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Sample records for 4center dot2hsub 2o

  1. Intercalation of aliphatic amines into the layered structure of vanadyl(IV) hydrogen phosphate hemihydrate (VOHPO[sub 4][center dot]0. 5H[sub 2]O)

    SciTech Connect

    Guliants, V.V.; Benziger, J.B.; Sundaresan, S. )

    1994-04-01

    The vanadyl(IV) hydrogen phosphate hemihydrate, VOHPO[sub 4][center dot]0.5H[sub 2]O, is a pyrolytic precursor of the vanadyl(IV) pyrophosphate phase, (VO)[sub 2]P[sub 2]O[sub 7], generally believed to be the active phase in the selective oxidation of n-butane into maleic anhydride. Pyrolytic transformation into the pyrophosphate phase occurs with conservation of a morphology of the material. VOHPO[sub 4][center dot]0.5H[sub 2]O is a layered hydrogen phosphate, where -POH groups form interlayer hydrogen bonds with the water molecules shared by two face-linked vanadyl octahedra. The structure of the hemihydrate is similar to that of [alpha]-zirconium hydrogen phosphate ([alpha]-ZrP), where hydrogen bonds are within the same layer and -POH groups are also pointed into the interlayer space. In contrast to [alpha]-ZrP, where extensive data exist, intercalation chemistry of the layered vanadyl(IV) hydrogen phosphate hemihydrate at present is a terra incognita. This paper reports the results of the first systematic study of VOHPO[sub 4][center dot]0.5H[sub 2]O intercalation with aliphatic amines as a new route to novel vanadyl(IV) phosphate phases. N-Alkylamines have been commonly known as excellent intercalation agents for testing the intracrystalline reactivity of layered oxides. Intercalated alkylamines may also facilitate introduction of thermostable guest molecules, or [open quotes]pillars[close quotes], by ion exchange producing microporous materials which can modify catalytic and sorptive properties. 9 refs., 6 figs., 2 tabs.

  2. La2SrCr2O7F2: A Ruddlesden-Popper Oxyfluoride Containing Octahedrally Coordinated Cr(4+) Centers.

    PubMed

    Zhang, Ronghuan; Read, Gareth; Lang, Franz; Lancaster, Tom; Blundell, Stephen J; Hayward, Michael A

    2016-03-21

    The low-temperature fluorination of the n = 2 Ruddlesden-Popper phase La2SrCr2O7 yields La2SrCr2O7F2 via a topochemical fluorine insertion reaction. The structure-conserving nature of the fluorination reaction means that the chromium centers of the initial oxide phase retain an octahedral coordination environment in the fluorinated product, resulting in a material containing an extended array of apex-linked Cr(4+)O6 units. Typically materials containing networks of octahedrally coordinated Cr(4+) centers can only be prepared at high pressure; thus, the preparation of La2SrCr2O7F2 demonstrates that low-temperature topochemical reactions offer an alternative synthesis route to materials of this type. Neutron diffraction, magnetization, and μ(+)SR data indicate that La2SrCr2O7F2 undergoes a transition to an antiferromagnetic state below TN ≈ 140 K. The structure-property relations of this phase and other Cr(4+) oxide phases are discussed.

  3. Crystal structure of the complex neptunyl(V) chromate CsNpO{sub 2}CrO{sub 4}{center_dot}2H{sub 2}O

    SciTech Connect

    Grigor`ev, M.S.; Plotnikova, T.E.; Baturin, N.A.

    1995-03-01

    Crystal structure of CsNpO{sub 2}CrO{sub 4}{center_dot}2H{sub 2}O has been determined using a CAD4 autodiffractometer (MoK{sub alpha} radiation, graphite monochromator, {omega}/2{theta} scanning). Crystal data: a = 7.359(3), b = 7.523(2), c = 15.457(3) {angstrom}; space group Pnma, Z = 4, d{sub calc} = 4.30 g cm{sup -3}, {mu}(MoK{sub alpha}) = 163 cm{sup -1}, R = 0.043, and R{sub omega} = 0.057 for 1103 reflections with I > 5{sigma}(I) and sin {theta}/{lambda} > 0.10 {angstrom}{sup -1}. The crystal structure consists of infinite chains with the composition (NpO{sub 2}CrO{sub 4}(H{sub 2}O)){sup n-}{sub n}, in which the coordination polyhedra of Np atoms (pentagonal bipyramids) are linked by common edges through the bridging chromate ions. The IR and electronic absorption spectra are discussed.

  4. Synthesis and crystal structure of 3-ammoniumphenyl sulfone selenate, 3-aminophenyl sulfone [C{sub 12}H{sub 14}N{sub 2}O{sub 2}S]SeO{sub 4} {center_dot} [C{sub 12}H{sub 12}N{sub 2}O{sub 2}S

    SciTech Connect

    Mahroug, A.; Belhouchet, M. Mhiri, T.

    2013-07-15

    The crystal structure of [C{sub 12}H{sub 14}N{sub 2}O{sub 2}S]SeO{sub 4} {center_dot} [C{sub 12}H{sub 12}N{sub 2}O{sub 2}S] was determined by X-ray diffraction on single crystal. Crystals are orthorhombic, space group Pbca, with cell parameters a = 11.545 (1), b = 8.143 (1), c = 55.783(1)A, V = 5244.2 (8)A{sup 3} and Z = 8. The structure can be described as organic layers built by [C{sub 12}H{sub 14}N{sub 2}O{sub 2}S]{sup 2+} cations and [C{sub 12}H{sub 12}N{sub 2}O{sub 2}S] molecules, parallel to ab plane, between which the inorganic groups SeO{sub 4}{sup 2-} are inserted. In this atomic arrangement, H-bonds between the different species play an important role in the three-dimensional network cohesion.

  5. Copper uranyl phosphate and arsenate incorporating an organic ligand with a pillared layer structure: [Cu(4,4 Prime -bpy)(UO{sub 2}){sub 0.5}(HPO{sub 4})(H{sub 2}PO{sub 4})]{center_dot}H{sub 2}O and [Cu(4,4 Prime -bpy)(UO{sub 2}){sub 0.5}(HAsO{sub 4})(H{sub 2}AsO{sub 4})]{center_dot}1.5H{sub 2}O

    SciTech Connect

    Wang, Chih-Min; Lii, Kwang-Hwa

    2013-01-15

    Two mixed-metal uranium compounds, [Cu(4,4 Prime -bpy)(UO{sub 2}){sub 0.5}(HPO{sub 4})(H{sub 2}PO{sub 4})]{center_dot}H{sub 2}O (1) and [Cu(4,4 Prime -bpy)(UO{sub 2}){sub 0.5}(HAsO{sub 4})(H{sub 2}AsO{sub 4})]{center_dot}1.5H{sub 2}O (2) have been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction, fluorescence spectroscopy, and magnetic susceptibility. They are the first examples of mixed-metal uranium phosphate and arsenate incorporating an organic ligand. Their structures contain copper uranyl phosphate/arsenate layers which are covalently linked by 4,4 Prime -bpy pillars to form a 3-D framework structure. The fluorescence spectrum of 1 shows the characteristic vibronic structure of the UO{sub 2}{sup 2+} moiety despite the presence of copper(II) ions in its structure. The two compounds are isostructural and crystallize in the monoclinic space group C2/c with a=20.184(4) A, b=8.921(2) A, c=19.095(3) A, {beta}=115.15(1) Degree-Sign , and R{sub 1}=0.0244 for 1, and a=20.184(1) A, b=9.0210(5) A, c=19.714(1) A, {beta}=114.879(1) Degree-Sign , and R{sub 1}=0.0399 for 2. - Graphical abstract.: A new copper uranyl phosphate and the arsenate analog have been presented. The compounds contain copper uranyl phosphate/arsenate layers covalently linked by 4,4 Prime -bipyridine pillars into an open-framework structure.

  6. 4. CENTER COURTYARD, FROM WEST SIDE OF SOUTHEAST PORTION OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. CENTER COURTYARD, FROM WEST SIDE OF SOUTHEAST PORTION OF BUILDING, LOOKING WEST. - Oakland Naval Supply Center, Administration Building-Dental Annex-Dispensary, Between E & F Streets, East of Third Street, Oakland, Alameda County, CA

  7. 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...

  8. Cr{sup 6+}-containing phases in the system CaO-Al{sub 2}O{sub 3}-CrO{sub 4}{sup 2-}-H{sub 2}O at 23 Degree-Sign C

    SciTech Connect

    Poellmann, Herbert

    2012-01-15

    Synthesis and investigation of lamellar calcium aluminium hydroxy salts was performed to study the incorporation of chromate ions in the interlayer of lamellar calcium aluminium hydroxy salts. Different AFm-phases (calcium aluminate hydrate with alumina, ferric oxide, mono-anion phase) containing chromate were synthesized. These AFm-phases belong to the group of layered double hydroxides (LDHs). 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaCrO{sub 4}{center_dot}nH{sub 2}O and C{sub 3}A{center_dot}1/2Ca(OH){sub 2}{center_dot}1/2CaCrO{sub 4}{center_dot}12H{sub 2}O were obtained as pure phases and their different distinct interlayer water contents and properties determined. Solid solution of chromate-containing phases and tetracalcium-aluminate-hydrate (TCAH) were studied. The uptake of chromate into TCAH from solutions was proven. Chromate contents in solution decrease to <0.2 mg/l. - Graphical abstract: Chromate can be incorporated in LDH-phases with compositions like: 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}1/2CaCrO{sub 4}{center_dot}1/2Ca(OH){sub 2}{center_dot}nH{sub 2}O, 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaCrO{sub 4}{center_dot}nH{sub 2}O, 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}1/6CaCrO{sub 4}.{center_dot}5/6Ca(OH){sub 2}{center_dot}nH{sub 2}O, 3CaO{center_dot}Al{sub 2}O{sub 3}(0-x)CaCrO{sub 4}(1-x) Ca(OH){sub 2}{center_dot}12H{sub 2}O, (02}O{sub 3}{center_dot}CaCrO{sub 4}{center_dot}nH{sub 2}O and C{sub 3}A{center_dot}1/2 Ca(OH){sub 2}{center_dot}1/2 CaCrO{sub 4}{center_dot}12 H{sub 2}O are given. Black-Right-Pointing-Pointer Different hydrates of Ca-Al-hydroxysalts (LDH) with chromate-anions synthesized and characterized. Black-Right-Pointing-Pointer Interlayer exchange reaction of 2OH{sup -} and CrO{sub 4}{sup 2-} investigated. Black-Right-Pointing-Pointer Thermal dehydration and change of lattice parameters are given

  9. The Vaporization of B2O3(l) to B2O3(g) and B2O2(g)

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Myers, Dwight L.

    2011-01-01

    The vaporization of B2O3 in a reducing environment leads to formation of both B2O3(g) and B2O2(g). While formation of B2O3(g) is well understood, many questions about the formation of B2O2(g) remain. Previous studies using B(s) + B2O3(l) have led to inconsistent thermodynamic data. In this study, it was found that after heating, B(s) and B2O3(l) appear to separate and variations in contact area likely led to the inconsistent vapor pressures of B2O2(g). To circumvent this problem, an activity of boron is fixed with a two-phase mixture of FeB and Fe2B. Both second and third law enthalpies of formation were measured for B2O2(g) and B2O3(g). From these the enthalpies of formation at 298.15 K are calculated to be -479.9 +/- 41.5 kJ/mol for B2O2(g) and -833.4 +/- 13.1 kJ/mol for B2O3(g). Ab initio calculations to determine the enthalpies of formation of B2O2(g) and B2O3(g) were conducted using the W1BD composite method and show good agreement with the experimental values.

  10. Hydrothermal transformation of magadiite into ferrierite in Al 2O 3-Na 2O-ethylenediamine-H 2O system

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Yang, Yang; Cui, Miao; Sun, Jiangbo; Qi, Lin; Ji, Shouhua; Meng, Changgong

    2011-12-01

    This study investigated the transformation of magadiite into ferrierite in Al 2O 3-Na 2O-ethylenediamine (EDA)-H 2O system. The influence of various parameters such as reaction temperature, time, alkalinity, the reactant Na 2O/SiO 2 ratio and EDA/SiO 2 ratio were examined. Thermal and acid stability of the synthetic ferrierite are presented. Highly crystallized and pure ferrierite could be obtained from dispersion with the molar composition: 0.01 Na 2O: 0.005 Al 2O 3: SiO 2: 30 H 2O: 20 EDA by heating at 433 K for 48 h. The structure of ferrierite was destroyed when the temperature rose above 873 K and the framework of the sample, stirred in 5 mol/L HCl for 3 h, is consistent with the untreated ferrierite.

  11. Thermodynamics of Cr2O3, FeCr2O4, ZnCr2O4 and CoCr2O4

    SciTech Connect

    Ziemniak SE, Anovitz LM, Castelli RA, Porter WD

    2007-01-09

    High temperature heat capacity measurements were obtained for Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4}, ZnCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4} using a differential scanning calorimeter. These data were combined with previously-available, overlapping heat capacity data at temperatures up to 400 K and fitted to 5-parameter Maier-Kelley C{sub p}(T) equations. Expressions for molar entropy were then derived by suitable integration of the Maier-Kelley equations in combination with recent S{sup o}(298) evaluations. Finally, a database of high temperature equilibrium measurements on the formation of these oxides was constructed and critically evaluated. Gibbs energies of Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4} were referenced by averaging the most reliable results at reference temperatures of 1100, 1400 and 1373 K, respectively, while Gibbs energies for ZnCr{sub 2}O{sub 4} were referenced to the results of Jacob [Thermochim. Acta 15 (1976) 79-87] at 1100 K. Thermodynamic extrapolations from the high temperature reference points to 298.15 K by application of the heat capacity correlations gave {Delta}{sub f}G{sup o}(298) = -1049.96, -1339.40, -1428.35 and -1326.75 kJ mol{sup -1} for Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4}, ZnCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4}, respectively.

  12. H2O2: A Dynamic Neuromodulator

    PubMed Central

    Rice, Margaret E.

    2012-01-01

    Increasing evidence implicates hydrogen peroxide (H2O2) as an intra- and intercellular signaling molecule that can influence processes from embryonic development to cell death. Most research has focused on relatively slow signaling, on the order of minutes to days, via second messenger cascades. However, H2O2 can also mediate subsecond signaling via ion channel activation. This rapid signaling has been examined most thoroughly in the nigrostriatal dopamine (DA) pathway, which plays a key role in facilitating movement mediated by the basal ganglia. In DA neurons of the substantia nigra, endogenously generated H2O2 activates ATP-sensitive K+ (KATP) channels that inhibit DA neuron firing. In the striatum, H2O2 generated downstream from glutamatergic AMPA receptor activation in medium spiny neurons acts as a diffusible messenger that inhibits axonal DA release, also via KATP channels. The source of dynamically generated H2O2 is mitochondrial respiration; thus, H2O2 provides a novel link between activity and metabolism via KATP channels. Additional targets of H2O2 include transient receptor potential (TRP) channels. In contrast to the inhibitory effect of H2O2 acting via KATP channels, TRP channel activation is excitatory. This review describes emerging roles of H2O2 as a signaling agent in the nigrostriatal pathway and other basal ganglia neurons. PMID:21666063

  13. H2O2: a dynamic neuromodulator.

    PubMed

    Rice, Margaret E

    2011-08-01

    Increasing evidence implicates hydrogen peroxide (H(2)O(2)) as an intracellular and intercellular signaling molecule that can influence processes from embryonic development to cell death. Most research has focused on relatively slow signaling, on the order of minutes to days, via second messenger cascades. However, H(2)O(2) can also mediate subsecond signaling via ion channel activation. This rapid signaling has been examined most thoroughly in the nigrostriatal dopamine (DA) pathway, which plays a key role in facilitating movement mediated by the basal ganglia. In DA neurons of the substantia nigra, endogenously generated H(2)O(2) activates ATP-sensitive K(+) (K-ATP) channels that inhibit DA neuron firing. In the striatum, H(2)O(2) generated downstream from glutamatergic AMPA receptor activation in medium spiny neurons acts as a diffusible messenger that inhibits axonal DA release, also via K-ATP channels. The source of dynamically generated H(2)O(2) is mitochondrial respiration; thus, H(2)O(2) provides a novel link between activity and metabolism via K-ATP channels. Additional targets of H(2)O(2) include transient receptor potential (TRP) channels. In contrast to the inhibitory effect of H(2)O(2) acting via K-ATP channels, TRP channel activation is excitatory. This review describes emerging roles of H(2)O(2) as a signaling agent in the nigrostriatal pathway and basal ganglia neurons.

  14. Photolysis of H2O-H2O2 Mixtures: The Destruction of H2O2

    NASA Technical Reports Server (NTRS)

    Loeffler, M. J.; Fama, M.; Baragiola, R. A.; Carlson, R. W.

    2013-01-01

    We present laboratory results on the loss of H2O2 in solid H2O + H2O2 mixtures at temperatures between 21 and 145 K initiated by UV photolysis (193 nm). Using infrared spectroscopy and microbalance gravimetry, we measured the decrease of the 3.5 micrometer infrared absorption band during UV irradiation and obtained a photodestruction cross section that varies with temperature, being lowest at 70 K. We use our results, along with our previously measured H2O2 production rates via ionizing radiation and ion energy fluxes from the spacecraft to compare H2O2 creation and destruction at icy satellites by ions from their planetary magnetosphere and from solar UV photons. We conclude that, in many cases, H2O2 is not observed on icy satellite surfaces because the H2O2 photodestruction rate is much higher than the production rate via energetic particles, effectively keeping the H2O2 infrared signature at or below the noise level.

  15. In2O3/Bi2Sn2O7 heterostructured nanoparticles with enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Xing, Yonglei; Que, Wenxiu; Yin, Xingtian; He, Zuoli; Liu, Xiaobin; Yang, Yawei; Shao, Jinyou; Kong, Ling Bing

    2016-11-01

    In2O3/Bi2Sn2O7 composite photocatalysts with various contents of cubic In2O3 nanoparticles were fabricated by using impregnation method. A thriving modification of Bi2Sn2O7 by an introduction of In2O3 was confirmed by using X-ray diffraction, UV-vis diffuse reflectance spectrometry, transmission electron microscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The samples composed of hybrids of In2O3 and Bi2Sn2O7 exhibited a much higher photocatalytic activity for the degradation of Rhodamine B under visible light, as compared with pure In2O3 and Bi2Sn2O7 nanoparticles. Optimized composition of the composite photocatalysts was 0.1In2O3/Bi2Sn2O7, which shows a rate constant higher than those of pure In2O3 and Bi2Sn2O7 by 4.06 and 3.21 times, respectively. Based on Mott-Schottky analysis and active species detection, the photoexcited electrons in the conduction band of In2O3 and the holes in the valence band of Bi2Sn2O7 participated in reduction and oxidation reactions, respectively. Hence, rad OH, rad O2- and h+ were the main active species involved in the photocatalytic reaction of the In2O3/Bi2Sn2O7 composite photocatalysts. The effective separation process of the photogenerated electron-hole pairs was testified by photocurrent test.

  16. Terahertz Characteristics of Liquid D{sub 2}O in H{sub 2}O

    SciTech Connect

    Chong, Joonggun; Maeng, Inhee; Shin, Hee Jun; Son, Joo-Hiuk

    2009-04-19

    D{sub 2}O used in nuclear power generation is very slightly different from H{sub 2}O. Deuterium (D) is the isotope of hydrogen (H) and has one more neutron than H. D{sub 2}O is heaver than H{sub 2}O by about 11% and its melting and boiling points are 3.81 deg. C and 101.42 deg. C, respectively. Moreover, D{sub 2}O is toxic. It is harmful for human body if it replaces more than approximately 25-50% of a human's body water. So, knowledge of the properties of D{sub 2}O included in H{sub 2}O is necessary. The confinement energy and hydrogen bonding energy of large molecules are in the terahertz frequency region (2{approx}10 THz, 3{approx}66 cm{sup -1}). Particularly, the polar molecules such as H{sub 2}O and D{sub 2}O react to this frequency region well because the time of hydrogen relaxation motion is subpicosecond. Terahertz time-domain spectroscopy (THz-TDS) using terahertz pulses has been used in the study of ultrafast dynamics of hydrogen bonds in biomolecules and carriers in semiconductors. We obtained the refractive index and power absorption of H{sub 2}O and D{sub 2}O at room temperature. The results show that the refractive index and power absorption of H{sub 2}O are larger than for D{sub 2}O.

  17. Excellent ethanol sensing properties based on Er2O3-Fe2O3 nanotubes

    NASA Astrophysics Data System (ADS)

    Liu, Chang-Bai; He, Ying; Wang, Sheng-Lei

    2015-11-01

    In this work, pure α-Fe2O3 and Er2O3-Fe2O3 nanotubes were synthesized by a simple single-capillary electrospinning technology followed by calcination treatment. The morphologies and crystal structures of the as-prepared samples were characterized by scanning electron microscopy and x-ray diffraction, respectively. The gas-sensing properties of the as-prepared samples have been researched, and the result shows that the Er2O3-Fe2O3 nanotubes exhibit much better sensitivity to ethanol. The response value of Er2O3-Fe2O3 nanotubes to 10 ppm ethanol is 21 at the operating temperature 240°, which is 14 times larger than that of pure α-Fe2O3 nanotubes (response value is 1.5). The ethanol sensing properties of α-Fe2O3 nanotubes are remarkably enhanced by doping Er, and the lowest detection limit of Er2O3-Fe2O3 nanotubes is 300 ppb, to which the response value is about 2. The response and recovery times are about 4 s and 70 s to 10 ppm ethanol, respectively. In addition, the Er2O3-Fe2O3 nanotubes possess good selectivity and long-term stability. Project supported by Jilin Provincial Science and Technology Department, China (Grant No. 20140204027GX) and the Challenge Cup for College Students, China (Grant No. 450060497053).

  18. 40 CFR Table I-8 to Subpart I of... - Default Emission Factors (1-UN2O,j) for N2O Utilization (UN2O,j)

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Default Emission Factors (1-UN2O,j) for N2O Utilization (UN2O,j) I Table I-8 to Subpart I of Part 98 Protection of Environment... Factors (1-UN2O,j) for N2O Utilization (UN2O,j) Process type factors N2O CVD 1-Ui 0.8 Other...

  19. 40 CFR Table I-8 to Subpart I of... - Default Emission Factors (1-UN2O j) for N2O Utilization (UN2O j)

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Default Emission Factors (1-UN2O j) for N2O Utilization (UN2O j) I Table I-8 to Subpart I of Part 98 Protection of Environment... Factors (1-UN 2 O j) for N2O Utilization (UN2 O j) Process type factors N2O CVD 1-Ui 0.8...

  20. Cl2O4 in the Stratosphere

    ERIC Educational Resources Information Center

    Whisnant, David M.; Lever, Lisa; Howe, Jerry

    2005-01-01

    A comprehensive project in which the students use computational chemistry to investigate a larger chlorine oxide, Cl2O4 is described. The students start the project by reading a scenario and then follow a series of hyperlinks to develop, along with their colleagues, a better understanding of the implications of the presence of Cl2O4 in the…

  1. N2O molecular tagging velocimetry

    NASA Astrophysics Data System (ADS)

    ElBaz, A. M.; Pitz, R. W.

    2012-03-01

    A new seeded velocity measurement technique, N2O molecular tagging velocimetry (MTV), is developed to measure velocity in wind tunnels by photochemically creating an NO tag line. Nitrous oxide "laughing gas" is seeded into the air flow. A 193 nm ArF excimer laser dissociates the N2O to O(1D) that subsequently reacts with N2O to form NO. O2 fluorescence induced by the ArF laser "writes" the original position of the NO line. After a time delay, the shifted NO line is "read" by a 226-nm laser sheet and the velocity is determined by time-of-flight. At standard atmospheric conditions with 4% N2O in air, ˜1000 ppm of NO is photochemically created in an air jet based on experiment and simulation. Chemical kinetic simulations predict 800-1200 ppm of NO for 190-750 K at 1 atm and 850-1000 ppm of NO for 0.25-1 atm at 190 K. Decreasing the gas pressure (or increasing the temperature) increases the NO ppm level. The presence of humid air has no significant effect on NO formation. The very short NO formation time (<10 ns) makes the N2O MTV method amenable to low- and high-speed air flow measurements. The N2O MTV technique is demonstrated in air jet to measure its velocity profile. The N2O MTV method should work in other gas flows as well (e.g., helium) since the NO tag line is created by chemical reaction of N2O with O(1D) from N2O photodissociation and thus does not depend on the bulk gas composition.

  2. Phase equilibria in the oxide system Nd 2O 3-K 2O-P 2O 5

    NASA Astrophysics Data System (ADS)

    Szczygieł, Irena; Znamierowska, Teresa; Mizer, Dagmara

    2010-07-01

    A phase equilibria diagram of the partial system NdPO 4-K 3PO 4-KPO 3 has been developed as part of the research aimed at determining the phase equilibrium relationships in the oxide system Nd 2O 3-K 2O-P 2O 5. The investigations were conducted using thermoanalytical techniques, X-ray powder diffraction analysis and reflected-light microscopy. Three isopleths existing between: K 3Nd(PO 4) 2-K 4P 2O 7, NdPO 4-K 5P 3O 10 and NdPO 4-K 4P 2O 7 have been identified in the partial NdPO 4-K 3PO 4-KPO 3 system. Previously unknown potassium-neodymium phosphate "K 4Nd 2P 4O 15" has been discovered in the latter isopleth section. This phosphate exists in the solid phase up to a temperature of 890 °C at which it decomposes into the parent phosphates NdPO 4 and K 4P 2O 7. Four invariant points: two quasi-ternary eutectics, E 1 (1057 °C) and E 2 (580 °C) and two quasi-ternary peritectics, P 1 (1078 °C) and P 2 (610 °C), occur in the NdPO 4-K 3PO 4-KPO 3 region.

  3. Plasma etching behavior of Y2O3 ceramics: Comparative study with Al2O3

    NASA Astrophysics Data System (ADS)

    Cao, Yu-Chao; Zhao, Lei; Luo, Jin; Wang, Ke; Zhang, Bo-Ping; Yokota, Hiroki; Ito, Yoshiyasu; Li, Jing-Feng

    2016-03-01

    The plasma etching behavior of Y2O3 coating was investigated and compared with that of Al2O3 coating under various conditions, including chemical etching, mixing etching and physical etching. The etching rate of Al2O3 coating declined with decreasing CF4 content under mixing etching, while that of Y2O3 coating first increased and then decreased. In addition, the Y2O3 coating demonstrated higher erosion-resistance than Al2O3 coating after exposing to fluorocarbon plasma. X-ray photoelectron spectroscopy (XPS) analysis confirmed the formations of YF3 and AlF3 on the Y2O3 and Al2O3 coatings, respectively, which acted as the protective layer to prevent the surface from further erosion with fluorocarbon plasma. It was revealed that the etching behavior of Y2O3 depended not only on the surface fluorination but also on the removal of fluoride layer. To analyze the effect of porosity, Y2O3 bulk samples with high density were prepared by spark plasma sintering, and they demonstrated higher erosion-resistances compared with Y2O3 coating.

  4. In2O3/Al2O3 Catalysts for NOx Reduction in Lean Condition

    SciTech Connect

    Park, Paul W.; Ragle, Christie; Boyer, Carrie S.; Balmer, M Lou; Engelhard, Mark H. ); McCready, David E. )

    2002-01-01

    The lean NOx performance and catalytic properties of In2O3/Al2O3 catalysts were investigated. High lean NOx activity was observed when propene was used as a reductant in the presence of 9% O2 and 7% H2O at a space velocity of 30,000h-1. The optimum lean NOx activity of In2O3/Al2O3 catalysts was observed at a loading of 2.5 wt.% indium on -Al2O3 which was prepared by a sol-gel technique (230 m2/g). When propane was used as a reductant, the In2O3/Al2O3 catalyst did not promote NOx reduction compared to the alumina substrate. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and temperature programmed reduction (TPR) have been used to characterize a series of In2O3/Al2O3 catalysts to better understand the surface structure of indium oxide species on the alumina support. The XRD data indicated that crystalline In2O3 was present at In2O3 loadings > 5wt.% and the quantity of the crystalline phase increased as a function of indium loading. XPS results suggested that indium oxide existed as a well-dispersed phase up to 10wt.% indium. The well dispersed or reducible indium oxide species below 400 C in TPR experiments were assigned as the sites which activate propene to oxygenated hydrocarbons such as acetaldehyde and acrolein. Alumina sites readily utilize the oxygenated hydrocarbons to reduce NOx. Dual-function mechanism was proposed to explain NOx reduction over In2O3/Al2O3 catalysts.

  5. H2O Adsorption Kinetics on Smectites

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Howard, J.; Quinn, R. C.

    2000-01-01

    The adsorptive equilibration of H2O with montomorillonite has been measured. At low temperatures and pressures equilibration can require many hours, effectively preventing smectites at the martian surface from responding to diurnal pressure and temperature variations.

  6. Investigation of luminescence and laser transition of Dy3+ in Li2O-Gd2O3-Bi2O3-B2O3 glasses

    NASA Astrophysics Data System (ADS)

    Zaman, F.; Kaewkhao, J.; Srisittipokakun, N.; Wantana, N.; Kim, H. J.; Rooh, G.

    2016-05-01

    The aim of this study is to develop Li2O-Gd2O3-Bi2O3-B2O3 glass doped with different concentration of Dy3+ ions by melt quenching technique for different applications in photonics and laser devices. From the experimental oscillator strength (fexp) of the absorption spectra the JO intensity parameters (Ω λ = 2, 4, 6) have been calculated, and by using these JO intensity parameters various radiative parameters were calculated. By using JO theory the radiative transition probability (AR), radiative lifetime (τR) and branching ratio (βR) for Dy3+ ion have been found. A decrease in lifetimes of the prepared glass by increasing concentration of Dy3+ is because of the energy transfer through cross relaxation and resonant energy transfer channels in the present glass matrix. Using experimental and calculated lifetimes, the quantum efficiency (η) and non-radiative relaxation rates (WNR) of 4F9/2 excited state have been calculated. From emission spectra, effective bandwidths (Δλeff) and emission stimulated emission cross section σ (λp) were found for 4F9/2 → 6HJ (J = 15/2, 13/2, 11/2 and 9/2). Chromaticity results revealed that the CCT values of the LGBiBDy glass samples are in between to those of day light and commercial white light LED sources. Further investigations are under way for the optimization of dopant concentration in the Li2O-Gd2O3-Bi2O3-B2O3 glass.

  7. Acetone Sensing with In2O3-Coated Nb2O5 Nanorod Sensors.

    PubMed

    Park, Sunghoon; Kim, Soohyun; Jung, Jihwan; Lee, Chongmu

    2016-03-01

    Nb2O5-core/In2O3-shell nanorods were synthesized by thermal oxidation of Nb foil followed by sputter deposition of In2O3. The 1D nanostructures exhibited a rod-like morphology with widths and lengths ranging from 20 to 70 nm and 10 to 20 /jm, respectively. The sensing properties of Nb2O5-core/In2O3-shell nanorod sensors toward acetone gas were examined. The pristine Nb2O5 nanorods showed responses ranging from -121 to -253% to CH3COCH3 concentrations of 200-1,000 ppm. In contrast, Nb2O5-core/In2O3-shell nanorods showed responses ranging from -167 to -563% over the same concentration range. These responses are comparable or superior to other metal oxide semiconductor gas sensors in the literature. The underlying mechanism of the enhanced sensing properties of Nb2O5-core/In2O3-shell nanorods toward CH3COCH3 is also discussed.

  8. Metastability in the MgAl2O4-Al2O3 System

    DOE PAGES

    Wilkerson, Kelley R.; Smith, Jeffrey D.; Hemrick, James G.

    2014-07-22

    Aluminum oxide must take a spinel form ( γ-Al2O3) at elevated temperatures in order for extensive solid solution to form between MgAl2O4 and α-Al2O3. The solvus line between MgAl2O4 and Al2O3 has been defined at 79.6 wt% Al2O3 at 1500°C, 83.0 wt% Al2O3 at 1600°C, and 86.5 wt% Al2O3 at 1700°C. A metastable region has been defined at temperatures up to 1700°C which could have significant implications for material processing and properties. Additionally, initial processing could have major implications on final chemistry. The spinel solid solution region has been extended to form an infinite solid solution with Al2O3 at elevatedmore » temperatures. A minimum in melting at 1975°C and a chemistry of 96 wt% Al2O3 rather than a eutectic is present, resulting in no eutectic crystal formation during solidification.« less

  9. Bacterial Ice Nucleation in Monodisperse D2O and H2O-in-Oil Emulsions.

    PubMed

    Weng, Lindong; Tessier, Shannon N; Smith, Kyle; Edd, Jon F; Stott, Shannon L; Toner, Mehmet

    2016-09-13

    Ice nucleation is of fundamental significance in many areas, including atmospheric science, food technology, and cryobiology. In this study, we investigated the ice-nucleation characteristics of picoliter-sized drops consisting of different D2O and H2O mixtures with and without the ice-nucleating bacteria Pseudomonas syringae. We also studied the effects of commonly used cryoprotectants such as ethylene glycol, propylene glycol, and trehalose on the nucleation characteristics of D2O and H2O mixtures. The results show that the median freezing temperature of the suspension containing 1 mg/mL of a lyophilized preparation of P. syringae is as high as -4.6 °C for 100% D2O, compared to -8.9 °C for 100% H2O. As the D2O concentration increases every 25% (v/v), the profile of the ice-nucleation kinetics of D2O + H2O mixtures containing 1 mg/mL Snomax shifts by about 1 °C, suggesting an ideal mixing behavior of D2O and H2O. Furthermore, all of the cryoprotectants investigated in this study are found to depress the freezing phenomenon. Both the homogeneous and heterogeneous freezing temperatures of these aqueous solutions depend on the water activity and are independent of the nature of the solute. These findings enrich our fundamental knowledge of D2O-related ice nucleation and suggest that the combination of D2O and ice-nucleating agents could be a potential self-ice-nucleating formulation. The implications of self-nucleation include a higher, precisely controlled ice seeding temperature for slow freezing that would significantly improve the viability of many ice-assisted cryopreservation protocols. PMID:27495973

  10. Bacterial Ice Nucleation in Monodisperse D2O and H2O-in-Oil Emulsions.

    PubMed

    Weng, Lindong; Tessier, Shannon N; Smith, Kyle; Edd, Jon F; Stott, Shannon L; Toner, Mehmet

    2016-09-13

    Ice nucleation is of fundamental significance in many areas, including atmospheric science, food technology, and cryobiology. In this study, we investigated the ice-nucleation characteristics of picoliter-sized drops consisting of different D2O and H2O mixtures with and without the ice-nucleating bacteria Pseudomonas syringae. We also studied the effects of commonly used cryoprotectants such as ethylene glycol, propylene glycol, and trehalose on the nucleation characteristics of D2O and H2O mixtures. The results show that the median freezing temperature of the suspension containing 1 mg/mL of a lyophilized preparation of P. syringae is as high as -4.6 °C for 100% D2O, compared to -8.9 °C for 100% H2O. As the D2O concentration increases every 25% (v/v), the profile of the ice-nucleation kinetics of D2O + H2O mixtures containing 1 mg/mL Snomax shifts by about 1 °C, suggesting an ideal mixing behavior of D2O and H2O. Furthermore, all of the cryoprotectants investigated in this study are found to depress the freezing phenomenon. Both the homogeneous and heterogeneous freezing temperatures of these aqueous solutions depend on the water activity and are independent of the nature of the solute. These findings enrich our fundamental knowledge of D2O-related ice nucleation and suggest that the combination of D2O and ice-nucleating agents could be a potential self-ice-nucleating formulation. The implications of self-nucleation include a higher, precisely controlled ice seeding temperature for slow freezing that would significantly improve the viability of many ice-assisted cryopreservation protocols.

  11. Thermal and fragility studies on microwave synthesized K2O-B2O3-V2O5 glasses

    NASA Astrophysics Data System (ADS)

    Harikamalasree, Reddy, M. Sudhakara; Viswanatha, R.; Reddy, C. Narayana

    2016-05-01

    Glasses with composition xK2O-60B2O3-(40-x) V2O5 (15 ≤ x ≤ 39 mol %) was prepared by an energy efficient microwave method. The heat capacity change (ΔCp) at glass transition (Tg), width of glass transition (ΔTg), heat capacities in the glassy (Cpg) and liquid (Cpl) state for the investigated glasses were extracted from Modulated Differential Scanning Calorimetry (MDSC) thermograms. The width of glass transition is less than 30°C, indicating that these glasses belongs to fragile category. Fragility functions [NBO]/(Vm3Tg) and (ΔCp/Cpl)increases with increasing modifier oxide concentration. Increase in fragility is attributed to the increasing coordination of boron. Further, addition of K2O creates NBOs and the flow mechanism involves bond switching between BOs and NBOs. Physical properties exhibit compositional dependence and these properties increase with increasing K2O concentration. The observed variations are qualitatively analyzed.

  12. Galactic H2O maser surveys

    NASA Astrophysics Data System (ADS)

    Felli, Marcello; Palagi, Francesco

    The first part is devoted to give an updated situation of the single dish surveys of galactic H2O masers, with particular emphasis on those associated with star forming regions (SFR). The main input for this comes from the updated Arcetri Atlas of H2O masers obtained with the Medicina 32m radio telescope. Available information on variability of the maser emission is also briefly reviewed. The second part gives a description of the results derived from the comparison of VLA observations of H2O masers in SFR and near IR images. J, H, K images are able to reveal the stellar cluster present in these highly obscured regions. IT is found that a stellar source with strong H-K excess is almost always associated with the maser spots (and not necessarily with an ultracompact HII region) and represents the direct evidence of the Young Stellar Object (YSO) which is required for the maser pumping. There are several indications suggesting that the H2O maser/near IR source may represent one of the earliest manifestation of a recently formed star. Finally, the importance of a coordination between near IR full sky surveys and H2O maser surveys is briefly discussed.

  13. Cu2O nanoparticles synthesis by microplasma

    PubMed Central

    Du, ChangMing; Xiao, MuDan

    2014-01-01

    A simple microplasma method was used to synthesize cuprous oxide (Cu2O) nanoparticles in NaCl–NaOH–NaNO3 electrolytic system. Microplasma was successfully used as the cathode and copper plate was used as the anode. The Cu2O products are characterized by X–ray powder diffraction (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The results show that the morphology of Cu2O nanocrystals obtained by this technology is mainly dependent on the electrolytic media, stirring, current density and reaction temperature. The uniform and monodisperse sphere Cu2O nanoparticles with the size about 400 ~ 600 nm can be easily obtained in H2O–ethylene glycol mix–solvent (volume ratio 1:1) and appropriate current density with stirring at room temperature. In addition, the possible mechanism has been reported in the article. And the average energy consumed in producing 1 g Cu2O nanoparticles is 180 kJ. For the flexibility and effectiveness of this microplasma technology, it will have broad application prospects in the realm of nanoscience, energy and environment. PMID:25475085

  14. Glass transition temperature and conductivity in Li2O and Na2O doped borophosphate glasses

    NASA Astrophysics Data System (ADS)

    Ashwajeet, J. S.; Sankarappa, T.; Ramanna, R.; Sujatha, T.; Awasthi, A. M.

    2015-08-01

    Two alkali doped Borophosphate glasses in the composition, (B2O3)0.2. (P2O5)0.3. (Na2O)(0.5-x). (Li2O)x, where x = 0.05 to 0.50 were prepared by standard melt quenching method at 1200K. Non-crystalline nature was confirmed by XRD studies. Room temperature density was measured by Archimedes principle. DC conductivity in the temperature range from 300K to 575K has been measured. Samples were DSC studied in the temperature range from 423K to 673K and glass transition temperature was determined. Glass transition temperature passed through minima for Li2O con.2centration between 0.25 and 0.30 mole fractions. Activation energy of conduction has been determined by analyzing temperature variation of conductivity determining Arrhenius law. Conductivity passed through minimum and activation passed through maximum for Li2O content from 0.25 to 0.30 mole fractions. Glass transition temperature passed through minimum for the same range of Li2O content. These results revealed mixed alkali effect taking place in these glasses. It is for the first time borophosphate glasses doped with Li2O and Na2O have been studied for density and dc conductivity and, the mixed alkali effect (MAE) has been observed.

  15. Dependence of electrostatic potential distribution of Al2O3/Ge structure on Al2O3 thickness

    NASA Astrophysics Data System (ADS)

    Wang, Xiaolei; Xiang, Jinjuan; Wang, Wenwu; Zhao, Chao; Zhang, Jing

    2016-09-01

    Electrostatic potential distribution of Al2O3/Ge structure is investigated vs. Al2O3 thickness by X-ray photoelectron spectroscopy (XPS). The electrostatic potential distribution is found to be Al2O3 thickness dependent. This interesting phenomenon is attributed to the appearance of gap states on Al2O3 surface (GSAl2O3) and its higher charge neutrality level (CNL) compared with the CNL of gap states at Al2O3/Ge interface (GSAl2O3/Ge), leading to electron transfer from GSAl2O3 to GSAl2O3/Ge. In the case of thicker Al2O3, fewer electrons transfer from GSAl2O3 to GSAl2O3/Ge, resulting in a larger potential drop across Al2O3 and XPS results.

  16. Ion transport studies on Li2O-PbO-B2O3-P2O5 glass system

    NASA Astrophysics Data System (ADS)

    Muralidhara, R. S.; Anavekar, R. V.

    2009-07-01

    Electrical conductivity of Li+ ion conducting borophosphate glass system with the general formula xLi2O -10PbO-(90-x) [55B2O3 + 45 P2O5] where x=20, 25, 30 and 35 has been carried out both as a function of temperature and frequency in the temperature range 303K to 503K and over frequencies 20 Hz to 12 MHz. The dc conductivities show Arrhenius behaviour while exhibiting composition dependence. Edc estimated from Arrhenius plots varies from 0.82 eV 0.88 eV. The ac conductivity behaviour has been analyzed using a single power law. The exponent `s' obtained from the power law fits is found to have values ranging from 0.45 to 0.84.in these glasses and shows moderate temperature dependence The stretched exponent β also is seen to vary slightly with temperature. Scaling behaviour also has been carried out using the reduced plots of conductivity and frequency. The time-temperature superposition of data points is found to be satisfactory indicating that the ion transport mechanism remains the same in the entire range of temperatures and compositions studied. The results have been explained considering the borophosphate network and the role of Li2O as a glass modifier.

  17. Isotopic separation of D.sub.2 O from H.sub.2 O using ruthenium adsorbent

    DOEpatents

    Thiel, Patricia A.

    1990-04-10

    A method of enrichment of D.sub.2 O in solutions of D.sub.2 O in H.sub.2 O by contacting said solutions in the steam phase with hexagonal crystalline to produce enriched D.sub.2 O. The passages may be repeated to achieve a desired amount of D.sub.2 O.

  18. The adsorption of water on Cu2O and Al2O3 thin films

    SciTech Connect

    Deng, Xingyi; Herranz, Tirma; Weis, Christoph; Bluhm, Hendrik; Salmeron, Miquel

    2008-06-27

    The initial stages of water condensation, approximately 6 molecular layers, on two oxide surfaces, Cu{sub 2}O and Al{sub 2}O{sub 3}, have been investigated by using ambient pressure X-ray photoelectron spectroscopy at relative humidity values (RH) from 0 to >90%. Water adsorbs first dissociatively on oxygen vacancies producing adsorbed hydroxyl groups in a stoichiometric reaction: O{sub lattic} + vacancies + H{sub 2}O = 2OH. The reaction is completed at {approx}1% RH and is followed by adsorption of molecular water. The thickness of the water film grows with increasing RH. The first monolayer is completed at {approx}15% RH on both oxides and is followed by a second layer at 35-40% RH. At 90% RH, about 6 layers of H{sub 2}O film have been formed on Al{sub 2}O{sub 3}.

  19. Thermodynamic Assessment of the Y2o3-yb2o3-zro2 System

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Liu, Zi-Kui; Kaufman, Larry; Zhang, Fan

    2002-01-01

    Yttria-zirconia (Y2O3-ZrO2) is the most widely used of the rare earth oxide-zirconia systems. There are numerous experimental studies of the phase boundaries in this system. In this paper, we assess these data and derive parameters for the solution models in this system. There is current interest in other rare earth oxide-zirconia systems as well as systems with several rare earth oxides and zirconia, which may offer improved properties over the Y2O3-ZrO2 system. For this reason, we also assess the ytterbia-zirconia (Yb2O3-ZrO2) and Y2O3-Yb2O3-ZrO2 system.

  20. The Successive H2O Binding Energies for Fe(H2O)n(+)

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    The binding energy, computed using density functional theory (DFT), are in good agreement with experiment. The bonding is electrostatic (charge-dipole) in origin for all systems. The structures are therefore determined mostly by metal-ligand and ligand-ligand repulsion. The computed structure for FeH2O(+) is C(2v) where sp hybridization is important in reducing the Fe-H2O repulsion. Fe(H2O)2(+) has D2d symmetry where sdo hybridization is the primary factor leading to the linear O-Fe-O geometry. The bonding in Fe(H2O)3(+) and Fe(H2O)4(+) are very complex because ligand-ligand and metal-ligand repulsion, both for the in-plane and out-of-plane water lone-pair orbitals, are important.

  1. EPA H2O User Manual

    EPA Science Inventory

    EPA H2O is a software tool designed to support research being conducted in the Tampa Bay watershed to provide information, data, and approaches and guidance that communities can use to examine alternatives when making strategic decisions to support a prosperous and environmentall...

  2. H2O Adsorption Kinetics on Smectites

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Quinn, Richard C.; Howard, Jeanie; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The adsorptive equilibration of H2O a with montomorillonite, a smectite clay has been measured. At low temperatures and pressures, equilibration can require many hours, effectively preventing smectites at the martian surface from responding rapidly to diurnal pressure and temperature variations.

  3. EPA H2O Software Tool

    EPA Science Inventory

    EPA H2O allows user to: Understand the significance of EGS in Tampa Bay watershed; visually analyze spatial distribution of the EGS in Tampa Bay watershed; obtain map and summary statistics of EGS values in Tampa Bay watershed; analyze and compare potential impacts of development...

  4. Isotopomer mapping approach to determine N_{2}O production pathways and N_{2}O reduction

    NASA Astrophysics Data System (ADS)

    Lewicka-Szczebak, Dominika; Well, Reinhard; Cardenas, Laura; Bol, Roland

    2016-04-01

    Stable isotopomer analyses of soil-emitted N2O (δ15N, δ18Oand SP = 15N site preference within the linear N2O molecule) may help to distinguish N2O production pathways and to quantify N2O reduction to N2. Different N2O forming processes are characterised by distinct isotopic characteristics. Bacterial denitrification shows significantly lower SP and δ18Ovalues when compared to fungal denitrification and nitrification processes. But SP and δ18Ovalues are also altered during N2O reduction to N2, when the residual N2O is enriched in 18Oand centrally located 15N, resulting in increased δ18Oand SP values. Hence, the interpretation of these isotope characteristics is not straightforward, because higher δ18Oand SP values may be due to admixture of N2O from fungal denitrification or nitrification, or due to N2O reduction to N2. One of these processes, either admixture or reduction, can be quite well quantified if the other one is determined with independent methods. But usually both processes are unknown and the ability to estimate both of them simultaneously would be very beneficial. Here we present an attempt to determine both the admixture and the reduction simultaneously using the isotopomer mapping, i.e. the relation between δ18Oand SP. The measured sample points are typically situated between the two lines: reduction line with a typical slope of about 0.35 and mixing line with a higher slope of about 0.8. Combining the reduction and the mixing vector allows for the determination of both processes based on the location of the sample point between the lines. We tested this new approach for laboratory incubation studies, where a reference method for N2O reduction quantification was applied, i.e. 15N gas flux method or incubations in He atmosphere. This allowed us to check how well the calculated amounts for N2O reduction agree with the results provided by the reference method. The general trend was quite well reflected in our calculated results, however, quite

  5. Reaction of N2O5 with H2O on carbonaceous surfaces

    NASA Technical Reports Server (NTRS)

    Brouwer, L.; Rossi, M. J.; Golden, D. M.

    1986-01-01

    The heterogeneous reaction of N2O5 with commercially available ground charcoal in the absence of H2O revealed a physisorption process (gamma = 0.003), together with a redox reaction generating mostly NO. Slow HNO3 formation was the result of the interaction of N2O5 with H2O that was still adsorbed after prolonged pumping at 0.0001 torr. In the presence of H2O, the same processes with gamma = 0.005 are observed. The redox reaction dominates in the early stages of the reaction, whereas the hydrolysis gains importance later at the expense of the redox reaction. The rate law for HNO3 generation was found to be d(HNO3)/dt = k(bi)(H2O)(N2O5) with k(bi), the effective bimolecular rate constants, for 10 mg of carbon being (1.6 + or - 0.3) x 10 to the -13th cu cm/s.

  6. H2O Outgassing from Silicones

    SciTech Connect

    Dinh, L N; Maxwell, R S; Schildbach, M A; Balazs, B; McLean II, W

    2004-11-09

    In this fiscal year, we have tested the H{sub 2}O outgassing model for TR55 against independent core tests performed at different temperatures by our collaborators at Y12. At higher temperature ({approx} 71 C), the model properly predicts moisture outgassing from TR55 over the entire experiment. At lower temperature ({approx} 42.5 C), the model correctly predicts long-term moisture outgassing. However, in short-term limit, a better fit with core tests might be expected when the diffusion effect of H{sub 2}O through the silicone matrix is included into the model in the near future. A lookup table for the moisture content as well as moisture outgassing kinetics for M9787 which have previously been heated to 460K for one day and then exposed to relevant low levels of moisture is also now available as a reference for engineers/technicians in the fields.

  7. Strain dynamics during La2O3/Lu2O3 superlattice and alloy formation

    NASA Astrophysics Data System (ADS)

    Proessdorf, André; Niehle, Michael; Grosse, Frank; Rodenbach, Peter; Hanke, Michael; Trampert, Achim

    2016-06-01

    The dynamics of strain relaxation and intermixing during molecular beam epitaxy of La2O3 and Lu2O3 superlattices and alloys consisting of both binaries on Si(111) have been studied by real-time in situ grazing incidence x-ray diffraction and high resolution transmission electron microscopy. The presence of both hexagonal and cubic polymorphs of La2O3 influences the epitaxial formation within the superlattice. The process of strain relaxation is closely related to the presence of a (La,Lu)2O3 alloy adopting a cubic symmetry. It is formed by interdiffusion of La and Lu atoms reducing internal lattice mismatch within the superlattice. An interface thickness dominated by interdiffusion regions of about 3 monolayers is determined by high-angle annular dark field scanning transmission electron microscopy.

  8. [Ribonuclease hydration and its heat stability in solutions of H2O and D2O].

    PubMed

    Mrevlishvili, G M; Lobyshev, V I; Dzhaparidze, G Sh; Sokhadze, V M; Tatishvili, D A

    1980-01-01

    Ribonuclease hydration in wide concentration and temperature range using differential scanning microcalorimetry and NMR technique was studied. The temperature- concentration equilibrium diagram for H2O--ribonuclease system was suggested. Protein hydration in D2O was shown to be higher than in ordinary water. NMR measurements in dilute protein solutions showed that cooperative temperature denaturation was followed by solvation changes. Models of globular protein hydration are discussed. PMID:6245723

  9. Unconventional exchange bias in CoCr2O4/Cr2O3 nanocomposites

    NASA Astrophysics Data System (ADS)

    Guo, S.; Liu, X. H.; Cui, W. B.; Liu, W.; Zhao, X. G.; Li, D.; Zhang, Z. D.

    2009-03-01

    Unconventional exchange bias (EB) has been studied in CoCr2O4/Cr2O3 nanocomposites, in which the Curie temperature of the ferrimagnetic CoCr2O4 is much lower than the Néel temperature of the antiferromagnetic Cr2O3. A negative EB field of about 2.5 kOe at 5 K is achieved upon cooling in a field of 30 kOe. Meanwhile, the coercivity of the CoCr2O4 nanoparticles has been enhanced significantly by coupling with Cr2O3. The effect of the cooling field on the EB field and coercivity at 10 K has also been investigated. The domain-state model is used to interpret the unconventional EB. Cooling field may play a decisive role in the creation of the interfacial spin configuration for the unconventional EB, not only by exchange interaction between the induced magnetization of a polarized paramagnet and interfacial spins of an antiferromagnet but also by Zeeman interaction between the domain-state surplus magnetization and the external field.

  10. Corrosion of soda lime silicate glasses co-doped with Gd2O3 and Y2O3

    NASA Astrophysics Data System (ADS)

    Wang, Mitang; Li, Mei; Cheng, Jinshu; He, Feng; Liu, Zhaogang; Hu, Yanhong

    2014-01-01

    Corrosion behaviors of Gd2O3 and Y2O3 co-doped silicate glasses have been carried out at low reaction progress. The better enhance effect of co-doping with Gd2O3 and Y2O3 on the silicate glass resistance against attacking of neutral and acid media is observed, while the alkaline resistance is Y2O3 > Gd2O3 + Y2O3 > Gd2O3. Moreover, extreme value is also observed in variation of released ions concentration, pH value and mass loss of glass when substituting Y2O3 for Gd2O3.

  11. The H2O2-H2O Hypothesis: Extremophiles Adapted to Conditions on Mars?

    NASA Astrophysics Data System (ADS)

    Houtkooper, Joop M.; Schulze-Makuch, Dirk

    2007-08-01

    The discovery of extremophiles on Earth is a sequence of discoveries of life in environments where it had been deemed impossible a few decades ago. The next frontier may be the Martian surface environment: could life have adapted to this harsh environment? What we learned from terrestrial extremophiles is that life adapts to every available niche where energy, liquid water and organic materials are available so that in principle metabolism and propagation are possible. A feasible adaptation mechanism to the Martian surface environment would be the incorporation of a high concentration of hydrogen peroxide in the intracellular fluid of organisms. The H2O2-H2O hypothesis suggests the existence of Martian organisms that have a mixture of H2O2 and H2O instead of salty water as their intracellular liquid (Houtkooper and Schulze-Makuch, 2007). The advantages are that the freezing point is low (the eutectic freezes at 56.5°C) and that the mixture is hygroscopic. This would enable the organisms to scavenge water from the atmosphere or from the adsorbed layers of water molecules on mineral grains, with H2O2 being also a source of oxygen. Moreover, below its freezing point the H2O2-H2O mixture has the tendency to supercool. Hydrogen peroxide is not unknown to biochemistry on Earth. There are organisms for which H2O2 plays a significant role: the bombardier beetle, Brachinus crepitans, produces a 25% H2O2 solution and, when attacked by a predator, mixes it with a fluid containing hydroquinone and a catalyst, which produces an audible steam explosion and noxious fumes. Another example is Acetobacter peroxidans, which uses H2O2 in its metabolism. H2O2 plays various other roles, such as the mediation of physiological responses such as cell proliferation, differentiation, and migration. Moreover, most eukaryotic cells contain an organelle, the peroxisome, which mediates the reactions involving H2O2. Therefore it is feasible that in the course of evolution, water-based organisms

  12. Crystallization of MgFe2O4 from a glass in the system K2O/B2O3/MgO/P2O5/Fe2O3

    NASA Astrophysics Data System (ADS)

    El Shabrawy, Samha; Bocker, Christian; Rüssel, Christian

    2016-10-01

    Spherical magnetic Mg-Fe-O nanoparticles were successfully prepared by the crystallization of glass in the system K2O/B2O3/MgO/P2O5/Fe2O3. The magnetic glass ceramics were prepared by melting the raw materials using the conventional melt quenching technique followed by a thermal treatment at temperatures in the range 560-700 °C for a time ranging from 2 to 8 h. The studies of the X-ray diffraction, electron microscopy and FTIR spectra confirmed the precipitation of finely dispersed spherical (Mg, Fe) based spinel nanoparticles with a minor quantity of hematite (α-Fe2O3) in the glass matrix. The average size of the magnetic nano crystals increases slightly with temperature and time from 9 to 15 nm as determined by the line broadening from the XRD patterns. XRD studies show that annealing the glass samples for long periods of time at temperature ≥604 °C results in an increase of the precipitated hematite concentration, dissolution of the spinel phase and the formation of magnesium di-borate phase (Mg2B2O5). For electron microscopy, the particles were extracted by two methods; (i) replica extraction technique and (ii) dissolution of the glass matrix by diluted acetic acid. An agglomeration of the nano crystals to larger particles (25-35 nm) was observed.

  13. Synthesis, Structure, and Ethanol Gas Sensing Properties of In2O3 Nanorods Decorated with Bi2O3 Nanoparticles.

    PubMed

    Park, Sunghoon; Kim, Soohyun; Sun, Gun-Joo; Lee, Chongmu

    2015-04-22

    Bi2O3-decorated In2O3 nanorods were synthesized using a one-step process, and their structure, as well as the effects of decoration of In2O3 nanorods with Bi2O3 on the ethanol gas-sensing properties were examined. The multiple networked Bi2O3-decorated In2O3 nanorod sensor showed responses of 171-1774% at ethanol concentrations of 10-200 ppm at 200 °C. The responses of the Bi2O3-decorated In2O3 nanorod sensor were stronger than those of the pristine-In2O3 nanorod sensors by 1.5-4.9 times at the corresponding concentrations. The two sensors exhibited short response times and long recovery times. The optimal Bi concentration in the Bi2O3-decorated In2O3 nanorod sensor and the optimal operation temperature of the sensor were 20% and 200 °C, respectively. The Bi2O3-decorated In2O3 nanorod sensor showed selectivity for ethanol gas over other gases. The origin of the enhanced response, sensing speed, and selectivity for ethanol gas of the Bi2O3-decorated In2O3 nanorod sensor to ethanol gas is discussed.

  14. Tensile Behavior of Al2o3/feal + B and Al2o3/fecraly Composites

    NASA Technical Reports Server (NTRS)

    Draper, S. L.; Eldridge, J. I.; Aiken, B. J. M.

    1995-01-01

    The feasibility of Al2O3/FeAl + B and Al2O3/FeCrAlY composites for high-temperature applications was assessed. The major emphasis was on tensile behavior of both the monolithics and composites from 298 to 1100 K. However, the study also included determining the chemical compatibility of the composites, measuring the interfacial shear strengths, and investigating the effect of processing on the strength of the single-crystal Al2O3 fibers. The interfacial shear strengths were low for Al203/FeAl + B and moderate to high for Al203/FeCrAlY. The difference in interfacial bond strengths between the two systems affected the tensile behavior of the composites. The strength of the Al203 fiber was significantly degraded after composite processing for both composite systems and resulted in poor composite tensile properties. The ultimate tensile strength (UTS) values of the composites could generally be predicted with either rule of mixtures (ROM) calculations or existing models when using the strength of the etched-out fiber. The Al2O3/FeAl + B composite system was determined to be unfeasible due to poor interfacial shear strengths and a large mismatch in coefficient of thermal expansion (CTE). Development of the Al2O3/FeCrAlY system would require an effective diffusion barrier to minimize the fiber strength degradation during processing and elevated temperature service.

  15. The Elevation of Boiling Points in H_2O and D_2O Electrolytes

    NASA Astrophysics Data System (ADS)

    Miles, M. H.; Arman, H. D.; Carrick, J. D.; Gren, C. K.; Haggerty, K. A.; Kim, H. Y.; Ky, A. G.; Markham, J. E.; Meeks, C. F.; Noga, D. E.

    2002-03-01

    The excess enthalpy effect in cold fusion experiments for Pd/D_2O systems is subject to positive feedback, i.e., increasing the cell temperature increases the excess enthalpy . Therefore, the largest excess enthalpy effects are often observed near or at the boiling point corresponding to that of the electrolyte solution in the cell(M.H. Miles, M. Fleischmann and M.A. Imam, "Calorimetric Analysis of a Heavy Water Electrolysis Experiment Using a Pd-B Alloy Cathode", Naval Research Lab Mem. Rep.,#6320-01-8526, pp. 27-30 (2001).). However, the actual boiling point increases as the D_2O content of the cell decreases. The purpose of this project will be to compare experimental values of the change in temperature ΔT obtained using H_2O and D_2O solutions with theoretical values of ΔT calculated by assuming ideal solutions. The emphasis will be on higher concentrations as well as on saturated solutions where ΔT values may be quite large. Preliminary results for LiOH in H_2O show reasonable agreement with ideal solution ΔT values up to LiOH concentrations of 1.0 molal (m).

  16. [Simulation of N2O emissions in agroecosystems].

    PubMed

    Liu, Jiandong; Zhou, Xiuji; Ding, Guoan; Ouyang, Zhiyun; Wang, Xiaoke

    2002-11-01

    A numerical model for simulating N2O emissions in agroecosystem was established. Validation of the model with the observed data showed that the model simulated the process of N2O emissions in fields fairly well. The numerical analysis showed that the N2O emissions were interrelated well with average temperature during rice growth periods. Analysis of N2O emissions and meteorological factors by using power spectrum found that the change of N2O emissions had 7-9 year cycles. Sensitivity test showed that the N2O emission increased with temperature enhancement. PMID:12619275

  17. N2O emission from full-scale urban wastewater treatment plants: a comparison between A(2)O and SBR.

    PubMed

    Sun, Shichang; Cheng, Xiang; Li, Sha; Qi, Fei; Liu, Yan; Sun, Dezhi

    2013-01-01

    The emission of nitrous oxide (N2O) from full-scale anoxic/anaerobic/oxic (A(2)O) and sequencing batch reactor (SBR) processes was measured to evaluate N2O emission from urban wastewater treatment plants (WWTPs). The results showed that N2O flux in the A(2)O WWTP followed an order of A(2)O-oxic zone > aerated grit tank > A(2)O-anaerobic zone > A(2)O-anoxic zone > final clarifier > primary clarifier, while in the SBR WWTP the order was SBR tank > swirl grit tank > wastewater distribution tank and within the SBR tank in an order of SBR-feeding period > SBR-aeration period > SBR-settling period > SBR-decanting period. N2O emission from the A(2)O WWTP was approximately 486.61 kg d(-1), 96.9% of which was from the A(2)O-oxic zone. In the SBR WWTP, the emission of N2O was 339.24 kg d(-1) with 99.9% of the total emission coming from the periods of feeding and aeration. There was 6.52% of nitrogen-load in the influent being transformed to the emitted N2O in the SBR WWTP; the percentage was 3.35 times higher than that in the A(2)O WWTP.

  18. N2O and δ15N-N2O and δ18O-N2O from polar ice cores: interpretable data for interglacials

    NASA Astrophysics Data System (ADS)

    Bock, Michael; Schmitt, Jochen; Seth, Barbara; Beck, Jonas; Fischer, Hubertus

    2014-05-01

    Ice cores provide a wealth of information on climate change. For instance, the history of the atmospheric greenhouse gas N2O can be reconstructed using air entrapped in polar ice cores. N2O has several sources in both terrestrial and marine ecosystems, predominantly wetland soils and oxygen minimum zones in the ocean. N2O records generally follow the climatic changes during the glacial-interglacial cycles with higher N2O mixing ratios during warmer climate stages. However, the underlying processes driving these changes are difficult to identify from N2O mixing ratios alone. Additional information on the individual sources and sinks are provided by stable isotope measurements. The emission fluxes of the dominant N2O sources are ascribed to several pathways (nitrification, denitrification), with characteristic fractionation factors for the nitrogen and oxygen isotope signatures of the generated N2O (δ15N-N2O and δ18O-N2O). In the end, the individual proportions of pathways are responsible for distinct δ15N-N2O and δ18O-N2O for the average terrestrial and marine sources. Here, we present new ice core measurements of δ15N-N2O and δ18O-N2O covering the Holocene, MIS 5 and MIS 11. For the past 15 kyrs the δ15N-N2O record shows a continuous decrease starting at 15 kyrs to about 6 kyrs; during the past 6 kyrs δ15N-N2O remains rather constant. The resemblance with a recently published global reconstruction of bulk δ15N is remarkable (McLauchlan et al. 2013, Nature). Taken at face value this could mean that mainly the terrestrial source signature changed rather than a shift in the relative proportions of the terrestrial and marine source. The integrity of N2O ice core records relies on the assumption that the measurements truly represent the past atmosphere. However, comparative analyses of different ice cores from the same age intervals show offsets in the N2O mixing ratios among the records. One likely assumption is that higher mixing ratios are due to in

  19. Polynuclear complexes with bridging pyrophosphate ligands: synthesis and characterisation of {[(bipy)Cu(H2O)(mu-P2O7)Na2(H2O)6] x 4H2O}, {[(bipy)Zn-(H2O)(mu-P2O7)Zn(bipy)]2 x 14H2O} and {[(bipy)(VO)2]2(mu-P2O7)] x 5H2O}.

    PubMed

    Doyle, Robert P; Nieuwenhuyzen, Mark; Kruger, Paul E

    2005-12-01

    The reaction in water of M(II) ions (M = Cu, 1; Zn, 2; VO, 3) with 2,2'-bipyridine (bipy) followed by Na4P2O7 leads to the formation of three new complexes which feature the pyrophosphate anion, P2O7(4-), as a bridging ligand. Single crystal X-ray diffraction revealed 1 to be {[(bipy)Cu(H2O)(micro-P2O7)Na2(H2O)6] x 4H2O}, and 2 as a tetranuclear Zn(II) complex, {[(bipy)Zn(H2O)(micro-P2O7)Zn(bipy)]2 x 14H2O}. The structure of 1 consists of a mononuclear [(bipy)Cu(H2O)(P2O7)]2- unit that links via a pyrophosphate bridge to two Na atoms. The hydrated six-coordinate Na atoms themselves join together through bridging water molecules to generate a 2D Na-water sheet. The structure of 2 consists of a tetranuclear Zn(II) cluster (dimer-of-dimers) with two pyrophosphate ligands bridging between four metal centres. Adjacent clusters interact through face-to-face pi-pi interactions via the bipy ligands to yield a 2D sheet. Adjacent sheets pack in register to create channels, which are filled by the water molecules of crystallisation. An intricate 2D H-bonded water network separates adjacent sheets and encapsulates the tetranuclear clusters. Aspects of the pyrophosphate coordination modes in 1 and 2 are of structural relevance to those found within the inorganic pyrophosphatases. Compound 3, {[(bipy)(VO)2]2(micro-P2O7)] x 5H2O}, was isolated as an insoluble lime-green powder. Its dinuclear structure was elucidated from elemental and thermal analysis, magnetic susceptibility measurement and IR spectroscopy. The latter displayed characteristic bridging pyrophosphate and signature V=O stretches, which were corroborated by contrast to the IR spectra of 1 and 2 and through comparison with those found in the structurally characterised dinuclear complex, {[(bipy)Cu(H2O)]2(micro-P2O7) x 7H2O}, 4. PMID:16471055

  20. Room-temperature Formation of Hollow Cu2O Nanoparticles

    SciTech Connect

    Hung, Ling-I; Tsung, Chia-Kuang; Huang, Wenyu; Yang, Peidong

    2010-01-18

    Monodisperse Cu and Cu2O nanoparticles (NPs) are synthesized using tetradecylphosphonic acid as a capping agent. Dispersing the NPs in chloroform and hexane at room temperature results in the formation of hollow Cu2O NPs and Cu@Cu2O core/shell NPs, respectively. The monodisperse Cu2O NPs are used to fabricate hybrid solar cells with efficiency of 0.14percent under AM 1.5 and 1 Sun illumination.

  1. Ca3Mn2O7.

    PubMed

    Guiblin, Nicolas; Grebille, Dominique; Leligny, Henri; Martin, Christine

    2002-01-01

    The tricalcium dimanganese heptaoxide (Ca3Mn2O7) member of the Ruddlesden-Popper series Ca(n+1)Mn(n)O(3n+1), i.e. with n = 2, was previously reported with an I-centred tetragonal lattice [a(t) = 3.68 and c(t) = 19.57 A] by Fawcett, Sunstrom, Greenblatt, Croft & Ramanujachary [Chem. Mater. (1998), 10, 3643-3651]. It is now found to be orthorhombic, with an A-centred lattice [a = 5.2347 (6), b = 5.2421 (2) and c = 19.4177 (19) A]. The structure has been refined in space group A2(1)am using X-ray single-crystal diffraction data and assuming the existence of twin domains related by the (1-10) plane. A comparison with the basic perovskite structure CaMnO3 (n = infinity) is proposed.

  2. Identification and stability of U sub 2 O sub 2 , U sub 2 O sub 3 , and U sub 2 O sub 4 gaseous oxides molecules

    SciTech Connect

    Guido, M. ); Balducci, G. )

    1991-10-01

    The U{sub 2}O{sub 3}{sub ({ital g})} and U{sub 2}O{sub 4}{sub ({ital g})} species have been for the first time identified by Knudsen cell-mass spectrometry and their heats of formation and atomization energies have been tentatively derived. A redetermination of these quantities for the already known UO{sub 3}{sub ({ital g})} and U{sub 2}O{sub 2}{sub ({ital g})} molecules has been also attempted.

  3. PREPARATION, CHARACTERIZATION AND ACTIVITY OF AL2O3-SUPPORTED V2O5 CATALYSTS

    EPA Science Inventory

    A series of activated alumina supported vanadium oxide catalysts with various V2O5 loadings ranging from 5 to 25 wt% has been prepared by wet impregnation technique. A combination of various physico-chemical techniques such as BET surface areas, oxygen chemisorption, X-ray diffra...

  4. High Temperature Mechanical Characterization and Analysis of Al2O3 /Al2O3 Composition

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, John Z.; Jaskowiak, Martha H.

    1999-01-01

    Sixteen ply unidirectional zirconia coated single crystal Al2O3 fiber reinforced polycrystalline Al2O3 was tested in uniaxial tension at temperatures to 1400 C in air. Fiber volume fractions ranged from 26 to 31%. The matrix has primarily open porosity of approximately 40%. Theories for predicting the Young's modulus, first matrix cracking stress, and ultimate strength were applied and evaluated for suitability in predicting the mechanical behavior of Al2O3/Al2O3 composites. The composite exhibited pseudo tough behavior (increased area under the stress/strain curve relative to monolithic alumina) from 22 to 1400 C. The rule-of-mixtures provides a good estimate of the Young's modulus of the composite using the constituent properties from room temperature to approximately 1200 C for short term static tensile tests in air. The ACK theory provides the best approximation of the first matrix cracking stress while accounting for residual stresses at room temperature. Difficulties in determining the fiber/matrix interfacial shear stress at high temperatures prevented the accurate prediction of the first matrix cracking stress above room temperature. The theory of Cao and Thouless, based on Weibull statistics, gave the best prediction for the composite ultimate tensile strength.

  5. Electrochemistry of LiCl-Li2O-H2O Molten Salt Systems

    SciTech Connect

    Natalie J. Gese; Batric Pesic

    2013-03-01

    Uranium can be recovered from uranium oxide (UO2) spent fuel through the combination of the oxide reduction and electrorefining processes. During oxide reduction, the spent fuel is introduced to molten LiCl-Li2O salt at 650 degrees C and the UO2 is reduced to uranium metal via two routes: (1) electrochemically, and (2) chemically by lithium metal (Li0) that is produced electrochemically. However, the hygroscopic nature of both LiCl and Li2O leads to the formation of LiOH, contributing hydroxyl anions (OH-), the reduction of which interferes with the Li0 generation required for the chemical reduction of UO2. In order for the oxide reduction process to be an effective method for the treatment of uranium oxide fuel, the role of moisture in the LiCl-Li2O system must be understood. The behavior of moisture in the LiCl-Li2O molten salt system was studied using cyclic voltammetry, chronopotentiometry and chronoamperometry, while reduction to hydrogen was confirmed with gas chromatography.

  6. Solid Solution Effects on the MgAl2O4-MgGa2O4 System

    SciTech Connect

    O'Hara, Kelley; Smith, Jeffrey D; Hemrick, James Gordon

    2009-01-01

    Phase relations between two spinel compounds (MgAl2O4 and MgGa2O4) were studied. Stoichiometric MgAl2O4 was formed in the laboratory through a coprecipitation method. Complete solid solution formation int eh MgAl2O4-MgGa2O4 systems was confirmed through X-ray diffraction analysis. Solid solution between MgAl2O4-MgGa2O4 decreases thermal conductivity at all temperatures up to 900oC. At 200oC with 10 mol% additoin of MgGa2O4 thermal conductivity decreases approximately 25%, and at 900oC there was still an 8% decrease. Additionally, preliminary studies show that porosity between 5% and 10% does not have an appreciable effect on the thermal conductivity in this study.

  7. Effects of the substitution of P2O5 by B2O3 on the structure and dielectric properties in (90-x) P2O5-xB2O3-10Fe2O3 glasses.

    PubMed

    Sdiri, N; Elhouichet, H; Dhaou, H; Mokhtar, F

    2014-01-01

    90%[xB2O3 (1-x) P2O5] 10%Fe2O3, glass systems where (x=0 mol%, 5 mol%, 10 mol%, 15 mol%, 20 mol%) was prepared via a melt quenching technique. The structure of glass is investigated at room temperature by, Raman and EPR spectroscopy. Raman studies have been performed on these glasses to examine the distribution of different borate and phosphate structural groups. We have noted an increase from 3 to 4 in the coordination number of the boron atoms from 3 to 4, i.e., the conversion of the BO3 triangular structural units into BO4 tetrahedra. The samples have been investigated by means of electron paramagnetic resonance (EPR). The results obtained from the gef=4.28 EPR line are typical of the occurrence of iron (III) occupying substitutional sites. Moreover, the dielectric sizes such as ε'(ω), ε″(ω), imaginary parts of the electrical modulus, M(*)(ω) and the loss tanδ, their variation with frequency at room temperature show a decrease in relaxation intensity with an increase in the concentration of (B2O3). On the present work, we have found a weak extinction index with our new glass.

  8. Formation and characterization of the oxygen-rich hafnium dioxygen complexes: OHf(eta2-O2)(eta2-O3), Hf(eta2-O2)3, and Hf(eta2-O2)4.

    PubMed

    Gong, Yu; Zhou, Mingfei

    2007-09-20

    Hafnium atom oxidation by dioxygen molecules has been investigated using matrix isolation infrared absorption spectroscopy. The ground-state hafnium atom inserts into dioxygen to form primarily the previously characterized HfO(2) molecule in solid argon. Annealing allows the dioxygen molecules to diffuse and react with HfO(2) to form OHf(eta(2)-O(2))(eta(2)-O(3)), which is characterized as a side-on bonded oxo-superoxo hafnium ozonide complex. Under visible light (532 nm) irradiation, the OHf(eta(2)-O(2))(eta(2)-O(3)) complex either photochemically rearranges to a more stable Hf(eta(2)-O(2))(3) isomer, a side-on bonded di-superoxo hafnium peroxide complex, or reacts with dioxygen to form an unprecedented homoleptic tetra-superoxo hafnium complex: Hf(eta(2)-O(2))(4). The Hf(eta(2)-O(2))(4) complex is determined to possess a D(2d) geometry with a tetrahedral arrangement of four side-on bonded O(2) ligands around the hafnium atom, which thus presents an 8-fold coordination. These oxygen-rich complexes are photoreversible; that is, formation of Hf(eta(2)-O(2))(3) and Hf(eta(2)-O(2))(4) is accompanied by demise of OHf(eta(2)-O(2))(eta(2)-O(3)) under visible (532 nm) light irradiation and vice versa with UV (266 nm) light irradiation.

  9. H2O Formation in C-rich AGB Winds

    NASA Astrophysics Data System (ADS)

    Lombaert, R.; Decin, L.; Royer, P.; de Koter, A.; Cox, N. L. J.; De Ridder, J.; Khouri, T.; Agúndez, M.; Blommaert, J. A. D. L.; Cernicharo, J.; González-Alfonso, E.; Groenewegen, M. A. T.; Kerschbaum, F.; Neufeld, D.; Vandenbussche, B.; Waelkens, C.

    2015-08-01

    The Herschel detection of warm H2O vapor emission from C-rich winds of AGB stars challenges the current understanding of circumstellar chemistry. Two mechanisms have been invoked to explain warm H2O formation. In the first, penetration of UV interstellar radiation through a clumpy circumstellar medium causes the formation of H2O molecules in the inner envelope. In the second, periodic shocks passing through the medium immediately above the stellar surface lead to H2O formation. We have identified H2O emission trends from distance-independent line-strength ratios in a sample of 18 C-rich AGB sources, by comparing to a theoretical model grid. We detect warm H2O emission close to or inside the acceleration zone of all sample stars. We find an anti-correlation between the H2O/CO line-strength ratios and the mass-loss rate for Mgas>3×10-7 M⊙/yr. This implies that the H2O formation mechanism becomes less efficient with increasing envelope column density. The anti-correlation breaks down for SRb objects, which clump together at an overall lower H2O abundance. Finally, a radial dependence of the H2O abundance within individual sources is unlikely. These findings lend support to shock-induced non-equilibrium chemistry as the primary source of H2O formation in C-rich AGB stars.

  10. Three new phosphates with isolated P2O7 units: noncentrosymmetric Cs2Ba3(P2O7)2 and centrosymmetric Cs2BaP2O7 and LiCsBaP2O7.

    PubMed

    Li, Lin; Han, Shujuan; Lei, Bing-Hua; Wang, Ying; Li, Hongyi; Yang, Zhihua; Pan, Shilie

    2016-03-01

    Three new phosphates, a noncentrosymmetric (NCS) Cs2Ba3(P2O7)2 and centrosymmetric (CS) Cs2BaP2O7 and LiCsBaP2O7, have been synthesized from high-temperature solutions for the first time. Analysis of the structures determined by single-crystal X-ray diffraction showed that although the three compounds contained isolated P2O7 units, they yielded different three-dimensional (3D) networks: Cs2Ba3(P2O7)2 crystallized in the NCS Orthorhombic space group P212121, Cs2BaP2O7 in the CS monoclinic space group P21/n, and LiCsBaP2O7, having an identical stoichiometry with Cs2BaP2O7, crystallized in monoclinic space group, P21/c. Structural comparisons suggested the differences between their 3D frameworks to be due to differences between the sizes and coordination environments of the cations. Characterizations including thermal and optical analyses showed Cs2Ba3(P2O7)2 and Cs2BaP2O7 to melt congruently, and Cs2Ba3(P2O7)2 to exhibit a wide transparent region with a cut-off edge below 176 nm. The NLO properties and electronic structures of these compounds were investigated using first-principles calcualtions. PMID:26831497

  11. Soil invertebrate fauna affect N2 O emissions from soil.

    PubMed

    Kuiper, Imke; de Deyn, Gerlinde B; Thakur, Madhav P; van Groenigen, Jan Willem

    2013-09-01

    Nitrous oxide (N2 O) emissions from soils contribute significantly to global warming. Mitigation of N2 O emissions is severely hampered by a lack of understanding of its main controls. Fluxes can only partly be predicted from soil abiotic factors and microbial analyses - a possible role for soil fauna has until now largely been overlooked. We studied the effect of six groups of soil invertebrate fauna and tested the hypothesis that all of them increase N2 O emissions, although to different extents. We conducted three microcosm experiments with sandy soil and hay residue. Faunal groups included in our experiments were as follows: fungal-feeding nematodes, mites, springtails, potworms, earthworms and isopods. In experiment I, involving all six faunal groups, N2 O emissions declined with earthworms and potworms from 78.4 (control) to 37.0 (earthworms) or 53.5 (potworms) mg N2 O-N m(-2) . In experiment II, with a higher soil-to-hay ratio and mites, springtails and potworms as faunal treatments, N2 O emissions increased with potworms from 51.9 (control) to 123.5 mg N2 O-N m(-2) . Experiment III studied the effect of potworm density; we found that higher densities of potworms accelerated the peak of the N2 O emissions by 5 days (P < 0.001), but the cumulative N2 O emissions remained unaffected. We propose that increased soil aeration by the soil fauna reduced N2 O emissions in experiment I, whereas in experiment II N2 O emissions were driven by increased nitrogen and carbon availability. In experiment III, higher densities of potworms accelerated nitrogen and carbon availability and N2 O emissions, but did not increase them. Overall, our data show that soil fauna can suppress, increase, delay or accelerate N2 O emissions from soil and should therefore be an integral part of future N2 O studies. PMID:23625707

  12. On the neutron scattering length density of proteins in H2O/D2O

    NASA Astrophysics Data System (ADS)

    Efimova, Y. M.; van Well, A. A.; Hanefeld, U.; Wierczinski, B.; Bouwman, W. G.

    2004-07-01

    The structure of the protein layers adsorbed at different interfaces can be determined by using neutron-reflection and small-angle neutron scattering. For highlighting the adsorbed protein layer at the interface, the technique of contrast-variation by changing the H2O/D2O ratio, is often used. For determining the scattering length density, both the protein volume in solution and the total scattering length of the protein is needed. The volume is calculated from the amino-acid sequence. For calculating the scattering length, the H/D exchange of the labile protons of the protein should be taken into account. For monitoring the H/D exchange, Positive Electrospray Ionization Mass Spectroscopy was applied. We compare experimental results for the exchange in lysozyme and β-casein with theoretical calculations. The importance of using the correct protein scattering-length density is elucidated by simultaneous model fitting to neutron reflection data at different water contrasts.

  13. Vibrational Anylasis on I(H{_2}O){^-} and I(D{_2}O){^-} Spectra

    NASA Astrophysics Data System (ADS)

    Huang, Meng; McCoy, Anne B.

    2013-06-01

    Hydrated halide clusters provide good systems for investigating the effect of the intramolecular hydrogen-bond on the spectrum of ions and molecules. In this work, the vibrational spectra of I(H{_2}O){^-} and I(D{_2}O){^-} were studied. We focused on the couplings between the two O-H stretch modes and the in-plane bending mode, which is the frustrated rotation of the water molecule in the plane of the complex. A reduced-dimensional analysis with these three modes was developed to investigate the effect of the couplings on the spectra. The model potential in the analysis was obtained from ab initio calculation with MP2/aug-cc-pVTZ-PP level of method and basis set. The doublet structure of the O-H stretch mode in the spectrum was attributed to the tunneling splitting from the in-plane bending mode double-well potential energy surface.

  14. H2O2 space shuttle APU

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A cryogenic H2-O2 auxiliary power unit (APU) was developed and successfully demonstrated. It has potential application as a minimum weight alternate to the space shuttle baseline APU because of its (1) low specific propellant consumption and (2) heat sink capabilities that reduce the amount of expendable evaporants. A reference system was designed with the necessary heat exchangers, combustor, turbine-gearbox, valves, and electronic controls to provide 400 shp to two aircraft hydraulic pumps. Development testing was carried out first on the combustor and control valves. This was followed by development of the control subsystem including the controller, the hydrogen and oxygen control valves, the combustor, and a turbine simulator. The complete APU system was hot tested for 10 hr with ambient and cryogenic propellants. Demonstrated at 95 percent of design power was 2.25 lb/hp-hr. At 10 percent design power, specific propellant consumption was 4 lb/hp-hr with space simulated exhaust and 5.2 lb/hp-hr with ambient exhaust. A 10 percent specific propellant consumption improvement is possible with some seal modifications. It was demonstrated that APU power levels could be changed by several hundred horsepower in less than 100 msec without exceeding allowable turbine inlet temperatures or turbine speed.

  15. Thermophysical Properties of Fluid H2O

    NASA Astrophysics Data System (ADS)

    Kestin, J.; Sengers, J. V.; Kamgar-Parsi, B.; Sengers, J. M. H. Levelt

    1984-01-01

    In view of the important role that water substance plays in science and industry, this paper lists the thermophysical properties of fluid H2O which are most needed for engineering applications. The properties are described in a very compact form with the aid of explicit expressions for programing on a computer and for inclusion in data banks. The paper includes a fundamental equation in the form of the Helmholtz free energy expressed as an analytic function of temperature and density. This fundamental equation is a dimensionless version of the Provisional IAPS Formulation 1982 for the Thermodynamic Properties of Ordinary Water Substance for Scientific and General Use, which enables one to calculate all equilibrium thermodynamic properties in a wide range of states, but with the exclusion of a small region near the critical point. In the latter region, the equilibrium properties are described by a scaled fundamental equation in the form of the pressure as a function of chemical potential and temperature. In addition, the paper gives equations for the viscosity, thermal conductivity, and surface tension. All equations in the paper are mutually thermodynamically consistent. The set of equations and their constants listed here represents the most reliable information according to the judgment of the authors.

  16. Structure, dielectric and bioactivity of P2O5-CaO-Na2O-B2O3 bioactive glass

    NASA Astrophysics Data System (ADS)

    Maheswaran, A.; Hirankumar, G.; Heller, Nithya; Karthickprabhu, S.; Kawamura, Junichi

    2014-06-01

    Bioactive phosphate glasses have been widely investigated for bone repair. Phosphate glass system of 47P2O5-30.5CaO-(22.5-x)Na2O-xB2O3 has been prepared by melt quenching technique. From the Raman analysis, it is confirmed that phosphate network form metaphosphate structure. Bioactivity of the glass is studied by immersing the prepared glass in simulated body fluid (SBF). All the glasses exhibited bioactivity after soaking in SBF. Addition of B2O3 to the glass by replacing the Na2O produces considerable effect on the dielectric and bioactivity of the glass. Ion dynamics are also analyzed through imaginary modulus and imaginary dielectric permittivity.

  17. Redetermination of junitoite, CaZn2Si2O7·H2O

    PubMed Central

    Yang, Hexiong; Jenkins, Neil G.; Downs, Robert T.

    2012-01-01

    The crystal structure of the mineral junitoite, ideally CaZn2Si2O7·H2O (calcium dizinc disilicate monohydrate), was first determined by Hamilton & Finney [Mineral. Mag. (1985), 49, 91–95] based on the space group Ama2, yielding a reliability factor R of 0.10, with isotropic displacement parameters for all non-H atoms. The present study reports a structure redetermination of junitoite using single-crystal X-ray diffraction data from a natural sample, demonstrating that the space group of this mineral is actually Aea2, which can be attained simply by shifting the origin. Topologically, the structure models in the space groups Aea2 and Ama2 are analogous, consisting of chains of corner-sharing ZnO4 tetra­hedra parallel to the b axis, cross-linked by Si2O7 tetra­hedral dimers (the site symmetry of the bridging O atom is ..2) along a and c, forming a three-dimensional framework. The Ca2+ cations (site symmetry ..2) are situated in cavities of the framework and are bonded to five O atoms and one H2O mol­ecule (site symmetry ..2) in a distorted octa­hedral coordination environment. However, some bond lengths, especially for the SiO4 tetra­hedron, are noticeably different between the two structure models. Hydrogen bonding in junitoite is found between the water mol­ecule and a framework O atom. PMID:23125564

  18. Study on Viscosity of the La2O3-SiO2-Al2O3 Slag System

    NASA Astrophysics Data System (ADS)

    Deng, Yong-chun; Wu, Sheng-li; Jiang, Yin-ju; Jia, Su-qi

    2016-08-01

    The viscosities and free-running temperatures of slag in a La2O3-SiO2-Al2O3 slag system were measured using an internal rotating cylinder method. For different La2O3 mass contents (45, 50, and 55 pct) in the La2O3-SiO2-Al2O3 ternary slag, the slag viscosity and free-running temperature decreased with a decrease in SiO2 content and an increase in Al2O3 content, and decreased with an increase in La2O3 content. Minor components B2O3, FeO, and MnO could decrease the viscosity and free-running temperature of La2O3-SiO2-Al2O3 ternary slag, especially FeO, and a small amount of FeO and B2O3 had an additive effect on slag viscosity and free-running temperature reduction.

  19. Electron collisions with the CH{sub 2}O-H{sub 2}O complex

    SciTech Connect

    Freitas, T. C.; Lima, M. A. P.; Canuto, S.; Bettega, M. H. F.

    2009-12-15

    We report cross sections for elastic collisions of low-energy electrons with the CH{sub 2}O-H{sub 2}O complex. We employed the Schwinger multichannel method with pseudopotentials in the static-exchange and in the static-exchange-polarization approximations for energies from 0.1 to 20 eV. We considered four different hydrogen-bonded structures for the complex that were generated by classical Monte Carlo simulations. Our aim is to investigate the effect of the water molecule on the pi* shape resonance of formaldehyde. Previous studies reported a pi* shape resonance for CH{sub 2}O at around 1 eV. The resonance positions of the complexes appear at lower energies in all cases due to the mutual polarization between the two molecules. This indicates that the presence of water may favor dissociation by electron impact and may lead to an important effect on strand breaking in wet DNA by electron impact.

  20. N2O emissions from a nitrogen-enriched river

    USGS Publications Warehouse

    McMahon, P.B.; Dennehy, K.F.

    1999-01-01

    Nitrous oxide (N2O) emissions from the South Platte River in Colorado were measured using closed chambers in the fall, winter, and summer of 1994- 1995. The South Platte River was enriched in inorganic N (9-800 ??M) derived from municipal wastewater effluent and groundwater return flows from irrigated agricultural fields. River water was as much as 2500% supersaturated with N2O, and median N2O emission rates from the river surface ranged from less than 90 to 32 600 ??g-N m-2 d-1. Seventy-nine percent of the variance in N2O emission rates was explained by concentrations of total inorganic N in river water and by water temperature. The estimated total annual N2O emissions from the South Platte River were 2 x 1013-6 x 1013 ??g-N yr-1. This amount of annual N2O emissions was similar to the estimated annual N2O emissions from all primary municipal wastewater treatment processes in the United States (1). Results from this study indicate that N-enriched rivers could be important anthropogenic sources of N2O to the atmosphere. However, N2O emission measurements from other N-enriched rivers are needed to better quantify this source.Nitrous oxide (N2O) emissions from the South Platte River in Colorado were measured using closed chambers in the fall, winter, and summer of 1994-1995. The South Platte River was enriched in inorganic N (9-800 ??M) derived from municipal wastewater effluent and groundwater return flows from irrigated agricultural fields. River water was as much as 2500% supersaturated with N2O, and median N2O emission rates from the river surface ranged from less than 90 to 32 600 ??g-N m-2 d-1. Seventy-nine percent of the variance in N2O emission rates was explained by concentrations of total inorganic N in river water and by water temperature. The estimated total annual N2O emissions from the South Platte River were 2??1013-6??1013 ??g-N yr-1. This amount of annual N2O emissions was similar to the estimated annual N2O emissions from all primary municipal

  1. Thermodynamic investigation on MTe2O6 (M = Th, Ce)

    NASA Astrophysics Data System (ADS)

    Jain, Ashish; Pankajavalli, R.; Anthonysamy, S.

    2013-11-01

    The standard Gibbs energies of formation of MTe2O6 (s) (where M = Th, Ce) were derived from vapour pressure measurements by employing thermogravimetry (TG) based transpiration technique. The vapour pressures of TeO2 (g) over the mixtures MTe2O6 (s) + MO2 (s) generated by the incongruent vapourisation reaction, MTe2O6 (s) → MO2 (s) + 2 TeO2 (g) were measured in the temperature range 1034-1167 K and 986-1129 K for ThTe2O6 (s) and CeTe2O6 (s) respectively. From the vapour pressure measurements the standard Gibbs energies of formation of MTe2O6 (s) were derived. The derived values of Δf G∘ < ThTe2O6, s > and Δf G∘ < CeTe2O6, s > were combined with free energy functions to obtain ΔfH298K∘ of ThTe2O6 (s) and CeTe2O6 (s).

  2. Global distribution of N2O and the ΔN2O-AOU yield in the subsurface ocean

    NASA Astrophysics Data System (ADS)

    Nevison, Cynthia; Butler, James H.; Elkins, J. W.

    2003-12-01

    We present and analyze a data set of subsurface N2O from a range of oceanic regions. Observed N2O concentrations are highest in the eastern tropical Pacific (ETP), intermediate in the northern Pacific and Indian Oceans, and relatively low in the Southern and Atlantic Oceans. Tongues of high N2O, which propagate along sigma surfaces, provide evidence that N2O from the ETP is exported widely. Correlation slopes of ΔN2O (the level above atmospheric equilibrium) versus apparent oxygen utilization (AOU) are found to be an unreliable gauge of the biological N2O yield per mole O2 consumed because the slopes are strongly influenced by mixing gradients. Most features of the subsurface data set are consistent with an N2O source dominated by nitrification, including the widespread, robust ΔN2O-AOU correlation and the lack of a widespread anticorrelation between ΔN2O and N*. In addition, ΔN2O/NO3- ratios tend to increase with decreasing O2 in a manner consistent with laboratory studies of nitrifying bacteria. The sensitivity of the nitrifier N2O/NO3- yield to O2 can explain much of the variability in ΔN2O/AOU observed in the ocean. A parameterization is derived for the instantaneous production of N2O per mole O2 consumed as a nonlinear function of O2 and depth. The parameterization is based on laboratory and oceanic data and is designed for use in ocean biogeochemistry models. It is coupled to a global dissolved O2 climatology and ocean carbon model output to estimate a total oceanic N2O inventory of 610-840 Tg N and a global production rate of ˜5.8 ± 2 Tg N/y.

  3. Decrease of H2O2 plasma membrane permeability during adaptation to H2O2 in Saccharomyces cerevisiae.

    PubMed

    Branco, Miguel R; Marinho, H Susana; Cyrne, Luisa; Antunes, Fernando

    2004-02-20

    Contrary to what is widely believed, recent published results show that H2O2 does not freely diffuse across biomembranes. The fast removal of H2O2 by antioxidant enzymes is able to generate a gradient if H2O2 is produced in a different compartment from that containing the enzymes (Antunes, F., and Cadenas, E. (2000) FEBS Lett. 475, 121-126). In this work, we extended these studies and tested whether an active regulation of biomembranes permeability characteristics is part of the cell response to oxidative stress. Using Saccharomyces cerevisiae as a model, we showed that: (a) H2O2 gradients across the plasma membrane are formed upon exposure to external H2O2; (b) there is a correlation between the magnitude of the gradients and the resistance to H2O2; (c) there is not a correlation between the intracellular capacity to remove H2O2 and the resistance to H2O2; (d) the plasma membrane permeability to H2O2 decreases by a factor of two upon acquisition of resistance to this agent by pre-exposing cells either to nonlethal doses of H2O2 or to cycloheximide, an inhibitor of protein synthesis; and (e) erg3Delta and erg6Delta mutants, which have impaired ergosterol biosynthesis pathways, show higher plasma membrane permeability to H2O2 and are more sensitive to H2O2. Altogether, the regulation of the plasma membrane permeability to H2O2 emerged as a new mechanism by which cells respond and adapt to H2O2. The consequences of the results to cellular redox compartmentalization and to the origin and evolution of the eukaryotic cell are discussed.

  4. Structure evolution of nanoparticulate Fe2O3.

    PubMed

    Erlebach, Andreas; Kurland, Heinz-Dieter; Grabow, Janet; Müller, Frank A; Sierka, Marek

    2015-02-21

    The atomic structure and properties of nanoparticulate Fe2O3 are characterized starting from its smallest Fe2O3 building unit through (Fe2O3)n clusters to nanometer-sized Fe2O3 particles. This is achieved by combining global structure optimizations at the density functional theory level, molecular dynamics simulations by employing tailored, ab initio parameterized interatomic potential functions and experiments. With the exception of nearly tetrahedral, adamantane-like (Fe2O3)2 small (Fe2O3)n clusters assume compact, virtually amorphous structures with little or no symmetry. For n = 2-5 (Fe2O3)n clusters consist mainly of two- and three-membered Fe-O rings. Starting from n = 5 they increasingly assume tetrahedral shape with the adamantane-like (Fe2O3)2 unit as the main building block. However, the small energy differences between different isomers of the same cluster-size make precise structural assignment for larger (Fe2O3)n clusters difficult. The tetrahedral morphology persists for Fe2O3 nanoparticles with up to 3 nm in diameter. Simulated crystallization of larger nanoparticles with diameters of about 5 nm demonstrates pronounced melting point depression and leads to formation of ε-Fe2O3 single crystals with hexagonal morphology. This finding is in excellent agreement with the results obtained for Fe2O3 nanopowders generated by laser vaporization and provides the first direct indication that ε-Fe2O3 may be thermodynamically the most stable phase in this size regime. PMID:25587689

  5. Isotopologue signatures of N2O from denitrification in soil

    NASA Astrophysics Data System (ADS)

    Well, R.; Flessa, H.

    2009-04-01

    There is few information on N2 fluxes from denitrification in the field, because this process is difficult to measure in situ. Isotopologue signatures of N2O such as δ18O, average δ15N (δ15Nbulk) and 15N site preference (SP = difference in δ15N between the central and peripheral N positions of the asymmetric N2O molecule) can be used to constrain the atmospheric N2O budget and to characterize N2O turnover processes including N2O reduction to N2. However, the use of this approach to study N2O dynamics in soils requires knowledge of isotopologue fractionation factors (ɛ) for the various partial processes involved, e.g. N2O production by nitrification or denitrification, N2O reduction by denitrification and diffusive transport. The aim of our study was to investigate whether isotopologue signatures of soil-emitted N2O can be used to estimate N2O reduction, and accordingly N2 formation. Two arable soils were incubated in the laboratory under varying conditions in order to manipulate the partial processes of N2O turnover. ɛ of δ18O, δ15Nbulk and SP was determined in experiments, where only one of the partial processes was governing the isotopic signature of N2O in the incubation system of the respective treatment. ɛ of N2O reduction to N2 was derived by (i) comparing treatments with and without inhibition of N2O reduction (indirect approach) or (ii) by monitoring the time course of isotopic signatures of N2O applied to the headspace of NO3--depleted anaerobic soil (direct approach). Moreover, we incubated the soils under conditions favoring denitrification (high moisture, low O2 level, NO3- fertilization) and monitored isotopic signatures of emitted N2O. In parallel experiments with 15N-labeled NO3- pool we measured N2 fluxes directly. Isotopologue signatures were compared with 15N2 flux data in order to check their relationship with N2 production. References Well R, Kurganova, I., Lopes, V., Flessa H. (2006), Isotopomer signatures of N2O emitted from an arable

  6. Modeling the H2O submillimeter emission in extragalactic sources

    NASA Astrophysics Data System (ADS)

    González-Alfonso, E.; Fischer, J.; Aalto, S.; Falstad, N.

    2014-07-01

    Recent observational studies have shown that H2O emission at (rest) submillimeter wavelengths is ubiquitous in infrared galaxies, both in the local and in the early Universe, suggestive of far-infrared pumping of H2O by dust in warm regions. In this work, models are presented that show that (i) the highest-lying H2O lines (Eupper > 400 K) are formed in very warm (Tdust ≳ 90 K) regions and require high H2O columns (NH2O ≳ 3 × 1017 cm-2), while lower lying lines can be efficiently excited with Tdust ~ 45-75 K and NH2O ~ (0.5-2) × 1017 cm-2; (ii) significant collisional excitation of the lowest lying (Eupper < 200 K) levels, which enhances the overall LH2O-LIR ratios, is identified in sources where the ground-state para-H2O 111-000 line is detected in emission; (iii) the H2O-to-infrared (8-1000 μm) luminosity ratio is expected to decrease with increasing Tdust for all lines with Eupper ≲ 300 K, as has recently been reported in a sample of LIRGs, but increases with Tdust for the highest lying H2O lines (Eupper > 400 K); (iv) we find theoretical upper limits for LH2O/LIR in warm environments, owing to H2O line saturation; (v) individual models are presented for two very different prototypical galaxies, the Seyfert 2 galaxy NGC 1068 and the nearest ultraluminous infrared galaxy Arp 220, showing that the excited submillimeter H2O emission is dominated by far-infrared pumping in both cases; (vi) the LH2O - LIR correlation previously reported in observational studies indicates depletion or exhaustion time scales, tdep = Σgas/ ΣSFR, of ≲12 Myr for star-forming sources where lines up to Eupper = 300 K are detected, in agreement with the values previously found for (U)LIRGs from HCN millimeter emission. We conclude that the submillimeter H2O line emission other than the para-H2O 111-000 transition is pumped primarily by far-infrared radiation, though some collisional pumping may contribute to the low-lying para-H2O 202-111 line, and that collisional pumping of the

  7. Differences in electrophysical and gas sensing properties of flame spray synthesized Fe2O3(gamma-Fe2O3 and alpha-Fe2O3).

    PubMed

    Flak, Dorota; Braun, Artur; Michalow, Katarzyna A; Wyrwa, Jan; Parlinska-Wojtan, Magdalena; Graule, Thomas; Rekas, Mieczyslaw

    2012-08-01

    Nanoscaled Fe2O3 powders as candidates for gas sensing material for hydrogen detection were synthesized by the high temperature flame spray assisted combustion of ferrocene dissolved in benzene. X-ray diffraction (XRD) and selected area electron diffraction (SAED) show that the as prepared nanopowder consists of maghemite (gamma-Fe2O3) with low crystallinity. Thermal post-treatment causes a phase transformation towards hematite (alpha-Fe2O3) accompanied by an increase in the crystallinity. Upon exposure to air and hydrogen at elevated temperatures, both phases show a significant variation of conductivity and activation energy-as evidenced by impedance spectra-and thus a favorable sensor response, surpassing even that of flame-synthesized nanocrystalline tin dioxide. The conductivity has been identified as of electronic origin, affected by trap states located in the region adjacent to grain boundaries. Quantitative analysis of the impedance spectra with equivalent circuits shows that the conductivity is thermally activated and affected by the interaction of hydrogen with the sensor material. The calculated Debye screening length of gamma-Fe2O3 and alpha-Fe2O3 is about 27 nm and 16 nm, respectively, what contributes significantly to the sensitivity of the material. Gamma-Fe2O3 and alpha-Fe2O3 exhibit high sensor response towards hydrogen in a wide concentration range. Gamma-Fe2O3 shows n-type semiconducting behavior up to 573 K. Alpha-Fe2O3 shows p-type semiconducting behavior, as reflected in the dynamic changes of the resistivity. For both sensor materials, 523 K was the optimal operating temperature. PMID:22962756

  8. Mechanical properties and histological evaluation of sintered beta-Ca2P2O7 with Na4P2O7.10H2O addition.

    PubMed

    Lin, F H; Lin, C C; Lu, C M; Liu, H C; Sun, J S; Wang, C Y

    1995-07-01

    The ultimate goal of implantation of biomaterials in the skeleton is to reach full integration of the non-living implant with the living bone. The biomaterial can be used much as a bone graft, resorbing or dissolving as bone growth occurs, and the end result is a new remoulded bone. Calcium pyrophosphate, Ca2P2O7, is one of the intermediate products of bone mineralization. beta-Dicalcium pyrophosphate (beta-DCP) doped with certain amounts of Na4P2O7.10H2O was prepared as the developed material. Na4P2O7.10H2O was used as a liquid-phase additive to improve the sintering process and promote physiological bioresorbability. Compressive strength and four-point bending strength were measured by the Bionix test system 858. The mechanical strength of the sintered beta-DCP increased with the addition of Na4P2O7.10H2O up to 5 wt%, but thereafter decreased. The microstructure and crystal structure were analysed by the techniques of SEM, EPMA, TEM and XRD. The relationship between the mechanical strength of the sintered bioceramics and the Na4P2O7.10H2O dopant was examined in terms of the presence of NaCa(PO3)3, grain growth and abnormal grain coalescence while the dopant increased. Preliminary in vivo evaluation was studied by rabbit femur condyle implantation. There was no inflammation or any toxic sign during the experimental period. The histological section of intraosseous implantation revealed that the new bone deposited directly on the surface of the material in the fourth week after operation. The implant gradually decreased in volume and was replaced by the surrounding regenerated bone in the rabbit condyle in vivo environment. The results led us to conclude that the developed material has great potential as a biodegradable bone substitute.

  9. Uncovering the complex behavior of hydrogen in Cu2O.

    PubMed

    Scanlon, David O; Watson, Graeme W

    2011-05-01

    The behavior of hydrogen in p-type Cu(2)O has been reported to be quite unusual. Muon experiments have been unable to ascertain the preferential hydrogen site within the Cu(2)O lattice, and indicate that hydrogen causes an electrically active level near the middle of the band gap, whose nature, whether accepting or donating, is not known. In this Letter, we use screened hybrid-density-functional theory to study the nature of hydrogen in Cu(2)O, and identify for the first time the "quasiatomic" site adopted by hydrogen in Cu(2)O. We show that hydrogen will always act as a hole killer in p-type Cu(2)O, and is one likely cause of the low performance of Cu(2)O solar cell devices. PMID:21635109

  10. Effect of Fe2O3 concentration on the structure of the SiO2-Na2O-Al2O3-B2O3 glass system.

    PubMed

    Dantas, Noelio O; Ayta, Walter E F; Silva, Anielle C A; Cano, Nilo F; Silva, Sebastião W; Morais, Paulo C

    2011-10-15

    The structural properties of the glass matrix 40SiO(2)·30Na(2)O·1Al(2)O(3)·(29-x)B(2)O(3)·xFe(2)O(3) (mol%), 0.0≤x≤29.0 were studied by X-ray diffraction (XRD), differential thermal analysis (DTA) and Raman and infrared spectroscopy (FT-IR). XRD demonstrated Fe(3)O(4) crystal formation for Fe(2)O(3) concentrations of 29.0 mol%. DTA showed that glass transition and crystallization temperatures changed as a function of Fe(2)O(3) concentration and that these alterations were related to structural change in the glass system. Interesting aspects of Raman and FT-IR spectra were found, and this gives information about of the structure changes in Si-O-Si units of these glasses as a function of Fe(2)O(3) concentration.

  11. Non-linear Electrical Characteristics of ZnO Modified by Trioxides Sb2O3, Bi2O3, Fe2O3, Al2O3 and La2O3

    NASA Astrophysics Data System (ADS)

    Mekap, Anita; Das, Piyush R.; Choudhary, R. N. P.

    2016-08-01

    The non-linear behavior of polycrystalline-ZnO-based voltage-dependent resistors is considered in the present study. A high-temperature solid-state reaction route was used to synthesize polycrystalline samples of ZnO modified by small amounts of the trioxides Sb2O3, Bi2O3, Fe2O3, etc. in various proportions. X-ray diffraction and scanning electron microscopy techniques were used to study the structural and microstructural characteristics of modified ZnO. Detailed studies of non-linear phenomena of the I-V characteristics, dielectric permittivity ( ɛ r), impedance ( Z), etc. of the samples have provided many interesting results. All the samples exhibited dielectric anomaly. Non-linear variation in polarization with electric field for all the samples was observed. Moreover, significant non-linearity in the I-V characteristics was observed in the breakdown region of all the samples at room temperature. The non-linear coefficient ( α) in different cases, i.e. for I- V, ɛ r- f, ɛ r- T, and ɛ r- Z, was calculated and found to be appreciable. The frequency dependence of ac conductivity suggests that the material obeys Jonscher's universal power law.

  12. Synthesis and characterization of Cu2O-modified Bi2O3 nanospheres with enhanced visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Luo, Yidan; Huang, Qingqing; Li, Bin; Dong, Lihui; Fan, Minguang; Zhang, Feiyue

    2015-12-01

    In this work, a series of Cu2O-modified Bi2O3 nanospheres with perfect visible-light catalytic activity were successfully synthesized via the two-step method. The obtained products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area, UV-visible diffuse reflectance spectroscopy (UV-vis DRS), and X-ray photoelectron spectroscopy (XPS). In the catalysts of Cu2O-modified Bi2O3 nanospheres, Cu2O was dispersed on the surface of Bi2O3 nanospheres. All of Cu2O-modified Bi2O3 nanospheres showed uniformly nanospheres with the size of 80-150 nm, and exhibited enhanced photocatalytic activity in the degradation of Rhodamine B. The higher BET surface area, the band gap narrowing, and the interfacial charge transfer effect were considered to cause the excellent photocatalysis of Cu2O loading Bi2O3 samples. Furthermore, the possible photocatalysis mechanism was proposed.

  13. The irradiation effects of Gd2Hf2O7 and Gd2Ti2O7

    NASA Astrophysics Data System (ADS)

    Li, Y. H.; Wen, J.; Wang, Y. Q.; Wang, Z. G.; Tang, M.; Valdez, J. A.; Sickafus, K. E.

    2012-09-01

    In this report, we present dramatically different behavior between isostructural Gd2Hf2O7 and Gd2Ti2O7 pyrochlore using 400 keV Ne2+ irradiation under cryogenic conditions (˜77 K), in which the lattice volume of the irradiated layer of Gd2Ti2O7 increased with ion fluence up to 1 × 1015 ions/cm2, whereas, the lattice volume of the irradiated layer of Gd2Hf2O7 decreased with increasing fluence from 1 × 1015 to 6 × 1016 ions/cm2. The cation radius ratio rA/rB, the bond-type of A-O and B-O bonds, the order-to-disorder transition energy of Gd2Hf2O7 and Gd2Ti2O7, temperature-composition (T-C) phase diagrams of HfO2-Gd2O3 and TiO2-Gd2O3 mixtures were used to explain the response of Gd2Hf2O7 and Gd2Ti2O7 to ion irradiation-induced structure transformation.

  14. 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.

  15. Sources and sinks for atmospheric N2O

    NASA Technical Reports Server (NTRS)

    Mcelroy, M. B.; Elkins, J. W.; Wofsy, S. C.; Yung, Y. L.

    1976-01-01

    Observations of the temporal and spatial distribution of N2O in solution are not yet sufficient to permit quantitative assessment of the role of the ocean in the budget of atmospheric N2O. Consideration of the global nitrogen cycle suggests that the land should be the primary source of N2O. The gas is removed in the atmosphere by photolysis and by reaction with O(1D), and there may be additional sinks in the ocean.

  16. N2O production, a widespread trait in fungi.

    PubMed

    Maeda, Koki; Spor, Aymé; Edel-Hermann, Véronique; Heraud, Cécile; Breuil, Marie-Christine; Bizouard, Florian; Toyoda, Sakae; Yoshida, Naohiro; Steinberg, Christian; Philippot, Laurent

    2015-04-20

    N2O is a powerful greenhouse gas contributing both to global warming and ozone depletion. While fungi have been identified as a putative source of N2O, little is known about their production of this greenhouse gas. Here we investigated the N2O-producing ability of a collection of 207 fungal isolates. Seventy strains producing N2O in pure culture were identified. They were mostly species from the order Hypocreales order-particularly Fusarium oxysporum and Trichoderma spp.-and to a lesser extent species from the orders Eurotiales, Sordariales, and Chaetosphaeriales. The N2O (15)N site preference (SP) values of the fungal strains ranged from 15.8‰ to 36.7‰, and we observed a significant taxa effect, with Penicillium strains displaying lower SP values than the other fungal genera. Inoculation of 15 N2O-producing strains into pre-sterilized arable, forest and grassland soils confirmed the ability of the strains to produce N2O in soil with a significant strain-by-soil effect. The copper-containing nitrite reductase gene (nirK) was amplified from 45 N2O-producing strains, and its genetic variability showed a strong congruence with the ITS phylogeny, indicating vertical inheritance of this trait. Taken together, this comprehensive set of findings should enhance our knowledge of fungi as a source of N2O in the environment.

  17. N2O production, a widespread trait in fungi

    NASA Astrophysics Data System (ADS)

    Maeda, Koki; Spor, Aymé; Edel-Hermann, Véronique; Heraud, Cécile; Breuil, Marie-Christine; Bizouard, Florian; Toyoda, Sakae; Yoshida, Naohiro; Steinberg, Christian; Philippot, Laurent

    2015-04-01

    N2O is a powerful greenhouse gas contributing both to global warming and ozone depletion. While fungi have been identified as a putative source of N2O, little is known about their production of this greenhouse gas. Here we investigated the N2O-producing ability of a collection of 207 fungal isolates. Seventy strains producing N2O in pure culture were identified. They were mostly species from the order Hypocreales order--particularly Fusarium oxysporum and Trichoderma spp.--and to a lesser extent species from the orders Eurotiales, Sordariales, and Chaetosphaeriales. The N2O 15N site preference (SP) values of the fungal strains ranged from 15.8‰ to 36.7‰, and we observed a significant taxa effect, with Penicillium strains displaying lower SP values than the other fungal genera. Inoculation of 15 N2O-producing strains into pre-sterilized arable, forest and grassland soils confirmed the ability of the strains to produce N2O in soil with a significant strain-by-soil effect. The copper-containing nitrite reductase gene (nirK) was amplified from 45 N2O-producing strains, and its genetic variability showed a strong congruence with the ITS phylogeny, indicating vertical inheritance of this trait. Taken together, this comprehensive set of findings should enhance our knowledge of fungi as a source of N2O in the environment.

  18. Nitrous oxide (N2O) emission from aquaculture: a review.

    PubMed

    Hu, Zhen; Lee, Jae Woo; Chandran, Kartik; Kim, Sungpyo; Khanal, Samir Kumar

    2012-06-19

    Nitrous oxide (N(2)O) is an important greenhouse gas (GHG) which has a global warming potential 310 times that of carbon dioxide (CO(2)) over a hundred year lifespan. N(2)O is generated during microbial nitrification and denitrification, which are common in aquaculture systems. To date, few studies have been conducted to quantify N(2)O emission from aquaculture. Additionally, very little is known with respect to the microbial pathways through which N(2)O is formed in aquaculture systems. This review suggests that aquaculture can be an important anthropogenic source of N(2)O emission. The global N(2)O-N emission from aquaculture in 2009 is estimated to be 9.30 × 10(10) g, and will increase to 3.83 × 10(11)g which could account for 5.72% of anthropogenic N(2)O-N emission by 2030 if the aquaculture industry continues to increase at the present annual growth rate (about 7.10%). The possible mechanisms and various factors affecting N(2)O production are summarized, and two possible methods to minimize N(2)O emission, namely aquaponic and biofloc technology aquaculture, are also discussed. The paper concludes with future research directions. PMID:22594516

  19. N2O production, a widespread trait in fungi

    PubMed Central

    Maeda, Koki; Spor, Aymé; Edel-Hermann, Véronique; Heraud, Cécile; Breuil, Marie-Christine; Bizouard, Florian; Toyoda, Sakae; Yoshida, Naohiro; Steinberg, Christian; Philippot, Laurent

    2015-01-01

    N2O is a powerful greenhouse gas contributing both to global warming and ozone depletion. While fungi have been identified as a putative source of N2O, little is known about their production of this greenhouse gas. Here we investigated the N2O-producing ability of a collection of 207 fungal isolates. Seventy strains producing N2O in pure culture were identified. They were mostly species from the order Hypocreales order—particularly Fusarium oxysporum and Trichoderma spp.—and to a lesser extent species from the orders Eurotiales, Sordariales, and Chaetosphaeriales. The N2O 15N site preference (SP) values of the fungal strains ranged from 15.8‰ to 36.7‰, and we observed a significant taxa effect, with Penicillium strains displaying lower SP values than the other fungal genera. Inoculation of 15 N2O-producing strains into pre-sterilized arable, forest and grassland soils confirmed the ability of the strains to produce N2O in soil with a significant strain-by-soil effect. The copper-containing nitrite reductase gene (nirK) was amplified from 45 N2O-producing strains, and its genetic variability showed a strong congruence with the ITS phylogeny, indicating vertical inheritance of this trait. Taken together, this comprehensive set of findings should enhance our knowledge of fungi as a source of N2O in the environment. PMID:25894103

  20. N2O production, a widespread trait in fungi.

    PubMed

    Maeda, Koki; Spor, Aymé; Edel-Hermann, Véronique; Heraud, Cécile; Breuil, Marie-Christine; Bizouard, Florian; Toyoda, Sakae; Yoshida, Naohiro; Steinberg, Christian; Philippot, Laurent

    2015-01-01

    N2O is a powerful greenhouse gas contributing both to global warming and ozone depletion. While fungi have been identified as a putative source of N2O, little is known about their production of this greenhouse gas. Here we investigated the N2O-producing ability of a collection of 207 fungal isolates. Seventy strains producing N2O in pure culture were identified. They were mostly species from the order Hypocreales order-particularly Fusarium oxysporum and Trichoderma spp.-and to a lesser extent species from the orders Eurotiales, Sordariales, and Chaetosphaeriales. The N2O (15)N site preference (SP) values of the fungal strains ranged from 15.8‰ to 36.7‰, and we observed a significant taxa effect, with Penicillium strains displaying lower SP values than the other fungal genera. Inoculation of 15 N2O-producing strains into pre-sterilized arable, forest and grassland soils confirmed the ability of the strains to produce N2O in soil with a significant strain-by-soil effect. The copper-containing nitrite reductase gene (nirK) was amplified from 45 N2O-producing strains, and its genetic variability showed a strong congruence with the ITS phylogeny, indicating vertical inheritance of this trait. Taken together, this comprehensive set of findings should enhance our knowledge of fungi as a source of N2O in the environment. PMID:25894103

  1. Nitrous oxide (N2O) emission from aquaculture: a review.

    PubMed

    Hu, Zhen; Lee, Jae Woo; Chandran, Kartik; Kim, Sungpyo; Khanal, Samir Kumar

    2012-06-19

    Nitrous oxide (N(2)O) is an important greenhouse gas (GHG) which has a global warming potential 310 times that of carbon dioxide (CO(2)) over a hundred year lifespan. N(2)O is generated during microbial nitrification and denitrification, which are common in aquaculture systems. To date, few studies have been conducted to quantify N(2)O emission from aquaculture. Additionally, very little is known with respect to the microbial pathways through which N(2)O is formed in aquaculture systems. This review suggests that aquaculture can be an important anthropogenic source of N(2)O emission. The global N(2)O-N emission from aquaculture in 2009 is estimated to be 9.30 × 10(10) g, and will increase to 3.83 × 10(11)g which could account for 5.72% of anthropogenic N(2)O-N emission by 2030 if the aquaculture industry continues to increase at the present annual growth rate (about 7.10%). The possible mechanisms and various factors affecting N(2)O production are summarized, and two possible methods to minimize N(2)O emission, namely aquaponic and biofloc technology aquaculture, are also discussed. The paper concludes with future research directions.

  2. Cu2O-based solar cells using oxide semiconductors

    NASA Astrophysics Data System (ADS)

    Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

    2016-01-01

    We describe significant improvements of the photovoltaic properties that were achieved in Al-doped ZnO (AZO)/n-type oxide semiconductor/p-type Cu2O heterojunction solar cells fabricated using p-type Cu2O sheets prepared by thermally oxidizing Cu sheets. The multicomponent oxide thin film used as the n-type semiconductor layer was prepared with various chemical compositions on non-intentionally heated Cu2O sheets under various deposition conditions using a pulsed laser deposition method. In Cu2O-based heterojunction solar cells fabricated using various ternary compounds as the n-type oxide thin-film layer, the best photovoltaic performance was obtained with an n-ZnGa2O4 thin-film layer. In most of the Cu2O-based heterojunction solar cells using multicomponent oxides composed of combinations of various binary compounds, the obtained photovoltaic properties changed gradually as the chemical composition was varied. However, with the ZnO-MgO and Ga2O3-Al2O3 systems, higher conversion efficiencies (η) as well as a high open circuit voltage (Voc) were obtained by using a relatively small amount of MgO or Al2O3, e.g., (ZnO)0.91-(MgO)0.09 and (Ga2O3)0.975-(Al2O3)0.025, respectively. When Cu2O-based heterojunction solar cells were fabricated using Al2O3-Ga2O3-MgO-ZnO (AGMZO) multicomponent oxide thin films deposited with metal atomic ratios of 10, 60, 10 and 20 at.% for the Al, Ga, Mg and Zn, respectively, a high Voc of 0.98 V and an η of 4.82% were obtained. In addition, an enhanced η and an improved fill factor could be achieved in AZO/n-type multicomponent oxide/p-type Cu2O heterojunction solar cells fabricated using Na-doped Cu2O (Cu2O:Na) sheets that featured a resistivity controlled by optimizing the post-annealing temperature and duration. Consequently, an η of 6.25% and a Voc of 0.84 V were obtained in a MgF2/AZO/n-(Ga2O3-Al2O3)/p-Cu2O:Na heterojunction solar cell fabricated using a Cu2O:Na sheet with a resistivity of approximately 10 Ω·cm and a (Ga0.975Al0.025)2

  3. Calculation of Phase Equilibria in the Y2O3-Yb2O3-ZrO2 System

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Liu, Zi-Kui; Kaufman, Larry; Zhang, Fan

    2001-01-01

    Rare earth oxide stabilized zirconias find a wide range of applications. An understanding of phase equilibria is essential to all applications. In this study, the available phase boundary data and thermodynamic data is collected and assessed. Calphad-type databases are developed to completely describe the Y2O3-ZrO2, Yb2O3-ZrO2, and Y2O3-Yb2O3 systems. The oxide units are treated as components and regular and subregular solution models are used. The resultant calculated phase diagrams show good agreement with the experimental data. Then the binaries are combined to form the database for the Y2O3-Yb2O3-ZrO2 psuedo-ternary.

  4. Ionic liquid-based hydrothermal synthesis of Lu2O3 and Lu2O3:Eu3+ microcrysals

    NASA Astrophysics Data System (ADS)

    Li, Yinyan; Xu, Shiqing

    2016-09-01

    Uniform and well-defined Lu2O3 and Lu2O3:Eu3+ microarchitectures have been successfully synthesized via a green and facile ionic liquid-based hydrothermal method followed by a subsequent calcination process. Novel 3D micro-rodbundles and 1D microrods of Lu2O3 and Lu2O3:Eu3+ were controllably obtained through this method. X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and photoluminescence spectra were used to characterize the micromaterials. The proposed formation mechanisms have been investigated on the basis of a series of SEM studies of the products obtained at different hydrothermal durations. The results indicated that hydrothermal temperature and the ionic liquid-tetrabutylammonium hydroxide were two key factors for the formation as well as the morphology control of the Lu2O3 and Lu2O3:Eu3+ microarchitectures.

  5. Tuning the conductance of H2O@C60 by position of the encapsulated H2O

    PubMed Central

    Zhu, Chengbo; Wang, Xiaolin

    2015-01-01

    The change of conductance of single-molecule junction in response to various external stimuli is the fundamental mechanism for the single-molecule electronic devices with multiple functionalities. We propose the concept that the conductance of molecular systems can be tuned from inside. The conductance is varied in C60 with encapsulated H2O, H2O@C60. The transport properties of the H2O@C60-based nanostructure sandwiched between electrodes are studied using first-principles calculations combined with the non-equilibrium Green’s function formalism. Our results show that the conductance of the H2O@C60 is sensitive to the position of the H2O and its dipole direction inside the cage with changes in conductance up to 20%. Our study paves a way for the H2O@C60 molecule to be a new platform for novel molecule-based electronics and sensors. PMID:26643873

  6. Pressure induced structural transformation in Gd2Ti2O7 and Gd2Zr2O7

    NASA Astrophysics Data System (ADS)

    Xiao, H. Y.; Weber, W. J.

    2011-01-01

    Ab initio total energy calculations have been performed to study the phase stability of Gd2Ti2O7 and Gd2Zr2O7 pyrochlores over the pressure range from 0 to 60 GPa. Both compounds are unstable under pressure, and phase transformations to the defect-cotunnite structure are predicted. The phase transformation pressure of 43.6 GPa for Gd2Ti2O7 is considerably larger than the value of 13 GPa for Gd2Zr2O7, in good agreement with experiments. The decreased structural stability of Gd2Zr2O7 under pressure, relative to Gd2Ti2O7, is a consequence of the lower compressibility of the langZr-Orang bond and the higher compressibility of the langGd-Orang bond. In addition, the Gd 4f electrons are found to have only a small effect in determining the pressure induced phase transformation.

  7. The band alignment of Cu2O/ZnO and Cu2O/GaN heterostructures

    NASA Astrophysics Data System (ADS)

    Kramm, B.; Laufer, A.; Reppin, D.; Kronenberger, A.; Hering, P.; Polity, A.; Meyer, B. K.

    2012-02-01

    Using photoelectron spectroscopy, we investigate the band alignments of the Cu2O/ZnO heterointerface and compare the findings with the corresponding values for Cu2O/GaN. While for Cu2O/ZnO, we find a valence band offset (VBO) of 2.17 eV and a conduction band offset (CBO) of 0.97 eV, both values are considerably reduced for Cu2O/GaN where the numbers are 1.47 eV (VBO) and 0.24 eV (CBO), respectively. The large CBO between ZnO and Cu2O will very likely result in low photovoltaic power conversion efficiencies as is the current status of Cu2O/ZnO solar cells.

  8. The H2O/D2O isotope effect in crystalline lanthanide sulfates at photo-, radio-, and triboluminescence

    NASA Astrophysics Data System (ADS)

    Sharipov, G. L.; Tukhbatullin, A. A.; Mescheryakova, E. S.

    2016-02-01

    We comparatively studied the H2O/D2O isotope effect of lanthanide sulfate crystallohydrates on photo-, radio-, and triboluminescence and lifetimes of the excited Ln3+ ions. Replacing H2O by D2O leads to an increase in the luminescence intensity whereas this process does not affect the maxima positions in photo-, radio-, and triboluminescence spectra. This isotope effect agrees with the known concepts of changes in luminescence quantum yields of the Ln3+ ions being the main emitters. The bands of OH and OD radicals arise in triboluminescence spectra of lanthanide sulfate crystallohydrates (with H2O or D2O) registered in argon atmosphere in UV region. This supports the proposition that water destruction occurs at the degradation of the crystallohydrates.

  9. Effect of H2O, and combined effects of H2O + F, H2O + CO2, and H2O + F + CO2 on the viscosity of a natural basalt from Fuego volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Robert, G.; Whittington, A. G.; Knipping, J.; Scherbarth, S.; Stechern, A.; Behrens, H.

    2012-12-01

    We measured the viscosity of 5 series of remelted natural basalt from Fuego volcano, Guatemala. These series include single and multiple volatile species: H2O, F, H2O-F, H2O-CO2, and H2O-CO2-F. The hydrous glasses were synthesized at 3 kbar and 1250°C in Internally Heated Pressure Vessels. The multiple volatile series were synthesized at 5 kbar and 1250°C. CO2 was added as Ag2C2O4, F as AlF3, and H2O as distilled water. The anhydrous, F-bearing series was synthesized at 1 atm by simply remelting the Fuego basalt and adding F as CaF2.The natural, dry, remelted Fuego basalt has an NBO/T of 0.64. The following comparisons are based on parallel-plate viscosity measurements in the range ~108 to 1012 Pa s. The temperature at which the viscosity is 1012 Pa s (T12) is taken to be the viscosimetric glass transition temperature (Tg). The addition of 2 wt.% H2O results in a decrease of T12 of ~150°C for basalt. Fluorine on its own has a measurable, but much smaller effect, than the equivalent amount of water. Indeed, ~2 wt.% F results in a T12 depression of only ~30°C. When H2O and F are both present, their effects are approximately additive. For example, the viscosity of a basalt with 1.44 wt.% H2O is very similar to the viscosity of a basalt with ~1 wt.% H2O and ~1.25 wt.% F, and the viscosities of a basalt with 2.29 wt.% H2O and a basalt with ~1.65 wt.% H2O and ~1.3 wt.% F are also very similar. The effect of CO2 is somewhat ambiguous. The viscosity of a basalt with ~1.7 wt.% H2O, ~1.3 wt.% F and ~0.2 wt.% CO2 is essentially the same as the viscosity of a basalt with 2.29 wt.% H2O, so CO2 seems to have a negligible or even viscosity-increasing effect when F and H2O are also present. However, a basalt with ~0.84 wt.% H2O and ~0.09 wt.% CO2 has about the same viscosity as a basalt with 1.34 wt.% H2O, which could suggest a strong (viscosity-decreasing) effect of very small amounts of CO2. These results suggest that the effects on viscosity of F in basaltic systems are

  10. Photoelectrochemical properties of Fe2O3-Nb2O5 films prepared by sol-gel method.

    PubMed

    Miyake, Hidekazu; Kozuka, Hiromitsu

    2005-09-29

    Fe2O3-Nb2O5 coating films of various Nb/(Fe + Nb) mole ratios were prepared on nesa silica glass substrates from Fe(NO3)3.9H2O - NbCl5 - CH3(CH2)2CH2OH - CH3COOH solutions by the sol-gel method. The photoanodic properties were studied in a three-electrode cell with an aqueous buffer solution of pH = 7 as the supporting electrolyte. The crystalline phases identified were alpha-Fe2O3 (Nb/(Fe + Nb) = 0), alpha-Fe2O3 + FeNbO4 (Nb/(Fe + Nb) = 0.25), FeNbO4 (Nb/(Fe + Nb) = 0.5), FeNbO4 + Nb2O5 (Nb/(Fe + Nb) = 0.75), and Nb2O5 (Nb/(Fe + Nb) = 1). When the Nb/(Fe + Nb) mole ratio increased from 0 to 0.25, the crystalline phases changed from alpha-Fe2O3 to alpha-Fe2O3 + FeNbO4, the photoanodic current under white light illumination increased, and the photoanodic current under monochromatized light illumination increased in both visible and ultraviolet regions. When the Nb/(Fe + Nb) ratio increased over 0.25, the crystalline phases changed to FeNbO4, FeNbO4 + Nb2O5, or Nb2O5, and the photoanodic current decreased. The sample consisting of alpha-Fe2O3 and FeNbO4 (Nb/(Fe + Nb) = 0.25) exhibited photoresponse extending to 600 nm and an IPCE of 18% at a wavelength of 325 nm. PMID:16853304

  11. Evaluation of CaO-SiO2-P2O5-Na2O-Fe2O3 bioglass-ceramics for hyperthermia application.

    PubMed

    Singh, Rajendra Kumar; Srinivasan, A; Kothiyal, G P

    2009-12-01

    Magnetic bioglass ceramics (MBC) are being considered for use as thermoseeds in hyperthermia treatment of cancer. While the bioactivity in MBCs is attributed to the formation of the bone minerals such as crystalline apatite, wollastonite, etc. in a physiological environment, the magnetic property arises from the magnetite [Fe3O4] present in these implant materials. A new set of bioglasses with compositions 41CaO x (52-x)SiO2 x 4P2O5 x xFe2O3 x 3Na2O (2 < or = x < or = 10 mol% Fe2O3) have been prepared by melt quenching method. The as-quenched glasses were then heat treated at 1050 degrees C for 3 h to obtain the glass-ceramics. The structure and microstructure of the samples were characterized using X-ray diffraction and microscopy techniques. X-ray diffraction data revealed the presence of magnetite in the heat treated samples with x > or = 2 mol% Fe2O3. Room temperature magnetic property of the heat treated samples was investigated using a Vibrating Sample Magnetometer. Field scans up to 20 kOe revealed that the glass ceramic samples had a high saturation magnetization and low coercivity. Room temperature hysteresis cycles were also recorded at 500 Oe to ascertain the magnetic properties at clinically amenable field strengths. The area under the magnetic hysteresis loop is a measure of the heat generated by the MBC. The coercivity of the samples is another important factor for hyperthermia applications. The area under the loop increases with an increase in Fe2O3 molar concentration and the. coercivity decreases with an increase in Fe2O3 molar concentration The evolution of magnetic properties in these MBCs as a function of Fe2O3 molar concentration is discussed and correlated with the amount of magnetite present in them. PMID:18560766

  12. Synthesis and characterization of phosphates in molten systems Cs 2O-P 2O 5-CaO- MIII2O 3 ( MIII—Al, Fe, Cr)

    NASA Astrophysics Data System (ADS)

    Zatovsky, Igor V.; Strutynska, Nataliya Yu.; Baumer, Vyacheslav N.; Slobodyanik, Nikolay S.; Ogorodnyk, Ivan V.; Shishkin, Oleg V.

    2011-03-01

    The crystallization of complex phosphates from the melts of Cs 2O-P 2O 5-CaO- MIII2O 3 ( MIII—Al, Fe, Cr) systems have been investigated at fixed value Cs/P molar ratios equal to 0.7, 1.0 and 1.3 and Са/Р=0.2 and Ca/ МIII=1. The fields of crystallization of CsCaP 3O 9, β-Ca 2P 2O 7, Cs 2CaP 2O 7, Cs 3CaFe(P 2O 7) 2, Ca 9MIII(PO 4) 7 ( MIII—Fe, Cr), Cs 0.63Ca 9.63Fe 0.37(PO 4) 7 and CsCa 10(PO 4) 7 were determined. Obtained phosphates were investigated using powder X-ray diffraction and FTIR spectroscopy. Novel whitlockite-related phases CsCa 10(PO 4) 7 and Cs 0.63Ca 9.63Fe 0.37(PO 4) 7 have been characterized by single crystal X-ray diffraction: space group R3c, a=10.5536(5) and 10.5221(4) Å, с=37.2283(19) and 37.2405(17) Å, respectively.

  13. Studies on the properties of Al2O3:Cr2O3 (50:50) thin film

    NASA Astrophysics Data System (ADS)

    Ponmudi, S.; Sivakumar, R.; Sanjeeviraja, C.

    2016-05-01

    Aluminium oxide (Al2O3) and chromium oxide (Cr2O3) thin films have received great attention of researchers because of their unique properties of corrosion/oxidation resistance and high dielectric constant. In addition, chromium aluminium oxide has been considered as a best candidate for deep-ultraviolet optical masks. In the present work, thin films of Al2O3:Cr2O3 (50:50) were deposited on pre-cleaned microscopic glass substrate by RF magnetron sputtering technique. The substrate temperature and RF power induced changes in structural, surface morphological, compositional and optical properties of the films have been studied.

  14. High-temperature heat capacity of stannates Pr2Sn2O7 and Nd2Sn2O7

    NASA Astrophysics Data System (ADS)

    Denisova, L. T.; Irtyugo, L. A.; Beletskii, V. V.; Denisov, V. M.

    2016-07-01

    Oxide compounds Pr2Sn2O7 and Nd2Sn2O7 have been obtained by solid-phase synthesis. The effect of temperature on the heat capacity of Pr2Sn2O7 (360-1045 K) and Nd2Sn2O7 (360-1030 K) has been studied using differential scanning calorimetry. The thermodynamic properties of the compounds (changes in enthalpy, entropy, and the reduced Gibbs energy) have been calculated by the experimental data of C p = f( T).

  15. Heat capacity of the frustrated magnetic pyrochlores Gd2Zr2O7 and Gd2Hf2O7

    NASA Astrophysics Data System (ADS)

    Durand, Alice M.; Klavins, Peter; Corruccini, L. R.

    2008-06-01

    The heat capacities of Gd2Zr2O7 and Gd2Hf2O7 both show sharp peaks in the vicinity of 0.77 K, consistent with the existence of long range magnetic order. They are superimposed in both cases on broader maxima centered at approximately 1 K, presumably due to short range spin correlations. Both compounds exhibit antiferromagnetic interactions, with Weiss constants of approximately -7 K. Comparisons are made to earlier results for the isomorphic compounds Gd2Ti2O7 and Gd2Sn2O7.

  16. N2O fluxes at the soil-atmosphere interface in various ecosystems and the global N2O budget

    NASA Technical Reports Server (NTRS)

    Banin, Amos

    1987-01-01

    The overall purpose of this research task is to study the effects of soil properties and ecosystem variables on N2O exchanges at the soil-atmosphere interface, and to assess their effects on the globle N2O budget. Experimental procedures are implemented in various sites to measure the source/sink relations of N2O at the soil-atmosphere interface over prolonged periods of time as part of the research of biogeochemical cycling in terrestrial ecosystems. A data-base for establishing quantitative correlations between N2O fluxes and soil and environmental parameters that are of potential use for remote sensing, is being developed.

  17. Vibrational Predissociation Dynamics of the (H_2O)_2 Dimer

    NASA Astrophysics Data System (ADS)

    Ch'ng, L. C.; Rocher, B. E.; Mollner, A. K.; Reisler, H.

    2011-06-01

    The state-to-state vibrational predissociation dynamics of the (H_2O)_2 dimer were studied by resonance-enhanced multiphoton ionization (REMPI) and velocity-map imaging (VMI) to obtain pair-correlated product energy distributions. The 2+1 REMPI spectra of the H_2O photofragments were recorded via the tilde{C}^1B_1 (000) ← tilde{X}^1A_1 (000 and 010) transition following a vibrational excitation of the dimer's bound-OH stretch fundamental. The fragment' center-of-mass translational energy (c.m. E_T) distributions were determined from VMI of selected rotational states of the detected H_2O photofragments. The c.m. E_T distributions were then converted to pair-correlated H_2O cofragment rotational level distributions. This is the first experiment in which H_2O products with bend (ν_2) excitation were observed by REMPI. The dissociation energy of the dimer was determined from the images with spectroscopic accuracy. The predissociation mechanism of (H_2O)_2 will be discussed and compared with the corresponding hydrogen bonded dimers of an acid (HCl-H_2O) and a base (NH_3-H_2O).

  18. Compressibilities of MnFe2O4 polymorphs

    NASA Astrophysics Data System (ADS)

    Ye, Lijin; Zhai, Shuangmeng; Wu, Xiang; Xu, Chaowen; Yang, Ke; Higo, Yuji

    2015-07-01

    The high-pressure behavior and stability of synthetic jacobsite MnFe2O4 have been investigated up to 39.55 GPa at room temperature by means of in situ synchrotron X-ray diffraction using diamond anvil cell and multi-anvil high-pressure apparatus. The MnFe2O4 spinel undergoes a phase transition at about 18 GPa to form a denser antiferromagnetic CaMn2O4-type (CM afm ) polymorph. The CM afm MnFe2O4 is stable up to 39.55 GPa in this study and remains after decompression. Fitting the pressure-volume data using a third-order Birch-Murnaghan equation of state, the isothermal bulk modulus values and the first pressure derivatives were obtained as K 0 = 169.7 (35) GPa, = 2.87 (40) for spinel-type MnFe2O4 and K 0 = 149.2 (24) GPa, = 3.98 (19) for CM afm MnFe2O4, respectively. If is fixed to 4, K 0 was obtained as 160.6 (11) GPa for spinel-type MnFe2O4 and 148.9 (7) GPa for CM afm MnFe2O4. The effects of cation substitution on the isothermal bulk modulus and pressure for phase transition of Fe3+-bearing spinels were discussed.

  19. Scavenging of H2O2 by mouse brain mitochondria.

    PubMed

    Starkov, Anatoly A; Andreyev, Alexander Yu; Zhang, Steven F; Starkova, Natalia N; Korneeva, Maria; Syromyatnikov, Mikhail; Popov, Vasily N

    2014-12-01

    Mitochondrial reactive oxygen species (ROS) metabolism is unique in that mitochondria both generate and scavenge ROS. Recent estimates of ROS scavenging capacity of brain mitochondria are surprisingly high, ca. 9-12 nmol H2O2/min/mg, which is ~100 times higher than the rate of ROS generation. This raises a question whether brain mitochondria are a source or a sink of ROS. We studied the interaction between ROS generation and scavenging in mouse brain mitochondria by measuring the rate of removal of H2O2 added at a concentration of 0.4 μM, which is close to the reported physiological H2O2 concentrations in tissues, under conditions of low and high levels of mitochondrial H2O2 generation. With NAD-linked substrates, the rate of H2O2 generation by mitochondria was ~50-70 pmol/min/mg. The H2O2 scavenging dynamics was best approximated by the first order reaction equation. H2O2 scavenging was not affected by the uncoupling of mitochondria, phosphorylation of added ADP, or the genetic ablation of glutathione peroxidase 1, but decreased in the absence of respiratory substrates, in the presence of thioredoxin reductase inhibitor auranofin, or in partially disrupted mitochondria. With succinate, the rate of H2O2 generation was ~2,200-2,900 pmol/min/mg; the scavenging of added H2O2 was masked by a significant accumulation of generated H2O2 in the assay medium. The obtained data were fitted into a simple model that reasonably well described the interaction between H2O2 scavenging and production. It showed that mitochondria are neither a sink nor a source of H2O2, but can function as both at the same time, efficiently stabilizing exogenous H2O2 concentration at a level directly proportional to the ratio of the H2O2 generation rate to the rate constant of the first order scavenging reaction.

  20. Hormetic Effect of H2O2 in Saccharomyces cerevisiae

    PubMed Central

    Valishkevych, Bohdana V.

    2016-01-01

    In this study, we investigated the relationship between target of rapamycin (TOR) and H2O2-induced hormetic response in the budding yeast Saccharomyces cerevisiae grown on glucose or fructose. In general, our data suggest that: (1) hydrogen peroxide (H2O2) induces hormesis in a TOR-dependent manner; (2) the H2O2-induced hormetic dose–response in yeast depends on the type of carbohydrate in growth medium; (3) the concentration-dependent effect of H2O2 on yeast colony growth positively correlates with the activity of glutathione reductase that suggests the enzyme involvement in the H2O2-induced hormetic response; and (4) both TOR1 and TOR2 are involved in the reciprocal regulation of the activity of glucose-6-phosphate dehydrogenase and glyoxalase 1. PMID:27099601

  1. N2O emissions from full-scale nitrifying biofilters.

    PubMed

    Bollon, Julien; Filali, Ahlem; Fayolle, Yannick; Guerin, Sabrina; Rocher, Vincent; Gillot, Sylvie

    2016-10-01

    A full-scale nitrifying biofilter was continuously monitored during two measurement periods (September 2014; February 2015) during which both gaseous and liquid N2O fluxes were monitored on-line. The results showed diurnal and seasonal variations of N2O emissions. A statistical model was run to determine the main operational parameters governing N2O emissions. Modification of the distribution between the gas phase and the liquid phase was observed related to the effects of temperature and aeration flow on the volumetric mass transfer coefficient (kLa). With similar nitrification performance values, the N2O emission factor was twice as high during the winter campaign. The increase in N2O emissions in winter was correlated to higher effluent nitrite concentrations and suspected increased biofilm thickness.

  2. Theoretical characterization of the reaction NH2 + O yields products

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1993-01-01

    The potential energy surface for NH2+O has been characterized using complete active space self-consistent field (CASSCF)/derivative calculations to determine stationary point geometries and frequencies followed by internally contracted configuration interaction (ICCI) calculations to determine the energetics. The calculations predict a NO bond strength of 85.8 kcal/mol for NH2O. The barrier for isomerization of NH2O to trans-HNOH is predicted to be 48.0 kcal/mol and the barriers for H+HNO forming NH2O and NHOH are predicted to be 2.1 and 8.3 kcal/mol, respectively (all corrected for zero-point energy). The computed heats of formation for NH2O and cis- and trans-HNOH are in good agreement with the present results. The barrier for H + HNO yields H2 + NO is computed to be about 0.3 kcal/mol.

  3. Isotopic Monitoring of N2O Emissions from Wastewater Treatment: Evidence for N2O Production Associated with Anammox Metabolism?

    NASA Astrophysics Data System (ADS)

    Harris, E. J.; Wunderlin, P.; Joss, A.; Emmenegger, L.; Kipf, M.; Wolf, B.; Mohn, J.

    2015-12-01

    Microbial production is the major source of N2O, the strongest greenhouse gas produced within the nitrogen cycle, and the most important stratospheric ozone destructant released in the 21st century. Wastewater treatment is an important and growing source of N2O, with best estimates predicting N2O emissions from this sector will have increased by >25% by 2020. Novel treatment employing partial nitritation-anammox, rather than traditional nitrification-denitrification, has the potential to achieve a neutral carbon footprint due to increased biogas production - if N2O production accounts for <0.5-1% of total nitrogen turnover. As a further motivation for this research, microbial pathways identified from wastewater treatment can be applied to our understanding of N cycling in the natural environment. This study presents the first online isotopic measurements of offgas N2O from a partial-nitritation anammox reactor 1. The measured N2O isotopic composition - in particular the N2O isotopic site preference (SP = δ15Nα - δ15Nβ) - was used to understand N2O production pathways in the reactor. When N2O emissions peaked due to high dissolved oxygen concentrations, low SP showed that N2O was produced primarily via nitrifier denitrification by ammonia oxidizing bacteria (AOBs). N2O production by AOBs via NH2OH oxidation, in contrast, did not appear to be important under any conditions. Over the majority of the one-month measurement period, the measured SP was much higher than expected following our current understanding of N2O production pathways 2. SP reached 41‰ during normal operating conditions and achieved a maximum of 45‰ when nitrite was added under anoxic conditions. These results could be explained by unexpectedly strong heterotrophic N2O reduction despite low dissolved organic matter concentrations, or by an incomplete understanding of isotopic fractionation during N2O production from NH2OH oxidation by AOBs - however the explanation most consistent with all

  4. Oxygen potentials in Ni + NiO and Ni + Cr2O3 + NiCr2O4 systems

    NASA Astrophysics Data System (ADS)

    Kale, G. M.; Fray, D. J.

    1994-06-01

    The chemical potential of O for the coexistence of Ni + NiO and Ni + Cr2O3 + NiCr2O4 equilibria has been measured employing solid-state galvanic cells, (+) Pt, Cu + Cu2O // (Y2O3)ZrO2 // Ni + NiO, Pt (-) and (+) Pt, Ni + NiO // (Y2O3)ZrO2 // Ni + Cr2O3 + NiCr2O4, Pt (-) in the temperature range of 800 to 1300 K and 1100 to 1460 K, respectively. The electromotive force (emf) of both the cells was reversible, reproducible on thermal cycling, and varied linearly with temperature. For the coexistence of the two-phase mixture of Ni + NiO, δΜO 2(Ni + NiO) = -470,768 + 171.77T (±20) J mol-1 (800 ≤ T ≤ 1300 K) and for the coexistence of Ni + Cr2O3 + NiCr2O4, δΜO 2(Ni + Cr2O3 + NiCr2O4) = -523,190 + 191.07T (±100) J mol-1 (1100≤ T≤ 1460 K) The “third-law” analysis of the present results for Ni + NiO gives the value of ‡H{298/o} = -239.8 (±0.05) kJ mol-1, which is independent of temperature, for the formation of one mole of NiO from its elements. This is in excellent agreement with the calorimetric enthalpy of formation of NiO reported in the literature.

  5. VIBRATIONAL RELAXATION OF D2O ( v2)

    SciTech Connect

    Miljanic, Scepan S.; Moore, C.Bradley

    1980-01-01

    The method of laser-excited vibrational fluorescence has been used to measure vibrational relaxation rates for the bending mode of D{sub 2}O in collisions with D{sub 2}O, D{sub 2}, HD, H{sub 2}, He, and Ar. The rate constants at 295 K are found to be (3.2 {+-} 0.2) x 10{sup -11}, (3.6 {+-} 0.2) x 10{sup -13}, (1.2 {+-} 0.1) x 10{sup -12}, (3.3 {+-} 0.2) x 10{sup -12}, (7.1 {+-} 0.9) x 10{sup -14}, and (3.0 {+-} 1.2) x 10{sup -14} cm{sup 3} molecule{sup -1} sec{sup -1}, respectively. Relaxation times have been measured for two D{sub 2}O-HDO-H{sub 2}O mixtures and relaxation probabilities, PD{sub 2}O-HDO and PD{sub 2}O-H{sub 2}O were estimated to be not very different from PD{sub 2}O-D{sub 2}O. The temperature dependence of the relaxation was measured for pure D{sub 2}O. The rates are (1.80 {+-} 0.08) x 10{sup -11} at 400, (2.1 {+-} 0.1) x 10{sup -11} at 350 and (4.0 {+-} 0.3) x 10{sup -11} cm{sup 3} molecule{sup -1} sec{sup -1} at 260 K. The corresponding probabilities are fit by P(T) = C exp({epsilon}/kT) with {epsilon} = (778 {+-} 34) K and C = 1.1 x 10{sup -2}.

  6. UV-induced N2O emission from plants

    NASA Astrophysics Data System (ADS)

    Bruhn, Dan; Albert, Kristian R.; Mikkelsen, Teis N.; Ambus, Per

    2014-12-01

    Nitrous oxide (N2O) is an important long-lived greenhouse gas and precursor of stratospheric ozone-depleting mono-nitrogen oxides. The atmospheric concentration of N2O is persistently increasing; however, large uncertainties are associated with the distinct source strengths. Here we investigate for the first time N2O emission from terrestrial vegetation in response to natural solar ultra violet radiation. We conducted field site measurements to investigate N2O atmosphere exchange from grass vegetation exposed to solar irradiance with and without UV-screening. Further laboratory tests were conducted with a range of species to study the controls and possible loci of UV-induced N2O emission from plants. Plants released N2O in response to natural sunlight at rates of c. 20-50 nmol m-2h-1, mostly due to the UV component. The emission response to UV-A is of the same magnitude as that to UV-B. Therefore, UV-A is more important than UV-B given the natural UV-spectrum at Earth's surface. Plants also emitted N2O in darkness, although at reduced rates. The emission rate is temperature dependent with a rather high activation energy indicative for an abiotic process. The prevailing zone for the N2O formation appears to be at the very surface of leaves. However, only c. 26% of the UV-induced N2O appears to originate from plant-N. Further, the process is dependent on atmospheric oxygen concentration. Our work demonstrates that ecosystem emission of the important greenhouse gas, N2O, may be up to c. 30% higher than hitherto assumed.

  7. Evaluation to the effect of B2O3-La2O3-SrO-Na2O-Al2O3 bonding agent on Ti6Al4V-porcelain bonding.

    PubMed

    Zhao, C Q; Wu, S Q; Lu, Y J; Gan, Y L; Guo, S; Lin, J J; Huang, T T; Lin, J X

    2016-10-01

    Low-fusing bonding agents have been widely applied in Ti-ceramics restorations. As an important category, borate bonding agents have great potentials in increasing Ti-porcelain bonding. The purpose of this study is to evaluate the effect of borate bonding agent with addition of Na2O and Al2O3 on Ti6Al4V-porcelain bonding. The thermal properties of borate bonding agent, such as glass transition temperature (Tg) and crystallization peak temperature (Tp), were investigated to establish the sintering process. And the coefficient of thermal expansion (CTE) was to evaluate the matching effect of porcelain to Ti6Al4V. The bond strength was analyzed by the three point bending test. The microscopic morphology of the borate bonding agent surface after sintering, the interface of Ti-borate bonding agent-porcelain, and the fracture mode after porcelains fracture, were studied to assess the influence of borate bonding agent on Ti6Al4V-ceramics. With the addition of Na2O and Al2O3, the porcelain residues were observed increased indication on the Ti6Al4V surface after porcelain fracture and the bond strength was acquired the maximum (49.45MPa) in the bonding agent composition of 75.70B2O3-5.92La2O3-11.84SrO-4.67Na2O-1.87Al2O3. Those results suggest that borate bonding agent is an effective way to improve the Ti6Al4V-ceramics bond strength. And the addition of Na2O and Al2O3 strengthen this effect. PMID:27344231

  8. Effects of CaO/SiO2 Ratio and Na2O Content on Melting Properties and Viscosity of SiO2-CaO-Al2O3-B2O3-Na2O Mold Fluxes

    NASA Astrophysics Data System (ADS)

    Wang, Lin; Zhang, Chen; Cai, Dexiang; Zhang, Jianqiang; Sasaki, Yasushi; Ostrovski, Oleg

    2016-09-01

    This paper investigated the effects of CaO/SiO2 ratio (0.8 to 1.5) and Na2O concentration (6 to 9 wt pct) on melting properties and viscosity of SiO2-CaO-Al2O3-B2O3-Na2O mold fluxes with a fixed B2O3 content. Melting properties of fluxes (softening temperature T s, hemispherical temperature T h, and fluidity temperature T f) were determined by the hot-stage microscopy method. Viscosity was measured using rotating cylindrical viscometer, and structure of quenched fluxes was studied using Raman spectroscopy. Equilibrium phases in the SiO2-CaO-Al2O3-B2O3-Na2O system were calculated using FactSage. It was found that T h decreased with increasing CaO/SiO2 ratio from 0.8 to 1.0 and increased with a further increase in the CaO/SiO2 ratio to 1.5. The effect of Na2O content in the range of 6 to 9 wt pct on T h of the flux with a fixed CaO/SiO2 ratio at 1.3 was marginal. Increasing CaO/SiO2 ratio and Na2O content increased the break temperature and reduced the value of viscosity at 1673 K (1400 °C). Viscosity of liquid fluxes was discussed in the relationship with the flux structure. Melting properties and viscosity of boracic fluxes were compared with those of industrial fluorine-containing mold fluxes.

  9. Constraining the N2O budget using isotopologues and isotopomers

    NASA Astrophysics Data System (ADS)

    Yung, Y. L.; Kim, P.; Liang, M.; Shia, R.

    2007-12-01

    The continued increase of N2O in the atmosphere is a serious environmental concern. As a consequence, N2O is one of the gases targeted for regulation by the Kyoto Protocol. Therefore, to stabilize concentrations at the present level, an immediate reduction of the additional flux of N2O that has occurred since the Industrial Revolution would be necessary. However, the N2O budget is at present not well quantified, making it difficult to determine the sources and the cause of its increase precisely (IPCC 2007). In order to find the best constraints to the N2O budget, we carried out a time dependent box model study similar to that of Rahn and Wahlen (2000) for N2O and its isotopologues and isotopomers from 1700 A.D. to the present. An adjoint code was constructed from the box model via the Tangent linear and Adjoint Model Compiler (TAMC) to calculate the gradient of a cost function, in this case the least squared sum of residuals, with respect to the initial conditions. These gradient calculations were then fed to optimization algorithms to minimize the value of the cost function, thereby acquiring the optimal parameters and the best fit to the observed data. Preliminary results are as follows: (1) The IPCC 2007 N2O budget appears to be consistent with the isotopic data, which help to refine some of the fluxes; (2) The mean nitrification/denitrification ratio for N2O sources is obtained from this analysis in order to explain the time evolution of both 15-N and 18-O data; (3) Our model confirms and extends the "depleted ocean" model of Rahn and Wahlen (2000) for the N2O oceanic source; and (4) Site preference data for 15-N provides the most sensitive discrimination between natural and anthropogenic sources of N2O.

  10. Electronic properties of compounds of the Li{sub 2}O-B{sub 2}O{sub 3} system

    SciTech Connect

    Maslyuk, Volodymyr V.; Islam, Mazharul M.; Bredow, Thomas

    2005-09-15

    The electronic properties of (Li{sub 2}O){sub x}(B{sub 2}O{sub 3}){sub 1-x} (x=0.0, 0.25, 0.33, 0.5, 0.75, and 1.0) compounds were studied by periodic quantum-chemical calculations at density functional theory level using localized atomic basis functions. A good agreement between calculated and measured values of the band gap was obtained for Li{sub 2}O. The band gaps were predicted for other compounds of the Li{sub 2}O-B{sub 2}O{sub 3} system where less reliable experimental data are available. The calculated band gap of (Li{sub 2}O){sub x}(B{sub 2}O{sub 3}){sub 1-x} decreases with increasing mole fraction x of Li{sub 2}O. This was interpreted by the decreasing bonding interaction between BO{sub n} groups. By an analysis of the electron density distribution, it was shown that in all systems under consideration the B-O bonds are mainly covalent, and that B-O bonds in BO{sub 3} units are stronger than in BO{sub 4}. The Li-O interaction is predominantly ionic.

  11. Superior high-temperature oxidation resistance of a novel (Al2O3-Y2O3)/Pt laminated coating

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoxu; He, Yedong; Wang, Deren; Zhang, Jin

    2012-03-01

    A 7-layer (Al2O3-Y2O3)/Pt laminated coating was successfully prepared on a Ni-based superalloy by magnetron sputtering methods. It is observed that the as-prepared coating has dense and refined brittle/ductile laminated nanostructure. Cyclic oxidation tests were adopted to investigate the oxidation and spallation resistance of this novel laminated coating. The results revealed that the 7-layer (Al2O3-Y2O3)/Pt laminated coating can significantly improve the high-temperature oxidation resistance and spallation resistance of the Ni-based superalloy. In such laminated coating, the multi-sealed (Al2O3-Y2O3) and Pt layers can effectively suppress the inward diffusion of oxygen to an extremely low level, providing super oxidation resistance at 1200 °C for 1000 h. In addition, the excellent high-temperature mechanical properties of the (Al2O3-Y2O3)/Pt laminated coating are mainly induced by the increased thermal expansion coefficient and the brittle/ductile laminated composite structure by means of energy release mechanisms.

  12. N2O - direct versus indirect effects on emissions

    NASA Astrophysics Data System (ADS)

    Zechmeister-Boltenstern, Sophie; Kitzler, Barbara

    2013-04-01

    The concentration of N2O in the atmosphere is much lower than that of CO2, but it is an important GHG because on an equivalent mass basis, N2O has c. 300 times the global warming potential of CO2. In addition to being a strong GHG, N2O is the primary stratospheric ozone depleting substance. The dominant sources of N2O are closely related to microbial production processes in soils, sediments and water bodies. Agricultural emissions due to N fertilizer use and manure management (4.3-5.8 Tg N2O-N yr-1) and emissions from natural soils (6-7 Tg N2O-N yr-1) are already representing 56-70% of all global N2O sources. The main agricultural sources of nitrous oxide include emissions from soils after application of inorganic and organic forms of nitrogen (N) as synthetic fertilizers, crop residues, manures or composts. Livestock operations also result in emissions from urine and faeces deposited on soils during grazing. In addition to the direct sources of N2O, there are also indirect ones that include N deposited onto land surfaces following ammonia and NOx volatilization, and nitrate leached from agricultural land in drainage water which, on passing into aquifers or into surface waters and their sediments, can be partially transformed to N2O (Smith et al., 2012). For inventories a default emission factor (EF) of 1.0 % of N fertilizer application has been fixed. The default indirect EFs are 1.0 % of N deposited from the atmosphere, and 0.75 % of N lost to watercourses by leaching or runoff. Depending on fertilizer type and environmental conditions field measurements reveal emission factors which deviate largely from the theoretical values. As soil moisture and temperature are major drivers of N2O emissions, warming and precipitation changes strongly affect the emission of N2O. More difficult is the prediction of climate extremes and their feedback on N2O which may occur via soil processes as well as limitations for plant growth and N uptake. Based on examples of recent

  13. Field-assisted Densification of Superhard B6O Materials with Y2O3/Al2O3 Addition

    NASA Astrophysics Data System (ADS)

    Herrmann, M.; Raethel, J.; Sempf, K.; Thiele, M.; Bales, A.; Sigalas, I.

    B6O is a possible candidate of superhard materials with a hardness of 45 GPa measured on single crystals. Up to now, densification of these materials was only possible at high pressure. However, recently it was found that different oxides can be utilized as effective sintering additives. In this work the effect of addition of Y2O3/Al2O3 on the densification behaviour as a function of applied pressure, its microstructure evolution, and resulting mechanical properties were investigated. A strong dependence of the densification with increasing pressure was found. The material revealed characteristic triple junctions filled with amorphous residue composed of B2O3, Al2O3 and Y2O3, while no amorphous grain-boundary films were observed along internal interfaces. Mechanical testing revealed on average hardness of 33 GPa, a fracture toughness of 4 MPam1/2, and a strength value of 500 MPa.

  14. Structural study of Al2O3-Na2O-CaO-P2O5 bioactive glasses as a function of aluminium content.

    PubMed

    Smith, J M; King, S P; Barney, E R; Hanna, J V; Newport, R J; Pickup, D M

    2013-01-21

    Calcium phosphate based biomaterials are extensively used in the context of tissue engineering: small changes in composition can lead to significant changes in properties allowing their use in a wide range of applications. Samples of composition (Al(2)O(3))(x)(Na(2)O)(0.11-x)(CaO)(0.445)(P(2)O(5))(0.445), where x = 0, 0.03, 0.05, and 0.08, were prepared by melt quenching. The atomic-scale structure has been studied using neutron diffraction and solid state (27)Al MAS NMR, and these data have been rationalised with the determined density of the final glass product. With increasing aluminium concentration the density increases initially, but beyond about 3 mol. % Al(2)O(3) the density starts to decrease. Neutron diffraction data show a concomitant change in the aluminium speciation, which is confirmed by (27)Al MAS NMR studies. The NMR data reveal that aluminium is present in 4, 5, and 6-fold coordination and that the relative concentrations of these environments change with increasing aluminium concentration. Materials containing aluminium in 6-fold coordination tend to have higher densities than analogous materials with the aluminium found in 4-fold coordination. Thus, the density changes may readily be explained in terms of an increase in the relative concentration of 4-coordinated aluminium at the expense of 6-fold aluminium as the Al(2)O(3) content is increased beyond 3 mol. %.

  15. Novel gold nanocluster electrochemiluminescence immunosensors based on nanoporous NiGd-Ni2O3-Gd2O3 alloys.

    PubMed

    Lv, Xiaohui; Ma, Hongmin; Wu, Dan; Yan, Tao; Ji, Lei; Liu, Yixin; Pang, Xuehui; Du, Bin; Wei, Qin

    2016-01-15

    Herein, three-dimensional nanoporous NiGd alloy (NP-NiGd) was prepared by selectively dealloy Al from NiGdAl alloy in mild alkaline solution, then Ni2O3 and Gd2O3 grew further on the surface of NP-NiGd to obtain the NP-NiGd-Ni2O3-Gd2O3. On this basis, NP-NiGd-Ni2O3-Gd2O3 was further functionalized with gold nanoparticles (NP-NiGd-Ni2O3-Gd2O3@Au) and acted as sensor platform to fabricate a novel electrochemiluminescence (ECL) immunosensor. Bovine serum albumin protected gold nanoclusters (AuNCs@BSA) were prepared and acted as illuminant. AuNCs@BSA modified graphene oxide (GO/AuNCs@BSA) were used as labels of second antibody. In order to characterize the performance of the ECL immunosensor, carcino embryonie antigen (CEA) was used as the model to complete the experiments. Due to the good performances of NP-NiGd-Ni2O3-Gd2O3@Au (high surface area, excellent electron conductivity) and AuNCs@BSA (low toxicity, biocompatibility, easy preparation and good water solubility), the ECL immunosensor exhibited a wide range from 10(-4) to 5ng/mL with a detection limit of 0.03pg/mL (S/N=3). The immunosensor with excellent stability, acceptable repeatability and selectivity provided a promising method to detect CEA in human serum sample sensitively. PMID:26318782

  16. Uncertainties in United States agricultural N2O emissions: comparing forward model simulations to atmospheric N2O data.

    NASA Astrophysics Data System (ADS)

    Nevison, C. D.; Saikawa, E.; Dlugokencky, E. J.; Andrews, A. E.; Sweeney, C.

    2014-12-01

    Atmospheric N2O concentrations have increased from 275 ppb in the preindustrial to about 325 ppb in recent years, a ~20% increase with important implications for both anthropogenic greenhouse forcing and stratospheric ozone recovery. This increase has been driven largely by synthetic fertilizer production and other perturbations to the global nitrogen cycle associated with human agriculture. Several recent regional atmospheric inversion studies have quantified North American agricultural N2O emissions using top-down constraints based on atmospheric N2O data from the National Oceanic and Atmospheric Administration (NOAA) Global Greenhouse Gas Reference Network, including surface, aircraft and tall tower platforms. These studies have concluded that global N2O inventories such as EDGAR may be underestimating the true U.S. anthropogenic N2O source by a factor of 3 or more. However, simple back-of-the-envelope calculations show that emissions of this magnitude are difficult to reconcile with the basic constraints of the global N2O budget. Here, we explore some possible reasons why regional atmospheric inversions might overestimate the U.S. agricultural N2O source. First, the seasonality of N2O agricultural sources is not well known, but can have an important influence on inversion results, particularly when the inversions are based on data that are concentrated in the spring/summer growing season. Second, boundary conditions can strongly influence regional inversions but the boundary conditions used may not adequately account for remote influences on surface data such as the seasonal stratospheric influx of N2O-depleted air. We will present a set of forward model simulations, using the Community Land Model (CLM) and two atmospheric chemistry tracer transport models, MOZART and the Whole Atmosphere Community Climate Model (WACCM), that examine the influence of terrestrial emissions and atmospheric chemistry and dynamics on atmospheric variability in N2O at U.S. and

  17. KCo(H2O)2BP2O8·0.48H2O and K0.17Ca0.42Co(H2O)2BP2O8·H2O: two cobalt borophosphates with helical ribbons and disordered (K,Ca)/H2O schemes.

    PubMed

    Guesmi, Abderrahmen; Driss, Ahmed

    2012-08-01

    The two title compounds, potassium diaquacobalt(II) borodiphosphate 0.48-hydrate and potassium-calcium(0.172/0.418) diaquacobalt(II) borodiphosphate monohydrate, were synthesized hydrothermally. They are new members of the borophosphate family characterized by (∞)[BP(2)O(8)](3-) helices running along [001] and constructed of boron (Wyckoff position 6b, twofold axis) and phosphorus tetrahedra. The [CoBP(2)O(8)](-) anionic frameworks in the two materials are structurally similar and result from a connection in the ab plane between the CoO(4)(H(2)O)(2) coordination octahedra (6b position) and the helical ribbons. Nevertheless, the two structures differ in the disorder schemes of the K,Ca and H(2)O species. The alkali cations in the structure of the pure potassium compound are disordered over three independent positions, one of them located on a 6b site. Its framework is characterized by double occupation of the tunnels by water molecules located on twofold rotation axes (6b) and a fraction of alkali cations; its cell parameters, compared with those for the mixed K,Ca compound, show abnormal changes, presumably due to the disorder. For the K,Ca compound, the K and Ca cations are on twofold axes (6b) and the channels are occupied only by disordered solvent water molecules. This shows that it is possible, due to the flexibility of the helices, to replace the alkali and alkaline earth cations while retaining the crystal framework.

  18. CO DIFFUSION INTO AMORPHOUS H{sub 2}O ICES

    SciTech Connect

    Lauck, Trish; Karssemeijer, Leendertjan; Cuppen, Herma M.; Shulenberger, Katherine; Rajappan, Mahesh; Öberg, Karin I. E-mail: koberg@cfa.harvard.edu

    2015-03-10

    The mobility of atoms, molecules, and radicals in icy grain mantles regulates ice restructuring, desorption, and chemistry in astrophysical environments. Interstellar ices are dominated by H{sub 2}O, and diffusion on external and internal (pore) surfaces of H{sub 2}O-rich ices is therefore a key process to constrain. This study aims to quantify the diffusion kinetics and barrier of the abundant ice constituent CO into H{sub 2}O-dominated ices at low temperatures (15–23 K), by measuring the mixing rate of initially layered H{sub 2}O(:CO{sub 2})/CO ices. The mixed fraction of CO as a function of time is determined by monitoring the shape of the infrared CO stretching band. Mixing is observed at all investigated temperatures on minute timescales and can be ascribed to CO diffusion in H{sub 2}O ice pores. The diffusion coefficient and final mixed fraction depend on ice temperature, porosity, thickness, and composition. The experiments are analyzed by applying Fick’s diffusion equation under the assumption that mixing is due to CO diffusion into an immobile H{sub 2}O ice. The extracted energy barrier for CO diffusion into amorphous H{sub 2}O ice is ∼160 K. This is effectively a surface diffusion barrier. The derived barrier is low compared to current surface diffusion barriers in use in astrochemical models. Its adoption may significantly change the expected timescales for different ice processes in interstellar environments.

  19. [N2O emission by trees under natural condition].

    PubMed

    Xu, H; Zhang, Z; Han, S; Wang, Y; Chen, G

    2001-09-01

    The sources of N2O, one of the major greenhouse gases in the atmosphere, are still unclear till now. It was previously thought that only soil microbial process produced N2O. The aim of this study was to provide evidences that plant can emit N2O under the natural condition. The measurement of aboveground vertical profiles of N2O concentrations were conducted within coniferous-deciduous mixed forests in Changbai Mountain, China. Significant high N2O concentrations were found at or near the height of canopy. High concentrations in profiles were 3.03% to 64.9% higher than the "normal concentrations". Differences between the high concentrations and the "normal concentrations" were statistically significant. The simultaneous occurrence of high concentrations at/nearby the canopy height and normal concentrations at the trunk space height indicated an efflux of N2O from foliage to atmosphere. This study afforded evidences supporting that plant per se, besides forest soil, was an important source of atmospheric N2O in a forest ecosystem.

  20. Silver indium diphosphate, AgInP(2)O(7).

    PubMed

    Zouihri, Hafid; Saadi, Mohamed; Jaber, Boujemaa; El Ammari, Lehcen

    2010-01-01

    Polycrystalline material of the title compound, AgInP(2)O(7), was synthesized by traditional high-temperature solid-state methods and single crystals were grown from the melt of a mixture of AgInP(2)O(7) and B(2)O(3) as flux in a platinium crucible. The structure consists of InO(6) octa-hedra, which are corner-shared to PO(4) tetra-hedra into a three-dimensional network with hexa-gonal channels running parallel to the c axis. The silver cation, located in the channel, is bonded to seven O atoms of the [InP(2)O(7)] framework with Ag-O distances ranging from 2.370 (2) to 3.015 (2) Å. The P(2)O(7) diphosphate anion is characterized by a P-O-P angle of 137.27 (9) and a nearly eclipsed conformation. AgInP(2)O(7) is isotypic with the M(I)FeP(2)O(7) (M(I) = Na, K, Rb, Cs and Ag) diphosphate family. PMID:21522510

  1. 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.

  2. Nitrogen fertiliser formulation: The impact on N2O emissions

    NASA Astrophysics Data System (ADS)

    Harty, Mary; Krol, Dominika; Carolan, Rachael; McNeill, Gavin; McGeough, Karen; Laughlin, Ronnie; Watson, Catherine; Richards, Karl; Lanigan, Gary; Forrestal, Patrick

    2015-04-01

    Agriculture was responsible for 31% of Ireland's Agricultural Greenhouse Gas (GHG) emissions in 2012, with 39% of these emissions arising from chemical/organic fertilizers in the form of nitrous oxide (N2O). Switching from calcium ammonium nitrate (CAN) to a urea based fertiliser limits the soil residence period of nitrate, the major substrate for denitrification loss in the N2O form. However, urea is susceptible to ammonia (NH3) volatilisation but this risk can be managed using urease inhibitors. The aim of this study was to evaluate the effect of switching from CAN to urea, urea with the urease inhibitor N- (n-butyl) thiophosphoric triamide (trade name Agrotain®) and/or the nitrification inhibitor dicyandiamide (DCD on direct and indirect N2O emissions. The experiment is a two year study (commenced March 2013) at six permanent pasture sites located on the island of Ireland, at Johnstown Castle Co. Wexford, Moorepark Co. Cork and Hillsborough Co. Down, covering a range of soil textures and drainage characteristics. The experiment simulated a grazing environment; annual fertiliser N was applied at different rates (0, 100, 200, 300, 400 or 500 kg N ha-1) in five equal splits, with grass harvested prior to fertilizer application. Direct N2O emissions were quantified regularly using static chambers over 1 year and indirect N2O from ammonia volatilisation was measured using wind tunnels and annual emission factors calculated. Switching from CAN to urea dramatically reduced direct N2O emissions, but had little effect on dry-matter yield. However, there was evidence of pollution swapping of direct for indirect N2O from NH3. In the first year, two urea based formulations successfully reduced both direct and indirect N2O emissions at all sites. Fertiliser formulation strategy has the potential to be a solution for reduction of direct and indirect N2O emissions.

  3. A new room-temperature ultraviolet emission material: K2[Ni(C2O4)2(H2O)2]·4H2O

    NASA Astrophysics Data System (ADS)

    Narsimhulu, M.; Raju, B.; Saritha, A.; Narayana Rao, D.; Hussain, K. A.

    2015-09-01

    In this study, we investigated the crystal structure, ultraviolet (UV) luminescence, and magnetic properties of potassium bis oxalate nickel(II) tetrahydrate {K2[Ni(C2O4)2(H2O)2]·4H2O} crystals. This compound crystallizes in the monoclinic system with a P21/c space group and exhibits a one-dimensional (1D) chain structure. The Ni(II) metal center possesses an octahedral environment, with four oxygen atoms from two bidentate oxalate ligands and two oxygen atoms from water molecules. Infrared spectroscopy was used to study the vibrational modes of the compound. Interestingly, the complex exhibits intense UV emission at 364 nm when excited at 323 nm. Furthermore, the luminescence lifetime is approximately 50 μs. The magnetic susceptibility and field dependent magnetization measurements revealed a paramagnetic behavior above 20 K and antiferromagnetic ordering at low temperatures.

  4. Optical Properties of K2O-Li2O-WO3-B2O3 Glasses: Evidence of Mixed Alkali Effect

    NASA Astrophysics Data System (ADS)

    Edukondalu, Avula; Sripathi, T.; Kareem Ahmmad, Shaik; Rahman, Syed; Sivakumar, K.

    2016-10-01

    Glass with compositions xK2O-(30 - x)Li2O-10WO3-60B2O3 for 0 ≤ x ≤ 30 mol.% have been prepared using the normal melt quenching technique. The optical reflection and absorption spectra were recorded at room temperature in the wavelength range 300-800 nm. From the absorption edge studies, the values of the optical band gap (E opt) and Urbach energy (ΔE) have been evaluated. The values of E opt and ΔE vary non-linearly with composition parameter, showing the mixed alkali effect. The dispersion of the refractive index is discussed in terms of the single oscillator Wemple Di-Domenico model.

  5. In vitro evaluation of bioactivity of CaO-SiO 2-P 2O 5-Na 2O-Fe 2O 3 glasses

    NASA Astrophysics Data System (ADS)

    Singh, Rajendra Kumar; Kothiyal, G. P.; Srinivasan, A.

    2009-05-01

    Glasses with compositions 41CaO(52 - x)SiO 24P 2O 5· xFe 2O 33Na 2O (2 ≤ x ≤ 10 mol.%) were prepared by melt quenching method. Bioactivity of the different glass compositions was studied in vitro by treating them with simulated body fluid (SBF). The glasses treated for various time periods in SBF were evaluated by examining apatite formation on their surface using grazing incidence X-ray diffraction, Fourier transform infrared reflection spectroscopy, scanning electron microscopy and energy dispersive spectroscopy techniques. Increase in bioactivity with increasing iron oxide content was observed. The results have been used to understand the evolution of the apatite surface layer as a function of immersion time in SBF and glass composition.

  6. Broadband 1.5- μm emission of high erbium-doped Bi 2O 3-B 2O 3-Ga 2O 3 glasses

    NASA Astrophysics Data System (ADS)

    Fan, Huiyan; Wang, Guonian; Li, Kefeng; Hu, Lili

    2010-07-01

    High Erbium-doped glass showing the wider 1.5-μm emission band is reported in the Bi 2O 3-B 2O 3-Ga 2O 3 system and its thermal stability and optical properties such as absorption, emission spectra, absorption and stimulated emission cross-sections and fluorescence lifetime are investigated. Compared with other glass hosts, the gain bandwidth properties of high Er 3+ content in BBG glass are better than those of tellurite, germanate, silicate and phosphate glasses. The broad and flat 4I 13/2→ 4I 15/2 emission and the larger stimulated emission cross-section of Er 3+ ions around 1.5 μm enable it to be used as a host material for potential broadband optical amplifiers at C and L bands in the microchip configuration.

  7. In vitro bioactivity evaluation, mechanical properties and microstructural characterization of Na2O-CaO-B2O3-P2O5 glasses

    NASA Astrophysics Data System (ADS)

    Abo-Naf, Sherief M.; Khalil, El-Sayed M.; El-Sayed, El-Sayed M.; Zayed, Hamdia A.; Youness, Rasha A.

    2015-06-01

    Na2O-CaO-B2O3-P2O5 glasses have been prepared by the melt-quenching method. B2O3 content was systematically increased from 5 to 30 mol%, at the expense of P2O5, in the chemical composition of these glasses. Density, Vickers microhardness and fracture toughness of the prepared glasses were measured. In vitro bioactivity of the glasses was assessed by soaking in the simulated body fluid (SBF) at 37 ± 0.5 °C for 3, 7, 14 and 30 days. The glasses were tested in the form of glass grains as well as bulk slabs. The structure and composition of the solid reaction products were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The kinetics of degradation of the glass particles were monitored by measuring the weight loss of the particles and the ionic concentration of Ca, P and B in the SBF solution using inductive coupled plasma-atomic emission spectroscopy (ICP-AES). The obtained results revealed the formation of a bioactive hydroxyapatite (HA) layer, composed of nano-crystallites, on the surface of glass grains after the in vitro assays. The results have been used to understand the formation of HA as a function of glass composition and soaking time in the SBF. It can be pointed out that increasing B2O3 content in glass composition enhances the bioactivity of glasses. The nanometric particle size of the formed HA and in vitro bioactivity of the studied glasses make them possible candidates for tissue engineering application.

  8. Electrical conductivity studies of Bi{sub 2}O{sub 3}-Li{sub 2}O-ZnO-B{sub 2}O{sub 3} glasses

    SciTech Connect

    Bale, Shashidhar; Rahman, Syed

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Ac conductivity measurements and its analysis has been performed on Bi{sub 2}O{sub 3}-Li{sub 2}O-ZnO-B{sub 2}O{sub 3} glasses in the temperature range 30-300 Degree-Sign C and a frequency range of 100 Hz to 1 MHz. Black-Right-Pointing-Pointer The dc conductivity increased and the activation energy decreased with lithium content. Black-Right-Pointing-Pointer The frequency dependent conductivity has been analyzed employing conductivity and modulus formalisms. Black-Right-Pointing-Pointer The onset of conductivity relaxation shifts towards higher frequencies with temperature. Black-Right-Pointing-Pointer The Almond-West conductivity formalism is used to explain the scaling behavior, and the relaxation mechanism is independent of temperature. -- Abstract: Ac conductivity measurements and its analysis has been performed on xBi{sub 2}O{sub 3}-(65-x)Li{sub 2}O-20ZnO-15B{sub 2}O{sub 3} (0 {<=} x {<=} 20) glasses in the temperature range 30-300 Degree-Sign C and a frequency range of 100 Hz to 1 MHz. The dc conductivity increased and the activation energy decreased with lithium content. The frequency dependent conductivity has been analyzed employing conductivity and modulus formalisms. The onset of conductivity relaxation shifts towards higher frequencies with temperature. The Almond-West conductivity formalism is used to explain the scaling behavior, and the relaxation mechanism is independent of temperature.

  9. The vibration-rotation-tunneling levels of N2-H2O and N2-D2O.

    PubMed

    Wang, Xiao-Gang; Carrington, Tucker

    2015-07-14

    In this paper, we report vibration-rotation-tunneling levels of the van der Waals clusters N2-H2O and N2-D2O computed from an ab initio potential energy surface. The only dynamical approximation is that the monomers are rigid. We use a symmetry adapted Lanczos algorithm and an uncoupled product basis set. The pattern of the cluster's levels is complicated by splittings caused by H-H exchange tunneling (larger splitting) and N-N exchange tunneling (smaller splitting). An interesting result that emerges from our calculation is that whereas in N2-H2O, the symmetric H-H tunnelling state is below the anti-symmetric H-H tunnelling state for both K = 0 and K = 1, the order is reversed in N2-D2O for K = 1. The only experimental splitting measurements are the D-D exchange tunneling splittings reported by Zhu et al. [J. Chem. Phys. 139, 214309 (2013)] for N2-D2O in the v2 = 1 region of D2O. Due to the inverted order of the split levels, they measure the sum of the K = 0 and K = 1 tunneling splittings, which is in excellent agreement with our calculated result. Other splittings we predict, in particular those of N2-H2O, may guide future experiments. PMID:26178101

  10. The vibration-rotation-tunneling levels of N2-H2O and N2-D2O

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Gang; Carrington, Tucker

    2015-07-01

    In this paper, we report vibration-rotation-tunneling levels of the van der Waals clusters N2-H2O and N2-D2O computed from an ab initio potential energy surface. The only dynamical approximation is that the monomers are rigid. We use a symmetry adapted Lanczos algorithm and an uncoupled product basis set. The pattern of the cluster's levels is complicated by splittings caused by H-H exchange tunneling (larger splitting) and N-N exchange tunneling (smaller splitting). An interesting result that emerges from our calculation is that whereas in N2-H2O, the symmetric H-H tunnelling state is below the anti-symmetric H-H tunnelling state for both K = 0 and K = 1, the order is reversed in N2-D2O for K = 1. The only experimental splitting measurements are the D-D exchange tunneling splittings reported by Zhu et al. [J. Chem. Phys. 139, 214309 (2013)] for N2-D2O in the v2 = 1 region of D2O. Due to the inverted order of the split levels, they measure the sum of the K = 0 and K = 1 tunneling splittings, which is in excellent agreement with our calculated result. Other splittings we predict, in particular those of N2-H2O, may guide future experiments.

  11. Retardation mechanism of ultrathin Al2O3 interlayer on Y2O3 passivated gallium nitride surface.

    PubMed

    Quah, Hock Jin; Cheong, Kuan Yew

    2014-05-28

    A systematic investigation was carried out by incorporating an ultrathin aluminum oxide (Al2O3) as an interlayer between yttrium oxide (Y2O3) passivation layer and GaN substrate. The sandwiched samples were then subjected to postdeposition annealing in oxygen ambient from 400 to 800 °C. The Al2O3 interlayer was discovered to play a significant role in slowing down inward diffusion of oxygen through the Y2O3 passivation layer as well as in impeding outward diffusion of Ga(3+) and N(3-) from the decomposed GaN surface. These beneficial effects have suppressed subsequent formation of interfacial layer. A mechanism in association with the function of Al2O3 as an interlayer was suggested and discussed. The mechanism was explicitly described on the basis of the obtained results from X-ray diffraction, X-ray photoelectron spectroscopy, energy-filtered transmission electron microscopy (TEM), high resolution TEM, and electron energy loss spectroscopy line scan. A correlation between the proposed mechanism and metal-oxide-semiconductor characteristics of Y2O3/Al2O3/GaN structure has been proposed.

  12. Neutron irradiation and compatibility testing of Li 2O

    NASA Astrophysics Data System (ADS)

    Porter, D. L.; Krsul, J. R.; Laug, M. T.; Walters, L. C.; Tetenbaum, M.

    1984-05-01

    A study was made of the neutron irradiation behavior of 6Li-enriched Li 2O in EBR-II. In addition, a stress corrosion study was performed ex-reactor to test the compatibility of Li 2O with a variety of stainless steels. The irradiation tests showed that tritium and helium retention in the Li 2O (˜ 89% dense) lessened with neutron exposure, and the retentions appear to approach a steady-state after ˜ 1% 6Li burnup. The stress corrosion studies, using 316 stainless steel (Ti-modified) and a 35% Ni alloy, showed that stress does not enhance the corrosion, and that dry Li 2O is not significantly corrosive, the LiOH content producing the corrosive effects. Corrosion, in general, was not severe because a passivation in sealed capsules seemed to occur after a time which greatly reduced corrosion rates.

  13. Structural Study of x(Fe2O3·V2O5)·(100-x)[P2O5·Li2O] Glass System by FTIR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ardelean, I.; Andronache, C.; Cîmpean, C.; PǍŞCUŢǍ, P.

    Glasses of the x(Fe2O3·V2O5)·(100-x)[P2O5·Li2O] system, with 0≤x≤50 mol%, were prepared and investigated by FTIR spectroscopy in an attempt to determine the local structure of glasses. The interpretation of the obtained IR spectra revealed the presence and the dependence of the local structural units in the studied glasses on the iron and vanadium ions content. The results showed that phosphate units are the main structural units of the glass system and the iron and vanadium ions are located in the network. The increasing of iron and vanadium ions content indicate a gradual decreasing in the number of bridging oxygen ions and an increasing in the number of nonbridging oxygen ions.

  14. Effects of Substitution of K2O for Na2O on the Bioactivity of CaO-Na2O-SiO2-P2O5 glasses

    NASA Astrophysics Data System (ADS)

    Kim, Taehee; Hwang, Chawon; Gwoo, Donggun; Park, Hoyyul; Ryu, Bong-Ki

    2012-10-01

    The compositional dependences of bioactivity, thermal properties, atomic structure, and surface morphology have been investigated in the CaO-Na2O-SiO2-P2O5 system; this system is known as a bioglass. 45S5 Bioglass® is known to be a general and highly bioactive material. However, the bioactivity of this glassy material is expected to be improved by modifying the alkali-metal composition. Thermal properties, density, and molar volume were measured to investigate the structural packing. FT-IR spectra and X-ray diffraction were used to confirm the structures of these glasses. The morphology was examined using field emission electron microscopy, and the formation of a Ca-P layer was studied using an energy-dispersive system. This study shows that the tendency to form a calcium phosphate layer is increased with the substitution of K2O for Na2O.

  15. A comparison of ice VII formed in the H2O, NaCl-H2O, and CH3OH-H2O systems: Implications for H2O-rich planets

    NASA Astrophysics Data System (ADS)

    Frank, Mark R.; Aarestad, Elizabeth; Scott, Henry P.; Prakapenka, Vitali B.

    2013-02-01

    High-pressure H2O polymorphs, namely ice VI, ice VII, and ice X, are hypothesized to make up a considerable portion of the interiors of large icy satellites and select extra-solar planets. The incorporation of foreign ions or molecules into these high-pressure phases is possible through ocean-ice interaction, rock-ice interaction at depth, or processes that occurred during accretion. Recent research concerning the effects charged ions have on ice VII has shown that these ions notably affect the structure of ice VII (Frank et al., 2006; Klotz et al., 2009). This study was designed to determine the effects of a molecular impurity on ice VII and compare those effects to both pure H2O ice and ice with an ionic impurity. Ice samples were formed in this study via compression in a diamond anvil cell from either H2O, a 1.60 mol% NaCl aqueous solution, a 1.60 mol% CH3OH aqueous solution, or a 5.00 mol% CH3OH aqueous solution and were compressed up to 71 GPa at room temperature. Ice formed from pure H2O had no impurities whereas ices formed in the NaCl-H2O and CH3OH-H2O systems contained the impurities Na+ and Cl- and CH3OH, respectively. Pressure-volume relations were observed in situ by using synchrotron based X-ray diffraction and were used to determine the equations of state for ices formed in the H2O, NaCl-H2O and CH3OH-H2O systems. The data illustrate that ice VII formed from a NaCl-bearing aqueous solution exhibited a depressed volume when compared to that of H2O-only ice VII at any given pressure, whereas ice VII formed from CH3OH-bearing aqueous solutions showed an opposite trend, with an increase in volume relative to that of pure ice VII. The ices within planetary bodies will most likely have both ionic and molecular impurities and the trends outlined in this study can be used to improve density profiles of H2O-rich planetary bodies.

  16. Helium Diffusion Through H2O and D2O Amorphous Ice: A Lattice Inverse Istope Effect

    SciTech Connect

    Daschbach, John L.; Schenter, Gregory K.; Ayotte, Patrick; Smith, R. Scott; Kay, Bruce D.

    2004-05-14

    The diffusion of helium through both H2O and D2O amorphous solid water (ASW) has been measured between 55K and 110K. We find the diffusion rate is dependent on the isotopic composition of the ASW lattice. This lattice isotope effect is the "inverse" of a normal isotope effect, in that diffusion is faster in the heavier (D2O) isotope. Transition state theory calculations show that the isotope effect is due to a tight transition state results in a large zero point vibrational energy differences at the transition state predominantly due to hindered rotations of water in the lattice.

  17. Ionization yield and absorption spectra reveal superexcited Rydberg state relaxation processes in H2O and D2O

    NASA Astrophysics Data System (ADS)

    Fillion, J.-H.; Dulieu, F.; Baouche, S.; Lemaire, J.-L.; Jochims, H. W.; Leach, S.

    2003-07-01

    The absorption cross section and the ionization quantum yield of H2O have been measured using a synchrotron radiation source between 9 and 22 eV. Comparison between the two curves highlights competition between relaxation processes for Rydberg states converging to the first tilde A 2A 1 and to the second tilde B 2B 2 excited states of H2O+. Comparison with D2O absorption and ionization yields, derived from Katayama et al (1973 J. Chem. Phys. 59 4309), reveals specific energy-dependent deuteration effects on competitive predissociation and autoionization relaxation channels. Direct ionization was found to be only slightly affected by deuteration.

  18. Interaction energy and the shift in OH stretch frequency on hydrogen bonding for the H2O --> H2O, CH3OH --> H2O, and H2O --> CH3OH dimers.

    PubMed

    Campen, Richard Kramer; Kubicki, James D

    2010-04-15

    The ability to use calculated OH frequencies to assign experimentally observed peaks in hydrogen bonded systems hinges on the accuracy of the calculation. Here we test the ability of several commonly employed model chemistries--HF, MP2, and several density functionals paired with the 6-31+G(d) and 6-311++G(d,p) basis sets--to calculate the interaction energy (D(e)) and shift in OH stretch fundamental frequency on dimerization (delta(nu)) for the H(2)O --> H(2)O, CH(3)OH --> H(2)O, and H(2)O --> CH(3)OH dimers (where for X --> Y, X is the hydrogen bond donor and Y the acceptor). We quantify the error in D(e) and delta(nu) by comparison to experiment and high level calculation and, using a simple model, evaluate how error in D(e) propagates to delta(nu). We find that B3LYP and MPWB1K perform best of the density functional methods studied, that their accuracy in calculating delta(nu) is approximately 30-50 cm(-1) and that correcting for error in D(e) does little to heighten agreement between the calculated and experimental delta(nu). Accuracy of calculated delta(nu) is also shown to vary as a function of hydrogen bond donor: while the PBE and TPSS functionals perform best in the calculation of delta(nu) for the CH(3)OH --> H(2)O dimer their performance is relatively poor in describing H(2)O --> H(2)O and H(2)O --> CH(3)OH.

  19. Luminescence in Li2BaP2O7.

    PubMed

    Hatwar, L R; Wankhede, S P; Moharil, S V; Muthal, P L; Dhopte, S M

    2015-09-01

    The photo-, thermo- and optically stimulated luminescence in Li2BaP2O7 activated with Eu(2+) /Cu(+) are reported. Strong thermoluminescence, which is about two times greater than LiF-TLD 100 was observed in the Eu(2+) -activated sample. It also exhibited optically stimulated luminescence sensitivity of ~20% that of commercial Al2O3:C phosphor. PMID:25351563

  20. Photochemical synthesis of H2O2 from the H2O...O(3P) van der Waals complex: experimental observations in solid krypton and theoretical modeling.

    PubMed

    Pehkonen, Susanna; Marushkevich, Kseniya; Khriachtchev, Leonid; Räsänen, Markku; Grigorenko, Bella L; Nemukhin, Alexander V

    2007-11-15

    Productive photochemical synthesis of hydrogen peroxide, H(2)O(2), from the H(2)O...O((3)P) van der Waals complex is studied in solid krypton. Experimentally, we achieve the three-step formation of H(2)O(2) from H(2)O and N(2)O precursors frozen in solid krypton. First, 193 nm photolysis of N(2)O yields oxygen atoms in solid krypton. Upon annealing at approximately 25 K, mobile oxygen atoms react with water forming the H(2)O...O complex, where the oxygen atom is in the triplet ground state. Finally, the H(2)O...O complex is converted to H(2)O(2) by irradiation at 300 nm. According to the complete active space self-consistent field modeling, hydrogen peroxide can be formed through the photoexcited H(2)O+-O- charge-transfer state of the H(2)O...O complex, which agrees with the experimental evidence.

  1. Amorphous Li2 O2 : Chemical Synthesis and Electrochemical Properties.

    PubMed

    Zhang, Yelong; Cui, Qinghua; Zhang, Xinmin; McKee, William C; Xu, Ye; Ling, Shigang; Li, Hong; Zhong, Guiming; Yang, Yong; Peng, Zhangquan

    2016-08-26

    When aprotic Li-O2 batteries discharge, the product phase formed in the cathode often contains two different morphologies, that is, crystalline and amorphous Li2 O2 . The morphology of Li2 O2 impacts strongly on the electrochemical performance of Li-O2 cells in terms of energy efficiency and rate capability. Crystalline Li2 O2 is readily available and its properties have been studied in depth for Li-O2 batteries. However, little is known about the amorphous Li2 O2 because of its rarity in high purity. Herein, amorphous Li2 O2 has been synthesized by a rapid reaction of tetramethylammonium superoxide and LiClO4 in solution, and its amorphous nature has been confirmed by a range of techniques. Compared with its crystalline siblings, amorphous Li2 O2 demonstrates enhanced charge-transport properties and increased electro-oxidation kinetics, manifesting itself a desirable discharge phase for high-performance Li-O2 batteries. PMID:27486085

  2. Evidence of multiferroicity in NdMn2O5

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, S.; Balédent, V.; Damay, F.; Gukasov, A.; Moshopoulou, E.; Auban-Senzier, P.; Pasquier, C.; André, G.; Porcher, F.; Elkaim, E.; Doubrovsky, C.; Greenblatt, M.; Foury-Leylekian, P.

    2016-03-01

    Recently, R Mn2O5 (R =rare earth, Bi, Y) type multiferroics have drawn considerable attention, because of magnetically induced ferroelectricity along with an extremely large magnetoelectric coupling. Here, we present a detailed study on NdMn2O5 which is a crucial composition between the nonferroelectric PrMn2O5 and ferroelectric SmMn2O5 . We report the results of heat capacity, magnetization, dielectric permittivity, and electric polarization measurements along with an accurate description of the structural and microscopic magnetic properties obtained from high resolution x-ray and neutron diffraction studies. We show that NdMn2O5 is ferroelectric, although the magnitude of polarization is much weaker than that of the other multiferroic members. The direction of the polarization is along the crystallographic b axis and its magnitude can be tuned with the application of a magnetic field. Moreover, unlike the other multiferroic members of this series, ferroelectricity in NdMn2O5 emerges in an incommensurate magnetic state. The present study also provides evidence in support of the influence of the rare-earth size on the magnetoelectric phase diagram.

  3. Microfaceting of Cu2O and its implications in photochemistry

    NASA Astrophysics Data System (ADS)

    Lee, Yunjae; Lee, Taehun; Lee, Yonghyuk; Soon, Aloysius

    The high Miller-index microfacets e.g. {211}, {311}, and {522} have been proposed to play a key role in shape-controlled crystal engineering of Cu2O polyhedrons for various clean energy applications. These Cu2O microcrystals with high Miller-index microfacets are found to have a higher photocatalytic activity than those with octahedra and cube morphologies, and thus suggesting that the catalytically active sites are more abundant on the high Miller-index surfaces. Although much effort has been devoted to the actual synthesis and characterizations of these shaped Cu2O nanocrystals with various morphologies, a firm theoretical understanding of these system are currently limited to low Miller-index facets of Cu2O. Here, we perform first-principles density-functional theory (DFT) calculations to study the surface energetics and electronic structure of these high Miller-index Cu2O surfaces, and evaluate their overpotential for water redox reactions on Cu2O, in comparison with that for the low Miller-index surfaces.

  4. Greywater treatment by UVC/H2O2.

    PubMed

    Chin, W H; Roddick, F A; Harris, J L

    2009-09-01

    Greywater treatment by UVC/H(2)O(2) was investigated with regard to the removal of chemical oxygen demand (COD). A COD reduction from 225 to 30 mgl(-1) (overall removal of 87%) was achieved after settling overnight and subsequent irradiation for 3h with 10mM H(2)O(2). Most of the contaminants were removed by oxidation since only 13% COD was removed by settlement. The removal of COD in the greywater followed a second-order kinetic equation, r=0.0637[COD][H(2)O(2)], up to 10mM H(2)O(2). A slightly enhanced COD removal was observed at the initial pH of 10 compared with pH 3 and 7. This was attributed to the dissociation of H(2)O(2) to O(2)H(-). The treatment was not affected by total concentration of carbonate (c(T)) of at least 3 mM, above which operation between pH 3 and 5 was essential. The initial biodegradability of the settled greywater (as BOD(5):COD) was 0.22. After 2h UVC/H(2)O(2) treatment, a higher proportion of the residual contaminants was biodegradable (BOD(5):COD=0.41) which indicated its potential as a pre-treatment for a biological process. PMID:19656542

  5. Greywater treatment by UVC/H2O2.

    PubMed

    Chin, W H; Roddick, F A; Harris, J L

    2009-09-01

    Greywater treatment by UVC/H(2)O(2) was investigated with regard to the removal of chemical oxygen demand (COD). A COD reduction from 225 to 30 mgl(-1) (overall removal of 87%) was achieved after settling overnight and subsequent irradiation for 3h with 10mM H(2)O(2). Most of the contaminants were removed by oxidation since only 13% COD was removed by settlement. The removal of COD in the greywater followed a second-order kinetic equation, r=0.0637[COD][H(2)O(2)], up to 10mM H(2)O(2). A slightly enhanced COD removal was observed at the initial pH of 10 compared with pH 3 and 7. This was attributed to the dissociation of H(2)O(2) to O(2)H(-). The treatment was not affected by total concentration of carbonate (c(T)) of at least 3 mM, above which operation between pH 3 and 5 was essential. The initial biodegradability of the settled greywater (as BOD(5):COD) was 0.22. After 2h UVC/H(2)O(2) treatment, a higher proportion of the residual contaminants was biodegradable (BOD(5):COD=0.41) which indicated its potential as a pre-treatment for a biological process.

  6. Neutron scattering study on cathode LiMn2O4 and solid electrolyte 5(Li2O)(P2O5)

    NASA Astrophysics Data System (ADS)

    Kartini, E.; Putra, Teguh P.; Jahya, A. K.; Insani, A.; Adams, S.

    2014-09-01

    Neutron scattering is very important technique in order to investigate the energy storage materials such as lithium-ion battery. The unique advantages, neutron can see the light atoms such as Hydrogen, Lithium, and Oxygen, where those elements are negligible by other corresponding X-ray method. On the other hand, the energy storage materials, such as lithium ion battery is very important for the application in the electric vehicles, electronic devices or home appliances. The battery contains electrodes (anode and cathode), and the electrolyte materials. There are many challenging to improve the existing lithium ion battery materials, in order to increase their life time, cyclic ability and also its stability. One of the most scientific challenging is to investigate the crystal structure of both electrode and electrolyte, such as cathodes LiCoO2, LiMn2O4 and LiFePO4, and solid electrolyte Li3PO4. Since all those battery materials contain Lithium ions and Oxygen, the used of neutron scattering techniques to study their structure and related properties are very important and indispensable. This article will review some works of investigating electrodes and electrolytes, LiMn2O4 and 5(Li2O)(P2O5), by using a high resolution powder diffraction (HRPD) at the multipurpose research reactor, RSG-Sywabessy of the National Nuclear Energy Agency (BATAN), Indonesia.

  7. V2O2F4(H2O)2·H2O: a new V(4+) layer structure related to VOF3.

    PubMed

    Black, Cameron; Lightfoot, Philip

    2016-01-01

    V(IV) oxyfluorides are of interest as frustrated magnets. The successful synthesis of two-dimensionally connected vanadium(IV) oxyfluoride structures generally requires the use of ionic liquids as solvents. During solvothermal synthesis experiments aimed at producing two- and three-dimensional vanadium(IV) selenites with triangular lattices, the title compound, diaquatetra-μ-fluorido-dioxidodivanadium(IV) monohydrate, V2O2F4(H2O)2·H2O, was discovered and features a new infinite V(4+)-containing two-dimensional layer comprised of fluorine-bridged corner- and edge-sharing VOF4(H2O) octahedral building units. The synthesis was carried out under solvothermal conditions. The V(4+) centre exhibits a typical off-centring, with a short V=O bond and an elongated trans-V-F bond. Hydrogen-bonded water molecules occur between the layers. The structure is related to previously reported vanadium oxyfluoride structures, in particular, the same layer topology is seen in VOF3. PMID:26742832

  8. Strain-induced topological transition in SrRu2O6 and CaOs2O6

    NASA Astrophysics Data System (ADS)

    Ochi, Masayuki; Arita, Ryotaro; Trivedi, Nandini; Okamoto, Satoshi

    2016-05-01

    The topological property of SrRu2O6 and isostructural CaOs2O6 under various strain conditions is investigated using density functional theory. Based on an analysis of parity eigenvalues, we anticipate that a three-dimensional strong topological insulating state should be realized when band inversion is induced at the A point in the hexagonal Brillouin zone. For SrRu2O6 , such a transition requires rather unrealistic tuning, where only the c axis is reduced while other structural parameters are unchanged. However, given the larger spin-orbit coupling and smaller lattice constants in CaOs2O6 , the desired topological transition does occur under uniform compressive strain. Our study paves a way to realize a topological insulating state in a complex oxide, which has not been experimentally demonstrated so far.

  9. Thermoelectric properties of rhodates: Layered β-SrRh2O4 and spinel ZnRh2O4

    NASA Astrophysics Data System (ADS)

    Wilson-Short, G. B.; Singh, D. J.; Fornari, M.; Suewattana, M.

    2007-01-01

    Density functional calculations are used to obtain the electronic structure of β-SrRh2O4 in comparison with spinel ZnRh2O4 . Both materials are band insulators, with substantial crystal field induced band gaps, reflecting strong transition-metal-O hybridization. However, due to the bonding topology in these materials, the valence bands are very narrow. This leads to high thermopowers within standard Boltzmann transport theory, and indicates that they can be the basis of good thermoelectric materials provided that they can be doped into metallic states with reasonable carrier mobility. In the case of β-SrRh2O4 , scattering due to Sr disorder is important. Also, again in β-SrRh2O4 , the band gap may be large enough to be of interest for photoelectrochemical H2 production.

  10. Geometry of α-Cr2O3(0001) as a Function of H2O Partial Pressure

    PubMed Central

    2015-01-01

    Surface X-ray diffraction has been employed to elucidate the surface structure of α-Cr2O3(0001) as a function of water partial pressure at room temperature. In ultra high vacuum, following exposure to ∼2000 Langmuir of H2O, the surface is found to be terminated by a partially occupied double layer of chromium atoms. No evidence of adsorbed OH/H2O is found, which is likely due to either adsorption at minority sites, or X-ray induced desorption. At a water partial pressure of ∼30 mbar, a single OH/H2O species is found to be bound atop each surface Cr atom. This adsorption geometry does not agree with that predicted by ab initio calculations, which may be a result of some differences between the experimental conditions and those modeled. PMID:26877825

  11. Strain-induced topological transition in SrRu2O6 and CaOs2O6

    DOE PAGES

    Ochi, Masayuki; Arita, Ryotaro; Trivedi, Nandini; Okamoto, Satoshi

    2016-05-24

    The topological property of SrRu$_2$O$_6$ and isostructural CaOs$_2$O$_6$ under various strain conditions is investigated using density functional theory. Based on an analysis of parity eigenvalues, we anticipate that a three-dimensional strong topological insulating state should be realized when band inversion is induced at the A point in the hexagonal Brillouin zone. For SrRu$_2$O$_6$, such a transition requires rather unrealistic tuning, where only the $c$ axis is reduced while other structural parameters are unchanged. However, given the larger spin-orbit coupling and smaller lattice constants in CaOs$_2$O$_6$, the desired topological transition does occur under uniform compressive strain. Our study paves a waymore » to realize a topological insulating state in a complex oxide, which has not been experimentally demonstrated so far.« less

  12. Lateral variation of H2O/K2O ratios in Quaternary Magma of the Northeastern Japan arc

    NASA Astrophysics Data System (ADS)

    Miyagi, I.

    2012-12-01

    Water plays a fundamental role in the magma genesis beneath subduction zones. In order to estimate a spatial distribution of the density of water flux in the wedge mantle of the Northeastern Japan arc, this study examines a lateral variation of pre-eruptive bulk rock H2O/K2O contents among volcanoes located both in the frontal and in back arc settings. The analytical targets are the frontal volcanoes Nigorikawa (N42.12 E140.45), Zenikame (N41.74 E140.85), Adachi (N38.22 E140.65), and Nanashigure (N40.07 E141.11), and the back arc ones Hijiori (N38.61 E140.17) and Kanpu (N39.93 E139.88). The bulk magmatic H2O content (TH2O) is calculated from a mass balance of hydrogen isotopic ratios among three phases in a batch of magma; dissolved water in melt, excess H2O vapor, and hydrous phenocrysts such as amphiboles (Miyagi and Matsubaya, 2003). Since the amount of H2O in hydrous phenocryst is negligible, the bulk magmatic H2O content can be written as TH2O = (30 XD CD) / (15 - dT + dMW), where dMW is the measured hydrogen isotopic ratio of hydrous phenocrysts, XD is a melt fraction of magma, CD is a water concentration of the melt, and dT is hydrogen isotopic ratios of a bulk magma (assumed to be -50 per-mil). Both XD and CD are estimated from bulk rock chemistry of the sample using the MELTS program (Ghiorso and Sack, 1995). Hydrogen isotopic fractionation factors are assumed to be -15 and -30 per-mil for vapor and hydrous mineral, and vapor and silicate melt, respectively. There observed a clear difference among the H2O/K2O ratios of bulk magmas from the frontal and back arc volcanoes. For instance higher H2O/K2O wt ratios was observed in the frontal volcanoes (Nigorikawa 5.3, Zenikame 11-12, Adachi 8-10, and Nanashigure 4-18), while lower H2O/K2O wt ratios was observed in the back arc ones (Kanpu 0-2.5 and Hijiori 1.4). The lateral variation of H2O/K2O ratios infer the higher water flux through the frontal side of wedge mantle, which can be a potential cause of the

  13. Oceanic N2O emissions in the 21st century

    NASA Astrophysics Data System (ADS)

    Martinez-Rey, J.; Bopp, L.; Gehlen, M.; Tagliabue, A.; Gruber, N.

    2014-12-01

    The ocean is a substantial source of nitrous oxide (N2O) to the atmosphere, but little is known on how this flux might change in the future. Here, we investigate the potential evolution of marine N2O emissions in the 21st century in response to anthropogenic climate change using the global ocean biogeochemical model NEMO-PISCES. We implemented two different parameterizations of N2O production, which differ primarily at low oxygen (O2) conditions. When forced with output from a climate model simulation run under the business-as-usual high CO2 concentration scenario (RCP8.5), our simulations suggest a decrease of 4 to 12% in N2O emissions from 2005 to 2100, i.e., a reduction from 4.03/3.71 to 3.54/3.56 Tg N yr-1 depending on the parameterization. The emissions decrease strongly in the western basins of the Pacific and Atlantic oceans, while they tend to increase above the Oxygen Minimum Zones (OMZs), i.e., in the Eastern Tropical Pacific and in the northern Indian Ocean. The reduction in N2O emissions is caused on the one hand by weakened nitrification as a consequence of reduced primary and export production, and on the other hand by stronger vertical stratification, which reduces the transport of N2O from the ocean interior to the ocean surface. The higher emissions over the OMZ are linked to an expansion of these zones under global warming, which leads to increased N2O production associated primarily with denitrification. From the perspective of a global climate system, the averaged feedback strength associated with the projected decrease in oceanic N2O emissions amounts to around -0.009 W m-2 K-1, which is comparable to the potential increase from terrestrial N2O sources. However, the assesment for a compensation between the terrestrial and marine feedbacks calls for an improved representation of N2O production terms in fully coupled next generation of Earth System Models.

  14. Borate mineral assemblages in the system Na2OCaOMgOB2O3H2O

    USGS Publications Warehouse

    Christ, C.L.; Truesdell, A.H.; Erd, Richard C.

    1967-01-01

    he significant known hydrated borate mineral assemblages (principally of the western United States) in the system Na2OCaOz.sbnd;MgOB2O3H2O are expressible in three ternary composition diagrams. Phase rule interpretation of the diagrams is consistent with observation, if the activity of H2O is generally considered to be determined by the geologic environment. The absence of conflicting tie-lines on a diagram indicates that the several mineral assemblages of the diagram were formed under relatively narrow ranges of temperature and pressure. The known structural as well as empirical formulas for the minerals are listed, and the more recent (since 1960) crystal structure findings are discussed briefly. Schematic Gibbs free energy-composition diagrams based on known solubility-temperature relations in the systems Na2B4O7-H2O and Na2B4O7-NaCl-H2O, are highly useful in the interpretation and prediction of the stability relations in these systems; in particular these diagrams indicate clearly that tincalconite, although geologically important, is everywhere a metastable phase. Crystal-chemical considerations indicate that the same thermodynamic and kinetic behavior observed in the Na2B4O7-H2O system will hold in the Ca2B6O11-H2O system. This conclusion is confirmed by the petrologic evidence. The chemical relations among the mineral assemblages of a ternary diagram are expressed by a schematic "activity-activity" diagram. These activity-activity diagrams permit the tracing-out of the paragenetic sequences as a function of changing cation and H2O activities. ?? 1967.

  15. Low temperature magnetic properties of geometrically frustrated Gd2Sn2O7 and Gd2Ti2O7

    NASA Astrophysics Data System (ADS)

    Bonville, P.; Hodges, J. A.; Ocio, M.; Sanchez, J. P.; Vulliet, P.; Sosin, S.; Braithwaite, D.

    2003-11-01

    We have examined the low temperature magnetic properties of the geometrically frustrated antiferromagnetic pyrochlores Gd2Sn2O7 and Gd2Ti2O7 using specific heat, 155Gd Mössbauer, magnetic susceptibility and magnetization measurements. For Gd2Sn2O7, the specific heat evidences a single, strongly first order magnetic transition near 1.0 K in Gd2Ti2O7, we confirm the presence of both the transition near 1.0 K and the second transition near 0.75 K. Below 1 K, magnetic irreversibilities are present in both compounds, but their signature (the difference between the FC and ZFC branches) is more marked in Gd2Sn2O7. At 0.03 K in each compound, the Mössbauer data show that the four Gd3+ of a tetrahedron carry moments of equal sizes and on a frequency scale of 120 × 106 s-1 each is oriented perpendicular to the local \\langle 111 \\rangle direction. In Gd2Ti2O7, the Mössbauer data also indicates that the transition at 0.75 K involves a small change in the magnetic structure.

  16. N2O Emission Trends From a Global Atmospheric Inversion

    NASA Astrophysics Data System (ADS)

    Thompson, R.; Chevallier, F.; Zaehle, S.; Dlugokencky, E. J.

    2015-12-01

    Nitrous oxide (N2O) is the third most important long-lived greenhouse gas and contributes strongly to stratospheric ozone depletion through the formation of NO. Concentrations of N2O in the atmosphere have increased by approximately 20% since the pre-industrial era owing largely to the intensification of agriculture and the use of mineral nitrogen fertilizers. Top-down methods can be used to constrain the emissions of N2O using observations of atmospheric concentrations. Inverse modelling is a top-down approach, which relates changes in N2O concentrations to the emissions with the help of an atmospheric transport model. Using the global inverse model, LMDz-PyVar, we estimated N2O emissions from 1996 to 2012 (covering the period when sufficient atmospheric observations are available). Emissions were estimated monthly with a horizontal resolution of 3.25° × 1.875°. From the inversion, we estimate a global mean emission of 17.0 ± 0.8 TgN y-1, however, the emissions varied substantially from year-to-year. The largest inter-annual variability was located in the tropics and subtropics, where it appears to be correlated with ENSO climate variability. We did not find any significant trend in the global emission over 1996 - 2012, however, we did find important trends on continental scales. In South and East Asia, South America and Africa, N2O emissions increased, consistent with increasing use of N-fertilizer. In contrast, in Europe and North America, N2O emissions decreased. In Europe, this is correlated with a decrease in N-fertilizer use, while in North America the decrease is possibly due to climate variability and changes in agricultural practices.

  17. 40 CFR 721.10018 - Calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... substance identified as calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3) (PMN P-01-442; CAS No. 13169...(OH)2O2(Si2O5)3). 721.10018 Section 721.10018 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10018 Calcium hydroxide oxide silicate...

  18. 40 CFR 721.10018 - Calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... substance identified as calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3) (PMN P-01-442; CAS No. 13169...(OH)2O2(Si2O5)3). 721.10018 Section 721.10018 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10018 Calcium hydroxide oxide silicate...

  19. 40 CFR 721.10018 - Calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... substance identified as calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3) (PMN P-01-442; CAS No. 13169...(OH)2O2(Si2O5)3). 721.10018 Section 721.10018 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10018 Calcium hydroxide oxide silicate...

  20. 40 CFR 721.10018 - Calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... substance identified as calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3) (PMN P-01-442; CAS No. 13169...(OH)2O2(Si2O5)3). 721.10018 Section 721.10018 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10018 Calcium hydroxide oxide silicate...

  1. 40 CFR 721.10018 - Calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... substance identified as calcium hydroxide oxide silicate (Ca6(OH)2O2(Si2O5)3) (PMN P-01-442; CAS No. 13169...(OH)2O2(Si2O5)3). 721.10018 Section 721.10018 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10018 Calcium hydroxide oxide silicate...

  2. Synthesis and Luminescent Performanices of Red emited Phosphors in systems Y2O3-La2O3-Gd2O3-La2O2S-Gd2O2S and YVO4-GDVO4 doped by EU^3+

    NASA Astrophysics Data System (ADS)

    Nazarov, Michael; Bukesov, Sergey; Kang, Jong Hyuk; Jeon, Duk Young; Popovici, Elisabeth-Jeanne; Muresan, Laura; Akmaeva, Tatiana

    2003-04-01

    Phospors based on solid solutions of Y2O3-La2O3-Gd2O3 and Y2O2S-La2O2S-Gd2O2S and YVO4-GdVO4 doped by Eu^3+ were synthesized by different methods. Influence of synthesis conditions, composition of the matrix and activator concentration on light emitting performances of the phosphors is described.Various experimental methods are applied to better understand the influence of synthesis perameters on luminescent properties. Optimized synthesis conditions are proposed. The solid solutions Y2O3-La2O3-Gd2O3 and Y2O2S-La2O2S-Gd2O2S are formed at temperatures of the phosphor synthesis. Europium-doped Y, La, Gd oxysulphides phosphors show higher CL efficiency at low applied voltages than oxides ones. The presented results confirm that europium doped solid solutions of Y-Ga-La oxides, oxysulphides and vanadates are perspective for PL and CL application

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

    PubMed

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

    2015-07-01

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

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

    PubMed

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

    2015-07-01

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

  5. Interaction between sulphide and H 2O in silicate melts

    NASA Astrophysics Data System (ADS)

    Stelling, Jan; Behrens, Harald; Wilke, Max; Göttlicher, Jörg; Chalmin-Aljanabi, Emilie

    2011-06-01

    Reaction between dissolved water and sulphide was experimentally investigated in soda-lime-silicate (NCS) and sodium trisilicate (NS3) melts at temperatures from 1000 to 1200 °C and pressures of 100 or 200 MPa in internally heated gas pressure vessels. Diffusion couple experiments were conducted at water-undersaturated conditions with one half of the couple being doped with sulphide (added as FeS or Na 2S; 1500-2000 ppm S by weight) and the other with H 2O (˜3.0 wt.%). Additionally, two experiments were performed using a dry NCS glass cylinder and a free H 2O fluid. Here, the melt was water-saturated at least at the melt/fluid interface. Profiling by electron microprobe (sulphur) and infrared microscopy (H 2O) demonstrate that H 2O diffusion in the melts is faster by 1.5-2.3 orders of magnitude than sulphur diffusion and, hence, H 2O can be considered as a rapidly diffusing oxidant while sulphur is quasi immobile in these experiments. In Raman spectra a band at 2576 cm -1 appears in the sulphide - H 2O transition zone which is attributed to fundamental S-H stretching vibrations. Formation of new IR absorption bands at 5025 cm -1 (on expense of the combination band of molecular H 2O at 5225 cm -1) and at 3400 cm -1 was observed at the front of the in-diffusing water in the sulphide bearing melt. The appearance and intensity of these two IR bands is correlated with systematic changes in S K-edge XANES spectra. A pre-edge excitation at 2466.5 eV grows with increasing H 2O concentration while the sulphide peak at 2474.0 eV decreases in intensity relative to the peak at 2477.0 eV and the feature at 2472.3 eV becomes more pronounced (all energies are relative to the sulphate excitation, calibrated to 2482.5 eV). The observations by Raman, IR and XANES spectroscopy indicate a well coordinated S 2- - H 2O complex which was probably formed in the glasses during cooling at the glass transition. No oxidation of sulphide was observed in any of the diffusion couple

  6. Destruction and Sequestration of H2O on Mars

    NASA Astrophysics Data System (ADS)

    Clark, Benton

    2016-07-01

    The availability of water in biologically useable form on any planet is a quintessential resource, even if the planet is in a zone habitable with temperature regimes required for growth of organisms (above -18 °C). Mars and most other planetary objects in the solar system do not have sufficient liquid water at their surfaces that photosynthesis or chemolithoautotrophic metabolism could occur. Given clear evidence of hydrous mineral alteration and geomorphological constructs requiring abundant supplies of liquid water in the past, the question arises whether this H2O only became trapped physically as ice, or whether there could be other, more or less accessible reservoirs that it has evolved into. Salts containing S or Cl appear to be ubiquitous on Mars, having been measured in soils by all six Mars landed missions, and detected in additional areas by orbital investigations. Volcanoes emit gaseous H2S, S, SO2, HCl and Cl2. A variety of evidence indicates the geochemical fate of these gases is to be transformed into sulfates, chlorides, chlorates and perchlorates. Depending on the gas, the net reaction causes the destruction of between one and up to eight molecules of H2O per atom of S or Cl (although hydrogen atoms are also released, they are lost relatively rapidly to atmospheric escape). Furthermore, the salt minerals formed often incorporate H2O into their crystalline structures, and can result in the sequestration of up to yet another six (sometimes, more) molecules of H2O. In addition, if the salts are microcrystalline or amorphous, they are potent adsorbents for H2O. In certain cases, they are even deliquescent under martian conditions. Finally, the high solubility of the vast majority of these salts (with notable exception of CaSO4) can result in dense brines with low water activity, aH, as well as cations which can be inimical to microbial metabolism, effectively "poisoning the well." The original geologic materials on Mars, igneous rocks, also provide some

  7. Role of Metabolic H2O2 Generation

    PubMed Central

    Sies, Helmut

    2014-01-01

    Hydrogen peroxide, the nonradical 2-electron reduction product of oxygen, is a normal aerobic metabolite occurring at about 10 nm intracellular concentration. In liver, it is produced at 50 nmol/min/g of tissue, which is about 2% of total oxygen uptake at steady state. Metabolically generated H2O2 emerged from recent research as a central hub in redox signaling and oxidative stress. Upon generation by major sources, the NADPH oxidases or Complex III of the mitochondrial respiratory chain, H2O2 is under sophisticated fine control of peroxiredoxins and glutathione peroxidases with their backup systems as well as by catalase. Of note, H2O2 is a second messenger in insulin signaling and in several growth factor-induced signaling cascades. H2O2 transport across membranes is facilitated by aquaporins, denoted as peroxiporins. Specialized protein cysteines operate as redox switches using H2O2 as thiol oxidant, making this reactive oxygen species essential for poising the set point of the redox proteome. Major processes including proliferation, differentiation, tissue repair, inflammation, circadian rhythm, and aging use this low molecular weight oxygen metabolite as signaling compound. PMID:24515117

  8. Thortveitite-type Tm2Si2O7

    PubMed Central

    Kahlenberg, Volker; Aichholzer, Paul

    2014-01-01

    Single crystals of dithulium disilicate, Tm2Si2O7, were obtained in flux synthesis experiments in the system SiO2–Tm2O3–LiF at ambient pressure. The compound belongs to the group of sorosilicates, i.e. it is based on [Si2O7]-units and crystallizes in the thortveitite (Sc2Si2O7) structure type. The Tm3+ cation (site symmetry .2.) occupies a distorted octa­hedral site, with Tm—O bond lengths in the range 2.217 (4)–2.289 (4) Å. Each of the octa­hedra shares three of its edges with adjacent [TmO6] groups, resulting in the formation of layers parallel to (001). The individual [SiO4] tetra­hedra are more regular, i.e. the differences between the bond lengths between Si and the bridging and non-bridging O atoms are not very pronounced. The layers containing the octa­hedra and the sheets containing the [Si2O7] groups (point group symmetry 2/m) form an alternating sequence. Linkage is provided by sharing common oxygen vertices. PMID:25161507

  9. Electrochemical, H2O2-Boosted Catalytic Oxidation System

    NASA Technical Reports Server (NTRS)

    Akse, James R.; Thompson, John O.; Schussel, Leonard J.

    2004-01-01

    An improved water-sterilizing aqueous-phase catalytic oxidation system (APCOS) is based partly on the electrochemical generation of hydrogen peroxide (H2O2). This H2O2-boosted system offers significant improvements over prior dissolved-oxygen water-sterilizing systems in the way in which it increases oxidation capabilities, supplies H2O2 when needed, reduces the total organic carbon (TOC) content of treated water to a low level, consumes less energy than prior systems do, reduces the risk of contamination, and costs less to operate. This system was developed as a variant of part of an improved waste-management subsystem of the life-support system of a spacecraft. Going beyond its original intended purpose, it offers the advantage of being able to produce H2O2 on demand for surface sterilization and/or decontamination: this is a major advantage inasmuch as the benign byproducts of this H2O2 system, unlike those of systems that utilize other chemical sterilants, place no additional burden of containment control on other spacecraft air- or water-reclamation systems.

  10. 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)

  11. Magnetic Phase Diagram of Co3V2O8

    NASA Astrophysics Data System (ADS)

    Yen, Fei; Lorenz, Bernd; Wang, Y. Q.; Sun, Y. Y.; Chu, C. W.

    2007-03-01

    Kagom'e-staircase lattice structures like Ni3V2O8 and Co3V2O8 have recently attracted attention because of their complex magnetic phase diagrams and the magnetically induced ferroelectric (FE) phase observed in Ni3V2O8. Co3V2O8 at zero magnetic field exhibits five subsequent magnetic phase transition in a narrow temperature range. It has an incommensurate antiferromagnetic phase below TN=11.4 K and weak ferromagnetic behavior along the a-axis at TC=6.2 K. Along with three other phase transitions in between; T1=8.9 K, T2=7.0 K and T3=6.9 K, the evolution of these five phase transitions under magnetic field, phase boundaries, is traced through magnetic susceptibility and dielectric constant anomalies. We resolve the complete magnetic phase diagram of Co3V2O8 with the magnetic field applied along the principal crystallographic orientations.

  12. Intracavity dye laser spectroscopy studies of the Ba + N(2)O, Ca + N(2)O + CO, and Sr + N(2)O + CO reactions.

    PubMed

    Eckstrom, D J; Barker, J R; Hawley, J G; Reilly, J P

    1977-08-01

    A search for gain or absorption on several candidate visible chemical laser transitions has been carried out using the intracavity dye laser probe technique. Absorption was found on the following v'' ? v' bands of the BaO(A(1)Sigma ? X(1)Sigma) bands in the Ba + N(2)O reaction: 0 ? 1; 0 ? 4; 1 ? 1; 1 ? 2, and 5 ? 1. No gain or absorption could be detected on the 7 ? 1, 6 ? 0, and 4 ? 0 bands (sensitivity ~10(-4)/cm). In Ca, Sr + N(2)O + CO flames, absorption was found in the green arc bands of CaO and the red arc bands of SrO. Several new bandhead wavelengths are reported. Our results support assignment of the arc bands to the diatomic metal oxides. Absorptions and enhancements were found on various Sr, Ba, and Ba(+) transitions. PMID:20168881

  13. Surfactant Effects on the Morphology and Pseudocapacitive Behavior of V2 O5 ⋅H2 O.

    PubMed

    Qian, Aniu; Zhuo, Kai; Shin, Myung Sik; Chun, Woo Won; Choi, Bit Na; Chung, Chan-Hwa

    2015-07-20

    To overcome the drawback of low electrical conductivity within supercapacitor applications, several surfactants are used for nanoscale V2 O5 to enhance the specific surface area. Polyethylene glycol 6000 (PEG-6000), sodium dodecylbenzene sulfonate (SDBS), and Pluronic P-123 (P123) controllers, if used as soft templates, easily form large specific surface area crystals. However, the specific mechanism through which this occurs and the influence of these surfactants is not clear for V2 O5 ⋅H2 O. In the present study, we aimed to investigate the mechanism of crystal growth through hydrothermal processes and the pseudocapacitive behavior of these crystals formed by using diverse surfactants, including PEG-6000, SDBS, and P123. Our results show that different surfactants can dramatically influence the morphology and capacitive behavior of V2 O5 ⋅H2 O powders. Linear nanowires, flower-like flakes, and curly bundled nanowires can be obtained because of electrostatic interactions in the presence of PEG-6000, SDBS, and P123, respectively. Furthermore, the electrochemical performance of these powders shows that the nanowires, which are electrodes mediated by PEG-6000, exhibit the highest capacitance of 349 F g(-1) at a scan rate of 5 mV s(-1) of all the surfactants studied. However, a symmetric P123 electrode comprising curly bundled nanowires with numerous nanopores showed an excellent and stable specific capacitance of 127 F g(-1) after 200 cycles. This work is beneficial to understanding the fundamental role of the surfactant in the assisted growth of V2 O5 ⋅H2 O and the resulting electrochemical properties of the pseudocapacitors, which could be useful for the future design of appropriate materials.

  14. Raman spectroscopy of CaCoSi2O6-Co2Si2O6 clinopyroxenes

    NASA Astrophysics Data System (ADS)

    Mantovani, Luciana; Tribaudino, Mario; Aliatis, Irene; Lambruschi, Erica; Lottici, Pier Paolo; Bersani, Danilo

    2014-08-01

    Raman spectra were collected on a set of synthetic clinopyroxenes along the series CaCoSi2O6-Co2Si2O6. Changes in peak position and peak width show: (1) evidence of a phase transition from C2/c to P21/c, at Ca0.4Co1.6Si2O6, in agreement with previous X-ray observations; (2) peak broadening for intermediate compositions, with sharper peaks close to the end members. The phase transition is revealed by a decrease or inversion in the slope of the peak position versus composition and by peak splitting of the peaks at 660 and 1,000 cm-1, related to Si-O bending and stretching modes within the tetrahedral chains, respectively. The observed changes with composition depend more on variation in bond lengths due to structural rearrangement with cation substitution, rather than by changes of the M2 cation mass. A comparison with the structurally analogous CaMgSi2O6-Mg2Si2O6 (Diopside-Estatite, Ca-Mg) series shows that one of the two splitted peaks is fainter than the Ca-Co pyroxenes. Therefore the frequency of the peak at about 1,000 cm-1 does not change for Ca-Mg substitution, whereas it shifts by as much as 20 cm-1 between CaCoSi2O6 and Co2Si2O6. Despite the mechanism of cation substitution is qualitatively similar in the two series, the effect of structural changes and polyhedral deformation on the Raman spectra appeared different. Peak broadening in samples with intermediate compositions could be interpreted as arising by compositional disorder, due to coexistence of local Ca-rich and Co-rich configurations which affect the short range interactions and therefore the Raman frequencies.

  15. Raman spectroscopy of CaCoSi2O6-Co2Si2O6 clinopyroxenes

    NASA Astrophysics Data System (ADS)

    Mantovani, Luciana; Tribaudino, Mario; Aliatis, Irene; Lambruschi, Erica; Lottici, Pier Paolo; Bersani, Danilo

    2015-03-01

    Raman spectra were collected on a set of synthetic clinopyroxenes along the series CaCoSi2O6-Co2Si2O6. Changes in peak position and peak width show: (1) evidence of a phase transition from C2/ c to P21/ c, at Ca0.4Co1.6Si2O6, in agreement with previous X-ray observations; (2) peak broadening for intermediate compositions, with sharper peaks close to the end members. The phase transition is revealed by a decrease or inversion in the slope of the peak position versus composition and by peak splitting of the peaks at 660 and 1,000 cm-1, related to Si-O bending and stretching modes within the tetrahedral chains, respectively. The observed changes with composition depend more on variation in bond lengths due to structural rearrangement with cation substitution, rather than by changes of the M2 cation mass. A comparison with the structurally analogous CaMgSi2O6-Mg2Si2O6 (Diopside-Estatite, Ca-Mg) series shows that one of the two splitted peaks is fainter than the Ca-Co pyroxenes. Therefore the frequency of the peak at about 1,000 cm-1 does not change for Ca-Mg substitution, whereas it shifts by as much as 20 cm-1 between CaCoSi2O6 and Co2Si2O6. Despite the mechanism of cation substitution is qualitatively similar in the two series, the effect of structural changes and polyhedral deformation on the Raman spectra appeared different. Peak broadening in samples with intermediate compositions could be interpreted as arising by compositional disorder, due to coexistence of local Ca-rich and Co-rich configurations which affect the short range interactions and therefore the Raman frequencies.

  16. Ferrielectricity in DyMn2O5: A golden touchstone for multiferroicity of RMn2O5 family

    NASA Astrophysics Data System (ADS)

    Liu, J.-M.; Dong, S.

    2015-06-01

    The RMn2O5 manganite compounds represent one class of multiferroic family with magnetic origins, which has been receiving continuous attention in the past decade. So far, our understanding of the magnetic origins for ferroelectricity in RMn2O5 is associated with the nearly collinear antiferromagnetic structure of Mn ions, while the exchange striction induced ionic displacements are the consequence of the spin frustration competitions. While this scenario may be applied to almost all RMn2O5 members, its limitation is either clear: the temperature-dependent behaviors of electric polarization and its responses to external stimuli are seriously materials dependent. These inconsistences raise substantial concern with the state-of-the-art physics of ferroelectricity in RMn2O5. In this mini-review, we present our recent experimental results on the roles of the 4f moments from R ions which are intimately coupled with the 3d moments from Mn ions. DyMn2O5 is a golden figure for illustrating these roles. It is demonstrated that the spin structure accommodates two nearly collinear sublattices which generate respectively two ferroelectric (FE) sublattices, enabling DyMn2O5 an emergent ferrielectric (FIE) system rarely identified in magnetically induced FEs. The evidence is presented from several aspects, including FIE-like phenomena and magnetoelectric responses, proposed structural model, and experimental check by nonmagnetic substitutions of the 3d and 4f moments. Additional perspectives regarding possible challenges in understanding the multiferroicity of RMn2O5 as a generalized scenario are discussed.

  17. Degradation behaviour of a new bioceramic: Ca2P2O7 with addition of Na4P2O7.10H2O.

    PubMed

    Lin, F H; Liao, C J; Chen, K S; Sun, J S; Liu, H C

    1997-07-01

    A newly produced bioceramic, beta-Ca2P2O7 with addition of Na4P2O7.10H2O (SDCP), has been implanted into the femoral condyle of rabbits. Within 6 weeks after implantation, most of the bioceramic is replaced by new woven bone. On the contrary, block from hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP), which are osteoconductible, do not resorb within a short period of time. We believe that the biodegradable behaviour of SDCP may occur in two steps. The first and most important step is the digestion of particles and migration of the particles by phagocytosis. The object of this study is to examine the change in morphologies, chemical compositions and crystal structure of SDCP after soaking in distilled water for a certain period of time. The SDCP ceramic was also co-cultured with leucocytes to observe how the SDCP particles were digested by the leucocytes, so that the mechanism of biodegradable behaviour of SDCP ceramic in vivo might be clarified. Four types of sintered calcium phosphate ceramics were tested in the experiment: SDCP, pure beta-Ca2P2O7 (DCP), HA and beta-TCP. They wee soaked in distilled water at 37 degrees C for up to 30 days. The microstructure and morphology of crystals deposited on the surface were observed using scanning electron microscopy. Sodium, calcium and phosphorus ion contents in the supernatant solution were detected by atomic absorption analysis and ion coupled plasma. In summary, HA and DCP showed no significant evidence of dissolution in distilled water. In static distilled water, calcium ions may be released from beta-TCP into solution during the initial 7 days and then converted into HA by reprecipitation. The results showed that the SDCP was firstly dissolved into small grains or fragments by the solution. The small fragments should be so small as to be digested by the phagocytes in a physiological environment.

  18. Super-high photocatalytic activity of Fe2O3 nanoparticles anchored on Bi2O2CO3 nanosheets with exposed {0 0 1} active facets

    NASA Astrophysics Data System (ADS)

    Hu, Dandan; Zhang, Kaiyou; Yang, Qi; Wang, Mingjun; Xi, Yi; Hu, Chenguo

    2014-10-01

    Structure engineering enables us to design novel photocatalysts with high efficiency and stability. Here visible light absorbing Fe2O3 semiconductor is chosen as sensitizer to modify wide band-gap Bi2O2CO3 semiconductor in order to enhance its photocatalytic properties by shifting the UV-driven catalytic activity to visible-light-driven catalytic activity. The Bi2O2CO3@Fe2O3 nanosheets with exposed active {0 0 1} facet were fabricated by a facile one-step modified hydrothermal method. The thermal stability, crystal structure, morphology and optical band gap were characterized. The photocatalytic activities of the Bi2O2CO3 and Bi2O2CO3@Fe2O3 with different molar ratio of Fe2O3 to Bi2O2CO3 were compared. It was found that the Bi2O2CO3@Fe2O3 catalyst can degrade rhodamine-B within 25 min under the simulated sunlight, displaying greatly enhanced photocatalytic activity with respect to the Bi2O2CO3 catalyst. The photocatalyst showed good photostability and recyclability. A mixture of multi-colored dyes including rhodamine-B, methylene blue and methyl orange can be completely degraded by the Bi2O2CO3@Fe2O3 catalyst (5 mol% Fe2O3) within 45 min under the simulated sunlight irradiation. The photocatalytic mechanism was discussed in detail.

  19. AC conductivity and its scaling behavior in MgO-Li2O-B2O3-Bi2O3 glasses

    NASA Astrophysics Data System (ADS)

    Purnima, M.; Bale, Shashidhar; Samee, M. A.; Ahmmad, Shaik Kareem; Rahman, Syed

    2013-02-01

    In the present work, the compositional dependence of density, refractive index and glass transition temperature of xMgO-(25-x)Li2O-50B2O3-25Bi2O3 glasses is studied. Impedance spectroscopy technique is employed on these samples and the data are analyzed using Cole-Cole type impedance response function. The AC conductivity behavior of the present glasses has been investigated in the frequency range from 100 Hz to 1 MHz and as a function of temperature the measured AC data are analyzed using the Jonscher’s universal power law to explain the observed dispersive behavior of the electrical conductivity. The temperature and composition dependence scaling behavior in the AC conductivity are satisfactorily explained by scaling the AC conductivity σ‧(ω) by hopping frequency ωp. The frequency response of dielectric constant ɛ‧ and dielectric loss tanδ as a function of temperature were studied. The tanδ peak shifts to higher frequency with increasing temperature, indicating dipolar relaxation character of dielectric loss in the present glasses.

  20. Raman spectra and density of Li 2O-B 2O 3-GeO 2 glasses with high Li 2O content

    NASA Astrophysics Data System (ADS)

    Mansour, E.

    2010-01-01

    One series of glass having the molar formula y[42.5Li 2O·57.5GeO 2]·(1- y)[42.5Li 2O·57.5B 2O 3] where y ranged between 0 and 0.55 has been prepared and measured for density, molar volume and Raman spectra. No density anomaly was observed throughout the composition range of the studied glasses. The large difference in molecular mass between that of B 2O 3 and GeO 2 is the reason for the density change. The linear change in density reveals that each oxide in the glass would contribute to the density by a specific factor. Alkali oxide is incorporated into the borate as well as the germanate networks. There are three essential Raman broad bands at ∼525, ∼775 and ∼835 cm -1. With increasing GeO 2 content, the number of NBOs associated with Q 2 decreases in the germanate network while three-membered rings of GeO 4 tetrahedra are formed. The number of borate groups containing four coordinated boron decreases with increasing GeO 2 content at the expense of B 2O 3.

  1. Structural properties of Bi2O3-B2O3-SiO2-Na2O glasses for gamma ray shielding applications

    NASA Astrophysics Data System (ADS)

    Kaur, Kulwinder; Singh, K. J.; Anand, Vikas

    2016-03-01

    Glass samples of the xBi2O3-(0.70-x)B2O3-0.15SiO2-0.15Na2O (where x=0 up to 0.5 mol fraction) have been prepared in the laboratory by using melt quenching technique. 137Cs source has been used for experimental measurements of mass attenuation coefficient of γ-rays at 662 keV. Mass attenuation coefficient of our glass samples has been compared with standard nuclear radiation shield "barite concrete". It has been concluded that bismuth containing glass samples can be potential candidates for γ-ray shielding applications. Glasses must have appreciable elastic moduli values for their practical utility as γ-ray shields which are related to coordination number and non-bridging oxygens. Structural properties including coordination number and non-bridging oxygens of the structural units of the glass system have been estimated from the detailed analysis of Optical, Raman and FTIR spectra. Reported investigations can contribute to the development of transparent gamma ray shields.

  2. H2O2 Release from Human Granulocytes during Phagocytosis

    PubMed Central

    Root, Richard K.; Metcalf, Julia A.

    1977-01-01

    Normal and cytochalasin B-treated human granulocytes have been studied to determine some of the interrelationships between phagocytosis-induced respiration and superoxide and hydrogen peroxide formation and release into the extracellular medium by intact cells. By using the scopoletin fluorescent assay to continuously monitor extracellular hydrogen peroxide concentrations during contact of cells with opsonized staphylococci, it was demonstrated that the superoxide scavengers ferricytochrome c and nitroblue tetrazolium significantly reduced the amount of H2O2 released with time from normal cells but did not abolish it. This inhibitory effect was reversed by the simultaneous addition of superoxide dismutase (SOD), whereas the addition of SOD alone increased the amount of detectable H2O2 in the medium. The addition of sodium azide markedly inhibited myeloperoxidase-H2O2-dependent protein iodination and more than doubled H2O2 release, including the residual amount remaining after exposure of the cells to ferricytochrome c, suggesting its origin from an intracellular pool shared by several pathways for H2O2 catabolism. When cells were pretreated with cytochalasin B and opsonized bacteria added, reduced oxygen consumption was observed, but this was in parallel to a reduction in specific binding of organisms to the cells when compared to normal. Under the influence of inhibited phagosome formation by cytochalasin B, the cells released an increased amount of superoxide and peroxide into the extracellular medium relative to oxygen consumption, and all detectable peroxide release could be inhibited by the addition of ferricytochrome c. Decreased H2O2 production in the presence of this compound could not be ascribed to diminished bacterial binding, decreased oxidase activity, or increased H2O2 catabolism and was reversed by the simultaneous addition of SOD. Furthermore, SOD and ferricytochrome c had similar effects on another H2O2-dependent reaction, protein iodination, in

  3. Pb(3)Te(2)O(6)Br(2).

    PubMed

    Weil, Matthias; Stöger, Berthold

    2010-01-16

    Single crystals of the title compound, trilead(II) bis-[tellurate(IV)] dibromide, have been grown under hydro-thermal conditions. The structure is isotypic with that of the chloride analogue, Pb(3)Te(2)O(6)Cl(2), and consists of three Pb, two Te, two Br and four O atoms in the asymmetric unit. Except for two of the O atoms, all atoms are located on mirror planes. The Pb(3)Te(2)O(6)Br(2) structure can be described as being built up from (∞) (2)[Pb(3)Te(2)O(6)](2+) layers extending parallel to (20) and Br(-) anions between the layers. Cohesion of the structure is accomplished through Pb-Br contacts of two of the three lead atoms, leading to highly asymmetric coordination polyhedra. The lone-pair electrons of both Te(IV) and Pb(II) atoms are stereochemically active and point towards the anionic halide layers.

  4. Non-Potassic Melts In CMAS-CO2-H2O-K2O Model Peridotite

    NASA Astrophysics Data System (ADS)

    Buisman, I.; Walter, M. J.; Keshav, S.

    2009-12-01

    Volatile mediated model systems have been fundamental in shaping our knowledge about the way we view melting phase relations of peridotite at various depths in the Earth. Volatiles not only affect the melting temperatures, but the resulting liquids are, in some case, dramatically different than those witnessed in melting of dry peridotite. For example, the influence of CO2 and H2O on the melting phase relations of model peridotite shows a remarkable decrease in the solidus temperatures when compared to the dry peridotite (Gudfinnsson and Presnall, 2005). These model systems illustrate a gradational change above the solidus from carbonatites to kimberlites over several hundreds of degrees. Group-II kimberlites are ultrapotassic rocks with high water content where the mineral phlogopite is abundant. To get a better understanding of the melting phase relations related to carbonatitic and kimberlitic magmas, K2O was added to the system CMAS-CO2-H2O. In these systems, fluid and melt can co-exist in P-T space. However, from past studies, it is also known that in hydrous systems, both the fluid and melt will become indistinguishable from one another creating a singularity (second critical endpoint). Starting from the solidus located in six components (Keshav and Gudfinnsson, AGU abstract, 2009), with seven phases, melting phase relations in CMAS-CO2-H2O-K2O involving, fo-opx-cpx-garnet-carbonate-melt-fluid, are divariant. Fluid was recognized with the observation of large cavities seen in exposed capsules. Moreover, the presence of bright, needle-like grains found in large cavities in backscattered images implies the presence of solute in the fluid phase. Significantly, liquids on this divariant region have about 1000 ppm K2O, and so is the case with accompanying cpx. Hence, with this non-interesting amount of K2O in the mentioned phases, fluid must have all the potassium. At 30 kbar/1100C, with fo-opx-cpx-garnet-carbonate-phlogopite-melt-fluid, the melting phase

  5. Gas sensing behaviour of Cr2O3 and W6+: Cr2O3 nanoparticles towards acetone

    NASA Astrophysics Data System (ADS)

    Kohli, Nipin; Hastir, Anita; Singh, Ravi Chand

    2016-05-01

    This paper reports the acetone gas sensing properties of Cr2O3 and 2% W6+ doped Cr2O3 nanoparticles. The simple cost-effective hydrolysis assisted co-precipitation method was adopted. Synthesized samples were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. XRD revealed that synthesized nanoparticles have corundum structure. The lattice parameters have been calculated by Rietveld refinement; and strain and crystallite size have been calculated by using the Williamson-Hall plots. For acetone gas sensing properties, the nanoparticles were applied as thick film onto alumina substrate and tested at different operating temperatures. The results showed that the optimum operating temperature of both the gas sensors is 250°C. At optimum operating temperature, the response of Cr2O3 and 2% W6+ doped Cr2O3 gas sensor towards 100 ppm acetone was found to be 25.5 and 35.6 respectively. The investigations revealed that the addition of W6+ as a dopant enhanced the sensing response of Cr2O3 nanoparticles appreciably.

  6. FT-IR and thermoluminescence investigation of P2O5-BaO-K2O glass system

    NASA Astrophysics Data System (ADS)

    Ivascu, C.; Timar-Gabor, A.; Cozar, O.

    2013-11-01

    The 0.5P2O5ṡxBaOṡ(0.5-x)K2O glass system (0≤x≤0.5mol%) is investigated by FT-IR and thermoluminescence as a possible dosimetic material. FT-IR spectra show structural network modifications with the composition variations of the studied glasses. The predominant absorption bands are characterized by two broad peaks near 500 cm-1, two weak peaks around 740 cm-1 and three peaks in the 900-1270 cm-1 region. The shift in the position of the band assigned to asymmetric stretching of PO2- group, υas(PO2-) modes from ˜1100 cm-1 to 1085 cm-1 and the decrease in its relative intensity with the increasing of K2O content shows a network modifier role of this oxide.. Luminescence investigations show that by adding modifier oxides in the phosphate glass a dose dependent TL signals result upon irradiation. Thus P2O5-BaO-K2O glass system is a possible candidate material for dosimetry in the dose 0 - 50 Gy range.

  7. Cu2O and Au/Cu2O Particles: Surface Properties and Applications in Glucose Sensing

    PubMed Central

    Won, Yu-Ho; Stanciu, Lia A.

    2012-01-01

    In this work we investigated the surface and facet-dependent catalytic properties of metal oxide particles as well as noble metal/metal oxide heterogeneous structures, with cuprous oxide (Cu2O) and Au/Cu2O being selected as model systems. As an example of application, we explored the potential of these materials in developing electrocatalytic devices. Cu2O particles were synthesized in various shapes, then used for testing their morphology-dependent electrochemical properties applied to the detection of glucose. While we did not attempt to obtain the best detection limit reported to date, the octahedral and hexapod Cu2O particles showed reasonable detection limits of 0.51 and 0.60 mM, respectively, which are physiologically relevant concentrations. However, detection limit seems to be less affected by particle shapes than sensitivity. Heterogeneous systems where Au NPs were deposited on the surface of Cu2O particles were also tested with similar results in terms of the effect of surface orientation. PMID:23201983

  8. Structural investigations of vanadyl doped Nb2O5·K2O·B2O3 glasses

    NASA Astrophysics Data System (ADS)

    Anshu; Sanghi, S.; Agarwal, A.; Lather, M.; Bhatnagar, V.; Khasa, S.

    2009-07-01

    Pottasium nioborate glasses of composition xNb2O5·(30-x)K2O·69B2O3 containing 1 mol % of V2O5 were prepared by melt quench technique (1473K, 1h). The electron paramagnetic resonance spectra of VO2+ in these glasses have been recorded in X- band (v approx 9.14 GHz) at room temperature (RT). The spin Hamiltonian parameters, dipolar hyperfine coupling parameters, P and Fermi contact interaction parameter, K have been calculated. It is found that V4+ ions in these glasses exist as VO2+ in octahedral coordination with a tetragonal distortion. The tetragonality of V4+O6 complex decreases with increasing Nb2O5: K2O ratio and also there is an expansion of 3dXY orbit of unpaired electron in the vanadium ion. The study of IR transmission spectra over a range 400- 4000 cm-1 depicts the presence of both BO3 and BO4 structural units and Nb5+ ions are incorporated into the glass network as NbO6 octahedra, substituting BO4 groups.

  9. Phase equilibria investigations and thermodynamic modeling of the system Bi2O3-Al2O3

    NASA Astrophysics Data System (ADS)

    Oudich, F.; David, N.; Mathieu, S.; Vilasi, M.

    2015-02-01

    The system Bi2O3-Al2O3 has been experimentally investigated above 600 °C by DTA, XRD and EPMA under air and low oxygen pressure. Only two compounds were found to exist in equilibrium, which are Bi2Al4O9(1Bi2O3:2Al2O3) and Bi25AlO39(25:1). The latter exhibits a sillenite structure and does not contain pentavalent bismuth. A peritectoid decomposition of (25:1) and a peritectic melting of (1:2) occur at 775 °C and 1075 °C respectively, while an eutectic transformation was observed at 815 °C for 97 mol% Bi2O3. On the basis of the results obtained within the present work as well as experimental data provided from literature, a thermodynamic modeling where the liquid phase is described by the two-sublattice ionic liquid model was performed according to the Calphad approach. The resulting thermodynamic optimization yielded good agreement with experimental results in the investigated region.

  10. Dielectric spectra of Li 2O-CaF 2-P 2O 5 glasses doped by silver ions

    NASA Astrophysics Data System (ADS)

    Sambasiva Rao, K.; Srinivasa Reddy, M.; Ravi Kumar, V.; Veeraiah, N.

    2007-06-01

    Dielectric constant ε‧, loss tan δ and a.c. conductivity σ( ω) Li 2O-CaF 2-P 2O 5 glasses doped with small concentrations of Ag 2O (ranging from 0 to 1.0 mol%) are studied as a function of frequency and temperature over moderately wide ranges. The variation of dielectric loss with temperature for these glasses has exhibited dielectric relaxation effects. The relaxation effects have been analyzed by a pseudo Cole-Cole plot method and the spreading of relaxation times has been established. The variation of a.c. conductivity with the concentration of Ag 2O pass through a minimum at 0.6 mol% Ag 2O. In the high-temperature region, the a.c. conduction seems to be connected with the mixed conduction, viz., electronic and ionic conduction. The low-temperature part of the a.c. conductivity which is observed to be nearly temperature independent has been explained on the basis of quantum mechanical-tunneling (QMT) model. The results have been further analyzed in detail with the aid of the data on optical absorption, IR and Raman spectral studies.

  11. NASA Lewis H2-O2 MHD program

    NASA Technical Reports Server (NTRS)

    Smith, M.; Nichols, L. D.; Seikel, G. R.

    1974-01-01

    Performance and power costs of H2-O2 combustion powered steam-MHD central power systems are estimated. Hydrogen gas is assumed to be transmitted by pipe from a remote coal gasifier into the city and converted to electricity in a steam MHD plant having an integral gaseous oxygen plant. These steam MHD systems appear to offer an attractive alternative to both in-city clean fueled conventional steam power plants and to remote coal fired power plants with underground electric transmission into the city. Status and plans are outlined for an experimental evaluation of H2-O2 combustion-driven MHD power generators at NASA Lewis Research Center.

  12. Re-quantifying China's N2O emissions from croplands

    NASA Astrophysics Data System (ADS)

    Zhou, F.; Shang, Z.

    2015-12-01

    Reactive nitrogen (Nr) entering agricultural soils from fertilizer applications worldwide results into a 43%~63% of global anthropogenic N2O emissions (EDGAR, 2014; Saikawa et al., 2014; Tian et al., 2014). This contribution is likely to increase in countries with intensive agricultural systems such as China (Zhou et al., 2014). yet the patterns, trends, and the associated causes of Chinese emissions remains subject to large uncertainty; inventories of China's total agricultural soils N2O emissions at present varied by ~150% (Zhou et al., 2015). The primary sources of this uncertainty are conflicting estimates of emission factors, nitrogen inputs, and the associated environmental conditions, yet none of previous estimates are based upon large-scale measurements and high-resolution activity data. Here, we re-quantify China's N2O emissions from croplands from 1990 to 2012, including direct and indirect pathways, using updated and harmonized N input data, high-resolution environmental factors data, and a comprehensive dataset of global N2O observation networks. The spatially-variable emission factor, and leaching and runoff rates are derived by empirical upscaling of ground-based observations, but validated by ecosystem models and atmospheric inversions of N2O concentration data. N inputs, such as synthetic fertilizer, manure, crop residues, human excretion applied to croplands, are compiled at county-scale, and atmospheric N depositions are simulated by using LMDZ-OR-INCA atmospheric transport chemistry model that has been calibrated by Asian observation networks. We also develop the high-resolution datasets including landuse dynamics (1-km), SOC changes (0.1-deg), climates (0.1-deg), and irrigation rates (city-scale). Three main tasks have been performed in this study: i) the magnitude and spatiotemporal patterns of N2O emissions over China croplands from 1990 to 2012; ii) the attributions of anthropogenic causes of the spatial variations, interannual variability

  13. The dynamics of the H + H2O reaction.

    PubMed

    Castillo, Jesús F

    2002-04-15

    This article reviews the history and recent progress in the study of the dynamics of the H + H2O reaction, which has become a benchmark for experimental research in the field of gas-phase reaction dynamics. The dynamics of H + H2O is discussed in terms of the different observable properties: integral cross-sections, rate coefficients, product state distributions, differential cross-sections, and vector correlations. It is shown how experimental measurements and first-principle theoretical calculations have revealed the interesting microscopic aspects of this elementary chemical reaction.

  14. Biologically produced volatile compounds: N2O emissions from soils

    NASA Technical Reports Server (NTRS)

    Banin, A.

    1985-01-01

    Tropospheric nitrous concentration has increased by 0.2 0.4% per year over the period 1975 to 1982, amounting to net addition to the atmosphere of 2.8 - 5.6 Tg N2O-N per year. This perturbation, if continued into the future, will affect stratospheric chemical cycles, and the thermal balance of the Earth. In turn it will have direct and indirect global effects on the biosphere. Though the budget and cycles of N2O on Earth are not yet fully resolved, accumulating information and recent modelling efforts permit a more complete evaluation and better definition of gaps in our knowledge.

  15. Photoionization and fragmentaton of (N2O)n clusters

    NASA Astrophysics Data System (ADS)

    Kamke, W.; Kamke, B.; Kiefl, H. U.; Hertel, I. V.

    1986-02-01

    A supersonic molecular beam and monochromatized synchrotron radiation are presently used to measure photoionization efficiency curves for (N2O)n, at n = 1-6, in the 55-110 nm wavelength region. By measuring the energy loss of cluster ions which fragment in a field free drift region of the ion source, it becomes possible to detect delayed unimolecular and collision-induced fragmentations of the cluster ions. From a study of the dependence of the 'metastable' signals on background pressure, it appears that only the removal of a single N2O molecule at a time can occur by unimolecular decay.

  16. Diffusion of oxygen in amorphous Al{sub 2}O{sub 3}, Ta{sub 2}O{sub 5}, and Nb{sub 2}O{sub 5}

    SciTech Connect

    Nakamura, R. Tsukui, S.; Toda, T.; Tane, M.; Suzuki, T.; Ishimaru, M.; Nakajima, H.

    2014-07-21

    The self-diffusivity of oxygen in amorphous Al{sub 2}O{sub 3} (a-Al{sub 2}O{sub 3}), a-Ta{sub 2}O{sub 5}, and a-Nb{sub 2}O{sub 5} was investigated along with structural analysis in terms of pair distribution function (PDF). The low activation energy, ∼1.2 eV, for diffusion in the oxides suggests a single atomic jump of oxygen ions mediated via vacancy-like defects. However, the pre-exponential factor for a-Ta{sub 2}O{sub 5} and a-Nb{sub 2}O{sub 5} with lower bond energy was two orders of magnitude larger than that for a-Al{sub 2}O{sub 3} with higher bond energy. PDF analyses revealed that the short-range configuration in a-Ta{sub 2}O{sub 5} and a-Nb{sub 2}O{sub 5} was more broadly distributed than that in a-Al{sub 2}O{sub 3}. Due to the larger variety of atomic configurations of a-Ta{sub 2}O{sub 5} and a-Nb{sub 2}O{sub 5}, these oxides have a higher activation entropy for diffusion than a-Al{sub 2}O{sub 3}. The entropy term for diffusion associated with short-range structures was shown to be a dominant factor for diffusion in amorphous oxides.

  17. The Effect of Chlorine on the Rheology of Na2O-Fe2O3-Al2O3-SiO2 Melts

    NASA Astrophysics Data System (ADS)

    Zimova, M.; Webb, S.

    2004-12-01

    Because of the high fluid mobility of chlorine, the mantle wedge in subduction zone settings may be enriched in chlorine by the fluids released by the subducted altered oceanic crust plus sediments. The presence of chlorine (and other halogens) will affect the solidus temperature and the rheology of melts, thus influencing the magma evolution, eruption and degassing. Very little is known about the solubility mechanism and diffusivity of Cl in silicate melts and even less is known about the effect of Cl on viscosity. The present study addresses the effect of the halogen chlorine on the viscosity of silicate melts. The shear viscosities of Cl-bearing melts in the system Na2O-Fe2O3-Al2O3-SiO2 were determined over the temperature range 550-950C at room pressure in air. Viscosities were determined using the micropenetration technique in the range of 108.5 to 1012.0 Pa s. The compositions are based on addition of Fe2O3 or FeCl3 to aluminosilicate glasses with a fixed amount of SiO2 (67 mol %). Although there was loss of Cl- during the glass syntheses, no loss occurred during the viscometry experiments. It is to be expected that Cl- takes the structural position of an oxygen, and thus reduces the polymerization of the melt structure, and therefore the viscosity of the melt; as F- does. Our measurements show that, depending upon the melt composition, the addition of Cl- will either increase or decrease the viscosity of the melt. In the present melts at least 20% of the iron exists as network modifying, viscosity reducing Fe2+; while the rest exists as network forming Fe3+. It is proposed here that the different effects of chlorine on viscosity are due to the preferred Cl--Fe2+NBO bonding together with the different structure of peralkaline and peraluminous melts. In peralkaline aluminosilicate melts, the addition of Cl2O-1 will destroy 2 NBOs and create one BO if Cl- bonds primarily to the Fe2+ creating non-bridging oxygens. This would result in an increase in viscosity

  18. 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

  19. THE HIGH TEMPERATURE CHEMICAL REACTIVITY OF LI2O

    SciTech Connect

    Kessinger, G.; Missimer, D.

    2009-11-13

    The ultimate purpose of this study was to investigate the use of a Li-Ca mixture for direct reduction of actinide oxides to actinide metals at temperatures below 1500 C. For such a process to be successful, the products of the reduction reaction, actinide metals, Li{sub 2}O, and CaO, must all be liquid at the reaction temperature so the resulting actinide metal can coalesce and be recovered as a monolith. Since the established melting temperature of Li{sub 2}O is in the range 1427-1700 C and the melting temperature of CaO is 2654 C, the Li{sub 2}O-CaO (lithium oxidecalcium oxide) pseudo-binary system was investigated in an attempt to identify the presence of low-melting eutectic compositions. The results of our investigation indicate that there is no evidence of ternary Li-Ca-O phases or solutions melting below 1200 C. In the 1200-1500 C range utilizing MgO crucibles, there is some evidence for the formation of a ternary phase; however, it was not possible to determine the phase composition. The results of experiments performed with ZrO{sub 2} crucibles in the same temperature range did not show the formation of the possible ternary phase seen in the earlier experiment involving MgO crucibles, so it was not possible to confirm the possibility that a ternary Li-Ca-O or Li-Mg-O phase was formed. It appears that the Li{sub 2}O-CaO materials reacted, to some extent, with all of the container materials, alumina (Al{sub 2}O{sub 3}), magnesia (MgO), zirconia (ZrO{sub 2}), and 95% Pt-5% Au; however, to clarify the situation additional experiments are required. In addition to the primary purpose of this study, the results of this investigation led to the conclusions that: (1) The melting temperature of Li{sub 2}O may be as low as 1250 C, which is considerably lower than the previously published values in the range 1427-1700 C; (2) Lithium oxide (Li{sub 2}O) vaporizes congruently; (3) Lithium carbonate and Li2O react with 95% Pt-5% Au, and also reacts with pure Pt; and (4

  20. Thermoluminescence investigations on xY2O3 (60-x)P2O5·40SiO2 vitroceramics.

    PubMed

    Biró, Barna; Pascu, Andrada; Timar-Gabor, Alida; Simon, Viorica

    2015-04-01

    Thermoluminescence properties of xY2O3·(60-x)P2O5·40SiO2 vitroceramic compounds doped with xY2O3 at various concentrations (0≤x≤30mol%) were studied. Compounds with reduced Y2O3 concentration showed unsatisfactory dosimetric properties, while the vitroceramics composed of 20Y2O3·40P2O5·40SiO2 and 30Y2O3·30P2O5·40SiO2 exhibited bright signals, linear dose response and minimum detectable doses of 16mGy and 4mGy, respectively. Moreover, 30mol% Y2O3 doped vitroceramic exhibited good repeatability, acceptable batch homogeneity and poor fading signal, features that are recommending this material for dosimetry purposes.

  1. Selective catalytic reduction of NO with NH3 over V2O5 supported on TiO2 and Al2O3: A comparative study

    NASA Astrophysics Data System (ADS)

    Huang, Xianming; Zhang, Shule; Chen, Huinan; Zhong, Qin

    2015-10-01

    This study aimed at investigating the interaction of V2O5 species with TiO2 and Al2O3 supports to understand the effect of supports on SCR reaction. Analysis by XRD, BET, UV-vis, and DFT theoretical calculations, XPS, EPR and in situ DRIFT showed that the two kinds of supports could interact with V2O5. The interaction of electron excitation and charge transfer of supports to V2O5 species was important to the formation of the reduced V2O5. These aspects increased the formation of superoxide ions that could improve the NO oxidation over V2O5/TiO2. It was responsible for the higher SCR catalytic activity of V2O5/TiO2 than V2O5/Al2O3.

  2. Global Flux Balance in the Terrestrial H2O Cycle: Reconsidering the Post-Arc Subducted H2O Flux

    NASA Astrophysics Data System (ADS)

    Parai, R.; Mukhopadhyay, S.

    2010-12-01

    Quantitative estimates of H2O fluxes between the mantle and the exosphere (i.e., the atmosphere, oceans and crust) are critical to our understanding of the chemistry and dynamics of the solid Earth: the abundance and distribution of water in the mantle has dramatic impacts upon mantle melting, degassing history, structure and style of convection. Water is outgassed from the mantle is association with volcanism at mid-ocean ridges, ocean islands and convergent margins. H2O is removed from the exosphere at subduction zones, and some fraction of the subducted flux may be recycled past the arc into the Earth’s deep interior. Estimates of the post-arc subducted H2O flux are primarily based on the stability of hydrous phases at subduction zone pressures and temperatures (e.g. Schmidt and Poli, 1998; Rüpke et al., 2004; Hacker, 2008). However, the post-arc H2O flux remains poorly quantified, in part due to large uncertainties in the water content of the subducting slab. Here we evaluate estimated post-arc subducted fluxes in the context of mantle-exosphere water cycling, using a Monte Carlo simulation of the global H2O cycle. Literature estimates of primary magmatic H2O abundances and magmatic production rates at different tectonic settings are used with estimates of the total subducted H2O flux to establish the parameter space under consideration. Random sampling of the allowed parameter space affords insight into which input and output fluxes satisfy basic constraints on global flux balance, such as a limit on sea-level change over time. The net flux of H2O between mantle and exosphere is determined by the total mantle output flux (via ridges and ocean islands, with a small contribution from mantle-derived arc output) and the input flux subducted beyond the arc. Arc and back-arc output is derived mainly from the slab, and therefore cancels out a fraction of the trench intake in an H2O subcycle. Limits on sea-level change since the end of the Archaean place

  3. Improvement of crystallinity of GaN layers grown using Ga2O vapor synthesized from liquid Ga and H2O vapor

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Yohei; Taniyama, Yuuki; Takatsu, Hiroaki; Kitamoto, Akira; Imade, Mamoru; Yoshimura, Masashi; Isemura, Masashi; Mori, Yusuke

    2016-05-01

    Growth methods using Ga2O vapor allow long-term growth of bulk GaN crystals. Ga2O vapor is generated by the reduction of Ga2O3 powder with H2 gas (Ga2O3-H2 process) or by the oxidation of liquid Ga with H2O vapor (Ga-H2O process). We investigated the dependence of the properties of grown GaN layers on the synthesis of Ga2O. In the Ga-H2O process, the polycrystal density and full width at half maximum (FWHM) GaN(0002) X-ray rocking curves (XRC) at a high growth rate were lower than those in the Ga2O3-H2 process, and a GaN layer with FWHM of 99 arcsec and growth rate of 216 µm/h was obtained. A low H2O partial pressure in the growth zone improved crystallinity in the Ga-H2O process, realized by the high efficiency of conversion from liquid Ga to Ga2O vapor. We concluded that using Ga2O vapor in the Ga-H2O process has the potential for obtaining higher crystallinity with high growth rate.

  4. New Optical Constants for Amorphous and Crystalline H2O-ice and H2O-mixtures.

    NASA Technical Reports Server (NTRS)

    Mastrapa, Rachel; Bernstein, Max; Sandford, Scott

    2006-01-01

    We will present the products of new laboratory measurements of ices relevant to Trans-Neptunian Objects. We have calculated the real and imaginary indices of refraction for amorphous and crystalline H2O-ice and also H2O-rich ices containing other molecular species. We create ice samples by condensing gases onto a cold substrate. We measure the thickness of the sample by reflecting a He-Ne laser off of the sample and counting interference fringes as it grows. We then collect transmission spectra of the samples in the wavelength range from 0.7-22 micrometers. Using the thickness and the transmission spectra of the ice we calculate the imaginary part of the index of refraction. We then use a Kramers-Kronig calculation to calculate the real part of the index of refraction (Berland et al. 1994; Hudgins et al. 1993). These optical constants can then be used to create model spectra for comparison to spectra from Solar System objects, including TNOs. We will summarize the difference between the amorphous and crystalline H2O-ice spectra. These changes include weakening of features and shifting of features to shorter wavelength. One important result is that the 2 pm feature is stronger in amorphous H2O ice than it is in crystalline H2O-ice. We will also discuss the changes seen when H2O is mixed with other components, including CO2, CH4, HCN, and NH3 (Bernstein et al. 2005; Bernstein et al. 2006).

  5. A laser flash photolysis kinetics study of the reaction OH + H2O2 yields HO2 + H2O

    NASA Technical Reports Server (NTRS)

    Wine, P. H.; Semmes, D. H.; Ravishankara, A. R.

    1981-01-01

    Absolute rate constants for the reaction are reported as a function of temperature over the range 273-410 K. OH radicals are produced by 266 nm laser photolysis of H2O2 and detected by resonance fluorescence. H2O2 concentrations are determined in situ in the slow flow system by UV photometry. The results confirm the findings of two recent discharge flow-resonance fluorescence studies that the title reaction is considerably faster, particularly at temperatures below 300 K, than all earlier studies had indicated. A table giving kinetic data from the reaction is included.

  6. Low energy spin dynamics of a quantum ferrimagnetic chain, NiCu(pba)(H 2O) 32H 2O

    NASA Astrophysics Data System (ADS)

    Fujiwara, N.; Hagiwara, M.

    2000-01-01

    Nuclear magnetic resonance (NMR) for 1H nuclei was performed in a Heisenberg chain with alternating spins S=1 and 1/2, NiCu(pba)(H 2O) 32H 2O (pba=1,3-propylenebis (oxamato)) from 4.2 to 280 K. The relaxation rate (1/ T1) is proportional to 1/ H ( H is applied field), whereas the temperature dependence is weak and is almost constant at high temperatures. The temperature and field dependences are investigated on the basis of the spin-wave theory.

  7. Compositional dependence of bioactivity of glasses in the system Na2O-K2O-MgO-CaO-B2O3-P2O5-SiO2.

    PubMed

    Brink, M; Turunen, T; Happonen, R P; Yli-Urpo, A

    1997-10-01

    The bioactivity, i.e., bone-bonding ability, of 26 glasses in the system Na2O-K2O-MgO-CaO-B2O3-P2O5-SiO2 was studied in vivo. This investigation of bioactivity was performed to establish the compositional dependence of bioactivity, and enabled a model to be developed that describes the relation between reactions in vivo and glass composition. Reactions in vivo were investigated by inserting glass implants into rabbit tibia for 8 weeks. The glasses and the surrounding tissue were examined using scanning electron microscopy (SEM), light microscopy, and energy-dispersive X-ray analysis (EDXA). For most of the glasses containing < 59 mol % SiO2, SEM and EDXA showed two distinct layers at the glass surface after implantation, one silica-rich and another containing calcium phosphate. The build-up of these layers in vivo was taken as a sign of bioactivity. The in vivo experiments showed that glasses in the investigated system are bioactive when they contain 14-30 mol % alkali oxides, 14-30 mol % alkaline earth oxides, and < 59 mol % SiO2. Glasses containing potassium and magnesium bonded to bone in a similar way as bioactive glasses developed so far.

  8. Growth and characterization of electrodeposited Cu2O thin films

    NASA Astrophysics Data System (ADS)

    Laidoudi, S.; Bioud, A. Y.; Azizi, A.; Schmerber, G.; Bartringer, J.; Barre, S.; Dinia, A.

    2013-11-01

    This work demonstrates the electrodeposition of cuprous oxide (Cu2O) thin films onto a fluorine-doped tin oxide (FTO)-coated conducting glass substrates from Cu(II) sulfate solution with C6H8O7 chelating agent. During cyclic voltammetry experiences, the potential interval where the electrodeposition of Cu2O is carried out was established. The thin films were obtained potentiostatically and were characterized through different techniques. From the Mott-Schottky measurements, the flat-band potential and the acceptor density for the Cu2O thin films are determined. All the films showed a p-type semiconductor character with a carrier density varying between 2.41 × 1018 cm-3 and 5.38 × 1018 cm-3. This little difference is attributed to the increase of the stoichiometric defects in the films with the deposition potential. Atomic force microscopy analysis showed that the Cu2O thin films obtained at high potential are more homogenous in appearance and present lower crystallites size. X-ray diffraction measurements indicate a cubic structure with good crystallization state and the deposition potential was found to have an influence on the size of the crystallites. The optical measurements show a direct band gap between 2.07-2.49 eV depending on the applied potential.

  9. Neutron Studies of Tb2Mo2O7

    SciTech Connect

    Gardner, Jason; Ehlers, Georg; Diallo, Souleymane Omar

    2012-01-01

    We have used the new high energy resolution spectrometer (BaSiS), at the Spallation Neutron Source in Oak Ridge, to conclusively prove the existence of a low energy mode at 0.34(1) meV in the spin glass Tb{sub 2}Mo{sub 2}O{sub 7}. This mode is reminiscent of the excitation observed in the ordered phases of both Tb{sub 2}Ti{sub 2}O{sub 7} and Tb{sub 2}Sn{sub 2}O{sub 7}. The dynamical nature of the transition seen in the magnetization at {approx} 25 K suggests that this frustrated magnet shows a dynamic crossover between a high-temperature phase of poorly correlated, quickly relaxing spins to a low-temperature regime with much slower, short ranged spin correlations extending no further than to the next nearest neighbor. Existing theories explain the spin glass transition in terms of a phase transition and order parameters, and assume the existence of a distinct spin glass phase. There is no evidence for such a phase in Tb{sub 2}Mo{sub 2}O{sub 7}.

  10. High performance N2O4/amine elements blowapart

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Hypergolic earth-storable N2O4/Amine propellants are used for a wide range of liquid propulsion system applications. These propellants are highly reactive and can experience reactive stream separation (RSS, i.e., blowapart) which can inhibit intraelement mixing, hence reducing the overall spray mixture ratio and mass distribution, which can result in altered combustion efficiency, gas-side heat transfer coefficient, and stability. An experimental and analytical program was conducted to develop an understanding of the mechanisms controlling RSS. The program and product was development of design criteria for coping with RSS to allow the design of high performing, stable injectors. RSS mechanisms were identified using high speed color photography to observe reactive stream mixing of single element injectors tested with N2O4/MMH, N2O4/A-50, and N2O4/N2H4 propellants. The parametric characterization included modeling of the Space Shuttle Orbital Maneuvering System and Reaction Control System engine injectors.

  11. Recent progress in Ga2O3 power devices

    NASA Astrophysics Data System (ADS)

    Higashiwaki, Masataka; Sasaki, Kohei; Murakami, Hisashi; Kumagai, Yoshinao; Koukitu, Akinori; Kuramata, Akito; Masui, Takekazu; Yamakoshi, Shigenobu

    2016-03-01

    This is a review article on the current status and future prospects of the research and development on gallium oxide (Ga2O3) power devices. Ga2O3 possesses excellent material properties, in particular for power device applications. It is also attractive from an industrial viewpoint since large-size, high-quality wafers can be manufactured from a single-crystal bulk synthesized by melt-growth methods. These two features have drawn much attention to Ga2O3 as a new wide bandgap semiconductor following SiC and GaN. In this review, we describe the recent progress in the research and development on fundamental technologies of Ga2O3 devices, covering single-crystal bulk and wafer production, homoepitaxial thin film growth by molecular beam epitaxy and halide vapor phase epitaxy, as well as device processing and characterization of metal-semiconductor field-effect transistors, metal-oxide-semiconductor field-effect transistors and Schottky barrier diodes.

  12. Multidimentional Normal Mode Calculations for the OH Vibrational Spectra of (H_2O)_3^+, (H_2O)_3^+Ar, H^+(H_2O)_3, and H^+(H_2O)_3Ar

    NASA Astrophysics Data System (ADS)

    Li, Ying-Cheng; Chuang, Hsiao-Han; Tan, Jake Acedera; Takahashi, Kaito; Kuo, Jer-Lai

    2014-06-01

    Recent experimental observations of (H_2O)_3^+, (H_2O)_3^+Ar, H^+(H_2O)_3, and H^+(H_2O)_3Ar clusters in the region 1400-3800 wn show that the OH stretching vibration has distinct characteristics. Multidimensional normal mode calculations were carried out for OH stretching vibrations in the 1200-4000 wn photon energy range. The potential energy and dipole surfaces were evaluated by using first-principles methods. By comparing the calculated frequencies and intensities of OH stretching vibration with experimental spectra, we found that the assignment of OH strecthing of H_3O^+ moiety and free OH strectching vibration have resonable agreement with experimental data. Jeffrey M. Headrick, Eric G. Diken, Richard S. Walters, Nathan I. Hammer, Richard A. Christie, Jun Cui, Evgeniy M. Myshakin, Michael A. Duncan, Mark A. Johnson, Kenneth D. Jordan, Science, 2005, 17, 1765. Kenta Mizuse, Jer-Lai Kuo and Asuka Fujii, Chem. Sci., 2011, 2, 868 Kenta Mizuse and Asuka Fujii, J. Phys. Chem. A, 2013, 117, 929.

  13. Magnetic characterization of iron oxides formed after thermal treatment of nontronite and the formation of three polymorphs of Fe2O3: α-Fe2O3, γ-Fe2O3, ɛ-Fe2O3

    NASA Astrophysics Data System (ADS)

    Berquo, T. S.; Moskowitz, B. M.

    2011-12-01

    Nontronite is an Fe-rich smectite clay that occurs widely in terrestrial soils, sediments and weathering formations and may also be present in the Martian regolith. The thermal decomposition of nontronite is known to form various magnetic iron oxides but their compositions, magnetic properties, and formation pathways remain poorly understood. The magnetic alteration products of nontronite have been proposed as a source for the magnetic phases in the surface layers and dust on Mars as well as in some archeological fired-bricks and ceramic pottery. One alteration product of nontronite is ɛ-Fe2O3 which is ferrimagnetic with a Curie temperature of ~ 500 K and extremely large coercivity (HC ~ 1-2 T) at 300 K. In this work nontronite samples from eight source localities were heated to 1000°C in air for one hour. The magnetic properties of the alteration products were investigated with low-temperature (LT) magnetization and AC susceptibility curves, hysteresis loops, Mossbauer spectroscopy, and X-ray diffraction. The thermal treatment was effective in converting the nontronite to a combination of different polymorphs of ferric oxide depending on source locality and included: hematite (α-Fe2O3), ɛ-Fe2O3, and a cubic spinel phase that suggest the presence of maghemite (γ-Fe2O3). Mossbauer spectra at 300 K identified hematite and ɛ-Fe2O3 as the main phases in 7 samples with amounts ranging from 26-100% for hematite 0-69% for ɛ-Fe2O3. One sample showed a paramagnetic Fe3+ doublet and a broad sextet characteristic of magnetic relaxation effects. Upon cooling to 4.2 K, the Mossbauer spectrum was consistent with maghemite. In all samples except one, the magnetic hyperfine fields for the hematite phase are slightly reduced as compared with its stoichiometric form indicating some iron substitution with ions such as Al. This is consistent with the observation that all but one sample lacked the characteristic Morin transition for pure hematite on LT-remanence warming curves

  14. Temporal and latitudinal distributions of stratospheric N2O isotopomers

    NASA Astrophysics Data System (ADS)

    Toyoda, Sakae; Yoshida, Naohiro; Urabe, Taichiro; Nakayama, Yusuke; Suzuki, Takeshi; Tsuji, Kazuhide; Shibuya, Kazuhiko; Aoki, Shuji; Nakazawa, Takakiyo; Ishidoya, Shigeyuki; Ishijima, Kentaro; Sugawara, Satoshi; Machida, Toshinobu; Hashida, Gen; Morimoto, Shinji; Honda, Hideyuki

    2004-04-01

    Temporal and latitudinal variations of vertical profiles of N2O isotopomers were observed in the stratosphere over Japan (39°N, 142°E), Sweden (68°N, 20°E), and Antarctica (69°N, 40°E) during the period between 1990 and 2001. Samples were collected with a balloon-borne cryogenic sampler and analyzed by mass spectrometry in the laboratory. Observed enrichment factors for heavier isotopomers (15N14N16O, 14N15N16O, and 14N14N18O) relative to 14N14N16O were nearly constant in the lower stratosphere (less than ˜22 km) but increased at higher altitudes (˜22-35 km) while showing seasonal and latitudinal differences. Enrichment factors during the photolysis and photo-oxidation of N2O were also obtained in laboratory experiments and compared with those observed. We found that in the higher-altitude region (1) fractionation of the isotopomers is mainly determined by photolysis, but is also affected by physical processes, (2) subsidence of air masses in the winter polar vortex induces the intrusion of an upper stratospheric air mass depleted in N2O, and (3) decay of the vortex in the local spring leads to rapid horizontal advection of midlatitude air masses. At lower altitudes, isotopomer ratios are determined by photolysis, photo-oxidation, and the mixing of air masses within the stratosphere or between the stratosphere and the troposphere. Secular trend of isotopomer profiles was not detectable over Japan during 11 years. Assuming that the lower stratospheric air over midlatitudes is exchanged with the troposphere, isotopomer ratios of the N2O "back-flux" from the stratosphere were estimated. These values can be used in the isotopomeric mass balance model to constrain the global N2O budget.

  15. Phase evolution of Na2O-Al2O3-SiO2-H2O gels in synthetic aluminosilicate binders.

    PubMed

    Walkley, Brant; San Nicolas, Rackel; Sani, Marc-Antoine; Gehman, John D; van Deventer, Jannie S J; Provis, John L

    2016-04-01

    This study demonstrates the production of stoichiometrically controlled alkali-aluminosilicate gels ('geopolymers') via alkali-activation of high-purity synthetic amorphous aluminosilicate powders. This method provides for the first time a process by which the chemistry of aluminosilicate-based cementitious materials may be accurately simulated by pure synthetic systems, allowing elucidation of physicochemical phenomena controlling alkali-aluminosilicate gel formation which has until now been impeded by the inability to isolate and control key variables. Phase evolution and nanostructural development of these materials are examined using advanced characterisation techniques, including solid state MAS NMR spectroscopy probing (29)Si, (27)Al and (23)Na nuclei. Gel stoichiometry and the reaction kinetics which control phase evolution are shown to be strongly dependent on the chemical composition of the reaction mix, while the main reaction product is a Na2O-Al2O3-SiO2-H2O type gel comprised of aluminium and silicon tetrahedra linked via oxygen bridges, with sodium taking on a charge balancing function. The alkali-aluminosilicate gels produced in this study constitute a chemically simplified model system which provides a novel research tool for the study of phase evolution and microstructural development in these systems. Novel insight of physicochemical phenomena governing geopolymer gel formation suggests that intricate control over time-dependent geopolymer physical properties can be attained through a careful precursor mix design. Chemical composition of the main N-A-S-H type gel reaction product as well as the reaction kinetics governing its formation are closely related to the Si/Al ratio of the precursor, with increased Al content leading to an increased rate of reaction and a decreased Si/Al ratio in the N-A-S-H type gel. This has significant implications for geopolymer mix design for industrial applications. PMID:26911317

  16. Phase evolution of Na2O-Al2O3-SiO2-H2O gels in synthetic aluminosilicate binders.

    PubMed

    Walkley, Brant; San Nicolas, Rackel; Sani, Marc-Antoine; Gehman, John D; van Deventer, Jannie S J; Provis, John L

    2016-04-01

    This study demonstrates the production of stoichiometrically controlled alkali-aluminosilicate gels ('geopolymers') via alkali-activation of high-purity synthetic amorphous aluminosilicate powders. This method provides for the first time a process by which the chemistry of aluminosilicate-based cementitious materials may be accurately simulated by pure synthetic systems, allowing elucidation of physicochemical phenomena controlling alkali-aluminosilicate gel formation which has until now been impeded by the inability to isolate and control key variables. Phase evolution and nanostructural development of these materials are examined using advanced characterisation techniques, including solid state MAS NMR spectroscopy probing (29)Si, (27)Al and (23)Na nuclei. Gel stoichiometry and the reaction kinetics which control phase evolution are shown to be strongly dependent on the chemical composition of the reaction mix, while the main reaction product is a Na2O-Al2O3-SiO2-H2O type gel comprised of aluminium and silicon tetrahedra linked via oxygen bridges, with sodium taking on a charge balancing function. The alkali-aluminosilicate gels produced in this study constitute a chemically simplified model system which provides a novel research tool for the study of phase evolution and microstructural development in these systems. Novel insight of physicochemical phenomena governing geopolymer gel formation suggests that intricate control over time-dependent geopolymer physical properties can be attained through a careful precursor mix design. Chemical composition of the main N-A-S-H type gel reaction product as well as the reaction kinetics governing its formation are closely related to the Si/Al ratio of the precursor, with increased Al content leading to an increased rate of reaction and a decreased Si/Al ratio in the N-A-S-H type gel. This has significant implications for geopolymer mix design for industrial applications.

  17. Impedance spectroscopy study of SiO2-Li2O:Nd2O3 glasses

    SciTech Connect

    Pereia, R.; Gozzo, C B; Guedes, I.; Boatner, Lynn A; Terezo, A J; Costa, M M

    2014-01-01

    In the present study, neodymium-doped lithium silicate glasses have been prepared by the conventional melt-quenching technique. The dielectric properties, electric modulus and electrical conductivity of SiO2-Li2O (SiLi-0Nd) and SiO2-Li2O:Nd2O3 (SiLi-1.35Nd) have been studied from 1 Hz to 1 MHz in the 333 423 K temperature range. At a given temperature and frequency, we observe that the resistivity increases while the conductivity accordingly decreases when neodymium ions are added to the glass matrix. The activation energy of two distinct regions was evaluated from the ln( dc)=f(1/T) plot and was found to be E1(T<363K)=0.61(0.66)eV and E2(T>363K)=1.26(1.09)eV for SiLi-0Nd (SiLi-1,35Nd). The dielectric constant ( Re) decreases while the dielectric loss (tan ( )) increases under Nd2O3 doping. We also observe that for both glasses, Re and tan ( ) tend to increase with increasing temperature and decrease with increasing frequency.

  18. Aqueous chemical growth of alpha-Fe2O3-alpha-Cr2O3 nanocomposite thin films.

    PubMed

    Vayssieres, L; Guo, J; Nordgren, J

    2001-12-01

    We are reporting here on the inexpensive fabrication and optical properties of an iron(III) oxide-chromium(III) oxide nanocomposite thin film of corundum crystal structure. Its novel and unique-designed architecture consists of uniformed, well-defined and oriented nanorods of Hematite (alpha-Fe2O3) of 50 nm in diameter and 500 nm in length and homogeneously distributed nonaggregated monodisperse spherical nanoparticles of Eskolaite (alpha-Cr2O3) of 250 nm in diameter. This alpha-Fe2O3-alpha-Cr2O3 nanocomposite thin film is obtained by growing, directly onto transparent polycrystalline conducting substrate, an oriented layer of hematite nanorods and growing subsequently, the eskolaite layer. The synthesis is carried out by a template-free, low-temperature, multilayer thin film coating process using aqueous solution of metal salts as precursors. Almost 100% of the light is absorbed by the composite film between 300 and 525 nm and 40% at 800 nm which yields great expectations as photoanode materials for photovoltaic cells and photocatalytic devices. PMID:12914078

  19. Oxidative degradation of endotoxin by advanced oxidation process (O3/H2O2 & UV/H2O2).

    PubMed

    Oh, Byung-Taek; Seo, Young-Suk; Sudhakar, Dega; Choe, Ji-Hyun; Lee, Sang-Myeong; Park, Youn-Jong; Cho, Min

    2014-08-30

    The presence of endotoxin in water environments may pose a serious public health hazard. We investigated the effectiveness of advanced oxidative processes (AOP: O3/H2O2 and UV/H2O2) in the oxidative degradation of endotoxin. In addition, we measured the release of endotoxin from Escherichia coli following typical disinfection methods, such as chlorine, ozone alone and UV, and compared it with the use of AOPs. Finally, we tested the AOP-treated samples in their ability to induce tumor necrosis factor alpha (TNF-α) in mouse peritoneal macrophages. The production of hydroxyl radical in AOPs showed superior ability to degrade endotoxin in buffered solution, as well as water samples from Korean water treatment facilities, with the ozone/H2O2 being more efficient compared to UV/H2O2. In addition, the AOPs proved effective not only in eliminating E. coli in the samples, but also in endotoxin degradation, while the standard disinfection methods lead to the release of endotoxin following the bacteria destruction. Furthermore, in the experiments with macrophages, the AOPs-deactivated endotoxin lead to the smallest induction of TNF-α, which shows the loss of inflammation activity, compared to ozone treatment alone. In conclusion, these results suggest that AOPs offer an effective and mild method for endotoxin degradation in the water systems.

  20. The influence of Cu2O crystal structure on the Cu2O/ZnO heterojunction photovoltaic performance

    NASA Astrophysics Data System (ADS)

    Elfadill, Nezar G.; Hashim, M. R.; Chahrour, Khaled M.; Qaeed, M. A.; Bououdina, M.

    2015-09-01

    Cuprous oxide (Cu2O) films were potentiostatically electrodeposited onto platinum (Pt) film coated onto silicon (Si) wafer from lactic solution at pH 9. The influence of applied potential on Cu2O crystal structure was carefully examined. At higher electrochemical applied potential, a polycrystalline structure was observed, and then as the applied potential decreased, a single crystalline structure oriented along (1 1 1) was obtained. Further decrease in the applied potential leads to the formation of a polycrystalline structure and finally at much lower applied potential, a single crystalline structure growing along (2 0 0) orientation (equivalent to (1 0 0) orientation) was revealed. Cu2O/ZnO heterojunction photodiodes based on these three crystal structures were fabricated and studied under dark and illuminated conditions. The best performance of the solar cell efficiency was achieved by the heterojunction based on (1 1 1) oriented Cu2O film (≈1.45%) compared to other structures (0.34% and 0.25%), which may be attributed to the formation of high quality heterojunction interface due to the heteroepitaxial-like growth of (0 0 2) oriented ZnO.

  1. Negative thermal expansion and local dynamics in Cu{sub 2}O and Ag{sub 2}O

    SciTech Connect

    Sanson, A.; Rocca, F.; Dalba, G.; Fornasini, P.; Grisenti, R.; Dapiaggi, M.; Artioli, G.

    2006-06-01

    High-resolution x-ray powder diffraction and extended x-ray-absorption fine-structure (EXAFS) measurements have been performed on the iso-structural framework crystals Cu{sub 2}O and Ag{sub 2}O as a function of temperature. According to diffraction, both compounds exhibit a negative thermal expansion (NTE) of the lattice parameter over extended temperature intervals (from 9 to 240 K for Cu{sub 2}O, up to 470 K for Ag{sub 2}O) and anisotropic thermal displacements of M atoms (M=Cu,Ag). EXAFS measures a positive expansion of the nearest-neighbors M-O pair distance and a perpendicular to parallel anisotropy of relative motion, much stronger than the anisotropy of the absolute M motion. The M-O bond is much stiffer against stretching than against bending. According to EXAFS, out of the 12 M-M next-nearest-neighbor pairs, the 6 connected via a bridging oxygen undergo negative expansion, while the 6 lacking the bridging oxygen undergo positive expansion. These results show a rather complex local behavior, which, while confirming the connection of NTE to strong perpendicular vibrations, is inconsistent with rigid unit modes models and suggests a more flexible model based on rigid M-O rods.

  2. Synthesis and characterization of magnetic diphase ZnFe2O4 /γ-Fe2O3 electrospun fibers

    PubMed Central

    Arias, M.; Pantojas, V.M.; Perales, O.; Otaño, W.

    2011-01-01

    Magnetic nanofibers of ZnFe2O4 / γ-Fe2O3 composite were synthesized by electrospinning from a sol-gel solution containing a molar ratio Fe/Zn of 3. The effects of the calcination temperature on the phase composition, particle size and magnetic properties have been investigated. Zinc ferrite fibers were obtained by calcinating the electrospun fibers in air from 300 °C to 800 °C and characterized by thermogravimetric analyses, Fourier transformed infrared spectroscopy, x-ray photoemission spectroscopy, x-ray diffraction, vibration sample magnetometry and magnetic force microscopy. The resulting fibers, with diameters ranging from 90 to 150 nm, were ferrimagnetic with high saturation magnetization as compared to bulk. Increasing the calcination temperature resulted in an increase in particle size and saturation magnetization. The observed increase in saturation magnetization was most likely due to the formation and growth of ZnFe2O4 /γ-Fe2O3 diphase crystals. The highest saturation magnetization (45 emu/g) was obtained for fibers calcined at 800 °C. PMID:21779141

  3. Electronic structure of the kagome staircase compounds Ni3V2O8 and Co3V2O8

    NASA Astrophysics Data System (ADS)

    Laverock, J.; Chen, B.; Preston, A. R. H.; Smith, K. E.; Wilson, N. R.; Balakrishnan, G.; Glans, P.-A.; Guo, J.-H.

    2013-03-01

    The electronic structure of the kagome staircase compounds, Ni3V2O8 and Co3V2O8, has been investigated using soft x-ray absorption, soft x-ray emission, and resonant inelastic x-ray scattering. Comparison between the two compounds, and with first-principles band structure calculations and crystal-field multiplet models, provides unique insight into the electronic structure of the two materials. Whereas the location of the narrow (Ni,Co) d bands is predicted to be close to EF, we experimentally find they lie deeper in the occupied O 2p and unoccupied V 3d manifolds, and determine their energy via measured charge-transfer excitations. Additionally, we find evidence for a dd excitation at 1.5 eV in Ni3V2O8, suggesting the V d states may be weakly occupied in this compound, contrary to Co3V2O8. Good agreement is found between the crystal-field dd excitations observed in the experiment and those predicted by atomic multiplet theory.

  4. Transparent athermal glass-ceramics in Li2O-Al2O3-SiO2 system

    NASA Astrophysics Data System (ADS)

    Himei, Yusuke; Nagakane, Tomohiro; Sakamoto, Akihiko; Kitamura, Naoyuki; Fukumi, Kohei; Nishii, Junji; Hirao, Kazuyuki

    2005-04-01

    An attempt has been conducted to develop multicomponent transparent glass-ceramics which have athermal property better than silica glass. Transparent Li2O-Al2O3-SiO2 (LAS) glass-ceramics with small thermal expansion coefficient was chosen as a candidate. Athermal property of the glass-ceramics was improved by the independent control of temperature coefficients of electronic polarizability and thermal expansion coefficient, both of which govern the temperature coefficient of optical path length. It was found that temperature coefficient of electronic polarizability and thermal expansion coefficient of the LAS glass-ceramics were controllable by the additives and crystallization conditions. The doping of B2O3 and the crystallization under a hydrostatic pressure of 196 MPa were very effective to reduce temperature coefficient of electronic polarizability without a remarkable increase in thermal expansion coefficient. It was deduced that the reduction in temperature coefficient of electronic polarizability by the crystallization under 196 MPa resulted from the inhibition of the precipitation of beta-spodumene solid solution. The relative temperature coefficients of optical path length of B2O3-doped glass-ceramic crystallized under 196 MPa was 11.7 x 10-6/°C, which was slightly larger than that of silica glass. Nevertheless, the thermal expansion coefficient of this glass-ceramic was smaller than that of silica glass.

  5. Silicate-H2O Systems at High Pressure Conditions

    NASA Astrophysics Data System (ADS)

    Tailby, N.; Mavrogenes, J. A.; Hermann, J.; O'Neill, H. S.

    2008-12-01

    Since the discovery of the second critical endpoint (CP2) in the albite-water system, numerous attempts have been made to determine the pressure and temperature of this CP2 and the mutual solubilities within more complex systems. The P-T position of the CP2 has been estimated for many systems: SiO2 (<10 kb/900 °C, Newton and Manning, 2008); NaAlSi3O8 (15 kb/800 °C, Burnham and Davis, 1974; Shen and Keppler, 1997); Pelite (50 kb/1,000 °C, Schmidt et al., 2004), basalt (50 kb/ 1000 °C, Kessel et al., 2004), Peridotite (38 kb/1000 °C, Mibe et al., 2007). A number of experimental techniques have been used to determine phase relations and H2O solubility in experiments. These include in-situ experimental techniques (e.g., HYDAC; Shen and Keppler, 1997), fluid trap techniques (e.g., diamond traps; Stalder et al., 2000), and single crystal weight-loss techniques (e.g., SiO2-H2O techniques employed by Newton and Manning, 2008). None of these techniques is without difficulties, as H2O rich experiments need to overcome huge retrograde fluid solubilities upon quench in order to determine mutual solubilities at experimental conditions. We have developed a new technique to determine "rock"-H2O relationships at high-P conditions, with particular focus on the shape and locus of solvi in pressure temperature space. In this series of experiments, an oxygen fugacity buffer (Re-ReO2) and a sliding H-fugacity sensor (NiO-Ni-Pd mixture) are combined to monitor H2O activity over the entire range of pressure and temperature. Unlike other techniques, the use of sensor capsules does not require textural interpretation of experiments. H2O activity is related to oxygen and hydrogen fugacity by the reaction: H2O = H2 + ½O2 NiO-Ni-Pd mixtures were placed within a ZrO2 jacket and sealed within a welded 2.3 mm Pt capsule. This 2.3 mm Pt sensor capsule was then encased within a larger, thick walled 6 mm diameter Ag capsule. Pelite-H2O mixtures and oxygen buffers were held within this larger

  6. Keggin polyoxoanion supported organic-inorganic trinuclear lutetium cluster, {Na(H2O)3[Lu(pydc)(H2O)3]3}[SiW12O40]·26.5H2O.

    PubMed

    Li, Suzhi; Zhang, Dongdi; Guo, Yuan Yuan; Ma, Pengtao; Qiu, Xiaoyang; Wang, Jingping; Niu, Jingyang

    2012-09-01

    A novel strawberry-like organic-inorganic hybrid, {Na(H(2)O)(3)[Lu(pydc)(H(2)O)(3)](3)}[SiW(12)O(40)]·26.5H(2)O (H(2)pydc = pyridine-2,6-dicarboxylate) containing an intriguing trinuclear lutetium cluster {Na(H(2)O)(3)[Lu(pydc)(H(2)O)(3)](3)}(4+) has been synthesized and its luminescent properties, IR, UV, TG, PXRD analyses and single crystal X-ray diffraction were investigated.

  7. Vibrational investigations of CO2-H2O, CO2-(H2O)2, and (CO2)2-H2O complexes isolated in solid neon

    NASA Astrophysics Data System (ADS)

    Soulard, P.; Tremblay, B.

    2015-12-01

    The van der Waals complex of H2O with CO2 has attracted considerable theoretical interest as a typical example of a weak binding complex with a dissociation energy less than 3 kcal/mol. Up to now, experimental vibrational data are sparse. We have studied by FTIR the complexes involving CO2 and water molecules in solid neon. Many new absorption bands close to the well known monomers fundamentals give evidence for at least three (CO2)n-(H2O)m complexes, noted n:m. Concentration effects combined with a detailed vibrational analysis allow for the identification of sixteen, twelve, and five transitions for the 1:1, 1:2, and 2:1 complexes, respectively. Careful examination of the far infrared spectral region allows the assignment of several 1:1 and 1:2 intermolecular modes, confirmed by the observation of combinations of intra + intermolecular transitions, and anharmonic coupling constants have been derived. Our results demonstrate the high sensibility of the solid neon isolation to investigate the hydrogen-bonded complexes in contrast with the gas phase experiments for which two quanta transitions cannot be easily observed.

  8. Vibrational investigations of CO2-H2O, CO2-(H2O)2, and (CO2)2-H2O complexes isolated in solid neon.

    PubMed

    Soulard, P; Tremblay, B

    2015-12-14

    The van der Waals complex of H2O with CO2 has attracted considerable theoretical interest as a typical example of a weak binding complex with a dissociation energy less than 3 kcal/mol. Up to now, experimental vibrational data are sparse. We have studied by FTIR the complexes involving CO2 and water molecules in solid neon. Many new absorption bands close to the well known monomers fundamentals give evidence for at least three (CO2)n-(H2O)m complexes, noted n:m. Concentration effects combined with a detailed vibrational analysis allow for the identification of sixteen, twelve, and five transitions for the 1:1, 1:2, and 2:1 complexes, respectively. Careful examination of the far infrared spectral region allows the assignment of several 1:1 and 1:2 intermolecular modes, confirmed by the observation of combinations of intra + intermolecular transitions, and anharmonic coupling constants have been derived. Our results demonstrate the high sensibility of the solid neon isolation to investigate the hydrogen-bonded complexes in contrast with the gas phase experiments for which two quanta transitions cannot be easily observed. PMID:26671379

  9. Vibrational investigations of CO2-H2O, CO2-(H2O)2, and (CO2)2-H2O complexes isolated in solid neon.

    PubMed

    Soulard, P; Tremblay, B

    2015-12-14

    The van der Waals complex of H2O with CO2 has attracted considerable theoretical interest as a typical example of a weak binding complex with a dissociation energy less than 3 kcal/mol. Up to now, experimental vibrational data are sparse. We have studied by FTIR the complexes involving CO2 and water molecules in solid neon. Many new absorption bands close to the well known monomers fundamentals give evidence for at least three (CO2)n-(H2O)m complexes, noted n:m. Concentration effects combined with a detailed vibrational analysis allow for the identification of sixteen, twelve, and five transitions for the 1:1, 1:2, and 2:1 complexes, respectively. Careful examination of the far infrared spectral region allows the assignment of several 1:1 and 1:2 intermolecular modes, confirmed by the observation of combinations of intra + intermolecular transitions, and anharmonic coupling constants have been derived. Our results demonstrate the high sensibility of the solid neon isolation to investigate the hydrogen-bonded complexes in contrast with the gas phase experiments for which two quanta transitions cannot be easily observed.

  10. CaO--P2O5--Na2O-based sintering additives for hydroxyapatite (HAp) ceramics.

    PubMed

    Kalita, S J; Bose, S; Hosick, H L; Bandyopadhyay, A

    2004-05-01

    We have assessed the effect of CaO--P2O5--Na2O-based sintering additives on mechanical and biological properties of hydroxyapatite (HAp) ceramics. Five different compositions of sintering additives were selected and prepared by mixing of CaO, P2O5, and Na2CO3 powders. 2.5 wt% of each additive was combined with commercial HAp powder, separately, followed by ball milling, and sintering at 1250 degrees C and 1300 degrees C in a muffle furnace. Green and sintered densities of the compacts were analyzed for the influence of additives on densification of HAp. Phase analyses were carried out using an X-ray diffractometer. Vickers microhardness testing was used to evaluate hardness of sintered compacts of different compositions. A maximum microhardness of 4.6 (+/- 0.28) GPa was attained for a composition with 2.5 wt% addition of CaO:P2O5:Na2O in the ratio of 3:3:4. Results from mechanical property evaluation showed that some of these sintering additives improved failure strength of HAp under compressive loading. Maximum compressive strength was observed for samples with 2.5 wt% addition of CaO. Average failure strength for this set of samples was calculated to be 220 (+/- 50) MPa. Cytotoxicity, and cell attachment studies were carried out using a modified human osteoblast cell line called OPC-1. In vitro results showed that these compositions were non-toxic. Some sintering aids enhanced cell attachment and proliferation, which was revealed from SEM examination of the scaffolds seeded with OPC-1 cells. PMID:14741598

  11. Structural properties of Y2O3–Al2O3 liquids and glasses: An overview

    SciTech Connect

    Wilding, Martin C.; Wilson, Mark; McMillan, Paul F.; Benmore, Chris J.; Weber, J. K.R.; Deschamps, Thierry; Champagnon, Bernard

    2015-01-01

    Liquids in the system Y2O3- Al2O3 have been the subject of considerable study because of the reported occurrence of a first-order density and entropy-driven liquid-liquid phase transition (LLPT) in the supercooled liquid state. The observations have become controversial because of the presence of crystalline material that can be formed simultaneously and that can mask the nucleation and growth of the lower density liquid. The previous work is summarized here along with arguments for and against the different viewpoints. Also two studies have been undertaken to investigate the LLPT in this refractory system with emphasis on determining the structure of unequivocally amorphous materials. These include the in situ high energy X-ray diffraction (HEXRD) of supercooled Y2O3 - Al2O3 liquids and the low frequency vibrational dynamics of recovered glasses. Manybody molecular dynamics simulations are also used to interpret the results of both studies. The HEXRD measurements, combined with aerodynamic levitation and rapid data acquisition techniques, show that for the 20 mol% Y2O3 (i.e. AlY20) liquid there is a shift in the position of the first peak in the diffraction pattern over a narrow temperature range (2100-1800 K) prior to crystallization. Microbeam Raman spectroscopy measurements made on AlY20 glasses clearly show contrasting spectra in the low frequency part of the spectrum for low(LDA) and high-density (HDA) glassy regions. The molecular dynamics simulations identify contrasting coordination environments around oxygen anions for the high- (HDL) and low-density (LDL) liquids. (C) 2014 Elsevier B.V. All rights reserved.

  12. LiOH - H2O2 - H2O trinary system study for the selection of optimal conditions of lithium peroxide synthesis

    NASA Astrophysics Data System (ADS)

    Nefedov, R. A.; Ferapontov, Yu A.; Kozlova, N. P.

    2016-01-01

    Using solubility method the decay kinetics of peroxide products contained in liquid phase of LiOH - H2O2 - H2O trinary system with 2 to 6% by wt hydrogen peroxide content in liquid phase in 21 to 33 °C temperature range has been studied. Conducted studies have allowed to determine temperature and concentration limits of solid phase existence of Li2O2·H2O content, distinctness of which has been confirmed using chemical and qualitative X- ray phase analysis. Stabilizing effect of solid phase of Li2O2·H2O content on hydrogen peroxide decay contained in liquid phase of LiOH - H2O2 - H2O trinary system under conditions of experiments conducted has been shown.

  13. High-Efficiency Cu2O-Based Heterojunction Solar Cells Fabricated Using a Ga2O3 Thin Film as N-Type Layer

    NASA Astrophysics Data System (ADS)

    Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

    2013-04-01

    High-efficiency heterojunction solar cells consisting of a nondoped Ga2O3 thin film as an n-type semiconductor layer and a p-type Cu2O sheet as the active layer as well as the substrate, prepared by thermally oxidizing a Cu sheet, are demonstrated. The use of an n-type Ga2O3 thin film can greatly improve the performance of n-Ga2O3/p-Cu2O heterojunction solar cells. The highest efficiency of 5.38% was obtained in an Al-doped ZnO/Ga2O3/Cu2O heterojunction solar cell fabricated with an n-Ga2O3 thin-film layer prepared at room temperature with a thickness of 75 nm by a pulsed laser deposition method.

  14. Microstructural Characterization and Strengthening-Toughening Mechanism of Plasma-Sprayed Al2O3-Cr2O3 Composite Coatings

    NASA Astrophysics Data System (ADS)

    Yang, Kai; Feng, Jingwei; Zhou, Xiaming; Tao, Shunyan

    2012-09-01

    In this study, Al2O3, Cr2O3, and Al2O3-Cr2O3 coatings were fabricated by plasma spraying. X-ray diffraction was employed to determine the phase composition of powders and coatings. The morphologies and microstructures of the coatings were characterized using electron probe microanalyzer and transmission electron microscopy. Vickers hardness, fracture toughness, and bending strength of the coatings were measured. Al2O3-Cr2O3 composite coatings show better comprehensive mechanical properties than the individual Al2O3 and Cr2O3 coatings, which are attributed to the former's larger intersplat adhesion or interlamellar cohesion and lower porosity. Solid solution strengthens the phase interfaces and grain boundaries, which is beneficial to improve the mechanical performance of the composite coatings.

  15. New observations of stratospheric N2O5

    NASA Technical Reports Server (NTRS)

    Rinsland, C. P.; Toon, G. C.; Farmer, C. B.; Norton, R. H.; Namkung, J. S.

    1989-01-01

    The unequivocal detection of N2O5 in the stratosphere was reported by Toon et al. based on measurements of the absorption by the N2O5 bands at 1246 and 1720/cm in solar occulation spectra recorded at sunrise near 47 S latitude by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment during the Spacelab 3 (SL3) shuttle mission. Additional measurements and analysis of stratospheric N2O5 derived from the ATMOS/SL3 spectra are reported. The primary results are the detection and measurement of N2O5 absorption at sunset in the lower stratosphere, the inversion of a precise (approximately 10 percent) N2O5 sunrise vertical distribution between 25.5 and 37.5 km altitude, and the identification and measurement of absorption by the N2O5 743/cm band at sunrise. Assuming 4.32 x 10(sup -17) and 4.36 x 10(sup -17)/cm/molecule/sq cm respectively for the integrated intensities of the 1246 and 743/cm bands at stratospheric temperatures, retrieved volume mixing ratios in parts per billion by volume (ppbv) at sunrise (47 S latitude) are 1.32 + or - 0.34 at 37.5 km, 1.53 + or - 0.35 at 35.5 km, 1.63 + or - 0.36 at 33.5 km, 1.60 + or - 0.34 at 31.5 km, 1.43 + or - 0.30 at 29.5 km, 1.15 + or - 0.24 at 27.5 km, and 0.73 + or - 0.15 at 25.5 km. Retrieved VMRs in ppbv at sunset (30 N latitude) are 0.13 + or - 0.05 at 29.5 km, 0.14 + or - 0.05 at 27.5 km, and 0.10 + or - 0.04 at 25.5 km. Quoted error limits (1 sigma) include the error in the assumed band intensities (approximately 20 percent). Within the error limits of the measurements, the inferred mixing ratios at sunrise agree with diurnal photochemical model predictions obtained by two groups using current photochemical data. The measured mixing ratios at sunset are lower than the model predictions with differences of about a factor of 2 at 25 km altitude.

  16. Global and regional emissions estimates for N2O

    NASA Astrophysics Data System (ADS)

    Saikawa, E.; Prinn, R. G.; Dlugokencky, E.; Ishijima, K.; Dutton, G. S.; Hall, B. D.; Langenfelds, R.; Tohjima, Y.; Machida, T.; Manizza, M.; Rigby, M.; O'Doherty, S.; Patra, P. K.; Harth, C. M.; Weiss, R. F.; Krummel, P. B.; van der Schoot, M.; Fraser, P. B.; Steele, L. P.; Aoki, S.; Nakazawa, T.; Elkins, J. W.

    2013-07-01

    We present a comprehensive estimate of nitrous oxide ( N2O) emissions using observations and models from 1995 to 2008. High-frequency records of tropospheric N2O are available from measurements at Cape Grim, Tasmania; Cape Matatula, American Samoa; Ragged Point, Barbados; Mace Head, Ireland; and at Trinidad Head, California using the Advanced Global Atmospheric Gases Experiment (AGAGE) instrumentation and calibrations. The Global Monitoring Division of the National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL) has also discrete air samples collected in flasks and in situ measurements from remote sites across the globe and analyzed them for a suite of species including N2O. In addition to these major networks, we include in situ and aircraft measurements from the National Institute for Environmental Studies (NIES) and flask measurements from the Tohoku University and Commonwealth Scientific and Industrial Research Organization (CSIRO) networks. All measurements show increasing atmospheric mole fractions of N2O, with a varying growth rate of 0.1-0.7 % yr-1, resulting in a 7.4% increase in the background atmospheric mole fraction between 1979 and 2011. Using existing emission inventories as well as bottom-up process modeling results, we first create globally-gridded a priori N2O emissions over the 37 yr since 1975. We then use the three-dimensional chemical transport model, Model for Ozone and Related Chemical Tracers version 4 (MOZART v4), and a Bayesian inverse method to estimate global as well as regional annual emissions for five source sectors from 13 regions in the world. This is the first time that all of these measurements from multiple networks have been combined to determine emissions. Our inversion indicates that global and regional N2O emissions have an increasing trend between 1995 and 2008. Despite large uncertainties, a significant increase is seen from the Asian agricultural sector in the recent years, most likely

  17. Global and regional emissions estimates for N2O

    NASA Astrophysics Data System (ADS)

    Saikawa, E.; Prinn, R. G.; Dlugokencky, E. J.; Ishijima, K.; Dutton, G. S.; Hall, B. D.; Langenfelds, R.; Tohjima, Y.; Machida, T.; Manizza, M.; Rigby, M. L.; Odoherty, S. J.; Patra, P. K.; Harth, C.; Weiss, R. F.; Krummel, P. B.; van der Schoot, M.; Fraser, P.; Steele, P.; Aoki, S.; Nakazawa, T.; Elkins, J. W.

    2013-12-01

    We present a comprehensive estimate of nitrous oxide (N2O) emissions using observations and models from 1995 to 2008. High-frequency records of tropospheric N2O are available from measurements at Cape Grim, Tasmania; Cape Matatula, American Samoa; Ragged Point, Barbados; Mace Head, Ireland; and at Trinidad Head, California using the Advanced Global Atmospheric Gases Experiment (AGAGE) instrumentation and calibrations. The Global Monitoring Division of the National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL) has also discrete air samples collected in flasks and in situ measurements from remote sites across the globe and analyzed them for a suite of species including N2O. In addition to these major networks, we include in situ and aircraft measurements from the National Institute for Environmental Studies (NIES) and flask measurements from the Tohoku University and Commonwealth Scientific and Industrial Research Organization (CSIRO) networks. All measurements show increasing atmospheric mole fractions of N2O, with a varying growth rate of 0.1-0.7%yr-1, resulting in a 7.4% increase in the background atmospheric mole fraction between 1979 and 2011. Using existing emission inventories as well as bottom-up process modeling results, we first create globally-gridded a priori N2O emissions over the 37 yr since 1975. We then use the three-dimensional chemical transport model, Model for Ozone and Related Chemical Tracers version 4 (MOZART v4), and a Bayesian inverse method to estimate global as well as regional annual emissions for five source sectors from 13 regions in the world. This is the first time that all of these measurements from multiple networks have been combined to determine emissions. Our inversion indicates that global and regional N2O emissions have an increasing trend between 1995 and 2008. Despite large uncertainties, a significant increase is seen from the Asian agricultural sector in the recent years, most likely due

  18. Global and regional emissions estimates for N2O

    NASA Astrophysics Data System (ADS)

    Saikawa, E.; Prinn, R. G.; Dlugokencky, E.; Ishijima, K.; Dutton, G. S.; Hall, B. D.; Langenfelds, R.; Tohjima, Y.; Machida, T.; Manizza, M.; Rigby, M.; O'Doherty, S.; Patra, P. K.; Harth, C. M.; Weiss, R. F.; Krummel, P. B.; van der Schoot, M.; Fraser, P. J.; Steele, L. P.; Aoki, S.; Nakazawa, T.; Elkins, J. W.

    2014-05-01

    We present a comprehensive estimate of nitrous oxide (N2O) emissions using observations and models from 1995 to 2008. High-frequency records of tropospheric N2O are available from measurements at Cape Grim, Tasmania; Cape Matatula, American Samoa; Ragged Point, Barbados; Mace Head, Ireland; and at Trinidad Head, California using the Advanced Global Atmospheric Gases Experiment (AGAGE) instrumentation and calibrations. The Global Monitoring Division of the National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL) has also collected discrete air samples in flasks and in situ measurements from remote sites across the globe and analyzed them for a suite of species including N2O. In addition to these major networks, we include in situ and aircraft measurements from the National Institute of Environmental Studies (NIES) and flask measurements from the Tohoku University and Commonwealth Scientific and Industrial Research Organization (CSIRO) networks. All measurements show increasing atmospheric mole fractions of N2O, with a varying growth rate of 0.1-0.7% per year, resulting in a 7.4% increase in the background atmospheric mole fraction between 1979 and 2011. Using existing emission inventories as well as bottom-up process modeling results, we first create globally gridded a priori N2O emissions over the 37 years since 1975. We then use the three-dimensional chemical transport model, Model for Ozone and Related Chemical Tracers version 4 (MOZART v4), and a Bayesian inverse method to estimate global as well as regional annual emissions for five source sectors from 13 regions in the world. This is the first time that all of these measurements from multiple networks have been combined to determine emissions. Our inversion indicates that global and regional N2O emissions have an increasing trend between 1995 and 2008. Despite large uncertainties, a significant increase is seen from the Asian agricultural sector in recent years, most likely

  19. Crystalline and amorphous H2O on Charon

    NASA Astrophysics Data System (ADS)

    Dalle Ore, Cristina M.; Cruikshank, Dale P.; Grundy, Will M.; Ennico, Kimberly; Olkin, Catherine B.; Stern, S. Alan; Young, Leslie A.; Weaver, Harold A.

    2015-11-01

    Charon, the largest satellite of Pluto, is a gray-colored icy world covered mostly in H2O ice, with spectral evidence for NH3, as previously reported (Cook et al. 2007, Astrophys. J. 663, 1406-1419 Merlin, et al. 2010, Icarus, 210, 930; Cook, et al. 2014, AAS/Division for Planetary Sciences Meeting Abstracts, 46, #401.04). Images from the New Horizons spacecraft reveal a surface with terrains of widely different ages and a moderate degree of localized coloration. The presence of H2O ice in its crystalline form (Brown & Calvin 2000 Science 287, 107-109; Buie & Grundy 2000 Icarus 148, 324-339; Merlin et al, 2010) along with NH3 is consistent with a fresh surface.The phase of H2O ice is a key tracer of variations in temperature and physical conditions on the surface of outer Solar System objects. At Charon’s surface temperature H2O is expected to be amorphous, but ground-based observations (e.g., Merlin et al. 2010) show a clearly crystalline signature. From laboratory experiments it is known that amorphous H2O ice becomes crystalline at temperatures of ~130 K. Other mechanisms that can change the phase of the ice from amorphous to crystalline include micro-meteoritic bombardment (Porter et al. 2010, Icarus, 208, 492) or resurfacing processes such as cryovolcanism.New Horizons observed Charon with the LEISA imaging spectrometer, part of the Ralph instrument (Reuter, D.C., Stern, S.A., Scherrer, J., et al. 2008, Space Science Reviews, 140, 129). Making use of high spatial resolution (better than 10 km/px) and spectral resolving power of 240 in the wavelength range 1.25-2.5 µm, and 560 in the range 2.1-2.25 µm, we report on an analysis of the phase of H2O ice on parts of Charon’s surface with a view to investigate the recent history and evolution of this small but intriguing object.This work was supported by NASA’s New Horizons project.

  20. The Molar Volume of FeO-MgO-Fe2O3-Cr2O3-Al2O3-TiO2 Spinels

    NASA Astrophysics Data System (ADS)

    Hamecher, E. A.; Antoshechkina, P. M.; Ghiorso, M. S.; Asimow, P. D.

    2011-12-01

    A new model of molar volume has been calibrated in the spinel supersystem (Mg,Fe2+)(Al,Cr,Fe3+)2O4 - (Mg,Fe2+)2TiO4. A total of 832 X-ray and neutron diffraction experiments performed on spinels at ambient and in situ high-P, T conditions (from the American Mineralogist Crystal Structure Database (Downs and Hall-Wallace, 2003) and other sources) were used to calibrate end-member equations of state and an excess volume model for this system. The effect on molar volume of cation ordering over the octahedral and tetrahedral sites is captured with linear dependence on Mg2+, Al3+, and Fe3+ site occupancy terms. We allowed standard state volumes and coefficients of thermal expansion of the end members to vary within their uncertainties during extraction of the mixing properties, in order to achieve the best fit. Published equations of states of the various spinel end members were analyzed to obtain optimal values of the bulk modulus and its pressure derivative, for each explicit end member. For any spinel composition in the supersystem, the model molar volume is obtained by adding excess volume and cation order-dependent terms to a linear combination of the five end member volumes, estimated at pressure and temperature using the high-T Vinet equation of state. The model has a total of 31 parameters and fits nearly all experiments to within 0.02 J/bar/mol, or better than 0.5% in volume. The model is compared to the current MELTS (Ghiorso and Sack, 1995; Ghiorso et al., 2002) spinel model with a demonstration of the impact of the model difference on the estimated spinel-garnet lherzolite transition pressure. Our primary motivation in this work is the development of a comprehensive spinel molar volume model for use in calibration of activity-composition models of garnet and pyroxene solid solutions. The thermodynamic models, along with a new silicate liquid equation of state, will be incorporated into the next generation MELTS model, xMELTS. The new solid solution models

  1. Structural investigation of BaOsbnd B2O3sbnd P2O5 glasses by NMR and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Koudelka, Ladislav; Kalenda, Petr; Mošner, Petr; Černošek, Zdeněk; Montagne, Lionel; Revel, Bertrand

    2016-09-01

    Glasses of the ternary system BaOsbnd B2O3sbnd P2O5 were prepared and studied in broad concentration limits covering the whole vitrification domain: 20-50 mol% BaO, 0-40 mol% B2O3 and 20-60 mol% P2O5. Their structure was studied with combinations of Raman spectroscopy, 31P MAS NMR spectroscopy and 11B MAS NMR spectroscopy. The obtained results are discussed in several compositional lines A: (100-x)Ba(PO3)2sbnd xB2O3, B: 40BaOsbnd yB2O3sbnd (60-y)P2O5, C: (50-z)BaOsbnd zB2O3sbnd 50P2O5, D: (60-w)BaOsbnd wB2O3sbnd 40P2O5 and E: uBaOsbnd 40B2O3sbnd (60-u)P2O5. Boron oxide incorporates into the phosphate network in the form of BO4 and BO3 groups and increases their glass transition temperature. Nevertheless, the increase in Tg is only steep within the region of 0-20 mol% B2O3 reaching a maximum at the glasses with ∼30 mol% B2O3. In the lines A, B and E a decrease in the P2O5 and an increase of B2O3 content results in the shortening of phosphate chains with decreasing P2O5 content; these changes are most pronounced in line B with a constant BaO content. In lines C and D with a constant P2O5 content a decrease in the BaO content results, in contrast, in the reverse transformation of phosphate structural units in the direction Q1 → Q2 → Q3 as detected from Raman spectra and 31P MAS NMR spectra. 11B MAS NMR spectra revealed that only BO4 units are present in the glasses with 0-20 mol% B2O3. In the glasses of the E series the fraction of BO3 units increases with a decreasing P2O5 content. By the decomposition of the 11B MAS NMR spectra it is possible to estimate the fractions of basic structural units formed by boron - B(OP)3O, B(OP)2O2 and BO3 in all the glasses of the glass forming region.

  2. Three-dimensional Ag{sub 2}O/WO{sub 3}·0.33H{sub 2}O heterostructures for improving photocatalytic activity

    SciTech Connect

    He, Xiaoyu; Hu, Chenguo; Xi, Yi; Zhang, Kaiyou; Hua, Hao

    2014-02-01

    Highlights: • Ag{sub 2}O/WO{sub 3}·0.33H{sub 2}O 3D network heterostructures are prepared via a simple precipitatation method. • Ag{sub 2}O/WO{sub 3}·0.33H{sub 2}O networks exhibit much enhanced photocatalytic activity. • High photocatalytic activity is attributed to its heterostructure and 3D architectures. - Abstract: Three-dimensional Ag{sub 2}O/WO{sub 3}·0.33H{sub 2}O heterostructures were fabricated by loading Ag{sub 2}O nanoparticles on WO{sub 3}·0.33H{sub 2}O 3D networks via a simple chemical precipitation method. The Ag{sub 2}O/WO{sub 3}·0.33H{sub 2}O heterostructures exhibited much enhanced photocatalytic activity for the degradation of methylene blue (MB) under simulated solar light irradiation. The optimal molar ratio of Ag{sub 2}O and WO{sub 3}·0.33H{sub 2}O is 1:2. The outstanding photocatalytic activity of the Ag{sub 2}O/WO{sub 3}·0.33H{sub 2}O can be attributed to its large surface area of the three-dimensional networks, the enhanced sunlight absorption and the prevention of electrons–holes combination from the heterostructures. The experiment result demonstrates that wide band gap semiconductor (WO{sub 3}·0.33H{sub 2}O) modified by narrow band gap metal oxide (Ag{sub 2}O) with 3D architecture will be an effective route to enhance its photocatalytic activity.

  3. Interaction of Nd dopants with broadband emission centers in Bi2O3-B2O3 glass: local energy balance and its influence on optical properties

    NASA Astrophysics Data System (ADS)

    Ishii, Masashi; Fuchi, Shingo; Takeda, Yoshikazu

    2015-10-01

    Chemical and energetic interactions between broadband infrared intrinsic emission centers (IECs) of bismuthates and extrinsic emission centers (EECs) of Nd2O3 dopants were optically and electronically investigated. Although no visible absorption from the IEC was found in untreated Bi2O3-B2O3 glass, it was clearly observed after a moderate thermal treatment of  <200 °C, indicating chemical activity of O-deficient sites as the origin of IECs. On the other hand, Nd2O3 doping chemically stabilized the Bi2O3-B2O3 glass and suppressed IEC formation. By using a microwave measurement sensitive to electric dipoles, we found a ‘switching’ in local energy balance resulting from the Nd2O3 doping. This was explained by metallization of the O-deficient sites in the Bi2O3-B2O3 glass and multi-phonon excitation of IEC and EEC complexes in the Nd2O3-Bi2O3-B2O3 glass phosphor. Although the electric dipole observed by the microwave measurement was not necessarily caused by IEC, emission properties of the IEC and EEC complexes were consistent with energy balance switching; emissions from IECs after thermal treatment were quenched by EECs with multi-phonon excitation.

  4. Ab initio investigation of the structure, stability, and atmospheric distribution of molecular clusters containing H2O, CO2, and N2O

    NASA Astrophysics Data System (ADS)

    Lemke, Kono H.; Seward, Terry M.

    2008-10-01

    We present results from ab initio calculations for the structures and energetic properties of neutral clusters containing water, carbon dioxide, and nitrous oxide using the complete basis set CBS-Q multilevel procedure. Gas phase hydration energies ΔG0, enthalpies ΔH0, and entropies ΔS0 for the stepwise attachment of water onto clusters according to X·(H2O)n + H2O ↔ X·(H2O)n+1 (X = CO2, N2O, and H2O) are reported for n ≤ 4. In particular, our results demonstrate that values for the incremental hydration enthalpies and entropies of all three gases CO2, N2O, and H2O asymptotically approach values characteristic of bulk water (i.e., -44.0 kJ mol-1 for the enthalpy and -118.8 J K-1 mol-1 for the entropy of condensation) following attachment of around three to four water molecules. Our ab initio calculations indicate that water attachment onto CO2, N2O, and H2O is a thermodynamically favorable process, such that hydrated CO2·(H2O)n, N2O·(H2O)n, and H2O·(H2O)n clusters would form a significant atmospheric repository of these species.

  5. Interaction of Nd dopants with broadband emission centers in Bi2O3-B2O3 glass: local energy balance and its influence on optical properties.

    PubMed

    Ishii, Masashi; Fuchi, Shingo; Takeda, Yoshikazu

    2015-10-01

    Chemical and energetic interactions between broadband infrared intrinsic emission centers (IECs) of bismuthates and extrinsic emission centers (EECs) of Nd2O3 dopants were optically and electronically investigated. Although no visible absorption from the IEC was found in untreated Bi2O3-B2O3 glass, it was clearly observed after a moderate thermal treatment of  <200 °C, indicating chemical activity of O-deficient sites as the origin of IECs. On the other hand, Nd2O3 doping chemically stabilized the Bi2O3-B2O3 glass and suppressed IEC formation. By using a microwave measurement sensitive to electric dipoles, we found a 'switching' in local energy balance resulting from the Nd2O3 doping. This was explained by metallization of the O-deficient sites in the Bi2O3-B2O3 glass and multi-phonon excitation of IEC and EEC complexes in the Nd2O3-Bi2O3-B2O3 glass phosphor. Although the electric dipole observed by the microwave measurement was not necessarily caused by IEC, emission properties of the IEC and EEC complexes were consistent with energy balance switching; emissions from IECs after thermal treatment were quenched by EECs with multi-phonon excitation.

  6. Structural and physical properties in the system ZnO-B 2O 3-P 2O 5-R nO m

    NASA Astrophysics Data System (ADS)

    Li, Shengchun; Chen, Pei; Li, Yaogang

    2010-12-01

    The glass forming region in the quaternary system ZnO-B 2O 3-P 2O 5-R nO m has been determined. Glass transition temperature ( Tg), glass density ( ρ), thermal expansion coefficient ( α) and weight loss percentage ( WL) of these glasses were measured. The structure of (90- x- y)ZnO- xB 2O 3- yP 2O 5-10R nO m glass was characterized by infrared spectra (IR), Raman spectra and X-ray diffraction (XRD). Results of IR and Raman indicated that B 2O 3 participated in the glass network as a glass modifier and the IR band around 1440 cm -1 was ascribed to the v as(B-O-B) vibrations. Glass intensity increased with increase in B 2O 3 content. The disappearance of v s(P-O-P) vibration around 760 cm -1 indicated that P-O-B linkage was formed. XRD results revealed that the major crystalline phase changes with substitution of different amounts of B 2O 3: Zn 2P 2O 7 for 45ZnO- xB 2O 3-35P 2O 5-10R nO m glass, where x=0-20, and BPO 4 for 45ZnO- xB 2O 3-35P 2O 5-10R nO m glass, where x=30-40.

  7. Antiferromagnetism of UO2⋅2H2O

    USGS Publications Warehouse

    Pankey, T.; Senftle, F.E.; Cuttitta, F.

    1963-01-01

    Magnetic susceptibility measurements have been made on UO2⋅xH2O for x=1.78 to x=2.13, and from 77° to 375°K. As the value of x decreased the susceptibility increased. Both these data and structural arguments imply that the formula of this compound is U(OH)4 rather than the dihydrate form. Based on this concept the data have been corrected for diamagnetism and also small amounts of UO2 and H2O which were present. The molar susceptibility of U4+ in U(OH)4 is nearly an order of magnitude less than in other uranium compounds, and it is suggested that this is probably due to superexchange between adjacent uranium atoms through intervening oxygen atoms.

  8. Structure of Gd2O3 nanoparticles at high temperature

    NASA Astrophysics Data System (ADS)

    Jamnezhad, H.; Jafari, M.

    2016-06-01

    The present study aimed to investigate the structure of Gd2O3 nanoparticles by X-ray diffraction between 25 °C and 1000 °C and compare it with the bulk sample. For the nanoparticles at room temperature, the structure was monoclinic; with an increase in temperature, mixed phases containing the monoclinic and cubic phases were observe between 500 °C and 1000 °C, whereas the bulk sample was transformed from cubic (at room temperature) into hexagonal structures at high pressure. The trends observed for nanoparticles and bulk materials may be different. The scanning electron microscope (SEM) analyses confirmed the existence of Gd2O3 nanoparticles. Moreover, since this material has the magnetic properties, especially during the phase transition, so it was one of the point of our attention in this paper.

  9. Free radical scavenging activity of morin 2'-O(-) phenoxide anion.

    PubMed

    Marković, Zoran; Milenković, Dejan; Dorović, Jelena; Dimitrić Marković, Jasmina M; Stepanić, Višnja; Lučić, Bono; Amić, Dragan

    2012-12-01

    Due to intramolecular H-atom transfer, deprotonation of the most acidic 3-OH group of morin yields 2'-O(-) phenoxide anion. The reaction enthalpies related to mechanisms of free radical scavenging activity of this dominant species at a physiological pH of 7.4 were calculated by PM6 and DFT methods in gas-phase, water, benzene and DMSO. Results indicate the 4'-OH group of 2'-O(-) phenoxide anion is the active site for radical inactivation. The thermodynamically favoured mechanism depends on the polarity of the reaction media: in polar solvents (water and DMSO), the sequential proton loss electron transfer (SPLET) mechanism is preferred while in non-polar benzene (and in gas-phase), the hydrogen atom transfer (HAT) mechanism is responsible for the free radical scavenging activity of the morin phenoxide anion. Results show that the fast, semiempirical PM6 method fairly mimics more accurate, though time-consuming DFT methodologies.

  10. 55 Mn NMR for Antiferromagnetic α- Mn2 O 3

    NASA Astrophysics Data System (ADS)

    Jo, Euna; Kim, Changsoo; Lee, Soonchil

    2011-03-01

    The zero-field 55 Mn NMR spectrum for antiferromagnetic α - Mn 2 O3 was measured at low temperatures. Manganese sesquioxide (Mn 2 O3) is used in combustion catalysis, a method of reducing the emissions of organic compounds and nitrous oxide from waste gas, as an environmentally - friendly and inexpensive catalyzer instead of Pt and Pd. The magnetic moment estimated from the resonance frequency was 2.6 μB per Mn 3+ ion. The temperature dependence of the sublattice magnetization fits not Bloch's T2 law well but the exponential form applicable because there is an initial energy gap in the dispersion relation of the spin wave. From the fitting, an energy gap of 1.82 meV and an anisotropy energy of 0.22 meV were obtained. The spin-spin relaxation rate was measured as a function of the frequency and the Suhl-Nakamura interaction is suppressed by this energy gap.

  11. Fast neutron detection with Al 2O 3 thermoluminescence dosimeter

    NASA Astrophysics Data System (ADS)

    Ranogajec-Komor, Maria; Osvay, Margit; Dvornik, Igor; Biró, Tamàs

    1983-07-01

    The technique of thermoluminescent (TL) dosimeter activation can be used to detect any radiation making TL dosimeters radioactive. In the experiment discussed in this paper Al2O3:Mg, Y TL dosimeters were irradiated by cyclotron neutrons with 5±1 MeV mean energy and by accompanying gamma rays. The gamma and the fast neutron component can be separately measured by the same dosimeter. Because of low neutron sensitivity of Al2O3 the gamma dose can be determined by the first TL reading while the 27Al(n, α)24 Na reaction provides the possibility of fast neutron detection by the subsequent reading of thermoluminescence induced in the TL material by the decay of 24Na.

  12. Cation self-diffusion in Fe2O3

    NASA Astrophysics Data System (ADS)

    Hoshino, K.; Peterson, N. L.

    Self-diffusion of Fe(59) in single crystals of Fe2O3 parallel to the c-axis has been measured as a function of temperature (1150 to 1340 C) and oxygen partial pressure 0.002 less than or equal to Po2 less than or equal to 1 atm). The oxygen partial pressure dependence of the diffusivity indicates that cation self-diffusion occurs by an interstitial-type mechanism. The simultaneous diffusion of Fe(52) and Fe(59) was measured in Fe2O3 at 1251 C and Po2 = .0191 atm. The small value of the isotope effect (f(DELTA)K = 0.067 + or - 0.016) is consistent with diffusion of Fe ions by an interstitially mechanism.

  13. The Bi based superconductors doped with B 2O 3

    NASA Astrophysics Data System (ADS)

    Veverka, M.; Smrčková, O.; Sýkorová, D.; Vašek, P.

    1997-04-01

    The influence of the addition of B2O3on the properties of the oxide ceramic materials Bi-Pb-Sr-Ca-Cu-O was investigated. The samples with nominal com-posi-tion BiaPbbBcSr2Ca2Cu3Ox(a = 0.8-1.6,b = 0.06-0.26,c = 0.05-1.0) were prepared and studied by the measurement of the temperature dependence of the electrical resistivity and critical current density. The addition of a small amount of B2O3(c = 0.05,a = 1.8,b = 0.26) had positive influence on the critical current density. On the other hand, a high content of boron (c > 0.6,b = 0.26,a + b = 1.8) reversed the superconductor to an insulator.

  14. Optimal filling fraction of Ta2O5 inverse opals

    NASA Astrophysics Data System (ADS)

    Tubio, C. R.; Guitian, F.; Gil, A.

    2013-12-01

    Tantalum pentoxide (Ta2O5) inverse opals were prepared by combining the self-assembly process and sol-gel chemistry-based opal infiltration. The inverse opal was made by the infiltration of a tantalum(V) ethoxide solution in the interstices of the polystyrene colloidal crystal template, and then removing the original opal template by calcination. The infiltration process as well as the optimal precursor concentration has been investigated in order to obtain Ta2O5 inverse opals with the optimal filling fraction. The effects of processing, template sphere size, morphology, structural properties, filling fraction and composition of the inverse opal are provided by scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy analysis (EDS) and powder X-ray diffraction (XRD). The results correlate the concentration of the precursor with the filling fraction of the template.

  15. The Target: H2O on the Moon

    NASA Technical Reports Server (NTRS)

    Green, J.; Wys, J. Negusde; Zuppero, A.

    1992-01-01

    The importance of H2O on the lunar surface has long been identified as a high priority for the existence of a human colony for mining activities and, more recently, for space fuel. Using the Earth as an analog, volcanic activity would suggest the generation of water during lunar history. Evidence of volcanism is found not only in present lunar morphology, but in over 400 locations of lunar transient events cataloged by Middlehurst and Kuiper in the 1960's. These events consisted of sightings since early history of vapor emissions and bright spots or flares. Later infrared scanning by Saari and Shorthill showed 'hot spots', many of which coincided with transient event sites. Many of the locations of Middlehurst and Kuiper were the sites of repeat events, leading to the conclusion that these were possibly volcanic in nature. The detection and use of H2O from the lunar surface is discussed.

  16. 40 CFR 1065.375 - Interference verification for N2O analyzers.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... verification test, measure the H2O mole fraction,x H 2 O, of the humidified interference test gas as close as possible to the inlet of the analyzer. For example, measure dewpoint, T dew, and absolute pressure, p total, to calculatex H 2 O.Verify that the H2O content meets the requirement in paragraph (d)(2) of...

  17. H2O diffusion in Mount Changbai peralkaline rhyolitic melt

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Xu, Z.; Wang, H.; Behrens, H.

    2008-05-01

    For quantitative modeling of bubble growth and volcanic eruption dynamics, it is necessary to know H2O diffusivity in the melt. Mount Changbai Volcano at the border of China and North Korea has produced explosive peralkaline rhyolitic eruptions, including a 30-km3 eruption with an age of 1 ky (Horn and Schmincke, 2000). H2O diffusivity is expected to be greater in a peralkaline rhyolitic melt than a calc-alkaline rhyolitic melt. We have experimentally investigated H2O diffusion in Mount Changbai peralkaline rhyolite. Because phenocryst-free glass is not available from Mount Changbai eruption products, the starting materials (nominally dry and hydrous) are synthesized. The diffusion couple technique, with one half dry and the other half wet, is adopted. Three high- temperature experiments have been carried out at 500 MPa and one at 1500 MPa in a piston-cylinder apparatus. After the experiment, the sample is prepared into a doubly-polished section of about 0.2 mm thickness, which is analyzed by a Perkin-Elmer FTIR microscope. The data are fit following the procedures of Zhang and Behrens (2000) and Ni and Zhang (2008). Preliminary data show that H2O diffusivity in peralkaline rhyolitic melt is greater than that in calc-alkaline rhyolitic melt (Zhang and Behrens, 2000), as expected. The exact difference depends on temperature and pressure, and the ratio of diffusivity in the peralkaline rhyolitic melt to that in the calc-alkaline rhyolitic melt ranges from 1 to 3. More experiments will be conducted on this melt to provide the basic data for specific modeling of bubble growth and volcanic eruption dynamics in past and future Mount Changbai eruptions and other peralkaline rhyolitic eruptions. References: Horn S and Schmincke H U (2000) Bull. Volcanol., 61, 537. Ni H and Zhang Y (2008) Chem. Geol., doi: 10.1016/j.chemgeo.2008.01.011. Zhang Y and Behrens H (2000) Chem. Geol., 169, 243.

  18. Near Infrared Spectra of H2O/HCN Mixtures

    NASA Technical Reports Server (NTRS)

    Mastrapa, R. M.; Bernstein, M. P.; Sanford, S. A.

    2006-01-01

    Cassini's VIMS has already returned exciting results interpreting spectra of Saturn's icy satellites. The discovery of unidentified features possibly due to CN compounds inspired the work reported here. We wanted to test HCN as a possibility for explaining these features, and also explore how the features of HCN change when mixed with H2O. We have previously noted that mixing H20 and CO2 produces new spectral features and that those features change with temperature and mixing ratio.

  19. High-field magnetization of Dy2O3

    NASA Technical Reports Server (NTRS)

    Flood, D. J.

    1974-01-01

    The magnetization of powdered samples of Dy2O3 has been measured at temperatures between 1.45 deg and 4.2 K, in applied magnetic fields ranging to 7 Teslas. A linear dependence of magnetization on applied field is observable in high field region, the slope of which is independent of temperature over the range investigated. The extrapolated saturation magnetic moment is 2.77 + or - 0.08 Bohr magnetons per ion.

  20. High-field magnetization of Dy2O3

    NASA Technical Reports Server (NTRS)

    Flood, D. J.

    1974-01-01

    The magnetization of powdered samples of Dy2O3 has been measured at temperatures between 1.45 and 4.2 K, in applied magnetic fields ranging to 70 kilogauss. A linear dependence of magnetization on applied field is observable in the high-field region, the slope of which is independent of temperature over the range investigated. The extrapolated saturation magnetic moment is about 2.77 Bohr magnetons per ion.

  1. Detection Of OH+ And H2O+ Towards Orion KL

    NASA Astrophysics Data System (ADS)

    Gupta, Harshal; Rimmer, P.; Pearson, J. C.; Herbst, E.; Yu, S.; Bergin, E. A.; Key Program, HEXOS

    2011-01-01

    The reactive molecular ions, OH+, H2O+, and H3O+, key probes of the oxygen chemistry of the interstellar gas, have been observed toward Orion KL with the Heterodyne Instrument for Far Infrared on board the Herschel Space Observatory. All three N = 1 - 0 fine-structure transitions of OH+ at 909, 971, and 1033 GHz and both fine-structure components of the doublet ortho-H2O+ 111 - 000 transition at 1115 and 1139 GHz were detected, and an upper limit was obtained for H3O+. OH+ and H2O+ are observed purely in absorption, showing a narrow component at the source velocity of 9 km s-1, and a broad blue shifted absorption similar to that reported recently for HF and para-H218O, and attributed to the low velocity outflow of Orion KL. We estimate column densities of OH+ and H2O+ for the 9 km s-1 component of 9 ± 3 x 1012 cm-2 and 7 ± 2 x 1012 cm-2, and those in the outflow of 1.9 ± 0.7 x 1013 cm-2 and 1.0 ± 0.3 x 1013 cm-2. Upper limits of 2.4 x 1012 cm-2 and 8.7 ± 1012 cm-2 were derived for the column densities of ortho and para-H3O+ from transitions near 985 and 1657 GHz. The column densities of the three ions are up to an order of magnitude lower than those obtained from recent observations of W31C and W49N. A higher gas density, despite the assumption of a large ionization rate, may explain the comparatively low column densities of the ions. A part of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. Copyright 2010© California Institute of Technology. All rights reserved.

  2. Visible Light Assisted Photocatalytic Hydrogen Generation by Ta2O5/Bi2O3, TaON/Bi2O3, and Ta3N5/Bi2O3 Composites

    DOE PAGES

    Adhikari, Shiba; Hood, Zachary D.; More, Karren Leslie; Ivanov, Ilia N.; Zhang, Lifeng; Gross, Michael; Lachgar, Abdou

    2015-06-15

    Composites comprised of two semiconducting materials with suitable band gaps and band positions have been reported to be effective at enhancing photocatalytic activity in the visible light region of the electromagnetic spectrum. Here, we report the synthesis, complete structural and physical characterizations, and photocatalytic performance of a series of semiconducting oxide composites. UV light active tantalum oxide (Ta2O5) and visible light active tantalum oxynitride (TaON) and tantalum nitride (Ta3N5) were synthesized, and their composites with Bi2O3 were prepared in situ using benzyl alcohol as solvent. The composite prepared using equimolar amounts of Bi2O3 and Ta2O5 leads to the formation ofmore » the ternary oxide, bismuth tantalate (BiTaO4) upon calcination at 1000 °C. The composites and single phase bismuth tantalate formed were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) surface area measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis diffuse reflectance spectroscopy, and photoluminescence. The photocatalytic activities of the catalysts were evaluated for generation of hydrogen using aqueous methanol solution under visible light irradiation (λ ≥ 420 nm). The results show that as-prepared composite photocatalysts extend the light absorption range and restrict photogenerated charge-carrier recombination, resulting in enhanced photocatalytic activity compared to individual phases. The mechanism for the enhanced photocatalytic activity for the heterostructured composites is elucidated based on observed activity, band positions calculations, and photoluminescence data.« less

  3. Detection of OH+ and H2O+ towards Orion KL

    NASA Astrophysics Data System (ADS)

    Gupta, H.; Rimmer, P.; Pearson, J. C.; Yu, S.; Herbst, E.; Harada, N.; Bergin, E. A.; Neufeld, D. A.; Melnick, G. J.; Bachiller, R.; Baechtold, W.; Bell, T. A.; Blake, G. A.; Caux, E.; Ceccarelli, C.; Cernicharo, J.; Chattopadhyay, G.; Comito, C.; Cabrit, S.; Crockett, N. R.; Daniel, F.; Falgarone, E.; Diez-Gonzalez, M. C.; Dubernet, M.-L.; Erickson, N.; Emprechtinger, M.; Encrenaz, P.; Gerin, M.; Gill, J. J.; Giesen, T. F.; Goicoechea, J. R.; Goldsmith, P. F.; Joblin, C.; Johnstone, D.; Langer, W. D.; Larsson, B.; Latter, W. B.; Lin, R. H.; Lis, D. C.; Liseau, R.; Lord, S. D.; Maiwald, F. W.; Maret, S.; Martin, P. G.; Martin-Pintado, J.; Menten, K. M.; Morris, P.; Müller, H. S. P.; Murphy, J. A.; Nordh, L. H.; Olberg, M.; Ossenkopf, V.; Pagani, L.; Pérault, M.; Phillips, T. G.; Plume, R.; Qin, S.-L.; Salez, M.; Samoska, L. A.; Schilke, P.; Schlecht, E.; Schlemmer, S.; Szczerba, R.; Stutzki, J.; Trappe, N.; van der Tak, F. F. S.; Vastel, C.; Wang, S.; Yorke, H. W.; Zmuidzinas, J.; Boogert, A.; Güsten, R.; Hartogh, P.; Honingh, N.; Karpov, A.; Kooi, J.; Krieg, J.-M.; Schieder, R.; Zaal, P.

    2010-10-01

    We report observations of the reactive molecular ions OH+, H2O+, and H3O+ towards Orion KL with Herschel/HIFI. All three N = 1-0 fine-structure transitions of OH+ at 909, 971, and 1033 GHz and both fine-structure components of the doublet ortho-H2O+ 111-000 transition at 1115 and 1139 GHz were detected; an upper limit was obtained for H3O+. OH+ and H2O+ are observed purely in absorption, showing a narrow component at the source velocity of 9 km s-1, and a broad blueshifted absorption similar to that reported recently for HF and para-H218O, and attributed to the low velocity outflow of Orion KL. We estimate column densities of OH+ and H2O+ for the 9 km s-1 component of 9 ± 3 × 1012 cm-2 and 7 ± 2 × 1012 cm-2, and those in the outflow of 1.9 ± 0.7 × 1013 cm-2 and 1.0 ± 0.3 × 1013 cm-2. Upper limits of 2.4 × 1012 cm-2 and 8.7 × 1012 cm-2 were derived for the column densities of ortho and para-H3O+ from transitions near 985 and 1657 GHz. The column densities of the three ions are up to an order of magnitude lower than those obtained from recent observations of W31C and W49N. The comparatively low column densities may be explained by a higher gas density despite the assumption of a very high ionization rate.

  4. The Effect of H2O on Ice Photochemistry

    NASA Astrophysics Data System (ADS)

    Öberg, Karin I.; van Dishoeck, Ewine F.; Linnartz, Harold; Andersson, Stefan

    2010-08-01

    UV irradiation of simple ices is proposed to efficiently produce complex organic species during star formation and planet formation. Through a series of laboratory experiments, we investigate the effects of the H2O concentration, the dominant ice constituent in space, on the photochemistry of more volatile species, especially CH4, in ice mixtures. In the experiments, thin (~40 ML) ice mixtures, kept at 20-60 K, are irradiated under ultra-high vacuum conditions with a broadband UV hydrogen discharge lamp. Photodestruction cross sections of volatile species (CH4 and NH3) and production efficiencies of new species (C2H6, C2H4, CO, H2CO, CH3OH, CH3CHO, and CH3CH2OH) in water-containing ice mixtures are determined using reflection-absorption infrared spectroscopy during irradiation and during a subsequent slow warm-up. The four major effects of increasing the H2O concentration are: (1) an increase of the destruction efficiency of the volatile mixture constituent by up to an order of magnitude due to a reduction of back reactions following photodissociation, (2) a shift to products rich in oxygen, e.g., CH3OH and H2CO, (3) trapping of up to a factor of 5 more of the formed radicals in the ice, and (4) a disproportional increase in the diffusion barrier for the OH radical compared with the CH3 and HCO radicals. The radical diffusion temperature dependencies are consistent with calculated H2O-radical bond strengths. All the listed effects are potentially important for the production of complex organics in H2O-rich icy grain mantles around protostars and should thus be taken into account when modeling ice chemistry.

  5. First-Principles Modeling of Multiferroic RMn2O5

    NASA Astrophysics Data System (ADS)

    Cao, Kun; Guo, Guang-Can; Vanderbilt, David; He, Lixin

    2009-12-01

    We investigate the phase diagrams of RMn2O5 via a first-principles effective-Hamiltonian method. We are able to reproduce the most important features of the complicated magnetic and ferroelectric phase transitions. The calculated polarization as a function of temperature agrees very well with experiments. The dielectric-constant step at the commensurate-to-incommensurate magnetic phase transition is well reproduced. The microscopic mechanisms for the phase transitions are discussed.

  6. Knowledge of the systems H2O-SO3-N2O3. Report 1: The system H2SO4-H2O-N2O3

    NASA Technical Reports Server (NTRS)

    Stopperka, K.; Kilz, F.

    1977-01-01

    The amount of N2O3 being absorbed in 50-100% H2SO4 at 19, 60, and 95 C is directly proportional to the acid concentration and inversely proportional to the temperature. NO+ formation according to the above-formulated equation occurs only at H2SO4 concentrations greater than 52%. Absorption in highly concentrated sulfuric acid results in the formation of crystalline NOHSO4.

  7. Efficient lasing in Yb:(YLa)2O3 ceramics

    NASA Astrophysics Data System (ADS)

    Snetkov, I. L.; Mukhin, I. B.; Balabanov, S. S.; Permin, D. A.; Palashov, O. V.

    2015-02-01

    A high-optical-quality sample of Yb0.1Y1.7La0.2O3 ceramics is prepared using a recently developed technique of selfpropagating high-temperature synthesis of rare-earth-doped yttrium oxide nanopowder from acetate - nitrates of metals. Its optical and spectral characteristics are studied, and quasi-cw lasing at a wavelength of 1033 nm is achieved with a power of 7 W and a slope efficiency of 25%.

  8. Potential energy surface of triplet N2O2

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  9. X-Ray Diffraction of Shock Compressed H2O

    NASA Astrophysics Data System (ADS)

    Gleason, A. E.

    2014-12-01

    H2O, critical for life and ubiquitous in biology, is one of the most abundant molecules in the solar system and is relevant to many fields, including fundamental physics and chemistry. Phase transformation information of H2O is also important to applied areas like planetary science where it is a constituent of giant planets Neptune and Uranus, icy satellites (e.g., Europa, Ganymede), and extrasolar planets (icy "super-Earths"). Using the MEC (Matter in Extreme Conditions) hutch at LCLS, we reach simultaneous high pressure (P) and temperature (T) with laser-driven shock waves and the capability of taking snapshots during a dynamic process with the X-ray Free Electron Laser (xFEL). We report the only shock-driven diffraction data on H2O ever collected to date, and examine time-resolved diffraction from ice Ih to high pressure ice VII. At 2 Mbar we find evidence of ice X - this has significant implications for planetary interiors and providing a bound for the onset of the superionic phase.

  10. An Accurate Potential Energy Surface for H2O

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.; Partridge, Harry; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    We have carried out extensive high quality ab initio electronic structure calculations of the ground state potential energy surface (PES) and dipole moment function (DMF) for H2O. A small adjustment is made to the PES to improve the agreement of line positions from theory and experiment. The theoretical line positions are obtained from variational ro-vibrational calculations using the exact kinetic energy operator. For the lines being fitted, the root-mean-square error was reduced from 6.9 to 0.08 /cm. We were then able to match 30,092 of the 30,117 lines from the HITRAN 96 data base to theoretical lines, and 80% of the line positions differed less than 0.1 /cm. About 3% of the line positions in the experimental data base appear to be incorrect. Theory predicts the existence of many additional weak lines with intensities above the cutoff used in the data base. To obtain results of similar accuracy for HDO, a mass dependent correction to the PH is introduced and is parameterized by simultaneously fitting line positions for HDO and D2O. The mass dependent PH has good predictive value for T2O and HTO. Nonadiabatic effects are not explicitly included. Line strengths for vibrational bands summed over rotational levels usually agree well between theory and experiment, but individual line strengths can differ greatly. A high temperature line list containing about 380 million lines has been generated using the present PES and DMF

  11. Potential energy surface of triplet N2O2.

    PubMed

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

    2016-01-14

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

  12. Magnetoelectric effect in Cr2O3 thin films

    NASA Astrophysics Data System (ADS)

    He, Xi; Wang, Yi; Sahoo, Sarbeswar; Binek, Christian

    2008-03-01

    Magnetoelectric materials experienced a recent revival as promising components of novel spintronic devices [1, 2, 3]. Since the magnetoelectric (ME) effect is relativistically small in traditional antiferromagnetic compounds like Cr2O3 (max. αzz 4ps/m ) and also cross- coupling between ferroic order parameters is typically small in the modern multiferroics, it is a challenge to electrically induce sufficient magnetization required for the envisioned device applications. A straightforward approach is to increase the electric field at constant voltage by reducing the thickness of the ME material to thin films of a few nm. Since magnetism is known to be affected by geometrical confinement thickness dependence of the ME effect in thin film Cr2O3 is expected. We grow (111) textured Cr2O3 films with various thicknesses below 500 nm and study the ME effect for various ME annealing conditions as a function of temperature with the help of Kerr-magnetometry. [1] P. Borisov et al. Phys. Rev. Lett. 94, 117203 (2005). [2] Ch. Binek, B.Doudin, J. Phys. Condens. Matter 17, L39 (2005). [3] R. Ramesh and Nicola A. Spaldin 2007 Nature Materials 6 21.

  13. Increasing extracellular H2O2 produces a bi-phasic response in intracellular H2O2, with peroxiredoxin hyperoxidation only triggered once the cellular H2O2-buffering capacity is overwhelmed.

    PubMed

    Tomalin, Lewis Elwood; Day, Alison Michelle; Underwood, Zoe Elizabeth; Smith, Graham Robert; Dalle Pezze, Piero; Rallis, Charalampos; Patel, Waseema; Dickinson, Bryan Craig; Bähler, Jürg; Brewer, Thomas Francis; Chang, Christopher Joh-Leung; Shanley, Daryl Pierson; Veal, Elizabeth Ann

    2016-06-01

    Reactive oxygen species, such as H2O2, can damage cells but also promote fundamental processes, including growth, differentiation and migration. The mechanisms allowing cells to differentially respond to toxic or signaling H2O2 levels are poorly defined. Here we reveal that increasing external H2O2 produces a bi-phasic response in intracellular H2O2. Peroxiredoxins (Prx) are abundant peroxidases which protect against genome instability, ageing and cancer. We have developed a dynamic model simulating in vivo changes in Prx oxidation. Remarkably, we show that the thioredoxin peroxidase activity of Prx does not provide any significant protection against external rises in H2O2. Instead, our model and experimental data are consistent with low levels of extracellular H2O2 being efficiently buffered by other thioredoxin-dependent activities, including H2O2-reactive cysteines in the thiol-proteome. We show that when extracellular H2O2 levels overwhelm this buffering capacity, the consequent rise in intracellular H2O2 triggers hyperoxidation of Prx to thioredoxin-resistant, peroxidase-inactive form/s. Accordingly, Prx hyperoxidation signals that H2O2 defenses are breached, diverting thioredoxin to repair damage. PMID:26944189

  14. Increasing extracellular H2O2 produces a bi-phasic response in intracellular H2O2, with peroxiredoxin hyperoxidation only triggered once the cellular H2O2-buffering capacity is overwhelmed.

    PubMed

    Tomalin, Lewis Elwood; Day, Alison Michelle; Underwood, Zoe Elizabeth; Smith, Graham Robert; Dalle Pezze, Piero; Rallis, Charalampos; Patel, Waseema; Dickinson, Bryan Craig; Bähler, Jürg; Brewer, Thomas Francis; Chang, Christopher Joh-Leung; Shanley, Daryl Pierson; Veal, Elizabeth Ann

    2016-06-01

    Reactive oxygen species, such as H2O2, can damage cells but also promote fundamental processes, including growth, differentiation and migration. The mechanisms allowing cells to differentially respond to toxic or signaling H2O2 levels are poorly defined. Here we reveal that increasing external H2O2 produces a bi-phasic response in intracellular H2O2. Peroxiredoxins (Prx) are abundant peroxidases which protect against genome instability, ageing and cancer. We have developed a dynamic model simulating in vivo changes in Prx oxidation. Remarkably, we show that the thioredoxin peroxidase activity of Prx does not provide any significant protection against external rises in H2O2. Instead, our model and experimental data are consistent with low levels of extracellular H2O2 being efficiently buffered by other thioredoxin-dependent activities, including H2O2-reactive cysteines in the thiol-proteome. We show that when extracellular H2O2 levels overwhelm this buffering capacity, the consequent rise in intracellular H2O2 triggers hyperoxidation of Prx to thioredoxin-resistant, peroxidase-inactive form/s. Accordingly, Prx hyperoxidation signals that H2O2 defenses are breached, diverting thioredoxin to repair damage.

  15. Reconstructing Final H2O Contents of Hydrated Rhyolitic Glasses: Insights into H2O Degassing and Eruptive Style of Silicic Submarine Volcanoes

    NASA Astrophysics Data System (ADS)

    McIntosh, I. M.; Nichols, A. R.; Tani, K.; Llewellin, E. W.

    2015-12-01

    H2O degassing influences the evolution of magma viscosity and vesicularity during ascent through the crust, and ultimately the eruptive style. Investigating H2O degassing requires data on both initial and final H2O contents. Initial H2O contents are revealed by melt inclusion data, while final H2O contents are found from dissolved H2O contents of volcanic glass. However volcanic glasses, particularly of silicic composition, are susceptible to secondary hydration i.e. the addition of H2O from the surrounding environment at ambient temperature during the time following pyroclast deposition. Obtaining meaningful final H2O data therefore requires distinguishing between the original final dissolved H2O content and the H2O added subsequently during hydration. Since H2O added during hydration is added as molecular H2O (H2Om), and the species interconversion between H2Om and hydroxyl (OH) species is negligible at ambient temperature, the final OH content of the glass remains unaltered during hydration. By using H2O speciation models to find the original H2Om content that would correspond to the measured OH content of the glass, the original total H2O (H2Ot) content of the glass prior to hydration can be reconstructed. These H2O speciation data are obtained using FTIR spectroscopy. In many cases, particularly where vesicular glasses necessitate thin wafers, OH cannot be measured directly and instead is calculated indirectly as OH = H2Ot - H2Om. Here we demonstrate the importance of using a speciation-dependent H2Ot molar absorptivity coefficient to obtain accurate H2Ot and H2O speciation data and outline a methodology for calculating such a coefficient for rhyolite glasses, with application to hydrated silicic pumice from submarine volcanoes in the Japanese Izu-Bonin Arc. Although hydrated pumice from Kurose Nishi and Oomurodashi now contain ~1.0 - 2.5 wt% H2Ot, their pre-hydration final H2O contents were typically ~0.3 - 0.4 wt% H2Ot. Furthermore, we show that pre

  16. Development and bioactivity evaluation of bioglasses with low Na2O content based on the system Na 2O-CaO-MgO-P 2O 5-SiO 2.

    PubMed

    El-Meliegy, Emad; Hamzawy, Esmat M A; El-Kady, Abeer M; Salama, Aida; El-Rashedi, Ahalam

    2012-09-01

    Osteoconductive bioglasses, free of K(2)O and Al(2)O(3) and with content of Na(2)O lower than 10 mol%, were designed based on the ratio (SiO(2) + MgO)/(P(2)O(5) + CaO + Na(2)O) in the system Na(2)O-CaO-MgO-P(2)O(5)-SiO(2). The developed glasses have shown a strong potential for the formation of hydroxycarbonated apatite (HCA) in vitro. The particles of HCA aggregates tend to be of finer size with increasing the ratio of (SiO(2) + MgO)/(CaO + P(2)O(5) + Na(2)O) in the glass chemical composition indicating significant bioactivity. Critical size bone defects created in the femurs of albino adult female rats, and grafted with the glass particles for 12 weeks post implantation, were completely healed by filling with mineralized bone matrix without infection showing a strong potential for new bone formation in vivo. Osteoblasts and osteocytes were observed close to the surface of the granular implants with active areas of bone deposition, resorption and remodelling. The bioglass with lowest (SiO(2) + MgO)/(CaO + P(2)O(5) + Na(2)O) ratio has shown the highest bioactivity while the bioglass with the highest (SiO(2) + MgO)/(CaO + P(2)O(5) + Na(2)O) has shown the lowest bioactivity. The newly formed bone in vivo has shown a similar structure to that of the original bone as indicated by the histology and microstructural results. In addition, Ca/P molar ratio of the newly formed bone was found to be (~1.67), which is similar to that of the original bone.

  17. Infrared spectra and tunneling dynamics of the N{sub 2}–D{sub 2}O and OC–D{sub 2}O complexes in the v{sub 2} bend region of D{sub 2}O

    SciTech Connect

    Zhu, Yu; Zheng, Rui; Li, Song; Yang, Yu; Duan, Chuanxi

    2013-12-07

    The rovibrational spectra of the N{sub 2}–D{sub 2}O and OC–D{sub 2}O complexes in the v{sub 2} bend region of D{sub 2}O have been measured in a supersonic slit jet expansion using a rapid-scan tunable diode laser spectrometer. Both a-type and b-type transitions were observed for these two complexes. All transitions are doubled, due to the heavy water tunneling within the complexes. Assuming the tunneling splittings are the same in K{sub a} = 0 and K{sub a} = 1, the band origins, all three rotational and several distortion constants of each tunneling state were determined for N{sub 2}–D{sub 2}O in the ground and excited vibrational states, and for OC–D{sub 2}O in the excited vibrational state, respectively. The averaged band origin of OC–D{sub 2}O is blueshifted by 2.241 cm{sup −1} from that of the v{sub 2} band of the D{sub 2}O monomer, compared with 1.247 cm{sup −1} for N{sub 2}–D{sub 2}O. The tunneling splitting of N{sub 2}–D{sub 2}O in the ground state is 0.16359(28) cm{sup −1}, which is about five times that of OC–D{sub 2}O. The tunneling splittings decrease by about 26% for N{sub 2}–D{sub 2}O and 23% for OC–D{sub 2}O, respectively, upon excitation of the D{sub 2}O bending vibration, indicating an increase of the tunneling barrier in the excited vibrational state. The tunneling splittings are found to have a strong dependence on intramolecular vibrational excitation as well as a weak dependence on quantum number K{sub a}.

  18. Development and bioactivity evaluation of bioglasses with low Na2O content based on the system Na 2O-CaO-MgO-P 2O 5-SiO 2.

    PubMed

    El-Meliegy, Emad; Hamzawy, Esmat M A; El-Kady, Abeer M; Salama, Aida; El-Rashedi, Ahalam

    2012-09-01

    Osteoconductive bioglasses, free of K(2)O and Al(2)O(3) and with content of Na(2)O lower than 10 mol%, were designed based on the ratio (SiO(2) + MgO)/(P(2)O(5) + CaO + Na(2)O) in the system Na(2)O-CaO-MgO-P(2)O(5)-SiO(2). The developed glasses have shown a strong potential for the formation of hydroxycarbonated apatite (HCA) in vitro. The particles of HCA aggregates tend to be of finer size with increasing the ratio of (SiO(2) + MgO)/(CaO + P(2)O(5) + Na(2)O) in the glass chemical composition indicating significant bioactivity. Critical size bone defects created in the femurs of albino adult female rats, and grafted with the glass particles for 12 weeks post implantation, were completely healed by filling with mineralized bone matrix without infection showing a strong potential for new bone formation in vivo. Osteoblasts and osteocytes were observed close to the surface of the granular implants with active areas of bone deposition, resorption and remodelling. The bioglass with lowest (SiO(2) + MgO)/(CaO + P(2)O(5) + Na(2)O) ratio has shown the highest bioactivity while the bioglass with the highest (SiO(2) + MgO)/(CaO + P(2)O(5) + Na(2)O) has shown the lowest bioactivity. The newly formed bone in vivo has shown a similar structure to that of the original bone as indicated by the histology and microstructural results. In addition, Ca/P molar ratio of the newly formed bone was found to be (~1.67), which is similar to that of the original bone. PMID:22648420

  19. Transparent and flexible capacitors based on nanolaminate Al2O3/TiO2/Al2O3

    NASA Astrophysics Data System (ADS)

    Zhang, Guozhen; Wu, Hao; Chen, Chao; Wang, Ti; Yue, Jin; Liu, Chang

    2015-02-01

    Transparent and flexible capacitors based on nanolaminate Al2O3/TiO2/Al2O3 dielectrics have been fabricated on indium tin oxide-coated polyethylene naphthalate substrates by atomic layer deposition. A capacitance density of 7.8 fF/μm2 at 10 KHz was obtained, corresponding to a dielectric constant of 26.3. Moreover, a low leakage current density of 3.9 × 10-8 A/cm2 at 1 V has been realized. Bending test shows that the capacitors have better performances in concave conditions than in convex conditions. The capacitors exhibit an average optical transmittance of about 70% in visible range and thus open the door for applications in transparent and flexible integrated circuits.

  20. ESR and magnetization studies of Fe2O3-Bi2O3-ZnO-PbO glass system

    NASA Astrophysics Data System (ADS)

    Pelluri, Sandhya Rani; Singh, Rajender

    2016-11-01

    The electron spin resonance (ESR) and magnetization measurements were undertaken to understand the magnetic phenomena in the glass system with composition (Fe2O3)x (70 Bi2O3 20 ZnO 10 PbO)1-x (x=15, 20 and 25 mol%). At high temperature the ESR spectra consists of narrow resonance at g~2. As the temperature decreases a second resonance peak emerges and with further decrease in temperature, the second resonance peak progressively shifts towards lower field value. The ESR data shows the formation of superparamagnetic clusters. The temperature dependent magnetization data exhibits a spin glass-like transition and a superparamagnetic blocking at a temperature which increases with increase in x value.

  1. Mesospheric H2O and H2O2 densities inferred from in situ positive ion composition measurement

    NASA Technical Reports Server (NTRS)

    Kopp, E.

    1984-01-01

    A model for production and loss of oxonium ions in the high-latitude D-region is developed, based on the observed excess of 34(+) which has been interpreted as H2O2(+). The loss mechanism suggested in the study is the attachment of N2 and/or CO2 in three-body reactions. Furthermore, mesospheric water vapor and H2O2 densities are inferred from measurements of four high-latitude ion compositions, based on the oxonium model. Mixing ratios of hydrogen peroxide of up to two orders of magnitude higher than previous values were obtained. A number of reactions, reaction constants, and a block diagram of the oxonium ion chemistry in the D-region are given.

  2. Effects of H2O and H2O2 on Thermal Desorption of Tritium from Stainless Steel

    SciTech Connect

    Quinlan, M.J.; Shmayda, W.T.; Lim, S.; Salnikov, S.; Chambers, Z.; Pollock, E.; Schroder, W.U.

    2010-03-12

    Tritiated stainless steel was subjected to thermal desorption at various temperatures, different temperature profiles, and in the presence of different helium carrier gas additives. In all cases the identities of the desorbing tritiated species were characterized as either water-soluble or insoluble. The samples were found to contain 1.1 mCi±0.4 mCi. Approximately ninety-five percent of this activity was released in molecular water-soluble form. Additives of H2O or H2O2 to dry helium carrier gas increase the desorption rate and lower the maximum temperature to which the sample must be heated, in order to remove the bulk of the tritium. The measurements validate a method of decontamination of tritiated steel and suggest a technique that can be used to further explore the mechanisms of desorption from tritiated metals.

  3. Computational study of the I2O5 + H2O = 2 HOIO2 gas-phase reaction

    NASA Astrophysics Data System (ADS)

    Khanniche, Sarah; Louis, Florent; Cantrel, Laurent; Černušák, Ivan

    2016-10-01

    This paper presents the mechanism and the kinetics of the I2O5 (g) + H2O (g) = 2 HOIO2 (g) reaction. The potential energy surface was explored with the B3LYP and MP2 methods with the aug-cc-pVTZ basis set. The rate constants were computed as a function of temperature (250-750 K) using transition state theory. At the CCSD(T)/CBS level, the rate constants were estimated to be: (k in cm3 molecule-1 s-1) kforward(T) = 3.61 × 10-22 × T2.05 exp (-32.3 (kJ mol-1)/RT) and kreverse (T) = 6.73 × 10-27 × T2.90 exp (-24.5 (kJ mol-1)/RT). Implications for atmospheric chemistry and nuclear safety issues are discussed.

  4. Transparent and flexible capacitors based on nanolaminate Al2O3/TiO2/Al2O3.

    PubMed

    Zhang, Guozhen; Wu, Hao; Chen, Chao; Wang, Ti; Yue, Jin; Liu, Chang

    2015-01-01

    Transparent and flexible capacitors based on nanolaminate Al2O3/TiO2/Al2O3 dielectrics have been fabricated on indium tin oxide-coated polyethylene naphthalate substrates by atomic layer deposition. A capacitance density of 7.8 fF/μm(2) at 10 KHz was obtained, corresponding to a dielectric constant of 26.3. Moreover, a low leakage current density of 3.9 × 10(-8) A/cm(2) at 1 V has been realized. Bending test shows that the capacitors have better performances in concave conditions than in convex conditions. The capacitors exhibit an average optical transmittance of about 70% in visible range and thus open the door for applications in transparent and flexible integrated circuits.

  5. H2O Adsorption on Smectites: Application to the Diurnal Variation of H2O in the Martian Atmosphere

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Howard, J.; Quinn, R. C.

    2000-01-01

    Observations of the Martian planetary boundary layer lead to interpretations that are baffling and contradictory. In this paper, we specifically address the question of whether or not water vapor finds a substantial diurnal reservoir in the Martian regolith. To address this issue, we have measured H2O adsorption kinetics on SWy-1, a Na-rich montmorillonite from Wyoming. The highest-temperature (273 K) data equilibrates rapidly. Data gathered at realistic H2O partial pressures and temperatures appropriate to early morning show two phenomena that preclude a significant role for smectites in diurnally exchanging a large column abundance. First, the equilibration timescale is longer than a sol. Second, the equilibrium abundances are a small fraction of that predicted by earlier adsorption isotherms. The explanation for this phenomenon is that smectite clay actually increases its surface area as a function of adsorptive coverage. At Mars-like conditions, we show that the interlayer sites of smectites are likely to be unavailable.

  6. Kagome staircase compounds Ni3V2O8 and Co3V2O8 studied with implanted muons

    NASA Astrophysics Data System (ADS)

    Lancaster, T.; Blundell, S. J.; Baker, P. J.; Prabhakaran, D.; Hayes, W.; Pratt, F. L.

    2007-02-01

    We present the results of muon-spin relaxation (μ+SR) measurements on the kagome staircase compounds Ni3V2O8 and Co3V2O8 . The magnetic behavior of these materials may be described in terms of two inequivalent magnetic ion sites, known as spine sites and cross-tie sites. Our μ+SR results allow us to probe each of these sites individually, revealing the distribution of the local magnetic fields near these positions. We are able not only to confirm the magnetic structures of the various phases proposed on the basis of bulk measurements but also to give an insight into the temperature evolution of the local field distribution in each phase.

  7. Photoionization of rotationally cooled H2O and D2O in the region 650-990 A

    NASA Astrophysics Data System (ADS)

    Dehmer, P. M.; Holland, D. M. P.

    1991-03-01

    Room temperature and rotationally cooled relative photoionization cross sections for H2O and D2O were determined in the wavelength region 650-990 A with a wavelength resolution of 0.06-0.11 A. The spectra were normalized to the absolute photoionization cross sections determined by Katayama et al. (1973) with lower resolution. A rotational analysis of the Pi subbands in the (0,6,0) and (0,8,0) bands of a Rydberg transition determined the symmetry of the upper state; in addition, the series was extended to higher principal quantum numbers. The analysis of these and other bands was made difficult both by the large natural linewidths of the rotational transitions and by the absence of transitions to rotational levels with N-prime above 3.

  8. MgV 2O 5and δLi xV 2O 5: A Comparative Structural Investigation

    NASA Astrophysics Data System (ADS)

    Millet, Patrice; Satto, Christine; Sciau, Philippe; Galy, Jean

    1998-02-01

    The structures of MgV 2O 5and δLiV 2O 5have been determined form X-ray powder diffraction Rietveld analysis at 294 and 83 K. The compounds crystallize in the orthorhombic system, space group Cmcm, with the following cell parameters (Å): at 294 K, aMg=3.6913(2), bMg=9.9710(4), cMg=11.0173(4), aLi= 3.6047(2), bLi=9.9157(5), cLi=11.2479(4); at 83 K, aMg= 3.6928(2), bMg=9.9576(3), cMg=11.0096(4), aLi=3.6031(2), bLi=9.8734(4), cLi=11.2350(4). The general network, with four formulas per unit, is built up by parallel puckered [V 2O 5] nlayers of [VO 5] square pyramids sharing edges and corners alternately shifted by a/2 in the [100] direction and held together by intercalated Mg or Li atoms. The main difference between the two is induced by the higher polarization of the magnesium atoms compared to the lithium atoms, which leads to higher puckering angles of 21.0° and 11.3°, respectively. Both magnesium and lithium atoms are surrounded by four close oxygens making a distorted tetrahedron. Despite the presence of both V 4+and V 5+in δLiV 2O 5, no electronic localization occurs at the crystallographic sites corresponding to these vanadium species. This fact could be attributed to the low energy available to the system during the low-temperature synthesis.

  9. Impedance spectroscopy of V2O5-Bi2O3-BaTiO3 glass-ceramics

    NASA Astrophysics Data System (ADS)

    Al-syadi, Aref M.; Yousef, El Sayed; El-Desoky, M. M.; Al-Assiri, M. S.

    2013-12-01

    The glasses within composition as: (80 - x)V2O5/20Bi2O3/xBaTiO3 with x = 2.5, 5, 7.5 and 10 mol% have been prepared. The glass transition (Tg) increases with increasing BaTiO3 content. Synthesized glasses ceramic containing BaTi4O9, Ba3TiV4O15 nanoparticles of the order of 25-35 nm and 30-46 nm, respectively were estimated using XRD. The dielectric properties over wide ranges of frequencies and temperatures were investigated as a function of BaTiO3 content by impedance spectroscopy measurements. The hopping frequency, ωh, dielectric constant, ɛ', activation energies for the DC conduction, Eσ, the relaxation process, Ec, and stretched exponential parameter β of the glasses samples have been estimated. The, ωh,β, decrease from 51.63 to 0.31 × 106 (s-1), 0.84 to 0.79 with increasing BaTiO3 respectively. Otherwise, the Eσ, increase from 0.279 to 0.306 eV with increasing BaTiO3. The value of dielectric constant equal 9.5·103 for the 2.5BaTiO3/77.5V2O5/20Bi2O3 glasses-ceramic at 330 K for 1 KHz which is ten times larger than that of same glasses composition. Finally the relaxation properties of the investigated glasses are presented in the electric modulus formalism, where the relaxation time and the respective activation energy were determined.

  10. Al6Ti2O13, a new phase in the Al2O3-TiO2 system.

    PubMed

    Norberg, Stefan T; Hoffmann, Stefan; Yoshimura, Masahiro; Ishizawa, Nobuo

    2005-03-01

    The compound Al6Ti2O13 (hexaaluminium dititanium tridecaoxide) has been synthesized using an arc-imaging furnace, which allows fast cooling of melted oxides. The structure consists of infinite double chains of polyhedra running along the c axis. These chains are built up by four kinds of strongly distorted oxygen octahedra randomly occupied by either Ti or Al (point symmetry m or m2m), and by trigonal bipyramids exclusively occupied by Al (point symmetry m2m).

  11. Comparison of the growth kinetics of In2O3 and Ga2O3 and their suboxide desorption during plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Vogt, Patrick; Bierwagen, Oliver

    2016-08-01

    We present a comprehensive study of the In2O3 growth kinetics during plasma-assisted molecular beam epitaxy and compare it to that of the related oxide Ga2O3 [P. Vogt and O. Bierwagen, Appl. Phys. Lett. 108, 072101 (2016)]. The growth rate and desorbing fluxes were measured during growth in-situ by a laser reflectometry set-up and line-of-sight quadrupole mass spectrometer, respectively. We extracted the In incorporation as a function of the provided In flux, different growth temperatures TG, and In-to-O flux ratios r. The data are discussed in terms of the competing formation of In2O3 and desorption of the suboxide In2O and O. The same three growth regimes as in the case of Ga2O3 can be distinguished: (i) In-transport limited, O-rich (ii) In2O-desorption limited, O-rich, and (iii) O-transport limited, In-rich. In regime (iii), In droplets are formed on the growth surface at low TG. The growth kinetics follows qualitatively that of Ga2O3 in agreement with their common oxide and suboxide stoichiometry. The quantitative differences are mainly rationalized by the difference in In2O and Ga2O desorption rates and vapor pressures. For the In2O, Ga2O, and O desorption, we extracted the activation energies and frequency factors by means of Arrhenius-plots.

  12. Thermodynamics and Structure of CaO-Al2O3-3 Mass Pct B2O3 Slag at 1773 K (1500 °C)

    NASA Astrophysics Data System (ADS)

    Shu, Qifeng; Li, Pengfei; Zhang, Xiang; Chou, Kuochih

    2016-08-01

    Activity values of Al2O3 in CaO-Al2O3-B2O3 systems at 1773 K (1500 °C) were determined experimentally using a gas-copper-slag equilibrium technique. The oxygen partial pressure was controlled by C/CO equilibrium. A negative deviation from ideality was found in measured activity of Al2O3. The activity coefficient of Al2O3 decreases with the increase of CaO/Al2O3 ratio. To interpret the variation of Al2O3 activity with composition, structures of CaO-Al2O3-B2O3 glassy slag were investigated by using Raman spectroscopy. It was found that the number of bridging oxygen decreases with increasing CaO/Al2O3 ratio. With increase of CaO content, the aluminate network was gradually depolymerized, which corresponds to the decrease of the activity coefficient of Al2O3.

  13. Spectroscopic studies of In2O3 nanostructures; photovoltaic demonstration of In2O3/p-Si heterojunction.

    PubMed

    Bhat, Thirumaleshwara N; Roul, Basanta; Rajpalke, Mohana K; Kumar, Mahesh; Krupanidhi, S B

    2013-01-01

    The thermal oxidation process of the indium nitride (InN) nanorods (NRs) was studied. The SEM studies reveal that the cracked and burst mechanism for the formation of indium oxide (In2O3) nanostructures by oxidizing the InN NRs at higher temperatures. XRD results confirm the bcc crystal structure of the as prepared In2O3 nanostructures. Strong and broad photoluminescence spectrum located at the green to red region with maximum intensity at 566 nm along with a weak ultraviolet emission at 338 nm were observed due to oxygen vacancy levels and free excitonic transitions, respectively. The valence band onset energy of 2.1 eV was observed from the XPS valence band spectrum, clearly justifies the alignment of Fermi level to the donor level created due to the presence of oxygen vacancies which were observed in the PL spectrum. The elemental ratio In:O in as prepared In2O3 was found to be 42:58 which is in close agreement with the stoichiometric value of 40:60. A downward shift was observed in the Raman peak positions due to a possible phonon confinement effect in the nanoparticles formed in bursting mechanism. Such single junction devices exhibit promising photovoltaic performance with fill factor and conversion efficiency of 21% and 0.2%, respectively, under concentrated AM1.5 illumination.

  14. Characterization and electrical properties of V 2O 5-CuO-P 2O 5 glasses

    NASA Astrophysics Data System (ADS)

    Al-Assiri, M. S.

    2008-08-01

    Characterization and electrical properties of vanadium-copper-phosphate glasses of compositions xV 2O 5-(40- x)CuO-60P 2O 5 have been reported. X-ray diffraction (XRD) confirms the amorphous nature of these glasses. It was observed that, the density ( d) decreases gradually while the molar volume ( Vm) increases with the increase of the vanadium oxide content in such glasses. This may be due to the effect of the polarizing power strength, PPS, which is a measure of ratio of the cation valance to its diameter. The dc conductivity increases while the activation energy decreases with the increase of the V 2O 5 content. The dc conductivity in the present glasses is electronic and depends strongly upon the average distance, R, between the vanadium ions. Analysis of the electrical properties has been made in the light of small polaron hopping model. The parameters obtained from the fits of the experimental data to this model are reasonable and consistent with glass composition. The conduction is attributed to non-adiabatic hopping of small polaron.

  15. Optimizing Colorimetric Assay Based on V2O5 Nanozymes for Sensitive Detection of H2O2 and Glucose

    PubMed Central

    Sun, Jiaheng; Li, Chunyan; Qi, Yanfei; Guo, Shuanli; Liang, Xue

    2016-01-01

    Nanozyme-based chemical sensing is a rapidly emerging field of research. Herein, a simple colorimetric assay for the detection of hydrogen peroxide and glucose based on the peroxidase-like activity of V2O5 nanozymes has been established. In this assay, the effects of pH, substrate, nanozyme concentrations and buffer solution have been investigated. It was found that compared with 3,3′,5,5′-tetramethylbenzidine (TMB), the enzyme substrate o-phenylenediamine (OPD) seriously interfered with the H2O2 detection. Under the optimal reaction conditions, the resulting sensor displayed a good response to H2O2 with a linear range of 1 to 500 μM, and a detection limit of 1 μM at a signal-to-noise ratio of 3. A linear correlation was established between absorbance intensity and concentration of glucose from 10 to 2000 μM, with a detection limit of 10 μM. The current work presents a simple, cheap, more convenient, sensitive, and easy handling colorimetric assay. PMID:27110794

  16. Effect of Cu2O morphology on photocatalytic hydrogen generation and chemical stability of TiO2/Cu2O composite.

    PubMed

    Zhu, Lihong; Zhang, Junying; Chen, Ziyu; Liu, Kejia; Gao, Hong

    2013-07-01

    Improving photocatalytic activity and stability of TiO2/Cu2O composite is a challenge in generating hydrogen from water. In this paper, the TiO2 film/Cu2O microgrid composite was prepared via a microsphere lithography technique, which possesses a remarkable performance of producing H2 under UV-vis light irradiation, in comparison with pure TiO2 film, Cu2O film and TiO2 film/Cu2O film. More interesting is that in TiO2 film/Cu2O microgrid, photo-corrosion of Cu2O can be retarded. After deposition of Pt on its surface, the photocatalytic activity of TiO2/Cu2O microgrid in producing H2 is improved greatly. PMID:23901536

  17. Current conduction and resistive switching characteristics of Sm2O3 and Lu2O3 thin films for low-power flexible memory applications

    NASA Astrophysics Data System (ADS)

    Mondal, Somnath; Chueh, Ching-Hao; Pan, Tung-Ming

    2014-01-01

    In this article, the current conduction and resistive switching (RS) behavior in flexible Sm2O3 and Lu2O3 resistive random access memories (ReRAM) are investigated. Amorphous Sm2O3 and Lu2O3 thin films were deposited at room temperature by radio-frequency magnetron sputtering on flexible polyethylene terephthalate substrate. The structural morphologies of the Sm2O3 and Lu2O3 thin films strongly depend on the lattice energy of the oxides. The dominant current conduction mechanism in the oxide layer changes from electrode control Schottky emission in Sm2O3 to bulk controlled space-charge-limited-current in Lu2O3. The barrier height extracted from Schottky emission model is 0.96 eV in Sm2O3 thin film, while the activation energy of traps calculated from the Arrhenius plots is about 0.23 eV in Lu2O3 thin film. Additionally, the Ni/Sm2O3/ITO flexible memory device shows promising RS behavior with very low power of operation (˜30 μW) and small distribution of switching parameters. The memory reliability characteristics of switching endurance, data retention, good flexibility, and mechanical endurance show promising for future memory applications. The filament conduction model is adopted to describe the RS behavior in the Sm2O3 and Lu2O3 ReRAM devices. The improved RS performance in Sm2O3 thin film is attributed to the different physical properties of the thin films.

  18. Nb2O5-γ-Al2O3 nanofibers as heterogeneous catalysts for efficient conversion of glucose to 5-hydroxymethylfurfural

    NASA Astrophysics Data System (ADS)

    Jiao, Huanfeng; Zhao, Xiaoliang; Lv, Chunxiao; Wang, Yijun; Yang, Dongjiang; Li, Zhenhuan; Yao, Xiangdong

    2016-09-01

    One-dimensional γ-Al2O3 nanofibers were modified with Nb2O5 to be used as an efficient heterogeneous catalyst to catalyze biomass into 5-hydroxymethylfurfural (5-HMF). At low Nb2O5 loading, the niobia species were well dispersed on γ-Al2O3 nanofiber through Nb–O–Al bridge bonds. The interaction between Nb2O5 precursor and γ-Al2O3 nanofiber results in the niobia species with strong Lewis acid sites and intensive Brønsted acid sites, which made 5-HMF yield from glucose to reach the maximum 55.9~59.0% over Nb2O5-γ-Al2O3 nanofiber with a loading of 0.5~1 wt% Nb2O5 at 150 °C for 4 h in dimethyl sulfoxide. However, increasing Nb2O5 loading could lead to the formation of two-dimensional polymerized niobia species, three-dimensional polymerized niobia species and crystallization, which significantly influenced the distribution and quantity of the Lewis acid sites and Brönst acid sites over Nb2O5-γ-Al2O3 nanofiber. Lewis acid site Nbδ+ played a key role on the isomerization of glucose to fructose, while Brønsted acid sites are more active for the dehydration of generated fructose to 5-HMF. In addition, the heterogeneous Nb2O5-γ-Al2O3 nanofiber catalyst with suitable ratio of Lewis acid to Brönsted sites should display an more excellent catalytic performance in the conversion of glucose to 5-HMF.

  19. Short belt-like Ca 2 B 2 O 5 ·H 2 O nanostructures: Hydrothermal formation, FT-IR, thermal decomposition, and optical properties

    NASA Astrophysics Data System (ADS)

    Zhu, Wancheng; Zhang, Xiao; Wang, Xiaoli; Zhang, Heng; Zhang, Qiang; Xiang, Lan

    2011-10-01

    Uniform high crystallinity short belt-like Ca 2B 2O 5·H 2O nanostructures (nanobelts) were facilely synthesized through a room temperature coprecipitation of CaCl 2, H 3BO 3, and NaOH solutions, followed by a mild hydrothermal treatment (180 °C, 12.0 h). By a preferential growth parallel to the (1 0 0) planes, Ca 2B 2O 5·H 2O nanobelts with a length of 1-5 μm, a width of 100-400 nm, and a thickness of 55-90 nm were obtained. The calcination of the nanobelts at 500 °C for 2.0 h led to short Ca 2B 2O 5 nanobelts with well preserved 1D morphology. Calcination at 800 °C led to a mixture of Ca 2B 2O 5 and Ca 3B 2O 6. The products were with belt-like and quasi-polyhedron morphology, while they turned into pore-free micro-rod like and polyhedron morphology when the calcination was taken in the presence of NaCl. NaCl assisted high temperature calcination at 900 °C promoted the formation of Ca 3B 2O 6 in the products. When dispersed in deionized water or absolute ethanol, the Ca 2B 2O 5·H 2O nanobelts and Ca 2B 2O 5 nanobelts showed good transparency from the ultraviolet to the visible region. The as-synthesized Ca 2B 2O 5·H 2O and Ca 2B 2O 5 nanobelts can be employed as novel metal borate nanomaterials for further potential applications in the area of glass fibers, antiwear additive, ceramic coatings, and so on.

  20. Nb2O5-γ-Al2O3 nanofibers as heterogeneous catalysts for efficient conversion of glucose to 5-hydroxymethylfurfural

    PubMed Central

    Jiao, Huanfeng; Zhao, Xiaoliang; Lv, Chunxiao; Wang, Yijun; Yang, Dongjiang; Li, Zhenhuan; Yao, Xiangdong

    2016-01-01

    One-dimensional γ-Al2O3 nanofibers were modified with Nb2O5 to be used as an efficient heterogeneous catalyst to catalyze biomass into 5-hydroxymethylfurfural (5-HMF). At low Nb2O5 loading, the niobia species were well dispersed on γ-Al2O3 nanofiber through Nb–O–Al bridge bonds. The interaction between Nb2O5 precursor and γ-Al2O3 nanofiber results in the niobia species with strong Lewis acid sites and intensive Brønsted acid sites, which made 5-HMF yield from glucose to reach the maximum 55.9~59.0% over Nb2O5-γ-Al2O3 nanofiber with a loading of 0.5~1 wt% Nb2O5 at 150 °C for 4 h in dimethyl sulfoxide. However, increasing Nb2O5 loading could lead to the formation of two-dimensional polymerized niobia species, three-dimensional polymerized niobia species and crystallization, which significantly influenced the distribution and quantity of the Lewis acid sites and Brönst acid sites over Nb2O5-γ-Al2O3 nanofiber. Lewis acid site Nbδ+ played a key role on the isomerization of glucose to fructose, while Brønsted acid sites are more active for the dehydration of generated fructose to 5-HMF. In addition, the heterogeneous Nb2O5-γ-Al2O3 nanofiber catalyst with suitable ratio of Lewis acid to Brönsted sites should display an more excellent catalytic performance in the conversion of glucose to 5-HMF. PMID:27666867

  1. From strong van der Waals complexes to hydrogen bonding: From CO⋯H2O to CS⋯H2O and SiO⋯H2O complexes.

    PubMed

    Zhang, Yan; Hollman, David S; Schaeffer, Henry F

    2012-06-28

    Structures and interaction energies of complexes valence isoelectronic to the important CO⋯H(2)O complex, namely SiO⋯H(2)O and CS⋯H(2)O, have been studied for the first time using high-level ab initio methods. Although CO, SiO, and CS are valence isoelectronic, the structures of their complexes with water differ significantly, owing partially to their widely varied dipole moments. The predicted dissociation energies D(0) are 1.8 (CO⋯H(2)O), 2.7 (CS⋯H(2)O), and 4.9 (SiO⋯H(2)O) kcal∕mol. The implications of these results have been examined in light of the dipole moments of the separate moieties and current concepts of hydrogen bonding. It is hoped that the present results will spark additional interest in these complexes and in the general non-covalent paradigms they represent.

  2. Silver(I) diaqua-nickel(II) catena-borodiphosphate(V) hydrate, (Ag(0.57)Ni(0.22))Ni(H(2)O)(2)[BP(2)O(8)]·0.67H(2)O.

    PubMed

    Zouihri, Hafid; Saadi, Mohamed; Jaber, Boujemaa; El Ammari, Lahcen

    2011-08-01

    The structure framework of the title compound, (Ag(0.57)Ni(0.22))Ni(H(2)O)(2)[BP(2)O(8)]·0.67H(2)O, is the same as that of its recently published counterpart AgMg(H(2)O)(2)[BP(2)O(8)]·H(2)O. In the title structure, the Ag, Ni, B and one O atom are located on special positions (sites symmetry 2). The structure consists of infinite borophosphate helical [BP(2)O(8)](3-) ribbons, built up from alternate BO(4) and PO(4) tetra-hedra arranged around the 6(5) screw axes. The vertex-sharing BO(4) and PO(4) tetra-hedra form a spiral ribbon of four-membered rings in which BO(4) and PO(4) groups alternate. The ribbons are connected through slightly distorted NiO(4)(H(2)O)(2) octa-hedra, four O atoms of which belong to the phosphate groups. The resulting three-dimensional framework is characterized by hexa-gonal channels running along [001]. However, the main difference between the structures of these two compounds lies in the filling ratio of Wyckoff positions 6a and 6b in the tunnels. Indeed, in this work, the refinement of the occupancy rate of sites 6a and 6b shows that the first is occupied by water at 67% and the second is partially occupied by 56.6% of Ag and 21.6% of Ni. In the AgMg(H(2)O)(2)[BP(2)O(8)]·H(2)O structure, these two sites are completely occupied by H(2)O and Ag(+), respectively. The title structure is stabilized by O-H⋯O hydrogen bonds between water mol-ecules and O atoms that are part of the helices. PMID:22090808

  3. Nuclear magnetic relaxation in the ferrimagnetic chain compound NiCu(C7H6N2O6)(H2O)3·2H2O : three-magnon scattering?

    NASA Astrophysics Data System (ADS)

    Hori, Hiromitsu; Yamamoto, Shoji

    2004-12-01

    Recent proton spin-lattice relaxation-time (T1) measurements on the ferrimagnetic chain compound NiCu(C7H6N2O6)(H2O)3·2H2O are explained by an elaborately modified spin-wave theory. We give strong evidence of the major contribution to 1/T1 being made by the three-magnon scattering rather than the Raman scattering.

  4. Response of Prochlorococcus to varying CO2:O2 ratios.

    PubMed

    Bagby, Sarah C; Chisholm, Sallie W

    2015-10-01

    Carbon fixation has a central role in determining cellular redox poise, increasingly understood to be a key parameter in cyanobacterial physiology. In the cyanobacterium Prochlorococcus-the most abundant phototroph in the oligotrophic oceans-the carbon-concentrating mechanism is reduced to the bare essentials. Given the ability of Prochlorococcus populations to grow under a wide range of oxygen concentrations in the ocean, we wondered how carbon and oxygen physiology intersect in this minimal phototroph. Thus, we examined how CO2:O2 gas balance influenced growth and chlorophyll fluorescence in Prochlorococcus strain MED4. Under O2 limitation, per-cell chlorophyll fluorescence fell at all CO2 levels, but still permitted substantial growth at moderate and high CO2. Under CO2 limitation, we observed little growth at any O2 level, although per-cell chlorophyll fluorescence fell less sharply when O2 was available. We explored this pattern further by monitoring genome-wide transcription in cells shocked with acute limitation of CO2, O2 or both. O2 limitation produced much smaller transcriptional changes than the broad suppression seen under CO2 limitation and CO2/O2 co-limitation. Strikingly, both CO2 limitation conditions initially evoked a transcriptional response that resembled the pattern previously seen in high-light stress, but at later timepoints we observed O2-dependent recovery of photosynthesis-related transcripts. These results suggest that oxygen has a protective role in Prochlorococcus when carbon fixation is not a sufficient sink for light energy.

  5. Heating rate effects in simulated liquid Al2O_3

    NASA Astrophysics Data System (ADS)

    van Hoang, Vo

    2006-01-01

    The heating rate effects in simulated liquid Al{2}O{3} have been investigated by Molecular Dynamics (MD) method. Simulations were done in the basic cube under periodic boundary conditions containing 3000 ions with Born-Mayer type pair potentials. The temperature of the system was increasing linearly in time from the zero temperature as T(t)=T0 +γ t, where γ is the heating rate. The heating rate dependence of density and enthalpy of the system was found. Calculations show that static properties of the system such as the coordination number distributions and bond-angle distributions slightly depend on γ . Structure of simulated amorphous Al{2}O{3} model with the real density at the ambient pressure is in good agreement with Lamparter's experimental data. The heating rate dependence of dynamics of the system has been studied through the diffusion constant, mean-squared atomic displacement and comparison of partial radial distribution functions (PRDFs) for 10% most mobile and immobile particles with the corresponding mean ones. Finally, the evolution of diffusion constant of Al and O particles and structure of the system upon heating for the smallest heating rate was studied and presented. And we find that the temperature dependence of self-diffusion constant in the high temperature region shows a crossover to one which can be described well by a power law, D∝ (T-Tc )^γ . The critical temperature Tc is about 3500 K and the exponent γ is close to 0.941 for Al and to 0.925 for O particles. The glass phase transition temperature Tg for the Al{2}O{3} system is at anywhere around 2000 K.

  6. Response of Prochlorococcus to varying CO2:O2 ratios

    PubMed Central

    Bagby, Sarah C; Chisholm, Sallie W

    2015-01-01

    Carbon fixation has a central role in determining cellular redox poise, increasingly understood to be a key parameter in cyanobacterial physiology. In the cyanobacterium Prochlorococcus—the most abundant phototroph in the oligotrophic oceans—the carbon-concentrating mechanism is reduced to the bare essentials. Given the ability of Prochlorococcus populations to grow under a wide range of oxygen concentrations in the ocean, we wondered how carbon and oxygen physiology intersect in this minimal phototroph. Thus, we examined how CO2:O2 gas balance influenced growth and chlorophyll fluorescence in Prochlorococcus strain MED4. Under O2 limitation, per-cell chlorophyll fluorescence fell at all CO2 levels, but still permitted substantial growth at moderate and high CO2. Under CO2 limitation, we observed little growth at any O2 level, although per-cell chlorophyll fluorescence fell less sharply when O2 was available. We explored this pattern further by monitoring genome-wide transcription in cells shocked with acute limitation of CO2, O2 or both. O2 limitation produced much smaller transcriptional changes than the broad suppression seen under CO2 limitation and CO2/O2 co-limitation. Strikingly, both CO2 limitation conditions initially evoked a transcriptional response that resembled the pattern previously seen in high-light stress, but at later timepoints we observed O2-dependent recovery of photosynthesis-related transcripts. These results suggest that oxygen has a protective role in Prochlorococcus when carbon fixation is not a sufficient sink for light energy. PMID:25848872

  7. N2O decomposition by mesoporous silica supported Rh catalysts.

    PubMed

    Hussain, Murid; Fino, Debora; Russo, Nunzio

    2012-04-15

    Nitrous oxide (N(2)O), a greenhouse gas produced by nitric acid and adipic acid plants, damages the ozone layer and causes many environmental problems. The potential of MCM-41, SBA-15-Conventional (SBA-15-C), SBA-15-Spherical (SBA-15-S) and KIT-6 supported Rh catalysts has been explored at specific conditions for N(2)O decomposition in order to investigate the characteristics of new catalyst supports (SBA-15-S, KIT-6) for this application. A Rh metal loading of 1 wt% was impregnated to synthesize mesoporous silica supported Rh catalysts. The catalysts were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), N(2) adsorption/desorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and CO-chemisorption techniques. Of all the catalysts, Rh/SBA-15-S not only showed the highest activity, but also the best strength against ageing impact, O(2) inhibiting effect and long-term stability. The higher metal dispersion due to the smaller Rh particle size and a greater formation of Rh(+1) than Rh(0) or Rh(+3) on SBA-15-S compared to the other supports, favoured a higher N(2)O decomposition. The larger pore size of SBA-15-S in Rh/SBA-15-S might favour a better Rh access, diffusion and dispersion and lead to higher activity. The higher long-term stability of Rh/SBA-15-S, with preserved support characteristics, than the other supports indicates its significance.

  8. Coordination Modes of Americium in the Am2(C2O4)3(H2O)6·4H2O Oxalate: Synthesis, Crystal Structure, Spectroscopic Characterizations and Comparison in the M2(C2O4)3(H2O)6·nH2O (M = Ln, An) Series.

    PubMed

    Tamain, C; Arab-Chapelet, B; Rivenet, M; Legoff, X F; Loubert, G; Grandjean, S; Abraham, F

    2016-01-01

    Americium oxalate single crystals, Am2(C2O4)3(H2O)6·4H2O, were prepared by in situ oxalic acid generation by slow hydrolysis of the diester. Their structure was determined by single-crystal X-ray diffraction and was solved by the direct methods and Fourier difference techniques. The structure (space group P21/c, a = 11.184(4) Å, b = 9.489(4) Å, c = 10.234(4) Å, β = 114.308(8)°, Z = 2) consists of layers formed by six-membered rings of actinide metals connected through oxalate ions. The americium atoms are nine-coordinated by six oxygen atoms from three bidentate oxalate ligands and three water molecules. The distances within the coordination sphere as well as infrared and Raman spectra of several isostructural lanthanide (Ce(III), Pr(III), Nd(III), Sm(III), Gd(III)) and actinide (Pu(III), Am(III)) oxalates were compared to evaluate the similarities and the differences between the two series. PMID:26675037

  9. Photodissociation of N2O: excitation of 1A" states.

    PubMed

    Schinke, Reinhard; Schmidt, Johan A

    2012-11-26

    We investigate the contributions of the lowest two (1)A" states in the UV photodissociation of N(2)O employing three-dimensional potential energy surfaces and transition dipole moment functions. Because the transition dipole moments are much smaller than for the 2 (1)A' state, we conclude that excitation of the (1)A" states has a marginal effect. The dense vibrational spectrum of the quasi-bound 2(1)A" state possibly explains some of the tiny, noise-like structures of the measured absorption spectrum. PMID:22536943

  10. Frank-Condon factors for H2O(+) molecular bands

    NASA Astrophysics Data System (ADS)

    Shefov, N. N.

    1983-11-01

    The Frank-Condon factors q sub (v' v'') are calculated for the spectra of the H2O(+) molecule by the method of Volkenstein et al. (1972). The results are presented in a table for values of v' from 5 to 17 and of v'' from zero to 4, indicating which bands have been observed either in the laboratory or in comets. It is shown that the photon scattering coefficient of Chamberlain (1978) can be calculated using these data for the (8,0) band; values of about 0.060 for the earth and about 0.17 for Halley's comet (at its 1986 perihelion) are determined.

  11. Large magnetoelectric coupling in Co4Nb2O9

    PubMed Central

    Fang, Y.; Song, Y. Q.; Zhou, W. P.; Zhao, R.; Tang, R. J.; Yang, H.; Lv, L. Y.; Yang, S. G.; Wang, D. H.; Du, Y. W.

    2014-01-01

    Magnetoelectric materials which simultaneously exhibit electric polarization and magnetism have attracted more and more attention due to their novel physical properties and promising applications for next-generation devices. Exploring new materials with outstanding magnetoelectric performance, especially the manipulation of magnetization by electric field, is of great importance. Here, we demonstrate the cross-coupling between magnetic and electric orders in polycrystalline Co4Nb2O9, in which not only magnetic-field-induced electric polarization but also electric field control of magnetism is observed. These results reveal rich physical phenomenon and potential applications in this compound. PMID:24463631

  12. A neutron diffraction study of RMn2O5 multiferroics

    NASA Astrophysics Data System (ADS)

    Radaelli, P. G.; Chapon, L. C.

    2008-10-01

    The magnetic properties of RMn2O5 multiferroics as obtained by unpolarized and polarized neutron diffraction experiments are reviewed. We discuss the qualitative features of the magnetic phase diagram in both zero magnetic field and in field and analyze the commensurate magnetic structure and its coupling to an applied electric field. The origin of ferroelectricity is discussed based on calculations of the ferroelectric polarization predicted by different microscopic coupling mechanisms (exchange-striction and cycloidal spin-orbit models). A minimal model containing a small set of parameters is also presented in order to understand the propagation of the magnetic structure along the c-direction.

  13. INTERSTELLAR H{sub 2}O MASERS FROM J SHOCKS

    SciTech Connect

    Hollenbach, David; Elitzur, Moshe; McKee, Christopher F.

    2013-08-10

    We present a model in which the 22 GHz H{sub 2}O masers observed in star-forming regions occur behind shocks propagating in dense regions (preshock density n{sub 0} {approx} 10{sup 6}-10{sup 8} cm{sup -3}). We focus on high-velocity (v{sub s} {approx}> 30 km s{sup -1}) dissociative J shocks in which the heat of H{sub 2} re-formation maintains a large column of {approx}300-400 K gas; at these temperatures the chemistry drives a considerable fraction of the oxygen not in CO to form H{sub 2}O. The H{sub 2}O column densities, the hydrogen densities, and the warm temperatures produced by these shocks are sufficiently high to enable powerful maser action. The observed brightness temperatures (generally {approx} 10{sup 11}-10{sup 14} K) are the result of coherent velocity regions that have dimensions in the shock plane that are 10-100 times the shock thickness of {approx}10{sup 13} cm. The masers are therefore beamed toward the observer, who typically views the shock ''edge-on'', or perpendicular to the shock velocity; the brightest masers are then observed with the lowest line-of-sight velocities with respect to the ambient gas. We present numerical and analytic studies of the dependence of the maser inversion, the resultant brightness temperature, the maser spot size and shape, the isotropic luminosity, and the maser region magnetic field on the shock parameters and the coherence path length; the overall result is that in galactic H{sub 2}O 22 GHz masers, these observed parameters can be produced in J shocks with n{sub 0} {approx} 10{sup 6}-10{sup 8} cm{sup -3} and v{sub s} {approx} 30-200 km s{sup -1}. A number of key observables such as maser shape, brightness temperature, and global isotropic luminosity depend only on the particle flux into the shock, j = n{sub 0} v{sub s} , rather than on n{sub 0} and v{sub s} separately.

  14. The Influence of Na2O on the Solidification and Crystallization Behavior of CaO-SiO2-Al2O3-Based Mold Flux

    NASA Astrophysics Data System (ADS)

    Gao, Jinxing; Wen, Guanghua; Sun, Qihao; Tang, Ping; Liu, Qiang

    2015-08-01

    The reaction between [Al] and SiO2 sharply increased the Al2O3 and decreased SiO2 contents in mold flux during the continuous casting of high-Al steels. These changes converted original CaO-SiO2-based flux into CaO-SiO2-Al2O3-based flux, promoting the crystallization and deteriorating the mold lubrication. Therefore, study on the solidification and crystallization behavior of CaO-SiO2-Al2O3-based mold flux, with the applicable fluidizers, is of importance. The effect of Na2O, predominantly used as the fluidizer in mold flux, on the solidification and crystallization behavior of CaO-SiO2-Al2O3-based mold flux needs to be investigated. In this study, a CaO-SiO2-Al2O3-based mold flux containing 6.5 wt pct Li2O was designed; the effect of Na2O on the solidification and crystallization behavior of these mold fluxes was investigated using the single hot thermocouple technique (SHTT) and the double hot thermocouple technique (DHTT). Moreover, the slag film obtained by a heat flux simulator was analyzed using X-ray diffraction (XRD). The results indicate that the solid fraction of molten slag (Fs) and the crystalline fraction of solid slag (Fc) in the mold slag films decrease with increasing Na2O content from 0 to 2 wt pct. However, Fs and Fc increased when the Na2O content increased from 2 to 6 wt pct. The critical cooling rates initially decreases and then increases with increasing Na2O content. The XRD analysis results show that LiAlO2 and CaF2 were the basic crystals for all the mold fluxes. Increasing the Na2O content both inhibits the Ca2Al2SiO7 formation and promotes the production of Ca12Al14O33, indicating that the mold lubrication deteriorated because of the high melting-point phase formation of Ca2Al2SiO7 in the CaO-SiO2-Al2O3-based mold flux containing 6.5 wt pct Li2O, without Na2O. The strong crystallization tendency also deteriorated the mold lubrication for the mold flux with a higher Na2O content. Therefore, the addition of Na2O was less than 2 wt pct in

  15. Controlled direct growth of Al2O3-doped HfO2 films on graphene by H2O-based atomic layer deposition.

    PubMed

    Zheng, Li; Cheng, Xinhong; Yu, Yuehui; Xie, Yahong; Li, Xiaolong; Wang, Zhongjian

    2015-02-01

    Graphene has been drawing worldwide attention since its discovery in 2004. In order to realize graphene-based devices, thin, uniform-coverage and pinhole-free dielectric films with high permittivity on top of graphene are required. Here we report the direct growth of Al2O3-doped HfO2 films onto graphene by H2O-based atom layer deposition (ALD). Al2O3-onto-HfO2 stacks benefited the doping of Al2O3 into HfO2 matrices more than HfO2-onto-Al2O3 stacks did due to the micro-molecular property of Al2O3 and the high chemical activity of trimethylaluminum (TMA). Al2O3 acted as a network modifier, maintained the amorphous structure of the film even to 800 °C, and made the film smooth with a root mean square (RMS) roughness of 0.8 nm, comparable to the surface of pristine graphene. The capacitance and the relative permittivity of Al2O3-onto-HfO2 stacks were up to 1.18 μF cm(-2) and 12, respectively, indicating the high quality of Al2O3-doped HfO2 films on graphene. Moreover, the growth process of Al2O3-doped HfO2 films introduced no detective defects into graphene confirmed by Raman measurements. PMID:25519447

  16. Indium-free, highly transparent, flexible Cu2O/Cu/Cu2O mesh electrodes for flexible touch screen panels

    PubMed Central

    Kim, Dong-Ju; Kim, Hyo-Joong; Seo, Ki-Won; Kim, Ki-Hyun; Kim, Tae-Wong; Kim, Han-Ki

    2015-01-01

    We report on an indium-free and cost-effective Cu2O/Cu/Cu2O multilayer mesh electrode grown by room temperature roll-to-roll sputtering as a viable alternative to ITO electrodes for the cost-effective production of large-area flexible touch screen panels (TSPs). By using a low resistivity metallic Cu interlayer and a patterned mesh structure, we obtained Cu2O/Cu/Cu2O multilayer mesh electrodes with a low sheet resistance of 15.1 Ohm/square and high optical transmittance of 89% as well as good mechanical flexibility. Outer/inner bending test results showed that the Cu2O/Cu/Cu2O mesh electrode had a mechanical flexibility superior to that of conventional ITO films. Using the diamond-patterned Cu2O/Cu/Cu2O multilayer mesh electrodes, we successfully demonstrated TSPS of the flexible film-film type and rigid glass-film-film type TSPs. The TSPs with Cu2O/Cu/Cu2O mesh electrode were used to perform zoom in/out functions and multi-touch writing, indicating that these electrodes are promising cost-efficient transparent electrodes to substitute for conventional ITO electrodes in large-area flexible TSPs. PMID:26582471

  17. Catalase activity is stimulated by H(2)O(2) in rich culture medium and is required for H(2)O(2) resistance and adaptation in yeast.

    PubMed

    Martins, Dorival; English, Ann M

    2014-01-01

    Catalases are efficient scavengers of H2O2 and protect cells against H2O2 stress. Examination of the H2O2 stimulon in Saccharomyces cerevisiae revealed that the cytosolic catalase T (Ctt1) protein level increases 15-fold on H2O2 challenge in synthetic complete media although previous work revealed that deletion of the CCT1 or CTA1 genes (encoding peroxisomal/mitochondrial catalase A) does not increase the H2O2 sensitivity of yeast challenged in phosphate buffer (pH 7.4). This we attributed to our observation that catalase activity is depressed when yeast are challenged with H2O2 in nutrient-poor media. Hence, we performed a systematic comparison of catalase activity and cell viability of wild-type yeast and of the single catalase knockouts, ctt1∆ and cta1∆, following H2O2 challenge in nutrient-rich medium (YPD) and in phosphate buffer (pH 7.4). Ctt1 but not Cta1 activity is strongly induced by H2O2 when cells are challenged in YPD but suppressed when cells are challenged in buffer. Consistent with the activity results, exponentially growing ctt1∆ cells in YPD are more sensitive to H2O2 than wild-type or cta1∆ cells, whereas in buffer all three strains exhibit comparable H2O2 hypersensitivity. Furthermore, catalase activity is increased during adaptation to sublethal H2O2 concentrations in YPD but not in buffer. We conclude that induction of cytosolic Ctt1 activity is vital in protecting yeast against exogenous H2O2 but this activity is inhibited by H2O2 when cells are challenged in nutrient-free media.

  18. Catalase activity is stimulated by H2O2 in rich culture medium and is required for H2O2 resistance and adaptation in yeast☆

    PubMed Central

    Martins, Dorival; English, Ann M.

    2014-01-01

    Catalases are efficient scavengers of H2O2 and protect cells against H2O2 stress. Examination of the H2O2 stimulon in Saccharomyces cerevisiae revealed that the cytosolic catalase T (Ctt1) protein level increases 15-fold on H2O2 challenge in synthetic complete media although previous work revealed that deletion of the CCT1 or CTA1 genes (encoding peroxisomal/mitochondrial catalase A) does not increase the H2O2 sensitivity of yeast challenged in phosphate buffer (pH 7.4). This we attributed to our observation that catalase activity is depressed when yeast are challenged with H2O2 in nutrient-poor media. Hence, we performed a systematic comparison of catalase activity and cell viability of wild-type yeast and of the single catalase knockouts, ctt1∆ and cta1∆, following H2O2 challenge in nutrient-rich medium (YPD) and in phosphate buffer (pH 7.4). Ctt1 but not Cta1 activity is strongly induced by H2O2 when cells are challenged in YPD but suppressed when cells are challenged in buffer. Consistent with the activity results, exponentially growing ctt1∆ cells in YPD are more sensitive to H2O2 than wild-type or cta1∆ cells, whereas in buffer all three strains exhibit comparable H2O2 hypersensitivity. Furthermore, catalase activity is increased during adaptation to sublethal H2O2 concentrations in YPD but not in buffer. We conclude that induction of cytosolic Ctt1 activity is vital in protecting yeast against exogenous H2O2 but this activity is inhibited by H2O2 when cells are challenged in nutrient-free media. PMID:24563848

  19. Catalase activity is stimulated by H(2)O(2) in rich culture medium and is required for H(2)O(2) resistance and adaptation in yeast.

    PubMed

    Martins, Dorival; English, Ann M

    2014-01-01

    Catalases are efficient scavengers of H2O2 and protect cells against H2O2 stress. Examination of the H2O2 stimulon in Saccharomyces cerevisiae revealed that the cytosolic catalase T (Ctt1) protein level increases 15-fold on H2O2 challenge in synthetic complete media although previous work revealed that deletion of the CCT1 or CTA1 genes (encoding peroxisomal/mitochondrial catalase A) does not increase the H2O2 sensitivity of yeast challenged in phosphate buffer (pH 7.4). This we attributed to our observation that catalase activity is depressed when yeast are challenged with H2O2 in nutrient-poor media. Hence, we performed a systematic comparison of catalase activity and cell viability of wild-type yeast and of the single catalase knockouts, ctt1∆ and cta1∆, following H2O2 challenge in nutrient-rich medium (YPD) and in phosphate buffer (pH 7.4). Ctt1 but not Cta1 activity is strongly induced by H2O2 when cells are challenged in YPD but suppressed when cells are challenged in buffer. Consistent with the activity results, exponentially growing ctt1∆ cells in YPD are more sensitive to H2O2 than wild-type or cta1∆ cells, whereas in buffer all three strains exhibit comparable H2O2 hypersensitivity. Furthermore, catalase activity is increased during adaptation to sublethal H2O2 concentrations in YPD but not in buffer. We conclude that induction of cytosolic Ctt1 activity is vital in protecting yeast against exogenous H2O2 but this activity is inhibited by H2O2 when cells are challenged in nutrient-free media. PMID:24563848

  20. 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.

  1. Al2O3-based nanofluids: a review

    NASA Astrophysics Data System (ADS)

    Sridhara, Veeranna; Satapathy, Lakshmi Narayan

    2011-07-01

    Ultrahigh performance cooling is one of the important needs of many industries. However, low thermal conductivity is a primary limitation in developing energy-efficient heat transfer fluids that are required for cooling purposes. Nanofluids are engineered by suspending nanoparticles with average sizes below 100 nm in heat transfer fluids such as water, oil, diesel, ethylene glycol, etc. Innovative heat transfer fluids are produced by suspending metallic or nonmetallic nanometer-sized solid particles. Experiments have shown that nanofluids have substantial higher thermal conductivities compared to the base fluids. These suspended nanoparticles can change the transport and thermal properties of the base fluid. As can be seen from the literature, extensive research has been carried out in alumina-water and CuO-water systems besides few reports in Cu-water-, TiO2-, zirconia-, diamond-, SiC-, Fe3O4-, Ag-, Au-, and CNT-based systems. The aim of this review is to summarize recent developments in research on the stability of nanofluids, enhancement of thermal conductivities, viscosity, and heat transfer characteristics of alumina (Al2O3)-based nanofluids. The Al2O3 nanoparticles varied in the range of 13 to 302 nm to prepare nanofluids, and the observed enhancement in the thermal conductivity is 2% to 36%.

  2. Al2O3 Scale Development on Iron Aluminides

    SciTech Connect

    Zhang, Xiao-Feng; Thaidigsmann, Katja; Ager, Joel; Hou, Peggy Y.

    2005-11-10

    The structure and phase of the Al{sub 2}O{sub 3} scale that forms on an Fe{sub 3}Al-based alloy (Fe-28Al-5Cr) (at %) was investigated by transmission electron microscopy (TEM) and photoluminescence spectroscopy (PL). Oxidation was performed at 900 C and 1000 C for up to 190 min. TEM revealed that single-layer scales were formed after short oxidation times. Electron diffraction was used to show that the scales are composed of nanoscale crystallites of the {theta}, {gamma}, and {alpha} phases of alumina. Band-like structure was observed extending along three 120{sup o}-separated directions within the surface plane. Textured {theta} and {gamma} grains were the main components of the bands, while mixed {alpha} and transient phases were found between the bands. Extended oxidation produced a double-layered scale structure, with a continuous {alpha} layer at the scale/alloy interface, and a {gamma}/{theta} layer at the gas surface. The mechanism for the formation of Al{sub 2}O{sub 3} scales on iron aluminide alloys is discussed and compared to that for nickel aluminide alloys.

  3. Fe2O3 nanoparticles for airborne organophosphate detection

    NASA Astrophysics Data System (ADS)

    Phillips, Joshua; Soliz, Jennifer; Hauser, Adam

    Dire need for early detection of organophosphates (OP) exists in both civilian (pesticide/herbicide buildup) and military (G/V nerve agents) spheres. Nanoparticle materials are excellent candidates for the detection and/or decontamination of hazardous materials, owing to their large surface to volume ratios and tailored surface functionality. Within this category, metal oxides include structures that are stable with the range of normal environmental conditions (temperature, humidity), but have strong, specific reaction mechanisms (hydrolysis, oxidation, catalysis, stoichiometric reaction) with toxic compounds. In this talk, we will present on the suitability of Fe2O3 nanoparticles as airborne organophosphate detectors. 23 nm particles were exposed to a series of organophosphate compounds (dimethyl methylphosphonate, dimethyl chlorophosphonate, diisopropyl methylphosphonate), and studied by x-ray magnetic circular dichroism and x-ray absorption spectroscopy to confirm the stoichiometric Fe2O3 to FeO mechanism and determine magnetic sensor feasibility. AC Impedance Spectroscopy shows both high sensitivity and selectivity via frequency dependence in both impedance and resistivity, suggesting some feasibility for impedimetric devices. We acknowledge funding under Army Research Office STIR Award #W911F-15-1-0104. J.R.S. acknowledges funding from the Defense Threat Reduction Agency under Projects BA13PHM210 and BA07PRO104. J.R.S. also acknowledges funding under a NRC fellowship.

  4. Determination of the Evaporation Coefficient of D2O

    SciTech Connect

    Drisdell, Walter S.; Cappa, Christopher D.; Smith, Jared D.; Saykally, Richard J.; Cohen, Ronald C.

    2008-03-26

    The evaporation rate of D{sub 2}O has been determined by Raman thermometry of a droplet train (12-15 {micro}m diameter) injected into vacuum ({approx}10{sup -5} torr). The cooling rate measured as a function of time in vacuum was fit to a model that accounts for temperature gradients between the surface and the core of the droplets, yielding an evaporation coefficient ({gamma}{sub e}) of 0.57 {+-} 0.06. This is nearly identical to that found for H{sub 2}O (0.62 {+-} 0.09) using the same experimental method and model, and indicates the existence of a kinetic barrier to evaporation. The application of a recently developed transition state theory (TST) model suggests that the kinetic barrier is due to librational and hindered translational motions at the liquid surface, and that the lack of an isotope effect is due to competing energetic and entropic factors. The implications of these results for cloud and aerosol particles in the atmosphere are discussed.

  5. Specific heat capacity of nanoporous Al2O3

    NASA Astrophysics Data System (ADS)

    Huang, Cong-Liang; Feng, Yan-Hui; Zhang, Xin-Xin; Li, Jing; Wang, Ge

    2013-09-01

    Based on Lindemann's criterion, a specific heat capacity model for nanoporous material was proposed by defining the surface-atom layer, to take the surface atoms and the volume atoms separately into account. The height of the surface-atom layer was determined from the experiment, and results show that only the first layer atoms on the surface should be separately considered for nanoporous Al2O3. The shape factor of the pore was also introduced in the model with values between 2 (for cylindrical pore) and 3 (for spherical pore) to characterize the morphology of the pore. It turns out experimentally that the specific heat capacity of the analyzed nanoporous Al2O3 is much larger than that of the bulk, which can be interpreted as due to the fact that the surface atom plays a more important role than the volume one. And the smaller the radius and/or the larger the porosity, which lead to a larger surface-volume ratio, the larger the specific heat capacity becomes. The nanoporous material could be a better heat storage medium than the corresponding bulk with a much lighter weight, smaller volume but higher heat storage capacity.

  6. Decomposition of N2O over particulate matter

    NASA Technical Reports Server (NTRS)

    Rebbert, R. E.; Ausloos, P.

    1978-01-01

    Nitrous oxide is shown to undergo both a thermal and a photochemical decomposition at 296 K when it is adsorbed on various dry sands. The photochemical process occurs with light of wavelengths greater than 280 nm, where gaseous N2O does not absorb. At low pressures (less than 0.1 torr) the half-life for the thermal decomposition of nitrous oxide to nitrogen when placed in contact with about 5 gm of heat-treated Tunisian sand in a one-liter vessel was 350 + or - 35 days. Under certain photolytic conditions this half-life was reduced. The efficiency of the photolytic process for a particular sand depends on the pressure and on the wavelength of light. For Tunisian sand at 1.1 torr and with the full mercury arc, the destruction efficiency is about 0.00002 molecule/incident photon. These results indicate that particulate matter in the troposphere may be responsible for the decomposition of nitrous oxide and hence act as an atmospheric sink for N2O. However, moisture causes a drastic reduction in the number of molecules dissociated per incident photon.

  7. Magnetic and ferroelectric properties of multiferroic RMn2O5

    NASA Astrophysics Data System (ADS)

    Noda, Y.; Kimura, H.; Fukunaga, M.; Kobayashi, S.; Kagomiya, I.; Kohn, K.

    2008-10-01

    The magnetic and ferroelectric properties of multiferroic RMn2O5 (R = Y, Tb, Ho, Er, Tm) are reviewed based on recent neutron diffraction and dielectric measurements. Successive phase transitions of magnetic and dielectric ordering were found to occur simultaneously in this system. The characteristic magnetic ordering of the system exhibits an incommensurate-commensurate phase transition, and again transitions to an incommensurate phase. Special attention is given to the magnetic structure in order to discuss the mechanism for the introduction of ferroelectric polarization. For all the compounds examined, the spin configuration for Mn4+ and Mn3+ ions in the commensurate magnetic phase, where spontaneous electric polarization occurs, was determined to be a transverse spiral spin structure propagating along the c-axis. By contrast, the alignment of the induced 4f moment of R3+ ions showed variation, depending on the character of each of the elements. Corresponding responses to external fields such as a magnetic field, hydrostatic pressure etc at low temperature are strongly dependent on the rare earth element present in the RMn2O5 system. The so-called colossal magnetoelectric effect in this system can be easily interpreted by the phase transition from the magnetic incommensurate and weak ferroelectric phase to the commensurate and ferroelectric phase.

  8. Photodissociation of N{sub 2}O: Energy partitioning

    SciTech Connect

    Schmidt, J. A.; Johnson, M. S.; Lorenz, U.; McBane, G. C.; Schinke, R.

    2011-07-14

    The energy partitioning in the UV photodissociation of N{sub 2}O is investigated by means of quantum mechanical wave packet and classical trajectory calculations using recently calculated potential energy surfaces. Vibrational excitation of N{sub 2} is weak at the onset of the absorption spectrum, but becomes stronger with increasing photon energy. Since the NNO equilibrium angles in the ground and the excited state differ by about 70 degree sign , the molecule experiences an extraordinarily large torque during fragmentation producing N{sub 2} in very high rotational states. The vibrational and rotational distributions obtained from the quantum mechanical and the classical calculations agree remarkably well. The shape of the rotational distributions is semi-quantitatively explained by a two-dimensional version of the reflection principle. The calculated rotational distribution for excitation with {lambda}= 204 nm and the translational energy distribution for 193 nm agree well with experimental results, except for the tails of the experimental distributions corresponding to excitation of the highest rotational states. Inclusion of nonadiabatic transitions from the excited to the ground electronic state at relatively large N{sub 2}-O separations, studied by trajectory surface hopping, improves the agreement at high j.

  9. (H2O)20 Water Clusters at Finite Temperatures

    NASA Astrophysics Data System (ADS)

    Parkkinen, P.; Riikonen, S.; Halonen, L.

    2013-10-01

    We have performed an exhaustive study of energetics of (H2O)20 clusters. Our goal is to study the role that various free-energy terms play in this popular model system and see their effects on the distribution of the (H2O)20 clusters and in the infrared spectrum at finite temperatures. In more detail, we have studied the electronic ground-state structure energy and its long-range correlation (dispersion) part, vibrational zero-point corrections, vibrational entropy, and proton configurational entropy. Our results indicate a delicate competition between the energy terms; polyhedral water clusters are destabilized by dispersion interaction, while vibrational terms (zero-point and entropic) together with proton disorder entropy favor them against compact structural motifs, such as the pentagonal edge- or face-sharing prisms. Apart from small water clusters, our results can be used to understand the influence of these energy terms in water/ice systems in general. We have also developed energy expressions as a function of both earlier proposed and novel hydrogen-bond connectivity parameters for prismatic water clusters.

  10. Al2O3-based nanofluids: a review

    PubMed Central

    2011-01-01

    Ultrahigh performance cooling is one of the important needs of many industries. However, low thermal conductivity is a primary limitation in developing energy-efficient heat transfer fluids that are required for cooling purposes. Nanofluids are engineered by suspending nanoparticles with average sizes below 100 nm in heat transfer fluids such as water, oil, diesel, ethylene glycol, etc. Innovative heat transfer fluids are produced by suspending metallic or nonmetallic nanometer-sized solid particles. Experiments have shown that nanofluids have substantial higher thermal conductivities compared to the base fluids. These suspended nanoparticles can change the transport and thermal properties of the base fluid. As can be seen from the literature, extensive research has been carried out in alumina-water and CuO-water systems besides few reports in Cu-water-, TiO2-, zirconia-, diamond-, SiC-, Fe3O4-, Ag-, Au-, and CNT-based systems. The aim of this review is to summarize recent developments in research on the stability of nanofluids, enhancement of thermal conductivities, viscosity, and heat transfer characteristics of alumina (Al2O3)-based nanofluids. The Al2O3 nanoparticles varied in the range of 13 to 302 nm to prepare nanofluids, and the observed enhancement in the thermal conductivity is 2% to 36%. PMID:21762528

  11. The spectroscopic studies of gel-derived glasses and glass-ceramics in the Na 2O (Li 2O)-B 2O 3-P 2O 5-SiO 2 system

    NASA Astrophysics Data System (ADS)

    Adamczyk, A.; Handke, M.

    2001-09-01

    The gel-derived borophosphosilicate materials containing Na + and Li + cations by FTIR spectroscopy and X-ray diffraction methods were studied. The results obtained enabled one to define the structure of samples containing up to 10% mol. BPO 4. The alkali ions, Na + and Li + can be treated as borate and phosphate network depolymerisators. There is also no evidence of boron coordination changes, from trigonal to tetrahedral caused by Na 2O and Li 2O oxide addition to pure borophosphosilicate materials. Concurrently, the silicate network is left unchanged. The bands due to the B-O bond vibrations are not observed in the IR spectra of the crystalline materials, obtained by heating samples of composition analogous to amorphous ones. Such bands are present in the spectra of crystalline alkali-free samples of the same BPO 4 content. The amorphous and crystalline alkali-containing samples by the EDX microprobe were also studied. The results obtained showed that the heating of alkali borophosphosilicate samples caused the volatilisation of boron, phosphorus and alkali compounds from the structures studied. Such a process does not take place in case of alkali-free samples.

  12. Competition between H2O and (H2O)2 reactions with CH2OO/CH3CHOO.

    PubMed

    Lin, Liang-Chun; Chang, Hung-Tzu; Chang, Chien-Hsun; Chao, Wen; Smith, Mica C; Chang, Chun-Hung; Jr-Min Lin, Jim; Takahashi, Kaito

    2016-02-14

    In this study, we performed ab initio calculations and obtained the bimolecular rate coefficients for the CH2OO/CH3CHOO reactions with H2O/(H2O)2. The energies were calculated with QCISD(T)/CBS//B3LYP/6-311+G(2d,2p) and the partition functions were estimated with anharmonic vibrational corrections by using the second order perturbation theory. Furthermore, we directly measured the rate of the CH2OO reaction with water vapor at high temperatures (348 and 358 K) to reveal the contribution of the water monomer in the CH2OO decay kinetics. We found that the theoretical rate coefficients reproduce the experimental results of CH2OO for a wide range of temperatures. For anti- (syn-) CH3CHOO, we obtained theoretical rate coefficients of 1.60 × 10(-11) (2.56 × 10(-14)) and 3.40 × 10(-14) (1.98 × 10(-19)) cm(3) s(-1) for water dimer and monomer reactions at room temperature. From the detailed analysis of the quantum chemistry and approximations for the thermochemistry calculations, we conclude that our calculated values would be within a factor of 3 of the correct values. Furthermore, at [H2O] = 1 × 10(17) to 5 × 10(17) cm(-3), we estimate that the effective first-order rate coefficients for CH2OO, anti- and syn-CH3CHOO reactions with water vapor will be ∼10(3), ∼10(4), and ∼10(1) s(-1), respectively. Thereby, for Criegee intermediates with a hydrogen atom on the same side as the terminal oxygen atom, the reaction with water vapor will likely dominate the removal processes of these CIs in the atmosphere. PMID:26797528

  13. Thermal equation of state of CaFe 2O 4-type MgAl 2O 4

    NASA Astrophysics Data System (ADS)

    Sueda, Yuichiro; Irifune, Tetsuo; Sanehira, Takeshi; Yagi, Takehiko; Nishiyama, Norimasa; Kikegawa, Takumi; Funakoshi, Ken-ichi

    2009-05-01

    In situ X-ray diffraction measurements of CaFe 2O 4-type MgAl 2O 4 have been conducted at pressures up to 42 GPa and temperatures to 2400 K using Kawai-type multianvil apparatus with sintered diamond anvils. Additional measurements have also been conducted at pressures to 12 GPa using diamond anvil cell with helium as a pressure medium at room temperature, and at temperatures to 836 K at the ambient pressure using a high-temperature X-ray diffractometer. The analysis of room-temperature data yielded V0 = 240.1(2) Å 3, K0 = 205(6) GPa, and K0=4.1(3). A fit of the present data to high-temperature Birch-Murnaghan equation of state (EOS) yielded (∂ K0/∂ T) P = -0.030(2) GPa/K and α0 = a0 + b0T with values of a0 = 1.96(13) × 10 -5 K -1 and b0 = 1.64(24) × 10 -8 K -2. The present data set was also fitted to Mie-Grüneisen-Debye (MGD) EOS and we obtained γ0 = 1.73(7), q = 2.03(37), and θ0 = 1546(104) K. Density changes of MORB have been estimated using the newly obtained thermoelastic parameters, assuming that the Al-rich phase in this composition possesses the CaFe 2O 4-type structure under the lower mantle P, T conditions. The calculated densities along geotherms for the normal mantle and subducting cold slabs are both significantly higher than those of typical seismological models, confirming the conclusion of some recent results on MORB by laser-heated diamond anvil cell experiments.

  14. 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

  15. Photodissociation spectroscopy of Ca{sup +}(H{sub 2}O) and Ca{sup +}(D{sub 2}O)

    SciTech Connect

    Scurlock, C.T.; Reddic, E.; Duncan, M.A.

    1996-12-31

    Electronic spectra are observed for the mono-solvated metal cation complexes Ca{sup +}-H{sub 2}O and Ca{sup +}-D{sub 2}O using Resonance Enhanced Photodissociation Spectroscopy. The clusters are produced in a laser vaporization/supersonic expansion source and the mass-analyzed product ion is observed using a time-of-flight mass spectrometer. Both Ca{sup +} and CaOH{sup +} (or CaOD{sup +}) dissociation products are observed on sharp resonances. The observed features are assigned to the (2){sup 2}B{sub 2}{l_arrow}X{sup 2}A, and (2){sup 2}B{sub 1}{l_arrow}X{sup 1}A, transitions, with vibrational progressions in the Ca-OH, stretching mode. Spectroscopic constants are Ca{sup +}-H{sub 2}O: (2){sup 2}B{sub 2}{l_arrow}X{sup 2}A{sub 1} (T{sub 0}= 21,464 cm{sup -1}, {Delta}G{sub 1/2}=357.9 cm{sup -1}) and (2){sup 2}B{sub 2}{l_arrow}X{sup 2}A{sub 1} (T{sub 0}=22,273 cm{sup -1}, {Delta}G{sub 1/2}335.9 cm{sup -1}); and Ca{sup +}-D{sub 2}O: (2){sup 2}B{sub 2}{l_arrow}X{sup 2}A{sub 1} (T{sub 0}=21,447 cm{sup -1}, {Delta}G{sub {1/2}}=350.9 cm{sup -1}) and (2){sup 2}B{sub 2}{l_arrow}X{sup 2}A{sub 1} (T{sub 0}=22,261 cm{sup -1}, {Delta}G{sub {1/2}}=324.1 cm{sup -1}). These transitions are rotationally resolved about the a- principal axis, and confirm the structure of the complex to possess C{sub 2v} symmetry. In addition the Ca{sup +}-OH{sub 2} bond distance is determined to be 2.22 {Angstrom} and the H-O-H bond angle 106.8{degrees} in the ground state.

  16. Microcrystalline phase transformation from ZrF4·HF·2H2O to ZrO2 through the intermediate phases ZrF4·3H2O, ZrF4·H2O, Zr2OF6·H2O and ZrF4

    NASA Astrophysics Data System (ADS)

    Dey, C. C.

    2014-09-01

    The behavior of hydrated zirconium fluoride has been studied by perturbed angular correlation spectroscopy. It is found that the crystalline compound ZrF4·HF·2H2O, formed initially by drying solution of Zr metal in concentrated HF, transforms spontaneously to ZrF4·3H2O. This trihydrated compound dehydrates to ZrF4 through the intermediate monohydrates ZrF4·H2O and Zr2OF6·H2O. The compound ZrF4 finally transforms to ZrO2 at ∼343 K. Different crystalline phases of ZrF4·HF·2H2O, ZrF4·3H2O, ZrF4·H2O, Zr2OF6·H2O, ZrF4 and ZrO2 have been identified and characterized by PAC spectroscopy. From previous PAC measurements, the intermediate ZrF4·H2O and Zr2OF6·H2O were not observed and the dehydration from ZrF4·3H2O to ZrF4 was found to be routed directly. Present measurements by PAC exhibits dissimilar crystal structures for ZrF4·3H2O and ZrF4·H2O unlike the crystal structures found in hafnium analogous compounds.

  17. The reaction of B 2O 3 with the β-rhombohedral boron (111) surface

    NASA Astrophysics Data System (ADS)

    Wei Cho Foo; Ozcomert, John S.; Trenary, Michael

    1992-02-01

    We have studied the reaction of isotopically pure 10B 2O 3 with the (111) surface of β-rhombohedral boron using temperature-programmed desorption. The 10B 2O 3 was directly deposited on the boron surface from a Knudsen cell operated at 1200 K. The boron crystal contained the natural abundance ratio of the 11B : 10B isotopes of 4:1. The thermal desorption results show a B 2O 3 peak near 1200 K consisting solely of the 10B 2O 3 isotope followed by B 2O 2 and B 2O 3 peaks in the range 1300-1350 K with a B 2O 2: B 2O 3 peak area ratio of about 2:1. The higher temperature B 2O 2 and B 2O 3 desorption peaks follow zero-order desorp kinetics with an activation energy of 554 ± 41 kJmol-1. The higher temperature peaks show substantial incorporation of the 11B isotope from the substrate. The results are consistent with a reaction mechanism in which boron from the substrate first dissolves in the molten B 2O 3 layer and then reacts to form a B 6O suboxide which then decomposes to yield B 2O 3 and B 2O 2. However, we have no direct evidence for the presence of the B 6O suboxide on the surface.

  18. The orientational relationship between monoclinic β-Ga2O3 and cubic NiO

    NASA Astrophysics Data System (ADS)

    Nakagomi, Shinji; Kubo, Shohei; Kokubun, Yoshihiro

    2016-07-01

    The orientational relationship between β-Ga2O3 and NiO was studied by X-ray diffraction measurements and cross-sectional high resolution transmission electron microscopy. A β-Ga2O3 thin film was formed on a (100) NiO layer on a (100) MgO substrate by gallium evaporation in an oxygen plasma. It was found that the resulting β-Ga2O3 had a four-fold domain structure satisfying both (100) β-Ga2O3 ‖ (100) NiO and (010) β-Ga2O3 ‖ {011} NiO. A γ-Ga2O3 layer was observed at the interface between the β-Ga2O3 and the NiO. An NiO film was also formed on a (100) β-Ga2O3 single-crystal substrate by the sol-gel method. An epitaxial (100) NiO film was formed on a (100) β-Ga2O3 substrate, and satisfied (011) NiO ‖ (010) β-Ga2O3. The crystal orientations of β-Ga2O3 on (100) NiO and NiO on (100) β-Ga2O3 can be explained using atomic arrangement models of the (100) plane of NiO and the (100) plane of β-Ga2O3.

  19. Growth of single-crystalline Cu2O (111) film on ultrathin MgO modified α-Al2O3 (0001) substrate by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Li, Junqiang; Mei, Zengxia; Ye, Daqian; Liang, Huili; Liu, Yaoping; Du, Xiaolong

    2012-08-01

    We report the synthesis of Cu2O single crystalline films on the c-plane α-Al2O3 substrate by radio-frequency plasma assisted molecular beam epitaxy. An ultrathin MgO layer was adopted to modify the complex surface structure of sapphire (0001) and engineer the interfacial atomic matching between the epilayer and the substrate. The experimental results solidly proved the single crystallinity of cubic Cu2O (111) without twin crystals. A coincident match mode was proposed to explain the unusual in-plane orientation between strained MgO (111) and Cu2O (111). It was found that the crystal quality of Cu2O is very sensitive to the thickness of MgO layer, which is optimized to be ˜2 nm. The reason why MgO has a critical thickness in Cu2O single crystal growth was also tentatively discussed.

  20. Responsive mechanism of a newly synthesized fluorescent probe for sensing H2O2, NO and H2O2/NO

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Jin; Wang, Xin; Zhou, Yong; Zhao, Ke; Wang, Chuan-Kui

    2016-10-01

    Optical properties of a newly synthesized fluorescent probe for H2O2, NO and H2O2/NO are investigated by employing time-dependent density functional theory. Three different sets of fluorescence signals are obtained when the probe reacts with H2O2, NO and H2O2/NO. Analysis of molecular orbitals is presented to explore responsive mechanism of the probe for the detected objects, where the fluorescent resonance energy transfer process is for H2O2 (H2O2/NO) and the intramolecular charge transfer process is for NO. Our results provide theoretical explanation of the experimental results, and importantly, suggest possibility of the probe as a two-photon fluorescent sensor.

  1. Modifications of structural and physical properties induced by swift heavy ions in Gd2Ti2O7 and Y2Ti2O7 pyrochlores

    NASA Astrophysics Data System (ADS)

    Sellami, N.; Sattonnay, G.; Grygiel, C.; Monnet, I.; Debelle, A.; Legros, C.; Menut, D.; Miro, S.; Simon, P.; Bechade, J. L.; Thomé, L.

    2015-12-01

    The structural transformations induced by ionization processes in Gd2Ti2O7 and Y2Ti2O7 pyrochlores irradiated with swift heavy ions have been studied using XRD and Raman experiments. Results show that irradiation induces amorphization and that the phase transformation build-up can be accounted for in the framework of a model involving a single-impact mechanism. The radiation induced amorphization build-up is faster in Gd2Ti2O7 than in Y2Ti2O7. Moreover, a decrease of the thermal conductivity (measured by the laser flash method) is induced by irradiation both in Gd2Ti2O7 and Y2Ti2O7.

  2. Dependence of catalytic properties of Al/Fe2O3 thermites on morphology of Fe2O3 particles in combustion reactions

    NASA Astrophysics Data System (ADS)

    Zhao, Ningning; He, Cuicui; Liu, Jianbing; Gong, Hujun; An, Ting; Xu, Huixiang; Zhao, Fengqi; Hu, Rongzu; Ma, Haixia; Zhang, Jinzhong

    2014-11-01

    Three Fe2O3 particle samples with the same crystal structure but different morphologies were prepared by the hydrothermal method and then combined with Al nanoparticles to produce Al/Fe2O3 thermites using ultrasonic mixing. The properties of Fe2O3 and Al/Fe2O3 were studied using a combination of experimental techniques including scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The influences of the three Al/Fe2O3 thermites on the combustion properties of the AP/HTPB (ammonium perchlorate/hydroxyl-terminated polybutadiene) composite propellant were investigated in comparison to those of Fe2O3. The results show that the Al/Fe2O3 thermites are better than Fe2O3 in enhancing the combustion performance of AP/HTPB. Furthermore, the surface area, which depends on size and mophology, of Fe2O3 particles was found to play a vital role in improving the burning rate of the thermites-containing propellant formulation, with the smallest particles with the largest surface-to-volume (S/V) ratio performing the best. The enhanced catalytic property of the granular-shape Fe2O3 and the corresponding thermite is attributed to the large specific surface area of Fe2O3. The different thermal behaviors of these three superthemites were supposed to be attributed to the surface site of Fe2O3 particles. This work provides a better understanding on the catalytic properties of thermites that are important for combustion applications.

  3. High-pressure X-ray diffraction and Raman spectroscopy of CaFe2O4-type β-CaCr2O4

    NASA Astrophysics Data System (ADS)

    Zhai, Shuangmeng; Yin, Yuan; Shieh, Sean R.; Shan, Shuangming; Xue, Weihong; Wang, Ching-Pao; Yang, Ke; Higo, Yuji

    2016-04-01

    In situ high-pressure synchrotron X-ray diffraction and Raman spectroscopic studies of orthorhombic CaFe2O4-type β-CaCr2O4 chromite were carried out up to 16.2 and 32.0 GPa at room temperature using multi-anvil apparatus and diamond anvil cell, respectively. No phase transition was observed in this study. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields a zero-pressure volume of V 0 = 286.8(1) Å3, an isothermal bulk modulus of K 0 = 183(5) GPa and the first pressure derivative of isothermal bulk modulus K 0' = 4.1(8). Analyses of axial compressibilities show anisotropic elasticity for β-CaCr2O4 since the a-axis is more compressible than the b- and c-axis. Based on the obtained and previous results, the compressibility of several CaFe2O4-type phases was compared. The high-pressure Raman spectra of β-CaCr2O4 were analyzed to determine the pressure dependences and mode Grüneisen parameters of Raman-active bands. The thermal Grüneisen parameter of β-CaCr2O4 is determined to be 0.93(2), which is smaller than those of CaFe2O4-type CaAl2O4 and MgAl2O4.

  4. Ab Initio Investigation of the Structure, Stability and Atmospheric Distribution of Molecular Clusters Containing H2O, CO2 and N2O.

    NASA Astrophysics Data System (ADS)

    Lemke, K. H.; Seward, T. M.

    2007-12-01

    We present results from ab initio calculations for the structures, energetics and atmospheric abundances of neutral clusters containing water, carbon dioxide and nitrous oxide up to 45km altitude using the complete basis set CBS-Q and G3 multi-level procedures. Gas phase hydration energies, enthalpies and entropies for the stepwise attachment of water onto clusters according to X(H2O)n + H2O = X(H2O)n+1 (where X = H2O, CO2 and N2O) are reported for up to n=5. In particular, our results demonstrate that values for the incremental hydration enthalpies and entropies of all three gases H2O, CO2 and N2O asymptotically approach values characteristic of bulk liquid water (i.e. -44.0 kJ/mol for the enthalpy and -118.8 J/Kmol for the entropy of condensation) following attachment of around 3-4 water molecules. Interestingly, our calculated number densities for the water dimer at 292Kelvin are in excellent agreement with recent values obtained from IR measurements of atmospheric media (Pfeilsticker et al., 2003, Science). Our quantum chemical calculations indicate that water attachment onto H2O, CO2 and N2O is a thermodynamically favorable process, such that hydrated clusters would form a significant atmospheric repository of these species.

  5. Unraveling the Origin of Structural Disorder in High Temperature Transition Al2O3: Structure of θ-Al2O3

    SciTech Connect

    Kovarik, Libor; Bowden, Mark E.; Shi, Dachuan; Washton, Nancy M.; Anderson, Amity; Hu, Jian Z.; Lee, Jaekyoung; Szanyi, Janos; Kwak, Ja Hun; Peden, Charles HF

    2015-09-22

    The crystallography of transition Al2O3 has been extensively studied in the past due to the advantageous properties of the oxide in catalytic and a range of other technological applications. However, existing crystallographic models are insufficient to describe the structure of many important Al2O3 polymorphs due to their highly disordered nature. In this work, we investigate structure and disorder in high-temperature treated transition Al2O3, and provide a structural description for θ-Al2O3 by using a suite of complementary imaging, spectroscopy and quantum calculation techniques. Contrary to current understanding, our high-resolution imaging shows that θ-Al2O3 is a disordered composite phase of at least two different end members. By correlating imaging and spectroscopy results with DFT calculations, we propose a model that describes θ-Al2O3 as a disordered intergrowth of two crystallographic variants at the unit cell level. One variant is based on β-Ga2O3, and the other on a monoclinic phase that is closely-related to δ-Al2O3. The overall findings and interpretations afford new insight into the origin of poor crystallinity in transition Al2O3, and also provide new perspectives on structural complexity that can emerge from intergrowth of closely related structural polymorphs.

  6. Growth characteristics of corundum-structured α-(AlxGa1-x)2O3/Ga2O3 heterostructures on sapphire substrates

    NASA Astrophysics Data System (ADS)

    Kaneko, Kentaro; Suzuki, Kenta; Ito, Yoshito; Fujita, Shizuo

    2016-02-01

    We report improved growth conditions for corundum-structured α-(AlxGa1-x)2O3, followed by the growth characteristics of α-(AlxGa1-x)2O3/Ga2O3 heterostructures with the use of mist chemical vapor deposition (CVD) technology. Higher growth temperatures, 700-800 °C, were effective for better crystalline quality especially for higher Al composition x. Coherent growth of α-(AlxGa1-x)2O3 was achieved for x=0.03 and 0.11 with the film thickness of about 100 nm. The type-I band lineup was expected for the heterostructure.

  7. Phase Stability and Pressure Dependence of Defect Formation in Gd2Ti2O7 and Gd2Zr2O7 Pyrochlores

    NASA Astrophysics Data System (ADS)

    Zhang, F. X.; Wang, J. W.; Lian, J.; Lang, M. K.; Becker, U.; Ewing, R. C.

    2008-02-01

    We report dramatically different behaviors between isostructural Gd2Ti2O7 and Gd2Zr2O7 pyrochlore at pressures up to 44 GPa, in which the substitution of Ti for Zr significantly increases structural stability. Upon release of pressure, the Gd2Ti2O7 becomes amorphous. In contrast, the high-pressure phase of Gd2Zr2O7 transforms to a disordered defect-fluorite structure. First-principle calculations for both compositions revealed that the response of pyrochlore to high pressure is controlled by the intrinsic energetics of defect formation.

  8. Phase stability and pressure dependence of defect formation in Gd2Ti2O7 and Gd2Zr2O7 pyrochlores.

    PubMed

    Zhang, F X; Wang, J W; Lian, J; Lang, M K; Becker, U; Ewing, R C

    2008-02-01

    We report dramatically different behaviors between isostructural Gd2Ti2O7 and Gd2Zr2O7 pyrochlore at pressures up to 44 GPa, in which the substitution of Ti for Zr significantly increases structural stability. Upon release of pressure, the Gd2Ti2O7 becomes amorphous. In contrast, the high-pressure phase of Gd2Zr2O7 transforms to a disordered defect-fluorite structure. First-principle calculations for both compositions revealed that the response of pyrochlore to high pressure is controlled by the intrinsic energetics of defect formation.

  9. Formation Mechanism of CuAlO2 Prepared by Rapid Thermal Annealing of Al2O3/Cu2O/Sapphire Sandwich Structure

    NASA Astrophysics Data System (ADS)

    Shih, C. H.; Tseng, B. H.

    Single-phase CuAlO2 films were successfully prepared by thin-film reaction of an Al2O3/Cu2O/sapphire sandwich structure. We found that the processing parameters, such as heating rate, holding temperature and annealing ambient, were all crucial to form CuAlO2 without second phases. Thermal annealing in pure oxygen ambient with a lower temperature ramp rate might result in the formation of CuAl2O4 in addition to CuAlO2, since part of Cu2O was oxidized to form CuO and caused the change in reaction path, i.e. CuO + Al2O3 → CuAl2O4. Typical annealing conditions successful to prepare single-phase CuAlO2 would be to heat the sample with a temperature rampt rate higher than 7.3 °C/sec and hold the temperature at 1100 °C in air ambient. The formation mechanism of CuAlO2 has also been studied by interrupting the reaction after a short period of annealing. TEM observations showed that the top Al2O3 layer with amorphous structure reacted immediately with Cu2O to form CuAlO2 in the early stage and then the remaining Cu2O reacted with the sapphire substrate.

  10. Spin reorientation in α-Fe2O3 nanoparticles induced by interparticle exchange interactions in α-Fe2O3/NiO nanocomposites

    NASA Astrophysics Data System (ADS)

    Frandsen, C.; Lefmann, K.; Lebech, B.; Bahl, C. R. H.; Brok, E.; Ancoña, S. N.; Theil Kuhn, L.; Keller, L.; Kasama, T.; Gontard, L. C.; Mørup, S.

    2011-12-01

    We report that the spin structure of α-Fe2O3 nanoparticles rotates coherently out of the basal (001) plane at low temperatures when interacting with thin plate-shaped NiO nanoparticles. The observed spin reorientation (up to ˜70∘) in α-Fe2O3 nanoparticles has, in appearance, similarities to the Morin transition in bulk α-Fe2O3, but its origin is different—it is caused by exchange coupling between aggregated nanoparticles of α-Fe2O3 and NiO with different directions of easy axes of magnetization.

  11. Effect of Nd2O3 Additive on Microstructure and Tribological Properties of Plasma-Sprayed NiCr-Cr2O3 Composite Coatings

    NASA Astrophysics Data System (ADS)

    Chen, Jie; An, Yulong; Zhao, Xiaoqin; Yan, Fengyuan; Zhou, Huidi; Chen, Jianmin

    2014-02-01

    Four types of NiCr-Cr2O3 composite coatings doped with different mass fraction of Nd2O3 were deposited by atmospheric plasma spraying. The microstructure and phase composition of as-sprayed coatings were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). Furthermore, their friction and wear behaviors at 20 and 600 °C under unlubricated condition were evaluated using CSM high temperature tribometer. The results showed that Nd2O3 could refine microstructure of NiCr-Cr2O3 composite coating and make Cr2O3 distribution more uniform in the coating, which leads to the increase of average microhardness. In addition, NiCr-Cr2O3 composite coatings doped with Nd2O3 had better wear resistance than that without Nd2O3 at experimental temperatures. Especially, the coating containing 8 wt.% Nd2O3 showed the best wear resistance at 20 and 600 °C, which was attributed to the refined microstructure and improved microhardness. At 20 °C, the wear mechanism of the coating was abrasive wear, brittle fracture and splat detachment. At 600 °C, the wear mechanism was adhesion wear and plastic deformation.

  12. Intermediate magnetization state and competing orders in Dy2Ti2O7 and Ho2Ti2O7.

    PubMed

    Borzi, R A; Gómez Albarracín, F A; Rosales, H D; Rossini, G L; Steppke, A; Prabhakaran, D; Mackenzie, A P; Cabra, D C; Grigera, S A

    2016-01-01

    Among the frustrated magnetic materials, spin-ice stands out as a particularly interesting system. Residual entropy, freezing and glassiness, Kasteleyn transitions and fractionalization of excitations in three dimensions all stem from a simple classical Hamiltonian. But is the usual spin-ice Hamiltonian a correct description of the experimental systems? Here we address this issue by measuring magnetic susceptibility in the two most studied spin-ice compounds, Dy2Ti2O7 and Ho2Ti2O7, using a vector magnet. Using these results, and guided by a theoretical analysis of possible distortions to the pyrochlore lattice, we construct an effective Hamiltonian and explore it using Monte Carlo simulations. We show how this Hamiltonian reproduces the experimental results, including the formation of a phase of intermediate polarization, and gives important information about the possible ground state of real spin-ice systems. Our work suggests an unusual situation in which distortions might contribute to the preservation rather than relief of the effects of frustration. PMID:27558021

  13. Effect of Processing Parameters on Thermal Cycling Behavior of Al2O3-Al2O3 Brazed Joints

    NASA Astrophysics Data System (ADS)

    Dandapat, Nandadulal; Ghosh, Sumana; Guha, Bichitra Kumar; Datta, Someswar; Balla, Vamsi Krishna

    2016-06-01

    In the present study, alumina ceramics were active metal brazed at different temperatures ranging from 1163 K to 1183 K (890 °C to 910 °C) using TICUSIL (68.8Ag-26.7Cu-4.5Ti in wt pct) foil as filler alloy of different thicknesses. The brazed joints were subjected to thermal cycling for 100 cycles between 323 K and 873 K (50 °C and 600 °C). The microstructural and elemental composition analysis of the brazed joints were performed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) before and after thermal cycling. Helium (He) leak test and brazing strength measurement were also conducted after thermal cycling for 100 cycles. The joint could withstand up to 1 × 10-9 Torr pressure and brazing strength was higher than 20 MPa. The experimental results demonstrated that joints brazed at the higher temperature with thinner filler alloy produced strong Al2O3-Al2O3 joints.

  14. Correlation among electronic polarizability, optical basicity and interaction parameter of Bi 2O 3-B 2O 3 glasses

    NASA Astrophysics Data System (ADS)

    Zhao, Xinyu; Wang, Xiaoli; Lin, Hai; Wang, Zhiqiang

    2007-03-01

    For optical basicity and electronic polarizability, the previous studies basically concentrate on the wavelength range of the visible light region. However, heavy metal oxides glasses have a reputation of being good materials for infrared region. In this study, new data of the average electronic polarizability of the oxide ion α, optical basicity Λ and Yamashita-Kurosawa's interaction parameter A of Bi 2O 3-B 2O 3 glasses have been calculated in a wavelength range from 404.66 to 1083.03 nm. The present investigation suggests that both α and Λ increase gradually with increasing wave number, and A decreases with increasing wave number. Furthermore, close correlations are studied among α, Λ, A and refractive index n in this paper. Particularly, it has been found that a quantitative relationship between electronic polarizability and optical basicity is observed in a wavelength range from 404.66 to 1083.03 nm. Our present study extends over a wide range of α, Λ and A values.

  15. Intermediate magnetization state and competing orders in Dy2Ti2O7 and Ho2Ti2O7

    NASA Astrophysics Data System (ADS)

    Borzi, R. A.; Gómez Albarracín, F. A.; Rosales, H. D.; Rossini, G. L.; Steppke, A.; Prabhakaran, D.; MacKenzie, A. P.; Cabra, D. C.; Grigera, S. A.

    2016-08-01

    Among the frustrated magnetic materials, spin-ice stands out as a particularly interesting system. Residual entropy, freezing and glassiness, Kasteleyn transitions and fractionalization of excitations in three dimensions all stem from a simple classical Hamiltonian. But is the usual spin-ice Hamiltonian a correct description of the experimental systems? Here we address this issue by measuring magnetic susceptibility in the two most studied spin-ice compounds, Dy2Ti2O7 and Ho2Ti2O7, using a vector magnet. Using these results, and guided by a theoretical analysis of possible distortions to the pyrochlore lattice, we construct an effective Hamiltonian and explore it using Monte Carlo simulations. We show how this Hamiltonian reproduces the experimental results, including the formation of a phase of intermediate polarization, and gives important information about the possible ground state of real spin-ice systems. Our work suggests an unusual situation in which distortions might contribute to the preservation rather than relief of the effects of frustration.

  16. Effect of Processing Parameters on Thermal Cycling Behavior of Al2O3-Al2O3 Brazed Joints

    NASA Astrophysics Data System (ADS)

    Dandapat, Nandadulal; Ghosh, Sumana; Guha, Bichitra Kumar; Datta, Someswar; Balla, Vamsi Krishna

    2016-10-01

    In the present study, alumina ceramics were active metal brazed at different temperatures ranging from 1163 K to 1183 K (890 °C to 910 °C) using TICUSIL (68.8Ag-26.7Cu-4.5Ti in wt pct) foil as filler alloy of different thicknesses. The brazed joints were subjected to thermal cycling for 100 cycles between 323 K and 873 K (50 °C and 600 °C). The microstructural and elemental composition analysis of the brazed joints were performed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) before and after thermal cycling. Helium (He) leak test and brazing strength measurement were also conducted after thermal cycling for 100 cycles. The joint could withstand up to 1 × 10-9 Torr pressure and brazing strength was higher than 20 MPa. The experimental results demonstrated that joints brazed at the higher temperature with thinner filler alloy produced strong Al2O3-Al2O3 joints.

  17. Structural and spectroscopic studies of Eu3+ doped Lu2O3-Gd2O3 solid solutions

    NASA Astrophysics Data System (ADS)

    Krsmanović Whiffen, Radenka M.; Antić, Željka; Speghini, Adolfo; Brik, Mikhail G.; Bártová, Barbora; Bettinelli, Marco; Dramićanin, Miroslav D.

    2014-04-01

    A series of europium doped (LuxGd1-x)2O3 (x = 1, 0.75, 0.5, 0.25 and 0) nanocrystalline powders were prepared using a polymer complex solution method based on a polyethylene glycol (PEG) as fuel. The samples were systematically characterized by powder X-ray diffraction, scanning and transmission electron microscopies and luminescence spectroscopy. The powders consisted of well-crystalline, cubic phase nanoparticles of 20-50 nm in size, which unit cell parameter increased with Gd content complying with Vegard's law. Upon blue light excitation all samples exhibited strong red luminescence typical of trivalent europium ion. The maximum splitting of the 7F1 manifold changed linearly with the composition change and decreased with lowering of the crystal field strength. Relatively long lifetime values were obtained for 5D0 (˜1.4 ms) and 5D1 (˜120 μs) levels. For all samples we estimated theoretical densities, refractive index coefficients, optical filling factors and Zeff, in order to estimate the Judd-Ofelt intensity parameters and branching ratios. The calculated lifetime of 5D0 level was in line with experimentally obtained luminescence lifetime values. Relative integrated emissions were measured on all samples and Gd2O3 sample proved to have a maximum amount of the characteristic Eu3+ luminescence.

  18. Perovskite solid solutions in the BaO-CuO-Y 2O 3-Nb 2O 5 system

    NASA Astrophysics Data System (ADS)

    Bremer, M.; Langbein, H.

    1999-07-01

    Freeze dried complex carboxylates are highly reactive precursors for complex perovskite solid solutions in the system BaO-CuO-Y 2O 3-Nb 2O 5 On thermal decomposition of the amorphous precursors the formation of complex crystalline phases begins at 600 °C. In most cases the themodynamically controlled phase composition is reached after a reaction time of two hours at about 900 °C. Beginning from the perovskite compound Ba 2YNbO 6 a partial substitution of Y by Cu or by a combination 2/3 Cu,1/3 Nb leads to extended fields of solid solutions with cubic perovskite structure. Substitution according to Y 0,5xBa 2(Y 1-0,5xCu xNb)O 6+x is limited to x ≤ 0,4. A compound LBa 2Cu 2NbO 8 (x=2), well characterized for L=La, does not exist for L=Y. The composition of solid solutions depends on the preparation conditions. There are some signs for an inhomogeneous distribution of B-cations in the cubic perovskites.

  19. Influence of tabletting pressure upon internal morphology of a Fe_2O_3-Cr_2O_3 catalyst

    NASA Astrophysics Data System (ADS)

    Rotaru, P.; Blejoiu, Ş. I.

    2001-12-01

    A study on the influence of tabletting pressure upon the internal morphology of Fe2O3-Cr2O3 catalytic system shows the behaviour of that system at crystallite level or even below it. On increasing tabletting pressure of catalytic powder, remanent stresses are left in the tablets formed which can be calculated in terms of the remanent strain. The macrostresses are constant and small at tabletting pressures ranging within 10^8-5× 10^8 Pa and increase linearly between 6× 10^8 and 14 × 10^8 Pa. The microstresses take measurable values only in samples tabletted at pressures higher than 7 × 10^8 Pa. Besides the formation of remanent stresses, the increase of tabletting pressure brings about the overall change of porous structure and mechanical resistance of the catalytic system. The remanent stresses that appeared at tabletting result in cracks along some planes which, in most instances, are parallel to the planar faces of tablets. The maximum acceptable tabletting pressure of the catalytic system studied amounts to 5 × 10^8 Pa.

  20. Intermediate magnetization state and competing orders in Dy2Ti2O7 and Ho2Ti2O7

    PubMed Central

    Borzi, R. A.; Gómez Albarracín, F. A.; Rosales, H. D.; Rossini, G. L.; Steppke, A.; Prabhakaran, D.; Mackenzie, A. P.; Cabra, D. C.; Grigera, S. A.

    2016-01-01

    Among the frustrated magnetic materials, spin-ice stands out as a particularly interesting system. Residual entropy, freezing and glassiness, Kasteleyn transitions and fractionalization of excitations in three dimensions all stem from a simple classical Hamiltonian. But is the usual spin-ice Hamiltonian a correct description of the experimental systems? Here we address this issue by measuring magnetic susceptibility in the two most studied spin-ice compounds, Dy2Ti2O7 and Ho2Ti2O7, using a vector magnet. Using these results, and guided by a theoretical analysis of possible distortions to the pyrochlore lattice, we construct an effective Hamiltonian and explore it using Monte Carlo simulations. We show how this Hamiltonian reproduces the experimental results, including the formation of a phase of intermediate polarization, and gives important information about the possible ground state of real spin-ice systems. Our work suggests an unusual situation in which distortions might contribute to the preservation rather than relief of the effects of frustration. PMID:27558021

  1. Antarctic ozone depletion chemistry - Reactions of N2O5 with H2O and HCl on ice surfaces

    NASA Technical Reports Server (NTRS)

    Tolbert, Margaret A.; Rossi, Michel J.; Golden, David M.

    1988-01-01

    In a study concerning Antarctic ozone depletion, reactions of dinitrogen pentoxide with water and hydrochloric acid were studied on ice surfaces in a Knudsen cell flow reactor. The N2O5 reacted on ice at 185 K to form condensed-phase nitric acid (HNO3). This reaction may provide a sink for odd nitrogen, NO(x), during the polar winter, a requirement in nearly all models of Antarctic ozone depletion. The reaction of N2O5 on HCl-ice surfaces at 185 K produced gaseous nitryl chloride (ClNO2) and condensed-phase HNO3 and proceeded until all of the HCl within the ice was depleted. The ClNO2 which did not react or condense on ice at 185 K, can be readily photolyzed in the Antarctic spring to form atomic chlorine for catalytic ozone destruction cycles. The other photolysis product, gaseous nitrogen dioxide may be important in the partitioning of NO(x) between gaseous and condensed phases in the Antarctic winter.

  2. Intermediate magnetization state and competing orders in Dy2Ti2O7 and Ho2Ti2O7.

    PubMed

    Borzi, R A; Gómez Albarracín, F A; Rosales, H D; Rossini, G L; Steppke, A; Prabhakaran, D; Mackenzie, A P; Cabra, D C; Grigera, S A

    2016-08-25

    Among the frustrated magnetic materials, spin-ice stands out as a particularly interesting system. Residual entropy, freezing and glassiness, Kasteleyn transitions and fractionalization of excitations in three dimensions all stem from a simple classical Hamiltonian. But is the usual spin-ice Hamiltonian a correct description of the experimental systems? Here we address this issue by measuring magnetic susceptibility in the two most studied spin-ice compounds, Dy2Ti2O7 and Ho2Ti2O7, using a vector magnet. Using these results, and guided by a theoretical analysis of possible distortions to the pyrochlore lattice, we construct an effective Hamiltonian and explore it using Monte Carlo simulations. We show how this Hamiltonian reproduces the experimental results, including the formation of a phase of intermediate polarization, and gives important information about the possible ground state of real spin-ice systems. Our work suggests an unusual situation in which distortions might contribute to the preservation rather than relief of the effects of frustration.

  3. Isotopic Signature of N2O Produced by Marine Ammonia-Oxidizing Archaea

    NASA Astrophysics Data System (ADS)

    Santoro, Alyson E.; Buchwald, Carolyn; McIlvin, Matthew R.; Casciotti, Karen L.

    2011-09-01

    The ocean is an important global source of nitrous oxide (N2O), a greenhouse gas that contributes to stratospheric ozone destruction. Bacterial nitrification and denitrification are thought to be the primary sources of marine N2O, but the isotopic signatures of N2O produced by these processes are not consistent with the marine contribution to the global N2O budget. Based on enrichment cultures, we report that archaeal ammonia oxidation also produces N2O. Natural-abundance stable isotope measurements indicate that the produced N2O had bulk δ15N and δ18O values higher than observed for ammonia-oxidizing bacteria but similar to the δ15N and δ18O values attributed to the oceanic N2O source to the atmosphere. Our results suggest that ammonia-oxidizing archaea may be largely responsible for the oceanic N2O source.

  4. Isotopic signature of N(2)O produced by marine ammonia-oxidizing archaea.

    PubMed

    Santoro, Alyson E; Buchwald, Carolyn; McIlvin, Matthew R; Casciotti, Karen L

    2011-09-01

    The ocean is an important global source of nitrous oxide (N(2)O), a greenhouse gas that contributes to stratospheric ozone destruction. Bacterial nitrification and denitrification are thought to be the primary sources of marine N(2)O, but the isotopic signatures of N(2)O produced by these processes are not consistent with the marine contribution to the global N(2)O budget. Based on enrichment cultures, we report that archaeal ammonia oxidation also produces N(2)O. Natural-abundance stable isotope measurements indicate that the produced N(2)O had bulk δ(15)N and δ(18)O values higher than observed for ammonia-oxidizing bacteria but similar to the δ(15)N and δ(18)O values attributed to the oceanic N(2)O source to the atmosphere. Our results suggest that ammonia-oxidizing archaea may be largely responsible for the oceanic N(2)O source. PMID:21798895

  5. Photocatalytic performance of Cu2O composite octahedra prepared by a propanetriol-reduced process

    NASA Astrophysics Data System (ADS)

    Zhang, Lihui; Wang, Xiangfu

    2014-12-01

    Cu2O and Ag/Cu2O composite octahedra were synthesized via a hydrothermal reaction of CuAc2 with urea in H2O-propanetriol binary solution by adjusting the quantity of AgNO3 at 180 °C for 10 h. The influence of reaction temperature and time on the morphology and phase of the products was investigated, and a possible growth mechanism of Cu2O octahedron was also proposed. The photocatalytic activities of the as-prepared Cu2O and Ag/Cu2O octahedra for the degradation of methyl orange aqueous solution were studied. The results show that they are effective photocatalysts for the degradation of methyl orange, and the photocatalytic ability of Ag/Cu2O composite is stronger than that of Cu2O octahedra, which are expected to be useful in the treatment of wastewaters.

  6. The Characteristics of -OH/H2O in Plagioclase by Solar Wind Implantation Simulate

    NASA Astrophysics Data System (ADS)

    Tang, H.; Li, X. Y.; Wang, S. J.; Yu, W.; Li, S. J.; Li, Y.

    2016-08-01

    FTIR analyses has showed the obvious increased hydroxyl and H2O peak about 3622 cm-1 and about 3356 cm-1after ion implantation respectively, compared with small OH and H2O absorption before ion implantation.

  7. Invar effect in n-Nb{sub 2}O{sub 5}, {alpha}{sub ht}-Nb{sub 2}O{sub 5}, and L-Nb{sub 2}O{sub 5}

    SciTech Connect

    Reznichenko, L. A. Akhnazarova, V. V.; Shilkina, L. A.; Razumovskaya, O. N.; Dudkina, S. I.

    2009-05-15

    An X-ray diffraction analysis of two commercial sets of niobium pentaoxide (Nb{sub 2}O{sub 5}) of Nbo-Pt grade has been performed. Each set reveals the coexistence of three modifications: n-Nb{sub 2}O{sub 5}, {alpha}{sub ht}-Nb{sub 2}O{sub 5}, and L-Nb{sub 2}O{sub 5}. Anomalous behavior in the structural characteristics, with the occurrence of plateaus upon heating (the invar effect), is established for each phase. It is suggested that the coincidence of the temperature ranges with constant unit-cell parameters in Nb{sub 2}O{sub 5} and complex Nb-containing oxides indicates the unified nature of the invar effect, which is related to the defect state of objects under study.

  8. Co-precipitation synthesis of Y2O2SO4:Eu3+ nanophosphor and comparison of photoluminescence properties with Y2O3:Eu3+ and Y2O2S:Eu3+ nanophosphors

    NASA Astrophysics Data System (ADS)

    Lian, Jingbao; Qin, Hua; Liang, Ping; Liu, Feng

    2015-10-01

    Eu3+ ions activated yttrium oxysulfate (Y2O2SO4:Eu3+) nanophosphor has been successfully synthesized by a co-precipitation method from commercially available Y(NO3)3·6H2O, Eu(NO3)3·6H2O, (NH4)2SO4 and NH3·H2O as the starting materials. Detailed characterizations of the synthetic products were obtained by differential thermal analysis, thermogravimetry and derivative thermogravimetry (DTA-TG-DTG), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. The results revealed that the precursor was composed of amorphous yttrium hydroxide sulfate when (NH4)2SO4 was introduced in the reaction system. Moreover, the precursor could be converted into pure Y2O2SO4 phase by calcining at 800 °C for 2 h in air and pure Y2O2S phase could be obtained by calcining Y2O2SO4 at 800 °C for 1 h in hydrogen atmosphere. The as-synthesized Y2O2SO4 phosphor particles are quasi-spherical in shape, slight aggregation and about 20-30 nm in size. PL spectra of the Y2O2SO4:Eu3+ nanophosphor under 270 nm ultraviolet (UV) light excitation show a red emission at 620 nm as the most prominent peak, which attributes to the 5D0→7F2 transition of Eu3+ ions. The quenching concentration of Eu3+ ions was 5 mol%, and its corresponding fluorescence lifetime was 1.49 ms according to the linear fitting result. Furthermore, the Y2O3 nanophosphor was synthesized by similar reaction and comparison of PL properties among three kinds of Eu3+ activated nanophosphors was also systematically discussed.

  9. Vertical profiles of N2O5 along with CH4, N2O, and H2O in the late Arctic winter retrieved from MIPAS-B infrared limb emission measurements

    NASA Astrophysics Data System (ADS)

    Wetzel, G.; von Clarmann, T.; Oelhaf, H.; Fischer, H.

    1995-11-01

    Vertical profiles of N2O5, CH4, N2O, and H2O inside the arctic vortex were retrieved from nighttime infrared limb emission spectra obtained during a flight of the Michelson interferometer for passive atmospheric sounding, balloonborne version (MIPAS-B) Fourier spectrometer from Kiruna (Sweden, 68°N) on March 14/15, 1992, as part of the European Arctic Stratospheric Ozone Experiment. Spectra were analyzed by a nonlinear multiparameter least squares fitting procedure in combination with an onion-peeling retrieval algorithm. The N2O5 results were derived from the intensity of the v12 band near 8 μm. These data represent the first ever reported N2O5 profile inside the polar vortex. Between 21.5 and 31.7 km altitude, N2O5 mixing ratios from 0.38 to 0.74 parts per billion by volume (ppbv) were inferred. Below 21.5 km there is a steep decrease in the mixing ratio toward values lower than 0.07 ppbv at 18.9 and 16.1 km. This discontinuity in the vertical profile correlates in altitude with the bulk of the Pinatubo aerosol layer inside the arctic vortex. N2O5 concentrations are calculated as a function of time since local sunset by using initial NO2 concentrations, O3 concentrations, aerosol surface area densities, and reaction rate coefficients, as found in the literature; calculated N2O5 concentrations are consistent with the MIPAS results. These suggest efficient heterogeneous hydrolysis of N2O5 having taken place on sulphate aerosol particles. Retrieved CH4 and N2O profiles reflect the subsided polar vortex air.

  10. Observation of Combination Bands Involving Intermolecular Vibrations of N_2O-N_2, N_2O-OCS and N_2O-CO_2 Complexes Using AN External Cavity Quantum Cascade Laser

    NASA Astrophysics Data System (ADS)

    Rezaei, M.; Sheybani-Deloui, S.; Moazzen-Ahmadi, N.; McKellar, A. R. W.

    2013-06-01

    Spectra of the weakly-bound N_2O-CO_2, N_2O-OCS, and N_2O-N_2 complexes in the region of the N_2O ν_1 fundamental band (˜2224 cm^{-1}) are observed in a pulsed supersonic slit jet expansion probed with a quantum cascade laser. One new band is observed for each complex: two combination bands involving the intermolecular in-plane bending for N_2O-CO_2 and N_2O-N_2 complexes, and the out-of-plane torsional vibration for N_2O-OCS. The resulting intermolecular frequencies are 34.17, 17.11 and 22.33 cm^{-1} for N_2O-CO_2, N_2O-OCS, and N_2O-N_2 complexes, respectively. The intermolecular vibrations provide clear spectroscopic data against which theory can be benchmarked. These results will be discussed, along with a brief introduction to our pulsed-jet supersonic apparatus which has been retrofitted by an infrared cw external-cavity quantum cascade laser (QCL) manufactured by Daylight Solutions. The QCL is used in the rapid-scan signal averaging mode. Although the repetition rate of the QCL is limited by its PZT scan rate, which is 100 Hz, we describe a simple technique to increase the effective repetition rate to 625 Hz. In addition, we have significantly reduced the long term frequency drift of the QCL by locking the laser frequency to the sides of a reference line. Limin Zheng, Soo-Ying Lee, Yunpeng Lu, and Minghui Yang, J. Chem. Phys. 138, 044302 (2013).

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

    NASA Technical Reports Server (NTRS)

    Ajello, J. M.; Rayermann, P.

    1975-01-01

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

  12. H 2O in basalt and basaltic andesite glass inclusions from four subduction-related volcanoes

    NASA Astrophysics Data System (ADS)

    Sisson, T. W.; Layne, G. D.

    1993-06-01

    Total dissolved H 2O and major element abundances were measured in basalt and basaltic andesite glass inclusions in olivine phenocrysts from Quaternary eruptions of four subduction-related volcanoes to test the hypothesis that low-MgO high-alumina basalts contain high H 2O at depth [1] and to reveal any petrogenetically significant correlations between arc basalt compositions and H 2O contents. Total dissolved H 2O (combined molecular H 2O and OH groups) measured by ion microprobe in mafic glass inclusions from the 1974 eruption of Fuego, Guatemala, reaches 6.2 wt.%. Dissolved H 2O contents decrease in more evolved Fuego glasses. Correlations of H 2O with MgO, Na 2O, K 2O, S and Cl indicate that aqueous fluid exsolution during magma ascent forced crystallization and differentiation of residual liquids. Low-K 2O magnesian high-alumina basalt glass inclusions from the 3 ka eruption of Black Crater (Medicine Lake volcano, California) have low H 2O contents, near 0.2 wt.%, which are consistent with the MORB-like character of these and other primitive lavas of the Medicine Lake region. Basalt and basaltic andesite glass inclusions from Copco Cone and Goosenest volcano on the Cascade volcanic front north of Mt. Shasta have H 2O contents of up to 3.3 wt.%. The range of H 2O contents in Cascade mafic magmas is too large to have resulted solely from enrichment by crystallization and indicates the participation of an H 2O-rich component in magma generation or crustal-level modification. Whereas fluid-absent melting of amphibole-bearing peridotite can account for the H 2O in most mafic arc liquids, the very high H 2O/alkali ratios of the 1974 Fuego eruptives suggest that an aqueous fluid was involved in the generation of Fuego basalts.

  13. Theoretical studies of photoexcitation and ionization in H2O

    NASA Technical Reports Server (NTRS)

    Diercksen, G. H. F.; Kraemer, W. P.; Rescigno, T. N.; Bender, C. F.; Mckoy, B. V.; Langhoff, S. R.; Langhoff, P. W.

    1982-01-01

    Theoretical studies using Franck-Condon and static-exchange approximations are reported for the complete dipole excitation and ionization spectrum in H2O, where (1) large Cartesian Gaussian basis sets are used to represent the required discrete and continuum electronic eigenfunctions at the ground state equilibrium geometry, and (2) previously devised moment-theory techniques are employed in constructing the continuum oscillator-strength densities from the calculated spectra. Comparisons are made of the calculated excitation and ionization profiles with recent experimental photoabsorption studies and corresponding spectral assignments, electron impact-excitation cross sections, and dipole and synchrotron-radiation studies of partial-channel photoionization cross sections. The calculated partial-channel cross sections are found to be atomic-like, and dominated by 2p-kd components. It is suggested that the latter transition couples with the underlying 1b(1)-kb(1) channel, accounting for a prominent feature in recent synchrotron-radiation measurements.

  14. Experiments on H2-O2MHD power generation

    NASA Technical Reports Server (NTRS)

    Smith, J. M.

    1980-01-01

    Magnetohydrodynamic power generation experiments utilizing a cesium-seeded H2-O2 working fluid were carried out using a diverging area Hall duct having an entrance Mach number of 2. The experiments were conducted in a high-field strength cryomagnet facility at field strengths up to 5 tesla. The effects of power takeoff location, axial duct location within the magnetic field, generator loading, B-field strength, and electrode breakdown voltage were investigated. For the operating conditions of these experiments, it is found that the power output increases with the square of the B-field and can be limited by choking of the channel or interelectrode voltage breakdown which occurs at Hall fields greater than 50 volts/insulator. Peak power densities of greater than 100 MW/cu M were achieved.

  15. 12Cao-7Al2o3 Electride Hollow Cathode

    NASA Technical Reports Server (NTRS)

    Rand, Lauren P. (Inventor); Williams, John D. (Inventor); Martinez, Rafael A. (Inventor)

    2016-01-01

    The use of the electride form of 12CaO-7Al.sub.2O.sub.3, or C12A7, as a low work function electron emitter in a hollow cathode discharge apparatus is described. No heater is required to initiate operation of the present cathode, as is necessary for traditional hollow cathode devices. Because C12A7 has a fully oxidized lattice structure, exposure to oxygen does not degrade the electride. The electride was surrounded by a graphite liner since it was found that the C12A7 electride converts to it's eutectic (CA+C3A) form when heated (through natural hollow cathode operation) in a metal tube.

  16. Surface phase diagram for Cr_2O_3(0001)

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Gang; Smith, John R.

    2004-03-01

    Surface phases of Cr_2O3 (0001) as a function of ambient oxygen pressure and temperature were computed by ab initio density-functional theory for a solid surface^1. The surface can be (1×1) or (√3×√3) Cr-terminated, (1×1) O-terminated, and (1×1) or (√3×√3) (O=Cr)-terminated. This is the first theory of the chromyl (O=Cr) termination. The terminations critically depend on the environment, i.e., on the temperature and on the ambient oxygen partial pressure. The first-principles phase diagram is compared with a substantial number of experimental observations of surface phases. 1. Xiao-Gang Wang and John R. Smith, Phys. Rev. B 68, 201402(R) (2003).

  17. NO and N2O detection employing cavity enhanced technique

    NASA Astrophysics Data System (ADS)

    Wojtas, J.; Medrzycki, R.; Rutecka, B.; Mikolajczyk, J.; Nowakowski, M.; Szabra, D.; Gutowska, M.; Stacewicz, T.; Bielecki, Z.

    2012-06-01

    The article describes an application of cavity enhanced absorption spectroscopy for nitric oxide and nitrous oxide detection. Both oxides are important greenhouse gases that are of large influence on environment, living organisms and human health. These compounds are also biomarkers of some human diseases. They determine the level of acid rain, and can be used for characterization of specific explosive materials. Therefore the sensitive detectors of these gases are of great importance for many applications: from routine air monitoring in industrial and intensive traffic areas, to detection of explosives in airports, finally for medicine investigation, for health care, etc. Our compact detection system provides opportunity for simultaneous measure of both NO and N2O concentration at ppb level. Its sensitivity is comparable with sensitivities of instruments based on other methods, e.g. gas chromatography or mass spectrometry.

  18. Intermolecular potential for thermal H2O-He collisions

    NASA Technical Reports Server (NTRS)

    Palma, Amedeo; Green, Sheldon; Defrees, D. J.; Mclean, A. D.

    1988-01-01

    Theoretical potentials for rotational excitation of H2O by He were constructed via several methods, all of which start with a large basis set SCF interaction. The semiempirical Hartree-Fock with damped dispersion model adds a damped long-range attraction with parameters adjusted to fit experimental total differential cross sections. Purely ab initio potentials add correlation energies obtained via perturbation theory (MP2 and MP4) or a variational method (ICF1). Scattering calculations were performed on all surfaces to compare wih available beam scattering and pressure broadening data and to assess sensitivity of state-to-state rates to uncertainties in the potential. From comparison with the limited experimental data, the ICF1 surface appears to be marginally better than the MP4 surface. Thermal rates calculated from this surface should be accurate to better than 50 percent, at least for the larger, more important rates.

  19. Ferroelectricity in high-density H2O ice.

    PubMed

    Caracas, Razvan; Hemley, Russell J

    2015-04-01

    The origin of longstanding anomalies in experimental studies of the dense solid phases of H2O ices VII, VIII, and X is examined using a combination of first-principles theoretical methods. We find that a ferroelectric variant of ice VIII is energetically competitive with the established antiferroelectric form under pressure. The existence of domains of the ferroelectric form within anti-ferroelectric ice can explain previously observed splittings in x-ray diffraction data. The ferroelectric form is stabilized by density and is accompanied by the onset of spontaneous polarization. The presence of local electric fields triggers the preferential parallel orientation of the water molecules in the structure, which could be stabilized in bulk using new high-pressure techniques.

  20. Magnetic properties of Dy2Ti2O7

    NASA Technical Reports Server (NTRS)

    Flood, D. J.

    1973-01-01

    Measurements were made of the magnetization, differential magnetic susceptibility, and magnetic entropy of powered samples of Dy2Ti2O7. The saturation magnetic moment is 4.7 + or - 0.2 Bohr magnetons per Dy ion, instead of 10 as predicted by Hund's rules. A temperature-independent magnetization is observed in the saturation region. Absolute values of magnetic entropy have been obtained for temperatures from 1.25 to 20 K, in applied fields up to 10.4 tesla. The magnetic entropy approaches a maximum value consistent with a ground-state multiplicity of 2. Low field magnetization and differential susceptibility data show a transition to antiferromagnetism near 1.35 K. A construction of the magnetic specific heat from the zero field entropy shows an anomaly near the same temperature.

  1. Utilization of membranes for H2O recycle system

    NASA Technical Reports Server (NTRS)

    Ohya, H.; Oguchi, M.

    1986-01-01

    Conceptual studies of closed ecological life support systems (CELSS) carried out at NAL in Japan for a water recycle system using membranes are reviewed. The system will treat water from shower room, urine, impure condensation from gas recycle system, and so on. The H2O recycle system is composed of prefilter, ultrafiltration membrane, reverse osmosis membrane, and distillator. Some results are shown for a bullet train of toilet-flushing water recycle equipment with an ultraviltration membrane module. The constant value of the permeation rate with a 4.7 square meters of module is about 70 1/h after 500th of operation. Thermovaporization with porous polytetrafluorocarbon membrane is also proposed to replce the distillator.

  2. First Principle Predictions of Isotopic Shifts in H2O

    NASA Technical Reports Server (NTRS)

    Schwenke, David W.; Kwak, Dochan (Technical Monitor)

    2002-01-01

    We compute isotope independent first and second order corrections to the Born-Oppenheimer approximation for water and use them to predict isotopic shifts. For the diagonal correction, we use icMRCI wavefunctions and derivatives with respect to mass dependent, internal coordinates to generate the mass independent correction functions. For the non-adiabatic correction, we use scaled SCF/CIS wave functions and a generalization of the Handy method to obtain mass independent correction functions. We find that including the non-adiabatic correction gives significantly improved results compared to just including the diagonal correction when the Born-Oppenheimer potential energy surface is optimized for H2O-16. The agreement with experimental results for deuterium and tritium containing isotopes is nearly as good as our best empirical correction, however, the present correction is expected to be more reliable for higher, uncharacterized levels.

  3. Fabry-Perot observations of Comet Halley H2O(+)

    NASA Astrophysics Data System (ADS)

    Scherb, F.; Magee-Sauer, K.; Roesler, F. L.; Harlander, J.

    1990-07-01

    Fabry-Perot scanning spectrometer observations of Comet Halley's H2O(+) emissions have yielded 6158.64 and 6158.85 A spin doublet data at distances in the range of 0 to 2 million km from the comet heat in the antisunward direction. Cometary plasma outflow velocities were ascertained on the basis of the emissions' Doppler shifts, yielding results that were mostly but not exclusively consistent with the plasma's constant antisunward acceleration; the acceleration varied from night to night of observations over a 30-300 cm/sec range. The unusual plasma kinematics of December 14-15, 1985, and January 10, 1986, may be associated with the tail-disconnection activity observed by others.

  4. H2O at the Phoenix landing site.

    PubMed

    Smith, P H; Tamppari, L K; Arvidson, R E; Bass, D; Blaney, D; Boynton, W V; Carswell, A; Catling, D C; Clark, B C; Duck, T; Dejong, E; Fisher, D; Goetz, W; Gunnlaugsson, H P; Hecht, M H; Hipkin, V; Hoffman, J; Hviid, S F; Keller, H U; Kounaves, S P; Lange, C F; Lemmon, M T; Madsen, M B; Markiewicz, W J; Marshall, J; McKay, C P; Mellon, M T; Ming, D W; Morris, R V; Pike, W T; Renno, N; Staufer, U; Stoker, C; Taylor, P; Whiteway, J A; Zent, A P

    2009-07-01

    The Phoenix mission investigated patterned ground and weather in the northern arctic region of Mars for 5 months starting 25 May 2008 (solar longitude between 76.5 degrees and 148 degrees ). A shallow ice table was uncovered by the robotic arm in the center and edge of a nearby polygon at depths of 5 to 18 centimeters. In late summer, snowfall and frost blanketed the surface at night; H(2)O ice and vapor constantly interacted with the soil. The soil was alkaline (pH = 7.7) and contained CaCO(3), aqueous minerals, and salts up to several weight percent in the indurated surface soil. Their formation likely required the presence of water. PMID:19574383

  5. Submillimeter H2O and H2O+emission in lensed ultra- and hyper-luminous infrared galaxies at z 2-4

    NASA Astrophysics Data System (ADS)

    Yang, C.; Omont, A.; Beelen, A.; González-Alfonso, E.; Neri, R.; Gao, Y.; van der Werf, P.; Weiß, A.; Gavazzi, R.; Falstad, N.; Baker, A. J.; Bussmann, R. S.; Cooray, A.; Cox, P.; Dannerbauer, H.; Dye, S.; Guélin, M.; Ivison, R.; Krips, M.; Lehnert, M.; Michałowski, M. J.; Riechers, D. A.; Spaans, M.; Valiante, E.

    2016-11-01

    We report rest-frame submillimeter H2O emission line observations of 11 ultra- or hyper-luminous infrared galaxies (ULIRGs or HyLIRGs) at z 2-4 selected among the brightest lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we have detected 14 new H2O emission lines. These include five 321-312ortho-H2O lines (Eup/k = 305 K) and nine J = 2 para-H2O lines, either 202-111(Eup/k = 101 K) or 211-202(Eup/k = 137 K). The apparent luminosities of the H2O emission lines are μLH2O 6-21 × 108 L⊙ (3 <μ< 15, where μ is the lens magnification factor), with velocity-integrated line fluxes ranging from 4-15 Jy km s-1. We have also observed CO emission lines using EMIR on the IRAM 30 m telescope in seven sources (most of those have not yet had their CO emission lines observed). The velocity widths for CO and H2O lines are found to be similar, generally within 1σ errors in the same source. With almost comparable integrated flux densities to those of the high-J CO line (ratios range from 0.4 to 1.1), H2O is found to be among the strongest molecular emitters in high-redshift Hy/ULIRGs. We also confirm our previously found correlation between luminosity of H2O (LH2O) and infrared (LIR) that LH2O LIR1.1-1.2, with ournew detections. This correlation could be explained by a dominant role of far-infrared pumping in the H2O excitation. Modelling reveals that the far-infrared radiation fields have warm dust temperature Twarm 45-75 K, H2O column density per unit velocity interval NH2O /ΔV ≳ 0.3 × 1015 cm-2 km-1 s and 100 μm continuum opacity τ100> 1 (optically thick), indicating that H2O is likely to trace highly obscured warm dense gas. However, further observations of J ≥ 4 H2O lines are needed to better constrain the continuum optical depth and other physical conditions of the molecular gas and dust. We have also detected H2O+ emission in three sources. A tight correlation

  6. Radiation damage in MgAl2O4

    NASA Astrophysics Data System (ADS)

    Summers, G. P.; White, G. S.; Lee, K. H.; Crawford, J. H., Jr.

    1980-03-01

    Exposure of single crystals of MgAl2O4 to fast neutrons and to Van de Graaff electrons with energies in excess of 0.35 MeV introduces an optical-absorption band at 5.3 eV with a 1-eV half-width. This band can be partially bleached at temperatures as low as 40 K and a shoulder at 4.75 eV develops concurrently. This bleaching treatment also partially destroys a previously reported V-type absorption centered at 3.2 eV. Subsequent exposure to ionizing radiation destroys the 4.75-eV band and restores both the 5.3- and 3.2-eV bands to their original intensities. Since this behavior is analogous to the interconversion of F to F+ centers in Al2O3, it is concluded that the 5.3-eV band is the principal optical transition of the F center (two electrons trapped at an oxide-ion vacancy) and the 4.75-eV band is attributed to absorption by the F+ center (one electron trapped at an oxide-ion vacancy). In electron-irradiated crystals the 5.3-eV absorption begins to anneal near 110°C and is about 90% destroyed upon isochronal annealing (10-min pulses) up to 355°C. Neutron-irradiated crystals behave similarly. Measurement of the threshold energy for damage by electrons at 77 K yields a displacement energy for the creation of O2- interstitial-vacancy pairs of 59 eV. The defect yield drops off substantially with increasing temperature, and at room temperature the apparent O2- displacement energy is 130 eV. Possible reasons for this strong temperature effect are discussed.

  7. The cellular steady-state of H2O2: latency concepts and gradients.

    PubMed

    Marinho, H Susana; Cyrne, Luísa; Cadenas, Enrique; Antunes, Fernando

    2013-01-01

    Hydrogen peroxide (H2O2) is able to diffuse across biomembranes but, when cells are exposed to external H2O2, the fast consumption of H2O2 inside the cells due to H2O2-removing enzymes provides the driving force for setting up a H2O2 gradient across the plasma membrane. Knowing this gradient is fundamental to standardize studies with H2O2 as for the same extracellular H2O2 concentration cells with different H2O2 gradients may be exposed to different intracellular H2O2 concentrations. Here, we present the kinetic background behind the establishment of the H2O2 gradient and show how the gradient can be determined experimentally using the principle of enzyme latency. Furthermore, we discuss some of the caveats that may arise when determining the H2O2 gradient. Finally, we describe detailed protocols for the experimental determination of the H2O2 gradient across the plasma membrane in Saccharomyces cerevisiae cells and in mammalian cell lines. PMID:23830623

  8. Observations of H2O in Titan's atmosphere with Herschel

    NASA Astrophysics Data System (ADS)

    Moreno, R.; Lellouch, E.; Lara, L. M.; Courtin, R.; Hartogh, P.; Rengel, M.

    2012-04-01

    Disk averaged observations of several H2O far infrared lines in Titan’s atmosphere were performed with the Herschel Space Observatory, as part of the guaranteed time key program "Water and related chemistry in the Solar System" (HssO, see Hartogh et al 2011). Two instruments were used: (i) HIFI, a heterodyne instrument (R~ 106 ) in the sub-millimeter, which measured the H2O(110-101) rotational transition at 557 GHz on June 10 and Dec. 31, 2010 (ii) PACS, a photoconductor spectrometer (R~103) which measured three water lines at 108.1, 75.4 and 66.4 microns on June 22, 2010. Additional PACS measurements at 66.4 microns on Dec. 15 and 22, 2010 and on July 09, 2011, do not show any significant line intensity variation with time, nor between the leading/trailing sides (i.e. longitude). Spectra were analyzed with a line-by-line radiative transfer code accounting for spherical geometry (Moreno et al. 2011). This model considers the H2O molecular opacity from JPL catalog (Pickett et al. 1998) and also includes collision-induced opacities N2-N2, N2-CH4 and CH4-CH4 (Borysow and Frommhold 1986, 1987, Borysow and Tang 1993). Far infrared aerosol opacities derived by CIRS were included, following Anderson and Samuelson (2011) for their vertical distribution and spectral dependencies. Analysis of the 557 GHz narrow line (FWHM ~ 2 MHz) indicates that it originates at altitudes above 300 km, while lines measured with PACS probe mainly deeper levels (80-150 km). The HIFI and PACS observations are fitted simultaneously, considering a vertical distribution of H2O mixing ratio which follows a power law dependency q=q0(P/P0)n, where q0 is the mixing ratio at some reference pressure level P0, taken near the expected condensation level. Model fits will be presented, and compared with previously proposed H2O vertical distributions. We show in particular that both the steep profile proposed by Lara et al. (1996) (and adopted by Coustenis et al. (1998) to model the first detection of H2O

  9. A HIFI view on circumstellar H2O in M-type AGB stars: radiative transfer, velocity profiles, and H2O line cooling

    NASA Astrophysics Data System (ADS)

    Maercker, M.; Danilovich, T.; Olofsson, H.; De Beck, E.; Justtanont, K.; Lombaert, R.; Royer, P.

    2016-06-01

    Aims: We aim to constrain the temperature and velocity structures, and H2O abundances in the winds of a sample of M-type asymptotic giant branch (AGB) stars. We further aim to determine the effect of H2O line cooling on the energy balance in the inner circumstellar envelope. Methods: We use two radiative-transfer codes to model molecular emission lines of CO and H2O towards four M-type AGB stars. We focus on spectrally resolved observations of CO and H2O from HIFI aboard the Herschel Space Observatory. The observations are complemented by ground-based CO observations, and spectrally unresolved CO and H2O observations with PACS aboard Herschel. The observed line profiles constrain the velocity structure throughout the circumstellar envelopes (CSEs), while the CO intensities constrain the temperature structure in the CSEs. The H2O observations constrain the o-H2O and p-H2O abundances relative to H2. Finally, the radiative-transfer modelling allows to solve the energy balance in the CSE, in principle including also H2O line cooling. Results: The fits to the line profiles only set moderate constraints on the velocity profile, indicating shallower acceleration profiles in the winds of M-type AGB stars than predicted by dynamical models, while the CO observations effectively constrain the temperature structure. Including H2O line cooling in the energy balance was only possible for the low-mass-loss-rate objects in the sample, and required an ad hoc adjustment of the dust velocity profile in order to counteract extreme cooling in the inner CSE. H2O line cooling was therefore excluded from the models. The constraints set on the temperature profile by the CO lines nevertheless allowed us to derive H2O abundances. The derived H2O abundances confirm previous estimates and are consistent with chemical models. However, the uncertainties in the derived abundances are relatively large, in particular for p-H2O, and consequently the derived o/p-H2O ratios are not well constrained.

  10. I + (H2O)2 → HI + (H2O)OH Forward and Reverse Reactions. CCSD(T) Studies Including Spin-Orbit Coupling.

    PubMed

    Wang, Hui; Li, Guoliang; Li, Qian-Shu; Xie, Yaoming; Schaefer, Henry F

    2016-03-01

    The potential energy profile for the atomic iodine plus water dimer reaction I + (H2O)2 → HI + (H2O)OH has been explored using the "Gold Standard" CCSD(T) method with quadruple-ζ correlation-consistent basis sets. The corresponding information for the reverse reaction HI + (H2O)OH → I + (H2O)2 is also derived. Both zero-point vibrational energies (ZPVEs) and spin-orbit (SO) coupling are considered, and these notably alter the classical energetics. On the basis of the CCSD(T)/cc-pVQZ-PP results, including ZPVE and SO coupling, the forward reaction is found to be endothermic by 47.4 kcal/mol, implying a significant exothermicity for the reverse reaction. The entrance complex I···(H2O)2 is bound by 1.8 kcal/mol, and this dissociation energy is significantly affected by SO coupling. The reaction barrier lies 45.1 kcal/mol higher than the reactants. The exit complex HI···(H2O)OH is bound by 3.0 kcal/mol relative to the asymptotic limit. At every level of theory, the reverse reaction HI + (H2O)OH → I + (H2O)2 proceeds without a barrier. Compared with the analogous water monomer reaction I + H2O → HI + OH, the additional water molecule reduces the relative energies of the entrance stationary point, transition state, and exit complex by 3-5 kcal/mol. The I + (H2O)2 reaction is related to the valence isoelectronic bromine and chlorine reactions but is distinctly different from the F + (H2O)2 system.

  11. I + (H2O)2 → HI + (H2O)OH Forward and Reverse Reactions. CCSD(T) Studies Including Spin-Orbit Coupling.

    PubMed

    Wang, Hui; Li, Guoliang; Li, Qian-Shu; Xie, Yaoming; Schaefer, Henry F

    2016-03-01

    The potential energy profile for the atomic iodine plus water dimer reaction I + (H2O)2 → HI + (H2O)OH has been explored using the "Gold Standard" CCSD(T) method with quadruple-ζ correlation-consistent basis sets. The corresponding information for the reverse reaction HI + (H2O)OH → I + (H2O)2 is also derived. Both zero-point vibrational energies (ZPVEs) and spin-orbit (SO) coupling are considered, and these notably alter the classical energetics. On the basis of the CCSD(T)/cc-pVQZ-PP results, including ZPVE and SO coupling, the forward reaction is found to be endothermic by 47.4 kcal/mol, implying a significant exothermicity for the reverse reaction. The entrance complex I···(H2O)2 is bound by 1.8 kcal/mol, and this dissociation energy is significantly affected by SO coupling. The reaction barrier lies 45.1 kcal/mol higher than the reactants. The exit complex HI···(H2O)OH is bound by 3.0 kcal/mol relative to the asymptotic limit. At every level of theory, the reverse reaction HI + (H2O)OH → I + (H2O)2 proceeds without a barrier. Compared with the analogous water monomer reaction I + H2O → HI + OH, the additional water molecule reduces the relative energies of the entrance stationary point, transition state, and exit complex by 3-5 kcal/mol. The I + (H2O)2 reaction is related to the valence isoelectronic bromine and chlorine reactions but is distinctly different from the F + (H2O)2 system. PMID:26562487

  12. The effect of H2O on the adsorption of NO2 on γ-Al2O3: an in situ FTIR/MS study

    SciTech Connect

    Szanyi, Janos; Kwak, Ja Hun; Chimentao, Ricardo J.; Peden, Charles HF

    2007-02-15

    The effect of water on the adsorption of NO2 onto a γ-Al2O3 catalyst support surface was investigated using Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS). Upon room temperature exposure of the alumina surface to small amounts of NO2, nitrites and nitrates are formed, and at higher NO2 doses only nitrates are observed. The surface nitrates formed were of bridging monodentate, bridging bidentate, and monodentate configuration. At elevated NO2 pressures, the surface hydroxyls were consumed in their reaction with NO2 giving primarily bridge-bound nitrates. A significant amount of weakly adsorbed N2O3 was seen as well. Exposure of the NO2-saturated γ-Al2O3 surface to H2O resulted in the desorption of some NO2 + NO as H2O interacted with the weakly-held N2O3, while the bridging monodentate surface nitrates converted into monodentate nitrates. The conversion of these oxide-bound nitrates to water-solvated nitrates was observed at high water doses when the presence of liquid-like water is expected on the surface. The addition of H2O to the NO2-saturated γ-Al2O3 did not affect the amount of NOx strongly adsorbed on the support surface. In particular, no NOx desorption was observed when the NO2-saturated sample was heated to 573K prior to room temperature H2O exposure. The effect of water is completely reversible; i.e., during TPD experiments following NO2 and H2O coadsorption, the same IR spectra were observed at temperatures above that required for H2O desorption as seen for NO2 adsorption only experiments.

  13. The synergetic effect of metal oxide support on Fe2O3 for chemical looping combustion: A theoretical study

    NASA Astrophysics Data System (ADS)

    Qin, Wu; Wang, Yang; Dong, Changqing; Zhang, Junjiao; Chen, Qiuluan; Yang, Yongping

    2013-10-01

    This study deals with the synergetic effect of Al2O3 on Fe2O3 for chemical-looping combustion (CLC) of CO, in comparison with the synergetic effects of ZrO2 and MgO reported in our previous works. Property analysis of Fe2O3/Al2O3 shows that new bonds form cross the interface making Fe2O3 less prone to agglomerate on Al2O3, and 0.129 e transfers from Al2O3 to Fe2O3 to activate the electronic state of Fe2O3. Al2O3 [ZrO2 and MgO] favors the thermal stability of Fe2O3 by preventing the phase transformation, markedly regulates charge populations on the O-Fe bonds and their overlaps and hence tunes the redox properties of Fe2O3. The reaction mechanism analysis demonstrates that Al2O3 [ZrO2 and MgO] activates Fe2O3 for oxidizing CO into CO2 (accompanied by the reduction of Fe2O3) in the fuel reactor, which decrease the height of barrier energy (Ea), and the Ea follows clearly Fe2O3 > Fe2O3/Al2O3 > Fe2O3/MgO > Fe2O3/ZrO2. However, these supports usually increase the Ea for oxidizing Fe2O2 into Fe2O3 by O2 in the air reactor, and the Ea follows clearly Fe2O3/ZrO2 > Fe2O3/Al2O3 > Fe2O3/MgO > Fe2O3. It is argued that different supports could be applied to a given CLC system of different thermodynamic properties.

  14. 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

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

    PubMed

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

    2006-01-28

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

  16. Zeta-Fe2O3--A new stable polymorph in iron(III) oxide family.

    PubMed

    Tuček, Jiří; Machala, Libor; Ono, Shigeaki; Namai, Asuka; Yoshikiyo, Marie; Imoto, Kenta; Tokoro, Hiroko; Ohkoshi, Shin-ichi; Zbořil, Radek

    2015-10-15

    Iron(III) oxide shows a polymorphism, characteristic of existence of phases with the same chemical composition but distinct crystal structures and, hence, physical properties. Four crystalline phases of iron(III) oxide have previously been identified: α-Fe2O3 (hematite), β-Fe2O3, γ-Fe2O3 (maghemite), and ε-Fe2O3. All four iron(III) oxide phases easily undergo various phase transformations in response to heating or pressure treatment, usually forming hexagonal α-Fe2O3, which is the most thermodynamically stable Fe2O3 polymorph under ambient conditions. Here, from synchrotron X-ray diffraction experiments, we report the formation of a new iron(III) oxide polymorph that we have termed ζ-Fe2O3 and which evolved during pressure treatment of cubic β-Fe2O3 (Ia3 space group) at pressures above 30 GPa. Importantly, ζ-Fe2O3 is maintained after pressure release and represents the first monoclinic Fe2O3 polymorph (I2/a space group) that is stable at atmospheric pressure and room temperature. ζ-Fe2O3 behaves as an antiferromagnet with a Néel transition temperature of ~69 K. The complex mechanism of pressure-induced transformation of β-Fe2O3, involving also the formation of Rh2O3-II-type Fe2O3 and post-perovskite-Fe2O3 structure, is suggested and discussed with respect to a bimodal size distribution of precursor nanoparticles.

  17. Quantum Tunneling Enhancement of the C + H2O and C + D2O Reactions at Low Temperature.

    PubMed

    Hickson, Kevin M; Loison, Jean-Christophe; Nuñez-Reyes, Dianailys; Méreau, Raphaël

    2016-09-15

    Recent studies of neutral gas-phase reactions characterized by barriers show that certain complex forming processes involving light atoms are enhanced by quantum mechanical tunneling at low temperature. Here, we performed kinetic experiments on the activated C((3)P) + H2O reaction, observing a surprising reactivity increase below 100 K, an effect that is only partially reproduced when water is replaced by its deuterated analogue. Product measurements of H- and D-atom formation allowed us to quantify the contribution of complex stabilization to the total rate while confirming the lower tunneling efficiency of deuterium. This result, which is validated through statistical calculations of the intermediate complexes and transition states has important consequences for simulated interstellar water abundances and suggests that tunneling mechanisms could be ubiquitous in cold dense clouds.

  18. Transport properties of PbO-P2O5-ZnO-Li2O glass system

    NASA Astrophysics Data System (ADS)

    Lakshmikantha, R.; Rajaramakrishna, R.; Ayachit, N. H.; Anavekar, R. V.

    2012-06-01

    The electrical conductivity of Li+ ion conducting lead zinc phosphate glasses have been carried out both as a function of temperature and frequency in the temperature range 458-510K and over frequencies 40 Hz to 10 MHz. The dc conductivities show Arrhenius behavior and show compositional dependence. The σ decreases with increase in Li2O content. The ac conductivity behavior has been analyzed using Almond-West power law using a single exponent. The exponent 's' obtained from the power law fits is found to have values ranging from 0.74 - 0.80 in these glasses and shows moderate temperature dependence, which is attributed to high degree of modification in the glass network.

  19. Quantum Tunneling Enhancement of the C + H2O and C + D2O Reactions at Low Temperature.

    PubMed

    Hickson, Kevin M; Loison, Jean-Christophe; Nuñez-Reyes, Dianailys; Méreau, Raphaël

    2016-09-15

    Recent studies of neutral gas-phase reactions characterized by barriers show that certain complex forming processes involving light atoms are enhanced by quantum mechanical tunneling at low temperature. Here, we performed kinetic experiments on the activated C((3)P) + H2O reaction, observing a surprising reactivity increase below 100 K, an effect that is only partially reproduced when water is replaced by its deuterated analogue. Product measurements of H- and D-atom formation allowed us to quantify the contribution of complex stabilization to the total rate while confirming the lower tunneling efficiency of deuterium. This result, which is validated through statistical calculations of the intermediate complexes and transition states has important consequences for simulated interstellar water abundances and suggests that tunneling mechanisms could be ubiquitous in cold dense clouds. PMID:27574866

  20. Preparation of BaTiO3/Cu2O and BaTiO3/Cu2O/Au Complexes: Their Photocatalytic and Antipathogenic Effect.

    PubMed

    Cho, Sung-Woo; Nam, Dae-Hyun; Kim, Lee-Han; Jung, Dongwoon

    2016-05-01

    BaTiO3/Cu2O and BaTiO3/Cu2O/Au complexes were prepared from CuCl2, HAuCl4 solution, and BaTiO3 by the solution method. BaTiO3 particles were dispersed in a CuCl2 solution, and the BaTiO3/CuO complex was produced through crystallization of CuO onto the BaTiO3 surface by hydrolysis of CuCl2 in the first stage. After the reaction, CuO was reduced to Cu2O by treatment with glucose, thereby yielding the BaTiO3/Cu2O complex. The BaTiO3/Cu2O/Au complex was prepared by treating the BaTiO3/Cu2O particles with HAuCl4. Under visible light, the obtained BaTiO3/Cu2O0/Au complex showed higher photocatalytic activity than the Degussa P-25sample. In addition, the BaTiO3/Cu2O complex showed excellent antipathogenic effect. PMID:27483887

  1. Synthesis, characterization and crystal structure of zinc dimolybdate pentahydrate ZnMo{sub 2}O{sub 7}.5H{sub 2}O

    SciTech Connect

    Grzywa, M.; Lasocha, W. Surga, W.

    2007-05-15

    The method of synthesis of zinc dimolybdate pentahydrate ZnMo{sub 2}O{sub 7}.5H{sub 2}O has been elaborated. The crystal structure has been solved by X-ray powder diffraction methods. The space group of ZnMo{sub 2}O{sub 7}.5H{sub 2}O is P2{sub 1}/c (14), with lattice parameters: 6.0021(9), 18.886(3), 8.725(1)A, {beta}=93.85(1){sup o}, V=986.8(2)A{sup 3}. The decomposition of ZnMo{sub 2}O{sub 7}.5H{sub 2}O in air and nitrogen was studied in situ by X-ray diffraction. Results of crystal structure determination and refinement by the Rietveld method, as well as results of IR and TGA, DTA studies performed for ZnMo{sub 2}O{sub 7}.5H{sub 2}O, are presented.

  2. Experimental determination of the activation energies of CH4 , SO2 and O2 reactions on Cr2O3 / γ -Al2O3

    NASA Astrophysics Data System (ADS)

    Hernández Guiance, S. N.; Coria, I. D.; Irurzun, I. M.; Mola, E. E.

    2016-09-01

    In the present work we experimentally determine the activation energies of CH4,SO2 and O2 reactions on Cr2O3 / γ -Al2O3 . To our knowledge there is no previous determination of these parameters, so fundamental information is provided to determine the velocity laws of these reactions and understand their kinetic behavior.

  3. Density functional investigations on the (H 2O) n·CCH and (H 2O) n·HCC complexes ( n=1-3)

    NASA Astrophysics Data System (ADS)

    Qu, Zheng-wang; Zhu, Hui; Zhang, Xing-kang; Zhang, Qi-yuan

    2003-01-01

    The electronic structures and energies of (H 2O) n·CCH and (H 2O) n·HCC complexes ( n=1-3) between CCH and water have been theoretically investigated at the UB3LYP/6-311++G(2df,p)//UB3LYP/6-311G(d,p) level. The complexes with n=2-3 are cyclic structures with homodromic hydrogen-bond chain. The (H 2O) n·CCH ( n=1-3) complexes show increasing stabilities towards CCH- or H 2O-eliminations of 2.3, 5.8 and 7.6 kcal/mol and are energetically more stable than the corresponding (H 2O) n·HCC complexes by 0.8, 2.7 and 3.4 kcal/mol, respectively, due to the charge-separation-enhanced hydrogen bonds within (H 2O) n·CCH ( n=2,3). Strong interactions between CCH and (H 2O) 2 and (H 2O) 3 clusters suggest special solvent effects of water on the chemical behavior of unsaturated radicals.

  4. Self-sufficing H2O2-responsive nanocarriers through tumor-specific H2O2 production for synergistic oxidation-chemotherapy.

    PubMed

    Li, Junjie; Ke, Wendong; Wang, Lei; Huang, Mingming; Yin, Wei; Zhang, Ping; Chen, Qixian; Ge, Zhishen

    2016-03-10

    One of distinct features in tumor tissues is the elevated concentration of reactive oxygen species (ROS) during tumor immortality, proliferation and metastasis. However, ROS-responsive materials are rarely utilized in the field of in vivo tumoral ROS-responsive applications due to the fact that the intrinsic ROS level in the tumors could not escalate to an adequate level that the developed materials can possibly respond. Herein, palmitoyl ascorbate (PA) as a prooxidant for hydrogen peroxide (H2O2) production in tumor tissue is strategically compiled into a H2O2-responsive camptothecin (CPT) polymer prodrug micelle, which endowed the nanocarriers with self-sufficing H2O2 stimuli in tumor tissues. Molecular oncology manifests the hallmarks of tumoral physiology with deteriorating propensity in eliminating hazardous ROS. H2O2 production was demonstrated to specifically sustain in tumors, which not only induced tumor cell apoptosis by elevated oxidation stress but also served as autochthonous H2O2 resource to trigger CPT release for chemotherapy. Excess H2O2 and released CPT could penetrate into cells efficiently, which showed synergistic cytotoxicity toward cancer cells. Systemic therapeutic trial revealed potent tumor suppression of the proposed formulation via synergistic oxidation-chemotherapy. This report represents a novel nanomedicine platform combining up-regulation of tumoral H2O2 level and self-sufficing H2O2-responsive drug release to achieve novel synergistic oxidation-chemotherapy.

  5. SOLID SOLUTION EFFECTS ON THE THERMAL PROPERTIES IN THE MgAl2O4-MgGa2O4

    SciTech Connect

    O'Hara, Kelley; Smith, Jeffrey D; Sander, Todd P.; Hemrick, James Gordon

    2013-01-01

    Solid solution eects on thermal conductivity within the MgO-Al2O3-Ga2O3 system were studied. Samples with systematically varied additions of MgGa2O4 to MgAl2O4 were prepared and the laser ash technique was used to determine thermal diusivity at temperatures between 200C and 1300C. Heat capacity as a function of temperature from room temperature to 800C was also determined using dierential scanning calorimetry. Solid solution in the MgAl2O4-MgGa2O4 system decreases the thermal conductivity up to 1000C. At 200C thermal conductivity decreased 24% with a 5 mol% addition of MgGa2O4 to the system. At 1000C the thermal conductivity decreased 13% with a 5 mol% addition. Steady state calculations showed a 12.5% decrease in heat ux with 5 mol% MgGa2O4 considered across a 12 inch thickness.

  6. Anharmonic RRKM calculation for the dissociation of (H(2)O)(2)H(+) and its deuterated species (D(2)O)(2)D(+).

    PubMed

    Song, Di; Su, Hongmei; Kong, Fan-Ao; Lin, Sheng-Hsien

    2010-09-23

    Investigations on the dissociation kinetics of hydrated protonium ions, (H(2)O)(2)H(+) and their deuterated species (D(2)O)(2)D(+), are reported based on the harmonic and anharmonic oscillator model using the transition state theory and ab initio calculations. We find that the dissociation of (H(2)O)(2)H(+) and (D(2)O)(2)D(+) exhibits a distinct threshold behavior due to the existence of activation energies. Moreover, the deviation between the harmonic and anharmonic dissociation rate constants becomes larger in the high energy or temperature range, with the rate constants becoming unreasonably large under the harmonic oscillator model. The isotope effect is found to become more distinct but only in the case of the anharmonic oscillator model. These results show that the anharmonic Rice-Ramsperger-Kassel-Marcus (RRKM) theory can provide a reasonably good description for the dissociation of (H(2)O)(2)H(+) and (D(2)O)(2)D(+). Furthermore, a theoretical model to demonstrate the principle of vibrational predissociation spectroscopy (VPS) is established from the viewpoint of RRKM theory and applied in determining the experimental conditions and understanding the role of the dissociation rate constant k(E) played in the VPS experiment, using (H(2)O)(2)H(+) and (D(2)O)(2)D(+) as examples.

  7. Effect of Bi2O3 particle sizes and addition of starch into Bi2O3-PVA composites for X-ray shielding

    NASA Astrophysics Data System (ADS)

    Noor Azman, Nurul Z.; Musa, Nur F. L.; Nik Ab Razak, Nik N. A.; Ramli, Ramzun M.; Mustafa, Iskandar S.; Abdul Rahman, Azhar; Yahaya, Nor Z.

    2016-09-01

    The effect of Bi2O3 particle sizes filled PVA composites on X-ray transmission for X-ray shielding purpose had been successfully fabricated and analyzed by using X-ray fluorescent spectroscopy (XRF) and mammography units with various low X-ray energy ranges. Besides, a preliminary investigation was carried out by using XRF unit to obtain the effect of starch addition into the composite on the X-ray transmissions by both particle sizes of Bi2O3-PVA composites. The results showed that the ability of the composite to attenuate the initial X-ray beam was augmented with the increased Bi2O3 weight percentage (wt%). The density of both particle sizes of Bi2O3-PVA composites was compared with the addition of 1 and 3 wt% starch, while a fluctuation of density occurred for the composites without starch. Moreover, the nano-sized Bi2O3-PVA composite without starch did not exemplify better X-ray attenuation capability compared to its micro-sized counterpart even though their density was higher than the micro-sized Bi2O3-PVA composite. However, the nano-sized Bi2O3-PVA composite with starch offered better particle size effect for X-ray shielding ability than its micro-sized counterpart compared to the Bi2O3-PVA composites without starch.

  8. A Ca substitution study of NaV2O4: High-pressure synthesis of the Na1-xCaxV2O4 solid solution

    SciTech Connect

    Varga, Tamas; Mitchell, John F.; Yamaura, Kazunari; Mandrus, David; Wang, Jun

    2009-01-01

    Ambient pressure CaV{sub 2}O{sub 4} and high-pressure NaV{sub 2}O{sub 4} crystallize in the CaFe{sub 2}O{sub 4} structure type containing double chains of edge-sharing VO{sub 6} octahedra. Recent measurements on NaV{sub 2}O{sub 4} reveal low-dimensional metallicity and evidence of half-metallic ferromagnetism. In contrast, CaV{sub 2}O{sub 4} is an antiferromagnetic insulator. To explore the evolution of these ground-state behaviors, we have prepared a series of Ca-doped NaV{sub 2}O{sub 4} compounds with the formula Na{sub 1-x}Ca{sub x}V{sub 2}O{sub 4} (x = 0-1) using high-pressure synthesis. Samples at the Na end (x = 0-0.07) show a broad antiferromagnetic transition in the 120-160 K range in accordance with earlier reports. Transport measurements show an insulator-metal transition at x {approx} 0.2. Samples with higher Ca concentrations (x = 0.4-0.7) exhibit a metal-insulator transition around 150 K. The results for the Na{sub 1-x}Ca{sub x}V{sub 2}O{sub 4} solid solution is discussed in comparison to existing studies at the Ca- and Na-rich ends.

  9. Ionic liquid-assisted solvothermal synthesis of hollow Mn2O3 anode and LiMn2O4 cathode materials for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    He, Xin; Wang, Jun; Jia, Haiping; Kloepsch, Richard; Liu, Haidong; Beltrop, Kolja; Li, Jie

    2015-10-01

    Mn-based Mn2O3 anode and LiMn2O4 cathode materials are prepared by a solvothermal method combined with post annealing process. Environmentally friendly ionic liquid 1-Butyl-3-methylimidazolium tetrafluoroborate as both structure-directing agent and fluorine source is used to prepare hollow polyhedron MnF2 precursor. Both target materials Mn2O3 anode and LiMn2O4 cathode have the morphology of the MnF2 precursor. The Mn2O3 anode using carboxymethyl cellulose as binder could deliver slight better electrochemical performance than the one using poly (vinyldifluoride) as binder. The former has an initial charge capacity of 800 mAh g-1 at a current density of 101.8 mA g-1, and exhibits no obvious capacity decay for 150 cycles at 101.8 mA g-1. The LiMn2O4 cathode material prepared with molten salt assistant could display much better electrochemical performance than the one prepared without molten salt assistance. In particular, it has an initial discharge capacity of 117.5 mAh g-1 at a current density of 0.5C and good rate capability. In the field of lithium ion batteries, both the Mn2O3 anode and LiMn2O4 cathode materials could exhibit enhanced electrochemical performance due to the well formed morphology based on the ionic liquid-assisted solvothermal method.

  10. Visible light catalysis of rhodamine B using nanostructured Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) thin films.

    PubMed

    Mahadik, M A; Shinde, S S; Mohite, V S; Kumbhar, S S; Moholkar, A V; Rajpure, K Y; Ganesan, V; Nayak, J; Barman, S R; Bhosale, C H

    2014-04-01

    The Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) composite films are deposited using spray pyrolysis method onto glass and FTO coated substrates. The structural, morphological, optical and photocatalytic properties of Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) thin films are studied. XRD analysis confirms that films are polycrystalline with rhombohedral and tetragonal crystal structures for Fe2O3 and TiO(2) respectively. The photocatalytic activity was tested for the degradation of Rhrodamine B (Rh B) in aqueous medium. The rate constant (-k) was evaluated as a function of the initial concentration of species. Substantial reduction in concentrations of organic species was observed from COD and TOC analysis. Photocatalytic degradation effect is relatively higher in case of the TiO(2)/Fe(2)O(3) than TiO(2) and Fe(2)O(3) thin film photoelectrodes in the degradation of Rh B and 98% removal efficiency of Rh B is obtained after 20min. The photocatalytic experimental results indicate that TiO(2)/α-Fe(2)O(3) photoelectrode is promising material for removing of water pollutants.

  11. Preparation of iron aluminate (FeAl2O4) nanoparticles from FeAl2O4 hollow particles fabricated by using a spray pyrolysis process

    NASA Astrophysics Data System (ADS)

    Yun, Jaecheol; Kim, Yangdo; Park, Dahee; Yun, Jung-Yeul

    2015-05-01

    Iron aluminate (FeAl2O4) hollow particles with a spinel structure were synthesized by using a spray pyrolysis process. FeAl2O4 hollow particles were formed at a reaction temperature of 900 °C at a flow rate of 40 L/min as a result of the rapid solvent evaporation and decomposition gases from the droplets in the spray solution prepared from metal salts and organic reagents. FeAl2O4 hollow particles were fabricated at a reaction temperature of 900 °C with a flow rate of 40 L/min. The FeAl2O4 hollow particles were heat treated for 3 hours at 600 °C in a 5% H2/Ar atmosphere to form the crystal particles. Subsequently, FeAl2O4 nanoparticles were fabricated from the FeAl2O4 hollow particles by using the wet milling process. After milling for 60 minutes, transmission electron microscopy revealed the FeAl2O4 particles to have a mean size of approximately 50 nm. The FeAl2O4 nanoparticles were fabricated successfully by using a two-step process, spray pyrolysis and wet milling.

  12. Stability relations in the system CaSiO3-CaMnSi2O6-CaFeSi2O6

    NASA Astrophysics Data System (ADS)

    Abrecht, Jürgen

    1980-10-01

    In the system CaSiO3-CaMnSi2O6-CaFeSi2O6 extensive miscibility gaps between pyroxenoids and clinopyroxenes are observed. The miscibility gap between Mn-bustamite and Mn-wollastonite has been determined experimentally by a hydrothermal technique between 400° and 1200° C at P f= 2 kbar. Further experiments have been performed at P f=9 kbar, which revealed a shifting of the miscibility gap towards more Ca-rich compositions. The bustamite phase is stabilized by high pressures and the wollastonite structure is the stable phase at high temperatures. Similar phase relations as along the join CaSiO3-CaMnSi2O6 exist along the join CaSiO3-CaFeSi2O6 but with a more extensive two-phase field of bustamite-clinopyroxene. Possible phase relations along the joins CaSiO3-CaMnSi2O6, CaSiO3-CaFeSi2O6 and CaFeSi2O6-CaMnSi2O6 are given in temperature-composition diagrams for low pressures, based on natural and experimental data.

  13. Catalytic performance of V2O5-MoO3/γ-Al2O3 catalysts for partial oxidation of n-hexane1

    NASA Astrophysics Data System (ADS)

    Mahmoudian, R.; Khodadadi, Z.; Mahdavi, Vahid; Salehi, Mohammed

    2016-01-01

    In the current study, a series of V2O5-MoO3 catalyst supported on γ-Al2O3 with various V2O5 and MoO3 loadings was prepared by wet impregnation technique. The characterization of prepared catalysts includes BET surface area, powder X-ray diffraction (XRD), and oxygen chemisorptions. The partial oxidation of n-hexane by air over V2O5-MoO3/γ-Al2O3 catalysts was carried out under flow condition in a fixed bed glass reactor. The effect of V2O5 loading, temperature, MoO3 loading, and n-hexane LHSV on the n-hexane conversion and the product selectivity were investigated. The partial oxygenated products of n-hexane oxidation were ethanol, acetic anhydride, acetic acid, and acetaldehyde. The 10% V2O5-1%MoO3/γ-Al2O3 was found in most active and selective catalyst during partial oxidation of n-hexane. The results indicated that by increasing the temperature, the n-hexane conversion increases as well, although the selectivity of the products passes through a maximum by increasing the temperature.

  14. Isotope signatures of N2O emitted from vegetable soil: Ammonia oxidation drives N2O production in NH4+-fertilized soil of North China

    PubMed Central

    Zhang, Wei; Li, Yuzhong; Xu, Chunying; Li, Qiaozhen; Lin, Wei

    2016-01-01

    Nitrous oxide (N2O) is a potent greenhouse gas. In North China, vegetable fields are amended with high levels of N fertilizer and irrigation water, which causes massive N2O flux. The aim of this study was to determine the contribution of microbial processes to N2O production and characterize isotopic signature effects on N2O source partitioning. We conducted a microcosm study that combined naturally abundant isotopologues and gas inhibitor techniques to analyze N2O flux and its isotopomer signatures [δ15Nbulk, δ18O, and SP (intramolecular 15N site preference)] that emitted from vegetable soil after the addition of NH4+ fertilizers. The results show that ammonia oxidation is the predominant process under high water content (70% water-filled pore space), and nitrifier denitrification contribution increases with increasing N content. δ15Nbulk and δ18O of N2O may not provide information about microbial processes due to great shifts in precursor signatures and atom exchange, especially for soil treated with NH4+ fertilizer. SP and associated two end-member mixing model are useful to distinguish N2O source and contribution. Further work is needed to explore isotopomer signature stability to improve N2O microbial process identification. PMID:27387280

  15. Communication: quasiclassical trajectory calculations of correlated product-state distributions for the dissociation of (H2O)2 and (D2O)2.

    PubMed

    Czakó, Gábor; Wang, Yimin; Bowman, Joel M

    2011-10-21

    Stimulated by recent experiments [B. E. Rocher-Casterline, L. C. Ch'ng, A. K. Mollner, and H. Reisler, J. Chem. Phys. 134, 211101 (2011)], we report quasiclassical trajectory calculations of the dissociation dynamics of the water dimer, (H(2)O)(2) (and also (D(2)O)(2)) using a full-dimensional ab initio potential energy surface. The dissociation is initiated by exciting the H-bonded OH(OD)-stretch, as done experimentally for (H(2)O)(2). Normal mode analysis of the fragment pairs is done and the correlated vibrational populations are obtained by (a) standard histogram binning (HB), (b) harmonic normal-mode energy-based Gaussian binning (GB), and (c) a modified version of (b) using accurate vibrational energies obtained in the Cartesian space. We show that HB allows opening quantum mechanically closed states, whereas GB, especially via (c), gives physically correct results. Dissociation of both (H(2)O)(2) and (D(2)O)(2) mainly produces either fragment in the bending excited (010) state. The H(2)O(J) and D(2)O(J) rotational distributions are similar, peaking at J = 3-5. The computations do not show significant difference between the ro-vibrational distributions of the donor and acceptor fragments. Diffusion Monte Carlo computations are performed for (D(2)O)(2) providing an accurate zero-point energy of 7247 cm(-1), and thus, a benchmark D(0) of 1244 ± 5 cm(-1).

  16. Highly Facet-Dependent Photocatalytic Properties of Cu2 O Crystals Established through the Formation of Au-Decorated Cu2 O Heterostructures.

    PubMed

    Yuan, Guo-Zhi; Hsia, Chi-Fu; Lin, Zhen-Wen; Chiang, Chieh; Chiang, Yun-Wei; Huang, Michael H

    2016-08-22

    This work confirms the presence of a large facet-dependent photocatalytic activity of Cu2 O crystals through sparse deposition of gold particles on Cu2 O cubes, octahedra, and rhombic dodecahedra. Au-decorated Cu2 O rhombic dodecahedra and octahedra showed greatly enhanced photodegradation rates of methyl orange resulting from a better separation of the photogenerated electrons and holes, with the rhombic dodecahedra giving the best efficiency. Au-Cu2 O core-shell rhombic dodecahedra also displayed a better photocatalytic activity than pristine rhombic dodecahedra. However, Au-deposited Cu2 O cubes, pristine cubes, and Au-deposited small nanocubes bound by entirely {100} facets are all photocatalytically inactive. X-ray photoelectron spectra (XPS) showed identical copper peak positions for these Au-decorated crystals. Remarkably, electron paramagnetic resonance (EPR) measurements indicated a higher production of hydroxyl radicals for the photoirradiated Cu2 O rhombic dodecahedra than for the octahedra, but no radicals were produced from photoirradiated Cu2 O cubes. The Cu2 O {100} face may present a high energy barrier through its large band edge bending and/or electrostatic repulsion, preventing charge carriers from reaching to this surface. The conventional photocatalysis model fails in this case. The facet-dependent photocatalytic differences should be observable in other semiconductor systems whenever a photoinduced charge-transfer process occurs across an interface. PMID:27470656

  17. Isotope signatures of N2O emitted from vegetable soil: Ammonia oxidation drives N2O production in NH4(+)-fertilized soil of North China.

    PubMed

    Zhang, Wei; Li, Yuzhong; Xu, Chunying; Li, Qiaozhen; Lin, Wei

    2016-01-01

    Nitrous oxide (N2O) is a potent greenhouse gas. In North China, vegetable fields are amended with high levels of N fertilizer and irrigation water, which causes massive N2O flux. The aim of this study was to determine the contribution of microbial processes to N2O production and characterize isotopic signature effects on N2O source partitioning. We conducted a microcosm study that combined naturally abundant isotopologues and gas inhibitor techniques to analyze N2O flux and its isotopomer signatures [δ(15)N(bulk), δ(18)O, and SP (intramolecular (15)N site preference)] that emitted from vegetable soil after the addition of NH4(+) fertilizers. The results show that ammonia oxidation is the predominant process under high water content (70% water-filled pore space), and nitrifier denitrification contribution increases with increasing N content. δ(15)N(bulk) and δ(18)O of N2O may not provide information about microbial processes due to great shifts in precursor signatures and atom exchange, especially for soil treated with NH4(+) fertilizer. SP and associated two end-member mixing model are useful to distinguish N2O source and contribution. Further work is needed to explore isotopomer signature stability to improve N2O microbial process identification. PMID:27387280

  18. Structural investigation in the TiB{sub 2}-(Na{sub 2}O.B{sub 2}O{sub 3}.Al{sub 2}O{sub 3}) system

    SciTech Connect

    Buixaderas, Elena; Maria Anghel, Elena; Petrescu, Simona; Osiceanu, Petre

    2010-09-15

    Composites in the TiB{sub 2}-Na{sub 2}O.B{sub 2}O{sub 3}.Al{sub 2}O{sub 3} systems, TiB{sub 2}-MBA (MB stands for sodium metaborate and A is Al{sub 2}O{sub 3}), were prepared by self-propagating high-temperature synthesis (SHS), in simultaneous mode. Selection of these compositions was ruled by the interesting properties of both TiB{sub 2} and double borates of alkali metal and aluminum. The structure of the obtained materials was evaluated by micro-Raman spectroscopy, from room temperature up to 600 {sup o}C, and X-ray photoelectron spectroscopy (XPS). Formation of the TiB{sub 2} and TiO{sub 2-x}B{sub x} phases along with TiO{sub 2} as rutile were identified as titanium speciation in the grain phase embedded in a sodium aluminum borate matrix. Integration of the Raman spectra of the grain phases revealed a TiB{sub 2} content of 16.99% and 23.32% for the two composite investigated 2TiB{sub 2}.2MBA and 3TiB{sub 2}.5MBA. A constrained-width model for the spectral deconvolution of the high-frequency Raman band was forwarded to calculate the proportion of tetrahedral boron atoms (7.424%) in the blank borate matrix Na{sub 2}B{sub 2}O{sub 4}.Al{sub 2}O{sub 3} in solid phase. - Graphical abstract: Deconvolution of the reduced Raman spectrum of the grain phase in TiB{sub 2}-(Na{sub 2}O.B{sub 2}O{sub 3}.Al{sub 2}O{sub 3}) composite along with its Raman micrographs collected at room temperature.

  19. H2O2 levels in rainwater collected in south Florida and the Bahama Islands

    NASA Technical Reports Server (NTRS)

    Zika, R.; Saltzman, E.; Chameides, W. L.; Davis, D. D.

    1982-01-01

    Measurements of H2O2 in rainwater collected in Miami, Florida, and the Bahama Islands area indicate the presence of H2O2 concentration levels ranging from 100,000 to 700,000 M. No systematic trends in H2O2 concentration were observed during an individual storm, in marked contrast to the behavior of other anions for example, NO3(-), SO4(-2), and Cl(-). The data suggest that a substantial fraction of the H2O2 found in precipitation is generated by aqueous-phase reactions within the cloudwater rather than via rainout and washout of gaseous H2O2.

  20. OPTICAL PROPERTIES OF N-DOPED Cu2O THIN FILMS DEPOSITED BY RF-MAGNETRON SPUTTERING Cu2O TARGET

    NASA Astrophysics Data System (ADS)

    Lai, Guozhong; Wu, Yangwei; Lin, Limei; Qu, Yan; Lai, Fachun

    2014-05-01

    N-doped Cu2O films were deposited on quartz substrates by reactive magnetron sputtering a Cu2O target. The optical constants and thicknesses of the films with different nitrogen partial pressure (NPP) were retrieved from transmittance data by an optical model which combines the Forouhi-Bloomer model with modified Drude model. The results show that when NPP increases from 0.0 to 0.033 Pa, the optical gap decreases from 2.14 to 1.95 eV. Additionally, an optical absorption process in the infrared region below the optical band gap was observed for N-doped Cu2O films, which was not found in the pure Cu2O film. This is because an intermediate band (IB) in the band gap results from nitrogen doping. It is believed that N-doped Cu2O film with suitable NPP could be used to enhance the energy conversion efficiency for photovoltaic cells.

  1. Comprehensive copper ion hydration: experimental and theoretical investigation of Cu2+(H2O)n, Cu+(H2O)n, CuOH+(H2O)n

    NASA Astrophysics Data System (ADS)

    Sweeney, Andrew

    Guided ion beam tandem mass spectrometry is used to probe the kinetic energy dependence of both Cu2+(H2O)n, where n = 5--10, and CuOH+(H2O)n, where n = 0--4 colliding with Xe. The resulting cross sections are analyzed using statistical models to yield 0 K bond dissociation energies (BDEs). The primary dissociation pathway for Cu2+(H2O)n consists of water loss followed by the sequential loss of additional waters at higher energies until n = 7, at which point charge separation to form CuOH+(H2O) m + H+(H2O)n-m-2 is energetically favored. The primary dissociation pathway for CuOH+(H 2O)n is also water loss and is followed by the sequential loss of additional waters at higher energies until n = 1, at which point OH loss become competitive. The BDEs for loss of water and OH from CuOH +(H2O) are combined in a thermodynamic cycle with literature values to derive BDEs for the loss of OH from CuOH+(H 2O)n, where n = 0, 2--4. Infrared multiple photon dissociation (IRPD) spectroscopy is performed on CuOH+(H2O)n, where n = 2--9. These spectra are characterized through comparison to theoretical spectra of low energy isomers. It is found that CuOH+(H2O) n prefers a 4-coordinate inner shell, although contributions from 5-coordinate geometries cannot be ruled out in most cases and are clearly present for n = 7. This preference is found in the Cu2+(H2O) n system as well and differs from the Cu+(H2O) n system, which prefers a 2-coordinate inner shell. Electronic structure calculations are further employed to yield BDEs which agree reasonably well with experimental values. A method for modeling kinetic energy release distributions (KERD) on a guided ion beam tandem mass spectrometer is proposed. This method achieves reasonable agreement with dissociations occurring over loose transition states when reactants have little energy in excess of the dissociation threshold. Current limitations and future possibilities of this method are discussed in detail.

  2. Significance of the direct relaxation process in the low-energy spin dynamics of a one-dimensional ferrimagnet NiCu(C 7H 6N 2O 6)(H 2O) 3·2H 2O

    NASA Astrophysics Data System (ADS)

    Yamamoto, S.

    2000-11-01

    In response to recent nuclear magnetic resonance measurements on a ferrimagnetic chain compound NiCu(C 7H 6N 2O 6)(H 2O) 3·2H 2O [Solid State Commun. 113 (2000) 433], we calculate the nuclear spin-lattice relaxation rate 1/ T1 in terms of a modified spin-wave theory. Emphasizing that the dominant relaxation mechanism arises from the direct (single-magnon) process rather than the Raman (two-magnon) one, we explain the observed temperature and applied-field dependences of 1/ T1. Ferrimagnetic relaxation phenomena are generally discussed and novel ferrimagnets with extremely slow dynamics are predicted.

  3. [Effects of applying controlled release fertilizers on N2O emission from a lateritic red soil].

    PubMed

    Du, Ya-qin; Zheng, Li-xing; Fan, Xiao-lin

    2011-09-01

    Static closed chamber technique and contrast method were adopted to study the effects of three coated compound fertilizers (N:P2O5:K2O = 19:8.6:10.5, high N; 14.4:14.4:14.4, balanced NPK; and 12.5:9.6:20.2, high K) on the NO2O emission from a lateritic red soil under the condition of no crop planting, taking uncoated compound fertilizers (N:P2O5:K2O = 20:9:11, high N; 15:15:15, balanced NPK; and 13:10:21, high K) as the contrasts. Different formula of fertilizer NPK induced significant difference in the N2O emission. Under the application of uncoated compound fertilizers, the cumulative N2O emission was in the order of balanced NPK > or = high N > high K. Applying coated compound fertilizers decreased the N2O emission significantly, and the emission amount under the application of high N, balanced NPK, and high K was 34.4%, 30.5%, and 89.3% of the corresponding uncoated compound fertilizers, respectively. Comparing with the application of uncoated compound fertilizers, applying coated compound fertilizers also decreased the daily N2O flux significantly, and delayed and shortened the N2O peak, suggesting that coated fertilizers could reduce soil nitrogen loss and the global warming potential induced by N2O emission. PMID:22126050

  4. Microstructure of a commercial W-1% La2O3 alloy

    NASA Astrophysics Data System (ADS)

    Shen, Yinzhong; Xu, Zhiqiang; Cui, Kai; Yu, Jie

    2014-12-01

    W-1% La2O3 alloy is considered as the most promising material for plasma-facing components of fusion reactors. The microstructure of a commercial W-1% La2O3 alloy was investigated using optical and transmission electron microscopes. The microstructure of pure tungsten can be improved significantly by fabrication of W-1% La2O3 alloys. W-1% La2O3 alloys can be produced with no porosities and cracks, and with various oxide phases dispersed in alloy matrix. La2O3 with different crystal structures, La6W2O15, WO2, WO3 and W3O8 phases were identified in as-forged W-1% La2O3 alloy. Long strip-like La2O3 has a very large size, whereas spherical La6W2O15, navicular WO3, hexagonal W3O8 and short rod-like La2O3 are smaller particles. Most identified phases have a heterogeneous distribution. Forging leads to a more dispersive distribution of large-sized La2O3 particles but not of fine WO3 particles compared with rolling. The mechanical properties of the alloys are also discussed.

  5. Electronic polarizability, optical basicity, and interaction parameter of La2O3 and related glasses

    NASA Astrophysics Data System (ADS)

    Honma, T.; Benino, Y.; Fujiwara, T.; Komatsu, T.; Sato, R.; Dimitrov, V.

    2002-03-01

    The electronic polarizability and optical basicity of La2O3 and related glasses have been determined from ultraviolet absorption spectra and calculations based on the Lorentz-Lorenz equation. The optical basicity for La2O3 oxide is found to be 1.07, being much larger compared with typical glass-forming oxides such as B2O3 (0.42) and SiO2 (0.48) but being similar to heavy element oxides such as TeO2 (0.93). The Yamashita and Kurosawa's interaction parameter of La2O3 is 0.03 Å-3, indicating that La2O3 is classified as a normal ionic (basic) oxide, i.e., an ionic bonding character in the La3+-O bond is proposed. Close correlations are confirmed among optical basicity, interaction parameter, and oxygen 1s binding energy in x-ray photoelectron (XPS) spectra for La2O3-P2O5 and other La2O3-containing glasses. It is found from XPS and Raman spectra that La3+ ions in La2O3-P2O5 glasses act as network modifiers, supporting an ionic bonding character in the La3+-O bond. The parameters related to electronic polarizability in La2O3 determined in the present study would be useful for the design of rare-earth containing optical functional glasses.

  6. Isotopomer Analysis of N2O Produced During Waste Water Treatment

    NASA Astrophysics Data System (ADS)

    Toyoda, S.; Fujiwara, A.; Yoshida, N.

    2007-12-01

    Nitrous oxide (N2O) is an important trace gas in the atmosphere since it is radiatively active in the troposphere and also a precursor of nitric oxide which catalytically destroys ozone in the stratosphere. Isotopomer ratios (elemental N and O isotope ratios and site-specific N isotope ratios in asymmetric molecule of NNO) have been studied to understand its complex geochemical cycle. Microbial processes such as nitrification and denitrification are the largest N2O sources, and pure culture incubation studies showed that intramolecular 15N-site preference (SP) in N2O can differentiate the two N2O producing processes, hydroxylamine oxidation and nitrite reduction. However, there have been still few studies on N2O isotopomer ratios in complex bacterial systems. In this paper, we investigated the isotopomer ratios in N2O produced in waste water treatment system in order to evaluate characteristics of N2O emitted from human sewage and to understand N2O dynamics in microbial consortia (activated sludge). Water and gas samples were collected step by step in two different treatment systems in a sewage plant in Tokyo. High dissolved N2O concentration (up to 7600%\\ saturation) was observed in biological reaction tanks and isotopomer ratios confirmed active N2O production by microbes. Moreover, isotopomer ratios showed large variations throughout the whole treatment system and suggested that N2O is produced in settling and chlorination steps as well as biological reaction steps.

  7. [Effects of applying controlled release fertilizers on N2O emission from a lateritic red soil].

    PubMed

    Du, Ya-qin; Zheng, Li-xing; Fan, Xiao-lin

    2011-09-01

    Static closed chamber technique and contrast method were adopted to study the effects of three coated compound fertilizers (N:P2O5:K2O = 19:8.6:10.5, high N; 14.4:14.4:14.4, balanced NPK; and 12.5:9.6:20.2, high K) on the NO2O emission from a lateritic red soil under the condition of no crop planting, taking uncoated compound fertilizers (N:P2O5:K2O = 20:9:11, high N; 15:15:15, balanced NPK; and 13:10:21, high K) as the contrasts. Different formula of fertilizer NPK induced significant difference in the N2O emission. Under the application of uncoated compound fertilizers, the cumulative N2O emission was in the order of balanced NPK > or = high N > high K. Applying coated compound fertilizers decreased the N2O emission significantly, and the emission amount under the application of high N, balanced NPK, and high K was 34.4%, 30.5%, and 89.3% of the corresponding uncoated compound fertilizers, respectively. Comparing with the application of uncoated compound fertilizers, applying coated compound fertilizers also decreased the daily N2O flux significantly, and delayed and shortened the N2O peak, suggesting that coated fertilizers could reduce soil nitrogen loss and the global warming potential induced by N2O emission.

  8. One-pot synthesis of porphyrin functionalized γ-Fe2O3 nanocomposites as peroxidase mimics for H2O2 and glucose detection.

    PubMed

    Liu, Qingyun; Zhang, Leyou; Li, Hui; Jia, Qingyan; Jiang, Yanling; Yang, Yanting; Zhu, Renren

    2015-10-01

    Meso-tetrakis(4-carboxyphenyl)-porphyrin-functionalized γ-Fe2O3 nanoparticles (H2TCPP-γ-Fe2O3) were successfully prepared by one-pot method under hydrothermal conditions and were found to possess intrinsic peroxidase-like activity. The H2TCPP-γ-Fe2O3 nanocomposites can catalytically oxidize peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2 to produce a blue color reaction, which can be easily observed by the naked eye. Furthermore, kinetic studies indicate that the H2TCPP-γ-Fe2O3 nanocomposites have an even higher affinity to TMB than that of the natural enzyme, horseradish peroxidase (HRP). On the basis of the high activity, the reaction provides a simple, sensitive and selective method for colorimetric detection of H2O2 over a range of 10-100 μM with a minimum detection limit of 1.73 μM. Moreover, H2TCPP-γ-Fe2O3/glucose oxidase (GOx)/TMB system provides a novel colorimetric sensor for glucose and shows good response toward glucose detection over a range of 5-25 μM with a minimum detection limit of 2.54 μM. The results indicated that it is a simple, cheap, convenient, highly selective, sensitive and easy handling colorimetric assay. Results of a fluorescent probe suggest that the catalase-mimic activity of the H2TCPP-γ-Fe2O3 nanocomposites effectively catalyze the decomposition of H2O2 into H2O and O2.

  9. Morphological evolution of (NH4)(0.5)V2O5·mH2O fibers into belts, triangles, and rings.

    PubMed

    Chandrappa, Gujjarahalli Thimmanna; Chithaiah, Pallellappa; Ashoka, Siddaramanna; Livage, Jacques

    2011-08-15

    In this contribution, single-crystalline (NH(4))(0.5)V(2)O(5)·mH(2)O xerogels made of belts, rings, triangles, and ovals have been synthesized using a surfactant-free hydrothermal method. The analytical techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR), high-resolution TEM (HRTEM), and selected area electron diffraction (SAED) have been used to characterize the morphology, composition, and structure of the as-prepared products. On the basis of SEM and TEM observations, we suggested that the as-prepared (NH(4))(0.5)V(2)O(5)·mH(2)O rings, triangles, and ovals have been formed by connecting two ends of the vanadium oxide sheet made of edge and corner sharing VO(5) square pyramids. The as-prepared (NH(4))(0.5)V(2)O(5)·mH(2)O nanobelts are up to several hundreds of micrometers long, 402-551 nm wide, and 235-305 nm thick. The thickness and width of the rings are respectively ∼454 nm and ∼1 μm. Triangles with three unequal sides having a thickness of ∼143 nm and a width of ∼1 μm were also formed. The crystalline orthorhombic phase of shcherbianite V(2)O(5) was obtained on calcination of (NH(4))(0.5)V(2)O(5)·mH(2)O at 350 °C for 2 h. The SEM image of this V(2)O(5) product retains the parent morphology of the preheated compound. A possible reaction mechanism and the growth process involved in the formation of belts/rings/triangles and ovallike microstructures are discussed. PMID:21774460

  10. Formation and stability of crystalline and amorphous Al2O3 layers deposited on Ga2O3 nanowires by atomic layer epitaxy

    NASA Astrophysics Data System (ADS)

    Katz, M. B.; Twigg, M. E.; Prokes, S. M.

    2016-09-01

    Although the crystalline α and γ phases are the most stable forms of alumina, small-diameter (<6 nm) nanoparticles are known to be completely amorphous, due to the surface energy being correspondingly lower for the less stable non-crystalline phase. Al2O3 films with a thickness of 5 nm grown by low temperature (200 °C) atomic layer deposition (ALD) on small-diameter (<20 nm) Ga2O3 nanowires (NWs), however, are identified by transmission electron microscopy as belonging to the α, γ, and possibly θ crystalline phases of Al2O3, while films deposited on larger diameter (>20 nm) NWs are found to be amorphous. Indeed, until recently, all Al2O3, films deposited by low-temperature ALD using trimethylaluminum and water have been reported to be amorphous, regardless of film thickness or substrate. The formation of a crystalline ALD film can be understood in terms of the energetics of misfit dislocations that maintain the registry between the ALD film and the NW substrate, as well as the influence of strain and surface energy. The decreasing energy of co-axial misfit dislocations with NW diameter results in a corresponding decrease in the contribution of the Al2O3/Ga2O3 interface to the free energy, while the interfacial energy for an amorphous film is independent of the NW diameter. Therefore, for NW cores of sufficiently small diameter, the free energy contribution of the Al2O3/Ga2O3 interface is smaller for crystalline films than for amorphous films, thereby favoring the formation of crystalline films for small-diameter NWs. For ALD Al2O3 films of 10 nm thickness deposited on small-diameter Ga2O3 NWs, however, only the first 5 nm of the ALD film is found to be crystalline, possibly due to well-established kinetic limitations to low temperature epitaxial growth.

  11. An unusual density evolution between SrCdB2O5 polymorphs.

    PubMed

    Zhang, Xingwen; Zhou, Zhengyang; Wu, Hongping; Pan, Shilie; Lei, Chen; Liu, Lu; Yang, Zhihua

    2015-09-28

    Owing to the effect of atomic vibrations, a high-temperature phase usually features a relatively smaller density when compared with a low-temperature phase. In this work, a new SrCdB2O5 phase has been discovered. According to the crystallization temperature from low to high, the new SrCdB2O5 phase can be regarded as the high-temperature β-SrCdB2O5 phase. The density of β-SrCdB2O5 is obviously larger than that of α-SrCdB2O5, meanwhile β-SrCdB2O5 is energetically favored. This unusual density evolution phenomenon has been investigated. In addition, the Pb(2+)-doped compounds, PbxSr1-xCdB2O5 (x = 0.125, 0.25, 0.375, 0.5), have also been investigated by powder refinement. PMID:26266583

  12. Hydrogen-bond-directed assemblies of [La(18-crown-6)(H2O)4](BiCl6)·3H2O and [Nd(18-crown-6)(H2O)4](BiCl6)·3.5H2O regulated by different symmetries

    NASA Astrophysics Data System (ADS)

    Zhang, Shi-Yong; Li, Jian; Zeng, Ying; Wen, He-Rui; Du, Zi-Yi

    2016-12-01

    The reactions of La2O3 or Nd2O3 with BiCl3 and 18-crown-6 in the presence of excessive hydrochloric acid afforded two ion-pair compounds, namely [La(18-crown-6)(H2O)4](BiCl6)·3H2O (1) and [Nd(18-crown-6)(H2O)4](BiCl6)·3.5H2O (2). Although these two compounds contain similar building blocks, they exhibit two distinct hydrogen-bonded networks, which are mainly induced by the slightly different geometries of their large-sized cationic [Ln(18-crown-6)(H2O)4]3+ components.

  13. Fabrication and characterization of highly transparent Yb3+: Y2O3 ceramics

    NASA Astrophysics Data System (ADS)

    Ning, Kaijie; Wang, Jun; Luo, Dewei; Ma, Jie; Zhang, Jian; Dong, Zhi Li; Kong, Ling Bing; Tang, Ding Yuan

    2015-12-01

    Highly transparent Yb3+ doped Y2O3 (Yb3+: Y2O3) ceramics was fabricated by a solid-state reaction method using ZrO2 and La2O3 as additives. The morphology of the prepared powder was investigated and the phase of the sintered Yb3+: Y2O3 ceramics sample was identified. The microstructure, transmittance spectrum, Vickers hardness and fracture toughness for the as-sintered Yb3+: Y2O3 ceramics were measured. The average grain size was about 9.11 μm and the transmittance at the wavelength of 2000 nm was about 82.0%, which was 99% of the theoretical value. ZrO2 and La2O3 were useful additives for highly transparent Yb3+: Y2O3 ceramics fabrication and mechanical properties improvement.

  14. Transit of H2O2 across the endoplasmic reticulum membrane is not sluggish.

    PubMed

    Appenzeller-Herzog, Christian; Bánhegyi, Gabor; Bogeski, Ivan; Davies, Kelvin J A; Delaunay-Moisan, Agnès; Forman, Henry Jay; Görlach, Agnes; Kietzmann, Thomas; Laurindo, Francisco; Margittai, Eva; Meyer, Andreas J; Riemer, Jan; Rützler, Michael; Simmen, Thomas; Sitia, Roberto; Toledano, Michel B; Touw, Ivo P

    2016-05-01

    Cellular metabolism provides various sources of hydrogen peroxide (H2O2) in different organelles and compartments. The suitability of H2O2 as an intracellular signaling molecule therefore also depends on its ability to pass cellular membranes. The propensity of the membranous boundary of the endoplasmic reticulum (ER) to let pass H2O2 has been discussed controversially. In this essay, we challenge the recent proposal that the ER membrane constitutes a simple barrier for H2O2 diffusion and support earlier data showing that (i) ample H2O2 permeability of the ER membrane is a prerequisite for signal transduction, (ii) aquaporin channels are crucially involved in the facilitation of H2O2 permeation, and (iii) a proper experimental framework not prone to artifacts is necessary to further unravel the role of H2O2 permeation in signal transduction and organelle biology.

  15. Ag/α-Fe2O3 hollow microspheres: Preparation and application for hydrogen peroxide detection

    NASA Astrophysics Data System (ADS)

    Kang, Xinyuan; Wu, Zhiping; Liao, Fang; Zhang, Tingting; Guo, Tingting

    2015-09-01

    In this paper, we demonstrated a simple approach for preparing α-Fe2O3 hollow spheres by mixing ferric nitrate aqueous and glucose in 180 °C. The glucose was found to act as a soft template in the process of α-Fe2O3 hollow spheres formation. Ag/α-Fe2O3 hollow nanocomposite was obtained under UV irradiation without additional reducing agents or initiators. Synthesized Ag/α-Fe2O3 hollow composites exhibited remarkable catalytic performance toward H2O2 reduction. The electrocatalytic activity mechanism of Ag/α-Fe2O3/GCE were discussed toward the reduction of H2O2 in this paper.

  16. Effects of substrates on N2O emissions in an anaerobic ammonium oxidation (anammox) reactor.

    PubMed

    Jin, Yue; Wang, Dunqiu; Zhang, Wenjie

    2016-01-01

    N2O emission in the anaerobic ammonium oxidation (anammox) process is of growing concern. In this study, effects of substrate concentrations on N2O emissions were investigated in an anammox reactor. Extremely high N2O emissions of 1.67 % were led by high NH4-N concentrations. Results showed that N2O emissions have a positive correlation with NH4-N concentrations in the anammox reactor. Reducing NH4-N concentrations by recycling pump resulted in decreasing N2O emissions. In addition, further studies were performed to identify a key biological process that is contributed to N2O emissions from the anammox reactor. Based on the results obtained, Nitrosomonas, which can oxidize ammonia to nitrite, was deemed as the main sources of N2O emissions. PMID:27376009

  17. Structure and thermal behaviour of ScK(C 2O 4) 2(H 2O) 2 and InRb 1- x(H 3O) x(C 2O 4) 2(H 2O) 2ṡ0.5(H 2O): Two members of a family of open-framework oxalates with isotypic helical structures and zeolite-like properties

    NASA Astrophysics Data System (ADS)

    Mahé, Nathalie; Audebrand, Nathalie

    2006-08-01

    Two new mixed oxalates with an open architecture, ScK(C 2O 4) 2(H 2O) 2 ( I) and InRb 0.77(H 3O) 0.23(C 2O 4) 2(H 2O) 2ṡ0.5(H 2O) ( II), have been synthesised from precipitation methods at ambient temperature. They crystallize in hexagonal system, space group P622 (No. 180), Z=3, with the following unit-cell parameters for I: a=8.8667(2) Å, c=11.4908(4) Å, V=782.36(4) Å, for II: a=9.0148(3) Å, c=11.4645(3) Å, V=806.86(4) Å. The two structures belong to a family of isotypic helical anionic open-frameworks built from square antiprismatic coordinated metals and bischelating oxalates. The counter-cations K + and Rb +/H 3O + are located in the tunnels of the framework. The thermal decomposition process has demonstrated zeolite-like properties associated with weakly-bonded water molecules located in the voids of the framework.

  18. Differential regulation of TRPV1 channels by H2O2: implications for diabetic microvascular dysfunction.

    PubMed

    DelloStritto, Daniel J; Connell, Patrick J; Dick, Gregory M; Fancher, Ibra S; Klarich, Brittany; Fahmy, Joseph N; Kang, Patrick T; Chen, Yeong-Renn; Damron, Derek S; Thodeti, Charles K; Bratz, Ian N

    2016-03-01

    We demonstrated previously that TRPV1-dependent coupling of coronary blood flow (CBF) to metabolism is disrupted in diabetes. A critical amount of H2O2 contributes to CBF regulation; however, excessive H2O2 impairs responses. We sought to determine the extent to which differential regulation of TRPV1 by H2O2 modulates CBF and vascular reactivity in diabetes. We used contrast echocardiography to study TRPV1 knockout (V1KO), db/db diabetic, and wild type C57BKS/J (WT) mice. H2O2 dose-dependently increased CBF in WT mice, a response blocked by the TRPV1 antagonist SB366791. H2O2-induced vasodilation was significantly inhibited in db/db and V1KO mice. H2O2 caused robust SB366791-sensitive dilation in WT coronary microvessels; however, this response was attenuated in vessels from db/db and V1KO mice, suggesting H2O2-induced vasodilation occurs, in part, via TRPV1. Acute H2O2 exposure potentiated capsaicin-induced CBF responses and capsaicin-mediated vasodilation in WT mice, whereas prolonged luminal H2O2 exposure blunted capsaicin-induced vasodilation. Electrophysiology studies re-confirms acute H2O2 exposure activated TRPV1 in HEK293A and bovine aortic endothelial cells while establishing that H2O2 potentiate capsaicin-activated TRPV1 currents, whereas prolonged H2O2 exposure attenuated TRPV1 currents. Verification of H2O2-mediated activation of intrinsic TRPV1 specific currents were found in isolated mouse coronary endothelial cells from WT mice and decreased in endothelial cells from V1KO mice. These data suggest prolonged H2O2 exposure impairs TRPV1-dependent coronary vascular signaling. This may contribute to microvascular dysfunction and tissue perfusion deficits characteristic of diabetes.

  19. Coin-like α-Fe2O3@CoFe2O4 core-shell composites with excellent electromagnetic absorption performance.

    PubMed

    Lv, Hualiang; Liang, Xiaohui; Cheng, Yan; Zhang, Haiqian; Tang, Dongming; Zhang, Baoshan; Ji, Guangbin; Du, Youwei

    2015-03-01

    In this paper, we designed a novel core-shell composite for microwave absorption application in which the α-Fe2O3 and the porous CoFe2O4 nanospheres served as the core and shell, respectively. Interestingly, during the solvothermal process, the solvent ratio (V) of PEG-200 to distilled water played a key role in the morphology of α-Fe2O3 for which irregular flake, coin-like, and thinner coin-like forms of α-Fe2O3 can be produced with the ratios of 1:7, 1:3, and 1:1, respectively. The porous 70 nm diameter CoFe2O4 nanospheres were generated as the shell of α-Fe2O3. It should be noted that the CoFe2O4 coating layer did not damage the original shape of α-Fe2O3. As compared with the uncoated α-Fe2O3, the Fe2O3@CoFe2O4 composites exhibited improved microwave absorption performance over the tested frequency range (2-18 GHz). In particular, the optimal reflection loss value of the flake-like composite can reach -60 dB at 16.5 GHz with a thin coating thickness of 2 mm. Furthermore, the frequency bandwidth corresponding to the RLmin value below -10 dB was up to 5 GHz (13-18 GHz). The enhanced microwave absorption properties of these composites may originate from the strong electron polarization effect (i.e., the electron polarization between Fe and Co) and the electromagnetic wave scattering on this special porous core-shell structure. In addition, the synergy effect between α-Fe2O3 and CoFe2O4 also favored balancing the electromagnetic parameters. Our results provided a promising approach for preparing an absorbent with good absorption intensity and a broad frequency that was lightweight.

  20. Understanding hydrothermal transformation from Mn2O3 particles to Na0.55Mn2O4·1.5H2O nanosheets, nanobelts, and single crystalline ultra-long Na4Mn9O18 nanowires

    PubMed Central

    Park, Yohan; Woo Lee, Sung; Kim, Ki Hyeon; Min, Bong-Ki; Kumar Nayak, Arpan; Pradhan, Debabrata; Sohn, Youngku

    2015-01-01

    Manganese oxides are one of the most valuable materials for batteries, fuel cells and catalysis. Herein, we report the change in morphology and phase of as-synthesized Mn2O3 by inserting Na+ ions. In particular, Mn2O3 nanoparticles were first transformed to 2 nm thin Na0.55Mn2O4·1.5H2O nanosheets and nanobelts via hydrothermal exfoliation and Na cation intercalation, and finally to sub-mm ultra-long single crystalline Na4Mn9O18 nanowires. This paper reports the morphology and phase-dependent magnetic and catalytic (CO oxidation) properties of the as-synthesized nanostructured Na intercalated Mn-based materials. PMID:26667348

  1. Two forms of sodium titanium(III) diphosphate: α-NaTiP 2O 7 closely related to β-cristobalite and β-NaTiP 2O 7 isotypic with NaFeP 2O 7

    NASA Astrophysics Data System (ADS)

    Leclaire, A.; Benmoussa, A.; Borel, M. M.; Grandin, A.; Raveau, B.

    1988-12-01

    The structures of two new forms of a titanium(III) phosphate NaTiP 2O 7 have been determined. One of them, β-NaTiP 2O 7 [ a = 7.394(1)Å, b = 7.936(3)Å, c = 9.726(3)Å β = 11.85(2)° {P2 1}/{c}], is isotypic with NaFeP 2O 7 which has been previously described. The other form, α-NaTiP 2O 7 [ a = 8.697(1)Å, b = 5.239(7)Å, c = 13.293(3)Å, β = 116.54(1)°, {P2 1}/{c}], is found to be closely related to the structure of β-cristobalite and of carnegieite and is described as a "pseudo-hexagonal" framework characterized by intersecting tunnels.

  2. Equation of state measurements in Ta2O5 aerogel

    NASA Astrophysics Data System (ADS)

    Miller, Joshua; Boehly, Tom; Meyerhofer, David; Eggert, Jon

    2007-06-01

    The examination of the equation of state of Ta2O5 aerogel using laser driven shock compression has been performed at OMEGA. The foams, with densities in the range of 0.1 to 0.25 g/cc, were loaded by shocks with pressures in the range of 50 to 300 Gpa. Hugoniot parameters inferred from mechanical measurements of the shock evolution and temperatures inferred from the shock front self-emission were resolved on the sub-nanosecond time scale during this study. Comparisons between these experimental results and the existing qEOS model show that the aerogel is much more compressible than qEOS predicts at pressures below 100 GPa. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460, the University of Rochester, and the New York State Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE of the views expressed in this article.

  3. Radiation endurance in Al2O3 nanoceramics

    PubMed Central

    García Ferré, F.; Mairov, A.; Ceseracciu, L.; Serruys, Y.; Trocellier, P.; Baumier, C.; Kaïtasov, O.; Brescia, R.; Gastaldi, D.; Vena, P.; Beghi, M. G.; Beck, L.; Sridharan, K.; Di Fonzo, F.

    2016-01-01

    The lack of suitable materials solutions stands as a major challenge for the development of advanced nuclear systems. Most issues are related to the simultaneous action of high temperatures, corrosive environments and radiation damage. Oxide nanoceramics are a promising class of materials which may benefit from the radiation tolerance of nanomaterials and the chemical compatibility of ceramics with many highly corrosive environments. Here, using thin films as a model system, we provide new insights into the radiation tolerance of oxide nanoceramics exposed to increasing damage levels at 600 °C –namely 20, 40 and 150 displacements per atom. Specifically, we investigate the evolution of the structural features, the mechanical properties, and the response to impact loading of Al2O3 thin films. Initially, the thin films contain a homogeneous dispersion of nanocrystals in an amorphous matrix. Irradiation induces crystallization of the amorphous phase, followed by grain growth. Crystallization brings along an enhancement of hardness, while grain growth induces softening according to the Hall-Petch effect. During grain growth, the excess mechanical energy is dissipated by twinning. The main energy dissipation mechanisms available upon impact loading are lattice plasticity and localized amorphization. These mechanisms are available in the irradiated material, but not in the as-deposited films. PMID:27653832

  4. Potential dual imaging nanoparticle: Gd2O3 nanoparticle

    NASA Astrophysics Data System (ADS)

    Ahmad, Md. Wasi; Xu, Wenlong; Kim, Sung June; Baeck, Jong Su; Chang, Yongmin; Bae, Ji Eun; Chae, Kwon Seok; Park, Ji Ae; Kim, Tae Jeong; Lee, Gang Ho

    2015-02-01

    Gadolinium (Gd) is a unique and powerful element in chemistry and biomedicine which can be applied simultaneously to magnetic resonance imaging (MRI), X-ray computed tomography (CT), and neutron capture therapy for cancers. This multifunctionality can be maximized using gadolinium oxide (Gd2O3) nanoparticles (GNPs) because of the large amount of Gd per GNP, making both diagnosis and therapy (i.e., theragnosis) for cancers possible using only GNPs. In this study, the T1 MRI and CT dual imaging capability of GNPs is explored by synthesizing various iodine compound (IC) coated GNPs (IC-GNPs). All the IC-GNP samples showed stronger X-ray absorption and larger longitudinal water proton relaxivities (r1 = 26-38 s-1mM-1 and r2/r1 = 1.4-1.9) than the respective commercial contrast agents. In vivo T1 MR and CT images of mice were also acquired, supporting that the GNP is a potential dual imaging agent.

  5. Potential dual imaging nanoparticle: Gd2O3 nanoparticle

    PubMed Central

    Ahmad, Md. Wasi; Xu, Wenlong; Kim, Sung June; Baeck, Jong Su; Chang, Yongmin; Bae, Ji Eun; Chae, Kwon Seok; Park, Ji Ae; Kim, Tae Jeong; Lee, Gang Ho

    2015-01-01

    Gadolinium (Gd) is a unique and powerful element in chemistry and biomedicine which can be applied simultaneously to magnetic resonance imaging (MRI), X-ray computed tomography (CT), and neutron capture therapy for cancers. This multifunctionality can be maximized using gadolinium oxide (Gd2O3) nanoparticles (GNPs) because of the large amount of Gd per GNP, making both diagnosis and therapy (i.e., theragnosis) for cancers possible using only GNPs. In this study, the T1 MRI and CT dual imaging capability of GNPs is explored by synthesizing various iodine compound (IC) coated GNPs (IC-GNPs). All the IC-GNP samples showed stronger X-ray absorption and larger longitudinal water proton relaxivities (r1 = 26–38 s−1mM−1 and r2/r1 = 1.4–1.9) than the respective commercial contrast agents. In vivo T1 MR and CT images of mice were also acquired, supporting that the GNP is a potential dual imaging agent. PMID:25707374

  6. Vanadium magnetoelectric multipoles in V2O3

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.; Fernández-Rodríguez, J.; Blanco, J. A.; Sivia, D. S.; Knight, K. S.; Paolasini, L.

    2007-01-01

    We establish the contributions made by the vanadium anapole, and other magnetoelectric multipoles, to the electron ground state of V2O3 in its antiferromagnetic modification. To this end, observations made by resonant x-ray Bragg diffraction are analyzed in terms of a scattering amplitude derived within the atomic model. The amplitude is a coherent sum of E1-E2 and E2-E2 resonance events that is fully compliant with the established chemical (I2/a) and magnetic space groups. One set of values for the V multipoles are found to give a totally satisfactory account of all data collected at two space-group forbidden Bragg reflections in the two polarization channels σ'σ and π'σ ( σ primary polarization, and σ' and π' secondary polarizations). Derived estimates of the V anapole (E1-E2) and V octupole (E2-E2) are good to within a few percent, and the E1-E2 event alone is shown not to adequately describe the diffraction data.

  7. Radiation endurance in Al2O3 nanoceramics

    NASA Astrophysics Data System (ADS)

    García Ferré, F.; Mairov, A.; Ceseracciu, L.; Serruys, Y.; Trocellier, P.; Baumier, C.; Kaïtasov, O.; Brescia, R.; Gastaldi, D.; Vena, P.; Beghi, M. G.; Beck, L.; Sridharan, K.; di Fonzo, F.

    2016-09-01

    The lack of suitable materials solutions stands as a major challenge for the development of advanced nuclear systems. Most issues are related to the simultaneous action of high temperatures, corrosive environments and radiation damage. Oxide nanoceramics are a promising class of materials which may benefit from the radiation tolerance of nanomaterials and the chemical compatibility of ceramics with many highly corrosive environments. Here, using thin films as a model system, we provide new insights into the radiation tolerance of oxide nanoceramics exposed to increasing damage levels at 600 °C –namely 20, 40 and 150 displacements per atom. Specifically, we investigate the evolution of the structural features, the mechanical properties, and the response to impact loading of Al2O3 thin films. Initially, the thin films contain a homogeneous dispersion of nanocrystals in an amorphous matrix. Irradiation induces crystallization of the amorphous phase, followed by grain growth. Crystallization brings along an enhancement of hardness, while grain growth induces softening according to the Hall-Petch effect. During grain growth, the excess mechanical energy is dissipated by twinning. The main energy dissipation mechanisms available upon impact loading are lattice plasticity and localized amorphization. These mechanisms are available in the irradiated material, but not in the as-deposited films.

  8. Dipole defects in Al2O3:Mg,Cr.

    PubMed

    Blak, A R; Gobbi, V; Ayres, F

    2002-01-01

    In this work, dipole defects are investigated applying the thermally stimulated depolarisation currents (TSDC) technique. The TSDC spectra of Al2O3 doped with Mg and Cr show two bands centred at 230 K and 250 K, respectively. The maximum intensity of the bands increases linearly with the polarisation field, a typical behaviour of defects with dipole origin. An increase of the band at 250 K with gamma irradiation has been observed and a thermal decrease of the bands for heat treatments between 1000 K and 1400 K. Above this temperature the bands are partially recovered. Impurity neutron activation analysis shows that magnesium. chromium and iron content varies from 15 to 60 ppm. Optical absorption (AO) measurements show a broad band centred in 2.6 eV (21000 cm(-1)) associated with trapped holes localised on an O- ion adjacent to a cation site which is deficient in positive charge. It has been assumed that a substitutional Mg2+ ion occupies the cation site near a trapped hole on one of the six oxygen ions surrounding the magnesium impurity giving rise to the dipole responsible for the observed TSDC bands. Calculations carried out through defect simulation methods confirm that the probability of Al3+ being replaced by Mg2+ is higher than Mn2+, Co2+, Fe2+ and Cr2+. PMID:12382829

  9. The thermodynamic properties of hydrated -Al2O3 nanoparticles

    SciTech Connect

    Spencer, Elinor; Huang, Baiyu; Parker, Stewart F.; Kolesnikov, Alexander I; Ross, Dr. Nancy; Woodfield, Brian

    2013-01-01

    In this paper we report a combined calorimetric and inelastic neutron scattering (INS) study of hydrated -Al2O3 ( -alumina) nanoparticles. These complementary techniques have enabled a comprehensive evaluation of the thermodynamic properties of this technological and industrially important metal oxide to be achieved. The isobaric heat capacity (Cp) data presented herein provide further critical insights into the much-debated chemical composition of -alumina nanoparticles. Furthermore, the isochoric heat capacity (Cv) of the surface water, which is so essential to the stability of all metal-oxides at the nanoscale, has been extracted from the high-resolution INS data and differs significantly from that of ice Ih due to the dominating influence of strong surface-water interactions. This study also encompassed the analysis of four -alumina samples with differing pore diameters [4.5 (1), 13.8 (2), 17.9 (3), and 27.2 nm (4)], and the results obtained allow us to unambiguously conclude that the water content and pore size have no influence on the thermodynamic behaviour of hydrated -alumina nanoparticles.

  10. Effect of concentration of Sm2O3 and Yb2O3 and synthesizing temperature on electrical and crystal structure of (Bi2O3)1-x-y(Sm2O3)x(Yb2O3)y electrolytes fabricated for IT-SOFCs

    NASA Astrophysics Data System (ADS)

    Kayalı, Refik; Özen, Mürivet Kaşıkcı; Bezir, Nalan Çiçek; Evcin, Atilla

    2016-05-01

    For intermediate temperature solid oxide fuel cells (IT-SOFCs), (Bi2O3)1-x-y(Sm2O3)x(Yb2O3)y ternary systems (x=0.01 and y= 0.11), (x=0.05 and y= 0.07), (x=0.07 and y=0.05), and (x=0.11 and y=0.01) as electrolytes have been fabricated at different temperatures (700, 750, and 800 °C) by solid state ceramic technique (SST). The characterization of the samples has been performed by X-ray powder diffractometer (XRD), scanning electron microscopy (SEM), four point-probe method (FPPM), X-ray energy diffraction spectroscopy (EDX), and differential thermal analysis (DTA). XRD measurements have shown that only the samples (Bi2O3)1-x-y(Sm2O3)x(Yb2O3)y (x=0.01, y=0.11 synthesized at 700, 750, and 800 °C) and (x=0.05, y=0.07 synthesized at 800 °C) have stable fluorite type face centered cubic (FCC) δ-phase. SEM images have shown the morphology of the stable samples. The conductivity and the operation temperature region of the samples have been determined from Arrhenius curves obtained from the FPPM measurements data and they vary from 1.83 to 9.95×10-1 S cm-1. Moreover, activation energy of the samples have been calculated by means of Arrhenius curves of