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Sample records for air o2 n2

  1. Fundamental Insulation Characteristics of Air, N2, CO2, N2/O2 and SF6/N2 Mixed Gases

    NASA Astrophysics Data System (ADS)

    Rokunohe, Toshiaki; Yagihashi, Yoshitaka; Endo, Fumihiro; Oomori, Takashi

    SF6 gas has excellent dielectric strength and interruption performance. For these reasons, it has been widely used for gas insulated switchgear (GIS). However, use of SF6 gas has become regulated under agreements set at the 1997 COP3. Presently, development of a gas circuit breaker (GCB) using CO2 gas and development of a high voltage vacuum circuit breaker (VCB) are being pursued. GIS consists of disconnectors (DS), earthing switches (ES) and buses in addition to GCB. Since the interruption performance is not an important requirement for DS, ES and BUS, use of a gas with high dielectric strength is better than use of a gas with good interruption performance. Air and N2 are not greenhouse gases, and their dielectric strengths are higher than those of other SF6 alternative gases, but only about one-third of the dielectric strength of SF6 gas. This paper deals with a suitable insulation gas which has no greenhouse effect as an SF6 alternative gas. The N2/O2 mixed gas was investigated by changing the ratio of O2. Moreover, the effect of an insulation coating was investigated and compared with the dielectric strength of SF6/N2 mixed gas. The dielectric strength of air under the coating condition was equal to that of 10%SF6/N2 mixed gas.

  2. 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

  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. Characteristics of surface-wave plasma with air-simulated N2 O2 gas mixture for low-temperature sterilization

    NASA Astrophysics Data System (ADS)

    Xu, L.; Nonaka, H.; Zhou, H. Y.; Ogino, A.; Nagata, T.; Koide, Y.; Nanko, S.; Kurawaki, I.; Nagatsu, M.

    2007-02-01

    Sterilization experiments using low-pressure air discharge plasma sustained by the 2.45 GHz surface-wave have been carried out. Geobacillus stearothermoplilus spores having a population of 3.0 × 106 were sterilized for only 3 min using air-simulated N2-O2 mixture gas discharge plasma, faster than the cases of pure O2 or pure N2 discharge plasmas. From the SEM analysis of plasma-irradiated spores and optical emission spectroscopy measurements of the plasmas, it has been found that the possible sterilization mechanisms of air-simulated plasma are the chemical etching effect due to the oxygen radicals and UV emission from the N2 molecules and NO radicals in the wavelength range 200-400 nm. Experiment suggested that UV emission in the wavelength range less than 200 nm might not be significant in the sterilization. The UV intensity at 237.0 nm originated from the NO γ system (A 2Σ+ → X 2Π) in N2-O2 plasma as a function of the O2 percentage added to N2-O2 mixture gas has been investigated. It achieved its maximum value when the O2 percentage was roughly 10-20%. This result suggests that air can be used as a discharge gas for sterilization, and indeed we have confirmed a rapid sterilization with the actual air discharge at a sample temperature of less than 65 °C.

  5. Close Resemblance Between Local Summer Insolation, O2/N2 and Total Air Content from the Dome Fuji Ice Core, Antarctica

    NASA Astrophysics Data System (ADS)

    Kawamura, K.; Nakazawa, T.; Aoki, S.; Fujii, Y.; Watanabe, O.; Severinghaus, J. P.

    2004-12-01

    O2/N2 ratio from ice cores has shown depleted values compared to the atmosphere due to selective exclusion of O2 during bubble formation at the base of firn. The long record from the Vostok ice core revealed that O2/N2 ratio records the local summer insolation. Insolation may affect physical properties of the firn near the surface, which later determines how much O2/N2 is fractionated the during bubble close-off process. We present here a supportive record of O2/N2 ratio for the last 340 kyr along the Dome Fuji ice core, Antarctica, which shows variations similar to the summer insolation at 77° S. Moreover, the variation of total air content (TAC) in the Dome Fuji core resembles that of O2/N2. High TAC and high O2/N2 ratio appear at times of low summer insolation. Since the TAC variation is too large to be explained by the elevation change at the Dome Fuji site in the past, a possible cause is variation of the so-called ``lock-in zone'' thickness on the orders of several meters. The lock-in zone is a region 0-10 m thick at the bottom of firn where horizontal impermeable layers prevent vertical gas mixing. At times of low insolation, the firn would retain inhomogeneities such as wind crusts and high-density layers. These small-scale inhomogeneities do not affect bulk density very much but may help trap the gases at a lower bulk density (and higher porosity and thus TAC) through formation of a thicker lock-in zone than in times of high insolation. High insolation would homogenize the firn structure through recrystallization. O2/N2 ratio would be less depleted if there is a lock-in zone within the total close-off zone, because O2 molecules once excluded from bubbles would eventually be re-trapped in the ice in the lock-in zone.

  6. Space and time analysis of the nanosecond scale discharges in atmospheric pressure air: I. Gas temperature and vibrational distribution function of N2 and O2

    NASA Astrophysics Data System (ADS)

    Lo, A.; Cessou, A.; Boubert, P.; Vervisch, P.

    2014-03-01

    Reliable experimental data on nanosecond discharge plasmas in air become more and more crucial considering their interest in a wide field of applications. However, the investigations on such nonequilibrium plasmas are made difficult by the spatial non-homogeneities, in particular under atmospheric pressure, the wide range of time scales, and the complexity of multi-physics processes involved therein. In this study, we report spatiotemporal experimental analysis on the gas temperature and the vibrational excitation of N2 and O2 in their ground electronic state during the post-discharge of an overvoltage nanosecond-pulsed discharge generated in a pin-to-plane gap of air at atmospheric pressure. The gas temperature during the pulsed discharge is measured by optical emission spectroscopy related to the rotational bands of the 0-0 vibrational transition N2(C 3 Πu, v = 0) → N2(B3 Πg, v = 0) of nitrogen. The results show a rapid gas heating up to 700 K in tens of nanoseconds after the current rise. This fast gas heating leads to a high gas temperature up to 1000 K measured at 150 ns in the first stages of the post-discharge using spontaneous Raman scattering (SRS). The spatiotemporal measurements of the gas temperature and the vibrational distribution function of N2 and O2, also obtained by SRS, over the post-discharge show the spatial expansion of the high vibrational excitation of N2, and the gas heating during the post-discharge. The present measurements, focused on thermal and energetic aspect of the discharge, provide a base for spatiotemporal analysis of gas number densities of N2, O2 and O atoms and hydrodynamic effects achieved during the post-discharge in part II of this investigation. All these results provide space and time database for the validation of plasma chemical models for nanosecond-pulsed discharges at atmospheric pressure air.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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.

  8. 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

  9. Comparison of the effects of room air and N2O + O2 used for ProSeal LMA cuff inflation on cuff pressure and oropharyngeal structure.

    PubMed

    Tekin, Murat; Kati, Ismail; Tomak, Yakup; Yuca, Koksal

    2008-01-01

    This study aimed to evaluate the effects of different inflating gases used for ProSeal LMA (PLMA) cuff inflation on cuff pressure, oropharyngeal structure, and the incidence of sore throat. Eighty patients (American Society of Anesthesiologists; ASA I-II) were randomly divided into two groups. PLMA cuff inflation was achieved with appropriate volumes of 50% N2O + 50% O2 in group I and room air in group II, respectively. When the PLMA was removed, oropharyngeal examination was carried out immediately, using a rigid optical telescope. Patients were asked about sore throat symptoms postoperatively. Cuff pressures were significantly lower in group I, except at the initial pressure measurement. Cuff pressure was positively correlated with the length of the operation in group II, and negatively correlated in group I. PLMA cuff inflation with room air led to increased cuff pressure during the operation, possibly due to the diffusion of N2O into the cuff. We consider that a PLMA cuff inflated with an N2O-O2 mixture is convenient, especially in operations in which N2O has been used.

  10. Measurements and Calculations of the Halfwidth of Two Rotational Transitions of Water Vapor Perturbed by N 2, O 2, and Air

    NASA Astrophysics Data System (ADS)

    Colmont, Jean-Marcel; Priem, Dominique; Wlodarczak, Georges; Gamache, Robert R.

    1999-02-01

    In this paper we report the results of both an experimental and theoretical study of the halfwidths of two transitions of water vapor. Measurements on the lines of the H216O and H218O isotopomers located at 325.1 and 203.4 GHz, respectively, were carried out in the temperature range 300-393 K, with N2and O2as perturbing gases. The foreign-broadening coefficients and their temperature-dependence parameters were determined assuming a Voigt profile and the usual temperature dependence for the halfwidth. The retrieved values are compared to values calculated using the complex semiclassical formalism of Robert and Bonamy. The assumed intermolecular potential is a combination of electrostatic and atom-atom components. This last contribution is defined as the sum of pairwise Lennard-Jones 6-12 interactions between the atoms of H2O and the atoms of the perturbing molecules expanded to eighth order. Also calculated are the pressure-induced shifts of the spectral lines for temperatures from 200 to 400 K. Calculated and experimental results are in good agreement, within ±3.2%, except for the N2-broadening temperature coefficients, for which there are discrepancies as high as 23%. Air-broadening parameters are determined following the classical relation: γ (air) = 0.79γ (N2) + 0.21γ (O2).

  11. 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.

  12. Air-Water Exchange of N2 and O2 from In Situ Measurements in the Subarctic and Subtropical Pacific Oceans: Oxygen Flux and Net Biological Production

    NASA Astrophysics Data System (ADS)

    Emerson, S.

    2008-12-01

    In-situ measurements of wind speed, atmospheric pressure, surface-ocean total dissolved gas pressure and oxygen concentration are used to determine the flux of nitrogen and oxygen between the ocean and atmosphere in the subarctic and subtropical Pacific Oceans. Measurements were made hourly over a period of about one year on surface moorings at the Hawaii Ocean Time series (HOT) in 2005 and at Station P in 2007. Gas pressures in the mixed layer were determined using a gas tension device (GTD) and an oxygen sensor calibrated by Winkler O2 titrations. The pressures of nitrogen and oxygen vary smoothly within a few percent of atmospheric saturation in the subtropical Pacific Ocean, but in the subarctic surface waters these values are punctuated by very rapid excursions caused by storms. The primary flux of oxygen in the upper ocean is between the ocean and atmosphere. We use a simple ocean mixed-layer model to determine this flux and estimate the net biological oxygen production at these sites. Assuming that the net biological oxygen and carbon production are stoichiometrically related over an annual cycle, this method provides a measure of the annual carbon export from the mixed layer, an important component of the ocean's role in the global carbon cycle. There is net biological O2 production most of the year in the subtropical ocean; however, little evidence of net O2 production in the wintertime in the subarctic Pacific. This contrasts with earlier 14C primary production measurements which indicate that wintertime production is about half that in summer at both locations. Annual estimates of biologically produced carbon export at these two sites will be contrasted at the presentation in the fall meeting. This research indicates that it should be possible to derive estimates of the net annual air-water oxygen fluxes caused by biological production at any location of the open ocean where there is a surface mooring. Large, abrupt atmospheric pressure changes (up to 50

  13. The structure of the O2-N2O complex.

    PubMed

    Salmon, Steven R; Lane, Joseph R

    2015-09-28

    We have investigated the lowest energy structures and interaction energies of the oxygen nitrous oxide complex (O2-N2O) using explicitly correlated coupled cluster theory. We find that the intermolecular potential energy surface of O2-N2O is very flat, with two minima of comparable energy separated by a low energy first order saddle point. Our results are able to conclusively distinguish between the two sets of experimental geometric parameters for O2-N2O that were previously determined from rotationally resolved infrared spectra. The global minimum structure of O2-N2O is therefore found to be planar with a distorted slipped parallel structure. Finally, we show that the very flat potential energy surface of O2-N2O is problematic when evaluating vibrational frequencies with a numerical Hessian and that consideration should be given as to whether results might change if the step-size is varied.

  14. 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.

  15. 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.

  16. 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

  17. Thermogravimetric analyses of combustion of lignocellulosic materials in N2/O2 and CO2/O2 atmospheres.

    PubMed

    Lai, ZhiYi; Ma, XiaoQian; Tang, YuTing; Lin, Hai; Chen, Yong

    2012-03-01

    The combustion of paper, fruit waste and plant residue mixtures representing the lignocellulosic materials of municipal solid waste (MSW) in different atmospheres (80N(2)/20O(2), 70N(2)/30O(2), 60N(2)/40O(2), 50N(2)/50O(2), 80CO(2)/20O(2), 70CO(2)/30O(2), 60CO(2)/40O(2), 50CO(2)/50O(2)) was analyzed thermogravimetrically. Replacement of 80% N(2) by 80% CO(2) resulted in a slightly later ignition, a lower maximum weight loss rate and a change in reactions occurring above 600°C; however, as the oxygen concentration increased from 20% to 50% in CO(2)/O(2) atmosphere, the ignition temperature decreased from 318.5 to 310.8°C and the maximum weight loss rate increased from 20.82% to 23.57%/min. An oxygen content of 30% in the CO(2)/O(2) atmosphere achieved a similar combustion performance as a 80N(2)/20O(2). The fruit waste mixture had the least residual weight (about 5%) and the earliest ignition (about 220°C). This work contributes to the comprehensive understanding of lignocellulosic materials combustion and development of MSW oxy-fuel combustion.

  18. 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.

  19. Rate constant and thermochemistry for K + O2 + N2 = KO2 + N2.

    PubMed

    Sorvajärvi, Tapio; Viljanen, Jan; Toivonen, Juha; Marshall, Paul; Glarborg, Peter

    2015-04-09

    The addition reaction of potassium atoms with oxygen has been studied using the collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) method. KCl vapor was photolyzed with 266 nm pulses and the absorbance by K atoms at 766.5 nm was measured at various delay times with a narrow line width diode laser. Experiments were carried out with O2/N2 mixtures at a total pressure of 1 bar, over 748-1323 K. At the lower temperatures single exponential decays of [K] yielded the third-order rate constant for addition, kR1, whereas at higher temperatures equilibration was observed in the form of double exponential decays of [K], which yielded both kR1 and the equilibrium constant for KO2 formation. kR1 can be summarized as 1.07 × 10(-30)(T/1000 K)(-0.733) cm(6) molecule(-2) s(-1). Combination with literature values leads to a recommended kR1 of 5.5 × 10(-26)T(-1.55) exp(-10/T) cm(6) molecule(-2) s(-1) over 250-1320 K, with an error limit of a factor of 1.5. A van't Hoff analysis constrained to fit the computed ΔS298 yields a K-O2 bond dissociation enthalpy of 184.2 ± 4.0 kJ mol(-1) at 298 K and ΔfH298(KO2) = -95.2 ± 4.1 kJ mol(-1). The corresponding D0 is 181.5 ± 4.0 kJ mol(-1). This value compares well with a CCSD(T) extrapolation to the complete basis set limit, with all electrons correlated, of 177.9 kJ mol(-1).

  20. Comparison of Gas Temperatures Measured by Coherent Anti-Stokes Raman Spectroscopy (CARS) of O(2) and N(2).

    PubMed

    Reichardt, T A; Schrader, P E; Farrow, R L

    2001-02-20

    We investigate the accuracy of temperature measurements by coherent anti-Stokes Raman spectroscopy (CARS) of O(2) and use measurements taken with N(2) CARS and a thermocouple for comparison. Scanning vibrational CARS spectra of O(2) and N(2) were recorded over a broad range of temperatures: between 294 K and 1900 K in air that was heated in a tube furnace and at approximately 2450 K in a fuel-lean CH(4)-O(2)-N(2) flame. Temperatures were derived from least-squares fits of simulated and experimental spectra. Both the fundamental vibrational band and the first hot vibrational band were included in fitting. In the case of the tube furnace, the N(2) and the O(2) CARS temperature measurements agreed to within 3%, and results were similar with the thermocouple; in the flame the agreement was to within 1%. We conclude that, for cases in which O(2) is present in sufficient concentrations ( approximately 10% or greater), the accuracy of O(2) thermometry is comparable with that of N(2).

  1. Electrical characterization of the flowing afterglow of N2 and N2/O2 microwave plasmas at reduced pressure

    NASA Astrophysics Data System (ADS)

    Afonso Ferreira, J.; Stafford, L.; Leonelli, R.; Ricard, A.

    2014-04-01

    A cylindrical Langmuir probe was used to analyze the spatial distribution of the number density of positive ions and electrons as well as the electron energy distribution function (EEDF) in the flowing afterglow of a 6 Torr N2 and N2/O2 plasma sustained by a propagating electromagnetic surface wave in the microwave regime. In pure N2 discharges, ion densities were in the mid 1014 m-3 in the pink afterglow and in the mid 1012 m-3 early in the late afterglow. In both pink and late afterglows, the ion population was much higher than the electron population, indicating non-macroscopically neutral media. The EEDF was close to a Maxwellian with an electron temperature of 0.5 ± 0.1 eV, except in the pink afterglow where the temperature rose to 1.1 ± 0.2 eV. This latter behavior is ascribed to N2 vibration-vibration pumping in the pink afterglow that increases the concentration of high N2 vibrational states and thus rises the electron temperature by vibration-electron collisions. After addition of small amounts of O2 in the nominally pure N2 discharge, the charged particles densities and average electron energy first strongly increased and then decreased with increasing O2 concentration. Based on these data and the evolution of the N2+(B) band emission intensities, it is concluded that a significant change in the positive ion composition of the flowing afterglow occurs, going from N2+ in nominally pure N2 discharges to NO+ after addition of trace amounts of O2 in N2.

  2. 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.

  3. 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

  4. Estimates of N2 narcosis and O2 toxicity during submarine escapes from 600 to 1,000 fsw.

    PubMed

    Connor, Christopher W; Ferrigno, Massimo

    2009-01-01

    The U.S. Navy recommends submarine escape for depths down to 600 fsw, with deeper escapes entailing the risks of decompression sickness, nitrogen (N2) narcosis and CNS oxygen (O2) toxicity. However, the escape equipment, including the submarine escape and immersion equipment and the escape trunk, could probably function even at 1,000 fsw. Here we report a theoretical analysis of the risks of both N2 narcosis and CNS O2 toxicity for different escape profiles from 600 to 1,000 fsw. The effect of N2 narcosis, calculated as a function of N2 pressure in the brain using Gas Man software, was expressed as equivalent narcosis depth (END), corresponding to the depth at which the same pressure of N2 would be produced in the brain after five minutes of scuba diving with air. The risk of O2-induced convulsions was estimated using the model developed by Arieli et al. Different dwell times (DTs) at maximal pressure in the escape trunk (from 0 to 60 s) and lungs-to-brain circulation times (10 to 30 s) were included in our analysis. When DT in the escape trunk is very short (e.g., 10 s), the risk of either incapacitating N2 narcosis and/or O2-induced convulsions occurring in the trunk is low, even during escapes from 1,000 fsw.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. Method for measuring changes in the atmospheric O2/N2 ratio by a gas chromatograph equipped with a thermal conductivity detector

    NASA Astrophysics Data System (ADS)

    Tohjima, Yasunori

    2000-06-01

    We present a method for measuring changes in the atmospheric O2/N2 ratio based on data from a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD). In this method, O2 and N2 in an air sample are separated on a column filled with molecular sieve 5A with H2 carrier gas. Since the separated O2 includes Ar, which has a retention time similar to that of O2, the (O2+Ar)/N2 ratio is actually measured. The change in the measured (O2+Ar)/N2 ratio can be easily converted to that in the O2/N2 ratio with a very small error based on the fact that the atmospheric Ar/N2 ratio is almost constant. The improvements to achieve the high-precision measurement include stabilization of the pressure at the GC column head and at the outlets of the TCD and the sample loop. Additionally, the precision is improved statistically by repeating alternate analyses of sample and a reference gas. The standard deviation of the replicate cycles of reference and sample analyses is about 18 per meg (corresponding to 3.8 parts per million (ppm) O2 in air). This means that the standard error is about 7 per meg (1.5 ppm O2 in air) for seven cycles of alternate analyses, which takes about 70 min. The response of this method is likely to have a 2% nonlinearity. Ambient air samples are collected under pressure in glass flasks equipped with two stopcocks sealed by Viton O-rings at both ends. Pressure depletion in the flask during the O2/N2 measurement does not cause any detectable change in the O2/N2 ratio, but the O2/N2 ratio in the flask was found to gradually decrease during the storage period. We also present preliminary results from air samples collected at Hateruma Island (latitude 24°03'N, longitude 123°49') from July 1997 through March 1999. The observed O2/N2 ratios clearly show a seasonal variation, increasing in spring and summer and decreasing in autumn and winter.

  11. Ozone production and losses in N2/O2 mixtures in an ozone generator

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    Nonunique ozone concentrations at the output of an ozone generator under identical external conditions of barrier discharge activation of N2/O2 mixtures but with different prehistories of operating practice and employed gas mixtures are investigated theoretically. An analytical approach is developed to determine the ozone yield with regard for its heterogeneous loss. Plasma-chemical and electron kinetics in the N2/O2-mixtures are calculated numerically. The results of numerical calculations are compared to experimental data obtained by the authors. It is noted that the heterogeneous loss of ozone is the probable reason for the observed variety of behavior of O3 concentrations, depending on prehistory of ozone generator operation, along with the N2 and O2 gas flow rates and the specific active power.

  12. Vibrational relaxation in expanding N2 and air

    NASA Technical Reports Server (NTRS)

    Sebacher, D. I.; Guy, R. W.

    1974-01-01

    New N2 vibrational temperature data, obtained in expanding N2 and air using the electron beam technique, are analyzed permitting the vibrational relaxation times to be determined as a function of temperature. In addition, the effects on N2 vibrational relaxation times of direct vibrational energy transfer between N2 and H2O, between N2 and O2, and between N2 and free electrons introduced from arc contaminants are analyzed. The vibrational relaxation times determined from the present measurements agree with those measured in the expanding flows of shock tunnels and impact tubes. These expanding data also agree with relaxation times observed in acoustical resonant cavities where alternating compressions and expansions take place. The relaxation times in expanding flows (vib-tran exchange process) are found to be approximately 50 times faster than those measured in the compressing flow of shock tubes (tran-vib exchange process). This evidence strongly supports the concept that one relaxation time distribution cannot be applied to both exchange processes.

  13. 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.

  14. 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

  15. 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.

  16. Production of NO, N2O and N2 by extracted soil bacteria, regulation by NO2(-) and O2 concentrations.

    PubMed

    Morley, Nicholas; Baggs, Elizabeth M; Dörsch, Peter; Bakken, Lars

    2008-07-01

    The oxygen control of denitrification and its emission of NO/N2O/N2 was investigated by incubation of Nycodenz-extracted soil bacteria in an incubation robot which monitors O2, NO, N2O and N2 concentrations (in He+O2 atmosphere). Two consecutive incubations were undertaken to determine (1) the regulation of denitrification by O2 and NO2(-) during respiratory O2 depletion and (2) the effects of re-exposure to O2 of cultures with fully expressed denitrification proteome. Early denitrification was only detected (as NO and N2O) at O2 in treatments with NO2(-), and the rates were three orders of magnitude lower than the rates observed after oxygen depletion (with N2 as the primary product). When re-exposed to O2, the cultures continued to denitrify (8-55% of the rates during the foregoing anoxic phase), but its main product was N2O. The N2O reductase activity recovered as oxygen was being depleted. The results suggest that expression of the denitrifying proteome may result in significant subsequent aerobic denitrification, and this has profound implications for the understanding and modelling of denitrification and N2O emission. Short anoxic spells caused by transient flooding during rainfall, could lead to subsequent unbalanced aerobic denitrification, in which N2O is a major end product.

  17. Environmental conditions affecting concentrations of He, CO2, O2 and N2 in soil gases

    USGS Publications Warehouse

    Hinkle, Margaret E.

    1994-01-01

    The measurement of concentrations of volatile species in soil gases has potential for use in geochemical exploration for concealed ore deposits and for monitoring of subsurface contaminants. However, the interpretation of anomalies in surficial gases can be difficult because soil-gas concentrations are dependent on both meteorological and environmental conditions.For this study, concentrations of He, CO2, O2 and N2 and meteorological conditions were monitored for 10–14 months at eight nonmineralized sites in both humid and dry environments. Gases were collected at 0.6–0.7-m depth at seven sites. At one site, gases were collected from 0.3-, 0.6-, 1.2-, and 2.0-m depths; diurnal monitoring studies were conducted at this site also. Rain and snowfall, soil and air temperatures, barometric pressure, and relative humidity were monitored at all the sites. The sand, silt and clay content, and the organic carbon content of surficial soil were measured at each site.Meteorological conditions generally affected He and CO2 concentrations in the same way at all the sites; however, these effects were modified by local environmental conditions. Both seasonal and diurnal concentration changes occurred. The most important seasonal concentration changes were related to rain and snowfall and soil and air temperatures. Seasonal changes tended to be larger then the diurnal changes, but both could be related to the same processes. Local conditions of soil type and organic content affected the amount of pore space and moisture present in the soil and therefore the soil-gas concentrations.

  18. 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.

  19. N 2- and O 2-broadening coefficients of C 2H 2 IR lines

    NASA Astrophysics Data System (ADS)

    Bouanich, J. P.; Lambot, D.; Blanquet, G.; Walrand, J.

    1990-04-01

    Pressure-broadening parameters of six lines belonging to the ν5 band of C 2H 2 in collision with N 2 have been measured with a tunable diode-laser spectrometer in order to complete up to J = 33 our earlier measurements (D. Lambot, G. Blanquet, and J. P. Bouanich, J. Mol. Spectrosc.136, 86-92 (1989)) on the broadening of C 2H 2 by N 2 and O 2 at 297 K. These N 2- and O 2-broadening coefficients have been first calculated on the basis of the Anderson-Tsao-Curnutte theory; in this approach, we show that the short-range interactions which contribute significantly to the linewidths are not correctly treated. Next, we consider the improved semiclassical model proposed by Robert and Bonamy. The intermolecular potential consists in the addition of the atom-atom interaction model to the quadrupolar interactions. The limited radial spherical harmonics expansion of the atom-atom potential, from which expressions for the differential cross section were derived, appears to be quite insufficient at short intermolecular distances. Therefore, we use a more accurate representation of this potential, avoiding an inadequate truncation and keeping the analytic expressions obtained by Bonamy and Robert. In the calculations we take into account the contributions derived from the radial functions U000( r), U200( r), and U220( r), as well as from U400( r). A theoretical expression is obtained for the U400 contribution to the differential cross section. The results of the calculations arising from the exact radial expansion of the atom-atom potential appear to be significantly larger for high J lines than those arising from the truncated expansion. The latter results, which do not include adjustable atom-atom parameters, are in good agreement with experimental broadening coefficients for C 2H 2O 2 and in reasonable agreement (except at large J values) for C 2H 2N 2. It is also shown that the contributions to the linewidths derived from U400 are rather small for C 2H 2N 2 and more

  20. 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.

  1. Vibrational frequency shifts of H2, N2 and O2 adsorbed in NaA zeolite.

    NASA Astrophysics Data System (ADS)

    Koubi, Laure; Blain, Monique; Cohen De Lara, Evelyne; Leclercq, Jean-Marie

    1995-04-01

    We report ab initio calculations on H2,N2 and O2 and on the same molecules in interaction with a Na+ cation. The results are compared to experimental data on induced infrared band of H2, N2 and O2 adsorbed in NaA zeolite. (AIP)

  2. 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

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

    DOE PAGES

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

    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

  4. 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.

  5. 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.

  6. 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.

  7. N2-, O2- and He-collision-induced broadening of sulfur dioxide ro-vibrational lines in the 9.2 μm atmospheric window

    NASA Astrophysics Data System (ADS)

    Tasinato, Nicola; Pietropolli Charmet, Andrea; Stoppa, Paolo; Giorgianni, Santi; Buffa, Giovanni

    2014-01-01

    Sulfur dioxide (SO2) is a molecule of considerable interest for both atmospheric chemistry and astrophysics. In the Earth's atmosphere, it enters in the sulfur cycle and it is ubiquitous present in polluted atmospheres, where it is responsible for acid rains. It is also of astrophysical and planetological importance, being present on Venus and in interstellar clouds. In this work the collisional broadening of a number of ν1 ro-vibrational lines of SO2 perturbed by N2, O2 and He are investigated at room temperature in the 9 μm atmospheric region by means of high resolution tunable diode laser (TDL) infrared spectroscopy. From N2- and O2-broadening coefficients, the broadening parameters of sulfur dioxide in air, useful for atmospheric applications, are derived as well. From the present measurements some conclusions on the quantum number dependence of the N2-, O2- and He-broadening coefficients are drawn. While the J dependence is weak for all the perturbers investigated, different trends with Ka are reported. N2-broadening coefficients show a slight decrease with increasing values of Ka, whereas O2 and He broadening cross sections first increase up to Ka″≈6 and then they keep a nearly constant value. A comparison and a brief discussion on the efficiency of self-, N2-, O2- and He-collisional dynamics are given. The data obtained represent a significant analysis on foreign broadening of SO2 useful for atmospheric remote sensing and astrophysical applications.

  8. New metallicity calibration for Seyfert 2 galaxies based on the N2O2 index

    NASA Astrophysics Data System (ADS)

    Castro, C. S.; Dors, O. L.; Cardaci, M. V.; Hägele, G. F.

    2017-01-01

    We derive a new relation between the metallicity of Seyfert 2 Active Galactic Nuclei (AGNs) and the intensity of the narrow emission-lines ratio N2O2=log([N II]λ6584/[O II]λ3727). The calibration of this relation was performed determining the metallicity (Z) of a sample of 58 AGNs through a diagram containing the observational data and the results of a grid of photoionization models obtained with the CLOUDY code. We find the new Z/Z⊙-N2O2 relation using the obtained metallicity values and the corresponding observational emission line intensities for each object of the sample. Estimations derived through the use of this new calibration indicate that narrow line regions of Seyfert 2 galaxies exhibit a large range of metallicities (0.3 ≲ Z/Z_{⊙} ≲ 2.0), with a median value Z ≈ Z⊙. Regarding the possible existence of correlations between the luminosity L(Hβ), the electron density, and the color excess E(B-V) with the metallicity in this kind of objects, we do not find correlations between them.

  9. Effect of N2O ratio on the crystallization temperature of ZrO2 film deposited on Si by reactive sputtering in Ar/O2/N2O plasma

    NASA Astrophysics Data System (ADS)

    Faruque, Sk Abdul Kader Md; Prasad Giri, Rajendra; Chakraborty, Supratic

    2016-11-01

    The effect of nitrous oxide ratios in the Ar/ O2/ N2O plasma on the ZrO2 films deposited on Si using dc magnetron reactive system is studied by differential scanning calorimetry (DSC) where the Ar:O2 ratio is fixed at 4:1. Further, grazing angle x-ray reflectivity (GIXRR), grazing angle x-ray diffraction (GIXRD) and atomic force microscopy (AFM) techniques are also employed to characterize the films. The DSC study shows an anomalous variation of the glass temperature when the N2O ratio in the Ar/O2/N2O plasma changes from 0.25 to 2 with respect to the control ZrO2 sample deposited without N2O. An increase in glass temperature by ∼70 °C is observed for the N2O ratio at 1. A further rise in N2O ratio results in the reduction of the glass temperature. The GIXRR study indicates that the thickness of the samples decreases with the increase in N2O ratios beyond 0.8. Further, increasing N2O ratio results in an increase in surface and interface roughness for the as-deposited samples. But both the roughnesses decrease upon annealing the samples above their respective crystallization temperatures. The AFM results also corroborates the observation. Moreover, the GIXRD study indicates the formation of Γ-Zr2ON2 along with the monoclinic and tetragonal ZrO2 at the highest ratio of N2O in the Ar:O2:N2O plasma.

  10. The influence of bremsstrahlung on electric discharge streamers in N2, O2 gas mixtures

    NASA Astrophysics Data System (ADS)

    Köhn, C.; Chanrion, O.; Neubert, T.

    2017-01-01

    Streamers are ionization filaments of electric gas discharges. Negative polarity streamers propagate primarily through electron impact ionization, whereas positive streamers in air develop through ionization of oxygen by UV photons emitted by excited nitrogen; however, experiments show that positive streamers may develop even for low oxygen concentrations. Here we explore if bremsstrahlung ionization facilitates positive streamer propagation. To discriminate between effects of UV and bremsstrahlung ionization, we simulate the formation of a double headed streamer at three different oxygen concentrations: no oxygen, 1 ppm O2 and 20% O2, as in air. At these oxygen levels, UV-relative to bremsstrahlung ionization is zero, small, and large. The simulations are conducted with a particle-in-cell code in a cylindrically symmetric configuration at ambient electric field magnitudes three times the conventional breakdown field. We find that bremsstrahlung induced ionization in air, contrary to expectations, reduces the propagation velocity of both positive and negative streamers by about 15%. At low oxygen levels, positive streamers stall; however, bremsstrahlung creates branching sub-streamers emerging from the streamer front that allow propagation of the streamer. Negative streamers propagate more readily forming branching sub-streamers. These results are in agreement with experiments. At both polarities, ionization patches are created ahead of the streamer front. Electrons with the highest energies are in the sub-streamer tips and the patches.

  11. The calculation of high-temperature equilibrium and nonequilibrium specific heat data for N2, O2 and NO

    NASA Technical Reports Server (NTRS)

    Jaffe, Richard L.

    1987-01-01

    Specific heat data for high-temperature air species are needed to compute the temperature and enthalpy of gas mixtures in aerothermodynamics flowfield calculations. Accurate data are known only for temperatures under 6000 K, but are required for temperatures exceeding 25,000 K. In the present study, CP data are computed for N2, O2 and NO. The calculations are based on summations over all the vibration-rotation energy levels for all known bound electronic states. Estimates are made for the error introduced by the neglect of possible additional high-lying electronic states. In addition, a scheme for the partitioning of the internal energy into vibrational, rotational and electronic contributions is presented which consistently accounts for the nonseparable nature of the various energy modes. The multitemperature specific heat data are recommended for use in nonequilibrium flowfield models.

  12. 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.

  13. 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.

  14. Respiratory depressant action of tilidine during N2O + O2 anaesthesia.

    PubMed

    Tammisto, T; Tigerstedt, I

    1976-01-01

    The respiratory depressant actions of pethidine and tilidine during anaesthesia were compared in 18 surgical patients anaesthetized with N2O + O2 after thiopental induction. Five minutes after thiopental, 0.5 mg/kg pethidine or 1.5 mg/kg tilidine were each given intravenously to six patients, the remaining six patients serving as controls. Minute ventilation, respiratory rate, end-tidal CO2 and PCO2 from arterialized venous blood were measured up to 30 min. Pethidine caused the following maximal changes: V -0.98 +/- 0.24 (s.e. mean) 1/min, rate -5.5 +/- 0.7/min, CO2ET + 0.7 +/- 0.1 vol % and PCO2 + 5.7 +/- 1.1 mm Hg. These changes occurred within 10 min of the injection.

  15. Influence of Ar/O2/H2O Feed Gas and N2/O2/H2O Environment on the Interaction of Time Modulated MHz Atmospheric Pressure Plasma Jet (APPJ) with Model Polymers

    NASA Astrophysics Data System (ADS)

    Oehrlein, Gottlieb; Luan, Pingshan; Knoll, Andrew; Kondeti, Santosh; Bruggeman, Peter

    2016-09-01

    An Ar/O2/H2O fed time modulated MHz atmospheric pressure plasma jet (APPJ) in a sealed chamber was used to study plasma interaction with model polymers (polystyrene, poly-methyl methacrylate, etc.). The amount of H2O in the feed gas and/or present in the N2, O2, or N2/O2 environment was controlled. Short lived species such as O atoms and OH radicals play a crucial role in polymer etching and surface modifications (obtained from X-ray photoelectron spectroscopy of treated polymers without additional atmospheric exposure). Polymer etching depth for Ar/air fed APPJ mirrors the decay of gas phase O atoms with distance from the APPJ nozzle in air and is consistent with the estimated O atom flux at the polymer surface. Furthermore, whereas separate O2 or H2O admixture to Ar enhances polymer etching, simultaneous addition of O2 and H2O to Ar quenches polymer etching. This can be explained by the mutual quenching of O with OH, H and HO2 in the gas phase. Results where O2 and/or H2O in the environment were varied are consistent with these mechanisms. All results will be compared with measured and simulated species densities reported in the literature. We gratefully acknowledge funding from US Department of Energy (DE-SC0001939) and National Science Foundation (PHY-1415353).

  16. 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.

  17. Nqrs Data for C6H16I2N2O8 [C6H14N2O2·2(HIO3)] (Subst. No. 0931)

    NASA Astrophysics Data System (ADS)

    Chihara, H.; Nakamura, N.

    This document is part of Subvolume A `Substances Containing Ag … C10H15' of Volume 48 `Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Börnstein - Group III `Condensed Matter'. It contains an extract of Section `3.2 Data tables' of the Chapter `3 Nuclear quadrupole resonance data' providing the NQRS data for C6H16I2N2O8 [C6H14N2O2·2(HIO3)] (Subst. No. 0931)

  18. Nqrs Data for C6H20I6N2O20 [C6H14N2O2·6(HIO3)] (Subst. No. 0939)

    NASA Astrophysics Data System (ADS)

    Chihara, H.; Nakamura, N.

    This document is part of Subvolume A `Substances Containing Ag … C10H15' of Volume 48 `Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Börnstein - Group III `Condensed Matter'. It contains an extract of Section `3.2 Data tables' of the Chapter `3 Nuclear quadrupole resonance data' providing the NQRS data for C6H20I6N2O20 [C6H14N2O2·6(HIO3)] (Subst. No. 0939)

  19. Nqrs Data for C6H17I3N2O11 [C6H14N2O2·3(HIO3)] (Subst. No. 0933)

    NASA Astrophysics Data System (ADS)

    Chihara, H.; Nakamura, N.

    This document is part of Subvolume A `Substances Containing Ag … C10H15' of Volume 48 `Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Börnstein - Group III `Condensed Matter'. It contains an extract of Section `3.2 Data tables' of the Chapter `3 Nuclear quadrupole resonance data' providing the NQRS data for C6H17I3N2O11 [C6H14N2O2·3(HIO3)] (Subst. No. 0933)

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

    PubMed

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

    2015-08-03

    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.

  1. 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

  2. Observations of the Annual Cycle of Dissolved O2, N2, pCO2 on the Alaskan Shelf

    NASA Astrophysics Data System (ADS)

    Morison, J. H.; McNeil, C. L.; Zhang, J.

    2012-12-01

    To better understand air-sea gas exchange processes in the complex and changing seasonal ice zone of the Arctic, and to better understand carbon/oxygen dynamics over the continental shelf, we deployed a mooring with biogeochemical sensors at about 28 m depth on the Beaufort Shelf at 71.4° N and 152.0° W, just east of Barrow Canyon, in approximately 150 m deep water. We present our first time series observations from September 2010 through October 2011 which include water temperature, salinity, three dissolved gases (O2, N2, and pCO2), and chlorophyll fluorescence. The dataset provide our first look at the annual cycle of the dissolved gases as they are influenced by seasonal changes in ice cover and productivity. The data show the entrance and exit to the region of the warmer summer waters, and chlorophyll blooms. Under-ice changes in gas levels at the depth of the sensors are particularly intriguing. They show a gradual decline and increase in saturation levels of CO2 and O2, respectively. This would normally indicate net productivity; however, photosynthetic solar radiation under the ice cover in winter is very low as was the observed chlorophyll fluorescence. We compare the data to model results to provide more background for interpretation of the data set and compare the timing of the observed versus model chlorophyll blooms.

  3. 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

  4. BiVO4/TiO2(N2) Nanotubes Heterojunction Photoanode for Highly Efficient Photoelectrocatalytic Applications

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Bai, Jing; Li, Yunpo; Zeng, Qingyi; Li, Jinhua; Zhou, Baoxue

    2017-04-01

    We report the development of a novel visible response BiVO4/TiO2(N2) nanotubes photoanode for photoelectrocatalytic applications. The nitrogen-treated TiO2 nanotube shows a high carrier concentration rate, thus resulting in a high efficient charge transportation and low electron-hole recombination in the TiO2-BiVO4. Therefore, the BiVO4/TiO2(N2) NTs photoanode enabled with a significantly enhanced photocurrent of 2.73 mA cm-2 (at 1 V vs. Ag/AgCl) and a degradation efficiency in the oxidation of dyes under visible light. Field emission scanning electron microscopy, X-ray diffractometry, energy-dispersive X-ray spectrometer, and UV-Vis absorption spectrum were conducted to characterize the photoanode and demonstrated the presence of both metal oxides as a junction composite.

  5. 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

  6. Band Gap Tailoring of TiO2 Nanowires by Nitrogen Doping Under N2/Ar Plasma Environment.

    PubMed

    Dhar, J C; Mondal, A; Bhattacharya, S; Singh, N K; Ngangbam, C; Chattopadhyay, K K

    2015-05-01

    Glancing angle deposited TiO2 nanowires (NWs) were doped with nitrogen (N) using plasma-enhanced chemical vapour deposition technique, under the treatment of N2/Ar plasma. A red shift (- 0.51 eV) in the main band transition and oxygen defect related transition (-2.1 eV) was observed for the N doped TiO2 nanowires. The interstitial nitrogen introduces mid-gap levels N (2P) above the O (2P) in the TiO2 forbidden gap. The photoluminescence measurement revealed a small red shift of -7 nm of anatase band gap from N doped TiO2 nanowires due to radiative recombination of carriers from conduction band to the N (2P) trap state. The low frequency Raman peaks at 304 cm(-1) (acoustical phonons with LA mode), 618 cm(-1) (optical phonons with LO modes) and the high frequency peak at 832 cm(-1) was observed from Ti-O-N due to the partial replacement of oxygen molecules by nitrogen into TiO2, during the doping process.

  7. 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.

  8. 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).

  9. Assessment of the interaction of hyperbaric N2, CO2, and O2 on psychomotor performance in divers.

    PubMed

    Freiberger, J J; Derrick, B J; Natoli, M J; Akushevich, I; Schinazi, E A; Parker, C; Stolp, B W; Bennett, P B; Vann, R D; Dunworth, S A S; Moon, R E

    2016-10-01

    Diving narcosis results from the complex interaction of gases, activities, and environmental conditions. We hypothesized that these interactions could be separated into their component parts. Where previous studies have tested single cognitive tasks sequentially, we varied inspired partial pressures of CO2, N2, and O2 in immersed, exercising subjects while assessing multitasking performance with the Multi-Attribute Task Battery II (MATB-II) flight simulator. Cognitive performance was tested under 20 conditions of gas partial pressure and exercise in 42 male subjects meeting U.S. Navy age and fitness profiles. Inspired nitrogen (N2) and oxygen (O2) partial pressures were 0, 4.5, and 5.6 ATA and 0.21, 1.0, and 1.22 ATA, respectively, at rest and during 100-W immersed exercise with and without 0.075-ATA CO2 Linear regression modeled the association of gas partial pressure with task performance while controlling for exercise, hypercapnic ventilatory response, dive training, video game frequency, and age. Subjects served as their own controls. Impairment of memory, attention, and planning, but not motor tasks, was associated with N2 partial pressures >4.5 ATA. Sea level O2 at 0.925 ATA partially rescued motor and memory reaction time impaired by 0.075-ATA CO2; however, at hyperbaric pressures an unexpectedly strong interaction between CO2, N2, and exercise caused incapacitating narcosis with amnesia, which was augmented by O2 Perception of narcosis was not correlated with actual scores. The relative contributions of factors associated with diving narcosis will be useful to predict the effects of gas mixtures and exercise conditions on the cognitive performance of divers. The O2 effects are consistent with O2 narcosis or enhanced O2 toxicity.

  10. Kinetics of ozone and nitric oxides in dielectric barrier discharges in O2/NOx and N2/O2/NOx mixtures

    NASA Astrophysics Data System (ADS)

    Stefanovic, I.; Bibinov, N. K.; Deryugin, A. A.; Vinogradov, I. P.; Napartovich, A. P.; Wiesemann, K.

    2001-08-01

    Concentrations of NO, NO2, NO3, N2O5, and O3 were measured by classical absorption spectroscopy in dielectric barrier discharges in flowing O2/NOx and N2/O2/NOx mixtures. The results of measurements in different parts of the discharge chamber and in its exhaust are compared to a numerical zero-dimensional kinetic model and good agreement is found. The experimentally found upper limit of the NOx concentration allowing ozone production is confirmed by the kinetic calculations for both gas mixtures. The rotational temperature of different nitrogen bands was measured by high-resolution emission spectroscopy. The results are explained on the basis of a simplified model and related to the gas temperature in the microdischarge channel and the surrounding gas.

  11. Thermogravimetric study of the combustion of Tetraselmis suecica microalgae and its blend with a Victorian brown coal in O2/N2 and O2/CO2 atmospheres.

    PubMed

    Tahmasebi, Arash; Kassim, Mohd Asyraf; Yu, Jianglong; Bhattacharya, Sankar

    2013-12-01

    The combustion characteristics of microalgae, brown coal and their blends under O2/N2 and O2/CO2 atmospheres were studied using thermogravimetry. In microalgae combustion, two peaks at 265 and 485°C were attributable to combustion of protein and carbohydrate with lipid, respectively. The DTG profile of coal showed one peak with maximum mass loss rate at 360°C. Replacement of N2 by CO2 delayed the combustion of coal and microalgae. The increase in O2 concentration did not show any effect on combustion of protein at the first stage of microalgae combustion. However, between 400 and 600°C, with the increase of O2 partial pressure the mass loss rate of microalgae increased and TG and DTG curves of brown coal combustion shifted to lower temperature zone. The lowest and highest activation energy values were obtained for coal and microalgae, respectively. With increased microalgae/coal ratio in the blends, the activation energy increased due to synergy effect.

  12. 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.

  13. 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.

  14. Development of Polysulfone (PSF)-Carbon Molecular Sieve (CMS) Mixed Matrix Membrane (MMM) For O2/N2 Gas Separation

    NASA Astrophysics Data System (ADS)

    Ismail, A. F.; Rahman, W. R.; Aziz, F.

    2009-06-01

    Mixed matrix membranes (MMMs) comprising polysulfone (PSF) Udel® P-1700 and synthesized carbon molecular sieve (CMS) particles (<25 μm) have been fabricated and characterized. CMS were synthesized by using polyacrylonitrile (PAN) as polymer precursor. The casting process was performed at the processing temperature close to Tg of PSF in order to maintain the flexibility of polymer during film formation. This study investigated the effects of CMS loadings (10, 20, 30 and 35 wt%) on the morphology and the gas separation performance of PSF-CMS MMMs. The fabricated MMMs were characterized using TGA, DSC, FESEM and single gas permeation test using high purity O2 and N2. Based on FESEM micrograph, a good polymer-sieve adhesion was achieved in MMMs using the combination of PSF-CMS even at high sieve loading (up to 35 wt%). The formation of `sieve-in-the-cage' morphology in PSF-CMS MMMs has been minimized to a great extend by implementing casting procedure at the operating temperature close to the Tg of polymer matrix. The O2 and N2 permeability for MMMs were increased with increasing CMS loading; while at 20 wt% CMS loading the O2/N2 selectivity attain the highest value which is 5.97 with the O2 permeability of 7.9617 barrers.

  15. Novel measurements of refractive index, density and mid-infrared integrated band strengths for solid O2, N2O and NO2 : N2O4 mixtures

    NASA Astrophysics Data System (ADS)

    Fulvio, D.; Sivaraman, B.; Baratta, G. A.; Palumbo, M. E.; Mason, N. J.

    2009-06-01

    We present novel measurements of the refractive index, density and integrated band strengths of mid-infrared features of solid N2O at 16 K and of NO2 and N2O4 in two frozen NO2:N2O4 mixtures deposited at 16 and 60 K. The refractive index and density measurements were performed also for frozen O2 deposited at 16 K. In this case, the integrated band strength values could not be determined since O2 is a homonuclear molecule and therefore its fundamental mode is not infrared active. The solid samples were analysed by infrared spectroscopy in the 8000.800 cm -1 range. The sample thickness was measured by the interference curve obtained using a He-Ne laser operating at 543 nm. The refractive index at this laser wavelength was obtained, by numerical methods, from the measured amplitude of the interference curve. The density values were obtained using the Lorentz-Lorenz relation. Integrated band strength values were then obtained by a linear fit of the integrated band intensities plotted versus column density values. The astrophysical relevance of these novel measurements is briefly discussed.

  16. Kinetic modeling of the formation and growth of inorganic nano-particles during pulverized coal char combustion in O2/N2 and O2/CO2 atmospheres

    DOE PAGES

    Shaddix, Christopher R.; Niu, Yanqing; Hui, Shi'en; ...

    2016-08-01

    In this formation of nano-particles during coal char combustion, the vaporization of inorganic components in char and the subsequent homogeneous particle nucleation, heterogeneous condensation, coagulation, and coalescence play decisive roles. Furthermore, conventional measurements cannot provide detailed information on the dynamics of nano-particle formation and evolution, In this study, a sophisticated intrinsic char kinetics model that considers ash effects (including ash film formation, ash dilution, and ash vaporization acting in tandem), both oxidation and gasification by CO2 and H2O, homogeneous particle nucleation, heterogeneous vapor condensation, coagulation, and and coalescence mechanisms is developed and used to compare the temporal evolution of themore » number and size of nano-particles during coal char particle combustion as a function of char particle size, ash content, and oxygen content in O2/N2 and O2/CO2 atmospheres .« less

  17. 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

  18. Synthesis and characterization of amorphous SiO2 nanowires via pulsed laser deposition accompanied by N2 annealing

    NASA Astrophysics Data System (ADS)

    Li, Hui; Guan, Leilei; Xu, Zhuoqi; Zhao, Yu; Sun, Jian; Wu, Jiada; Xu, Ning

    2016-12-01

    Amorphous SiO2 nanowires are successfully fabricated on fused silica substrates covered by nickel/carbon catalyst bilayers via a method of pulsed laser deposition accompanied by annealing in ambient N2. The field emission scanning electron microscopy images show that the optimum annealing temperature for the growth of SiO2 nanowires is about 1200 °C and the grown SiO2 nanowires become denser, longer and more uniform with the increment of annealing duration. The results of transmission electron microscopy and high-resolution transmission electron microscopy show that the grown nanowires are amorphous and have dark spheres on their tops. The analyses of energy dispersive X-ray spectroscopy reveal that the nanowires are composed of SiO2 and the dark spheres on their tops contain little nickel. It is inferred that nickel, carbon and CO are the key elements to promote the SiO2 nanowire growth in the solid-liquid-solid mode. Transmission spectra demonstrate that the as-grown nanowire thin films can have about 94% average transmittance in the range of 350-800 nm, meanwhile the photoluminescence spectra of the as-grown SiO2 nanowire samples show stable ultraviolet emission centered at about 363 nm with a shoulder at about 393 nm.

  19. 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.

  20. Nqrs Data for C10H11AuCl4N2O2 (Subst. No. 1239)

    NASA Astrophysics Data System (ADS)

    Chihara, H.; Nakamura, N.

    This document is part of Subvolume A `Substances Containing Ag … C10H15' of Volume 48 `Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Börnstein - Group III `Condensed Matter'. It contains an extract of Section `3.2 Data tables' of the Chapter `3 Nuclear quadrupole resonance data' providing the NQRS data for C10H11AuCl4N2O2 (Subst. No. 1239)

  1. 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.

  2. 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

  3. Thymidine decomposition induced by low-energy electrons and soft X rays under N2 and O2 atmospheres.

    PubMed

    Alizadeh, Elahe; Sanz, Ana G; Madugundu, Guru S; García, Gustavo; Wagner, J Richard; Sanche, Léon

    2014-06-01

    A novel technique has been employed to investigate the simultaneous damage to DNA components induced by soft X rays (1.5 keV) and low-energy electrons (0-30 eV) in thin films of thymidine deposited on glass and tantalum substrates and irradiated under atmospheric pressure and temperature. The films were surrounded by either an N2 or O2 environment. The formation of four radiation-induced products is reported in this article: base release, 5-hydroxymethyl-2'-deoxyuridine (5-HMdUrd), 5-formyl-2'-deoxyuridine (5-FordUrd) and 5,6-dihydrothymidine (5,6-DHThd). Analysis with LC-MS/MS shows larger damage yields in the samples deposited on tantalum than in those deposited on glass, which is attributed to the interaction of the additional low-energy electrons that are photoemitted from the metal surface. From a comparison of the results obtained from N2 and O2 environment, we report a dramatic effect from 6 O2: an approximately threefold increase in the yield of products, attributed to the reaction of O2 with initial carbon-centered thymidine radicals generated in the film during irradiation.

  4. CoNi@SiO2 @TiO2 and CoNi@Air@TiO2 Microspheres with Strong Wideband Microwave Absorption.

    PubMed

    Liu, Qinghe; Cao, Qi; Bi, Han; Liang, Chongyun; Yuan, Kaiping; She, Wen; Yang, Yongji; Che, Renchao

    2016-01-20

    The synthesis of CoNi@SiO2 @TiO2 core-shell and CoNi@Air@TiO2 yolk-shell microspheres is reported for the first time. Owing to the magnetic-dielectric synergistic effect, the obtained CoNi@SiO2 @TiO2 microspheres exhibit outstanding microwave absorption performance with a maximum reflection loss of -58.2 dB and wide bandwidth of 8.1 GHz (8.0-16.1 GHz, < -10 dB).

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

    PubMed Central

    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

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Dissociation of N2O on anatase TiO2 (001) surface - The effect of oxygen vacancy and presence of Ag cluster

    NASA Astrophysics Data System (ADS)

    Sowmiya, M.; Senthilkumar, K.

    2016-12-01

    The increase in concentration of nitrous oxide (N2O) in the atmosphere is one of the major contributors to the greenhouse effect, ozone depletion and climate change. Therefore, it is important to decompose harmful N2O molecule into harmless N2. In the present work, we have studied the decomposition of N2O on anatase TiO2 (001) surface using first principle calculations. The results indicates that the N2O molecule is physisorbed on perfect TiO2 surface without any dissociation, and is dissociated into N2 and oxygen on the reduced TiO2 surface. In addition, it has been found that the interaction between N2O and TiO2 is augmented by the presence of Ag cluster on anatase (001) surface. On the basis of Bader charge analysis and electron density difference plot, it has been found that the excess charge in the reduced anatase TiO2 (001) surface is transferred to the adsorbed N2O molecule, which results the weakening of N

  14. The need for fentanyl supplementation of N2O-O2 relaxant anaesthesia in chronic alcoholics.

    PubMed

    Tammisto, T; Tigerstedt, I

    1977-01-01

    In order to find out how the need for analgesic supplementation during N2O-O2-relaxant anaesthesia is affected by chronic alcohol consumption, 82 patients with various known alcohol habits were anaesthetized for gastric or biliary surgery. Muscular relaxation was kept constant with the aid of a peripheral neurostimulator, and fentanyl was given in increments of 0.05-0.1 mg for nociceptive symptoms during the anaesthesia. For induction, alcoholics (annual consumption above 151 pure alcohol) needed significantly more thiopental/kg body weight than social drinkers (1--151 annually) or non-alcoholics (less than 11 annually), and excitative symptoms were more frequent in alcoholics. A positive correlation was found between fentanyl supplementation and alcohol consumption (r = 0.41), non-alcoholics requiring on average 3.8 microng/kg/h of fentanyl, as compared with 6.4 microng/kg/h in alcoholics. This correlation was clearer than that found previously under similar conditions by the authors between halothane supplementation and alcohol consumption (r = 0.20). In both studies the correlation was partly due to the higher incidence of gastric surgery among alcoholics, since gastric surgery itself requires more supplementation. An analysis of the different symptoms pointing to the need for fentanyl supplementation revealed that the simultaneous occurrence of several symptoms and the prevalence of motor responses were more common in alcoholics. In one patient halothane had to be used as well. In other patients no special difficulties were observed, and none of the patients reported dreams or recollections. The results suggest that during N2O-O2-relaxant anaesthesia the demand for fentanyl supplementation is increased by about 70% in chronic alcoholics with a mean annual consumption of 311 pure alcohol.

  15. 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

  16. Mixed ligand Cu(II)N2O2 complexes: biomimetic synthesis, activities in vitro and biological models, theoretical calculations.

    PubMed

    Li, Chen; Yin, Bing; Kang, Yifan; Liu, Ping; Chen, Liang; Wang, Yaoyu; Li, Jianli

    2014-12-15

    Three new mixed ligand Cu(II)N2O2 complexes, namely, [Cu(II)(2-A-6-MBT)2(m-NB)2] (1), [Cu(II)(2-ABT)2(m-NB)2] (2), and [Cu(II)(2-ABT)2(o-NB)2] (3), (2-A-6-MBT = 2-amino-6-methoxybenzothiazole, m-NB = m-nitrobenzoate, 2-ABT = 2-aminobenzothiazole, and o-NB = o-nitrobenzoate), have been prepared by the biomimetic synthesis strategy, and their structures were determined by X-ray crystallography studies and spectral methods. These complexes exhibited the effective superoxide dismutase (SOD) activity and catecholase activity. On the basis of the experimental data and computational studies, the structure-activity relationship for these complexes was investigated. The results reveal that electron-accepting abilities of these complexes and coordination geometries have significant effects on the SOD activity and catecholase activity. Then, we found that 1 and 2 exerted potent intracellular antioxidant capacity in the model of H2O2-induced oxidative stress based on HeLa cervical cancer cells, which were screened out by the cytotoxicity assays of different kinds of cells. Furthermore, 1-3 showed the favorable biocompatibility in two different biological models: Saccharomyces cerevisiae and human vascular endothelial cells. These biological experimental data are indicative of the promising application potential of these complexes in biology and pharmacology.

  17. 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.

  18. Interactive effects of MnO2, organic matter and pH on abiotic formation of N2O from hydroxylamine in artificial soil mixtures.

    PubMed

    Liu, Shurong; Berns, Anne E; Vereecken, Harry; Wu, Di; Brüggemann, Nicolas

    2017-02-01

    Abiotic conversion of the reactive nitrification intermediate hydroxylamine (NH2OH) to nitrous oxide (N2O) is a possible mechanism of N2O formation during nitrification. Previous research has demonstrated that manganese dioxide (MnO2) and organic matter (OM) content of soil as well as soil pH are important control variables of N2O formation in the soil. But until now, their combined effect on abiotic N2O formation from NH2OH has not been quantified. Here, we present results from a full-factorial experiment with artificial soil mixtures at five different levels of pH, MnO2 and OM, respectively, and quantified the interactive effects of the three variables on the NH2OH-to-N2O conversion ratio (RNH2OH-to-N2O). Furthermore, the effect of OM quality on RNH2OH-to-N2O was determined by the addition of four different organic materials with different C/N ratios to the artificial soil mixtures. The experiments revealed a strong interactive effect of soil pH, MnO2 and OM on RNH2OH-to-N2O. In general, increasing MnO2 and decreasing pH increased RNH2OH-to-N2O, while increasing OM content was associated with a decrease in RNH2OH-to-N2O. Organic matter quality also affected RNH2OH-to-N2O. However, this effect was not a function of C/N ratio, but was rather related to differences in the dominating functional groups between the different organic materials.

  19. Interactive effects of MnO2, organic matter and pH on abiotic formation of N2O from hydroxylamine in artificial soil mixtures

    NASA Astrophysics Data System (ADS)

    Liu, Shurong; Berns, Anne E.; Vereecken, Harry; Wu, Di; Brüggemann, Nicolas

    2017-02-01

    Abiotic conversion of the reactive nitrification intermediate hydroxylamine (NH2OH) to nitrous oxide (N2O) is a possible mechanism of N2O formation during nitrification. Previous research has demonstrated that manganese dioxide (MnO2) and organic matter (OM) content of soil as well as soil pH are important control variables of N2O formation in the soil. But until now, their combined effect on abiotic N2O formation from NH2OH has not been quantified. Here, we present results from a full-factorial experiment with artificial soil mixtures at five different levels of pH, MnO2 and OM, respectively, and quantified the interactive effects of the three variables on the NH2OH-to-N2O conversion ratio (RNH2OH-to-N2O). Furthermore, the effect of OM quality on RNH2OH-to-N2O was determined by the addition of four different organic materials with different C/N ratios to the artificial soil mixtures. The experiments revealed a strong interactive effect of soil pH, MnO2 and OM on RNH2OH-to-N2O. In general, increasing MnO2 and decreasing pH increased RNH2OH-to-N2O, while increasing OM content was associated with a decrease in RNH2OH-to-N2O. Organic matter quality also affected RNH2OH-to-N2O. However, this effect was not a function of C/N ratio, but was rather related to differences in the dominating functional groups between the different organic materials.

  20. Interactive effects of MnO2, organic matter and pH on abiotic formation of N2O from hydroxylamine in artificial soil mixtures

    PubMed Central

    Liu, Shurong; Berns, Anne E.; Vereecken, Harry; Wu, Di; Brüggemann, Nicolas

    2017-01-01

    Abiotic conversion of the reactive nitrification intermediate hydroxylamine (NH2OH) to nitrous oxide (N2O) is a possible mechanism of N2O formation during nitrification. Previous research has demonstrated that manganese dioxide (MnO2) and organic matter (OM) content of soil as well as soil pH are important control variables of N2O formation in the soil. But until now, their combined effect on abiotic N2O formation from NH2OH has not been quantified. Here, we present results from a full-factorial experiment with artificial soil mixtures at five different levels of pH, MnO2 and OM, respectively, and quantified the interactive effects of the three variables on the NH2OH-to-N2O conversion ratio (RNH2OH-to-N2O). Furthermore, the effect of OM quality on RNH2OH-to-N2O was determined by the addition of four different organic materials with different C/N ratios to the artificial soil mixtures. The experiments revealed a strong interactive effect of soil pH, MnO2 and OM on RNH2OH-to-N2O. In general, increasing MnO2 and decreasing pH increased RNH2OH-to-N2O, while increasing OM content was associated with a decrease in RNH2OH-to-N2O. Organic matter quality also affected RNH2OH-to-N2O. However, this effect was not a function of C/N ratio, but was rather related to differences in the dominating functional groups between the different organic materials. PMID:28145407

  1. 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.

  2. 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.

  3. First-principles calculation on electronic structure and optical property of BaSi2O2N2:Eu2+ phosphor

    NASA Astrophysics Data System (ADS)

    Tong, Zhi-Fang; Wei, Zhan-Long; Xiao, Cheng

    2017-04-01

    The crystal structure, electronic structure and optical properties of BaSi2O2N2:Eu2+ with varying Eu doping concentrations are computed by the density functional theory (DFT) and compared with experimental results. The results show that the lattice parameters of primitive cells of Ba1-xSi2O2N2:Eux become smaller and Eu-N bond length shortens as Eu concentration increases. The band structure of Ba1-xSi2O2N2:Eux exhibits a direct optical band gap and it's propitious to luminescence. The energy differences from the lowest Eu 5d state to the lowest Eu 4f state decrease with increasing Eu concentrations. The analysis of simulative absorption spectra indicates that the electron transition from Eu 4f states to 5d states of both Eu and Ba atoms contributes to the absorption of Ba1-xSi2O2N2:Eux. Under the coupling effect between Eu and Ba, Ba in BaSi2O2N2 exhibits longer wavelength absorption and increases absorption efficiency. The emission wavelength is deduced by measuring energy differences from the lowest Eu 5d state to the lowest Eu 4f state, and the result is in good agreement with experimental value within experimental Eu2+ doping range.

  4. Comparative study of CO 2 formation in CO oxidation by O 2, NO and N 2O on Pd(1 1 0) surface using infrared chemiluminescence

    NASA Astrophysics Data System (ADS)

    Nakao, Kenji; Ito, Shin-ichi; Tomishige, Keiichi; Kunimori, Kimio

    2006-09-01

    The infrared (IR) chemiluminescence spectra of CO 2 were measured during steady-state CO oxidation by O 2, NO and N 2O over Pd(1 1 0) surface. Kinetics of these reactions were studied using a molecular-beam reaction system, and the order of the activity was as follows: CO + O 2 > CO + NO > CO + N 2O. From the analysis of the IR emission spectra, it is found that the antisymmetric vibrational mode of CO 2 was more excited in the case of the CO + O 2 and CO + N 2O reactions, in contrast, the bending vibrational mode was more excited in the case of the CO + NO reaction. These results suggest that the activated complex of CO 2 in the CO + NO reaction has more bent structure than those in the CO + O 2 and CO + N 2O reactions. The reason of this different behavior of the CO + NO reaction is discussed based on higher structure-sensitivity of the CO + NO reaction than the CO + O 2 and CO + N 2O reactions.

  5. Analysis of degenerate four-wave mixing spectra of NO in a CH4/N2/O2 flame

    NASA Astrophysics Data System (ADS)

    Farrow, R. L.; Rakestraw, D. J.

    We report comparisons of degenerate four-wave mixing (DFWM) spectra of NO measured in a CH4/N2/O2 flame to spectral simulations based on a two-level theory for stationary, saturable absorbers by Abrams et al. Temperatures determined from least-squares fits of simulations to experimental spectra in the A2Σ+?X2Π+(0,0) band are compared to temperatures obtained from OH absorption spectroscopy and a radiation-corrected thermocouple. We find that DFWM rotational temperatures derived from Q-branch spectra agree with thermocouple and are independent of pump laser intensity for low to moderate saturation (I Isat). However, the temperatures are systematically low and depend on pump intensity if the analysis neglects saturation effects. We demonstrate a method for obtaining an effective pump saturation intensity for use with the two-level model. This approach for analyzing saturated DFWM line intensities differs from previous work in that the use of the theory of Abrams et al. rather than a transition-dipole-moment power law allows treatment of a much wider range of saturation. Based on the observed signal-to-noise ratio an NO detection sensitivity of 25 ppm is projected, limited by a DFWM background interference specific to hydrocarbon flames.

  6. 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.

  7. 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.

  8. A kinetic study of Mg+ and Mg-containing ions reacting with O3, O2, N2, CO2, N2O and H2O: implications for magnesium ion chemistry in the upper atmosphere.

    PubMed

    Whalley, Charlotte L; Martín, Juan C Gómez; Wright, Timothy G; Plane, John M C

    2011-04-07

    Reactions between Mg(+) and O(3), O(2), N(2), CO(2) and N(2)O were studied using the pulsed laser photo-dissociation at 193 nm of Mg(C(5)H(7)O(2))(2) vapour, followed by time-resolved laser-induced fluorescence of Mg(+) at 279.6 nm (Mg(+)(3(2)P(3/2)-3(2)S(1/2))). The rate coefficient for the reaction Mg(+) + O(3) is at the Langevin capture rate coefficient and independent of temperature, k(190-340 K) = (1.17 ± 0.19) × 10(-9) cm(3) molecule(-1) s(-1) (1σ error). The reaction MgO(+) + O(3) is also fast, k(295 K) = (8.5 ± 1.5) × 10(-10) cm(3) molecule(-1) s(-1), and produces Mg(+) + 2O(2) with a branching ratio of (0.35 ± 0.21), the major channel forming MgO(2)(+) + O(2). Rate data for Mg(+) recombination reactions yielded the following low-pressure limiting rate coefficients: k(Mg(+) + N(2)) = 2.7 × 10(-31) (T/300 K)(-1.88); k(Mg(+) + O(2)) = 4.1 × 10(-31) (T/300 K)(-1.65); k(Mg(+) + CO(2)) = 7.3 × 10(-30) (T/300 K)(-1.59); k(Mg(+) + N(2)O) = 1.9 × 10(-30) (T/300 K)(-2.51) cm(6) molecule(-2) s(-1), with 1σ errors of ±15%. Reactions involving molecular Mg-containing ions were then studied at 295 K by the pulsed laser ablation of a magnesite target in a fast flow tube, with mass spectrometric detection. Rate coefficients for the following ligand-switching reactions were measured: k(Mg(+)·CO(2) + H(2)O → Mg(+)·H(2)O + CO(2)) = (5.1 ± 0.9) × 10(-11); k(MgO(2)(+) + H(2)O → Mg(+)·H(2)O + O(2)) = (1.9 ± 0.6) × 10(-11); k(Mg(+)·N(2) + O(2)→ Mg(+)·O(2) + N(2)) = (3.5 ± 1.5) × 10(-12) cm(3) molecule(-1) s(-1). Low-pressure limiting rate coefficients were obtained for the following recombination reactions in He: k(MgO(2)(+) + O(2)) = 9.0 × 10(-30) (T/300 K)(-3.80); k(Mg(+)·CO(2) + CO(2)) = 2.3 × 10(-29) (T/300 K)(-5.08); k(Mg(+)·H(2)O + H(2)O) = 3.0 × 10(-28) (T/300 K)(-3.96); k(MgO(2)(+) + N(2)) = 4.7 × 10(-30) (T/300 K)(-3.75); k(MgO(2)(+) + CO(2)) = 6.6 × 10(-29) (T/300 K)(-4.18); k(Mg(+)·H(2)O + O(2)) = 1.2 × 10(-27) (T/300 K)(-4.13) cm

  9. 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.

  10. 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.

  11. Catalytic wet air oxidation of phenol over CeO2-TiO2 catalyst in the batch reactor and the packed-bed reactor.

    PubMed

    Yang, Shaoxia; Zhu, Wanpeng; Wang, Jianbing; Chen, Zhengxiong

    2008-05-30

    CeO2-TiO2 catalysts are prepared by coprecipitation method, and the activity and stability in the catalytic wet air oxidation (CWAO) of phenol are investigated in a batch reactor and packed-bed reactor. CeO2-TiO2 mixed oxides show the higher activity than pure CeO2 and TiO2, and CeO2-TiO2 1/1 catalyst displays the highest activity in the CWAO of phenol. In a batch reactor, COD and TOC removals are about 100% and 77% after 120 min in the CWAO of phenol over CeO2-TiO2 1/1 catalyst at reaction temperature of 150 degrees C, the total pressure of 3 MPa, phenol concentration of 1000 mg/L, and catalyst dosage of 4 g/L. In a packed-bed reactor using CeO2-TiO2 1/1 particle catalyst, over 91% COD and 80% TOC removals are obtained at the reaction temperature of 140 degrees C, the air total pressure of 3.5 MPa, the phenol concentration of 1000 mg/L for 100 h continue reaction. Leaching of metal ions of CeO2-TiO2 1/1 particle catalyst is very low during the continuous reaction. CeO2-TiO2 1/1 catalyst exhibits the excellent activity and stability in the CWAO of phenol.

  12. Influence of alternative cations distribution in AgxLi96-x-LSX on dehydration kinetics and its selective adsorption performance for N2 and O2

    NASA Astrophysics Data System (ADS)

    Panezai, Hamida; Sun, Jihong; Jin, Xiaoqi

    2016-12-01

    Adsorption characteristics of pure gases N2 and O2 on various silver exchanged low silica X-type (AgxLi96-x-LSX) zeolites were investigated. The equilibrium adsorption isotherms of N2 and O2 were measured at 273 and 298 K. Textual and structural properties of parent and resultant AgxLi96-x-LSX were characterized by XRD, BET surface area, and SEM techniques. Kinetics of their thermal dehydration were studied by exploiting thermogravimetric and differential data (TG-DTG) obtained at three heating rates (5, 10 and 15 K) using two model-free (Kissinger and Flynn-Wall-Ozawa) and one model fitting (Coats-Redfern) methods. Forty one mechanism functions were used to evaluate kinetic triplet (activation energy, frequency factor, and most probable mechanism/model) for different stages of dehydration. Results revealed that the impact of very small content of silver on the adsorption of N2 is pronounced and attributed to weak chemical bonds formed between N2 and Ag+ clusters due to strong adsorption of N2 at low pressure, whereas O2 adsorption is affected to a negligible extent. In addition, the N2/O2 adsorption selectivity shows unexpected low values for Ag87.08Li7.94Na0.98-LSX with higher Ag+ content (91.00 %), which might be due to low crystalline water content as well as Ag+ clusters located at SIII sites. N2 adsorption strongly depends on temperature as higher adsorption occurs at low temperature 273 K as compared to 298 K.

  13. Accurate high-pressure and high-temperature effective pair potentials for the systems N2-N and O2-O

    NASA Astrophysics Data System (ADS)

    van Thiel, M.; Ree, F. H.

    1996-04-01

    Statistical mechanical chemical equilibrium calculations of N2 and O2 show that these molecules dissociate behind strong shock waves. Our determination of accurate intermolecular potentials has required the consideration of the dissociation products N and O. Our previous theoretical efforts to predict the thermodynamic properties of these molecules relied in part on corresponding states theory and shock wave data of argon, without consideration of the dissociation products. Recent high-pressure Hugoniot measurements, however, allowed a more accurate determination of the potentials and the explicit inclusion of the dissociation products. The best fit to the data is obtained with the exponential-6 coefficients, for O2-O2: ɛ/k=125 K, r*=3.86 Å, α=13.2; for O-O: ɛ/k=700 K, r*=2.40 Å, α=11.0; for N2-N2: ɛ/k=293 K, r*=3.91 Å, α=11.5; and for N-N: ɛ/k=600 K, r*=2.47 Å, α=10.0. The unlike pair interactions are obtained from these like interactions with a modified Lorentz-Berthelot rule. The coefficients in the modified Lorentz-Berthelot equations are k/l/m=1/1/0.93 for O2-O- and k/l/m=1/1/0.90 for N2-N interactions.

  14. 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.

  15. 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...

  16. 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.

  17. 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.

  18. Photocatalytic decomposition of N2O over TiO2/g-C3N4 photocatalysts heterojunction

    NASA Astrophysics Data System (ADS)

    Kočí, K.; Reli, M.; Troppová, I.; Šihor, M.; Kupková, J.; Kustrowski, P.; Praus, P.

    2017-02-01

    TiO2/g-C3N4 photocatalysts with the various TiO2/g-C3N4 weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO2 was prepared by thermal hydrolysis and pure g-C3N4 was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO2 and g-C3N4 were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO2/g-C3N4 nanocomposites showed moderate improvement compared to pure g-C3N4 but pure TiO2 proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO2/g-C3N4 (1:2) nanocomposite exhibited an increase compared to pure TiO2. Nevertheless, further increase of g-C3N4 amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO2 and g-C3N4 have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C3N4. This is probably due to the generation of heterojunction on the TiO2/g-C3N4 interface.

  19. [Catalytic wet air oxidation of phenol with Ru/ZrO2-CeO2 catalyst].

    PubMed

    Wang, Jian-bing; Zhu, Wan-peng; Wang, Wei; Yang, Shao-xia

    2007-07-01

    Wet air oxidation of phenol with Ru/ZrO2-CeO2 was systematically investigated and results showed that Ru/ZrO2-CeO2 could significantly increase the removal of COD and phenol. At the reaction temperature of 170 degrees C and pressure of 3MPa, about 99% COD and 100% phenol was removed respectively after 120 min. The optimal conditions were: reaction temperature, 170 degrees C; reaction pressure, 3 MPa; catalyst dosage, 5 g/L; agitator speed, 500 r/min. By analyzing intermediates, a simplified scheme of phenol oxidation was brought out. It includes two main steps. The first step is the production of organic acids, which is fast. The second step is the oxidation of organic acid, in which the oxidation of acetic acid is slow. Complete oxidation of acetic acid needs high temperature at which the radicals assault the C-H bond of a carbon and acetic acid is oxidized into carbon dioxide and water through formic acid.

  20. 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

  1. 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.

  2. 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.

  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. Morphological modification of alpha-MnO2 catalyst for use in Li/air batteries.

    PubMed

    Park, Min-Sik; Kim, Jae-Hun; Kim, Ki Jae; Jeong, Goojin; Kim, Young-Jun

    2013-05-01

    Single crystal alpha-MnO2 nanowires and nanopowders have been successfully synthesized in order to facilitate a comparison of their catalytic activity for use in Li-air batteries. The importance of the morphological modification of the alpha-MnO2 catalyst for facilitating electrochemical reactions between Li and O2 is addressed. Distinctive catalytic activity of alpha-MnO2 is observed, which is in line with its different morphologies. The catalytic activity significantly affects the reversible capacity of Li-air batteries. A high aspect ratio, large surface area and good dispersibility of alpha-MnO2 in the nanowire form are advantageous providing larger active surfaces for promoting the fundamental reactions in Li-air batteries. We also introduce a robustly designed air-electrode composed of highly porous carbon and nanostructured alpha-MnO2 catalysts, with employs a metal foam current collector to ensure sufficient air-permeability and to maximize electronic conduction during cycles. Our suggestions should prove helpful in forming a basis for further investigations in developing advanced Li-air batteries.

  5. Theoretical study of CO and O2 adsorption and CO oxidation on linear-shape gold molecules (LGMn) (n=2, 4, 8, 16, and 24)

    NASA Astrophysics Data System (ADS)

    Ohkawa, Tetsuya; Kuramoto, Kei

    2016-09-01

    Density functional theory is used to study the effect of increase of the number of Au atom in the adsorption of CO and O2 as well as CO oxidation on anionic, neutral, and cationic Linear-shape Gold Molecules (LGMn) (n=2, 4, 8, 16, and 24). The more the number of Au atom increases, the more the adsorption energies of CO lower and larger in the cationic and anionic LGMnCO complexes, respectively. In contrast, the adsorption energies of both CO and O2 on neutral LGMn exhibit approximately constant values. There are little differences of both adsorption energies and net charge of CO and O2 on the number of Au atom in LGM regardless of each charge state. This indicates that the charge state of LGM plays a less important role for the adsorption of CO and O2 with increase of the number of Au atom in LGM. The trend of the overall activation energies of reaction pathway is switched between LGM-14 and LGM-18 with increase of the number of Au atom in LGM, and OC-OO intermediate of the initial state in n-1LGM (n=8, 16, and 24) are unstable compared to the separated reactants (LGMn, CO, O2). These are caused by the values of charge of O2 of OC-OO intermediate.

  6. The Dependence of Quenching Rate Coefficients for Singlet and Triplet States of n2 and o2 on Vibrational and Translational Temperatures

    NASA Astrophysics Data System (ADS)

    Kirillov, Andrey

    We apply Landau-Zener and Rosen-Zener approximations to obtain analytical formulas for the calculation of quenching rate coefficients of electronically excited states of N2 and O2. This method has allowed us to estimate contributions of intramolecular and intermolecular electron energy transfer processes in the quenching. Using a modified Treanor distribution on vibrational levels for in ground state molecules we have investigated an influence of the vibrational excitation on the rate coefficients. Special attention is paid to energy transfer processes related with the afterglow in laboratory discharges. It is found that there is the influence of vibrational temperature on the coefficients. A dependence of the rate coefficients on translational temperature is studied for few states of N2 and O2. It is shown that for some states there is good agreement of results of theoretical calculations with available experimental data.

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

    PubMed

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

    2013-12-01

    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. 1×10(9) 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.

  8. Tuning the afterglow plasma composition in Ar/N2/O2 mixtures: characteristics of a flowing surface-wave microwave discharge system

    NASA Astrophysics Data System (ADS)

    Kutasi, Kinga; Noël, Cédric; Belmonte, Thierry; Guerra, Vasco

    2016-10-01

    A self-consistent kinetic model is used to study the possibility of tuning the plasma composition in the afterglow of a flowing surface-wave microwave discharge by the different discharge and system parameters in the case of 90%Ar-10%(N2-O2) and N2-O2 mixtures. The afterglow system consists of a 0.5 cm diameter quartz tube of 50 cm in length—where the discharge is generated and the early-afterglow develops—and an afterglow reactor. The plasma composition is studied at the end of the discharge plasma column and at the reactor inlet as a function of the N2:O2 ratio for selected conditions, which are set with the system parameters and are illustrated in the experimental set-up. The validity of the model used is proven by the agreement of the calculated atomic densities with those measured by mass spectrometry. Due to the pressure drop along the tube, the position of the discharge (which also defines the lengths of the early-afterglow, t aft) and the discharge pressure (p dis) can be set with the position of the wave coupler—surfatron—along the tube at a constant gas flow rate (which defines the pressure in the reactor, p reac). It is shown that the relative densities of species at the end of plasma column, which constitute the initial condition for the afterglow, depend on the discharge pressure. Therefore, at a constant gas flow rate with the position of the surfatron the plasma composition in the reactor is changing due to the variation of both the p dis and t aft. The evolution of the plasma composition is also studied when both the surfatron’s position and the gas flow rate are changed, realizing conditions (i) with the same p dis, and different t aft and p reac, and (ii) with the same t aft, and different p dis and p reac. Comparing the N2-O2 binary and the ternary mixtures, it is shown that the atomic densities obtained in the binary mixtures can be reproduced in ternary mixtures with different N2:O2 ratios. Furthermore, according to the spectra

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Prevalence of Bimolecular Routes in the Activation of Diatomic Molecules with Strong Chemical Bonds (O2, NO, CO, N2) on Catalytic Surfaces.

    PubMed

    Hibbitts, David; Iglesia, Enrique

    2015-05-19

    Dissociation of the strong bonds in O2, NO, CO, and N2 often involves large activation barriers on low-index planes of metal particles used as catalysts. These kinetic hurdles reflect the noble nature of some metals (O2 activation on Au), the high coverages of co-reactants (O2 activation during CO oxidation on Pt), or the strength of the chemical bonds (NO on Pt, CO and N2 on Ru). High barriers for direct dissociations from density functional theory (DFT) have led to a consensus that "defects", consisting of low-coordination exposed atoms, are required to cleave such bonds, as calculated by theory and experiments for model surfaces at low coverages. Such sites, however, bind intermediates strongly, rendering them unreactive at the high coverages prevalent during catalysis. Such site requirements are also at odds with turnover rates that often depend weakly on cluster size or are actually higher on larger clusters, even though defects, such as corners and edges, are most abundant on small clusters. This Account illustrates how these apparent inconsistencies are resolved through activations of strong bonds assisted by co-adsorbates on crowded low-index surfaces. Catalytic oxidations occur on Au clusters at low temperatures in spite of large activation barriers for O2 dissociation on Au(111) surfaces, leading to proposals that O2 activation requires low-coordination Au atoms or Au-support interfaces. When H2O is present, however, O2 dissociation proceeds with low barriers on Au(111) because chemisorbed peroxides (*OOH* and *HOOH*) form and weaken O-O bonds before cleavage, thus allowing activation on low-index planes. DFT-derived O2 dissociation barriers are much lower on bare Pt surfaces, but such surfaces are nearly saturated with CO* during CO oxidation. A dearth of vacant sites causes O2* to react with CO* to form *OOCO* intermediates that undergo O-O cleavage. NO-H2 reactions occur on Pt clusters saturated with NO* and H*; direct NO* dissociation requires vacant

  14. Tree Growth-Hybrid Genetic Algorithm for Predicting the Structure of Small (TiO2)n, n = 2-13, Nanoclusters.

    PubMed

    Chen, Mingyang; Dixon, David A

    2013-07-09

    The initial structures for the search for the global minimum of TiO2 nanoclusters were generated by combining a tree growth (TG) algorithm with a hybrid genetic algorithm (HGA). In the TG algorithm, the clusters grow from a small seed to the size of interest stepwise. New atoms are added to the smaller cluster from the previous step, by analogy to new leaves grown by a tree. The addition of the new atoms is controlled by predefined geometry parameters to reduce the computational cost and to provide physically meaningful structures. In each step, the energies for the various generated structures are evaluated, and those with the lowest energies are carried into the next step. The structures that match the formulas of interest are collected as HGA candidates during the various steps. Low energy candidates are fed to the HGA component to search for the global minimum for each formula of interest. The lowest energy structures from the HGA are then optimized by using density functional theory to study the dissociation energies of the clusters and the evolution in the structure as the size of the cluster increases. The optimized geometries of the (TiO2)n nanoclusters for n = 2-13, do not show the character of a TiO2 bulk crystal with a hexacoordinate Ti. The average clustering energy ⟨ΔEn⟩ converges slowly to the bulk value for rutile. The TiO2 dissociation energies for (TiO2)n clusters approach the bulk value for rutile more quickly but show larger variations. The (TiO2)12 cluster appears to be quite stable, and the (TiO2)13 cluster is quite unstable on a relative scale.

  15. Characterization of nanocrystalline nitrogen-containing titanium oxide obtained by N2/O2/Ar low-field helicon plasma sputtering

    NASA Astrophysics Data System (ADS)

    Sarra-Bournet, C.; Haberl, B.; Charles, C.; Boswell, R.

    2011-11-01

    TiO2 and nitrogen-containing TiO2 thin films were deposited on glass and silicon wafer substrates using a helicon-assisted reactive plasma sputtering process in a gas mixture of Ar/O2/N2. The growth mechanism, chemical composition and crystalline structure were probed by x-ray photoelectron spectroscopy, x-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy. The presence of nitrogen in the film induces the formation of some Ti3+ defects states, which introduces oxygen vacancies in the TiOxNy structure. It is also observed that nitrogen substitution selectively hinders the formation of the crystalline rutile phase and promotes the growth of a polycrystalline anatase phase film. Moreover, the film exhibits a red-shift in light absorption from UV to visible spectrum as a function of the nitrogen doping. This work shows that crystalline TiO2 thin films can be obtained with a low temperature process and also shows that using nitrogen can control the desired crystalline structure.

  16. The α and γ plasma modes in plasma-enhanced atomic layer deposition with O2N2 capacitive discharges

    NASA Astrophysics Data System (ADS)

    Napari, M.; Tarvainen, O.; Kinnunen, S.; Arstila, K.; Julin, J.; Fjellvåg, Ø. S.; Weibye, K.; Nilsen, O.; Sajavaara, T.

    2017-03-01

    Two distinguishable plasma modes in the O2N2 radio frequency capacitively coupled plasma (CCP) used in remote plasma-enhanced atomic layer deposition (PEALD) were observed. Optical emission spectroscopy and spectra interpretation with rate coefficient analysis of the relevant processes were used to connect the detected modes to the α and γ modes of the CCP discharge. To investigate the effect of the plasma modes on the PEALD film growth, ZnO and TiO2 films were deposited using both modes and compared to the films deposited using direct plasma. The growth rate, thickness uniformity, elemental composition, and crystallinity of the films were found to correlate with the deposition mode. In remote CCP operations the transition to the γ mode can result in a parasitic discharge leading to uncontrollable film growth and thus limit the operation parameters of the capacitive discharge in the PEALD applications.

  17. Ab initio molecular dynamics determination of competitive O2 vs. N2 adsorption at open metal sites of M2 (dobdc)

    DOE PAGES

    Parkes, Marie V.; Greathouse, Jeffery A.; Hart, David B.; ...

    2016-04-04

    The separation of oxygen from nitrogen using metal–organic frameworks (MOFs) is of great interest for potential pressure-swing adsorption processes for the generation of purified O2 on industrial scales. This study uses ab initio molecular dynamics (AIMD) simulations to examine for the first time the pure-gas and competitive gas adsorption of O2 and N2 in the M2(dobdc) (M = Cr, Mn, Fe) MOF series with coordinatively unsaturated metal centers. Effects of metal, temperature, and gas composition are explored. Lastly, this unique application of AIMD allows us to study in detail the adsorption/desorption processes and to visualize the process of multiple guestsmore » competitively binding to coordinatively unsaturated metal sites of a MOF.« less

  18. Parity-dependent rotational energy transfer in CN(A(2)Π, ν = 4, j F(1)ε) + N2, O2, and CO2 collisions.

    PubMed

    McGurk, Stephen J; Halpern, Joshua B; McKendrick, Kenneth G; Costen, Matthew L

    2014-03-20

    We report state-resolved total removal cross sections and state-to-state rotational energy transfer (RET) cross sections for collisions of CN(A(2)Π, ν = 4, j F1ε) with N2, O2, and CO2. CN(X(2)Σ(+)) 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(A(2)Π, 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. A 2009 , 113 , 3922 ). Our results with CO2 as a collider are similarly in strong

  19. 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

  20. 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

    2011-08-04

    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.

  1. Study of OH radical generation in atmospheric pressure microwave plasma jets of Ar, N2 and O2 gases using pulsed cavity ringdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Chuji; Srivastava, Nimisha

    2009-11-01

    We employ UV-pulsed laser cavity ringdown spectroscopy, optical emission spectroscopy and visual imaging, to characterize OH radical generation in atmospheric pressure microwave plasma jets created, respectively, by argon, mixture of Ar and N2, mixture of Ar and O2, and mixture of Ar, N2 and O2. OH radicals were observed in far downstream for all of these plasma jets (Far downstream is referred to as the location where ratio of the distance from the jet orifice to the length of the jet column is > 3).We also investigated the effect of variations in humidity on OH generation in the APJs. Absolute number densities were measured for OH (v'' = 0, J''= 3.5) along the plasma column axis. Effects on OH radical concentrations along the plasma column axis with variations of plasma powers, gas flow rates with different mixing ratios and humidity levels were also studied. The rotational Trot, vibrational Tvib and electronic excitation temperature Telex were provided by simulations of emission spectra of the plasmas.

  2. Studies via Near-Infrared Cavity Ringdown Spectroscopy and Electronic Structure Calculations of the Products of the Photolysis of Dihalomethane/N2/O2 Mixtures.

    PubMed

    Huang, Meng; Kline, Neal; Miller, Terry A; Dawes, Richard

    2017-01-12

    Near-infrared cavity ringdown spectra were recorded following the photolysis of dihalomethanes in O2/N2 mixtures. In particular, photolysis of CH2I2 under conditions previously reported to produce the simplest Criegee intermediate, CH2O2, gave a complex, structured spectrum between 6800 and 9000 cm(-1), where the lowest triplet-singlet transition (ã-X̃) of CH2O2 might be expected. To help identify the carrier of the spectrum, extensive electronic structure calculations were performed on the ã and X̃ states of CH2O2 and the lowest two doublet states of the iodomethylperoxy radical, CH2IO2, which also could be produced by the chemistry and whose Ã-X̃ transition likely lies in this spectral region. The conclusion of these calculations is that the ã-X̃ transition of CH2O2 clearly falls outside the observed spectral range and would be extremely weak both because it is spin-forbidden and because of a large geometric change between the ã and X̃ states. Moreover, only a shallow well (with a barrier to dissociation of less than 1900 cm(-1)) is predicted on the ã state, which likely precludes the existence of long-lived states. Calculations for the Ã-X̃ transition of CH2IO2 are generally consistent with the observed spectrum in terms of both the electronic origin and vibrational frequencies in the à state. To confirm the carrier assignment to CH2IO2, calculations beyond the Franck-Condon approximation were carried out to explain the hot band structure of the large-amplitude, low-frequency O-O-C-I torsion mode, ν12. Photolysis of other dihalomethanes produced similar spectra which were analyzed and assigned to CH2ClO2 and CH2BrO2. Experimental values for the electronic energies and frequencies for several à state vibrations and the ν12 vibration of the X̃ state of each are reported. In addition, the observed spectra were used to follow the self-reaction of the CH2IO2 species and its reaction with SO2. The rates of these reactions are dramatically faster than

  3. Nickel(II) in chelate N2O2 environment. DFT approach and in-depth molecular orbital and configurational analysis.

    PubMed

    Trifunović, Srećko R; Miletić, Vesna D; Jevtić, Verica V; Meetsma, Auke; Matović, Zoran D

    2013-10-07

    The O-N-N-O-type tetradentate ligands H2S,S-eddp (H2S,S-eddp stands for S,S-ethylenediamine-N,N'-di-2-propionic acid) and H2edap (H2edap stands for ethylenediamine-N-acetic-N'-3-propionic acid) and the corresponding novel octahedral nickel(II) complexes have been prepared and characterized. N2O2 ligands coordinate to the nickel(II) ion via four donor atoms (two deprotonated carboxylate atoms and two amine nitrogens) affording octahedral geometry in the case of all investigated Ni(II) complexes. A six coordinate, octahedral geometry has been verified crystallographically for the s-cis-[Ni(S,S-eddp)(H2O)2] complex. Structural data correlating similarly chelated Ni(II) complexes have been used to carry out an extensive configuration analysis. Molecular mechanics and Density Functional Theory (DFT) have been used to model the most stable geometric isomer, yielding, at the same time, significant structural and spectroscopic (TDDFT) data. The results from density functional studies have been compared to X-ray data. Natural Bond Orbital (NBO) and Natural Energetic Decomposition Analysis (NEDA) have been done for the [Ni(edda-type)(H2O)(2-n)] and nH2O fragments. Molecular orbital analysis (MPA) is given as well. The infra-red and electronic absorption spectra of the complexes are discussed in comparison to the related complexes of known geometries.

  4. Oxidation of atomic gold ions: thermochemistry for the activation of O(2) and N(2)O BY Au(+) ((1)S(0) and (3)D).

    PubMed

    Li, Feng-Xia; Gorham, Katrine; Armentrout, P B

    2010-10-28

    Reaction of Au(+) ((1)S(0) and (3)D) with O(2) and N(2)O is studied as a function of kinetic energy using guided ion beam tandem mass spectrometry. A flow tube ion source produces Au(+) primarily in its (1)S(0) (5d(10)) electronic ground state level but with some (3)D and perhaps higher lying excited states. The distribution of states can be altered by adding N(2)O, which completely quenches the excited states, or CH(4) to the flow gases. Cross sections as a function of kinetic energy are measured for both neutral reagents and both ground and excited states of Au(+). Formation of AuO(+) is common to both systems with the N(2)O system also exhibiting AuN(2)(+) and AuNO(+) formation. All reactions of Au(+) ((1)S(0)) are observed to be endothermic, whereas the excitation energy available to the (3)D state allows some reactions to be exothermic. Because of the closed shell character of ground state Au(+) ((1)S(0), 5d(10)), the reactivity of these systems is low and has cross sections with onsets and peaks at higher energies than expected from the known thermochemistry but lower than energies expected from impulsive processes. Analyses of the endothermic reaction cross sections yield the 0 K bond dissociation energy (BDE) in eV of D(0)(Au(+)-O) = 1.12 ± 0.08, D(0)(Au(+)-N(2)) ≥ 0.30 ± 0.04, and D(0)(Au(+)-NO) = 0.89 ± 0.17, values that are all speculative because of the unusual experimental behavior. Combining the AuO(+) BDE measured here with literature data also yields the ionization energy of AuO as 10.38 ± 0.23 eV. Quantum chemical calculations show reasonable agreement with the experimental bond energies and provide the electronic structures of these species.

  5. Stabilizing MoS2 Nanosheets through SnO2 Nanocrystal Decoration for High-Performance Gas Sensing in Air.

    PubMed

    Cui, Shumao; Wen, Zhenhai; Huang, Xingkang; Chang, Jingbo; Chen, Junhong

    2015-05-20

    The unique properties of MoS(2) nanosheets make them a promising candidate for high-performance room temperature sensing. However, the properties of pristine MoS(2) nanosheets are strongly influenced by the significant adsorption of oxygen in an air environment, which leads to instability of the MoS(2) sensing device, and all sensing results on MoS(2) reported to date were exclusively obtained in an inert atmosphere. This significantly limits the practical sensor application of MoS(2) in an air environment. Herein, a novel nanohybrid of SnO(2) nanocrystal (NC)-decorated crumpled MoS(2) nanosheet (MoS(2)/SnO(2)) and its exciting air-stable property for room temperature sensing of NO(2) are reported. Interestingly, the SnO(2) NCs serve as strong p-type dopants for MoS(2), leading to p-type channels in the MoS(2) nanosheets. The SnO(2) NCs also significantly enhance the stability of MoS(2) nanosheets in dry air. As a result, unlike other MoS(2) sensors operated in an inert gas (e.g. N(2)), the nanohybrids exhibit high sensitivity, excellent selectivity, and repeatability to NO(2) under a practical dry air environment. This work suggests that NC decoration significantly tunes the properties of MoS(2) nanosheets for various applications.

  6. 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

  7. Impact of Mixture Gas Plasma of N2 and O2 as the N Source on ZnO-Based Ultraviolet Light-Emitting Diodes Fabricated by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Kato, Hiroyuki; Yamamuro, Tomofumi; Ogawa, Akio; Kyotani, Chizu; Sano, Michihiro

    2011-09-01

    ZnO-based double-heterostructure ultraviolet light-emitting diodes (LEDs) were fabricated on n-type Zn-polar ZnO substrates by plasma-assisted molecular beam epitaxy employing mixture gas plasma of N2 and O2 as the N source. By using mixture gas plasma of N2 with a little added O2, the number of N atoms increased and N2 molecules decreased, as confirmed by optical emission spectrometry. The fabricated LEDs had an ultraviolet near-band-emission of around 380 nm. The integrated electroluminescence intensity of the LED fabricated using N2 and O2 plasma was more than 10 times higher than that of an LED fabricated using N2 plasma.

  8. FAST TRACK COMMUNICATION: On the application of inductively coupled plasma discharges sustained in Ar/O2/N2 ternary mixture for sterilization and decontamination of medical instruments

    NASA Astrophysics Data System (ADS)

    Stapelmann, K.; Kylián, O.; Denis, B.; Rossi, F.

    2008-10-01

    Non-equilibrium low pressure-plasma discharges are extensively studied for their high potential in the field of sterilization and decontamination of medical devices. This increased interest in plasma discharges arises from, among other reasons, their capability not only to inactivate bacterial spores but also to eliminate, destroy or remove pathogenic biomolecules and thus to provide a one-step process assuring safety of treated instruments. However, recent studies have shown that optimal conditions leading to inactivation of spores and physical removal of pathogens differ significantly—the efficiency of spores sterilization is above all dependent on the UV radiation intensity, whereas high etching rates are connected with the presence of the etching agent, typically atomic oxygen. The aim of this contribution is to discuss and demonstrate the feasibility of Ar/N2/O2 low-pressure inductively coupled plasma discharges as an option to provide intense UV radiation while maintaining the high etching rates of biomolecules.

  9. Pressure broadening and collisional narrowing in OH(v=1 <-- 0) rovibrational transitions with Ar, He, O2, and N2

    NASA Astrophysics Data System (ADS)

    Schiffman, A.; Nesbitt, David J.

    1994-02-01

    Line shapes are measured for OH(v=1←0) transitions in the presence of Ar, He, O2, and N2 as a function of N rotational, spin-orbit, and λ doublet states. Pressure broadening coefficients for all transitions and buffer gases are determined from fits of the observed line shapes to the Voigt profile. The dependencies of the observed broadening coefficients on the OH quantum levels are discussed and compared with previous pressure broadening studies in HF and NO. The observed OH line shapes are interpreted in terms of their impact on the determination of mesospheric and stratospheric OH populations, temperatures, and quantum state distributions from OH nightglow and dayglow emission. In the case of OH+Ar, evidence for Dicke narrowing is presented and narrowing coefficients are reported from fits to a ``hard collision'' model.

  10. Mass spectrometry of diffuse coplanar surface barrier discharge: influence of discharge frequency and oxygen content in N2/O2 mixture*

    NASA Astrophysics Data System (ADS)

    Čech, Jan; Brablec, Antonín; Černák, Mirko; Puač, Nevena; Selaković, Nenad; Petrović, Zoran Lj.

    2017-02-01

    Diffuse Coplanar Surface Barrier Discharge (DCSBD) has been studied extensively for industrial applications in recent decade. So far, limited information was available on the production of ozone or nitrogen oxides important for industrial deployment of DCSBD. In this paper results of mass spectrometry of DCSBD performed at atmospheric pressure are presented. DCSBD mass spectra were studied for different oxygen contents in N2/O2 working gas mixture at low flow rate (estimated residence time in discharge chamber was approx. 3 s). Influence of the driving frequency (15, 30 and 50 kHz) at constant high voltage amplitude was studied as well. Ozone and NO production in DCSBD are given as typical representatives. Production of ozone decreases with the driving frequency, which could be attributed to the gas heating at higher frequencies.

  11. 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.

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

    SciTech Connect

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

    2016-03-03

    The desorption kinetics for Ar, Kr, Xe, N2, O2, CO, methane, ethane, and propane from grapheme 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 multi- layer 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 non-alignment 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.

  13. 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.

  14. Relaxation of H2O from its |04>- vibrational state in collisions with H2O, Ar, H2, N2, and O2

    NASA Astrophysics Data System (ADS)

    Barnes, Peter W.; Sims, Ian R.; Smith, Ian W. M.

    2004-03-01

    We report rate coefficients at 293 K for the collisional relaxation of H2O molecules from the highly excited |04>± vibrational states in collisions with H2O, Ar, H2, N2, and O2. In our experiments, the |04>- state is populated by direct absorption of radiation from a pulsed dye laser tuned to ˜719 nm. Evolution of the population in the (|04>±) levels is observed using the combination of a frequency-quadrupled Nd:YAG laser, which selectively photolyses H2O(|04>±), and a frequency-doubled dye laser, which observes the OH(v=0) produced by photodissociation via laser-induced fluorescence. 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 of H2O(|04>±) obtained from these experiments, in units of cm3 molecule-1 s-1, are: k(H2O)=(4.1±1.2)×10-10, k(Ar)=(4.9±1.1)×10-12, k(H2)=(6.8±1.1)×10-12, k(N2)=(7.7±1.5)×10-12, k(O2)=(6.7±1.4)×10-12. The implications of these results for our previous reports of rate constants for the removal of H2O molecules in selected vibrational states by collisions with H atoms (P. W. Barnes et al., Faraday Discuss. Chem. Soc. 113, 167 (1999) and P. W. Barnes et al., J. Chem. Phys. 115, 4586 (2001).) are fully discussed.

  15. Relaxation of H2O from its /04>- vibrational state in collisions with H2O, Ar, H2, N2, and O2.

    PubMed

    Barnes, Peter W; Sims, Ian R; Smith, Ian W M

    2004-03-22

    We report rate coefficients at 293 K for the collisional relaxation of H2O molecules from the highly excited /04>(+/-) vibrational states in collisions with H2O, Ar, H2, N2, and O2. In our experiments, the mid R:04(-) state is populated by direct absorption of radiation from a pulsed dye laser tuned to approximately 719 nm. Evolution of the population in the (/04>(+/-)) levels is observed using the combination of a frequency-quadrupled Nd:YAG laser, which selectively photolyses H2O(/04>(+/-)), and a frequency-doubled dye laser, which observes the OH(v=0) produced by photodissociation via laser-induced fluorescence. 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 of H2O(/04>(+/-)) obtained from these experiments, in units of cm3 molecule(-1) s(-1), are: k(H2O)=(4.1+/-1.2) x 10(-10), k(Ar)=(4.9+/-1.1) x 10(-12), k(H2)=(6.8+/-1.1) x 10(-12), k(N2)=(7.7+/-1.5) x 10(-12), k(O2)=(6.7+/-1.4) x 10(-12). The implications of these results for our previous reports of rate constants for the removal of H2O molecules in selected vibrational states by collisions with H atoms (P. W. Barnes et al., Faraday Discuss. Chem. Soc. 113, 167 (1999) and P. W. Barnes et al., J. Chem. Phys. 115, 4586 (2001).) are fully discussed.

  16. 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.

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

    PubMed

    Sobha, S; Mahalakshmi, R; Raman, N

    2012-06-15

    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 N(2)O(2) 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 H(2)O(2.) 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.

  18. 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.

  19. Validity of actinometry to monitor oxygen atom concentration in microwave discharges created by surface wave in O2-N2 mixtures

    NASA Astrophysics Data System (ADS)

    Granier, A.; Chéreau, D.; Henda, K.; Safari, R.; Leprince, P.

    1994-01-01

    The validity of actinometry to monitor oxygen atom concentration in O2-N2 microwave discharges created by surface wave is investigated. The plasma is created with a gas flow in a quartz tube of inner diameter 16 mm at pressures in the Torr range. First, it is shown that the reliability of actinometry can be deduced from the longitudinal profile of the actinometry signal. Second, absolute concentrations of oxygen atoms are estimated from the experimental actinometry signal and agree satisfactorily with concentrations simultaneously measured by vacuum ultraviolet (VUV) absorption downstream from the plasma. Moreover, upon varying the nitrogen percentage (0%-100%), it is evidenced that the actinometry signal is proportional to the concentration measured by VUV absorption. Furthermore, it is evidenced that the oxygen dissociation rate is only 2% in pure oxygen plasmas, while it reaches 15% (433 MHz) or 30% (2450 MHz) for mixtures containing more than 20% of nitrogen. This drastic increase in [O] upon the addition of N2 is extensively discussed and, finally, attributed to a decrease in the recombination frequency of oxygen atoms on the quartz wall, in the presence of nitrogen.

  20. Oxonitridosilicate Y10(Si6O22N2)O2:Ce3+,Mn2+ phosphors: a facile synthesis via the soft-chemical ammonolysis process, luminescence, and energy-transfer properties.

    PubMed

    Geng, Dongling; Lian, Hongzhou; Shang, Mengmeng; Zhang, Yang; Lin, Jun

    2014-02-17

    Ce(3+)- and/or Mn(2+)-activated Y10(Si6O22N2)O2 phosphors have been prepared via a soft-chemical ammonolysis method. Structure refinement, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared, and thermogravimetry analysis have been employed to characterize the phase purity, crystal structure, morphology, crystallization condition, chemical composition, and thermal stability of the products. The photoluminescence and cathodoluminescence properties for Ce(3+)- and Mn(2+)-doped Y10(Si6O22N2)O2 phosphors were studied in detail. For Ce(3+)/Mn(2+) singly doped Y10(Si6O22N2)O2 phosphors, typical emissions of Ce(3+) (blue) and Mn(2+) (reddish-orange) ions can be observed. Especially, Ce(3+) emission at different lattice sites 4f and 6h has been identified and discussed. Energy transfer from Ce(3+)(I) and Ce(3+)(II) to Mn(2+) ions in Y10(Si6O22N2)O2:Ce(3+),Mn(2+) samples has been validated and confirmed by the photoluminescence spectra and luminescence decay times. A color-tunable emission in Y10(Si6O22N2)O2:Ce(3+),Mn(2+) phosphors can be achieved by an energy-transfer process and a change in the doping concentration of the activators. The temperature-dependent photoluminescence properties and degradation property of cathodoluminescence under continuous electron bombardment of as-synthesized phosphors prove that the Y10(Si6O22N2)O2 host has good stability. Therefore, the Y10(Si6O22N2)O2:Ce(3+),Mn(2+) phosphors may potentially serve as single-phase blue/reddish-orange phosphors for white-light-emitting diodes and field-emission displays.

  1. 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.

  2. Design strategies for P-containing fuels adaptable CeO2-MoO3 catalysts for DeNO(x): significance of phosphorus resistance and N2 selectivity.

    PubMed

    Chang, Huazhen; Jong, Min Tze; Wang, Chizhong; Qu, Ruiyang; Du, Yu; Li, Junhua; Hao, Jiming

    2013-10-15

    Phosphorus compounds from flue gas have a significant deactivation effect on selective catalytic reduction (SCR) DeNOx catalysts. In this work, the effects of phosphorus over three catalysts (CeO2, CeO2-MoO3, and V2O5-MoO3/TiO2) for NH3-SCR were studied, and characterizations were performed aiming at a better understanding of the behavior and poisoning mechanism of phosphorus over SCR catalysts. The CeO2-MoO3 catalyst showed much better catalytic behavior with respect to resistance to phosphorus and N2 selectivity compared with V2O5-MoO3/TiO2 catalyst. With addition of 1.3 wt % P, the SCR activity of V2O5-MoO3/TiO2 decreased dramatically at low temperature due to the impairment of redox property for NO oxidation; meanwhile, the activity over CeO2 and CeO2-MoO3 catalysts was improved. The superior NO oxidation activity contributes to the activity over P-poisoned CeO2 catalyst. The increased surface area and abundant acidity sites contribute to excellent activity over CeO2-MoO3 catalyst. As the content of P increased to 3.9 wt %, the redox cycle over CeO2 catalyst (2CeO2 ↔ Ce2O3 + O*) was destroyed as phosphate accumulated, leading to the decline of SCR activity; whereas, more than 80% NOx conversion and superior N2 selectivity were obtained over CeO2-MoO3 at T > 300 °C. The effect of phosphorus was correlated with the redox properties of SCR catalyst for NH3 and NO oxidation. A spillover effect that phosphate transfers from Ce to Mo in calcination was proposed.

  3. 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.

  4. Observation of positronium formation with inner orbital electrons for O2, CO2, C2H2, and N2O using PsARS

    NASA Astrophysics Data System (ADS)

    Edwards, J. J.; Kauppila, W. E.; Miller, E. G.; Stein, T. S.; Surdutovich, E.

    2006-05-01

    We are investigating ortho- and para-positronium (Ps) formation for positrons interacting with simple gas molecules in a gas scattering cell using Ps annihilation ratio spectroscopy (PsARS)[1]. These measurements involve the detection of two gamma rays in coincidence for energy windows (a) centered at 511 keV resulting from the decay of short-lived (0.1 ns) para-Ps and the destruction of longer-lived (0.1 μs) ortho-Ps at the scattering cell walls, and (b) from 300 to 460 keV resulting from the three gamma decay of ortho-Ps. By taking the ratios of these signals versus positron impact energy we find we are able to compare the resulting curves with that obtained for argon as a reference. These comparisons reveal departures from the argon curve at well defined energies and are interpreted as Ps formation with inner orbital electrons. The fractions of the overall Ps formation cross-section due to inner orbital electrons are estimated to be as high as 30% for O2, 25% for CO2, 15% for N2O and 5% for C2H2 near their respective threshold energies. [1] W.E. Kauppila, E.G. Miller, H.F.M. Mohamed, K. Pipinos, T.S. Stein, E. Surdutovich, Phys. Rev. Lett. 93, 113401 (2004).

  5. 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.

  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. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Photocatalytic performance of electrospun CNT/TiO2 nanofibers in a simulated air purifier under visible light irradiation.

    PubMed

    Wongaree, Mathana; Chiarakorn, Siriluk; Chuangchote, Surawut; Sagawa, Takashi

    2016-11-01

    The photocatalytic treatment of gaseous benzene under visible light irradiation was developed using electrospun carbon nanotube/titanium dioxide (CNT/TiO2) nanofibers as visible light active photocatalysts. The CNT/TiO2 nanofibers were fabricated by electrospinning CNT/poly(vinyl pyrrolidone) (PVP) solution followed by the removal of PVP by calcination at 450 °C. The molar ratio of CNT/TiO2 was fixed at 0.05:1 by weight, and the quantity of CNT/TiO2 loaded in PVP solution varied between 30 and 60 % wt. CNT/TiO2 nanofibers have high specific surface area (116 m(2)/g), significantly higher than that of TiO2 nanofibers (44 m(2)/g). The photocatalytic performance of the CNT/TiO2 nanofibers was investigated by decolorization of 1 × 10(-5) M methylene blue (MB) dye (in water solution) and degradation of 100 ppm gaseous benzene under visible light irradiation. The 50-CNT/TiO2 nanofibers (calcined CNT/TiO2 nanofibers fabricated from a spinning solution of 50 % wt CNT/TiO2 based on PVP) had higher MB degradation efficiency (58 %) than did other CNT/TiO2 nanofibers and pristine TiO2 nanofibers (15 %) under visible light irradiation. The photocatalytic degradation of gaseous benzene under visible light irradiation on filters made of 50-CNT/TiO2 nanofibers was carried out in a simulated air purifier system. Similar to MB results, the degradation efficiency of gaseous benzene by 50-CNT/TiO2 nanofibers (52 %) was higher than by other CNT/TiO2 nanofibers and pristine TiO2 nanofibers (18 %). The synergistic effects of the larger surface area and lower band gap energy of CNT/TiO2 nanofibers were presented as strong adsorption ability and greater visible light adsorption. The CNT/TiO2 nanofiber prepared in this study has potential for use in air purifiers to improve air treatment efficiency with less energy.

  12. 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.

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

    PubMed

    Sarkar, Saikat; Dey, Kamalendu

    2005-11-01

    A novel interesting hexadentate dibasic N(2)S(2)O(2) donor Schiff base ligand, H(4)dcsalpte, 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, H(4)dcsalpte, 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, (1)H NMR, and Mössbauer) data. Based on magnetic susceptibility, Mössbauer and electronic spectral data the iron(III) complex [Fe(III)(H(2)dcsalpte)]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(III)(3)(H(2)dcsalpte)(H(3)dcsalpte)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 H(4)dcsalpte and Co(CH(3)COO)(2).4H(2)O in ethanol under reflux gave two products, [Co(H(2)dcsalpte)]CH(3)COO (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 CS 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 H(4)dcsalpte.

  14. 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.

  15. Are TiO2 nanotubes worth using in photocatalytic purification of air and water?

    PubMed

    Pichat, Pierre

    2014-09-19

    Titanium dioxide nanotubes (TNT) have mainly been used in dye sensitized solar cells, essentially because of a higher transport rate of electrons from the adsorbed photo-excited dye to the Ti electrode onto which TNT instead of TiO2 nanoparticles (TNP) are attached. The dimension ranges and the two main synthesis methods of TNT are briefly indicated here. Not surprisingly, the particular and regular texture of TNT was also expected to improve the photocatalytic efficacy for pollutant removal in air and water with respect to TNP. In this short review, the validity of this expectation is checked using the regrettably small number of literature comparisons between TNT and commercialized TNP referring to films of similar thickness and layers or slurries containing an equal TiO2 mass. Although the irradiated geometrical area differed for each study, it was identical for each comparison considered here. For the removal of toluene (methylbenzene) or acetaldehyde (ethanal) in air, the average ratio of the efficacy of TNT over that of TiO2 P25 was about 1.5, and for the removal of dyes in water, it was around 1. This lack of major improvement with TNT compared to TNP could partially be due to TNT texture disorders as seems to be suggested by the better average performance of anodic oxidation-prepared TNT. It could also come from the fact that the properties influencing the efficacy are more numerous, their interrelations more complex and their effects more important for pollutant removal than for dye sensitized solar cells and photoelectrocatalysis where the electron transport rate is the crucial parameter.

  16. 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.

  17. Comparative Study of Al2O3 Optical Crystalline Thin Films Grown by Vapor Combinations of Al(CH3)3/N2O and Al(CH3)3/H2O2

    NASA Astrophysics Data System (ADS)

    Kumagai, Hiroshi; Toyoda, Koichi; Matsumoto, Masahiko; Obara, Minoru

    1993-12-01

    We compared the use of nitrous oxide (N2O) and hydrogen peroxide (H2O2) as the oxidant in digital chemical vapor deposition to obtain high-quality optical crystalline thin films of Al2O3. Optical constants and thicknesses of these films were investigated in terms of growth temperature, by using variable-angle spectroscopic ellipsometry.

  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. 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

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

    PubMed

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2014-03-20

    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.

  1. 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

  2. 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.

  3. Carnation-like MnO2 modified activated carbon air cathode improve power generation in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Li, Kexun; Liu, Xianhua

    2014-10-01

    Highly active and low-cost electrocatalysts are of great importance for large-scale commercial applications of microbial fuel cells (MFCs). In this work, we prepared an activated carbon (AC) air cathode containing electrodeposited γ-MnO2 using a potentiostatic method. The results indicated that carnation-like MnO2 crystals were bound to the surface of the AC air cathode after a deposition time of 10 min, which greatly improved the performance of the cathode. BET analysis results demonstrated that the electrodeposition of MnO2 decreased the micropore surface area of the cathode but increased the mesopore surface area. When compared with a bare AC air cathode, the electrodeposited MnO2 cathode exhibited higher catalytic activity for oxygen reduction reaction. The maximum power density of the MFC equipped with the electrodeposited MnO2 AC air cathode was 1554 mW m-2, which is 1.5 times higher than the control cathode.

  4. Highly dispersed platinum nanoparticles on TiO2 prepared by using the microwave-assisted deposition method: an efficient photocatalyst for the formation of H2 and N2 from aqueous NH3.

    PubMed

    Fuku, Kojirou; Kamegawa, Takashi; Mori, Kohsuke; Yamashita, Hiromi

    2012-06-01

    A simple and practical technique to synthesize nanosized platinum particles loaded on TiO(2) (Pt-TiO(2)) by using a microwave (Mw)-assisted deposition method has been exploited in the development of a highly efficient photocatalyst for the formation of H(2) and N(2) gases from harmful nitrogen-containing chemical wastes, for example, aqueous ammonia (NH(3)). Upon Mw irradiation, a platinum precursor can be deposited quickly on the TiO(2) surface from an aqueous solution of platinum and subsequent reduction with H(2) affords the nanosized platinum metal particles with a narrow size distribution (Mw-Pt-TiO(2)). Characterization by CO adsorption, platinum L(III)-edge X-ray absorption fine structure analysis, and TEM analysis revealed that the size of the metal nanoparticles strongly depended on the preparation methods. Smaller platinum nanoparticles were obtained by the Mw heating method than those obtained by conventional preparation techniques, such as photoassisted deposition (PAD), impregnation (Imp), and equilibrium adsorption (EA) deposition by conventional convective heating. The H(2) and N(2) formation rates increased with increasing dispersity of platinum. Pt-TiO(2) prepared by the Mw heating method exhibited a specifically high H(2) formation activity in the photocatalytic decomposition of aqueous NH(3) in a nearly stoichiometric 3:1 (H(2)/N(2)) molar ratio under inert conditions. The present Mw heating method is applicable to a variety of anatase-type TiO(2) species possessing different specific surface areas to provide small and highly dispersed platinum nanoparticles with a narrow size distribution.

  5. Synergistic influence of inorganic oxides (ZrO2 and SiO2) with N2H4 to protect composite coatings obtained via plasma electrolyte oxidation on Mg alloy.

    PubMed

    Zoubi, Wail Al; Kamil, Muhammad Prisla; Ko, Young Gun

    2017-01-18

    Different electrochemical approaches were proposed in this study to introduce nanoparticles to the coating layers, aiming at their in situ incorporation into the coating layers fabricated via plasma electrolytic oxidation (PEO). The addition of nanoparticles to the coating layers provided an electrochemical pathway to generate the functionalized coatings with a wide range of compositions and constituent phases as well giving the appearance of sealing the pores. In this study, the microstructure, chemical composition, and electrochemical response of the composite coating formed via one-stage PEO were compared with those obtained by means of structural modification of PEO coatings together with either impregnation or pre-deposition. For the combination of PEO and pre-deposition, the coating layer demonstrated less porous and better corrosion performance in the conditions used in this study, which were attributed to the denser and/or thicker layer resulting after incorporating the nanoparticles, such as SiO2 and ZrO2. In these methods, the nanoparticles were detected mainly not only near the coating surface, but also within the micro-defects inside the coating layers. Accordingly, the electrochemical analysis based on potentiodynamic polarization tests in 3.5 wt% NaCl solution clearly showed that the corrosion resistance of Mg alloy would be enhanced significantly due to the incorporation of SiO2 and ZrO2 or ZrO2 nanoparticles.

  6. Novel TiO2/C3N4 Photocatalysts for Photocatalytic Reduction of CO2 and for Photocatalytic Decomposition of N2O.

    PubMed

    Reli, Martin; Huo, Pengwei; Šihor, Marcel; Ambrožová, Nela; Troppová, Ivana; Matějová, Lenka; Lang, Jaroslav; Svoboda, Ladislav; Kuśtrowski, Piotr; Ritz, Michal; Praus, Petr; Kočí, Kamila

    2016-11-03

    TiO2/g-C3N4 photocatalysts with the ratio of TiO2 to g-C3N4 ranging from 0.3/1 to 2/1 were prepared by simple mechanical mixing of pure g-C3N4 and commercial TiO2 Evonik P25. All the nanocomposites were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy, photoluminescence, X-ray photoelectron spectroscopy, Raman spectroscopy, infrared spectroscopy, transmission electron microscopy, photoelectrochemical measurements, and nitrogen physisorption. The prepared mixtures along with pure TiO2 and g-C3N4 were tested for the photocatalytic reduction of carbon dioxide and photocatalytic decomposition of nitrous oxide. The pure g-C3N4 exhibited the lowest photocatalytic activity in both cases, pointing to a very high recombination rate of charge carriers. On the other hand, the most active photocatalyst toward all the products was (0.3/1)TiO2/g-C3N4. The highest activity is achieved by combination of a number of factors: (i) specific surface area, (ii) adsorption edge energy, (iii) crystallite size, and (iv) efficient separation of the charge carriers, where the efficient charge separation is the most decisive parameter.

  7. Decomposition of benzene and toluene in air streams in fixed-film photoreactors coated with TiO2 catalyst.

    PubMed

    Ku, Young; Chen, Juan-Shiang; Chen, Hua-Wei

    2007-03-01

    The decomposition of benzene and toluene in air streams by UV/TiO2 process was studied in different annular photoreactors under various operating conditions. The shells of reactors used in this research are made of stainless steel, Pyrex glass, or titanium. The TiO2 film was coated to the inner surface of the reactors by either rotating coating or sol-gel techniques. The TiO2 films coated by sol-gel technique were found to be smoother and more uniform than those coated by rotating coating. However, experimental results indicated that the photocatalysis of benzene or toluene in a glass reactor with rotating-coated TiO2 film delivered higher decompositions in air streams than that with sol-gel coated reactors. Benzene and toluene were decomposed more effectively in a coated glass reactor than in a coated stainless steel reactor under the same operating conditions. The presence of water vapor in air-stream plays an important role in the decomposition of benzene and toluene, and a relative humidity of approximately 5-6% was found to be adequate. The presence of excessive amounts of humidity retarded the decomposition to certain extents possibly results from the competitive adsorption of water molecules on the active sites of TiO2.

  8. Constraining N2O emissions over the last century by firn air isotope measurements in both hemispheres

    NASA Astrophysics Data System (ADS)

    Prokopiou, Markella; Sapart, Celia; Martinerie, Patricia; Witrant, Emmanuel; Ishijima, Kentaro; Magand, Sophie; Kaiser, Jan; van de Wal, Roderik; Röckmann, Thomas

    2014-05-01

    N2O is a greenhouse gas that it is responsible for increased radiative forcing of the climate system. In addition to this, it is primarily destroyed in the stratosphere providing an important source of NOx, which in turn plays an important role in ozone depletion. Large uncertainties remain as to the actual strength of the individual sources of N2O. Knowledge of the historical record, of the temporal evolution of N2O emissions, can provide insight on how its sources and sinks altered during the industrial period. Data from air trapped in firn enables us to better determine the source/sink strength emissions over time. In this study we analyze firn measurements on 15N, 18O and position dependent 15N isotopic composition of N2O, from both hemispheres, combining new and previously published data, in order to constrain the N2O budget. From the Northern Hemisphere we use data from North Greenland Ice core Project (NGRIP) and North Eemian Ice core Project (NEEM) and for the Southern Hemisphere we use data from Berkner Island (BI), Dronning Maud Land (DML) and Dome Concordia (DOME C). Results show that the isotopic composition of 15N, 18O of N2O is presently more depleted which indicates a strong depleting source contribution probably originating from agricultural activities. The LGGE-GIPSA firn air diffusion model allows single site reconstructions, as well as using all data together in a multi-site inversion, in order to reconstruct the temporal evolution of N2O and its isotopic composition. We investigate the consistency between the different datasets and present a best-guess isotope history based on the firn air data. A simple two-box atmospheric model is applied in order to simulate the N2O atmospheric contribution from different sources and sinks.

  9. A computational study of hydrogen bonds in intermolecular systems of high complexity: arachno-pentaborane(11)···Y with Y = O2 and N 2.

    PubMed

    Zabardasti, Abedin; Goudarziafshar, Hamid; Salehnassaj, Maryam; Oliveira, Boaz G

    2014-09-01

    The interactions of arachno-B(5)H(11) with N(2) and O(2) were theoretically studied. In the B(5)H(11)···N(2) and B(5)H(11)···O(2) complexes, the terminal hydrogens of B(5)H(11) work as electron donors whereas the bridge ones as electron acceptors. The optimized structures and the corresponding harmonic vibration spectra were investigated through the MP2/aug-cc-pVDZ level of theory. In order to characterize the hydrogen bonds, the topological calculations inherent to the QTAIM protocol and MEP analysis were carried out. The NBO analyses were useful in the interpretation of the red-shifts and blue-shifts on the stretch frequencies of the proton donors, of course in agreement with the Bent rule for the chemical bonding as well as by the conceptions of hyperconjugation or hybridization.

  10. Rotational Temperature and Number Density Measurements of N2, O2, CO, and CO2 in a Hypersonic Flow Field Using Laser-Raman Spectroscopy

    DTIC Science & Technology

    1975-07-01

    SPECTROSCOPY , , VON KARMAN GAS DYNAMICS FACILITY ARNOLD ENGINEERING DEVELOPMENT CENTER AIR FORCE SYSTEMS COMMAND ARNOLD AIR FORCE STATION, TENNESSEE 37389 July...LIDRARY - ARNOLD AfB t TN 37339 Prepared for DIRECTORATE OF TECHNOLOGY ARNOLD ENGINEERING DEVELOPMENT CENTER ARNOLD AIR FORCE STATION, TENNESSEE...wORK UNIT NUMBERS Arnold Engineering Development Center (DY) Program Element Arnold Air Force Station, Tennessee 37389 65802F 11. CONTROLLING OFFICE

  11. Quantitative absorption spectroscopy of residual water vapor in high-purity gases: pressure broadening of the 1.39253-microm H2O transition by N2, HCl, HBr, Cl2, and O2.

    PubMed

    Vorsa, Vasil; Dheandhanoo, Seksan; Ketkar, Suhas N; Hodges, Joseph T

    2005-02-01

    We determined the respective pressure-broadening coefficients of HCl, HBr, Cl2, and O2 (expressed relative to that of the reference gas N2) for the (v1,v2,v3)J(Ka,Kc) = (0,0,0)3(0,3) --> (1,0,1)2(0,2) rovibrational transition of H2 16O that occurs at 1.39253 microm. The experiment used a continuous-wave cavity ring-down spectroscopy analyzer to measure the peak absorption losses as a function of added moisture concentration. The measured pressure-broadening coefficients for HCl, HBr, Cl2, and O2 are, respectively, 2.76, 2.48, 1.39, and 0.49 times that of the N2 pressure-broadening coefficient, and detection limits for water vapor range from 0.22 nmol mol(-1) for O2 matrix gas to 2.3 nmol mol(-1) for HBr matrix gas. The degradation of the detection limit (relative to the N2 matrix gas) is ascribed to a pressure-broadening-induced reduction in peak absorption cross section and to elevated background loss from the matrix gas.

  12. 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

  13. 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.

  14. 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

  15. The Role of Air-Electrode Structure on the Incorporation of Immiscible PFCs in Nonaqueous Li-O2 Battery.

    PubMed

    Balaish, Moran; Ein-Eli, Yair

    2017-03-22

    Perfluorocarbons (PFCs) are considered advantageous additives to nonaqueous Li-O2 battery due to their superior oxygen solubility and diffusivity compared to common battery electrolytes. Up to now, the main focus was concentrated on PFCs-electrolyte investigation; however, no special attention was granted to the role of carbon structure in the PFCs-Li-O2 system. In our current research, immiscible PFCs, rather than miscible fluorinated ethers, were added to activated carbon class air electrode due to their higher susceptibility toward O2(•-) attack and to their ability to shift the reaction from two-phase to an artificial three-phase reaction zone. The results showed superior battery performance upon PFCs addition at lower current density (0.05 mA cm(-2)) but unexpectedly failed to do so at higher current density (0.1 and 0.2 mA cm(-2)), where oxygen transport limitation is best illustrated. The last was a direct result of liquid-liquid displacement phenomenon occurring when the two immiscible liquids were introduced into the porous carbon medium. The investigation and role of carbon structure on the mechanism upon PFCs addition to Li-O2 system are suggested based on electrochemical characterization, wettability behavior studies, and the physical adsorption technique. Finally, we suggest an optimum air-electrode structure enabling the incorporation of immiscible PFCs in a nonaqueous Li-O2 battery.

  16. Improved Wetting Characteristics in TiO2–Modified Ag-CuO Air Braze Filler Metals

    SciTech Connect

    Weil, K. Scott; Kim, Jin Yong Y.; Hardy, John S.; Darsell, Jens T.

    2006-01-01

    In this paper we report on the results of a series of sessile drop experiments designed to examine the effect of TiO2 on the wetting behavior of Ag-CuO air braze filler metals. It was found that TiO2 concentrations as small as 0.5 mol% can significantly decrease the contact angle of Ag-CuO on alumina over a compositional range of 1 – 34mol% CuO. The effect appears to maximize at a copper oxide concentration of ~4 mol% CuO regardless of the titania content.

  17. 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.

  18. 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.

  19. Nanoscale mechanochemical wear of phosphate laser glass against a CeO2 particle in humid air

    NASA Astrophysics Data System (ADS)

    Yu, Jiaxin; He, Hongtu; Zhang, Yafeng; Hu, Hailong

    2017-01-01

    Using an atomic force microscope, the friction and wear of phosphate laser glass against a CeO2 particle were quantitatively studied both in humid air and in vacuum, to reveal the water molecules induced mechanochemical wear mechanism of phosphate laser glass. The friction coefficient of the glass/CeO2 pair in air was found to be 5-7 times higher than that in vacuum due to the formation of a capillary water bridge at the friction interface, with a contribution of the capillary-related friction to the total friction coefficient as high as 65-79%. The capillary water bridge further induced a serious material removal of glass and CeO2 particle surfaces, while supplying both a local liquid water environment to corrode the glass surface and a high shearing force to assist the stretching of the Cesbnd Osbnd P bond, accelerating the reaction between water and the glass/CeO2 pair. In vacuum, however, no discernable wear phenomena were observed, but the phase images captured by AFM tapping mode suggested the occurrence of potential strain hardening in the friction area of the glass surface.

  20. Structural and Electrical Characterization of SiO2 Gate Dielectrics Deposited from Solutions at Moderate Temperatures in Air.

    PubMed

    Esro, Mazran; Kolosov, Oleg; Jones, Peter J; Milne, William I; Adamopoulos, George

    2017-01-11

    Silicon dioxide (SiO2) is the most widely used dielectric for electronic applications. It is usually produced by thermal oxidation of silicon or by using a wide range of vacuum-based techniques. By default, the growth of SiO2 by thermal oxidation of silicon requires the use of Si substrates whereas the other deposition techniques either produce low quality or poor interface material and mostly require high deposition or annealing temperatures. Recent investigations therefore have focused on the development of alternative deposition paradigms based on solutions. Here, we report the deposition of SiO2 thin film dielectrics deposited by spray pyrolysis in air at moderate temperatures of ≈350 °C from pentane-2,4-dione solutions of SiCl4. SiO2 dielectrics were investigated by means of UV-vis absorption spectroscopy, spectroscopic ellipsometry, XPS, XRD, UFM/AFM, admittance spectroscopy, and field-effect measurements. Data analysis reveals smooth (RRMS < 1 nm) amorphous films with a dielectric constant of about 3.8, an optical band gap of ≈8.1 eV, leakage current densities in the order of ≈10(-7) A/cm(2) at 1 MV/cm, and high dielectric strength in excess of 5 MV/cm. XPS measurements confirm the SiO2 stoichiometry and FTIR spectra reveal features related to SiO2 only. Thin film transistors implementing spray-coated SiO2 gate dielectrics and C60 and pentacene semiconducting channels exhibit excellent transport characteristics, i.e., negligible hysteresis, low leakage currents, high on/off current modulation ratio on the order of 10(6), and high carrier mobility.

  1. 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.

  2. Optimal frequency selection of multi-channel O2-band different absorption barometric radar for air pressure measurements

    NASA Astrophysics Data System (ADS)

    Lin, Bing; Min, Qilong

    2017-02-01

    Through theoretical analysis, optimal selection of frequencies for O2 differential absorption radar systems on air pressure field measurements is achieved. The required differential absorption optical depth between a radar frequency pair is 0.5. With this required value and other considerations on water vapor absorption and the contamination of radio wave transmission, frequency pairs of present considered radar system are obtained. Significant impacts on general design of differential absorption remote sensing systems are expected from current results.

  3. 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.

  4. Effects of CO2/N2 dilution on laminar burning velocity of stoichiometric DME-air mixture at elevated temperatures.

    PubMed

    Mohammed, Abdul Naseer; Juhany, Khalid A; Kumar, Sudarshan; Kishore, V Ratna; Mohammad, Akram

    2017-03-21

    The laminar burning velocity of CO2/N2 diluted stoichiometric dimethyl ether (DME) air mixtures is determined experimentally at atmospheric pressure and elevated mixture temperatures using a mesoscale high aspect-ratio diverging channel with inlet dimensions of 25mm×2mm. In this method, planar flames at different initial temperatures (Tu) were stabilized inside the channel using an external electric heater. The magnitude of burning velocities was acquired by measuring the flame position and initial temperature. The mass conservation of the mixture entering the inlet and the stationary planar flame front is applied to obtain the laminar burning velocity. Laminar burning velocity at different initial mixture temperatures is plotted with temperature ratio (Tu/Tu,o), where a reference temperature (Tu,o) of 300K is used. Enhancement in the laminar burning velocity is observed with mixture temperature for DME-air mixtures with CO2 and N2 dilutions. A significant decrease in the burning velocity and slight increase in temperature exponent of the stoichiometric DME-air mixture was observed with dilution at same temperatures. The addition of CO2 has profound influence when compared to N2 addition on both burning velocity and temperature exponent.

  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. 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.

  7. 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.

  8. Predicting solvent stability in aprotic electrolyte Li-air batteries: nucleophilic substitution by the superoxide anion radical (O2(•-)).

    PubMed

    Bryantsev, Vyacheslav S; Giordani, Vincent; Walker, Wesley; Blanco, Mario; Zecevic, Strahinja; Sasaki, Kenji; Uddin, Jasim; Addison, Dan; Chase, Gregory V

    2011-11-10

    There is increasing evidence that cyclic and linear carbonates, commonly used solvents in Li ion battery electrolytes, are unstable in the presence of superoxide and thus are not suitable for use in rechargeable Li-air batteries employing aprotic electrolytes. A detailed understanding of related decomposition mechanisms provides an important basis for the selection and design of stable electrolyte materials. In this article, we use density functional theory calculations with a Poisson-Boltzmann continuum solvent model to investigate the reactivity of several classes of aprotic solvents in nucleophilic substitution reactions with superoxide. We find that nucleophilic attack by O(2)(•-) at the O-alkyl carbon is a common mechanism of decomposition of organic carbonates, sulfonates, aliphatic carboxylic esters, lactones, phosphinates, phosphonates, phosphates, and sulfones. In contrast, nucleophilic reactions of O(2)(•-) with phenol esters of carboxylic acids and O-alkyl fluorinated aliphatic lactones proceed via attack at the carbonyl carbon. Chemical functionalities stable against nucleophilic substitution by superoxide include N-alkyl substituted amides, lactams, nitriles, and ethers. The results establish that solvent reactivity is strongly related to the basicity of the organic anion displaced in the reaction with superoxide. Theoretical calculations are complemented by cyclic voltammetry to study the electrochemical reversibility of the O(2)/O(2)(•-) couple containing tetrabutylammonium salt and GCMS measurements to monitor solvent stability in the presence of KO(2)(•) and a Li salt. These experimental methods provide efficient means for qualitatively screening solvent stability in Li-air batteries. A clear correlation between the computational and experimental results is established. The combination of theoretical and experimental techniques provides a powerful means for identifying and designing stable solvents for rechargeable Li-air batteries.

  9. Synthesis, characterization, EPR spectroscopy and catalytic activity of a new oxidovanadium(IV) complex with N2O2-donor ligand

    NASA Astrophysics Data System (ADS)

    Mahboubi-Anarjan, Parisa; Bikas, Rahman; Hosseini-Monfared, Hassan; Aleshkevych, Pavlo; Mayer, Peter

    2017-03-01

    A new oxidovanadium(IV) complex, 2[VOL(OH2)] CH3OH (1), was synthesized from the reaction of VO(acac)2 with a symmetric N,O-donor Schiff base ligand (H2L), in which H2L is 6,6'-((1E,1‧E)-((2-hydroxypropane-1,3-diyl)bis(azanylylidene))bis(methanylylidene))bis(2-methoxyphenol). The compounds were characterized by elemental analysis and spectroscopic methods. The molecular structure of complex was determined by single-crystal X-ray analysis which indicated that the crystal packing of complex contains two independent mononuclear vanadium complexes connected together by several strong hydrogen bonding interactions. The EPR spectrum of powdered complex 1 at liquid helium temperature showed two intensive octets which proved to be associated with V4+ ions with 3d1 electronic configuration. From EPR spectrum the values of the parameters: g|| = 1.9454 ± 0.0004, g⊥ = 1.9491 ± 0.0004, A|| = 0.0084 ± 0.0008 cm-1 and A⊥ = 0.0033 ± 0.0006 cm-1 were calculated for this complex. Complex 1 was employed as catalyst for oxidation of cyclooctene in the presence of H2O2 as oxidant. In order to obtain the suitable condition of catalytic oxidation, the effect of various parameters including the amount of the catalyst, temperature and solvent was studied. The results of catalytic studies showed that complex 1 can provide an effective and selective catalytic system for epoxidation of cyclooctene.

  10. 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.

  11. 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.

  12. 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.

  13. Vibrational and thermodynamic properties of Ar, N2, O2, H2 and CO adsorbed and condensed into (H,Na)-Y zeolite cages as studied by variable temperature IR spectroscopy.

    PubMed

    Gribov, Evgueni N; Cocina, Donato; Spoto, Giuseppe; Bordiga, Silvia; Ricchiardi, Gabriele; Zecchina, Adriano

    2006-03-14

    The adsorption of Ar, H2, O2, N2 and CO on (H,Na)-Y zeolite (Si/Al = 2.9, H+/Na+ approximately 5) has been studied at variable-temperature (90-20 K) and sub-atmospheric pressure (0-40 mbar) by FTIR spectroscopy. Unprecedented filling conditions of the zeolite cavities were attained, which allowed the investigation of very weakly adsorbed species and of condensed, liquid-like or solid-like, phases. Two pressure regimes were singled out, characterized by: (i) specific interaction at low pressure of the probe molecules (P) with the internal Brønsted and Lewis sites, and (ii) multilayer adsorption at higher pressure. In the case of CO the perturbation of the protonic sites located inside the sodalite cages was also observed. As the molecule is too large to penetrate the sodalite cage, the perturbation is thought to involve a proton jump tunneling mechanism. The adsorption energy for the (HF)OH...P (P = Ar, H2, O2, N2 and CO) specific interaction involving the high frequency Brønsted acid sites exposed in the supercages was derived following the VTIR (variable temperature infrared spectroscopy) method described by E. Garrone and C. Otero Areán (Chem. Soc. Rev., 2005, 34, 846).

  14. 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.

  15. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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.

  17. Improved Wetting Characteristics in TiO2–Modified Ag-CuO Air Braze Filler Metals

    SciTech Connect

    Weil, K. Scott; Kim, Jin Yong; Hardy, John S.; Darsell, Jens T.

    2006-01-04

    A silver-based joining technique referred to as reactive air brazing (RAB) has been recently developed for joining high temperature structural ceramic components of the type used in high-temperature electrochemical devices. In prior work, it was found that additions of CuO to silver have a significant effect on the wettability and joint strength characteristics of the resulting braze on polycrystalline alumina substrates. More recently, it has been found that by adding as little as 0.5 mol % titania to these Ag-CuO brazes, the wettability of the RAB on alumina surfaces is further enhanced. The results of wettabilty measurements of Ag-CuO-TiO2 RAB compositions on alumina will be presented along with the microstructural characterization of Ag-CuO-TiO2 braze joints in alumina.

  18. Surface diffusion control of the photocatalytic oxidation in air/TiO2 heterogeneous reactors

    NASA Astrophysics Data System (ADS)

    Tsekov, R.; Evstatieva, E.; Smirniotis, P. G.

    2002-10-01

    The diffusion of superoxide radical anions on the surface of TiO 2 catalysts is theoretically considered as an important step in the kinetics of photocatalytic oxidation of toxic pollutants. A detailed analysis is performed to discriminate the effects of rotation and adsorption bond vibrations on the diffusion coefficient. A resonant dependence of the diffusivity on the lattice parameters of the TiO 2 surface is discovered showing that the most rapid diffusion takes place when the lattice parameters are twice as large as the the bond length of the superoxide radical anions. Whereas the rotation and vibrations normal to the catalyst surface are important, the anion bond vibrations do not affect the diffusivity due to their low amplitudes as compared to the lattice parameters.

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

    DOE PAGES

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

    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

  20. 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.

  1. 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.

  2. 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.

  3. Energy Transfer Collisional Process Involving Heteromolecular Collisions Between Methyl Fluoride and N_2, Ar, He, CO_2, and Air

    NASA Astrophysics Data System (ADS)

    Phillips, Dane J.; Everitt, Henry O.

    2013-06-01

    Time resolved IR/THz double resonance (DR) spectroscopy has been performed with a Q-switched CO_2 laser and heterodyne THz detection. The rate constants associated with allowed rotational- and vibrational-state changing collisions of CH_3F with N_2, Ar, He, CO_2, and air are measured by monitoring the temporal evolution of the absorption strength for numerous rotational transitions as a function of pressure. Collision partner dependent energy transfer processes are studied and compared with homomolecular collisions. Energy transfer maps and associated collisional cross sections will be presented for each collision partner.

  4. 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.

  5. 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.

  6. Tribology of Si/SiO2 in humid air: transition from severe chemical wear to wearless behavior at nanoscale.

    PubMed

    Chen, Lei; He, Hongtu; Wang, Xiaodong; Kim, Seong H; Qian, Linmao

    2015-01-13

    Wear at sliding interfaces of silicon is a main cause for material loss in nanomanufacturing and device failure in microelectromechanical system (MEMS) applications. However, a comprehensive understanding of the nanoscale wear mechanisms of silicon in ambient conditions is still lacking. Here, we report the chemical wear of single crystalline silicon, a material used for micro/nanoscale devices, in humid air under the contact pressure lower than the material hardness. A transmission electron microscopy (TEM) analysis of the wear track confirmed that the wear of silicon in humid conditions originates from surface reactions without significant subsurface damages such as plastic deformation or fracture. When rubbed with a SiO2 ball, the single crystalline silicon surface exhibited transitions from severe wear in intermediate humidity to nearly wearless states at two opposite extremes: (a) low humidity and high sliding speed conditions and (b) high humidity and low speed conditions. These transitions suggested that at the sliding interfaces of Si/SiO2 at least two different tribochemical reactions play important roles. One would be the formation of a strong "hydrogen bonding bridge" between hydroxyl groups of two sliding interfaces and the other the removal of hydroxyl groups from the SiO2 surface. The experimental data indicated that the dominance of each reaction varies with the ambient humidity and sliding speed.

  7. Differential scattering cross sections for collisions of 0.5-, 1.5-, and 5.0-keV helium atoms with He, H2, N2, and O2. [for atmospheric processes modeling

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    This paper reports the first results of an experimental program established to provide cross section data for use in modeling various atmospheric processes. Absolute cross sections, differential in the scattering angle, have been measured for collisions of 0.5-, 1.5-, and 5.0-keV helium atoms with He, H2, N2, and O2 at laboratory scattering angles between 0.1 deg and 5 deg. The results are the sums of cross sections for elastic and inelastic scattering of helium atoms; charged collision products are not detected. Integration of the differential cross section data yields integral cross sections consistent with measurements by other workers. The apparatus employs a position-sensitive detector for both primary and scattered particles and uses a short target cell with a large exit aperture to ensure a simple and well-defined apparatus geometry.

  8. Impulsive rotational Raman scattering of N2 by a remote "air laser" in femtosecond laser filament.

    PubMed

    Ni, Jielei; Chu, Wei; Zhang, Haisu; Zeng, Bin; Yao, Jinping; Qiao, Lingling; Li, Guihua; Jing, Chenrui; Xie, Hongqiang; Xu, Huailiang; Cheng, Ya; Xu, Zhizhan

    2014-04-15

    We report on experimental realization of impulsive rotational Raman scattering from neutral nitrogen molecules in a femtosecond laser filament using an intense self-induced white-light seeding "air laser" generated during the filamentation of an 800 nm Ti:sapphire laser in nitrogen gas. The impulsive rotational Raman fingerprint signals are observed with a maximum conversion efficiency of ∼0.8%. Our observation provides a promising way of remote identification and location of chemical species in the atmosphere by a rotational Raman scattering of molecules.

  9. [Alveolar arterial O2 gradient in patients with cardiopulmonary pathology. Its study at rest with respiration of environmental air].

    PubMed

    Martínez Guerra, M L; Fernández Bonett, P; Lupi Herrera, E

    1979-01-01

    The arterial oxygen pressure (PAO2) and the arterial carbon dioxide pressure (PACO2) are the mirror of the whole stage in alveolar ventilation, because there is a numerical correlation between them, in the alveolar air equation. In our material no difference was found when the respiratory cocient is used to calculate the equation modifying the PACO2 value. On the other hand, the PaO depends on a great amount of variables, i.e., the rationship V/Q. Qs/Qt and the arteriovenous oxygen difference in volume percentage, which reflect the functional stage of the gaseous interchange; other variables depend essentially of technical factors as the methodology used in the obtention and management of the samples and the measurement of the PAO2 at the laboratory. Thus, the alveolo-arterial oxigen Difference delta (A-a)O2 is considered as a mirror of the fluctuations in gaseous interchange, only if the alveolar ventilation the cardiac output, the systemic arterial-vein oxygen difference and in minor importance the respiratory cocient (RP remain constant. The delta (A-a)O2 is not always correlated with other parameters far from the gaseous interchange at lung level in the critically ill patient, for this, it has not a pronostic mecaning by itself. Nevertheless, we believe that delta (A-a)O2 continues being a useful measurement to evaluate the gaseous interchange if at the same time all the factors which may have influence in it are analysed. We consider, for trying to be simple in the management of the acute respiratory failure at the bedside that the (A-a)O2 must not be linked to only one parameter of the respiratory function, i.e. the intrapulmonar veno-arterial shunt, without considering the cardiac output and the systemic arterial-vein oxygen difference.

  10. Air versus He-O2 Recompression Treatment of Decompression Sickness in Guinea Pigs

    DTIC Science & Technology

    1988-01-01

    le traitement do la MDC chez los cobayes apr~s des plong~es A IPair. Lila RS, MacCallum ME, Pitkin RB. Tratamiento do recompresioa con aire vs. He-C...2 pars enfermeded por desconipresioa en conejillos do indiss. Undersea Biomed Res 1988; 15(4):283- 300-So *studio el tratamiento do roconapresion con...del tratamiento mejoro con profundidades mayores con airs, pewo no con He-C),. Es"o datos indica las difereacias potenciales en Is respuesta alan

  11. Co3O4-CeO2/C as a Highly Active Electrocatalyst for Oxygen Reduction Reaction in Al-Air Batteries.

    PubMed

    Liu, Kun; Huang, Xiaobing; Wang, Haiyan; Li, Fuzhi; Tang, Yougen; Li, Jingsha; Shao, Minhua

    2016-12-21

    Developing high-performance and low-cost electrocatalysts for oxygen reduction reaction (ORR) is still a great challenge for Al-air batteries. Herein, CeO2, a unique ORR promoter, was incorporated into ketjenblack (KB) supported Co3O4 catalyst. We developed a facile two-step hydrothermal approach to fabricate Co3O4-CeO2/KB as a high-performance ORR catalyst for Al-air batteries. The ORR activity of Co3O4/KB was significantly increased by mixing with CeO2 nanoparticles. In addition, the Co3O4-CeO2/KB showed a better electrocatalytic performance and stability than 20 wt % Pt/C in alkaline electrolytes, making it a good candidate for highly active ORR catalysts. Co3O4-CeO2/KB favored a four-electron pathway in ORR due to the synergistic interactions between CeO2 and Co3O4. In full cell tests, the Co3O4-CeO2/KB exhibited a higher discharge voltage plateau than CeO2/KB and Co3O4/KB when used in cathode in Al-air batteries.

  12. Theoretical studies of UO2(H2O)n2+,NpO2(H2O)n+, and PuO2(H2O)n2+ complexes (n=4-6) in aqueous solution and gas phase

    NASA Astrophysics Data System (ADS)

    Cao, Zhiji; Balasubramanian, K.

    2005-09-01

    Extensive ab initio calculations both in gas phase and solution have been carried out to study the equilibrium structure, vibrational frequencies, and bonding characteristics of various actinyl (UO22+,NpO2+, and PuO22+) and their hydrated forms, AnO2(H2O)nz + (n =4, 5, and 6). Bulk solvent effects were studied using a continuum method. The geometries were fully optimized at the coupled-cluster singles + doubles (CCSD), density-functional theory (DFT), and Møller-Plesset (MP2) level of theories. In addition vibrational frequencies have been obtained at the CCSD as well as MP2/DFT levels. The results show that both the short-range and long-range solvent effects are important. The combined discrete-continuum model, in which the ionic solute and the solvent molecules in the first and second solvation shells are treated quantum mechanically while the solvent is simulated by a continuum model, can predict accurately the bonding characteristics. Moreover, our values of solvation free energies suggest that five- and six-coordinations are equally preferred for UO22+, and five-coordinated species are preferred for NpO2+ and PuO22+. On the basis of combined quantum-chemical and continuum treatments of the hydrated complexes, we are able to determine the optimal cavity radii for the solvation models. The coupled-cluster computations with large basis sets were employed for the vibrational spectra and equilibrium geometries both of which compare quite favorably with experiment. Our most accurate computations reveal that both five- and six-coordination complexes are important for these species.

  13. Markers of lipid oxidative damage among office workers exposed intermittently to air pollutants including nanoTiO2 particles.

    PubMed

    Pelclova, Daniela; Zdimal, Vladimir; Kacer, Petr; Komarc, Martin; Fenclova, Zdenka; Vlckova, Stepanka; Zikova, Nadezda; Schwarz, Jaroslav; Makes, Otakar; Navratil, Tomas; Zakharov, Sergey; Bello, Dhimiter

    2017-03-01

    Nanoscale titanium dioxide (nanoTiO2) is a commercially important nanomaterial used in numerous applications. Experimental studies with nanotitania have documented lung injury and inflammation, oxidative stress, and genotoxicity. Production workers in TiO2 manufacturing with a high proportion of nanoparticles and a mixture of other air pollutants, such as gases and organic aerosols, had increased markers of oxidative stress, including DNA and protein damage, as well as lipid peroxidation in their exhaled breath condensate (EBC) compared to unexposed controls. Office workers were observed to get intermittent exposures to nanoTiO2 during their process monitoring. The aim of this study was to investigate the impact of such short-term exposures on the markers of health effects in office workers relative to production workers from the same factory. Twenty-two office employees were examined. They were occupationally exposed to (nano)TiO2 aerosol during their daily visits of the production area for an average of 14±9 min/day. Median particle number concentration in office workers while in the production area was 2.32×104/cm3. About 80% of the particles were <100 nm in diameter. A panel of biomarkers of lipid oxidation, specifically malondialdehyde (MDA), 4-hydroxy-trans-hexenal (HHE), 4-hydroxy-trans-nonenal (HNE), 8-isoprostaglandin F2α (8-isoprostane), and aldehydes C6-C12, were studied in the EBC and urine of office workers and 14 unexposed controls. Nine markers of lipid oxidation were elevated in the EBC of office employees relative to controls (p<0.05); only 8-isoprostane and C11 were not increased. Significant association was found in the multivariate analysis between their employment in the TiO2 production plant and EBC markers of lipid oxidation. No association was seen with age, lifestyle factors, or environmental air contamination. The EBC markers in office employees reached about 50% of the levels measured in production workers, and the difference between

  14. Statistical temperature profile retrievals in clear-air using passive 118-GHz O2 observations

    NASA Technical Reports Server (NTRS)

    Gasiewski, A. J.; Johnson, J. T.

    1993-01-01

    The clean-air temperature profile accuracy yielded by a localized linear statistical retrieval operator applied to passive aircraft-based 118-GHz spectra is demonstrated. A comparison of the statistically and physically derived correlation coefficients of antenna temperature and kinetic temperature furnishes a physical justification of the statistical retrieval technique. The atmospheric temperature mean and covariance significantly depend on such geophysical parameters as latitude, longitude, local season, and time, as well as the prevailing meteorological state and orographic effects.

  15. Effects of He-O2 Breathing during Experimental Decompression Sickness Following Air Dives

    DTIC Science & Technology

    1987-03-01

    ventilator volume or rate was made during the experiment. The oxygen content of the He-0 2 mixture used in the He-Or group was measured using a...e ne modifia pas ces rdponses. mats la respiratton de He-O? produtst une augmentation de 11% dans Ia rdsistance vasculaire pulmonaire (RVP). Chez 3...d’une plong~e A F’air peut aggraver l’obstruction vasculaire pulmonaire. plongde hdlium-oxygtne maladie de decompression suffocation embolie gazeuse

  16. 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

  17. Colour changes of a historical Gotland sandstone caused by laser surface cleaning in ambient air and N2 flow

    NASA Astrophysics Data System (ADS)

    Jasińska, M.; Nowak, A.; Łukaszewicz, J. W.; Śliwiński, G.

    2008-07-01

    The surface discoloration due to laser cleaning was investigated for a historical Gotland sandstone. The difference in discoloration for cleaning performed in air and in the shielding environment of N2 flowing at low velocities was studied by means of colorimetry and scanning electron microscopy and energy dispersive X-ray spectroscopy techniques. For ablative removal of the natural as well as artificially applied encrustation a pulsed 1064-nm laser operated at a fluence of 0.5 J/cm2 was applied. It was observed that the natural colour variations (ΔL*=21; Δb*=23) of the stone can completely screen the laser-induced changes. Under conditions of shielding with nitrogen, darkening and yellowing slightly stronger than those occurring in the ambient air were revealed for the laser-cleaned, artificially crusted samples and the effect was independent of the gas-flow velocity. The observed difference confirmed the contribution of iron oxidation to the laser-induced yellowing and showed that the presence of oxygen in the ambient air affects favourably the cleaning by supporting removal of a variety of combustible surface remnants and crust components of organic as well as inorganic origin.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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).

  3. 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

    2016-08-30

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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.

  5. Thermal decomposition of sewage sludge under N2, CO2 and air: Gas characterization and kinetic analysis.

    PubMed

    Hernández, Ana Belén; Okonta, Felix; Freeman, Ntuli

    2017-03-25

    Thermochemical valorisation processes that allow energy to be recovered from sewage sludge, such as pyrolysis and gasification, have demonstrated great potential as convenient alternatives to conventional sewage sludge disposal technologies. Moreover, these processes may benefit from CO2 recycling. Today, the scaling up of these technologies requires an advanced knowledge of the reactivity of sewage sludge and the characteristics of the products, specific to the thermochemical process. In this study the behaviour of sewage sludge during thermochemical conversion, under different atmospheres (N2, CO2 and air), was studied, using TGA-FTIR, in order to understand the effects of different atmospheric gases on the kinetics of degradation and on the gaseous products. The different steps observed during the solid degradation were related with the production of different gaseous compounds. A higher oxidative degree of the atmosphere surrounding the sample resulted in higher reaction rates and a shift of the degradation mechanisms to lower temperatures, especially for the mechanisms taking place at temperatures above 400 °C. Finally, a multiple first-order reaction model was proposed to compare the kinetic parameters obtained under different atmospheres. Overall, the highest activation energies were obtained for combustion. This work proves that CO2, an intermediate oxidative atmosphere between N2 and air, results in an intermediate behaviour (intermediate peaks in the derivative thermogravimetric curves and intermediate activation energies) during the thermochemical decomposition of sewage sludge. Overall, it can be concluded that the kinetics of these different processes require a different approach for their scaling up and specific consideration of their characteristic reaction temperatures and rates should be evaluated.

  6. Synthesis, structure and physicochemical characterization of the hybrid material [C6H16N2O]2 SnCl6·2Cl·2H2O

    NASA Astrophysics Data System (ADS)

    Belhaj Salah, S.; Pereira da Silva, P. S.; Lefebvre, F.; Ben Nasr, C.; Ammar, S.; Mrad, M. L.

    2017-04-01

    The current study reports the chemical preparation, crystal structure, Hirshfeld surface analysis and spectroscopic characterization of the novel compound [C6H16N2O]2SnCl6·2Cl·2H2O. This compound crystallizes in the triclinic system (space group P - 1, Z = 1) with the following unit cell dimensions: a = 7.9764(9), b = 8.2703(9), c = 12.1103(14)Å, α = 84.469(6), β = 75.679(6), and γ = 64.066(5)°. The structure was solved using 3093 independent reflections down to R = 0.020. The atomic arrangement shows alternation of organic and inorganic entities. The cohesion between these entities is ensured by Nsbnd H…Cl and Osbnd H…Cl hydrogen bonds that build a three-dimensional network. The 3D Hirshfeld surfaces and the associated 2D fingerprint plots were investigated for intermolecular interactions. The 13C and 15N CP-MAS NMR spectra are in agreement with the X-ray structure. The vibrational absorption bands were identified by infrared spectroscopy. DFT calculations allowed the attribution of the IR and NMR bands. X-ray powder, XPS and UV spectrum have been carried out. The DSC profile shows that the title material exhibits dehydration at 339 K.

  7. 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.

  8. 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

  9. Steady-state radiolysis and product analysis of aqueous diphenyloxide in the presence of air and N 2O

    NASA Astrophysics Data System (ADS)

    Popov, P.; Getoff, N.; Grodkowski, J.; Zimek, Z.; Chmielewski, A. G.

    2004-01-01

    The radiation-induced decomposition and product analysis of diphenyloxide (DPO; diphenylether), selected as a representative of the toxic polyaromatic, volatile, hydrocarbons produced by combustion of coal, was investigated in aqueous solution. In the presence of air an initial degradation yield, Gi(-DPO)0=4.6 was obtained. Phenol ( Gi=1.3) appeared to be the major decomposition product in addition to a number of hydroxy-compounds as well as a mixture of aldehydes and carboxylic acids. DPO as well as the resulting products can be decomposed at an absorbed radiation dose of about 5 kGy. By performing analogous studies in solution saturated with N 2O an initial yield of Gi(-DPO)=5.0 and similar radiolytic products were found. Again phenol ( Gi=1.5) is observed as the main product. In this case a much lower radiation dose (˜2.5 kGy) is found to be sufficient for the decomposition of DPO and its radiolytic products. Most likely reaction mechanisms are presented for explanation of the observed products.

  10. Computed self-consistent field and singles and doubles configuration interaction spectroscopic data and dissociation energies for the diatomics B2, C2, N2, O2, F2, CN, CP, CS, PN, SiC, SiN, SiO, SiP, and their ions

    NASA Astrophysics Data System (ADS)

    McLean, A. D.; Liu, B.; Chandler, G. S.

    1992-12-01

    Results are presented for single-configuration self-consistent field (SCF) calculations near the Hartree-Fock limit. Singles and doubles configuration-interaction calculations from this single SCF configuration were performed for the ground states and selected excited states of the molecules B2, B2(+), C2, C2(+), N2, N2(+), O2, O2(+), F2, F2(+), CN, CN(-), CP, CS, PN, SiC, SiC(-), SiN, SiN(-), SiO, and SiP. Results include potential energy curves, equilibrium bond lengths, vibrational energies, ionization potentials, and dissociation energies.

  11. 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.

  12. 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.

  13. 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).

  14. 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.

  15. 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.

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

    PubMed

    Arve, Louise E; Carvalho, Dália R A; 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.

  17. S(p)O(2) values in acute medical admissions breathing air--implications for the British Thoracic Society guideline for emergency oxygen use in adult patients?

    PubMed

    Smith, Gary B; Prytherch, David R; Watson, Duncan; Forde, Val; Windsor, Alastair; Schmidt, Paul E; Featherstone, Peter I; Higgins, Bernie; Meredith, Paul

    2012-10-01

    S(p)O(2) is routinely used to assess the well-being of patients, but it is difficult to find an evidence-based description of its normal range. The British Thoracic Society (BTS) has published guidance for oxygen administration and recommends a target S(p)O(2) of 94-98% for most adult patients. These recommendations rely on consensus opinion and small studies using arterial blood gas measurements of saturation (S(a)O(2)). Using large datasets of routinely collected vital signs from four hospitals, we analysed the S(p)O(2) range of 37,593 acute general medical inpatients (males: 47%) observed to be breathing room air. Age at admission ranged from 16 to 105 years with a mean (SD) of 64 (21) years. 19,642 admissions (52%) were aged <70 years. S(p)O(2) ranged from 70% to 100% with a median (IQR) of 97% (95-98%). S(p)O(2) values for males and females were similar. In-hospital mortality for the study patients was 5.27% (range 4.80-6.27%). Mortality (95% CI) for patients with initial S(p)O(2) values of 97%, 96% and 95% was 3.65% (3.22-4.13); 4.47% (3.99-5.00); and 5.67% (5.03-6.38), respectively. Additional analyses of S(p)O(2) values for 37,299 medical admissions aged ≥18 years provided results that were distinctly different to those upon which the current BTS guidelines based their definition of normality. Our findings suggest that the BTS should consider changing its target saturation for actively treated patients not at risk of hypercapnic respiratory failure to 96-98%.

  18. 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.

  19. A critical review of macroscopic modeling studies on Li O2 and Li-air batteries using organic electrolyte: Challenges and opportunities

    NASA Astrophysics Data System (ADS)

    Li, Xianglin; Huang, Jing; Faghri, Amir

    2016-11-01

    A comprehensive review of the state-of-the-art macroscopic modeling studies on lithium oxygen (Li O2) and lithium air (Li-air) batteries has been presented. The Li O2 battery is a promising device for energy storage in portable electronics and electric vehicles due to its high specific energy. A number of technical challenges need to be addressed in order to bring this technology from laboratory concept to real products. The multi-scale, multi-physics phenomena in a Li O2 battery encompasses a wide range of scientific disciplines, including electrochemistry, heat and mass transfer, and material science. Modeling study provides a powerful tool to understand the charge-species transport phenomena inside a battery that cannot be captured by experimentation. It offers insight to optimize battery design and fabrication. Macroscopic models that treat battery components as continuous media will be the focus of this review while pore-scale sub-models that are integrated with macroscopic models to describe structural changes of battery components (mainly electrodes) will be presented and compared as well. Recent developments and opportunities for future improvement and advancement are also discussed. Finally, a detailed summary of property data relevant to Li O2 batteries is provided because of their critical role in modeling studies.

  20. 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.

  1. Impact of air exposure and annealing on the chemical and electronic properties of the surface of SnO2 nanolayers deposited by rheotaxial growth and vacuum oxidation

    PubMed Central

    Krzywiecki, Maciej

    2017-01-01

    In this paper the SnO2 nanolayers were deposited by rheotaxial growth and vacuum oxidation (RGVO) and analyzed for the susceptibility to ambient-air exposure and the subsequent recovery under vacuum conditions. Particularly the surface chemistry of the layers, stoichiometry and level of carbon contamination, was scrutinized by X-ray photoelectron spectroscopy (XPS). The layers were tested i) pristine, ii) after air exposure and iii) after UHV annealing to validate perspective recovery procedures of the sensing layers. XPS results showed that the pristine RGVO SnO2 nanolayers are of high purity with a ratio [O]/[Sn] = 1.62 and almost no carbon contamination. After air exposure the relative [O]/[Sn] concentration increased to 1.80 while maintaining a relatively low level of carbon contaminants. Subsequent UHV annealing led to a relative [O]/[Sn] concentration comparable to the pristine samples. The oxidation resulted in a variation of the distance between the valence band edge and the Fermi level energy. This was attributed to oxygen diffusion through the porous SnO2 surface as measured by atomic force microscopy. PMID:28382240

  2. Effect of Au clustering on ferromagnetism in Au doped TiO2 films: theory and experiments investigation

    NASA Astrophysics Data System (ADS)

    Zou, Zhaorui; Zhou, Zhongpo; Wang, Haiying; Yang, Zongxian

    2017-01-01

    In this paper, we investigated the physical properties especially the magnetic properties of the TiO2 films and Au cluster doped TiO2 films fabricated by sol-gel and sputtering methods combined experiments and first-principles calculations. All the samples annealed under air and N2 atmosphere respectively exhibit room temperature ferromagnetism with the crystal phase of anatase. The values of the saturation magnetizations are in the order of Au δ-doped TiO2 (annealed in N2)>undoped TiO2 (annealed in air)>Au δ-doped TiO2 (annealed in air). The first principles calculation results show that the formation energy of Au cluster doped TiO2 films is lower than that of the oxygen vacancy and Au cluster codoped TiO2 films. The effects of the Au cluster dopant are the retard of the formation of surface oxygen vacancy and the electrons transfer from 3d states of Ti atoms to Au 5d states in Au cluster doped TiO2 films. The codoping of surface oxygen vacancies, bulk oxygen vacancies and Au clusters led to the spin-split of Ti 3d and O 2p in Au cluster doped TiO2 films (annealed in N2) which yield the highest saturation magnetization.

  3. 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

  4. Performance of air plasma spraying parameters in the fabrication of ZrO2-10%Y2O3-18% TiO2 thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Liscano, S.; Gil, L.

    2013-11-01

    In this research, ZrO2-10%Y2O3-18% TiO2 thermal barrier coatings (TBCs) were sprayed by employing an air plasma thermal spray (APS) technique following a 23 factorial design experiment in order to obtain the best favorable spraying conditions able to enhance their properties. The effect of the spraying parameters on the porosity, microhardness, microstructure and morphology were determined by using different techniques such as optical microscopy (OP), image analysis, Vickers indentation and scanning electron microscopy (SEM) technique, this latter coupled with X-Ray microanalysis (EDS). It was found that both the arc voltage and the powder feed rate, as well as their interaction had a significant effect on the values of the reported hardness and these results were related to the existing level of porosity in the coatings. It was concluded that the best coatings properties, for the level of the variables studied in this work, could be obtained if the arc voltage is maintained at 36 V, the arc current at 900 A and the powder feed rate to 24 g/min.

  5. 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.

  6. 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.

  7. Catalytic evaluation on liquid phase oxidation of vanillyl alcohol using air and H2O2 over mesoporous Cu-Ti composite oxide

    NASA Astrophysics Data System (ADS)

    Saha, Subrata; Hamid, Sharifah Bee Abd; Ali, Tammar Hussein

    2017-02-01

    A mesoporous, highly crystalline Cu-Ti composite oxide catalyst was prepared via facile, simple and modified solution method varying Cu and Ti ratio for selective liquid phase oxidation of vanillyl alcohol. Various spectroscopic procedures were employed to systematically characterize the catalyst structural and physicochemical properties. The defect chemistry of the catalyst was confirmed from the presence of surface defects revealed through HRTEM imagery between the TiO2 (101) and Cu3TiO4 (012) planes, complemented by the XRD profiling. Further, presence of oxygen vacancy evidenced by O 1s XPS spectra were observed on the catalyst surface. Moreover, the stoichiometry of Cu and Ti in the catalyst synthesis protocol was notably found to be the vital determinant to alter the redox properties of Cu-Ti composite oxide catalyst supported by H2-TPR. O2-TPD analysis. Moreover, a rational investigation was done using different oxidants such as air and H2O2 with variables reaction conditions. The catalyst was active for liquid phase oxidation of vanillyl alcohol to vanillin with performance of 66% conversion and 71% selectivity using H2O2 in base free condition. And also, catalytic activity was significantly improved by 94% conversion with 86% selectivity to vanillin in liquid phase aerobic oxidation at the optimum reaction conditions. To expand the superiority of the catalyst, three times reusability study was also examined with appreciable catalytic activity.

  8. Determination of the rate coefficients for the reactions IO + NO2 + M (air) --> IONO2 + M and O(3P) + NO2 --> O2 + NO using laser-induced fluorescence spectroscopy.

    PubMed

    Dillon, Terry J; Blitz, Mark A; Heard, Dwayne E

    2006-06-01

    Laser-induced fluorescence spectroscopy via excitation of the A2pi(3/2) <-- X2pi(3/2) (2,0) band at 445 nm was used to monitor IO in the presence of NO2 following its generation in the reactions O(3P) + CF3I and O(3P) + I2. Both photolysis of O3 (248 nm) and NO2 (351 nm) were used to initiate the production of IO. The rate coefficients for the thermolecular reaction IO + NO2 + M --> IONO2 + M were measured in air, N2, and O2 over the range P = 18-760 Torr, covering typical tropospheric conditions, and were found to be in the falloff region. No dependence of k1 upon bath gas identity was observed, and in general, the results are in good agreement with recent determinations. Using a Troe broadening factor of F(B) = 0.4, the falloff parameters k0(1) = (9.5 +/- 1.6) x 10(-31) cm6 molecule(-2) s(-1) and k(infinity)(1) = (1.7 +/- 0.3) x 10(-11) cm3 molecule(-1) s(-1) were determined at 294 K. The temporal profile of IO at elevated temperatures was used to investigate the thermal stability of the product, IONO2, but no evidence was observed for the regeneration of IO, consistent with recent calculations for the IO-NO2 bond strength being approximately 100 kJ mol(-1). Previous modeling studies of iodine chemistry in the marine boundary layer that utilize values of k1 measured in N2 are hence validated by these results conducted in air. The rate coefficient for the reaction O(3P) + NO2 --> O2 + NO at 294 K and in 100 Torr of air was determined to be k2 = (9.3 +/- 0.9) x 10(-12) cm3 molecule(-1) s(-1), in good agreement with recommended values. All uncertainties are quoted at the 95% confidence limit.

  9. 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.

  10. The Influence of Carbonaceous Matrices and Electrocatalytic MnO2 Nanopowders on Lithium-Air Battery Performances

    PubMed Central

    Minguzzi, Alessandro; Longoni, Gianluca; Cappelletti, Giuseppe; Pargoletti, Eleonora; Di Bari, Chiara; Locatelli, Cristina; Marelli, Marcello; Rondinini, Sandra; Vertova, Alberto

    2016-01-01

    Here, we report new gas diffusion electrodes (GDEs) prepared by mixing two different pore size carbonaceous matrices and pure and silver-doped manganese dioxide nanopowders, used as electrode supports and electrocatalytic materials, respectively. MnO2 nanoparticles are finely characterized in terms of structural (X-ray powder diffraction (XRPD), energy dispersive X-ray (EDX)), morphological (SEM, high-angle annular dark field (HAADF)-scanning transmission electron microscopy (STEM)/TEM), surface (Brunauer Emmet Teller (BET)-Barrett Joyner Halenda (BJH) method) and electrochemical properties. Two mesoporous carbons, showing diverse surface areas and pore volume distributions, have been employed. The GDE performances are evaluated by chronopotentiometric measurements to highlight the effects induced by the adopted materials. The best combination, hollow core mesoporous shell carbon (HCMSC) with 1.0% Ag-doped hydrothermal MnO2 (M_hydro_1.0%Ag) allows reaching very high specific capacity close to  1400 mAh·g−1. Considerably high charge retention through cycles is also observed, due to the presence of silver as a dopant for the electrocatalytic MnO2 nanoparticles. PMID:28344267

  11. 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.

  12. Optical absorption in air/monolayer MoS2/S (Sdbnd SiO2 or Si) trilayer stacks at oblique incidence

    NASA Astrophysics Data System (ADS)

    Ansari, N.; Moradi, M.

    2017-04-01

    The monolayer MoS2 with strong light-matter interaction and optoelectronic properties is useful to design different optical devices such as photonic absorbers. In this paper, the MoS2 monolayer is sandwiched in the following stacks: SiO2/MoS2/air and Si/MoS2/air to study of increasing optical absorption. We study theoretically the absorption of these stacks as a function of polarization, incident angle and wavelength to reach the maximum value in the visible regime. The absorption intensity reaches to be as high as 65% for internal reflection and s polarization, around the blue wavelength for air/MoS2/SiO2 stack. Absorption behavior including maxima points as a function of wavelength is correlated with imaginary component of refractive index of the monolayer MoS2 except around critical angle. Our results recommend important role of internal and external reflection, cover and substrate layer, angle of incidence and polarization to design elements for optical energy harvesting applications.

  13. Engendering Long-Term Air and Light Stability of a TiO2-Supported Porphyrinic Dye via Atomic Layer Deposition.

    PubMed

    Hoffeditz, William L; Son, Ho-Jin; Pellin, Michael J; Farha, Omar K; Hupp, Joseph T

    2016-12-21

    Organic and porphyrin-based chromophores are prevalent in liquid-junction photovoltaic and photocatalytic solar-cell chemistry; however, their long-term air and light instability may limit their practicality in real world technologies. Here, we describe the protection of a zinc porphyrin dye, adsorbed on nanoparticulate TiO2, from air and light degradation by a protective coating of alumina grown with a previously developed post-treatment atomic layer deposition (ALD) technique. The protective Al2O3 ALD layer is deposited using dimethylaluminum isopropoxide as an Al source; in contrast to the ubiquitous ALD precursor trimethylaluminum, dimethylaluminum isopropoxide does not degrade the zinc porphyrin dye, as confirmed by UV-vis measurements. The growth of this protective ALD layer around the dye can be monitored by an in-reactor quartz crystal microbalance (QCM). Furthermore, greater than 80% of porphyrin light absorption is retained over ∼1 month of exposure to air and light when the protective coating is present, whereas almost complete loss of porphyrin absorption is observed in less than 2 days in the absence of the ALD protective layer. Applying the Al2O3 post-treatment technique to the TiO2-adsorbed dye allows the dye to remain in electronic contact with both the semiconductor surface and a surrounding electrolyte solution, the combination of which makes this technique promising for numerous other electrochemical photovoltaic and photocatalytic applications, especially those involving the dye-sensitized evolution of oxygen.

  14. Improved electrical properties of Ge metal-oxide-semiconductor capacitors with high-k HfO2 gate dielectric by using La2O3 interlayer sputtered with/without N2 ambient

    NASA Astrophysics Data System (ADS)

    Xu, H. X.; Xu, J. P.; Li, C. X.; Lai, P. T.

    2010-07-01

    The electrical properties of n-Ge metal-oxide-semiconductor (MOS) capacitors with HfO2/LaON or HfO2/La2O3 stacked gate dielectric (LaON or La2O3 as interlayer) are investigated. It is found that better electrical performances, including lower interface-state density, smaller gate leakage current, smaller capacitance equivalent thickness, larger k value, and negligible C-V frequency dispersion, can be achieved for the MOS device with LaON interlayer. The involved mechanism lies in that the LaON interlayer can effectively block the interdiffusions of Ge, O, and Hf, thus suppressing the growth of unstable GeOx interlayer and improving the dielectric/Ge interface quality.

  15. Study on the Conductance and Photo-Conductance of ZnO Thin Films at Different Temperatures in Air and N2-Atmosphere

    NASA Astrophysics Data System (ADS)

    Burruel-Ibarra, S. E.; Cruz-Vázquez, C.; Bernal, R.; Aceves, R.; Orante-Barrón, V. R.; Grijalva-Monteverde, H.; Piters, T. M.; Castaño, V. M.

    2016-01-01

    We report the photoconductance of ZnO thin films obtained from thermally treated ZnS films grown by a chemical bath deposition method. The measurements of photo-conductance were performed in an atmosphere of air or nitrogen (N2) at different temperatures between 300 K and 375 K. The augmented conductance after ultraviolet (UV) irradiation (330-380 nm) in air fades away slowly to its original value, whereas in a nitrogen atmosphere, a significant part of the augmented conductance remains. Measurements of electrical conductance as a function of temperature in N2 or air, in the dark or the light, seem to indicate that the donor concentration is increased during the UV irradiation, suggesting that oxygen vacancies and interstitials are created. An alternative model for the photoconduction in ZnO is proposed in which the slow increase of conduction during irradiation is explained by an increase of donors instead of photoelectrons. In this model, the photoelectrons would only play a role in the mechanism of the creation of donors.

  16. Bis(3,5-dimethyl-1H-pyrazole-κN 2)(pyridine-2,6-dicarboxyl­ato-κ3 O 2,N,O 6)copper(II)

    PubMed Central

    Lin, Yuan-Yuan; Yu, Yan-Ping; Liu, Bing-Xin; Zhang, Liang-Jun

    2009-01-01

    In the crystal structure of the title compound, [Cu(C7H3NO4)(C5H8N2)2], the CuII cation assumes a distorted trigonal–bipyramidal coordination geometry formed by a pyridine-2,6-dicarboxyl­ate dianion and two 3,5-dimethyl-1H-pyrazole mol­ecules. N—H⋯O hydrogen bonding is present in the crystal structure. PMID:21582065

  17. Photocatalytic oxidation of methyl ethyl ketone over sol-gel and commercial TiO2 for the improvement of indoor air.

    PubMed

    Raillard, C; Héquet, V; Le Cloirec, P; Legrand, J

    2006-01-01

    This work focuses on the photocatalytic oxidation of gaseous methyl ethyl ketone chosen as a typical indoor air pollutant. Two types of TiO coatings were prepared and deposited on glass plates: one using the commercial Degussa P25 TiO2 and the other one by sol-gel method. The first objective of this study was to compare different ways of preparing thin films of sol-gel TiO2 coated on glass plates, taking into account their general aspect and their photocatalytic efficiency. Several parameters were tested, such as the stabilising agent, the glass type of the support, the number of coatings and the calcination temperature. One of the synthesised materials was then kept to carry out the following study. The study aimed to assess the influence of TiO2 coating types on the effect of water vapour. This was achieved by performing MEK photocatalytic degradation kinetics under two levels of humidity at a fixed temperature. Experimental results were then modelled by the Langmuir-Hinshelwood equation. The obtained parameters gave specific trends in function of the considered catalyst. The second part of this work was to identify MEK degradation byproducts during its photocatalytic oxidation. The main detected intermediate was acetaldehyde, followed by methyl formate. A MEK degradation pathway was then proposed.

  18. Nonhomogeneous surface properties of parylene-C film etched by an atmospheric pressure He/O2 micro-plasma jet in ambient air

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Yang, Bin; Chen, Xiang; Wang, Xiaolin; Yang, Chunsheng; Liu, Jingquan

    2016-10-01

    Surface properties of parylene-C film etched by an atmospheric pressure He/O2 micro-plasma jet in ambient air were investigated. The morphologies and chemical compositions of the etched surface were analyzed by optical microscopy, SEM, EDS, XPS and ATR-FTIR. The microscopy and SEM images showed the etched surface was nonhomogeneous with six discernable ring patterns from the center to the outside domain, which were composed of (I) a central region; (II) an effective etching region, where almost all of the parylene-C film was removed by the plasma jet with only a little residual parylene-C being functionalized with carboxyl groups (Cdbnd O, Osbnd Cdbnd O-); (III) an inner etching boundary; (IV) a middle etching region, where the film surface was smooth and partially removed; (V) an outer etching boundary, where the surface was decorated with clusters of debris, and (VI) a pristine parylene-C film region. The analysis of the different morphologies and chemical compositions illustrated the different localized etching process in the distinct regions. Besides, the influence of O2 flow rate on the surface properties of the etched parylene-C film was also investigated. Higher volume of O2 tended to weaken the nonhomogeneous characteristics of the etched surface and improve the etched surface quality.

  19. Flow-field differences and electromagnetic-field properties of air and N2 inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Yu, Minghao; Yamada, Kazuhiko; Takahashi, Yusuke; Liu, Kai; Zhao, Tong

    2016-12-01

    A numerical model for simulating air and nitrogen inductively coupled plasmas (ICPs) was developed considering thermochemical nonequilibrium and the third-order electron transport properties. A modified far-field electromagnetic model was introduced and tightly coupled with the flow field equations to describe the Joule heating and inductive discharge phenomena. In total, 11 species and 49 chemical reactions of air, which include 5 species and 8 chemical reactions of nitrogen, were employed to model the chemical reaction process. The internal energy transfers among translational, vibrational, rotational, and electronic energy modes of chemical species were taken into account to study thermal nonequilibrium effects. The low-Reynolds number Abe-Kondoh-Nagano k-ɛ turbulence model was employed to consider the turbulent heat transfer. In this study, the fundamental characteristics of an ICP flow, such as the weak ionization, high temperature but low velocity in the torch, and wide area of the plasma plume, were reproduced by the developed numerical model. The flow field differences between the air and nitrogen ICP flows inside the 10-kW ICP wind tunnel were made clear. The interactions between the electromagnetic and flow fields were also revealed for an inductive discharge.

  20. Air annealing effects on the optical properties of ZnO SnO2 thin films deposited by a filtered vacuum arc deposition system

    NASA Astrophysics Data System (ADS)

    Çetinörgü, E.; Goldsmith, S.; Boxman, R. L.

    2006-03-01

    ZnO-SnO2 transparent and conducting thin films were deposited on microscope glass substrates by a filtered vacuum arc deposition (FVAD) system. The cathode was prepared with 50%:50% atomic concentration of Zn:Sn. The films were annealed in air at 500 °C for 1 h. Structural and compositional analyses were obtained using XRD and XPS diagnostics. X-ray diffraction analysis indicated that as-deposited and air-annealed thin ZnO-SnO2 films were amorphous. The atomic ratio of Zn to Sn in the film obtained using the 50%:50% cathode as determined by XPS analysis was ~2.7:1 in the bulk film. The optical properties were determined from normal incidence transmission measurements. Film transmission in the visible was 70% to 90%, affected by interference effects. Annealed films did not show higher transmission in the VIS compared to as-deposited films. Assuming that the interband electron transition is direct, the optical band gap was found to be in the range 3.34-3.61 eV for both as-deposited and annealed films. However, the average Eg for annealed films was 3.6 eV, larger by 0.2 eV than that of as-deposited. The refractive index n increased while the extinction index k decreased significantly with annealing.

  1. 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)

  2. 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.

  3. Fundamental understanding of the thermal degradation mechanisms of waste tires and their air pollutant generation in a N2 atmosphere.

    PubMed

    Kwon, Eilhann; Castaldi, Marco J

    2009-08-01

    The thermal decomposition of waste tires has been characterized via thermo-gravimetric analysis (TGA) tests, and significant mass loss has been observed between 300 and 500 degrees C. A series of gas chromatography-mass spectrometer (GC-MS) measurements, in which the instrument was coupled to a TGA unit, have been carried out to investigate the thermal degradation mechanisms as well as the air pollutant generation including volatile organic carbons (VOCs) and polycyclic aromatic hydrocarbons (PAHs) in a nitrogen atmosphere. In order to understand fundamental information on the thermal degradation mechanisms of waste tires, the main constituents of tires, poly-isoprene rubber (IR) and styrene butadiene rubber (SBR), have been studied under the same conditions. All of the experimental work indicated that the bond scission on each monomer of the main constituents of tires was followed by hydrogenation and gas phase reactions. This helped to clarify the independent pathways and species attributable to IR and SBR during the pyrolysis process. To extend that understanding to a more practical level, a flow-through reactor was used to test waste tire, SBR and IR samples in the temperature range of 500-800 degrees C at a heating rate of approximately 200 degrees C. Lastly, the formation of VOCs (approximately 1-50 PPMV/10 mg of sample) and PAHs (approximately 0.2-7 PPMV/10 mg of sample) was observed at relatively low temperatures compared to conventional fuels, and its quantified concentration was significantly high due to the chemical structure of SBR and IR. The measurement of chemicals released during pyrolysis suggests not only a methodology for reducing the air pollutants but also the feasibility of petrochemical recovery during thermal treatment.

  4. 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.

  5. 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.

  6. 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.

  7. Influence of Enhanced O2 Provision on the Discharge Performance of Li-air Batteries by Incorporating Fluoroether.

    PubMed

    Wan, Hao; Mao, Ya; Liu, Zixuan; Bai, Qingyou; Peng, Zhe; Bao, Jingjing; Wu, Gang; Liu, Yang; Wang, Deyu; Xie, Jingying

    2017-01-29

    As the first step during discharge, the mass transfer of oxygen should play a crucial role in Li-air batteries to tailor the growth of discharge products, however, not enough attention has been paid to this issue. Herein, we introduce an oxygen-enriching cosolvent, 1,2-(1,1,2,2-tetrafluoroethoxy) ethane (FE1), into the electrolyte, and investigate its influence on the discharge performance. The incorporation of this novel cosolvent consistently enhances the oxygen solubility of the electrolyte, and improves the oxygen diffusivity following a volcano-shape trend peaking at 50 % FE1. It is interesting that the discharge capacities obtained with the investigated electrolytes share the similar volcano trends as the oxygen transport under 50 mA gcarbon(-1) and higher current densities. The improved oxygen diffusion could benefit the volumetric utilization of the air cathode, especially at the separator side, probably owing to the fast oxygen transport to moderate its concentration gradient. Our results demonstrate the importance of oxygen provision, which easily becomes the capacity-determining factor.

  8. 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.

  9. Removal of organic dye by air and macroporous ZnO/MoO3/SiO2 hybrid under room conditions

    NASA Astrophysics Data System (ADS)

    Yuan, Mengjia; Wang, Shengtian; Wang, Xiaohong; Zhao, Lingling; Hao, Tianhong

    2011-07-01

    A new macroporous ZnO/MoO3/SiO2 hybrid was synthesized by a method involving sol-gel technology and biomimetic synthesis. It was characterized by Elemental analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS) and scanning electron microscopy (SEM). Chemical degradation of 0.3 g/L Safranin T (ST) by air oxidation over macroporous ZnO/MoO3/SiO2 hybrid was studied. It was found that the decolorization efficiency and the chemical oxygen demand (COD) removal of ST reached above 95.3% and 93.2%, respectively, within 25 min at room temperature and atmospheric pressure. And the organic pollutant was mineralized to simple inorganic species such as HCO3-, Cl- and NO3-, while the total organic carbon (TOC) decreased 95.4%. The structure and morphology of the catalyst were still stable after six cycling runs and the leaching test showed negligible leaching effect.

  10. 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.

  11. 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

  12. Photochemistry of the indoor air pollutant acetone on Degussa P25 TiO2 studied by chemical ionization mass spectrometry.

    PubMed

    Schmidt, Catherine M; Buchbinder, Avram M; Weitz, Eric; Geiger, Franz M

    2007-12-20

    We have used chemical ionization mass spectrometry (CIMS) to study the adsorption and photochemistry of several oxygenated organic species adsorbed to Degussa P25 TiO2, an inexpensive catalyst that can be used to mineralize volatile organic compounds. The molecules examined in this work include the common indoor air pollutant acetone and several of its homologs and possible oxidation and condensation products that may be formed during the adsorption and/or photocatalytic degradation of acetone on titanium dioxide catalysts. We report nonreactive uptake coefficients for acetone, formic acid, acetic acid, mesityl oxide, and diacetone alcohol, and results from photochemical studies that quantify, on a per-molecule basis, the room-temperature photocatalytic conversion of the species under investigation to CO2 and related oxidation products. The data presented here imply that catalytic surfaces that enhance formate and acetate production from acetone precursors will facilitate the photocatalytic remediation of acetone in indoor environments, even at room temperature.

  13. 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.

  14. Influence of velocity effects on the shape of N2 (and air) broadened H2O lines revisited with classical molecular dynamics simulations.

    PubMed

    Ngo, N H; Tran, H; Gamache, R R; Bermejo, D; Domenech, J-L

    2012-08-14

    The modeling of the shape of H(2)O lines perturbed by N(2) (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)], 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 H(2)O broadened by N(2) (and air) in the ν(3) and 2ν(1) + ν(2) + ν(3) 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.

  15. Volume properties and refraction of aqueous solutions of bisadducts of light fullerene C60 and essential amino acids lysine, threonine, and oxyproline (C60(C6H13N2O2)2, C60(C4H8NO3)2, and C60(C5H9NO2)2) at 25°C

    NASA Astrophysics Data System (ADS)

    Semenov, K. N.; Ivanova, N. M.; Charykov, N. A.; Keskinov, V. A.; Kalacheva, S. S.; Duryagina, N. N.; Garamova, P. V.; Kulenova, N. A.; Nabieva, A.

    2017-02-01

    Concentration dependences of the density of aqueous solutions of bisadducts of light fullerene C60 and essential amino acids are studied by pycnometry. Concentration dependences of the average molar volumes and partial volumes of components (H2O and corresponding bisadducts) are calculated for C60(C6H13N2O2)2-H2O, C60(C4H8NO3)2-H2O, and C60(C5H9NO2)2-H2O binary systems at 25°C. Concentration dependences of the indices of refraction of C60(C6H13N2O2)2-H2O, C60(C4H8NO3)2-H2O, and C60(C5H9NO2)2-H2O binary systems are determined at 25°C. The concentration dependences of specific refraction and molar refraction of bisadducts and aqueous solutions of them are calculated.

  16. 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

  17. 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

  18. A Pleistocene ice core record of atmospheric O2 concentrations

    NASA Astrophysics Data System (ADS)

    Stolper, D. A.; Bender, M. L.; Dreyfus, G. B.; Yan, Y.; Higgins, J. A.

    2016-09-01

    The history of atmospheric O2 partial pressures (PO2) is inextricably linked to the coevolution of life and Earth’s biogeochemical cycles. Reconstructions of past PO2 rely on models and proxies but often markedly disagree. We present a record of PO2 reconstructed using O2/N2 ratios from ancient air trapped in ice. This record indicates that PO2 declined by 7 per mil (0.7%) over the past 800,000 years, requiring that O2 sinks were ~2% larger than sources. This decline is consistent with changes in burial and weathering fluxes of organic carbon and pyrite driven by either Neogene cooling or increasing Pleistocene erosion rates. The 800,000-year record of steady average carbon dioxide partial pressures (PCO2) but declining PO2 provides distinctive evidence that a silicate weathering feedback stabilizes PCO2 on million-year time scales.

  19. 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.

  20. 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.

  1. Photocatalytic degradation of humic acid in saline waters. Part 1. Artificial seawater: influence of TiO2, temperature, pH, and air-flow.

    PubMed

    Al-Rasheed, Radwan; Cardin, David J

    2003-06-01

    We report the first systematic study on the photocatalytic oxidation of humic acid (HA) in artificial seawater (ASW). TiO(2) (Degussa P25) dispersions were used as the catalyst with irradiation from a medium-pressure mercury lamp. The optimum quantity of catalyst was found to be between 2 and 2.5 gl(-1); while the decomposition was fastest at low pH values (pH 4.5 in the range examined), and the optimum air-flow, using an immersion well reactor with a capacity of 400 ml, was 850 ml min(-1). Reactivity increased with air-flow up to this figure, above which foaming prevented operation of the reactor. Using pure oxygen, an optimal flow rate was observed at 300 ml min(-1), above which reactivity remains essentially constant. Following treatment for 1 h, low-salinity water (2700 mg l(-1)) was completely mineralised, whereas ASW (46000 mg l(-1)) had traces of HA remaining. These effects are interpreted and kinetic data presented. To avoid problems of precipitation due to change of ionic strength humic substances were prepared directly in ASW, and the effects of ASW on catalyst suspension and precipitation have been taken into account. The Langmuir-Hinshelwood kinetic model has been shown to be followed only approximately for the catalytic oxidation of HA in ASW. The activation energy for the reaction derived from an Arrhenius treatment was 17 (+/-0.6) kJ mol(-1).

  2. 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.

  3. Insights on the High-Temperature Operational Limits of ZrO2-Y2O3 TBCs Manufactured via Air Plasma Spray

    NASA Astrophysics Data System (ADS)

    Lima, Rogerio S.; Marple, Basil R.

    2017-02-01

    The effective high-temperature operation limit of a ZrO2-7-8 wt.%Y2O3 (YSZ) thermal barrier coating (TBC) manufactured via air plasma spray (APS) is considered to be 1300 °C. This is related to the metastable tetragonal t'-phase formed during the rapid quenching of the YSZ particles during spraying. The t'-phase transforms into the equilibrium tetragonal and cubic phases at temperatures ≥ 1300 °C, which can lead to the formation of the monoclinic phase of YSZ upon cooling to room temperature. This formation of the monoclinic phase is accompanied by a volume expansion that leads to TBC failure due to extensive micro-cracking. To further investigate this limitation, an APS YSZ TBC was sprayed on a CMSX-4 substrate. By using a thermal (laser) gradient cyclic testing, a temperature gradient was generated across the TBC/substrate system. The YSZ T-front and substrate backside T-back temperature levels were 1500 and 1000 °C, respectively. In cycle conditions (5-min or 1-h hot and 2-min cool), no TBC failure has been observed. This behavior was partially attributed to the unexpected absence of the monoclinic phase of the YSZ in the cycled coatings. Although preliminary, these results are promising regarding increasing the effective high-temperature operational limits of APS YSZ TBCs.

  4. 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.

  5. Interaction of the indoor air pollutant acetone with Degussa P25 TiO2 studied by chemical ionization mass spectrometry.

    PubMed

    Schmidt, Catherine M; Weitz, Eric; Geiger, Franz M

    2006-11-07

    Preventing a build-up of indoor pollutant concentrations has emerged as a major goal in environmental chemistry. Here, we have applied chemical ionization mass spectrometry to study the interaction of acetone, a common indoor air pollutant, with Degussa P25 TiO2, an inexpensive catalyst that is widely used for the degradation of volatile organic compounds into CO2 and water. To better understand the adsorption of acetone onto Degussa P25, the necessary first step for its degradation, the experiments were carried out at room temperature in the absence of UV light. This allowed for the deconvolution of the nonreactive and reactive thermal binding processes on Degussa P25 at acetone partial pressures (10(-7)-10(-4) Torr) commonly found in indoor environments. On average, 30% of the adsorbed acetone is bound irreversibly, resulting in a surface coverage of irreversibly bound acetone of approximately 1 x 10(12) molecules/cm2 at 3-4 x 10(-5) Torr. Equilibrium and dynamic experiments yield a sticking coefficient of approximately 1 x 10(-4) that is independent of the acetone partial pressures examined here. Equilibrium binding constants and free energies of adsorption are reported.

  6. Insights on the High-Temperature Operational Limits of ZrO2-Y2O3 TBCs Manufactured via Air Plasma Spray

    NASA Astrophysics Data System (ADS)

    Lima, Rogerio S.; Marple, Basil R.

    2017-03-01

    The effective high-temperature operation limit of a ZrO2-7-8 wt.%Y2O3 (YSZ) thermal barrier coating (TBC) manufactured via air plasma spray (APS) is considered to be 1300 °C. This is related to the metastable tetragonal t'-phase formed during the rapid quenching of the YSZ particles during spraying. The t'-phase transforms into the equilibrium tetragonal and cubic phases at temperatures ≥ 1300 °C, which can lead to the formation of the monoclinic phase of YSZ upon cooling to room temperature. This formation of the monoclinic phase is accompanied by a volume expansion that leads to TBC failure due to extensive micro-cracking. To further investigate this limitation, an APS YSZ TBC was sprayed on a CMSX-4 substrate. By using a thermal (laser) gradient cyclic testing, a temperature gradient was generated across the TBC/substrate system. The YSZ T- front and substrate backside T- back temperature levels were 1500 and 1000 °C, respectively. In cycle conditions (5-min or 1-h hot and 2-min cool), no TBC failure has been observed. This behavior was partially attributed to the unexpected absence of the monoclinic phase of the YSZ in the cycled coatings. Although preliminary, these results are promising regarding increasing the effective high-temperature operational limits of APS YSZ TBCs.

  7. 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.

  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.

  9. Self-assembly formation of Bi-functional Co3O4/MnO2-CNTs hybrid catalysts for achieving both high energy/power density and cyclic ability of rechargeable zinc-air battery.

    PubMed

    Xu, Nengneng; Liu, Yuyu; Zhang, Xia; Li, Xuemei; Li, Aijun; Qiao, Jinli; Zhang, Jiujun

    2016-09-20

    α-MnO2 nanotubes-supported Co3O4 (Co3O4/MnO2) and its carbon nanotubes (CNTs)-hybrids (Co3O4/MnO2-CNTs) have been successfully developed through a facile two-pot precipitation reaction and hydrothermal process, which exhibit the superior bi-functional catalytic activity for both ORR and OER. The high performance is believed to be induced by the hybrid effect among MnO2 nanotubes, hollow Co3O4 and CNTs, which can produce a synergetic enhancement. When integrated into the practical primary and electrochemically rechargeable Zn-air batteries, such a hybrid catalyst can give a discharge peak power density as high as 450 mW cm(-2). At 1.0 V of cell voltage, a current density of 324 mA cm(-2) is achieved. This performance is superior to all reported non-precious metal catalysts in literature for zinc-air batteries and significantly outperforms the state-of-the-art platinum-based catalyst. Particularly, the rechargeable Zn-air battery can be fabricated into all-solid-state one through a simple solid-state approach, which exhibits an excellent peak power density of 62 mW cm(-2), and the charge and discharge potentials remain virtually unchanged during the overall cycles, which is comparable to the one with liquid electrolyte.

  10. Self-assembly formation of Bi-functional Co3O4/MnO2-CNTs hybrid catalysts for achieving both high energy/power density and cyclic ability of rechargeable zinc-air battery

    PubMed Central

    Xu, Nengneng; Liu, Yuyu; Zhang, Xia; Li, Xuemei; Li, Aijun; Qiao, Jinli; Zhang, Jiujun

    2016-01-01

    α-MnO2 nanotubes-supported Co3O4 (Co3O4/MnO2) and its carbon nanotubes (CNTs)-hybrids (Co3O4/MnO2-CNTs) have been successfully developed through a facile two-pot precipitation reaction and hydrothermal process, which exhibit the superior bi-functional catalytic activity for both ORR and OER. The high performance is believed to be induced by the hybrid effect among MnO2 nanotubes, hollow Co3O4 and CNTs, which can produce a synergetic enhancement. When integrated into the practical primary and electrochemically rechargeable Zn-air batteries, such a hybrid catalyst can give a discharge peak power density as high as 450 mW cm−2. At 1.0 V of cell voltage, a current density of 324 mA cm−2 is achieved. This performance is superior to all reported non-precious metal catalysts in literature for zinc-air batteries and significantly outperforms the state-of-the-art platinum-based catalyst. Particularly, the rechargeable Zn-air battery can be fabricated into all-solid-state one through a simple solid-state approach, which exhibits an excellent peak power density of 62 mW cm−2, and the charge and discharge potentials remain virtually unchanged during the overall cycles, which is comparable to the one with liquid electrolyte. PMID:27646032

  11. Self-assembly formation of Bi-functional Co3O4/MnO2-CNTs hybrid catalysts for achieving both high energy/power density and cyclic ability of rechargeable zinc-air battery

    NASA Astrophysics Data System (ADS)

    Xu, Nengneng; Liu, Yuyu; Zhang, Xia; Li, Xuemei; Li, Aijun; Qiao, Jinli; Zhang, Jiujun

    2016-09-01

    α-MnO2 nanotubes-supported Co3O4 (Co3O4/MnO2) and its carbon nanotubes (CNTs)-hybrids (Co3O4/MnO2-CNTs) have been successfully developed through a facile two-pot precipitation reaction and hydrothermal process, which exhibit the superior bi-functional catalytic activity for both ORR and OER. The high performance is believed to be induced by the hybrid effect among MnO2 nanotubes, hollow Co3O4 and CNTs, which can produce a synergetic enhancement. When integrated into the practical primary and electrochemically rechargeable Zn-air batteries, such a hybrid catalyst can give a discharge peak power density as high as 450 mW cm‑2. At 1.0 V of cell voltage, a current density of 324 mA cm‑2 is achieved. This performance is superior to all reported non-precious metal catalysts in literature for zinc-air batteries and significantly outperforms the state-of-the-art platinum-based catalyst. Particularly, the rechargeable Zn-air battery can be fabricated into all-solid-state one through a simple solid-state approach, which exhibits an excellent peak power density of 62 mW cm‑2, and the charge and discharge potentials remain virtually unchanged during the overall cycles, which is comparable to the one with liquid electrolyte.

  12. Fabrication of Bi2O3/TiO2 nanocomposites and their applications to the degradation of pollutants in air and water under visible-light.

    PubMed

    Chakraborty, Ashok Kumar; Hossain, Md Emran; Rhaman, Md Masudur; Sobahan, K M A

    2014-02-01

    A nanoheterojunction composite photocatalyst Bi2O3/TiO2 working under visible-light (lambda > or = 420 nm) was prepared by combining two semiconductors Bi2O3 and TiO2 varying the Bi2O3/TiO2 molar ratio. Maleic acid was employed as an organic binder to unite Bi2O3 and TiO2 nanoparticles. The SEM, TEM, XRD and diffuse reflectance spectra were utilized to characterize the prepared Bi2O3/TiO2 nanoheterojunction. The nanocomposite exhibited unusual high photocatalytic activity in decomposing 2-propanol in gas phase and phenol in aqueous phase and, evolution of CO2 under visible light irradiation while the end members exhibited low photocatalytic activity. The composite was optimized to 5 mol% Bi2O3/TiO2. The remarkable high photocatalytic efficiency originates from the unique relative energy band position of Bi2O3 and TiO2 as well as the absorption of visible light by Bi2O3.

  13. 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

  14. Computation provides chemical insight into the diverse hydride NMR chemical shifts of [Ru(NHC)4(L)H](0/+) species (NHC = N-heterocyclic carbene; L = vacant, H2, N2, CO, MeCN, O2, P4, SO2, H(-), F(-) and Cl(-)) and their [Ru(R2PCH2CH2PR2)2(L)H](+) congeners.

    PubMed

    Häller, L Jonas L; Mas-Marzá, Elena; Cybulski, Mateusz K; Sanguramath, Rajashekharayya A; Macgregor, Stuart A; Mahon, Mary F; Raynaud, Christophe; Russell, Christopher A; Whittlesey, Michael K

    2017-02-28

    Relativistic density functional theory calculations, both with and without the effects of spin-orbit coupling, have been employed to model hydride NMR chemical shifts for a series of [Ru(NHC)4(L)H](0/+) species (NHC = N-heterocyclic carbene; L = vacant, H2, N2, CO, MeCN, O2, P4, SO2, H(-), F(-) and Cl(-)), as well as selected phosphine analogues [Ru(R2PCH2CH2PR2)2(L)H](+) (R = (i)Pr, Cy; L = vacant, O2). Inclusion of spin-orbit coupling provides good agreement with the experimental data. For the NHC systems large variations in hydride chemical shift are shown to arise from the paramagnetic term, with high net shielding (L = vacant, Cl(-), F(-)) being reinforced by the contribution from spin-orbit coupling. Natural chemical shift analysis highlights the major orbital contributions to the paramagnetic term and rationalizes trends via changes in the energies of the occupied Ru dπ orbitals and the unoccupied σ*Ru-H orbital. In [Ru(NHC)4(η(2)-O2)H](+) a δ-interaction with the O2 ligand results in a low-lying LUMO of dπ character. As a result this orbital can no longer contribute to the paramagnetic shielding, but instead provides additional deshielding via overlap with the remaining (occupied) dπ orbital under the Lz angular momentum operator. These two effects account for the unusual hydride chemical shift of +4.8 ppm observed experimentally for this species. Calculations reproduce hydride chemical shift data observed for [Ru((i)Pr2PCH2CH2P(i)Pr2)2(η(2)-O2)H](+) (δ = -6.2 ppm) and [Ru(R2PCH2CH2PR2)2H](+) (ca. -32 ppm, R = (i)Pr, Cy). For the latter, the presence of a weak agostic interaction trans to the hydride ligand is significant, as in its absence (R = Me) calculations predict a chemical shift of -41 ppm, similar to the [Ru(NHC)4H](+) analogues. Depending on the strength of the agostic interaction a variation of up to 18 ppm in hydride chemical shift is possible and this factor (that is not necessarily readily detected experimentally) can aid in the

  15. Partial oxidation of methanol catalyzed with Au/TiO2, Au/ZrO2 and Au/ZrO2-TiO2 catalysts

    NASA Astrophysics Data System (ADS)

    Hernández-Ramírez, E.; Wang, J. A.; Chen, L. F.; Valenzuela, M. A.; Dalai, A. K.

    2017-03-01

    Mesoporous TiO2, ZrO2 and ZrO2-TiO2 mixed oxides were synthesized by the sol-gel method and the Au/TiO2, Au/ZrO2 and Au/ZrO2-TiO2 catalysts were prepared by deposition-precipitation method using urea solution as a precipitating agent. These materials were characterized by UV-vis spectroscopy, X-ray diffraction (XRD), N2 adsorption-desorption isotherms, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and in situ FTIR-pyridine (FTIR-Py) adsorption. XRD patterns of the samples confirmed the formation of ZrTiO4 phase in the ZrO2-TiO2 mixed oxides. TEM micrographs showed that nanosized gold particles on the catalyst had an average diameter smaller than 5 nm. Metallic gold (Au0) and oxidized Au species (Aunδ+) on the surface of the catalysts were evidenced by UV-vis and XPS characterization. In the partial oxidation of methanol (POM) reaction, among the six catalysts, the high metallic Au0/Au+ ratio and low surface acidity in the Au/ZrO2 catalysts are chiefly responsible for the highest hydrogen production rate in the whole temperature range between 210 and 300 °C. Methanol decomposition as secondary reaction was favored on TiO2-based catalysts at higher temperature, producing a large amount of CO. Formation of ZrO2-TiO2 solid solution resulted in generation of both Brønsted and Lewis acid sites; as a result, dehydrogenation and oxidative dehydrogenation of methanol was allowed over Au/ZrO2-TiO2 catalysts.

  16. Probing the Self-Assembly Mechanism of Lanthanide-Containing Sandwich-Type Silicotungstates [{Ln(H2O)n}2{Mn4(B-α-SiW9O34)2(H2O)2}](6-) Using Time-Resolved Mass Spectrometry and X-ray Crystallography.

    PubMed

    Fan, Lin-Yuan; Lin, Zheng-Guo; Cao, Jie; Hu, Chang-Wen

    2016-03-21

    The reaction of [γ-SiW10O36](8-) with Mn(2+) and Ln(3+) in an aqueous solution led to the isolation of a series of new lanthanide-containing sandwich-type polyoxometalates (POMs) [{Ln(H2O)n}2{Mn4(B-α-SiW9O34)2(H2O)2}](6-) (1-5a) (Ln = La (1), Nd (2), Gd (3), Dy (4), Er (5); n = 5, 6), which crystallize in the space groups C2/c with a = 33.0900(2)-32.9838(15) Å, b = 12.8044(10)-12.7526(6) Å, c = 22.8273(17)-22.6368(11) Å, V = 9669.2(12)-9519.7(8) Å(3), Z = 2 (1, 2); P1̅ with a = 11.9502(4)-11.8447(6) Å, b = 13.2203(4)-13.1164(5) Å, c = 15.8291(5)-15.8524(7) Å, V = 2221.25(13)-2189.95(18) Å(3), Z = 1 (3, 4, 5), respectively. X-ray diffraction analysis reveals that they consist of two-dimensional networks based on a sandwich-type polyanion [Mn4(B-α-SiW9O34)2(H2O)2](12-) (6a, {Mn4(SiW9)2}) and lanthanide cations (Ln(3+)), which are further connected into three-dimensional frameworks by potassium cations for 3, 4, and 5. The unprecedented combination of time-resolved electrospray ionization mass spectrometry (ESI-MS) studies and X-ray crystallography allows us not only to directly observe the in-solution rearrangement of divant anion [γ-SiW10O36](8-) into the sandwich-type POM 6a via an intermediate species [Mn3(B-β-SiW8O30(OH))(B-β-SiW9O33(OH))(H2O)](12-) (7a, {Mn3(SiW8)(SiW9)}) from ESI-MS results, but also to gain the solid-state structures of intermediate and final product isolated from reaction solutions from X-ray crystallography results, from which the self-assembly mechanism of the lanthanide-containing sandwich-type POMs 1-5a was proposed.

  17. 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.

  18. 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…

  19. Novel MoO2/carbon hierarchical nano/microcomposites: synthesis, characterization, solid state transformations and thiophene HDS activity.

    PubMed

    Avendaño, Carlos; Briceño, Alexander; Méndez, Franklin J; Brito, Joaquín L; González, Gema; Cañizales, Edgar; Atencio, Reinaldo; Dieudonné, Philippe

    2013-02-28

    Novel MoO(2)/C nano/microcomposites were prepared via a bottom-up approach by hydrothermal carbonization of a solution of glucose as a carbon precursor in the presence of polyoxometalates (POMs: phosphomolybdic acid [H(3)PMo(12)O(40)] and ammonium heptamolybdate tetrahydrate [(NH(4))(6)Mo(7)O(24)]·4H(2)O). The structural characterization by FT-IR, XRPD, SEM and TEM analyses revealed the controlled formation of hierarchical MoO(2)/C composites with different morphologies: strawberry-like, based on carbon microspheres decorated with MoO(2) nanoparticles; MoO(2)/C core-shell composites; and irregular aggregates in combination with ring-like microstructures bearing amorphous Mo species. These composites can be fine-tuned by varying reaction time, glucose/POM ratio and type of POM precursor. Subsequent transformations in the solid state through calcinations of MoO(2)/C core-shell composites in air lead to hollow nanostructured molybdenum trioxide microspheres together with nanorods and plate microcrystals or cauliflower-like composites (MoO(2)/C). In addition, the MoO(2)/C composite undergoes a morphology evolution to urchin-like composites when it is calcined under nitrogen atmosphere (MoO(2)/C-N(2)). The MoO(2)/C strawberry-like and MoO(2)/C-N(2) composites were transformed into Mo carbide and nitride supported on carbon microspheres (Mo(2)C/C, MoN/C, and MoN/C-N(2)). These phases were tested as precursors in thiophene hydrodesulphurization (HDS) at 400 °C, observing the following trend in relation to the thiophene steady-state conversion: MoN/C-N(2) > MoN/C > Mo(2)C/C > MoO(2)/C-N(2) > MoO(2)/C. According to these conversion values, a direct correlation was observed between higher HDS activity and decreasing crystal size as estimated from the Scherrer equation. These results suggest that such composites represent interesting and promising precursors for HDS catalysts, where the activity and stability can be modified either by chemical or structural changes of the

  20. Isolation of H5N6, H7N9 and H9N2 avian influenza A viruses from air sampled at live poultry markets in China, 2014 and 2015

    PubMed Central

    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

    2016-01-01

    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

  1. 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.

  2. Experimental studies on the extinction of hydrogen-air counterflow diffusion flames

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    The paper presents data on the extinction of hydrogen-air counterflow diffusion flames (CFDFs). In the experiments, five coaxial tubular opposed jet burners were used to form dish-shaped CFDFs, centered by opposing laminar jets of N2-diluted H2 and both clean and contaminated air in the argon-purged chamber at 1 atm. Air jet velocities, U(air), characterized extinction of the air-side flame (blowoff) as functions of input H2/N2 (20-100 mole pct) on the fuel side, and air contaminant (0-20 percent) steam, CO2 and O2 (16-30 percent) on the air side.

  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. 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.

  5. Synthesis cathode material LiNi0.80Co0.15Al0.05O2 with two step solid-state method under air stream

    NASA Astrophysics Data System (ADS)

    Xia, Shubiao; Zhang, Yingjie; Dong, Peng; Zhang, Yannan

    2014-01-01

    A facile generic strategy of solid-state reaction under air atmosphere is employed to prepare LiNi0.8Co0.15Al0.05O2 layer structure micro-sphere as cathodes for Li-ion batteries. The impurity phase has been eliminated wholly without changing the R-3m space group of LiNi0.8Co0.15Al0.05O2. The electrochemical performance of LiNi0.8Co0.15Al0.05O2 cathodes depend on the sintering step, temperature, particle size and uniformity. The sample pre-sintered at 540 °C for 12 h and then sintered at 720 °C for 28 h exhibits the best electrochemical performance, which delivers a reversible capacity of 180.4, 165.8, 154.7 and 135.6 mAhg-1 at 0.2 C, 1 C, 2 C and 5 C, respectively. The capacity retention keeps over 87% after 76 cycles at 1 C. This method is simple, cheap and mass-productive, and thus suitable to large scale production of NCA cathodes directly used for lithium ion batteries.

  6. 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.

  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. Cavity Ring Down Absorption of O2 in Air as a Temperature Sensor for an Open and a Cryogenic Optical Cavity.

    PubMed

    Nyaupane, Parashu R; Perez-Delgado, Yasnahir; Camejo, David; Wright, Lesley M; Manzanares, Carlos E

    2016-06-30

    The A-band of oxygen has been measured at low resolution at temperatures between 90 K and 373 K using the phase shift cavity ring down (PS-CRD) technique. For temperatures between 90 K and 295 K, the PS-CRD technique presented here involves an optical cavity attached to a cryostat. The static cell and mirrors of the optical cavity are all inside a vacuum chamber at the same temperature of the cryostat. The temperature of the cell can be changed between 77 K and 295 K. For temperatures above 295 K, a hollow glass cylindrical tube without windows has been inserted inside an optical cavity to measure the temperature of air flowing through the tube. The cavity consists of two highly reflective mirrors which are mounted parallel to each other and separated by a distance of 93 cm. In this experiment, air is passed through a heated tube. The temperature of the air flowing through the tube is determined by measuring the intensity of the oxygen absorption as a function of the wavenumber. The A-band of oxygen is measured between 298 K and 373 K, with several air flow rates. To obtain the temperature, the energy of the lower rotational state for seven selected rotational transitions is linearly fitted to a logarithmic function that contains the relative intensity of the rotational transition, the initial and final rotational quantum numbers, and the energy of the transition. Accuracy of the temperature measurement is determined by comparing the calculated temperature from the spectra with the temperature obtained from a calibrated thermocouple inserted at the center of the tube. This flowing air temperature sensor will be used to measure the temperatures of cooling air at the input (cold air) and output (hot air) after cooling the blades of a laboratory gas turbine. The results could contribute to improvements in turbine blade cooling design.

  9. Thermal and sonochemical synthesis of porous (Ce,Zr)O2 mixed oxides from metal β-diketonate precursors and their catalytic activity in wet air oxidation process of formic acid.

    PubMed

    Cau, Camille; Guari, Yannick; Chave, Tony; Larionova, Joulia; Nikitenko, Sergey I

    2014-07-01

    Porous (Ce0.5Zr0.5)O2 solid solutions were prepared by thermolysis (T=285 °C) or sonolysis (20 kHz, I=32 W cm(-2), Pac=0.46 W mL(-1), T=200 °C) of Ce(III) and Zr(IV) acetylacetonates in oleylamine or hexadecylamine under argon followed by heat treatment of the precipitates obtained in air at 450 °C. Transmission Electron Microscopy images of the samples show nanoparticles of ca. 4-6 nm for the two synthetic approaches. The powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and μ-Raman spectroscopy of solids obtained after heat treatment indicate the formation of (Ce0.5Zr0.5)O2 solid solutions with a metastable tetragonal crystal structure for the two synthetic routes. The specific surface area of the samples varies between 78 and 149 m(2) g(-1) depending on synthesis conditions. The use of Barrett-Joyner-Halenda and t-plot methods reveal the formation of mixed oxides with a hybrid morphology that combines mesoporosity and microporosity regardless of the method of preparation. Platinum nanoparticles were deposited on the surface of the mixed oxides by sonochemical reduction of Pt(IV). It was found that the materials prepared by sonochemistry exhibit better resistance to dissolution during the deposition process of platinum. X-ray photoelectron spectroscopy analysis shows the presence of Pt(0) and Pt(II) on the surface of mixed oxides. Porous (Ce0.5Zr0.5)O2 mixed oxides loaded with 1.5%wt. platinum exhibit high activity in catalytic wet air oxidation of formic acid at 40 °C.

  10. 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.

  11. Kinetics of HO2 + HO2 -> H2O2 + O2: Implications for Stratospheric H2O2

    NASA Astrophysics Data System (ADS)

    Christensen, L. E.; Okumura, M.; Sander, S. P.; Salawitch, R. J.; Toon, G. C.; Sen, B.; Blavier, J.-F.; Jucks, K. W.

    2002-05-01

    The reaction HO2 + HO2 -> H2O2 + O2(1) has been studied at 100 Torr and 222 K to 295 K. Experiments employing photolysis of Cl2/CH3OH/O2/N2 and F2/H2/O2/N2 gas mixtures to produce HO2 confirmed that methanol enhanced the observed reaction rate. At 100 Torr, zero methanol, k1 = (8.8 +/- 0.9) 10-13 × exp[(210 +/- 26)/T] cm3 molecule-1 s-1 (2σ uncertainties), which agrees with current recommendations at 295 K but is nearly 2 times slower at 231 K. The general expression for k1, which includes the dependence on bath gas density, is k1 = (1.5 +/- 0.2) × 10-12 × exp[(19 +/- 31)/T] + 1.7 × 10-33 × [M] × exp[1000/T], where the second term is taken from the JPL00-3 recommendation. The revised rate largely accounts for a discrepancy between modeled and measured [H2O2] in the lower to middle stratosphere.

  12. The remarkable effect of oxygen on the N2 selectivity of water catalytic denitrification by hydrogen.

    PubMed

    Constantinou, Costas L; Costa, Costas N; Efstathiou, Angelos M

    2007-02-01

    The selective catalytic reduction of nitrates (NO3-) in pure water toward N2 formation by the use of gaseous H2 and in the presence of O2 (air) at 1 atm total pressure and 25 degrees C has been investigated over Pd-Cu supported on various mixed metal oxides, x wt % MO(x(/gamma-Al2O3 (MO(x) = CeO2, SrO, Mn2O3, Cr2O3, Y2O3, and TiO2). It is demonstrated for the firsttime that a remarkable improvement in N2 reaction selectivity (by 80 percentage units) can be achieved when oxygen is present in the reducing feed gas stream. In particular, significantly lower reaction selectivities toward NH4+ and NO2- can be obtained, whereas the rate of NO3- conversion is not significantly affected. Moreover, it was shown thatthe same effect is obtained over the Pd-Cu-supported catalysts irrespective to the chemical composition of support and the initial concentration of nitrates in water used. The Pd-Cu clusters supported on 4.8 wt%TiO2/gamma-Al2O3 resulted in a solid with the best catalytic behavior compared with the rest of supports examined, both in the presence and in the absence of oxygen in the reducing feed gas stream. DRIFTS studies performed following catalytic reduction by H2 of NO3- in water revealed that the presence of TiO2 in the Pd-Cu/TiO2-Al2O3 system enhanced the reactivity of adsorbed bidentate nitrate species toward H2. Nitrosyl species adsorbed on the alumina and titania support surfaces are considered as active intermediate species of the selective catalytic reduction of NO3- by H2 in water. Pd-Cu/TiO2-Al2O3 appears to be the most selective catalyst ever reported in the literature for the reduction of nitrates present in pure water into N2 by a reducing gas mixture of H2/air.

  13. 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

  14. 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

  15. Fast and Low-Temperature (70 °C) Mineralization of Inkjet Printed Mesoporous TiO2 Photoanodes Using Ambient Air Plasma.

    PubMed

    Homola, Tomáš; Dzik, Petr; Veselý, Michal; Kelar, Jakub; Černák, Mirko; Weiter, Martin

    2016-12-14

    Hybrid mesoporous titania/silica electron-generating and transporting layers were prepared using wet-coating with a dispersion consisting of prefabricated titania nanoparticles and a methyl-silica binder. Titania/methyl-silica wet layers were deposited by inkjet printing and further mineralized by low-temperature atmospheric-pressure air plasma using diffuse coplanar surface barrier discharge (DCSBD) to form a titania/silica hybrid nanocomposite coating. Morphological analysis performed by scanning electron microscopy revealed no damage to the titania nanoparticles and chemical analysis performed by X-ray photoelectron spectroscopy disclosed a rapid decrease in carbon and increase in oxygen, indicating the oxidation effect of the plasma. The coatings were further electrochemically investigated with linear sweep voltammetry and chronoamperometry. The magnitude of photocurrent and photocatalytic activity were found to increase significantly with the plasma exposure on the order of 10s of seconds. The results obtained demonstrate the potential of DCSBD ambient air plasma for fast and low-temperature mineralization of titania mesoporous coatings.

  16. Characterization of transparent conductive delafossite-CuCr1-xO2 films

    NASA Astrophysics Data System (ADS)

    Chen, Hong-Ying; Chang, Kuei-Ping; Yang, Chun-Chao

    2013-05-01

    In this study, the CuCr1-xO2 films with x = 0.00-0.25 were prepared on a quartz substrate by sol-gel processing. The films were first deposited onto a quartz substrate by spin-coating. The specimens were annealed at 500 °C in air for 1 h and post-annealed in N2 at 700 °C for 2 h. As the films were post-annealed in N2, a pure delafossite-CuCrO2 phase appeared in the CuCr1-xO2 films below x = 0.20. However, an additional CuO phase appeared at x = 0.25. The pure delafossite-CuCrO2 phase can exist within x ≤ 0.20 in CuCr1-xO2 films. The binding energies of Cu-2p3/2 and Cr-2p3/2 in the CuCr1-xO2 films with the pure delafossite-CuCrO2 phase were 932.1 ± 0.2 eV and 576.0 ± 0.2 eV, respectively. The surface exhibited elongated grain features when the pure delafossite-CuCrO2 phase was present in the CuCr1-xO2 films. The maximum transmittance of the CuCr1-xO2 films with the pure delafossite-CuCrO2 phase was approximately 80%, which moved toward the visible region with the increasing x-value. The film absorption edges were observed at 400 nm, which were sharper with the increasing x-value. The optical bandgaps of CuCr1-xO2 films with the pure delafossite-CuCrO2 phase were approximately 3.0 eV. The electrical conductivity of CuCr1-xO2 films with the pure delafossite-CuCrO2 phase was 1.1 × 10-3 S cm-1 (x = 0.00), and increased to 0.16 S cm-1 (x = 0.20). The corresponding carrier concentration of CuCr1-xO2 films with the pure delafossite-CuCrO2 phase was 2.8 × 1014 cm-3 (x = 0.00), and markedly increased to 1.8 × 1016 cm-3 (x = 0.20). The Cr-deficient condition in delafossite-CuCrO2 films enhances film electrical conductivity and carrier concentration, but retains the film's high-visible transparency.

  17. Photocatalytic discoloration of aqueous malachite green solutions by UV-illuminated TiO2 nanoparticles under air and nitrogen atmospheres: effects of counter-ions and pH.

    PubMed

    Rengifo-Herrera, Julián Andrés; Pizzio, Luis René; Blanco, Mirta Noemí; Roussel, Christophe; Pulgarin, César

    2011-01-01

    Under air atmosphere, the photocatalytic discoloration of malachite green (MG) aqueous solutions (a triphenylmethane dye) in the presence of TiO(2) and UV light followed an oxidative pathway, involving an N-demethylation process evidenced by a blue shifting of the main absorption band with a maximum at 618 nm. This oxidative process was affected by the nature of the dye counter-ion and the pH of the solution. At pH 6.0, the oxidation was found to be faster than at pH 3.0, perhaps due to the poor interactions between MG and the semiconductor surface. Furthermore, with the presence of oxalate as counter-ion, the oxidative photocatalytic discoloration was negatively affected mainly at acidic pH. Under nitrogen atmosphere, some evidence was found about the double behaviour of MG when involved in the photocatalytic discoloration reactions pertaining to TiO(2) under these conditions. MG could be simultaneously oxidized, forming N-demethylated by-products, or reduced, thus leading to leuco-malachite green (LMG) (a colorless and toxic substance) as the main product. The LMG formation is favoured at low pH in the presence of oxalate as counter-ion.

  18. 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.

  19. Fe-Cluster Pushing Electrons to N-Doped Graphitic Layers with Fe3C(Fe) Hybrid Nanostructure to Enhance O2 Reduction Catalysis of Zn-Air Batteries.

    PubMed

    Yang, Jie; Hu, Jiangtao; Weng, Mouyi; Tan, Rui; Tian, Leilei; Yang, Jinlong; Amine, Joseph; Zheng, Jiaxin; Chen, Haibiao; Pan, Feng

    2017-02-08

    Non-noble metal catalysts with catalytic activity toward oxygen reduction reaction (ORR) comparable or even superior to that of Pt/C are extremely important for the wide application of metal-air batteries and fuel cells. Here, we develop a simple and controllable strategy to synthesize Fe-cluster embedded in Fe3C nanoparticles (designated as Fe3C(Fe)) encased in nitrogen-doped graphitic layers (NDGLs) with graphitic shells as a novel hybrid nanostructure as an effective ORR catalyst by directly pyrolyzing a mixture of Prussian blue (PB) and glucose. The pyrolysis temperature was found to be the key parameter for obtaining a stable Fe3C(Fe)@NDGL core-shell nanostructure with an optimized content of nitrogen. The optimized Fe3C(Fe)@NDGL catalyst showed high catalytic performance of ORR comparable to that of the Pt/C (20 wt %) catalyst and better stability than that of the Pt/C catalyst in alkaline electrolyte. According to the experimental results and first principle calculation, the high activity of the Fe3C(Fe)@NDGL catalyst can be ascribed to the synergistic effect of an adequate content of nitrogen doping in graphitic carbon shells and Fe-cluster pushing electrons to NDGL. A zinc-air battery utilizing the Fe3C(Fe)@NDGL catalyst demonstrated a maximum power density of 186 mW cm(-2), which is slightly higher than that of a zinc-air battery utilizing the commercial Pt/C catalyst (167 mW cm(-2)), mostly because of the large surface area of the N-doped graphitic carbon shells. Theoretical calculation verified that O2 molecules can spontaneously adsorb on both pristine and nitrogen doped graphene surfaces and then quickly diffuse to the catalytically active nitrogen sites. Our catalyst can potentially become a promising replacement for Pt catalysts in metal-air batteries and fuel cells.

  20. ZrO2-functionalized magnetic mesoporous SiO2 as effective phosphate adsorbent.

    PubMed

    Wang, Wenjuan; Zhou, Juan; Wei, Dan; Wan, Haiqin; Zheng, Shourong; Xu, Zhaoyi; Zhu, Dongqiang

    2013-10-01

    Phosphate pollution may cause eutrophication of the aquatic environment. In the present study, magnetic mesoporous SiO2 (denoted as MMS) and ZrO2-functionalized magnetic mesoporous SiO2 (denoted as ZrO2-MMS) were prepared and phosphate adsorption over the materials was investigated. The adsorbents were characterized by X-ray diffraction, transition electron microscopy, vibration sample magnetometer, N2 adsorption/desorption, zeta-potential measurement, and X-ray photoelectron spectroscopy. The results showed that MMS consisted of magnetite with particle sizes of 10-20 nm and ordered mesoporous SiO2 with the most probable pore diameter of 2.0 nm. The adsorbents could be readily separated and recovered under external magnetic field. The surface grafting of ZrO2 onto MMS led to an increase in surface zeta potential due to the formation of covalently linked ZrO2 functionality on the surface of MMS. Moreover, ZrO2 functionalization resulted in enhanced phosphate adsorption. Phosphate adsorption isotherms over the adsorbents could be well described by the Freundlich model. Phosphate adsorption kinetics followed the pseudo-second-order kinetics and the adsorption rate decreased with initial phosphate concentration. Additionally, increasing pH led to suppressed phosphate adsorption, and phosphate adsorption slightly increased with ionic strength.

  1. Disentangling gross N2O production and consumption in soil

    NASA Astrophysics Data System (ADS)

    Wen, Yuan; Chen, Zhe; Dannenmann, Michael; Carminati, Andrea; Willibald, Georg; Kiese, Ralf; Wolf, Benjamin; Veldkamp, Edzo; Butterbach-Bahl, Klaus; Corre, Marife D.

    2016-11-01

    The difficulty of measuring gross N2O production and consumption in soil impedes our ability to predict N2O dynamics across the soil-atmosphere interface. Our study aimed to disentangle these processes by comparing measurements from gas-flow soil core (GFSC) and 15N2O pool dilution (15N2OPD) methods. GFSC directly measures soil N2O and N2 fluxes, with their sum as the gross N2O production, whereas 15N2OPD involves addition of 15N2O into a chamber headspace and measuring its isotopic dilution over time. Measurements were conducted on intact soil cores from grassland, cropland, beech and pine forests. Across sites, gross N2O production and consumption measured by 15N2OPD were only 10% and 6%, respectively, of those measured by GFSC. However, 15N2OPD remains the only method that can be used under field conditions to measure atmospheric N2O uptake in soil. We propose to use different terminologies for the gross N2O fluxes that these two methods quantified. For 15N2OPD, we suggest using ‘gross N2O emission and uptake’, which encompass gas exchange within the 15N2O-labelled, soil air-filled pores. For GFSC, ‘gross N2O production and consumption’ can be used, which includes both N2O emitted into the soil air-filled pores and N2O directly consumed, forming N2, in soil anaerobic microsites.

  2. Disentangling gross N2O production and consumption in soil

    PubMed Central

    Wen, Yuan; Chen, Zhe; Dannenmann, Michael; Carminati, Andrea; Willibald, Georg; Kiese, Ralf; Wolf, Benjamin; Veldkamp, Edzo; Butterbach-Bahl, Klaus; Corre, Marife D.

    2016-01-01

    The difficulty of measuring gross N2O production and consumption in soil impedes our ability to predict N2O dynamics across the soil-atmosphere interface. Our study aimed to disentangle these processes by comparing measurements from gas-flow soil core (GFSC) and 15N2O pool dilution (15N2OPD) methods. GFSC directly measures soil N2O and N2 fluxes, with their sum as the gross N2O production, whereas 15N2OPD involves addition of 15N2O into a chamber headspace and measuring its isotopic dilution over time. Measurements were conducted on intact soil cores from grassland, cropland, beech and pine forests. Across sites, gross N2O production and consumption measured by 15N2OPD were only 10% and 6%, respectively, of those measured by GFSC. However, 15N2OPD remains the only method that can be used under field conditions to measure atmospheric N2O uptake in soil. We propose to use different terminologies for the gross N2O fluxes that these two methods quantified. For 15N2OPD, we suggest using ‘gross N2O emission and uptake’, which encompass gas exchange within the 15N2O-labelled, soil air-filled pores. For GFSC, ‘gross N2O production and consumption’ can be used, which includes both N2O emitted into the soil air-filled pores and N2O directly consumed, forming N2, in soil anaerobic microsites. PMID:27812012

  3. Identification of three major DNA adducts formed by the carcinogenic air pollutant 3-nitrobenzanthrone in rat lung at the C8 and N2 position of guanine and at the N6 position of adenine.

    PubMed

    Arlt, Volker M; Schmeiser, Heinz H; Osborne, Martin R; Kawanishi, Masanobu; Kanno, Takaharu; Yagi, Takashi; Phillips, David H; Takamura-Enya, Takeji

    2006-05-01

    3-Nitrobenzanthrone (3-NBA) is a potent mutagen and potential human carcinogen identified in diesel exhaust and ambient air particulate matter. Previously, we detected the formation of 3-NBA-derived DNA adducts in rodent tissues by 32P-postlabeling, all of which are derived from reductive metabolites of 3-NBA bound to purine bases, but structural identification of these adducts has not yet been reported. We have now prepared 3-NBA-derived DNA adduct standards for 32P-postlabeling by reacting N-acetoxy-3-aminobenzanthrone (N-Aco-ABA) with purine nucleotides. Three deoxyguanosine (dG) adducts have been characterised as N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone-3'-phosphate (dG3'p-C8-N-ABA), 2-(2'-deoxyguanosin-N2-yl)-3-aminobenzanthrone-3'-phosphate (dG3'p-N2-ABA) and 2-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone-3'-phosphate (dG3'p-C8-C2-ABA), and a deoxyadenosine (dA) adduct was characterised as 2-(2'-deoxyadenosin-N6-yl)-3-aminobenzanthrone-3'-phosphate (dA3'p-N6-ABA). 3-NBA-derived DNA adducts formed experimentally in vivo and in vitro were compared with the chemically synthesised adducts. The major 3-NBA-derived DNA adduct formed in rat lung cochromatographed with dG3'p-N2-ABA in two independent systems (thin layer and high-performance liquid chromatography). This is also the major adduct formed in tissue of rats or mice treated with 3-aminobenzanthrone (3-ABA), the major human metabolite of 3-NBA. Similarly, dG3'p-C8-N-ABA and dA3'p-N6-ABA cochromatographed with two other adducts formed in various organs of rats or mice treated either with 3-NBA or 3-ABA, whereas dG3'p-C8-C2-ABA did not cochromatograph with any of the adducts found in vivo. Utilizing different enzymatic systems in vitro, including human hepatic microsomes and cytosols, and purified and recombinant enzymes, we found that a variety of enzymes [NAD(P)H:quinone oxidoreductase, xanthine oxidase, NADPH:cytochrome P450 oxidoreductase, cytochrome P450s 1A1 and 1A2, N,O-acetyltransferases 1 and 2

  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

    2016-06-08

    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.

  5. 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 ...

  6. [In situ FTIR spectroscopic studies of the catalytic combustion of acid red B on CuFe2O4 in the presence and absence of O2].

    PubMed

    Wu, Rong-cheng; Qu, Jiu-hui; Yu, Yun-bo; He, Hong

    2005-02-01

    The reaction process of catalytic combustion of ARB on CuFe2O4 in the presence and absence of O2 was studied by in situ DRIFT spectroscopy. The results showed that the decomposition of the sulfonic group of ARB molecule was not affected by the reaction atmosphere, but the decompositions of azo group and aromatic ring were markedly affected by the presence or absence of O2. The catalytic combustion of ARB was faster in air atmosphere than that in N2 atmosphere, and ARB could be completely oxidized to CO2 and nitrate at 300 degrees C. But in N2 atmosphere, it was very difficult for the decomposition of ARB to complete at 300 degrees C, even though air was introduced following this process. The temperature required for the rapid and complete decomposition would be as high as 500 degrees C.

  7. Comparative Study of Two Different TiO2 Film Sensors on Response to H2 under UV Light and Room Temperature

    PubMed Central

    Peng, Xiaoying; Wang, Zhongming; Huang, Pan; Chen, Xun; Fu, Xianzhi; Dai, Wenxin

    2016-01-01

    An anatase TiO2 film sensor was prepared by a facile in-situ method on the interdigitated Au electrode deposited on the alumina substrate. The structure, morphology and the optical properties of the in-situ TiO2 film sensor were characterized by X-ray diffraction, Scanning Electron Microscopy, and UV-vis diffuse reflectance spectra. The photo-assisted gas sensitivities of the prepared film towards H2 gas were evaluated at room temperature in N2 and synthetic air atmospheres. As compared to TiO2 film sensor prepared by drop-coating method, this in-situ TiO2 film sensor exhibited a more compact structure composed of uniform TiO2 microspheres as well as a better gas sensitivity towards H2 under UV irradiation, especially in synthetic air. The photo-electrochemical measurements suggest that these improvements may be associated with the efficient charge transfer in the TiO2 interface induced by the TiO2 microsphere structure. This study might offer a feasible approach to develop photo-assisted gas sensors at ambient temperature. PMID:27509502

  8. 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.

  9. 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)

  10. High thermal stability of La2O3 and CeO2-stabilized tetragonal ZrO2

    DOE PAGES

    Wang, Shichao; Xie, Hong; Lin, Yuyuan; ...

    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

  11. Superconductivity in SrCuO2-BaCuO2 Superlattices: Formation of Artificially Layered Superconducting Materials.

    PubMed

    Norton, D P; Chakoumakos, B C; Budai, J D; Lowndes, D H; Sales, B C; Thompson, J R; Christen, D K

    1994-09-30

    Pulsed-laser deposition was used to synthesize artificially layered high-temperature superconductors. Thin-film compounds were formed when the constraint of epitaxy was used to stabilize SrCuO(2)-BaCuO(2) superlattices in the infinite layer structure. Using this approach, two new structural families, Ba(2)Srn-1,Cun+1 O2n+2+delta and Ba(4)Srn-1 Cun+3O2n+6+delta have been synthesized; these families superconduct at temperatures as high as 70 kelvin.

  12. Preparation of (U,Pu)O 2 pellets through sol-gel microsphere pelletization technique

    NASA Astrophysics Data System (ADS)

    Kumar, N.; Pai, Rajesh V.; Joshi, J. K.; Mukerjee, S. K.; Vaidya, V. N.; Venugopal, V.

    2006-12-01

    Mixed uranium-plutonium oxide microspheres were prepared by internal gelation process using feed solution of optimized composition. In the feed, total metal concentration was maintained at 1.5 M and hexamethylenetetramine (HMTA)-urea to metal mole ratio ( R) was kept at 1.0. The gel particles obtained from each batch were dried and heated at 250 °C in air and then calcined in O 2 at 800 °C followed by reduction in 8%H 2/92%N 2 at 600 °C for 1 h to obtain soft (U,Pu)O 2 microspheres containing 4 mol% Pu. The soft (U,Pu)O 2 microspheres were directly taken for the preparation of pellets. The microspheres were characterized with respect to surface area, tap density, crush strength and O/M ratio. X-ray diffraction analysis of the mixed oxide microspheres was carried out to identify the phases. The mixed oxide pellets were characterized for their density and micro-homogeneity. The sintering behaviour was studied by dilatometric investigations. The green pellets were sintered in 8%H 2/92%N 2 at 1600 °C for 2 h. The density of the sintered pellet was found to be 10.40 ± 0.05 g/cm 3 with grains in the size range of 3-6 μm with an excellent micro-homogeneity.

  13. 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

  14. Following the N2O consumption at the Oxygen Minimum Zone in the eastern South Pacific

    NASA Astrophysics Data System (ADS)

    Cornejo, M.; Farías, L.

    2012-03-01

    Oxygen deficient zones (OMZs), such as those found in the eastern South Pacific (ESP), are the most important N2O sources in the world 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 range (from 5° to 30° S and 71°-76° to ~84° W) based on ~890 N2O measurements. The intense consumption of N2O appears to be related to secondary NO2- accumulation, the best indicator of very low O2 levels. Using relationships that depend on threshold levels of O2 (<8 μM) and nitrite (>0.75 μM), we reproduced the apparent N2O production (ΔN2O) with high reliability (r2=0.73 p=0.01). Our results contribute to quantify the ratio of N2O production/consumption that is being cycling in O2 deficient water of N2O and may improve the prediction of N2O behavior under future scenarios of the OMZ expansion.

  15. 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.

  16. 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.

  17. Biotemplate fabrication of SnO2 nanotubular materials by a sonochemical method for gas sensors

    NASA Astrophysics Data System (ADS)

    Zhu, Shenmin; Zhang, Di; Gu, Jiajun; Xu, Jiaqiang; Dong, Junping; Li, Jinlong

    2010-05-01

    A sonochemical method is developed to fabricate SnO2 nanotubular materials from biological substances (here, it is cotton). The cotton fibers in SnCl2 solution were first treated with ultrasonic waves in air, followed by calcinations to give nanotubular materials that faithfully retain the initial cotton morphology. The microstructure and morphology of the obtained SnO2 nanotubules were characterized by the combination of field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and N2 adsorption/desorption measurements. The thermal behavior and crystalline properties were examined in the temperature range of 450-700 °C. The nanocrystals composing of SnO2 nanotubules were estimated about 8.5, 13.2, and 14.2 nm corresponding to calcination temperatures of 450, 550, and 700 °C, respectively. The sensor performance of biomorphic SnO2 nanotubules calcined at 700 °C was investigated in the atmosphere of ethanol, formaldehyde, carbinol, carbon monoxide, hydrogen, ammonia, and acetone, respectively, which exhibited a good selectivity for acetone at a working temperature of 350 °C. The sensitivity to 20 ppm acetone, S, was 6.4 at 350 °C with rapid response and recovery (around 10-9 s). These behaviors were well explained in relation to the morphology of the nanotubules thus produced.

  18. Ion beam analysis of the effect of O 2 and H 2O on the oxidation of iron under irradiation

    NASA Astrophysics Data System (ADS)

    Lapuerta, S.; Moncoffre, N.; Bérerd, N.; Jaffrezic, H.; Millard-Pinard, N.; Crusset, D.

    2006-08-01

    In this paper, the role of air humidity on the iron corrosion under irradiation is studied in the context of geological disposal of nuclear wastes. The irradiation experiments are performed at room temperature using a 3 MeV extracted proton beam with a 10 nA intensity. Different atmospheres are studied: humid air with a relative humidity (RH) fixed at 45%, dry air and a 15N2 atmosphere (45% RH). The hydrogen and oxygen distribution profiles at the iron surface in contact with atmosphere are measured using respectively ERDA (Elastic Recoil Detection Analysis) and RBS (Rutherford Backscattering Spectrometry) analysis. From these experiments it is clearly demonstrated that the coupling of O2 + H2O enhances iron oxidation whereas for iron hydrogenation, humidity is sufficient whatever the atmosphere. An interpretation is given, which is based on the reaction mechanisms and the species formed by air ionisation.

  19. Species and velocity visualization of unseeded heated air and combusting hydrogen jets using laser and flashlamp sources

    NASA Technical Reports Server (NTRS)

    Diskin, Glenn S.; Lempert, Walter R.; Miles, Richard B.

    1990-01-01

    Three techniques for the visualization of species and/or velocity in unseeded H2/air flames and heated air jets are described and preliminary image data are presented. The techniques described are: (1) simultaneous ArF laser imaging of H2, O2, and Rayleigh cross-section weighted density in an H2, O2, and Rayleigh cross-section weighted density in an H2/air flame; (2) ultraviolet flashlamp imaging of O2, OH, and Rayleigh cross-section weighted density in an H2/air flame; and (3) Raman Excitation plus Laser Induced Electronic Fluorescence velocimetry in heater air flows, up to static temperatures of 700 K. Application of these techniques, individually or in combination, should provide useful insight into mixing and reacting flows containing H2, O2, N2 and reaction intermediates such as OH.

  20. Effect of TiO2, ZrO2, and TiO2-ZrO2 on the performance of CuO-ZnO catalyst for CO2 hydrogenation to methanol

    NASA Astrophysics Data System (ADS)

    Xiao, Jie; Mao, Dongsen; Guo, Xiaoming; Yu, Jun

    2015-05-01

    The influence of TiO2, ZrO2, and TiO2-ZrO2 mixed oxide on the catalytic performance of CuO-ZnO catalyst in the methanol synthesis from CO2 hydrogenation was studied. The catalysts were prepared by oxalate co-precipitation method and characterized by TGA, N2 adsorption, XRD, reactive N2O adsorption, XPS, H2-TPR, H2-TPD, and CO2-TPD techniques. Characterization results reveal that all the additives improve the CuO dispersion in the catalyst body and increase the Cu surface area and adsorption capacities of CO2 and H2. The results of catalytic test reveal that the additives increase both the CO2 conversion and methanol selectivity, and TiO2-ZrO2 mixed oxide is more effective than single components of TiO2 or ZrO2. Moreover, the activity of methanol synthesis is correlated directly with CO2 adsorption capacity over the catalysts.

  1. Combining Accurate O2 and Li2O2 Assays to Separate Discharge and Charge Stability Limitations in Nonaqueous Li-O2 Batteries.

    PubMed

    McCloskey, Bryan D; Valery, Alexia; Luntz, Alan C; Gowda, Sanketh R; Wallraff, Gregory M; Garcia, Jeannette M; Mori, Takashi; Krupp, Leslie E

    2013-09-05

    Li-air batteries have generated enormous interest as potential high specific energy alternatives to existing energy storage devices. However, Li-air batteries suffer from poor rechargeability caused by the instability of organic electrolytes and carbon cathodes. To understand and address this poor rechargeability, it is essential to elucidate the efficiency in which O2 is converted to Li2O2 (the desired discharge product) during discharge and the efficiency in which Li2O2 is oxidized back to O2 during charge. In this Letter, we combine many quantitative techniques, including a newly developed peroxide titration, to assign and quantify decomposition pathways occurring in cells employing a variety of solvents and cathodes. We find that Li2O2-induced electrolyte solvent and salt instabilities account for nearly all efficiency losses upon discharge, whereas both cathode and electrolyte instabilities are observed upon charge at high potentials.

  2. Self-assembly of (NH4)0.3TiO1.1F2.1 crystal by dinitrogen fixation as a precursor of N-doped TiO2 nanosheets

    NASA Astrophysics Data System (ADS)

    Wang, Weiwei; Zhu, Dan; Luo, Jie; Zhu, Junwu; Liu, Xiaoheng

    2016-06-01

    Semiconductor TiO2 has been always extensively studied for maximizing its environmental- and energy-related applications with tailored facets or doped crystal structure, especially for photocatalysis, solar cell devices, sensors, catalyst supports, and supercapacitor. In this study, in air or argon atmosphere, a novel facile and effective method has been successfully exploited to prepare N-doped TiO2 nanosheets (air-TiO2 and Ar-TiO2) by annealing treatment of non-stoichiometric ammonium oxofluorotitanates crystal ((NH4)0.3TiO1.1F2.1) with layer-by-layer self-assembled morphology, which is obtained based on the dinitrogen fixation of TiCl4 in the presence of hydrogen fluoride under mild condition. In this method, the conversion of dinitrogen to ammonium salt has been demonstrated by means of isotopic labeling experiments with labeled 15N2 gas acting as benign oxidant and isopropanol as suitable reductant. The resultant of N-doped TiO2 nanosheets exhibits an enhancement of photocatalytic activity by degrading RhB under visible-light irradiation. In addition, the as-prepared Ar-TiO2 of N-doped TiO2 nanosheets obtained from Ar atmosphere also shows a higher electrochemical performance compared with reported pure TiO2 in the application of supercapacitor.

  3. 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

    2016-05-05

    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.

  4. Pt and Pd catalyzed oxidation of Li2O2 and DMSO during Li–O2 battery charging

    DOE PAGES

    Gittleson, Forrest S.; Ryu, Won-Hee; Schwab, Mark; ...

    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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. Thermal-energy reactions of O2(2+) ions with O2, N2, CO2, NO, and Ne

    NASA Technical Reports Server (NTRS)

    Chatterjee, B. K.; Johnson, R.

    1989-01-01

    The paper presents results of drift-tube mass-spectrometer studies of the reactivity of doubly charged molecular oxygen ions with several molecules and neon atoms. Thermal-energ rate coefficients for the reactions with the molecular reactants were found to be large, close to the limiting Langevin rates. Charge transfer with neon atoms was observed, but the measured rate coefficient was only a small fraction of the Langevin rate. It is concluded that the measured rate constants for the reactions considereed refer to vibrationally excited ions.

  10. Electron Excitation of O(2) Metastables in O(2)-N(2) Mixtures and of Free-Free Radiation in Argon.

    DTIC Science & Technology

    1982-05-01

    nations. This technical report has been reviewed and is approved for publication. ALLAN GARSCADDEN DONALD P. MORTEL Project Engineer Chief, Energy ...radiation, quenching, ratios and mean electron energies . The results are in agreement with calcula- tions using the best available electron collision cross...controlled ,(continued over) D FOA I"" 1473 EDITION OF INOV so IS OUSOLaTe U c a i T SECURITY CLASIFICATION OF THIS PACE (When Does Efifaced) StCuITV

  11. The effect of anaerobicity and temperature on N2 and N2O dynamics in forestry drained boreal peat soils

    NASA Astrophysics Data System (ADS)

    Pihlatie, Mari; Hongisto, Isto; Dannenmann, Michael; Georg, Willibald; Rainer, Gasche; Klaus, Butterbach-Bahl

    2013-04-01

    Molecular nitrogen (N2) is the dominant end-product of microbial denitrification in soils; however, due to difficulties in measuring N2 exchange, the emissions of N2 from terrestrial ecosystems are largely unknown. In boreal peatland soils, the combination of high soil carbon and nitrogen contents, fluctuating water-table and high decomposition activity of the peat make these soils potentially large emitters of N gases via microbial denitrification processes. This motivated us to quantify the N2 and nitrous oxide (N2O) losses from boreal drained peat soils varying in fertility status. Soil samples were collected from two drained peatland forests: a nutrient-rich (Lettosuo) and a nutrient-poor (Kalevansuo) site, both located in the boreal zone of Southern Finland. N2 and N2O emissions from intact soil cores were measured using the helium gas flow soil core method. Two incubation experiments were conducted focusing on the effects of anaerobicity and temperature on N2 and N2O dynamics of the top-soil (experiment 1), and the effect of anaerobicity on N2 and N2O dynamics in the peat profile (experiment 2). Soil samples in experiment 1 were incubated under 1) cold (2° C) aerobic (20% O2, 80% He), 2) cold (2° C) anaerobic (0% O2, 100% He), and 3) warm (15° C) anaerobic conditions, while those in experiment 2 were incubated under 1) warm aerobic and 2) warm anaerobic conditions. Dynamics of N2 and N2O fluxes for each incubation condition were followed until fluxes stabilized. In general, the N2 and N2O fluxes in the nutrient-rich Lettosuo peat were higher and more variable than those at the nutrient-poor Kalevansuo peat. In the nutrient-rich Lettosuo, both the N2 and N2O emissions increased dramatically after the change from aerobic to anaerobic conditions, and again after the temperature rise from 2 to 15° C. This latter peak in emissions was followed by a switch from N2O production to N2O consumption and a simultaneous sharp decrease in N2 emissions. Although, the N2

  12. Freestanding MoO2/Mo2C imbedded carbon fibers for Li-ion batteries.

    PubMed

    Li, Hongqin; Ye, Haijun; Xu, Zheng; Wang, Chuanyi; Yin, Jiao; Zhu, Hui

    2017-01-25

    Flexible and freestanding MoO2/Mo2C imbedded carbon fibers (MoO2/Mo2C ICFs) have been successfully synthesized via an integrated procedure including electrospinning, thermo-plastication in air and reduction/carbonization at high temperature. A series of techniques such as SEM, TEM, N2 adsorption-desorption analysis, XRD, TGA, IR and XPS have been employed to systemically characterize the MoO2/Mo2C ICFs. In particular, it is observed that the MoO2/Mo2C ICFs derived from phosphomolybdic acid have more highly porous structures than those derived from molybdic acid. Most impressively, the obtained MoO2/Mo2C ICFs are directly used as binder- and current collector-free anode materials for LIBs, which exhibit desirable rate capability and satisfactory cycling performance. The electrochemical investigations illustrated that the MoO2/Mo2C ICFs could deliver an initial discharging capacity of 1422.0 mA h g(-1) with an original coulombic efficiency of 63.3%, and the subsequent reversible capacity could reach as high as 1103.6 mA h g(-1) even after 70 cycles at a current density of 0.1 A g(-1). Such a capacity is larger than the theoretical capacity of MoO2 (838 mA h g(-1)) and pure carbon fibers (460.5 mA h g(-1)). More importantly, the MoO2/Mo2C ICFs exhibited an excellent rate performance with a capacity of 445.4 mA h g(-1) even at a charging current density of 1.6 A g(-1). The remarkable enhancement in rate capability and long cycling performance resulted from a synergistic effect between the MoO2 nanoparticles and porous carbon fiber matrix. This methodology can be widely extended to fabricate other metal oxide/carbon composites for significant energy storage and conversion applications.

  13. Ultraviolet-visible absorption spectra of N-doped TiO2 film deposited on sapphire

    NASA Astrophysics Data System (ADS)

    Park, Jaewon; Lee, Jung-Yup; Cho, Jun-Hyung

    2006-12-01

    The optical-response properties of nitrogen(N)-doped titanium dioxide (TiO2) films are investigated by means of a combination of ultraviolet-visible absorption spectroscopy and first-principles density-functional calculations. The TiO2 films were epitaxially grown on the sapphire substrate by the pulsed laser deposition method. The doping of N atoms was achieved by 70keV of N+ ion implantation, followed by postirradiation heat treatment at 550°C for 2h in air. We find that when 5×1016 (1×1017)Nions/cm2 were implanted into the epitaxially grown TiO2 film, the absorption edge is reproducibly shifted to lower energy by about 0.06 (0.12)eV together with a significant optical absorption extending into the visible-light region. These experimental data can be explained by our calculated band structure of N-doped TiO2, where the bands originating from N 2p states locate above the valence band edge, while the band gap narrowing due to the mixing of N with O 2p states is 0.04eV.

  14. Production of O2 through dismutation of H2O2 during water ice desorption: a key to understanding comet O2 abundances

    NASA Astrophysics Data System (ADS)

    Dulieu, F.; Minissale, M.; Bockelée-Morvan, D.

    2017-01-01

    Context. Detection of molecular oxygen and prediction of its abundance have long been a challenge for astronomers. The low abundances observed in few interstellar sources are well above the predictions of current astrochemical models. During the Rosetta mission, an unexpectedly high abundance of O2 was discovered in the comet 67P/Churyumov-Gerasimenko's coma. A strong correlation between O2 and H2O productions is observed, whereas no such correlation is observed between O2 and either of CO or N2. Aims: We suggest that the O2 molecule may be formed during the evaporation of water ice. We propose a possible reaction: the dismutation of H2O2 (2 H2O2-→ 2 H2O + O2), a molecule which should be co-produced during the water ice mantle growth on dust grains. We aim to test this hypothesis under realistic experimental conditions. Methods: We performed two sets of experiments. They consist of producing a mixture of D2O and D2O2 via the reaction of O2 and D on a surface held at 10 K. The first set is made on a silicate substrate, and explores the limit of thin films, in order to prevent any complication due to trapping during the desorption. The second set is performed on a pre-deposited H2O ice substrate and mimics the desorption of mixed ice. Results: In thin films, O2 is produced by the dismutation of H2O2, even at temperatures as low as 155 K. Mixed with water, H2O2 desorbs after the water ice sublimation and even more desorption of O2 is observed. Conclusions: H2O2, synthesised during the growth of interstellar ices (or by later processing), desorbs at the latest stage of the water sublimation and undergoes the dismutation reaction. Therefore an O2 release in the gas phase should occur at the end of the evaporation of ice mantles. Temperature gradients along the geometry of clouds, or interior of comets, should blend the different stages of the sublimation. Averaged along the whole process, a mean value of the O2/H2O ratio of a few percent in the gas phase seems

  15. Study on preparation of SnO2-TiO2/Nano-graphite composite anode and electro-catalytic degradation of ceftriaxone sodium.

    PubMed

    Guo, Xiaolei; Wan, Jiafeng; Yu, Xiujuan; Lin, Yuhui

    2016-12-01

    In order to improve the electro-catalytic activity and catalytic reaction rate of graphite-like material, Tin dioxide-Titanium dioxide/Nano-graphite (SnO2-TiO2/Nano-G) composite was synthesized by a sol-gel method and SnO2-TiO2/Nano-G electrode was prepared in hot-press approach. The composite was characterized by X-ray photoelectron spectroscopy, fourier transform infrared, Raman, N2 adsorption-desorption, scanning electrons microscopy, transmission electron microscopy and X-ray diffraction. The electrochemical performance of the SnO2-TiO2/Nano-G anode electrode was investigated via cyclic voltammetry and electrochemical impedance spectroscopy. The electro-catalytic performance was evaluated by the degradation of ceftriaxone sodium and the yield of ·OH radicals in the reaction system. The results demonstrated that TiO2, SnO2 and Nano-G were composited successfully, and TiO2 and SnO2 particles dispersed on the surface and interlamination of the Nano-G uniformly. The specific surface area of SnO2 modified anode was higher than that of TiO2/Nano-G anode and the degradation rate of ceftriaxone sodium within 120 min on SnO2-TiO2/Nano-G electrode was 98.7% at applied bias of 2.0 V. The highly efficient electro-chemical property of SnO2-TiO2/Nano-G electrode was attributed to the admirable conductive property of the Nano-G and SnO2-TiO2/Nano-G electrode. Moreover, the contribution of reactive species ·OH was detected, indicating the considerable electro-catalytic activity of SnO2-TiO2/Nano-G electrode.

  16. 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...

  17. 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...

  18. 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.... 15, 2011] Air-to-Fuel Ratio Measurements...

  19. 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...

  20. 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...

  1. N2(A) vibrational kinetics in streamer discharges: effect of oxygen on formation of low vibrational levels

    NASA Astrophysics Data System (ADS)

    Simek, Milan; Ambrico, Paolo Francesco; Prukner, Vaclav

    2016-09-01

    In the present study we report on the N2(A) vibrational kinetics in nitrogen-oxygen mixtures revealed by LIF technique under DBD streamer discharge conditions at low pressures. In pure nitrogen, the observed evolution of the N2(A) LIF signal during the decaying streamer channel period evidences fast initial relaxation of high vibrational levels towards the v = 2 and 3 levels, followed by a delayed increase of terminal v = 0 and 1 levels. In nitrogen-oxygen mixtures however, the efficient quenching of higher N2(A) levels by oxygen significantly inhibits vibrational relaxation towards the lower and terminal levels, causing much lower populations of the v = 0-3 levels. This is already clearly visible in the N2 + 0.8% O2 mixture with all the kinetics limited to the first 10 microseconds. In synthetic air, the kinetics is limited to few microseconds in the post discharge. Furthermore, much more effective quenching of fluorescence makes the measurements extremely challenging. Obtained results show that with the addition of oxygen the evolution of the N2(A) vibrational distribution is effectively terminated during the collisional-radiative cascade inhibiting energy pooling mechanism which is effective in pure nitrogen Work supported by GACR (Contract No. GA15-04023S).

  2. Transmucosal gas-loss rates in middle ears initially filled with O2 or CO2.

    PubMed

    Kania, Romain E; Vérillaud, Benjamin; Ars, Bernard; Tran Ba Huy, Patrice; Herman, Philippe; Ar, Amos

    2016-10-01

    This study investigates the role of different gases in clearance of gas in the middle ear cavity (ME) by its mucosal blood flow. A rat model was used to measure gas volume changes in the ME cavity at constant pressure without ventilation. We disturbed the normal gas composition of the ME by filling it with O2 or CO2, measured the consequent changes in gas volume over time and compared these results with previously obtained ones for air and N2. The first 5 min of the primary transient phase (phase I) for O2 or CO2 was characterized by a volume loss decrease of -0.49 ± 0.34 μL and -46.28 ± 8.49 μL, respectively, with volume loss increase for air and N2 differing greatly, at +0.17 ± 0.17 and +2.31 ± 0.81, respectively. The CO2 value of -46.28 μL showed that a volume of gas equivalent to that of the ME cleft volume was eliminated within the first 5 min. In the second phase (phase II), all gases showed a linear decrease in volume, which presumably represents a steady-state gas loss rate. However, the gas loss rate of -0.307 ± 0.170 μL min(-1) for O2-filled MEs was significantly higher than the mean of -0.124 μL min(-1) for all other gases. We used a previously established mathematical model to calculate the effective ME mucosal blood flow rate under steady-state (phase II) conditions. The blood flow results for O2-filled MEs differed greatly from those of the other gases (89.0 ± 49.28 vs. 26.5 μL min(-1), on average), which suggest that the model used to calculate blood flow should be modified if used with O2-filled MEs. Further work should involve a comparison of our method with different methods to verify ME blood flow rate.

  3. 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.

  4. Selective oxidation of cyclohexane using Ce1-xMnxO2 nanocatalysts.

    PubMed

    Selvamani, A; Selvaraj, M; Gurulakshmi, M; Ramya, R; Shanthi, K

    2014-04-01

    The Ce1-xMnxO2 nanocatalysts (x = 0.25, 0.50 and 0.75 wt.%) were synthesized by sol-gel method. The catalysts were characterized using various techniques such as XRD, N2 sorption study, DRSUV-Vis, TPR, SEM and TEM. The incorporation of Mn ions into the ceria lattice was confirmed by XRD analysis. DRUV-Vis spectra confirm the presence of Ce3+ ions in the lattice of Ce1-xMnxO2. H2-TPR study revealed the oxygen storage capacity of the catalyst. The 3D flowerlike morphology of the nanocatalysts was confirmed from FESEM and HRTEM images. The catalytic activity was tested for the vapor phase oxidation of cyclohexane using air as an oxidant. The key reaction parameters were varied to study the stability, activity and selectivity of the catalysts. The study concluded that suitable amount of manganese content is essential for the selective oxidation of cyclohexane at low temperature and Ce0.25Mn0.75O2 is the most suitable catalyst for high conversion and selectivity under the given reaction conditions. The activity of the catalyst is correlated with the characterization results.

  5. {ELECTRONIC Structure and Spectroscopy of O_2 and O_2^+}

    NASA Astrophysics Data System (ADS)

    Vazquez, Gabriel J.; Lefebvre-Brion, H.; Liebermann, Hans P.

    2014-06-01

    We carried out a comprehensive SCF MRD--CI ab initio study of the electronic structure of O_2 and O_2^+. Potential energy curves (PECs) of about 150 electronic states of O_2 and about 100 of O_2^+, as well as a number of states of O_2++ were computed. The cc--pVQZ basis set augmented with diffuse functions was employed. Spectroscopic parameters (T_e, T_v, ω_e, ω_ex_e, B_e, D_e, D_0, μ, IP, etc.) are reported. A preliminary sample of the results will be presented. The electronic absorption spectrum of O_2 has proved difficult to analyze/interpret due to the unusually large number of electronic states which arise from the peculiar open--shell structure of both the oxygen atomic fragments and the O_2 molecule. For instance, there are 62 valence molecular electronic states which correlate to the six lowest dissociation limits resulting from the three valence O atom fragment states (^3P, ^1D, ^1S). In addition, there are several nlλ Rydberg series converging to the X^2Π_g ground ionic state and to the lowest two excited states of the cation, a^4Π_u_i and A^2Π_u. Furthermore, a number of interactions of various types among several electronic states result in rovibronic perturbations which manifest themselves, e.g., as irregular vibronic structure, hence severely complicating the assignment of the absorption features and the analysis and interpretation of the spectrum. An overview of the electronic states and spectroscopy of O_2 will be presented. A chief motivation of this study of O_2 was to try to provide a theoretical insight on the nature, energetic position, shape, and dissociation asymptotes, of electronic states located in the 4 eV energy region encompassed between the O_2^+ ground state X^2Π_g (IP=12.07 eV) and the first excited state of the cation a^4Π_u_i (IP=16.10 eV). This in order to aid in the interpretation of experimental data related to the mechanism(s) of the neutral dissociation of the O_2** (Rydberg) superexcited states, which competes with

  6. Nonthermal metabolic response of rats to He-O2, N2-O2, and Ar-O2 at 1 atm.

    NASA Technical Reports Server (NTRS)

    Schatte, C. L.; Jordan, J. P.; Phillips, R. W.; Clarkson, D. P.; Simmons, J. B., II

    1973-01-01

    Experiments were performed to describe qualitatively and quantitatively the nonthermal metabolic response of rats to normoxic mixtures of helium, nitrogen, or argon at 1 atm ambient pressure. Hypoxic mixtures were similarly tested to determine any differences in hypoxic response as a function of the diluent gas. Rats exposed to argon for 5 days had a reduced metabolic rate relative to nitrogen, as evidenced by oxygen and food consumption, CO2 production, and the catabolism of radiosubstrates. While some parameters indicated that helium increased metabolic rate, oxygen consumption did not significantly differ from that in nitrogen. The physiologic and metabolic response to an imposed hypoxia varied among the different environments. Certain indices suggested that the hypoxic effects were less severe in helium and more pronounced in argon than in nitrogen. The mechanisms by which the diluent gases produced the observed changes could not be identified, but some possibilities are discussed.

  7. Synergistic Effect of Atmospheric-pressure Plasma and TiO2 Photocatalysis on Inactivation of Escherichia coli Cells in Aqueous Media.

    PubMed

    Zhou, Renwu; Zhou, Rusen; Zhang, Xianhui; Li, Jiangwei; Wang, Xingquan; Chen, Qiang; Yang, Size; Chen, Zhong; Bazaka, Kateryna; Ken Ostrikov, Kostya

    2016-12-22

    Atmospheric-pressure plasma and TiO2 photocatalysis have been widely investigated separately for the management and reduction of microorganisms in aqueous solutions. In this paper, the two methods were combined in order to achieve a more profound understanding of their interactions in disinfection of water contaminated by Escherichia coli. Under water discharges carried out by microplasma jet arrays can result in a rapid inactivation of E. coli cells. The inactivation efficiency is largely dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N2, He and air microplasma arrays, O2 microplasma had the highest activity against E. coli cells in aqueous solution, and showed >99.9% bacterial inactivation efficiency within 4 min. Addition of TiO2 photocatalytic film to the plasma discharge reactor significantly enhanced the inactivation efficiency of the O2 microplasma system, decreasing the time required to achieve 99.9% killing of E. coli cells to 1 min. This may be attributed to the enhancement of ROS generation due to high catalytic activity and stability of the TiO2 photocatalyst in the combined plasma-TiO2 systems. Present work demonstrated the synergistic effect of the two agents, which can be correlated in order to maximize treatment efficiency.

  8. 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.

  9. Synergistic Effect of Atmospheric-pressure Plasma and TiO2 Photocatalysis on Inactivation of Escherichia coli Cells in Aqueous Media

    NASA Astrophysics Data System (ADS)

    Zhou, Renwu; Zhou, Rusen; Zhang, Xianhui; Li, Jiangwei; Wang, Xingquan; Chen, Qiang; Yang, Size; Chen, Zhong; Bazaka, Kateryna; (Ken) Ostrikov, Kostya

    2016-12-01

    Atmospheric-pressure plasma and TiO2 photocatalysis have been widely investigated separately for the management and reduction of microorganisms in aqueous solutions. In this paper, the two methods were combined in order to achieve a more profound understanding of their interactions in disinfection of water contaminated by Escherichia coli. Under water discharges carried out by microplasma jet arrays can result in a rapid inactivation of E. coli cells. The inactivation efficiency is largely dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N2, He and air microplasma arrays, O2 microplasma had the highest activity against E. coli cells in aqueous solution, and showed >99.9% bacterial inactivation efficiency within 4 min. Addition of TiO2 photocatalytic film to the plasma discharge reactor significantly enhanced the inactivation efficiency of the O2 microplasma system, decreasing the time required to achieve 99.9% killing of E. coli cells to 1 min. This may be attributed to the enhancement of ROS generation due to high catalytic activity and stability of the TiO2 photocatalyst in the combined plasma-TiO2 systems. Present work demonstrated the synergistic effect of the two agents, which can be correlated in order to maximize treatment efficiency.

  10. Synergistic Effect of Atmospheric-pressure Plasma and TiO2 Photocatalysis on Inactivation of Escherichia coli Cells in Aqueous Media

    PubMed Central

    Zhou, Renwu; Zhou, Rusen; Zhang, Xianhui; Li, Jiangwei; Wang, Xingquan; Chen, Qiang; Yang, Size; Chen, Zhong; Bazaka, Kateryna; (Ken) Ostrikov, Kostya

    2016-01-01

    Atmospheric-pressure plasma and TiO2 photocatalysis have been widely investigated separately for the management and reduction of microorganisms in aqueous solutions. In this paper, the two methods were combined in order to achieve a more profound understanding of their interactions in disinfection of water contaminated by Escherichia coli. Under water discharges carried out by microplasma jet arrays can result in a rapid inactivation of E. coli cells. The inactivation efficiency is largely dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N2, He and air microplasma arrays, O2 microplasma had the highest activity against E. coli cells in aqueous solution, and showed >99.9% bacterial inactivation efficiency within 4 min. Addition of TiO2 photocatalytic film to the plasma discharge reactor significantly enhanced the inactivation efficiency of the O2 microplasma system, decreasing the time required to achieve 99.9% killing of E. coli cells to 1 min. This may be attributed to the enhancement of ROS generation due to high catalytic activity and stability of the TiO2 photocatalyst in the combined plasma-TiO2 systems. Present work demonstrated the synergistic effect of the two agents, which can be correlated in order to maximize treatment efficiency. PMID:28004829

  11. 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

    2016-04-06

    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.

  12. 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

  13. 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.

  14. 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

  15. Stability of polymer binders in Li-O2 batteries

    SciTech Connect

    Nasybulin, Eduard N.; Xu, Wu; Engelhard, Mark H.; Nie, Zimin; Li, Xiaohong S.; Zhang, Jiguang

    2013-06-24

    A number of polymers with various chemical structures were studied as binders for air electrodes in Li-O2 batteries. The nature of the polymer significantly affects the binding properties in the carbon electrodes thus altering the discharge performance of Li-O2 batteries. Stability of polymers to the aggressive reduced oxygen species generated during discharge was tested by ball milling them with KO2 and Li2O2, respectively. Most of the polymers decomposed under these conditions and mechanisms of the decompositions are proposed for some of the polymers. Polyethylene was found to have excellent stability and is suggested as robust binder for air electrodes in Li-O2 batteries.

  16. On sol-gel derived Au-enriched TiO2 and TiO2-ZrO2 photocatalysts and their investigation in photocatalytic reduction of carbon dioxide

    NASA Astrophysics Data System (ADS)

    Matějová, Lenka; Kočí, Kamila; Reli, Martin; Čapek, Libor; Matějka, Vlastimil; Šolcová, Olga; Obalová, Lucie

    2013-11-01

    Gold-enriched TiO2 and TiO2-ZrO2 and their parent counterparts were prepared by using the sol-gel process controlled within the reverse micelles environment, followed by impregnation in AuCl3 solution. Catalysts were characterized by organic elementary analysis (OEA), inductively coupled plasma mass spectrometry (ICP MS), N2 physisorption, powder X-ray diffraction (XRD), transmission electron microscopy (TEM) combined with electron diffraction, UV-vis spectroscopy, and tested in CO2 photocatalytic reduction. The performance of photocatalysts iluminated by UV-lamp with the wavelenght maximum at 254 nm was decreasing in the order TiO2-ZrO2 > Au/TiO2-ZrO2 > TiO2 > Au/TiO2 > TiO2 Evonic P25. The photocatalytic performance decrease over Au/TiO2-ZrO2 and Au/TiO2, compared to their parent counterparts, can be explained by the presence of too large Au particles, which block the oxide surface and either reduce the light absorption capability of the catalysts, or serve as the recombination centres. Higher photocatalytic performance of the amorphous TiO2-ZrO2 than of the nanocrystalline TiO2 can be ascribed to the enlarged surface area and higher photoactivity of titania-zirconia oxide mixture under the UV lamp with the wavelenght maximum at 254 nm. With regard to crystalline materials the appropriate anatase crystallite-size plays a key role in performance of CO2 photocatalytic reduction. Moreover, correlation between the adsorption edge and the anatase crystallite-size was revealed.

  17. 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.

  18. 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.

  19. GeO2-SiO2-chitosan-medium-coated hollow optical fiber for cell immobilization.

    PubMed

    Zhong, Nian-Bing; Zhu, Xun; Liao, Qiang; Wang, Yong-Zhong; Chen, Rong

    2013-08-15

    A GeO(2)-SiO(2)-chitosan-medium (GSCM)-coated hollow optical fiber (HOF) is proposed. The HOF consists of three parts: the fiber core (air), cladding (SiO(2)), and coating (GSCM), which shows the highest refractive index of the three. The HOF's luminescence properties and surface morphology are investigated. Their adsorption capacity for Rhodopseudomonas palustris CQK 01 is also assayed. We discovered that when the amount of 2GeO(2)-SiO(2) sol dopant is 0.9 mass percent, the HOF exhibits the highest luminous intensity and uniform light distribution, and the adsorption capacity for the cell is 3.2 times higher than that of a normal solid optical fiber.

  20. 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...

  1. 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.

  2. Wavelength- and alignment-dependent photoionization of N2 and O2

    NASA Astrophysics Data System (ADS)

    Petretti, Simon; Magaña, Álvaro; Saenz, Alejandro; Decleva, Piero

    2016-11-01

    The ionization behavior of the two diatomic molecules nitrogen and oxygen in strong laser fields has been investigated. For this purpose, the time-dependent Schrödinger equation is solved numerically within the many-electron single-determinant approximation. Three different orientations of the molecular axis with respect to the laser field have been considered: 0∘,45∘ , and 90∘. The photon wavelength has been varied from 25 to 800 nm, covering a range from XUV to infrared radiation. Nitrogen and oxygen were chosen as they possess the same molecular symmetry but different orbital structures. The ionization from different orbitals is discussed.

  3. Materials Data on BH5C4(N2O)2 (SG:34) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2016-02-10

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  4. Pressure dependence of intramolecular mode frequencies in solid N2, O2, and CO2

    NASA Technical Reports Server (NTRS)

    Etters, R. D.; Helmy, A.

    1983-01-01

    A microscopic description of the pressure dependence of intramolecular vibrational modes in simple molecular crystals has been formulated using a classical perturbation theory. Quantitative agreement with experiment is demonstrated and it is shown that frequency changes at phase transitions are large enough to be observed optically.

  5. Electrochemical System Would Supply O2, H2O, N2, And H2

    NASA Technical Reports Server (NTRS)

    Walter, Richard T.; Van Buskirk, Paul D.

    1992-01-01

    Electrochemical system includes fuel cells that convert high-energy-density chemical propellants to atmospheric gases. System provides cooling, water, and electrical energy. Applicable to terrestrial enclosed environments, laboratories, chemical processing plants, or portable medical facilities.

  6. Nanosecond Plasma Enhanced H2/O2/N2 Premixed Flat Flames

    DTIC Science & Technology

    2014-01-01

    a function of height above the burner surface. As shown in Fig. 1b, the configuration referred to as “direct flame coupling” ( DFC ) is...single exponential decay and the radiative lifetime is taken from German [14]. For the spatially-resolved measurements, only one time delay ( t =8 µs...between the plasma discharge and the Nd:YAG laser is reported. This  t corresponds to the time delay after which the largest increase of OH (due to

  7. The Radiative Lifetime of N2(a 1IIg, v=O-2)

    DTIC Science & Technology

    1990-04-03

    8217!, N,!-ihcr study’ uhd.’ standing of such plenatnea ts energy transfer processes ill radiative decay ofth a’ state in the italyi, of lii line-ut...strength is due to contributions from measurements. tile magnetic dipole and electric quadrupole moments. In Several studies nave eliployCd abSorl)tiun...GarstangŘ analyzed lieasurenlelis of gen- diative exchange of energy in this coupled system. A poten- tial- energy level diagram of these states is

  8. Ag-TiO2 nanoparticle codoped SiO2 films on ZrO2 barrier-coated glass substrates with antibacterial activity in ambient condition.

    PubMed

    Mukhopadhyay, Anindita; Basak, Sujit; Das, Jugal Kishore; Medda, Samar Kumar; Chattopadhyay, Krishnananda; De, Goutam

    2010-09-01

    Anatase TiO2 and Ag nanoparticles (NPs) codoped SiO2 films were prepared by the sol-gel method. Proportionate amounts of 3-(glycidoxypropyl)trimethoxysilane (GLYMO), tetraethylorthosilicate (TEOS) and 3-(methacryloxypropyl)trimethoxysilane (MEMO) derived inorganic-organic silica sol, commercially available dispersed anatase TiO2 NPs, and AgNO3 were used to prepare the sols. The films were prepared on ZrO2 (cubic) precoated soda-lime glass substrates by a single-dipping technique and heat-treated at 450 °C in air and H2/Ar atmosphere to obtain hard, relatively porous, and transparent coatings of thickness>600 nm. The ZrO2 barrier layer was previously applied on soda-lime glass to restrict the diffusion of Ag into the substrate. The Ag-TiO2 NPs incorporated SiO2 films were intense yellow in color and found to be fairly stable at ambient condition for several days under fluorescent light. These films show a considerable growth inhibition on contact with the gram negative bacteria E. coli.

  9. Photochemistry on TiO2: Mechanisms Behind the Surface Chemistry

    DTIC Science & Technology

    2009-01-21

    photoinduced antimicrobial [11,13] properties of TiO2 films have recently been discovered and these ideas are now employed for new photochemically acti...ation in air causes water droplets to wet the TiO2 film surface, resulting in a lowering of the contact angle over time. The anatase TiO2 film was...Hydrophilic H2O Hydrocarbon film a b s t r a c t Photochemistry from TiO2 surfaces is described for two cases: The UV-induced photodesorption of O2 from TiO2

  10. The development of polymer membranes and modules for air separation

    NASA Astrophysics Data System (ADS)

    Vinogradov, N. E.; Kagramanov, G. G.

    2016-09-01

    Technology of hollow fiber membrane and modules for air separation was developed. Hollow fibers from the polyphenylene oxide (PPO) having a diameter of 500 μm were obtained. The permeability of the fibers by oxygen was up to 250 Ba, while the separation factor by O2/N2 was 4.3. The membrane module has been made by using these fibers and tested for permeability of individual gases.

  11. 40 CFR 1065.284 - Zirconia (ZrO2) analyzer.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 34 2013-07-01 2013-07-01 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...

  12. Lan+1NinO3n+1 (n = 2 and 3) phases and composites for solid oxide fuel cell cathodes: Facile synthesis and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Sharma, Rakesh K.; Burriel, Mónica; Dessemond, Laurent; Bassat, Jean-Marc; Djurado, Elisabeth

    2016-09-01

    In this work we present a modified citrate-nitrate route using citric acid as a chelating agent as an effective and facile strategy to obtain nanocrystalline La3Ni2O7+δ (L3N2) and La4Ni3O10-δ (L4N3) powders for the preparation of solid oxide fuel cell cathodes. Both samples crystallize in a Fmmm orthorhombic layered Lan+1NinO3n+1 Ruddlesden-Popper structure, with n = 2 and 3, respectively. The oxygen non-stoichiometry, determined by TGA is equal to 0.05 and 0.06 for L3N2 and L4N3, respectively. The thermal expansion coefficient values of L3N2 and L4N3 are 11.0 × 10-6 K-1 and 11.5 × 10-6 K-1, respectively. This study focused on L3N2, L4N3 and on novel composite electrodes with CGO (Ce0.9Gd0.1O2-δ): L3N2-CGO and L4N3-CGO with a view to taking advantage of their complimentary properties, i.e. high ionic conductivity of CGO and high electronic conductivity of Lan+1NinO3n+1 (n = 2 and 3). A significant improvement of the polarization resistance, from 1.0 to 0.03 Ω cm2 and from 1.5 to 0.52 Ω cm2 at 700 °C, is obtained when 50 wt% CGO is added to L3N2 and L4N3, respectively. In addition, the L3N2-CGO composite shows good long-term stability at 900 °C for 2 weeks in air, confirming its suitability as a SOFC cathode.

  13. Groundwater N speciation and redox control of organic N mineralization by O 2 reduction to H 2O 2

    NASA Astrophysics Data System (ADS)

    Washington, John W.; Thomas, Robert C.; Endale, Dinku M.; Schroer, Katherine L.; Samarkina, Lidia P.

    2006-07-01

    Excess N from agriculture induces eutrophication in major river systems and hypoxia in coastal waters throughout the world. Much of this N is from headwaters far up the watersheds. In turn, much of the N in these headwaters is from ground-water discharge. Consequently, the concentrations and forms of N in groundwater are important factors affecting major aquatic ecosystems; despite this, few data exist for several species of N in groundwater and controls on speciation are ill-defined. Herein, we report N speciation for a spring and well that were selected to reflect agricultural impacts, and a spring and well that show little to no agricultural-N impact. Samples were characterized for NO 3-, NO 2-, N 2O, NH 4+, urea, particulate organic N( Nporg), and dissolved organic N( Ndorg). These analytes were monitored in the agricultural spring for up to two years along with other analytes that we reported upon previously. For all samples, when oxidized N was present, the dominant species was NO 3- (88-98% of total fixed N pool) followed by Ndorg (<4-12%) and only trace fractions of the other N analytes. In the non-agriculturally impacted well sample, which had no quantifiable NO 3- or dissolved O 2, Ndorg comprised the dominant fraction (68%) followed by NH 4+ (32%), with only a trace balance comprised of other N analytes. Water drawn from the well, spring and a wetland situated in the agricultural watershed also were analyzed for dissolved N 2 and found to have a fugacity in excess of that of the atmosphere. H 2O 2 was analyzed in the agricultural spring to evaluate the O 2/H 2O 2 redox potential and compare it to other calculated potentials. The potential of the O 2/H 2O 2 couple was close in value to the NO 3-/NO 2- couple suggesting the important role of H 2O 2 as an O 2-reduction intermediate product and that O 2 and NO 3- are reduced concomitantly. The O 2/H 2O 2 and NO 3-/NO 2- couples also were close in value to a cluster of other inorganic N and Fe couples

  14. Field-based measurements of gross N2O production in soils using a 15N2O pool dilution technique

    NASA Astrophysics Data System (ADS)

    Yang, W. H.; Teh, Y.; Silver, W. L.

    2011-12-01

    Soils are a major source and sink of nitrous oxide (N2O), a potent greenhouse gas and catalyst for stratospheric ozone depletion. The controls on soil N2O emissions are poorly understood due to the difficulty in measuring gross N2O production and consumption rates. We tested a 15N2O pool dilution technique for simultaneously measuring gross N2O production and consumption rates from soils in the field. Our study site was a managed grassland in the Sacramento-San Joaquin River Delta that exhibited high N2O emissions, averaging 6.4 ± 2.6 mg N m-2 d-1. In the laboratory, gross N2O production and consumption compared well between the 15N2O pool dilution and acetylene inhibition methods whereas the 15NO3- tracer method measured significantly higher rates. In the field, N2O emissions were not significantly affected by increasing chamber headspace concentrations up to 100 ppb 15N2O. The pool dilution model estimates of 14N2O and 15N¬2O concentrations as well as net N2O fluxes fit observed data very well, suggesting that the technique yielded robust estimates of gross N2O production. Gross N2O production rates averaged 8.4 ± 3.2 mg N m-2 d-1 and were most strongly correlated to mineral N concentrations and denitrifying enzyme activity together (R2 = 0.73). Gross N2O consumption rates estimated using the pool dilution technique were 55 ± 1 % less than rates calculated as the difference between gross N2O production rates and net N2O fluxes, possibly due to heterogeneous and/or inadequate 15N2O tracer diffusion to deeper layers in the soil profile. Estimated and calculated gross N2O consumption rates constrained the proportion of produced N2O released to the atmosphere (termed the N2O yield) from 0.70 to 0.84. Gross N2O consumption rates and N2O yields were not strongly correlated to any soil property measured (i.e., soil moisture, pH, DEA, mineral N concentration, soil O2 concentration). Our study demonstrates that the 15N2O pool dilution technique is a valuable tool for

  15. 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.

  16. Preparation and structural evolution of SiO(2)-TiO(2) pillared layered manganese oxide nanocomposite upon intercalating reaction.

    PubMed

    Wang, Jianfang; Liu, Zong-Huai; Tang, Xiuhua; Ooi, Kenta

    2007-03-15

    SiO(2)-TiO(2) pillared layered manganese oxide nanohybrid was successfully synthesized by preliminarily expanding the interlayer of H-type layered manganese oxide using dodecylamine, followed by reacting it with a mixture solution of titanium isopropoxide and tetraethylorthosilicate. The basal spacing and the pillared agent content of the obtained materials connected with the length of intercalated n-alkylamine, incorporated Si/Ti molar ratios and the solvothermal treatment temperature. The structural evolution of SiO(2)-TiO(2) pillared layered manganese oxide nanohybrid was characterized by XRD, DSC-TGA, SEM, IR, N(2) adsorption-desorption and element analyses. TiO(2) particles exhibited a stronger affinity for the negatively charged manganese layers, and the TiO(2) particles incorporated were independently intercalated without any distinct chemical bonding with the co-intercalated SiO(2) particles. SiO(2)-TiO(2) pillared layered manganese oxide nanohybrid had a BET surface area of 98 m(2)/g with a gallery height of about 1.43 nm between layers. The obtained SiO(2)-TiO(2) co-pillared layered manganese oxide nanohybrid is expected as a selective catalyst, or an improved battery material.

  17. The 1.27-μm O2 continuum absorption in O2/CO2 mixtures

    NASA Astrophysics Data System (ADS)

    Fraser, G. T.; Lafferty, W. J.

    2001-12-01

    The collision-induced, near-infrared O2 continuum band overlapping the weak a1Δg-X3Σg-, v = 0-0, 1.27 μm discrete band of O2 has been investigated in O2/CO2 mixtures at room temperature (T = 296 K) for total densities from 1.8 to 9.3 times that of an ideal gas under standard conditions (T = 273.15 K and P = 101.325 kPa), i.e., from 1.8 to 9.3 amagats. Absorption spectra were recorded at 0.5 cm-1 resolution using a Fourier transform spectrometer and an 84-m pathlength. A least squares analysis of the integrated band strength, Stotal = SO2ρO2 + SO2 - O2 ρO22 + SO2 - CO2ρO2ρCO2, as a function of the carbon dioxide density, ρCO2, and the oxygen density, ρ02, yields SO2-Co2 = 2.953(32) × 10-43 cm-2 (molecule/cm3)-2 (i.e., 2.132(23) × 10-4 cm-2 amagat-2). The SO2-CO2 coefficient is ˜3 times greater than the corresponding SO2-N2 coefficient determined from studies of O2/N2 mixtures, illustrating the efficiency of large electric multipolar moments in inducing continuum absorption in the 1.27-μm band of O2. The results support the calculations by Brown and Tipping [2000], which demonstrate the importance of water, with its large electric dipole moment, in enhancing the collision-induced absorption bands of O2 and N2 in the atmosphere. We suggest that the apparent inability of radiative transfer models to accurately account for the increased atmospheric absorption present when water vapor levels increase may be due in part to the neglect of the intensity enhancement of a number of continuum bands and of the far wings of discrete bands by water molecule collisions.

  18. Effect of fluorine additive on CeO2(ZrO2)/TiO2 for selective catalytic reduction of NO by NH3.

    PubMed

    Jin, Qijie; Shen, Yuesong; Zhu, Shemin

    2017-02-01

    A series of CeO2(ZrO2)/TiO2 catalysts with fluorine additive were prepared by impregnation method and tested for selective catalytic reduction (SCR) of NO by NH3. These samples were characterized by XRD, N2-BET, Raman spectra, SEM, TEM, NH3-TPD, H2-TPR and XPS, respectively. Results showed that the optimal catalyst with the appropriate HF exhibited excellent performance for NH3-SCR and more than 96% NO conversion at 360°C under GHSV of 71,400h(-1). It was found that the grain size of TiO2 increased and the specific surface area reduced with the modulation of HF, which was not good for the adsorption of gas molecule. However, the modulation of HF exposed the high energy (001) facets of TiO2 and increased the surface chemisorbed oxygen concentration, oxygen storage capacity and Ce(3+) concentration of catalyst. In addition, the synergy of (101) and (001) facets was beneficial to the improvement of catalytic activity.

  19. Photodissociation of interstellar N2

    NASA Astrophysics Data System (ADS)

    Li, X.; Heays, A. N.; Visser, R.; Ubachs, W.; Lewis, B. R.; Gibson, S. T.; van Dishoeck, E. F.

    2013-07-01

    Context. Molecular nitrogen is one of the key species in the chemistry of interstellar clouds and protoplanetary disks, but its photodissociation under interstellar conditions has never been properly studied. The partitioning of nitrogen between N and N2 controls the formation of more complex prebiotic nitrogen-containing species. Aims: The aim of this work is to gain a better understanding of the interstellar N2 photodissociation processes based on recent detailed theoretical and experimental work and to provide accurate rates for use in chemical models. Methods: We used an approach similar to that adopted for CO in which we simulated the full high-resolution line-by-line absorption + dissociation spectrum of N2 over the relevant 912-1000 Å wavelength range, by using a quantum-mechanical model which solves the coupled-channels Schrödinger equation. The simulated N2 spectra were compared with the absorption spectra of H2, H, CO, and dust to compute photodissociation rates in various radiation fields and shielding functions. The effects of the new rates in interstellar cloud models were illustrated for diffuse and translucent clouds, a dense photon dominated region and a protoplanetary disk. Results: The unattenuated photodissociation rate in the Draine (1978, ApJS, 36, 595) radiation field assuming an N2 excitation temperature of 50 K is 1.65 × 10-10 s-1, with an uncertainty of only 10%. Most of the photodissociation occurs through bands in the 957-980 Å range. The N2 rate depends slightly on the temperature through the variation of predissociation probabilities with rotational quantum number for some bands. Shielding functions are provided for a range of H2 and H column densities, with H2 being much more effective than H in reducing the N2 rate inside a cloud. Shielding by CO is not effective. The new rates are 28% lower than the previously recommended values. Nevertheless, diffuse cloud models still fail to reproduce the possible detection of interstellar N2

  20. Stress and environmental shift characteristics of HfO2/SiO2 multilayer coatings

    NASA Astrophysics Data System (ADS)

    Anzellotti, J. F.; Smith, Douglas J.; Sczupak, Robert J.; Chrzan, Z. Roman

    1997-05-01

    HfO2/SiO2 polarizer coatings for 1054 nm have been produced that have low stress at explicit environmental conditions without the employment of backside stress- compensation films. In this process hafnia is condensed from a metallic melt and silica from an oxide source, both via electron-beam evaporation. Specifically, this process has been adopted for multilayer designs with stringent requirements on spectral control and wavefront distortion. Efforts to meet these requirements have prompted various investigations of coating stress and spectral behavior, especially under changing environmental conditions. Results have shown that coating stress and optical thickness vary significantly with humidity. THese quantities have been measured under both ambient air and dry nitrogen atmospheres. The effects of coating parameters on stress and environmental stability have been examined for an experimental hafnia/silica polarizer coating. The aforementioned parameters are hafnia deposition rate, oxygen pressure during hafnia deposition, and oxygen pressure during silica deposition. Results indicate a strong correlation of coating stress to oxygen pressure during the silica evaporation. Data on the aging of stress in hafnia/silica coatings will also be presented. The HfO2/SiO2 process has ben utilized in high-laser-damage- threshold coatings for the OMEGA laser system and for National Ignition Facility development coatings at the Laboratory for Laser Energetics.

  1. Effects of Fe-doping on the photocatalytic activity of mesoporous TiO2 powders prepared by an ultrasonic method.

    PubMed

    Zhou, Minghua; Yu, Jiaguo; Cheng, Bei

    2006-10-11

    Highly photoactive nanocrystalline mesoporous Fe-doped TiO(2) powders were prepared by the ultrasonic-induced hydrolysis reaction of tetrabutyl titanate (Ti(OC(4)H(9))(4)) in a ferric nitrate aqueous solution (pH 5) without using any templates or surfactants. The as-prepared samples were characterized by thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), N(2) adsorption-desorption measurements, UV-visible adsorbance spectra (UV-vis) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities were evaluated by the photocatalytic oxidation of acetone in air. The results showed that all the Fe-doped TiO(2) samples prepared by ultrasonic methods were mesoporous nanocrystalline. A small amount of Fe(3+) ions in TiO(2) powders could obviously enhance their photocatalytic activity. The photocatalytic activity of Fe-doped TiO(2) powders prepared by this method and calcined at 400 degrees C exceeded that of Degussa P25 (P25) by a factor of more than two times at an optimal atomic ratio of Fe to Ti of 0.25. The high activities of the Fe-doped TiO(2) powders could be attributed to the results of the synergetic effects of Fe-doping, large BET specific surface area and small crystallite size.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. Enhanced photocatalytic activity of S-doped TiO2-ZrO2 nanoparticles under visible-light irradiation.

    PubMed

    Tian, Guohui; Pan, Kai; Fu, Honggang; Jing, Liqiang; Zhou, Wei

    2009-07-30

    Porous nanocrystalline S-doped TiO2-ZrO2 visible-light photocatalysts were prepared through a one-step method. The resulting materials were characterized by X-ray diffraction (XRD), N(2) adsorption-desorption measurements, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS), Fourier transform infrared spectra (FT-IR) and electron paramagnetic resonance (ESR). It was found that modification by ZrO2 could effectively inhibit phase transformation, enhance visible-light absorption, and possess more surface hydroxyl groups. The photocatalytic activity of S-doped TiO2-ZrO2 was higher than that of unmodified S-doped TiO2 and Degussa P25. The enhanced photocatalytic activity could be attributed to the higher specific area, smaller crystal size, porous structure and more surface hydroxyl groups in the catalyst.

  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. N2O FIELD STUDY

    EPA Science Inventory

    The report gives results of measurements of nitrous oxide (N2O) emissions from coal-fired utility boilers at three electric power generating stations. Six units were tested, two at each site, including sizes ranging from 165 to 700 MW. Several manufacturers and boiler firing type...

  10. N2O and NOy

    NASA Technical Reports Server (NTRS)

    Kawa, S. R.; Jackman, C. H.; Douglass, A. R.; Strahan, S. E.

    2003-01-01

    The principal loss processes for ozone in the stratosphere are either directly or indirectly closely coupled to the abundance and distribution of reactive oxides of nitrogen (NOy). The main source of NOy in the stratosphere is N2O, a trace gas that is changing significantly as a result of anthropogenic forcing. Thus diagnosis of the distributions of N2O, NOy, and their coupling is required to evaluate any chemistry-climate model aspiring to accurately simulate ozone change. In the NASA Assessment of the Effects of High-speed Aircraft in the Stratosphere: 1998 we found that the sensitivity of various models ozone to perturbation did correspond consistently with their background NOy distribution. Coordinated NOy and N2O mixing ratio distributions are available from observations: ER-2 aircraft in the lower stratosphere and ATMOS and balloon profiles to higher altitudes at a subset of latitudes and seasons. Although close comparison to these diagnostics is crucial, unfortunately the distributions are due to a combination of transport and chemical processes, and isolating the source of differences is not always simple. However, in combination with other transport and photochemical diagnostics, comparison with N2O and NOy can be very instructive in evaluation of model processes and performance.

  11. 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.

  12. Well-organized meso-macroporous TiO2/SiO2 film derived from amphiphilic rubbery comb copolymer.

    PubMed

    Jeon, Harim; Lee, Chang Soo; Patel, Rajkumar; Kim, Jong Hak

    2015-04-15

    We report the facile synthesis of a well-organized meso-macroporous TiO2/SiO2 thin film with high porosity and good interconnectivity from a binary mixture (i.e., titania precursor and polymer template). Our process is based on self-assembly of the amphiphilic rubbery comb copolymer, poly(dimethylsiloxane)-g-poly(oxyethylene methacrylate) (PDMS-g-POEM) with titanium tetraisopropoxide (TTIP). SiO2 is self-provided by thermal oxidation of PDMS chains during calcination under air. The selective, preferential interaction between TTIP and the hydrophilic POEM chains was responsible for the formation of well-organized TiO2/SiO2 films, as supported by transmission electron microscopy, scanning electron microscopy, X-ray photospectroscopy, and X-ray diffraction analyses. We investigated in detail the effect of precursor content, solvent type, and polymer concentration on thin film morphology. Photodegradation of methyl orange by the well-organized meso-macroporous TiO2/SiO2 film was greater than that of a dense TiO2 film prepared without PDMS-g-POEM as well as a SiO2-etched TiO2 film. These results indicate that the well-organized structure and SiO2 doping of the TiO2 film play a pivotal role in enhancing its photocatalytic properties.

  13. Insights into Electrochemical Oxidation of NaO2 in Na-O2 Batteries via Rotating Ring Disk and Spectroscopic Measurements.

    PubMed

    Morasch, Robert; Kwabi, David G; Tulodziecki, Michal; Risch, Marcel; Zhang, Shiyu; Shao-Horn, Yang

    2017-02-08

    O2 reduction in aprotic Na-O2 batteries results in the formation of NaO2, which can be oxidized at small overpotentials (<200 mV) on charge. In this study, we investigated the NaO2 oxidation mechanism using rotating ring disk electrode (RRDE) measurements of Na-O2 reaction products and by tracking the morphological evolution of the NaO2 discharge product at different states of charge using scanning electron microscopy (SEM). The results show that negligible soluble species are formed during NaO2 oxidation, and that the oxidation occurs predominantly via charge transfer at the interface between NaO2 and carbon electrode fibers rather than uniformly from all NaO2 surfaces. X-ray absorption near edge structure (XANES), and X-ray photoelectron spectroscopy (XPS) measurements show that the band gap of NaO2 is smaller than that of Li2O2 formed in Li-O2 batteries, in which charging overpotentials are much higher (∼1000 mV). These results emphasize the importance of discharge product electronic structure for rationalizing metal-air battery mechanisms and performance.