or p =100 Pa. A total flow of 1800 sccm of mixtures of N_2 and O_2 is injected directly into the reactor. The molecular abundances of the species formed in the plasma vessel are investigated as function of the ratio of admixed O_2 flow over the total flow of O_2 and N_2. In Figure 1 the symbols denote the measured mole fractions of Ar, N_2, O_2, NO, N_2O and NO_2, which are plotted on a semi-logarithmic scale. All the species are measured with the quadrupole mass spectrometer, while NO and N_2O are also measured by infrared absorption spectroscopy, using the IRMA system (Ropcke et al. 2000). The results of both the mass spectrometry measurements and tunable diode laser absorption spectroscopy measurements showed good agreement (within 10 %). For both pressures the molecules N_2 and O_2 are dominantly present. The abundance of the other types of molecules (NO, NO_2 and N_2O

  5. N2O seasonal distributions and air-sea exchange in UK estuaries: Implications for the tropospheric N2O source from European coastal waters

    NASA Astrophysics Data System (ADS)

    Barnes, J.; Upstill-Goddard, R. C.

    2011-03-01

    We report measurements of dissolved nitrous oxide (N2O), dissolved inorganic nitrogen, and turbidity in surveys of six UK inner estuaries between February 2000 and October 2002: the Humber, Forth, Tamar, Tyne, Tees, and Tay. We also present dissolved N2O data for the Wash outer estuary from May 1995 and dissolved O2 data for the Forth estuary from June 2001. N2O was always supersaturated relative to air and was highest in the Humber (range 140-6500%) and generally higher at all sites during summer. In estuaries with well defined turbidity maximum zones (TMZs) at low salinity, N2O was maximal in the TMZ, coincident with high NH4+ and/or NO3-. Inspection of the broad relationships between N2O, NH4+, NO3-, NO2-, and O2 revealed a predominantly nitrification source for the N2O in the estuaries studied; denitrification-derived N2O was apparently unimportant and denitrification did not constitute a significant NO3- sink. In the anthropogenically impacted Tees estuary N2O (saturation 140-2000%) was attributed to high NH4+ in sewage and industrial effluent. N2O emissions were thus primarily a function of NH4+ derived from internal resuspension and/or ammonification, or external inputs and were independent of river-borne NO3-. We reevaluated total UK and European estuarine N2O emissions using these and published data, based on an aerially weighted approach that separately identified inner and outer estuaries, and a downward revision of the total European estuarine area used in a recent synthesis. Our revised estimates, ˜1.9 ± 1.2 × 109 g N2O yr-1 for the UK and 6.8 ± 13.2 × 109 g N2O yr-1 for Europe (including UK) are dominated by large (area ˜200-500 km2) anthropogenically impacted macrotidal inner estuaries. By contrast large pristine macrotidal systems, small inner estuaries, and large outer estuaries appear to be comparatively minor N2O sources. The UK estuarine N2O source is <2% of the UK N2O budget. Our revised European estuarine N2O emission is around 2 orders

  6. Low-energy proton stopping power of N2, O2 and water vapor and deviations from Bragg's rule

    NASA Technical Reports Server (NTRS)

    Xu, Y. J.; Khandelwal, G. S.; Wilson, J. W.

    1984-01-01

    A modified local plasma model, based on the works of Lindhard and Winther; and Bethe, Brown, and Walske, is established. The Gordon-Kim model for molecular electron density is used to calculate stopping power of N2, O2, and water vapor for protons of energy ranging from 40 keV to 2.5 MeV, resulting in good agreement with experimental data. Deviations from Bragg's rule are evaluated and are discussed under the present theoretical model.

  7. Vibration-dissociation coupling in CO, N2 and O2 - An evaluation of analytic transition rate expressions

    NASA Technical Reports Server (NTRS)

    Gonzales, David A.; Varghese, Philip L.

    1993-01-01

    Closed form expressions for inelastic state-to-state and state-specific dissociative rate coefficients for utilization in vibrational master equation studies of shock heated CO, N2, and O2 highly dilute in Ar are considered. The master equation is linearized by neglecting diatom-diatom collisions and recombination. Master equation results indicate that the most significant contribution to dissociation comes from low and mid lying vibrational levels.

  8. Crystal structure, physical properties and HRTEM investigation of the new oxonitridosilicate EuSi2O2N2.

    PubMed

    Stadler, Florian; Oeckler, Oliver; Höppe, Henning A; Möller, Manfred H; Pöttgen, Rainer; Mosel, Bernd D; Schmidt, Peter; Duppel, Viola; Simon, Arndt; Schnick, Wolfgang

    2006-09-01

    The new layered oxonitridosilicate EuSi(2)O(2)N(2) has been synthesized in a radio-frequency furnace at temperatures of about 1400 degrees C starting from europium(III) oxide (Eu(2)O(3)) and silicon diimide (Si(NH)(2)). The structure of the yellow material has been determined by single-crystal X-ray diffraction analysis (space group P1 (no. 1), a=709.5(1), b=724.6(1), c=725.6(1) pm, alpha=88.69(2), beta=84.77(2), gamma=75.84(2) degrees ,V=360.19(9)x10(6) pm(3), Z=4, R1=0.0631, 4551 independent reflections, 175 parameters). Its anionic Si(2)O(2)N(2) (2-) layers consist of corner-sharing SiON(3) tetrahedra with threefold connecting nitrogen and terminal oxygen atoms. High-resolution transmission electron micrographs indicate both ordered and disordered crystallites as well as twinning. Magnetic susceptibility measurements of EuSi(2)O(2)N(2) exhibit Curie-Weiss behavior above 20 K with an effective magnetic moment of 7.80(5) mu(B) Eu(-1), indicating divalent europium. Antiferromagnetic ordering is detected at 4.5(2) K. EuSi(2)O(2)N(2) shows a field-induced transition with a critical field of 0.50(5) T. The four crystallographically different europium sites cannot be distinguished by (151)Eu Mössbauer spectroscopy. The room-temperature spectrum is fitted by one signal at an isomer shift of delta=-12.3(1) mm s(-1) subject to quadrupole splitting of DeltaE(Q)=-2.3(1) mm s(-1) and an asymmetry parameter of 0.46(3). Luminescence measurements show a narrow emission band with regard to the four crystallographic europium sites with an emission maximum at lambda=575 nm. PMID:16819723

  9. Low Temperature Rate Constants for the Reactions of O((1)D) with N2, O2, and Ar.

    PubMed

    Grondin, Romain; Loison, Jean-Christophe; Hickson, Kevin M

    2016-07-14

    The kinetics of the gas-phase quenching reactions O((1)D) + N2, O((1)D) + O2, and O((1)D) + Ar have been studied over the 50-296 K temperature range using the Laval nozzle method. O((1)D) atoms were created in situ by the pulsed photolysis of O3 precursor molecules at 266 nm. Rate constants for these processes were measured directly, following the decay of O((1)D) atoms through vacuum ultraviolet laser-induced fluorescence at 115.215 nm. For the O((1)D) + N2 and O((1)D) + O2 reactions, the quenching efficiencies are seen to increase as the temperature falls. For the O((1)D) + N2 system, this indicates the likely influence of the intermediate complex lifetime on the quenching rate through nonadiabatic processes. For the O((1)D) + O2 system, which is considerably more complex, this behavior could result from the interactions between several potential energy surfaces. PMID:26814664

  10. Mesoporous α-MnO 2/Pd catalyst air electrode for rechargeable lithium-air battery

    NASA Astrophysics Data System (ADS)

    Thapa, Arjun Kumar; Ishihara, Tatsumi

    Rechargeable lithium-air battery is studied using Pd/mesoporous α-MnO 2 air composite electrode. In the present work, we have studied the preparation and electrochemical performance of ordered mesoporous α-MnO 2 as a cathode catalyst for rechargeable Li-air batteries. α-MnO 2 was prepared by reduction of KMnO 4 solution in acidic aqueous solution followed by successive proton and alkali-ion exchange method. α-MnO 2 with high surface area of 33-133.0 m 2 g -1 was successively synthesized and used as an electrode catalyst for Li-air battery. It was found that the mixture of Pd and mesoporous α-MnO 2 electrode shows the high activity to oxidation and reduction of Li to form Li 2O 2 or Li 2O. Application of Pd/mesoporous α-MnO 2, which is mixed with teflonized acetylene binder (TAB), for air electrode is effective for decreasing the charge potential and also improved the energy efficiency as well as cyclability.

  11. The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations.

    PubMed

    Owens, Michael S; Cornwell, Jeffrey C

    2016-01-01

    The measurement of sediment-water exchange of gases and solutes in aquatic sediments provides data valuable for understanding the role of sediments in nutrient and gas cycles. After cores with intact sediment-water interfaces are collected, they are submerged in incubation tanks and kept under aerobic conditions at in situ temperatures. To initiate a time course of overlying water chemistry, cores are sealed without bubbles using a top cap with a suspended stirrer. Time courses of 4-7 sample points are used to determine the rate of sediment water exchange. Artificial illumination simulates day-time conditions for shallow photosynthetic sediments, and in conjunction with dark incubations can provide net exchanges on a daily basis. The net measurement of N2 is made possible by sampling a time course of dissolved gas concentrations, with high precision mass spectrometric analysis of N2:Ar ratios providing a means to measure N2 concentrations. We have successfully applied this approach to lakes, reservoirs, estuaries, wetlands and storm water ponds, and with care, this approach provides valuable information on biogeochemical balances in aquatic ecosystems. PMID:27583833

  12. A kinetic study of the reactions of Fe+ with N2O, N2, O2, CO2 and H2O, and the ligand-switching reactions Fe+.X + Y --> Fe+.Y + X (X = N2, O2, CO2; Y = O2, H2O).

    PubMed

    Vondrak, T; Woodcock, K R I; Plane, J M C

    2006-01-28

    A series of reactions involving Fe(+) ions were studied by the pulsed laser ablation of an iron target, with detection of ions by quadrupole mass spectrometry at the downstream end of a fast flow tube. The reactions of Fe(+) with N(2)O, N(2) and O(2) were studied in order to benchmark this new technique. Extending measurements of the rate coefficient for Fe(+) + N(2)O from 773 K to 185 K shows that the reaction exhibits marked non-Arrhenius behaviour, which appears to be explained by excitation of the N(2)O bending vibrational modes. The recombination of Fe(+) with CO(2) and H(2)O in He was then studied over a range of pressure and temperature. The data were fitted by RRKM theory combined with ab initio quantum calculations on Fe(+).CO(2) and Fe(+).H(2)O, yielding the following results (120-400 K and 0-10(3) Torr). For Fe(+) + CO(2): k(rec,0) = 1.0 x 10(-29) (T/300 K)(-2.31) cm(6) molecule(-2) s(-1); k(rec,infinity) = 8.1 x 10(-10) cm(3) molecule(-1) s(-1). For Fe(+) + H(2)O: k(rec,0) = 5.3 x 10(-29) (T/300 K)(-2.02) cm(6) molecule(-2) s(-1); k(rec,infinity) = 2.1 x 10(-9) (T/300 K)(-0.41) cm(3) molecule(-1) s(-1). The uncertainty in these rate coefficients is determined using a Monte Carlo procedure. A series of exothermic ligand-switching reactions were also studied at 294 K: k(Fe(+).N(2) + O(2)) = (3.17 +/- 0.41) x 10(-10), k(Fe(+).CO(2) + O(2)) = (2.16 +/- 0.35) x 10(-10), k(Fe(+).N(2) + H(2)O) = (1.25 +/- 0.14) x 10(-9) and k(Fe(+).O(2) + H(2)O) = (8.79 +/- 1.30) x 10(-10) cm(3) molecule(-1) s(-1), which are all between 36 and 52% of their theoretical upper limits calculated from long-range capture theory. Finally, the role of these reactions in the chemistry of meteor-ablated iron in the upper atmosphere is discussed. The removal rates of Fe(+) by N(2), O(2), CO(2) and H(2)O at 90 km altitude are approximately 0.1, 0.07, 3 x 10(-4) and 1 x 10(-6) s(-1), respectively. The initially formed Fe(+).N(2) and Fe(+).O(2) are converted into the H(2)O complex at

  13. Measurements and Modeling of Nitric Oxide Formation in Counterflow, Premixed CH4/O2/N2 Flames

    NASA Technical Reports Server (NTRS)

    Thomsen, D. Douglas; Laurendeau, Normand M.

    2000-01-01

    Laser-induced fluorescence (LIF) measurements of NO concentration in a variety of CH4/O2/N2 flames are used to evaluate the chemical kinetics of NO formation. The analysis begins with previous measurements in flat, laminar, premixed CH4/O2/N2 flames stabilized on a water-cooled McKenna burner at pressures ranging from 1 to 14.6 atm, equivalence ratios from 0.5 to 1.6, and volumetric nitrogen/oxygen dilution ratios of 2.2, 3.1 and 3.76. These measured results are compared to predictions to determine the capabilities and limitations of the comprehensive kinetic mechanism developed by the Gas Research Institute (GRI), version 2.11. The model is shown to predict well the qualitative trends of NO formation in lean-premixed flames, while quantitatively underpredicting NO concentration by 30-50%. For rich flames, the model is unable to even qualitatively match the experimental results. These flames were found to be limited by low temperatures and an inability to separate the flame from the burner surface. In response to these limitations, a counterflow burner was designed for use in opposed premixed flame studies. A new LIF calibration technique was developed and applied to obtain quantitative measurements of NO concentration in laminar, counterflow premixed, CH4/O2/N2 flames at pressures ranging from 1 to 5.1 atm, equivalence ratios of 0.6 to 1.5, and an N2/O2 dilution ratio of 3.76. The counterflow premixed flame measurements are combined with measurements in burner-stabilized premixed flames and counterflow diffusion flames to build a comprehensive database for analysis of the GRI kinetic mechanism. Pathways, quantitative reaction path and sensitivity analyses are applied to the GRI mechanism for these flame conditions. The prompt NO mechanism is found to severely underpredict the amount of NO formed in rich premixed and nitrogen-diluted diffusion flames. This underprediction is traced to uncertainties in the CH kinetics as well as in the nitrogen oxidation chemistry

  14. Cryogenically formed prestressed composite fiber-metal structures for O2/N2 high pressure gas tanks.

    NASA Technical Reports Server (NTRS)

    Gleich, D.

    1971-01-01

    Demonstration of high-structural-performance ARDEFORM cryoformed 301 stainless-steel glass-fiber-reinforced (GFR) vessels by room temperature tests of 13 1/2-in. diam spheres. Tests verified that the structural performance of ARDEFORM spherical GFR vessels not only exceeded that of all metal construction, but also bettered previous GFR experimental results by 50%. Achievement of essentially the full strength of fiberglass in a spherical wrap pattern was again verified. Significant weight advantages for this construction are projected for O2/N2 high-pressure gas tanks for Space Shuttle environmental control/life support system missions.

  15. Full CI benchmark calculations on N2, NO, and O2 - A comparison of methods for describing multiple bonds

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

    1987-01-01

    Full configuration interaction (CI) calculations on the ground states of N2, NO, and O2 using a DZP Gaussian basis are compared with single-reference SDCI and coupled pair approaches (CPF), as well as with CASSCF multireference CI approaches. The CASSCF/MRCI technique is found to describe multiple bonds as well as single bonds. Although the coupled pair functional approach gave chemical accuracy (1 kcal/mol) for bonds involving hydrogen, larger errors occur in the CPF approach for the multiple bonded systems considered here. CI studies on the 1Sigma(g +) state of N2, including all single, double, triple, and quadruple excitations show that triple excitations are very important for the multiple bond case, and accounts for most of the deficiency in the coupled pair functional methods.

  16. Calculated potential surfaces for the reactions: O + N2 yields NO + N and N + O2 yields NO + O

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Jaffe, Richard J.

    1986-01-01

    Complete Active Space SCF/Contracted CI (CASSCF/CCI) calculations, using large Gaussian basis sets, are presented for selected portions of the potential surfaces for the reactions in the Zeldovich mechanism for the conversion of N2 to NO. The N + O2 reaction is exoergic by 32 kcal/mole and is computed to have an early barrier of 10.2 kcal/mole for the (sup 2)A(sup prime) surface and 18.0 kcal/mole for the (sup 4)A(sup prime) surface. The O + N2 reaction is endoergic by 75 kcal/mole. The (sup 3)A(sup double prime) surface is calculated to have a late barrier of 0.5 kcal/mole, while the (sup 3)A(sup prime) surface is calculated to have a late barrier of 14.4 kcal/mole.

  17. APO observations in Southern Greenland: evaluation of modelled air-sea O2 and CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Bonne, Jean-Louis; Bopp, Laurent; Delmotte, Marc; Cadule, Patricia; Resplandy, Laure; Nevison, Cynthia; Manizza, Manfredi; Valentin Lavric, Jost; Manning, Andrew C.; Masson-Delmotte, Valérie

    2014-05-01

    Since September 2007, the atmospheric CO2 mole fraction and O2/N2 ratio (a proxy for O2 concentration) have been monitored continuously at the coastal site of Ivittuut, southern Greenland (61.21° N, 48.17° W). From 2007 to 2013, our measurements show multi-annual trends of +2.0 ppm/year and -20 per meg/year respectively for CO2 and O2/N2, with annual average peak-to-peak seasonal amplitudes of 14+/-1 ppm and 130+/-15 per meg. We investigate the implications of our data set in terms of APO (Atmospheric Potential Oxygen). This tracer, obtained by a linear combination of CO2 and O2/N2 data, is invariant to CO2 and O2 exchanges in the land biota, but sensitive to the oceanic component of the O2 cycle. It is used as a bridge to evaluate air-sea CO2 and O2 fluxes from atmospheric variations of CO2 and O2/N2. Global ocean biogeochemical models produce estimates of CO2 and O2 air-sea fluxes. Atmospheric APO variations can be simulated through transportation of these fluxes in the atmosphere by Eulerian transport models. Thus, model values of atmospheric APO can be extracted at the station location. This study is based on air-sea flux outputs from CMIP5 simulations. After atmospheric transportation, they give access to atmospheric APO climatologies which can be compared, in terms of seasonal cycles and inter-annual variability, to the in situ observations. A preliminary study is based on the CCSM ocean model air-sea fluxes transported in the atmosphere with the MATCH transport model, over the period 1979-2004. The amplitude of the APO seasonal cycle is correctly captured, but year to year variations on this seasonal cycle appears to be underestimated compared to observations. The LMDZ atmospheric transport model is also used to transport the ocean fluxes from five CMIP5 models, over the period 1979-2005, showing different amplitudes and timings of APO seasonal cycles. This methodology is a first step to evaluate the origin of observed APO variations at our site and then

  18. An improvement of HfO2/Ge interface by in situ remote N2 plasma pretreatment for Ge MOS devices

    NASA Astrophysics Data System (ADS)

    Chi, Xiaowei; Lan, Xiaoling; Lu, Chao; Hong, Haiyang; Li, Cheng; Chen, Songyan; Lai, Hongkai; Huang, Wei; Xu, Jianfang

    2016-03-01

    In situ remote N2 plasma pretreatment of Ge substrate before deposition of HfO2 is proved effective to reduce GeOx interlayer at the HfO2/Ge interface, resulting in a smaller capacitance equivalent oxide thickness, lower interface trap density and leakage current density for the metal/HfO2/n-Ge capacitors. However, it has no obvious impact on the metal/HfO2/p-Ge capacitors, showing a much higher interface trap density than that on n-Ge. The high equivalent permittivity of the HfO2 gate stacks (∼24.2) confirmed the removal of GeOx interlayer by N2 plasma pretreatment. In situ remote N2 plasma pretreatment is demonstrated perspective to make metal/HfO2/n-Ge MOSFET with scaling capacitance equivalent oxide thickness.

  19. EUV studies of N2 and O2 produced by low energy electron impact

    NASA Technical Reports Server (NTRS)

    Morgan, H. D.; Mentall, J. E.

    1983-01-01

    The emission spectra resulting from electron impact excitation on molecular nitrogen and oxygen in the 500-1200 A spectral region are investigated. Electron energies are from 0 to 300 eV. Numerous bands of N2 are found between 800 and 1000 A. Excitation functions are measured for the NII 916 A, the OI 879 A, and the OII 834 multiplets, and nitrogen band emission. Cross sections were measured at 200 eV for several of the band emissions plus the NI 1135 A, NI 1164 A, NI 1177 A, NII 776 A, NII 1084 A, OI 1152 A, OI 1041 A, OI 999 A, OI 989 A, OI 879 A, OII 834 A, OII 616 A, OII 555 A, OII 539 A, and OII 718 A multiplets.

  20. Effect of excited nitrogen atoms on inactivation of spore-forming microorganisms in low pressure N2/O2 surface-wave plasma

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoli; Chang, Xijiang; Tei, Reitou; Nagatsu, Masaaki

    2016-06-01

    Using a vacuum ultraviolet (VUV) absorption spectroscopy with a compact low pressure plasma light source, the absolute nitrogen atom density was measured to study its role in the spore inactivation with low pressure N2/O2 gas mixture surface-wave plasmas (SWPs). Self-absorption effect of the resonance emission lines of nitrogen atoms near 120 nm was minimized by optimizing its discharge conditions of the plasma light source. Experimental results showed that excited nitrogen atom densities monotonically decreased with the decrease of N2 gas percentage in N2/O2 gas mixture SWPs, concomitantly with similar decrease of VUV/UV emission intensities of nitrogen atoms and molecules. In the pure N2 gas SWPs, it was confirmed that a dominant lethal factor was VUV/UV emission generated by N2 plasma, while spore etching occurred via physical and chemical interactions with nitrogen species. With an addition of O2 gas, significant spore etching by excited oxygen atoms made it much easier for the VUV/UV photons emitted by nitrogen atoms, N2 and NO molecules to penetrate through the etched spore coats to the core and cause the fatal DNA damage of the microorganisms. As a result, more rapid inactivation was achieved in the middle region of N2/O2 gas mixture ratio, such as 30–80% O2 gas addition, in the present N2/O2 gas mixture SWPs.

  1. Effects of H2O, CO2, and N2 Air Contaminants on Critical Airside Strain Rates for Extinction of Hydrogen-Air Counterflow Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Wilson, L. G.; Northam, G. B.; Guerra, Rosemary

    1989-01-01

    Coaxial tubular opposed jet burners (OJB) were used to form dish shaped counterflow diffusion flames (CFDF), centered by opposing laminar jets of H2, N2 and both clean and contaminated air (O2/N2 mixtures) in an argon bath at 1 atm. Jet velocities for flame extinction and restoration limits are shown versus wide ranges of contaminant and O2 concentrations in the air jet, and also input H2 concentration. Blowoff, a sudden breaking of CFDF to a stable ring shape, occurs in highly stretched stagnation flows and is generally believed to measure kinetically limited flame reactivity. Restore, a sudden restoration of central flame, is a relatively new phenomenon which exhibits a H2 dependent hysteresis from Blowoff. For 25 percent O2 air mixtures, mole for mole replacement of 25 percent N2 contaminant by steam increased U(air) or flame strength at Blowoff by about 5 percent. This result is consistent with laminar burning velocity results from analogous substitution of steam for N2 in a premixed stoichiometric H2-O2-N2 (or steam) flame, shown by Koroll and Mulpuru to promote a 10 percent increase in experimental and calculated laminar burning velocity, due to enhanced third body efficiency of water in: H + O2 + M yields HO2 + M. When the OJB results were compared with Liu and MacFarlane's experimental laminar burning velocity of premixed stoichiometric H2 + air + steam, a crossover occurred, i.e., steam enhanced OJB flame strength at extinction relative to laminar burning velocity.

  2. Spectroscopic studies of MW plasmas containing HMDSO, O2 and N2

    NASA Astrophysics Data System (ADS)

    Nave, Andy; Roepcke, Juergen; Mitschker, Felix; Awakowicz, Peter

    2015-09-01

    The deposition of SiOx layers based on organosilicon plasmas is used to implement advantageous mechanical, electrical, and/or optical properties on various substrates. The development of such coating processes resulting in a wide range of chemical and physical film properties, using hexamethyldisiloxane (HMDSO) as a precursor, has been in the center of interest of various studies. In plasma, the dissociation of HMDSO into a large amount of fragments is a complex chemical phenomenon. The monitoring of the precursor and of formed species is very valuable to understand the plasma chemistry. Infrared absorption spectroscopy based on lead salt lasers and EC Quantum Cascade Laser have been used to monitor the concentrations of HMDSO, and of the reaction products CH4, C2H2, C2H4,C2H6, CO, CO2 and CH3 as a function of the HMDSO/O2 mixture ratio, and the power at various pressures in a MW plasma deposition reactor. Optical emission spectroscopy has been applied as complementary diagnostics to evaluate electron density and electron temperature. Supported by the German Research Foundation within SFB-TR24 and SFB-TR87.

  3. Picosecond-TALIF and VUV absorption measurements of absolute atomic nitrogen densities from an RF atmospheric pressure plasma jet with He/O2/N2 gas mixtures

    NASA Astrophysics Data System (ADS)

    West, Andrew; Niemi, Kari; Schröter, Sandra; Bredin, Jerome; Gans, Timo; Wagenaars, Erik

    2015-09-01

    Reactive Oxygen and Nitrogen species (RONS) from RF atmospheric pressure plasma jets (APPJs) are important in biomedical applications as well as industrial plasma processing such as surface modification. Atomic oxygen has been well studied, whereas, despite its importance in the plasma chemistry, atomic nitrogen has been somewhat neglected due to its difficulty of measurement. We present absolute densities of atomic nitrogen in APPJs operating with He/O2/N2 gas mixtures in open air, using picosecond Two-photon Absorption Laser Induced Fluorescence (ps-TALIF) and vacuum ultra-violet (VUV) absorption spectroscopy. In order to apply the TALIF technique in complex, He/O2/N2 mixtures, we needed to directly measure the collisional quenching effects using picosecond pulse widths (32ps). Traditional calculated quenching corrections, used in nanosecond TALIF, are inadequate due to a lack of quenching data for complex mixtures. Absolute values for the densities were found by calibrating against a known density of Krypton. The VUV absorption experiments were conducted on the DESIRS synchrotron beamline using a unique VUV Fourier-transform spectrometer. Atomic nitrogen densities were on the order of 1020 m-3 with good agreement between TALIF and VUV absorption. UK EPSRC grant EP/K018388/1.

  4. Possibility of controlling the chemical pattern of He and Ar "guided streamers" by means of N2 or O2 additives

    NASA Astrophysics Data System (ADS)

    Gazeli, K.; Svarnas, P.; Held, B.; Marlin, L.; Clément, F.

    2015-03-01

    Plasma chemistry at atmospheric pressure and low temperature has met an increased interest due to the effective production of reactive species (mainly reactive nitrogen species and reactive oxygen species) which are demanded in many applications like in biomedicine. Τhe generation of such emissive reactive species is herein studied. A single parameter, i.e., the gas composition, is tuned and abundant chemical species are obtained in a quite controllable manner. The system refers to a small dielectric barrier discharge based reactor fed with He-N2/O2 or Ar-N2/O2 gases, which provides plasma in the form of "guided streamers." The plasma is sustained by positive high voltage pulses, and the emissive transitions versus the gas composition is determined by UV-VIS optical emission spectroscopy. The relative intensities of emissive species are recorded in the ambient air where the streamers propagate. The evolution of dominant species as a function of the gas composition is mapped, and optimal conditions in terms of species production are clearly revealed. The results show that additives do not necessarily enhance the density of all species, implying the need for plasma chemistry optimization in respect to every application. The study is extended inside the reactor, supporting the above statements. Finally, the rotational and vibrational distributions of critical probe molecules are recorded, testing the dependence of the gas temperature and energy transfer, respectively, on the gas composition.

  5. Effect of oxygen on the conversion of acetaldehyde in homogeneous plasmas of N2/O2/CH3CHO mixtures

    NASA Astrophysics Data System (ADS)

    Faider, W.; Pasquiers, S.; Blin-Simiand, N.; Magne, L.

    2013-12-01

    A photo-triggered discharge producing a homogeneous plasma was used to investigate, experimentally and with the help of a self-consistent 0D model, the decomposition processes of acetaldehyde (concentration up to 0.5%) in N2/O2/CH3CHO mixtures containing up to 20% oxygen, at a total pressure of 460 mbar. This work follows a previous one about N2/CH3CHO, having provided the necessary data about the quenching of the N2 metastable states by the acetaldehyde molecule. For the condition of the experiment, it was shown that oxygen has a weak influence on the acetaldehyde removal. Nevertheless, the kinetic reactions involved drastically change when the oxygen percentage is increased. Quenching reactions gradually give way to oxidation reactions by O(3P) and OH. Oxidation by OH dominates for a high acetaldehyde concentration or a high oxygen percentage. Moreover, CH3 is an important primary compound for the formation of CH4 and C2H6. Ethane is less populated than methane in the whole range of oxygen percentage values studied, and there are still hydrocarbon molecules in the gas mixture at 20% oxygen. This is well explained by the adopted kinetic scheme.

  6. Unexpected luminescence properties of Sr(0.25)Ba(0.75)Si2O2N2:Eu(2+)--a narrow blue emitting oxonitridosilicate with cation ordering.

    PubMed

    Seibald, Markus; Rosenthal, Tobias; Oeckler, Oliver; Fahrnbauer, Felix; Tücks, Andreas; Schmidt, Peter J; Schnick, Wolfgang

    2012-10-15

    Owing to a parity allowed 4f(6)((7)F)5d(1)→4f(7)((8)S(7/2)) transition, powders of the nominal composition Sr(0.25)Ba(0.75)Si(2)O(2)N(2):Eu(2+) (2 mol% Eu(2+)) show surprising intense blue emission (λ(em)=472 nm) when excited by UV to blue radiation. Similarly to other phases in the system Sr(1-x)Ba(x)Si(2)O(2)N(2):Eu(2+), the described compound is a promising phosphor material for pc-LED applications as well. The FWHM of the emission band is 37 nm, representing the smallest value found for blue emitting (oxo)nitridosilicates so far. A combination of electron and X-ray diffraction methods was used to determine the crystal structure of Sr(0.25)Ba(0.75)Si(2)O(2)N(2):Eu(2+). HRTEM images reveal the intergrowth of nanodomains with SrSi(2)O(2)N(2) and BaSi(2)O(2)N(2)-type structures, which leads to pronounced diffuse scattering. Taking into account the intergrowth, the structure of the BaSi(2)O(2)N(2)-type domains was refined on single-crystal diffraction data. In contrast to coplanar metal atom layers which are located between layers of condensed SiON(3)-tetrahedra in pure BaSi(2)O(2)N(2), in Sr(0.25)Ba(0.75)Si(2)O(2)N(2):Eu(2+) corrugated metal atom layers occur. HRTEM image simulations indicate cation ordering in the final structure model, which, in combination with the corrugated metal atom layers, explains the unexpected and excellent luminescence properties. PMID:22968845

  7. Enhancement of Photoluminescence in BaSi2O2N2:Eu2+ by Partial Ge4+ Substitution for Si4+.

    PubMed

    Wang, Baochen; Chen, Jian; Xia, Yufei; Liu, Yangai

    2016-04-01

    Ge4+-doped BaSi2O2N2: Eu2+ phosphors were prepared by a high temperature solid-state reaction method. The phase structure, photoluminescence (PL) properties and PL thermal stability of the as-synthesized samples were investigated. The emission intensity of the Ba(Si0.99Ge0.01)2O2N2: 0.05Eu2+ phosphor was 41.7% greater than that of BaSi2O2N2:0.05Eu2+. When the temperature increased to 150 °C, the emission intensity of Ba(Si0.99Ge0.01)2O2N2:0.05Eu2+ phosphor was 67.0% of the initial value at room temperature. This value was 22.9% greater than that of BaSi2O2N2:0.05Eu2+. The related mechanism has also been explained through the crystal field theory. All these results indicated that the Ge4+-doped BaSi2O2N2:0.05Eu2+ phosphor is a promising material for application in white light emitting diodes. PMID:27451674

  8. Studies of iron(II) and iron(III) complexes with fac-N2O, cis-N2O2 and N2O3 donor ligands: models for the 2-His 1-carboxylate motif of non-heme iron monooxygenases.

    PubMed

    Cappillino, Patrick J; Miecznikowski, John R; Tyler, Laurie A; Tarves, Paul C; McNally, Joshua S; Lo, Wayne; Kasibhatla, Bala Sundari T; Krzyaniak, Matthew D; McCracken, John; Wang, Feng; Armstrong, William H; Caradonna, John P

    2012-05-14

    Enzymes in the oxygen-activating class of mononuclear non-heme iron oxygenases (MNOs) contain a highly conserved iron center facially ligated by two histidine nitrogen atoms and one carboxylate oxygen atom that leave one face of the metal center (three binding sites) open for coordination to cofactor, substrate, and/or dioxygen. A comparative family of [Fe(II/III)(N(2)O(n))(L)(4-n))](±x), n = 1-3, L = solvent or Cl(-), model complexes, based on a ligand series that supports a facially ligated N,N,O core that is then modified to contain either one or two additional carboxylate chelate arms, has been structurally and spectroscopically characterized. EPR studies demonstrate that the high-spin d(5) Fe(III)g = 4.3 signal becomes more symmetrical as the number of carboxylate ligands decreases across the series Fe(N(2)O(3)), Fe(N(2)O(2)), and Fe(N(2)O(1)), reflecting an increase in the E/D strain of these complexes as the number of exchangeable/solvent coordination sites increases, paralleling the enhanced distribution of electronic structures that contribute to the spectral line shape. The observed systematic variations in the Fe(II)-Fe(III) oxidation-reduction potentials illustrate the fundamental influence of differential carboxylate ligation. The trend towards lower reduction potential for the iron center across the [Fe(III)(N(2)O(1))Cl(3)](-), [Fe(III)(N(2)O(2))Cl(2)](-) and [Fe(III)(N(2)O(3))Cl](-) series is consistent with replacement of the chloride anions with the more strongly donating anionic O-donor carboxylate ligands that are expected to stabilize the oxidized ferric state. This electrochemical trend parallels the observed dioxygen sensitivity of the three ferrous complexes (Fe(II)(N(2)O(1)) < Fe(II)(N(2)O(2)) < Fe(II)(N(2)O(3))), which form μ-oxo bridged ferric species upon exposure to air or oxygen atom donor (OAD) molecules. The observed oxygen sensitivity is particularly interesting and discussed in the context of α-ketoglutarate-dependent MNO enzyme

  9. Spectral modulation of ultraviolet femtosecond laser pulse by molecular alignment of CO2, O2, and N2

    NASA Astrophysics Data System (ADS)

    Wang, Yongdong; Dai, Xiaomin; Wu, Jian; Ding, Liang'en; Zeng, Heping

    2010-01-01

    We demonstrate efficient third harmonic generation of a near infrared femtosecond pulse through cascaded frequency doubling and sum-frequency generation processes, where the group velocity mismatching between the involved fundamental and generated second harmonic pulses, before they are sent to frequency mixing, are precompensated with a properly inserted nonlinear crystal. The spectrum of the generated third harmonic pulse with energy of 1.1 mJ is further modulated by using impulsive molecular alignments of CO2, O2, and N2, where significantly broadened spectrum in the ultraviolet spectral region is observed due to the additional cross-focusing effect from the parallel aligned molecules and the consequently enhanced self-phase modulation.

  10. The effects of additive gases (Ar, N2, H2, Cl2, O2) on HCl plasma parameters and composition

    NASA Astrophysics Data System (ADS)

    Efremov, A.; Yudina, A.; Davlyatshina, A.; Murin, D.; Svetsov, V.

    2013-01-01

    The direct current (dc) glow discharge plasma parameters and active species kinetics in HCl-X (X = Ar, N2, H2, Cl2, O2) mixtures were studied using both plasma diagnostics Langmuir probes and modeling. The 0-dimensional self-consistent steady-state model included the simultaneous solution of Boltzmann kinetic equation, the equations of chemical kinetics for neutral and charge particles, plasma conductivity equation and the quasi-neutrality conditions for volume densities of charged particles as well as for their fluxes to the reactor walls. The data on the steady-state electron energy distribution function, electron gas characteristics (mean energy, drift rate and transport coefficients), volume-averaged densities of plasma active species and their fluxed to the reactor walls were obtained as functions of gas mixing ratios and gas pressure at fixed discharge current.

  11. Enhanced Flexibility of the O2 + N2 Interaction and Its Effect on Collisional Vibrational Energy Exchange.

    PubMed

    Garcia, E; Laganà, A; Pirani, F; Bartolomei, M; Cacciatore, M; Kurnosov, A

    2016-07-14

    Prompted by a comparison of measured and computed rate coefficients of Vibration-to-Vibration and Vibration-to-Translation energy transfer in O2 + N2 non-reactive collisions, extended semiclassical calculations of the related cross sections were performed to rationalize the role played by attractive and repulsive components of the interaction on two different potential energy surfaces. By exploiting the distributed concurrent scheme of the Grid Empowered Molecular Simulator we extended the computational work to quasiclassical techniques, investigated in this way more in detail the underlying microscopic mechanisms, singled out the interaction components facilitating the energy transfer, improved the formulation of the potential, and performed additional calculations that confirmed the effectiveness of the improvement introduced. PMID:26982814

  12. Feature Scale Simulation of PECVD of SiO2 in SiH4/N2O Mixture

    NASA Astrophysics Data System (ADS)

    Liu, Xuan; Ge, Jie; Yang, Yi; Song, Yixu; Ren, Tianling

    2014-04-01

    In this paper, to simulate the process of PECVD (plasma enhanced chemical vapor deposition) of SiO2, the plasma chemistry and plasma density of SiH4/N2O mixture have been studied with an inductive coupled plasma model, and the level set methodology has been used to obtain the feature scale variation during the process. In this simulation, the goal is to fill a trench. We studied how ion sputtering and chamber pressure affect the feature scale model. After the simulation, we found that the trench will close up at the top after a few steps, and if we add the ion sputtering into the surface reactions, the trench top will close up a little later. When the chamber pressure is improved, the plasma density will increase, so the trench top will close up earlier. In semiconductor device manufacture, people can control the trench's feature scale through adjusting these two parameters.

  13. Tricrystalline TiO2 with enhanced photocatalytic activity and durability for removing volatile organic compounds from indoor air.

    PubMed

    Chen, Kunyang; Zhu, Lizhong; Yang, Kun

    2015-06-01

    It is important to develop efficient and economic techniques for removing volatile organic compounds (VOCs) in indoor air. Heterogeneous TiO2-based semiconductors are a promising technology for achieving this goal. Anatase/brookite/rutile tricrystalline TiO2 with mesoporous structure was synthesized by a low-temperature hydrothermal route in the presence of HNO3. The obtained samples were characterized by X-ray diffraction and N2 adsorption-desorption isotherm. The photocatalytic activity was evaluated by photocatalytic decomposition of toluene in air under UV light illumination. The results show that tricrystalline TiO2 exhibited higher photocatalytic activity and durability toward gaseous toluene than bicrystalline TiO2, due to the synergistic effects of high surface area, uniform mesoporous structure and junctions among mixed phases. The tricrystalline TiO2 prepared at RHNO3=0.8, containing 80.7% anatase, 15.6% brookite and 3.7% rutile, exhibited the highest photocatalytic activity, about 3.85-fold higher than that of P25. The high activity did not significantly degrade even after five reuse cycles. In conclusion, it is expected that our study regarding gas-phase degradation of toluene over tricrystalline TiO2 will enrich the chemistry of the TiO2-based materials as photocatalysts for environmental remediation and stimulate further research interest on this intriguing topic. PMID:26040745

  14. Chlorine mobility during annealing in N2 in ZrO2 and HfO2 films grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Ferrari, S.; Scarel, G.; Wiemer, C.; Fanciulli, M.

    2002-12-01

    Atomic layer deposition (ALD) growth of high-κ dielectric films (ZrO2 and HfO2) was performed using ZrCl4, HfCl4, and H2O as precursors. In this work, we use time of flight secondary ion mass spectrometry to investigate the chlorine distribution in ALD grown ZrO2 and HfO2 films, and its evolution during rapid thermal processes in nitrogen atmosphere. Chlorine outdiffusion is found to depend strongly upon annealing temperature and weakly upon the annealing time. While in ZrO2 chlorine concentration is significantly decreased already at 900 °C, in HfO2 it is extremely stable, even at temperatures as high as 1050 °C.

  15. Self-, N2-, O2-broadening coefficients and line parameters of HFC-32 for ν7 band and ground state transitions from infrared and microwave spectroscopy

    NASA Astrophysics Data System (ADS)

    Tasinato, Nicola; Turchetto, Arianna; Puzzarini, Cristina; Stoppa, Paolo; Pietropolli Charmet, Andrea; Giorgianni, Santi

    2014-09-01

    Hydrofluorocarbons have been used as replacement gases of chlorofluorocarbons, since the latter have been phased out by the Montreal Protocol due to their environmental hazardous ozone-depleting effects. This is also the case of difluoromethane (CH2F2, HFC-32), which nowadays is widely used in refrigerant mixtures together with CF3CH3, CF3CH2F, and CF3CHF2. Due to its commercial use, in the last years, the atmospheric concentration of HFC-32 has increased significantly. However, this molecule presents strong absorptions within the 8-12 μm atmospheric window, and hence it is a greenhouse gas which contributes to global warming. Although over the years several experimental and theoretical investigations dealt with the spectroscopic properties of CH2F2, up to now pressure broadening coefficients have never been determined. In the present work, the line-by-line parameters of CH2F2 are retrieved for either ground state or ν7 band transitions by means of microwave (MW) and infrared (IR) absorption spectroscopy, respectively. In particular, laboratory experiments are carried out on 9 pure rotational transitions of the ground state and 26 ro-vibrational transitions belonging to the ν7 band lying around 8.2 μm within the atmospheric region. Measurements are carried out at room temperature on self-perturbed CH2F2 as well as on CH2F2 perturbed by N2 and O2. The line shape analysis leads to the first determination of self-, N2-, O2-, and air-broadening coefficients, and also of line intensities (IR). Upon comparison, broadening coefficients of ground state transitions are larger than those of the ν7 band, and no clear dependence on the rotational quantum numbers can be reported. The obtained results represent basic information for the atmospheric modelling of this compound as well as for remote sensing applications.

  16. Synthesis, spectral characterization, molecular modeling and antimicrobial activity of new potentially N2O2 Schiff base complexes

    NASA Astrophysics Data System (ADS)

    Adly, Omima M. I.; Taha, Ali; Fahmy, Shery A.

    2013-12-01

    Metal complexes of a new potentially tetradentate symmetrical Schiff base ligand (H2L) with Cu(II), Ni(II), Co(II), VO(IV), Zn(II), Cd(II), Ce(III), Fe(III) and UO2(VI) metal ions have been synthesized and characterized based on their elemental analyses, spectral (IR, UV-Vis, 1H NMR and mass spectra), magnetic and molar conductance studies as well as thermal gravimetric analysis (TGA). The synthesized complexes have the general formula [MHxL(H2O)yXn]: x = 0-1, y = 0-4 and n = 0-1; where: L = dianion of 6-hydroxy-5-[N-(2-{[(1E)-1-(6-hydroxy-2,4-dioxo-3,4-dihydro-2H-1,3-thiazin-5-yl)ethylidene]amino}ethyl) ethanimidoyl]-2H-1,3-thiazine-2,4(3H)-dione and X = nitrate or sulphate anion. The ligand behaves as diabasic tetradentate N2O2 sites, except in cases of Co(II), VO(IV) and UO2(VI) metal ions, it behaves as monobasic tetradentate Schiff base ligand. The metal complexes exhibited square planar, square-pyramidal and octahedral geometrical arrangements except for Ce(III) and UO2(VI) complexes, they are octa-coordinated. The Coats-Redfern equation was used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition stages of some complexes. Structural parameters of the ligand and its metal complexes have been theoretically computed on the basis of semiemperical PM3 level, and the results were correlated with their experimental data. The antimicrobial activities of the ligand and its metal complexes were tested against some Gram-positive and Gram-negative bacteria; and fungus strain and the results were discussed.

  17. Effects of H2O, CO2, and N2 air contaminants on critical airside strain rates for extinction of hydrogen-air counterflow diffusion flames

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Northam, G. B.; Wilson, L. G.; Guerra, Rosemary

    1989-01-01

    Dish-shaped counterflow diffusion flames centered by opposing laminar jets of H2 and clean and contaminant O2/N2 mixtures in an argon bath at 1 atm were used to study the effects of contaminants on critical airside strain. The jet velocities for both flame extinction and restoration are found for a wide range of contaminant and O2 concentrations in the air jet. The tests are also conducted for a variety of input H2 concentrations. The results are compared with those from several other studies.

  18. A SnO2-Based Cathode Catalyst for Lithium-Air Batteries.

    PubMed

    Mei, Delong; Yuan, Xianxia; Ma, Zhong; Wei, Ping; Yu, Xuebin; Yang, Jun; Ma, Zi-Feng

    2016-05-25

    SnO2 and SnO2@C have been successfully synthesized with a simple hydrothermal procedure combined with heat treatment, and their performance as cathode catalysts of Li-air batteries has been comparatively evaluated and discussed. The results show that both SnO2 and SnO2@C are capable of catalyzing oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) at the cathode of Li-air batteries, but the battery with SnO2@C displays better performance due to its unique higher conductivity, larger surface area, complex pore distribution, and huge internal space. PMID:27152996

  19. Collision spectroscopy of ion-diatom systems - He/plus/-N2 and -O2 at medium energies

    NASA Astrophysics Data System (ADS)

    Dowek, D.; Dhuicq, D.; Pommier, J.; Tuan, V. N.; Sidis, V.; Barat, M.

    1981-11-01

    Energy-loss measurements of direct-excitation and electron-capture processes are performed for the He(plus)-N2, -O2 collisional systems in the 0.2-4-keV energy range and in the 0-3 deg angular range. Pure vibrational excitation and vibrational excitation in excited electronic states are studied using a high-resolution spectrometer (100 meV). Pure vibrational excitation is always found to be a weak process. The analysis of vibrational distributions in excited states strongly supports an interpretation in terms of the Franck-Condon principle. Relative probabilities as functions of energy and angle are reported for the identified excitation and electron-capture processes. The results show the importance of electron-capture processes, among which quasi-resonant and endothermic processes dominate the exothermic processes. The striking resemblance of the present data with those available on the He(plus)-rare-gas systems conveys a similar quasi-molecular interpretation of the collision mechanisms.

  20. Structural and functional mimic of galactose oxidase by a copper complex of a sterically demanding [N2O2] ligand.

    PubMed

    John, Alex; Shaikh, Mobin M; Ghosh, Prasenjit

    2008-06-01

    A structural and functional mimic of the galactose oxidase (GOase) enzyme active-site by a copper complex supported over a sterically demanding ligand having [N2O2] donor sites is reported. Specifically, the binding of the histidine (496 and 581) and tyrosine (272 and 495) residues to the copper center in a square-pyramidal fashion in the active-site of galactose oxidase (GOase) enzyme has been modeled in a copper complex, ([(3-tert-butyl-5-methyl-2-hydoxybenzyl)(3'-tert-butyl-5'-methyl-2'-oxobenzyl)(2-pyridylmethyl)]amine)Cu(OAc)) (1b), stabilized over a sterically demanding ligand in which the two phenolate-O atoms mimicked the tyrosine binding while an amine-N and pyridyl-N atoms emulated the histidine binding to the metal center, similar to that in the enzyme active-site. Furthermore, the copper complex 1b is found to be an effective functional model of the enzyme as it efficiently catalyzed the chemoselective oxidation of primary alcohols to aldehydes in high turnover numbers under ambient conditions. An insight into the nature of the active-species was obtained by EPR and CV studies, which in conjunction with the DFT studies, revealed that the active-species is an anti-ferromagnetically coupled diamagnetic radical cation, (1)1b+, obtained by one electron oxidation at the equatorial phenolate-O atom of the ligand in the 1b complex. PMID:18478142

  1. Transport properties of SF_{6}^{-} in SF6-Ne, SF6-N2 and SF6-O2 mixtures

    NASA Astrophysics Data System (ADS)

    Benhenni, M.; Yousfi, M.; de Urquijo, J.; Hennad, A.

    2009-06-01

    The mobility of SF_{6}^{-} has been calculated for the gas mixtures SF6-Ne, SF6-N2 and SF6-O2 using an optimized Monte Carlo code for the ion transport simulation in a drift tube. The elastic momentum transfer collision cross sections needed for the calculation were determined from a semi-classical JWKB approximation, while the inelastic ones (detachment, dissociative charge transfer and SF_{6}^{-} conversion to SF_{5}^{-} and F-) were taken from the literature for the case of the SF_{6}^{-}/Ne collision system. The resulting sets of collision cross sections were validated by comparing the SF_{6}^{-} calculated mobilities with those measured in the above mixtures with a time-resolved pulsed Townsend technique. The SF_{6}^{-} longitudinal and transverse density-normalized diffusion coefficients were calculated for these mixtures for the case where the share of SF6 in the mixture was 50%. Finally, the validity of Blanc's law was discussed at low and high electric fields, whereby we show that it fails at high fields, where inelastic processes are dominant.

  2. Selected-ion flow tube temperature-dependent measurements for the reactions of O2+ with N atoms and N2+ with O atoms

    NASA Astrophysics Data System (ADS)

    Martinez, Oscar; Sanchez, Jenny C.; Ard, Shaun G.; Li, Anyang; Melko, Joshua J.; Shuman, Nicholas S.; Guo, Hua; Viggiano, Albert A.

    2015-04-01

    The temperature variation of rate constants has been measured for the gas phase reactions of the oxycation O2+ with N atoms and of N2+ with O atoms from 120 to 400 K using a variable temperature-selected ion flow tube. Measured room temperature rate constants, 0.75 × 10-10 cm3 s-1 (±30%) for O2+ with N and 1.4 × 10-10 cm3 s-1 (±30%) for N2+ with O, are in agreement with previously reported values. A temperature dependence of T-0.7(±0.3) is observed for the O2+ + N reaction; however, the N2+ + O reaction is found to be independent of temperature. Calculations at varying levels of theory were used in tandem with experiments to evaluate likely pathways in potential energy surfaces for the reactions of concern.

  3. Novel chemical vapor deposition process of ZnO films using nonequilibrium N2 plasma generated near atmospheric pressure with small amount of O2 below 1%

    NASA Astrophysics Data System (ADS)

    Nose, Yukinori; Yoshimura, Takeshi; Ashida, Atsushi; Uehara, Tsuyoshi; Fujimura, Norifumi

    2016-05-01

    We propose a novel chemical vapor deposition (CVD) process of ZnO films involving a nonequilibrium N2 plasma generated near atmospheric pressure with small O2 concentration (O2%) below 1%. In the optical emission (OE) spectra of the plasma, OE lines corresponding to the NO-γ system ( A 2 Σ + → X 2 Πγ + ) were observed, despite the only introduced gases being N2 and O2; these vanish at an O2% of more than 1%. ZnO films were grown on a glass substrate placed in the plasma at a growth temperature of as low as 200 °C and at an O2% of below 1% in the presence of the NO-γ system. This plasma yielded almost the same growth rate for ZnO films as O2 plasma including atomic O radicals that are often observed in low-pressure O2 plasma, suggesting that some highly reactive oxidant was sufficiently generated in such a small O2%. ZnO films synthesized using this plasma exhibited excellent ( 0001 ) preferred orientation without other diffractions such as 10 1 ¯ 1 diffraction, and with an optical bandgap of 3.30 eV. Based on the analyses of the plasma and the exhaust gases, the coexistence state of NO-γ and O3 should be essential and useful for the decomposition and oxidation of Zn source material in the proposed CVD process.

  4. Characteristics of ZrO2 gate dielectrics on O2- and N2O-plasma treated partially strain-compensated Si0.69Ge0.3C0.01 layers

    NASA Astrophysics Data System (ADS)

    Mahapatra, R.; Maikap, S.; Lee, Je-Hun; Ray, S. K.

    2006-08-01

    The characteristics of ZrO2 gate dielectric along with the interfacial layer on O2- and N2O-plasma treated partially strain-compensated Si0.69Ge0.3C0.01/Si heterostructures have been investigated using spectroscopic and electrical measurements. Time-of-flight secondary ion mass spectroscopy and x-ray photoelectron spectroscopy analyses show the formation of an oxygen or nitrogen rich Zr-germanosilicate interfacial layer between the deposited ZrO2 and SiGeC films. The electrical and charge trapping properties under a constant current stressing have been studied using a metal-oxide-semiconductor structure. The N2O-plasma treated SiGeC film has a higher effective dielectric constant (k ˜14) than that of the O2-plasma treated (k˜12) films. The equivalent areal densities of charge defects, Neq (cm-2), are found to be ˜1.8×1012 and ˜6×1011cm-2 for O2- and N2O-plasma treated films, respectively. Considerably less trapped charges in the N2O-treated gate dielectric stack under constant current stressing make it highly attractive for SiGeC based scaled metal-oxide-semiconductor device applications.

  5. Carbon-based air electrodes carrying MnO 2 in zinc-air batteries

    NASA Astrophysics Data System (ADS)

    Wei, Zidong; Huang, Wenzhang; Zhang, Shengtao; Tan, Jun

    Catalysts prepared from the carbon black impregnated with manganous nitrate solution and then heated at temperature from 270°C to 450°C were investigated. It was found that the impregnated catalysts heated at temperature of 340°C exhibited the best catalytic activity for oxygen reduction in alkaline electrolyte. It was also found that the XRD spectra of pyrolytic MnO 2 from manganous nitrate over 340°C were different from those below 340°C. The enhanced catalysis of air electrodes was ascribed to the formation of MnO 2 crystal with d-value of 2.72 Å as the impregnated-catalysts was heated at temperature of 340°C. The other factors in preparation of air electrodes were also discussed.

  6. Characterization of the bridged hyponitrite complex {[Fe(OEP)](2)(μ-N(2)O(2))}: reactivity of hyponitrite complexes and biological relevance.

    PubMed

    Berto, Timothy C; Xu, Nan; Lee, Se Ryeon; McNeil, Anne J; Alp, E Ercan; Zhao, Jiyong; Richter-Addo, George B; Lehnert, Nicolai

    2014-07-01

    The detoxification of nitric oxide (NO) by bacterial NO reductase (NorBC) represents a paradigm of how NO can be detoxified anaerobically in cells. In order to elucidate the mechanism of this enzyme, model complexes provide a convenient means to assess potential reaction intermediates. In particular, there have been many proposed mechanisms that invoke the formation of a hyponitrite bridge between the heme b3 and nonheme iron (FeB) centers within the NorBC active site. However, the reactivity of bridged iron hyponitrite complexes has not been investigated much in the literature. The model complex {[Fe(OEP)]2(μ-N2O2)} offers a unique opportunity to study the electronic structure and reactivity of such a hyponitrite-bridged complex. Here we report the detailed characterization of {[Fe(OEP)]2(μ-N2O2)} using a combination of IR, nuclear resonance vibrational spectroscopy, electron paramagnetic resonance, and magnetic circular dichroism spectroscopy along with SQUID magnetometry. These results show that the ground-state electronic structure of this complex is best described as having two intermediate-spin (S = (3)/2) iron centers that are weakly antiferromagnetically coupled across the N2O2(2-) bridge. The analogous complex {[Fe(PPDME)]2(μ-N2O2)} shows overall similar properties. Finally, we report the unexpected reaction of {[Fe(OEP)]2(μ-N2O2)} in the presence and absence of 1-methylimidizole to yield [Fe(OEP)(NO)]. Density functional theory calculations are used to rationalize why {[Fe(OEP)]2(μ-N2O2)} cannot be formed directly by dimerization of [Fe(OEP)(NO)] and why only the reverse reaction is observed experimentally. These results thus provide insight into the general reactivity of hyponitrite-bridged iron complexes with general relevance for the N-N bond-forming step in NorBC. PMID:24971721

  7. Opposed jet burner studies of effects of CO, CO2, and N2 air-contaminants on hydrogen-air diffusion flames

    NASA Technical Reports Server (NTRS)

    Guerra, Rosemary; Pellett, Gerald L.; Northam, G. Burton; Wilson, Lloyd G.

    1987-01-01

    The blowoff/restore characteristics for jets of various H2/N2 mixtures opposed to jets of air contaminated by N2, CO, and CO2 have been determined using a counterflow diffusion flame formed by a tubular opposed jet burner. Both blowoff and restore limits are found to be sensitive to fuel and air composition. Empirically derived variations in the limits of the average mass flux of incoming H2 with percent contaminant, at fixed incoming fuel and H2/O2 inputs, are used to quantify the effects of oxygen dilution, flame augmentation, and flame retardation by N2, CO, and CO2 contaminants. The implications of the results are discussed.

  8. Heterogeneous reaction of N2O5 with airborne TiO2 particles and the implication for stratospheric particle injection

    NASA Astrophysics Data System (ADS)

    Tang, Mingjin; Abraham, Luke; Braesicke, Peter; Cox, Tony; McGregor, James; Pope, Francis; Pyle, John; Rkiouak, Laylla; Telford, Paul; Watson, Matt; Kalberer, Markus

    2014-05-01

    Injection of aerosol particles (or their precursors) into the stratosphere to scatter solar radiation back into space, has been suggested as a solar-radiation management (SRM) scheme for the mitigation for global warming. TiO2 has recently been highlighted as a possible candidate aerosol because of its high light scattering ability with a refractive index of 2.5 (Pope et al. 2012). The impact of particles injection on stratospheric ozone requires systematical assessment via laboratory and modelling studies. In this work, the heterogeneous reaction of airborne sub-micrometre TiO2 particles with N2O5 has been investigated at room temperature and different relative humidities (RH), using an atmospheric pressure aerosol flow tube. The uptake coefficient of N2O5 onto TiO2, γ(N2O5), was determined to be ~1.0×10-3 at low RH, and increase to ~3×10-3 at 60% RH. The dependence of γ(N2O5) on RH can be explained by the water adsorption isotherm of TiO2 particles. In addition, the uptake of N2O5 onto TiO2 aerosol particles has been included in the UKCA chemistry-climate model to assess the effect of N2O5 uptake onto TiO2 particles on the stratospheric composition. We construct a case study based on the eruption of Mt. Pinatubo, comparing the effects of TiO2 to those from the volcanic sulfate and to the situation with only background amount of aerosol. The changes in reactive nitrogen species and ozone due to the heterogeneous reaction of TiO2 with N2O5 are assessed relative to sulfate aerosol impacts. Pope, F. D., Braesicke, P., Grainger, R. G., Kalberer, M., Watson, I. M., Davidson, P. J., and Cox, R. A.: Stratospheric aerosol particles and solar-radiation management, Nature Clim. Change, 2, 713-719, 2012

  9. Heterogeneous reactions of TiO2 aerosol particles with N2O5 and ClONO2 and their implications for stratospheric particle injection

    NASA Astrophysics Data System (ADS)

    Tang, Mingjin; Keeble, James; Telford, Paul; Pope, Francis; Rkiouak, Laylla; Abraham, Luke; Braesicke, Peter; Pyle, John; Mcgregor, James; Watson, Matt; Cox, Tony; Kalberer, Markus

    2015-04-01

    Injection of aerosol particles (or their precursors) into the stratosphere to scatter solar radiation back into space has been suggested as a solar radiation management scheme for climate engineering. Several minerals, including TiO2, have been as possible candidate particles (instead of sulfuric acid) to be injected into the stratosphere, due to their high refractive indices. However, their heterogeneous reactivity towards important reactive trace gases in the stratosphere has seldom been investigated, impeding us from a reliable assessment of their impact on stratospheric O3. In this work, the heterogeneous reactions of airborne TiO2 particles with N2O5 and ClONO2 have been studied at room temperature and at different RH, using an atmospheric pressure aerosol flow tube. The uptake coefficient of N2O5, γ(N2O5), increased from ~1.8E-3 at 5% RH to 4.5E-3 at ~60% RH for TiO2, significantly smaller than that for sulfuric acid particles in the stratosphere. The uptake of ClONO2 onto TiO2 aerosols particles have been found to be quite inefficient, with γ(ClONO2) not larger than 1E-3. Therefore, compared to stratospheric sulfuric acid particles, TiO2 particles show similar reactivity towards ClONO2 and much less reactivity towards N2O5. The UKCA chemistry-climate model has been used to assess the impact of TiO2 particles on stratospheric chemistry. A few scenarios have been constructed for TiO2 particle injection to have the same radiative effect as the eruption of Mt. Pinatubo. We find that the impact of TiO2 injection on stratospheric N2O5 is much smaller than the eruption of Mt. Pinatubo. The heterogeneous reaction of ClONO2 with TiO2 particles is being included in the model, and a comprehensive assessment of the effect of TiO2 injection on stratospheric chemistry will be presented.

  10. On the collision quenching of N_2^+(B\\,^2\\Sigma_u^+, v=0) by N2 and O2 and its influence on the measurement of E/N by intensity ratio of nitrogen spectral bands

    NASA Astrophysics Data System (ADS)

    Dilecce, G.; Ambrico, P. F.; De Benedictis, S.

    2010-05-01

    Laser induced fluorescence measurements of the rate coefficients of N_2^+(B\\,^2\\!\\Sigma_u^+, v=0) collision quenching by N2 and O2 are presented. The values of (8.84 ± 0.37) × 10-10 cm3 s-1 and (10.45 ± 0.45) × 10-10 cm3 s-1 have been found for N2 and O2, respectively. The present results agree well with the literature data obtained by selective methods for ion B state excitation. The data are discussed in the framework of the spectroscopic evaluation of the reduced electric field in electrical discharges at high pressure, which makes use of the second positive system and first negative system emissions of nitrogen.

  11. Rat calvaria osteoblast behavior and antibacterial properties of O(2) and N(2) plasma-implanted biodegradable poly(butylene succinate).

    PubMed

    Wang, Huaiyu; Ji, Junhui; Zhang, Wei; Wang, Wei; Zhang, Yihe; Wu, Zhengwei; Zhang, Yumei; Chu, Paul K

    2010-01-01

    Poly(butylene succinate), a novel biodegradable aliphatic polyester with excellent processability and mechanical properties, was modified by O(2) or N(2) plasma immersion ion implantation (PIII). X-ray photoelectron spectroscopy and contact angle measurements were carried out to reveal the surface characteristics of the treated and control specimens. The in vitro effects of the materials on seeded osteoblasts were detected by cell viability assay, alkaline phosphatase activity test, and real-time polymerase chain reaction analysis. Plate counting was performed to investigate the antibacterial properties. Our results show that both PIII treatments significantly improve the hydrophilicity of PBSu, and CO and nitrogen groups (CNH and CNH(2)) can be detected on the PBSu after O(2) and N(2) PIII, respectively. The modified samples exhibit similar compatibility to osteoblasts, which is better than that of the control, but O(2) PIII and N(2) PIII produce different effects according to the osteogenic gene expressions of seeded osteoblasts on the materials. Moreover, the N(2) plasma-modified PBSu exhibits anti-infection effects against Staphylococcus aureus and Escherichia coli but no such effects can be achieved after O(2) PIII. PMID:19631768

  12. Laser-induced fluorescence measurements of nitric oxide in laminar C2H6/O2/N2 flames at high pressure

    NASA Technical Reports Server (NTRS)

    Reisel, John R.; Carter, Campbell D.; Laurendeau, Normand M.

    1993-01-01

    Quantitative measurements of nitric oxide in C2H6/O2/N2 flames at 1-9 atm were successfully carried out using laser-induced fluorescence. The location of maximum NO concentration is found to shift towards leaner equivalence ratios with increasing pressure. Details of the experimental apparatus and measurement procedure are described.

  13. Response to suxamethonium during propofol-fentanyl-N2O/O2 anaesthesia in a patient with active myasthenia gravis receiving long-term anticholinesterase therapy.

    PubMed

    Vanlinthout, L E; Robertson, E N; Booij, L H

    1994-06-01

    We describe the effect of repeated suxamethonium doses during propofol-fentanyl-N2O/O2 anaesthesia in a 29-year-old woman with active myasthenia gravis receiving chronic pyridostigmine therapy. Despite adequate pre-operative pseudocholinesterase activity, suxamethonium resistance occurred. Neither bradycardia nor residual neuromuscular block were seen after repeated doses of suxamethonium. PMID:8017595

  14. Sediment-water fluxes of dissolved inorganic carbon, O2,nutrients, and N2 from the hypoxic region of the Louisianacontinental shelf

    EPA Science Inventory

    Sediment fluxes of dissolved inorganic carbon (DIC), O2, nutrients, and N2 (denitrification) were measured on the Louisiana Continental Shelf during six cruises from 2005 to 2007. On each cruise, three to seven stations were occupied in regions of the shelf that experience summer...

  15. Simultaneous and time-resolved temperature and relative CO2-N2 and O2-CO2-N2 concentration measurements with pure rotational coherent anti-Stokes Raman scattering for pressures as great as 5 MPa

    SciTech Connect

    Schenk, Martin; Seeger, Thomas; Leipertz, Alfred

    2005-09-10

    Pure rotational coherent anti-Stokes Raman-scattering (CARS) measurements have been performed in binary CO2-N2 and ternary CO2-O2-N2 mixtures in a temperature range between 300 and 773 K and pressures from 0.1 to 5 MPa to prove its potential for simultaneous single-shot thermometry and multispecies concentration measurements. In pressurized systems the CO2 component has a strong spectral influence on the pure rotational CARS spectra. Because of this dominance, pure rotational CARS proves to be a sensitive tool to measure in high-pressure combustion systems and the relative CO2-N2 concentration in the lower temperature range simultaneously with the temperature and the relative O2-N2 concentration. The evaluation of the spectra utilized a least-sum-squared differences fit of the spectral shape, weighted either constantly or inversely with respect to the normalized signal intensity. The results of the simultaneous temperature and relative CO2-N2 and O2-CO2-N2 concentration measurements provided a good accuracy and precision both in temperature and in concentrations. Because of the strong increase in the relative spectral contribution of CO2 with rising pressure, the precision of the CO2 concentration determination is in general significantly improved toward higher pressures, thus also clearly enhancing the CO2 detectability. The influence of temperature, O2 and CO2 concentration, pressure, and the evaluation techniques employed on both the accuracy and the precision is explained as well as their cross dependencies. The influence and limitations of the approximations used to model the CO2 molecule are discussed.

  16. Heterogeneous interaction of SiO2 with N2O5: aerosol flow tube and single particle optical levitation-Raman spectroscopy studies.

    PubMed

    Tang, M J; Camp, J C J; Rkiouak, L; McGregor, J; Watson, I M; Cox, R A; Kalberer, M; Ward, A D; Pope, F D

    2014-09-25

    Silica (SiO2) is an important mineral present in atmospheric mineral dust particles, and the heterogeneous reaction of N2O5 on atmospheric aerosol is one of the major pathways to remove nitrogen oxides from the atmosphere. The heterogeneous reaction of N2O5 with SiO2 has only been investigated by two studies previously, and the reported uptake coefficients differ by a factor of >10. In this work two complementary laboratory techniques were used to study the heterogeneous reaction of SiO2 particles with N2O5 at room temperature and at different relative humidities (RHs). The uptake coefficients of N2O5, γ(N2O5), were determined to be (7.2 ± 0.6) × 10(-3) (1σ) at 7% RH and (5.3 ± 0.8) × 10(-3) (1σ) at 40% RH for SiO2 particles, using the aerosol flow tube technique. We show that γ(N2O5) determined in this work can be reconciled with the two previous studies by accounting for the difference in geometric and BET derived aerosol surface areas. To probe the particle phase chemistry, individual micrometer sized SiO2 particles were optically levitated and exposed to a continuous flow of N2O5 at different RHs, and the composition of levitated particles was monitored online using Raman spectroscopy. This study represents the first investigation into the heterogeneous reactions of levitated individual SiO2 particles as a surrogate for mineral dust. Relative humidity was found to play a critical role: while no significant change of particle composition was observed by Raman spectroscopy during exposure to N2O5 at RH of <2%, increasing the RH led to the formation of nitrate species on the particle surface which could be completely removed after decreasing the RH back to <2%. This can be explained by the partitioning of HNO3 between the gas and adsorbed phases. The atmospheric implications of this work are discussed. PMID:25188692

  17. Plasma-Assisted Chemical Vapor Deposition of Titanium Oxide Films by Dielectric Barrier Discharge in TiCl4/O2/N2 Gas Mixtures

    NASA Astrophysics Data System (ADS)

    Niu, Jinhai; Zhang, Zhihui; Fan, Hongyu; Yang, Qi; Liu, Dongping; Qiu, Jieshan

    2014-07-01

    Low-pressure dielectric barrier discharge (DBD) TiCl4/O2 and N2 plasmas have been used to deposit titanium oxide films at different power supply driving frequencies. A homemade large area low pressure DBD reactor was applied, characterized by the simplicity of the experimental set-up and a low consumption of feed gas and electric power, as well as being easy to operate. Atomic force microscopy, scanning electron microscopy, energy dispersive spectroscopy, and contact angle measurements have been used to characterize the deposited films. Experimental results show all deposited films are uniform and hydrophilic with a contact angle of about 15°. Compared to titanium oxide films deposited in TiCl4/O2 gas mixtures, those in TiCl4/O2/N2 gas mixtures are much more stable. The contact angle of titanium oxide films in TiCl4/O2/N2 gas mixtures with the addition of 50% N2 and 20% TiCl4 is still smaller than 20°, while that of undoped titanium oxide films is larger than 64° when they are measured after one week. The low-pressure TiCl4/O2 plasmas consist of pulsed glow-like discharges with peak widths of several microseconds, which leads to the uniform deposition of titanium oxide films. Increasing a film thickness over several hundreds of nm leads to the film's fragmentation due to the over-high film stress. Optical emission spectra (OES) of TiCl4/O2 DBD plasmas at various power supply driving frequencies are presented.

  18. Oxygen Selective Membranes for Li-Air (O2) Batteries

    PubMed Central

    Crowther, Owen; Salomon, Mark

    2012-01-01

    Lithium-air (Li-air) batteries have a much higher theoretical energy density than conventional lithium batteries and other metal air batteries, so they are being developed for applications that require long life. Water vapor from air must be prevented from corroding the lithium (Li) metal negative electrode during discharge under ambient conditions, i.e., in humid air. One method of protecting the Li metal from corrosion is to use an oxygen selective membrane (OSM) that allows oxygen into the cell while stopping or slowing the ingress of water vapor. The desired properties and some potential materials for OSMs for Li-air batteries are discussed and the literature is reviewed. PMID:24958173

  19. Oxygen selective membranes for li-air (o2) batteries.

    PubMed

    Crowther, Owen; Salomon, Mark

    2012-01-01

    Lithium-air (Li-air) batteries have a much higher theoretical energy density than conventional lithium batteries and other metal air batteries, so they are being developed for applications that require long life. Water vapor from air must be prevented from corroding the lithium (Li) metal negative electrode during discharge under ambient conditions, i.e., in humid air. One method of protecting the Li metal from corrosion is to use an oxygen selective membrane (OSM) that allows oxygen into the cell while stopping or slowing the ingress of water vapor. The desired properties and some potential materials for OSMs for Li-air batteries are discussed and the literature is reviewed. PMID:24958173

  20. Phase stability and magnetic behavior of hexagonal phase of N2-O2 system with kagome lattice under high pressure and low temperature

    NASA Astrophysics Data System (ADS)

    Akahama, Y.; Ishihara, D.; Yamashita, H.; Fujihisa, H.; Hirao, N.; Ohishi, Y.

    2016-08-01

    The pressure-temperature (P -T ) phase diagram of N2-O2 mixture with a composition of N2-48 mol % O2 has been investigated using x-ray diffraction and the phase stability of a hexagonal phase (space group: P 6 /mmm), with the kagome lattice examined under high-pressure and low-temperature conditions. While the phase appears as a low-temperature phase of the cubic phase (P m 3 n ) with the structure of γ -O2 or δ -N2 and is stable in a wide range of pressures and temperatures, it transforms to lower symmetry monoclinic or orthorhombic phases at lower temperature, accompanied with a distortion of the kagome lattice. Based on Rietveld refinements, the monoclinic and orthorhombic phases are found to be in the P 21/a and Cmmm space groups, respectively. In magnetization measurements, a magnetic transition is observed with a relatively large drop of magnetization, corresponding to the cubic-to-hexagonal phase transition. This suggests that the hexagonal phase has a certain magnetic ordered state that arises from the molecular magnetic moment of O2.

  1. Inactivation factors of spore-forming bacteria using low-pressure microwave plasmas in an N2 and O2 gas mixture

    NASA Astrophysics Data System (ADS)

    Singh, M. K.; Ogino, A.; Nagatsu, M.

    2009-11-01

    In this study, we investigated the inactivation characteristics of Geobacillus stearothermophilus spores under different plasma exposure conditions using low-pressure microwave plasma in nitrogen, oxygen and an air-simulated (N2:O2=4:1) gas mixture. The microwave-excited surface-wave plasma discharges were produced at low pressure by a large volume device. The directly plasma-exposed spores, up to 106 populations, were successfully inactivated within 15, 10 and 5 min of surface-wave plasma treatment using nitrogen, oxygen and an air-simulated gas mixture, respectively, as working gases within the temperature of 75 °C. The contribution of different inactivation factors was evaluated by placing different filters (e.g. a LiF plate, a quartz plate and a Tyvek® sheet) as indirect exposure of spores to the plasma. It was observed that optical emissions (including vacuum UV (VUV)/UV) play an important role in the inactivation process. To further evaluate the effect of VUV/UV photons, we placed an evacuated isolated chamber, inside which spores were set, into the main plasma chamber. The experimental results show that the inactivation time by VUV/UV photons alone, without working gas in the immediate vicinity of the spores, is longer than that with working gas. This suggests that the VUV/UV emission is responsible not only for direct UV inactivation of spores but also for generation of reactive neutral species by photoexcitation. The scanning electron microscopy images revealed significant changes in the morphology of directly plasma-exposed spores but no change in the spores irradiated by VUV/UV photons only.

  2. The 2140 cm-1 (4.673 microns) Solid CO Band: The Case for Interstellar O2 and N2 and the Photochemistry of Nonpolar Interstellar Ice Analogs

    NASA Astrophysics Data System (ADS)

    Elsila, Jamie; Allamandola, Louis J.; Sandford, Scott A.

    1997-04-01

    The infrared spectra of CO frozen in nonpolar ices containing N2, CO2, O2, and H2O and the UV photochemistry of these interstellar/precometary ice analogs are reported. The spectra are used to test the hypothesis that the narrow 2140 cm-1 (4.673 μm) interstellar absorption feature attributed to solid CO might be produced by CO frozen in ices containing nonpolar species such as N2 and O2. It is shown that mixed molecular ices containing CO, N2, O2, and CO2 provide a good match to the interstellar band at all temperatures between 12 and 30 K both before and after photolysis. The optical constants (real and imaginary parts of the index of refraction) in the region of the solid CO feature are reported for several of these ices. The N2 and O2 absorptions at 2328 cm-1 (4.296 μm) and 1549 cm-1 (6.456 μm), respectively, are also shown. The best matches between the narrow interstellar band and the feature in the laboratory spectra of nonpolar ices are for samples which contain comparable amounts of N2, O2, CO2, and CO. Co-adding the CO band from an N2:O2:CO2:CO=1:5:1/2:1 ice with that of an H2O:CO = 20:1 ice provides an excellent fit across the entire interstellar CO feature. The four-component, nonpolar ice accounts for the narrow 2140 cm-1 portion of the feature which is associated with quiescent regions of dense molecular clouds. Using this mixture, and applying the most recent cosmic abundance values, we derive that between 15% and 70% of the available interstellar N is in the form of frozen N2 along several lines of sight toward background stars. This is reduced to a range of 1%-30% for embedded objects with lines of sight more dominated by warmer grains. The cosmic abundance of O tied up in frozen O2 lies in the 10%-45% range toward background sources, and it is between 1% and 20% toward embedded objects. The amount of oxygen tied up in CO and CO2 frozen in nonpolar ices can be as much as 2%-10% toward background sources and on the order of 0.2%-5% for embedded

  3. The 2140 cm-1 (4.673 microns) solid CO band: the case for interstellar O2 and N2 and the photochemistry of nonpolar interstellar ice analogs

    NASA Technical Reports Server (NTRS)

    Elsila, J.; Allamandola, L. J.; Sandford, S. A.

    1997-01-01

    The infrared spectra of CO frozen in nonpolar ices containing N2, CO2, O2, and H2O and the UV photochemistry of these interstellar/precometary ice analogs are reported. The spectra are used to test the hypothesis that the narrow 2140 cm-1 (4.673 microns) interstellar absorption feature attributed to solid CO might be produced by CO frozen in ices containing nonpolar species such as N2 and O2. It is shown that mixed molecular ices containing CO, N2, O2, and CO2 provide a good match to the interstellar band at all temperatures between 12 and 30 K both before and after photolysis. The optical constants (real and imaginary parts of the index of refraction) in the region of the solid CO feature are reported for several of these ices. The N2 and O2 absorptions at 2328 cm-1 (4.296 microns) and 1549 cm-1 (6.456 microns), respectively, are also shown. The best matches between the narrow interstellar band and the feature in the laboratory spectra of nonpolar ices are for samples which contain comparable amounts of N2, O2, CO2, and CO. Co-adding the CO band from an N2:O2:CO2:CO = 1:5:1/2:1 ice with that of an H2O:CO = 20:1 ice provides an excellent fit across the entire interstellar CO feature. The four-component, nonpolar ice accounts for the narrow 2140 cm-1 portion of the feature which is associated with quiescent regions of dense molecular clouds. Using this mixture, and applying the most recent cosmic abundance values, we derive that between 15% and 70% of the available interstellar N is in the form of frozen N2 along several lines of sight toward background stars. This is reduced to a range of 1%-30% for embedded objects with lines of sight more dominated by warmer grains. The cosmic abundance of O tied up in frozen O2 lies in the 10%-45% range toward background sources, and it is between 1% and 20% toward embedded objects. The amount of oxygen tied up in CO and CO2 frozen in nonpolar ices can be as much as 2%-10% toward background sources and on the order of 0

  4. The 2140 cm-1 (4.673 microns) solid CO band: the case for interstellar O2 and N2 and the photochemistry of nonpolar interstellar ice analogs.

    PubMed

    Elsila, J; Allamandola, L J; Sandford, S A

    1997-04-20

    The infrared spectra of CO frozen in nonpolar ices containing N2, CO2, O2, and H2O and the UV photochemistry of these interstellar/precometary ice analogs are reported. The spectra are used to test the hypothesis that the narrow 2140 cm-1 (4.673 microns) interstellar absorption feature attributed to solid CO might be produced by CO frozen in ices containing nonpolar species such as N2 and O2. It is shown that mixed molecular ices containing CO, N2, O2, and CO2 provide a good match to the interstellar band at all temperatures between 12 and 30 K both before and after photolysis. The optical constants (real and imaginary parts of the index of refraction) in the region of the solid CO feature are reported for several of these ices. The N2 and O2 absorptions at 2328 cm-1 (4.296 microns) and 1549 cm-1 (6.456 microns), respectively, are also shown. The best matches between the narrow interstellar band and the feature in the laboratory spectra of nonpolar ices are for samples which contain comparable amounts of N2, O2, CO2, and CO. Co-adding the CO band from an N2:O2:CO2:CO = 1:5:1/2:1 ice with that of an H2O:CO = 20:1 ice provides an excellent fit across the entire interstellar CO feature. The four-component, nonpolar ice accounts for the narrow 2140 cm-1 portion of the feature which is associated with quiescent regions of dense molecular clouds. Using this mixture, and applying the most recent cosmic abundance values, we derive that between 15% and 70% of the available interstellar N is in the form of frozen N2 along several lines of sight toward background stars. This is reduced to a range of 1%-30% for embedded objects with lines of sight more dominated by warmer grains. The cosmic abundance of O tied up in frozen O2 lies in the 10%-45% range toward background sources, and it is between 1% and 20% toward embedded objects. The amount of oxygen tied up in CO and CO2 frozen in nonpolar ices can be as much as 2%-10% toward background sources and on the order of 0

  5. Collisional Removal of O2 (c(sup 1) Sigma(sup-)(sub u), nu=9) by O2, N2, and He

    NASA Technical Reports Server (NTRS)

    Copeland, Richard A.; Knutsen, Karen; Onishi, Marc E.; Yalcin, Talat

    1996-01-01

    The collisional removal Of 02 molecules in selected vibrational levels of the c state is studied using a two-laser double-resonance technique. The output of the first laser excites the 02 to nu = 9 or 10 of the c Sigma - state, and the ultraviolet output of the second laser monitors specific rovibrational levels via resonance-enhanced ionization. The temporal evolution of the c Sigma u state vibrational level is observed by scanning the time delay between the two pulsed lasers. As the rate constants for 02 and N2 are similar in magnitude, N2 collisions dominate the removal rate in the earth's atmosphere. For v= 10 colliding with 02, we find a removal rate constant that is 2-5 times that for v=9 and that single quantum collision cascade is an important pathway for removal.

  6. Photochemical Removal of SO2 and CO2 by 172 nm Xe2 and 146 nm Kr2 Excimer Lamps in N2 or Air at Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Tsuji, Masaharu; Kawahara, Takashi; Kawahara, Masashi; Kamo, Naohiro; Hishinuma, Nobuyuki

    2008-12-01

    The photochemical removal of SO2 and CO2 was investigated in N2 or air using 172 nm Xe2 (50 or 300 mW/cm2) and 146 nm Kr2 (25 mW/cm2) excimer lamps and without using any expensive catalysts. After 30 min photoirradiation, 45 and 75% of SO2 (1000 ppm) were removed in N2 and air (20% O2) at 172 nm photoirradiation, respectively, whereas 39 and 8% of SO2 were removed in N2 and air at 146 nm, respectively. By using a high-power Xe2 lamp, ˜10 and ˜45% of SO2 (200 ppm) could be removed in N2 and air in a flow system, respectively. Although no photolysis of CO2 (1000 ppm) was observed at 172 nm, ˜16 and ˜8% of CO2 were converted to CO+O2 in N2 and air at 146 nm after about 10 min photoirradiation, respectively. Possible decomposition mechanisms were discussed.

  7. Performance of MnO2 Crystallographic Phases in Rechargeable Lithium-Air Oxygen Cathode

    NASA Astrophysics Data System (ADS)

    Oloniyo, Olubukun; Kumar, Senthil; Scott, Keith

    2012-05-01

    Manganese dioxide (MnO2) has been shown to be effective for improving the efficiency of cathodes in lithium-air cells. Different crystallographic phases including α-, β-, and γ-MnO2 nanowires, α-MnO2 nanospheres, and α-MnO2 nanowires on carbon ( α-MnO2/C) were synthesized using the hydrothermal method. Their physical properties were examined using x-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area measurements, and scanning electron microscopy (SEM) and found to be in agreement with the literature. Electrochemical properties of the synthesized catalyst particles were investigated by fabricating cathodes and testing them in a lithium-air cell with lithium hexafluorophosphate in propylene carbonate (LiPF6/PC) and tetra(ethylene glycol)dimethyl ether (LiTFSi/TEGDME) electrolytes. α-MnO2 had the highest discharge capacity in the LiTFSi/TEGDME electrolyte (2500 mAh/g), whilst α-MnO2/C in LiPF6/PC showed a significantly higher discharge capacity of 11,000 mAh/g based on total mass of the catalytic cathode. However, the latter showed poor capacity retention compared with γ-MnO2 nanowires, which was stable for up to 30 cycles. The reported discharge capacity is higher than recorded in previous studies on lithium-air cells.

  8. Air detoxification with nanosize TiO2 aerosol tested on mice.

    PubMed

    Besov, A S; Krivova, N A; Vorontsov, A V; Zaeva, O B; Kozlov, D V; Vorozhtsov, A B; Parmon, V N; Sakovich, G V; Komarov, V F; Smirniotis, P G; Eisenreich, N

    2010-01-15

    A method for fast air purification using high concentration aerosol of TiO(2) nanoparticles is evaluated in a model chemical catastrophe involving toxic vapors of diisopropyl fluorophosphate (DFP). Mice are used as human model in a closed 100 dm(3) chamber. Exposure of mice to 37 ppm of DFP vapor for 15 min resulted in acute poisoning. Spraying TiO(2) aerosol in 2 min after the start of exposure to DFP vapors resulted in quick removal of DFP vapors from the chamber's air. Animals did not show signs of poisoning after the decontamination experiment and exposure to TiO(2) aerosol alone. Reactive oxygen species (ROS) and antioxidant activity (AOA) of mice blood plasma were measured for animals exposed to sound of aerosol generator, DFP vapors, TiO(2) aerosol and DFP vapors+TiO(2) aerosol. Reduced ROS and increased AOA were found for mice exposure to sound, DFP and TiO(2) aerosol. Exposure to DFP and decontamination with TiO(2) nanoparticles resulted in decreased AOA in 48 h following the exposure. The results suggest that application of TiO(2) aerosol is a powerful method of air purification from toxic hydrolysable compounds with moderate health aftermaths and requires further study and optimization. PMID:19765900

  9. Electron Transport Coefficients and Effective Ionization Coefficients in SF6-O2 and SF6-Air Mixtures Using Boltzmann Analysis

    NASA Astrophysics Data System (ADS)

    Wei, Linsheng; Xu, Min; Yuan, Dingkun; Zhang, Yafang; Hu, Zhaoji; Tan, Zhihong

    2014-10-01

    The electron drift velocity, electron energy distribution function (EEDF), density-normalized effective ionization coefficient and density-normalized longitudinal diffusion velocity are calculated in SF6-O2 and SF6-Air mixtures. The experimental results from a pulsed Townsend discharge are plotted for comparison with the numerical results. The reduced field strength varies from 40 Td to 500 Td (1 Townsend=10-17 V·cm2) and the SF6 concentration ranges from 10% to 100%. A Boltzmann equation associated with the two-term spherical harmonic expansion approximation is utilized to gain the swarm parameters in steady-state Townsend. Results show that the accuracy of the Boltzmann solution with a two-term expansion in calculating the electron drift velocity, electron energy distribution function, and density-normalized effective ionization coefficient is acceptable. The effective ionization coefficient presents a distinct relationship with the SF6 content in the mixtures. Moreover, the E/Ncr values in SF6-Air mixtures are higher than those in SF6-O2 mixtures and the calculated value E/Ncr in SF6-O2 and SF6-Air mixtures is lower than the measured value in SF6-N2. Parametric studies conducted on these parameters using the Boltzmann analysis offer substantial insight into the plasma physics, as well as a basis to explore the ozone generation process.

  10. Effect of N2 dielectric barrier discharge treatment on the composition of very thin SiO2-like films deposited from hexamethyldisiloxane at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Reuter, R.; Gherardi, N.; Benedikt, J.

    2012-11-01

    The continuous deposition of thin SiO2-like films by means of a dielectric barrier discharge with helium or nitrogen gas with small admixture of hexamethyldisiloxane (HMDSO) has been compared to a layer-by-layer deposition process, in which a very thin (0.7 nm and 2.5 nm) films are deposited from HMDSO precursor and treated afterwards by a pure N2 dielectric barrier discharge (DBD). Presented results clearly show that a carbon-free SiO2-like films can be obtained in the latter process, even if the continuous deposition led to carbon-rich material. Surface reactions of N2-DBD generated excited species (metastables, ions, or possibly photons) with surface bonded carbon are responsible for this effect. Moreover, OH-free and oxidation-resistant films can be produced even at the room substrate temperature.

  11. Self-, N2, O2, H2, Ar, and He broadening in the nu3 band Q branch of CH4

    NASA Technical Reports Server (NTRS)

    Pine, A. S.

    1992-01-01

    Self-, N2-, O2-, H2-, Ar-, and He-broadening coefficients, pressure shifts, and integrated intensities have been measured for most transitions in the Q branch of the nu3 fundamental band of methane using a difference-frequency laser spectrometer. A systematic dependence of the broadening coefficients on the tetrahedral symmetry species and order index is observed with striking similarities for N2, O2, and Ar and for H2 and He buffer gases. Comparison with earlier measurements on other bands and branches of methane indicates very little vibrational, branch, or carbon isotope dependence. Dicke narrowing is evident at intermediate pressures, yielding an average narrowing coefficient and an optical diffusion constant for each gas mixture.

  12. Inactivation of Gram-Negative Bacteria by Low-Pressure RF Remote Plasma Excited in N2-O2 Mixture and SF6 Gases

    PubMed Central

    Al-Mariri, Ayman; Saloum, Saker; Mrad, Omar; Swied, Ghayath; Alkhaled, Bashar

    2013-01-01

    The role of low-pressure RF plasma in the inactivation of Escherichia coli O157, Klebsiella pneumoniae, Proteus mirabilis, and Enterobacter sakazakii using N2-O2 and SF6 gases was assessed. 1×109 colony-forming units (CFUs) of each bacterial isolate were placed on three polymer foils. The effects of pressure, power, distance from the source, and exposure time to plasma gases were optimized. The best conditions to inactivate the four bacteria were a 91%N2-9%O2 mixture and a 30-minute exposure time. SF6 gas was more efficient for all the tested isolates in as much as the treatment time was reduced to only three minutes. Therefore, low-pressure plasma could be used to sterilize heat and/or moisture-sensitive medical instruments. PMID:24293788

  13. Theoretical views on activation of methane catalyzed by Hf2+ and oxidation of CO (x(1)Σ(+)) by N2O (x(1)Σ(+)) Catalyzed by HfO2+ and TaO2+.

    PubMed

    Nian, Jingyan; Tie, Lu; Wang, Ben; Guo, Zhiguang

    2013-09-12

    The mechanisms of activation of CH4 catalyzed by (1/3)Hf(2+) and oxidation of CO by N2O catalyzed by (1/3)HfO(2+) or (2/4)TaO(2+) have been investigated using the B3LYP level of theory. For the activation of methane, the TSR (two-state reactivity) mechanism has been certified through the spin-orbit coupling (SOC) calculation and the Landau-Zener-type model. In the vicinity of the minimum energy crossing point (MECP), SOC equals 900.23 cm(-1) and the probability of intersystem crossing is approximately 0.62. Spin inversion makes the activation barrier decline from 1.63 to 0.57 eV. NBO analysis demonstrates that empty 6s and 5d orbitals of the Hf atom play the major role for the activation of C-H bonds. Finally, CH4 dehydrogenates to produce Hf-CH2(2+). For oxidation of CO by N2O catalyzed by HfO(2+) or TaO(2+), the covalent bonds between transition metal atoms and the oxygen atom restrict the freedom of valence electrons. Therefore, they are all SSR (single-state reactivity). The oxygen atom is directly extracted during the course of oxygen transfer, and its microscopic essence has been discussed. The detailed kinetic information of two catalytic cycles has been calculated by referencing the "energetic span (δE)" model. Finally, TOF(HfO(2+))/TOF(TaO(2+)) = 2.7 at 298.15 K, which has a good consistency with the experimental result. PMID:23947756

  14. Differential cross sections for scattering of 0.5-, 1.5-, and 5.0 keV oxygen atoms by He, N2, and O2

    NASA Technical Reports Server (NTRS)

    Schafer, D. A.; Newman, J. H.; Smith, K. A.; Stebbings, R. F.

    1987-01-01

    This paper reports measurements of absolute scattering cross sections, differential in angle, for collisions of ground-state oxygen atoms with He, N2, and O2. Data are presented for scattering of 0.5-, 1.5-, and 5.0-keV oxygen-atom projectiles in the range of laboratory frame angles between 0.06 and 5 deg. These measurements provide information relevant to calculations of the aeronomic consequences of O(+) precipitation in the earth's upper atmosphere.

  15. Synthesis, antioxidant activities of the nickel(II), iron(III) and oxovanadium(IV) complexes with N2O2 chelating thiosemicarbazones

    NASA Astrophysics Data System (ADS)

    Bal-Demirci, Tülay; Şahin, Musa; Özyürek, Mustafa; Kondakçı, Esin; Ülküseven, Bahri

    The nickel(II), iron(III) and oxovanadium(IV) complexes of the N2O2 chelating thiosemicarbazones were synthesized using 4-hydroxysalicyladehyde-S-methylthiosemicarbazone and R1-substitute-salicylaldehyde (R1: 4-OH, H) in the presence of Ni(II), Fe(III), VO(IV) ions by the template reaction. The structures of the thiosemicarbazone complexes were characterized by FT-IR, 1H NMR, elemental, ESI-MS and APCI-MS analysis. The synthesized compounds were screened for their antioxidant capacity by using the cupric reducing antioxidant capacity (CUPRAC) method. Trolox equivalent antioxidant capacity (TEAC) of iron(III) complex, 1c, was measured to be higher than that of the other complexes. Other parameters of antioxidant activity (scavenging effects on rad OH, O2rad - and H2O2) of these compounds were also determined. All the compounds have shown encouraging ROS scavenging activities.

  16. Synthesis, antioxidant activities of the nickel(II), iron(III) and oxovanadium(IV) complexes with N2O2 chelating thiosemicarbazones.

    PubMed

    Bal-Demirci, Tülay; Sahin, Musa; Ozyürek, Mustafa; Kondakçı, Esin; Ulküseven, Bahri

    2014-05-21

    The nickel(II), iron(III) and oxovanadium(IV) complexes of the N2O2 chelating thiosemicarbazones were synthesized using 4-hydroxysalicyladehyde-S-methylthiosemicarbazone and R1-substitute-salicylaldehyde (R1: 4-OH, H) in the presence of Ni(II), Fe(III), VO(IV) ions by the template reaction. The structures of the thiosemicarbazone complexes were characterized by FT-IR, (1)H NMR, elemental, ESI-MS and APCI-MS analysis. The synthesized compounds were screened for their antioxidant capacity by using the cupric reducing antioxidant capacity (CUPRAC) method. Trolox equivalent antioxidant capacity (TEAC) of iron(III) complex, 1c, was measured to be higher than that of the other complexes. Other parameters of antioxidant activity (scavenging effects on •OH, O2(•-) and H2O2) of these compounds were also determined. All the compounds have shown encouraging ROS scavenging activities. PMID:24656797

  17. Aspects of Supercritical Turbulence: Direct Numerical Simulation of O2/H2 and C7H16/N2 Temporal Mixing Layers

    NASA Technical Reports Server (NTRS)

    Bellan, J.; Okongo, N. A.; Harstad, K. G.; Hutt, John (Technical Monitor)

    2002-01-01

    Results from Direct Numerical Simulations of temporal, supercritical mixing layers for two species systems are analyzed to elucidate species-specific turbulence aspects. The two species systems, O2/H2 and C7HG16/N2, have different thermodynamic characteristics; thus, although the simulations are performed at similar reduced pressure (ratio of the pressure to the critical pressure), the former system is dose to mixture ideality and has a relatively high solubility with respect to the latter, which exhibits strong departures from mixture ideality Due to the specified, smaller initial density stratification, the C7H16/N2 layers display higher growth and increased global molecular mixing as well as larger turbulence levels. However, smaller density gradients at the transitional state for the O2/H2 system indicate that on a local basis, the layer exhibits an enhanced mixing, this being attributed to the increased solubility and to mixture ideality. These thermodynamic features are shown to affect the irreversible entropy production (i.e. the dissipation), which is larger for the O2/H2 layer and is primarily concentrated in high density-gradient magnitude regions that are distortions of the initial density stratification boundary. In contrast, the regions of largest dissipation in the C7H16/N2 layer are located in high density-gradient magnitude regions resulting from the mixing of the two fluids.

  18. Production and characterization of thin a-C:(H) films for gas permeation barrier functionality against He, CO(2), N(2), O(2) and H(2)O.

    PubMed

    Laidani, N; Bartali, R; Gottardi, G; Anderle, M; Chuste, G; Bellachioma, C

    2006-07-01

    This work reports on (i) the gas barrier properties of a-C:H films rf-sputtered in Ar-H(2) plasmas from a graphite target on polyethylene terephthalate (PET) and (ii) the influence of the film chemical structure and defect properties on the gas permeability. The intrinsic permeabilities of the films to He, CO(2), O(2), N(2) gases and H(2)O vapour were determined and found to be orders of magnitude lower than that of the bare PET. Indirect evidence was given to a solubility-diffusion process as the more probable permeation mechanism, over a gas flow through microdefects or gas transport through nanodefects by a Knudsen diffusion mechanism. The barrier capability of the films was found to scale as the gas molecular diameter within the He, CO(2), O(2) and N(2) series, and inversely with the gas critical temperature for the CO(2), O(2), N(2) and H(2)O series. A correlation between the film Urbach energy, E(u), and the gas permeability was established, except for H(2)O. Such findings further favour a bulk diffusion contributing mechanism to permeation over the gas state transport. Conversely, this E(u)-permeability relation shed more light on the origin of the valence band tailing of the amorphous carbon electron structure. PMID:21690810

  19. Production and characterization of thin a-C:(H) films for gas permeation barrier functionality against He, CO2, N2, O2 and H2O

    NASA Astrophysics Data System (ADS)

    Laidani, N.; Bartali, R.; Gottardi, G.; Anderle, M.; Chuste, G.; Bellachioma, C.

    2006-07-01

    This work reports on (i) the gas barrier properties of a-C:H films rf-sputtered in Ar-H2 plasmas from a graphite target on polyethylene terephthalate (PET) and (ii) the influence of the film chemical structure and defect properties on the gas permeability. The intrinsic permeabilities of the films to He, CO2, O2, N2 gases and H2O vapour were determined and found to be orders of magnitude lower than that of the bare PET. Indirect evidence was given to a solubility-diffusion process as the more probable permeation mechanism, over a gas flow through microdefects or gas transport through nanodefects by a Knudsen diffusion mechanism. The barrier capability of the films was found to scale as the gas molecular diameter within the He, CO2, O2 and N2 series, and inversely with the gas critical temperature for the CO2, O2, N2 and H2O series. A correlation between the film Urbach energy, Eu, and the gas permeability was established, except for H2O. Such findings further favour a bulk diffusion contributing mechanism to permeation over the gas state transport. Conversely, this Eu-permeability relation shed more light on the origin of the valence band tailing of the amorphous carbon electron structure.

  20. Oxidation of Flash-Anodized Al-Mg Alloy in Dry Atmospheres of N2, CO2, and O2 and Humid Atmosphere of Ar

    NASA Astrophysics Data System (ADS)

    LaPointe, Kyle; Bao, Sarina; Kvithyld, Anne

    2015-03-01

    Production of anodized Al alloy is increasing with increased recycling of Al. To study recycling of anodized material, a flash-anodized 3000 series Al alloy containing 0.34 wt pct Mg was remelted in pure atmospheres of CO2, O2, and N2, and Ar with 5 mol pct H2O at 1073 K (800 °C). Hopefully, the results should be of general influence concerning dross formation and scrap remelting in the Al industry. Oxidation studies using a thermogravimetric analyser were performed. Following the treatment, the samples oxide layers were characterized. The highest oxidation rates were observed in atmospheres of O2 and CO2. However, the onset of a break-away oxidation period in O2 is delayed in comparison to CO2. Oxidation in CO2 showed substantially less MgO formation compared to O2. The main source of mass gain can be attributed to the reaction of Mg with oxygen to form MgO and MgAl x O y . Heating in N2 resulted in the lowest mass gain of all atmospheres. Experiments in humid (5 mol pct H2O) Ar atmospheres indicate that there is a minimum threshold of Mg activity to initiate oxidation via H2O. Oxidation kinetics (mechanisms) has been investigated.

  1. Determination, through titration with NO, of the concentration of oxygen atoms in the flowing afterglow of Ar-O2 and N2-O2 plasmas used for sterilization purposes

    NASA Astrophysics Data System (ADS)

    Ricard, A.; Moisan, M.; Moreau, S.

    2001-04-01

    Les méthodes existantes de titrage de N et O d'une post-décharge au moyen de l'intensité d'émission de la molécule NO excitée ne permettant pas d'aller au-delà de x = 5% dans un mélange xO2-(100%-x)N2, nous présentons une démarche valable pour x≤20%. Cette technique est fondée sur la mesure de l'intensité d'émission de NO2(A), en fonction du débit de NO introduit, en relation avec une dérivation analytique des équations des concentrations [N] et [O]. La concentration d'oxygène atomique obtenue par cette méthode est validée de façon indépendante à partir de la mesure du rapport des intensités d'émission de NO(B) et de N2(B, 11) (celle-ci détectable pour x≤8%). Enfin, la méthode proposée est mise en oeuvre pour apprécier l'influence de la valeur de la concentration d'oxygène atomique sur le temps de stérilisation dans une post-décharge en flux à partir d'un plasma de N2-O2. \\engabstract Existing titration methods of N and O in an afterglow based on the emission intensity of the excited NO molecule cannot be used at x values exceeding 5% in the xO2-(100%-x)N2 mixture. Our technique extends the x range to 20%. It utilizes the emission intensity measurement of NO2(A), as a function of the introduced NO flow, in relation with analytically derived equations for the O and N concentrations. The atomic oxygen concentration obtained in this way is validated independently through measurements of the emission intensity ratio of NO(B) and N2(B, 11) (detectable for x≤8%). Finally, the proposed method is used to assess the influence of the oxygen atom concentration on the sterilization time in the flowing afterglow of an N2-O2 plasma.

  2. Low-Temperature Desorption of N2O from NO on Rutile TiO2(110)-1x1

    SciTech Connect

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

    2014-05-08

    We find that NO dosed on rutile TiO2(110)-1×1 at substrate temperatures as low as 50 K readily reacts to produce N2O which desorbs promptly from the surface leaving an oxygen adatom behind. The desorption rate of N2O reaches a maximum value after 1 – 2 sec at an NO flux of 1.2 ×1014 NO/cm2∙sec and then decreases rapidly as the initially clean, reduced TiO2(110) surface with ~5% oxygen vacancies (VO’s) becomes covered with oxygen adatoms and unreacted NO. The maximum desorption rate is also found to increase as the substrate temperature is raised up to about 100 K. Interestingly, the N2O desorption during the low-temperature (LT) NO dose is strongly suppressed when molecular oxygen is predosed, whereas it persists on the surface with VO’s passivated by surface hydroxyls. Our results show that the surface charge, not the VO sites, plays a dominant role in the LT N2O desorption induced by a facile NO reduction at such low temperatures.

  3. Photoinduced interaction studies on N-(2-methylthiophenyl)-2-hydroxy-1-naphthadiamine with TiO2 nanoparticles: A combined experimental and theoretical (DFT and spectroscopic) approach

    NASA Astrophysics Data System (ADS)

    Pushpam, S.; Gayathri, S.; Ramakrishnan, V.

    2014-12-01

    Schiff base derivative synthesized by the reaction of 2-(methylthio) aniline and 2-hydroxy-1-naphthaldehyde exhibits keto-amine tautomerism in methanol solvent. The fluorescence quenching of N-(2-methyl thiophenyl)-2-hydroxy-1-naphthadiamine (NMTHN) by TiO2 nanoparticles in methanol has been studied. The excitation and emission peaks have been observed at 439 and 509 nm respectively. The apparent association constant has been deduced from the absorption spectral changes of NMTHN-TiO2 nanoparticles using Bensi-Hildebrand equation. The number of binding sites and the binding constant have been calculated from the relevant fluorescence data. Quenching of fluorescence of NMTHN by TiO2 could be due to a dynamic mode. Density Functional Theory (DFT) calculations also have been performed to study the charge distribution of NMTHN-TiO2 both in ground and excited states. The HOMO-LUMO analysis of NMTHN-TiO2 in the ground state has been made.

  4. Formation of small polarons in Li2O2 and implications for Li-air batteries

    NASA Astrophysics Data System (ADS)

    Kang, Joongoo; Jung, Yoon-Seok; Wei, Su-Huai; Dillon, Anne

    2012-02-01

    Lithium-air batteries (LABs) have recently been revitalized as a promising electrical energy storage system due to their exceptionally high theoretical energy density. However, its usage is limited by poor rate capability and large polarization in the cell voltage due primarily to the formation of Li2O2 in the air cathode. Here, using hybrid density functional theory, we found that the formation of small polarons in Li2O2 is the origin that limits the electron transport in Li2O2. Consequently, the low electron mobility contributes to the hysteresis in cell voltage and limits the power density of the LABs. We suggest that similar behavior should exist in other peroxides, and p-type doping in Li2O2 could significantly improve the performance of LABs at high current densities.

  5. Spectroscopic investigation of the NO C 2Π de-excitation process by collision with O2 X 3Σg- in a low-pressure N2-O2 mixture microwave discharge

    NASA Astrophysics Data System (ADS)

    Tan, Hao; Nezu, Atsushi; Akatsuka, Hiroshi

    2016-01-01

    We use a spectroscopic method to diagnose the microwave discharge plasma of N2-O2 mixtures. We succeed in observing NO δ-band radiation peaks when the oxygen partial pressure is smaller than 3%. In order to quantitatively investigate the de-excitation processes of the NO C 2Π excited state, we improve our self-consistent kinetic model to include some of the main excited states of NO molecules. In providing our numerical results, we discuss a reasonable NO C 2Π de-population process by that involves collision with the O2 X 3Σg- state molecule, which leads to the disappearance of δ-band radiation. We propose an indirect proof that this de-population process results in an increase in the vibrational temperature of NO A 2Σ+.

  6. Kinetic model and spectroscopic measurement of NO (A, B, C) states in low-pressure N2-O2 microwave discharge

    NASA Astrophysics Data System (ADS)

    Tan, Hao; Nezu, Atsushi; Akatsuka, Hiroshi

    2015-09-01

    A self-consistent kinetic model is developed to study the atomic and molecular processes in the microwave discharge plasma of N2-O2 mixtures. We focus on the NO A 2Σ+, B 2Π, and C 2Π states in the mixture discharge. We find good agreement between the calculated and experimental NO A 2Σ+ densities. On the other hand, the radiation bands from the NO B 2Π and C 2Π states are observed only when the oxygen partial pressure is less than 3%. We discuss the de-excitation processes for the NO B 2Π and C 2Π states in this low-pressure plasma. We also propose that the de-excitation processes involve collision with O2 X 3Σ \\text{g} - for these levels, which can explain the observed spectral disappearance.

  7. Mechanistic Evaluation of LixOy Formation on δ-MnO2 in Nonaqueous Li-Air Batteries.

    PubMed

    Liu, Zhixiao; De Jesus, Luis R; Banerjee, Sarbajit; Mukherjee, Partha P

    2016-09-01

    Transition metal oxides are usually used as catalysts in the air cathode of lithium-air (Li-air) batteries. This study elucidates the mechanistic origin of the oxygen reduction reaction catalyzed by δ-MnO2 monolayers and maps the conditions for Li2O2 growth using a combination of first-principles calculations and mesoscale modeling. The MnO2 monolayer, in the absence of an applied potential, preferentially reacts with a Li atom instead of an O2 molecule to initiate the formation of LiO2. The oxygen reduction products (LiO2, Li2O2, and Li2O molecules) strongly interact with the MnO2 monolayer via the stabilization of Li-O chemical bonds with lattice oxygen atoms. As compared to the disproportionation reaction, direct lithiation reactions are the primary contributors to the stabilization of Li2O2 on the MnO2 monolayer. The energy profiles of (Li2O2)2 and (Li2O)2 nucleation on δ-MnO2 monolayer during the discharge process demonstrate that Li2O2 is the predominant discharge product and that further reduction to Li2O is inhibited by the high overpotential of 1.21 V. Interface structures have been examined to study the interaction between the Li2O2 and MnO2 layers. This study demonstrates that a Li2O2 film can be homogeneously deposited onto δ-MnO2 and that the Li2O2/MnO2 interface acts as an electrical conductor. A mesoscale model, developed based on findings from the first-principles calculations, further shows that Li2O2 is the primary product of electrochemical reactions when the applied potential is smaller than 2.4 V. PMID:27532334

  8. Gold-Palladium nanoparticles supported by mesoporous β-MnO2 air electrode for rechargeable Li-Air battery

    NASA Astrophysics Data System (ADS)

    Thapa, Arjun Kumar; Shin, Tae Ho; Ida, Shintaro; Sumanasekera, Gamini U.; Sunkara, Mahendra K.; Ishihara, Tatsumi

    2012-12-01

    The electrochemical performance and electrode reaction using Au-Pd nanoparticle (NP) supported mesoporous β-MnO2 as a cathode catalyst for rechargeable Lithium-Air (Li-Air) battery is reported here for the first time. In this study, Au-Pd NP-supported mesoporous β-MnO2 was successfully synthesized by hydrothermal process using a silica KIT-6 template. It has an initial discharge capacity of ca. 775 mAh g-1 with high reversible capacity at a current density of 0.13 mA cm-2. The Au-Pd NP-supported mesoporous β-MnO2 cathode catalyst, which enhances the kinetic of oxygen reduction and evolution reactions (ORR/OERs), thereby improves energy and coulombic efficiency of the Li-Air cell. Raman spectroscopy and ex-situ XRD results of the Au-Pd NP-supported mesoporous β-MnO2 air electrode suggest that the observed capacity comes from oxidation of Li+ to form Li2O2 during discharge to 2.0 V.

  9. A new cyclic supramolecular Zn(II) complex derived from a N2O2 oxime chelate ligand with luminescence mechanochromism.

    PubMed

    Zhang, Shou-Ting; Li, Tian-Rong; Wang, Bao-Dui; Yang, Zheng-Yin; Liu, Jian; Wang, Zhi-Yi; Dong, Wen-Kui

    2014-02-21

    A new Zn(II) complex was synthesized based on a new Salen-type tetradentate N2O2 bisoxime chelate ligand (H2L) derived from 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) and 1,2-bis(aminooxy)ethane. Single-crystal X-ray diffraction analysis reveals that the structure of the Zn(II) complex features a three-dimensional (3D) cyclic supramolecular system via intermolecular hydrogen bonds. Moreover, the solid-state photoluminescent properties demonstrate that the Zn(II) complex exhibits unusual luminescence mechanochromism tuned by CH3OH. PMID:24352216

  10. Investigation of the liquid/vapor composition of compressed liquid CO2 with N2 and O2 in integrated pollutant removal systems for coal combustion

    SciTech Connect

    Oryshchyn, Danylo B.; Ochs, Thomas L.; Summers, Cathy A.; Penner, Larry R.; Gerdemann, Stephen J.

    2005-01-01

    Accurate prediction of the processes in Integrated Pollutant Removal (IPR) using compression and condensation of coal combustion products requires an understanding of the liquid/vapor ternary CO2/O2/N2 system. At conditions close to the critical point of CO2 the existing equations of state deviate from the sparse measured results available in the literature. Building on existing data and procedures, the USDOE/Albany Research Center has designed an apparatus for examining compositions in this region. The design of the apparatus and planned initial experiments are presented.

  11. 15N2 formation and fast oxygen isotope exchange during pulsed 15N18O exposure of MnOx/CeO2

    SciTech Connect

    Kwak, Ja Hun; Szanyi, Janos

    2014-12-23

    Pulsing 15N18O onto an annealed 1% Mn16Ox/Ce16O2 catalyst resulted in very fast oxygen isotope exchange and 15N2 formation at 295 K. In the 1st 15N18O pulse, due to the presence of large number of surface oxygen defects, extensive 15N218O and 15N2 formations were observed. In subsequent pulses oxygen isotope exchange dominated as a result of highly labile oxygen in the oxide. We gratefully acknowledge the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy/Vehicle Technologies Program for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

  12. Investigation on the charging process of Li 2O 2-based air electrodes in Li-O 2 batteries with organic carbonate electrolytes

    NASA Astrophysics Data System (ADS)

    Xu, Wu; Viswanathan, Vilayanur V.; Wang, Deyu; Towne, Silas A.; Xiao, Jie; Nie, Zimin; Hu, Dehong; Zhang, Ji-Guang

    The charging process of Li 2O 2-based air electrodes in Li-O 2 batteries with organic carbonate electrolytes was investigated using in situ gas chromatography/mass spectroscopy (GC/MS) to analyze gas evolution. A mixture of Li 2O 2/Fe 3O 4/Super P carbon/polyvinylidene fluoride (PVDF) was used as the starting air electrode material, and 1-M lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) in carbonate-based solvents was used as the electrolyte. We found that Li 2O 2 was actively reactive to 1-methyl-2-pyrrolidinone and PVDF that were used to prepare the electrode. During the first charging (up to 4.6 V), O 2 was the main component in the gases released. The amount of O 2 measured by GC/MS was consistent with the amount of Li 2O 2 that decomposed during the electrochemical process as measured by the charge capacity, which is indicative of the good chargeability of Li 2O 2. However, after the cell was discharged to 2.0 V in an O 2 atmosphere and then recharged to ∼4.6 V, CO 2 was dominant in the released gases. Further analysis of the discharged air electrodes by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy indicated that lithium-containing carbonate species (lithium alkyl carbonates and/or Li 2CO 3) were the main discharge products. Therefore, compatible electrolytes and electrodes, as well as the electrode-preparation procedures, need to be developed for rechargeable Li-air batteries for long term operation.

  13. Sterilization/disinfection of medical devices using plasma: the flowing afterglow of the reduced-pressure N2-O2 discharge as the inactivating medium

    NASA Astrophysics Data System (ADS)

    Moisan, Michel; Boudam, Karim; Carignan, Denis; Kéroack, Danielle; Levif, Pierre; Barbeau, Jean; Séguin, Jacynthe; Kutasi, Kinga; Elmoualij, Benaïssa; Thellin, Olivier; Zorzi, Willy

    2013-07-01

    Potential sterilization/disinfection of medical devices (MDs) is investigated using a specific plasma process developed at the Université de Montréal over the last decade. The inactivating medium of the microorganisms is the flowing afterglow of a reduced-pressure N2-O2 discharge, which provides, as the main biocidal agent, photons over a broad ultraviolet (UV) wavelength range. The flowing afterglow is considered less damaging to MDs than the discharge itself. Working at gas pressures in the 400—700 Pa range (a few torr) ensures, through species diffusion, the uniform filling of large volume chambers with the species outflowing from the discharge, possibly allowing batch processing within them. As a rule, bacterial endospores are used as bio-indicators (BI) to validate sterilization processes. Under the present operating conditions, Bacillus atrophaeus is found to be the most resistant one and is therefore utilized as BI. The current paper reviews the main experimental results concerning the operation and characterization of this sterilizer/disinfector, updating and completing some of our previously published papers. It uses modeling results as guidelines, which are particularly useful when the corresponding experimental data are not (yet) available, hopefully leading to more insight into this plasma afterglow system. The species flowing out of the N2-O2 discharge can be divided into two groups, depending on the time elapsed after they left the discharge zone as they move toward the chamber, namely the early afterglow and the late afterglow. The early flowing afterglow from a pure N2 discharge (also called pink afterglow) is known to be comprised of N2+ and N4+ ions. In the present N2-O2 mixture discharge, NO+ ions are additionally generated, with a lifetime that extends over a longer period than that of the nitrogen molecular ions. We shall suppose that the disappearance of the NO+ ions marks the end of the early afterglow regime, thereby stressing our intent

  14. N2 and O2 pressure broadening and pressure shift in the 4ν2 band of 16O12C32S

    NASA Astrophysics Data System (ADS)

    Galalou, S.; Ben Mabrouk, K.; Aroui, H.; Kwabia Tchana, F.; Willaert, F.; Flaud, J.-M.

    2011-12-01

    To measure accurately OCS concentrations in planetary atmospheres, it is important to know precisely nitrogen and oxygen pressure broadening and pressure-induced shift coefficients for the lines used in the retrievals. We present in this study the corresponding coefficients for lines of the P and R branches of the 4ν2 band of the primary isotopologue of carbonyl sulfide (16O12C32S).For this purpose, infrared absorption spectra of a natural carbonyl sulfide (OCS) gas sample were recorded at an unapodized resolution of 0.004 cm-1, at room temperature for different pressures of N2 and O2, using a Bruker IFS125HR spectrometer at the LISA Laboratory in France. The line parameters were derived using the multispectrum fitting method applied to the measured shapes of the lines, including the interference effects caused by the line overlaps.The results are compared with earlier measurements and with values calculated using a semi-classical model based upon the Robert and Bonamy formalism that reproduces rather well the experimental m (m=-J for P(J) lines and m=J+1 for R(J) lines) quantum number dependence of the N2 and O2 broadening coefficients. On the other hand most of the lines studied here have positive shift coefficients, which do not show any systematic dependence on m. However, in previous studies of the ν3, 2ν3 and ν2 bands, these coefficients were negative for all lines.

  15. Prediction of the temperature dependence of the surface tension of SO2, N2, O2, and Ar by Monte Carlo molecular simulations.

    PubMed

    Neyt, Jean-Claude; Wender, Aurélie; Lachet, Véronique; Malfreyt, Patrice

    2011-08-01

    We report Monte Carlo simulations of the liquid-vapor interface of SO(2), O(2), N(2), and Ar to reproduce the dependence of the surface tension with the temperature. Whereas the coexisting densities, critical temperature, density, and pressure are very well reproduced by the two-phase simulations showing the same accuracy as the calculations performed using the Gibbs ensemble Monte Carlo technique (GEMC), the performance of the prediction of the variation of the surface tension with the temperature depends on the magnitude of the electrostatic and repulsive-dispersive interactions. The surface tension of SO(2) is very well reproduced, whereas the prediction of this property is less satisfactory for O(2) and N(2), for which the average intermolecular electrostatic interactions are several orders smaller than the dispersion interactions. For argon, we observe significant deviations from experiments. The representation of the surface tension of argon in reduced units shows that our calculations are in line with the existing surface tensions of the Lennard-Jones fluid in the literature. This underlines the difficulty of reproducing the temperature dependence of the surface tension of argon with interactions only modeled by the Lennard-Jones pair potential. PMID:21711018

  16. Non-equilibrium kinetics, diffusion and heat transfer in shock heated flows of N2/N and O2/O mixtures

    NASA Astrophysics Data System (ADS)

    Kunova, O.; Kustova, E.; Mekhonoshina, M.; Nagnibeda, E.

    2015-12-01

    In this paper, the influence of vibrational and dissociation kinetics on heat transfer and diffusion in non-equilibrium flows of N2/N and O2/O mixtures in the relaxation zone behind shock waves is studied on the basis of the state-to-state and one-temperature kinetic theory approaches. The results of calculations of vibrational level populations ni , gas temperature T, total energy flux q, diffusion velocities of molecules at different vibrational states Vi and atoms Va in the relaxation zone behind a shock front are presented for the free stream Mach numbers M = 18, 15, 10. The contribution of different dissipative processes to the total energy flux is evaluated for various flow conditions. Characteristic features of non-equilibrium kinetics, diffusion and energy transfer in two considered mixtures are discussed. The impact of vibrational excitation of N2 and O2 molecules in the free stream on a relaxation zone structure and transport properties behind a shock is shown.

  17. Absorption of solar radiation by O2 - Implications for O3 and lifetimes of N2O, CFCl3, and CF2Cl2

    NASA Technical Reports Server (NTRS)

    Minschwaner, K.; Salawitch, R. J.; Mcelroy, M. B.

    1993-01-01

    An accurate line-by-line model is used to evaluate effects of absorption in the Schumann-Runge bands of O2 on transmission of UV radiation. The model is used to evaluate rates of photolysis for N2O, CFCl3, and CF2Cl2, and to infer global loss rates and instantaneous lifetimes appropriate for 1980. A parameterized version of the line-by-line model enabling rapid evaluation of transmission in the Schumann-Runge region is described. Photochemical calculations employing the parameterization and constrained by data from the Atmospheric Trace Molecule Spectroscopy experiment are used to examine the budget of odd oxygen. Consistent with previous studies, it is shown that photochemical loss of odd oxygen exceeds production by photolysis of O2 for altitudes above 40 km. The imbalance between production and loss is shown to be consistent with a source of odd oxygen proportional to the product of the mixing ratio and photolysis rate of ozone, which suggests that processes involving vibrationally excited O2 may play an important role in production of odd oxygen.

  18. Absorption of solar radiation by O2 - Implications for O3 and lifetimes of N2O, CFCl3, and CF2Cl2

    NASA Astrophysics Data System (ADS)

    Minschwaner, K.; Salawitch, R. J.; McElroy, M. B.

    1993-06-01

    An accurate line-by-line model is used to evaluate effects of absorption in the Schumann-Runge bands of O2 on transmission of UV radiation. The model is used to evaluate rates of photolysis for N2O, CFCl3, and CF2Cl2, and to infer global loss rates and instantaneous lifetimes appropriate for 1980. A parameterized version of the line-by-line model enabling rapid evaluation of transmission in the Schumann-Runge region is described. Photochemical calculations employing the parameterization and constrained by data from the Atmospheric Trace Molecule Spectroscopy experiment are used to examine the budget of odd oxygen. Consistent with previous studies, it is shown that photochemical loss of odd oxygen exceeds production by photolysis of O2 for altitudes above 40 km. The imbalance between production and loss is shown to be consistent with a source of odd oxygen proportional to the product of the mixing ratio and photolysis rate of ozone, which suggests that processes involving vibrationally excited O2 may play an important role in production of odd oxygen.

  19. Investigation on the Charging Process of Li2O2-Based Air Electrodes in Li-O2 Batteries with Organic Carbonate Electrolytes

    SciTech Connect

    Xu, Wu; Viswanathan, Vilayanur V.; Wang, Deyu; Towne, Silas A.; Xiao, Jie; Nie, Zimin; Hu, Dehong; Zhang, Jiguang

    2011-04-15

    The charge processes of Li-O2 batteries were investigated by analyzing the gas evolution by in situ gas chromatography-mass spectroscopy (GC/MS) technique. The mixture of Li2O2/Fe3O4/Super P carbon/polyvinylidene fluoride (PVDF) was used as the starting air electrode material and 1M LiTFSI in carbonate-based solvents was used as electrolyte. It was found that Li2O2 is reactive to 1-methyl-2-pyrrolidinone and PVDF binder used in the electrode preparation. During the 1st charge (up to 4.6 V), O2 was the main component in the gases released. The amount of O2 measured by GC/MS was consistent with the amount of Li2O2 decomposed in the electrochemical process as measured by the charge capacity, indicative of the good chargeability of Li2O2. However, after the cell was discharged to 2.0 V in O2 atmosphere and re-charged to ~ 4.6 V in the second cycle, CO2 was dominant in the released gases. Further analysis of the discharged air electrode by X-ray diffraction and Fourier transform infrared spectroscopy indicated that lithium-containing carbonate species (lithium alkyl carbonate and/or Li2CO3) were the main reaction products. Therefore, compatible electrolyte and electrodes as well as the electrode preparation procedures need to be developed for long term operation of rechargeable Li-O2 or Li-air batteries.

  20. Pt-TiO2/MWCNTs Hybrid Composites for Monitoring Low Hydrogen Concentrations in Air

    PubMed Central

    Trocino, Stefano; Donato, Andrea; Latino, Mariangela; Donato, Nicola; Leonardi, Salvatore Gianluca; Neri, Giovanni

    2012-01-01

    Hydrogen is a valuable fuel for the next energy scenario. Unfortunately, hydrogen is highly flammable at concentrations higher than 4% in air. This aspect makes the monitoring of H2 leaks an essential issue for safety reasons, especially in the transportation field. In this paper, nanocomposites based on Pt-doped TiO2/multiwalled carbon nanotubes (MWCNTs) have been introduced as sensitive materials for H2 at low temperatures. Pt-TiO2/MWNTs nanocomposites with different composition have been prepared by a simple wet chemical procedure and their morphological, microstructural and electrical properties were investigated. Resistive thick-film devices have been fabricated printing the hybrid nanocomposites on alumina substrates provided with Pt interdigitated electrodes. Electrical tests in air have shown that embedding MWCNTs in the TiO2 matrix modify markedly the electrical conductivity, providing a means to decrease the resistance of the sensing layer. Pt acts as a catalytic additive. Pt-TiO2/MWNTs-based sensors were found to be sensitive to hydrogen at concentrations between 0.5 and 3% in air, satisfying the requisites for practical applications in hydrogen leak detection devices.

  1. Vibrational relaxation of H2O(|04> ) in collisions with H2O, Ar, H2, N2 and O2: dynamical and atmospheric implications

    NASA Astrophysics Data System (ADS)

    Barnes, P. W.; Sims, I. R.; Smith, I. W.

    2003-04-01

    It has been suggested that sequential two-photon dissociation of water might provide a mechanism for the atmospheric production of OH radical. ^1 This mechanism requires that photodissociation of vibrationally excited molecules must occur at a rate competitive with their relaxation by collisions with atmospheric gases. In this paper, we shall describe new experiments on the collisional relaxation of H_2O molecules from the highly excited mid04>± vibrational state in collisions with H_2O, Ar, H_2, N_2 and O_2. In our experiments, the mid04>^- state is populated by direct absorption of radiation from a pulsed dye laser tuned to ca. 719 nm. Evolution of the population in the (mid04>±) levels is observed using the combination of a frequency-quadrupled Nd:YAG laser, which selectively photolyses H_2O(mid04>±), and a frequency-doubled dye laser, which observes the OH(v = 0) produced via laser-induced fluorescence (LIF). The delay between the pulse from the pump laser and those from the photolysis and probe lasers was systematically varied to generate kinetic decays. The rate coefficients for relaxation obtained from these experiments, in units of cm^3 molecule-1 s-1, are: k(H_2O) = (4.1 ± 1.2) x 10-10, k(Ar) = (4.9 ± 1.1) x 10-12, k(H_2) = (6.8 ± 1.1) x 10-12, k(N_2) = (7.7 ± 1.5) x 10-12, k(O_2) = (6.7 ± 1.4) x 10-12. The results will be discussed in two contexts. First, we shall consider the implications of our new results for the interpretation of our previous experiments on the reactions of vibrationally excited H_2O with H atoms.^2 Second, we shall consider the proposal of Goss et al.1 in the light of our finding that the collisional relaxation of H_2O(mid04>±) by N_2 and O_2 is rather rapid. ^1 L. M Goss, V. Vaida, J. W. Brault and R. T. Skodje, J. Phys. Chem. A, 05, 70 (2001). ^2 (a) G. Hawthorne, P. Sharkey and I. W. M. Smith, J. Chem. Phys., 108, 4693(1998); (b) P. W. Barnes, P. Sharkey, I. R. Sims and I. W. M. Smith, Faraday Discuss. Chem. Soc., 13, 167

  2. On the impact of Vibrational Raman Scattering of N2/O2 on MAX-DOAS Measurements of atmospheric trace gases

    NASA Astrophysics Data System (ADS)

    Lampel, Johannes; Zielcke, Johannes; Frieß, Udo; Platt, Ulrich; Wagner, Thomas

    2015-04-01

    In remote sensing applications, such as the applications of differential optical absorption spectroscopy (DOAS), atmospheric scattering processes need to be considered since they can modify the observed spectra. Inelastic scattering of photons by N2 and O2 molecules can be observed as additional intensity, effectively leading to filling-in of both, solar Fraunhofer lines and absorption bands of atmospheric constituents. The main contribution is due to rotational Raman scattering, which can lead to changes in observed optical densities of absorption lines up to several percent. Measured optical densities are typically corrected for this effect (also known as Ring Effect). In contrast to that Vibrational Raman scattering of N2 and O2 was often thought to be negligible, but also contributes to this effect. We present calculations of Vibrational Raman cross-sections for O2 and N2 for the application in passive DOAS measurements. Consequences of vibrational Raman scattering are red-shifted Fraunhofer structures, so called 'Fraunhofer Ghost' lines (FGL), in scattered light spectra and filling-in of Fraunhofer lines, additional to rotational Raman scattering. We also present first unequivocal observations of FGL at optical densities of up to several 104. From our measurements and calculations of the optical density of these FGL, we conclude, that this phenomenon has to be included in the spectral evaluation of weak absorbers. Its relevance is demonstrated in spectral evaluations of Multi-Axis (MAX)-DOAS data and an agreement with calculated scattering cross-sections is found. To exclude cross-sensitivities with other absorbers, such as water vapour, MAX-DOAS data from different latitudes and different instruments were analysed. We evaluate the influence of the additional intensities due to vibrational Raman scattering on the spectral retrieval of IO, Glyoxal, H2O and NO2 in the blue wavelength range. In the case of NO2 the column densities derived from certain wavelength

  3. Excitation of N2(C3 Πu,v) and N2 +(B2 Σu +,v) vibronic levels by streamer discharge in atmospheric pressure air

    NASA Astrophysics Data System (ADS)

    Hoder, Tomas; Simek, Milan; Bonaventura, Zdenek

    2015-09-01

    Ionizing waves in air often take the form of thin filaments called streamers. Propagating streamer head is a place where the major part of reactive species is produced and that is of considerable interest for various applications, such as pollution control, ozone formation, etc. Knowledge of vibrational distributions of N2(C3 Πu,v) and N2 +(B2 Σu +,v) electronic states induced by the streamer head electrons is of particular interest, namely for determination of the self-enhanced electric field in the nitrogen/air streamer discharge. Indeed, vibrational distributions of N2(C3 Πu,v) and N2 +(B2 Σu +,v) states are very sensitive to the electric field variations occurring due to the streamer head action and might be used as a complementary spectrometric tool for monitoring streamer head parameters. In this work, a numerical study on streamer induced excitation of N2(C3 Πu,v =0-4) and N2 +(B2 Σu +,v =0-4) vibronic levels in air is presented and discussed from the point of view of improved determination of the streamer head parameters. This research has been supported by the Czech Science Foundation research project 15-04023S.

  4. Desorption Kinetics of Ar, Kr, Xe, N2, O2, CO, Methane, Ethane, and Propane from Graphene and Amorphous Solid Water Surfaces.

    PubMed

    Smith, R Scott; May, R Alan; Kay, Bruce D

    2016-03-01

    The desorption kinetics for Ar, Kr, Xe, N2, O2, CO, methane, ethane, and propane from graphene-covered Pt(111) and amorphous solid water (ASW) surfaces are investigated using temperature-programmed desorption (TPD). The TPD spectra for all of the adsorbates from graphene have well-resolved first, second, third, and multilayer desorption peaks. The alignment of the leading edges is consistent the zero-order desorption for all of the adsorbates. An Arrhenius analysis is used to obtain desorption energies and prefactors for desorption from graphene for all of the adsorbates. In contrast, the leading desorption edges for the adsorbates from ASW do not align (for coverages < 2 ML). The nonalignment of TPD leading edges suggests that there are multiple desorption binding sites on the ASW surface. Inversion analysis is used to obtain the coverage dependent desorption energies and prefactors for desorption from ASW for all of the adsorbates. PMID:26595145

  5. Sterilization of dental bacteria in a N2text{-O2} microwaves post-discharge, at low pressure: influence of temperature

    NASA Astrophysics Data System (ADS)

    Villeger, S.; Ricard, A.; Sixou, M.

    2004-06-01

    Recently, plasmas have been largely studied to develop a new cold and safe sterilization process. The plasma efficiency on bacteria destruction has been proved at low or near atmospheric pressure. In our investigation we used a N{2}-O{2} post discharge at low pressure, where the experimental conditions allowing the optimal production of active species have been determined: 100 Watt, 1 Ln.min-1, 5 Torr. By exposing E. coli to these plasma conditions, it is demonstrated a synergy of N and O active atoms on substrate temperature: a reduction of 6 log was achieved after a treatment time of 20 minutes at 80 °C and of 12 log after 5 minutes at 120 °C.

  6. Transferable force-field for modelling of CO2, N2, O2 and Ar in all silica and Na+ exchanged zeolites

    NASA Astrophysics Data System (ADS)

    Vujić, Bojan; Lyubartsev, Alexander P.

    2016-05-01

    In this work we propose a new force field for modelling of adsorption of CO2, N2, O2 and Ar in all silica and Na+ exchanged Si-Al zeolites. The force field has a standard molecular-mechanical functional form with electrostatic and Lennard-Jones interactions satisfying Lorentz-Berthelot mixing rules and thus has a potential for further extension in terms of new molecular types. The parameters for the zeolite framework atom types are optimized by an iterative procedure minimizing the difference with experimental adsorption data for a number of different zeolite structures and Si:Al ratios. The new force field shows a good agreement with available experimental data including those not used in the optimization procedure, and which also shows a reasonable transferability within different zeolite topologies. We suggest a potential usage in screening of different zeolite structures for carbon capture and storage process, and more generally, for separation of other gases.

  7. Application of a Theoretical Model of State Equation for Calculation of N2, O2, and CO2 Shock Adiabatic Curves

    NASA Astrophysics Data System (ADS)

    Bogdanova, Yu. A.; Gubin, S. A.; Victorov, S. B.; Anikeev, A. A.

    2016-06-01

    An improved version of the equation of state model for two-component fluid mixtures whose molecules interact with the Exp-6 type potential has been proposed in previous works. The thermodynamic parameters of N2, O2, and CO2 shock-wave compression are calculated using the equation of state model for two-component fluid mixtures based on perturbation theory. Products of compression of these substances are two-component mixtures. Analogous calculations are also performed using an effective one-fluid model. A comparison of the results obtained with the available experimental data and results of Monte Carlo simulation allows us to conclude that the proposed theoretical equation of state model is superior to effective one-fluid model in accuracy and reliably describes the thermodynamic properties of two-component fluid mixtures in a wide pressure and temperature ranges.

  8. Solvatochromism, spectral properties and antimicrobial activities of new azo-azomethine dyes with N2S2O2 donor set of atoms

    NASA Astrophysics Data System (ADS)

    Khanmohammadi, Hamid; Pass, Maryam; Rezaeian, Khatereh; Talei, Gholamreza

    2014-08-01

    Six new azo-azomethine dyes, H2Ln (n = 1-6), with N2S2O2 donor set of atoms have been prepared via condensation reaction of 1,10-diaza-4,7-dithiadecane, I, with substituted azo-coupled salicylaldehyde. The dyes were characterized by IR, UV-Vis and 1H NMR spectroscopic methods as well as elemental analysis. The solvatochromic behavior of the dyes was also probed by studying their UV-Vis spectra in four pure organic solvents of different polarities and a meaningful correlation was observed. Furthermore, all prepared dyes were assayed for their antibacterial and antifungal activities by disc diffusion method. The results indicated that all prepared dyes show good inhibition against Staphylococcus epidermidis and Bacillus cereus and did not show any antibacterial activity against Escherichia coli as compared to standard drugs.

  9. Parity-Dependent Rotational Energy Transfer in CN(A2Π, ν = 4, jF1ε) + N2, O2, and CO2 Collisions

    PubMed Central

    2015-01-01

    We report state-resolved total removal cross sections and state-to-state rotational energy transfer (RET) cross sections for collisions of CN(A2Π, ν = 4, jF1ε) with N2, O2, and CO2. CN(X2Σ+) was produced by 266 nm photolysis of ICN in a thermal bath (296 K) of the collider gas. A circularly polarized pulse from a dye laser prepared CN(A2Π, ν = 4) in a range of F1e rotational states, j = 2.5, 3.5, 6.5, 11.5, 13.5, and 18.5. These prepared states were monitored using the circularly polarized output of an external cavity diode laser by frequency-modulated (FM) spectroscopy on the CN(A–X)(4,2) band. The FM Doppler profiles were analyzed as a function of pump–probe delay to determine the time dependence of the population of the initially prepared states. Kinetic analysis of the resulting time dependences was used to determine total removal cross sections from the initially prepared levels. In addition, a range of j′ F1e and j′ F2f product states resulting from rotational energy transfer out of the j = 6.5 F1e initial state were probed, from which state-to-state RET cross sections were measured. The total removal cross sections lie in the order CO2 > N2 > O2, with evidence for substantial cross sections for electronic and/or reactive quenching of CN(A, ν = 4) to unobserved products with CO2 and O2. This is supported by the magnitude of the state-to-state RET cross sections, where a deficit of transferred population is apparent for CO2 and O2. A strong propensity for conservation of rotational parity in RET is observed for all three colliders. Spin–orbit-changing cross sections are approximately half of those of the respective conserving cross sections. These results are in marked disagreement with previous experimental observations with N2 as a collider but are in good agreement with quantum scattering calculations from the same study (Khachatrian et al. J. Phys. Chem. A2009, 113, 392219215110). Our results with CO2 as a collider are similarly in strong

  10. Correction of mass spectrometric isotope ratio measurements for isobaric isotopologues of O2, CO, CO2, N2O and SO2.

    PubMed

    Kaiser, Jan; Röckmann, Thomas

    2008-12-01

    Gas isotope ratio mass spectrometers usually measure ion current ratios of molecules, not atoms. Often several isotopologues contribute to an ion current at a particular mass-to-charge ratio (m/z). Therefore, corrections have to be applied to derive the desired isotope ratios. These corrections are usually formulated in terms of isotope ratios (R), but this does not reflect the practice of measuring the ion current ratios of the sample relative to those of a reference material. Correspondingly, the relative ion current ratio differences (expressed as delta values) are first converted into isotopologue ratios, then into isotope ratios and finally back into elemental delta values. Here, we present a reformulation of this data reduction procedure entirely in terms of delta values and the 'absolute' isotope ratios of the reference material. This also shows that not the absolute isotope ratios of the reference material themselves, but only product and ratio combinations of them, are required for the data reduction. These combinations can be and, for carbon and oxygen have been, measured by conventional isotope ratio mass spectrometers. The frequently implied use of absolute isotope ratios measured by specially calibrated instruments is actually unnecessary. Following related work on CO2, we here derive data reduction equations for the species O2, CO, N2O and SO2. We also suggest experiments to measure the required absolute ratio combinations for N2O, SO2 and O2. As a prelude, we summarise historic and recent measurements of absolute isotope ratios in international isotope reference materials. PMID:19016255

  11. Synthesis, spectral characterization, thermal analysis, molecular modeling and antimicrobial activity of new potentially N2O2 azo-dye Schiff base complexes

    NASA Astrophysics Data System (ADS)

    Alaghaz, Abdel-Nasser M. A.; Ammar, Yousry A.; Bayoumi, Hoda A.; Aldhlmani, Sharah A.

    2014-09-01

    The azo-dye Schiff's base of N2O2 dibasic ligand, H2L [N,N‧-bis(5-(4-sulfanilamidophenylazosalicylidene)ethylenediamine] was prepared by the condensation of ethylenediamine with [5-(4-sulfanilamidophenylazo-salicylaldehyde] in ethanol. New complexes of with metal ions Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II), Pt(IV), Fe(III) and Cr(III) are synthesized. Elemental, spectroscopic and thermal analyses as well as conductivity and magnetic susceptibility measurements are used to elucidate the structure of the newly prepared metal complexes. The azo-dye Schiff's base behaves as a di-negative N2O2 tetradentate ligand. The metal complexes exhibited square planar, tetrahedral and octahedral geometrical arrangements, the molar conductivity data indicates that all complexes are neutral. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the Cu(II), Mn(II), Cr(III) and Co(II) complexes were carried out in the range of 30-800 °C. The complexes were decomposed in one and two stages of the Cu(II), Mn(II), Cr(III) and Co(II) complexes, respectively. Also, decomposition of the synthesized complexes is related to the Schiff's base characteristics. The thermal decomposition of the studied reactions was first order. The kinetic parameters for the decomposition steps in Cu(II), Mn(II), Cr(III) and Co(II) complexes thermograms have been calculated using Broido's method. In molecular modeling the geometries of azo-dye Schiff base ligand H2L and its metal(II/III/IV) complexes were fully optimized with respect to the energy using the 6-31G basis set. Antimicrobial activities of the azo-dye Schiff's base ligand and its corresponding metal complexes were screened against various organisms. The azo-dye Schiff's base ligand and some of its complexes were found to be biologically inactive.

  12. Review of the absorption spectra of solid O2 and N2 as they relate to contamination of a cooled infrared telescope

    NASA Technical Reports Server (NTRS)

    Smith, S. M.

    1977-01-01

    During contamination studies for the liquid helium cooled shuttle infrared telescope facility, a literature search was conducted to determine the absorption spectra of the solid state of homonuclear molecules of O2 and N2, and ascertain what laboratory measurements of the solid have been made in the infrared. With the inclusion of one unpublished spectrum, the absorption spectrum of the solid oxygen molecule has been thoroughly studied from visible to millimeter wavelengths. Only two lines appear in the solid that do not also appear in the gas or liquid. A similar result is implied for the solid nitrogen molecule because it also is homonuclear. The observed infrared absorption lines result from lattice modes of the alpha phase of the solid, and disappear at the warmer temperatures of the beta, gamma, and liquid phases. They are not observed from polycrystalline forms of O2, while strong scattering is. Scattering, rather than absorption, is considered to be the principal natural contamination problem for cooled infrared telescopes in low earth orbit.

  13. Studies on DNA binding behaviour of biologically active transition metal complexes of new tetradentate N2O2 donor Schiff bases: Inhibitory activity against bacteria

    NASA Astrophysics Data System (ADS)

    Sobha, S.; Mahalakshmi, R.; Raman, N.

    A series of Cu(II), Ni(II) and Zn(II) complexes of the type ML have been synthesized with Schiff bases derived from o-acetoacetotoluidide, 2-hydroxybenzaldehyde and o-phenylenediamine/1,4-diaminobutane. The complexes are insoluble in common organic solvents but soluble in DMF and DMSO. The measured molar conductance values in DMSO indicate that the complexes are non-electrolytic in nature. All the six metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic data. The analytical data helped to elucidate the structure of the metal complexes. The Schiff bases are found to act as tetradentate ligands using N2O2 donor set of atoms leading to a square-planar geometry for the complexes around all the metal ions. The binding properties of metal complexes with DNA were investigated by absorption spectra, viscosity measurements and cyclic voltammetry. Detailed analysis reveals that the metal complexes intercalate into the DNA base stack as intercalators. All the metal complexes cleave the pUC19 DNA in presence of H2O2. The Schiff bases and their complexes have been screened for their antibacterial activity against five bacterial strains (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, Klebsiella pneumoniae) by disk diffusion method. All the metal complexes have potent biocidal activity than the free ligands.

  14. Sub-10-fs population inversion in N2+ in air lasing through multiple state coupling

    PubMed Central

    Xu, Huailiang; Lötstedt, Erik; Iwasaki, Atsushi; Yamanouchi, Kaoru

    2015-01-01

    Laser filamentation generated when intense laser pulses propagate in air has been an attractive phenomenon having a variety of potential applications such as detection and spectroscopy of gases at far distant places. It was discovered recently that the filamentation in air induces ‘lasing', showing that electronically excited N2+ is population-inverted, exhibiting marked contrast to the common understanding that molecular ions generated by intense laser fields are prepared mostly in their electronic ground states. Here, to clarify the mechanism of the population inversion, we adopt few-cycle laser pulses, and experimentally demonstrate that the lasing at 391 nm occurs instantaneously after N2+ is produced. Numerical simulations clarify that the population inversion is realized by the post-ionization couplings among the lowest three electronic states of N2+. Our results shed light on the controversy over the mechanism of the air lasing, and show that this post-ionization coupling can be a general mechanism of the atmospheric lasing. PMID:26403139

  15. Laser-induced fluorescence from N2(+) ions generated by a corona discharge in ambient air.

    PubMed

    Konthasinghe, Kumarasiri; Fitzmorris, Kristin; Peiris, Manoj; Hopkins, Adam J; Petrak, Benjamin; Killinger, Dennis K; Muller, Andreas

    2015-09-01

    In this work, we present the measurement of laser-induced fluorescence from N2(+) ions via the B(2)Σu(+)-X(2)Σg(+) band system in the near-ultraviolet. The ions were generated continuously by a plasma glow discharge in low pressure N2 and by a corona discharge in ambient air. The fluorescence decay time was found to rapidly decrease with increasing pressure leading to an extrapolated decay rate of ≍10(10) s(-1) at atmospheric pressure. In spite of this quenching, we were able to observe laser induced fluorescence in ambient air by means of a time-gated spectral measurement. In the process of comparing the emission signal with that of N2 spontaneous Raman scattering, ion concentrations in ambient air of order 10(8-)10(10) cm(-3) were determined. With moderate increases in laser power and collection efficiency, ion concentrations of less than 10(6) cm(-3) may be measurable, potentially enabling applications in atmospheric standoff detection of ionizing radiation from hazardous radioactive sources. PMID:26414524

  16. Treatment of aniline by catalytic wet air oxidation: comparative study over CuO/CeO2 and NiO/Al2O3.

    PubMed

    Ersöz, Gülin; Atalay, Süheyda

    2012-12-30

    The treatment of aniline by catalytic wet air oxidation (CWAO) was studied in a bubble reactor. The experiments were performed to investigate the effects of catalyst loading, temperature, reaction time, air flow rate, and pressure on aniline removal. The catalytic effects of the prepared nanostructured catalysts, CuO/CeO(2) (10% wt) and NiO/Al(2)O(3) (10% wt), on the CWAO treatment efficiency were also examined and compared. The prepared catalysts seem to be active having an aniline removal of 45.7% with CuO/CeO(2) and 41.9% with NiO/Al(2)O(3). The amount of N(2) formed was approximately the same for both of the catalysts. PMID:23041516

  17. Synergy effect of heat and UV photons on bacterial-spore inactivation in an N2-O2 plasma-afterglow sterilizer

    NASA Astrophysics Data System (ADS)

    Boudam, M. K.; Moisan, M.

    2010-07-01

    As a rule, medical devices (MDs) made entirely from metals and ceramics can withstand, for sterilization purposes, elevated temperatures such as those encountered in autoclaves (moist heat >=120 °C) or Poupinel (Pasteur) ovens (dry heat >=160 °C). This not the case with MDs containing polymers: 70 °C seems to be a limit beyond which their structural and functional integrity will be compromised. Nonetheless, all the so-called low-temperature sterilization techniques, relying essentially on some biocidal chemistry (e.g. ethylene oxide, H2O2, O3), are operated at temperatures close to 65 °C, essentially to enhance the chemical reactivity of the biocidal agent. Based on this fact, we have examined the influence of increasing the temperature of the polystyrene Petri dish containing B. atrophaeus bacterial spores when exposing them to UV radiation coming from an N2-O2 flowing plasma afterglow. We have observed that, for a given UV radiation intensity, the inactivation rate increases with the temperature of the Petri dish, provided heat and UV photons are applied simultaneously, a clear case of synergistic effect. More specifically, it means that (i) simply heating the spores at temperatures below 65 °C without irradiating them with UV photons does not induce mortality; (ii) there is no additional increase in the inactivation rate when the Petri has been pre-heated and then brought back to ambient temperature before the spores are UV irradiated; (iii) no additional inactivation results from post-heating spores previously inactivated with UV radiation. Undoubtedly, the synergistic effect shows up only when the physico-chemical agents (UV photons and temperature) are simultaneously in action.

  18. Feasibility of measuring temperature and density fluctuations in air using laser-induced O2 fluorescence

    NASA Technical Reports Server (NTRS)

    Massey, G. A.; Lemon, C. J.

    1984-01-01

    A tunable line-narrowed ArF laser can selectively excite several rotation al lines of the Schumann-Runge band system of O2 in air. The resulting ultraviolet fluorescence can be monitored at 90 deg to the laser beam axis, permitting space and time resolved observation of density and temperature fluctuations in turbulence. Experiments and calculations show that + or - 1 K, + or - 1 percent density, 1 cu mm spatial, and 1 microsecond temporal resolution can be achieved simultaneously under some conditions.

  19. Model of Odd N in the Terrestrial Thermosphere: 1. A First Principles Calculation of the NO2 Potential Energy Surfaces Relevant to the Production of NO via the N(2D)+O2 Reaction.

    NASA Astrophysics Data System (ADS)

    Dothe, H.; Braunstein, M.; Duff, J. W.; Sharma, R. D.

    2001-12-01

    The daytime observation of 5.3 μ m thermospheric emission from the NO fundamental vibration-rotation band by the interferometer aboard the cryogenic infrared radiance instrumentation for shuttle (CIRRIS 1A) has provided important insight into the phenomenology of NO formation. The four major mechanisms to the 5.3 μ m emission considered by previous modeling are solar pumping, inelastic collisions of O with NO(v=0), the reactions of N(2D) with O2, and the reactions of N(4S) with O2. It has previously been shown that the reaction of N(4S) with O2 is consistent with rotationally nonthermal 5.3 μ m emission, while the N(2D)+O2 reaction has been assumed to contribute to rotationally thermal emission. The assumption of a thermal rotational distribution from the N(2D)+O2 reaction cannot be confirmed by the CIRRIS 1A data. The existence of a significant fraction of nonthermal atoms in the tail of the N(2D) energy distribution function (EDF) in the daylit thermosphere was demonstrated earlier (AGU Spring 2001). Therefore the investigation of possible nonthermal behavior in NO formation via the N(2D)+O2 reaction in the daylit and aurorally dosed thermosphere requires energy dependent cross sections for the reaction between N(2D) and O2. To calculate the N(2D)+O2 cross sections, potential energy surfaces (PES) of the NO2 system are required. The output of these calculations include the energy dependent cross sections and the vibrational and rotational distribution of the nascent NO needed for accurate calculation of the cooling rates due to 5.3 μ m emission. This work concentrates on the first step towards the calculation of such cross sections, the ab initio calculations of the NO2 PES. Previous existing PES, using different basis sets and electron correlation levels, have shown disagreements in the magnitude of the barriers for the lowest lying doublet surfaces in the reaction entrance channel. Comparative results from our calculations are presented here, showing PES

  20. The role of rotational mechanisms in electron swarm parameters at low reduced electric field in N2, O2 and H2

    NASA Astrophysics Data System (ADS)

    Ridenti, M. A.; Alves, L. L.; Guerra, V.; Amorim, J.

    2015-06-01

    The homogeneous Boltzmann equation for electrons in N2, O2 and H2 is solved under the classical two-term approximation, for reduced electric fields in the interval 10  -  4  -10 Td where the electron-neutral encounters are limited to elastic, rotational and vibrational collisions. Rotational excitations/de-excitations are described using the following three different approaches: the discrete inelastic/superelastic collisional operator, written for a number of rotational levels that depends on the molecular gas and the specific rotational cross sections considered the continuous approximation for rotations; a modified version of the continuous approximation for rotations, including a Chapman-Cowling corrective term proportional to the gas temperature. The expression of the rotational collision operator for this latter approach is deduced here and the results show that it bridges the gap between the discrete and the continuous descriptions at low/intermediate reduced electric fields. The calculations are compared with the measurements for the available swarm parameters to assess the validity of the different approaches and cross sections adopted to describe the rotational mechanisms.

  1. Synthesis and spectroscopic studies of binuclear metal complexes of a tetradentate N 2O 2 Schiff base ligand derived from 4,6-diacetylresorcinol and benzylamine

    NASA Astrophysics Data System (ADS)

    Shebl, Magdy

    2008-09-01

    A tetradentate N 2O 2 donor Schiff base ligand, H 2L, was synthesized by the condensation of 4,6-diacetylresorcinol with benzylamine. The structure of the ligand was elucidated by elemental analyses, IR, 1H NMR, electronic and mass spectra. Reaction of the Schiff base ligand with nickel(II), cobalt(II), iron(III), cerium(III), vanadyl(IV) and uranyl(VI) ions in 1:2 molar ratio afforded binuclear metal complexes. Also, reaction of the ligand with several copper(II) salts, including Cl -, NO 3-, AcO -, ClO 4- and SO 42- afforded different metal complexes that reflect the non-coordinating or weakly coordinating power of the ClO 4- anion as compared to the strongly coordinating power of SO 42- and Cl - anions. Characterization and structure elucidation of the prepared complexes were achieved by elemental and thermal analyses, IR, 1H NMR, electronic, mass and ESR spectra as well as magnetic susceptibility measurements. The metal complexes exhibited different geometrical arrangements such as square planar, octahedral, square pyramidal and pentagonal bipyramidal arrangements. The variety in the geometrical arrangements depends on the nature of both the anion and the metal ion.

  2. Saturated fluorescence measurements of the hydroxyl radical in laminar high-pressure C2H6/O2/N2 flames

    NASA Technical Reports Server (NTRS)

    Carter, Campbell D.; King, Galen B.; Laurendeau, Normand M.

    1992-01-01

    Saturation of a transition of the OH molecule in high-pressure flames is demonstrated by obtaining saturation curves in C2H6/O2/N2 laminar flames at 1, 6.1, 9.2, and 12.3 atm. Quantitative fluorescence measurements of OH number density at pressures to 12.3 atm are presented. To assess the efficacy of the balanced cross-rate model for high-pressure flames, laser-saturated fluorescence measurements, which were calibrated in an atmospheric-pressure flame, are compared with absorption measurements at 3.1 and 6.1 atm. At 3.1 atm the absorption and fluorescence measurements compare well. At 6.1 atm, however, the concentrations given by lasre-saturated fluorescence are about 25 percent lower than the absorption values, indicating some depletion of the laser-coupled levels beyond that at atmospheric pressure. By using a reasonable estimate for the finite sensitivity to quenching, it is anticipated that fluorescence measurements that are calibrated at 1 atm can be applied to flames at about 10 atm with absolute errors within +/- 50 percent.

  3. ACTIVE MEDIA: Gain dynamics in a pulsed laser amplifier on CO-He, CO-N2 and CO-O2 gas mixtures

    NASA Astrophysics Data System (ADS)

    Vetoshkin, S. V.; Ionin, Andrei A.; Klimachev, Yu M.; Kozlov, A. Yu; Kotkov, A. A.; Rulev, O. A.; Seleznev, L. V.; Sinitsyn, D. V.

    2007-02-01

    Small-signal gain (SSG) dynamics G(t) in the active medium of a pulsed laser amplifier operating on the v+1→vP(J) vibrational-rotational transitions of the CO molecule, including high (v > 15) vibrational transitions, is studied experimentally. It is demonstrated that as the vibrational number increases from 7 to 31, G changes with time slower, while Gmax decreases in this case by three times. It is found that at a fixed value of v the rate of the SSG rise increases with increasing the rotational number J > 6. It is shown that in oxygen-containing gas mixtures (CO:O2 = 1:19) the value of Gmax at low vibrational levels (for v < 13) can substantially exceed Gmax in mixtures containing nitrogen (CO:N2 = 1:19) instead of oxygen. It is found that the efficiency (47%) of a CO laser on mixtures with a high concentration of oxygen considerably exceeds the efficiency (30%) of a CO laser operating on a nitrogen-containing mixture.

  4. Bio-relevant complexes of novel N2O2 type heterocyclic ligand: Synthesis, structural elucidation, biological evaluation and docking studies.

    PubMed

    Arun, T; Packianathan, S; Malarvizhi, M; Antony, R; Raman, N

    2015-08-01

    Organic and inorganic entities [Cu(II), Co(II), Ni(II) and Zn(II)] have been bridged by N2O2 type heterocyclic imine (CN) ligand for the synthesis of novel organic-inorganic bridged complexes of the type [M(H2L)]. The synthesized complexes were characterized by spectral techniques such as FT-IR, UV-visible, (1)H NMR, (13)C NMR, EPR, ESI-Mass, elemental analysis, magnetic susceptibility and molar conductivity measurements. The metal complexes adopt square planar geometrical arrangement around the metal ions. DNA binding ability of these complexes has been explored by different techniques viz. electronic absorption, fluorescence, cyclic voltammetry, differential pulse voltammetry and viscosity measurements. These studies prove that CT DNA interaction of the complexes follows intercalation mode. The oxidative cleavage of the complexes with pUC19 DNA has been investigated by gel electrophoresis. Molecular docking calculations have been performed to understand the nature of binding of the complexes with DNA. Moreover, the anti-pathogenic actions of the complexes were tested in vitro against few bacteria and fungi by disk diffusion method. The data reveal that the complexes have higher anti-pathogenic activity than the ligand. PMID:26057019

  5. Effects of O 2 and N 2/H 2 plasma treatments on the neuronal cell growth on single-walled carbon nanotube paper scaffolds

    NASA Astrophysics Data System (ADS)

    Yoon, Ok Ja; Lee, Hyun Jung; Jang, Yeong Mi; Kim, Hyun Woo; Lee, Won Bok; Kim, Sung Su; Lee, Nae-Eung

    2011-08-01

    The O 2 and N 2/H 2 plasma treatments of single-walled carbon nanotube (SWCNT) papers as scaffolds for enhanced neuronal cell growth were conducted to functionalize their surfaces with different functional groups and to roughen their surfaces. To evaluate the effects of the surface roughness and functionalization modifications of the SWCNT papers, we investigated the neuronal morphology, mitochondrial membrane potential, and acetylcholine/acetylcholinesterase levels of human neuroblastoma during SH-SY5Y cell growth on the treated SWCNT papers. Our results demonstrated that the plasma-chemical functionalization caused changes in the surface charge states with functional groups with negative and positive charges and then the increased surface roughness enhanced neuronal cell adhesion, mitochondrial membrane potential, and the level of neurotransmitter in vitro. The cell adhesion and mitochondrial membrane potential on the negatively charged SWCNT papers were improved more than on the positively charged SWCNT papers. Also, measurements of the neurotransmitter level showed an enhanced acetylcholine level on the negatively charged SWCNT papers compared to the positively charged SWCNT papers.

  6. Ru(II) complexes of N 4 and N 2O 2 macrocyclic Schiff base ligands: Their antibacterial and antifungal studies

    NASA Astrophysics Data System (ADS)

    Shanker, Kanne; Rohini, Rondla; Ravinder, Vadde; Reddy, P. Muralidhar; Ho, Yen-Peng

    2009-07-01

    Reactions of [RuCl 2(DMSO) 4] with some of the biologically active macrocyclic Schiff base ligands containing N 4 and N 2O 2 donor group yielded a number of stable complexes, effecting complete displacement of DMSO groups from the complex. The interaction of tetradentate ligand with [RuCl 2(DMSO) 4] gave neutral complexes of the type [RuCl 2(L)] [where L = tetradentate macrocyclic ligand]. These complexes were characterized by elemental, IR, 1H, 13C NMR, mass, electronic, thermal, molar conductance and magnetic susceptibility measurements. An octahedral geometry has been proposed for all complexes. All the macrocycles and macrocyclic Ru(II) complexes along with existing antibacterial drugs were screened for antibacterial activity against Gram +ve ( Bacillus subtilis, Staphylococcus aureus) and Gram -ve ( Escherichia coli, Klebsiella pneumonia) bacteria. All these compounds were found to be more active when compared to streptomycin and ampicillin. The representative macrocyclic Schiff bases and their complexes were also tested in vitro to evaluate their activity against fungi, namely, Aspergillus flavus and Fusarium species.

  7. Low Temperature Heat Capacities and Standard Molar Enthalpy of Formation of 2-Pyrazinecarboxylic Acid (C5H4N2O2)(s).

    PubMed

    Kong, Yu-Xia; Di, You-Ying; Yang, Wei-Wei; Gao, Sheng-Li; Tan, Zhi-Cheng

    2010-06-01

    Low-temperature heat capacities of 2-pyrazinecarboxylic acid (C5H4N2O2)(s) were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. A polynomial equation of heat capacities as a function of temperature was fitted by least squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at 10 K intervals. The constant-volume energy of combustion of the compound at T = 298.15 K was measured by a precision rotating-bomb combustion calorimeter to be ΔcU = -(17839.40 ± 7.40) J g-1. The standard molar enthalpy of combustion of the compound was determined to be ΔcH0m = -(2211.39 ± 0.92) KJ mol-1, according to the definition of combustion enthalpy. Finally, the standard molar enthalpy of formation of the compound was calculated to be ΔfH0m = -(327.82 ± 1.13) kJ mol-1 in accordance with Hess law. PMID:24061733

  8. The advantage of spectrophotometric measurement for size-selective complexing of Cu(II) with O2N2-azacrown ligands

    NASA Astrophysics Data System (ADS)

    Ghanbari, Bahram; Gholamnezhad, Parisa

    2015-03-01

    A comparative investigation of the interaction of Cu(II) with a series of 15- to 19-membered mixed-donor dibenzo-substituted macrocyclic ligands, each incorporating an O2N2-donor set, has been carried out using UV-Visible studies in methanol. Although a ring size effect has been reported for a related series of Ni(II) complexes, no such metal ion discrimination has been reported for Cu(II) in terms of its binding constants with 14- to 17-membered macrocycles. Employing Job's method of continuous variation established 1:1 stoichiometry for the interaction between Cu(II) and 1-5. From UV-Visible studies applying the Benesi-Hildebrand equation, the binding constants (K) of Cu(II) with 1-5 were determined to be Cu(II)/1 = 3330 (±321) dm3 mol-1, Cu(II)/2 = 33,700 (±71) dm3 mol-1, Cu(II)/3 = 7260 (±151) dm3 mol-1, Cu(II)/4 = 57,000 (±257) dm3 mol-1 and Cu(II)/5 = 13,900 (±398) dm3 mol-1 in methanol at 25 °C, respectively. The calculated binding constants showed a saw-tooth pattern in which 4 (18-membered ring) gives the highest K value for these complexes. The thermodynamic parameters (ΔG, ΔH, and TΔS) of the respective complexes have also been determined.

  9. Computer program of data reduction procedures for facilities using CO2-N2-O2-Ar equilibrium real-gas mixtures

    NASA Technical Reports Server (NTRS)

    Miller, C. G., III

    1972-01-01

    Data reduction procedures for determining free-stream and post-normal-shock flow conditions are presented. These procedures are applicable to flows of CO2, N2, O2, Ar, or mixtures of these gases and include the effects of dissociation and ionization. The assumption of thermochemical equilibrium free-stream and post-normal-shock flow is made. Although derived primarily to meet the immediate needs of an expansion tube of a hot gas radiation research facility, these procedures are applicable to any supersonic or hypersonic test facility using these gases or mixtures thereof. The data reduction procedures are based on combinations of three of the following flow parameters measured in the immediate vicinity of the test section: (1) stagnation pressure behind normal shock, (2) free-stream static pressure, (3) stagnation-point heat-transfer rate, (4) free-stream velocity, and (5) free-stream density. Thus, these procedures do not depend explicitly upon measured or calculated upstream flow parameters. The procedures are incorporated into a single computer program written in FORTRAN IV language. A listing of this computer program is presented, along with a description of the inputs required and a sample of the data printout.

  10. Modeling disequilibrium in gas ensembles: How quantum state populations evolve under multicollision conditions; CO*+Ar, CO, O2, and N2

    NASA Astrophysics Data System (ADS)

    McCaffery, Anthony J.; Marsh, Richard J.

    2010-02-01

    The method of Marsh and McCaffery [J. Chem. Phys. 117, 503 (2002)] is used to quantify how rovibrational populations and mode temperatures change as an ensemble of CO molecules, initially excited to (v;j)=(8;12), evolves to thermal equilibrium in a bath gas. The bath gases considered are Ar, N2, O2, and CO all at 300 K with the diatomics in their (0;8) rovibrational states. Ensembles generally contain 1000 molecules, 10% of which are excited CO (CO∗) molecules. State (v;j) populations and mode temperatures of CO∗ and bath molecules are calculated for successive collisions to 1000 or more. We find that relaxation to local thermodynamic equilibrium occurs in distinct phases that vary widely in rate of cooling. There is especially fast vibration-vibration (VV) exchange in CO∗-CO mixtures that is largely decoupled from rotation and translation. Several aspects of ensemble behavior may be rationalized using concepts established in quantum state resolved single collision studies. We demonstrate the existence of a simultaneous energy quasiresonant, angular momentum conserving, low Δj VV process that can cause either ultrafast relaxation or up pumping of the kind seen in a number of experiments.

  11. In situ and air index measurements: influence of the deposition parameters on the shift of TiO2/SiO2 Fabry-Perot filters.

    PubMed

    Schmitt, B; Borgogno, J P; Albrand, G; Pelletier, E

    1986-11-01

    We measure the refractive index of thin films of TiO2 and SiO2 for given deposition parameters. Two complementary methods are used. The first is a postdeposition technique which uses the measurements of reflectance and transmittance in air. The second, in contrast, makes use of in situ measurements (under vacuum and during the actual deposition of the layer). The differences between the values deduced from the two methods can be explained by the amount of atmospheric moisture adsorbed by films. One tries to minimize these shifts for the two materials by choosing deposition parameters. The difficulties come from the absorption losses which must be as small as possible. We use the measured refractive indices of individual layers to give good numerical prediction of the wavelength shift (observed during the admittance of air after deposition in the vacuum chamber) of the transmittance peak of multidielectric Fabry-Perot filters. PMID:18235719

  12. The 2140 cm(exp -1) (4.673 Microns) Solid CO Band: The Case for Interstellar O2 and N2 and the Photochemistry of Non-Polar Interstellar Ice Analogs

    NASA Technical Reports Server (NTRS)

    Elsila, Jamie; Allamandola, Louis J.; Sandford, Scott A.; Witteborn, Fred C. (Technical Monitor)

    1996-01-01

    The infrared spectra of CO frozen in non-polar ices containing N2, CO2, O2, and H2O, and the ultraviolet photochemistry of these interstellar/precometary ice analogs are reported. The spectra are used to test the hypothesis that the narrow 2140/cm (4.673 micrometer) interstellar absorption feature attributed to solid CO might be produced by CO frozen in ices containing non-polar species such as N2 and O2. It is shown that mixed molecular ices containing CO, N2, O2, and CO2 provide a very good match to the interstellar band at all temperatures between 12 and 30 K both before and after photolysis. The optical constants (real and imaginary parts of the index of refraction) in the region of the solid CO feature are reported for several of these ices.

  13. Air-suspended TiO2-based HCG reflectors for visible spectral range

    NASA Astrophysics Data System (ADS)

    Hashemi, Ehsan; Bengtsson, Jörgen; Gustavsson, Johan; Carlsson, Stefan; Rossbach, Georg; Haglund, Åsa

    2015-02-01

    For GaN-based microcavity light emitters, such as vertical-cavity surface-emitting lasers (VCSELs) and resonant cavity light emitting diodes (RCLEDs) in the blue-green wavelength regime, achieving a high reflectivity wide bandwidth feedback mirror is truly challenging. The material properties of the III-nitride alloys are hardly compatible with the conventional distributed Bragg reflectors (DBRs) and the newly proposed high-contrast gratings (HCGs). Alternatively, at least for the top outcoupling mirror, dielectric materials offer more suitable material combinations not only for the DBRs but also for the HCGs. HCGs may offer advantages such as transverse mode and polarization control, a broader reflectivity spectrum than epitaxially grown DBRs, and the possibility to set the resonance wavelength after epitaxial growth by the grating parameters. In this work we have realized an air-suspended TiO2 grating with the help of a SiO2 sacrificial layer. The deposition processes for the dielectric layers were fine-tuned to minimize the residual stress. To achieve an accurate control of the grating duty cycle, a newly developed lift-off process, using hydrogen silesquioxan (HSQ) and sacrificial polymethyl-methacrylate (PMMA) resists, was applied to deposit the hard mask, providing sub-10 nm resolution. The finally obtained TiO2/air HCGs were characterized in a micro-reflectance measurement setup. A peak power reflectivity in excess of 95% was achieved for TM polarization at the center wavelength of 435 nm, with a reflectivity stopband width of about 80 nm (FWHM). The measured HCG reflectance spectra were compared to corresponding simulations obtained from rigorous coupled-wave analysis and very good agreement was found.

  14. Morphological and crystalline evolution of nanostructured MnO2 and its application in lithium--air batteries.

    PubMed

    Truong, Tu T; Liu, Yuzi; Ren, Yang; Trahey, Lynn; Sun, Yugang

    2012-09-25

    Single-crystal α-MnO(2) nanotubes have been successfully synthesized by microwave-assisted hydrothermal of potassium permanganate in the presence of hydrochloric acid. The growth mechanism including the morphological and crystalline evolution has been carefully studied with time-dependent X-ray diffraction, electron microscopy, and controlled synthesis. The as-synthesized MnO(2) nanostructures are incorporated in air cathodes of lithium--air batteries as electrocatalysts for the oxygen reduction and evolution reactions. The characterization reveals that the electrodes made of single-crystalline α-MnO(2) nanotubes exhibit much better stability than those made of α-MnO(2) nanowires and δ-MnO(2) nanosheet-based microflowers in both charge and discharge processes. PMID:22866870

  15. Evaluation of clay-TiO2 nanocomposite efficiency on the photocatalytic elimination of a model hydrophobic air pollutant.

    NASA Astrophysics Data System (ADS)

    Cervini-Silva, J.; Kibanova, D.; Destaillats, H.

    2008-12-01

    Clay-supported TiO2 photocatalysts can potentially improve the performance of air treatment technologies due to enhanced adsorption and reactivity of volatile organic compounds (VOCs). In this study, a bench-top photocatalytic flow reactor was used to evaluate hectorite-TiO2 and kaolinite-TiO2, two novel composite materials synthesized in our laboratory. Toluene, a model hydrophobic VOC and a common indoor air pollutant, was introduced in the air stream at realistic concentrations and reacted under UVA (?max = 365 nm) or UVC (?max = 254 nm) irradiation. The UVC lamp presented secondary emission at 185 nm, leading to the formation of ozone and other short-lived reactive species. Performance of clay-TiO2 composites was compared with that of pure TiO2 (Degussa P25) and with UV irradiation in the absence of photocatalyst under identical conditions. Films of clay-TiO2 composites and of P25 were prepared by a dip- coating method on the surface of Raschig rings placed inside the flow reactor. An upstream toluene concentration of 150 ppbv was generated by diluting a constant vapor flow with dry air, or with humid air at 10, 33, and 66 % relative humidity (RH). Toluene concentrations downstream were determined by collecting Tenax-TA ® sorbent tubes and subsequent thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) analysis. The fraction of toluene removed, %R, and the reaction rate, Tr, were calculated for each experimental condition from the concentration changes registered with and without UV irradiation. Use of UVC light (UV/TiO2/O3) led to overall higher reactivity, which can be partially attributed to contribution of gas phase reactions by O3 and other short-lived species. When the reaction rate was normalized by the light irradiance, Tr/Iλ, the UV/TiO2 reaction under UVA irradiation was more efficient for samples with a higher content of TiO2 (P25 and Hecto-TiO2), but not for Kao-TiO2. Considering the effect of relative humidity, in all cases reaction

  16. Synthesis and spectroscopic characterization of some transition metal complexes of a new hexadentate N 2S 2O 2 Schiff base ligand

    NASA Astrophysics Data System (ADS)

    Sarkar, Saikat; Dey, Kamalendu

    2005-11-01

    A novel interesting hexadentate dibasic N 2S 2O 2 donor Schiff base ligand, H4dcsalpte, was synthesized by the condensation of 3-formylsalicylic acid and 1,2-di( o-aminophenylthio)ethane and characterized. The reactions of the ligand with different metal(II/III)salts under varied reaction conditions afforded a series of metal complexes. The ligand, H4dcsalpte, behaves either as a dibasic or neutral hexadentate one, depending on the reaction conditions. Structural investigations on the ligand and their complexes have been made based on elemental analyses, molar conductance values, magnetic moment values, cryomagnetic and spectral (UV-vis, IR, 1H NMR, and Mössbauer) data. Based on magnetic susceptibility, Mössbauer and electronic spectral data the iron(III) complex [Fe III( H2dcsalpte)]ClO 4 ( 8), isolated in the present investigation, it is inferred that the spin states 5/2 and 1/2 are in equilibrium. Similarly a tri-iron(III) complex [Fe III3( H2dcsalpte)( H3dcsalpte)Cl 3]Cl 3 ( 7), isolated in this study, has been inferred to contain two iron(III) sites in tetrahedral environment and one in the octahedral environment. The aerial oxidation of an equimolar mixture of H4dcsalpte and Co(CH 3COO) 2·4H 2O in ethanol under reflux gave two products, [Co( H2dcsalpte)]CH 3COO ( 10) and [( Hbtcsaldm)Co( Hbvcsaldm)] ( 11), a cobalt(III) complex bound to two dissimilar tridentate NSO donor ligands formed as a result of the oxidative cleavage of the C sbnd S bond. In the complex 11, Hbtcsaldm stands for the dianion of the tridentate Schiff base ligand N-(2'-benzenethiol)-3-carboxysalicylaldimine and Hbvcsaldm stands for the mono anion of the tridentate Schiff base ligand N-(benzene-2'-S-vinyl)-3-carboxysalicylaldimine, both being formed as a result of the oxidative cleavage of H4dcsalpte.

  17. Vehicle emissions of greenhouse gases and related tracers from a tunnel study: CO : CO2, N2O : CO2, CH4 : CO2, O2 : CO2 ratios, and the stable isotopes 13C and 18O in CO2 and CO

    NASA Astrophysics Data System (ADS)

    Popa, M. E.; Vollmer, M. K.; Jordan, A.; Brand, W. A.; Pathirana, S. L.; Rothe, M.; Röckmann, T.

    2014-02-01

    Measurements of CO2, CO, N2O and CH4 mole fractions, O2 / N2 ratios and the stable isotopes 13C and 18O in CO2 and CO have been performed in air samples from the Islisberg highway tunnel (Switzerland). The molar CO : CO2 ratios, with an average of (4.15 ± 0.34) ppb:ppm, are lower than reported in previous studies, pointing to a reduction in CO emissions from traffic. The 13C in CO2 reflects the isotopic composition of the fuel. 18O in CO2 is slightly depleted compared to the 18O in atmospheric O2, and shows significant variability. In contrast, the δ13C values of CO show that significant fractionation takes place during CO destruction in the catalytic converter. 13C in CO is enriched by 3‰ compared to the 13C in the fuel burnt, while the 18O content is similar to that of atmospheric O2. We compute a fractionation constant of (-2.7 ± 0.7)‰ for 13C during CO destruction. The N2O : CO2 average ratio of (1.8 ± 0.2) × 10-2 ppb:ppm is significantly lower than in past studies, showing a reduction in N2O emissions likely related to improvements in the catalytic converter technology. We also observed small CH4 emissions, with an average CH4 : CO2 ratio of (4.6 ± 0.2) × 10-2 ppb:ppm. The O2 : CO2 ratios of (-1.47 ± 0.01) ppm:ppm are very close to the expected, theoretically calculated values of O2 depletion per CO2 enhancement.

  18. Functionalization of graphene by atmospheric pressure plasma jet in air or H2O2 environments

    NASA Astrophysics Data System (ADS)

    Huang, Weixin; Ptasinska, Sylwia

    2016-03-01

    The functionalization of graphene, which deforms its band structure, can result in a metal-semiconductor transition. In this work, we report a facile strategy to oxidize single-layer graphene using an atmospheric pressure plasma jet (APPJ) that generates a variety of reactive plasma species at close to ambient temperature. We systematically characterized the oxygen content and chemical structure of the graphene films after plasma treatment under different oxidative conditions (ambient air atmosphere or hydrogen peroxide solution) by X-ray Photoelectron Spectroscopy (XPS). Plasma-treated graphene films containing more than 40% oxygen were obtained in both oxidative environments. Interestingly, prolonged irradiation led to the reduction of graphene oxides. N-doping of graphene also occurred during the APPJ treatment in H2O2 solution; the nitrogen content of the doped graphene was dependent on the duration of irradiation and reached up to 8.1% within 40 min. Moreover, the H2O2 solution served as a buffer layer that prevented damage to the graphene during plasma irradiation. Four-point probe measurement revealed an increase in sheet resistance of the plasma-treated graphene, indicating the transition of the material property from semi-metallic to semiconducting.

  19. Characterization of the flowing afterglows of an N2 O2 reduced-pressure discharge: setting the operating conditions to achieve a dominant late afterglow and correlating the NOβ UV intensity variation with the N and O atom densities

    NASA Astrophysics Data System (ADS)

    Boudam, M. K.; Saoudi, B.; Moisan, M.; Ricard, A.

    2007-03-01

    The flowing afterglow of an N2-O2 discharge in the 0.6-10 Torr range is examined in the perspective of achieving sterilization of medical devices (MDs) under conditions ensuring maximum UV intensity with minimum damage to polymer-based MDs. The early afterglow is shown to be responsible for creating strong erosion damage, requiring that the sterilizer be operated in a dominant late-afterglow mode. These two types of afterglow can be characterized by optical emission spectroscopy: the early afterglow is distinguished by an intense emission from the N_{2}^{+} 1st negative system (band head at 391.4 nm) while the late afterglow yields an overpopulation of the v' = 11 ro-vibrational level of the N2(B) state, indicating a reduced contribution from the early afterglow N2 metastable species. We have studied the influence of operating conditions (pressure, O2 content in the N2-O2 mixture, distance of the discharge from the entrance to the afterglow (sterilizer) chamber) in order to achieve a dominant late afterglow that also ensures maximum and almost uniform UV intensity in the sterilization chamber. As far as operating conditions are concerned, moving the plasma source sufficiently far from the chamber entrance is shown to be a practical means for significantly reducing the density of the characteristic species of the early afterglow. Using the NO titration method, we obtain the (absolute) densities of N and O atoms in the afterglow at the NO injection inlet, a few cm before the chamber entrance: the N atom density goes through a maximum at approximately 0.3-0.5% O2 and then decreases, while the O atom density increases regularly with the O2 percentage. The spatial variation of the N atom (relative) density in the chamber is obtained by recording the emission intensity from the 1st positive system at 580 nm: in the 2-5 Torr range, this density is quite uniform everywhere in the chamber. The (relative) densities of N and O atoms in the discharge are determined by using

  20. Synthesis, spectroscopic characterization, thermal studies, catalytic epoxidation and biological activity of chromium and molybdenum hexacarbonyl bound to a novel N 2O 2 Schiff base

    NASA Astrophysics Data System (ADS)

    Abdel Aziz, Ayman A.

    2010-08-01

    Complexes of M(CO) 6 (M = Cr and Mo) with novel Schiff base N,N'-bis(salicylidene)4,5-dichloro-1,2-phenylenediamine (H 2L) were prepared in benzene in two different conditions: (i) under reduced pressure resulting the dicarbonyl precursors [Cr(CO) 2(H 2L)] and [Mo(CO) 2(L)] and (ii) in air resulting the oxo complex [Cr(O)(L)] and the dioxo complex [Mo(O) 2(L)]. The complexes were characterized by elemental analysis, IR, 1H NMR, mass spectrometry, and magnetic measurement. Thermal behaviors of the complexes were also studied by using thermogravimetric analysis (TGA). The catalytic activity of the novel complexes in the epoxidation of cyclooctene, cyclohexene, 1-octene and 1-hexene with tert-butyl-hydroperoxide (TBHP) in methylene chloride was investigated. The antimicrobial activities of the ligand and their complexes have been screened against various strains of bacteria and fungi and the results have been compared with some known antibiotics.

  1. A new Raman-N2 lidar dedicated to air quality survey

    NASA Astrophysics Data System (ADS)

    Royer, P.; Chazette, P.; Lardier, M.; Raut, J.-C.; Sauvage, L.

    2010-05-01

    The Commissariat à l'Energie Atomique (CEA) and the Centre National de la Recherche Scientifique (CNRS) have developed the Lidar Aérosols UltraViolet Aéroporté (LAUVA). The new version of this prototype is now commercialized with success under license by the LEOSPHERE Company with the name EZ LIDAR®. This eye-safe lidar is based on a Nd:YAG laser giving pulses of 16 mJ at 355 nm with a frequency of 20 Hz. The CEA and LEOSPHERE have recently upgraded this instrument into a three detection channels lidar measuring the two elastic cross-polarizations and the Raman-N2 backscatter signal at 387 nm. It is able to retrieve aerosol optical properties (extinction, backscatter coefficients and depolarization ratio) and atmospheric structures (boundary layer height and clouds) with a resolution of 1.5 m along the line-of-sight in analog mode and 15 m in photon-counting mode. This new lidar is particularly well-adapted to air quality survey thanks to a full overlap reached at ~150 m. This compact (90x50x20 cm) and light (less than50 kg) instrument has been integrated into the Mobile Aerosol Station (MAS) onboard a small truck and enables mobile measurements. We will here present and analyze some results obtained around Paris area with this Raman-N2 lidar.

  2. Comparison of CO2 and O2 concentrations in soil air: A lesson learned about CO2 diffusivity in soils

    NASA Astrophysics Data System (ADS)

    Angert, A.; Davidson, E. A.; Savage, K.; Yakir, D.; Luz, B.

    2002-12-01

    Soil respiration is a major component of the global carbon and oxygen cycles and accounts for about one quarter of global respiration. Since respiration consumes O2 and emits CO2, a simple relationship may be expected between the concentration of these gases in soil-air. However, because the [O2] signal in well-drained soils is small, deriving this relationship from field observations is not trivial. In this study, we present high accuracy measurements of O2 concentrations in soil air, that for the first time, enable precise comparison of these concentrations with CO2 concentrations. Soil air was sampled in two sites: an orchard in Israel, and a temperate forest (Harvard forest). The expected ratio of the decrease in [O2] in soil air to the increase in [CO2] can be calculated from the ratio of O2 consumption to CO2 emission in respiration, and the ratio between the diffusivities of these two gases in air as 0.79-0.07. The measured ratio of the decrease in [O2] to the increase in [CO2] in soil air was 0.56-2.48 in the orchard site and 1.06-1.20 in Harvard Forest. These ratios deviate strongly from the expected relationship. In the orchard site, these deviations were probably caused by reactions in the carbonate system due to the calcareous soil of this site. At Harvard Forest, such reactions cannot be quantitatively important because of the low pH of the soil. In this site, we propose that the relationship between CO2 and O2 in the soil air indicates that the ratio of diffusivity of O2 and CO2 in soils is higher than the diffusivity ratio in air. Our results demonstrate that a combination of high accuracy measurements of the O2 and CO2 in soil air is important for better understanding of the soil CO2 dynamics. Such observations will improve estimates of soil respiration that are based only on CO2 concentration and diffusivity.

  3. Feasibility of silver doped TiO2/glass fiber photocatalyst under visible irradiation as an indoor air germicide.

    PubMed

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2014-03-01

    This study investigated the feasibility of using Ag-TiO2 photocatalyst supported on glass fiber (Ag-TiO2/GF) prepared by a sol-gel method as an indoor air germicide. An experimental model was designed to investigate the bacterial disinfection efficiency of Staphylococcus (Staph), the most popular bacterium in hospitals in Korea, by the Ag-TiO2/GF photocatalyst. The silver content in Ag/TiO2 was altered from 1 to 10% to investigate the optimal ratio of Ag doped on TiO2/glass fiber (TiO2/GF) for photocatalytic disinfection of Staph. This study confirmed that Ag in Ag-TiO2/GF could work as an electron sink or donor to increase photocatalytic activity and promote the charge separation of electron-hole pairs generated from TiO2 after photon absorption. Ag also acts as an intermediate agent for the transfer of photo-generated electrons from the valence band of TiO2 to an acceptor (O2 gas) to promote photo-oxidation processes. The photocatalytic disinfection activity of Ag-TiO2/GF under visible light increased with the increase in silver content up to 7.5% and then slightly decreased with further increasing silver content. The highest disinfection efficiency and disinfection capacity of Staph using 7.5% Ag-TiO2/GF were 75.23% and 20 (CFU∙s-1∙cm-2) respectively. The medium level of humidity of 60% ± 5% showed better photocatalytic disinfection than the lower (40% ± 5%) or higher (80% ± 5%) levels. PMID:24658408

  4. Feasibility of Silver Doped TiO2/Glass Fiber Photocatalyst under Visible Irradiation as an Indoor Air Germicide

    PubMed Central

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2014-01-01

    This study investigated the feasibility of using Ag-TiO2 photocatalyst supported on glass fiber (Ag-TiO2/GF) prepared by a sol-gel method as an indoor air germicide. An experimental model was designed to investigate the bacterial disinfection efficiency of Staphylococcus (Staph), the most popular bacterium in hospitals in Korea, by the Ag-TiO2/GF photocatalyst. The silver content in Ag/TiO2 was altered from 1 to 10% to investigate the optimal ratio of Ag doped on TiO2/glass fiber (TiO2/GF) for photocatalytic disinfection of Staph. This study confirmed that Ag in Ag-TiO2/GF could work as an electron sink or donor to increase photocatalytic activity and promote the charge separation of electron-hole pairs generated from TiO2 after photon absorption. Ag also acts as an intermediate agent for the transfer of photo-generated electrons from the valence band of TiO2 to an acceptor (O2 gas) to promote photo-oxidation processes. The photocatalytic disinfection activity of Ag-TiO2/GF under visible light increased with the increase in silver content up to 7.5% and then slightly decreased with further increasing silver content. The highest disinfection efficiency and disinfection capacity of Staph using 7.5% Ag-TiO2/GF were 75.23% and 20 (CFU∙s−1∙cm−2) respectively. The medium level of humidity of 60% ± 5% showed better photocatalytic disinfection than the lower (40% ± 5%) or higher (80% ± 5%) levels. PMID:24658408

  5. The Performance Improvement of N2 Plasma Treatment on ZrO2 Gate Dielectric Thin-Film Transistors with Atmospheric Pressure Plasma-Enhanced Chemical Vapor Deposition IGZO Channel.

    PubMed

    Wu, Chien-Hung; Huang, Bo-Wen; Chang, Kow-Ming; Wang, Shui-Jinn; Lin, Jian-Hong; Hsu, Jui-Mei

    2016-06-01

    The aim of this paper is to illustrate the N2 plasma treatment for high-κ ZrO2 gate dielectric stack (30 nm) with indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs). Experimental results reveal that a suitable incorporation of nitrogen atoms could enhance the device performance by eliminating the oxygen vacancies and provide an amorphous surface with better surface roughness. With N2 plasma treated ZrO2 gate, IGZO channel is fabricated by atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) technique. The best performance of the AP-PECVD IGZO TFTs are obtained with 20 W-90 sec N2 plasma treatment with field-effect mobility (μ(FET)) of 22.5 cm2/V-s, subthreshold swing (SS) of 155 mV/dec, and on/off current ratio (I(on)/I(off)) of 1.49 x 10(7). PMID:27427669

  6. Characteristics of dye-sensitized solar cell with TiO2 anode under UV irradiation

    NASA Astrophysics Data System (ADS)

    Lee, Ming-Kwei; Hsiao, Chih-Chen; Weng, Hao-Wei

    2016-03-01

    The anatase phase crystalline quality of commercial TiO2 (P25) nanoparticle sintered in air and N2 is improved. Compared DSSC with air-sintered TiO2 anode, DSSC with N2-sintered TiO2 anode has better performance mainly from high optical absorption efficiency. Under UV irradiation, organic contaminants adsorbed on TiO2 are dissociated by the photocatalysis, and the dye adsorption is enhanced. The DSSC performance with UV-treated/N2-sintered TiO2 anode is further improved.

  7. Continuous in-situ Measurements of Gases (H2, H2S, CH4, N2, O2, Ar, He, and CO2) at the Fumarole "Soffionissimo" (Solfatara volcano, Southern Italy)

    NASA Astrophysics Data System (ADS)

    Wiersberg, T.; Somma, R.; Rocco, A.; de Rosa, M.; Zimmer, M.; Quattrocchi, F.; de Natale, G.; de Natale, P.

    2007-05-01

    second half of the monitoring, additionally CO2 gas concentration measurements were performed using a laser spectrometer based on a semiconductor laser source emitting around 2 m connected on-line with the gas line. Gas samples were taken from the gas line for laboratory gas-chromatographic analysis and noble gas analyses. Although data processing is still ongoing, the residual (=water-free) average gas composition can be preliminary described as follows: CO2 >97 vol%, H2S ~0.16 vol%, H2 ~0.15 vol%, N2 <2 vol%, O2 <0.5 vol%, Ar <0.02 vol%, CH4 ~0.05 vol%, He <20ppmv. O2 and most of the N2 and Ar are due to atmospheric contamination of the system. Besides the varying air contribution, the gas composition shows no significant variations over time within the analytical uncertainties of the experiment.

  8. Experimental and modeling study on effects of N2 and CO2 on ignition characteristics of methane/air mixture

    PubMed Central

    Zeng, Wen; Ma, Hongan; Liang, Yuntao; Hu, Erjiang

    2014-01-01

    The ignition delay times of methane/air mixture diluted by N2 and CO2 were experimentally measured in a chemical shock tube. The experiments were performed over the temperature range of 1300–2100 K, pressure range of 0.1–1.0 MPa, equivalence ratio range of 0.5–2.0 and for the dilution coefficients of 0%, 20% and 50%. The results suggest that a linear relationship exists between the reciprocal of temperature and the logarithm of the ignition delay times. Meanwhile, with ignition temperature and pressure increasing, the measured ignition delay times of methane/air mixture are decreasing. Furthermore, an increase in the dilution coefficient of N2 or CO2 results in increasing ignition delays and the inhibition effect of CO2 on methane/air mixture ignition is stronger than that of N2. Simulated ignition delays of methane/air mixture using three kinetic models were compared to the experimental data. Results show that GRI_3.0 mechanism gives the best prediction on ignition delays of methane/air mixture and it was selected to identify the effects of N2 and CO2 on ignition delays and the key elementary reactions in the ignition chemistry of methane/air mixture. Comparisons of the calculated ignition delays with the experimental data of methane/air mixture diluted by N2 and CO2 show excellent agreement, and sensitivity coefficients of chain branching reactions which promote mixture ignition decrease with increasing dilution coefficient of N2 or CO2. PMID:25750753

  9. Experimental and modeling study on effects of N2 and CO2 on ignition characteristics of methane/air mixture.

    PubMed

    Zeng, Wen; Ma, Hongan; Liang, Yuntao; Hu, Erjiang

    2015-03-01

    The ignition delay times of methane/air mixture diluted by N2 and CO2 were experimentally measured in a chemical shock tube. The experiments were performed over the temperature range of 1300-2100 K, pressure range of 0.1-1.0 MPa, equivalence ratio range of 0.5-2.0 and for the dilution coefficients of 0%, 20% and 50%. The results suggest that a linear relationship exists between the reciprocal of temperature and the logarithm of the ignition delay times. Meanwhile, with ignition temperature and pressure increasing, the measured ignition delay times of methane/air mixture are decreasing. Furthermore, an increase in the dilution coefficient of N2 or CO2 results in increasing ignition delays and the inhibition effect of CO2 on methane/air mixture ignition is stronger than that of N2. Simulated ignition delays of methane/air mixture using three kinetic models were compared to the experimental data. Results show that GRI_3.0 mechanism gives the best prediction on ignition delays of methane/air mixture and it was selected to identify the effects of N2 and CO2 on ignition delays and the key elementary reactions in the ignition chemistry of methane/air mixture. Comparisons of the calculated ignition delays with the experimental data of methane/air mixture diluted by N2 and CO2 show excellent agreement, and sensitivity coefficients of chain branching reactions which promote mixture ignition decrease with increasing dilution coefficient of N2 or CO2. PMID:25750753

  10. Total cross sections for high-energy electron scattering by H2 (1Σ+g), N2 (1Σ+g), and O2 (3Σ-g)

    NASA Astrophysics Data System (ADS)

    Liu, J. W.

    1987-01-01

    Total inelastic cross sections are calculated for collisions of ground-state H2, N2, and O2 with fast electrons according to the revised Bethe theory given by Inokuti et al. The asymptotic forms of the total elastic-scattering cross sections in the first Born approximation due to Inokuti and McDowell and including an electron exchange correction are also evaluated for these molecules. For H2, various accurate configuration-interaction wave functions are used to compute the total inelastic and the integral elastic-scattering cross sections. Good agreement between theory and experiment is found for the total cross sections (inelastic and elastic) for high incident energies as well as incident energies near 1 keV. The cross sections are also given for N2 and O2. Since there are no experimental reports for the integral elastic cross section for N2 or O2 at very high incident energies, the comparison is made only for the experimental data at incident energies near 1 keV. It is found that the theoretical results overestimate the experimental data by about 30% for N2. However, the Bethe total inelastic cross sections are in good agreement with experiments. Since the Born-Bethe approximation may not be valid at lower incident energies, more accurate experimental data at very high incident energies are required for valid comparison with the theoretical results reported here.

  11. Vehicle emissions of greenhouse gases and related tracers from a tunnel study: CO : CO2, N2O : CO2, CH4 : CO2, O2 : CO2 ratios, and the stable isotopes 13C and 18O in CO2 and CO

    NASA Astrophysics Data System (ADS)

    Popa, M. E.; Vollmer, M. K.; Jordan, A.; Brand, W. A.; Pathirana, S. L.; Rothe, M.; Röckmann, T.

    2013-09-01

    Measurements of CO2, CO, N2O and CH4 mole fractions, O2/N2 ratios and the stable isotopes 13C and 18O in CO2 and CO have been performed in air samples from the highway tunnel Islisberg (Switzerland). The CO : CO2 ratios, with an average of (4.15 ± 0.34) ppb : ppm, are lower than reported by previous studies, pointing to a reduction in CO emissions from traffic. The 13C in CO2 reflects the isotopic composition of the fuel. 18O in CO2 is slightly depleted compared to the 18O in atmospheric O2, and shows significant variability. In contrast, the δ13C values of CO show that significant fractionation takes place during CO destruction in the catalytic converter. 13C in CO is enriched by 3 ‰ compared to the 13C in the fuel burnt, while the 18O content is similar to that of atmospheric O2. We compute a fractionation constant of (-2.7 ± 0.7) ‰ for 13C during CO destruction. The N2O : CO2 average ratio (1.8 ± 0.2) × 10-2 ppb : ppm is significantly lower than in past studies, showing a reduction in N2O emissions likely related to improvements in the catalytic technology. We also observed small CH4 emissions, with an average CH4 : CO2 ratio of (4.6 ± 0.2) × 10-2 ppb : ppm. The O2 : CO2 ratios of (-1.47 ± 0.01) ppm : ppm are very close to the expected, theoretically calculated values.

  12. Improved light output power of LEDs with embedded air voids structure and SiO2 current blocking layer

    NASA Astrophysics Data System (ADS)

    Zhou, Shengjun; Yuan, Shu; Liu, Sheng; Ding, Han

    2014-06-01

    GaN-based light-emitting diodes (LEDs) with an embedded air voids structure and a SiO2 current blocking layer (CBL) was fabricated and investigated. The air voids structure was formed between cone-shaped patterned sapphire substrate and GaN epitaxial layer by combining laser scribing with H3PO4-based hot chemical etching. The air voids embedded high power LED showed 8.9% higher light output power due to a strong light reflection and redirection at the interface between GaN and air voids, which could increase the top light extraction of the high power LED. Compared to the air voids embedded high power LED, the light output power of the high power LED by integrating air voids structure with SiO2 CBL was 9.1% higher than that of the air voids embedded LED without SiO2 CBL. It was also found that the simulation results agree well with the experimental results.

  13. Efficiency of clay-TiO2 nanocomposites on the photocatalytic eliminationof a model hydrophobic air pollutant

    SciTech Connect

    Kibanova, Daria; Cervini-Silva, Javiera; Destaillats, Hugo

    2009-01-01

    Clay-supported TiO2 photocatalysts can potentially improve the performance of air treatment technologies via enhanced adsorption and reactivity of target volatile organic compounds (VOCs). In this study, a bench-top photocatalytic flow reactor was used to evaluate the efficiency of hectorite-TiO2 and kaolinite-TiO2, two novel composite materials synthesized in our laboratory. Toluene, a model hydrophobic VOC and a common indoor air pollutant, was introduced in the air stream at realistic concentrations, and reacted under UVA (gamma max = 365 nm) or UVC (gamma max = 254 nm) irradiation. The UVC lamp generated secondary emission at 185 nm, leading to the formation of ozone and other short-lived reactive species. Performance of clay-TiO2 composites was compared with that of pure TiO2 (Degussa P25), and with UV irradiation in the absence of photocatalyst under identical conditions. Films of clay-TiO2 composites and of P25 were prepared by a dip-coating method on the surface of Raschig rings, which were placed inside the flow reactor. An upstream toluene concentration of ~;;170 ppbv was generated by diluting a constant flow of toluene vapor from a diffusion source with dry air, or with humid air at 10, 33 and 66percent relative humidity (RH). Toluene concentrations were determined by collecting Tenax-TA (R) sorbent tubes downstream of the reactor, with subsequent thermal desorption -- GC/MS analysis. The fraction of toluene removed, percentR, and the reaction rate, Tr, were calculated for each experimental condition from the concentration changes measured with and without UV irradiation. Use of UVC light (UV/TiO2/O3) led to overall higher reactivity, which can be partially attributed to the contribution of gas phase reactions by short-lived radical species. When the reaction rate was normalized to the light irradiance, Tr/I gamma, the UV/TiO2 reaction under UVA irradiation was more efficient for samples with a higher content of TiO2 (P25 and Hecto-TiO2), but not for Kao-TiO

  14. Synthesis of Cu/TiO2/organo-attapulgite fiber nanocomposite and its photocatalytic activity for degradation of acetone in air

    NASA Astrophysics Data System (ADS)

    Zhang, Gaoke; Wang, He; Guo, Sheng; Wang, Junting; Liu, Jin

    2016-01-01

    The Cu/TiO2/organo-attapulgite fiber (CTOA) nanocomposite was synthesized by a facile method and was used for photocatalytic degradation of acetone in air under UV light irradiation. The as-prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectrum (UV-vis DRS), inductively coupled plasma (ICP) spectrometry and N2 adsorption-desorption measurement. The results showed that the structure of organo-attapulgite (OAT) had no obvious change as compared to unmodified attapulgite (AT) and the attapulgite fibers in the OAT were well-dispersed. Both micropores and mesopores exist in the CTOA catalyst. The CTOA catalysts prepared at the Cu/TiO2 molar ratio of 0.003 shows an excellent photocatalytic activity for the degradation of acetone in air. The synergistic effect of Cu species and cetyltrimethylammonium bromide modification can be responsible for the enhanced photocatalytic activity of the CTOA catalyst. The mechanism of the photocatalytic degradation of acetone by the CTOA catalyst was discussed.

  15. Implications of the formation of small polarons in Li2O2 for Li-air batteries

    NASA Astrophysics Data System (ADS)

    Kang, Joongoo; Jung, Yoon Seok; Wei, Su-Huai; Dillon, Anne C.

    2012-01-01

    Lithium-air batteries (LABs) are an intriguing next-generation technology due to their high theoretical energy density of ˜11 kWh/kg. However, LABs are hindered by both poor rate capability and significant polarization in cell voltage, primarily due to the formation of Li2O2 in the air cathode. Here, by employing hybrid density functional theory, we show that the formation of small polarons in Li2O2 limits electron transport. Consequently, the low electron mobility μ = 10-10-10-9 cm2/V s contributes to both the poor rate capability and the polarization that limit the LAB power and energy densities. The self-trapping of electrons in the small polarons arises from the molecular nature of the conduction band states of Li2O2 and the strong spin polarization of the O 2p state. Our understanding of the polaronic electron transport in Li2O2 suggests that designing alternative carrier conduction paths for the cathode reaction could significantly improve the performance of LABs at high current densities.

  16. Comparison of Benzene & Toluene removal from synthetic polluted air with use of Nano photocatalyticTiO2/ ZNO process

    PubMed Central

    2014-01-01

    Background Mono aromatic hydrocarbons (BTEX) are a group of hazardous pollutants which originate from sources such as refineries, gas, and oil extraction fields, petrochemicals and paint and glue industries. Conventional methods, including incineration, condensation, adsorption and absorption have been used for removal of VOCs. None of these methods is economical for removal of pollutants of polluted air with low to moderate concentrations. The heterogeneous photocatalytic processes involve the chemical reactions to convert pollutant to carbon dioxide and water. The aim of this paper is a comparison of Benzene & Toluene removal from synthetic polluted air using a Nano photocatalytic TiO2/ ZNO process. Results The X-ray diffraction (XRD) patterns showed that Nano crystals of TiO2 and ZNO were in anatase and rutile phases. Toluene & benzene were decomposed by TiO2/ ZNO Nano photocatalyst and UV radiation. Kruskal-wallis Test demonstrated that there are significant differences (pvalue < 0.05) between pollutant concentrations in different operational conditions. Conclusions Degradation of toluene & benzene increases with increasing UV intensity and decreasing initial concentrations. Effect of TiO2/ZNO Nano photocatalyst on benzene is less than that on toluene. In this research, Toluene & benzene removal by TiO2/ZNO and UV followed first-order reactions. PMID:24499601

  17. Global ab initio potential energy surface for the O2((3)Σ(g)(-)) + N2((1)Σ(g)(-)) interaction. Applications to the collisional, spectroscopic, and thermodynamic properties of the complex.

    PubMed

    Bartolomei, Massimiliano; Carmona-Novillo, Estela; Hernández, Marta I; Campos-Martínez, José; Moszyński, Robert

    2014-08-21

    A detailed characterization of the interaction between the most abundant molecules in air is important for the understanding of a variety of phenomena in atmospherical science. A completely ab initio global potential energy surface (PES) for the O2((3)Σg(–)) + N2((1)Σg(+)) interaction is reported for the first time. It has been obtained with the symmetry-adapted perturbation theory utilizing a density functional description of monomers [SAPT(DFT)] extended to treat the interaction involving high-spin open-shell complexes. The computed interaction energies of the complex are in a good agreement with those obtained by using the spin-restricted coupled cluster methodology with singles, doubles, and noniterative triple excitations [RCCSD(T)]. A spherical harmonics expansion of the interaction potential containing a large number of terms due to the anisotropy of the interaction has been built from the ab initio data. The expansion coefficients, which are functions of the intermolecular distance, are matched in the long-range with the analytical functions based on the recent ab initio calculations of the electric properties of the monomers [M. Bartolomei et al. J. Comput. Chem. 2011, 32, 279]. The PES is tested against the second virial coefficient B(T) data and the integral cross sections measured with rotationally hot effusive beams, leading in both cases to a very good agreement. The lowest lying states of the complex have been computed and relevant spectroscopic features of the interacting complex are reported. A comparison with a previous experimentally derived PES is also provided. PMID:24824559

  18. Fractal analysis methods for solid alkane monolayer domains at SiO2/air interfaces.

    PubMed

    Knüfing, Lydia; Schollmeyer, Hauke; Riegler, Hans; Mecke, Klaus

    2005-02-01

    A systematic evaluation of various fractal analysis methods is essential for studying morphologies of finite and noisy experimental patterns such as domains of long chain alkanes at SiO(2)/air interfaces. The derivation of trustworthy fractal dimensions crucially relies on the definition of confidence intervals for the assumed scaling range. We demonstrate that the determination of the intervals can be improved largely by comparing the scaling behavior of different morphological measures (area, boundary, curvature). We show that the combination of area and boundary data from coarse-grained structures obtained with the box-counting method reveals clear confidence limits and thus credible morphological data. This also holds for the Minkowski density method. It also reveals the confidence range. Its main drawback, the larger swing-in period at the lower cutoff compared to the box-counting method, is compensated by more details on the scaling behavior of area, boundary, and curvature. The sandbox method is less recommendable. It essentially delivers the same data as box-counting, but it is more susceptible to finite size effects at the lower cutoff. It is found that the domain morphology depends on the surface coverage of alkanes. The individual domains at low surface coverage have a fractal dimension of approximately 1.7, whereas at coverages well above 50% the scaling dimension is 2 with a large margin of uncertainty at approximately 50% coverage. This change in morphology is attributed to a crossover from a growth regime dominated by diffusion-limited aggregation of individual domains to a regime where the growth is increasingly affected by annealing and the interaction of solid growth fronts which approach each other and thus compete for the alkane supply. PMID:15667180

  19. Synthesis and characterizations of MnO2/multi-wall carbon nanotubes nanocomposites for lithium-air battery.

    PubMed

    Eom, Hye Ri; Kim, Min Kyung; Kim, Moon Su; Kim, Gil-Pyo; Baeck, Sung-Hyeon

    2013-03-01

    In this work, rechargeable lithium-air battery using MnO2/MWNTs nanocomposites as a catalyst was studied. MnO2/MWNTs nanocomposites were synthesized by a hydrothermal method, and their physical and chemical properties were investigated. X-ray diffraction (XRD) was used to examine crystallinity and morphology was investigated by transmission electron microscopy (TEM). Charge-discharge behavior and cell impedance with electrolyte replacement were investigated, and charge-discharge capacity decreased with cycles mainly due to the decomposition of carbonate-based electrolyte. PMID:23755590

  20. Effect of air annealing on structure and magnetic properties of Sn1-xFexO2 thin films

    NASA Astrophysics Data System (ADS)

    Kuppan, M.; Begam, M. Regana; Babu, S. Harinath; Kaleemulla, S.; Rao, N. Madhusudhana; Krishnamoorthi, C.

    2016-05-01

    Sn1-xFexO2 (x = 0.07) thin films were prepared on to glass substrates using flash evaporation technique and annealed in air at different temperatures. The X-ray diffraction study showsed that all the thin films annealed at different temperatures were in tetragonal rutile structure of SnO2. The Elemental analysis confirms the presence of Fe and Sn and O in the films. The magnetic measurements were carried out using vibrating sample magnetometer and found that the strength of magnetization decreased with increase of annealing temperature.

  1. A novel thermally stable hydroperoxo-copper(II) complex in a Cu(N2O2) chromophore of a potential N4O2 donor Schiff base ligand: synthesis, structure and catalytic studies.

    PubMed

    Biswas, Surajit; Dutta, Arpan; Debnath, Mainak; Dolai, Malay; Das, Kalyan K; Ali, Mahammad

    2013-09-28

    The generation and study of metal-hydroperoxo/metal-peroxo (LCu(II)-OOH or LCu(II)-OO˙) complexes is a fascinating area of research of many chemical and biochemical researchers, because of their involvement as active intermediates in many biological and industrial catalytic oxidation processes. For this purpose we have designed a bulky hexa-coordinating ligand with potential N4O2 donor atoms which could provide an opportunity to synthesize a mononuclear Cu(II) complex with an aim to utilize it in the catalytic oxidation of aromatic hydrocarbons by an environmentally benign oxidant, H2O2. The Cu(II) complex (1) was structurally characterized and found to have square-planar geometry with the two pyrazolyl groups remaining in dangling mode. A novel mononuclear complex [Et3NH][LCu(II)-OOH] (2) was found to form in the reaction between 1 and H2O2 in the presence of Et3N. The presence of this dangling groups favours the stability of hydroperoxo species, [LCu-OOH](-) (2) through H-bonding with the coordinated phenoxo oxygen atom, which was confirmed by ESI-MS(+) and MS(-) (m/z) mass analysis and DFT calculations. This complex was found to be thermally stable at room temperature [k(d) = (5.67 ± 0.03) × 10(-5) s(-1) at 25 °C] and may be due to the formation of O-O-H···O(phenoxo) H-bonding as delineated by the DFT calculations. Complex 1 was found to be an efficient catalyst for the oxidation of aromatic hydrocarbons to the corresponding aldehyde and alcohol in 2:1 mole ratio with TON ~300. PMID:23884097

  2. Effect of CuO2 planes on the structural and superconducting transport properties of [CuTl ‑ 12(n ‑ 1)n;n = 2,3,4] superconductor family

    NASA Astrophysics Data System (ADS)

    Muzaffar, M. Usman; Khan, Nawazish A.

    2016-06-01

    Cu0.5Tl0.5Ba2Can‑1CunO2n+4‑δ (n = 2, 3, 4) superconducting bulk samples have been synthesized by using two-step solid state reaction method. We investigated the effects of CuO2 planes on the structural and superconducting transport properties of [CuTl ‑ 12(n ‑ 1)n; n = 2, 3, 4] superconducting family. These samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) absorption spectroscopy and DC-resistivity (ρ) measurements. These samples are c-axis length oriented and have shown orthorhombic crystal structure. All the samples have shown metallic variations of resistivity from room temperature down to onset of superconductivity. The zero resistivity critical temperature Tc(R = 0) increases with the increase in superconducting planes and normal state resistivity systematically decreases, which show the density of inadvertent defects decreases in the final compound. The apical oxygen phonon modes are hardened as observed in the FTIR absorption measurements. The intrinsic microscopic superconducting parameters, such as the cross-over temperatures, coherence length along c-axis (ξc(0)) at 0 K, inter-layer coupling (J), inter-grain coupling (α) and fermi velocity (VF), were extracted from the fluctuation-induced conductivity (FIC) analysis. FIC analysis also showed the improvement in superconductivity with the increase in CuO2 planes.

  3. Development of automated preparation system for isotopocule analysis of N2O in various air samples

    NASA Astrophysics Data System (ADS)

    Toyoda, Sakae; Yoshida, Naohiro

    2016-05-01

    Nitrous oxide (N2O), an increasingly abundant greenhouse gas in the atmosphere, is the most important stratospheric ozone-depleting gas of this century. Natural abundance ratios of isotopocules of N2O, NNO molecules substituted with stable isotopes of nitrogen and oxygen, are a promising index of various sources or production pathways of N2O and of its sink or decomposition pathways. Several automated methods have been reported to improve the analytical precision for the isotopocule ratio of atmospheric N2O and to reduce the labor necessary for complicated sample preparation procedures related to mass spectrometric analysis. However, no method accommodates flask samples with limited volume or pressure. Here we present an automated preconcentration system which offers flexibility with respect to the available gas volume, pressure, and N2O concentration. The shortest processing time for a single analysis of typical atmospheric sample is 40 min. Precision values of isotopocule ratio analysis are < 0.1 ‰ for δ15Nbulk (average abundances of 14N15N16O and 15N14N16O relative to 14N14N16O), < 0.2 ‰ for δ18O (relative abundance of 14N14N18O), and < 0.5 ‰ for site preference (SP; difference between relative abundance of 14N15N16O and 15N14N16O). This precision is comparable to that of other automated systems, but better than that of our previously reported manual measurement system.

  4. Measurement of vibrationally excited N2(v) in an atmospheric-pressure air pulsed corona discharge using coherent anti-Stokes Raman scattering

    NASA Astrophysics Data System (ADS)

    Teramoto, Yoshiyuki; Ono, Ryo

    2014-08-01

    Vibrationally excited N2(v = 1, 2) in an atmospheric-pressure air pulsed corona discharge was measured using coherent anti-Stokes Raman scattering (CARS). In a dry air discharge, the vibrational temperature determined from the ratio N2(v = 2)/N2(v = 0), Tv2, was approximately 500 K higher than that determined from N2(v = 1)/N2(v = 0), Tv1, immediately after the discharge pulse. Both vibrational temperatures reached equilibrium within 100 μs after the discharge pulse by the vibration-to-vibration (V-V) process of N2-N2. The translational temperature was also measured using CARS. The rise in the translational temperature due to vibration-to-translation (V-T) energy transfer was not observed for a postdischarge time of 5 μs-1 ms in the dry-air discharge. However, when the air was humidified, a significant V-T energy transfer was observed. It was due to an extremely rapid V-T process of H2O-H2O following the V-V process of N2-H2O. Measurements showed that the humidification of the ambient air accelerated the decrease in the N2 vibrational temperature and increased the translational temperature. N2(v) was generated mostly in the secondary streamer, not in the primary one, according to estimation from the measured N2(v) density.

  5. Effect of fuel to air ratio on Mach 0.3 burner rig hot corrosion of ZrO2-Y2O3 thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Hodge, P. E.

    1982-01-01

    A Mach 0.3 burner rig test program was conducted to determine how the fuel to air mass ratio affects the durability of ZrO2-Y2O3/Ni-16Cr-6Al-0.31Y thermal barrier coating systems in combustion products containing 5 ppm Na and 2 ppm V. As the fuel to air mass ratio was increased from 0.039 to 0.049, the durability of ZrO2-6Y2O3, ZrO2-8Y2O3 and ZrO2-12Y2O3 coatings decreased. ZrO2-8Y2O3 coatings were approximately 2X and 1.3X more durable than ZrO2-12Y2O3 and ZrO2-6Y2O3 coatings respectively at the fuel to air mass ratio of 0.039. The number of one hour cycles endured by ZrO2-8Y2O3 coatings varied from averages of 53 to 200 for the fuel to air mass ratios of 0.049 and 0.039, respectively. At the fuel to air mass ratio of 0.049, all ZrO2-Y2O3 coated specimens failed in 40 to 60 one hour cycles

  6. Nitrogen, oxygen and air broadened widths and relative intensities of N2O lines near 2450/cm

    NASA Technical Reports Server (NTRS)

    Hawkins, R. L.

    1982-01-01

    Spectra of the v sub 1 + 2v sub 2 and the weak underlying v sub 1 + 3v sub 2 - v sub 2 band of N2O near 2450/cm were analyzed by the nonlinear, least squares, whole band technique. The oxygen, nitrogen, and air broadened line widths and the relative line intensities were determined. The air broadened widths, for/m/3, are in agreement with those in the 1980 AFGL line listing and the relative band intensities also agree, within about 20% with the values in this listing.

  7. Differential cross sections for scattering of 0.5-, 1.5-, and 5.0-keV hydrogen atoms by He, H2, N2, and O2

    NASA Technical Reports Server (NTRS)

    Newman, J. H.; Chen, Y. S.; Smith, K. A.; Stebbings, R. F.

    1986-01-01

    This paper reports measurements of absolute cross sections, differential in angle, for scattering of 0.5-, 1.5-, and 5.0-keV hydrogen atoms by He, H2, N2, and O2 at laboratory scattering angles between 0.1 and 5 deg. The measured cross sections are the sums of those for elastic and inelastic collisions having a fast H atom product and are needed for calculating energy transfer to the upper atmosphere from precipitating ring current particles.

  8. Highly efficient photocatalytic TiO2 coatings deposited by open air atmospheric pressure plasma jet with aerosolized TTIP precursor

    NASA Astrophysics Data System (ADS)

    Fakhouri, H.; Ben Salem, D.; Carton, O.; Pulpytel, J.; Arefi-Khonsari, F.

    2014-07-01

    A simple method to deposit photocatalytic TiO2 coatings, at a high rate (20-40 µm s-1), and with a high porosity, is reported in this paper. This method, which allows the treatment of membranes (with an 800 nm pore size), is based on the introduction of a liquid precursor sprayed into an open-air atmospheric pressure plasma jet (APPJ). The photocatalytic activity of the TiO2 thin films prepared by APPJ have been compared with our best N-doped TiO2 thin films, deposited by reactive radio frequency (RF) magnetron sputtering, previously reported in the literature. The morphology, chemical composition, photoelectrochemical, and photocatalytic properties of the coatings have been studied in this paper. Significant control of the porosity and crystallinity was achieved by varying the deposition parameters and the annealing temperature. Under optimized conditions, the TiO2 coatings deposited by APPJ are characterized by a higher photocatalytic activity as compared to the optimized thin films deposited by RF sputtering. This difference can be explained by the higher specific surface of the APPJ coatings. Finally, the most interesting characteristic of this APPJ-liquid spray process is its capacity to treat membranes without blocking the pores, and to produce photocatalytic membranes which can efficiently combine filtration and photocatalysis for water treatment.

  9. Characteristics of TiO2 Thin Film Surfaces Treated by Helium and Air Dielectric Barrier Discharge Plasmas

    NASA Astrophysics Data System (ADS)

    Kawakami, Retsuo; Niibe, Masahito; Takeichi, Atsushi; Mori, Yuta; Konishi, Masashi; Kotaka, Takuya; Matsunaga, Fumihiko; Takasaki, Toshihide; Kitano, Takanori; Miyazaki, Takahiro; Inaoka, Takeshi; Tominaga, Kikuo

    2012-08-01

    The characteristics of TiO2 thin film surfaces treated with He and air dielectric barrier discharge (DBD) plasmas at different gas pressures are investigated. There is a difference between the two DBD plasma characteristics: for He-DBD, which is an atmospheric pressure glow discharge (APGD), the breakdown voltage and discharge current hardly change with increasing gas pressure, whereas for air-DBD, which is basically a filamentary discharge, they increase with increasing gas pressure. There is also a difference between the characteristics of TiO2 surfaces treated with the two DBDs. The surface roughness for He-DBD is lower than the roughness of the as-grown surface, whereas that for air-DBD is higher. The surface hydrophilicity for He-DBD is more enhanced than the hydrophilicity of the as-grown surface regardless of UV irradiation. The hydrophilicity for air-DBD is dependent on UV irradiation. It is more enhanced with UV irradiation; it is not improved adequately without UV irradiation.

  10. Graphene oxide electrocatalyst on MnO2 air cathode as an efficient electron pump for enhanced oxygen reduction in alkaline solution

    PubMed Central

    Basirun, Wan Jeffrey; Sookhakian, Mehran; Baradaran, Saeid; Endut, Zulkarnain; Mahmoudian, Mohammad Reza; Ebadi, Mehdi; Yousefi, Ramin; Ghadimi, Hanieh; Ahmed, Sohail

    2015-01-01

    Graphene oxide (GO) was deposited on the surface of a MnO2 air cathode by thermal evaporation at 50°C from a GO colloidal suspension. Fourier transformed infrared spectroscopy and field emission scanning electron microscopy confirmed the presence of GO on the MnO2 air cathode (GO-MnO2). Voltammetry and chrono-amperometry showed increased currents for the oxygen reduction reaction (ORR) in 6 M KOH solution for GO-MnO2 compared to the MnO2 cathode. The GO-MnO2 was used as an air cathode in an alkaline tin-air cell and produced a maximum power density of 13 mW cm−2, in contrast to MnO2, which produced a maximum power density of 9.2 mW cm−2. The electrochemical impedance spectroscopy results suggest that the chemical step for the ORR is the rate determining step, as proposed earlier by different researchers. It is suggested that the presence of GO and electrochemically reduced graphene oxide (ERGO) on the MnO2 surface are responsible for the increased rate of this step, whereby GO and ERGO accelerate the process of electron donation to the MnO2 and to adsorbed oxygen atoms. PMID:25765731

  11. Palladium(II) and zinc(II) complexes of neutral [N2O2] donor Schiff bases derived from furfuraldehyde: synthesis, characterization, fluorescence and corrosion inhibitors of ligands.

    PubMed

    Ali, Omyma A M

    2014-11-11

    Metal complexes of Schiff bases derived from furfuraldehyde and 4,5-dimethyl-1,2-phenylendiamine (L1) or 4,5-dichloro-1,2-phenylendiamine (L2) have been reported and characterized based on elemental analyses, IR, 1H NMR, UV-Vis, magnetic moment, molar conductance and thermal analysis. The complexes are found to have the formulae [PdL1-2]Cl2 and [ZnL1-2](AcO)2·H2O. The molar conductance data reveal that Pd(II) and Zn(II) chelates are ionic in nature and are of the type 2:1 electrolytes. The spectral data are consistent with a square planar and tetrahedral geometry around Pd(II) and Zn(II), respectively, in which the ligands act as tetradentate ligands. The thermal behavior of some chelates is studied and the activation thermodynamic parameters are calculated using Coats-Redfern method. The corrosion inhibition of stainless steel types 410 and 304 in 1 M HCl using the synthesized Schiff bases as inhibitors have been studied by weight loss method. The obtained data considered these ligands as efficient corrosion inhibitors. The ligands and their metal complexes exhibited considerable antibacterial activity against Staphylococcusaureus, and Escherichiacoli and antifungal activity against Candida albicans. PMID:24858346

  12. Palladium(II) and zinc(II) complexes of neutral [N2O2] donor Schiff bases derived from furfuraldehyde: Synthesis, characterization, fluorescence and corrosion inhibitors of ligands

    NASA Astrophysics Data System (ADS)

    Ali, Omyma A. M.

    2014-11-01

    Metal complexes of Schiff bases derived from furfuraldehyde and 4,5-dimethyl-1,2-phenylendiamine (L1) or 4,5-dichloro-1,2-phenylendiamine (L2) have been reported and characterized based on elemental analyses, IR, 1H NMR, UV-Vis, magnetic moment, molar conductance and thermal analysis. The complexes are found to have the formulae [PdL1-2]Cl2 and [ZnL1-2](AcO)2·H2O. The molar conductance data reveal that Pd(II) and Zn(II) chelates are ionic in nature and are of the type 2:1 electrolytes. The spectral data are consistent with a square planar and tetrahedral geometry around Pd(II) and Zn(II), respectively, in which the ligands act as tetradentate ligands. The thermal behavior of some chelates is studied and the activation thermodynamic parameters are calculated using Coats-Redfern method. The corrosion inhibition of stainless steel types 410 and 304 in 1 M HCl using the synthesized Schiff bases as inhibitors have been studied by weight loss method. The obtained data considered these ligands as efficient corrosion inhibitors. The ligands and their metal complexes exhibited considerable antibacterial activity against Staphylococcusaureus, and Escherichiacoli and antifungal activity against Candida albicans.

  13. Using elastin protein to develop highly efficient air cathodes for lithium-O2 batteries

    NASA Astrophysics Data System (ADS)

    Guo, Guilue; Yao, Xin; Ang, Huixiang; Tan, Huiteng; Zhang, Yu; Guo, Yuanyuan; Fong, Eileen; Yan, Qingyu

    2016-01-01

    Transition metal-nitrogen/carbon (M-N/C, M = Fe, Co) catalysts are synthesized using environmentally friendly histidine-tag-rich elastin protein beads, metal sulfate and water soluble carbon nanotubes followed by post-annealing and acid leaching processes. The obtained catalysts are used as cathode materials in lithium-O2 batteries. It has been discovered that during discharge, Li2O2 nanoparticles first nucleate and grow around the bead-decorated CNT regions (M-N/C centres) and coat on the catalysts at a high degree of discharge. The Fe-N/C catalyst-based cathodes deliver a capacity of 12 441 mAh g-1 at a current density of 100 mA g-1. When they were cycled at a limited capacity of 800 mAh g-1 at current densities of 200 or 400 mA g-1, these cathodes showed stable charge voltages of ˜3.65 or 3.90 V, corresponding to energy efficiencies of ˜71.2 or 65.1%, respectively. These results are considerably superior to those of the cathodes based on bare annealed CNTs, which prove that the Fe-N/C catalysts developed here are promising for use in non-aqueous lithium-O2 battery cathodes.

  14. Using elastin protein to develop highly efficient air cathodes for lithium-O2 batteries.

    PubMed

    Guo, Guilue; Yao, Xin; Ang, Huixiang; Tan, Huiteng; Zhang, Yu; Guo, Yuanyuan; Fong, Eileen; Yan, Qingyu

    2016-01-29

    Transition metal-nitrogen/carbon (M-N/C, M = Fe, Co) catalysts are synthesized using environmentally friendly histidine-tag-rich elastin protein beads, metal sulfate and water soluble carbon nanotubes followed by post-annealing and acid leaching processes. The obtained catalysts are used as cathode materials in lithium-O2 batteries. It has been discovered that during discharge, Li2O2 nanoparticles first nucleate and grow around the bead-decorated CNT regions (M-N/C centres) and coat on the catalysts at a high degree of discharge. The Fe-N/C catalyst-based cathodes deliver a capacity of 12,441 mAh g(-1) at a current density of 100 mA g(-1). When they were cycled at a limited capacity of 800 mAh g(-1) at current densities of 200 or 400 mA g(-1), these cathodes showed stable charge voltages of ∼3.65 or 3.90 V, corresponding to energy efficiencies of ∼71.2 or 65.1%, respectively. These results are considerably superior to those of the cathodes based on bare annealed CNTs, which prove that the Fe-N/C catalysts developed here are promising for use in non-aqueous lithium-O2 battery cathodes. PMID:26657319

  15. Tunable diode laser measurements of air-broadened linewidths in the nu6 band of H2O2

    NASA Technical Reports Server (NTRS)

    Malathy Devi, V.; Benner, D. C.; Rinsland, C. P.; Smith, M. A. H.; Fridovich, B.

    1986-01-01

    Air-broadened half-widths of 18 transitions in the nu6 band of H2O2 between 1252/cm and 1291/cm have been determined from spectra recorded at room temperature using a tunable diode laser spectrometer. The preparation of the H2O2 gas samples for the measurements is described, and the data analysis is discussed, including the derivation of Lorentz broadening coefficients and the contribution of molecular collisions to the measured Lorentz half-widths. For the 18 transitions, the half-widths varied from 0.0923/cm/atm to 0.1155/cm/atm at 296 K, with a mean value of 0.1020/cm/atm. An error of less than 10 percent is estimated for these results.

  16. Long-term measurements of atmospheric trace gases (CO2, CH4, N2O, SF6, CO, H2), O2, and δ13CH4 isotopes at Weybourne Atmospheric Observatory, UK: past, present and future

    NASA Astrophysics Data System (ADS)

    Manning, Andrew C.; Forster, Grant L.; Oram, David E.; Reeves, Claire E.; Pickers, Penelope A.; Barningham, S. Thomas; Sturges, William T.; Bandy, Brian; Nisbet, Euan G.; Lowry, David; Fisher, Rebecca; Fleming, Zoe

    2016-04-01

    The Weybourne Atmospheric Observatory (WAO) is situated on the north Norfolk Coast (52.95°N, 1.13°E) in the United Kingdom and is run by the University of East Anglia (UEA), with support from the UK National Centre for Atmospheric Science (NCAS). In 2016, the WAO became a UK-ICOS (Integrated Carbon Observing System) monitoring station. Since 2008, we have been collecting high-precision long-term in situ measurements of atmospheric carbon dioxide (CO2), oxygen (O2), carbon monoxide (CO) and molecular hydrogen (H2), as well as regular bag sampling for δ13CH4. In early 2013, the measurement of atmospheric methane (CH4) commenced, and nitrous oxide (N2O) and sulphur hexafluoride (SF6) began in 2014. We summarise the CO2, O2, CH4, N2O, SF6, CO, H2 and δ13CH4 measurements made to date and highlight some key features observed (e.g. seasonal cycles, long-term trends, pollution events and deposition events). We summarise how the long-term measurements fit into other broader projects which have helped to support the long term time-series at WAO over the years, and highlight how we contribute to broader global atmospheric observation networks.

  17. Synthesis, spectral and electrochemical studies of Cu(II) and Ni(II) complexes with new N 2O 2 ligands: A new precursor capable of depositing copper nanoparticles using thermal reduction

    NASA Astrophysics Data System (ADS)

    Habibi, Mohammad Hossein; Mokhtari, Reza; Mikhak, Maryam; Amirnasr, Mehdi; Amiri, Ahmad

    2011-09-01

    Cu(II) and Ni(II) complexes of the general type [M(N 2O 2)] are described. The N 2O 2 ligands used are [N,N'-bis(2-hydroxy-6-methoxybenzylidene)propane-1,3-diamine] (HOMeSalpn) and [N,N'-bis(2-hydroxy-6-methoxybenzylidene)propane-1,2-diamine (HOMeSalpr). These complexes have been characterized by IR, UV-vis, CV, TG-DTA and 1H NMR spectroscopy. The electrochemical behavior of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Cu(II)-Cu(I) and Ni(II)-Ni(I) is electrochemically irreversible. The new copper complexes have been applied for the preparation of copper nanoparticles using non-ionic surfactant (Triton X-100) by thermal reduction. The copper nanoparticles with average size of 48 nm were formed by thermal reduction of [N,N'-bis(2-hydroxy-6-methoxybenzylidene)propane-1,3-diamine]copper(II) in the presence of triphenylphosphine thus releasing the reduced copper and affording the high-purity copper nanoparticles.

  18. Synthesis, spectral and electrochemical studies of Cu(II) and Ni(II) complexes with new N2O2 ligands: a new precursor capable of depositing copper nanoparticles using thermal reduction.

    PubMed

    Habibi, Mohammad Hossein; Mokhtari, Reza; Mikhak, Maryam; Amirnasr, Mehdi; Amiri, Ahmad

    2011-09-01

    Cu(II) and Ni(II) complexes of the general type [M(N2O2)] are described. The N2O2 ligands used are [N,N'-bis(2-hydroxy-6-methoxybenzylidene)propane-1,3-diamine] (HOMeSalpn) and [N,N'-bis(2-hydroxy-6-methoxybenzylidene)propane-1,2-diamine (HOMeSalpr). These complexes have been characterized by IR, UV-vis, CV, TG-DTA and 1H NMR spectroscopy. The electrochemical behavior of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Cu(II)-Cu(I) and Ni(II)-Ni(I) is electrochemically irreversible. The new copper complexes have been applied for the preparation of copper nanoparticles using non-ionic surfactant (Triton X-100) by thermal reduction. The copper nanoparticles with average size of 48nm were formed by thermal reduction of [N,N'-bis(2-hydroxy-6-methoxybenzylidene)propane-1,3-diamine]copper(II) in the presence of triphenylphosphine thus releasing the reduced copper and affording the high-purity copper nanoparticles. PMID:21641857

  19. TOPICAL REVIEW: High-pressure synthesis, crystal growth, phase diagrams, structural and magnetic properties of Y2Ba4CunO2n+x, HgBa2Can- 1CunO2n+2+delta and quasi-one-dimensional cuprates

    NASA Astrophysics Data System (ADS)

    Karpinski, J.; Meijer, G. I.; Schwer, H.; Molinski, R.; Kopnin, E.; Conder, K.; Angst, M.; Jun, J.; Kazakov, S.; Wisniewski, A.; Puzniak, R.; Hofer, J.; Alyoshin, V.; Sin, A.

    1999-09-01

    In this paper we present a review of high-gas-pressure single crystal growth studies of YBa2Cu4O8 and Y2Ba4Cu7O15-x performed in oxygen pressure up to 3000 bar and Hg1-xMxBa2Can- 1CunO2n+2+icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> (M = Pb, Re; n = 1-7) compounds in argon pressure up 11 000 bar at temperature up to 1200 °C. Chain compounds A1-xCuO2 (A = Sr, Ca, Ba) have been synthesized at high oxygen pressure up to 2000 bar. High-pressure phase diagram studies of the investigated systems are also discussed. Structure analyses of Y2Ba4CunO2n+x (n = 6-8), Hg1-xMxBa2Can- 1CunO2n+2+icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> (M = Pb, Re; n = 1-8), Sr0.73CuO2 and (Sr,Ca)4Cu6O10 single crystals have been performed. The effects of substitutions and trends in bondlengths are discussed. The vortex state properties of HgBa2Ca2Cu3O8+icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> and YBa2Cu4O8 single crystals are compared. For Hg-based compounds, the influence of oxygen content, chemical substitutions and radiation defects on vortex pinning were determined. The quasi-one-dimensional cuprates Ca0.83CuO2 and Sr0.73CuO2 show an antiferromagnetically ordered state of long-range 3D character at T < 10 K. The spin dynamics of Sr0.73CuO2, measured by inelastic neutron scattering, indicate that this ordered state coexists with a dimerized singlet ground state.

  20. High-pressure phases of SiO2 made in air by Fedoseev-Derjaguin laser process

    NASA Astrophysics Data System (ADS)

    Alam, M.; DebRoy, T.; Roy, R.; Breval, E.

    1988-10-01

    Exposure of a falling stream of 1 μm average size α-quartz particles to a continuous wave or pulsed CO2 laser beam in air resulted in the formation of a complete series of high-pressure phases of silica: coesite, stishovite, and apparently even denser forms with α-PbO2 and Fe2N structures. Since the laser exposure technique works with the carbon black to diamond transition, the technique is confirmed as a simple and generally applicable means to achieve the same effects as exposure to several hundred kilobars pressure.

  1. Visible-Light Responsive Catalysts Using Quantum Dot-Modified TiO2 for Air and Water Purification

    NASA Technical Reports Server (NTRS)

    Coutts, Janelle L.; Hintze, Paul E.; Clausen, Christian A.; Richards, Jeffrey T.

    2014-01-01

    Photocatalysis, the oxidation or reduction of contaminants by light-activated catalysts, utilizing titanium dioxide (TiO2) as the catalytic substrate has been widely studied for trace contaminant control in both air and water applications. The interest in this process is due primarily to its low energy consumption and capacity for catalyst regeneration. Titanium dioxide requires ultraviolet light for activation due to its relatively large band gap energy of 3.2 eV. Traditionally, Hg-vapor fluorescent light sources are used in PCO reactors; however, the use of mercury precludes the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure.

  2. Degradation of phenol via wet-air oxidation over CuO/CeO2-ZrO2 nanocatalyst synthesized employing ultrasound energy: physicochemical characterization and catalytic performance.

    PubMed

    Parvas, Mohsen; Haghighi, Mohammad; Allahyari, Somaiyeh

    2014-01-01

    Catalytic wet air oxidation (CWAO) of phenol was carried out under atmospheric pressure of oxygen at 160 degrees C in a stirred batch reactor over copper catalysts supported by CeO2-ZrO2. The copper with different loadings were impregnated over the composite support by a sonication process. The catalysts were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), Brunauer-Emmett-Teller (BET) specific surface area and Fourier-transformed infrared analyses. Characteristic peaks attributed to copper were not found in XRD patterns even at high loadings, but based on EDX results, the existence of copper particles was confirmed. It means that sonochemical synthesis method even at high loadings produced small copper particles with low crystallinity and excellent dispersion over the CeO2-ZrO2 composite. FESEM micrographs indicated just slight enhancement in particle size at high loadings of Cu. Blank CWAO experiments illustrated low conversion of phenol using bare CeO2-ZrO2 support. Although some agglomeration of particles was found at high loadings of copper but owning to the fact that almost all ZrO2 particles incorporated into the CeO2 lattice at high contents of Cu, catalyst activity not only did not decrease but also the phenol conversion reached to the higher values. The optimal catalyst loading for phenol degradation was found to be 9 g/l. Complete conversion of phenol was achieved using CuO/CeO2-ZrO2 in 9 g/l catalyst loading with initial phenol concentration of 1000 ppm after 3 h of reaction. PMID:24701909

  3. Mean Ages of Stratospheric Air Derived From in Situ Observations of CO2, CH4, and N2O

    NASA Technical Reports Server (NTRS)

    Andrews, A. E.; Boering, K. A.; Daube, B. C.; Wofsy, S. C.; Loewenstein, M.; Jost, H.; Podolske, J. R.; Webster, C. R.; Herman, R. L.; Scott, D. C.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Accurate mean ages for stratospheric air have been derived from a spatially and temporally comprehensive set of in situ observations of CO2, CH4, and N2O obtained from 1992 to 1998 from the NASA ER-2 aircraft and balloon flights. Errors associated with the tropospheric CO2 seasonal cycle and interannual variations in the CO2 growth rate are less than 0.5 year throughout the stratosphere and less than 0.3 year for air older than 2 years (N2O less than 275 ppbv), indicating that the age spectra are broad enough to attenuate these influences over the time period covered by these observations. The distribution of mean age with latitude and altitude provides detailed, quantitative information about the general circulation of the stratosphere. At 20 km, sharp meridional gradients in the mean age are observed across the subtropics. Between 20 and 30 km, the average difference in mean age between the tropics and midlatitudes is approximately 2 years, with slightly smaller differences at higher and lower altitudes. The mean age in the midlatitude middle stratosphere (approx. 25-32 km) is relatively constant with respect to altitude at 5 plus or minus 0.5 years. Comparison with earlier balloon observations of CO2 dating back to the 1970s indicates that the mean age of air in this region has remained within 11 year of its current value over the last 25 years. A climatology of mean age is derived from the observed compact relationship between mean age and N2O. These characteristics of the distribution of mean age in the stratosphere will serve as critically needed diagnostics for models of stratospheric transport.

  4. Effect of metal in M3(btc)2 and M2(dobdc) MOFs for O2/N2 separations: A combined density functional theory and experimental study

    DOE PAGESBeta

    Parkes, Marie V.; Sava Gallis, Dorina F.; Greathouse, Jeffery A.; Nenoff, Tina M.

    2015-03-02

    Computational screening of metal-organic framework (MOF) materials for selective oxygen adsorption from air could lead to new sorbents for the oxyfuel combustion process feedstock streams. A comprehensive study on the effect of MOF metal chemistry on gas binding energies in two common but structurally disparate metal-organic frameworks has been undertaken. Dispersion-corrected density functional theory methods were used to calculate the oxygen and nitrogen binding energies with each of fourteen metals, respectively, substituted into two MOF series, M2(dobdc) and M3(btc)2. The accuracy of DFT methods was validated by comparing trends in binding energy with experimental gas sorption measurements. A periodic trendmore » in oxygen binding energies was found, with greater oxygen binding energies for early transition-metal-substituted MOFs compared to late transition metal MOFs; this was independent of MOF structural type. The larger binding energies were associated with oxygen binding in a side-on configuration to the metal, with concomitant lengthening of the O-O bond. In contrast, nitrogen binding energies were similar across the transition metal series, regardless of both MOF structural type and metal identity. Altogether, these findings suggest that early transition metal MOFs are best suited to separating oxygen from nitrogen, and that the MOF structural type is less important than the metal identity.« less

  5. Air broadening of the hydrogen halides. I - N2-broadening and shifting in the HCl fundamental

    NASA Technical Reports Server (NTRS)

    Looney, J. P.; Herman, R. M.

    1987-01-01

    The resolvent operator formalism of Kolb, Griem (1964), and Baranger (1962) is used to determine the widths and shifts of the fundamental band vibration-rotation lines of HCl under N2 pressure. Time-development operator matrix elements are evaluated accounting for all bilinear and second order anisotropic terms, in addition to isotropic effects to all orders. The method employs the use of a parabolic trajectory model and explicit velocity averaging. The major contributions to the linewidths are found to arise from dipole-quadrupole, quadrupole-quadrupole, and vibrationally dependent isotropic dispersion forces. Good overall agreement is found between calculated and measured widths and linewidths over a 163-295 K temperature range.

  6. Investigation of Dipodal oxy-Schiff base and its salen and salophen Fe(III)/Cr(III)/Mn(III) Schiff bases (N2O2) caped complexes and their magnetic and thermal behaviors

    NASA Astrophysics Data System (ADS)

    Çelikbilek, Şeyma; Koç, Ziya Erdem

    2014-05-01

    Six new dinuclear Fe(III)/Cr(III)/Mn(III) complexes have been involved tetradentate (N2O2) Schiff bases (salenH2) and (salophenH2) with 2,4-bis(4-hydroxyphenylimino-4‧-formylphenoxy)-6-methoxy-1,3,5-triazine have been synthesized. The complexes were characterized as high-spin (S = 5/2) distorted trigonal bipyramidal salen/salophenFe(III) bridged, distorted trigonal bipyramidal (S = 3/2) salen/salophenCr(III) and high-spin distorted trigonal bipyramidal (S = 2) salen/salophenMn(III) by OH- groups. The structures of ligand and complexes were identified by using elemental analysis, thermal analysis, magnetic susceptibility, LC-MS, ICP-AES, 1H NMR and FT-IR spectral data.

  7. Co3O4 nanoparticle-modified MnO2 nanotube bifunctional oxygen cathode catalysts for rechargeable zinc-air batteries

    NASA Astrophysics Data System (ADS)

    Du, Guojun; Liu, Xiaogang; Zong, Yun; Hor, T. S. Andy; Yu, Aishui; Liu, Zhaolin

    2013-05-01

    We report the preparation of MnO2 nanotubes functionalized with Co3O4 nanoparticles and their use as bifunctional air cathode catalysts for oxygen reduction reaction and oxygen evolution reaction in rechargeable zinc-air batteries. These hybrid MnO2/Co3O4 nanomaterials exhibit enhanced catalytic reactivity toward oxygen evolution reaction under alkaline conditions compared with that in the presence of MnO2 nanotubes or Co3O4 nanoparticles alone.We report the preparation of MnO2 nanotubes functionalized with Co3O4 nanoparticles and their use as bifunctional air cathode catalysts for oxygen reduction reaction and oxygen evolution reaction in rechargeable zinc-air batteries. These hybrid MnO2/Co3O4 nanomaterials exhibit enhanced catalytic reactivity toward oxygen evolution reaction under alkaline conditions compared with that in the presence of MnO2 nanotubes or Co3O4 nanoparticles alone. Electronic supplementary information (ESI) available: Zinc-air cell device, XPS survey scan and power density of the cell. See DOI: 10.1039/c3nr00300k

  8. Zn/gelled 6 M KOH/O 2 zinc-air battery

    NASA Astrophysics Data System (ADS)

    Mohamad, A. A.

    The gel electrolyte for the zinc-air cell was prepared by mixing hydroponics gel with a 6 M potassium hydroxide aqueous solution. The self-discharge of cells was characterized by measuring the open-circuit voltage. The effect of a discharge rate of 50 mA constant current on cell voltage and plateau hour, as well as the voltage-current and current density-power density were measured and analysed. The electrode degradation after discharge cycling was characterized by structural and surface methods. The oxidation of the electrode surface further blocked the utilization of the Zn anode and was identified as a cause for the failure of the cell.

  9. Temperature measurements in hypersonic air flows using laser-induced O2 fluorescence

    NASA Technical Reports Server (NTRS)

    Laufer, Gabriel; Mckenzie, Robert L.

    1988-01-01

    An investigation is reported of the use of laser-induced fluorescence on oxygen for the measurement of air temperature and its fluctuations owing to turbulence in hypersonic wind tunnel flows. The results show that for temperatures higher than 60 K and densities higher than 0.01 amagat, the uncertainty in the temperature measurement can be less than 2 percent if it is limited by photon-statistical noise. The measurement is unaffected by collisional quenching and, if the laser fluence is kept below 1.5 J/sq cm, it is also unaffected by nonlinear effects which are associated with depletion of the absorbing states.

  10. Formation of oxygen vacancies and Ti3+ state in TiO2 thin film and enhanced optical properties by air plasma treatment

    PubMed Central

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-01-01

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti3+, Ti4+, O2−, oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti3+ and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti3+ and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift. PMID:27572095

  11. RuO2 nanoparticles decorated MnOOH/C as effective bifunctional electrocatalysts for lithium-air battery cathodes with long-cycling stability

    NASA Astrophysics Data System (ADS)

    Kim, Gil-Pyo; Lim, Dongwook; Park, Inyeong; Park, Hyelee; Shim, Sang Eun; Baeck, Sung-Hyeon

    2016-08-01

    Manganite (MnOOH) is one of the most effective electrocatalysts for oxygen reduction reaction (ORR), and RuO2 nanoparticles exhibit high activity for oxygen evolution reaction (OER). We herein report a facile means of producing well dispersed RuO2/MnOOH on Ketjen black (RuO2/MnOOH/C) as a bifunctional catalyst for lithium-air (Li-air) batteries. RuO2/MnOOH/C was simply synthesized using a hydrothermal/precipitation based method, and was used as a cathode for a Li-air battery using a Swagelok-type cell. The importance of dispersing active catalysts on a carbon support was clearly demonstrated by textural, charge-discharge voltammetric, and electrochemical impedance spectroscopic (EIS) analyses, comparing results with a catalyst produced by physically mixing RuO2/MnOOH with carbon (RuO2/MnOOH + C). RuO2/MnOOH/C showed low overpotential and stable cycleability up to 170th cycles with 1000 mAh g-1 of charge-discharge capacity, which was attributed to its enhanced active surface area and low charge-transfer resistance. The results obtained suggest that this strategy can be widely applied to bifunctional electrocatalysis, such as secondary batteries and regenerative fuel cell (RFC).

  12. Formation of oxygen vacancies and Ti(3+) state in TiO2 thin film and enhanced optical properties by air plasma treatment.

    PubMed

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-01-01

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti(3+), Ti(4+), O(2-), oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti(3+) and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti(3+) and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift. PMID:27572095

  13. Impact of air-exposure on the chemical and electronic structure ofZnO:Zn3N2 thin films

    SciTech Connect

    Bar, M.; Ahn, K.-S.; Shet, S.; Yan, Y.; Weinhardt, L.; Fuchs, O.; Blum, M.; Pookpanratana, S.; George, K.; Yang, W.; Denlinger, J.D.; Al-Jassim, M.; Heske, C.

    2008-09-08

    The chemical and electronic surface structure of ZnO:Zn3N2 ("ZnO:N") thin films with different N contents was investigated by soft x-ray emission spectroscopy. Upon exposure to ambient air (in contrast to storage in vacuum), the chemical and electronic surface structure of the ZnO:N films changes substantially. In particular, we find that the Zn3N2/(Zn3N2+ZnO) ratio decreases with exposure time and that this change depends on the initial N content. We suggest a degradation mechanism based on the reaction of the Zn3N2 content with atmospheric humidity.

  14. Interaction of multiple atmospheric-pressure micro-plasma jets in small arrays: He/O2 into humid air

    NASA Astrophysics Data System (ADS)

    Babaeva, Natalia Yu; Kushner, Mark J.

    2014-02-01

    Arrays of atmospheric-pressure plasma jets are being considered as a means to increase the area being treated in surface modification and in plasma medicine in particular. A unique challenge of scaling plasma jet arrays is that individual plasma jets in an array tend to interact with each other, which can lead to quenching of some individual jets. To investigate these potential interactions, a computational study of one-, two- and three-tube arrays of micro-plasma jet arrays was performed. An atmospheric-pressure He/O2 = 99.8/0.2 mixture was flowed through the tubes into humid room air. We found that the jets interact through electrostatic, hydrodynamic and photolytic means. The hydrodynamic interactions result from the merging of individual He channels emerging from individual tubes as air diffuses into the extended gas jets. Ionization waves (IWs) or plasma bullets, which form the jets on the boundaries of an array, encounter higher mole fractions of air earlier compared with the center jet and so are slower or are quenched earlier. The close proximity of the jets produces electrostatic repulsion, which affects the trajectories of the IWs. If the jets are close enough, photoionizing radiation from their neighbors is an additional form of interaction. These interactions are sensitive to the spacing of the jets.

  15. Chemical reactivity of aprotic electrolytes on a solid Li2O2 surface: screening solvents for Li-air batteries

    NASA Astrophysics Data System (ADS)

    Laino, Teodoro; Curioni, Alessandro

    2013-09-01

    Nowadays, simulation techniques are routinely used to generate accurate models of the structures of crystalline and amorphous solids, to study surfaces, defects and the properties of complex systems, and to screen possible candidate materials for the most diverse types of technological applications. The screening of novel molecular structures has been so far pursued by calculation of intrinsic properties with first-principle methods. Still, the use of intrinsic properties as scoring functions may not always be optimal for systems of high complexity. In these cases, increasingly detailed and realistic simulations that take into account the interaction with the surrounding molecules are of crucial importance. In this paper, we present an effective way to screen different solvents with respect to their chemical stability versus Li2O2 solid particles. To achieve this, the minimum energy paths for different types of reactions of a series of aprotic solvents (acetonitrile and pivalonitrile, dimethyl sulphoxide, N-methyl-2-pyrrolidone and some of its derivatives, penta ethylene glycol (PEG-5) and a fluorinated derivative) with solid Li2O2 are computed and reported. From these data, we can extract the reaction energy barriers, which compare extremely well with the available experimental data and offer a convenient way for screening and designing suitable solvents for Li-air batteries from first-principle calculations.

  16. Air-sea gas transfer for two gases of different solubility (CO2 and O2)

    NASA Astrophysics Data System (ADS)

    Rutgersson, A.; Andersson, A.; Sahlée, E.

    2016-05-01

    At the land-based marine measuring site Östergarnsholm in the Baltic Sea, the eddy covariance technique was used to measure air-sea fluxes of carbon dioxide and oxygen. High- frequency measurements of oxygen were taken with a Microx TX3 optode using the luminescence lifetime technique. The system gives reasonable oxygen fluxes after the limited frequency response of the sensor was corrected for. For fluxes of carbon dioxide the LICOR-7500 instrument was used. Using flux data to estimate transfer velocities indicates higher transfer velocity for oxygen compared to carbon dioxide for winds above 5 m/s. There are too few data for any extensive conclusions, but a least-square fit of the data gives a cubic wind speed dependence of oxygen corresponding to k 660 = 0.074U 3 10. The more effective transfer for oxygen compared to carbon dioxide above 5 m/s is most likely due to enhanced efficiency of oxygen exchange across the surface. Oxygen has lower solubility compared with carbon dioxide and might be more influenced by near surface processes such as microscale wave breaking or sea spray.

  17. Relative rate study of the kinetics, mechanism, and thermodynamics of the reaction of chlorine atoms with CF3CF═CH2 (HFO-1234yf) in 650-950 Torr of N2 or N2/O2 diluent at 296-462 K.

    PubMed

    Kaiser, E W; Wallington, T J

    2012-06-21

    The rate constant of the reaction Cl + CF(3)CF═CH(2) (k(1)) has been measured relative to several reference species using the relative rate technique with either gas chromatographic analysis with flame-ionization detection (GC/FID) or Fourier transform infrared (FTIR) analysis. Cl atoms were generated by UV irradiation of Cl(2)/CF(3)CF═CH(2)/reference/N(2)/O(2) mixtures. At 300-400 K in the presence of >20 Torr O(2), k(1) = 1.2 × 10(-11) e((+1100/RT)) cm(3) molecule(-1) s(-1). In N(2) diluent, k(1) has a sharp negative temperature coefficient resulting from the relatively small exothermicity of the following reactions: (1a) Cl + CF(3)CF═CH(2) ↔ CF(3)CFClCH(2)(•); (1b) Cl + CF(3)CF═CH(2) ↔ CF(3)CF(•)CH(2)Cl (reaction 1), which were determined in these experiments to be ∼16.5 (±2.0) kcal mol(-1). This low exothermicity causes reaction 1 to become significantly reversible even at ambient temperature. The rate constant ratio for the reaction of the chloroalkyl radicals formed in reaction 1 with Cl(2) (k(2)) or O(2) (k(3)) was measured to be k(2)/k(3) = 0.4 e(-(3000/RT)) for 300-400 K. At 300 K, k(2)/k(3) = 0.0026. The reversibility of reaction 1 combined with the small value of k(2)/k(3) leads to a sensitive dependence of k(1) on the O(2) concentration. Products measured by GC/FID as a function of temperature are CF(3)CFClCH(2)Cl, CF(3)COF, and CH(2)Cl(2). The mechanism leading to these products is discussed. The rate constant for the reaction Cl + CF(3)CFClCH(2)Cl (k(11)) was measured as a function of temperature (300-462 K) at 760 Torr to be k(11) = 8.2 × 10(-12) e(-(4065/RT)) cm(3) molecule(-1) s(-1). Rate constants relative to CH(4) for the reactions of Cl with the reference compounds CH(3)Cl, CH(2)Cl(2), and CHCl(3) were measured at 470 K to resolve a literature discrepancy. (R = 1.986 cal K(-1) mol(-1)). PMID:22229765

  18. Implications of the Formation of Small Polarons in Li2O2 for Li-Air Batteries

    SciTech Connect

    Kang, J.; Jung, Y. S.; Wei, S. H.; Dillon, A. C.

    2012-01-15

    Lithium-air batteries (LABs) are an intriguing next-generation technology due to their high theoretical energy density of {approx}11 kWh/kg. However, LABs are hindered by both poor rate capability and significant polarization in cell voltage, primarily due to the formation of Li{sub 2}O{sub 2} in the air cathode. Here, by employing hybrid density functional theory, we show that the formation of small polarons in Li{sub 2}O{sub 2} limits electron transport. Consequently, the low electron mobility {mu} = 10{sup -10}-10{sup -9} cm{sup 2}/V s contributes to both the poor rate capability and the polarization that limit the LAB power and energy densities. The self-trapping of electrons in the small polarons arises from the molecular nature of the conduction band states of Li{sub 2}O{sub 2} and the strong spin polarization of the O 2p state. Our understanding of the polaronic electron transport in Li{sub 2}O{sub 2} suggests that designing alternative carrier conduction paths for the cathode reaction could significantly improve the performance of LABs at high current densities.

  19. Satellite retrieval of cloud properties from the O2 A-band for air quality and climate applications

    NASA Astrophysics Data System (ADS)

    Wang, P.; Stammes, P.; van der A, R.

    2009-04-01

    The FRESCO (Fast Retrieval Scheme for Clouds from the Oxygen A-band) algorithm has been used to retrieve cloud information from measurements of the O2 A-band around 760 nm by GOME, SCIAMACHY and GOME-2. The cloud parameters retrieved by FRESCO are the effective cloud fraction and cloud pressure, which are used for cloud correction in the retrieval of trace gases like O3 and NO2. To improve the cloud pressure retrieval for partly cloudy scenes, single Rayleigh scattering has been included in an improved version of the algorithm, called FRESCO+. FRESCO+ gives more reliable cloud pressures over partly cloudy pixels. Simulations and comparisons with ground-based radar measurements of clouds shows that the FRESCO+ cloud pressure is about the optical midlevel of the cloud. Globally averaged, the FRESCO+ cloud pressure is about 50 hPa higher than the FRESCO cloud pressure, while the FRESCO+ effective cloud fraction is about 0.01 larger. From ground-based validation (P. Wang et al., Atmos. Chem. Phys., 8, 6565-6576, 2008) it appears that the FRESCO+ cloud retrievals improve the retrieval of tropospheric NO2 as compared to FRESCO. So FRESCO+ contributes to better monitoring of air quality from space. The FRESCO+ cloud algorithm has been applied to GOME and SCIAMACHY measurements since the beginning of the missions. Monthly averaged SCIAMACHY FRESCO+ effective cloud fraction and cloud pressure maps show similar patterns as the ISCCP cloud maps, although there are some differences, due to the different meaning of the cloud products and due to the fact that photons in the O2 A-band penetrate into clouds. The 6-year averaged seasonal cloud maps from SCIAMACHY data have good agreement with the global circulation patterns. Therefore, the FRESCO+ products are not only efficient for cloud correction of trace gas retrievals but also contribute additional information for climate research.

  20. Visible-Light-Responsive Catalysts Using Quantum Dot-Modified TiO2 for Air and Water Purification

    NASA Technical Reports Server (NTRS)

    Coutts, Janelle L.; Hintze, Paul E.; Clausen, Christian; Richards, Jeffrey Todd

    2014-01-01

    Photocatalysis, the oxidation or reduction of contaminants by light-activated catalysts, utilizing titanium dioxide (TiO2) as the catalytic substrate has been widely studied for trace contaminant control in both air and water applications. The interest in this process is due primarily to its low energy consumption and capacity for catalyst regeneration. Titanium dioxide requires ultraviolet light for activation due to its relatively large band gap energy of 3.2 eV. Traditionally, Hg-vapor fluorescent light sources are used in PCO reactors; however, the use of mercury precludes the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure. The development of a visible-light responsive (VLR) TiO2-based catalyst would eliminate the concerns over mercury contamination. Further, VLR development would allow for the use of ambient visible solar radiation or highly efficient LEDs, both of which would make PCO approaches more efficient, flexible, economical, and safe. Though VLR catalyst development has been an active area of research for the past two decades, there are few commercially available VLR catalysts. Those VLR catalysts that are commercially available do not have adequate catalytic activity, in the visible region, to make them competitive with those operating under UV irradiation. This study was initiated to develop more effective VLR catalysts through a novel method in which quantum dots (QD) consisting of narrow band gap semiconductors (e.g., CdS, CdSe, PbS, ZnSe, etc.) are coupled to TiO2 via two preparation methods: 1) photodeposition and 2) mechanical alloying using a high-speed ball mill. A library of catalysts was developed and screened for gas and aqueous phase applications using ethanol and 4-chlorophenol as the target contaminants, respectively. Both target compounds are well studied in photocatalytic systems and served as model contaminants for this research. Synthesized catalysts were compared in terms of

  1. The use of radiative transition rates to study the changes in the excitation of Cu ions in a Ne glow discharge caused by small additions of H2, O2 and N2

    NASA Astrophysics Data System (ADS)

    Weiss, Z.; Steers, E. B. M.; Mushtaq, S.; Hoffmann, V.; Pickering, J. C.

    2016-04-01

    The excitation of Cu+ ions in a Ne glow discharge with small additions of H2, O2 and N2 was studied. Ratios of radiative transition rates between different Cu II levels in a discharge in neon, with and without the molecular gas added, were calculated, and the formalism of transition rate ratio (TRR) diagrams was developed and used to study the changing excitation conditions. Virtually no changes in the excitation of Cu+ ions occur in a neon discharge if nitrogen is added. Additions of hydrogen and oxygen to neon as the discharge gas affect excitation of the 4d, 5s and some other Cu II levels in the vicinity of the ionization energy of neon (21.56 eV). Also some lower Cu II levels, excited by radiative decay of those higher energy levels, are affected. The 4p 3P2 level at 15.96 eV is enhanced by additions of hydrogen. It was suggested that this enhancement is caused by the asymmetric charge transfer reaction between neutral copper atoms and the H2+ molecular ions.

  2. Superior Performance of High-Velocity Oxyfuel-Sprayed Nanostructured TiO2 in Comparison to Air Plasma-Sprayed Conventional Al2O3-13TiO2

    NASA Astrophysics Data System (ADS)

    Lima, R. S.; Marple, B. R.

    2005-09-01

    Air plasma-sprayed conventional alumina-titania (Al2O3-13wt.%TiO2) coatings have been used for many years in the thermal spray industry for antiwear applications, mainly in the paper, printing, and textile industries. This work proposes an alternative to the traditional air plasma spraying of conventional aluminatitania by high-velocity oxyfuel (HVOF) spraying of nanostructured titania (TiO2). The microstructure, porosity, hardness (HV 300 g), crack propagation resistance, abrasion behavior (ASTM G65), and wear scar characteristics of these two types of coatings were analyzed and compared. The HVOF-sprayed nanostructured titania coating is nearly pore-free and exhibits higher wear resistance when compared with the air plasma-sprayed conventional alumina-titania coating. The nanozones in the nanostructured coating act as crack arresters, enhancing its toughness. By comparing the wear scar of both coatings (via SEM, stereoscope microscopy, and roughness measurements), it is observed that the wear scar of the HVOF-sprayed nanostructured titania is very smooth, indicating plastic deformation characteristics, whereas the wear scar of the air plasma-sprayed alumina-titania coating is very rough and fractured. This is considered to be an indication of a superior machinability of the nanostructured coating.

  3. Selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation.

    PubMed

    Miao, Guang; Ye, Feiyan; Wu, Luoming; Ren, Xiaoling; Xiao, Jing; Li, Zhong; Wang, Haihui

    2015-12-30

    This study investigates selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation. The TiO2/SiO2 adsorbents were prepared and then characterized by N2 adsorption, X-ray diffraction and X-ray photoelectron spectroscopy. Adsorption isotherms, selectivity and kinetics of TiO2/SiO2 were measured in a UV built-in batch reactor. It was concluded that (a) with the employment of UV-irradiation, high organosulfur uptake of 5.12 mg/g was achieved on the optimized 0.3TiO2/0.7SiO2 adsorbent at low sulfur concentration of 15 ppmw-S, and its adsorption selectivity over naphthalene was up to 325.5; (b) highly dispersed TiO2 served as the photocatalytic sites for DBT oxidation, while SiO2 acted as the selective adsorption sites for the corresponding oxidized DBT using TiO2 as a promoter, the two types of active sites worked cooperatively to achieve the high adsorption selectivity of TiO2/SiO2; (c) The kinetic rate-determining step for the UV photocatalysis-assisted adsorptive desulfurization (PADS) over TiO2/SiO2 was DBT oxidation; (d) consecutive adsorption-regeneration cycles suggested that the 0.3TiO2/0.7SiO2 adsorbent can be regenerated by acetonitrile washing followed with oxidative air treatment. This work demonstrated an effective PADS approach to greatly enhance adsorption capacity and selectivity of thiophenic compounds at low concentrations for deep desulfurization under ambient conditions. PMID:26223016

  4. Ozone generation in a kHz-pulsed He-O2 capillary dielectric barrier discharge operated in ambient air

    NASA Astrophysics Data System (ADS)

    Sands, Brian L.; Ganguly, Biswa N.

    2013-12-01

    The generation of reactive oxygen species using nonequilibrium atmospheric pressure plasma jet devices has been a subject of recent interest due to their ability to generate localized concentrations from a compact source. To date, such studies with plasma jet devices have primarily utilized radio-frequency excitation. In this work, we characterize ozone generation in a kHz-pulsed capillary dielectric barrier discharge configuration comprised of an active discharge plasma jet operating in ambient air that is externally grounded. The plasma jet flow gas was composed of helium with an admixture of up to 5% oxygen. A unipolar voltage pulse train with a 20 ns pulse risetime was used to drive the discharge at repetition rates between 2-25 kHz. Using UVLED absorption spectroscopy centered at 255 nm near the Hartley-band absorption peak, ozone was detected over 1 cm from the capillary axis. We observed roughly linear scaling of ozone production with increasing pulse repetition rate up to a "turnover frequency," beyond which ozone production steadily dropped and discharge current and 777 nm O(5P→5S°) emission sharply increased. The turnover in ozone production occurred at higher pulse frequencies with increasing flow rate and decreasing applied voltage with a common energy density of 55 mJ/cm3 supplied to the discharge. The limiting energy density and peak ozone production both increased with increasing O2 admixture. The power dissipated in the discharge was obtained from circuit current and voltage measurements using a modified parallel plate dielectric barrier discharge circuit model and the volume-averaged ozone concentration was derived from a 2D ozone absorption measurement. From these measurements, the volume-averaged efficiency of ozone production was calculated to be 23 g/kWh at conditions for peak ozone production of 41 mg/h at 11 kV applied voltage, 3% O2, 2 l/min flow rate, and 13 kHz pulse repetition rate, with 1.79 W dissipated in the discharge.

  5. Agent consumption with the Zeus® in the automated closed circuit anesthesia mode with O2/air mixtures

    PubMed Central

    2014-01-01

    Background Earlier software versions of the Zeus® (Lübeck, Dräger, Germany) failed to provide true closed circuit anesthesia (CCA) conditions. We examined whether the latest software (SW 4.03 MK 04672–00) achieves this goal. Methods In 8 ASA I–III patients, the CCA mode of the Zeus® was used to maintain the inspired O2 (FIO2) and end-expired sevoflurane % (FAsevo) at 50 and 1.8%, respectively. The fresh gas flow (FGF) of O2 and air and the sevoflurane injection rate (=Vinjsevo, mL liquid sevo/h) were videotaped from the control screen and entered offline into a spreadsheet. Cumulative sevoflurane usage during early wash-in (=0-1 min, CDsevo0-1), late wash-in (=1-5 min, CDsevo1-5), and maintenance (=5-60 min, CDsevo5-60) was calculated, and Vinjsevo between 1 and 60 min was compared with published uptake data. Results FAsevo reached 1.8% within 101 (23) sec. CDsevo0-1 was between 1.24 (0.03) and 3.01(0.25) mL (a range is provided because no absolute Vinjsevo values were displayed once Vinjsevo was > 100 mL/h, which occurred between 15 ± 2 and 46 ± 6 sec). CDsevo1-5 was 0.81 (0.37) mL, and CDsevo5-60 was 4.63 (0.94) mL. The Vinjsevo pattern between 1 and 60 min matched previously published uptake data. Brief high FGF periods were used to maintain the target FIO2, and to refill the reservoir bag after external pressure had been applied to the abdomen; subsequent “spikes” wasted 0.08-0.19 mL and 0.14-0.49 mL sevoflurane (1-3% and 3-9% of total agent usage between 1 and 60 min, respectively). Conclusion Under the conditions specified, the Zeus® approaches CCA conditions so closely that further reductions in agent usage would have minimal economic significance. PMID:25056252

  6. Direct Measurement of Air-Sea Exchange of N2O5 and ClNO2 at a Polluted Coastal Site (Invited)

    NASA Astrophysics Data System (ADS)

    Bertram, T. H.; Kim, M.; Ryder, O. S.; Farmer, D.

    2013-12-01

    The reactive uptake of N2O5 at aqueous interfaces can serve as both an efficient NOx removal mechanism and regionally significant halogen activation process through the production of photo-labile ClNO2 molecules. Both the reaction rate and ClNO2 product yield are a complex function of the chemical composition and chloride molarity of the reactive surface. To date, analysis of the impact of N2O5 chemistry on oxidant loadings in the marine boundary layer has been limited to reactions occurring on aerosol particles, with little attention paid to reactions occurring at the air-sea interface. Here, we report the first direct measurements of the air-sea flux of N2O5 and ClNO2 made via eddy covariance in the polluted marine boundary layer in La Jolla, CA. We observe rapid N2O5 deposition to the ocean surface, while ClNO2 deposition rates were significantly lower and fastest during the first three hours following sunset. The results are interpreted using a time-dependent box-model, suggesting that under conditions characterized by shallow marine boundary layer heights (< 100 m) and representative aerosol reactive uptake coefficients (< 0.01), N2O5 deposition to the ocean surface can account for over 50% of the total N2O5 loss rate.

  7. Synthesis of hectorite-TiO2 and kaolinite-TiO2 nanocomposites with photocatalytic activity for the degradation of model air pollutants

    SciTech Connect

    Destaillats, Hugo; Kibanova, D.; Trejo, M.; Destaillats, H.; Cervini-Silva, J.

    2008-03-01

    We studied the synthesis and photocatalytic activity of small-sized TiO{sub 2} supported on hectorite and kaolinite. Deposition of TiO{sub 2} on the clay mineral surface was conducted by using a sol-gel method with titanium isopropoxide as precursor. Anatase TiO{sub 2} particles formation was achieved by hydrothermal treatment at 180 C. Material characterization was conducted using XRD, SEM, XPS, ICP-OES, BET and porosimetry analysis. Efficiency in synthesizing clay-TiO{sub 2} composites depended strongly on the clay mineral structure. Incorporation of anatase in hectorite, an expandable clay mineral, was found to be very significant (> 36 wt.% Ti) and to be followed by important structural changes at the clay mineral surface. Instead, no major structural modifications of the clay were observed for kaolinite-TiO{sub 2}, as compared with the untreated material. Photocatalytic performance of clay-TiO{sub 2} composites was evaluated with ATR-FTIR following the oxidation of adsorbed toluene and d-limonene, two model air pollutants. In either case, the photocatalytic removal efficiency of these hydrophobic substrates by the synthesized clay-TiO{sub 2} composites was comparable to that observed using pure commercial TiO{sub 2} (Degussa P25).

  8. Reactive uptake coefficients for N2O5 determined from aircraft measurements during the Second Texas Air Quality Study: Comparison to current model parameterizations

    NASA Astrophysics Data System (ADS)

    Brown, Steven S.; Dubé, William P.; Fuchs, Hendrik; Ryerson, Thomas B.; Wollny, Adam G.; Brock, Charles A.; Bahreini, Roya; Middlebrook, Ann M.; Neuman, J. Andrew; Atlas, Elliot; Roberts, James M.; Osthoff, Hans D.; Trainer, Michael; Fehsenfeld, Frederick C.; Ravishankara, A. R.

    2009-04-01

    This paper presents determinations of reactive uptake coefficients for N2O5, γ(N2O5), on aerosols from nighttime aircraft measurements of ozone, nitrogen oxides, and aerosol surface area on the NOAA P-3 during Second Texas Air Quality Study (TexAQS II). Determinations based on both the steady state approximation for NO3 and N2O5 and a plume modeling approach yielded γ(N2O5) substantially smaller than current parameterizations used for atmospheric modeling and generally in the range 0.5-6 × 10-3. Dependence of γ(N2O5) on variables such as relative humidity and aerosol composition was not apparent in the determinations, although there was considerable scatter in the data. Determinations were also inconsistent with current parameterizations of the rate coefficient for homogenous hydrolysis of N2O5 by water vapor, which may be as much as a factor of 10 too large. Nocturnal halogen activation via conversion of N2O5 to ClNO2 on chloride aerosol was not determinable from these data, although limits based on laboratory parameterizations and maximum nonrefractory aerosol chloride content showed that this chemistry could have been comparable to direct production of HNO3 in some cases.

  9. Semi-rechargeable Aluminum-Air Battery with a TiO2 Internal Layer with Plain Salt Water as an Electrolyte

    NASA Astrophysics Data System (ADS)

    Mori, Ryohei

    2016-07-01

    To develop a semi-rechargeable aluminum-air battery, we attempted to insert various kinds of ceramic oxides between an aqueous NaCl electrolyte and an aluminum anode. From cyclic voltammetry experiments, we found that some of the ceramic oxide materials underwent an oxidation-reduction reaction, which indicates the occurrence of a faradaic electrochemical reaction. Using a TiO2 film as an internal layer, we successfully prepared an aluminum-air battery with secondary battery behavior. However, cell impedance increased as the charge/discharge reactions proceeded probably because of accumulation of byproducts in the cell components and the air cathode. Results of quantum calculations and x-ray photoelectron spectroscopy suggest the possibility of developing an aluminum rechargeable battery using TiO2 as an internal layer.

  10. Semi-rechargeable Aluminum-Air Battery with a TiO2 Internal Layer with Plain Salt Water as an Electrolyte

    NASA Astrophysics Data System (ADS)

    Mori, Ryohei

    2016-04-01

    To develop a semi-rechargeable aluminum-air battery, we attempted to insert various kinds of ceramic oxides between an aqueous NaCl electrolyte and an aluminum anode. From cyclic voltammetry experiments, we found that some of the ceramic oxide materials underwent an oxidation-reduction reaction, which indicates the occurrence of a faradaic electrochemical reaction. Using a TiO2 film as an internal layer, we successfully prepared an aluminum-air battery with secondary battery behavior. However, cell impedance increased as the charge/discharge reactions proceeded probably because of accumulation of byproducts in the cell components and the air cathode. Results of quantum calculations and x-ray photoelectron spectroscopy suggest the possibility of developing an aluminum rechargeable battery using TiO2 as an internal layer.

  11. The Use of Small-Particle Sized TiO2 Supported on Clays as Photocatalytic Materials: A Low- Cost Alternative Technology for the Degradation of Air Pollutants

    NASA Astrophysics Data System (ADS)

    Kibanova, D.; Trejo, M.; Destaillats, H.; Cervini-Silva, J.

    2007-05-01

    Assisted photocatalysis by TiO2 is an advanced oxidation process that has been employed for air and water remediation. Clays are natural porous materials bearing high surface areas and interlayer spacing that allows entrapment of small-sized particles. Pillared clays exchanged with small-sized TiO2 can constitute materials with interesting photocatalytic properties because high surface area values and large contents of mesospores, which enables analyte trapping. Furthermore, intercalation at the clay interlayer enables TiO2 to become more resistant to aggregation when in solution. Just recently it has been reported that clays can lead to increases in the photocatalytic activity of TiO2 when the mesopores size is adequate to host organic solutes and ensure their effective interaction with the TiO2 particles. In this paper we study the photocatalytic properties of small-sized TiO2 supported on the following clay samples: Montmorillonite [SWy-2, Na0.2Ca0.1Al2Si4O10(OH)2(H2O)10 ] from Crook Country, Wyoming, USA; Hectorite [SHCa-1, Na0.4Mg2.7Li0.3Si4O10(OH)2 ] from San Bernardino. Country, California, USA; Kaolinite [KGa-1b, Al2Si2O5(OH)4 ] from Washington Country, Georgia, USA. Deposition of TiO2 on the clay surface was conducted by using a sol-gel synthetic method. Anatase TiO2 particles transformation at the clay interlayer was achieved by thermic treatment at 180 °C. Material characterization was conducted using FTIR microspectroscopy, Scanning Electron Microscopy (SEM), and XRD analysis. The organic compound used as probe was ethanol

  12. ABA induces H2O2 production in guard cells, but does not close the stomata on Vicia faba leaves developed at high air humidity

    PubMed Central

    Arve, Louise E; Carvalho, Dália RA; Olsen, Jorunn E; Torre, Sissel

    2014-01-01

    Plants developed under constant high (> 85%) relative air humidity (RH) have larger stomata that are unable to close completely. One of the hypotheses for the less responsive stomata is that the plants have reduced sensitivity to abscisic acid (ABA). Both ABA and darkness are signals for stomatal closure and induce the production of the secondary messenger hydrogen peroxide (H2O2). In this study, the ability of Vicia faba plants developed in moderate or high RH to close the stomata in response to darkness, ABA and H2O2 was investigated. Moreover, the ability of the plants to produce H2O2 when treated with ABA or transferred to darkness was also assessed. Our results show that the ABA concentration in moderate RH is not increased during darkness even though the stomata are closing. This indicates that stomatal closure in V. faba during darkness is independent of ABA production. ABA induced both H2O2 production and stomatal closure in stomata formed at moderate RH. H2O2 production, as a result of treatment with ABA, was also observed in stomata formed at high RH, though the closing response was considerably smaller as compared with moderate RH. In either RH, leaf ABA concentration was not affected by darkness. Similarly to ABA treatment, darkness elicited both H2O2 production and stomatal closure following plant cultivation at moderate RH. Contrary to this, neither H2O2 production nor stomatal closure took place when stomata were formed at high RH. These results suggest that the reduced stomatal response in plants developed in continuous high RH is caused by one or more factors downstream of H2O2 in the signaling pathway toward stomatal closure. PMID:25763494

  13. Comparative study on the reactivity of Fe/Cu bimetallic particles and zero valent iron (ZVI) under different conditions of N2, air or without aeration.

    PubMed

    Xiong, Zhaokun; Lai, Bo; Yang, Ping; Zhou, Yuexi; Wang, Juling; Fang, Shuping

    2015-10-30

    In order to further compare the degradation capacity of Fe(0) and Fe/Cu bimetallic system under different aeration conditions, the mineralization of PNP under different aeration conditions has been investigated thoroughly. The results show that the removal of PNP by Fe(0) or Fe/Cu system followed the pseudo-first-order reaction kinetics. Under the optimal conditions, the COD removal efficiencies obtained through Fe(0) or Fe/Cu system under different aeration conditions followed the trend that Fe/Cu (air)>Fe/Cu (N2: 0-30 min, air: 30-120 min)>control-Fe (air)>Fe/Cu (without aeration)>Fe/Cu (N2)>control-Fe (N2). It revealed that dissolved oxygen (DO) could improve the mineralization of PNP, and Cu could enhance the reactivity of Fe(0). In addition, the degradation of PNP was further analyzed by using UV-vis, FTIR and GC/MS, and the results suggest that Fe/Cu bimetallic system with air aeration could completely break the benzene ring and NO2 structure of PNP and could generate the nontoxic and biodegradable intermediate products. Meanwhile, most of these intermediate products were further mineralized into CO2 and H2O, which brought about a high COD removal efficiency (83.8%). Therefore, Fe/Cu bimetallic system with air aeration would be a promising process for toxic refractory industry wastewater. PMID:25978189

  14. Measurements of N2O and SF6 mole fraction between 1977 and 1998 in archived air samples from Cape Meares, Oregon

    NASA Astrophysics Data System (ADS)

    Rolfe, T.; Rice, A. L.; Radda, J.

    2015-12-01

    The quantification of greenhouse gas concentrations in the atmosphere is important for monitoring imbalances in their global budgets between sources and sinks and their changes in time. Nitrous oxide (N2O) is a strong radiative trace gas with a GWP of ~300 times CO2 over a 100 year period and an atmospheric lifetime of ~100 years. The preindustrial revolution background concentration of N2O was ~270 ppb. Today, the concentration is ~330 ppb. Sulfur hexafluoride (SF6) is another potent greenhouse gas with a long lifetime (800 to 3200 years) and very large GWP (~23000 times CO2 over a 100 year period). Its current atmospheric concentration is low (~8 ppt today). Direct measurements of N2O and SF6 in air prior to the mid-1990s are few. Over 200 archived atmospheric gas samples collected at Cape Meares, Oregon between 1977 and 1998 were analyzed for their N2O and SF6 concentrations using an Agilent (model 6890 N) gas chromatograph fitted with an electron capture detector using a two column "heart-cut" technique. Precision of measurement of N2O and SF6 is calculated at 0.13% (1σ) and 1.35% (1σ) respectively. N2O concentrations in the late 1970s and early 1980s average around 303 ppb, rising to 309 ppb in the early 1990s. Between 1980 and 1990, the increase in N2O concentrations is found to be ~0.5 ppb/yr. SF6 concentrations during the late 1970s and early 1980s average around 0.9 ppt and rise slowly, reaching 1.6 ppt in the 1990s. We find that the increase in SF6 between 1980 and 1990 to be ~0.07 ppt/yr. We also discuss sample integrity in storage and observed temporal trends of N2O and SF6.

  15. α-MnO2 nanowire catalysts with ultra-high capacity and extremely low overpotential in lithium-air batteries through tailored surface arrangement.

    PubMed

    Song, Kyeongse; Jung, Jaepyeong; Heo, Yoon-Uk; Lee, Yoon Cheol; Cho, Kyeongjae; Kang, Yong-Mook

    2013-12-14

    We here report on very high capacity (11,000 mA h g(-1)), superb rate capability (4500 mA h g(-1) at 5000 mA g(-1)) and high reversibility of Li-air batteries using α-MnO2 NW catalysts mainly associated with their relatively large amount of Mn(3+) exposed on the NW surface and a unique mechanism for deposition of discharge products. Our findings of the unprecedentedly fast Li ion transport and reversible formation-decomposition of discharge products attributed to the modified surface arrangement of α-MnO2 NWs suggest a strategy for achieving high-power Li-air batteries in combination with nano-architecture tailoring. PMID:24154608

  16. Performance enhancement of an experimental air conditioning system by using TiO2/methanol nanofluid in heat pipe heat exchangers

    NASA Astrophysics Data System (ADS)

    Monirimanesh, Negin; Nowee, S. Mostafa; Khayyami, Shideh; Abrishamchi, Iman

    2016-05-01

    The effect of using nanofluid in thermosyphon-type heat pipe heat exchangers on energy conservation of an air-conditioning system was sought in this study. Innovatively, two heat exchangers in-series were deployed using TiO2/methanol nanofluids with 0-4 wt% concentrations as working fluids. The impacts of temperature and relative humidity on the effectiveness of 2 and 4-row heat exchangers were analyzed experimentally and more that 40 % energy saving was obtained.

  17. Preparation and characterization of amine-functionalized SiO 2/TiO 2 films for formaldehyde degradation

    NASA Astrophysics Data System (ADS)

    Photong, Somjate; Boonamnuayvitaya, Virote

    2009-09-01

    This paper investigated the gaseous formaldehyde degradation by the amine-functionalized SiO 2/TiO 2 photocatalytic films for improving indoor air quality. The films were synthesized via the co-condensation reaction of methyltrimethoxysilane (MTMOS) and 3-aminopropyltrimethoxysilane (APTMS). The physicochemical properties of prepared photocatalysts were characterized with N 2 adsorption/desorption isotherms measurement, X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FT/IR). The effect of amine-functional groups and the ratio of MTMOS/APTMS precursors on the formaldehyde adsorption and photocatalytic degradation were investigated. The results showed that the formaldehyde adsorption and photocatalytic degradation of the APTMS-functionalized SiO 2/TiO 2 film was higher than that of SiO 2/TiO 2 film due to the surface adsorption on amine sites and the relatively high of the specific surface area of the APTMS-functionalized SiO 2/TiO 2 film (˜15 times higher than SiO 2/TiO 2). The enhancement of the formaldehyde degradation of the film can be attributed to the synergetic effect of adsorption and subsequent photocatalytic decomposition. The repeatability of photocatalytic film was also tested and the degradation efficiency was 91.0% of initial efficiency after seven cycles.

  18. High-Precision Measurement of The Oxygen Isotopic Composition of Tropospheric O2: Implications for Δ17O of air as a Biosignature

    NASA Astrophysics Data System (ADS)

    Young, E. D.; Ziegler, K.

    2006-05-01

    Here we present high-precision measurements of 18O/16O and 17O/16O in samples of tropospheric O2 using a standard calibrated with measurements of terrestrial and extraterrestrial rock samples. These new data provide a measure of Δ17O on an absolute scale that aids in the interpretation of the cause of the disparity in Δ17O between O2 in the troposphere and terrestrial rocks. We measured the isotopic composition of four separate aliquotes of ground-level air O2. Oxygen was isolated from air cryogenically using molecular sieve substrates. Correction was made for the influence of Ar scattered across the Faraday collectors (~0.06 per mil in δ17O) of the gas- source mass spectrometer. The reference gas used as an internal standard was calibrated against terrestrial rock samples and meteorites analyzed using infrared laser heating fluorination. All results are reported as linearized delta values (signified with a prime superscript symbol). With a mean terrestrial rock Δ17O'of 0.00 ‰ ± 0.02 we obtain Δ17O values of -0.25 ‰ ± 0.04 1σ, -0.22 ‰ ± 0.03, and -0.23 ‰ ± 0.05 for 5 mesosiderite meteorites, 7 pallasites, and 12 HED meteorites, respectively. The latter meteorite data are consistent with results from three other laboratories and serve to establish the absolute scale for the air O2 measurements. Our results for the O2 samples give a mean linearized δ18O' of 23.237 ‰ ± 0.008 1 std err (corresponding to a normal, non-linearized δ18O SMOW value of 23.509 ‰), a mean δ17O' of 11.922 ‰ ± 0.018, and a mean linearized Δ17O' of -0.347 ‰ ± 0.018 based on a rock-water terrestrial fractionation reference line with a slope (β) of 0.528. The latter is the exponent in a normal fractionation law described by the relation α17=(α18)β. This result can be reconciled with the suggestion by Young et al (2002) that the whole of the departure in Δ17O' of tropospheric O2 relative to terrestrial rocks can be attributed to respiration (a Δ17O Dole effect

  19. Phase Equilibria Study in the TeO2-Na2O-SiO2 System in Air Between 723 K (500 °C) and 1473 K (1200 °C)

    NASA Astrophysics Data System (ADS)

    Santoso, Imam; Taskinen, Pekka

    2016-06-01

    Knowledge of phase equilibria in the TeO2-Na2O-SiO2 system at elevated temperatures is important for ceramic and glass industries and for improving the operation of the smelting process of tellurium-containing materials. A review of previous investigations has indicated, however, that there are omissions in the available datasets on the liquidus temperatures of the molten TeO2-Na2O-SiO2 mixtures. The employed experimental method included equilibration of mixtures made from high purity oxides, rapid quenching of the equilibrated samples in water and followed by compositional analysis of the phases using an electron probe X-ray microanalyzer. The liquidus and phase equilibria in the TeO2-SiO2, TeO2-Na2O, and SiO2-TeO2-Na2O systems have been studied for a wide range of compositions between 723 K (500 °C) and 1473 K (1200 °C) at TeO2, SiO2, and Na2SiO3 saturations. New data have been generated in the SiO2-TeO2-Na2O system at SiO2 saturation. The liquidus compositions in the TeO2-Na2O system at TeO2 saturation have been compared with the previous data and an assessed phase diagram.

  20. Phase Equilibria Study in the TeO2-Na2O-SiO2 System in Air Between 723 K (500 °C) and 1473 K (1200 °C)

    NASA Astrophysics Data System (ADS)

    Santoso, Imam; Taskinen, Pekka

    2016-08-01

    Knowledge of phase equilibria in the TeO2-Na2O-SiO2 system at elevated temperatures is important for ceramic and glass industries and for improving the operation of the smelting process of tellurium-containing materials. A review of previous investigations has indicated, however, that there are omissions in the available datasets on the liquidus temperatures of the molten TeO2-Na2O-SiO2 mixtures. The employed experimental method included equilibration of mixtures made from high purity oxides, rapid quenching of the equilibrated samples in water and followed by compositional analysis of the phases using an electron probe X-ray microanalyzer. The liquidus and phase equilibria in the TeO2-SiO2, TeO2-Na2O, and SiO2-TeO2-Na2O systems have been studied for a wide range of compositions between 723 K (500 °C) and 1473 K (1200 °C) at TeO2, SiO2, and Na2SiO3 saturations. New data have been generated in the SiO2-TeO2-Na2O system at SiO2 saturation. The liquidus compositions in the TeO2-Na2O system at TeO2 saturation have been compared with the previous data and an assessed phase diagram.

  1. Synthesis of LaVO4/TiO2 heterojunction nanotubes by sol-gel coupled with hydrothermal method for photocatalytic air purification.

    PubMed

    Zou, Xuejun; Li, Xinyong; Zhao, Qidong; Liu, Shaomin

    2012-10-01

    With the aim of improving the effective utilization of visible light, the LaVO(4)/TiO(2) heterojunction nanotubes were fabricated by sol-gel coupled with hydrothermal method. The photocatalytic ability was demonstrated through catalytic removal of gaseous toluene species. The nanotube samples were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), surface photovoltage (SPV), Raman spectra and N(2) adsorption-desorption measurements. The characterization results showed that the samples with high specific surface areas were of typical nanotubular morphology, which would lead to the high separation and transfer efficiency of photo induced electron-hole pairs. The as-prepared nanotubes exhibited high photocatalytic activity in decomposing toluene species under visible light irradiation with fine photochemical stability. The enhanced photocatalytic performance of LaVO(4)/TiO(2) nanotubes might be attributed to the matching band potentials, the interconnected heterojunction of LaVO(4) versus TiO(2), and the large specific surface areas of nanotubes. PMID:22795044

  2. Inactivation and mineralization of aerosol deposited model pathogenic microorganisms over TiO2 and Pt/TiO2.

    PubMed

    Kozlova, E A; Safatov, A S; Kiselev, S A; Marchenko, V Yu; Sergeev, A A; Skarnovich, M O; Emelyanova, E K; Smetannikova, M A; Buryak, G A; Vorontsov, A V

    2010-07-01

    Air disinfection from bacteria and viruses by means of photocatalytic oxidation is investigated with microorganisms loaded over photocatalysts' films from aerosols. Deposition method and equipment have been developed to load Mycobacterium smegmatis , Bacillus thuringiensis , vaccinia virus, and influenza A (H3N2) virus on slides with undoped TiO(2) and platinized sulfated TiO(2) (Pt/TiO(2)). Inactivation dynamics was measured under UVA irradiation and in the dark. About 90% inactivation is reached in 30 min irradiation on TiO(2) and from 90 to 99.8% on Pt/TiO(2). The first-order inactivation rate coefficient ranged from 0.18 to 0.03 min(-1), over Pt/TiO(2) being higher than on TiO(2) for all microorganisms except Bacillus thuringiensis. The photocatalytic mineralization of Bacillus thuringiensis was performed on TiO(2) and Pt/TiO(2) with different photocatalyst and microorganism loadings. Completeness of mineralization depended on the TiO(2) to bacteria mass ratio. The rate of the photocatalytic carbon dioxide production grows with both the cell mass increase and the photocatalyst mass increase. Pt/TiO(2) showed increased rate of mineralization as well as of the inactivation likely due to a better charge carrier separation in the doped semiconductor photocatalyst. The results demonstrate that photocatalytic filters with deposited TiO(2) or Pt/TiO(2) are able to inactivate aerosol microorganisms and completely decompose them into inorganic products and Pt/TiO(2) provides higher disinfection and mineralization rates. PMID:20521809

  3. A selected ion flow tube study of the reactions of NO + and O + 2 ions with some organic molecules: The potential for trace gas analysis of air

    NASA Astrophysics Data System (ADS)

    Španěl, Patrik; Smith, David

    1996-02-01

    A study has been carried out using our selected ion flow tube apparatus of the reactions of NO+ and O+2 ions in their vibronic ground states with ten organic species: the hydrocarbons, benzene, toluene, isoprene, cyclopropane, and n-pentane; the oxygen-containing organics, methanol, ethanol, acetaldehyde, acetone, and diethyl ether. The major objectives of this work are, on the one hand, to fully understand the processes involved in these reactions and, on the other hand, to explore the potential of NO+ and O+2 as chemical ionization agents for the analysis of trace gases in air and on human breath. Amongst the NO+ reactions, charge transfer, hydride-ion transfer, and termolecular association occur, and the measured rate coefficients, k, for the reactions vary from immeasurably small to the maximum value, collisional rate coefficient, kc. The O+2 reactions are all fast, in each case the k being equal to or an appreciable fraction of kc, and charge transfer producing the parent organic ion or dissociative charge transfer resulting in two or three fragments of the parent ion are the reaction processes that occur. We conclude from these studies, and from previous studies, that NO+ ions and O+2 ions can be used to great effect as chemical ionization agents for trace gas analysis, especially in combination with H3O+ ions which we now routinely use for this purpose.

  4. Determination of Phosphorescence Quantum Yield of Singlet Oxygen O 2( 1Δ g) Photosensitized by Phenalenone in Air-Saturated Carbon Tetrachloride

    NASA Astrophysics Data System (ADS)

    Shimizu, Okiyasu; Watanabe, Jun; Imakubo, Keiichi; Naito, Shizuo

    1998-11-01

    The phosphorescence quantum yield Φ P (=einsteins emitted/einsteins absorbed by sensitizer) of singlet oxygen (1O2) was measured for an air-saturated CCl4 solution of phenalenone (PH) used as a photosensitizer, by means of a photon-counting technique based on the use of a near-IR-sensitive photomultiplier. Employment of steady-state excitation allowed for the determination of the absolute quantum yield of Φ P=(1.38±0.05)×10-3 in CCl4. The result was obtained by direct comparison of the areas under the corrected emission spectra of 1O2 and of quinine bisulfate (QBS) in 1N H2SO4 as a luminescence standard.

  5. Investigations of the vibrational and rotational excitation of N2, CO, NO, O2, CO2, CH4, CF4 and SF6 during collision with protons and deuterons at an energy of 9.8 eV

    NASA Astrophysics Data System (ADS)

    Gierz, U.

    1980-07-01

    Inelastic collision processes of the class H(+) + AB(0,0) yields H(+) + AB(J,v) + Delta (translation energy), with (J,v) the excited state, were studied experimentally. The measurements show varying results, in such a way that an unified interpretation is impossible. The strong vibrational excitation of O2 is characteristic. A series of models that deal with energy transmission processes are discussed. Only for NO and O2 do measurements agree, at least qualitatively, with theoretical predictions at hand. Trajectory calculations lead only in rare cases to usable results. Better calculation methods for the systems considered are called for.

  6. Water absorption lines, 931-961 nm - Selected intensities, N2-collision-broadening coefficients, self-broadening coefficients, and pressure shifts in air

    NASA Technical Reports Server (NTRS)

    Giver, L. P.; Gentry, B.; Schwemmer, G.; Wilkerson, T. D.

    1982-01-01

    Intensities were measured for 97 lines of H2O vapor between 932 and 961 nm. The lines were selected for their potential usefulness for remote laser measurements of H2O vapor in the earth's atmosphere. The spectra were obtained with several different H2O vapor abundances and N2 broadening gas pressures; the spectral resolution was 0.046/cm FWHM. Measured H2O line intensities range from 7 x 10 to the -25th to 7 x 10 to the -22nd/cm per (molecules/sq cm). H2O self-broadening coefficients were measured for 13 of these strongest lines; the mean value was 0.5/cm per atm. N2-collision-broadening coefficients were measured for 73 lines, and the average was 0.11 cm per atm HWHM. Pressure shifts in air were determined for a sample of six lines between 948 and 950 nm; these lines shift to lower frequency by an amount comparable to 0.1 of the collision-broadened widths measured in air or N2. The measured intensities of many lines of 300-000 band are much larger than expected from prior computations, in some cases by over an order of magnitude. Coriolis interactions with the stronger 201-000 band appear to be the primary cause of the enhancement of these line intensities.

  7. Benefits and technological challenges in the implementation of TiO2-based ultraviolet photocatalytic oxidation (UVPCO) air cleaners

    SciTech Connect

    Hodgson, Al; Destaillats, Hugo; Hotchi, Toshifumi; Fisk, William J.

    2008-10-01

    Heating, ventilating, and cooling classrooms in California consume substantial electrical energy. Indoor air quality (IAQ) in classrooms affects student health and performance. In addition to airborne pollutants that are emitted directly by indoor sources and those generated outdoors, secondary pollutants can be formed indoors by chemical reaction of ozone with other chemicals and materials. Filters are used in nearly all classroom heating, ventilation and air-conditioning (HVAC) systems to maintain energy-efficient HVAC performance and improve indoor air quality; however, recent evidence indicates that ozone reactions with filters may, in fact, be a source of secondary pollutants. This project quantitatively evaluated ozone deposition in HVAC filters and byproduct formation, and provided a preliminary assessment of the extent to which filter systems are degrading indoor air quality. The preliminary information obtained will contribute to the design of subsequent research efforts and the identification of energy efficient solutions that improve indoor air quality in classrooms and the health and performance of students.

  8. Electrochemical properties of graphene flakes as an air cathode material for Li-O2 batteries in an ether-based electrolyte.

    PubMed

    Kim, Se Young; Lee, Ho-Taek; Kim, Kwang-Bum

    2013-12-14

    We employed graphene flakes as an air-cathode material for Li-O2 batteries and investigated their electrochemical properties in the dimethyl ether electrolyte. Graphene flakes were prepared by microwave-assisted reduction of graphene oxide, and their electrochemical properties were compared with those of Ketjen Black and carbon nanotubes. The catalytic effect of the prepared graphene flake-air cathode was demonstrated using cyclic voltammetry and discharge-charge testing performed under a limited discharge capacity. The catalytic effect of graphene flakes was also supported by morphological and spectroscopic analysis of the discharge-charge products formed on the graphene surface. Scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy revealed that Li2O2, Li2O, and Li2CO3 were the main discharge products on all carbon-air cathode surfaces. Raman spectroscopy revealed that LiRCO3 was additionally formed on Ketjen Black and carbon nanotubes during the first discharge; however, its formation was not observed on the graphene flakes. The catalytic effect of the graphene flakes and the absence of LiRCO3 in the discharge product could explain the higher Coulombic efficiency in the discharge-charge tests. PMID:24166701

  9. Surface Catalysis Modeling of Air-SiO2 Systems Under Hypersonic Conditions Using ReaxFF MD Simulation

    NASA Astrophysics Data System (ADS)

    Norman, Paul; Schwartzentruber, Tom; Cozmuta, Ioana

    2009-11-01

    The high-speed entry of a blunt body into Earth's atmosphere brings about the dissociation of diatomic nitrogen and oxygen molecules via the shockwave formed in front of the body. Through surface catalysis, these dissociated atoms can recombine on the heat shield of the body, increasing its overall heating. The goal of this project is to study surface catalysis on amorphous silicon-dioxide (SiO2), a significant component in the reusable thermal protection system used on the Space Shuttle. Specifically, our objective is to determine the rates of recombination of monatomic N and O for the range of temperatures and pressures experienced by a heat shield during Earth re-entry. Additionally, we aim to determine the rates of specific reaction mechanisms on a SiO2 surface, including adsorption, desorption, surface diffusion, and various recombination processes. This is accomplished by performing large reactive molecular dynamics simulations using the ReaxFF force field, which naturally allows bond formation/breaking to occur during the course of a molecular dynamics simulation. Several methods for speeding up the equilibration and collection of rates for low-pressure gas-surface systems (typical of re-entry conditions) where events become infrequent will also be discussed.

  10. Hierarchical mesoporous perovskite La0.5Sr0.5CoO2.91 nanowires with ultrahigh capacity for Li-air batteries

    PubMed Central

    Zhao, Yunlong; Xu, Lin; Mai, Liqiang; Han, Chunhua; An, Qinyou; Xu, Xu; Liu, Xue; Zhang, Qingjie

    2012-01-01

    Lithium-air batteries have captured worldwide attention due to their highest energy density among the chemical batteries. To provide continuous oxygen channels, here, we synthesized hierarchical mesoporous perovskite La0.5Sr0.5CoO2.91 (LSCO) nanowires. We tested the intrinsic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity in both aqueous electrolytes and nonaqueous electrolytes via rotating disk electrode (RDE) measurements and demonstrated that the hierarchical mesoporous LSCO nanowires are high-performance catalysts for the ORR with low peak-up potential and high limiting diffusion current. Furthermore, we fabricated Li-air batteries on the basis of hierarchical mesoporous LSCO nanowires and nonaqueous electrolytes, which exhibited ultrahigh capacity, ca. over 11,000 mAh⋅g –1, one order of magnitude higher than that of LSCO nanoparticles. Besides, the possible reaction mechanism is proposed to explain the catalytic activity of the LSCO mesoporous nanowire. PMID:23150570

  11. Hierarchical mesoporous perovskite La0.5Sr0.5CoO2.91 nanowires with ultrahigh capacity for Li-air batteries.

    PubMed

    Zhao, Yunlong; Xu, Lin; Mai, Liqiang; Han, Chunhua; An, Qinyou; Xu, Xu; Liu, Xue; Zhang, Qingjie

    2012-11-27

    Lithium-air batteries have captured worldwide attention due to their highest energy density among the chemical batteries. To provide continuous oxygen channels, here, we synthesized hierarchical mesoporous perovskite La(0.5)Sr(0.5)CoO(2.91) (LSCO) nanowires. We tested the intrinsic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity in both aqueous electrolytes and nonaqueous electrolytes via rotating disk electrode (RDE) measurements and demonstrated that the hierarchical mesoporous LSCO nanowires are high-performance catalysts for the ORR with low peak-up potential and high limiting diffusion current. Furthermore, we fabricated Li-air batteries on the basis of hierarchical mesoporous LSCO nanowires and nonaqueous electrolytes, which exhibited ultrahigh capacity, ca. over 11,000 mAh⋅g(-1), one order of magnitude higher than that of LSCO nanoparticles. Besides, the possible reaction mechanism is proposed to explain the catalytic activity of the LSCO mesoporous nanowire. PMID:23150570

  12. Nitrogen metastable (N2(A3 Σu + )) in a cold argon atmospheric pressure plasma jet: Shielding and gas composition

    NASA Astrophysics Data System (ADS)

    Iseni, Sylvain; Bruggeman, Peter J.; Weltmann, Klaus-Dieter; Reuter, Stephan

    2016-05-01

    N 2 ( A 3 Σu + ) metastable species are detected and measured in a non-equilibrium atmospheric pressure plasma jet by laser induced fluorescence. A shielding device is used to change the ambient conditions additionally to the feeding gas composition. Varying the amount of N2 and air admixed to the feeding gas as well as changing the shielding gas from N2 to air reveals that the highest N 2 ( A 3 Σu + ) is achieved in the case of air admixtures in spite of the enhanced collisional quenching due to the presence of O2. The reasons for these observations are discussed in detail.

  13. Measurements of the CO_2 15 μm Band System Broadened by Air, N_2 and CO_2 at Terrestrial Atmospheric Temperatures

    NASA Astrophysics Data System (ADS)

    Smith, M. A. H.; Devi, V. Malathy; Benner, D. Chris; Blake, T. A.; Sams, R. L.

    2009-06-01

    In earth remote sensing, retrievals of atmospheric temperature profiles are often based on observed radiances in infrared spectral regions where emission from atmospheric CO_2 predominates. To achieve improved retrieval accuracy, systematic errors in the forward model must be reduced, especially those associated with errors in the spectroscopic line calculation. We have recorded more than 110 new high-resolution infrared spectra of the 15-μm band system of CO_2 to accurately determine line intensities, self-, air- and N_2-broadened widths and pressure-induced line shifts, along with their temperature dependences. The spectra were recorded with the Bruker IFS 120 HR Fourier transform spectrometer at Pacific Northwest National Laboratory (PNNL) and temperature-controlled sample cells. Sample temperatures were between 206K and 298K. Maximum total pressures were 15 Torr for self-broadening and 613 Torr for air- and N_2-broadening. Analysis is done using a multispectrum fitting technique to retrieve the spectroscopic parameters. Line mixing and other non-Lorentz, non-Voigt line shapes are also assessed. The resulting line parameters are compared with the HITRAN database and with other measurements. D. Chris Benner, C.P. Rinsland, V. Malathy Devi, M.A.H. Smith, and D. Atkins, J. Quant. Spectrosc. Radiat. Transfer 53, 705-721 (1995) L.S. Rothman et al., J. Quant. Spectrosc. Radiat. Transfer 96, 139-204 (2005) L.S. Rothman et al., J. Quant. Spectrosc. Radiat. Transfer, in press (2009)

  14. 193Ir Mössbauer spectroscopy of Pt-IrO 2 nanoparticle catalysts developed for detection and removal of carbon monoxide from air

    NASA Astrophysics Data System (ADS)

    Sawicki, J. A.; Marcinkowska, K.; Wagner, F. E.

    2010-08-01

    Mössbauer spectroscopy of 73.0 keV gamma-ray transition in 193Ir and supplementary analytical techniques were used to study the microstructure and chemical form of polymer-supported hydrophobic bimetallic Pt-Ir catalysts for detection and removal of CO from humid air at ambient conditions. The catalysts, typically with a composition of 9 wt.% Pt and 1 wt.% Ir, were prepared by incipient wetness impregnation of polystyrene-divinylbenzene (SDB) granules with ethanol solutions of hexachloroplatinic and hexachloroiridic acids. This procedure, followed by reduction in H 2 or CO at only 200 °C or 250 °C, resulted in formation of highly-dispersed Pt-Ir particles usually smaller than 20 nm and having high catalytic activity and selectivity. Mössbauer spectra of 73.0 keV gamma-ray transition in 193Ir were taken after consecutive steps of preparation and exposure of catalysts to better understand and further improve the fabrication processes. In the as-impregnated state, iridium was found mostly as Ir(III) in [IrCl 6] 3- ions, with only a small fraction of Ir(IV) in [IrCl 6] 2- ions. The iridium in bimetallic clusters formed by reduction in hydrogen showed a strong tendency towards oxidation on exposure to air at room temperature, while Pt remained mostly metallic. In the most active and stable catalysts, the Ir and Pt in metallic regions of the clusters did not tend to segregate, unlike in Pt-Ir/silica-supported catalysts studied by us earlier. Further, this study shows that the IrO 2-like regions in the clusters exhibit stronger deviations from local symmetry and stoichiometry of crystalline IrO 2 than observed previously in Pt-Ir/silica catalysts. Our study also indicates that in the examined Pt-IrO 2 nanoparticles iridium largely provides the dissociative O 2 adsorption sites, while the CO adsorption occurs primarily at metallic Pt sites.

  15. Heat-transfer distributions on biconics at incidence in hypersonic-hypervelocity He, N2, air, and CO2 flows

    NASA Technical Reports Server (NTRS)

    Miller, C. G.; Micol, J. R.; Gnoffo, P. A.; Wilder, S. E.

    1983-01-01

    Laminar heat transfer rates were measured on spherically blunted, 13 deg/7 deg on axis and bent biconics (fore cone bent 7 deg upward relative to aft cone) at hypersonic hypervelocity flow conditions in the Langley Expansion Tube. Freestream velocities from 4.5 to 6.9 km/sec and Mach numbers from 6 to 9 were generated using helium, nitrogen, air, and carbon dioxide test gases, resulting in normal shock density ratios from 4 to 19. Angle of attack, referenced to the axis of the aft cone, was varied from 0 to 20 deg in 4 deg increments. The effect of nose bend, angle of attack, and real gas phenomena on heating distributions are presented along with comparisons of measurement to prediction from a code which solves the three dimensional parabolized Navier-Stokes equations.

  16. Electrical Behavior of SnO2 Polycrystalline Ceramic Pieces Formed by Slip Casting: Effect of Surrounding Atmosphere (Air and CO)

    NASA Astrophysics Data System (ADS)

    Aguilar-Paz, C. J.; Ochoa-Muñoz, Y.; Ponce, M. A.; Rodríguez-Páez, J. E.

    2016-01-01

    Pieces of porous polycrystalline SnO2 with and without cobalt have been formed by the slip-casting method, using ceramic powders synthesized by the controlled precipitation method. A suitable methodology was developed for forming and sintering the pieces to enable controlled modification of their microstructure, principally grain size, porosity, and type of intergranular contacts. Better control of the microstructure was obtained in the samples containing cobalt. In these, predominance of open necks and intergranular contacts was observed, which can represent Schottky barriers. Because of its good structural homogeneity, porosity, and small grain size (of the order of 1 μm), the sample with 2 mol.% Co sintered at 1250°C for 2 h was selected for electrical characterization by complex impedance spectroscopy, varying the operating temperature, concentration and nature of the surrounding gas (air or CO), and bias voltage. The resulting R p and C p curves were very sensitive to variation in these parameters, being most obvious for the C p curves, which showed a phenomenon of low-frequency dispersion when bias voltages other than zero were used, in the presence of O2, and at operating temperature of 280°C. The electrical behavior of the SnO2 with 2 mol.% Co sample sintered at 1250°C was consistent with the nature and microstructural characteristics of the active material and was justified based on the presence of shallow- and deep-type defects, and variations in barrier height and width, caused by adsorption of gas molecules.

  17. Graphene supported heterogeneous catalysts for Li-O2 batteries

    NASA Astrophysics Data System (ADS)

    Alaf, M.; Tocoglu, U.; Kartal, M.; Akbulut, H.

    2016-09-01

    In this study production and characterization of free-standing and flexible (i) graphene, (ii) α-MnO2/graphene, (iii) Pt/graphene (iv) α-MnO2/Pt/graphene composite cathodes for Li-air batteries were reported. Graphene supported heterogeneous catalysts were produced by a facile method. In order to prevent aggregation of graphene sheets and increase not only interlayer distance but also surface area, a trace amount multi-wall carbon nano tube (MWCNT) was introduced to the composite structure. The obtained composite catalysts were characterized by SEM, X-ray diffraction, N2 adsorption-desorption analyze and Raman spectroscopy. The electrochemical characterization tests including galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) measurement of catalyst were carried out by using an ECC-Air test cell. These highly active graphene supported heterogeneous composite catalysts provide competitive properties relative to other catalyst materials for Li-air batteries.

  18. Air purification equipment combining a filter coated by silver nanoparticles with a nano-TiO2 photocatalyst for use in hospitals

    NASA Astrophysics Data System (ADS)

    Son Le, Thanh; Hien Dao, Trong; Nguyen, Dinh Cuong; Chau Nguyen, Hoai; Balikhin, I. L.

    2015-03-01

    X-ray diffraction, scanning electron microscopy and transmission electron microscopy showed that TiO2 particles synthesized by a sol-gel procedure exhibited uniform size about 16-20 nm. This nanopowder was deposited on a porous quartz tube (D = 74 mm, L = 418 mm, deposit density ˜16.4 mg cm-2) through an intermediate adhesive polymethylmethacrylate layer to manufacture a photocatalytic filter tube. A polypropylene pre-filter was coated with a nanosilver layer (particle size ˜20 nm) prepared by aqueous molecular solution method. An air cleaner of 250 m3 h-1 capacity equipped with this pre-filter, an electrostatic air filter, 4 photocatalytic filter tubes and 4 UV-A lamps (36 W) presented the high degradation ability for certain volatile organic compounds (VOCs), bacteria and fungi. The VOCs degradation performances of the equipment with respect to divers compounds are different: in a 10 m3 box, 91.6% of butanol was removed within 55 min, 80% of acetone within 100 min, 70.1% of diethyl ether within 120 min and only 43% of benzene was oxidized within 150 min. Over 99% of bacteria and fungi were killed after the air passage through the equipment. For application, it was placed in the intensive care room (volume of 125 m3) of E hospital in Hanoi; 69% of bacteria and 63% of fungi were killed within 6 h.

  19. TiO2-modified Ag-CuO Reactive Air Brazes for Improved Wettability on Mixed Ionic/Electronic Conductors

    SciTech Connect

    Hardy, John S.; Weil, K. Scott; Kim, Jin Yong Y.; Thomsen, Ed C.; Darsell, Jens T.

    2005-03-01

    Mixed ionic/electronic conducting perovskite oxides such as lanthanum strontium cobalt ferrite (LSCF) are strong candidates for potential use in a number of electrochemical devices, including gas separation membranes and solid oxide fuel cells (SOFC). Underlying the excitement over the these novel ceramics is the engineering challenge of effectively incorporating them into practical devices. Taking full advantage of the unique properties of advanced ceramics such as mixed conducting oxides depends in large part on being able to develop reliable joining techniques. Earlier studies have indicated that Ag-CuO reactive air braze (RAB) compositions are effective in joining to LSCF. Meanwhile, it has been found that small additions of as little as 0.5 mol% titanium oxide to Ag-CuO RAB compositions cause a dramatic increase in the wettability of RAB on many oxide ceramic surfaces. Therefore the wettabilty of Ag-CuO-TiO2 brazes on LSCF substrates will be examined and the flexural strength, microstructure, and conductivity of joints in LSCF made using Ag-CuO-TiO2 brazes will be discussed. Long-term aging effects on conductivity and microstructure will also be presented.

  20. Method for measuring temperatures and densities in hypersonic wind tunnel air flows using laser-induced O2 fluorescence

    NASA Technical Reports Server (NTRS)

    Laufer, Gabriel; Mckenzie, Robert L.; Fletcher, Douglas G.

    1990-01-01

    Laser-induced fluorescence in oxygen, in combination with Raman scattering, is shown to be an accurate means by which temperature, density, and their fluctuations owing to turbulence can be measured in air flows associated with high-speed wind tunnels. For temperatures above 60 K and densities above 0.01 amagat, the uncertainties in the temperature and density measurements can be less than 2 percent, if the signal uncertainties are dominated by photon statistical noise. The measurements are unaffected by collisional quenching and can be achieved with laser fluences for which nonlinear effects are insignificant. Temperature measurements using laser-induced fluorescence alone have been demonstrated at known densities in the range of low temperatures and densities which are expected in a hypersonic wind tunnel.

  1. A method for measuring temperatures and densities in hypersonic wind tunnel air flows using laser-induced O2 fluorescence

    NASA Technical Reports Server (NTRS)

    Laufer, Gabriel; Fletcher, Douglas G.; Mckenzie, Robert L.

    1990-01-01

    Laser-induced fluorescence in oxygen, in combination with Raman scattering, is shown to be an accurate means by which temperature, density, and their fluctuations due to turbulence can be measured in air flows associated with high-speed wind tunnels. For temperatures above 60 K and densities above 0.01 amagat, the uncertainty in the temperature and density measurements can be less than 2 and 3 percent, respectively, if the signal uncertainties are dominated by photon-statistical noise. The measurements are unaffected by collisional quenching and can be achieved with laser fluences for which nonlinear effects are insignificant. Temperature measurements using laser-induced fluorescence alone have been demonstrated at known densities in the range of low temperatures and densities which are expected in a hypersonic wind tunnel.

  2. Discussion on "field study of air purification paving elements containing TiO2" by Folli et al. (2015)

    NASA Astrophysics Data System (ADS)

    Kleffmann, Jörg

    2016-03-01

    In the study by Folli et al. (2015) photocatalytic pavement blocks were used on both sidewalks of a street canyon in Copenhagen (Denmark) for the purpose of air remediation of nitrogen oxides (NOx). Outstanding nitrogen monoxide (NO) degradation was observed with an average (day and night) reduction of 22% during summer months reaching values >45% at noontime. In contrast, for nitrogen dioxide (NO2) no significant improvement was obtained. Although these results would be of significant importance for many European urban environments usually suffering from high NOx levels, the results are highly unrealistic. Two simple back-to-the-envelope calculations show that the upper limit photocatalytic reduction of NO will be <1% for the investigated street canyon conditions. In addition, an alternative explanation of the experimental observations by the gas phase titration of NO by ozone (O3) is discussed.

  3. A Study of a QCM Sensor Based on TiO2 Nanostructures for the Detection of NO2 and Explosives Vapours in Air

    PubMed Central

    Procek, Marcin; Stolarczyk, Agnieszka; Pustelny, Tadeusz; Maciak, Erwin

    2015-01-01

    The paper deals with investigations concerning the construction of sensors based on a quartz crystal microbalance (QCM) containing a TiO2 nanostructures sensor layer. A chemical method of synthesizing these nanostructures is presented. The prepared prototype of the QCM sensing system, as well as the results of tests for detecting low NO2 concentrations in an atmosphere of synthetic air have been described. The constructed NO2 sensors operate at room temperature, which is a great advantage, because resistance sensors based on wide gap semiconductors often require much higher operation temperatures, sometimes as high as 500 °C. The sensors constructed by the authors can be used, among other applications, in medical and chemical diagnostics, and also for the purpose of detecting explosive vapours. Reactions of the sensor to nitroglycerine vapours are presented as an example of its application. The influence of humidity on the operation of the sensor was studied. PMID:25912352

  4. Development of a Thermal Transport Database for Air Plasma Sprayed ZrO2 ? Y2O3 Thermal Barrier Coatings

    SciTech Connect

    Wang, Hsin; Dinwiddie, Ralph Barton; Porter, Wallace D

    2010-01-01

    Thermal Diffusivities of Air Plasma Sprayed (APS) thermal barrier coatings (TBCs) are measured by the laser flash method. The data are used to calculate thermal conductivity of TBCs when provided with density and specific heat data. Due to the complicated microstructure and other processing related parameters, thermal diffusivity of TBCs can vary as much as three to four fold. Data collected from over 200 free-standing ZrO2 7-8 wt%Y2O3 TBCs are presented. The large database gives a clear picture of the expected band of thermal diffusivity values. When this band is used as reference for thermal diffusivity of a specific TBC, the thermal transport property of TBC can be more precisely described. The database is intended to serve researchers and manufacturers of TBCs as a valuable source for evaluating their coatings.

  5. Increased cardiac output, not pulmonary artery systolic pressure, increases intrapulmonary shunt in healthy humans breathing room air and 40% O2

    PubMed Central

    Elliott, Jonathan E; Duke, Joseph W; Hawn, Jerold A; Halliwill, John R; Lovering, Andrew T

    2014-01-01

    Blood flow through intrapulmonary arteriovenous anastomoses (IPAVAs) has been demonstrated to increase in healthy humans during a variety of conditions; however, whether or not this blood flow represents a source of venous admixture (/) that impairs pulmonary gas exchange efficiency (i.e. increases the alveolar-to-arterial difference (A–aDO2)) remains controversial and unknown. We hypothesized that blood flow through IPAVAs does provide a source of /. To test this, blood flow through IPAVAs was increased in healthy humans at rest breathing room air and 40% O2: (1) during intravenous adrenaline (epinephrine) infusion at 320 ng kg−1 min−1 (320 ADR), and (2) with vagal blockade (2 mg atropine), before and during intravenous adrenaline infusion at 80 ng kg−1 min−1 (ATR + 80 ADR). When breathing room air the A–aDO2 increased by 6 ± 2 mmHg during 320 ADR and by 5 ± 2 mmHg during ATR + 80 ADR, and the change in calculated / was +2% in both conditions. When breathing 40% O2, which minimizes contributions from diffusion limitation and alveolar ventilation-to-perfusion inequality, the A–aDO2 increased by 12 ± 7 mmHg during 320 ADR, and by 9 ± 6 mmHg during ATR + 80 ADR, and the change in calculated / was +2% in both conditions. During 320 ADR cardiac output () and pulmonary artery systolic pressure (PASP) were significantly increased; however, during ATR + 80 ADR only was significantly increased, yet blood flow through IPAVAs as detected with saline contrast echocardiography was not different between conditions. Accordingly, we suggest that blood flow through IPAVAs provides a source of intrapulmonary shunt, and is mediated primarily by increases in rather than PASP. PMID:25085889

  6. Line parameters including temperature dependences of self- and air-broadened line shapes of 12C16O2: 1.6-μm region

    NASA Astrophysics Data System (ADS)

    Devi, V. Malathy; Benner, D. Chris; Sung, Keeyoon; Brown, Linda R.; Crawford, Timothy J.; Miller, Charles E.; Drouin, Brian J.; Payne, Vivienne H.; Yu, Shanshan; Smith, Mary Ann H.; Mantz, Arlan W.; Gamache, Robert R.

    2016-07-01

    Pressure-broadened line shapes in the 30013←00001 (ν1+4 ν20 +ν3) band of 12C16O2 at 6228 cm-1 are reanalyzed using new spectra recorded with sample temperatures down to 170 K. High resolution, high signal-to-noise (S/N) laboratory measurements of line shapes (Lorentz air- and self-broadened half-width coefficients, pressure-shift coefficients and off-diagonal relaxation matrix element coefficients) as a function of gas sample temperatures for various pressures and volume mixing ratios are presented. The spectra were recorded using two different Fourier transform spectrometers (FTS): (1) the McMath-Pierce FTS located at the National Solar Observatory on Kitt Peak, Arizona (and reported in Devi et al., J Mol Spectrosc 2007;245:52-80) and, (2) the Bruker IFS-125HR FTS at the Jet Propulsion Laboratory in Pasadena, California. The 19 spectra taken at Kitt Peak were all recorded near room temperature while the 27 Bruker spectra were acquired both at room temperature and colder temperatures (170-296 K). Various spectral resolutions (0.004-0.011 cm-1), absorption path lengths (2.46-121 m) and CO2 samples (natural and 12C-enriched) were included in the dataset. To maximize the accuracies of the various retrieved line parameters, a multispectrum nonlinear least squares spectrum fitting software program was used to adjust the ro-vibrational constants (G,B,D etc.) and intensity parameters (including Herman-Wallis terms) instead of directly measuring the individual line positions and intensities. To minimize systematic residuals, line mixing (via off-diagonal relaxation matrix elements) and quadratic speed dependence parameters were included in the analysis. Contributions from other weakly absorbing bands: the 30013←00001 and 30012←00001 bands of 13C16O2, the 30013←00001 band of 12C16O18O, hot bands 31113←01101 and 32212←02201 of 12C16O2, as well as the 40013←10001 and the 40014←10002 bands of 12C16O2, present within the fitted interval were also measured

  7. Transport properties of CF3I thermal plasmas mixed with CO2, air or N2 as an alternative to SF6 plasmas in high-voltage circuit breakers

    NASA Astrophysics Data System (ADS)

    Cressault, Y.; Connord, V.; Hingana, H.; Teulet, Ph; Gleizes, A.

    2011-12-01

    This paper is devoted to the calculation of equilibrium compositions, thermodynamic properties (mass density, enthalpy and specific heat at constant pressure) and transport coefficients (viscosity, electrical conductivity and thermal conductivity) of air/CO2/N2-CF3I mixtures. These data are computed in the temperature range 300 K-50 kK and pressure between 1 and 32 bar. Results obtained for pure gases (CF3I, CO2, air and N2) are systematically compared with SF6. Transport coefficients for N2, CO2, CF3I and mixtures of CO2, N2 or air with CF3I are also confronted with previous published values. Particular attention is paid to the collision integral database by the use of the most accurate and recent cross-sections or interaction potentials available in the literature.

  8. Laser-induced breakdown spectroscopy of gas mixtures of air, CO2, N2, and C3H8 for simultaneous C, H, O, and N measurement

    NASA Astrophysics Data System (ADS)

    Sturm, Volker; Noll, Reinhard

    2003-10-01

    Laser-induced breakdown spectroscopy (LIBS) was applied for simultaneous measurement of the elements C, H, N, and O in CO2-air, C3H8-CO2, and C3H8-N2 gas mixtures at atmospheric pressure. A single 7-mm-diameter aperture at the sample chamber was used for 1064-nm Nd:YAG laser irradiation and plasma signal output to an echelle spectrometer. Double-pulse laser bursts of ~8-ns pulse width (FWHM) and 250-ns interpulse separation were applied to increase the plasma signal. Calibration curves of the LIBS signal versus the partial pressure or the atomic abundance ratios were taken by dilution series in intervals that are relevant in the combustion of heptane (C7H16) near an equivalence ratio of 1.

  9. The Effect of O2, H2O, and N2 on the Fatigue Crack Growth Behavior of an Alpha + Beta Titanium Alloy at 24 C and 177 C

    NASA Technical Reports Server (NTRS)

    Smith, Stephen W.; Piascik, Robert S.

    2001-01-01

    To study the effects of atmospheric species on the fatigue crack growth behavior of an a+B titanium alloy (Ti 6-2-2-2-2) at room temperature and 177 C, fatigue tests were performed in laboratory air, ultrahigh vacuum, and high purity water vapor, oxygen, nitrogen and helium at various partial pressures. Accelerated fatigue crack growth rates in laboratory air compared to ultrahigh vacuum are linked to the damaging effects of both water vapor and oxygen. Observations of the fatigue crack growth behavior in ultrahigh purity environments, along with surface film analysis using X-ray photoelectron spectroscopy (XPS), suggest that multiple crack-tip processes govern the damaging effects of air. Three possible mechanisms are proposed: 1) at low pressure (less than 10(exp -1) Pa), accelerated da/dN is likely due to monolayer adsorption on crack-tip surfaces presumably resulting in decreased bond strengths at the fatigue crack tip, 2) for pressures greater than 10(exp -1) Pa, accelerated da/dN in oxygen may result from oxidation at the crack tip limiting reversible slip, and 3) in water vapor, absorption of atomic hydrogen at the reactive crack tip resulting in process zone embrittlement.

  10. MWCNT-supported phthalocyanine cobalt as air-breathing cathodic catalyst in glucose/O2 fuel cells

    NASA Astrophysics Data System (ADS)

    Elouarzaki, Kamal; Haddad, Raoudha; Holzinger, Michael; Le Goff, Alan; Thery, Jessica; Cosnier, Serge

    2014-06-01

    Simple and highly efficient glucose fuel cells using abiotic catalysts and different ion exchange membranes were designed. The glucose fuel cells are based on a multi-walled carbon nanotube (MWCNT)-supported cobalt phthalocyanine (CoPc) cathode and a carbon black/platinum (C/Pt) anode. The electrocatalytic activity of the MWCNT/CoPc electrode for oxygen reduction was investigated by cyclic and linear sweep voltammetry. The electrochemical experiments show that CoPc exhibits promising catalytic properties for oxygen reduction due to its high overpotential and efficiency at reduced metal load. The MWCNT/CoPc electrodes were applied to the oxygen reduction reaction as air-breathing cathode in a single-chambered glucose fuel cell. This cathode was associated with a C/Pt anode in fuel cell configurations using either an anion (Nafion®) or a cation (Tokuyama) exchange membrane. The best fuel cell configuration delivered a maximum power density of 2.3 mW cm-2 and a cell voltage of 0.8 V in 0.5 M KOH solution containing 0.5 M glucose using the Tokuyama membrane at ambient conditions. Beside the highest power density per cathodic catalyst mass (383 W g-1), these glucose fuel cells exhibit a high operational stability, delivering 0.3 mW cm-2 after 50 days.

  11. Influence of velocity effects on the shape of N2 (and air) broadened H2O lines revisited with classical molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Ngo, N. H.; Tran, H.; Gamache, R. R.; Bermejo, D.; Domenech, J.-L.

    2012-08-01

    The modeling of the shape of H2O lines perturbed by N2 (and air) using the Keilson-Storer (KS) kernel for collision-induced velocity changes is revisited with classical molecular dynamics simulations (CMDS). The latter have been performed for a large number of molecules starting from intermolecular-potential surfaces. Contrary to the assumption made in a previous study [H. Tran, D. Bermejo, J.-L. Domenech, P. Joubert, R. R. Gamache, and J.-M. Hartmann, J. Quant. Spectrosc. Radiat. Transf. 108, 126 (2007)], 10.1016/j.jqsrt.2007.03.009, the results of these CMDS show that the velocity-orientation and -modulus changes statistically occur at the same time scale. This validates the use of a single memory parameter in the Keilson-Storer kernel to describe both the velocity-orientation and -modulus changes. The CMDS results also show that velocity- and rotational state-changing collisions are statistically partially correlated. A partially correlated speed-dependent Keilson-Storer model has thus been used to describe the line-shape. For this, the velocity changes KS kernel parameters have been directly determined from CMDS, while the speed-dependent broadening and shifting coefficients have been calculated with a semi-classical approach. Comparisons between calculated spectra and measurements of several lines of H2O broadened by N2 (and air) in the ν3 and 2ν1 + ν2 + ν3 bands for a wide range of pressure show very satisfactory agreement. The evolution of non-Voigt effects from Doppler to collisional regimes is also presented and discussed.

  12. Nitrogen transfers and air-sea N2O fluxes in the upwelling off Namibia within the oxygen minimum zone: a 3-D model approach

    NASA Astrophysics Data System (ADS)

    Gutknecht, E.; Dadou, I.; Le Vu, B.; Cambon, G.; Sudre, J.; Garçon, V.; Machu, E.; Rixen, T.; Kock, A.; Flohr, A.; Paulmier, A.; Lavik, G.

    2011-04-01

    As regions of high primary production and being often associated to Oxygen Minimum Zones (OMZs), Eastern Boundary Upwelling Systems (EBUS) represent key regions for the oceanic nitrogen (N) cycle. Indeed, by exporting the Organic Matter (OM) and nutrients produced in the coastal region to the open ocean, EBUS can play an important role in sustaining primary production in subtropical gyres. Losses of fixed inorganic N, through denitrification and anammox processes and through nitrous oxide (N2O) emissions to the atmosphere, take place in oxygen depleted environments such as EBUS, and alleviate the role of these regions as a source of N. In the present study, we developed a 3-D coupled physical/biogeochemical (ROMS/BioBUS) model for investigating the full N budget in the Namibian sub-system of the Benguela Upwelling System (BUS). The different state variables of a climatological experiment have been compared to different data sets (satellite and in situ observations) and show that the model is able to represent this biogeochemical oceanic region. The N transfer is investigated in the Namibian upwelling system using this coupled model, especially in the Walvis Bay area between 22° S and 24° S where the OMZ is well developed (O2 < 0.5 ml O2 l-1). The upwelling process advects 24.2 × 1010 mol N yr-1 of nitrate enriched waters over the first 100 m over the slope and over the continental shelf. The meridional advection by the alongshore Benguela current brings also nutrient-rich waters with 21.1 × 1010 mol N yr-1. 10.5 × 1010 mol N yr-1 of OM are exported outside of the continental shelf (between 0 and 100-m depth). 32.4% and 18.1% of this OM are exported by advection in the form of Dissolved and Particulate Organic Matters (DOM and POM), respectively, however vertical sinking of POM represents the main contributor (49.5%) to OM export outside of the first 100-m depth of the water column on the continental shelf. The continental slope also represents a net N export

  13. Inorganic Carbon-Stimulated O2 Photoreduction Is Suppressed by NO2- Assimilation in Air-Grown Cells of Synechococcus UTEX 625.

    PubMed

    Mir, N. A.; Salon, C.; Canvin, D. T.

    1995-12-01

    The effect of NO2- assimilation on O2 exchange and CO2 fixation of the cyanobacterium, Synechococcus UTEX 625, was studied mass spectrometrically. Upon addition of 1 mM inorganic carbon to the medium, inorganic carbon pools developed and accelerated O2 photoreduction 5-fold when CO2 fixation was inhibited. During steady-state photosynthesis at saturating light, O2 uptake represented 32% of O2 evolution and balanced that portion of O2 evolution that could not be accounted for by CO2 fixation. Under these conditions, NO2- assimilation reduced O2 uptake by 59% but had no influence on CO2 fixation. NO2- assimilation decreased both CO2 fixation and O2 photoreduction at low light and and increased net O2 evolution at all light intensities. The increase in net O2 evolution observed during simultaneous assimilation of carbon and nitrogen over carbon alone was due to a suppression of O2 photoreduction by NO2- assimilation. When CO2 fixation was precluded, NO2- assimilation inhibited O2 photoreduction and stimulated O2 evolution. When the electron supply was limiting (low light), competition among O2, CO2, and NO2- for electrons could be observed, but when the electron supply was not limiting (saturating light), O2 photoreduction and/or NO2- reduction caused electron transport that was additive to that for maximum CO2 fixation. PMID:12228670

  14. Air-gating and chemical-gating in transistors and sensing devices made from hollow TiO2 semiconductor nanotubes

    NASA Astrophysics Data System (ADS)

    Alivov, Yahya; Funke, Hans; Nagpal, Prashant

    2015-07-01

    Rapid miniaturization of electronic devices down to the nanoscale, according to Moore’s law, has led to some undesirable effects like high leakage current in transistors, which can offset additional benefits from scaling down. Development of three-dimensional transistors, by spatial extension in the third dimension, has allowed higher contact area with a gate electrode and better control over conductivity in the semiconductor channel. However, these devices do not utilize the large surface area and interfaces for new electronic functionality. Here, we demonstrate air gating and chemical gating in hollow semiconductor nanotube devices and highlight the potential for development of novel transistors that can be modulated using channel bias, gate voltage, chemical composition, and concentration. Using chemical gating, we reversibly altered the conductivity of nanoscaled semiconductor nanotubes (10-500 nm TiO2 nanotubes) by six orders of magnitude, with a tunable rectification factor (ON/OFF ratio) ranging from 1-106. While demonstrated air- and chemical-gating speeds were slow here (˜seconds) due to the mechanical-evacuation rate and size of our chamber, the small nanoscale volume of these hollow semiconductors can enable much higher switching speeds, limited by the rate of adsorption/desorption of molecules at semiconductor interfaces. These chemical-gating effects are completely reversible, additive between different chemical compositions, and can enable semiconductor nanoelectronic devices for ‘chemical transistors’, ‘chemical diodes’, and very high-efficiency sensing applications.

  15. Air-gating and chemical-gating in transistors and sensing devices made from hollow TiO2 semiconductor nanotubes.

    PubMed

    Alivov, Yahya; Funke, Hans; Nagpal, Prashant

    2015-07-24

    Rapid miniaturization of electronic devices down to the nanoscale, according to Moore's law, has led to some undesirable effects like high leakage current in transistors, which can offset additional benefits from scaling down. Development of three-dimensional transistors, by spatial extension in the third dimension, has allowed higher contact area with a gate electrode and better control over conductivity in the semiconductor channel. However, these devices do not utilize the large surface area and interfaces for new electronic functionality. Here, we demonstrate air gating and chemical gating in hollow semiconductor nanotube devices and highlight the potential for development of novel transistors that can be modulated using channel bias, gate voltage, chemical composition, and concentration. Using chemical gating, we reversibly altered the conductivity of nanoscaled semiconductor nanotubes (10-500 nm TiO2 nanotubes) by six orders of magnitude, with a tunable rectification factor (ON/OFF ratio) ranging from 1-10(6). While demonstrated air- and chemical-gating speeds were slow here (∼seconds) due to the mechanical-evacuation rate and size of our chamber, the small nanoscale volume of these hollow semiconductors can enable much higher switching speeds, limited by the rate of adsorption/desorption of molecules at semiconductor interfaces. These chemical-gating effects are completely reversible, additive between different chemical compositions, and can enable semiconductor nanoelectronic devices for 'chemical transistors', 'chemical diodes', and very high-efficiency sensing applications. PMID:26134618

  16. Discharge performance of solid-state oxygen shuttle metal-air battery using Ca-stabilized ZrO2 electrolyte.

    PubMed

    Inoishi, Atsushi; Kim, Hack-Ho; Sakai, Takaaki; Ju, Young-Wan; Ida, Shintaro; Ishihara, Tatsumi

    2015-04-13

    The effects of metal choice on the electrochemical performance of oxygen-shuttle metal-air batteries with Ca-stabilized ZrO2 (CSZ) as the electrolyte and various metals as the anodes were studied at 1073 K. The equilibrium oxygen partial pressure (P O 2) in the anode chamber was governed by the metal used in the anode chamber. A lower-P O 2 environment in the anode decreased the polarization resistance of the anode. The oxidation of oxide ions to oxygen in the anode is drastically enhanced by the n-type conduction generated in the CSZ electrolyte when it is exposed to a reducing atmosphere. A high discharge potential and high capacity can be achieved in an oxygen-shuttle battery with a Li or Mg anode because of the fast anode reaction compared to that of cells with a Zn, Fe, or Sn anode. However, only the mildly reducing metals (Zn, Si, Fe, and Sn) can potentially be used in rechargeable metal-air batteries because the transport number of the CSZ electrolyte must be unity during charge and discharge. Oxygen shuttle rechargeable batteries with Fe, and Sn electrodes are demonstrated. PMID:25727525

  17. Adsorption of O2 and C2Hn (n = 2, 4, 6) on the Al9Co2(0 0 1) and o-Al13Co4(1 0 0) complex metallic alloy surfaces

    NASA Astrophysics Data System (ADS)

    Wardé, M.; Herinx, M.; Ledieu, J.; Serkovic Loli, L. N.; Fournée, V.; Gille, P.; Le Moal, S.; Barthés-Labrousse, M.-G.

    2015-12-01

    Oxidation of the Al9Co2(0 0 1) and Al13Co4(1 0 0) surfaces has been performed in a wide range of temperatures at 2 × 10-8 or 1 × 10-7 mbar oxygen pressure. Only Alsbnd O bonding is observed. The oxidation kinetics are controlled by the quantity of oxygen sticking on the surface. Oxidation results from a competition between several effects: formation of an oxide film, dissolution of the film, oxygen desorption and oxygen dissolution into the bulk. For temperatures lower than 710 K for the Al9Co2(0 0 1) surface and 925 K for the Al13Co4(1 0 0) surface, a ∼5 Å thick oxide film is formed which does not show any long-range order and desorbs upon annealing. When oxidation is performed at higher temperatures, oxygen diffusion into the bulk is observed. A poorly ordered oxide film having a sixton structure is formed on the Al9Co2(0 0 1) surface when oxidation is performed at 775 K, which is dissolved when annealing at higher temperatures. On the Al13Co4(1 0 0) surface, only a weak streaky polar circle is observed following annealing at 925 K the film formed at room temperature, which corresponds to an hexagonal network of O atoms into small ultrathin oxide layers domains. The oxidation behaviour of the Al9Co2(0 0 1) and Al13Co4(1 0 0) surfaces has been ascribed to the strong covalent character of bonds present in these Alsbnd Co phases, which prevents aluminium diffusion. C2Hn molecules (n = 2, 4, 6) do not adsorb on the Al13Co4(1 0 0) surface in the experimental conditions used in this study, thus suggesting that this surface might not be the active one in the semi-hydrogenation of acetylene.

  18. Characteristics of a laser triggered spark gap using air, Ar, CH4, H2, He, N2, SF6, and Xe

    NASA Astrophysics Data System (ADS)

    Kimura, W. D.; Kushner, M. J.; Seamans, J. F.

    1988-03-01

    A KrF discharge laser (248 nm) has been used to laser trigger, by volume preionization, a spark gap switch (38-65 kV, >10 kA, 100 ns pulse duration) filled with 20 different gas mixtures using various combinations of air, Ar, CH4, H2, He, N2 SF6, and Xe. A pulsed laser interferometer is used to probe the spark column. Characteristics studied include the internal structure of the column, the arc expansion rate, and evidence of any photoionization precursor effect. Our results show that the rate of arc expansion varies depending on the average molecular weight of the mixtures. In this experiment, pure H2 has the highest rate (≊9.5×105 cm/s) and air has one of the lowest (≊7×105 cm/s) for the same hold-off voltage. A computer model of the spark column formation is able to predict most of the structure observed in the arcs, including the effect of mixing gases with widely different molecular weights. The work suggests that, under proper circumstances, the spark gap switch performance may be improved by using gases lighter than conventional switch gases such as SF6.

  19. Atomic Layer Deposition of TiO2 for a High-Efficiency Hole-Blocking Layer in Hole-Conductor-Free Perovskite Solar Cells Processed in Ambient Air.

    PubMed

    Hu, Hang; Dong, Binghai; Hu, Huating; Chen, Fengxiang; Kong, Mengqin; Zhang, Qiuping; Luo, Tianyue; Zhao, Li; Guo, Zhiguang; Li, Jing; Xu, Zuxun; Wang, Shimin; Eder, Dominik; Wan, Li

    2016-07-20

    In this study we design and construct high-efficiency, low-cost, highly stable, hole-conductor-free, solid-state perovskite solar cells, with TiO2 as the electron transport layer (ETL) and carbon as the hole collection layer, in ambient air. First, uniform, pinhole-free TiO2 films of various thicknesses were deposited on fluorine-doped tin oxide (FTO) electrodes by atomic layer deposition (ALD) technology. Based on these TiO2 films, a series of hole-conductor-free perovskite solar cells (PSCs) with carbon as the counter electrode were fabricated in ambient air, and the effect of thickness of TiO2 compact film on the device performance was investigated in detail. It was found that the performance of PSCs depends on the thickness of the compact layer due to the difference in surface roughness, transmittance, charge transport resistance, electron-hole recombination rate, and the charge lifetime. The best-performance devices based on optimized TiO2 compact film (by 2000 cycles ALD) can achieve power conversion efficiencies (PCEs) of as high as 7.82%. Furthermore, they can maintain over 96% of their initial PCE after 651 h (about 1 month) storage in ambient air, thus exhibiting excellent long-term stability. PMID:27340730

  20. Effects of CO 2 in air on Li deintercalation from LiNi 1- x- yCo xAl yO 2

    NASA Astrophysics Data System (ADS)

    Matsumoto, Kazutoshi; Kuzuo, Ryuichi; Takeya, Kaname; Yamanaka, Atsushi

    The reaction of CO 2 and practical high-performance cathode materials LiNi 1- x- yCo xAl yO 2 was examined with XRD at RT and high temperature, TGA, IR, and chemical analysis. Even at room temperature, Li deintercalation took place and formed Li 2CO 3 on the mother surface. The conversion to Li 2CO 3 in air at 55% RH at 25°C was in proportion to the square root of exposure time. It was 8% after being left for 500 h. Using high-temperature XRD at 25-800°C, the Li 2CO 3 phase formation was confirmed from about 500°C, and the conversion exceeded 70% under atmospheric CO 2 at 675°C. The activation energy of the reaction of deintercalated Li and CO 2 was estimated by Ozawa's method. The activation energy obtained using Ozawa's method was 130 kJ/mol for CO 2 diffusing through the Li 2CO 3 layer which formed on the surface during the reaction.

  1. Binder-Free and Carbon-Free 3D Porous Air Electrode for Li-O2 Batteries with High Efficiency, High Capacity, and Long Life.

    PubMed

    Luo, Wen-Bin; Gao, Xuan-Wen; Shi, Dong-Qi; Chou, Shu-Lei; Wang, Jia-Zhao; Liu, Hua-Kun

    2016-06-01

    Pt-Gd alloy polycrystalline thin film is deposited on 3D nickel foam by pulsed laser deposition method serving as a whole binder/carbon-free air electrode, showing great catalytic activity enhancement as an efficient bifunctional catalyst for the oxygen reduction and evolution reactions in lithium oxygen batteries. The porous structure can facilitate rapid O2 and electrolyte diffusion, as well as forming a continuous conductive network throughout the whole energy conversion process. It shows a favorable cycle performance in the full discharge/charge model, owing to the high catalytic activity of the Pt-Gd alloy composite and 3D porous nickel foam structure. Specially, excellent cycling performance under capacity limited mode is also demonstrated, in which the terminal discharge voltage is higher than 2.5 V and the terminal charge voltage is lower than 3.7 V after 100 cycles at a current density of 0.1 mA cm(-2) . Therefore, this electrocatalyst is a promising bifunctional electrocatalyst for lithium oxygen batteries and this depositing high-efficient electrocatalyst on porous substrate with polycrystalline thin film by pulsed laser deposition is also a promising technique in the future lithium oxygen batteries research. PMID:27120699

  2. A new portable infrared laser spectrometer for field measurements of N2O and CH4 emissions at the air / land interface

    NASA Astrophysics Data System (ADS)

    Guimbaud, Christophe; Catoire, Valéry; Gogo, Sébastien; Robert, Claude; Laggoun-Defarge, Fatima; Nicoullaud, Bernard; Richard, Guy

    2010-05-01

    A new type of portable infra red spectrometer (SPIRIT : SPectromètre Infra-Rouge In situ Troposphérique) using a quantum cascade laser and a patented new long multipass optical cell has been set up for the simultaneous flux measurements of two Greenhouse Gases (GHG): nitrous oxide (N2O) and methane (CH4), at the air land interface. The basics of the instrument, the data derivation for trace gas concentration determination in the atmosphere, and the chamber method to derive emission fluxes of these GHG from lands are described. The analytical performances of SPIRIT are tested in two types of lands in Region Centre (France): (i) an anthropogenized sphagnum peatland (Laguette; Neuvy sur Barangeon) characterized by vascular plants invasion (ii) a sandy soil in the site of INRA-Orléans. The ability of SPIRIT to assess with precision spatial and temporal dependence emissions of these GHG in the field is demonstrated. In addition emission modes (diffusive episodes and bubbling events) can be observed and quantified due to the high frequency (1 Hz) of the concentration measured. SPIRIT adaptation for detailed process-oriented studies of GHG flux emissions is also demonstrated by the investigation of emission dependence as a function of biotic and abiotic parameters (including diurnal cycle sensibility and emission modes); processes of C exchanges between different compartments of the biota can be studied. Such investigations are required for a better understanding of the lands to atmosphere exchange mechanisms of GHG and for the prediction of feedbacks on GHG emissions in response to anthropogenic or climate change perturbations of terrestrial ecosystems. Implications of SPIRIT in other air lands studies are also presented.

  3. Preparing non-volatile resistive switching memories by tuning the content of Au@air@TiO2-h yolk-shell microspheres in a poly(3-hexylthiophene) layer

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Liu, Quan; Zhang, Chun-Yu; Jiang, Jun; Wang, Li-Hua; Chen, Dong-Yun; Xu, Qing-Feng; Lu, Jian-Mei

    2015-11-01

    Crystalline hybrid microspheres, encapsulating a Au nanocore in the hollow cavity of a hairy semiconductor TiO2 shell (Au@air@TiO2-h microspheres) were prepared using template-assisted synthesis methods. The as-prepared microspheres are dispersed into a poly(3-hexylthiophene) (P3HT) matrix and used as a memory active layer. The electrical rewritable memory effects of Al/[Au@air@TiO2-h + P3HT]/ITO sandwich devices can be effectively and exactly controlled by tuning the microsphere content in the electroactive layer. To clarify the switching mechanism, different components in the device, such as P3HT and the microspheres, have been investigated. And it was determined that the switching mechanism can be attributed to the formation and rupture of oxygen vacancy filaments. These results suggest that the Au@air@TiO2-h microspheres are potentially capable of high density data storage. In addition, this finding could provide important guidelines for the reproducibility of nanocomposite-based memory devices and is helpful to demonstrate the switching mechanism of these devices.Crystalline hybrid microspheres, encapsulating a Au nanocore in the hollow cavity of a hairy semiconductor TiO2 shell (Au@air@TiO2-h microspheres) were prepared using template-assisted synthesis methods. The as-prepared microspheres are dispersed into a poly(3-hexylthiophene) (P3HT) matrix and used as a memory active layer. The electrical rewritable memory effects of Al/[Au@air@TiO2-h + P3HT]/ITO sandwich devices can be effectively and exactly controlled by tuning the microsphere content in the electroactive layer. To clarify the switching mechanism, different components in the device, such as P3HT and the microspheres, have been investigated. And it was determined that the switching mechanism can be attributed to the formation and rupture of oxygen vacancy filaments. These results suggest that the Au@air@TiO2-h microspheres are potentially capable of high density data storage. In addition, this

  4. Temperature dependences for N2- and air-broadened Lorentz half-width coefficients of methane transitions around 3.38 μm

    NASA Astrophysics Data System (ADS)

    Ma, Hongliang; Liu, Qiang; Cao, Zhensong; Chen, Weidong; Vicet, Aurore; Huang, Yinbo; Zhu, Wenyue; Gao, Xiaoming; Rao, Ruizhong

    2016-03-01

    We have measured high-resolution absorption spectra of methane broadened by N2 and air at sample temperatures between 173.0 K and room temperature. The measurements were performed based on direct laser absorption spectroscopy using a tunable diode laser combined with a temperature controlled cryogenically cooled absorption cell. These spectra have been analyzed to determine the pressure-broadened half-width coefficients as well as their temperature dependences for six singlet lines belonging to the ν3 band of methane near 3.38 μm. To our knowledge, the temperature dependence exponents for the pressure-broadened half-width coefficients are reported experimentally for the first time for six transitions of 12CH4 with intensities stronger than 4×10-20 cm-1/(molecule cm-2). The measured half-width coefficients and the temperature dependence exponents of these transitions are compared with the available values reported in the literature and the HITRAN2012 database. Agreements and discrepancies are discussed.

  5. Vought O2U-1 Corsair

    NASA Technical Reports Server (NTRS)

    1930-01-01

    Vought O2U-1 Corsair: The Vought O2U-1 was the first Vought airplane to carry the name Corsair. The O2U was built as an observation aircraft for the Navy, and the example flown by the NACA for evaluation and cowling tests was one of the last O2U-1s built. This Corsair came from the Naval Reserve squadron at Naval Air Station Anacostia, Washington, D. C.

  6. Dissociative recombination of O2(+), NO(+) and N2(+)

    NASA Technical Reports Server (NTRS)

    Guberman, S. L.

    1983-01-01

    A new L(2) approach for the calculation of the threshold molecular capture width needed for the determination of DR cross sections was developed. The widths are calculated with Fermi's golden rule by substituting Rydberg orbitals for the free electron continuum coulomb orbital. It is shown that the calculated width converges exponentially as the effective principal quantum number of the Rydberg orbital increases. The threshold capture width is then easily obtained. Since atmospheric recombination involves very low energy electrons, the threshold capture widths are essential to the calculation of DR cross sections for the atmospheric species studied here. The approach described makes use of bound state computer codes already in use. A program that collects width matrix elements over CI wavefunctions for the initial and final states is described.

  7. Preparing non-volatile resistive switching memories by tuning the content of Au@air@TiO2-h yolk-shell microspheres in a poly(3-hexylthiophene) layer.

    PubMed

    Wang, Peng; Liu, Quan; Zhang, Chun-Yu; Jiang, Jun; Wang, Li-Hua; Chen, Dong-Yun; Xu, Qing-Feng; Lu, Jian-Mei

    2015-12-14

    Crystalline hybrid microspheres, encapsulating a Au nanocore in the hollow cavity of a hairy semiconductor TiO2 shell (Au@air@TiO2-h microspheres) were prepared using template-assisted synthesis methods. The as-prepared microspheres are dispersed into a poly(3-hexylthiophene) (P3HT) matrix and used as a memory active layer. The electrical rewritable memory effects of Al/[Au@air@TiO2-h + P3HT]/ITO sandwich devices can be effectively and exactly controlled by tuning the microsphere content in the electroactive layer. To clarify the switching mechanism, different components in the device, such as P3HT and the microspheres, have been investigated. And it was determined that the switching mechanism can be attributed to the formation and rupture of oxygen vacancy filaments. These results suggest that the Au@air@TiO2-h microspheres are potentially capable of high density data storage. In addition, this finding could provide important guidelines for the reproducibility of nanocomposite-based memory devices and is helpful to demonstrate the switching mechanism of these devices. PMID:26541116

  8. Effects of elevated ozone concentration on CH4 and N2O emission from paddy soil under fully open-air field conditions.

    PubMed

    Tang, Haoye; Liu, Gang; Zhu, Jianguo; Kobayashi, Kazuhiko

    2015-04-01

    We investigated the effects of elevated ozone concentration (E-O3) on CH4 and N2O emission from paddies with two rice cultivars: an inbred Indica cultivar Yangdao 6 (YD6) and a hybrid one II-you 084 (IIY084), under fully open-air field conditions in China. A mean 26.7% enhancement of ozone concentration above the ambient level (A-O3) significantly reduced CH4 emission at tillering and flowering stages leading to a reduction of seasonal integral CH4 emission by 29.6% on average across the two cultivars. The reduced CH4 emission is associated with O3-induced reduction in the whole-plant biomass (-13.2%), root biomass (-34.7%), and maximum tiller number (-10.3%), all of which curbed the carbon supply for belowground CH4 production and its release from submerged soil to atmosphere. Although no significant difference was detected between the cultivars in the CH4 emission response to E-O3, a larger decrease in CH4 emission with IIY084 (-33.2%) than that with YD6 (-7.0%) was observed at tillering stage, which may be due to the larger reduction in tiller number in IIY084 by E-O3. Additionally, E-O3 reduced seasonal mean NOx flux by 5.7% and 11.8% with IIY084 and YD6, respectively, but the effects were not significant statistically. We found that the relative response of CH4 emission to E-O3 was not significantly different from those reported in open-top chamber experiments. This study has thus confirmed that increasing ozone concentration would mitigate the global warming potential of CH4 and suggested consideration of the feedback mechanism between ozone and its precursor emission into the projection of future ozone effects on terrestrial ecosystem. PMID:25403809

  9. Impacts on Air Quality due to Photosensitized Production of Excited State O2 (1Δg) by PAHs and Oxy-PAHs in the Lower Atmosphere: An Experimental and Computational Modeling Approach

    NASA Astrophysics Data System (ADS)

    Montoya, G. A.; Carreras-Sospedra, M.; Montoya, J.; Dabdub, D.; Foster, K. L.

    2014-12-01

    Complex reactions between hydroxyl radicals (OH) and volatile organic compounds (VOCs) in the lower atmosphere have a high impact on the formation/fates of airborne toxic chemicals, polycyclic aromatic hydrocarbons (PAHs), and particulate matter.1 Recently, air quality models have been implemented to identify OH sources, but have underpredicted OH concentrations. Studies suggest that O2 (1Δg) is produced via an energy transfer (ET) mechanism initiated by the electronic excitation of PAH and oxygenated-PAH. Energy transfer involves the formation of triplet excited state PAH which is then quenched by the surrounding ground state O2 (3∑g) resulting in excited state O2 (1Δg) formation. Excited state O2 (1Δg) is known to readily react with mono-olefins to produce organic hydroperoxides.2,3 Furthermore, the organic hydroperoxide can photodegrade to yield OH. In this study, a Nd:YAG laser coupled to a time-resolved near infrared detector was used to obtain quantum yields of O2 (1Δg) production by irradiating PAHs and oxy-PAHs at both 355 nm and 532 nm in different solvents. Select PAHs, primarily emitted by combustion engines (e.g. pyrene and benzo[a]pyrene), and their oxygenated forms (oxy-PAHs) have been identified as highly efficient O2 (1Δg) photosensitizers. For example, the measured quantum yield for pyrene in toluene was 0.90 ± 0.02. The measured quantum yields were used to calculate the photochemical rate constants for O2 (1Δg) production via ET from electronically excited PAHs and oxy-PAHs. These results were incorporated into the University of California, Irvine-California Institute of Technology (UCI-CIT) model to assess the impact on OH concentrations and the overall air quality of the South Coast Air Basin of California. References 1 Finlayson-Pitts, B.J., and J. N. Pitts (1997), Science, 276(5315),1045-1052. 2 Foote, C. S. (1968), Accts. Chem. Res., 1, 104-110; Gollnick, K. (1968), Adv. Photochem., 6, 1-112; Kearns, D. R. (1971), Chem. Rev., 71, 395

  10. Weak interactions in ion–ligand complexes of C3H3(+) isomers: competition between H-bound and C-bound structures in c-C3H3(+)·L and H2CCCH(+)·L (L = Ne, Ar, N2, CO2, and O2).

    PubMed

    Botschwina, Peter; Oswald, Rainer; Dopfer, Otto

    2011-08-21

    Explicitly correlated coupled cluster theory at the CCSD(T)-F12x level (T. B. Adler, G. Knizia, and H.-J. Werner, J. Chem. Phys.127, 221106, 2007) has been employed to study structures and vibrations of complexes of type c-C(3)H(3)(+)·L and H(2)C(3)H(+)·L (L = Ne, Ar, N(2), CO(2), and O(2)). Both cations have different binding sites, allowing for the formation of weak to moderately strong hydrogen bonds as well as "C-bound" or "π-bound" structures. In contrast to previous expectations, the energetically most favourable structures of all H(2)C(3)H(+)·L complexes investigated are "C-bound", with the ligand bound to the methylenic carbon atom. The theoretical predictions enable a more detailed interpretation of infrared photodissociation (IRPD) spectra than was possible hitherto. In particular, the bands observed in the range 3238-3245 cm(-1) (D. Roth and O. Dopfer, Phys. Chem. Chem. Phys.4, 4855, 2002) are assigned to essentially free acetylenic CH stretching vibrations of the propargyl cation in "C-bound" H(2)C(3)H(+)·L complexes. PMID:21637871

  11. Synthesis and characterization of MnO 2 colloids

    NASA Astrophysics Data System (ADS)

    Yadav, Pooja; Olsson, Richard T.; Jonsson, Mats

    2009-11-01

    This work addresses the issue of radiation chemical synthesis of MnO 2 nanoparticles and also illustrates the ease of formation of nanorods and sheets by adroit manipulation of experimental conditions. The radiation chemical yield ( G-value) for reduction of Mn (VII) by the hydrated electron was found to be 0.27 μmol J -1 and 0.17 μmol J -1 respectively, when tert. butanol and isopropanol were used as scavengers in nitrogen-saturated solutions. The colloids formed upon irradiation of air-saturated solution and N 2-purged solution with tert. butanol as scavenger were found to be most stable. Irradiation of air-saturated solution containing 4×10 -4 M KMnO 4 at a dose of 1692 Gy resulted in the formation of nanorods of the dimension 100-150 nm and nanospheres in the range 10-20 nm. Irradiation of N 2-purged solution containing tert. butanol as scavenger for rad OH-produced reticulated structure of nanorods with length varying from 50 to 100 nm at a dose of 1692 Gy. Elemental analysis was performed using scanning electron microscope on MnO 2 formed by reduction and oxidation and the purity was found to be 98% of elemental Mn content.

  12. General model for N2O and N2 gas emissions from soils due to dentrification

    NASA Astrophysics Data System (ADS)

    Del Grosso, S. J.; Parton, W. J.; Mosier, A. R.; Ojima, D. S.; Kulmala, A. E.; Phongpan, S.

    2000-12-01

    Observations of N gas loss from incubations of intact and disturbed soil cores were used to model N2O and N2 emissions from soil as a result of denitrification. The model assumes that denitrification rates are controlled by the availability in soil of NO3 (e- acceptor), labile C compounds (e- donor), and O2 (competing e- acceptor). Heterotrophic soil respiration is used as a proxy for labile C availability while O2 availability is a function of soil physical properties that influence gas diffusivity, soil WFPS, and O2 demand. The potential for O2 demand, as indicated by respiration rates, to contribute to soil anoxia varies inversely with a soil gas diffusivity coefficient which is regulated by soil porosity and pore size distribution. Model inputs include soil heterotrophic respiration rate, texture, NO3 concentration, and WFPS. The model selects the minimum of the NO3 and CO2 functions to establish a maximum potential denitrification rate for particular levels of e- acceptor and C substrate and accounts for limitation of O2 availability to estimate daily N2+N2O flux rates. The ratio of soil NO3 concentration to CO2 emission was found to reliably (r2=0.5) model the ratio of N2 to N2O gases emitted from the intact cores after accounting for differences in gas diffusivity among the soils. The output of the ratio function is combined with the estimate of total N gas flux rate to infer N2O emission. The model performed well when comparing observed and simulated values of N2O flux rates with the data used for model building (r2=0.50) and when comparing observed and simulated N2O+N2 gas emission rates from irrigated field soils used for model testing (r2=0.47).

  13. Characteristics of N2 and N2/O2 atmospheric pressure glow discharges

    NASA Astrophysics Data System (ADS)

    Klas, Matej; Ptasinska, Sylwia

    2013-04-01

    Due to its richness in various active species a nitrogen plasma discharge is a promising tool for many applications. However, owing to the difficulties in igniting and sustaining this type of discharge, the construction of plasma sources operating in nitrogen gas is still very challenging. In this work we describe and characterize two home-built plasma sources with two different electrode configurations able to work in a nitrogen atmosphere. For this purpose, the jets of plasma species formed are studied by emission spectroscopy, and thermal and electrical measurements. It is noted that the addition of a small amount of oxygen to the nitrogen flow changes the optical and thermal properties of the jet and these results are also discussed.

  14. Enhanced Photoelectrochemical Performance of TiO2 Nanorod Arrays by a 500°C Annealing in Air: Insights into the Mechanism

    NASA Astrophysics Data System (ADS)

    Zhang, Shuang; Gu, Xiuquan; Zhao, Yulong; Qiang, Yinghuai

    2016-01-01

    Oriented, single-crystal TiO2 nanorod arrays (NRAs) were synthesized for photoelectrochemical (PEC) water-splitting by a facile hydrothermal route. It was observed that a 500°C annealing process facilitated enhancing the PEC activity of TiO2 NRAs, in agreement with our previous reports on NRA-related solar cells. Further, electrochemical impedance measurements were employed to investigate the underlying mechanism. Compared with pristine TiO2 NRAs, the 500°C sintered samples showed a positive flat-band shifting of ˜0.12 V as well as a suppression of the donor density. Thus, suggesting that the enhanced PEC performance might be attributed to the widening of depletion layer regions due to the reduction of crystal defects after sintering. The mechanism was also expanded to explain why the dye-sensitized solar cells made with sintered TiO2 NRAs exhibited an 11-times higher power conversion efficiency than those consisting of pristine arrays.

  15. Absolute intensities and self-, N2-, and air-broadened Lorentz halfwidths for selected lines in the nu3 band of (C-12)H3D from measurements with a tunable diode laser spectrometer

    NASA Technical Reports Server (NTRS)

    Malathy Devi, V.; Benner, D. C.; Rinsland, C. P.; Smith, M. A. H.; Thakur, K. B.

    1986-01-01

    Absolute intensities and self-, air- and N2-broadened half-widths have been determined for the first time for individual lines in the nu3(A1) band of (C-12)H3D near 7.6 microns from measurements of individual vibration-rotation lines using a tunable diode laser spectrometer. The intensity measurements are believed to be accurate to within three percent. Within experimental uncertainties, equal broadening efficiencies are found for both air and nitrogen. Self-broadened half-widths determined for three transitions yield an average half-width value of 0.803 + or -0.0010/cm/atm at 296 K.

  16. Extension of pulmonary O2 tolerance in man at 2 ATA by intermittent O2 exposure

    NASA Technical Reports Server (NTRS)

    Hendricks, P. L.; Hall, D. A.; Hunter, W. L., Jr.; Haley, P. J.

    1977-01-01

    To study extension of O2 tolerance by interruption of hyperoxic exposure, five healthy volunteers were exposed to oxygen at 2 ATA on an intermittent schedule of 20 min breathing O2, alternating with 5 min on a normoxic N2-O2 mixture. The cycle was repeated until symptoms or signs of O2 toxicity caused cessation of the experiment. Tracheal irritation and burning on inspiration occurred after 6-9 'oxygen hours' of exposure and progressed to severe tracheobronchial burning sensation, chest pain, and dyspnea after 11-15 h of O2. With intermittent O2 administration, nearly a doubling of the average duration of actual oxygen breathing was required to induce marked vital capacity change (more than 10%) as compared to the previous studies of continuous O2 exposure.

  17. Fractional Distillation of Air and Other Demonstrations with Condensed Gases

    ERIC Educational Resources Information Center

    Oliver-Hoyo, Maria; Switzer, William L., III; Eierman, Robert

    2005-01-01

    The learning objectives of the fractional distillation of air and other demonstrations includes observing N2, O2, CO2 and H2O in air, studying the fractional separation of components based on boiling point differences and so on. The materials, reagent and equipment preparation, experimental procedures, hazards of the demonstration are also…

  18. Doyle O-2 Oriole

    NASA Technical Reports Server (NTRS)

    1929-01-01

    Doyle O-2 Oriole: The parasol-winged Doyle O-2 Oriole monoplane was flown by the NACA at Langley starting in 1929. The O-2 designation was not a military type number, but rather a company designation. The Oriole was later traded as partial payment for a Fairchild 22. The O-2 was outfitted with a fore-and-aft sliding weight in the cockpit for longitudinal stability tests.

  19. Isolation of H5N6, H7N9 and H9N2 avian influenza A viruses from air sampled at live poultry markets in China, 2014 and 2015.

    PubMed

    Zhou, Jie; Wu, Jie; Zeng, Xianqiao; Huang, Guofeng; Zou, Lirong; Song, Yingchao; Gopinath, Divya; Zhang, Xin; Kang, Min; Lin, Jinyan; Cowling, Benjamin J; Lindsley, William G; Ke, Changwen; Peiris, Joseph Sriyal Malik; Yen, Hui-Ling

    2016-09-01

    Zoonotic infections by avian influenza viruses occur at the human-poultry interface, but the modes of transmission have not been fully investigated. We assessed the potential for airborne and fomite transmission at live poultry markets in Guangzhou city and in Hong Kong Special Administrative Region (SAR), China, during 2014 and 2015. Viral genome and infectious avian influenza A viruses of H5N6, H7N9, and H9N2 subtypes were detected predominantly from particles larger or equal to 1 μm in diameter in the air sampled with cyclone-based bioaerosol samplers at the live poultry markets in Guangzhou. Influenza A(H9N2) viruses were ubiquitously isolated every month during the study period from air and environmental swabs, and different lineages of H9N2 virus were isolated from markets where chickens and minor land-based poultry were sold. The use of de-feathering devices increased the quantity of virus-laden airborne particles while market closure reduced the amount of such particles. The results highlight the possibility of airborne transmission of avian influenza viruses among poultry or from poultry to humans within such settings. This may explain epidemiological observations in which some patients with H7N9 infection reported being in markets but no direct contact with live poultry or poultry stalls. PMID:27608369

  20. Membraneless enzymatic ethanol/O2 fuel cell: Transitioning from an air-breathing Pt-based cathode to a bilirubin oxidase-based biocathode

    NASA Astrophysics Data System (ADS)

    Aquino Neto, Sidney; Milton, Ross D.; Hickey, David P.; De Andrade, Adalgisa R.; Minteer, Shelley D.

    2016-08-01

    The bioelectrooxidation of ethanol was investigated in a fully enzymatic membraneless ethanol/O2 biofuel cell assembly using hybrid bioanodes containing multi-walled carbon nanotube (MWCNT)-decorated gold metallic nanoparticles with either a pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase (ADH) enzyme or a nicotinamide adenine dinucleotide (NAD+)-dependent ADH enzyme. The biofuel cell anode was prepared with the PQQ-dependent enzyme and designed using either a direct electron transfer (DET) architecture or via a mediated electron transfer (MET) configuration through a redox polymer, 1,1‧-dimethylferrocene-modified linear polyethyleneimine (FcMe2-C3-LPEI). In the case of the bioanode containing the NAD+-dependent enzyme, only the mediated electron transfer mechanism was employed using an electropolymerized methylene green film to regenerate the NAD+ cofactor. Regardless of the enzyme being employed at the anode, a bilirubin oxidase-based biocathode prepared within a DET architecture afforded efficient electrocatalytic oxygen reduction in an ethanol/O2 biofuel cell. The power curves showed that DET-based bioanodes via the PQQ-dependent ADH still lack high current densities, whereas the MET architecture furnished maximum power density values as high as 226 ± 21 μW cm-2. Considering the complete membraneless enzymatic biofuel cell with the NAD+-dependent ADH-based bioanode, power densities as high as 111 ± 14 μW cm-2 were obtained. This shows the advantage of PQQ-dependent ADH for membraneless ethanol/O2 biofuel cell applications.

  1. Membraneless enzymatic ethanol/O2 fuel cell: Transitioning from an air-breathing Pt-based cathode to a bilirubin oxidase-based biocathode

    NASA Astrophysics Data System (ADS)

    Aquino Neto, Sidney; Milton, Ross D.; Hickey, David P.; De Andrade, Adalgisa R.; Minteer, Shelley D.

    2016-08-01

    The bioelectrooxidation of ethanol was investigated in a fully enzymatic membraneless ethanol/O2 biofuel cell assembly using hybrid bioanodes containing multi-walled carbon nanotube (MWCNT)-decorated gold metallic nanoparticles with either a pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase (ADH) enzyme or a nicotinamide adenine dinucleotide (NAD+)-dependent ADH enzyme. The biofuel cell anode was prepared with the PQQ-dependent enzyme and designed using either a direct electron transfer (DET) architecture or via a mediated electron transfer (MET) configuration through a redox polymer, 1,1‧-dimethylferrocene-modified linear polyethyleneimine (FcMe2-C3-LPEI). In the case of the bioanode containing the NAD+-dependent enzyme, only the mediated electron transfer mechanism was employed using an electropolymerized methylene green film to regenerate the NAD+ cofactor. Regardless of the enzyme being employed at the anode, a bilirubin oxidase-based biocathode prepared within a DET architecture afforded efficient electrocatalytic oxygen reduction in an ethanol/O2 biofuel cell. The power curves showed that DET-based bioanodes via the PQQ-dependent ADH still lack high current densities, whereas the MET architecture furnished maximum power density values as high as 226 ± 21 μW cm-2. Considering the complete membraneless enzymatic biofuel cell with the NAD+-dependent ADH-based bioanode, power densities as high as 111 ± 14 μW cm-2 were obtained. This shows the advantage of PQQ-dependent ADH for membraneless ethanol/O2 biofuel cell applications.

  2. Reaction paths leading from O2/+/ to water clusters under cold mesospheric conditions

    NASA Astrophysics Data System (ADS)

    McCrumb, J. L.

    1982-06-01

    Reference is made to reported D-region positive ion measurements (Arnold and Krankowsky, 1974) in which a number of new cluster ions of minor abundance were apparent. It is noted that these ions, which were attributed to clusters with N2, O2, and CO2 ligands, were observable owing to enhanced O2(+) production and the low temperatures during the flight. Consideration is given here to these in situ ion data in view of recent laboratory ion-molecule reaction experiments that shed light on the mechanism leading from O2(+) to water clusters in air mixtures. Possible intermediates are discussed in terms of ion stability and the existence of effective reaction paths under the given atmospheric conditions. The intermediates proposed here are then fitted into a coherent reaction mechanism resulting in significant new pathways for the formation of protonated water clusters. A semiquantitative measure of the importance of each of the pathways is then calculated using signal flow graph theory.

  3. Multiphoton ionization of N2 by the third harmonic of a Nd:YAG laser - A new avenue for air diagnostics

    NASA Technical Reports Server (NTRS)

    Laufer, Gabriel; Krauss, Roland H.; Grinstead, Jay H.

    1991-01-01

    Laser-induced N2 ionization is accomplished using a commercially available Nd:YAG laser, and confirmed by means of ion-collection and spectral measurements. Neutral N2 is excited by six photons of the third harmonic frequency, or 355 nm, and is transformed to an ionized state. The radiation at 355 nm is separated from the fundamental and frequency-doubled Nd:YAG radiation to guarantee monochromatic incident radiation. Intense lines near 391.4 nm are found in the initial laser polarization and for a 90-degree rotation of polarization. The radiation at 391.4 nm is associated with an incoherent laser-induced flourescence process related to an ionized-state transition, and increases quadratically with laser power. A 45-mJ laser pulse focused to a diameter of 17 microns can produce an ion concentration of 3.25 x 10 to the 13th ions/cu cm. The large ion concentration and robust fluorescence signal make this technique an efficient method for time-of-flight velocimetry and in-flight testing.

  4. Towards high efficiency air-processed near-infrared responsive photovoltaics: bulk heterojunction solar cells based on PbS/CdS core-shell quantum dots and TiO2 nanorod arrays.

    PubMed

    Gonfa, Belete Atomsa; Kim, Mee Rahn; Delegan, Nazar; Tavares, Ana C; Izquierdo, Ricardo; Wu, Nianqiang; El Khakani, My Ali; Ma, Dongling

    2015-06-14

    Near infrared (NIR) PbS quantum dots (QDs) have attracted significant research interest in solar cell applications as they offer several advantages, such as tunable band gaps, capability of absorbing NIR photons, low cost solution processability and high potential for multiple exciton generation. Nonetheless, reports on solar cells based on NIR PbS/CdS core-shell QDs, which are in general more stable and better passivated than PbS QDs and thus more promising for solar cell applications, remain very rare. Herein we report high efficiency bulk heterojunction QD solar cells involving hydrothermally grown TiO2 nanorod arrays and PbS/CdS core-shell QDs processed in air (except for a device thermal annealing step) with a photoresponse extended to wavelengths >1200 nm and with a power conversion efficiency (PCE) as high as 4.43%. This efficiency was achieved by introducing a thin, sputter-deposited, uniform TiO2 seed layer to improve the interface between the TiO2 nanorod arrays and the front electrode, by optimizing TiO2 nanorod length and by conducting QD annealing treatment to enhance charge carrier transport. It was found that the effect of the seed layer became more obvious when the TiO2 nanorods were longer. Although photocurrent did not change much, both open circuit voltage and fill factor clearly changed with TiO2 nanorod length. This was mainly attributed to the variation of charge transport and recombination processes, as evidenced by series and shunt resistance studies. The optimal PCE was obtained at the nanorod length of ∼450 nm. Annealing is shown to further increase the PCE by ∼18%, because of the improvement of charge carrier transport in the devices as evidenced by considerably increased photocurrent. Our results clearly demonstrate the potential of the PbS/CdS core-shell QDs for the achievement of high PCE, solution processable and NIR responsive QD solar cells. PMID:25975363

  5. Rate coefficient for H + O2 + M = HO2 + M evaluated from shock tube measurements of induction times

    NASA Technical Reports Server (NTRS)

    Slack, M. W.

    1977-01-01

    Shock tube experiments measured hydrogen-air induction times near the second explosion limit. By matching these experimental results with numerically predicted induction times, the rate coefficient for the reaction H + O2 + M = HO2 + M was evaluated as k-sub 4,N2 = 3.3 (plus or minus .6) x 10 to the 15 cm to the 6th/sq mole/s.

  6. Enhancement of photocatalytic properties of TiO2 nanoparticles doped with CeO2 and supported on SiO2 for phenol degradation

    NASA Astrophysics Data System (ADS)

    Hao, Chunjing; Li, Jing; Zhang, Zailei; Ji, Yongjun; Zhan, Hanhui; Xiao, Fangxing; Wang, Dan; Liu, Bin; Su, Fabing

    2015-03-01

    A series of CeO2-TiO2 and CeO2-TiO2/SiO2 composites were prepared with TiCl4 and Ce (NO3)3·6H2O as precursors via a facile co-precipitation method. The obtained samples were characterized by various techniques such as X-ray diffraction (XRD), nitrogen adsorption (N2-BET), Fourier transformation infrared spectrum (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-Vis spectroscopy measurements. The results indicated that TiO2 doped with CeO2 and supported on SiO2 could reduce the crystallite size, inhibit the phase transformation, enhance the thermal stability, and effectively extend the spectral response from UV to visible range. When applied to the phenol photodegradation on a homemade batch reactor with an external cooling jacket, the CeO2-TiO2/SiO2 catalysts exhibited significantly enhanced photodegradation efficiency in comparison with commercial Degussa P25 and CeO2-TiO2. The unique catalytic properties of CeO2-TiO2/SiO2 were ascribed to improved electron-hole pairs separation efficiency and formation of more reactive oxygen species owing to the presence of Ce3+/Ce4+, as well as high dispersion of active component of CeO2-TiO2 as a result of the introduction of SiO2 support. Furthermore, the catalysts can be easily recovered from the reaction solution by centrifugation and reused for four cycles without significant loss of activity.

  7. Aqueous-phase chemistry and bactericidal effects from an air discharge plasma in contact with water: evidence for the formation of peroxynitrite through a pseudo-second-order post-discharge reaction of H2O2 and HNO2

    NASA Astrophysics Data System (ADS)

    Lukes, P.; Dolezalova, E.; Sisrova, I.; Clupek, M.

    2014-02-01

    The formation of transient species (OH·, NO2·, NO radicals) and long-lived chemical products (O3, H2O2, NO_{3}^{-} , NO_{2}^{-} ) produced by a gas discharge plasma at the gas-liquid interface and directly in the liquid was measured in dependence on the gas atmosphere (20% oxygen mixtures with nitrogen or with argon) and pH of plasma-treated water (controlled by buffers at pH 3.3, 6.9 or 10.1). The aqueous-phase chemistry and specific contributions of these species to the chemical and biocidal effects of air discharge plasma in water were evaluated using phenol as a chemical probe and bacteria Escherichia coli. The nitrated and nitrosylated products of phenol (4-nitrophenol, 2-nitrophenol, 4-nitrocatechol, 4-nitrosophenol) in addition to the hydroxylated products (catechol, hydroquinone, 1,4-benzoquinone, hydroxy-1,4-benzoquinone) evidenced formation of NO2·, NO· and OH· radicals and NO+ ions directly by the air plasma at the gas-liquid interface and through post-discharge processes in plasma-activated water (PAW) mediated by peroxynitrite (ONOOH). Kinetic study of post-discharge evolution of H2O2 and NO_{2}^{-} in PAW has demonstrated excellent fit with the pseudo-second-order reaction between H2O2 and NO_{2}^{-} . The third-order rate constant k = 1.1 × 103 M-2 s-1 for the reaction NO_{2}^{-} +H_{2}O_{2}+H^{+}\\to ONOOH+H_{2}O was determined in PAW at pH 3.3 with the rate of ONOOH formation in the range 10-8-10-9 M s-1. Peroxynitrite chemistry was shown to significantly participate in the antibacterial properties of PAW. Ozone presence in PAW was proved indirectly by pH-dependent degradation of phenol and detection of cis,cis-muconic acid, but contribution of ozone to the inactivation of bacteria by the air plasma was negligible.

  8. Influence of air/N2 treatment on the structural, morphological and optoelectronic traits of nanostructured ZnO:Mn thin films

    NASA Astrophysics Data System (ADS)

    Amoupour, E.; Abdolahzadeh Ziabari, A.; Andarva, H.; Ghodsi, F. E.

    2014-01-01

    Nanocrystalline ZnO:Mn thin films have been prepared by sol-gel dip-coating method. The content of Mn in sol was varied from 0 to 12 wt%. The influence of Mn concentration and annealing ambient (i.e. air and nitrogen) on the structural, morphological, optical and electrical properties of ZnO thin films were studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-visible spectroscopy and Hall Effect measurements. XRD results show that the films have hexagonal wurtzite structure and the crystallite size varies between 38 and 10 nm. The samples annealed in nitrogen indicate better crystallinity than those annealed in air. SEM results revealed that the surface smoothness of the films improved at higher content of Mn. AFM measurements exhibit that the RMS roughness of the samples reduces with Mn concentration. In comparison with air ambient, the electrical mobility improved with annealing in nitrogen. Meanwhile, it was found that introducing Mn decreased the electrical conductivity. The optical transparency and band gap of the doped films decreased with Mn doping. The band gap variation of the films due to Mn doping was discussed in details.

  9. Line parameters including temperature dependences of air- and self-broadened line shapes of 12C16O2: 2.06-μm region

    NASA Astrophysics Data System (ADS)

    Benner, D. Chris; Devi, V. Malathy; Sung, Keeyoon; Brown, Linda R.; Miller, Charles E.; Payne, Vivienne H.; Drouin, Brian J.; Yu, Shanshan; Crawford, Timothy J.; Mantz, Arlan W.; Smith, Mary Ann H.; Gamache, Robert R.

    2016-08-01

    This study reports the results from analyzing a number of high resolution, high signal-to-noise ratio (S/N) spectra in the 2.06-μm spectral region for pure CO2 and mixtures of CO2 in dry air. A multispectrum nonlinear least squares curve fitting technique has been used to retrieve the various spectral line parameters. The dataset includes 27 spectra: ten pure CO2, two 99% 13C-enriched CO2 and fifteen spectra of mixtures of 12C-enriched CO2 in dry air. The spectra were recorded at various gas sample temperatures between 170 and 297 K. The absorption path lengths range from 0.347 to 49 m. The sample pressures for the pure CO2 spectra varied from 1.1 to 594 Torr; for the two 13CO2 spectra the pressures were ∼10 and 146 Torr. For the air-broadened spectra, the pressures of the gas mixtures varied between 200 and 711 Torr with CO2 volume mixing ratios ranging from 0.014% to 0.203%. The multispectrum fitting technique was applied to fit simultaneously all these spectra to retrieve consistent set of line positions, intensities, and line shape parameters including their temperature dependences; for this, the Voigt line shape was modified to include line mixing (via the relaxation matrix formalism) and quadratic speed dependence. The new results are compared to select published values, including recent ab initio calculations. These results are required to retrieve the column averaged dry air mole fraction (XCO2) from space-based observations, such as the Orbiting Carbon Observatory-2 (OCO-2) satellite mission that NASA launched in July 2014.

  10. Effect of blood haemoglobin concentration on V̇O2,max and cardiovascular function in lowlanders acclimatised to 5260 m

    PubMed Central

    Calbet, J A L; Rådegran, G; Boushel, R; Søndergaard, H; Saltin, B; Wagner, P D

    2002-01-01

    The principal aim of this investigation was to determine the influence of blood haemoglobin concentration ([Hb]) on maximal exercise capacity and maximal O2 consumption (V̇O2,max) in healthy subjects acclimatised to high altitude. Secondarily, we examined the effects of [Hb] on the regulation of cardiac output (CO), blood pressure and muscular blood flow (LBF) during exercise. Eight Danish lowlanders (three females and five males; 24 ± 0.6 years, mean ± s.e.m.) performed submaximal and maximal exercise on a cycle ergometer after 9 weeks at an altitude of 5260 m (Mt Chacaltaya, Bolivia). This was done first with the high [Hb] resulting from acclimatisation and again 2-4 days later, 1 h after isovolaemic haemodilution with Dextran 70 to near sea level [Hb]. After measurements at maximal exercise while breathing air at each [Hb], subjects were switched to hyperoxia (55 % O2 in N2) and the measurements were repeated, increasing the work rate as tolerated. Hyperoxia increased maximal power output and leg V̇O2,max, showing that breathing ambient air at 5260 m, V̇O2,max is limited by the availability of O2 rather than by muscular oxidative capacity. Altitude increased [Hb] by 36 % from 136 ± 5 to 185 ± 5 g l−1 (P < 0.001), while haemodilution (replacing 1 l of blood with 1 l of 6 % Dextran) lowered [Hb] by 24 % to 142 ± 6 g l−1 (P < 0.001). Haemodilution had no effect on maximal pulmonary or leg V̇O2,max, or power output. Despite higher LBF, leg O2 delivery was reduced and maximal V̇O2 was thus maintained by higher O2 extraction. While CO increased linearly with work rate irrespective of [Hb] or inspired oxygen fraction (FI,O2), both LBF and leg vascular conductance were systematically higher when [Hb] was low. Close and significant relationships were seen between LBF (and CO) and both plasma noradrenaline and K+ concentrations, independently of [Hb] and FI,O2. In summary, under conditions where O2 supply limits maximal exercise, the increase in [Hb] with

  11. Legumes, N2 fixation and the H2 cycle

    NASA Astrophysics Data System (ADS)

    Layzell, D. B.

    2004-12-01

    Legume plants such as soybean or pea can form symbiotic, N2 fixing associations with bacteria that exist in root nodules. For every N2 fixed, 1 to 3 H2 are produced as a by-product of the nitrogenase reaction. Therefore, a typical N2 fixing legume crop produces about 200,000 L H2 gas (at STP) per hectare per crop season. This paper will summarize our current understanding of the processes leading to H2 production in legumes, the magnitude of H2 production associated with global cropping systems, and the implications for its production and oxidation on both the legumes and the soils in which they grow. Specific points may include: ˜ In symbioses lacking uptake hydrogenase (HUP) activity (thought to be the majority of crop legumes), the H2 diffuses into the soil where it is oxidized by soil microbes that grow up around the legume nodules. The kinetic properties of these microbes are very different (higher Km and Vmax) from that of microbes in soils exposed to normal air (ca. 0.5 ppm H2); ˜ Laboratory studies indicate that 60% of the reducing power from H2 is coupled to O2 uptake, whereas 40% is coupled to autotrophic CO2 fixation. The latter process should increase soil carbon stocks by about 25 kg C/ha/yr; ˜ At the site of the nitrogenase enzyme, H2 production is autocatalytic such that the higher the H2 concentration, the more H2 is produced and the less N2 fixed. The variable O2 diffusion barrier in legumes can act to restrict H2 diffusion from the nodule, thereby increasing the relative magnitude of H2 production versus N2 fixation; ˜ Studies to understand why legume symbioses make such an energy investment in H2 production have led to the discovery that H2 treated soils have improved fertility, supporting the growth and yield of legume and non-legume crops. This observation may account for the benefits of legumes when used in rotation with cereal crops, a phenomenon that has been used by farmers for over 2000 years, but which has remained unexplained. An

  12. Estimating Seasonal Cycles of Atmospheric CO2 and APO Resulting from Terrestrial NEE and Air-Sea O2 Fluxes using the Transcom T3L2 Pulse-Response Functions

    NASA Astrophysics Data System (ADS)

    Nevison, C. D.

    2011-12-01

    We present a method for translating modeled terrestrial net ecosystem exchange (NEE) fluxes of carbon into the corresponding annual mean cycles in atmospheric CO2. The method is based on the pulse-response functions from the Transcom 3 atmospheric tracer transport model (ATM) intercomparison. An oceanic version of the method is applied to air-sea O2 fluxes to estimate the corresponding annual mean cycles in atmospheric potential oxygen (APO). The estimated atmospheric seasonal cycles can be evaluated against observed atmospheric CO2 and APO data, which are measured at high precision at a wide range of monitoring sites and reflect the integrated impact of surface CO2 and O2 fluxes, respectively, across broad regions. The pulse-response function method is considerably faster than a full forward ATM simulation, allowing seasonal cycles from 13 different ATMS to be computed in minutes, rather than the days or weeks required for a single forward simulation. We evaluate the method against the results of full forward ATM simulations and examine the uncertainties associated with neglecting additional surface fluxes, e.g., from fossil fuel combustion, that may contribute to the observed seasonal cycles of CO2 and APO.

  13. Promotion effects of SiO2 or/and Al2O3 doped CeO2/TiO2 catalysts for selective catalytic reduction of NO by NH3.

    PubMed

    Zhao, Wenru; Tang, Yu; Wan, Yaping; Li, Liang; Yao, Si; Li, Xiaowei; Gu, Jinlou; Li, Yongsheng; Shi, Jianlin

    2014-08-15

    A series of the CeO2-based catalysts loaded on TiO2, TiO2-SiO2, TiO2-Al2O3, and TiO2-SiO2-Al2O3 supports were prepared by incipient impregnation method for the selective catalytic reduction (SCR) of NO by NH3 in the presence of oxygen. The SCR activities of the catalysts with different supports increases in the order of Ce/TiO2 < Ce/TiO2-20SiO2 ≈ Ce/TiO2-3.5Al2O3 < Ce/TiO2-20SiO2-3.5Al2O3. The Ce/TiO2-20SiO2-3.5Al2O3 catalyst showed 100% NO conversion in the temperature range of 250-425°C and 100% N2 selectivity in the whole temperature range. The catalytic activity of Ce/TiO2-20SiO2-3.5Al2O3 exhibited good stability and strong resistance to SO2 and H2O poisoning. The co-introduction of SiO2 and Al2O3 into TiO2 could increase the amount of chemisorbed oxygen and Lewis acid sites on the surface of catalyst, which should be responsible for the excellent SCR activity. PMID:24996153

  14. Odd oxygen formation in the laser irradiation of O2 at 248 nm - Evidence for reactions of O2 in the Herzberg states with ground state O2

    NASA Technical Reports Server (NTRS)

    Shi, Jichun; Barker, John R.

    1992-01-01

    Two O3 formation processes (initiation and autocatalytic) are studied in pure O2 and in O2+N2 and O2+Ar mixtures at pressures between 200 and 1600 torr and at temperatures between 298 and 370 K. Evidence is presented that the initiation process produces O3 through chemical reactions between ground state O2 and excited O2 in the Herzberg states, which are produced by the photoabsorption of O2 at 248 nm. For the autocatalytic process, the results are consistent with the proposal that the O3 formation is accelerated by photodissociating vibrationally excited O2(nu), produced in the photolysis of O3 following its initial formation. It is argued that the O2 Herzberg states and O2(nu) may play important roles in the odd oxygen chemistry in the middle atmosphere. It is estimated that the O2(A3Sigma-u(+))+O2 reaction may yield up to about 6 percent of the total odd oxygen production rate near 50 km.

  15. Air

    MedlinePlus

    ... do to protect yourself from dirty air . Indoor air pollution and outdoor air pollution Air can be polluted indoors and it can ... this chart to see what things cause indoor air pollution and what things cause outdoor air pollution! Indoor ...

  16. A new visible-light photocatalyst: CdS quantum dots embedded mesoporous TiO2.

    PubMed

    Li, Gui-Sheng; Zhang, Die-Qing; Yu, Jimmy C

    2009-09-15

    Cadmium sulfide quantum dots (QDs) sensitized mesoporous TiO2 photocatalysts were prepared by preplanting cadmium oxide as crystal seeds into the framework of ordered mesoporous titanium dioxide and then converting CdO to CdS QDs through ion-exchange. The presence of CdS QDs in the TiO2 framework extended its photoresponse to the visible-light region by accelerating the photogenerated electron transfer from the inorganic sensitizer to TiO2. The new photocatalyst showed excellent photocatalytic efficiency for both oxidation of NO gas in air and degradation of organic compounds in aqueous solution under visible light irradiation. The photocatalysts were characterized byX RD, N2 adsorption-desorption, TEM, XPS, UV/vis, and PL spectroscopy. The relationship between the physicochemical properties and the photocatalytic performance of the sample is discussed. PMID:19806745

  17. Mn3O4-CeO2 nano-catalysts: Synthesis, characterization and application

    NASA Astrophysics Data System (ADS)

    Anushree, Sharma, C.; Kumar, S.

    2016-05-01

    Nano-sized Mn3O4-CeO2 catalysts were synthesized by a cost effective co-precipitation method, and were studied as a heterogeneous catalyst for wet air oxidation of paper industry wastewater at mild operating conditions of 90 °C and 1 atm. The structural, micro-structural and textural properties of synthesized catalysts were studied through various characterization techniques, i.e. XRD, TEM, N2-sorption and EDS. The catalytic activity of Mn3O4-CeO2 was interestingly found to be higher than the corresponding single-metal oxides, and the Ce50Mn50 nano-catalyst with small crystallite size (4.5 nm), high specific surface area (75 m2g-1) and high porosity (0.24 ccg-1) was found to be most efficient with 69% color, 60% COD, 59% TOC, 48% AOX removal.

  18. High thermal stability of La2O3 and CeO2-stabilized tetragonal ZrO2

    DOE PAGESBeta

    Wang, Shichao; Xie, Hong; Lin, Yuyuan; Poeppelmeier, Kenneth R.; Li, Tao; Winans, Randall E.; Cui, Yanran; Ribeiro, Fabio H.; Canlas, Christian P.; Elam, Jeffrey W.; et al

    2016-02-15

    Catalyst support materials of tetragonal ZrO2, stabilized by either La2O3 (La2O3-ZrO2) or CeO2 (CeO2-ZrO2), were synthesized under hydrothermal conditions at 200 °C with NH4OH or tetramethylammonium hydroxide as the mineralizer. From In Situ synchrotron powder X-ray diffraction and small-angle X-ray scattering measurements, the calcined La2O3-ZrO2 and CeO2-ZrO2 supports were nonporous nanocrystallites that exhibited rectangular shapes with thermal stability up to 1000 °C in air. These supports had an average size of ~10 nm and a surface area of 59-97 m2/g. The catalysts Pt/La2O3-ZrO2 and Pt/CeO2-ZrO2 were prepared by using atomic layer deposition with varying Pt loadings from 6.3-12.4 wt %.more » Mono-dispersed Pt nanoparticles of ~3 nm were obtained for these catalysts. As a result, the incorporation of La2O3 and CeO2 into the t-ZrO2 structure did not affect the nature of the active sites for the Pt/ZrO2 catalysts for the water-gas-shift (WGS) reaction.« less

  19. High Thermal Stability of La2O3- and CeO2-Stabilized Tetragonal ZrO2.

    PubMed

    Wang, Shichao; Xie, Hong; Lin, Yuyuan; Poeppelmeier, Kenneth R; Li, Tao; Winans, Randall E; Cui, Yanran; Ribeiro, Fabio H; Canlas, Christian P; Elam, Jeffrey W; Zhang, Hongbo; Marshall, Christopher L

    2016-03-01

    Catalyst support materials of tetragonal ZrO2, stabilized by either La2O3 (La2O3-ZrO2) or CeO2 (CeO2-ZrO2), were synthesized under hydrothermal conditions at 200 °C with NH4OH or tetramethylammonium hydroxide as the mineralizer. From in situ synchrotron powder X-ray diffraction and small-angle X-ray scattering measurements, the calcined La2O3-ZrO2 and CeO2-ZrO2 supports were nonporous nanocrystallites that exhibited rectangular shapes with a thermal stability of up to 1000 °C in air. These supports had an average size of ∼10 nm and a surface area of 59-97 m(2)/g. The catalysts Pt/La2O3-ZrO2 and Pt/CeO2-ZrO2 were prepared by using atomic layer deposition with varying Pt loadings from 6.3 to 12.4 wt %. Monodispersed Pt nanoparticles of ∼3 nm were obtained for these catalysts. The incorporation of La2O3 and CeO2 into the t-ZrO2 structure did not affect the nature of the active sites for the Pt/ZrO2 catalysts for the water-gas shift reaction. PMID:26878202

  20. N2O Decomposed by Discharge Plasma with Catalysts

    NASA Astrophysics Data System (ADS)

    Hu, Hui; Huang, Hao; Xu, Jie; Yang, Qi; Tao, Gongkai

    2015-12-01

    A great deal of attention has been focused on discharge plasma as it can rapidly decompose N2O without additives, which is not only a kind of greenhouse gas but also a kind of damages to the ozone layer. The thermal equilibrium plasma is chosen to combine with catalysts to decompose N2O, and its characteristics are analyzed in the present paper. The results indicate that NO and NO2 were formed besides N2 and O2 during N2O decomposition when N2O was treated merely by discharge plasma. Concentration of NO declined greatly when the discharge plasma was combined with catalysts. Results of Raman spectra analysis on CeO2, Ce0.75Zr0.25O2 and Ce0.5Zr0.5O2 imply that the products selectivity has been obviously improved in discharge plasma decomposing N2O because of the existence of massive oxygen vacancies over the composite oxide catalysts. supported by National Natural Science Foundation of China (No. 50677026) and the Applied Basic Research Program of Wuhan, China (No. 2015060101010068)

  1. On the production of N2O from the reaction of O(1 D) with N2

    NASA Technical Reports Server (NTRS)

    Simonaitis, R.; Lissi, E.; Heicklen, J.

    1972-01-01

    Ozone was photolyzed at 2537 A and 25 C in the presence of 42-115 torr of O2 and about 880 torr of N2 to test the relative importance of the two reactions: (1) O(1D) + N2 + M yields N2O + M, and (2) O(1D) + N2 yields O(3P) + N2. N2O was not found as a product. Thus from our detectability limit for N2O (0.3 micron), an upper limit to the efficiency of the first reaction relative to the second of 0.0000025 at 1000 torr total pressure was computed. This corresponds to k1/k2 smaller than 0.8 x 10 to the minus 25 power cu cm/particle.

  2. Nanostructured porous RuO2/MnO2 as a highly efficient catalyst for high-rate Li-O2 batteries.

    PubMed

    Wang, Guoqing; Huang, Liliang; Huang, Wei; Xie, Jian; Du, Gaohui; Zhang, Shichao; Zhu, Peiyi; Cao, Gaoshao; Zhao, Xinbing

    2015-12-28

    Despite the recent advancements in Li-O(2) (or Li-air) batteries, great challenges still remain to realize high-rate, long-term cycling. In this work, a binder-free, nanostructured RuO(2)/MnO(2) catalytic cathode was designed to realize the operation of Li-O(2) batteries at high rates. At a current density as high as 3200 mA g(-1) (or ∼1.3 mA cm(-2)), the RuO(2)/MnO(2) catalyzed Li-O(2) batteries with LiI can sustain stable cycling of 170 and 800 times at limited capacities of 1000 and 500 mA h g(-1), respectively, with low charge cutoff potentials of ∼4.0 and <3.8 V, respectively. The underlying mechanism of the high catalytic performance of MnO(2)/RuO(2) was also clarified in this work. It was found that with the catalytic effect of RuO(2), Li(2)O(2) can crystallize into a thin-sheet form and realize a conformal growth on sheet-like δ-MnO(2) at a current density up to 3200 mA g(-1), constructing a sheet-on-sheet structure. This crystallization behavior of Li(2)O(2) not only defers the electrode passivation upon discharge but also renders easy decomposition of Li(2)O(2) upon charge, leading to low polarizations and reduced side reactions. This work provides a unique design of catalytic cathodes capable of controlling Li(2)O(2) growth and sheds light on the design of high-rate, long-life Li-O(2) batteries with potential applications in electric vehicles. PMID:26592423

  3. Closed N=2 Strings

    NASA Astrophysics Data System (ADS)

    Lechtenfeld, Olaf; Popov, Alexander D.

    We study the action of picture-changing and spectral flow operators on a ground ring of ghost number zero operators in the chiral BRST cohomology of the closed N=2 string and describe an infinite set of symmetry charges acting on physical states. The transformations of physical string states are compared with symmetries of self-dual gravity which is the effective field theory of the closed N=2 string. We derive all infinitesimal symmetries of the self-dual gravity equations in (2+2)-dimensional space-time and introduce an infinite hierarchy of commuting flows on the moduli space of self-dual metrics. The dependence on moduli parameters can be recovered by solving the equations of the SDG hierarchy associated with an infinite set of Abelian symmetries generated recursively from translations. These nonlocal Abelian symmetries are shown to coincide with the hidden Abelian string symmetries responsible for the vanishing of most scattering amplitudes. Therefore, N=2 string theory ``predicts'' not only self-dual gravity but also the SDG hierarchy.

  4. Detailed mechanism of the CH2I + O2 reaction: Yield and self-reaction of the simplest Criegee intermediate CH2OO

    NASA Astrophysics Data System (ADS)

    Ting, Wei-Lun; Chang, Chun-Hung; Lee, Yu-Fang; Matsui, Hiroyuki; Lee, Yuan-Pern; Lin, Jim-Min, Jr.

    2014-09-01

    The application of a new reaction scheme using CH2I + O2 to generate the simplest Criegee intermediate, CH2OO, has stimulated lively research; the Criegee intermediates are extremely important in atmospheric chemistry. The detailed mechanism of CH2I + O2 is hence important in understanding kinetics involving CH2OO. We employed ultraviolet absorption to probe simultaneously CH2I2, CH2OO, CH2I, and IO in the reaction system of CH2I + O2 upon photolysis at 248 nm of a flowing mixture of CH2I2, O2, and N2 (or SF6) in the pressure range 7.6-779 Torr to investigate the reaction kinetics. With a detailed mechanism to model the observed temporal profiles of CH2I, CH2OO, and IO, we found that various channels of the reaction CH2I + O2 and CH2OO + I play important roles; an additional decomposition channel of CH2I + O2 to form products other than CH2OO or ICH2OO becomes important at pressure less than 60 Torr. The pressure dependence of the derived rate coefficients of various channels of reactions of CH2I + O2 and CH2OO + I has been determined. We derived a rate coefficient also for the self-reaction of CH2OO as k = (8 ± 4) × 10-11 cm3 molecule-1 s-1 at 295 K. The yield of CH2OO from CH2I + O2 was found to have a pressure dependence on N2 and O2 smaller than in previous reports; for air under 1 atm, the yield of ˜30% is about twice of previous estimates.

  5. The effect of soil pH on N2O/(N2O+N2) product ratio of denitrification depends on soil NO3- concentration

    NASA Astrophysics Data System (ADS)

    Senbayram, Mehmet; Dittert, Klaus; Well, Reinhard; Lewicka-Szczebak, Dominika; Lammel, Joachim; Bakken, Lars

    2015-04-01

    Globally, agricultural soils account for about 60% of the atmospheric N2O emissions and denitrification in soil is the major source of atmospheric N2O, which contributes to global warming and destruction of stratospheric ozone. Denitrification is the microbially mediated process of dissimilatory nitrate reduction that may produce not only N2O but also nitric oxide (NO), and molecular nitrogen (N2). The major controls on denitrification rates are soil NO3, O2, and labile C levels. Typically, when soils become more anoxic, larger proportions of N2O produced in denitrification are further reduced to N2 before leaving the soil. Microbial ecology may possibly find solutions to this major environmental problem of agricultural systems once mechanisms controlling the product ratio of denitrification (N2O/N2O+N2) are better understood. Recent investigations of these gaseous microbial products provided the evidence for a negative effect of soil acidity on the N2O/N2O+N2 product ratio. However, in an earlier study, we showed that, regardless of soil type, higher NO3- concentrations in soil may also retard the reduction of N2O to N2. In this context, the positive effect of higher soil pH on the N2O/(N2O+N2) product ratio in soils with high NO3- content is still poorly understood. Therefore, we set up a number of incubation experiments in order to test short-term and long-term effects of soil pH and NO3- concentration on denitrification rates and the product stoichiometry of denitrification. We measured N2O, NO as well as elemental N2 in soils with pH levels ranging 4.1 to pH 6.9 collected from a long-term liming experiment. In a continuous flow incubation system we evacuated and flushed all vessels with He. Then, fresh He was directed through an inlet in the lid at a flow rate of 15-30 ml min-1. Gas samples were analyzed twice a day for N2O by ECD and for N2 by TCD detectors. Denitrification rates increased significantly with increasing soil pH, however, during the initial

  6. Effects of water-contaminated air on blowoff limits of opposed jet hydrogen-air diffusion flames

    NASA Technical Reports Server (NTRS)

    Pellett, Gerald L.; Jentzen, Marilyn E.; Wilson, Lloyd G.; Northam, G. Burton

    1988-01-01

    The effects of water-contaminated air on the extinction and flame restoration of the central portion of N2-diluted H2 versus air counterflow diffusion flames are investigated using a coaxial tubular opposed jet burner. The results show that the replacement of N2 contaminant in air by water on a mole for mole basis decreases the maximum sustainable H2 mass flow, just prior to extinction, of the flame. This result contrasts strongly with the analogous substitution of water for N2 in a relatively hot premixed H2-O2-N2 flame, which was shown by Koroll and Mulpuru (1986) to lead to a significant, kinetically controlled increase in laminar burning velocity.

  7. Detection and spectroscopy of the v1 + v3 band of N2O by difference-frequency spectrometer at 3 microm.

    PubMed

    Bruno, A; Pesce, G; Rusciano, G; Sasso, A

    2002-09-01

    We report the realisation of a laser spectrometer in the mid-infrared spectral region based on difference-frequency generation in a periodically poled LiNbO3 crystal. Tunable coherent radiation around 3 microm was produced by mixing a diode-pumped monolithic cw Nd-YAG laser and an injection-locked diode laser at 0.785 microm. High sensitivity N2O detection was demonstrated by observing pure absorption spectra of lines in the v1 + v3 combination band. We estimate a minimum detectable pressure of pure N2O of 1 x 10(-2) Pa with 0.9 m absorption path-length, corresponding to an absorbance of 3 x 10(-4). Nitrous oxide was also detected in presence of O2, N2 and air. Collisional broadening coefficients for the P(33) line at 3447.678 per cm are reported for N2O-N2 and N2O-O2 mixtures. PMID:12353698

  8. Synthesis of superamphiphobic breathable membranes utilizing SiO2 nanoparticles decorated fluorinated polyurethane nanofibers.

    PubMed

    Wang, Jialin; Raza, Aikifa; Si, Yang; Cui, Lingxiao; Ge, Jianfeng; Ding, Bin; Yu, Jianyong

    2012-12-01

    Superamphiphobic nanofibrous membranes exhibiting robust water/oil proof and breathable performances were prepared by the combination of a novel synthesized fluorinated polyurethane (FPU) containing a terminal perfluoroalkane segment and incorporated SiO(2) nanoparticles (SiO(2) NPs). By employing the FPU/SiO(2) NPs incorporation, the hybrid membranes possess superhydrophobicity with a water contact angle of 165° and superoleophobicity with an oil contact angle of 151°. Surface morphological studies have indicated that the wettability of resultant membranes could be manipulated by tuning the surface composition as well as the hierarchical structures. The quantitative hierarchical roughness analysis using N(2) adsorption method has confirmed a major contribution of SiO(2) NPs on enhancing the porous structure, and a detailed correlation between the fractal dimension and amphiphobicity is proposed. Furthermore, a designed concept test shows that the as-prepared membranes could load 1.5 kg water or oil at the same time maintained an extremely high air permeability of 2 L min(-1), suggesting their use as promising materials for a variety of potential applications in protective clothing, bioseparation, water purification, tissue engineering, microfluidic systems, etc., and also provided new insight into the design and development of functional hybrid membranes based on FPU. PMID:23108344

  9. The source of stratospheric NO and N2O

    NASA Technical Reports Server (NTRS)

    Slanger, T. G.

    1984-01-01

    The photodissociation of O3 was investigated as a possible sources of N2O production in the stratosphere. Photolysis was conducted at 1576 A to generate the excited O2 states that react with N2 to form N2O. At this wavelength, there is a quantum yield of two for prompt production of oygen atoms, which is a consequence of the existence of two photodissociative channels giving comparable yields. One of these channels gives O(D1) and O2(b1sigma(+)subg), with a quantum yield of 0.6, whereas the other results in fragmentation of the O3, with production of three ground state oxygen atoms. The O2(b) is generated with vibrational excitation, and there are comparable populations in levels O to 3. These observations are the first to show O2(b) production from any photodissociative process, and were made under conditions in which the kinetics of vibrationally excited O2(b) can be studied. It appears that O3 photodissociation at 1576 A is not a good system for generating the higher electronic states of O2; it is likely that better results will be obtained at 1930 A.

  10. Preparation and characterization of CNT-CeO2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Kaur, Jasmeet; Anand, Kanika; Singh, Ravi Chand

    2015-06-01

    This paper reports decoration of CeO2 nanoparticles on multi-walled carbon nanotubes through a reflux process in which Ce (NO3) 3.6H2O serves as precursor and hydrazine hydrate (N2H4.H2O) as reducing agent. Successful deposition of cubic fluorite CeO2 nanoparticles onto multi-walled carbon nanotubes has been confirmed by x-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM) and energy dispersive x-ray spectroscopy (EDS). It was found that CeO2 nanoparticles formed in the presence of CNTs were larger as compared to pure CeO2 nanoparticles. Raman analysis showed that CeO2 induced a decrease in the size of the carbon grain in the CNTs. A red shift from 460 cm-1 to 463 cm-1 for F2g mode of CeO2 has also been observed in Raman spectra of CNT- CeO2 nanocomposite as compared to pure CeO2. The CeO2 coated multi-wall carbon nanotubes (CNT-CeO2) nanocomposite would be a promising candidate for practical applications such as catalysis, sensing and power source applications.

  11. Cyanobacterial lactate oxidases serve as essential partners in N2 fixation and evolved into photorespiratory glycolate oxidases in plants.

    PubMed

    Hackenberg, Claudia; Kern, Ramona; Hüge, Jan; Stal, Lucas J; Tsuji, Yoshinori; Kopka, Joachim; Shiraiwa, Yoshihiro; Bauwe, Hermann; Hagemann, Martin

    2011-08-01

    Glycolate oxidase (GOX) is an essential enzyme involved in photorespiratory metabolism in plants. In cyanobacteria and green algae, the corresponding reaction is catalyzed by glycolate dehydrogenases (GlcD). The genomes of N(2)-fixing cyanobacteria, such as Nostoc PCC 7120 and green algae, appear to harbor genes for both GlcD and GOX proteins. The GOX-like proteins from Nostoc (No-LOX) and from Chlamydomonas reinhardtii showed high L-lactate oxidase (LOX) and low GOX activities, whereas glycolate was the preferred substrate of the phylogenetically related At-GOX2 from Arabidopsis thaliana. Changing the active site of No-LOX to that of At-GOX2 by site-specific mutagenesis reversed the LOX/GOX activity ratio of No-LOX. Despite its low GOX activity, No-LOX overexpression decreased the accumulation of toxic glycolate in a cyanobacterial photorespiratory mutant and restored its ability to grow in air. A LOX-deficient Nostoc mutant grew normally in nitrate-containing medium but died under N(2)-fixing conditions. Cultivation under low oxygen rescued this lethal phenotype, indicating that N(2) fixation was more sensitive to O(2) in the Δlox Nostoc mutant than in the wild type. We propose that LOX primarily serves as an O(2)-scavenging enzyme to protect nitrogenase in extant N(2)-fixing cyanobacteria, whereas in plants it has evolved into GOX, responsible for glycolate oxidation during photorespiration. PMID:21828292

  12. Physicochemical aspects of novel surfactantless, self-templated mesoporous SnO2 thin films.

    PubMed

    Velasquez, Celso; Rojas, Fernando; Esparza, J Marcos; Ortiz, Armando; Campero, Antonio

    2006-06-22

    A novel method of synthesis consisting of the production of ordered arrangements of tubular pores distributed inside SnO2 annealed thin films, which are prepared from a rotating disk process carried out at 2000-3500 rpm, is herein described. The main novelty is that no surfactant molecules are required in order to create these ordered pore structures; the templating entities are supramolecular assemblies of oligomeric chains formed during the extra-long aging allowed to the sol-gel processing of tin(IV) tetra-tert-amiloxide, Sn(OAm(t))4, chelated with acetylacetone molecules. Low angle X-ray diffraction peaks of SnO2 thin films calcined at 500 degrees C clearly certify the existence of ordered mesostructures when employing the right H2O/Sn(OAm(t))4 molar ratio during the SnO2 sol-gel synthesis. The final SnO2 ordered mesostructures are reminiscent of those linked to MCM-41 and SBA-15 substrates. Pore-size distribution analyses proceeding from N2 sorption isotherms at 76 K on the SnO2 thin films calcined at 500 degrees C unequivocally confirm the presence of tubular mesopores (mode pore sizes ranging from 5 to 7 nm). The thicknesses of the SnO2 films range from 80 to 150 nm after performing a drying process at 100 degrees C and from 70 to 125 nm after calcining in air at 500 degrees C; these film thicknesses show, in general, decreasing trends when either the spinning rate or the H2O/(Sn(OAm(t))4 ratio is increased. PMID:16800485

  13. Evaluating Soil Oxygen as a Control on N2O Emissions from Ruminant Urine Patches under Different Irrigation Frequencies

    NASA Astrophysics Data System (ADS)

    Owens, J.; Clough, T. J.; Laubach, J.; Hunt, J.; Venterea, R. T.; Phillips, R. L.

    2015-12-01

    Urine patches from grazing ruminant animals are a significant source of nitrous oxide (N2O) emissions, and irrigation is increasingly used to improve forage quality and yield for grazing cattle. The objective of this study was to test whether irrigation frequency influenced N2O emissions from urine patches on a free-draining grazed pasture soil. It was hypothesized that greater irrigation frequency would increase soil moisture thereby lowering soil oxygen (O2), and that these O2-limited conditions would increase the potential for N2O to be reduced to nitrogen gas (N2), resulting in lower N2O emissions. A field trial tested the effects of two irrigation frequencies and urine deposition on N2O fluxes measured daily for 35 days. Denitrification potential measurements using the acetylene inhibition technique were completed to infer N2O/(N2O+N2) ratios, and soil O2 concentrations were measured continuously at three depths within the soil profile. While a more frequent irrigation treatment resulted in a lower N2O/(N2O+N2) ratio, this did not give rise to lower N2O emissions. Nitrous oxide fluxes were not influenced by irrigation frequency, and approximately 0.09% of the nitrogen applied as urine was emitted as N2O from both irrigation treatments. Neither N2O nor soil O2 varied with individual irrigation events. Soil O2 ranged from 17 to 20% expect following urine deposition, where it temporarily decreased to 13%. Soil O2 measurements failed to explain N2O emissions, but a relationship was derived between N2O fluxes and estimates of soil gas diffusivity (Dp/Do). This work is the first to show how soil O2 concentrations vary under a urine patch and under different irrigation treatments, and supports Dp/Do as robust predictor of N2O emissions in situ.

  14. Following the N2O consumption in the oxygen minimum zone of the eastern South Pacific

    NASA Astrophysics Data System (ADS)

    Cornejo, M.; Farías, L.

    2012-08-01

    Oxygen minimum zones (OMZs), such as those found in the eastern South Pacific (ESP), are the most important N2O sources in the global ocean relative to their volume. N2O production is related to low O2 concentrations and high primary productivity. However, when O2 is sufficiently low, canonical denitrification takes place and N2O consumption can be expected. N2O distribution in the ESP was analyzed over a wide latitudinal and longitudinal range (from 5° to 30° S and from 71-76° to ~ 84° W) based on ~ 890 N2O measurements. Intense N2O consumption, driving undersaturations as low as 40%, was always associated with secondary NO2- accumulation (SNM), a good indicator of suboxic/anoxic O2 levels. First, we explore relationships between ΔN2O and O2 based on existing data of denitrifying bacteria cultures and field observations. Given the uncertainties in the O2 measurements, a second relationship between ΔN2O and NO2- (> 0.75 μM) was established for suboxic waters (O2 < 8 μM). We reproduced the apparent N2O production (ΔN2O) along the OMZ in ESP with high reliability (r2 = 0.73 p = 0.01). Our results will contribute to the quantification of the N2O that is recycled in O2 deficient waters, and improve the prediction of N2O behavior under future scenarios of OMZ expansion and intensification.

  15. Pt and Pd catalyzed oxidation of Li2O2 and DMSO during Li-O2 battery charging.

    PubMed

    Gittleson, Forrest S; Ryu, Won-Hee; Schwab, Mark; Tong, Xiao; Taylor, André D

    2016-05-01

    Rechargeable Li-O2 and Li-air batteries require electrode and electrolyte materials that synergistically promote long-term cell operation. In this study, we investigate the role of noble metals Pt and Pd as catalysts in the Li-O2 oxidation process and their compatibility with dimethyl sulfoxide (DMSO) based electrolytes. We identify a basis for low potential Li2O2 evolution followed by oxidative decomposition of the electrolyte to form carbonate side products. PMID:27111589

  16. Pt and Pd catalyzed oxidation of Li2O2 and DMSO during Li–O2 battery charging

    DOE PAGESBeta

    Gittleson, Forrest S.; Ryu, Won-Hee; Schwab, Mark; Tong, Xiao; Taylor, André D.

    2016-01-01

    Rechargeable Li-O2 and Li-air batteries require electrode and electrolyte materials that synergistcally promote long-term cell operation. We investigate the role of noble metals Pt and Pd as catalysts for the Li-O2 oxidation process and their compatibility with a dimethyl sulfoxide (DMSO) based electrolyte. Lastly, we identify a basis for low potential Li2O2 evolution followed by oxidative decomposition of the electrolyte to form carbonate side products.

  17. TiO2-TiO2 composite resistive humidity sensor: ethanol crosssensitivity

    NASA Astrophysics Data System (ADS)

    Ghalamboran, Milad; Saedi, Yasin

    2016-03-01

    The fabrication method and characterization results of a TiO2-TiO2 composite bead used for humidity sensing along with its negative cross-sensitivity to ethanol vapor are reported. The bead shaped resistive sample sensors are fabricated by the drop-casting of a TiO2 slurry on two Pt wire segments. The dried bead is pre-fired at 750°C and subsequently impregnated with a Ti-based sol. The sample is ready for characterization after a thermal annealing at 600°C in air. Structurally, the bead is a composite of the micron-sized TiO2 crystallites embedded in a matrix of nanometric TiO2 particle aggregates. The performance of the beads as resistive humidity sensors is recorded at room temperature in standard humidity level chambers. Results evince the wide dynamic range of the sensors fabricated in the low relative humidity range. While the sensor conductance is not sensitive to ethanol vapor in dry air, in humid air, sensor's responses are negatively affected by the contaminant.

  18. Enhanced oxygen evolution activity of IrO2 and RuO2 (100) surfaces

    SciTech Connect

    Stoerzinger, Kelsey; Qiao, Liang; Biegalski, Michael D; Christen, Hans M; Shao-Horn, Yang

    2014-01-01

    The activities of the oxygen evolution reaction (OER) on IrO2 and RuO2 catalysts are among the highest known to date. However, the intrinsic OER activities of surfaces with defined crystallographic orientations are not well established experimentally. Here we report that the (100) surface of IrO2 and RuO2 is more active than the (110) surface that has been traditionally explored by density functional theory studies. The relation between the OER activity and density of coordinatively undersaturated metal sites exposed on each rutile crystallographic facet is discussed. The surface-orientation dependent activities can guide the design of high-surface-area catalysts with increased activity for electrolyzers, metal-air batteries, and photoelectrochemical water splitting applications.

  19. An automated setup to measure paleoatmospheric δ13C-CH4, δ15N-N2O and δ18O-N2O in one ice core sample

    NASA Astrophysics Data System (ADS)

    Sperlich, P.; Buizert, C.; Jenk, T. M.; Sapart, C. J.; Prokopiou, M.; Röckmann, T.; Blunier, T.

    2013-02-01

    Air bubbles in ice core samples represent the only opportunity to study the isotopic variability of paleoatmospheric CH4 and N2O. The highest possible precision in isotope measurements is required to maximize the resolving power for CH4 and N2O sink and source reconstructions. We present a new setup to measure δ13C-CH4, δ15N-N2O and δ18O-N2O isotope ratios in one ice core sample, with a precision of 0.09‰, 0.6‰ and 0.7‰, respectively, as determined on 0.6-1.6 nmol CH4 and 0.25-0.6 nmol N2O. The isotope ratios are referenced to the VPDB scale (δ13C-CH4), the N2-air scale (δ15N-N2O) and the VSMOW scale (δ18O-N2O). Ice core samples of 200-500 g are melted while the air is constantly extracted to minimize gas dissolution. A helium carrier gas flow transports the sample through the analytical system. A gold catalyst is used to oxidize CO to CO2 in the air sample without affecting the CH4 and N2O sample. CH4 and N2O are then separated from N2, O2, Ar and CO2 before they get pre-concentrated and separated by gas chromatography. While the separated N2O sample is immediately analysed in the mass spectrometer, a combustion unit is required for δ13C-CH4 analysis, which is equipped with a constant oxygen supply as well as a post-combustion trap and a post-combustion GC-column (GC-C-GC-IRMS). The post combustion trap and the second GC column in the GC-C-GC-IRMS combination increase the time for δ13C-CH4 analysis which is used to measure δ15N-N2O and δ18O-N2O first and then δ13C-CH4. The analytical time is adjusted to ensure stable conditions in the ion-source before each sample gas enters the IRMS, thereby improving the precision achieved for measurements of CH4 and N2O on the same IRMS. After the extraction of the air from the ice core sample, the analysis of CH4 and N2O takes 42 min. The setup is calibrated by analyzing multiple isotope reference gases that were injected over bubble-free-ice samples. We show a comparison of ice core sample measurements for

  20. Synthesis and characterization of oxalate-bridged binuclear iron(III) complex: [(N)2(O)2Fe(μ-ox)Fe(N)2(O)2

    NASA Astrophysics Data System (ADS)

    Karimpour, Touraj; Safaei, Elham; Wojtczak, Andrzej; Cotič, Patricia

    2013-04-01

    In the present work, a novel oxalate-bridged binuclear iron(III) complex of aminophenol derivative, (μ-ox-FeLNEM), where LNEM is deprotonated form of a tetradentate aminophenol ligand and ox stands for oxalate, was synthesized. The iron complex has been characterized by X-ray crystallography, infrared spectroscopy, UV-Vis, magnetic susceptibility studies and cyclic voltammetry techniques. X-ray structure analysis has revealed that each iron(III) is coordinated by two oxygen atoms of the oxalate group, two amine nitrogen's and two oxygen atoms of phenolate ligand in an octahedral arrangement. The temperature variable magnetic susceptibility exhibits quite strong antiferromagnetic coupling between the two iron(III) centers. Cyclic voltammograms of the complex in dichloromethane at low temperatures showed two quasi-reversible cathodic peaks, corresponding to FeIIIsbnd FeIII to FeIIIsbnd FeII followed by FeIIIsbnd FeII to FeIIsbnd FeII process.

  1. A fundamental study on biological removal of N2O in the presence of oxygen.

    PubMed

    Figueroa-González, Ivonne; Quijano, Guillermo; Laguna, Inés; Muñoz, Raúl; García-Encina, Pedro A

    2016-09-01

    The biodegradation of N2O by a non-acclimated secondary activated sludge in the presence of O2 was studied. Batch tests with a headspace containing an initial N2O concentration of ∼400 mg m(-3) (∼200 ppmv) and initial O2 gas concentrations of 0%, 1%, 2%, 5% and 21% were investigated. The effect of O2 on the biokinetic parameters qmax (maximum specific N2O uptake rate) and KS (half-saturation constant), as well as on the bacterial population structure, was evaluated. A complete N2O removal was recorded in the presence of up to 2% O2, while O2 at 5% and 21% mediated inhibitions of 37% and 95% in the removal of N2O compared with the control without O2. The elemental analysis of the biomass obtained at the end of the batch tests strongly suggested that NN2O was not used as a nitrogen source. The presence of O2 mediated decreases of up to 12.6- and 4.8-fold in qmax and KS, respectively, compared to the control without O2. Likewise, the presence of O2 induced changes in the structure of the bacterial population. The predominant microorganisms in the presence of O2 belonged to the phyla Proteobacteria, Firmicutes and Chlamydiae. Bacteria belonging to the Proteobacteria phylum, particularly the Dokdonella genus, were predominant at 2% O2, which was the highest O2 concentration without inhibitory effects on N2O biodegradation. PMID:27236493

  2. Rapid photochemical equilibration of isotope bond ordering in O2

    NASA Astrophysics Data System (ADS)

    Yeung, Laurence Y.; Ash, Jeanine L.; Young, Edward D.

    2014-09-01

    The abundances of 18O18O and 17O18O in the atmosphere were recently found to be enriched relative to the stochastic distribution of isotopes in O2. The enrichment is believed to arise from O(3P) + O2 isotope exchange reactions, which reorder the isotopes in O2 to a distribution that favors bonds between heavy isotopes. Theoretical predictions and laboratory experiments suggest that the reordered distribution of isotopes should reflect internal isotopic equilibrium, but a laboratory test of this hypothesis for the complete O2 isotopologue system has not yet been realized. Here we use a simple photochemical experiment that reorders the isotopes in O2 at temperatures between 200 K and 350 K. Using simultaneous measurements of five O2 isotopologues, we show that O(3P) + O2 reorders the isotopes in O2 to isotopic equilibrium. Furthermore, we use this scheme to calibrate measurements of isotopic ordering in samples of O2, obtaining Δ36 and Δ35 values within ±0.1‰. Measurements of atmospheric O2 sampled at the University of California, Los Angeles, from 2012 to 2014 have mean values of Δ36 = 1.97 ± 0.07‰ and Δ35 = 1.0 ± 0.1‰ (2 SE; n = 23), with no detectable long-term trend. These measurements are consistent with values for air reported earlier, but with a threefold to fourfold improvement in precision. Together, the experiments and observations support the case that isotopic ordering in tropospheric O2 is altered by O(3P) + O2; however, they also suggest that tropospheric Δ36 and Δ35 values do not reflect complete isotopic equilibration in the troposphere. Isotopic ordering in atmospheric O2 likely reflects the decadal-scale balance of stratospheric and tropospheric air masses modulated by variations in tropospheric photochemistry and convection.

  3. Crystal structure of aqua-1κO-{μ-2-[(2-hydroxy­ethyl)methylamino]ethanolato-2:1κ4 O 1,N,O 2:O 1}[μ-2,2′-(methylimino)diethanolato-1:2κ4 O,N,O′:O]dithiocyanato-1κN,2κN-chromium(III)copper(II)

    PubMed Central

    Rusanova, Julia A.; Semenaka, Valentina V.; Dyakonenko, Viktoriya V.; Shishkin, Oleg V.

    2015-01-01

    The title compound, [CrCu(C5H11NO2)(C5H12NO2)(NCS)2(H2O)] or [Cr(μ-mdea)Cu(μ-Hmdea)(NCS)2H2O], (where mdeaH2 is N-methylethanolamine, C5H13NO2) is formed as a neutral heterometal CuII/CrIII complex. The mol­ecular structure of the complex is based on a binuclear {CuCr(μ-O)2} core. The coordination environment of each metal atom involves the N,O,O atoms of the tridentate ligand, one bridging O atom of the ligand and the N atom of the thio­cyanato ligands. The CuII ion adopts a distorted square-pyramidal coordination while the CrIII ion has a distorted octa­hedral coordination geometry completed by the aqua ligand. In the crystal, the binuclear complexes are linked via two pairs of O—H⋯O hydrogen bonds to form inversion dimers, which are arranged in columns parallel to the a axis. In the μ-mdea ligand two –CH2 groups and the methyl group were refined as disordered over two sets of sites with equal occupancies. The structure was refined as a two-component twin with a twin scale factor of 0.242 (1). PMID:26396853

  4. Preparation of SnO2 -TiO2 /Fly Ash Cenospheres and its Application in Phenol Degradation.

    PubMed

    Liu, Shaomin; Zhu, Jinglin; Yang, Qing; Xu, Pengpeng; Ge, Jianhua; Guo, Xuetao

    2015-11-01

    SnO2 -TiO2 /fly ash cenospheres (FAC) were prepared via hydrothermal method and used as an active photocatalyst in a photocatalytic system. Scanning electron microscopy, X-ray diffraction analysis, UV-Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy and N2 adsorption-desorption measurements were used to determine the structure and optical property of SnO2 -TiO2 /FAC. Phenol was selected as the model substance for photocatalytic reactions to evaluate catalytic ability. Results showed that the degradation efficiency of phenol by SnO2 -TiO2 /FAC was 90.7% higher than that decomposed by TiO2 /FAC. Increased efficiency could be due to the enhanced synergistic effect of semiconductors and FAC could provide more adsorption sites for the pollutant in the photocatalytic reaction. Furthermore, SnO2 -TiO2 /FAC composites exhibited excellent photocatalytic stability in four reuse cycles. Radical-trapping experiments further revealed the dominating functions of holes in the photocatalytic reaction. PMID:26342185

  5. Phase relationships between orbital forcing and the composition of air trapped in Antarctic ice cores

    NASA Astrophysics Data System (ADS)

    Bazin, Lucie; Landais, Amaelle; Capron, Emilie; Masson-Delmotte, Valérie; Ritz, Catherine; Picard, Ghislain; Jouzel, Jean; Dumont, Marie; Leuenberger, Markus; Prié, Frédéric

    2016-03-01

    Orbital tuning is central for ice core chronologies beyond annual layer counting, available back to 60 ka (i.e. thousands of years before 1950) for Greenland ice cores. While several complementary orbital tuning tools have recently been developed using δ18Oatm, δO2N2 and air content with different orbital targets, quantifying their uncertainties remains a challenge. Indeed, the exact processes linking variations of these parameters, measured in the air trapped in ice, to their orbital targets are not yet fully understood. Here, we provide new series of δO2/N2 and δ18Oatm data encompassing Marine Isotopic Stage (MIS) 5 (between 100 and 160 ka) and the oldest part (340-800 ka) of the East Antarctic EPICA Dome C (EDC) ice core. For the first time, the measurements over MIS 5 allow an inter-comparison of δO2/N2 and δ18Oatm records from three East Antarctic ice core sites (EDC, Vostok and Dome F). This comparison highlights some site-specific δO2/N2 variations. Such an observation, the evidence of a 100 ka periodicity in the δO2/N2 signal and the difficulty to identify extrema and mid-slopes in δO2/N2 increase the uncertainty associated with the use of δO2/N2 as an orbital tuning tool, now calculated to be 3-4 ka. When combining records of δ18Oatm and δO2/N2 from Vostok and EDC, we find a loss of orbital signature for these two parameters during periods of minimum eccentricity (˜ 400 ka, ˜ 720-800 ka). Our data set reveals a time-varying offset between δO2/N2 and δ18Oatm records over the last 800 ka that we interpret as variations in the lagged response of δ18Oatm to precession. The largest offsets are identified during Terminations II, MIS 8 and MIS 16, corresponding to periods of destabilization of the Northern polar ice sheets. We therefore suggest that the occurrence of Heinrich-like events influences the response of δ18Oatm to precession.

  6. Experimental and kinetic modeling of oxygen-enriched air combustion of municipal solid waste.

    PubMed

    Liu, Guo Hui; Ma, Xiao Qian; Yu, Zhaosheng

    2009-02-01

    The characteristics of oxygen-enriched air combustion of raw municipal solid waste (MSW) were studied by thermogravimetric analysis. Experiments on oxidative pyrolysis of MSW were carried out under different atmospheres (N(2), N(2):O(2)=7:3, N(2):O(2)=5:5, N(2):O(2)=4:6, and N(2):O(2)=2:8) at 30 degrees C/min. Two distinct peaks of weight loss were obtained according to the derivative thermogravimetric curves; one of them is centered on 305 degrees C with about 40% weight loss, and the second is centered on 420 degrees C with about 20% weight loss. Effects of oxygen concentration on the decomposition process and char combustion were analyzed, and then the process of oxygen-enriched air combustion of MSW was divided into four steps. Kinetic parameters were observed by direct non-linear regressions. According to the obtained data, the apparent activation energy and reaction order decreases along with the combustion process, while that of char combustion increases as oxygen concentration increases. PMID:18691862

  7. 40 CFR 1065.280 - Paramagnetic and magnetopneumatic O2 detection analyzers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments O2 Measurements § 1065... diluted exhaust for batch or continuous sampling. You may use O2 measurements with intake air or fuel flow...), regardless of the uncompensated signal's bias. Air-to-Fuel Ratio Measurements...

  8. 40 CFR 1065.280 - Paramagnetic and magnetopneumatic O2 detection analyzers.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments O2 Measurements § 1065... diluted exhaust for batch or continuous sampling. You may use O2 measurements with intake air or fuel flow...), regardless of the uncompensated signal's bias. Air-to-Fuel Ratio Measurements...

  9. 40 CFR 1065.280 - Paramagnetic and magnetopneumatic O2 detection analyzers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments O2 Measurements § 1065... diluted exhaust for batch or continuous sampling. You may use O2 measurements with intake air or fuel flow...), regardless of the uncompensated signal's bias. Air-to-Fuel Ratio Measurements...

  10. 40 CFR 1065.280 - Paramagnetic and magnetopneumatic O2 detection analyzers.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments O2 Measurements § 1065... diluted exhaust for batch or continuous sampling. You may use O2 measurements with intake air or fuel flow...), regardless of the uncompensated signal's bias. Air-to-Fuel Ratio Measurements...

  11. 40 CFR 1065.280 - Paramagnetic and magnetopneumatic O2 detection analyzers.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments O2 Measurements § 1065... diluted exhaust for batch or continuous sampling. You may use O2 measurements with intake air or fuel flow... must meet the linearity verification in § 1065.307. Air-to-Fuel Ratio Measurements...

  12. Chlorine Gas Sensing Performance of On-Chip Grown ZnO, WO3, and SnO2 Nanowire Sensors.

    PubMed

    Tran, Van Dang; Nguyen, Duc Hoa; Nguyen, Van Duy; Nguyen, Van Hieu

    2016-02-01

    Monitoring toxic chlorine (Cl2) at the parts-per-billion (ppb) level is crucial for safe usage of this gas. Herein, ZnO, WO3, and SnO2 nanowire sensors were fabricated using an on-chip growth technique with chemical vapor deposition. The Cl2 gas-sensing characteristics of the fabricated sensors were systematically investigated. Results demonstrated that SnO2 nanowires exhibited higher sensitivity to Cl2 gas than ZnO and WO3 nanowires. The response (RCl2/Rair) of the SnO2 nanowire sensor to 50 ppb Cl2 at 50 °C was about 57. Hence, SnO2 nanowires can be an excellent sensing material for detecting Cl2 gas at the ppb level under low temperatures. Abnormal sensing characteristics were observed in the WO3 and SnO2 nanowire sensors at certain temperatures; in particular, the response level of these sensors to 5 ppm of Cl2 was lower than that to 2.5 ppm of Cl2. The sensing mechanism of the SnO2 nanowire sensor was also elucidated by determining Cl2 responses under N2 and dry air as carrier gases. We proved that the Cl2 molecule was first directly adsorbed on the metal oxide surface and was then substituted for pre-adsorbed oxygen, followed by lattice oxygen. PMID:26816341

  13. Nanostructured porous RuO2/MnO2 as a highly efficient catalyst for high-rate Li-O2 batteries

    NASA Astrophysics Data System (ADS)

    Wang, Guoqing; Huang, Liliang; Huang, Wei; Xie, Jian; Du, Gaohui; Zhang, Shichao; Zhu, Peiyi; Cao, Gaoshao; Zhao, Xinbing

    2015-12-01

    Despite the recent advancements in Li-O2 (or Li-air) batteries, great challenges still remain to realize high-rate, long-term cycling. In this work, a binder-free, nanostructured RuO2/MnO2 catalytic cathode was designed to realize the operation of Li-O2 batteries at high rates. At a current density as high as 3200 mA g-1 (or ~1.3 mA cm-2), the RuO2/MnO2 catalyzed Li-O2 batteries with LiI can sustain stable cycling of 170 and 800 times at limited capacities of 1000 and 500 mA h g-1, respectively, with low charge cutoff potentials of ~4.0 and <3.8 V, respectively. The underlying mechanism of the high catalytic performance of MnO2/RuO2 was also clarified in this work. It was found that with the catalytic effect of RuO2, Li2O2 can crystallize into a thin-sheet form and realize a conformal growth on sheet-like δ-MnO2 at a current density up to 3200 mA g-1, constructing a sheet-on-sheet structure. This crystallization behavior of Li2O2 not only defers the electrode passivation upon discharge but also renders easy decomposition of Li2O2 upon charge, leading to low polarizations and reduced side reactions. This work provides a unique design of catalytic cathodes capable of controlling Li2O2 growth and sheds light on the design of high-rate, long-life Li-O2 batteries with potential applications in electric vehicles.Despite the recent advancements in Li-O2 (or Li-air) batteries, great challenges still remain to realize high-rate, long-term cycling. In this work, a binder-free, nanostructured RuO2/MnO2 catalytic cathode was designed to realize the operation of Li-O2 batteries at high rates. At a current density as high as 3200 mA g-1 (or ~1.3 mA cm-2), the RuO2/MnO2 catalyzed Li-O2 batteries with LiI can sustain stable cycling of 170 and 800 times at limited capacities of 1000 and 500 mA h g-1, respectively, with low charge cutoff potentials of ~4.0 and <3.8 V, respectively. The underlying mechanism of the high catalytic performance of MnO2/RuO2 was also clarified in this

  14. Removal of anionic azo dye from aqueous solution via an adsorption-photosensitized regeneration process on a TiO2 surface.

    PubMed

    Bao, Nan; Li, Yuan; Yu, Xiao-Hong; Niu, Jun-Jian; Wu, Guo-Lin; Xu, Xiao-Hong

    2013-02-01

    Textile dye effluents are typically characterized by strong color and recalcitrance, even at very low concentration. The process of enrichment of anionic azo dye on the surface of TiO(2) fibers followed by photosensitization degradation under ambient air conditions was extensively investigated. Adsorption isotherms and zeta potentials were used to describe the "dye/TiO(2) surface" interface, taking into account the effects of pH on the nature and population of the surface groups on the TiO(2) fibers. The extent of the photocatalytic degradation of dye on TiO(2) surface was determined by FTIR. N(2) adsorption isotherms and optical spectra were employed to investigate the effect of photosensitization. The adsorption of dyes on the TiO(2) surface occurs via electrostatic attraction through the formation of single- or multidentate-coordinated surface complexes. Almost complete photobleaching of the absorption band at 534 nm is achieved in ~4 h. Dye-sensitized TiO(2) fiber could absorb part of the visible light spectrum (λ < 600 nm). Interfacial electron transfer can potentially alter the degradation efficiency. The regenerated TiO(2) fiber could be reused for subsequent decolorization without a decline in adsorption efficiency compared with freshly prepared TiO(2) samples, which may be attributed to preservation of the hierarchical pore structure and restoration of the original surface properties. In summary, we propose an efficient "adsorption-photoregeneration-reuse" process applying TiO(2) fibers for the degradation of dyes in water. PMID:22544602

  15. Diurnal variation in n(2) fixation and photosynthesis by aquatic blue-green algae.

    PubMed

    Peterson, R B; Friberg, E E; Burris, R H

    1977-01-01

    Rates of (14)CO(2) fixation, O(2) evolution, and N(2) fixation (acetylene reduction) by natural populations of blue-green algae recovered from Lake Mendota were measured at frequent intervals between sunrise and sunset. Photosynthesis and N(2) fixation were depressed during midday when light intensity was greatest. As the light intensity rose, most of the algal population migrated to deeper, light-limited waters where radiation damage would be diminished. As the relative rate of N(2) fixation compared to CO(2) fixation increases with depth, it is suggested that the algae maintain balanced growth by migrating vertically via buoyancy regulation. High concentrations of dissolved O(2) in lake water may inhibit N(2) fixation by enhancing photorespiration. Several factors such as photosynthetic rate, light intensity, dissolved O(2), species composition, and vertical and horizontal migration all affect observed rates of in situ N(2) fixation. PMID:16659792

  16. Diurnal Variation in N2 Fixation and Photosynthesis by Aquatic Blue-Green Algae 1

    PubMed Central

    Peterson, Richard B.; Friberg, Eugene E.; Burris, R. H.

    1977-01-01

    Rates of 14CO2 fixation, O2 evolution, and N2 fixation (acetylene reduction) by natural populations of blue-green algae recovered from Lake Mendota were measured at frequent intervals between sunrise and sunset. Photosynthesis and N2 fixation were depressed during midday when light intensity was greatest. As the light intensity rose, most of the algal population migrated to deeper, light-limited waters where radiation damage would be diminished. As the relative rate of N2 fixation compared to CO2 fixation increases with depth, it is suggested that the algae maintain balanced growth by migrating vertically via buoyancy regulation. High concentrations of dissolved O2 in lake water may inhibit N2 fixation by enhancing photorespiration. Several factors such as photosynthetic rate, light intensity, dissolved O2, species composition, and vertical and horizontal migration all affect observed rates of in situ N2 fixation. PMID:16659792

  17. Identifying N2O formation and emissions from a full-scale partial nitritation reactor.

    PubMed

    Mampaey, Kris E; De Kreuk, Merle K; van Dongen, Udo G J M; van Loosdrecht, Mark C M; Volcke, Eveline I P

    2016-01-01

    In this study, N2O formation and emissions from a full-scale partial nitritation (SHARON) reactor were identified through a three-weeks monitoring campaign during which the off-gas was analysed for N2O, O2, CO2 and NO. The overall N2O emission was 3.7% of the incoming ammonium load. By fitting the N2O emission to a theoretical gas stripping profile, the N2O emissions could be assigned to aerobically formed N2O and N2O formed under anoxic conditions. This was further substantiated by liquid N2O measurements. Under standard operation, 70% of the N2O emission was attributed to anoxic N2O formation. Dedicated experiments revealed that low dissolved oxygen concentrations (<1.0 gO2·m(-3)) and longer anoxic periods resulted in an increased N2O emission. Minimising or avoiding anoxic conditions has the highest effect in lowering the N2O emissions. As an additional result, the use of the off-gas N2O concentration measurements to monitor the gas-liquid mass transfer rate coefficient (kLa) during dynamic reactor operation was demonstrated. PMID:26558709

  18. Denitrogenation interruptions with air. [resulting in decompression sickness

    NASA Technical Reports Server (NTRS)

    Cooke, J. P.

    1976-01-01

    A 3-h denitrogenation period at ground-level pressure with 95% O2-5% N2, with an air interruption of 5 min or more and matched with additional denitrogenation time equal to the interruption, will later result occasionally in altitude decompression sickness ('bends') during a 2-h decompression exposure at 3.8 psia (10,058 m equivalent) with 92% O2- 8% N2. Thus the equal time or 'mirror-image' make-up time for loss of denitrogenation did not prevent bends 7 times in 17 subjects during 71 exposures with air interruptions; on the other hand, no case of bends was reported after uninterrupted denitrogenation periods. Nitrogen-loading during the interruptive period is believed to resupply the bends sites with additional nitrogen, which re-establishes conditions favoring a return to a high incidence of bends.

  19. CARS Temperature and Species Measurements For Air Vehicle Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Danehy, Paul M.; Gord, James R.; Grisch, Frederic; Klimenko, Dmitry; Clauss, Walter

    2005-01-01

    The coherent anti-Stokes Raman spectroscopy (CARS) method has recently been used in the United States and Europe to probe several different types of propulsion systems for air vehicles. At NASA Langley Research Center in the United States, CARS has been used to simultaneously measure temperature and the mole fractions of N2, O2 and H2 in a supersonic combustor, representative of a scramjet engine. At Wright- Patterson Air Force Base in the United States, CARS has been used to simultaneously measure temperature and mole fractions of N2, O2 and CO2, in the exhaust stream of a liquid-fueled, gas-turbine combustor. At ONERA in France and the DLR in Germany researchers have used CARS to measure temperature and species concentrations in cryogenic LOX-H2 rocket combustion chambers. The primary aim of these measurements has been to provide detailed flowfield information for computational fluid dynamics (CFD) code validation.

  20. An automated GC-C-GC-IRMS setup to measure palaeoatmospheric δ13C-CH4, δ15N-N2O and δ18O-N2O in one ice core sample

    NASA Astrophysics Data System (ADS)

    Sperlich, P.; Buizert, C.; Jenk, T. M.; Sapart, C. J.; Prokopiou, M.; Röckmann, T.; Blunier, T.

    2013-08-01

    Air bubbles in ice core samples represent the only opportunity to study the mixing ratio and isotopic variability of palaeoatmospheric CH4 and N2O. The highest possible precision in isotope measurements is required to maximize the resolving power for CH4 and N2O sink and source reconstructions. We present a new setup to measure δ13C-CH4, δ15N-N2O and δ18O-N2O isotope ratios in one ice core sample and with one single IRMS instrument, with a precision of 0.09, 0.6 and 0.7‰, respectively, as determined on 0.6-1.6 nmol CH4 and 0.25-0.6 nmol N2O. The isotope ratios are referenced to the VPDB scale (δ13C-CH4), the N2-air scale (δ15N-N2O) and the VSMOW scale (δ18O-N2O). Ice core samples of 200-500 g are melted while the air is constantly extracted to minimize gas dissolution. A helium carrier gas flow transports the sample through the analytical system. We introduce a new gold catalyst to oxidize CO to CO2 in the air sample. CH4 and N2O are then separated from N2, O2, Ar and CO2 before they get pre-concentrated and separated by gas chromatography. A combustion unit is required for δ13C-CH4 analysis, which is equipped with a constant oxygen supply as well as a post-combustion trap and a post-combustion GC column (GC-C-GC-IRMS). The post-combustion trap and the second GC column in the GC-C-GC-IRMS combination prevent Kr and N2O interferences during the isotopic analysis of CH4-derived CO2. These steps increase the time for δ13C-CH4 measurements, which is used to measure δ15N-N2O and δ18O-N2O first and then δ13C-CH4. The analytical time is adjusted to ensure stable conditions in the ion source before each sample gas enters the IRMS, thereby improving the precision achieved for measurements of CH4 and N2O on the same IRMS. The precision of our measurements is comparable to or better than that of recently published systems. Our setup is calibrated by analysing multiple reference gases that were injected over bubble-free ice samples. We show that our measurements

  1. Alumina decorated TiO2 nanotubes with ordered mesoporous walls as high sensitivity NOx gas sensors at room temperature

    NASA Astrophysics Data System (ADS)

    Lü, Renjiang; Zhou, Wei; Shi, Keying; Yang, Ying; Wang, Lei; Pan, Kai; Tian, Chungui; Ren, Zhiyu; Fu, Honggang

    2013-08-01

    Alumina (Al2O3) decorated anatase TiO2 nanotubes with ordered mesoporous pore walls (Al2O3/meso-TiO2 nanotubes) are successfully synthesized through vacuum pressure induction technology, and then combined with the thermal decomposition of a mesoporous TiO2 sol precursor, inside the cylindrical nanochannels of an anodic aluminium oxide (AAO) template. The decorated Al2O3 was formed by in situ deposition via direct reaction of the strong acid sol precursor and the nanochannel wall of the AAO template. The resultant Al2O3/meso-TiO2 nanotubes are characterized in detail by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and N2 adsorption-desorption. The experimental results reveal that the Al2O3/meso-TiO2 nanotubes have a tubular structure with an average diameter of ~200 nm and highly ordered mesopores in the tubular walls. The Al2O3 is distributed evenly on the anatase TiO2 nanotubes. Moreover, the Al2O3/meso-TiO2 nanotubes possess a large specific surface area (136 m2 g-1) and narrow mesopore size distribution (~10 nm). By using NOx as a probe molecule, the Al2O3/meso-TiO2 nanotube films exhibit better sensing performance than that of mesoporous TiO2 nanotubes, in terms of their high sensitivity, fast response-recovery time, and good stability in air at room temperature. The outstanding performance in the gas sensing ability of Al2O3/meso-TiO2 nanotubes is a result of their one-dimensional tubular and mesoporous nanostructures, advantageous for the adsorption and diffusion of NOx gas. In addition, the sensing response is greatly improved by virtue of the decorated Al2O3 on the surfaces of the TiO2 nanotubes, which acts as an energy barrier to suppress charge recombination. The structural properties of the Al2O3/meso-TiO2 nanotubes makes them a viable novel gas sensor material at room temperature.Alumina (Al2O3) decorated anatase TiO2 nanotubes with ordered mesoporous pore walls

  2. Design and Preparation of MnO2/CeO2-MnO2 Double-Shelled Binary Oxide Hollow Spheres and Their Application in CO Oxidation.

    PubMed

    Zhang, Jian; Cao, Yidan; Wang, Chang-An; Ran, Rui

    2016-04-01

    Herein, we designed an extremely facile method to prepare well-defined MnO2@CeO2-MnO2 ball-in-ball binary oxide hollow spheres by employing carbon spheres (CSs) as sacrificial templates. The synthesis process involves a novel self-assembled approach to prepare core-shell CSs@CeO2 precursor, which would directly react with KMnO4 aqueous solution to form yolk-shell CSs@MnO2/CeO2-MnO2 precursor in the following step. Well-dispersed Ce-Mn binary oxide with double-shelled hollow sphere structure could be achieved after annealing the precursor in air. The evolution process and formation mechanism of this novel structure were thoroughly studied in this paper. Especially the as-prepared double-shell MnO2/CeO2-MnO2 hollow spheres exhibited enhanced catalytic activity for CO oxidation compared with the pure MnO2 hollow spheres and pure CeO2 hollow spheres. We believe the high surface area, hierarchical porous structures, and strong synergistic interaction between CeO2 and MnO2 contribute to the excellent catalytic activity. Most importantly, this method could be extended to prepare other transition metal oxides. As an example, triple-shelled Co-Mn composite hollow spheres assembled by ultrathin nanoplates were successfully prepared. PMID:26998672

  3. Selective, Tunable O2 Binding in Cobalt(II)–Triazolate/Pyrazolate Metal–Organic Frameworks

    PubMed Central

    2016-01-01

    The air-free reaction of CoCl2 with 1,3,5-tri(1H-1,2,3-triazol-5-yl)benzene (H3BTTri) in N,N-dimethylformamide (DMF) and methanol leads to the formation of Co-BTTri (Co3[(Co4Cl)3(BTTri)8]2·DMF), a sodalite-type metal–organic framework. Desolvation of this material generates coordinatively unsaturated low-spin cobalt(II) centers that exhibit a strong preference for binding O2 over N2, with isosteric heats of adsorption (Qst) of −34(1) and −12(1) kJ/mol, respectively. The low-spin (S = 1/2) electronic configuration of the metal centers in the desolvated framework is supported by structural, magnetic susceptibility, and computational studies. A single-crystal X-ray structure determination reveals that O2 binds end-on to each framework cobalt center in a 1:1 ratio with a Co–O2 bond distance of 1.973(6) Å. Replacement of one of the triazolate linkers with a more electron-donating pyrazolate group leads to the isostructural framework Co-BDTriP (Co3[(Co4Cl)3(BDTriP)8]2·DMF; H3BDTriP = 5,5′-(5-(1H-pyrazol-4-yl)-1,3-phenylene)bis(1H-1,2,3-triazole)), which demonstrates markedly higher yet still fully reversible O2 affinities (Qst = −47(1) kJ/mol at low loadings). Electronic structure calculations suggest that the O2 adducts in Co-BTTri are best described as cobalt(II)–dioxygen species with partial electron transfer, while the stronger binding sites in Co-BDTriP form cobalt(III)–superoxo moieties. The stability, selectivity, and high O2 adsorption capacity of these materials render them promising new adsorbents for air separation processes. PMID:27180991

  4. Selective, Tunable O2 Binding in Cobalt(II)-Triazolate/Pyrazolate Metal-Organic Frameworks.

    PubMed

    Xiao, Dianne J; Gonzalez, Miguel I; Darago, Lucy E; Vogiatzis, Konstantinos D; Haldoupis, Emmanuel; Gagliardi, Laura; Long, Jeffrey R

    2016-06-01

    The air-free reaction of CoCl2 with 1,3,5-tri(1H-1,2,3-triazol-5-yl)benzene (H3BTTri) in N,N-dimethylformamide (DMF) and methanol leads to the formation of Co-BTTri (Co3[(Co4Cl)3(BTTri)8]2·DMF), a sodalite-type metal-organic framework. Desolvation of this material generates coordinatively unsaturated low-spin cobalt(II) centers that exhibit a strong preference for binding O2 over N2, with isosteric heats of adsorption (Qst) of -34(1) and -12(1) kJ/mol, respectively. The low-spin (S = 1/2) electronic configuration of the metal centers in the desolvated framework is supported by structural, magnetic susceptibility, and computational studies. A single-crystal X-ray structure determination reveals that O2 binds end-on to each framework cobalt center in a 1:1 ratio with a Co-O2 bond distance of 1.973(6) Å. Replacement of one of the triazolate linkers with a more electron-donating pyrazolate group leads to the isostructural framework Co-BDTriP (Co3[(Co4Cl)3(BDTriP)8]2·DMF; H3BDTriP = 5,5'-(5-(1H-pyrazol-4-yl)-1,3-phenylene)bis(1H-1,2,3-triazole)), which demonstrates markedly higher yet still fully reversible O2 affinities (Qst = -47(1) kJ/mol at low loadings). Electronic structure calculations suggest that the O2 adducts in Co-BTTri are best described as cobalt(II)-dioxygen species with partial electron transfer, while the stronger binding sites in Co-BDTriP form cobalt(III)-superoxo moieties. The stability, selectivity, and high O2 adsorption capacity of these materials render them promising new adsorbents for air separation processes. PMID:27180991

  5. N2O and δ15N-N2O and δ18O-N2O from polar ice cores: interpretable data for interglacials

    NASA Astrophysics Data System (ADS)

    Bock, Michael; Schmitt, Jochen; Seth, Barbara; Beck, Jonas; Fischer, Hubertus

    2014-05-01

    Ice cores provide a wealth of information on climate change. For instance, the history of the atmospheric greenhouse gas N2O can be reconstructed using air entrapped in polar ice cores. N2O has several sources in both terrestrial and marine ecosystems, predominantly wetland soils and oxygen minimum zones in the ocean. N2O records generally follow the climatic changes during the glacial-interglacial cycles with higher N2O mixing ratios during warmer climate stages. However, the underlying processes driving these changes are difficult to identify from N2O mixing ratios alone. Additional information on the individual sources and sinks are provided by stable isotope measurements. The emission fluxes of the dominant N2O sources are ascribed to several pathways (nitrification, denitrification), with characteristic fractionation factors for the nitrogen and oxygen isotope signatures of the generated N2O (δ15N-N2O and δ18O-N2O). In the end, the individual proportions of pathways are responsible for distinct δ15N-N2O and δ18O-N2O for the average terrestrial and marine sources. Here, we present new ice core measurements of δ15N-N2O and δ18O-N2O covering the Holocene, MIS 5 and MIS 11. For the past 15 kyrs the δ15N-N2O record shows a continuous decrease starting at 15 kyrs to about 6 kyrs; during the past 6 kyrs δ15N-N2O remains rather constant. The resemblance with a recently published global reconstruction of bulk δ15N is remarkable (McLauchlan et al. 2013, Nature). Taken at face value this could mean that mainly the terrestrial source signature changed rather than a shift in the relative proportions of the terrestrial and marine source. The integrity of N2O ice core records relies on the assumption that the measurements truly represent the past atmosphere. However, comparative analyses of different ice cores from the same age intervals show offsets in the N2O mixing ratios among the records. One likely assumption is that higher mixing ratios are due to in

  6. Highly active Ce 1- xCu xO 2 nanocomposite catalysts for the low temperature oxidation of CO

    NASA Astrophysics Data System (ADS)

    Mai, Hailing; Zhang, Dengsong; Shi, Liyi; Yan, Tingting; Li, Hongrui

    2011-06-01

    A series of Ce 1- xCu xO 2 nanocomposite catalysts with various copper contents were synthesized by a simple hydrothermal method at low temperature without any surfactants, using mixed solutions of Cu(II) and Ce(III) nitrates as metal sources. These bimetal oxide nanocomposites were characterized by means of XRD, TEM, HRTEM, EDS, N 2 adsorption, H 2-TPR and XPS. The influence of Cu loading (5-25 mol%) and calcination temperature on the surface area, particle size and catalytic behavior of the nanocomposites have been discussed. The catalytic activity of Ce 1- xCu xO 2 nanocomposites was investigated using the test of CO oxidation reaction. The optimized performance was achieved for the Ce 0.80Cu 0.20O 2 nanocomposite catalyst, which exhibited superior reaction rate of 11.2 × 10 -4 mmol g -1 s -1 and high turnover frequency of 7.53 × 10 -2 s -1 (1% CO balanced with air at a rate of 40 mL min -1, at 90 °C). No obvious deactivation was observed after six times of catalytic reactions for Ce 0.80Cu 0.20O 2 nanocomposite catalyst.

  7. First-time electrical characterization of nanotubular ZrO2 films for micro-solid oxide fuel cell applications.

    PubMed

    Buyukaksoy, Aligul; Fürstenhaupt, Tobias; Birss, Viola I

    2015-05-14

    In this work, anodically grown ZrO2 nanotubes (NTs) are examined for the first time for use in micro solid oxide fuel cell (μ-SOFC) applications. This is due to their high surface area to volume ratio and useful nanoscale morphological features (e.g., 5-100 nm thick NT bases that could serve as the electrolyte layer). To understand their full potential for these applications, the determination of their electrical properties is necessary. Therefore, ZrO2 NTs, in the form of a uniform and crack-free film, were obtained by the two-step anodization of Zr foil in aqueous solutions. The films exhibited excellent adhesion to the Zr substrate, which facilitated impedance spectroscopy analyses, used for the first time to obtain the resistivity of the nanotubular array separately from the contact resistances. This gave a conductivity of the ZrO2 NTs of 1.6 × 10(-6) S cm(-1) at 600 °C in N2, approximately twice that reported for dense ZrO2 films measured at the same temperature in air, and also a very reasonable activation energy of 0.90 eV in the 400-600 °C temperature range. PMID:25877824

  8. First-time electrical characterization of nanotubular ZrO2 films for micro-solid oxide fuel cell applications

    NASA Astrophysics Data System (ADS)

    Buyukaksoy, Aligul; Fürstenhaupt, Tobias; Birss, Viola I.

    2015-04-01

    In this work, anodically grown ZrO2 nanotubes (NTs) are examined for the first time for use in micro solid oxide fuel cell (μ-SOFC) applications. This is due to their high surface area to volume ratio and useful nanoscale morphological features (e.g., 5-100 nm thick NT bases that could serve as the electrolyte layer). To understand their full potential for these applications, the determination of their electrical properties is necessary. Therefore, ZrO2 NTs, in the form of a uniform and crack-free film, were obtained by the two-step anodization of Zr foil in aqueous solutions. The films exhibited excellent adhesion to the Zr substrate, which facilitated impedance spectroscopy analyses, used for the first time to obtain the resistivity of the nanotubular array separately from the contact resistances. This gave a conductivity of the ZrO2 NTs of 1.6 × 10-6 S cm-1 at 600 °C in N2, approximately twice that reported for dense ZrO2 films measured at the same temperature in air, and also a very reasonable activation energy of 0.90 eV in the 400-600 °C temperature range.

  9. Myoglobin O2 desaturation during exercise. Evidence of limited O2 transport.

    PubMed Central

    Richardson, R S; Noyszewski, E A; Kendrick, K F; Leigh, J S; Wagner, P D

    1995-01-01

    The assumption that cellular oxygen pressure (PO2) is close to zero in maximally exercising muscle is essential for the hypothesis that O2 transport between blood and mitochondria has a finite conductance that determines maximum O2 consumption. The unique combination of isolated human quadriceps exercise, direct measures of arterial, femoral venous PO2, and 1H nuclear magnetic resonance spectroscopy to detect myoglobin desaturation enabled this assumption to be tested in six trained men while breathing room air (normoxic, N) and 12% O2 (hypoxic, H). Within 20 s of exercise onset partial myoglobin desaturation was evident even at 50% of maximum O2 consumption, was significantly greater in H than N, and was then constant at an average of 51 +/- 3% (N) and 60 +/- 3% (H) throughout the incremental exercise protocol to maximum work rate. Assuming a myoglobin PO2 where 50% of myoglobin binding sites are bound with O2 of 3.2 mmHg, myoglobin-associated PO2 averaged 3.1 +/- .3 (N) and 2.1 +/- .2 mmHg (H). At maximal exercise, measurements of arterial PO2 (115 +/- 4 [N] and 46 +/- 1 mmHg [H]) and femoral venous PO2 (22 +/- 1.6 [N] and 17 +/- 1.3 mmHg [H]) resulted in calculated mean capillary PO2 values of 38 +/- 2 (N) and 30 +/- 2 mmHg(H). Thus, for the first time, large differences in PO2 between blood and intracellular tissue have been demonstrated in intact normal human muscle and are found over a wide range of exercise intensities. These data are consistent with an O2 diffusion limitation across the 1-5-microns path-length from red cell to the sarcolemma that plays a role in determining maximal muscle O2 uptake in normal humans. PMID:7560083

  10. Control of silica-zirconia nanoparticles for uniform porous SiO2-ZrO2 membranes.

    PubMed

    Ryeon Lee, Hye; Lee, Jinkyeong; Seo, Bongkuk

    2014-11-01

    Silica-zirconia composite sols were prepared by means of a sol-gel method, using tetraethylorthosilicate (TEOS) and zirconium tetra-n-butoxide (ZrTB) precursors. TEOS, ZrTB, HCl, H2O and EtOH were mixed at 70 degrees C for 24 hours to give molar ratios of 1:1:8-80:0.2-1.0:100-300. The mean particle size of the silica-zirconia sol was controlled by the concentration of the alkoxides and catalyst, as well as the water molar ratio in the starting solution. The particle size of the SiO2-ZrO2 sol, which was analyzed by dynamic light scattering (DLS) and field emission scanning electron microscopy (FE-SEM), was in the range of 20 to 350 nm. The SiO2-ZrO2 sol solutions of different sol sizes were coated onto porous stainless steel supports (O.D. 10 mm, length: 20 mm, 316L SUS, Mott corp. USA) by a dipping-rolling-freezing-fast drying (DRFF) and soaking-rolling-freezing-fast drying (SRFF) method. After coating with SiO2-ZrO2 sol, the single gas permeation characteristics (He, H2 and N2) of the resulting SiO2-ZrO2 membranes were evaluated at room temperature. This produced a decrease in the mean flow diameter and H2/N2 permselectivity in the range of 2.0-3.5. Finally, following the results of gas permeation testing, the pore size of the membranes was controlled by changing their particle size. PMID:25958574

  11. Partial nitrogen loss in SrTaO2N and LaTiO2N oxynitride perovskites

    NASA Astrophysics Data System (ADS)

    Chen, Daixi; Habu, Daiki; Masubuchi, Yuji; Torii, Shuki; Kamiyama, Takashi; Kikkawa, Shinichi

    2016-04-01

    SrTaO2N heated in a helium atmosphere began to release nitrogen of approximately 30 at% at 950 °C while maintaining the perovskite structure and its color changed from orange to dark green. Then it decomposed above 1200 °C to a black mixture of Sr1.4Ta0.6O2.73, Ta2N, and Sr5Ta4O15. The second decomposition was not clearly observed when SrTaO2N was heated in a nitrogen atmosphere below 1550 °C. After heating at 1500 °C for 3 h under a 0.2 MPa nitrogen atmosphere, the perovskite product became dark green and conductive. Structure refinement results suggested that the product was a mixture of tetragonal and cubic perovskites with a decreased ordering of N3-/O2-. The sintered body was changed to an n-type semiconductor after a partial loss of nitrogen to be reduced from the originally insulating SrTaO2N perovskite lattice. LaTiO2N was confirmed to have a similar cis-configuration of the TiO4N2 octahedron as that of TaO4N2 in SrTaO2N. It also released some of its nitrogen at 800 °C changing its color from brown to black and then decomposed to a mixture of LaTiO3, La2O3, and TiN at 1100 °C. These temperatures are lower than those in SrTaO2N.

  12. CFD Simulation of the distribution of ClO2 in fresh produce to improve safety

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The shelf life of fresh-cut produce may be prolonged with the injection of bactericide gases like chlorine dioxide (ClO2). A comparative study has been conducted by modeling the injection of three different gases, CO2, ClO2 and N2 inside a PET clamshell containers commonly use to package fresh produ...

  13. 40 CFR 1065.284 - Zirconia (ZrO2) analyzer.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Zirconia (ZrO2) analyzer. 1065.284 Section 1065.284 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION... Zirconia (ZrO2) analyzer. (a) Application. You may use a zirconia (ZrO2) analyzer to measure...

  14. Synthesis of superamphiphobic breathable membranes utilizing SiO2 nanoparticles decorated fluorinated polyurethane nanofibers

    NASA Astrophysics Data System (ADS)

    Wang, Jialin; Raza, Aikifa; Si, Yang; Cui, Lingxiao; Ge, Jianfeng; Ding, Bin; Yu, Jianyong

    2012-11-01

    Superamphiphobic nanofibrous membranes exhibiting robust water/oil proof and breathable performances were prepared by the combination of a novel synthesized fluorinated polyurethane (FPU) containing a terminal perfluoroalkane segment and incorporated SiO2 nanoparticles (SiO2 NPs). By employing the FPU/SiO2 NPs incorporation, the hybrid membranes possess superhydrophobicity with a water contact angle of 165° and superoleophobicity with an oil contact angle of 151°. Surface morphological studies have indicated that the wettability of resultant membranes could be manipulated by tuning the surface composition as well as the hierarchical structures. The quantitative hierarchical roughness analysis using N2 adsorption method has confirmed a major contribution of SiO2 NPs on enhancing the porous structure, and a detailed correlation between the fractal dimension and amphiphobicity is proposed. Furthermore, a designed concept test shows that the as-prepared membranes could load 1.5 kg water or oil at the same time maintained an extremely high air permeability of 2 L min-1, suggesting their use as promising materials for a variety of potential applications in protective clothing, bioseparation, water purification, tissue engineering, microfluidic systems, etc., and also provided new insight into the design and development of functional hybrid membranes based on FPU.Superamphiphobic nanofibrous membranes exhibiting robust water/oil proof and breathable performances were prepared by the combination of a novel synthesized fluorinated polyurethane (FPU) containing a terminal perfluoroalkane segment and incorporated SiO2 nanoparticles (SiO2 NPs). By employing the FPU/SiO2 NPs incorporation, the hybrid membranes possess superhydrophobicity with a water contact angle of 165° and superoleophobicity with an oil contact angle of 151°. Surface morphological studies have indicated that the wettability of resultant membranes could be manipulated by tuning the surface composition as

  15. Direct sun and airborne MAX-DOAS measurements of the collision induced oxygen complex, O2O2 absorption with significant pressure and temperature differences

    NASA Astrophysics Data System (ADS)

    Spinei, E.; Cede, A.; Herman, J.; Mount, G. H.; Eloranta, E.; Morley, B.; Baidar, S.; Dix, B.; Ortega, I.; Koenig, T.; Volkamer, R.

    2014-09-01

    The collision induced O2 complex, O2O2, is a very important trace gas in remote sensing measurements of aerosol and cloud properties. Some ground based MAX-DOAS measurements of O2O2 slant column density require correction factors of 0.75 ± 0.1 to reproduce radiative transfer modeling (RTM) results for a near pure Rayleigh atmosphere. One of the potential causes of this discrepancy is believed to be uncertainty in laboratory measured O2O2 absorption cross section temperature and pressure dependence, due to difficulties in replicating atmospheric conditions in the laboratory environment. This paper presents direct-sun (DS) and airborne multi-axis (AMAX) DOAS measurements of O2O2 absorption optical depths under actual Earth atmospheric conditions in two wavelength regions (335-390 nm and 435-490 nm). DS irradiance measurements were made by the research grade MFDOAS instrument from 2007-2014 at seven sites with significant pressure (778-1013 hPa) and O2O2 profile weighted temperature (247-275 K) differences. Aircraft MAX-DOAS measurements were conducted by the University of Colorado AMAX-DOAS instrument on 29 January 2012 over the Southern Hemisphere subtropical Pacific Ocean. Scattered solar radiance spectra were collected at altitudes between 9 and 13.2 km, with O2O2 profile weighted temperatures of 231-244 K, and near pure Rayleigh scattering conditions. Due to the well defined DS air mass factors and extensively characterized atmospheric conditions during the AMAX-DOAS measurements, O2O2"pseudo" absorption cross sections, σ, are derived from the observed optical depths and estimated O2O2column densities. Vertical O2O2 columns are calculated from the atmospheric sounding temperature, pressure and specific humidity profiles. Based on the atmospheric DS observations, there is no pressure dependence of the O2O2 σ, within the measurement errors (3%). The two data sets are combined to derive peak σ temperature dependence of 360 and 477 nm absorption bands from 231

  16. Thermal degradation mechanism of triangular Ag@SiO2 nanoparticles.

    PubMed

    Gangishetty, Mahesh K; Scott, Robert W J; Kelly, Timothy L

    2016-06-14

    Triangular silver nanoparticles are promising materials for light harvesting applications because of their strong plasmon bands; these absorption bands are highly tunable, and can be varied over the entire visible range based on the particle size. A general concern with these materials is that they are unstable at elevated temperatures. When thermally annealed, they suffer from changes to the particle morphology, which in turn affects their optical properties. Because of this stability issue, these materials cannot be used in applications requiring elevated temperatures. In order to address this problem, it is important to first understand the degradation mechanism. Here, we measure the changes in particle morphology, oxidation state, and coordination environment of Ag@SiO2 nanotriangles caused by thermal annealing. UV-vis spectroscopy and TEM reveal that upon annealing the Ag@SiO2 nanotriangles in air, the triangular cores are truncated and smaller nanoparticles are formed. Ag K-edge X-ray absorption spectroscopy (XANES and EXAFS) shows that the small particles consist of Ag(0), and that there is a decrease in the Ag-Ag coordination number with an increase in the annealing temperature. We hypothesize that upon annealing Ag in air, it is first oxidized to AgxO, after which it subsequently decomposes back to well-dispersed Ag(0) nanoparticles. In contrast, when the Ag@SiO2 nanotriangles are annealed in N2, since there is no possibility of oxidation, no small particles are formed. Instead, the triangular core rearranges to form a disc-like shape. PMID:26875498

  17. 40 CFR 1065.284 - Zirconia (ZrO2) analyzer.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Zirconia (ZrO2) analyzer. 1065.284... Zirconia (ZrO2) analyzer. (a) Application. You may use a zirconia (ZrO2) analyzer to measure air-to-fuel...O2-based system must meet the linearity verification in § 1065.307. You may use a Zirconia...

  18. Gas analysis using Raman spectroscopy demonstrates the presence of intraperitoneal air (nitrogen and oxygen) in a cohort of children undergoing pediatric laparoscopic surgery.

    PubMed

    Taylor, Susan P; Sato, Thomas T; Balcom, Anthony H; Groth, Travis; Hoffman, George M

    2015-02-01

    Clinically significant gas embolism during laparoscopy is a rare but potentially catastrophic event. Case reports suggest that air, in addition to the insufflation gas, may be present. We studied the effects of equipment design and flushing techniques on the composition of gas present under experimental and routine pediatric surgical conditions. Concentrations of nitrogen (N2), oxygen (O2), and carbon dioxide (CO2) were measured by Raman spectroscopy in gas delivered to and retrieved from a mock peritoneum during simulated laparoscopy. We then analyzed the composition of insufflated and recovered gases during elective laparoscopic procedures conducted with CO2-preflushed and unflushed tubing to determine the presence of significant (10%) quantities of air. In vitro, CO2 was not detected at the distal end of insufflator tubing until after delivery of approximately 0.2 L of gas, and N2 persisted until >0.4 L was delivered, with 40% ± 8% (mean ± SD, range 33%-49%) recovered from the mock peritoneum at the termination of initial insufflation. In clinical studies, preflushing reduced the initial concentration of N2 from 78% ± 0.5% to 23% ± 15%, but >10% air was detected in all subsequent samples, regardless of insufflation technique. Laparoscopic equipment and practice routinely permit delivery of air to the insufflated cavity. Purging the equipment with CO2 reduces but does not eliminate air (N2, O2) within the peritoneal cavity during laparoscopy. Thus, when vascular injury occurs, embolized gases will contain variable quantities of N2, O2, and CO2. As the initial insufflation volume diminishes and approaches the volume of the insufflation tubing, which occurs in infants and young pediatric patients, the concentration of N2 will approximate that of room air in an unflushed system. Small insufflation volumes containing high N2 concentrations can contribute to catastrophic air emboli in neonates and small pediatric patients. PMID:25602452

  19. GdxZryTizCe1-x-y-zO2 mesoporous catalysts for oxidation reactions

    NASA Astrophysics Data System (ADS)

    Zagaynov, Igor V.; Liberman, Elena Yu.; Naumkin, Alexander V.

    2015-12-01

    GdxZryTizCe1-x-y-zO2 solid solutions with a crystallite size of 5-10 nm have been prepared by the sonochemical method from inorganic salts. Ceria-based materials exhibited a mesoporous structure with diameter of 2-10 nm. The activity of the solid solution in the oxidation of carbon monoxide is determined by the flow method within a temperature range of 20-500 °C at atmospheric pressure for the following gas mixture composition, vol.%: CO - 4.2; O2 - 9.6; N2 - balance or CO - 1.8; CH4 - 1.6; O2 - 9.6; N2 - balance. It was shown that the temperature of full conversion of CO was 250-270 °C for CO-O2-N2 mixture and 380-420 °C for CO-CH4-O2-N2 mixture without methane oxidation.

  20. Steady-State Nitrogen Isotope Effects of N2 and N2O Production in Paracoccus denitrificans

    PubMed Central

    Barford, Carol C.; Montoya, Joseph P.; Altabet, Mark A.; Mitchell, Ralph

    1999-01-01

    Nitrogen stable-isotope compositions (δ15N) can help track denitrification and N2O production in the environment, as can knowledge of the isotopic discrimination, or isotope effect, inherent to denitrification. However, the isotope effects associated with denitrification as a function of dissolved-oxygen concentration and their influence on the isotopic composition of N2O are not known. We developed a simple steady-state reactor to allow the measurement of denitrification isotope effects in Paracoccus denitrificans. With [dO2] between 0 and 1.2 μM, the N stable-isotope effects of NO3− and N2O reduction were constant at 28.6‰ ± 1.9‰ and 12.9‰ ± 2.6‰, respectively (mean ± standard error, n = 5). This estimate of the isotope effect of N2O reduction is the first in an axenic denitrifying culture and places the δ15N of denitrification-produced N2O midway between those of the nitrogenous oxide substrates and the product N2 in steady-state systems. Application of both isotope effects to N2O cycling studies is discussed. PMID:10049852

  1. Activated Carbon Composites for Air Separation

    SciTech Connect

    Baker, Frederick S; Contescu, Cristian I; Tsouris, Costas; Burchell, Timothy D

    2011-09-01

    Coal-derived synthesis gas is a potential major source of hydrogen for fuel cells. Oxygen-blown coal gasification is an efficient approach to achieving the goal of producing hydrogen from coal, but a cost-effective means of enriching O2 concentration in air is required. A key objective of this project is to assess the utility of a system that exploits porous carbon materials and electrical swing adsorption to produce an O2-enriched air stream for coal gasification. As a complement to O2 and N2 adsorption measurements, CO2 was used as a more sensitive probe molecule for the characterization of molecular sieving effects. To further enhance the potential of activated carbon composite materials for air separation, work was implemented on incorporating a novel twist into the system; namely the addition of a magnetic field to influence O2 adsorption, which is accompanied by a transition between the paramagnetic and diamagnetic states. The preliminary findings in this respect are discussed.

  2. Plasma model of discharge along a dielectric surface in N2/O2 mixtures

    NASA Astrophysics Data System (ADS)

    Sima, Wenxia; Liu, Chunxiang; Yang, Ming; Shao, Qianqiu; Xu, Hang; Liu, Sanwei

    2016-06-01

    Surface discharge phenomena often occur across the insulator in power systems, damaging the electrical equipment, but the mechanism of the electron multiplication stage during surface discharge is not yet fully understood. As such, it is necessary to investigate the mechanism of discharge along a dielectric surface. In this paper, we develop a numerical fluid model, analyzing the dynamic characteristics of discharge including the electron density, electron temperature, surface charge density, and electric field. Our results show that the electron density peaks in the head of the streamer channel, at which time the electron temperature also reaches its maximum. A thin layer of plasma can be formed, filled with a mix of positive and negative charges, so the space normal electric field in the streamer channel can be positive or negative. In addition, the surface tangential electric field and electric potential are closely related, and the potential steadily increases because there is a steady tangential electric field in the streamer channel.

  3. Structure and electrical properties of sputtered TiO2/ZrO2 bilayer composite dielectrics upon annealing in nitrogen.

    PubMed

    Dong, Ming; Wang, Hao; Ye, Cong; Shen, Liangping; Wang, Yi; Zhang, Jieqiong; Ye, Yun

    2012-01-01

    The high-k dielectric TiO2/ZrO2 bilayer composite film was prepared on a Si substrate by radio frequency magnetron sputtering and post annealing in N2 at various temperatures in the range of 573 K to 973 K. Transmission electron microscopy observation revealed that the bilayer film fully mixed together and had good interfacial property at 773 K. Metal-oxide-semiconductor capacitors with high-k gate dielectric TiO2/ZrO2/p-Si were fabricated using Pt as the top gate electrode and as the bottom side electrode. The largest property permittivity of 46.1 and a very low leakage current density of 3.35 × 10-5 A/cm2 were achieved for the sample of TiO2/ZrO2/Si after annealing at 773 K. PMID:22221384

  4. Structure and electrical properties of sputtered TiO2/ZrO2 bilayer composite dielectrics upon annealing in nitrogen

    PubMed Central

    2012-01-01

    The high-k dielectric TiO2/ZrO2 bilayer composite film was prepared on a Si substrate by radio frequency magnetron sputtering and post annealing in N2 at various temperatures in the range of 573 K to 973 K. Transmission electron microscopy observation revealed that the bilayer film fully mixed together and had good interfacial property at 773 K. Metal-oxide-semiconductor capacitors with high-k gate dielectric TiO2/ZrO2/p-Si were fabricated using Pt as the top gate electrode and as the bottom side electrode. The largest property permittivity of 46.1 and a very low leakage current density of 3.35 × 10-5 A/cm2 were achieved for the sample of TiO2/ZrO2/Si after annealing at 773 K. PMID:22221384

  5. Continuous Remote Measurements of Atmospheric O2 Concentrations in Relation to Interannual Variations in Biological Production and Carbon Cycling in the Oceans

    NASA Technical Reports Server (NTRS)

    Keeling, Ralph F.; Campbell, J. A. (Technical Monitor)

    2002-01-01

    We successfully initiated a program to obtain continuous time series of atmospheric O2 concentrations at a semi-remote coastal site, in Trinidad, California. The installation, which was completed in September 1999, consists of a commercially-available O2 and CO2 analyzers interfaced to a custom gas handling system and housed in a dedicated building at the Trinidad site. Ultimately, the data from this site are expected to provide constraints, complementing satellite data, on variations in ocean productivity and carbon exchange on annual and interannual time scales, in the context of human-induced changes in global climate and other perturbations. The existing time-series, of limited duration, have been used in support of studies of the O2/CO2 exchange from a wild fire (which fortuitously occurred nearby in October 1999) and to quantify air-sea N2O and O2 exchanges related to coastal upwelling events. More generally, the project demonstrates the feasibility of obtaining semi-continuous O2 time series at moderate cost from strategic locations globally.

  6. The simultaneous measurement of low rates of CO2 and O2 exchange in biological systems.

    PubMed

    Willms, J R; Dowling, A N; Dong, Z M; Hunt, S; Shelp, B J; Layzell, D B

    1997-12-15

    An instrument for measuring low rates of biological O2 exchange using an open-flow gas analysis system is described. A novel differential O2 sensor that is capable of measuring as little as 0.4 Pa O2 against a back-ground of ambient air (20,900 Pa O2), yet has a dynamic range of +/- 2000 Pa O2 (i.e., +/- ca. 2% O2) is described. Baseline drift was typically less than 0.025 Pa min-1. The differential O2 sensor was incorporated into a respiratory quotient/photosynthetic quotient analyzer that contained other environmental sensors for atmospheric pressure, absolute O2 and CO2 concentration, temperature of the differential O2 sensor block, and differential pressure between reference and sample streams. Protocols for how these sensors can be used to calibrate the differential O2 sensor and to improve its stability with time are described. Together, the differential O2 sensor, the environmental sensors, and the simple calibration techniques allow for simultaneous, noninvasive, and accurate measurements of O2 and CO2 exchange in tissues with metabolic rates as low as about 0.1 mumol O2 or CO2 h-1. Example data are provided in which O2 differentials of 3 to 41 Pa O2 were measured in an open-flow system. PMID:9417789

  7. Alumina decorated TiO2 nanotubes with ordered mesoporous walls as high sensitivity NO(x) gas sensors at room temperature.

    PubMed

    Lü, Renjiang; Zhou, Wei; Shi, Keying; Yang, Ying; Wang, Lei; Pan, Kai; Tian, Chungui; Ren, Zhiyu; Fu, Honggang

    2013-09-21

    Alumina (Al2O3) decorated anatase TiO2 nanotubes with ordered mesoporous pore walls (Al2O3/meso-TiO2 nanotubes) are successfully synthesized through vacuum pressure induction technology, and then combined with the thermal decomposition of a mesoporous TiO2 sol precursor, inside the cylindrical nanochannels of an anodic aluminium oxide (AAO) template. The decorated Al2O3 was formed by in situ deposition via direct reaction of the strong acid sol precursor and the nanochannel wall of the AAO template. The resultant Al2O3/meso-TiO2 nanotubes are characterized in detail by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and N2 adsorption-desorption. The experimental results reveal that the Al2O3/meso-TiO2 nanotubes have a tubular structure with an average diameter of ∼200 nm and highly ordered mesopores in the tubular walls. The Al2O3 is distributed evenly on the anatase TiO2 nanotubes. Moreover, the Al2O3/meso-TiO2 nanotubes possess a large specific surface area (136 m(2) g(-1)) and narrow mesopore size distribution (∼10 nm). By using NO(x) as a probe molecule, the Al2O3/meso-TiO2 nanotube films exhibit better sensing performance than that of mesoporous TiO2 nanotubes, in terms of their high sensitivity, fast response-recovery time, and good stability in air at room temperature. The outstanding performance in the gas sensing ability of Al2O3/meso-TiO2 nanotubes is a result of their one-dimensional tubular and mesoporous nanostructures, advantageous for the adsorption and diffusion of NO(x) gas. In addition, the sensing response is greatly improved by virtue of the decorated Al2O3 on the surfaces of the TiO2 nanotubes, which acts as an energy barrier to suppress charge recombination. The structural properties of the Al2O3/meso-TiO2 nanotubes makes them a viable novel gas sensor material at room temperature. PMID:23892951

  8. Extreme Emission of N2O from Tropical Wetland Soil (Pantanal, South America)

    PubMed Central

    Liengaard, Lars; Nielsen, Lars Peter; Revsbech, Niels Peter; Priemé, Anders; Elberling, Bo; Enrich-Prast, Alex; Kühl, Michael

    2013-01-01

    Nitrous oxide (N2O) is an important greenhouse gas and ozone depleter, but the global budget of N2O remains unbalanced. Currently, ∼25% of the global N2O emission is ascribed to uncultivated tropical soils, but the exact locations and controlling mechanisms are not clear. Here we present the first study of soil N2O emission from the Pantanal indicating that this South American wetland may be a significant natural source of N2O. At three sites, we repeatedly measured in situ fluxes of N2O and sampled porewater nitrate (NO3-) during the low water season in 2008 and 2009. In 2010, 10 sites were screened for in situ fluxes of N2O and soil NO3- content. The in situ fluxes of N2O were comparable to fluxes from heavily fertilized forests or agricultural soils. An important parameter affecting N2O emission rate was precipitation, inducing peak emissions of >3 mmol N2O m−2 day−1, while the mean daily flux was 0.43 ± 0.03 mmol N2O m−2 day−1. Over 170 days of the drained period, we estimated non-wetted drained soil to contribute 70.0 mmol N2O m−2, while rain-induced peak events contributed 9.2 mmol N2O m−2, resulting in a total N2O emission of 79.2 mmol N2O m−2. At the sites of repeated sampling, the pool of porewater nitrate varied (0.002-7.1μmolNO3-gdW-1) with higher concentrations of NO3- (p < 0.05) found in drained soil than in water-logged soil, indicating dynamic shifts between nitrification and denitrification. In the field, O2 penetrated the upper 60 cm of drained soil, but was depleted in response to precipitation. Upon experimental wetting the soil showed rapid O2 depletion followed by N2O accumulation and a peak emission of N2O (2.5 - 3.0mmolN2Om-2day-1). Assuming that the observed emission of N2O from these wetland soils is generally representative to the Pantanal, we suggest that this undisturbed tropical wetland potentially contributes ∼1.7% to the global N2O emission budget, a significant

  9. Coherent Anti-Stokes Raman Scattering (CARS) as a Probe for Supersonic Hydrogen-Fuel/Air Mixing

    NASA Technical Reports Server (NTRS)

    Danehy, P. M.; O'Byrne, S.; Cutler, A. D.; Rodriguez, C. G.

    2003-01-01

    The dual-pump coherent anti-Stokes Raman spectroscopy (CARS) method was used to measure temperature and the absolute mole fractions of N2, O2 and H2 in a supersonic non-reacting fuel-air mixing experiment. Experiments were conducted in NASA Langley Research Center s Direct Connect Supersonic Combustion Test Facility. Under normal operation of this facility, hydrogen and air burn to increase the enthalpy of the test gas and O2 is added to simulate air. This gas is expanded through a Mach 2 nozzle and into a combustor model where fuel is then injected, mixes and burns. In the present experiment the O2 of the test gas is replaced by N2. The lack of oxidizer inhibited combustion of the injected H2 fuel jet allowing the fuel/air mixing process to be studied. CARS measurements were performed 427 mm downstream of the nozzle exit and 260 mm downstream of the fuel injector. Maps were obtained of the mean temperature, as well as the N2, O2 and H2 mean mole fraction fields. A map of mean H2O vapor mole fraction was also inferred from these measurements. Correlations between different measured parameters and their fluctuations are presented. The CARS measurements are compared with a preliminary computational prediction of the flow.

  10. NOAA's Global Network of N2O Observations

    NASA Astrophysics Data System (ADS)

    Dlugokencky, E. J.; Crotwell, A. M.; Crotwell, M.; Masarie, K. A.; Lang, P. M.; Dutton, G. S.; Hall, B. D.

    2014-12-01

    Nitrous oxide has surpassed CFC-12 to become the third largest contributor to radiative forcing. When climate impacts for equal emitted masses of N2O and CO2 are integrated over 100 years, N2O impacts are about 300 times greater than those of CO2. Increasing the atmospheric burden of N2O also decreases the abundance of O3 in the stratosphere. With reductions in emissions of ODSs as a result of the Montreal Protocol, N2O now has the largest ODP-weighted emissions of all gases. Given its long lifetime of about 130 years, today's emissions will impact climate and stratospheric O3 for a long time. Because emission rates are very small and spread over enormous areas, the detailed N2O budget has large uncertainties. It also means measurement requirements on precision and accuracy are stringent, especially for the background atmosphere. The Carbon Cycle Group of NOAA ESRL's Global Monitoring Division began measuring N2O in discrete air samples collected as part of its global cooperative air sampling network in 1998. Data from about 60 air sampling sites provide important constraints on the large-scale budget of N2O and provide boundary conditions for continental and regional-scale studies. This presentation will briefly describe the procedures used to ensure the data are of sufficient quality to meet scientific demands, and describe remaining limitations. Although sampling is infrequent (weekly), the data are quite useful in N2O budget studies. Examples will be given of large scale constraints on N2O's budget, including the global burden, trends in the burden, global emissions, spatial distributions, vertical gradients, and seasonal patterns.

  11. Diurnality of soil nitrous oxide (N2O) emissions

    NASA Astrophysics Data System (ADS)

    Gelfand, I.; Moyer, R.; Poe, A.; Pan, D.; Abraha, M.; Chen, J.; Zondlo, M. A.; Robertson, P.

    2015-12-01

    Soil emissions of nitrous oxide (N2O) are important contributors to the greenhouse gas balance of the atmosphere. Agricultural soils contribute ~65% of anthropogenic N2O emissions. Understanding temporal and spatial variability of N2O emissions from agricultural soils is vital for closure of the global N2O budget and the development of mitigation opportunities. Recent studies have observed higher N2O fluxes during the day and lower at night. Understanding the mechanisms of such diurnality may have important consequences for our understanding of the N cycle. We tested the hypothesis that diurnal cycles are driven by root carbon exudes that stimulate denitrification and therefore N2O production. Alternatively, we considered that the cycle could result from higher afternoon temperatures that accelerate soil microbial activity. We removed all plants from a corn field plot and left another plot untouched. We measured soil N2O emissions in each plot using a standard static chamber technique throughout the corn growing season. And also compared static chamber results to ecosystem level N2O emissions as measured by eddy covariance tower equipped with an open-path N2O sensor. We also measured soil and air temperatures and soil water and inorganic N contents. Soil N2O emissions followed soil inorganic N concentrations and in control plot chambers ranged from 10 μg N m-2 hr-1 before fertilization to 13×103 after fertilization. We found strong diurnal cycles measured by both techniques with emissions low during night and morning hours and high during the afternoon. Corn removal had no effect on diurnality, but had a strong effect on the magnitude of soil N2O emissions. Soil temperature exhibited a weak correlation with soil N2O emissions and could not explain diurnal patterns. Further studies are underway to explore additional mechanisms that might contribute to this potentially important phenomena.

  12. Spectroscopic analysis of Al and N diffusion in HfO2

    NASA Astrophysics Data System (ADS)

    Lysaght, P. S.; Woicik, J. C.; Sahiner, M. A.; Price, J.; Weiland, C.; Kirsch, P. D.

    2012-09-01

    X-ray photoelectron core level spectroscopy, secondary ion mass spectroscopy, spectroscopic ellipsometry, and extended x-ray absorption fine structure measurements have been employed to distinguish the effects of Al and N diffusion on the local bonding and microstructure of HfO2 and its interface with the Si substrate in (001)Si/SiOx/2 nm HfO2/1 nm AlOx film structures. The diffusion of Al from the thin AlOx cap layer deposited on both annealed and unannealed HfO2 has been observed following anneal in N2 and NH3 ambient. Both N2 and NH3 subsequent anneals were performed to decouple incorporated nitrogen from thermal reactions alone. Causal variations in the HfO2 microstructure combined with the dependence of Al and N diffusion on initial HfO2 conditions are presented with respect to anneal temperature and ambient.

  13. Plasmonic properties of Ag nanoparticles embedded in GeO2-SiO2 matrix by atom beam sputtering.

    PubMed

    Mohapatra, Satyabrata

    2016-02-01

    Nanocomposite thin films containing Ag nanoparticles embedded in the GeO2-SiO2 matrix were synthesized by the atom beam co-sputtering technique. The struc